A Miniaturized Four-Element MIMO Antenna with EBG for Implantable Medical Devices
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A cross-shaped slot etched in the radiator, a branch extending on the conductor ground, and a pair of electromagnetic band gaps (EBGs) are integrated to achieve high isolation. The proposed MIMO antenna has the compact dimensions of 18.5 mm × 18.5 mm × 1.27 mm. The simula-tion in the three-layer phantom indicates that the impedance matching is good with a bandwidth of 18.64% (2.14-2.58 GHz) and a maximum gain of -15.18 dBi and the mutual coupling is reduced to less than -15.99 dB at the ISM band. An ex-vivo test was implemented in a fresh pork slab and the measurement results are well matched with the simulation ones. Health safety considerations and link budget are discussed to validate the antenna’s availability in biomedical telemetry, and the envelope correlation coefficient is computed, illustrating the high independence between antenna elements.
Magnetic and Thermal Characterization of Core-Shell Fe-oxide@SiO2Nanoparticles for Hyperthermia Applications
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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.
Computational Low Frequency Electromagnetic Dosimetry Based on Magnetic Field Measurements
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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.
Numerical Investigation Of Bone Tumer Hyperthermia Treatment Using Magnetic Scaffolds
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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.
Lead Electromagnetic Model to Evaluate RF-Induced Heating of a Coax Lead: A Numerical Case Study at 128 MHz
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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.
Optimized Design of Coils for Wireless Power Transfer in Implanted Medical Devices
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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.
