Normalized histogram of the deviation of the reconstruction from the true solution, in sigmas (gray curve). The black curve is the probability density function of a standard normal distribution, which is plotted as a reference. We note that the values were clipped to the range from − 10 to 10, i.e., the bump in the gray curve at − 10 corresponds to outliers that can be up to 250 sigma. These outliers correspond to about 0.15% of all voxels.