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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Reconstruction and analysis of 4D heart motion from tagged MR images.

January 2003 (has links)
Luo Guo. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 97-109). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.2 / Chapter 1.2 --- Basics --- p.3 / Chapter 1.2.1 --- Anatomy of Human Heart --- p.3 / Chapter 1.2.2 --- The Philosophy of MRI --- p.5 / Chapter 1.2.3 --- MRI in Practice --- p.7 / Chapter 1.3 --- Cardiac MR Images Analysis --- p.7 / Chapter 1.3.1 --- Heart Boundary Segmentation --- p.7 / Chapter 1.3.2 --- Motion Reconstruction --- p.13 / Chapter 1.4 --- Summary and Thesis Overview --- p.17 / Chapter 2 --- Tracking Tags in SPAMM Images --- p.21 / Chapter 2.1 --- Introduction --- p.21 / Chapter 2.2 --- The Snake Model --- p.28 / Chapter 2.3 --- The Improved Snake Model: Tracking Tags Using Snakes --- p.30 / Chapter 2.3.1 --- Imaging Protocol --- p.30 / Chapter 2.3.2 --- Model Formulation --- p.31 / Chapter 2.3.3 --- Numerical Solution --- p.39 / Chapter 2.4 --- Experimental Results --- p.44 / Chapter 3 --- B-Spline Based LV Motion Reconstruction --- p.52 / Chapter 3.1 --- Introduction --- p.52 / Chapter 3.2 --- LV Shape: Generalized Deformable Ellipsoid --- p.56 / Chapter 3.3 --- The New Geometric Model: Generalized Prolate Spheroid --- p.58 / Chapter 3.3.1 --- Generalized Prolate Spheroid --- p.58 / Chapter 3.3.2 --- Initial Geometric Fitting --- p.59 / Chapter 3.4 --- Fast Motion Reconstruction: The Enhanced Hi- erarchical Motion Decomposition --- p.65 / Chapter 3.4.1 --- Hierarchical Motion Decomposition --- p.65 / Chapter 3.4.2 --- Motion Reconstruction --- p.68 / Chapter 3.4.3 --- Implementation --- p.76 / Chapter 3.4.4 --- Time Smoothing --- p.77 / Chapter 3.5 --- Experimental Results --- p.79 / Chapter 3.5.1 --- Geometric Fitting --- p.79 / Chapter 3.5.2 --- Motion Reconstruction --- p.79 / Chapter 4 --- Conclusion --- p.93 / Bibliography --- p.109
122

Functional magnetic resonance imaging: diffusion weighted and chemical shift imaging in head and neck.

