Electronic Posters: Cardiovascular

Tuesday 13:30-15:30 Computer 37

13:30 3700. Carotid Artery Wall Shear Stress: Distribution, Correlation with Geometry and Effect of Atherosclerosis

Michael Markl¹, Timo Zech², Simon Bauer¹, Felix Wegent², Aurelien F. Stalder¹, Christoph Strecker², Andreas Harloff<sup>2

1</sup>Diagnostic Radiology, Medical Physics, University Hospital, Freiburg, Germany; ²Neurology, University Hospital, Freiburg, Germany

The purpose of this study was to assess the physiological distribution of absolute wall shear stress and oscillatory shear index in the entire carotid bifurcation in healthy volunteers (n=64 carotid bifurcations) and to evaluate their dependence on individual bifurcation geometry. Further, the distribution of critical wall parameters was compared with findings in patients with moderate internal carotid artery (ICA) stenosis before (n=6) and after surgical recanalization (n=11). Bifurcation geometry predicted exposure to critical wall parameters and may thus be an indicator for the risk of developing flow-mediated atherosclerosis. Carotid artery stenosis and treatment altered the distribution of critical wall parameters.

14:00 3701. 3-Component Phase-Contrast MRI WSS Vectors in the Carotid Bifurcation Are Concurrent with Local Atherosclerotic Plaque Risk Hypotheses

Alex J. Barker¹, Fuxing Zhang², P E. Gates³, L A. Mazzaro⁴, A Stalder¹, J Fulford³, C J. Lanning^4,5, M Markl¹, Robin Shandas<sup>4,5

1</sup>Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; ²Mechanical Engineering, University of Colorado, Boulder, CO, United States; ³Peninsula Medical School, University of Exeter, United Kingdom; ⁴Center for Bioengineering, University of Colorado at Denver Health Sciences, CO, United States; ⁵Division of Cardiology, The Children's Hospital, CO, United States need to fill this out

14:30 3702. Onset Time of Retrograde Flow in the Pulmonary Artery in Pulmonary Arterial Hypertension Patients: An Estimator for Pulmonary Arterial Pressure?

Frank Helderman¹, Gert Jan Mauritz¹, J. Tim Marcus¹, Kirsten Andringa¹, Nico Westerhof¹, Anton Vonk Noordegraaf<sup>1

1</sup>VU University Medical Center, Amsterdam, Netherlands

The objective was to assess if mean pulmonary artery pressure (mPAP) could be estimated using a standard 2D MR phase-contrast velocity quantification in the main pulmonary artery. Included were 37 Pulmonary Arterial Hypertension (PAH) patients vs 8 controls. Onset time of the retrograde flow (Retrograde Onset Time = ROT) as fraction of cardiac cycle time, and cross sectional area (CSA) of the main pulmonary artery were measured. Regression analysis revealed an association between mPAP and ROT (r=0.74; p<0.001), and between mPAP and CSA (r=0.68; p<0.001). The early retrograde flow in PAH is explained with a recirculation zone.

15:00 3703. Time-Resolved 3D MR Velocity Mapping of the Great Hepatic Vessels at 3T: Simultaneous Visualization of Arterial and Venous Hemodynamics and Comparison with Ultrasound

Zoltan Csatari¹, Zoran Stankovic¹, Peter Deibert², Wulf Euringer¹, Wolfgang Kreisel², Mathias Langer¹, Michael Markl<sup>1

1</sup>Department of Diagnostic Radiology and Medical Physics, University Hospital Freiburg, Freiburg, Baden Württemberg, Germany; ²Gastroenterology, University Hospital Freiburg, Freiburg, Baden Württemberg, Germany

Flow-sensitive 4D-MRI allows the detailed depiction and quantification of the great hepatic vessels including the portal venous system as well as the coeliac trunc at the same time. As expected our results demonstrate differences in blood flow characteristics between the portal venous system and the arteries. In accordance with the literature lower values for velocities and higher values for areas were measured by MRI, but linear regression analysis showed an excellent agreement between MRI and the reference standard Doppler Ultrasound (r = 0,72; p < 0.001). In consideration of these results our findings underline that 4D-MRI could be an alternative, user indipendent method to Doppler US in investigating normal and pathological hemodynamics of the great hepatic vessels.

