Дисертації з теми "Perfusion techniques"
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1
Paolani, Giulia. "Brain perfusion imaging techniques." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Знайти повний текст джерелаАнотація:
In questo lavoro si sono analizzate due diverse tecniche di imaging di perfusione implementate in Risonanza Magnetica e Tomografia Assiale Computerizzata (TAC). La prima analisi proposta riguarda la tecnica di Arterial Spin Labeling che permette di ottenere informazioni di perfusione senza la somministrazione di un mezzo di contrasto. In questo lavoro si è sviluppata e testata una pipeline completa, attraverso lo sviluppo sia di un protocollo di acquisizione che di post-processing. In particolare, sono stati definiti parametri di acquisizione standard, che permettono di ottenere una buona qualità dei dati, successivamente elaborati attraverso un protocollo di post processing che, a partire dall'acquisizione di un esperimento di ASL, permette il calcolo di una mappa quantitativa di cerebral blood flow (CBF). Nel corso del lavoro, si è notata una asimmetria nella valutazione della perfusione, non giustificata dai dati e probabilmente dovuta ad una configurazione hardware non ottimale. Risolta questa difficoltà tecnica, la pipeline sviluppata sarà utilizzata come standard per l’acquisizione e il post-processing di dati ASL. La seconda analisi riguarda dati acquisiti attraverso esperimenti di perfusione TAC. Si è presa in considerazione la sua applicazione a casi di infarti cerebrali in cui le tecniche di trombectomia sono risultate inefficaci. L'obiettivo di questo lavoro è stata la definizione di una pipeline che permetta il calcolo autonomo delle mappe di perfusione e la standardizzazione della trattazione dei dati. In particolare, la pipeline permette l’analisi di dati di perfusione attraverso l’utilizzo di soli software open-source, contrapponendosi alla metodologia operativa comunemente utilizzata in clinica e rendendo le analisi riproducibili. Il lavoro proposto è inserito in un progetto più ampio, che include future analisi longitudinali con coorti di pazienti più ampie per definire e validare parametri predittivi degli outcome dei pazienti.
2
Francis, S. T. "Magnetic Resonance Imaging of perfusion : techniques and applications." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243771.
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Perthen, Joanna Elizabeth. "Measurement of cerebral perfusion using magnetic resonance techniques." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406739.
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4
王晴兒 and Ching-yee Oliver Wong. "Measurement of cerebrovascular perfusion reserve using single photon emission tomographic techniques." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31981677.
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Wong, Ching-yee Oliver. "Measurement of cerebrovascular perfusion reserve using single photon emission tomographic techniques." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19605328.
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6
Filipovic, Marina. "Application des techniques adaptatives à l'imagerie par résonance magnétique de perfusion." Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10030/document.
Повний текст джерелаАнотація:
L'Imagerie par Résonance Magnétique (IRM) nécessite des outils pour gérer le mouvement physiologique et autre du sujet. La création des images par l'IRM comporte trois étapes: l'acquisition de données avec une séquence d'impulsions, la reconstruction d'images, et le post-traitement. Les techniques adaptatives de reconstruction d'images visent à intégrer des informations liées au mouvement dans le processus de génération d'images à partir de données acquises, ceci dans le but de compenser les artéfacts et problèmes provoqués par le mouvement. L'IRM dynamique avec rehaussement de contraste est une technique destinée à l'estimation de la fonction des organes, en suivant le passage d'un produit de contraste dans le corps. Les problèmes dus au mouvement, surtout dans l'application thoraco-abdominale de cette technique, se présentent sous forme d'artéfacts de mouvement et de décalages. Une nouvelle méthode de reconstruction d'images, DCE-GRICS (Reconstruction généralisée dynamique avec rehaussement de contraste par inversion d'un système couplé), a été développée pour résoudre ces problèmes. Le mouvement est estimé avec un modèle linéaire non rigide basé sur les signaux physiologiques issus de capteurs externes. Les changements d'intensité causés par le passage de l'agent de contraste sont rendus avec un modèle linéaire de changement de contraste basé sur le fonctions B-spline. Cette méthode a été appliquée et validée sur l'imagerie de la perfusion myocardique. Les inexactitudes causées par le mouvement dans les courbes intensité-temps sont compensées, afin de rendre plus fiable le post-tratement des courbes pour l'estimation de la perfusion myocardiqueMagnetic Resonance Imaging (MRI) requires tools for managing physiological and other motion of the patient. The generation of MR images consists of three steps: data acquisition with a pulse sequence, image reconstruction and image post-processing. Adaptive image reconstruction techniques aim at integrating motion information into the process of image generation from the acquired data, in order to compensate for motion-induced artefacts and problems. Dynamic contrast-enhanced (DCE) MRI is a technique designed for assessing the function of organs, by following dynamically the passage of a contrast agent in the body after a bolus injection. Motion-induced problems, especially in abdominal and thoracic DCE-MRI, consist of motion artefacts and misregistration. A new image reconstruction method, DCE-GRICS (Dynamic Contrast-Enhanced Generalized Reconstruction by Inversion of Coupled Systems), has been developed for solving these issues. Motion is estimated with a non rigid linear model based on physiological signals obtained from external sensors. Dynamic intensity changes caused by the passage of the contrast agent are described using a linear contrast change model based on B-splines. The method is applied and validated on myocardial perfusion imaging. Motion-induced inaccuracies in intensity-time curves are compensated, in order to allow for more reliable myocardial perfusion quantification by curve post-processing
7
Petric, Martin Peter. "Quantitative multi-slice cerebral perfusion imaging using arterial spin labelling MR techniques." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33821.
Повний текст джерелаАнотація:
This thesis presents the development and implementation of a quantitative multi-slice cerebral perfusion imaging technique using magnetic resonance imaging. An acquisition sequence capable of acquiring up to 9 slices was designed and implemented into two final pulse sequences: an interleaved perfusion/BOLD (blood oxygenation level dependent) sequence and a perfusion-only sequence. A number of practical imaging issues were addressed and resolved, including the design of an appropriate inversion pulse for labelling of arterial spins, spatial offsetting of this pulse for use in the arterial spin labelling technique chosen for implementation, and the design of various saturation pulses necessary for quantification of the technique. Experimental validation of the quantitative multi-slice perfusion technique was performed by measuring visual cortex cerebral blood flow (CBF) values in a group of 8 subjects using a block-design visual stimulus paradigm. Results indicated good sequence stability and CBF measurements agreed well with quantitative values found in the literature.
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Maredia, Neil. "Advanced techniques in first pass myocardial perfusion imaging by cardiac magnetic resonance." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.535669.
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Sam, Mpaballeng Catherine. "Calibration of sap flow techniques in citrus using the stem perfusion method." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/60855.
Повний текст джерелаАнотація:
The aim of this study was to calibrate and decide on the most appropriate sap flow technique for citrus species in the laboratory by pushing water through cut branches. Various sap flux density techniques, including heat pulse techniques (heat ratio and compensation heat pulse methods) and the heat dissipation technique were calibrated in four citrus species, namely Citrus sinensis (Oranges), Citrus reticulata (Soft citrus), Citrus paradise (Grapefruit) and Citrus limon (Lemons). Sap flux density, determined by these three techniques, was compared to that determined gravimetrically, which was calculated as the rate of change in the mass of water passing through the stem segment divided by the area of conducting wood. Results showed that the sap flux density was consistently underestimated by all techniques and across all citrus species/varieties. However, fairly good correlations (R2>0.7) between sap flux densities determined by a sap flow technique and gravimetric determinations were found for all techniques in some stems. Despite the good correlations found in the study, a single calibration factor for each technique could not be found for citrus using the stem perfusion method. Calibration factors were determined as the inverse of the slope of the linear relationship between sap flux density determined with a sap flow technique and that determined gravimetrically. These correction factors varied between citrus species and even within stems of the same species.
Vessel dimensions (lumen diameter) and distance between groups of xylem vessels in citrus species was determined in order to try and explain the underestimation of sap flux density and the large variations in the calibration factors obtained during the calibration of the various sap flow techniques. The results revealed that the variation and underestimation were caused by contact of the probes with inactive xylem and due to differences in the nature of sapwood. The xylem vessels were unevenly distributed throughout the sapwood with large distance between the vessels, meaning that the sapwood of the studied species was considered inhomogeneous and therefore departed from the idealised theory of heat pulse measurements. The theory needs to be adapted to account for such sapwood and because of the large variation in the sapwood properties between different citrus species, calibration of these techniques is probably necessary for each new species and orchard in which measurements are to be made. Our analysis of the performance of sap flow techniques showed that the HR method should perhaps be considered before the CHP and TD methods.Dissertation (MSc (Agric))--University of Pretoria, 2016.
Plant Production and Soil Science
MSc (Agric)
Unrestricted
10
Ball, Daniel. "Development of novel hyperpolarized magnetic resonance techniques and compounds for perfused organs." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:21f6b661-cf21-46e7-9c7a-7c5d9ccf2b28.
Повний текст джерелаАнотація:
Hyperpolarization via the Dynamic Nuclear Polarization (DNP) technique has revolutionized our ability to study metabolic changes in real time. The aim of this thesis was to build upon previous work centered around the use of DNP within the isolated perfused rat heart, a well established model system for the study of cardiac metabolism, to enhance the information that can be obtained through the combination of DNP with perfused organs. Initially this was done by using the widely studied DNP probe, [1-13C]pyruvate, to generate images of metabolism within the isolated perfused rat heart. The developed technique was then successfully demonstrated in two models of myocardial infarction. The thesis then proceeds to develop an understanding of how the supra-physiological concentrations of [1-13C]pyruvate commonly used in DNP experiments can affect metabolism in the isolated perfused rat heart, and the way in which the myocardium responds to those changes if it is not adequately supplied with substrates ordinarily present in vivo, namely fatty acids. New methods of providing the heart with these required substrates were developed, without significant interference to the biochemical information acquired from DNP experiments. As [1-13C]pyruvate only provides information on a small subset of carbohydrate metabolism, the next chapter develops new compounds to be used with DNP, which would allow the exploration of short chain fatty acid metabolism (butyrate) as well as ketone body metabolism (β-hydroxybutyrate and acetoacetate), and other aspects of carbohydrate metabolism (lactate and alanine). These compounds were developed and then tested for their potential usefulness in the isolated perfused heart. Finally, as the isolated perfused rat heart lacks the diversity of genetic disease models available in the mouse, the final chapter expanded the use of DNP to the isolated perfused mouse heart with all the size challenges that this entails, and makes the transition from the heart to the liver, in order to provide an alternative metabolic viewpoint on the biochemistry of disease models. This thesis thereby permits studies involving isolated perfused organs to be carried out whilst exploiting all the tools that DNP has to offer and consequentially, allows for a vast array of physiologically derived information to help us better understand metabolic diseases.
