Table 1.
Overview of different radiation dose units.17
| Radiation dose | Unit | Symbol | Calculation | What does it mean? |
|---|---|---|---|---|
| Absorbed dose | Gray (Gy) (J•kg−1) | D | D = | Represents the amount of radiation energy that is absorbed per unit of mass of a substance.17,18 ( |
| Equivalent dose | Sievert (Sv) (J•kg−1) | HT | HT = | Takes into account the type of radiation as well as its effectiveness. When exposed to multiple radiation types, the equivalent doses of each radiation type must be calculated and then summated.18,19 |
| Effective dose | Sievert (Sv) (J•kg−1) | E | E = | Takes into account the equivalent doses in all specified tissues and organs of the body, which is multiplied by a tissue-specific weighting factor. Represents the health risk, i.e. the probability of cancer induction and/or genetic effects.19 |
| Dose-length product | DLP | Gy•cm | CTDIvol ((1/3) x radiationcenter + (2/3) x radiationperiphery)/pitch)x scan length | Used to calculate the total absorbed dose of radiation a patient is exposed to in a computed tomography examination and is therefore directly related to the stochastic risk.20 Note: DLP is not equal to the effective dose. |
| Dose area product | DAP | Gy·cm² | D x Scan area | Dose Area Product (DAP) is a measure of the total amount of radiation delivered to a person, with the area of the irradiated tissue taken into account. |
ε ®, mean energy; D_(T,R), D in a target tissue (T) due to radiation type ‘R’; ω_R, radiation weighting factor; ω_T, tissue weighting factor; m_T, mass of volume of interest; rem, remainder tissues.