Contrast agent

A contrast agent (or contrast medium) is a <a href="/facts/Chemical_substance/EWcXU41d">substance</a> used to increase the <a href="/facts/Display_contrast/JG93kjsH">contrast</a> of structures or fluids within the body in <a href="/facts/Medical_imaging/pL6JyJEp">medical imaging</a>. Contrast agents absorb or alter external <a href="/facts/Electromagnetism/oAkmALHT">electromagnetism</a> or <a href="/facts/Ultrasound/31Pa5IH9">ultrasound</a>, which is different from <a href="/facts/Radiopharmaceutical/x3g6zbB6">radiopharmaceuticals</a>, which emit <a href="/facts/Radiation/RwMocyeq">radiation</a> themselves. In <a href="/facts/X-ray/wseP79cN">X-ray</a> imaging, contrast agents enhance the <a href="/facts/Radiodensity/TakP45NW">radiodensity</a> in a target tissue or structure. In <a href="/facts/Magnetic_resonance_imaging/Vh9yG9qq">magnetic resonance imaging</a> (MRI), contrast agents shorten (or in some instances increase) the relaxation times of <a href="/facts/Cell_nucleus/D7sFRa3c">nuclei</a> within body tissues in order to alter the contrast in the image.
Contrast agents are commonly used to improve the visibility of <a href="/facts/Blood_vessel/FG3GjPNW">blood vessels</a> and the <a href="/facts/Gastrointestinal_tract/nK2zwqBS">gastrointestinal tract</a>.
The types of contrast agent are classified according to their intended imaging modalities.

Contrast agent open-in-new

Contrast agent