- Used in radiation protection to describe internal and external dose measurements
- quantity used describe radiation exposure of a population or group from low doses of different sources of ionizing radiation
- Person-sievert is the radiation unit for this quantity.
Collective EfD( effective dose )
Useful for measuring dose for Nuclear Medicine Technologists.
- Annual Limits: 50mSv (0.05 Sv) for exposed personal
- 1 mSv (0.001 Sv) for the general public
total effective dose equivalent (TEDE)
EqD= DxWr
- measuring biologic effects
- used for radiation protection:when a person received exposure from various types of ionizing radiation
Equivalent dose
Dimensionless factor used for radiation protection purposes to account for differences in ionizing radiation
- place risks associated with biological effects on a common scale
- determining EqD
Radiation weight factor ( Wr)
Radiation weight factor for x rays and gamma rays photons and electrons
1
Radiation weight factor for protons
2
Radiation weight factor for alpha particles
20
Overall risk of exposure to human from ionizing
- incorporates both effect of the radiation used and the variability in radio sensitivity in organs
- D x Wr x Wt
Effective dose - EFD
Value that denotes the percentage of the summed stochastic ( cancer plus genetic ) risk stemming from irradiation of tissue ( T) to all inclusive risk
- accounts for the risk to the entire organism
Tissue weight factor ( Wt)
(damage to cells of the human body
Somatic Damage
Coulombs per
kilogram (C/kg)
> Gray (Gy)
• Centigray (cGy)
• Milligray (mGy)
• Sievert (Sv)
> Millisievert (mSV)
Radiation units
Exposure
> Air kerma
> Absorbed dose (D)
> Equivalent dose (EqD)
> Effective Dose (EfD)
Radiation quantities
- the total electric charge of one sign,
either all plus or all minus, per unit mass that x-ray and gamma ray photons with energies up to
3 million electron volts (MeV) generated in dry air at standard temperature (22°C) and pressure (760 mm Hg or 1 atmosphere at sea level).
Exposure
- The basic unit of electric charge
> It is equal to the “amount of electrical charge moving
past a point in a conductor in 1 second when an electric current amounting to 1 ampere is used.
Coulomb ( C/kg)
- The SI unit of electric current
• SI unit of measure for the radiation quantity, exposure, is equal to an electric charge of 1 produced in a kilogram of dry air by ionizing
radiation.
Ampere
-SI quantity used to express how energy is transferred from a beam of radiation to a material
- calculation of radiation intensity in air
- Quantity that can be used to express ×-ray tube output
and inputs to image receptors
Air Kerma
• Expressed in metric units of joule per
kilogram (J/kg)
- si unit : gray ( gy)
Coventional unit: RAD
Air kerma
- sum total of air kerma over the exposed area of the patient’s surface, or the amount of radiant energy that has been thrust into a portion of the patients body surface
- units of mGy-cm
Dose Area Product (DAP)
- quantity is the amount of energy per unit mass absorbed by an irradiated object.
- D (absorbed in tissue; not
expression of biologic effect) - conventional unit: RAD
- si unit: gray ( gy)
Absorb dose
EqD (D x WR) (biologic effect)
- Conventional units: REM
- si unit: Sv ( sievert )
Equivalent dose (EqD)
D (D xWR × W,) (biologic effect)
- conventional unit: REM
Si unit : sievert (sv)
Effective dose EfD
