124 results on '"Stoeck, Christian T"'
Search Results
102. Coronary MR Imaging: Effect of Timing and Dose of Isosorbide Dinitrate Administration
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Hu, Peng, primary, Chuang, Michael L., additional, Ngo, Long H., additional, Stoeck, Christian T., additional, Peters, Dana C., additional, Kissinger, Kraig V., additional, Goddu, Beth, additional, Goepfert, Lois A., additional, Manning, Warren J., additional, and Nezafat, Reza, additional
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- 2010
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103. In vivo comparison of DENSE and CSPAMM for cardiac motion analysis
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Stoeck, Christian T, primary, Kozerke, Sebastian, additional, Maredia, Neil, additional, Crean, Andrew, additional, Greenwood, John P, additional, and Plein, Sven, additional
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- 2009
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104. Analysis of 3D cardiac deformations with 3D SinMod.
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Wang, Hui, Stoeck, Christian T., Kozerke, Sebastian, and Amini, Amir A.
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- 2013
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105. Motion-Induced Signal Loss in In Vivo Cardiac Diffusion-Weighted Imaging.
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Stoeck, Christian T., Scott, Andrew D., Ferreira, Pedro F., Tunnicliffe, Elizabeth M., Teh, Irvin, Nielles‐Vallespin, Sonia, Moulin, Kevin, Sosnovik, David E., Viallon, Magalie, Croisille, Pierre, Kozerke, Sebastian, Firmin, David N., Ennis, Daniel B., Schneider, Jurgen E., and Nielles-Vallespin, Sonia
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DIFFUSION magnetic resonance imaging ,CARDIAC imaging - Abstract
Level Of Evidence: 5 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:319-320. [ABSTRACT FROM AUTHOR]- Published
- 2020
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106. Left ventricular blood flow patterns at rest and under dobutamine stress in healthy pigs.
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Cesarovic, Nikola, Busch, Julia, Lipiski, Miriam, Fuetterer, Maximilian, Fleischmann, Thea, Born, Silvia, Deuster, Constantin, Sauer, Mareike, Maisano, Francesco, Kozerke, Sebastian, and Stoeck, Christian T.
- Abstract
Intracardiac blood flow patterns are affected by the morphology of cardiac structures and are set up to support the heart's pump function. Exercise affects contractility and chamber size as well as pre‐ and afterload. The aim of this study was to test the feasibility of four‐dimensional phase contrast cardiovascular MRI under pharmacological stress and to study left ventricular blood flow under stress. 4D flow data were successfully acquired and analysed in 12 animals. During dobutamine infusion, heart rate and ejection fraction increased (82 ± 5 bpm versus 124 ± 3 bpm/46 ± 9% versus 65 ± 7%; both p < 0.05). A decrease in left ventricular end‐diastolic volume (72 ± 14 mL versus 55 ± 8 mL; p < 0.05) and end‐systolic volume (40 ± 15 mL versus 19 ± 6 mL; p < 0.05) but no change in stroke volume were observed. Trans‐mitral diastolic inflow velocity increased under dobutamine and the trajectory of inflowing blood was directed towards the anterior septum with increased inflow angle (26 ± 5°) when compared with controls (15 ± 2°). In 5/6 animals undergoing stress diastolic vortices developed later, and in 3/6 animals vortices collapsed earlier with significantly smaller cross‐sectional area during diastole. The vorticity index was not affected. Under the stress condition direct flow (% ejection within the next heart beat) increased from 43 ± 6% to 53 ± 8%. 4D MRI blood flow acquisition and analysis are feasible in pig hearts under dobutamine‐induced stress. Flow patterns characterized by high blood velocity and antero‐septally oriented diastolic inflow as well as decreased ventricular volumes are unfavourable conditions for diastolic vortex development under pharmacological stress, and cardiac output is increased by a rise in heart rate and directly ejected left ventricular blood volume. In this study the feasibility of 4D flow MRI during dobutamine‐induced stress was assessed, and changes in intraventricular blood flow patterns are reported for the porcine heart. A decrease in cardiac volume, antero‐septally oriented diastolic inflow and high velocity flow was found, providing unfavorable conditions for diastolic vortex development compared with the rest condition. [ABSTRACT FROM AUTHOR]
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- 2019
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107. Quantitative myocardial first-pass cardiovascular magnetic resonance perfusion imaging using hyperpolarized [1-13C] pyruvate.
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Fuetterer, Maximilian, Busch, Julia, Traechtler, Julia, Wespi, Patrick, Peereboom, Sophie M., Sauer, Mareike, Lipiski, Miriam, Fleischmann, Thea, Cesarovic, Nikola, Stoeck, Christian T., and Kozerke, Sebastian
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ANIMAL experimentation ,BLOOD circulation ,CARBOXYLIC acids ,CARDIOVASCULAR disease diagnosis ,MAGNETIC resonance imaging ,PERFUSION ,RADIONUCLIDE imaging ,SWINE ,QUANTITATIVE research ,IN vivo studies - Abstract
Background: The feasibility of absolute myocardial blood flow quantification and suitability of hyperpolarized [1-
13 C] pyruvate as contrast agent for first-pass cardiovascular magnetic resonance (CMR) perfusion measurements are investigated with simulations and demonstrated in vivo in a swine model. Methods: A versatile simulation framework for hyperpolarized CMR subject to physical, physiological and technical constraints was developed and applied to investigate experimental conditions for accurate perfusion CMR with hyperpolarized [1-13 C] pyruvate. Absolute and semi-quantitative perfusion indices were analyzed with respect to experimental parameter variations and different signal-to-noise ratio (SNR) levels. Absolute myocardial blood flow quantification was implemented with an iterative deconvolution approach based on Fermi functions. To demonstrate in vivo feasibility, velocity-selective excitation with an echo-planar imaging readout was used to acquire dynamic myocardial stress perfusion images in four healthy swine. Arterial input functions were extracted from an additional image slice with conventional excitation that was acquired within the same heartbeat. Results: Simulations suggest that obtainable SNR and B0 inhomogeneity in vivo are sufficient for the determination of absolute and semi-quantitative perfusion with ≤25% error. It is shown that for expected metabolic conversion rates, metabolic conversion of pyruvate can be neglected over the short duration of acquisition in first-pass perfusion CMR. In vivo measurements suggest that absolute myocardial blood flow quantification using hyperpolarized [1-13 C] pyruvate is feasible with an intra-myocardial variability comparable to semi-quantitative perfusion indices. Conclusion: The feasibility of quantitative hyperpolarized first-pass perfusion CMR using [1-13 C] pyruvate has been investigated in simulations and demonstrated in swine. Using an approved and metabolically active compound is envisioned to increase the value of hyperpolarized perfusion CMR in patients. [ABSTRACT FROM AUTHOR]- Published
- 2018
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108. Insight Into Myocardial Microstructure of Athletes and Hypertrophic Cardiomyopathy Patients Using Diffusion Tensor Imaging
