Radiation Risk of Medical Imaging for Adults and Children
April 24, 2018
What is radiation – am I exposed to background radiation each day even if I do not have an X-ray examination?
- Background radiation refers to the ionising radiation from high energy particles or rays that we are unavoidably exposed to in our daily lives, which gives each of us a small but continuous dose of ionising radiation.
- Part of background radiation is due to the electromagnetic radiation spectrum, and this includes ‘ionising’ components such as X-radiation (X-rays) and gamma rays, and ‘non-ionising’ components such as visible light and radio waves.
- X-rays, gamma rays and some other high energy particles are called ‘ionising radiation’ because they can deposit enough energy into a body tissue to change its molecules or proteins by ejecting an electron from an atom.
- The sources of ionising radiation in our environment are cosmic rays from the universe, naturally occurring radioactive substances in the food and water we eat and drink, the air we breathe, in the ground, in building materials, and so on.
- We are all weakly radioactive due to the presence of radioactive elements in our bodies (such as potassium 40 and carbon 14), and this contributes to our background radiation exposure.
- Background radiation is most commonly given in units of millisievert (mSv), which both measures and combines the radiation dose and the consequent risk delivered by an exposure.
- The amount of background radiation varies widely in different parts of the world due to the radioactivity of the soil, latitude, height above sea level and lifestyle (predominantly indoors or outdoors). In Australia, the background radiation is estimated to be 2 mSv, which is approximately equivalent to 100 single chest X-rays per year. A few parts of the world have background radiation 10 or more times greater than that generally found in Australia, but there are no studies that have shown an increased risk of cancer in populations living in areas with a higher background radiation level.
- Visible light and X-rays both travel in straight lines, and cast a shadow when they interact with a solid object.
- X-rays have more energy than visible light, and can go much deeper into and through objects. An
- X-ray beam is absorbed differently by different parts of the body, and these differences make shadows that are used to create an image or picture.
- A dense structure, such as bone, [Read more…]