Macrophage accumulation of inhaled gallium-67 citrate in normal lungs

Injected 67Ga has been used extensively to monitor inflammatory processes in the peripheral lung. We hypothesized that inhaled 67Ga may be useful in marking early airway inflammation in smokers. Eight nonsmokers and eight smokers breathed a 67Ga aerosol and imaging was performed immediately and 24 and 96 hr later. Approximately two-thirds of the initial dose remained in the lungs at 24 hr in both groups and no difference was seen between the groups. Only a very slight decrease was seen in both groups at 96 hr suggesting the gallium becomes bound to lung tissue or to cells not rapidly removed from the lungs. Autoradiography was performed on tissue from two smoke-exposed guinea pigs and two human patients undergoing resection surgery who breathed the gallium aerosol 24 hr prior to tissue removal. Silver grain accumulations were seen only over macrophages. We conclude that macrophage associated accumulation of 67Ga occurs in healthy lungs, and that it is not feasible to use aerosolized gallium to assess airway inflammation in smokers.