This study quantitatively assessed changes in lung perfusion after thoracic radiotherapy and analyzed its correlation with radiation dose. Researchers examined 34 lung cancer patients using chest CT scans before, 3 months after, and 12 months after radiotherapy for pulmonary vasculature analysis. The results showed that the ipsilateral lung (where the tumor was located) received a mean radiation dose of 22.9 Gy, and higher radiation exposure was significantly associated with reductions in total blood volume (TBV), small vessel blood volume (BV5, BV10), and subpleural vessel count and density (p<0.05). Specifically, TBV decreased by 0.852% per 1-Gy increase in radiation dose (p=0.044). In contrast, the contralateral lung showed relatively minor changes. Aview (Coreline Soft) was used for 3D reconstruction and quantitative pulmonary vasculature analysis, enabling precise assessment of lung perfusion changes. This study contributes to understanding radiation-induced vascular damage and perfusion loss in lung cancer patients.