Monte Carlo Simulation and Experimentation of Non-Collinear Gamma Ray Correlations as a Novel Medical Imaging Modality
Date
2023-08-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-3252-6440
Type
Thesis
Degree Level
Masters
Abstract
This thesis describes the simulation, experiment, and image analysis of a new modality of nuclear medical imaging. We propose the measurement of cascade gamma rays emitted by radioactive isotopes as an improvement over conventional Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT). This modality employs the coincidence detection of non-collinear cascade gamma rays as a means to perform event-by-event image reconstruction. This is unlike PET and SPECT, which require multiple events to locate the image point as they lack depth information of the photon trajectories. Our modality can be considered a marriage of PET and SPECT imaging as it employs coincidence techniques as in PET and collimation as in SPECT.
For the prototype experiment, we employed In-111 (2.8 days half-life). with a pair of high-intensity cascade gamma rays of energies Eγ1 = 171 keV and Eγ2 = 245 keV. We performed the measurement using the small-animal PET machine of the Institute of Physical and Chemical Research in Kobe, Japan (RIKEN-BDR). We employed Geant4 Application of Tomographic Emission (GATE) public domain software for the simulation and design of the collimators. We had them built at the Physics Machine Shop of the University of Saskatchewan.
We employed the cascade emissions of Ba-133 (half-life=10.5 years) for calibration purposes, procured the In-111 source from suppliers to RIKEN-BDR, and performed the measurements in the summer of 2022. We carried out the measurements for single and multiple point-like source arrangements. We have successfully performed the image reconstruction with the use of individual decay events in the coincidence detection.
The results are quite promising, as the image reconstruction and image resolutions are comparable to those of conventional PET images without resorting to involved statistical algorithms. The sources used were <5 MBq and measurements were taken for 2 to 15 hours. Thus, it seems this new modality offers promise of utility for molecular imaging applications. In conclusion, the thesis suggests the next steps in this direction.
Description
Keywords
medical imaging, image reconstruction, applied nuclear physics, simulation, radiation collimator
Citation
Degree
Master of Science (M.Sc.)
Department
Physics and Engineering Physics
Program
Physics