用几何参数表实现快速三维重建CT图像

重建时间过长一直是影响三维直接重建在 CT(com puted tom ography)中广泛使用的主要原因之一 ,对于很少采用专用硬件的工业 CT,影响更为严重。用几何参数表方法替代 FDK(Feldkamp- Davis- Kress)算法可以避免由于周期函数的存在而产生的大量重复计算。预先计算出反投影的地址和权重 ,使得反投影的过程中只需从存储的几何参数表中查找。这使得计算量减少到微机可以接受的程度。预插值和最近邻插值的办法能避免大量的插值运算 ,分离变量能避免存储庞大的三维查找表。实验结果说明这些简化在实际系统中是令人满意的

Fast 3-D reconstruction of CT images using a geometric parameter table

Excessive computation cost is one of the major reasons hindering wider use of three dimensional direct image reconstruction in computed tomography (CT). The problem is more severe in industrial computed tomography (ICT) because ICT seldom utilizes specially designed hardware. This paper presents a geometric parameter lookup table method for fast implementation of the FDK (Feldkamp-Davis-Kress) algorithm using periodic functions, i.e., the backprojection addresses and weights are calculated in advance. Therefore, the lookup only occurs in the backprojection. The table avoids repeated calculations in the FDK algorithm, reducing the calculation burden to a level that a PC can perform well. Pre-interpolation and nearest neighbor interpolation are utilized to avoid repeated interpolations. The effect of pre-interpolation on the image quality is investigated. This method was implemented on an X-CT system (BCT-4) with the experimental results showing that the method is practical.