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CT SCANS ARE CLEAR, BUT RISKS ARE NOT
[October 24, 2007]

CT SCANS ARE CLEAR, BUT RISKS ARE NOT


(New Zealand Press Association Via Thomson Dialog NewsEdge) Fort Lauderdale, Florida, MCT - The CT scan -- a medical darling for its detailed images, diagnostic power and big profits -- is being overused so much that some experts worry the radiation might cause cases of cancer.



New reports this year say computed-tomography scans expose patients to small but significant doses of radiation that can add up over time, findings that CT defenders dismiss as alarmist.

The reports warn doctors to limit CT-radiation exposure to patients, especially children and small adults who are at elevated risk, and to use radiation-free ultrasound and magnetic-resonance imaging, or MRI, if possible. Imaging specialists said some doctors order CT scans needlessly because they don't know the risks, to protect them if they get sued, out of habit or to make money.


``CT scans are very valuable. But people should know that these are not innocuous,'' said Dr Charles F Tate, a radiologist helping educate doctors about CT radiation.

``There's definitely a risk with these procedures, and they and their doctors should act responsibly.''

ECRI Institute, an independent research group, estimates that CT scans cause 6000 cases of cancer per year, half of them fatal, making them more of a risk than wrong-site surgeries.

But radiology officials who swear by CTs call the warnings an overreaction, saying the death estimates are unproven and that the body heals radiation damage over time, negating the risk of cancer.

``It's not like someone's going to be getting a CT scan every week,'' said Roger Hampton, president of Palm Beach Broward Medical Imaging Centre in Deerfield Beach, Florida.

There is no study proving that medical radiation causes cases of cancer. Scientists do not know how large a dose is dangerous or whether several small doses from CT scans are as harmful as one large one, nor can they say how many scans in a year would be safe.

CT scans have been embraced for 30 years for their quick, sharp images of organs, bones, blood vessels and disease that are far more accurate and rich than older methods of testing.

Americans received 72 million CT scans in 2005, twice as many as in 1998, according to the American College of Radiology, a physician association.

``The rapid growth of CT and certain nuclear medicine studies over the past quarter century may result in an increased incidence of radiation-related cancer in the not-too-distant future,'' the radiology association said in a policy paper.

The scans work well because of the radiation levels. An abdominal CT can expose patients to 250 times the radiation dose of a regular X-ray, a chest CT 150 times more.

CTs deliver doses of 3 to 12 millisieverts -- a radiation measure -- and some patients receive multiple scans in a short time. By comparison, one study estimated that atomic-bomb survivors in Japan had an increased risk of cancer at doses of 50 mSv. Americans get about 3 mSv yearly from the environment.

Recent reports raised new concerns about CT scans.

The radiology association in May urged doctors, regulators, insurers and patients to think twice about CT scans for unnecessary uses, such as minor injuries or confirming a known illness. CTs are worth the radiation risk, but only to diagnose a specific ailment.

In September, the American Academy of Paediatrics warned doctors that children are at higher risk than adults from CTs, because radiation penetrates small bodies, their fast-dividing cells are sensitive to it and they face decades of future exposure.

A study in July's Journal of the American Medical Association found the odds of developing fatal cancer from a 10 mSv chest CT were just one in 2,000 on average but as high as one in 143 for a 20-year-old woman. Young women also face much future exposure, researchers said, and breast tissue is sensitive to radiation.

ECRI in February warned doctors that true radiation risks from CTs might be higher than they think, because patients could need several scans during an illness.

And also in September, Consumer Reports magazine named CT scans for the heart and the whole body in the top 10 of the most overused procedures.

The US Food and Drug Administration and some physician groups strongly discourage full-body scans, calling them an example of needless radiation.

The FDA has found no proof that the scans catch enough problems to justify the exposure of 12 mSv or the complications from checking so-called false positives.

MCT reg

Copyright 2007 New Zealand Press Association, Source: The Financial Times Limited

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