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. 2018 Aug 7;81(1):670–685. doi: 10.1002/mrm.27371

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© 2018 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine

This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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Computation time for 20 Bregman iterations and different problem sizes. (A) Using the preconditioner, the total computation time for the PCG part in 20 Bregman iterations is reduced by more than a factor of 4.5 for all studied problem sizes. (B) The computation time for 20 Bregman iterations of the entire algorithm also includes the Bregman update steps, so that the total speedup factor is approximately 2.5 for the considered problem sizes. (C) The two methods converge to the same solution, plotted here for R = 4 and a reconstruction matrix size 256 × 256.