Traditionally, in Positron emission tomography (PET) scanners, the detection of simultaneous gamma ray emissions resulting from positron annihilations has been achieved using Photo-multiplier tubes (PMTs) optically coupled to dense scintillators. The recent development of the Avalanche photo-diode (APD) offers the possibility of replacing the PMT, however, such a step is not without its problems. The introduction of APD technology into scintillation detector design offers: more compact scanner design; the possibility of a multi-layer scintillation detector, with an inherent reduction in parallax errors; improved spatial, energy and timing resolutions; increased count-rate; and a higher packaging fraction with correspondingly increased scanner sensitivity. A well-designed APD-based scintillation detector can only be realised if all stages of the detection process are fully understood. The work described in this thesis shows that it is possible to model the complex processes of gamma ray interaction, scintillation, and light transport, using Monte Carlo methods; and to model the photo-detector output signal and its processing using both simplified circuit analysis and a standard circuit simulation software. These models were then combined to form a powerful modelling tool for APD-based scintillation detector design; this modelling tool was then used to design a multi-layer scintillation detector, which was built and tested. The performance of the detector closely matched the simulations. The measured performance parameters of the laboratory prototype were: intrinsic spatial resolution 2.0 mm (FWHM at 0.511 MeV), energy resolution 15% (FWHM at 0.511 MeV) and timing resolution of 2.2ns (FWHM), with a reconstructed image resolution of 1.6 mm (FWHM). THE prototype performance figures match any known commercially available Small animal PET scanner at this time.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:440056 |
| Date | January 2006 |
| Creators | Clowes, Peter |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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