Nous remercions les Drs. Raimond Winslow, Elliot McVeigh, et ​​Helm Patrick à la Johns Hopkins University de fournir les bases de données ex vivo ligne.C recherche a été financée par le National Institutes of Health subvention R01-HL082729, et la National Science Foundation subvention CBET-0933029.

1. Fibre Orientations Estimation <ol><li> Acquérir des images IRM structurelles et IRMtd d&#39;un cœur humain adulte normal en diastole, à une résolution de 1 mm 3. Utiliser ImageJ, extraire le myocarde ventriculaire de l&#39;image structurelle de l&#39;atlas raccord, pour chaque tranche de petit axe, est fermée par des cannelures d&#39;un ensemble de points de repère sont placées le long des frontières endocardique et épicardique de la tranche (figure 2A et la figure 2B). Effectuer la mise en place de points de repère manuellement pour chaque tranche de 10 e dans l&#39;image. Obtenir des points de repère pour les tranches restantes en interpolant linéairement les points identifiés manuellement, à l&#39;aide MATLAB.Reconstruct les orientations des fibres du coeur atlas en calculant les vecteurs propres principaux des DTS dans l&#39;image IRMd (figure 2C). </li><li> Acquérir une image de la géométrie du coeur du patient en utilisant la diastole cardiaque in vivo CT ou IRM. Reconstruct de la géométrie cardiaque du patient à partir de l&#39;image de manière similaire à la façon dont l&#39;atlas a été construit (figure 3A et la figure 3B). L&#39;image de patient doit être ré-échantillonnée avant la reconstruction de sorte que la résolution dans le plan est de 1 mm 2. De même, le nombre de tranches pour lesquelles repères sont cueillies manuellement, et l&#39;intervalle de out-of-plan d&#39;interpolation doit être ajustée de sorte que l&#39;image du patient segmenté coeur a une épaisseur de coupe de 1 mm. </li><li> Déformer l&#39;image ventriculaire atlas pour correspondre à l&#39;image géométrie du patient en deux étapes. Dans la première étape, effectuer une transformation affine basée sur un ensemble de points de repères treize: le ventricule gauche (LV) apex, le ventricule droit deux (RV) des points d&#39;insertion, à la base, le deux points d&#39;insertion RV à mi-chemin entre la base et le sommet, et quatre ensembles de deux points qui divisent équitablement RV et les contours LV épicardiques à la base, et à mi-chemin entre la base et le sommet (figure 4A &amp; <strong&gt; Figure 4B). Dans la seconde étape, la déformation affine transformée atlas ventricules en outre en fonction de la géométrie du patient, en utilisant la cartographie à grande déformation difféomorphique métrique (LDDMM) (figure 4C). </li><li> Morph l&#39;image IRMtd de l&#39;atlas par le repositionnement de voxels d&#39;image et de réorienter les DTS en fonction de la matrice de transformation affine de l&#39;appariement et le champ de déformation de la transformation LDDMM. Effectuer la réorientation des DTS à l&#39;aide de la préservation des directions principales (PPD) de la méthode. </li><li> Obtenir l&#39;estimation des orientations des fibres de patients de l&#39;image morphed atlas IRMtd en calculant le vecteur propre principal de la DT (figure 5). </li></ol> 2. Mesure de l&#39;erreur d&#39;estimation <ol><li> Acquérir ex vivo par résonance magnétique structurelle et images DTMR de six normales et trois coeurs canins à défaut, à une résolution de 312,5 × 312,5 × 800 um 3. Ici, le cœur faiappât doit être généré dans les canines par l&#39;ablation par radiofréquence de la gauche de branche suivie de 3 semaines de tachypacing à 210 min -1. </li><li> Segmenter les ventricules du cœur canines de même du cœur humain atlas, telles que décrites au § 1.1. Notons ventricules segmentés à partir normales coeurs canins que les coeurs 1 à 6, et ceux segmenté de cœurs défaillants canines que les cœurs 7 à 9 (figure 6). </li><li> Obtenir des cinq estimations différentes orientations de fibres ventriculaires du coeur 1 en utilisant chacun des coeurs 2 à 6 comme un atlas (figure 7). </li><li> Estimation des orientations de