Los Angeles — Too many medical imaging procedures, commonly used to diagnose and treat diseases, could harm patients, according to a new study.

Each medical imaging procedure, from X-rays to mammograms, exposes patients to ionizing radiation. Researchers found that more people are being exposed to high and moderate doses of radiation.

The study looked at the insurance claims of nearly 1 million adults. About 70 percent had at least one procedure over three years.

"About a fifth of patients were exposed to moderate radiation," said Dr. Andrew Einstein, with Columbia University College of Physicians and Surgeons.

A smaller number of patients were exposed to high levels, and multiple procedures could become a problem over time.

"Radiation may increase their chances of having cancer in the future, but we're not sure about that," said Dr. Javier Sanz,with the Mount Sanai School of Medicine.

Researchers hope the study will be a wake-up call for doctors.

"I think we have to be aware that the radiation we give may come at a cost, and we don't have to use it freely," Sanz said.

John Wilkes, 65, said he needs a CAT scan to help fix a heart problem.

"If there is a risk involved, I'm certainly willing to take it," Wilkes said. "I can't get my heart fixed without having a CAT scan."