Wednesday 13:30-15:30 Computer 37

13:30 3704. Combined PCMRI and CFD Hemodynamics in a Flow-Model and in the Thoracic Aorta

Aurelien F. Stalder^1,2, Zhenyu Liu³, Ramona Lorenz², Juergen Hennig^2,4, Jan Gerrit Korvink, ^4,5, Michael Markl<sup>2

1</sup>Dept. of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China; ²Dept. of Diagnostic Radiology - Medical Physics, University Hospital, Freiburg, Germany; ³Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP), Chinese Academy of Science, Changchun, China; ⁴Freiburg Institute for Advanced Studies (FRIAS), Freiburg, Germany; ⁵Dept. of Microsystems Engineering, University of Freiburg, Germany

Both flow-sensitive 4D MRI and computational fluid dynamics (CFD) have successfully been applied to analyze complex 3D flow. However, both modalities suffer from limitations related to measurements (MRI) or model assumptions (CFD). In this study, we compared both modalities in a model in vitro and in the complex 3D blood flow of the thoracic aorta in vivo. Although discrepancies were observed, overall coherent patterns were observed. The further potential of the method is illustrated by calculating detailed Wall Shear Stress maps using very fine boundary layer mesh. The combination of 4D flow-sensitive MRI and CFD may be used to enhance the assessment of blood flow in vivo.

14:00 3705. Visualization and Quantification of Increased Tangential Velocities in Ascending Aortic Aneurysms Using 4D Phase Contrast

Benjamin R. Landgraf¹, Kevin M. Johnson², Erik T. Bieging¹, Oliver Wieben², Christopher J. François<sup>1

1</sup>Radiology, University of Wisconsin - Madison, Madison, WI, United States; ²Medical Physics, University of Wisconsin - Madison, Madison, WI, United States

Complex blood flow patterns in the ascending aorta have been associated with the pathophysiology of various cardiovascular diseases, including ascending aortic aneurysms. Helical and vortical flow in patients with aneurysms present an increased tangential force that could lead to further aortic dilation, dissection, or rupture. Characterization and quantification of these flow patterns could help predict disease progression. This study investigates several hemodynamic parameters of the ascending aorta in 11 normal volunteers and 13 patients, including peak and mean velocities, calculation of a tangential percentage of velocity, and characterization of flow patterns.

14:30 3706. Long Term Follow-Up of Patients Status Post Valve-Sparing Aortic Surgery with 4D-Flow

Thomas A. Hope¹, Michael D. Hope¹, D Craig Miller², Michael Markl³, John-Peder E. Kvitting², Charles B. Higgins¹, Robert J. Herfkens<sup>4

1</sup>Department of Radiology, University of California San Francisco, San Francisco, CA, United States; ²Department of Cardiothoracic Surgery, Stanford University, Stanford, CA, United States; ³Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; ⁴Department of Radiology, Stanford University, Stanford, CA, United States

12 patients status post valve sparing correction of ascending aortic aneurysms were imaged with 4D flow and were followed up for an average of 5 years. One patient had abnormal flow patterns in the ascending and descending aorta. Subsequently during the follow-up period, this patient developed a Stanford Type B aortic dissection. This is the first long-term follow-up study to correlate adverse outcomes to in vivo visualized abnormal flow patterns using MRI. Although this study is limited due to the small number of patients, it does suggest that abnormal flow patterns in the thoracic aorta may provide prognostic information.

15:00 3707. Elevated Aortic Wall Shear Stress in a Subgroup of Patients with Bicuspid Valves

Michael D. Hope¹, Thomas A. Hope¹, Thomas H. Urbania¹, Karen G. Ordovas¹, Alison K. Meadows¹, Marcus T. Alley², Charles B. Higgins<sup>1

1</sup>Radiology, UCSF, San Francisco, CA, United States; ²Stanford Radiology

4D Flow demonstrates significantly higher aortic wall shear stress in a subgroup of BAV patients with eccentric systolic flow jets. Studies have shown that only a subset of BAV patients have aortic dilation, and that those with dilation develop asymmetric aneurysms of the AsAo at the location where we have demonstrated elevated vWSS. As altered WSS can give rise to pathologic endothelial gene expression and extracellular matrix remodeling, we may have identified the mechanism that places a subgroup of BAV patients at risk for asymmetric AsAo aneurysm.

