Department of Radiation Oncology, University of Wuerzburg, Josef-Schneider-Str, 11 97080 Wuerzburg, Germany.
Radiat Oncol. 2012 Jun 8;7:81. doi: 10.1186/1748-717X-7-81.
To analyze the accuracy and inter-observer variability of image-guidance (IG) using 3D or 4D cone-beam CT (CBCT) technology in stereotactic body radiotherapy (SBRT) for lung tumors.
Twenty-one consecutive patients treated with image-guided SBRT for primary and secondary lung tumors were basis for this study. A respiration correlated 4D-CT and planning contours served as reference for all IG techniques. Three IG techniques were performed independently by three radiation oncologists (ROs) and three radiotherapy technicians (RTTs). Image-guidance using respiration correlated 4D-CBCT (IG-4D) with automatic registration of the planning 4D-CT and the verification 4D-CBCT was considered gold-standard. Results were compared with two IG techniques using 3D-CBCT: 1) manual registration of the planning internal target volume (ITV) contour and the motion blurred tumor in the 3D-CBCT (IG-ITV); 2) automatic registration of the planning reference CT image and the verification 3D-CBCT (IG-3D). Image quality of 3D-CBCT and 4D-CBCT images was scored on a scale of 1-3, with 1 being best and 3 being worst quality for visual verification of the IGRT results.
Image quality was scored significantly worse for 3D-CBCT compared to 4D-CBCT: the worst score of 3 was given in 19 % and 7.1 % observations, respectively. Significant differences in target localization were observed between 4D-CBCT and 3D-CBCT based IG: compared to the reference of IG-4D, tumor positions differed by 1.9 mm ± 0.9 mm (3D vector) on average using IG-ITV and by 3.6 mm ± 3.2 mm using IG-3D; results of IG-ITV were significantly closer to the reference IG-4D compared to IG-3D. Differences between the 4D-CBCT and 3D-CBCT techniques increased significantly with larger motion amplitude of the tumor; analogously, differences increased with worse 3D-CBCT image quality scores. Inter-observer variability was largest in SI direction and was significantly larger in IG using 3D-CBCT compared to 4D-CBCT: 0.6 mm versus 1.5 mm (one standard deviation). Inter-observer variability was not different between the three ROs compared to the three RTTs.
Respiration correlated 4D-CBCT improves the accuracy of image-guidance by more precise target localization in the presence of breathing induced target motion and by reduced inter-observer variability.
分析使用三维或四维锥形束 CT（CBCT）技术在立体定向体放射治疗（SBRT）中进行肺部肿瘤图像引导的准确性和观察者间变异性。
本研究纳入了 21 例接受图像引导 SBRT 治疗的原发性和继发性肺部肿瘤患者。呼吸相关的 4D-CT 和计划轮廓被用作所有 IG 技术的参考。三位放射肿瘤学家（RO）和三位放射治疗技师（RTT）独立进行了三种 IG 技术。使用自动配准计划 4D-CT 和验证 4D-CBCT 的呼吸相关 4D-CBCT 图像引导（IG-4D）被认为是金标准。结果与使用三维 CBCT 的两种 IG 技术进行比较：1）手动配准计划内部靶区（ITV）轮廓和三维 CBCT 中运动模糊的肿瘤（IG-ITV）；2）自动配准计划参考 CT 图像和验证三维 CBCT（IG-3D）。三维 CBCT 和 4D-CBCT 图像的图像质量评分范围为 1-3，1 分为最佳，3 分为最差，用于视觉验证 IGRT 结果。
与 4D-CBCT 相比，三维 CBCT 的图像质量评分明显更差：分别有 19%和 7.1%的观察结果得分为 3 分。在基于 4D-CBCT 的 IG 中观察到靶区定位的显著差异：与参考的 IG-4D 相比，使用 IG-ITV 的肿瘤位置平均相差 1.9 毫米±0.9 毫米（3D 向量），使用 IG-3D 的相差 3.6 毫米±3.2 毫米；IG-ITV 的结果明显比 IG-3D 更接近参考的 IG-4D。随着肿瘤运动幅度的增大，4D-CBCT 与三维 CBCT 技术之间的差异显著增加；同样，随着三维 CBCT 图像质量评分的降低，差异也增大。在 SI 方向上，观察者间变异性最大，使用三维 CBCT 的 IG 比使用 4D-CBCT 的 IG 变异性更大：0.6 毫米比 1.5 毫米（一个标准差）。与三位 RTT 相比，三位 RO 之间的观察者间变异性没有差异。
呼吸相关的 4D-CBCT 通过更精确的靶区定位改善了图像引导的准确性，在呼吸诱导的靶区运动存在的情况下减少了观察者间变异性。
