A medical contrast medium (or contrast agent) is a substance used to enhance the contrast of structures or fluids within the body in medical imaging.[1] It is commonly used to enhance the visibility of blood vessels and the gastrointestinal tract.
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Types
Several types of contrast media are in use in medical imaging and they can roughly be classified based on the imaging modalities where they are used. Although other types exist, most common contrast agents work based on X-ray attenuation and magnetic resonance signal enhancement.
X-ray attenuation
Iodine and barium are the most common types of contrast medium for enhancing x-ray based imaging methods.
MR signal enhancing
This would include gadolinium for use in magnetic resonance imaging as a MRI contrast agent. In the 3+ oxidation state the metal has 7 unpaired f electrons. This causes water around the contrast agent to relax quickly, enhancing the quality of the MRI scan.
Ultrasonography
Microbubbles contrast agents are used to aid the sonographic, specifically echocardiograms, for the detection of a cardiac shunt. The bubbles are composed of tiny amounts of nitrogen or perfluorocarbons strengthened and supported by a protein, lipid, or polymer shell. The drop in density on the interface between the gas in the bubble and the surrounding liquid strongly scatters and reflects the ultrasound back to the probe. This process of backscattering gives the liquid with these bubbles a high signal, which can be seen in the resulting image.
Adverse effects
Although it is not very common, medical conditions can be caused by the administration of various contrast media. Reactions can range from minor to severe, sometimes resulting in death.
See also
References
External links
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