However, this can lead to errors in estimation of dosimetric quantities on non-planar body parts with local curvature radii comparable to the wavelength of the incident field. In this study, we address this problem by developing an averaging technique for the assessment of the absorbed power density ( S_ab ) on the anatomically-accurate electromagnetic (EM) model of the human ear. The dosimetric analysis is performed for the plane-wave exposure at 26 and 60 GHz, and the accuracy of the proposed method is verified by using two commercial EM software. Furthermore, we compare the two definitions of S_ab provided in the international guidelines and standards for limiting exposure to EM fields above 6 GHz. Results show marginal relative differences between the obtained values from the two different definitions (within about 6 %) in all considered scenarios. On the other hand, in comparison to flat models, the spatial maximum S_ab on the ear is up to about 20 % larger regardless of definition. These findings demonstrate a promising potential of the proposed method for the assessment of S_ab on surfaces of anatomical models at frequencies upcoming for the 5th generation (5G) wireless networks and beyond

Functional magnetic resonance imaging (fMRI) has been introduced as an effective neuroimaging technique to explore neural activity. However, images within PFC region are subject to susceptibility artifacts, which give rise to undesired image distortion and signal drop-out. In this work, we proposed a method of adding a static magnetic field with high-order spatial pattern for artifact correction. Based on that, a compact attachable 8-channel coil array was constructed. Two toroid chokes were optimized and connected to each coil loop to minimize radiofrequency coupling. To evaluate the array performance, bench measurements and MRI experiments over phantoms and a human subject at 7T were conducted. With the proposed array applied, only 0.3 MHz and 1 MHz frequency shift were introduced to the RF coil, and no apparent RF performance change was observed; the inhomogeneity was reduced by 15%∼24%; in fMRI images over the human subject, “notorious” artifacts within target region were relatively mitigated. The present setup offers a feasible means for practical artifact correction, which is promising for the research that focuses on PFC regions.

To compensate this, it is desired to have a high coil sensitivity of the solenoid coil that works in such a system. Hence in this paper, an asymmetrical tapered solenoid was proposed and an optimization was carried out for both the coil profile and pitches between turns for high coil sensitivity and homogeneity. Multi-objective genetic algorithm was used. B₁ -field was calculated using Biot-Savart’s law in the optimization process. The targeted field of view (FoV) is a 190 mm diameter of spherical volume (DSV) for head imaging. The optimized solenoid coils were simulated using frequency domain solver in CST Microwave studio, physically constructed, and compared with a reference coil of comparable dimensions. The optimal design shows B₁ field increase of ∼ 35% (calculation), ∼ 33% (simulation) and minimal trade-off in homogeneity of ∼ 10% (calculation and simulation) within 190 mm DSV. For validation, the B₁ sensitivity of the constructed coils were measured in the FoV on the xy− plane at z=0 . The measured results are in good agreement with the simulated and calculated results.

However, large aperture of detector usually results in the limited spatial sampling points. Meanwhile, for considering the safety and comfort, the microwave radiation power is also limited. Due to these limitations, the signal to noise ratio (SNR) of TA signals may not be ideal to reconstruct an image with satisfactory quality. In addition, the TA image often suffers the artifacts resulted by sparsely sampling data. Herein, we propose a deep learning-based scheme to process the TA images which are reconstructed with time reversal (TR) method. Since the obvious artifacts removing performance in photoacoustic tomography (PAT), fully dense U-Net (FD U-Net) is employed to be the base deep learning architecture. Due to the amount limitation of real experimental TA data, the network is mainly trained by synthetic data which are generated in TAT simulating scheme. Furthermore, in order to ensuring the trained network could correctly detect the targets in the TA image, we propose a scheme termed data augmentation FD U-Net (DAFD U-Net) in which a few experimental TA images are added to the training procedure and perform data augmentation.The performance of DAFD U-Net is verified by an experimental image. Results show that the proposed scheme could significantly improve the quality of TAT image.

the permissible specific absorption rate (SAR) for whole-body exposure has been extended from 3 or 10 GHz to 300 GHz. The rationale for this revision is the extrapolation from findings of conventional radio-frequency exposure and infrared radiation. However, experiments of whole-body exposure in human subjects are limited to a few studies, which were conducted below 6 GHz. In this study, an exposure system at 28 GHz targeting a wide area of the human back was developed, which consists of two horn antennas with a dielectric lens. The effectiveness of the proposed exposure system was evaluated by computational dosimetry and experiments. The computed power absorption and measured distributions in the wave absorber and the back of the human subject were in good agreement. Under the compliance with the local exposure limits, the whole-body average SAR was 0.35 W/kg, which is comparable to the limit for whole-body exposure of 0.4 W/kg for occupational exposure in the international guidelines and standard. The developed exposure system would be useful to evaluate the thermophysiological response to whole-body exposure above 6 GHz.

The proposed sensor consists of a complementary split ring resonators (CSRR)-based structure with the sensing region surrounded by air vias to improve the confinement of the E-field within the sensing region. The proposed RF sensor is designed using the full wave EM simulator, the computer simulation technology (CST) Microwave Studio, and fabricated on Rogers 6002 ( ${{\rm{\varepsilon }}}_{\mathrm{r}}$ = 2.2) having a thickness of 3.75 mm. The various parameters of the designed sensor are optimized for improved performance, and its equivalent circuit model is developed using the ADS software. The proposed sensor confines the field in the sensing area and the test fluid is injected into the sensing region through a specially designed 1.5 mm fluidic channel made across the width of the substrate. This kind of channel embedded in the substrate limits the quantity of fluid interacting with the sensing region thereby facilitating testing of Simulated Body Fluid (SBF) possessing even high-value permittivity in the range of 80–100. The SBF in the present situation is primarily being used to mimic human blood plasma to detect Na + concentrations in a lab environment. The developed RF sensor prototype is successfully utilized to determine the Sodium ion constituent variation in the body fluid, which is an important aspect as Na + concentration affects the metabolic functioning in the body. The measured sensitivity for Na + ions in the body fluid is recorded to be 0.03 dB/(mmol/dm 3 ) for the fabricated RF sensor.

Established studies focused more on the effect of the myocardium. However, our preliminary in-vitro experiments suggested that blood volume variations also significantly impacted signal transmission. In this article, we analyzed the blood volume variations during the cardiac cycle and designed an in-vitro experimental platform containing a simulated heart beating system and an automatic channel characteristic acquisition system, which controlled two peristaltic pumps to realize the periodic blood volume variations and the continuous acquisition of channel gain. Through the in-vitro porcine heart experiment, the effect of frequency and blood volume variations during the cardiac cycle on two channel gains was analyzed. Considering the impact of high-frequency signal leakage, the channel gain variations of the low frequency are the main concern. The results showed that the channel gain was positively correlated with frequency; it changed periodically with blood volume variations in the cardiac cycle, and the trends were different due to the different signal paths of the two channels. For the Right Ventricle-Right Atrium channel, the gain varied from $-67$ dB to $-53$ dB and is inversely correlated with blood volume. The gain fluctuation range was smaller for the Right Ventricle-Left Ventricle channel, about 2 dB. This study shows that the gain of intracardiac communication channels, especially the RV-RA channel, is influenced by blood volume variations during the cardiac cycle.

To investigate the effects of different measurement positions and feature parameters on the results of handgrip force prediction, a model based on electrical impedance myography (EIM) and long short-term memory (LSTM) networks was proposed to compare and determine a better scheme for handgrip force prediction. We conducted the signal acquisition experiments of impedance and handgrip force on the anterior forearm muscles and brachioradialis muscle. Afterwards, three evaluation metrics were introduced to compare the prediction results of various models, and the variability between models was analyzed using paired sample t-tests. The results showed that the model of handgrip force prediction based on anterior forearm muscles exhibited better performance in predicting. The evaluation metrics of $\mathbf {R^{2}}$ , explained variance score (EVS) and normalized mean square error (NMSE) for the model fusing the feature parameters resistance (R) and reactance (X) were 0.9023, 0.9173 and 0.0114, respectively. Therefore, the feature parameters fusing R and X are the optimal input for the handgrip force prediction model. The anterior forearm muscles are the preferred position for impedance measurement over the brachioradialis muscle. This paper validated the feasibility of EIM for handgrip force prediction and provided a new reference and implementation scheme for muscle rehabilitation training and prosthetic control.

These phantoms must accurately emulate the dielectric properties for both healthy and malignant skin tissues. In this work, we develop and experimentally investigate multiple skin phantoms with tumor inclusions in the frequency range of 0.5–26.5 GHz. These heterogeneous phantoms are realized by varying the tumor size and placement relative to the skin. The tumors with irregular borders are also investigated. For analyzing the effect of underlying skin on dielectric properties, two skin thicknesses are considered: 8 mm and 2.5 mm. The proposed heterogeneous phantoms are developed using inexpensive materials: oil, gelatin, deionized water and formaldehyde. The dielectric properties of fabricated phantoms are characterized with Keysight performance probe connected with a FieldFox handheld vector network analyzer. Our results demonstrate that the dielectric properties of the developed phantoms closely agree with those of the excised malignant human tissues reported in the literature over the entire frequency range of 0.5–26.5 GHz and can be hence reliably used for experimental validation in studies towards microwave-based diagnostics of skin lesions.

Methods: two arrays were constructed, a conventional rigid array used as a control and an array composed of flexible bowing elements. Bowing elements comprise of a flexible half and a rigid half. The arrays were then supported on translating boards connected so that a flexible gap between the boards corresponds to the bowing elements. The gap between the rigid coil elements was varied by discrete values to assess its performance under different bowing conditions. Results: signal-to-noise-ratio (SNR) and noise performance was compared between the two arrays. It is seen that a bowing array outperforms its rigid counterpart in terms of average SNR, max SNR, and signal coverage. We conclude that bowing array elements present a viable solution to the proposed hybrid rigid-flexible coil arrays.

Traditional approaches rely on hospitalization or body-attached instruments, which are costly and intrusive. However, in recent years there is an emergence of contact-less vital sign monitoring techniques that rely on radio frequency signals. Early studies with continuous wave radars/WiFi devices have shown good success in detecting the vital signs of a single individual, while simultaneous monitoring of the vital signs of multiple, closely spaced subjects remains a challenge. In this paper, using an off-the-shelf Texas Instrument automotive FMCW radar, we design and implement a time-division multiplexing (TDM) phased-MIMO radar sensing system that allows high-precision vital sign monitoring of multiple subjects. The proposed sensing system can steer the beam towards the desired directions with a micro-second delay. The steerable beam enables capturing the vital signs of multiple individuals at the same radial distance to the radar. The proposed system enables the formation of a virtual array with aperture longer than that of the physical array. A Capon beamformer is used at the receiver side to combine the data collected from different transmit and receive antenna pairs corresponding to the virtual array. As all those pairs provide independent information about the targets, their combination significantly boosts the receiver signal-to-noise ratio. Based on the designed TDM phased-MIMO radar, we develop a system to automatically localize multiple human subjects and estimate their vital signs. Extensive evaluations show that under two-subject scenarios, our system can achieve more than 98.06% accuracy for breathing rate (BR) and more than 82.89% accuracy for heartbeat rate (HR) estimation, at a subject-to-radar distance of $\text{1.6}\;m$ when the targets are facing the radar. The minimal subject-to-subject angle separation is $30^\circ $ at a subject-to-radar distance of $\text{1.6}\;m$, corresponding to a close distance of $\text{0.3}\;m$ between two subjects, which outperforms the state-of-the-art.

In vitro, EFs were shown to direct the growth of retinal ganglion cell (RGC) axons, the neurons that make up the optic nerve. As larger EF gradients were shown to direct more efficient growth,investigations into the most effective stimulation strategies that can generate the greatest voltage gradient are needed before EF application can be developed into a technology to direct optic nerve regeneration in vivo. We performed ex-vivo experiments to compare the ability of different electrode materials, platinum vs. tungsten, to generate an EF gradient along the rat optic nerve. Platinum electrodes at both source and ground positions were found to generate the greatest voltage gradient along the optic nerve. Experimental results were used to inform an equivalent computational model of the optic nerve, which was subsequently employed to predict more effective electrode pair combinations. Our results confirmed that the platinum-platinum electrode pair generates the maximum voltage gradient which are highly dependent on electrode size and electrode-electrolyte interfaces. This computational platform can serve as a foundation for the development of electrical stimulation therapies for nerve regeneration.

Hence, this study proposes an electromagnetic technique to assist in observation and detection of hepatic steatosis. Effective permittivity contrast between left and right sides of the torso is exploited for the aim of detection. Firstly, the transfer functions of the transmitter-receiver paths on the left and right sides of the torso are modeled using a 2D line source approximation to form a non-linear equation system. Secondly, the system is solved with respect to the vector of effective permittivity values in a successive iteration. Thirdly, the estimated permittivity values are stacked together to create a dispersive permittivity curve. Permittivity modeling and statistical frequency selection are performed to remove outliers. Finally, the left/right effective permittivity contrast is calculated over the selected samples. The method is validated by realistic computer simulations and human measurements. In both scenarios, left/right permittivity contrast is higher and distinguishable in steatotic livers, which have 15% more diffused fat than healthy cases. The results verify the potential of electromagnetic systems, which are safe, low-cost, and portable, in the detection of hepatic steatosis.

This paper presents the design and development of a new miniature implantable battery-less gastrostimulator, operated by wireless radio-frequency powers. The device harvests electromagnetic-wave energy and delivers controlled electrical pulses to the stomach tissues to initiate neural activities in vagus nerves and regain normal motility and contraction. With the goal to optimize the wireless power transfer efficiency, various antenna configurations have been investigated. To enable remotely reconfiguring the device to meet the patients’ needs after implantation, a novel method of changing the settings, without an additionally dedicated wireless communication channel and protocols that could increase the implant size and power consumption, has been proposed and demonstrated in this work.

In this paper, we designed two coil antennas for wireless implant communication, including a small dual-band transmitting antenna that can be placed inside the human body and a corresponding receiving antenna that can be mounted on the abdomen of the human body. The proposed antenna is fed from a battery-powered impulse radio (IR) transceiver peaking at 10–60 MHz, and the antenna is designed to be wideband for higher data communication rate. Simulation and measurement of reflection and transmission coefficients confirmed operation at 40–60 MHz. In addition, a battery-powered IR transceiver is used to measure the transmission performance in a 2/3 muscle phantom. As a result, communication at a data rate of 20 Mbps is achieved at a distance of 90 mm in the 2/3 muscle phantom.

Pennes’s bioheat equation is applied to a six-layer human head model to generate the expected layered temperature profile during the development of a fever. The resulting temperature profile is fed into the forward electromagnetic (EM) model to determine the emitted brightness temperature at various points in time. To accurately retrieve physical temperature via radiometry, the utilized model must incorporate population variation statistics and cover a wide frequency band. The effect of human population variation on emitted brightness temperature is studied by varying the relevant thermal and EM parameters, and brightness temperature emissions are simulated from 0.1 MHz to 10 GHz. A Monte Carlo simulation combined with literature-derived statistical distributions for the thermal and EM parameters is performed to analyze population-level variation in resulting brightness temperature. Variation in thermal parameters affects the offset of the resulting brightness temperature signature, while EM parameter variation shifts the key maxima and minima of the signature. The layering of high and low permittivity layers creates these key maxima and minima via wave interference. This study is one of the first to apply a coherent model to and the first to examine the effect of population-representative variable distributions on radiometry for core temperature measurement. These results better inform the development of an on-body radiometer useful for core body temperature measurement across the human population.

Undoubtedly, its channel characteristics provide deep insights to select parameters that are beneficial for the physical layer design of the Body Area Network (BAN). Nevertheless, such analysis has not been systematically addressed. To this end, the transfer function from the quasi-static model in the electromagnetic field is considered at first. Then, the linearity of the galvanic coupling IBC channel is verified. Besides, the proper frequency band for data transmission is investigated using the water-filling algorithm. Moreover, the theoretical Bit Error Rate (BER) performances of different modulations are studied. Results revealed that the galvanic coupling IBC channel can be modeled as a linear band-limited Additive White Gaussian Noise (AWGN) channel. Finally, suitable modulations for various scenarios are discussed based on the channel characteristics found. Consequently, this work can further enrich the design of the IBC for medical applications.

Inverse scattering analysis for quantitative dielectric profile reconstruction is promising for a higher recognition rate for cancer detection, especially for malignant breast tumors. We focus on CSI as a low complexity approach, and implement a deep convolutional autoencorder (CAE) scheme using radar raw-data, which enhances the convergence speed and reconstruction accuracy. Numerical tests using MRI-derived realistic phantoms demonstrate that the proposed method significantly enhances the reconstruction performance of the CSI.

The concentration of a drug in blood at any given time depends on the prescribed routine of drug intake. Conventional methods of drug intake do not always maintain the required consistent drug concentration. Controlled drug release mechanisms can help in maintaining drug dosage levels while optimizing therapeutic effects. Microparticles and nanoparticles, initially developed as carriers for vaccines and anticancer drugs, are being used in drug delivery systems for drug targeting, improved release profile and efficiency. The drugs can be encapsulated inside the particles, suspended in or with them. However, release of the drug depends on the type of techniques used to trigger drug delivery. This review outlines the major techniques used for drug delivery applications based on external triggering mechanisms while utilising micro and/or nanoparticles. These techniques include ultrasound, light, radiofrequency, electric and magnetic field exposures. Most of these techniques have largely remained in vitro owing to challenges concerning safety due to exposure levels and penetration of external signals due to human physiology. Considering these aspects of the challenge, microwave based external triggering can be a prospective technology for drug delivery using micro and nanoparticles.

