Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 115-121). Also available in electronic format on the Internet.

Thesis (M.Sc.) - Carleton University, 2008. / Includes bibliographical references (p. 94-99). Also available in electronic format on the Internet.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 26, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Ping Yu. Vita. Includes bibliographical references.

Habil.-Schr. Technische Hochschule Aachen, 1997.

The fluorinase enzyme, originally isolated from Streptomyces cattleya, has the unique ability to generate a C–F bond from aqueous fluoride ion and S-adenosylmethionine, making the fluorinase an attractive biochemical tool for radiolabelling biomolecules with fluorine-18 for application to positron emission tomography (PET). The inherent substrate specificity of the enzyme is, however, limiting, as only small modifications to the natural nucleoside substrate were known to be tolerated. This thesis describes an exploration and expansion of the substrate scope of the fluorinase enzyme, and its application to radiolabelling biomolecules for PET. The design and synthesis of a novel acetylene bearing substrate for the fluorinase, 5'-chloro-5'-deoxy-2-ethynyladenosine (ClDEA) is described. ClDEA proved an excellent substrate for the fluorinase, and the kinetics of the transformation and binding affinities of the new substrate and product were investigated. The fluorinated acetylenic product was demonstrated to undergo a copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction with an azide bearing RGD peptide, and this methodology was investigated for the synthesis of a novel fluorine-18-bearing prosthetic group for the synthesis of a radiolabelled RGD peptide, which was assessed in vivo in a rat. After the demonstration that the fluorinase can be used for “last step” radiolabelling of bioactive peptides, the synthesis of dimeric and tetrameric RGD-bearing substrates for the fluorinase was investigated. These large constructs underwent efficient enzymatic fluorination, and the fluorinated products showed increased binding affinity to their targets, compared to monomeric analogues. The challenges encountered during radiolabelling of these multimers with fluorine-18 using the fluorinase are discussed. A difluoromethyl-bearing nucleoside substrate (F₂DA) was synthesised as a potential substrate in the reverse direction for the fluorinase, to further probe the substrate specificity if the fluorinase. Upon incubation with the enzyme, F₂DA did not appear to undergo reaction, despite the demonstration that F₂DA binds to the enzyme. Finally, the optimisation of a fluorinase-based protocol for the synthesis of the PET radiotracer [¹⁸F]fluoroacetate is described. The enzymatic method proved unsuitable for a small animal study due to contamination of the final product, and a chemical method was investigated and optimised as an alternative approach. [¹⁸F]Fluoroacetate synthesised using the developed chemical method was employed in an in vivo evaluation of acetyl CoA synthetase (ACSS2) activity in healthy and tumour-bearing mouse models, in an study to assess the activity of ACSS2 in breast and colon cancer models in mice.

This thesis focuses on the development of a novel nucleophilic ¹⁸F-fluorination of (hetero)arenes and of a rapid screening experiment to facilitate the application of this reaction to complex heterocyclic targets of medicinal importance. <strong>Chapter 1</strong> introduces the use of molecules labelled with fluorine-18 as tracers in positron emission tomography and reviews methods for the preparation of [¹⁸F]fluoroarenes published prior to the start of the work in this thesis. <strong>Chapter 2</strong> describes the development of a novel method for the preparation of electronically-diverse [¹⁸F]fluoroarenes from aryl boronic esters and [¹⁸F]fluoride, mediated by a copper complex. Application of this ¹⁸F-fluorodeboronation to electron-rich radiotracers is demonstrated. Methods for the preparation of [¹⁸F]fluoroarenes published after the start of the work in this thesis are reviewed. <strong>Chapter 3</strong> outlines a rapid screening experiment for assessing the tolerance of the ¹⁸F-fluorodeboronation towards heterocycles, and the use of this method to guide the retro-radiosynthesis of heterocycle-rich, medicinally relevant molecules. <strong>Chapter 4</strong> contains synthetic procedures and characterisation data for compounds in Chapters 2 and 3.

M.Phil. (Energy Studies) / This dissertation details the radiation shielding analysis and optimization performed to design a shield for the mineral-PET (Positron Emission Tomography) facility. PET is a nuclear imaging technique currently used in diagnostic medicine. The technique is based on the detection of 511 keV coincident and co-linear photons produced from the annihilation of a positron (produced by a positron emitter) and a nearby electron. The technique is now being considered for the detection of diamonds in Kimberlite rock, in which mineral-PET technology aims to improve diamond mining through the early detection of diamond bearing rocks. High energy photons are produced via Bremsstrahlung (which occurs when electrons from an accelerator, impinge on a high density target)...

