Hall D Wednesday 13:30-15:30
yuichi yamashita1, Takao Yamamoto, Syuhei Takemoto, Ayako Ninomiya, Ikuo Aoki, Masao Yui
1Toshiba Medical Systems Corporation, Tokyo, Japan
Adamkiewicz artery is am important artery to identify before the surgery in patients with aortic disease. Present studies reported that CTA and CE MRA show visualization of the Adamkiewicz artery. An arterial spin labeling, time-spatial labeling inversion pulse (time-SLIP) allows visualization of marked blood vessels without use of contrast medium. Combination of time-SLIP with 3D balanced SSFP (bSSFP) allows depiction of marked blood traveled within an inversion time (TI) range with good contrast. In this study, we have investigated the technique to depict the Adamkiewicz artery by adjusting TI and the position of a free-hand tag to mark the vessel.
Isabelle Parienty1
1Bois de Verrières Medical Imaging Center, Antony, France
Renal Artery Stenosis (RAS) is the major cause of renovascular hypertension and an important cause of chronic renal insufficiency and end-stage renal disease. Until recently, Contrast Enhanced MRA (CE-MRA) was considered a non-invasive and totally safe technique for the evaluation of RAS. The recent link between gadolinium and nephrogenic systemic fibrosis (NSF) in patient with renal insufficiency ranked down CE-MRA to the least invasive technique with a considerable risk for patients with RAS. In this work we evaluated the clinical usefulness of a totally safe new commercially available non-enhanced MRA technique, Time-SLIP, in the screening of RAS.
919.
Automatic Detection of Systolic and Diastolic Phase for NATIVE
Alto Stemmer1, Peter Schmitt1, Berthold Kiefer1
1Siemens Medical Solutions, Erlangen, Germany
Blood flow synchronized 3D turbo spin echo imaging can be used for non contrast enhanced peripheral MRA. The optimal trigger times are often determined in a 2D scout scan, which acquires multiple single shot images in various cardiac phases. Here we introduce a technique that evaluates the scout images by means of image processing methods.
920. Non-Contrast Pulmonary Vein Angiography Using Off-Resonance RF Excitation
Reza Nezafat1, Christian Stoeck1, Prity Bengani2, Dana C. Peters1, Thomas Hauser1, Neil M. Rofsky1, Warren J. Manning1
1Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA; 2Boston Univeristy, Boston, Massachusetts, USA
Atrial fibrillation is a disorder afflicting over 2 million Americans with higher likelihood occurrence with increasing age. Radiofrequency pulmonary veins isolation is commonly used to treat patients with AF. For these patients evaluation of PV anatomy is essential in pre-procedural planning and post-procedural assessment of this treatment. Today, contrast-enhanced MR angiography is commonly used to evaluate PVs in RF ablation. In today’s clinical practice, PV image acquisition is performed during first pass injection of gadolinium contrast or with computed tomography and iodinated contrast. However, contrast enhanced approaches have adverse safety implications for patients with renal insufficiency. In this study, we investigated the use of off-resonance RF excitation demonstrate the blood in the pulmonary veins without exogenous contrast media.
Yasuo Amano1, Katsuya Takahama1, Shinichiro Kumita1
1Nippon Medical School, Tokyo, Japan
The purpose of this study was to evaluate the usefulness of free-breathing non-contrast-enhanced 3D SSFP MR angiography for the detection of the thoracic aortic diseases and simultaneous visualization of internal thoracic and coronary arteries. The 3D SSFP imaging was combined with cardiac and navigator-gating techniques, and T2-prepared and fat-suppression pulses. Coronal contrast-enhanced 3D MR angiography was performed for comparison. High correlation was observed for diameter of the thoracic aorta between the two MR angiography techniques. Accurate diagnoses of the diseases were made in most patients. Internal thoracic and coronary arteries were visualized better by free-breathing non-contrast-enhanced 3D MR angiography.
922. STAR and STARBURST for Combined Flow Dependent and Flow Independent Carotid MR Angiography
Ioannis Koktzoglou1, 2, Robert R. Edelman1, 2
1Evanston Northwestern Healthcare, Evanston, Illinois, USA; 2Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
In the evaluation of extracranial carotid artery disease, non-contrast MR angiography must be improved to compete with contrast-enhanced examinations. We present the combination STAR and STARBURST, flow dependent and flow independent sequences capable of generating high quality carotid MR angiograms without the need for contrast material.
Isabelle Parienty1
1Bois de Verrieres Medical Imaging Center, Antony, France
CT Angiography and contrast-enhanced MR Angiography (CE-MRA) techniques have become widely established and are nowadays used in routine clinical exploration of peripheral, lower extremities and renal arteries. However, in-patient with renal dysfunction, there is a growing amount of evidence against the systematic use of gadolinium-based CE-MRA as it has been linked to the development of nephrogenic systemic fibrosis. In this work, we investigated the reliability of the commercially available non-contrast enhanced MRA technique: Fresh blood imaging (FBI) in our clinical setting to explore patients with obstructive vascular disease.
Randall B. Stafford1, 2, Mohammad Sabati1, 2, Michael J. Haakstad2, Houman Mahallati1, 2, Richard Frayne1, 2
1University of Calgary, Calgary, Canada; 2Foothills Medical Centre, Calgary Health Region, Calgary, Canada
Huang et al. showed that the balanced steady-state free precession Dixon method provides good fat-water separation. Separation is achieved by adjusting the centre frequency to collect two images where fat and water are in-phase and opposed-phase, respectively. Adding these two images results in a fat-suppressed water-only image. We hypothesize that this technique can perform fast 3D non-contrast enhanced (NCE) MR angiography (MRA). We collected 3D image volumes in the legs of five healthy volunteers using this method. Good vessel conspicuity was found in our water-only image volumes. We conclude that this technique has the potential for non-contrast-enhanced MR angiography.
Zheng Chang1, Qing-San Xiang2, Jim Ji3
1Duke University, Durham, USA; 2University of British Columbia, Vancouver, Canada; 3Texas A&M University, College Station, Texas, USA
The efficient multiple acquisition technique using shared spatial information by Skipped Phase Encoding and Edge Deghosting (SPEED) has been successfully demonstrated in water-fat imaging with double acquisitions. In this work, the technique is further used to accelerate phase-contrast (PC) MRA. Multiple acquisitions in PC-MRA share similar spatial information. By making use of the shared information, PC-MRA is accelerated by SPEED with factors greater than that achievable for a single acquisition. In this work, a PC-MRA study with two acquisitions is accelerated by a factor of nearly 2, reducing scan time to that of about one acquisition.
926. Axial 2D TOF-Venography with Continuously Moving Table Acquisitions
Sandra Huff1, Dominik Paul1, Michael Markl1, Ute Ludwig1
1University Hospital Freiburg, Freiburg, Germany
Time-of-Flight MR-Angiography (TOF-MRA) allows for vessel imaging without the application of contrast agents. A difference method for TOF-MRA of an extended Field of View is presented while the patient table is continuously moved during data acquisition. The peripheral veins from the bifurcation to the feet were imaged using the proposed acquisition technique. Furthermore an optimal flip angle was determined resulting in a high venous signal for the chosen sequence parameters.
