P197] Measurement of neutron-induced radioactivity in animal tissue

Abstract

Purpose The basis of neutron radiotherapy is to induce the decay of 10B to 7Li, an alpha particle and gamma ray. Emitted particles deposit dose in surrounding cancer cells what lead to their death. Though neutron beam can also lead to production other radioactive isotopes with lives longer than 11B∗. The main goal of out project is to measure the induced radioactivity in human tissues after the irradiation and identify the produced radioisotopes and estimate the dose from those nuclides. The secondary aim of this work is the validation of simulation calculations in comparison with experimental results. Methods In order to estimate which radioisotopes are produced during the irradiation the GATE/Geant4 Monte Carlo code was used. For tissue materials, the pig liver and beef bone were chosen. The irradiation will be performed using PuBe neutron source and neutron beam which is available in BNCT treatment room at National Center for Nuclear Research, Otwock. The samples will be irradiated with high dose in order to create a large number of short-lived isotopes or with fractionated dose in order to express the radiation of long-lived isotopes. For gamma spectroscopy measurements the HPGe or LaBr3 detectors will be used. Results The Monte Carlo calculations show the most intense, for gamma spectroscopy, radioisotopes produced within the liver sample by neutron irradiation are 24Na, 28Al and 31Si. In case of bone sample neutron irradiation mostly produced gamma radioisotopes are 28Al, 31Si and 42K. As a result of high occupancy of neutron sources the experimental data will be obtained in April. Conclusions Based on theoretical calculations, one can conclude that a lot of radioisotopes are created in human tissues. For example, the 24Na can wash out from the irradiated volume and circulate through patients body with blood. That is why the dose from induced radioactivity cannot be omitted in calculations of received total dose. In addition, some of the mentioned above nuclides (high cross-section for production) can be useful for off-line measurements of fast neutron fluence.