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  • 1 Institute of Nuclear Technology and Radiation Protection, NCSR “Demokritos”, Aghia Paraskevi, Attikis, 15310 Greece
  • 2 Medical Physics Laboratory, Medical School, University of Ioannina, Ioannina, 45 110 Greece
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We investigated the spatial dependence of the sensitivity of nitrogen measurement with a prompt gamma neutron activation analysis (PGNAA) system for small animals and developed an analysis procedure that permits the reduction of systematic errors due to that dependence. The analysis procedure is based on neutron and photon transport calculations performed using the MCNP code in order to evaluate the sensitivity of the PGNAA facility. The system can be calibrated experimentally using a small number of phantoms of known size and composition. The calculation approach can then be used to predict responses for animal body sizes and shapes relatively to those experimentally determined and to include the effect of tissue inhomogeneities. Our calculations were verified by experimental measurements performed for a set of cylindrical inhomogeneous phantoms. The calculated to experimental ratios observed were within 6%.