14:00 2825. Flow Sensitive MRI in a Realistic Model System of the Thoracic Aorta with Aortic Coarctation
Ramona Lorenz1, Aurélien F. Stalder1, Jelena Bock1, Dominic Klausmann2, Christoph Benk1, Jürgen Hennig1, Michael Markl1
1University Hospital Freiburg, Freiburg, Germany; 2University Freiburg, Freiburg, Germany
The purpose of this study was to establish a realistic model system for the evaluation of hemodynamics consequences of aortic coarctation with different stenosis grades. Flow sensitive 4D MRI was performed within a realistic rapid prototyping vascular model of the thoracic aorta with attached flexible stenosis in the descending aorta which was integrated into a pulsatile flow circuit. A novel approach for generating realistic pulsatile waveforms was realized by a pneumatically driven VAD (ventricular assistant device) pump system. The study presents an evaluation of the impact of stenosis grade on local and global flow dynamics.
14:30 2826. Flow Sensitive 4D MRI: Descending Aortic Retrograde Flow and Embolization Risk in Acute Stroke Patients
Michael Markl1, Christoph Strecker2, Patrick Dudler2, Andrea Nußbaumer2, Jelena Bock1, Aurelien F. Stalder1, Alex Frydrychowicz1, Anna L. Stroh3, Cornelius Weiller2, Jürgen Hennig1, Andreas Harloff2
1Dept. of Diagnostic Radiology, Medical Physics, University Hospital, Freiburg, Germany; 2Dept. of Neurology, University Hospital, Freiburg, Germany; 3Dept. of Cardiology, University Hospital, Freiburg, Germany
Flow-sensitive 4D MRI allows the detailed visualization of both physiological and pathological 3D aortic blood flow characteristics and was used to determine the role of retrograde flow in the descending aorta (DAo) in patients with acute embolic stroke. Our findings demonstrate a high incidence of retrograde flow in the proximal DAo suggesting that complex DAo plaques should be considered as a novel high-risk embolic source in patients with undetermined stroke etiology.
15:00 2827. Analysis of 3D Flow Dynamics in a Ventricular Assist Device by Flow Sensitive 4D MRI
Michael Markl1, Ramona Lorenz1, Jelena Bock1, Christoph Benk2, Dominic Klausmann2, Alex Frydrychowicz1, Jürgen Hennig1, Friedhelm Beyersdorf2
1Dept. of Diagnostic Radiology, Medical Physics, University Hospital, Freiburg, Germany; 2Dept. of Cardiovascular Surgery, University Hospital, Freiburg, Germany
The assessment of flow characteristics inside ventricular assist devices (VADs) using MRI techniques may provide insight into the mechanisms underlying the high rate of thrombo-embolic events after VAD implantation. These investigations may form the basis to optimize the devices design and its need for anticoagulation. The purpose of this study was to integrate a clinical routine VAD into a flow circuit with realistic geometric and pulsatile inflow conditions. Flow sensitive Magnetic Resonance Imaging (MRI) at 3 Tesla permitted the detailed analysis of local and global 3D flow dynamics in a realistic environment.
15:30 2828. Diameter-Dependence of Aortic Hemodynamics: Does Size Matter?
Alex Frydrychowicz1, Alexander Berger1, Aurélien F. Stalder1, Maximilian F. Russe1, Andreas Harloff1, Mathias Langer1, Jürgen Hennig1, Michael Markl1
1University Hospital Freiburg, Freiburg, Germany
It was the aim of this study based on flow-sensitive 4D MRI to analyze the diameter dependence of aortic hemodynamics with respect to characteristic blood flow patterns such as time to maximum arterial flow, duration of backward flow, number of vortices, and the presence of helical flow, which can be correlated to wall shear stress (WSS) and oscillatory shear index (OSI). The results of this study indicate the method¡¯s potential to identify characteristic, diameter dependent, aortic flow patterns. In a cohort of 62 individuals which were subgrouped by the diameter of the ascending aorta (SAD-group ¡Ü 3.5cm < LAD-group) we showed that the size of the aorta influences the hemodynamic properties.
14:00 2829. Multi-Dimensional Velocity Field Reconstruction from Sparsely Sampled 3D Phase Contrast MRI
Kartik Sivaram Sundareswaran1, Dave Harold Frakes1, Mark Fogel2, Oskar Skrinjar1, Ajit P. Yoganathan1
1Georgia Institute of Technology, Atlanta, Georgia, USA; 2Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
A new technique for velocity field reconstruction is presented in this paper that utilizes blood flow incompressibility as a property for estimating continuous flow field representation in blood vessels using a stack of contiguous phase contrast MRI. The methodology has been tested on 15 in vivo datasets of patients with a single ventricle circulation, and the results indicate superior qualitative and quantitative velocity reconstruction compared to other traditional techniques for flow reconstruction from PC MRI. This opens up new avenues for higher order analysis (vortex structures, energy loss) of PC MRI flow fields.
14:30 2830. In Vivo MR Determination of Flow Fields in Patients with Intracranial Aneurysms Using 7D PC-MRI
Gabriel Acevedo-Bolton1, Alastair Martin1, Vitaliy Rayz1, Loic Boussel1, David Saloner1,2
1UCSF, San Francisco, California , USA; 2VAMC San Francisco, San Francisco, California , USA
7D PC-MRI was used to measure and map the blood flow within intracranial aneurysms in vivo. These flow results were compared with in vitro reproductions and with the predictions of computational fluid dynamics(CFD) models. It was found to be essential to determine all three components of the velocity to adequately visualize the complex flow structures
15:00 2831. Patient-Specific Hemodynamics of the Descending Aorta: Combination of CFD and 4D Flow-Sensitive MRI
Aurélien F. Stalder1, Zhenyu Liu2, Michael Markl1, Jürgen Hennig1, Jan Korvink2
1University Hospital Freiburg, Freiburg, Germany; 2University of Freiburg, Freiburg, Germany
Flow-sensitive 4D MRI allows in vivo 3D blood flow visualization and flow parameter estimation but is limited by spatio-temporal resolution and measurement errors. In contrast, Computational Fluid Dynamics (CFD) can compute very accurate flow fields from modeled arteries but depends on the validity of the hemodynamic model and boundary conditions. We show for the first time an integration of 4D flow-sensitive MRI and CFD into a single framework. A combination of those 2 complementary approaches offers reciprocal validation possibilities and has the potential to refine flow measurements which may result in more accurate quantification of complex in vivo hemodynamic phenomena.
15:30 2832. 4D Flow of the Whole Heart and Great Vessels at 3T Using Real Time Self Respiratory Gating
Sergio Andres Uribe1, Philipp Beerbaum1, Allan Rasmusson2, Thomas Sangild Sørensen2, Reza Razavi1, Tobias Schaeffter1
1Kings College London, London, UK; 2University of Aarhus, Aarhus, Denmark
We present an extension of a self-respiratory technique to acquire 4D flow data. Self-navigation is obtained from k-space center profiles and the breathing signal is used in real time to gate the scan. The method allows us to acquire an isotropic non-angulated volume, 4D flow encoded, of the whole heart and great vessel in a single free-breathing scan. Results showed a strong correspondence between flow patterns obtained using this technique and with 2D flow. This approach represents an important advance for the characterization of the flow hemodynamics in the whole heart and a step forward to simplify cardiac MR examinations.
14:00 2833. A New Methodology for Determining Aortic Pulse Wave Velocity Using 2D PCMR Velocity Data
Samuel Fielden1,2, Brandon Fornwalt2, Michael Jerosch-Herold3, Robert Eisner1, Arthur Stillman1, John Oshinski1,2
1Emory University, Atlanta, USA; 2Georgia Institute of Technology/Emory University, Atlanta, USA; 3Oregon Health & Science University, Portland, USA
A novel method for estimating aortic pulse wave velocity is presented. This method uses 2D PCMR data to construct blood velocity magnitude images in order to determine multiple flow waveforms in the ascending, transverse, and descending sections of aorta. The waveform at each location is compared to the most proximal waveform via cross correlation to determine the time delay of the wave at that location and thus the pulse wave velocity. This method is more reproducible than either of two more established methods examined.
14:30 2834. Measurement of Aortic Pulse Wave Velocity in Volunteers
Neva Hiten Patel1, Mark Butlin2, Richard T. Black1, Martin J. Graves,13, Stacey Hickson4, Carmel McEniery4, Ian B. Wilkinson4, David J. Lomas3
1Addenbrooke's Hospital NHS Trust, Cambridge, UK; 2Macquarie University, Sydney, Australia; 3University of Cambridge, UK; 4University of Cambridge, Cambridge, UK
Aortic pulse wave velocity (PWV) can be used as an index of the increased risk of cardiovascular disease which is associated with aortic wall stiffness. A number of groups have looked at measuring PWV using MRI, however we are not aware of any reported studies addressing the best method of obtaining the transit-time used to calculate the PWV, and the reproducibility of PWV measurement. We have performed repeated MRI PWV measurements in healthy volunteers and investigated several different methods of transit-time calculations.
15:00 2835. The Effect of Wall Compliance on Aortic Hemodynamics in the Mouse: Implications for AAA Pathogenesis
Smbat Amirbekian1, Robert C. Long1, Jin Suo2, W Robert Taylor1,2, Don P. Giddens2, John N. Oshinski1,2
1Emory University, Atlanta, Georgia, USA; 2Georgia Tech, Atlanta, Georgia, USA
MRA and PC-MRI were used to provide geometric and flow boundary conditions for a computational study of the hemodynamics of the mouse aorta. The study showed that incorporating vessel compliance changes the flow patterns seen in the aorta and that a rigid vessel creates areas of oscillatory wall shear stress.
15:30 2836. Measurement of Common Carotid Artery Lumen Dynamics During Cardiac Cycle Using TrueFISP Cine MR Imaging
Tracy Yee Mau Chow1,2, Jerry S. Cheung1, Yin Wu1, Ed X. Wu1
1The University of Hong Kong, Pokfulam, Hong Kong
Vascular MR imaging provides detailed anatomical information of blood vessels, yielding lumen size and wall thickness measurements. However, many of the studies often specify the morphology and composition of vessel walls without examining the dynamic pulsatile properties of these vessels. In this study, the vascular dynamics of the right and left common carotid arteries throughout the whole cardiac cycle was investigated using TrueFISP cine cardiac imaging. Consistent results and area waveform patterns were observed among the normal subjects. This lumen dynamics can better describe physiological behaviour correlated with other vascular parameters, therefore has potential clinical importance in differentiating abnormalities. Furthermore, TrueFISP cine MRI produces high contrast images, allowing high accuracy in area measurements and thus waveform tracing.
Myocardial T2 & T2* Imaging
14:00 2837. Spiral T2 Quality Evaluation in Patients with Coronary Artery Disease
Warren Foltz1, Kim Alexander Connelly1, Ram Vijayaraghavan1, Venkat Ramanan, Gideon Paul1, Graham Wright1, Alexander Dick1
1Sunnybrook Health Sciences Centre, Toronto, Canada
T2 has proven to be a valuable contrast mechanism for myocardial characterization because it is a quantitative biomarker of acute and sub-acute inflammatory processes. Clinical integration of T2 relies on T2-weighted black-blood fast-spin echo (FSE) imaging because cardiac-gated imaging is achievable in breath-hold scan times and with useful spatial resolutions. However the information is semi-qualitative and the echo-train readout compromises T2 contrast. A magnetization-prepared spiral imaging method, termed T2prep, should improve reproducibility in clinical quantification of myocardial T2 relaxation because variability associated with coil shading is removed. In the absence of gross relaxation fluctuations, current clinical myocardial FSE scanning is useful only to delineate cardiac margins. Quantitative T2prep mapping reduces variability towards physiological noise levels, providing more reproducible measurements with the potential for faster scan times at minor cost to spatial resolution and ROImin.
14:30 2838. Using T2*-Maps as a Quantitative Indicator for Myocarditis
Karl-Heinz Herrmann1, Diane Renz1, Pascal Baltzer1, Ines Krumbein1, Jürgen R. Reichenbach1
1Friedrich-Schiller-University, Jena, Germany
Diagnosis of myocarditis with standard sequences like late enhancement, T2 TSE or T2-weighted TIRM is not always conclusive because any through plane motion of the myocardium causes inhomogeneous signal due to the repeated slice selective inversion and excitation pulses. A quantitative T2*-map may be helpful in quantifying, delineating and detecting edema associated with myocarditis.
15:00 2839. Retrospective Correction for Induced Magnetic Field Inhomogeneity in Measurements of Large-Vessel Hemoglobin Oxygen Saturation by MR Susceptometry
Michael Langham1, Tom Floyd2, Jeremy Magland1, Felix W. Wehrli1
1University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA; 2Univesity of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
The main source of error in MR susceptometry is the static field inhomogeneity that is characterized by low spatial-frequency modulation on the phase image. High-pass filtering has previously been used in conjunction with shimming. We propose an alternative method which acquires data without scanner-implemented default shimming, and fit, after appropriate weighting and masking, the static field inhomogeneity to a second-order polynomial. Compared to shimming, the retrospective correction technique improved agreement between hemoglobin saturations measured in different segments of a vessel (femoral versus popliteal artery and vein) from three standard errors to less than one.
15:30 2840. Multislice Multiecho T2* Cardiovascular Magnetic Resonance Can Detect Heterogeneous Myocardial Iron Distribution in Thalassemia Patients
Vincenzo Positano1, Alessia Pepe1, Anna Ramazzotti1, Daniele De Marchi1, Brunella Favilli1, Eliana Cracolici2, Maria Gabriella Brizi3, Maria Filomena Santarelli1, Massimo Lombardi1, Luigi Landini4
1Institute of Clinical Physiology, Pisa, Italy; 2University of Palermo, Palermo, Italy; 3A. Gemelli University Hospital, Roma, Italy; 4University of Pisa, Pisa, Italy
In this study we investigate the relationship between segmental R2* heterogeneity assessed by multi-slice multi-echo MRI and iron overload progression in a large thalassemia major patient population. Real data were compared with a surrogate data sets obtained stating that the inhomogeneous segmental distribution of R2* would be generated by susceptibility artefacts. Inhomogeneities in R2* myocardial distribution in iron overloaded subjects cannot be explained by the effect of susceptibility artefacts, that are additive in the R2* domain and should vanish at high iron overload levels. A possible interpretation is that a true heterogeneity in iron overload distribution in TM patients exists.
Vessel Wall Imaging
14:00 2841. An Optimized 3D Inversion Recovery Prepared Fast Spoiled Gradient Recalled Sequence with Multiple Echoes (IR FSPGR ME) for Carotid Plaque Imaging
David C. Zhu1, J Kevin DeMarco1, Anthony T. Vu2
1Michigan State University, East Lansing, Michigan, USA; 2GE Healthcare, Waukesha, Wisconsin, USA
An optimized 3D inversion recovery prepared fast spoiled gradient recalled sequence with multiple echoes (IR FSPGR ME) on a 3T scanner for carotid plaque imaging is presented. It maintains the ability of its single-echo counterpart in blood and fat signal suppression at the carotid region as well as the benefits of high-resolution volumetric visualization and hemorrhage detection. The IR FSPGR ME sequence can potentially further characterizes hemorrhage types through the generated T8* maps. In addition, combining images from the individual echoes provides a higher signal-to-noise ratio and thus improve image visualization.
14:30 2842. Optimization of Motion Sensitized Driven Equilibrium (MSDE) Preparation Scheme for Multi Contrast 3D Vessel Wall Imaging at 3.0T
Makoto Obara1,2, Masatoshi Honda3, Rie Nozaki2, Marc Van Cauteren1, Kagayaki Kuroda2
1Philips Medical Systems, Minato-ku, Japan; 2Tokai University, Hiratsuka-shi, Japan; 3Tokai University Hospital, Isehara-shi, Japan
3D turbo field echo (TFE) sequence prepared by motion sensitized driven equilibrium (3D-MSDE-TFE) was optimized for T1W and T2W carotid artery wall imaging and compared to the conventional 2D double inversion recovery (DIR) turbo spin echo (TSE). T1 and T2 contrasts of 3D-MSDE-TFE were controlled by adjusting the MSDE preparation time, shot interval and acquisition flip angle. MSDE optimization was achieved by changing the number of refocusing pulses from 1 to 4 using MLEV scheme. Achieved T1 and T2 contrasts of the optimized 3D-MSDE-TFE were similar to those of conventional 2D-DIR while scan time was 2 times faster. Therefore, this approach may be appropriate for vessel wall screening.
15:00 2843. Evaluation of the Relationship Between the Superficial Calcification and Intraplaque Hemorrhage in the Atherosclerotic Carotid Plaque by 3T High Resolution MRI
Haiyue Ju1, Xian Xu1, Lin Ma1, Zulong Cai1, Youquan Cai1, Xinjiang Wang1, Jianming Cai1
1Chinese PLA General Hospital, Beijing, People's Republic of China
We aim to evaluate the relationship between the shape and location of superficial calcification and intraplaque hemorrhage in the atherosclerotic carotid plaque. One hundred and eighty three slices with superficial calcification in 51 patients were enrolled in this study. All the patients underwent 3T MRI examination with a contrast-enhanced multi-contrast weighted protocol. This study showed that the nodular type of superficial calcification in the atherosclerotic carotid plague has higher possibility of simultaneous occurrence with intraplaque hemorrhage than that of patchy type, whereas, in hemorrhage group, the percentage of either marginal or central type of superficial calcification is not significantly different from that in non-hemorrhage group.
15:30 2844. Gadolinium Contrast Enhancement of Carotid Atherosclerotic Plaque is Associated with Symptomatic Status
Jianming Cai1, Niranjan Balu2, Dongxiang Xu2, Haiyue Ju1, Xian Xu1, Xihai Zhao1, Chun Yuan2
1Chinese PLA General Hospital, Beijing, People's Republic of China; 2University of Washington, Seattle, USA
Symptomatic carotid atherosclerosis is known to be associated with plaque neovasculature and inflammation. An increase in vasa vasorum accompanies the increased inflammation and plaque neovasculature of advanced atheorsclerosis. The increased blood supply from the vasa vasorum plexus surrounding the carotid artery may be reflected in contrast enhancement (CE) patterns of the outerwall. The association between outerwall CE on black-blood contrast-enhanced MRI (CE-MRI) and symptomatic status was investigated in 24 patients. Outerwall CE was clearly visualized by CE-MRI. Symptomatic status was found to be associated with a more homogenous outerwall CE compared to asymptomatic arteries.
14:00 2845. DSCT and 3T MR for Characterization of Carotid Plaque in Patients
John J. Sheehan1, Natasha Berg2, Timothy Carroll2, Peter J. Weale3, Renate Jerecic3, James C. Carr2
1Northwestern University, Chicago, Ireland; 2Northwestern University, Chicago, Illinois, USA; 3Siemens Medical Solutions, Chicago, Illinois, USA
Atherosclerotic disease is a significant cause of morbidity and mortality. Recent studies have suggested that plaque composition is an important prognostic factor and may be more predictive of adverse outcomes than overall degree of stenosis. Previous studies have attempted to characterize carotid plaque components using various imaging modalities. In this small patient study, we looked at the relative efficacy of two new technologies, 3 Tesla (3T) MR and Dual Source CT (DSCT) to evaluate plaque components. We hypothesized that these modalities could provide improved depiction of plaque components, which may have important diagnostic and therapeutic implications.
14:30 2846. Single-Shot DENSE MRI of the Carotid Arteries
Alexander Peter Lin1,2, Eric Bennett2, Yuan Le2, Scott Fraser1, Han Wen2
1California Institute of Technology, Pasadena, California , USA; 2National Institutes of Health, Bethesda, Maryland, USA
DENSE strain mapping of the carotid artery wall systolic distension provides regional stiffness measures. However, the scan lasts several minutes, and segmented k-space acquisition suffers from artifacts due to head-neck motion and turbulent in-plane blood flow. This problem is solved with a single-shot imaging sequence and rigid body image registration in postprocessing.
15:00 2847. MRI-Based Biomechanical Imaging: Role of Hemodynamic Forces on the Early Plaque Remodeling
Jie Zheng1, Dana Abendschein1, Ruth J. Okamoto2, Deshan Yang1, Kyle McCommis1, Bernd Misselwitz3, Robert J. Gropler1, Dalin Tang4
1Washington University School of Medicine, Saint Louis, USA; 2Washinton University, Saint Louis, USA; 3Bayler Schering Pharma AG, Berlin, Germany; 4Worcester Polytechnic Institute, Worcester, Massachusetts, USA
Local hemodynamic forces play important roles in the regulation of early atherosclerosis progression and vessel remodeling. A MRI-based biomechanical imaging technique was developed and evaluated in vivo in a porcine atherosclerotic plaque model. A plaque targeted contrast-enhanced MR images provided plaque structure for the computational modeling in this technique. Progression and regression of the early plaques were observed and flow shear stress show consistent findings with other reports. Furthermore, structures stress and strain also demonstrated strong correlations with plaque progression and regression, indicating multi-factors of hemodynamic effect to the early atherogenesis.
15:30 2848. Characterization of Ex Vivo Carotid Plaque with 3T MRI: A Comparison with Histology
Natasha Berg1, John Joseph Sheehan1, Peter J. Weale2, Mark Morasch1, Nicole Mascheri1, James C. Carr1, Timothy Carroll1
1Northwestern University, Chicago, Illinois, USA; 2Siemens Medical Solutions, Chicago, Illinois, USA
Atherosclerotic disease of the carotid artery is a significant cause of morbidity and mortality. Previous imaging techniques have focused on quantifying stenosis in the vessel, but recent research suggests that composition of plaque may be a more important prognostic factor. Ex vivo studies of carotid plaques have attempted to characterize plaque using 1.5 T MR and have shown that 2D PDW, T1W and T2W sequences on MRI may have some utility in demonstrating areas of fibrous matrix and necrotic core. Here, we perform an intial evaluation of 3T MRI in the characterization of ex-vivo carotid plaque specimens.
14:00 2849. High-Resolution Multi-Contrast MRI Characterization of Rabbit Atherosclerosis Using Clinical Pulse Sequences
Andre Jean-Louis Belisle1,2, John A. Ronald,12, Kem A. Rogers1, Brian K. Rutt,12
1University of Western Ontario, London, Canada; 2Robarts Research Institute, London, Canada
We used multi-contrast ex vivo 3T MRI of aortic specimens from defined regions of a low-level long-term cholesterol-fed rabbit model of atherosclerosis. The objective was to collect high-resolution images using clinically available pulse sequences to resolve the structural components of plaques and to provide histological verification. The most complex regions of plaque appear to be in the descending aortic arch which was demonstrated by all sequences and is especially evident when compared to T2w controls. Eventually this research could be used for visualizing the vulnerable plaque and direct further in vivo research by specifying imaging target regions in the aorta.
14:30 2850. In Vivo & Ex Vivo Micro-MRI in Detection of Mouse Atherosclerotic Plaques: An MRI-Histopathology Correlation Study
Daohai Xie1,2, Bensheng Qiu1, Jiangyang Zhang3, Xiaoming Yang1
1University of Washington, Seattle, Washington, USA; 2Suzhou University School of Medicine, Suzhou, People's Republic of China; 3Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
Atherosclerotic cardiovascular disease remains the leading cause of death in the developed countries. Continuous efforts are warranted to understand more about the pathogenesis and management of atherosclerotic cardiovascular disease. High-field micro-MR technology offers both high spatial resolution and whole-body coverage. This study focused on evaluation of capability using in vivo and ex vivo micro-MRI to detect mouse atherosclerotic plaques, which was correlated with histopathology. The results of the current study may encourage the continued efforts to develop high-field MR imaging techniques to characterize atherosclerotic plaques in vivo, so-called ¡°in-vivo plaque pathology,¡± which should become an essential imaging tool for early diagnosis and efficient treatment of atherosclerotic cardiovascular disease.
15:00 2851. in vivo MRI and MRA Assessment of Patency in a Novel Model of Vascular Remodelling Using Patent Aortic Grafts
King Kenneth Cheung1,2, Andrew R. Thompson3, H Hafez4, Andrew M. Taylor2, Roger J. Ordidge1, Stephen E. Humphries3, Mark F. Lythgoe2
1University College London (UCL), London, UK; 2UCL, London, UK; 3Royal Free & University College London Medical School, London, UK; 4St Richards Hospital, Chichester, UK
Fibulin-5 (fbln-5) is an extracellular matrix protein that is central to elastic fibre maturation and vessel development. A novel model has been devised to investigate the role of fbln-5 in vascular remodelling in a patent vessel. As sustained graft patency is central to this model, we evaluated the accuracy of MRI and MRA for determining graft patency in vivo. MRI and MRA correctly identified all patent (n=8) and non-patent (n=3) grafts. The non-invasive and robust nature of MRI and MRA offers an excellent alternative to traditional assessment through repeated invasive surgery, thus improving survival and reducing animal usage.
