Post-irradiation lung density changes measured by computerized tomography.

To investigate the possibility of using computerized tomography (CT) as a prognostic indicator of radiation induced lung toxicity, a series of CT scans were performed on one patient. These scans suggested an increase in lung density at day 73 after an upper half body irradiation. Because of the difficulty in lung density follow-up in patients irradiated for palliation, further studies were performed with LAF1 mice. Serial scans were taken on three groups of mice: (1) control group, (2) irradiated to 11.0 Gy and (3) irradiated to 14.0 Gy. Lung density increases between 10 and 15% were observed in the two irradiated groups. The time course was dependent on dose with an earlier onset for the high dose group (14 weeks) than for the low dose group (24 weeks). These density changes were observed only a few weeks prior to the death of the animals, indicating that small animals such as mice will not likely be useful for assessing CT scanning as an early predictor of radiation damage to lungs.