[¹⁸F]Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography In Diagnosis Of Polymyositis/Dermatomyositis

Objective:To investigate the diagnostic value of[¹⁸F]fluorodeoxyglucose positron emission tomography/computed tomography([¹⁸F]FDG-PET/CT)in polymyositis and dermatomyositis?PM/DM?.Methods:?1?A total of 22 patients?females:males=16:6?diagnosed with definite or probable PM/DM?the PM/DM group?who underwent[¹⁸F]FDG-PET/CT examinations prior to receiving an initial corticosteroid treatment at Tianjin Medical University General Hospital from October 2013 to August 2016 were included in the present study.The same number of age?and sex-matched individuals were included in the non-myopathy control group.Meanwhile,4 cases of Takayasu arteritis?TA group??female:male=3:1?and9 cases of polymyalgia rheumatica?PMR group??female:male=8:1?were compared with[18F]FDG-PET/CT.?2?Clinical data from PM/DM and non-myopathy control group,including sex,age,mean limb muscle strength,FDG standardized uptake value?SUV?of all patients,laboratory results,such as creatine kinase?CK?,creatine kinase isozyme?CK-MB?,aspartate aminotransferase?AST?and lactate dehydrogenase?LDH?were recorded.?3?SUV_max represented the FDG uptake of seven muscle groups,including the cervical,thoracic,lumbar,upper arm,shoulder,pelvic and thigh regions muscle groups.The average SUV_max of the bilateral muscles was calculated to represent the average FDG uptake of the proximal muscle of the individual patient,and it was referred to as the SUV_average.?4?Statistical analysis was performed using SPSS?version 20?and Graphpad Prism?version 5.0?software.They were used for t test,Mann-Whitney U test,Spearman's correlation coefficients,etc.And the difference was statistically significant at P<0.05.Receiver operating characteristic?ROC?curve analysis for the SUV_average of the proximal muscle was performed to discriminate between PM/DM and control groups.Results:?1?There were significant differences in FDG uptake value between the PM/DM group and the non-myopathy group,PMR group,TA group?P<0.001?.The muscle FDG uptake values of upper arm,thigh,cervical,thoracic and lumbar region muscle groups in myositis group were significantly different from those in PMR group?P<0.05?.But there was no significant difference in FDG uptake of shoulder and pelvic muscle groups between the two groups?P>0.05?.FDG uptake in thigh,cervical,thoracic and lumbar region muscle groups in PM/DM group was significantly different from that in TA group?P<0.05?,but there was no significant difference in FDG uptake in shoulder,pelvic and upper arm muscle groups between the two groups?P>0.05?.The FDG uptake of pelvic muscles in PMR group was significantly different from that in TA group?P<0.05?,but there was no significant difference in other parts?P>0.05?.?2?Serum CK level and SUV_average were negatively correlated with the mean proximal muscle strength?r=-0.493,P=0.038,r=-0.641,P=0.004?.The FDG uptake of the cervical,thoracic,lumbar,shoulder,pelvic regions muscle groups?r=-0.566,P=0.014;r=-0.622,P=0.006;r=-0.580,P=0.012;r=-0.619,P=0.006;r=-0.482,P=0.043?were all negatively correlated with the average level of the proximal muscle strength,except the FDG uptake value of the upper arm and thigh region muscle groups?r=-0.341,P=0.166;r=-0.466,P=0.051?.?3?The FDG uptake values in the cervical,thoracic,lumbar regions muscle groups were correlated with serum CK levels?r=0.489,P=0.021;r=0.457,P=0.032;r=0.503,P=0.017?.Thoracic,lumbar,upper arm regions muscle groups were correlated with serum CK-MB levels?r=0.424,P=0.049;r=0.442,P=0.039;r=0.488,P=0.021?.?4?ROC analysis for the SUV_average to discriminate between PM/DM and non-myopathy conditions revealed an area under the curve of 0.96?95%confidence interval,0.89?1.03?.The optimal cut-point of SUV_average was at 1.86 g/ml,giving the sensitivity of 95.5%and the specificity of95.5%.The Youden Index was 0.910.Conclusion:In conclusion,[¹⁸F]FDG-PET/CT has a diagnostic value for distinguishing PM/DM from non-myopathy.And PMR with similar clinical manifestations as PM/DM has distinct manifestations on PET/CT images.PMR is easy to be complicated with giant cell arteritis,which is different from the typical manifestation of giant cell arteritis on PET/CT images.PM/DM and TA have different FDG uptake value on PET/CT images.Furthermore,it may indicate novel and more suitable locations for muscle biopsy in patients with myositis.