CT scan radiation can equal nuclear bomb exposure
NewScientist
May 11, 2007
Roxanne Khamsi
Overzealous doctors who order unnecessary body scans that use X-ray technology are placing their patients at risk of cancer, radiologists warn.
Radiation from such scans is in some cases equivalent to that received by some survivors of the Hiroshima and Nagasaki atomic bombs, they say. In response, hospitals and professional associations, such as the American College of Radiologists, are taking new steps to promote more careful use of scanning technologies.
Radiologists are particularly concerned about the use of computed tomography, also known as CT or CAT scans. This technology involves the use of an X-ray generating device that rotates around the patient's body. These powerful beams are picked up by an array of detectors and used by a computer to generate a three-dimensional view of a body region.
Experts agree that when used correctly, such scans can save lives. However, according to some estimates, the radiation exposure a patient receives from a full-body CT scan is often 500 times that of a conventional X-ray and about the same as that received by people living 2.4 kilometres away from the centres of the World War II atomic blasts in Japan.
A CT scan might increase a person's risk of cancer by about 0.05%, although experts stress that on average a person's lifetime risk of cancer is about 20%.
Unnecessary scans
Radiologist Steven Birnbaum, who works in Nashua, New Hampshire, US, says he became acutely aware of the problem after his 23-year-old daughter suffered a head injury, including severe concussion and skull fracture.
Over the ensuing week, Birnbaum's daughter received a total of nine scans – including multiple scans to assess the bladder – until he ordered doctors to stop. Some of the scans she received were medically unnecessary, he says.
"I was horrified. I asked the surgical chief resident if any thought had been given to radiation exposure in patients when doctors ordered CT studies," says Birnbaum, who is a paid consultant for Anthem Blue Cross and Blue Shield, a major healthcare provider.
Short cuts
Magellan Health's National Imaging Associates, a leading US company that helps hospitals and healthcare providers manage their use of medical screening technologies, has initiated a new system to flag up patients that have received too many scans.
Radiologist Thomas Dehn, the company's chief medical officer, says that there are numerous reasons why CT scans are ordered unnecessarily. Doctors are often pressed for time and use the technology as a shortcut, he says. And patients sometimes demand the extra reassurance that a scan can give – a scan can help confirm they are healthy.
A task force within the American College of Radiologists (ACR) published a report earlier in May outlining ways to address the problem of excessive CT scanning.
One recommendation in the report suggests that medical students should receive mandatory training on this issue. It also says that the risks of these scans need to be better conveyed to the public. "We're concerned and we're aware of it," says Arl Van Moore, chair of the ACR.
Journal reference: BMJ (vol 334, p 1006)
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Weblinks
CT scans, Mayo Clinic fact sheet
http://www.mayoclinic.com/health/ct-scan/FL00065
BMJ
http://www.bmj.com/
ACR task force report on radiation dose in medicine
http://www.acr.org/s_acr/bin.asp?CID=2528&DID=26119&DOC=FILE.PDF