A Faster Ordered-Subset Convex Algorithm for Iterative Reconstruction

We present a faster iterative reconstruction algorithm based on the ordered-subset convex (OSC) algorithm for transmission CT. The OSC algorithm was modified such that it calculates the normalization term before the iterative process in order to save computational cost. The modified version requires only one backprojection per iteration as compared to two required for the original OSC. We applied the modified OSC algorithm to a dense linear source array X-ray CT system that we proposed previously, observed its performance and compared with the original OSC and BIT algorithms. Spatial measures of point spread functions in reconstructed images show that the new algorithm is quite similar with the original algorithm; for reconstructions with simulated Poisson noise, the standard deviation of the new algorithm is slightly lower than that of the original algorithm. We conclude that the new OSC algorithm is more efficient than the original one and provides comparable images.