Non-invasive quantification of iron⁵⁶Fe in beef liver using neutron stimulated emission computed tomography

Neutron spectroscopy is being developed as a noninvasive tool to measure element concentration in the body at molecular levels. We are developing a neutron stimulated emission computed tomography (NSECT) system to identify element concentrations in tissue, using inelastic scattering of neutrons by target nuclei. An incident neutron scatters inelastically with an atomic nucleus to emit a gamma photon whose energy is characteristic of the scattering nucleus. This energy is detected by an energy-sensitive gamma detector to identify the target atom. Here we describe an experiment to noninvasively determine the concentration of natural iron (⁵⁶Fe) in beef liver. A 7.5 MeV neutron beam was used to scan a known quantity of solid iron and establish a ratio of iron concentration to gamma counts for the experimental setup. A known quantity of beef liver was then scanned using the same experimental setup, to obtain gamma spectra showing element concentrations in the liver. Counts from gamma peaks corresponding to excited states in iron were compared with counts from the known iron sample, to yield the iron concentration in the liver. A high purity germanium (HPGe) detector was used to measure the emitted gamma energy. Although the results obtained in this experiment are slightly higher than normal iron limits reported in various studies, they demonstrate the technique's ability to noninvasively quantify iron concentration in a biological organ.