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Dissertations / Theses on the topic 'Oxygenation imaging'
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1
Huang, Jiwei. "Multispectral Imaging of Skin Oxygenation." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1356637098.
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Sivaramakrishnan, Mathangi. "In vivo blood oxygenation level measurements using photoacoustic microscopy." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5851.
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We investigate the possibility of extracting accurate functional information such
as local blood oxygenation level using multi-wavelength photoacoustic measurements.
Photoacoustic microscope is utilized to acquire images of microvasculature in smallanimal
skin. Owing to endogenous optical contrast, optical spectral information obtained
from spectral photoacoustic measurements are successfully inverted to yield oxygenation
level in blood. Analysis of error propagation from photoacoustic measurements to
inverted quantities showed minimum inversion error in the optical wavelength region of
570-600 nm. To obtain accurate and vessel size independent blood oxygenation
measurements, transducers with central frequency of more than 25 MHz are needed for
the optical region of 570-600 nm used in this study. The effect of transducer focal
position on accuracy of blood oxygenation level quantification was found to be
negligible. To obtain accurate measurements in vivo, one needs to compensate for
factors such as spectral dependent optical attenuation.
3
Lidegran, Marika. "Advanced radiological imaging in patients treated with extracorporeal membrane oxygenation /." Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-933-5/.
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Chen, T. "Hyperspectral imaging for the remote sensing of blood oxygenation and emotions." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7502.
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This PhD project is a basic research and it concerns with how human’s physiological features, such as tissue oxygen saturation (StO2), can be captured from a stand-off distance and then to understand how this remotely acquired physiological feature can be deployed for biomedical and other applications. This work utilises Hyperspectral Imaging (HSI) within the diffuse optical scattering framework, to assess the StO2 in a contactless remote sensing manner. The assessment involves a detailed investigation about the wavelength dependence of diffuse optical scattering from the skin as well as body tissues, under various forms of optical absorption models. It is concluded that the threechromophore extended Beer Lambert Law model is better suited for assessing the palm and facial tissue oxygenations, especially when spectral data in the wavelengths region of [516-580]nm is used for the analysis. A first attempt of using the facial StO2 to detect and to classify people’s emotional state is initiated in this project. The objective of this work is to understand how strong emotions, such as distress that caused by mental or physical stimulations, can be detected using physiological feature such as StO2. Based on data collected from ~20 participants, it is found that the forehead StO2 is elevated upon the onset of strong emotions that triggered by mental stimulation. The StO2 pattern in the facial region upon strong emotions that are initiated by physical stimulations is quite complicated, and further work is needed for a better understanding of the interplays between bodily physique, individual’s health condition and blood transfusion control mechanism. Most of this work has already been published and future research to follow up when the author returns back to China is highlighted.
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Tomaszewski, Michal Robert. "Functional imaging of cancer using Optoacoustic Tomography." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/284931.
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Poor oxygenation of solid tumours has been linked with resistance to chemo- and radio-therapy and poor patient outcomes. Measuring the functional status of the tumour vasculature, including blood flow fluctuations and changes in oxygenation is important in cancer staging and therapy monitoring. A robust method is needed for clinical non-invasive measurement of the oxygen supply and demand in tumours. Current clinically approved imaging modalities suffer high cost, long procedure times and limited spatio-temporal resolution. Optoacoustic tomography (OT) is an emerging clinical imaging modality that can provide static images of endogenous haemoglobin concentration and oxygenation. In this work, an integrated framework for quantitative analysis of functional imaging using OT is developed and applied in vivo with preclinical cancer models. Oxygen Enhanced (OE)-OT is established here to provide insight into tumour vascular function and oxygen availability in the tissue. Tracking oxygenation dynamics using OE-OT reveals significant differences between two prostate cancer models in nude mice with markedly different vascular function (PC3 & LNCaP), which appear identical in static OT. OE-OT metrics are shown to be highly repeatable and correlate directly on a per-tumour basis to tumour vascular maturity, hypoxia and necrosis, assessed ex vivo. Dynamic Contrast Enhanced (DCE) OT demonstrates the relationship between OE-OT response and tumour perfusion in vivo. Finally, the possibility of using OT data acquired at longer wavelengths to report on tumour water and lipid content is investigated, with a view to future providing intrinsically co-registered imaging of tumour oxygenation and cellular necrosis. These findings indicate that OE-OT holds potential for application in prostate cancer patients, to improve delineation of aggressive and indolent disease, while combined with DCE-OT, it may offer significant advantage for localised imaging of tumour response to vascular targeted therapies. Further work is needed to establish whether OT can provide a new method to detect tumour necrosis in vivo.
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Alonzi, Roberto. "Evaluation of the oxygenation and vascularity of prostate cancer using magnetic resonance imaging." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444256/.
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The outcome of radical treatment for prostate cancer is appreciably influenced by the presence of hypoxia. Oxygenation status may therefore be another underlying biological parameter, beyond the classic prognostic factors (age, clinical stage, Gleason score and prostate specific antigen), that predicts for treatment failure in this malignancy. Angiogenesis plays a pivotal role in the growth, invasion, metastasis and survival of prostate tumours. Measurements of angiogenesis have been linked with clinical and pathological stage, histological grade and the potential for metastasis formation. They also provide prognostic information and have been correlated with disease-specific survival and progression after treatment. Magnetic resonance imaging techniques are capable of detecting the molecular, biochemical, physiological and metabolic changes that occur due to pathological processes within tissues. Experiments presented in this thesis have sought to evaluate the ability of Dynamic Contrast Enhanced MRI (DCE-MRI), Dynamic Susceptibility Contrast MRI (DSC-MRI), Intrinsic Susceptibility Weighted MRI (also known as Blood Oxygen Level Dependent (BOLD) MRI) and Diffusion Weighted Imaging (DWI) to characterise the oxygenation and vascular status of prostate tumours in animal models and in patients with prostate cancer. This research has demonstrated the feasibility of hypoxia imaging in prostate cancer. Although MRI can not precisely map tissue p02, the combination of BOLD-MRI and dynamic susceptibility contrast MRI provides a valuable surrogate and predicts the pattern of hypoxia, as determined by pimonidazole immunohistochemistry, with reasonable accuracy. The research has also shown that prostate cancer responds to carbogen gas breathing and that androgen deprivation causes profound vascular collapse within one month of starting therapy. These findings should help in the rational design of future studies that aim to target tumour vasculature and combat tumour hypoxia in prostate cancer.
