How Do MRI Contrast Agents Work?

While most MRI scans are simple affairs that don’t require intravenous injections, occasionally your radiologist will recognize the need for a shot of contrast dye. It all depends on what your medical team is looking for, and the level of resolution that the radiologist needs to spot potential health threats.

In general, your doctor won’t order the use of a contrast dye unless it is strictly necessary. So when exactly must contrast agents be used during an MRI? More to the point, what exactly is this substance, and how does it work? Keep reading for the answers.

Explaining Contrast Agents Used in MRI Scans

The first thing to understand about contrast “dyes” is that they aren’t dyes at all. They don’t stain your insides. Rather, the most common contrast agents used in MRI scans work on the molecular level, affecting the behavior of hydrogen nuclei in the body.

Let’s back up a few steps. The way that MRI machines create their images has everything to do with these hydrogen nuclei. The MRI tube creates a strong magnetic field, which brings the rotation and polarity of hydrogen nuclei within the body to a uniform state.

Then the technologists trigger blasts of radio waves, which scatters this uniformity. When the radio wave passes, hydrogen nuclei return to their lock-step rotation. The rate at which that occurs is the mechanism by which the computer is able to create accurate images of the various tissues found within a human body.

Phew. So, MRI contrast agents affect the rate of the hydrogen atoms’ return to uniformity. This gives the image-creation software a stronger signal to work with, ultimately creating clearer images with much finer definition.

That’s the hard part. Now we can move on to what really matters: what an MRI contrast agent actually is and why radiologists sometimes choose to use them.

Gadolinium MRI Contrast Agents: Understanding the Risks

The most common contrast agents used in MRI scans contain a substance called gadolinium. While gadolinium-based contrast agents are generally considered safe for use, there are a few conditions that might prevent radiologists from using these substances.

First off, in its free state, gadolinium is toxic. Pharmaceutical manufacturers bond gadolinium ions to carrier molecules, thereby isolating the toxicity of the substance while preserving its effect on image contrast. Still, that toxicity prevents safe use in rare cases.

Radiologists usually won’t use gadolinium with patients who have severe kidney disease because of the risk of a serious condition called Nephrogenic systemic fibrosis. It’s important to tell your physicians if you have a history of kidney disease.

Doctors rarely order the use of a gadolinium-based contrast agent with pregnant women, as well. Keep in mind that, for most patients, these substances have been found to be overwhelmingly safe.

When Radiologists Use Contrast Media for MRI Scans

The bottom line is this: Your doctor won’t order the use of a contrast agent unless it will help with an important diagnosis. The benefits must outweigh the risks, as they do in most cases. Currently, contrast is used in only one out of every three MRI scans.

Because of a contrast agent’s image-enhancing abilities for certain tissues, they may be used to study tumors, blood vessels, inflammation, and the brain. When your doctor orders an MRI with or without contrast agents, call at 888-322-7785 to schedule an appointment.