June 2008
A whole-body guide
Some doctors or clinics promote "wholebody" CT scans to screen for cancer, heart disease, and other illnesses. But such exams
are likely to reveal harmless abnormalities and expose you to high doses of radiation. Our advice is to steer clear of whole-body
screening.
Here's a guide to imaging tests that screen for disease in specific body parts:
Aorta
As people age, the body's main artery sometimes develops a bulging weak spot, or aneurysm, usually in the center of the abdomen. If not detected and surgically repaired, such aortic aneurysms can rupture, often fatally. Several studies suggest that performing abdominal ultrasound in men age 65 and over can cut the death rate from ruptured aortas by up to two-thirds. Men in that age group, as well as anyone with a family history of a ruptured aortic aneurysm, should ask their doctor about the test.
Bones
Women and possibly men age 65 and over often require periodic bone-density measurements to detect osteoporosis. Younger people might also need such testing if they're at high risk because of a strong family history of the disease or other factors. The standard test, called dual-energy X-ray absorptiometry, exposes you to very low doses of radiation. But you might be able to avoid radiation entirely. A recent study found that a simple questionnaire focusing on the 11 most important hip-fracture risk factors, such as age, health, height, weight, and physical activity, predicted five-year fracture risks almost as well as the X-ray test. If your risk is low, ask your doctor if bone-density testing is still necessary.
Breast
For women between the ages of 50 and 70, mammograms every year or so clearly save lives. Regular screening probably benefits women over age 70, too. For women in their 40s, the evidence is controversial, but the higher your risk of breast cancer—based on such factors as how old you were when you started menstruating, the number of children you have had, and whether you have a personal or family history of the disease—the more sensible testing becomes. You can assess your risk by taking the National Cancer Institute's self-test.
Digital mammography exposes women to less radiation than conventional mammography, and can provide clearer images for some women, including those who have dense breasts. But when digital mammography is read by a computer it can also lead to more false-positive results, just like a breast MRI. So if you undergo digital mammography, make sure that the results are read by a radiologist. And breast MRIs should generally for reserved for high-risk women.
Colon
In March the American Cancer Society added virtual colonoscopy, which uses a CT scan to produce a three-dimensional image of the colon, to its list of approved colon-cancer tests. Another test the group recommends involves taking an X-ray of the abdomen after giving the patient an enema containing barium sulfate, a contrast agent. The group hopes that the options will encourage more people to get screened.
While any colon-cancer test is better than none, traditional colonoscopy has certain advantages over the other two. For one thing, both expose you to radiation. And they often require the same bowel-cleansing preparation as traditional colonoscopy. Moreover, suspicious lesions must be followed up with the standard exam, which not only can detect worrisome growths but also allows doctors to remove them.
Heart
The chance that a CT scan of the heart will identify a severe blockage that needs immediate care is usually outweighed by the risks from radiation exposure and false-positives. Instead, people without chest pain who want information about their coronary risk should find out their blood pressure, cholesterol, and blood-sugar levels, as well as their level of C-reactive protein, which indicates the extent of arterial inflammation. People with chest pain are usually better served by undergoing the time-tested route of exercise stress-testing and standard angiography, still the gold standard for diagnosing potentially deadly heart blockages.
Lungs
A CT scan can detect lung tumors earlier than other screening techniques. But recent reports that a cigarette company underwrote a study claiming to document the test's benefits have brought the test into question. Until the results of an ongoing trial come in, probably in 2010, smokers and ex-smokers should carefully discuss the tests' risks and benefits with their doctor before agreeing to undergo it.
Teeth
Bitewing X-rays, which target specific teeth, are necessary every year only if you have a history of diseased or receding gums or a proclivity for cavities. Otherwise, get them every two to three years. And you need a comprehensive X-ray of your whole mouth only every five to eight years, depending on risk factors such as whether you're a smoker or have a history of periodontal disease. Those with healthy teeth and gums may be able to get by with a single, panoramic X-ray instead of the typical full-mouth series, which involves 14 to 21 exposures. New digital X-rays used by some dentists expose you to slightly less radiation than standard ones. But they can be more uncomfortable because a rigid sensor is put in your mouth. If you switch dentists, have your X-rays forwarded so you don't have to have them repeated.
Uterus
Most gynecologists do at least one ultrasound during a woman's pregnancy to check on the fetus's health. Most research suggests that ultrasounds, which use soundwaves to produce images, are safe. But some laboratory evidence shows that the exam does have some side effects, such as increased tissue temperature. The American College of Obstetricians and Gynecologists cautions against the casual taking of sonograms to produce "keepsake" images of the fetus.
