e 0D projections to yield filtered 0D projections; calculating a filtered back-projection density distribution from the filtered 0D projections by way of filtered back-projection; calculating, by way of filtered back-projection, at least one modified filtered back-projection density distribution, indicative of outlier values included in the filtered 0D projections; and calculating a revised filtered back-projection density distribution as a weighted linear combination of the filtered back-projection density distribution calculated and the at least one modified filtered back-projection density distribution calculated