June 2008
Is that imaging test really needed?
How to recognize and avoid overexposure to radiation.
The use of imaging tests is soaring. In 2007 doctors performed nearly 69 million computed tomography (CT) scans, compared
with 30 million a decade earlier. Up to a third of those tests may not have been really needed, unnecessarily exposing people
to potentially harmful radiation, says David Brenner, Ph.D., director of the Center for Radiological Research at the Columbia
University Medical Center in New York City.
"CT scans are very accurate, fast, and readily available, which means that there are pressures from patients and the medical system to use them," Brenner says. "While the great majority of CT exams are appropriate, in some cases they could be replaced by nonradiation or low-radiation technologies."
Even tests that don't expose you to radiation, such as magnetic resonance imaging (MRI) and ultrasound, can pose certain other risks. And the tests can be expensive and time-consuming. Of course, imaging tests can also help detect and diagnose disease. Here's how to know when testing is warranted.
IMAGING HAZARDS
Although the cancer risk from a standard X-ray or CT scan is small for any individual, as use of the tests increases so does the cancer risk for the total population. Moreover, the effect of radiation from each test is cumulative, so each one you undergo incrementally increases your still small chance of eventually developing a radiation-induced cancer. That's especially true for children, because they're particularly sensitive to radiation.
And some CT scans use high doses of radiation. For example, "64-slice" CT angiography, a test that some say can catch coronary disease early, can expose you to 200 times as much radiation as standard chest X rays, and twice the radiation of many CT scans. A July 2007 study in the Journal of the American Medical Association estimated that 1 in every 1,300 60-year-olds who undergoes the test may develop cancer as a result.
MRI scans don't use radiation, but they're not problem-free. Their ability to produce detailed images, for example, makes them prone to spotting "incidentalomas," or abnormalities that ultimately prove to be harmless after follow-up tests and sometimes even treatments. A recent study of breast MRIs found that about 80 percent of high-risk women who thought they had cancer based on the test did not.
BASIC SAFETY
To minimize the risk from X-rays and CT scans, ask:
This article first appeared in the June 2008 issue of Consumer Reports on Health.
"CT scans are very accurate, fast, and readily available, which means that there are pressures from patients and the medical system to use them," Brenner says. "While the great majority of CT exams are appropriate, in some cases they could be replaced by nonradiation or low-radiation technologies."
Even tests that don't expose you to radiation, such as magnetic resonance imaging (MRI) and ultrasound, can pose certain other risks. And the tests can be expensive and time-consuming. Of course, imaging tests can also help detect and diagnose disease. Here's how to know when testing is warranted.
IMAGING HAZARDS
Although the cancer risk from a standard X-ray or CT scan is small for any individual, as use of the tests increases so does the cancer risk for the total population. Moreover, the effect of radiation from each test is cumulative, so each one you undergo incrementally increases your still small chance of eventually developing a radiation-induced cancer. That's especially true for children, because they're particularly sensitive to radiation.
And some CT scans use high doses of radiation. For example, "64-slice" CT angiography, a test that some say can catch coronary disease early, can expose you to 200 times as much radiation as standard chest X rays, and twice the radiation of many CT scans. A July 2007 study in the Journal of the American Medical Association estimated that 1 in every 1,300 60-year-olds who undergoes the test may develop cancer as a result.
MRI scans don't use radiation, but they're not problem-free. Their ability to produce detailed images, for example, makes them prone to spotting "incidentalomas," or abnormalities that ultimately prove to be harmless after follow-up tests and sometimes even treatments. A recent study of breast MRIs found that about 80 percent of high-risk women who thought they had cancer based on the test did not.
BASIC SAFETY
To minimize the risk from X-rays and CT scans, ask:
- Your doctor if there are lower-dose or nonradiation alternatives.
- Your radiologist if the facility is accredited by the American College of Radiology, to ensure that the people who perform
and interpret the exam have the appropriate training and that the equipment is properly maintained. Also ask for copies of
your exam so you don't have to repeat the test if you see another health provider for the same problem.
- The technician if you need to wear a special shield to protect, for example, the reproductive organs or the thyroid gland.
This article first appeared in the June 2008 issue of Consumer Reports on Health.