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Fan, Audrey Peiwen. "Development, testing, and application of quantitative oxygenation imaging from magnetic susceptibility by MRI." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89990.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 101-133).
The healthy brain consumes 20% of total oxygen used by the body under normal conditions. Continuous oxygen delivery to neural tissue is needed to maintain normal brain function and viability. Reliable measurements of brain oxygenation can provide critical information to diagnose and manage diseases in which this oxygen supply is disturbed, including stroke and tumor. In acute stroke, for instance, metabolic biomarkers such as local oxygen extraction fraction (OEF) have been shown to identify tissue at risk of infarction by positron emission tomography. This knowledge can then be used to identify patients who are candidates for reperfusion therapies or to avoid thrombolytic therapy in futile situations. Unfortunately, there is currently no clinically feasible method for radiologists to assess brain oxygenation in patients. My thesis aims to address this need through development of a clinically viable tool to examine regional OEF in the brain with magnetic resonance imaging (MRI). We have designed a novel imaging and analysis method to quantify oxygenation in cerebral veins. MRI phase images are sensitive to local, oxygenation-dependent magnetic field variations in brain vessels, due to the presence of paramagnetic deoxyhemoglobin molecules in venous blood. Our method was developed on a 3 Tesla MRI scanner and tested in 10 healthy volunteers during hypercapnia, i.e. breathing of low levels of CO₂. This respiratory challenge changes the baseline oxygenation state of the brain, enabling us to test whether our MRI method can detect different levels of OEF in vivo. We also show that OEF is reduced in 23 patients with multiple sclerosis, an autoimmune disease of the central nervous disease, and relates to their performance on cognitive tasks.
by Audrey P. Fan.
Ph. D.
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Huen, Isaac Kwong-Ping. "Assessment of placental and fetal oxygenation in normal and abnormal pregnancy using magnetic resonance imaging." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/assessment-of-placental-and-fetal-oxygenation-in-normal-and-abnormal-pregnancy-using-magnetic-resonance-imaging(8cd3f9a2-22cb-4c95-bee3-06b5c4bfc2d2).html.
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Fetal growth restriction (FGR) is a common pregnancy complication resulting in increased neonatal mortality and morbidity. The aetiology of fetal growth restriction is not fully understood, but abnormalities in placental development are, leading to abnormalities in placental structure which are thought to affect supply of oxygen to the fetus. The source of fetal hypoxia is unknown due to the difficulty in obtaining oxygenation data in the context of pregnancy using existing techniques. There is also an absence of data relating to oxygenation in FGR pregnancies. Oxygen-Enhanced MRI (OE-MRI) and Blood Oxygen-Level Dependent (BOLD) MRI permit noninvasive acquisition of data related to changes in the concentration of dissolved oxygen (pO2) and changes in hemoglobin saturation (sO2) under air- and oxygen- breathing (hyperoxic challenge).The aim of this project was to determine whether MRI methods can provide information relating to placental oxygenation in normal and FGR-compromised pregnancy, to investigate fetal brain oxygenation and to assess the potential confound of placental perfusion changes under hyperoxic challenge. After optimization of sequences in non-pregnant volunteers, similar pO2 and sO2 increases under hyperoxic challenge were seen in normal and FGR pregnancy. This suggested placental oxygenation was similar and that fetal extraction of oxygen may be a likelier cause of fetal hypoxia. Normal fetal brain oxygenation was found not to increase under hyperoxic challenge, which may be due to hemodynamic adaptation to limit cerebral hyperoxygenation. Finally, the robustness of these oxygenation results was supported by the lack of placental perfusion changes observed under hyperoxia using Arterial Spin Labeling (ASL).In conclusion, MRI methods successfully provided information on placental and fetal oxygenation in normal and abnormal pregnancy, obtaining novel data informing the aetiology of FGR and the physiology of the fetal brain.
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Schafer, Rachel Lynn. "Mammary Window Chamber Model: A Platform For Multi-Modality Cancer Imaging And Dynamic Oxygenation Assessment." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/556436.