By employing the series zeroth-order resonance (ZOR), the resonance of proposed sensor is only determined by surface capacitance and inductance. The short-circuit structure reduces the energy loss due to edge radiation and generates a highly concentrated electric field on the top surface of the substrate, which can be used to detect the dielectric loading samples. The presented sensor has been simulated, fabricated and tested. The sensor on the printed circuit board (PCB) is integrated with the fluidic container made of polydimethylsiloxane (PDMS) to form the test device. The water-ethanol binary mixture and sucrose solution are used to proof the concept. Finally, the prediction model for the water-ethanol mixture based on measured parameters has been established and the analysis of prediction error has been carried out. The sensor works around 4 GHz, and the maximum sensitivity reaches 1.04. Due to the high sensitivity and simple structure, the proposed structure is a competitive candidate for the applications including bio-sensing and portable biomedical device.

A combination of measurement and finite element modelling was used to assess sensitivity of measurement to sensor placement, for temperature rises at the ends of a set of calibration cylinders. The simulations used a coupled thermal-electromagnetic model created using COMSOL Multiphysics to replicate the measurement conditions virtually. Thermal gradients in parametric models of cylindrical implants of varying length and diameter were evaluated to quantify the sensor placement accuracy required for the measurement of implant heating within the estimated temperature measurement uncertainty. In this way we aim to enhance the understanding of the requirements for experimental procedures and safety standards dealing with implant heating in MRI.

Typically, THz measurements are conducted with electro-optical setups that penetrate tissue just a few microns deep. The study demonstrates a robust, efficient, and cost-effective electronic sub-THz waveguide probe for detecting tumor margins intraoperatively during lumpectomies. The proposed iris waveguide probe is capable of detecting fat, fibrous, and tumorous tissue in breast tissue. The device can identify both positive and negative margins in the frequency range of 110-170 GHz. The scanning probe can be used to rapidly and effectively depict the excised tissue surface by placing it in contact with it. According to the imaging results, this probe has a lateral sensitivity of 0.2 mm and a detection depth of 1 mm. It is manufactured using CNC micromachining technology to ensure easy and cost-effective production. The probe was designed and tested in HFSS as well as fabricated and validated on an artificial excised breast mimicking phantom. In this research, sub-terahertz waves are used for tissue penetrating imaging of breast tumor margins, which is an application requiring high resolution and accurate techniques.

The analysis is performed at millimeter-wave (mmW) frequencies upcoming for 5G and future generations, with a special attention to $26 \,\mathrm{GHz}$ and $60 \,\mathrm{GHz}$. A cylindrical model is used to calculate EM power density and heat in fingers (radii $\boldsymbol{a\leq }10 \,\mathrm{mm}$) and EM power density in ears ($1 \,\mathrm{mm}\boldsymbol{\leq a\leq }5 \,\mathrm{mm}$). To compute the temperature rise in the ear, the model is modified to account for heat conduction in the tissue connecting the ear to the head. Our results show that for transverse electric (TE) polarization the maximal absorbed power density remains generally lower than for a planar interface (up to $-38.2 \,\%$ at $26 \,\mathrm{GHz}$ and $-18.7 \,\%$ at $60 \,\mathrm{GHz}$) and exceeds this value for transverse magnetic (TM) polarization (up to $72.3 \,\%$ at $26 \,\mathrm{GHz}$ and $15 \,\%$ at $60 \,\mathrm{GHz}$). The resulting heating is always higher than for the planar model. For the ear model ($\boldsymbol{a=}1 \,\mathrm{mm}$), the variations at steady state reach $93.11 \,\%$ at $26 \,\mathrm{GHz}$ and $103.62 \,\%$ at $60 \,\mathrm{GHz}$.

Two novel sensing systems are deployed for the measurement. A very sensitive wideband near-zone radiative system specifically designed for this application is first used to search for signals in the 1–50 GHz frequency region. Notable radiation is observed in the 3–4 GHz band. Exposure to lethal doses of Zinc oxide nanopyramids (ZnO-NPY) is used to verify that the signals are indeed produced by living cells rather than material thermal emission. Afterwards, a spiral antenna system is exploited to further examine the band of interest in the near-field region. Radiation from 3 identical biofilm samples is monitored and recorded over 70 days. Two distinct frequency bands, namely the 3.18 GHz and the 3.45 GHz bands, are identified as potential “communication bands”. Furthermore, long-term and short-term cycles of the total radiation intensity within the band are observed over the course of the experiment. This work confirms the presence of EM radiation within bacterial communities, which is a key requirement to demonstrate EM signaling among bacterial cells. The insight could lead to breakthroughs in demystifying how cells communicate as well as advancement of important technologies in biology and communication systems.

However, their received signals are more sensitive to random body motions (RBM) which degrades the accuracy of heart rate (HR) detection. To overcome this challenge, multi-input multi-output (MIMO) configuration can be used to reduce RBM’s impact as each channel has different points of view with respect to the subject under test (SUT). Here we propose the use of a Frequency Modulated Continuous Wave (FMCW) radar from Texas Instruments (TI) at 77 GHz to collect data from its 192-channel configuration. Since vital sign information extracted using Arctangent Demodulation (AD) could be corrupted by either RBM or respiratory harmonics, a method is needed to minimize such effects. Hence, we develop an algorithm where a Heartbeat Template (HBT) is extruded based on the Constellation Diagram that shows the Quadrature signals from the target’s range profile. The HBT is then used to design an adapted-wavelet for Continuous Wavelet Transform (CWT) to magnify the heartbeat signals. Under circumstances where RBM overwhelms the heartbeat signal that the HBT cannot completely reduce its effects, a spectral-based HR selection method is also developed to estimate the HR. By employing the proposed methods, we have reduced mean-error ${\mu _e}$ of HR estimation significantly from 9 bpm to less than 2 bpm.

In this paper, we propose and experimentally demonstrate the efficient, multi-band wireless power transfer (WPT) systems that are symmetric with respect to the combined parity (P) and time reversal (T) transformations (i.e., space-time reflection symmetry). In analogy with non-Hermitian PT-symmetric physical systems that can have branching real eigenfrequencies as a function of the dimensionless non-Hermiticity and the coupling factor, the PT-symmetric WPT system exhibits multi-band and/or wideband operations via adjustment of the non-Hermiticity (i.e., quality-factor of resonant tanks) and their mutual inductive or capacitive coupling strength. Here, we put forward design and implementation for achieving dual-band, tri-band, and wideband PT-symmetric WPT systems, capable of operating in the industrial, scientific, and medical (ISM) bands (27.12 MHz and 40.68 MHz) with high transmission efficiency. This compact and low-cost WPT technique may be exploited in many practical applications, such as wireless charging of bioimplants and wearables, as well as interrogation of battery-free medical devices and internet-of-things (IoT) sensors to assist smart healthcare.

It not only represents an advanced system able to warn the user of potential obstacles, but also discerns between human and nonhuman targets. Since real scenarios would likely have moving targets, a new range alignment technique has been proposed with the aim of detecting the tiny chest displacement due to the physiological activity as the key sign of the human presence. The proposed system is able to properly recognize humans in complex environments with multiple moving targets, thus providing to the user a complete set of information, namely presence, position and nature of the available targets. The operating principle and the effectiveness of the system are shown both by simulated case studies and by employing a 122 GHz radar board for carrying out suitable measurements.

It has always been hard to bake the physical setup of the imaging array into the structure of the network, resulting in a data-intensive models that are not practical. This work put forward a graph formulation of the microwave imaging array. The architectures proposed is made cognizant of the physical setup, allowing it to incorporate the symmetries, resulting in a less data requirements. Graph convolution and attention mechanism is deployed to handle the cases of fully-connected graphs corresponding to multi-static arrays. The model works with a modular fashion at node level to strike a trade-off between flexibility and efficient capture of mutual information present in measured signals. Additionally, the modular working fashion endows the model with immunity to overfitting. The graph-treatment of the problem is evaluated on experimental setup in context of anomaly localization with imaging array and has shown higher performance as compared to the popular radar technique. The thin model was realized with a feasibly procured reasonably-sized dataset in the order of few hundreds, thus eliminating the need to resort to simulations for augmentation.

Accordingly, an interrogating antenna placed onto the skin is capable to monitor only a limited region just below its footprint. In some applications like the hand prosthesis controlled by Electromyographic signals emitted by muscle contractions, multiple IMDs have to be used to increase the degrees of freedom in driving the actuators. An array of interrogators, working in the near-field can mitigate this bottleneck by greatly extend the read region inside the body. Sequentially- and simultaneously-fed arrays by a same reader are here investigated to optimize the multi-sensor backscattering modulated links. The conditions (feeding scheme and alignment) to guarantee a robust interrogation of a relevant number of implanted sensors with no battery onboard are identified also accounting for the safety constraints related to the SAR. Numerical simulations and experimentation with a cylindrical phantom resembling human limbs, hosting reference antennas, demonstrate that the simultaneous feed permits to interact with eight IMDs by using nearly all the available power from typical readers (30 dBm, 22 dBm as a minimum) without exceeding the SAR limit with a power margin (w.r.t. sensor-oriented ICs with −10 dBm power sensitivity) of more than 5 dB for any angular alignment between the array and the sensors.

A correlation radiometer is designed from off-the-shelf parts to operate in the quiet 1.4-GHz band and tested on aqueous phantoms. The radiometer is first tested with a matched load, and then with a near-field planar probe antenna, both with two water phantoms of different volumes. The measurement resolution, sensitivity and long-term stability is quantified in terms of integration time for a simple three-point calibration. The lowest measured absolute error compared to a ground-truth thermocouple measurement is ±0.25K over one hour of data collection with a single calibration. Measurements show that an integration time >1 s results in an absolute error limited by the radiometer gain fluctuations. A probe on a seven-layer tissue stack is designed for measuring brain temperature.

the proposed radar sensor, including a one-dimensional (1D) MTM LWA and a tunable voltage-controlled oscillator (VCO), is designed to perform frequency-dependent space mapping with the main-beam angle sweeping from −50 $^\circ $ to +30 $^\circ $ with respect to the varying frequency from 1.85 to 2.85 GHz. The proposed SRO-integrated MTM LWA system is operated in the logarithmic mode with a quench signal imposed at the drain port of transistor. Experiments have been conducted to show that vital sign information for two human targets can be successfully detected when they are located along different scanning angles of −10 $^\circ $ and −30 $^\circ $, respectively. Furthermore, compared with MTM LWA radar sensor based on the self-injection-locked (SIL) architecture, vibrating motion at a farther distance can be detected accurately using the proposed radar sensor, indicating a higher sensitivity with reduced system complexity.

Exploiting the self-injection locking radar technique, it is possible to perform FM-to-AM demodulation that allows the detection of the voltage peaks at the output of the sensor’s receiving part. If compared with existing solutions, this device is of reduced dimensions and fully wearable; in fact, it can be worn by the user at a certain distance from the body at the chest position, and work without the need of any dedicated remotely synchronized anchor nodes nor bulky analyzers to be carried close by. As a more distinctive peculiarity, the receiving circuit is designed as an RF-to-DC rectifier in order to also enable the possibility to harvest energy that can be exploited, for instance, to feed a microcontroller unit and a transceiver with the aim of sending wirelessly the breath rate data to a laptop or a smartphone. Circuit simulations are corroborated by measurements in order to ensure the feasibility of the proposed solution.

The open-ended coaxial probe technique is commonly used to measure the complex permittivity of tissues at microwave frequencies. Since the open-ended coaxial probe technique provides an average complex permittivity for the tissues within its sensing volume, when measuring heterogeneous tissues, a post-measurement histological analysis is often conducted to accurately associate the measured dielectric properties to the tissue content. Subsequently, it is crucial to quantify the sensing volume of the probe accurately. Sensing volume is generally defined as a cylindrical volume (rectangular cross-section) based on sensing depth and sensing radius. In this article, the sensing volume is modified based on the field distribution of the probe. Since in practice defining the sensing depth and sensing radius for a given probe is straightforward, the resulting sensing volume is defined as an ellipsoid based on sensing depth and sensing radius values. Considering a finite heterogeneity in a homogeneous background, it is shown that the ellipsoidal sensing volume is a more accurate representation than the typical cylindrical volume for open-ended coaxial probes, and therefore, results in a more accurate dielectric characterization of heterogeneous tissues.

adapted to use 16 flexible monopole antennas previously designed for ultrawideband (2 – 4 GHz). The use of narrowband permits a more accessible and compact system with the final goal of a wearable device for frequent scans, targeting early detection through tracking alterations on patients over time. This motivates the research of phantom measurement repeatability. Our narrowband system is described and results are presented for five measurement dates using two phantoms with skin layers and similar low percentages of glands, along with interchangeable plugs for all-fat and three tumor cases. Preliminary clutter rejection uses average trace subtraction on antenna pairs with same distance in-between. Significant signal distinction is noted between baseline and tumors on specific antenna pairs and some distinction is found on central tendencies over all signals. This is promising as the presence of skin and glands can heavily attenuate microwave signals. High variability is found on distinct measurement dates, increasing the standard deviation across all dates considerably. The measurement noise includes comparatively high and easier to remove systematic offsets as well as other confounders that occasionally increase standard deviation, which may mask signal features. This highlights the need to research further techniques to mitigate this variability between measurements in order to increase reliability of microwave breast screening devices and, even more generally, other biomedical devices based on similar principles.

The impedance spectrum measured from 9 kHz to 9 GHz is analyzed by using the double-shell cell model to separate the contribution of the nucleus from that of the cytoplasm. The model parameters include the nucleus-to-cell radius ratio (r) and a parallel R-C circuit for each of the four cell compartments: the cell membrane (CM), the cytoplasm (CP), the nuclear membrane (NM), and the nucleoplasm (NP). In general, the extracted radius ratio agrees with that measured by optical microscopy, and the extracted resistances and capacitances agree with the literature and order-of-magnitude estimates. For example, for a human lymphocytes cell with r ≈ 0.8, the nuclear contribution is approximately linear. Therefore, the membrane parameters are constant so that RCM = 1.5 MΩ, CCM = 1.5 pF, RNM = 0.05 MΩ, and CNM = 1.2 pF, but the plasma parameters are linearly scaled so that RCP → 0.5(1 − r) MΩ, CCP → 6.7/(1 − r) fF, RNP → 0.12r MΩ, and CNP → 9.4/r fF. Because morphological and structural changes of a cell nucleus are important screening, diagnostic, and prognostic markers, these results suggest that ultra-wideband impedance spectroscopy may be a fast, compact, and label-free technique in cancer cytology.

An analytical approach is used to solve the scattered field by the cylinders in each medium through expansions into cylindrical waves, expressed through plane-wave spectra. The multilayer models a biological tissue consisting of skin, fat and muscle covered by a cotton textile. Several numerical examples are presented considering the electrical parameters of the biological and textile tissues at the millimeter frequency range (24 GHz). The results show that it is possible to obtain an intensification of the electric field in the underlying tissues in case of TM polarization of the incident wave, finding an interesting application for the charging of implantable or wearable devices.

Resonant sensors often do not show very sharp resonance peak, due also to losses which reduce the quality factor. Moreover, since the sensor response is collected over a discrete set of frequencies, the actual resonance peak may not be properly captured. To overcome these drawbacks, an algorithm is presented in this paper which aims at sharpening the microwave sensors response, and mitigating the mentioned frequency discretization problem so to eventually estimate the resonance frequency more accurately. The algorithm is first explained and checked against synthetic data mimicking the response of a resonant sensor. Then, as a further validation, measured data collected by a microwave resonant sensor, properly designed for blood glucose monitoring, just located in contact to human fingers are considered.

An early detection of surface defects by means of local sensors can prevent dangerous complications and prompt for a preventive replacement of the medical device. For this purpose, a tattoo-like sensing mechanism based on pre-fractal Space Fulling Curves is wrapped onto the medical device and coupled with a zero-power RFID transponder. The resulting smart prosthesis is capable to identify the early formation of cracks and to communicate with the exterior of the body by backscattering communication. The crack detection method exploits the anti-tamper port of common Radiofrequency Identification (RFID) ICs and a small antenna, acting as harvester, closely integrated with the metal prosthesis. Simulations and tests with a mockup of metallic hip prosthesis and a leg phantom demonstrate that the device can identify surface cracks as small as 0.6 mm and can be wireless interrogated outside the body from up to 70 cm distance. The required geometrical change to the prosthesis is modest and does not hinder its mechanical robustness. Experiments also confirmed that the health status of the prosthesis could be even monitored on-the-fly when the patient crosses a door equipped with a UHF reader. The sensorized prosthesis could hence become an enabler for the emerging Precision Medicine and for the Internet of Bodies paradigm.

In this work, we report a systematic method for broadband investigation of RF NT effects on Saccharomyces cerevisiae yeast growth. The method includes a transverse electro-magnetic (TEM) device and a dielectric spectroscopy technique for RF frequency selection. A stripline-based TEM device has two 240-μL chambers 3D printed for cell cultures. The fabricated device operates up to a few GHz and produces uniform RF fields for cell exposure testing. A vector network analyzer (VNA) was used to provide −20 dBm continuous-wave (CW) RF power. The heating effects on cell growth were estimated to be negligible. Frequency regions, where large permittivity differences between the medium and yeast cultures were obtained and used to select RF testing frequencies, e.g., 1.0 MHz, 3.162 MHz, 10 MHz. These differences may indicate RF field gradients near cell membrane, and the gradients may affect local nutrient transport. Additionally, RF at 905 MHz is tested for comparison purpose. Yeast cells in the exponential growth phase were examined at four RF frequencies and compared with two controls. One control device held at the same temperature as the test device, while the other control was held at a temperature 1 °C higher. The results showed that the RF fields at 3.162 MHz reduced yeast growth rates by 15.1%; however, the RF fields at 1.0 MHz enhanced cell growth by 13.7%, while the observed 4.3% growth rate increase at 10 MHz is insignificant and the RF fields at 905 MHz had no effects on the cell growth. These results showed a clear RF NT effects on S. cerevisiae growth that was frequency dependent. The hypothesized mechanisms of these effects, i.e., non-uniform RF fields near cell membranes and fluidic diodes in cell membrane ion channels may play important roles in nutrient transport, need to be further investigated.

