In children: Exposure levels for a child can be higher than they would be for an adult when using the same amount of radiation, so the settings on the scanner need to be adjusted to account for body size.įor children, exposure to radiation from imaging tests is of particular concern, because: The amount of radiation used in many imaging tests has gone down over time as technology has improved. Fluoroscopy, which uses x-rays to make real-time moving images, exposes people to different amounts of radiation depending on how long it is used. The exposure from a PET/CT scan (which combines a PET scan of the body with a CT scan) is typically about 23 mSv. For example, the exposure for an averaged-sized adult from a 2-view chest x-ray is about 0.1 mSv, while exposure from a CT scan of the chest is about 6 mSv. In adults: The amount of radiation a person is exposed to varies depending on the test, as well as on a person's size. (Some imaging tests, such as MRI and ultrasound, do not expose people to ionizing radiation.) Imaging testsĬertain types of imaging tests, such as x-rays, CT scans, and nuclear medicine tests (such as PET scans and bone scans) expose people to low levels of radiation to create pictures of the inside of the body. The radiation can be directed at your body from a machine, or radioactive particles can be swallowed or put into your body. X-rays, gamma rays, and other forms of ionizing radiation are used to diagnose and treat some medical conditions. Some people, such as people who work in mines, are exposed to higher radon levels at work.įor more on radon and its possible health effects, see Radon and Cancer. Radon levels can vary a great deal, depending on where you live. Radon levels are usually higher inside buildings and homes, especially in levels closer to the ground such as basements. This is an odorless, colorless gas that is formed from the breakdown of radioactive elements in the ground. The largest source of natural background radiation for most people is radon. For people who smoke, tobacco can account for a significant portion of the yearly radiation they receive. Tiny amounts of radiation may even be found in drinking water and in some plant-based foods as a result of being in contact with the soil. Some of these may end up in building materials used in houses and other structures. People are also exposed to small amounts of radiation from radioactive elements that occur naturally in rocks and soil. Airline pilots and flight attendants, who spend many hours at high elevations, are exposed to more of these rays, but it is not clear if they have an increased risk of cancer because of it. People are also exposed to higher levels of cosmic rays during airplane flights. For example, people who live in Denver, Colorado, which is at a high elevation, are exposed to slightly more cosmic rays than people living at sea level. The earth’s atmosphere blocks a portion of these rays, but some of them reach the ground.īecause the atmosphere blocks some cosmic rays, exposure is greater at higher altitudes. They come from the sun and from other stars. Cosmic raysĬosmic rays are radioactive particles that hit the earth from outer space. For most people, background radiation is most of their exposure to ionizing radiation during the year. In the United States this averages about 3 millisieverts (mSv) per year. We are all exposed to some amount of radiation just from being on this planet. Radiation is also used in small amounts in some consumer products, as well as in food irradiation. Non-medical, man-made radiation exposure can happen in certain workplaces, or in communities as a result of above ground nuclear weapons testing or nuclear accidents.Radiation therapy is used to treat some types of cancer, and it generally uses doses much higher than those used in imaging tests. Medical radiation used for imaging tests such as x-rays, CT scans, and PET scans, as well as for radiation therapy.This is the major contributor to worldwide radiation exposure. Natural background radiation from cosmic rays from outer space and from radioactive elements normally in rocks and soil.People can be exposed to x-rays and gamma rays from 3 main sources:
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