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Too much radiation from medical testing?

August 26, 2009 |  4:22 pm

Ctscan Americans may be receiving too much radiation from medical tests whose value has not been proven, researchers reported today in the New England Journal of Medicine. More than two-thirds of Americans underwent at least one such imaging procedure in the three years covered by the study, reported Dr. Reza Fazel of the Emory University School of Medicine and colleagues. The two biggest contributors to the radiation exposure are CT scans, which use a series of X-rays to produce a three-dimensional image of the body, and heart perfusion scanning to measure blood flow through the arteries leading to the heart. In that test, radioactive technetium-99m is injected into blood vessels and its progress through the heart monitored with external radiation detectors.

Radiation is known to cause cancer, typically years after exposure. By some estimates, medical testing radiation contributes 2% of all cancer cases, but experts fear that it may be higher in the future as more and more patients are exposed to these relatively new procedures. They are also concerned because increasing numbers of tests are being performed on younger people, which allows more time for tumors to develop, and on women, who normally live longer than men.

Some studies have suggested that the growing number of CT scans being performed results at least in part from ownership of the machines by physicians, who view them as a new profit source and prescribe unnecessary tests. There is also a growing incidence of whole-body CT scans in which physicians check for any signs of potential disease in healthy individuals. Such scans were not included in the report because they are not covered by insurance.

The researchers studied medical records of 952,420 adutls between the ages of 18 and 64 who were insured by United Healthcare plans in Arizona, Dallas, Orlando, South Florida and Wisconsin. Between 2005 and 2007, 655,613 of them underwent at least one procedure that exposed them to radiation. The mean dose of radiation was 2.6 milliSieverts (mSv), a relatively low dose. A dose of 3 to 20 mSv is considered moderate, from 21 to 50 MSv is considered high and a dose over 50mSv is considered very high. Federal regulations put the maximum annual safe dose at 50 mSv.

Cardiac stress testing was the procedure that exposed patients to the highest radiation levels, an average of 15.6 mSv, and accounted for 22% of all radiation exposure. CT scans of the abdomen, which typically produce about 8 mSv, accounted for more than 18% of exposure. A mammogram -- a single X-ray -- produces about 0.4 mSv.

If the findings are extrapolated to the entire population, more than 4 million Americans are receiving a dose greater than 20 mSv each year, the authors said. "It is important to note that we are talking about radiation doses that are incurred in one year," said Dr. Brahmajee Naliamothu of the University of Michigan, senior author of the study. "Cumulative doses over a lifetime may be much higher."

About 79% of women in the study had at least one exposure to radiation, compared with 58% of men. Mammograms accounted for only a small part of the difference, Fazel said.

Dr. Michael Lauer, director of the division of prevention and population sciences at the National Heart, Lung and Blood Institute, said in an editorial in the same journal that clinical trials of the efficacy of such testing should be conducted before their use is expanded further. Despite the wide use of nuclear perfusion for cardiac imaging, he noted, there is no evidence that it increases survival.

-- Thomas H. Maugh II

Photo credit: Lawrence K. Ho / Los Angeles Times

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Comments (9)

The government should audit each doctor to find ones prescribing unnecessary CT scans. I know there are many out there because I was prescribed a cranial CT scan just because I fainted due to the stress induced by my grandmother's death. I was 23-24 at that time and physically healthy and now I will probably die of brain cancer or leukemia.

It was about 2 years since I had the CT scan.
My doctors never told me about the risk, yet when I search the net, I found that this information has been public for quite some time. Why did my doctor prescribe a cranial CT scan when there are alternatives like the MRI?

The NEJM article refers to radiation doses that are "moderate, high, and very high". Assigning that description to an arbitrary number (50 mSv for example) does not aid this important discussion, nor does it address the real issue. Appropriate studies provide great benefit and should continue without fear of the assumed increased cancer risk. Likewise, studies that provide no clinical information should not be performed even if they are “low dose”. Medical decisions always involve weighing the risks and benefits of a procedure or medication. You can visit the radiation dose calculator at to calculate cancer risk based on CT scans, x-rays, nuclear medicine and interventional procedures performed.

There is money to be made in each procedure like CT scans that pays hospital or private clinic. Before appendectomy CT is done to ? "confirm" the diagnosis. I question routine scanning and exposing the patients to unnecessary radiation when all other signs are positive. T

Excess cancer is not the only serious risk from medical irradiation. In 1999, John W. Gofman, M.D., Ph.D., authored a groundbreaking study that produced powerful epidemiological evidence that an equal risk is excess coronary artery disease if the heart is irradiated (deliberately or as a consequence of imaging breasts, thoracic spine, esophagus, shoulders, lungs, etc.). Extensive peer-review has not invalidated his surprising observations. How could medical irradiation cause coronary artery disease? He proposed that certain radiation-induced "somatic" mutations are carcinogenic and others are atherogenic --- that is, they can initiate mini-tumors in the coronary arteries that grow into atherosclerotic plaques, some of which are deadly. Professor Gofman (UC Berkeley) is no longer able to speak for himself, for he died in August 2007. Therefore I, who edited his books, am speaking for him. The executive summary of his 1999 study is available online, free, at . The full monograph is available from books. Its title is "Radiation from Medical Procedures in the Pathogenesis of Cancer and Ischemic Heart Disease: Dose-Response Studies with Physicians per 100,000 Population."

A mammogram is not a "single X-ray," it is a series of four images (two of each breast), often more if magnified or repeat imaging is prescribed by the radiologist. Are women exposed to at least 1.6 mSv for each mammography session?

Doctors that own their own CT scanners order 5-TO-8 TIMES MORE CT scans than those that do not own their own scanners. Why? PURE PROFIT AND GREED. A bill has been trying to make it through Congress to close the loophole that allows this abuse, however the lobby of doctors who abuse the system, and the manufacturers who sell that scanners, is too strong. The bill/amendment (HR2962) has been squashed by those who will continue over-radiating patients for profit.

Here is some more information on radiation and medical testing: Radiation Testing Concerns:

The biased article doesn't mention lack of tort reform requiring doctors to practice defensive medicine and order tests that are not really needed.


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