Low–cost phantom samples of normal and malignant tissues have been prepared using naturally occurring components, i.e. , agar, water, olive oil, and pectin. A waveguide probe-based calibration technique was used to extract the complex permittivities of the two-component (water–agar) and three-component (water-oil–agar) phantoms. The two-component phantoms were used to study the change in the dielectric properties of phantom with change in agar concentration. Water, agar, and varying proportions of oil were used to develop three-component phantom mixtures to mimic the dielectric properties of fat, fibrous and malignant breast tissues. Finally, the reflection and transmission properties of tissue-mimicking phantoms were tested using the waveguide probe calibration-based measurement setup. The difference in the S parameters between the three types of phantoms demonstrates the potential utility of D band-based data acquisition setups for tumor margin assessment applications .

It affects the livelihood of not just patients, but those who take care of them, including care givers, nurses, and close family members. Current progression monitoring techniques are based on MRI and PET scans which are inconvenient for patients to use. In addition, more intelligent and efficient methods are needed to predict what the current stage of the disease is and strategies on how to slow down its progress over time. Technology or Method: In this paper, machine learning was used with S-parameter data obtained from 6 antennas that were placed around the head to noninvasively capture changes in the brain in the presence of Alzheimer’s disease pathology. Measurements were conducted for 9 different human models that varied in head sizes. The data was processed in several machine learning algorithms. Each algorithm’s prediction and accuracy score were generated, and the results were compared to determine which machine learning algorithm could be used to efficiently classify different stages of Alzheimer’s disease. Results: Results from the study showed that overall, the logistic regression model had the best accuracy of 98.97% and efficiency in differentiating between 4 different stages of Alzheimer’s disease. Clinical or Biological Impact: The results obtained here provide a transformative approach to clinics and monitoring systems where machine learning can be integrated with noninvasive microwave medical sensors and systems to intelligently predict the stage of Alzheimer’s disease in the brain.

An existing compact patch antenna working at 434 MHz is re-designed using the proposed methodology. The proposed general approach is used to investigate the specific case of the hyperthermia treatment of abdominal rhabdomyosarcoma. Instead of using patient-specific geometries with discrete vascular tree models, a surface phantom with a continuum 3D blood perfusion model of tumors is used. The geometrical parameters of the antennas are selected to provide a robust design against the variation of the phantom parameters. The effectiveness of the antenna is evaluated simulating the treatment with a recent non-linear multi-physic model, considering the different description of tumor vasculature. A more robust and effective design is obtained, with respect to its previous version. Indeed, the antenna bandwidth is increased with about 7%. The treatment performed using the old version of the antenna lead to unsuccessful results (40 °C after 60 min), whilst the novel robust design could successfully treat the target region. The new version of the patch can withstand a temperature of 42.5 °C for 60 min of treatment. To further enhance the effectiveness of the treatment, the use of a time-modulated power is studied. The proposed model could be extended to different body regions and used to develop an application-oriented design of antennas for hyperthermia treatment.

During hyperthermia, tumour tissue is heated to 40-43 °C using radiofrequency or microwave antennas, which strongly enhances effectiveness of radiotherapy and chemotherapy. Hyperthermia treatment quality depends on tumour temperatures achieved and treatment planning (i.e., simulation and optimization of absorbed power and temperature distributions) could be very useful to ensure and improve treatment quality. Hyperthermia treatment planning was mainly a research tool for decades, because of high computational costs and limited quantitative accuracy of treatment planning predictions due to a lack of patient-specific tissue properties. Thanks to developments over the past decade, treatment planning becomes increasingly important in the clinical workflow. Presently, main clinical applications of hyperthermia treatment planning are 1) applicator selection, 2) heating ability evaluation and 3) on-line treatment guidance. To improve the reliability and further increase applicability of treatment planning, ongoing developments focus on 1) dielectric imaging to derive patient-specific dielectric properties, 2) advanced thermal modelling including discrete vasculature and 3) biological modelling to predict the radiosensitizing effect of hyperthermia in terms of equivalent radiation dose. The increased clinical application and ongoing efforts will further improve treatment quality.

standing between the patient and the phased array applicator, and the operating frequency. This is crucial to improve the efficiency both from a technical and clinical points of view. In this paper, we propose a new approach, based on the propagation theory, to support the selection of the matching medium properties and the working frequency in a robust way by accounting for patient body shape and properties variability. The case of adjuvant hyperthermia treatment administered to patient with tumors in the pelvic region has been used as a numerical assessment in both 2D and 3D patient specific models. For this case, the proposed approach suggests an optimal range of working frequencies (130MHz <; f <; 500MHz) and of matching material properties (ε _b <; 20), wherein one can select the working conditions depending on the trade-off between penetration and focal spot dimensions as well as other specific requirements. Results have been compared to the working frequencies used by commercial applicators and using demineralized water as matching material. In conclusion, this work assesses the proposed approach in its general-purpose mathematical formulation, thus, paving the way for its wide application.

However, a significant drawback of the technique is the lack of effective imaging modalities for monitoring the changes undergoing in the thermally treated tissue. In this respect, microwave imaging has been proposed as a possible candidate, owing to its portability, low-cost, non-ionizing nature, and capability to detect changes in dielectric properties of tissues induced by the temperature. The goal of this paper is to provide the guidelines for the design of a microwave imaging system for thermal ablation monitoring of liver tumors. To this end, an analytical study is performed to determine the proper working conditions, in terms of frequency band and matching medium. Then, three antipodal Vivaldi antennas on different dielectric substrates are designed and numerically assessed. Among those antennas, the Vivaldi antenna on RT/duroid 6010LM substrate proved to be the most suitable choice. The results of this study pave the way to an experimental assessment of microwave imaging as a modality to monitor thermal ablation treatments.

The analysis is meant as a preliminary step towards the full experimental characterization of the system, with the aim of assessing the achievable results and highlight possible critical points. The system consists of an array of twenty-four printed monopole antennas, placed conformal to the upper part of the head; each monopole is immersed into a semi-solid dielectric brick with custom permittivity, acting as coupling medium. The whole system, including the antennas and their feeding mechanism, has been numerically modeled via a custom full-wave software based on the finite element method. The numerical model generates reliable electromagnetic operators and accurate antenna scattering parameters, which provide the input data for the implemented imaging algorithm. In particular, the numerical analysis assesses the capability of the device of reliably monitoring the evolution of hemorrhages and ischemias, considering the progression from a healthy state to an early-stage stroke.

As an alternative to the gold standard techniques for breast cancer diagnosis, microwave imaging has been proposed from research community and many microwave systems have been designed mainly to work at low microwave frequencies. Based both on the results of recent dielectric characterization campaigns on human breast ex-vivo tissues up to 50 GHz and on the promising feasibility studies of mm-wave imaging systems, in this article, we propose and test inverse scattering techniques as effective tool to process mm-wave data to image breast cancer. Differently from radar techniques so far adopted in conjunction with mm-wave imaging system, inverse scattering techniques turn out to be more versatile and robust with respect to the reduction of the amount of data and eventually also able to characterize the anomaly in terms of electromagnetic properties. In particular, in the above, two image reconstruction techniques, the Linear Sampling Method and the Born Approximation, are proposed and compared against both simulated and experimental data.

Given the shortcomings of the available treatment options, the interest in alternative and less invasive treatment modalities such as microwave ablation (MWA), has increased. In order to develop and optimize this novel electromagnetic-based therapy, an accurate knowledge of the dielectric properties of human adrenal glands, as well as preclinical animal models, is crucial. In particular, ovine models represent a feasible animal model to test the safety and performances of MWA. In this study, the dielectric properties of ovine adrenal glands and of normal and diseased human adrenal glands are characterized ex vivo in the microwave frequency range. The dielectric properties of the two functional tissues (cortex and medulla) composing ovine adrenal glands are measured using the open-ended coaxial probe technique and represented with a two pole Cole-Cole model in the frequency range from 0.5 GHz to 8 GHz. This paper presents the first dielectric data of normal and diseased human adrenal tissues, including a functioning adenoma responsible for PA and it compares the human data with data from the animal model.

In some exposure scenarii, presence of textiles impacts the interaction of the electromagnetic field radiated by wireless devices with human tissues. We investigate the impact of a textile layer in contact or in proximity of skin on the power transmission coefficient, absorbed power density and temperature rise using a near-surface tissue model at 26 GHz and 60 GHz. Cotton and wool are considered as representative textiles. Our results demonstrate that the textile in contact with skin increases the absorbed power density up to 41.5% at 26 GHz and 34.4% at 60 GHz. The presence of an air gap between a textile and skin modifies the electromagnetic power deposition in the tissues depending on the thicknesses and permittivity. The temperature rise increases compared to the bare skin by up to 52% at 26 GHz and 46% at 60 GHz with the textile in direct contact with skin. With an air gap, for typical textile thicknesses, the temperature variations range from -3.5% to 20.6% and from -11.1% to 20.9% at 26 GHz and 60 GHz, respectively.

considering the novelties introduced by the incoming 5G networks. Specifically, a possible future case of indoor exposure scenario is investigated, where the presence of a 5G access point (AP) in a room is simulated. The AP was modelled by two different indoor uniform planar array (UPA) antennas at 3.7 GHz and at 14 GHz, to evaluate how the beamforming and the higher frequency use could impact the exposure levels. Different scenarios were evaluated, considering the maximum antenna gain, two different human computational models, an adult model and a child one, and by varying the distance and the orientation between the UPA antenna and the two models head. All the simulations were conducted using the Sim4Life platform and in particular the exposure levels were expressed by the specific absorption rate averaged on 10 g of tissue (SAR _10g ), which was analyzed for the skin and for some specific tissues. The work underlined that the highest SAR _10g values were obtained in the head area for all scenarios, with the skin SAR _10g highest peaks when the UPA is placed laterally to the human model (195.73 mW/kg and 223.29 mW/kg for the adult and child model, respectively, for 100 mW input power). Furthermore, the work permitted to highlight that the SAR _10g exposure levels are slightly higher for the child model, compared to the adult one and that the distance between the UPA antenna and the human models could greatly lower the SAR _10g levels. At last, it was found that the SAR _10g exposure levels obtained with the UPA antenna at 14 GHz were lower than the ones at 3.7 GHz, although further investigations will be necessary.

The aim is the diagnosis of cervical myelopathy, which is a disease that affects the first part of the spinal cord (between the C3 and C7 vertebra). A preliminary feasibility analysis oriented toward the development of an imaging system is reported. The system prototype includes a set of antennas that illuminate the neck and retrieve samples of the scattered electric field. The related inverse scattering problem is solved by using a nonlinear Newton-type reconstruction procedure, which provides two-dimensional images of the dielectric parameters of a neck cross section. A simplified cylindrical phantom mimicking the human neck has been designed for assessing the feasibility of the envisioned microwave measurement system and processing technique. Numerical results are reported to evaluate the capabilities of the proposed approach. Moreover, initial experimental results have been obtained by using cylindrical containers and a 3D printed version of the developed neck phantom.

For non-superficial tumors, this can be achieved by means of an antenna array equipped with a proper cooling system (the water bolus) to avoid overheating of the skin. In patient-specific treatment planning, antenna feedings are optimized to maximize the specific absorption rate (SAR) inside the tumor, or to directly maximize the temperature there, involving a higher numerical cost. We present here a method to effect a low-complexity temperature-based planning. It arises from recognizing that SAR and temperature have shifted peaks due to thermal boundary conditions at the water bolus and for physiological effects like air flow in respiratory ducts. In our method, temperature focusing on the tumor is achieved via a SAR-based optimization of the antenna excitations, but optimizing its target to account for the cooling effects. The temperature optimization process is turned into finding a SAR peak position that maximizes the chosen temperature objective function. Application of this method to the 3D head and neck region provides a temperature coverage that is consistently better than that obtained with SAR-optimization alone, also considering uncertainties in thermal parameters. This improvement is obtained by solving the bioheat equation a reduced number of times, avoiding its inclusion in a global optimization process.

According to the thermoacoustic (TA) signals obtained, which are superimposed with the corresponding time inversion of each pixel in the region of interest (ROI), the BP algorithm can function in a quick response and is suitable for a fast real-time MITAT system reconstruction. However, high artifacts and background noises which can be caused by incomplete sampling of TA signals seriously affect the image quality. Method: In this paper, a multiple back-projection with impact factor (MBP-IF) algorithm based on circular scanning is proposed to solve this problem. Compared with the BP algorithm, the MBP-IF method calculates not only the initial acoustic pressure of the TA signal of each pixel, but also the complete acoustic pressure distribution at different moments of the thermoacoustic wave transmission, which based on the derivation of time. Then the influencing factors can be obtained which can effectively suppress artifacts and eliminate noises. Results: Through numerical simulation and phantom experiments, the MBP-IF algorithm has excellent advantages in suppressing image artifacts and noises. The method of image quantification is also used to verify this conclusion. Clinical or Biological Impact: In addition, due to the independence of acoustic pressure distribution at different time, the MBP-IF can be computing in parallel with GPU, which can be widely used in real-time medical clinical MITAT system construction.

The current available temperature measurement techniques have some deficiencies in noninvasiveness, applicability, sensitivity and resolution. Microwave-induced thermoacoustic tomography (MITAT) has found diversified applications in biomedical related disciplines. It has been shown that MITAT can be used to estimate the temperature in a noninvasive manner. However, the applicability of the technique is still limited. This work presents experimental demonstration of two-dimensional (2-D) temperature detection of biological samples based on compressive TAT, referred to as MICTAT. Detailed principle of the method is established. A phantom sample and a biological sample are tested by experiments and 2-D temperature maps are obtained. This work provides a new route of getting 2-D temperature maps of biological samples and may find many applications in biomedical related areas.

In this work, we report a systematic method for broadband investigation of RF NT effects on Saccharomyces cerevisiae yeast growth. The method includes a transverse electro-magnetic (TEM) device and a dielectric spectroscopy technique for RF frequency selection. Frequency regions, where large permittivity differences between the medium and yeast cultures were obtained and used to select RF testing frequencies, e.g., 1.0 MHz, 3.162 MHz, 10 MHz. Additionally, RF at 905 MHz is tested for comparison purpose. Yeast cells in the exponential growth phase were examined at four RF frequencies and compared with two controls. One control device held at the same temperature as the test device, while the other control was held at a temperature 1C higher. The results showed that the RF fields at 3.162 MHz reduced yeast growth rates by 15.1%; however, the RF fields at 1.0 MHz enhanced cell growth by 13.7%, while the observed 4.3% growth rate increase at 10 MHz is insignificant and the RF fields at 905 MHz had no effects on the cell growth. These results showed a clear RF NT effects on S. cerevisiae growth that was frequency dependent.

the consistency of results over time is important to characterize so that relevant changes can be distinguished from normal measurement and tissue variation. In this paper, we analyze the consistency of microwave imaging when scanning frequently over several weeks, similar to the treatment monitoring timeframe. A custom microwave transmission system was used to acquire 15 scans from a breast phantom and 14-15 scans from each of 5 volunteers. As expected, the breast phantom showed high similarity when comparing signals, property estimates, and images at different time points. Scans of each volunteer also generally demonstrated consistency over time, as well as between right and left breasts. The characterization of consistency from scanning healthy women provides a baseline from which significant changes due to disease or treatment can be identified.

Common ALN screening modalities lack high enough sensitivity and specificity. Level I ALNs produce detectable backscattering of microwaves, opening the way for Microwave Imaging (MWI) as a complementary screening modality. Radar-based MWI is a low-cost, non-invasive technique, widely studied for breast cancer and brain stroke detection. However, new specific challenges arise for ALN detection, which deter a simple extension of existing MWI methods. We present a complete study that proposes dedicated imaging algorithms to detect ALNs, and evaluate their effectiveness experimentally. We describe the developed setup based on a 3D-printed anthropomorphic phantom, and the antenna-positioning configuration. To the authors’ knowledge, this is the first ALN-MWI study involving a fully functional anatomically compliant setup. A Vivaldi antenna, operating in a monostatic radar mode at 2-5 GHz, scans the axillary region. Pre-clinical assessment in different representative scenarios shows Signal-to-Clutter Ratio higher than 2.8 dB and Location Error lower than 15 mm, which is smaller than considered ALN dimensions. Our study shows promising level I ALN detection results despite the new challenges, confirming MWI potential to aid breast cancer staging.

