Answer to Question #13164 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Diagnostic X Ray and CT

The following question was answered by an expert in the appropriate field:


My daughter is 18 months old. She had to have a computed tomography (CT) scan of her head after a fall. I am now very concerned about her risk. How bad is it for a child this young to receive a CT scan? Is it worse as the articles indicate because she is a baby girl?


I'm sorry you've had to deal with the stress of your daughter's injury. The bottom line is that the current science supports that your daughter should not suffer negative consequences as a result of the CT and the potential benefit to her care is worth any very small amount of risk.

The American Association of Physicists in Medicine (AAPM) in Report 96 provides a calculation to convert the procedure dose to a whole body effective dose. If you know the dose-length product (DLP) of your daughter's head CT scan, multiply that number by 0.0067. The result is an estimate of the effective dose in millisieverts (mSv). 

If you read about particular studies that showed a link between pediatric head CT scans and brain tumors or leukemia, there were several issues with how the research was conducted. Those studies did not account for the fact that the people who most need to go into the hospital for head CT scans are often the same people who are most at risk for acquiring cancers due to underlying health issues. Accidents happen that result in the need for a CT scan. This helps moderate the effects reported in the paper. But most who need CT scans have issues like tumors which require the CT scans to diagnose the tumor in the first place. (Note: More information on some flaws with some of those studies are available in the answers to the ATE questions Q12489Q11310, and Q11944).

Lastly, the position of the Health Physics Society is covered in the "Radiation Risk in Perspective" position statement. As stated in the document the effects of radiation below 100 mSv above background are not measurable if they exist at all. In other words, the risks are "not statistically different from zero."

There are several different models that scientists can use when considering the effects of radiation. These include the linear no threshold (all radiation has an effect) hypothesis, the threshold (effects start after a certain level) hypothesis, and hormesis (small amounts of radiation are beneficial). Our best current data suggests that there is at least a threshold for radiation effects so you can rest easy knowing that getting your daughter imaged was the right decision for her long-term health. The CT gave you and your medical team useful information for her immediate care.

Peter James Seel, MS

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 6 November 2019. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.