The existing intermediate image nuclear spectrometer has been modified to count either positrons or negatrons by the addition of a helical baffle. Design considerations of the helical baffle and source requirements for the present investigation have been discussed. An investigation of the positron spectrum of ¹⁵²Eu has been completed. Kurie-plot analysis of the data has confirmed the presence of two primary positron groups with end point energies 713.5 ± 2KeV and 471 ± 5KeV, and intensities (1.0 ± 0.1) x 10⁻⁴ per decay and (0.6 ± 0.2) x 10⁻⁴ per decay respectively. It has been possible to assign error limits to these intensities for the first time. The presence of an internal pair formation positron distribution has also been confirmed. The intensity of the pair formation positrons was deduced from the data for the first time as (0.4 ± 0.05) x 10⁻⁴ per decay, in good agreement with theoretical predictions. The results are in good agreement with previous investigations, excepting the intensity of the 713.5KeV primary positron group. The disparity may be caused by effects due to source and backing thickness in previous work. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Image noise in Positron Emission Tomography (PET) is the result of statistical fluctuation in projection data. The variance properties of images obtained with the UBC/TRIUMF PETT VI tomograph are studied by analytical methods, computer simulations, and phantom experiments. The PETT VI image reconstruction algorithm is described and analyzed for noise propagation properties. Procedures for estimating both point-wise (pixel) and region of interest (ROI) variances are developed: these include the effects of corrections for non-uniform sampling, detector efficiency variation, object self-attenuation and random coincidences. The analytical expression for image-plane variance is used in computer simulations to isolate the effects of the various data corrections: It is shown that the image precision is degraded due to non-uniform sampling of the projections. The RMS noise is found to be increased by 9% due to the wobble motion employed in PETT VI. Analytical predictions for both pixel and ROI variances are verified with phantom experiments. The average error between measured and predicted ROI variances due to noise in emission data for a set of seven regions placed on a 20 cm cylindrical phantom is 9.5%. Images showing variance distributions due to noise in emission data and due to noise in transmission data are produced from human subject brain scan data collected by the UBC/TRIUMF PET group. The maximum ratio of image variance due to noise in transmission data to that due to noise in emission data is calculated as 2.6 for a typical FDG study, and 0.082 for a typical fluorodopa study. Total RMS noise varies between 0.4% and 11.6% for a typical set of ROI's placed on mid-brain slices reconstructed from these data sets. Procedures are suggested for improving the statistical accuracy of quantitative PET measurements. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

published_or_final_version / Physics / Master / Master of Philosophy

Orientador: Sadhan K. Adhikari / Doutor

Thesis (M. Phil.)--University of Hong Kong, 1985.

No description available.

No description available.

No description available.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 4, 2009) Includes bibliographical references (p. 78-82).