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 simulations. An optimized spiral coil leads to improved field homogeneity, relative to the birdcage coil, up to (at least) 400MHz.
Bu Sik Park1, Christopher M. Collins2
1Penn State University , Hershey, Pennsylvania, USA; 2Penn State University, Hershey, Pennsylvania, USA
Although it is generally believed that almost all of the sample loss for the Birdcage Coil is magnetically-induced, there have been some suggestions that conservative E-fields may play a significant role, including suggestions that low-pass (LP) and high-pass (HP) BCs have significantly different E-field distributions (and may couple to the human subject very differently) due to their differing capacitor placement. Here we apply a recently-developed method to evaluate the conservative and magnetically-induced E-fields, as well as the sample power loss for a birdcage coil loaded with the head.
1186. Investigation of Mutual Inductance Coupling and Capacitive Decoupling of N-Element Array System
Lian Xue1, L.-M Xie1, Maged R. Kamel1, Flora Ip1, Jarek Wosik1, Alexander C. Wright2, Felix W. Wehrli2
1University of Houston, Houston, USA; 2University of Pennsylvania Medical Center, Philadelphia, USA
We report on the analyzes of the inductive coupling and capacitive decoupling of N-element array resonant system. A two-state rf current direction model for magnetically coupled coils was developed to calculate number of possible resonant modes in N-element array. We have obtained an analytical solution for number of possible frequency modes in a symmetric resonant linear and circular system of N-element array. Decoupling was achieved by using a set of capacitors to reduce the frequencies of higher modes to the lowest mode frequency. Examples of capacitive-only decoupling of 2x1, 2x2 and 4x1 arrays are shown and mechanism of such decoupling is analyzed.
1187. Exchange of Surface Coil Antenna Patterns Due to Gyrotropism
Cornelius von Morze1, 2, Albert Pofu Chen1, Duan Xu1, Daniel B. Vigneron1, 2, James Tropp3
1UCSF, San Francisco, USA; 2UCSF/UCB Joint Graduate Group in Bioengineering, San Francisco, USA; 3GE Healthcare, Fremont, USA
A recent formulation of NMR reciprocity that accounts for the gyrotropism of spins was tested through experiments on oppositely polarized 3.0T MRI scanners. The transmit and receive antenna patterns of a surface coil are distinct, and furthermore exchange on field reversal. The receive patterns of a bilaterally symmetric dual array were first measured through a receive-only experiment. Following the proper pattern exchanges and multiplications, these results predicted the distinct appearance of images obtained by operating the coil in transmit-receive mode on oppositely polarized systems.
1188. Fast, Accurate Calculation of Maximum Local N-Gram Specific Absorption Rate
Adam Charles Zelinski1, Vivek K. Goyal1, Elfar Adalsteinsson1, 2, Lawrence L. Wald, 23
1MIT, Cambridge, Massachusetts, USA; 2Harvard-MIT Division of Health Sciences & Technology, Cambridge, Massachusetts, USA; 3Harvard Medical School, MGH, Charlestown, Massachusetts, USA
SAR is a major concern in MRI; it is crucial to be able to quickly and accurately calculate maximum N-gram local SAR due to a pulse. In contrast with low-resolution models that lack many compartments and have overly-smooth tissue-boundaries, high-resolution models permit accurate local SAR calculations. Unfortunately, the fine resolution of such models makes calculating average N-gram SAR at each location a computationally intractable problem (straightforward region-growth methods may no longer be used). We pose a rapid algorithm that is equal in speed to the fixed-cube method, yet always averages over a N-gram region, ensuring accuracy of local SAR estimates.
1189. Phased Array Evaluation Using a Human Body Model at 3T
Selaka Bandara Bulumulla1, Christopher J. Hardy1
1GE Global Research, Niskayuna, USA
We use an anatomically accurate human body model with distinct electrical properties for different tissue types for evaluating the SNR of a 16-element phased array used for body imaging at 3T. Using numerical methods, we estimate the electromagnetic fields in the model and calculate an intrinsic SNR metric to evaluate the imaging performance of the array. The results highlight many of the artifacts common in 3T imaging, including left-right shading arising from wavelength effects. This method can be used to evaluate the imaging performance of a given array, and to optimize array configurations at various field strengths.
1190.
Lower RF Power Absorption Combined with Uniform Excitation
Using Multi-Port B1 Shimming: Numerical
Simulations and
Experiments at 7T
Lin Tang1, YiK-Kiong Hue2, Tamer S. Ibrahim, 12
1University of Oklahoma, Norman, Oklahoma, USA; 2University of Pittsburgh, Pittsburgh, Pennsylvania, USA
We show using the finite difference time domain method that improving the B1+ field homogeneity over 3-D regions with volumes as large as the whole head while simultaneously reducing the total RF absorption by human head to values lower than that associated with quadrature excitation can be achieved at 7T. The concept of B1 shimming with reduced RF power absorption was validated using a 7T whole-body system with a Tx array.
1191. Estimation of Local SAR Using B1 Mapping
Ulrich Katscher1, Tobias Voigt2, Christian Findeklee1, Kay Nehrke1, Steffen Weiss1, Olaf Doessel2
1Philips Research Europe - Hamburg, Hamburg, Germany; 2University Karlsruhe, Karlruhe, Germany
The local specific energy absorption rate (SAR) is one of the major issues for MRI at 3T and above. For an exact determination of local SAR, the spatial distribution of the electric field and electric conductivity throughout the patient are required. Alternatively, according to Maxwell's equations, the required quantities can be deduced by the magnetic field of the RF coil. In this study, the local SAR is estimated via suitable post-processing of a standard B1 map. Simulations show, that the information content of a B1 map might be sufficient to estimate local SAR close to the correct local SAR.
1192. A BiCG Solution Based Quasi-Static Finite-Difference Scheme for Induced Field Evaluation in MRI
Hua Wang1, Feng Liu1, Adnan Trakic1, Stuart Crozier1
1The University of Queensland, Brisbane, Australia
This study presents a biconjugate gradient method (BiCG) that can significantly improve the performance of the quasi-static finite-difference scheme, which has been widely used to model field induction phenomena in voxel phantoms. The proposed BiCG method offers remarkable computational advantages in terms of convergence performance and memory consumption over the conventional iterative, successive over-relaxation algorithm. The wide application capability and computational performance of the BiCG method is demonstrated by modelling the exposures of MRI healthcare workers to fields produced by pulsed field gradients, which is presently an important topic of research in light of the Physical Agents Directive 2004/40/EC.
1193. A Complete Modeling System with Experimental Validation for Calculating the Transmit and ReceiveFields, Total Power Deposition, Input Impedance, and Coupling Between Coil Elements
YiK-Kiong Hue1, Tiejun Zhao, Yongxian Qian1, Fernando E. Boada1, Tamer S. Ibrahim1
1University of Pittsburgh, Pittsburgh, Pennsylvania, USA
A complete finite-difference time-domain (FD-TD) model of a highly coupled RF coil is provided at 7T. Experimental results that validate all of the coil’s (while loaded) electromagnetic characteristics (calculated using the FD-TD method) including coupling, excite and receive field, input impedance, and total RF power deposition are presented.
1194. Time-Domain Finite-Difference/Finite-Element Hybrid Simulations of High-Field RF Coils
Shumin Wang1, Jeff H. Duyn1
1LFMI/NINDS/NIH, Bethesda, Maryland, USA
A Time-Domain Finite-Difference/Finite-Element (TD-FD/FE) hybrid method was developed to simulate high-field RF coils with realistic modeling of both the human body and the RF coils. The FEM is only applied to model curved coil structures while the human body is simulated by the FDTD method. Since both methods are applied simultaneously in a same simulation, the interaction between the human body and RF coils are fully accounted for with well balanced accuracy and efficiency. Numerical results demonstrate the validity, accuracy and capability of this approach.
Bob van den Bergen1, Chris C. Stolk2, Jan Bouwe van den Berg3, Cornelis A. T. van den Berg1
1University Medical Center Utrecht, Utrecht, Netherlands; 2University of Twente, Enschede, Netherlands; 3VU University Amsterdam, Amsterdam, Netherlands
RF shimming and parallel transmission have shown to be able to improve the image quality and reduce the SAR for high field MR imaging. However, both methods require information about the electromagnetic fields, of which only the magnetic part can be measured. FDTD calculations have become standard as alternative to measurements, although these calculations are time-consuming and therefore unsuitable for on-line use. We present a new method that can calculate the electric and magnetic field in the body in one or two minutes, thereby increasing the on-line feasibility of both RF shimming and parallel transmission drastically.
Can Akgun1, Carl J. Snyder1, Steen Moeller1, Pat John Bolan1, Thomas Vaughan1, Kamil Ugurbil1, Pierre-Francois Van de Moortele1, Greg Metzger1
1University of Minnesota, Minneapolis, Minnesota, USA
In an era where large arrays and complex geometries are being proposed for UHF to maximize parallel imaging performance, B1+ shimming flexibility, and receive sensitivity, the ability to predict transmit and receive characteristics in vivo becomes imperative. In support of our 7T prostate imaging, we measured in vivo B1+ maps and g-factor maps with 8- and 16-channel phased array coils and found the results were correctly predicted by simulations using Remcom’s XFDTD software. These findings build confidence in our ability to evaluate SAR for the development of future optimization procedures, as well as guiding future RF coil development.
Parallel RF Transmission Methods
Hall D Wednesday 13:30-15:30
William Allyn Grissom1, Dan Xu2, Jeffrey A. Fessler1, Douglas C. Noll1
1University of Michigan, Ann Arbor, USA; 2GE Healthcare, Waukesha, USA
When applied to parallel excitation, the optimal control pulse design method has some nice advantages over other methods. However, the method requires long computation times, limiting its practical use. We introduce a fast optimal control method that reduces computation time by linearizing the Bloch equation about an underlying pulse, and designs perturbations to the pulse using the linear conjugate gradient algorithm. The new method also has reduced memory requirements compared to conventional optimal control.
1302. Sparsity-Enforced Coil Array Mode Compression for Parallel Transmission
Adam Charles Zelinski1, Vijayanand Alagappan2, Vivek K. Goyal1, Elfar Adalsteinsson1, 3, Lawrence L. Wald2, 3
1MIT, Cambridge, Massachusetts, USA; 2Harvard Medical School, MGH, Longwood, Massachusetts, USA; 3Harvard-MIT Division of Health Sciences & Technology, Cambridge, Massachusetts, USA
Forming linear combinations of the elements of a parallel transmission array can transform its spatial modes into a different basis set, potentially capturing TX efficiency and acceleration capabilities in a subset of the modes. Available TX channels are then applied to only a subset of array modes, those that best contribute to TX efficiency and encoding. Here we propose a target-dependent sparsity-enforced subset selection (SESS) algorithm that explicitly accounts for the desired excitation when choosing the mode subset. Brute-force search shows that SESS actually determines the best of all 12,871 possible subsets during an experiment using a 16-mode, 8-channel system.
1303. Sparsity-Enforced Joint Spiral Trajectory & RF Excitation Pulse Design
Adam Charles Zelinski1, Vivek K. Goyal1, Lawrence L. Wald2, 3, Elfar Adalsteinsson1, 3
1MIT, Cambridge, Massachusetts, USA; 2Harvard Medical School, MGH, Charlestown, Massachusetts, USA; 3Harvard-MIT Division of Health Sciences & Technology, Cambridge, Massachusetts, USA
A fast sparsity-enforcement algorithm that applies to both single-channel and parallel transmission systems is proposed that generates sparse, quickly-traversable k-space trajectories & a corresponding RF excitation pulses when provided with user-defined target patterns. L1-regularization is used to tractably search over a number of possible candidate k-space trajectory segments and determine a small subset of these segments, along with an RF pulse, that best form the desired excitation. A trajectory algorithm then connects the segments in the small subset into an overall smooth trajectory. Here, we provide the method with candidate rings and generate trajectories that significantly outperform conventionally-accelerated spirals.
1304.
Magnitude Least Squares Optimization for Parallel RF
Excitation Design Demonstrated at 7 Tesla
with 8 Channels
Kawin Setsompop1, Vijayanand Alagappan2, Borjan Gagoski1, Lawrence Wald3, Elfar Adalsteinsson1
1Massachusetts Institute of Technology, Cambridge, Massachusetts, USA; 2A. A. Martinos Center for Biomedical Imaging, MGH, Charlestown, Massachusetts, USA; 3A. A. Martinos Center for Biomedical Imaging, Department of Radiology, MGH, Charlestown, Massachusetts, USA
Parallel RF excitations are often designed as a least-squares (LS) optimized approximation to a target magnitude and phase profile. However, adherence to the target phase profile is usually not important as long as the excitation phase is slowly varying compared to the voxel dimension. We describe and validate an MLS method with slice selective spoke and 4X spiral square target excitations, using an 8-channel transmit array on a 7T human MRI scanner. The method resulted in significant benefits, particularly for the spoke, where a 34% drop in root magnitude mean square error and 49% drop in RF power were observed.
1305.
Slice-Selective RF Pulses for in Vivo B1+ Inhomogeneity
Mitigation at 7 Tesla Using Parallell RF Excitation
with a 16-Element
Coil
Kawin Setsompop1, Vijayanand Alagappan2, Borjan Gagoski1, Thomas Witzel2, 3, Jonathan Polimeni2, Andreas Potthast4, Ulrich Fontius5, Franz Schmitt5, Lawrence Wald, 36, Elfar Adalsteinsson1, 3
1Massachusetts Institute of Technology, Cambridge, Massachusetts, USA; 2A. A. Martinos Center for Biomedical Imaging, MGH, Charlestown, Massachusetts, USA; 3Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts, USA; 4Siemens Medical Solutions, Charlestown, Massachusetts, USA; 5Siemens Medical Solutions, Erlangen, Germany; 6A. A. Martinos Center for Biomedical Imaging, Department of Radiology, MGH, Charlestown, Massachusetts, USA
At 7T, B1+ inhomogeneity for human brain imaging causes spatially inhomogeneous flip-angle with detrimental non-uniformity for both SNR and CNR. In this work we applied 8-channel parallel excitation waveforms in the low-flip-angle regime with echo-volumnar k-space trajectories that deposit slice-selective sinc “spokes” in kz, whose complex amplitudes are modulated in (kx,ky) to mitigate in-plane B1+ inhomogeneity. We designed parallel RF spoke pulses with magnitude least squares criteria, spoke location optimization, and B0 field map incorporation that demonstrated excellent B1+ mitigation for brain imaging on three human subjects at 7T.
1306. High-Flip-Angle Slice-Selective Parallel RF Excitation with 8 Channels at 7 Tesla
Kawin Setsompop1, Vijayanand Alagappan2, Andreas Potthast3, Ulrich Fontius4, Lawrence Wald5, Elfar Adalsteinsson1
1Massachusetts Institute of Technology, Cambridge, Massachusetts, USA; 2A. A. Martinos Center for Biomedical Imaging, MGH, Charlestown, Massachusetts, USA; 3Siemens Medical Solutions, Charlestown, Massachusetts, USA; 4Siemens Medical Solutions, Erlangen, Germany; 5A. A. Martinos Center for Biomedical Imaging, Department of Radiology, MGH, Charlestown, Massachusetts, USA
At high magnetic field, B1+ inhomogeneity causes undesired non-uniformity in SNR and contrast. Parallel RF “spoke”-based designs have been shown to correct this problem and produce highly uniform in-plane magnetization with excellent slice selection with relatively short excitation durations. However, at large flip angles the excitation k-space based design method fails. Recently, several large-flip-angle excitation designs have been proposed. In this work we propose and successfully demonstrate a large-flip parallel excitation design for 90º and 180º spin-echo pulses for 8 channels at 7T in the presence of B1+ variation similar to that of human brain.
1307. In-Vivo Comparison of B1 Shimming and Spatially Tailored Parallel Excitation at 7T
Vijayanand Alagappan1, 2, Kawin Setsompop3, Andreas Potthast4, Ulrich J. Fontius5, Franz Schmitt5, Elfar Adalsteinsson3, Lawrence L. Wald1
1Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA; 2Tufts University, Medford, Massachusetts, USA; 3MIT, Cambridge, Massachusetts, USA; 4Siemens Medical Solutions, Charlestown, USA; 5Siemens Medical Solutions, Erlangen, Germany
The inhomogeneous transmit B1 pattern in conventional volume coils at higher field strengths has motivated the development of new RF excitation strategies with multiple transmit channels. The array approach allows the transmit B1+ field inhomogeneity to be addressed by B1 shimming or by using accelerated spatially tailored 2D or 3D RF pulses. In this work we have compared the achievable flip angle homogeneity of the 2 techniques on a slice selective excitation using 8 transmit channels.
