Regional pulmonary function after irradiation of the canine lung: radionuclide evaluation.

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Abstract
The pulmonary effects of neutron and gamma irradiation were compared in a group of beagle dogs that were subjected to hemithorax irradiation with Co-60 gamma rays of 15-MeV neutrons. Integral Co-60 doses of 3000, 4500 or 6750 rad (30, 45 or 67.5 Gy [Grays]) and neutron doses of 1000, 1500 or 2250 rad (10, 15 or 22.5 Gy) were given on a [cancer] therapy-type schedule of 4 equal fractions per week for 6 wk. Serial Tc-99m-macroaggregated albumin perfusion, Tc-99m-Sn-phytate aerosol, and Xe-133 ventilation studies were performed before irradiation and at 3, 6, 9, 12, 18 and 24 mo. postexposure. Pulmonary damage was more severe and persistent with neutron than with gamma radiation, but the changes were dose-dependent for both types of radiation. The perfusion and radioaerosol imaging studies provided the best scintigraphic evidence of lung damage. Abnormalities in the Xe-133 studies were relatively minor and were more apparent on the single-breath than on the equilibrium or clearance studies. The scintigraphic studies provided evidence of radiation-induced ventilation perfusion inequalities with both types of radiation, but required several times less neutron radiation than gamma radiation to produce similar alterations in ventilation-perfusion relationships.