Myocardial Function: Experimental Models & Human Studies
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Tuesday May 10th
Room 511A-C  16:00 - 18:00 Moderators: Thoralf Niendorf and Mihaela Pop

16:00 274.   A Feasibility Study: MR Elastography as a Method to Compare Stiffness Estimates in Hypertrophic Obstructive Cardiomyopathy and in Normal Volunteers  
Arunark Kolipaka1, Kiaran McGee1, Shivani Aggarwal1, Nandan Anavekar1, Armando Manduca1, Richard Ehman1, and Philip Araoz1
1Mayo Clinic, Rochester, Minnesota, United States

Hypertrophic cardiomyopathy (HOCM) is a genetic cardiac disease and is thought to increase myocardial stiffness. Recently, MR elastography (MRE) has been adapted to measure stiffness in the myocardium. The purpose of this study was to demonstrate the feasibility of using MRE to identify changes in the stiffness of LV in HOCM’s when compared to normals. MRE was performed on 18 normal volunteers and 2 HOCM patients. During end-systole an increased stiffness with a mean value of 14.5 kPa was found as compared to normals with a mean value of 5.6 kPa.

16:12 275.   Direct elastography of in vivo human heart 
Heiko Tzschätzsch1, Thomas Elgeti1, Sebastian Hirsch1, Thoralf Niendorf2, Jürgen Braun3, and Ingolf Sack1
1Department of Radiology, Charité University Medicine, Berlin, Germany, 2Berlin Ultrahigh Field Facility, Charité University Medicine, Berlin, Germany, 3Institute of Medical Informatics, Charité University Medicine, Berlin, Germany

The variation of myocardial elasticity enables the heart to circulate blood through the cardiovascular system. Thus, measurement of heart elasticity by elastography techniques may play a key role in the diagnosis of cardiac dysfunction. This paper presents a novel approach in cardiac MR elastography. The method relies on shear waves with amplitudes in the order of the in-plane resolution of vibration-synchronized MRI. Wall oscillations in the heart can directly be monitored in magnitude images without the need of specialized motion encoding gradients and phase unwrapping algorithms.

16:24 276.   Anatomic and Functional Cardiac MR at 7T: A Comparison of 4, 8 and 16 Element Transceive RF Coil Designs 
Lukas Winter1, Christof Thalhammer1, Matthias Dieringer1,2, Celal Özerdem1, Jan Rieger1, Fabian Hezel1, Wolfgang Renz3, and Thoralf Niendorf1,2
1Berlin Ultrahigh-Field Facility, Max Delbrueck Center for Molecular Medicine, Berlin, Germany, 2Experimental and Clinical Research Center (ECRC), Charité Campus Buch, Humboldt-University, Berlin, Germany, 3Siemens AG, Erlangen, Germany

Multichannel transmit and receive coil arrays give promising results to overcome the challenges towards clinical cardiac imaging at ultrahigh field strengths. The comparison of 4-, 8- and 16-channel cardiac coils shows a higher SNR, CNR as well as image homogeneity while moving towards a higher number of TX/RX elements. Clinically relevant short axis and four chamber view cardiac 2D CINE FLASH, tag band prepared 2D CINE FLASH and 2D CINE SSFP images were acquired and compared.

16:36 277.   Free-Breathing 3D Whole Heart Black Blood Imaging with Motion Sensitized Driven Equilibrium 
Subashini Srinivasan1,2, Peng Hu2, Kraig V. Kissinger2, Beth Goddu2, Lois Geopfert2, Ehud J. Schmidt3, Sebastian Kozerke1, and Reza Nezafat2
1Institute of Biomedical Engineering, ETH, Zurich, Switzerland, 2Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States, 3Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States

2D black blood imaging of the heart is commonly used in the assessment of myocardial wall anatomy, cardiac masses and other pathologic conditions. In this study, we describe a free-breathing whole heart 3D black-blood imaging using MSDE preparation pulse. Images with T1 weighted turbo spin echo, spoiled gradient echo, and balanced steady state free precession in axial and short axis planes were acquired from 7 healthy adult subjects. Excellent suppression of blood and clear delineation of the cardiac chamber walls and papillary muscle was observed with all the imaging sequences but with additional undesired signal loss in the myocardium (14%-27%).

16:48 278.   Temporal evolution of cardiac function in mice with myocardial hypertrophy and heart failure 
Bastiaan J van Nierop1, Elza D van Deel2, Dirk J Duncker2, Gustav J Strijkers1, and Klaas Nicolay1
1Biomedical NMR, department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, 2Department of Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands

In this study the temporal evolution of cardiac function was studied in C57BL/6 mice with a mild constriction of the aorta, resulting in compensated hypertrophy, and in mice with a severe constriction of the aorta. Only the mice with a severe constriction showed a progressive increase in left ventricular mass accompanied by a progressive decline of left and right ventricular ejection fraction, as well as lung edema. The different disease progression between both animal models opens unique opportunities to study interventions, and to study different aspects of myocardial hypertrophy during the transition from compensated hypertrophy towards overt HF.

