Barium sulfate

Barium sulfate (BaSO₄) is a white, highly insoluble compound used as a radiopaque contrast agent because it strongly attenuates X-rays.

Barium meal: An upper gastrointestinal X-ray examination in which swallowed contrast material outlines the esophagus, stomach, and duodenum. Barium sulfate coats the upper digestive tract for these examinations.
Radiopacity: The ability of a material to attenuate X-rays and appear relatively bright on radiographic images. Barium sulfate is radiopaque because barium strongly attenuates diagnostic X-rays.
Sulfate: The polyatomic anion SO₄²⁻, consisting of sulfur bonded to four oxygen atoms. Sulfate pairs with barium ions to form the poorly soluble solid.
Water-soluble iodinated contrast media: Iodine-containing contrast agents that dissolve in water and are used in radiographic and CT imaging. They are preferred over barium sulfate when leakage outside the digestive tract is a concern.
Barium enema: An X-ray examination of the large intestine using contrast material introduced through the rectum. Barium sulfate outlines the colon when introduced as an enema.
X-ray attenuation: The reduction in X-ray beam intensity as photons interact with matter. Its contrast effect arises from strong attenuation by barium atoms.
Precipitation reaction: A chemical reaction in which dissolved substances form an insoluble solid. Mixing soluble barium and sulfate salts can produce barium sulfate precipitate.
Gastrografin: A water-soluble oral or rectal contrast agent containing diatrizoate salts. This iodinated agent can substitute for barium sulfate when perforation is suspected.
Barium swallow: An imaging examination that uses swallowed contrast material to show the pharynx and esophagus. Barium sulfate makes swallowing and esophageal structure visible on X-rays.
Barium: A soft, silvery alkaline-earth metal with atomic number 56. Barium supplies the high-atomic-number atoms responsible for the compound’s X-ray visibility.

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