锥形线束CT引导下盆腔肿瘤调强适形放射治疗摆位误差及影响因素分析

Analysis of Setup Errors and Affected Factors in Intensity Modulated Radiation Therapy of Pelvic Tumor with CBCT Guidance

目的:旨在通过锥形线束CT(CBCT)图像引导技术,获取盆腔肿瘤调强适形放射治疗(IMRT)中的摆位误差,并分析探讨计划靶区外扩边界范围及其影响因素。方法:选取2022年1月~2023年12月在复旦大学附属金山医院肿瘤诊断与治疗中心接受IMRT的54例盆腔肿瘤患者,每周治疗前行CBCT扫描1次,将得到的数据与计划CT图像进行匹配融合,获取头脚、前后和左右方向的平移摆位误差。采用肿瘤靶区边界外放公式,计算不同方向上由临床靶区外扩至计划靶区的外放边界。同时,对可能影响摆位误差的临床参数(如年龄、性别、腹围和肿瘤位置等)进行分层比较,为个性化的靶区外放边界提供参考。结果:考虑误差方向时,54例患者293次CBCT配准摆位误差分析结果为:前后方向(0.21±2.82)mm、头脚方向(0.90±3.71)mm和左右方向(0.27±1.96)mm。只考虑误差数值大小时,配准摆位误差分析结果为:前后方向(1.96±2.03)mm、头脚方向(2.76±2.58)mm和左右方向(1.54±1.23)mm。摆位误差在头脚方向最大,前后方向次之,左右方向最小。根据摆位误差得到计划靶区外扩边界在前后、头脚和左右方向分别为6.3、8.7、4.7mm。且摆位误差大小与体重指数和腹围呈正相关。体重指数≥24.0kg/m^(2)的患者头脚及左右方向摆位误差更大(P=0.025,0.019),腹围≥900mm的患者前后、头脚及左右方向摆位误差均更大(P=0.033、0.005和0.025)。结论:盆腔肿瘤患者在放疗过程中,头脚和前后方向的摆位误差较大,患者体重指数、腹围越大,摆位误差越明显。对于肥胖且体重指数≥24kg/m^(2)、腹围≥900mm的患者,应适当增加计划靶区外扩边界范围。

Objective:This study investigated the setup errors and the range of margin of planning target volume(MPTV)in patients with malignant pelvic tumor receiving IMRT with cone beam computed tomography(CBCT)image and analyzed the related factors affecting setup errors.Methods:The CBCT images of 54 pelvic tumor patients who treated in the Center for Tumor Diagnosis&Therapy,Jinshan Hospital,Fudan University between January 2022 and December 2023 were analyzed.Each patient underwent IMRT with CBCT before treatment in every week,and the data were matched and fused with the planned CT images to obtain the setup errors at three directions included vertical translation(Vrt),lateral translation(Lat),and longitudinal translation(Lng).According to the external boundary formula of the target area,the ranges of clinical target volume(CTV)to planning target volume(PTV)in different directions were calculated.And the impacts of clinical parameters in setup error were analyzed,such as age,gender,abdominal circumference and tumor location,to provide reference for personalized margin expansion of the target area.Results:The results of 293 CBCT setup errors of 54 patients with pelvic tumor were as follows:Vrt(0.21±2.82)mm,Lng(0.90±3.71)mm and Lat(0.27±1.96)mm,respectively.The results of absolute setup errors were as follows:Vrt(1.96±2.03)mm,Lng(2.76±2.58)mm and Lat(1.54±1.23)mm respectively.The boundary values of MPTV were 6.3,8.7,4.7mm at the Vrt,Lng and Lat directions according to the setup errors.Patient characteristics such as body mass index(BMI)and abdominal circumference were significantly correlated with setup errors.The setup errors at the Lng and Lat directions of BMI≥24.0kg/m^(2) and at all three directions of abdominal circumference≥900mm were relatively larger(P=0.033,0.005 and 0.025).Conclusion:In patients with malignant pelvic tumors receiving IMRT,the setup errors were more obvious at the Lng and Lat directions.The higher the BMI and the larger the abdominal circumference,the more obvious the setup error is.For obese patients,especially BMI≥24.0kg/m^(2) or abdominal circumference≥900mm,it is recommended to increase the range of MPTV.