No description available.

No description available.

Geiger-mode avalanche photodiodes, or silicon photomultipliers, are promising light sensors for the next generation Positron Emission Tomography (PET) scanners. The sensor is being used in the scanner’s gamma ray detector to measure scintillation light. This thesis describes the test results of three gamma ray detectors that utilize silicon photomultipliers. The first one is a commercial detector, and the other two are custom made. The detectors are tested for their 511 keV photon energy and timing resolution, as well as their ability to measure light from small scintillator crystals. The two custom made detectors had smaller active area, but outperformed the commercial detector in energy resolution. The introduction of buffer amplifiers improved the timing resolution of one detector. All three detectors had their crystal decoding ability limited by signal multiplexing and the sensor’s dark noise. Finally, a detector design was proposed for the PET system being developed in our group.

Geiger-mode avalanche photodiodes, or silicon photomultipliers, are promising light sensors for the next generation Positron Emission Tomography (PET) scanners. The sensor is being used in the scanner’s gamma ray detector to measure scintillation light. This thesis describes the test results of three gamma ray detectors that utilize silicon photomultipliers. The first one is a commercial detector, and the other two are custom made. The detectors are tested for their 511 keV photon energy and timing resolution, as well as their ability to measure light from small scintillator crystals. The two custom made detectors had smaller active area, but outperformed the commercial detector in energy resolution. The introduction of buffer amplifiers improved the timing resolution of one detector. All three detectors had their crystal decoding ability limited by signal multiplexing and the sensor’s dark noise. Finally, a detector design was proposed for the PET system being developed in our group.

No description available.

Thesis (M.Sc.). / Written for the Medical Physics Unit. Title from title page of PDF (viewed 2008/01/15. Includes bibliographical references.

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In 3-dimensional positron emission tomography (PET), the proportion of the detected photon coincidences arising from scatter can be very high, up to 60%. A standard approach to scatter correction in 3D PET is to estimate the scattered coincidences and subtract them from the list of recorded events. More recently, novel techniques have been proposed in which the information carried by the scattered photons was extracted and directly used in the image reconstruction step. In this work, the algorithms were extended for use in non-TOF 3D PET systems and were qualitatively and quantitatively evaluated. Despite some promising initial outcomes, standard performance metrics of images reconstructed with each technique, representing the quality of images, was shown to be deteriorated under specified conditions. Further work is required to investigate potential benefits of the proposed algorithms for both ideal and clinical conditions.

Stem cell therapy is emerging as a possible method for treating many diseases and disorders, such as cardiovascular disease. In particular, stem cells may be able to revive the dead tissue caused by acute myocardial infarction (heart attack). Adipose-derived stem cells were labelled with 18F-fluorodeoxyglucose (FDG) and superparamagnetic iron oxide (SPIO) particles, for imaging with positron emission tomography (PET) and magnetic resonance imaging (MRI), respectively, and injected into several rats following induced myocardial infarction. Stem cell retention in the heart was investigated following three injection sites; two within the heart (intramyocardial and left intraventricular), and one easily accessible vein (tail vein). The PET and MR images were registered and the initial distributions analyzed using region of interest (ROI) analysis, to determine which injection method would result in the highest stem cell retention in the infarcted heart. The ROI results determined that the intramyocardial injection had the highest % injected dose (%ID) in the heart with 14 +/- 4%, followed by left intraventricular and tail vein with %IDs of 3.6 +/- 0.8% and 1.2 +/- 0.6%, respectively. The results indicate that stem cell delivery via intramyocardial injection should be utilized for optimal retention in the heart.

Stem cell therapy is emerging as a possible method for treating many diseases and disorders, such as cardiovascular disease. In particular, stem cells may be able to revive the dead tissue caused by acute myocardial infarction (heart attack). Adipose-derived stem cells were labelled with 18F-fluorodeoxyglucose (FDG) and superparamagnetic iron oxide (SPIO) particles, for imaging with positron emission tomography (PET) and magnetic resonance imaging (MRI), respectively, and injected into several rats following induced myocardial infarction. Stem cell retention in the heart was investigated following three injection sites; two within the heart (intramyocardial and left intraventricular), and one easily accessible vein (tail vein). The PET and MR images were registered and the initial distributions analyzed using region of interest (ROI) analysis, to determine which injection method would result in the highest stem cell retention in the infarcted heart. The ROI results determined that the intramyocardial injection had the highest % injected dose (%ID) in the heart with 14 +/- 4%, followed by left intraventricular and tail vein with %IDs of 3.6 +/- 0.8% and 1.2 +/- 0.6%, respectively. The results indicate that stem cell delivery via intramyocardial injection should be utilized for optimal retention in the heart.