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Window chamber models have served as a tool for optically visualizing a tissue environment over time. Their use throughout the years has furthered the study of cancer. However, optical imaging techniques utilized with the model are limited in the depth from which light can penetrate and signal can be received. Further, ectopic placement of a xenograft in a model animal may modify the relevancy of findings by altering the normal environmental conditions. In the first section of the dissertation, improvements on the traditional window chamber model are described in the context of enabling multiple imaging modalities (optical, MR and nuclear) to be complementarily applied. The developed model, specifically geared toward breast cancer, is orthotopic and supports uninhibited tumor growth into the body of the animal. The three main imaging modalities applied provide unique strengths in obtaining information from the model system. Optical imaging allows for use of targeted fluorescent contrast agents, as well as sufficient resolution to visualize individual cells and capillaries. Magnetic resonance imaging provides the possibility of acquiring quantitative information about tumor morphology as well as a variety of physiological processes. This can be accomplished over the entire 3D volume of the tumor. Nuclear imaging provides functional and/or metabolic information using radiolabeled agents. The MWC model provides a platform for more specifically focused cancer imaging approaches to be applied and tested. The presence of hypoxia in tumors has a broad impact on cancer development and treatment. Current oxygenation assessment methods for longitudinally following spatially resolved oxygen changes over time are lacking. The development and testing of an oxygen sensitive porphyrin coating used in conjunction with the mammary window chamber model is detailed in the second section of the dissertation. Three different modulations were applied to induce physiologic oxygenation changes. All were capable of being detected over time utilizing a phosphorescence lifetime approach. An assessment of the stability of the coating found the coating remained suitable for a minimum of one week. The oxygen dependent phosphorescence lifetime of the coating was determined to be worthwhile for temporally and spatially monitoring oxygen changes of the tissue in contact with the surface of the coating. The third section of this dissertation work utilized the developed window chamber and oxygen measurement technique to investigate a novel oxygen modulator. The effectiveness of radiation therapy is reduced in tumors with low oxygen. The drug, NVX-108, is under investigation as a means to increase oxygenation prior to radiation treatment. NVX-108 is given while the patient breaths carbogen and has not been thoroughly tested when the patient is breathing oxygen or air. The study described herein focused on measuring the increase in oxygenation when NVX-108 was delivered while an anesthetized mouse breathed carbogen, oxygen or air. A similar average increase was measured under carbogen and oxygen breathing at two dosage levels of NVX-108. The increase was higher than with air breathing conditions. Additional animal experiments are needed in order to obtain a statistically significant finding.
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Hu, Qiuhua. "Investigating prostate tumour vasculature and oxygenation status in response to androgen-targeted therapies using photoacoustic-ultrasound imaging." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/228679/8/Qiuhua_Hu_Thesis.pdf.
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This project provides a holistic view of changes in the prostate cancer microenvironment in response to androgen targeted therapies. Oxygen saturation and total haemoglobin were monitored using the ultrasound and photoacoustic imaging capabilities of the VEVO LAZR system (FUJIFILM Visual Sonics Inc) and compared with measuring hypoxic and vascular markers using conventional protein and gene expression techniques. Understanding the effects of castration and enzalutamide on the vasculature and oxygenation status of prostate cancer subcutaneous xenografts has the potential to reveal novel mechanisms of therapy resistance and may improve the prediction of patient therapy responses.
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Thomas, Sebastian Fritjof [Verfasser], and Lothar R. [Akademischer Betreuer] Schad. "Quantification of brain tissue oxygenation using magnetic resonance imaging - simulation and in vivo study / Sebastian Fritjof Thomas ; Betreuer: Lothar R. Schad." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1222596059/34.
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Dolet, Aneline. "2D and 3D multispectral photoacoustic imaging - Application to the evaluation of blood oxygen concentration." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI070/document.
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L'imagerie photoacoustique est une modalité d'imagerie fonctionnelle basée sur la génération d'ondes acoustiques par des tissus soumis à une illumination optique (impulsion laser). L'utilisation de différentes longueurs d'ondes optiques permet la discrimination des milieux imagés. Cette modalité est prometteuse pour de nombreuses applications médicales liées, par exemple, à la croissance, au vieillissement et à l'évolution de la vascularisation des tissus. En effet, l'accès à l'oxygénation du sang dans les tissus est rendu possible par l'imagerie photoacoustique. Cela permet, entre autres applications, la discrimination de tumeurs bénignes ou malignes et la datation de la mort tissulaire (nécrose). Ce travail de thèse a pour objectif principal la construction d'une chaîne de traitement des données photoacoustiques multispectrales pour le calcul de l'oxygénation du sang dans les tissus. Les principales étapes sont, d'une part, la discrimination des données (clustering), pour extraire les zones d'intérêt, et d'autre part, la quantification des différents constituants présents dans celles-ci (unmixing). Plusieurs méthodes non supervisées de discrimination et de quantification ont été développées et leurs performances comparées sur des données photoacoustiques multispectrales expérimentales. Celles-ci ont été acquises sur la plateforme photoacoustique du laboratoire, lors de collaborations avec d'autres laboratoires et également sur un système commercial. Pour la validation des méthodes développées, de nombreux fantômes contenant différents absorbeurs optiques ont été conçus. Lors du séjour de cotutelle de thèse en Italie, des modes d'imagerie spécifiques pour l'imagerie photoacoustique 2D et 3D temps-réel ont été développés sur un échographe de recherche. Enfin, des acquisitions in vivo sur modèle animal (souris) au moyen d'un système commercial ont été réalisées pour valider ces développementsPhotoacoustic imaging is a functional technique based on the creation of acoustic waves from tissues excited by an optical source (laser pulses). The illumination of a region of interest, with a range of optical wavelengths, allows the discrimination of the imaged media. This modality is promising for various medical applications in which growth, aging and evolution of tissue vascularization have to be studied. Thereby, photoacoustic imaging provides access to blood oxygenation in biological tissues and also allows the discrimination of benign or malignant tumors and the dating of tissue death (necrosis). The present thesis aims at developing a multispectral photoacoustic image processing chain for the calculation of blood oxygenation in biological tissues. The main steps are, first, the data discrimination (clustering), to extract the regions of interest, and second, the quantification of the different media in these regions (unmixing). Several unsupervised clustering and unmixing methods have been developed and their performance compared on experimental multispectral photoacoustic data. They were acquired on the experimental photoacoustic platform of the laboratory, during collaborations with other laboratories and also on a commercial system. For the validation of the developed methods, many phantoms containing different optical absorbers have been produced. During the co-supervision stay in Italy, specific imaging modes for 2D and 3D real-time photoacoustic imaging were developed on a research scanner. Finally, in vivo acquisitions using a commercial system were conducted on animal model (mouse) to validate these developments
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Ségaud, Silvère. "Multispectral optical imaging in real-time for surgery." Electronic Thesis or Diss., Strasbourg, 2022. http://www.theses.fr/2022STRAD055.
