281 |
Development of an MRI-compatible Multi-compartment Phantom for Dynamic Studies / Utveckling av MRI-kompatibel flerkammarfantom för dynamiska studierStröm Seez, Jonas, Holmer Fann, Frederick January 2020 (has links)
Medical imaging based on radioactive tracers exposes the patient to radiation. For this reason, a phantom is preferably used for non-clinical studies such as routine quality assurance and research. The aim of this project was to design, build and test a multi-compartment phantom to be used in dynamic SPECT/CT, PET/CT and PET/MRI studies. By treating each compartment as a biological system and plotting activity distribution, desired characteristics of the phantom can be obtained. A software program was created to simulate compartment activity distribution for different input parameters. Such parameters include number of compartments, administered activity, flow rates between compartments and compartment volume. Based on the simulation, the phantom was designed to meet the desired characteristics. Due to the outbreak of the SARS-CoV-2 virus, no phantom could be built nor tested. Consequently, leading the project to create a foundation that facilitates future building of the phantom. / Medicinsk avbildning med radioaktiva spårämnen utsätter patienter för en stråldos. Av detta skäl används företrädesvis en fantom för icke-kliniska studier såsom rutinmässig kvalitetssäkring och forskning. Syftet med detta projekt var att designa, bygga och testa ett flerkammarfantom som ska användas i dynamiska SPECT/CT, PET/CT och PET/MRI studier. Genom att behandla varje kammare som ett biologiskt system och plotta aktivitetsfördelning kan önskade egenskaper hos fantomen erhållas. Ett program skapades för att simulera aktivitetsdistributionen i flerkammarfantomer för olika in parametrar så som antal kammare, administrerad aktivitet, flöden mellan kammare och kammarvolym. Baserat på simuleringen utformades fantomen för att uppfylla de önskade egenskaperna. På grund av utbrottet av SARS-CoV-2 viruset kunde ingen fantom byggas eller testas. Följaktligen leddes projektet till att skapa en grund som underlättar framtida byggande av fantomen.
|
282 |
Krigföringens principer : Fina ord eller nyttiga lärdomar? En teoriprövande studie av Marvin Pokrants krigföringsprinciperÅkerström, Andreas January 2024 (has links)
The Principles of War have long been debated about their relevance and usefulness within the military context. Some theorists think that the Principles of War are laws that should be followed to achieve success in battle, while others see them more as guidelines. The principles have also been discussed on which level and type of warfare they should apply on, furthermore which types of principles to include. A theorist that has published a revised set of nine principles is Marvin Pokrant (2021), these Principles of War aim to be relevant across all levels and types of warfare. They are also one of the most contemporary sets of principles and has not yet been tested. Therefore, are the purpose of this study to both contribute to the overall research about the principles of war and more specifically if Pokrant’s (2021) set of principles has any explanatory value about success in modern military operations. The result of this study shows that this set of principles has explanatory value about the success in modern military operations. This is because the successful case had eight out of nine principles present, while the unsuccessful case only had two.
|
283 |
Akvizice a předzpracování MRI obrazových sekvencí pro klinické perfusní zobrazování / MRI Acquisition and Preprocessing of Image Sequences for Clinical Perfusion ImagingKrchňavý, Jan January 2012 (has links)
This thesis describes the theory for static and dynamic magnetic-resonance imaging using contrast agents affecting T1 relaxation time. The available acquisition methods in the specified facility of Masaryk Oncological Institute in Brno are described. The sequences for subsequent experimental measurements are selected. The used phantoms are described. Acquisition protocol for measuring is described briefly and the evaluation method for the measured data is suggested. The best acquisition sequence and a method of measurements is chosen influenced by estimation of relaxation time T1, sensitivity and signal to noise ratio. Perfusion analysis is executed and perfusion parameters are calculated. The work was supported by the European Regional Development Fund and the State Budget of the Czech Republic (RECAMO, CZ.1.05/2.1.00/03.0101).
