Background 18F-FDG PET has been used in sarcoidosis for diagnosis and determination of the extent of the disease. However, assessing inflammatory lesions in cardiac sarcoidosis using 18F-FDG can be challenging because it accumulates physiologically in normal myocardium. Another radiotracer, 3′-deoxy-3′-18F-fluorothymidine (18F-FLT), has been investigated as a promising PET tracer for evaluating tumor proliferative activity. In contrast to 18F-FDG, 18F-FLT uptake in the normal myocardium is low. The purpose of this retrospective study was to compare the uptake of 18F-FLT and 18F-FDG in the evaluation of cardiac and extra-cardiac thoracic involvement in patients with newly diagnosed sarcoidosis.Data for 20 patients with newly diagnosed sarcoidosis were examined. 18F-FLT and 18F-FDG PET/CT studies had been performed at 1 h after each radiotracer injection. The patients had fasted for at least 18 h before 18F-FDG PET/CT but were given no special dietary instructions regarding the period before 18F-FLT PET/CT. Uptake of 18F-FLT and 18F-FDG was examined visually and semiquantitatively using maximal standardized uptake value (SUVmax).ResultsTwo patients had cardiac sarcoidosis, 7 had extra-cardiac thoracic sarcoidosis, and 11 had both cardiac and extra-cardiac thoracic sarcoidosis. On visual analysis for diagnosis of cardiac sarcoidosis, 4/20 18F-FDG scans were rated as inconclusive because the 18F-FDG pattern was diffuse, whereas no FLT scans were rated as inconclusive. The sensitivity of 18F-FDG PET/CT for detection of cardiac sarcoidosis was 85%; specificity, 100%; and accuracy, 90%. The corresponding values for 18F-FLT PET/CT were 92, 100, and 95%, respectively. Using semiquantitative analysis of cardiac sarcoidosis, the mean 18F-FDG SUVmax was significantly higher than the mean 18F-FLT SUVmax (P < 0.005). Both 18F-FDG and 18F-FLT PET/CT studies detected all 24 extra-cardiac lesions. Using semiquantitative analysis of extra-cardiac sarcoidosis, the mean 18F-FDG SUVmax was significantly higher than the mean 18F-FLT SUVmax (P < 0.001).ConclusionsThe results of this preliminary study suggest that 18F-FLT PET/CT can detect cardiac and extra-cardiac thoracic involvement in patients with newly diagnosed sarcoidosis as well as 18F-FDG PET/CT, although uptake of 18F-FLT in lesions was significantly lower than that of 18F-FDG. However, 18F-FLT PET/CT may be easier to perform since it requires neither prolonged fasting nor a special diet prior to imaging.

This study demonstrates a weak correlation between hypoxic volume measured by F-FMISO PET and expressions of HIF-1α and p53 in head and neck cancer.

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Purpose The efficiency of [18F]FDG PET/CT using volume-based indices was evaluated to assess the disease activity and response to therapy in patients with immunoglobulin G4-related disease (IgG4-RD). Methods A total of 17 patients with IgG4-RD were examined with [18F]FDG PET/CT before and during treatment. The lesion boundary was determined using a fixed threshold of standardized uptake value (SUV) ≥ 2.5. The highest maximum SUV (SUVmax) among all affected lesions was calculated for individual patients. We summed metabolic tumor volume (MTV) and total lesion glycolysis (TLG) of each affected lesion to generate a total MTV and total TLG. PET results were compared with those of serum IgG4 and soluble interleukin-2 receptor (sIL-2R) levels. Results The mean number of involved organs per patient was 3.8 as determined by [18F]FDG uptake. The number of involved organs, total MTV and total TLG were significantly correlated with IgG4 (P = 0.046, < 0.001, < 0.001, respectively) and sIL-2R (P < 0.001, = 0.031, 0.031, respectively). According to the clinical assessments for therapy response, all patients were classified as improved. The SUVmax, total MTV, and total TLG during therapy were all significantly lower than those before therapy (all P < 0.001). Conclusion [18F]FDG PET/CT is valuable for assessing the extent of multi-organ involvement before therapy and monitoring subsequent therapy in patients with IgG4-RD. [18F]FDG PET/CT using volumetric indices correlated with serum IgG4 and sIL-2R levels.

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FDG PET has been proposed to play a role in the diagnosis and therapy monitoring of sarcoidosis including cardiac involvement. However, assessing inflammatory lesions in cardiac sarcoidosis using FDG can be challenging because the FDG accumulates in normal myocardium. We report a case of sarcoidosis with cardiac involvement that underwent 3'-deoxy-3'-F-fluorothymidine (FLT) PET. FLT PET images demonstrated increased uptake in the lymph nodes and left ventricle. After immunosuppressive therapy, a follow-up PET scan showed disappearance of FLT uptake in the lymph nodes and left ventricle.