There is a large need for accurate methods detecting cardiovascular diseases, since they are one of the leading causes of mortality in the world, accounting for 29.3% of all deaths. Due to the complexity of the cardiovascular system, it is very challenging to develop methods for quantification of its function in order to diagnose, prevent and treat cardiovascular diseases. Ultrasound is a technique allowing for inexpensive, noninvasive imaging, but requires an experienced echocardiographer. Nowadays, methods like Tissue Doppler imaging (TDI) and Speckle tracking imaging (STI), measuring motion and deformation in the myocardium and the vessel walls, are getting more common in routine clinical practice, but without a proper visualization of the data provided by these methods, they are time-consuming and difficult to interpret. Thus, the general aim of this thesis was to develop novel ultrasound-based methods for accurate quantification and easily interpretable visualization of cardiovascular function. Five methods based on TDI and STI were developed in the present studies. The first study comprised development of a method for generation of bull’s-eye plots providing a color-coded two-dimensional visualization of myocardial longitudinal velocities. The second study proposed the state diagram of the heart as a new circular visualization tool for cardiac mechanics, including segmental color-coding of cardiac time intervals. The third study included development of a method describing the rotation pattern of the left ventricle by calculating rotation axes at different levels of the left ventricle throughout the cardiac cycle. In the fourth study, deformation data from the artery wall were tested as input to wave intensity analysis providing information of the ventricular – arterial interaction. The fifth study included an in-silico feasibility study to test the assessment of both radial and longitudinal strain in a kinematic model of the carotid artery. The studies showed promising results indicating that the methods have potential for the detection of different cardiovascular diseases and are feasible for use in the clinical setting. However, further development of the methods and both quantitative comparison of user dependency, accuracy and ease of use with other established methods evaluating cardiovascular function, as well as additional testing of the clinical potential in larger study populations, are needed. / QC 20100727

Pain and disorders of the human skeletal muscles are one of the most common reasons for medical consultations in the western countries today and there is a great need to improve both the understanding and treatment of several different muscular conditions. Techniques describing the muscle function in vivo are often limited by either their invasiveness or lack of spatial resolution. Electromyography (EMG) is the most common approach to assess the skeletal muscle function in vivo, providing information on the neurological input. However, the spatial resolution is in general limited and there are difficulties reaching deep musculature without using invasive needles. Moreover, it does not provide any information about muscle structure or mechanical aspects. Quantitative ultrasound techniques have gained interest in the area of skeletal muscles and enables non-invasive and in-vivo insight to the intramuscular activity, through the mechanical response of the activation. However, these techniques are developed and evaluated for cardiovascular applications and there are important considerations to be made when applying these methods in the musculoskeletal field.  This thesis is based on the work from four papers with the main focus to investigate and describe some of these considerations in combination with the development of processing and analyzing methods that can be used to describe the physiological characteristics of active muscle tissue. In the first paper the accuracy of the Doppler based technique Tissue Velocity Imaging (TVI) was evaluated in a phantom study for very low tissue velocities and the effect of the pulse repetition frequency was considered. The second paper presents a biomechanical model to describe the TVI strain’s dependency on the muscle fiber pennation angle. In the third and fourth papers the intramuscular activity pattern was assessed through the regional tissue deformation by motion mode (M-mode) strain imaging. The activity patterns were analyzed during force regulation and for the effects of fatigue. The work of this thesis show promising results for the application of these methods on skeletal muscles and indicate high clinical potential where quantitative ultrasound may be a valuable tool to reach a more multifaceted and comprehensive insight in the musculoskeletal function. However, the methodological considerations are highly important for the optimized application and further evaluation and development of analyzing strategies are needed. / <p>QC 20130516</p>

