Semi-quantitative gallium-67 lung scanning as a measure of the intensity of alveolitis in pulmonary sarcoidosis

Gallium-67 (⁶⁷Ga) lung scanning has been applied for some years in pulmonary sarcoidosis to assess the activity of the alveolitis. Interpreting the scans, however, is difficult due to the low uptake of ⁶⁷Ga in the disease process relative to background activity. In this study we have measured the mean parenchymal lung activity of ⁶⁷Ga and have compared the lung activity to that at three remote sites, the liver, the abdomen and the thigh. The results obtained were compared with the percentage of lymphocytes in broncho-alveolar lavage fluid. There was a very good correlation with the lung-to-thigh uptake measurements and a much poorer correlation with the lung-to-liver and the lung-to-abdomen measurements. It was observed that steroid therapy reduced dramatically the correlation between the broncho-alveolar lavage findings and the ⁶⁷Ga scan measurements. The results suggest that in patients not on steroid therapy, the ⁶⁷Ga lung-to-thigh measurements may be used, similarly to the broncho-alveolar lavage lymphocyte counts, to identify those with high-intensity alveolitis from those with low-intensity alveolitis.