Magnetic resonance T1w/T2w ratio: A parsimonious marker for Parkinson disease

Objective Newer magnetic resonance imaging (MRI) techniques have shown promise in capturing early Parkinson disease (PD)‐related changes in the substantia nigra pars compacta (SNc), the key pathological loci. Their translational value, however, is hindered by technical complexity and inconsistent results. Methods A novel yet simple MRI contrast, the T1w/T2w ratio, was used to study 76 PD patients and 70 controls. The T1w/T2w ratio maps were analyzed using both voxel‐based and region‐of‐interest approaches in normalized space. The sensitivity and specificity of the SNc T1w/T2w ratio in discriminating between PD and controls also were assessed. In addition, its diagnostic performance was tested in a subgroup of PD patients with disease duration ≤2 years (PDE). A second independent cohort of 73 PD patients and 49 controls was used for validation. Results Compared to controls, PD patients showed a higher T1w/T2w ratio in both the right (cluster size = 164mm3, p