15:30 2852. Characterisation of Vascular Injury Responses Following Balloon Injury of the Rat Carotid Artery Using Combined in vivo Imaging and ex Vivo Microscopy
King Kenneth Cheung*1,2, Manfred Junemann-Ramirez*2, Pauliina Lehtolainen2, Alan Rudiger2, Mark Turmaine, David Sanz2, Roger J. Ordidge1, John F. Martin2, Mark F. Lythgoe2
1University College London (UCL), London, UK; 2UCL, London, UK
The vascular endothelium is crucial in regulating biological functions such as haemostasis. However this layer is often impaired in cardiovascular diseases. Understanding the evolution of vascular remodelling is therefore of great importance and may provide insights for the development of novel interventions. Here we present the use of in vivo MRI and vascular ultrasound in combination with ex vivo electron microscopy for extensive characterisation of the events involved in vascular remodelling following balloon angioplasty of the rat carotid artery over a 28 day follow-up period.
14:00 2853. New Insights Into Ruptured Plaques: Enhanced Detection of Neovasculature and Fibrous Tissue by MRI
Alkystis Phinikaridou1, Kevin J. Hallock1, Ye Qiao1, James A. Hamilton1
1Boston University, Boston, Massachusetts, USA
We used the Constantinides New Zealand White rabbit model to study atherosclerosis and controlled plaque rupture associated with thrombosis. We combined contrast enhanced (Gd-DTPA) in vivo (3T) and magnetization transfer (MT) ex vivo (11.7T) MRI coupled to histology to identify features associated with vulnerable plaques. In vivo, Gd-DTPA uptake was associated with plaque regions rich in neovasculature as well as fibrous tissue. Ex vivo MT identified the location of fibrous cap rupture and fibrosis seen within organized thrombi. Further studies about the kinetics of Gd-DTPA within plaques together with the in vivo application of MT will provide insights about plaque vulnerability.
Enhancement of the Atherosclerotic Plaque and the Vessel Wall of the
Carotid Artery After Injection of a Blood-Pool Contrast Agent
Sietske Rozie1, Piotr A. Wielopolski1, Mohamed Ouhlous1, Wiro Niessen, Theo van Walsum, Aad van der Lugt1
1Erasmus Medical Center, Rotterdam, Netherlands
Purpose: We hypothesized that a blood-pool agent enhances the outer wall of the carotid artery and specific parts of the atherosclerotic carotid plaque
Methods: We studied 26 atherosclerotic plaques of 15 consecutive patients with severe carotid stenosis. On a 3.0T scanner a 3DT1-weighted scan was performed before injection and 20 minutes after injection.
Results: The mean enhancement on the 20 minute delay scan was 40.9% ± 32.5% in the non-calcified part of the plaque and 60.0% ± 21.7% in the vessel wall of the symptomatic carotid arteries.
Conclusions: Images obtained before and after contrast injection with Vasovist® may improve atherosclerotic plaque characterisation and quantification.
15:00 2855. In Vivo and ex Vivo plaque Characterisation in the Aortic Arch of ApoE -/- Mice with High-Resolution Multi-Parametric Magnetic Resonance Imaging at 17.6 Tesla
Gert Klug1, Volker Herold1, Marco Parczyk1, Elisabeth Bauer1, Thomas Schulze-Till1, Eberhard Rommel1, Peter Jakob1, Wolfgang Bauer1
1University of Wuerzburg, Wuerzburg, Germany
High-Resolution plaque imaging in atherosclerotic apoE knock-out (-/-) mice has been recently shown to correlate closely with histology. However these results are limited to the aortic-root. We intended to further enhance the ability of high-field magnetic resonance (MR) to characterize plaque formation in murine models of atherosclerosis at microscopic levels. Our results demonstrate that high resolution multi-parametric plaque imaging at 17.6 Tesla is feasible with good correlation to HE histology but further studies are necessary to distinguish plaque components compared to a more comprehensive histology protocol.
15:30 2856. Molecular Imaging of Atherosclerosis Using Paramagnetic Cy5.5-Labeled PEG-Micelles
Sjoerd Hak1, Geralda A.F. van Tilborg1, Esad Vucice2, Gustav J. Strijkers1, Klaas Nicolay1, Zahi A. Fayad2, Willem Jan Menno Mulder2
1Eindhoven University of Technology, Eindhoven, Netherlands; 2Mount Sinai School of Medicine, New York, New York, USA
In this study a new contrast agent for molecular imaging of atherosclerosis was used, paramagnetic Cy5.5-labeled PEG-micelles. The targeting ligand used was the RGD-peptide. In vivo MRI and ex vivo fluorescence techniques demonstrated active uptake of RGD-PEG-micelles into atherosclerotic plaque in apoE-knockout mice. The near infrared Cy5.5 fluorophore proofed to be very valuable for ex vivo fluorescence imaging as there is less autofluorescence and better penetration at higher wavelengths. The non-specific uptake of bare PEG-micelles in mouse plaques was very limited. This makes this contrast agent very attractive for molecular imaging of atherosclerosis, also when directed to other targets.
Cardiac Image Processing
13:30 2857. Real-Time Cardiovascular Imaging Using a Combination of HYPR, McKinnon-Bates, and COM Gating Algorithms
Lauren A. Keith1, Dana C. Peters, Julia V. Velikina1
1University of Wisconsin - Madison, Madison, Wisconsin, USA
We use a combination of the HYPR and McKinnon-Bates algorithms along with center of mass self-gating in order to improve spatial resolution, signal-to-noise ratio and reduce artifact levels in real-time cardiovascular imaging.
14:00 2858. Characteristics and Performance of the Karhunen-Loeve Transform Filter in Dynamic Cardiac Magnetic Resonance Imaging
Yu Ding1, Yiu-Cho Chung2, Subha V. Raman3, Orlando P. Simonetti3
1The Ohio State University, Columbus, Ohio, USA; 2Siemens Medical Solutions, Inc., Columbus, Ohio, USA; 3The Ohio State University, Columbus, Ohio, USA
We describe the characteristics and performance of a new temporal filter based on the optimal linear transform, the Karhunen-Loeve Transform. The filter is designed to suppress noise in dynamic cardiac MR images without compromising the sharpness of stationary or moving edges or other structures. We derive a simple mathematical formula for the noise reduction effect of this filter, and then verify it in real-time cardiac cine MRI with TSENSE acceleration factor 4 in normal volunteers. A SNR gain of 144% was achieved after filtering without edge blurring or other artifacts.
14:30 2859. Dyadic Wavelet-Based Image Noise Suppression and Enhancement in High-Speed Cardiac MR Parallel Acquisition
Qi Duan1, Jian Chen1, Andrew Francis Laine1, Vinay M. Pai2
1Columbia University, New York, New York, USA; 2SUNY Upstate Medical University, Syracuse, New York, USA
An automated integrated denoising/enhancing approach was applied to images acquired by parallel acquisition techniques in cardiac imaging. In comparison with previous denoising only framework, this new proposed method could future increase the CNR of the denoised images. Quantitative evaluation on phantom and clinical data confirmed the benefit of this new method in terms of improving CNR on parallel MR images. Preliminary results suggested that this new integrated denoising/enhancing framework could further push the limits on the temporal resolution by improving the SNR and CNR simultaneously.
15:00 2860. 3D Right Ventricular Strain and Geometry in Pulmonary Hypertension and Normals
Bharath Ambale1, Steven Lloyd2, Thomas Stewart Denney Jr.1, Louis Dell'Italia2, Raymond Benza2, Himanshu Gupta2
1Auburn University, Auburn, Alabama, USA; 2University of Alabama at Birmingham, Birmingham, Alabama, USA
Accurate assessment of right ventricular (RV) function is clinically important particularly in pulmonary hypertension (PHTN). Compared to the left ventricle (LV), however, analysis of RV function is relatively difficult. Unlike the LV, the RV does not have geometric symmetry, precluding use of simple geometric models to calculate RV volumes and wall stress. Also, in PHTN, higher systolic blood pressure in the RV can cause excursion of the interventricular septum into the LV cavity. As a result, the LV cavity can also lose its geometric symmetry. This abstract presents methods for reconstructing three-dimensional biventricular geometry and strain in both normal volunteers and PTN patients.
13:30 2861. Direct Quantification of 3-D Myocardial Principal Strain Orientations: A New Insight Into Heart Regional Function Abnormality
Khaled Zakarya Abd-Elmoniem1, Matthias Stuber1, Amr A. Youssef1, Tetsuo Sasano1, Theodore P. Abraham1, Xiaofeng Lui1, Sandeep Mullur1, Evert-Jan P. A. Vonken1, M. Roselle Abraham1, Jerry L. Prince1
1The Johns Hopkins University, Baltimore, Maryland, USA
We present afast algorithm for direct and complete characterization of 3-D time-course of principle strain orientations using data acquired with zHARP imaging protocol from SA slices without the need for LA data. Using this scheme, two or more SA slices are acquired and processed using zHARP and the 3-D strain tensor and principal strain angles are calculated. Results from infarct swine model shows that strain orientations time-course can provide more information about heart dynamics, especially when combined with efficient 3-D motion imaging.
14:00 2862. Quantification of Myocardial Strain at Early Systole in Mouse Heart: Restoration of Undeformed Tagging Grid with Single Point HARP
Wei Li1, Jia Zhong2, Xin Yu2
1Case Western Reserve University, Cleveland , Ohio, USA; 2Case Western Reserve University, Cleveland, Ohio, USA
Current MRI tagging analysis often employs the first tagging image as the reference frame. However, for a mouse heart, the first tagging image is frequently acquired at early systole with significant tag line deformation due to fast heart rate. In this study, a HARP-based method was develop to generate an undeformed tagging grids. Myocardial deformation at early systole was analyzed using this method.
14:30 2863. Noise Measurement in Real-Time Cardiac Cine MRI Using Eigenvalues of Karhunen-Loeve Transform
Yu Ding1, Yiu-Cho Chung2, Subha V. Raman3, Orlando P. Simonetti3
1The Ohio State University, Columbus, Ohio, USA; 2Siemens Medical Solutions, Inc., Columbus, Ohio, USA; 3The Ohio State University, Columbus, Ohio, USA
Noise measurement is difficult in real-time cine MRI using parallel acquisition techniques because of cardiac and respiratory motion and the spatially variant nature of both signal and noise. In this work, we investigate using eigenvalues derived from the Karhunen-Loeve Transform to assess mean noise standard deviation in dynamic MR cardiac images. This method may have general application in the evaluation of dynamic imaging methods, and other situations other methods of noise measurement are difficult to apply.
15:00 2864. DENSE-MR-Elastography for Cardiac Application
Benjamin Robert1, Ralph Sinkus1, Jean-Luc Gennisson1, Mathias Fink1
1Laboratoire Ondes et Acoustique, Paris, France
Imaging of mechanical shear waves via MR-Elastography (MRE) allows the assessment of inherent viscoelastic tissue parameters. Cardiac MRE poses several technical challenges: small relaxation times, time dependant viscoelastic properties during the heart beat, respiratory motion. To overcome the short relaxation time and the externally induced mechanical wave problems, a MRE sequence has been adapted from a DENSE sequence.
MRA -Other Techniques
13:30 2865. Increased Volume of Coverage for Abdominal Contrast-Enhanced MRA with 2D Autocalibrating Parallel Imaging: Initial Experience at 3.0T
Darren Lum1, Reed Busse2, Christopher Francois1, Anja Brau3, Philip Beatty3, Joshua Huff1, Jean Brittain2, Scott Reeder1
1University of Wisconsin - Madison, Madison, Wisconsin, USA; 2GE Healthcare, Madison, Wisconsin, USA; 3GE Healthcare, Menlo Park, California , USA
We utilize a 2D parallel imaging method (Autocalibrating Reconstruction for Cartesian sampling - ARC) with 3D contrast enhanced MRA for complete abdominal coverage within a breath hold. An intra-individual comparison study between both parallel imaging accelerated and non-accelerated exams was performed in 6 healthy volunteers. In addition 8 consecutive patients were evaluated with 2D-ARC MRA. We find that the subjective image quality of exams with 2D-ARC to be essentially equivalent to those acquired without parallel imaging. However, the 2D-ARC sequence provided a 3.5 fold increase in imaging volume and a 30% reduction in voxel size in the same acquisition time.
14:00 2866. Whole-Body MR Angiography with Parallel Imaging Benefit of a Dedicated 32 Channel Whole-Body MR Scanner Equipped with a Matrix Coil System at 1.5 and 3.0 Tesla
Harald Kramer1, Konstantin Nikolaou1, Henrik J. Michaely2, Christian Glaser1, Maximilian F. Reiser1
1University Hospitals Munich - Grosshadern Campus, Munich, Germany; 2University Hospital Mannheim, Mannheim, Germany
Atherosclerosis is a systemic vessel disease. MRI offers the possibility of whole body MRA with excellent image quality and without ionizing radiation. First attempts to WB MRA suffered from MR system Hardware restrictions, recent developments in MR Hard- and Software like parallel imaging, dedicated coil systems and higher field strength helped to increase image quality of WB MRA exams significantly.
14:30 2867. Comparison of Scoutless EZ-STEP and Conventional Contrast Enhanced Magnetic Resonance Angiography in Thoracic Aorta at 3T
Xiaohai Ma1,2, Zhaoqi Zhang1, Yi He1, Zhanming Fan1
1Beijing Anzhen Hospital, Beijing, People's Republic of China; 2Michigan State University, East Lansing, USA
Compared to conventional CE-MRA, EZ-STEP is a timesaving method for thoracic aorta imaging in 3T MR scanner, and also provides comparable image quality.
15:00 2868. Calculating Peripheral MRA Bolus Timing Using Cine-Phase Contrast Flow Measurements
Grace Choi1, Ryan Brown1, Minh Chao1, Yi Wang1, Martin R. Prince1
1Cornell University - Weill Cornell Medical College, New York, USA
Total Gadolinium dose can be reduced on whole body and peripheral MRA by using 2D cine phase contrast MRA to calculate bolus velocity at 7 locations along the arterial tree. Accuracy of this approach was confirmed by comparison to bolus transit measurements from 1.8s temporal resolution time-resolved MRA. Example cases show diagnostic peripheral MRA with single dose gadolinium based contrast agent. These data also show a 2-fold reduction in bolus transit time with venous compression applied to thighs.
Time-resolved (YD) MRA
13:30 2869. High Spatial and Temporal Resolution MRA of the Entire Peripheral Vascular System Using a New 3D Time-Resolved MRA Technique (TWIST)
Florian M. Vogt1, Stefan Maderwald1, Knut Kroeger1, Gerhard Laub2, Randall Kroeker3, Joerg Barkhausen1, Harald H. Quick1
1University Hospital, Essen, Germany; 2University of California Los Angeles, Los Angeles, California , USA; 3Siemens Medical Solutions, USA
Purpose was to develop a triple injection scan protocol for dynamic, high-resolution, isotropic MRA of the entire peripheral vascular system applying a recently developed time-resolved 3D MRA sequence (TWIST). Ten patients with PAD underwent contrast-enhanced MRA collecting dynamic 3D data sets at three consecutive stations. Catheter-based DSA served as standard of reference. For corresponding segments, the number of visible segments was equal to DSA. TWIST MRA provided identical functional information in regions with reduced arterial blood flow or increased venous enhancement. TWIST-MRA is a robust technique that combines functional with high spatial morphological information of the entire peripheral vascular system.
14:00 2870. Leg MR Angiography with Cuff-Compression: Quantitative Dynamic Analysis
Marcel Koenigkam Santos1, Puneet Sharma1, Bobby Kalb1, John Oshinski1, Diego Martin1
1Emory University, Atlanta, USA
The purpose of this study is to evaluate quantitatively the effect of mid-femoral cuff compression on arterial inflow and venous outflow kinetics using high temporal resolution 3D CE-MRA of the calves. The arterial in-flow time was significantly reduced on the pressure cuff side in comparison to the control side and, in 2 of 4 subjects, no increased signal (above background) was observed in the veins with the pressure cuff after 300 seconds. Our findings quantitatively evaluate the delay in venous filling and indirectly show that this results from multi-factorial events that occur subsequent to supravenous-subarterial blood pressure cuff inflation.
14:30 2871. Cartesian Acquisition with Projection-Reconstruction-Like Sampling (CAPR): An Optimum Sequence for Time-Resolved CE-MRA
Clifton R. Haider1, Houchun Harry Hu2, Nobert G. Campeau1, John Huston1, Stephen J. Riederer1
1Mayo Clinic, Rochester, Minnesota, USA; 2Univ. of Southern California, California , USA
In time-resolved acquisitions there is a need for both high temporal and spatial resolution. The purpose of this work is to describe the incorporation of 2D SENSE acceleration into a view-shared CArtesian Projection Reconstruction-like (CAPR) acquisition, yielding a time-resolved sequence which has high SNR robustness, a high level of consistency, and high temporal fidelity. The sequence is capable of 1 mm3 isotropic resolution with sufficient temporal resolution to distinguish intracranial arterial and venous phases of contrast passage in whole-brain angiography.
15:00 2872. Comprehensive Magnetic Resonance Imaging of Hands Vasculature at 3 Tesla: Preliminary Clinical Results
Ugur Bozlar1,2, Patrick T. Norton1, Ahmed Mohamed Housseini1,3, Thomas Huerta1, Hendricks E. Daniel1, Bobby Chhabra1, David B. Drake1, Peter B. Arnold1, Klaus D. Hagspiel1
1University of Virginia Health System, Charlottesville, USA; 2Gulhane Military Medical Academy, Ankara, Turkey; 3Suez Canal University, Ismailia , Egypt
Comprehensive MR evaluation of the vasculature of the hand employing high resolution time resolved contrast enhance MRA (tr-ceMRA) and volume interpolated breath-hold examination (VIBE) was performed in patients with clinical symptoms attributable to vascular etiologies. This combine complimentary approach requires a single 20ml administration of contrast agent and utilizes the power of arterial-venous separation provided by the tr-ceMRA and high contrast to noise ratio of the VIBE sequence to allow for assessment of both proximal and distal arterial vessels of the hand. To the best of our knowledge, there is no published study which evaluates the hand vasculature at 3T in such a population.
13:30 2873. 4D Dynamic Contrast Enhanced MRA of the Pulmonary Vasculature with Isotropic Resolution Using a Combination of GRAPPA and TWIST Acceleration
Robert C. Gilkeson1,2, Martin Blaimer3, Randall Kroeker4, Gerhard Laub4, Jeffrey L. Duerk1,2, Jeffrey L. Sunshine1,2, Robert O. Schilz2, Mark A. Griswold1,2
1Case Western Reserve University, Cleveland, Ohio, USA; 2University Hopitals of Cleveland, Cleveland, Ohio, USA; 3University of Wuerzburg, Wuerzburg, Germany; 4Siemens Medical Solutions, Germany
14:00 2874. Time-Resolved 3D MR-Angiography of the Thoracic Aorta at 3 Tesla: Comparison of First-Pass Imaging Characteristics of a Low Albumin-Binding and a Blood-Pool Contrast Agent
Alex Frydrychowicz1, Maximilian F. Russe1, Aurélien F. Stalder1, Alexander Berger1, Andreas Harloff1, Raoul Arnold1, Mathias Langer1, Jürgen Hennig1, Michael Markl1
1University Hospital Freiburg, Freiburg, Germany
Gadofosveset trisodium has reached approval for diagnostic purposes in Europe as the first gadolinium-based blood-pool contrast agent. Its imaging characteristics have not been fully evaluated with respect to imaging at 3T and during time-resolved 3D MR-angiography. Therefore, it was the purpose of this study to compare the first-pass imaging characteristics of a blood-pool contrast agent (BPA) to a low albumin-binding standard contrast agent (SCA) in time-resolved contrast-enhanced 3-dimensional MR angiography (tr-CE-MRA) at 3T. Results show that first-pass imaging characteristics of the blood-pool agent are equally well suited for tr-CE-MRA at 3T.
14:30 2875. Contrast-Enhanced MR Angiography Using Time-Resolved Interleaved Projection Sampling Along the 3D Cartesian Phase and Slice Encodings (TRIPPS)
Jiang Du1, Nick Pinto1, Michael S. Middleton1, Claude Sirlin1, Graeme M. Bydder1
1University of California, San Diego, San Diego, California , USA
Contrast-enhanced three-dimensional (3D) magnetic resonance angiography (CE-MRA) is a useful noninvasive method for evaluating the vascular system. Time-resolved imaging is of great importance in providing contrast dynamics and eliminating contrast timing. Here we present a novel technique called time-resolved interleaved projection sampling along the 3D Cartesian phase and slice encodings (TRIPPS), which is robust and provides high spatial and temporal resolution 3D images with minimal undersampling artifact.
15:00 2876. The Effect of Time-Resolved K-Space Sampling on Contrast-Enhanced MRA: A Method to Optimize Imaging Parameters
Ting Song1, Pippa Storey2, Qun Chen2, Henry Rusinek2, Ruth Lim2, Andrew F. Laine1, Vivian S. Lee2
1Columbia University, New York, New York, USA; 2NYU School of Medicine, New York, New York, USA
We have analyzed k-space sampling strategies for time-resolved MRA by studying the effects of varying (a) the center area of k-space assumed to be fully sampled and (b) the sampling density of k-space periphery. Outcome measures consist of vessel ringing artifacts and diameter measurement accuracy. Overall, we observed that for smaller vessels, higher sampling density of k-space periphery is more important than the size of the fully sampled center area, while for larger vessels, larger center areas gave better accuracy of diameter resolving ability.
13:30 2877. Controlled Experimental Study Depicting Moving Objects in View-Shared Time-Resolved 3D MRA
Petrice Marie Mostardi1, Clifton R. Haider1, Phil J. Rossman1, Stephen J. Riederer1
1Mayo Clinic, Rochester, Minnesota, USA
The purpose of this work was to develop and use a computer-controlled motion phantom for study of the fidelity with which 3D time-resolved sequences with view-sharing can portray dynamic phenomena. This allowed determination not only of such properties as ghosting, blurring, and undesired vascular enhancement, but also the fidelity of portraying a rapid influx of contrast into a vessel as well as the smooth passage of contrast across an extended field of view. These studies helped to identify desirable characteristics of a pulse sequence used for time-resolved studies.
14:00 2878. Three-Dimensional Time-Resolved Flow Quantification with Balanced SSFP
Francesco Santini1, Stephan G. Wetzel2, Klaus Scheffler1
1University of Basel/University Hospital, Basel, Switzerland; 2Basel University Hospital, Basel, Switzerland
Balanced SSFP sequences do not suffer from spin saturation effects that result in signal loss for tissues with long T1. Their contrast is therefore optimal for the imaging of fluids (blood and CSF) and flow quantification, especially when inflow enhancement effects cannot be exploited, as in three-dimensional sequences. In this work, a three-dimensional, three-directional time-resolved phase contrast bSSFP sequence is presented, along with methods to minimize the artifacts commonly associated with bSSFP sequences, and the application to the study of cerebro-spinal fluid circulation is demonstrated.
14:30 2879. Femoral Artery Compression in the Adductor Canal During Isometric Thigh Contraction Using a Rapid 3D Steady-State Free Precession Acquisition
Ryan Brown1,2, Thanh Nguyen1, Martin R. Prince1, Yi Wang1,2
1Weill Medical College of Cornell University, New York, USA; 2Weill Graduate School of Medical Sciences of Cornell University, New York, USA
A rapid 3D steady-state free precession (SSFP) sequence was implemented to image the femoral artery. A long section (15-20 cm) of artery was imaged during isometric thigh contraction to analyze artery compression. Sufficient resolution and contrast to visualize the artery lumen were achieved in a short scan time (approximately 22 sec), which was required for minimal motion artifacts during thigh contraction. Significant artery compression was observed in the adductor canal region, while the artery was less disturbed inferior and superior to the adductor canal.
15:00 2880. Quantification of Hemodynamics in Abdominal Aortic Aneurysms During Rest and Exercise Using Magnetic Resonance Imaging and Computational Fluid Dynamics
Andrea Seba Les1, Carlos Alberto Figueroa1, Mary Therese Draney Blomme1, Maureen M. Tedesco1, Jinha M. Park1, Adrianne Thompson1, Ronald L. Dalman1, Robert J. Herfkens1, Charles A. Taylor1
1Stanford University, Stanford, California , USA
We hypothesize that exercise may slow the growth of abdominal aortic aneurysms (AAAs). A gadolinium-enhanced magnetic resonance angiography sequence (MRA) was used to image the aortas of three males with small AAAs using a 1.5T scanner. Infrarenal and supraceliac aortic blood velocities were also measured using a cardiac-gated phase contrast (PC-MRI) sequence. Blood flow was simulated by solving the Navier-Stokes equations on finite-element meshes generated from the MRA and using rest and exercise boundary conditions specified from the PC-MRI data. Mean wall shear stress was calculated at four locations. Infrarenal volumetric flow waveforms obtained from simulation and PC-MRI were compared.
Animal Cardiovascular Imaging
13:30 2881. Multiple-Mouse Self-Gated Cardiac Cine MRI with Multiple Arrays of Receive Coils (MARCs)
Emilio Esparza-Coss1, Marc Stephen Ramirez1, James Andrew Bankson1
1The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA
Simultaneous multiple-animal, self-gated cardiac cine MRI has been shown to drastically improve the imaging efficiency in small animal models of cardiac disease. Here we propose that further improvements can be achieved by dedicating a phased-array coil to each animal to increased SNR and achieve parallel imaging acceleration. Self-gated cardiac cine data was acquired with a four-channel spoiled gradient echo pulse sequence developed to acquire navigator information before application of readout gradients. Preliminary results indicate that accelerated self-gated cardiac cine MRI using phased-array coils is both feasible and desirable since SNR enhancement can be achieved by averaging oversampled data.
