Abstract
Single photon emission computed tomography (SPECT) is the subject whereby we wish to measure and display the in-vivo concentration of single photon emission sources within a thin transverse slice of the medium in which the radioactive source is embedded while still retaining the simple, atraumatic, non-invasive nature of the radionuclide investigation. The ultimate goal of SPECT systems is the determination of absolute regional radionuclide concentrations as a function of time. However achievement of accurate quantitative results in SPECT is impeded by geometric variation in counter efficiency, self-absorption inside the matrix containing the distributed gamma-source and by the intrinsically low detection efficiency of the photon detector when good spatial resolution is required. This Thesis describes studies of various methods for overcoming these difficulties and reducing the error contributed by them. This work requires the transmission scanner to be modified to perform in emission mode and is described in this Thesis. The question of geometric variation is approached by the mathematical and geometrical techniques. This study deals with the attenuation problem by considering a few methods theoretically and uses a constant attenuation coefficient procedure experimentally. The subject of detection efficiency leads to the investigation of the plastic bar scintillator and the proportional counter as position sensitive detectors with the aim of using such detector to optimise collection efficiency. Use of the proportional counter requires some investigations on its lifetime and are reported in this Thesis.