Cumulative Radiation Doses Seen in Cardiac Imaging

But experts say heart tests save lives

By Amanda Gardner
HealthDay Reporter

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FRIDAY, July 9 (HealthDay News) -- Cardiac imaging procedures, the use of which has exploded in the United States in recent years, are exposing patients to potentially cumulative doses of radiation, according to the largest analysis of its kind.

But experts really don't know whether the amounts of radiation are harmful or what the long-term effects will be, according to new research published online July 7 in the Journal of the American College of Cardiology.

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The analysis, which covered nearly one million adults in five parts of the United States, found that almost one in 10 people under 65 had a heart procedure involving radiation from 2005 to 2007.

About half (47.8 percent) of the imaging was done in physicians' offices, and older individuals, men in particular, tended to have more exposure.

Most of the patients who did have radiation exposure "had more than the background radiation we get just by living in the U.S., from radon, from the food we eat, from cosmic rays," said study co-author Dr. Andrew Einstein, director of cardiac computed tomography research at Columbia University Medical Center in New York City. "That means their main source of radiation is not radon, not cosmic rays, but tests."

According to the study, the "mean cumulative effective dose over three years was 16.4 millisieverts (mSv)," which is more than background radiation exposure (less than 3 mSv) but less than the upper limit of occupational exposure (more than 20 mSv).

When the authors extended the findings to an overall U.S. adult population of about 191 million, they estimated that about 636,000 Americans might get annual doses of more than 20 mSv/year.

So how safe are you if you need a heart imaging test?

"The basic thinking in the U.S. is that there's no dose of radiation that is completely safe. The lower the dose, the lower the risk," Einstein said. "Can you ever say that there's any street safe to cross? No."

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