A study of high-purity germanium detector arrays for the in vivo measurement of low-energy photon-emitting radionuclides

This investigation compares the response of high-purity Germanium (HpGe) detector arrays with that of dual NaI/CsI(Tl) (or Phoswich) detectors. The sources of the errors encountered during a routine measurement of internally deposited radionuclides have been identified and quantified using surrogate human structures (phantoms). Because the detection efficiency associated with an in vivo measurement is variable, a new statistical treatment of measurement errors and resultant detection criteria have been developed. The prediction of the background count rate for an in vivo measurement is a function of the photon scattering contribution provided by the subject being measured as well as the natural radionuclide background (and its variability) of the subject, the environment and all counting facility components. The scattering contribution for a human subject will vary according to body mass, body size, and body composition. Several methods for predicting the background have been developed and tested for Phoswich detector systems, however a rigorous statistical evaluation of subject specific background prediction methods used for HpGe detector arrays has never been performed