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Thomas, David Lee. "Magnetic resonance imaging of diffusion and perfusion : techniques and applications to cerebral ischaemia." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391829.
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Diederich, Chris John 1960. "THE IMPLEMENTATION AND EVALUATION OF TWO THERMAL TECHNIQUES FOR MEASURING LOCAL TISSUE PERFUSION." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/277137.
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Wang, Haonan. "Novel Techniques for Rapid Cardiac Perfusion Magnetic Resonance Imaging with Whole Heart Coverage." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6435.
Повний текст джерелаАнотація:
Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging method that is used in the diagnosis of many common diseases. Compared to other medical imaging modalities, MRI has the ability to provide high-resolution 2D and 3D images in arbitrary orientations, without the use of potentially damaging ionizing radiation. Myocardial perfusion MRI is a promising non- invasive clinical way to detect cardiac disease. It can also provide quantitative analysis for blood flow within the heart. However, MRI requires longer scan times to acquire images at comparable resolutions to some other imaging modalities. Increasing image resolution, both spatially and temporally, is very important to myocardial perfusion MRI. The work presented in this dissertation focuses on the development of novel dynamic contrast-enhanced (DCE) MRI that is able to achieve both high spatial and temporal resolutions, as well as suitable spatial coverage of the heart. Three novel acquisition and reconstruction frame- works are proposed and analyzed in this dissertation. The first framework we propose uses a highly undersampled 3D Cartesian acquisition and total variation (TV) constrained reconstruction to accelerate the acquisition of myocardial perfu- sion images. This technique increases temporal resolution for contrast tracking without sacrificing spatial resolution. An analysis of the effect of different k-space trajectories using this technique is performed. The purpose of the second framework is to simplify cardiac perfusion studies. An ECG- gated saturation recovery sequence is regularly used for cardiac perfusion imaging. However, using an ungated acquisition has the potential benefit of reducing the acquisition time by eliminating the need for the ECG trigger signal. We present a novel non-Cartesian 2D multi-slice ungated acquisition, and demonstrate that it is a promising alternative to ECG-gated cardiac perfusion studies. An optimization analysis of our ungated acquisition is also presented. The third method in this dissertation combines the 2D ungated acquisition with multi-band excitation, which enables the excitation of multiple slices simultaneously. This method is able to reduce scan time not only through the ungated acquisition, but also from obtaining multiple slices at once. This allows us to achieve whole heart coverage without sacrificing temporal resolution. The contributions presented in this dissertation demonstrate the basic feasibility of car- diac perfusion MRI achieving whole-heart coverage in a clinical setting by overcoming the major existing limitations: speed of acquisition and spatial coverage.
14
Gerfault, Laurent. "Imagerie des produits de contraste ultrasonore : simulation et approche de la perfusion myocardique." Lyon, INSA, 2000. http://www.theses.fr/2000ISAL0041.
Повний текст джерелаАнотація:
A l'instar des autres méthodes d'imagerie (IRM, Rayons X), l'échographie est devenue une imagerie de contraste. Elle consiste en l'amélioration des performances de l'imagerie classique par injection intraveineuse d'un produit de contraste, constitué par une population de microparticules gazeuses (diamètre inférieur à 10 pm). L'agent de contraste ultrasonore est strictement vasculaire, il permet d'augmenter l'intensité vidéo sur 1 'image écho graphique et le signal Doppler des zones vascularisées dans le but d'améliorer la visualisation de structures internes du corps humain et d'aborder l'imagerie fonctionnelle telle que la perfusion myocardique. Les performances acoustiques in vitro de ces produits sont avérées. Cependant, l'utilisation de ceux ci dans le corps humain n'a pas permis d'obtenir la même efficacité. Ainsi, ce travail à pour but de mieux connaître le produit et ses interactions avec le milieu intracorporel. Les int1uences du milieu (filtrage pulmonaire, dilution du bolus de l'agent de contraste, diffusion du gaz interne des particules, pression cardiaque,. . . ) et de l'onde acoustique sont abordées pour connaître les modifications physiques du produit in vivo. L'impact de ces paramètres physiques sur la réponse acoustique des particules est étudié à partir d'un modèle acoustique linéaire dont nous précisons le domaine de validité. L'évaluation clinique se réalisant sur l'image échographique, nous présentons une simulation des signaux échographiques des produits de contraste. Cette approche qualitative est complétée par une approche quantitative portant sur la mesure de la perfusion. En premier lieu, nous comparons un modèle basé sur la mécanique des fluides, décrivant la dilution d'un bolus d'agent, à des mesures acoustiques effectuées sur un système circulant tubulaire. En second lieu, nos conclusions sur ce fantôme sont appliquées à l'étude de la perfusion myocardique sur des cœurs isolés de porcsLike other imaging modalities (MRI or X-Ray), ultrasound scanning has become a contrast imaging modality. It consists in the enhancement of standard ultrasound imaging using an intra-veinously injected ultrasound contrast agent (USCA). Video intensity and Doppler signals of perfused region, reached by the contrast agent, are enhanced. Then, contrast imaging allows a better visualization of perfusion of different organs, and the approach of functional imaging like myocardial perfusion study. In vitro efficiency of USCA has been demonstrated, but its in vivo use has shown a decrease of efficiency. This work studies the interactions between contrast agent and intra-corporal medium, and the influence of measurement method in the aims of understanding this lack of efficiency. The influences of intra-corporal medium actions (pulmonary filtering, dilution of USCA bolus, diffusion of internal gas of USCA micro particles cardiac pressure) and ultrasound waves are inspected to evaluate physical modifications of USCA in in-vivo conditions. The impact of these physical changes on acoustical responses of USCA is then studied. As clinical evaluation is performed on echographic images, simulations of echographic signals are computed. Finally, the feasibility of absolute measurement of blood flow rate is evaluated. A comparison between a newly developed fluid dynamics based model of bolus dilution and acoustical measurements made on a circulating tubular phantom is made. Our conclusions are applied to the study of myocardial perfusion using an isolated pig heart model
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Ashooor, Habib. "First-pass techniques for the assessment of tissue perfusion using dynamic contrast-enhanced imaging." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499907.
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Arnold, J. R. "Evolving non-invasive techniques for the assessment of myocardial perfusion in ischaemic heart disease." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543046.
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Freeman, Kendra D. "Microangiographic comparison of the effects of the three-loop pulley and six strand Savage tenorrhaphy techniques on the equine superficial digital flexor tendon." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/56839.
Повний текст джерелаАнотація:
Injuries to the equine distal limb are common and often involve synovial, tendinous and/or ligamentous structures. Historically, lacerations involving the equine digital flexor tendons carried a poor prognosis for return to athletic function due to contamination of the site at presentation, involvement of multiple anatomic structures and the need for immediate weight bearing after surgery. The need for weight bearing after surgery places strain on the tenorrhaphy site that exceeds the strength of the repair itself. Extrapolation of complex, stronger tenorrhaphy patterns from human literature and applying them to equine patients has been challenging.
Human tenorrhaphy techniques initially focused on strong repairs, which are able to match or exceed the strength of tendon itself. Adhesion formation is problematic in human flexor tenorrhaphies, as most injuries occur to tendons surrounded by synovial structures. Human literature now focuses on using repairs that provide initial strength, minimal damage to intrinsic tendon architecture, and allow for early mobilization. This treatment protocol has greatly improved the functional outcome of human tenorrhaphies.
Recent studies have evaluated the strength of complex tenorrhaphy patterns in equine superficial digital flexor tendons, using modifications of the Savage technique. The newly evaluated patterns are stronger than previously tested and commonly used techniques, such as the three-loop pulley (3LP). A review of tendon vasculature across species and healing characteristics of tendons highlights the importance of intrinsic tendon vasculature in the healing process. Using tenorrhaphy techniques that preserve this vasculature may improve the clinical outcome in these cases. Only one study has previously evaluated the effect of tenorrhaphy patterns on intrinsic tendon vasculature in equine superficial digital flexor tendon.
This study compared perfusion of intrinsic tendon vasculature of equine superficial digital flexor tendon (SDFT) after 3LP and six-strand Savage (SSS) tenorrhaphies. We hypothesized that the SSS technique would significantly decrease vascular perfusion compared to the 3LP technique.
Under general anesthesia, eight pairs of forelimb SDFTs were transected and either SSS or 3LP tenorrhaphy was performed on each forelimb. The horses were heparinized, euthanatized, and forelimbs perfused with barium sulfate solution then fixed with formalin under tension. The tendons were transected every 5mm and microangiographic images were obtained using a Faxitron X-ray cabinet with computed radiography imaging. Microvascular analysis of sections proximal to the tenorrhaphy, throughout the tenorrhaphy and distal to the tenorrhaphy was completed using Image J software and a custom macro.
A significant reduction in the number of perfused vessels was seen in the SSS compared to the 3LP at two locations within the tenorrhaphy (p=0.004 and 0.039). The SSS technique took on average 4.7 ± 0.9 times longer to place.
The SSS technique causes a reduction in tendon perfusion compared to the 3LP, which may limit its clinical use. Further research is required to elucidate the clinical significance of this difference.Master of Science
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Parzy, Elodie. "Mise au point de techniques d'imagerie RMN par écho de spin rapide ou ultra-rapide adaptées à l'étude in vivo du petit animal." Paris 6, 2003. http://www.theses.fr/2003PA066471.
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Kyriacou, Panayiotis A. "Investigation of new electro optical techniques for monitoring patients with compromised peripheral perfusion in anaesthesia." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251876.
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Thomassin-Naggara, Isabelle. "Etude des tumeurs annexielles du pelvis féminin en IRM fonctionnelle : mise au point des techniques et applications cliniques." Paris 11, 2008. http://www.theses.fr/2008PA112116.
