Department of Bioimaging and Radiological Sciences, Catholic University, A. Gemelli Hospital, Largo A. Gemelli 8, 00168 Rome, Italy.
Radiographics. 2011 May-Jun;31(3):771-89. doi: 10.1148/rg.313105096.
Three-dimensional (3D) conformal radiation therapy (CRT) and stereotactic body radiation therapy (SBRT) are designed to deliver the maximum therapeutic radiation dose to the tumor, allowing improved local disease control, while minimizing irradiation of surrounding normal structures. The complex configuration of the multiple beams that deliver the radiation dose to the tumor in 3D CRT and SBRT produces patterns of lung injury that differ in location and extent from those seen after conventional radiation therapy. Radiation-induced changes in lung tissue after 3D CRT and SBRT occur within the radiation portals. The imaging appearance of irradiated tissues varies according to the time elapsed after the completion of therapy, with acute-phase changes of radiation pneumonitis represented by ground-glass opacities and consolidation and with late-phase changes of radiation fibrosis manifesting as volume loss, consolidation, and traction bronchiectasis. Knowledge of treatment timelines and radiation field locations, as well as familiarity with the full spectrum of possible radiation-induced lung injuries after 3D CRT and SBRT, is important to correctly interpret the abnormalities that may be seen at computed tomography (CT). Differential diagnoses in this context might include infections, lymphangitic carcinomatosis, local recurrence of malignancy, and radiation-induced tumors. The integration of morphologic information obtained at CT with metabolic information obtained at positron emission tomography is helpful in distinguishing radiation-induced parenchymal abnormalities from residual, recurrent, and new cancers. Thus, multimodality follow-up imaging may lead to substantial changes in disease management.
三维（3D）适形放射治疗（CRT）和立体定向体部放射治疗（SBRT）旨在将最大治疗剂量的辐射传递到肿瘤部位，从而提高局部疾病控制率，同时使周围正常结构的照射最小化。3D CRT 和 SBRT 中，传递辐射剂量的多束复杂配置会导致肺损伤的位置和程度与常规放射治疗后不同。3D CRT 和 SBRT 后肺组织的辐射诱导变化发生在辐射门内。受照射组织的影像学表现因治疗完成后时间的推移而有所不同，急性放射性肺炎的变化表现为磨玻璃影和实变，而晚期放射性肺纤维化的变化表现为体积损失、实变和牵引性支气管扩张。了解治疗时间和辐射野位置，以及熟悉 3D CRT 和 SBRT 后可能出现的所有辐射诱导性肺损伤的全貌，对于正确解读 CT 上可能出现的异常非常重要。在这种情况下，鉴别诊断可能包括感染、淋巴管癌病、恶性肿瘤局部复发和放射性肿瘤。在 CT 上获得的形态学信息与正电子发射断层扫描（PET）上获得的代谢信息相结合，有助于将放射性肺实质异常与残留、复发和新发癌症区分开来。因此，多模态随访成像可能会导致疾病管理的重大变化。
