Answer to Question #11742 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:


I have a child who was exposed to radiation in the form of a computed tomography (CT) scan to her head at age two. Should I now be concerned with minimizing her future exposure to radiation on the basis of its cumulative effect on the human body? Particularly, we live in Sydney, Australia, and I have thought I should not take her on long-haul flights to other parts of the world due to the background radiation she would receive spending many hours at high altitude.


I encourage you not to limit your daughter's activities because of the CT scan she received as a toddler. The amount of radiation from her CT scan was very low—your daughter will receive that same amount of background radiation just by living an extra eight months or so. The opportunity to travel and see the world will greatly enrich her life; there are huge benefits to traveling and virtually no risk. (Actually, I suppose that depends on your destination.) I also want to discourage you from refusing future, clinically indicated, diagnostic imaging examinations; refusing medical imaging procedures may result in real and substantial risk by not receiving the clinical benefits of the procedures.

There are a lot of articles on the internet and elsewhere that state that any amount of radiation increases the risk of cancer or genetic effects. The problem is that there is no credible scientific evidence to support this. There is clear and convincing evidence that the chances of cancer increase at high doses (greater than 100 millisieverts [mSv]) and that the chances increase linearly as the dose increases above 100 mSv. These risks are often extrapolated to low doses of radiation (such as from a CT scan), assuming that the risk is proportional no matter how low the dose. Even after a century of study, there is no scientific evidence to support these extrapolations.

I encourage you to check out the Image Gently website ( for additional information and resources.

Kent Lambert, CHP

Answer posted on 5 October 2016. 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.