Song Ju-Young, Nam Taek-Keun, Ahn Sung-Ja, Chung Woong-Ki, Yoon Mee-Sun, Nah Byunk-Sik
Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Republic of Korea.
Med Dosim. 2009 Summer;34(2):117-25. doi: 10.1016/j.meddos.2008.07.004. Epub 2008 Sep 9.
The cone-beam CT (CBCT), which is acquired using an on-board imager (OBI) attached to a linear accelerator, is used effectively in the verification of setup accuracy for lung radiation surgery. In this study, the respiratory organ motional effect on the CBCT was evaluated with a properly devised phantom system, and the level of possible error in conditions of a real clinical process was assessed. In a comparison study between the CBCT in static status and CBCT images acquired in 20 different motional cases, we confirmed that the image quality and information of CBCT were degraded, with an increase of motional ranges in the region of inhomogeneous structures. The 4D-CT MIP (50 approximately 55%) for the planning of lung radiation surgery and the 4D-CT MIP (full phase) were compared with CBCT in the various motional cases for the evaluation of the influence of the motional effect on CBCT in the process of the setup error correction. The average ratio of relative difference between plan CT: 4D-CT MIP (50% approximately 55%) and CBCT was 5.79% and between plan CT: 4D-CT MIP (50% approximately 55%) and 4D-CT MIP (full phase) was 42.95% in the phantom study. In the analysis of clinical cases of lung radiation surgery, the gross tumor volumes were compared in each CT image. The average ratio of relative difference between plan CT: 4D-CT MIP (50 approximately 55%) and CBCT was 10.72% and between plan CT: 4D-CT MIP (50 approximately 55%) and 4D-CT MIP (full phase) was 28.19%. These results showed that, although a respiratory organ motional effect on CBCT introduced variation in image quality, the error as a result of this variation could be estimated relatively low in the setup error correction for a gated-lung radiation surgery when the planning was performed in 4D-CT MIP (50 approximately 55%), which already included a related signal of motional effect.
锥形束CT（CBCT）通过连接在直线加速器上的机载成像仪（OBI）获取，在肺部放射手术的摆位精度验证中得到有效应用。在本研究中，使用精心设计的体模系统评估了呼吸器官运动对CBCT的影响，并评估了实际临床过程中可能的误差水平。在静态CBCT与20种不同运动情况下获取的CBCT图像的对比研究中，我们证实，在结构不均匀区域，随着运动范围的增加，CBCT的图像质量和信息会下降。在各种运动情况下，将用于肺部放射手术规划的4D-CT MIP（50%至55%）和4D-CT MIP（全相位）与CBCT进行比较，以评估运动效应在摆位误差校正过程中对CBCT的影响。在体模研究中，计划CT与4D-CT MIP（50%至55%）和CBCT之间相对差异的平均比率为5.79%，计划CT与4D-CT MIP（50%至55%）和4D-CT MIP（全相位）之间相对差异的平均比率为42.95%。在肺部放射手术临床病例分析中，比较了每个CT图像中的大体肿瘤体积。计划CT与4D-CT MIP（50%至55%）和CBCT之间相对差异的平均比率为10.72%，计划CT与4D-CT MIP（50%至55%）和4D-CT MIP（全相位）之间相对差异的平均比率为28.19%。这些结果表明，尽管呼吸器官运动对CBCT的影响会导致图像质量变化，但在门控肺部放射手术的摆位误差校正中，当在已经包含运动效应相关信号的4D-CT MIP（50%至55%）中进行规划时，这种变化导致的误差相对较低。
