Dosimetry Quantities and their units By Mr Hamzah

Dosimetry Quantities and their units By : Mr. Hamzah Hassnein

Radioactive Decay: is the process in which an unstable atomic nucleus spontaneously losses energy by emitting particles and radiation.

- Activity is measured in Becquerel (Bq) (one decay per second) “Disintegration”. - In the old system of units source activity was expressed in Curie (Ci) 10 1 Ci=3. 7*10 Bq

It’s the exposure of the dry air at standard temperature and pressure (STP) to X-ray or low gamma ray.

-The SI unit of exposure is coulomb per Kg dry air, (c/Kg). - The old unit is the Roentgen ( R ) It is a unit to measurement Ionizing radiation. -4 1 R=2. 58*10 c/Kg

The absorbed dose is the amount of energy deposited from any type of ionizing radiation , into a unit mass of any matter.

- The old unit of the absorbed dose is rad. RAD: “ Radiation Absorbed Dose” 1 RAD=100 erg/1 gram - The SI system of the absorbed dose is the GRAY (Gy). 1 Gy=1 J/ 1 Kg 1 Gy=100 rad

It is the absorbed dose averaged over a tissue or organ T due to radiation of type R and weighted by the radiation factor Wr.

It is the sum of the tissue equivalent doses each multiplied by the appropriate tissue weighting factor.

- The REM “ Roentgen Equivalent Man” is the unit of the equivalent dose in the old system where the absorbed dose is measured in (rad). - The (Seivert) “Sv” is the unit in the SI system where the absorbed dose is measured in (Gray) ”Gy”