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In situ measurement of tissue impedance using an inductive coupling interface circuit
Hung-Wei Chiu1, Jia-min Chuang, Chien-Chi Lu
1Department of Electronic Engineering and Graduate Institute of Computer and Communication Engineering, National Taipei University of Technology, Taipei 10608, Taiwan. hwchiu@ntut.edu.tw
IEEE Transactions on Biomedical Circuits and Systems
|July 16, 2013
Summary
This study introduces inductive coupling impedance measurement (ICIM) for contactless nerve impedance assessment during pulsed radiofrequency (PRF) stimulation. Lower excitation voltages prevent DRG nonlinear responses, crucial for pain relief effectiveness.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Medical Devices
Background:
- Pulsed radiofrequency (PRF) stimulation is used for pain relief.
- Accurate measurement of nerve impedance is crucial for understanding PRF effectiveness.
- Current methods for nerve impedance measurement can be invasive or lack precision.
Purpose of the Study:
- To propose and validate a contactless method, inductive coupling impedance measurement (ICIM), for assessing dorsal root ganglion (DRG) nerve impedance during PRF stimulation.
- To develop a calibration procedure and circuit model for accurate ICIM measurements.
- To investigate the relationship between DRG impedance and PRF stimulation effectiveness in pain relief.
Main Methods:
- Developed an ICIM system for contactless impedance measurement with a low excitation voltage (7 mV).
- Implemented a calibration procedure using a 50-Ω reference resistor.
- Utilized a de-embedding technique to create an equivalent transformer circuit model for the ICIM.
- Conducted in situ and in vivo acute measurements of DRG impedance.
- Performed an in vivo animal experiment correlating DRG impedance with PRF pain relief efficacy.
Main Results:
- The ICIM system demonstrated good accuracy for acute DRG impedance measurements.
- A batteryless PRF stimulator integrated with ICIM was successfully developed.
- In vivo experiments showed a decline in PRF pain relief effectiveness as nerve impedance increased.
- Excitation voltages below 25 mV were found to prevent nonlinear DRG responses.
Conclusions:
- ICIM is a viable contactless technique for measuring DRG impedance during PRF stimulation.
- Nerve impedance is a critical factor influencing the efficacy of PRF for pain management.
- Low excitation voltages are essential for accurate impedance measurements and to avoid altering DRG physiological responses.
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