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Acousto-optic-based time domain electric field sensor for magnetic resonance imaging applications
Yusuf S Yaras1, Lee W Bradley1, D Korel Yildirim2
1Georgia Institute of Technology, G.W. Woodruff School of Mechanical Engineering, Atlanta, Georgia, United States.
Optical Engineering (Redondo Beach, Calif.)
|August 2, 2024
Summary
A new acousto-optic (AO) electric field sensor offers precise time-domain measurements during MRI scans. This MR-compatible sensor achieves high sensitivity and directivity, enabling accurate monitoring of electric fields in critical medical applications.
Area of Science:
- Biomedical Engineering
- Electromagnetics
- Sensor Technology
Background:
- Accurate electric field measurement is crucial for Magnetic Resonance Imaging (MRI) safety and efficacy.
- Existing sensors face challenges with MRI compatibility and sensitivity.
- Need for robust, real-time electric field monitoring during interventional procedures within MRI environments.
Purpose of the Study:
- To develop and characterize an acousto-optic (AO) based electric field sensor for time-domain measurements compatible with MRI.
- To enhance sensor sensitivity by matching mechanical resonance to MRI operating frequencies.
- To evaluate the sensor's performance for detecting electric fields in complex MRI scenarios, including around implants.
Main Methods:
- Fabrication of a fully MR-compatible sensor using a phase-shifted fiber Bragg grating coupled to a piezoelectric transducer.
- Matching the piezoelectric transducer's mechanical resonance to common MRI frequencies to boost sensitivity.
- Characterization of sensor sensitivity, minimum detectable electric field, directivity, and dynamic range.
- In-situ testing within MRI studies to assess performance around a reference implant.
Main Results:
- Achieved a sensor sensitivity of 1.27 mV/V/m and a minimum detectable electric field of 4.4 mV/m/√Hz.
- Measured 18 dB orthogonal component rejection for directivity and a dynamic range of 117 dB/Hz.
- Successfully detected local hot spots around an implant with high signal-to-noise ratio during MRI studies.
- Demonstrated comparable or superior performance against existing commercial MRI-compatible electric field sensors.
Conclusions:
- The developed AO electric field sensor is a viable tool for precise, real-time electric field measurements within MRI.
- Its high sensitivity, directivity, and dynamic range support accurate monitoring, even in the presence of implants.
- The sensor's small size and flexible fiber optic link enable potential use as an MRI dosimeter during interventional procedures.
