A fast eddy currents correction method based on field probe in portable low-field MRI

Motivation: Significant field inhomogeneity, more pronounced residual magnetism of supporting structure, and field drift over time of portable systems preclude accurate eddy currents measurement. Goal(s): To propose a fast eddy currents measurement and correction method based on field probe, tailored to the characteristics of portable low-field systems. Approach: A frequency correction term was introduced in the probe localization sequence. The testing gradients and fitting algorithms for the eddy currents measurement were optimized. The correction quality was evaluated in vivo with diffusion-weighted EPI. Results: The calibration took approximately 5min, reducing eddy currents to below 0.03% and effectively minimizing distortions in DW-EPI. Impact: Eddy currents in a samarium cobalt two-plate permanent magnet portable design can be reliably characterized in 5 minutes, which can be used to minimize impacts of field inhomogeneity, instability, and remanence, as well as improving clinical image quality (e.g., DWI).