Bariatric MRI: Challenges and Work-arounds
ThedaCare is Northeastern Wisconsin’s largest community-owned health system; its numerous radiology units strive to provide the highest-quality imaging to attract new referrals while simultaneously retaining hard-won existing business. Until relatively recently, however, performing MRI exams for patients weighing more than 300 pounds was a problem.
Paul Ho, MD
Larger patients were often too big to fit into the bore of the organization’s conventional high-field MRI scanners, and when they did fit, the cramped confines could trigger bouts of claustrophobia. Depending on the intensity of anxiety at feeling entombed, these patients would squirm or try to get out of the scanner. ThedaCare, based in Appleton, attempted to solve this problem with the addition of an open MRI scanner. The new machine quickly found favor among bariatric patients and the claustrophobic. Obtaining good images remained a challenge, though. “It was an open MRI, but one with a low-field magnet,” radiologist Paul Ho, MD, explains. “What we really needed was an open MRI with a high-field magnet.” Bigger and Better ThedaCare installed a high-field open MRI system from Hitachi Medical Systems America Inc, Twinsburg, Ohio, at the organization’s new OIC in Appleton just in time for its launch in September 2009. Finally, Ho says, bariatric patients could fit comfortably into an MRI scanner delivering the horsepower necessary to generate pictures of optimal diagnostic usefulness. ThedaCare, for its part, wasted no time making this capability known throughout the community. As a result, roughly half of the imaging center’s MRI volume now involves exams for bariatric patients. Peter L. Rizzardi, lead MRI technologist, reports that the Hitachi Oasis system is completely open on the sides and is generous enough to accept patients weighing up to 500 pounds comfortably (the patient table can support up to 660 pounds). To date, the heaviest patient encountered weighed 460 pounds, he says. A selling point of the Hitachi product was a configuration friendly to patients with high weights or confined-space problems. It features a cradle-style patient table that can be lowered to within a foot of the floor, making it easy for bariatric patients to get on and to be positioned properly for imaging. Carrying the Weight Even with the open-sided design, however, obtaining diagnostically useful images of obese patients still requires extra effort on the part of the technologists, just as before. “No matter what, very heavy patients do not scan as nicely as average-sized patients for the reason that, often, they can’t hold their breaths as long,” Ho says. “It’s also harder for them to hold perfectly still during scanning.” Rizzardi notes a correlation between obesity and claustrophobia. “The larger the patients, the more confined they are inside the scanner bore—even an open one. The more confined they are, the greater the potential to feel anxious or claustrophobic,” he says. From the vantage point of productivity, few things can hamstring workflow quite like the mistake of assigning a patient to a conventional scanner only to discover, at the last minute, that the patient is too big to fit inside. At the ThedaCare imaging center, the MRI fleet includes a conventional scanner; to ensure that obese patients are not inadvertently put in its queue, the central scheduling department attempts to determine, ahead of time, whether the patient is obese and/or claustrophobic. Those who meet one or both those criteria are automatically slotted for imaging on the Hitachi Oasis, Rizzardi explains. Another productivity hurdle arises from the fact that many obese patients do not fit inside the scanner in certain positions, requiring alternative positioning. Because of this complicating setup factor, often compounded by the patient’s agility/mobility limitations, ThedaCare allots ample extra minutes to each such exam. The rule of thumb is to allow an hour for bariatric MRI exams without a contrast agent and 1.5 hours for exams with one. During the entire process, the technologists do everything possible to put patients at ease and keep them comfortable, Rizzardi emphasizes. “We also give them lots of reassurance that it’s okay if, midway through, they suddenly feel like they can’t handle being inside the scanner anymore,” he says. “Building trust with these patients, right from the start, is crucial to getting them all the way through their exams successfully.” Dry Run Half of the high-field MRI exams performed on severely obese patients at ThedaCare’s imaging center involve orthopedic conditions, while 30% pertain to neurological problems. “Bariatric patients have the same imaging needs as nonbariatric patients,” Ho says. “We can do brain, spine, abdominal, bone/joint, and vascular imaging on them.” Four technologists run the various MRI scanners at the facility. No one is dedicated solely to working with obese patients, but all are intimately familiar with the protocols for setting up and imaging the demographic. Acquired images are digitally routed from the MRI to the radiologists’ reading room, and Ho notes, “It doesn’t take any longer to read an obese patient’s scan than it does to read the same type performed on a person of average weight.” Rizzardi notes that it is advantageous to invite bariatric patients to come to the imaging center for a dry run a few days ahead of their scheduled exams. “This gives the patient—and us—a good idea of what to expect,” he says. “It tells us whether the patient can fit in the scanner and, if so, whether he or she is likely to be able to make it all the way through the exam without panicking. From this, we can get a good sense of what we’re going to need to do to accommodate the patient on the day of the exam itself. Things go a lot more smoothly this way.” A patient’s weight turns out to be a poor indicator of his or her ability to be positioned within the scanner. “Weight doesn’t always distribute evenly on an obese person’s body,” Rizzardi explains. “Weight accumulates in various places, and it’s different from patient to patient. What decides whether the patient can fit is the anterior-to-posterior aspect.” ThedaCare technologists know they have done right by the patient when, after the exam, the patient expresses gratitude—a frequent occurrence, these days. “A lot of first-time patients come here under the impression that they’re too large for an exam they desperately need,” Rizzardi says. “They have that impression because it’s what they were told, time and time again, at other imaging centers. With us, though, it’s the opposite. They leave here feeling that we’ve done something truly wonderful for them—something no one else before has been able or willing to do.” Rich Smith is a contributing writer for