Investigating spatial distribution of metabolite diffusion using diffusion-weighted chemical exchange saturation transfer

Motivation: Metabolite diffusion provides information on distinctive intracellular environments compared to water diffusion. Conventional diffusion-weighted MRS (DW-MRS) is a useful tool, but it lacks spatial information. Goal(s): We aimed to investigate the spatial distribution of metabolite diffusion in the human brain using diffusion-weighted CEST (DW-CEST). Approach: We performed DW-CEST on a phantom and five human subjects, and then compared ADCs of amide and water in brain tissues. Results: The amide-weighted ADC was 0.2 × 10-3 mm2/s and ~7.5 times smaller than water ADC in the brain. The gray matter / white matter ratio was ~0.8 for the amide-weighted ADC. Impact: Analysis on amide-weighted ADC showed comparable results to findings in DW-MRS studies with more spatial information. This suggests that DW-CEST has the potential to examine metabolite diffusion with better spatial resolution than DW-MRS.