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

Abstract

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.

Gray matter T1‐w/T2‐w ratios are higher in Alzheimer's disease

“…Recent transcriptomic studies have further observed correlations of the T1-w/T2-w intensity in the cortex with expression of genes associated with cortical microcircuit specialization and myelin (Burt et al, 2018;Ritchie, Pantazatos, & French, 2018). In contrast, recently a study with Parkinson disease patients showed a higher T1-w/T2-w ratio in the substantia nigra pars compacta compared to controls (Du, Lewis, Sica, Kong, & Huang, 2018).…”

Application of T1-/T2-Weighted Ratio Mapping to Elucidate Intracortical Demyelination Process in the Alzheimer’s Disease Continuum

“…Future ratio mapping studies with the same isotropic spatial resolution of the T1W and T2W images is thus required. Third, although the cortical T1W/T2W ratio is a parsimonious marker for neurodegenerative disease, however, it is still clear that how accurately it represents myelin contents (Righart et al, 2017; Yasuno et al, 2017; Du et al, 2019). Thus, it is possible that some pathological changes (iron deposition, free water or fiber density), other than demyelination, may also change T1W/T2W ratio.…”

“…Also, some recent work proposed the enhanced sensitivity of detecting changes in intracortical signal intensity associated well with the disease, such as multiple sclerosis, Parkinson disease, and normal subject with amyloid accumulation (Granberg et al, 2017; Righart et al, 2017; Yasuno et al, 2017). Thus, given that the T1W/T2W ratio is a clinically easy-to-implement measure, researchers regarded the technique as a parsimonious intracortical myelin marker (Du et al, 2019; Li et al, 2019).…”

Diagnostic Ability of Radiofrequency Ultrasound in Parkinson’s Disease Compared to Conventional Transcranial Sonography and Magnetic Resonance Imaging

“…In a study by Minati et al [ 39 ], the SN area of the PD patients was significantly smaller compared to that of HC subjects while no difference was found in a study by Oikawa et al [ 40 ]. Recently the SN pars compacta T1w/T2w ratio value on 3T MRI was proposed as a novel, parsimonious in vivo biomarker for the PD [ 41 ].…”