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.
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.
Impedance and Noise Characterizations of Utah and Microwire Electrode Arrays
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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.
A Comparison of Solid, Mesh, and Segmented Strip Dipoles in a Subdermal Environment
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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.
Magnetic Targeted Drug Delivery to the Human Eye Retina: an Optimization Methodology
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In this paper we demonstrate how a system of magnets can be optimized to provide the maximal magnitude of the magnetic field gradient with a prescribed orientation in an extended area (vitreous body). The presented methodology is applicable for all tasks involving a magnetic targeted drug delivery to biological objects.
