I’ve recently been looking over the statistics about this blog. The most popular posts are those which talk about common issues — croup and concussions, for example. But one of the most often read posts gets its popularity from people using search engines like Google to answer this question: how risky are x-rays, especially CT scans, to children? You can read my actual posts about that here and here, but what struck me most about the popularity of this topic is what it tells us regarding how we think about risk. In particular, how do we tend to think about the risk of events occurring which are very rare, but which carry grave consequences if they happen? Lawyers call these events “small probability — large loss events.” Economists have studied the subject quite a bit, too, especially as it relates to investment decisions people make.
We humans are not entirely rational when we think about risk. We tend to focus on low-probability but high seriousness events, particularly if we are thinking about them in the context of choosing to do or not do something. So, for example, if your child needs a CT scan, as a parent you many think about how the radiation in that test increases your child’s chances of getting cancer. What we don’t think about is that your child is far, far more likely to suffer harm in a car accident while you are driving to the CT scanner than he is to suffer harm from the scan. But since we drive our children around every day, we don’t think much about that risk.
According to the National Cancer Institute, a child’s overall risk of developing any form of cancer is 1-2/10,000 children, or 0.01-0.02%. Also according to the NCI, this number has changed very little, if at all, over the past 30 years. The use of diagnostic x-rays in children, especially CT scans, has increased enormously during that time, so we should be reassured by these statistics. Even so, radiologists are increasingly vigilant about how they can reduce radiation exposure when they use x-rays.
Bottom line — it is always worth asking if the risk of a test exceeds the value of the information the test will give. But for x-rays, the benefit virtually always outweighs the risk.
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Related Posts
CT scans and cancer: thinking about the meaning of risk
04/03/2010 • I've written before about how to think about the risk of x-rays that we doctors do -- here, here, and here. These posts, particularly the first one, are the most read and commented upon ones ...more
CT scans and radiation risk
12/01/2007 • I've written before about the radiation risk of x-ray studies. Most of this risk is in the form of increased lifetime cancer risk. This is a particular concern for children because lifetime risk is cumulative, ...more
Dear Dr. Christopher,
It happened three days ago, on 16-10-11.
My grand daughter, 7 months old, fell down from the sofa, to the floor, which had a cushion. It was a fall head down. The child cried for some time and became normal. I felt bad because the child was under my care.
Her father was not at home. I had to take a decision.
It was 7 pm. I had to rule out the possibility for any complication.
I took her to the emergency ward of the nearest public hopsital. The doctor said there was no visible complication and advised a head x ray. I asked what
was the risk invovled. He did not give an answer and said head xray was needed.
The Radiologist who did the xray appeared to be totally unprofessional. He was messy. He had no to handle a baby. He did not cover the areas not to be x rayed.
He took two photos, one staight on the face, other from the side view.I do not know the ratiation level used.
I am terribly upset. Have I caused life long problem for rhe baby.
Can you tell be what are the possible complications and what are the precautions possible?
Please.
I wouldn’t worry about 2 simple skull x-rays. Really, there should be no life-long complications from this — the radiation received is about the equivalent of the normal background radiation of about a month of normal living at sea level or of a long airplane flight.