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As a screening device for breast cancer, CT scans do not work. Some radiologists are alarmed that women might think a chest or body scan can replace a mammogram. There are many differences between a CT scan and a mammogram. Mammograms were designed specifically for screening the breasts. They have a history of development and refinement behind them. They use far less radiation (200 millirads, or approximately eight chest x rays), and they reveal far more. While CT scans can be used for guiding breast biopsies, they are not a good screening device for breast cancer.
Unlike CT scan centers which are regulated by the state only, mammogram facilities have to be certified by the FDA. They must use the lowest radiation possible and they must retain radiologists who read at least 480 mammograms a year and attend continuing education classes. Radiologists who read mammograms have a lot of experience in looking for breast cancer.
Most people don't think about what will happen after the scan. But according to a Wall Street Journal report, one scan center sends 80% of its scanees to specialists post-scan. Either a whole lot of people are very sick or scan centers really don't know what they're doing. Stanley points to comments like one recently attributed to the director of a scan center who said that he's never seen a normal body scan-to argue that something is wrong with what they're doing. "Their motivation is misdirected," he argues. CT scans, he says, were never intended to be used without contrast material in asymptomatic people. Scans used in this way can reveal all sorts of "abnormalities". "When you're looking for abnormalities millimeter-by-millimeter, you're going to find them," he says. A person may go through thousands of dollars of unnecessary and invasive tests after a scan, including more radiation, to find out they have. . . nothing. It's like believing every mole on your body is melanoma. Stanley points out that if you take anyone who has died and section their kidneys millimeter-by-millimeter, in 22% of them you will find renal tumors. (A similar situation exists in the liver where "cavernous angiomas" develop). But these tumors are rarely cancerous, and rarely develop into full-blown cancer which is detectable anyway by other means, is uncommon, and treatable.
Stanley is not against screening. Mammograms and other screening modalities save lives (although he's quick to point out that diagnosing cancer early does not always lower the mortality rate-it depends on the type of cancer). But he and other radiologists are adamantly against asymptomatic people undergoing whole body scans as part of a health program.
Supplements for Radiation
If you must undergo radiation diagnostics for serious medical reasons, you may want to take thiol antioxidants including N-Acetylcysteine (NAC), S-adenosylmethionine (SAMe) or glutathione. Studies show that thiols help stop free radicals generated by ionizing radiation. NAC also works in at least one other very interesting way. It actually facilitates the destruction of damaged cells. By not allowing such cells to survive, the risk of mutations is reduced. (Mutations inevitably result, even though the body repairs most DNA damage). A substantial amount of thiol antioxidants has to be taken both before the scan and after.
Melatonin is another antioxidant that can protect against ionizing radiation. And caffeine seems like an unlikely protectant, but it is apparently-as long as it's taken during irradiation. If taken after, it may actually enhance damage. Be aware that although supplements can help, nothing short of a lead apron significantly protects against radiation.
Karbownik M, et al. 2000. Protective effects of melatonin against oxidation of guanine bases in DNA and decreased microsomal membrane fluidity in rat liver induced by whole body ionizing radiation. Mol Cell Biochem 211:137-44
Killoran PL, et al. 1999. Inhibition of store-operated calcium entry in human lymphocytes by radiation: protection by glutathione. Radiat Res 152:611-21.
Kim BC, et al. 2001. Melatonin reduces x ray irradiation-induced oxidative damages in cultured human skin fibroblasts. J Dermatol Sci 26:194-200..
Kumare SS, et al. 2001. Mechanism of protection against radiation-induced DNA damage in plasmid pBR322 by caffeine. Int J Radiat Biol 77:617-23.
Mohan N, et al. 1994. Induction of nuclear factor kappa B after low-dose ionizing radiation involves a reactive oxygen intermediate signaling pathway. Radiat Res 140:97-104.
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Walther M, et al. 1999. Influence of clinically used antioxidants on radiation-induced expression of intercellular cell adhesion molecule-1 on HUVEC. Int J Radiat Biol 75:1317-25.
