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Information for Patients

Radiation is a natural part of our lives. Visible light is the most common type of radiation that we use for seeing things every day.There are also forms of invisible radiation in our environment that come to us from outer space and from the small amount of natural radioactive substances that are in the earth, the air we breathe, the water we drink, the food we eat, as well as in our own bodies. This is called natural background radiation.

A limitation of visible light is that it does not penetrate into the human body and let us see what’s there.

However, other forms of radiation can pass through the body and be used to produce images of the interior parts of the body.

The most commonly used are X rays. When a beam of X rays is passed through the body it produces shadow-type images that doctors can use to see possible signs of diseases or injury that might be there. Gamma radiation, which is emitted by radioactive materials, is another form of radiation used in medicine. This makes it possible to make an image of the diseased area using equipment known as a gamma camera. Certain radioactive materials, such as iodine-131, are selected because when given to a patient they will collect or concentrate in specific tissues and in some cases in cancer.

All forms of radiation, including visible light and the invisible forms: X rays, gamma radiation, etc., can produce some effects on the tissues that absorb the radiation energy. The usual effects of visible light, especially sunlight, are to the skin. Because X rays and gamma radiation penetrate into the body, their effects can be on other organs and tissues inside the body. The effects of radiation when high doses are used can be utilized for treating cancer i.e. in radiotherapy.

The amount of X ray or gamma radiation received by a patient during an examination or treatment procedure is known as the radiation dose. It is measured in the unit sievert (Sv). In diagnostic procedures the dose is a small fraction of a sievert and is expressed in millisieverts (mSv).

As a reference, natural background radiation, to which we all are exposed, provides each of us with a dose (averaged globally) of 2.4 millisievert (mSv) per year according to United Nations Scientific Committee on the Effects of Atomic Radiation.

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