Answer to Question #13191 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues

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


In 2018, the American Association of Physicists in Medicine (AAPM) position statement 25C on Radiation Risks from Medical Imaging was revised.

Previous versions of the statement read, "At the present time, there is no convincing epidemiological evidence of increased cancer incidence or mortality from low radiation doses (< 100 mSv)" and "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." Those phrases have been either removed or modified.

The current language of the AAPM statement reads, "At the present time, epidemiological evidence supporting increased cancer incidence or mortality from radiation doses below 100 mSv is inconclusive." This revised language is much less comforting to me as a patient concerned with the dose I received from a head computerized tomography (CT) scan. Is there new evidence that prompted the need to change position? Is it still the position of the HPS and others in the radiation protection community that cancer risk from low dose radiation, <100 mSv (or <50 mSv), to the extent a risk exists at all, is still likely too small to be detected against the normal background risk? Have I sealed my fate?


The change in wording was to appease some new and more cautious members of the committee. It was not based on any new evidence. You have not "sealed your fate" and should be reassured that medically indicated head CT exams carry a very high benefit with very low risk. The additional brain cancer risk from the CT exams is a very small addition to the natural risk of brain cancer. Understand that whether or not any additional risk exists from low dose diagnostic medical examinations like head CT remains controversial and that if some small additional risk does exist, it is not likely to occur for 20 to 40 years after the exposure.

Jerrold Bushberg, PhD

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 31 January 2020. 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.