基于射束方向优化思想鼻咽癌调强放疗计划正向设计技术

目的 探讨使用多叶准直器（MLC）正向设计鼻咽癌调强治疗（IMRT）计划，丰富实现IMRT照射计划设计手段。方法 总结分析了自2000年9月-2003年7月间和2005年11月-2006年3月间，在哈尔滨医科大学附属肿瘤医院接受IMRT照射的78例鼻咽癌患者计划，研究鼻咽癌正向IMRT计划设计的技巧。全部病例都采用螺旋CT扫描定位，并在ACQSim工作站上完成勾画PTV、GTV及敏感器官，通过DICOM RT网络将患者定位影像及器官勾画数据资料由ACQsim工作站送入ELEKTA Precise PLAN 3D计划系统。笔者基于射束方向优化思想，根据危险器官和PTV形态预设射束方向，用传统3D计划和正向方式完成主野及补野（或子野）优化设计，获得IMRT计划。结果 78个病例计划中，预设鼻咽PTV的射束方向为六个，颈部PTV2射束方向为前后两个；全部射野数量（含补野、子野，及颈部照射野）为18～27个，平均为24个；以90％相对剂量作为靶剂量，靶区剂量均匀性约在10％左右；适形度以鼻咽部PTV的适形度为评价指标，78例的CI为0．58～0．71，平均为0．65；脑干、脊髓控制剂量均≤55％，平均总机器跳数（MU）为950MU左右；另外，在处理鼻咽部PTV与颈部PTV的射野衔接上，不存在剂量问题。从这78例IMRT计划的剂量分布、DVH数据评估结果、射野总数（含补野、子野）、总MU数等评价结果看，结果很好。结论 IMRT是一种目前先进的放疗技术，实现这种照射技术的照射计划从运算方式看分逆向和正向两种，方法技巧运用得当的正向计划可以得到与逆向计划相当的结果，且正向剂量调强计划方式表现出更多的灵活性。

Forward IMRT planning of nasopharyngeal carcinoma by field aperture shape optimazing based beam direction

Objective To evaluate and summarize a new way of forward intensity modulated radia- tion therapy (IMRT) plan for nasopharyngeal carcinoma with 3Dmulti-leaf collimator (MLC) planning sys- tems is practised routinely in our department.Methods From September 2000 to July 2003 and November 2005 to March 2006,78 patients with nasopharyngeal carcinoma who were treated with eonformal radiothera- py used CT simulation for localizing,then doctors supervised the delineation of the planned tumor volume (PTV),gross tumor volume (GTV) and other sensitive organs on ACQsim workstation,and then sent the CT imagines to ELEKTA Precise Plan by DICOM RT Ethernet.Then,the physicists take over the responsibility of all directions of beam projection according to these organs and PTV shape,and completed the IMRT plan by manual correction making and the optimization of fields or segments shaped with forward 3D planning sys- tem.Results To analyse all the patient's dose distributions taking conformal radiotherapy in our hospital, we found the dose distribution and DVH data excellent,even better than the inverse planning of nasopharyn- geal carcinoma.Conclusions Intensity modulated radiation therapy (IMRT) is an advanced radiotherapy technique.A very good IMRT plan of nasopharyngeal carcinoma by forward planning can be obtained with 3D multiple leaf collimator (MLC) planning system.This planning method is more flexible,but the radia- tion physicists should be very much experienced in professional skill.