<p>We have studied fundamental aspects of time-resolved two-photon excited fluorescence depolarisation. The thesis presents experimental as well as theoretical progress. We show that a multi-photon induced instrumental response function obtained from a suspension of gold nanoparticles is appropriate for the analysis of two-photon excited fluorescence decays obtained using time-correlated single photon counting detection. Theoretical expressions have been derived for the fluorescence anisotropy decay obtained upon two-photon excitation of various molecular systems in liquid solutions: a) an anisotropic rigid rotor that undergoes rotational diffusion in the presence of ultrafast unresolved restricted reorientations, e.g. librations. b) a molecular group covalently attached to a stationary macromolecule, and undergoing local reorientation in a uniaxial ordering potential. A new approach to the analysis of two-photon excited fluorescence depolarisation experiments was developed, which combines data obtained by using linearly and circularly polarised excitation light, in a global manner. In the analysis, knowledge about unresolved reorientations was obtained from one-photon excitation studies of the corresponding systems. By means of this procedure it has been possible to obtain quantitative information about the molecular two-photon absorption tensor for perylene and two of its derivatives. Thereby the symmetry of the final excited and intermediate vibronic states could be assigned. The analysis reveals that the two-photon transition studied with the 800 nm laser exhibits mixed character. An important finding from the experiments was that the two-photon absorption tensor appears to be solvent dependent. Furthermore, the thesis presents the first theoretical treatment of two-photon excited donor-donor energy migration in the presence of molecular reorientation and which applies the extended Förster theory. Explicit expressions for molecules that belong to the point groups D_2h, D₂ and C_2v are given. Preliminary experiments are finally also reported on a two-photon excited donor-donor energy migration system consisting of a bisanthryl-bisteroid. </p>

This dissertation attempts to understand how energy transfer in a molecular wire and a spherical organic assembly are affected by molecular structure. The molecular wire is a DNA-hybrid structure composed of a strand of thymine bases appended by a cyanine dye. Hydrogen bonded to each base is a naphthalene-derivative molecule. Using time-integrated photoluminescence and time-correlated single photon counting measurements, energy transfer from the naphthalene donors to the cyanine acceptors was confirmed, and its dependence on temperature and DNA-template length investigated. Donor-thymine bonding was disrupted at temperatures above about 25 degrees Celcius resulting in poor donor template decoration and low rates of energy transfer. Increasing numbers of donors attach to the scaffold, forming an orderly array, as the template length increases due to the stabilising effects of the donor-donor pi-stacking interactions. Conversely, modelled energy transfer rates fall as the scaffold length increases because of the longer donor-acceptor distances involved. Therefore, the energy transfer rate was greatest for a template built from 30 thymines. The spherical organic assemblies (nanoparticles) are formed by fast injection of a small volume of molecularly dissolved fluorene-derivative amphiphilic molecules into a polar solvent. The amphiphilic molecules contained either a naphthalene (donor) or a benzothiadiazole (acceptor) core. The donor-acceptor mixed nanoparticles resemble an amorphous polymer film and were modelled as such using the Foerster resonance energy transfer theory. The Foerster radii extracted from the measurements depends intricately on the donor-acceptor spectral overlap and distance. The latter effect was controlled by the stacking interactions between the molecules. Altering the morphology of the structural units is the key to optimising energy transfer in molecular structures. To achieve efficient organic molecule-based devices, the importance of this property needs to be fully appreciated and effectively exploited.

Bone is a remarkable multifunctional tissue with the ability to regenerate and remodel without generating any scar tissue. However, bone loss due to injury or diseases can be a great challenge and affect the patient significantly. Autologous bone grafting is commonly used throughout the world. Autograft both fills the void and is bone inductive, housing the particular cells that are needed for bone regeneration. However, a regenerative complement to autograft is of great interest as the use of biomaterials loaded with bioactive molecules can avoid donor site morbidity and the problem of a limited volume of material. Two such regenerative products that utilise bone morphogenetic protein (BMP)-7 and -2 have been used for more than a decade clinically. Unfortunately, several side effects have been reported, such as severe swelling due to inflammation and ectopic bone formation. Additionally, the products require open surgery and use of supra physiological doses of the BMPs due to poor localisation and retention of the growth factor. The purpose of this thesis was to harness the strong inductive capacity of the BMP-2 by optimising the carrier of this bioactive protein, thereby minimising the side effects that are associated with the clinical products and facilitating safe and localised bone regeneration. We focused on an injectable hyaluronan-based carrier developed through polymer chemistry at the University of Uppsala. The strategy was to use the body’s own regenerative pathway to stimulate and enhance bone healing in a manner similar to the natural bone-healing process. The hyaluronan-based carrier has a similar composition to the natural extracellular matrix and is degraded by resident enzymes. Earlier studies have shown improved properties when adding hydroxyapatite, a calcium phosphate that constitutes the inorganic part of the bone matrix. In Paper I, the aim was to improve the carrier by adding other forms of calcium phosphate. The results indicated that bone formation was enhanced when using nano-sized hydroxyapatite. In Paper II, we discovered the importance of crushing the material, thus enhancing permeability and enlarging the surface area. We wished to further develop the carrier system, but were lacking an animal model with relatively high throughput, facilitated access, paired data, and we were also committed to the 3Rs of refinement, reduction, and replacement. To meet these challenges, we developed and refined an animal model, and this is described in Paper III. In Paper IV, we sought to further optimise the biomaterial properties of the hydrogel through covalent bonding of bisphosphonates to the hyaluronan hydrogel. This resulted in exceptional retention of the growth factor BMP-2. In Paper V, SPECT/PET/µCT was combined as a tri-modal imaging method to allow visualisation of the biomaterial’s in situ action, in terms of drug retention, osteoblast activity and mineralisation. Finally, in Paper VI the correlation between existing in vitro results with in vivo outcomes was observed for an array of biomaterials. The study identified a surprisingly poor correlation between in vitro and in vivo assessment of biomaterials for osteogenesis.