Technology or Method: A novel method named electrical impedance myography (EIM) is proposed to evaluate muscle fatigue degree during NMES. The experiments were performed on the anterior tibialis muscle on several voluunteers. Two EIM parameters : impedance amplitude (|Z|) and phase (), were measured in real time, while applying six NMES parameter combinations. The mean power frequency (MPF) of the surface electromyography (sEMG) was selected for verification of the proposed method. Results: |Z| and of EIM signals decreased significantly after NMES (p < 0.05). They also both showed a linear downward trend during NMES, which was also observed in MPF of sEMG signals. At the measurement frequency of 20 kHz, steady-state fatigue was achieved when |Z| decreased to approximately 14% of the initial value. Clinical or Biological Impact: This study provides a method for monitoring muscle fatigue induced by NMES, which is beneficial to the application of NMES.

further understanding is needed to aid interpreting EIM outcomes in nonhomogeneous skeletal muscle measurements. Methods: The framework presented models needle EIM measurements in a bidomain isotropic model. Finite element method (FEM) simulations verify the validity of our model predictions studying two cases: a spherical volume surrounded by tissue and a two-layered tissue. Results: Our models show that EIM is influenced by the vicinity of tissue with different electrical properties. The apparent resistance, reactance and phase relative errors between our theoretical predictions and FEM simulations in the spherical volume case study are 0.2%, 1.2% and 1.0%, respectively. For the two-layered tissue model case study, the relative errors are 2%. Conclusions: We propose a bio-physics driven analytical framework describing needle EIM measurements in a nonhomogeneous bidomain tissue model. Clinical impact: Our theoretical predictions may lead to new ways for interpreting needle EIM data in neuromuscular diseases that cause compositional changes in muscle content, e.g. connective tissue deposition within the muscle. These changes will manifest themselves by changing the electric properties of the conductor media and will impact impedance values.

but those who take care of them, including care givers, nurses, and close family members. Current progression monitoring techniques are based on scans from MRI and PET, which can be inconvenient for patients to use. In addition, more intelligent and efficient methods are needed in order to provide predictions on what the current stage of the disease is and strategies on how to slow down its progress over time. Machine learning has been around for several decades and has recently been making important contributions in medical applications. While machine learning methods have been utilised for diagnosing Alzheimers disease, they focus on using image data from MRI and PET scans, which can be difficult for patients to obtain. In this paper, machine learning was used with RF data captured from 9 different head models showing different stages of Alzheimers disease. The RF data was processed in several machine learning algorithms. Each machine learning models prediction and accuracy was generated and the results were compared to determine which machine algorithm could be used to classify different stages of Alzheimers disease using RF data that was obtained noninvasively. Results from the study showed that overall the logistic regression model had the best accuracy of 98.97% and efficiency in differentiating between 4 different stages of Alzheimers dise

To obtain higher glucose selectivity, we apply spectral preprocessing to the dielectric loss spectra to extract feature values of glucose. Using regression models derived from different concentrations of glucose in a solution with bovine serum albumin (BSA), we analyze solutions considering the physiological range of both components. Prediction errors for the glucose and BSA concentrations are estimated to be 54 and 83 mg/dL, respectively, even for varied concentrations of each component. We also investigate the dependence of the glucose prediction error on the solution temperature. The prediction error for the glucose concentrations is estimated to be 99 mg/dL at a difference of 1 K. This technique will be ease to implement with a broadband microwave sensor or with biomedical sensors that require the capability to analyze multiple components in solutions.

This work reports a novel MITAI modality to homogenize the microwave power deposition in the sample and improve the image quality for small animal imaging via scanning orthogonal polarization (SOP) excitation. Although circular polarization excitation has been reported to enhance MITAI, we perform some simulation works using realistic breast phantoms to prove that the homogeneity of microwave power distribution in the phantoms using orthogonal polarization excitation is comparable to that using circular polarization excitation. Compressive sensing is also applied to enhance the time efficiency of the system. Experiments applying a mouse and a frog sample are conducted. The results indicate that the SOP excitation mechanism can completely reveal the structure of the small animals due to improved power homogeneity. The proposed MITAI-SOP technique is superior to circularly polarized antenna (CPA) based modality since the former avoids the deficiency of CPA in bandwidth, power capacity and efficiency. This work presents a practical and easy-to-implement paradigm for high-quality imaging of small animals and big biological samples using MITAI.

and for treating GI dysmotility and functional disorders through electrical stimulation pulses have emerged over the recent years. These implants construct a bidirectional interface between the clinician and the patients GI tract, to record and monitor slow waves and to provide electrical therapies. Because of the limited battery lifetime of the implants, wireless power transfer (WPT) is a fundamental requirement to conduct studies and provide treatments for extended period. Furthermore, the WPT link provides the opportunity to establish near-field data communication over the same link. Currently, there are three main wireless power and data transfer (WPDT) approaches for GI tract implants consisting of resonant inductive, ultrasonic and capacitive couplings. Each approach provides a tradeoff based on the size of the implant, depth of implantation in vivo, the amount of power received by the implant, and the WPT efficiency. In this review, we present the theory and an overview of the major research works accomplished for each of the aforementioned WPT approaches. In particular, this paper focuses on simultaneous WPDT for systems implanted in the GI tract, while fluctuations of the wireless link efficiency and fidelity due to body movements and stomach motility are investigated, and techniques are introduced to improve the WPDT fidelity.

These sensors are significantly reduced in size, but still face serious electromagnetic (EM) propagation loss and signal obstructions resulting in lower signal-to-noise ratios (SNR). As mmWave received signals also have higher sensitivity to body motions, these effects typically degrade the accuracy of heart rate (HR) detection. To overcome this challenge, MIMO configuration can be used to improve the SNR level by taking advantage of its channel diversity. We use here a Frequency Modulated Continuous Wave (FMCW) radar from Texas Instruments (TI) at 77 GHz to collect data from 192 channels. Additionally, vital sign information is extracted using Arctangent Demodulation (AD) and Maximal Ratio Combining (MRC) combined with an adapted-wavelet Continuous Wavelet Transform (CWT) are utilized to demonstrate improvement of HR estimation accuracy.

that dielectrically represent the breast tissues and allow for repeated experiments in controlled laboratory environment. In this study, we compare the dielectric properties of three different skin phantoms in to assess their suitability for prototype testing in the frequency range of 0.5 10 GHz. First, we verify the properties of two polyurethane-based fat-mimicking phantoms. Then, we evaluate the skin phantoms in larger blocks and as 2-mm thin layers. Finally, we conduct two separate experiments with the 2-mm skin phantoms layered over the two different fat phantoms. All the results are compared to dielectric properties of excised human skin tissue reported in the literature.

The process is based on the application of a liquid film on the surface or object under sterilization (OUS). A beacon signal is required to self-steer the transmitted power from the designed retrodirective antenna array (RDA) towards the OUS; once the liquid film reaches the required temperature, the sterilization can be considered complete. Results suggest that the process takes 5 minutes or less for an angular coverage range over 60 whilst abiding by the relevant safety protocols. This paper also models the power incident onto the OUS and results are consistent with full-wave simulations. A practical RDA system is developed operating at 2.5 GHz and tested through the positioning of a representative target aperture surface. Measurements, developed by sampling the power transmitted by the heterodyne RDA, are reported for various distances and angles, operating in the near-field of the system. To further validate the methodology, an additional experiment investigating virus deactivation through microwave heating was also reported using live Coronavirus (strain 229E). Possible applications of the method include the sterilization of ambulances, medical equipment, and internet of things (IoT) devices.

based on the dielectric and mechanical properties of the tissues. In this study, we analyze the effect of dielectric and elastic contrasts between a small (tumor) inclusion (3 mm) and the surrounding normal tissue on the HMMDI signal as functions of inclusion position and vibration frequency (from 10 Hz to 95 Hz) using simulations. To solve the forward problem of HMMDI, we developed a Discrete Dipole Approximation (DDA) based simulation method, and analyzed the received HMMDI signal for low to medium dielectric contrast (1:1.17, 1:2.6, 1:3.5) and elastic contrast (1:1.5, 1:2.5, 1:5) levels. DDA solver decreased the simulation time by a factor of 146 compared to the Finite Difference Time Domain method and facilitated the extensive number of simulations required for the analysis. The results of this study provide useful information for the development of the HMMDI method as a tool for breast cancer detection in dense tissues.

supported by a Convolution Neural Network (CNN). This hybrid method is based on the difference in the transmitted electromagnetic power between healthy and tumorous breasts. This variation in transmitted power results from the electrical property variance between healthy and cancerous tissues. Under microwave radiation, the power of the transmitted waves leads to a heat distribution pattern on a sensitive screen placed under the breast. This work utilizes the change in the heat pattern to indicate the presence of abnormality inside the breast. Involving a CNN elevates the proposed technique’s detection capability and extracts quantitative data that characterize the tumor’s location and size. The proposed modality shows a capability to detect and determine the size and location of an artificial tumor with a 5 mm radius and a 2:1 permittivity contrast with normal tissue.

The use of 3D electromagnetic simulations can avoid expensive physical coil prototyping while providing quantities to determine local patient safety which is not measurable in vivo. Currently, 3D electromagnetic simulations are mostly solved on variations of two solver types, namely the time domain and the frequency domain solver. In this work, we compared these solvers and tested key simulation parameters using a single computational platform with state-of-the-art computational methods and computational human models. Our analysis included computational cost, B1+-field and power loss density for a range of common radio frequency setups used at different Larmor frequencies (field strengths, respectively) in magnetic resonance imaging systems. We found that a coarse mesh in a time solver has large unpredictable focal errors (>50%) due to partial volume artifacts while the frequency solver showed more linearity in the errors when reducing computational cost which could allow for more efficient simulations with reduced safety concerns. We expect our work to provide further insights into parameter and solver selection and contribute towards standardization in coil simulation in magnetic resonance imaging.

Methods: A convolutional neural network (CNN) was used to predict the presence of a cancerous lesion in data from experimental scans of MRI-derived phantoms. An experimental dataset containing data from 1257 scans was used. The CNN was compared to a similarly sized dense neural network (DNN) and logistic regression classifier. Results: The CNN was able to exploit the sinogram data structure to achieve diagnostic performance significantly better than random classification, while neither the DNN nor logistic regression classifiers could generalize to unseen test data. The area under the curve of the receiver operating characteristic curve of the CNN classifier was estimated to be between (78 3)% and (90 3)%, where the upper estimate was obtained when the testing set was constrained to consist of phantoms with breast volumes that are within the volume bounds of the training set and when the tumour was located at the same vertical position as the system antennas. Conclusion: The results obtained in this investigation demonstrate the potential of combining deep learning and BMS systems for breast cancer detection. Significance: This paper provides an estimate of the diagnostic performance of an air-based BMS system using deep learning methods for automatic tumour detection on a sizable experimental dataset. The performance was found to be comparable to that of AI-assisted mammography and marks a first step toward larger-scale investigations in BMS.

(e.g. in terms of current distribution within different cell layers) of a cell exposed to an external electric field. The aim is to provide a model which is easily adaptable to different cell types and cell sizes such that it can be used in the frame of different studies where cells are exposed to electric fields, e.g. Tumor Treating Fields, operating at frequencies around 200 kHz. Originating from the usual model of a spherical cell, an electric lumped element model is derived under consideration of the electric field distribution within a cell. Possible simplifications of the model are suggested, which are justified by consideration of electrical material properties. Lumped element parameters of the model are approximated with formulas containing only cell dimensional parameters and electrical material parameters. The lumped element model is validated on the basis of a glioblastoma cell model with two different nuclei sizes. The proposed lumped element model with the according formulas for the lumped element parameters is easily adaptable to different cell types and cell sizes. It leads to a sufficient approximation of the general electrical behavior of cells in terms of current distribution and general frequency behavior in frequency ranges up to several hundreds of megahertz. The model is an easy to handle electrical description of a biological cell.

An analytic and parametric approach was utilized to create an optimized monopole antenna that was impedance-matched to aerated lung tissue. This lung-tuned antenna was then fabricated using a copper 0.085” semi-rigid copper coaxial cable. For validation, the lung-tuned antenna was inserted centrally into lobes of a ex vivo porcine lung that was fully inflated to physiologically appropriate volumes. Microwave ablations were then created at 50 and 100 W for 1 minute and 5 minutes. Reflected power, cross sectional ablation sizes and spherical shape of the lung-tuned antenna were compared against a liver-tuned antenna in the ventilatorcontrolled ex vivo lung tissue. The study showed that the lungtuned antennas delivered energy significantly more efficiently, with less reflected power, compared to the conventionally-used liver-tuned antennas at 50 W at 1 minute (11.8±3.0 vs 16.3±3.1 W; p value=0.03) and 5 minutes (16.2±2.8 vs 19.4±2.9 W; p value=0.04), although this was only true using 100 W at the 1 minute time point (29.0±3.5 vs 38.0±5.3 W; p value=0.02). While overall ablation zone sizes were comparable between the two types of antenna, the lung-tuned antenna did create a significantly more spherical ablation zone compared to the liver-tuned antenna at the 1 minute, 50 W setting (aspect ratio: 0.43±0.07 vs 0.38±0.04; p value=0.04). In both antenna groups, there was a significant rise in the ablation zone aspect ratio between 1 and 5 minutes, indicating that higher power and time settings can increase the spherical shape of ablation zones when using tuned antennas. Adapting this combined analytic and parametric approach to antenna design can be implemented in adaptive tissue-tuning for real-time microwave ablation optimization in lung tissue.

The hearing of pulsed microwaves is a unique exception to sounds encountered in human auditory perception. The hearing of microwave pulses involves electromagnetic waves. This paper reviews the research on humans and animals leading to scientific documentation the absorption of a single microwave pulse impinging on the head may be perceived as an acoustic zip, click, or knocking sound. A train of microwave pulses may be sensed as a buzz, chirp, or tune by humans. It describes neurophysiological, psychophysical, and behavioral observations from laboratory studies involving humans and animals. Mechanistic investigations show that the microwave pulse, upon absorption by tissues in the head, launches a pressure wave that travels by bone conduction to the inner ear, where it activates the cochlear receptors via the same process involved for normal sound hearing. Depending on the impinging microwave pulse power, the level of induced sound pressure could be considerably above the threshold of perception to cause tissue injury. The microwave auditory effects and pressure waves could potentially render damage to brain tissues to cause lethal or nonlethal injuries.

This paper addresses the effects of frequency variation on the induced electric and magnetic fields for deep brain stimulation scenario, considering the hippocampus region of the brain. A modified magnetic resonance coupling (MMRC) coil is designed and utilised to stimulate a realistic human head model at frequencies from 1 to 30 kHz, with constant and variable excitation current scenarios, while considering the safety guidelines on the head phantom. It is found that the maximum value of the induced electric field increases with the increase of operating frequency, while the general pattern of that field distribution inside the head demonstrates similarity over the frequency. Both depth of stimulation and field’s focality demonstrate a noticeable change with frequency at frequencies below 12 kHz, while these attributes are almost saturated above this frequency band when using the MMRC coil. It is also noted that although increasing operating frequency can reduce the excitation current, the safety of the patient is prone to be jeopardized. Hence, to choose the optimum frequency range for the TMS coil, several factors including, safety limits, stimulation threshold, desired magnetic flux density, power consumption, and target depth need to be considered. This study provides a systematic approach to design deep TMS (dTMS) systems while making adequate tradeoffs for the frequency selection to stimulate the targeted depth without exceeding the safety limits, while using minimum possible power.

in order to enable efficient delivery of DNA into the cells that comprise subcutaneous tumors. A 5-7 °C temperature elevation of tumors that are located near the fat-muscle boundary and 3-7 mm below the skin surface can be achieved in a short period of time without damaging surrounding tissues. This capability is demonstrated through a combination of a directional antenna applicator operating at 8 GHz, and utilization of forced air cooling of the outer surface (skin layer). The directionality of the antenna is improved by cladding its high permittivity core with 3D printed, low permittivity dielectric material. Experimental data using a pork skin-fat-muscle tissue show that the desired temperature elevation at the tumor location is obtained after 2.5 W RF illumination for 3 minutes, which is in good agreement with electro-thermal simulations. With the addition of realistic human body model parameters to the same simulation setup, the results indicate that tumors can be uniformly heated with 3 minutes of illumination at 2.5 W input power while keeping the surrounding healthy tissues at a safe temperature.

e.g. people, caused by the narrow bandwidth of the systems due to a high quality factor (Q). In this paper, a compact broadband planar double-spiral resonator with a via is proposed to obtain a robust SCMR system with a stable efficiency where interference from high-dielectric surrounding objects is mitigated. The increased bandwidth is obtained without compromising power transfer efficiency by introducing coupling enhancement to the structure while Q is reduced. The bandwidth of the system is increased by over 15% compared to a conventional system with single-sided resonators, and the efficiency is comparable. In this paper, it is found that the location of the via affects both the efficiency and bandwidth of the SCMR system. Meanwhile, this paper reports an experiment with human hand phantom and a simulation study with multi-layered tissue model, both of which mimic a real human-involved environment, and successfully demonstrate the stability and high efficiency of power transfer of the proposed broadband resonators in a WPT system. Moreover, the proposed structure is tested to be less sensitive to misalignment between the transmitter and the receiver, and its advantages are further shown by comparing it to the systems proposed for similar human-involved environments. This proposed viaed double-spiral resonator is a promising candidate for a robust WPT system for human-involved environments.

Given the shortcomings of the available treatment options, the interest in alternative and less invasive treatment modalities such as microwave ablation (MWA), has increased. In order to develop and optimize this novel electromagnetic-based therapy, an accurate knowledge of the dielectric properties of human adrenal glands, as well as preclinical animal models, is crucial. In particular, ovine models represent a feasible animal model to test the safety and performances of MWA. In this study, the dielectric properties of ovine adrenal glands and of normal and diseased human adrenal glands are characterized ex vivo in the microwave frequency range. The dielectric properties of the two functional tissues (cortex and medulla) composing ovine adrenal glands are measured using the open-ended coaxial probe technique and represented with a two pole Cole-Cole model in the frequency range from 0.5 GHz to 8 GHz. This paper presents the first dielectric data of normal and diseased human adrenal tissues, including a functioning adenoma responsible for PA and it compares the human data with data from the animal model.

microwave imaging has been proposed from research community and many microwave systems have been designed mainly to work at low microwave frequencies. Based both on the results of recent dielectric characterization campaigns on human breast ex-vivo tissues up to 50 GHz and on the promising feasibility studies of mm-wave imaging systems, in this article, we propose and test inverse scattering techniques as effective tool to process mm-wave data to image breast cancer. Differently from the radar techniques so far adopted in conjunction with mm-wave imaging system, inverse scattering techniques turn out to be more versatile and robust with respect to the reduction of the number of processed frequencies and eventually also able to characterize the anomaly in terms of electromagnetic properties. In particular, in the above, two image reconstruction techniques, the Linear Sampling Method and the Born Approximation, are proposed and compared against both simulated and experimental data.

Realistic tissues distribution, size, shape, and dielectric properties of tissue-mimicking materials across the desired frequency band; in addition, long-term stability is required. In this study, a polymer composition that use to develop head tissues-mimicking materials that satisfy the aforementioned requirements. Polyepoxides (Epoxy), and assorted types of micro scale additive, including graphite, aluminium oxide, carbon black, and brass powders, are used to fabricate the phantom. Different mixing ratios are used to mimic four healthy head tissues; white matter, grey matter, skull, and skin. Blood-mimicking material is also included in the unhealthy phantom to represent stroke (hemorrhagic) at different locations and sizes. Also, water-based mimicking material is used to emulate cerebrospinal fluid (CSF) tissue. The measurements confirm close agreement to properties of actual head tissues across the frequency band 0.5- 5 GHz, which has been used in the ongoing research activities of electromagnetic head imaging systems. Stability over time is investigated and compared with the widely used gelatin-in water-based mimicking materials. The results show the superiority of the developed phantom compared to currently using gelatin-based phantoms.

