An efficient post-processing pipeline for improved phase-cycled 23Na Multi-Quantum Coherences MRI

Motivation: To develop an improved post-processing pipeline for robust phase-cycled Cartesian single (SQ) and triple quantum (TQ) sodium MRI of the in vivo human brain at 7T. Goal(s): Enhanced denoising and SQ/TQ signal separation capabilities to allow for substantially improved sodium SQ and TQ imaging. Approach: A k-space-based low-rank denoising technique exploiting structural redundancies is proposed. Additionally, enhanced signal separation of SQ and TQ via Dynamic Mode Decomposition (DMD) is presented. Results: The low-rank denoising approach produced high-quality images across all echo times, allowing up to 4-fold reduction in acquisition time. Interestingly, DMD separated SQ and TQ signals even under corrupted RF phase-cycling conditions. Impact: This pipeline's algorithms provide the sodium MRI community with powerful tools for signal separation and denoising, enabling clearer, more reliable SQ and TQ images even in challenging conditions, expanding applicability to clinical and experimental settings.