Factors causing radiation pneumonitis and the CT findings in lung cancer cases

By using chest CT, we investigated the factors and CT findings of radiation pneumonitis. In 70 cases which were treated by radiotherapy with a total dose of over 30 Gy and followed up over 2 months after radiotherapy, radiation pneumonitis was detected in 49 cases (70.0%). There was no significant correlation between the occurrence of radiation pneumonitis and the size of the radiation field. Combined chemotherapy was not related to the occurrence of radiation pneumonitis. However, there was a higher incidence of radiation pneumonitis in cases with over 4 courses of chemotherapy. In 25 cases with diffuse lung disease, radiation pneumonitis was detected in 22 cases (88.0%) and extended beyond the radiation field in 12 cases. Diffuse lung disease had significant influence on the occurrence of radiation pneumonitis. We found various CT findings of radiation pneumonitis, including ground glass appearance, patchy, reticular, honeycomb and subpleural increased density. We investigated the clinical usefulness of 3-D imaging using helical scan CT. 3-D CT imaging was useful to observe the extent of radiation pneumonitis and to follow changes in CT findings. (author)