What to Expect: Common Questions about Radiation

Providing safe, expert imaging for your child

Modern medicine provides us various types of advanced imaging to look inside your child’s body for diagnosis or to rule out a medical condition. Some of these imaging instruments (such as CT scans, nuclear medicine, and radiographic or fluoroscopic x-rays) produce radiation to obtain these images while others (such as ultrasound and MRI) do not. Each of these methods have their strengths and weaknesses.

Parents often ask about which imaging techniques use radiation and safety of each. The team at Children's Mercy has put together answers for some of these common questions.

Which type of medical imaging uses radiation?

Modern medicine provides us various types of advanced imaging to look inside your child’s body for diagnosis or to rule out a medical condition. Some of these imaging instruments (such as CT scans, nuclear medicine, and radiographic or fluoroscopic x-rays) produce radiation to obtain these images while others (such as ultrasound and MRI) do not. Each of these methods have their strengths and weaknesses. At Children's Mercy we use all of these methods, and while the key principle is to recognize which imaging tests are best suited for common clinical indications, our radiologists and care providers are trained to recognize when alternative methods such as MRI and ultrasound can be substituted for radiological imaging. 

How much radiation will my child receive?

The amount of absorbed dose received varies with each patient and type of examination. A CT scan, for example, delivers an effective dose of anywhere from less than 1 to around 10mSv, depending on the type of scan the patient receives. For example, the exposure from a head CT scan can be approximately 1 to 2mSv. And some procedures require multiple scans over a region, requiring higher doses. However, the total dose would still be considered low. The US Environmental Protection Agency estimates the total annual average dose from natural background radiation to be 4.06mSv for residents of Missouri and 5.32mSv for residents of Kansas.[4] Hence a CT scan would deliver doses in the same range as your annual natural background radiation level, although in a much shorter time, and targeted to specific body parts, rather than to the whole body.

For radiographic exams, this dose is even lower. A chest x-ray for example can result in 0.02 mSv, which is less radiation than you receive on a round-trip flight from Kansas City to Los Angeles. An astronaut who travels on a mission to the International Space Station is estimated to receive around 100 mSv of radiation.

How does radiation exposure affect newborns?

Minimizing radiation exposure to the newborn is especially important, since the younger the child, the more sensitive their tissues are to the effects of radiation. However, in the complex medical scenario described, imaging is often vital to proper medical treatment. In a premature infant, chest radiographs are often necessary to make sure that life saving lines and tubes are in the proper place, and brain imaging is often needed to make sure that there is no brain injury that might need special treatment. Again, it is a balance between medical need and the very small future risk that most experts think exists for medical radiation. As far as her individual increased risk of getting cancer as she gets older, it is much smaller than the risks that we take every day, such as driving a car.

Is there an increased risk of cancer from medical radiation, especially CT scans?

While no one can point to a single individual and say that their cancer was caused by medical radiation, there is increasingly strong evidence that exposures to radiation levels found during some scans may slightly increase the risk of future cancer. The estimated risk for developing cancer is variable, but for every 1000 children undergoing a single CT scan of the abdomen for example, there will be 1 cancer caused by CT (risk of 1 in 1,000). This needs to be interpreted against the risk of developing cancer over one’s lifetime. For those same 1,000 children, 200 will eventually develop cancer regardless of exposure to medical radiation (risk of 1 in 5). So the additional risk is small, but the best available research indicates that there is in fact some risk.

If children are much more sensitive to radiation than adults, is it appropriate to use examinations like CT in children? Lower doses are frequently warranted in children because of their smaller size and because they have a longer life expectancy than do adults, which may enable tumors with long latency to develop. For a body CT scan of a baby, the amount of radiation used should be approximately 20% of that used for an adult.[6] Appropriately adjusting the radiation dose for children has been a major area of focused attention and improvement over the past 10 years. The “Image Gently” campaign, which Children's Mercy has pledged to, as well as other efforts have been effective at bringing this issue to the attention of the imaging community, referring physicians, and parents of our patients.