1308. RF Encoding Via Non-Linear, Iteratively Determined Encoding Functions
Ulrich Katscher1, Jonathan Lisinski2, Peter Boernert1
1Philips Research Europe - Hamburg, Hamburg, Germany; 2University of Applied Sciences, Hamburg, Germany
For spatial MRI signal encoding, RF encoding via B1-gradients are an alternative to the standard Bo-gradients. RF encoding might omit all Bo-gradients, allowing for MR scanning almost free of acoustic noise. This study investigates RF encoding using non-linear encoding functions using an eight-channel transmit array for phantom imaging. Encoding functions are determined iteratively by randomized superposition of the array element sensitivities. The possibility of pure RF phase encoding (via constant B1 amplitude encoding functions) is investigated to allow future steady state-like applications. Furthermore, RF encoding was combined with 1D Fourier encoding as additional alternative for sequence acceleration.
Sukhoon Oh1, Sylvie Garrett2, Christopher M. Collins1
1The Pennsylvania State University, Hershey, USA; 2The Pennsylvania State University, State College, USA
In this numerical study, an array-optimized composite RF pulse is designed to simultaneously improve the excitation homogeneity and reduce the peak SAR within the human body at 3T. The composite RF pulse can achieve both significantly better excitation homogeneity and significantly lower SAR levels than are possible with RF shimming alone.
1310. Transmit-PILS RF Pulse Design for Small-Tip-Angle Parallel Excitation
William Allyn Grissom1, Jeffrey A. Fessler1, Douglas C. Noll1
1University of Michigan, Ann Arbor, USA
Existing pulse design methods for small-tip-angle parallel excitation either design pulses iteratively and can have high computational cost, or design pulses non-iteratively and are restricted to echo-planar trajectories. We introduce a method that is non-iterative and applicable to general trajectories. Compared to iterative methods, transmit-PILS achieves lower computational cost by dividing the pulse design problem for R coils into R sub-problems that are solved individually using conjugate phase pulse design.
1311. 3D RF Shimming Using Multi-Frequency Excitation
Ulrich Katscher1, Holger Eggers1, Ingmar Graesslin1, Giel Mens2, Peter Boernert1
1Philips Research Europe - Hamburg, Hamburg, Germany; 2Philips Medical Systems, Best, Netherlands
For RF shimming, amplitudes and phases of a transmit RF coil array are optimized to obtain a homogeneous B1 profile. In this study, the different Tx elements are driven with different frequencies (Multi-Frequency Excitation, "MULTIFEX"). Thus, the different elements relate to different slices due to the underlying slice selection gradient. MULTIFEX enables the simultaneous excitation of different slices with different B1 profiles. It might also be used for saturation pulses, refocusing pulses, 3D RF encoding, and 3D local excitation. The study demonstrates the feasibility of MULTIFEX experimentally using a whole-body, eight-channel Tx system at 3T.
1312. Toeplitz-Based Acceleration of RF Pulse Design for Parallel Excitation
Daehyun Yoon1, William A. Grissom2, Jeffrey A. Fessler2, Douglas C. Noll2
1University of Michigan, Ann Arbor, USA; 2University of Michigan, Ann Arbor, Michigan, USA
Recently, an iterative algorithm for designing the RF pulses in the spatial domain for parallel excitation using a Conjugate Gradient(CG) algorithm together with Non-Uniform FFT(NUFFT) operations was proposed. This abstract presents a method based on Toeplitz matrices to further accelerate the computation time of the aforementioned method. This method eliminates the need for interpolation and in certain circumstances, can reduce the dimensionality of the minimization problem.
1313. Parallel Excitation Experiments Using Measured K-Space Trajectories for Pulse Calculation
Peter Ullmann1, Martin Haas2, Franciszek Hennel1, Markus Wick1, Jerôme Voiron1, Maxim Zaitsev2, Jürgen Hennig2, Wolfgang Ruhm1
1Bruker BioSpin MRI GmbH, Ettlingen, Germany; 2University Hospital Freiburg, Freiburg, Germany
Parallel Excitation has proven to be a powerful tool to reduce the typically long durations of spatially selective pulses and the resultant degradation of the excitation patterns due to off-resonance or B0-inhomogeneity effects. However, the effects of some experimental imperfections such as k-space trajectory deviations, e.g. by eddy currents, are not reduced by Parallel Excitation. In this study it is demonstrated that using measured k-space trajectories for the calculation of Parallel Excitation pulses is an effective and convenient method of reducing errors in the excitation patterns caused by such experimental imperfections of the gradient system.
1314. Automated Pulse Sequence Design for Minimal SAR in Parallel Transmission
Yinan Liu1, Jim Ji1
1Texas A&M University, College Station, Texas, USA
Managing and reducing SAR is a critical issue for parallel transmission. In this work, an automated pulse sequence design method is presented to achieve minimal SAR for a given excitation pattern without extending the pulse duration. The Lagrange dual method is used to iteratively optimize the RF pulses and corresponding k-trajectory. The method is verified using computer simulations of a 4-channel parallel transmission system.
1315.
Specific Absorption Rate Studies of the Parallel Transmission
of Inner-Volume Selective Excitations
at 7 Tesla
Adam Charles Zelinski1, Leonardo M. Angelone2, Vivek K. Goyal1, Giorgio Bonmassar2, Elfar Adalsteinsson1, Lawrence L. Wald, 12
1MIT, Cambridge, Massachusetts, USA; 2MGH, Charlestown, Massachusetts, USA
SAR is a major concern in the parallel transmission (pTX) of spatially-tailored 2D and 3D excitation pulses due to E field superposition that occurs when driving multiple channels concurrently and the inefficiency of producing excitations via regional cancellation. In this work, we model average and local SAR using FDTD-simulated field data of an 8-channel pTX array and a human head model. Mean and local SAR are analyzed for 2D spiral-trajectory, inner-volume, spatially-selective RF excitation pulses as a function target flip angle, position, size, smoothness, orientation, and trajectory acceleration factor.
1316. Equiripple Design of Multidimensional RF Pulses Via Convex Optimization
Daeho Lee1, Michael Lustig1, John Mark Pauly1
1Stanford University, Stanford, USA
We propose a new approach to designing RF pulses which achieves equiripple excitation profile. It formulates the RF design problem as a convex optimization problem. Thus, other physical constraints (e.g. peak RF) and regularization terms (e.g. RF power) can be easily embedded into the problem if they are represented in the form of convex functions. This approach can be extended to parallel RF transmission.
1317.
Improved Accuracy of Actual Flip Angle Imaging (AFI)
Kay Nehrke1, Peter Börnert1, Ulrich Katscher1
1Philips Research Europe, Hamburg, Germany
Simulations based on configuration theory have been performed to study the accuracy of the AFI technique depending on different sequence and tissue parameters. The simulation show that the spoil properties, and hence, the accuracy of the technique may be controlled by the RF spoil phase shift increment along with the diffusion sensitivity resulting from spoiling gradients. For a favorable spoil phase, moderate gradient spoiling is already sufficient to allow a good performance of the technique for a reasonable range of tissue parameters. Phantom and in-vivo experiments showed an excellent accordance with the simulations.
1318. Multidimensional Spatial Encoding by Parallel ExcitationWolfgang Ruhm1, Peter Ullmann1
1Bruker BioSpin MRI GmbH, Ettlingen, Germany
A method of MRI and spectroscopic imaging is described which allows multidimensional spatial encoding during the excitation period. It is called SPEEDI (Spatial Encoding by Excitation with Multidimensional RF Pulses) and uses multidimensional RF pulses not only for spatial modulation of the transverse magnetization magnitude, but also for generating a targeted spatial distribution of the transverse magnetization phase. Repeated excitation with different phase distributions according to a spatial encoding scheme allows measuring multidimensional images with different contrasts or spatial distributions of spectral information. SPEEDI has been implemented using Parallel Excitation and its successful experimental verification is reported.
Martin Haas1, Peter Ullmann2, Jürgen Hennig1, Maxim Zaitsev1
1University Hospital Freiburg, Freiburg, Germany; 2Bruker BioSpin MRI GmbH, Ettlingen, Germany
A new method for designing two-dimensional spatially selective 180° pulsesis presented, which is based on the observation that the design equation for the small tip angle regime also holds when the spin population is aligned close to both the +z and -z directions. In combination with one Bloch integration, the gap between these regimes is bridged.We demonstrate that these new pulses can perform both selective inversion and refocusing in an arbitrarily shaped target area. Similarly to transmit SENSE, STM pulses can be accelerated and RF transmit profiles of multiple coils and B0 inhomogeneities can be taken into account.
Hall D Wednesday 13:30-15:30
with Short-Axis PROPELLER EPI
Tzu-Chao Chuang1, Teng-Yi Huang2, Fu-Nien Wang3, Hsaio-Wen Chung1
1National Taiwan University, Taipei, Taiwan; 2National Taiwan University of Science and Technology, Taipei, Taiwan; 3National Tsing Hua University, Hsinchu, Taiwan
Due to the largely shortened echo spacing, short-axis PROPELLER EPI (SAP-EPI) reduces the image blurring without the k-space weighting scheme, which has been previously proposed for de-blurring in long-axis PROPELLER EPI (LAP-EPI) by emphasizing data suffering less from off-resonance field during the combination of blades. Results in this simulation study revealed that the k-space weighting scheme dramatically improved sharpness on LAP-EPI by suppressing side lobes of point spread function in magnitude, while little influence was found for SAP-EPI. As a result, LAP-EPI using a proper weighting function has potentials to obtain images without blurring at the cost of SNR.
1351.
PROPELLER EPI Using Asymmetric Blades: A Preliminary Study on
Point Spread Function
Fu-Nien Wang1, Tzu-Chao Chuang2, Teng-Yi Huang3
1National Tsing Hua University, Hsinchu, Taiwan; 2National Taiwan University, Taipei, Taiwan; 3National Taiwan University of Science and Technology, Taipei, Taiwan
Blades with asymmetric number of positive and negative phase encoding lines are implemented to long-axis PROPELLER EPI. Simulations and in vivo experiments are performed. The point spread function investigated in this study validate that the proposed method could reduce the image blurring effect introduced by distorted EPI blade.
1352. 3D SAP-EPI for Self-Navigated T1w Spoiled Gradient Echo Imaging
Samantha J. Holdsworth1, Stefan Skare1, Anders Nordell2, Rexford D. Newbould1, Roland Bammer1
1Stanford University, Palo Alto, California , USA; 2Karolinska University Hospital, Stockholm, Sweden
3D T1w Spoiled Gradient Echo (SPGR) imaging is commonly used in the clinical care due to its high gray-white matter contrast and isotropic resolution. While the short TR makes the total scan time reasonable (~3-10 mins), it is prone to motion-induced ghosting. Short-axis readout propeller EPI (SAP-EPI) has been suggested as an approach to efficient self-navigated imaging. A 3D GRE version of the SAP-EPI sequence is implemented here, by acquiring 3D ‘bricks’ instead of blades. We demonstrate motion and distortion-corrected phantom data from controlled motion experiments. Initial human images acquired in a sub-minute scan time are presented.
1353.
View-Sharing PROPELLER with Pixel-Based Optimal Blade
Selection (POBS) for Dynamic Contrast-
Enhanced MRI
Tzu-Chao Chuang1, Fu-Nien Wang2, Teng-Yi Huang3, Chih-Ching Wu1, Hsaio-Wen Chung1
1National Taiwan University, Taipei, Taiwan; 2National Tsing Hua University, Hsinchu, Taiwan; 3National Taiwan University of Science and Technology, Taipei, Taiwan
A novel method termed pixel-based optimal blade selection (POBS) to minimize reconstruction artifacts in dynamic contrast-enhanced view-sharing PROPELLER imaging due to under-sampled outer k-space data. POBS is based on an iterative process to search for one set of blades exhibiting the closest image contrast with the target blade, on a pixel-by-pixel basis by least square error estimation. Results from computer simulations and animal experiments show that POBS yields errors less than 15% with five-fold acceleration as compared with the fully sampled images, with reduction of reconstruction artifacts visually perceivable.
1354. CNR Optimization in Variable Pitch PROPELLER MRA
Nicholas R. Zwart1, James G. Pipe1
1Barrow Neurological Institute, Phoenix, USA
The optimization of inflow enhancement in Variable Pitch PROPELLER relies on the fine tuning of the RF-chirp pulse design, refocussing of slice selective gradient and the order in which blade-slabs are overlapped. These mechanisms provide eight distinctive parameters that are optimized in terms of an image quality metric that is constrained through the experimental results using a custom flow phantom.
1355.
BLADE-VAT for Geometric Distortion Correction
Guobin Li1, Bida Zhang1, Hua Guo, Qiang Zhang1
1Siemens Mindit Magnetic Resonance Ltd., Shenzhen, People's Republic of China
The View angle tilting (VAT) corrects for in-plane geometric distortion from field inhomogeneity, but may introduce serious image blurring. In this abstract,a novel method, called BLADE-VAT, which employs low resolution acquisition in readout direction, provides high efficient reduction of such blurring.
1356. Accelerating PROPELLER-MRI by Means of Under-Sampling and Iterative Image ReconstructionUsing the Non-Uniform Fast Fourier Transform
Ashish A. Tamhane1, Mark A. Anastasio1, Konstantinos Arfanakis1
1Illinois Institute of Technology, Chicago, Illinois, USA
PROPELLER-MRI is a multi-shot fast spin-echo (FSE) data acquisition technique with reduced sensitivity to motion and B0 inhomogeneities. However, PROPELLER acquisitions are at least 50% slower than conventional FSE. Under-sampling k-space in PROPELLER by reducing the number of blades per acquisition, while increasing the distance between lines, can significantly reduce imaging time, but leads to severe image artifacts when reconstructing images using conventional gridding. In this study, we investigated the trade-off between imaging time, artifacts and noise, for under-sampled PROPELLER acquisitions with iterative reconstruction using the non-uniform fast Fourier transform.
Hall D Wednesday 13:30-15:30
Jeffrey Tsao1, Yun Jiang1
1Novartis Institutes for BioMedical Research, Cambridge, Massachusetts, USA
IDEAL is an attractive water-fat separation method. A drawback is the prolonged scan time due to the need to acquire at least 3 echo times. Dynamic imaging with IDEAL can be combined with k-t acceleration to reduce scan time below the nominal time for a single image. In this work, we demonstrated net acceleration factors of 4.3x and 6.3x, resulting in scan times of 70% or 47% compared to a single-average scan. The combination of IDEAL and k-t acceleration is favorable since the IDEAL echo times present an extra data dimension, which can be used for signal packing and acceleration.
1381. Water-Fat Separation with IDEAL, Undersampled Radial Acquisition, and Off-Resonance Deblurring
Yun Jiang1, Jeffrey Tsao1
1Novartis Institutes for BioMedical Research, Cambridge, Massachusetts, USA
In this work, we combined radial acquisition with IDEAL water-fat separation and off-resonance correction. Phantom and in vivo data demonstrate that it is a robust method to accelerate fat-water separation.
1382. Water-Fat Decomposition with Regularized Field Map
Wonseok Huh1, Jeffrey A. Fessler1, Alexey A. Samsonov2
1University of Michigan, Ann Arbor, Michigan, USA; 2University of Wisconsin-Madison, Madison, Wisconsin, USA
We proposed a method for water-fat decomposition with regularized field map estimation. In this work, we describe a penalized-likelihood method for jointly estimating water, fat, and the field map. The method uses the a priori knowledge that field maps are usually smooth by including a regularization term in the cost function. The fat and water components can be solved for analytically as a function of the field map. By providing a field map estimate that is inherently smooth even in regions of low signal intensity, the method may yield improved water and fat images.