Повний текст джерелаАнотація:
La caractérisation préopératoire des tumeurs annexielles est déterminante pour la prise en charge chirurgicale. L’IRM fonctionnelle dynamique avec injection (DCE-MRI) permet une optimisation de la caractérisation des tissus. Les tumeurs annexielles se distinguent selon leur courbe dynamique de rehaussement qui reflètent l’immaturité de la paroi vasculaire et l’expression du VEGFR-2 sur les cellules endothéliales. En vue d’une analyse quantitative du rehaussement, il est souhaitable de réaliser une séquence turbo-FLASH avec des angles élevés pour obtenir une dynamique de rehaussement optimale associée à une quasi linéarité de la relation entre le signal et la concentration de gadolinium. L’initialisation par un modèle de Kéty étendu stabilise la modélisation compartimentale à 4 paramètres qui permet la description la plus complète des échanges entre les compartiments vasculaire et interstitiel. L’optimisation de l ’acquisition et du post traitement des datas ont permis la réalisation d ’une analyse quantitative de la prise de contraste, analyse reproductible et pertinente pour comprendre les phénomènes physiopathologiques au sein des tissus. Dans le domaine des tumeurs annexielles, la perfusion tissulaire et la fraction volumique sanguine sont plus élevées dans les tumeurs malignes que dans les tumeurs bénignes. Enfin, l ’analyse quqntitative du rehaussement a permis la mise en évidence de données pertinentes sur la perfusion du myométre et tout particulièrement du myomètre interne qui pourrait avoir une rôle majeur dans l ’avenir dans le cadre des programmes de procréation médicalement assistéeThe preoperative characterization of adnexal tumors is crucial for surgical care. Dynamic contrast enhanced MR imaging (DCE-MRI) allows an optimization of the tissue characterization. Adnexal tumors differ according to their dynamic curve enhancement, which reflect the immaturity of the vascular wall and the expression of VEGFR-2 on endothelial cells. For a quantitative analysis of enhancement, a turbo-FLASH sequence with high angles is better to get both optimal dynamic enhancement range and an almost linear relationship between the signal and the concentration of gadolinium. Initialization by a extended Kéty model stabilizes our two-compartmental model which allows the best description of exchanges between the capillary and the interstitial spaces. Using quantitative DCE MRI, malignant adnexal tumors display higher tissue perfusion and blood volume fraction than benign tumors. Finally, quantitative DCE-MRI is a suitable, non-invasive tool to assess physiological microvascular states and variations in normal myometrium, and could potentially be used to assess the role of the inner myometrium in assisted reproductive therapy
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MacEwen, Clare. "Can data fusion techniques predict adverse physiological events during haemodialysis?" Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:1ef92d5d-920d-4ff4-b368-5e892527e675.
Повний текст джерелаАнотація:
Intra-dialytic haemodynamic instability is a common and disabling problem which may lead to morbidity and mortality though repeated organ ischaemia, but it has proven difficult to link any particular blood pressure threshold with hard patient outcomes. The relationship between blood pressure and downstream organ ischaemia during haemodialysis has not been well characterised. Previous attempts to predict and prevent intra-dialytic hypotension have had mixed results, partly due to patient and event heterogeneity. Using the brain as the indicator organ, we aimed to model the dynamic relationship between blood pressure, real-time symptoms, downstream organ ischaemia during haemodialysis, in order to identify the most physiologically grounded, prognostic definition of intra-dialytic decompensation. Following on from this, we aimed to predict the onset of intra-dialytic decompensation using personalised, probabilistic models of multivariate, continuous physiological data, ultimately working towards an early warning system for intra-dialytic adverse events. This was a prospective study of 60 prevalent haemodialysis patients who underwent extensive, continuous physiological monitoring of haemodynamic, cardiorespiratory, tissue oxygenation and dialysis machine parameters for 3-4 weeks. In addition, longitudinal cognitive function testing was performed at baseline and at 12 months. Despite their use in clinical practice, we found that blood pressure thresholds alone have a poor trade off between sensitivity and specificity for predicting downstream tissue ischaemia during haemodialysis. However, the performance of blood pressure thresholds could be improved by stratification for the presence or absence of cerebral autoregulation, and personalising thresholds according to the individual lower limit of autoregulation. For patients without autoregulation, the optimal blood pressure target was a mean arterial pressure (MAP) of 70mmHg. A key finding was that cumulative intra-dialytic exposure to cerebral ischaemia, but not to hypotension per se, corresponded to change in executive cognitive function over 12 months. Therefore we chose cerebral ischaemia as the definition of intra-dialytic decompensation for predictive modelling. We were able to demonstrate that the development of cerebral desaturation could be anticipated from earlier deviations of univariate physiological data from the expected trajectory for a given patient, but sensitivity was limited by the heterogeneity of events even within one individual. The most useful phys- iological data streams included peripheral saturation variance, cerebral saturation variance, heart rate and mean arterial pressure. Multivariate data fusion techniques using these variables created promising personalised models capable of giving an early warning of decompensation. Future work will involve the refinement and prospective testing of these models. In addition, we envisage a prospective study assessing the benefit of autoregulation-guided blood pressure targets on short term outcomes such as patient symptoms and wellbeing, as well as longer term outcomes such as cognitive function.
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Vera, Pierre. "Optimisation de la détectabilité des anomalies de la perfusion cérébrale en tomographie d'émission monophotonique (Temp) : application à l'étude de l'épilepsie." Paris 11, 1999. http://www.theses.fr/1999PA11T012.
Повний текст джерелаАнотація:
Ce travail sur l'optimisation de la détectabilité des anomalies de perfusion en tomographie d'émission monophotonique (TEMP) comprend 3 parties : Premièrement, nous avons optimisé la détectabilité des hyperfixations en TEMP. Nous avons testé avec un fantôme de Jaszczak, l'influence de la géométrie du collimateur, de la taille de la matrice d'acquisition, de l'échantillonnage angulaire et du filtre de reconstruction sur la détectabilité de différentes tailles d'hyperfixation et différents niveaux de contraste. Le principal facteur permettant une augmentation de la restitution de contraste des hyperfixations est l'utilisation de collimateurs fan-beam. Deuxièmement, nous avons optimisé la localisation des anomalies de perfusion en TEMP dans l'espace stéréotaxique de Talairach. Nous avons proposé une méthode et développé un logiciel permettant (i) d'identifier les commissures antérieure (CA) et postérieure (CP) sur les images TEMP, et (ii) de construire la grille de l'atlas deTalairach sur chaque image TEMP. Cette méthode a été validée en comparant la localisation des points CA et CP définis par notre méthode, à leur localisation par la méthode IRM de référence. La précision moyenne de la localisation des points CA et CP est inférieure à 3 mm dans les 3 directions de l'espace. La reproductibilité de la méthode a été montrée. Le logiciel fait l'objet d'un développement industriel. Troisièmement, nous avons développé une méthode d'imagerie pour optimiser la localisation des hyperfixations en TEMP ictale. La méthode développée consiste à réaliser le recalage, la normalisation puis la soustraction de l'examen TEMP interictal à celui réalisé en période ictale. L'image de soustraction étant ensuite recalée puis superposée sur l'IRM. Cette méthode a été validée dans le cadre d'une étude prospective chez 27 enfants épileptiques. Cette méthode est concordante avec les données cliniques, EEG et IRM, plus précise, plus reproductible et plus simple à interpréter que la simple analyse des images TEMP ictales et interictales.
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Dhermain, Frédéric. "Apports des techniques d'imagerie par résonance magnétique de perfusion dans la caractérisation et le suivi des gliomes cérébraux." Paris 11, 2010. http://www.theses.fr/2010PA115045.
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Kay, Mark. "Evaluation of normothermic flush and perfusion techniques, using a novel normothermic preservation solution, in an isolated porcine haemoperfusion model." Thesis, University of Leicester, 2010. http://hdl.handle.net/2381/8326.
Повний текст джерелаАнотація:
The basis of the work in this thesis is an assessment of renal preservation techniques. The first chapter comprises a review of the pathophysiology of ischaemic injury and the role of hypothermic preservation. In the second chapter a review of the various preservation solutions in use is presented as well as the constituents of preservation solutions. The role of the organ flush is then presented, comparing warm and cold flush. The effect of viscosity and pressure is then examined followed by a review of hypothermic and normothermic preservation methods. The five main experimental chapters are then presented as a series of papers. The first of these aimed to assess the rate of organ cooling during back-table flush using different preservation solutions. In this paper, porcine kidneys were flushed with UW or Soltran solution, and the perfusion rate and cooling of the kidney was assessed. The second paper follows on comparing organ cooling using either a cold flush or a warm flush followed by a cold flush to compare flush rates and cooling times. The third paper assesses different flush techniques using a novel normothermic preservation solution, AQIX® RS-I, to assess the optimal flush conditions and functional outcomes. The fourth paper compares functional results of AQIX with the more commonly used cold flush solutions, Soltran and University of Wisconsin solution. The final experiment assesses the effectivness of complete normothermic preservation using AQIX® RS-I. An isolated organ perfusion system using cardiopulmonary bypass equipment was used for normothermic preservation and as a surrogate for transplantation. Porcine kidneys were used throughout all experiments as large animal models best reflect the human condition.
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Zimmer, Fabian [Verfasser], and Lothar Rudi [Akademischer Betreuer] Schad. "Development of Arterial Spin Labeling Techniques for Quantitative Perfusion Measurements at 3 Tesla / Fabian Zimmer ; Betreuer: Lothar Rudi Schad." Heidelberg : Universitätsbibliothek Heidelberg, 2014. http://d-nb.info/1180031709/34.
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Troalen, Thomas. "IRM quantitative de la perfusion myocardique par marquage de spins artériels = Quantitative myocardial perfusion MRI using arterial spin labeling." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5006/document.
Повний текст джерелаАнотація:
La perfusion est un facteur important dans la viabilité et la fonction du myocarde. Des atteintes microvasculaires diffuses, précédant l'infarctus ou l'insuffisance cardiaque sont impliqués dans bon nombre de pathologies cardiaques. Ce travail vise à améliorer les techniques existantes de mesure quantitatives et non-invasive de la perfusion myocardique par marquage de spins artériels (ASL). La première partie de mon travail de thèse a consisté en la mise place chez la souris d'une technique alternative pour mesurer la perfusion myocardique. Celle-ci est basée sur un marquage pulsé et régulièrement répété afin de construire un état d'équilibre de l'aimantation sous l'influence de la perfusion (approche steady-pulsed ASL). Le modèle théorique associé à cette technique spASL a été développé en parallèle afin de quantifier le flux sanguin tissulaire. Il a été montré que spASL permettait d'obtenir un résultat similaire aux techniques existantes avec en plus, les avantages d'améliorer la sensibilité au signal de perfusion ainsi que de réduire le temps d'acquisition. Dans un second temps, un transfert vers l'imagerie clinique pour une application chez l'homme a été entrepris. Le marquage de type spASL a été conservé et le module de lecture a été adapté aux spécificités de l'imagerie cardiaque chez l'homme pour une acquisition en respiration libre. Un post-traitement dédié qui comprend une correction de mouvement rétrospective a ensuite vu le jour afin d'améliorer la robustesse de nos mesures. Parallèlement aux développements conduits chez l'homme, nous avons exploité l'approche spASL chez l'animal en proposant diverses améliorations en fonction des études menéesMyocardial blood flow is an important factor of tissue viability and function. Diffuse changes in microcirculation preceding heart failure are involved in various cardiac pathologies. This work aim at improving existing techniques allowing quantitative and non-invasive myocardial perfusion assessment using arterial spin labeling. The first step of my work was to design an alternative approach to quantify myocardial blood flow in mice. The so called steady-pulsed ASL (spASL) is based on a regularly repeated pulsed labeling in order to build up a stationary regime of the magnetization under the influence of perfusion. The associated theoretical model has been developed in parallel to quantify tissue blood flow. We have shown that spASL allows to obtain similar results than the previously employed techniques, with the additional advantages of an increased sensitivity to the perfusion signal and a reduced acquisition time. A transfer towards clinical imaging for human applications was then undertaken. The spASL labeling scheme has been preserved while adapting the readout module to the specificities of cardiac MRI when applied to free-breathing human acquisitions. A dedicated post-processing, which includes a retrospective motion correction, has emerged subsequently to improve the robustness of our measurements. In parallel to the developments made for human studies, some optimization of the spASL technique when applied to rodent have been carried out depending on the conducted studies
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Lecocq, Angèle. "Optimisation des techniques non invasives d'IRM de perfusion cérébrale et d'imagerie spectroscopique par résonance magnétique pour l'exploration des pathologies cérébrales." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5065.
