Methods and systems for iterative image reconstruction. The method includes selecting a particular X and Y location corresponding to one or more selected voxels in an image volume. Further, one or more Z locations are iteratively selected for the particular X and Y location. One or more partial sums corresponding to channel dependent portions of a separable system model associated with the particular X and Y location are pre-computed. Additionally, row-dependent portions of the separable system model are computed independent of the pre-computing of the one or more partial sums. The partial sums and the row-dependent portions of the separable system model are combined to compute corresponding updates for the selected voxels. The one or more partial sums are then updated to be consistent with the computed updates. Additionally, the computed updates are applied to the selected voxels independent of updating the one or more partial sums.