Magnetic resonance T1w/T2w ratio: A parsimonious marker for Parkinson disease. Issue 1 (19th December 2018) - Du, Guangwei
Abstract : 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 = 164mm 3, p < 0.0001) and left (cluster size = 213mm 3, p < 0.0001) midbrain that was located ventrolateral to the red nucleus and corresponded to the SNc. The region‐of‐interest approach confirmed the group difference in the SNc T1w/T2w ratio between PD and controls ( p < 0.0001). The SNc T1w/T2w ratio had high sensitivity (0.908) and specificity (0.80) to separate PD and controls (area under the curve [AUC] = 0.926), even for PDE patients (AUC = 0.901, sensitivity = 0.857, specificity = 0.857). These results were validated in the second cohort. Interpretation: The T1w/T2w ratio can detect PD‐related changes in the SNc and may be used as a novel, parsimonious in vivo biomarker for the disease, particularly for early stage patients, with high translational value for clinical practice and research.ANN NEUROL 2019;85:96–104.