Source:http://linkedlifedata.com/resource/umls/id/C0184484
UMD: Monitors designed to continuously measure and display, usually in digital format, the parameters of the position of the x-ray tube, such as tube angulation (i.e., angle in degrees), focal spot-to-film distance (in centimeters or inches), and source-to-image distance relative to the Bucky tray, tabletop, or floor. Some monitors also display additional parameters, such as magnification factor and field size. X-ray tube monitors are usually ceiling-mounted (in overhead tube support systems); they are frequently attached to the positioning control.