Myocardial Tissue Characterization & Spectroscopy
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Wednesday 9 May 2012
Room 212-213  10:00 - 12:00 Moderators: Jeanette Schultz-Menger, David E. Sosnovik

10:00 0388.   Detection of Myocardial Cell Hypertrophy in a Mouse Model of Hypertension: Transcytolemmal Water Exchange and its Sensitivity to Cell Size
Michael Jerosch-Herold1, Otavio Rizzi Coelho-Filho2, Richard Mitchell3, Heitor Moreno Junior4, and Raymond Y Kwong5
1Brigham & Women's Hospital, Boston, MA, United States, 2Medicine, Brigham & Women's Hospital, 3Harvard Medical School, 4State University of Campinas (UNICAMP), 5Brigham & Women's Hospital

To-date, no imaging technique has been validated to detect in-vivo cardiac cell hypertrophy, a common physiological response in the heart muscle to cardiac disease and pathological stress. We tested the hypothesis that determination of the rate of transcytolemmal water exchange, based on T1 measurements after fractionated gadolium contrast injections, could be used to detect cell-size changes in a mouse model of hypertensive heart disease. The intra-cellular lifetime of water correlated positively with direct morphological measurements of both minor and major cell diameters, and estimates of cell volume, assuming an oblong cylindrical shape.

10:12 0389.   Non-invasive in vivo imaging of inflammation in experimental viral myocarditis by 19F cellular MRI permission withheld
Yu-Xiang Ye1, Martina Sauter2, Thomas C Basse-Lüsebrink1, Thomas Kampf1, Xavier Helluy1,3, Karl-Heinz Hiller3, Ali Yilmaz4, Udo Sechtem4, Wolfgang R Bauer5, Reinhard Kandolf2, Karin Klingel2, and Peter M Jakob1,3
1Dept. Experimental Physics V, University of Würzburg, Würzburg, Bavaria, Germany, 2Dept. Molecular Pathology, University Hospital Tübingen, Tübingen, Germany, 3Research Center for Magnetic Resonance Bavaria, Würzburg, Bavaria, Germany, 4Division of Cardiology, Robert-Bosch-Krankenhaus, Stuttgart, Germany, 5Dept. Internal medicine I, University hospitals Würzburg, Würzburg, Bavaria, Germany

The gold standard to diagnose myocarditis is histopathology and immunohistochemistry to define cardiac injury and inflammatory cells in the myocardium within endomyocardial biopsies. However, this invasive procedure is often insensitive to detect myocarditis. In this study, fluorine-19 (19F) cellular MRI was applied to non-invasively visualize inflammation of viral myocarditis in a mouse model in vivo. This method might be clinically translational to assist early diagnosis of viral myocarditis and might be valuable to improve the management of patients suffering from acute and chronic viral myocarditis by localization and quantification of macrophage infiltrates, also in follow up studies.

10:24 0390.   
In vivo ultra short TE (UTE) MRI of mouse myocardial infarction
Bastiaan J. van Nierop1, Jules L. Nelissen1, Noortje A.M. Bax2, Larry de Graaf1, Klaas Nicolay1, and Gustav J. Strijkers1
1Biomedical NMR, department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, 2Soft Tissue Biomechanics and Engineering, department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands

Fibrosis is an important hallmark of various cardiac pathologies. A method is presented for 3D ultra short TE (UTE) imaging of fibrotic tissue in the in vivo infarcted mouse myocardium. UTE images were acquired with ultra-short (21lower case Greek mus) and long-TE (4ms). Next, subtraction images were obtained highlighting infarcted, myocardial tissue with high transversal relaxation rates, most likely caused by collagen deposition in the scar. Infarct locations were confirmed by late gadolinium enhancement MRI and the presence of collagen by Picrosirius Red stainings. Thus, in vivo UTE MRI enables collagen detection for the study of the role of fibrosis in myocardial disease.

