应用锥体束 CT分析肝癌图像引导放疗的摆位误差及外放边界

目的：分析千伏级锥体束CT （ KV-CBCT ）肝癌图像引导放疗摆位误差，为肝癌放疗计划靶区（PTV）的外放边界提供参考。方法应用医科达Synergy直线加速器治疗31例肝癌患者，KV-CBCT扫描采集的X线容积图像（ XVI）与计划CT图像的靶中心匹配，获得腹背（ X）、头脚（ Y）、左右（ Z）三个方向的线性误差x、y、z和绕X、Y、Z轴旋转形成的旋转误差u、v、w。由公式计算出肝癌临床靶区（ CTV）到计划靶区（ PTV）的外放边界值（ MPTV ）。结果共进行275次 CBCT 扫描，其在 X、Y、Z 方向上摆位误差 x、y、z 中位数分别为1．70 mm、1．30 mm、0．80 mm，旋转误差u、v、w分别为0．65°、0．38°、0．31°。 MPTV在X、Y、Z方向上分别为4．11 mm、8．49 mm、4．94 mm。结论采用KV-CBCT技术测量肝癌图像引导放疗的摆位误差，为肝癌放疗MPTV提供参考，提高了肝癌放疗的精准性。

Cone Beam CT Applied to Analysis of Set-up Error and Safety Margin in Image-Guided Radiation Therapy for Liver Cancer

Objective To analyze the set-up errors in image-guided radiation therapy for liver cancer guided with kilo-voitage cone beam computed tomography （ CBCT ） to calculate the referential safety margin of plan target volume （ PTV） .Methods Thirty-one patients with liver cancer were involved in the treatment with Elekta Synergy linear accelerator , the kilo-voltage CBCT-collected volume of X-ray images（XVI） was matched with the center of target of planning CT images to obtain the linearity errors（x,y,z） and the rotational errors（u,v,w） in three directions：back-belly（X）,head-feet（Y）,left-right （Z）.The margin（MPTV） between clinical target volume（CTV） and PTV was calculated based on the formula .Results A total of 275 CBCT scans showed that in the X ,Y,Z directions,the mean linear errors （ x,y,z） were 1.70 mm, 1.30 mm,0.80 mm,respectively,and the rotational errors（u,v,w） were 0.65°,0.38°,0.31°,respectively.MPTV in three-dimensional directions（X,Y,Z） were 4.11 mm,8.49 mm,4.94 mm,respectively.Conclusion Kilo-voltage CBCT applied to evaluating the set-up errors of image-guided radiation therapy can provide the references for determining MPTV of radiotherapy for liver cancer ,which improves the accuracy of radiotherapy for liver cancer .