927. 3D Dark Blood MR Angiography of the Thoracic Vessels
Yiu-Cho Chung1, Stephen Cook, Jaeseok Park2, Marshall Winner, Renate Jerecic, Orlando Simonetti
1Siemens Medical Solutions USA, Inc., Columbus, USA; 2Siemens Medical Solutions, Germany
Followup of patients with aortopathy and congenital heart diseases post-surgery is difficult with current 3D MR angiographic techniques because of their sensitivity to susceptibility artifacts from metallic stents commonly found in these patients. The conventional 2D turbo spin echo techniques suffer from partial volume effects, long scan time and difficult slice positioning in patients with congenital diseases. We propose a new 3D turbo spin echo technique that provides isotropic, high resolution dark blood thoracic MR angiography. The technique has reduced susceptibility artifacts and was found to improve visualization of vessel patency in patients with aortic stents.
928. Non-Contrast, Free Breathing 3D SSFP MR Angiography of Pulmonary Veins: Initial Experience
Aparna Singhal1, Anderanik Tomasian1, ALex Sassani2, Vibhas Deshpande2, Gerhard Laub2, J. Paul Finn2, Stefan Ruehm2, Mayil S. Krishnam3
1UCLA, Los Angeles, USA; 2UCLA, USA; 3UCLA, Los ANgeles, USA
We sought to investigate the feasibility of non-contrast, free breathing 3D-SSFP MR Angiography for pulmonary veins evaluation and to correlate with conventional contrast-enhanced MRA. 3D-SSFP MRA provides sufficient vascular delineation and SNR, CNR to support confident evaluation of pulmonary veins.
929. A Method for Removing Fluid-Bearing Voxels from STARBURST MR Angiographic Images
Ioannis Koktzoglou1, 2, Robert R. Edelman1, 2
1Evanston Northwestern Healthcare, Evanston, Illinois, USA; 2Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
STARBURST is a newly proposed method for creating high quality flow-independent angiograms. When acquired with a trueFISP image readout, the STARBURST technique enhances signals from fluids that may obscure view of the angiogram. We present a method for identifying and automatically removing fluid-bearing voxels.
930. Fast Spin-Labeled Projectional Carotid MR Angiography
Ioannis Koktzoglou1, 2, Robert R. Edelman1, 2
1Evanston Northwestern Healthcare, Evanston, Illinois, USA; 2Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
Non-contrast methods for angiography may reduce procedural cost and risk of adverse reactions to contrast material. We present an arterial spin-labeled technique that allows for projectional carotid MR angiography in twenty seconds.
931. Investigation of Background Suppression Strategies in Interactive Fresh Blood Imaging
Pauline Wong1, Martin John Graves1, David John Lomas1
1University of Cambridge and Addenbrooke's Hospital, Cambridge, UK
Background suppression in subtraction MR angiography can be a problem when the TR of two acquisitions are different, causing unequal tissue signal which results in an angiogram with high background signal. This is encountered in interactive FBI where triggering occurs alternately in systole and diastole at short TR. Five tissue suppression strategies are investigated to improve the flow contrast in this case: Magnetisation Transfer (MT) prep, Projection dephaser, Inversion Recovery prep, Variable Refocusing Flip Train and single-triggered Fixed TR. Preliminary results suggest that MT, IR, variable flip and Fixed TR can be optimised for background suppression in interactive subtraction angiography.
932.
“Inflow“ Renal MR-Angiography with Steady-State Free-Precession and
Slab-Selective Spin Inversion:
Intraindividual Comparison with Ce-MRA in
Patients
Marcus Katoh1, Jan Weidner2, Arno Buecker1, Matthias Stuber3, Rolf W. Gunther2, Elmar Spuentrup2
1University Hospital Saarland, Homburg, Germany; 2RWTH Aachen University Hospital, Aachen, Germany; 3Johns Hopkins University Medical School, Baltimore, Maryland, USA
The reliability of a previously introduced inversion-prepared renal MRA technique was evaluated in patients. 103 renal arteries in 45 patients were investigated on a 1.5 T whole-body MR-system using a free-breathing navigator-gated and cardiac-triggered 3D steady-state free-precession sequence with a preceding slab-selective inversion pulse (inflow-MRA). For comparison contrast-enhanced MRA (ce-MRA) was performed. Images were evaluated in terms of artifacts and visualization of the renal arteries. In addition, the stenosis grade was assessed. Inflow-MRA yielded sonsistently good image quality and showed excellent correlation to ce-MRA with respect to the assessment of the stenosis grade without the need for contrast medium application or breath-hold.
933.
Non Contrast Enhanced MRA of the Lower Extremities Using an ECG-Gated
Variable Flip Angle 3D Fast
Spin Echo Sequence
Ruth P. Lim1, Andrew D. Hardie1, Elizabeth M. Hecht1, Danny C. Kim1, Jian Xu2, Pippa Storey1, Thomas P. Mulholland1, Sooah Kim1, James S. Babb1, Vivian S. Lee1
1NYU Medical Center, New York, USA; 2Siemens Medical Solutions, New York, USA
The association of Nephrogenic Systemic Fibrosis with gadolinium chelates has increased interest in the development of clinically viable non contrast MRA techniques. We describe our initial clinical experience with an ECG-gated variable flip angle fast spin echo technique to image the lower limb vasculature. This has the advantage of shorter interecho spacing and a shorter acquisition window compared with a previously described ECG-gated HASTE MRA technique, with improved spatial resolution and timing of systolic and diastolic acquisitions. The technique is feasible with a high negative predictive value, however further optimization includes addressing B1 inhomogeneity.
934. Comparison of Image Reconstruction Algorithms for the Depiction of Vessel Anatomy in PC VIPR Datasets
Ashley Gould Anderson1, Kevin M. Johnson1, Jelena Bock2, Michael Markl2, Oliver Wieben1
1University of Wisconsin, Madison, Wisconsin, USA; 2University Hospital Freiburg, Freiburg, Germany
This study compares eight algorithms for the generation of angiograms from cine phase contrast VIPR imaging, a truly 3D radial trajectory with radial undersampling. The motivation for this investigation is based on the renewed interest in non-contrast enhanced MRA methods and the need for accurate depiction of vessel anatomy and boundaries for clinical evaluations and for the direct derivation of hemodynamic parameters such as wall shear stress and trans-stenotic pressure gradients from the velocity vector fields.
Hall D Wednesday 13:30-15:30
Peter D. Gatehouse1, Jennifer Keegan, Ricardo Wage, David N. Firmin
1Royal Brompton Hospital, London, UK
Aiming to avoid the need for stabilisation cycles, real-time cine bSSFP imaging was modified to slide the image slice continuously along the long axis of the heart. Cardiac function measurements and blood-myocardium contrast were compared against real-time as normally used with stabilisation on alternate cycles. The sliding-slice continuous cine enables more rapid volume acquisition at reduced blood-to-myocardium contrast.
977.
Evaluation of Right Ventricular Function and Pulmonary Perfusion in
Ross Procedure Patients Using
Magnetic Resonance Imaging
Anna Lakoma1, David Tuite1, John Sheehan1, Peter Weale, James Carr1
1Northwestern University, Chicago, Illinois, USA
The purpose of this retrospective study was to evaluate whether valve dynamics and pulmonary perfusion parameters as measured by MRI can predict right heart dysfunction in patients post Ross procedure.
