Technical Note: Proximal Ordered Subsets Algorithms for TV Constrained   Optimization in CT Image Reconstruction
  This article is intended to supplement our 2015 paper in Medical Physics titled "Noise properties of CT images reconstructed by use of constrained total-variation, data-discrepancy minimization", in which ordered subsets methods were employed to perform total-variation constrained data-discrepancy minimization for image reconstruction in X-ray computed tomography. Here we provide details regarding implementation of the ordered subsets algorithms and suggestions for selection of algorithm parameters. Detailed pseudo-code is included for every algorithm implemented in the original manuscript. 
Sean Rose, Martin S. Andersen, Emil Y. Sidky, Xiaochuan Pan
physics.med-ph