|
284 |
Semi-quantitative röntgentomographische Untersuchungen zur Biodistribution von magnetischen Nanopartikeln in biologischem GewebeRahn, Helene 13 February 2012 (has links) (PDF)
Im Rahmen der vorliegenden Dissertationsschrift „Semi-quantitative röntgentomographische Untersuchungen zur Biodistribution von magnetischen Nanopartikeln in biologischem Gewebe“ wurden tomographische Untersuchungen an biologischen Objekten durchgeführt. Bei diesen Objekten handelt es sich um Gewebeproben nach minimal-invasiven Krebstherapien wie zum Beispiel magnetischem Drug Targeting und magnetischer Wärmebehandlung. Der Erfolg dieser Therapien ist sowohl abhängig von der korrekten Verteilung der magnetischen Nanopartikel als auch von der Tatsache, dass diese in der Zielregion in einer ausreichenden Menge vorhanden sind. Das Vorliegen dieser beiden Voraussetzungen ist in der vorliegenden Arbeit untersucht worden.
Dabei lag der Schwerpunkt der Arbeit auf der Quantifizierung von magnetischem Material in unterschiedlichen biologischen Gewebeproben mittels Röntgenmikrocomputertomographie (XµCT). Für diesen Zweck wurde ein Kalibrationssystem mit speziellen Phantomen entwickelt, mit dessen Hilfe eine Nanopartikelkonzentration einem Grauwert voxelweise zugewiesen werden kann.
Mit Hilfe der Kalibration kann der Nanopartikelgehalt sowohl in monochromatischen als auch in polychromatischen tomographischen Daten im Vergleich zu magnetorelaxometrischen Ergebnissen mit wenigen Prozent Abweichung ermittelt werden. Trotz Polychromasie und damit einhergehenden Artefakten können 3-dimensionale röntgentomographische Datensätze mit einer geringfügigen Konzentrationsabweichung im Vergleich zur quantitativen Messmethode Magnetorelaxometrie semi-quantitativ ausgewertet werden. / The success of the minimal invasive cancer therapies, called magnetic drug targeting and magnetic heating treatment, depends strongly on the correct distribution of the magnetic nanoparticles on one side. On the other side it depends on the fact that a sufficient amount of magnetic nanoparticles carrying drugs is accumulated in the target region. To study whether these two requirements are fulfilled motivates this PhD thesis „Semi-quantitative X-ray-tomography examinations of biodistribution of magnetic nanoparticles in biological tissues“.
The analysis of the distribution of the magnetic nanoparticles in tumours and other tissue examples is realized by means of X-ray-micro computer tomography (XμCT).
The work focuses on the quantification of the magnetic nanoparticles in different biological tissue samples by means of XµCT. A calibration of the tomographic devices with adequate phantoms, developed in the frame of this work, opens now the possibility to analyze tomographic data in a semi-quantitative manner. Thus, the nanoparticle concentration can be allocated voxel-wise to the grey values of the three-dimensional tomographic data.
With the help of calibration of the tomography equipments used, polychromatic as well as monochromatic three-dimensional representations of objects can be analyzed with regard to the biodistribution of magnetic nanoparticles as well as with regard to their quantity. The semi-quantitative results have been compared with results obtained with a quantitative measurement method magnetorelaxometry (MRX). Thereby a good agreement of the semi-quantitative and quantitative data has been figured out.
|
285 |
Semi-quantitative röntgentomographische Untersuchungen zur Biodistribution von magnetischen Nanopartikeln in biologischem GewebeRahn, Helene 12 December 2011 (has links)
Im Rahmen der vorliegenden Dissertationsschrift „Semi-quantitative röntgentomographische Untersuchungen zur Biodistribution von magnetischen Nanopartikeln in biologischem Gewebe“ wurden tomographische Untersuchungen an biologischen Objekten durchgeführt. Bei diesen Objekten handelt es sich um Gewebeproben nach minimal-invasiven Krebstherapien wie zum Beispiel magnetischem Drug Targeting und magnetischer Wärmebehandlung. Der Erfolg dieser Therapien ist sowohl abhängig von der korrekten Verteilung der magnetischen Nanopartikel als auch von der Tatsache, dass diese in der Zielregion in einer ausreichenden Menge vorhanden sind. Das Vorliegen dieser beiden Voraussetzungen ist in der vorliegenden Arbeit untersucht worden.