Here's a guide to imaging tests that screen for disease in specific body parts:
Aorta
As people age, the body's main artery sometimes develops a bulging weak spot, or aneurysm, usually in the center of the abdomen. If not detected and surgically repaired, such aortic aneurysms can rupture, often fatally. Several studies suggest that performing abdominal ultrasound in men age 65 and over can cut the death rate from ruptured aortas by up to two-thirds. Men in that age group, as well as anyone with a family history of a ruptured aortic aneurysm, should ask their doctor about the test.
Bones
Women and possibly men age 65 and over often require periodic bone-density measurements to detect osteoporosis. Younger people might also need such testing if they're at high risk because of a strong family history of the disease or other factors. The standard test, called dual-energy X-ray absorptiometry, exposes you to very low doses of radiation. But you might be able to avoid radiation entirely. A recent study found that a simple questionnaire focusing on the 11 most important hip-fracture risk factors, such as age, health, height, weight, and physical activity, predicted five-year fracture risks almost as well as the X-ray test. If your risk is low, ask your doctor if bone-density testing is still necessary.
Breast
For women between the ages of 50 and 70, mammograms every year or so clearly save lives. Regular screening probably benefits women over age 70, too. For women in their 40s, the evidence is controversial, but the higher your risk of breast cancer—based on such factors as how old you were when you started menstruating, the number of children you have had, and whether you have a personal or family history of the disease—the more sensible testing becomes. You can assess your risk by taking the National Cancer Institute's self-test.
Digital mammography exposes women to less radiation than conventional mammography, and can provide clearer images for some women, including those who have dense breasts. But when digital mammography is read by a computer it can also lead to more false-positive results, just like a breast MRI. So if you undergo digital mammography, make sure that the results are read by a radiologist. And breast MRIs should generally for reserved for high-risk women.
Colon
In March the American Cancer Society added virtual colonoscopy, which uses a CT scan to produce a three-dimensional image of the colon, to its list of approved colon-cancer tests. Another test the group recommends involves taking an X-ray of the abdomen after giving the patient an enema containing barium sulfate, a contrast agent. The group hopes that the options will encourage more people to get screened.
While any colon-cancer test is better than none, traditional colonoscopy has certain advantages over the other two. For one thing, both expose you to radiation. And they often require the same bowel-cleansing preparation as traditional colonoscopy. Moreover, suspicious lesions must be followed up with the standard exam, which not only can detect worrisome growths but also allows doctors to remove them.
Heart
The chance that a CT scan of the heart will identify a severe blockage that needs immediate care is usually outweighed by the risks from radiation exposure and false-positives. Instead, people without chest pain who want information about their coronary risk should find out their blood pressure, cholesterol, and blood-sugar levels, as well as their level of C-reactive protein, which indicates the extent of arterial inflammation. People with chest pain are usually better served by undergoing the time-tested route of exercise stress-testing and standard angiography, still the gold standard for diagnosing potentially deadly heart blockages.
Lungs
A CT scan can detect lung tumors earlier than other screening techniques. But recent reports that a cigarette company underwrote a study claiming to document the test's benefits have brought the test into question. Until the results of an ongoing trial come in, probably in 2010, smokers and ex-smokers should carefully discuss the tests' risks and benefits with their doctor before agreeing to undergo it.
Teeth
Bitewing X-rays, which target specific teeth, are necessary every year only if you have a history of diseased or receding gums or a proclivity for cavities. Otherwise, get them every two to three years. And you need a comprehensive X-ray of your whole mouth only every five to eight years, depending on risk factors such as whether you're a smoker or have a history of periodontal disease. Those with healthy teeth and gums may be able to get by with a single, panoramic X-ray instead of the typical full-mouth series, which involves 14 to 21 exposures. New digital X-rays used by some dentists expose you to slightly less radiation than standard ones. But they can be more uncomfortable because a rigid sensor is put in your mouth. If you switch dentists, have your X-rays forwarded so you don't have to have them repeated.
Uterus
Most gynecologists do at least one ultrasound during a woman's pregnancy to check on the fetus's health. Most research suggests that ultrasounds, which use soundwaves to produce images, are safe. But some laboratory evidence shows that the exam does have some side effects, such as increased tissue temperature. The American College of Obstetricians and Gynecologists cautions against the casual taking of sonograms to produce "keepsake" images of the fetus.
