Quantitative Gallium Scanning in Pulmonary Sarcoidosis

Abstract

Pulmonary parenchymal involvement in sarcoidosis is due to noncaseating granuloma, fibrosis or both. To assess the granulomatous activity in pulmonary sarcoidosis, we performed gallium-67 citrate scans in 41 patients with sarcoidosis and in 13 non-sarcoid patients, who were free of pulmonary disease and served as controls. Gallium score, a measure of gallium accumulation in lung parenchyma, was obtained from the sum of activity indices (ratio of accumulated gallium activity over a chest quadrant and soft tissues of the mid-thigh) from each of the quadrants over the anterior and posterior aspects of the chest. The gallium score in patients with sarcoidosis was significantly higher than the gallium score in controls. The gallium scores in patients with sarcoidosis, with radiographically apparent pulmonary infiltrate were significantly higher than the scores in the patients with no radiographic evidence of pulmonary parenchymal involvement. The gallium scores in patients not receiving corticosteroids were significantly higher compared to patients who were receiving corticosteroids, and furthermore, the gallium scores fell significantly when corticosteroids were initiated. There was a significant correlation between serum angiotensin-converting enzyme (SACE) activity and gallium score. In 11 patients, 27 sequential gallium scans were performed and changes in gallium score correlated well with the changes in SACE activity and clinical assessment. These findings suggest that quantitative evaluation of gallium scans may be useful in assessing granulomatous activity of pulmonary sarcoidosis and following its response to therapy.