14:00 2882. Microembolization Contributes to Acute and Subacute Left Ventricular Dysfunction: MR Assessment of Left Ventricular Function and Strain
Marcus Carlsson1, Alastair J. Martin1, Mark Wilson1, Loi Do1, David Saloner1, Maythem Saeed1
1University of California San Francisco, San Francisco, California , USA
Microembolization causes microinfarction in patients with unstable angina pectoris and following PCI and CABG. It thought to explain part of decreased ejection fraction in patients. In this study, microembolization was simulated by selective injection of embolic agents in LAD. Cine and tagging MR imaging was used to assess the acute and subacute effects of microembolization on LV volumes, ejection fraction, systolic wall thickening and strain. Cine MRI showed persistent decline in wall thickening and strain associated with increased LV volumes and decreased EF; markers of LV remodeling. Thus, microembolization could be the cause of LV dysfunction in patients.
14:30 2883. Self-Gated MR Cardiac Imaging of Developing Chick Embryos in the Egg
William Matthew Holmes1, Christopher McCabe1, Barrie Condon1, Jim M. Mullin1, Maureen M. Bain1
1University of Glasgow, Glasgow, UK
The chick embryo is a well-known animal model for cardiovascular research. The lack of MRI application to chick embryos is partly due to the difficultly of monitoring chick ECG and respiration signals, which are conventionally essential in acquiring images free of motion artefact. In this study we remove these obstacles by employing a self-gated multi-slice CINE MRI protocol that incorporates a navigator-based retrospective gating technique, making possible for the first time cardiac MRI images of a chick embryo inside the egg.
15:00 2884. Retrospective Gating Strategies for Small Animal MR Imaging at 9.4 Tesla
S David Smith1,2, Shams Rashid3, Mark Wagshul3, Mei Yu1, Helene Benveniste1,3
1Brookhaven National Laboratory, Upton, New York, USA; 2SA Instruments, Inc, Stony Brook, New York, USA; 3SUNY at Stony Brook, Stony Brook, New York, USA
A Data acquistion system with application software has been developed allowing the retrospective reodering of acquired MR data prior to reconstruction, and is used for the Cardiac Imaging of mice on a 9.4 T Bruker MRI system. Waveforms for respiratory, Electrocardiogram, Blood pressure and Peripheral pulse measurements were acquired simultaneously to the MRI acquisiton, thereby allowing the same MRI dataset to be reconstructed using reodering schemes based upon each of the different physiological waveforms. Quantitative evaluation of the cine images made using each of the monitoring waveforms is presented. Advanced strategies refining the reordering using data from multiple waveforms is also presented.
13:30 2885. MRI Tagging of in Vivo Ventricular Function Reflects Histological and Cellular Changes in α-Dystrobrevin Knockout Mice
Wei Li1,2, Wei Liu3, Allen Ye4, Priyanajana Chaudhuri4, Suhanti Banerjee4, Xin Yu,24
1Case Western Reserve University, Cleveland , Ohio, USA; 2Cleveland, Ohio, USA; 3Philips Research North America, Bariarcliff Manor, New York, USA; 4Case Western Reserve University, Cleveland, Ohio, USA
Dystrophin-glycoprotein complex (DGC) maintains the structural integrity of myocardium. It also plays important signaling roles through nNOS. α-Dystrobrevin deficiency leads to nNOS displacement from DGC, leading to the development of cardiac lesions at an older age. In the current study, the impact of impaired DGC signaling and the development of cardiac lesions on in vivo ventricular function was examined with MRI tagging in α-dystrobrevin knockout mice. Potential mechanisms responsible for altered ventricular function were explored by histological and cellular studies.
14:00 2886. Functional Cardiac Phenotyping of Vasoactive Intestinal Peptide (VIP) Deficient Mice by MR Microscopy
S. David Smith1, Anthony Szema2, Sami I. Said2, Helene Benveniste1,2
1Brookhaven National Laboratory, Upton, New York, USA; 2Stony Brook University, Stony Brook, New York, USA
Mice with deletion of the gene for VIP exhibit spontaneous pulmonary arterial hypertension (PAH) and vessel remodeling in the absence of hypoxemia with pathology showing thickened pulmonary vessels. We hypothesized that VIP deficient mice with known spontaneous PAH would also develop a decreased functional capacity of their right ventricle. We tested this hypothesis using MR microscopy. Quantitative analysis of cardiac MR microscopy images of VIP deficient mice revealed dilated right ventricles and reduced ejection fractions.
14:30 2887. Effect of Iron Oxides on Tag MRI at 1.5T in a Rat Myocardial Infarct Model
Jean-Luc Daire1, Jean-Noel Hyacinthe1, Karin Montet-Abou1, Jean-Pascal Jacob1, Denis Morel1, Jean-Paul Vallée1, Xavier Montet1
1Geneva University Hospital, Geneva, Switzerland
This paper proves that despite high accumulation of iron oxides in myocardium infarct, Tag MRI at 1.5T can be realized and analysed in small rodent. The observed defect of contraction in circumferential strains corresponds to the hypointense region containing iron oxides.
15:00 2888. A Spiral K-Space Trajectory Enables Phase Contrast Measurements of Blood Flow in Curved Sections of the Mouse Aorta
Robert L. Janiczek1, Brett R. Blackman1, R. Jack Roy1, Scott T. Acton1, Craig H. Meyer1, Frederick H. Epstein1
1University of Virginia, Charlottesville, Virginia , USA
Conventional rectilinear k-space trajectories can result in displacement artifacts due to movement of spins between excitation and data acquisition, and signal loss due to phase dispersion. Spiral trajectories have long been used for human MRI due to their desirable flow characteristics caused by their short echo-times and low gradient moments. However, these methods have yet to be applied to imaging small animals on high-field small-bore MRI systems. We present phase-contrast data at 7T in the mouse aorta and demonstrates these advantages allow PC data to be obtained in more regions of the mouse vasculature than a rectilinear trajectory.
Effect of SEA0400 on Cardiac Mn2+ Efflux Rates, Using T1-Mapping
Manganese-Enhanced MRI (MEMRI) in a Murine Model [Not Available]
Ben Waghorn1,2, Yuhui Yang2, Brianna Klein2, Akemichi Baba3, Toshio Matsuda3, Nathan Yanasak2, Tom Hu2
1Georgia Institute of Technology, Augusta, Georgia, USA; 2Medical College of Georgia, Augusta, Georgia, USA; 3Osaka University, Osaka, Japan
The Na+/Ca2+ exchanger (NCX) is an important transporter for the regulation of intracellular Ca2+ concentration. This study uses T1-mapping of murine cardiac Manganese-Enhanced MRI to quantitatively assess the rate of signal decay post Mn2+ infusion. A 50% attenuation of the signal in the left ventricular free wall, normally enhanced by Mn2+, is observed within approximately 2.5 hours post infusion. By inhibiting the NCX with SEA0400, we can proceed to characterize a trend of Mn2+ efflux modulation. Future work to study the actions of the NCX in detail will be undertaken using various pharmaceutical agents.
Non-Contrast Enhanced MRA
13:30 2890. The Non-Contrast-Enhanced Hepatic MR Angiography with True Steady-State Free-Precession and Time Spatial Labeling Inversion Pulse: Optimization of the Technique and Preliminary Results
Kotaro Shimada1, Hiroyoshi Isoda2, Tomohisa Okada2, Yoji Maetani2, Shigeki Arizono2, Yuusuke Hirokawa2, Toshikazu Kamae2, Kaori Togashi2
1Kyoto University Graduate School of Medicine , Kyoto, Japan; 2Kyoto University Graduate School of Medicine, Kyoto, Japan
Our purpose is to delineate the hepatic arteries selectively by using respiratory-triggered three-dimensional true steady-state free-precession with time spatial labeling inversion pulse (T-SLIP). T-SLIP is a kind of arterial spin labeling which can provide quantitative and selective inflow information by placing the inversion pulse at any place independent of the imaging area before data acquisition and suppress background signal. 21 healthy volunteers were examined. As a result, selective and high contrast visualization of the hepatic arteries was acquired in 20 cases without exogenous contrast agent. We report our initial experience and describe the optimization of this protocol.
14:00 2891. Renal Artery MRA at 3.0T: Initial Clinical Experience with Respiratory-Triggered Non-Contrast-Enhanced Phase Contrast with Vastly Under-Sampled Isotropic Projection Reconstruction (PC-VIPR)
Darren Lum1, Christopher Francois1, Kevin Johnson1, Scott Reeder1, Oliver Wieben1, Thomas Grist1
1University of Wisconsin - Madison, Madison, Wisconsin, USA
In this study, we present our initial clinical experience with respiratory-triggered, non-contrast enhanced PC-VIPR MRA of the abdominal vessels at 3.0T. We demonstrate comparable image quality between PC-VIPR and 3D contrast enhanced MRA. Furthermore, PC-VIPR provides improved conspicuity of the segmental renal arteries due to the subtraction of stationary background tissues. Finally, we find good agreement between the two techniques for measurements of vessel diameter. In patients who cannot receive contrast secondary to the risk of nephrogenic systemic fibrosis, PC-VIPR may serve as an alternative to abdominal 3D contrast enhanced MRA. Further validation and optimization of this technique is ongoing.
14:30 2892. ECG Triggered Acquisition Non-Contrast Enhanced (TRANCE) MRA at 3.0Tesla in Peripheral MRA
Takeshi Ishimoto1, Takayuki Ikeda1, Naomi Yamamoto1, momoe Kawakami1, Masaru Ishihara2, Eiji Okamoto3, Tomoyuki Okuaki4
1Hyogo Brain and Heart Center, Himeji, Japan; 2Hyogo Prefectural Kakogawa Hospital, Kakogawa, Japan; 3Philips Electronics Japan, LTD., Osaka, Japan; 4Philips Electronics Japan, LTD., Minato-ku, Japan
Recently, non-contrast enhanced MRA techniques were clinically useful and widely use in routine examination, rapidly gaining in clinical importance. The purpose of this study was to evaluation the technical feasibility and clinical utility of ECG triggered acquisition Non-Contrast Enhanced (TRANCE) MRA at 3.0Tesla in patients with peripheral vascular disease. In peripheral MRA, TRANCE MRA at 3.0Tesla provided diagnostic images comparable with those of CTA and DSA without the administration of contrast agent. This technique will be noninvasive standard examination in the diagnosis of peripheral vascular disease as well as 1.5Tesla.
Visualization of the Lenticulostriate Artery with Flow-Sensitive
Black-Blood Imaging in Comparison with Time-Of-Flight MR Angiography [Not Available]
K. Gotoh1, T. Okada1, Y. Miki1, M. Ikedo2, A. Ninomiya2, T. Kamae1, K. Togashi1
1Kyoto University Graduate School of Medicine, Kyoto, Japan; 2Toshiba Medical Systems, Ohtawara, Japan
We visualized lenticulostriate arteries (LSAs) by using Flow-sensitive Black Blood (FSBB) method, which is a variant of 3D-FE (field echo) and make it possible to attenuate the signal of arteries by applying very weak motion probing gradients to disturb refocusing of moving spins only. We compared FSBB with TOF on visualzed LSAs of 19 volunteers and had good results.
Non-Contrast-Enhanced MR Portography Using 3D Inversion Recovery-In Flow
Iterative Spatial Saturation Pulses (IR-IFIS) Steady-State Free Precession
(FIESTA) [Not Available]
Motoyuki Katayama1, Takayuki Masui1, Kimihiko Sato1, Hidekazu Seo1, Megumi Ishii1, Masayoshi Sugimura1, Kazuhiko Ito1, Mitsuharu Miyoshi2, Naoyuki Takei2, Tetsuji Tsukamoto2
1Seirei Hamamatsu General Hospital, Hamamatsu, Japan; 2GE Yokogawa Medical Systems. Ltd, Hino, Japan
We optimized the parameters of IFIS FIESTA technique in normal volunteer, and applied this technique to the MR examinations in patients with hepatobiliary disorder. The non-contrast-enhanced 3D IR-IFIS FIESTA technique provides good image quality MR portography. When gadolinium is not usable, this sequence might be an alternative choice of method.
14:00 2895. T1 Insensitive Background Saturation by Two Inversion Pulses for Flow-Prep Non-Contrast-Agent MR Angiography
Mitsuharu Miyoshi1, Naoyuki Takei1, Tetsuji Tsukamoto1
1GE Yokogawa Medical Systems, Hino, Japan
Flow-Preparation-pulse (Flow-Prep) is a preparation pulse that enhances flow signal and suppresses stationary signal. This is used for Non-Contrast-Agent MRA in this study. However, the stationary background signals remain because of T1 relaxation between the Flow-Prep preparation and the data acquisition. Although T2-Prep and Spectral IR can suppress the kidney and the fat signals, short-T1 intestinal contents remain high signal background. We developed Flow-Prep with two IR pulses, which enabled T1 insensitive background suppression. Aorta and renal artery signals were depicted in high contrast. Intestinal contents, kidney and fat signals were suppressed homogeneously.
14:30 2896. Using Phase Contrast MRA for the Diagnosis of Pelvic Congestion Syndrome
Luis Andres Meneses1,2, Cristian Tejos1,3, Mario Fava1, Marcelo Andia1,3, Moshe Pincu4, Jorge Cifuentes4, Pablo Irarrazaval1,3
1Pontificia Universidad Catolica de Chile, Santiago, Chile; 2Biomedical Imaging Center, Santiago, Chile; 3Biomedical Imaging Center, Santiago, Chile; 4Hospital Sotero del Rio, Santiago, Chile
In Pelvic congestion syndrome (PCS) ovarian veins (OV) is characterized by abnormal blood flow. We evaluated the accuracy of flow velocity (measured with PC-MRA) as a diagnostic criterion. We studied 16 OV with PC-MRA and with direct venography (DV) as a reference test. PC-MRA showed the same results as DV for the 12 pathological veins. PC-MRA correctly identified 2 of the 4 normal veins. We believe that in the 2 cases with discrepancy, PC-MRA could to detect an early stage of the PCS which DV could not to identify. PC-MRA provides useful diagnostic tools for the diagnosis of PCS.
Non-Contrast MRA Using ECG-Triggered 3D Valuable Flip Angle Fast Spin
Echo for the Vessels of the Pelvis and Legs with Total Imaging Matrix Coil [Not Available]
Satoru Kitano1, Shinji Hirohashi2, Nagaaki Marugami1, Junko Takahama1, wataru higashiura1, Toshiaki Taoka1, Kimihiko Kichikawa1
1Nara Mediacl University, Kashihara, Japan; 2Osaka gyoumeikan Hospital, Osaka, Japan
The purpose of this study is to clearly 3D valuable flip angle TSE with Tim (Total imaging matrix) array coil system can be applied to 3D non contrast body MRA. 5 patients underwent 3D non contrast body MRA in a three step table feed technique. Pelvic, femoral and lower leg MRA were obtained ECG-triggered 3D valuable flip angle TSE (space). 3D non-contrast MRA with Tim coil system is a promising technique in the diagnosis of the arterial vascular system of the vessels of the pelvis and legs.
Non-Contrast MRA with FIESTA Using IR-IFIS for Selective Visualization
the Renal Arteries [Not Available]
Takayuki Masui1, Motoyuki Katayama1, Kimihiko Sato1, Hidekazu Seo1, Kazuhiko Ito1, Hiroki Ikuma1, Masayoshi Sugimura1, Naoyuki Takei2, Mitsuaharu Miyoshi2, Tetsuji Tsukamoto2, Megumi Ishii1, Akihiko Kutsuna1
1Seirei Hamamatsu General Hospital, Hamamatsu, Japan; 2GEYMS, Hino, Japan
Non-contrast MRA for the aorta and renal arteries was obtained using respiratory-triggered peripheral-gated 3D FIESTA with Inversion recovery-In Flow Iterative Spatial Saturation pulse (IR-IFIS), based on tagging of the blood in the heart and thoracic aorta, which is running through the abdominal aorta, with background suppression by non-selective inversion pulse. The optimal parameters for normal volunteers were evaluated and the abdominal aorta and renal arteries were successfully visualized. In the patients with suspected renal tumors, contrast MRA provide still better information of the aorta and renal arteries, non contrast MRA has potentials to visualize the selected arteries of interest.
14:00 2899. Non-Enhanced MR Angiography of the Uterine Vessels; Optimization of the Sequence Parameters
Takashi Koyama1, Tomohisa Okada2, Koji Fujimoto2, Toshikazu Kamae2, Ayako Niyomiya3, Saori Satou3, Nobuyasu Ichinose3, Kaori Togashi2
1Kyoto University Hospital, Kyoto, Japan; 2Kyoto University, graduate school of medicine, Kyoto, Japan; 3Toshiba Medical Systems, Tokyo, Japan
The purpose of this study is to evaluate the difference of depiction and contrast of the uterine vessels in different inversion time in non-enhanced MRA utilizing Time-SLIP. Nonenhanced Time-SLIP MRA was performed in eight healthy volunteers combining separately with SSFP and FASE at different TI times. With FASE, images the difference of contrast between arteries and veins dose not significantly differ, although images with longer TI tend to show better depiction of the uterine veins. With SSFP, TI of 1800ms provides best depiction of the both arteries and veins, and best contrast between them.
Non-Contrast Time-Resolved 2D Fresh Blood Imaging (FBI) [Not Available]
Mitsue Miyazaki1,2, Toshiro Fukuta2, Girish Srinivasan1, Robert Anderson3, nobuyasu Ichinose2, Shinichi Kitane4
1Toshiba Medical Research Institute, Vernon Hills, USA; 2Toshiba Medical Systems Corp., Otawara, Japan; 3Toshiba Medical Research Institute, Ohio, USA; 4Toshiba Medical Engineering Co., Japan
With the recent association of gadolinium contrast agent and nephrogenic systemic fibrosis (NSF) disease, there is growing interest in using non-contrast MRA techniques as alternatives for contrast enhanced (CE) MRA. As a result, there have been many non-contrast MRA techniques reported. However, many of studies were limited to the morphology of the vessel lumen. In this study, a new non-contrast time-resolved MRA technique, using a keyhole technique and parallel imaging, is proposed to shorten scan time. Furthermore, assessment of the proposed technique was investigated to obtain the peripheral arterial hemodynamic information.
Non-Contrast MRA of the Toes Using Time-Spatial Labeling Inversion Pulse
(Time-SLIP) and Optimization of Flow-Spoiled Gradient Pulses for the Assessment
of Foot Arteries in Flow-Spoiled Fresh Blood Imaging (FBI) [Not Available]
Jun Isogai1, Mitsue Miyazaki2, Takeshi Shimada1, Hideo Hatakeyama1, Takashi Yamada1, Naoto Matsuo1, Shizuaki Maejima1, Kenji Yodo3, Tomoko Miyata3
1Hasuda Hospital, Hasuda, Japan; 2Toshiba Medical Research Institute USA, Illinois, USA; 3Toshiba Medical Systems Corporation, Japan
Visualization of small arteries of the foot and toes is quite difficult in using conventional non-contrast MR angiography (MRA) techniques, including time-of-flight (TOF) and phase contrast MRA, due to tortuous vessels out of plane and slow velocity. In addition, Gadolinium-enhanced MRA has also several problems on an injection rate or the amount of contrast materials. Due to the recent concerns of Gadolinium-related Nephrogenic Systemic Fibrosis (NSF), non-contrast MRA solutions have gained interest. Non-contrast flow-spoiled fresh blood imaging (FBI) and time-spatial labeling inversion pulse (time-SLIP) were investigated for visualization of small arteries of the foot and toes.
FBI-Navi for Easy Determination of Diastolic and Systolic Triggering Phases
in Non-Contrast Fresh Blood Imaging (FBI) [Not Available]
Naoyuki Furudate1, Mitsue Miyazaki,12
1Toshiba Medical Systems, Otawara, Japan; 2Toshiba Medical Research Institute USA, Vernon Hills, USA
Due to the recent association of gadolinium contrast agent dose and nephrogenic systemic fibrosis (NSF) disease, there have been increasing interests in MRA examination using non-contrast MRA techniques as alternatives. Cardiac gated FSE-based flow-spoiled fresh blood imaging (FS-FBI), allows separation of arteries from veins in peripheral MRA. To find the suitable systolic and diastolic delays, single-slice multiple phases (ECG-prep) images are acquired. However, the determination of systolic and diastolic triggering delays can be problematic. In this study, we propose a new software algorithm, (FBI-Navi), to determine the diastolic and systolic trigger delays to reduce the operational burden.
Optimization of Non-Contrast Renal MRA Using a TI-Prep Scan for
Time-Spatial Labeling Pulse (Time-SLIP) in 3D Balanced SSFP [Not Available]
Junji Takahashi1, Yoshinori Tsuji1, Yusuke Hamada1, Takashi Yoshida1, Sachiko Isono2, Ayako Ninomiya2, Yoshimori Kassai3, Mitsue Miyazaki,34
1Toranomon Hospital, Tokyo, Japan; 2Toshiba Medical Systems, Tokyo, Japan; 3Toshiba Medical Systems Corp., Otawara, Japan; 4Toshiba Medical Research Institute USA, Vernon Hills, USA
Non-contrast-enhanced renal 3D MRA using time-spatial labeling inversion pulse (time-SLIP) is presented to depict the renal arteries. The contrast between the renal arteries and background signals was best visualized with a black blood inversion time (BBTI) of around 1100 msec. However, the depiction of the smaller renal branches depends on the flow speed in patients. We have applied a 2D BBTI preparation scan, which provides a series of single shot images with different BBTI times, prior to the 3D scan. Good correlation was obtained between the 2D BBTI preparation scan and 3D scan in both volunteers and patients.
The Value of CINE Bright Blood Sequences in the Evaluation of
Larry Allen Kramer1, Eduardo J. Matta2, Anuradha T. Rao2, Durga K. Pai2, Khader M. Hasan2
1University of Texas-Houston, Houston, USA; 2UT-Houston, Houston, USA
Magnetic Resonance Venography (MRV) of the pelvic venous system is utilized to evaluate for occult pelvic venous thrombosis in patients with crytogenic stroke. Echocardiographic evidence of a right to left shunt and negative clinical exam or lower extremity venous doppler study results in investigation of the pelvic venous system with MRV. Because of tortuosity of the pelvic venous system and valves flow artifacts are common. To improve specificity CINE bright blood sequences were utilized to evaluate flow defects seen on the conventional 2D time-of-Flight gradient-echo sequences. Our results show that CINE sequences readily distinguishes clot from flow artifact.
15:00 2905. Accelerated 3D Phase-Contrast MR Angiography Using Time-Interleaved Autocalibration (TCAL)
Anja C.S. Brau1, Wei Sun2, Philip J. Beatty1
1GE Healthcare, Menlo Park, California , USA; 2GE Healthcare, Waukesha, Wisconsin, USA
This work demonstrates the feasibility of time-interleaved autocalibration (TCAL) for improving the imaging efficiency of accelerated 3D PC MRA. By sharing the calibration burden across velocity-encoding measurements, TCAL reduces the calibration time penalty by 4x while retaining robustness to motion and compatibility with PC reconstruction.
13:30 2906. Non-Contrast Enhanced Renal Artery Angiography with a Respiratory Gated 3D Radial Linear Combination SSFP Sequence
Jessica L. Klaers1, Kevin M. Johnson1, Christopher Francois1, Ethan K. Brodsky1, Youngkyoo Jung1, Oliver Wieben1, Walter F. Block1
1University of Wisconsin - Madison, Madison, USA
An ultrashort TR dual-echo 3D radial Linear Combination SSFP (LCSSFP) sequence is used in conjunction with a novel real-time adaptive expiratory respiratory gating method for high resolution renal non-contrast enhanced MRA. This is especially applicable for use in patients with renal insufficiency in the wake of the recent discovery of the link between Nephrogenic Systemic Fibrosis (NSF) and Gd based contrast agents. The promising initial results give excellent depiction of the renal arteries, including branch vessels, not typically seen in contrast enhanced exams.
14:00 2907. Phase Contrast Stack of Stars Imaging
Steven Kecskemeti1,2, Kevin M. Johnson1, Oliver Wieben1, Charles Mistretta1,2
1University of Wisconsin , Madison, Wisconsin, USA; 2University of Wisconsin - Madison, Madison, Wisconsin, USA
A hybrid radial-Cartesian stack of stars(SOS) phase contrast (PC)method has been developed to overcome some of the limitations of conventional Cartesian based PC acquisitions, such as long scan times and artifacts from cardiac pulsatility and intravoxel dephasing. The PC SOS method can be undersampled without aliasing artifact or a loss of resolution as in the Cartesian method, thereby reducing scan times. In addition, the distributed nature and low frequency over sampling of this sequence reduces cardiac pulsatility artifacts. We present results comparing the PC SOS images to those obtained with a clinical Cartesian PC sequence.
