We have designed and demonstrated a new class of medical navigation methods that use the fingerprint-like biometrically distinct ultrasound echo patterns produced by different locations in tissue. As an example of this new biometric navigation approach, we have constructed and tested a system that uses ultrasound data to achieve prospective motion compensation in MRI, especially for respiratory motion during interventional MRI procedures in moving organs such as the liver. The ultrasound measurements are collated with geometrical information from MRI during a training stage to form a mapping table that relates ultrasound measurements to positions. During prospective correction, the system makes frequent ultrasound measurements and uses the map to determine the corresponding position. Results in motorized linear motion phantoms and freely breathing animals indicate that the system performs well. Apparent motion is reduced by up to 97.8%, and motion artifacts are reduced or eliminated in 2D Spoiled Gradient-Echo images. The motion compensation is sufficient to permit MRI thermometry of focused ultrasound heating during respiratory-like motion, with results similar to those obtained in the absence of motion. This new technique may have applications for MRI thermometry and other dynamic imaging in the abdomen during free breathing. We have also extended this technique to situations in which external position information during training is unavailable or incomplete, by extending the concept of Simultaneous Localization and Mapping to include determining the topology of a dense motion path through a gaussian random field. In the course of these investigations, we have also developed modified forms of referenceless MRI thermometry and Kalman filtering, specially adapted to optimize accuracy under our experimental conditions.

Posterior tibial tendon dysfunction (PTTD) is a common degenerative condition leading to a severe impairment of gait. There is currently no effective method to determine whether a patient with advanced PTTD would benefit from several months of bracing and physical therapy or ultimately require surgery. Tendon degeneration is closely associated with irreversible degradation of its collagen structure, leading to changes to its mechanical properties. If these properties could be monitored in vivo, it could be used to quantify the severity of tendonosis and help determine the appropriate treatment. Ultrasound elasticity imaging (UEI) is a real-time, noninvasive technique to objectively measure mechanical properties in soft tissue. It consists of acquiring a sequence of ultrasound frames and applying speckle tracking to estimate displacement and strain at each pixel. The goals of my dissertation were to 1) use acoustic simulations to investigate the performance of UEI during tendon deformation with different geometries; 2) develop and validate UEI as a potentially noninvasive technique for quantifying tendon mechanical properties in human cadaver experiments; 3) design a platform for UEI to measure mechanical properties of the PTT in vivo and determine whether there are detectable and quantifiable differences between healthy and diseased tendons. First, ultrasound simulations of tendon deformation were performed using an acoustic modeling program. The effects of different tendon geometries (cylinder and curved cylinder) on the performance of UEI were investigated. Modeling results indicated that UEI accurately estimated the strain in the cylinder geometry, but underestimated in the curved cylinder. The simulation also predicted that the out-of-the-plane motion of the PTT would cause a non-uniform strain pattern within incompressible homogeneous isotropic material. However, to average within a small region of interest determined by principal component analysis (PCA) would improve the estimation. Next, UEI was performed on five human cadaver feet mounted in a materials testing system (MTS) while the PTT was attached to a force actuator. A portable ultrasound scanner collected 2D data during loading cycles. Young's modulus was calculated from the strain, loading force and cross sectional area of the PTT. Average Young's modulus for the five tendons was (0.45±0.16GPa) using UEI. This was consistent with simultaneous measurements made by the MTS across the whole tendon (0.52±0.18GPa). We also calculated the scaling factor (0.12±0.01) between the load on the PTT and the inversion force at the forefoot, a measurable quantity in vivo. This study suggests that UEI could be a reliable in vivo technique for estimating the mechanical properties of the human PTT. Finally, we built a custom ankle inversion platform for in vivo imaging of human subjects (eight healthy volunteers and nine advanced PTTD patients). We found non-linear elastic properties of the PTTD, which could be quantified by the slope between the elastic modulus (E) and the inversion force (F). This slope (ΔE/ΔF), or Non-linear Elasticity Parameter (NEP), was significantly different for the two groups: 0.16±0.20 MPa/N for healthy tendons and 0.45±0.43 MPa/N for PTTD tendons. A receiver operating characteristic (ROC) curve revealed an area under the curve (AUC) of 0.83±0.07, which indicated that the classifier system is valid. In summary, the acoustic modeling, cadaveric studies, and in vivo experiments together demonstrated that UEI accurately quantifies tendon mechanical properties. As a valuable clinical tool, UEI also has the potential to help guide treatment decisions for advanced PTTD and other tendinopathies.

