The application value of quantitative susceptibility mapping in evaluating substantia nigra "swallow tail sign" in the diagnosis of Parkinson's disease

Abstract

Objective To explore the diagnostic value of substantia nigra "swallow tail sign" in identifying Parkinson's disease (PD) as visualized by quantitative susceptibility mapping (QSM).  Methods A total of 76 PD patients and 47 sex- and age-matched normal controls were retrospectively enrolled in the study. They were performed MRI examination, including three-dimensional high-resolution MRI (3D-HRMRI), diffusion tensor imaging (DTI), resting-state functional magnetic resonance imaging (rs-fMRI) and enhanced gradient echo T2*-weighted angiography (ESWAN). ESWAN images were used to calculate the map of QSM. A radiologist blinded to the clinical results read the images and determined the existence of "swallow tail sign" in the dorsolateral part of substantia nigra pars compacta. Then the sensitivity, specificity and accuracy of PD diagnosis according to the disappearing of "swallow tail sign" was calculated.  Results With high contrast of magnetic susceptibility, QSM can display substantia nigra clearly, so as to evaluate the existence or disappering of "swallow tail sign". Among 76 PD patients, 73 (96.05%) showed the absence of unilateral or bilateral "swallow tail sign". Among 47 normal subjects, 28 (59.57%) showed the absence of unilateral or bilateral "swallow tail sign". There was significant difference between 2 groups (χ² = 26.311, P = 0.000). The sensitivity, specificity and accuracy of discriminating PD patients from normal subjects with "swallow tail sign" were 96.05%, 40.43% and 74.80% respectively.  Conclusions Although "swallow tail sign" can be detected sensitively by QSM in PD patients, the specificity of discrimination between PD patients and normal controls is relatively low. The utility of high-resolution MRI and precise quantitative analysis may be helpful to improve its diagnostic value in PD patients.

DOI: 10.3969/j.issn.1672-6731.2018.04.004