Answer to Question #12016 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 son, who just turned 14, has chronic sinusitis. He had a computed tomography (CT) exam of his sinuses in January 2015 at age 11.5 and another one 18 months later in August 2016. A week ago, he had a complete spine x ray (two pictures) for scoliosis screening. I was shocked when I found out how high the radiation dose from a spine x ray is. Now I'm horrified about his future cancer risk. I feel like I have poisoned him and that the spine x-ray was not 100% necessary. Can you tell me how much radiation he might have gotten?


A two-image scoliosis screening exam should result in an effective dose of around 0.1–0.3 millisievert (mSv) (Lee et al. 2005). The typical effective dose from a head CT is 1.5–2 mSv.

It is unlikely that your son will experience any health effects from these procedures, and here's why. At effective doses below 100 mSv, the risk of health effects cannot be seen. The Health Physics Society (HPS) position statement Radiation Risk in Perspective states, "Substantial and convincing scientific data show evidence of health effects following high-dose exposures (many multiples of natural background). However, below levels of about 100 mSv above background from all sources combined, the observed radiation effects in people are not statistically different from zero." Similarly, the American Association of Physicists in Medicine has a position statement which says, "Risks of medical imaging at effective doses below 50 mSv for single procedures or 100 mSv for multiple procedures over short time periods are too low to be detectable and may be nonexistent. Predictions of hypothetical cancer incidence and deaths in patient populations exposed to such low doses are highly speculative and should be discouraged."

The benefits from properly performed, clinically indicated, diagnostic imaging procedures (including CT scans) far outweigh any hypothetical cancer risk. Diagnostic medical imaging procedures provide a medical benefit to you (even if they do not appear to reveal anything), and they are of less risk than the alternatives, such as exploratory surgery.

Kent Lambert, CHP, FHPS


Lee C-I, McLean D, Robinson J. Measurement of effective dose for paediatric scoliotic patients. Radiography 11:89–97; 2005.

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 14 June 2017. 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.