BACKGROUND Aortic stenosis is a common and potentially fatal condition in which fibro-calcific changes within the valve leaflets lead to the obstruction of blood flow. Severe symptomatic stenosis is an indication for aortic valve replacement and timely referral is essential to prevent adverse clinical events. Calcification is believed to represent the central process driving disease progression. 18F-Fluoride positron emission tomography computed tomography (PET-CT) and CT aortic valve calcium scoring (CT-AVC) quantify calcification activity and burden respectively. The overarching aim of this thesis was to evaluate the applications of these techniques to the study and management of aortic stenosis. METHODS AND RESULTS REPRODUCIBILITY The scan-rescan reproducibility of 18F-fluoride PET-CT and CT-AVC were investigated in 15 patients with mild, moderate and severe aortic stenosis who underwent repeated 18F-fluoride PET-CT scans 3.9±3.3 weeks apart. Modified techniques enhanced image quality and facilitated clear localization of calcification activity. Percentage error was reduced from ±63% to ±10% (tissue-to-background ratio most-diseased segment (MDS) mean of 1.55, bias -0.05, limits of agreement - 0·20 to +0·11). Excellent scan-rescan reproducibility was also observed for CT-AVC scoring (mean of differences 2% [limits of agreement, 16 to -12%]). AORTIC VALVE CALCIUM SCORE: SINGLE CENTRE STUDY Sex-specific CT-AVC thresholds (2065 in men and 1271 in women) have been proposed as a flow-independent technique for diagnosing severe aortic stenosis. In a prospective cohort study, the impact of CT-AVC scores upon echocardiographic measures of severity, disease progression and aortic valve replacement (AVR)/death were examined. Volunteers (20 controls, 20 with aortic sclerosis, 25 with mild, 33 with moderate and 23 with severe aortic stenosis) underwent CT-AVC and echocardiography at baseline and again at either 1 or 2-year time-points. Women required less calcification than men for the same degree of stenosis (p < 0.001). Baseline CT-AVC measurements appeared to provide the best prediction of subsequent disease progression. After adjustment for age, sex, peak aortic jet velocity (Vmax) ≥ 4m/s and aortic valve area (AVA) < 1 cm2, the published CT-AVC thresholds were the only independent predictor of AVR/death (hazard ratio = 6.39, 95% confidence intervals, 2.90-14.05, p < 0.001). AORTIC VALVE CALCIUM SCORE: MULTICENTRE STUDY CT-AVC thresholds were next examined in an international multicenter registry incorporating a wide range of patient populations, scanner vendors and analysis platforms. Eight centres contributed data from 918 patients (age 77±10, 60% male, Vmax 3.88±0.90 m/s) who had undergone ECG-gated CT within 3 months of echocardiography. Of these 708 (77%) had concordant echocardiographic assessments, in whom our own optimum sex-specific CT-AVC thresholds (women 1377, men 2062 AU) were nearly identical to those previously published. These thresholds provided excellent discrimination for severe stenosis (c-statistic: women 0.92, men 0.88) and independently predicted AVR and death after adjustment for age, sex, Vmax ≥4 m/s and AVA < 1 cm2 (hazards ratio, 3.02 [95% confidence intervals, 1.83-4.99], p < 0.001). In patients with discordant echocardiographic assessments (n=210), CT-AVC thresholds predicted an adverse prognosis. BICUSPID AORTIC VALVES Within the multicentre study, higher continuity-derived estimates of aortic valve area were observed in patients with bicuspid valves (n=68, 1.07±0.35 cm) compared to those with tri-leaflet valves (0.89±0.36 cm p < 0.001,). This was despite no differences in measurements of Vmax (p=0.152), or CT-AVC scores (p=0.313). The accuracy of AVA measurments in bicuspid valves was therefore tested against alternative markers of disease severity. AVA measurements in bicuspid valves demonstrated extremely weak associations with CT-AVC scores (r2=0.08, p=0.02) and failed to correlate with downstream markers of disease severity in the valve and myocardium and against clinical outcomes. AVA measurements in bicuspid patients also failed to independently predict AVR/death after adjustment for Vmax ≥4 m/s, age and gender. In this population CT-AVC thresholds (women 1377, men 2062 AU) again provided excellent discrimination for severe stenosis. CONCLUSIONS Optimised 18F-fluoride PET-CT scans quantify and localise calcification activity, consolidating its potential as a biomarker or end-point in clinical trials of novel therapies. CT calcium scoring of aortic valves is a reproducible technique, which provides diagnostic clarity in addition to powerful prediction of disease progression and adverse clinical events.

