An evaluation method for encoding capability of rSEM with non-linear gradients and its application to angle selection

Motivation: For non-linear encoding technology for portable MRI, the evaluation of encoding capability is by checking the image quality, which is time-consuming and hard to integrate into an optimization process. Goal(s): Here, we aim to propose a fast evaluation method for the encoding capability of rotational spatial encoding magnetic field (rSEM). Approach: The filling factor of local k-spaces is proposed to evaluate the encoding capability of an rSEM with non-linear gradients. Results: The proposed evaluation of encoding capability is fast and agrees with the resultant image quality. It was used for angle selections to accelerate imaging, showing improved image quality experimentally. Impact: A rapid evaluation method for the encoding capability of rSEMs with non-linear gradients is validated using simulation and experimental data. It allows fast evaluations of SEMs without checking the image quality in a design process, which accelerate the optimization.