This thesis reports observations of kink and tearing modes in the High Beta Tokamak - ExtendedPulse (HBT-EP) experiment. When unstable, these modes could limit the operation of tokamaks used for fusion power by terminating the plasma discharge and causing rapid loss of plasma energy. The aim of this work is to characterize the sudden transition after a sawtooth crash of coupled 2/1-3/1 tearing-kink modes into a sustained and disruptive 2/1 tearing mode. The following diagnostic techniques are used. Kink and tearing modes in HBT-EP distort the plasma edge, measured by a large array of Mirnov sensors, and perturb the interior of the plasma, observed routinely with Extreme Ultraviolet (EUV) detector arrays. Two arrays, with different transmission filters, are located with tangential views to estimate the time evolution of the plasma temperature profile. Four EUV arrays, with 16 detectors each, are positioned with different poloidal views for poloidal Extreme Ultraviolet (pEUV) emission tomography. The 2D emissive structures producing the pEUV signals are reconstructed with tomographic inversion using a pixel basis and fixed weighting smoothness regularization. Spatial and temporal correlations across these independent diagnostics are used to measure the evolution and structure of coupled modes using a technique called multidiagostic Singular Value Decomposition (mdSVD). In mdSVD, orthogonal modes are identified within any fixed time window with their unique spatial and temporal characteristics. The technique uncovers: coherent behavior of coupled (𝑚/𝑛) = (2/1) and (3/1) tearing-kink modes and rapid changes in plasma structure associated with sawtooth crashes which trigger disruptive and nondisruptive tearing modes. HBT-EP’s unique radially movable wall is found to significantly influence sawtooth triggering of disruptive tearing modes. The onset of sawtooth-triggered modes depends both on the plasma-wall separation, or wall coupling, and on the value of edge safety factor qₐ. We confirm that the condition for sawtooth triggering of disruptive (𝑚/𝑛) = (2/1) tearing modes does not correspond to the mode’s single-helicity stability condition Δ′₂/₁. We identify a dependency of the sawtooth period 𝝉_𝑠𝑡 on the wall position and qa as a candidate to explain the onset of the saturated tearing mode. This thesis motivates future efforts to model the influence of a nearby resistive wall on sawtooth triggering of tearing modes.

I NTRODUÇÃO: Na cintilografia de perfusão do miocárdio, contrariamente ao desenvolvimento tecnológico ao longo do tempo, manteve-se desde o princípio a mesma forma, por vezes desconfortável ou mesmo inviável, de posicionamento na aquisição das imagens: decúbito dorsal com os braços elevados. OBJETIVOS: O objetivo da pesquisa foi o de avaliar se na aquisição da cintilografia de perfusão do miocárdio o posicionamento com os membros superiores abaixados(T) apresenta os mesmos resultados que os obtidos com os membros superiores elevados(C), tanto em termos de alterações perfusionais como em relação aos parâmetros funcionais. . MÉTODOS: Foram estudados 120 pacientes, 83 (69%) do sexo masculino, com idade 59,4 ± 11,4 anos e peso 72,8 ± 14 kg. Foi realizada primeiramente a aquisição C e na seqüência a aquisição T, utilizando protocolo de um dia de repouso-estresse (dose 370 MBq e 1110 MBq de sestamibi-99mTc), com estresse sincronizado ao eletrocardiograma (gated- SPECT). Três modelos distintos de equipamentos de dois detectores foram utilizados no estudo. Os estudos foram processados usando reconstrução iterativa (OSEM). Na interpretação foi utilizado o modelo de segmentação miocárdica de 17 segmentos, pontuados de 0 a 4 (normal a ausente) segundo o grau de captação. Baseada na análise de um observador dentre um grupo de sete, foi realizada a comparação da totalidade dos segmentos e também segmento a segmento das aquisições C e T nas etapas de estresse e de repouso. Foi comparada também a somatória das pontuações das etapas de estresse(SSS) e repouso(SRS). Os pacientes foram divididos segundo dois critérios: primeiramente, normais (SSS=0) e anormais (SSS>1) e posteriormente, em de baixo risco (SSS3) e de maior risco (SSS>3) A comparação dos parâmetros funcionais de fração de ejeção do ventrículo esquerdo (FEVE), volume diastólico final (VDF), volume sistólico final(VSF), somatória dos escores de motilidade (SMS) e somatória dos escores de espessamento (STS) foi baseada nos valores obtidos de modo automático utilizando o programa computacional Quantitative Gated SPECT. RESULTADOS: No modo C, 23,3% dos pts referiram algum grau de dor no membro superior ou no ombro e no modo T 5 %. Houve diferença significativa (p<0,05) na comparação dos 2040 segmentos miocárdicos entre C e T, ao estresse e ao repouso. Nos 63 pts normais não houve diferença significativa dos escores entre C e T ao estresse e ao repouso. O mesmo foi