Preliminary study for 18F-FDG PET/MR findings of autoimmune encephalitis
Objective:To investigate the image findings of autoimmune encephalitis (AE) based on 18F-fludeoxyglucose positron emission tomography/magnetic resonance (18F-FDG PET/MR) images and explore imaging markers that can improve the diagnostic efficacy of AE. Materials and Methods:Twenty-five patients with AE (AE group) and 11 healthy controls (HC) group were included in this study. All subjects were undergoing head 18F-FDG PET/MR scan. The areas of brain abnormal FDG uptake in AE group were obtained using statistical parametric mapping 12 (SPM12) processing package. The volume/total intracranial volume (volume/TIV) and average standardized uptake value ratio (SUVr) of brain areas were extracted using multimodal brain analysis software,and statistical analysis was performed to obtain the differences between the AE group and the HC group. Brain regions with significant differences in volume/TIV and SUVr were selected respectively to make receiver operating characteristic (ROC) curves,and the diagnostic efficiency of single parameters and their pairwise combinations were calculated. DeLong test was performed predict the best model. Calibration curve and decision curve were drawn to evaluate the accuracy of the prediction model. Permutation testing was employed to evaluate the statistical significance. Results:Analysis using SPM12 showed the abnormal FDG uptake areas in AE group increased in brain stem and cerebellum (P<0.001),and decreased in bilateral frontal,parietal and right occipital lobes (P<0.001). The results of brain structural analysis showed that the volume/TIV of insula,cingulate gyrus and talar gyrus decreased (P<0.05),SUVr decreased in the middle cingulate gyrus,parietal lobe,cuneus and lateral occipital gyrus (P<0.05). The volume/TIV of the left talar gyrus and the SUVr of the left middle cingulate gyrus were the two parameters with the most significant differences between the two groups. The ROC curve found that the combination of the volume/TIV of the left talar gyrus and the SUVr of the left middle cingulate gyrus had the highest diagnostic efficiency (area under the curve=0.964). DeLong test showed that there was a significant difference between the diagnostic efficacy of any two quantitative parameters combined with any single parameter (P<0.05). The calibration curve showed that the calibration of the diagnostic model was general,but the decision curve showed that patients could obtain relatively high net benefits within a certain risk threshold. Permutation test showed that there were significant differences in volume/TIV of the left calcarine gyrus and SUVr of the left middle cingulate gyrus between AE group and HC group. Conclusions:Multiple brain regions with FDG metabolism abnormalities and brain volume changes are found in 18F-FDG PET/MR of AE patients. The combination of the volume/TIV of the left talar gyrus and the SUVr of the left middle cingulate gyrus is a potential biomarker of diagnosing AE.
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