1383. Simultaneous Water-Fat and T2* Mapping with 3-Point Acquisitions
Qing-San Xiang1
1University of British Columbia, Vancouver, Canada
Water and fat images are obtainable using either gradient-echo or spin-echo sequences with incremental echo shifts. Similar sequences can also be used for T2* mapping. This work demonstrates simultaneous mapping of both water-fat and T2* with as few as 3 acquisitions. Three complex images were acquired with water and fat vectors at (90, 270, 450) degrees, forming Three-Orthogonal-Phase (TOP) sampling. Orthogonality between water and fat allows decoupling of T2* and chemical shift effects. T2* map is readily computed from three otherwise identical magnitude images while water-fat images are obtained after phase correction with Regional Iterative Phasor Extraction (RIPE).
1384. Water Fat Shift Displacement Artifact Correction in Two Point Dixon Imaging
Olof Dahlqvist Leinhard1, 2, Andreas Johansson1, Peter Lundberg1, 2
1Linköping University, Linköping, Sweden; 2Center for Medical Image Science and Visualization (CMIV), Linköping, Sweden
The chemical shift artifact in a two point Dixon acquisition can be removed by an iterative solver taking advantage of the known fat water shift. A simple implementation has been made and the initial results are presented with promising results.
1385. Multislice Water-Fat Imaging with Simultaneous Echo Refocusing (SER-Dixon)
Kuan J. Lee1
1University of Sheffield, Sheffield, UK
A new multislice water-fat imaging sequence is introduced which combines Simultaneous Echo Refocusing (SER) with Partially-Opposed-Phase (POP) acquisition. By slightly increasing the interval between echoes from one slice, echoes from another slice may be fitted in between.
1386. TIDE BSSFP as a Fat-Suppression Preparation
Yin-Cheng Kris Huang1, Hsiao-Wen Chung2, Teng-Yi Huang3
1National Taiwan University , Taipei City, Taiwan; 2National Taiwan University, Taipei City, Taiwan; 3National Taiwan University of Science and Technology, Taipei City, Taiwan
The Transition into Driven Equilibrium balanced steady-state free precession (TIDE bSSFP) sequence has been shown to carry an intrinsic suppression of off-resonance signals after experiencing a certain number of RF pulses, just with an appropriate choice of the timing passing through the k-space center. The stopbands are wide in comparison to other fat-suppression schemes such as CHESS. Therefore, it should be possible to incorporate TIDE bSSFP fat suppression into other routine readout module, by truncating the TIDE bSSFP up to the null point for off-resonance signals. In regions where good shimming is harder to achieve, the wide stopbands of TIDE may be helpful.
1387. RF
Phase-Cycling Water-Saturated 3D B-SSFP for Fast Abdominal Fat Imaging
Yao Ding1, Anqi Zhou2, Roderick W. McColl1, Paul T. Weatherall1, Qi Peng2
1UT Southwestern Medical Center at Dallas, Dallas, Texas, USA; 2UT Health Science Center at San Antonio, San Antonio, Texas, USA
A fast water-suppressed b-SSFP sequence was reported previously for abdominal fat imaging using a manual f0 shift of -220Hz (at 1.5T) to fat resonant frequency peak to avoid banding artifacts on fat. We propose here a clinically available, automatic phase-cycling b-SSFP scheme to avoid manual f0 shift difficulties. Theoretical analysis of the new phase-cycling approach is provided and three subjects were scanned using both techniques. No image quality difference was noticed, and fat quantification on those images show little differences (<0.5%). Therefore, the proposed approach can replace the previously reported manual f0 shift approach for fast abdominal fat imaging.
1388. Comparison of Fat-Water Separation by 2D RF Pulse and Dixon Method in Balanced Steady-StateFree Precession
Jing Yuan1, Bruno Madore1, Lawrence P. Panych1
1Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
2drf pulse excitation is presented as a novel method for fat-water separation in b-SSFP imaging. It has the advantages of only single acquisition and no image post-processing. This study compares fat-water separation by 2-point Dixon method and 2drf pulse in b-SSFP sequence. The results show that 2drf pulse has comparable separation performance to Dixon method. Pros and cons by these two fat-water separation are discussed.
Hall D Wednesday 13:30-15:30
Torsten Rohlfing1, Martin H. Rademacher1, Adolf Pfefferbaum1
1SRI International, Menlo Park, California , USA
Patient motion between passes of an interleaved image acquisition makes the resulting image stack unusable for 3D image analysis. This paper introduces an algorithm for retrospective correction of characteristic interleaved motion artifacts. The correction is cast as an image reconstruction problem, which is solved by an inverse interpolation algorithm.
1463. Spectral Selective Pencil-Beam Navigator for Abdominal Imaging
Max Köhler1, Chrit Moonen2, Mario Ries2
1Philips Medical Systems, Finland; 2IMF, CNRS / Univ. Bordeaux2, Bordeaux, France
A spectral selective pencil-beam navigator is presented, which is based on a 121-binomial pulse train of 2D-selective pulses. The beam allows robust real-time slice tracking of abdominal organs without interference with water-selective MR-imaging.
1464. Parallel Imaging PROPELLER with Across-Blade Calibration: In Vivo Results
Philip James Beatty1, Zhiqiang Li2, Zachary William Slavens3, Anja C. S. Brau1
1GE Healthcare, Menlo Park, California , USA; 2GE Healthcare, Phoenix, Arizona , USA; 3GE Healthcare, Waukesha, Wisconsin, USA
Parallel imaging PROPELLER with across-blade calibration supplements intra-blade calibration with an external "calibration blade". This allows the number of calibration phase encodes acquired with each accelerated blade to be minimized, increasing the net acceleration factor. Using in vivo acquisitions performed during subject motion, it is demonstrated that the across-blade approach is resilient to motion. This study used an acceleration factor of three with two additional calibration phase encodes on each accelerated blade; combined with an echo-train length of 24, this resulting in a net acceleration factor of 2.67 per accelerated blade.
1465. Decoupling Motion Navigation from Imaging Using Spatial-Spectral RF Pulses
Andre J. W. van der Kouwe1, Thomas Benner1, Lawrence L. Wald1
1Massachusetts General Hospital, Charlestown, Massachusetts, USA
Cloverleaf navigators can be used for real-time motion correction of anatomy that moves as a single rigid body. The technique requires that the signal for imaging and navigation come from the same slab and that the magnetization be kept in steady-state. These requirements may be relaxed by separately exciting fat for the navigation and water for imaging. The utility of cloverleaf navigator motion correction may thus be expanded to include imaging techniques such as clinical 2D fast spin echo and DTI. The principle of decoupling imaging and navigation is shown for translational motions in a phantom and human volunteer.
1466.
Navigator Gated Imaging with Phase Based Edge Detection
Kenichi Kanda1, Yuji Iwadate1, Aki Yamazaki1, Tetsuji Tsukamoto1, Susumu Kosugi1
1GE Yokogawa Medical Systems, Hino, Japan
In navigator echo technique, accurate position detection of the diaphragm is essential. As most algorithms rely on the magnitude of the navigator spatial profile, they have some difficulties in the accurate detection when the navigator tracker is partially saturated by the RF pulse of the imaging sequence. We propose a new navigator algorithm that uses the phase profile of navigator echo data to improve the accuracy of the position detection even with the saturation effect. Our results show that the phase based algorithm is feasible and can be used in the navigator gated imaging to reduce motion artifacts.
1467. Head Movement Correction for MRI with a Single Camera
Lei Qin1, 2, Peter van Gelderen1, Jacco de Zwart1, Fenghua Jin2, Yang Tao2, Jeff H. Duyn1
1AMRI, LFMI,NINDS,National Institutes of Health, Bethesda, Maryland, USA; 2University of Maryland, College Park, Maryland, USA
We propose a new motion correction method for MRI using single camera that does not require calibration. A short training scan is required to relate the camera images to motion parameters derived from concurrently acquired EPI data. With this information, motion during an actual MRI scan with arbitrary pulse sequence is estimated by matching each newly captured camera image with one or more images from the training data. The average motion parameters of these training images served as motion estimate for that new image. Initial results show an overall accuracy of better than 0.3 mm translation and 0.3° rotation.
1468. Navigator Echo Analysis Hybridizing Magnitude and Phase Edge Detection
Yuji Iwadate1, Kenichi Kanda1, Aki Yamazaki1, Susumu Kosugi1, Tetsuji Tsukamoto1
1GE Yokogawa Medical Systems, Hino, Japan
Applicability of navigator echo is limited to the series where the main sequence FOV is distant from the navigator position, due to interference of RF pulses. We developed a hybrid algorithm utilizing both magnitude and phase information to detect the diaphragm position robustly. The proposed method could detect the diaphragm position correctly without RF interference affection. This method can be used to improve the abdominal image quality of the patients who have difficulty in breath hold.
1469. Spiral Projection Imaging Motion Correction Using Lines of Intersection
Ken O. Johnson1, James G. Pipe1
1Barrow Neurological Institute, Phoenix, Arizona , USA
In Spiral Projection Imaging, planes of data are collected to fill a sphere in k-space. Every plane intersects every other plane on a line. Therefore, any two planes can be compared, to determine which line from each plane is common between them. Planar orientations can then be deduced, that are consistent with the calculated lines of intersection.
1470. In-Plane Estimation Based Motion Correction for Spiral Projection Imaging
Ryan K. Robison1, Eric Aboussouan1, James G. Pipe1
1Barrow Neurological Institute, Phoenix, USA
Prior studies have asserted the potential of SPI (Spiral Projection Imaging) to accomplish 3D self-navigated motion estimation and correction. The goal of this study was to verify the capability of SPI to correct for three degrees of rotational motion. Through the application of an in-plane estimation based correction algorithm to simulated SPI data, it was determined that SPI is capable of producing a motion corrected 3D data set.
Juergen Rahmer1, Jochen Keupp1, Shelton D. Caruthers2, 3
1Philips Research Europe, Hamburg, Germany; 2Washington University, St. Louis, Missouri, USA; 3Philips Medical Systems, Andover, Massachusetts, USA
MR detection of low concentrations of imaging agents labeled with 19F often requires long signal averaging times and therefore motion compensation is desirable. Simultaneous acquisition of 1H and 19F signal allows self-navigated motion tracking using the stronger 1H signal. In this work, 3D isotropic radial imaging has been combined with a profile acquisition order based on the 2D golden means. Thereby, the intrinsic robustness of radial sequences against motion and undersampling can be combined with a flexible, motion-adaptive temporal frame rate. The technique is demonstrated in 19F/1H in-vivo scans with 1D translational motion and phantom scans with 3D rigid-body motion.
1472. k-Space Sampling for Motion Correction with Parallel Imaging Techniques
Philip Martyn Robson1, Aaron K. Grant1, David C. Alsop1
1Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
Motion related artifacts are a common cause of image corruption in MRI. For many protocols, even speeding image acquisition with parallel imaging is not sufficient to freeze motion. Rigid body motion can be detected with a variety of MRI and non MRI methods, and potentially used to correct for motion during reconstruction. However, the ability to faithfully reconstruct a motion corrected image depends upon the chosen k-space trajectory, the number of receive coils employed, and the time dependence of the motion. We implemented a general least squares reconstruction algorithm for motion correction using all redundant information in the receive coils. In simulated data, occasional, sudden translation and rotation can be fully corrected if a suitable k-space acquisition order is employed.
1473. Automatic Motion Correction of FSE Wrist Exams: Towards Full Clinical Implementation
Armando Manduca1, David S. Lake1, Heidi A. Ward1, Jie Liang1, Lauren C. Edge1, Scott O. Stiving1, Natalia Khaylova1
1Mayo Clinic, Rochester, Minnesota, USA
Fully automatic translational motion correction of high resolution FSE wrist exams, based on optimization of an image quality measure, was tested on all FSE wrist exams acquired on a clinical scanner over a 3 month period. Motion correction was automatically performed on all exams in an average time of 1 min 51 sec. 44% of the 160 series acquired were judged to have some sign of motion, and 91% of these were improved to some degree. A separate study in which the corrected exams are returned to the scanner and evaluated by radiologists is now under way.
1474. Extraction of Abdominal Motion for Molecular Imaging
Frederik J. de Bruijn1, Munibe Simsek-Yildirim, 12, Aart J. Nederveen3, Muhammed Yildirim1, 4, Andre M.J. Sprengers3, Jaap Stoker3, Rolf M.J.N. Lamerichs1
1Philips Research, Eindhoven, Netherlands; 2Gebze Institute of Technology, Gebze, Turkey; 3Academic Medical Center, Amsterdam, Netherlands; 4Eindhoven University of Technology, Eindhoven, Netherlands
MRI of the human bowel is generally complicated due to its motility and due to the intrinsically weak and often ambiguous tissue contrast. We present a method to extract colon motion from volumetric time sequences without the need for extensive bowel preparation. The method combines the use of chemical-shift induced tissue features with a recursive spatiotemporal method to generate spatially consistent motion patterns without the use of prior tissue-segmentation and -modelling. Its application is discussed to motion-corrected signal accumulation of 19F-based targeted contrast agents.
1475.
Motion Insensitive 3D T2 and T1-Weighted Imaging with a
Real-Time, Image-Based PROspective MOtion
Correction Technique (3D
PROMO) and Automated Re-Acquisition of Motion-Corrupted K-Space Segments
Ajit Shankaranarayanan1, Eric Han1, Cooper Roddey2, Nate White2, Reed Busse3, Joshua Kuperman2, Juan Santos4, Dan Rettmann5, Ehud Schmidt6, Anders Dale2
1GE Healthcare, Menlo Park, California , USA; 2UCSD, San Diego, California , USA; 3GE Healthcare, Madison, Wisconsin, USA; 4Stanford University, Palo Alto, California , USA; 5GE Healthcare, Rochester, USA; 6GE Healthcare, Boston, Massachusetts, USA
A complete motion correction solution for 3D imaging has been presented here. The real time image-based 3D PROspective MOtion correction method (3D PROMO) previously presented has been integrated with a 3D T2-weighted imaging sequence (3D FSE acquisition) as well as a 3D T1 weighted imaging sequence (3D IR-SPGR acquisition.). In addition, an automated re-acquisition of left over motion-corrupted k-space views to further increase the robustness of PROMO has been described. In vivo scans demonstrate the efficacy of both 3D T2w and T1w PROMO in presence of motion.
John Cooper Roddey1, Ajit Shankaranarayanan, Eric Han, Nathan White, Anders M. Dale
1University of California, San Diego, La Jolla, California , USA
A region-of-interest (brain) in navigator images is automatically specified and tracked. Regions within the navigator FOV that move non-rigidly relative to the ROI are effectively ignored during tracking. Motion insensitive 3D MR images are acquired.
Image Analysis - Parameter Mapping
Hall D Wednesday 13:30-15:30
Weighted Imaging Study
Andreas Ebel1, 2, Lara Stables3, Gail A. Kang4, Graham Glass, 34, Rachel Millin1, 2, Daniel McCoy1, 3, Peter Lorenzen1, 3, Yu Zhang1, 3, Wang Zhan1, 3, Michael W. Weiner1, 3, William Marks, 34, Norbert Schuff1, 3
1Center for Imaging of Neurodegenerative Diseases, San Francisco, California , USA; 2Northern California Institute for Research and Education, San Francisco, California , USA; 3University of California, San Francisco, California , USA; 4VA Medical Center, San Francisco, California , USA
Susceptibility-weighted imaging (SWI) was used to assess abnormalities in the nigrostriatal system in Parkinson’s disease (PD). Abnormal SWI phase values, consistent with increased iron content in brain tissue, were observed in the caudate nucleus, putamen, and the subthalamic nucleus. Furthermore, the regional dispersion of SWI phase, measured in terms of entropy, strongly correlated with PD severity. Taken together, these results imply that SWI has potential for diagnosing PD, assessing disease severity, and tracking response to disease modifying interventions.
1512.
Phase-Based Quantification of Magnetic Susceptibility in
Healthy Volunteers and Patients with
Neurological Disorders at 7T
Kathryn E. Hammond1, Janine M. Lupo, Suchandrima Banerjee, Doug A. Kelley, Dan B. Vigneron, 1, Susan M. Chang, Pratik Mukherjee, Sarah J. Nelson, 1
1University of California San Francisco (UCSF) / Berkeley Joint Graduate Group in Bioengineering, San Francisco, California , USA
This study presents a technique for quantifying magnetic susceptibilities c by post-processing the phase of gradient echo images acquired at 7T at a spatial resolution of 0.35x0.35x1mm. The c of hemorrhages and calcifications was calculated by comparing phase images of the B0 field to theoretical models of c effects. Model c-effects were also used to automatically separate hemorrhage from veins. Detection and characterization of c-shifted compounds is clinically relevant as a surrogate for brain injury following trauma or secondary to therapeutic radiation and may have an enormous impact on studies of iron deposition in neurodegenerative disorders.
