AbstractsAstronomy & Space Science

Studies in single photon emission imaging

by Jeremy Michael Brown

Institution: Monash University
Department: School of Physics and Astronomy
Year: 2015
Keywords: Single photon emission imaging; Compton scattering; Hybrid emission imaging; Compton imaging; Geant4; Monte Carlo radiation transport modelling
Record ID: 1067974
Full text PDF: http://arrow.monash.edu.au/hdl/1959.1/1158737


This thesis presents a number of studies into Single Photon Emission Imaging (SPEI) that can be grouped into three main sections: Monte Carlo Radiation Transport Modelling, Development of a Hybrid SPEI System and Fundamental Study of Advanced Compton Imaging. The first section of this thesis, Monte Carlo Radiation Transport Modelling, presents an overview of the Monte Carlo radiation transport modelling toolkit Geant4 and a newly derived low energy Compton scattering model, the Monash University Compton scattering model. This Compton scattering model was developed to address the limitation present in the majority of Monte Carlo bound atomic electron Compton scattering models: incorrect determination of the ejected direction of Compton electrons due to the non-zero momentum of the bound atomic electron. A theoretical foundation that ensures the conservation of energy and momentum in the relativistic impulse approximation was utilised to develop energy and directional algorithms for both the scattered photon and ejected Compton electron from first principles. Assessment of this model was undertaken in two steps: comparison with respect to two Compton scattering classes of Geant4 adapted from Ribberfors' work, and experimental comparison with respect to Compton electron kinetic energy spectra obtained from the Compton scattering of 662 keV photons off the K-shell of gold. It was shown that this new Compton scattering model was a viable replacement for the majority of computational models that have been adapted from Ribberfors' work. Additionally, this model was shown to be able to reproduce the Compton scattering triply differential cross-section Compton electron kinetic energy spectra of 662 keV photons K-shell scattering off of gold to within experimental uncertainty. The second section of this thesis, Development of a Hybrid SPEI System, presents the development of a novel hybrid collimated SPEI system: the Pixelated Emission Detector for RadiOisotopes (PEDRO). The PEDRO is a conceptual proof of principle hybrid SPEI system that was designed to explore and quantify the relationship between spatial resolution and sensitivity, inherent in SPEI, over the energy range of 30 keV to 511 keV. This system was originally intended to be constructed from a Compton camera stack located behind a coded mask composed of a mix of pinholes, slats and/or open areas. A total of three studies are presented in this section that outline the development of: 1) a Geant4 application to be used for optimisation of PEDRO with respect to a robust metric, 2) an automated routine for the optimisation of large-area slits in the outer regions of a coded mask for PEDRO which has a central region allocated for pinholes, and 3) a novel experimentally motivated image deblurring technique for multi-plane Gamma cameras such as PEDRO. These three studies illustrated two main points: 1) it may indeed be possible to overcome the trade-off between spatial resolution and sensitivity inherent in SPEI through hybrid Compton-mechanical collimation, and 2) the…