fibres pour chacun des ventricules cardiaques défaillantes en utilisant 1, comme l&#39;atlas (figure 8). </li><li> Foreach point de données dans chaque ensemble d&#39;orientations de fibres estimé, calculer l&#39;erreur d&#39;estimation en tant que | θ c-θ a |, où θ c θ et A sont les angles d&#39;inclinaison des estimations d&#39;d acquise orientations des fibres à ce point, respectivement. </li><li> Pour chaque point de données dans chaque ensemble d&#39;orientations de fibres estimé, calculer l&#39;angle aigu et betweenestimated acquis directions des fibres dans trois dimensions (3D) par l&#39;intermédiaire d&#39;thevector produit scalaire. </li></ol> 3. La mesure des effets de l&#39;erreur d&#39;estimation sur les simulations <ol><li> De coeur 1, de construire six modèles, l&#39;un avec les orientations IRMtd acquises fibre de coeur 1 (appelé modèle 1), et cinq avec les cinq orientations de fibres estimé ensembles de données (modèles 2 à 6). Pour chacun des trois coeur défaillant géométries, construire deux modèles ventriculaires, une des IRMtd acquises orientations des fibres et l&#39;autre avec les orientations des fibres estimés. Voici la résolution spatiale des modèles, calculé en fonction de la longueur moyenne des arêtes des mailles, devrait être d&#39;environ 600 um. Représentent les modèles d&#39;insuffisance cardiaque avec des fibres IRMtd acquises en tant que modèles de 7 à 9, et ceux avec estimated fibres que les modèles de 10 à 12.In les modèles, utiliser la représentation monodomaine pour décrire le tissu cardiaque, avec des équations régissant: </li></ol><img src="/files/ftp_upload/50125/50125eq1.jpg" alt="L&#39;équation 1" fo:content-width="2.18in" fo:src="/files/ftp_upload/50125/50125eq1highres.jpg" /> où σ b est le tenseur de conductivité en vrac, qui est calculée à partir des tenseurs de conductivité bidomaine comme décrit par Potse et al 30, V m est le potentiel transmembranaire; C m est la capacité membranaire spécifique, et I d&#39;ions est la densité de courant la transmembranaire, qui à son tour dépend de V m et un ensemble de variables d&#39;état μ décrit la dynamique des flux ioniques à travers la m membrane.For C, utilisez une valeur de 1 μ F / cm 2. Pour i σ dans des conditions normales modèles cardiaque canine, utilisez longitudinalesLes valeurs de conductivité internes et transversale de 0,34 S / m et 0,06 S / m, respectivement. Représenter l lon par les modèles Greenstein-Winslow ioniques de la myocyte ventriculaire canine. Diminution de la conductivité électrique dans les modèles cardiaques ventriculaires canins échec de 30% (figure 9). <ol start="2"><li> Utilisation du logiciel CARP (CardioSolv, LLC), le rythme sinusal simuler avec tous les modèles. Provoquer réentrante tachycardie ventriculaire (VT) dans les six modèles défaillants en utilisant un protocole de stimulation S1-S2. Choisissez l&#39;intervalle entre S1 et S2 pour obtenir une activité soutenue VT pendant 2 secondes après la livraison S2. Si VT n&#39;est pas induite pour n&#39;importe quelle synchronisation S1-S2, diminuer les conductivités jusqu&#39;à 70% jusqu&#39;au VT a été induite (figure 10). </li><li> Pour chaque simulation, le calcul des pseudo-ECG en prenant la différence des potentiels extracellulaires entre deux points dans un bain isotrope entourant le cœur. Placez les deux points près de la base du cœur séparéspar 18 cm, de sorte que la ligne qui les relie est perpendiculaire au plan de base-sommet de la cloison comme illustré sur la Figure 10. Pour chaque simulation, avec des orientations de fibres estimé, calculer la métrique comme MAD </li></ol><img src="/files/ftp_upload/50125/50125eq2.jpg" alt="Équation 2" fo:content-width="2.77in" fo:src="/files/ftp_upload/50125/50125eq2highres.jpg" /> où X est la forme d&#39;onde ECG de la simulation avec des orientations de fibres estimées, Y est la forme d&#39;onde ECG de thecorresponding simulation avec des orientations de fibres acquises, X est la valeur moyenne de X, Y est la valeur moyenne de Y, et n est la longueur de X et Y.