Повний текст джерелаАнотація:
L'IRM de perfusion et de spectroscopie restent encore peu utilisées en raison de leur mise en oeuvre difficile et de leur manque de quantification. L'objectif de ces travaux a été d'optimiser et de valider des techniques IRM totalement non invasives chez l'Homme en vue d'applications cliniques permettant une exploration sur un large volume cérébral et une quantification absolue des paramètres de perfusion et du métabolisme cérébraux. Concernant la perfusion, 3 séquences de type marquage de spins,PASL PICORE, PASL FAIR et pCASL, ont été comparées en termes de sensibilité et de reproductibilité. pCASL a ensuite été intégrée dans un protocole de recherche sur des patients atteints de sclérose en plaques ou SEP. Quant au métabolisme cérébral, un protocole a été mis en place afin d'accéder à une quantification absolue et pseudo absolue des métabolites par la normalisation du signal de l'eau issue de la CSI par la densité de protons acquise en IRM. Cette technique a été validée en CSI 2D puis transposée en 3D avec la séquence EPSI sur deux orientations différentes : CACP et CACP+15°afin de constituer des valeurs normatives fiables des métabolites principaux sur tout le cerveau. L'élaboration de ces techniques en spectroscopie a abouti à une étude sur des patients souffrant de SEP démontrant la faisabilité de l'utilisation de ces techniques en clinique. Ces travaux démontrent que la quantification absolue en IRM de perfusion et en IRM de spectroscopie peut être obtenue sur un large volume cérébral de manière fiable sur un système IRM disponible en environnement clinique dans un temps d'acquisition acceptable à travers les corrections diverses spécifiques à chaque imagerieConventional MRI's lack of specificity in clinical routine limits our ability to perform correct diagnoses or follow-ups of pathological diseases. Two forms of NMR imaging, perfusion weighed and spectroscopic imaging provide information about two closely related characteristics :cerebral perfusion and metabolism. However, these techniques are not widely used due to the complexity of implementation and a lack of quantification.The general aim was to optimize and validate completely non-invasive NMR techniques for further human clinical applications in the context of exploring large cerebral volumes and determining absolute or pseudo-absolute quantification of cerebral perfusion and metabolism. Concerning perfusion, three arterial spin labeling sequences, PASL PICORE, PASL FAIR and pCASL, were compared in terms of sensitivity and reproducibility. The pCASL sequence was then integrated to a protocol applied to patients suffering from multiple sclerosis. In relation to metabolism, a protocol was applied in order to access absolute and pseudo-absolute metabolite quantification by water SI normalization from MRI proton density. This technique was validated on 2D CSI and then on 3D with EPSI sequence with two orientations, AC-PC and AC-PC+15 in order to generate reliable normative values of metabolites for the whole brain. The use of those spectroscopic techniques on patients suffering from multiple sclerosis allowed demonstrating the feasibility in clinic.This work demonstrates that reliable absolute quantification in perfusion weighted and spectroscopic imaging can be obtained with extensive coverage and with an acquisition time compatible with the reality of clinical exams
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Djaoui, Fahima. "Quantification et systématisation 3D du débit sanguin cérébral à partir des images tomoscintigraphiques d'un traceur de perfusion à l'équilibre (HMPAO-TC99m,ECD-TC99m)." Université Louis Pasteur (Strasbourg) (1971-2008), 2003. http://www.theses.fr/2003STR13247.
Повний текст джерелаАнотація:
La méthode d'analyse graphique de Patlak est une technique non invasive de quantification du débit sanguin cérébral global (DSC). Elle repose sur une modélisation bi-compartimentale qui tient compte des caractéristiques physico-chimiques des traceurs employés (ECD-TC99m, HMPAO-TC99m). Le temps de transit du traceur, à travers la membrane hémato encéphalique, est déterminé par analyse graphique des courbes activité-temps. La correction de ce paramètre permet le calcul de l'indice de perfusion cérébrale préalable au calcul du DSC global. Des mesures du DSC global effectuées sur des cas cliniques montrent une forte corrélation entre les valeurs du DSC mesurées en intra- et inter-observateurs. En revanche, l'analyse des résultats expérimentaux relatifs à la quantification du DSC régional par tracé de régions d'intérêt (ROIs) sur des coupes TEMP de perfusion, met en évidence les limites de cette technique, en particulier pour les mesures inter observateurs et dans les cas pathologiques. Les paramètres engendrant cette variabilité sont : le choix des coupes planaires représentant la structure neuro-anatomique à étudier, l'épaisseur de ces coupes, ainsi que la taille des ROIs tracées. Il découle de ces tests expérimentaux qu'une approche volumique par recalage automatique d'un atlas cérébral représentant les structures à analyser constituerait la solution à ce problème. Ceci a fait l'objet de la deuxième partie de notre travail qui a consisté à caractériser automatiquement la variation du DSC dans des ROIs définies par recalage des images TEMP de perfusion et un modèle conceptuel de la systématisation vasculaire cérébrale conçu au sein de notre laboratoire. Cette approche de systématisation et de quantification automatique de la perfusion cérébrale a été testée sur une vingtaine de patients. Les résultats qui en ont découlé montrent l'efficacité de la technique et son utilité potentielle en routine cliniqueIn routine clinical studies it is certainly helpful to use non-invasive and simple techniques, to evaluate quantitatively the mean cerebral blood flow (CBF). Patlak graphical analysis approach, using intravenous radionuclide angiography with 99mTC-ECD or 99m TC-HMPAO, is a method witch does not require the determination of a specific compartment model, and based, only, on the evaluation of the unidirectional influx constant of the tracer across the blood brain barrier. The brain perfusion index, required to estimate the mean CBF, is calculated by standardisation of this influx rates value. The intra and inter observer variability studies indicates high reproducibility of this technique. However, after applying Lassen's correction algorithm to quantify SPECT images, the evaluation of regional CBF (rCBF) with conventional ROIs setting showed significant variability especially in inter-observer and for the pathological cases. This variability is due to many parameters like ROIs sizes, images selection and/or thickness, etc. To perform more precise results and less variability of cerebral perfusion quantification we have developed an original approach by constructing a 3D atlas of the systematisation of the brain vascularisation. This template is deformed to match rCBF SPECT volume. This process allows automatic characterisation of rCBF variation into vascular cerebral territories. In order to validate this technique, we examined the rCBF values of 26 patients with various cerebrovascular diseases. The results obtained from this experimentation showed that this technique is suitable for automatic quantification and systematisation of CBF in clinical routine
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Riou, Laurent. "Mecanismes de fixation cellulaire de tcn-noet, un nouveau traceur radioactif de la perfusion myocardique." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10111.
Повний текст джерелаАнотація:
Les maladies cardiovasculaires representent la premiere cause de mortalite en france. L'ischemie myocardique est principalement responsable de ces accidents. Le diagnostic de l'ischemie myocardique est actuellement effectue grace a la realisation de scintigraphies myocardiques apres injection d'un traceur radioactif du debit sanguin coronaire, le thallium 201. Cependant, le thallium 201 presente des inconvenients (dosimetrie elevee, energie d'emission mal adaptee, cout de production eleve). Le technetium-99m est un isotope mieux adapte (dosimetrie faible, energie d'emission bien adaptee, cout de production faible). Plusieurs complexes techneties ont ete proposes en remplacement du thallium 201, mais aucun ne presente le meme comportement. Le thallium 201 reste donc le traceur de debit le plus utilise. Tcn-noet est un nouveau complexe technetie presentant le meme comportement que le thallium 201 chez le chien et chez l'homme. Ce traceur est actuellement en essais cliniques de phase iii. L'objectif de ce travail est la determination des mecanismes de fixation cellulaire de tcn-noet. Les etudes realisees in vitro sur cardiomyocytes de rats nouveau-nes indiquent que la fixation cellulaire du traeur est independante de l'etat metabolique des cellules. Cette fixation est inhibee et augmentee par des drogues inhibant et activant, respectivement, les canaux calciques voltage-dependants membranaires. Compte-tenu de l'utilisation frequente des antagonistes calciques en pratique clinique, l'effet du verapamil, du diltiazem et de la nifedipine sur la fixation cardiaque de tcn-noet a ete evalue sur le modele du cur isole et perfuse de rat. Ces drogues sont sans effet sur l'activite cardiaque en tcn-noet. De meme, le verapamil n'affecte pas la fixation myocardique de tcn-noet in vivo chez le chien. Ceci peut s'expliquer par une fixation du traceur ex-vivo et in vivo sur l'endothelium vasculaire, qui ne presente pas de canaux calciques voltage-dependants. En conclusion, tcn-noet est le premier complexe technetie presentant le meme comportement que le thallium 201. In vitro sur cardiomyocytes, ses mecanismes de fixation cellulaire impliquent les canaux calciques voltage-dependants. L'effet d'inhibiteurs de ces canaux n'est pas mis en evidence ex vivo et in vivo, ce qui suggere qu'un traitement par inhibiteurs calciques n'affectera pas la fixation myocardique de tcn-noet en pratique clinique.
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Ferré, Jean-Christophe. "Evaluation et optimisation de lʹacquisition et du post-traitement de lʹétude de la perfusion cérébrale par ʺ Arterial Spin Labeling ʺ". Rennes 1, 2011. http://www.theses.fr/2011REN1B149.
