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Just how much radiation am I really getting from medical x-rays and CT scans? Let’s review the things required for radiation to cause short-term injuries and long-term effects, and then compare that to medical radiation. So the strength of individual rays has to be above a certain threshold, like we discussed, to cause tissue injury. Medical x-rays used in taking x-rays and CT scans are in fact above this threshold, but not by much. Basically the rays have to be strong enough to penetrate your body, and if you think about it, this is how we make the projectional pictures. Like when you look at a hand x-ray, you see the bones, because the bones block the rays, but your skin and muscle does not. So it’s right around that strength that rays can become potentially injurious. But medical x-rays are still much lower energy than most forms of “dangerous radiation” that people are thinking about, in those found in association with nuclear bombs or industrial nuclear accidents. The intensity, or how many rays there are in each exposure, is also significant, but that number is intentionally limited to be just enough that we need to make the picture that we want to see. The scary exposures you might hear about from history or on the news generally involve extremely high intensity radiation. The number of potentially damaging rays is much, much, much lower than the number of rays that you might encounter in an accidental exposure from Chernobyl or a nuclear bomb, let’s say.
So the energy the x-rays we use, and the number of x-rays we use are well under our control at the time we’re doing your radiology exam. The technologist that runs the machine sets that machine according to well-established protocols developed under the cooperation with radiologists like me, who know exactly what it is we need to see and a medical physicist who’s a PhD in physics that specifically is trained to understand exactly the process that we’re talking about. So we only give the minimum amount of radiation to each patient tailored to that patient size required in order to get the images we need to answer the questions of your doctor as to the reason why they ordered the exam in the first place. To give an example, we talked about naturally existing radiation, like from the sun or from the Earth’s core, rocks, and other background radiation coming in from outer space. When you take a flight over an ocean, for example, you fly so high that you actually get a little bit more cosmic radiation and radiation from the sun because there’s less of Earth’s atmosphere shielding you. So that radiation exposure level that you get in flying from, let’s say New York City to London, is actually five times greater than the amount of radiation exposure you get from a chest X-ray. Now, granted, the exposure in a CT scan is significantly higher than that. Usually 10 to 20 times higher than a transatlantic flight, although still no one ever worries about radiation exposure when they take a plane somewhere. So by extension, you can feel a similar level of comfort when thinking about getting a chest x-ray.
