Answer to Question #12016 Submitted to "Ask the Experts"
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.