January 2010 (has links)
Fong, Kwan Ying. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 90-103). / Abstracts in English and Chinese. / Chapter Chapter 1: --- "Introduction, problems and objectives" --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Problems --- p.3 / Chapter 1.3 --- Objectives --- p.3 / Chapter Chapter 2: --- Background --- p.4 / Chapter 2.1. --- Head and Neck Cancer --- p.4 / Chapter 2.2 --- Diagnostic Imaging of Head and Neck Cancer --- p.5 / Chapter 2.3. --- Magnetic Resonance Imaging- Physics --- p.8 / Chapter 2.3.1 --- Nuclear Magnetic Resonance Principle --- p.8 / Chapter 2.3.2 --- Proton Magnetic Resonance Imaging --- p.8 / Chapter 2.3.3 --- Relaxation --- p.12 / Chapter 2.3.4 --- Tl- and T2-weighted Imaging --- p.12 / Chapter 2.3.5 --- Diffusion Weighted Imaging (DWI) --- p.13 / Chapter 2.3.6 --- Magnetic Resonance Spectroscopy- Single Voxel Spectroscopy and Chemical Shift Imaging --- p.15 / Chapter Chapter 3: --- Diffusion-weighted imaging in the evaluation head of and neck cancer --- p.21 / Chapter 3.1 --- Introduction - Diffusion-Weighted Imaging in Tumors --- p.21 / Chapter 3.2 --- DWI of Nasopharyngeal Carcinoma --- p.22 / Chapter 3.2.1 --- Introduction and Objectives --- p.22 / Chapter 3.2.2. --- Methods --- p.23 / Chapter 3.2.3. --- Results --- p.27 / Chapter 3.2.4 --- Discussion --- p.31 / Chapter 3.3 --- DWI of Primary Tumors: Comparison of NPC with Squamous Cell Carcinoma and Extra-nodal Non-Hodgkin Lymphoma --- p.33 / Chapter 3.3.1 --- Introduction and Objectives --- p.33 / Chapter 3.3.2. --- Methods --- p.34 / Chapter 3.3.3. --- Results --- p.35 / Chapter 3.3.4 --- Discussion --- p.42 / Chapter 3.3.5 --- Summary of DWI in Head and Neck Cancer --- p.44 / Chapter Chapter 4: --- Chemical shift imaging of head and neck tumors --- p.45 / Chapter 4.1 --- Introduction - Single Voxel Spectroscopy and Chemical Shift Imaging --- p.45 / Chapter 4.2 --- CSI - Methods Used to Reduce Magnetic Field Inhomogeneity --- p.48 / Chapter 4.3 --- Phantom studies - CSI Experiments Using Phantoms --- p.51 / Chapter 4.3.1 --- Introduction and Objectives --- p.51 / Chapter 4.3.2. --- Methods --- p.51 / Chapter 4.3.3 --- Experiment and MR Protocol --- p.54 / Chapter 4.3.4 --- Data Analysis --- p.58 / Chapter 4.3.5 --- Phantom Experimental Results --- p.59 / Chapter 4.3.6 --- Discussion and Conclusion on Phantom Experiments --- p.69 / Chapter 4.4 --- In vivo CSI Study of Human Head and Neck Tumors --- p.72 / Chapter 4.4.1 --- Introduction and Objectives --- p.72 / Chapter 4.4.2 --- Patient Selection --- p.73 / Chapter 4.4.3 --- MRI and CSI Protocol --- p.73 / Chapter 4.4.4 --- Data Analysis --- p.74 / Chapter 4.4.5 --- Results from CSI on Patients --- p.74 / Chapter 4.4.6 --- Discussion and Conclusion of CSI on Patients --- p.81 / Chapter Chapter 5: --- "Summary, conclusion and future studies" --- p.87 / Chapter 5.1 --- Summary --- p.87 / Chapter 5.2 --- Conclusion --- p.89 / Chapter 5.3 --- Future Studies --- p.89 / References --- p.90 / Publications --- p.104
123

Use of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) on head and neck cancer. / CUHK electronic theses & dissertations collection

January 2011 (has links)
Lee, Kar Ho Francis. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 148-163). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
124

Developing Compatible Techniques for Magnetic Resonance Imaging of Stroke Pathophysiology

Brevard, Mathew E. 27 September 2001 (has links)
Stroke is the most prevalent neurological disease facing our nation today. Treatments, however, are few and insufficient at reducing the impact of this neurological condition. Experimental animal models are important to improving our understanding of stroke, and for developing new therapies to counter the pathology of stroke. Magnetic Resonance Imaging is the leading tool for the non-invasive investigation of stroke pathophysiology. While most MRI work in animals is conducted under anesthesia, anesthesia has profound effects on cerebral circulation and metabolism, and can affect stroke outcome. Several novel methods were combined with MRI compatible physiologic monitoring equipment to conduct stroke studies in conscious animals. Stress was studied as a factor in these studies and conditioning was utilized to reduce the impact of stress on the animals' physiology. Models of both occlusive and hemorrhagic strokes were successfully implemented within the MRI apparatus. Lastly, experiments using a macrosphere model showed evidence of a pathophysiologic difference between awake and anesthetized animals that undergo stroke.
125

Design and Implementation of Magnetic Field Control in Magnetic Resonance Imaging and B0 Shimming

