What is effective dose, and how is it calculated?
Effective dose is defined as “the mean absorbed dose from a uniform whole-body irradiation that results in the same total radiation detriment as from the nonuniform, partial-body irradiation in question”  . It was introduced in 1975 to provide a means by which the “detriment,” or underlying risk of biological injury, could be normalized for exposures of different parts of the body to different types of radiation at different levels. Numerically speaking, effective dose is the weighted sum of the absorbed organ and tissue doses; the weighting factors are designed to convey the radiation detriment associated with each organ or tissue. However, organ and tissue doses are impossible to measure and can only be calculated with a large number of assumptions. The concept of effective dose was originally intended for use at the population level for the general population or the population of radiation workers. It was never intended to describe the radiation exposure to an individual patient, even though conversion factors exist for calculating effective dose estimates from DLP. Effective dose continues to be used as a surrogate for radiation exposure in the absence of more appropriate and accurate metrics. Effective dose is not actual patient dose and should not be reported as such or used to determine if a patient has had “too much” radiation that would preclude another imaging examination.