Pour ce travail de thèse, nous avons réalisé cinq études originales en utilisant trois technologies d'imageries cardiovasculaires non-invasives.-Nous avons démontré, à partir d'une étude ex-vivo sur des artères coronaires humaines, que le scanner64 détecteurs ne permettait pas de caractériser précisément les différents composants des plaques. Ladistinction des plaques fibreuses et des plaques lipidiques est en effet impossible. Par ailleurs, notretravail a montré que l'IVUS ne devait pas servir d'imagerie de référence lors des études sur la plaque carcet examen présente lui aussi de nombreuses imprécisions.-Notre travail sur la thrombo-aspiration rapporte un effet très significatif de l'extraction effective dethrombus lors des thrombo-aspirations à la phase aiguë des STEMI, avec une réduction de la taille du no-reflow et de l'infarctus, évaluées en IRM ; une thrombo-aspiration positive représentant par ailleurs dansnotre travail, un critère indépendamment lié à la taille finale de l'infarctus. L'extraction effective dethrombus pourrait être considéré, en salle de cathétérisme, comme un critère de jugement de l'efficacitéde la thrombo-aspiration.-Notre étude sur les syndomes coronaires à coronaires angiographiquement normales a confirmé l'intérêtde l'IRM dans le bilan étiologique de cette présentation clinique, permettant un diagnostic étiologiquedans 2/3 des cas. Par ailleurs, nous avons observé une excellente évolution pour le tiers des patients chezqui l'IRM ne décèle pas d'anomalie myocardique. Des études d'une plus grande envergure serontnécessaires afin de confirmer nos résultats.-A partir d'IRM cardiaque réalisées chez des patients ayant présenté un premier épisode de STEMI, nousavons pu déterminer une valuer seuil de troponine prédictive de la survenue d'un no-reflow.-Enfin, à partir d'analyses en Speckle Tracking, nous avons mis en évidence une dysfonction systolique VD,objectivée par une altération des valeurs de Strain longitudinal VD, chez les patients présentant une EPgrave ou de gravité intermédiaire, comparativement à un groupe de patients avec une EP non grave. / In this doctoral thesis, we report on five original studies that use three différent non-invasive cardiovascular imaging techniques:- In an ex vivo study of human coronary arteries, we show that 64-slice computed tomography (CT) scan isnot capable of distinguishing between différent components of plaques. Indeed, it is impossible todifferentiate between fibrous and lipid plaques. Our study also showed that intravascular ultrasound(IVUS) should not be used as thé référence method in studies of plaque composition, since this techniquealso suffers from numerous limitations.- Our study of thé efficacy of thrombo-aspiration showed a significant benefit with effective extraction ofthrombus during thrombo-aspiration at thé acute phase of ST élévation myocardial infarction (STEMI),notably with a réduction of thé extent of no-reflow and of infarct size as evaluated by magnetic résonanceimaging (MRI). Productive thrombo-aspiration was shown in our study to be an independent predictor offinal infarct size. Effective extraction of thrombotic material could be considered in thé cathlab as acriterion for evaluating thé success of thé thrombo-aspiration procédure.- Our study of acute coronary syndromes with normal coronary arteries confirmed thé utility of MRI inestablishing thé etiology of this clinical présentation, and made it possible to establish an etiologicaldiagnosis in two-thirds of patients. We also observed excellent outcomes in thé third of patients in whomMRI did not find any myocardial anomalies. Larger studies are warranted to confirm thèse findings.- Based on cardiac MRI performed in patients presenting a first épisode of STEMI, we established athreshold value of troponin that predicts thé occurrence of no-reflow.- Lastly, using speckle-tracking analysis, we demonstrated impaired systolic right ventricular function inpatients with intermediate to high risk pulmonary embolism (PE), evaluated by altérations in longitudinalstrain values at thé level of thé right ventricle, compared to a control group of patients with low risk PE.