Die hier vorgelegte Dissertation beschäftigt sich mit Untersuchungen an nanoskopischen Emittern und den Möglichkeiten, deren Fluoreszenzverhalten durch kontrollierte Ankopplung an photonische und plasmonische Strukturen zu beeinflussen. Zum einen werden mit Ytterbium- und Erbium-Ionen kodotierte NaYF4 -Nanokristalle untersucht, die hervorragende Eigenschaften bei der Umwandlung von niederenergetischen Photonen in solche höherer Energie besitzen. Das so entstehende Fluoreszenzlicht einer Ansammlung von Nanokristallen wird auf seine Abhängigkeit von der Anregungsintensität untersucht. Mit der Hilfe eines Rasterkraftmikroskops (AFM) wird eine Abhängigkeit der spektralen Zusammensetzung des Fluoreszenzlichts einzelner Nanokristalle von deren Größe im Bereich von wenigen bis 50 nm aufgezeigt. Durch gezielte Manipulation mit dem AFM werden ebenfalls einzelne Nanokristalle an Goldnanokügelchen gekoppelt und die Mechanismen der beobachteten plasmonischen Verstärkung der Emission durch zeitaufgelöste Messungen analysiert. Einzelne Stickstoff-Fehlstellen-Zentren in Nanodiamanten werden in einem zweiten Themenkomplex als Einzelphotonenquellen eigesetzt. Diese werden durch den Einsatz einer Nahfeld-Sonde auf Mikrokugel-Resonatoren aufgebracht, wodurch die Emission aufgrund der Ankopplung an die Flüstergalerie-Moden der Kugeln die typischen, scharfen Überhöhungen im Spektrum aufweist. Diese Methode lässt sich nicht nur verwenden, um zwei oder mehr Emitter an die selben Resonanzen einer Kugel zu koppeln. Es ist auch möglich, die Kugeln in einem Vorbereitungsschritt zu charakterisieren, und so kann insbesondere eine spektrale Übereinstimmung zwischen einer der Resonanzen und dem Emitter erreicht werden. Desweiterne wird demonstriert, wie durch die Kopplung an eine plasmonische Antenne aus Goldnanokugeln mittels AFM auch die Effizienz der Einzelphotonenquelle gesteigert werden kann. / The topic of the dissertation presented here is the investigation of nanoscopic emitters and the possibilities to influence their fluorescence behavior by controlled coupling to photonic and plasmonic structures. NaYF4 nanocrystals codoped with ytterbium and erbium are investigated since they provide excellent properties in upconverting of low-energetic photons to photons with higher energy. The fluorescence light that is generated in this process of a small cluster of nanocrystals is investigated on its dependence on the excitation intensity. With the help of an atomic force microscope (AFM) a dependence of the spectral composition of the fluorescence light from single nanocrystals on their size ranging between a few to 50 nm is demonstrated. By selective manipulation with the AFM, individual nanocrystals are coupled to gold nanospheres and the mechanisms of the observed plasmonic amplification of the emission is analyzed with time-resolved measurements. Single nitrogen–vacancy centers in nanodiamonds are employed as single-photon sources in a second subject area. A near-field probe is employed to attach these single quantum systems to microspherical resonators, by which their emission features the typical peaks in the spectrum due to the coupling to the whispering gallery modes of the spheres. This method can not only be applied to couple two or more single-photon emitters to the very same modes of a microsphere, but the resonators themselves can be pre-characterized to match one of the modes with the emitter. Furthermore, it will be demonstrated how the efficiency of a single-photon source can be enhanced by coupling the nitrogen-vacancy center to a plasmonic antenna made of gold nanospheres.