Laser altimetry and satellite gravity surveys indicate that the St Elias Icefields are currently losing mass and are among the largest non-polar sea level contributors in the world. However, a poor understanding of glacier dynamics in the region is a major hurdle in evaluating regional variations in ice motion and the relationship between changing surface conditions and ice flux. This study combines in-situ dGPS measurements and advanced Radarsat-2 (RS-2) processing techniques to determine daily and seasonal ice velocities for the Kaskawulsh Glacier from summer 2009 to summer 2011. Three permanent dGPS stations were installed along the centreline of the glacier in 2009, with an additional permanent station on the South Arm in 2010. The Precise Point Positioning (PPP) method is used to process the dGPS data using high accuracy orbital reconstruction. RS-2 imagery was acquired on a 24-day cycle from January to March 2010, and from October to March 2010-2011 in a combination of ultra-fine and fine beam modes. Seasonal velocity regimes are readily identifiable in the dGPS results, with distinct variations in both horizontal velocity and vertical motion. The Spring Regime consists of an annual peak in horizontal velocity that corresponds closely with the onset of the melt season and progresses up-glacier, following the onset of melt at each station. The Summer Regime sees variable horizontal velocity and vertical uplift, superimposed on a long-term decline in motion. The Fall Regime sees a gradual slowing at all stations with little variation in horizontal velocity or vertical position. Rapid but short accelerations lasting up to 10 days were seen in the Winter regimes in both 2010 and 2011, occurring at various times throughout each regime. These events initiated at the Upper Station and progress down-glacier at propagation speeds up to 16,380 m day-1 and were accompanied by vertical uplift lasting for similar periods. Three velocity maps, one from the winter of 2010 and two from the fall/winter of 2011, produced from speckle tracking were validated by comparison with dGPS velocity, surface flow direction, and bedrock areas of zero motion, with an average velocity error of 2.0% and average difference in orientation of 4.3º.

We demonstrated simultaneous intrinsic optical signal imaging (IOSI) and laser speckle contrast imaging (LSCI) using coherence modulation of vertical-cavity surface-emitting laser (VCSEL) diodes. The unique properties of VCSELs were exploited to deliver rapidly switched coherent and non-coherent illumination suitable for high resolution LSCI and IOSI, respectively. Utilizing three near-infrared VCSELs we were able to map changes in cortical blood oxygenation and flow during ischemia. Additionally, the subtle reflectance changes associated with cortical spreading depression were imaged using non-coherent VCSEL illumination. We are currently using two-photon laser-scanning microscopy to quantify the accuracy of LSCI and IOSI implementations. The small size and efficiency of VCSELs and modern photo diodes, makes the development of implantable dual-mode imaging devices feasible. Devices capable of chronic imaging of cortical hemodynamics could significantly enhance the range of studies available to neuroscientists and significantly aid clinicians postoperatively. The research presented in this thesis significantly furthers this objective.

We demonstrated simultaneous intrinsic optical signal imaging (IOSI) and laser speckle contrast imaging (LSCI) using coherence modulation of vertical-cavity surface-emitting laser (VCSEL) diodes. The unique properties of VCSELs were exploited to deliver rapidly switched coherent and non-coherent illumination suitable for high resolution LSCI and IOSI, respectively. Utilizing three near-infrared VCSELs we were able to map changes in cortical blood oxygenation and flow during ischemia. Additionally, the subtle reflectance changes associated with cortical spreading depression were imaged using non-coherent VCSEL illumination. We are currently using two-photon laser-scanning microscopy to quantify the accuracy of LSCI and IOSI implementations. The small size and efficiency of VCSELs and modern photo diodes, makes the development of implantable dual-mode imaging devices feasible. Devices capable of chronic imaging of cortical hemodynamics could significantly enhance the range of studies available to neuroscientists and significantly aid clinicians postoperatively. The research presented in this thesis significantly furthers this objective.

