利用模拟机及挡铅托架进行放疗前的治疗模拟

目的：通过对食管癌实例分析，理清放射治疗的全部过程，重点是利用模拟机模拟病人放疗过程，从中探讨模拟机的模拟过程在三维适形放射治疗中的临床应用价值。方法：以10位4野照射的食管癌病人为例，首先进行常规放疗模拟机的质量保证和质量控制（QA／QC），本文重点介绍等中心精度的检验和光野射野的一致性；然后利用双螺旋CT机、体位固定装置、三维激光定位系统、常规放疗模拟机及挡铅托架对放疗病人进行体模制作、CT定位、制定治疗计划、制作挡铅及进行模拟验证，分别从寻找射野中心、射野验证、计算深度验证、治疗计划各项参数的可行性验证四个方面进行分析。结果：常规放疗模拟机的各项指标达到QA规定的允许限度内。通过治疗计划显示的各种参数（挡块、楔形等）的调整及修饰后，在常规X线模拟机下对照射野位置及计算深度进行验证可发现：全部患者的计算深度符合临床要求；大部分患者的剂量分布符合临床要求，成功率达90％；射野中心偏移误差最大为3．5mm，最小为0．5mm。在整个治疗过程中，两位患者出现了与床相撞的情况。结论：对放疗患者进行放疗前模拟的过程是三维适形放疗的重要环节，用于验证放疗计划的可行性，保证放疗过程安全有效地进行。

Simulator and Block Carriage Based Treatment Simulation Before Radiotherapy

Objective： To clarify the whole process of radiotherapy through the analysis of esophageal cancer cases, and the focus is the simulation process by simulator, exploring the clinical significance of simulation process in three-dimensional conformal radiation therapy from it. Methods： Taking the 10 esophageal cancer patients rayed by 4 fields as examples,Doing the quality assurance and quality control （QA / QC） of the conventional radiotherapy simulator.this paper focuses on the examination of the isocentre accuracy and the consistency between the light field and the radiation field firstly;Secondly Considering the practical situation of our hospital,We will make the body mold ,do the CT positioning, make treatment plan, make the block, and do the simulations using the double spiral CT, posture fixing device, three-dimensional laser positioning system, conventional radio- therapy simulator and block carriag, Adjusting the center of radiation field, radiation field verification,depth of calculation verifi- cation, the feasibility of the each parameters from the treatment planning verification were analyzed respectively.Results： Every indexes of the conventional radiotherapy simulator is within the QA allowable scope.We verified the radiation fields position and depth of calculation with the conventional X-ray simulation after the adjustment and modification of the various parameters （such as block, wedge）,which is showed in the treatment planning, formal：All patients＇depth of calculation meet the clinical re- quirement;Most patients＇dose distribution meet the clinical requirementand the success rate was 90%;The offset error of radia- tion field center is changing.the maximum value is 3.5 mm and the minimum is 0.5 mm.In the whole course of treatment, only 2 patients appeare collision between the bed and gantry. Conclusions： Doing the simulation for patients before radiotherapy is an important link of three-dimensional conformal radiotherapy ,thus we can verify the feasibility of the radiotherapy treatment plan- ning and ensure the safety and availability of radiotherapy process.