千伏级锥形束CT与兆伏级电子摄野影像系统在鼻咽癌影像引导放疗的对比研究

摘要

目的:分析千伏级锥形束CT与兆伏级电子射野影像系统用于测量鼻咽癌调强放射治疗的摆位误差,评价两种技术在鼻咽癌调强放疗摆位修正中的应用价值.方法:选取施行IMRT的鼻咽癌患者21例,于放疗实施前先进行EPID正侧位片的拍摄,再进行KV-CBCT的扫描.将EPID拍摄的正侧位片与数字重建射线影像(DRR)配准,得出x、y、z三个线性方向的摆位误差值,同时将扫描的CBCT图像与计划CT图像进行自动的骨性配准,得出x、y、z三个线性方向和绕x轴、y轴和z轴的三个旋转方向的摆位误差值;最终对EPID和CBCT获得的两组数据进行分析比较,分别计算摆位误差以及计划靶体积(planning target volume,PTV)边界;两种技术校正前后的结果进行配对t检验;两种技术的残余误差进行配对t检验结果.结果:CBCT组校正前x、y、z轴的MPTV分别是:3.30 mm、2.58 mm、2.99 mm,校正后分别是1.71 mm、1.71 mm、1.98 mm,t检验有统计学意义(P＜0.05);EPID组校正前x、y、z轴的MPTV分别是:2.56 mm、4.02 mm、3.40 mm,校正后为校正前后各个方向0.9 mm、2.37 mm、4.23 rnm,t检验有统计学意义(P＜0.05).CBCT与EPID残余误差的数据有统计学意义(P＜0.05).结论:与EPID相比较,CBCT在校正后能使MPTV缩小至2mm,大大提高了放疗精度,通过残余误差的比较发现CBCT校正误差的能力优于EPID.%Objective: Analyzing the set-up errors detected by the EPID and the KV-CBCT for the nasopharyngeal carcinoma patients to evaluate the application value of these two methods. Methods: 21 nasopharyngeal carcinoma patients were included in this study.First,we took the EPID images before the treatment,then matched the EPID images with the DRR,acquired the set-up errors in x、y、z axies;Second,we took the kv-CBCT images and auto-matched the CBCT images with the reference images in bone value, acquired the set-up errors in x、y、z、u、v、w axies. These two groups errors were analyzed to calculate the margin from the CTV to the PTV.Do the Paired-Samples T Test between the results of before adjustment and after adjustment which respectively acquired by the CBCT and EPID. Do the Paired-Samples T Test between the residual errors of these two methods. Results: The MPTV of the CBCT before adjustment respectively were 3.3 mm、2.58 mm、2.99 mm. The MPTV of the CBCT after adjustment respectively were 1.71 mm、1.71 mm、1.98 mm. There were significances in statistics (P<0.05). The MPTV of the EPID before adjustment were 2.56 mm,4.02 mm,3.40 mm. The Mm of the EPID after adjustment respectively were 0.90 mm、2.37 mm、4.23 mm. There were significances in statistics(P<0.05). There were significant in statistics between residual errors of the CBCT and EPID (P<0.05).Conclusions: Compared with the EPID,the MPTV can be reduced to 2 mm by the CBCT.Meanwhile, using the CBCT,we can adjust the set-up errors accurately.