978. TGRAPPA Accelerated Free Breathing Real-Time Cine Cardiac Imaging with a 32-Channel Coil
Neil Isaac1, Sven Zuehlsdorff2, Peter Weale2, Sonia Nielles-Vallespin3, Renate Jerecic2, Harold Litt1
1University of Pennsylvania, Philadelphia, Pennsylvania, USA; 2Siemens Medical Solutions, Chicago, Illinois, USA; 3Siemens Medical Solutions, Erlangen, Germany
A comparison of TGRAPPA accelerated real time cine images of the heart using a 32 channel phased array coil, in comparison with traditional segmented k-space acquisitions using a 32 channel coil, as well as traditional 8 channel phased array coil.
979. Increased Diastolic Pressure Gradients Are Measured During Dobutamine Stress Tests
June Cheng Baron1, Ian Paterson1, Mark Haykowsky1, John Mackey1, Richard Thompson1
1University of Alberta, Edmonton, Canada
Measurement of blood pressure gradients (ÄP) between the atrium and ventricle during diastole provides insight into the ability of the ventricle to facilitate filling by rapid relaxation. We examine, for the first time, changes in ÄP during a dobutamine stress test to characterize stress-related increases in these gradients. In 8 subjects, heart rates increase from 58-77 (rest) to 106-160bpm at peak stress, with corresponding increases in filling pressure gradients from 2.4±0.5mmHg (rest) to 4.8±1.8mmHg at peak stress. We attribute increases in ÄP to increased diastolic suction and not pre-load, since end-diastolic volumes drop with stress by 35±16ml.
980. Volumetric Cardiac Quantification Using Three Dimensional Dual Phase Whole Heart MRI
Sergio Andres Uribe1, Tarinee Tangcharoen1, Victoria Parish1, Ivo Wolf2, Reza Razavi1, Gerald Greil1, Tobias Schaeffter1
1Kings College London, London, UK; 2Deutsches Krebsforschungszentrum, Heidelberg, Germany
In this abstract we propose a new acquisition that allows precise cardiac volume quantification. The technique acquires isotropic data sets of the whole heart during systole and diastole in a single free breathing scan using independent navigators for each cardiac phase. Quantification of LV and RV cardiac volumes is performed using a semi-automatic segmentation tool. A comparison between the standard Simpson approach and the proposed method shows a good agreement for all volunteers and patients.
981. Inflow Quantification in 3D Cardiac MR: Implications for Whole Heart Coronary Imaging and 3D Cine
Reza Nezafat1, Daniel A. Herzka2, Christian Stehning3, Dana C. Peters1, Anne Riley4, Kay Nehrke3, Warren J. Manning1
1Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA; 2Clinical Sites Research Program, Philips Research North America, Briarcliff Manor, New York, USA; 3Tomographic Imaging, Philips Research Europe, Hamburg, Germany; 4Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, USA
Large volume 3D cardiac MR imaging (CMR) is becoming more appealing with applications both in 3D cardiac cine and whole heart coronary imaging. The transition from single 2D slices or small 3D slabs to thicker 3D slabs theoretiecally could result in an increased SNR and better image registration. However, for CMR there is an associated penalty that results from saturation of blood flowing into the imaging volume which can affect blood SNR and blood-myocardium CNR. In this study, we investigated inflow enhancement (or lack thereof) in 3D single-phase imaging (for coronary applications) as well as cardiac cines (for function evaluation).
Chun Xu1, Lawrence Dougherty2, Gamaliel Isaac2, Aaron Blom1, Joseph H. Gorman1, Robert C. Gorman1, James J. Pilla1
1University of Pennsylvania, Glennolden, Pennsylvania, USA; 2University of Pennsylvania, Philadelphia, Pennsylvania, USA
The aim of this work is to investigate the use of a 3-D MR tissue-tagging imaging sequence combined with a motion estimation approach using a 3-D Optical Flow Method (OFM) for the quantification of left ventricular (LV) mechanics. Utilizing imaging and OFM parameters optimized in a previous simulation study, this method was applied to a healthy volunteer, from which 3-D displacement fields were derived and used to quantify LV contractile functions. Regional heterogeneity of 3-D displacement and strain was characterized in high spatial resolution through out the human LV, with significantly shorter acquisition and analysis time compared with other methods
983.
Association Between Elevated Fasting Glucose, in the Absence of
Diabetes, and Increased Left
Ventricular Mass in Women
Michael L. Chuang1, Philimon Gona2, 3, Carol J. Salton1, Noriko Oyama1, Susan J. Blease2, Daniel Levy2, Christopher J. O'Donnell2, Warren J. Manning1
1Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; 2the NHLBI's Framingham Heart Study, Framingham, Massachusetts, USA; 3Boston University, Boston, Massachusetts, USA
Elevated fasting glucose, in the absence of diabetes, is associated with increased left ventricular (LV) mass in adult women but not men. There were no differences in LV geometry or ejection fraction between subjects with normal or elevated fasting glucose for either women or men.
984.
Automated Segmentation of the Left Ventricle Using Myocardial
Effusion Threshold Reduction and
Intravoxel Computation (METRIC)
Noel Christopher Codella1, Jonathan W. Weinsaft1, Matthew D. Cham1, Matt Janik1, Martin Prince1, Yi Wang1
1Weill Medical College of Cornell University, New York, New York, USA
An automated left ventricular segmentation algorithm for cine balanced SSFP images that accounts for partial voxel effects through linear interpolation between the signals of blood and myocardium is presented.
985. Motion-Corrected Strain Calculation from Long-Axis MRI Strain-Encoded (SENC) Images
Ahmed Amr Harouni1, Khaled Z. Abd-Elmoniem1, Monda L. Shehata1, David A. Bluemke1, Nael F. Osman1
1Johns Hopkins University, Baltimore, Maryland, USA
Strain measured from Strain-Encoded (SENC) images are currently extracted from fixed regions, which introduce large error especially in the LV freewall. In this work, we developed a novel algorithm to automatically detect and track the motion of heart wall in long-axis SENC images. We showed that strain values calculated from our algorithm are acceptable and close to strain values calculated from the manual segmentation.
Daniel B. Ennis1, J Andrew Derbyshire2
1Stanford University, Stanford, California , USA; 2National Institutes of Health, Bethesda, Maryland, USA
We first define a simplified 4x4 matrix expression that describes the mathematics of an MRI displacement encoding experiment using homogenous coordinates. This expression is then used to characterize the effect of imaging noise on the strain calculated from simulated displacement measurements. It is shown that the error in estimating the strain is non-linearly related to both the image SNR and the imaging resolution. The highest strain errors occur for combined low SNR and high image resolution. Increases in imaging resolution (decreasing pixel size) can increase the error in the strain estimate even when SNR is held constant.
987. Tracking Motion in TMRI Data Using Binary Image Processing Techniques
Tareq Alrefae1, Mohammed D. Alenezy2, Elena I. Popel2, Mehmet Bilgen3
1Kuwait University, Kuwait City, Kuwait; 2University of Kansas, Lawrence, Kansas, USA; 3Medical University of South Carolina, Charleston, South Carolina, USA
Tagged magnetic resonance imaging (tMRI) has found wide-spread applications in various clinical and research areas. The strength of this technique lies in its ability to reveal regional motion of tissue such as that observed in cardiac studies. For purposes of quantification, offline applied algorithms are developed to track the tissue motion of user-selected regions of interest (ROI). Examples of such algorithms include harmonic phase (HARP) techniques and others. To further enrich the library of tracking algorithms, we present an automated method that utilizes binary image processing techniques to follow the tissue motion of user-selected ROI in tMRI data.
