Cardiac Function Techniques & Clinical Applications
Friday 24 April 2009
Room 316A 10:30-12:30

Moderators:

 Daniel B. Ennis and Han Wen
 
10:30 812. In-Line Automated Tracking in Cardiac Cine MRI
    Bo Li1, Yingmin Liu1, Brett Raymond Cowan1, Alistair Andrew Young1
1Auckland MRI Research Group, The University of Auckland, Auckland, New Zealand
    Feature tracking in cardiac cine MR images facilitates the analysis of heart function, but requires extensive computation. We implemented an efficient non-rigid registration algorithm as part of the image reconstruction process to enable in-line calculation of deformation. The method was evaluated in a clinical setting by comparing wall thickening measurements between automated and manual methods in N=36 patients with cardiovascular disease. The time required for the in-line registration was ~10 seconds per slice, and the % wall thickening was more reliably calculated using the automated method. In-line non-rigid registration is clinically feasible and useful for cardiac mechanics.
     
10:42 813. Accurate Assessment of Ventricular Volumes in a Single Breath Hold Using a 32-Channel Coil and an Extracellular Contrast Agent
    Victoria Parish1, Sergio Uribe1, Gerald Greil1, Tobias Schaeffter1
1Division of Imaging Sciences, King's College, London, UK
    In this study, we propose to evaluate a 3D cine whole heart balanced SSFP sequence on a 1.5T scanner which allows ventricular volume assessment in a single breath hold without compromising accuracy of volumetric analysis. This was achieved using a 32 channel cardiac coil with increased SENSE factors. The loss of myocardial-blood pool contrast due to the 3d-acquisition is overcome by administration of a Gd-DTPA contrast agent. Comparison of the 3D balanced SSFP sequence acquired post injection of contrast with the traditional 2D method showed excellent agreement.
     
10:54 814. Influence of Outflow Tract Reconstruction on Long-Term Right Ventricular Function and Pulmonary Regurgitation After Repair of Tetralogy of Fallot: A Clinical Magnetic Resonance Imaging Study
    C-A Chen1, J-K Wang, M-H Wu, M-Y Su2,3, H-Y Yu4, C-I Chang4, I-S Chiu4, I-S Chen4, W-Y Isaac Tseng5
1Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan; 2Institute of Biomedical Engineering, National Yang-Ming University; 3Department of Medical Imaging, National Taiwan University Hospital; 4Department of Surgery, National Taiwan University Hospital; 5Center for Optoelectronic Biomedicine, College of Medicine, National Taiwan University
    The purpose of this study was to evaluate the influence of different types of right ventricular outflow tract (RVOT) reconstruction during repair of tetralogy of Fallot (TOF) on long-term right ventricular function and pulmonary regurgitation (PR) severity using cardiac magnetic resonance (CMR). Our results showed that the use of transannular patch (TAP) during RVOT reconstruction was significantly associated with advanced degree of PR, increased extent of RV dilatation, and higher incidence of RVOT aneurysm or akinesia late after TOF correction. Pericardial monocuspid valve used for TAP failed to demonstrate long-term beneficial effect in the prevention of PR and RV dilatation.
     
11:06 815. Model-Based Reconstruction for Free-Breathing Cardiac CINE Imaging Using GRICS
    Pierre-André Vuissoz1,2, Freddy Odille1,3, Brice Fernandez1,4, Maelene Lohezic1,4, Adnane Benhadid1,2, Damien Mandry1,5, Jacques Felblinger2,6
1IADI, Nancy-Université, Nancy, France; 2U947, INSERM, Nancy, France; 3Centre for Medical Image Computing, University College London, London, UK; 4Global Applied Science Lab., GE healthcare, Nancy, France; 5CHU de Nancy, Nancy, France; 6CIC-IT 801, INSERM, Nancy, France
    A new reconstruction method (GRICS) constrained by physiological signals such as respiratory belt has recently been applied to ECG triggered black blood images. We propose here an extension of GRICS for 2D SSFP Cardiac CINE imaging. A description of the piecewise linear cardiac phase reconstruction is presented. From a free breathing subject, 18 slices covering the whole heart volume in short and long axis were reconstructed. For each of these (256x256) 40 seconds long acquisitions, image quality was comparable to breath hold acquisitions. This demonstrates the possibility of whole volume cardiac CINE imaging in free breathing.
     
11:18 816. Measuring Changes in Morphology, Hemodynamics, and Mechanical Function by Controlling Ventricular Preload Using an MRI-Compatible Lower Body Negative Pressure Chamber
    June Cheng Baron1, Jessica Scott2, Ben Esch2, Kelvin Chow1, Ian Paterson3, Mark Haykowsky4, Richard Thompson1
1Biomedical Engineering, University of Alberta, Edmonton, AB, Canada; 2Cardiovascular Physiology and Rehabilitation Laboratory, University of British Columbia, Vancouver, BC, Canada; 3Division of Cardiology, University of Alberta, Edmonton, AB, Canada; 4Physical Therapy, University of Alberta, Edmonton, AB, Canada
    Cardiac performance is modulated in part by ventricular preload, which is determined largely by venous return to the heart and ventricular compliance. We illustrate control of preload using a custom MRI-compatible lower body negative pressure chamber to control venous return. Using standard cines, phase contrast and tissue tagging we measured ventricular volumes, hemodynamics and tissue mechanics at atmospheric (control) and -30 mmHg lower-body pressure (unloading similar to standing). We found significant changes in end-diastolic volumes, stroke volume, blood velocities, intraventricular pressure gradients, torsion and tissue velocity and strain rates, showing effective control of loading in a comprehensive cardiac MRI exam.
     
