Obesity Limits Quality of Imaging Techniques
Imaging Obese Patients Is Often Difficult and Sometimes Impossible
Dec. 1, 2004 (Chicago) -- Here's more troubling news about America's obesity epidemic: Being too fat may limit the ability of doctors to diagnose conditions through imaging techniques such as ultrasound, MRI, or CT scan.
"Hospital radiology departments are increasingly unable to adequately image and assess obese patients because of the limitations in current radiology equipment," explains Raul Uppot, MD, a fellow in abdominal imaging and interventional radiology at Massachusetts General Hospital in Boston.
Uppot says he reviewed all radiological reports at Massachusetts General Hospital between 1989 and 2003. He extracted information about patients for whom radiology reports were "limited by body habitus" -- a medical euphemism used to describe patients who are simply too big to properly assess. Uppot discussed his findings at a news conference at the Radiological Society of North America annual meeting in Chicago.
Uppot says obesity affects the quality of all types of imaging. For example, obesity interferes with ultrasound assessment because it is difficult for ultrasound wave signals to penetrate fat to picture the organs underneath. As a result, the image becomes unreadable.
For imaging studies that use CT or magnetic resonance imaging (MRI), the problem is one of fit. The equipment can only hold a limited amount of weight. MRI equipment is also limited by the size of the tunnel in which a person must enter in order to be scanned.
Under most circumstances, quality CT images can be obtained in patients weighing up to 450 pounds. Most MRI equipment can accommodate patients up to 350 pounds.
In 1989, Uppot determined that 0.1% of patients at Massachusetts General could not be imaged because of their obesity. In 2003, that rate had nearly doubled to 0.19%.
In 1989, about 9% of the population of Massachusetts was considered obese, while in 2003, about 16% of the population fit the obesity definition, he says.
In a separate study, he tracked 28 obese patients during 2004 who could not be imaged. About a third received no further treatment, although they had been sent for an X-ray procedure because of some type of symptom. A similar number was sent to institutions where open MRI devices were available for follow-up imaging for their symptoms.
Unfortunately, several patients were sent to surgery with no imaging procedures, a situation that neither surgeons nor radiologists recommend.
"I have seen similar problems with obesity in my practice. There is no question about it. I see it over and over and over again," says Levon Nazarian, MD, professor of radiology at Thomas Jefferson University in Philadelphia.
"What people do not realize is that not only does obesity affect the ability to perform imaging studies, it also affects the doctor's ability to treat the patients because they do not have the imaging guidance. It ultimately can impact outcomes."
Uppot says his study indicates that ultrasound is the imaging procedure that is most frequently affected by obesity. He says almost 2% of patients sent for an ultrasound examination are unable to have a satisfactory study performed because of size. Similarly, almost 1% of patients sent for chest X-rays were unable to have useful examinations performed.
Uppot says he became interested in how often imaging examinations were less than adequate because Massachusetts General has a number of patients who undergo gastric bypass procedures in an attempt to control obesity. When these patients were sent to radiology to see how well the procedure was doing, several were turned away because they were too big.