To see the other types of publications on this topic, follow the link: Real-Time MRI.
Dissertations / Theses on the topic 'Real-Time MRI'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Real-Time MRI.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
De, Silva Weeraddana Manjula Kumara. "Correlation Imaging for Real-time Cardiac MRI." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1471346206.
Full text
2
Mitsouras, Dimitrios 1976. "Near real-time 2D non-Fourier basis MRI." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86546.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 114-118).
by Dimitrios Mitsouras.
S.M.
3
Lin, Hung-Yu. "REAL-TIME FLOW QUANTIFICATION TECHNIQUES IN CARDIOVASCULAR MRI APPLICATIONS." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1238594589.
Full text
4
Li, Hao [Verfasser]. "Real-time cardiac MRI in the mouse model / Hao Li." Ulm : Universität Ulm, 2020. http://d-nb.info/1222109360/34.
Full text
5
Elgort, Daniel Robert. "Real-Time Catheter Tracking and Adaptive Imaging for Interventional Cardiovascular MRI." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1111437062.
Full text
6
Kollmeier, Jost M. [Verfasser]. "Multi-Directional Phase-Contrast Flow MRI in Real Time / Jost M. Kollmeier." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2021. http://d-nb.info/1225936535/34.
Full text
7
Storrs, Judd M. "Automatic Real-time Targeting of Single-Voxel Magnetic Resonance Spectroscopy." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282576722.
Full text
8
Gardström, Karin. "3D Navigation for Real-Time MRI using Six Degree of Freedom Interaction Devices." Thesis, Linköping University, Department of Science and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2280.
Full textAbstract:
Real-time MRI scanning is used to visualize tissue and organs in motion. The real-time approach requires new interaction techniques to facilitate interaction with the scanning plane. The aim of this thesis is to investigate the use of input with six degrees of freedom – 6DOF. An overview over existing 6DOF input devices is given. Three devices are chosen for implementation and evaluation, Flock of Birds, SpaceBall and SpaceMouse.
A simulator application is developed to test the different input devices. The simulator purpose is to imitate the real-time scanning situation. To be able to evaluate speed andaccuracy of the different interaction techniques, methods for measuring time and error are developed. A statistical survey is done on two different tasks to gather data of the interaction. The data is analyzed and the result is that the test subjects find the SpaceMouse superior to the other devices thanks to its kinesthetic feed-back properties and ergonomic benefits. However, the statistical data shows that Flock of Birds is the fastest device and no great difference is showed in accuracy between Flock of Birds and SpaceMouse. SpaceBall was the device that generated the least satisfying data.
9
Gandomi-Bernal, Katie. "Implementation of a Modular Software Architecture on a Real-Time Operating System for Generic Control over MRI Compatible Surgical Robots." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1227.
Full textAbstract:
Software used in medical settings operate in complex and variable environments. Programs need to integrate well not only with their electrical and mechanical components, but also within the socio-technological setting they participate in. In this Master's Thesis, a modular software architecture for controlling surgical robot systems within magnetic resonance scanners is designed and implemented. The C++ program runs on a sbRIO 9651 real-time operating system and an object oriented design is taken. Robot kinematics and controls are put into effect in software and validated. Communication with up to ten daughter cards occurs via SPI and external information is exchanged via OpenIGTLink. A web-based engineering console made with ReactJS is also constructed to provide a visual interface for actuating motor axes and executing robot functionality. Documentation of the code is provided and the program was validated quantitatively with software tests and qualitatively through experimentation in MRI suites.
10
Untenberger, Markus [Verfasser], and Oliver [Akademischer Betreuer] Speck. "Multi-echo radial FLASH techniques for real-time MRI / Markus Untenberger. Betreuer: Oliver Speck." Magdeburg : Universitätsbibliothek, 2015. http://d-nb.info/1080560777/34.
Full text
11
Anand, Suma(Suma M. ). "OCRA : a low-cost, open-source FPGA-based MRI console capable of real-time control." Thesis, Massachusetts Institute of Technology, 2018. https://hdl.handle.net/1721.1/121619.
Full textAbstract:
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 85-86).
This thesis describes the development of a low-cost, open source, FPGA-based con- sole (hardware controller) for an educational MRI scanner. The console is known as OCRA: Open-source Console for Real-time Acquisition. Conventional MRI con- soles may be high cost, closed-source, and inflexible, in that it is not possible to change acquisition parameters once the scan is started. In contrast, OCRA is under $500, open-source, and capable of real-time updates to the acquisition. In particular, the console can update the sequence of excitations played out by the MRI console, known as the pulse sequence, in real time, a feature unique to this console. For hard- ware, OCRA uses the Red Pitaya, a commercially available Zync SoC board with a dual-core ARM CPU and Xilinx FPGA. The functionality of the console has been demonstrated on the MGH/MIT Tabletop scanners [2] developed in 2014 and used in MIT courses to teach students about signal processing. The major contributions of this thesis are the software programs for controlling and programming the console. They are: a Python-based Graphical User Interface (GUI) or client for controlling the acquisition and manipulating acquired data, a C-based server program for setting the memory of the sequence, and a low-level programming language for developing custom pulse sequences. The software is demonstrated in a basic example of real-time motion correction. In future work, OCRA can be extended to other MRI systems, particularly low-cost and custom built systems. Additionally, the console could be made more user-friendly through a higher-level programming language for developing pulse sequences, which would be built on top of the low-level language developed in this work. Finally, the real-time updating capabilities can be developed further, to correct artifacts (e.g. temperature-based drift) and even to develop a completely automated, data-driven acquisition that builds itself based on the acquired data.
by Suma Anand.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
12
de, Freitas Andreia Calisto. "Improving real-time MRI for the clinical assessment of velar closure and velopharyngeal motion during speech." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/41786.
Full textAbstract:
Magnetic Resonance Imaging (MRI) has been used to provide high-resolution tomographic information, valuable in the study of static vocal tract. However, speech does not present a static behaviour but relies on the continuous and dynamic interaction of the vocal tract articulators and neighbouring tissues. Thus, this could make real-time MRI (rt-MRI) an essential tool to assess speech, with numerous advantages over the current clinical techniques. However, using rt-MRI to image the upper vocal tract remains challenging; the motion of the articulators, including the velum is fast while MRI data acquisition is slow thus inherently limiting temporal resolution. Additionally, an intrinsic loss in SNR, spatial resolution and/or visual image quality is present. The main focus of this thesis is to increase clinical reliability of rt-MRI in speech by investigating novel methodologies for the imaging of velopharyngeal motion. Firstly, commercial rt-MRI protocols at 1.5 T and 3 T were compared, regarding image quality and temporal resolution compromise. Optimal imaging protocols were suggested for both eld strengths. This provided a starting point for future clinical translation and the use of commercial and currently available protocols to image velopharyngeal motion. Furthermore, imaging of velopharyngeal motion was further improved with non-standard acquisition methods, such as non-Cartesian sampling and more advanced reconstruction schemes. An improved imaging protocol for the assessment of velopharyngeal motion was suggested. This was based on a highly accelerated radial trajectory with a novel parallel imaging reconstruction method (radial tt-GRAPPA). The suggested protocol not only allowed for improved image quality and image sharpness,but it was also viable for future clinical translation regarding o offline computation times compared to other reconstruction methodologies also investigated in this thesis. In summary, this thesis added some novel insights into the eld of speech rt-MRI, presenting improved and time effcient imaging protocols, adequate for the assessment of velopharyngeal motion.
13
Chang, Yu-Chun [Verfasser], and Anke [Akademischer Betreuer] Henning. "Real-time Feedback of B0 Shimming at Ultra High Field MRI / Yu-Chun Chang ; Betreuer: Anke Henning." Tübingen : Universitätsbibliothek Tübingen, 2018. http://d-nb.info/116880390X/34.
Full text
14
Ma, Yunzhao. "Passive Resonant Coil Based Fast Registration And Tracking System For Real-Time Mri-Guided Minimally Invasive Surgery." Digital WPI, 2013. https://digitalcommons.wpi.edu/etd-theses/867.
