roentgenogram, photograph of internal structures that is made by passing X-rays through the body to produce a shadow image on specially sensitized film. The roentgenogram is named after German physicist Wilhelm Conrad Röntgen, who discovered X-rays in 1895. The value of a roentgenogram is considerably enhanced by the use of contrast material, such as barium, to make structures visible on the film that would otherwise not appear. Today the photographs produced are widely called X-ray images.
One of the most common screening roentgenograms is the chest film, taken to look for infections such as tuberculosis and conditions such as heart disease and lung cancer. Treatment of tuberculosis detected by a roentgenogram can prevent more extensive infection, but, unfortunately, this technique is of little value in screening for lung cancer because the stage at which the disease is detectable by this method is too far advanced for treatment to be of value. Another common procedure employs a barium enema, administered to the patient before the X-ray examination, which allows identification of polyps as small as one centimetre in diameter when air is inserted after the barium (a double-contrast barium enema). This screening is effective if precancerous polyps are identified at an early stage.