基于IGRT技术的直肠癌俯卧位摆位误差及外放边界的研究

Study on the Position Error and Outer Boundary of Rectal Cancer Prone Position Based on IGRT Technique

目的:利用IGRT技术,对ORFIT架固定,俯卧体位放疗的直肠癌患者进行分次间摆位误差分析研究,确定放疗计划临床靶区CTV至计划靶区PTV的外放边界大小,为临床精确治疗提供依据。方法:选取某院IGRT放疗的直肠癌患者29例,均采用俯卧位,热塑定位膜联合ORFIT架固定。每位患者从放疗开始,连续3次行治疗前锥形束CT扫描,后续治疗期间不定期行CBCT扫描7次,共采集10次锥形束CT图像,与计划CT图像进行配准,得出校正前的摆位误差数据。结果:29例患者共扫描290次图像,左右x、头脚y和前后z方向的摆位误差数值分别为(0.20±0.06)cm、(0.27±0.10)cm、(0.19±0.07)cm。根据Van Herk等推导的摆位扩边公式外放边界=2.5Σ+0.7σ,推算出CTV至PTV的x、y、z轴方向上外扩边界为0.56cm、0.75cm、0.53cm。

Objective Using the technology of IGRT, putting ORFIT on the fixed frame,analysis on the position error of intersecting pendulum of the rectal cancerpatients treated with rectal radiotherapy on prone position, determine the outer boundary size of CTV to PTV of the planning target volume, provide the basis for clinical precise treatment. Methods： 29 patients with rectal cancer treated by IGRT radiotherapy in a hospital were selected. They were all treayted with prone position, thermoplastic positioning film combined with Orfit fixation. Each patient from the start of radiotherapy, 3 times of conical beam CT scan before treatment consecutively,during the follow-up treatment, CBCT scanning was performed 7 times irregularly, a total of 10 conical beam CT images were collected, coordinated with the planned CT image to get the position error data before correction. Results： A total of 290 images were scanned in 29 patients, and the setup errors of left and right x , head foot y and front back z directions were （0.20±0.06） cm, （0.27±0.10） cm, and （0.19±0.07） cm, respectively. According to Van Herk＇s formula of the lateral expansion of the pendulum,the outer boundary is=2.5Σ＋0.7σ.Calculating x, y, z axis outer expansion boundaries of CTV to PTV are： 0.56cm, 0.75cm, 0.53cm.