North Western Medical Physics, The Christie NHS Foundation Trust, Manchester, UK.
Br J Radiol. 2011 Mar;84(999):251-64. doi: 10.1259/bjr/90983944. Epub 2010 Nov 16.
We describe the development and testing of a motion correction method for flat panel imager-based cone beam CT (CBCT) based on warping of projection images.
Markers within or on the surface of the patient were tracked and their mean three-dimensional (3D) position calculated. The two-dimensional (2D) cone beam projection images were then warped before reconstruction to place each marker at the projection from its mean 3D position. The motion correction method was tested using simulated cone beam projection images of a deforming virtual phantom, real CBCT images of a moving breast phantom and clinical CBCT images of a patient with breast cancer and another with pancreatic cancer undergoing radiotherapy.
In phantom studies, the method was shown to greatly reduce motion artefacts in the locality of the radiotherapy target and allowed the true surface shape to be accurately recovered. The breast phantom motion-compensated surface was within 1 mm of the true surface shape for 90% of surface points and greater than 2 mm from the true surface at only 2% of points. Clinical CBCT images showed improved image quality in the locality of the radiotherapy target after motion correction.
The proposed method is effective in reducing motion artefacts in CBCT images.
我们描述了一种基于投影图像变形的平板成像体式锥形束 CT（CBCT）运动校正方法的开发和测试。
跟踪患者体内或表面的标记物，并计算其三维（3D）平均位置。然后，在重建之前对二维（2D）锥形束投影图像进行变形，以使每个标记物位于其 3D 平均位置的投影处。使用变形虚拟体的模拟锥形束投影图像、移动乳房体模的真实 CBCT 图像以及接受放射治疗的乳腺癌和胰腺癌患者的临床 CBCT 图像对运动校正方法进行了测试。
在体模研究中，该方法被证明可以大大减少放射治疗靶区附近的运动伪影，并允许准确恢复真实表面形状。对于 90%的表面点，乳房体模运动补偿后的表面在 1 毫米内与真实表面形状一致，只有 2%的点大于 2 毫米。临床 CBCT 图像显示运动校正后放射治疗靶区的图像质量得到改善。
所提出的方法可有效减少 CBCT 图像中的运动伪影。
