Answer to Question #14655 Submitted to "Ask the Experts"

I am a 35-year-old female. During the past two years, I've had a number of health issues. During this period, I have had, in total two chest computed tomography (CT) scans, three abdomen/pelvis CT scans (one with contrast, to which I was severely allergic), three chest x rays, two abdomen x rays, three mammograms, and a ventilation/perfusion, known as a V/Q scan of my lungs. It was a bit much.

Prior to that, my history includes one abdominal x ray, one foot x ray, one other chest x ray, one full-spine x ray, and a few dental x rays.

I understand that the cancer risk under 100 mSv is too small to observe, but I have received well over 100 mSv from diagnostic imaging in my young lifetime—not to mention background radiation and airline flights, which I tend to take frequently (from Florida to California). Because I was quite distressed and malnourished/under-hydrated during this period of testing, I am worried I was even more vulnerable to cellular mutation.

Could you offer me some advice on my level of risk and how it might affect my future? Is there anything I can do? I'm quite scared. Thank you.

The quick answer to your question is that your risk from all of your diagnostic imaging examinations is too small to be observed and would have little to no impact on your future health.  

As you've indicated the cancer risk from radiation exposures less than 100 mSv are too small to observe. The diagnostic examinations you have received all have effective radiation exposures that are much lower than 100 mSv.   

One thing to keep in mind is that cancer risk from the low radiation doses (<100 mSv) encountered in diagnostic imaging examinations and background radiation are not cumulative. The risk from each exam is not dependent on the radiation dose received from a prior exam. The radiation risk for each examination is independent of the dose from prior exams so each time you received a medical imaging exam with a dose under 100 mSv, the risk of cancer from that exam would be too small to observe.   

To put this in another way, the fact sheet from the US Nuclear Regulatory Commission titled Biological Effects of Radiation, issued in December 2004 indicates that the average background radiation exposure in Denver, Colorado, is over 10 mSv per year. Individuals living in Denver would accumulate 100 mSv of background radiation in 10 years and would exceed 100 mSv if they receive any medical imaging examinations in the time. However, the risk from any imaging exam after they exceeded the 100 mSv "threshold" is no different than if they lived somewhere else in the United States where the background radiation was lower. To put it another way, individuals in Denver, Colorado, have a background radiation exposure that is more than three times (3x) higher than the average background radiation dose in the United States (Denver = 10 mSv/year, US Average = 3.1 mSv/year), but they do not have a cancer incidence rate that is 3x the US average. In fact, individuals living in Denver, have a cancer incidence rate no different than the rest of the US population.  

In summary, your risk from future medical imaging exams is not impacted by the previous exams you have received. There is no need to be concerned about the risk from medical examinations with radiation exposures <100 mSv. I would like to add that it is important to keep in mind that there is a very real benefit from the medical imaging you have received. Your physician used the information to provide an accurate diagnosis and appropriate treatment.

John Gough, MS, CHP, DABMP