An approach for the efficiency calibration of whole body counters

An approach is outlined for the evaluation of the efficiency of whole body counters using experimental data for a point source and Monte Carlo simulat ion of the efficiency of photon arrival at a large volume NaI(TI) detector. The approach was applied to the measurement of an experimental whole body phantom. The experimental and the predicted efficiencies were found to diff er from -2.5% to 8.4%. An investigation of the geometry dependence of the c ounting efficiency was made using theoretical dimensions of phantoms of dif ferent sizes. The relative geometry dependence was found to be less than 9% for the "Reference Man" and "Reference 10-y-old Child" phantoms.