The analysis is meant as a preliminary step towards the full experimental characterization of the system, with the aim of assessing the achievable results and highlight possible critical points. The system consists of an array of twenty-four printed monopole antennas, placed conformal to the upper part of the head; each monopole is immersed into a semi-solid dielectric brick with custom permittivity, acting as coupling medium. The whole system, including the antennas and their feeding mechanism, has been numerically modeled via a custom full-wave software based on the finite element method. The numerical model generates reliable electromagnetic operators and accurate antenna scattering parameters, which provide the input data for the implemented imaging algorithm. In particular, the numerical analysis assesses the capability of the device of reliably monitoring the evolution of hemorrhages and ischemias, considering the progression from a healthy statet o an early-stage stroke.

However, a significant drawback of the technique is the lack of effective imaging modalities for monitoring the changes undergoing in the thermally treated tissue. In this respect, microwave imaging has been proposed as a possible candidate, owing to its portability, low-cost, non-ionizing nature, and capability to detect changes in dielectric properties of tissues induced by the temperature. The goal of this paper is to provide initial guidelines for the design of a microwave imaging system for thermal ablation monitoring. To this end, an analytical study is performed to determine the proper working conditions, in terms of frequency band and matching medium. Then, three antipodal Vivaldi antennas on different dielectric substrates are designed and numerically assessed. Among those antennas, the Vivaldi antenna on RT/duroid 6010LM substrate proved to be the most suitable choice. The results of this study pave the way to an experimental assessment of the potential of microwave imaging as a modality to monitor thermal ablation treatments.

standing between the patient and the phased array applicator, and the operating frequency. This is crucial to improve the efficiency both from a technical and clinical points of view. In this paper, we propose a new approach, based on the propagation theory, to support the selection of the matching medium properties and the working frequency in a robust way by accounting for patient body shape and properties variability. The case of adjuvant hyperthermia treatment administered to patient with tumors in the pelvic region has been used as a numerical validation in both 2D and 3D patient specific. For this case, the proposed approach suggests an optimal range of working frequencies (130MHz)

exposure, considering the novelties introduced by the incoming 5G networks. Specifically, a possible future case of indoor exposure scenario is investigated, where the presence of a 5G access point (AP) in a room is simulated. The AP was modelled by two different indoor uniform planar array (UPA) antennas at 3.7 GHz and at 14 GHz, to evaluate how the beamforming and the higher frequency use could impact the exposure levels. Different scenarios were evaluated, considering the maximum antenna gain, two different human computational models, an adult model and a child one, and by varying the distance and the orientation between the UPA antenna and the two models head. All the simulations were conducted using the Sim4Life platform and in particular the exposure levels were expressed by the specific absorption rate averaged on 10 g of tissue ( SAR_10g ), which was analyzed for the skin and for some specific tissues. The work underlined that the highest SAR_10g values were obtained in the head area for all scenarios, with the skin SAR_10ghighest peaks when the UPA is placed laterally to the human model (195.73 mW/kg and 223.29 mW/kg for the adult and child model, respectively, for 100 mW input power). Furthermore, the work permitted to highlight that the SAR_10g exposure levels are slightly higher for the child model, compared to the adult one and that the distance between the UPA antenna and the human models could greatly lower the SAR_10g levels. At last, it was found that the SAR_10g exposure levels obtained with the UPA antenna at 14 GHz were lower than the ones at 3.7 GHz, although further investigations will be necessary.

The aim is the diagnosis of cervical myelopathy, which is a disease that affects the first part of the spinal cord (between the C3 and C7 vertebra). A preliminary feasibility analysis oriented toward the development of an imaging system is reported. The system prototype includes a set of antennas that illuminate the neck and retrieve samples of the scattered electric field. The related inverse scattering problem is solved by using a nonlinear Newton-type reconstruction procedure, which provides two-dimensional images of the dielectric parameters of a neck cross section. A simplified cylindrical phantom mimicking the human neck has been designed for assessing the feasibility of the envisioned microwave measurement system and processing technique. Numerical results are reported to evaluate the capabilities of the proposed approach. Moreover, initial experimental results have been obtained by using cylindrical containers and a 3D printed version of the developed neck phantom.

However, there are some difficulties in providing an accurate dielectric profile of breast media. This is because additive noises severely contaminate scattered signals. In this study, we apply a post-processing multi-frequency integration scheme to contrast source inversion (CSI) data to suppress image fluctuations. These are caused by the additive noise expected in a UWB system, which is also applicable to other inversion schemes. To deal with the dispersive dielectric properties in the CSI scheme, we introduce a first-derivative model of the Debye dispersion model to compensate for the dispersive effect. The FDTD numerical validations, using realistic breast phantoms with dispersive properties, show that a multi-frequency integration scheme considerably upgrades noise-robustness in complex permittivity reconstruction tissues.

In some exposure scenarii, presence of textiles impacts the interaction of the electromagnetic field radiated by wireless devices with human tissues. We investigate the impact of a textile layer in contact or in proximity of skin on the power transmission coefficient, absorbed power density and temperature rise using a near-surface tissue model at 26GHz and 60 GHz. Cotton and wool are considered as representative textiles. Our results demonstrate that the textile in contact with skin increases the absorbed power density up to 41.5% at 26 GHz and 34.4% at 60 GHz. The presence of an air gap between a textile and skin modifies the electromagnetic power deposition in the tissues depending on the thicknesses and permittivity. The temperature rise increases compared to the nude skin by up to 52% at 26 GHz and 46% at 60 GHz with the textile in direct contact with skin. With an air gap, for typical textile thicknesses, the temperature variations range from -3.5% to 20.6% and from -11.1% to 20.9% at 26 GHz and 60 GHz, respectively.

During hyperthermia, tumour tissue is heated to 40-43°C using radiofrequency or microwave antennas, which strongly enhances effectiveness of radiotherapy and chemotherapy. Hyperthermia treatment quality depends on tumour temperatures achieved and treatment planning (i.e. simulation and optimization of absorbed power and temperature distributions) could be very useful to ensure and improve treatment quality. Hyperthermia treatment planning was mainly a research tool for decades, because of high computational costs and limited quantitative accuracy of treatment planning predictions due to a lack of patient-specific tissue properties. Thanks to developments over the past decade, treatment planning becomes increasingly important in the clinical workflow. Presently, main clinical applications of hyperthermia treatment planning are 1) applicator selection, 2) heating ability evaluation and 3) on-line treatment guidance. To improve the reliability and further increase applicability of treatment planning, ongoing developments focus on 1) dielectric imaging to derive patient-specific dielectric properties, 2) advanced thermal modelling including discrete vasculature and 3) biological modelling to predict the radiosensitizing effect of hyperthermia in terms of equivalent radiation dose. The increased clinical application and ongoing efforts will further improve treatment quality.

In order to possibly obtain a minimally-invasive wearable device, the electrodes are located on the head, near mastoid bones, and measure the variations induced in the electrical impedance by the physiological changes in the pharynx produced by respiration. The feasibility of the adopted configuration has been assessed by means of electromagnetic simulations involving a simplified model. Moreover, an ad-hoc data processing algorithm has been developed for extracting the breath rate from the measured signals. Preliminary experimental results are provided for investigating the capabilities of the developed setup.

This dielectric contrast can be exploited by microwave imaging for monitoring human bone health. The tissue mimicking phantoms play a vital role for preclinical testing of microwave imaging system. This paper presents anatomically realistic multi-layered 3D printed and carbon black based human calcaneus structure. The liquid and solid based tissue mimicking mixtures are also proposed to mimic the dielectric properties of skin, muscle, cortical bone, and trabecular bone. The liquid tissue mimicking mixtures are composed of Triton X-100, water, and salt, whereas the solid tissue mimicking mixtures are composed of carbon black, graphite, polyurethane, and isopropanol. The dielectric properties of the tissue mimicking mixtures were measured using an open-ended coaxial probe measurement technique across 0.5 8.5 GHz. The average percentage difference between the relative permittivity and conductivity of reference data and proposed liquid tissue mimicking mixtures was found to be 7.8% and 9.6% for skin, 0.38% and 14% for muscle, 9.6% and 5% for cortical bone, and 3.4% and 2.4 % for trabecular bone, respectively, across 0.5 8.5 GHz. For solid tissue mimicking mixtures, this difference was found to be 3.93% and 0.64% for skin, 6.13% and 9.21% for cortical bone, and 10.66% and 41.82% for trabecular bone, respectively for relative permittivity and conductivity. The proposed tissue mimicking mixtures along with 3D printed structures can be used as a valuable test platform for microwave bone imaging system development.

This technology has made it feasible to monitor the physiological signs of patient remotely without traditional hospital appointments and follow up routine check-ups. Implantable Medical Devices(IMDs) play an important role to monitor the patients through wireless telemetry. IMDs consist of nodes and implantable sensors in which antenna is a major component. The implantable sensors suffer a lot of limitations. Various factors need to be considered for the implantable sensors such as miniaturization, patient safety, bio-compatibility, low power consumption, lower frequency band of operation and dual-band operation to have a robust and continuous operation. The selection of the antenna is a challenging task in implantable sensor design as it dictates performance of the whole implant. In this paper a critical review on implantable antennas for biomedical applications is presented.

We introduce an integrated circuit (IC) pulse radio as a suitable replacement for both a bulky and expensive off-the-shelf pulse generator and a clock. To assess the system’s suitability as a breast screening prototype, we compare measurements on two different experimental breast models (phantoms) with the established and previously reported prototype using off-the-shelf components and the here-introduced IC. We test both systems on a homogeneous fat-mimicking phantom with a 2-mm skin layer as well as a phantom with a 2-mm skin layer and glandular insertions, while the antennas, antenna housing, and sampling oscilloscope are the same for both systems. Additionally, we advance with the IC to higher frequencies, aiming to comply with the band intended for microwave imaging devices with medical applications. Furthermore, we compare the economic requirements of the IC and of the previously reported system by evaluating their cost and compactness. The objective of this study is to investigate if the IC pulse radio can replace bulky off-shelf components to allow us to implement the pulse generation circuitry in one flexible circuit board with the switching and antennas.

Robust signal processing technique is utilized, where a 1-D block processing technique, based on state-space method (SSM) is developed in two dimensions to form an enhanced Hankel matrix to track human motions from two-dimensional (2-D) data collected using the developed SFCW radar system in single- or multi-subject motion scenarios. Experimental datasets are used to track body parts’ motions and velocities with high accuracy. The significant improvement, besides de-noising the data, is due to the fact that applying the 1-D block processing technique to 2-D dataset matrix accounts for the correlation between motion’s estimates from consecutive frames. Results agree well with our reference, the human Boulic model.

multistatic radar for breast health monitoring in the presence of a titanium site marker, typically inserted post-biopsy. We show results of breast phantom measurements for a homogenous fat phantom in several scenarios: all-fat phantom simulating a simple healthy case, a case with an added small 1 cm diameter tumor, a case with a glandular insertion, and finally, a scenario of a tumor embedded in gland. To evaluate the system’s performance with respect to post-biopsy site markers, we then show investigations of the system performance with the same phantom and a biopsy marker attached to a glandular insertion with and without an embedded tumor, and compare the imaging results to those phantoms without the biopsy marker. We conclude that our RF radar can detect the tumor despite the presence of a biopsy site marker, and that the conductive titanium marker does not interfere with the system’s intended function.

The fabricated phantom is based on a composite material of polymer and additive materials such as aluminium-oxide, and graphite. These materials are selected to achieve high dielectric properties and realistic distribution of knee tissues in addition to long-life stability. A positive mold of muscle tissue and a negative mold of skin tissue are extracted from MRI data, whilst the positive molds for bones, tendons, ligaments, and tibia are extracted from a 1:1 commercial knee joint model. Due to a lack of data about dielectric properties of human knee ligaments in microwave frequency (0.5-10 GHz), dog’s ligament tissues are characterized. The fabricated tissues of the knee phantom are stable and accurately match the dielectric properties of knee tissues across the wideband 0.5 GHz to 10 GHz. The phantom will open the door for a portable, low cost, and onsite electromagnetic imaging techniques to detect knee injuries.

The filter topology comprises a tapered feed line at a top layer that excites four modified log-periodic open loop resonators on the bottom layer, achieving a broadband reject response. Size reduction techniques are applied on the embedded resonators that are optimized to exhibit an enhanced sensitivity to track the variations of the glucose level across a frequency span from 1.25 GHz to 2.65 GHz. The proposed flexible filter is tested pre-clinically and clinically, where a high correlation between its scattering parameters and the variations in glucose levels is attained. Regression models are also developed using experimental data obtained from healthy patients that are subjected to glucose tolerance tests. Results demonstrate less than 4% mean absolute relative difference between the reference and estimated glucose levels, and the predicted glucose levels lie 100% within the clinically acceptable zones as shown by the Clarke Error Grid analysis.

An existing compact patch antenna working at 434 MHz is re-designed using the proposed methodology. The proposed general approach is used to investigate the peculiar case of the hyperthermia treatment of abdominal rhabdomyosarcoma. Instead of patient-specific geometries with discrete vascular tree models, a surface phantom with a 3D blood perfusion model of tumors is used. The antenna is reworked to be robust. The effectiveness of the antenna is evaluated simulating the treatment with a recent non-linear multi-physic model, considering the different descriptions of tumor vasculature. A more robust and effective design is obtained, with respect to its previous version. The antenna bandwidth is increased of about 7%. The treatments with the old version of the antenna were unsatisfactory (40°C after 60 min), whilst the novel design could successfully treat the target region, reaching 42.5°C for 60 min of treatment. To enhance the effectiveness of the treatment, the use of a time-modulated power is studied. The proposed model could be extended to different body region and used to develop an application-oriented design of antennas for hyperthermia treatment.

However, for brain tumors, it is difficult to heat due to high perfusion and thermal conductivity of the head. Therefore, in this research, the technique of non-invasive heat focalization in multiple tumors, simultaneously, without affecting healthy tissue based on adaptive beamforming was investigated and presented. It is done by controlling the feeding of the antenna array surrounding the brain using a modified hybrid version of gravitational search algorithm and particle swarm optimization (MGSA-PSO). An antenna system in the form of a head helmet was designed and evaluated with 48 antenna elements each of them has a separate excitation that controls the field intensity and beamforming direction towards the tumors. Many scenarios considering a single tumor in different positions with different volumes or multiple tumors are studied to evaluate the performance of the applicator. The helmet was tested on the challenging scenario of a very mature and dense brain with realistic thermal and dielectric properties. The results confirmed the ability of the helmet technology and the proposed antenna system to use a microwave power of 65 W to lift the neoplasm temperature to over 42oC while keeping healthy tissue safe at 37 degrees with none hot spots. Furthermore, the results showed the capability of the proposed model to treat multiple tumors simultaneously.

This paper reports the first measurements of the dielectric spectra of viable and non-viable cells over the full beta-dispersion (interfacial) frequency range. Dielectrophoresis (DEP) single cell in-flow techniques were employed to quantitatively measure the Clausius-Mossotti factor spectrum of individual cells over the 300 kHz 400 MHz range, covering both the MF and UHF DEP cross-over frequencies. Experiments were performed on Chinese hamster ovary (CHO) cells, one set cultured in growth media, the other in nutrient depleted media to induce apoptotic cells. Both cell states were measured using multi-frequency DEP flow cytometry, which provides the equivalent complex dielectric permittivity of individual cells. The measured dielectric spectra facilitate determination of a cell’s morphology and the dielectric properties of its intracellular compartments, and are used to develop multi-shell dielectric models of viable and non-viable cells. The developed dielectric models can aid in biosensor design, in interpretation of bulk biomedia measurements where the heterogeneity in cell population can be masked, and in relating measured dielectric responses of cells to stimuli with changes in cellular physiology.

We present a surgical device which employs the thermal effect produced by microwave energy. High power microwave energy can generate a coagulated region at the surface of the biological tissue such as organs. By coagulating organs, bleeding can be stopped. However, a microwave surgical device cannot cut the tissue without any device support, such as a blade. On the other hand, radio frequency (RF) current capable of cutting tissue without any support. This study presents a combination of a forceps type microwave surgical device combined with RF current for biological tissue cutting mechanism. Furthermore, ten sealed porcine blood vessels, sealed by the device, capability to withstand pressure were measured. Sealed blood vessels can withstand up to 200 mmHg of pressure and sufficient to withstand human blood pressure.

especially applied to vascular diseases. Tracking the catheter’s tip during an iMRI procedure using active electronic components has mayor benefits but still faces challenges regarding safety and the quality of visualization, which has prevented its clinical use up to now. Here we propose a novel micro detector with a total length of 8 mm built upon a flexible substrate with a total thickness of less than 60 um. The design of the detector is based on two perpendicularly oriented saddle coils that together create a homogeneous magnetic field when wrapped onto the catheter tube, thus maintaining constant visibility of the catheter under rotation, with practically no dead angle. Being self-resonant, the proposed detector allows wireless tracking of the catheter position, whilst preventing any heating hazard due to the absence of radiofrequency cables. The micro-resonator was fabricated using a multilayer flexible electronics fabrication process.

