Guanidino Chemical Exchange Saturation Transfer MRI (GuanCEST) signal intensity reductions as a surrogate biomarker for Parkinson’s Disease

Motivation: Creatine (Cr) is a potential biomarker for Parkinson's disease (PD), yet the relationship between PD severity and Cr levels in subcortical brain regions remains unclear. Goal(s): To investigate the relationship between Cr-weighted CEST signals in subcortical regions and PD severity. Approach: Guanidino chemical exchange saturation transfer (GuanCEST) MRI is a Cr-weighted metric. Reductions of GuanCEST intensity in thalamic subregions in PD patients versus healthy controls were correlated with disease duration and severity. Results: Greater reduction in GuanCEST levels was observed with increasing PD severity, particularly in thalamic subregions. This is tentatively interpreted to be due to lower Cr levels in these regions. Impact: Reductions in Cr-weighted GuanCEST MRI signal in several sensitive brain regions correlated to Parkinson's severity, based on motor system scores, suggesting a potential biomarker to help identify responsive cohorts for targeted treatments and trial design.