Q+A-What is the radiation threat from CT scans?

By Julie Steenhuysen

CHICAGO, June 7 (BestGrowthStock) – A number of studies in the past
year have raised concerns that Americans are exposed to too
much radiation from CT scans, increasing their risk of cancer.
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Here are some questions and answers about CT scans:

Q: WHAT IS A CT SCAN?

A: CT, short for computed tomography, is an advanced type
of X-ray that gives doctors the ability to see inside the body,
in some cases eliminating the need for exploratory surgery.
CT scanners take cross-sectional pictures of the body and a
computer program assembles these into an image.

CT scans deliver more radiation than conventional X-rays. A
chest CT gives patient more than 100 times the radiation dose
of a typical chest X-ray. A CT scan of the abdomen is roughly
equivalent to 400 chest X-rays. Too much radiation can cause
skin burns, cataracts and other injuries, and in extreme cases,
cancer and death.

CT scan use in the United States has grown sharply.
About 70 million CT scans were done on Americans in 2007, up
from 3 million in 1980.

Q: HOW MUCH RADIATION DO THEY GIVE?

A: Radiation, which is measured in millisieverts, from CT
scans varies widely.

A study in December by Dr. Rebecca Smith-Bindman of the
University of California, San Francisco, looked at the 11 most
common types of diagnostic CT scans at four institutions in
2008. They found radiation dosage varied from a median or
midpoint of 2 millisieverts for a routine head CT scan to 31
millisieverts for a scan of the abdomen and pelvis, which often
involves taking multiple images of the same organ.

Q: HOW MUCH RADIATION IS TOO MUCH?

A: The average American receives about 3 millisieverts a
year from ground radon or flying in an airplane. This level is
not considered a risk to health.

Researchers say a radiation dose of 50 millisieverts starts
to raise concerns about human health and a dose of 100
millisieverts is thought to raise the risk of cancer.

All of the studies estimating the risk from CT radiation
exposure are based on the rates of cancer that occurred in
people exposed to radiation from the atomic bombs dropped on
the Japanese cities of Hiroshima and Nagasaki at the end of
World War Two.

But many experts disagree over whether that model offers a
fair comparison. Meanwhile, imaging equipment makers such as GE
Healthcare (GE.N: ), Siemens (SIEGn.DE: ), Philips (PHG.AS: ) and
Toshiba Medical Systems (6502.T: ) are working to develop
low-dose CT scanners.

Q: HOW DO PATIENTS BECOME OVEREXPOSED TO RADIATION FROM A
CT SCAN?

A: This can happen in two ways. Accidental overdoses can
occur when CT equipment settings are improperly programmed or
technicians running the machines make an error.

These kinds of accidents are rare. To prevent them, the
U.S. Food and Drug Administration has asked the top makers of
CT scanners to add safeguards to their machines.

The Medical Imaging & Technology Alliance says
manufacturers will add a color-coded warning system to give
healthcare providers clear warning when scans could harm
patients. These changes are being phased in later this year.

The American College of Radiology has called for an
accreditation program for facilities that deliver radiation
therapy to cancer patients, something the medical equipment
industry group AdvaMed supports as a way to enhance patient
safety.

Repeated CT scans can also pose a risk as the cumulative
radiation dose builds over time.

Researchers are working on new computer programs that help
doctors make better decisions about whether a CT scan is the
best way to diagnose a condition. Equipment manufacturers are
developing software that allows radiologists to use a much
lower dose of radiation while still producing a sharp picture.

Money

(Editing by Maggie Fox and Bill Trott)

Q+A-What is the radiation threat from CT scans?