17:00 279.   Molecular and Microstructural Changes Accompanying Left Ventricular Hypertrophy Revealed with In-Vivo Diffusion Tensor MRI (DTI) and Molecular Imaging of the Mouse Heart 
Shuning Huang1, Choukri Mekkaoui1, Miloslav Polasek1, Howard H. Chen1, Ruopeng Wang1, Soeun Ngoy2, Ronglih Liao2, Van J Wedeen1, Guangping Dai1, Peter Caravan1, and David E Sosnovik1,3
1Martinos Center for Biomedical Imaging, Mass General Hospital, Charlestown, MA, United States, 2Cardiology, Brigham and Woman's Hospital, Boston, MA, United States,3Cardiology, Mass General Hospital, Boston, MA, United States

The transition from adaptive hypertrophy to heart failure is poorly understood. Here, we use molecular MRI of a collagen-binding gadolinium chelate and in-vivo diffusion tensor MRI (DTI) of the mouse heart to characterize the response of the left ventricle to pressure overload. We show that pressure overload results in significant amounts of fibrosis and circumferential realignment of myofibers well before the overt transition to diastolic heart failure.

17:12 280.   Human Statistical Atlas of Cardiac Fiber Architecture from DT-MRI 
Herve Lombaert1,2, Jean-Marc Peyrat3, Stanislas Rapacchi4, Laurent Fanton5, Herve Delingette2, Nicholas Ayache2, and Pierre Croisille4
1Ecole Polytechnique, Montreal, QC, Canada, 2Asclepios, INRIA, Sophia-Antipolis, France, 3Siemens Molecular Imaging, Oxford, United Kingdom, 4Creatis-LRMN, HCL, Lyon, France, 5Institut Universitaire de Médecine Légale, Lyon, France

A human statistical atlas of the cardiac fiber architecture is constructed from ex-vivo diffusion tensor images and is based on a set of 10 normal human hearts. To the best of our knowledge, this is the first time that such study has been conducted with human data. We have developed a semi-automated method where only minimal interactions are required for the segmentation of the myocardium, and where the registrations are fully automated via symmetric log domain diffeomorphic demons. The results on the variability of human cardiac fibers concur with studies on other mammals. The cardiac fiber orientation is indeed much more consistent across our population than the orientation of the cardiac laminar sheets.

17:24 281.   In vivo Characterization of Myocardial Microstructure in Normal and Infarcted Hearts Using the Supertoroidal Model 
Choukri Mekkaoui1, Shuning Huang1, Guangping Dai1, Timothy G Reese1, Marcel P Jackowski2, and David Sosnovik3
1Radiology, Harvard Medical School, Massachusetts General Hospital, Martinos Center For Biomedical Imaging, Charlestown, MA, United States, 2Computer Science, University of São Paulo, Institute of Mathematics and Statistics, São Paulo, Brazil, 3Cardiology, Harvard Medical School, Massachusetts General Hospital, Martinos Center For Biomedical Imaging, Charlestown, MA, United States

The supertoroid-based representation of cardiac diffusion tensor MRI (DT-MRI) has previously been shown to enhance the three-dimensional perception of myocardial tissue structure and organization. In this work, the quantification of DT-MRI data using the supertoroidal model is performed in vivo for the first time. The toroidal indices TV and TC revealed that diffusivity and anisotropy values are homogeneous and highly reproducible in the myocardium in vivo. Changes in diffusivity in infarcted myocardium are detected with greater sensitivity with TV than MD. The supertoroidal formalism thus holds significant promise for the analysis of myocardial microstructure with DT-MRI.

17:36 282.   Sequence timing optimization in multi-slice diffusion tensor imaging of the beating heart 
Christian Torben Stoeck1, Nicolas Toussaint2, Peter Boesiger1, Philip G Batchelor2, and Sebastian Kozerke1,2
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2Imaging Sciences, King's College London, London, United Kingdom

Cardiac DTI faces major challenges due to underlying physiological motion such as breathing and the heart beat. Therefore the timing of diffusion encoding is essential for the success of diffusion weighted imaging in the heart. In this Study we introduce a dynamic timing scout sequence and investigate time windows during the cardiac cycle usable for DTI. Imaging is possible during the upslope of circumferential contraction and symmetry point of rotational motion. It appears that the optimal timing window is independent of the subject’s heart rate.

17:48 283.   Imaging Three-Dimensional Myocardial Mechanics in Mice using Volumetric Spiral Cine DENSE 
Xiaodong Zhong1, Lauren B Gibberman2, Andrew D Gilliam3, Craig H Meyer2,4, Brent A French4, and Frederick H Epstein2,4
1MR R&D Collaborations, Siemens Healthcare, Atlanta, GA, United States, 2Radiology Department, University of Virginia, Charlottesville, VA, United States, 3Andrew D. Gilliam Consulting, Providence, RI, United States, 4Biomedical Engineering Department, University of Virginia, Charlottesville, VA, United States

MRI of myocardial mechanics in mice enables the investigation of the roles of individual genes and experimental therapies in cardiac function. While two-dimensional tagging, HARP, and DENSE have previously been demonstrated in the mouse heart, myocardial mechanics are more comprehensively assessed using three-dimensional (3D) methods. In this study, 3D cine DENSE acquisition and analysis methods for mice imaging were developed, and were evaluated in normal mice. A comprehensive assessment of 3D myocardial mechanics in mice can be performed with a scan time of less than 25 minutes and a segmentation time of about an hour, followed by automatic post-processing.