1513. High Resolution Positive Contrast Via Post-Processing from Conventional 3D Imaging
Hannes Dahnke1, Wei Liu2, Richard Bowtell3, Joseph A. Frank4
1Philips Research Europe, Hamburg, Germany; 2Philips Research North America, Briarcliff, USA; 3University of Nottingham, Nottingham, UK; 4National Institutes of Health, Bethesda, USA
We demonstrate a method to calculate positive contrast from a conventional gradient echo image, without loss in resolution. The method combines the high resolution, up to now only achieved by means of dedicated positive contrast sequences, with the advantages of a post-processing method that requires no extra measurement time and less a-priori knowledge about the induced susceptibility. We show that it allows for the selective imaging of SPIO labeled cells at higher CNR than in the original image. First 7T data demonstrate the selective imaging of blood vessels by means of this method.
1514. Estimation of Sparse Magnetic Susceptibility Distributions from MRI Using Non-Linear Regularization
Bryan Kressler1, 2, Ludovic de Rochefort2, Pascal Spincemaille2, Tian Liu1, 2, Yi Wang1, 2
1Cornell University, Ithaca, USA; 2Weill-Cornell Medical College, New York, USA
Non-linear regularization techniques are used to estimate sparse magnetic susceptibility distributions from MRI field maps. Use of regularization terms that promote sparsity of susceptibilities or sparsity of boundaries between regions of different susceptibilities leads to reduced streaking artifacts, improved boundary delineation, and more accurate estimation of susceptibilities than conventional Tikhonov regularization. The techniques are demonstrated on gadolinium phantoms and agar gels containing superparamagnetic iron oxide particles, and yield estimates of the susceptibility of every voxel in the image.
1515. Estimation of Field Maps with Susceptibility Gradient Mapping
Sunbok Lee1, Qun Zhao1
1University of Georgia, Athens, Georgia, USA
In this study a new method based on the Susceptibility Gradient Mapping (SGM) is proposed for estimating a field map without a phase unwrapping procedure. The shift theorem of Fourier Transform shows that the SGM map and field map are equivalent with a proportional constant. Compared with traditional methods of acquiring a field map that needs two phase maps at two different TEs and requires a reliable phase unwrapping algorithm, only one phase map acquired with a single TE is required by the SGM method to generate a field map.
1516. Visceral Fat Assessment with 3D Dual Echo Dixon Technique
Kajoli Banerjee Krishnan1, Rakesh Mullick1, Uday Patil1, Ajay Narayanan1, Anthony T. Vu2, Patrice Hervo3
1GE Global Research, Bangalore, India; 2GE Healthcare, Wisconsin, USA; 3GE Healthcare, Buc, France
We have devised an acquisition-based threshold to automatically assess visceral fat fraction from fat-only MEDAL images. The threshold works on a slice-by-slice basis and has been applied to seven clinical datasets representing varying age, gender and body weight. The results are compared with manually drawn visceral masks on water-only MEDAL images that are used to demarcate the subcutaneous layer from the visceral region on the fat-only image. The automatic algorithm provides a systematic estimate of visceral fat within a fraction of 0.1 of the manually assisted method comparable to the range of values reported in the literature.
1517. Estimation of Water/fat Images, B0 Field Map and T2* Map Using VARPRO
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
T2* estimation in Dixon imaging is important for obtaining accurate water/fat intensity estimates when the relaxation effect cannot be neglected. Moreover, the T2* map can have diagnostic value of its own. Here we present a method for estimating B0- and T2*-maps along with water/fat images from Dixon acquisitions, by extending a recently proposed variable projection method. This method provides accurate estimates regardless of the nonconvexity of the corresponding estimation problem. Furthermore, an efficient approximate algorithm is derived based on Cramer-Rao bound analysis. The performance of the proposed methods has been validated using cardiac imaging data.
1518. Fully-Automated Abdominal Fat Quantification on Water-Saturated MRI
Anqi Zhou1, Yao Ding2, Roderick W. McColl2, Paul T. Weatherall2, Qi Peng1
1UT Health Science Center at San Antonio, San Antonio, Texas, USA; 2UT Southwestern Medical Center at Dallas, Dallas, Texas, USA
A fully automated abdominal fat quantification method on water-saturated MR images is presented here. This method combines automatic SAT and VAT segmentation with an automated gray-scale thresholding method for fat voxel determination. 64 slices MR images obtained from 8 subjects were tested using this fully-automated method. A slower semi-automated approach was also used as a reference technique. SAT and VAT quantified using the automated method were slightly smaller (4.4% and 2.7%, respectively) than those obtained by the reference method. About 95% of the slices were quantified with excellent accuracy. We conclude that fully-automated abdominal fat quantification is feasible.
1519. Intensity Inhomogeneity Correction in Two Point Dixon Imaging
Olof Dahlqvist Leinhard1, 2, Andreas Johansson1, Joakim Rydell1, 2, Magnus Borga1, 2, Peter Lundberg1, 2
1Linköping University, Linköping, Sweden; 2Center for Medical Image Science and Visualization (CMIV), Linköping, Sweden
A simple and effective approach for correcting intensity inhomogeneity in fat volumes reconstructed from a two point Dixon protocol is to identify pure adipose tissue values and interpolate a correction field with normalized convolution from these. An implementation has been made and tested on 50 acquisitions from 20 different subjects showing high stability.
1520. Phase-Correction Algorithms for Fat-Water Separation with Dual-Echo Sequences
Maria A. Schmidt1
1St George's Hospital NHS Trust, London, UK
Dual-echo sequences for two-point fat-water separation often result in images characterised by phase changes along the readout direction due to asymmetric echoes and eddy currents. This work compares phase-correction algorithms in test objects and volunteers, using dual-echo sequences. Pre-processing to remove linear phase drifts and different quality maps to guide the region-growing process were investigated. Algorithms starting from low resolution images and stepping up towards the original resolution were found to provide the best performance. Phase shifts up to 4.1º/pixel were found, and for the largest shifts a linear correction of the phase map was required for correct fat-water separation.
Joakim Rydell1, 2, Andreas Johansson1, Olof Dahlqvist Leinhard1, 2, Hans Knutsson1, 2, Gunnar Farnebäck1, Peter Lundberg1, 2, Magnus Borga1, 2
1Linköping University, Linköping, Sweden; 2Center for Medical Image Science and Visualization (CMIV), Linköping, Sweden
Three dimensional phase sensitive reconstruction on two point Dixon volumes has been implemented with use of the inverse gradient. The results has been compared with the inverse gradient method in two dimensions as well as with the well established region growing method proposed by Ma. The inverse gradient method in 3D is able to unwrap the phase field in uncertain regions where the region growing method and the inverse gradient method in 2D come to a stop.
1522. R2* Measurement Errors at Ultrahigh Field in the Presence of Nonlinear B0 Inhomogeneities
Xiangyu Yang1, Petra Schmalbrock1, Steffen Sammet1, Michael V. Knopp1
1The Ohio State University, Columbus, Ohio, USA
Accurate measurement of R2* was hindered by B0-inhomogeneity-induced errors in 2D MRI. While such inhomogeneities can be neglected or corrected as a linear gradient at low field, nonlinearity must be taken into consideration at ultrahigh field. In this study, we demonstrated that all three commonly-used relaxation models (exponential, exponential-plus-constant, and sinc-modulated exponential) generate severe biases in R2* estimation in the presence of quadratic B0 inhomogeneity. Phantom study results suggest that such biases can be largely compensated by a quadratic correction using measured B0 map, even when the actual B0 inhomogeneity is not strictly quadratic.
1523. Comparison of ASSETx1 and Corrected Power Images for T2 Quantification
Andrew James Patterson1, Martin John Graves1, Tjun Tang1, Jonathan H. Gillard1
1University of Cambridge and Addenbrooke's Hospital, Cambridge, UK
The accuracy of T2 quantification is limited by the decay of the signal into the background noise. In low SNR conditions an optimal multi-coil B1 reconstruction method decreases the mean background noise in comparison to the standard root-sum-of-squares (RSS) reconstruction. We compared the RSS and optimal reconstruction method with a previously published power corrected algorithm. Quantitative T2 measurements obtained in a phantom demonstrated that the optimal reconstruction and the power method are both effective and comparable at improving accuracy and precision.
Berengere M. Aubert-Broche1, Christophe Grova1, Bruce G. Pike1, Louis D. Collins1
1MNI, Montreal, Canada
The aims of the present study were to use rapid volumetric relaxometry methods to (1) quantify T1 and T2 values in specific cortical grey matter (GM) regions for healthy volunteers at 1.5T and (2) aggregate regions showing statistically dependent relaxation times to define cortical areas. To study the spatial statistical dependencies seen in cortical GM relaxation times, the method combines standardized anatomic segmentation, correspondence analysis and ascending hierarchical clustering. Groups of structures that are related statistically are identified and correspond to large cortical regions that have been previously defined anatomically.
1525. Determining Uncertainty in Estimates of Relaxation Time (T2) and Proton Density (S0) Derived fromT2 –weighted MRI Using Bootstrap Method
Ruiwang Huang1
1Research Center Juelich, Juelich, Germany
T2–weighted spin echo MRI permits determination of the transverse relaxation time (T2) and proton density (S0) within image voxels. Several MR sequences for T2 mapping have been proposed, but little effort has been made to estimate the uncertainty of T2–map. Here, we use the bootstrap approach to investigate uncertainties of (S0, T2) from real T2-weighted MR human brain images and to examine the influence of voxel size on the reliability of (S0, T2) derived from fitting a mono–exponential function.
1526.
Polar Decomposition Radio-Frequency Current Density Imaging
with Dual-Unwrapping: Simulation and
Experimental Results
Weijing Ma1, 2, Dinghui Wang1, Tim P. DeMonte2, Adrian I. Nachman1, Michael L. G Joy1
1University of Toronto, Toronto, Canada; 2Field Metrica Inc., Toronto, Canada
Polar Decomposition Radio-frequency Current Density Imaging (PD-RFCDI) is an imaging technique that non-invasively measures current density components inside a sample using a MRI imager. However, due to the requirement of PD-RFCDI to avoid phase wraps, this method was noisier than the rotary echo method and was not implemented on clinical MRI scanners. This work proposes a novel dual-unwrapping technique that removes these constraints on PD-RFCDI. Both the simulation and experiment were used to verify this algorithm.
Dinghui Wang1, 2, Weiing Ma1, Tim P. DeMonte2, Adrian I. Nachman1, Michael L. G Joy1
1University of Toronto, Toronto, Canada; 2Field Merica Inc., Toronto, Canada
Previously implemented radio frequency current density imaging (RF-CDI) techniques can evaluate the component of the injected Larmor frequency current density in the direction of the static magnetic field only under strict assumption which can be easily violated in biomedical applications. The goal of this work is to experimentally verify a new reconstruction method based on one 180-degree rotation. The results show that with this method one component of the current density can be fully recovered by the two sample orientations.
1528. A Robust Method for Estimation of Regional Pulmonary Parameters in the Presence of Noise
Richard A. Guyer1, Michael D. Hellman2, Kiarash Emami1, Stephen Kadlecek1, Robert V. Cadman1, Jiangsheng Yu1, Vahid Vadhat1, Masaru Ishii1, 3, John MacDuffie Woodburn1, Hans Hyonchang Kim1, Rahim R. Rizi1
1University of Pennsylvania, Philadelphia, Pennsylvania, USA; 2Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania, USA; 3Johns Hopkins University, Baltimore, Maryland, USA
Principal component analysis (PCA) permits data points in a series of hyperpolarized gas MR images to be clustered based upon their similar signal kinetics rather than their spatial proximity in the images. This allows points to be grouped and averaged to control noise without degrading the resolution of the image. As a result, more reliable estimations of regional lung parameters, such as the alveolar partial pressure of oxygen and the oxygen depletion rate, can be obtained. This is demonstrated with a synthetic dataset derived from images of a rabbit’s lungs.
1529. Noise Statistics, Discretization Artifacts, and SNR Measurements at Very Low Noise Levels
Olaf Dietrich1, José G. Raya1, Maximilian F. Reiser1
1Ludwig Maximilian University of Munich, Munich, Germany
The well-known noise distributions of MRI data (Rayleigh, Rician, or non-central chi-distribution) describe the probability density of real-valued (i.e. floating-point) intensity signals; however, MR image data is typically discretized to integers before visualization or archiving in the DICOM format. Depending on the scaling factors used for the discretization and the signal-to-noise ratio (SNR), very low noise levels with substantial discretization artifacts can occur. The purpose of this study was to analyze the consequences of such discretization artifacts and to suggest an improved method for noise and SNR measurements in the presence of very low noise levels.
1530. A Method for Automatic Estimation of Noise Variance and SNR
Philip James Beatty1
1GE Healthcare, Menlo Park, California , USA
This work proposes a straightforward method to automatically estimate the noise variance of each receive channel directly from parallel imaging calibration data. The proposed method can be used to identify low SNR channels that do not contribute in a meaningful way to the image reconstruction. By using only data acquired during image acquisition, the need for a separate scan to determine noise variance is eliminated and there is no possibility of incorrect registration between a noise variance acquisition and the image acquisition.
Hall D Wednesday 13:30-15:30
Åsa Carlsson1, 2, Maria Ljungberg1, 2, Göran Starck1, 2, Eva Forssell-Aronsson1, 2
1Göteborg University, Gothenburg, Sweden; 2Sahlgrenska University Hospital, Gothenburg, Sweden
The spurious echo artifact is often encountered in in vivo MRS and is once again actualized with application of MRS in more susceptibility influenced regions. It originates from signals excited in regions outside the VOI that refocus into an echo during signal acquisition. Here k-space formalism was used as a new approach to analyze the spurious echo artifact of the PRESS sequence, and in vitro measurements were performed for verifications and characterisations. Different coherences were separately refocused and studied. The FID of the second refocusing pulse was most probable to cause an artifact and also caused the most pronounced.
1552.
Exploiting the Chemical Shift Displacement Effect in the
Detection of Glutamate and Glutamine (Glx)
with PRESS
Atiyah Yahya1, 2, B. Gino Fallone1, 2
1Cross Cancer Institute, Edmonton, Canada; 2University of Alberta, Edmonton, Canada
The observation of the collective levels of glutamate/glutamine (Glx) by proton magnetic resonance spectroscopy is of value in the study of cancer, neurodegenerative and psychiatric disorders. A PRESS sequence is presented in this work that can yield high signal, comparable to that which can be achieved by a one-pulse acquire sequence, from the C2 protons of Glx at long echo times which is favourable for the decay of macromolecule signal. The efficacy of the sequence was verified on phantoms and in vivo on brain.
Changho Choi1
1University of Texas Southwestern Medical Center, Dallas, USA
A preliminary result of a numerical study for suppression of myo-inositol (mI) for detection of the glycine (Gly) singlet at 3.55 ppm for 1.5T is reported. Multiple refocusing was investigated with density-matrix simulation to calculate the responses of the strongly-coupled resonances of mI. The study indicated that suppression of mI enhances with increasing number of 180° pulses, N. It is predicted that, for an mI-to-Gly concentration ratio of 8, ignoring T1 and T2 effects, mI-to-Gly peak amplitude ratio is 39%, 35%, 31%, 12% and 4% at TE = 108, 146, 176, 239, and 298 ms, for N = 3, 4, 5, 6, and 7, respectively.
1554. Glutamate and Glutamine Discrimination Via Constant Echo Time Difference SpectroscopyJeff Snyder1, Richard B. Thompson1, Alan H. Wilman1
1University of Alberta, Edmonton, Canada
This study investigates the discrimination of glutamate and glutamine using a simple constant echo time subtraction spectroscopy method based on PRESS. The technique relies on coupled spin signal variation differences between glutamate and glutamine along a constant TE line. The theoretical simulations calculated 96% of the glutamate/glutamine signal in the 2.06-2.15 ppm was due to glutamate. Phantom and volunteer measurements were performed to support the simulations and validate the technique. The results illustrate a large signal remaining in the above noted ppm range, with other resonances suppressed.
