Contrast (redirected from Contrast agents)

contrast /con·trast/ (kon´trast)

1. the degree to which light and dark areas of an image differ in brightness or in optical density.

2. in radiology, the difference in optical density in a radiograph that results from a difference in radiolucency or penetrability of the subject.

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Contrast (agent, medium)

A substance injected into the body that illuminates certain structures that would otherwise be hard to see on the radiograph (film).

Mentioned in: Arthrography, Computed Tomography Scans

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contrast

radiographically the degree of perceptible difference between two color tones. Black and white images on the one film is said to be high contrast; an all gray film has low or nil contrast.

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contrast agents

contrast agents are used for injection into the vascular system for either a local visualization of a system or organ or for outlining an excretory system. Radiolucent (negative) contrast media are gases such as air, oxygen or carbon dioxide. The radiopaque (positive) contrast media include the insoluble salt barium sulfate and a variety of organic iodine compounds.

Barium is used for gastrointestinal studies. Water-soluble, iodinated contrast media excreted by the kidneys are used for many procedures, including all types of angiography and for intravenous and retrograde urography. Those excreted by the liver are used for oral or intravenous cholangiography or cholecystography. New, nonirritant iodine compounds have been developed for myelography. Oily iodinated media are used for lymphangiography and bronchography.

double contrast

the use of two contrast agents or two routes of administration in the one patient. For example, radiopaque dye and then air in the urinary bladder.

contrast materials

see contrast agents (above).

contrast medium

a substance used in radiography to permit visualization of internal body structures. Called also contrast agent, contrast material.

negative contrast

a contrast material that is not radiopaque such as air or carbon dioxide.

contrast pattern

the pattern made by the contrast agent. Includes confined extension patterns in diverticula and similar confined spaces, and unconfined extensions, e.g. in bladder rupture.

positive contrast

the use of a contrast material that is radiopaque such as barium sulfate and iodinated products.

triple contrast

the use of three contrast media or routes in the one patient at the one time.

water-soluble contrast agents

agents used for injection into the vascular system for either a local visualization of a system or organ or for outlining an excretory system. In the past these have consisted mostly of iodine preparations which are irritant and cause tissue damage so that they must be injected intravenously. However, there are now available some recently developed water-soluble iodine preparations that are nonirritant and which can be used in myelography. See also contrast.