“…Given that a recent study showed that the signal intensity in neuromelanin‐sensitive MRI (NM‐MRI) is correlated with NM concentration (Cassidy et al, 2019), an analysis using NM‐MRI may help determine which area is most impacted in early‐stage IPD. In previous studies, in order to determine abnormality in the SNpc, a contrast ratio (CR) was measured in the two or three subdivisions of the SNpc (Fabbri et al, 2017; Ohtsuka et al, 2014; Prasad et al, 2018; Wang et al, 2018; Xiang et al, 2017), or a whole or regional volume of the SN was calculated using a specific threshold (Castellanos et al, 2015; Isaias et al, 2016; Kashihara, Shinya, & Higaki, 2011; Kuya et al, 2018; Le Berre et al, 2019; Matsusue et al, 2019; Ogisu et al, 2013; Okuzumi et al, 2019; Pyatigorskaya et al, 2018; Reimao, Pita Lobo, Neutel, Correia Guedes, et al, 2015; Reimao, Pita Lobo, Neutel, Guedes, et al, 2015; Schwarz et al, 2011; Schwarz, Xing, Tomar, Bajaj, & Auer, 2017; Takahashi et al, 2018; Taniguchi et al, 2018; Vitali et al, 2020; Zupan, Suput, Pirtosek, & Vovk, 2019), and the values were compared between IPD patients and healthy subjects. These results failed to specify the most affected region of the SNpc.…”