magnetic resonance imaging

Magnetic resonance imaging (MRI) is a very versatile imaging modality which can be used to acquire several different types of images. Some examples include anatomical images, images showing local brain activation and images depicting different types of pathologies. Brain activation is detected by means of functional magnetic resonance imaging (fMRI). This thesis presents two methods for adaptive spatial filtering of fMRI data. Contents 1 Introduction 1.1 Detection of brain activity 1.2 Separation of fat and water 1.3 How to read this thesis 1.4 Contributions 1.5 Publications 1.6 Notation 1.7 ...

A Riemannian manifold is a mathematical concept that generalizes curved surfaces to higher dimensions, giving a precise meaning to concepts like angle, length, area, volume and curvature. A glimpse of the consequences of a non-flat geometry is given on the sphere, where the shortest path between two points – a geodesic – is along a great circle. Different from Euclidean space, the angle sum of geodesic triangles on the sphere is always larger than 180 degrees. Signals and data found ...

Digital image analysis is the field of extracting relevant information from digital images. Recent developments in imaging techniques have made 3-dimensional volume images more common. This has created a need to extend existing 2D image analysis tools to handle images of higher dimensions. Such extensions are usually not straightforward. In many cases, the theoretical and computational complexity of a problem increases dramatically when an extra dimension is added.A fundamental problem in image analysis is image segmentation, i.e., identifying and separating ...

Turbulence is described by its main characteristics that are irregularity in time and space In hydromechanics, turbulence is referred to as chaotic movement superimposed on the flow of a fluid In the human body, turbulence typically arises in flows through heart valve prostheses and vascular or valvular stenoses. This thesis exploits a magnetic resonance imaging (MRI) phenomenon referred to as signal loss in order to develop a method for estimating turbulence intensity in blood flow. MRI measurements were carried out ...

Title: Simulation of Phase Contrast MRI Measurements from Numerical Flow Data Phase-contrast magnetic resonance imaging (PC-MRI) is a powerful tool for measuring blood flow and has a wide range of cardiovascular applications. Simulation of PC-MRI from numerical flow data would be useful for addressing the data quality of PC-MRI measurements and to study and understand different artifacts. It would also make it possible to optimize imaging parameters prior to the PC-MRI measurements and to evaluate different methods for measuring wall shear ...

Delivering ocular therapeutics to a target site with minimal side effects requires detailed information about the distribution and elimination pathways. This knowledge can guide the development of new drug delivery devices. In this study, we investigated the movement of two drug surrogates, H-110, which is lipophilic, and Gd-DTPA, which is hydrophilic, released from polymer-based implants using a fluorescein technique and magnetic resonance imaging (MRI). We also studied the pharmacokinetics of intravitreally injected triamcinolone acetonide, a low water soluble drug... Contents Chapter 1 ...

With the rapid increase in the elderly population, the number of Americans afflicted with vision impairment due to ocular disease is projected to rise substantially by the year 2020. Ocular disorders are becoming a major public health problem, and efforts have increased in recent years to develop methods of efficient drug delivery. Currently, the most effective method for treating serious ocular disorders is to inject drug solutions directly into the vitreous. However, injecting in this manner carries a high risk ...

The stethoscope is a recognized icon for the medical profession, and for a long time, physicians have relied on auscultation for detection and characterization of cardiac disease. New advances in cardiac imaging have however changed this picture. Echocardiography and magnetic resonance imaging (MRI) have become so dominating in cardiac assessment that the main use of cardiac auscultation is nowadays as a preliminary test in the primary health care. The aim of this thesis work has been to develop signal analysis methods ...

Multidimensional signals are generated in a large area of applications. In health care, such signals are used extensively and are generated with imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI) and ultra-sound imaging. These techniques produce large data sets that has to be processed and visualized, a process that is computationally complex and time consuming. Improvements in imaging techniques has made it possible to acquire not only ordinary images but e.g. 3-D ’pictures’ of the human body. The ...

Image enhancement in two dimension is a well known and used technique. But the technologies in image acquisition have developed and these techniques often provide image volumes in three or more dimensions, as in computer tomography, CT and magnetic resonance imaging, MRI. Three dimensions may contain two spatial coordinates and one temporal coordinate or three spatial coordinates as in 3D image volumes, which will be used in this thesis work. The aims of this work are; to find a method which ...