胰腺癌患者螺旋断层放疗摆位误差分析

目的：通过兆伏级CT（MVCT）在线测量校正胰腺癌患者螺旋断层放疗的摆位误差，确定临床靶区CTV和计划靶区PTV之间的外放距离。方法：2012年5月至12月，21例接受TomoTherapy治疗的胰腺癌患者，每次治疗前均行靶区部位MVCT扫描。并将扫描后的MVCT图像与定位时千伏级CT（kVCT）图像进行配准，分别记录患者左右x、头脚y、腹背z和横断面旋转Roll四个方向的偏差数值，对其误差值进行统计分析。结果：21例患者共行358次MVCT扫描，其摆位误差值在x、y、z和Roll方向分别为：（-0．14±0．60）mm、（-1．21±0．44）mm、（0．69±0．93）mm和（0．02±0．26）。x、y、z方向CTV和PTV之间的外放距离分别为：5．5mm、7．4mm和3．9mm。结论：胰腺癌患者治疗摆位误差较大，Tomotherapy通过在线摆位校正能有效减小摆位误差。临床上建议胰腺癌患者在x、y、z方向上CTV和PTV之间可分别外扩5mm、7mm和4mm，为精确照射提供必要的质量保证。

Analysis of The Setup Errors in Patients with Pancreatic Cancer in Tomotherapy Treatment

Objective： To analyze the setup errors of pancreatic cancer patients by Tomotherapy with megavoltage CT （MVCT）, and measure the margins between the clinical target volume （CTV） and plan target volume （PTV）. Methods： Twenty-one patients with pancreatic cancer treated with Tomotherapy were selected. MVCT scanning was performed before each treatment. The MVCT images were registered with the kilovoltage CT （KVCT） images. The setup errors of the left-right （x）, anterior-posterior （y）, superior-inferior （z） and transverse profile rotation （Roll） were recorded and analyzed. Results： The average setup errors in the x, y, z and Roll directions were （-0.14±0.60） mm, （-1.21±0.44） mm, （0.69±0.93） mm, （0.02±0.26）mm, respectively. The margins in x, y, and z directions between CTV and PTV were 5.5 mm, 7.4 mm, and 3.9 mm, respectively. Conclusions： Online correction can effectively reduce the setup errors in pancreatic cancer treated with Tomotherapy. It is suggested that the margins in x, y and z directions between CTV and PTV were 5.5 mm, 7.4 mm, and 3.9 mm, respectively. It can provide necessary quality assurance for precise radiation.