In a method for reconstructing a 3D CT image from a number of 2D projection images each 2D projection image is divided at an arbitrarily selectable position by a substantially vertical image line and the projection image is automatically electronically analyzed to detect whether clipping occurs on the left side or on the right side, or on both sides, of the image line. For each side of the image line at which clipping is detected, a horizontal coordinate at which the clipping ends is identified. The grayscale values at the side of the horizontal coordinate opposite to the side at which the image line is located are extrapolated so that the clipping is removed. The corrected 2D projection images are then used to reconstruct a 3D image, in which capping artifacts, that would otherwise be present, or avoided or substantially minimized due to the corrections made in the 2D projections.