Shang, Yun January 2024 (has links)
High image fidelity in Magnetic Resonance Imaging (MRI) relies on precise magnetic field control of encoding gradient fields and background B0 magnetic fields. To ensure a high degree of accuracy in the spatial location of the proton spins and the resultant object geometry, conventional image encoding using linear gradient fields, as well as advanced techniques with non-linear encoding, requires field generating hardware capable of excellent field shaping capabilities and accuracy. Non-homogeneous B0 background fields in MR imaging cause faster relaxation, signal dropout, and geometry distortion, resulting in inferior image quality and reduced diagnostic accuracy. Besides manufacturing imperfections in the magnet and site conditions, the magnetic field inside the imaging object is not homogeneous due to the differences in geometries and magnetic properties of individual human tissues, which is recognized as the primary source of B0 variation in MRI. Considering the differences of B0 conditions across subjects, it is essential for MR imaging to utilize flexible B0 shimming techniques such as active shimming in order to produce a highly homogeneous B0 field. The control capability and optimized control strategy for these magnetic fields require the development of new hardware and methodologies. B0 background field generated by the magnet and the encoding gradient field from gradient coil are two critical pillars of MR imaging. Since the multi-coil array provides advanced shim capability and is proven to be capable of imaging encoding with a compact size, it is considered a perfect component as a combination of B0 shim coil and encoding gradient coil for an accessible head-only MR scanner. MR scanners like this type provide unique features that will enable researchers to develop new MRI methodologies and conduct research into the functionalities of the human brain through more natural human behaviors. Its clinical applications will be more accessible to the general population for disease screening and diagnosis due to its portability and low energy requirements. Since the multi-coil array has the advantage of smaller volume and wall thickness than the traditional gradient coil, its design and implementation is challenging because of its compact space, irregular curved shape of coil elements, mechanical reliability requirements during scan and good thermal control for long working periods. It was the challenges involved in the design and implementation of the multi-coil array that initiated the first project of my dissertation. In this project, we present 1) a novel molding method for the construction of resin-impregnated wire patterns with irregular curved shapes along with a microcontroller-driven motorized machine for automated coil construction, 2) the design and validation of a water-cooling system using multiple parallel pipes impregnated with thermal epoxy, 3) a quality-controlled procedure of building the multi-coil array employing the technique of vacuum resin infusion. A multi-coil array was fabricated successfully and evaluated in multiple sites and then integrated into the first-prototype of the accessible head-only MR scanner. The similar quality of experimental images from the fabricated multi-coil array compared to those from conventional gradient coils indicates that the multi-coil array can effectively shape fields for both image encoding and B0 shimming. Our lab has shown that multi-coil technology offers advanced shim capability when imaging the human brain, but it could potentially benefit the imaging of other organs like the heart. The MR imaging of the heart is subject to dark band artifacts or signal loss caused by B0 inhomogeneity, which can result in misinterpretation of lesions and a reduction in diagnostic accuracy. It has been demonstrated in a recent study that the use of multi-coil techniques can significantly reduce B0 inhomogeneity within the heart based on shim analysis using in vivo B0 maps. Multi-coil arrays are not a standard configuration in commercial scanners but are normally used for research, B0 shimming is typically implemented by using the commonly-installed spherical harmonic shim coils in the first, second, and potentially third orders. The development of multi-coil technology, more in-depth design of the coil structure and geometry as well as the optimal use of the current spherical harmonic shim technology require a thorough understanding of cardiac B0 conditions across subjects and at a population level. Since the in vivo cardiac B0 measurement is not a routine clinical protocol and dedicated in vivo measurement for a large sample size are extremely labor intensive and expensive, the lack of such B0 data is a long-standing problem, especially for the subject groups like pediatric or elderly patients who cannot undergo B0 map measurement with breath hold. This challenge could be resolved by the use of B0 simulation on the basis of structural images from different imaging modalities, assuming that the B0 distributions inside the human heart depends on the anatomical structures surrounding heart and across the entire body. The challenge and assumption led to my second project regarding B0 magnetic field simulation in the human heart. We proposed a novel B0 simulation approach based on chest-abdomen-pelvis structural CT images and validated it using in vivo acquired B0 maps in the heart from the same subjects. This B0 simulation approach was then applied to CT images from more than one thousand subjects and the resultant large set of simulated B0 maps were analyzed with different shim types for searching optimal shim solution based on popular spherical harmonic decomposition. The derived B0 conditions were also statistically analyzed for potential correlation and linear association with demographic parameters of these subjects for investigating potential population-based shim strategy. By the use of in vivo acquisition, we also investigated the B0 magnetic field variation across cardiac cycle and evaluated the impact of these variations on in vivo cardiac B0 shimming. The results of this study allow us to better understand the primary sources and characteristics of B0 distributions in the heart as well as pave the way for developing optimal B0 shim methods within heart in both subject-specific and population-based manners.
126

