A dynamic shim approach for correcting eddy current effects in diffusion-prepared MRI acquisition using a multi-coil AC/DC shim-array

TL;DR

This paper introduces a dynamic shim method using a 46-channel AC/DC shim array to correct eddy current effects in diffusion MRI, enabling high b-value imaging without SNR loss from stabilizers.

Contribution

A novel dynamic B0 shimming approach with a multi-coil AC/DC shim array that corrects eddy current phase errors in diffusion MRI without magnitude stabilizers.

Findings

Enables high-quality diffusion imaging at b-values up to 2000 s/mm2.

Successfully corrects eddy current effects in phantom and in vivo experiments.

Preserves full SNR in diffusion-prepared MRI without using stabilizers.

Abstract

Purpose: We developed a dynamic B0 shimming approach using a 46-channel AC/DC shim array to correct phase errors caused by eddy currents from diffusion-encoding gradients in diffusion-prepared MRI, enabling high b-value imaging without the SNR loss from the use of magnitude stabilizer. Methods: A 46-channel AC/DC shim array and corresponding amplifier system were built. Spin echo prescans with and without diffusion preparation were then used to rapidly measure eddy current induced phase differences. These phase maps were used as targets in an optimization framework to compute compensatory shim currents for multi-shot 3D diffusion-prepared acquisitions. Results: The proposed method allows flexible use of the AC/DC shim array to correct undesirable eddy current effects in diffusion-prepared MRI. Phantom and in vivo experiments demonstrate whole-brain, cardiac-gated, multi-shot 3D diffusion-prepared imaging without the use of magnitude stabilizers. The approach enables preservation of full SNR while achieving reliable diffusion encoding at b-values up to 2000 s/mm2. Conclusions: This work demonstrates a new strategy for applying an AC/DC shim array to compensate for eddy current induced phase errors in diffusion-prepared MRI. By eliminating the need for magnitude stabilizer, it enables efficient high-quality diffusion imaging with full signal sensitivity retained.