Department of Radiology, University of Michigan Hospitals, 1500 E Medical Center Dr, UH B1D530H, Ann Arbor, MI 48109-5030, USA.
Radiographics. 2013 Mar-Apr;33(2):599-619. doi: 10.1148/rg.332125119.
Accurate interpretation of posttherapeutic images obtained in radiation oncology patients requires familiarity with modern radiation therapy techniques and their expected effects on normal tissues. Three-dimensional conformal external-beam radiation therapy techniques (eg, intensity-modulated radiation therapy, stereotactic body radiation therapy), although they are designed to reduce the amount of normal tissue exposed to high-dose radiation, inevitably increase the amount of normal tissue that is exposed to low-dose radiation, with the potential for resultant changes that may evolve over time. Currently available internal radiation therapy techniques (eg, arterial radioembolization for hepatic malignancies, brachytherapy for prostate cancer and gynecologic cancers) also carry risks of possible injury to adjacent nontargeted tissues. The sensitivity of tissues to radiation exposure varies according to the tissue type but is generally proportional to the rate of cellular division, with rapidly regenerating tissues such as intestinal mucosa being the most radiosensitive. The characteristic response to radiation-induced injury likewise varies according to tissue type, with atrophy predominating in epithelial tissue whereas fibrosis predominates in stromal tissue. Moreover, changes in irradiated tissues evolve over time: In the liver, decreased attenuation at computed tomography and increased signal intensity at T2-weighted magnetic resonance imaging reflect hyperemia and edema in the early posttherapeutic period; later, veno-occlusive changes alter the hepatic enhancement pattern; and finally, fibrosis develops in some patients. In the small bowel, wall thickening and mucosal hyperenhancement predominate initially, whereas luminal narrowing is the most prominent feature of chronic enteropathy. Correlation of posttherapeutic images with images used for treatment planning may be helpful when interpreting complex cases.
准确解读放射肿瘤学患者治疗后的图像需要熟悉现代放射治疗技术及其对正常组织的预期影响。三维适形外照射放射治疗技术（如调强放射治疗、立体定向体部放射治疗）虽然旨在减少暴露于高剂量辐射的正常组织量，但不可避免地会增加暴露于低剂量辐射的正常组织量，从而可能导致随着时间的推移而发生变化。目前可用的内部放射治疗技术（例如，肝恶性肿瘤的动脉放射性栓塞、前列腺癌和妇科癌症的近距离放射治疗）也存在邻近非靶向组织损伤的风险。组织对辐射暴露的敏感性取决于组织类型，但通常与细胞分裂率成正比，具有快速再生能力的组织（如肠黏膜）对辐射最敏感。辐射损伤引起的特征性反应也根据组织类型而有所不同，上皮组织以萎缩为主，而基质组织则以纤维化为主。此外，受照射组织的变化随着时间的推移而演变：在肝脏中，CT 扫描时衰减降低和 T2 加权磁共振成像时信号强度增加反映了治疗后早期的充血和水肿；随后，静脉闭塞性改变改变了肝脏增强模式；最后，一些患者会发生纤维化。在小肠中，最初以壁增厚和黏膜强化为主，而慢性肠炎最突出的特征是管腔狭窄。在解释复杂病例时，将治疗计划中使用的图像与治疗后的图像进行关联可能会有所帮助。
