Christoph, Jan

[["dc.bibliographiccitation.journal","Frontiers in Physiology"],["dc.bibliographiccitation.volume","11"],["dc.contributor.author","Kappadan, Vineesh"],["dc.contributor.author","Telele, Saba"],["dc.contributor.author","Uzelac, Ilija"],["dc.contributor.author","Fenton, Flavio"],["dc.contributor.author","Parlitz, Ulrich"],["dc.contributor.author","Luther, Stefan"],["dc.contributor.author","Christoph, Jan"],["dc.date.accessioned","2021-04-14T08:25:09Z"],["dc.date.available","2021-04-14T08:25:09Z"],["dc.date.issued","2020"],["dc.description.abstract","Optical mapping is a high-resolution fluorescence imaging technique, that uses voltage- or calcium-sensitive dyes to visualize electrical excitation waves on the heart surface. However, optical mapping is very susceptible to the motion of cardiac tissue, which results in so-called motion artifacts in the fluorescence signal. To avoid motion artifacts, contractions of the heart muscle are typically suppressed using pharmacological excitation-contraction uncoupling agents, such as Blebbistatin. The use of pharmacological agents, however, may influence cardiac electrophysiology. Recently, it has been shown that numerical motion tracking can significantly reduce motion-related artifacts in optical mapping, enabling the simultaneous optical measurement of cardiac electrophysiology and mechanics. Here, we combine ratiometric optical mapping with numerical motion tracking to further enhance the robustness and accuracy of these measurements. We evaluate the method's performance by imaging and comparing cardiac restitution and ventricular fibrillation (VF) dynamics in contracting, non-working vs. Blebbistatin-arrested Langendorff-perfused rabbit hearts (N = 10). We found action potential durations (APD) to be, on average, 25 ± 5% shorter in contracting hearts compared to hearts uncoupled with Blebbistatin. The relative shortening of the APD was found to be larger at higher frequencies. VF was found to be significantly accelerated in contracting hearts, i.e., 9 ± 2Hz with Blebbistatin and 15 ± 4Hz without Blebbistatin, and maintained a broader frequency spectrum. In contracting hearts, the average number of phase singularities was NPS = 11 ± 4 compared to NPS = 6 ± 3 with Blebbistatin during VF on the anterior ventricular surface. VF inducibility was reduced with Blebbistatin. We found the effect of Blebbistatin to be concentration-dependent and reversible by washout. Aside from the electrophysiological characterization, we also measured and analyzed cardiac motion. Our findings may have implications for the interpretation of optical mapping data, and highlight that physiological conditions, such as oxygenation and metabolic demand, must be carefully considered in ex vivo imaging experiments."],["dc.identifier.doi","10.3389/fphys.2020.00464"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/81537"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-399"],["dc.publisher","Frontiers Media S.A."],["dc.relation.eissn","1664-042X"],["dc.rights","http://creativecommons.org/licenses/by/4.0/"],["dc.title","High-Resolution Optical Measurement of Cardiac Restitution, Contraction, and Fibrillation Dynamics in Beating vs. Blebbistatin-Uncoupled Isolated Rabbit Hearts"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Physical Review X"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Molavi Tabrizi, A."],["dc.contributor.author","Mesgarnejad, A."],["dc.contributor.author","Bazzi, M."],["dc.contributor.author","Luther, Susanne"],["dc.contributor.author","Christoph, J."],["dc.contributor.author","Karma, A."],["dc.date.accessioned","2022-07-01T07:35:07Z"],["dc.date.available","2022-07-01T07:35:07Z"],["dc.date.issued","2022"],["dc.description.abstract","Ventricular fibrillation (VF) is a life-threatening electromechanical dysfunction of the heart associated with complex spatiotemporal dynamics of electrical excitation and mechanical contraction of the heart muscle. It has been hypothesized that VF is driven by three-dimensional rotating electrical scroll waves, which can be characterized by filamentlike electrical phase singularities or vortex filaments, but visualizing their dynamics has been a long-standing challenge. Recently, it was shown that rotating excitation waves during VF are associated with rotating waves of mechanical deformation. Three-dimensional mechanical scroll waves and mechanical filaments describing their rotational core regions were observed in the ventricles by using high-resolution ultrasound. The findings suggest that the spatiotemporal organization of cardiac fibrillation may be assessed from waves of mechanical deformation. However, the complex relationship between excitation and mechanical waves during VF is currently not understood. Here, we study the fundamental nature of mechanical phase singularities, their spatiotemporal organization, and their relation with electrical phase singularities. We demonstrate the existence of two fundamental types of mechanical phase singularities: “paired singularities,” which are colocalized with electrical