Abstract:
A new gamma imaging method, Neutron Stimulated Emission Computed Tomography (NSECT), is being developed to non-invasively and non-destructively measure and image elemental concentrations in vivo. In NSECT a beam of fast neutrons (3 - 5 MeV) bombards a target, inelastically scattering with target nuclei and exciting them. Decay from this excited state produces characteristic gamma emissions. Collecting the resulting gamma energy spectrum allows identification of elements present in the target. As these gamma rays range in energy from 0.3 - 1.5 MeV, outside the useable energy range for existing gamma cameras (0.1 - .511 MeV), a new gamma imaging method must be developed. The purpose of this dissertation is to design and develop a near-field (less then 0.5 m) high-energy (0.3 - 1.5 MeV) gamma camera to facilitate planar NSECT imaging. Modifying a design implemented in space-based imaging (focus of infinity), a prototype camera was built. Experimental testing showed that the far-field space-based assumptions were inapplicable in the near-field. A new mathematical model was developed to describe the modulation behavior in the near-field. Additionally, a Monte Carlo simulation of the camera and imaging environment was developed. These two tools were used to facilitate optimization of the camera parameters. Simulated data was then used to reconstruct images for both small animal and human fields of view. Limitations of the camera design were identified and quantified. Image analysis demonstrated that the camera has the potential to identify regions of interest in a human field of view.
