BAY AREA / Hospitals flummoxed by patients too big for MRI machines

When Dr. Susannah Cornes' patient came in with paralysis and numbness, she wanted an MRI to look at the spinal cord. But the machine couldn't handle someone of her patient's size -- more than 350 pounds.

Absent that option, Cornes, a UCSF resident in neurology, recommended exploratory surgery. The patient declined, choosing instead to live with the numbness and limited movement.

It's a problem doctors say they see as frequently as once a month as the number of people with morbid obesity climbs in the United States: A patient complains of abdominal pain. A CT scan or MRI could pinpoint the problem, but the patient is too heavy or too large for the machine to handle.

"In many ways, we have to regress to the old days and rely on physical findings, some of which are very subtle," said Dr. John Husted, a gastric bypass surgeon with Laparoscopic Associates of San Francisco.

And that, said Cornes, could have significant implications for the health of a patient. "It can delay the diagnosis of medical problems that could be potentially intervened or treatable," she said.

Imaging machines built strong enough to handle the morbidly obese -- those who suffer severe medical problems because of their obesity -- are available, but to a great extent have not been employed in Bay Area hospitals and clinics.

When the opportunity to buy a new machine comes up, hospitals opt for machines that give better images rather than systems that handle larger patients. And that rankles some people.

"With the obesity epidemic ... the hospitals should realize that they're going to have to get equipment that services our needs," said Oakland resident Frances White, who is treasurer of the National Association to Advance Fat Acceptance.

"The majority of MRI scanners in clinical use are 1.5 tesla (in strength). For those who are in the market for new scanners, there is now a new trend to get higher field strength," said Dr. Rajul Pandit, head of neuroradiology at Santa Clara Valley Medical Center.

A 1.5-tesla MRI from Siemens Medical Solutions USA that can handle larger patients is available, but no Bay Area hospital has one yet. Instead, hospitals sometimes send patients to private imaging centers, most of which have open MRIs usually used for claustrophobic patients. Still, most open machines aren't wide enough to image the abdomen or spine of an obese patient.

The Centers for Disease Control and Prevention says 5 percent of Americans are severely obese.

A CT scan creates three-dimensional pictures from two-dimensional X-ray images to look at internal organs. An MRI, using more advanced technology, gives three-dimensional images of better contrast and resolution.

The average CT is of no use for people who weigh more than 450 pounds, and most MRIs can't handle people who weigh more than 350 pounds. With both machines, the table that carries the patient into a small tunnel, or bore, where the images are taken can't support the weight. In some cases, the bore is too small.

Jenny Mount, a patient services representative at the San Francisco Magnetic Resonance Center, said the imaging center accepts about one obese patient a month from a local hospital. It has an open MRI that can handle patients who weigh up to 375 pounds, but because its entry is only 17 inches high, it can be limited in scanning the abdomen and spine in large patients. The center sees which position and equipment can be used to put a patient in the machine comfortably and get acceptable images.

In 2004, Pennsylvania-based Siemens Medical Solutions developed an open MRI scanner that could take people weighing up to 550 pounds and was then the gold standard of 1.5 tesla in image strength.

But Jennifer Thomas, a spokeswoman for Siemens, said only Valley Imaging Partners in San Jose carries the machine in the Bay Area. The Siemens machine, the Espree, costs about $1.5 million.

Still, hospitals are mostly opting for scanners that cost $2 million to $2.2 million; the 3.0-tesla closed MRI machines can't take patients who weigh more than 350 pounds but are twice as powerful as their predecessors.

Recently, UCSF officials discussed buying a new MRI scanner that could accommodate very obese patients, but decided against it, said Dr. Fergus Coakley, UCSF radiologist and chief of abdominal imaging. They selected a machine with superb image quality, but with the same size capacity as previous scanners, he said.

Santa Clara Valley Medical Center also chose not to invest in an open MRI scanner that could handle larger patients, said Dr. Young Kang, chair of radiology at the county hospital.

"The thing about open magnets is that the signal quality is not that good, so for the remainder of the patients that aren't going to be in that category (too large for closed MRI scanners), we would lose out on image quality," Pandit said.

Other ways to image a patient -- such as ultrasound -- exist, but obesity also limits their effectiveness. The images tend to be distorted, said Dr. Raul Uppot, a Harvard radiologist who correlated an increase in obesity in the Massachusetts General Hospital area with an increase in the number of radiology reports citing limitations due to body build.

If an ultrasound or CT can't be done, MRI is the tool of last resort. "MRI has been a problem-solving modality," Kang said. "It's the end of the line, and if we don't have that, there are no big alternatives." This article has been corrected since it appeared in print editions.