A computer-implemented method of deriving 3D image data of a reconstruction volume from a plurality of 2D projections (P i) by means of filtered back-projection, comprising the steps of - receiving a plurality of 2D projections (P i) of an imaged object, each 2D projection (P i) corresponding to a projection plane; - applying a filter to each of the 2D projections (P i) to yield filtered 2D projections ( P̂ l); - calculating a filtered back-projection density distribution (f) from the filtered 2D projections ( P̂ l) by means of filtered back-projection, the computer-implemented method further comprising the steps of - calculating at least one modified filtered back-projection density distribution (f C1, f C2) that is indicative of outlier values included in the filtered 2D projections ( P̂ l) by means of filtered back-projection, - calculating a revised filtered back-projection density distribution (f impr) as a weighted linear combination of the filtered back-projection density distribution (f) and the at least one modified filtered back-projection density distribution (f C1, f C2) characterized in that calculating the at least one modified filtered back-projection density distribution (f C1, f C2) comprises the steps of - defining at least one look-up table (l 1, l 2) that overweighs outlier values in at least a relevant domain; - defining an inverted look-up ( l̂ 1, l̂ 2) table that is inverse to the look-up table (l 1, l 2); - determining, for each volume position (x) in the reconstruction volume and for each 2D projection (P i), two-dimensional in-plane coordinates ( u ∗, v ∗) by projecting the volume positions (x) onto the projection plane defined by the 2D projections (P i); - determining, for each volume position (x) in the reconstruction volume and for each 2D projection (P i), a modified weighted contribution of each of the filtered 2D projections ( P̂ l), wherein determining the modified weighted contributions includes evaluating the filtered 2D projections ( P̂ l) at the in-plane coordinates ( u ∗, v ∗) corresponding to the volume position (x) and applying the look-up table (l 1, l 2) to the filtered 2D projections ( P̂ l) evaluated at the in-plane coordinates ( u ∗, v ∗); and - accumulating, for each volume position (x) in the reconstruction volume, the modified weighted contributions of the 2D projections ( P̂ l) corresponding to different projection planes and applying the inverted look-up table ( l̂ 1, l̂ 2) to the result to yield the modified filtered back-projection density distribution (f C1, f C2). - receiving a plurality of 2D projections (P i) of an imaged object, each 2D projection (P i) corresponding to a projection plane; - applying a filter to each of the 2D projections (P i) to yield filtered 2D projections ( P̂ l); - calculating a filtered back-projection density distribution (f) from the filtered 2D projections ( P̂ l) by means of filtered back-projection, the computer-implemented method further comprising the steps of - calculating at least one modified filtered back-projection density distribution (f C1, f C2) that is indicative of outlier values included in the filtered 2D projections ( P̂ l) by means of filtered back-projection, - calculating a revised filtered back-projection density distribution (f impr) as a weighted linear combination of the filtered back-projection density distribution (f) and the at least one modified filtered back-projection density distribution (f C1, f C2) characterized in that calculating the at least one modified filtered back-projection density distribution (f C1, f C2) comprises the steps of - defining at least one look-up table (l 1, l 2) that overweighs outlier values in at least a relevant domain; - defining an inverted look-up ( l̂ 1, l̂ 2) table that is inverse to the look-up table (l 1, l 2); - determining, for each volume position (x) in the reconstruction volume and for each 2D projection (P i), two-dimensional in-plane coordinates ( u ∗, v ∗) by projecting the volume positions (x) onto the projection plane defined by the 2D projections (P i); - determining, for each volume position (x) in the reconstruction volume and for each 2D projection (P i), a modified weighted contribution of each of the filtered 2D projections ( P̂ l), wherein determining the modified weighted contributions includes evaluating the filtered 2D projections ( P̂ l) at the in-plane coordinates ( u ∗, v ∗) corresponding to the volume position (x) and applying the look-up table (l 1, l 2) to the filtered 2D projections ( P̂ l) evaluated at the in-plane coordinates ( u ∗, v ∗); and - accumulating, for each volume position (x) in the reconstruction volume, the modified weighted contributions of the 2D projections ( P̂ l) corresponding to different projection planes and applying the inverted look-up table ( l̂ 1, l̂ 2) to the result to yield the modified filtered back-projection density distribution (f C1, f C2).