Quantitative validation of optical flow based myocardial strain measures using sonomicrometry

Dynamic cardiac metrics, including myocardial strains and displacements, provide a quantitative approach to evaluate cardiac function. However, in current clinical diagnosis, largely 2D strain measures are used despite that cardiac motions are complex 3D volumes over time. Recent advances in 4D ultrasound enable the capability to capture such complex motion in a single image data set. In our previous work, a 4D optical flow based motion tracking algorithm was developed to extract full 4D dynamic cardiac metrics from such 4D ultrasound data. In order to quantitatively evaluate this tracking method, in-vivo coronary artery occlusion experiments at various locations were performed on three canine hearts. Each dog was screened with 4D ultrasound and sonomicrometry data was acquired during each occlusion study. The 4D ultrasound data from these experiments was then analyzed with the tracking method and estimated principal strain measures were directly compared to those recorded by sonomicrometry. Strong agreement was observed independently for the three canine hearts. This is the first validation study of optical flow based strain estimation for 4D ultrasound with a direct comparison with sonomicrometry using in-vivo data

Comparing Optical-Flow Based Methods for Quantification of Myocardial Deformations on RT3D Ultrasound

This paper presents a new homogeneity measure for variational segmentation with multiple level set functions. We propose to modify the quadratic homogeneity measure to trade off the convexity of the function against a faster rate of convergence. We tested in two series of experiments the performance of this new homogeneity force at converging to appropriate partitioning of brain MRI data sets, over a large range of image spatial resolution and image quality, in terms of tissue homogeneity and contrast

Quantification of right and left ventricular function with real-time three-dimensional ultrasound

Presents a study for validation of real-time three-dimensional ultrasound as a diagnostic tool in patients with primary pulmonary hypertension. Dynamic analysis of the heart is performed via quantification of right and left ventricle volumes. Segmentation of ventricular cavities is performed via a deformable-model for a set of denoised frames spread over an entire cardiac cycle. Spatio-temporal denoising is carried out by brushlet analysis that has been optimized by incorporating space and time coherence. in. texture characterization. Quantitative measures for right and left ventricular ejection fraction are compared to clinical MRI of the same patients

Joint state and parameter estimation for distributed mechanical systems

We present a novel strategy to perform estimation for a dynamical mechanical system in standard operating conditions, namely, without ad hoc experimental testing. We adopt a sequential approach, and the joint state-parameter estimation procedure is based on a state estimator inspired from collocated feedback control. This type of state estimator is chosen due to its particular effectiveness and robustness, but the methodology proposed to adequately extend state estimation to joint state-parameter estimation is general, and - indeed -applicable with any other choice of state feedback observer. The convergence of the resulting joint estimator is mathematically established. In addition, we demonstrate its effectiveness with a biomechanical test problem defined to feature the same essential characteristics as a heart model, in which we identify localized contractility and stiffness parameters using measurements of a type that is available in medical imaging