By the end of 2023, more than 72 million vehicles worldwide will be equipped with devices and technologies that enable to exchange data and communicate with other cars. This challenging scenario is raising cross-cutting issues, such as those related to new radio-frequency exposures of the human body also when travelling. We evaluate the Specific Absorption Rate (SAR) induced in a realistic smart mobility communication scenario operated at 5.9 GHz. V2V antennas were modeled and placed on a realistic 3D model of a city-car to numerically estimate SAR in the body regions and tissues of a human phantom (adult male) inside the car. We found that both local and whole-body average exposures were below the ICNIRP and IEEE limits for the general public in the 100 kHz-6 GHz band, being equal in the worst case scenario to 1.58 W/kg (head) and 0.008 W/kg, respectively. The highest SAR was found in the most superficial tissues (the skin) of body regions very close to the sources. The distance of the passenger from the antennas played an important role in the resulting SAR. This research has a potentially great clinical impact as it contributes to new and realistic knowledge on the exposure scenario in smart mobility communication to assess possible health effects and for the design of policies for public health management.

This method is proposed for creating conductive lines in the body for focusing electromagnetic fields on a very small (4mm on a side) implantable medical device. A 2450 MHz sleeved slot coaxial applicator with a pointed, extended, hollow tip is designed to heat 400 mm3 of polymer from body temperature to its crosslinking temperature of 40°C in 10s.

and ISM band (433-434.8 MHz, 902-928 MHz) in this paper. By introducing split resonant rings, the proposed antenna has achieved ultra-wideband characteristics, which can cover from 272 MHz to 1504 MHz, and the relative bandwidth is 138.7%. Additionally, a new wireless power transfer (WPT) system is designed by integrating with a miniaturized metasurface to enhance the WPT efficiency and extend the lifetime of the implantable device. The transmission coefficient S21 of the WPT system loaded with metasurface is 11 dB higher than the initial system at the resonance point. Furthermore, biosafety is taken into consideration for practical applications. The experiments in the equivalent body environment are performed to demonstrate the reliability of the proposed antenna. The measured and simulated results are in good agreement, which shows that the proposed antenna is appropriate to be applied in wireless body area network communication and power transfer systems simultaneously.

Due to their unique body structure, vital signs of chelonians cannot be recorded without substantial animal handling in previous methods, which would severely bias the brumation condition. In contrast, our sensor on harness can couple significant RF energy into various body parts to evaluate the heartbeat, respiration and activity levels. The self-contained unit is lightweight for ease of wearable deployment and low power to avoid unnecessary heat generation as well as frequent battery replacement. We recorded the shell temperature, heart rate, respiration rate and activity levels of a Russian tortoise during the entire brumation cycle and found that the heart rate correlated with the ambient temperature well, while the breath rate did not significantly reduce during brumation. This experimental study is minimally invasive and thus least biased.

While Biofuel cells (BFCs) such as enzymatic glucose/O2 are ensured to benefit from abundant chemical resources that can be harvested in the immediate environment of the human body, the highly critical in vivo kinetics of biofuel cell is not yet fully understood. Unfortunately, existing solutions for real-time monitoring of the reaction on rodents are not possible today, or too bulky, which has a biasing impact on the animal behavior. This work presents a light, battery-less, and wireless strategy to continuously monitor a BFC implanted in a laboratory rat using a Frequency Identification (RFID) link. An extremely lightweight and flexible tag antenna of footprint lower than 10 cm is presented with communication capability above 60 cm in field environment. The operational capabilities are demonstrated with a 24-hour continuous monitoring of an enzymatic glucose/O2 reaction, both in vitro and in vivo.

applications in neuroscience research and the treatment of neurological disorders. Current systems are effective but research continues on improving key performance metrics such as precise targeting, focality, and depth of penetration. Additional functions are also being studied; tunable excitation field patterning, reconfigurable depth of penetration, multiple excitation sites, power efficient waveforms and reduced extraneous excitation. Multichannel, multi-coil arrays show promise in achieving many of these parameters in one multifunctional array as opposed to the single-function commercial coils (circular, figure-8 or H coil) being used today. As such, our central focus is to determine whether multifunction dense arrays, despite their many challenges, are a tractable technical approach for future neuromodulation systems. Therefore, the results in this paper are twofold. First, we report the design, fabrication and demonstration of a scalable multichannel (12 channels) or multifunction dense array system to assess the potential to perform these functions in one system. Second, we demonstrate that the depth of penetration of the magnetic field can be reconfigured by varying current magnitude and phase of the smaller coil diameters in the array to achieve the same decay profile performance of a larger diameter coil. Only simulations exist in the literature to date, to the best of our knowledge, we report the first measurements of hexagonal shaped coils in multi-coil arrays have increased depth of penetration over circular shaped coil-based arrays.

This paper presents a novel graph degree mutual information (GDMI) approach to distinguish Intracranial Haemorrhage (ICH) from Ischemic Stroke (IS). A total of 50 ICH and 50 IS signals simulated using a 16-antenna electromagnetic head imaging system are analysed to evaluate GDMI. The data collected from each model consists of 256 reflected and received signal. Subsequently, noise is injected into the collected signals to generate three groups of signals with different signal-to-noise ratios (40~dB, 25~dB and 10~dB SNR), to emulate measurement noise and to test the algorithm’s robustness}. Each signal is converted into a graph to avoid the variable signal amplitudes. Then, the relationship between each pair of graph degrees is calculated by mutual information and forwarded to a support vector machine to identify stroke type. The results indicate that signals from ICH subjects exhibit a significantly higher GDMI compared to the IS group (p<0.01). An accuracy of 88% is achieved in identifying ICH from IS without the need to use time- and resource-expensive brain image reconstruction algorithms even under 25~dB signal-to-noise levels. The execution time for graph feature extraction and classification is less than one minute on a PC. Such a short time is suitable for stroke emergency requirements.

it has involved the detection of motion and vital sign signals with minimal discomfort. Self-injection-locked (SIL) radar systems exhibit several useful advantages over conventional continuous-wave (CW) radar systems in healthcare applications, including a low system complexity, high sensitivity, and high clutter immunity. Several approaches to detecting vital sign signals and locations using SIL radar systems have been proposed. This paper summarizes developments in vital sign detection and localization. Finally, some results of detecting animals using SIL radar systems are presented.

In order to describe the 2D spatial distribution of electric field induced in the whole apartment for whatever position of the WiFi source, an innovative approach that combines Principal Component Analysis (PCA) and Gaussian process regression (Kriging method) was applied. The 2D surrogate model was used to investigate the exposure in three different usage scenarios of the WiFi sources, i.e. surfing to a new web site, using a Skype video call and watching a You Tube video at 1080p, evaluating the electric field E induced at each location of the apartment for 10,000 different positions of the source. Across all the examined conditions, we found E values distributions with median values in the range 2.2 ? 96.1 mV/m and 90th percentiles in the range 4.9-209.3 mV/m. The 2D surrogate model allowed obtaining a complete description of the exposure for any positions of the WiFi source in the apartment, with a computational effort equal to about 10% of the one needed by using only the WiCa Heuristic Indoor Propagation Prediction (WHIPP) network planner.

The developed setup is composed by an ad-hoc measurement prototype equipped with an efficient imaging method for the reconstruction of the distribution of the electric conductivity of the body under test. In particular, a time-difference formulation is adopted, and the resulting ill-posed equation is solved by means of an iterative procedure performing a regularization in the framework of Lebesgue spaces. The performance of the method has been assessed by means of several numerical simulations. Moreover, a preliminary validation with experimental data has been performed, too. The obtained results confirm that the approach is able to effectively detect inclusions with different sizes and locations inside the considered head models.

anatomical human body models located at the head landmark position. Both generic and vendor-specific birdcage coil models were created and analyzed using a radio-frequency (RF) circuit and a three-dimensional electromagnetic (EM) co-simulation approach to evaluate EM properties of the coil used in a commercial 3T magnetic resonance imaging (MRI) scanner. The fidelity of the coil geometry and excitation, as well as consideration of permissible variations of the coil electrical components and capacitor losses, had a significant impact on the estimated electric field distributions inside the human models. Therefore, the variety of electric fields generated in humans should be carefully considered for a reliable RF safety assessment of a patient with a passive or active implant undergoing a scan in a modern MRI scanner with dual-channel transmit RF coils.

The proposed antenna is initially modelled and designed with the aid of commercial software (CST-Microwave Studio). To ensure that the proposed designs are meeting the required specifications with reduced design time, the parallel surrogate model-assisted hybrid differential evolution for antenna optimization (PSADEA) is proposed to optimize the design. Based on the best set of geometry parameter for the optimum antenna performance, the antenna prototype is realized on an FR-4 substrate and analyzed in terms of bandwidth, gain, efficiency, and radiation pattern with and without the tissue models. All measured results are found to be in good agreement with the simulated results. The antenna provides a good reflection coefficient (S11 <-10 dB) in the UWB frequency band from 3.1 GHz to 10.6 GHz and maintains its bandwidth UWB operation without detuning when placed in closed contact with the human body or breast mimicking tissues (phantoms).

Optogenetic neuromodulation is proven to be one of the possible cures for this chronic disease. To stimulate multiple neurons simultaneously, distributed miniaturized implants are needed to cover a wide range of areas. In this paper, an on-chip design of an inductively coupled wireless power transfer (WPT) system for an optogenetic implant is presented. A $0.3 \text{mm} \times 0.3 \text{mm}$ on-chip spiral coil is designed using a standard $0.5 \mu m$ CMOS process and characterized as the receiver of the WPT system. The EM field distribution through different tissue layers is investigated which helps to further evaluate the maximum Specific Absorption Rate (SAR) and temperature through the brain tissue. The system achieves a power transfer efficiency (PTE) of 0.65% and 0.96% with matching networks through 10 mm tissue layer and air links respectively. At 10 dBm transmitted power, the maximum SAR value is simulated to be 1.51 W/kg with the maximum temperature increase of 0.73 °C through the skin layer due to the EM field exposure. A case study of the proposed on-chip coil based WPT system shows the different light intensity level that can be achieved for optognetic neuromodulation application. Thus, the proposed miniaturized system proves to be a good candidate for the future distributive neural interfacing application.

An algorithm is developed and presented which takes field measurements external to the phantom and provides the electromagnetic sources required to obtain the SAR distribution. The unique aspect of this inverse source algorithm is that it casts the problem as the simultaneous inversion (SI) of two sets of equivalent currents: one for the device under test (DUT), and the other for the phantom. The dependency of these two sets of currents is then incorporated as an explicit regularization term in the resulting algorithm. The method is proposed to be relatively robust in terms of measurement noise. A simplified two-dimensional problem is presented to support this proposition.

Focusing is achieved using two lines that guide the incident wave deeper into the body and concentrate it around their respective tips. The small gap between the tips of the lines provides constructive coupling and augments the focused field. Compared to the case where no lines are used, the focused power is 8 times and 16 times larger if one line and two lines are utilized, respectively. The proposed design can be modified to focus fields with arbitrary polarizations at different depths inside the body. We propose a method to create this focusing structure by extrusion inside the body using heat-activated polymer-based conductors.

Despite the few side-effects reported by clinical studies, the assessment of potential localized temperature increases in tissues is still not solved. In this study, the temperature increase induced by a 3 mA stimulation in the tissue target (i.e. the spinal cord), in its surrounding tissues and in other tissues possibly more vulnerable to temperature increase were assessed through a computational approach. That solves Laplace equation and BioHeat equation for electric field and temperature distribution, respectively, on six whole body high resolution anatomical models, including three models of pregnant women at different gestational ages. Results show that temperature increase distribution in those targets is guided by a complex interaction between different mechanism in which electric stimulation plays a secondary role, in particular when blood perfusion is active. The very low heating assessed (below 1.5 m°C) is not consistent with the hypothesis that the induced temperature increase would critically activate metabolic changes in the target tissues here considered or would contribute to the few side effect that the applications of spinal direct current stimulation protocols have shown.

However, RF ablation is proven to have an inconsistent result of reducing hypertension, for the reason that it has a limited heating capability. We present the feasibility of using microwave energy as a different energy source for RDN ablation treatment, by comparing to RF current energy source. In this paper, we designed a coaxial-slot antenna for microwave (2.45 GHz) and an electrode for RF current (500 kHz), with phantoms that match human muscle dielectric properties at each respective working frequency. Both phantoms thermal properties and material density were measured, and then used in simulation. A total of 10 ablation experiments were conducted to validate the numerical simulation results. Each temperature points of the experiments were measured at 1 mm interval between thermometer probes. The results of the experiment temperature distributions agree well with the simulation results, RF achieved 5-6 mm while microwave achieved 7-8 mm. Additionally, numerical calculations with different input power were conducted to understand the temperature characteristics of both energy source. Microwave energy offers higher input power for a more profound and broader ablation area as opposed to RF current.

State-of-the-art electromagnetic solvers resort to a computationally expensive volumetric discretization of the full head to account for its complex and heterogeneous electric profile. The more efficient, popular in biomedical imaging circles, but unfortunately oversimplifying Boundary Element Method (BEM) relies instead on a piecewise-uniform approximation that severely curbs its application in high resolution EEGs. This contribution lifts the standard BEM contraints by treating the local anisotropies with adequate fiber and thin volume integral equations that are tailored to specific structures of the fibrous white matter and the inhomogeneous skull. The proposed hybrid integral equation formulation thereby avoids the full volumetric discretization of the head medium and allows for a realistic and efficient BEM-like solution of the anisotropic EEG forward problem. The accuracy and flexibility of the proposed formulation is demonstrated through numerical experiments involving both canonical and realistic MRI-based head models.

Compared to traditional continuous wave (CW) radars which suffer mixed and distorted phases from multiple reflections, frequency modulation continuous wave (FMCW) radars have the nature of suitable range resolution and the inherent capabilities of multi-target monitoring. By using FMCW radars to extract vital signs separately based on our proposed algorithm, the vital sign of the two targets can be detected simultaneously even within the limitation of the resolution bin. Furthermore, adding a RF switch, as a multiplexer, enables a single transceiver to detect the vital signs from multiple directions and multiple targets straightforward. Moreover, this RF switch provides the mixing function. A low-IF architecture is proposed and demonstrated for multi-direction vital sign detection simultaneously, and the signal to noise ratio (SNR) can be improved by choosing IF properly to reduce the flicker noise. The demodulation of heart rate (HR) is challenge due to low SNR and the harmonic of respiratory rate (RR) for FMCW vital sign radars. We apply an ensemble empirical mode decomposition (EEMD) algorithm to extract intrinsic mode functions of RR and HR. Experiments show the proposed algorithm improve SNR and accuracy significantly.

Tissue dielectric properties, which can be obtained by thermoacoustic tomography (TAT), are considered as potential parameters correlated with both BMD and bone quality. Therefore, here we propose to use TAT to detect osteoporosis and to monitor the formation of osteoporosis over a long period. Technology or Method: This study used the bilateral ovariectomy to obtain an osteoporotic rat model (n=4) along with a sham control. During the 100 days after the operation, the right tibia of each rat was in vivo thermoacoustically imaged at 5 time points. After the last TAT imaging, micro computed tomography (Micro-CT) was performed on each rat to validate the TAT findings. Visual observation and semi-quantitative methods were used to analyze the thermoacoustic data. Results: During the monitoring period, the thermoacoustic signal intensity of the tibia of the sham-operated rat continued to increase, while the thermoacoustic signal intensities of the tibia of osteoporotic model rats showed fluctuations. The TAT findings were verified by Micro-CT. Conclusions: Osteoporosis can be clearly detected by TAT. Significant differences in thermoacoustic signal intensities between normal bone growth and osteoporotic bone formation are observed. Clinical or Biological Impact: This study provides initial facts that TAT may become a new tool for noninvasive detection and monitoring of osteoporosis.

Typically, hyperthermia systems involve several antennas that transfer electromagnetic energy into the tissue. The principal need in hyperthermia treatment is to optimally focus the heating into the target while minimising heating in the surrounding healthy tissue. Patient-specific treatment planning is done to optimize the specific absorption rate and the resulting temperature distribution. Uncertainties associated with the thermal model used for temperature simulations represent an important challenge. Our previous work has demonstrated that the occurrence of hotspots can be reduced and target heating enhanced using time-multiplexed steering procedures. In this paper, the robustness of time-multiplexed hyperthermia against temperature dependent thermal tissue properties is investigated. Temperature simulations are used to predict the time-dependent heating achieved by multiple antenna phase and amplitude configurations that are generated by a multi-objective genetic algorithm and applied sequentially. The proposed strategy is compared with the heating obtained using one single heating setting obtained by particle swarm optimization as typically used in clinical hyperthermia. Thermal performance of the static and time-multiplexed methods are assessed by applying two thermal models, one that uses constant properties of blood perfusion and thermal conductivity of tumor, muscle and fat, and a second one that uses temperature dependent perfusion values. This study shows that time-multiplexed hyperthermia enhances target heating and limits the hotspot appearance regardless of the thermal model used in thermal simulations.

The electric field induced by the time-varying magnetic field in a stimulating coil could activate nerve fibers in the brain, resulting in depolarization or hyperpolarization of the neurons. However, the potential adverse effects of rTMS on heart rhythm have not been extensively investigated. This study aims to develop an optimized design of rTMS system to evaluate the potential adverse effects of rTMS on mouse heart rhythm via vagus nerve modulation for pre-clinical application. The rTMS-induced electric field in the vagus nerve of brain produced by the strong rate of current change of 1.04×108 A/s in a stimulating coil, which was directly determined by circuit design in charging voltage of the capacitor bank and inductance value of a stimulating coil. A finite element method (FEM) mathematical simulation indicated that the maximum eddy current was 25.4μA/mm2, which was greatly exceeded the vagus nerve activation threshold of 5.6μA/mm2. The animal experiment results also verify that the induced electric field activates the RR-interval prolonging effect might be attributed to vagus nerve stimulation (VNS) from rTMS, and the most pronounced heart rhythm prolonging effect at 20Hz magnetic field treatment, causing the average heart rate decreased to 58.65% of that before rTMS in 10 mice. In conclusion, above-threshold rTMS at 20 Hz could produce maximum adverse effect on heart rhythm through direct vagus nerve activation for pre-clinical applications such as safety screening.