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Le développent technologique des salles d’opérations a accéléré de manière spectaculaire ces dernières années. Cependant, la capacité des praticiens à différencier les tissus sains des tissus malsains à travers le champ chirurgical est principalement basée sur leur propre perception et expérience. Ceci est pourtant d’une importance majeure en chirurgie oncologique, tant pour la résection de tumeurs que pour les actes de reconstruction. C’est pourquoi la capacité d’évaluer le statut des tissus biologiques à travers des zones étendues en temps réel est cruciale. Le manque d’outils permettant l’évaluation de la viabilité des tissus biologique dans un contexte intra opératoire a été la motivation principale de ce projet. Un prototype d’imageur multimodal clinique a été développé pour l’imagerie d’oxygénation et de fluorescence en temps-réel. La capacité de la plateforme à quantifier l’ischémie a été démontrée lors de tests précliniques, par comparaison avec les méthodes standards. Le caractère multimodal de la plateforme d’imagerie a été exploité pour combiner l’imagerie endogène mesurant les propriétés optiques des tissus et l’imagerie exogène par fluorescence, dans le cadre de la chirurgie du cancer. Une méthode de quantification a été employée lors d’essais précliniques sur des modèles de cancers colorectaux et pancréatiques, mettant en évidence les défaillances de l’imagerie de fluorescence conventionnelleThe deployment of technology in operating rooms dramatically accelerated over the last decades. More precisely, the surgeons’ ability to distinguish healthy from diseased tissues is still mostly based on their own subjective perception. As tissue status assessment is of upmost importance in oncologic surgery, both for tumor resection and reconstruction procedures, the ability to assess the tissues intraoperatively and in real-time over a large field is crucial for surgical act guidance. The lack of tools for biological intraoperative tissue status assessment has been the main source of motivation for this thesis work. A clinically-compatible imaging platform has been developed for oxygenation and fluorescence imaging in real-time. The capability of the platform to detect and quantify ischemia has been demonstrated through preclinical trials, by comparison with standard of care methods. Furthermore, the multimodal nature of the developed imaging device has been exploited by combining endogenous imaging of optical properties with exogenous fluorescence imaging, in the context of oncologic surgery. A fluorescence quantification technique was validated in preclinical trials with colorectal and pancreatic cancer models, highlighting the limitations of conventional fluorescence imaging
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Kluge, Anne Kathrin [Verfasser], Christine [Akademischer Betreuer] [Gutachter] Preibisch, and Axel [Gutachter] Haase. "From Tissue Perfusion to Oxygenation: Characterizing Glioma Heterogeneity with Dynamic Susceptibility Contrast Enhanced Magnetic Resonance Imaging / Anne Kathrin Kluge ; Gutachter: Axel Haase, Christine Preibisch ; Betreuer: Christine Preibisch." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1147968136/34.
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Glielmi, Christopher B. "Expanding the role of functional mri in rehabilitation research." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33972.
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Functional magnetic resonance imaging (fMRI) based on blood oxygenation level dependent (BOLD) contrast has become a universal methodology in functional neuroimaging. However, the BOLD signal consists of a mix of physiological parameters and has relatively poor reproducibility. As fMRI becomes a prominent research tool for rehabilitation studies involving repeated measures of the human brain, more quantitative and stable fMRI contrasts are needed. This dissertation enhances quantitative measures to complement BOLD fMRI. These additional markers, cerebral blood flow (CBF) and cerebral blood volume (CBV) (and hence cerebral metabolic rate of oxygen (CMRO₂) modeling) are more specific imaging markers of neuronal activity than BOLD. The first aim of this dissertation assesses feasibility of complementing BOLD with quantitative fMRI measures in subjects with central visual impairment. Second, image acquisition and analysis are developed to enhance quantitative fMRI by quantifying CBV while simultaneously acquiring CBF and BOLD images. This aim seeks to relax assumptions related to existing methods that are not suitable for patient populations. Finally, CBF acquisition using a low-cost local labeling coil, which improves image quality, is combined with simultaneous acquisition of two types of traditional BOLD contrast. The demonstrated enhancement of CBF, CBV and CMRO₂measures can lead to better characterization of pathophysiology and treatment effects.
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Grimault, Stephan. "Détermination des propriétés du signal RMN par une approche numérique : application aux expériences de diffusion et d'imagerie fonctionnelle." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10157.
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Ce travail etaient est centre sur l'etude et la quantification du signal rmn dans certaines conditions in vivo. Une approche numerique de type monte carlo a ete utilisee. Une premiere etude porte sur la mesure in vivo du coefficient apparent de diffusion (cad) de lipides mobiles detectes dans des tumeurs cerebrales et confines dans des micro-domaines. Le modele numerique permet d'estimer la taille des micro-domaines sur la base du cad mesure. Un diametre de 10 a 12 m a ete trouve, valeur qui concorde avec les etudes par microscopie. Une seconde etudes porte sur la quantification des effets de la desoxygenation du sang sur la baisse du cad observee experimentalement lors de l'etude de l'ischemie. Une double etude numerique et experimentale nous a permis de conclure que la desoxygenation du sang n'est pas la principale cause de la baisse du cad. L'approche numerique est basee sur un modelisation du tissu cerebral prenant en compte la diffusion des molecules d'eau, le reseau vasculaire et les gradients internes generes autour ce dernier. Une troisieme etude porte sur la quantification du contraste bold (blood oxygenation level dependent) utilise en imagerie fonctionnelle. Differents parametres lies au secteur vasculaire, a la diffusion des molecules d'eau, et a la sequence d'impulsions ont ete considere. A partir de simulations basees sur une modelisation du tissu cerebral, des equations analytiques de la vitesse de relaxation de l'aimantation transversale en fonction des differents parametres d'interets ont ete. Dans ce travail, nous avons developpe un outil numerique aidant a la quantification du signal rmn et facilement adaptable aux diverses problematiques rencontrees dans differents secteurs de la rmn (diffusion, imagerie fonctionnelle).
