Absorbed dose
Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation. It is equal to the energy deposited per unit mass of a medium, and so has the unit joules (J) per kilogram (kg), with the adopted name of gray (Gy) where 1 Gy = 1 J.kg-1.
The absorbed dose is not a good indicator of the likely biological effect. 1 Gy of alpha radiation would be much more biologically damaging than 1 Gy of photon radiation for example. Appropriate weighting factors can be applied reflecting the different relative biological effects to find the equivalent dose.
The risk of stochastic effects due to radiation exposure for the population can be quantified using the effective dose, which is a weighted average of the equivalent dose to each organ depending upon its radiosensitivity.
Other related values include:
- absorbed dose rate (Gy.s-1): amount of radiation delivered over a time period
- rad: the international unit of absorbed dose pre-1980 where 1 Gy = 100 rad
- kerma (Gy): kinetic energy released per unit mass
Related Radiopaedia articles
Imaging physics
- imaging physics
- imaging in practice
- imaging technology
-
x-ray physics
- ionizing radiation
- interaction with matter
- x-ray spectrum
- radiation units
- effective dose
- exposure
- legacy units
- radiation safety
- radiation damage (biomolecular)
- radiation damage (skin injury)
- stochastic effect
- CT physics
-
MRI physics
- B0
- chemical shift
- dependence of magnetization (proton density, field strength and temperature)
- echo time
- eddy currents
- electromagnetic induction
- Ernst angle
- flip angle
- Larmor frequency
- magnetic dipole magnetic field gradient
- magnetic susceptibility
- magnetism
- molecular tumbling rate effects on T1 and T2
- net magnetization vector (NMV)
- relaxation
- repetition time
- resonance and radiofrequency (RF)
- units of magnetism
- ultrasound physics
- nuclear medicine physics