Since its inception around 1975, Positron Emission Tomography (PET) has proved to be an important tool in medical research as it allows imaging of the brain function in vivo with high sensitivity. It has been widely used in clinical dementia research with [18F]2-Fluoro-2-Deoxy-D-Glucose (FDG) and amyloid tracers as imaging biomarkers in Alzheimer's Disease (AD). The high resolution offered by modern scanner technology has the potential to provide new insight into the interaction of structural and functional changes in AD. However, the high resolution of PET is currently limited by movement and resolution (even for high resolution dedicated brain PET scanner) which results in partial volume effects, the undersampling of activity within small structures. A modified frame-by-frame (FBF) realignment algorithm has been developed that uses estimates of the centroid of activity within the brain to detect movement and subsequently reframe data to correct for intra-frame movement. The ability of the centroid to detect motion was assessed and the added benefit of reframing data for real clinical scans with patient motion was evaluated through comparison with existing FBF algorithms. Visual qualitative analysis on 6 FDG PET scans from 4 blinded observers demonstrated notable improvements (ANOVA with Tukey test, p < 0.001) and time-activity curves were found to deliver biologically more plausible activity concentrations. A new method for Partial Volume Correction (PVC) is also proposed, PARtially-Segmented Lucy-Richardson (PARSLR),that combines the strength of image based deconvolution approach of the Lucy-Richardson (LR) Iterative Deconvolution Algorithm with a partial segmentation of homogenous regions. Such an approach is of value where reliable segmentation is possible for part but not all of the image volume or sub-volume. Its superior performance with respect to region-based methods like Rousset or voxel-based methods like LR was successfully demonstrated via simulations and measured phantom data. The approach is of particular importance for studies with pathological abnormalities where complete and accurate segmentation across or with a sub-volume of the image volume is challenging and for regions of the brain containing heterogeneous structures which cannot be accurately segmented from co-registered images. The developed methods have been shown to recover radioactivity concentrations from small structures in the presence of motion and limited resolution with higher accuracy when compared to existing methods. It is expected that they will contribute significantly to future PET studies where accurate quantitation in small or atrophic brain structures is essential.

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.

The introduction of clinical Positron Emission Tomography (PET) in oncology in the 1990s has substantially changed the management of patients with cancer and become one of the diagnostic modalities with the fastest growth worldwide (Buck et al., 2010). The major hurdle delaying the proliferation of PET was partly due to its high initial investment and insufficient third-party reimbursement (Keppler & Conti, 2001). Hong Kong, a region with about half the economic strength of Germany, was able to sustain a higher ratio of PET-CT scanners than that of Germany. Through the study of the PET utilization in Hong Kong, this research is to (i) explore the factors contributing to this phenomenon; and (ii) find out if those factors are applicable to other developing countries. The key factors found contributed to a higher ratio of PET-CT scanners in Hong Kong were: 1) medical expertise in a regionally profound disease; 2) the direct payment culture which enables an economically efficient and a cost-effective operation; 3) the influx of patients from neighboring countries; and 4) the reputation of its medical services. Applying these factors, citizens in developing countries were able to have access to the latest and expensive medical technology.

Positron emission tomography (PET) is a non-invasive medical imaging technique that allows visualisation and quantification of biochemical, physiological and pharmacological processes in living subjects. This is achieved through application of radiotracers – compounds labelled with positron emitting radionuclides. Neurodegeneration is the progressive loss of neurons resulting in impairment of brain function leading to cognitive decline and can affect movement. The underlying pathology of many neurodegenerative diseases is misfolding of proteins such as α-synuclein, the key pathological hallmark of Parkinson’s disease. Also implicated in the processes of neurodegeneration is neuroinflammation, which is observed by the activation of microglia – the immune cells of the brain. Activation of microglia is associated with the upregulation of the 18 kDa mitochondrial translocator protein (TSPO). This work has involved the synthesis and characterisation of novel compounds that have the potential for being applied as radiotracers for imaging α-synuclein fibrils (project 1), or TSPO (project 2) via PET. Over the course of project 1 a library of compounds was synthesised based upon structural modifications of a lead structure identified from the literature. These compounds then underwent screening via biophysical methodologies in order to determine their affinity to α-synuclein fibrils. This stage of the work involved the development of a novel biophysical technique – microscale thermophoresis (MST). A general automated radiosynthetic method to afford the [18F]fluoro-derivatives of these compounds has also been developed, and preliminary in vitro autoradiography studies and an in vivo microPET scan has been performed. For project 2, an automated radiosynthetic method was developed to produce [18F]GE387, a lead compound identified through collaboration with GE Healthcare. This radiotracer has then been applied to preliminary in vitro autoradiography and an in vivo microPET study using rats with induced neuroinflammation alongside control rats.

