Deep-inspiration breath-hold (18)F-FDG-PET/CT is useful for assessment of connective tissue disease associated interstitial pneumonia.

Objective: To examine clinical utility of F-18-flurodeoxyglucose (FDG)-positron emission tomography (PET)/CT for assessment of interstitial lung disease (ILD) in patients with connective tissue diseases (CTDs).Methods: A total of 69 F-18-FDG PET/CT scans were conducted under deep inspiratory breath hold (DIBH) conditions in 45 CTD patients with ILD, including 16 dermatomyositis/polymyositis, nine systemic scleroderma and seven rheumatoid arthritis. Intensity and distribution of F-18-FDG signals in PET/CT were determined by standardized uptake value (SUVmax) and visual score in 18 regions, respectively. ILD was defined as active when immunosuppressive therapy was initiated or intensified.Results: Both SUVmax and visual score were higher in active phase (n=32) than inactive phase (n=37) (both p<0.05), regardless of the underlying CTD and plain CT findings. The both parameters reduced after initiating or intensifying treatment in the follow-up study of 17 active patients except two died patients who showed increased visual score. Another two died patients showed high visual score (15 and 6/18, respectively). Changing ratio of visual score, but not SUVmax was correlated with KL-6 (r(2)=0.38, p<0.05) and CRP (r(2)=0.52, p<0.05).Conclusion: The DIBH F-18-FDG PET/CT procedure sensitively illustrates active ILD lesions in CTD and the extended signal distribution is associated with unfavorable clinical outcome.