Jogo patológico (JP) pode ser definido pela persistência e recorrência do comportamento de apostar em jogos de azar, apesar de prejuízos em diversas áreas da vida decorrentes dessa atividade. O JP é considerado um transtorno do controle de impulso e um modelo de dependência comportamental. Diferentes estudos têm comprovado o envolvimento de vias dopaminérgicas em dependências de substâncias e em jogadores patológicos. O transportador de doamina (DAT) é uma proteína présináptica de neurônios dopaminérgicos nigroestriatais, responsável pela recaptação da dopamina (DA) da fenda sináptica, e tem sido relatada alterações em sua densidade em dependentes de substâncias. O objetivo deste trabalho foi investigar em pacientes com jogo patológico, a densidade de DAT no estriado, através de imagens do exame de SPECT com TRODAT-1- 99mTc verificar por meio de estudo de correlação a associação entre comportamento de jogo (freqüência, tempo, dinheiro, gastos com jogo e fissura/craving) e a densidade DAT em jogadores patológicos. Foram selecionados 15 jogadores e 15 controles normais pareados para gênero, idade e escolaridade. Para inclusão ou exclusão de sujeitos foram utilizados instrumentos de verificação e principais Transtornos Psiquiátricos do Eixo 1 do DSM IV e escalas para depressão e ansiedade; para jogadores patológicos os instrumentos utilizados foram escalas para avaliação do padrão de jogo recente, para avaliação da fissura pelo jogo; para rastreamento de outras dependências comportamentais (sexo e comida). Observou-se que: 1) jogadores patológicos não apresentaram aumento de densidade DAT quando comparados a controles normais; 2) nos jogadores a densidade de DAT foi diretamente proporcional a intensidade de jogo no último mês e inversamente proporcional a auto-eficácia na abstinência do jogo. Não houve correlação significativa entre densidade de DAT e comportamentos de abuso relacionados com sexo ou comida. Desta forma, faz-se necessário estudos futuros para a avaliação da densidade de DAT no início e no fim do tratamento, a fim de verificar se a diminuição da densidade de DAT ao longo do tratamento pode ser utilizada como preditor de boa resposta e bom prognóstico em jogadores patológicos. / Pathological gambling (PG) can be defined by the persistence and recurrence of the behavior of gambling on games of chance, despite losses in many areas of life from this activity. The JP is considered a disorder of impulse control and a model of behavioral dependence. Different studies have demonstrated the involvement of dopaminergic pathways in substance dependency and pathological gamblers. The dopamine transporter (DAT) is a protein pre-synaptic dopaminergic neurons nigroestriatais responsible for the reuptake of dopamine (DA) from the synaptic cleft, and has been reported changes in the density-dependent substances. The objective of this study was to investigate in patients with pathological gambling, the density of DAT in the striatum, through examination of SPECT images with TRODAT-1 - 99mTc to verify through correlation study the association between gambling behavior (frequency, time, money spent on gambling and urge / craving) and DAT density in pathological gamblers. We selected 15 plathological gamblers and 15 controls matched for gender, age and education. For inclusion or exclusion of subjects were used verification tools and major psychiatric disorders in the DSM IV Axis 1 and scales for depression and anxiety; for pathological gamblers were the instruments used scales for assessing the standard of play recently, to evaluate the crack for the game; for tracking other behavioral addictions (sex and food). It was observed that: 1) pathological gamblers did not have increased DAT density compared with normal controls, 2) players in the density of DAT was directly proportional to the intensity of gambling in the last month and inversely proportional to self-efficacy on abstinence of gambling. There was no significant correlation between DAT density and behavior of abuse related to sex or food. Thus, it is necessary to future studies for evaluating the density of DAT at the beginning and end of treatment in order to determine whether the decrease in density during the treatment DAT can be used as predictor of good response and a good prognosis in pathological gamblers.

