Contrast agents are used in X-ray examinations, MRI and ultrasound examinations. These agents help visualize organs that are otherwise difficult to distinguish. Imaging is often performed immediately after the administration of the agent. In some examinations, it is necessary to wait for the agent to reach the target area. Contrast agents do not impose restrictions on normal daily life.
Contrast agents in X-ray examinations
Iodinated contrast agents are used in CT and fluoroscopy examinations, and occasionally in standard X-ray examinations. The contrast agent is administered via a cannula, typically into a vein in the elbow crease. Intravenous contrast may cause a temporary sensation of warmth and a metallic taste in the mouth.
Contrast agents can also be administered into the gastrointestinal tract via the mouth or a nasogastric tube. In urinary tract examinations, contrast may be introduced into the bladder via a catheter.
Iodinated contrast agents are excreted from the body within a few hours through the kidneys and urine. If kidney function is impaired, excretion may be slower. Therefore, you may be asked to undergo laboratory tests before the imaging examination. Orally administered barium contrast is excreted in the stool and may appear as a white substance.
Iodinated contrast agents and barium are not dangerous. However, iodinated contrast agents carry a risk of allergic reactions, whereas barium rarely does. Side effects are usually mild hypersensitivity reactions, such as hives or nausea. Citric acid is added to barium to improve its taste, but it may cause allergic reactions in some individuals.
Imaging units are prepared to manage allergic symptoms. Allergic reactions can be prevented and treated with medication. It is important to inform the imaging staff if you know you are allergic to iodinated contrast agents.
Contrast agents in MRI examinations
Soft tissues are well visualized in MRI examination. Sometimes, for example when searching for inflammation, contrast agents are needed. MRI contrast agents are various gadolinium compounds. The agent is administered via a cannula into a vein in the elbow crease.
MRI contrast agents are excreted from the body via the liver or kidneys. These agents are generally well tolerated, and serious allergic reactions are rare.
Contrast agents in ultrasound examinations
Contrast agents may also be used in ultrasound examinations, typically administered via a vein in the elbow crease. Ultrasound contrast agents contain microscopic gas bubbles that enhance the echo returning to the ultrasound probe and improve image visibility.
The microbubbles are excreted from the body through the lungs via exhalation. Ultrasound contrast agents are safe and well tolerated, and the risk of allergic reaction is very low.