Respiratory correlated cone beam CT
Respiratory correlated cone beam CT
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DOI：
10.1118/1.1869074
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发表时间：
2005-04-01
期刊：
影响因子：
3.8
通讯作者：
van Herk, M
中科院分区：
文献类型：
--
作者：
Sonke, JJ;Zijp, L;van Herk, M
与直线加速器集成的锥形束计算机断层扫描（CBCT）扫描仪是图像引导放射治疗的有力工具。然而，呼吸运动在CBCT中引起伪影，而为减少轴向和螺旋CT中的运动伪影而开发的呼吸相关程序不适合于这种CBCT扫描仪。我们已经开发了一种替代的呼吸相关的程序CBCT和评估其性能。该呼吸相关CBCT流程包括投影空间中的回顾性排序，产生投影子集，每个投影子集对应于某个呼吸相位。随后，这些子集被重建为四维（4D）CBCT数据集。呼吸相关所需的呼吸信号直接从2D投影数据中提取，无需额外的呼吸监测系统。由于每个相位的投影数量减少，与基于所有投影的3D扫描相比，4D扫描中的对比度-色调噪声比降低了2.6-3.7倍。采集以3和5 s周期移动的球形体模的投影数据，并将其重建为3D和4D CBCT数据集。4D CBCT和荧光透视之间的体模重心位置偏差很小：规则运动为0.13 +/- 0.09 mm，不规则运动为0.39 +/- 0.24 mm。在3D CBCT数据集中明显存在的运动伪影在4D数据集中大幅减少，即使在存在呼吸不规则的情况下，也可以更准确地识别运动结构的形状。此外，4D CBCT数据集提供了3D数据中缺少的关于移动结构的3D轨迹的信息。然而，相当大的呼吸不规则性大大降低了图像质量。三名不同肺癌患者的数据与体模研究的结果一致。总之，我们已经成功地实施了呼吸相关CBCT程序，产生了4D数据集。使用线性加速器上的呼吸相关CBCT，可以在治疗前验证移动肿瘤的平均位置、轨迹和形状。这种验证减少了呼吸引起的几何不确定性，使得能够安全地递送4D放射治疗，例如具有小边缘的门控放射治疗。(c)2005年美国医学物理学家协会。
A cone beam computed tomography (CBCT) scanner integrated with a linear accelerator is a powerful tool for image guided radiotherapy. Respiratory motion, however, induces artifacts in CBCT, while the respiratory correlated procedures, developed to reduce motion artifacts in axial and helical CT are not suitable for such CBCT scanners. We have developed an alternative respiratory correlated procedure for CBCT and evaluated its performance. This respiratory correlated CBCT procedure consists of retrospective sorting in projection space, yielding subsets of projections that each corresponds to a certain breathing phase. Subsequently, these subsets are reconstructed into a four-dimensional (4D) CBCT dataset. The breathing signal, required for respiratory correlation, was directly extracted from the 2D projection data, removing the need for an additional respiratory monitor system. Due to the reduced number of projections per phase, the contrast-tonoise ratio in a 4D scan reduced by a factor 2.6-3.7 compared to a 3D scan based on all projections. Projection data of a spherical phantom moving with a 3 and 5 s period with and without simulated breathing irregularities were acquired and reconstructed into 3D and 4D CBCT datasets. The positional deviations of the phantoms center of gravity between 4D CBCT and fluoroscopy were small: 0.13 +/- 0.09 mm for the regular motion and 0.39 +/- 0.24 mm for the irregular motion. Motion artifacts, clearly present in the 3D CBCT datasets, were substantially reduced in the 4D datasets, even in the presence of breathing irregularities, such that the shape of the moving structures could be identified more accurately. Moreover, the 4D CBCT dataset provided information on the 3D trajectory of the moving structures, absent in the 3D data. Considerable breathing irregularities, however, substantially reduces the image quality. Data presented for three different lung cancer patients were in line with the results obtained from the phantom study. In conclusion, we have successfully implemented a respiratory correlated CBCT procedure yielding a 4D dataset. With respiratory correlated CBCT on a linear accelerator, the mean position, trajectory, and shape of a moving tumor can be verified just prior to treatment. Such verification reduces respiration induced geometrical uncertainties, enabling safe delivery of 4D radiotherapy such as gated radiotherapy with small margins. (c) 2005 American Association of Physicists in Medicine.