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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. 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," according to the study co-author of the
Mayo Clinic in Jacksonville, Florida. The researcher headed
an American Heart Association panel that called on 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. The scientists of the Technical
University, Munich, Germany 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. 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. "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," according to the researcher.
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