Wireless, Battery-Free, and Fully Implantable Micro-Coil System for 7 T Brain MRI
IEEE Transactions on Biomedical Circuits and Systems
|June 3, 2022
Summary
This study introduces a novel microcoil antenna for wireless power and data transmission in implantable magnetic resonance imaging (MRI) systems. The antenna operates at multiple frequencies, enabling efficient power delivery and data telemetry for enhanced medical imaging.
Area of Science:
- Biomedical Engineering
- Electromagnetics
- Medical Imaging
Background:
- Concurrent data and power transmission is crucial for implantable wireless systems, particularly for magnetic resonance imaging (MRI).
- Existing solutions face challenges in efficiency and biocompatibility for in-vivo applications.
Purpose of the Study:
- To present a self-tuned open interior microcoil (MC) antenna for concurrent data and power transmission in implantable wireless MRI.
- To evaluate the antenna's performance across multiple operating bands for different functionalities.
Main Methods:
- Design and fabrication of a flexible polyimide-based microcoil antenna with specific dimensions to minimize blood flow obstruction.
- Integration of the microcoil with a rectifier and micro-LED for wireless power demonstration.
- Analysis of power transfer efficiency (PTE) through rotation and varying distances.
- Specific absorption rate (SAR) analysis for human brain safety compliance.
- S-parameter measurements using saline and blood vessel models to simulate realistic head conditions.
Main Results:
- The microcoil antenna demonstrated three operating bands (300 MHz for 7T MRI, 400 MHz for data telemetry, 920 MHz for power transmission).
- Successful wireless activation of a micro-LED was achieved, demonstrating power transmission capabilities.
- A power transfer efficiency of -27.1 dB was recorded at a distance of 30 mm.
- Simulated and measured s-parameters showed reasonable correlation in realistic head models.
- Specific absorption rate analysis indicated compliance with safety guidelines.
Conclusions:
- The proposed self-tuned open interior microcoil antenna offers a viable solution for concurrent data and power transmission in implantable wireless MRI.
- The multi-band capability and demonstrated wireless power transfer highlight its potential for advanced biomedical applications.
- The design addresses critical factors like biocompatibility and safety, paving the way for future implantable devices.
