Multi-Shot Multi-Echo xSPEN technique for permanent gradient portable low-field MRI systems

Motivation: In single-sided/built-in gradient portable low-field MRI systems, imaging suffers from severe distortions due to significant field inhomogeneity and gradient nonlinearity. Goal(s): Develop a multi-shot multi-echo cross-term Spatiotemporal Encoding (MSME xSPEN) sequence in a constant gradient low-field environment. Approach: The MSME xSPEN technique, by designing a image-domain multi-shot technique, achieves multiple contrasts and higher acquisition efficiency. It was evaluated against traditional xSPEN using a 110mT portable MRI system that emulates a constant gradient low-field environment. Results: MSME xSPEN exhibited in-plane resilience to field inhomogeneities and demonstrated higher SNRs with multiple contrasts compared with traditional xSPEN. Impact: MSME xSPEN provides a novel image-domain distortionless acquisition approach for highly inhomogeneous low-field MRI systems. This technique will improve image quality and inspire new acquistion strategies in portable single-sided or built-in gradient systems.