A method and apparatus for generating a panoramic image of part of a target, comprises providing a scanner having a source of penetrating radiation facing a detector having an array of sensors for the penetrating radiation. The target is positioned between the source of penetrating radiation and the detector, and scanned with relative rotation of the scanner and the target. Radiation received at a plurality of the sensors spaced apart in the circumferential direction of the relative rotation is separately recorded. A panoramic image is generated by combining for each pixel of the panoramic image outputs from different sensors 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. The generated panoramic image and a graphical representation of the defined curve are displayed. Instructions are received from a user to alter the defined curve. The generating and displaying of the panoramic image are repeated using the altered curve.