Contrast agent
A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging.[1] Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radiopharmaceuticals, which emit radiation themselves. In x-ray imaging, contrast agents enhance the radiodensity in a target tissue or structure. In magnetic resonance imaging, contrast agents shorten (or in some instances increase) the relaxation times of nuclei within body tissues in order to alter the contrast in the image.
Contrast agents are commonly used to improve the visibility of blood vessels and the gastrointestinal tract.
The types of contrast agent are classified according to their intended imaging modalities.
Radiocontrast media
For
MRI contrast agents
Gadolinium is used in magnetic resonance imaging as an MRI contrast agent or gadolinium-based contrast agent (GBCA).[3] In the 3+ oxidation state the metal has seven unpaired electrons. This causes water around the contrast agent to relax quickly, enhancing the quality of the MRI scan.
Ultrasound contrast agents
See also
- Iodinated contrast
- Ipodate sodium
- Medical imaging
- Radiology
- Barium meal
- Contrast-induced nephropathy
References
- ^ "contrast agent" at Dorland's Medical Dictionary
- ^ Thomson K, Varma D (2010). "Safe use of radiographic contrast media". Australian Prescriber. 33: 19–22. Archived from the original on 2011-03-17.
- ^ "MR Contrast Agents". 2014.
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