The introduction of fast multi-detector row CT technology, has led to the development of optimized contrast injection techniques. The use of special biliary contrast agents is suitable for gallbladder CT and cholecystograms because they are concentrated by the liver to be detectable in the hepatic bile. The liver (gall bladder) and small intestine provide alternate routes of elimination particularly in patients with severe renal impairment. The main route of excretion is through the kidneys, related to the poor binding of the agent to serum albumin. Injectable contrast agents are diluted in the bloodstream and rapidly distributed throughout the extracellular fluid. Intravascular iodinated contrast agents are required for a large number of x-ray and CT studies to enhance vessels and organs dependent on the blood supply. Nonionic monomer ( low-osmolar contrast media). Iodinated contrast media are differentiated in Negative contrast agents attenuate x-rays less than body soft tissues, for example gas. Barium sulfate is only used for opacification of the gastrointestinal tract. Iodinated contrast materials are most administered intravenous, but can also be introduced intraarterial, intrathecal, oral, rectal, intravesical, or installed in body cavities. Iodine-based contrast agents are water-soluble and the solutions are used nearly anywhere in the body. Iodine and barium have been identified as suitable materials with high radio density and are used until today in x-ray and CT contrast agents. These positive contrast agents attenuate x-rays more than body soft tissues due to their high atomic weight. The ideal imaging agent provides enhanced contrast with little biological interaction.įirst investigations with radiopaque materials are done shortly after the discovery of x-rays. Contrast agents are also used to increase the contrast between different tissues in MRI ( magnetic resonance imaging) and ultrasound imaging. Radiocontrast agents (also called photon-based imaging agents) are used to improve the visibility of internal body structures in x-ray and CT procedures. (CA) Contrast agents are used to change the imaging characteristics, resulting in additional information about anatomy, morphology or physiology of the human body.
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