利用OBI系统进行普放模拟定位的可行性研究

The feasible study of OBI system in routine radiotherapy simulation

目的:研究利用瓦里安23EX机载影像系统(On Board Imager System,以下简称OBI系统)进行普通放疗模拟定位的可行性,开发其新的功能,拓展其使用范围。材料与方法:选取欲行全盆腔前后两野对穿照射患者一例,在源皮距为100cm时摆好位,通过OBI系统拍摄平片,调整患者体位或治疗床参数,使治疗部位全部位于图像窗口之内,根据临床要求确定照射野大小、形状及准直器转角,机架转角等射野参数。根据定位参数设置加速器,打开加速灯光野进行体表射野的勾画,记录相关治疗参数。结果与讨论:OBI系统可以用于常规放疗中的模拟定位,但其范围受非晶硅探测板灵敏区大小(X方向397mm、Y方向298mm)等因素的限制,对于上下(Y方向)超过298mm的病变,因图像范围不能全部包括靶区,无法进行定位。结论:在未配置普通X线模拟定位机或普通X线模拟定位机出现故障时,OBI系统在一定范围内可以临时替代常规X线模拟定位机用于常规放疗模拟定位。

ObjectiveTo study the feasibility of the application of On Board Imager System on common radiotherapy simulation.Method：To choose a patient who will be carried out radiotherapy with two opposite fields about total pelvic,SSD set to 100 cm.A plain film should be captured by using Varian 23EX On Board Imager System.In order to make sure that the SSD is at 100 cm and the region where should be treated is all located within the image widow,the patient＇s position and the parameters of the couch will be adjusted.Then the size and shape of the field,the angle of the collimator and gantry can be determined based on clinical requirement.In the end,to setup accelerator with the simulated parameter,then drawing the field on patient＇s skin helped by field light projector.Result：The OBI system can be used for simulation.Conclusion：The OBI system can certainly be used to perform routine radiotherapy simulation,but it is limited by the size of the kV detector which made of amorphous silicon,therefore,it should be only used as a temporary replacement.