1555. 13C MRS Study of Human Ornithine Transcarbamylase Deficiency
Andrea Lynne Gropman1, Napapon Sailasuta2, Lawrence Robertson3, Kent Harris4, Peter S. Allen5, Brian D. Ross
1Children's National Medical Center, Washington, USA; 2Huntington Medical Research Institutes, Pasadena, California , USA; 3Spin Dynamics, South Pasadena, USA; 4Huntington Medical Research Institutes, Pasadena, USA; 5University of Alberta, Edmonton, Canada
Ornithine transcarbamylase deficiency leads to hyperammonemic encephalopathy. 1H MRS shows elevations in glutamine and decreases in myoinositol and choline. Specificity of 1H MRS suffers from complex peak patterns due to J-coupling. 13C MRS can quantitate distinct signals from Glu and Gln. We imaged three subjects with partial OTCD and compared to controls using natural abundance 13C MRS followed by intravenous low dose 99% 1-13C glucose infusion. 1-13C glucose appeared in the 13C brain spectra; enrichment of C1 – thru C5 glutamate and glutamine occurred. Excess enrichment in glutamine C4 and C2 in subjects was consistent with abnormality in glial glutamine synthesis.
1556.
13C Isotopomer Metabolic Modeling: Automatic Generation of
the Mathematical Model
Julien Valette1, Alexander Shestov1, Kamil Ugurbil1, Pierre-Gilles Henry1
1CMRR, University of Minnesota, Minneapolis, Minnesota, USA
Because they describe 13C spectra fine structure, 13C isotopomer metabolic models take full advantage of the biochemical information that can be measured by 13C NMR during an infusion of labelled substrate, allowing the measurement of metabolic fluxes with an increased accuracy. In this work, a concept related to isotopomers, dubbed “probabimer”, which allows reducing the number of equations compared to isotopomer models, is briefly introduced. Then a program is presented that automatically generates and simplifies the differential equations describing the time evolution of probabimers. This program is finally exemplified on the neuron-glia model.
Vladimir Mlynárik1, Cristina Cudalbu1, Lijing Xin1, Rolf Gruetter1, 2
1Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; 2Universities of Lausanne and Geneva, Switzerland
Ultra-short-echo time spectra of rat brain were obtained at 14.1 Tesla. Metabolite concentrations were calculated using LCModel and were compared with those obtained at 9.4 T. It was found that quantitation of metabolites, which are poorly characterized in proton MR spectra in vivo (such as alanine, glycerophosphocholine, GABA, glycine and NAAG), was improved.
1558.
Determination of the Glutamate-Glutamine Cycling Flux Using
Two-Compartment Dynamic Metabolic
Modeling is Sensitive to Astroglial
Dilution
Jun Shen1, Douglas Rothman, Kevin Behar
1NIMH, Bethesda, Maryland, USA
13C MRS combined with the infusion of [1-13C]glucose has been used to measure the rate of the glutamate-glutamine cycling. Here we evaluated the accuracy and precision of 13C MRS measurement of this cycling rate using Monte Carlo analysis of a previously published two-compartment metabolic model of the glutamate-glutamine cycle which takes into account astroglial dilution. The Monte Carlo analysis confirmed that the neuronal TCA cycle and glutamate-glutamine cycle fluxes can be determined reliably from the 13C enrichment time courses measured with 13C MRS during infusion of [1-13C]glucose.
Alexander Gussew1, Reinhard Rzanny1, Hans Christoph Scholle2, Werner Alois Kaiser1, Jürgen Rainer Reichenbach1
1Friedrich-Schiller University of Jena, Jena, Germany; 2Friedrich-Schiller-University of Jena, Jena, Germany
Cortical alternations of glutamate concentrations induced by cyclic peripheral painful heat stimulations at the left forearm were measured by means of time resolved in vivo 1H-fMRS in the left insular cortex of 3 volunteers. Synchronization between the stimulation unit and the MR-scanner allowed acquisition of spectra at two different time points (stimulus and rest) of the stimulation cycle. For all volunteers spectra acquired during the stimulus showed increases of glutamate concentration (up to 17%) compared to the reference spectrum without stimulation. However, observed differences of glutamate concentration during the resting period among the volunteers indicate interindividual variability.
1560. In Vivo 13C Spectroscopy of Human Brain on a Clinical 3T Scanner Using [2-13C]Glucose Infusion
Shizhe Steve Li1, Yang Zhang1, Jehoon Yang1, Maria Ferraris Araneta1, Robert B. Innis1, Jun Shen1
1NIH, Bethesda, Maryland, USA
Contaminatiion from subcutaneous lipid signals and strong RF decoupling power requirement are two major technical difficulties in human brain 13C spectroscopy when [1-13C]glucose is used. In a recent study of monkey brain, we proposed a novel strategy of using [2-13C]glucose infusion and detecting 13C label incorporation into the caboxylic/amide spectral region to overcome those difficulties. Here we report results of human brain 13C spectroscopy using [2-13C]glucose infusion on a 3 Tesla clinical scanner. With pseudo noise decoupling, we were able to acquire 13C spectra of carboxylic/amide carbons with reduced average RF power deposition and without lipid contamination.
1561. A Strategy for 13C MRS Study of Human Frontal Lobes
Napapon Sailasuta1, Larry Robertson2, Kent Harris1, Brian Ross1
1Huntington Medical Research Institutes, Pasadena, California , USA; 2Spin Dynamics, South Pasadena, California , USA
Evaluation of several low power noise proton decoupled carbon detect MRS method for glutamatergic neurotransmission of the human frontal lobes.
Stefan Kirsch1, William Edmund Hull1
1German Cancer Research Center (DKFZ), Heidelberg, Germany
In contrast to the decay of a conventional pulse-acquire FID, the time-domain signal from of a CRAZED-type pulse sequence for coherence order n > 1 increases from initially zero to a maximum, followed by an exponential decay. We show that the finite duration of the coherence rephasing gradient and any subsequent recovery delays lead to loss of the initial portion of the time-domain signal. This so-called “time-zero truncation artefact” results in an altered frequency-domain lineshape with incorrect integral and linewidth. Correct analysis requires time-domain fitting of right-shifted data.
1563. In Vivo Human Whole Cerebellum MRS Under Severe Field Inhomogeneity with IDQC Method
Tianliang Gu1, 2, Zhong Chen1, Xiaoxu Liu1, Ling-chih Lin1, Jianhui Zhong1
1University of Rochester, Rochester, New York, USA
An intermolecular double quantum coherence (iDQC) 2D MRS pulse sequence was created and implemented on a 3T scanner for acquisition of human brain 1H spectra in regions susceptible to field inhomogeneity such as the cerebellum. High resolution 1D MRS could be obtained in a few minutes with iDQC over the whole cerebellum, whereas conventional single voxel 1D MRS was working successfully only when regions much smaller were covered. NAA/Cr and Cho/Cr measured with both methods in 5 healthy subjects agreed well with each other.
1564. Two-Dimensional Zero-Quantum Coherence 1H NMR Spectroscopy of Glutamate and Glutamine
Sarah Rebecca Snyder1, Stefan Kirsch1, Katharina Kraus1, Peter Bachert1
1German Cancer Research Center, Heidelberg, Germany
Strong signal overlap of glutamate and glutamine creates a spectroscopic imaging challenge. To more precisely differentiate the two, we recorded series of ¹H NMR stimulated-echo acquisition mode (STEAM) spectra with varying mixing time intervals from Glu and Gln model solutions on a 3 Tesla whole-body MR tomograph. For scalar-coupled molecules, this leads to an intrinsic phase modulation frequency of zero-quantum coherences (ZQC). The outer peaks of the α -CH triplet of both glutamate and glutamine could be clearly identified due to their chemical shifts and ZQC modulation. This provides an additional parameter for the identification of glutamate and glutamine.
1565.
Double Quantum Spectroscopy Using Phase Rotation at 7T
Saadallah Ramadan1, Eva M. Ratai2, Lawrence L. Wald2, Graham C. Wiggins2, Carolyn E. Mountford3
1Brigham and Women's Hospital, Boston, Massachusetts, USA; 2Massachusetts General Hospital, Boston, Massachusetts, USA; 3Brigham and Womens Hospital, Boston, Massachusetts, USA
1566. Sensitivity of Single Shot Multiple J-Coupled Metabolite Detection Using Dual Sel-MQC (D-Sel-MQC) Editing
Gerd Melkus1, Philipp Mörchel1, Markus Kotas1, Michael Flentje1, Peter Michael Jakob1
1University of Würzburg, Würzburg, Germany
The spectral editing technique Sel-MQC (Selective Multiple Quantum Coherence) is extended by an additional spectral selective pulse to increase the number of detectable J-coupled resonances in a single scan. The first frequency selective pulse is placed on the 1.1-1.7 ppm region to excite lactate and alanin, the second frequency selective pulse is placed on the 1.8-2.4 ppm region to excite g-aminobutyric acid, glutamate and glutamine. The timing of the sequence is defined by J of the edited resonances. Double-quantum coherences are filtered using gradients. The sensitivity of the one scan editing sequence is evaluated using simulations and phantom experiments.
1567. Shortening of Metabolite Relaxation Times of Prefrontal Cortex in Mild Cognitive Impairment
Antonio Napolitano1, 2, Federico Giove, 23, Gianfranco Spalletta4, Dorothee P. Auer1, Bruno Maraviglia2, 3
1University of Nottingham, Nottingham, UK; 2La Sapienza University, Rome, Italy; 3Enrico Fermi Center, Rome, Italy; 4Santa Lucia Foundation, Rome, Italy
A spectroscopy study was performed to measure the T2 values of NAA, tCrin Alzheimer’s patients and in controls. The amplitudes of NAA, tCr and Cho from 16 spectra with different TE were fitted and the T2 values of control subjects were compared with those of Alzheimer’s patients. We found a 13% decrease in T2 of NAA (p<0.035), a 9% decrease in T2 of tCr (p<0.01) and a 15% decrease in T2 of Cho (p<0.033). Such decreases we found in the metabolite relaxation times can be correlated to the presence of elevated iron levels associated with neurodegenerative disorders such as Alzheimer’s disease.
1568.
Bone Marrow 1D and 2D Correlation MR Spectroscopy at 7T
Saadallah Ramadan1, Eva M. Ratai2, Lawrence L. Wald2, Graham C. Wiggins2, Carolyn E. Mountford3
1Brigham and Women's Hospital, Boston, Massachusetts, USA; 2Massachusetts General Hospital, Boston, Massachusetts, USA; 3Brigham and Womens Hospital, Boston, Massachusetts, USA
When compared to low field MRS, high field MRS offers additional benefits, including spectral dispersion. However, benefits come with more technological challenges from an RF, Bo and pulse sequence design perspective. An attempt to implement 1D and 2D spectroscopic correlation experiments on a 7T whole body magnet is carried out, with application to tibial bone marrow. The resulting spectra are analyzed and compared to existing spectra at lower fields.
1569.
1D and 2D Correlation Spectroscopy of Muscle at 7T
Saadallah Ramadan1, Eva M. Ratai2, Lawrence L. Wald2, Graham C. Wiggins2, Carolyn E. Mountford3
1Brigham and Women's Hospital, Boston, Massachusetts, USA; 2Massachusetts General Hospital, Boston, Massachusetts, USA; 3Brigham and Womens Hospital, Boston, Massachusetts, USA
1570. 1H MRS in the Human Calf with a Spatially Selective RF Surface Coil
Maria Alfonsetti1, Claudia Testa2, Stefano Iotti2, Emil Malucelli2, Valeria Clementi2, Bruno Barbiroli2, Giuseppe Placidi1, Antonello Sotgiu1, Marcello Alecci1
1Università di L'Aquila, L'Aquila, Italy; 2Università di Bologna, Bologna, Italy
In this work we describe the use of transverse field RF coils to improve proton MRS SNR and spatial selectivity at 1.5T in the resting calf of a healthy volunteer. The RF coil of diameter 10 cm allows in the calf muscle an improved 1H-PRESS SNR along the A/P direction within a given depth from the surface. These features should be of benefit in clinical MRS studies of muscle metabolism and in brain metabolites quantification.
1571. An Integrated Analysis Platform for Magnetic Resonance Spectroscopy
Jordan Hovdebo1, 2, Herve Momo-Jeufack2, Michael West2, Lawrence Ryner1, 2
1National Research Council Institute for Biodiagnostics, Winnipeg, Canada; 2University of Manitoba, Winnipeg, Canada
We present a new system for individual and population analyses of magnetic resonance spectroscopy data. The system consists of two parts: a database for storage, and a client application for accessing the information and performing analyses. Combined, these two parts give an analysis platform capable of managing the large volumes of information generated and sufficiently flexible to accommodate several sources of clinically-relevant data.
1572. On the Importance of Quality Assurance in Spectroscopic Imaging of Prostate
Mahir Sinan Ozdemir1, Yves De Deene2, Geert Villeirs2, Eric Achten2, Ignace Lemahieu1
1Gent University, Gent, Belgium; 2Gent University Hospital, Gent, Belgium
Spectroscopic imaging of prostate (SI) aided by endorectal coils (ER) has gained considerable interest recently as it provides high SNR and spatial resolution and allows one to detect signal changes, in particular, of the metabolites such as citrate (Cit) and choline (Cho). Although the diagnostic statements are based on the obtained data and the quality of the data and accuracy of the methods used are important for a correct diagnosis, a routine quality assurance of prostate spectroscopy is lacking. In this contribution, we duplicated a typical clinical prostate SI as performed commonly by using a homogenous phantom to assess the accuracy of ratio-based results.
1573.
Benign and Atypical Meningioma Metabolic Differences by
HR-MAS Molecular Profiling
Daniel Monleon1, Jose Manuel Morales2, Jose Gonzalez, Fernando Talamantes, Concha Lopez-Gines2, Miguel Cerda-Nicolas2, Bernardo Celda2, 3
1Fundacion Investigacion Hospital Clinico Universitario Valencia, Valencia, Spain; 2University of Valencia, Valencia, Spain; 3Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Spain
Meningiomas are neoplasms that arise from the leptomeningeal covering of the brain and spinal cord, accounting for 15%–20% of CNS tumors. Although the majority of these tumors are histologically benign, some meningiomas show signs of malignancy such as marked vascularity, mitotic figures, nuclear pleomorphism, focal necrosis, or infiltration to the adjacent brain. The WHO classifies meningiomas into three histologic grades: benign, atypical, and anaplastic in accordance with the clinical prognosis. Atypical and anaplastic meningiomas tend to recur. In this communication, we show differences between benign and atypical meningiomas in HRMAS molecular profiles of meningioma biopsies.
1574. Three-Dimensional Isotropic Filter Design with Arbitrary Pass-Band and Stop-Band Specifications
Joonsung Lee1, Elfar Adalsteinsson1
1Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
Variable-density sampling of k-space with accompanying proportional filtering, offers improved spatial impulse response without SNR tradeoffs . Prior work relied on 1-D filter specifications, a widely investigated topic, while the general three-dimensional case is much less studied. While three dimensional filters can be derived by simple transformations from 1D, optimality of the filter will in general be lost. We present here an algorithm for the direct design of an optimal, spherically symmetric, three-dimensional filter with arbitrary extent in k-domain, and pass-band (i.e. voxel size) and stop-band (side lobe suppression) specified in the image domain.
1575. Optimal Phased Array Combination for Spectroscopy
Mark Bydder1, Gavin Hamilton1
1University of California San Diego, San Diego, California , USA
A method is described for making a weighted linear combination of the spectra acquired by a phased array coil. Unlike previous combination methods, no reference points in the data are chosen to represent the coil weights. Instead all the data points are used, which results in more reliable estimation.
NMR of Cells, Body Fluids & Other
Hall D Wednesday 13:30-15:30
Pratima Tripathi1, Ashish Gupta1, Raja Roy1, S K. Mandal1, Rajan Saxena2, S K. Yachha2, Chunni Lal Khetrapal1
1Centre of Biomedical Magnetic Resonance, Lucknow, India; 2Sanjay Ghandhi Post-graduate Institute of Medical Sciences, Lucknow, India
1H NMR spectroscopy has been used to study the metabolic profile of serum in Fulminant Hepatic Failure (FHF) patients and liver grafts (LG). Both in FHF and LG concentrations of alanine, lysine, glutamine, tyrosine, histidine and phenylalanine were significantly elevated in fatal cases when compared to recovered cases. Additionally in LG lactate, methionine and citrate were significantly more in fatal cases compared to successful cases. Principal Component Analysis showed lysine, glutamine, tyrosine and histidine to be the early discriminants for predicting the status of both FHF and LG.