Tareq Alrefae1, Mehmet Bilgen2
1Kuwait University, Kuwait, Kuwait; 2Medical University of South Carolina, Charleston, USA
Application of tMRI combined with sensitive motion estimation techniques, such as harmonic phase (HARP) analysis, has proven to be feasible and diagnostically valuable in evaluating the performance of normal or diseased hearts in live subjects using conventional global and regional measures. In the presence of large motions, however, the current analysis techniques including HARP fail to accurately describe the absolute displacement of the myocardial tissue. This paper addresses this issue and offers a solution - a simple time-dependent model and its time-reversal- providing motion estimates with improved performance even when the tissue is subject to large movements.
989. Improved Cardiac Strain Estimation from DENSE Using Automatic Outlier Rejection
Sandeep Narendra Gupta1, Anthony Aletras2, Maureen N. Hood3, Vincent B. Ho3, Ehud J. Schmidt4, Pelin Aksit5
1GE Global Research, Niskayuna, New York, USA; 2NIH, Bethesda, Maryland, USA; 3NNMC and USUHS, Bethesda, Maryland, USA; 4GE Healthcare, Boston, Massachusetts, USA; 5GE Healthcare, Bethesda, Maryland, USA
DENSE technique allows quantification of regional myocardial strain. We present here a novel method for processing of DENSE data which automatically detects and rejects pixels with poorly conditioned strain calculation. With this outlier rejection method, a three-fold reduction in the variability of circumferential shortening and radial thickening quantification is demonstrated in human studies.
990.
A Premature Ventricular Contraction Detection Method for Cardiac MR
Acquisitions Using Morphology
Feature
Liewei Sha1
1GE Healthcare, waukesha, Wisconsin, USA
Premature Ventricular Contractions are ectopic heart beats with ventricular origin. The presence of PVCs degrades image quality, if the gated scans do not differentiate PVCs from normal beats. Accurate detection of PVC not only improves image, but also provides auxiliary information to facilitate diagnosis of ventricular arrhythmias. Many PVC detection algorithms have been proposed [1,2], few consider the noise in MR environment,including distortion due to magnetohydrodynamic effect, gradient noise, and radio-frequency interference. This work proposed a method to detect R-wave and PVC, using combined feature of MR noise resistant 2D VCG morphological distance, the R-peak duration and RR interval.
991. Relation of Myocardial Fiber Structure with Cardiac Wall Motion Using DTI and MR Tagging
Yin Wu1, 2, Tracy Yee Chow1, 2, Ke Xia Cai1, 2, Ed X. Wu1, 2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong; 2Dept. of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong
LV structure is known to be associated with cardiac function, but the relation of myocardial fiber distribution with regional wall motion remains to be elucidated. In this study, both tagging and DTI were performed in adult rats. LV myocardium twist, circumferential strain, and myocardial fiber architecture were investigated. Results show that the myocardial fiber distribution has direct relation with the LV myocardium twist angle and magnitude of circumferential strain. Such integrated functional and structural analysis may provide more information for understanding the fundamental cardiac mechanics and assessment of pathological changes.
992. Model-Based Estimation of 3D Myocardial Motion Based on Cine DENSE MRI
Patrick Helm1, Frederick Epstein1
1University of Virginia, Charlottesville, Virginia , USA
Multi-slice cine DENSE can acquire displacement-encoded images representing the 3D motion of the entire left ventricle with high spatial resolution and accuracy relative to conventional myocardial tagging, but still with finite signal-to-noise ratio and discrete spatiotemporal sampling. We developed a technique where a patient-specific cardiac model was employed to improve DENSE estimates of the continuous spatiotemporal displacement field throughout the 3D left ventricle. The model-based reconstruction of cardiac motion agreed closely with tagging when undersampled to similar spatial resolution. The higher spatial resolution of DENSE enabled the use of fewer model constraints and potentially improved estimation of 3D motion.
993. Epicardial Contour Extraction by LV-Metric and Active Contour Model Using Cardiac MRI
Hae-Yeoun Lee1, Yi Wang1
1Cornell University, New York, USA
In this study, an automatic left ventricle (LV) segmentation algorithm using short-axis cine cardiac MRI is presented. To segment LV and detect endocardial contour, we compensate the coil sensitivity of magnitude images and apply region-growing scheme, termed LV-METRIC. To detect epicardial contour and segment myocardium (MC), we generate a circular map by polar mapping, extract and filter edge information using segmented LV. After defining the external force with prior knowledge, we apply guided active contour model to find epicardial contour, where initial contour is the endocardial contour from LV and only moves to radius direction on the circular map.
994. One Touch Imaging for Improved Cardiac Workflow
Robert D. Darrow1, Vivek Vaidya2, Ambey Govenkar3, Rakesh Mullick2, Thomas K.F. Foo4
1GE Global Research, Niskayuna, USA; 2GE Global Research, Bangalore, India; 3Extenprise, Inc., Pune, India; 4GE Global Research, Niskayuna, USA
Cardiac examinations demand highly proficient technologists or operators to complete clinical studies in an efficacious and time-efficient manner. One Touch imaging minimizes operator impact on the quality of the cardiac examination and produces highly repeatable examinations. In addition, by reducing the number of steps needed to identify the cardiac scan planes to a single button push, a simplified cardiac exam is demonstrated with substantial timesavings. We demonstrate a seamlessly integrated image acquisition/feature recognition method that produces short-axis cardiac CINE images with a single button push in less than 10 minutes, including breath-holding time.
Hall D Wednesday 13:30-15:30
Arteries: Overview of Phase III Clinical Trials
Gilles Soulez1, Siegfried Thurnher2, Nicoletta Anzalone3, Gianpaolo Pirovano4
1University of Montreal, Montreal, Canada; 2University of Vienna, Vienna, Austria; 3San Raffaele Hospital, Milan, Italy; 4Bracco Diagnostics Inc., Princeton, New Jersey, USA
Results of clinical trial evaluating Gd-BOPTA for CE-MRA are presented. In the carotid arteries, blinded readers noted significantly (p<0.001) increased specificity and accuracy compared to 2D-TOF MRA. The sensitivity, specificity, and accuracy of CE-MRA for renal artery stenoses ranged between 60–84%, 89–95%, and 80–87%, respectively. For peripheral MRA, the sensitivity (54–81%), specificity (90%–95%), and accuracy (85%–88%) of CE-MRA for detection of significant iliofemoral disease was significantly (p<0.001) better than TOF MRA (33–63%, 74–89% and 68–77%, respectively). Gd-BOPTA was safe and accurate for CE-MRI at a dose of 0.1 mmol/kg.
