The most serious problem with the widespread use of CAT scans is the radiation these devices leave in our bodies. CAT scans are not simple chest X-rays, which deliver only a small amount of radiation. Instead, they expose the patient to a significant amount of radiation, and radiation in significant doses has been shown to increase the risk of cancer.
We are all exposed to "natural background radiation" -- that is, radiation from the sun, radon gas, rocks in the ground, cosmic rays, and other sources that usually can't be avoided in our daily lives. Radiation is measured in units called "millisieverts" (mSv), and we can use millisieverts to compare this natural radiation to the levels of radiation we get from other sources, such as medical tests. For instance, a chest X-ray provides about 0.02 mSv, or the equivalent of 2.4 days of natural background radiation. A CAT scan of the abdomen, on the other hand, provides about 10.0 mSv, or the equivalent of 500 chest X-rays or 3.3 years of natural background radiation. And a 64-slice wholebody CAT scan provides 15.2 mSv for men and 21.4 mSv for women (women's denser body tissue and breasts require higher doses to get clear images) -- quite a difference, especially when you realize that the radiation you receive is cumulative.
Now compare these numbers with the level of radiation to which Japanese survivors of the atomic bomb explosions at Hiroshima and Nagasaki were exposed: an average dose of between 5 and 20 mSv, with some doses as high as 50 mSv. A single CAT scan can easily exceed that average. And since radiation from all sources remains in our bodies for life, the likelihood of the average twenty-first-century patient matching or exceeding that average, even without a CAT scan, is very high. In the New York Times, Roni Caryn Rabin reported that recent studies indicate that the amount of radiation in the bodies of Americans increased 600 percent between 1980 and 2006, with the bulk of this increase attributed to diagnostic imaging procedures. In 1980 about 3 million of these procedures were performed, but by 2006 the number had skyrocketed to 62 million. If you were to follow some popular recommendations to have an annual CAT scan, plus one virtual colonoscopy and a coronary angiogram (both of which also deliver large doses of radiation), in the space of only a few years you could easily be exposed to more radiation than even the most highly exposed Hiroshima survivor.
The World Health Organization, Centers for Disease Control and Prevention, and the National Institute of Environmental Health Sciences have all classified X-rays as carcinogens based on the fact that they have been linked to leukemia and cancers of the breast, lungs, and thyroid. The risk of a fatal cancer from a chest X-ray has been estimated as one in a million or more- in other words, very remote. But the risk of a fatal cancer in a person who has had just one of these new 64-slice CAT scans is estimated to be one in 2,000. In one study reported in the Journal of the American Medical Association, the risk of cancer in people having 64-slice CAT scans of the heart was found to be greater for young women than young men. Researchers found that one of every 143 women scanned at age twenty will develop cancer, usually breast cancer; the risk for forty-year-old women falls to one in 284. For men, the cancer risk was one in 686 for a twenty-year-old, and one in 1,007 for a forty-year-old. The reason for the gender difference in risk lies in the fact that breast tissue is very sensitive to radiation and the heart can't be scanned without radiation exposure to breast tissue. Clearly, administering CAT scans simply for screening is a risk we shouldn't be recommending people take.
There is no level of radiation exposure below which you can assume you're safe. Of course, everyone is different and no one will be affected by radiation in the same way. And when we talk about the radiation doses for various medical procedures, we are always talking about estimates rather than exact figures. Depending on where you have your CAT scan done, who is performing it, what machine is being used, and what condition is being screened for, the doses can vary. But radiation interferes with the body's natural immune system the same way regardless of dose. Your body keeps you healthy by attacking free radicals, scavengers, and cancer cells inside you, but its resources are finite. A sudden blast of radiation can be just the impetus needed to allow leukemia, breast cancer, or some other cancer to begin developing.
Cost
When CAT scan machines were first widely introduced in the early 1980s, they were heavily publicized and marketed. Because the scans were normally not covered by insurance, the cost was all out-of-pocket for the patient. So a lot of people, especially those who had cause to be worried about potential health risks due to family history, put thousands of dollars on the table -- even if they couldn't afford it -- all because they and their families believed the tests would "save their lives" by revealing hidden life-threatening conditions. Some of my own patients told me that imaging centers had charged them up to $2,500 for a single scan; other patients have reported paying anywhere from $500 to $5,000. And many of these centers were not run by doctors but by business people who were very aggressive in their marketing.
Hospitals, doctors, and scanning centers had invested several million dollars in each one of these scanners, and naturally they wanted to recoup their costs. So there was a lot of pressure put on patients to have CAT scans when they may not have needed them and a lot of marketing done to doctors about how they could double their income by using these machines in their practices. The dangers were being completely ignored. Unfortunately, this is still largely the case.
Effectiveness
Here's what most people do not realize: there is absolutely no data to prove that CAT scans are medically useful for people who do not have any symptoms. According to the FDA website:
The FDA has never approved CT for screening any part of the body for any specific disease, let alone for screening the whole body when there are no specific symptoms of disease at all. No manufacturer has submitted data to FDA to support the safety and efficacy of screening claims for whole-body CT screening.
They further state:
the FDA knows of no data demonstrating that whole-body CT screening is effective in detecting any particular disease early enough for the disease to be managed, treated, or cured and advantageously spare a person at least some of the detriment associated with serious illness or premature death.
In addition, the American College of Radiology, the American College of Cardiology/American Heart Association, the American Association of Physicists in Medicine, and the American Medical Association, among others, do not recommend CAT scans. Medicare and most insurance companies do not cover CAT scans for screening because the tests have never been shown to provide information in addition to what we can already learn through doing a medical history, a physical exam, and blood tests.
Michael Ozner, MD, FACC, FAHA, is the author of The Great American Heart Hoax: Lifesaving Advice Your Doctor Should Tell You About Heart Disease Prevention (But Probably Never Will). For more information on his book and the research behind it, please visit www.drozner.com