X-Rays, Scans, Radiation, and Kids

What Parents Need to Know Before the Doctor or Dentist Orders a Scan

Medically Reviewed by Hansa D. Bhargava, MD on August 16, 2012
5 min read

When a child is ill or injured, you want your child to get whatever medical tests are needed, as soon as possible.

But when it comes to imaging tests -- such as X-rays, PET scans, and CT scans -- the key word is "needed."

Those tests use radiation that, if exposed to often enough, has been linked to a greater chance of getting cancer later in life. And because kids are still growing, they're more sensitive to radiation.

"No patients should be exposed to more radiation than they need at any age," says pediatric radiologist Marta Hernanz-Schulman, MD, chair of the American College of Radiology's Pediatric Imaging Commission.

No doubt: X-rays and scans can be helpful, even life-saving. But sometimes, they're not necessary.

So when are these tests really needed? Here's what you should know.

The average child now gets seven scans that rely on radiation before age 18, one recent study shows.

Most of those tests are X-rays, which use relatively low levels of radiation. About one in eight scans ordered for kids is a CT scan.

Because they spin around the body taking multiple images, CT scans can deliver radiation doses that are up to 200 times higher than an average chest X-ray.

About 7 million CT scans are done on U.S. kids each year. And that number is rising about 10% per year.

Why? Pediatric surgeon Thomas Pranikoff, MD, of Brenner Children's Hospital in Winston-Salem, N.C., has studied that.

He says it's partly about doctors' use of technology. "People aren't focusing as much on clinical skills like taking a patient's history and doing a physical examination," he says.

It's also about parents demanding tests. "They want an answer right away and that puts a lot of pressure on the doctors taking care of them," Pranikoff says.

Sometimes kids don't need a scan at all. They just need to be watched in a safe setting.

One study showed that kids who went to an ER after suffering a minor head injury were less likely to get a CT scan if they were simply observed in the ER for 4-6 hours -- and that observation period didn't compromise their safety.

You may have heard about a study showing that kids who have two to three CT scans were nearly three times as likely to develop a brain tumor or leukemia in the decade following their first scan, compared to children who were not scanned.

But you should know that it's very unlikely that a child will develop a brain tumor or leukemia -- scan or no scan. The odds that a child will develop a brain tumor or leukemia are very low to begin with, and they're still low, even if that number triples.

Put another way, experts estimate that 10,000 CT scans would lead to one additional case of cancer.

Kids are smaller than adults, so they get a higher dose of radiation unless the scanning machine is adjusted for them. It's not uncommon for a child to get an adult-sized dose of radiation, especially if they're scanned at a general hospital.

General hospitals, where 90% of child imaging occurs, don't always change the settings on their scanners. Children's hospitals, on the other hand, routinely adjust their machines to compensate for a child's size.

The FDA has urged makers of medical scanning equipment to make new devices that would minimize the radiation dose delivered to children.

It's important to use the lowest dose possible with scanning a child. But it's even more important to avoid unnecessary scans in the first place.

There's a growing body of medical evidence questioning the use of CT scans in these circumstances:

  • After a child suffers blunt trauma, such as a blow to the head after a fall.
  • To evaluate seizures or chronic headaches.
  • As the main tool a doctor uses to diagnose appendicitis.

"We've seen kids who've been 8 or 10 years old who've already had six CT scans. They come in multiple times for belly pain to an ER and they get scanned. And sometimes it's at several ERs so the doctors who are ordering the scans don't really even realize how many the child has had," Pranikoff says.

There are simple things parents can do to make sure that their kids only get the imaging tests when it's really necessary.

Ask questions. Here are the four questions parents should always ask, according to Marilyn J. Goske, MD, a pediatric radiologist at Cincinnati Children's Hospital Medical Center:

  1. Does this test use radiation?
  2. Why is this exam being done?
  3. How is it going to help my child?
  4. Are there alternatives that don't use ionizing radiation, like an ultrasound?

Goske helped to create "Image Gently," a campaign to educate parents and doctors about the risks of radiation.

Consider going to a children's hospital. If a scan is necessary, and you have time to choose where to go to get it, consider going to a children's hospital. Pediatric facilities are more likely to adjust the scanner to deliver a child-sized dose of radiation.

Keep records. Write down each scan your child gets, where they got it, and the date.

It's also a good idea to keep a copy of the scan. That keeps tests from being unnecessarily repeated if a child gets seen at more than one hospital within a short period of time.

Check on the dentist's office. Kids are likely to get regular X-rays at dental check-ups. When used appropriately, experts say the risk from those X-rays is probably low.

The American Dental Association (ADA) recommends that kids and teens get bitewing X-rays every six to 12 months if they have cavities. Those who don't have cavities can go a year or two between scans.

Cone-beam CTs are mainly used by oral surgeons and orthodontists. They deliver doses of radiation that are far higher than regular dental X-rays, but lower than the doses patients get from medical CTs, says Joel Berg, DDS, dean of the University of Washington School of Dentistry and president-elect of the American Academy of Pediatric Dentistry.

Berg says cone-beam CTs are best used in cases where there's been trauma to the jaw or to help dentists correctly position implants. For routine check-ups, an ordinary X-ray may be all that's needed, with less radiation exposure.