10:36 0391.   
23Na Chemical Shift Imaging and Late Gadolinium enhanced (LGE) MRI of acute ischemia reperfusion myocardial injury
Eissa N. E. Aguor1,2, Fatih Arslan1, Gustav J. Strijkers3, Marcel G. J. Nederhoff1, Cees W. van de Kolk1, Gerard Pasterkamp1, Pieter doevendans1,2, and Cees J. van Echteld1
1University Medical Center, Utrecht, Utrecht, Netherlands, 2The Netherlands Heart Institute (ICIN), Utrecht, Utrecht, Netherlands, 3Eindhoven University of Technology

LGE MRI is commonly used to assess infarct size, however provides little information on the physiological state of the injured myocytes. In this respect, 23Na MRI and particularly imaging of intracellular (Nai) and extracellular (Nae) sodium concentrations is known to provide additional information on cellular integrity and ion homeostasis after myocardial ischemia. In this study, we assessed the ability of 23Na CSI complemented by 1H LGE MRI in isolated rat heart to characterize the injured myocardium as soon as 2 hours after the IR injury, which was induced while the rats were still alive.

10:48 0392.   Diffusion MRI Tractography of the Human Heart In Vivo Reveals Differences in Myofiber Organization at End-Diastole and End-Systole
Choukri Mekkaoui1, Sonia Nielles-Vallespin2, Peter Gatehouse2, Marcel P Jackowski3, David Firmin2, and David E Sosnovik4
1Radiology, Harvard Medical School - Massachusetts General Hospital, Boston, MA, United States, 2Royal Brompton Hospital, 3University of São Paulo,4Harvard Medical School - Massachusetts General Hospital

Diffusion Tensor MRI (DTI) of the heart in vivo is complicated significantly by cardiac motion. Here, for the first time, we perform DTI tractography of the human heart in vivo without the need for image interpolation or transformation. Myofiber tracts were derived from 3D in vivo DTI datasets obtained at end-diastole and end-systole. We show, for the first time, that robust in vivo tractograms of the human heart can be derived with a scan duration of less than 20 minutes. In addition, we show that myofiber orientation in the subepicardium increases in obliquity during systole as the myocardium contracts.

11:00 0393.   
Statistical Atlas of the Human Left Ventricular Fibre Architecture using In-Vivo DT-MRI
Nicolas Toussaint1, Christian Stoeck2, Sebastian Kozerke2, Maxime Sermesant3, and Tobias Schaeffter1
1Imaging Sciences, King's College London, London, London, United Kingdom, 2Biomedical Engineering, ETH, Zurich, Switzerland, 3asclepios research project, INRIA, Sophia Antipolis, France

Myocardial fibre architecture plays a major role in the heart morphology and mechanics. Recent advances in DT-MRI now provide a window to investigate this architecture in-vivo. In this work propose a statistical atlas of myocardial fibres reconstructed from in-vivo DT Images acquired in 5 volunteers. Results indicate a strong correlation with ex-vivo studies and opens possibilities for larger studies and patient applications.

11:12 0394.   Cardiac lipids show diurnal variations: An in-vivo 1H-MR Spectroscopy study in humans permission withheld
Michael Ith1, Christoph Stettler2, Jian Xu3, Chris Boesch4, and Roland Kreis4
1University Institute of Diagnostic Interventional and Pediatric Radiology, University & Inselspital Bern, Bern, Switzerland, 2Division of Endocrinology, Diabetes & Clinical Nutrition, University & Inselspital Bern, Bern, Switzerland, 3Siemens Medical Solutions USA, New York, NY, United States, 4Depts Clinical Research and Radiology, University Bern, Bern, Switzerland

In-vivo 1H-MRS was used to measure cardiac lipids (ICCL). The goal of the study was to investigate methodological reproducibility as well as diurnal variations. Nine volunteers were studied three times on one day and two times on another day separated by 1-2weeks to determine short- and long-term-reproducibility, as well as changes between morning and evening. Data analysis revealed a highly significant decrease of ICCL/Cr during the day, whereas ICCL/Cr and TMA/Cr remained stable on repeated measurements. Methodological reproducibility was excellent for all metabolites (CV¡Ö10%). ¡°Long-term¡± variations were in the same range for TMA/Cr but substantially larger for ICCL/Cr.