La thématique de la thèse est très vaste. Sont présentées les grandeurs cinématiques locales ou régionales qui agissent sur le corps humain. La deuxième partie de la thèse décrit les méthodes optiques, par lesquelles on peut mesurer les vibrations produites par les machines-outils sur le système humain main-bras au cours de l'activité au travail. Dans la troisième partie sont donnés les effets négatifs des vibrations qui se produisent sur le système humain main-bras pendant l'exposition aux vibrations. La quatrième partie de cette thèse contient la base théorique des techniques optiques utilisées pour mesurer les vibrations. Le chapitre cinq présente la méthodologie d'expérimentation pour mesurer les vibrations. Les résultats des mesures sont indiqués dans le sixième chapitre de la thèse. Dans le chapitre sept on présente la modélisation mécanique et mathématique du système humain main-bras avec trois degrés de liberté et le dernier chapitre contient les conclusions finales.

This project presents regional velocity measurements for the eastern portion of the St. Elias Mountains, including the entire glaciated area of Kluane National Park, derived from speckle tracking of Radarsat-2 imagery acquired in winter 2011 and 2012. This technique uses a cross-correlation approach to determine the displacement of the ‘speckle’ pattern of radar phase returns between two repeat-pass images. Further reconstruction of past velocities is performed on a selection of key glaciers using feature tracking of Landsat-5 imagery, allowing for the investigation of variability in glacier motion on interannual and decadal time scales. The results of the analysis showed that there is a strong velocity gradient across the region reflecting high accumulation rates on the Pacific-facing slope of the mountain range. These glaciers may have velocities an order of magnitude greater than glaciers of a similar size on the landward slope. Interannual variability was high, both in relation to surge events, of which a number were identified, and variation of other unknown controls on glacier motion. A long-term trend of velocity decrease was observed on the Kaskawulsh Glacier when comparing the results of this analysis to work carried out in the 1960s, the pattern of which is broadly congruent to measurements of surface elevation change over a similar period.

The work present in this thesis report introduces a novel non-destructive technique for experimentally measuring through thickness hygro-thermal strain of Nafion membranes though digital image correlation. An Optical Coherence Tomography (OCT) system was used to acquire images of a Nafion-TiO2 (titanium dioxide powder) composite membranes in a fuel cell like device. The proposed technique, commonly known as optical coherence elastography (OCE) makes use of the normalized correlation algorithm to calculate strain between two successive scans of different relative humidity step values. Different normalized correlation parameters were compared to measured results of PDMS-TiO2 phantoms in order to analyze accuracy. The effect of TiO2 on Nafion membranbes mechanical properties was further analysed by comparing the swelling behaviour of membranes with different concentrations. It has been found that Nafion undergoes approximately 25 – 30% more strain on the land section than on the channel section, regardless gas diffusion electrode (GDE) layer presence. Furthermore, it was shown that the overall strain on the material decrease by approximately 10% when GDE layers are present. Overall this work demonstrated how OCE is a viable technique for measuring through thickness strain distribution in Nafion composite membranes and has the potential to be implemented for non-destructive in situ measurements. / Graduate / 0548 / kellerv@uvic.ca

A novel delamination identification technique based on a low-population genetic algorithm for the quantitative characterisation of a single delamination in composite laminated panels is developed, and validated experimentally The damage identification method is formulated as an inverse problem through which system parameters are identified. The input of the inverse problem, the central geometric moments (CGM), is calculated from the surface out-of-plane displacements measurements of a delaminated panel obtained from Digital Speckle Pattern Interferometry (DSPI). The output parameters, the planar location, size and depth of the flaw, are the solution to the inverse problem to characterise an idealised elliptical flaw. The inverse problem is then reduced to an optimisation problem where the objective function is defined as the L2 norm of the difference between the CGM obtained from a finite element (FE) model with a trial delamination and the moments computed from the DSPI measurements. The optimum crack parameters are found by minimising the objective function through the use of a low-population real-coded genetic algorithm (LARGA). DSPI measurements of ten delaminated T700/LTM-45EL carbon/epoxy laminate panels with embedded delaminations are used to validate the methodology presented in this thesis.