phase singularities, and “unpaired singularities,” which can form independently. We show that the unpaired singularities emerge due to the anisotropy of the active force field, generated by fiber anisotropy in cardiac tissue, and the nonlocality of elastic interactions, which jointly induce strong spatiotemporal inhomogeneities in the strain fields. The inhomogeneities lead to the breakup of deformation waves and create mechanical phase singularities, even in the absence of electrical singularities, which are typically associated with excitation wave break. We exploit these insights to develop an approach to discriminate paired and unpaired mechanical phase singularities, which could potentially be used to locate electrical rotor cores from a mechanical measurement. Our findings provide a fundamental understanding of the complex spatiotemporal organization of electromechanical waves in the heart and a theoretical basis for the analysis of high-resolution ultrasound data for the three-dimensional mapping of heart rhythm disorders."],["dc.description.sponsorship"," Northeastern University http://dx.doi.org/10.13039/501100004184"],["dc.description.sponsorship"," Deutsches Zentrum für Herz-Kreislaufforschung http://dx.doi.org/10.13039/100010447"],["dc.description.sponsorship"," University of California, San Francisco http://dx.doi.org/10.13039/100008069"],["dc.description.sponsorship"," Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659"],["dc.description.sponsorship"," Massachusetts Green High Performance Computing Center http://dx.doi.org/10.13039/100019861"],["dc.description.sponsorship"," National Science Foundation http://dx.doi.org/10.13039/100000001"],["dc.description.sponsorship"," National Institute of Health http://dx.doi.org/10.13039/100000002"],["dc.description.sponsorship"," Gordon and Betty Moore Foundation http://dx.doi.org/10.13039/100000936"],["dc.identifier.doi","10.1103/PhysRevX.12.021052"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/112092"],["dc.identifier.url","https://sfb1002.med.uni-goettingen.de/production/literature/publications/441"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-581"],["dc.relation","SFB 1002: Modulatorische Einheiten bei Herzinsuffizienz"],["dc.relation.eissn","2160-3308"],["dc.relation.workinggroup","RG Luther (Biomedical Physics)"],["dc.rights","CC BY 4.0"],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0/"],["dc.title","Spatiotemporal Organization of Electromechanical Phase Singularities during High-Frequency Cardiac Arrhythmias"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.journal","Frontiers in Physiology"],["dc.bibliographiccitation.volume","9"],["dc.contributor.author","Christoph, Jan"],["dc.contributor.author","Luther, Stefan"],["dc.date.accessioned","2020-12-10T18:44:37Z"],["dc.date.available","2020-12-10T18:44:37Z"],["dc.date.issued","2018"],["dc.description.abstract","Optical mapping is a high-resolution fluorescence imaging technique, which provides highly detailed visualizations of the electrophysiological wave phenomena, which trigger the beating of the heart. Recent advancements in optical mapping have demonstrated that the technique can now be performed with moving and contracting hearts and that motion and motion artifacts, once a major limitation, can now be overcome by numerically tracking and stabilizing the heart's motion. As a result, the optical measurement of electrical activity can be obtained from the moving heart surface in a co-moving frame of reference and motion artifacts can be reduced substantially. The aim of this study is to assess and validate the performance of a 2D marker-free motion tracking algorithm, which tracks motion and non-rigid deformations in video images. Because the tracking algorithm does not require markers to be attached to the tissue, it is necessary to verify that it accurately tracks the displacements of the cardiac tissue surface, which not only contracts and deforms, but also fluoresces and exhibits spatio-temporal physiology-related intensity changes. We used computer simulations to generate synthetic optical mapping videos, which show the contracting and fluorescing ventricular heart surface. The synthetic data reproduces experimental data as closely as possible and shows electrical waves propagating across the deforming tissue surface, as seen during voltage-sensitive imaging. We then tested the motion tracking and motion-stabilization algorithm on the synthetic as well as on experimental data. The motion tracking and motion-stabilization algorithm decreases motion artifacts approximately by 80% and achieves sub-pixel precision when tracking motion of 1–10 pixels (in a video image with 100 by 100 pixels), effectively inhibiting motion such that little residual motion remains after tracking and motion-stabilization. To demonstrate the performance of the algorithm, we present optical maps with a substantial reduction in motion artifacts showing action potential waves propagating across the moving and strongly deforming ventricular heart surface. The tracking algorithm reliably