Comparative evaluation of 18F-FDG PET and 67Ga scintigraphy in patients with sarcoidosis.

67Ga scintigraphy has been used for years in sarcoidosis for diagnosis and the extent of the disease. However, little information is available on the comparison of 18F-FDG PET and 67Ga scintigraphy in the assessment of sarcoidosis. The purpose of this study was to compare the uptake of 18F-FDG and 67Ga in the evaluation of pulmonary and extrapulmonary involvement in patients with sarcoidosis. METHODS: Eighteen patients with sarcoidosis were examined. 18F-FDG PET was performed at 1 h after injection of 185-200 MBq 18F-FDG. 67Ga whole-body planar and thoracic SPECT images were acquired 72 h after injection of 111 MBq 67Ga. We evaluated 18F-FDG and 67Ga uptake visually and semiquantitatively using standardized uptake values (SUVs) and the ratio of lesion to normal lumbar spine (L/N ratio), respectively. The presence of pulmonary and extrapulmonary lesions was evaluated histopathologically or by the radiologic findings. RESULTS: Five patients had only pulmonary lesions, 12 patients had both pulmonary and extrapulmonary lesions, and 1 patient had only an extrapulmonary lesion. Both 67Ga planar and SPECT images detected 17 of 21 (81%) clinically observed pulmonary sites. The mean +/- SD of the L/N ratio was 1.97 +/- 1.09. 67Ga planar images detected 15 of 31 (48%) clinically observed extrapulmonary sites. The mean +/- SD of the L/N ratio was 1.17 +/- 0.33. 18F-FDG PET detected all 21 (100%) clinically observed pulmonary sites. The mean +/- SD of the SUV was 7.40 +/- 2.48. 18F-FDG PET detected 28 of 31 (90%) clinically observed extrapulmonary sites. The mean +/- SD of the SUV was 5.90 +/- 2.75. CONCLUSION: The results of this clinical study suggest that 18F-FDG PET can detect pulmonary lesions to a similar degree as 67Ga scintigraphy. However, 18F-FDG PET appears to be more accurate and contributes to a better evaluation of extrapulmonary involvement in sarcoidosis patients.