Background: Loading conditions are recognized to influence ventricular function according to the Starling relationship for length/stretch and force.  Many modern echocardiographic parameters which have been announced as describing ventricular function and contractile status, may be confounded by uncontrolled and unmeasured load.  These studies aimed to measure the relation between four differ­ent types of assessments of ventricular dysfunction and degrees of load.  Study examined the ‘myo­cardial performance index’ (MPI).  Study II examined long axis segmental mechanical dyssynchrony.  Study III examined tissue velocities, and Study IV examined ventricular twist.  All studies aimed to describe the relation of these parameters both to load and to inotropic changes. Methods:  In anesthetized juvenile pigs, left ventricular (LV) pressure and volume were measured continuously and their relationship (LVPVR) was analysed.  Preload alterations were brought about by inflation of a balloon tipped catheter in the inferior vena cava (IVCBO).  Inotropic interventions were brought about by either an overdose of anesthetic (combine intravenous pentobarbital and inhaled isoflurane, Study I), or beta blocker and calcium channel blocker given in combination (Stud­ies III and IV).  In one study (II), global myocardial injury and dysfunction was induced by endotoxin infusion.  MPI measurements were derived from LVPVR heart cycle intervals for isovolumic contrac­tion and relaxation as well as ejection time.  Long axis segmental dyssynchrony was derived by ana­lyzing for internal flow and time with segmental dyssynchronous segment volume change during systole, hourly before and during 3 hours of endotoxin infusion.  Myocardial tissue velocities were measured during IVCBO at control, during positive and then later negative inotropic interventions.  The same for apical and base circumferential rotational velocities by speckle tracking.  Load markers (including end-diastolic volume) were identified for each beat, and the test parameters were analysed together with load for a relation.  The test parameters were also tested during single apneic beats for a relation to inotropic interventions. Results: MPI demonstrated a strong and linear relationship to both preload and after-load, and this was due to changes in ejection time, and not the isovolumic intervals.  Long axis segmental dyssyn­chrony increased during each hour of endotoxin infusion and global myocardial injury.  This dysyn­chrony parameter was independent of load when tested by IVCBO. Peak systolic velocities were strongly load-independent, though not in all the inotropic situations and by all measurement axes.  Peak systolic strain was load-dependent, and not strongly related to inotropic conditions.  Peak sys­tolic LV twist and untwist were strongly load-dependent. Conclusions: MPI is strongly load-dependent, and can vary widely in value for the same contractile status if the load is varied.  Mechanical dyssynchrony measures are load-independen in health and also in early global endotoxin myocardial injury and dysfunction.  Peak sytole velocities are a clinically robust parameter of LV regional and global performance under changing load, though peak systolic strain seems to be load-dependent.  Left ventricular twist and untwist are load-dependent in this pig model.

This research demonstrates the feasibility of a full-field photographic method for remotely measuring the movement of large deforming objects. 'Large objects' could include civil engineering structures such as dam walls, buildings and bridges, and geological phenomena such as glaciers. Such structures must be examined in situ and preferably by a non contacting method. The objective is to measure motion from time lapsed photographs of the moving object. The method is based on speckle photography which is a well developed optical metrology technique for deformation measurement of engineering structures in laboratory conditions. Its application to large scale structures illuminated in sunlight at high imaging demagnifications has demanded some significant extensions and modifications to the technique. Imaging these large objects offers a unique set of challenges which include the establishment of rigid tripods from which to take the time lapsed photographs in rugged glacial terrain, the variation of illumination in terms of both quality and angle of incidence, imaging through several kilometres of turbulent atmosphere and recording the signature texture of the object surface onto film at high imaging demagnifications. The effects of these factors are considered both conceptually and experimentally, providing fundamental understanding of the problem. Displacement analysis is performed primarily by interrogation of time lapsed negative pairs using an unexpanded laser beam, as is generally the case in speckle photography. An automated system is developed to make practical the analysis of multiple points in the field of view. In parallel, a new digital technique is introduced where displacement results are obtained by pattern matching in digital versions of the speckle images. This analysis method is shown to be highly suitable for the application to glacier flow. Registration of the pair of time lapsed images is performed by calculating the affine transform describing the image misalignment (introduced at either the recording or analysis stage) within the non-deforming areas of the field of view. Use of this novel technique allows pairs of single exposures, rather than double exposures, to be examined, and it also increases the sensitivity of measurement. Two dimensional motion fields representing glacier flow are presented, leading to the conclusion that the technique is feasible in sunlight illumination, for a variety of glacial surface types and at high imaging demagnifications.

Stuttgart, Univ, Diss., 2007 (Nicht für den Austausch).