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What’s the actual chance of getting a significant radiation injury from having an x-ray taken or a CT scan performed for medical reasons? Well, let me answer this question in a relatively oversimplified, perhaps even controversial way, but basically the answer is you have essentially zero chance of a significant radiation effect from routine medical imaging that is appropriately performed. Let’s unpack that a bit. So one: having x-rays performed even on many occasions carries basically zero risk to an adult human being when properly administered. As we discussed, you get even more radiation on a plane flight over the ocean from the sun and space than you do from having chest x-ray. Well, many x-rays are also performed on the extremities to look for broken bones, et cetera, and muscle and bone are surprisingly resistant to radiation injury. As far as soft tissues and organs go.
Number two: a single CT scan, like, let’s say if you’ve gone to the ER for an unknown cause of severe pain, or we’re working up some sort of a newly discovered illness or cancer, carries basically zero risk to adult human beings when properly administered. CT scans have significantly more exposure than x-rays, it’s true. But if we look closely at the estimated dose, and forget what the funny units mean for now, just remember the number, most CT scans expose a patient to between one and five millisieverts. One and five. So the average US person accumulates a radiation dose of about two and a half, so right in the middle of that range, millisieverts per year, just from background, meaning the sun, cosmic rays, rocks and certain foods. Yeah, that’s right. Bananas are radioactive, but that’s a fun fact probably for another topic of discussion. So at any rate, if you had a CT scan every year, you’d only be doubling the background exposure everyone receives all the time throughout their entire life.
Three: this is a bit controversial, but much research suggests that there is zero increased risk of radiation induced cancer below 100 millisievers of cumulative medical radiation. So that’s about 20 to 40 CTs worth of radiation. Even at that excess dose, 20 to 40 CTs, still only 1% of those people get a radiation induced cancer. And this is straight out of the BEIR VII report on radiation. The International Council on Radiation Protection, ICRP, their most recent report says that in a group of people with a cumulative dose of a full Sievert, now that’s 300 CTs worth of radiation, only about one in 10 of them will get a cancer that was caused by that radiation. And less than half of those people will die from that radiation induced cancer.
Number four: there is essentially zero chance of a short-term radiation from any standard medical imaging test that is appropriately performed. There is simply not enough radiation to cause significant direct damage. Now note, that does not mean medically induced radiation injury does not exist, but now that we know a lot more about it, we can see that it must only happen in certain circumstances. For example, someone with tons and tons of medical imaging all the time, they might accumulate enough radiation to have a significant effect. The flip side of this though, is that this only happens in extremely ill patients that are usually battling some medical illness that is severely and constantly threatening their life for other reasons. Maybe a cancer patient who is rapidly declining and failing multiple treatment attempts keeps getting multiple CTs and PET scans as well as multiple IR interventions and / or radiation therapies. If your person has had a heart attack and it’s a complex heart attack, and the interventional cardiologist has to keep them under the fluoroscope, which is like an x-ray movie that they use while trying to put stents in their coronary arteries.
Maybe they’re doing that for minutes, but it’s in order to save their life. That person probably won’t mind losing a large patch of chest hair, right? With a little bit of education, you can see that the chances of getting a radiation related injury when undergoing a medical imaging procedure like x-ray or CT scan are essentially zero under normal conditions. In the rare instances where a patient starts to receive amounts of medical radiation capable of a radiation injury, it is only ever done for a very good reason when the risk of injury is strongly outweighed by the benefit of imaging or other intervention. I hope this helps to shed some light on the fear and mystery surrounding medical radiation exposure. In general, it’s not nearly as dangerous or detrimental as the average patient I’ve talked to about it believes that it is.