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Obrig, Hellmuth. "Nahinfrarotspektroskopie des Gehirns." Doctoral thesis, [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=96640775X.
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ROTH, MURIEL. "Développements méthodologiques en imagerie d'activation cérébrale chez l'homme par résonance magnétique nucléaire : quantification de flux, imagerie de l'effet BOLD et correction des mouvements de la tête." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10016.
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Ce travail est centre sur les developpements methodologiques en imagerie par resonance magnetique des fonctions du cerveau. Une nouvelle methode d'irm fonctionnelle quantitative basee sur la mesure du debit sanguin est tout d'abord decrite. Des images angiographiques ont permis de mesurer le debit dans une veine drainant le cortex moteur. Des variations significatives du debit sanguin entre des periodes de repos, de simulation mentale et d'execution d'un acte moteur ont ete mises en evidence. Ces informations fonctionnelles ne permettent pas de localiser precisement les regions corticales activees. Cette localisation a ete effectuee en appliquant un traitement approprie sur des images sensibles aux variations du taux d'oxygenation sanguine. Des cartes d'activation cerebrale de bonne resolution spatiale ( 3 mm) sont ainsi obtenues. Nous avons alors demontre que l'aire motrice primaire est activee lors de la simulation mentale d'un acte moteur. Les mouvements de la tete survenant pendant un examen fonctionnel induisent des erreurs sur les cartes d'activation. Un nouvel algorithme de correction des deplacements dans le plan des images est presente. Cet algorithme utilise les proprietes de la transformation de fourier concernant les rotations et les translations afin de determiner rapidement les parametres du deplacement. Des tests sur des images simulees ont permis de montrer la fiabilite et la precision de l'algorithme.
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Xu, Dong. "The relationship between executive function, postural instability and gait disturbance in Parkinson's disease." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/91606/1/Dong%20Xu%20Thesis.pdf.
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The thesis investigated the relationships between executive function, balance and gait using assessments of cognitive and executive function, a wide range of clinical and biomedical measures of balance and gait, and different dual task paradigms in people with Parkinson's disease (PD) and healthy controls. Furthermore, functional association between executive function and brain activation in the prefrontal cortex was explored using functional near-infrared spectroscopy. The study has revealed greater postural instability and profound changes of gait parameters under dual-tasking for people with PD. Improving executive function may be an effective intervention to improve balance and gait in people with PD.
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Hsu, Yung-Chieh, and 徐永杰. "Real-Time Photoacoustic Imaging and Its Applications in Blood Oxygenation Measurements." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/84672412208945522917.
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碩士國立臺灣大學
生醫電子與資訊學研究所
100
In this study we discuss the feasibility of using dual-wavelength photoacoustic imaging, along with a high pulse repetition frequency laser for real-time measurements of blood oxygen level. Blood oxygen level is an important physiological parameter. Conventionally, there are two ways to measure the blood oxygen level. One is direct blood analysis and the other is using a pulse oximeter. The direct method, which draws blood from patients invasively, is the current gold standard for blood oxygen level measurement. Pulse oximeter, on the other hand, is a non-invasive and thus more convenient method. But the accuracy is inferior. The hypothesis of this research is that by combining photoacoustic imaging with blood oxygen level measurements, 2D functional imaging can be achieved. To this end, the goal of this research is to develop and implement a signal processing method, utilizing absorption spectrum difference between oxyhemoglobin and deoxyhemoglobin, to measure the blood oxygen level distribution in real time. In our experimental setup, a high PRF pulsed dye laser is used to achieve a frame rate up to 5 frames/sec. On the other hand, a Ti-Sapphire tunable laser, pumped by a 532nm Nd:YAG laser, is used for dual wavelength measurements. Due to system limitations, currently real-time imaging only with a single wavelength (722nm) is achieved. Various samples, including blue/red ink and gold nano-particles, were used to test our methods. Results show that the measured concentration of blue ink had a mean error of -24%, and a standard deviation of 32%. For gold nanoparticles, the mean error was -3.43%, and the standard deviation was 14.5%. For human blood, the calculated blood oxygen level for both gas-filled blood and no gas-filled blood was above 85%, but the oxygen level was higher for no gas-filled blood. It is suggested that 720nm and 800nm should be the two wavelengths used for future investigation.
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Ming-Long, Wu. "FMRI Utilizing Blood Oxygenation Sensitive Steady-state Imaging: Techniques and Applications at High Field." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1506200612593700.
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Wu, Ming-Long, and 吳明龍. "FMRI Utilizing Blood Oxygenation Sensitive Steady-state Imaging: Techniques and Applications at High Field." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/21322982989244381277.
