Given the choice, most patients would rather undergo an "open" MRI test rather than be encased in the narrow cylinder of traditional MRI machines.

"A lot of people don’t even realize they’re claustrophobic until they get inside that dark, noisy tunnel," said Dr. Colby Chastain, a Gainesville radiologist.

But while the open configuration is popular with patients, there’s sometimes a trade-off. MRI, or magnetic resonance imaging, creates pictures of the inside of the human body by using superconducting magnets. These magnets work better when they’re shaped like a cylinder.

"With open MRI, you’re giving up some of the conductivity of the magnet," said Debbie Duke, director of imaging at Northeast Georgia Medical Center.

The hospital has tried to address that issue with its recent purchase of a more powerful open MRI machine, now installed at the Imaging Center. The $1 million device is rated at 0.7 teslas, a measure of magnetic strength. Most open MRIs, including the machine that this one replaced, have a strength of 0.2.

Duke said there are only a few 0.7-tesla open MRI machines currently in use in Georgia.

"The highest (strength) open MRI available anywhere is 1.0," she said. "There’s none of those in our area, and they’re very expensive."

By contrast, most enclosed MRIs are rated at least 1.0. The hospital has two 1.5 machines, one at the Imaging Center, the other at the Lanier Park campus. And within the main hospital itself, there’s a super-strong 3.0 machine.

"I love the 3-tesla magnet, and it is better in certain situations, such as visualizing musculoskeletal injuries and neurological disorders," Chastain said.

But many patients are not able to use that high-tech machine. In fact, until now, some patients were not able to have an MRI performed at all.

"We’ve been having to turn people away," Duke said. "With the previous (open MRI) table, it was supposed to handle up to 350 pounds, but we had trouble with patients weighing more than 300. We really felt the need to accommodate larger people, especially with our bariatric (weight-loss surgery) program."

According to the manufacturer’s claims, the hospital’s new open MRI machine can handle patients weighing up to 500 pounds, though Duke said they haven’t tried it with anyone that size yet. They just started using the machine last Monday.

"Patient reaction has been good, so far," she said.

Open MRIs are useful not just for large patients, but for those who are claustrophobic.

"We were having to sedate a lot of patients (so they could tolerate the procedure)," Duke said.

She said open MRI is also helpful in pediatric cases.

"Usually kids have to be sedated because they can’t lie still," she said. "The table of this new machine is actually big enough that a parent could lie down alongside the child (to keep the patient calm without using sedation)."

It wouldn’t harm the parent to be on the table because, unlike X-rays and CT scans, MRI machines emit no radiation.

Chastain said when patients are anxious and agitated, they fidget. But in order to get a clear MRI image, the patient needs to lie completely still.

"And it’s a long exam. A lot of studies run 30 to 40 minutes," Chastain said.

In some cases, an open MRI can yield more information than a closed MRI, even though the magnet is weaker.

"We often end up getting better studies with open MRI, because the patient is more comfortable and doesn’t move as much," Chastain said. "I think with most of the new (open MRI machines) coming out, the imaging is just as good (as with closed MRI). And we have computer software that can enhance the images."