Dabei lag der Schwerpunkt der Arbeit auf der Quantifizierung von magnetischem Material in unterschiedlichen biologischen Gewebeproben mittels Röntgenmikrocomputertomographie (XµCT). Für diesen Zweck wurde ein Kalibrationssystem mit speziellen Phantomen entwickelt, mit dessen Hilfe eine Nanopartikelkonzentration einem Grauwert voxelweise zugewiesen werden kann.
Mit Hilfe der Kalibration kann der Nanopartikelgehalt sowohl in monochromatischen als auch in polychromatischen tomographischen Daten im Vergleich zu magnetorelaxometrischen Ergebnissen mit wenigen Prozent Abweichung ermittelt werden. Trotz Polychromasie und damit einhergehenden Artefakten können 3-dimensionale röntgentomographische Datensätze mit einer geringfügigen Konzentrationsabweichung im Vergleich zur quantitativen Messmethode Magnetorelaxometrie semi-quantitativ ausgewertet werden. / The success of the minimal invasive cancer therapies, called magnetic drug targeting and magnetic heating treatment, depends strongly on the correct distribution of the magnetic nanoparticles on one side. On the other side it depends on the fact that a sufficient amount of magnetic nanoparticles carrying drugs is accumulated in the target region. To study whether these two requirements are fulfilled motivates this PhD thesis „Semi-quantitative X-ray-tomography examinations of biodistribution of magnetic nanoparticles in biological tissues“.
The analysis of the distribution of the magnetic nanoparticles in tumours and other tissue examples is realized by means of X-ray-micro computer tomography (XμCT).
The work focuses on the quantification of the magnetic nanoparticles in different biological tissue samples by means of XµCT. A calibration of the tomographic devices with adequate phantoms, developed in the frame of this work, opens now the possibility to analyze tomographic data in a semi-quantitative manner. Thus, the nanoparticle concentration can be allocated voxel-wise to the grey values of the three-dimensional tomographic data.
With the help of calibration of the tomography equipments used, polychromatic as well as monochromatic three-dimensional representations of objects can be analyzed with regard to the biodistribution of magnetic nanoparticles as well as with regard to their quantity. The semi-quantitative results have been compared with results obtained with a quantitative measurement method magnetorelaxometry (MRX). Thereby a good agreement of the semi-quantitative and quantitative data has been figured out.
|
286 |
Život po životě. Revenanti v českých zemích raného novověku. / Life after Life. The Revenants in the Early Modern Period Bohemia Lands.Chalupová, Helena January 2015 (has links)
The master's thesis deals with one of the specifics of the cultural history of the Czech lands in the Early Modern period - i. e. the general perception of the afterlife (approximately between 1500 and 1800) and revenant issues. A revenant is meant originally a human being, who, after his death, for various reasons returns to the light of the living world, with exhibits of material (revived corpses, zombies, vampires, fexts) and immaterial (spirits, white ladies, wild hunting). In this respect, the main source are Czech demonological legends. One part of the study is to evaluate the social, religious and cultural aspects that had effect on what was said above in the specific historical period. The main emphasis is placed on the individual cases of revenants in the Czech lands, preserved in historical sources, as well as comparison with the same case in other European countries. The study will also focus on the description of biographies of historical personalities, drawing conclusions about what may have caused the conviction of being revenant.