Évaluation des propriétés mécaniques du tissu cardiaque par échocardiographie

RÉSUMÉ Les survivants de leucémie lymphoblastique aigüe (LLA) sont à risque de développer une insuffisance cardiaque à long terme à cause de l’effet cardiotoxique intrinsèque au traitement par anthracyclines. Une dysfonction cardiaque peut apparaître plusieurs années après la fin du traitement. Les outils diagnostiques actuels détectent tardivement des changements au niveau fonctionnel du coeur. L’hypothèse à l’étude dans ce projet est que les changements au niveau cellulaire qui précèdent la dysfonction cardiaque ont une influence sur les propriétés mécaniques du tissu. Ce faisant, l’identification des propriétés mécaniques du coeur pourrait être utilisée pour suivre la progression de la maladie. Ce projet s’intègre au projet PETALE du Centre Universitaire Hospitalier Ste-Justine qui étudie les effets secondaires tardifs chez les survivants de LLA. L’objectif à long terme est de développer une méthode diagnostique non-invasive permettant de prédire des changements fonctionnels du coeur. Les objectifs spécifiques de ce projet sont 1) évaluer la santé cardiaque d’une cohorte de survivants de leucémie lymphoblastique aigüe, 2) développer une approche basée sur la méthode des champs virtuels (MCV) permettant d’identifier les propriétés mécaniques du tissu cardiaque à partir d’images échocardiographiques et 3) valider cette méthode à l’aide de modèles éléments finis. Une étude clinique a d’abord été conduite auprès de la cohorte PETALE. Une évaluation échocardiographique complète a été effectuée chez tous les patients incluant le mode M, le mode Doppler, Doppler tissulaire et le suivi des déformations par speckle-tracking. Les résultats ont été analysés en fonction du groupe de risque de comorbidités et de l’administration d’un agent cardioprotecteur (dexrazoxane). Les patients à haut risque ont reçu une dose cumulative d’anthracycline plus élevée que les patients à risque standard. Les résultats démontrent que les patients du groupe à risque élevé n’ayant pas reçu de dexrazoxane ont une fonction cardiaque diminuée par rapport aux patients à haut risque ayant reçu un cardioprotecteur et aux patients à risque standard. De plus, l’obésité et la résistance à l’insuline sont les facteurs déterminants de la santé cardiovasculaire à long terme chez cette population. Toutefois, les outils actuels sont limités et ne permettent pas d’évaluer de manière précise le risque de développer une insuffisance cardiaque dans un futur rapproché. Suivant cette analyse, une méthode d’identification de propriétés mécaniques du myocarde spécifique à l’échocardiographie est décrite. Dans cette approche, le coeur est considéré homogène, isotrope et ayant un comportement hyperélastique suivant une loi d’Ogden incompressible.----------ABSTRACT Long-term cardiotoxicity has been described in acute lymphoblastic leukemia (ALL) survivors. These patients often suffer from a wide spectrum of cardiac abnormalities associated with anthracycline administration. Actual follow-up of these patients is not sensitive enough to detect cardiac changes before the onset of the functional incapacity. As a matter of fact, the evaluation of mechanical properties of the cardiac muscle is not part of the common diagnostic tools. We hypothesized that changes at a cellular level preceding cardiac dysfunction have an impact on the mechanical behaviour of the myocardium. Identification of mechanical properties could be used in the monitoring of patients at risk of developing heart failure. This project was part of the PETALE project at University Hospital Center Ste-Justine that aims to study long-term chronic side effects in ALL survivors. The long-term objective of this project was to develop a non-invasive and sensitive technique that makes use of myocardial mechanical parameters for the prediction of functional changes in the heart. This project specifically aimed to 1) assess the cardiac health of an ALL survivors cohort, 2) develop a framework based on the virtual fields method to identify mechanical properties of myocardium in echocardiographic images and 3) validate this method using finite element models. Therefore, a clinical study was conducted on ALL survivors from the PETALE cohort. These patients underwent a complete echocardiographic assessment, including M mode, Doppler, Tissue Doppler and Speckle-tracking echocardiography. Results were analyzed according to initial ALL risk status and cardioprotection administration (dexrazoxane). Patients treated for high risk ALL received a higher cumulative anthracycline dose than patients treated for standard risk ALL. Results showed that patients treated for high risk ALL who did not receive dexrazoxane had a decreased heart function when compared with patients who received dexrazoxane or those who had a standard risk of comorbidities. Moreover, obesity and insulin resistance are the strongest determinants of cardiovascular health in the long term for ALL survivors. However, current diagnostic tools are limited and cannot evaluate the risk of future heart failure adequately. Following this analysis, an identification method specific to echocardiography was described. In this framework, heart was considered homogeneous with an incompressible isotropic hyperelastic behaviour that fits an Ogden law. Intraventricular pressure was used as a boundary condition. Pressure was obtained from a lumped parameter model that represents the heart as three thick wall mechanically coupled (CircAdapt model)

Early Detection of Doxorubicin-Induced Cardiotoxicity Using Combined Biomechanical Modeling and Multi-Parametric Cardiovascular MRI

