Definition

An estimate of the overall risk of potential harm from exposure to ionizing radiation. Ionizing radiation can come from natural sources, such as radon and radiation from outer space, and from medical imaging tests, such as x-rays, CT scans, or PET scans. The effective radiation dose is calculated based on certain factors, such as the type of radiation and its likelihood to cause harm, the amount of radiation absorbed by all organs of the body, and the sensitivity of different tissues and organs to radiation. The effective radiation dose is used to compare different levels of exposure to ionizing radiation in a population. It does not predict the risk of health effects from radiation exposure in individual people. Effective radiation dose may help in understanding the risk of potential long-term health effects from radiation exposure, such as the risk of developing cancer later in life. It is used to set radiation safety standards in health care and other industries. Sievert (Sv) is the unit of measurement for effective radiation dose.