1628.
Metabolic Profiling of Renal Cell Carcinoma Studied by
High-Resolution 1H NMR Spectroscopy on Human
Serum in
Combination with Multivariate Data Analysis
Hongchang Gao1, Baijun Dong2, Xia Liu1, Yiran Huang2, Donghai Lin1
1Shanghai Institute of Materia Medica, the Chinese Academy of Sciences, Shanghai, People's Republic of China; 2Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China
1H NMR-based metabonomics was applied in human serum samples to characterize the metabolic profiling of the renal cell carcinoma (RCC) tumor. The results showed that (a) the early RCC patients can be well distinguished from the healthy humans, and (b) the RCC patients after nephrectomy can be discriminated well from those before nephrectomy. Compared to healthy human serum, the RCC serum displayed higher levels of lipid (mainly very low-density lipoproteins), lactate, alanine, pyruvate, glycerol, and unsaturated lipid, but declined levels of acetoacetate, choline, and glucose/glycogen. Such systemic changes of metabolite concentrations were reversed after nephrectomy.
1629. Study on Vanadyl Sulfate Toxicity Using NMR-Based Metabonomics
Jiyang Dong1, Xiaoxia Dai1, Hongting Cao1, Zhong Chen1
1Xiamen University, Xiamen, People's Republic of China
This study investigated the toxicity effects of VOSO4 oral administration in male Wistar rats using 1H NMR-based metabonomic analysis and clinical chemistry analysis. Urine was collected and their 1H NMR spectra were acquired, and then subjected to multi-variable statistical analysis. Compared to control groups, urinary excretion of lactate, TMAO, creatinine, taurine and hippurate increased following VOSO4 dosing, with concomitant decrease in the level of acetate and succinate. The dosed groups can be readily discriminated from the controls by principle component analysis. All of the results show that VOSO4 can affect energy metabolism process and induce hepatic and renal lesion.
1630. Phospholipid Composition of Postmortem Schizophrenic Brain by 31P NMR Spectroscopy
Richard A. Komoroski1, 2, John M. Pearce1, 2, Robert E. Mrak2
1University of Cincinnati, Cincinnati, Ohio, USA; 2University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
Cell membrane abnormalities due to changes in phospholipid (PL) composition and metabolism have been implicated in schizophrenia pathogenesis. High resolution 31P NMR spectroscopy was used to characterize PLs of gray matter in three regions of postmortem brain for 20 schizophrenic and 20 control subjects. There were no statistically significant differences (p<0.05) between the groups for any of the individual PLs. The sum of all phosphatidylethanolamine headgroups was significantly lower (p=0.047) for schizophrenics than for controls in frontal cortex. The present results are minimally correlated with previous results for aqueous PL metabolites on these same samples.
Alina Nicolescu1, Tedros Bezabeh2, Brion Dolenko2, Lorena Ivona Stefan3, Coziana Ciurtin4, Eugenia Kovacs5, Ian C. P. Smith2, Calin Deleanu6
1 “Petru Poni” Institute of Macromolecular Chemistry, Iasi, Romania; 2Institute for Biodiagnostics, National Research Council, Winnipeg, Canada; 3Craiova Clinical Hospital, Craiova, Romania; 4 “Dr. I. Cantacuzino” Clinical Hospitat, Bucharest, Romania; 5 “Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania; 6Institute of Organic Chemistry, Bucharest, Romania
While 1H NMR spectroscopy of urine can detect glucose in patients with type II diabetes mellitus, such information may not help much for the early diagnosis of diabetes. Changes in other metabolites present in urine may precede glucosuria and 1H NMR spectroscopy can play a role in the assessment of such changes. In patients already exhibiting glucosoria, the spectrum is dominated by signals from glucose. In such instances, conventional methods of analysis are not helpful. In this study, the use of a statistical classification strategy (SCS) has resulted in high accuracy in classifying urine spectra of normal controls from those of diabetic patients using the non-glucose spectral regions.
1632.
High Resolution Nmr Based Analysis of Serum Lipids in
Duchenne Muscular Dystrophy Patients and Its
Possible Diagnostic
Significance
Niraj Kumar Srivastava1, Sunil Pradhan1, Balraj Mittal1, Raja Roy2
1Sanjay Ghandhi Post-graduate Institute of Medical Sciences, Lucknow, India; 2Center of Biomedical Magnetic Resonance, Lucknow, India
Lipid extract of serum of thirty-one clinically, genetically and biochemically proven Duchenne Muscular Dystrophy patients (DMD) was studied by 1H NMR spectroscopy. Triglycerides, phospholipids, free-cholesterol, cholesterol-esters and total cholesterol were 2 to 3 times higher in DMD patients than controls. Ratio of free-cholesterol to cholesterol-esters was also significantly higher. Ten cases of DMD that showed negative gene-deletion-test due to point-mutation, demonstrated similar lipid profile like proven-cases in NMR analysis. Among all these variables, there was a consistent increase in the quantity of phospholipids in DMD patients when compared to controls. These observations indicate the potential of NMR to discriminate DMD.
1633. Multiple-Oocyte in Vivo Localized MR Spectroscopy
Verena Hoerr1, Armin Purea1, Cornelius Faber1
1University of Wuerzburg, Wuerzburg, Germany
A novel approach to intracellular MR spectroscopy, which combines solvent-localized (SOLO) NMR with chemical shift reagents, allowed for recording of intracellular MR spectra from a sample with 100 Xenopus leavis oocytes. Upon selective excitation of either intra or extracellular water signal, only intra or extracellular components were observed, respectively. SOLO afforded a 30-fold sensitivity gain compared to PRESS. Since only a single-axis gradient is required, the method was also implemented on a high-resolution NMR-system with cryo-probe. The method is readily applicable on most NMR spectrometers, making novel applications in pharmaceutics and developmental biology possible.
1634. Development of the Layered Dumbbell Shape Phantom for MRS Quality Assurance
Dong-Cheol Woo1, Sang-Soo Kim1, Hyang-Shuk Rhim1, Hyun-Man Baik2, Orhan Nalcioglu2, Geon-Ho Jahng3, Bo-Young Choe1
1The Catholic University of Korea, Seoul, Republic of Korea; 2University of California, Irvine, Irvine, USA; 3East-West Neo Medical Center, Kyung-Hee University, Seoul, Republic of Korea
The purpose of this study was to develop a standard MRS phantom, to establish a QA protocol with principal factors and to perform QA of an MR system. For the QA of MRS, seven principal factors were selected and measured. The form of the phantom was made of acrylic resin and the layered dumbbell shape vial was filled with various metabolite and all experiments were performed on two 3T systems. All MRS QA factors of each MRI/MRS system were calibrated. The follow-up study showed that the QA factor values in September 2007 were superior to those obtained in June 2007.
1635. Silicon-Cylinder Nano Liter NMR-Probe for Biomedical Analysis Systems
Stefan Leidich1, Thomas Riemer2
1Chemnitz University of Technology, Chemnitz, Germany; 2University of Leipzig, Leipzig, Germany
We present a new NMR-micro-probe designed for the analysis of sample volumes in the range of 10 nl to 50 nl. It is based on spiral micro-coils in a Helmholtz configuration which is housed in a silicon cylinder for susceptibility matching purpose.
1636.
Development of a Diagnostic Test Based on Nanoscale Distance
Measurements Between the Fatty
Acid
Binding Sites in Human Serum Albumin
Dariush Hinderberger1, Marcos Gelos2
1Max Planck Institute for Polymer Research, Mainz, Germany; 2Augusta-Kranken-Anstalt, Bochum, Germany
We characterize the affinity of the fatty acid binding sites by exposing HSA in different ratios to paramagnetic fatty acids spin labels. We employ double-electron-electron resonance (DEER), a modern method of pulse EPR that measures dipolar couplings between individual spin labels. Through the known r-3-dependence of the dipolar coupling the distances r between the spin labels are obtained. Data analysis is so far in an experimental stage but we aim at standardizing the method and developing it into a diagnostic tool by expanding the studies from simple HSA in solution to actual blood samples from patients with different disease backgrounds.
Hall D Wednesday 13:30-15:30
Jonatan Ashchar Snir1, Greg A. Dekaban2, Peta O’Connell2, Paula J. Foster1
1Robarts Research Institute, London, Canada; 2Robarts research Institute, London, Canada
The immune system plays an important role in preventing cancer. Dendritic Cells (DC) are considered effective therapeutic candidates for treatment of cancer; however, many fundamental questions about how to best prepare and administer them are unanswered. At present, it is not possible to quantitate the delivery and migration of DC-based vaccines without biopsy or excision of the lymphoid tissue. Our study shows that DC can be labeled with Feridex and imaged using a 1.5T GE MR scanner. Further, the lymph node volume, signal void volume and fractional signal loss measured correlate with the delivery and migration of in vitro-generated DC.
1674.
Magnetically Labeled Neural Stem Cells Exhibit Differential
Gene Expression of Zinc (Finger) Binding
Proteins
Dorota Anna Kedziorek1, Piotr Walczak1, Chunfa C. Jie1, Naser Muja1, Jesus Ruiz-Cabello2, Assaf A. Gilad1, Jeff W.M. Bulte1
1Johns Hopkins University, Baltimore, USA; 2Universidad Complutense de Madrid, Madrid, Spain
We assessed the time-dependent changes in gene expression following labeling of neural stem cells with Feridex and poly-L-lysine.A pronounced difference in the time course of the expression of zinc (finger) binding proteins was found. These specific regulatory proteins are responsible for maintaining cellular homeostasis indirectly through DNA and RNA binding interference. Our results are relevant for further clinical implementation of MRI cell tracking.
1675.
Developing Cellular MPI: Initial Experience
Jeff W. M. Bulte1, 2, Bernhard Gleich3, Jurgen Weizenecker3, Segun Bernard1, Piotr Walczak1, Dennis E. Markov4, Hans C. J. Aerts5, Jorgen Borgert3, Hans Boeve4
1The Johns Hopkins University School of Medicine, Baltimore, USA; 2The Johns Hopkins University Whiting School of Engineering, Baltimore, USA; 3Philips Research Europe, Hamburg, Germany; 4Philips Research Europe, Eindhoven, Netherlands; 5Philips Medical Systems, Best, Netherlands
Using clinical formulations of SPIO particles used as MRI contrast agents, we investigated the potential of magnetic particle imaging (MPI) for quantitative stem cell tracking. We observed a linear correlation between MPI signal and iron content, representative for the total cell number over a wide range of concentrations, independent of the particle state as free or intracellular entity. Unlike in MRI, Resovist had a 4–fold higher efficacy per unit Fe than Feridex for two different stem cell types tested. MPI has potential for non-invasive quantitative cell tracking and deserves further exploration with or without the use of MRI in parallel.
1676.
Non-Invasive Assessment of Chronic Cardiac Allograft
Rejection in a Rat Model with in Vivo MR
Imaging of Immune
Cells Labeled with MPIO Particles
Qing Ye1, Yijen L. Wu1, Lesley M. Foley1, T. Kevin Hitchens1, Haosen Zhang1, Haval Shirwan2, Chien Ho1
1Carnegie Mellon University, Pittsburgh, Pennsylvania, USA; 2University of Lousville, Louisville, Kentucky, USA
Chronic cardiac allograft rejection (CCAR) constitutes a major obstacle to the long-term success of heart transplantation. Studies indicate the involvement of immune cells in the development of CCAR. In this study, we used a chronic rejection working heart rat model. Immune cells (mainly macrophages) were labeled in situ with micrometer-sized paramagnetic iron oxide (MPIO) particles, and their accumulation in the rejecting allograft was monitored non-invasively with MRI. Our data showed that the distribution of macrophage can be non-invasively assessed using in vivo MRI, and the MRI results were well correlated with ex vivo MR microscopy and the pathology changes.
1677. Does Prussian Blue Staining Correlate with Dextran Staining of Ferumoxides Labeled Cells?
Aneeka Chaudhry1, Joseph A. Frank1, Edyta Pawelczyk1
1National Institutes of Health, Bethesda, USA
Dextran coated iron oxide nanoparticles (SPION) are used to magnetically label cells for cellular MRI. Prussian blue (PB) and/or dextran staining has been used to identify SPION labeled cells in tissue on histology. However, no comparisons have been made on the detection efficiency of SPION in cells. Ferumoxides (FE) labeled cells were followed over 14 days for dextran positive cells compared to PB + cells and iron content. Results demonstrated that there was greater percentage of PB +cells compared to dextran positive cells at 7 and 14 days post FE labeling.
1678. MRI of Neural Stem Cell Migration in the Adult Mouse Brain
Jeffrey You Ling Shyu1, Brian J. Nieman1, Daniel H. Turnbull1
1New York University School of Medicine, New York, New York, USA
Iron-oxide particles, a favored agent for cellular MRI, can be used to label endogenous neural stem cells (NSCs) in situ in rodents. Previous studies required the injection of large numbers of micron-sized particles of iron oxide (MPIOs), creating a large hypointensity artifact that restricts the study of NSC response to injury. In this work, MPIOs were injected directly into the subventricular zone of the adult mouse brain; a much smaller volume of iron-oxide particles was needed to observe migration along the rostral migratory stream. This method may greatly aid the study of endogenous NSC responses to brain injury and disease.
1679.
Quantitative Cellular Tracking MRI of Human Mesenchymal Stem
Cells Home to the Metastatic Breast
Cancer in the Rat Brain
Ho-Taek Song1, 2, Elain K. Jordan1, Bobbi K. Lewis1, Jae-Hyun Lee, Young-wook Jun, Jinwoo Choen, Joseph A. Frank1
1Clinical Center, National Institite of Health, Bethesda, USA; 2College of Medicine, Yonsei University, Seoul, Republic of Korea
In this study we demonstrate that the MR T2* map histogram can be used to monitor the homing of magnetically labeled human mesenchymal stem cells (hMSCs) to sites of metastatic breast cancer in rat brains at 3T. hMSCs were labeled with ferumoxides-protamine sulfate, micron sized iron oxide particles and engineered manganese iron oxide nanoparticles. Quantitative T2* maps revealed no difference among the labeled MSC to home to sites of brain metastatsis as confirmed by immunohistochemical stainning for MSCs<
1680. In Vivo Serial Monitoring of Implanted Chemically Biotinylated Cells by MRI
Po-Wah So1, Tammy Kalber1, Jimmy D. Bell1
1Hammersmith Hospital, Imperial College London, London, UK
In vivo monitoring of specific cell populations is essential for the development of cell based therapies. Recently, chemical biotinylation of cells and their subsequent ‘tagging’ by antibodies to biotin conjugated to SPIOs has been proposed as a ready and rapid method of labeling cells for MRI tracking in vivo. In this study we have demonstrated the feasibility of cells labeled in this manner for serial MRI monitoring over a period of 3 days after implantation.
1681. Direct Incubation of PBMCs with Ferumoxides Labels Monocytes and B Cells
John S. Pratt1, Anna Moore1, Alma Gregory Sorensen1
1Massachusetts General Hospital, Charlestown, Massachusetts, USA
The purpose of this study was determine the feasibility of labeling peripheral blood mononuclear cells (PBMCs) by direct incubation with ferumoxides, and to evaluate the types of leukocytes labeled by this method for the eventual development of MRI-based clinical monitoring of leukocytes in patients. Human peripheral blood mononuclear cells are readily labeled by direct incubation with clinically approved ferumoxides. Labeling was sufficient for detection of cells by 4.7T MRI. Detailed analysis of the cell types labeled revealed B cells were primary lymphocytes labeled. Application of this methodology may contribute new knowledge to the poorly understood role of B cells in leukemia and other diseases, and further clinical translation of MRI-based cellular imaging.
1682. Quantification of Magnetically Labeled Cells with an SPIO Labeled Tumor Model in Rats
wei liu1, E Kay Jordan2, Hannes Dahnke3, Joseph A. Frank2
1Philips Research North America, Briarcliff Manor, New York, USA; 2National Institutes of Health, Bethesda, Maryland, USA; 3Philips Research Europe, Hamburg, Germany
Quantifying the number of labeled stem cells in target tissues in experimental models is of great importance to optimize dose and timing of cellular therapy. In this study, we investigated the quantitative relationship between labeled cells and tumor R2* relaxation rate at different stages of the tumor development with an SPIO labeled tumor model in rats. The individual linear relationship from each tumor was consistent with the gross linear correlation between tumor R2* and number of SPIO labeled cells/mm3. The detection limit for SPIO labeled tumor cells was estimated at about 316 cells/mm3 in this model.
