CV Technology & Methodology
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Monday 7 May 2012
Room 210-211  14:15 - 16:15 Moderators: Thoralf Niendorf, Sonia Nielles-Vallespin

14:15 0082.   Sodium Imaging of the Heart at 7T: Design, Evaluation and Application of a Four-Channel Transmit/Receive Surface Coil Array
Anjuli Ruehle1, Wolfgang Renz1,2, Lukas Winter1, Harald Pfeiffer1,3, Jan Ruff2, Jan Rieger1, and Thoralf Niendorf1,4
1Berlin Ultrahigh Field Facility, Max-Delbrueck-Centrum for Molecular Medicine, Berlin, Germany, 2Siemens Healthcare, Erlangen, Germany, 3Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany, 4Experimental and Clinical Research Center (ECRC), Charité Campus Buch, Humboldt-University, Berlin, Germany

Insight of physiological processes and cellular metabolism makes 23Na-MRI conceptually appealing as non-invasive imaging discipline. Several studies report the applicability of 23Na-MRI for the detection and assessment of acute and chronic heart disease due to increased sodium concentration after myocardial infarctions. Bi-exponential decay of the signal and a low SNR compared to 1H-MRI makes 23Na-MRI unattractive for clinical use. With a high SNR and fast imaging technologies ultrahigh field MRI brings 23Na-MRI back into focus. In this study a new radiofrequency coil for cardiac MRI at 7T was developed and a volunteer study, as a precursor to a broader clinical study was performed.

14:27 0083.   
Predistorted B1 shimming: a new concept based on mutual enhancement between static B1 shim and 1D spoke RF pulse design. Application for cardiac imaging at 7 Tesla.
Sebastian Schmitter1, Xiaoping Wu1, Lance DelaBarre1, Kamil Ugurbil1, and Pierre-Francois Van de Moortele1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

B1 shimming achieves high transmit B1 (B1+) efficiency with satisfactory B1+ homogeneity in small targets at 7T, however in large targets, e.g. heart, uniform |B1+| with static B1 shim results in low efficiency. Taking advantage of typical |B1+| profiles observed with transceiver arrays in the heart at 7T, we propose a new concept where, instead of aiming at homogeneous |B1+| profile, B1 shim is applied to achieve a predefined spatially distorted |B1+| pattern which, in turn, allows for efficient use of 1D spoke RF pulse design to provide homogeneous excitation in the heart while preserving high B1+ efficiency.

14:39 0084.   Myocardial T1 Mapping with Phase-Sensitive Motion Correction and Inversion Recovery Fitting
Hui Xue1, Andreas Greiser2, Christoph Guetter1, Sven Zuehlsdorff3, Marie-Pierre Jolly1, Andrew E. Arai4, Jens Guehring2, and Peter Kellman4
1Siemens Corporate Research, Princeton, New Jersey, United States, 2Imaging & IT Division, Siemens AG, Healthcare Sector, Erlangen, Germany, 3CMR R&D, Siemens Medical Solutions USA, Inc., Chicago, IL, United States, 4Laboratory of Cardiac Energetics, National Institutes of Health, National Heart, Lung and Blood Institute, Bethesda, MD, United States

The image quality of myocardial T1 mapping using the modified Look-Locker Inversion Recovery (MOLLI) sequence is often degraded by the motion among sampled images. A fully automated motion correction directly utilizing MOLLI images is highly challenging due to significantly varying image contrast and the signal inversion. To overcome this difficulty, we propose to restore the signal polarity for the entire MOLLI series using the phase sensitive image reconstruction. The inversion recovery fitting on MOLLI signals with restored polarity is more efficient and leads to lower residual errors. In vivo evaluation was performed on a cohort of 17 patients.

14:51 0085.   
Development of a hybrid MR-US system for the assessment of cardiac function during free breathing
W. B. Buchenberg1, S. Gruhlke1, J. Maclaren1, M. Markl2, A. Bongers3, J. Jenne3, M. Zaitsev1, and B. Jung1
1Dept. of Radiology, Medical Physics, University Medical Center, Freiburg, Germany, 2Dept. of Radiology and Biomedical Engineering, Northwestern University, Chicago, United States, 3mediri GmbH, Heidelberg, Germany

The aim of this work was to establish a hybrid MR-ultrasound (US) system to be used for respiratory gating in cardiac imaging on a 1.5T system, and to perform initial in vitro and in vivo measurements as a first test of the developed procedures. Since the ultrasound system operates independently from the MR acquisitions, the update rate of the respiratory position can be significantly improved in Cine imaging compared to the standard navigator technique. This advantage was exploited by including one respiratory update per cardiac phase instead of a conventional update rate per heartbeat.

15:03 0086.   Navigator Based Free Breathing Diffusion Tensor MRI of the Human Heart In Vivo
Sonia Nielles-Vallespin1, Choukri Mekkaoui2, Peter Gatehouse1, Timothy G Reese2, Jenny Keegan1, Steve Collins1, Peter Speier3, Thorsten Feiweier3, Ranil de Silva1, Marcel P Jackowski4, David E Sosnovik2, and David Firmin1
1Royal Brompton Hospital, Imperial College, London, London, United Kingdom, 2Martinos Center for Biomedical Imaging, Massachusetts General Hospital, United States, 3Siemens AG Healthcare Sector, Germany, 4Institute of Mathematics and Statistics, University of São Paulo, Brazil

A novel modification of a prospective navigator technique was implemented to allow free-breathing (FB) in vivo DTI of the heart to be performed. 11 healthy volunteers were scanned on two different days; each day using both FB and breathhold (BH) diffusion-weighted stimulated-echo single-shot EPI protocols. Images were post-processed to derive mean diffusivity and fractional anisotropy maps. Statistical analysis showed no significant differences between the BH and FB techniques for FA, and no major increase in scan duration. We show here for the first time that a free-breathing navigator-based approach to DTI produces high quality in vivo images of the heart.