Full textAbstract:
"This thesis presents a single-slice based fast stereotactic registration and tracking technique along with a corresponding modular system for guiding robotic mechanism or interventional instrument to perform needle-based interventions under live MRI guidance. The system can provide tracking of full 6 degree-of-freedom (DOF) in stereotactic interventional surgery based upon a single, rapidly acquired cross-sectional image. The whole system is constructed with a modular data transmission software framework and mechanical structure so that it supports remote supervision and manipulation between a 3D Matlab tracking user interface (UI) and an existing MRI robot controller by using the OpenIGTLink network communication protocol. It provides better closed-loop control by implementing a feedback output interface to the MRI-guided robot. A new compact fiducial frame design is presented, and the fiducial is wrapped with a passive resonant coil. The coil resonates at the Larmor frequency for 3T MRI to enhance signal strength and enable for rapid imaging. The fiducial can be attached near the distal end of the robot and coaxially with a needle so as to visualize target tissue and track the surgical tool synchronously. The MRI-compatible design of fiducial frame, robust tracking algorithm and modular interface allow this tracking system to be conveniently used on different robots or devices and in different size of MRI bores. Several iterations of the tracking fiducial and passive resonant coils were constructed and evaluated in a Phillips Achieva 3T MRI. To assess accuracy and robustness of the tracking algorithm, 25 groups of images with different poses were successively scanned along specific sequence in and MRI experiment. The translational RMS error along depth is 0.271mm with standard deviation of 0.277mm for totally 100 samples. The overall angular RMS error is less than 0.426 degree with standard deviation of 0.526 degree for totally 150 samples. The passive resonant coils were shown to significantly increase signal intensity in the fiducial relative to the surroundings and provide for rapid imaging with low flip angles. "
15
Joseph, Arun Antony Verfasser], Peter [Gutachter] Jakob, and Jens [Gutachter] [Frahm. "Real-time MRI of Moving Spins Using Undersampled Radial FLASH / Arun Antony Joseph. Gutachter: Peter Jakob ; Jens Frahm." Würzburg : Universität Würzburg, 2013. http://d-nb.info/1111886806/34.
Full text
16
Joseph, Arun Antony [Verfasser], Peter Gutachter] Jakob, and Jens [Gutachter] [Frahm. "Real-time MRI of Moving Spins Using Undersampled Radial FLASH / Arun Antony Joseph. Gutachter: Peter Jakob ; Jens Frahm." Würzburg : Universität Würzburg, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-94000.
Full text
17
Carvalho, Paulo A. "Advancing Technologies for Interventional MRI Robotics with Clinical Applications." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/577.
Full textAbstract:
An MRI’s superior soft tissue contrast and ability to perform parametric scanning make it a powerful tool for use during medical procedures; from surgery to rehabilitation. However, the MRI’s strong static magnetic field, fast switching gradients and constrained space make accomplishing procedures within it difficult. Recent advances in the field of robotics have enabled the creation of devices capable of assisting medical practitioners in this environment. In this work, technologies to enable the use and control of robotic assistive devices for MRI interventions are presented. This includes a modular controller that is designed, built and used to control two surgical systems with minimal effect on image quality. Progressive improvements to an MRI conditional actuator including the construction of a first of a kind plastic piezoelectric resonant motor stator that improves the motor’s compatibility with the MRI is presented. Finally, control algorithms are evaluated for real-time functional MRI based control of a rehabilitation robot which includes the use of a robot for controlling brain activity of a subject in an online experiment.
18
Carvalho, Paulo A. "Advancing Technologies for Interventional MRI Robotics with Clinical Applications." Digital WPI, 2020. https://digitalcommons.wpi.edu/etd-dissertations/616.
Full textAbstract:
An MRI’s superior soft tissue contrast and ability to perform parametric scanning make it a powerful tool for use during medical procedures; from surgery to rehabilitation. However, the MRI’s strong static magnetic field, fast switching gradients and constrained space make accomplishing procedures within it difficult. Recent advances in the field of robotics have enabled the creation of devices capable of assisting medical practitioners in this environment. In this work, technologies to enable the use and control of robotic assistive devices for MRI interventions are presented. This includes a modular controller that is designed, built and used to control two surgical systems with minimal effect on image quality. Progressive improvements to an MRI conditional actuator including the construction of a first of a kind plastic piezoelectric resonant motor stator that improves the motor’s compatibility with the MRI is presented. Finally, control algorithms are evaluated for real-time functional MRI based control of a rehabilitation robot which includes the use of a robot for controlling brain activity of a subject in an online experiment.
19
Palaniappan, Prashanth. "De-noising of Real-time Dynamic Magnetic Resonance Images by the Combined Application of Karhunen-Loeve Transform (KLT) and Wavelet Filtering." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1357269157.
Full text
20
Gollvik, Martin. "Metamodeling for ultra-fast parameter estimation : Theory and evaluation of use in real-time diagnosis of diffuse liver disease." Thesis, Linköpings universitet, Institutionen för medicinsk teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-108750.
Full textAbstract:
Diffuse liver disease is a growing problem and a major cause of death worldwide. In the final stages the treatment often involves liver resection or transplant and in deciding what course of action is to be taken it is crucial to have a correct assessment of the function of the liver. The current “gold standard” for this assessment is to take a liver biopsy which has a number of disadvantages. As an alternative, a method involving magnetic resonance imaging and mechanistic modeling of the liver has been developed at Linköping University. One of the obstacles for this method to overcome in order to reach clinical implementation is the speed of the parameter estimation. In this project the methodology of metamodeling is tested as a possible solution to this speed problem. Metamodeling involve making models of models using extensive model simulations and mathematical tools. With the use of regression methods, clustering algorithms, and optimization, different methods for parameter estimation have been evaluated. The results show that several, but not all, of the parameters could be accurately estimated using metamodeling and that metamodeling could be a highly useful tool when modeling biological systems. With further development, metamodeling could bring this non-invasive method for estimation of liver function a major step closer to application in the clinic.
21
Simegn, Gizeaddis Lamesgin. "Double volumetric navigators for real-time simultaneous shim and motion measurement and correction in Glycogen Chemical Exchange Saturation Transfer (GlycoCEST) MRI." Doctoral thesis, Faculty of Health Sciences, 2018. http://hdl.handle.net/11427/30039.
Full textAbstract:
Glycogen is the primary glucose storage mechanism in in living systems and plays a central role in systemic glucose homeostasis. The study of muscle glycogen concentrations in vivo still largely relies on tissue sampling methods via needle biopsy. However, muscle biopsies are invasive and limit the frequency of measurements and the number of sites that can be assessed. Non-invasive methods for quantifying glycogen in vivo are therefore desirable in order to understand the pathophysiology of common diseases with dysregulated glycogen metabolism such as obesity, insulin resistance, and diabetes, as well as glycogen metabolism in sports physiology. Chemical Exchange Saturation Transfer (CEST) MRI has emerged as a non-invasive contrast enhancement technique that enables detection of molecules, like glycogen, whose concentrations are too low to impact the contrast of standard MR imaging. CEST imaging is performed by selectively saturating hydrogen nuclei of the metabolites that are in chemical exchange with those of water molecules and detecting a reduction in MRI signal in the water pool resulting from continuous chemical exchange. However, CEST signal can easily be compromised by artifacts. Since CEST is based on chemical shift, it is very sensitive to field inhomogeneity which may arise from poor initial shimming, subject respiration, heating of shim iron, mechanical vibrations or subject motion. This is a particular problem for molecules that resonate close to water, such as - OH protons in glycogen, where small variations in chemical shift cause misinterpretation of CEST data. The purpose of this thesis was to optimize the CEST MRI sequence for glycogen detection and implement a real-time simultaneous motion and shim correction and measurement method. First, analytical solution of the Bloch-McConnell equations was used to find optimal continuous wave RF pulse parameters for glycogen detection, and results were validated on a phantom with varying glycogen concentrations and in vivo on human calf muscle. Next, the CEST sequence was modified with double volumetric navigators (DvNavs) to measure pose changes and update field of view and zero- and first-order shim parameters. Finally, the impact of B0 field fluctuations on the scan-rescan reproducibility of CEST was evaluated in vivo in 9 volunteers across 10 different scans. Simulation results showed an optimal RF saturation power of 1.5µT and duration of 1s for glycoCEST. These parameters were validated experimentally in vivo and the ability to detect varying glycogen concentrations was demonstrated in a phantom. Phantom data showed that the DvNav-CEST sequence accurately estimates system frequency and linear shim gradient changes due to motion and corrects resulting image distortions. In addition, DvNav-CEST was shown to yield improved CEST quantification in vivo in the presence of motion and motion-induced field inhomogeneity. B0 field fluctuations were found to lower the reproducibility of CEST measures: the mean coefficient of variation (CoV) for repeated scans was 83.70 ± 70.79 % without shim correction. However, the DvNav-CEST sequence was able to measure and correct B0 variations, reducing the CoV to 2.6 ± 1.37 %. The study confirms the possibility of detecting glycogen using CEST MRI at 3 T and shows the potential of the real-time shim and motion navigated CEST sequence for producing repeatable results in vivo by reducing the effect of B0 field fluctuations.