|
287 |
Tales of Ash: Phantom Bodies as Testimony in Artistic Representations of TerrorismLavi, Tali, talilavi@netspace.net.au January 2007 (has links)
This paper delves into the realms of tragedy, memory and representation. Drawing upon the phenomenon of the Phantom Limb and extending it towards a theory of Phantom Bodies, various artworks - literary, theatrical and visual - are examined. After the conflagration of the terrorist attack, how are these absences grieved over and remembered through artistic representation? The essay examines this question by positioning itself amongst the scarred landscapes of post-September 11 New York and suicide bombings in Israel (2000-2006). Furthermore, it investigates whether humanity can be restored in the aftermath of an event in which certain individuals have sought to eradicate it. The fragmentation of the affected body in these scenarios is understood as further complicating processes of grief and remembrance. Artists who reject political polemic and engage with the dimensions of human loss are seen to have discovered means of referring to the absence caused by the act of terrorism. Three such recurring representations present themselves: ash and remnants, presence/absence and memory building. Phantom Bodies are perceived as simultaneously functioning as a reminder of the event itself, insisting upon the response of bearing witness, and as a symbol of the overwhelming power of humanity. Challenges arise when individuals or sections of the affected society deem these artworks to be inappropriate or explicit. Works considered include: Neil LaBute's play The Mercy Seat, Sigalit Landau's art installation The Country, Jonathan Safran Foer's Extremely Loud & Incredibly Close, Spike Lee's 25th Hour, Daniel Libeskind's architectural plans for the World Trade Center site, Eric Fischl's sculpture 'Tumbling Woman', Honor Molloy's autodelete://beginning dump of physical memory and A.B.Yehoshua's A Woman in Jerusalem. The accompanying play, Tales of Ash: A diptych for the theatre, is set in Melbourne, New York and Tel Aviv and deals with life in the face of and after terror. It veers between naturalism, poetic monologue and the epic. Tales of Ash contains two plays. The first centres on Mia, a young sculptor living in New York, who loses both her lover and her creativity on September 11. Upon returning to her home in Melbourne, she finds familial bonds still entwined with guilt and family trauma. The second play revolves around Ilana and Benny, two people living in Tel Aviv, who find themselves suddenly thrust together after a devastating bombing. As they attempt to resume rhythms of life, in the face of all the inherent ferocity of a modern existence in Israel, the struggle between The Ash Woman and The Ash Takers escalates.
|
288 |
Using MCNPX to calculate primary and secondary dose in proton therapyRyckman, Jeffrey M. 24 January 2011 (has links)
Proton therapy is a relatively new treatment modality for cancer, having recently been incorporated into hospitals in the last two decades. Although proton therapy has much higher start up and treatment costs than traditional methods of radiotherapy, it continues to expand in use today. One reason for this is that proton therapy has the advantage of a more precise localization of dose compared to traditional radiotherapy. Other proposed advantages of proton therapy in the treatment of cancer may lead to a faster expanse in its use if proven to be more effective than traditional radiotherapy. Therefore, much research must be done to investigate the possible negative and positive effects of using proton therapy as a treatment modality.
In proton therapy, protons do account for the vast majority of dose. However, when protons travel through matter, secondary particles are created by the interactions of protons and matter en route to and within the patient. It is believed that secondary dose can lead to secondary cancer, especially in pediatric cases. Therefore, the focus of this work is determining both primary and secondary dose.
In order to develop relevant simulations, the specifications of the treatment room and beam were based off of real-world facilities as closely as possible. Using available data from proton accelerators and clinical facilities, an accurate proton therapy nozzle was designed. Dose calculations were performed by MCNPX using a simple water phantom, and then beam characteristics were investigated to ensure the accuracy of the model. After validation of the beam nozzle, primary and secondary dose values were tabulated and discussed. By demonstrating the method of these calculations, the purpose of this work is to serve as a guide into the relatively recent field of Monte Carlo methods in proton therapy.
