探测器偏置扫描的常用重建算法是根据投影的冗余性,对投影数据进行归一化函数加权,再采用标准滤波反投影算法重建。但是,在加权区域过窄的情况下,加权函数衰减过快,导致在重建图像的中心区域出现了圆形加权伪影。本文提出一种针对加权伪影的校正方法。首先,通过增加虚拟探测器来拓展加权区域长度;然后,对虚拟探测器缺失的投影数据进行补齐,并提出共轭插值法和正投影方法;最后,对插值后的投影数据进行探测器偏置重建。本文分别对不同长度加权区域的探测器偏置扫描投影数据进行重建,实验结果表明,当加权区域过窄时,采用本文提出的校正方法能够对加权伪影进行有效抑制。

Based on the redundant property of projection data, the common reconstruction algorithm for the detector-displaced scan weighs the projection data for normalization function, and then reconstructs CT images using a standard filtered back projection method. However, in the condition of a narrow weighting region, the circular weighting artifact is generated in the center area of the image because of the fast attenuation of weighting function. This study proposes a correction scheme for weighting artifacts. First, a virtual detector is used to extend the weighting region. Second, the missing projection data corresponding to the virtual detector can be interpolated by conjugate and forward projection. Finally, the interpolated projection data is reconstructed by the detector-displaced scan reconstruction algorithm. The detector-displaced scan projection data with various weighting region sizes is reconstructed herein. The experimental result shows that the proposed correction method can effectively suppress the weighting artifact.