Mayo Clinic is now the proud owner of the only 7-Tesla MRI scanner earmarked for clinical use.

Most MRI (magnetic resonance imaging) machines are either 1.5-Tesla or 3-Tesla scanners, said Kimberly Amrami, a musculoskeletal radiologist at Mayo.

The new machine, called a MAGNETOM Terra, has more than two times the magnetic field strength of any other clinical MRI scanner in North America (though there are some 7-Teslas used for research purposes) — and it cost two to three times as much as any other machine at Mayo as well, Amrami said. Mayo did not disclose a price for the scanner.

For now, the scanner is approved by the U.S. Food and Drug Administration only to scan patients' knees and brains. The limited scope of use is to limit patients' exposure to radiofrequency energy.

But the "exquisite imaging" the new scanner offers should allow physicians to see, for example, the source of seizures that were previously invisible to the 3-Tesla scanners, Amrami said, since "they stand out like a lightbulb with this."

The machine will also help physicians detect signs of multiple sclerosis early and allow musculoskeletal clinicians, like Amrami, determine whether a knee cartilage transplant is healing well.

At a nearby monitor, Amrami pointed out the distinct dark blood vessels in an image of a brain, and the delineation between the gray matter and white matter. The same image, done by a 3-Tesla scanner, was far less precise.

"It starts to look like what you'd see in an anatomic text," she said. "You really see clearly what is normal and what is abnormal."

Functional MRIs, when the brain is monitored for activity in certain areas, will also benefit from the clearer images, Amrami said. The machine is also "extremely sensitive to small amounts of blood," which could help physicians detect micro-hemorrhages from a concussion.

"You're seeing these super, super tiny details," Amrami said. "It's the kind of thing that can have a huge impact in a person's life."

Located in the Charlton North building, the 7-Tesla scanner is already being used in clinical work, Amrami said, but in a limited capacity. Several volunteers have been scanned, and some other patients as well.

The magnetic strength of the machine poses a potential safety risk (as with all MRI machines), and the clinic is well aware of its status as the only possessor of the machine outside of Europe.

"We're being very, very careful while we're deciding safety practices," Amrami said. "We're on the bleeding, cutting edge of this."

And in the near future, it'll be available for scheduled scans, like any other MRI machine at the clinic.

"It's a reason for patients to come here," Amrami said. "They can't get this machine anywhere else — at least not in North America."

A display in the Siebens Building explains Mayo Clinic's history with MRI scanners and provides more information and a small model of the 7-Tesla scanner.

The display will be up through Friday.


What's a Tesla?

A Tesla is a unit of magnetic field strength. It can also be described as a unit of magnetic flux density — those terms mean basically the same thing.

Another unit of magnetic field strength is a gauss. A strong fridge magnet is around 100 gauss, according to There are about 10,000 gauss in one Tesla. So one Tesla is about as strong as 100 strong fridge magnets all pulling together.

The unit is named for Nikola Tesla, a Serbian-American inventor who discovered the rotating magnetic field that is the basis of most alternating current (AC) machinery.

Sources: National Institute of Biomedical Imaging and Bioengineering,

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Anne writes for Rochester Magazine and the Post Bulletin, and edits 507 Magazine. She hails from Lafayette, Indiana and enjoys reading, tea-drinking, and her cat, Newt Scameownder.

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