|
289 |
Rheo-NMR studies of viscoelastic secondary flows in ducts of non-circular cross-sectionSchroeder, Christian Berthold Karl 07 May 2012 (has links)
The existence of hydrodynamically developed, laminar Viscoelastic Secondary Flows (VSFs) of non-Newtonian fluids in straight ducts of non-circular cross-section was proposed in the 1950's. VSFs have since been observed sporadically, and only once with a velocimetric technique. Using axial and transverse full flow-field velocity-position raster maps made with Rheological Nuclear Magnetic Resonance (Rheo-NMR), Newtonian and non-Newtonian fluid flows were quantified in Hagen-Poiseuille and Power Law contexts, over more than two orders of magnitude of flow rate, in ducts of circle, square, triangle, and pentagon cross-section. VSF was reliably and repeatedly observed to occur at between one part in 130 and one part in 600 of the primary axial flow velocity. Velocity measurements ranged from <10 µm/s to approximately 30 cm/s, suggesting a velocity dynamic range >3E4 without optimization. To obtain VSF flow direction information, a novel flow directional phantom was developed and characterized. Aqueous solutions of Polyethylene Oxide (PEO), Viscarin GP-109NF, Viscarin GP-209NF (V209), Hyaluronan (HA) in a Phosphate-Buffered Saline-like solvent, and an aqueous Polyethylene Glycol/PEO-based Boger fluid were investigated. Axial data was corroborated with related data gathered by an independent method. Basic simulations corroborated the VSF observations. Duct hydraulic diameters (>= 1.6 mm) approached the micro-channel regime. VSF detections in HA --- synovial fluid's principal component --- and V209 were novel, as were observations of some artifacts which were subsequently characterized and corrected. The detection of VSF in HA represents the first experimental evidence suggesting that its second normal stress (N_2) is comparable to that of better-characterized fluids. In the first application of a new VSF-based method, a particular Boger fluid's constant viscosity and, in the square duct, its lack of VSF were used with established criteria to suggest that the fluid's N_2 approached zero. The development of a rudimentary, but versatile and inexpensive home-built velocimetric spectrometer is detailed, as are several new components. An exhaustive VSF literature review is included. The remarkable transverse velocimetric ability of Rheo-NMR in both optically opaque and transparent system is highlighted, suggesting that perhaps the technique might represent, in both micro-channels and conventional ducts, the gold-standard in flow velocimetry.
|
290 |
Three-dimensional statistical shape models for multimodal cardiac image analysisTobón Gómez, Catalina 30 June 2011 (has links)
Las enfermedades cardiovasculares (ECVs) son la principal causa de mortalidad en el mundo
Occidental. El interés de prevenir y tratar las ECVs ha desencadenado un rápido desarrollo de los
sistemas de adquisición de imágenes médicas. Por este motivo, la cantidad de datos de imagen
recolectados en las instituciones de salud se ha incrementado considerablemente. Este hecho ha
aumentado la necesidad de herramientas automatizadas para dar soporte al diagnóstico, mediante
una interpretación de imagen confiable y reproducible. La tarea de interpretación requiere traducir
los datos crudos de imagen en parámetros cuantitativos, los cuales son considerados relevantes
para clasificar la condición cardiaca de un paciente. Para realizar tal tarea, los métodos basados en
modelos estadísticos de forma han recibido favoritismo dada la naturaleza tridimensional (o 3D+t)
de las imágenes cardiovasculares. Deformando el modelo estadístico de forma a la imagen de un
paciente, el corazón puede analizarse de manera integral.
Actualmente, el campo de las imágenes cardiovasculares esta constituido por diferentes modalidades.