Thursday 13:30-15:30 Computer 37

13:30 3708. Vortex Core Detection and Visualization Using 4D Flow-Sensitive MRI

Aurelien F. Stalder^1,2, Alex Frydrychowicz³, Andreas Harloff⁴, Qi Yang¹, Jelena Bock², Juergen Hennig², Kuncheng Cheng Li¹, Michael Markl<sup>2

1</sup>Dept. of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China; ²Dept. of Diagnostic Radiology - Medical Physics, University Hospital, Freiburg, Germany; ³Dept. of Radiology, University of Wisconsin-Madison, Freiburg, Germany; ⁴Dept. of Neurology, University Hospital, Freiburg, Germany

4D flow-sensitive MRI was used with 3D flow visualization techniques and a vortex core detection algorithm to detect patterns of swirling flow in the aorta, the carotid arteries as well as intracranial arteries in volunteers and patients. While aneurysms presented strong vortex cores, weaker vortex cores were identified in the healthy aortic arch and the healthy internal carotid artery. The vortex core detection provided a fast and simple way to detect locations of swirling flow within 4D flow-sensitive MRI datasets.

14:00 3709. Age Relation of Aortic Wall Compliance in Marfan Syndrome: Evaluation with Velocity-Encoded MRI

Jos J.M. Westenberg¹, Arthur J.H.A. Scholte², Zuzana Vaskova³, Rob J. van der Geest¹, Maarten Groenink⁴, Gerda Labadie¹, Pieter J. van den Boogaard¹, Teodora R. Radonic⁴, Yvonne Hilhorst-Hofstee⁵, Lucia J.M. Kroft¹, Albert de Roos¹, Johan H.C. Reiber<sup>1

1</sup>Radiology, Leiden University Medical Center, Leiden, Zuid-Holland, Netherlands; ²Cardiology, Leiden University Medical Center; ³Radiology, St. Anne's University Hospital, Brno, Czech Republic; ⁴Cardiology, Academic Medical Center, Amsterdam, Netherlands; ⁵Clinical Genetics, Leiden University Medical Center

The purpose of this study is to describe age relation of aortic wall compliance, expressed in Pulse Wave Velocity, Distensibility and Stiffness Index, with Velocity-Encoded MRI in Marfan syndrome. Twenty-five patients with Marfan syndrome and twenty-five age-matched healthy volunteers are examined and measures for compliance are compared. In Marfan, the Pulse Wave Velocity is generally increased in the aortic arch, distal aorta and total aorta. Distensibility is decreased. Only the Stiffness Index is not statistically significantly different. Age-related change in compliance is best expressed in increasing Pulse Wave Velocity.

14:30 3710. Aortic Compliance Evaluation: Comparison of Time Delay Algorithms

Yi Wang¹, Edwin Estrada¹, Jianping Zhang<sup>2

1</sup>Research and Education, St. Francis Hospital, Roslyn, NY, United States; ²Applied Mathematics and Statistics, State University of New York, Stony Brook, NY, United States

Aortic pulse wave velocity (PWV), a measurement of the flow pulse traveling along aorta as a surrogate for aortic compliance, can be assessed using a single breath-hold through-plane phase contrast imaging technique. Accurate determination of the time delay between flows in ascending and descending aorta is critical in PWV assessment. Various approaches have been studied, including measuring the intervals between flow onset points, between maximal flow points, and between parallel upslopes after least squares fittings. We compared five automated approaches for time delay detection and evaluated their effects on aortic compliance and their relationship to age in 186 normal volunteers.

15:00 3711. Improved Simulation of 3D Flow Characteristics in a Pressure Controlled in Vitro Model System

Ramona Lorenz¹, Christoph Benk², Jelena Bock¹, Jan Korvink³, Michael Markl<sup>1

1</sup>Dept. of Diagnostic Radiology, University Hospital, Freiburg, Germany; ²Dept. of Cardiovascular Surgery, University Hospital, Freiburg, Germany; ³Dept. of Microsystems Technology, IMTEK, Freiburg, Germany

In-vitro model systems provide a useful tool for the systematic evaluation of hemodynamic changes associated with geometric vascular modifications. However, realistic in-vivo in-flow and boundary conditions are necessary for accurate flow simulations. This paper presents a novel approach for an in-vitro model setup which includes a pulsatile pump chamber in combination with flexible and monitored pressure control using an adjustable mock loop to simulate physiological pre- and after load conditions. In contrast to measurements without pressure control an improved generation of qualitative and quantitative flow characteristics compared to in-vivo flow conditions could be achieved.

