Fast ray-tracing technique to calculate line integral paths in voxel arrays

The ray-driven projection and back-projection methods, frequently represented as calculating the path of line integration through a pixel or voxel space, are widely applied in various imaging research fields such as positron emission tomography (PET), computerized tomography (CT) and other volumetric ray tracing studies. For high resolution iterative image reconstruction with large amount of sample events, computing the projections event-by-event is an extremely time consuming task. This work presents a novel ray-tracing calculation technique applying to a list-mode EM image reconstruction algorithm as a part of the system model to accelerate its projection operations. Compared to both the conventional Siddon algorithm and its accelerated methods, the new algorithm has less average computation operation time on each voxel. The results show that the new algorithm significantly improves the calculation speed up to twice as fast than the incremental Siddon algorithm.