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

I love it when something simple yet really effective...

We are in an era when imaging and laboratory investigations are ever more complex and expensive, and here we have a wonderful study showing that a very simple, cheap and easily-obtained ratio from an MRI scan can be used to accurately diagnose Parkinson's. Importantly the researchers were not satisfied with showing this once and went on to demonstrate similarly impressive results in a separate patient and control group.

Now it is important for other researchers to replicate these findings and to work how far back they go... could it be used to detect people in the pre-symptomatic/pre-diagnostic phase??

Du G, Lewis MM, Sica C, Kong L, Huang X

Ann Neurol 2018 Nov 8

https://onlinelibrary.wiley.com/doi/abs/10.1002/ana.25376

Objective

Newer MRI techniques have shown promise in capturing early Parkinson's 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 SN 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 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=164 mm3, p<0.0001) and left (cluster size=213 mm3, 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 (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 SN and may be used as a novel, parsimonious in vivo biomarker for the disease, particularly early stage patients, with high translational value for clinical practice and research.