Differentiating the Substantia Nigra and Ventral Tegmental Area in Early-stage Parkinson\u27s Disease Using Iron Imaging

Excessive midbrain iron accumulation in Parkinson’s Disease (PD) contributes to degeneration of the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA). Despite this understanding, there are no validated PD biomarkers. Magnetic resonance imaging (MRI) can localize and quantify brain iron for diagnosis of PD. Seventeen early-stage PD patients and twenty-one controls were scanned at 3T and 7T MRI. Using quantitative susceptibility mapping (QSM) and R2* relaxometry, we analyzed the average iron content in the SNc, substantia nigra pars reticulata (SNr), and VTA. QSM detected significantly higher SNc iron content in PD patients compared to controls at both field strengths. R2* only detected differences at 7T and showed lower sensitivity and diagnostic accuracy in diagnostic biomarker analyses. As predicted, the SNr and VTA were spared from iron accumulation. SNc iron overload in early-stage PD, best detected using QSM, could be the first diagnostic biomarker of PD following validation