基于同心圆轨道的锥形束CT重建算法

由于基于圆轨道锥形束 CT(com putertom ography)重建算法 (如 FDK算法 )只有在小锥角的条件下才能得到比较好的重建质量 ,因此在实际应用中时受到很多的限制。该文利用外推的思想提出了一种基于同心圆轨道的锥束 CT重建算法。利用不同半径的同心圆轨道对物体重建两次 ,并根据平方反比关系 ,利用两次 FDK算法重建结果的差异估计出真实值和重建值的差异 ,然后利用这个差异来修正重建结果。得益于这个修正 ,该算法可以很好地抑制FDK算法由于锥角变大引起的伪影。仿真模拟结果表明 :该算法对高对比度和低对比度物体锥束重建的锥角使用范围比 FDK提高 1～ 3倍

Cone beam reconstruction algorithm based on two concentric circles

Cone beam reconstruction algorithms (such as FDK) based on circular orbits can only be used when the cone angle is small. This paper developed a cone beam reconstruction algorithm based on extrapolation. The algorithm reconstructs the object through two concentric circles, first twice reconstructing the object with different orbit radii and then correcting one reconstruction result based on the relation between the reconstruction error and the orbit radius. The algorithm yields improved image quality reflected by decreased drop, which is a well-known problem for cone beam reconstruction with circular trajectories for both low-intensity and high-intensity objects. The applicable cone angle range is 2 to 4 times larger than that of the FDK algorithm.