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博士國立臺灣大學
電機工程學研究所
94
One major challenge of Blood Oxygenation Sensitive Steady-state (BOSS) fMRI is that the frequency band corresponding to highest functional sensitivity is extremely narrow, leading to substantial loss of functional contrast in the presence of magnetic field drifts. In this thesis, a frequency stabilization scheme was proposed for BOSS fMRI at 3T, where an radio-frequency (RF) pulse with very small flip angle was applied before each image scan, with the initial phase of the excited free induction decay signals extracted to reflect the temporal field drifts. A simple infinite impulse response (IIR) filter was further employed to obtain a low-pass filtered estimate of the central reference frequency for the upcoming scan. Experimental results suggest that the proposed scheme was able to stabilize the central reference frequency settings in accordance with the magnetic drifts, with oscillation amplitudes less than 0.5Hz. Phantom studies show that both the slow drifts and the fast fluctuations were prominently reduced for the dynamic BOSS scans, resulting in less than 5% signal variations. Visual fMRI at sub-millimeter in-plane resolution further demonstrated 10-17% activation signals nicely registered in the microvessels within the sulci. It is concluded that the IIR-filtered frequency stabilization is effective for reliable BOSS fMRI at high fields.
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"Non-invasive Choroidal Imaging And Retinal, Choroidal And Optic Nerve Head Oxygen Saturation Calculations Using A Multispectral Snapshot Imaging System With Visible And Near Infrared Wavelengths." Tulane University, 2014.
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PURPOSE. To image the fundus non-invasively at two different penetration depths using a multispectral imaging system. Monochromatic images at visible spectrum wavelengths and near-infrared wavelengths were qualitatively assessed for choroidal visibility. These images were used calculate oxygen saturation in retinal tissue, optic nerve head tissue, vein, and choroidal tissue in healthy controls and glaucoma patients. METHODS. A fundus camera-based multispectral snapshot oximeter imaged the fundus of healthy subjects and patients with varying ophthalmological pathology. The images of healthy controls and glaucoma patients were analyzed to determine oxygen saturation in the optic nerve head cup and rim, superficial and deep vein, macula and choroidal tissue. RESULTS. Visible: Average oxygen saturation for the ONH cup was 65 ± 6 percent for healthy controls and 61 ± 10 percent for glaucoma patients. For the ONH rim, it was 67 ± 3 percent for healthy controls and 64 ± 17 percent for glaucoma patients. For the vein, it was 67 ± 15 percent for healthy controls and 56 ± 22 percent for glaucoma patients. For the macula, it was 87 ± 10 percent for healthy controls and 93 ± 1 percent for glaucoma patients. NIR: The average oxygen saturation for the vein was 66 ± 20 percent for healthy controls, 58 ± 0.4 percent for glaucoma suspects and 54 ± 17 percent for glaucoma patients. For the choroidal tissue below the macula, it was 99 ± 5 percent in healthy controls and 81 ± 8 percent in glaucoma patients. CONCLUSIONS. Choroidal visibility is enhanced in near infrared monochromatic images from visible spectrum monochromatic images. Oxygen saturation results were lower in glaucoma patients for all anatomical areas analyzed except the avascular macula.acase@tulane.edu
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Al-Hallaq, Hania A. "Measurement of changes in tumor oxygenation by high spectral and spatial resolution MRI /." 2000. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:9977996.
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Nadeshalingam, Gobinath. "Oxygenation-sensitive cardiovascular magnetic resonance imaging (OS-CMR) : potential confounding factors in use of OS-CMR." Thèse, 2015. http://hdl.handle.net/1866/13794.
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La résonance magnétique cardiovasculaire sensible à l'oxygénation (OS-CMR) est devenue une modalité d'imagerie diagnostique pour la surveillance de changements dans l'oxygénation du myocarde. Cette technique offre un grand potentiel en tant qu'outil diagnostic primaire pour les maladies cardiovasculaires, en particulier la détection non-invasive d'ischémie. Par contre, il existe plusieurs facteurs potentiellement confondants de cette technique, quelques-uns d'ordre méthodologique comme les paramètres de séquençage et d'autres de nature physiologiques qui sont peut compris. En raison des effets causés par le contenu tissulaire d'eau, l'état d'hydratation peut avoir un impact sur l'intensité du signal. Ceci est un des aspects physiologiques en particulier dont nous voulions quantifier l'effet confondant par la manipulation de l'état d'hydratation chez des humains et l'observation des changements de l'intensité du signal dans des images OS-CMR.
Méthodes:
In vitro: Du sang artériel et veineux de huit porcs a été utilisé pour évaluer la dilution en série du sang et son effet correspondant sur l'intensité du signal de la séquence OS. In vivo: Vingt-deux volontaires en santé ont subi OS-CMR. Les concentrations d'hémoglobine (Hb) ont été mesurées au niveau de base et immédiatement après une l'infusion cristalloïde rapide de 1000 mL de solution Lactate Ringer's (LRS). Les images OS-CMR ont été prises dans une vue mid-ventriculaire court axe. L'intensité du signal myocardique a été mesurée durant une rétention respiratoire volontaire maximale, suite à une période d'hyperventilation de 60 secondes. Les changements dans l'intensité du signal entre le début et la fin de la rétention de la respiration ont été exprimés relativement au niveau de base (% de changement).
Résultats:
L'infusion a résulté en une diminution significative de l'Hb mesurée (142.5±3.3 vs. 128.8±3.3 g/L; p<0.001), alors que l'IS a augmenté de 3.2±1.2% entre les images du niveau de base en normo- et hypervolémie (p<0.05). L'IS d'hyperventilation ainsi que les changements d'IS induits par l'apnée ont été attenués après hémodilution (p<0.05). L'évaluation quantitative T2* a démontré une corrélation négative entre le temps de T2* et la concentration d'hémoglobine (r=-0.46, p<0.005).