observado nos 80 pts de baixo risco. Nos 57 pts anormais houve boa correlação entre os valores de SSS (Rho=0,93, p=0,0001) e SRS (Rho=0,93, p=0,0001), mas com valores não equivalentes (p<0,05), sendo a média dos valores de SSS (9,28±8,10) e SRS (7,89±7,34) da aquisição T inferiores à média dos valores de SSS (10,07±7,71) e SRS (8,46±7,35) encontrada na aquisição C. Nos 40 pts de risco, houve boa correlação dos valores de SSS(Rho=0,95, p=0,0001) e SRS(Rho=0,96 p=0,0001), porém a média dos valores de SSS (12,53±7,54) e SRS (10,60±7,08) da aquisição T foi significantemente (p<0,05) inferior à média dos valores de SSS (13,43±6,81) e SRS(11,33±6,97) encontrados na aquisição C. Os parâmetros funcionais apresentaram boa correlação entre C e T, exceto o VDF(p=0,0001). CONCLUSÕES: Os modos C e T apresentam boa correlação dos parâmetros funcionais, exceto o VDF. Embora a aquisição T tenha sido um pouco mais confortável e tenha demonstrado boa correlação nos achados perfusionais, em pts anormais e de maior risco há tendência à subestimação dos defeitos perfusionais. Considerando a importância da medida precisa da intensidade e extensão das alterações perfusionais em termos de avaliação prognostica e decisão terapêutica, a aquisição com membro superior abaixado deve ser evitada. Em situações onde a aquisição com membros superiores abaixados é a única alternativa, os resultados da cintilografia devem ser interpretados com cuidado, especialmente em pacientes anormais e de maior risco, onde as alterações podem estar subestimadas / Contrary to the advances in imaging technology for nuclear cardiology applications, we keep using the same often uncomfortable and sometimes impracticable patient position- supine with arms raised above the head (C). We tested another position modality: supine with arms down at the sides of the trunk (T). The purpose of this study was to verify if the functional and perfusion results of the acquisition T are equivalent to those of the acquisition mode C. We studied 120 patients (pts), 83 (69%) male, aged 59.4±11.4 years and weighting 72.8±14 kg. We performed a one-day protocol (rest gated/stress), using 99mTc-sestamibi (370 MBq and 1110 MBq). In both times (rest and stress), we first performed acquisition in C and in sequence the acquisition in T. The studies were performed in three types of dual detector SPECT systems. T mode was executed successfully in all pts. Images were processed by the iterative reconstruction method (OSEM). Each study was independently interpreted by one nuclear medicine specialist from a group of seven physicians using the 17-segment model. The segments were scored using a 5-point model ranging from 0 (normal uptake) to 4 (uptake absent). The total score of the left ventricle at stress is referred to as the summed stress score (SSS) and at rest as the summed rest score (SRS). The patients were categorized in subgroups by two criteria: normal (SSS=0) or abnormal (SSS1) and low risk (SSS3) or risk (SSS>3). The values of the functional parameters of left ventricular ejection fraction (LVEF), end diastolic volume (EDV), end systolic volume (ESV), stress motion score (SMS) and stress thickening score (STS) for both C and T were automatically obtained by the quantitative gated SPECT (QGS) program and results were compared. Shoulder and/or back pain occurred in 23.3% of C patients and in 5% of T patients. There was no agreement between the 2040 segmental scores of both rest and stress in C and T modes (p<0.05). No significant differences between C and T were found for SSS and SRS in the 63 normal individuals nor in the 80 low risk patients. Good correlation between C and T was found for SSS (Rho=0.95, p=0.0001) and SRS (Rho=0.96 p=0.0001) in the 57 abnormal pts, but the mean SSS (9.28±8.10) and SRS (7.89±7.34) values of T were significantly lower (p<0.05) than the mean for SSS (10.07±7,71) and SRS(8.46±7,35) of C mode. Similar patterns were observed in the 40 risk pts; good correlation was found between C and T modes for SSS (Rho=0.95, p=0.0001) and SRS (Rho=0.96 p=0.0001), but the mean SSS (12.53±7.54) and SRS (10.60±7.08) values of T were significantly lower (p<0.05) than SSS (13.43±6.81) and SRS (11.33±6.97) of C mode. Good correlation between C and T was found for all functional parameters, except for EDV (p=0.0001). Although T mode appears to be more comfortable and presented a good correlation between SSS and SRS values, in abnormal and risk pts, the extent and severity of defects can be underestimated. Considering the important therapeutic and prognostic implications of an accurate perfusion measurement, the cardiac SPECT acquisition with the arms in down position should be avoided. When arms-down acquisition is the only alternative, scintigraphy results must be carefully interpreted, especially in abnormal scans whereas the amount of perfusion abnormalities can be underestimated.

