锥束CT圆轨迹反投影滤波(BPF)算法能够有效处理数据截断问题, 在感兴趣区域成像研究中具有重要的地位。但是当锥角增大时, 重建图像的顶端和底端会出现严重的伪影, 从而影响图像质量。为解决该问题, 从扇束圆轨迹BPF算法出发, 重新推导了锥束圆轨迹BPF算法, 通过对锥束伪影成因分析, 提出了一种基于锥角大小和轴向距离大小的权重函数, 修正了重建过程中差分反投影图像求解部分, 达到抑制伪影的目的。实验结果表明, 改进的大锥角锥束CT圆轨迹BPF算法能够在锥角增大时有效地抑制锥角效应, 提高重建图像质量。

The backprojection filtered (BPF) algorithm,which can provide a good reconstruction with data truncation, plays an important role in reconstruction of region of interest for circular cone-beam CT.However,when the cone-angle increases, there will be serious artifacts in the top and the bottom of the reconstruction image.Aiming for solving this problem, the paper rederives the cone-beam BPF algorithm based on fan-beam circle BPF algorithm, then purposes a new weighting function through analyzing the cause of the artifacts.The weighting function based on cone-angle and the axial distance can restrain the artifacts by modifying the solution of the differential backprojection image in the reconstruction process.The experimental results show that the proposed algorithm can inhibit the artifacts and improve the image quality compared with the BPF algorithm at a large cone-angle.