The ROC analyses provided areas under the curve of 0.66 for whole SNc volume, 0.61 for Cvol, and 0.70 for CNR between HCs and LRRK2, 0.79 for Vol, 0.75 for Cvol, and 0.78 for CNR between HCs and PD, and 0.66 for Vol, 0.61 for Cvol, and 0.61 for CNR between LRRK2 and PD (Fig. 2). The gene discussed is LRRK2; the disease is Parkinson disease.