It involves evaluation of bioassay data, evaluation of the intake, distribution, retention, and elimination of radionuclides, and evaluation of various absorbed doses and dose equivalent quantities.
Internal dosimetry is inherently indirect in nature.
It is not possible to determine the exact organ absorbed dose, dose equivalent, or effective dose equivalent in a living human being resulting from an intake of radioactive materials. Internal dose is usually a derived or inferred quantity, obtained by evaluation of indirect measurements and computational models. Direct measurements of internalized photon-emitting radionuclides in organs also may be difficult because of attenuation and scattering by overlying tissues. 10 CFR 835 contains requirements affecting internal dosimetry programs throughout DOE and contractor facilities. The quantity committed effective dose equivalent is the mechanism by which internal doses are added to external doses on the basis of equal risk.