Simulating, Modeling, and Sensing Variable Tissues for Wireless Implantable Medical Devices

Wirelessly powered implantable medical devices require efficient power transfer through biological tissue within safety constraints on energy absorption, often in the presence of environmental variability. Accurate modeling of the tissue medium is essential to evaluate the performance and sensitivit...

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Bibliographic Details
Published in:IEEE transactions on microwave theory and techniques 2018-07, Vol.66 (7), p.3547-3556
Main Authors: Bocan, Kara N., Mickle, Marlin H., Sejdic, Ervin
Format: Article
Language:English
Subjects:
Antenna measurements
Antennas
Change detection
Computer simulation
Conductivity
Dielectric measurement
Dielectrics
Dipole antennas
Electronic implants
Energy absorption
Environment models
Frequency analysis
Frequency measurement
Implantable medical devices
Input impedance
Medical devices
Medical electronics
Medical equipment
Phantoms
Power transfer
Properties (attributes)
Sensitivity analysis
tissue dielectric properties
tissue phantoms
Topology
Wireless communications
wireless power transfer
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Summary:Wirelessly powered implantable medical devices require efficient power transfer through biological tissue within safety constraints on energy absorption, often in the presence of environmental variability. Accurate modeling of the tissue medium is essential to evaluate the performance and sensitivity of transcutaneous powering systems. Here, we investigate loop and dipole antenna topologies in proximity to simulated tissue models and experimental phantoms, with emphasis on representing heterogeneous tissue with functionally equivalent simplified models, and modeling variability in tissue properties for sensitivity analyses. We first present a modified phantom formulation that provides greater control over frequency-dependent properties. We then show that homogeneous phantoms have limited use at representing input impedance and energy absorption at ultrahigh operating frequency by analyzing each antenna topology in proximity to layered or homogeneous tissue across frequency. We compare loop and dipole antenna topologies in terms of specific absorption rate and impedance, and show that frequency-dependent tissue behavior must be considered even at fixed operating frequencies. Finally, we discuss the dual utility of a transmitting antenna as a resonator to detect changes in tissue properties in addition to powering an implanted device.
ISSN:0018-9480
1557-9670
DOI:10.1109/TMTT.2018.2811497