1683. Tracking Magnetotactic Bacteria Using an MRI System for Future In-Vivo Therapeutic Targeting
Ouajdi Felfoul1, Sylvain Martel1
1École Polytechnique de Montréal (EPM), Montreal, Canada
Magnetotactic bacteria (MTB) are flagellated microorganisms that can be controlled using an external magnetic field. MTB synthesize intracellular magnetite nanoparticles, called magnetosomes, assembled in a chain acting as a compass to influence through magnetotaxis the swimming direction of the bacteria. The magnetosomes that disturb the local magnetic field could allow MTB tracking deep in the human body using an MRI system. MR-images of MTB are studied in order to validate the possibility of tracking MTB-based drug delivery operations using a clinical MR scanner. MTB affect more the T2 than the T1-relaxation rate and can be though as a negative contrast agent.
1684.
Superparamagnetic Iron Oxide and Protamine Sulfate Do Not
Affect the Viability and Multi-
Transdifferentiation Capacity of Adult
Stem Cells
Jixian Deng1, Bo Xiang1, Tonghua Yang1, Lei Wang1, Gang Li1, Jian Wang1, Tarek Kashour1, Alan Menkis2, Boguslaw Tomanek1, Roxanne Deslauriers1, Rakesh Arora2, Ganghong Tian1
1National Research Council Canada, Winnipeg, Canada; 2St. Boniface General Hospital, Winnipeg, Canada
This study was designed to assess the effects of superparamagnetic iron oxide (SPIO) and protamine sulfate (PS) on the viability and multi-transdifferentiation capacity of adult stem cells. To achieve the objective, adipose-derived stem cells (ADSCs) were cultured in a medium containing different concentrations of SPIO and PS. Then, the ADSCs were subjected to three types of transdifferentiation inductions (adipogenic, osteogenic, and myogenic induction). We found that SPIO and PS did not affect the viability and multipotent transdifferentiation capacity of the ADSCs. We therefore conclude that SPIO is a safe MR contrast reagent for in vivo tracking of the adult stem cells and PS is a safe SPIO-loading reagent.
1685.
USPIO-Enhanced MR Imaging of Macrophage Recruitment Into the
Rat Brain Following MCP-1
Microinjection
Andrew Peter Brown1, 2, Irene Tracey1, Daniel C. Anthony1, Sebastien Serres1, Yanyan Jiang1, Nicola R. Sibson1
1University of Oxford, Oxford, UK; 2Glaxosmithkline, Hammersmith Hospital, UK
USPIOs can be visualised as a distinct reduction in signal intensity on T2* weighted MR images and can provide a method of tracking macrophage recruitment to sites of neuroinflammation. There are issues regarding the distinction between iron-laden recruited macrophages and the entry of free iron across a permeable blood brain barrier (BBB) in disease cases. In the current study we have shown that USPIO-enhanced MRI can provide a technique to determine the relationship between the number of recruited macrophages to an area of CNS tissue damage and signal change following microinjection of MCP-1 into the rodent striatum.
1686. Biocompatible Chitosan Nanoparticles Encapsulating Iron Oxide with a MRI High-Relaxivity
Hsiao-Yun Kuo1, 2, Jiun-Jie Wang, Rei-Tsan Tsai, I-Ru Chang1, KoonKuan Ng, Chao-Lin Liu3, Chia-Rui Shen1
1Chang Gung University, Kweishan, Taiwan; 2 Chang Gung Memorial Hospital, Kweishan, Taiwan; 3Min Chi University of Technology, Taishan, Taiwan
Chitosan encapsulating superparamagnetic iron oxide maintains the desirable high relaxivity and less cytotoxicity
1687. T1 and T2 Quantification of Free USPIO and USPIO-Labeled Macrophages at 4.7T and 7T
Jean-Christophe Brisset1, Virginie Desestret1, Sebastien Marcellino2, Emilie Devillard1, Florence Lagarde2, Norbert Nighoghossian1, Yves Berthezene1, Marlene Wiart1
1Université de lyon, CREATIS-LRMN, UMR CNRS 5220, Inserm U630, Lyon, France; 2Université de lyon, Laboratoire des Sciences Analytiques, UMR 5180 CNRS-UCBL, Lyon, France
USPIO-enhanced MRI is a promising tool for the experimental study of inflammation. The aim of this study was to quantify the effects of compartmentalization of USPIO on T1 and T2 relaxivities at 4.7T and 7T, using phantoms of free USPIO versus USPIO-labeled macrophages. Compartmentalization of USPIO resulted in a decrease of T1 and T2 effects of the iron particles. T1 and T2 relaxivities of USPIO-labeled cells were lower at 7T than at 4.7T. Taken together, these results suggest that working at 4.7T may be a good compromise between sufficient spatial resolution achievable to image small animals and USPIO relaxivity properties
1688.
19F MRI Detection of Acute Cardiac Allograft
Rejection with in Situ Perfluorocarbon Labeling of Immune
Cells
T Kevin Hitchens1, 2, Qing Ye1, Haosen Zhang1, Lesley M. Foley1, Jelena M. Janjic1, Eric T. Ahrens1, Chien Ho1
1Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
The gold standard for diagnosing and staging rejection after organ transplantation is biopsy, which is not only invasive but also prone to sampling errors. Cellular imaging of the immune cell accumulation in the rejecting graft may provide a better approach. We present a method to detect rejection in a rodent cardiac transplantation model via in situ labeling of immune cells with a perfluorocarbon nanoemulsion. The accumulation of 19F labeled cells can be located and quantified, unambiguously, by 19F MRI, then the labeled cells can then be placed in their correct anatomical context with a conventional 1H image.
Mayumi Yamada1, Paul T. Gurney1, William Stein1, Pratima Kundu1, Alan Smith2, Robert C. Robbins1, Phillip C. Yang1
1Stanford University, Stanford, California , USA; 2Cognate Bio Services, Inc., Sunnyvale, California , USA
Manganese chloride can demonstrate the potential to detect cellular viability and biological property and it can be used for non invasive biological evaluation of transplanted human stromal stem cells within injured myocardium.
1690.
In Vivo Mitochondrial Labeling Using Mito-Carboxy Proxyl
(Mito-CP) Enhanced Magnetic Resonance
Imaging
Douglas Edward Prah1, Eric S. Paulson1, Melissa Lynn Wagner-Schuman1, J Zielonka1, Marcos Lopez1, Miguel J. Hardy1, Joy Joseph1, B Kalyanaraman1, Kathleen M. Schmainda1
1Medical College of Wisconsin, Milwaukee, Wisconsin, USA
Due to their single unpaired electron, nitroxides could potentially be used as MR contrast agents. Recent evidence suggests that the nitroxide, Mito-Carboxy Proxyl (Mito-CP), preferentially targets mitochondria. MR contrast agents specific to mitochondria would provide another avenue to study mitochondrial diseases or pathologies that exhibit abnormal metabolic and/or mitotic activity (e.g., tumors). We demonstrate here, in an in vivo study, the uptake of Mito-CP into rat breast tumor.
1691. SPIO Labeled Cells: Magnetic Resonance Source Quantification by Inverting the Dipole Field
Ludovic de Rochefort1, Maire Poirier-Quinot2, Bryan Kressler1, Claire Wilhelm3, Florence Gazeau3, Jean-Christophe Ginefri2, Luc Darrasse2, Yi Wang1
1Weill Medical College of Cornell University, New York, New York, USA; 2Unité de Recherche en Résonance Magnétique Médicale, U2R2M, Université Paris-Sud, CNRS UMR8081, Le Kremlin-Bicêtre, France; 3Laboratoire Matières et Systèmes complexes, Université Paris 7, CNRS UMR7057, Paris, France
The local dipole field resulting from the strong magnetic moment surrounding superparamegnetic iron oxides creates signal voids (T2* effects) very well observed with gradient-echo imaging. Here, we propose the MR-SQUID technique which combines field mapping and data processing to allow quantification of the magnetic source causing the field shifts. This quantitative 'positive contrast' technique is applied on SPIO-loaded cells. Measured mass of iron per cell agrees with calibrated quantities down to the pg level.
1692. In Vitro / in Vivo MRI Visualization of PFC / VSOP Double-Labeled Mesenchymal Stem Cells
Thomas Kampf1, Thomas Christian Basse-Luesebrink2, Meike Weber1, Andrea Heymer1, Regina Ebert1, Christian Stoetzel1, Uwe Gbureck1, Ulrich Noeth1, Peter Michael Jakob1, Wolfgang Rudolf Bauer3, Daniel Haddad2
1University of Wuerzburg, Wuerzburg, Germany; 2Research Center Magnetic Resonance Bavaria, Wuerzburg, Germany; 3Universtity of Wuerzburg, Wuerzburg, Germany
In this work we introduce an new double lable scheme for non ambigouse monitoring of iron oxide labeled cells. The superparamagnetic iron oxide particles can be used as MRI markers in high resolution T2* weighted 1H-MR images. To distinguish the iron oxide labeled cells from other hypointensities in the MR image cells are additionally labeled with PF15C nanoparticles. In lower resolved 19F-MR images the position of the double labeled cells can be verified.
1693. Rat Glioma C6 Cells Labeled with a Fluorinated Gd-GlyMe-DOTA-Complex
Markus Plaumann1, Jan Willmann1, Ekkehard Küstermann1, Uwe Schüssler1, Dieter Leibfritz1
1University of Bremen, Bremen, Germany
Fluorine is of interest in medical chemistry and diagnostics, because of its very low natural abundance in living organisms and high MR sensitivity. Fluorinated contrast agents allow to record 19F-images without any background signals. Six different 3,5-Bis(trifluoromethyl)benzyl derivatives were selected as model compounds to compare Gd-DTPA- and Gd-GlyMe-DOTA-complexes with respect to their T1-times. Furthermore the lipophilic properties of these Gd-complexes and also of different M3+ ions complexes of 3,5-Bis(trifluoromethyl)phenylhydrazine-DTPA, -GlyMeDOTA and -GlyMeAsp-DOTA were determined. MRI experiments and ICP-MS measurements proof the possibility to label rat glioma C6 cells with 3,5-Bis(trifluoromethyl)phenylhydrazine-Gd-GlyMeDOTA.
Yidong Yang1, 2, Ben Waghorn1, 2, Yuhui Yang1, Brianna Klein1, Nathan Yanasak1, William David Hill1, Tom C-C. Hu1, 2
1Medical College of Georgia, Augusta, Georgia, USA; 2Georgia Institute of Technology, Atlanta, Georgia, USA
MRI could serve as a powerful tool to clarify the role of mesenchymal stem cells (MSCs) in myocardial injury and the subsequent recovery process. In this study, MSCs were labeled in vitro with micrometer-sized particles of iron oxide (MPIOs) with an efficiency of 98% plus and introduced to mice via transplantation. Region of attenuated signal and dark spots in MRI were observed in the myocardial infarction site. Further work to quantify the trafficking of MSCs is needed.
Electron Spin Resonance/Oximetry
Hall D Wednesday 13:30-15:30
Sankaran Subramanian1, Shingo Matsumoto, Sonny Batra, Nallathamby Devasahayam, Fuminori Hyodo, Murali C. Krishna
1National Institutes of Health, Bethesda, USA
Time-domain radiofrequency EPR imaging has been developed to study the distribution of free radicals in vivo and to quantitatively assess the spatial distribution of oxygen non-invasively. Quantitative oxymetry is important in the treatment of tumor by radiation. Oxygen estimates are based on the spatially resolved spectral characteristics (local line width) of the free radical. Two modalities, namely, (a) the 90-t 80 spin echo and filtered back projection that can provide T2-weighted images, and (b) the single point imaging (with pure phase-encoding and Fourier reconstruction) that can provide a series of T2*-weighted images, are examined for their relative merits.
1726.
3D Superresolution EPR Imaging of Nitroxyl Radicals in Mice
Yusuke Ikebata1, Hideo Sato-Akaba1, Hirotada Fujii2, Hiroshi Hirata1
1Yamagata University, Yonezawa, Japan; 2Sapporo Medical University, Sapporo, Japan
We report the superresolution technique of three-dimensional (3D) continuous-wave (CW) EPR imaging of live mice. This post-processing technique could improve the spatial resolution of 3D EPR images. We used anesthetized ICR mice, and administered 0.2-0.25 ml solution of 200 mM 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (hydroxymethyl-PROXYL) spin probes intraperitoneally. We show a superresolution EPR image that was generated from a blurred image of nitroxyl probes in mouse head.
1727.
EPR Imaging of Short-Lifetime Nitroxyl Radicals in Mouse Head
Hideo Sato-Akaba1, Hirotada Fujii2, Hiroshi Hirata1
1Yamagata University, Yonezawa, Japan; 2Sapporo Medical University, Sapporo, Japan
Three-dimensional (3D) EPR imaging of 4-Hydroxy-2,2,6,6-tetramethylpiperidine-d17-1-15N-1-oxyl in mouse head was reported. To enable EPR imaging of nitroxyl spin probes that have a half-life of a few minutes possible, the time of field scanning was decreased to 0.5 s in animal experiments. The total acquisition time of 46 projections for a 3D image was achieved at 30 s. Applicability of 3D continuous-wave (CW) EPR imaging to short-lifetime nitroxyl spin probes in animals was demonstrated.
1728. Nanoencapsulation of Perfluorinated Trityl Radicals and Evaluation as Sensors for EPR Oximetry
Nicolas Charlier1, Benoît Driesschaert1, Jacqueline Marchand1, Véronique Préat1, Bernard Gallez1
1Université catholique de Louvain, Brussels, Belgium
Trityls radicals are interesting probes for EPR spectroscopy/imaging as they possess a narrow EPR Line Width (LW) (high signal-to-noise ratio). However, they have a low sensitivity to changes in oxygenation. It is possible to increase the sensitivity by using lipophilic solvent, such as perfluocarbon solvents as they have high oxygen solubility and biocompatibility. We developed a nanoemulsion containing a newly synthesized perfluorinated trityl. X-band measurements of LW were carried out at 21% and 0% and showed LW variation of 2.3G compared to 0.1G for hydrophilic trityl. In vivo results showed that emulsion is higly responsive to subtle pO2 variations.
1729. Molecular Electron Paramagnetic Resonance Imaging of Melanin in Melanomas: A Proof-Of-Concept
Nicolas s. Charlier1, Emilia Vanea1, Julie De Wever1, Mustapha Dinguizli1, Olivier Feron1, Jean-François Baurain1, Bernard Gallez1
1Université catholique de Louvain, Brussels, Belgium
Taking into account the abundance of the naturally occurring free radicals (melanin pigments) in proliferating melanocytes and their localization pattern, we hypothesized that EPR Imaging (EPRI) could be a unique tool to map melanomas with high sensitivity and high resolution. The potential of EPR to image melanoma samples was demonstrated in vitro in animal and human samples. Using EPR systems operating at low frequency, we were also able to record in vivo EPR spectra and images from the melanin present in a subcutaneous melanoma implanted in a mouse.
1730.
Relationship Between Oxygenation Status and Tumor
Metabolites. Noninvasive Evidence for Aerobic
Glycolysis (Warburg
Effect) in Tumor by Sequential EPR Oxymetric Imaging and MRS
Shingo Matsumoto1, Fuminori Hyodo1, Jeeva Munasinghe2, Sonny Batra1, Sankaran Suburamanian1, Nallathamby Devasahayam1, James B. Mitchell1, Murali C. Krishna1
1National Cancer Institute, NIH, Bethesda, Maryland, USA; 2National Institute of Neurological Disorder and Stroke, NIH, Bethesda, Maryland, USA
Tumor hypoxia is an important prognostic factor in radiotherapy, and non-invasive methods to assess tumor hypoxia such as Electron Paramagnetic Resonance Imaging (EPRI) can provide useful a priori information to guide therapy. To investigate the correlation between oxygenation status and tumor metabolites detectable by MR spectroscopy (MRS), we developed a pulsed EPRI 3D oxygen imaging technique that operates at 300 MHz enables to be sequentially combined with 7T MRI/MRS using a common RF coil without disturbing the object. This combined system clearly shown the oxygenation dependent MRS metabolic change in tumor, especially aerobic glycolysis (lactate production) known as Warburg effect.
