[18F]FDG uptake in proximal muscles assessed by PET/CT reflects both global and local muscular inflammation and provides useful information in the management of patients with polymyositis/dermatomyositis

• Published in: Rheumatology (Oxford, England) England), 2013-07, Vol.52 (7), p.1271-1278
• Main Authors: Tanaka, Shigeru, Ikeda, Kei, Uchiyama, Katsuhiro, Iwamoto, Taro, Sanayama, Yoshie, Okubo, Ayako, Nakagomi, Daiki, Takahashi, Kentaro, Yokota, Masaya, Suto, Akira, Suzuki, Kotaro, Nakajima, Hiroshi
• Format: Article
• Language: English
• Subjects: Adult; Aged; Case-Control Studies; Dermatomyositis - diagnostic imaging; Diagnosis, Differential; Female; Fluorodeoxyglucose F18 - pharmacokinetics; Humans; Magnetic Resonance Imaging; Male; Medical Records; Middle Aged; Multimodal Imaging; Muscle Strength; Muscles - diagnostic imaging; Muscles - metabolism; Polymyositis - diagnostic imaging; Positron-Emission Tomography; Radiopharmaceuticals - pharmacokinetics; Retrospective Studies; Severity of Illness Index; Tomography, X-Ray Computed
• ISSN: 1462-0324; 1462-0332
• DOI: 10.1093/rheumatology/ket112

This study aimed to determine whether [(18)F]fluorodeoxyglucose-PET/CT ([(18)F]FDG-PET/CT) discriminates PM/DM from non-muscular diseases and also whether FDG uptake in proximal muscles reflects the activity and severity of muscular inflammation in PM/DM. Twenty treatment-naïve PM/DM patients who underwent [(18)F]FDG-PET/CT were retrospectively identified by reviewing medical records. The same number of age- and sex-matched control patients with non-muscular diseases were also identified. Standardized uptake value (SUV) was calculated for each of the seven proximal muscles. For patient-based assessment, mean proximal muscle SUV was calculated by averaging the SUVs for these proximal muscles bilaterally. Mean proximal muscle SUVs were significantly greater in PM/DM patients than in control patients (median 1.05 vs 0.69, P < 0.001). Mean proximal muscle SUVs significantly correlated with mean proximal manual muscle test scores (ρ = 0.49, P = 0.028) and serum levels of creatine kinase (ρ = 0.54, P = 0.015) and aldolase (ρ = 0.64, P = 0.002). Furthermore, SUVs in proximal muscles from which biopsy specimens were obtained significantly correlated with histological grade for inflammatory cell infiltration (ρ = 0.66, P = 0.002). Our results suggest that [(18)F]FDG-PET/CT is useful in the diagnosis of PM/DM when inflammation in proximal muscles is globally assessed with quantitative measurements. Our results also indicate that local FDG uptake in a proximal muscle reflects the activity of inflammation in the same muscle and provides useful information in determining the region for muscle biopsy.