Eager as they might be to find out what's going on inside their bodies, many people are frightened of magnetic resonance imaging machines.
Manufacturers have made significant changes to make the process more comfortable. But for some people, sliding into a narrow tube for an extended period of time with nothing but a very loud pounding noise for company is unbearable. It's estimated that up to 15 percent of potential MRI patients won't have a scan because the machine is so confining, it makes them feel claustrophobic. Then there are those who don't fit in a conventional MRI machine, a significant problem given the obesity epidemic.
Open MRI—machines that are open on two sides—were introduced years ago, and have been heavily promoted as the solution to confining closed machines. But the ads don't tell you what many doctors know: Open scan machines, particularly those with lower-strength magnets, yield poorer-quality images than a good practitioner can get with a closed machine.
MRI scans offer a view inside the body that other types of imaging—X-ray, CT and ultrasound—can't provide. A powerful magnet and pulses of radio wave energy generate highly detailed pictures revealing tumors, damage to organs and blood vessels, broken bones, infection, blockages and problems with discs, cartilage, ligaments, tendons and nerves.
The stronger the magnet, the better the picture — and for complicated reasons involving geometry and physics, open machines must use weaker magnets. Measured in units called Tesla, magnet strength ranges from 0.2 to 3.0 in most clinical settings. Open machines' magnets usually are less than 1.0. But closed MRI ranges from 1.0 to 3.0.
Most radiologists, the physicians who read MRIs, prefer conventional closed MRI.
"You can still get a look inside the body (with an open scan), but it's not as good a look as you get with a closed scan," said Dr. Reed Murtagh, a neuroradiologist and professor of oncology and neuroradiology at Moffitt Cancer Center and USF Health.
Murtagh said that's especially important when imaging the brain, for example, his specialty. "Open MRI is better than no scan at all, but it's not ideal," he said, explaining that it's possible to miss key findings with a low-quality scan.
"Do you want the best MRI scan possible? Then go with closed," he said.
Still, patients prefer open machines, and manufacturers are finding ways to balance comfort and image quality.
"The real workhorse in the clinical setting is the 1.5 T machine," said David Nelson, imaging director at BayCare.
In the past three years, BayCare added five new conventional 1.5 Tesla machines. They are not open, but they feel less intimidating than other closed machines because the opening is 5 inches wider and the tube is about 2 feet shorter than other closed MRIs.
"We survey our patients to find out how their experience was and there is very low claustrophobia with these machines. Less than 1 percent of our patients still have problems," Nelson said.
He cited a 2003 medical journal study that compared MRI screenings of shoulder injuries. The open machines missed one-fourth of the torn ligaments that the closed machines revealed.
But not surprisingly, the higher-powered machines come with a higher price tag. Nelson said an MRI with 0.7 Tesla and below runs about $250,000 to $500,000. The 1.5 T machine costs $1 million to $1.4-million, depending on options. At most imaging centers, patient charges vary by the body part being screened, not the machine used.
Jonnie-Mae Smith of Tampa appreciates the need for high resolution images, but, unless she's completely sedated, she can tolerate only an open machine. "I have severe claustrophobia and can't be in a closed MRI machine or CT scanner. I can't even get in an elevator," said the 44-year- old who requires at least six scans each year because of a genetic disorder that affects her bones and connective tissue.
"It's like being in a coffin. Just thinking about it, I can't breathe," she said.
For most of her scans, Smith goes to Tower Open Scan MRI in New Tampa, where she is lightly sedated and gets lots of soothing support from the technicians. "They make it easier for me to get through," she said.
Some MRI centers offer special goggles and headphones that play movies or calming music, aromatherapy and specially trained technicians who can talk most patients through bouts of mild to moderate claustrophobia. Many allow a patient to have someone hold their hand during the scan.
Radiologist Raj Kedar specializes in orthopedic and abdominal imaging at Tower and is an associate professor of diagnostic and musculoskeletal imaging at USF Health. He says about 10 percent of Tower's patients opt for open MRI.
"Open MRI fills a need for a lot of patients, those who are large and those who can't be in small, closed spaces," said Kedar, who is involved in Smith's care.
"But it's no question that closed MRI has the advantage of giving better pictures, better resolution, and it's faster."
Closed scans can be about twice as fast as open scans, if patients remain very still.
"In some cases it can take 45 to 50 minutes to get images in an open scan," Kedar said.
Jonnie-Mae Smith recently had a two-hour appointment to scan an elbow and a wrist. As long as the scans are clear enough to get the information doctors need to treat her, she'll find the time.