Radiation-induced pulmonary change: CT findings.

Four patterns of radiation change in the lung were identified in 53 computed tomographic studies of 41 patients at various times following completion of radiotherapy. (a) The homogeneous pattern shows slight increase in density uniformly involving irradiated portions of lung and is believed to represent a diffuse, minimal radiation pneumonitis. (b) Patchy consolidation is contained within irradiated lung but does not conform to the shape of the radiation field. It is analogous to radiation pneumonitis seen on chest radiographs. (c) Discrete consolidation that conforms to the radiation portal but does not uniformly involve it has several possible analogues. (d) Solid consolidation totally involves the irradiated lung and contains ectatic bronchi within it. This finding is analogous to radiation fibrosis. The temporal sequence and dose relationships of these appearances are discussed and related to those seen with conventional studies.