|  | Conditions Treatments | Prescription Drugs

Types of Contrast Mediums

A contrast medium is administered to a patient who is being prepared for a medical imaging procedure. The contrast medium enhances the visibility of the part of the body that is being imaged. This is especially useful when viewing structures in the circulatory system or the digestive tract. Each contrast medium is formulated to take advantage of a particular imaging technology.

  1. Barium Sulfate

    • Barium blocks X-rays so organs that are filled with a barium contrast agent will show up as white on an X-ray image. Barium sulfate liquid is thick and white, and is often given to patents who are having their digestive tract examined by X-ray. Depending on the part of the digestive tract that needs to be viewed, the barium sulfate may be administered orally or rectally.

    Iodine Solutions

    • Contrast agents that are used to image the circulatory system, urinary tract and hepatic (liver) system usually contain iodine and are injected into the body part that will be viewed. These iodine solutions are used when imaging with a traditional X-ray or with a CT scan. Some people have an allergic reaction to these contrast mediums, and many people report a metallic taste in their mouth and strange sensations after they have been injected.

    MRI Contrast Agent

    • This is usually a solution including gadolinium, which is a rare earth metal, but can also be based on iron or manganese. The magnetic metal ions in the solution vibrate and show up on the magnetic resonance imaging. These contrast agents are used for blood vessel imaging or for finding brain or liver tumors and lesions.

    Microbubble Contrast Medium

    • These contrast agents are used in conjunction with ultrasound. The tiny bubbles that are dissolved in a solution are usually made of nitrogen, though another gas may be used. The microbubbles may be encased in a polymer shell or the solution itself may be formulated to maintain the bubbles' integrity. The change in material density (from a liquid to the gas in the bubble) scatters ultrasound waves, which improves imaging of the structure that the contrast medium is injected into.

    Reactions to Contrast Agents

    • Some patients have negative reactions to contrast agents, and those reactions are difficult to predict. For instance, gadolinium, which is used commonly as an MRI contrast agent, can remain in the body longer than expected if the kidneys do not eliminate it. The gadolinium migrates to other parts of the body and causes blackening and hardening of tissues. Also, some people have allergic reactions to the iodine used in the contrast solution for X-rays or CT scans, which causes them to go into anaphylactic shock.

Prescription Drugs - Related Articles