<ol>
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Cette recherche montre que quantitativement, en l&#39;absence de IRMtd, des orientations de fibres myocardiques normales et des ventricules défaut peut être estimé à partir des images in vivo de leurs géométries pour l&#39;utilisation dans des simulations de l&#39;électrophysiologie cardiaque. La méthodologie proposée est démontrée avec des données in vivo CT, mais elle est également applicable aux images IRM in vivo de la géométrie ventriculaire, pallier le ma...

<html> L&#39;approche de calcul devient centrale pour l&#39;avancement de la compréhension de la fonction du cœur dans la santé et la maladie. State-of-the-art tout-cardiaques modèles de l&#39;électrophysiologie et de l&#39;électromécanique sont actuellement utilisées pour étudier un large éventail de phénomènes, comme la propagation ventriculaire normale, de l&#39;arythmie, la défibrillation, couplage électromécanique et de resynchronisation cardiaque 1. Cependant, à l&#39;approche de calcul pour être directement applicable dans l&#39;environnement clinique, il est impératif que les modèles soient spécifiques au patient, à savoir les modèles doivent être basés sur l&#39;architecture spécifique et les propriétés électrophysiologiques ou électromécanique du cœur malade du patient. Simulation avec ces modèles aideront les médecins à prendre des décisions hautement personnalisés pour les interventions électrophysiologiques ainsi que la prophylaxie, ce qui améliore considérablement la santé cardiaque 2-4. contenu &quot;&gt; Création de modèles réalistes cardiaque nécessite l&#39;acquisition de la structure de la géométrie et de la fibre d&#39;un cœur patient. orientations de fibre de déterminer les orientations de la propagation électrique et les distributions de contrainte dans le cœur, et donc de les acquérir est essentiel à la modélisation cardiaque 5, 6. Avec les progrès récents de l&#39;imagerie médicale, il est maintenant possible d&#39;obtenir la géométrie d&#39;un patient cardiaque, remodelage includingstructural comme un infarctus, in vivo à haute résolution à l&#39;aide imagerie par résonance magnétique (IRM) et la tomodensitométrie (TDM) technologies. Toutefois, il n&#39;est pas méthode pratique pour l&#39;acquisition d&#39;une structure de fibre cardiaque du patient in vivo. du tenseur de diffusion (DT) IRM 7, 8, la seule technique pour acquérir des orientations des fibres du cœur intact, n&#39;est pas largement disponible in vivo en raison de certaines limitations 9. Une brève description des efforts précédents pour traduire IRMtd à la clinique peut être trouvé elsewhavant 2. Bien que des méthodologies telles que fondé sur des règles d&#39;affectation des orientations des fibres offrir des alternatives aux IRMtd, ces méthodes présentent certaines limitations graves 2, 10. Ainsi, des difficultés à acquérir structure de fibre cardiaque in vivo actuellement obstacle à l&#39;application de électrophysiologiques cardiaques et électromécaniques simulations en milieu clinique. L&#39;objectif de cette recherche était de s&#39;attaquer directement à ce besoin. Nous avons supposé que des orientations de fibres ventriculaires d&#39;un cœur peut être prédit avec précision compte tenu de la géométrie du cœur et un atlas, où l&#39;atlas est un cœur dont la géométrie et de la fibre orientations sont disponibles. En conséquence, nous avons utilisé l&#39;état de l&#39;art des techniques pour développer une méthodologie pour l&#39;estimation des orientations des fibres cardiaques in vivo, et testé l&#39;hypothèse normale et de ne pas ventricules canines 2. L&#39;idée centrale de notre méthode d&#39;estimation de la fibre est d&#39;exploiter similarities dans les orientations des fibres, par rapport à la géométrie, entre les différents cœurs afin de rapprocher la structure des fibres d&#39;un cœur (cible) pour lesquels l&#39;information est disponible géométrie. Au cœur de notre méthode d&#39;estimation est l&#39;enregistrement de la géométrie de l&#39;atlas avec la géométrie de la cible à l&#39;aide cartographie à grande difféomorphe déformation métrique (LDDMM) 11, et le morphing des orientations des fibres atlas en utilisant la préservation des composantes principales (PPD) 2, 12. L&#39;diffeomorphicproperty des garanties LDDMM que l&#39;atlas ne «repliement» lui-même lors de la déformation, ce qui préserve les structures anatomiques integrityof. Figure 1 illustre le pipeline de traitement de notre méthodologie. La section texte du protocole § 1 décrit les divers composants du pipeline en démontrant comment l&#39;estimation peut être réalisée pour un patient par exemple. Les chiffres à l&#39;intérieur une partie des blocs de la figure 1 se référer au correspondantparagraphes vertu de l&#39;article § 1 du texte du protocole. Nous avons évalué les performances de la méthode proposée par la quantification de l&#39;erreur d&#39;estimation et de mesurer l&#39;effet de cette erreur onsimulations de l&#39;électrophysiologie cardiaque, par calcul simulant les cartes locales activation électrique ainsi que les pseudo-électrocardiogrammes (ECG pseudo-). En raison de l&#39;indisponibilité du cœur de l&#39;homme, l&#39;évaluation de la performance a été réalisée à l&#39;aide coeurs canins disponibles à partir des études antérieures 13-15. L&#39;erreur d&#39;estimation a été calculée au moyen d&#39;angles d&#39;inclinaison 16, de la tradition de followingthe histologie, où les mesures d&#39;angle sont des coupes de tissus qui sont coupés performedon parallèle à la epicardialsurface. Depuis le anglebetween la direction des fibres et épicardique plan tangent est generallysmall 17, 18, ​​la perte d&#39;informations dans la description d&#39;un fiberdirection entièrement à l&#39;aide de son angle d&#39;inclinaison est insignifiante. Pour l&#39;ordisimulations ational, l&#39;image des modèles ont été construits comme indiqué précédemment 19, 20, et le tissu cardiaque dans des modèles a été représenté établies sur la base de techniques mathématiques et les données expérimentales 21-25. Rythme sinusal a été simulé par une activation de réplication provenant du réseau de Purkinje 26, et une tachycardie ventriculaire, par une stimulation S1-S2 protocole 27. Les pseudo-ECG ont été calculés par rapport à l&#39;aide 28 et l&#39;écart absolu moyen (EAM) métrique 29.

