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#### Feature Article

###### Cancer Occurrences in Laboratory Rats from Exposure to RF and Microwave Radiation

James C. Lin

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###### Review on Advanced Short-Range Multimode Continuous-Wave Radar Architectures for Healthcare Applications

José-María Muñoz-Ferreras, Zhengyu Peng, Roberto Gómez-GarcíaChangzhi Li

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##### A Comparison of Solid, Mesh, and Segmented Strip Dipoles in a Subdermal Environment

Andrew Chrysler, Kaitlin L. Hall, Cynthia M. Furse.

Abstract:The objective of this paper is to evaluate the feasibility of subdermal (tattoo) antennas in the fat layer, which use the low conductivity of the fat to electrically insulate a dipole antenna.

Current research in polymer engineering is moving towards materials that can be injected as fluids that turn to soft, conductive solids at body temperature; this paper anticipates using these materials for tattooed subdermal antennas. Simulations and measurements were used to evaluate the current distributions that are shared between antennas with and without voids (solid, segmented, and meshed strip dipole antennas) and surrounding body tissues to give insight into the performance of subdermal antennas and their coupling to the body. The body tissues play a strong role in adapting the current distributions. The high dielectric materials electrically shorten the antenna. The high conductivity muscle conducts or guides current into the body. Any voids in the antennas (e.g. gaps between segments or holes in the mesh) are particularly important, as they generate stronger coupling to the tissues. The feasibility of using fat as insulation is verified in simulation and confirmed with measurement.
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##### Impedance and Noise Characterizations of Utah and Microwire Electrode Arrays

Avery Tye Gardner, Hunter S. Stratham, David J. Warren, Ross M. Walker.

Abstract:This work presents an in-depth noise and impedance characterization of two of the most widely used microelectrode arrays

(the Utah Electrode Array and the TDT Microwire Array) and provides quantitative analysis of how properties change when implanted in rodent cortex. Custom low-noise circuits and de-embedding methods were designed to acquire $\mathrm{nV} /\sqrt {\mathrm{Hz}}$ noise power spectral densities from high impedance electrodes. A total of 80 electrodes were implanted across five rats and measured under deep anesthesia, demonstrating a 1.5x to 3x increase in noise and 2.25x to 9x in impedance compared to in vitro measurements. Low frequency biological noise was also observed and studied through post mortem measurements. These results are informative for designing neural interfacing systems for both neuroscience and medical applications.
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##### Optimized Design of Coils for Wireless Power Transfer in Implanted Medical Devices

Yufeng Zeng, Dongyuan Qiu, Xiangtian Meng, Bo Zhang, Sai Chun Tang.

Abstract:Implanted medical device (IMD) wirelessly powered by magnetic resonant coupling has attracted wide attention recently.

In this study, an optimized 2-coil wireless power transfer (WPT) system is adopted to eliminate the requirement of embedded battery in an IMD. In order to deliver stable power to implantable devices with wide coverage range and high efficiency, coil optimization is investigated, including the consideration of the coil structure, pitch and number of turns. By using finite element analysis (FEA), both the transmitting and receiving coils have been optimized at 6.78MHz. A 200 mm $\times$ 300 mm rounded rectangular transmitting coil and a novel double-layer circular receiving coil with an outer diameter of 24 mm were developed, and the transmitting coil was segmented by multiple resonant capacitors to significantly reduce the coil voltage to a safe level. Experiment results show that stable power transfer efficiency over 40% can be achieved at a distance of 5 cm with the optimized transmitting and receiving coils.
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##### Lead Electromagnetic Model to Evaluate RF-Induced Heating of a Coax Lead: A Numerical Case Study at 128 MHz

Mikhail Kozlov, Wolfgang Kainz

Abstract:One of the major components of magnetic resonance imaging safety for patients with an active implantable medical device is the evaluation of in vivo radio frequency induced heating of tissue near a lead electrode, which can result in tissue damage.

This numerical case study investigated a number of the recommendations, assumptions, and requirements of Clause 8 of the technical specification ISO/TS10974. For this, a lead electromagnetic model (LEM) of a generic coax lead at 128 MHz was evaluated with 3D electromagnetic and thermal co-simulations of the entire lead. Two sets of 120 incident electric fields with different profiles were generated in a homogenous medium using the electrical properties of blood by an array of four antennas. Substantial dependence of power deposition and temperature profiles around lead electrodes on the incident electric field did not reduce the quotient of the variances of the fitted LEM values, observed values of power deposition, and the net temperature increase, above background, with the presence of the generic coax lead. The power injection approach based only on the comparison of the temperature increase in the medium along the lead tip electrode axis can result in substantial underestimation or overestimation of power deposition around lead electrodes.
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##### Numerical Investigation Of Bone Tumer Hyperthermia Treatment Using Magnetic Scaffolds

Alessandro Fanti, Matteo Bruno Bruno Lodi, Giuliano Vacca, Giuseppe Mazzarella.

