Fig. 3: Receiver operating characteristic (ROC) curves demonstrating comparisons of magnetic susceptibility among groups in each region of interest.

The diagnostic performance of the magnetic susceptibility value was quantified by the area under the curve (AUC). a, b QSM and χ_para values for the PD-RBD⁺ and HC groups. c, d QSM and χ_para values for the PD-RBD^- and HC groups. PD-RBD⁺ Parkinson’s disease with secondary rapid eye movement sleep behavior disorder, PD-RBD^- Parkinson’s disease without rapid eye movement sleep behavior disorder, QSM quantitative susceptibility mapping (value), χ_para paramagnetic susceptibility mapping (value), SNpc_R right substantia nigra pars compacta, SNpc_L left substantia nigra pars compacta, Multi-Index joint indicator of bilateral substantia nigra pars compacta, AUC area under the curve.