O presente estudo comparou o fluxo sanguíneo cerebral regional avaliado através da tomografia por emissão de fóton simples (SPECT) de pacientes com crises epilépticas temporais com pacientes com crises não epilépticas psicogênicas (CNEP). Todos os SPECT foram realizado no período ictal, tendo as CNEP sido induzidas por métodos sugestivos e de hipnose. Os grupos de pacientes com epilepsia e CNEP foram ainda comparados com um terceiro grupo, denominado grupo de sujeitos saudáveis. As comparações dos SPECT foram feitas através da análise visual (radiologista cego ao estudo) e semiquantitativa pelo programa Statistical Parametric Mapping (SPM). Os objetivos do estudo foram: (1) estabelecer a sensibilidade e a especificidade do SPECT ictal para o diagnóstico diferencial entre CNEP e crises epilépticas parciais complexas em pacientes com epilepsia do lobo temporal, em comparação com o VEEG associado a técnicas de hipnose; (2) avaliar através da análise quantitativa voxel a voxel do SPECT as alterações de perfusão cerebral dos pacientes com CNEP em relação aos pacientes com epilepsia, dos pacientes com CNEP em relação a um grupo controle de sujeitos normais e dos pacientes com epilepsia em relação a um grupo controle de sujeitos saudáveis. Foram estudados 30 pacientes no grupo com CNEP, 22 pacientes no grupo com epilepsia e 29 sujeitos saudáveis. Os resultados mostram que os SPECT ictais dos pacientes do grupo CNEP foram diferentes dos SPECT ictais dos pacientes com epilepsia. Na análise visual o SPECT ictal apresentou sensibilidade de 50% e especificidade de 91% para o diagnóstico de CNEP . Na análise comparativa voxel a voxel entre os grupos os resultados revelaram que: (a) houve aumento de perfusão cerebral em lobo temporal esquerdo e tronco cerebral nos pacientes do grupo epilepsia em relação ao grupo controle normal; (b) houve diminuição de perfusão cerebral no lobo frontal esquerdo e córtex anterior do cíngulo nos pacientes do grupo epilepsia em relação ao grupo controle normal; (c) houve aumento de perfusão cerebral no giro do cíngulo e precuneus á direita nos pacientes do grupo CNEP em relação ao grupo epilepsia; (d) houve diminuição perfusão cerebral em amígdala direita nos pacientes do grupo CNEP em relação ao grupo epilepsia; (e) houve aumento de perfusão cerebral na cauda do núcleo caudado esquerdo, giro précentral esquerdo e tálamo direito nos pacientes do grupo CNEP em relação ao grupo controle normal. Desta forma, após a análise estatística dos resultados concluímos que na análise visual, um SPECT ictal positivo em um paciente com suspeita de CNEP não confirma nem afasta tal suspeita, já que a sensibilidade do método foi baixa (50%). Na análise visual, um SPECT ictal negativo em um paciente com suspeita de CNEP afasta a possibilidade de epilepsia do lobo temporal com 91% de acerto (especificidade do método). O resultado da análise visual do SPECT ictal de CNEP revelou valor de sensibilidade abaixo do encontrado na literatura, e valor de especificidade superior ao encontrado na literatura. A análise quantitativa dos SPECT de crise epiléptica em comparação com os de sujeitos saudáveis em repouso, mostrou concordância com a análise visual em relação à lateralidade. Tal comparação revelou ainda ativação de áreas compatíveis com o que se encontra na literatura. A análise quantitativa dos SPECT ictais do grupo CNEP em comparação com os do grupo epilepsia revelou ativação de estruturas cerebrais posteriores (precuneus e giro cíngulo), não havendo comparação semelhante na literatura. A análise quantitativa dos SPECT ictais do grupo CNEP em comparação com os de sujeitos saudáveis em repouso, mostrou ativação do sistema estriatotalamocortical, achado em concordância com a literatura. A ativação do sistema estriatotalamocortical nos pacientes com CNEP mostrou ser um correlato neuroanatômico clinicamente relevante, com forte associação estatística. / The study compared regional cerebral blood flow assessed by positron emission tomography single photon (SPECT) in patients with temporal lobe epilepsy and patients with psychogenic nonepileptic seizures (PNES). All SPECT were performed in the ictal period, PNES having been induced by and suggestive methods of hypnosis. The groups of patients with epilepsy and PNES were compared with a third group, called group of healthy subjects. SPECT comparisons were made by visual analysis (radiologist blinded to the study) and semiquantitative analysis by Statistical Parametric Mapping (SPM). The study objectives were: (1) to establish the sensitivity and specificity of ictal SPECT for the differential diagnosis between PNES and complex partial seizures in patients with temporal lobe epilepsy, compared with VEEG associated with hypnosis techniques, (2) to assess by quantitative analysis of SPECT voxel to voxel changes in cerebral perfusion of patients with PNES compared to patients with epilepsy, patients with PNES compared to a control group of normal subjects and patients with epilepsy compared to a control group of healthy subjects. We studied 30 patients in the PNES group, 22 patients in the group with epilepsy and 29 healthy subjects. The results show that ictal SPECT of patients in the PNES group were different from the ictal SPECT of patients with epilepsy. The visual analysis of ictal SPECT had a sensitivity of 50% and specificity of 91% for the diagnosis of PNES. In the voxel voxel comparative analysis between the groups the results showed that: (a) increased cerebral perfusion in the left temporal lobe and brain stem in patients of epilepsy group compared to normal control group, (b) a decrease in cerebral perfusion in the left frontal lobe and anterior cingulate cortex in patients of epilepsy group compared to normal control group, (c) increased cerebral perfusion in the cingulate gyrus and precuneus in the right group of PNES patients compared to epilepsy group, (d) decreased cerebral perfusion in the right amygdala in patients PNES group compared to the epilepsy group, (e) increased cerebral perfusion in the left tail of the caudate nucleus, left pre-central gyrus and right thalamus in patients in the PNES group compared to group