22
Brion, Véronique. "Towards real-time diffusion imaging : noise correction and inference of the human brain connectivity." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112058/document.
Full textAbstract:
La plupart des constructeurs de systèmes d'imagerie par résonance magnétique (IRM) proposent un large choix d'applications de post-traitement sur les données IRM reconstruites a posteriori, mais très peu de ces applications peuvent être exécutées en temps réel pendant l'examen. Mises à part certaines solutions dédiées à l'IRM fonctionnelle permettant des expériences relativement simples ainsi que d'autres solutions pour l'IRM interventionnelle produisant des scans anatomiques pendant un acte de chirurgie, aucun outil n'a été développé pour l'IRM pondérée en diffusion (IRMd). Cependant, comme les examens d'IRMd sont extrêmement sensibles à des perturbations du système hardware ou à des perturbations provoquées par le sujet et qui induisent des données corrompues, il peut être intéressant d'investiguer la possibilité de reconstruire les données d'IRMd directement lors de l'examen. Cette thèse est dédiée à ce projet innovant. La contribution majeure de cette thèse a consisté en des solutions de débruitage des données d'IRMd en temps réel. En effet, le signal pondéré en diffusion peut être corrompu par un niveau élevé de bruit qui n'est plus gaussien, mais ricien ou chi non centré. Après avoir réalisé un état de l'art détaillé de la littérature sur le bruit en IRM, nous avons étendu l'estimateur linéaire qui minimise l'erreur quadratique moyenne (LMMSE) et nous l'avons adapté à notre cadre de temps réel réalisé avec un filtre de Kalman. Nous avons comparé les performances de cette solution à celles d'un filtrage gaussien standard, difficile à implémenter car il nécessite une modification de la chaîne de reconstruction pour y être inséré immédiatement après la démodulation du signal acquis dans l'espace de Fourier. Nous avons aussi développé un filtre de Kalman parallèle qui permet d'appréhender toute distribution de bruit et nous avons montré que ses performances étaient comparables à celles de notre méthode précédente utilisant un filtre de Kalman non parallèle. Enfin, nous avons investigué la faisabilité de réaliser une tractographie en temps-réel pour déterminer la connectivité structurelle en direct, pendant l'examen. Nous espérons que ce panel de développements méthodologiques permettra d'améliorer et d'accélérer le diagnostic en cas d'urgence pour vérifier l'état des faisceaux de fibres de la substance blancheMost magnetic resonance imaging (MRI) system manufacturers propose a huge set of software applications to post-process the reconstructed MRI data a posteriori, but few of them can run in real-time during the ongoing scan. To our knowledge, apart from solutions dedicated to functional MRI allowing relatively simple experiments or for interventional MRI to perform anatomical scans during surgery, no tool has been developed in the field of diffusion-weighted MRI (dMRI). However, because dMRI scans are extremely sensitive to lots of hardware or subject-based perturbations inducing corrupted data, it can be interesting to investigate the possibility of processing dMRI data directly during the ongoing scan and this thesis is dedicated to this challenging topic. The major contribution of this thesis aimed at providing solutions to denoise dMRI data in real-time. Indeed, the diffusion-weighted signal may be corrupted by a significant level of noise which is not Gaussian anymore, but Rician or noncentral chi. After making a detailed review of the literature, we extended the linear minimum mean square error (LMMSE) estimator and adapted it to our real-time framework with a Kalman filter. We compared its efficiency to the standard Gaussian filtering, difficult to implement, as it requires a modification of the reconstruction pipeline to insert the filter immediately after the demodulation of the acquired signal in the Fourier space. We also developed a parallel Kalman filter to deal with any noise distribution and we showed that its efficiency was quite comparable to the non parallel Kalman filter approach. Last, we addressed the feasibility of performing tractography in real-time in order to infer the structural connectivity online. We hope that this set of methodological developments will help improving and accelerating a diagnosis in case of emergency to check the integrity of white matter fiber bundles
23
Tan, Zhengguo Verfasser], Jens [Akademischer Betreuer] [Gutachter] [Frahm, and Annette [Gutachter] Zippelius. "Advances in real-time phase-contrast flow MRI and multi-echo radial FLASH / Zhengguo Tan. Betreuer: Jens Frahm. Gutachter: Jens Frahm ; Annette Zippelius." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2016. http://d-nb.info/1102536059/34.
Full text
24
Roujol, Sébastien. "MR-guided thermotherapies of mobile organs : advances in real time correction of motion and MR-thermometry." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14263/document.
Full textAbstract:
L'ablation des tissus par hyperthermie locale guidée par IRM est une technique prometteuse pour le traitement du cancer et des arythmies cardiaques. L'IRM permet d'extraire en temps réel des informations anatomiques et thermiques des tissus. Cette thèse a pour objectif d'améliorer et d'étendre la méthodologie existante pour des interventions sur des organes mobiles comme le rein, le foie et le coeur. La première partie a été consacrée à l'introduction de l'imagerie rapide (jusqu'à 10-15 Hz) pour le guidage de l'intervention par IRM en temps réel. L'utilisation de cartes graphiques (GPGPU) a permis une accélération des calculs afin de satisfaire la contrainte de temps réel. Une précision, de l'ordre de 1°C dans les organes abdominaux et de 2-3°C dans le coeur, a été obtenue. Basé sur ces avancées, de nouveaux développements méthodologiques ont été proposés dans une seconde partie de cette thèse. L'estimation du mouvement basée sur une approche variationnelle a été améliorée pour gérer la présence de structures non persistantes et de fortes variations d'intensité dans les images. Un critère pour évaluer la qualité du mouvement estimé a été proposé et utilisé pour auto-calibrer notre algorithme d'estimation du mouvement. La méthode de correction des artefacts de thermométrie liés au mouvement, jusqu'ici restreinte aux mouvements périodiques, a été étendue à la gestion de mouvements spontanés. Enfin, un nouveau filtre temporel a été développé pour la réduction du bruit sur les cartographies de température. La procédure interventionnelle apparaît maintenant suffisamment mature pour le traitement des organes abdominaux et pour le transfert vers la clinique. Concernant le traitement des arythmies cardiaques, les méthodes ont été évaluées sur des sujets sains et dans le ventricule gauche. Par conséquent, la faisabilité de l'intervention dans les oreillettes mais aussi en présence d'arythmie devra être abordéeMR-guided thermal ablation is a promising technique for the treatment of cancer and atrial fibrillation. MRI provides both anatomical and temperature information. The objective of this thesis is to extend and improve existing techniques for such interventions in mobile organs such as the kidney, the liver and the heart. A first part of this work focuses on the use of fast MRI (up to 10-15 Hz) for guiding the intervention in real time. This study demonstrated the potential of GPGPU programming as a solution to guarantee the real time condition for both MR-reconstruction and MR-thermometry. A precision in the range of 1°C and 2-3°C was obtained in abdominal organs and in the heart, respectively. Based on these advances, new methodological developments have been carried out in a second part of this thesis. New variational approaches have proposed to address the problem of motion estimation in presence of structures appearing transient and high intensity variations in images. A novel quality criterion to assess the motion estimation is proposed and used to autocalibrate our motion estimation algorithm. The correction of motion related magnetic susceptibility variation was extended to treat the special case of spontaneous motion. Finally, a novel temporal filter is proposed to reduce the noise of MR-thermometry measurements while controlling the bias introduced by the filtering process. As a conclusion, all main obstacles for MR-guided HIFU-ablation of abdominal organs have been addressed in in-vivo and ex-vivo studies, therefore clinical studies will now be realized. However, although promising results have been obtained for MR-guided RF-ablation in the heart, its feasibility in the atrium and in presence of arrhythmia still remains to be investigated
25
Liu, Taoming. "A MAGNETICALLY-ACTUATED ROBOTIC CATHETER FOR ATRIAL FIBRILLATION ABLATION UNDER REAL-TIME MAGNETIC RESONANCE IMAGING GUIDANCE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1484654444253783.
Full text
26
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.
Full text
27
Neumann, Markus. "Automatic multimodal real-time tracking for image plane alignment in interventional Magnetic Resonance Imaging." Phd thesis, Université de Strasbourg, 2014. http://tel.archives-ouvertes.fr/tel-01038023.
