The study evaluated a novel Fast-MRSI technique with tissue segmentation in determining metabolic alterations in NAWM and WM-lesions in MS compared to healthy controls. 3D-MPRAGE and 3D-Spiral-MRSI covering 70% of total brain on 16 RRMS and 9 HCs (aged 22-55yrs) were used. MRSI was processed using MATLAB and LCModel. Findings revealed that (NAA/tCr) in WM-lesions was significantly lower than NAWM-MS and HCs. Volumetric segmentation using SIENAX, revealed a significant WBV reduction and CSF increase in RRMS compared to HCs. Fast-MRSI may enhance diagnosis and clinical monitoring of MS patients, and is sensitive in diagnosing MS even in NAWM.