基于锥形束CT体部肿瘤图像引导放疗的摆位误差分析

目的 应用千伏级锥形束CT (KVCBCT)评价采用负压成型垫作体位固定和最终等中心标记法作定位的体部肿瘤图像引导放疗的摆位误差。方法 回顾分析2009—2011年的223例体部肿瘤患者资料,这些患者在配有LAP可移动式激光定位系统的飞利浦 PQS CT或飞利浦 BrillianceCT Big Bore上采用负压成型垫体位固定和最终等中心标记法定位。CT图像通过网络传输给瓦里安Eclipse治疗计划系统用来勾画靶区和设计计划。在治疗前使用瓦里安直线加速器的机载影像系统行KVCBCT扫描和配准,得出左右、上下和前后方向的摆位误差。使用SPSS 16.0软件对数据行独立样本t检验。

Analysis of setup errors on CBCT - based image guided radiation therapy for body tumors patients

Objective To evaluate setup errors of image guided radiation therapy (IGRT) for body tumors immbilized with vacuum cushions and localized with final isocenter marked method using kilovoltage cone beam CT (KVCBCT).Methods A retrospective study has been carried out for 223 patients from March 2009 to April 2011.All patients were immobilized with vacuum cushions and localized with final isocenter marked method in Philips PQS CT or Philips Brilliance CT Big Bore scanner,which were equipped with LAP movable laser systems. The CT images were transferred to a Varian Eclipse workstation for contouring and treatment planning.Before irradiation,a KVCBCT scan was performed and image registration was done on a Varian iX linear accelerator via OBI system.Each set of setup errors in right-left ( RL),superior-inferior (SI),and anterior-posterior (AP) directions were gathered.An independent-samples t-test statistical analysis was conducted with the 758 sets of data using SPSS 16.0.Results The statistical analysis showed that setup errors from the 758 datasets were depicted a Gaussian distribution.The system errors ± random errors in RL,SI and AP were ( -0.5 ±2.8) mm,(0.0±3.0) mm and (0.4±3.4)mm,respectively.Referring to the formula for planning target volume margin calculation,M =2.5Σ + 0.7δ,the margins were calculated as 3.2,2.1 and 3.4 mm,respectively.Conclusions The margins derived from this retrospective study have confirmed the premise that the treatment plans were executed in patients with high reliability,thereby created a high sense of confidence for the clinicians.