(HealthScoutNews) -- They're high-powered X-rays known as CT scans, and each year more than 1.5 million American children receive at least one.

Now, the U.S. Food and Drug Administration (FDA) is warning that radiologists often expose those children to doses of radiation far greater than is safe for their age and weight -- by some estimates, up to six times more than what is needed to produce clear images.

In a public health notification, FDA officials warned recently that, despite earlier efforts by the American College of Radiology to warn doctors to reduce radiation levels when imaging children, the problem still exists.

"This is a very hot topic in radiology right now. It's well known that in many instances children are receiving far too much radiation, and the primary reason is because adjustments are not being made to the machines to accommodate the children's weight and overall smaller size," says Dr. Kevin Roche, a pediatric radiologist at New York University Medical Center.

CT scans -- short for "computerized tomography" -- differ from traditional X-rays in that they take pictures, or "slices" as they're called, of cross sections of the body. This lets doctors "see inside" many areas -- such as the chest, abdomen or brain -- that would only be visible as a flat, one-dimensional picture on a traditional X-ray.

In children, CT scans are most often used to diagnose appendicitis, trauma from injury and tumors.

The pictures that result from a CT scan definitely make diagnosis easier and more definitive. However, when radiation levels aren't adjusted to a child's size and weight, serious health threats can ensue.

"Because children are still growing and their cells are rapidly dividing, they are more susceptible to cell damage from radiation," explains Roche.

"This, combined with their longer life expectancy, increases their odds significantly over adults that they will develop cancer from radiation," he says.

According to the American College of Radiology, many CT scan machines are equipped with software that automatically calibrates the system for optimal image quality. However, those calibrations are almost always based on adult size and weight. Children can easily end up with far too much radiation, even from a single session.

"If they don't bother to change the settings, then this is invariably going to occur," says Roche.

While there are guidelines for calibrating the machines according to the patient's weight, studies have shown that few institutions are paying attention.

In a study of pediatric CT scans published last year in the American Journal of Roentgenology, researchers found machines were not being adjusted to suit the children's smaller size, and 90 percent of children getting CT scans were receiving twice the radiation they should.

Compounding the problem, it's not always easy to tell when a CT scan's levels are in the danger zone.

When radiation levels are too high on traditional X-rays, images appear overexposed; it's easy to see that something is wrong. With CT scans, the picture is so good it's not likely to be compromised, even when radiation levels are way above normal, according to the American College of Radiology.

"This is one reason that many centers don't even recognize that there is a problem," says Roche.

The FDA says something must be done to correct the situation. In its recent public health notification, it not only hoped to raise awareness of the problem, but to reinforce a series of guidelines issued early last year that included recommendations urging technicians to pay more attention to machine settings as they pertain to children.

In addition, the FDA is calling on technicians to reduce the number of unnecessary exposures on children by eliminating "pre-contrast" pictures, a kind of base-line image that is often taken before the actual CT scan is performed.

In one final measure, the FDA is also urging doctors to reduce the number of referrals for CT scans in children, suggesting they make better use of conventional X-rays, as well as ultrasounds or MRIs. All of these techniques deliver little or no radiation, says Dr. David W. Feigal Jr., director of the FDA's Center for Devices and Radiological Health.

Roche says parents can also play a role, simply by asking the radiologist a couple of key questions.

"Ask them if their machine is calibrated for pediatric use, if they are going to adjust the radiation to coincide with the weight of your child, and if they are following both ACR and FDA guidelines for radiation exposure in children," says Roche.

If they can't -- or won't -- answer these questions, then, say experts, parents should consider a different facility.

"As long as it's not an emergency, parents should feel free to call various radiology centers or hospitals and ask about their ability to safely give CT scans to kids," says Roche.

What to Do: For a simple primer on what CT scans do and how they work, visit Brigham and Women's Hospital's radiology department. To learn more about the effects of radiation on children's health, visit The Children's Hospital Medical Center of Cincinnati.

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