Resonance Frequency Retuning System for Flexible MRI Coils

Magnetic resonance imaging plays a vital role in advancing medical diagnostic capabilities. Flexible and stretchable RF coils provide better adaptability to patient anatomy and offers the potential for superior MRI image quality. However, these coils are prone to resonance frequency shifts caused by changes in inductance when stretched, compressed, or bent, which can degrade the signal-to-noise ratio and overall image quality. To address this challenge, we present a non-magnetic system capable of detecting and retuning the coil's resonance frequency to the Larmor frequency. The system operates inside the MRI bore at frequencies of up to 600 MHz, with retuning accuracy up to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 0.04 \text{MHz}$</tex> at 3T. During phantom scans with a stretched coil, our system demonstrated up to a 30% improvement in SNR. This system represents a significant step toward integrating automatic tuning and matching circuits in future MRI applications, ensuring reliable performance across diverse coil configurations, patient anatomies, and field strengths.