Multiorientation simultaneous computation of backprojection for tomographic image reconstruction

Based on the geometrical relationships between image pixels and projection rays at different viewing angles, a multi-orientation simultaneous backprojection approach is proposed. Backprojections for four views theta , pi /2- theta , pi /2+ theta and pi - theta are performed at the same time; the locating operations of pixels for interpolation are only required for one of them when the number of views is even. By using this method in the Shepp and Logan backprojection algorithm, implementation results on an Intel 80386-based computer show that the processing time is reduced by a factor of approximately 2.7 for linear interpolation and approximately 4.2 for nearest-neighbour interpolation.