Do you know the risk?November 2001
Scan centers make body scans sound like they're as safe as a stroll down Fifth Avenue. Our investigation into the scan industry raises grave doubts about the safety of so-called health scans.
Ever considered relaxing in a radioactive bath? Back in the 1920s, you could buy radioactive bath salts. They were a cure for insomnia. Once in bed, you could apply your Radium Ore Healing Pad-a nifty device said to be good for stomach, liver and spine. You might think this is laughable - you wouldn't consider taking a radioactive bath or curling up with a radioactive heating pad. But you might consider getting a body scan-something that may turn out to be just as laughable and far more dangerous in the long run.
Body scans are the latest health fad. A blizzard of media attention has healthy people flocking to "scan centers" to get their bodies scanned. The concept is terrific. State-of-the-art machines known as CTs (computed tomography) "slice" internal organs into wafer-thin serial images that are then viewed on a computer screen. CT scans can reveal cancer, heart disease, osteoporosis and more at their earliest stages. They don't hurt, they're fast and if you've got $700 to $1300, you too can see your insides.
"body scans" have gotten the
FDA's attention. CT scanners
were never intended to be
used in people with no
symptoms and unknown risk.
Sounds great and it is great-except for one thing. Radiation. And lots of it. In effective doses, one CT chest scan is the equivalent of 400 chest x rays or 3.6 years of background radiation; a scan of the abdomen 500 chest x rays or 4.5 years of natural background radiation. A scan of the head is the equivalent of 115 chest x rays, or one year of natural background radiation.* Combine the chest and abdomen, and you've got a body scan-almost 1,000 x rays (imagine sitting on an x ray table while 1,000 x rays are taken). These are "effective doses", meaning that depending on your body type and the scanner, you could get even more radiation. It's estimated that the risk of a chest x ray causing fatal cancer is 1-in-1,000,000. A CT scan of the abdomen has been estimated to up the risk to 1-in-2,000.** All of this for what experienced radiologists say are "unnecessary evaluations".
According to Dr. Robert Stanley, president of the American Roentgen Ray Society, a 45-year-old healthy person who gets one scan doesn't have to worry. But the FDA's Dr. Thomas Shope has cautioned that multiple scans can expose a person to radiation approaching the lower levels of Hiroshima and Nagasaki. A controversial new report estimates that if 600,000 children get head and abdomen CT scans, 500 will get cancer from those scans. The body doesn't forget radiation: it keeps count of every x ray you get. It's important to think about your own lifetime exposure before you volunteer to be irradiated. Radiation damage to DNA is never completely repaired.
So-called "health scans" or "body scans" have gotten the FDA's attention. CT scanners were never intended to be used in people with no symptoms and unknown risk. There are many diagnostics that can be done for a person who is concerned about their health that either don't involve radiation, or involve significantly less. These modalities can be used before a CT scan. CTs were designed as serious diagnostic devices, not health enhancers.
Experienced radiologists are also distancing themselves from whole body scans in a big way. The American Roentgen Ray Society wouldn't be the first place you'd look for a CT critic. Yet its president is highly critical of whole body CT screening in asymptomatic people. Stanley, who knows CTs inside and out, points out that the damage from a body scan might not be evident for many years. CT scans, he says, are much more complex than simply putting a person in a scanner and reading a computer print-out. That's like taking a jet fighter out for a joy ride.
It has been repeatedly proven that CT scans are subjecting people to unnecessarily high levels of radiation. New calls by radiologists themselves for radiation reductions are only the latest in a decades-old demand for radiation reductions. Radiation reductions of 50% or more are possible today without any effect on picture quality. A study published in 1991 on CT scans of the head is typical: "While computed tomography (CT) has become an important imaging modality in the evaluation of the paranasal sinuses, the radiation dose remains higher than is necessary… images were of diagnostic quality even when dose levels were reduced by a factor of 28."
Yet despite these kinds of findings, radiologists continue to ignore the issue of radiation exposure, and manufacturers carry on business as usual. The public has been in the dark about radiation and CT scans until recently when the media picked up on studies published in the American Journal of Roentgenology showing that CT radiation is off the map. One of the editorials is unprecedented in demanding that CT manufacturers lower the radiation. Another asserts that radiologists have been unaware or indifferent to the high doses of radiation associated with CTs.
Some scan centers offer "rapid scans"-usually for detecting calcium in arteries. A common perception is that a speedy scan exposes you to less radiation. This isn't necessarily true. "Rapid" scans are like a stop-action camera. They enable radiologists to capture an image of a beating heart or a scanee who moves. In order to do this, the machine must generate more intense radiation. However, although the person undergoing the scan is subjected to more radiation, it is for less time. For this reason, rapid scans expose a scanee to about the same amount of radiation as a regular scan, although some scanners generate more or less than others.