<table border="1"><tbody><tr><td> LDDMM </td><td> Johns Hopkins University </td><td></td><td> <a href="http://cis.jhu.edu/software/lddmm-volume/index.php" target="_blank">http://cis.jhu.edu/software/lddmm-volume/index.php</a> </td></tr><tr><td> MATLAB </td><td> Mathworks, Inc </td><td> R2011b </td><td> <a href="http://www.mathworks.com/products/matlab/" target="_blank">http://www.mathworks.com/products/matlab/</a> </td></tr><tr><td> ImageJ </td><td> National Institutes of Health </td><td></td><td> <a href="http://rsbweb.nih.gov/ij/" target="_blank">http://rsbweb.nih.gov/ij/</a> </td></tr><tr><td> Tarentule </td><td> CAE Software Solutions </td><td></td><td> <a href="http://www.meshing.at/Spiderhome/Tarantula.html" target="_blank">http://www.meshing.at/Spiderhome/Tarantula.html</a> </td></tr><tr><td> CARP </td><td> CardioSolv</td><td></td><td> <a href="http://cardiosolv.com/" target="_blank">http://cardiosolv.com/</a> </td></tr><tr><td> Images Canine </td><td> Johns Hopkins University </td><td></td><td> <a href="http://www.ccbm.jhu.edu/research/DTMRIDS.php" target="_blank">http://www.ccbm.jhu.edu/research/DTMRIDS.php</a> </td></tr></tbody></table>

patient-specific modeling of the heart: estimation of ventricular fiber orientations

Spécifiques au patient des simulations de coeur (dys) fonction vise à personnaliser thérapie cardiaque sont entravés par l&#39;absence de la technologie d&#39;imagerie in vivo pour l&#39;acquisition cliniquement orientations des fibres myocardiques. L&#39;objectif de ce projet était de développer une méthodologie pour estimer orientations des fibres cardiaques à partir des images in vivo de géométries cardiaques des patients. Une représentation précise de la géométrie ventriculaire et des orientations de fibres a été reconstruite, respectivement, de haute résolution, ex vivo par résonance magnétique structurelle (MR) et tenseur de diffusion (DT) des images RM d&#39;un coeur humain normal, dénommé atlas. Géométrie ventriculaire d&#39;un cœur patient a été extrait, par l&#39;intermédiaire de segmentation semi-automatique, à partir d&#39;une in vivo la tomodensitométrie (TDM) image. En utilisant des algorithmes de transformation d&#39;image, la géométrie ventriculaire atlas a été déformée pour correspondre à celle du patient. Enfin, le champ de déformation a été appliquée à la fibre orientat atlasions pour obtenir une estimation des orientations de fibres de patients. La précision des estimations de fibres a été évaluée au moyen de six normales et trois à défaut coeurs canins. La différence absolue moyenne entre les angles d&#39;inclinaison des orientations des fibres acquises et estimé était de 15,4 °. Simulations numériques de cartes d&#39;activation ventriculaire et pseudo-ECG en rythme sinusal et la tachycardie ventriculaire indiqué qu&#39;il n&#39;y ait pas de différences significatives entre les orientations des fibres estimés et acquis à une clinique observables level.The de nouvelles connaissances obtenues à partir du projet ouvrira la voie pour le développement de spécifiques au patient modèles du cœur qui peuvent aider les médecins dans le diagnostic personnalisé et des décisions concernant les interventions électrophysiologiques.

Figure 11, ca affiche des visualisations rationalisation des estimations ainsi que les orientations des fibres IRMtd dérivés dans les cœurs normaux et défaillants. Examen qualitatif montre que les orientations de fibres estimé cadrent bien avec IRMtd dérivés de ceux. Panneau D illustre, superposées sur la géométrie du cœur 1, la distribution de l&#39;erreur dans les angles d&#39;inclinaison des cœurs normaux », en moyenne sur les cinq estimations. Panneau E montre la répartition moyenne de...

Watch this Scientific Journal Video about Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations at JoVE.com

Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations

Une méthodologie pour estimer les orientations des fibres ventriculaires à partir des images in vivo de géométries cardiaques des patients pour la modélisation personnalisée est décrite. Validation de la méthodologie effectuée à l&#39;aide normaux et défaillants coeurs canins démontrer que qu&#39;il n&#39;y a pas de différences significatives entre les orientations des fibres estimés et acquis à un niveau cliniquement observable.

