Paramagnetic susceptibility mapping better quantifies brain iron content in Parkinson's disease with RBD.

The specific mechanism underlying the effect of changes in brain iron content on the development of RBD secondary to PD remains unclear. 27 PD patients with secondary RBD (PD-RBD+), 24 PD patients without RBD (PD-RBD-), and 32 healthy controls (HCs) were included. Paramagnetic susceptibility was isolated using APART-QSM. The QSM and paramagnetic susceptibility (χpara) values of the whole brain and subcortical nuclei were compared among groups. The diagnostic performance was evaluated using receiver operating characteristic curve analysis. Compared with PD-RBD-, PD-RBD+ patients presented a lower χpara value in the left middle temporal gyrus. The QSM and χpara values of bilateral substantia nigra pars compacta (SNpc) were increased in both groups. The diagnostic performance of the combined index of χpara values was superior to that of the QSM value or the single index. In conclusion, paramagnetic susceptibility isolated from QSM is helpful for iron quantification and exploring the mechanism of PD-RBD+.