Simulation Study of a High Resolution PET Detector Module with Depth of Interaction Information

Thompson, Kyle Edward
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Faculty of Graduate Studies and Research, University of Regina

This work focuses on the simulated performance of a high-resolution, depth-of-interaction (DOI) capable PET detector module with a single-ended readout. I propose the use of a monolithic scintillator up to several centimetres thick directly coupled to a 2D array of Silicon Photomultipliers. High resolution of reconstructed energy and 3D position of gamma rays interacting with the detector is achieved through the implementation of Maximum Likelihood Estimation (MLE) of said parameters. A notable difference in the implementation of MLE described herein is the direct estimation of the interacting gamma-ray energy. Additionally, a performance evaluation of two prominent event windowing techniques used in PET -- energy windowing and likelihood windowing -- is presented.

The proposed design and reconstruction algorithms have been validated using Geant4-based Monte Carlo simulations. Two different versions of the detector module -- one with an absorptive coating and the other with a reflective coating – were simulated, and a comparison of reconstruction performance is presented. It is found that the module with the reflective wrapping significantly out-performs the module with the absorptive wrapping in terms of the resolution of the reconstructed 3D position and energy of incoming gamma rays due to the increased amount of scintillation light detected with the reflective configuration. The reflective configuration simulated herein achieves an average 3D position resolution of ~ 1 mm, and an average energy resolution of ~ 11 %.

Based on an analysis of the simulated detector module performance versus scintillator thickness presented in this thesis, a scintillator thickness of 1.5 cm was chosen for future prototypes in order to strike a balance between position and energy resolution performance and detection efficiency. A small bore PET system employing this configuration of module will have volumetric resolution of reconstructed images in the sub-millimeter range, energy resolution of ~ 11 % and sensitivity of ~ 28 %.

A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Science in Physics, University of Regina. xii, 103 p.