title: [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.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Allergy and Clinical Immunology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba 260-8670, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Tanaka
authors.forename: Kei
authors.initials: K
authors.lastname: Ikeda
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Uchiyama
authors.forename: Taro
authors.initials: T
authors.lastname: Iwamoto
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Sanayama
authors.forename: Ayako
authors.initials: A
authors.lastname: Okubo
authors.forename: Daiki
authors.initials: D
authors.lastname: Nakagomi
authors.forename: Kentaro
authors.initials: K
authors.lastname: Takahashi
authors.forename: Masaya
authors.initials: M
authors.lastname: Yokota
authors.forename: Akira
authors.initials: A
authors.lastname: Suto
authors.forename: Kotaro
authors.initials: K
authors.lastname: Suzuki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakajima
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003882:Dermatomyositis / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D064847:Multimodal Imaging; D053580:Muscle Strength; D009132:Muscles / Q000000981:diagnostic imaging / Q000378:metabolism*; D017285:Polymyositis / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: MRI; [18F]FDG-PET/CT; aldolase; creatine kinase; dermatomyositis; manual muscle test; muscle biopsy; polymyositis