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Title: Theory of longitudinal emission computed tomography and the practical application to cardiac imaging
Author: Mills, John Alexander
ISNI:       0000 0001 3409 1156
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1986
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Longitudinal Emission Computed Tomography (LECT) is a radioisotope imaging technique which has found particular use in cardiac investigations. However, its clinical use has revealed Imaging problems which show themselves as reconstruction artefacts or false defects. The basis for the imaging problem of LECT is established theoretically using a simple analysis which shows that the reconstruction will predict that activity lies outside the object volume. The volume of the reconstruction lying outside the object volume is considered as an error volume, by using simple, unmodified back projection. This is the first time such a concept has been developed and it is used to calculate an error volume index (EVI). This index is shown to be useful for assessing and comparing LECT systems. It is used to examine the reduction of the error volume by modifications to LECT systems. Thallium-201 perfusion imaging for ischaemic heart disease and infarct detection using a rotating slant hole (RSH) LECT system is compared to conventional planar imaging and X-ray contrast arteriography. RSHLECT is shown not to improve the diagnostic performance of planar imaging. The tomograms suffer from artefacts which appear as defects in the myocardium. Although the presence of these artefacts have been demonstrated by other workers this study shows that they have a significant affect on the diagnostic performance of the technique. A computer simulation and experimental studies using a simulated cardiac chamber are used to study the source of the problem. The origin of the artefacts is demonstrated for the first time. The problem of the error volume in reconstructing the cardiac blood pool is considered. Three techniques to correct the reconstruction volume are examined and one is recommended which will reduce the error volume. Computer simulation and experimental studies with a simulated blood pool are used to examine this problem. It is shown that it is not possible to correct the reconstruction volume when an iterative least squares reconstruction technique is used together with the assumption of a uniform activity distribution; this implies the need for an alternative predictive function. The Inability to correct the reconstruction volume for a simple uniform activity distribution show that, for Thallium-201 perfusion Imaging where the distribution is non-uniform, there is a need for an imaging system modified to reduce the error volume. This work concerning a blood pool LECT reconstruction and correction of the reconstruction volume is original. For the clinical trial of Thallium-201 perfusion imaging and the experimental work with a simulated cardiac chamber, a rotating slant hole LECT system was used. The physical performance of this system was measured and compared with other LECT systems. In doing this a relationship between plane density in the reconstruction and inter-planar resolution is demonstrated for the first time.
Supervisor: Not available Sponsor: Coventry Health Authority
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics ; RC Internal medicine