Image Post-Processing

Hall B Monday 14:00-16:00 Computer 38

14:00 3712. Investigation of Myocardium Structure of Postinfarct Porcine Model Using Superquadric Glyphs

Yin Wu^1,2, Ed Xuekui Wu<sup>2,3

1</sup>Institute of Biomedical and Health Engineering, Shenzhen Institute of Advanced Technology, Shenzhen, Guangdong, China; ²Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong; ³Dept. of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong

Previous DTI studies on infarcted LV myocardium structure usually explored myocardial fiber orientation, diffusivity or diffusion anisotropies. In current study, superquadric glyphs were applied on infarcted porcine model. Diffusion tensor shape and laminar sheet structure were examined for the first time to describe infarcted myocardium structural alteration. Results show that significant change of diffusion tensor shape occurred in both infarct and adjacent regions. Apparent alteration of laminar sheet structure was observed in adjacent and remote regions. The current study demonstrates the ability of superquadric glyphs to detect myocardium structural degeneration and provides supplemental information for infarcted heart remodeling.

14:30 3713. Multiecho Dixon Fat and Water Separation Method for Diagnosing Pericardial Disease

Amir H. Davarpanah¹, Aya Kino¹, Kirsi Taimen¹, Philip Hodnet¹, Jeremy Collins¹, Cormac Farrelly¹, Saurabh Shah², Sven Zuehlsdorff², James Carr<sup>1

1</sup>Department of Radiology, Cardiovascular Imaging, Northwestern University, chicago, IL, United States; ²Siemens Medical Solutions, chicago, IL, United States

The VARPRO method (multi-echo gradient echo sequence with iterative fat/water decomposition reconstruction)for fat/water separation performs better than the standard fat saturation protocol currently used at our institution. The water image from this method presents with a more uniform fat suppression.

15:00 3714. Automated Evaluation of Left Ventricular Diastolic Function Using Velocity-Encoded Magnetic Resonance Imaging: Conventional and New Parameters

Emilie Bollache¹, Stéphanie Clément-Guinaudeau², Ludivine Perdrix³, Magalie Ladouceur^1,3, Muriel Lefort¹, Alain De Cesare¹, Alain Herment¹, Benoît Diebold^1,3, Elie Mousseaux^1,2, Nadjia Kachenoura<sup>1

1</sup>INSERM U678, UPMC, Paris, France; ²Radiology department, APHP, European Hospital Georges Pompidou, Paris, France; ³Echocardiography department, APHP, European Hospital Georges Pompidou, Paris, France

Phase-contrast (PC) Magnetic Resonance (MR) is not used in clinical routine to assess diastolic function, because of the lack of automated analyses. Thus, our aim was to develop a process to automatically analyze PC data. Automated segmentation of PC images and analysis of velocity and flow rate curves to derive diastolic parameters were developed and tested on 25 controls. Segmentation was successful in all subjects. Our conventional parameters were consistent with those previously presented in literature and our new parameters highly correlated with high prognosis value parameters. Our process may provide a valuable addition to the established cardiac MR tools.

15:30 3715. Unsupervised and Reproducible Image-Based Identification of Cardiac Phases in Cine SSFP MRI

Sotirios A. Tsaftaris^1,2, Xiangzhi Zhou², Richard Tang², Rohan Dharmakumar<sup>2

1</sup>Electrical Engineering and Computer Science, Northwestern University, Evanston, IL, United States; ²Radiology, Northwestern University, Chicago, IL, United States

It is particularly important for the evaluation of cardiac phase-resolved myocardial blood-oxygen-level-dependent (BOLD) MRI studies, to robustly and reproducibly identify end-systolic (ES) and end-diastolic (ED). Most automated methods rely on identifying the minimum and maximum of the blood pool area in the Left Ventricle chamber, but they are computationally intensive, susceptible to noise, and require prior localization and segmentation of the chamber. The purpose of this work is to develop automated methods to facilitate in the robust and reproducible evaluation of cardiac phase-resolved myocardial BOLD MRI through identification of ES and ED images.

