应用CTVision和千伏级CBCT研究鼻咽癌放疗摆位误差的比较分析

摘要

目的 比较分析应用CT加速器系统(CTVision)和千伏级锥形束CT(Cone-Beam Computer Tomography,CBCT)图像引导放疗技术校正鼻咽癌在放疗中摆位误差的差异性.方法 选取2015年1月~2016年8月收治的行调强放疗(Intensity Modulated Radiation Therapy,IMRT)的鼻咽癌患者30例,均采用U型热塑性面罩固定体位,将患者随机分为A、B两组,各15例.A组和B组每周分别行CTVision和千伏级CBCT图像引导放射治疗分析1次,各6次,对摆位误差超过3 mm的患者均进行在线校正,并对获得的两组数据进行组内和组间两两比较,采用t检验比较数据差异有无统计学意义.结果 采用相同体位固定方式,在不分周次的情况下,CTVision组和CBCT组在LR、SI、AP方向的摆位误差分别为(0.44±2.26)、(0.45±2.29)、(-0.13±2.10)mm和(0.85±2.46)、(0.50±2.64)、(0.69±2.53)mm,组间的摆位误差无统计学差异性(P>0.05).CTVision组的Σ和σ分别为0.75~0.96 mm和0.90~1.29 mm,而CBCT组的Σ和σ分别为0.76~1.01 mm和1.18~1.37 mm.根据ICRU 62、Stroom、Van Herk公式计算获得的MPTV,CTVision组分别为1.32~1.51、2.28~2.55和2.66~3.03 mm,而CBCT组分别为1.53~1.63、2.45~2.85和2.83~3.35 mm.CBCT组的MPTV比CTVision组的MPTV略大,但差异均无统计学意义(P>0.05).根据McKenzie公式求取的MPRV,CTVision组和CBCT组分别为1.54~1.70 mm和1.65~1.90 mm.此外,在分次放射治疗期间,CTVision组和CBCT组在LR、SI、AP方向的周次摆位误差均无统计学差异性(P>0.05).结论 CTVision和千伏级CBCT图像引导放疗技术均可有效地校正鼻咽癌患者在放射治疗时引起的摆位误差,但均未见明显的统计学差异性.在临床应用中,这可根据不同的患者及不同部位来择优选择.%Objective This paper aims to analyze the differences of setup error between CTVision and kilo-voltage cone-beam computer tomography (CBCT) comparatively, which used to calibrate the setup errors for nasopharyngeal carcinoma during radiotherapy. Methods A total number of 30 nasopharyngeal carcinoma patients, who underwent intensity-modulated radiation therapy (IMRT) with immobilization using a customized thermoplastic mask from January 2015 to August 2016, were randomly assigned to group A and group B, 15 cases. CTVision and kilo-voltage CBCT image-guided radiotherapy were performed in group A and group B respectively, once a week and 6 weeks each. If the setup error was>3 mm, setup errors were corrected by adjusting the treatment couch to match the treatment isocenter. Paired t-test was used to evaluate the differences. Results Regardless of the duration of the fractionated radiotherapy course, the setup errors in the LR, SI and AP directions were (0.44±2.26) , (0.45±2.29) , (-0.13±2.10) mm and (0.85±2.46), (0.50±2.64), (0.69±2.53) mm for group A and group B respectively, without significant differences between two groups (P>0.05). The Σ and σ of group A were 0.75~0.96 mm and 0.90~1.29 mm, respectively, and the Σ and σ of group B were 0.76~1.01 mm and 1.18~1.37 mm respectively. According to the formula of ICRU 62, Stroom and Van Herk, the MPTVs of group A were 1.32~1.51, 2.28~2.55 and 2.66~3.03 mm respectively, while 1.53~1.63, 2.45~2.85 and 2.83~3.35 mm were for group B. The MPTV in group B was slightly larger than those in group A, but the differences were not statistically significant (P>0.05). The MPRV based on the formula of McKenzie were 1.54~1.70 mm and 1.65~1.90 mm for group A and group B respectively. In addition, no significant differences in setup errors were observed during the fractionated radiotherapy course (P>0.05). Conclusion Application of CTVision and kilo-voltage CBCT can effectively correct the setup errors for nasopharyngeal carcinoma during radiotherapy. But there is no statistically significant difference between them. In clinical applications, this paper offer best choose for different patients and different body parts.