normal control. Therefore, after statistical analysis of the results we conclude that in visual analysis, a positive ictal SPECT in a patient with suspected PNES neither confirms nor removes the suspicion, since the sensitivity was low (50%). In visual analysis, a negative ictal SPECT in a patient with suspected PNES rules out the possibility of temporal lobe epilepsy with 91% accuracy (specificity of the method). The result of visual analysis of ictal SPECT of PNES revealed sensitivity value below that found in the literature and specificity value higher than that found in the literature. The quantitative analysis of SPECT of seizures compared with those of healthy subjects at rest, showed agreement with visual analysis in relation to laterality. This comparison also revealed activation in areas consistent with that found in the literature. The quantitative analysis of SPECT ictal PNES group compared with the epilepsy group showed activation of posterior brain structures (cingulate gyrus and precuneus), with no similar comparison in the literature. The quantitative analysis of SPECT ictal PNES group compared to healthy subjects at rest, showed activation of the estriatotalamocortical, a finding in agreement with the literature. The activation of the estriatotalamocortical circuit in patients with PNES proved to be a neuroanatomical correlate clinically relevant, with strong statistical association

A análise de imagens médicas auxiliada por computador permite a análise quantitativa das anormalidades e garante maior precisão diagnóstica. Esse tipo de análise é importante para medicina nuclear com Single Photon Emission Computed Tomography (SPECT), pois no grupo de dados tridimensionais de imagens, padrões sutis de anormalidades muitas vezes são importantes achados clínicos. Porém, as imagens podem sofrer interferência de artefatos de atenuação da emissão de fótons por partes moles corporais, o que reduz sua acurácia diagnóstica. Desde que se possuam parâmetros de atenuação computados em um modelo que permita a comparação com imagens de um dado paciente, a interferência dos artefatos pode ser corrigida com ganho na acurácia diagnóstica, sem a necessidade de utilização de técnicas de correção que aumentem a dose de exposição à radiação pelo paciente. A proposta desse estudo foi a criação de um atlas de cintilografia de perfusão miocárdica, que foi obtido a partir de imagens de indíviduos normais, e o desenvolvimento de um algoritmo computacional para a detecção de anormalidades perfusionais miocárdicas, através da comparação estatística dos modelos do atlas com imagens de pacientes. Métodos de corregistro de imagens de mesma modalidade e outras técnicas de processamento de imagens foram estudados e utilizados para a comparação das imagens dos pacientes com o modelo apropriado. Pela análise visual dos modelos, verificou-se a sua validade como imagem representativa de normalidade perfusional. Para avaliação da detecção, a situação dos segmentos miocárdicos (normal ou anormal) indicada pelo algoritmo de detecção foi comparada com a situação apontada no laudo obtido pela concordância de dois especialistas, de modo a se verificar as concordâncias e discordâncias da técnica em relação ao laudo e se obter a significância estatística. Com isso, verificou-se um índice de concordância positiva da técnica em relação ao laudo de aproximadamente 50%, de concordância negativa próxima a 82% e de concordância geral próxima a 68%. O teste exato de Fisher foi aplicado às tabelas de contingência, obtendo-se um valor de p bicaudal inferior a 0,0001, indicando uma probabilidade muito baixa de as concordâncias terem sido obtidas pelo acaso. Melhorias no algoritmo deverão ser implementadas e testes futuros com um padrão-ouro efetivo serão realizados para validação da técnica. / The computer-aided medical imaging analysis allows the quantitative analysis of abnormalities and enhances diagnostic accuracy. This type of analysis is important for nuclear medicine that uses Single Photon Emission Computed Tomography (SPECT), because in the group of three-dimensional data images, subtle patterns of abnormalities often are important clinical findings. However, images can suffer interference from attenuation artifacts of the emission of photons by soft parts of the body, which reduces their diagnostic accuracy. Since there are attenuation parameters computed in a template that allows for comparison with images of a given patient, the artifacts interference can be corrected with a gain in diagnostic accuracy, without the need of using correction techniques that increase the radiation exposure dose of the patient. The purpose of this study was to create an atlas of myocardial perfusion scintigraphy, which was obtained from images of normal individuals and the development of a computational algorithm for detection of myocardial perfusion abnormalities by statistical comparison of atlas templates with images of patients. Methods of image registration of same modality and other image processing techniques were studied and used for comparison of patient images with the appropriate template. By the visual analysis of the templates it was found its validity as a representative image of normal perfusion. For the detection evaluation, the situation of myocardial segments (normal or abnormal) indicated by the detection algorithm was compared with the situation indicated in the medical appraisal report obtained by agreement of two specialists in order to determine the agreement and disagreement of the technique regarding the medical appraisal report and obtaining the statistical significance. Thus, there was a positive agreement index of the technique regarding the medical appraisal report of approximately 50%, a negative agreement index close to 82% and a general agreement index near 68%. The Fisher exact test was applied to the contingency tables, yielding a two-sided p-value less than 0.0001, that indicates a very low probability of the agreements have been obtained by chance. Algorithm improvements should be implemented and further tests with an effective gold-standard will be conducted to validate the technique.