Full textAbstract:
Interventional magnetic resonance imaging (MRI) aims at performing minimally invasive percutaneous interventions, such as tumor ablations and biopsies, under MRI guidance. During such interventions, the acquired MR image planes are typically aligned to the surgical instrument (needle) axis and to surrounding anatomical structures of interest in order to efficiently monitor the advancement in real-time of the instrument inside the patient's body. Object tracking inside the MRI is expected to facilitate and accelerate MR-guided interventions by allowing to automatically align the image planes to the surgical instrument. In this PhD thesis, an image-based workflow is proposed and refined for automatic image plane alignment. An automatic tracking workflow was developed, performing detection and tracking of a passive marker directly in clinical real-time images. This tracking workflow is designed for fully automated image plane alignment, with minimization of tracking-dedicated time. Its main drawback is its inherent dependence on the slow clinical MRI update rate. First, the addition of motion estimation and prediction with a Kalman filter was investigated and improved the workflow tracking performance. Second, a complementary optical sensor was used for multi-sensor tracking in order to decouple the tracking update rate from the MR image acquisition rate. Performance of the workflow was evaluated with both computer simulations and experiments using an MR compatible testbed. Results show a high robustness of the multi-sensor tracking approach for dynamic image plane alignment, due to the combination of the individual strengths of each sensor.
28
Ting, Samuel T. "An Efficient Framework for Compressed Sensing Reconstruction of Highly Accelerated Dynamic Cardiac MRI." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452164320.
Full text
29
Wang, Xiaoqing Verfasser], Jens [Akademischer Betreuer] [Gutachter] [Frahm, Hans Christian [Gutachter] Hofsäss, Thorsten [Gutachter] Hohage, Stefan [Gutachter] Luther, Annette [Gutachter] Zippelius, and Ulrich [Gutachter] Parlitz. "Real-time MRI and Model-based Reconstruction Techniques for Parameter Mapping of Spin-lattice Relaxation / Xiaoqing Wang ; Gutachter: Jens Frahm, Hans Christian Hofsäss, Thorsten Hohage, Stefan Luther, Annette Zippelius, Ulrich Parlitz ; Betreuer: Jens Frahm." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/1139491555/34.
Full text
30
Rube, Martin. "Novel tools for interventional magnetic resonance imaging." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/7e3feb72-0102-431f-982a-b3cdd393994e.
Full textAbstract:
Magnetic Resonance Imaging (MRI) provides unique advantages such as superior soft tissue contrast, true multiplanar imaging, variable contrast mechanisms, measurement of temperature changes, perfusion and diffusion, and no ionizing radiation. Despite considerable research efforts in the field of interventional MRI, numerous challenges remain including restricted access to the patient, high acoustic noise and a shortage of MRI-safe devices. Novel methods and devices are presented in this thesis with the primary objective of enabling effective MRI-guided interventions, particularly abdominal needle and common catheter-based endovascular interventions. Firstly, a set of MRI-safe devices (guidewires, micro guidewires, catheters and micro catheters) were developed with passive or inductively coupling resonant markers for MRI visualisation. Secondly, a method was implemented for wireless tracking and dynamic guidance of instruments. Thirdly, a framework of technologies was developed for in-room display, wireless MRI remote control and multi-user communication along with a dedicated user interface and imaging protocol. These implementations were assessed in regards to MRI-safety, performance and usability and evaluated for MRI-guided liver biopsies, balloon angioplasty procedures and also for mechanical thrombolysis. Flow phantoms, Thiel soft-embalmed human cadavers with partially re-established perfusion and a porcine model were used for in vitro, ex vivo and in vivo validation, respectively. The results demonstrate that these interventions are experimentally feasible and practical when using the presented developments: automated device tracking and equipment designed for MRI-guided interventions streamlined procedural workflow. Specifically, it was shown that fast and accurate needle placements along complex trajectories were feasible using a wireless interactive display and control device with a dedicated user interface for interventions. Moreover, safe and efficacious balloon angioplasties of the iliac artery were practical using the described framework of technologies along with a dedicated MRI protocol. Finally, it was demonstrated that these developments could be adapted and applied to MRI-guided endovascular mechanical thrombolysis of the middle cerebral artery. The technologies, described in this thesis have been shown to overcome many of the present limitations and should therefore be useful for enabling MRI-guided interventions while not further constraining the operating physician in an already complex environment. Nevertheless, it is acknowledged that many crucial issues remain to be solved in the field of iMRI and in the context of the presented research. In particular further device optimisations, improvements of the tracking implementation along with further in vivo evaluations are required before moving towards clinical evaluation. This thesis sets the groundwork for moving ahead with the eventual clinical realisation of optimised MRI-guided interventions.
31
Garetier, Marc. "Développement et application de l'IRM dynamique dans le domaine musculo-squelettique In vivo ankle joint kinematics from dynamic magnetic resonance imaging using a registration-based framework, in Journal of Biomechanics 86, March 2019 Dynamic MRI for articulating joint evaluation on 1.5T and 3.0T scanners : Setup, protocols, and real-time sequences, in Insights Into Imaging, 2020." Thesis, Brest, 2020. http://www.theses.fr/2020BRES0023.
Full textAbstract:
Les troubles de l’appareil musculosquelettiques retentissent sur le mouvement avec un impact parfois important sur la qualité de vie.L’IRM dynamique est une technique d’imagerie qui peut être employée pour l’évaluation non invasive in vivo de cet appareil en mouvement. Elle regroupe trois principales méthodes, dont l’imagerie temps réel qui permet la visualisation d’images acquises de manière rapide et continue. L’IRM temps réel est basée sur des séquences d’écho de gradient rapide, en particulier les séquences avec destruction de l’aimantation transversale résiduelle et celles avec gradients équilibrés. Ces séquences permettent de concilier une résolution temporelle élevée et une qualité d’image suffisante pour l’analyse des données, avec cependant des limites inhérentes à leurs caractéristiques. L’IRM dynamique a été utilisée dans plusieurs applications musculo-squelettiques, participant ainsi à une meilleure compréhension de la biomécanique et de la pathologie, avec comme objectif une amélioration de la prise en charge des patients. Les paramètres biomécaniques estimés au niveau du doigt par IRM dynamique temps réel sont proches de ceux rapportés dans la littérature, comme le bras de levier ou la course du tendon. Cette technique d’imagerie peut également être employée pour évaluer la contraction du muscle par quantification sa déformation. L’intégration de cette technique d’imagerie dans la pratique clinique nécessite par contre une standardisation des paramètres des séquences utilisées et une connaissance de l’installation appropriée du patient et des antennesMusculoskeletal disorders affect the movement of the body, with a significant impact on quality of life. Dynamic MRI allows for the non-invasive and invivo evaluation of musculoskeletal system during motion. Dynamic MRI can be acquired by three main methods, including real-time imaging allowing rapid and continuous image acquisition. Real-time dynamic MRI is based on rapid gradient echo sequences, in particularly spoiled gradient echo sequence and balanced steady state free precession sequence. These sequences provide high temporal resolution and sufficient image quality for data analysis, but with their own limitations. Dynamic MRI has been used for many musculoskeletal applications, allowing to better understand biomechanics and diseases, inorder to improve patient management. The finger biomechanical parameters obtained with real-time dynamic MRI are close to those reported in the literature, as tendon excursion or moment arm. This technique can also be used to assess muscle contraction by quantifying muscle deformation. Clinical implementation of this imaging modality requires also standardization of the sequence parameters and knowledge of the suitable patient and coil installation
32
Sankarapandian, Dayala Ganesh R. Kamal Raj. "Profiling MPI Primitives in Real-time Using OSU INAM." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587336162238284.
Full text
33
Fovet, Thomas. "Détection automatisée des hallucinations auditives en IRM fonctionnelle et perspectives thérapeutiques dans la schizophrénie." Thesis, Lille 2, 2017. http://www.theses.fr/2017LIL2S036/document.
