a method and apparatus to calibrate and correct magnetic and geometrical distortions in an imaging system , specifically a computed tomography system , includes a distortion measuring object which is placed on the surface of an image intensifier . an image frame of the distortion measuring object is generated , and a correction table is generated to correct the image frame . once the correction table has been generated using the distortion measuring object , subsequent image frames are corrected using the correction values in the correction tables . a method and apparatus to calibrate and correct offsets , veiling glare and scatter in an imaging system , specifically a computed tomography system . an image frame is generated and areas not directly impinged by direct radiation are used to correct areas of the detector that are directly impinged . a method and apparatus for correcting and calibrating an imaging system , specifically a computed tomography system . an image frame is corrected for distortions and for the effects of offsets , veiling glare and scatter .