1. A method for image reconstruction, comprising: receiving measured data from an imaging system; determining a preliminary image update in a particular iteration based on one or more image variables computed using at least a subset of the measured data in the particular iteration; determining at least one momentum term based on the one or more image variables computed in the particular iteration, one or more further image variables computed in one or more iterations preceding the particular iteration, or a combination thereof; determining a subsequent image update using the preliminary image update and the momentum term; and iteratively computing the preliminary image update, the subsequent image update, or a combination thereof, for a plurality of iterations until one or more termination criteria are satisfied.