BOSTON -- Being overweight or obese can increase the risk of many diseases, and now, a new study out of Boston suggests it can also hamper doctor's ability to diagnose a medical problem.

"The ultrasound can penetrate only about 8 to 10 centimeters of thickness. After that, it can't see anything deeper than that," Massachusetts General Hospital's Dr. Raul Uppot said.

NewsCenter 5's Heather Unruh reported Tuesday that Uppot noticed a trend -- fewer imaging tests were readable. He analyzed 15 years worth of radiology records from scans, such as CTs and MRIs, and found that despite better imaging technology, the number of inconclusive exams about doubled in that time. The culprit? Obesity.

"You can miss lung tumors, lung masses," he said. "You won't be able to see tumors in the liver, appendicitis or inflammation in the abdomen, so it is a very big public health issue."

The numbers remain low. About 1 in every 525 tests was deemed unreadable due to weight. Those patients are often referred for exploratory surgery or to more expensive testing, which may also not be conclusive. The trend is concerning.

"This is coming like a freight train at us, this population of bigger and bigger Americans," Newton Wellesley Hospital's Dr. Joan Rastegar said.

Getting a clear scan is not the only problem. Newton Wellesley Hospital has invested $2 million in a new PET-scanner. But if you weigh more than 400 pounds -- or are too round to fit through the opening -- you can't use it.

"So suddenly, you're not in the year 2006, getting the latest diagnostic imaging, you're in 1960. All we can offer you is maybe an X-ray," Rastegar said.

Rastegar said that every time tests are done, the level of radiation for those who are obese is much higher -- adding to the risk of patients and staff.