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questioning everything: CT scans and cancer, coffee and diabetes

Computerized tomography, otherwise known as CT or Cat scanning, has imaged 70% of non-elderly adults in the last 3 years. The use of this technology has been steadily rising, and we now perform a total of over 19,500 CT scans per day in the US.

CT scans use a computer to organize x-ray data in such a way as to produce pictures that resemble cross sections of the human body, complete with bones, brains and soft tissues, tumors and blood vessels. The pictures are truly marvelous and have revolutionized the way we diagnose disease, allowing us to know many things about the insides of a person without actually cutting them open. We can see if a tumor is present, has spread, if an aneurysm is bursting or if the excruciating pain in a person's belly and back is a kidney stone or pancreatitis. We can tell if a victim of trauma is bleeding internally or if a mysterious fever is caused by a well hidden abscess.

In December's issue of the Archives of Internal Medicine, researchers from the National Cancer Institute and other participating institutions published an article looking at the cancer implications of all of these wonderful CT scans we have been doing. Based on risks of cancer predicted by a study of ionizing radiation done by the National Research Council, the CT scans done in the US in the year 2007 will be responsible for 29,000 cases of cancer, and 15,000 excess deaths. One CT scan of the abdomen and pelvis may be equivalent to 450 or more chest x-rays in terms of radiation exposure (though this varies by procedure and institution.)

CT scans, besides being life saving and revolutionary, are also killing us and eating up our health care budget. The trick is moderation. It is clear to me, from seeing my patients return from visits to emergency rooms or specialists, that we do far more CT scans than are truly necessary to diagnose serious disease. Sometimes an elective CT scan is interesting or reassuring, but just as often the tests done for interest or reassurance end up being confusing and anxiety provoking, as they show the benignly quirky internal makeup of individuals who might have cysts or enlargements of organs, duplicated spleens, liver hemangiomas, missing kidneys.

But moderation is not always a good thing. Take coffee, for instance. Another study reported in the month's Archives of Internal Medicine shows that a person who drinks coffee in large amounts has a significantly lower risk of getting diabetes than a person who drinks coffee moderately or not at all. Many studies have shown this, to varying degrees. The meta-analysis, a statistical combination of many small studies to produce a more robust result, suggests that for every additional cup of coffee you drink in a day, you reduce your risk of diabetes by 7%. Although fewer studies have looked at tea and decaf, they appear to carry the same benefits as real hi-test java. The best outcomes were seen in people who drank at least 6 cups of coffee a day.

Once again we see the limitations of science to address the concerns of the individual: if I drank that much coffee I would certainly die.

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