Schäfer Dirk, Borgert Jörn, Rasche Volker, Grass Michael
Philips Research, 22335 Hamburg, Germany.
IEEE Trans Med Imaging. 2006 Jul;25(7):898-906. doi: 10.1109/tmi.2006.876147.
This paper presents a method to reconstruct moving objects from cone beam X-ray projections acquired during a single rotational run using a given motion vector field. The method is applicable to voxel driven cone-beam filtered back-projection reconstruction approaches. Here, a formulation based on the algorithm of Feldkamp, Davis, and Kress (FDK) is presented. The motion correction is applied during the back-projection step by shifting the voxel to be reconstructed according to the motion vector field. The method is applied to three-dimensional (3-D) rotational X-ray angiography. Projections from a beating coronary heart phantom are simulated. Motion-compensated reconstructions with varying accuracy of the applied motion field are carried out for a late diastolic heart phase and compared to the reconstruction obtained with the standard FDK-method from projections of the corresponding motion-free model in the same heart phase. Furthermore, gated reconstructions are calculated by weighting the projections according to their cardiac phase without using a motion vector field. Different gating window widths are applied, and the reconstructions are compared. Using the correct motion field with the motion-compensated reconstruction, the image quality of the standard reconstruction from the corresponding motion-free coronary model can almost be recovered. The reconstructed image quality stays acceptable if the accuracy of the motion field sampling points is better than 1 mm. The gated reconstructions with a window width of 15%-20% of the cardiac cycle lead to superior results compared to nearest neighbor gating, especially for histogram based visualization and analysis. The motion-compensated reconstructions provide sharp images of the coronaries far surpassing the image quality of gated reconstructions.
本文提出了一种方法，可利用给定的运动矢量场，从单次旋转扫描过程中采集的锥束X射线投影重建运动物体。该方法适用于体素驱动的锥束滤波反投影重建方法。在此，提出了一种基于费尔德坎普（Feldkamp）、戴维斯（Davis）和克雷斯（Kress）算法（FDK）的公式。通过根据运动矢量场移动待重建的体素，在反投影步骤中应用运动校正。该方法应用于三维（3-D）旋转X射线血管造影。模拟了来自跳动的冠心病模型的投影。针对舒张期末期心脏阶段，对应用的运动场具有不同精度的运动补偿重建进行了操作，并与同一心脏阶段相应静止模型的投影采用标准FDK方法获得的重建结果进行了比较。此外，通过根据心动周期对投影进行加权来计算门控重建，而不使用运动矢量场。应用了不同的门控窗口宽度，并对重建结果进行了比较。使用正确的运动场进行运动补偿重建时，相应静止冠状动脉模型的标准重建的图像质量几乎可以恢复。如果运动场采样点的精度优于1毫米，则重建图像质量仍可接受。与最近邻门控相比，窗口宽度为心动周期15%-20%的门控重建可产生更好的结果，特别是对于基于直方图的可视化和分析。运动补偿重建提供了冠状动脉的清晰图像，其图像质量远远超过门控重建。
