[Detection of radiation-induced lung injury by 99mTc-DTPA aerosol inhalation method]

We prospectively monitored pulmonary 99mTc-DTPA (diethylene triamine penta acetate) clearance in patients who received chest radiation therapy, in order to determine whether this method allows us to predict the development of radiation pneumonitis. The rate constant of pulmonary 99mTc-DTPA clearance (k; %/min) was used to assess pulmonary epithelial damage. Fifteen nonsmoking patients who underwent radiation therapy were studied. The subjects included 4 patients who had already developed radiation pneumonitis at the time of study, and 11 in whom we prospectively observed 99mTc-DTPA clearance serially during the course of chest radiation therapy. In the 4 patients with pre-existing radiation pneumonitis, the mean k value obtained from the area with infiltration on the chest X-ray was significantly greater than that from the opposite lung (p < 0.02). In the prospective study, 3 out of 11 patients developed radiation pneumonitis. The mean k of the irradiated lung field in the 8 patients who did not develop radiation pneumonitis was unchanged. The mean k value obtained in the 3 patients who did develop radiation pneumonitis increased just before the onset, and further increased when the disease manifested clinically. We conclude that pulmonary 99mTc-DTPA clearance may be useful for predicting the development of radiation pneumonitis.