There has been a lot of coverage in the media lately about radiation exposure from medical imaging and it’s important to sort out fact from fiction.People are rightly concerned whether radiation from mammograms, bone density tests, computed tomography scans and the likes, would increase their risk of developing cancer.For most people, there is very little risk from routine X-ray imaging but many experts are concerned about an explosion in the use of higher radiation dose tests, such as CT and nuclear imaging. As an example, it is estimated that in 2015, about 90 million CT scans and nuclear tests were performed in the United States, compared with just three million in 1980. There are good reasons for this trend. CT scanning and nuclear imaging has revolutionised medical diagnosis and treatment, almost eliminating the need for once-common invasive and potentially risky procedures. The benefits of these tests, when they’re appropriate, far outweigh any radiation-associated cancer risks, and the risk from a single CT scan or a nuclear imaging test is small. However, in light of the 30-fold increase in the use of these tests, experts wonder if we are courting future public health problems.What is exposure to ionising radiation?The radiation you get from X-ray, CT and nuclear imaging is called ionising radiation. It is made of high-energy wavelengths or particles that penetrate tissue to reveal the body’s internal organs. Ionising radiation can damage DNA and, although body cells repair most of the damage, they sometimes do the job imperfectly, leaving small areas of “misrepair”. The result is DNA changes called “mutations” that may, years down the road, contribute to cancer. We’re exposed to small doses of ionising radiation from natural sources all the time, in particular, cosmic radiation from the sun, and radon, a radioactive gas that comes from the natural breakdown of uranium in soil, rock, water, and building materials. How much of this so-called background radiation one is exposed to depends on many factors, including altitude and home ventilation, but the average is 3 millisieverts per year (a millisievert is a measure of radiation exposure).While exposure to above ionising radiation from natural sources has not changed, Americans’ total per capita radiation exposure has doubled, and experts believe the main reason is increased use of medical imaging. The proportion of total radiation exposure that comes from medical sources has grown from 15 per cent in the early 1980s to 60 per cent today. Most of the increased exposure is due to CT scanning and nuclear imaging, which require larger radiation doses than traditional X-rays. A chest X-ray, for example, delivers 0.1 mSv, while a CT of the abdomen and pelvis delivers 14 mSv, or 140 times as much. And that’s not counting the very common follow-up CT scans.What to do?Unless you were exposed to high doses of radiation during cancer treatment in youth, any increase in your risk for cancer due to medical radiation appears to be slight. But we do not really know for sure, since the effects of radiation damage typically take many years to appear, and the increase in high-dose imaging has occurred only since 1980.So until we know more, you will want to keep your exposure to medical radiation as low as possible by the following ways:Discuss any high-dose diagnostic imaging with your clinician. If you need a CT or nuclear scan to diagnose a medical condition, the benefits usually outweigh the risks. Still, if your doctor has ordered a CT, it is reasonable to ask what difference the result will make in how your condition is managed; for example, will it save you an invasive procedure?Consider a lower-dose radiation or an alternative test by asking if another technique would work, such as a lower-dose X-ray or a test that uses no radiation, like an ultrasound (which uses sound waves) or MRI (which relies on magnetic energy). Neither testing modality appears to harm DNA or increase cancer risk.Consider less-frequent testing. If you are getting regular CT scans for a chronic condition, ask if it is possible to increase the time between scans.Don’t seek out scans. Don’t ask for a test just because you want to feel assured that you have had a “thorough check-up”. CT scans and nuclear tests rarely produce important findings in people without relevant symptoms. Plus, there is a chance the scan might find something incidental, spurring additional CT scans or X-rays that add to your total radiation exposure.•Joe Yammine is a cardiologist at Bermuda Hospitals Board. He trained at the State University of New York, Brown University and Brigham and Women’s Hospital. He holds five American Board certifications. He was in academic practice between 2007 and 2014, when he joined BHB. During his career in the US, he was awarded multiple teaching and patients’ care recognition awards. The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician. Never delay seeking medical advice, disregard medical advice or discontinue treatment because of any information in this article.[naviga:ul][naviga:li][/naviga:li][/naviga:ul]