Abordando las importantes características dinámicas del ojo, se han planteado una serie de experimentos que permiten el estudio de algunas de estas propiedades dinámicas, para proporcionar nueva información sobre el sistema visual. Para dichos experimentos, se han diseñado y construido tres instrumentos de medida basados todos en el concepto del sensor de Hartmann-Shack (HS), cada uno con características particulares: sensor HS de alta resolución temporal, sensor HS de campo amplio y sensor HS con iluminación invisible. Con estos instrumentos se abordan condiciones específicas que pueden afectar la dinámica del ojo, como los posibles efectos que tiene el cambio en la línea de mirada (o la torsión del ojo) sobre las aberraciones, así como las potenciales diferencias que se puede generar sobre las aberraciones cuando los sujetos observan con visión monocular o binocular, o evaluar si en el ojo existe una longitud de onda "preferida" para enfocar estímulos policromáticos. / Addressing the important dynamic characteristics of the eye, a number of experiments were performed to study some of these dynamic properties, in order to provide new information about the visual system. To carry out these experiments, three instruments were designed and implemented, all of them based on the Hartmann-Shack sensor (HS) principle, but each one with particular characteristics: high time resolution HS sensor, wide field HS sensor and HS sensor with invisible illumination. Specific conditions that can affect the dynamics of the eye were addressed with these instruments, for example the possible effects arising from changes in the line of sight (gaze) on the aberrations, or the potential differences that can be generated on aberrations when subjects are under monocular or binocular vision, or evaluate if is there a "preferential" wavelength the eye uses to focus polychromatic stimuli.

Image noise reduction, or denoising, is an active area of research, although many of the techniques cited in the literature mainly target additive white noise. With an emphasis on signal-dependent noise, this thesis presents the General Adaptive Monte Carlo Bayesian Image Denoising (GAMBID) algorithm, a model-free approach based on random sampling. Testing is conducted on synthetic images with two different signal-dependent noise types as well as on real synthetic aperture radar and ultrasound images. Results show that GAMBID can achieve state-of-the-art performance, but suffers from some limitations in dealing with textures and fine low-contrast features. These aspects can by addressed in future iterations when GAMBID is expanded to become a versatile denoising framework.

Image noise reduction, or denoising, is an active area of research, although many of the techniques cited in the literature mainly target additive white noise. With an emphasis on signal-dependent noise, this thesis presents the General Adaptive Monte Carlo Bayesian Image Denoising (GAMBID) algorithm, a model-free approach based on random sampling. Testing is conducted on synthetic images with two different signal-dependent noise types as well as on real synthetic aperture radar and ultrasound images. Results show that GAMBID can achieve state-of-the-art performance, but suffers from some limitations in dealing with textures and fine low-contrast features. These aspects can by addressed in future iterations when GAMBID is expanded to become a versatile denoising framework.

<p>This dissertation aims to demonstrate the feasibility of direct infarct visualization using 3D medical ultrasound. The dissertation proceeds by providing the first ever demonstration of fully-sampled 3D ultrasonic speckle tracking using raw B-Mode data of the heart. The initial demonstration uses a Cramer-Rao lower bound limited displacement estimator. The dissertation then proceeds to develop an implementable method for biased time-delay estimation. Biased time-delay estimation is shown to surpass the traditional limits described by the Cramer-Rao lower bound in a mean square error sense. Additional characterization of this new class of estimator is performed to demonstrate that with easily obtainable levels of prior information it is possible to estimate displacements that do surpass the Cramer-Rao lower bound. Finally, using 2D and 3D realizations of biased displacement estimation (Bayesian speckle tracking) the passive strain induced in the ventricle walls during atrial systole is shown to be sufficient to distinguish healthy and chronically infarcted myocardium.</p> / Dissertation

Phase-extraction from fringe patterns is an inevitable procedure in the field of optical metrology and interferometry. However, speckle noise will introduce and influence the precision of wrapped phase map when a coherent light is used. In this thesis, we use the bidimensional empirical mode decomposition (BEMD) to perform the speckle-reduction. Moreover, different interpolation method in BEMD will be used to compare their performance in speckle-reduction. Finally, the database will be developed to make the BEMD a robotic tool to reduce noises. And the database also points out that the performance of BEMD is highly related to the fringe period, the fringe visibility, and the SNR of speckle noise.