Full textAbstract:
L’hallucination est une expérience subjective vécue en pleine conscience consistant en une perception impossible à distinguer d’une perception réelle, mais survenant en l’absence de tout stimulus en provenance de l’environnement externe. Les symptômes hallucinatoires, qui peuvent concerner toutes les modalités sensorielles, sont retrouvés dans divers troubles neurologiques et psychiatriques mais également chez certains sujets indemnes de toute pathologie. Dans le champ de la psychiatrie, la pathologie la plus fréquemment associée aux hallucinations reste la schizophrénie et la modalité auditive est la plus représentée, puisque 60 à 80% des patients souffrant de ce trouble sont concernés. Le retentissement fonctionnel des hallucinations auditives peut être important, altérant significativement la qualité de vie des patients.Dans ce contexte, la prise en charge de ce type de symptômes s’avère un enjeu considérable pour les personnes souffrant de schizophrénie. Pourtant, les moyens thérapeutiques actuellement disponibles (traitements médicamenteux antipsychotiques notamment) ne permettent pas toujours une rémission complète de la symptomatologie hallucinatoire et l’on considère que 25 à 30% des hallucinations auditives sont « pharmaco-résistantes ». C’est à partir de ce constat que, ces dernières années, ont émergé, pour le traitement des hallucinations auditives, des techniques de neuromodulation comme la stimulation magnétique transcrânienne répétée ou la stimulation électrique transcrânienne par courant continu. Toutefois, les résultats de ces nouvelles thérapies sur les hallucinations auditives résistantes restent modérés et le développement de stratégies alternatives demeure un enjeu de recherche majeur.Actuellement, les travaux en imagerie fonctionnelle permettent d'affiner les modèles physiopathologiques des hallucinations auditives, mais leur intérêt pourrait aller au-delà de la recherche fondamentale, avec possiblement des applications cliniques telles que l'assistance thérapeutique. Ce travail de thèse s’inscrit précisément dans le développement de l’imagerie cérébrale de « capture » des hallucinations auditives, c’est-à-dire l’identification des patterns d’activation fonctionnels associés à la survenue des hallucinations auditives.La première partie de ce travail est consacrée à la détection automatisée des hallucinations auditives en IRM fonctionnelle. L’identification des périodes hallucinatoires survenues au cours d’une session d’IRM fonctionnelle est actuellement possible par une méthode de capture semi-automatisée validée. Celle-ci permet une labellisation des données acquises au cours d’une session de repos en périodes « hallucinatoires » et « non-hallucinatoires ». Toutefois, le caractère long et fastidieux de cette méthode limite largement son emploi. Nous avons donc souhaité montrer comment les stratégies d’apprentissage machine (support vector machine ou SVM, notamment) permettent l’automatisation de cette technique par le développement de classificateurs performants, généralisables et associés à un faible coût de calcul (indispensable en vue d’une utilisation en temps réel). Nous proposons également le développement d’algorithmes de reconnaissance de la période « pré-hallucinatoire », en mettant en évidence que ce type de classificateur présente aussi des performances largement significatives. Enfin, nous avons pu montrer que l’utilisation de stratégies d’apprentissage-machine alternatives au SVM (e.g, le TV-Elastic-net), obtient des performances significativement supérieures au SVM [...]Hallucination is a transient subjective experience perceived as real, but occurring in the absence of an appropriate stimulation coming from the external environment. Hallucinatory events, which can occur across every sensory modality, are observed in various neurological and psychiatric disorders but also among “non-clinical” populations. The most frequent disorder associated with hallucinations in the field of psychiatry is schizophrenia. Auditory-verbal experiences are particularly frequent, with a lifetime-prevalence of 60 to 80% in patients suffering from schizophrenia. Hallucinations may cause long-term disability and poorer quality of life.In this context, the management of auditory-verbal hallucinations in patients with schizophrenia constitutes a major challenge. However, despite the increasing sophistication of biological and psychosocial research methods in the field, no significant therapeutic breakthrough has occurred in the last decade and a consensus exists that a significant proportion of patients with schizophrenia (i.e., around 25 %), exhibit drug-resistant auditory-verbal hallucinations. Non-pharmacological treatments, such as repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) have been proposed as an option for addressing the unmet medical needs described above. However, these neuromodulation techniques show a moderate effect in alleviating drug-resistant auditory-verbal hallucinations and the development of innovative therapeutic strategies remains a major challenge.In recent years, the number of brain imaging studies in the field of auditory-verbal hallucinations has grown substantially, leading to a better pathophysiological understanding of this subjective phenomenon. Recent progress in deciphering the neural underpinnings of AVHs has strengthened transdiagnostic neurocognitive models that characterize auditory-verbal hallucinations, but more specifically these findings built the bases for new therapeutic strategies. In this regards the development of auditory hallucinations “capture" brain-imaging studies (i.e. the identification of functional patterns associated with the occurrence of auditory hallucinations), was the main topic of this thesis.The first part of this work is devoted to the automatized detection of auditory-verbal hallucinations using functional MRI (fMRI). The identification of hallucinatory periods occurring during a fMRI session is now possible using a semi-automatized procedure based on an independent component analysis applied to resting fMRI data combined with a post-fMRI interview (i.e. the patient is asked to report auditory-verbal hallucinations immediately after acquisition). This “two-steps method” allows for the identification of hallucination periods (ON) and non-hallucination ones (OFF). However, the time-consuming nature of this a posteriori labelling procedure considerably limits its use. In these regards, we show how machine-learning, especially support vector machine (SVM), allows the automation of hallucinations capture. We present new results of accurate and generalizable classifiers which could be used in real-time because of their low computational-cost. We also highlight that algorithms able to identify the "pre-hallucinatory" period exhibit significant performances. Finally, we propose the use of an alternative learning-machine strategy, based on TV-Elastic-net, which achieves slightly better performances and more interpretable discriminative maps than SVM [...]
34
Neelamegam, Jothi P. "Zero-sided communication : challenges in implementing time-based channels using the MPI/RT specification." Master's thesis, Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-03252002-153109.
Full text
35
Selva, Jové Laura. "Real-time PCR per a la vigilància epidemiològica de la malaltia pneumocòccica invasiva (MPI) en pacients pediàtrics." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/92298.
Full textAbstract:
Streptococcus pneumoniae (S. pneumoniae) és un colonitzador habitual del tracte respiratori superior dels humans. Es tracta d’un patogen comú de l’espècie humana que presenta una elevada taxa de morbiditat i mortalitat arreu del món.
El bacteri pot causar otitis mitjana, sinusitis o infeccions de tracte respiratori superior, (per contigüitat) però també pot causar malaltia invasiva, quan habita en un territori habitualment estèril, produint pneumònia, bacterièmia, septicèmies i meningitis, entre d’altres.
La malaltia pneumocòccica és un important problema de salut pública i és la principal causa individual de mortalitat infantil en el món. Segons dades de la Organització Mundial de la Salut (OMS), s’estima que a l’any 2000 es van produir 14.5 milions d’episodis greus de malaltia pneumocòccica, que va resultar en 826 000 morts en nens menors de dos anys. Un 61% d’aquestes morts es van produir a l’Àfrica subsahariana i al sud-est asiàtic. Tanmateix, en aquests països i, en especial a les zones rurals, les capacitats de diagnòstic són limitades o inexistents i la identificació de l’agent etiològic es basa en signes i símptomes clínics. És molt important aïllar l’agent etiològic causant de malaltia per tal de poder avaluar el millor tractament possible. No obstant, les tècniques actuals per al diagnòstic de la malaltia presenten una limitada sensibilitat i especificitat.
El cultiu microbiològic, com a mètode de diagnòstic clàssic, té una baixa sensibilitat per a detectar el pneumococ. L’objectiu d’aquesta tesi és avaluar el potencial de les tècniques moleculars per al diagnòstic i caracterització de la malaltia pneumocòccica i discernir si l’ús de tècniques moleculars com la reacció en cadena de la polimerasa (PCR) poden suposar un avantatge tant per la rapidesa del mètode com per la detecció del patogen present en una mostra a baixa concentració. L’aplicació d’aquest tipus de tècniques en mostres biològiques impregnades en paper de filtre (dried-spot) i conservades a temperatura ambient poden ser un excel•lent sistema per a la detecció i serotipat de S. pneumoniae en països en vies de desenvolupament on la falta de recursos econòmics esdevé una de les principals limitacions.