Magnetic resonance imaging in cardiovascular disease

Richards, Jennifer Margaret Jane January 2013 (has links)
Background Superparamagnetic particles of iron oxide (SPIO) are part of a novel and exciting class of ‘smart’ magnetic resonance imaging (MRI) contrast agents that are taken up by inflammatory cells. Ultrasmall SPIO (USPIO; ~30 nm diameter) can be used to assess cellular tissue inflammation and SPIO (80-150 nm) have the potential to be used to label cells ex vivo for in vivo cell tracking studies. Objectives The aims of the thesis were therefore (i) to develop and validate quantitative MRI methodology for assessing SPIO uptake within tissues, (ii) to demonstrate USPIO accumulation within the aortic wall and its implications in patients with abdominal aortic aneurysms (AAA), and (iii) to develop and apply a Good Manufacturing Practice (GMP) compliant method of SPIO cell labelling in healthy volunteers. Methods Patients with asymptomatic AAA >4.0 cm in diameter were recruited. Imaging sequences were optimised in eight patients using a 3 tesla MRI scanner. Data were analysed using the decay constant for multi echo T2* weighted (T2*W) sequences (T2*) or its inverse (R2*) and the repeatability of these measurements was established. A further twenty-nine patients underwent MRI scanning before and 24- 36 hours after administration of USPIO. T2 and multi echo T2*W sequences were performed and ultrasound-based growth rate data were collected. Operative aortic wall tissue samples were obtained from patients undergoing open surgical aneurysm repair. A GMP compliant protocol was developed for labelling cells with SPIO for clinical cell tracking studies. The effects of SPIO-labelling on cell viability and function were assessed in vitro. A phased-dosing protocol was used to establish the safety of intravenous administration of SPIO-labelled cells in healthy volunteers. The feasibility of imaging cells at a target site in vivo following local or systemic administration was assessed. Tracking of SPIO-labelled cells to a target site was investigated by inducing an iatrogenic inflammatory focus in the skin of the anterior thigh of healthy volunteers, following which autologous SPIO-labelled cells were administered and their accumulation was assessed using MRI scanning and histology of skin biopsies. Results Robust and semi-quantitative data acquisition and image analysis methodology was developed for the assessment of SPIO accumulation in tissues. In patients with AAA, histological analysis of aortic wall tissue samples confirmed USPIO accumulation in areas of cellular inflammation. USPIO-enhanced MRI detected aortic wall inflammation and mural USPIO uptake was associated with a 3-fold higher aneurysm expansion rate. Human mononuclear cells were labelled with SPIO under GMP compliant conditions without affecting cell viability or function. Both local and intravenous administration of SPIO-labelled cells was safe and cells were detectable in vitro and in vivo using a clinical MRI scanner. SPIO-labelled cells tracked to a focal iatrogenic inflammatory focus following intravenous administration in humans and were detectable on MRI scanning and histological examination of skin biopsies. Conclusions SPIO contrast agents have an extensive range of potential clinical applications. USPIO uptake in the wall of AAA appears to identify cellular inflammation and predict accelerated aneurysm expansion. This is therefore a promising investigative tool for stratifying the risk of disease progression in patients with AAA, and may also be considered as a biomarker for response to novel pharmacological agents. The ability to label cells for non-invasive cell tracking studies would facilitate the further development of novel cell-based therapies and would enable assessment of dynamic inflammatory processes through inflammatory cell tracking.
127

The analysis of dynamic contrast-enhanced magnetic resonance imaging data : treatment effects, sampling rates and repeatability

Gill, Andrew Brian January 2014 (has links)
No description available.
128

High resolution black blood magnetic resonance imaging of atherosclerotic plaque

Zhu, Chengcheng January 2014 (has links)
No description available.
129

Physical analysis of BOLD fMRI signals for functional brain mapping and connectomics

Kundu, Prantik January 2014 (has links)
No description available.
130

Medical imaging: applications of functional magnetic resonance imaging and the development of a magnetic resonancecompatible ultrasound system

Tang, Mei-yee., 鄧美宜. January 2006 (has links)
published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

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