A ferrous sulphate gel dosimetry system for NCT studies : response to slow neutron

Neutron capture therapy (NCT) is based on the localised release of energy in tumours from appropriate nuclei bombarded by slow neutrons. It is proposed to measure the spatial dose distribution for some selected nuclei having very large interaction cross sections with neutrons, for different concentrations and concentration gradients, for different geometries and for different neutron beams. To this purpose, it is planned to use a three-dimensional and tissue-equivalent phantom acting as a continuous dosemeter. The dosemeter is a gel solution of ferrous sulphate: the concentration of ferric ions produced by irradiation and correlated to the dose is deduced from the measurement of the proton relaxation times by means of a clinical NMR imaging system. The dosemeter can be used in a mixed field of γ rays, neutrons and heavy particles. As a first step, the response of the gel system to γ rays and slow neutrons was measured.