Повний текст джерелаАнотація:
L’étude de la perfusion cérébrale par marquage des protons artériels ou « arterial spin labeling » (ASL) est une technique IRM, qui utilise comme traceur endogène les protons du sang artériel marqués magnétiquement. Cette technique permet une quantification fiable et reproductible du débit sanguin cérébral sans injection de produit de contraste exogène ni rayonnement ionisant. Son principal inconvénient est son faible rapport signal-sur-bruit. Alors que cette technique devient disponible sur les IRM cliniques, l’objectif de ce travail a été d’évaluer et d’optimiser l’acquisition et le traitement des données ASL de séquences disponibles sur deux IRM 3T. Nous avons ainsi étudié l’influence des paramètres hémodynamiques carotidiens sur le choix de paramètres de la séquences et nous avons montré l’intérêt de l’utilisation d’une antenne 32 canaux et de l’imagerie parallèle sur la qualité des cartographies. Au niveau du traitement des images, de nouvelles méthodes de débruitage spécifique des images ASL ont été étudiées et la mise en œuvre d’une chaîne de traitement complète a permis la comparaison de l’ASL fonctionnelle à l’IRMf BOLD. Une approche « Template » a aussi été évaluée pour la détection de variations individuelles focales de la perfusion. Nous avons appliqué l’ASL à la phase aiguë de l’accident vasculaire constitué ischémique et dans un domaine où l’ASL a été peu utilisée, la psychiatrie. Nos résultats ont montré que la conjonction des conditions optimales d’acquisition et d’un traitement optimisé des données devrait rendre plus pertinente l’utilisation de l’ASL dans le domaine de la recherche clinique mais aussi en routine cliniqueArterial spin labeling (ASL) is a magnetic resonance perfusion imaging technique for measuring cerebral blood flow (CBF) which uses magnetically labeled arterial blood water as an endogenous tracer. ASL is completely noninvasive and can be repeated because it is performed without injection of contrast media, or radiation exposure. Moreover, CBF quantification is convenient and reproducible. However ASL is a low signal-to-noise ratio measurement technique. This technique becomes available on clinical MRI scanner. In this context, the aim of this work was to assess and optimize the image acquisition and the data processing acquired with two clinical techniques. We have demonstrated a correlation between acquisition parameters and hemodynamic parameters and we showed a maps’ quality improving using 32-channel coil combined with parallel imaging. New denoising methods were implemented and an optimized complete workflow was used to compare fASL and BOLD fMRI. A “template” approach was also assessed to detect individual increased perfusion area. Clinically, we used ASL to detect hypoperfusion defect on acute ischemic stroke and focal perfusion abnormalities in patients with chronic and resistant depression. Our results showed that a combination of optimized conditions acquisition and dedicated processing could help ASL to be more accurate in clinical research and practice
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Roeloffs, Volkert Brar Verfasser], Jens [Akademischer Betreuer] [Gutachter] [Frahm, Marina [Gutachter] Bennati, and Michael [Gutachter] Bock. "Development of Advanced Acquisition and Reconstruction Techniques for Real-Time Perfusion MRI / Volkert Brar Roeloffs ; Gutachter: Jens Frahm, Marina Bennati, Michael Bock ; Betreuer: Jens Frahm." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/1123282986/34.
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Poujol, Julie. "Techniques d'acquisitions et reconstructions IRM rapides pour améliorer la détection du cancer du sein." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0143/document.
Повний текст джерелаАнотація:
Le cancer du sein est aujourd’hui le cancer le plus fréquent chez la femme ainsi que la première cause de décès féminin par cancer. Actuellement, l’IRM mammaire n’est réalisée qu’en seconde intention lorsque les autres modalités d’imagerie ne suffisent pas à poser un diagnostic. Dans le cas des populations à risque, l’IRM mammaire est recommandée comme examen de dépistage annuel en raison de sa très haute sensibilité de détection. Par IRM, la détection d’un cancer du sein se fait à la suite de l’injection d’un produit de contraste qui permet de visualiser les lésions mammaires en hypersignal. La majeure partie du diagnostic repose sur l’analyse morphologique de ces lésions ; une acquisition hautement résolue spatialement est donc nécessaire. Malgré l’utilisation des techniques d’accélération courantes, le volume de données à acquérir reste important et la résolution temporelle de l’examen d’IRM mammaire est aujourd’hui aux alentours d’une minute. Cette faible résolution temporelle limite donc intrinsèquement la spécificité de l’examen d’IRM mammaire. Un examen avec une haute résolution temporelle permettrait l’utilisation de modèles pharmacocinétiques donnant accès à des paramètres physiologiques spécifiques des lésions. L’approche proposée dans ce travail de thèse est le développement d’une séquence IRM permettant à la fois la reconstruction classique d’images, telle que celle utilisée en routine clinique pour le diagnostic, ainsi qu’une reconstruction accélérée d’images avec une plus haute résolution temporelle permettant ainsi l’application de modèles pharmacocinétiques. Le développement de cette séquence a été réalisé en modifiant l’ordre d’acquisition du domaine de Fourier de la séquence utilisée en clinique, afin qu’il soit aléatoire et permette la reconstruction a posteriori de domaines sous-échantillonnés acquis plus rapidement. Des acquisitions sur des objets tests, sur des volontaires et sur des patientes ont montré que l’acquisition aléatoire ne modifiait pas les images obtenues par reconstruction classique permettant ainsi le diagnostic conventionnel. Une attention particulière a été portée pour permettre la suppression de graisse nécessaire à l’acquisition des images d’IRM mammaire. Les reconstructions des domaines sous-échantillonnés sont réalisées via des reconstructions Compressed Sensing permettant la suppression des artéfacts de sous-échantillonnage. Ces reconstructions Compressed Sensing ont été développées et testées sur des fantômes numériques reproduisant des IRMs mammaires. Le potentiel de cette nouvelle acquisition a enfin été testé sur une lésion artificielle mammaire, développée à cet effet, et reproduisant des prises de contraste mammairesBreast cancer is nowadays the first cause of female cancer and the first cause of female death by cancer. Breast MRI is only performed in second intention when other imaging modalities cannot lead to a confident diagnosis. In high risk women population, breast MRI is recommended as an annual screening tool because of its higher sensitivity to detect breast cancer. Breast MRI needs contrast agent injection to visualize enhancing lesions and the diagnosis is mostly based on morphological analysis of these lesions. Therefore, an acquisition with high spatial resolution is needed. Despite the use of conventional MRI acceleration techniques, the volume of data to be acquired remains quite large and the temporal resolution of the exam is around one minute. This low temporal resolution may be the cause of the low specificity of breast MRI exam. Breast MRI with higher temporal resolution will allow the use of pharmacokinetic models to access physiological parameters and lesion specifications. The main aim of this work is to develop a MRI sequence allowing a flexible use of the acquired data at the reconstruction stage. On the one hand, the images can be reconstructed with a conventional reconstruction like the protocol used in clinical routine. On the other hand, the new MRI sequence will also allow the reconstruction of images with a higher temporal resolution allowing the use of pharmacokinetic models. The development of this sequence was done by modifying the acquisition order in the Fourier domain. A random acquisition of the Fourier domain will allow the reconstruction of sub-sampled domains acquired faster. We paid attention to fat suppression efficiency with this new Fourier domain acquisition order. Tests were performed on phantom, female volunteers and patients. These tests showed that the random acquisition did not impact the quality of images (MRI signal and lesion morphology) obtained by conventional reconstruction thus allowing the conventional diagnosis. The reconstructions of the sub-sampled Fourier domains were made using Compressed Sensing reconstructions to remove sub-sampling artifacts. These reconstructions were developed and tested on digital phantoms reproducing breast MRI. The potential of this new MRI acquisition was tested on an artificial enhancing breast lesion developed especially for this purpose
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Adams, William P. "Thyroid Hormone as a Method of Reducing Damage to Donor Hearts after Circulatory Arrest." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4766.
Повний текст джерелаАнотація:
There is a chronic lack of donor hearts to meet the need for heart transplant both in the US and worldwide. Further, the use of available hearts is limited by the short period between collection and implantation during which the heart can be safely preserved ex vivo. Using mid-thermic Langendorff machine perfusion, we have been able to preserve the metabolic function of a healthy heart for up to 8 hours, twice the limit for current static cold storage. We have also been able to preserve the metabolic function of a damaged DCD Heart collected 30 minutes after cardiac arrest for a period of 8 hours. We further investigated whether it was possible to improve the preservation of DCD heart using treatment with 10 μM Triiodothyronine to stimulate the tissue metabolism and we did find a reduction in damage markers in the treated DCD hearts as compared to the untreated group.
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He, Rui. "Évaluation d'une analyse voxel à voxel dans l'accident vasculaire cérébral à partir d'images IRM multiparamétriques." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAS026/document.
