Scatter correction for cone-beam computed tomography using moving blocker strips: A preliminary study
Scatter correction for cone-beam computed tomography using moving blocker strips: A preliminary study
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DOI：
10.1118/1.3495819
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发表时间：
2010-11-01
期刊：
影响因子：
3.8
通讯作者：
Solberg, Timothy
中科院分区：
文献类型：
--
作者：
Wang, Jing;Mao, Weihua;Solberg, Timothy
目的：锥束计算机断层扫描（CBCT）的一个公认的挑战是投影图像中存在散射污染。散射通过降低对比度、引入阴影伪影并导致重建CT数不准确而降低CBCT图像质量。作者提出了一种基于阻断器的方法来同时估计散射信号并从单个CBCT扫描重建视场（FOV）内的完整体积。“阻挡器”）插入X射线源和患者之间。在机架旋转期间，阻挡器沿z轴沿着前后移动。通过这种设计，Feldkamp-Davis-Kress（FDK）算法的滤波步骤所需的数据在未遮挡区域中是完整的，并且FOV内的整个体积具有不同投影视图处的测量值。二维散射通量的估计通过内插的信号从阻塞区域。采用改进的FDK算法和基于约束优化的迭代重建算法，从去除散射信号后的未遮挡投影数据重建CBCT图像。仿真研究和实验研究进行评估所提出的散射校正scheme.Results的性能：散射引起的阴影/杯状伪影在CBCT使用所提出的策略大大减少。在仿真研究中，平均相对误差从25%降低到3%和2%，分别在改进的FDK和约束优化重建的图像。在使用CatPhan（R）600体模的实验研究中，所选感兴趣区域的CT数误差从256个减少到20个以下。结论：提出了一种有效的CBCT散射校正方案。在CBCT采集期间，将由铅条组成的移动阻挡器插入X射线源和患者之间。所提出的方法允许作者同时估计投影数据中的散射信号，减少成像剂量，并获得FOV内的完整体积信息。(C)2010年美国医学物理学家协会。[DOI 10.1118/1.3495819]
Purpose: One well-recognized challenge of cone-beam computed tomography (CBCT) is the presence of scatter contamination within the projection images. Scatter degrades the CBCT image quality by decreasing the contrast, introducing shading artifacts, and leading to inaccuracies in the reconstructed CT number. The authors propose a blocker-based approach to simultaneously estimate scatter signal and reconstruct the complete volume within the field of view (FOV) from a single CBCT scan.Methods: A physical strip attenuator (i.e., "blocker"), consisting of lead strips, is inserted between the x-ray source and the patient. The blocker moves back and forth along the z-axis during the gantry rotation. With such a design, the data required for the filtering step of the Feldkamp-Davis-Kress (FDK) algorithm are complete in the unblocked region and the entire volume within the FOV has the measurements at different projection views. The two-dimensional scatter fluence is estimated by interpolating the signal from the blocked regions. A modified FDK algorithm and an iterative reconstruction based on the constraint optimization are used to reconstruct CBCT images from unblocked projection data after the scatter signal is subtracted. A simulation study and an experimental study are performed to evaluate the performance of the proposed scatter correction scheme.Results: The scatter-induced shading/cupping artifacts are substantially reduced in CBCT using the proposed strategy. In the simulation study, the mean relative error is reduced from 25% to 3% and 2% in the images reconstructed by the modified FDK and constraint optimization, respectively. In the experimental study using a CatPhan (R) 600 phantom, CT number errors in the selected regions of interest are reduced from 256 to less than 20.Conclusions: An effective scatter correction scheme is proposed for CBCT. A moving blocker consisting of lead strips is inserted between the x-ray source and the patient during CBCT acquisition. The proposed method allows the authors to simultaneously estimate the scatter signal in projection data, reduce the imaging dose, and obtain complete volumetric information within the FOV. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3495819]