重排的半覆盖螺旋锥束CT的反投影滤波重建

由于传统的螺旋锥束CT系统采用的扫描方法使视场范围受到限制,本文深入分析了螺旋锥束CT的半覆盖扫描方式,提出了螺旋锥束半覆盖扫描的重建算法。该扫描方式只要求射线束覆盖物体横截面的一半以上,探测器的宽度和投影数据量大约是传统螺旋锥束CT的一半,从而节约了探测器的成本。结合扇形束投影的特点和二维反投影滤波(BPF)来实现这种横向截断投影的重建,研究了重排的加权BPF重建方法。该方法首先根据重建的层将半覆盖的螺旋锥束CT投影数据重排为半覆盖的扇形束CT投影,然后用加权的扇形束BPF算法进行重建。同传统视场区域横截面全覆盖的FDK算法相比,该方法即使在大螺距的情况下其重建结果也更接近于真实值,而且均方误差减少了一半,重建时间节约了3/5。

Rebinned BPF reconstruction for helical cone-beam CT with half-cover scaning

As the conventional scan mode in helical cone-beam CT limits the field of view of the CT system, this paper analyzes the half-cover scanning of helical cone-beam CT and presents a new reconstruction method combined the Backprojected Filter(BPF) reconstruction and the cone-beam CT with half-cover scanning.This scanning method only demands more than half of cross section to be covered by X-ray beam at each view angle,and the width of the planar detector is about half of the conventional helical cone-beam CT, so that the cost of planar detector is saved.By combing the fan projection and 2D BPF, this paper researches a rebinned-weighted BPF algorithm for half-cover helical cone-beam CT,in which the projection data are firstly rebinned to half-cover fan-beam data, and then the weighted BPF are used in reconstruction. The results validate that reconstruction time with rebinned-weighted BPF algorithm has reduced to 3/5 that of the conventional helical FDK algorithm. Furthermore, the reconstructed value is more closed to the real value than that of FDK algorithm with large helical pitchs, and the MSE has reduced by half.