1033. Low Dose, Contrast-Enhanced MR Angiography of the Lower Extremities at 3.0 Tesla
Reza Habibi1, Derek G. Lohan1, Mayil S. Krishnam1, Fatemeh Barkhordarian1, Mehdi Jalili1, Roya Saleh1, Stefan G. Ruehm1, John Paul Finn1
1UCLA, Los Angeles, USA
Even though the exact correlation between the gadolinium dosage and occurrence of nephrogenic systemic fibrosis (NSF) in patients with low GFR remains to be established, it seems reasonable to minimize dose in susceptible patient groups, awaiting further clarification. The purpose of this study was to assess the feasibility of low-dose CE-MRA of the lower extremities at 3.0 Tesla and to compare the image quality with high-dose and intermediate-dose protocols. The results of our study showed that, taking advantage of the higher SNR at 3.0T, contrast dose for lower extremity MRA can be reduced several fold without any compromise in image quality.
1034. Targeted Contrast Enhancement Using Linear System Theory
Daniel Kopeinigg1, 2, Dominik Fleischmann1, Matus Straka1, Rudolf Stollberger2, Roland Bammer1
1Stanford University, Stanford, California , USA; 2Medical University Graz, Graz, Austria
Correct timing of the contrast bolus arrival is a crucial part in CE-MRA. The inability to play continuous waveforms in clinically used power injectors is also an issue in achieving a constant vessel target enhancement. FORWARD was developed to account for this limitation, as well as of physiological limitations like maximum injections flows, among others. In the FORWARD process, characteristics of the test bolus are used to tailor the injection profile to create a more constant vessel enhancement. The possibility to analyze the contrast agent bolus over time and the corresponding dispersion leads to new optimization methods for k-space sampling.
1035.
Three-Dimensional High Spatial Resolution Magnetic Resonance
Angiography of the Supra-Aortic Arteries
at 3.0 Tesla: A Contrast Dose
Reduction Study
Anderanik Tomasian1, Noriko Salamon, Derek Lohan, Mayil Krishnam, J. Pablo Villablanca, J. Paul Finn
1UCLA, Los Angeles, USA
The purpose of our study was to prospectively establish the non-inferiority of diminished dose regimens compared to higher dose regimens as reflected in the diagnostic image quality of high-spatial-resolution three-dimensional MR angiography of the supra-aortic arteries at 3.0 Tesla.High spatial resolution CE-MRA of the supra-aortic arteries at 3.0T can be performed with a gadolinium dose at least as low as 0.05 mmol/kg, without compromising image quality compared to 0.1 mmol/kg and 0.15 mmol/kg. Although further work is warranted, these initial results suggest that adoption of low-dose protocols in clinical practice may diminish sensitivity to contrast dose-dependent complications and result in cost savings.
Hall D Wednesday 13:30-15:30
Carl Jason Snyder1, Lance DelaBarre1, Greg Metzger1, Can Akgun1, Patrick Bolan1, Kamil Ugurbil1, Thomas Vaughan1
1University of Minnesota, Minneapolis, USA
It is known that using separate volume transmit coil with local phased array receivers has benefits over using either coil separately. Unfortunately, most body imaging at 7T currently uses surface transceive arrays. We have designed an 8 channel TEM transmit array to be used in conjunction with a 16-channel loop receiver array and a B1+ shimming algorithm for body imaging at 7T. This combination provides a relatively homogeneous volume over a localized region in the body.
1066. Rotating Transmission Line Elements for Optimized Parallel Imaging
Zhangwei Wang1, Michael Craig1, Ye Li2, Qing X. Yang1, Christopher M. Collins1, Wei Chen2
1Penn State University, Hershey, Pennsylvania, USA; 2University of Minnesota, Minneapolis, Minnesota, USA
For transmit arrays, independent amplitude and phase control can be used in a variety of ways achieve a homogeneous excitation distribution. However, for a receive array manipulation of sensitivity distributions and the g-factor require variation of the coil geometry. Stemming from work with stripline transmission line elements, we propose a new type of transmission line element which can be used to optimize the field distribution and g-factor easily by adjusting the orientation of independent coils.
1067. Shielded Quadrature Coil Elements for NMR Phased-Arrays
Matthias F. Mueller1, 2, Titus Lanz2, Tobias Wichmann2, 3, Felix A. Breuer3, Mark A. Griswold4, Peter M. Jakob1
1University of Wuerzburg, Wuerzburg, Germany; 2Rapid Biomedical GmbH, Rimpar, Germany; 3Research Center Magnetic Resonance Bavaria (MRB), Wuerzburg, Germany; 4University Hospitals of Cleveland, Cleveland, Ohio, USA
Recently MR systems with 128 independent receiver channels have been developed. With these, phased-arrays with up to 128 coil elements have been introduced. While these arrays have provided impressive results, the minimal size of elements is limited if maintaining sample noise dominance is required. Thus, only a fraction of the receive channels can be used to full potential for imaging of more localized region-of-interests. To this end, the concept of shielded quadrature array coil elements is introduced which utilizes additional, perpendicular coil elements to improve signal-to-noise ratio and encoding capability for parallel imaging.
1068. A Novel Decoupling Technique for Non-Overlapped Microstrip Array Coil at 7T MR Imaging
Zhentian Xie1, Xiaoliang Zhang1, 2
1UC San Francisco, San Francisco, California , USA; 2UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, California , USA
. In this work, a new magnetic wall decoupling method for designing non-overlapped coil arrays is introduced by using microstrip lines. The micsrotrip lines are the magnetic-wall generators, laced between two adjacent resonant coil elements. There is no physical connection between the decoupling microstrip line and coil 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. The MR images from each resonant element have no signal is observed from other coil, indicating the effectiveness of the proposed decoupling technique at ultrahigh field of 7T. The proposed design provides a robust approach to design of parallel imaging arrays at ultrahigh fields.
1069. 1.5-Tesla Integrated Dual Mode Hand/Wrist Array Coil for Imaging
Jacob Weaver1, Joseph Herczak1, Tsinghua Zheng1, Xiaoyu Yang1, 2, Hiroyuki Fujita1, 2
1Quality Electrodynamics, LLC., Mayfield Village, USA; 2Case Western Reserve University, Cleveland, USA
A six-channel dual-mode array coil for hand/wrist MRI imaging at 1.5 Tesla was constructed and tested. The coil offers two variable FOV modes, a full mode with an S-I coverage of 20cm for the entire hand/wrist imaging and a magnifying FOV mode covering 10cm in S-I for high resolution wrist only imaging. The high resolution mode shows significant SNR gains in the wrist region compared to a commercially available QD wrist coil.
1070. 8 Channel Multi-Coil to Image Both Hands and Both Wrists Symmetrically for RA Diagnosis
Akira Nabetani1, Harushi Mori2, Atsushi Nozaki1
1GE Yokogawa Medical Systems, Ltd., Hino, Japan; 2University of Tokyo, Bunkyo-ku, Japan
8 channel muti-coil to image both hands and both wrists symmetrically for Rheumatoid Arthritis (RA) diagnosis was designed and developed. At first patientfs posture for symmetrical imaging of both hands and both wrists in comfortable manner was considered. Then holding fixture was designed to keep such posture stably and comfortably. 8 coil element size and layout was determined for the B1 sensitivity of the multi-coil to cover the area of both hands and both wrists as homogeneously as possible. The developed holding fixture had stable and comfortable holding capability so there were no apparent motion artifacts in the images.
1071.