La tomographie d'émission monophotonique (TEMP) dédiée au petit animal est une technique d'imagerie nucléaire qui joue un rôle important en imagerie moléculaire. Les systèmes TEMP, à l'aide de collimateurs pinholes ou multi-pinholes, peuvent atteindre des résolutions spatiales submillimétriques et une haute sensibilité pour un petit champ de vue, ce qui est particulièrement attractif pour imager des souris. Une géométrie de collimation originale a été proposée, dans le cadre d'un projet, appelé SIGAHRS, piloté par la société Biospace. Ce collimateur présente des longueurs focales qui varient spatialement dans le plan transaxial et qui sont fixes dans le plan axial. Une haute résolution spatiale est recherchée au centre du champ de vue, avec un grand champ de vue et une haute sensibilité. Grâce aux simulations Monte Carlo, dont nous pouvons maîtriser tous les paramètres, nous avons étudié cette collimation originale que nous avons positionnée par rapport à un collimateur parallèle et un collimateur monofocal convergent. Afin de générer des données efficacement, nous avons développé un module multi-CPU/GPU qui utilise une technique de lancer de rayons dans le collimateur et qui nous a permis de gagner un facteur ~ 60 en temps de calcul, tout en conservant ~ 90 % du signal, pour l'isotope ⁹⁹^mTc (émettant à 140,5 keV), comparé à une simulation Monte Carlo classique. Cependant, cette approche néglige la pénétration septale et la diffusion dans le collimateur. Les données simulées ont ensuite été reconstruites avec l'algorithme OSEM. Nous avons développé quatre méthodes de projection (une projection simple (S-RT), une projection avec volume d'intersection (S-RT-IV), une projection avec calcul de l'angle solide (S-RT-SA) et une projection tenant compte de la profondeur d'interaction (S-RT-SA-D)). Nous avons aussi modélisé une PSF dans l'espace image, anisotrope et non-stationnaire, en nous inspirant de la littérature existante. Nous avons étudié le conditionnement de la matrice système pour chaque projecteur et collimateur, et nous avons comparé les images reconstruites pour chacun des collimateurs et pour chacun des projecteurs. Nous avons montré que le collimateur original proposé est le système le moins bien conditionné. Nous avons aussi montré que la modélisation de la PSF dans l'image ainsi que de la profondeur d'intéraction améliorent la qualité des images reconstruites ainsi que le recouvrement de contraste. Cependant, ces méthodes introduisent des artefacts de bord. Comparé aux systèmes existants, nous montrons que ce nouveau collimateur a un grand champ de vue (~ 70 mm dans le plan transaxial), avec une résolution de 1,0 mm dans le meilleur des cas, mais qu'il a une sensibilité relativement faible (1,32x10⁻² %). / Small animal single photon emission computed tomography (SPECT) is a nuclear medicine imaging technique that plays an important role in molecular imaging. SPECT systems using pinhole or multi-pinhole collimator can achieve submillimetric spatial resolution and high sensitivity in a small field of view, which is particularly appropriate for imaging mice. In our work, we studied a new collimator dedicated to small animal SPECT, in the context of a project called SIGAHRS, led by the Biospace company. In this collimator, focal lengths vary spatially in the transaxial plane and are fixed in the axial plane. This design aims at achieving high spatial resolution in the center of the field of view, with a large field of view and high sensitivity. Using Monte Carlo simulations, where all parameters can be controlled, we studied this new collimator geometry and compared it to a parallel collimator and a cone-beam collimator. To speed up the simulations, we developed a multi-CPU/GPU module that uses a technique of ray tracing. Using this approach, the acceleration factor was ~ 60 and we restored ~ 90 % of the signal for ⁹⁹^mTc (140.5 keV emission), compared to a classical Monte Carlo simulation. The 10 % difference is due to the fact that the multi-CPU/GPU module neglects the septal penetration and scatter in the collimator. We demonstrated that the data acquired with the new collimator could be reconstructed without artifact using an OSEM algorithm. We developed four forward projectors (simple projector (S-RT), projector accounting for the surface of the detecting pixel (S-RT-IV), projection modeling the solid angle (S-RT-SA) of the projection tube, and projector modeling the depth of interaction (S-RT-SA-D)). We also modeled the point spread function of the collimator in the image domain, using an anisotropic non-stationary function. To characterize the reconstruction, we studied the conditioning number of the system matrix for each projector and each collimator. We showed that the new collimator was more ill-conditioned than a parallel collimator or a cone-beam collimator. We showed that the image based PSF and the modeling of the depth of interaction improved the quality of the images, but edge artefacts were introduced when modeling the PSF in the image domain. Compared to existing systems, we showed that this new collimator has a large field of view (~ 70 mm in the transaxial plane) with a resolution of 1.0 mm in the best case but suffers from a relatively low sensitivity (1.32x10⁻² %).