Spécifique au patient Modeling of the Heart: Estimation des orientations des fibres ventriculaires

Patient-specific  simulations of heart (dys)function aimed at personalizing cardiac therapy are hampered  by the absence of in vivo imaging technology for ...

patient-specific-modeling-heart-estimation-ventricular-fiber

Research

JoVE Journal

Bioengineering

13.6K vues.  Johns Hopkins University. Une méthodologie pour estimer les orientations des fibres ventriculaires à partir des images in vivo de géométries cardiaques des patients pour la modélisation personnalisée est décrite. Validation de la méthodologie effectuée à l'aide normaux et défaillants coeurs canins démontrer que qu'il n'y a pas de différences significatives entre les orientations des fibres estimés et acquis à un niveau cliniquement observable.

Vidéo: Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations

High-resolution Fiber-optic Microendoscopy for in situ Cellular Imaging

Many biological and clinical studies require the longitudinal study and analysis of morphology and function with cellular level resolution. Traditionally, multiple experiments are run in parallel, with individual samples removed from the study at sequential time points for evaluation by light microscopy. Several intravital techniques have been developed, with confocal, multiphoton, and second harmonic microscopy all demonstrating their ability to be used for imaging in situ 1. With these systems, however, the required infrastructure is complex and expensive, involving scanning laser systems and complex light sources. Here we present a protocol for the design and assembly of a high-resolution microendoscope which can be built in a day using off-the-shelf components for under US$5,000. The platform offers flexibility in terms of image resolution, field-of-view, and operating wavelength, and we describe how these parameters can be easily modified to meet the specific needs of the end user.
We and others have explored the use of the high-resolution microendoscope (HRME) in in vitro cell culture 2-5, in excised 6 and living animal tissues 2,5, and in human tissues in vivo 2,7. Users have reported the use of several different fluorescent contrast agents, including proflavine 2-4, benzoporphyrin-derivative monoacid ring A (BPD-MA) 5, and fluoroscein 6,7, all of which have received full, or investigational approval from the FDA for use in human subjects. High-resolution microendoscopy, in the form described here, may appeal to a wide range of researchers working in the basic and clinical sciences. The technique offers an effective and economical approach which complements traditional benchtop microscopy, by enabling the user to perform high-resolution, longitudinal imaging in situ.

High-resolution Fiber-optic Microendoscopy for in situ Cellular Imaging

In many biological and clinical situations it is advantageous to study cellular processes as they evolve in their native microenvironment. Here we describe the assembly and use of a low-cost fiber-optic microscope which can provide real time imaging in cell culture, animal studies, and clinical patient studies.

Haute résolution à fibre optique pour les Microendoscopy In situ Cellular Imaging

Many biological and clinical studies require the longitudinal study and analysis of morphology and function with cellular level resolution.  ...

Recherche

Bio-ingénierie

Multiparametric Optical Mapping of the Langendorff-perfused Rabbit Heart

Optical imaging and fluorescent probes have significantly advanced research methodology in the field of cardiac electrophysiology in ways that could not have been accomplished by other approaches1. With the use of the calcium- and voltage-sensitive dyes, optical mapping allows measurement of transmembrane action potentials and calcium transients with high spatial resolution without the physical contact with the tissue. This makes measurements of the cardiac electrical activity possible under many conditions where the use of electrodes is inconvenient or impossible1. For example, optical recordings provide accurate morphological changes of membrane potential during and immediately after stimulation and defibrillation, while conventional electrode techniques suffer from stimulus-induced artifacts during and after stimuli due to electrode polarization1. 
The Langendorff-perfused rabbit heart is one of the most studied models of human heart physiology and pathophysiology. Many types of arrhythmias observed clinically could be recapitulated in the rabbit heart model. It was shown that wave patterns in the rabbit heart during ventricular arrhythmias, determined by effective size of the heart and the wavelength of reentry, are very similar to that in the human heart2. It was also shown that critical aspects of excitation-contraction (EC) coupling in rabbit myocardium, such as the relative contribution of sarcoplasmic reticulum (SR), is very similar to human EC coupling3. Here we present the basic procedures of optical mapping experiments in Langendorff-perfused rabbit hearts, including the Langendorff perfusion system setup, the optical mapping systems setup, the isolation and cannulation of the heart, perfusion and dye-staining of the heart, excitation-contraction uncoupling, and collection of optical signals. These methods could be also applied to the heart from species other than rabbit with adjustments to flow rates, optics, solutions, etc.
Two optical mapping systems are described. The panoramic mapping system is used to map the entire epicardium of the rabbit heart4-7. This system provides a global view of the evolution of reentrant circuits during arrhythmogenesis and defibrillation, and has been used to study the mechanisms of arrhythmias and antiarrhythmia therapy8,9. The dual mapping system is used to map the action potential (AP) and calcium transient (CaT) simultaneously from the same field of view10-13. This approach has enhanced our understanding of the important role of calcium in the electrical alternans and the induction of arrhythmia14-16.