Twelve-Channel Receive-Only MRI Breast Coil at 3T
John A.J. de Groot1, Dennis W.J. Klomp2, Evert G.J. Beerens1
1Machnet BV, Maarn, Netherlands; 2Radboud UMC Nijmegen, Nijmegen, Netherlands
In this study we show simulation results of a twelve-channel MRI breast coil at 3T and measurements with phantoms and volunteers. The system consists of an existing 4-channel breast coil and a newly designed 8-channel add-on coil. The goal was to increase acquisition speed without compromising SNR compared to the existing breast coil. High reduction factors can be achieved by keeping coil couplings low and maintain good g-factor maps. We show that the system SNR is improved significantly and that high reduction factors can be applied.
Graham C. Wiggins1, Jonathan Polimeni1, Andreas Potthast2, Thomas Witzel1, Lawrence L. Wald1, 3
1Massachusetts General Hospital, Charlestown, Massachusetts, USA; 2Siemens Medical Solutions,Inc, Charlestown, Massachusetts, USA; 3Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts, USA
When using arrays with large numbers of small coils there is commonly a concern about the sensitivity provided by the small elements at distances farfrom the array. It is important to understand how the SNR in the center of the sample increases as a function of the number and distribution of coil elements around the head, whether in fact the SNR may decrease beyond a certain number of coils, and therefore how much benefit is gained from costly and complicated designs with 96 channels or more. We find particular benefit from the coils arranged over the dome of the head in our high-N arrays even for central SNR.
Nicola De Zanche1, Jurek Antonin Nordmeyer-Massner1, David Otto Brunner1, Klaas Paul Pruessmann1
1University and ETH Zurich, Zurich, Switzerland
Overlap is commonly used to minimize mutual inductance, and thereby coupling, among nearest neighbors in a coil array. In parallel imaging, however, it has been shown that non-overlapped coils provide more favorable sensitivity profiles than their overlapped counterparts. We provide data that demonstrate a clear advantage of non-overlapped over overlapped coils also in terms of noise correlation among channels when effective preamplifier decoupling provided by standard techniques is present.
Riccardo Lattanzi1, 2, Aaron K. Grant2, 3, Daniel K. Sodickson4
1Harvard-MIT, Cambridge, Massachusetts, USA; 2Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; 3Harvard Medical School, Boston, Massachusetts, USA; 4New York University Medical Center, New York, New York, USA
In this work we compare the SNR and current patterns of realistic coil models with the ultimate intrinsic SNR and the corresponding ideal current patterns for a homogeneous cylindrical sample. Calculations were repeated at different magnetic field strengths and for various acceleration factors, using coil arrays with increasing numbers of elements, in order to investigate how rapidly the ultimate behavior was approached in each case. In the center of the sample, 128-element arrays reached approximately 90% of the optimum SNR at 1.5T, whereas performance was lower at higher field strength due to increasing complexity in the ideal current patterns.
1075. Empirical Validation of 3T 96 Channel G-Factors and Comparison to Ultimate G-Factor
Graham C. Wiggins1, Jonathan R. Polimeni1, Andreas Potthast2, Thomas Witzel1, Lawrence L. Wald1, 3
1Massachusetts General Hospital, Charlestown, Massachusetts, USA; 2Siemens Medical Solution, Inc, Charlestown, Massachusetts, USA; 3Harvard-MIT Divisions Of Health Sciences and Technology, Cambridge, Massachusetts, USA
Accelerated imaging performance is one of the primary motivators for the development of receive arrays with higher and higher numbers of elements, typically characterized by the SENSE G-factor Metrics such as the maximum or the mean G-factor for a particular acceleration rate are frequently given as a key characteristic of a particular coil array. In practice, there are many factors which can influence the calculated G-factor map, including the field of view relative to object size (which determines the degree of aliasing), noise level and degree of smoothing in the sensitivity profiles, and whether regularization is used. We use time series data to validate analytical G-factor values for a 3T 96 Channel coil and compare these to the Ultimate G-factor. The 96 Channel coil appears to approach the ultimate G-factor for accelerations up to R=6
1076. A 1.5T 32-Channel Cardiac Array Coil for Coronary and Whole Heart MRI
Hiroyuki Fujita1, 2, Tsinghua Zheng1, Xiaoyu Yang1, 2, Joseph Herczak1, Jacob Weaver1, Kazuya Okamoto3, Takahiro Ishihara3
1Quality Electrodynamics, LLC., Mayfield Village, USA; 2Case Western Reserve University, Cleveland, USA; 3Toshiba Medical Systems Corporation, Otawara, Japan
MRI provides unparalleled soft-tissue contrast, and the temporal resolution has been much improved because of the rapid developments of high channel receiver count MRI hardware system and sophisticated parallel imaging applications. These state-of-the-art parallel imaging technologies enable effective real-time MR cardiac imaging. In this work, the authors constructed and tested a 1.5T 32-channel cardiac array, which is capable of higher acceleration factors to advance coronary and whole heart MRI.
1077. A 3D Parallel Imaging Capable Transmit and 15-Channel Receive Array Knee Coil at 3T
Matthew Finnerty1, Joseph Herczak1, Tsinghua Zheng1, Jacob Weaver1, Xiaoyu Yang1, 2, Hiroyuki Fujita1, 2
1Quality Electrodynamics, LLC., Mayfield Village, USA; 2Case Western Reserve University, Cleveland, USA
While knee imaging at 3T offers advantages over 1.5T in regards to greater spatial resolution and higher SNR, current commercial knee coils are susceptible to pulsation/flow artifacts since they only have one row of elements in the S-I direction. To address these challenges, a 15-channel knee coil with local 12-rung birdcage transmitter has been developed that utilizes three rows of elements in the S-I direction, which allows for 3D parallel imaging while providing high SNR and good uniformity with a larger coil inner diameter.
1078. SENSE Optimized Sixteen Element Receive Array for Cervical Spinal Cord Imaging at 3T
Jerzy Bodurka1, Patrick Ledden2, Peter Bandettini1
1National Institute of Mental Health, NIH, Bethesda, Maryland, USA; 2Nova Medical Inc., Wilmington, Massachusetts, USA
High quality and high resolution anatomical and functional imaging the human spinal cord remains a significant challenge in MRI. The benefits of parallel imaging with surface coil arrays have been clearly shown particularly in the brain imaging for both anatomical and fMRI studies. Here we demonstrate a custom design and build of a sixteen element receive-only surface coil array for spinal cord MRI imaging at 3 Tesla.
1079. Coil Design for Highly Accelerated 2D SENSE MRA of the Lower Legs
Casey P. Johnson1, Clifton R. Haider1, Phillip J. Rossman1, Thomas C. Hulshizer1, Eric A. Borisch1, Stephen J. Riederer1
1Mayo Clinic, Rochester, Minnesota, USA
Typical acceleration directions for 2D SENSE of the legs are left-right (L/R) and anterior-posterior (A/P). However, the fields of view along these directions can differ by a factor of three. In this work we describe an eight-element array in which the A/P elements are designed to have reduced depth of response compared to the L/R elements to account for the FOV differences. Compared to an eight-element array with uniformly-sized elements, the new design typically provides a 25% reduction in g-factors for acceleration factors >7. 2D SENSE CE-MRA of the lower legs at these high accelerations is of high quality.