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Das, Arka, Chowdhary, Amrit, Kelly, Chris, Teh, Irvin, Stoeck, Christian T., Kozerke, Sebastian, Maxwell, Nicholas, Craven, Thomas P., Jex, Nicholas J., Saunderson, Christopher E.D., Brown, Louise A.E., Ben-Arzi, Hadar, Sengupta, Anshuman, Page, Stephen P., Swoboda, Peter P., Greenwood, John P., Schneider, Jurgen E., Plein, Sven, and Dall'Armellina, Erica
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athlete's heart ,magnetic resonance imaging ,hypertrophic cardiomyopathy ,diffusion tensor imaging ,3. Good health - Abstract
Background Hypertrophic cardiomyopathy (HCM) remains the commonest cause of sudden cardiac death among young athletes. Differentiating between physiologically adaptive left ventricular (LV) hypertrophy observed in athletes' hearts and pathological HCM remains challenging. By quantifying the diffusion of water molecules, diffusion tensor imaging (DTI) MRI allows voxelwise characterization of myocardial microstructure. Purpose To explore microstructural differences between healthy volunteers, athletes, and HCM patients using DTI. Study Type Prospective cohort. Population Twenty healthy volunteers, 20 athletes, and 20 HCM patients. Field Strength/Sequence 3T/DTI spin echo. Assessment In‐house MatLab software was used to derive mean diffusivity (MD) and fractional anisotropy (FA) as markers of amplitude and anisotropy of the diffusion of water molecules, and secondary eigenvector angles (E2A)—reflecting the orientations of laminar sheetlets. Statistical Tests Independent samples t‐tests were used to detect statistical significance between any two cohorts. Analysis of variance was utilized for detecting the statistical difference between the three cohorts. Statistical tests were two‐tailed. A result was considered statistically significant at P ≤ 0.05. Results DTI markers were significantly different between HCM, athletes, and volunteers. HCM patients had significantly higher global MD and E2A, and significantly lower FA than athletes and volunteers. (MDHCM = 1.52 ± 0.06 × 10−3 mm2/s, MDAthletes = 1.49 ± 0.03 × 10−3 mm2/s, MDvolunteers = 1.47 ± 0.02 × 10−3 mm2/s, P, Journal of Magnetic Resonance Imaging, 53 (1), ISSN:1053-1807, ISSN:1522-2586
109. Studying Dynamic Myofiber Aggregate Reorientation in Dilated Cardiomyopathy Using in Vivo Magnetic Resonance Diffusion Tensor Imaging
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Deuster, von Deuster, Constantin, Sammut, Eva, Asner, Liya, Nordsletten, David, Lamata, Pablo, Stoeck, Christian T., Kozerke, Sebastian, and Razavi, Reza
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Diffusion tensor imaging ,Magnetic resonance imaging ,Myocardium ,Dilated cardiomyopathy ,Myofiber architecture ,3. Good health - Abstract
Background The objective of this study is to assess the dynamic alterations of myocardial microstructure and strain between diastole and systole in patients with dilated cardiomyopathy relative to healthy controls using the magnetic resonance diffusion tensor imaging, myocardial tagging, and biomechanical modeling. Methods and Results Dual heart-phase diffusion tensor imaging was successfully performed in 9 patients and 9 controls. Tagging data were acquired for the diffusion tensor strain correction and cardiac motion analysis. Mean diffusivity, fractional anisotropy, and myocyte aggregate orientations were compared between both cohorts. Cardiac function was assessed by left ventricular ejection fraction, torsion, and strain. Computational modeling was used to study the impact of cardiac shape on fiber reorientation and how fiber orientations affect strain. In patients with dilated cardiomyopathy, a more longitudinal orientation of diastolic myofiber aggregates was measured compared with controls. Although a significant steepening of helix angles (HAs) during contraction was found in the controls, consistent change in HAs during contraction was absent in patients. Left ventricular ejection fraction, cardiac torsion, and strain were significantly lower in the patients compared with controls. Computational modeling revealed that the dilated heart results in reduced HA changes compared with a normal heart. Reduced torsion was found to be exacerbated by steeper HAs. Conclusions Diffusion tensor imaging revealed reduced reorientation of myofiber aggregates during cardiac contraction in patients with dilated cardiomyopathy relative to controls. Left ventricular remodeling seems to be an important factor in the changes to myocyte orientation. Steeper HAs are coupled with a worsening in strain and torsion. Overall, the findings provide new insights into the structural alterations in patients with dilated cardiomyopathy., Circulation. Cardiovascular Imaging, 9 (10), ISSN:1941-9651, ISSN:1942-0080
110. In vivo myofibre architecture in the systemic right ventricle
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Harmer, Jack, Pushparajah, Kuberan, Toussaint, Nicolas, Stoeck, Christian T., Chan, Rachel, Atkinson, David, Razavi, Reza, Kozerke, Sebastian, Harmer, Jack, Pushparajah, Kuberan, Toussaint, Nicolas, Stoeck, Christian T., Chan, Rachel, Atkinson, David, Razavi, Reza, and Kozerke, Sebastian
111. Magnetic Resonance Imaging-Based Microstructural Models for Cardiac Biomechanics Simulations
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Stimm, Johanna, Kozerke, Sebastian, Stoeck, Christian T., and Young, Alistair
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Technology (applied sciences) ,ddc:600 - Abstract
Cardiovascular diseases are the leading cause of death globally with increasing prevalence due to the aging population. While advances in medical care improved patients’ prognosis for the first cardiac event, often secondary diseases develop. Early diagnosis and treatment could prevent irreversible damage and improve long-term prognosis. Consequently, advances in early detection and patient-specific treatment have a vital impact. Computational biomechanical models provide a tool to better understand cardiac function, test hypotheses, and reveal causal relations. Inferring non-measurable quantities from models can help to identify early bio-markers and differentiate phenotype categories. Patient-specific models based on in-vivo data might allow for predictions of disease progression and treatment outcome. This would enable personalized medicine with optimal therapy adaptation to the individuals manifestation of a pathology instead of relying on population-based statistical findings. Combining cardiac biomechanical modelling with cardiac Magnetic Resonance Imaging (MRI), which provides rich in-vivo data with a variety of imaging contrasts, has great potential to develop a detailed in-silico replica of the heart, rendering predictive patient-specific modelling feasible. Cardiac function is linked to the underlying tissue microstructure. Cardiac deformation is initiated by cardiomyocyte shortening and an anisotropic passive tissue response related to the fiber-sheet structure. In pathology associated with altered cardiac function or geometry, changes in microstructure have been observed, suggesting that the link between structure and function is important. Consequently, to study cardiac disease with patientspecific, biomechanical models, a data-based, individual representation of microstructure is essential. In-vivo cardiac Diffusion Tensor Imaging (cDTI) is an MRI technique to probe aggregated myocyte orientation. However, it suffers from low resolution, low signal-to-noise ratio, and limited spatial coverage. In this thesis approaches are proposed to bridge the gap between sparse in-vivo data and fine, 3D simulation meshes to enable