Cada modalidad explota diferentes fenómenos físicos, lo cual nos permite observar el
órgano cardiaco desde diferentes ángulos. El personal clínico recopila todas estas piezas de información
y las ensambla mentalmente en un modelo integral. Este modelo integral incluye información
anatómica y funcional que muestra un cuadro completo del corazón del paciente. Es
de alto interés transformar este modelo mental en un modelo computacional capaz de integrar la
información de manera global. La generación de un modelo como tal no es simplemente un reto de
visualización. Requiere una metodología capaz de extraer los parámetros cuantitativos relevantes
basados en los mismos principios técnicos. Esto nos asegura que las mediciones se pueden comparar
directamente. Tal metodología debe ser capaz de: 1) segmentar con precisión las cavidades
cardiacas a partir de datos multimodales, 2) proporcionar un marco de referencia único para integrar
múltiples fuentes de información, y 3) asistir la clasificación de la condición cardiaca del
paciente.
Esta tesis se basa en que los modelos estadísticos de forma, y en particular los Modelos Activos
de Forma, son un método robusto y preciso con el potencial de incluir todos estos requerimientos.
Para procesar múltiples modalidades de imagen, separamos la información estadística de forma
de la información de apariencia. Obtenemos la información estadística de forma a partir de una
modalidad de alta resolución y aprendemos la apariencia simulando la física de adquisición de
otras modalidades.
Las contribuciones de esta tesis pueden ser resumidas así: 1) un método genérico para construir
automáticamente modelos de intensidad para los Modelos Activos de Forma simulando la
física de adquisición de la modalidad en cuestión, 2) la primera extensión de un simulador de Resonancia
Magnética Nuclear diseñado para producir estudios cardiacos realistas, y 3) un método
novedoso para el entrenamiento automático de modelos de intensidad y de fiabilidad aplicado a
estudios cardiacos de Resonancia Magnética Nuclear. Cada una de estas contribuciones representa
un artículo publicado o enviado a una revista técnica internacional. / Cardiovascular diseases (CVDs) are the major cause of death in the Western world. The desire
to prevent and treat CVDs has triggered a rapid development of medical imaging systems. As
a consequence, the amount of imaging data collected in health care institutions has increased
considerably. This fact has raised the need for automated analysis tools to support diagnosis with
reliable and reproducible image interpretation. The interpretation task requires to translate raw
imaging data into quantitative parameters, which are considered relevant to classify the patient’s
cardiac condition. To achieve this task, statistical shape model approaches have found favoritism
given the 3D (or 3D+t) nature of cardiovascular imaging datasets. By deforming the statistical
shape model to image data from a patient, the heart can be analyzed in a more holistic way.
Currently, the field of cardiovascular imaging is constituted by different modalities. Each modality
exploits distinct physical phenomena, which allows us to observe the cardiac organ from
different angles. Clinicians collect all these pieces of information to form an integrated mental model.
The mental model includes anatomical and functional information to display a full picture
of the patient’s heart. It is highly desirable to transform this mental model into a computational
model able to integrate the information in a comprehensive manner. Generating such a model is
not simply a visualization challenge. It requires having a methodology able to extract relevant
quantitative parameters by applying the same principle. This assures that the measurements are
directly comparable. Such a methodology should be able to: 1) accurately segment the cardiac
cavities from multimodal datasets, 2) provide a unified frame of reference to integrate multiple
information sources, and 3) aid the classification of a patient’s cardiac condition.
This thesis builds upon the idea that statistical shape models, in particular Active Shape Models,
are a robust and accurate approach with the potential to incorporate all these requirements.
In order to handle multiple image modalities, we separate the statistical shape information from
the appearance information. We obtain the statistical shape information from a high resolution
modality and include the appearance information by simulating the physics of acquisition of other
modalities.
The contributions of this thesis can be summarized as: 1) a generic method to automatically
construct intensity models for Active Shape Models based on simulating the physics of acquisition
of the given imaging modality, 2) the first extension of a Magnetic Resonance Imaging (MRI)
simulator tailored to produce realistic cardiac images, and 3) a novel automatic intensity model and
reliability training strategy applied to cardiac MRI studies. Each of these contributions represents
an article published or submitted to a peer-review archival journal.
|
Page generated in 0.0165 seconds