Open-Source, High-Efficiency, Easily-Reconfigurable Switch-mode Current Driver for B0 Shimming and Local Field Control

Motivation: Multi-coil arrays have demonstrated utility for higher-order B0 shimming, spatial encoding, and local field control. However, existing amplifiers used to drive these coils typically trade off efficiency and imaging noise. Goal(s): Demonstrate a proof-of-concept amplifier with both high efficiency and low imaging noise, while being easily reconfigurable for different loads impedances. Approach: A switch-mode amplifier with highly-integrated power stages, 6th-order LC filtering, and fully-digital control was developed. Its thermal performance, dynamic performance, and impact on imaging noise was tested. Results: Our amplifier demonstrated heatsink-free 10ADC drive capability, <25μs step response rise-times with multiple loads, acceptable disturbance rejection, all while minimally impacting image quality. Impact: We have demonstrated an open-source, proof-of-concept amplifier achieving power efficiencies of switch-mode designs while maintaining imaging noise levels akin to linear designs. Such an amplifier unblocks novel spatial encoding techniques and local field control applications. Development is active and ongoing.