Повний текст джерелаАнотація:
L'accident vasculaire cérébral (AVC) est la principale cause de handicap acquis chez l'adulte. Au-delà de l'étroite fenêtre thérapeutique et des risques éventuels de la thrombolyse et de la thrombectomie mécanique, la thérapie cellulaire par cellules souches présente un fort potentiel. Plusieurs études ont montré que les cellules souches transplantées peuvent améliorer la récupération fonctionnelle après un AVC sur des modèles de rongeurs. L’imagerie multiparamétrique par résonance magnétique (IRM), qui inclue l'imagerie de diffusion et de perfusion, est aujourd’hui le protocole standard pour caractériser l'AVC. L'imagerie permet également de suivre in vivo les mécanismes sous-jacents de la thérapie cellulaire après un AVC de la phase aigüe à la phase chronique. Cependant, la quantification de l'hétérogénéité spatiale des lésions, clairement visible par IRM, reste un défi à l'heure actuelle. En effet, les techniques d'analyses d'images utilisées en routine sont basées sur le calcul des valeurs moyennes à partir de régions d'intérêts (ROI). Cette technique par ROI ne peut pas refléter l'hétérogénéité intra-lésionnelle. C'est pourquoi, de nouvelles stratégies d'analyses d'images doivent être développées et évaluées afin de quantifier l'hétérogénéité des lésions ischémiques mais aussi pour suivre l'évolution de cette hétérogénéité au cours du temps. Des approches utilisant des analyses par histogramme permettent d'évaluer l'hétérogénéité des lésions mais perdent l'information spatiale. Une alternative est l'utilisation d'une analyse d'image à l'échelle du voxel appelée "Parametric Response Map (PRM)". Cet outil a été décrit comme plus sensible que l'analyse par ROI dans le pronostic mais aussi dans le suivi thérapeutique chez des patients porteurs de tumeurs cérébrales ou encore atteints d'hémorragies cérébrales.Mon projet de thèse est divisé en deux parties: une étude préclinique chez le rat et une étude clinique (projet ISIS / HERMES). La première partie de ma thèse vise à évaluer les changements physiopathologiques mesurés par l'IRM après un traitement par cellules souches mésenchymateuses humaines (CSMh) sur un modèle d'AVC chez le rat. Des animaux présentant une occlusion transitoire de l'artère cérébrale moyenne (oACM) ou non (Sham) ont été traités ou non par une injection de CSMh. Au cours de cette étude, différents paramètres IRM ont été cartographiés en utilisant une IRM 7T (4 temps d'imagerie): le coefficient apparent de diffusion (ADC), le volume sanguin cérébral (CBV) et l'indice de taille des vaisseaux (VSI). Les cartes d'ADC, CBV et VSI ont été analysées en utilisant l'approche classique par ROI mais aussi par PRM. L'objectif de cette étude était de déterminer si l'analyse par PRM était capable de détecter plus précocement l'effet des CSMh que l'analyse par ROI. Durant la seconde partie de ma thèse, 6 paramètres IRM (imagerie de diffusion et de perfusion) ont été acquis chez 30 patients AVC. Les données IRM, analysées par valeur moyenne classique et par PRM, ont été corrélées avec des évaluations de la récupération fonctionnelle : le score NIHSS (National Institutes of Health Stroke Score) et l'échelle de Rankin modifiée (mRS) mesurés à différents temps post-ischémie. L’analyse PRM des cartes paramétriques IRM révèle des changements fins de la lésion et corrèle avec le pronostic à long terme après l’ischémie.En conclusion, la PRM pourrait être utilisée comme biomarqueur d’efficacité thérapeutique (combinaison d’images IRM et d’outils innovants d’analyse d'images) et comme biomarqueur pronostique des patients AVCStroke is the leading cause of disability in adults. Beyond the narrow time window and possible risks of thrombolysis and mechanical thrombectomy, cell-therapies have strong potential. Reports showed that transplanted stem cells can enhance functional recovery after ischemic stroke in rodent models.To assess the mechanisms underlying the cell-therapy benefit after stroke, imaging is necessary. Multiparametric magnetic resonance imaging (MRI), including diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI), has become the gold standard to evaluate stroke characteristics. MRI also plays an important role in the monitoring of cerebral tissue following stroke from the acute to the chronic phase. However, the spatial heterogeneity of each stroke lesion and its dynamic reorganization over time, which may be related to the effect of a therapy, remain a challenge for traditional image analysis techniques. To evaluate the effect of new therapeutic strategies, spatial and temporal lesion heterogeneities need to be more accurately characterized and quantified.The current image analysis techniques, based on mean values obtained from regions of interest (ROIs), hide the intralesional heterogeneity. Histogram-based techniques provide an evaluation of lesion heterogeneity but fail to yield spatial information. The parametric response map (PRM) is an alternative, voxel-based analysis technique, which has been established in oncology as a promising tool to better investigate parametric changes over time at the voxel level which concern the therapeutic response or prognosis of disease.The PhD project was divided into two parts: a preclinical and a clinical study. The goal of the first study was to evaluate the PRM analysis using MRI data collected after the intravenous injection of human mesenchymal stem cells (hMSCs) in an experimental stroke model. The apparent diffusion coefficient (ADC), cerebral blood volume (CBV) and vessel size index (VSI) were mapped using 7T MRI. Two analytic procedures, the standard whole-lesion approach and the PRM, were performed on data collected at 4 time points in transient middle cerebral artery occlusion (MCAo) models treated with either hMSC or vehicle and in sham animals. During the second PhD project, 6 MR parametric maps (diffusion and perfusion maps) were collected in 30 stroke patients (the ISIS / HERMES clinical trial). MRI data, analyzed with both a classic mean value and a PRM approaches, were correlated with the evaluation of functional recovery after stroke measured with the National Institutes of Health Stroke Scale (NIHSS) and the modified Rankin Scale (mRS) at 4 time points.In both studies, PRM analysis of MR parametric maps reveals fine changes of the lesion induced by a cell therapy (preclincal study) and correlate with long-term prognosis (clinical study).In conclusion, the PRM analysis could be used as an imaging biomarker of therapeutic efficacy and of prognostic biomarker of stroke patients
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Mouton, Olivier. "Étude du comportement biologique de bis (N-ethoxy, N-ethyldithiocarbamato) nitruro 99mTc(V), 99mTcN-NOET, un nouveau marqueur de la perfusion myocardique." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10296.
Повний текст джерелаАнотація:
Les traceurs radioactifs emetteurs de rayonnements sont les seuls outils disponibles permettant, par simple injection intraveineuse, l'analyse in vivo de la repartition regionale du debit sanguin coronaire. A l'heure actuelle, le radioelement utilise en medecine nucleaire est le thallium-201, un cation monovalent, considere comme un analogue du potassium. Cependant, le thallium-201 presente certains inconvenients (dosimetre et cout de production eleves). C'est pourquoi les recherches se sont orientees vers la synthese de molecules originales marquees au technetium-99m, les complexes techneties. Bis (n-ethoxy, n-ethyldithiocarbamato- nitrido #9#9#mtc (v), #9#9#mtcn-noet, un nouveau marqueur de la perfusion myocardique tres prometteur : du fait de sa redistribution, #9#9#mtcn-noet se presente comme un remplacant potentiel du thallium-201. Il est indispensable de connaitre les mecanismes de captation cellulaire de #9#9#mtcn-noet afin d'interpreter correctement les informations donnees par la tomoscintigraphie de perfusion myocardique. C'est pourquoi notre travail a consiste en etude du comportement biologique de #9#9#mtcn-noet. Comme ce marqueur lipophile et neutre est une molecule originale, nous avons choisi d'adopter une demarche systematique en considerant comme envisageable toute entree ou toute fixation par ou sur une structure membranaire. Des inhibitions specifiques de divers transports ioniques membranaires ont ete effectuees pour conclure en leur participation directe ou indirecte dans la fixation cellulaire de #9#9#mtcn-noet. Deux modeles experimentaux ont ete choisis : la culture primaire de cardiomyocytes de rats nouveau-nes (in vitro) et le cur isole et perfuse de rat (ex vivo). Les resultats obtenus in vitro ont montre que la fixation cellulaire de #9#9#mtcn-noet ne necessite pas d'atp et que parmi l'ensemble des transports ioniques inhibes, seuls les canaux calciques voltage-dependants de type l se sont reveles directement impliques dans les mecanismes de fixation cellulaire de #9#9#mtcn-noet. Le comportement biologique de #9#9#mtcn-noet est similaire sur les deux modeles biologiques. Ces resultats nous permettent d'envisager une interaction de #9#9#mtcn-noet avec les canaux calciques voltage-dependants de type l. Des etudes supplementaires seront necessaires pour mieux caracteriser la nature de cette interaction.
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Pagès, Pierre-Benoît. "Technique de perfusion pulmonaire isolée de chimiothérapie chez le porc." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOMU01/document.
Повний текст джерелаАнотація:
Introduction : La perfusion pulmonaire isolée (PPI) est une technique expérimentale dont l’objectif est d’administrer de fortes doses de chimiothérapie dans le poumon sans effets secondaires systémiques. Cette thèse s’est déroulée en trois étapes : première étape, déterminer in vitro la chimiothérapie la plus efficace en 30 minutes sur les cellules de cancers colo-rectaux (CCR). Deuxième étape, mettre au point la technique de PPI chez le porc. Troisième étape, mener une étude d’escalade de dose de chimiothérapie chez le porc en PPI.Méthodes : Première étape, des tests de cytotoxicité in vitro ont été menés sur un panel de cellules d’adénocarcinome colique humain avec les drogues de chimiothérapie les plus efficaces dans les essais cliniques. Deuxième étape, des porcs étaient traités par perfusion de chimiothérapie dans le poumon gauche isolé de la circulation générale pendant 30 minutes puis maintenus en vie pendant un mois. Troisième étape, les doses de chimiothérapie injectés étaient augmentées par palier jusqu’à obtenir une toxicité aigüe ou le décès des animaux.Résultats : La gemcitabine (GEM) fut la drogue ayant la plus grande efficacité anti-tumorale pour un traitement de 30 min. La PPI de GEM permit d’obtenir des concentrations élevées de GEM dans le parenchyme pulmonaire et la survie des animaux pendant un mois. Il n’existait pas de fuites systémiques de GEM. L’augmentation des doses de GEM permis de déterminer la dose maximale toxique à 320 mg et la toxicité limitant la dose à 640 mg. Conclusions : La technique de PPI avec la GEM est une technique sûre et reproductible permettant d’obtenir de fortes concentrations de GEM dans le parenchyme pulmonaireIntroduction: The isolated lung perfusion (ILP) is an experimental technique which main objective is to deliver high dose of cytotoxic agent to the lung tissue without systemic exposure. The thesis took place in three stages: first stage, setting in vitro the chemotherapy the most efficient against colorectal cancer (CCR) cells in 30 min. Second stage, develop the ILP technique in a pig model. Third stage, lead a dose escalation study with chemotherapy by ILP.Methods: First stage, efficacy of various cytotoxic molecules against a panel of human CCR cell lines was tested in vitro after a 30-minute exposure. Second stage, pigs were treated with chemotherapy delivered by ILP during 30 minutes and kept alive during a month. Third stage, chemotherapy doses were increase in order to obtain acute toxicity or death of animals.Results: Gemcitabine (GEM) was the most efficient drug against CCR cells in 30 minutes. ILP with GEM permit to maintain high concentration in the lung parenchyma and pigs survival during one month. No systemic leaks were detected. Dose increase of GEM conduct to determine the maximal tolerated dose of GEM by ILP to 320 mg. Conclusions: ILP with GEM is a safety and reproducible technique allowing high GEM concentrations in the lung tissue
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Ibarrola, Danielle. "Application des techniques d'imagerie par résonance magnétique nucléaire à l'étude préclinique de l'ischémie cérébrale focale : action d'un agent de contraste superparamagnétique et essai pharmacologique de l'effet d'un antagoniste du récepteur NMDA chez le rat in vivo." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE19003.
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Le, Gac de Lansalut Christina. "Chambres implantables pour perfusions intra-veineuses : bilan d'une expérience de 170 observations." Bordeaux 2, 1989. http://www.theses.fr/1989BOR25061.
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Verclytte, Sébastien. "Optimisation et évaluation de la perfusion cérébrale par technique de marquage de spin dans la Maladie d'Alzheimer à début précoce." Thesis, Lille 2, 2015. http://www.theses.fr/2015LIL2S029/document.
