Neutron Spectroscopy of Mouse Using Neutron Stimulated Emission Computed Tomography (NSECT)

Neutron spectroscopy is evolving as a non-invasive technique to measure element concentration in biological tissue. We have developed a neutron stimulated emission computed tomography (NSECT) system that maps the elemental composition of a body through a non-invasive scan. A neutron beam incident on a sample energizes the sample's atomic nuclei through inelastic scatter interactions. These energized nuclei then spontaneously return to their ground energy states emitting the extra energy as a characteristic gamma photon. An energy-sensitive gamma detector is used to detect this energy and hence identify the emitting atom. Such a technique has several applications in both humans and small animals. Here we demonstrate NSECT's feasibility in scanning small animals, and show results from a spectroscopic examination of a fixed mouse specimen. The mouse was flushed with saline and fixed using a gadolinium/formalin solution. Scanning was performed using a 5 MeV monochromatic neutron beam. Background was corrected using time-of-flight correction to reduce time-uncorrelated noise and polynomial curve-fit subtraction to remove the residual underlying background. The emitted gammas were measured using a high purity germanium (HPGe) clover detector. The resulting spectrum shows various peaks corresponding to elements expected in this specimen such as C, Ca and Gd, several other potential matches such as K and Zn, as well as some system related elements such as Fe, Al and Ge from the detector. This experiment demonstrates the ability of NSECT to obtain element information from an intact small animal specimen through a single non-invasive scan.