The density of mouse lung in vivo following X irradiation.

The lungs of mice were irradiated with single X radiation doses of 5 to 14 Gy. Six weeks after irradiation, computed tomographic (CT) scans of the mice were performed at two-week intervals. Beyond 14 weeks after irradiation, the animals were scanned at 1-week intervals. The mice irradiated to 5 and 7 Gy exhibited no change in lung density, in comparison with the unirradiated lungs of control mice up to times of 48 weeks. The mice irradiated to doses of greater than 10 Gy exhibited marked increases in lung density at 15 weeks after irradiation. Increases in density followed a similar time course for these doses, but the magnitude of the density increase was dependent on the radiation dose. An interpretation of these findings in terms of radiation pneumonitis is presented, and the possibility of using CT to monitor lung density in radiotherapy patients is discussed.