不同图像引导方法对盆腔部肿瘤调强放射治疗精度的影响

Research on the effect of ima ge guidance method on accuracy of pelvic tumor intensity modulated radiation therapy

目的应用锥形束CT(CBCT)比较不同图像引导方法对盆腔部肿瘤调强放射治疗精度的影响。方法应用瓦利安Trilogy直线加速器治疗盆腔部肿瘤30例,分为A、B、C 3组,分别采用不同CBCT图像引导方法进行比较,其中A组每天摆位后行CBCT扫描,B组隔天摆位后行CBCT扫描,C组每隔5 d摆位后行CBCT扫描,将获取的CBCT图像与CT模拟图像及其靶中心匹配,获取3组病例x轴(左右)、y轴(头脚)、z轴(腹背)3个方向的摆位误差修正值并估算其相应的摆位外扩边界(MPTV)。结果每天方案在x轴、y轴、z轴的摆位误差修正值分别为:(1.21±0.14)mm、(-2.04±7.94)mm、(-1.62±3.15)mm,MPTV分别为:3.12 mm、10.66 mm、6.26 mm。隔天方案在x轴、y轴、z轴的摆位误差修正值分别为:(1.31±4.02)mm、(2.28±13.17)mm、(1.72±8.33)mm,MPTV分别为:6.09 mm、14.92 mm、10.13 mm。每隔5 d方案在x轴、y轴、z轴的摆位误差修正值分别为:(2.13±4.26)mm、(2.48±16.6)mm、(2.65±8.09)mm,MPTV分别为:8.31 mm、17.82 mm、12.29 mm。结论增加CBCT图像引导次数可以明显提高盆腔部肿瘤调强放射治疗的精度。

Objective To compare the effects of different image guidance methods by Cone-beam CT（CBCT）on precision of pelvic tumors intensity modulated radiation therapy（IMRT）. Methods Thirty patients with pelvic tumors had been divided into A,B,C groups received radiotherapy by Varian Trilogy linear accelerator. These three groups used different image guidance methods by CBCT,then,A group scan CBCT images after daily reposition,B group scan CBCT images every other day,and C group scan CBCT images every five days. CBCT images of each patient were dimensionally matched with planned CT images in planning system,then analyzed setup error revisions and the corresponding external boundary of target area（MPTV）in x（left-right）,y（ventral-dorsal）,z（cranial-caudal） directions. Results The average setup error revisions of A group patients were（1.21±0.14） mm,（-2.04±7.94） mm,（-1.62±3.15） mm respectively,and the MPTV values were 3.12 mm,10.66 mm,6.26 mm respectively. In comparison,the average setup error revisions of B group patients were（1.31±4.02）mm,（2.28±13.17）mm,（1.72±8.33）mm,and the MPTV values were 6.09 mm,14.92 mm,10.13 mm. Meanwhile,the average setup error revisions of C group patients were（2.13±4.26） mm,（2.48±16.6）mm,（2.65±8.09）mm,and the MPTV values were 8.31 mm,17.82 mm,12.29 mm. Conclusion High image guidance frequency by CBCT can result in significantly improving the accuracy of pelvic tumor radiotherapy 。