06/13/2012 05:53 pm ET Updated Aug 13, 2012

CT Scans and Cancer: What Parents Need to Know and Do

Your child has fallen and hit her head. You rush her to an emergency room, where the doctor talks about doing a CT scan to look for any signs of bleeding or other injury to her brain.

Of course you want to know if there's a brain injury. But if you heard the recent news that CT scans may increase the risk of brain tumors and leukemia in children, you might feel very nervous. You might even want to say no.

For the most part, you should follow a doctor's advice. But asking some questions might be a good idea.

So here's the scoop. CT (computed tomography) scans allow doctors to see the inside of the body, taking detailed pictures quickly that can be extremely helpful when looking for things like internal injuries, tumors, appendicitis and all sorts of other conditions. They do this by using a small dose of ionizing radiation. It's a really small dose. But any exposure to radiation can increase the risk of cancer, especially in children whose small and growing bodies are particularly susceptible to radiation's effects.

Researchers looked carefully at this, and found that if a child has two to three CT scans it can triple their risk of brain cancer. Five to ten CT scans triples the risk of getting leukemia.

Now, this risk needs to be taken in context. According to the National Cancer Institute, the risk of getting a brain tumor as a child is three per 100,000 children and the risk of getting leukemia is just under five per 100,000 children. So even though it sounds scary to say that the risk is tripled, we're still talking tiny numbers here. And overall, since the risk of getting some kind of cancer in our lifetimes is somewhere around 40 percent, adding a little bit more doesn't seem like such a big deal.

But any risk, especially one to kids, is something we need to take seriously.

There are other ways of looking inside the body. There's ultrasound, which doesn't give the same level of detail but can be very useful -- and while babies still have their "soft spot," can be used to look inside the head. There is MRI, or magnetic resonance imaging -- which actually gives even more detail than CT scans, but it takes longer and kids need to hold really still. Since holding still is impossible for babies and little kids, and tough for some older ones, we often use sedation. But sedation has risks too.

So what do you do when a doctor starts talking about doing a CT on your child?

There are ways to lessen the risk. You can use lower doses of radiation -- that's something that many children's hospitals like mine (Boston Children's Hospital) have been doing for a long time. You can also be judicious in doing scans -- for example, one of my colleagues, Lise Nigrovic, did a study showing that observing kids with head bumps in the emergency room can eliminate the need for any kind of scan in lots of them.

The Alliance for Radiation Safety in Pediatric Imaging has a physician-led Image Gently campaign in which aims to raise awareness of ways to decrease radiation exposure to children. They suggest that parents ask these questions when doctors start talking about "imaging" tests:

▪ What is the name of the test you are suggesting for my child?
▪ Does the test involve ionizing radiation?
▪ How will the test improve my child's care?
▪ Are there any non-ionizing radiation tests that could be safely used?
▪ Will my child receive a "kid-sized" dose of radiation?
▪ Is this facility accredited by the American College of Radiology?

I'm not saying that you can't trust doctors. But as consumers, we should always ask questions. There is very little in medicine (or in life) that is risk-free. And there are very few clear-cut answers in medicine. All of us, doctors and patients and parents alike, weigh risks and benefits differently. What the Lancet study shouldn't do is stop us from doing CT scans on kids, because they can be life-saving. What it should do is empower and encourage us to talk more about imaging -- and help guide us in making better decisions and new innovations to keep our children safe and well.