CT Dosimetry - Terms
Effective Dose or ED
When a large group of people receive whole body exposure to radiation, epidemiologists study the long term effects of that on the group. One method of analysis is to determine the radiation dose to each radiation sensitive tissue or organ, and the number of detriments each tissue or organ experiences through the course of time. That information is used to create a dose model. In one dose model, the data is used to determine atissue weighting factor that gives the relative radiation sensitivity of each tissue or organ. When someone receives a non-uniform exposure, the relative risk of that can be calculated by determining the dose to each tissue or organ in the dose model and multiplying this against that tissue or organ's tissue weighting factor (derived from epidemiological data) and the sum of this for all tissues and organs in the body gives the effective dose for the exam. The effective dose should be comparable in risk to an equivalent whole body exposure. ED is also known as effective dose equivalent.
Chest X-ray Equivalency
compares the exam with the number of chest x-rays it would take to arrive at an equivalent effective dose.
BERT (Background Equivalent Radiation Time)
compares radiation dose from medical x-ray with the number of days it takes us to be exposed to the same amount of radiation due to background radiation in our environment.