Physician self-referral and the growing use of multislice CT and nuclear imaging have been blamed for a sevenfold increase in the exposure of U.S. residents to ionizing radiation from medical imaging in the 20 years ending in 2006.
A study by the National Council on Radiation Protection and Measurements, released in March, identified troubling trends. In 2006, medical imaging was responsible for about 50% of the total radiation exposure to the typical U.S. resident, up from just 20% in the 1980s. In the same period, the collective effective dose from medical imaging rose a staggering 630%, from 123,000 person-sieverts in the 1980s to 899,000 person-Sv in 2006. The increases were attributed mainly to CT and nuclear medicine.
Overall, however, medical procedures remained the second leading source of radiation exposure in this country through that 20-year period. Background radiation was the leading source. Consumer products ranked third.
Self-referral was a primary driver of the radiation exposure increase, according to NCRP executive director David A. Schauer. As much as $16 billion per year is spent on unnecessary self-referred noninvasive diagnostic imaging, Schauer reported at the International Congress of Radiology in June 2008.
Independent data support Schauer's conclusions. A 2008 Government Accountability Office report and peerreviewed medical studies noted that in-office CT, MRI, and nuclear medicine exams charged to Medicare from 1998 through 2005 grew at three times the rate of the same exams performed in hospitals and independent diagnostic testing facilities. A study by the Blue Cross Blue Shield organization suggested that nearly half of these exams might have been unnecessary.
“By definition, any CT, x-ray, etc., that uses radiation that is an unnecessary test is an unnecessary exposure to radiation,” said American College of Radiology spokesperson Shawn Farley.
“It's an easy connection of the dots.”
Countless diagnoses are both made and excluded with medical imaging on a minute-by-minute basis worldwide. But these unquestionable benefits must be weighed against the exposure to ionizing radiation and its attendant risks, said Dr. James A. Brink, chair of diagnostic radiology at Yale University.
Device manufacturers and medical imaging experts are working together to reduce the radiation dose associated with medical imaging to levels that are as low as possible. Several novel approaches have already led to dose reductions that were not thought possible a short time ago, Brink said.
“Continued innovation promises continued use of medical imaging with lower and lower doses of ionizing radiation,” he said.
