grid [ME, gredire, grate] , a device used during a radiographic examination to absorb radiation that is not heading along a straight line from the x-ray source to the film. Such scattered radiation does not contribute useful information and thus constitutes a source of unwanted density. A linear grid consists of alternating parallel strips of radiopaque and radiolucent material. Linear grids may cause variations in image density because of primary-photon attenuation. Density is at a maximum in the center of the film and decreases toward the edges.
