CardioExchange Archive

No doubt you’ve read about the FDA’s October announcement that it was investigating more than 200 cases of excess radiation exposure — at 8 times the expected level — during perfusion CT scans of the brain at a Los Angeles area medical center. In some patients, the excess exposure resulted in hair loss and reddening of the skin, which were the clues that first raised concerns. What you may not know is that, in early December, the FDA expanded its probe to include at least 50 additional cases of excess exposure, now implicating more than one manufacturer of scanners (and, possibly, healthcare facilities outside California). You might be wondering what other data are out there about radiation exposure from CT scans — and what you as a clinician should do in response.

First, for a bulleted list of what the FDA is recommending to facilities, radiologists, and radiology technologists in light of recent events, click here. Those recommendations by the FDA focus on perfusion CT scans, but the long-term implications of its investigation may be broader, as suggested by findings from two new studies in the Archives of Internal Medicine. 

One, by Smith-Bindman and colleagues, documented tremendous variation in radiation doses delivered by the 11 most common types of diagnostic CT scans at four facilities in San Francisco. Remarkably, large variations were found both across and within facilities for the same type of CT study. Effective doses for coronary CT angiograms, for example, varied more than 5-fold, and the median dose was more than twice as high as what can be achieved with simple protocol changes, as outlined in a JAMA article earlier this year. The take-home point for me is that we need to start standardizing commonly used CT imaging protocols to reduce both the magnitude of, and the variation in, radiation exposure. As the authors note, such standards have been successfully adopted and regulated by the FDA for mammography but do not exist yet for CT scans.

The other study, by Berrington de González and colleagues, used risk models to estimate that CT scans performed in 2007 will ultimately result in 29,000 excess cancers. Although one could quibble with these estimates, the article reports one cold-hard fact that is simply staggering: In 2007, the number of CT scans performed in the U.S. was about 72 million, nearly half in people younger than 55. Clearly, the use of CT scans (not to mention other advanced imaging techniques) has become pervasive in the everyday practice of clinical medicine.

How is all this news affecting my daily practice? First, I’ve started to discuss up front the potential long-term risks from radiation exposure — particularly in the outpatient setting — rather than waiting for patients to ask me about them. I take this opportunity to put those risks in proper perspective. For most patients with an appropriate clinical indication for an imaging test such as a CT scan, the small risk for cancer several years away is far outweighed by the immediate benefit of performing the test. I pause and explain to the patient — and to myself — why I’m doing the test and how that information will help us make the best decisions about his or her care. Second, I have started to look back more carefully at the number of imaging tests associated with radiation that a patient has undergone (something, I must admit, I was less likely to do a few years ago). In some cases, I now consider alternative tests that do not use ionizing radiation, such as echocardiography and MRI, and that could answer the same clinical question.

Now, it’s your turn to share your experiences with your colleagues. Tell us:

Have you changed your practice patterns in ordering imaging tests, particularly CT scans? If so, how?
Have patients or referring providers raised the issue of CT-scan safety with you in the last several weeks or months? What have they said?
If you perform or refer patients for CT angiography, does your imaging center implement standard measures to minimize the radiation dose?