L’expérience JEM-EUSO (traduction de Observatoire spatial de l’univers extrême à bord du module de l'expérience japonaise) est conçu pour observer les UHECR en détectant la lumière fluorescente UV émise par la gerbe qui se développe lorsque les UHECR interagissent avec l'atmosphère terrestre. Les gerbes atmosphériques sont constituées de dizaines de milliards de particules secondaires ou plus traversant l'atmosphère quasiment à la vitesse de la lumière, excitant les molécules d'azote qui émettent ensuite de la lumière dans la gamme UV. Alors que cette « technique de fluorescence » est habituellement utilisée au sol, en opérant ainsi à partir de l'espace, JEM-EUSO, pour la première fois, fournira des statistiques élevées sur ces événements. Avec un large champ de vue de ± 30 °, JEM-EUSO pourra observer depuis l’espace un volume d'atmosphère beaucoup plus grand que ce qui est possible du sol, en collectant un nombre sans précédent d'événements UHECR aux plus hautes énergies.Pour les quatre prototypes d’expériences construites par la collaboration, nous avons développé un ensemble commun d'électronique, en particulier le système central d'acquisition de données capable de fonctionner au sol, sur des ballons à haute altitude et dans l'espace.Ces expériences utilisent toutes un détecteur composé d'un module de détection de photo (PDM) identique aux 137 qui seront présents sur la surface focale JEM-EUSO. La lumière UV générée par les gerbes atmosphériques à haute énergie passe le filtre UV et frappe les tubes à photomultiplicateurs multi-anodes (MAPMT). Les photons UV sont alors transformés en électrons, qui sont multipliés par les MAPMT et le courant qu’ils créent est amplifié par des cartes ASIC de circuit intégré (EC-ASIC), qui effectuent également le comptage des photons et l'estimation de charge. Une carte FPGA nommé PDM board s'interface avec ces cartes ASIC, fournissant des paramètres d'alimentation et de configuration à ces cartes ASIC, collecte alors les données et exécute le déclenchement d’acquisition de niveau 1.Dans le cadre de ces travaux, je me suis occupée de la conception, du développement, de l'intégration et du test la carte FPGA PDM board pour les missions EUSO-TA et EUSO-Balloon ainsi que des tests d'algorithme de déclenchement autonomes d’acquisitions et j'ai également analysé les données de vol d’EUSO-Balloon et de la campagne sol EUSO-TA d’octobre 2015.Dans cette thèse, je donnerai un bref aperçu des rayons cosmiques à haute énergie, y compris de leur technique de détection et des principales expériences pour les détecter (chapitre 1), je décrirai JEM-EUSO et ses pathfinders (chapitre 2), je présenterai les détails de la conception et de la fabrication du PDM (chapitre 3) et de la carte FPGA PDM board (chapitre 4), ainsi que des tests d'intégration d’EUSO-TA et d’EUSO-Balloon (chapitre 5). Je ferai un rapport sur la campagne EUSO-Balloon de 2014 (chapitre 6) et sur ses résultats (chapitre 7), y compris une analyse spécifique développée pour rechercher des variations globales de l'émissivité UV au sol et j’appliquerai une analyse similaire aux données collectées sur le site de Telescope Array (Chapitre 8). Enfin, je présenterai la mise en œuvre et le test du déclencheur de premier niveau (L1) dans la carte de contrôle FPGA (chapitre 9). Un bref résumé de la thèse sera donné au chapitre 10. / The JEM-EUSO (Extreme Universe Space Observatory on-board the Japanese Experiment Module) international space mission is designed to observe UHECRs by detecting the UV fluorescence light emitted by the so-called Extensive Air Shower (EAS) which develop when UHECRs interact with the Earth’s atmosphere. The showers consist of tens of billions or more secondary particles crossing the atmosphere at nearly the speed of light, which excite nitrogen molecules which then emit light in the UV range. While this so-called “fluorescence technique'” is routinely used from the ground, by operating from space, JEM-EUSO will, for the first time, provide high-statistics on these events. Operating from space, with a large Field-of-View of ±30 °, allows JEM-EUSO to observe a much larger volume of atmosphere, than possible from the ground, collecting an unprecedented number of UHECR events at the highest energies.For the four pathfinder experiments built within the collaboration, we have been developing a common set of electronics, in particular the central data acquisition system, capable of operating from the ground, high altitude balloons, and space.These pathfinder experiments all use a detector consisting of one Photo-detection Modules (PDMs) identical to the 137 that will be present on the JEM-EUSO focal surface. UV light generated by high-energy particle air showers passes the UV filter and impacts the Multi-anode Photomultiplier Tubes (MAPMT). Here UV photons are converted into electrons, which are multiplied by the MAPMTs and fed into Elementary Cell Application-Specific Integrated Circuit (EC-ASIC) boards, which perform the photon counting and charge estimation. The PDM control board interfaces with these ASIC boards, providing power and configuration parameters, collecting data and performing the level 1 trigger. I was in charge of designing, developing, integrating, and testing the PDM control board for the EUSO-TA and EUSO-Balloon missions as well as the autonomous trigger algorithm testing and I also performed some analysis of the EUSO-Balloon flight data and data from the EUSO-TA October 2015 run.In this thesis, I will give a short overview of high-energy cosmic rays, including their detection technique and the leading experiments (Chapter 1), describe JEM-EUSO and its pathfinders including a description of each instrument (Chapter 2), present the details of the design and the fabrication of the PDM (Chapter 3) and PDM control board (Chapter 4), as well as the EUSO-TA and EUSO-Balloon integration tests (Chapter 5). I will report on the EUSO-Balloon campaign (Chapter 6) and results (Chapter 7), including a specific analysis developed to search for global variations of the ground UV emissivity, and apply a similar analysis to data collected at the site of Telescope Array (Chapter 8). Finally, I will present the implementation and testing of the first-level trigger (L1) within the FPGA of the PDM control board (Chapter 9). A short summary of the thesis will be given in Chapter 10.