This article describes the basic procedures for conducting optical mapping experiments in the Langendorff-perfused rabbit heart using the panoramic imaging system, and the dual (voltage and calcium) imaging modality.

Multiparamétrique cartographie optique du Cœur lapin perfusé de Langendorff

Optical imaging and fluorescent probes have significantly advanced research methodology in the field of cardiac electrophysiology in ways that could not ...

Targeting Neuronal Fiber Tracts for Deep Brain Stimulation Therapy Using Interactive, Patient-Specific Models

Deep brain stimulation (DBS), which involves insertion of an electrode to deliver stimulation to a localized brain region, is an established therapy for movement disorders and is being applied to a growing number of disorders. Computational modeling has been successfully used to predict the clinical effects of DBS; however, there is a need for novel modeling techniques to keep pace with the growing complexity of DBS devices. These models also need to generate predictions quickly and accurately. The goal of this project is to develop an image processing pipeline to incorporate structural magnetic resonance imaging (MRI) and diffusion weighted imaging (DWI) into an interactive, patient specific model to simulate the effects of DBS. A virtual DBS lead can be placed inside of the patient model, along with active contacts and stimulation settings, where changes in lead position or orientation generate a new finite element mesh and solution of the bioelectric field problem in near real-time, a timespan of approximately 10 seconds. This system also enables the simulation of multiple leads in close proximity to allow for current steering by varying anodes and cathodes on different leads. The techniques presented in this paper reduce the burden of generating and using computational models while providing meaningful feedback about the effects of electrode position, electrode design, and stimulation configurations to researchers or clinicians who may not be modeling experts.

The goal of this project is to develop an interactive, patient-specific modeling pipeline to simulate the effects of deep brain stimulation in near real-time and provide meaningful feedback as to how these devices influence neural activity in the brain.

Ciblage des fibres neuronales Tracts pour la thérapie de Stimulation cérébrale profonde à l’aide de modèles interactifs, spécifiques à un Patient

Deep brain stimulation (DBS), which involves insertion of an electrode to deliver stimulation to a localized brain region, is an established therapy for ...

Light-sheet Fluorescence Microscopy for the Study of the Murine Heart

Light-sheet fluorescence microscopy has been widely used for rapid image acquisition with a high axial resolution from micrometer to millimeter scale. Traditional light-sheet techniques involve the use of a single illumination beam directed orthogonally at sample tissue. Images of large samples that are produced using a single illumination beam contain stripes or artifacts and suffer from a reduced resolution due to the scattering and absorption of light by the tissue. This study uses a dual-sided illumination beam and a simplified CLARITY optical clearing technique for the murine heart. These techniques allow for deeper imaging by removing lipids from the heart and produce a large field of imaging, greater than 10 x 10 x 10 mm3. As a result, this strategy enables us to quantify the ventricular dimensions, track the cardiac lineage, and localize the spatial distribution of cardiac-specific proteins and ion-channels from the post-natal to adult mouse hearts with sufficient contrast and resolution.

This study uses a dual-sided illumination light-sheet fluorescence microscopy (LSFM) technique combined with optical clearing to study the murine heart.

Microscopie de Fluorescence lumière-feuille pour l’étude du coeur murin

Light-sheet fluorescence microscopy has been widely used for rapid image acquisition with a high axial resolution from micrometer to millimeter scale. ...

Biaxial Mechanical Characterizations of Atrioventricular Heart Valves

Extensive biaxial mechanical testing of the atrioventricular heart valve leaflets can be utilized to derive&#160;optimal parameters used in constitutive models, which provide a mathematical representation of the mechanical function of those structures. This presented biaxial mechanical testing protocol involves (i) tissue acquisition, (ii) the preparation of tissue specimens, (iii) biaxial mechanical testing, and (iv) postprocessing of the acquired data. First, tissue acquisition requires obtaining porcine or ovine hearts from a local Food and Drug Administration-approved abattoir for later dissection to retrieve the valve leaflets. Second, tissue preparation requires using tissue specimen cutters on the leaflet tissue to extract a clear zone for testing. Third, biaxial mechanical testing of the leaflet specimen requires the use of a commercial biaxial mechanical tester, which consists of force-controlled, displacement-controlled, and stress-relaxation testing protocols to characterize the leaflet tissue&#39;s mechanical properties. Finally, post-processing requires the use of data image correlation techniques and force and displacement readings to summarize the tissue&#39;s mechanical behaviors in response to external loading. In general, results from biaxial testing demonstrate that the leaflet tissues yield a nonlinear, anisotropic mechanical response. The presented biaxial testing procedure is advantageous to other methods since the method presented here allows for a more comprehensive characterization of the valve leaflet tissue under one unified testing scheme, as opposed to separate testing protocols on different tissue specimens. The proposed testing method has its limitations in that shear stress is potentially present in the tissue sample. However, any potential shear is presumed negligible.

