RadiologyInfo, Radiation Doses in CT & X-Ray, March 20, 2019
When radiation passes through the body, some of it gets absorbed. The x-rays that are not absorbed are used to create the image. The amount that is absorbed contributes to the patient’s radiation dose. The radiation that passes through the body does not. The scientific unit of measurement for whole body radiation dose, called “effective dose,” is the millisievert (mSv). Other radiation dose measurement units include rad, rem, roentgen, sievert, and gray.
Doctors use “effective dose” when they talk about the risk of radiation to the entire body. Risk refers to possible side effects, such as the chance of developing a cancer later in life. Effective dose takes into account how sensitive different tissues are to radiation. If you have an x-ray exam that includes tissues or organs that are more sensitive to radiation, your effective dose will be higher. Effective dose allows your doctor to evaluate your risk and compare it to common, everyday sources of exposure, such as natural background radiation.
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