New MRIs get patients out of the tube

By MELISSA KLEIN
THE JOURNAL NEWS
(Original publication: July 21, 2002)

LARCHMONT — Although Dawn Powell does not consider herself claustrophobic, the encased feeling she had in the tunnel of an MRI machine eight years ago was not an experience she wished to repeat.

"It's like a coffin," said Powell, of Scarsdale. "It's right at your face. It's right at your arms."

So when Powell's doctor recently recommended another MRI, she asked to go to an open machine, which does not have the same tunnel configuration. Her doctor sent her to the Open High Field MRI and CT of Westchester, a center in Larchmont with a new breed of open machines.

"This was much better, much better," Powell said. "You can see out the sides."

It is not unusual for patients to find the tunnel of traditional MRIs too confining. Some must be sedated during exams, which are used to take detailed pictures of the body, and others avoid them altogether.

But many patients who seek out open machines are unaware that the quality of the pictures, until recently, was not as high as those taken in the closed units.

In the past two years, a new, more powerful type of open MRI has become available. These so-called open high-field units have the same type of superconducting magnet as a traditional MRI and produce comparable images. Another option also on the market is an MRI in which patients can stand up if necessary and even watch television while the exam takes place.

Fewer than 150 of the open high-field units are available worldwide. The MRI at the Open High-Field MRI Institute in Larchmont is the second such unit made by Hitachi to be installed in New York.

"The picture quality that we're getting is the same or better than many of the closed high-field MRIs, and it's great because the patients no longer have to go in this tube," said Dr. David Stemerman, a radiologist and the medical director of the center, which opened a few weeks ago. "The doctors are happy, because they're walking out with the same picture quality as the closed MRIs."

The open design of the MRI and a wider exam table than those in traditional machines also allow very heavy patients to be scanned, Stemerman said.

The body part to be scanned must still be positioned under the magnet, which looks like a giant hamburger bun. The back and sides of the machine are open, and there is more room between a patient's head and the magnet than in a closed MRI.

Unlike the radiation used in X-rays or CAT scans, magnetic resonance imaging machines work by coupling a magnet field and radio waves. The magnet causes protons inside the body to line up in a certain way. The alignment is then disrupted by a radio signal, and the energy given off is transmitted to a computer that creates a cross-sectional image of a part of the body.

In traditional MRIs, the patient lies in a tube surrounded by the magnet, which is actually coils of wire in liquid helium that have been charged with electricity. The magnet remains charged as long as the helium is kept at super-cold temperatures. These magnets are usually 1.5 tesla, or 30,000 times more powerful than the magnetic pull of the Earth.

Until recently, most open MRIs used permanent magnets, which are like giant versions of refrigerator magnets. The strength of the magnetic field is typically about 0.3 tesla, meaning the images are not as crisp as in closed machines and the exams can take twice as long.

The open high-field units are 0.7 tesla. While the magnet is still not as powerful as in a closed unit, the lack of strength is made up for in the more efficient orientation of the magnetic field, which is vertical instead of horizontal, and the radio waves, said Sheldon Schaffer, vice president and general manager for magnetic resonance for Hitachi Medical Systems America Inc.

The open magnets do have the same safety concerns as traditional MRIs. Ferrous objects that come near the machines can be pulled into them, as was the case at Westchester Medical Center last year when a 6-year-old boy was killed when he was hit by a metal oxygen tank drawn to the machine's magnetic field.

The difference with open MRIs is that since they are weaker magnets, the magnetic field usually does not extend far from the machine, said Dr. Emanuel Kanal, director of Magnetic Resonance Services at the University of Pittsburgh Medical Center and an expert in MRI safety.

"The diameter of the region around the magnet that can get you into trouble is smaller," Kanal said.

At 92,000 pounds, the machines' design makes them heavier than traditional MRIs. At the Open High-Field MRI Institute, the glass front door of the building on Boston Post Road and some interior walls had to be removed to install the machine.

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