A measure of the differences between two adjacent areas in an image. Contrast may be based upon differences in optical density, on differences in radiation transmission or other parameters. Contrast plays an important role in the ability of a radiologist to perceive image detail.
In radiology, the difference between adjacent densities in an image. This is controlled by the energy of the beam and influenced by the characteristics of the part radiographed, production of scatter radiation, type of image receptor (i.e., direct or photostimulable plate, or combination of film and screen), and processing.
A contrast agent is a substance injected into the body that enhances the visibility of specific structures on a radiograph (film), making them more discernible than they would be without the use of such a substance.