La capacitat del pneumococ de causar malaltia depèn de la presència d’una càpsula polisacàrida que impedeix la fagocitosi. Tot i que la presència de la càpsula és un requisit perquè produeixi malaltia, no és suficient per conferir virulència, sinó que són necessaris una varietat de factors determinants addicionals, com ara les adhesines, les proteases, les toxines, els sistemes de transport i enzims que modifiquen el medi extracel•lular. Recentment, s’ha descobert un determinant de virulència del pneumococ que és la proteïna rica en repeticions de serina, PsrP (Pneumococcal-serine rich protein). Es tracta d’una adhesina que intervé en l’adhesió del pneumococ a les cèl•lules pulmonars. PsrP és un important factor de virulència capaç de causar malaltia i un potencial candidat a una nova vacuna proteica.Streptococcus pneumoniae (S. pneumoniae) is a common colonizer of the upper respiratory tract of humans. This is a major human pathogen and leading cause of morbidity and mortality worldwide. The bacteria can cause otitis media, sinusitis or upper respiratory tract infections (contiguity) but can also cause invasive disease, when living in an area usually sterile, causing pneumonia, bacteraemia, sepsis and meningitis, among others. According to the World Health Organization, in 2000, pneumococcal disease was estimated to have caused about 14.5 million severe episodes. There were approximately 826 000 deaths from pneumococcal disease in children under five years and 61% of these deaths occurred in sub-Saharan Africa and Southeast Asia. However, in these countries, especially in rural areas, diagnostic capabilities are limited or nonexistent and agent identification is based on clinical signs and symptoms. It is very important to isolate the etiologic agent of disease in order to assess the best treatment possible. However, present techniques for the diagnosis of the disease have a limited sensitivity and specificity. Microbiological culture, considered the “gold-standard” in microbiological diagnosis has low sensitivity to detect pneumococcus. The aim of this Thesis is to evaluate the potential of molecular techniques for diagnosis and characterization of pneumococcal disease and to discern whether the use of molecular techniques such as PCR, can be an advantage both for the speed of method as for the detection of the pathogen present in a sample in low concentration. The application of these techniques in biological samples impregnated filter paper (dried-spot) and kept at room temperature can be an excellent system for the detection and serotyping of S. pneumoniae in developing countries where lack of financial resources is a major constraint. The ability of the pneumococcus to cause disease depends on the presence of a polysaccharide capsule that prevents phagocytosis. Although the presence of the capsule is a requirement to produce disease, is not sufficient to confer virulence, but need a large number of additional factors such as adhesins, proteases, toxins, transportation systems and enzymes that modify the extracellular medium. One recently identified pneumococcal virulence determinant is the pneumococcal serine-rich repeat protein (PsrP). This is an adhesin involved in adherence of pneumococci to lung cells. PsrP is an important virulence factor capable of causing disease and a potential new vaccine candidate protein.
36
Sridhar, H. K. "Influence of Lot Sizing on Lead Time Error Costs in M.R.P. Systems- a Computer Simulation Study." Thesis, Indian Institute of Science, 1988. http://hdl.handle.net/2005/85.
Full textAbstract:
Timing of ordering of inventory items is of very great importance in Materials Requirement Planning. Uncertainties in timing can have an adverse effect on the system performance. Most often the lead time variation contribute to timing uncertainties; and their effects are reflected in added costs.
Lead time error effects are investigated in this thesis. The study attempts to estimate the effects through some relevant costs, and their variations across the lot sizing rules.
The hypotheses for this study are 1) Between any two lot sizing rules, there will be a significant difference in error coats due to combined effect of purchased lead time error and manufacturing lead time errors; 2) Relative cost performance of lot sizing rules in MRP is influenced by the lead time errors; 3) There will be a difference in error cost between lot for l o t rule and least total cost rule even with single source of lead time variation.
To carry out the study a MRP programme was developed, in FORTRAN 77 with provisions to include the lot sizing rules while exploding the structure. The lot sizing rules used in the study are Lot for Lot, Silver and Meal heuristics, Wagner-Whitin algorithm, Least total cost, Least unit cost and Part Period balancing.
A simulation model is developed using GPSS/PC, to test the hypotheses. An hypothetical production situation with three end items, each with a different product structure is designed. In addition, a master production schedule and a job shop are also structured. Appropriate distributions are assumed for both manufacturing lead times and purchase lead times. These provide the stochastic variables in the simulation experiments.
A series of experiments were carried out with the model to investigate into the variations of costs amongst lot sizing rules. Results of the simulation experiments prove that there are costs associated with lead time errors in MRP. These error costs vary significantly with different lot sizing rules.
It is also found that the resultant error costs vary significantly even with a single source of lead time variation. Least unit cost rule gives the beat performance having least error costs. Lot for Lot rule has shown the worst performance amongst the lot sizing rules considered. Other interesting results have emerged out of the study.
37
Mai, Timo [Verfasser], Robert [Akademischer Betreuer] Weigel, Robert [Gutachter] Weigel, and Ralf [Gutachter] Brederlow. "A Real-Time Capable and Configurable Analog Front-End for SAR-ADCs / Timo Mai ; Gutachter: Robert Weigel, Ralf Brederlow ; Betreuer: Robert Weigel." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2021. http://d-nb.info/1233010557/34.
Full text
38
Sattar, Anas Akram. "Lipopolysaccharide in marine bathing water : a potential real-time biomarker of bacterial contamination and relevance to human health." Thesis, University of Plymouth, 2014. http://hdl.handle.net/10026.1/3185.
Full textAbstract:
The quality of marine bathing water is currently assessed by monitoring the levels of faecal indicator bacteria. Among other drawbacks, results are retrospective using the traditional culture based methods. A rapid method is thus needed as an early warning to bathers for bacterial contamination in marine bathing waters. Total lipopolysaccharide (LPS) was chosen here as a potential general biomarker for bacterial contamination. Levels of total LPS, measured using a Kinetic QCL™ Limulus Amebocyte Lysate (LAL) assay, highly correlated with enumerated Escherichia coli and Bacteroides species. Levels of LPS in excess of 50 EU mL-1 were found to equate with water that was unsuitable for bathing under the current European Union regulations. Results showed that monitoring the levels of total LPS has a potential applicability as a rapid method for screening the quality of marine bathing water. More importantly, the LAL assay overcome the retrospective results when using culture based assessment since the LAL assay takes less than 30 minutes. Although false positive events were not detected, the occurrence of a false positive has been hypothesised, hence a more specific faecal biomarker was also investigated. LPS of five Bacteroides species (B. fragilis, B. caccae, B. ovatus, B. xylanisolvens and B. finegoldii) isolated from marine bathing waters samples were successfully profiled and showed high similarity between isolates in LPS gel electrophoresis banding pattern. Similar results were shown when investigating the endotoxic activity of Bacteroides species with the Kinetic QCL™ LAL assay. The potential biological relevance of Bacteroides LPS was also investigated in cell culture models indicating that Bacteroides showed similar induction of proinflammatory cytokines (TNF-α, IL-6 and IL-1α) and generally the biological activity was approximately 100 fold less than E. coli LPS. In addition, an ELISA assay was designed for the detection of Bacteroides LPS. Results showed that the Bacteroides LPS has a high potential to be used as a faecal biomarker, however, further work is required to develop a fully functional assay. The potential biological relevance of LPS present in contaminated bathing waters was also investigated in cell culture models. Results showed that there is a significant difference in the production of proinflammatory cytokines in comparison to “clean” bathing waters. Thus, results suggest that the European Directive regulations should be extended to cover the levels of total LPS in bathing waters to assure safety to the users of marine recreational water.
39
Björk, Anders. "Chemometric and signal processing methods for real time monitoring and modeling : applications in the pulp and paper industry." Doctoral thesis, KTH, Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4383.