14:30 2908. Non Contrast MRA of Renal Transplant Vasculature Using 3D TrueFISP
Natasha Berg1, John Joseph Sheehan1, Xiaoming Bi2, Peter J. Weale2, Randall Ramsay1, Renate Jerecic2, James C. Carr1
1Northwestern University, Chicago, Illinois, USA; 2Siemens Medical Solutions, Chicago, Illinois, USA
Contrast enhanced Magnetic Resonance Angiography (CEMRA) has previously been considered a safe alternative to CTA or conventional angiography in the assessment of the renal transplant patient. However, non contrast techniques may be more desirable in this population due to renal impairment. We examined a novel non contrast MRA (NCMRA) technique using a 3D True FISP sequence with selective inversion pulse to assess the renal vasculature in post-transplant patients. The NCMRA technique demonstrated equivalent and superior imaging of post-transplant vasculature compared to CEMRA. This technique may be clinically advantageous for renal transplant patients who are unsuitable candidates for contrast administration.
15:00 2909. Clinical Evaluation of IR Prepared 3D TrueFISP for Non-Contrast Abdominal Angiography - A Comparison to Ce-MRA
Peter J. Weale1, Natasha Berg2, John Sheehan2, Randall Ramsay2, James Carr2, Renate Jerecic1, Xiaoming Bi1
1Siemens Medical Solutions, Chicago, Illinois, USA; 2Northwestern University, Chicago, Illinois, USA
A qualitative and quantitative comparison in patients referred for MRA of a non-contrast approach to abdominal angiography using a 3D IR prepared TrueFISP sequence with a selective IR preparation with spatial localization independent from the imaging volume.
Myocardial Function: Human Studies
13:30 2910. Strain Encoding MRI (SENC) for the Quantification of Regional Ventricular Function in Pulmonary Arterial Hypertension
Monda L. Shehata1,2, Lynette Brown1, Dirk Lossnitzer3, Jens Vogel-Claussen1, Joao A. C. Lima1, Reda E. Girgis1, Paul M. Hassoun1, David A. Bluemke1, Nael F. Osman1
1Johns Hopkins University, Baltimore, USA; 2Ain Shams University, Cairo, Egypt; 3Universty of Heidelberg, Heidelberg, Germany
Right ventricular function evaluation and monitoring are considered important prognostic factors in many cardiac and/or pulmonary disorders especially pulmonary arterial hypertension (PAH)which eventually leads to RV dysfunction and failure. CMR is a versatile tool for global and regional ventricular function evaluation. Tagging has been used for LV function quantification . However, in RV, this technique is limited by thin wall. Strain encoding (SENC)MR is a technique that applies tags parellel to the imaging plane with narrow tag spacing yielding high spatial resolution images. Using 3T MRI, 5 PAH patients were imaged using SENC to quatify regional longitudinal strain (ELL) in RV and interventricular septum and we compared them to 6 healthy controls. Reduced ELL was noted at anterior RV free wall and septum (p<0.05). SENC MR can provide a rapid tool for RV function quantification and monitoring in PAH patients.
14:00 2911. Imaging Cardiac Motion and Flow Simultaneously During Exercise Stress Studies Using SPAMM N' EGGS
Smita Sampath1, John Andrew Derbyshire1, Maria J. Ledesma-Carbayo, Elliot R. McVeigh1
1National Institutes of Health, Bethesda, Maryland, USA
Detecting myocardial mechanical dysfunctions and trans-valvular flow abnormalities during the stress of exercise provides early diagnostic indicators in patients with valvular diseases. Since these events are transient in nature, the ability to acquire these measurements simultaneously is important. In this study, we apply a new MR imaging technique called SPAMM n EGGS (spatial modulation of magnetization acquisitions with encoded gradients for gauging speed), that combines tagging and phase-contrast imaging principles to provide simultaneous measurements of longitudinal left ventricular compression and trans-mitral chamber blood velocity during exercise stress studies in normal volunteers.
14:30 2912. Evaluation of CSPAMM with Steady State Free Precession for Myocardial Tagging at 3T
Jean-Noel Hyacinthe1, Jean-Luc Daire, Joost P.A. Kuijer2, Magalie Viallon1, Pierre-Frederic Keller1, Pierre Croisille3, Jean-Paul Vallée1
1Geneva University Hospital, Geneva, Switzerland; 2VU University Medical Center, Amsterdam, Netherlands; 3Université Claude Bernard lyon 1, Lyon, France
Imaging at 3T, using CSPAMM and/or SSFP are efficient means to improve myocardial tagging. In this study we evaluate the combination of all of them in 6 volunteers and 10 patients. CSPAMM with balanced SSFP at 3T combines gain of absolute CNR from the field strength with improved relative tag contrast, easing thus the post processing, and sensitivity to typical SSFP banding artefacts is drastically reduced. Moreover, the technique shows no loss of accuracy in strain measurements, and an accurate diagnosis was performed in patients.
15:00 2913. Real-Time Cine Imaging at Peak Exercise Stress with a 32-Channel Cardiac Array, TGRAPPA, and Karhunen-Loeve Image Filtering
Mihaela Jekic1,2, Yu Ding2, Eric Foster1,3, Subha V. Raman1,2, Orlando P. Simonetti1,2
1The Ohio State University, Columbus, USA; 2Dorothy M. Davis Heart and Lung Research Institute, Columbus, USA; 3Dorothy M. Davis Heart and Lung Research Institiute, Columbus, USA
Rapid heart rates and heavy breathing associated with exercise stress testing demand higher temporal resolution than is attainable by current methods. Our standard exercise stress protocol utilizes a 12-channel coil and parallel acceleration rate 4, resulting in temporal resolution of approximately 52 msec, but further gain in temporal resolution is desired. We investigated the performance of real-time cardiac imaging immediately after maximal treadmill exercise by the combined application of a 32-channel cardiac array coil, TGRAPPA rate 5 acceleration, and KLT filtering, and quantitatively compared SNR to our standard method. We successfully increased temporal resolution to 43.7 msec without compromising spatial resolution or SNR.
13:30 2914. Image Based Real-Time Monitoring of Cardiac Parameters for Stress Testing or Interventions
Corinna S. Maier1,2, Peter Kellman3, Michael Bock2, Wolfhard Semmler2, Christine H. Lorenz4
1Siemens Corporate Research, Princeton, New Jersey, USA; 2German Cancer Research Center (dkfz), Heidelberg, Germany; 3National Institutes of Health, Bethesda, Maryland, USA; 4Siemens Corporate Research, Baltimor
The proposed framework provides a method for real-time monitoring and detecting changes for regional and global ejection fraction (EF) and heart rate (HR) during a cardiovascular intervention or dobutamine stress test under MRI. Basal, mid and apical MRI left ventricular (LV) short axis images are acquired. End systolic and end diastolic volumes are estimated in each heart cycle based on the results of an Expectation-Maximization segmentation algorithm. EF and HR are calculated continuously, are corrected and smoothed and a change detection algorithm is applied. Estimated EF and HR are compared to the offline calculated EF and the recorded ECG, respectively.
14:00 2915. Left Ventricular Internal Flow in Patients with Dyssynchronous Heart Failure: Quantification by Cine MRI
Brandon K. Fornwalt1,2, Patrick C. Gonzales1, Jana G. Delfino1,2, Robert L. Eisner1,3, Angel R. León1,3, John N. Oshinski1,2
1Emory University, Atlanta, Georgia, USA; 2Emory/Georgia Institute of Technology, Atlanta, Georgia, USA; 3The Carlyle Fraser Heart Center, Atlanta, Georgia, USA
Better methods to quantify left ventricular dyssynchrony are needed to identify candidates for cardiac resynchronization therapy (CRT). Dyssynchrony creates abnormal displacement of blood within the left ventricle, and this internal flow may represent the most direct measure of dyssynchrony. We hypothesized that internal flow could be quantified from cine-MRI and would be increased in patients undergoing CRT compared to controls. Systolic internal flow was 21±10% in 10 patients and 2±2% in 10 controls (p<0.001). A threshold systolic internal flow of 6% discriminated patients from controls with 100% accuracy. MRI-based quantification of ventricular internal flow may be useful in diagnosing dyssynchrony.
14:30 2916. Saturation-Band Cine MRI Improves Detection of Intracardiac Shunt
Wiphada Patricia Bandettini1, Andrew Ernest Arai1
1National Institutes of Health, Bethesda, Maryland, USA
Saturation-bands interleaved with gradient echo cine MRI provides tagged blood, but its use in the assessment of congenital intracardiac shunt has been limited. The technique is easily implemented and can be added to a standard congenital imaging protocol. The purpose of this study was to demonstrate the utility of adding a saturation pulse to gradient recalled echo cine MRI to assist in the identification and anatomic delineation of intracardiac shunts.
15:00 2917. Assessment of Left Ventricular Volume and Mass at 3.0T Using SSFP and FLASH Cine Imaging
Neil Woodhouse1, Dan Hagger1, Jim M. Wild1
1University of Sheffield, Sheffield, UK
SSFP is the accepted standard for cine imaging of cardiac function at 1.5 T. Recent work at 3T suggests SSFP offers increased contrast to noise ratio (CNR) over spoiled gradient echo methods (FLASH). Left ventricular (LV) measurements were evaluated at 3.0T using SSFP and FLASH sequences in 6 healthy volunteers. Significant differences in both mass and volume were demonstrated between both imaging methods. FLASH systematically overestimated mass and underestimated volume (p<0.05) when compared to SSFP although it was significantly lees affected by magnetic susceptibility artefact. FLASH appears to be the more robust sequence at 3.0T despite having a lower CNR.
MRA Contrast Agents
13:30 2918. High Resolution Arterial MRA of the Lower Limb by Hybrid K-Space Reconstruction Before and After Administration of Vasovist Bloodpool Constrast Agent
Egbert Gedat1, Rainer Kirsch2, Mojgan Mohajer1, Bernhard Meyer1, Bernd Frericks1
1Charité Universitätsmedizin Berlin, Berlin, Germany; 2Siemens Medical Solutions, Erlangen, Germany
High resolution CE MRAs of the lower limb were acquired in the steady state phase after administration of bloodpool contrast agent gadofosveset trisodium. To remove the veins and facilitate the assessment of the arteries they were computationally combined with first pass image volumes by replacing central k-space. 18 patients were examined yielding resulting MIPs of the lower limbs arteries of good quality for 8 patients. The veins were mostly removed and the high resolution was preserved. For the other patients either the distribution of the contrast agent was inappropriate or patient motion had occurred.
14:00 2919. MR Phlebography with a Blood Pool Contrast Agent in Patients with Peripheral Arterial Occlusive Disease
Guido Matthias Kukuk1, Dariusch Reza Hadizadeh1, Markus Moehlenbruch1, Kai Wilhelm1, Arne Koscielny1, Frauke Verrel1, Hans Heinz Schild1, Winfried Albert Willinek1
1University of Bonn, Bonn, Germany
Contrast-enhanced MR angiography is routinely used for evaluation of peripheral arterial occlusive disease (PAOD). The introduction of the intravascular contrast agent Gadofosveset Trisodium allows for longer acquisition times with high T1 relaxivity resulting in higher spatial resolution imaging of both arteries and veins during the steady state phase. 139 patients were referred to MRA for evaluation of PAOD at 1.5T. In 46/139 patients (33%) we incidentally found clinically relevant venous diseases including deep vein thrombosis, varicosis or arteriovenous fistula. In conclusion, the combination of MRA and MR phlebography appears to be a promising clinical application for blood pool contrast agents.
14:30 2920. Gadofosveset-Enhanced Steady State MRA of the Peripheral Vessels with Dixon Fat-Saturation
Henrik Jakob Michaely1, Ulrike I. Attenberger2, Harald Kramer2, Maximilian F. Reiser2, Stefan O. Schoenberg1
1University Hosptial Mannheim, Mannheim, Germany; 2University of Munich, Munich, Germany
In this study the feasibility and image quality of a two-point Dixon MRA during the steady state after the injection of gadofosveset was compared to a MRA with conventional spectral fat-saturation. Using the Dixon technique a significantly higher SNR and CNR were achieved due to a more homogenous fat-suppression than with spectral fat-suppression.
15:00 2921. Comparison of Renal MRA and Angiography Data in the CORAL Study
Honglei Zhang1, Alan Matsumoto2, Timothy Murphy, Don Cutlip3, Katie Wade3, Christopher J. Cooper4, Lance Dworkin5, Martin R. Prince1
1Weill Medical College of Cornell University, New York, New York, USA; 2Virginia University, USA; 3Harvard Clinical Research Institute, USA; 4University of Toledo College of Medicine, Toledo, Ohio, USA
Fifty-five renal MRAs were reviewed by MRA core lab for randomization in to CORAL study, of which 26 (47%) were diagnosed as having > 60% stenosis. For the 7 randomized to balloon angioplasty and stent therapy, angiography confirmed that MRA correctly identified 8 lesions as hemodynamically significant with an accuracy of 100%. In 35 MRAs with local reports, MRA readings by coral lab were consistent with the readings by local radiologist in 19 patients (54%). These included 15 positive studies and 4 negative studies. In the remaining 16 patients, local radiologists overestimated the severity of renal artery stenoses.
13:30 2922. Whole Heart Coronary MR Angiography Acquired with 32-Channel Cardiac Coils for the Detection of Coronary Artery Disease
Motonori Nagata1, Hajime Sakuma1, Nanaka Ishida1, Tairo Kurita1, Yoko Mikami1, Hiroshi Nakajima1, Katsuya Onishi1, Masaaki Ito1, Kan Takeda1
1Mie university hospital, Tsu, Japan
Use of 32 channel coils allows for acquisition of whole heart coronary MRA in a reduced imaging time and with high study success rate, which resulted in considerably improved overall detection rate of CAD in subjects who underwent coronary MRA.
14:00 2923. Signal-To-Noise Ratio Enhancement in Coronary MRA Using Parallel Imaging
Jing Yu1, Michael Schär1, Evert-jan P.A. Vonken1, Sebastian Kelle1, Matthias Stuber1
1Johns Hopkins University, Baltimore, Maryland, USA
Coronary MRA with short acquisition windows is limited by SNR. We propose a method to enhance SNR based on parallel imaging in conjunction with a reduced number of radiofrequency excitations while the scanning time remains unchanged. A practical method to quantify SNR on images obtained with parallel imaging was developed as well. Numerical simulations predict that the SNR gain using the proposed method is greatest for very short acquisition windows. These theoretical findings are in good agreement with in vitro and in vivo results obtained in this study.
14:30 2924. Contrast-Enhanced MR Angiography: A Helpful Methodology to Detect Coronary Atherosclerotic Plaque
Xihai Zhao1,2, Xin Liu3, Liuquan Cheng2, Li Yang2, Zulong Cai2, Chun Yuan1
1Vascular imaging lab. , Seattle, Washington, USA; 2deparment of radiology, Beijing, People's Republic of China; 3Departments of Radiology, Chicago, Illinois, USA
This study focus on using contrast-enhanced MR angiography to improve the SNR and CNR of MR images and to increase the detection rate of coronary atherosclerotic plaque.
15:00 2925. Contrast-Kinetics-Resolved Whole-Heart Coronary MRA Using 3DPR
Peng Lai1, Feng Huang2, Sonia Nielles-Vallespin3, Xiaoming Bi4, Andrew C. Larson1, Renate Jerecic4, Debiao Li1
1Northwestern University, Chicago, Illinois, USA; 2Invivo Corporation, Gainesville, Florida, USA; 3Siemens AG Medical Solutions, Erlangen, Germany; 4Siemens Medical Solutions, Chicago, Illinois, USA
In contrast-enhanced coronary MRA, a bolus scan is usually necessary to estimate the transit time from contrast injection to peak arterial enhancement. However, optimal timing of data acquisition often remains elusive due to variations of heart rates and respiratory gating efficiency as well as simultaneous myocardial enhancement. In this work a contrast-kinetics-resolved technique using 3DPR was developed which eliminates the tedious planning task and enables retrospective selection of the optimal coronary artery visualization for different coronary artery segments. Also, the center-k-space magnitude change could be used to approximate contrast kinetics during a scan, enabling automatic selection of optimal time frames.
13:30 2926. Contrast-Enhanced Coronary MR Angiography with Gd-DTPA Slow Infusion
Liuquan Cheng1, Tao Li1, Haiyue Ju1, Xihai Zhao1,2, Yuangui Gao1, Yi Wang3
1Chinese PLA General Hospital, Beijing, People's Republic of China; 2Northwestern University Medical School, Chicago, USA; 3Weill Medical College of Cornell University, New York, USA
The navigator-gated FIESTA coronary MRA was acquired during the slow infusion of Gd-DTPA. The SNR and image quality could be improved and it is more accurate than the non-contrast study in stenosis detection.
14:00 2927. Breath-Hold Whole-Heart Coronary MR Angiography (CMRA) by 2D-Parallel Acquisition Compared with Respiration-Gated CMRA Using a Multi-Element Body Coil
Tomohisa Okada1, Shotaro Kanao1, Shigehide Kuhara2, Ikuo Aoki2, Ayako Ninomiya2, Saori Satou2, Toshikazu Kamae1, kimio Gotoh1, Kaori Togashi1
1Kyoto University Graduate School of Medicine, Kyoto, Japan; 2Toshiba Medical Systems Corporation, Ohtawara, Japan
The multi-element phased-array body coil is now widely available in clinical practice. It has capability of 2D-parallel imaging, which may largely reduce scan time. This study investigated the attainable quality of coronary MRA in breath-hold (BH) compared with respiration-gated (RG) CMRA. Examination of 14 healthy subjects resulted in scan time reduction approximately from 12 minutes to 34 seconds. The average quality score of visualization (0-4) was reduced by 0.93, however, proximal segments (#1-2, #5-7, #11) showed average scores over 2, which was considered usable for clinical evaluation.
14:30 2928. Whole Heart Coronary Vein Imaging
Christian Stoeck1,2, Dana C. Peters2, Yuchi Han2, Beth Goddu2, Warren J. Manning2, Sebastian Kozerke3, Reza Nezafat2
1ETH Zurich, Zurich, Switzerland; 2Beth Israel Deaconess Medical Center Harvard Medical School, Boston, Massachusetts, USA; 3Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
Transvenous BiV lead implantation in cardiac resynchronization (CRT) therapy is preferred to surgical placement. However, for the transvenous approach, knowledge of the coronary vein anatomy is needed prior or during the implantation procedure. Recent studies showed the strength of cardiovascular MR in assessing coronary vein anatomy. In this study we investigated the use of MT-SSFP whole heart imaging to assess coronary vein anatomy.
15:00 2929. 2D Spin-Labeling Coronary MR-Angiography with Cartesian and Radial K-Space Sampling
Marcus Katoh1,2, Matthias Stuber3, Arno Buecker1, Rolf W. Gunther2, Elmar Spuentrup2,4
1University Hospital Saarland, Homburg, Germany; 2RWTH Aachen University Hospital, Aachen, Germany; 3Johns Hopkins University Medical School, Baltimore, Maryland, USA; 4University Hospital Köln, Köln, Germany
3D spin-labeling coronary MR-angiography (cMRA) allows selective visualization of the coronary arteries. This technique is limited by a long scanning time as two 3D data sets must be subtracted. In this study, the value of a 2D approach was investigated. The coronary arteries of 8 volunteers were imaged on a 1.5 T MR-system using a navigator-gated and cardiac-triggered 2D SSFP cMRA sequence with Cartesian and radial k-space sampling. 2D spin-labeling cMRA allowed for selective visualization of the left and right coronary system within a minute. Radial k-space sampling proved to be superior with respect to artifact suppression, SNR, CNR and vessel border definition.
Contrast-Enhanced Myocardial Perfusion Imaging
13:30 2930. Free Breathing Myocardial Perfusion Using Navigator Slice Tracking and TSENSE
Bryan Kressler1, Pascal Spincemaille2, Thanh D. Nguyen2, Jonathan W. Weinsaft2, Martin R. Prince2, Yi Wang1
1Cornell University, Ithaca, USA; 2Weill-Cornell Medical College, New York, USA
Conventional contrast enhanced myocardial perfusion imaging relies on a prolonged breath hold to eliminate respiratory motion. However, the contrast enhancement time course may be too long for patients to successfully suspend respiration, resulting in breathing motion and rendering image analysis difficult. In this work, navigator slice tracking is applied to myocardial perfusion, eliminating the need to perform breath holding and enabling acquisition of the entire contrast enhancement time course with minimal breathing motion. TSENSE acquisition and processing are applied to increase the number of slices that can be acquired. The technique is demonstrated in healthy volunteers and patients.
14:00 2931. Dual Bolus Myocardial Stress Perfusion Quantification in Normals
Yi Wang1,2, Raphael Hazel1, Bin Luo1, Marguerite Roth1, Jing Han1, Nathaniel Reichek1,2
1St. Francis Hospital, Roslyn, New York, USA; 2SUNY, Stony Brook, New York, USA
We studied Fermi model-based quantitative perfusion quantification methods in dual bolus myocardial adenosine stress perfusion and evaluated their absolute perfusion values at different dose in 16 normal volunteers. The results showed significant difference in average perfusion values both under stress (5.64 ml/min/g) and at rest (2.30 ml/min/g) at 0.05mM/kg standard contrast dose versus stress perfusion (2.07 ml/min/g) and rest perfusion (0.69 ml/min/g) when 0.005mM/kg contrast dose blood signal was used as the arterial input function. However, their flow reserves both dual bolus or standard dose only were significantly associated and their means were close (2.49 at SD versus 2.31 at DB). The flow reserve values showed good correlation with subject age and are consistent with PET findings in normals.
14:30 2932. First-Pass Myocardial Perfusion: Comparison Between Full-Dose Hybrid-EPI and Half-Dose Balanced-SSFP
Peter D. Gatehouse1, Chiara Bucciarelli-Ducci, Jonathan C. Lyne, David N. Firmin, Dudley J. Pennell
1Royal Brompton Hospital, London, UK
Comparisons of these sequences at the same dose have shown abundant myocardial SNR for myocardial perfusion balanced SSFP compared to hybrid-EPI, but with more dark-rim subendocardial artefact in bSSFP. This study compared the two sequences for stress perfusion in 8 subjects, using reduced contrast agent dose for bSSFP to reduce one potential source of artefact (B0 distortion). While myocardial SNR with bSSFP remained equivalent or superior to hEPI, dark-rim artefact also occurred in normal segments more frequently in half-dose bSSFP than full-dose hEPI.
15:00 2933. Myocardial Magnetic Resonance Stress Perfusion Imaging at 3T Using a 1-Molar Contrast Agent
Bernhard Daniel Klumpp1, Christina Doesch1, Achim Seeger1, Joerg Doering1, Tobias Hoevelborn1, Ulrich Kramer1, Michael Fenchel1, Andreas May1, Claus D. Claussen1, Stephan Miller1
1Eberhard-Karls-University of Tuebingen, Tuebingen, Germany
Myocardial stress perfusion MR imaging (MRSPI) at 1.5T is limited by low SNR. This can be compensated by an increase of field strength and contrast agent concentration. Aim of our study was the evaluation of MRSPI at 3T using a 1-molar contrast agent. MRSPI was assessed in 57 patients with suspected coronary artery disease (CAD) using a 2D sr GRE sequence (0.1 mmol Gadobutrol / kg BW). Standard of reference was invasive coronary angiography. Sensitivity for coronary artery stenoses >70% was 97%, specificity 81%, diagnostic accuracy 93%. MRSPI under such optimized conditions provides increased sensitivity / specificity for CAD.
13:30 2934. Myocardial Perfusion Quantification: Effects from Contrast Dose, Imaging Plane and Sequence
Yi Wang1,2, Raphael Hazel1, Bin Luo1, Marguerite Roth1, Jie Jane Cao1, Nathaniel Reichek1,2
1St. Francis Hospital, Roslyn, New York, USA; 2SUNY, Stony Brook, New York, USA
The quantification of myocardial perfusion using MRI is an important research and clinical tool for evaluating ischemia. However, its dependence to contrast dosages, imaging sequences and imaging orientation has not been thoroughly investigated. We studied 14 normal volunteers using a dual bolus approach with 3 different sequences to acquire perfusion images in both long and short axis, and evaluated the regional absolute perfusion values. The objective of this study was to determine whether the resting perfusion quantification using the dual bolus approach is dependent on the MRI pulse sequence or imaging plane orientation.
14:00 2935. Value of First Pass Perfusion and Delayed Contrast Enhancemed MR Imaging in Detecting Microinfarction: Histopathologic Confirmation
Marcus Carlsson1, David Saloner1, Alastair J. Martin1, Loi Do1, Juha Koskenvuo1, Maythem Saeed1
1University of California San Francisco, San Francisco, California , USA
Coronary microembolization is a frequent complication of coronary interventions. We determined the effects of microembolization on perfusion and visualization of microinfarction 1hr and 1week after delivery of embolic agents. First pass perfusion and delayed contrast enhanced (CE) MR imaging was used to non-invasively monitor the serial changes in regional perfusion and viability. Histopathology was used to confirm the presence of microinfarction. The embolic agents were visualized in coronary tree surrounded by microinfarction. Acute and subacute microinfarction showed perfusion deficit. CE-MR imaging delineated subacute microinfarction due to the loss of membrane integrity of ischemic myocytes, but not all discrete acute microinfarction.
14:30 2936. Multislice Single Shot Spin Echo EPI Perfusion Imaging with Zone-Selection and Parallel Imaging
Pedro Ferreira1, Peter Gatehouse2, David Firmin1, Chiara Bucciarelli-Ducci1, Ricardo Wage2
1Imperial College, London, UK; 2Royal Brompton Hospital, UK
Myocardial perfusion images are often affected by a subendocardial Dark Rim Artifact (DRA). A sequence has been designed with the underlying ethos of greater robustness against the DRA, by reducing the echo train length and nulling the signal in the left ventricle blood pool. The sequence is a single-shot spin-echo EPI with zonal excitation and parallel imaging techniques.
