March 4, 2009

Americans Getting Higher Doses Of Radiation From Scans

A new report released Tuesday by the National Council on Radiation Protection and Measurement (NCRP) finds that Americans are exposed to seven times more radiation from diagnostic scans today than they were in 1980.

The figures support other evidence that doctors are ordering too many diagnostic tests, increasing healthcare costs and potentially harming patients.

A July study by the Government Accountability Office found Medicare spending on imaging doubled to nearly $14 billion annually between 2000 and 2006, driven primarily by increases in high-tech imaging.  And a 10-year study released last November by the University of California, San Francisco, found use of computed tomography (CT) scans doubled among members of a large managed care plan between 1997 and 2006.

Although these diagnostic scans provide doctors valuable information and are often necessary, some worry that too much radiation exposure can cause cancer, especially in younger patients.

"Imaging has literally become the guiding hand of medical practice," Dr. James Thrall, chairman of the American College of Radiology's Board of Chancellors and head of radiology at Massachusetts General Hospital in Boston, told Reuters.

"Unfortunately, one of the things we have seen in the imaging world is that many physicians look at imaging as the solution to their financial problems," said Thrall, who was not involved in the study.

"Such imaging technology has created a financial incentive for some physicians to profit by referring patients for imaging tests on equipment in their own practices," Thrall added. 

"This is one place the federal government can consider in enacting healthcare reform," he said.

Although these scans have revolutionized the way doctors treat patients, often eliminating the need for unnecessary exploratory surgeries, thousands of non-radiologists now own imaging equipment, something many studies suggest has driven up healthcare costs, Thrall said.

For instance, the GAO study found that from 1998 to 2005, the number of self-referred, in-office MRI, CT and nuclear medicine scans performed on Medicare patients increased at three times the rate of the same tests performed in other settings like hospitals or imaging centers.

"There is a fundamental problem when the person ordering the study has a direct financial interest in maximizing the use of a particular piece of equipment," said Thrall.

The American College of Radiology is now working with other radiology groups to establish imaging standards, Thrall added.

The American Association of Physicists in Medicine (AAPM) said the new NCRP report is not without scientific controversy and requires careful interpretation. The group offered additional background information to help the public avoid misinterpreting the findings.

They caution that the data contained in the NCRP report do not necessarily indicate that the U.S. population is at any higher risk due to this increased use of medical imaging.  And they say the report should not deter patients from getting medically appropriate imaging exams. 

"The NCRP findings on average population dose could be easily misinterpreted if applied to an individual patient's medical situation," the AAPM said.

"CT scans are critical for guiding the treatment of people who are in car accidents, people diagnosed with cancer, people who have blood clots in their lungs, and a vast number of other symptoms and conditions."

Nevertheless, "in the last few years reports in the medical literature and in the popular press have affected public perceptions of CT scans by raising questions of risk related to the use of X-rays, which in very high doses have the potential to damage cells and cause cancer," the AAPM said.

"The new NCRP report falls squarely into this controversy because it estimates the total U.S. exposure to all sources of ionizing radiation has increased six-fold since 1980 -- with about half of this increase due to CT scans."

"This increase is easily misinterpreted, however, because the report calculates the total radiation dose for all CT scans performed in 2006 and divides that by the U.S. population for that year. What is not considered in this global averaging approach is that CT scans are given disproportionally to certain people and groups -- for example, the elderly, people admitted to hospitals for serious trauma, and cancer patients having scans to evaluate their response to treatment."

"The vast majority of Americans receive no radiation from medical imaging at all, or they receive imaging exams that do not use ionizing radiation, such as magnetic resonance imaging (MRI) or ultrasound procedures."

"Adding up all the doses and then spreading out the total over the entire population, no matter a person's age, occupation, location, or health status is not appropriate for assessing risk to the general population," says Cynthia McCollough, a professor of radiological physics at the Mayo Clinic and who chaired an AAPM Task Group that issued a CT radiation dose management report last year.

"The NCRP report is very clear in this regard. The data summarize the sources and amounts of radiation exposure in the U.S. and the total values are normalized to the total U.S. population. The values reported are not appropriate for estimating potential health effects."

While the absolute number of CT exams has grown considerably since the 1980s, CT scanners can now tailor the radiation dose to the specific exam type and individual.  Additionally, all modern CT systems are now equipped with automatic exposure control systems that reduce patient dose levels to the minimum necessary for the examination, the AAPM said.

"The average dose per CT exam has fallen by a factor of 2-3 since the early 1980s. There are simply more people getting CT exams," McCollough added.

The AAPM said it strongly supports appropriate utilization standards be applied for all procedures using ionizing radiation.

"For an appropriately ordered CT examination, an individual derives much greater benefit than risk," says AAPM past-president Richard L. Morin, a medical physicist and Brooks-Hollern Professor at Mayo Clinic Florida.

"Ultimately, people who are scheduled to have CT exams should understand why their doctors have requested the exam "“ if the test will provide information to assist in their medical care, they should not worry about having the exam. There are likely higher risks associated with failing to have a needed medical test, as the correct diagnosis or treatment decision could be delayed or missed."

The National Council on Radiation Protection and Measurement is a non-profit body chartered by the U.S. Congress to make recommendations on radiation protection and measurements.

The AAPM is comprised of research scientists and board-certified health professionals who specialize in the use of radiation in medicine.


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