1080. SNR and Parallel Imaging Performance of a 32-Channel Array for Human Brain Imaging at 7 Tesla
Jacco A. de Zwart1, Peter van Gelderen1, Shumin Wang1, Jeff H. Duyn1
1National Institutes of Health, Bethesda, Maryland, USA
Multi-channel coil arrays have led to substantial sensitivity and resolution improvements in human brain MRI. These benefits generally increase with the number of coil elements but level off at large element counts. An increased number of array elements also increases parallel imaging (PI) performance. Data from a 32-channel array at 7T were compared with a simulation and with numerically derived lower element count arrays to investigate these two aspects. SNR improves about a factor of 4 on average over the brain compared to one channel. Up to ~6-fold acceleration can be achieved with a mean PI penalty of <~20%.
Hall D Wednesday 13:30-15:30
Jarek Wosik1, Krzysztof Nesteruk2, Maged R. Kamel1, Flora Ip1, L.-M Xie1, Alexander C. Wright3, Felix W. Wehrli3
1University of Houston, Houston, USA; 2Institute of Physiscs Polish Academy of Sciences, Warsaw, Poland; 3University of Pennsylvania Medical Center, Philadelphia, USA
We report on the design and fabrication of a novel planar superconducting 3.0 T coil for MRI. We have designed and fabricated a high Q coil which is, in principle, intrinsically isolated from the entire body scanner transmit coil. The coil was made out of YBa2Cu3O7-x thin film deposited on a low-loss dielectric substrate. The design consists of two connected double-sided split-gap resonators. Bench measurements as well as numerical simulations of the coils showed more than -40 dB isolation from the transmit coil. In a uniform rf field, this coil should not require special detuning circuitry.
1108.
Optimization of SNR Via Cryogenically Cooled Radiofrequency
Coils in Hyperpolarized Noble Gas MR
Imaging of the Lungs
Warren Berger1, 2, Willaim Dominguez – Viqueira1, 2, Juan Parra – Robles1, Giles Santyr1, 2
1J.P. Robarts Research Institute, London, Canada; 2University of Western Ontario, London, Canada
Operating at the low magnetic field strength provided by hyperpolarized noble gases allows significant increases in SNR to be achieved by decreasing the coil’s operating temperature. A receiver coil was constructed and used to image a Xe-129 phantom and rat ventilated with Xe-129. Experiments were performed at room temperature (300K) and at 118K (using liquid nitrogen as a coolant). The gain in SNR by operating at 118 K was measured to be 1.55 and 1.41 in the phantom and rat respectively (corresponding to theory) and are only possible because of the low noise from the sample provided by using Xe-129.
1109. HTS Volume Coil with Improved Imaging Volume
S. Y. Chong1, J. G. Liu1, X. G. Zhao2, Keddy Chandran3, S. M. Yeung1, Q. Y. Ma1, E. S. Yang2
1Time Medical System, Hong Kong, Hong Kong; 2University of Hong Kong, Pokfulam, Hong Kong; 3Duke University, USA
In this abstract, a multi-turn 5.5¡¨ large HTS solenoid volume coil & compact cryostat prototype with improved field-of-view (FOV) & high SNR is presented. Although HTS thin-film phased array coil has been demonstrated to increase imaging volume, coupling & isolation between multi-coil, tuning & matching element require complex operation. The result shows the possibility of future large HTS volume coil with compact cryostat for human neuro-imaging with increased FOV & SNR.
Mona Julia Katharina Klein1, 2, Takahito Ono3, Masayoshi Esashi4, Jan Gerrit Korvink2
1CSEM, Neuchâtel, Nebraska, Switzerland; 2IMTEK, University of Freiburg, Freiburg, Germany; 3Tohoku University, Sendai, Japan; 4Tohoku University, Tohoku, Japan
The objective of this work is the development of a MEMS-compatible process for the parallel fabrication of solenoidal micro-coils for MR microscopy of biological tissues, e.g. cells. The micro-coil is embedded within two bonded wafers and has a hollow core which enables direct micro-fluidic integration. Signal loss caused by connection to external circuitry may be minimized in this design due to the planar wafer geometry, enabling the use of well-established device bonding techniques. In this paper, we particularly focus on the mold metallization process.
1111. Noise Parameter Extraction in the Design of Low Noise Amplifiers (LNA) for MRI
Barbara L. Beck1
1University of Florida, Gainesville, Florida, USA
The first stage of amplification for the very small MRI signal is the Low Noise Amplifier (LNA). An engineering method commonly applied to LNA design in communications utilizes matching components that transform the source impedance to the optimum reflection coefficient of the transistor. Key parameters necessary to perform this method are listed on manufacturer data sheets, but typically for frequencies much higher than those used in MRI. This paper describes a technique to extract these key parameters from simulation, utilizes them to design an optimized LNA, and compares the LNA to one that has been configured for phased array operation.
Nelly A. Volland1, Ioannis Constantinidis2, Thomas H. Mareci2, Nicholas E. Simpson2
1University of Florida, Gainesville, Florida, USA; 2University of Florida, Gainesville, USA
Introduction: Development of an implantable inductively-coupled coil system for non-invasive in vivo monitoring of a bioartificial pancreas (tissue engineered construct) at 11.1T is discussed. Methods: System (implantable coil inductively coupled to external coil) was simulated and constructed. Coating and integration of implantable coil with the construct were pursued to test system in vitro. Results: Implantable coil was coated with 1-mm PDMS and cell-free and cell-containing beads were imaged. Sensitivity was shown to be over 10 times higher than sensitivity of previous studies. Conclusions: Implantable inductively coupled coil system was successfully developed and used to image bioartificial pancreas in vitro.
1113. A Dual-Tuned Quadrature Microstrip Volume Coil for 13C/1H MRI/S at 7T
Zhentian Xie1, Duan Xu1, Douglas A. Kelley2, Dan B. Vigneron1, 3, Xiaoliang Zhang1, 3
1UC San Francisco, San Francisco, California , USA; 2GE Healthcare, San Francisco, California , USA; 3UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, California , USA
We present an 8-element by 8-element dual-tuned microstrip volume coil for in vivo 13C/1H MRI/S animal studies at 7T. The design strategy of using a mix of half-wavelength resonators and ƒ8¡51/4 wavelength resonators was employed to the 300MHz and 75MHz operating frequencies simultaneously.Preliminary results from a corn oil phantom were acquired using the proposed coil at 7T. The results show that dual-tuned microstrip volume coil is feasible and efficient, 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.
1114. Dual Tuned Helmholtz Coil for Breast Cancer Imaging
Anderson Nnewihe1, 2, Ernesto Staroswiecki1, Neal Bangerter1, Brian Hargreaves1
1Stanford University, Stanford, California , USA
Clinical breast exams using x-ray mammography have limited specificity and sensitivity for detecting breast tumors. Additional imaging modalities such as sodium (23Na) MR have the potential to increase the sensitivity and specificity of breast cancer detection because 23Na MR can reflect the disruption of the membrane Na-K pump associated with cancer. The purpose of this study was to investigate the difference between a dual-tuned Helmholtz coil and a dual-tuned surface coil in providing high SNR and high quality B1 homogeneity for multinuclear imaging as well as perform preliminary breast imaging using the dual-tuned Helmholtz coil.
1115.