Preliminary results show no evidence of myocardial dephasing, or distortion by cardiac motion or field nonuniformity during first pass of contrast agent; although TSENSE is proving challenging to include with saturation recovery due to low SNR.
15:00 2937. Compressed Sensing Cardiac Perfusion Imaging
Viton Vitanis1, Robert Manka1,2, Urs Gamper1, Peter Boesiger1, Sebastian Kozerke1
1ETH Zurich, Zurich, Switzerland; 2German Heart Institute Berlin, Berlin, Germany
This work demonstrates the feasibility of accelerating perfusion imaging using Compressed Sensing and compares the method to k-t SENSE. Based on computer simulations and actual in-vivo measurements it is shown that Compressed Sensing yields lower reconstruction errors up to a net acceleration factor of three. Beyond this factor k-t SENSE outperforms with respect to root-mean-square reconstruction error. The lower error is, however, associated with some temporal low pass filtering of signal-intensity curves. In conclusion, both methods tested seem suitable to accelerate cardiac perfusion imaging up to net acceleration factors of five without compromising signal-intensity perfusion curves significantly.
13:30 2938. First-Pass Cardiac Perfusion MRI with 50%-Reduced Contrast Agent Dosage
1New York University, New York, New York, USA
While first-pass cardiac perfusion MRI is a promising modality for the assessment of coronary artery disease, there are safety concerns associated with Gadolinium-based MRI contrast agents, especially in patients with renal insufficiency. One strategy to reduce the contrast agent dosage is to achieve maximal myocardial contrast-to-noise ratio (CNR) through pulse sequence optimization and trade off a portion of CNR to reduce the dosage. The purpose of this study is to optimize the pulse sequence with optimal k-space trajectory and variable flip angles to achieve comparable image quality at 50%-reduced dosage to that produced by a convention sequence at standard dosage.
14:00 2939. Perfusion Phantom for Quantitative Imaging
Behzad Ebrahimi1,2, Scott D. Swanson, Timothy E. Chupp,2
1University of Michigan, Ann Arbor, USA; 2Focus Center, Ann Arbor, USA
A perfusion phantom with unique features and a wide variety of applications in MR and other imaging modalities is presented. The phantom is especially suited to tissue perfusion simulation with diffusible and non-diffusible MR tracers. A network of micro-channels in the scale of actual capillaries replicates the blood flow in tissues. Using microfabrication technique, networks with any desired pattern can be generated. Since the geometry of networks is known, flow rate, delay, dispersion and other fluid parameters can be exactly calculated, using finite elements numerical methods. These calculated results can be used to investigate the accuracy of experimental measurements and the precision of mathematical models.
14:30 2940. Quantitative Assessment of the Dark Rim Artifact in First Pass Perfusion Images: Effect of Stress and Rest, and Sequence Dependence
Raphael Delano Hazel1, Nathaniel Reichek1, Yi Wang1
1St Francis Hospital, Roslyn, New York, USA
Dark Rim Artifact (DRA) in Gadolinium enhanced saturation recovery TrueFISP cardiac first pass perfusion images from normal volunteers collected during stress and rest, show similar frequency affecting 12.5% of the rest and 10.2% of stress images, with comparable severity represented by signal loss of 32.9 % (rest) and 31.5 % (stress) in the endocardium. The duration and severity of the DRA coincides with the maximum contrast agent concentration and susceptibility difference between LV and myocardium. A comparison of three pulse sequences shows that TrueFISP is most affected by the DRA, followed by TFL while EPI shows no artifact.
15:00 2941. The Relationship Between Signal Intensity and Myocardial Gadolinium Concentration for Three MR Perfusion Pulse Sequences: Implications for Measuring Absolute Myocardial Blood Flow
Daniel C. Lee1,2, Nils P. Johnson1, Kathleen R. Harris1
1Northwestern University, Chicago, Illinois, USA
Calculation of absolute myocardial blood flow from magnetic resonance first-pass perfusion studies by deconvolution requires a linear relationship between signal intensity (SI) and gadolinium concentration [Gd] in both the blood pool and the myocardium. We measured this relationship in canine myocardium for three common perfusion pulse sequences. Inversion recovery-prepared single-shot steady-state free-precession demonstrates excellent myocardial signal enhancement and a linear SI-[Gd] relationship. Saturation recovery-prepared segmented echo-planar-imaging and saturation recovery-prepared turbo fast low-angle shot exhibit less robust myocardial signal enhancement and a curvilinear SI-[Gd] relationship. This nonlinear signal response may result in underestimation of absolute myocardial blood flow.
Cardiac Diffusion Tensor Imaging
13:30 2942. Myofiber Developmental Plasticity in Fetal Hearts Delineated with Diffusion Tensor MRI
Lei Zhang1, Junjie Chen1, Allyson Gibson1, Mark R. Holland1, Gregory M. Lanza1, Samuel A. Wickline1
1Washington University in St. Louis, St. Louis, Missouri, USA
Cardiac functions in prenatal and postnatal phases are different. We hypothesized that myocardial fiber structures in fetal hearts may also differ from that of the adult hearts. Diffusion tensor MRI was used to delineate myocardial fiber structures in fetal pig hearts. Balanced contributions from both left ventricle and right ventricles to the septal myofibers and a thick right ventricle free wall (RVFW) in fetal hearts were observed. In contrast, adult hearts showed thinner RVFW and a dominant contribution to the septal fibers from left ventricle. These structural differences may reflect the plasticity of myocardial fiber development in response to the programmed differential contractile functions before and after birth.
14:00 2943. A Study of Variability of the Mouse Myocardial Fiber Structure Obtained by MR Diffusion Tensor Imaging
Yi Jiang1, Sarang Joshi2, Kumar Pandya3, Oliver Smithies3, Edward W. Hsu2
1Duke University, Durham, North Carolina, USA; 2University of Utah, Salt Lake City, Utah, USA; 3University of North Carolina, Chapel Hill, North Carolina, USA
Principal component analysis (PCA) was used to assess the variability of the mouse myocardial fiber helix angle and fractional anisotropy obtained by MR diffusion tensor imaging (DTI). Leave-one-out tests indicate that structural variability of the normal mouse hearts can be represented by as few as 6 DTI datasets. Moreover, PCA successfully distinguished hypertrophic hearts from the normal group. These findings suggest a rather low degree of intra-group variability and lend validity to atlas-based representation and modeling of the myocardial fiber structure.
14:30 2944. Diffusion Tensor MRI Reflects Age-Associated Changes in Normal and Cardiomyopathic Syrian Hamsters
Wen Li1,2, Allen Ye1, Ming Lu1, Suhanti Banerjee1, Xin Yu1
1Case Western Reserve University, Cleveland, Ohio, USA
The purpose of this study is to explore the potential of diffusion tensor MRI (DTMRI) in evaluating aging and cardiomyopathy (CM)-associated myocardial remodeling in Syrian hamsters. DTMRI were performed on formalin-fixed hearts of both normal and CM hamsters. Our results suggest that DTMRI is sensitive to microscopic structural changes associated with aging and disease progression.
15:00 2945. Interspecies Variability in the Myocardial Fiber Structure Acquired Using MR Diffusion Tensor Imaging
Lindsey Healy1, Sarang Joshi1,2, Yi Jiang3, Edward Hsu1
1University of Utah, Salt Lake City, Utah, USA; 2Salt Lake City, USA; 3Duke University, Durham, North Carolina, USA
The variability in the fiber helix angle of mouse, rabbit, and sheep, obtained using MR diffusion tensor imaging (DTI), was assessed using principal component analysis (PCA). A significant difference was found between each of the rabbit and sheep hearts compared to the mouse hearts. The sheep and rabbit hearts were not significantly different. The significant difference between the rabbit and mouse and sheep and mouse hearts suggest that larger hearts cannot be directly scaled down to replace the structure of smaller animals.
Quantitative Assessment for Late Gadolinium Enhancement in Normal
Myocardium [Not Available]
Atsushi Kono1,2, Naoaki Yamada1, Masahiro Higashi1, Suzu Kanzaki1, Teruo Noguchi1, Kazuro Sugimura2, Hiroaki Naito1
1National Cardiovascular Center, Suita, Japan; 2Kobe University Graduate School of Medicine, Kobe, Japan
Current assessment of delayed gadolinium enhancement in myocardium has limitation in detection of diffuse myocardial disease as based on relative signal intensity to the apparently non-enhanced myocardium. Normalization of myocardial signals by lumen signals in delayed enhancement (M/L) is useful to cancel out sensitivity inhomogeneity of surface coil. We demonstrate that normal M/L is invariable in a wide range of time after gadolinium administration, heart rate, hematocrit, and renal function (serum creatinine). On the basis of the results, M/L can detect abnormality of diffuse myocardial disease such as cardiac amyloidosis and Fabry disease.
14:00 2947. Three Dimensional Phase Sensitive Inversion Recovery (PSIR) TurboFLASH for Evaluation of Left Ventricular Myocardial Scar
Aya Kino1, John Sheehan1, Sven Zuehlsdorff2, Peter Weale2, Xin Liu1, Randal Ramsey1, Renate Jerecic2, James Carr1
1Northwestern University, Chicago, Illinois, USA; 2Siemens Medical Solutions, Chicago, Illinois, USA
Delay enhanced (DE) imaging is a well-established method for detection of myocardial scar. 2D PSIR TurboFLASH is a widely accepted viability imaging technique and a 3D viability strategy, incorporating respiratory gating, have been shown to detect small myocardial scars compared to 2D approaches. The purpose of this study was to assess a 3D PSIR TurboFLASH imaging technique for detecting left ventricular myocardial scar and compare it to a conventional 2D PSIR TurboFLASH. This study demonstrated the navigator-gated 3D PSIR sequence shows equivalent results for the assessment of myocardial scar, quantitatively and qualitatively compared to routine segmented 2D-PSIR techniques
14:30 2948. Clinical Evaluation of Free-Breathing 3D Delayed Enhancement Imaging for Myocardial Viability Assessment: Comparison with Routine Breath-Hold 2D Imaging
Thanh D. Nguyen1, Matthew D. Cham1, Pascal Spincemaille1, Martin R. Prince1, Jonathan W. Weinsaft1, Yi Wang1
1Weill Medical College of Cornell University, New York, New York, USA
The objective of this study was to prospectively compare a recently developed free-breathing navigator-gated 3D (3DNAV) delayed enhancement MRI (DE-MRI) with routine breath-hold (2DBH) DE-MRI in patients with confirmed myocardial infarction. 23 patients were imaged with both techniques at 1.5T. Compared to 2DBH imaging, 3DNAV imaging provided significantly better image quality in 33% less scan time. 2DBH and 3DNAV imaging identified 90 and 91 involved segments and 22 and 24 transmural segments, respectively. There were a strong correlation and narrow limits of agreement between the two techniques with respect to detected infarct volumes.
15:00 2949. LV Infarct Size and Peri-Infarct Zone Measurements: A Comparison of High Resolution 3D and Conventional 2D Late Gadolinium Enhancement Imaging
Dana C. Peters1, Evan A. Appelbaum1, Reza Nezafat1, Yuchi Han1, Kraig V. Kissinger1, Beth Goddu1, Warren J. Manning1
1Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
A high spatial resolution 3D late gadolinium enhancement sequence was used to image seven patients with prior myocardial infarction. The results show a clearer picture of scar morphology compared to 2D images, demonstrating features such as islands of viability, subendocardial infarcts not visualized on the 2D images, and improved papillary muscle scar detection. The scar volume by 3D correlated well with 2D measurement, but the peri-infarct zone was larger by 2D. This 3D higher spatial resolution imaging may be a step towards correlating infarct morphology with arrhythmias.
13:30 2950. Signal Intensity in Myocardial Scars Detected by Delayed-Enhancement MRI Differs in Subjects with and Without Previously Known Myocardial Infarction
Raquel Espregueira Themudo1,2, Lars Johansson1,3, Charlotte Ebeling Barbier1, Lars Lind1, Håkan Ahlström1, Tomas Bjerner1
1Uppsala University Hospital, Uppsala, Sweden; 2Hospital Geral Santo António, Porto, Portugal; 3AstraZeneca, Gothenburg, Sweden
This study comprised signal intensity analysis of myocardial scars in delayed-enhancement Magnetic Resonance Imaging aiming to investigate if there was any difference between clinically recognized myocardial infarctions and clinically unrecognized myocardial scars. There was a significant difference between the signal intensity ratio between these 2 groups, suggesting that it might represent a difference in the scar tissue composition.
14:00 2951. Low Dose Dobutamine Adds Incremental Value to Delayed Enhancement Cardiac MR in the Prediction of Adverse Remodelling Following Acute Myocardial Infarction
Anne Elizabeth Scott1, Scott Ian Semple1, Thomas Redpath1, Graham Hillis1
1Aberdeen University, Aberdeen, UK
The development of left ventricular dilatation in the months following acute myocardial infarction (AMI) is known as adverse remodelling and confers a poor prognosis. Adverse remodelling is measured as changes in left ventricular end diastolic volume (LVEDV). We examined the relative utility of delayed enhancement (DE) and low dose dobutamine (LDD) CMR parameters, recorded 2 to 6 days post AMI, as predictors of changes in LVEDV six months later. LDD parameters added incremental value to DE parameters and were independently predictive of adverse remodelling.
14:30 2952. Cardiac Phase-Resolved Acute Myocardial Infarct Imaging in Swines
Rohan Dharmakumar1, Nirat Beohar1, Jain Mangalathu Arumana1, Zhouli Zhang1, Debiao Li1,2
1Northwestern University, Chicago, Illinois, USA; 2Evanston, Illinois, USA
work examines the feasibility of cardiac phase-resolved acute myocardial
15:00 2953. Delayed Enhancement of the Peri-Infarct Border Zone is Significantly Affected by Partial Volume Averaging: Insights from Ex Vivo Rat Heart Images at a Near-Cellular Resolution
Li-Yueh Hsu1, Erik B. Schelbert1, Stasia A. Anderson1, Bibhu D. Mohanty1, Syed M. Karim1, Peter Kellman1, Anthony H. Aletras1, Andrew E. Arai1
1National Institutes of Health, Bethesda, USA
We hypothesized that the intermediate signal intensity in the peri-infarct border zone between normal and infarcted myocardium maybe explained by partial volume averaging. Using 3D ex vivo rat heart MRI at an isotropic voxel resolution equivalent to 3 cardiomyocytes, we quantified the volume of peri-infarction on the acquired isotropic 3D high resolution images and on post-hoc slab averaged low resolution images.
13:30 2954. Detection of Recent Myocardial Infarction Using CINE SSFP Imaging
James William Goldfarb1, Lenore Barhak1, Jing Han1
1Saint Francis Hospital, Roslyn, USA
In this study, use of conventional CINE SSFP imaging for the detection of myocardial edema resulting from recent MI was investigated. The signal behavior of infarcted and viable myocardium as well as the LV bloodpool was investigated as a function of cardiac phase to determine the image parameters for optimal imaging of myocardial edema. In CINE SSFP images, the LV bloodpool and myocardial signal intensities vary normally with cardiac phase. Myocardial edema can be best detected at the end of systole when its contrast with adjacent myocardium is the greatest.
14:00 2955. Fat/Water Separated Delayed Hyperenhanced (DHE) Myocardial Infarct Imaging
James William Goldfarb1
1Saint Francis Hospital, Roslyn, USA
A three-point DIXON acquisition and reconstruction was combined with an inversion recovery gradient-echo pulse sequence. This allowed fat/water separation along with contrast-enhanced T1 sensitive delayed hyperenhanced myocardial infarct imaging. The technique was demonstrated in phantom experiments and subjects with chronic myocardial infarctions. Areas of infarction were well defined as conventional hyperenhancement in water images. Fatty deposition of myocardial infarction detected using this novel sequence was confirmed by precontrast opposed phase imaging.
14:30 2956. T2-Component of Conventional Cine SSFP Sequences is Sufficient to Detect Myocardial Edema in Patients with Acute Reperfused Myocardial Infarction
Andreas Kumar1, Rohan Dharmakumar2, Jordin D. Green3, Jacqueline Flewitt1, Matthias G. Friedrich1
1University of Calgary, Calgary, Canada; 2Northwestern University, Chicago, Illinois, USA; 3Siemens Canada, Calgary, Canada
T2 spin echo sequences are commonly used to detect edema in acute myocardial infarction. Here, we show that the inherent T2 weighting of cine SSFP sequences used for functional imaging of the heart may be sufficient to detect edema. This may abolish the need for a dedicated T2 spin echo sequence in the imaging protocol for acute myocardial infarction.
15:00 2957. Improved Myocardial Viability Imaging with T2-Prepared Inversion Recovery (T2PREP-IR)
Chia-Ying Liu1, Oliver Wieben1, Jean H. Brittain2, Scott Brian Reeder1
1University of Wisconsin-Madison, Madison, Wisconsin, USA; 2GE Healthcare, Madison, Wisconsin, USA
The clinical applications of delay-enhanced (DE) MRI using inversion recovery (IR) preparation are increasingly important for evaluation of myocardial viability. However, due to the similar T1 values of blood and infarcted tissue (MI), the contrast between the ventricular blood and subendocardial MI is often limited, adversely impacting the detection and evaluation of infarcted tissue. Exploiting differences between blood and myocardial T2, we propose a method that combines IR and T2 preparation into a single magnetization-prepared sequence (T2Prep-IR) to achieve T1 and T2 contrast within a single imaging acquisition to improve differentiation of enhancing subendocardial infarction and blood.
13:30 2958. Free-Breathing Delayed Contrast-Enhanced Three-Dimensional Viability MR Imaging of the Myocardium at 3T: A Feasibility Study
Yasuo Amano1, Morimasa Takayama2, Yoshio Matsumura3, Yuriko Suzuki4, Shinichiro Kumita1
1Nippon Medical School, Tokyo, Japan; 2Sakakibara Memorial Hospital, Tokyo, Japan; 3Nippon Medical Schhol, Tokyo, Japan; 4Philips Medical Systems, Tokyo, Japan
Free-breathing delayed contrast-enhanced three-dimensional (3D) viability imaging of the myocardium at three-tesla (3T) magnetic resonance was compared with breath-hold two-dimensional (2D) viability imaging for assessments of CNR and extensions of damaged myocardium. A k-space weighted navigator and cardiac gating were used. This 3D imaging technique depicted 83.8 % of hyperenhancing myocardia with high CNR between hyperenhancing myocardium and blood and excellent agreement for transmural extension of the damaged myocardia (k = 0.875). Free-breathing delayed contrast-enhanced 3D viability imaging was feasible for the evaluation of the hyperenhancing myocardium at 3T.
14:00 2959. Simulation of Artificial Delayed Hyperenhancement Resulting from Signal Modulation in the Phase Encoding Direction
Amol S. Pednekar1
1Philips Medical Systems, Bothell, Washington, USA
An artificial mid-spetal hyperenhancement often appears on the inversion recovery prepared interleaved segmented gradient recalled echo (IRISGRE) sequence with a low-high phase encoding order. In this simulation we studied the imaging artifacts resulting due to the signal modulation across the phase encode direction in the IRISGRE sequence. These hyperenhancement artifacts capable of leading to the spurious diagnosis of myocardial scarring, can be avoided by using liner phase encoding order.
14:30 2960. T1 Pulse Sequence Optimization in a Diabetic Cohort
Warren Foltz1, Kim Alexander Connelly1,2, Venkat Ramanan, Gideon Paul1, Graham Wright1, Alexander Dick1
1Sunnybrook Health Sciences Centre, Toronto, Canada; 2St Michael's Hospital, Toronto, Canada
Quantitative MRI measurements of left ventricular remodeling have the potential to facilitate earlier diagnosis and allow therapeutic monitoring of patients with diabetic cardiomyopathy. The Gd-DTPA partition coefficient or λ, defined as the tissue-to-blood ratio of extra-cellular volume fractions, should be valuable because changes in λ from control values of 0.3 reflect alterations in the extra-cellular volume, such as that seen in pathological ventricular remodeling. We performed quantitative λ measurements within a diabetic cohort using a cardiac-gated but free-breathing single-point spiral T1prep strategy. Mean λ appears to be elevated to 0.44 from control levels. The spiral methodology appears to provide reproducibility in global λ quantification which is on the order of 10%, which is the sensitivity target for monitoring diabetic remodeling.
15:00 2961. Myocardial T1ρ Mapping at 3T Using a Novel Spin-Locking Technique
Benjamin Edward Northrup1,2, Xiang He1, Kyle Stephan McCommis1, Jie Zheng1
1Washington University School of Medicine, St. Louis, USA; 2Dartmouth Medical School, Hanover / Lebanon, USA
A new spin-locking technique was used in conjunction with segmented gradient-recalled echo and TrueFISP acquisitions on a 3T MRI system to acquire cardiac T1-weighted images in a single (~20 second) breath-hold. This facilitated the calculation of single-section myocardial T1ρ maps with minimal intra-scan motion artifacts. No significant difference between GRE and TrueFISP myocardial T1ρ signal values was observed. No difference in T1ρ values among the three spin-locking frequencies was observed. This study provided baseline myocardial T1ρ mapping data in normal subjects, which will be useful for the evaluation of myocardial function with T1ρ techniques in the future.
Safety: Acoustic Noise
14:00 2962. Experimental Reduction of Acoustic Noise Through Cancellation of Impulsive Forces
Xin Chen1, Xingxian Shou1, Jamal J. Derakhshan1, Shmaryu M. Shvartsman,12, Jeffrey L. Duerk1,3, Robert W. Brown1
1Case Western Reserve University, Cleveland, Ohio, USA; 2Hitach Medical Systems, Twinsburg, Ohio, USA; 3University Hospitals, Cleveland, Ohio, USA
MRI acoustic noise is a long-standing problem exacerbated by higher field strengths and faster imaging. We investigate the idea of using the impulsive forces produced by gradient ramping to cancel each other. Guided by string simulations, we conduct experiments to test pulse sequences incorporating these cancellations. As examples of appropriate timings, combinations of trapezoid or quadratic pulses or pairs of trapezoids are shown to cancel three frequencies and their harmonics. All results are in good agreement with the simulations and Fourier theory. A rich variety of possibilities in sequence design, including the TR freedom, may be optimized for noise control.
14:30 2963. Analysis of Acoustic Noise Transfer Function in MRI: Multi-Center Trial
Takashi Hamaguchi1, Tosiaki Miyati2, Masaya Hirano3, Yasuhiro Fuziwara4, Hirohiko Kimura4, Hiroyasu Takeda5, Yasuo Takehara5, Kenro Nagashima6, Yuriko Suzuki6, Jousei Ueda2
1Kanazawa University Hospital, Kanazawa, Japan; 2Kanazawa University, Kanazawa, Japan; 3GE Medical Systems, Hino, Japan; 4University of Fukui Hospital, Japan; 5Hamamatsu University School of Medicine,
We determined a gradient-pulse-to-acoustic-noise transfer function (GPAN-TF) at various MRI centers. We measured sound pressure levels in the frequency domain in six clinical super-conducting MRI systems, and calculated a GPAN-TF in each gradient coil. GPAN-TF at a high frequency range was larger than that at low frequency for all MR scanners. For high frequency, the 3.0-T MR scanner had a larger GPAN-TF than that of 1.5-T. MR scanner with a vacuum chamber reduced GPAN-TF at a lower frequency. GPAN-TF analysis enables to obtain more detailed information on acoustic noise properties independent of pulse sequences or imaging parameter in MR scanner.
15:00 2964. Experimental Study of Active Acoustic Noise Control with MRI Compatible Headphones and Microphones in a 4T MRI Scanner
Jing-Huei Lee1, Brent W. Rudd1, Mingfeng Li1, Jeffrey Osterhage1, Teik C. Lim1
1University of Cincinnati, Cincinnati, USA
Typical speakers and microphones utilizing magnetic components are unable to be used in the vicinity of the MRI scanner. In this study, we reproduced MRI noise in a sound quality chamber while measuring SPL and running a feed-forward control system targeting one of the dominant frequencies. The noise reduction performance of a high fidelity headphone/microphone containing magnetic components is compared with an MRI compatible combination utilizing piezoelectric speakers and an optical microphone. In this report, the results from the sound quality chamber show that the MRI compatible system produces results that are comparable to that of the high fidelity system.
15:30 2965. Sound Pressure Level Prediction of Arbitrary Sequences
Sebastian Schmitter1, Lothar Rudi Schad2
1German Cancer Research Center, Heidelberg, Germany; 2University of Heidelberg, Mannheim, Germany
During MR image acquisition huge sound pressure levels are generated, which can tamper the results of auditory fMRI experiments. A prediction of the generated acoustic noise and its spectrum is necessary in order to adapt auditory stimuli to the scanning sequence. In this work the linearity between gradient amplitude and sound pressure is verified in a wide range between 60 and 115dB. This linearity is exploited in a simulation program which predicts the SPL of an arbitrary sequence.
A loud and a silent sequence were exemplarily simulated, the results deviate only 1.8dB from the measured values.
