Mapping Neurodegenerative Changes in Clinically Uncertain Parkinsonian Syndrome Patients Using Fast MR Spin TomogrAphy in Time‐Domain ( MR ‐ STAT ) Relaxometry at 3T

ABSTRACT Background MR Spin TomogrAphy in Time‐domain (MR‐STAT) enables accelerated multiparametric relaxometry (T 1 /T 2 ). Previous relaxometry studies predominantly compared Parkinson's disease patients with healthy controls (HC). The potential of relaxometry to distinguish neurodegenerative from non‐neurodegenerative parkinsonism in clinically uncertain parkinsonian syndrome (CUPS) patients is unclear. Purpose To investigate T 1 ‐/T 2 ‐differences between neurodegenerative and non‐neurodegenerative parkinsonism in CUPS patients. Study Type Prospective cross‐sectional study. Population 52 patients with neurodegenerative and 57 patients with non‐neurodegenerative parkinsonism, diagnosed via dopamine transporter single photon emission computed tomography (DAT SPECT) and neurologist review, and 10 HC. Fieldstrength/Sequence MP‐RAGE (magnetization‐prepared rapid acquisition with gradient‐echoes) and MR‐STAT, a 2D Cartesian‐encoded gradient‐spoiled gradient‐echo sequence with time‐varying flip‐angle preceded by a non‐selective inversion pulse, at 3T. Assessment Repeatability of T 1 ‐/T 2 ‐values was evaluated for cortical gray matter/cerebral white matter/thalamus/putamen/caudate nucleus/globus pallidus (GP) in HC. T 1 ‐ / T 2 ‐values of the parkinsonism groups were compared in the same regions per most/less affected hemisphere (MAH/LAH), determined by the putaminal uptake ratio on DAT SPECT. Statistical Tests Regional coefficients of variation (CoV) were computed to assess the repeatability of T 1 ‐/T 2 ‐values in HC. T‐tests ( α = 0.05) were used to compare T 1 −/T 2 ‐values between parkinsonism groups, and Cohen's D values were computed with bootstrapping to measure effect sizes with 95% confidence intervals (95% CI). Results CoVs ranged from 0.5% to 1.7% (T 1 ) to 1.5% to 2.7% (T 2 ). In the MAH, significant T 1 ‐differences were found in the thalamus (Cohen's D = 0.635, 95% CI = [0.251, 1.016]); GP (Cohen's D = 0.508, 95% CI = [0.129, 0.887]); internal GP (Cohen's D = 0.603, 95% CI = [0.220, 0.983]); external GP (Cohen's D = 0.411, 95% CI = [0.033, 0.787]); and centromedial putamen (Cohen's D = 0.447, 95% CI = [0.069, 0.824]). In the LAH, significant T 1 ‐differences were found in the thalamus (Cohen's D = 0.476, 95% CI = [0.097, 0.853]); GP (Cohen's D = 0.415, 95% CI = [0.037, 0.791]); anteromedial putamen (Cohen's D = 0.388, 95% CI = [0.011, 0.764]); and external GP (Cohen's D = 0.416, 95% CI = [0.038, 0.792]). T 2 ‐differences were non‐significant. Data Conclusion MR‐STAT showed high repeatability and showed potential to differentiate neurodegenerative from non‐neurodegenerative parkinsonism in CUPS patients. Evidence Level 1. Technical Efficacy 1.