"Hospital radiology departments are increasingly unable to adequately image and assess obese patients because of the limitations in current radiology equipment," says Raul Uppot, a physician at Massachusetts general hospital in Boston.
The main problem is that ultrasound waves have to penetrate body tissue to produce a quality image, and that can be hindered in even slightly overweight patients, the report said on Wednesday.
Equipment-makers need to think about design changes and technological advancements to obtain quality imaging in larger patients, Uppot added.
"In the meantime, radiologists need to be aware of the limitations of their current imaging equipment and optimise current protocols and equipment settings to accommodate America's fattening population," he said.
He and colleagues released their report at the annual meeting of the Radiological Society of North America.
More than 60% of Americans are
regarded as overweight or obese
It was based on a review of 15 years of radiological examinations that had been labelled as being of limited use because of body size at the Boston hospital.
The percentage of such reports nearly doubled over the period, the researchers said, and corresponded to increases in obesity in the United States.
During the 15 years, obesity increased in Massachusetts from 9% of the population to 16%.
More than 60% of Americans are overweight or obese, with a much higher risk of heart disease, stroke, diabetes and some cancers than people of a healthy weight.
The American Obesity Association estimates that 127 million people in the United States are overweight, 60 million are obese, and nine million are severely obese.