Safety: Implants & Devices
13:30 2966. An Evaluation of the Potential Extent of Catheter Heating During MR Imaging
Alastair Martin1, Bryant Baek2, Gabriel Acevedo-Bolton2, Randall Higashida1, John Comstock2, David Saloner1,2
1University of California, San Francisco, California , USA; 2San Francisco VA Medical Center, San Francisco, California , USA
An obstacle to the incorporation of MR methods in endovascular procedures is the potential for focal heating near catheters and guidewires. This study investigated the magnitude of heating near endovascular devices in a tissue mimicking phantom. A fiber-optic temperature sensing system was used to measure temperature changes in an assortment of geometric conditions and with SAR levels up to 4W/kg. Heating was found to be amplified near these devices and was a function of immersed device length, position within the bore, and SAR. SAR limits are proposed as sufficient for safely imaging catheterized patients without concern for thermal injury.
14:00 2967. MR Safety and Compatibility of Cardiac and Peripheral Stents at 7T
Ivan Emilov Dimitrov1,2, Aman Haider3, Emmanouil Brilakis2, Subhash Banerjee3, Craig Malloy2,3
1Philips Medical Systems, Cleveland, Ohio, USA; 2University of Texas Southwestern, Dallas, Texas, USA; 3Dallas VA Medical Center, Dallas, Texas, USA
We investigated the magnetic interactions (translational attraction, torque), RF heating, and artifact levels for five coronary and four peripheral stents (Express, Cypher, Ultra, Palmaz are made of stainless steel; Vision, Driver - cobalt chromium; Sentinol, Precise - nitinol) at 7T. With the exception of Palmaz, all stents showed deflection less than 45 degrees. All stents exhibited no torque and insignificant RF heating (0.1 0.2 0C). Artifact levels were different for the different stents, all of them creating a void few times their geometrical sizes. All stents, with the exception of the large stainless steel Palmaz, are MR safe at 7T.
14:30 2968. Evaluation of RF and Resistive Heating of Magnetically- Assisted Remote Control (MARC) Steering Coils in Endovascular Interventional MRI
Fabio Settecase1, Timothy P. L. Roberts2, Walter Kucharczyk3, Steven Hetts1, Mark Wilson1, Ron Arenson1
1University of California San Francisco, San Francisco, California , USA; 2Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA; 3University of Toronto, Toronto, Canada
Catheters can be steered in interventional MRI using magnetic moments induced by applying current to orthogonally arranged wire coils at a catheter tip. Nonferromagnetic conducting wires, however, can cause significant radiofrequency (RF) heating in MRI. This study demonstrates, in a worst case scenario without convective blood flow, RF-induced temperature increases using a MARC-steered catheter are less than 1ºC after 15 min of real-time MRI. Physiologically significant resistive heating (greater than 4ºC) occurs only above 200 mA for 30 s in multiple coils. MARC steering may be an attractive alternative to catheter navigation with heating safety concerns arising only at higher currents using this prototype.
15:00 2969. MR-Safety and Compatibility of Silver Based Wound Dressings at 7T
Steffen Sammet1, Zaid Chaudhry1, William TC Yuh1, Rebecca Coffey1, Andrew Crockett1, Sidney Miller1, Michael Vincent Knopp1
1The Ohio State University, Columbus, USA
The purpose of this study was to determine whether silver based wound dressings are compatible with MRI imaging by investigating if ultra high field MRI and silver based dressings produce either increased body surface temperature and/or caused distortions in the resulting MR image. All tested silver containing wound dressings are both safe and compatible with MRI at 7T.
RF Receive Coils
13:30 2970. Reduction of SNR Losses Due to RF Coil Coupling Via Coil Current Sensing
1Invivo Corporation, Gainesville, Florida, USA
This method employs a new paradigm in multi-channel RF coils in which coupling (in moderate amounts) is not detrimental as long as it is measurable, thus permitting algebraic inversion. Two preamplifiers are utilized in each loop, one preamplifier with the impedance mismatched used to provide inductive decoupling, but the other matched to produce minimal impact on the loop impedance. This second non-damping preamplifier measures the residual current in the loop and therefore a model of voltage coupled in other nearby coils. Utilization of this additional signal improves the SNR over standard methods when the coupling is moderate.
14:00 2971. Transmission Line Effects on the Noise Correlation Matrix for Multiple RF Coils
Ryan Brown1,2, Yi Wang1,2
1Weill Medical College of Cornell University, New York, USA; 2Weill Graduate School of Medical Sciences of Cornell University, New York, USA
The original noise correlation formula derived by Redpath showed correlation depends on the real part of the impedance matrix. In this work, we introduce a more generalized formula to include effects from transmission lines and preamplifier impedance mismatch. This formula is used to calculate correlation between two-channel circuits connected to preamplifiers using several transmission line lengths. The calculated correlation matches well with that measured on the MR scanner and suggests transmission line length can be utilized as an additional degree of freedom for coil decoupling, and can be adjusted to achieve zero noise correlation.
14:30 2972. An Eigenvalue/eigenvector Analysis of Decoupling Methods and Its Application at 7T MR Imaging
Zhentian Xie1, Xiaoliang Zhang1,2
1UC San Francisco, San Francisco, California , USA; 2UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, California , USA
this work, we report an eigenvalue/eigenvector analysis method for designing non-overlapped coil arrays and one of its immediate applications as a novel decoupling method. The proposed microstrip array coil for 7T MRI, consisted of 2 microstrip resonators and one microstrip decoupling line, was built on a Teflon cylinder. Bench test and preliminary imaging results show that the proposed design provides a robust approach to design of parallel imaging arrays at ultrahigh fields.
15:00 2973. An 8-Channel Microstrip Array Coil for Mouse Parallel MR Imaging at 7T by Using Magnetic Wall Decoupling Technique
Zhentian Xie1, Xiaoliang Zhang1,2
1UC San Francisco, San Francisco, California , USA; 2UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, California , USA
We present an 8-channel microstrip array coil for mouse studies at 7T. The decoupling strategy of using microstrip resonators was employed as adjustable magnetic walls in order to block couplings between coil elements. Different from some decoupling methods for non-overlapping design, the magnetic wall method has no physical connection between the coil elements and the decoupling elements, theoretically this method is not frequency-sensitive. Therefore the decoupling performance can be maintained in a broad frequency range. The Preliminary MR images indicate the effectiveness of the proposed magnetic wall decoupling technique at the ultrahigh field of 7T. The proposed coil array provides a robust approach to design of parallel imaging arrays at ultrahigh fields.
13:30 2974. An 8-Channel Non-Overlapped Spinal Cord Array Coil for 7T MR Imaging
Zhentian Xie1, Xiaoliang Zhang1,2
1UC San Francisco, San Francisco, California , USA; 2UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, California , USA
In this report, we designed and constructed an 8-channel non-overlapped surface coil array using with strong decoupling performance and good coverage for spine parallel imaging. Different from conventional decoupling methods for non-overlapping design such as the method using lumped L/C decoupling circuits , we use a new magnetic-wall decoupling method to decouple the resonant elements. The magnetic wall is generated by the microstrip circuits positioned between two adjacent surface coil elements. Without physical connection between the decoupling microstrip and array elements, theoretically this method is not frequency-sensitive. Therefore the decoupling performance can be maintained in a broad frequency range. Bench test and preliminary imaging results are shown using the proposed coil array at 7T.
14:00 2975. Investigation of Liquid Nitrogen Cooled Coils for Low Field MR Imaging
Hoon-Sin Cheong1, Ivo Volkov2, Eugeny Krjukov1, Neil Alford3, Chris Randell4, Jim Wild1, Martyn Paley1
1University of Sheffield, Sheffield, UK; 2London South Bank University, London, UK; 3Imperial College London, London, UK; 4Pulseteq Ltd., Gloucester, UK
Images have been acquired using a specially designed cryostat and a liquid nitrogen cooled copper coil on a dedicated 0.17T neonatal/orthopedic imaging system. A factor of 1.4 improvement in SNR was obtained. Future work will compare the cooled copper coil with an identical geometry HTSC coil.
14:30 2976. Double Loop-Asymmetric Saddle Coil Arrays Optimized for Spine and Torso Imaging
Pei H. Chan1, Dan Spence2, Vincent Chen1, Piero Ghedin2
1GE Healthcare Coils, Aurora, USA; 2GE Healthcare, Milwaukee, USA
In this abstract we present a double loop-asymmetric saddle (DLAS) coil array configuration which has two highly overlapped asymmetric saddle coils in the middle and two loop coils on the sides. The overlap and quadrature nature between the two asymmetric saddle coils result in significant SNR improvement at the spine region. A 3.0T posterior array coil built with multiple DLAS blocks has demonstrated better SNR than a 3.0T 8-channel cervical-thoracic-lumber coil for spine imaging as well as good parallel imaging capability for torso imaging.
15:00 2977. A Modular Approach to Large Arrays Using Stacked Segments
Wolfgang Driesel1, Harald E. Möller2
1Max Planck Institute for Human Cognitive and Brain Sciences , Leipzig, Germany; 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
We propose a stacked combination of loop coils and microstrip transmission-line elements (MTL), which are intrinsically orthogonal, to obtain a large number of coil segments. In a first prototype a 32-channel array based on 16 stacked segments was tested. Experimental results indicate, that array coils with a large number of segments and excellent decoupling between segements can be designed from stacks of MTLs plus one or more loop-structures consisting of one or more loops. Simulations indicate a potential for parallel imaging with acceleration in z-direction.
RF Transmit Coils & Calculations
13:30 2978. Characterization of a Novel 8 Channel Microstrip Head Array at 7 T Numerical Simulation and Experimental Verification
Achim Bahr1, Stefan Orzada1, Thomas Bolz1
1IMST GmbH, Kamp-Lintfort, Germany
Microstrip resonators are interesting basic elements for the design of RF volume coils at high frequencies. In this work we describe a novel 8 channel microstrip array at 7 T which provides good B1-Field homogeneity in combination with decreased mutual coupling. The novelty implemented in this coil is the use of meander line structures at both ends of the coil elements. Low mutual coupling is verified by S-parameter measurements. In addition simulation and measurement results of the B1-Field and SAR are shown.
14:00 2979. A Novel 7 T Microstrip Element Using Meanders to Enhance Decoupling
Stephan Orzada1, Achim Bahr1, Thomas Bolz1
1IMST GmbH, Kamp-Lintfort, Germany
In this work we describe a novel method to distinctly increase the decoupling of neighbouring microstip elements at 7 T. The novelty implemented in these coil elements is the use of meanders at both ends.
Symmetrically fed elements with different numbers of meanders are compared to a symmetrically fed stripline element without meanders via simulation and measurement.
While longitudinal homogeneity remains the same, decoupling between neighbouring elements is increased by up to 10 dB. Penetration depth, absolute field strength and separation between neighbouring sensitivities are improved. Therefore meander elements are superior compared to standard microstrip lines concerning the use of parallel transmit and receive techniques.
14:30 2980. Worst Case SAR Scenario as a New Metric for SAR Analysis in B1 Phase Shim
Xiaoping Wu1, Tsung-Hui Chang1, Zhi-Quan Luo1, Can Akgun1, J. Thomas Vaughan1, Kamil Ugurbil1,2, Pierre-Francois Van de Moortele1
1University of Minnesota, Minneapolis, Minnesota, USA; 2Max Planck Institute for Biological Cybernetics, Tübingen, Germany
It has been shown numerically and experimentally that B1 shim can efficiently address transmit B1 (B1+) inhomogeneity (1). However, the risk of increasing specific absorption rate (SAR) deposition with RF manipulation is a major concern especially at very high magnetic field. The impact of B1 shim on SAR has been considered but it remains difficult to compare SAR maps obtained with multi-transmit RF coils with a variety of phase and amplitude inputs. Here we propose a new metric, "pixel-wise worst case SAR scenario", to be used as a reference when comparing SAR for different B1 shim solutions. Computing this reference, based on electromagnetic models, consists of finding the maximum E2 value for each pixel for all of possible B1 input complex values. We propose a fast computational solution for solving this nonconvex optimization problem, and we apply this method to generate E2 maps for 16-channel RF coils at 7 T.
15:00 2981. An Inexpensive and Programmable Separated Coil CASL System
Qin Xu1, Lei Zhou1, Christopher Glielmi1, Kisueng Choi, Xiaoping Hu1
1Georgia Institute of Technology/Emory University, Atlanta, Georgia, USA
A low-cost and programmable design for two-coil continuous arterial spin labelling system with minimal scanner hardware modifications is presented. A system-on-chip direct digital frequency synthesizer is chosen to generate the RF without sacrificing signal performance. This system offers remote control and programmable capabilities for easy setup and debugging of the perfusion. Performance of this system for CASL is demonstrated experimentally.
RF Receive Coils: Dual Tuned & Microstrip
13:30 2982. A Theoretical Study on the Frequency Modes Separation of Double Tuned TEM Resonators
Assunta Vitacolonna1, Marcello Alecci1
1University of L'Aquila, L'Aquila, Italy
The poor high field mode separation in double tuned TEM Resonators, can produce shading artifacts when the TEM is loaded with human tissue. In this work we show theoretically that a suitable design and geometrical disposition of the coaxial elements allows a significant increase of the high frequency resonant modes splitting.
14:00 2983. A Novel Double-Tuned Head Coil with 16 Double-Tuned Elements for 7T MRI/S
Chunsheng Wang1, Bing Wu1, Duan Xu1, Xiaoliang Zhang1
1University of California San Francisco, San Francisco, USA
A Novel double-tuned head coil with 16 double-tuned elements was designed and tested successfully at 7T. Resonant modes at both low frequency and high frequency are well-defined at bench test. This kind of structure can provide almost identical B1 field distribution for both 13C MRS and 1H MRI because of identical symmetric of elements for both nuclei.
14:30 2984. Design of Quadrature Microstrip Transmission Line (MTL) Volume Coil for Cat MRI/fMRI Application at 9.4T
Ye Li1,2, Xiaohong Zhu2, Yi Zhang2, Xiaohua Jiang1, Wei Chen2
1Tsinghua University, Beijing, People's Republic of China; 2University of Minnesota, Minneapolis, USA
The ability to scan entire cat brain is important to investigate large-scale neural networks. A new design of MTL volume coil integrated with head holder for the whole cat brain MR imaging has been presented. A prototype coil was developed and constructed using 16 MTL resonant elements. The mineral oil images and in-vivo cat brain images were acquired for coil test and validation. The preliminary images suggest that the MTL volume coil provides good homogeneity and sensitivity in the entire cat brain. Moreover, the coil is superior for investigating brain functions, in particular, in deep brain regions, showing a clear thalamocortical visual network connecting LGNs and V1 in the cat brain.
15:00 2985. A Novel Dual-Frequency Volume Coil Using Common Mode/differential Mode (CMDM) Resonators at 7T
Zhentian Xie1, Xiaoliang Zhang1,2
In this work, we applied common mode and differential mode concepts to design dual frequency volume coil designs. Common mode and differential mode (CMDM) exist within two coupled parallel transmission lines, yielding two current distributions and magnetic radiation fields. At the common mode, the two currents on a resonator are identical. At the differential mode, the currents are opposite to form a loop on that resonator. Both currents and magnetic fields in a CMDM resonator are isolated between two modes. Therefore, these modes could be designed independently at two resonant frequencies without any interference. Based on CMDM algorithm, we presents a dual tuned carbon-proton volume coil working in 7T MR system. The volume coil had 8 CMDM elements with the 75MHz and 298.14MHz operating frequencies for in vivo 13C/1H MRI/S studies at 7T. Preliminary results from a corn oil phantom were acquired using the proposed coil at 7T. Based on the preliminary results on bench test and MR scans, dual-tuned microstrip volume coil with CMDM resonant elements is feasible, provided that sufficient radial separation is maintained between the strip conductor and the ground to provide sufficient coupling between corresponding elements. The proposed design may provide a simple approach to dual-tuned volume coil design for in vivo multinuclear MR at ultrahigh fields.
Systems, Subsystems, & Hybrid Systems
13:30 2986. Development of a Combined MicroPET®/MR System
Rob C. Hawkes1, Alun J. Lucas1, Richard E. Ansorge1, Stefan B. Siegel2, Robert Nutt2, John C. Clark1, Tim D. Fryer1, T Adrian Carpenter1
1University of Cambridge, Cambridge, UK; 2Siemens Molecular Imaging, Knoxville, Tennessee, USA
We have constructed a combined microPET®/MR system. This system delivers a complete PET detector ring of diameter 15cm and axial field of view 7.8cm for simultaneous PET/MR, with the unique facility to apply conventional PET-based attenuation correction for validation of MR-based techniques. We have previously reported detector module performance, and a 'dual module' PET/MR interaction study. Here we report on assembly and initial tests of the complete PET/MR system.
14:00 2987. Study of the Magnetic Interaction of a 4-Coil Array and Copper Shielding with a PET/MRI Using the Finite-Element Method
Sergio Enrique Solis1, Dardo Tomasi2, Alfredo Odon Rodriguez1
1UAM Iztapalapa, Mexico, Mexico; 2Brookhaven National Laboratory, Upton, New York, USA
A single imaging modality cannot provide information both structure information and function. The combination of PET and MRI offers tantalizing opportunities, with important challenges. Cross talk between the MRI transceiver and the PET digital electronics can lead to interfering RF noise in both imaging modalities. An electromagnetic shielding, decoupling the PET and MRI systems, must be tightly located between the RF coil and the PET scintillating crystals to minimize this interference without loosing sample space. We numerically studied the behaviour of a 4-coil array for a PET-MRI system. This is mainly motivated by the advantages offered by MRI parallel imaging.
14:30 2988. Understanding Acoustic Noise Suppression with Gradient Design: a Vibrating String Model
Xin Chen1, Xingxian Shou1, Timothy P. Eagan1,2, Robert W. Brown1
1Case Western Reserve University, Cleveland, Ohio, USA; 2Present address: Philips Medical Systems, Highland Heights, Ohio, USA
Gradient acoustic noise in MR scanners has long been a concern for patient comfort and, on occasion, hearing safety. We apply a forced damped vibrating string system to model sets of individual frequencies found in the coil response spectrum. The general string solution accounts for previous experiments on peak cancellation, provides a physical basis for understanding these results, is a robust embodiment of a linear response system, and offers a new approach to active noise suppression. The method opens up a number of different pulse profiles and combinations that can be used to attenuate important contributions to the acoustic spectrum.
15:00 2989. Ultra-Short Echo Time Imaging Using an Independent Spectrometer and Coil Insert
Martyn Paley1, Eugeny Krjukov1, Michael Lamperth2, Ian Young2
1University of Sheffield, Sheffield, UK; 2Imperial College, London, UK
Short echo time and repeat time sequences have been implemented and tested on an independent spectrometer and gradient/RF coil insert. Echo times a short as 10 microseconds for a radial sequence and repeat times as short as 680 microseconds for a 2D gradient echo sequence have been demonstrated.
13:30 2990. The Design of Planar Transverse Gradient Coils Using a Deformation Algorithm
Minhua Zhu1, Feng Liu2, Ling Xia1, Andrew Mehnert2, Hector Sanchez Lopez2, Qing Wei2, Stuart Crozier2, Jianfeng Zhu1, Zhaoyang Jin1
1Zhejiang University, Zhejiang, People's Republic of China; 2University of Queensland, Brisbane, Australia
In this work we have proposed an efficient real-space method for the design of bi-planar gradient coils for open MRI systems. The algorithm can be used for complicated gradient coil design through an appropriate parameterization of the current arcs. It represents each arc by a closed contour described by parametric equations such that the ensemble of closed contours can be deformed/reshaped in a simple manner controllable by just a few parameters. These parameters are then used to define system rearrangements in the design procedure. An iterative optimization procedure is used to adjust the control parameters to minimize target/cost functions including gradient homogeneity, inductance and other parameters. The given planar transverse coil example demonstrates the capability of the proposed deformation-space methodology.
14:00 2991. A New Shimming Approach Using the Equivalent Magnetizing Current (EMC) Method
Hector Sanchez Lopez1, Feng Liu1, Adnan Trakic1, Ewald Weber1, Stuart Crozier1
1University of Queensland, Brisbane, Australia
This paper presents a new alternative shimming procedure to correct the magnetic field inhomogeneities generated by horizontal and C-shape biplanar MRI magnets. A magnetization map obtained through the application of the Equivalent Magnetizing Current (EMC) method is used to define the domain where the discrete iron shim set is placed to generate a given field harmonic . Optionally, instead of iron a current pattern is used, then the magnetization is related to the stream function (SF) and the current pattern is placed at equally spaced contours of the SF . If a set of discrete iron pieces with no reversible magnetization direction is employed to mimic the continuous magnetization function (MF) map, then iron shims of unit strength are placed only in the positive domain (valid domain) of the MF map. The field source matrix is calculated only for the discrete elements located in the valid domain, which leads to a better conditioned matrix and superior solutions. An LP algorithm is used to calculate the optimal thickness and location of the discrete ferroshims to produce the target harmonics. Examples of simulated shimming of horizontal/C-shape magnets are presented. In the case of permanent open magnets, the magnetic coupling among the iron pieces and its influence over the magnetic field harmonics is studied for linear and nonlinear iron cases. The influence of the selection and arrangement of individual shim sizes over the field source matrix conditioning is also analysed.
14:30 2992. Generalized Two-Dimensional Orthogonal Spatial Encoding Fields
Gerrit Schultz1, Anna Welz1, Jürgen Hennig1, Maxim Zaitsev1
1University Hospital Freiburg, Freiburg, Germany
Orthogonality of the gradient fields is crucial to good image quality using non-bijective, curvilinear spatial encoding fields. Often it is advantageous to apply a linear z-gradient along with a pair of nonlinear encoding fields. We present a simple method capable of finding all possible mutually orthogonal fields for this actual two-dimensional encoding situation.
This can be achieved by defining the encoding fields to be the real and the imaginary part of any holomorphic function. The presented approach is flexible in the design of fields for specialized applications and its simple mathematical structure allows numerical accessibility to general optimal design formulations.
15:00 2993. Cardiovascular MRI in Mice in Vivo at 9.4T with a 1500 MT/m (150 Gauss/cm) Actively Shielded Gradient Coil
Guangping Dai1, Kai-Ming Lo1,12,23,34,4, Shuning Huang1,12,23,34,4, Piotr Starewicz1,12,23,34,4, David Sosnovik,1,2,3,45
1; 2; 3; 4; 5Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA
A novel 1500 mT/m gradient coil has been constructed for cardiac MRI in mice at 9.4 T. Echo times of 1 ms and less can be obtained with this coil allowing fine cardiovascular structures to be imaged with a new level of clarity and resolution.
MR-Guided Interventions (Non-Thermotherapy)
14:00 2994. Magnetic Resonance Delivery and Monitoring of Empty MR Visible Capsules: Long Term Follow-Up
David Arthur Woodrum1, Wesley D. Gilson2, Thomas Link2, Li Pan2, Christine H. Lorenz2, Di Qian2, Brad P. Barnett2, Dara L. Kraitchman2, Jeff WM Bulte2, Aravind Arepally2
1Mayo Clinic, Rochester, Minnesota, USA; 2Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
Cell microencapsulation provides immuno-protection where individual cells are surrounded with a thin shell that is impermeable to antibodies but is permeable to small molecules. However, basic questions for long-term implantation of clinical dose of magnetocapsules (140,000) into the portal vein need to be addressed. Therefore, in this survival study, five swine underwent MR guided transplantation with 140,000 empty magnetocapsules as a first step towards the goal of delivering encapsulated cells as therapy. All animals survived the procedure and were followed for 4 weeks. Magnetocapsules were intact at four-week follow-up without disruption or change in distribution.
14:30 2995. Marked Microspheres Assessment Using 1.5T Scanner for Embolization Follow Up
1Université de Technologie de Compiègne (UTC), Compiègne, France
Controlled embolization with MRI remains challenging due to the abscence of effective detection with another imaging modality. 4 sizes SPIO loaded microspheres were injected into 8 ex vivo sheep kidneys or were embedded in a hydrogel as different grouping. The feasibility of in vivo assessment was determined according to coils, FOV, and sequence. Marked microspheres appeared as black spots, a strong linear correlation between apparent and real sizes of microspheres regardless their number, a positive visualization in in vivo condition. Our methods demonstrate the efficiency of marked microspheres assessment, in vitro and in vivo conditions, with MRI according to different sizes.
15:00 2996. MR Assessment of Vasospasm Severity and the Impact of Endovascular Therapy
Alastair Martin1, Nerrisa Ko1, Randall Higashida1, Adrian Gelb1, Max Wintermark1, Van Halbach1, Christopher Dowd1, David Saloner1
1University of California, San Francisco, California , USA
An XMR suite is used to evaluate endovascular therapies aimed at patients suffering from cerebral vasospasm. Vasospasm usually occurs secondary to subarachnoid hemorrhage and can result in delayed infarction if not properly treated. Present methods for diagnosing and treating the condition have limitations and therefore we explored the utility of augmenting endovascular treatment with MR assays including quantitative flow and perfusion. An increase in bulk flow following therapy was evident even with substantially lower post-procedure mean arterial pressure. Abnormalities in perfusion timing maps resolved following therapy and a global increase in rCBF was evident.
