In vivo measurement of silicon in the lung and other body elements, using fast neutron inelastic scattering reactions

Silica dust inhalation by industrially exposed personnel can lead to serious lung disease, in particular silicosis. The quantitative measurement of lung silicon would be useful in the study of the silica exposure and patient symptoms relationship. Previous work has shown that the fast neutron inelastic scattering reaction 28Si(n,n'γ)28Si emitting 1779keV γ-rays is most suitable for Si measurement having a higher cross-section than other neutron-silica reactions. This technique is being developed further by the use of 5.2 MeV neutrons produced via the D-D reaction by a 2MV Van de Graaff generator accelerating deuterons on to a deuterated-Ti target. A 5MeV incident neutron energy has the advantage of corresponding to the maximum cross-section of the silicon inelastic scattering reaction and avoiding the interference from identical γ-rays from the 31P(n,α)28Al reaction which becomes significant above 5MeV. Pulsing the neutron flux also improves sensitivity by separating in time the prompt inelastic γ-rays from those emitted by slow neutron capture reactions, and measuring only during the neutron burst