RÉSUMÉ La chimiothérapie à la doxorubicine est efficace et est largement utilisée pour traiter la leucémie lymphoblastique aiguë. Toutefois, son efficacité est entravée par un large spectre de cardiotoxicités incluant des changements affectant à la fois la morphologie et la fonction du myocarde. Ces changements dépendent principalement de la dose cumulée administrée au patient. Actuellement, très peu de techniques sont disponibles pour détecter de telles cardiotoxicités. L'utilisation d’images de fibres musculaires (par exemple, à l’aide de l’imagerie des tenseurs de diffusion par IRM) ou des techniques d'imagerie 3D (par exemple, ciné DENSE IRM) sont des alternatives prometteuses, cependant, leur application en clinique est limitée en raison du temps d'acquisition d’images et les erreurs d'estimation qui en résultent. En revanche, l'utilisation de l'IRM multi-paramétrique ainsi que le ciné IRM sont des alternatives prometteuses, puisque ces techniques sont déjà disponibles au niveau clinique. L’IRM multiparamétrique incluant l’imagerie des temps de relaxation T1 et T2 peut être utile dans la détection des lésions dans le tissu du myocarde alors que l’imagerie ciné IRM peut être plus appropriée pour détecter les changements fonctionnels au sein du myocarde. La combinaison de ces deux techniques peut également permettre une caractérisation complète de la fonction du tissu myocardique. Dans ce projet, l'utilisation des temps de relaxation T1 pré- et post-gadolinium et T2 est d'abord évaluée et proposée pour détecter les dommages myocardiques induits par la chimiothérapie à la doxorubicine. En second lieu, l'utilisation de patrons 2D de déplacements myocardiques est évaluée dans le cadre de la détection des dommages myocardiques et altération fonctionnelle due au traitement à la doxorubicine. Enfin, l'utilisation de la modélisation par éléments finis, incluant les contraintes et déformations mécaniques est proposée pour évaluer les changements dans les propriétés mécaniques au niveau du myocarde, avec l’hypothèse que le traitement à base de doxorubicine induit des changements importants à la fois dans le tissu et au niveau de la fonction myocardique. Dans notre cohorte de survivants de cancer, des changements myocardiques locaux ont été trouvés entre le groupe à risque standard et le groupe à risque élevé lorsque le T1 pré-gadolinium fut utilisé. Ces changements ont été amplifiés avec l’utilisation d’agent de contraste tel que confirmé par le coefficient de partition, ce qui suggère que l’utilisation du T1 post-gadolonium et le coefficient de----------ABSTRACT Doxorubicin chemotherapy is effective and widely used to treat acute lymphoblastic leukemia. However, its effectiveness is hampered by a wide spectrum of dose-dependent cardiotoxicity including both morphological and functional changes affecting the myocardium. Currently, very few techniques are available for detecting such cardiotoxic effect. The use of muscle fibers orientation (e.g., diffusion tensor imaging DT-MRI) or 3D imaging techniques (e.g., cine DENSE MRI) are possible alternatives, however, their clinical application is limited due to the acquisition time and their estimation errors. In contrast, the use of multi-parametric MRI along with cine MRI is a promising alternative, since theses techniques are already available at a clinical level. Multiparametric MRI including T1 and T2 imaging may be helpful in detecting myocardial tissue damage, while cine MRI may be more appropriate to detect functional changes within the myocardium. The combination of these two techniques may further allow an extensive characterization of myocardial tissue function. In this doctoral project, the use of pre- and post-gadolinium T1 and T2 relaxation times is firstly assessed and proposed to detect myocardial damage induced by doxorubicin chemotherapy. Secondly, the use of 2D myocardial displacement patterns is assessed in detecting myocardial damage and functional alteration due to doxorubicin-based treatment. Finally, the use of finite element modeling including mechanical strains and stresses to evaluate mechanical properties changes within the myocardium is alternatively proposed, assuming that doxorubicin-based treatment induces significant changes to both myocardial tissue morphology and function. In our cohort of cancer survivors, local myocardial changes were found between standard risk and high risks group using pre-gadolinium T1 relaxation times. These changes were further amplified with gadolinium enhancement, as confirmed by the use of partition coefficient, suggesting this MRI parameter along with partition coefficient as candidates imaging markers of doxorubicin induced cardiomyopathy. The use of T2 on the other hand showed that the high risk group of cancer survivors had higher T2 relaxation times compared to the standard risk group and similar to reported values. Though, a larger cohort of cancer survivors may be required to assess the use of T1 and T2 relaxation time as possible indices for myocardial tissue damage in the onset of doxorubicin-induced cardiotoxicity

Proceedings of the Third International Workshop on Mathematical Foundations of Computational Anatomy - Geometrical and Statistical Methods for Modelling Biological Shape Variability

International audienceComputational anatomy is an emerging discipline at the interface of geometry, statistics and image analysis which aims at modeling and analyzing the biological shape of tissues and organs. The goal is to estimate representative organ anatomies across diseases, populations, species or ages, to model the organ development across time (growth or aging), to establish their variability, and to correlate this variability information with other functional, genetic or structural information. The Mathematical Foundations of Computational Anatomy (MFCA) workshop aims at fostering the interactions between the mathematical community around shapes and the MICCAI community in view of computational anatomy applications. It targets more particularly researchers investigating the combination of statistical and geometrical aspects in the modeling of the variability of biological shapes. The workshop is a forum for the exchange of the theoretical ideas and aims at being a source of inspiration for new methodological developments in computational anatomy. A special emphasis is put on theoretical developments, applications and results being welcomed as illustrations. Following the successful rst edition of this workshop in 20061 and second edition in New-York in 20082, the third edition was held in Toronto on September 22 20113. Contributions were solicited in Riemannian and group theoretical methods, geometric measurements of the anatomy, advanced statistics on deformations and shapes, metrics for computational anatomy, statistics of surfaces, modeling of growth and longitudinal shape changes. 22 submissions were reviewed by three members of the program committee. To guaranty a high level program, 11 papers only were selected for oral presentation in 4 sessions. Two of these sessions regroups classical themes of the workshop: statistics on manifolds and diff eomorphisms for surface or longitudinal registration. One session gathers papers exploring new mathematical structures beyond Riemannian geometry while the last oral session deals with the emerging theme of statistics on graphs and trees. Finally, a poster session of 5 papers addresses more application oriented works on computational anatomy

Automated Analysis of 3D Stress Echocardiography

__Abstract__ The human circulatory system consists of the heart, blood, arteries, veins and capillaries. The heart is the muscular organ which pumps the blood through the human body (Fig. 1.1,1.2). Deoxygenated blood flows through the right atrium into the right ventricle, which pumps the blood into the pulmonary arteries. The blood is carried to the lungs, where it passes through a capillary network that enables the release of carbon dioxide and the uptake of oxygen. Oxygenated blood then returns to the heart via the pulmonary veins and flows from the left atrium into the left ventricle. The left ventricle then pumps the blood through the aorta, the major artery which supplies blood to the rest of the body [Drake et a!., 2005; Guyton and Halt 1996]. Therefore, it is vital that the cardiovascular system remains healthy. Disease of the cardiovascular system, if untreated, ultimately leads to the failure of other organs and death