Evaluation of response of whole-body counter using the EGS4 code

Responses of a whole-body counter to distribution of ingested 137Cs within the body were evaluated using Monte Carlo simulation. The uncertainties in evaluation of 137Cs body burdens due to counting efficiencies of the whole-body counter were estimated. It was found from calculation that counting efficiencies of the whole-body counter are largely dependent on the 137Cs distribution within the body, and 137Cs body burdens would be underestimated by a factor of 3 in the worst case. To testify a calibration method for the whole-body counter using Monte Carlo simulation, counting efficiencies for simple-geometric-form models and phantoms were obtained by simulation and actual measurements. The calculations by Monte Carlo simulation are in good agreement with the measurements. (author)