腮腺癌术后不同放疗计划剂量学的比较

目的：通过比较腮腺癌术后常规放疗（CRT）、三维适形放疗（3DCRT）与调强放疗（IMRT）靶区剂量分布的均匀性、适形性和靶区剂量情况，以及各危及器官受照体积、剂量情况，探讨I M RT用于腮腺癌术后治疗的可行性。方法选取10例腮腺癌术后患者，放疗前行CT扫描并勾画靶区。在三维治疗计划系统（TPS）上分别对每例患者行二维电子线＋X线混合照射（X＋E）、3DCRT、IMRT设计计划，分析腮腺癌术后患者分别运用三种放疗方法的剂量体积直方图（DVH），比较患者的靶区适形度、均匀指数，靶区剂量、靶区覆盖情况及各个危及器官的受照射剂量，评价腮腺癌术后IMRT较3DCRT的剂量学优势。结果在靶区覆盖方面，3DCRT的V95%和适形指数（CI）（96.5%和0.76）明显优于二维照射（77.7%和0.49）（P均＜0.05），但劣于IMRT（99.1%和0.84）（P均＜0.05）。结论IMRT技术无论从靶区覆盖还是对正常器官保护方面均优于CRT及3DCRT。

The Dosimetric Comparison of Different Treatment Planning for Postoperative Radiotherapy of Parotid Cancer

Objective To compare the homogeneity and conformity of dose distribution in the target, the treatment period of patients and the dose to the organs at risk among conventional radiation therapy （CRT）, three-dimensional conformal radiation therapy （3DCRT） and intensity modulated radiation therapy （IMRT）, and then to evaluate the clinical value of IMRT for postoperative irradiation of parotid cancer. Methods Ten patients with parotid cancer postoperative were selected. Before the treatment, computed tomography scan image were transferred to an IMRT planning system. To design the unilateral field with mixture of 12 MV photon and electron beams （X＋E）, 3DCRT, IMRT plans respectively for each patient. Through the analysis of the dose volume histogram （DVH） by single lesions of the patients, using three kinds of radiation methods, three groups were compared for conformal radiotherapy target area conformal degree, uniform index area, target area dose and each endanger organ by irradiation dose, to investigate the dosimetry advantages of IMRT. Results Compared with conventional planning, the CRT, 3DCRT and IMRT plans produced adequate target coverage, and the comformity index （CI） showed 3DCRT plans （0.76） and CRT plans （0.49） produced poorer target coverage than IMRT （0.84）. Conclusion For postoperative irradiation of parotid cancer, IMRT planning techniques generated better target dose-coverage, without compromising the dose-sparing advantages of important structures.