Let's face it: blanketing yourself with radiation is not healthy. Because there is a risk involved, serious consideration should be given to whether the benefit is likely to be offset by the damage a CT scan does to the body. By all means, a person at risk for a disease, either because of lifestyle or genetics, should get whatever tests they need to assure them they are healthy. In most cases, tests not involving radiation can be done first. These tests should be exhausted before a CT is considered. If a CT scan is warranted, it should be done-correctly, with proper contrast material, by an experienced radiologist in that field. Contrast material increases the ability of the radiologist to detect small cancers, precancerous conditions, and distinguish between something important and something that isn't. If a body scan is chosen as the first-line diagnostic tool and it finds something, chances are the scan will have to be repeated with intravenous contrast material, subjecting the scanee to a double dose of radiation.
Many people who have undergone body scans did so because they weren't doing what they were supposed to do healthwise. The scan motivated them to pay attention to their health. And that would be fine if CT scans were totally benign. They're not, and any person contemplating a scan should ask themselves before they walk into a scan center if they really need a big dose of radiation to provoke them into doing what they already know they should be doing. Ask yourself: do I really need to undergo the equivalent of 1,000 x rays to find out I'm not exercising, I'm not eating right, and I need to buy a better mattress for my aching back? Can motivation and peace-of-mind be obtained another way?
CT scans have a place in diagnostics. To a person with symptoms of a serious disease or serious risk factors (such as smoking or familial heart disease), the benefit of getting a proper scan, with intravenous contrast, outweighs the risk. But the risk/benefit ratio collapses when the person getting a scan is a healthy individual with no symptoms; vague risk factors, and the scan is delivering a whopping dose of radiation. A person truly concerned about their health won't place that bet. We can't feel it, we don't see it, but we've got to believe that radiation is not healthy. We've got to listen to decades of data that tells us that radiation is something to be avoided when possible. Otherwise, we might as well sleep with Radium Ore Healing Pads tucked under our pillows, as the manufacturer of those devices once suggested.
For the European Commission guidelines on radiation imaging, go to http://europa.eu.int, choose "Commission" and search "Radiation Protection 118". For information on x ray/CT equivalency, see pg. 19.
The International Commission on Radiological Protection can be accessed at www.ICRP.org. See page 11 of "Diagnostic Reference Levels in Medical Imaging" for radiation levels of CT scans.
For the American College of Cardiology/American Heart Association's position paper on EBCT, see http://www.acc.org.
Dr. Stanley's comments will be published in an upcoming issue of the American Journal of Roentgenology.
For information on radiation, see http://www.x-raysandhealth.org.
Aronow WS, et al. 2000. Increased plasma homocysteine is an independent predictor of new coronary events in older persons. Am J Cardiol 86:346-7.
Brenner D, et al. 2001. Estimated risks of radiation-induced fatal cancer from pediatric CT. AJR Am J Roentgenol 176:289-96.
Fenlon HM, et al. 1999. A comparison of virtual and conventional colonoscopy for the detection of colorectal polyps. NEJM 341:1496-503.
Haaga JR. 2001. Radiation dose management: weighing risk versus benefit. AJR AM J Roentgenol 177:289 (editorial).
Huda W, et al. 2000. Technique factors and image quality as functions of patient weight at abdominal CT. Radiology 217:430-35.
Kimme-Smith, et al. 1994. Mammograms obtained with rhodium vs. molybdenum anodes: contrast and dose differences. AJR Am J Roentgenol 162:1313-17.
Kornitzer M, et al. 1995. Ankle/arm pressure index in asymptomatic middle-aged males: an independent predictor of ten-year coronary heart disease mortality. Angiology 46:211-19.
Lieberman DA, et al. 2000. Use of colonoscopy to screen asymptomatic adults for colorectal cancer. NEJM 343:162-68. (See related articles in same issue).
Marcus PM, et al. 2000. Lung cancer mortality in the Mayo Lung Project: impact of extended follow-up [see comments]. J Natl Cancer Inst 92:1308-16.
Marmolya G, et al. 1991. Paranasal sinuses: low-dose CT. Radiology 181:689-91.
