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Abstract #4400

A passively cooled amplifier with high output current for multi-coil shim arrays

Hong En Chew1, Daniel Abraham1, Juan Rivas-Davila1, Kawin Setsompop1,2, and Jason Stockmann3,4
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Radiological Sciences Laboratory, Stanford University, Stanford, CA, United States, 3Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 4Harvard Medical School, Boston, MA, United States

Synopsis

Keywords: New Devices, New Trajectories & Spatial Encoding Methods, Multi-coil array

Motivation: Existing power amplifiers for multi-coil shim arrays suffice for B0 inhomogeneity mitigation but cannot support novel supplementary spatial encoding techniques requiring 10x higher bandwidth and coil current.

Goal(s): Our goal was to develop an MR-compatible shim amplifier capable of 50kHz bandwidth and 50A current without active cooling.

Approach: We select multi-MHz switching frequencies to avoid imaging bands and eliminate ferromagnetic inductor cores, and use a parallel-interleaved circuit topology to increase control bandwidth and distribute losses to facilitate thermal management.

Results: We demonstrate feasibility of 50A passively-cooled operation and high open-loop bandwidth. Acquired images have minor artifacts which may be mitigated through additional filtering.

Impact: An MR-compatible power amplifier for multi-coil shim arrays with 10x the bandwidth and output current without active cooling will provide the MR community with a key hardware component to bridge the gap between multi-coil imaging technique development and clinical realization.

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