a multiple beam computed tomography scanner formed of plural interspaced groups of small , densely packed radiation detectors provided in a stationary ring around a body . the ring defines the cross - sectional slice of the body which is scanned by moving an x - ray source in a circle having a smaller radius and the same plane and center as that of the detector ring . a rotatably mounted collimator having a plurality of beam defining apertures is positioned between the x - ray source and patient . the collimator defines a plurality of fan - shaped x - ray beams that strike the detectors after passing through the patient and eliminates radiation from impinging on the patient that would pass through and strike the dead spaces between detector groups . the x - ray source and collimator rotate synchronously maintaining the registration between any given x - ray beam and detector group while the area of interest for the given detector group is scanned by the x - ray beam .