I NTRODUÇÃO: Na cintilografia de perfusão do miocárdio, contrariamente ao desenvolvimento tecnológico ao longo do tempo, manteve-se desde o princípio a mesma forma, por vezes desconfortável ou mesmo inviável, de posicionamento na aquisição das imagens: decúbito dorsal com os braços elevados. OBJETIVOS: O objetivo da pesquisa foi o de avaliar se na aquisição da cintilografia de perfusão do miocárdio o posicionamento com os membros superiores abaixados(T) apresenta os mesmos resultados que os obtidos com os membros superiores elevados(C), tanto em termos de alterações perfusionais como em relação aos parâmetros funcionais. . MÉTODOS: Foram estudados 120 pacientes, 83 (69%) do sexo masculino, com idade 59,4 ± 11,4 anos e peso 72,8 ± 14 kg. Foi realizada primeiramente a aquisição C e na seqüência a aquisição T, utilizando protocolo de um dia de repouso-estresse (dose 370 MBq e 1110 MBq de sestamibi-99mTc), com estresse sincronizado ao eletrocardiograma (gated- SPECT). Três modelos distintos de equipamentos de dois detectores foram utilizados no estudo. Os estudos foram processados usando reconstrução iterativa (OSEM). Na interpretação foi utilizado o modelo de segmentação miocárdica de 17 segmentos, pontuados de 0 a 4 (normal a ausente) segundo o grau de captação. Baseada na análise de um observador dentre um grupo de sete, foi realizada a comparação da totalidade dos segmentos e também segmento a segmento das aquisições C e T nas etapas de estresse e de repouso. Foi comparada também a somatória das pontuações das etapas de estresse(SSS) e repouso(SRS). Os pacientes foram divididos segundo dois critérios: primeiramente, normais (SSS=0) e anormais (SSS>1) e posteriormente, em de baixo risco (SSS3) e de maior risco (SSS>3) A comparação dos parâmetros funcionais de fração de ejeção do ventrículo esquerdo (FEVE), volume diastólico final (VDF), volume sistólico final(VSF), somatória dos escores de motilidade (SMS) e somatória dos escores de espessamento (STS) foi baseada nos valores obtidos de modo automático utilizando o programa computacional Quantitative Gated SPECT. RESULTADOS: No modo C, 23,3% dos pts referiram algum grau de dor no membro superior ou no ombro e no modo T 5 %. Houve diferença significativa (p<0,05) na comparação dos 2040 segmentos miocárdicos entre C e T, ao estresse e ao repouso. Nos 63 pts normais não houve diferença significativa dos escores entre C e T ao estresse e ao repouso. O mesmo foi observado nos 80 pts de baixo risco. Nos 57 pts anormais houve boa correlação entre os valores de SSS (Rho=0,93, p=0,0001) e SRS (Rho=0,93, p=0,0001), mas com valores não equivalentes (p<0,05), sendo a média dos valores de SSS (9,28±8,10) e SRS (7,89±7,34) da aquisição T inferiores à média dos valores de SSS (10,07±7,71) e SRS (8,46±7,35) encontrada na aquisição C. Nos 40 pts de risco, houve boa correlação dos valores de SSS(Rho=0,95, p=0,0001) e SRS(Rho=0,96 p=0,0001), porém a média dos valores de SSS (12,53±7,54) e SRS (10,60±7,08) da aquisição T foi significantemente (p<0,05) inferior à média dos valores de SSS (13,43±6,81) e SRS(11,33±6,97) encontrados na aquisição C. Os parâmetros funcionais apresentaram boa correlação entre C e T, exceto o VDF(p=0,0001). CONCLUSÕES: Os modos C e T apresentam boa correlação dos parâmetros funcionais, exceto o VDF. Embora a aquisição T tenha sido um pouco mais confortável e tenha demonstrado boa correlação nos achados perfusionais, em pts anormais e de maior risco há tendência à subestimação dos defeitos perfusionais. Considerando a importância da medida precisa da intensidade e extensão das alterações perfusionais em termos de avaliação prognostica e decisão terapêutica, a