Diagnostic scanning saves thousands of lives every year, but it might also be overused, contributing to skyrocketing health care costs and increasing Americans' exposure to dangerous radiation.

A recent study found that a dramatic increase in diagnostic tests – including X-rays, CT scans and mammograms – means that Americans are exposed to seven times more radiation than they were 30 years ago.

Many doctors say that such testing is essential for treating patients.

"A great example is a mammogram. We absolutely know that a mammogram saves lives," said Dr. Ronald Ennis, a radiation oncologist at St. Luke's Roosevelt Hospital in New York.

Mahshid Toghanian learned that she had breast cancer through a routine mammogram. The scan caught it at stage 1, early enough to save her life.

"I was doing self breast exams all the time, but I never felt anything, never found anything with the exam. But they were able to find it with the mammogram," Toghanian.

Doctors say that advances in diagnostic scans eliminate the need for exploratory surgery in many cases, but too much radiation can increase cancer risk.

"A rough estimate for a CAT scan is that it could cause cancer five, 10, 15, 20 years down the road in about 1 in 10,000 people," Ennis said.

The dramatic increase in the use of such scans is one reason why health care costs have skyrocketed. Recent studies, government reports and media articles have accused some doctors and hospitals of doing many unnecessary scans to cure their financial woes.

A government study found that Medicare spending on imaging has doubled since 2000 to about $14 billion a year.

Toghanian, who is in remission after surgery and radiation for her breast cancer, said that such scans are well worth the cost.

The American College of Radiology and other medical groups were developing national standards for the appropriate use of diagnostic imaging.