Objective:To explore the diagnostic value of the absence of "swallow tail" appearance at 3.0 T susceptibility weighted imaging（SWI）in Parkinson’s disease（PD） and analyze the correlation between visualization of nigrosome-1 and clinical data of PD patients.Methods:We enrolled 50 PD patients and 57 sex-and age-matched non-PD patients from the Department of Neurology

The First Affiliated Hospital of Chongqing Medical University from September 2017 to November 2019.All subjects underwent 3.0 T SWI.Bilateral "swallow tail" appearance on the SWI images were evaluated by two clinicians blinded to the clinical data and diagnosis.The absence of "swallow tail" on one side was diagnosed as PD.Then

the sensitivity

specificity

accuracy and predictive values of the absence of "swallow tail" appearance in the diagnosis of PD were calculated.The correlation between visualization of nigrosome-1 and clinical data was also assessed.Results:Taking clinical diagnosis as the gold standard

and the absence of "swallow tail" on one side as the image diagnosis standard for PD

45 patients were diagnosed correctly.Inter-rater agreement was excellent（k=0.963

P=0.000）.The sensitivity

specificity

accuracy

positive predictive value and negative predictive value of discriminating PD patients from non-PD patients with the absence of "swallow tail" appearance were 90.0%

91.2%

90.7%

90.0% and 91.2%

respectively.The clinical symptoms of 44 PD patients were asymmetrical

among which 32 cases of nigrosome-1 visualization were asymmetrical.There was no significant difference between poorly visualized nigrosome-1 and clinical symptoms in PD patients（χ

2

=5.756

P=0.056）.Bilateral nigrosome-1 absence occurred in 11 PD patients

which were "total absence group"

and the rest of PD patients were “non-total absence group".There was a significant difference in the Hamilton Depression Rating Scale score between "total absence group" and "non-total absence group"（U=126.500

P=0.038）

while

there were no significant differences in the duration

modified Hoehn-Yahr stage

the Unifie Parkinson’s disease Rating Scale part Ⅲ score

the Mini Mental State Examination score and the Montreal Cognitive Assessment score between two groups（P=0.768

P=0.140

P=0.839

P=0.054

P=0.067）.Conclusion:The absence of "swallow tail" appearance at 3.0 T SWI has a high accuracy in the diagnosis of PD and the degree of absence may be related to the depression degree of PD patients

and has certain reference value for the diagnosis of PD.