Medical Imaging Radiation Can Accumulate Overtime

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2009-08-27 12:50

Many types of medical imaging procedures, such as x-rays, computed tomography scans, and nuclear medicine scans, expose patients to ionizing radiation, which over time can accumulate to substantial doses, according to a study published this week in the New England Journal of Medicine.

“We know that radiation is not benign and some people are getting high exposures,” says Reza Fazel, M.D., the lead author of the study and a cardiologist at Emory University.

Researchers used claims data from UnitedHealthcare on nearly 1 million individuals in five regions across the United States to estimate the overall rates of exposure to radiation from medical imaging procedures over a three-year period.

The study was led by a team of doctors from several academic medical centers, including Emory University, the University of Michigan Health System, and Yale University.

Exposure was estimated for these individuals based on the effective dose (in millisieverts) of radiation associated with the procedure, a measure that is meant to reflect how harmful a given exposure is to the body on average. Exposure to radiation has been linked to higher rates of solid cancers and leukemias.

Levels of radiation exposure were categorized as:

* low, less than 3 millisieverts per year, roughly the background level from natural sources in the US

* moderate, up to 20 millisieverts per year, the annual limit for average occupational exposure over five years

* high, up to 50 millisieverts per year, the annual limit for occupational exposure

* very high, more than 50 millisieverts per year.

Nearly eight out of every 10 adults in the study population underwent at least one imaging procedure associated with radiation exposure during the three-year study period.

On average, the effective dose of radiation from these procedures was 2.4 mSv per year, resulting in overall radiation exposures in the average adult in the United States that almost doubled what would be expected from natural sources alone, the authors wrote.

More concerning doses (>20 mSv per year) that accumulated over time were not uncommon. For instance, the authors stated that, if their findings are generalized to the total adult population of the United States, this level of exposure may occur in over 4 million adults.

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