Conclusions:
Il existe plusieurs éléments confondants de la technique OS-CMR qui requièrent de l'attention et de l'optimisation pour une future implémentation clinique à grande échelle. Le statut d'hydratation en particulier pourrait être un élément confondant dans l'imagerie OS-CMR. L'hypervolémie mène à une augmentation en IS au niveau de base et atténue la réponse IS durant des manoeuvres de respiration vasoactives. Cette atténuation de l'intensité du signal devrait être tenue en compte et corrigée dans l'évaluation clinique d'images OS-CMR.Background: Oxygenation-sensitive cardiovascular magnetic resonance (OS-CMR) has become a feasible diagnostic imaging modality for monitoring changes of myocardial oxygenation. This technique has great potential for use as a primary diagnostic tool for cardiovascular disease, particularly non-invasive detection of ischemia. Yet, there are several potential confounding factors of this technique, some methodological, such as sequence parameters and others are physiological and not well understood. Due to T2 effects caused by tissue water content, the hydration status may impact signal intensity. This is one physiological aspect in particular that we aimed at quantifying the confounding effect by manipulating hydration status in humans and observing signal intensity (SI) changes in OS-CMR images. Methods: In vitro: Arterial and venous blood from eight swine were used to assess serial dilution of blood and it corresponding effect on OS sequence signal intensity. In vivo: Twenty-two healthy volunteers underwent OS-CMR. Hemoglobin (Hb) concentrations were measured at baseline and immediately following rapid crystalloid infusion of 1,000ml of Lactated Ringer’s solution (LRS). OS-CMR images were acquired in a mid-ventricular short axis view. Myocardial SI was measured during a maximal voluntary breath-hold, after a 60-second period of hyperventilation. SI changes were expressed relative to baseline (% change). Results: The infusion resulted in a significant decrease in measured Hb (142.5±3.3 vs. 128.8±3.3 g/L; p<0.001), while SI increased by 3.2±1.2% between baseline images at normo- and hypervolemia (p<0.05). Both hyperventilation SI and the SI changes induced by apnea were attenuated after hemodilution (p<0.05). Quantitative assessment showed a negative correlation between T2* and hemoglobin concentration (r=-0.46, p<0.005). Conclusions: There are several confounders to the OS-CMR technique that require attention and optimization for future larger scale clinical implementation. The hydration status in particular may be a confounder in OS-CMR imaging. Hypervolemia leads to an increase in SI at baseline and attenuates the SI response during vasoactive breathing maneuvers. This attenuation in signal intensity would need to be accounted for and corrected in clinical assessment of OS-CMR images.
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"PHOTOACOUSTIC IMAGING OF PLACENTAL ISCHEMIA AND DEVELOPMENT OF A THERANOSTIC TO INCREASE BLOOD OXYGENATION IN AN ANIMAL MODEL OF PREECLAMPSIA." Tulane University, 2019.
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archives@tulane.eduPreeclampsia is a condition that occurs during pregnancy and affects both the mother and fetus. It is the leading cause of fetal and maternal mortality, affecting up to 8% of pregnancies. The disorder is diagnosed after the new onset of maternal high blood pressure and proteinuria. There is currently no cure for preeclampsia, other than delivery of the baby (and placenta), which often has to occur pre-term. Abnormal placental development that results in placental ischemia is a precursor for the development of preeclampsia in the mother. Current clinical imaging systems have been unable to accurately characterize placental function enough to make diagnoses. Therefore, there is a need to further study placental ischemia so that better diagnostic tools and therapies can be developed. Spectral photoacoustic (PA) imaging of placental oxygen saturation is a promising approach to studying placental ischemia. PA imaging uses nanosecond light pulses to excite endogenous or exogenous chromophores in biological tissue. When a chromophore undergoes a thermo-elastic expansion after absorbing light, a pressure wave is released within the tissue. The pressure wave resulting from the chromophore’s expansion are received by an ultrasound transducer. Our endogenous chromophore of interest is hemoglobin, an oxygen carrier protein in the blood. Hemoglobin and deoxyhemoglobin have distinctly different absorption spectra, which allows for the estimation of sO2 in vivo. One aim of this work is to use photoacoustic imaging to study altered levels of induced placental ischemia. Exogenous contrasts, such as perfluorocarbon microbubbles are commonly used in ultrasound because of their acoustic impedance mismatch with surrounding tissues. Perfluorocarbon nanodroplets are their liquid counterpart and offer longer stability in vivo. Additionally, they can be targeted and phase-changed into gas by a surrounding change in pressure, offering multimodal use. We use a modified perfluorocarbon construct loaded with ICG as an exogenous contrast agent. In this work, we will first investigate the feasibility of nanodroplets as oxygen delivery agents to blood. Then, we explore the utility of oxygen-loaded nanodroplets targeted to the placenta as a potential theranostic for preeclampsia.
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Megan Escott
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Angelo, Joseph Paul. "Real-time tissue viability assessment using near-infrared light." Thesis, 2017. https://hdl.handle.net/2144/23379.
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Despite significant advances in medical imaging technologies, there currently exist no tools to effectively assist healthcare professionals during surgical procedures. In turn, procedures remain subjective and dependent on experience, resulting in avoidable failure and significant quality of care disparities across hospitals.
Optical techniques are gaining popularity in clinical research because they are low cost, non-invasive, portable, and can retrieve both fluorescence and endogenous contrast information, providing physiological information relative to perfusion, oxygenation, metabolism, hydration, and sub-cellular content. Near-infrared (NIR) light is especially well suited for biological tissue and does not cause tissue damage from ionizing radiation or heat.