Повний текст джерелаАнотація:
Le diagnostic de maladie d'Alzheimer (MA) chez les patients de moins de 65 ans ou early-onset Alzheimer's disease (EOAD) est souvent difficile car la présentation clinique est fréquemment atypique, dominée par des signes non amnésiques. Les études antérieures sur les marqueurs de diagnostic précoce en imagerie se sont intéressées à l'imagerie structurelle et fonctionnelle dans l'EOAD mais aucune à la perfusion en IRM par la technique de marquage de spin ou arterial spin labeling (ASL). En effet, l'analyse de l'ASL demeure complexe, en particulier à l'échelle individuelle, du fait du faible rapport signal sur bruit des cartographies de perfusion et de l'hétérogénéité des zones atteintes à la phase initiale de la maladie. Notre premier objectif était technique et a consisté à optimiser l'interprétation des cartographies d'ASL grâce à la projection des anomalies de perfusion sur la surface du cortex extraite de l'acquisition morphologique T1 réalisée au cours du même examen, permettant d'accéder à une représentation tridimensionnelle interactive des données perfusionnelles. Le traitement des cartographies intégrait plusieurs étapes successives dont une correction des effets de volume partiel, une normalisation d'intensité spécifique et un lissage surfacique. Ce procédé a été appliqué sur les cartographies de 18 patients atteints d'EOAD avec une qualité de segmentation et de représentation des cartographies surfaciques obtenues jugées respectivement optimale et bonne dans 72 % des cas par deux lecteurs. Notre deuxième objectif était clinique et avait pour but de caractériser les altérations perfusionnelles et métaboliques par ASL et 18fluorodésoxuglucose-TEP (18F-FDG-TEP) sur un groupe de 37 patients atteints d'EOAD. Cette étude préliminaire à montré : (i) un pattern anatomique pathologique commun au niveau des lobules pariétaux inférieurs et des lobes temporaux ; (ii) des discordances entre les 2 techniques avec des lésions plus étendues en 18F-FDG-TEP et la détection en ASL de zones hypoperfusées additionnelles au niveau des lobes frontaux non visibles en 18F-FDGTEP. Ces deux travaux suggèrent que l'ASL pourrait donc devenir une séquence complémentaire clef dans l'arsenal des techniques d'imagerie utiles à un diagnostic précoce de l'EOAD et de la MA. Son utilisation en pratique clinique nécessite cependant une optimisation de sa représentation visuelle, et l'application corticale surfacique utilisée dans ce travail en représente une des voies potentiellesThe diagnosis of Alzheimer's disease (AD) in patients under the age of 65 years, called early-onset Alzheimer's disease (EOAD), remains a challenging issue due to the high incidence of atypical clinical presentations with non-memory symptoms. Although EAOD has been widely explored by structural and functional imaging, no previous study has examined the contribution of ASL in the assessment of cortical perfusion in this disease. Indeed, the analysis of ASL remains complex, especially at the individual level, due to the weak signal-to-noise ratio of the perfusion maps and the heterogeneity of pathological areas in the initial phase of the disease. Our first objective was technical and has consisted in optimizing the visual interpretation of ASL maps by the cortical surface-based projection of the perfusion alterations on the structural T1 sequence acquired during the same imaging protocol, providing a 3D interactive display of the perfusion data. Data processing included several successive steps, such as a partial volume effect correction, a specific intensity normalization and a surface-based smoothing process. It was applied on the perfusion maps of eighteen EOAD patients and the quality of segmentation and of cortical surface-based perfusion maps were scored as optimal in 72% in both cases by two readers. Our second objective was clinical and aimed to characterize the cerebral hypoperfusion and hypometabolism by ASL and 18F-FDG-PET in a group of 37 EOAD patients. Our preliminary study showed: (i) a similar pathological pattern located in the inferior parietal lobules and in the temporal cortex, (ii) discrepancies between the two modalities with the presence of more widespread hypometabolic regions detected by 18F-FDGPET and additionnai areas of alterations in the frontal lobes detected by ASL without apparent hypometabolism. Our studies suggest that ASL may become a useful complementary tool which, in combination with the existing structural and functional techniques, could offer improved efficiency in the difficult early detection of EOAD and AD. Its use in clinical practice, however, requires an optimization of its visual representation, and the cortical surface-based projection applied in this work represents one of the potential ways to this image quality improvement
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GIKUNDA, MILLICENT NKIROTE. "An improved sample loading technique for cellular metabolic response monitoring under pressure." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1470194454.
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Strang, Christof. "The Effect of CO2-Pneumoperitoneum on Ventilation Perfusion Distribution of the Lung." Doctoral thesis, Uppsala universitet, Klinisk fysiologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-149746.
Повний текст джерелаАнотація:
Laparoscopic operations are a common and popular way for abdominal procedures. They are usually performed by insufflation of carbon dioxide (CO2) into the abdominal cavity. However, insufflation of CO2 may interfere with cardiac and circulatory as well as respiratory functions. The CO2-pneumoperitoneum (PP) may cause hypercarbia and acidosis. The direct effects of CO2 and acidosis lead to decreased cardiac contractility, sensitization of the myocardium to arrhythmogenic effects of catecholamines and systemic vasodilatation. There may even be long-lasting post-operative effects on breathing control. The pneumoperitoneum may also cause several respiratory changes, e.g. decreased functional residual capacity (FRC) and vital capacity (VC), formation of atelectasis, reduced respiratory compliance and increased airway pressure. Still, arterial oxygenation is mostly maintained or even improved during PP. In view of the apparently contradictory results in respiratory mechanics and gas exchange, the present studies were performed to evaluate respiratory changes on gas exchange and ventilation-perfusion distributions during PP in a porcine model. It was demonstrated that atelectasis during anaesthesia and PP may be estimated by an increased arterial to endtidal PCO2-gradient (study I). Perfusion was redistributed away from dorsal, collapsed lung regions when PP was established. This resulted in a better ventilation-perfusion match (study II). Increasing abdominal pressure shifted blood flow more and more away from collapsed lung tissue, decreased pulmonary shunt and improved oxygenation from 8 to 16 mmHg PP, despite an increase of atelectasis formation (study III). CO2-PP enhanced the shift of blood flow towards better ventilated parts of the lung compared to Air-PP. Moreover, sodium natriumprusside worsened the ventilation-perfusion match even more and blunted the effects previously seen with carbon dioxide. CO2 should therefore be the mediator of enhancing HPV during PP. In conclusion, pneumoperitoneum with CO2 causes atelectasis with elimination of ventilation in the dependent lung regions. However, an efficient shift of blood flow away from collapsed, non-ventilated regions results in a better ventilation-perfusion matching and better oxygenation of blood than without PP. A prerequisite for the beneficial effect is the use of carbon dioxide for the abdominal inflation, since it enhances HPV.
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Duncan, Henry J. "An isotope washout technique to study skin perfusion pressure and vascular resistance in diabetes, hypertension and peripheral vascular disease /." Cover title, title page, table of contents and summary only, 1986. http://web4.library.adelaide.edu.au/theses/09MD/09mdd911.pdf.
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Ben, Mahmoud Sinan Marie Pierre-Yves. "Tomoscintigraphie de perfusion cérébrale dans l'épilepsie lobaire temporale pharmacorésistante comparaison des différentes méthodes d'analyse /." [S.l.] : [s.n.], 2007. http://www.scd.uhp-nancy.fr/docnum/SCDMED_T_2007_BEN_MAHMOUD_SINAN.pdf.
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Stupar, Vasile. "Polarisation d'hélium3 par la technique d'échange de spin et applications en IRM de la ventilation et de la perfusion pulmonaire." Lyon 1, 2004. http://www.theses.fr/2004LYO10105.
Повний текст джерелаАнотація:
L'utilisation des gaz dits "hyperpolarisés" (HP) en (IRM) a permis le développement de nouvelles techniques d'imagerie. Le premier chapitre est consacré au dispositif de pompage optique de l'hélium3 par la méthode d'échange de spin que nous avons développé. Le deuxième chapitre présente un respirateur dédié au petit animal, compatible IRM et avec l'hélium3 HP que nous avons développé et avec lequel nous avons pu réaliser des images anatomiques de ventilation pulmonaire de haute résolution spatiale et temporelle. Le troisième chapitre est dédié à la perfusion pulmonaire utilisant de l'hélium3 HP et des agents de contraste sur petit animal (rat). Des images de perfusion ainsi que des cartes paramétriques du volume sanguin pulmonaire relatif (rPBV) ont été obtenues. Le dernier chapitre présente le développement de la séquence STEAM avec deux applications : la mesure des coefficients de diffusion apparent de l'hélium3 et l'imagerie pulmonaire de ventilation/perfusion
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Zaccariotto, Eva. "The blood-brain barrier and San Filippo Syndrome: a model for pathophisiology studies of CNS in lysosomal storage diseases." Doctoral thesis, Università degli studi di Padova, 2009. http://hdl.handle.net/11577/3426008.
Повний текст джерелаАнотація:
The lysosomal storage diseases (LSDs) are a large and heterogeneous group of disorders resulting from defects in various aspects of lysosomal function. They commonly afflict infants and young children and mostly involve pathology of the brain which is currently untreatable when it’s present. All animals with a well developed central nervous system (CNS) have a blood-brain barrier (BBB) that largely isolates the brain from alterations in the composition of the blood stream and the continuous changes that take place in these general body fluids. This BBB also impedes the global CNS delivery of many therapeutic materials. Some studies in mouse models of lysosomal storage diseases, such as Batten and Sandhoff diseases and GM1 gangliosidosis, have also suggested that the BBB may be damaged as an integral part of the disease process. The aim of the present project was to determine whether similar changes to the BBB occur in Sanfilippo Syndrome. The in situ brain perfusion technique is the elective system for this study as it is not necessary to consider the effects of plasma binding, metabolism and other interactions within the body. Furthermore, it offers a superior sensitivity over other tracer based methods and can be used to precisely quantify the transport of solutes across the BBB. We developed a novel modification of the original technique of Takasato and Smith (1984) which ensures that all regions of the mouse brain are perfused rather than just the territory of a single carotid artery. This is important as in LSDs all brain regions are affected and in different mouse strains the circulus arteriosus cerebri exhibits different degrees of completeness (Ward et al. 1990). Thus the method allows full regional BBB function to be assessed, and the method can be applied to a comparison of genetically modified animals on differing genetic backgrounds. Several parameters, such as cerebral perfusion flow, brain vascular volume, and carrier-mediated transport of excitatory amino acids glutamic acid and glycine, were then investigated to determine whether the in situ brain perfusion method may be applied to the mouse without disturbance to the physical or functional integrity of the BBB. Electron microscopy studies with lanthanum nitrate were also performed to assess whether the tight junctions became leaky during the course of perfusion.
Once the in situ brain perfusion technique was established as a real tool for assessing the penetrance of tracers across the BBB, this method was applied to determine if there were changes to the BBB in mouse models of two of the Sanfilippo Syndrome diseases (MPS IIIA and MPS IIIB) compared with their respective control strains of mouse. [14C]-sucrose and [3H]-inulin were used to assess vascular volume, but do not normally penetrate the BBB, unless it is defective. [14C]-diazepam was used as a marker of cerebral blood flow; and [3H]-glycine, [3H]-glutamic acid and [3H]-tyrosine as carrier-mediated substances with low brain penetrance. These are neuro-excitatory amino acids which can cause brain damage if their entry into brain is increased. Initial findings in Sanfilippo syndrome from in situ brain perfusion technique, though they need to be confirmed and examined more fully, showed the typical clinical heterogeneity of Sanfilippo patients and clearly highlight that some changes occurred in the BBB.
Also the BBB permeability of [3H]- N-butyl-deoxynojirimycin (NB-DNJ, miglustat, Zavesca®) was assessed as it is currently employed for substrate-reduction therapy (SRT), is believed to penetrate the BBB and theoretically could be used to treat secondary storage in Sanfilippo Syndrome. From intraperitoneal injections of [3H]- NB-DNJ and evaluation of the unidirectional influx constant Kin for time intervals up to 60 minutes, a slow but progressive brain uptake of this small molecule was demonstrated.