abstract: The OLYMPUS experiment measured the two-photon exchange contribution to elastic electron-proton scattering, over a range of four-momentum transfer from \(0.6 < Q^2 < 2.2\) \((\mathrm{GeV/c})^2\). The motivation for the experiment stemmed from measurements of the electric-to-magnetic form factor ratio of the proton \(\mu G_E/G_M\) extracted from polarization observables in polarized electron-proton scattering. Polarized electron-proton scattering experiments have revealed a significant decrease in \(\mu G_E/G_M\) at large \(Q^2\), in contrast to previous measurements from unpolarized electron-proton scattering. The commonly accepted hypothesis is that the discrepancy in the form factor ratio is due to neglected higher-order terms in the elastic electron-proton scattering cross section, in particular the two-photon exchange amplitude. The goal of OLYMPUS was to measure the two-photon exchange contribution by measuring the positron-proton to electron-proton elastic scattering cross section ratio, \(\sigma_{e^+p}/\sigma_{e^-p}\). The two-photon exchange contribution is correlated to the deviation of the cross section ratio from unity. In 2012, the OLYMPUS experiment collected over 4 fb\(^{-1}\) of \(e^+p\) and \(e^-p\) scattering data using electron and positron beams incident on a hydrogen gas target. The scattered leptons and protons were measured exclusively with a large acceptance spectrometer. OLYMPUS observed a slight rise in \(\sigma_{e^+p}/\sigma_{e^-p}\) of at most 1-2\% over a \(Q^2\) range of \(0.6 < Q^2 < 2.2\) \((\mathrm{GeV/c})^2\). This work discusses the motivations, experiment, analysis method, and the preliminary results for the cross section ratio as measured by OLYMPUS. / Dissertation/Thesis / Doctoral Dissertation Physics 2016

L’endométriose est une pathologie chronique qui provoque des douleurs pelviennes et une infertilité. On décrit trois phénotypes d’endométriose :l’endométriose péritonéale superficielle, les kystes ovariens d’endométriose (endométriomes) et l’endométriose profonde.L’examen standard pour le diagnostic de l’endométriose est, encore aujourd’hui, la laparoscopie. Nous avons étudié, de façon prospective, l’utilité d’un examen non invasif, la tomographie par émission de positrons (PET), chez les patientes avec suspicion d’endométriose. Nous n’avons pas mis en évidence d’hyperactivité métabolique sur les images de PET pré opératoires, après injection de déoxyglucose marqué au 18F (18FDG), des lésions d’endométriose ayant été confirmées par laparoscopie. Nous avons réalisé, dans un second temps, la même étude après injection d’un analogue de la somatostatine, le DOTATATE, marqué au 68Ga, qui montre une avidité pour les récepteurs à la somatostatine (SSTR) de type 2. Dans cette dernière étude, seules les lésions d’endométriose profonde se sont révélées hyperactives sur les images pré opératoires de PET. Nous avons ensuite réalisé une étude immunohistochimique rétrospective sur différents échantillons d’endométriose superficielle, d’endométriomes et d’endométriose profonde. Nos résultats ont confirmé l’expression de SSTR de type 1 et 5 par les cellules épithéliales des trois phénotypes d’endométriose. Par contre, seules les lésions d’endométriose profonde exprimaient les SSTR de type 2.Le traitement chirurgical des endométriomes et de l’endométriose superficielle est bien codifié. Par contre, la chirurgie de l’endométriose profonde reste au cœur des débats dans la littérature. Nous avons évalué notre aptitude à appliquer les techniques de chirurgie mini-invasive aux procédures complexes telles que la résection des nodules d’endométriose profonde du septum recto-vaginal (NEPSRV). Nous avons évalué la faisabilité de la laparoscopie avec assistance robotique pour une autre procédure complexe :la dissection des ganglions para-aortiques dans le cadre des cancers du col utérin localement avancés. Nous l’avons jugée faisable et sûre pour les patientes. En l’absence de bénéfice démontré de la laparoscopie avec assistance robotique sur la laparoscopie conventionnelle pour le traitement des NEPSRV, nous avons décidé d’évaluer une nouvelle stratégie opératoire mini-invasive de résection des NEPSRV. Nous avons réalisé une analyse des 10 premières patientes opérées selon cette stratégie et avons montré une amélioration significative des symptômes et de la qualité de vie des patientes. Nous avons également étudié la morbidité post opératoire. Nous avons finalement étudié l’apport de la laparoscopie guidée par la fluorescence au traitement des NEPSRV et observé des résultats prometteurs.A l’avenir, les lésions symptomatiques d’endométriose profonde exprimant les SSTR2 pourraient être sélectionnées à l’aide d’un PET au 68Ga-DOTATATE afin d’être traitées, dans le cadre d’essais cliniques, par des analogues de la somatostatine. Ces thérapies ciblées permettaient, dans ces cas, d’éviter la chirurgie. Notre stratégie opératoire mini-invasive pourraient dès lors être appliquée aux lésions n’exprimant pas les SSTR2. / Doctorat en Sciences médicales (Médecine) / info:eu-repo/semantics/nonPublished

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