Full textAbstract:
In the production of paper, the quality of the pulp is an important factor both for the productivity and for the final quality. Reliable real-time measurements of pulp quality are therefore needed. One way is to use acoustic or vibration sensors that give information-rich signals and place the sensors at suitable locations in a pulp production line. However, these sensors are not selective for the pulp properties of interest. Therefore, advanced signal processing and multivariate calibration are essential tools. The current work has been focused on the development of calibration routes for extraction of information from acoustic sensors and on signal processing algorithms for enhancing the information-selectivity for a specific pulp property or class of properties. Multivariate analysis methods like Principal Components Analysis (PCA), Partial Least Squares (PLS) and Orthogonal Signal Correction (OSC) have been used for visualization and calibration. Signal processing methods like Fast Fourier Transform (FFT), Fast Wavelet Transform (FWT) and Continuous Wavelet Transform (CWT) have been used in the development of novel signal processing algorithms for extraction of information from vibrationacoustic sensors. It is shown that use of OSC combined with PLS for prediction of Canadian Standard Freeness (CSF) using FFT-spectra produced from vibration data on a Thermo Mechanical Pulping (TMP) process gives lower prediction errors and a more parsimonious model than PLS alone. The combination of FFT and PLS was also used for monitoring of beating of kraft pulp and for screen monitoring. When using regular FFT-spectra on process acoustic data the obtained information tend to overlap. To circumvent this two new signal processing methods were developed: Wavelet Transform Multi Resolution Spectra (WT-MRS) and Continuous Wavelet Transform Fibre Length Extraction (CWT-FLE). Applying WT-MRS gave PLS-models that were more parsimonious with lower prediction error for CSF than using regular FFT-Spectra. For a Medium Consistency (MC) pulp stream WT-MRS gave predictions errors comparable to the reference methods for CSF and Brightness. The CWT-FLE method was validated against a commercial fibre length analyzer and good agreement was obtained. The CWT-FLE-curves could therefore be used instead of other fibre distribution curves for process control. Further, the CWT-FLE curves were used for PLS modelling of tensile strength and optical parameters with good results. In addition to the mentioned results a comprehensive overview of technologies used with acoustic sensors and related applications has been performed.Vid framställning av pappersprodukter är kvaliteten på massan en viktig faktor för produktiviteten och kvalitén på slutresultatet. Det är därför viktigt att ha tillgång till tillförlitliga mätningar av massakvalitet i realtid. En möjlighet är att använda akustik- eller vibrationssensorer i lämpliga positioner vid enhetsoperationer i massaprocessen. Selektiviteten hos dessa mätningar är emellertid relativt låg i synnerhet om mätningarna är passiva. Därför krävs avancerad signalbehandling och multivariat kalibrering. Det nu presenterade arbetet har varit fokuserat på kalibreringsmetoder för extraktion av information ur akustiska mätningar samt på algoritmer för signalbehandling som kan ge förbättrad informationsselektivitet. Multivariata metoder som Principal Component Analysis (PCA), Partial Least Squares (PLS) and Orthogonal Signal Correction (OSC) har använts för visualisering och kalibrering. Signalbehandlingsmetoderna Fast Fourier Transform (FFT), Fast Wavelet Transform (FWT) och Continuous Wavelet Transform (CWT) har använts i utvecklingen av nydanande metoder för signalbehandling anpassade till att extrahera information ur signaler från vibrations/akustiska sensorer. En kombination av OSC och PLS applicerade på FFT-spektra från raffineringen i en Termo Mechnaical Pulping (TMP) process ger lägre prediktionsfel för Canadian Standard Freeness (CSF) än enbart PLS. Kombinationen av FFT och PLS har vidare använts för monitorering av malning av sulfatmassa och monitorering av silning. Ordinära FFT-spektra av t.ex. vibrationssignaler är delvis överlappande. För att komma runt detta har två signalbehandlingsmetoder utvecklats, Wavelet Transform Multi Resolution Spectra (WT-MRS) baserat på kombinationen av FWT och FFT samt Continuous Wavelet Transform Fibre Length Extraction (CWT-FLE) baserat på CWT. Tillämpning av WT-MRS gav enklare PLS-modeller med lägre prediktionsfel för CSF jämfört med att använda normala FFT-spektra. I en annan tillämpning på en massaström med relativt hög koncentration (Medium Consistency, MC) kunde prediktioner för CSF samt ljushet erhållas med prediktionsfel jämförbart med referensmetodernas fel. Metoden CWT-FLE validerades mot en kommersiell fiberlängdsmätare med god överensstämmelse. CWT-FLE-kurvorna skulle därför kunna användas i stället för andra fiberdistributionskurvor för processtyrning. Vidare användes CWT-FLE kurvor för PLS modellering av dragstyrka samt optiska egenskaper med goda resultat. Utöver de nämnda resultaten har en omfattande litteratursammanställning gjorts över området och relaterade applikationer.
QC 20100629
40
Kollmeier, Jost M. "Multi-Directional Phase-Contrast Flow MRI in Real Time." Doctoral thesis, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-155C-D.
Full text
41
Joseph, Arun Antony. "Real-time MRI of Moving Spins Using Undersampled Radial FLASH." Doctoral thesis, 2013. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-94000.
Full textAbstract:
Nuclear spins in motion is an intrinsic component of any dynamic process when studied using magnetic resonance imaging (MRI). Moving spins define many functional characteristics of the human body such as diffusion, perfusion and blood flow. Quantitative MRI of moving spins can provide valuable information about the human physiology or of a technical system. In particular, phase-contrast MRI, which is based on two images with and without a flow-encoding gradient, has emerged as an important diagnostic tool in medicine to quantify human blood flow. Unfortunately, however, its clinical usage is hampered by long acquisition times which only provide mean data averaged across multiple cardiac cycles and therefore preclude Monitoring the immediate physiological responses to stress or exercise. These limitations are expected to be overcome by real-time imaging which constitutes a primary aim of this thesis. Short image acquisition times, as the core for real-time phase-contrast MRI, can be mainly realized through undersampling of the acquired data. Therefore the development focused on related technical aspects such as pulse sequence design, k-space encoding schemes and image reconstruction. A radial encoding scheme was experimentally found to be robust to motion and less sensitive to undersampling than Cartesian encoding. Radial encoding was combined with a FLASH acquisition technique for building an efficient real-time phase-contrast MRI sequence. The sequence was further optimized through overlapping of gradients to achieve the shortest possible echo time. Regularized nonlinear inverse reconstruction (NLINV), a technique which jointly estimates the image content and its corresponding coil sensitivities, was used for image reconstruction. NLINV was adapted specifically for phase-contrast MRI to produce both Magnitude images and phase-contrast maps. Real-time phase-contrast MRI therefore combined two highly undersampled (up to a factor of 30) radial gradient-echo acquisitions with and without a flow-encoding gradient with modified NLINV reconstructions. The developed method achieved real-time phase-contrast MRI at both high spatial (1.3 mm) and temporal resolution (40 ms). Applications to healthy human subjects as well as preliminary studies of patients demonstrated real-time phase-contrast MRI to offer improved patient compliance (e.g., free breathing) and immediate access to physiological variations of flow parameters (e.g., response to enhanced intrathoracic pressure). In most cases, quantitative blood flow was measured in the ascending aorta as an important blood vessel of the cardiovascular circulation system commonly studied in the clinic. The performance of real-time phase-contrast MRI was validated in comparison to standard Cine phase-contrast MRI using studies of flow phantoms as well as under in vivo conditions. The evaluations confirmed good agreement for comparable results. As a further extension to real-time phase-contrast MRI, this thesis implemented and explored a dual-echo phase-contrast MRI method which employs two sequential gradient echoes with and without flow encoding. The introduction of a flow-encoding gradient in between the two echoes aids in the further reduction of acquisition time. Although this technique was efficient under in vitro conditions, in vivo studies showed the influence of additional motion-induced Phase contributions. Due to these additional temporal phase information, the approach showed Little promise for quantitative flow MRI. As a further method three-dimensional real-time phase-contrast MRI was developed in this thesis to visualize and quantify multi-directional flow at about twice the measuring time of the standard real-time MRI method, i.e. at about 100 ms temporal resolution. This was achieved through velocity mapping along all three physical gradient directions. Although the method is still too slow to adequately cover cardiovascular blood flow, the preliminary results were found to be promising for future applications in tissues and organ systems outside the heart. Finally, future developments are expected to benefit from the adaptation of model-based reconstruction techniques to real-time phase-contrast MRIDie Bewegung der Kernspins ist eine wesentliche Eigenschaft von dynamischen Vorgängen, die mit Hilfe der Magnetresonanztomographie (MRT) untersucht werden. Bewegte oder fließende Spins charakterisieren viele Funktionen des menschlichen Körpers, wie z.B. die Gewebeperfusion und den Blutfluss in den Gefäßen. Die quantitative MRT von bewegten Spins kann