A calibration method for whole-body counters, using Monte Carlo simulation

A Monte Carlo simulation code was developed to estimate the counting efficiencies in whole-body counting for various body sizes. The code consists of mathematical models and parameters which are categorised into three groups: a geometrical model for phantoms and detectors, a photon transport model, and a detection system model. Photon histories were simulated with these models. The counting efficiencies for five Cs-137 block phantoms of different sizes were calculated by the code and compared with those measured with a whole-body counter at NIRS (Japan). The phantoms corresponded to a newborn, a 5 month old, a 6 year old, an 11 year old and an adult. The differences between the measured and calculated values were within 6%. For the adult phantom, the difference was 0.5%. The results suggest that the Monte Carlo simulation code can be used to estimate the counting efficiencies for various body sizes.