Prognostic value of dual‐time‐point ¹⁸F‐fluorodeoxyglucose positron emission tomography in patients with pulmonary sarcoidosis

BACKGROUND AND OBJECTIVE: The value of dual-time- point (18) F-FDG PET was investigated to predict the prognosis of patients with pulmonary sarcoidosis. METHODS: Twenty-one patients with pulmonary sarcoidosis underwent (18) F-FDG PET examinations at two time points: an early scan at 60min and a delayed scan at 180min after injection of (18) F-FDG. Standardized uptake values (SUVs) at the two time points and the retention index (RI-SUV) calculated from these were evaluated. To evaluate disease progression, all patients underwent chest CT 1year after (18) F-FDG PET. Using these results, the accuracy of (18) F-FDG PET parameters and (67) Ga uptake for predicting disease persistence were compared, and the correlations between those parameters and serum markers were assessed. RESULTS: RI-SUV was significantly higher in patients with increased or unchanged pulmonary lesions at follow-up CT (persistent group; 21.3±9.6%) than in patients with improved pulmonary lesions (improved group; -9.2±28.6%, P=0.0075). The diagnostic accuracy of RI-SUV in the persistent group was significantly greater than that of early SUV or (67) Ga uptake, and serum soluble IL-2 receptor showed a significant correlation with RI-SUV. CONCLUSIONS: RI-SUV showed better diagnostic accuracy compared with early SUV or (67) Ga uptake, in patients with persistent lung involvement at 1year. It may be a useful measure of persistent inflammation in patients with pulmonary sarcoidosis.