Mayo JR, et al. 1995. CT of the chest: minimal tube current required for good image quality with the least radiation dose. AJR Am J Roentgenol 164:603-7.
Newman AB, et al. 1999. Ankle-arm index as a predictor of cardiovascular disease and mortality in the Cardiovascular Health Study. The Cardiovascular Health Study Group. Arterioscler Thromb Vasc Biol 19:538-45.
Nickoloff EL, et al. 2001. Radiation exposures to patients from CT: reality, public perception and policy. AJR AM J Roentgenol 177:285 (editorial).
Ravenel JG, et al. 2001. Radiation exposure and image quality in chest CT examinations. AJR AM J Roentgenol 177:279-84.
Rex DK, et al. 1999. An initial experience with screening for colon polyps using spiral CT with and without CT colography (virtual colonoscopy) [see comments]. Gastrointest Endosc 50:309-13.
Rogers LF. 2001. Radiation exposure in CT: why so high? AJR AM J Roentgenol 177:277 (editorial).
Spinzi G, et al. 2001. Computed tomographic colonography and conventional colonoscopy for colon diseases: a prospective, blinded study. Am J Gastroenterol 96:394-400.
Stubbs PJ, et al. 2000. Effect of plasma homocysteine concentration on early and late events in patients with acute coronary syndromes. Circulation 102:605-10.
Tsai WC, et al. 2000. Correlation of homocysteine levels with the extent of coronary atherosclerosis in patients with low cardiovascular risk profiles. Am J Cardiol 85:49-52.
Zheng ZJ. 1997. Associations of ankle-brachial index with clinical coronary heart disease, stroke and preclinical carotid and popliteal atherosclerosis: the Atherosclerosis Risk in Communitis (ARIC) Study. Athero 131:115-25.
Important information you should have
According to the Code of Federal Regulations, Section 1020.33(c)(2), the manufacturers of CT scanners must provide information on radiation dose to the public. We contacted General Electric, a major manufacturer of radiation devices. GE representatives refused to provide us any numbers on radiation dose. They, instead, offered us a copy of the technical manual for a CT scanner. A representative told us that that is the extent of their obligation under the law. When repeatedly asked to "translate" highly technical specifications into something we could understand (like rads), or give us information on average radiation doses for any of their scanners, GE refused.
Siemens, another manufacturer, was more forthcoming; however, we ended up with no definite data from them either. The promotional brochure they gave us for one of its scanners contains one table on dose which requires multiple computations to arrive at dose figures which are still ambiguous. When questioned about what the table actually means to a person sitting under a scanner, they abandoned that, and gave us effective doses in millirads for men and for women, but the doses they provided were several magnitudes lower than anything else we had read (for example, they said the radiation exposure for a lung scan was about half that for a chest x ray). They later informed us that their computations had been wrong, but they still insist that high-radiation CT scans are a thing of the past, and that a "three dimensional dataset of the lungs can be acquired today with exposure on the order of magnitude of conventional chest x ray."
As we were going to press, a Siemens representative called and informed us that the company is testing a new device that can reduce radiation exposure up to 50%. The device, known as "Care Dose", can be installed in any scanner in about two hours. Once in place, the device continuously monitors radiation during the scan, and adjusts the amount according to the shape and body size of the scanee. The first "Care Dose" is being installed at the Cleveland Clinic.
Anyone contemplating a body scan should seek dose information from the scan center. Radiation doses are variable, depending on the type of scanner, the body size, what's being scanned and how the machine is operated. Do not accept answers such as "it's like a day in the sun" or "it's the same amount of radiation as flying across the country." These answers tell you nothing about the dose of radiation you yourself will be exposed to. A chest x ray is about 25 millirads, so if you find out how many millirads you will be exposed to, you can get a rough idea of the equivalent chest x rays. If the scan center can't, or refuses to give you information about radiation, find out the name of the scanner and call the manufacturer. By law, they must give you information.
GE can be reached through their web site at www.GEmedicalsystems.com.
Siemens can be reached at (800) 422-7120, or through their web site at http://siemensmedical.com.