Abstract: Objectives: To assess the diagnostic performance of nigrosome-1 degeneration on imaging by quantitative susceptibility mapping (QSM) for Parkinson's Disease (PD). Methods: Two cohorts (Cohort Ⅰ and Cohort Ⅱ) of patients were analyzed retrospectively in this study. For Cohort Ⅰ, forty-four early idiopathic PD patients and 35 age-and gender- matched healthy controls were recruited,and a three-dimensional 8-echo GRE sequence was acquired on a 3T MR scanner. For Cohort Ⅱ, 43 patients with idiopathic PD and 48 healthy gender- and age-matched controls were recruited. For each subject, a three-dimensional 16-echo GRE sequence was scanned. Then QSM was reconstructed from GRE data for all the subjects. Two neuro-radiologists who were blind to the diagnosis evaluated separately the visibility of nigrosome-1 on quantitative susceptibility mapping. There were three presenting types: present, possible present, and absent. Then all the subjects were classified into three groups based on the visibility of nigrosome-1: normal group, PD group, and non-diagnostic group. Clinical diagnosis was taken as the gold standard, and diagnostic performance of QSM for PD was assessed. Results: For Cohort Ⅰ, 42/44 PD and 10/35 controls were correctly classified, while there were 42/43 PD and 29/48 controls correctly classified in Cohort Ⅱ. Sensitivity of nigrosome-1 degeneration on imaging by QSM for diagnosing PD was 95.5%, specificity was 28.6%, positive predictive value (PPV) was 65.6%, negative predictive value (NPV) was 100% and accuracy rate was 66.0% in Cohort Ⅰ. While for cohort Ⅱ, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy rate were 97.7%, 60.4%, 75.0%, 100 % and 78.0%, respectively. Conclusions: QSM imaging could be used as a diagnostic tool for PD, which is feasible to assess the nigrosome-1 degeneration with a high negative predictive value.

Key words: Parkinson′ disease, Nigrosome-1, Quantitative susceptibility mapping