11:30 817. In Vivo Validation of Fast Cine DENSE MRI for the Quantification of Regional Cardiac Function
    Li Feng1, Robert M. Donnino2, James Babb3, Leon Axel4, Daniel Kim4
1Biomedical Enginnering, Polytechnic Institute of New York University, Brooklyn, NY, USA; 2Medicine, NYU Langone Medical Center, New York, NY, USA; 3Radiology, NYU Langone Medical Center, New York, NY, USA; 4Center for Biomedical Imaging and Radiology, NYU Langone Medical Center, New York, NY, USA
    Accurate assessment of cardiac function plays an important role in the management of heart disease. Quantitative assessment of regional cardiac function may additionally improve the accuracy of detecting subtle wall motion abnormalities due to heart disease. Recently, fast cine displacement-encoded (DENSE) MRI was developed to produce relatively high quality strain maps within clinically acceptable breath-hold duration of 12 cardiac cycles . While this pulse sequence is promising for clinical applications, it has not been validated. Therefore, the purpose of this study was to validate the relative accuracy of fast cine DENSE MRI in controls and patients with heart disease.
     
11:42 818.

Comparison of DENSE Reference Strategies
    Henrik Haraldsson1, Andreas Sigfridsson2, Hajime Sakuma2, Tino Ebbers1
1Linköping University, Linköping, Sweden; 2Mie University, Tsu, Mie, Japan
    Displacement encoding with stimulated echoes (DENSE) has been used to acquire non-invasive in-vivo displacement maps of the beating heart. A phase reference is required to compensate for magnetic field inhomogeneities, but the strategy used to acquire it may influence the data quality. We have compared displacement accuracy, in-vivo and in-vitro, for three relevant phase reference strategies and found that a symmetric reference approach was superior in terms of standard deviation, influence of chemical shift, displacement offset and black blood effect.
     
11:54 819. Navigator-Gated 3D Cine DENSE MRI of the Left Ventricle
    Xiaodong Zhong1,2, Craig H. Meyer1,3, Christopher M. Kramer3, Frederick H. Epstein1,3
1Biomedical Engineering, University of Virginia, Charlottesville, VA, USA; 2MR R&D Collaborations, Siemens Medical Solutions, Atlanta, GA, USA; 3Radiology, University of Virginia, Charlottesville, VA, USA
    A free-breathing navigator-gated 3D spiral cine DENSE pulse sequence and the corresponding data analysis algorithms were developed that provide high spatial and temporal resolutions, coverage of the entire left ventricle (LV), and measurement of 3D strain with a scan time of approximately 20 minutes. In normal volunteers, the resulting strain data show good agreement with those from 2D cine DENSE. With additional development aimed at further shortening the scan time and automating image analysis, these methods may enable routine clinical imaging that completely quantifies contractile function throughout the LV in patients with contractile dysfunction.
     
12:06 820. A Practical Estimator for Interventricular Mechanical Asynchrony in Pulmonary Arterial Hypertension
    Gert Jan Mauritz1, J. Tim Marcus2, Anton Vonk-Noordegraaf1
1Pulmonary Diseases, VU University Medical Center, Amsterdam, Netherlands; 2Physics & Medical Technology, VU University Medical Center, Amsterdam, North Holland, Netherlands
   

In 21 pulmonary arterial hypertension patients, the onset and peak times of myocardial shortening were measured with CMR myocardial tagging. Times of leftward septal bowing (Tlvsb) and aortic valve closure (Taocl) were measured with CMR cine imaging.

A large L-R delay (94±41 ms, p<0.001) in peak time of shortening was observed. A strong association (r2 = 0.85, p<0.001) was found between the delay between Taocl and Tlvsb, and the L-R delay in peak shortening. As the Taocl and Tlvsb are easily measured with CMR or echo, this estimate of L-R delay has relevance for clinical practice.

     
12:18 821. 7T Human In Vivo Cardiac Imaging with an 8-Channel Transmit/Receive Array
    Stefan Maderwald1,2, Stephan Orzada1,2, Lena C. Schäfer1,2, Andreas K. Bitz1,2, Irina Brote1,2, Oliver Kraff1,2, Jens M. Theysohn1,2, Mark E. Ladd1,2, Susanne C. Ladd1,2, Harald H. Quick1,2
1Erwin L. Hahn Institute for MRI, Essen, Germany; 2Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany
    High-field MRI at 7 Tesla inherently offers high signal-to-noise (SNR) and enhanced soft tissue contrasts when compared to 1.5 T or even 3 T MRI, which might improve image quality in selected imaging applications in humans. The increased SNR is in particular potentially beneficial for high-resolution cardiac MRI. In order to exploit the full potential for cardiac MRI at 7 T, a number of artifacts and imaging constraints related to 7 T have to be overcome. In this study four volunteers were imaged with a flexible 8-channel transmit/receive body coil to evaluate potential advantages and disadvantages specifically associated with cardiac MR imaging at this high field strength.