In dieser Arbeit wird das Stickstoff-Fehlstellenzentrum (NV Zentrum) in Diamant als ein solcher Einzelphotonenemitter untersucht. Durch Benutzung eines hybriden Ansatzes werden hier NV Zentren in Diamantnanopartikeln in photonische Strukturen integriert. Zuerst wird eine aufnehmen-und-ablegen-Nanomanipulationstechnik mittels eines Rasterkraftmikroskops verwendet um einzelne NV Zentren an eine photonische Kristallkavität und eine optische Faser zu koppeln. Durch Kopplung an die photonische Kristallkavität wird die Emission der Nullphononenlinie des NV Zentrums um den Faktor 12.1 erhöht und durch Kopplung an die optische Faser entsteht eine direkt gekoppelte Einzelphotonenquelle hoher effektiver numerischer Apertur. Durch Kopplung an plamonische Wellenleiter können einzelne Oberflächenplasmon-Polaritonen nachgewiesen werden. Zweitens wird ein anderer Ansatz, die Entwicklung eines hybriden Materials, verfolgt. Hier sind die Nanodiamanten, anstatt sie auf die Strukturen von Interesse zu legen, von Anfang in dem Material enthalten, aus dem die Strukturen hergestellt werden. Mittels direktem Zweiphotonen-Laserschreiben ist es dann möglich, Kombinationen aus chipintegrierten Wellenleitern, Resonatoren und Einzelphotonenemittern zu zeigen. Um mehr über die Dynamik von NV Zentren in Nanodiamant zu erfahren und Wege zu ihrer Verbesserung zu finden, wird die Dynamik der Nullphononenlinie des NV Zentrums mittels eines Photonenkorrelationsinterferometers untersucht. Zusätzlich zu Techniken zur Herstellung photonischer und plasmonischer Strukturen werden auch Methoden zu ihrer Charakterisierung benötigt. Hier für kann es ausgenutzt werden, dass das NV Zentrum weiter nicht nur ein Einzelphotonenemitters ist, sondern es ebenso als Sensor verwendet werden kann. Das NV Zentrum wird hier verwendet, um die lokale optische Zustandsdichte in einem Rastersondenverfahren zu messen, was die Technik der dreidimensionalen Quantenemitter Fluoreszenzlebensdauermikroskopie einführt. / In this thesis, one of such single photon emitters, the nitrogen vacancy centre (NV centre) in diamond, will be examined. By using different hybrid approaches, NV centres in diamond nanoparticles are integrated into photonic structures. Firstly, using a pick-and-place nanomanipulation technique with an atomic force microscope, a single NV centre is coupled to a photonic crystal cavity and an optical fibre. Coupling to the photonic crystal cavity results in an enhancement of the NV centre''s zero phonon line by a factor of 12.1 and coupling to the fibre yields a directly coupled single photon source with an effective numerical aperture of 0.82. By coupling to plasmonic waveguides, the signature of single surface plasmon polaritons is found. Secondly, instead of placing the nanodiamonds on the structures of interest, a hybrid material where the emitters are incorporated is used. With two-photon direct laser writing, on-chip integration and combination of waveguides, resonators, and single photon emitters is demonstrated. In order to learn more on the dynamics of NV centre in nanodiamonds and find ways for improvements, the dynamics of the ultra-fast spectral diffusion of the NV centre''s zero phonon line are investigated using a photon correlation interferometer. In addition to techniques for the fabrication of photonic and plasmonic structures, also methods for their characterisation are needed.For this, it can be exploited that the NV centre also is not only a single photon emitter, but can also be employed as a sensor. Here, the NV centre is used to measure the local density of optical states in a scanning probe experiment, establishing the technique of three-dimensional quantum emitter fluorescence lifetime imaging.