Kerma¶

From Wikipedia:

Kerma is the sum of the initial kinetic energies of all the charged particles liberated by uncharged ionizing radiation (i.e., indirectly ionizing radiation such as photons and neutrons) in a sample of matter, divided by the mass of the sample. It is defined by the quotient K = dEtr / dm. Kerma is different from absorbed dose, according to the energies involved. Whilst roughly equal at low energies, kerma is much higher than absorbed dose at higher energies, as some of the energy escapes from the absorbing volume in the form of bremsstrahlung X-rays or fast moving electrons.

The unit for absorbed dose is joule per kilogram, and the name given to it is the gray (Gy), where 1 Gy = 1 J/kg. The word "kerma" is an acronymn for "kinetic energy released in material", "kinetic energy released in matter", or sometimes "kinetic energy released per unit mass".

Kerma is used in Brachy Therapy, e. g. in the Brachy Treatment Summary Record Module belonging to the RT Brachy Treatment Record IOD.