CT scan may give patients high radiation dose

Posted on Apr 6, 2009 in Health & Wellness

Heart patients are getting equivalent of 600 chest X-rays, researchers sayupdated 6:03 p.m. ET, Tues., Feb. 3, 2009
CHICAGO – Patients are receiving the equivalent of 600 chest X-rays when they get CT scans for heart disease and not enough clinics are using known ways to reduce this exposure, researchers reported on Tuesday.

While the potential risk of developing cancer after a cardiac CT scan is slight, at less than 1 percent, researchers in the large, international study found the radiation doses from such tests varied widely among hospitals, suggesting more can be done to minimize patients’ exposure.

“It does drive home the fact that, yes, those scanners do impart a radiation dose, and the doctors together with their patients really have to think about whether or not the scan is the best approach for the particular patient,” study co-author Dr. Thomas Gerber of the Mayo Clinic in Jacksonville, Fla., said in a telephone interview.
Gerber headed an American Heart Association panel that called on Monday for more careful selection of patients who receive diagnostic tests such as CT scans to minimize the doses of ionizing radiation.
So called “64-slice” CT scans, which take dozens of images in one rotation around the body, are an increasingly popular tool to diagnose coronary artery disease, particularly in patients with symptoms such as chest pain or shortness of breath.

But a number of recent studies have raised alarm about the potential cancer risks from the radiation.
Gerber, Dr. Jorg Hausleiter of the Technical University, Munich, Germany, and colleagues studied 1,965 patients who had cardiac CT scans between February and December 2007 at 50 university and community hospitals worldwide.

They found the median dose from a heart CT scan, as calculated by a measurement of absorbed radiation, differed significantly from hospital to hospital. The median radiation dose from all sites was equivalent to 600 chest X-rays, they reported in the Journal of the American Medical Association.

Some variability in dosage was attributed to factors that included patient weight, absence of stable heart rhythm, the length of the scan and the type of CT system used.

Makers of the systems include General Electric Co, Siemens AG, Philips Electronics and Toshiba Corp..

While strategies are available that can substantially lower radiation doses from CT scans, such as reducing voltage, some of these techniques are not being widely used, the researchers found.

That could be because many clinicians may still be unfamiliar with the magnitude of radiation exposure that is received from a cardiac CT scan, they said.

In a commentary, Dr. Andrew Einstein of Columbia University in New York noted that the number of CT scanners installed in U.S. cardiology practices has tripled in the past two years.

“The findings suggest that dose-reduction methods can be used in the majority of patients, which should serve as a wake-up call to cardiac CT laboratories that do not routinely use these methods,” wrote Einstein, who has served as a consultant to GE and received other funding from Philips and Toshiba.