The amount of radiation a scanner generates is not regulated by the FDA; however, the agency does require that scan manufacturers disclose the radiation dose to anyone who asks. Excessive radiation exposure is often the end result of the quest for good picture quality. Picture quality is a big selling point for manufacturers. Their promotional material is full of information about how good the pictures are, but virtually silent when it comes to radiation doses.
The next generation of scanners is supposed to automatically adjust the amount of radiation according to a person's own absorption potential. For example, if a child is given the same amount of radiation as an adult, they will be much more affected by it. Similarly, a heavy person will diffuse or divert more of the radiation away from internal organs than a thin person, and be damaged less. The need for automatic adjustment is obvious, yet self-adjusting scanners are not on the market yet.
Scan centers are offering scans of the heart to detect calcium deposits in coronary arteries. The American Heart Association in collaboration with the American College of Cardiology has issued a statement of non-support of Electron-beam computed tomography (EBCT)-rapid scans-for heart disease detection in asymptomatic people. Their position is that rapid scans are no more predictive than usual risk factors. For example, ankle-brachial pressure index-a simple measurement-is highly predictive of whether or not a person with no symptoms will have a heart attack, whether they will die of that heart attack and whether they have narrowing of the arteries. The accuracy of ankle-brachial pressure as an indicator of heart disease risk is on par with smoking, the most predictive indicator. It and homocysteine levels are better predictors of heart disease than cholesterol levels, with one study suggesting that homocysteine is better at predicting the extent of atherosclerosis in low-risk patients than high-risk. C-reactive protein is another predictor. All are simple tests that can be performed at any doctor's office without exposing you to radiation.
The AHA and ACC also point out that CT scans only measure calcium, and calcium is only one facet of heart disease. EBCT does not detect "soft" lesions or unstable plaques. And while the presence of calcium is highly predictive of having a heart attack, the groups argue that false-positives "can result in additional expensive and unnecessary testing to rule out a diagnosis of CAD (coronary artery disease)." In other words, if you get a scan at a scan center and something shows up, you will have to undergo additional tests that may involve more radiation to find out what it means. One of those tests may be the same scan, only this time with intravenous contrast which can illuminate lesions, plaque and the like.
The failure to use intravenous contrast is one of the problems with scan centers. CT scans done at such centers are one-half of a proper scan. The other half is the contrast material. It's the contrast material that tells the story. It enables the radiologist to differentiate between cancer and a benign growth, heart disease and calcification only.
Another popular scan these days is a CT scan of the gut. "Virtual colonoscopies" appear to have widespread support, with some predicting they will become the next mammogram if they can be improved. However, radiation exposure is one of the hurdles that has to be overcome before virtual colonoscopies replace colonoscopies as the diagnostic tool for colon cancer, according to Dr. Joseph T. Ferrucci of the American Roentgen Ray Society. There are other problems as well.
Colon cancer is the second most deadly cancer in the U.S. (after lung cancer). The number of people who have colon cancer without knowing it is alarming. A study published in the New England Journal of Medicine found that 37% of men tested (only some of which were at high risk) had adenomas or invasive cancer without knowing it. Sigmoidoscopy, a procedure where the doctor examines the lowest part of the colon, is inadequate to diagnose this disease. Anyone age 50 or over with average risk factors is advised to get a colonoscopy which can enable the physician to see the entire colon. Men are especially at risk for colon cancer. The good news is that colon cancer responds to treatment if caught early. It's clear that colonoscopies save lives. Unfortunately, the unpleasantness of the procedure keeps some people away until they have symptoms so obvious, they can't ignore them anymore, and by then cancer can be advanced.
Virtual colonoscopy will change all that once it's perfected and put into widespread use. The studies already look very promising on virtual colonoscopy. But there are problems that have to be overcome before virtual colonoscopy replaces traditional colonoscopy. One of them is that although virtual colonoscopy detects most cancers and growths 10 mm or larger, it has trouble with small polyps and flat adenomas. Some cancers are simply undetectable by virtual colonoscopy at this time.
But, unlike other scan procedures where the risks of unnecessary radiation exposure and side effects may outweigh the benefits, the high incidence of colon cancer and the favorable response it has to early detection make the risk/benefit ratio of this CT scan very favorable. Older men are particularly at risk and they should undergo a colonoscopy no matter what. A virtual colonoscopy is better than no colonoscopy, but traditional colonoscopy remains the gold standard for diagnosing colon cancer and precancerous conditions. Young people with no symptoms and no risk factors should not get virtual colonoscopies. If such a person can't sleep at night wondering if they have colon cancer, they should get the traditional colonoscopy that involves no radiation.
*Data on x ray equivalencies obtained from the European Commission. The International Commission on Radiological Protection is in accordance with these figures as being average doses world-wide.
**European Commission Radiation Protection 118, p 20.