CT and MRI What's the Difference?

Woman preparing for an MRI
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You go into a donut- or tanning bed-shaped thing, right? Is it true that you can't move? And why do people make such a big deal about metal? What exactly are they looking for?

When it comes to CTs and MRIs, it's normal to have a lot of questions. After all, it's not every day that you come across these imaging scans, and when your doctor writes an order for one especially for the first time you probably feel a dose of worry and apprehension.

Some patients fear these scans because they are worried about feeling claustrophobic or having an implanted metal device or object in their body cause harm, explains William Lee, lead MRI tech at AdventHealth Orlando.

The good news, according to Brandi Sharpe, CT system modality manager for AdventHealth, is that most of these scans can be completed relatively quickly, painlessly, and at extremely low (if any) risks to the patient.

That said, most restlessness about these scans can be resolved by taking some time to learn a little more about them. Understanding their purpose and knowing what to expect during them is a good start. While both scans provide highly detailed information about your body to help your doctor get a clearer picture of your health, there are three important main differences that Lee and Sharpe further explain.

They differ in purpose.

"CT scans (also called CAT scans or computerized tomography) are usually ordered to diagnose serious injuries to the head, lungs, abdomen, spine, and pelvis. They can be used to diagnose fractures and to identify the size and location of tumors," explains Sharpe.

"On the other hand, MRIs (also called magnetic resonance imaging) provide a more detailed look, says Lee. The images from an MRI scan can diagnose problems with the joints, tendons, and ligaments, as well as the brain, spine, neck, breast, abdomen and muscles," he continues."

They differ in scan time.

Yes, it's true. Both scans require you to be still, but for different amounts of time.

"While 95 percent of our scans are completed within 10 to 15 minutes (in and out of the room), CTs take much less time compared to an MRI," Sharpe explains. The scan time for CTs can take as little as five minutes, while MRI scans can take 30 minutes to an hour to complete.

"MRIs tend to take a little longer, so our imaging centers try to make it more comfortable for patients by offering things to help them relax and pass the time, like music, video goggles or soothing wall murals," adds Lee.

Lee and Sharpe note that for children, MRI and CT scans can be challenging. Many children find it hard to stay still and can be more anxious about the process. At AdventHealth for Children, Child Life Specialists are available to explain the scan and offer strategies to support each child throughout the process, with anesthesia only used when medically necessary. They even offer a complimentary MRI Picture Perfect program that gives a child the opportunity to practice an MRI prior to their scheduled exam.

They differ in risks and restrictions.

Lee points out, "One of the major differences between the two scans is in the nature of the technology. To produce diagnostic images, CTs use X-ray technology where MRIs use radio waves and powerful magnets," he continues.

"Because CTs use X-rays, they do expose patients to a small amount of radiation. While radiation is always considered a health risk, we ensure that all AdventHealth locations and AdventHealth Imaging Centers use the safest, highest quality technology possible and follow protocols to minimize and monitor each patients radiation exposure," advises Sharpe. "We also collect data about our facility's overall radiation dosages and exposures, and follow the ALARA (as low as reasonably achievable) principles as well as the Image Gently guidelines (for children) to ensure the utmost safety," she adds.

MRIs also carry different risks and restrictions. Lee explains that MRI scan technology uses magnets, which are sensitive to metal materials. "Having metal on or in your body during the MRI scan can pose a safety risk and cause distortions that can interfere with getting quality images from the MRI scan," he adds.

It's important to tell your doctor and imaging technologist if you have any implantable device or object, like a pacemaker, metal pins/screws, aneurysm clips, or even have a job that involves working with metal because flecks of it can unknowingly get into the eye or under the skin, emphasizes Lee. If unsure, it's always good to check with a radiologist to make sure an MRI is safe for you.

But they have the same takeaway.

If you're holding a doctors order for an MRI or CT and feeling a lump in your throat, take a deep breath. Know your doctor wrote that order for a good reason, and there is an experienced and compassionate imaging team ready to support you. "If you have any concerns or questions about your imaging facility or scan, don't hesitate to call us," says Sharpe. "We want every patient to be comfortable and have a positive, safe imaging experience", she concludes.

Learn more about AdventHealth's imaging services.

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