Tuesday 13:30-15:30 Computer 38

13:30 3716. Estimation of LV Function from Navigator Triggered, Real-Time Cardiac Cine Steady-State Free Precession (SSFP) Imaging

Amol Pednekar¹, Benjamin Cheong², Raja Muthupillai², Claudio Arena<sup>2

1</sup>Philips Healthcare, Cleveland, OH, United States; ²Diagnostic and Interventional Radiology, St. Luke's Episcopal Hospital, Houston, TX, United States

We propose an integrated real-time data acquisition and retrospective post-processing strategy to estimate parameters characterizing global function of the left ventricle. Our initial evaluation of feasibility of this approach in normal subjects shows that slice-by-slice LV volumes estimated using the real-time cine imaging approach are comparable to the LV volumes obtained using conventional, breathhold cardiac cine SSFP techniques. The combination of respiratory navigator triggering, real-time unsegmented SSFP cine imaging, and integrated retrospective automated processing may make this approach particularly useful in patients with severe arrhythmias, and/or severely compromised respiratory function.

14:00 3717. ShMOLLI: Shortened Modified Look Locker Inversion Recovery for Cardiac T1 Mapping – from Theory to Normal Human Myocardium

Stefan K. Piechnik¹, Vanessa M. Ferreira², Erica Dall'Armellina², Lowri E. Cochlin³, Stefan Neubauer², Matthew D. Robson<sup>2

1</sup>Cardiovascular Medicine, OCMR, Oxford University , Oxford, Oxfordshire, United States; ²Cardiovascular Medicine, OCMR, Oxford University, Oxford, Oxfordshire, United States; ³Dept of Physiology, Anatomy and Genetics, Oxford University, Oxford, Oxfordshire, United States

We propose a cardiac T1-mapping method based on sequential Look-Locker measurements with conditional reconstruction of incomplete recovery periods. This new method assures that robust T1 mapping can be achieved in a 9 heartbeat breath-hold with accuracy comparable to existing methods.

14:30 3718. Preferential Patterns of Myocardial Iron Deposition by Multislice Multiecho T2* CMR in Thalassemia Major Patients.

Antonella Meloni¹, Vincenzo Positano¹, Alessia Pepe¹, Pasquale Pepe¹, Maria Chiara Dell'Amico¹, Cristina Salvatori¹, Petra Keilberg¹, Gianluca Valeri², Eliana Cracolici³, Pier Paolo Bitti⁴, Angelo Zuccarelli⁵, Maria Filomena Santarelli¹, Massimo Lombardi<sup>1

1</sup>MRI Lab, “G. Monasterio Foundation” and Institute of Clinical Physiology, CNR, Pisa, Italy; ²Azienda Ospedaliero-Universitaria Ospedali Riuniti "Umberto I-Lancisi-Salesi", Ancona, Italy; ³Policlinico "Paolo Giaccone" , Palermo, Italy; ⁴Dipartimento dei Servizi - P. O. San Francesco, Nuoro, Italy; ⁵Centro trasfusionale e di microcitemia - Ospedale civile, Olbia, Italy

Multislice multiecho T2* MRI allows quantification of iron overload in the whole myocardium. A preferential pattern of iron store in anterior and inferior regions appears to be present in thalassemia major patients with severe and mild-moderate iron overload. The preserved pattern between the groups prevents attributing this datum to additive susceptibility artefacts, which are negligible in heavily iron-loaded patients. A segmental T2* CMR approach could identify early iron deposit, useful for tailoring chelation therapy and preventing myocardial dysfunction in the clinical setting.

15:00 3719. RV Function from Cine MRI Using Contour Propagation

Wei Feng¹, Himanshu Gupta², Steven Lloyd², Louis Dell'Italia², Thomas S. Denney Jr<sup>3

1</sup>Biomedical Engineering, MRI Institute, Detroit, MI, United States; ²Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, AL, United States; ³Electrical Engineering, Auburn University, Auburn, AL, United States

This abstract presents a method for computing right-ventricular volume-versus-time curves and peak ejection and filling rates from standard cardiac cine MRI. The method uses RV contours drawn semi-automatically near end-diastole and end-systole and propagates them to the remaining time frames via a non-rigid registration technique. The propagated contours are validated by comparing them to contours manually drawn by a cardiologist with Level 3 training. In addition, peak ejection and filling rates computed from both manually-drawn and propagated contours are compared.