Not too long ago, I wrote about the mind-boggling high doses of radiation that CT scans deliver. In the (sort of) good news from the medical establishment department, researchers recently announced that they have developed new software that could cut the dose of radioactivity by half or more. The news is not exactly cause for jubilation, because even at half the normal dose, a single CT scan still exposes patients to more radiation than 200 chest x-rays.
According to Dr. Daniel Johnson of the Mayo Clinic in Scottsdale, Arizona, who authored the study, “This new technique allows us to use far less radiation than even a typical abdominal CT scan without compromising image quality.” The results of the study were published in the American Journal of Roentgenology, the publication of the American Roentgen Ray Society (ARRS), “the first and oldest radiology society in the United States.”
CT (computerized tomography) scans provide a cross-sectional view of a portion of the body by weaving together multiple x-ray images taken from different angles. Physicians can look at individual “slices” or use 3D imaging tools to get a full image of the area in question. The medical community loves CT scans because of the detail they provide, and so physicians use them for a variety of purposes — to quickly examine internal injuries resulting from accidents or trauma, for instance, or to get detailed views of the brain and circulatory system. Lately, doctors even have started using CT scans to perform “virtual colonoscopies” to detect cancers of the colon.
The problem, of course, is the radiation. As I’ve written before, a study published in 2009 blamed CT scans for 29,000 new cancers and 14,500 deaths in a single year. That translates to a one in 270 chance of getting cancer from a CAT scan if you’re a woman, and a one in 600 chance for men. The risk is even higher for young people, in part because they may have more CT scans in their lifetimes. Another study showed that one CT scan could deliver as much radiation as 74 mammograms or 442 chest x-rays.
Although the news about lower-dose CT scans may make some medical professionals happy, not all admit that there’s a problem in the first place. For instance, the America College of Radiology, an organization dedicated to medical imaging, says that it’s impossible to know whether or not those who had CT scans had some underlying predisposition to cancer, so the statistics may be misleading. (Remember when the tobacco industry made similar claims about the links between smoking and cancer? Probably best not to go there, though!) Also, the director of the organization, Dr. James Thrall, argues in favor of CT scans by claiming there’s no proof that “low” doses of radiation actually increase cancer risk and that it might be more a matter of exposure levels having to reach a certain threshold before cancer risk gets exacerbated. It’s an interesting argument, given that the typical CT scan delivers the equivalent of 442 chest x-rays, which sure makes the “low-doses aren’t dangerous” argument a bit tough to support.
In spite of the assurances of the industry groups, there is plenty of room for concern. For example, just last month, a New England Journal of Medicine editorial reported a case in which a 59-year-old teacher received an accidental radiation overdose from a brain perfusion test — a CT scan of the brain to detect strokes. Even though the dose could be read on the display by the technologist, the teacher was exposed to ten times the normal dose of radiation. The technologist was not aware of anything wrong. According to radiologist Rebecca Smith-Bindman, who authored the editorial, this was one of hundreds of cases nationwide of accidental over-exposure. In this case, the teacher, who had a non-threatening facial paralysis (Bell’s Palsy) that lasted for only a few weeks, became confused and sick and lost her hair. Smith-Bindman called for Congress to empower the FDA to regulate the use and radiation dosages of CT scans.
In 2009, the New York Times reported two cases of radiation overdoses accidentally delivered during CT scan procedures in California. In one case, eight times the normal dose of radiation was delivered to about 206 possible stroke victims over an 18-month period at Cedars-Sinai Medical Center in Los Angeles. Meanwhile, at the Mad River Community Hospital in Arcata, California, an x-ray technologist had his license revoked for exposing a two-and-a-half-year-old boy to over an hour of CT scans — a procedure that should take no more than two or three minutes.
When the former case was reported to the Food and Drug Administration (FDA), it responded with an alert to medical facilities throughout the nation to check their CT scan procedures. The statement that the FDA released said, “While this event involved a single kind of diagnostic event at one facility, the magnitude of these overdoses and the impact on the affected patients were significant. This situation may reflect more widespread problems with CT quality assurance programs and may not be isolated to this particular facility or this imaging procedure.”
Obviously, cutting down on the amount of radiation exposure that comes with CT scans can only be a good thing, but even a 50 percent reduction still exposes patients to frighteningly high radiation doses. And the thing is, all that radiation is not necessarily necessary. In many cases, replacing the CT scan with an MRI, ultrasound, or even simple x-ray procedure would provide enough information for diagnostic purposes at far reduced radiation levels. Also, scientists recently reported that radiation can be cut by as much as 97% when using multidetector computed tomography (MDCT, a type of CT scan that works more quickly and accurately than traditional CT technology) without negatively affecting image quality.
But keep in mind that sometimes there is just no replacement for the right scan. When it comes to cancer, for example, a PET/CT scan, which combines a CT scan with an injection of radioactive glucose (not quite as bad as it sounds), will literally “light up” any tumors in the body during the scan. No other diagnostic tool works quite as well for identifying all potential trouble spots in the body.
As I’ve said before, do your homework before submitting to any diagnostic tests involving radiation. In the world of x-ray exposure, “less is more.”