Normal lung tissue response following hypofractionated radiation based on radiological parameters / 中华放射医学与防护杂志

ABSTRACT

Objective To study dose-response relationships of fractionated irradiation induced pulmonary fibrosis in mice according to radiological imaging changes of lung. Methods A total of 8-10 week old-female C57BL6 mice were randomized into different groups for whole thoracic irradiation. The prescribed doses were 0, 2. 0, 4. 0, 6. 0, 7. 0, 8. 5 Gy per fraction in a total of 5 fractions. CT imaging was performed at 24 weeks post irradiation. The averaged lung density and volume changes were obtained by the three-dimensional segmentation algorithm, and further analyzed in Boltzmann regression modeling. Results At the endpoint of 24 weeks, the dose-dependent pulmonary radiological alternations were revealed by coronal view of CT images. Translational analysis of fibrosis-related gene-signatures as well as histological collagen stainings further corroborated the radiological findings. According to Boltzmann modeling, the E50 of radiation-induced lung density changes was found to be (30.80±0.80)Gy (adjusted R2 =0.97);whereas the E50 for radiation-induced lung volume reduction was determined as ( 31. 31 ± 7. 07 ) Gy(adjusted R2=0. 92). Both outcomes indicated a remarkable enhancement of tolerance to normal lung tissues after exposure with 5-fraction versus single fraction scheme. Conclusions The radiation-induced lung density and volume changes depend not only on total dose, but also the number and dose of fractions.