subject-specific cardiac simulations based on in-vivo cDTI data. Ex-vivo cDTI can provide high-resolution data of microstructure since cardiac and respiratory motion as well as scan time limitations of in-vivo scanning do not apply. Despite the variations between individuals and species, the structural similarity across hearts is exploited to demonstrate that the tissue can be represented by a limited number of structural basis functions. Two reduction methods, Proper Generalized Decomposition combined with Singular Value Decomposition and Proper Orthogonal Decomposition are employed to extract a low-rank representation from ex-vivo porcine data. Based on the resulting truncated basis, representing the main characteristics of the microstructure, two data-driven, parametric models with personalized weights are proposed. The models feature a higher flexibility than existing atlas and rule-based descriptions when adapted to data. The potential to transfer the data-based models of cardiac microstructure from animals to humans is demonstrated. To enable the use of sparse in-vivo data in 3D cardiac simulations, five interpolation techniques are compared, two tensor interpolation approaches, one rule-based approximation, and the two data-driven, low-rank models extracted in the first study. To this end, interpolation experiments with in-vivo and ex-vivo porcine data are performed, showing the advantage of tensor interpolation techniques, which result in lower interpolation errors than the low-rank models and the rule-based method. The low-rank models and the rule-based method are based on prior information and therefore feature a lower flexibility to adapt to cDTI input data, leading to an over-smoothed microstructure. Underestimation of helix angles and errors at the endo- and epicardial boundaries are most pronounced for the rule-based method. The ex-vivo and in-vivo experiments show the same qualitative results. In an ex-vivo comparison with synthetically downsampled data, the influence of three imaging parameters that can be traded off against acquisition time are studied: in-plane resolution, signal-to-noise ratio (SNR), and number of short-axis imaging slices. This experiment suggests that the increase in in-plane resolution of the measured input data improves the interpolation performance despite the associated SNR reduction when keeping acquisition duration constant. These findings help guiding experimental design and the choice of interpolation techniques for cardiac simulation studies that include in-vivo microstructural data for personalization. In a biomechanical modelling study it is demonstrated that the previously examined interpolation techniques enable cardiac simulations with personalized microstructure from in-vivo cDTI data. The influence of the interpolation technique on the simulation output is assessed. To this end, subject-specific cardiac models based on in-vivo cine MRI data of one porcine heart are generated and equipped with myocyte orientation from in-vivo cDTI data. Each interpolation technique results in one cardiac model with a different representation of microstructure obtained from the same input data. Small, however systematic trends are identified when comparing global functional parameters and strains between the simulation outputs. Cardiac twist is underestimated for all models, however, the model with the most realistic microstructure obtained from the tensor interpolation technique shows the highest twist, closest to physiological behavior. In conclusion, this thesis provides two data-driven, parametric low-rank models of aggregated myocyte orientation based on ex-vivo data that can be adapted to individual cardiac microstructure. These new models and existing interpolation methods are compared with respect to their interpolation performance, providing a data-based evaluation of techniques that can be applied to include microstructure from in-vivo data in cardiac modelling. In a modelling study, the feasibility of simulations using in-vivo microstructure is demonstrated and the potential bias due to the underlying interpolation method for cardiac simulations is estimated. Taken together, the work facilitates future computational studies on the link between structure, function, and remodelling in cardiac pathology., Herz-Kreislauf-Erkrankungen sind weltweit die häufigste Todesursache mit steigender Tendenz auf Grund des demographischen Wandels und des damit steigenden Altersdurchschnitts der Bevölkerung. Fortschritte in der medizinischen Versorgung und Therapie verbesserten in den vergangenen Jahren die kurzfristige Prognose der Parienten. Es entwickeln sich jedoch häufig Folgeerkrankungen. Eine frühzeitige Erkennung und Behandlung könnte jedoch irreversible Schädigungen verhindern und somit die Langzeitprognose der Patienten verbessern. Weitere Fortschritte in der Früherkennung und eine individuell auf den Patienten zugeschnittene Therapie sind daher von entscheidender Bedeutung. Mit Hilfe von Simulationsmodellen können die komplexen Mechanismen, die der Funktion des Herzens zugrundliegen, analysiert werden. Beispielsweise ermöglichen Computer Modelle das Testen von Hypothesen. Dies trägt zu einem besseren Verständnis der kausalen Zusammenhänge von Ursache und Symptomatik bei. Außerdem können Parameter untersucht werden, die im menschlichen Körper nicht gemessen werden können, wie zum Beispiel die mechanische Spannung im Gewebe. Diese zusätzlichen Erkenntnisse haben großes Potential für die Identifikation von Biomarkern und die Vorhersage der Ausprägung einer Erkrankung. Auf in-vivo Daten basierende, patientenspezifische Modelle könnten die Prognose des individuellen Krankheitsverlaufs und Therapieerfolgs verbessern. Daher würde eine personalisierte, durch Simulationen gestützte Medizin eine optimalere Anpassung der Therapie an die individuelle Ausprägung der Krankheit erlauben. Dazu ist die Anpassung der komplexen Simulationsmodelle des Herzens an klinische Patientendaten nötig. Die Magnetresonanz-Tomographie (MRT) bietet durch die Vielseitigkeit der Kontraste reichhaltige Informationen über Struktur und Funktion des Herzmuskels. Daher ist die Kombination von Modellierung und Magnetresonanz-Tomographie (MRT) vielversprechend für eine patienten-spezifische Medizin. Die Mikrostruktur des Herzmuskelgewebes hat einen wichtigen Einfluss auf die Deformation des Herzmuskels während des Herzschlags. Die Kontraktion des Herzes ist durch die Verkürzung der Kardiomyozyten bedingt und das anisotrope, passive Verhalten des Gewebes wird durch die unterschiedliche Steifigkeit entlang verschiedener Belastungsrichtungen der Muskelfaserstruktur hervorgerufen. In Pathologien mit veränderter Herzfunktion oder Herzform wurden Veränderungen ebendieser Mikrostruktur des Herzmuskelgewebes beobachtet. Dies weist darauf hin, dass der Zusammenhang zwischen Struktur und Funktion eine wichtige Rolle spielt. Daher ist es für patientenspezifische, biomechanische Simulationen essenziell, die individuelle Mikrostruktur aus Daten zu extrahieren und zu berücksichtigen. Die kardiale Diffusions-Tensor-Bildgebung ist eine MRT-Technik, die auf die räumliche Hauptausrichtung der Mikrostruktur schließen lässt. Bei der Anwendung in-vivo werden jedoch nur ein geringes Signal-Rausch-Verhältnis, eine geringe räumliche Auflösung, und eine begrenzte Anzahl von Kurzacheschichten erreicht. Diese Arbeit befasst sich daher mit Methoden, welche trotz geringer Datenqualität, die Integration der Mikrostruktur aus in-vivo Messdaten, in patienten-spezifischen, 3-D Simulationsmodellen ermöglichen. Die Anwendung der kardialen Diffusions-Tensor-Bildgebung ex-vivo ermöglicht die Aufnahme