An imaging system including an artifact reducer arranged to correct for a ring-shaped artifact in a three-dimensional reconstructed volume. The artifact reducer includes a first stage correction arranged to eliminate structured noise of an output screen of an image intensifier of an X-ray imaging apparatus using a first corrective image. A raw image of a patient is first processed with the first corrective image. The gain-corrected images are forwarded to an image deformation correction where a suitable unwarping function performed. The gain-corrected unwarped images are then made available to a second stage gain correction where a second corrective image is applied resulting in a final set of images with a substantially reduced ring-shaped artifact. The final set of images is made available to an image reconstructor arranged for further processing of the final set of images, the result thereof being visualized on a computer monitor for inspection purposes.