Monte Carlo modelling of a voxel head phantom for in vivo measurement of bone-seeker nuclides.

Whole-body counters (WBCs) are used for the assessment of the internal contamination of actinides in the human body. WBCs require adequate calibration procedures that rely on the use of suitable calibration phantoms. A previous study carried out at the ENEA-Radiation Protection Institute was aimed at designing a head calibration phantom in which a heterogeneous distribution of 241Am point sources could satisfactorily approximate an assumed homogeneous contamination throughout the head bones. Suitable correction factors for the WBC detection efficiencies were evaluated with Monte Carlo. The present paper summarises the main aspects and implications of an advanced modelling technique based on a VOXEL approach. The methodology could be extended to other bone-seeker radionuclides.