MULTIORIENTATION SIMULTANEOUS COMPUTATION OF BACKPROJECTION FOR TOMOGRAPHIC IMAGE-RECONSTRUCTION

Based on the geometrical relationships between image pixels and projec tion rays at different viewing angles, a multiorientation simultaneous backprojection approach is proposed. Backprojections for four views t heta, pi/2 - theta, pi/2 + theta and pi - theta are performed at the s ame time; the locating operations of pixels for interpolation are only required for one of them when the number of views is even. By using t his method in the Shepp and Logan back-projection algorithm, implement ation results on an Intel 80386-based computer show that the processin g time is reduced by a factor of approximately 2.7 for linear interpol ation and approximately 4-2 for nearest-neighbour interpolation.