Absorbed Dose to Water
Realization of the unit of absorbed dose to water
The absorbed dose is the quotient of the mean energy imparted by ionizing radiation to a material and the mass of the material. In case the material is water, the term is “absorbed dose to water”. The unit of measurement of absorbed dose is the Gray (Gy). (1 Gy = 1 J/kg)
The realization of the unit of the absorbed dose to water DW is carried out by BEV in two steps: The unit of the absorbed dose to graphite is realized by a graphite calorimeter as primary standard. The conversion of the absorbed dose to graphite to the absorbed dose to water is carried out by two different methods (a theoretical and an experimental one).
The absorbed dose to water is the measurand for therapy dosimeters.
Verification of therapy dosimeters
Therapy dosimeters are subject to mandatory verification in Austria. The first verification of a new measuring instrument is called initial verification. The verification of a not verified measuring instrument is called new verification. The verification during the period of validity of the verification is called subsequent verification.
Therapy dosimeters may be placed on the market or put into service for the first time only according to the regulations of the law on medical devices. The CE marking according to this law is equivalent to the initial verification.
The new and subsequent verification of therapy dosimeters are subject to national regulations and are carried out by accredited verification bodies.
The interval of subsequent verification for therapy dosimeters is 2 years.