title: Whole-body FDG-PET/CT on rheumatoid arthritis of large joints.
abstract: OBJECTIVE
  Fluorodeoxyglucose (FDG) uptake in joint lesions in patients with rheumatoid arthritis (RA) reportedly represents the degree of synovial inflammation. Most previous studies have focused on small joints, and the application of whole-body positron emission tomography (PET) combined with computed tomography (CT) (PET/CT) for the evaluation of inflammatory activity in large joints has not been well studied.
  
  
  METHODS
  Eighteen patients with RA underwent FDG-PET/CT. FDG uptake in the knee, hip, carpal, wrist, elbow, shoulder, and atlanto-axial joint (total of 13 joints) and in the axillary lymph nodes was evaluated by calculating the maximum standardized uptake value (SUV(max)) and the visual uptake scores as follows: 0, no uptake; 1, slight uptake; 2, moderate uptake (same as in liver); 3, higher than in liver; 4, highest uptake. The number of painful/swollen joints, the white blood cell (WBC) count, and the C-reactive protein (CRP) level were also evaluated.
  
  
  RESULTS
  Whole-body FDG-PET/CT delineated large-joint lesions in patients with RA, and the metabolic activity of inflammation was accurately overlaid on the joint anatomy. The total FDG score for all 13 joints was significantly correlated with the CRP level (r = 0.653, p < 0.01, n = 18). The total SUV(max) and the CRP level were weakly, but not significantly, correlated (r = 0.377, p > 0.05). The WBC count was not correlated with any other parameter. The mean number of joints per patient with an FDG uptake score of 2 or more was significantly larger than the mean number of painful/swollen joints (6.2 +/- 3.3 vs. 3.1 +/- 2.7, n = 18, p < 0.01) and both parameters were strongly correlated (r = 0.588, p < 0.01, n = 18). Also, FDG uptake score and SUV of painful/swollen joints were significantly higher than these of not painful/swollen joints. FDG uptake was significantly different from patients of remission and patients of active arthritis. Uptake in the atlanto-axial joint was observed in five (mostly asymptomatic) patients (5/18, 28%), and the uptake score was significantly correlated with the total FDG score (r = 0.669, p < 0.01, n = 18). The axillary lymph nodes score was correlated with the arm joints score.
  
  
  CONCLUSIONS
  FDG-PET/CT represents the inflammatory activity in large joints in patients with RA accurately and sensitively and may be helpful for early evaluations of the extent of RA throughout the whole body including high risk lesion of atlanto-axial joint. Furthermore, the visual FDG uptake score may be useful for evaluating arthritis in large joints.
authors.affiliation: Department of Radiology, Division of Nuclear Medicine, International Medical Center of Japan Toyama Hospital, Tokyo, Japan. kkubota@cpost.plala.or.jp
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kubota
authors.forename: Kimiteru
authors.initials: K
authors.lastname: Ito
authors.forename: Miyako
authors.initials: M
authors.lastname: Morooka
authors.forename: Takuya
authors.initials: T
authors.lastname: Mitsumoto
authors.forename: Kyoko
authors.initials: K
authors.lastname: Kurihara
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamashita
authors.forename: Yuko
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Akio
authors.initials: A
authors.lastname: Mimori
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging* / Q000378:metabolism; D001175:Arthrography; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000000981:diagnostic imaging / Q000378:metabolism; D007596:Joints / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging
chemical_list: D015415:Biomarkers; D019788:Fluorodeoxyglucose F18