肺部肿瘤立体定向放射治疗摆位误差及靶区外扩距离  

Set-up errors and target margin in stereotactic body radiation therapy for lung cancer

作　　者：邢晓汾[1] 郭瑞嵩[1] 傅翔宇 褚薛刚[1] 郑亚琴[1] 徐哲[3] 

机构地区：[1]山西省肿瘤医院,山西太原030013 [2]克莱蒙特麦肯纳学院,美国加州91711 [3]长治医学院和平医院,山西长治046000

出　　处：《中国医学物理学杂志》2015年第4期529-533,共5页Chinese Journal of Medical Physics

摘　　要：目的:应用锥形束CT(cone-Beam CT,CBCT)测量肺部肿瘤立体定向放射治疗分次间和分次内的摆位误差,测算在线校正和非在线校正时计划靶休积(PTV)的外扩距离。方法:选择25例肺部立体定向放射治疗患者,在分次治疗前和治疗后两次CBCT扫描,得到CBCT1和CBCT2两套图像。分别将两套CBCT图像与治疗计划CT图像进行配准,获得分次间和分次内各方向的摆位误差,分析校正前后摆位误差的变化情况,根据测量误差值计算在线校正和非在线校正时PTV的外放距离。结果:所有患者各方向分次间误差在线校正后均减小。校正前左右X、前后Y、头脚Z方向的摆位误差(系统误差+随机误差)分别为:(0.050+0.368)cm、(0.162±0.510)cm、(-0.156±0.151)cm,各方向的最大偏差分别为:1.07 cm、0.62 cm、1.07 cm,误差中位值分别为:(-0.1、-0.22、-0.15)cm;在线校正后X、Y、Z方向的摆位误差(系统误差±随机误差)分别为:(0.009±0.086)cm、(0.069±0.190)cm、(0.062±0.077)cm,各方向的最大偏差分别为:0.34 cm、0.21 cm、0.42 cm,误差中位值分别为:0.03 cm、0.07 cm、-0.15 cm。测算在线校正和非在线校正的PTV外放距离X、Y、Z方向分别为:0.754 cm、1.008 cm、0.398 cm和0.239 cm、0.368 cm、0.212 cm。结论:通过CBCT在线校正可提高位置精度、降低摆位误差,缩小PTV外放距离,减少正常组织照射体积。Objective By the application of cone-beam CT （CBCT）, to measure the interfractionat and intrafractional set-up errors and to calculate planning target volume （PTV） margins based on on-line correction or off-line correction in the stereotactic body radiation therapy （SBRT） for lung cancers. Methods Twenty-five lung cancer patients treated with SBRT were selected. All patients respectively received CBCT scan before and after fractional radiotherapy to acquire two sets of CBCT images, CBCT1 and CBCT2. The interfractional and intrafractional set-up errors were obtained by respectively registering these two sets of CBCT images to planning CT images. The changes of set-up errors before and after correction were analyzed. And the errors were measured to calculate PTV margins based on on-line correction and off-line correction. Results The interfractional set-up errors of all patients in three directions were significantly decreased after online correction. Before correction, the set-up errors （systematic error ＋ random errors） in lateral （X）, vertical （Y）, longitudinal （Z） directions were respectively （0.050±0.368） cm, （0.162±0.510） cm, （-0.156±0.151） cm. The maximum deviations in each direction were respectively 1.07 cm, 0.62 cm, 1.07 cm, and the median values were respectively -0.1 cm, -0.22 cm, -0.15 cm. After the on-line correction, the set-up errors in X, Y, Z directions were respectively （0.009±0.086） cm, （0.069±0.190） cm, （0.062±0.077） cm, and the maximum deviations in each direction were respectively 0.34 cm, 0.21 cm, 0.42 cm, and the median values were respectively 0.03 cm, 0.07 cm,-0.15 cm. The PTV margins of on-line correction and off-line correction were respectively 0.754 cm, 1.008 cm, 0.398 cm and 0.239 cm, 0.368 cm, 0.212 cm in X, Y, Z directions. Conclusion The CBCT of on-line correction can improve the positioning accuracy, reduce the set-up errors, narrow PTV margin and reduce the radiated volume of normal tissues.

关 键 词：肺肿瘤 摆位误差 靶区边界 锥形束CT 立体定向放射治疗 

分 类 号：R734.2[医药卫生—肿瘤]