UBC Theses and Dissertations
Development and validation of the quantitation of S.P.E.C.T. images for clinical applications Dixon, Katherine Louise
The obtaining of accurate quantitative information is essential to the future development of nuclear medicine. This thesis uses three clinical quantitative measurements: tumour dosimetry, myocardial wall thickness, and myocardial infarct size, to show that accurate quantitative diagnostic information can be extracted from nuclear medicine studies. Additionally, this thesis determines the importance of comprehensive corrections for photon attenuation, photon scatter and distance-dependent resolution loss in the production of this quantitative information. Dosimetry and myocardial perfusion data sets were acquired from computer simulations, physical phantoms and clinical patients. Each data set was reconstructed using (1) filtered back-projection (FBP), (2) ordered-subset expectation maximization (OSEM), (3) OSEM plus attenuation correction (AC), (4) OSEM plus detector response compensation (DRC), (5) OSEM plus AC and DRC, and (6) OSEM plus AC, DRC and scatter correction (SC). iQuant software was developed to affectively evaluate the biodistribution of activity required for dosimetry calculations, myocardial wall thickness and myocardial infarct size. iQuant measures infarct size with exceptional accuracy and reliability, and its advantages over other myocardial quantitation software include its 3-dimensional analysis that does not require the creation of polar maps or normal heart databases. The inclusion of AC in the reconstruction process significantly improved the accuracy of tumour activity estimates (by 30%) and myocardial infarct sizes in both the inferior and septal myocardial walls (by 1% of the total myocardial volume). The inclusion of DRC produced a myocardial wall thickness closer to the truth (by 25%). AC and DRC are therefore essential for an accurate diagnostic assessment of myocardial perfusion studies and dosimetry. The addition of SC improved the accuracy of tumour activity estimates, particularly in regions with non-uniform attenuation properties (to within 5% of the truth for tumors greater than 5ml). it also provided myocardial wall thickness values closer to the truth than any other technique (10% closer than OSEM+DRC), and improved the accuracy and precision of myocardial infarct sizes (to within 0.75% of the total myocardial volume). The application of SC in addition to AC and DRC is therefore indicated in research studies involving dosimetry or myocardial infarct size, where the accuracy of measurement is essential.
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