hoch-aufgelöster Daten, da Einflüsse aus Herz- und Atembewegung als auch Messzeitbeschränkungen keine Rolle spielen. Trotz existierender Unterschiede in der Mikrostruktur zwischen Individuen und Spezies kann gezeigt werden, dass grundlegende Ähnlichkeiten der Struktur zwischen verschiedenen Herzen es zulassen, die räumliche Variation der Mikrostruktur durch gemeinsame Basisfunktionen darzustellen. Solche Basisfunktionen werden in der vorliegenden Arbeit mit Hilfe zweier Reduktionsverfahren aus ex-vivo Diffusionsdaten von Schweinen bestimmt. Beide Ansätze liefern je eine reduzierte Basis, welche die Charakteristika der räumlichen Variation der Mikrostruktur im linken Ventrikel beschreiben. Diese Basisfunktionen werden mit Gewichtungskoeffizienten multipliziert und dienen als datenbasierte Modelle der Mikrostruktur. Gegenüber bestehenden statistischen Atlas-Modellen und vereinfachten generischen Modellen, welche aus Beobachtungen aus der Histologie abgeleitet wurden, sind beide vorgestellten Modelle flexibler und können durch Adaption der Gewichtungskoeffizienten Daten anderer Herzen besser approximieren. Mit Daten eines menschlichen Herzens wird die Übertragbarkeit dieser datenbasierten Modelle vom Tier auf den Menschen gezeigt. Im Hinblick auf die Verwendung von in-vivo Daten in 3D-Simulationen der Biomechanik des Herzens werden fünf Interpolationstechniken verglichen: zwei Tensor-Interpolationsansätze, ein vereinfachtes Modell, welches aus Beobachtungen in der Histologie abgeleitet wurde und die beiden vorgeschlagenen datenbasierten Modelle, die in der ersten Studie aus ex-vivo Daten extrahiert wurden. Zu diesem Zweck werden Interpolationsexperimente mit in-vivo und ex-vivo Schweinedaten durchgeführt. Die direkte Tensor-Interpolation liefert die genausten Interpolationsergebnisse, gefolgt von den datenbasierten Modellen und dem vereinfachten Modell. Gegenüber der direkten Tensor-Interpolation der Daten passen sich die Modelle den Daten weniger flexibel an, dies führt zu einer zu starken Glättung der Mikrostruktur an den endo- und epikardialen Oberflächen des linken Ventrikels und damit zu einer Unterschätzung des Helixwinkels. Diese Unterschätzung ist für das vereinfachte Modell am stärksten ausgeprägt. Experimente mit in-vivo und ex-vivo Daten zeigen qualitativ die gleichen Ergebnisse. In einem ex-vivo Experiment mit synthetisch reduzierter Datenqualität wird der Einfluss von drei Bildgebungsparametern untersucht, die gegen die Aufnahmezeit abgewogen werden können: die Auflösung in der Schicht, das Signal-Rausch-Verhältnis, und die Anzahl der Kurzachsenschichten. Dieses Experiment legt nahe, dass die Erhöhung der Auflösung in der Schicht, trotz der damit verbundenen Reduktion des Signal-Rausch-Verhältnisse, das Ergebnis der Interpolation verbessert. Diese Erkenntnisse können für die Planung zukünftiger Experimente und die Auswahl der Interpolationstechnik für patientenspezifische Simulationsmodelle mit individueller Mikrostruktur genutzt werden.
- Published
- 2022
112. Motion and eddy current-induced signal dephasing in in vivo cardiac DTI
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Christian T. Stoeck, Robbert J. H. van Gorkum, Constantin von Deuster, Sebastian Kozerke, University of Zurich, and Stoeck, Christian T
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Dephasing ,Phase (waves) ,Diastole ,610 Medicine & health ,Signal ,Imaging phantom ,030218 nuclear medicine & medical imaging ,170 Ethics ,03 medical and health sciences ,Motion ,0302 clinical medicine ,Nuclear magnetic resonance ,Fractional anisotropy ,Image Processing, Computer-Assisted ,2741 Radiology, Nuclear Medicine and Imaging ,Radiology, Nuclear Medicine and imaging ,10237 Institute of Biomedical Engineering ,Physics ,Attenuation ,Heart ,Diffusion Magnetic Resonance Imaging ,Diffusion Tensor Imaging ,Radiology Nuclear Medicine and imaging ,Anisotropy ,030217 neurology & neurosurgery ,Diffusion MRI - Abstract
Purpose To address motion in cardiac DWI, stimulated-echo acquisition mode (STEAM) and second-order motion-compensated spin-echo (SE) sequences have been proposed. Despite applying motion-compensation strategies, residual motion can cause misleading signal attenuation. The purpose of this study is to estimate the motion-induced error in both sequences by analysis of image phase. Methods Diffusion-weighted motion-compensated SE sequences and STEAM imaging was applied in vivo with diffusion encoding along 3 orthogonal directions. A b-value range of 100 to 600 s/mm2 and trigger delays of 25%, 50%, and 75% of end systole and middiastole were used. Eddy-current contributions were obtained from phantom measurements. After computation of motion-induced phase maps, the amount of signal dephasing was computed from phase gradients, and the resulting errors in diffusion tensor parameters were calculated. Results Motion-induced dephasing from the STEAM sequence showed less dependency on the b-value and no dependency on the heart phase, whereas SE imaging performed best at 75% end systole followed by 50% end systole and middiastole. For a typical experimental setting, errors of 3.3%/3.0% mean diffusivity, 4.9%/4.8% fractional anisotropy, 2.9o/3.2o helix angulation, 0.8o/0.7o transverse angulation, and 9.9o/10.0o sheet angulation (SE/STEAM) were calculated. Conclusion Image phase contains valuable information regarding uncompensated motion and eddy currents in cardiac DTI. Although the trigger delay window for SE is narrower compared with the STEAM-based approach, imaging in both systole and diastole is feasible and both sequences perform similarly if the trigger delays are selected carefully with SE.
- Published
- 2019
113. Left ventricular blood flow patterns at rest and under dobutamine stress in healthy pigs
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Miriam Lipiski, Francesco Maisano, Maximilian Fuetterer, Mareike Sauer, Silvia Born, Sebastian Kozerke, Constantin von Deuster, Nikola Cesarovic, Thea Fleischmann, Julia Busch, Christian T. Stoeck, University of Zurich, and Stoeck, Christian T
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Cardiac output ,medicine.medical_specialty ,Swine ,Heart Ventricles ,Rest ,Diastole ,1607 Spectroscopy ,610 Medicine & health ,Blood volume ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,Imaging, Three-Dimensional ,0302 clinical medicine ,Afterload ,Stress, Physiological ,Coronary Circulation ,Dobutamine ,Internal medicine ,Animals ,2741 Radiology, Nuclear Medicine and Imaging ,Medicine ,Radiology, Nuclear Medicine and imaging ,Spectroscopy ,Ejection fraction ,business.industry ,Blood flow ,Stroke volume ,10020 Clinic for Cardiac Surgery ,1313 Molecular Medicine ,cardiovascular system ,Cardiology ,Mitral Valve ,Molecular Medicine ,4D flow dobutamine stress left ventricular flow pattern porcine heart vortex formation ,business ,030217 neurology & neurosurgery ,medicine.drug - Abstract
Intracardiac blood flow patterns are affected by the morphology of cardiac structures and are set up to support the heart's pump function. Exercise affects contractility and chamber size as well as pre- and afterload. The aim of this study was to test the feasibility of four-dimensional phase contrast cardiovascular MRI under pharmacological stress and to study left ventricular blood flow under stress. 4D flow data were successfully acquired and analysed in 12 animals. During dobutamine infusion, heart rate and ejection fraction increased (82 ± 5 bpm versus 124 ± 3 bpm/46 ± 9% versus 65 ± 7%; both p
- Published
- 2018
114. Diffuse myocardial fibrosis precedes subclinical functional myocardial impairment and provides prognostic information in systemic sclerosis.