15:15 0087.   


Intravoxel Incoherent Motion Modeling Applied to Cardiac Diffusion Weighted MRI: toward Free Breathing Acquisition in Healthy Volunteers
Bénédicte MA Delattre1, Magalie Viallon2, Hui Xue3, Marie-Pierre Jolly3, Christoph Guetter3, Hongjiang Wei1, Yuemin Zhu1, Thorsten Feiweier4, Vinay M Pai5, Han Wen5, and Pierre Croisille1,6
1CREATIS, CNRS (UMR 5220), INSERM (U1044), INSA Lyon, University of Lyon, Lyon, France, 2Department of Radiology, University Hospitals of Geneva, Geneva, Switzerland, 3Siemens Corporate Research, Princeton, New Jersey 08540, United States, 4Siemens Healthcare, Erlangen, Germany, 5Imaging Physics Lab, BBC/NHLBI/NIH, Bethesda, Maryland 20892, United States, 6Jean-Monnet University, Saint-Etienne, France

Intravoxel Incoherent Motion (IVIM) model is currently a unique method for evaluating perfusion and diffusion parameters from DWI without the use of any contrast agent. Recently, an efficient cardiac DWI method was proposed where motion-induced signal-loss was compensated for by PCATMIP post-processing. While performing cardiac DWI acquisition using breath-hold yields accurate IVIM parameters, it can be difficult to apply in clinical routine. This study compares the IVIM parameters of perfusion fraction, diffusion coefficient and pseudo-diffusion coefficient estimated from PCATMIP-processed breath-hold and free breathing acquisitions. The results yield the possibility for acquiring perfusion measurements using free-breathing exams under non-contrast conditions.

15:27 0088.   Apparent Diffusion Coefficient of Intramyocelluler Lipid in Heart Muscle
Victor B. Xie1,2, Peng Cao1,2, Zhong wei Qiao1,2, Anna M. Wang1,2, Shujuan Fan1,2, and Ed X. Wu1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China, 2Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China

In this study, we investigated the intramyocellular lipid (IMCL) diffusion property in heart muscle. IMCL ADC was documented in fresh heart muscle samples at 80ms diffusion time, exhibiting slow and largely isotropic diffusion. IMCL ADC was found to be lower than that in skeletal muscle, which likely resulted from the smaller IMCL droplet size, i.e., more restricted diffusion. Such diffusion characterization of IMCL heart muscle may provide insights in study of the IMCL droplet microstructure and lipid dynamics in heart muscle.

15:39 0089.   An Integrated Pencil-Beam Probe for Assessing the Arterial Input Function in Quantitative 3D Myocardial Perfusion Imaging
Lukas Wissmann1, Johannes F.M. Schmidt1, Robert Manka1,2, and Sebastian Kozerke1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2Department of Cardiology, University Hospital Zurich, Zurich, Switzerland

The tracer dose in dynamic contrast-enhanced magnetic resonance imaging is crucial for myocardial perfusion quantification. Higher dose is beneficial for myocardial signal-to-noise ratio, but increases the risk of left-ventricular signal saturation in the image due to shorter T1. This study introduces a new acquisition method for the arterial input function using a pencil-beam probe. It is demonstrated that signal saturation in the probe can be avoided by reducing the delay after the saturation pulse. Perfusion quantification from 3D perfusion imaging with the pencil beam probe versus image based assessment of the arterial input function at half and full dose is shown.

15:51 0090.   Improved Cardiac Triggering by Combining Multiple Physiological Signals: A Cardiac MR Feasibility Study at 7.0 T
Tobias Frauenrath1, Katharina Fuchs1, Fabian Hezel1, Matthias Alexander Dieringer1,2, Jan Rieger1,3, and Thoralf Niendorf1,2
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin, Berlin, Germany, 2Experimental and Clinical Research Center (ECRC), Charité Campus Buch, Humboldt-University, Berlin, Germany, 3MRI.TOOLS GmbH, Berlin, Germany

Motivated by the challenges and limitations of conventional single physio-information systems like ECG, this study presents the advantages of combining two trigger methods into one trigger output. The approach is demonstrated for cardiac LV function assessment at 7.0T.

16:03 0091.   Assessment of Tissue Hypoxia and Vascular Reserve in a Porcine HindLimb Ischemia Model Using BOLD-MRI
Smita Sampath1, Mitchel Stacy2, Mark W Maxfield2, Prasanta Pal3, Donald P Dione2, and Albert J Sinusas2
1Diagnostic Radiology, Yale University, New Haven, CT, United States, 2Cardiology, Yale University, 3Diagnostic Radiology, Yale University

Peripheral artery disease (PAD) is a degenerative condition that can result in limb ischemia with associated limited mobility, and morbidity. Understanding the extent of hypoxia and regional vascular reserve may help identify treatment regimens that can improve long-term mobility in these patients. We present an investigative study that quantifies, using BOLD MRI, 1) tissue hypoxia and 2) functional vascular reserve in response to distal cuff occlusion and infusion of pharmacological vasodilatory agent, in a porcine animal model with hindlimb ischemia. Differential response between normal leg and ischemic leg are observed in select muscle groups.