11:24 0395.   
MOLLI T1 Values Have Systematic T2 and Inversion Efficiency Dependent Errors
Kelvin Chow1, Jacqueline A Flewitt2, Joseph J Pagano1, Jordin D Green3, Matthias G Friedrich2, and Richard B Thompson1
1Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada, 2Stephenson CMR Centre, University of Calgary, Calgary, Alberta, Canada,3Siemens Healthcare, Calgary, Alberta, Canada

The MOLLI T1 mapping sequence was modeled using simulations, its accuracy investigated in phantoms and in-vivo studies, and compared to a new SAturation-recovery single-SHot Acquisition "SASHA" technique. Bloch equation simulations of MOLLI predict systematic T1 underestimation with shorter T2s and also with imperfect inversion pulse efficiency. Measured MOLLI T1s in phantoms agree well with simulations (10% underestimation of myocardium-like phantoms). Incorporating actual inversion pulse efficiency (measured in-vivo at 91%) and T2s into simulations accurately predict observed ~200ms T1 underestimation by MOLLI compared to SASHA in the myocardium. SASHA had good agreement with gold-standard T1s and showed no T2 dependence.

11:36 0396.   
Quantitative MRI reveals action of iron chelator in hemorrhagic myocardial infarction
Nilesh R. Ghugre1, Jennifer Barry1, John C Wood2, Alan Moody3, Bradley H Strauss4, and Graham A. Wright1,5
1Imaging Research, Sunnybrook Research Institute, Toronto, ON, Canada, 2Division of Cardiology, Childrens Hospital Los Angeles, Los Angeles, CA, United States, 3Department of Medical Imaging, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 4Schulich Heart Program, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, 5Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

Reperfusion hemorrhage is an independent predictor of adverse left-ventricular remodeling following acute myocardial infarction. The role of iron chelation in hemorrhagic myocardial infarction has not yet been explored. The study involved serial imaging of two groups of animals subjected to a 90 min coronary occlusion followed by reperfusion with and without the iron chelator, deferiprone. Deferiprone was able to penetrate the infarct zone and was also effective in neutralizing hemorrhagic byproducts. Elimination of hemorrhage resulted in faster resolution of edema and normal ventricular volumes, representing a beneficial remodeling process. Tissue characterization by quantitative MRI (T2, T2* mapping) can offer insights into the interaction between the hemorrhage and iron chelator post-infarction. Iron chelation could potentially serve as an adjunctive therapy in hemorrhagic infarction.

11:48 0397.   MRI of acute atrial lesions: Immediately vs. next day post RF ablation MRI in patients with atrial fibrillation
Eugene G. Kholmovski1,2, Sathya Vijayakumar1,2, Chris J. McGann2,3, and Nassir F. Marrouche2,3
1UCAIR, Department of Radiology, University of Utah, Salt Lake City, Utah, United States, 2CARMA Center, University of Utah, Salt Lake City, Utah, United States, 3Department of Cardiology, University of Utah, Salt Lake City, Utah, United States

Radio-frequency ablation of the left atrium (LA) is effective for patients with atrial fibrillation. In this study, we have compared visibility of acute atrial lesions in late gadolinium enhancement (LGE) and double inversion recovery T2-weighted turbo spin echo (DIR-T2w-TSE) images performed immediately (< 2 hour) and the next day after RF ablation. Quantitative analysis and visual inspection of the images demonstrate that contrast between ablated regions of LA wall and surrounding tissues is significantly higher in immediately post-ablation images than in the next day post-ablation images. The obtained results indicate a fast physiological response of LA wall to injury.