My dissertation has been focused on developing rapid imaging techniques for mapping endogenous tissue constituents to aid surgical guidance. These techniques allow, for the first time, video-rate quantitative acquisition over a large field of view (> 100 cm2) in widefield and endoscopic implementations. The optical system analysis has been focused on the spatial-frequency domain for its ease of quantitative measurements over large fields of view and for its recent development in real-time acquisition, single snapshot of optical properties (SSOP) imaging.
Using these methods, this dissertation provides novel improvements and implementations to SSOP, including both widefield and endoscopic instrumentations capable of video-rate acquisition of optical properties and sample surface profile maps. In turn, these measures generate profile-corrected maps of hemoglobin concentration that are highly beneficial for perfusion and overall tissue viability. Also utilizing optical property maps, a novel technique for quantitative fluorescence imaging was also demonstrated, showing large improvement over standard and ratiometric methods. To enable real-time feedback, rapid processing algorithms were designed using lookup tables that provide a 100x improvement in processing speed. Finally, these techniques were demonstrated in vivo to investigate their ability for early detection of tissue failure due to ischemia. Both pre-clinical studies show endogenous contrast imaging can provide early measures of future tissue viability.
The goal of this work has been to provide the foundation for real-time imaging systems that provide tissue constituent quantification for tissue viability assessments.2018-01-09T00:00:00Z
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Wang, Chun-Yang, and 王俊揚. "Oxygenation dynamic measurement based on near-infrared diffuse optical multipatch imaging: study on artery occlusion test, venous occlusion test, and far-infrared illumination method." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/82742593979376249945.
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碩士國立交通大學
顯示科技研究所
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Microcirculation is the important mechanism to maintain the tissue metabolism. Therefore, the condition of microcirculation can provide useful physiological information. Diffuse optical image system with continuous wave laser diode and photodiode on flexible black rubber was designed to evaluate the microcirculation condition by measuring the information of oxy-hemoglobin, deoxy-hemoglobin, total hemoglobin and tissue oxygen saturation. In this thesis, the difference of venous occlusion hemodynamics are observed in vivo measurements form normal subjects, patients with heart failure and sepsis in intensive care unit. The correlation between artery occlusion test and far infrared illumination test in normal subjects are observed.
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Auger, Héloïse. "Techniques de spectroscopie proche infrarouge appliquées à la quantification de paramètres hémodynamiques." Thèse, 2016. http://hdl.handle.net/1866/18896.
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Ce mémoire est séparé en deux volets, tous deux axés sur la spectroscopie proche infra-rouge (NIRS) pour la quantification des paramètres hémodynamiques. La NIRS est principalement basée sur la mesure des coefficients d'absorption (μa) et de dispersion (μs’) des tissus afin de retrouver les concentrations d'oxy- et de déoxyhémoglobine dans le sang. L'imagerie à l'aide de la NIRS est basée sur le parcours des photons à travers le tissu biologique à différentes longueurs d'onde du spectre proche infra-rouge.
Le premier appareil de NIRS dont il sera question est un appareil de spectroscopie résolue dans le temps. Ce type de système retrouve des concentrations absolues d'hémoglobine à l'aide d'un bandeau placé sur la peau d’un sujet, dans ce cas-ci sur le front. Le modèle d’analyse des données permet la séparation des contributions extra-cérébrales et cérébrales aux données. Cette méthode fournit des données plus exactes sur la saturation en oxygène du cerveau, par rapport à un modèle homogène où le signal est contaminé par les couches superficielles. Une étude sur les changements hémodynamiques cérébraux de jeunes adultes pendant une activité physique a été réalisée, et l’article en détaillant les résultats est transcrit au chapitre 2. Le chapitre 3 comprend un retour sur cette étude et aborde les possibilités de travaux futurs.
La seconde partie de mes travaux s’est déroulée sous forme de stage en entreprise durant l’été 2016. Sous la supervision de Dennis Hueber, Ph. D., et Beniamino Barbieri, Ph. D., j’ai effectué des recherches portant sur un appareil de NIRS manufacturé par la compagnie ISS Inc. et dont un prototype se trouve actuellement dans le laboratoire de mon superviseur Mathieu Dehaes, Ph. D. Cet appareil combine deux modalités d’imagerie optique, soit la NIRS dans le domaine des fréquences et la spectroscopie de corrélation diffuse. Le chapitre 4 détaille les tâches que j’ai réalisées durant ce temps, de même que les résultats des analyses que j’ai effectuées.This master’s thesis is separated in two phases, both focused on near infrared spectroscopy for the quantification of hemodynamic parameters. NIRS is based on the measure of absorption (μa) and scattering (μs’) coefficients of tissues in order to recover the oxy- and deoxyhemoglobin concentrations in the blood. Its results are based on the photon propagation in tissue at different near-infrared wavelengths. The first NIRS system used during my studies is a time-resolved spectroscopy system. This device allowed us to retrieve absolute hemoglobin concentrations using a headband placed over the subject’s skin and centered on their forehead. The data analysis model which we used allowed us to separate extra-cerebral and cerebral contributions of the signal. This method yielded quantitative absolute measures of cerebral oxygen saturation as opposed to the traditional homogenous model where the signal is contaminated by superficial layers. A study on cerebral hemodynamic changes in young adults during exercise was conducted, and the published article detailing its results is transcribed in Chapter 2. Chapter 3 includes a review of this study and discusses potential future works. The second part of my research consisted in an industrial internship during the summer of 2016. Under the supervision of Dennis Hueber, Ph. D., and Beniamino Barbieri, Ph. D., I have worked on a NIRS device manufactured by ISS Inc., a prototype of which is currently in the laboratory of my supervisor Mathieu Dehaes, Ph. D. This device combines two NIRS modalities: frequency-domain NIRS and diffuse correlation spectroscopy. Chapter 4 details the work I have performed at ISS and the results of my research and analysis.