providing a scanner having a source of penetrating radiation facing a detector having an array of sensors for the penetrating radiation; positioning the target between the source of penetrating radiation and the detector; scanning the target with relative rotation of the scanner and the target; separately recording radiation received at a plurality of the sensor positions spaced apart in the circumferential direction of the relative rotation; generating a panoramic image by combining for each pixel of the panoramic image outputs from different sensor positions at different times during the relative rotation, the combined outputs being selected to represent rays of radiation passing through a point on a defined curve; displaying the generated panoramic image and a graphical representation of the defined curve; receiving from a, user instructions to alter the defined curve; and repeating the generating and displaying of the panoramic image using the altered curve.