15:30 2997. Phantom and Clinical Validation of 3T MRI for Gamma Knife® Radiosurgery Treatment Planning
Beibei Zhang1, Derek MacFadden2, Andrei Z. Damyanovich1, Marcus Rieker3, Kristy K. Brock1, Mojgan Hodaie4, Normand Laperriere1, Michael Schwartz4, May Tsao1, Jeffrey Stainsby5, David A. Jaffray1, Mark Bernstein4, David Mikulis6, Cynthia Ménard1
1Princess Margaret Hospital, Toronto, Canada; 2University of Toronto, Toronto, Canada; 3Physikalisch-Technische Gesellschaft für Radiologie mbH, Tübingen, Germany; 4Toronto Western Hospital, Toronto, Canada; <su
MRI is central to Gamma Knife® (GK) Radiosurgery (RS) treatment planning. In this study we explored the validity of using 3T MRI for GK RS planning. Geometric accuracy measured in fiducial reference deviations and anatomic landmark displacements yielded comparable results for 3T and 1.5T MRI. Inter- and intra-observer study on target volume definition and treatment isocenter placement also yielded similar results in spatial congruency. Hence we have demonstrated that 3T MRI is valid for GK RS planning under the imaging conditions investigated, but did not demonstrate an improvement in observer reproducibility despite a subjective improvement in image quality.
14:00 2998. Identification of the Pyramidal Tract Using Neuronavigation Based on Intraoperative DWI and Subcortical Stimulation
Norihiko Ozawa1,2, Yoshihiro Muragaki1, Hirokazu Suzukawa3, Ryoichi Nakamura1, Hiroshi Iseki1
1Tokyo Women's Medical University, Tokyo, Japan; 2Hitachi Medical co., Chiba, Japan; 3Infocom co., Tokyo, Japan
In surgical resection of brain tumor in the vicinity of the pyramidal tract, identification and preservation of the tract is extremely important to protect the motor function. Although DWI/DTI is useful to demonstrate the position and the direction of the deep white matter bundles, intraoperative imaging is essential during neurosurgical procedure which could cause brain deformation. To our knowledge, however, there are few reports on performing both gintraoperativeh DWI/DTI and subcortical electrical stimulation for identification of the pyramidal tract. In this study, we identified the pyramidal tract using neuronavigation based on intraoperative DWI in combination with subcortical electrical stimulation.
14:30 2999. MRI Sequences and Registration Approaches for Respiratory Motion Correction in XMR-Guided Cardiac Catheterisations Method and First Clinical Application
Andrew Peter King1, Redha Boubertakh1, Kawal S. Rhode1, Ying-Liang Ma1, Phani Chinchapatnam2, Gang Gao2, Tarinee Tangcharoen1, Matt Ginks1, David J. Hawkes2, Reza Razavi1, Tobias Schaeffter1
1Kings College, London, UK; 2University College, London, UK
We describe a novel technique for respiratory motion correction of roadmaps in XMR-guided cardiac catheterisations using a patient-specific motion model derived from MR imaging. Validation is performed on four volunteers and three clinical cases. We test two dynamic MR imaging sequences (low resolution 3-D and high resolution 2-D) and two different registration approaches (full affine and constrained affine) for forming the model. Accuracy in volunteers was 2-4mm and in clinical cases the 2-D accuracy of the roadmap was improved from up to 13mm to less than 4mm in all three cases.
15:00 3000. X-Ray Fused with Magnetic Resonance (XMR) Imaging for Accessing the Portal Vein
David Arthur Woodrum1, Wesley D. Gilson2,3, Robert Liddell2, R J. Lederman4, C Ozturk4, M Sonmez3, Thomas Link2, V Howland2, Dara L. Kraitchman2, Aravind Arepally2
1Mayo Clinic, Rochester, Minnesota, USA; 2Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; 3Siemens Corporate Research, Baltimore, Maryland, USA; 4National Institutes of Health, Bethesda, M
We evaluated use of real-time X-ray imaging fused with MRI (XFM) to guide interventions targeting portal vein. This technique uses roadmaps from MRI-derived data to provide roadmaps during conventional X-ray fluoroscopy. Using an interventional MRI/X-ray suite equipped Siemens Espree MRI scanner and AXIOM Artis dFC. After placement of multimodality external fudicial markers over abdomen, 3D gradient echo images were acquired for marker visualization and contrast-enhanced imaging was performed for portal vein imaging. Animal was transferred to a calibrated fluoroscopy system, while portal vein was manually segmented from MR images. Image overlay of portal vein with real time fluoroscopy was feasible.
15:30 3001. Real-Time and Color-Flow Spiral MR Imaging of Peripheral Chronic Total Occlusion (CTO)
Yoriyasu Suzuki1, William R. Overall1, Juan M. Santos1, Masahiro Terashima1, Fumiaki Ikeno1, Alan C. Yeung1, John M. Pauly1, Stephen B. Williams1, Michael V. McConnell1
1Stanford University, Stanford, USA
This study tested the feasibility of real-time spiral MRI (RT-MRI) techniques for visualizing peripheral arteries and chronic total occlusions (CTO) lesions in vivo in patients using RTHawk real-time system. Inflow enhancement resulted in high, pulsatile signal in patent portions of the vessel, while CTO regions exhibited consistently low signal. RT-color-flow-MRI showed pulsatile color signal in the patent segment and absence of color flow in the CTO. Post-intervention, RT-MRI confirmed vessel patency in both atherectomy and nitinol stent cases. This study demonstrates the capability of RT-MRI to visualize and assess peripheral CTO lesions prior to and following interventions at 1.5 T.
14:00 3002. A Framework for 3D Visualization of Active Catheters Using Compressed Sensing
Carsten Oliver Schirra1,2, Sascha Krueger3, Steffen Weiss3, Reza Razavi1, Tobias Schaeffter1, Sebastian Kozerke2
1King's College London, London, UK; 2University and ETH Zurich, Zurich, Switzerland; 3Philips Medical Systems, Hamburg, Germany
True three-dimensional visualization of the full length of catheters has hitherto been impossible given scan time constraints. Images acquired with active interventional devices are inherently sparse therefore render Compressed Sensing ideally suited for accelerating data acquisition.
We propose a framework for the visualization of active catheters in 3D employing CS to gain high undersampling factors making real-time applications feasible. Constraints are introduced taking into account prior knowledge of catheter geometry and catheter motion over time to improve and accelerate image reconstruction. The potential of the method is demonstrated using computer simulations and phantom experiments.
14:30 3003. A New System for Passive Tracking of a Prostate Biopsy Device with Automatic 3D Needle Position Estimation
Andre de Oliveira1, Jaane Rauschenberg1, Dirk Beyersdorff2, Wolfhard Semmler1, Michael Bock1
1Deutsches Krebsforschungszentrum (dkfz), Heidelberg, Germany; 2Charite Campus Mitte, Berlin, Germany
A new passive marker system is proposed to localize the 3D needle tip position during MR-guided prostate biopsies. Modifications to a previously existing tracking sequence were made to allow for depth tracking of the passive marker and to visualize the estimated position of the biopsy gun in real-time. In a phantom experiment the error of needle tip position estimation was about 1.5 mm, with an update rate of 1 image/s. This passive concept provides a cost-effective and simple to implement alternative that is expected to significantly speed up and improve the precision of MR-guided prostate biopsies.
15:00 3004. Real-Time MR Imaging Controlled by Transperineal Needle Placement Device for MRI-Guided Prostate Biopsy and Brachytherapy
Junichi Tokuda1,2, Simon DiMaio1,2, Gregory Fischer3, Csaba Csoma3, David Gobbi4, Gabor Fichtinger4, Nobuhiko Hata1,2, Clare Tempany1,2
1Brigham and Women's Hospital, Boston, Massachusetts, USA; 2Harvard Medical School, Boston, Massachusetts, USA; 3The Johns Hopikins University, Baltimore, Maryland, USA; 4Queen's University, Kingston, Canada
A real-time MR imaging integrated with surgical navigation software 3D Slicer and a MRI-compatible transperineal needle placement device using open-source software tools is presented. The system was designed to maintain the 2D imaging plane in parallel or perpendicular to the needle, allowing physicians to monitor needle advancement in the tissue in real-time. The latency and positional accuracy of the real-time image were evaluated by using a phantom in a 3T closed-bore scanner. The study showed that it is feasible to integrate the system using the open-source software tools, providing enough capability to guide prostate biopsy and brachytherapy.
15:30 3005. Control of Intravascular Catheters Using a 3D Array of Active Steering Coils
Natalia Gudino1,2, Jeremiah A. Heilman1,3, Jamal J. Derakhshan1,3, Jeffrey L. Sunshine3, Jeffrey L. Duerk1,3, Mark A. Griswold1,3
1Case Western Reserve University, Cleveland, USA; 2University Hospitals Case Medical Center, Cleveland , USA; 3University Hospitals Case Medical Center, Cleveland, USA
One of the challenges of endovascular procedures is directing a catheter tip into small or complicated blood vessels. The strong magnetic field of MRI systems provides a special environment that can be used to enable remote control of a catheter. In the present work we propose a 3D array of steering coils as a potential solution for remote control of catheters in an Interventional MRI setting. We also demonstrate methods for visualization of the catheter and/or surrounding areas.
14:00 3006. Catheter Steering in MRI Using Longitudinal Current Loops
Michael Vi-Nguyen Truong1, Kevan Anderson2, Mihaela Pop2, Hartwig Peemoeller1, Alexander Dick3, Graham A. Wright2
1University of Waterloo, Waterloo, Canada; 2University of Toronto, Toronto, Canada; 3Sunnybrook Health Sciences Centre, Toronto, Canada
Electrical mapping and RF ablation of the heart requires precise maneuvering and steering of a catheter. We have developed a method for steering a catheter that exploits the static magnetic field of an MR scanner by looping a wire around the wall of a catheter (along the longitudinal axis) and applying a DC electric current. Lorentz forces cause a separation between the portions of the wire inside and outside of the catheter, resulting in a deflection. Deflections of ~4 cm are achievable with 50 mA of current in the transverse plane perpendicular to the magnetic field.
14:30 3007. A 3-DOF MR Compatible Limb Positioning Manipulator to Facilitate Magic Angle Experiments in Vivo
Haytham Elhawary1, Zion Tsz Ho Tse1, Aleksandar Zivanovic1, Marc Rea1, Brian L. Davies1, M Paley2, G Bydder3, Ian Young1, Michael Lamperth1
1Imperial College London, London, UK; 2Sheffield University, Sheffield, UK; 3UCSD, USA
Magic angle studies provide useful clinical information about tissues such as tendon. We describe a system which can be used in an MRI system to orientate a patient¡¦s limb to map signal changes with angle. So that most of the patient¡¦s body does not have to move it uses three driven axes (using novel air motors) for positioning. Motion is constrained by the size of the machine DSV, the bore of the machine and the desire to keep imaging near the machine center using a computer-based algorithm. In vivo data from an early prototype is shown.
15:00 3008. The Development of Bone Cement for the Interventional MRI
Florian Wichlas1, Christian Seebauer1, Rene Schilling1, Jens Rump1, jens Pinkernelle1, Florian Streitparth1, Ioannis Papanikolaou1, Sascha Chopra1, Ulf Teichgräber1, Hermann Joseph Bail1
1Charité Berlin, Berlin, Germany
As bone cement is widely used in musculoskeletal surgery but has no signal in the MRI, it cannot be directly visualized during intervention. In order to establish vertebroplasty and cancer surgery in the open MRI, visible cement becomes necessary.
Several contrast agents were added to PMMA cement in order to create a signal in the MRI. Gd-DOTA, Gd-BOPTA, Mangafodipir and manganese were used.
PMMA bone cement can be prepared in order to give a positive contrast in the MRI. This cement may improve safe intervention in the open MRI, and allow early coping of complications due to leaking.
Three-Dimensional Localization of MR-Visible Markers with Potential
Applications in Position Tracking: Feasibility, Speed, and Precision [Not Available]
Harald Busse1, Wilfried Gründer2, Nikita Garnov2, Michael Moche1, Thomas Kahn1
1Leipzig University Hospital, Leipzig, Germany; 2Leipzig University, Leipzig, Germany
The purpose was to evaluate the performance of an image feature discrimination based on 2D-Gaussian peak fitting for fast localization of MR-visible markers and to determine its reliability and spatial precision using inductively-coupled RF micro coils that were scanned over a wide range of positions/orientations. By using a 128-matrix, half-Fourier balanced SSFP sequence, acquisition and localization could be performed in <1.0 sec with submillimeter precision. Therefore, that approach provides a relatively simple, flexible, and safe way for selected applications, such as the tracking of patient motion or interventional instruments/devices, that do not require extremely fast position updates.
Thermal Therapy & HIFU
13:30 3010. Clinical Use of Robot Assistance in MR Image-Guided Microwave Thermocoagulation Therapy of Liver Tumors
Shigehiro Morikawa1, Toshiro Inubushi1, Koichiro Murakami1, Shigeyuki Naka1, Yoshimasa Kurumi1, Tohru Tani1, Hasnine A. Haque2, Junichi Tokuda3, Nobuhiko Hata3
1Shiga University of Medical Science, Ohtsu, Japan; 2GE Yokogawa Medical Systems, Hino, Japan; 3Brigham and Women's Hospital, Boston, Massachusetts, USA
We have developed a motorized robot with a virtual remote-center-of-motion (RCM) control to assist the choice of the puncture route in MR image-guided microwave thermocoagulation therapy of liver tumors. After the certification of MR compatibility, accuracy and safety, we have commenced the clinical use of this robot and the results were feasible. Our navigation software showed the treated and untreated areas of the tumor. We could set the target point in this software and directly instruct this point to the robot. The robot immediately led the surgeon to this point and the procedure completed accurately and quickly.
14:00 3011. MRI-Guided, Percutaneous Thermoablation in Liver Using Interstitial Applicator of Contact Ultrasound Under Active Temperature Control : A Feasibility Study in Vivo
Eric Delabrousse1, Rares Salomir1, Alain Birer1, Christian Paquet2, Cyril Lafon1
1Inserm, Lyon, France; 2Ecole Nationale Veterinaire, Marcy l'Etoile, France
Contact ultrasound permits accurate control of the spatial pattern of heat deposition, with directive and angularly controlled beams. In this study we investigated the feasibility of percutaneous thermoablation in liver using an MR compatible device, delivering High Intensity Contact Ultrasound (HICU). Fast MR thermometry was used for therapy monitoring and active feedback on the applied power. No sonication-related RF artifacts were detected in any experiment. The standard deviation of the MR thermometry baseline was 1°C. The temperature controller converged to the target curve and further maintained the steady-state regime within a standard deviation of 2°C. MR followup and post mortem histology demonstrated that all individual sonications lead to near identical shape of the lesion (15±2 mm depth, 3cm equivalent diameter).
14:30 3012. MR-Guided Radiofrequency Ablation of Hepatocellular Carcinoma: Long-Term Clinical Effectiveness
Stephan Clasen1, Andreas Boss1, Christina Schraml1, Jan Fritz1, Diethard Schmidt1, Fritz Schick1, Claus D. Claussen1, Philippe L. Pereira1
1University of Tübingen, Tübingen, Germany
MR-guided radiofrequency (RF) ablation in the treatment of hepatocellular carcinoma (HCC) was evaluated. The entire ablation procedure was performed in an interventional 0.2-Tesla open MR-system. In 20 patients 28 HCC with a mean diameter of 2.8 cm were treated. Technique effectiveness was achieved in 27/28 HCC (96.4%) evidenced by dynamic MR imaging at 1.5-Tesla four months after RF ablation. At a mean follow-up of 24.2 months (range: 6 52 months) 26/28 HCC (92.9%) showed a complete coagulation. In conclusion, MR-guided RF ablation is an effective therapy option in the treatment of HCC.
15:00 3013. MRI Monitoring and Mathematical Modeling to Predict Tissue Lesion Size from Laser Thermal Ablation
Simi Paul1, Jeong Joon Park2, Stephen R. Yutzy,12, Ravi Patel2, Sherif G. Nour1,2, Fadi W. Abdul-Karim1, Gerald M. Saidel2, Jeffrey L. Duerk,12
1University Hospitals Case Medical Center, Cleveland, Ohio, USA; 2Case Western Reserve University, Cleveland, Ohio, USA
This study demonstrates how a mathematical model together with MR imaging can predict lesion size from thermal ablation of a tumor in tissue. Rabbit paraspinal muscles, with and without implanted VX-2 tumor, were thermally ablated. Model-based computer simulations of temperature and cell death dynamics via MR phase and magnitude images were used to follow lesion size development. Final lesion size predicted by computational analysis correspond closely with histopathological analysis. Since MR imaging and simulations can be accomplished in seconds, this approach has potential for real-time prediction of the lesion boundary during laser thermal ablation in clinical application.
13:30 3014. MRTI Evaluation of SPIO Core Gold Coated Nanoshells for Thermal Therapy and as T2* Contrast Agent
Andrew M. Elliott1, Anil M. Shetty1, Marites P. Melancon1, Xiaojun Ji1, Brian Taylor1, John D. Hazle Hazle1, Chun Li1, R. Jason Stafford1
1University of Texas M.D. Anderson Cancer Center, Houston, USA
Laser Induced Thermal Therapy (LITT) is used in conjunction with gold-silica nanoshells that have superpaprmagnetic iron oxide cores (SPIO). The optical properties of these nanoshells and their high absorbance in the near infra-red make them ideal for use in thermal therapy. The SPIO core alters the susceptibility and therefore the T2* value in regions where the nanoshells collect. The aim of this work is to validate and characterize the thermal response characteristics of these nanoparticles and to investigate their use as a T2* contrast agent.
14:00 3015. Assess Tumor Acute Response to Photothermal Therapies by DCE-MRI Using Biodegradable Macromolecule Contrast Agent
Yi Feng1, Eun-Kee Jeong2, Lyska Emerson2, Zheng-Rong Lu
1Unviersity of Utah, Salt Lake City, USA; 2Unviersity of Utah, USA
Biodegradable macromolecular contrast agents (BMCA) alleviate this toxicity problem of macromolecular contrast agents by in vivo degradation. (Gd-DTPA)-cystamine copolymers (GDCC at 40 KDa) was used to assess the acute response from tumor and to correlate it with residual tumor.
14:30 3016. A Fast Phase-Correction Algorithm for Improved Real-Time PRF Shift Thermometry
Roger Jason Stafford1, Roger J. McNichols2, Ashok Gowda2, John D. Hazle1
1The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA; 2BioTex, Inc., Houston, Texas, USA
A fast, simple loco-regional phase-correction algorithm for proton resonance frequency shift based magnetic resonance temperature imaging is tested in in vivo animal and human experiments to evaluate its potential to decrease the artifact in PRF thermometry due to motion, tissue swelling and drift. The technique is purely post-processing based and does not rely on specific acquisition techniques. Initial results relying on phase-correction only and no image registration show both a qualitative and quantitative increase in the quality of the PRF temperature map.
15:00 3017. Absolute MR Thermometry Using Time Domain Analysis of the Multi Gradient-Echo Modulus Signal
Sara Maria Sprinkhuizen1, Chris J. Bakker1, Lambertus Wilhelmus Bartels1
1University Medical Center, Utrecht, Netherlands
The modulus signal of a multi gradient-echo (mFFE) sequence contains spectral information of the substances involved. In substances containing two components of which only one has a temperature dependent resonance frequency, e.g. in tissue containing water and fat, the frequency difference ∆f between the peaks in the spectrum of the mFFE signal thus provides a measure of the absolute temperature. To proof this principle, absolute temperature maps of ethylene glycol are computed, using time domain analysis of multi gradient-echo modulus signal. This technique yielded absolute temperature maps which were insensitive to field disturbances and field drift.
13:30 3018. Temperature Mapping with IDEAL Water-Fat Phase Differences
Brian J. Soher1, Cory Wyatt1, Scott B. Reeder2, James R. MacFall1
1Duke University, Durham, North Carolina, USA; 2University of Wisconsin, Madison, Wisconsin, USA
Tissues containing both water and lipids, e.g. breast, confound standard MR phase methods for mapping temperatures. We demonstrate temperature changes in a water-fat phantom using an IDEAL acquisition. Active heating was applied in an OFF-ON-OFF pattern over 60 minutes. Water-fat phase angle changes were used to calculate temperature change. Calculated IDEAL-Temp values adjacent to the Luxtron probe showed excellent agreement. IDEAL water-fat methods which use fat as an internal frequency drift reference show great promise for improving MR thermometry in fatty tissues such as breast.
14:00 3019. A High Spatiotemporal Chemical Shift Imaging Technique for MR-Guided Thermal Therapy with Multi-Parametric Monitoring Capabilities
Brian Allen Taylor1, Ken-Pin Hwang,12, Andrew M. Elliott1, Anil Shetty1, John D. Hazle1, Roger Jason Stafford1
1The University of Texas M.D. Anderson Cancer Center, Houston, USA; 2GE Healthcare Technologies, Waukesha, USA
A chemical shift imaging (CSI) technique for magnetic resonance temperature imaging is presented with spatiotemporal resolutions comparable to complex phase difference (CPD) methods. This technique takes a novel approach to frequency estimation for temperature measurements via autoregressive moving average (ARMA) modeling to overcome limitations seen in low spectral resolution, Fourier-based frequency estimation methods. Also, additional measurements such as T1 and R2* can be simultaneously acquired with the PRF to facilitate a multi-parametric approach to temperature imaging.
14:30 3020. Feasibility of 1.5T MRI-Guided Transurethral 3-D Conformal Ultrasound Therapy of the Prostate: A Simulation Study
Mathieu Burtnyk1,2, Rajiv Chopra1,2, Michael Bronskill1,2
1Sunnybrook Health Sciences Centre, Toronto, Canada; 2University of Toronto, Toronto, Canada
The goal of this work is to use numerical simulations and 3D patient-specific models to investigate the feasibility of treating men with prostate cancer with a transurethral ultrasound therapy device and a feedback control algorithm based on clinically-relevant 1.5T MR thermometry temperature measurements (1°C noise stdev, 5s sampling). For all 20 patient models, the standard deviation of the treatment error remained below 1mm, while the maximum and minimum error were usually less than 5mm, demonstrating a high level of treatment accuracy. Treatment times are improved by a factor of six as compared to transrectal HIFU procedures.
15:00 3021. Spatial and Temporal Accuracy of Heating Using MRI-Guided Transurethral Ultrasound Therapy and Active MR Temperature Feedback
Rajiv Chopra1,2, Kee Tang1, Aaron Boyes1, Mathieu Burtnyk1, Laurence Klotz1, Michael Bronskill1
1Sunnybrook Health Sciences Centre, Toronto, Canada; 2University of Toronto, Toronto, Canada
MRI-guided transurethral ultrasound therapy was performed in a canine model to evaluate the accuracy (spatial and temporal) of heating using active MR temperature feedback.
Subzero Temperature Mapping in a Cryosurgery Ice Ball by Using MR Signal
Time Course [Not Available]
Toru Yamamoto1, Aogu Yamaguchi2, Tadashi Shimizu3
1Hokkaido University, Sapporo, Japan; 2Hokkaido University Hospital, Sapporo, Japan; 3Hokkaido University , Sapporo, Japan
Cryosurgery is a technique for freezing and killing tumors by cooling the cryoprobe inserted subcutaneously. The frozen area appears dark in MR monitoring because the water of ice is MR-invisible. The malignant tumor becomes necrotic at freezing temperatures below E0ºC. However, it is hard to discern the necrotic area below E0ºC in the frozen area, so-called ice ball. To visualize the necrotic area, we developed a method to map subzero temperatures in a black ice ball and an agar phantom was imaged using a 0.3-T MRI every 20 s during the cooling of the cryoprobe. The temperature at ten points around the cryoprobe was monitored by using thermocouples and our method was confirmed.
14:00 3023. Proton Resonant Frequency Shift and R2* in Frozen Ex Vivo Renal Tissue at 7T
Elena Kaye1,2, Stephen Lynch1, Christopher C. Caires1, Kim Butts Pauly1
1Stanford University, Palo Alto, USA
Image-guided cryoablation is a minimally invasive therapy for renal cancer. Temperature dependence of MR parameters of frozen tissue has already been studied on a low field interventional system. In this work proton resonance frequency shift and R2* of frozen renal tissue were studied on a 7T spectrometer. 1H frequency changed linearly with temperature (slope -0.009 ppm/°C). Following the transition to the solid phase, the behavior of the 1H frequency with temperature changed from linear to exponential. R2* increased linearly with decreasing temperature.
14:30 3024. To Characterize the Safety Window of Focused Ultrasound When Applied to Blood-Brain Barrier Disruption
HaoLi Liu1, Po-Hong Hsu1, KoonKwan Ng, YauYau Wai, JiunJie Wang1
1ChangGung University, KueiShan, Taiwan
High Intensity Focused Ultrasound provided a new method for blood-brain-barrier disruption, which might facilitate the drug delivery to the brain. However, side effects such as hemorrhage prevent it from clinical applications. In this study, a safety window can be characterized by the combination of susceptibility weighted imaging and contrast enhanced T1 MRI.
