Jiang Bo, Dai Jianrong, Zhang Ye, Zhang Ke, Men Kuo, Zhou Zongmei, Liang Jun, Wang Lvhua
Department of Radiation Oncology, Cancer Institute (Hospital), Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China.
Med Dosim. 2012 Spring;37(1):47-52. doi: 10.1016/j.meddos.2011.01.001. Epub 2011 Jul 8.
The purpose of this study was to compare setup errors obtained with kilovoltage cone-beam computed tomography (CBCT) and 2 different kinds of reference images, free-breathing 3D localization CT images (FB-CT) and the average images of 4-D localization CT images (AVG-CT) for phantom and lung cancer patients. This study also explored the correlation between the difference of translational setup errors and the gross tumor volume (GTV) motion. A respiratory phantom and 14 patients were enrolled in this study. For phantom and each patient, 3D helical CT and 4D CT images were acquired, and AVG-CT images were generated from the 4D CT. The setup errors were determined based on the image registration between the CBCT and the 2 different reference images, respectively. The data for both translational and rotational setup errors were analyzed and compared. The GTV centroid movement as well as its correlation with the translational setup error differences was also evaluated. In the phantom study, the AVG-CT method was more accurate than the FB-CT method. For patients, the translational setup errors based on FB-CT were significantly larger than those from AVG-CT in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) directions (p < 0.05). Translational setup errors differed by >1 mm in 32.6% and >2 mm in 12.9% of CBCT scans. The rotational setup errors from FB-CT were significantly different from those from AVG-CT in the LR and AP directions (p < 0.05). The correlation coefficient of the translational setup error differences and the GTV centroid movement in the LR, SI, and AP directions was 0.515 (p = 0.060), 0.902 (p < 0.001), and 0.510 (p = 0.062), respectively. For lung cancer patients, respiration may affect the on-line target position location. AVG-CT provides different reference information than FB-CT. The difference in SI direction caused by the 2 methods increases with the GTV movement. Therefore, AVG-CT should be the prefered choice of reference images.
本研究的目的是比较千伏级锥形束计算机断层扫描（CBCT）与两种不同参考图像（自由呼吸三维定位CT图像（FB-CT）和四维定位CT图像的平均图像（AVG-CT））在体模和肺癌患者中获得的摆位误差。本研究还探讨了平移摆位误差差异与肿瘤总体积（GTV）运动之间的相关性。本研究纳入了一个呼吸体模和14例患者。对于体模和每位患者，采集了三维螺旋CT和四维CT图像，并从四维CT生成了AVG-CT图像。分别基于CBCT与两种不同参考图像之间的图像配准来确定摆位误差。对平移和旋转摆位误差的数据进行了分析和比较。还评估了GTV质心运动及其与平移摆位误差差异的相关性。在体模研究中，AVG-CT方法比FB-CT方法更准确。对于患者，基于FB-CT的平移摆位误差在左右（LR）、上下（SI）和前后（AP）方向上显著大于基于AVG-CT的误差（p < 0.05）。在32.6%的CBCT扫描中，平移摆位误差相差>1 mm，在12.9%的扫描中相差>2 mm。FB-CT的旋转摆位误差在LR和AP方向上与AVG-CT的显著不同（p < 0.05）。平移摆位误差差异与GTV质心在LR、SI和AP方向上运动的相关系数分别为0.515（p = 0.060）、0.902（p < 0.001）和0.510（p = 0.062）。对于肺癌患者，呼吸可能会影响在线靶区位置定位。AVG-CT提供的参考信息与FB-CT不同。两种方法在SI方向上的差异随GTV运动而增加。因此，AVG-CT应是参考图像的首选。
