应用KV-CBCT分析鼻咽癌调强放射治疗的摆位误差

目的:应用KV-CBCT分析鼻咽癌调强放射治疗时的摆位误差,为鼻咽癌调强放射治疗计划设计时CTV外扩PTV边界的大小提供参考。方法:选取30例IMRT的鼻咽癌患者,治疗过程中每周一次应用KV-CBCT采集患者治疗前的CT图像,将所得图像与定位CT图像进行匹配,分别测定X、Y、Z轴三个方向的摆位误差。结果:30例患者共拍摄168次KV-CBCT,获得168组摆位误差结果,群体摆位误差分别为X轴-0.15±1.43 mm,Y轴0.20±1.58 mm,Z轴-0.21±1.65 mm;根据Van Herk公式计算得到各方向的CTV-PTV外放边界值X、Y、Z轴分别为3.1 mm、3.3 mm和3.4 mm。结论:应用KV-CBCT影像系统可实时测量摆位误差并在线进行纠正,减小摆位误差,为CTV-PTV外放边界提供参考。

Setup Error in IntensityModulated Radiotherapy for Nasopharyngeal Carcinoma by Kilo-Volt Cone-BeamComputed Tomography

Objective:To analyze the setup errors by KV-CBCT in nasopharyngeal carcinoma treated with Intensity Modulated Radiotherapy to provide the reference for calculate safety margins of PTV with CTV.Methods:30 patients with nasopharyngeal carcinoma who had received kilovoltage cone-beam computed tomography (KV-CBCT) and treated with IMRT were selected. The acquired images of KV-CBCT were compared to establish CT images with calculated setup errors of X-axis, Y-axis and Z-axis.Results:All the patients received the 168 KV-CBCT scans. The overall setup errors were below -0.15± 1.43 mm in X-axis, 0.20± 1.58 mm in Y-axis and -0.21± 1.65 mm in Z-axis; The margins required for CTV-PTV were calculated 3.1 mm, 3.3 mm and 3.4 mm, respectively, according to the Van Herk formula.Conclusion:The application of KV-CBCT imaging system on the margin of CTV-PTV can measure and reduce the setup errors by correcting online.