Circularly Polarized Surface Coil with a Single Port
Yoshihisa Soutome1, Hideta Habara1, Yoshitaka Bito1
1Hitachi Ltd., Kokubunji, Japan
A circularly polarized surface coil with a single port has been designed and fabricated. The designed coil was constructed with two series connected loop-coils with an overlap, and its capacitors were designed to have a phase difference of 90o between the two loop currents. A phantom image of the designed coil was very similar to that of a QD surface coil. The SNR profile of the phantom image of the designed coil was identical to that of the QD surface coil. These results indicate that our coil can receive a circularly polarized B1 field without having a QD hybrid like that of the QD surface coil.
1116. Wireless Control of an Implantable Coil System for MRI/S
Barbara L. Beck1, Brian S. Letzen1, Rizwan Bashirullah1, Thomas H. Mareci1
1University of Florida, Gainesville, Florida, USA
A proposed solution for monitoring a bioartificial pancreas is a microfabricated wirelessly-controlled multiple-frequency MRI/S coil system. This coil system consists of an external surface coil inductively coupled to an internal monitoring coil. The design incorporates a switchable capacitor/varactor array driven by a microcontroller based on information received wirelessly. The focus of this work was to build a proof-of-concept prototype before developing the entire micro fabricated integrated chip system.
1117.
An Efficient Switched Double-Frequency Birdcage Coil for 3He
and 1H Imaging
Jian-Xiong Wang1, Eddy B. Boskamp2, Giles E. Santyr3, Brian K. Rutt3
1GE Healthcare, London, Canada; 2GE Healthcare, Waukesha, USA; 3University of Western Ontario, London, Canada
This work presented a switched double-frequency birdcage coil aiming for the development of double-frequency clinic body coil. This new technique doesn’t have the coupling problem and it’s easy to be implemented into existing clinic system.
1118. Optimization of Internal MRI Coils Using Ultimate Intrinsic SNR
Yigitcan Eryaman1, Yusuf Öner2, Ergin Atalar1
1Bilkent University, Ankara, Turkey; 2Gazi University, Ankara, Turkey
In this work an optimization method for internal MRI coils is explained. Ultimate intrinsic SNR which is the maximum value of the intrinsic SNR that can be obtained by internal MRI coils is used as a measure of performance. As a sample optimization endorectal MRI coils are optimized. The optimized coil is tested in both phantom and patient studies for prostate imaging. Similar methods can be used to optimize different type of internal MRI coils.
Computational Electromagnetics
Hall D Wednesday 13:30-15:30
Method of Moments
Christian Findeklee1, Ulrich Katscher1
1Philips Research Europe, Hamburg, Germany
The distribution of the electric conductivity s; and permittivity e; of human tissue can be used as diagnostic parameter and for a prediction of local SAR during MR measurements. Electric Properties Tomography (EPT) offers a way to determine these electric properties via MRI. In this work, equivalent volume currents in the Method of Moments were used for the iterative 3D EPT reconstruction.
1179.
Electric Properties Tomography: Calculation of the In-Vivo
Electric Field Within Realistic Computation
Times Using Quasi-Stationary
Zooming
Cornelis A.T. Van den Berg1, Mikel Boute1, Bob Van den Bergen1, Jan J.W. Lagendijk1, Ulrich Katscher2
1University Medical Center Utrecht, Utrecht, Netherlands; 2Philips Research Europe-Hamburg, Hamburg, Germany
Electric Properties Tomography (EPT) is a method to determine the dielectric properties during an MRI scan. It can be used as a diagnostic parameter or more precise local SAR assessment. Using an iterative computation scheme the dielectric properties are determined from the curl of the measured transverse magnetic field and a calculated axial electric field distribution. Conventional methods such as FDTD solvers are too slow to calculate the electric field with millimetre resolution. We successfully tested a method called quasi-stationary zooming that reduced the computation time with a factor of 20 without serious degrading the EPT results.
1180. Empirical and Computed B0 Perturbations Induced by Metallic Implants
Kevin M. Koch1, R Scott Hinks1
1GE Healthcare, Waukesha, Wisconsin, USA
Metallic implants used in arthroplasty procedures can induce severe spatial B0 perturbations and significantly distort conventional MRI. Information on the nature of these field perturbations has previously been difficult to assess. Here, it is demonstrated that FFT-based computations of approximated solutions to Maxwell’s equations can be used to rapidly and accurately predict high-resolution B0 distributions induced by metallic implants. A novel method is also presented that allows for MR-based collections of far-off resonance (>8kHz) contour B0 maps. The presented techniques are utilized to determine the previously unpublished magnetic susceptibility of a commonly used cobalt-chromium metal alloy.
1181. A Physical Shepp-Logan Head Phantom
Julian R. Maclaren1, Philip Bones1, Rick P. Millane1, Richard Watts1
1University of Canterbury, Christchurch, New Zealand
An MR-compatible Shepp-Logan head phantom has been constructed from layers of polycarbonate. When imaged using the correct slice thickness, the partial volume effect generates the required contrast values for each region. This phantom can be used to validate simulations conducted using the well-known numerical version. The physical phantom has been combined with a computer controlled moving platform to allow the effect of motion on various pulse sequences to be studied. This abstract compares data obtained from the physical phantom with data generated using the mathematical model of the Shepp-Logan head phantom.
1182. B1 Field Optimization for Microstrip Transmission Line Volume Coil at High Field
Chunsheng Wang1, Xiaoliang Zhang1
1University of California San Francisco, San Francisco, USA
B1 field distributions within MTL head coils with different substrate thickness were investigated by finite difference time domain method. Although the B1 field homogeneity can be improved by increasing substrate thickness of MTL coils for unloaded case, the B1 field homogeneity of MTL coils after loading can be optimized by selecting appropriate substrate thickness by making use of ¡®dielectric resonance¡¯ effect.
1183. Numerical Model of a Dielectric Resonator for High Field MRI
Bu Sik Park1, Andrew G. Webb2, Michael B. Smith3, Christopher M. Collins3
1Penn State University, College of Medicine, Hershey, Pennsylvania, USA; 2Penn State University, University Park, Pennsylvania, USA; 3Pennsylvania State University, Hershey, Pennsylvania, USA
Based on previous research, we have designed a dielectric resonator of barium strontium titanate (having a dielectric constant of 323) with a diameter of 28 mm for high field MRI and performed full Maxwell numerical calculations of the electromagnetic fields to evaluate the resonator. The cylindrical dielectric resonator has a region of low loss and high sensitivity along its central axis, and should provide lower sample loss than (for example) a solenoid design, which is found to produce a significant electric field in the sample due to the electrical potential on the wires.
1184. A New Analytical Approach to RF Coils at High Frequency: the Spiral Coil Example
Xin Chen1, Xingxian Shou1, Hiroyuki Fujita, 12, Victor Taracila3, Robert W. Brown1
1Case Western Reserve University, Cleveland, Ohio, USA; 2Quality Electrodynamics, LLC., Mayfield Village, Ohio, USA; 3GE Healthcare, Aurora, Ohio, USA
RF field inhomogeneity continues to be a major challenge in today’s high-field MRI. The RF wavelength is significantly shortened in biological samples due to a high dielectric constant, leading to field nonuniformities. We present a new analytical approach that is robust for optimization studies. As an example, we analyze a spiral coil, with special attention paid to the interplay between transverse and axial wavelength effects. The analytical results are consistent with previously published experiments and preliminary numerical simulat