腮腺癌术后高危复发区放疗的不同治疗计划剂量学比较

目的 探讨腮腺癌术后高危复发区用何种照射方法可以更有效的使靶区剂量均匀及更好的保护危及器官.方法 对8例腮腺癌术后患者设计治疗计划,处方剂量为95%计划靶区(PTV)60 Gy/30次.对常规放疗、二维适形放疗(2D-CRT)、三维适形放疗(3D-CRT)和调强放疗(IMRT)等放射治疗技术的腮腺癌术后靶区进行放疗计划设计,分析比较各种治疗计划靶区适形度和在保护危及器官等方面的优劣.结果 在2D-CRT时,以计算点深度取3.5 cm,电子线能量采取12 MeV及X射线/电子射线(X/E)剂量比为1∶2时靶区的适形度和均匀度较好,危及器官的受量较低.与2D-CRT比较,常规放疗照射野能够较好地包括CT断层图像上勾画的靶区.与2D-CRT及3D-CRT相比,IMRT计划有最好的靶区适形度及均匀度,同时对危及器官有较好的保护作用.结论 X射线与电子线混合线束照射时,剂量计算点深度取3.5 cm左右、电子线能量采取12 MeV及X/E剂量比为1∶2时,靶区的适形度和均匀度较好,对正常组织的保护较好,但具体患者最好用计划系统来选择以上指标.常规放疗按解剖标志确定的照射野能够较好地包括三维靶区.IMRT计划的靶区适形度及均匀度最好,并且危及器官受量较低,在腮腺癌术后放射治疗中IMRT技术是值得推广并普及的放射治疗技术.

The dosimetric comparison of different treatment planning for parotid tumors postoperative radiotherapy

Objective To evaluate what is the optimum radiation technique for parotid tumors postoperative radiotherapy to achieve dose uniformity and protection organs at risk. Methods Dose distribution of different plans were calculated and compared for 8 patients treated in our hospital. In each case, the dose of 95 % PTV was prescribed to 60 Gy/30 fractions. The conventional radiotherapy, 2-dimensional conformal radiotherapy(2D-CRT), 3-dimensional conformal radiotherapy(3D-CRT) and intensity modulated radiotherapy ( IMRT ) planning are designed. The dose conformity, uniformity index and dose sparing of organs at risk of all plans were compared. Results The 2D-CRT plan of dose calculated depth 3.5with lower sparing dose of organs at risk. Compared to the 2D-CRT, conventional radiotheraphy plan could cover target drawn in CT slice. The IMRT plans were more preferable in achieving better dose conformity with lower sparing dose of majority organs at risk than that of the 2D-CRT and 3D-CRT. Conclusions The 2Dphoton and 12 MeV electron beams may be suitable to get a better coverage and uniformity for parotid tumors postoperative radiotherapy. In practice, we recommended to use treatment planning system to select the optimum plan for any patient. The conventional radiotheraphy field according to anatomic marker could get a better target coverage. The IMRT plan have best conformity and uniformity with a lower sparing dose of organs at risk. The IMRT technique should be used extensively for parotid tumors postoperative radiotherapy in future.