Investigation of uncertainties in image registration of cone beam CT to CT on an image-guided radiotherapy system
Investigation of uncertainties in image registration of cone beam CT to CT on an image-guided radiotherapy system
复制标题
DOI：
10.1088/0031-9155/54/24/002
复制
发表时间：
2009-12-21
影响因子：
3.5
通讯作者：
Thwaites, D. I.
中科院分区：
文献类型：
--
作者：
Sykes, J. R.;Brettle, D. S.;Thwaites, D. I.
在商业图像引导系统（Synergy, Elekta， UK）中，已经开发了测量扇束计算机断层扫描（FBCT）到锥束CT （CBCT）刚体图像配准不确定度的方法，用于自动图像配准算法。图像配准不确定度与成像剂量和图像分辨率之间的关系已通过拟人化颅骨幻影和进一步测量患者头部图像进行了研究。提出了一种新的目标配准误差度量。该度量计算5厘米球面上的一组等间距点所走过的平均距离，这些点以等心为中心，通过配准的残差进行变换。研究的目的是给实际指导使用协同自动图像配准，包括算法的选择和使用的剪贴盒报告。结果表明，该倒角匹配算法对低剂量采集引起的噪声增加具有很强的鲁棒性。这将使成像剂量从目前的临床标准2毫戈瑞降低到0.2毫戈瑞，而不会造成临床上显著的准确性损失。研究了FBCT切片厚度/间距和CBCT体素大小对图像配准性能的影响，结果表明，分别为2.5 mm和1 mm时，图像配准性能可以接受。如果不对准是典型的正常临床设置错误，注册失败是非常罕见的，这些很容易识别。用患者图像测量的平移配准误差的标准偏差在以治疗中心为中心的5cm球体表面为0.5 mm。倒角算法适用于常规临床使用，不需要近距离检查图像偏差。
Methods of measuring uncertainties in rigid body image registration of fan beam computed tomography (FBCT) to cone beam CT (CBCT) have been developed for automatic image registration algorithms in a commercial image guidance system (Synergy, Elekta, UK). The relationships between image registration uncertainty and both imaging dose and image resolution have been investigated with an anthropomorphic skull phantom and further measurements performed with patient images of the head. A new metric of target registration error is proposed. The metric calculates the mean distance traversed by a set of equi-spaced points on the surface of a 5 cm sphere, centred at the isocentre when transformed by the residual error of registration. Studies aimed at giving practical guidance on the use of the Synergy automated image registration, including choice of algorithm and use of the Clipbox are reported. The chamfer-matching algorithm was found to be highly robust to the increased noise induced by low-dose acquisitions. This would allow the imaging dose to be reduced from the current clinical norm of 2 mGy to 0.2 mGy without a clinically significant loss of accuracy. A study of the effect of FBCT slice thickness/spacing and CBCT voxel size showed that 2.5 mm and 1 mm, respectively, gave acceptable image registration performance. Registration failures were highly infrequent if the misalignment was typical of normal clinical set-up errors and these were easily identified. The standard deviation of translational registration errors, measured with patient images, was 0.5 mm on the surface of a 5 cm sphere centred on the treatment centre. The chamfer algorithm is suitable for routine clinical use with minimal need for close inspection of image misalignment.