Sequence-agnostic FOV Positioning in Pulseq for Cross-Platform Imaging

Motivation: Traditional off-center MRI scanning methods involve explicit calculation of frequency and phase offsets during MR pulse sequence implementation, which may interfere with phase cycles of specific sequences and can introduce artifacts if not handled carefully. Goal(s): Implement a general Field of View (FOV) positioning algorithm compatible with arbitrary MR pulse sequences and MRI systems. Approach: We implemented a Bloch-equation-based algorithm within Pulseq to calculate phase and frequency offsets for accurate FOV shifts for arbitrary sequences and combine this with explicit gradient rotations. Results: Results show precise FOV positioning with minimal artifacts for several example sequences. Impact: The universal FOV positioning method implemented in Pulseq supports off-center imaging on various MRI systems, including those that are currently hardware limited in this regard. Among those are in particular experimental ultra-low field systems and non-proton imaging on whole-body MRI.