Kwantifisering van radionukliedverspreiding deur planare beelding met 'n sintillasiekamera - Marais, Johan (University of the Free State, 2000)
In this study attenuation and scatter correction techniques in planar imaging were investigated as well as the practical implementation of these techniques in clinical studies. The attenuation correction technique that was investigated was the geometrical mean method where an iterative method was used to determine the attenuation coefficient. This adaptation made the attenuation correction method independent of depth. In this study the depth dependence of the geometrical mean method was solved which is an important contribution. The three-energy window scatter correction technique was investigated with Monte Carlo methods for planar imaging. These simulations showed that the scatter correction method under corrects by approximately 10%. The scatter correction technique cannot be performed on it's own but must be used in conjunction with the attenuation correction method. The overall effect of the quantitation (attenuation and scatter correction) was determined in two ways. First a known amount of activity was imaged. Then the correction was applied to the images. Subsequently the corrected activity obtained from the latter images was compared to the known value. The calculated activity was 98,6 % of the known activity value. Secondly clinical studies were performed where the bladder activity was quantitated in vivo and correlated to the in vitro measured value. In this case the correlation coefficient was 0,996. The quantitation technique was applied to the clinical determination of the glomerular filtration rate. The quantitation technique was compared to the routine method that requires handling of urine. The correlation coefficient was 0.96 and the linear regression line had a slope ofO.91 and a y-axis intercept of4.8l. The quantitation of the bladder activity leads to a simplification of the clinical study procedure since the physical handling of urine can be eliminated. The accuracy of this method depends on the conversion factor that compensates for the difference between the sensitivity of the camera and the well counter. This factor must be checked on a regular basis to ensure the accuracy of this method. The bladder as source organ was used in this study. The bladder is a relative isolated organ and therefor the influence of radioactive uptake in other organs is relatively small. If these quantitations are applied to organs that are not isolated, i.e. the heart where the liver can influence it, this problem has to be address. In this project a quantitative planar imaging technique was investigated that corrects for attenuation and scatter and thereby facilitates depth independent corrections.

Attenuasie- en verstrooiingskorreksie tegnieke vir planare radionuklied beelding is in hierdie studie ondersoek asook die praktiese toepassing hiervan in sekere kliniese studies. Die attenuasie korreksietegniek wat ondersoek is, is die geometriese gemiddelde metode met die aanpassing dat 'n iteratiewe metode gebruik is om die attenuasie koëffisiënte te bepaal. Hierdie aanpassing maak die attenuasie korreksie diepte onafhanklik. Aangesien die diepte afhanklikheid van die geometriese gemiddelde metode nog altyd 'n probleem was, sal hierdie metode 'n wesentlike bydrae lewer om die probleem uit te skakel. Die drie venster verstrooiingskorreksie tegniek is met behulp van Monte Carlo simulasies ge-evalueer vir planare beelding. Die simulasies dui daarop dat hierdie tegniek 'n onder-korreksie van ongeveer 10% uitvoer. Die verstrooiingskorreksie tegniek word egter nie op sy eie uitgevoer nie maar is noodsaaklik vir die akkurate toepassing van die attenuasie korreksie tegniek. Die effek van die kwantifisering (attenuasie- en verstrooiingskorreksie) is bepaal in twee gevalle. Die eerste was deur 'n bekende hoeveelheid aktiwiteit te beeld, die korreksies daarop uit te voer en dit te vergelyk met die bekende aktiwiteit. Die gemete aktiwiteit was 96,8% van die bekende waarde. Die tweede geval was in die kliniese studies waar die blaasaktiwiteit gekwantifiseer is maar ook in vitro gemeet is. In hierdie geval was die korrelasie koëffisiënt 0.996. Soos reeds genoem is hierdie kwantifiseringstegniek in kliniese studies uitgevoer, nl. die bepaling van die glomerulêre tempo. Die kwantifiseringstegniek is vergelyk met die roetine tegniek wat die hantering van uriene behels. Die korrelasie koëffisiënt was 0.96 en die regressie lyn helling 0.91 met 'n y-as afsnit van 4.81. Die kwantifisering van die blaas aktiwiteit veroorsaak 'n vereenvoudiging van die studie deurdat die fisiese hantering van uriene uitgeskakel word. Die akkuraatheid van hieride kwantifisering is afhanklik van die omskakelingsfaktor wat gebruik word om te kompenseer vir die verskil tussen die sensitiwiteit van die kamera en die putteller. Hierdie verband moet op 'n gereelde grondslag getoets word om te verseker dat die gekwantifiseerde waarde van die TOA akkuraat bereken word. In hierdie studie is kwantifiseringstegnieke toegepas op studies wat die blaas as bron orgaan gebruik. Die blaas is redelik geïsoleer van ander organe en dus sal die bydrae van hierdie organe tot die tellings in die blaas klein wees. Indien die kwantifisering op organe toegepas word waar 'n ander orgaan 'n bydrae kan maak, bv. die lewer tot die hart, moet hierdie probleem ondersoek word. In hierdie projek is 'n kwantifiseringstegniek ondersoek wat gebruik kan word in planare beelding wat korrigeer vir verstrooiing en attenuasie en wat diepte onafhanklike korreksies moontlik maak.
Dissertation (M.Med.Sc. (Medical Physics))--University of the Free State, 2000
Keywords: Nuclear medicine; Urinary organs