This protocol involves characterizations of atrioventricular valve leaflets with force-controlled, displacement-controlled, and stress-relaxation biaxial mechanical testing procedures. Results acquired with this protocol can be used for constitutive model development to simulate the mechanical behavior of functioning valves under a finite element simulation framework.

Biaxiales caractérisations mécaniques des valvules auriculo-ventriculaire

Extensive biaxial mechanical testing of the atrioventricular heart valve leaflets can be utilized to derive&#160;optimal parameters used in constitutive ...

Optical Imaging of Isolated Murine Ventricular Myocytes

The ability to isolate adult cardiac myocytes has permitted researchers to study a variety of cardiac pathologies at the single cell level. While advances in calcium sensitive dyes have permitted the robust optical recording of single cell calcium dynamics, recording of robust transmembrane optical voltage signals has remained difficult. Arguably, this is because of the low single to noise ratio, phototoxicity, and photobleaching of traditional potentiometric dyes. Therefore, single cell voltage measurements have long been confined to the patch clamp technique which while the gold standard, is technically demanding and low throughput. However, with the development of novel potentiometric dyes, large, fast optical responses to changes in voltage can be obtained with little to no phototoxicity and photobleaching. This protocol describes in detail how to isolate adult murine myocytes which can be used for cellular shortening, calcium, and optical voltage measurements. Specifically, the protocol describes how to use a ratiometric calcium dye, a single-excitation calcium dye, and a single excitation voltage dye. This approach can be used to assess the cardiotoxicity and arrhythmogenicity of various chemical agents. While phototoxicity is still an issue at the single cell level, methodology is discussed on how to reduce it.

We present the methodology for the isolation of murine myocytes and how to obtain voltage or calcium traces simultaneously with sarcomere shortening traces using fluorescence photometry with simultaneous digital cell geometry measurements.

Imagerie optique des myocytes ventriculaires murines isolés

The ability to isolate adult cardiac myocytes has permitted researchers to study a variety of cardiac pathologies at the single cell level. While advances ...

Evaluation of Left Ventricular Structure and Function using 3D Echocardiography

Three-dimensional (3D) quantification of the left ventricle (LV) provides significant added value in terms of diagnostic accuracy and precise risk stratification in various cardiac disorders. Recently, 3D echocardiography became available in routine cardiology practice; however, high-quality image acquisition and subsequent analysis have a steep learning curve. The present article aims to guide the reader through a detailed 3D protocol by presenting tips and tricks and also by highlighting the potential pitfalls to facilitate the widespread but technically sound use of this important technique concerning the LV. First and foremost, we show the acquisition of a high-quality 3D dataset with optimal spatial and temporal resolution. Then, we present the analytical steps toward a detailed quantification of the LV by using one of the most widely applied built-in software. We will quantify LV volumes, sphericity, mass and also systolic function by measuring ejection fraction and myocardial deformation (longitudinal and circumferential strain). We will discuss and provide clinical examples about the essential scenarios where the transition from a conventional echocardiographic approach to a 3D-based quantification is highly recommended.

In this article, we provide a step-by-step acquisition and analysis protocol for the volumetric assessment and speckle-tracking analysis of the left ventricle by 3D echocardiography, particularly focusing on practical aspects that maximize the feasibility of this technique.

Évaluation de la structure et de la fonction ventriculaires gauches à l’aide de l’échocardiographie 3D

Three-dimensional (3D) quantification of the left ventricle (LV) provides significant added value in terms of diagnostic accuracy and precise risk ...

Patient-Specific Polyvinyl Alcohol Phantom Fabrication with Ultrasound and X-Ray Contrast for Brain Tumor Surgery Planning

Phantoms are essential tools for clinical training, surgical planning and the development of novel medical devices. However, it is challenging to create anatomically accurate head phantoms with realistic brain imaging properties because standard fabrication methods are not optimized to replicate any patient-specific anatomical detail and 3D printing materials are not optimized for imaging properties. In order to test and validate a novel navigation system for use during brain tumor surgery, an anatomically accurate phantom with realistic imaging and mechanical properties was required. Therefore, a phantom was developed using real patient data as input and 3D printing of molds to fabricate a patient-specific head phantom comprising the skull, brain and tumor with both ultrasound and X-ray contrast. The phantom also had mechanical properties that allowed the phantom tissue to be manipulated in a similar manner to how human brain tissue is handled during surgery. The phantom was successfully tested during a surgical simulation in a virtual operating room.
The phantom fabrication method uses commercially available materials and is easy to reproduce. The 3D printing files can be readily shared, and the technique can be adapted to encompass many different types of tumor.

