What are the Different Types of Contrast Media?

J.M. Willhite

Contrast media, also known as medical contrast mediums and contrast agents, are chemical compounds and gases used to supplement medical imaging techniques by enhancing the image results during the medical testing processes. Contrast agents work in combination with either magnetic resonance signal augmentation or x-ray attenuation. Adverse effects related to contrast media are fairly uncommon, but can occur and vary in how they manifest and their severity.

A contrast media can be used to make certain parts of the anatomy stand out more clearly on an X-ray.
A contrast media can be used to make certain parts of the anatomy stand out more clearly on an X-ray.

Magnetic resonance imaging (MRI) employs gadolinium, a rare metal, as a contrasting agent to produce high contrast images of soft tissue in the body. Used for cardiovascular, oncological, and neurological imaging, the MRI does not utilize radioactive materials such as high frequency gamma or x-rays. Administered intravenously, the oxidized metal works with existing hydrogenated atoms of water in the body, resulting in enhanced imaging results.

Gadolinium is used as a contrast agent in MRI machines.
Gadolinium is used as a contrast agent in MRI machines.

X-ray attenuation, often referred to as radiocontrast, is a form of radiography that utilizes a contrast agent to improve image resonance. Historically, a concentration of thorium dioxide was used as a contrast agent until it was proven to be hazardous. Based on application, barium and iodine are the most commonly employed contrast agents in x-ray imaging.

Patients will sometimes receive contrast dye orally, through barium sulfate.
Patients will sometimes receive contrast dye orally, through barium sulfate.

Barium, a white insoluble powder, is generally used as a contrast agent for medical imaging tests of the gastrointestinal tract. When combined with water, the barium powder creates an opaque mixture that functions to define the digestive tract during the imaging process. Iodine contrast media, which can be classified as either ionic or non-ionic in composition, is used to accentuate blood vessels and soft tissue. As a soluble contrast agent, iodine is generally harmless and, as a result, most intravenous contrast dyes are iodine-based.

Contrast-enhanced ultrasound uses micro-bubbles filled with trace amounts of nitrogen or fluorocarbons as contrast agents which are administered intravenously. The bubbles reflect the sound waves back to the transducer as a higher signal which is used to formulate a high resolution image. Ultrasonography is employed to image organ-specific blood flow rate and perfusion.

Side effects associated with the use of contrast media are dose dependent on the type of media used and vary in severity. Mild side effects, including vomiting, nausea, and a metallic taste in the mouth, may manifest shortly after the contrast agent is administered and usually subside relatively quickly. More moderate to severe side effects, such as anaphylactic reactions and renal failure, can occur in individuals who have never had contrast agents administered before and can result in death if left untreated. Delayed reactions to contrast media, including abdominal pain, fatigue, and fever, are more common when ionic agents are administered.

Intravenous contrast dyes are often iodine-based.
Intravenous contrast dyes are often iodine-based.

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Discussion Comments


Barium actually has a somewhat sweet odor. Some facilities offer flavored barium, but it is all chalky. It is not that bad; I have tasted it before. Depending on what you are having done, you may have to be listening to directions on when to swallow and what directions to turn. If you focus on that, it may deter you from thinking about what you are drinking. Good luck!


I know that it must be safe because healthcare professionals do it all the time, but injecting someone with bubbles just sounds dangerous. I have heard that you can die if a bubble gets injected into you vein.

Of course, death only happens if the bubble is big enough to block the oxygen and blood from flowing. Since ultrasound technicians use microbubbles, they are so small that they do no harm.

Still, I worry about what would happen if the microbubbles stuck together to form one large bubble. I would prefer positive contrast media made of iodine any day over negative contrast media made of air bubbles.


My cousin had ionic contrast media injected into her vein before having a CT scan. She was pretty nervous about the whole thing, because she had just read the list of possible reactions to the media.

She was told to let the staff know right away if she started to swell, break out in hives, feel pain in her chest, or suddenly feel flushed. I think this freaked her out to the point that she started imagining things, because she had them stop the scan and check her out, but they found nothing wrong.

I realize that it is important for patients to be aware of what might happen to them so that they can recognize problems and alert the staff. However, I do think that it is a bit much to be told all that information right before the procedure. I think it would be better if they were given the information to read over days before they are actually given the contrast media.


@JackWhack - I had to drink a barium shake before my CT scan. You should be fine, because it doesn't smell bad or taste rotten at all.

I had been having pain in my abdomen around my belly button, and in order for the problem to show up, I needed a contrast agent. I had been instructed not to eat anything that morning before coming in. The technician gave me the white barium shake and told me to drink it all.

It had a very chalky texture. My gag reflex kicked in a little at first, but I managed to get it down. I didn't have any contrast media reactions like I feared I would.

Because of the barium, my doctor was able to see that I had multiple cysts on my kidneys. They were causing the abdominal pain.

Has anyone here ever had to drink barium before having X-rays? I was told that I will have to have a scan in a few weeks, and barium will be what they use as a contrast agent.

I'm scared that it will taste terrible. I've only heard bad things about it.

I can deal with a little bitterness, but I'm just hoping it isn't foul smelling and that it doesn't taste like anything spoiled. Those are the only things that make me vomit. If it is just slightly unpleasant, I will be fine.

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