Your soccer-obsessed 11-year-old daughter manages to run head-on into a teammate during practice. The teammate is OK, but your daughter’s vision is blurry and she complains of a blinding headache by the time she’s getting stitches for a cut in her scalp.

The physician at urgent care wants to send her for a CT scan to check for concussion – but mentions something about radiation involved.Do you, the parent, say “Yes”?

Or what about this: Your three-year-old has sharp pain in his tummy after spending a day eating corn dogs and cotton candy at the county fair. The family doc thinks it might be acute appendicitis – and orders up a CT to help see whether that’s true.

Do you sign the permission form?

That's a dilemma faced by countless parents in today's world, where technology has given us the ability to see far more deeply and clearly into the human body than medicine ever has before.

But all that clarity comes at a cost: High tech scans such as CT – it stands for computed- tomography – are not only expensive, but they subject the patient to ionizing radiation.

Radiation can increase the rate of certain cancers in the human body.

And most at risk – because they are young and still developing and because they can live for many more years, giving cancers time to develop – are children.

As parents, it can be difficult to weigh the risks and benefits of imaging – and there are no simple answers, says Dr. Alex Schabel, a radiologist with Oregon Imaging Centers in Eugene and Springfield. But physicians have developed guidelines for exposing children to radiation, and you should always ask your doctor to explain the risks and benefits of any procedure.

“It depends on the age of the child and exactly what we're looking for,” Schabel says.   “But we try to optimize CT use in young children because of the small risk of cancer over time.”

That said, CTs are an extremely useful tool for doctors dealing with certain conditions. There is no other way that is as quick and as sure as a CT scan to diagnose such urgent problems as stroke or head trauma.

“Someone who has had a significant head injury, we don't worry about the risk of the scan. One CT scan has a very low and acceptable risk, especially when compared to not diagnosing a severe injury or disease,” Schabel says.

Schabel's conservative approach is directly in line with national thinking about scans and radiation exposure.

According to the National Cancer Institute at the National Institutes of Health, the use of CT scans in both adults and children in the United States has increased eight-fold since 1980, and continues to grow at a rate of 10 percent each year.

“CT can be a lifesaving tool for diagnosing illness and injury in children. For an individual child, the risks of CT are small and the individual risk-benefit balance favors the benefit when used appropriately,” the NCI says on its website, cancer.gov.

There is no “safe” level of radiation exposure for children, the NCI says, so the use of CT scans will always mean a balancing act between risk and benefit.

The NCI recommends, first, using CTs on children only when medically necessary and, second, being sure that exposure is minimized. Children's bodies require less radiation for a scan than adults' bodies, the NCI notes, and not every scan has to be done in high resolution.

Whenever possible, other kinds of scans – not using radiation – should be considered. Ultrasounds and MRIs can be a good alternative, depending on the patient’s symptoms and the referring clinician’s concerns.

Schabel points out that CT scans are often used to diagnose appendicitis, often saving patients from unnecessary surgery or delay in care.  Increasingly, though, physicians are getting the same information by using ultrasound and MRI scans – which don't involve radiation. Often, but not always, these alternative imaging techniques can make the diagnosis without the associated risk of radiation. 

“In young kids, though, there are certain risks and limitations with MRI as well,” he says.

That's because the child has to stay very still for an MRI to be diagnostic. Some children can manage that on their own, but others require sedation or anesthesia, which carry their own small risks.

Schabel says that newborns, for example, can often stay still enough for an MRI if they're fed and swaddled before the procedure. “But a two-year-old – you're almost certainly going to require sedation.”

“CT is a very central technology for what we do in medical diagnosis,” the radiologist says. “I will usually recommend a non-radiation study (such as MRI or ultrasound) when there is more than one possibility. But with acute trauma or acute stroke – with someone in a motor vehicle accident or falling off an ATV – often times we need to perform CT. You can't always wait for an MRI.”

Under current best practices, the soccer girl with the blinding headache might well be diagnosed with the aid of a CT scan. The risk of radiation is small compared to the need to understand just what’s going on in a possible brain injury.

The little boy with the sore tummy? He might be on his way, first, for an ultrasound – which uses no ionizing radiation but could possibly tell his physicians and parents whether he needs emergency surgery, or just fewer corn dogs.

How can you tell if a child has a concussion? Here are some concussion symptoms from MayoClinic.org:

• Headache or a feeling of pressure in the head
• Temporary loss of consciousness
• Confusion or feeling as if in a fog
• Amnesia surrounding the traumatic event
• Dizziness or "seeing stars"
• Ringing in the ears
• Nausea
• Vomiting
• Slurred speech
• Delayed response to questions
• Appearing dazed
• Fatigue