15:00 3025. SuperParamagnetic Iron-Oxide in Monitoring of Focused Ultrasound Induced Blood-Brain Barrier Disruption
HaoLi Liu1, Po-Hong Hsu1, Zeitsan Tsai1, KoonKwan Ng2, Chia-Rui Shen1, JiunJie Wang1
1ChangGung University, KueiShan, Taiwan; 2ChangGung Memorial Hospital, Taiwan
super paramagnetic iron oxide particle (SPIO) was used to monitor the Blood Brain Barrier disruption and separate it from the potentially induced brain hemorrhage by use of susceptibility weighted imaging. SPIO-enhanced SWI provides a T2 based approach to in vivo monitoring of the focused ultrasound induced BBB disruption. The mismatched areas implied an area without brain tissue damage.
14:00 3026. Shimming Strategies for the Neck and C-Spine: a Computational Study
Kevin M. Koch1, J A. Stainsby2
1GE Healthcare, Waukesha, Wisconsin, USA; 2GE Healthcare, Toronto, Canada
Anatomy-induced B0 perturbations in the neck and c-spine can degrade the quality of MR acquisitions. A computational study is presented whereby the efficacies of different room-temperature shimming schemes are evaluated in this anatomic region. Static 1st-order, static 2nd-order, dynamic 1st-order, and dynamic 2nd-order shimming strategies are evaluated on a computed B0 distribution. It is shown that slice-specific updating of only 0th and 1st-order shim terms can result in significant improvement over static shimming scenarios in the neck and c-spine region.
14:30 3027. Simulating the Effect of TMS-Pulses on the Evolution of Magnetization
Andreas Bungert1, Richard W. Bowtell1
1University of Nottingham, Nottingham, UK
Transcranial magnetic stimulation (TMS) is a method for stimulating cortical regions of the brain using a pulsed magnetic field. In this study the influences of this field on the evolution of nuclear magnetization have been simulated based on the measured TMS pulse waveform and calculated spatial field variation due to the TMS coil. The results indicate that the TMS pulse has negligible effect on the longitudinal magnetization, but even in the case of a balanced biphasic TMS pulse causes strong dephasing of transverse magnetization over a large region adjacent to the coil.
15:00 3028. Effects of the TMS Coil on MR Image Quality in Combined TMS/fMRI
Andreas Bungert1, Richard W. Bowtell1
1University of Nottingham, Nottingham, UK
By applying MR-based field mapping to the head and simple spherical phantoms, the passive effects of a TMS coil on the Bo- and B1-field homogeneity have been investigated at 1.5 and 3 T, for different coil orientations. In addition measurements of EPI time series have been used to measure the effects of the TMS coil on the signal to noise ratio (SNR) in fMRI experiments. The results show that the presence of the TMS coil generally has only a small effect on B1 and Bo homogeneity and global SNR.
15:30 3029. Correcting for B0 Field Drift in MR Temperature Mapping with Oil References
Brian J. Soher1, Cory Wyatt1, Vadim Stakhursky1, James R. MacFall1
1Duke University, Durham, North Carolina, USA
Proton resonance frequency shift (PRFS) temperature mapping methods are confounded by changes in frequency not due to temperature changes, such as main B0 field drift. We demonstrate a method that uses oil filled references that are insensitive to temperature changes to estimate changes in B0 during hyperthermia treatments. A minimum curvature spline surface is fitted to phase change values in the oil references and a global B0 map is created. Phase changes not due to temperature change are removed from the PRFS data prior to temperature calculation. Corrections are demonstrated in both a phantom and a leg sarcoma patient.
14:00 3030. A Continuous Nyquist Ghost Correction for EPI-Based FMRI
Wietske van der Zwaag1,2, José Marques1,2, Tobias Kober1,2, Rolf Gruetter1,3
1Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland; 2University of Lausanne, Lausanne, Switzerland; 3Universities of Lausanne and Geneva, Switzerland
The traditional ghost correction approach based on acquiring reference k-space lines without phase-encode gradients was supplemented with schemes based on continually reversing read-out polarity in EPI in every other volume. Three strategies were evaluated using fMRI data acquired at 7 Tesla, all of which significantly reduced Nyquist ghost intensity by up to 62%, resulting in 13% higher maximum T-scores. It is concluded that at high B0 substantial Nyquist ghost reductions are possible by alternating the read-out gradient amplitude every other volume, allowing continuous artefact reduction.
14:30 3031. EPI Distortion Corrections at 4T: Multi-Channel Field Mapping and a Comparison with the Point-Spread Function Method
Simon Robinson1, Jorge Jovicich1
1University of Trento, Trento, Italy
EPI distortions arising from local field inhomogeneities are severe at 4T (~10 mm), but may be remedied via the field mapping and point-spread function correction methods. We show how high quality phase images and field maps may be generated using multi-channel data, using the multiplicity of measures of phase to eliminate erroneous boundary pixel values. We acquired data from six subjects over a wide range of receiver bandwidth, and corrected with the fieldmap and point-spread function method. Using measures of boundary shape, both measures provide excellent correction. No residual distortion was evident in the image interior.
15:00 3032. The Use of Three Navigator Echoes in Cartesian EPI Reconstruction Reduces Nyquist Ghosting
Andrew S. Nencka1, Andrew D. Hahn1, Daniel B. Rowe1
1Medical College of Wisconsin, Milwaukee, Wisconsin, USA
Reconstructed images from Cartesian echo planar imaging suffer from Nyquist ghosting because of hardware timing errors and eddy current effects shifting the odd and even k-space lines in opposite directions. Previous solutions to the ghosting problem have included acquiring a reference scan with no phase encoding blips or the omission of a phase encoding blip when the center line of k-space is acquired. We illustrate here a method for utilizing three navigator echoes to estimate the shifts and reduce the Nyquist ghost. This method is less computationally intensive than the two-navigator method and yields superior results to the reference scan methods. Like the two navigator method, this method additionally offers the ability to measure the center frequency offset and alternating line time shift with each image acquisition.
15:30 3033. Reduction of Shading Artifact with Center-Out View Order for Diffusion-Weighted PROPELLER
Xiaoli Zhao1, Ajeetkumar Gaddipati1, Shaorong Chang1, Dawei Gui1
1GE Healthcare, Waukesha, USA
The non-CPMG nature of diffusion-weighted PROPELLER imaging causes signal dropout if the refocus flip angles are out of the desirable range. This is particularly true for 3T due to B1 inhomogeneity, and shading artifact will be introduced. In the present work, center-out view order is demonstrated to significantly reduce the shading artifact. For each blade in PROPELLER acquisition, the echo train is phase encoded in the way the early echoes are placed near the center k-space. Center-out view order also improves the overall SNR because of the reduced TE.
14:00 3034. Presence and Reduction of Off-Resonance Ghosting in Magnetization Prepared TrueFISP
Jamal Jon Derakhshan1,2, Mark A. Griswold1,2, Jeffrey L. Sunshine2, Jeffrey L. Duerk,12
1Case Western Reserve University, Cleveland, Ohio, USA; 2University Hospitals Case Medical Center, Cleveland, Ohio, USA
Magnetization storage during bSSFP acquisitions has opened the door to various manipulations of the steady state signal. First, we demonstrate that conventional periodic magnetization preparation during TrueFISP acquisitions using α/2 at TR/2 pulses can lead to significant ghosting (>1/2 amplitude of object) of off-resonant spins. Second, simulations and experimental results demonstrate the amplitude of the ghosts can be reduced to near the non-prepared bSSFP levels by partially randomizing the number of readouts collected between magnetization preparations. Phantom and human in-vivo images demonstrate both the ghosting in regularly prepared bSSFP acquisitions and the significant reductions afforded by the proposed randomization scheme.
14:30 3035. Slice Offset Frequency Adjustment (SOFA) for SSFP Imaging
Martin John Graves1, Pauline Wong1, David John Lomas1
1University of Cambridge and Addenbrooke's Hospital, Cambridge, UK
Steady state free precession (SSFP) imaging is limited by off-resonance artifacts, particularly away from isocenter. We have developed a simple method to characterize the frequency offset as a function of position away from isocenter, using a uniform phantom. This correction is then applied to the scanner center frequency (f0) in either a multi-slice prescription or as part of a interactive imaging study. Initial evaluation in a phantom and normal volunteers shows a substantial reduction in artifacts when using this pre-determined correction.
15:00 3036. Contrast Enhanced T1W FLAIR PROPELLER MRI: Improvement in Flow-Related Phase Artifacts Compared to Conventional Cartesian Techniques
Leland S. Hu1, John p. Karis1, Donglai Huo1, Zhiqiang Li2, Eric Aboussouan1, Nabeel Farhataziz1, Josef Debbins1, Roger Bird1, Jeff Ross1, James Pipe1
1Barrow Neurological Institute, Phoenix, USA; 2General Electric Corporation, Milwaukee, USA
Conventional Cartesian methods for T1W contrast-enhanced magnetic resonance imaging (CE-MRI) produce flow-related phase artifacts which both obscure and simulate true pathologic lesions. PROPELLER MRI scanning techniques substantially diminish the perceptibility of flow-related phase artifacts on T1W CE-MRI compared to conventional techniques. Further work is necessary to determine if these differences result in significant changes in accuracy of lesion detection.
15:30 3037. Rapid Reference-Free Noise Reduction for Parallel MR Images Using a Principal Component Technique in Combination with Adaptive Dyadic Wavelet-Based Denoising
Qi Duan1,2, Anand S. Patel3, Andrew Francis Laine1, Philip M. Robson3, Charles A. McKenzie4, Daniel K. Sodickson2
1Columbia University, New York, New York, USA; 2New York University Medical Center, New York, New York, USA; 3Beth Israel Deaconess Medical Center and Harvard Medical School, USA; 4University of Western Ontario
Parallel acquisitions involve well-known tradeoffs between acceleration and signal-to-noise ratio (SNR). The principal component technique offers a rapid approach to noise reduction using information about the coil sensitivity encoding process. However, this method has in the past required an unaccelerated reference image. We have demonstrated a method based on dyadic wavelet expansion to adaptively derive the reference image from the accelerated one, thereby increasing ease of use. The new method also yielded sharper and more detailed image structures after noise reduction. Overall, the approach is a promising candidate for adaptive and rapid noise reduction in highly accelerated images.
Image Analysis - Parametric Mapping
14:00 3038. A Novel Method of Combining Multi-Coil MRI Images: The Level-Weighted Wavelet Fusion
Jeong Hwan Bang1, Andy Stenger, Todd Reed
1University of Hawaii, Honolulu, Hawaii, USA
Multi-coil MR images are conventionally combined using a magnitude sum. A problem with this approach is the loss of contrast due to the global lowpass filtering operation. Wavelet methods have been shown to be useful for reducing receiver sensitivity inhomogeneity in multi-coil applications, but not much work has been done to alleviate the loss of resolution. We present a novel Level-Weighted Wavelet Fusion (LWWF) scheme to address this. We show that the method is successful improving the contrast in multi-coil brain images at 3T.
14:30 3039. Hepatocyte Growth Factor Gene Delivered Intramyocardially Improves Cardiac Function and Strain on MR Imaging
Marcus Carlsson1, Nael Osman2, David Saloner1, Alastair J. Martin1, Loi Do1, Maythem Saeed1
1University of California San Francisco, San Francisco, California , USA; 2Johns Hopkins University, Baltimore, Maryland, USA
In animal models and patients with AMI, left ventricular (LV) remodeling is accompanied by interstitial fibrosis in remote myocardium. Such fibrosis in remote myocardium is considered to be a major histological landmark resulting in cardiac dysfunction after AMI. Previous studies have shown that VEGF has a potent effect on angiogenesis, but no effect on fibrosis, whereas the other angiogenic growth factor bFGF stimulates fibrosis. On the other hand, hepatocyte growth factor (HGF) has dual effects, namely angiogenic and antifibrotic effects. In this study MR imaging has been used to determine the effects of intramyocardial HGF gene therapy transferred by plasmid DNA on left ventricular function and strain. Intramyocardial injection of plasmid expressing HGF improved LV global function and prevents LV remodeling associated with infarction. It also improved regional strain in both peri-infarcted and infarcted regions.
15:00 3040. Fast and Accurate Voxel-By-Voxel Perfusion Imaging Using Convolution Models
Artem Mikheev1, Henry Rusinek1
1NYU School of Medicine, New York, New York, USA
Modeling of the perfusion using dynamic contrast-enhanced imaging based on convolution models is gaining increasing attention. To improve the computational speed and be able to control the convolution error due to discrete sampling we have developed and implemented the adaptive convolution algorithm. Algorithm was tested on the kidney perfusion model and MR renography acquisition. It enables fast and accurate analysis of DCE MR datasets.
15:30 3041. ADC Histogram Derived RGB Color-Maps for Characterizing Low Grade Glioma Subtypes
Inas S. Khayal1,2, Tracy R. McKnight1, Wei Bian1, Soonmee Cha1, Susan M. Chang1, Sarah J. Nelson1
1University of California, San Francisco, San Francisco, California , USA
Low grade gliomas are a heterogeneous group of brain tumors with variable prognosis and response to therapy. Prior studies have reported that the Apparent Diffusion Coefficient (ADC) may aid in subtyping low-grade gliomas. The goal of this study was to use ADC histograms from patients with astrocytoma and oligodendroglioma to generate RGB color-maps showing astrocytoma-like and oligodendroglioma-like regions. Because biopsies are limited to a very small piece of tissue, this technique allows for the visualization of the biologically different regions within the whole tumor mass, which may aid in image-guided biopsies, assessment of treatment response or prognosis of clinical outcome.
14:00 3042. Visceral Fat Quantification on MRI: The Impact of Partial Volume Effect
Qi Peng1, Anqi Zhou1, Yao Ding2, Roderick W. McColl2, Paul T. Weatherall2
1UT Health Science Center at San Antonio, San Antonio, Texas, USA; 2UT Southwestern Medical Center at Dallas, Dallas, Texas, USA
MR images are generally known to have lower spatial resolution than CT images. This greatly reduces the accuracy of visceral fat measurement on MRI since partial-volume fat may contribute a significant part to the total visceral fat. By employing a novel fat quantification strategy, we estimated the number of full- and partialvolume fat pixels (Nf and Np, respectively) in visceral area on 9 healthy volunteers. It is found that the average Np is more than twice the average Nf (Np/Nf=2.1), and fat volume from partial-volume fat voxels is 104.0% of that from full-volume voxels. Therefore, partial volume effect is significant on MR images with typical spatial resolution.
14:30 3043. On Automatic Regional Analysis of Quantitative Relaxation Times Mapping in the Brain
Benjamin Segun Aribisala1, Jiabao He1, Peter E. Thelwall1, Kieran G. Hollingsworth1, Andrew M. Blamire1
1Newcastle University, Newcastle upon Tyne, UK
Quantitative assessment of MR images is an important step in the analysis of many types of scan data. A significant step in many methods is registration of the individual brain to a standard space. Image registration requires smoothing and re-sampling and introduces partial volume effects, biasing analysis. Here we propose an automatic division into ROIs and we use the inverse process whereby regions of interest in standard space are registered to the individual, thereby analyzing each brain in its own real space. This approach reduces partial volume errors while taking into account variations in brain shapes and sizes.
15:00 3044. Reliability and Reproducibility of Myelin Water Fraction Analysis: A Comparison of Region of Interest and Pixel by Pixel Methods
Sandra M. Meyers1, Cornelia Laule2, Irene M. Vavasour2, Shannon H. Kolind2, Burkhard Maedler3, Roger Tam2, Jimmy S. Lee2, Anthony L. Traboulsee2, David K.B. Li2, Alex L. MacKay2
1University of Alberta, Edmonton, Canada; 2University of British Columbia, Vancouver, Canada; 3Philips Medical Systems, Vancouver, Canada
We compared region of interest (ROI) and pixel-by-pixel (PBP) analysis methods for myelin water fraction (MWF) determination. 20 controls were scanned twice using multi-echo T8-relaxation. For ROI-analysis, the mean pixel intensity within an ROI was fit using NNLS. In PBP-analysis, MWF was obtained for each pixel and the mean value within an ROI was calculated. PBP-analysis was more reliable among 4 different observers and gave a higher correlation, and a 3 times lower mean square difference between scans. As the PBP-method is more reproducible and gives more options for visualization and analysis of MWF, it is recommended over the ROI-method.
15:30 3045. Feasibility of Rapid B1 Mapping with RF Prepulse Tagging
Xin Chen1, Xingxian Shou1, Wayne R. Dannels2
1Case Western Reserve University, Cleveland, USA; 2Toshiba Medical Research Institute USA, Inc, Cleveland, USA
A B1 mapping technique which is fast and tolerant of patient motion is desired for measuring B1 field per subject due to the dependence of the B1 field patterns upon the sample. In this work, we propose an accurate and efficient method of 2-D B1 mapping with RF prepulse tagging. Our simulation shows that the calculated B1 profile agrees with the pre-assumed B1 profile very well. We also perform an error analysis to study the precision of our algorithm in the presence of noise.
14:00 3046. Imaging and Analysing Iron Accumulations in the Human Brain Using Magnetic Resonance Imaging
Guenther Grabner1, Dietrich Haubenberger1, Eduard Auff1, Siegfried Trattnig1
1Medical University of Vienna, Vienna, Austria
This work is about analyzing (phase-shift and phase-shift-symmetry) iron accumulations in brains of patients with Parkinson's disease (PD) and healthy controls by using susceptibility-weighted imaging phase. In order to perform image based phase-shift-symmetry comparisons and prevent bias due to shape differences, a symmetric phase model was build. All data-sets were non-linearly registered to the symmetric model and 3D correlation coefficients were used to determine symmetry (in the area of the Putamen). Phase-shift symmetry is a possible marker for unilaterally PD and largely independent of absolute phase-values. Phase-shift analysis show an increasing phase-shift (in anterior- posterior direction) within the Putamen.
14:30 3047. AnalyzeNNLS: Software Designed to Simplify Multiexponential Decay Image Analysis
Thorarin A. Bjarnason1, J Ross Mitchell1
1University of Calgary, Calgary, Canada
Multiecho MR studies provide unique insight into tissue microstructure. Two major hurdles prevent scientists from applying this technique in their research: creating the pulse program and developing the analysis technique. We provide a solution to the latter issue by creating an easy to use, cross-platform software package, called AnalyzeNNLS, capable of analyzing multiexponential decays. This software allows scientists to perform region of interest analysis on multiecho, multislice data, thus allowing them to focus on the sciences of MRI and biology.
15:00 3048. Accurate Estimation of T1 from SPGR Signals
Lin-Ching Chang1,2, Cheng Guan Koay2, Peter J. Basser2, Carlo Pierpaoli2
1The Catholic University of America, Washington, District Of Columbia, USA; 2NICHD, National Institutes of Health, Bethesda, USA
T1 can be estimated from two or more SPGR images acquired with different flip angles and/or repetition times. However, T1 estimated by a widely-used linear method is biased due to improper accounting for noise in the fitting. This bias can be significant for clinical SPGR images, for example, T1 estimated in brain tissue (800~1600ms) can be over-estimated by 10-20%. We propose a weighting scheme that correctly accounts for the noise contribution in the fitting procedure. Simulations of SPGR experiments are used to evaluate the accuracy of the estimated T1 from the widely-used linear, the proposed weighted-uncertainty linear, and the nonlinear methods.
Quantitative Estimation of Prostate Cancer Using Inner Product of
Intervoxel Eigenvector (IPIE) Method [Not Available]
Koji Ishihara1, Mikio Suga1,2, Riwa Kishimoto2, Susumu Kandatsu2, Hiroshi Tsuji2, Hiroo Ikehira2, Takayuki Obata2
1Chiba University, Chiba, Japan; 2National Institute of Radiological Sciences, Chiba, Japan
The apparent diffusion coefficient (ADC) provides the possibility of adding information for an accurate diagnosis of prostate cancer. The ADC use only eigenvalues from the DTI information. Itfs suspected that the structure will show deformities if prostate cancer exists. Eigenvectors of the DTI might be applicable to estimate tissue structures. We propose the quantitative evaluation method, the inner product of intervoxel eigenvector (IPIE) method, to assess structural tissue changes from eigenvectors. The IPIE values in the prostate cancer region are significantly changed before and after carbon-ion radiotherapy. These results suggest the IPIE method can quantitatively evaluate changes of tissue structure.
14:00 3050. Tagged Helium-3 MRI Analysis for Pulmonary Kinematic Quantitation
Nicholas James Tustison1, Jing Cai2, Tally A. Altes1, G. Wilson Miller2, Eduard E. de Lange2, John P. Mugler III2, James C. Gee1
1University of Pennsylvania, Philadelphia, Pennsylvania, USA; 2University Of Virginia, Charlottesville, Virginia , USA
Tagged helium-3 is used to quantify pulmonary kinematics. Sample results including visuals illustrate the feasibility of our approach.
14:30 3051. Comparison of Kinetic Parameters Estimated with Unmeasured, Partially Measured, or Fully Measured Input Functions
Arvind Balachandrasekaran1, Nathan Allen Pack1, Edward V.R DiBella1
1University of Utah, Salt Lake City, USA
In this paper,complete blind and partial blind estimation were compared for estimating the kinetic parameters.The first method (complete blind) estimates the Arterial Input Function (AIF) completely whereas the second method (partial blind) estimates only the samples around the peak because
gadolinium concentration is non-linearly proportional to the signal intensity changes near the peak.
The kinetic parameters estimated from partial blind estimation had a higher correlation with the truth than those obtained from complete blind estimation.
15:00 3052. Model Based Blind Estimation of Kinetic Parameters
Jacob Fluckiger1, Matthias Schabel1, E.V.R. DiBella1
1University of Utah, Salt Lake City, USA
This work introduces a novel functional form for the arterial input function consisting of two gamma variate curves and a sigmoid curve. This model is then applied in iterative blind estimation to determine perfusion kinetic parameters. The blind estimation technique used alternately estimates parameters for the input function and the tissue concentration. The kinetic parameter estimates were compared with truth obtained from standard deconvolution. The average kinetic parameter variance between the two methods was less than 10%, suggesting blind estimation may be confidently used in situations where a directly measured AIF is not easily obtained.
15:30 3053. Optimal Processing to Derive Static PC-MRA from Time-Resolved 3D PC-MRI Data
Jelena Bock1, Oliver Wieben2, Kevin M. Johnson2, Juergen Hennig1, Michael Markl1
1University Hospital, Freiburg, Germany; 2University of Wisconsin-Madison, USA
The purpose of this study was to implement and to evaluate several algorithms for the optimal extraction of PC-MRA data from flow-sensitive 4D MRI, since PC-MRA has proven to be a useful alternative to contrast-enhanced MRA. All algorithms were implemented within an interactive pre-processing tool and could be combined with additional noise masking and static tissue-removal. Results of all algorithms were compared and evaluated based on data sets with different SNR.
14:00 3054. Improved Field Map Estimation in the Presence of Multiple Spectral Components
Diego Hernando1, Peter Kellman2, Justin Haldar1, Zhi-Pei Liang1
1University of Illinois at Urbana-Champaign, Urbana, Illinois, USA; 2National Institutes of Health, Bethesda, Maryland, USA
B0 field map estimation in the presence of multiple spectral components is an important and challenging problem in MRI, e.g., for cardiac and abdominal imaging, where the B0 field may contain large variations across the image. This paper presents a novel method for regularized field map estimation, which formulates the estimation of the complete field map as a joint problem (instead of, e.g., voxel-by-voxel estimation followed by smoothing). In vivo cardiac results demonstrate good robustness of the proposed method.
14:30 3055. Fast Susceptibility Weighted Imaging: FSWI
Frederik Testud1, Jürgen Hennig1, Maxim Zaitsev1
1University Hospital Freiburg, Freiburg, Germany
Susceptibility weighted imaging (SWI) show a strong contrast between gray and white matter. SWI experiments are typically performed with a gradient recalled echo sequence. The image phases are highly affected by B0 fluctuations and sometimes by phase wraps which are leading to long measurement and computation times. We propose a method to obtain phase contrast images with a standard EPI sequence. The method has the advantage of rapid data acquisition and a fast computation, and is referred to as fast SWI (FSWI).
15:00 3056. A Fast and Robust Method for Quantifying Magnetic Susceptibility of Arbitrarily Shaped Objects Using MR
Jaladhar Neelavalli1, Yu-Chung Norman Cheng1, Ewart Mark Haacke1,2
1Wayne State University, Detroit, USA; 2The Magnetic Resonance Imaging Institute for Biomedical Research, Detroit, USA
We present here a novel, fast and robust method for quantifying the magnetic susceptibility of arbitrarily shaped objects using MR.
15:30 3057. Robust and Mask Free Phase Unwrapping Technique Dedicated to B0 and T8+ Phase Imaging
Cyril Poupon1,2, Christopher Wiggins1,2, Myriam Chaumeil1, Valdis Gudmundsdottir1,2, Fabrice Poupon1,2
1CEA NeuroSpin, Saclay, France; 2IFR49, Saclay, France
The phase unwrapping problem occurs in different engineering domains. It can be applied directly into clinical practice (e.g. in MR angiography), but also, it can be used to estimate and adjust various MR acquisition related parameters, or to correct for some image acquisition artifacts such as susceptibility artifacts. Existing unwrapping techniques often involves the use of masks of the brain that are not necessarily easy to obtain.We introduced a fast and robust technique for unwrapping phase that do not necessitate employment of region masks and applied the technique to the phase signal of GRE data acquired at 7T.