A computed tomography (CT) scan is a medical imaging method that uses many X-ray measurements taken from different angles to produce tomographic (cross-sectional) images of specific areas of the part of the body that was scanned. Since CT scans are created by several X-ray measurements, it exposes the body to ionized radiation. It is estimated that the extra risk of a person exposed to a typical CT procedure of developing a fatal cancer is about 1 in 2000. People who have CT procedures performed as children may have a higher risk since children have a longer life expectancy than adults and are more sensitive to radiation.
According to the Food and Drug Administration (FDA), the radiation dose from CT procedures varies from patient to patient and depending on the type of procedure, the size of the body part to be examined, and the type of CT equipment. Screening procedures adjust the radiation dose to lesser levels than those usually used for diagnostic CT procedures.
Radiation dose (sometimes referred as effective dose) is measured in milisieverts (mSv). Abdominal CT (8 to 10 mSv) and Coronary CT angiogram (16 mSv) are the CT procedures with the highest radiation dose, and head CT (2 mSv) has the lowest.