This protocol describes the fabrication of a patient specific skull, brain and tumor phantom. It uses 3D printing to create molds, and polyvinyl alcohol (PVA-c) is used as the tissue mimicking material.

Fabrication fantôme d’alcool de polyvinyle patient-spécifique avec l’ultrason et le contraste de rayon X pour la planification de chirurgie de tumeur de cerveau

Phantoms are essential tools for clinical training, surgical planning and the development of novel medical devices. However, it is challenging to create ...

Evaluating Regional Pulmonary Deposition using Patient-Specific 3D Printed Lung Models

Development of targeted therapies for pulmonary diseases is limited by the availability of preclinical testing methods with the ability to predict regional aerosol delivery. Leveraging 3D printing to generate patient-specific lung models, we outline the design of a high-throughput, in vitro experimental setup for quantifying lobular pulmonary deposition. This system is made with a combination of commercially available and 3D printed components and allows the flow rate through each lobe of the lung to be independently controlled. Delivery of fluorescent aerosols to each lobe is measured using fluorescence microscopy. This protocol has the potential to promote the growth of personalized medicine for respiratory diseases through its ability to model a wide range of patient demographics and disease states. Both the geometry of the 3D printed lung model and the air flow profile setting can be easily modulated to reflect clinical data for patients with varying age, race, and gender. Clinically relevant drug delivery devices, such as the endotracheal tube shown here, can be incorporated into the testing setup to more accurately predict a device&#8217;s capacity to target therapeutic delivery to a diseased region of the lung. The versatility of this experimental setup allows it to be customized to reflect a multitude of inhalation conditions, enhancing the rigor of preclinical therapeutic testing.

We present a high-throughput, in vitro method for quantifying regional pulmonary deposition at the lobe level using CT scan-derived, 3D printed lung models with tunable air flow profiles.

Évaluation des dépôts pulmonaires régionaux à l’aide de modèles pulmonaires imprimés 3D spécifiques au patient

Development of targeted therapies for pulmonary diseases is limited by the availability of preclinical testing methods with the ability to predict ...

Quantification of Mouse Heart Left Ventricular Function, Myocardial Strain, and Hemodynamic Forces by Cardiovascular Magnetic Resonance Imaging

Mouse models have contributed significantly to understanding genetic and physiological factors involved in healthy cardiac function, how perturbations result in pathology, and how myocardial diseases may be treated. Cardiovascular magnetic resonance imaging (CMR) has become an indispensable tool for a comprehensive in vivo assessment of cardiac anatomy and function. This protocol shows detailed measurements of mouse heart left ventricular function, myocardial strain, and hemodynamic forces using 7-Tesla CMR. First, animal preparation and positioning in the scanner are demonstrated. Survey scans are performed for planning imaging slices in various short- and long-axis views. A series of prospective ECG-triggered short-axis (SA) movies (or CINE images) are acquired covering the heart from apex to base, capturing end-systolic and end-diastolic phases. Subsequently, single-slice, retrospectively gated CINE images are acquired in a midventricular SA view, and in 2-, 3-, and 4-chamber views, to be reconstructed into high-temporal resolution CINE images using custom-built and open-source software. CINE images are subsequently analyzed using dedicated CMR image analysis software.
Delineating endomyocardial and epicardial borders in SA end-systolic and end-diastolic CINE images allows for the calculation of end-systolic and end-diastolic volumes, ejection fraction, and cardiac output. The midventricular SA CINE images are delineated for all cardiac time frames to extract a detailed volume-time curve. Its time derivative allows for the calculation of the diastolic function as the ratio of the early filling and atrial contraction waves. Finally, left ventricular endocardial walls in the 2-, 3-, and 4-chamber views are delineated using feature-tracking, from which longitudinal myocardial strain parameters and left ventricular hemodynamic forces are calculated. In conclusion, this protocol provides detailed in vivo quantification of the mouse cardiac parameters, which can be used to study temporal alterations in cardiac function in various mouse models of heart disease.

This study describes a comprehensive cardiovascular magnetic resonance imaging (CMR) protocol to quantify the left ventricular functional parameters of the mouse heart. The protocol describes the acquisition, post-processing, and analysis of the CMR images as well as assessment of different cardiac functional parameters.

Quantification de la fonction ventriculaire gauche du cœur de souris, de la tension myocardique et des forces hémodynamiques par imagerie par résonance magnétique cardiovasculaire

Mouse models have contributed significantly to understanding genetic and physiological factors involved in healthy cardiac function, how perturbations ...