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Gotschy A, Jordan S, Stoeck CT, von Deuster C, Peer T, Gastl M, Vishnevskiy V, Wissmann L, Dobrota R, Mihai C, Becker MO, Maurer B, Kozerke S, Ruschitzka F, Distler O, and Manka R
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- Humans, Prognosis, Ventricular Function, Left, Prospective Studies, Myocardium pathology, Fibrosis, Magnetic Resonance Imaging, Cine methods, Predictive Value of Tests, Cardiomyopathies pathology, Scleroderma, Systemic complications, Scleroderma, Systemic diagnostic imaging
- Abstract
Aims: Myocardial involvement is common in patients with systemic sclerosis (SSc) and causes myocardial fibrosis and subtle ventricular dysfunction. However, the temporal onset of myocardial involvement during the progression of the disease and its prognostic value are yet unknown. We used cardiovascular magnetic resonance (CMR) to investigate subclinical functional impairment and diffuse myocardial fibrosis in patients with very early diagnosis of SSc (VEDOSS) and established SSc and examined whether this was associated with mortality., Methods and Results: One hundred and ten SSc patients (86 established SSc, 24 VEDOSS) and 15 healthy controls were prospectively recruited. The patients were followed-up for a median duration of 7.0 years (interquartile range 6.0-7.3 years). Study subjects underwent CMR including assessment of myocardial fibrosis [native T1 and extracellular volume (ECV)] and measurement of global longitudinal (GLS) and circumferential (GCS) myocardial strain. Native T1 values and ECV were elevated in VEDOSS and SSc patients compared with controls (P < 0.001). GLS was similar in VEDOSS and controls but significantly impaired in patients with established SSc (P < 0.001). GCS was similar over all groups (P = 0.88). There were 12 deaths during follow-up. Elevated native T1 [hazard ratio (HR) 5.8, 95% confidence interval (CI): 1.7-20.4; P = 0.006] and reduced GLS (HR 6.1, 95% CI: 1.3-29.9; P = 0.038) identified subjects with increased risk of death. Only native T1 was predictive for cardiovascular mortality (P < 0.001)., Conclusion: Subclinical myocardial involvement first manifests as diffuse myocardial fibrosis identified by the expansion of ECV and increased native T1 in VEDOSS patients while subtle functional impairment only occurs in established SSc. Native T1 and GLS have prognostic value for all-cause mortality in SSc patients., Competing Interests: Conflict of interest: B.M. has/had grant/research support from Abbvie, Protagen, Novartis Biomedical Research, received speaker fees from Böhringer Ingelheim as well as congress support from Pfizer, Roche, Actelion, Mepha, and MSD. C.M. has received congress support from Actelion and Roche, and personal fees from Boehringer-Ingelheim, Mepha, and MEDtalks Switzerland, outside the submitted work. R.D. reports grants/research support from Pfizer, Actelion, and personal fees (speaker/consultancy) from Actelion and Boehringer-Ingelheim, outside the submitted work. O.D. has/had consultancy relationship with and/or has received research funding from or has served as a speaker for the following companies in the area of potential treatments for systemic sclerosis and its complications in the last 3 years: Abbvie, Acceleron, Alcimed, Amgen, AnaMar, Arxx, AstraZeneca, Baecon, Blade, Bayer, Boehringer-Ingelheim, ChemomAb, Corbus, CSL Behring, Galapagos, Glenmark, GSK, Horizon (Curzion), Inventiva, iQvia, Kymera, Lupin, Medac, Medscape, Miltenyi Biotec, Mitsubishi Tanabe, Novartis, Prometheus, Roche, Roivant, Sanofi, Serodapharm, Topadur and UCB. Patent issued ‘mir-29 for the treatment of systemic sclerosis’ (US8247389, EP2331143). O.D. and B.M. have a patent for ‘mir-29 for the treatment of systemic sclerosis’ (US8247389, EP2331143). All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (© The Author(s) 2022. Published by Oxford University Press on behalf of the European Society of Cardiology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)
- Published
- 2023
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115. Cardiovascular magnetic resonance imaging of functional and microstructural changes of the heart in a longitudinal pig model of acute to chronic myocardial infarction.
- Author
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Stoeck CT, von Deuster C, Fuetterer M, Polacin M, Waschkies CF, van Gorkum RJH, Kron M, Fleischmann T, Cesarovic N, Weisskopf M, and Kozerke S
- Subjects
- Animals, Contrast Media, Diffusion Tensor Imaging, Gadolinium, Magnetic Resonance Imaging, Magnetic Resonance Imaging, Cine, Myocardium, Predictive Value of Tests, Stroke Volume, Swine, Myocardial Infarction diagnostic imaging, Ventricular Function, Left
- Abstract
Background: We examined the dynamic response of the myocardium to infarction in a longitudinal porcine study using relaxometry, functional as well as diffusion cardiovascular magnetic resonance (CMR). We sought to compare non contrast CMR methods like relaxometry and in-vivo diffusion to contrast enhanced imaging and investigate the link of microstructural and functional changes in the acute and chronically infarcted heart., Methods: CMR was performed on five myocardial infarction pigs and four healthy controls. In the infarction group, measurements were obtained 2 weeks before 90 min occlusion of the left circumflex artery, 6 days after ischemia and at 5 as well as 9 weeks as chronic follow-up. The timing of measurements was replicated in the control cohort. Imaging consisted of functional cine imaging, 3D tagging, T2 mapping, native as well as gadolinium enhanced T1 mapping, cardiac diffusion tensor imaging, and late gadolinium enhancement imaging., Results: Native T1, extracellular volume (ECV) and mean diffusivity (MD) were significantly elevated in the infarcted region while fractional anisotropy (FA) was significantly reduced. During the transition from acute to chronic stages, native T1 presented minor changes (< 3%). ECV as well as MD increased from acute to the chronic stages compared to baseline: ECV: 125 ± 24% (day 6) 157 ± 24% (week 5) 146 ± 60% (week 9), MD: 17 ± 7% (day 6) 33 ± 14% (week 5) 29 ± 15% (week 9) and FA was further reduced: - 31 ± 10% (day 6) - 38 ± 8% (week 5) - 36 ± 14% (week 9). T2 as marker for myocardial edema was significantly increased in the ischemic area only during the acute stage (83 ± 3 ms infarction vs. 58 ± 2 ms control p < 0.001 and 61 ± 2 ms in the remote area p < 0.001). The analysis of functional imaging revealed reduced left ventricular ejection fraction, global longitudinal strain and torsion in the infarct group. At the same time the transmural helix angle (HA) gradient was steeper in the chronic follow-up and a correlation between longitudinal strain and transmural HA gradient was detected (r = 0.59 with p < 0.05). Comparing non-gadolinium enhanced data T2 mapping showed the largest relative change between infarct and remote during the acute stage (+ 33 ± 4% day 6, with p = 0.013 T2 vs. MD, p = 0.009 T2 vs. FA and p = 0.01 T2 vs. T1) while FA exhibited the largest relative change between infarct and remote during the chronic follow-up (+ 31 ± 2% week 5, with p = N.S. FA vs. MD, p = 0.03 FA vs. T2 and p = 0.003 FA vs. T1). Overall, diffusion parameters provided a higher contrast (> 23% for MD and > 27% for FA) during follow-up compared to relaxometry (T1 17-18%/T2 10-20%)., Conclusion: During chronic follow-up after myocardial infarction, cardiac diffusion tensor imaging provides a higher sensitivity for mapping microstructural alterations when compared to non-contrast enhanced relaxometry with the added benefit of providing directional tensor information to assess remodelling of myocyte aggregate orientations, which cannot be otherwise assessed., (© 2021. The Author(s).)