These scenarios represent a topic of high interest, because it was found that domestic appliances could be relevant for children exposure level. In details, in this paper the exposure of two child models to a hairdryer model was evaluated. Following the ICNIRP guidelines, the electric field amplitudes induced in specific tissues composing the central nervous system and the peripheral nervous system were analyzed. The analysis of the results permitted to highlight a high exposure variability depending on the near-field source position and to individuate the regions where the source could cause the highest levels of exposure, not limiting the analysis only to some worst-case exposure scenarios.

we report a novel in vitro test setup to validate BCIs. Past validation techniques used stand-alone 50-Ω function generators or function generators connected to high-valued resistors to replicate recording from clinical electrodes; however, neither of these two methods accounts for an electrode’s complex, frequency-dependent impedance, and both underestimate the normally high electrode impedance. As such, optimizing and testing via function generators and resistors overestimates BCI sensitivity by at least 250 times and 2 times, respectively. To more closely replicate a clinical recording environment and accurately assess BCI performance, we utilize a function generator to mimic neural signals sent to a human-body-mimicking electrolyte fluid via a Pt electrode. These signals are then recorded via a neural electrode connected to the BCI under test. To validate the proposed method, we compare sensitivity of a previously reported fully passive BCI via the three methods. The presented results demonstrate that recording via the proposed clinically accurate setup when the BCI has been optimized with one of the two other test methods gives the lowest sensitivity in the frequency domain and worst signal stability in the time domain. Overestimating BCI sensitivity during in vitro testing results in the potential inability to record desired neural signals in vivo. The proposed method provides a means by which to accurately assess BCI performance, therefore reducing errors during animal trials and saving time, money, and lives.

Confinement of heating generated by microwave radiation is one of the major concerns in cancer treatment to maintain the acceptable functionality of the organ and alleviate radiation exposure towards surrounding tissues. Development of baseball-bat shaped (BSB) antenna has been studied using electromagnetic and thermal simulations and evaluated experimentally. Numerical simulations showed less than -10-dB reflection stability is attained for more than 20 GHz. Electromagnetic simulation showed that highly directed end-fire radiation achieves confined power deposition within targeted model and yields in higher SAR attained. Nearly spherical ablated lesions are achieved with no healthy tissues being destroyed in the backward direction. Proposed antenna was fabricated and tested in ex-vivo bovine liver sample and egg-white solution. Good agreement between simulated and measured results where confined ablated lesions attained at only 1W were comparable to that obtained at much higher power ranges (20-60W). Efficacy of BSB antenna to efficiently radiate in different dielectric mediums is noticeably attained. The proposed antenna model may help improving the precision of microwave ablation associated with commonly broadside radiators previously used in literature and provide homogenous SAR and confined heating to overcome the limitations found in treating spherical tumors with heterogeneous properties using much high power with narrow-band feature.

A new distant microwave sensing platform to monitor the concentration of glycerol in a water and serum solution in a microfluidic channel is presented. The sensor is based on a microstrip line reader with defected ground plane coupled to a chipless microwave resonator tag. Due to the strong coupling between the reader and the tag, the distance between them can be increased up to 45 mm. The high level of sensitivity of the structure makes it suitable for nanolitre volume scale chemical sensing inside the microfluidic channel. The sensor demonstrates a frequency shift of 6 MHz when the volumetric percentage (V%) of glycerol in DI water changes from 70% to 0%. The proposed solution provides the opportunity of integrating the chipless passive tag with the microfluidic channel while the reader is distant from the microfluidic system.

reported dielectric properties since these properties are affected by multiple environmental confounders. This work investigates the effect of dehydration on dielectric properties as a function of time at different temperatures. Additionally, it proposes a dehydration mitigating technique. The dielectric properties of porcine liver samples were measured during a 35 minute measurement interval at different temperatures. A first set of six experiments was conducted in standard laboratory conditions. A second set of two experiments was conducted with a modified measurement setup with reduced air flow. Under standard conditions, relative changes in the dielectric properties up to 9% were observed. With the modified setup, the relative change was halved compared to standard conditions. This reduction indicates that the environmental conditions have a considerable influence and that modifying these conditions extends the stability of the dielectric properties over time. For several applications relying on the difference in dielectric properties between healthy and malignant tissue, an error of 9% in measured data is on the same order as the effects of interest. The expected difference in dielectric contrast could be obscured due to dehydration.

There is much information in the literature about DPs of healthy tissues, however, there is a gap in DPs of unhealthy tissues and DPs of tissues at different ages. DPs of any healthy tissue can be described by DPs of its solid fraction and water content values. The observed DPs of a tissue change with the level of tissue’s water content (increase or decrease) according to the condition of the tissue (i.e., pathology and age). For the existing study, DPs of solid fraction and water content of 19 different tissues from 61 pigs at different ages were measured and used to generate DPs of those tissues under different conditions using a simple mathematical model. The dry-weighing method was used to determine the water content of tissues and DPs of their solid fractions were measured. Then, DPs of those tissues were generated using the proposed method and found to be in a good agreement with some previously published data as well as with the measured data in this study. This study confirms the potential of using DPs of the solid fraction and water content to calculate DPs of tissues at any age or pathology.

First, the wrist-worn pressure sensor array (PSA) and Doppler radar are used to respectively identify static and dynamic gestures through a Quadratic-kernel SVM (Support Vector Machine) classifier. Then, a robust wrapper method is applied on the features from both sensors to search the optimal combination. Subsequently, two hierarchical approaches where one sensor acts as ‛enhancer‚ of the other are explored. In the first case, scores from Doppler radar related to the confidence level of its classifier and the prediction label corresponding to the posterior probabilities are utilized to maximize the static hand gestures classification performance by hierarchical combination with PSA data. In the second case, the PSA acts as an ‛Enhancer‚ for radar to improve the dynamic gesture recognition. In this regard, different weights of the ‛Enhancer‚ sensor in the fusion process have been evaluated and compared in terms of classification accuracy. A realistic cross-validation method is chosen to test one unknown participant with the model trained by data from others, demonstrating that this hierarchical fusion approach for static and dynamic gestures yields approximately 16.7% improvement in classification accuracy in the best cases.

We propose a functionalized contrast agent which is capable of decreasing the permittivity and increasing the electrical conductivity of the breast tumor based on the magnetosome concentration. Our results show that biogenic magnetosomes can increase relative permittivity contrast between 9-25% in the microwave frequency range from 1-10 GHz.

it can unobtrusively provide information about the physical and mental condition of people. In particular, the continuous measurement of a person’s time-varying instantaneous heart rate can estimate the activity level of the autonomic nervous system without the person wearing any sensors. Continuous heart rate measurement using radar is, however, a difficult task because accuracy is compromised by numerous factors, such as the posture and motion of the target person. In this study, we introduce techniques for increasing the accuracy and reliability of the noncontact measurement of heart rate variability. We demonstrate the performance of the proposed techniques by applying them to radar measurement data from a sleeping person, and we also compare its accuracy with electrocardiogram data.

In order to achieve high ecological validity in emotion elicitation, this paper proposed a novel Affective Virtual Reality System (AVRS) by utilizing the immersion, privacy and design flexibility of virtual reality. Design elements including subject features, sound features, motion features and color features were extracted by referring to the referenced emotion materials, art works and the existing VR scenes. Affective VR scenes were then designed by Unreal Engine 4.12 and their effectiveness was validated by Self-Assessment Manikin (SAM). Furthermore, arousal was used as an indicator to compare the difference of ecological validity between VR and video emotional materials with an intergroup experiment through Electroencephalography (EEG), Heart Rate (HR), Galvanic Skin Response (GSR), and SAM. Results proved that VR scenes could achieve the same emotion elicitation as video. Especially, there was significant difference in measures of Fearful in SAM evaluation, indicating that VR emotion materials were expected to deliver a good effect on negative emotional scenes. The proposed AVRS as well as the multimodal physiological signal database with valence, arousal and dominance (VAD) labels could help the development of emotion related studies.

We firstly designed a coil able to focus the magnetic field at the frequency (around 340 kHz) that maximizes the heat release from the chosen nanoparticles. Then, through an electromagnetic software based on the Method of Moments (MoM), we performed numerical simulations of the coil that resulted in excellent agreement with the experimental measurements conducted at the workbench on a fabricated prototype. After that, a radiating system consisting of the coil, a high-power radiofrequency signal generator and a set of magnetic nanoparticles have been set up. We carried out several experimental trials with different samples of magnetic nanoparticles in order to demonstrate the focusing property of the proposed system. The results we obtained suggested that a careful design of the radiating system could pave the way towards more efficient and safer magnetic hyperthermia treatments in clinical applications.

These signals, however, can suffer from artifacts due to complex EM wave interactions such as diffraction and surface wave propagation, which are often overlooked in the design phase of these sensors. This paper studies the impact of these wave phenomena on the signals transmitted and received from a pair of antennas designed to sense glucose changes via changes in transmission through a sample. Numerical simulations and controlled experiments with glucose solutions demonstrate for the first time that unwanted signal contributions from mm surface waves along the tissue can dominate the received signals but can be reduced with the use of appropriately placed absorbers around the antenna sensors. As a result, the sensitivity of such a sensing system to glucose changes is increased. This finding can be very useful in the design and development of the glucose sensor under study, as well as for other EM-based diagnostic medical applications.

clinical scenarios in patients undergoing magnetic resonance imaging. Four quantities, namely 1) the net dissipated power around an electrode of an AIMD, 2) the net temperature increase, 3) the current flowing from the lead to the electrode, and 4) the net specific absorption rate (SAR) increase were numerically compared for a set of leads to evaluate the analytical lead electromagnetic model (LEM) with respect to radio frequency energy-induced heating. The set included 32 single electrode leads with straight and helical wires. The LEMs were obtained and validated with 3D electromagnetic and thermal co-simulations at 128 MHz. A shift of the position of temperature or SAR sensor from the electrode tip to the electrode pedestal resulted in a decrease of the linear regression coefficient of determination for the LEM calibration factors. Behavior of different assessment quantities in terms of sensitivity of sensor location significantly varied between leads with the helical and straight wires. In conclusion, utilization of analysis made for generic leads with straight wire can be significantly misleading for the prediction of results for leads with helical wires.

Most of today’s research focuses on finding ways to harvest energy from the human body to avoid the use of batteries, which require surgical replacement. For example, current energy harvesters rely on piezoelectricity, thermoelectricity and solar electricity to drive the implantable device. However, the majority of these energy harvesting techniques suffer from a variety of limitations such as low power output, large size or poor efficiency. Due to their high efficiency, we focus our attention on solar photovoltaic cells. We demonstrate the tissue absorption losses severely influence their performance. We predict the performance of these cells using simulation through the verified experimental data. Our results show that our model can obtain 17.20% efficiency and 0.675 V open-circuit voltage in one sun condition. In addition, our device can also harvest up to 15 mW/ cm² in dermis and 11.84 mW/ cm² in hypodermis by using 100 mW/ cm² light source at 800 nm and 850 nm, respectively. We propose implanting our device in hypodermis to obtain a stable power output.

and are of interest for clinical applications due to their non-destructive nature and the lack of need for cell labelling. Here we report sensitive measurements on single, living, free-flowing cells (not electrostatically or dielectrophoretically trapped, cultured or fixed directly on sensing elements) in aqueous medium at ~9.8 GHz taken using a coupled dielectric-split ring resonator assembly. Inductive coupling between the two resonators enabled separation of microfluidic chips from RF connectors and allowed for time-resolved continuous-wave measurements on flowing single cells via the coaxial ports of a dielectric-loaded microwave cavity. Analysis via an equivalent circuit model showed that the novel resonator assembly maintained the permittivity-dependent sensitivity of a split ring resonator while operating at quality factors >1000 with lossy aqueous media (typically ~1900). Using a microfluidic channel with a 300 x 300 μm cross section, at a water-loaded resonant amplitude of ~-22 dB at 0 dBm input power level, shifts in amplitude due to individual cells passing through the sensing region of up to -0.0015 dB were observed. Correlations between averaged amplitude shifts and cell size as well as material properties demonstrate the diagnostic potential of this technique.

Practical application of the FMBH approach requires monitoring of microwave power deposition in the breast. Microwave-induced thermoacoustic imaging (MITAI) is naturally feasible for such power deposition monitoring task. This work conducts a computational study to evaluate feasibility of the novel FMBH-MITAI modality using realistic breast phantoms. Basic configuration and rationale of both FMBH and MITAI are introduced. Com-pressive sensing (CS) technique has to be applied in MITAI for sparse acoustic measurement in the FMBH-MITAI modality. Procedure of the computational study consists of microwave simulation, thermoacoustic numerical simulation, CS imaging, and performing the iterative optimization. Simulated results show that CS based MITAI is able to serve as a reliable monitor-ing mechanism to efficiently guide the iterative optimization toward the best obtainable focusing condition in most of the sim-ulated scenarios. Finally obtained thermoacoustic images agree well with simulated power deposition distribution well. This work offers valuable performance evaluation and is of significant meaning for potential clinical applications of the FMBH-MITAI modality.

The work reported here demonstrates the development of a battery free wearable sensing system with temperature and sweat sensors embedded into and powered by a smart textile NFC antenna. The NFC antenna is seamlessly integrated with closed-body garments, and sensor data can be easily acquired by NFC readers and smart phones in order to achieve real time and wireless monitor of health status in a convenient and non-intrusive way. A Dickson charge pump circuit has been designed and implemented in order to pump up the voltage and ensure a steady voltage supply for the sweat sensor. The maximum read range for accessing sensor data is 6 cm. The on-body measurement accuracy of the temperature sensor and sweat sensor are able to achieve ± 0.14°C and ± 0.2%, respectively. The presented system can provide wearable battery-free ubiquitous wireless connectivity for point-of-care and any time healthcare and wellbeing monitoring.

A pathological effect of Alzheimer’s disease is brain atrophy, which is the progressive shrinkage of the brain volume and weight. Another effect of Alzheimer’s disease is the enlargement of lateral ventricles in the brain. Currently, MRI and CT scanners can detect and show images of the brain during different stages of Alzheimer’s disease. However, its limited accessibility, high costs, and static structure make it inconvenient for some to use. This paper presents the design and novel application of a wearable device comprising of flexible microwave antennas, with an operating frequency range of 800 MHz to 2.5 GHz, that detects the progression of brain atrophy and lateral ventricle enlargement in patients with Alzheimer’s at the earliest stage possible. The operating principle of the antennas are simulated in near field using CST and the device is experimentally validated using lamb brain samples and samples representing cerebral spinal fluid (CSF). The measured reflection coefficients and transmission coefficients were found to correlate with changes in brain volume and changes in CSF volume successfully, thus giving an indication of the progression of Alzheimer’s disease in a patient.

A major challenge is achieving data quality that would ensure adequate image resolution for the specific diagnostic application. Imaging systems are typically designed with a theoretical resolution limit in mind, which is rarely achieved in practice due to measurement uncertainties, background clutter and system noise. Uncertainties and background clutter are particularly prominent in medical diagnostic imaging. This manuscript proposes a method for data quality assessment of an experimental imaging system that aims at a specific image resolution. It utilizes two measurements, one of a uniform background medium and one of the same medium with a small scattering probe embedded within it. The probe’s size and permittivity reflect the desired application-specific resolution. The method extracts the system point-spread function (PSF) from the two measurements and computes the PSF contrast-to-noise ratio (CNR). A case study is presented, demonstrating the quality control protocol and its ability to identify data sets of inadequate quality and provide an evaluation metric. The protocol also highlights possible sources of error and enables data filtering that increases significantly the reconstructed image quality.

The electrically small tag consists of nested-slot configuration and parallel strips. The tag antenna is exploited as a sensor by modifying its equivalent circuit to mitigate the effects of water, blood sample phantom, and the human body. As a result, the proposed RFID antenna features impedance match with Impinj R6 RFID chip from 880 MHz – 937 MHz with compact dimensions of 40 x 14 mm. Moreover, this tag has a read range of 3 m, 2.5 m and 1.5 m on the water bottle, intravenous (IV) solution and blood bag, respectively. However, the read range of RFID tag on an empty water bottle or IV solution bag is 0.5 m. By comparing the read range of tag on empty and solution filled IV bags, the proposed tag is used as a water proximity sensor. Experimental testing of the tag is performed for sensing the level of the IV solution. Also, this tag is tested by mounting on liquid mixture (a mixture of salt and sugar is used as a phantom to mimic the blood) filled plastic bags, which leads to a low-cost solution for blood storage management. Experimental results show a good agreement of proposed tag towards its use in healthcare applications, which leads to better healthcare facilitation regarding cost, time and care.

There remains several signal processing challenges in this field, which include overcoming the nonlinearities and harmonics that populate the power spectrum. Respiration harmonics distort and overwhelm the measurement of heartbeat due to the large signal amplitude. A supervised machine learning algorithm, the gamma filter, offers an efficient, calibration-free solution to model the time series heartbeat signal given respiration and respiration artifacts. The measured signal is provided by a 5.8-GHz quadrature Doppler radar and a modified ECG signal is used as the ground truth for training the filter. Experimental results show that the heartbeat is independent and separable from respiration and the algorithm can be implemented in real time.

The ischemic stroke (85% of total cases) and hemorrhagic stroke (15%) must be treated with opposing therapies, thus the nature of the stroke must be determined quickly in order to apply the appropriate treatment. Recent studies in biomedical imaging have shown that strokes produce variations in the complex electric permittivity of brain tissues, which can be detected by means of microwave tomography. Here we present some synthetic results obtained with an experimental microwave tomography-based portable system for the early detection and monitoring of brain strokes. The determination of electric permittivity first requires the solution of a coupled forward-inverse problem. We make use of massive parallel computation from domain decomposition method and regularization techniques for optimization methods. Synthetic data are obtained with electromagnetic simulations corrupted by noise, which have been derived from measurements errors of the experimental imaging system. Results demonstrate the possibility to detect hemorrhagic strokes with microwave systems when applying the proposed reconstruction algorithm with edge preserving regularization.

membrane resistance (as large as 1 MΩ) and cytoplasm capacitance (as small as 10 fF) from the scattering parameters. The scattering parameters were measured on a coplanar waveguide with a Jurkat cell trapped by dielectrophoresis either in a series or shunt configuration. The sensitivity analysis validated our previous empirical observation that the insertion loss of a series-trapped cell and the return loss of a shunt-trapped cell were most sensitive to the cell impedance. Additionally, the membrane resistance and cytoplasm capacitance were most sensitive to low- and high-frequency scattering parameters, respectively. In the future, the analysis can be used to optimize the test setup and protocol for fast, compact and label-free characterization of a cell at the subcelluar level.

