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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PTV1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。
Objective To explore the forward design of IMRT using multileaf collimator (MLC) and to enrich the design of IMRT plan. Methods A total of 78 patients with nasopharyngeal carcinoma who underwent IMRT irradiation at Affiliated Tumor Hospital of Harbin Medical University from September 2000 to July 2003 and from November 2005 to March 2006 were studied. IMRT planning design skills. Spiral CT scanning was performed in all cases. PTV, GTV and sensitive organs were sketched on the ACQSim workstation. The patient positioning images and organ delineation data were sent from the ACQsim workstation to the ELEKTA Precise PLAN 3D planning system through the DICOM RT network. Based on the optimization of the beam direction, the author pre-designates the direction of the beam according to the dangerous organs and the PTV shape, and completes the optimization design of the main field and the field (or subfield) using the traditional 3D plan and the forward method to obtain the IMRT plan. Results In the 78 case plans, the prefixed beam direction of PTV1 was six and the PTV2 beam direction of the neck was two before and after. The total number of fields (including compensatory field, subfield and neck irradiation field) was 18 to 27, an average of 24; 90% relative dose as the target dose, target dose uniformity of about 10%; conformal degree of nasopharyngeal PTV conformality as the evaluation index, 78 cases of CI 0.58 ~ 0.71 with an average of 0.65. The dose of brain stem and spinal cord were both less than 55% and the mean total machine hop (MU) was about 950 MU. In addition, PTV and PTV The convergence of the radio field, there is no dose problem. From these 78 IMRT plan dose distribution, DVH data assessment results, the total number of fields (including field, subfield), the total number of MU and other evaluation results, the results are good. Conclusion IMRT is a kind of advanced radiotherapy technology. The irradiation plan to realize this kind of irradiation technology can be divided into two types: backward and forward according to the operation method. Properly applied forward planning method can get the equivalent result with reverse plan, and positive The dose-escalation plan approach shows more flexibility.