Clinical value of 18F-FDG PET/CT in assessing muscular inflammation of dermatomyositis

Abstract

Objective To analyze the imaging characteristics and diagnostic value of 18F-fluorodeoxyglucose (FDG) PET/CT in muscular inflammation in dermatomyositis (DM), as well as the relationship between maximum standardized uptake value (SUVmax) and activity of muscular inflammation. Methods From July 2013 to November 2016, 17 hospitalized DM patients (8 males, 9 females, age range: 35-78 years) who underwent 18F-FDG PET/CT were retrospectively reviewed, including 13 typical DM (TDM) and 4 amyopathic DM (ADM). Seventeen healthy volunteers (8 males, 9 females, age range: 35-78 years) in the same period were enrolled as the control group. The proximal limb muscles of whole body were divided into 7 areas, and the SUVmax of each was measured and recorded. Two-sample t test, one-way analysis of variance, Dunnett-t test and Spearman correlation analysis were used to analyze data. Results Five TDM cases showed diffuse increased FDG uptake in global muscles; 8 TDM cases showed increased FDG uptake in local muscles, mainly in the shoulder and hip. The FDG uptake by muscles of 4 ADM patients was similar with that of controls. The SUVmax was lower and lower in the order of shoulder and back muscles, hip muscles, thoracic vertebra muscles, cervical vertebra muscles, biceps, proximal quadriceps and lumbar vertebra muscles in DM group. The muscle SUVmax of DM, TDM, ADM and the controls were 1.92±0.86, 2.14±0.85, 1.19±0.44 and 0.93±0.26, respectively (F=69.50, P<0.001). Muscle SUVmax of DM group was higher than that of controls, muscle SUVmax of TDM was higher than that of ADM, and muscle SUVmax of ADM was higher than that of controls (t values: 4.102-11.970, all P<0.05). Muscle SUVmax of 9 DM patients with interstitial lung disease (ILD) was lower than that of patients without ILD (1.73±0.09 vs 2.13±0.13; t=5.857, P<0.001). Muscle SUVmax of DM was positive correlated with serum levels of creatine kinase (CK) and creatine kinase isoenzyme composed by M and B subunits (CK-MB) (rs values: 0.814 and 0.751, both P<0.001). Conclusion 18F-FDG PET/CT is helpful to detect muscular inflammation of DM and it can reflect the activity and severity with SUVmax, and meanwhile evaluate the condition of ILD associated with DM. Key words: Dermatomyositis; Positron-emission tomography; Tomography, X-ray computed; Deoxyglucose