aquisição com membro superior abaixado deve ser evitada. Em situações onde a aquisição com membros superiores abaixados é a única alternativa, os resultados da cintilografia devem ser interpretados com cuidado, especialmente em pacientes anormais e de maior risco, onde as alterações podem estar subestimadas / Contrary to the advances in imaging technology for nuclear cardiology applications, we keep using the same often uncomfortable and sometimes impracticable patient position- supine with arms raised above the head (C). We tested another position modality: supine with arms down at the sides of the trunk (T). The purpose of this study was to verify if the functional and perfusion results of the acquisition T are equivalent to those of the acquisition mode C. We studied 120 patients (pts), 83 (69%) male, aged 59.4±11.4 years and weighting 72.8±14 kg. We performed a one-day protocol (rest gated/stress), using 99mTc-sestamibi (370 MBq and 1110 MBq). In both times (rest and stress), we first performed acquisition in C and in sequence the acquisition in T. The studies were performed in three types of dual detector SPECT systems. T mode was executed successfully in all pts. Images were processed by the iterative reconstruction method (OSEM). Each study was independently interpreted by one nuclear medicine specialist from a group of seven physicians using the 17-segment model. The segments were scored using a 5-point model ranging from 0 (normal uptake) to 4 (uptake absent). The total score of the left ventricle at stress is referred to as the summed stress score (SSS) and at rest as the summed rest score (SRS). The patients were categorized in subgroups by two criteria: normal (SSS=0) or abnormal (SSS1) and low risk (SSS3) or risk (SSS>3). The values of the functional parameters of left ventricular ejection fraction (LVEF), end diastolic volume (EDV), end systolic volume (ESV), stress motion score (SMS) and stress thickening score (STS) for both C and T were automatically obtained by the quantitative gated SPECT (QGS) program and results were compared. Shoulder and/or back pain occurred in 23.3% of C patients and in 5% of T patients. There was no agreement between the 2040 segmental scores of both rest and stress in C and T modes (p<0.05). No significant differences between C and T were found for SSS and SRS in the 63 normal individuals nor in the 80 low risk patients. Good correlation between C and T was found for SSS (Rho=0.95, p=0.0001) and SRS (Rho=0.96 p=0.0001) in the 57 abnormal pts, but the mean SSS (9.28±8.10) and SRS (7.89±7.34) values of T were significantly lower (p<0.05) than the mean for SSS (10.07±7,71) and SRS(8.46±7,35) of C mode. Similar patterns were observed in the 40 risk pts; good correlation was found between C and T modes for SSS (Rho=0.95, p=0.0001) and SRS (Rho=0.96 p=0.0001), but the mean SSS (12.53±7.54) and SRS (10.60±7.08) values of T were significantly lower (p<0.05) than SSS (13.43±6.81) and SRS (11.33±6.97) of C mode. Good correlation between C and T was found for all functional parameters, except for EDV (p=0.0001). Although T mode appears to be more comfortable and presented a good correlation between SSS and SRS values, in abnormal and risk pts, the extent and severity of defects can be underestimated. Considering the important therapeutic and prognostic implications of an accurate perfusion measurement, the cardiac SPECT acquisition with the arms in down position should be avoided. When arms-down acquisition is the only alternative, scintigraphy results must be carefully interpreted, especially in abnormal scans whereas the amount of perfusion abnormalities can be underestimated.