They found that more than half of the advanced x-ray scans weren't necessary under guidelines established by the American College of Radiology.
The concern is that the scans expose patients to radiation which could increase their risk of developing cancer.
The scientists say excess radiation exposure from the unnecessary scans could mean up to 20,000 radiation induced cancer cases per year in the U.S.
According to study author, Dr. J. Louis Hinshaw, "The fact of the matter is, we really don't know what the true risk is, and so in light of that we really need to do whatever we can to minimize the radiation patients receive."
The findings were presented at the annual meeting of the Radiological Society of North America.