- Published
- 2021
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116. Investigating the reference domain influence in personalised models of cardiac mechanics : Effect of unloaded geometry on cardiac biomechanics.
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Hadjicharalambous M, Stoeck CT, Weisskopf M, Cesarovic N, Ioannou E, Vavourakis V, and Nordsletten DA
- Subjects
- Algorithms, Animals, Biomechanical Phenomena, Biophysics, Computer Simulation, Female, Finite Element Analysis, Image Processing, Computer-Assisted, Stress, Mechanical, Swine, Systole, Heart physiology, Models, Cardiovascular
- Abstract
A major concern in personalised models of heart mechanics is the unknown zero-pressure domain, a prerequisite for accurately predicting cardiac biomechanics. As the reference configuration cannot be captured by clinical data, studies often employ in-vivo frames which are unlikely to correspond to unloaded geometries. Alternatively, zero-pressure domain is approximated through inverse methodologies, which, however, entail assumptions pertaining to boundary conditions and material parameters. Both approaches are likely to introduce biases in estimated biomechanical properties; nevertheless, quantification of these effects is unattainable without ground-truth data. In this work, we assess the unloaded state influence on model-derived biomechanics, by employing an in-silico modelling framework relying on experimental data on porcine hearts. In-vivo images are used for model personalisation, while in-situ experiments provide a reliable approximation of the reference domain, creating a unique opportunity for a validation study. Personalised whole-cycle cardiac models are developed which employ different reference domains (image-derived, inversely estimated) and are compared against ground-truth model outcomes. Simulations are conducted with varying boundary conditions, to investigate the effect of data-derived constraints on model accuracy. Attention is given to modelling the influence of the ribcage on the epicardium, due to its close proximity to the heart in the porcine anatomy. Our results find merit in both approaches for dealing with the unknown reference domain, but also demonstrate differences in estimated biomechanical quantities such as material parameters, strains and stresses. Notably, they highlight the importance of a boundary condition accounting for the constraining influence of the ribcage, in forward and inverse biomechanical models., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)
- Published
- 2021
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117. Analysis and correction of off-resonance artifacts in echo-planar cardiac diffusion tensor imaging.
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van Gorkum RJH, von Deuster C, Guenthner C, Stoeck CT, and Kozerke S
- Subjects
- Algorithms, Brain, Diffusion Magnetic Resonance Imaging, Echo-Planar Imaging, Humans, Image Processing, Computer-Assisted, Artifacts, Diffusion Tensor Imaging
- Abstract
Purpose: Cardiac diffusion tensor imaging using EPI readout is prone to image distortions in the presence of field inhomogeneities. In this work, a framework to analyze and correct image distortions in cardiac diffusion tensor imaging is presented., Methods: A multi-coil reconstruction framework was implemented to enable field map-based off-resonance correction. Numerical simulations were used to examine reconstruction performance for EPI phase-encode directions blip up-down and down-up for different degrees of off-resonance gradients and varying field map resolution. The impact of coil encoding was analyzed using the g-factor and normalized RMSE. Finally, the proposed method was tested on free-breathing in vivo cardiac diffusion tensor imaging data acquired in healthy subjects at 3 Tesla., Results: Depending on the local field map gradient strength and polarity and the selected phase-encode direction, field inhomogeneities lead to either local spatial compression or stretching with standard image reconstruction. Although spatial compression results in loss of image resolution upon field map-based reconstruction, spatial stretching can be recovered once multiple receive coils are utilized. Multi-coil reconstruction was found to reduce the normalized RMSE from 34.3% to 8.1% for image compression, and 33.6% to 1.8% for image stretching, with resulting average g-factors 14.7 ± 2.9 and 1.2 ± 0.1, respectively. In vivo, multi-coil field map-based reconstruction yielded improved alignment of angle maps with anatomical cine data., Conclusion: Multi-coil, field map-based image reconstruction for echo-planar cardiac diffusion tensor imaging allows accurate image reconstruction provided that the phase-encode direction and polarity is chosen to principally align with the direction and polarity of the prominent gradients of field inhomogeneities., (© 2020 International Society for Magnetic Resonance in Medicine.)
- Published
- 2020
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118. Characterizing cardiac involvement in amyloidosis using cardiovascular magnetic resonance diffusion tensor imaging.
