Improving Temporal Resolution in fMRS: Assessing Reduced Phase Cycling in semi-LASER MRS

Motivation: Phase cycling is important for removal of ghosts but limits temporal resolution of functional MRS (fMRS). Goal(s): To investigate the effects of reducing phase cycle steps in semi-LASER fMRS to enhance temporal resolution while maintaining data integrity. Approach: Static 1H-MRS on healthy volunteers using semi-LASER with varying amounts of phase cycle steps. Spectra were fit with FSL-MRS to extract glutamate peak areas and CRLBs. Results: Cycling only the phase of the excitation pulse resulted in Glu peak areas within 17% of the default 32-step acquisition and similarly low CRLBs. Temporal resolution in fMRS could be improved by only phase cycling the excitation pulse. Impact: This study demonstrates the impact of reducing phase cycles in MRS and provides guidance on how to reduce phase cycles to enhance temporal resolution and improve the feasibility of fMRS in clinical and research settings.