In this paper, the influence of modulation and bandwidth in eliciting the DNA damage of RF alone and in combination with mitomycin-C (MMC), is analyzed in human lymphocytes. Blood cultures from healthy donors were exposed to 1950 MHz, and Continuous Wave (CW), Wideband Direct-Sequence Code Division Multiple Access (WCDMA, 4.5 MHz bandwidth), and Additive White Gaussian Noise (AWGN, 9 MHz bandwidth) signals were considered. For each signal, SAR values of 0.15, 0.3, 0.6, 1.25 W/kg were tested. RF exposure alone never induced DNA damage in the micronucleus assay. When RF exposure was followed by MMC treatment, the effect depended on modulation and bandwidth. CW exposure never altered the MMC-induced DNA damage, while such damage was reduced when either signals WCDMA at 0.3 W/kg SAR or AWGN at 0.15 and 0.3 W/kg were applied. These results indicate the influence of modulation for the occurrence of the protective effect, with a relation between the bandwidth and the power absorbed by samples. If confirmed invivo , clinical applications using modulated RF signals could be devised, to protect cells from side effects of therapeutic treatments.

given the explosion in both the number of wireless devices and equipments radiating electromagnetic-fields(EMF)and the growing concerns in the general public linked to it. Indeed, the next generation of wireless systems aims at providing a higher data rate,better quality of service(QoS), and lower latency to users by increasing the number of access points,i.e.densification, which in turn will increase EMF exposure. Similarly, the multiplication of future connected devices,e.g. internet of things(IoT)devices, will also contribute to an increase in EMF exposure. This paper provides a detailed survey relating to the potential health hazards linked with EMF exposure and the different metrics that are currently used for evaluating,limiting and mitigating the effects of this type of exposure on the general public. This paper also reviews the possible impacts of new wireless technologies on EMF exposure and proposes some novel research directions for updating the EMF exposure evaluation framework and addressing these impacts in future wireless communication systems. For instance, the impact of mmWave or massive-MIMO/beamforming on EMF exposure has yet to be fully understood and included in the exposure evaluation framework.

However, existing assessment techniques lack the accuracy and/or convenience for ongoing monitoring, motivating the development of novel methods. We propose using low-power microwave measurements (2-12 GHz) at the extremities to monitor human hydration, relying on the strong relationship between dielectric properties of tissues and water content. Electromagnetic simulations of realistic models are used to explore changes in microwave signals transmitted through the forearm to changes in hydration. Tissue properties are adjusted according to expected changes in water content, and average dielectric properties are estimated from signals transmitted through the arm by ultra-wideband antennas placed in contact with the tissues. A causal relationship between weight loss due to water loss and dielectric permittivity is found in human simulation models. Little relationship is found with conductivity. The theoretical groundwork for hydration assessment with microwaves is developed through a model which relates changes in total body water content with changes in microwave properties at the extremities. This model could be useful for monitoring hydration in at-risk populations such as older adults and athletes.

Existing methods of assessment are either inaccurate or impractical for use in field settings, motivating the search for new approaches. Extremity microwave measurement is a promising method for ongoing hydration monitoring, owing to the inherent differences in dielectric properties with varying tissue water content. This paper reports on a feasibility study of \textit{in vivo} hydration assessment using microwave measurements in athletes undergoing acute water loss during exercise. We developed and then tested a system for performing reliable microwave property estimation at the forearm. This system was used to measure hydration status in varsity wrestlers before and after a training session. A relationship between estimated permittivity and body weight change due to water loss was found, showing promise for the use of microwaves to assess hydration status. No significant relationship with attenuation was found. A novel method of assessing changes in hydration status is described, which may be of practical use for athletes in guiding fluid replacement during and after exercise.

lead under magnetic resonance imaging (MRI) exposure is investigated. The specific absorption rate (SAR) distributions and the temperature rises of the leads with different electrodes were assessed. It is shown that increasing the size of lead electrode reduces the SAR distribution and temperature rise near the electrode. Our results indicate that a larger electrode size will reduce the magnitudes of the lead transfer function, and subsequently reduces the heating effect near the electrode. Both numerical simulations and experimental measurements were performed to verify the effectiveness of a large electrode in mitigating the RF-induced heating.

Some studies have been conducted to solve this issue using either permanent magnets, static current sources or RF fields. The permanent magnet fails due to low power, and static current source requires relatively high power source. The RF field source requires high frequencies to get enough precision, which undergoes high attenuation in the body. At low frequency, when the distance between the source and the receiver array is shorter than the wavelength, the far field assumption fails for localization methods. Therefore, we propose a novel method of mapping the magnetic field vector in the near field region, with which wavelength independent localization is done. We did extensive MATLAB and CST Microwave simulations followed by practical experiments. The proposed method has achieved localization accuracy of less than 1 cm in Y-Z plane, 2 cm in depth (in X-axis) and the maximum orientation error remained 10° in 3-D.

Efficiently delivering power to implants is a challenge due to the loose coupling between the transmitter (TX) and receiver (RX) coils because of the various displacements (coaxial, lateral and angular). The coupling coefficient deteriorates significantly due to the displacements thus decreasing the overall power transfer efficiency (PTE) of the system. In this paper, we present an analysis and modeling of the effects of various displacements on the efficiency and the overall performance of a miniaturized WPT system designed for an optogenetic implant. To emulate the tissue media inside a human head, skin, skull and gray matter layers are theoretically modeled using dielectric properties and simulation models are developed using the Ansys High Frequency Structure Simulator (HFSS) software. The propagation loss and link efficiency are modeled and simulated as a function of various displacement combinations. To validate the theoretical and simulation models, the WPT system is characterized in various displacement conditions using chicken breast as the media. The measurement results also show a good agreement with the simulation results, thus providing an estimation for the misalignment tolerance range for given specifications. The efficiency performance analysis of the proposed WPT system for various worst-case scenarios also provides a preliminary model for designing a closed-loop wireless power delivery regulation scheme in the future.

The system was developed to meet the requirements of ISO/TS 10974:2018(E). A directional lumped element coupler, power splitter, an attenuator/isolator, low pass filter and high pass filter were designed and implemented as part of the network. The RF injection network was developed in both a compact version implemented in a single PCB and discrete PCB version for use in different situations. The performance of each designed component was simulated and compared to measurement results. As an application example, a neuromodulation system was tested using the developed RF injection network for conductive emission testing.

To enhance flexibility, various solutions exploiting different frequencies, antenna element, number and applicator geometries have been proposed in the literature. Among them, increasing the frequency and the number of radiating elements has shown effective for achieving more conformal heating. However, as each radiating element requires a power amplifier to control it, increasing the number of antennas considerably impacts the overall cost and complexity of the system. Accordingly, a procedure capable of selecting an optimal patient-specific subset of antennas from an oversized phased array applicator (with more antenna elements than available amplifiers) could help improving cost-effectiveness. In this study, we present an original approach which allows improving performance by adaptively selecting the optimal subset of antennas to be activated for a given (redundant) applicator and a given patient. The proposed approach takes inspiration from the compressive sensing theory by embedding the sparsity promotion paradigm into a treatment planning procedure which casts power-deposition as a constrained convex optimization. Performance were demonstrated for the case of head and neck hyperthermia, and benchmarked against the antenna selection procedure presently used in the clinical practice.

particularly in the near-surface subdermal regions, rather than tethered to the surface of the implantable device. A simple test bed for evaluating subdermal antennas during the design phase is needed. Objectives: The objectives of this work are to create a simple biological test bed for subdermal implantable antennas that includes the normal expected variation of the tissues Technology or Method: A layered model using pork products with skin, pork fat or lard, and pork loin or ground pork is used. Results: The ex vivo porcine tissues are similar to in vivo human tissues. Pork fat and loin have more variability than lard and ground pork but are more difficult to imbed subdermal antennas in. This model provides an easy to use platform for testing subdermal antennas in the lab. This test bed was developed for 433 MHz, the ISM band closest to the MedRadio band (402-405 MHz). Initial tests are demonstrated on a two-wire passive system for focusing power within the muscle region.

We hypothesize that unwanted radio-frequency (RF) energy couples to the metal-based mouth retractor during tonsillectomy and could be a possible cause of dysgeusia. To validate our hypothesis, in vitro studies are performed in a ground beef phantom with sensors measuring: a) the unwanted current coupled to the mouth retractor, and b) the unwanted temperature rise in the tissues that surround the retractor. The simulated surgery was performed using two separate surgical techniques: monopolar electrosurgery and coblation. Results indicate that unintentional RF energy transfer is indeed a real issue. During electrosurgery, peak-to-peak unwanted currents vary from 80.53 to 181.48 mA for typical power levels ranging from 10W to 30W. Tissue temperature unintentionally increases by 1.3°C and 1.8°C, respectively. Coblation indicates smaller coupling effects, with peak-to-peak currents on the mouth retractor capped at 12.33 mA for a typical 7 W setting. Concurrently, tissue temperature is reduced by 0.73°C, as attributed to the saline solution inherent to coblation. As the first of its kind, this study illuminates possible causes of post-tonsillectomy dysgeusia and intends to trigger future studies. The ultimate goal is safe and complication-free tonsillectomies

a) passive, b) highly tolerant to the DC offset voltage caused by the electrochemical reaction in the recording electrode, and c) complemented by an improved external interrogator design that exhibits reduced phase noise. As compared to previous wireless and batteryless brain implants, the proposed approach offers a remarkable improvement in sensitivity by 25 times. The proposed system consists of an external interrogator and a neuro-recorder implanted under the scalp. For operation, the interrogator sends a 2.4 GHz carrier signal to “turn on” the implant. This carrier self-biases a PNP Bipolar Junction Transistor (BJT) that enables matching to the recording electrode at frequency f_neuro in a batteryless manner. Concurrently, the recorded neuropotentials (at frequency f_neuro ) pass through a Schottky diode that allows them to mix with the carrier and generate a 4.8GHz±f_neuro modulated signal. The latter is then transmitted back to the interrogator for demodulation. To verify the implant’s operation, in-vitro measurements are presented. Measurement results demonstrate that emulated neuropotentials as low as 200μV_pp can be detected at a 33kΩ electrode impedance. As such, the proposed system presents a game-changing capability for a wide range of applications.

Current state-of-the-art implantable devices suffer from various limitations. Electromagnetic-based wireless devices are big in size because of their large antenna, which must be larger than onetenth of the wavelength of the operational frequency. Ultrasound-based wireless devices, in addition to their low data rate, have a massive loss in the skull and need an intermediate electromagnetic transceiver under the skull. Furthermore, almost all state-ofthe- art wireless devices use micro-electrodes for neuronal recording, which are not reliable in long-term monitoring applications because of direct contact between the tissue and metal electrodes. In this paper, we propose a novel wireless and ultra-compact implantable device termed NanoNeuroRFID. At the core of this device there is a Magnetoelectric (ME) antenna array. ME antennas are smart and ultra-miniaturized (<200μm diameter), and can perform multiple tasks: 1) They can harvest electromagnetic energy to power the NanoNeuroRFID system. Their limit of detection for RF magnetic fields is 40pT. 2) They can sense quasi-static neuronal magnetic fields as small as 200pT without a direct contact to the tissue, allowing a long lifetime and reliable neural recording. 3) They can communicate with an external transceiver, and their operational frequency could be 10s to 100s of MHz where tissue loss is small.

To prevent image-corrupting motion, the head needs to be immobilized which is currently achieved via invasive surgical headpost implants. In this work, an RF coil holder was integrated into the design of a subject-specfic helmet to place the coil in closest distance to the head for improved signal-to-noise ratio (SNR). Additive manufacturing was used to print the helmet based upon CT images of the subject. A single channel transmit/receive loop coil was designed using electromagnetic simulations loaded with a voxel-based monkey head model. The Rhesus macaque used in this study underwent behavioral training based on positive reinforcement before engaging in MR imaging. Imaging was performed using the helmet coil which was successful in immobilizing the macaque head in an awake, unanesthetized subject. Results showed improved SNR by approximately 28% compared to a loop coil used with an implanted head post, and minimal motion artifact in structural imaging. The non-invasive helmet coil eliminates the need for permanently implanting monkeys with a headpost, provides the necessary head immobilization, and allows the use of more subjects for neuroimaging studies.

Current systems require the patient to be transported to the imaging device which increases the time taken to apply treatments, allowing the patient’s condition to worsen. This paper proposes a portable microwave head imaging system that can easily be taken to the patient. The system utilises a novel combination of a software-defined radio and solid-state switching network to collect the imaging data, and operates in the frequency band of 0.85 – 2 GHz. It can capture input signals over a range of approximately 106 dB, which is suitable for detecting realistic brain injuries. The concept has been validated through experimental data collection and confocal image generation, and was capable of producing images in less than a minute. A simplified head phantom was developed for gathering the verification data and proved that the system was capable of locating targets with dielectric properties similar to brain tumours and bleeds. The presented design is highly accessible, achieved through being small, light, and inexpensive: key factors that could help save lives in time-critical medical emergencies.

is frequency independent and solely depends on achieving high excitation purity of the fundamental m=1 mode. This necessitates that the capacitive coupling introduced by the interconnecting lumped capacitors should maximize the separation between the resonance frequency of the fundamental mode and that of all other higher order modes. Alternatively, full-orthogonal excitation of the coil, if possible, would mitigate this design challenge, especially if high-Q operation cannot be guaranteed. In this contribution a field theoretical technique for the optimization of the capacitive coupling is introduced and applied to the birdcage configuration as representative of TEM coils. A fairly general analysis of these coils is also introduced and/or revisited, which underlies the proposed technique and offers simple analytic design equations. Simulation results are presented to validate the considered approach. The presented analysis deals with the homogeneously filled coils and therefore does not consider the B+1 inhomogeneities caused by the loading. The latter will be the subject of future publications.

The present device is designed in a manner that allows electrical microwave spectroscopy measurements in subsequent studies. We demonstrate the applicability of our device for electroporation-mediated molecule transfer of adherent cells in standard laboratory conditions. Application of electric pulses (6 V, 100μs, 1 Hz) to the cells induces successful delivery of a fluorescent probe (∼98%), while maintaining a high viability rate (∼100%). The comparable delivery rate to existing systems along with the improved viability suggest that our proposed electroporation system has great potential in the research fields, considering that our system is conceived to perform electrical microwave spectroscopy measurements after electroporation.

This technique can access important physical properties including ion mobility and hydration, which are directly applicable to biochemistry. One critical step towards quantifying these effects is to develop accurate models for the behavior of buffer solutions containing mobile ions. Here, we show that ions in buffer solutions produce a weak ion-pairing response. We used microfluidic channels integrated with coplanar waveguides in combination with a hybrid microwave calibration protocol to extract the broadband microwave admittance spectra of a standard TAE-Mg2+ buffer solution between 100 kHz and 67 GHz. To characterize the ion-pairing response, we fit the calibrated admittance data with two models: a conventional model without ion-pairing and with a water relaxation described by a ‘Cole-Cole’ function, to our alternative model that includes ion-pairing and a single Debye-type water relaxation. Including ion-pairing improved the goodness of fit across the entire frequency range. In the higher concentration buffer solution, we saw a reduction in the max systematic error in the fit residuals from 10% to less than 4%. The measurement and fitting techniques are widely applicable, providing critical information about the behavior of solvated ions.

By considering the duality property of electrical coupling and magnetic coupling, mixed coupling coils make the efficiency of wireless power transfer nearly insensitive to axial and angular misalignment. A complete, sophisticated equivalent circuit is proposed and demonstrates the features of the dual-resonant characteristic and lateral and angular misalignment tolerance. Comparing to traditional printed spiral coil systems, the proposed mixed coupling structure reduces decline rate of S21 by 26.4 % and 78.1 % at 35 mm axial misalignment and 90° angular misalignment at low resonant frequency, respectively. Moreover, at high resonant frequency, S21 only drops 16.5% with 60 mm lateral misalignment and is almost flat for 90° angular misalignment. Last but not least, data communication is also validated by transmitting a 200 kHz frequency shift keying signal, and the probability errors remain at acceptable level when misalignment occurs.

although slow data rates limit its range of applications. In this paper, we designed two coil antennas for wireless capsule endoscopic (WCE) medical image transmission, including a small-sized dual-band transmitting antenna that can be placed inside the WCE, and a corresponding receiving antenna that can be mounted on the abdomen of the human body. The proposed antennas can be fed by a battery-powered impulse radio (IR) transceiver that contains five signal peaks in the MHz band, and two signal peaks (38.5 and 57.6 MHz) are selected for antenna design to realize dual-band communication with higher data rates. Dimensions of the transmitting antenna and the receiving antenna are π ×(5.5)2 × 2mm3 and π ×(40)2 × 4.8mm3, respectively. The antenna distance that satisfies the WCE medical image transmission requirements is roughly estimated by the received powerfrom the transceiver. With the antenna distance of 50 mm, the attenuation is 33 and 47 dB at 38.5 and 57.6 MHz, respectively. With the antenna distance of 100 mm, the attenuation is 39 and 59 dB at 38.5 and 57.6 MHz, respectively. It can be estimated thatproposed antennas can realize a total data rate of 2.5 Mbps within 100 mm antenna distance if two antennas are aligned, or within 50 mm antenna distance if two antennas are misaligned to 60 mm.