- Author
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Gotschy A, von Deuster C, van Gorkum RJH, Gastl M, Vintschger E, Schwotzer R, Flammer AJ, Manka R, Stoeck CT, and Kozerke S
- Subjects
- Aged, Amyloidosis pathology, Amyloidosis physiopathology, Cardiomyopathies pathology, Cardiomyopathies physiopathology, Case-Control Studies, Contrast Media administration & dosage, Female, Humans, Male, Middle Aged, Myocardium pathology, Organometallic Compounds administration & dosage, Predictive Value of Tests, Prospective Studies, Stroke Volume, Ventricular Function, Left, Amyloidosis diagnostic imaging, Cardiomyopathies diagnostic imaging, Diffusion Tensor Imaging, Magnetic Resonance Imaging, Cine
- Abstract
Background: In-vivo cardiovascular magnetic resonance (CMR) diffusion tensor imaging (DTI) allows imaging of alterations of cardiac fiber architecture in diseased hearts. Cardiac amyloidosis (CA) causes myocardial infiltration of misfolded proteins with unknown consequences for myocardial microstructure. This study applied CMR DTI in CA to assess microstructural alterations and their consequences for myocardial function compared to healthy controls., Methods: Ten patients with CA (8 AL, 2 ATTR) and ten healthy controls were studied using a diffusion-weighed second-order motion-compensated spin-echo sequence at 1.5 T. Additionally, left ventricular morphology, ejection fraction, strain and native T1 values were obtained in all subjects. In CA patients, T1 mapping was repeated after the administration of gadolinium for extracellular volume fraction (ECV) calculation. CMR DTI analysis was performed to yield the scalar diffusion metrics mean diffusivity (MD) and fractional anisotropy (FA) as well as the characteristics of myofiber orientation including helix, transverse and E2A sheet angle (HA, TA, E2A)., Results: MD and FA were found to be significantly different between CA patients and healthy controls (MD 1.77 ± 0.17 10
- 3 vs 1.41 ± 0.07 10- 3 mm2 /s, p < 0.001; FA 0.25 ± 0.04 vs 0.35 ± 0.03, p < 0.001). MD demonstrated an excellent correlation with native T1 (r = 0.908, p < 0.001) while FA showed a significant correlation with ECV in the CA population (r = - 0.851, p < 0.002). HA exhibited a more circumferential orientation of myofibers in CA patients, in conjunction with a higher TA standard deviation and a higher absolute E2A sheet angle. The transmural HA slope was found to be strongly correlated with the global longitudinal strain (r = 0.921, p < 0.001)., Conclusion: CMR DTI reveals significant alterations of scalar diffusion metrics in CA patients versus healthy controls. Elevated MD and lower FA values indicate myocardial disarray with higher diffusion in CA that correlates well with native T1 and ECV measures. In CA patients, CMR DTI showed pronounced circumferential orientation of the myofibers, which may provide the rationale for the reduction of global longitudinal strain that occurs in amyloidosis patients. Accordingly, CMR DTI captures specific features of amyloid infiltration, which provides a deeper understanding of the microstructural consequences of CA.- Published
- 2019
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119. Quantitative myocardial first-pass cardiovascular magnetic resonance perfusion imaging using hyperpolarized [1- 13 C] pyruvate.
- Author
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Fuetterer M, Busch J, Traechtler J, Wespi P, Peereboom SM, Sauer M, Lipiski M, Fleischmann T, Cesarovic N, Stoeck CT, and Kozerke S
- Subjects
- Animals, Blood Flow Velocity, Computer Simulation, Feasibility Studies, Female, Image Interpretation, Computer-Assisted, Models, Animal, Models, Cardiovascular, Predictive Value of Tests, Reproducibility of Results, Sus scrofa, Time Factors, Carbon Isotopes administration & dosage, Contrast Media administration & dosage, Coronary Circulation, Magnetic Resonance Imaging methods, Myocardial Perfusion Imaging methods, Pyruvic Acid administration & dosage
- Abstract
Background: The feasibility of absolute myocardial blood flow quantification and suitability of hyperpolarized [1-
13 C] pyruvate as contrast agent for first-pass cardiovascular magnetic resonance (CMR) perfusion measurements are investigated with simulations and demonstrated in vivo in a swine model., Methods: A versatile simulation framework for hyperpolarized CMR subject to physical, physiological and technical constraints was developed and applied to investigate experimental conditions for accurate perfusion CMR with hyperpolarized [1-13 C] pyruvate. Absolute and semi-quantitative perfusion indices were analyzed with respect to experimental parameter variations and different signal-to-noise ratio (SNR) levels. Absolute myocardial blood flow quantification was implemented with an iterative deconvolution approach based on Fermi functions. To demonstrate in vivo feasibility, velocity-selective excitation with an echo-planar imaging readout was used to acquire dynamic myocardial stress perfusion images in four healthy swine. Arterial input functions were extracted from an additional image slice with conventional excitation that was acquired within the same heartbeat., Results: Simulations suggest that obtainable SNR and B0 inhomogeneity in vivo are sufficient for the determination of absolute and semi-quantitative perfusion with ≤25% error. It is shown that for expected metabolic conversion rates, metabolic conversion of pyruvate can be neglected over the short duration of acquisition in first-pass perfusion CMR. In vivo measurements suggest that absolute myocardial blood flow quantification using hyperpolarized [1-13 C] pyruvate is feasible with an intra-myocardial variability comparable to semi-quantitative perfusion indices., Conclusion: The feasibility of quantitative hyperpolarized first-pass perfusion CMR using [1-13 C] pyruvate has been investigated in simulations and demonstrated in swine. Using an approved and metabolically active compound is envisioned to increase the value of hyperpolarized perfusion CMR in patients.- Published
- 2018
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120. Maximum likelihood estimation of cardiac fiber bundle orientation from arbitrarily spaced diffusion weighted images.
- Author
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Nagler A, Bertoglio C, Stoeck CT, Kozerke S, and Wall WA
- Subjects
- Humans, Algorithms, Diffusion Magnetic Resonance Imaging methods, Heart Ventricles anatomy & histology, Heart Ventricles diagnostic imaging, Likelihood Functions
- Abstract
We propose an estimation scheme for local fiber bundle direction in the left ventricle directly from gray values of arbitrarily spaced cardiac diffusion weighted images (DWI). The approach is based on a parametric and space-dependent mathematical representation of the myocardial fiber bundle orientation and hence the diffusion tensor (DT) for the ventricular geometry. By solving a nonlinear inverse problem derived from a maximum likelihood estimator, the degrees of freedom of the fiber and DT model can be estimated from the measured gray values of the DWIs. The continuity of the DT model allows to relax the restriction to the individual DWIs to match spatially like for voxelwise DT calculation. Hence, the spatial misalignment between image slices with different diffusion encoding directions, that is encountered in-vivo cardiac imaging practice can be integrated into the estimation scheme. This feature results then in a negligible impact of the spatial misalignment on the reconstructed solution. We illustrate the methodology using synthetic data and compare it against a previously reported fiber bundle reconstruction technique. To show the potential for real data, we also present results for multi-slice data constructed from ex-vivo cardiac diffusion weighted measurements in both mono- and bi-ventricular configurations., (Copyright © 2017 Elsevier B.V. All rights reserved.)
- Published
- 2017
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121. Hyperpolarized 13 C urea myocardial first-pass perfusion imaging using velocity-selective excitation.
