Friday, March 6, 2009

NCRP Report No. 160

In past entries to this blog, I have reported on a growing controversy over radiation exposure from medical procedures. On December 7, 2007 I described a study by David Brenner and Eric Hall warning that the increased popularity of CT scans, particularly in children, can lead to an increased incidence of cancer. Then, just three weeks ago, I discussed the "Image Gently" website, created to raise awareness in the imaging community of the need to adjust radiation dose when imaging children.

This week the debate intensified, with three simultaneous press releases. On Wednesday, the National Council on Radiation Protection and Measurement (NCRP) issued a new study titled "Medical Radiation Exposure of the U.S. Population Greatly Increased Since the Early 1980s." This report, also known as NCRP Report Number 160, updates NCRP Report Number 93, "Ionizing Radiation Exposure of the Population of the United States", published in 1987. Readers of the 4th Edition of Intermediate Physics for Medicine and Biology may recall that Russ Hobbie and I based much of our discussion in Chapter 16 about the risk of ionizing radiation on Report No. 93. The press release announcing Report No. 160 states that
"In 2006, Americans were exposed to more than seven times as much ionizing radiation from medical procedures as was the case in the early 1980s, according to a new report on population exposure released March 3rd by the National Council on Radiation Protection and Measurements (NCRP) at its annual meeting in Bethesda, Maryland. In 2006, medical exposure constituted nearly half of the total radiation exposure of the U.S. population from all sources."
The report triggered an immediate response from the American Association of Physicists in Medicine. Their press release, titled "NCRP Report No. 160 on Increased Average Radiation Exposure of the U.S. Population Requires Perspective and Caution", begins
"Scientists at the American Association of Physicists in Medicine (AAPM) are offering additional background information to help the public avoid misinterpreting the findings contained in a report issued today by the National Council on Radiation Protection and Measurements (NCRP), a non-profit body chartered by the U.S. Congress to make recommendations on radiation protection and measurements. The report is not without scientific controversy and requires careful interpretation."
Not to be outdone, the American College of Radiology also issued its own press release Wednesday.
"A recent National Council on Radiation Protection and Measurements (NCRP) Report (NCRP Report No. 160, Ionizing Radiation Exposure of the Population of the United States) stated that the U.S. population is now exposed to seven times more radiation each year from medical imaging exams than in 1980. The American College of Radiology (ACR), Society for Pediatric Radiology (SPR), Society of Breast Imaging (SBI), and the Society of Computed Body Tomography and Magnetic Resonance (SCBT-MR) urge Americans, including elected officials and medical providers, to understand why this increase occurred, consider the Report’s information in its proper context, and support appropriate actions to help lower the radiation dose experienced each year from these exams.

'It is essential that this Report not be interpreted solely as an increase in risk to the U.S. population without also carefully considering the tremendous and undeniable benefits of medical imaging. Patients must make these risk/benefit decisions regarding their imaging care based on all the facts available and in consultation with their doctors,' said James H. Thrall, MD, FACR, chair of the ACR Board of Chancellors."
Who says medical physics isn't exciting? Seriously, this is an important topic, and deserves the careful scrutiny of anyone interested in medical physics. As always, I recommend the 4th Edition of Intermediate Physics for Medicine and Biology as a good starting point to learn the basic physics that underlies this controversy. And keep coming back to this blog for updates as the debate unfolds.

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