A new approach for multislice spatiotemporal encoding MRI in a portable low-field system.

Abstract

Spatiotemporal encoding (SPEN) MRI offers a unique alternative to address image distortion problems in echo planar acquisition-based techniques, at portable low-field systems that lack multiple receiver coils. However, existing 2-π multislice SPEN schemes fail to keep consistent SNRs and contrasts with different numbers of slice settings. This work proposes a new multislice SPEN scheme (SPENms) to achieve stable quality imaging in portable low-field MRI systems. The proposed SPENms includes the insertion of one selective π pulse and one non-selective π pulse, closely arranged together, before the frequency-swept π pulse in the original 2D SPEN sequence. Theoretical simulations and experiments on phantoms and human brains were conducted to validate its SNR and contrast performances under different parameters compared to the existing 2-π multislice SPEN scheme. Both simulations and experiments demonstrate the consistent image quality of SPENms with different scanning parameters and targets, as well as good distortion resistance and scan efficiency. Robust diffusion weighted multislice SPEN images of diagnostic value were also highlighted. SPENms provides a robust fast echo planar acquisition approach to obtain multislice 2D images with less distortions, consistent SNRs and contrasts at portable low-field MRI systems.