- Author
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Fuetterer M, Busch J, Peereboom SM, von Deuster C, Wissmann L, Lipiski M, Fleischmann T, Cesarovic N, Stoeck CT, and Kozerke S
- Subjects
- Animals, Blood Flow Velocity, Disease Models, Animal, Feasibility Studies, Female, Myocardial Infarction physiopathology, Myocardial Perfusion Imaging instrumentation, Phantoms, Imaging, Predictive Value of Tests, Reproducibility of Results, Sus scrofa, Carbon Isotopes administration & dosage, Contrast Media administration & dosage, Coronary Circulation, Magnetic Resonance Imaging instrumentation, Myocardial Infarction diagnostic imaging, Myocardial Perfusion Imaging methods, Urea administration & dosage
- Abstract
Background: A velocity-selective binomial excitation scheme for myocardial first-pass perfusion measurements with hyperpolarized
13 C substrates, which preserves bolus magnetization inside the blood pool, is presented. The proposed method is evaluated against gadolinium-enhanced1 H measurements in-vivo., Methods: The proposed excitation with an echo-planar imaging readout was implemented on a clinical CMR system. Dynamic myocardial stress perfusion images were acquired in six healthy pigs after bolus injection of hyperpolarized13 C urea with the velocity-selective vs. conventional excitation, as well as standard1 H gadolinium-enhanced images. Signal-to-noise, contrast-to-noise (CNR) and homogeneity of semi-quantitative perfusion measures were compared between methods based on first-pass signal-intensity time curves extracted from a mid-ventricular slice. Diagnostic feasibility is demonstrated in a case of septal infarction., Results: Velocity-selective excitation provides over three-fold reduction in blood pool signal with a two-fold increase in myocardial CNR. Extracted first-pass perfusion curves reveal a significantly reduced variability of semi-quantitative first-pass perfusion measures (12-20%) for velocity-selective excitation compared to conventional excitation (28-93%), comparable to that of reference1 H gadolinium data (9-15%). Overall image quality appears comparable between the velocity-selective hyperpolarized and gadolinium-enhanced imaging., Conclusion: The feasibility of hyperpolarized13 C first-pass perfusion CMR has been demonstrated in swine. Comparison with reference1 H gadolinium data revealed sufficient data quality and indicates the potential of hyperpolarized perfusion imaging for human applications.- Published
- 2017
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122. High-resolution diffusion tensor imaging of the human kidneys using a free-breathing, multi-slice, targeted field of view approach.
- Author
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Chan RW, Von Deuster C, Stoeck CT, Harmer J, Punwani S, Ramachandran N, Kozerke S, and Atkinson D
- Subjects
- Adult, Anisotropy, Artifacts, Female, Humans, Image Processing, Computer-Assisted, Kidney Cortex anatomy & histology, Kidney Medulla anatomy & histology, Male, Motion, Reference Values, Reproducibility of Results, Respiration, Young Adult, Diffusion Tensor Imaging methods, Kidney anatomy & histology
- Abstract
Fractional anisotropy (FA) obtained by diffusion tensor imaging (DTI) can be used to image the kidneys without any contrast media. FA of the medulla has been shown to correlate with kidney function. It is expected that higher spatial resolution would improve the depiction of small structures within the kidney. However, the achievement of high spatial resolution in renal DTI remains challenging as a result of respiratory motion and susceptibility to diffusion imaging artefacts. In this study, a targeted field of view (TFOV) method was used to obtain high-resolution FA maps and colour-coded diffusion tensor orientations, together with measures of the medullary and cortical FA, in 12 healthy subjects. Subjects were scanned with two implementations (dual and single kidney) of a TFOV DTI method. DTI scans were performed during free breathing with a navigator-triggered sequence. Results showed high consistency in the greyscale FA, colour-coded FA and diffusion tensors across subjects and between dual- and single-kidney scans, which have in-plane voxel sizes of 2 × 2 mm(2) and 1.2 × 1.2 mm(2) , respectively. The ability to acquire multiple contiguous slices allowed the medulla and cortical FA to be quantified over the entire kidney volume. The mean medulla and cortical FA values were 0.38 ± 0.017 and 0.21 ± 0.019, respectively, for the dual-kidney scan, and 0.35 ± 0.032 and 0.20 ± 0.014, respectively, for the single-kidney scan. The mean FA between the medulla and cortex was significantly different (p < 0.001) for both dual- and single-kidney implementations. High-spatial-resolution DTI shows promise for improving the characterization and non-invasive assessment of kidney function., (© 2014 The Authors. NMR in Biomedicine published by John Wiley & Sons, Ltd.)
- Published
- 2014
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123. Dual-phase cardiac diffusion tensor imaging with strain correction.
- Author
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Stoeck CT, Kalinowska A, von Deuster C, Harmer J, Chan RW, Niemann M, Manka R, Atkinson D, Sosnovik DE, Mekkaoui C, and Kozerke S
- Subjects
- Adult, Anisotropy, Breath Holding, Diastole physiology, Female, Heart physiology, Heart Rate, Humans, Male, Systole physiology, Young Adult, Diffusion Tensor Imaging methods, Image Processing, Computer-Assisted methods, Imaging, Three-Dimensional methods, Movement physiology, Myocardium pathology
- Abstract
Purpose: In this work we present a dual-phase diffusion tensor imaging (DTI) technique that incorporates a correction scheme for the cardiac material strain, based on 3D myocardial tagging., Methods: In vivo dual-phase cardiac DTI with a stimulated echo approach and 3D tagging was performed in 10 healthy volunteers. The time course of material strain was estimated from the tagging data and used to correct for strain effects in the diffusion weighted acquisition. Mean diffusivity, fractional anisotropy, helix, transverse and sheet angles were calculated and compared between systole and diastole, with and without strain correction. Data acquired at the systolic sweet spot, where the effects of strain are eliminated, served as a reference., Results: The impact of strain correction on helix angle was small. However, large differences were observed in the transverse and sheet angle values, with and without strain correction. The standard deviation of systolic transverse angles was significantly reduced from 35.9±3.9° to 27.8°±3.5° (p<0.001) upon strain-correction indicating more coherent fiber tracks after correction. Myocyte aggregate structure was aligned more longitudinally in systole compared to diastole as reflected by an increased transmural range of helix angles (71.8°±3.9° systole vs. 55.6°±5.6°, p<0.001 diastole). While diastolic sheet angle histograms had dominant counts at high sheet angle values, systolic histograms showed lower sheet angle values indicating a reorientation of myocyte sheets during contraction., Conclusion: An approach for dual-phase cardiac DTI with correction for material strain has been successfully implemented. This technique allows assessing dynamic changes in myofiber architecture between systole and diastole, and emphasizes the need for strain correction when sheet architecture in the heart is imaged with a stimulated echo approach.
- Published
- 2014
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124. Analysis of 3D cardiac deformations with 3D SinMod.
- Author
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Wang H, Stoeck CT, Kozerke S, and Amini AA
- Subjects
- Algorithms, Humans, Reproducibility of Results, Diastole, Heart physiology, Image Processing, Computer-Assisted methods, Imaging, Three-Dimensional methods, Magnetic Resonance Imaging methods, Motion
- Abstract
In this paper, we propose a novel 3D sine wave modeling (3D SinMod) approach to automatic analysis of 3D cardiac deformations. An accelerated 3D complementary spatial modulation of magnetization (CSPAMM) tagging technique was used to modulate the myocardial tissue and to acquire 3D MR data sets of the whole-heart including three orthog- onal tags within three breath-holds. Each tag set is able to assess the motion along a direction perpendicular to the tag lines. With the application of CSPAMM, the effect of tag fading encountered in SPAMM tagging due to T1 relaxation is mitigated and tag deformations can be visualized for the entire cardiac cycle, including diastolic phases. In the proposed approach, the environment around each voxel in the 3D volume is modeled as a moving sine wavefront with local frequency and amplitude. The biggest advantage of the proposed technique is that the entire framework, from data acquisition to data analysis is in the 3D domain, which permits quantification of both the in-plane and through-plane motion components. The accuracy and the effectiveness of the proposed method has been validated using both simulated and in vivo tag data.
- Published
- 2013
- Full Text
- View/download PDF
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