Attenuation calculation of low energy photons: Application to in vivo spectrometry using multi-diode systems

The importance of spectrometry of low energy photons in in vivo burden assessment is increasing with the use of new radionuclides. This paper describes and applies ATT3D, a three-dimensional program for the calculation of γ ray attenuation in order to compare the capabilities of two types of room temperature diodes (silicon and CdZnTe) for in vivo counting. The different characteristics of these diodes are examined in the framework of lung counting. It is shown that the use of these detectors can improve accuracy by allowing longer counting times and by ensuring a correct positioning of the detectors on the organs. The localisation of the nuclides in the body and the follow-up of tracers at very low levels of intake are shown to be possible for different radionuclides.