tracks motion if the tissue surface is illuminated homogeneously and shows sufficient contrast or texture which can be tracked or if the contrast is artificially or numerically enhanced. In this study, we also show how a reduction in dissociation-related motion artifacts can be quantified and linked to tracking precision. Our results can be used to advance optical mapping techniques, enabling them to image contracting hearts, with the ultimate goal of studying the mutual coupling of electrical and mechanical phenomena in healthy and diseased hearts."],["dc.identifier.doi","10.3389/fphys.2018.01483"],["dc.identifier.pmid","30450053"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/78532"],["dc.identifier.url","https://sfb1002.med.uni-goettingen.de/production/literature/publications/290"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.relation","SFB 1002: Modulatorische Einheiten bei Herzinsuffizienz"],["dc.relation","SFB 1002 | C03: Erholung nach Herzinsuffizienz: Analyse der transmuralen mechano-elektrischen Funktionsstörung"],["dc.relation.eissn","1664-042X"],["dc.relation.workinggroup","RG Luther (Biomedical Physics)"],["dc.rights","http://creativecommons.org/licenses/by/4.0/"],["dc.title","Marker-Free Tracking for Motion Artifact Compensation and Deformation Measurements in Optical Mapping Videos of Contracting Hearts"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","S6"],["dc.bibliographiccitation.issue","Suppl 1"],["dc.bibliographiccitation.journal","Journal of Clinical Bioinformatics"],["dc.bibliographiccitation.volume","5"],["dc.contributor.author","Bauer, Christian"],["dc.contributor.author","Ganslandt, Thomas"],["dc.contributor.author","Baum, Benjamin"],["dc.contributor.author","Christoph, Jan"],["dc.contributor.author","Engel, Igor"],["dc.contributor.author","Löbe, Matthias"],["dc.contributor.author","Mate, Sebastian"],["dc.contributor.author","Prokosch, Hans-Ulrich"],["dc.contributor.author","Sax, Ulrich"],["dc.contributor.author","Stäubert, Sebastian"],["dc.contributor.author","Winter, Alfred"],["dc.date.accessioned","2016-03-17T17:03:59Z"],["dc.date.accessioned","2021-10-27T13:20:27Z"],["dc.date.available","2016-03-17T17:03:59Z"],["dc.date.available","2021-10-27T13:20:27Z"],["dc.date.issued","2015"],["dc.date.updated","2016-03-17T17:03:59Z"],["dc.identifier.doi","10.1186/2043-9113-5-S1-S6"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/13128"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/91967"],["dc.language.iso","en"],["dc.notes.intern","Migrated from goescholar"],["dc.relation.orgunit","Universitätsmedizin Göttingen"],["dc.rights","CC BY 4.0"],["dc.rights.holder","Bauer et al; licensee BioMed Central Ltd."],["dc.rights.uri","https://creativecommons.org/licenses/by/4.0"],["dc.title","The Integrated Data Repository Toolkit (IDRT): accelerating translational research infrastructures"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","150"],["dc.bibliographiccitation.journal","Progress in Biophysics and Molecular Biology"],["dc.bibliographiccitation.lastpage","169"],["dc.bibliographiccitation.volume","130"],["dc.contributor.author","Christoph, J."],["dc.contributor.author","Schröder-Schetelig, J."],["dc.contributor.author","Luther, Stefan"],["dc.date.accessioned","2019-02-20T14:58:52Z"],["dc.date.available","2019-02-20T14:58:52Z"],["dc.date.issued","2017"],["dc.description.abstract","Optical mapping is a widely used imaging technique for investigating cardiac electrophysiology in intact, Langendorff-perfused hearts. Mechanical contraction of cardiac tissue, however, may result in severe motion artifacts and significant distortion of the fluorescence signals. Therefore, pharmacological uncoupling is widely used to reduce tissue motion. Recently, various image processing algorithms have been proposed to reduce motion artifacts. We will review these technological developments. Furthermore, we will present a novel approach for the three-dimensional, marker-free reconstruction of contracting Langendorff-perfused intact hearts under physiological conditions. The algorithm allows disentangling the fluorescence signals (e.g. membrane voltage or intracellular calcium) from the mechanical motion (e.g. tissue strain). We will discuss the algorithms reconstruction accuracy, resolution, and robustness using experimental data from Langendorff-perfused rabbit hearts."],["dc.identifier.doi","10.1016/j.pbiomolbio.2017.09.015"],["dc.identifier.pmid","28947080"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/57607"],["dc.identifier.url","https://sfb1002.med.uni-goettingen.de/production/literature/publications/189"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.relation","SFB 1002: Modulatorische Einheiten bei Herzinsuffizienz"],["dc.relation","SFB 1002 | C03: Erholung nach Herzinsuffizienz: Analyse der transmuralen mechano-elektrischen Funktionsstörung"],["dc.relation.issn","0079-6107"],["dc.relation.workinggroup","RG Luther (Biomedical Physics)"],["dc.rights","CC BY-NC-ND 4.0"],["dc.title","Electromechanical optical mapping"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]