Fast implementation of area integral model SART algorithm based on look-up table

Forward projection and back-projection are two computationally intense operations in simultaneous algebraic reconstruction technique (SART), especially for area integral model (AIM). We have proposed a fast forward projection algorithm for AIM-based algebraic reconstruction technique, which can be used to accelerate the forward projection operation of area integral model SART. However, the back-projection operation is extremely time-consuming due to its complexity. In this paper, we propose a fast approach to improve the reconstruction speed of AIM-based SART algorithm. To avoid repeated computation of the intersection between rays and pixels, we construct three look up tables (LUTs) to store the number of rays that intersecting with a given pixel, and the corresponding ray indices and weighting factors, respectively, which can be done during the forward projection operation. In the back-projection operation, we update pixels value using these LUTs. On this basis, we utilize the multi-threading technique to implement the forward projection and back-projection operations on a multi-core platform. Experimental results show that the proposed LUT-based approach with multi-core acceleration achieves a speedup of 36.5 times over the conventional approach, and preserves accuracy of the results.