Contrast Agents
In some radiologic examinations a substance can be introduced into the body to enhance tissue contrast. This substance, termed a contrast agent (or contrast medium
or dye), is selected to provide a signal different from that of the surrounding tissues.
In angiography, a water-soluble agent containing iodine is injected into the circulatory system to displace blood and thereby enhance the contrast of blood vessels by
increasing the attenuation of x rays impinging on the vessels. This technique can be
further distinguished as arteriography or venography, depending on which side of
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