daher wertvolle Informationen über die menschliche Physiologie oder auch über ein technisches System geben. Insbesondere die Phasenkontrast-MRT, die auf der Aufnahme von zwei Bildern mit und ohne flusskodierenden Gradienten basiert, hat sich als ein wichtiges diagnostisches Werkzeug in der Medizin entwickelt, um den Blutfluss funktionell zu quantifizieren. Die klinische Nutzung ist jedoch durch die langen Messzeiten eingeschränkt, da die Daten über mehrere Herzzyklen gemittelt werden müssen und damit die Untersuchung unmittelbarer physiologischer Reaktionen auf Stress und/oder Muskelbelastung ausgeschlossen ist. Ein primäres Ziel dieser Arbeit war es, diese Einschränkungen durch die Entwicklung einer MRT-Flussmessung in Echtzeit zu überwinden. Entscheidende Grundlage jeder Echtzeit-MRT sind kurze Aufnahmezeiten, die vor allem durch eine Reduktion der aufgenommenen Daten (Unterabtastung) realisiert werden. Daher konzentrierte sich die hier vorgestellte Entwicklung auf die damit verbundenen technischen Aspekte wie die MRT-Sequenz zur Datenaufnahme, das räumliche Kodierungsschema, und die Bildrekonstruktion. Experimentell erwies sich ein radiales Kodierungsschema als robust gegenüber Bewegungen und relativ unempfindlich gegenüber milder Unterabtastung. Dieses Kodierungsschema wurde mit der FLASH Aufnahmetechnik für eine effiziente Phasenkontrast-Sequenz in Echtzeit kombiniert. Zusätzlich wurde die Sequenz durch Überlappung von Gradienten hinsichtlich einer kurzen Echozeit optimiert. Für die Bildrekonstruktion wurde die regularisierte nichtlineare inverse Rekonstruktion (NLINV) verwendet, bei der die Bildinformation und die entsprechenden pulensensitivitäten gleichzeitig geschätzt werden. NLINV wurde speziell für die Phasenkontrast-MRT angepasst, um sowohl Betragsbilder als auch robuste Phasenkontrast-Karten mit hoher raumzeitlicher Genauigkeit zu berechnen. Das erarbeitete Verfahren der Phasenkontrast-MRT in Echtzeit kombiniert daher zwei stark unterabgetastete (bis zu einem Faktor von 30) und unterschiedlich flusskodierte, radiale Gradientenecho-Aufnahmen mit einer modifizierten NLINV Rekonstruktion. Mit dieser Methode wurde sowohl eine gute räumliche Auflösung (1.3 mm), als auch eine hohe zeitliche Auflösung (40 ms) erreicht. Bei Anwendungen an gesunden Probanden sowie vorläufigen Untersuchungen von Patienten konnte nachgewiesen werden, dass die Phasenkontrast-MRT in Echtzeit einen verbesserten Komfort für die Patienten (z.B. freie Atmung) und unmittelbaren Zugang zu physiologischen Veränderungen der Flussparameter bietet (z.B. Reaktion auf erhöhten Druck im Brustraum). In den meisten Fällen wurden quantitative Blutflussmessungen in der aufsteigenden Aorta, einem klinisch wichtigen Gefäß des Herz-Kreislauf-Systems, vorgenommen. Die Messungen mit der Phasenkontrast-MRT in Echtzeit wurden mit der EKG-getriggerten Cine Phasenkontrast-MRT (klinischer Standard) an einem Flussphantom und unter in vivo Bedingungen verglichen. Die Ergebnisse zeigten unter vergleichbaren Bedingungen gute Übereinstimmung. Im Rahmen dieser Arbeit wurde zusätzlich eine Doppelecho-Variante der Phasenkontrast-MRT in Echtzeit implementiert. Das Einfügen eines flusskodierenden Gradienten zwischen den beiden Echos führte zu einer weiteren Reduzierung der Messzeit. Obwohl sich diese Technik unter in vitro Bedingungen als tauglich erwies, zeigten sich bei in vivo Studien störende Einflüsse durch bewegungsinduzierte Phasenbeiträge, die wenig Erfolg für quantitative Flussmessungen versprechen. Als weitere Methode wurde in dieser Arbeit eine dreifach kodierte Sequenz zur Phasenkontrast-MRT entwickelt, um multidirektionalen Fluss zu untersuchen. Die Geschwindigkeitskodierung entlang aller drei physikalischen Gradientenrichtungen führte zu einer verlängerten Messzeit (zeitliche Auflösung � 100 ms) gegenüber der Echtzeit-Flussmessung in nur einer Richtung. Obwohl das Verfahren noch zu langsam ist, um den kardiovaskulären Blutfluss adäquat zu beschreiben, waren vorläufige Ergebnisse in Körperregionen außerhalb des Herzens für zukünftige klinische Anwendungen sehr vielversprechend. Es ist zu erwarten, dass entsprechende Weiterentwicklungen von modellbasierten ekonstruktionsverfahren profitieren werden
42
Zhang, Shuo. "Real-time Magnetic Resonance Imaging." Doctoral thesis, 2009. http://hdl.handle.net/11858/00-1735-0000-000D-F258-8.
Full text
43
Tang, Yu-wei, and 唐育尉. "A Framework of Real-time Feedback System in MRI: Technique and Applications." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/cw6x84.
Full textAbstract:
博士國立臺灣科技大學
電機工程系
100
In MRI, some specific scan parameters such as inversion time or RF frequency offset have to be determined before applying clinical protocols. In general, the MR operators or doctors would utilize the developed scouting protocol and then select the proper imaging parameter according to the set of images manually. However, the additional scouting scan would diminish the fluency of clinical routine. In this thesis, we proposed a framework of real-time feedback system that could automatically and rapidly optimize the desired parameter. Two types of applications have been accomplished based on this real-time feedback system. The first application was to implement the optimization of compensative gradient moment for z-shim method in gradient-echo echo-planar-imaging (GE-EPI). In this type, the pre-scan and target sequences were identical. After about 20 iterations for evaluating optimal negative and positive z-shim gradient moments, the following z-shimmed GE-EPI for functional MRI (fMRI) study would contain images alternatively according to the inherited values. The second application is the calibration of RF frequency to suppress the dark banding artifact.in steady-state free precession (bSSFP) cardiac imaging at 3.0 T. The real-time feedback system combined two sequences: transition-band low flip-angle bSSFP (bSSSFP-L) for frequency calibration and conventional cine bSSFP. The optimal frequency obtained by real-time feedback calibration significantly reduced dark-band artifacts in cine bSSFP images (P < .01). The period of calibration and conventional protocol could be implemented within one breadth-hold. In conclusion, the proposed real-time feedback system is rapid and fully automatic and can thus serve as a pre-adjustment module in various MR researches which are in need of parameter calibration.
44
Roeloffs, Volkert Brar. "Development of Advanced Acquisition and Reconstruction Techniques for Real-Time Perfusion MRI." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-002B-7CF6-C.
Full textAbstract:
Diese Doktorarbeit befasst sich mit der methodischen Entwicklung von Akquisition- und Rekonstruktionstechniken zur Anwendung von Echtzeit-Bildgebungstechniken auf das Gebiet der dynamischen kontrastmittelgestützten Magentresonanztomographie. Zur Unterdrückung unerwünschter Bildartefakte wird eine neue Spoiling-Technik vorgeschlagen, die auf randomisierten Phasen der Hochfrequenzanregung basiert. Diese Technik erlaubt eine schnelle, artefaktfreie Aufnahme von T1-gewichteten Rohdaten bei radialer Abtastung. Die Rekonstruktion quantitativer Parameterkarten aus solchen Rohdaten kann als nichtlineares, inverses Problem aufgefasst werden. In dieser Arbeit wird eine modellbasierte Rekonstruktionstechnik zur quantitativen T1-Kartierung entwickelt, die dieses inverse Problem mittels der iterativ regularisierten Gauß-Newton-Methode mit parameterspezifischer Regularisierung löst. In Simulationen sowie in-vitro- und in-vivo-Studien wird Genauigkeit und Präzision dieser neuen Methode geprüft, die ihre direkte Anwendung in in-vitro-Experimenten zur "first-pass"-Perfusion findet. In diesen Experimenten wird ein kommerziell verfügbares Phantom verwendet, dass in-vivo-Perfusion simuliert und gleichzeitig vollständige Kontrolle über die vorherrschenden Austauschraten erlaubt.
45
Tan, Zhengguo. "Advances in real-time phase-contrast flow MRI and multi-echo radial FLASH." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0028-8763-3.
Full text
46
Kling, Olaf Ansgar Chrysanthus. "Vergleichende Analyse der Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) und der real-time-Magnetresonanztomographie." Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-B280-5.
Full text
47
Wang, Xiaoqing. "Real-time MRI and Model-based Reconstruction Techniques for Parameter Mapping of Spin-lattice Relaxation." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0023-3EEC-E.
Full text
48
Rotenberg, David. "Real-time Correction By Optical Tracking with Integrated Geometric Distortion Correction for Reducing Motion Artifacts in fMRI." Thesis, 2012. http://hdl.handle.net/1807/32275.
Full textAbstract:
Artifacts caused by head motion are a substantial source of error in fMRI that limits its use in neuroscience research and clinical settings. Real-time scan-plane correction by optical tracking has been shown to correct slice misalignment and non-linear spin-history artifacts, however residual artifacts due to dynamic magnetic field non-uniformity may remain in the data. A recently developed correction technique, PLACE, can correct for absolute geometric distortion using the complex image data from two EPI images, with slightly shifted k-space trajectories. We present a correction approach that integrates PLACE into a real-time scan-plane update system by optical tracking, applied to a tissue-equivalent phantom undergoing complex motion and an fMRI finger tapping experiment with overt head motion to induce dynamic field non-uniformity. Experiments suggest that including volume by volume geometric distortion correction by PLACE can suppress dynamic geometric distortion artifacts in a phantom and in vivo and provide more robust activation maps.
49
Zhang, Zhongshuai. "Dynamic Temperature Mapping - Real-time Strategies and Model-based Reconstructions." Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-002B-7D36-1.
Full text
50
Wiegand, Hagen Fritz. "Vergleichende Untersuchung zur Wirkweise unterschiedlicher Schienentherapiekonzepte bei anteriorer Diskusverlagerung mit Reposition." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-F00B-4.
Full text