Abstract:This works claims to define, via numerical simulations, magnetic field parameters to perform an effective in situ bone tumor hyperthermia treatment using magnetic scaffolds.

A Cole-Cole model to describe the frequency response of the magnetic susceptibility of nanoparticles embedded in novel magnetic biomaterials is explored. The heating phenomena is investigated considering both the ischemic and inflamed state of the fracture gap at the bone/implants interface. Both Osteosarcoma and Fibrosarcoma tumors are analyzed. Magnetic hydroxyapatite and poly-ε-caprolactone scaffolds are investigated. From the thermal analysis, it is found that the fracture behaves as a resistance to heat conduction, therefore strength and frequency of external magnetic field has to be tuned to perform the treatment taking the fracture status into account. Moreover, numerical experiments indicate that low perfused Fibrosarcoma can be treated using moderate-strength field, whereas more intense external fields are required to treat strongly vascularized Osteosarcoma without damaging healthy bone tissue. Magnetic hydroxyapatite stands out to be the most performant and versatile material to treat both tumors. These simulations can be regarded as a starting point to analyze possible clinical use of magnetic scaffolds for in situ bone hyperthermia.
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##### Computational Low Frequency Electromagnetic Dosimetry Based on Magnetic Field Measurements

Alessandro Arduino, Oriano Bottauscio, Mario Chiampi, Ilkka Laakso, Luca Zilberti.

Abstract:This paper compares different experimental-computational strategies for the estimation of electric fields induced in human bodies by low frequency magnetic sources

characterized by a set of magnetic field measurements. The analysis is carried out by considering three alternative procedures, which use, as the first input, the distribution of the magnetic flux density in a volume containing the studied body or on a surface surrounding the sources. The comparison is performed on a realistic model problem, related to transcranial magnetic stimulation (TMS), in which numerically simulated “virtual measurements” are employed. The comparative analysis is developed in terms of both result accuracy and robustness against noisy input due to unavoidable experimental uncertainties. It results that by performing the measurements on a surface surrounding the sources, a significant reduction of the experimental burden is found with respect to the case of volume measurements, without affecting neither the accuracy nor the robustness of the procedure. In particular, when whole body electric field evaluation must be carried out, the advantage of surface measurements with respect to volume ones becomes significant. Moreover, a preferable scheme obtained as hybridization of previously proposed strategies is identified. Besides the adoption of a TMS model problem in the comparison procedure, the achieved result can be extended to any low frequency dosimetric assessment where the magnetic sources are difficult to model or not completely known.
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##### Magnetic and Thermal Characterization of Core-Shell Fe-oxide@SiO2 Nanoparticles for Hyperthermia Applications

Gabriele Barrera, Marco Coïsson, Federica Celegato, Elena Sonia Olivetti, Luca Martino, Ivana Miletto, Paola Tiberto.

Abstract:Nanoparticles for magnetic hyperthermia pose significant constraints in their size and composition to ensure cellular uptake and biocompatibility,

while still requiring significant hysteresis losses exploitable at electromagnetic field values and intensities not exceeding safety limits for the human body. In this paper, core-shell Fe-oxide@SiO $_2$ nanoparticles have been synthesized and their size has been controlled so that the blocked-to-superparamagnetic transition is close to room temperature. Their size remains therefore as small as possible, while still displaying significant hysteresis losses in dynamic conditions (electromagnetic fields up to 48 kA/m at 100 kHz). Static loops measured by vibrating sample magnetometry and dynamic loops measured by a custom B-H tracer are used to characterize the particles magnetic properties, as well as a custom-built, fully modelled, hyperthermia setup. The specific absorption rate is obtained either from static and dynamic loops areas, and from direct hyperthermia measurements. Dynamic loops are shown to be a good estimator of specific absorption rate values.
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##### A Miniaturized Four-Element MIMO Antenna with EBG for Implantable Medical Devices

Yi Fan, JinHong Huang, TianHai Chang, Xiongying Liu.

Abstract:A miniaturized four-element multiple-input-multiple-output (MIMO) antenna operating in the band of In-dustrial, Scientific, and Medical (ISM) 2.4-2.48 GHz, is investigated to supply sufficient transmission rate and fight against multipath fading.