前列腺癌调强放疗重复CT模拟定位的作用

The effect of repeated CT simulation positioning for prostate cancer in the intensity-modulated radiation therapy

目的:探讨前列腺癌调强放疗重复CT模拟定位的作用。方法:前列腺癌调强放疗首次CT模拟定位后行CT扫描,在模拟定位工作站确定靶体积中心(等中心)做体表标记。于放射治疗4周左右进行重复CT模拟定位,扫描前用激光灯核对原等中心标记,记录等中心数值后进行CT扫描。在模拟定位工作站录入记录的原等中心数值传输至治疗计划系统,与首次CT模拟定位的图像融合后进行对比分析。结果:首次CT与重复CT图像融合后测量靶区位移的平均误差左右(RL)方向为1.9mm;头脚(SI)方向为2.8mm;前后(AP)方向为3.1mm。危及器官膀胱和直肠的最大剂量分别增加0.5～3.7Gy、0.9～5.0Gy;平均剂量分别增加0.7～4.9Gy、0.6～5.4Gy;最小剂量分别增加0.3～1.3Gy、0.6～2.8Gy。结论:前列腺癌调强放疗重复CT模拟定位便于对比分析靶区和危及器官的位移和对剂量的影响,为及时调整治疗计划提供依据。

Objective： To discuss the effect of repeated CT simulation positioning for prostate cancer in the intensity-modulated radiation therapy. Methods： The first CT simulation positioning for prostate cancer in the intensity-modulated radiation therapy, CT scanning after fixed position, establish isocenter mark in the workstation, make surface mark. In radiation 4 weeks repeated CT simulation positioning, before scanning, check the first isocenter mark with the laser, CT scanning after record the first isocenter mark numerical value, entry in the workstation for record the first isocenter mark numerical value, transmission to treatment planning system, fusion the first image of CT simulation positioning, comparison and analysis. Results： After fusion the image of the first CT simulation positioning and the repeated CT simulation positioning, measuring the three direction average error of target moving： Left-right direction （RL） 1.9mm; superior-inferior direction（SI） 2.8mm; anterior-posterior direction （AP） 3.1mm. Endanger organ including bladder and rectum, there are varying increase in the maximum doses： 0.5～3.7Gy, 0.9～5.0Gy; the average doses： 0.7～4.9Gy, 0.6～5.4Gy; the minimum doses： 0.3～1.3Gy, 0.6～2.8Gy. Conclusion： Repeated CT simulation positioning for prostate cancer in intensity-modulated radiation therapy is easy to comparison and analysis moving of the target and the endanger organs or influence of the dose also can provide the basis for adjust treatment plan.