An improved understanding of the BBB and its function, both in health and disease, is absolutely and critically necessary for development of successful new and improved drugs that may repair the BBB and in addition are also capable of crossing the normal BBB in order to further treat early CNS manifestations of Sanfilippo Syndrome. These studies will produce information which will aid drug targeting in general to the CNS and will further advance the possibility of treating a wide range of neurodegenerative diseases.Le patologie d’accumulo lisosomiale (LSD) rappresentano un grosso ed eterogeneo gruppo di malattie genetiche che derivano da difetti in diversi aspetti della biologia lisosomiale. Queste patologie interessano più comunemente i bambini, e per la maggior parte determinano coinvolgimento neurologico che, quando presente, non è trattabile. Tutti gli animali con un sistema nervoso centrale (SNC) ben sviluppato hanno una barriera emato-encefalica (BEE) che isola ampiamente il cervello dalle alterazioni nella composizione del flusso del sangue e dai continui cambiamenti che avvengono in generale in questi fluidi corporei. Questa barriera impedisce anche la somministrazione globale al SNC di molte sostanze terapeutiche. Diversi studi condotti in modelli murini delle malattie d’accumulo lisosomiale, come le patologie di Batten, Sandhoff e GM1 gangliosidosi, hanno inoltre suggerito che la BEE possa essere danneggiata come parte integrante del processo patologico. Lo scopo del presente progetto è stato quello di determinare se avvenissero simili cambiamenti nella BEE nella sindrome di Sanfilippo. La tecnica della perfusione cerebrale in situ è il sistema di elezione per questo studio in quanto per le molecole analizzate non è necessario considerare gli effetti dovuti ad eventuali legami con le proteine plasmatiche, metabolismo e altre interazioni all’interno del corpo. Inoltre, offre una sensibilità superiore rispetto ad altri metodi basati su tracciante e può essere usata per quantificare precisamente il trasporto di soluti attraverso la BEE. Abbiamo apportato una nuova modifica alla tecnica originale di Takasato e Smith (1984) che assicura che tutte le regioni del cervello del topo siano perfuse piuttosto che solo la zona di una singola carotide. Questo è importante poiché nelle LSD tutte le regioni cerebrali sono coinvolte e il circulus arteriosus cerebri presenta differenti gradi di completezza in diversi ceppi murini (Ward et al. 1990). Quindi il metodo permette che la funzione della BEE sia valutata in tutte le regioni, e può essere applicato per comparare animali modificati geneticamente di diversi background genetici. Diversi parametri, come il flusso della perfusione cerebrale, il volume vascolare del cervello, e il trasporto carrier-mediato degli amminoacidi acido glutammico e glicina, sono stati investigati per determinare se il metodo della perfusione cerebrale in situ possa essere applicato al topo senza disturbare l’integrità fisica e funzionale della BEE. Sono stati anche condotti studi con nitrato di lantano, e analizzati al microscopio elettronico, per valutare se le giunzioni occludenti subissero aperture durante il corso della perfusione. Una volta che la tecnica della perfusione cerebrale in situ è stata provata come strumento reale per la valutazione della penetrazione di traccianti attraverso la BEE, questo metodo è stato applicato per determinare se ci fossero cambiamenti nella BEE in modelli murini di due forme della sindrome di Sanfilippo (MPS IIIA e MPS IIIB) in confronto ai loro rispettivi ceppi murini di controllo. [14C]-saccarosio e [3H]-inulina sono stati impiegati per valutare il volume vascolare, ma normalmente non penetrano la membrana, a meno che non sia difettiva. [14C]-diazepam è stato utilizzato come marker del flusso sanguigno cerebrale; e [3H]-glicina, [3H]-acido glutammico e [3H]-tirosina come sostanze carrier-mediate a bassa penetrazione cerebrale. Questi sono amminoacidi neuro-eccitatori che possono causare danni al cervello se la loro entrata nel cervello è aumentata. Dati iniziali per la sindrome di Sanfilippo dalla tecnica della perfusione cerebrale in situ, sebbene necessitino di essere confermati e approfonditi, hanno dimostrato la tipica eterogeneità clinica dei pazienti di Sanfilippo ed evidenziano chiaramente che avvengono alcuni cambiamenti nella BEE. Anche la permeabilità di [3H]-N-butil-deossinojirimicina (NB-DNJ, miglustat, Zavesca®) alla BEE è stato valutata poichè è attualmente impiegata nella terapia di riduzione del substrato (SRT), si ritiene che penetri la BEE e teoricamente potrebbe essere usata per trattare l’accumulo secondario nella sindrome di Sanfilippo. Da iniezioni intraperitoneali di [3H]- NB-DNJ e valutazione della costante d’influsso unidirezionale Kin per intervalli di tempo fino a 60 minuti, un lento ma progressivo assorbimento di questa piccola molecola è stato dimostrato. Una comprensione maggiore della BEE e della sua funzione, sia in salute sia in malattia, è assolutamente e criticamente necessaria per lo sviluppo di farmaci nuovi e migliori che possano riparare la BEE e in più siano anche in grado di attraversare la BEE allo scopo di trattare manifestazioni precoci della sindrome di Sanfilippo nel SNC. Questi studi produrranno informazioni che aiuteranno la somministrazione di farmaci al SNC in generale e aumenteranno ulteriormente la possibilità di trattare un ampio numero di patologie neurodegenerative.
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Werndle, Melissa Cheng-Hwa. "Development of a novel technique to measure and characterise spinal cord perfusion pressure in patients with acute traumatic spinal cord injury." Thesis, St George's, University of London, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675934.
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Background There is no method in clinical use for measuring intraspinal pressure (ISP) and spinal cord perfusion pressure (SCPP) after traumatic spinal cord injury (TSCI) in humans. I hypothesised monitoring ISP and optimising SCPP may improve spinal cord function after injury. The thesis was performed in three stages. Methods (1) I ascertained the views of consultant neurosurgeons and neuroanaesthetists on the acute management of TSCI , via a survey. (2) A pressure probe was placed subdurally at the injury site in 18 patients with severe TSCI. Recording commenced within 72 hours of injury and continued for up to one week. Spinal cord blood flow was assessed using indocyanine green fluorescence, and spinal cord function using a limb motor score, motor evoked potentials (MEPs) and an index of autoregulation (sPRx). I explored the effect of different treatments on SCPP. (3) 134 magnetic resonance (MR) scans from 93 TSCI patients were analysed. In 14 patients with motor complete TSCI, I evaluated the effect of laminectomy on ISP, SCPP and compensatory reserve (sRAP). Results (1) The acute management of TSCI by U.K. neurosurgeons and neuroanaesthetists is highly variable, both surgically and in intensive care. (2) There were no procedure related complications with ISP monitoring. ISP was higher in 18 TSCI patients compared to 12 subjects without TSCI. Changes in PC02, sevoflurane concentration and mannitol administration had no significant effect on ISP or SCPP. Inotropes increased ISP with a net increase in SCPP. Increasing SCPP increased MEP amplitude and ICG fluorescence in some patients. (3) On MR, 26% TSCI patients had dural compression. Compared with intact lamina patients, the laminectomy group had lower ISP, comparable SCPP and comparable sRAP. In the laminectomy group, ISP remained high (>20mmHg) 41% of the time, and SCPP low «60mmHg) 24% of the time. Conclusions I provide proof-of-principle that subdural intraspinal pressure at the injury site can be measured with low risk after TSCI. Optimising SCPP improves motor function in some patients. The dura is responsible for spinal cord compression in a quarter of patients. Though bony realignment with laminectomy reduces ISP, it does not effectively decompress the spinal cord and does not increase spinal cord perfusion.
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Watanabe, Yuji, Gerhard P. Püschel, Andreas Gardemann, and Kurt Jungermann. "Presinusoidal and proximal intrasinusoidal confluence of hepatic artery and portal vein in rat liver : functional evidence by orthograde and retrograde bivascular perfusion." Universität Potsdam, 1994. http://opus.kobv.de/ubp/volltexte/2008/1670/.
Повний текст джерелаАнотація:
The site of confluence of the artery and the portal vein in the liver still appears to be controversial. Anatomical studies suggested a presinusoidal or an intrasinusoidal confluence in the first, second or even final third of the sinusoids. The objective of this investigation was to study the problem with functional biochemical techniques. Rat livers were perfused through the hepatic artery and simultaneously either in the orthograde direction from the portal vein to the hepatic vein or in the retrograde direction from the hepatic vein to the portal vein. Arterial how was linearly dependent on arterial pressure between 70 cm H2O and 120 cm H2O at a constant portal or hepatovenous pressure of 18 cm H2O. An arterial pressure of 100 cm H2O was required for the maintenance of a homogeneous orthograde perfusion of the whole parenchyma and of a physiologic ratio of arterial to portal how of about 1:3. Glucagon was infused either through the artery or the portal vein and hepatic vein, respectively, to a submaximally effective ''calculated'' sinusoidal concentration after mixing of 0.1 nmol/L. During orthograde perfusions, arterial and portal glucagon caused the same increases in glucose output. Yet during retrograde perfusions, hepatovenous glucagon elicited metabolic alterations equal to those in orthograde perfusions, whereas arterial glucagon effected changes strongly reduced to between 10% and 50%. Arterially infused trypan blue was distributed homogeneously in the parenchyma during orthograde perfusions, whereas it reached clearly smaller areas of parenchyma during retrograde perfusions. Finally, arterially applied acridine orange was taken up by all periportal hepatocytes in the proximal half of the acinus during orthograde perfusions but only by a much smaller portion of periportal cells in the proximal third of the acinus during retrograde perfusions. These findings suggest that in rat liver, the hepatic artery and the portal vein mix before and within the first third of the sinusoids, rather than in the middle or even last third.
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Desmoulin, Franck. "La Spectroscopie de résonance magnétique nucléaire : une nouvelle technique d'investigation du métabolisme hépatique. Application à l'étude du métabolisme énergétique et intermédiaire sur le Foie. Métabolisme. Résonance magnétique de rat excisé perfusé." Aix-Marseille 1, 1986. http://www.theses.fr/1986AIX11040.
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Pádua, Rodrigo Donizete Santana de. "Corregistro de imagens aplicado à construção de modelos de normalidade de SPECT cardíaco e detecção de defeitos de perfusão miocárdica." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/82/82131/tde-02052012-154125/.
Повний текст джерелаАнотація:
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.
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Favre, de Thierrens Carle. "Contribution à l'étude de l'incidence des molécules-signaux du système neuro-endocrinien dans la physiopathologie odontologique : apport de la technique de "perfusion push-pull modifiée" à l'étude in vivo des prostaglandines et des enképhalines pulpaires ; détection et quantification radioimmunologique de somatostatine-IR dans la pulpe dentaire du rat." Montpellier 1, 1996. http://www.theses.fr/1996MON12200.
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