1731. Surface Coil for EPR Irradiation to Reduce SAR in Fixed-Field PEDRI
Keerthi Shet1, 2, Sergey Petryakov3, Jay L. Zweier3
1Ohio State University, Columbus, Ohio, USA; 2Davis Heart and Lung Research Institute, Columbus , Ohio, USA; 3Davis Heart and Lung Research Institute, Columbus, Ohio, USA
Proton Electron Double Resonance Imaging (PEDRI) is a combination of proton nuclear magnetic resonance (NMR) imaging and electron paramagnetic resonance (EPR). The technique involves irradiating a paramagnetic sample at its electron spin resonance and this is followed by NMR signal acquisition to produce an Overhauser enhanced NMR signal. The EPR frequency at about 660 times the NMR frequency and may cause sample overheating if irradiated for longer periods of time. Proposed here is a study that uses surface coils for EPR irradiation instead of whole body EPR coils when the organ of interest is closer to the surface of the sample.
1732. Comparison of Methods to Measure the PO2
Mustapha Dinguizli1, Nelson Beghein1, Bernard Gallez1
1Université Catholique de Louvain, Brussels, Belgium
To clarify the source of discrepancy between pO2 vreported for SC tissue, we used sequential monitoring of pO2 using EPR oximetry and OxyLite probes. Initial pO2 measurements by EPR show low values in subcutaneous area (10 mm Hg). After insertion of the OxyLite probes, the pO2 recorded using this system indicate significant larger values (40 mm Hg). Immediately after the OxyLite measurements, the second EPR measurements indicate systematically pO2 increased compared to the first measurement. While comparison of oximetry methods is generally valuable in deep tissues, the use of invasive methods near the skin potentially disturb the local pO2
1733. Spin Density Distribution in Foodstuff After Heat Treatment or Irradiation
Philippe P. Levêque1, Quentin Godechal1, Bernard Gallez1
1Université catholique de Louvain, Brussels, Belgium
Irradiated food can be detected by EPR spectroscopy according to current European Standards. When spatial distribution of spin densities is needed, EPR imaging can be used to locate radicals in biomaterial.We applied on going developments of this technique to study spin density distribution in irradiated frog-leg and roasted coffee bean, as an illustration of the instrumentation capabilities.In irradiated frog leg, spin density is concentrated in bone tissue, whereas in roasted coffee bean it follows a gradient from the center to the edges.EPR imaging offers unique capabilities to monitor the fate of free radicals in biological sample.
Hall D Wednesday 13:30-15:30
1787. Change in Water Diffusion Properties with Altered Muscle Architecture
Anneriet M. Heemskerk1, 2, Tuhin K. Sinha1, Kevin J. Wilson1, Bruce M. Damon1
1Vanderbilt University, Nashville, Tennessee, USA
For skeletal muscle l2 and l3 are perpendicular to the fiber direction and previous studies suggest that they have different structural origins. The goal of this study was to determine whether and how the DTI indices change upon muscle lengthening. Ten subjects were studied with their foot in two different positions and twice in the same position. The latter showed reproducible DTI values. However, the second eigenvalue decreased with increased foot rotation, whereas the other indices remain constant. This confirms that the λ 2 and l3 have different structural origins.
Els Fieremans1, Chi Chen1, Yves De Deene2, Eric Achten3, Ignace Lemahieu1
1Ghent University, Ghent, Belgium; 2Ghent University Hospital, Ghent, Belgium; 3Ghent University Hospital, Belgium
Anisotropic fiber phantoms have been proposed for the validation of DTI on clinical MR-scanners and to test fiber tracking algorithms, particularly in the case of fiber crossings. Several fiber materials have been used: rayon, Dyneema®, hemp, linen, acrylic fibers, rayon, acrylic fiber, … Choosing the appropriate fiber material requires insight in the factors influencing the diffusion and the signal-to-noise ratio. This study enumerates the different parameters (fiber diameter, fiber density, surface relaxivity and susceptibility differences) and their impact in the resulting diffusion properties and T2.
Burkhard Mädler1, 2, Shannon H. Kolind2, Alex L. MacKay2
1Philips Medical Systems, Vancouver, Canada; 2University of British Columbia, Vancouver, Canada
We compare T2-relaxation data and diffusion tensor data from normal human brain. The relationships between myelin water fraction (MWF) and various diffusion tensor measures in white and grey matter structures in the brain were examined in 6 normal subjects at 3.0T. We found some degree of linear correlation between these measurements, but by using ROI-based analysis we also observed several structures which seemed to deviate significantly from a linear relationship. From all investigated relationships between various diffusion tensor measures and myelin-water content, fractional anisotropy (FA) and perpendicular diffusivity (ADCperp) yielded the highest correlation coefficients with MWF. However, diffusion anisotropy was also significantly influenced by factors other than myelin water content. The less operator dependent voxel-based analysis between myelin-water and diffusional anisotropy measures is proposed as an innovative alternative to ROI-based analysis.
1790. Investigation of Bi-Exponential Diffusion in Treated Brain Tumors
Benjamin Alan Hoff1, Denis Le Bihan2, Alnawaz Rehemtulla1, Thomas L. Chenevert1, Brian D. Ross1, Craig J. Galban1
1University of Michigan, Ann Arbor, Michigan, USA; 2NeuroSpin, CEA, Saclay, France
The purpose of this study was to investigate bi-exponential diffusion of water in a brain tumor following therapeutic treatment. Diffusion-weighted images at 17 different b-values were acquired in a 9L glioma rat model. Both fast and slow diffusion coefficients were found to peak significantly by day 6 of treatment, whereas the fast diffusion fraction in the bi-exponential fit peaked at day 9. We found that the fast diffusion coefficient was the most sensitive to therapy, indicating that the therapeutic response not only involves a shift in the relative fractional volume, but also the actual diffusion rates.
Markus Nilsson1, Jimmt Lätt1, Emil Nordh1, Ronnie Wirestam1, Freddy Ståhlberg1, Sara Brockstedt1
1Lund University, Lund, Sweden
The signal-vs-b curve was measured perpendicular to the corticospinal tract in vivo to determine whether effects of restricted diffusion could be observed when varying the diffusion time between 64 and 256 ms and sampling b-values up to 86 000 s/mm2. Restricted diffusion with exchange was simulated for equally sized cylinders. The measurements showed no effects of restriction perpendicular to the tract. Comparisons of the signal-vs-b curves from the measurements with the simulations further indicated that no effects of restricted diffusion could be observed perpendicular to the tract.
1792. Probing Intracellular Compartments in Normal Brain and Brain Tumor Using Short Diffusion Times
Douglas Edward Prah1, Eric Scott Paulson1, Melissa L. Wagner-Schuman1, Kathleen M. Schmainda1
1Medical College of Wisconsin, Milwaukee, Wisconsin, USA
Standard imaging techniques inadequately detect tumor cell invasion. Often the failure of surgical resection and radiation therapy, the primary treatments for gliomas, are attributed to tumor invasion. Treatment outcome may improve if more localized therapies are prescribed to areas of invasion. Results from this study demonstrate that diffusion data acquired at short diffusion times, may be more sensitive to the tissue/tumor intracellular environment, and therefore may be able to detect invading tumor cells.
1793. Diffusional Restrictivity: Looking at the Slow Water
Mariana Lazar1, Jens H. Jensen1, Joseph A. Helpern1
1New York University School of Medicine, New York, USA
In this abstract we introduce a new metric, the diffusional restrictivity (RD), which primarily depicts contributions from shorter diffusion paths. As a result, RD is more sensitive to restricted water compartments and smaller scale structures and less prone to partial volume averaging effects from the fast water compartments (such as CSF contamination). Thus, it should provide a more robust marker of the tissue microstructure. RD can be decomposed into Gaussian and non-Gaussian components. Restrictivity maps for human brain diffusion data show significant white matter/gray matter contrast with higher restrictivity being observed in white matter.
1794. A Realistic DTI Simulation Environment
Gregory T. Balls1, Lawrence R. Frank1
1University of California, San Diego, La Jolla, California , USA
Simulations of diffusion in neural tissues have traditionally been limited to analytical solutions or to grid-based solvers unable to simulate realistic complex neural tissues. We have built a simulation environment that combines a Monte Carlo Brownian dynamics simulator with a MR signal generator. The Monte Carlo simulator is capable of simulating diffusion in arbitrarily complex polygonal geometries and modeling chemical reactions and relaxation. The signal generator is flexible enough to handle a variety of pulse sequences. We demonstrate results for aligned and crossing straight fibers, varying fiber packing density and permeability.
1795. Multiexponential Diffusion Measurements of Varying Densities of Astrocytoma Cells
Pamela R. Jackson1, Roland G. Henry2, Tracy R. McKnight2
1University of California, Berkeley and San Francisco, San Francisco, California , USA; 2University of California, San Francisco, San Francisco, California , USA
To better understand how cell density affects diffusion, we suspended different densities of cells (0%, 25%, 50%, 75%, and 100%) in agarose and measured diffusion using 32 b values. Monoexponential, biexponential, and non negative least squares algorithms were used to fit the data, and the Spearman Rank test was used to test correlation . The monoexponential decrease in diffusion with increasing cell density was dominated the fast diffusion component. The faster diffusion component appeared to be associated with agar presence and the slower component may have been associated with the cells.
Jimmy Lätt1, Markus Nilsson1, Danielle van Westen1, Ronnie Wirestam1, Fredrik Örtendahl1, Freddy Ståhlberg1, Stig Holtås1, Sara Brockstedt1
1Clinical Sciences Lund University, Lund, Sweden
Diffusion weighted imaging (DWI) enables visualization of ischemic stroke in the acute phase. However, the underlying reasons for the altered signal characteristics of the ischemic lesion are still under debate. In this preliminary study, measurements at different diffusion times were performed, potentially providing information about the tissue microstructure, with respect to restricted diffusion and exchange mechanisms.
1797. Diffusion-Weighted Signal in White Matter: What is Behind the B-Factor Dependence?
Valerij G. Kiselev1, Kamil A. Il'yasov2
1University Hospital Freiburg, Freiburg, Germany; 2Kazan State University, Kazan, Russian Federation
Diffusion weighted signal can be characterised via an infinite set of coefficients of the expansion in b-factor. In practice, the number of detectable coefficients is restricted by the noise. This description is examined in the corpus callosum. It is shown that only two coefficient can be found using b-factors up to 2500 mm^2/s. Those are the diffusion coefficient and the kurtosis excess. This means that the contributions of the intra- and extra-axonal compartments cannot be recognised in the total signal. The discussion focuses on constraints this result imposes on the currently unknown diffusion parameters in extra-axonal space.
Crossing Fibers & Non-Tensor Approaches
Hall D Wednesday 13:30-15:30
1856. A Tensor Based Approach to Crossing Fibers Using the Wild Bootstrap
Ai Wern Chung1, Thomas Richard Barrick2, Chris A. Clark1
1UCL, Institute of Child Health, London, UK; 2Saint George's, University of London, London, UK
Multiple-fiber reconstruction algorithms are often mathematically and computationally intensive. We present a simple method for detecting crossing structures by using k-means clustering to group principal eigenvector distributions provided by the Wild bootstrap diffusion tensor model into two populations. Using this Wild-tensor approach, we were able to produce results in the frontal pericallosal region comparable to the Q-Ball method on a 60-directional dataset at b = 0 - 3000s mm-2. Our method shows potential by providing plausible trajectories. Furthermore, the availability of bootstrapped data enables calculation of a variety of indices within and between cluster groups.
1857. Random Effects Modelling of Crossing Fibre Voxels in Diffusion MRI
Martin D. King1, David G. Gadian1, Christopher A. Clark1
1UCL Institute of Child Health, London, UK
Synopsis Random effect (RE) models were applied to the crossing-fibre problem that arises in the analysis of multiple-directions diffusion-weighted MR data. Among these models is the Besag-York-Mollie model, which includes both exchangeable and spatial RE terms. The analyses were performed using a Markov chain Monte Carlo algorithm (Gibbs sampling). Two crossing fibre brain regions were used to show that RE modelling provides a useful alternative to current methods documented in the MR tractography literature.
1858.
Multi-Model Diffusion Image Analysis: A Correlative Study
Between Diffusion Spectrum Imaging
and Diffusion Tensor Imaging on
Structural Lateralization
Wen-Yang Chiang1, Li-Wei Kuo2, Van Jay Wedeen3, Wen-Yih Isaac Tseng1
1National Taiwan University College of Medicine, Taipei, Taiwan; 2Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; 3MGH Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
Since there are dramatic differences between each diffusion-based imaging modality, it is challenging to compare different diffusion indices from different imaging modalities. In this study, we used DSI data to analyze structural lateralization of arcuate fasciculus and compared the result which used DTI reconstruction method. The experiment results showed that both diffusion indices and lateralization index are highly correlated between DTI and DSI which means that the structural analysis, even with different diffusion imaging modalities, is comparable. This fundamental study, which might be the first one that compares diffusion indices and lateralization between different diffusion imaging modalities, may facilitate inter-sites collaborations of diffusion MR researches.
1859. Improved Detection of Non-Gaussian Diffusion with Nonlinear Fitting at High B-Values
Ryan Fobel1, Greg Stanisz2
1University of Toronto, Toronto, Canada; 2Sunnybrook HSC, Toronto, Canada
Higher-order diffusion models, including those based on the Spherical Harmonics and Generalized Diffusion Tensors, are typically fit using linear least-squares methods. This leads to limited performance at high b-values. A nonlinear fitting algorithm which compensates for magnitude bias results in more accurate fitting at b-values of up to 3000 s/mm2. The performance of model selection (ie. classification of voxels as having either isotropic, non-isotropic Gaussian or non-Gaussian diffusion) is significantly improved with this new fitting method. Experimental results show that more than twice as many voxels exhibiting non-Gaussian diffusion are detected at b=2000 s/mm2 relative to b=1000 s/mm2.
Flavio Dell'Acqua1, 2, Paola Scifo1, Giovanna Rizzo, 12, Giuseppe Scotti1, Ferruccio Fazio1, 2
1San Raffaele Scientific Institute, Milan, Italy; 2IBFM-CNR University of Milano-Bicocca, Milan, Italy
The presence of partial volume effect between white matter and isotropic tissues can increase the number of instabilities and spurious fiber orientations in spherical deconvolution methods. In this work, we proposed a modified damped version of the Richardson-Lucy algorithm to improve results also in these regions. Simulation and in-vivo results are shown.
1861. A Regularised Two-Tensor Model Fit to Low Angular Resolution Diffusion Images
Stamatios N. Sotiropoulos1, Christopher R. Tench1, Li Bai1, Paul S. Morgan1, Dorothee P. Auer1, Cris S. Constantinescu1
1University of Nottingham, Nottingham, UK
Diffusion Tensor Imaging (DTI) is prone to partial volume artefacts. Given that routine clinical use of high angular resolution diffusion imaging is still tentative, a regularised two-tensor model to resolve fibre crossings from conventional DTI datasets is presented. The model utilizes the planar diffusion profile depicted by DTI in regions of crossing fibres. Relaxation labelling is then applied to regularise and preserve slow changes in the two resolved orientations across a neighbourhood. Orientational, anisotropy, and diffusivity information can be resolved in regions of two fibre crossings using full brain coverage scans acquired in less than 6 minutes.
Cristina Granziera1, Thomas Benner2, Ashok Kumar2, Dave Tuch2, Aneesh Singhal3, Walter Koroshetz3, Gregory Alma Sorensen2
1CHUV, Lausanne, Switzerland; 2Martinos Center-MGH-Harvard medical school, Charlestown, Massachusetts, USA; 3MGH, Boston, Massachusetts, USA
Diffusion tensor imaging (DTI) has been advocated as a valuable non-invasive tool to monitor post-stroke recovery. However, its inaccuracy in regions of fibers crossing/kissing could limit its application in studying the complex white matter plasticity characterizing functional recovery after stroke. We compared DTI to q-ball imaging in the study of white matter remodeling during stroke recovery of five patients with small ischemic MCA strokes. Qball MRI appeared to be more accurate than DTI in monitoring post-stroke plasticity because : 1. it showed more fiber trajectories at all time points ; it better unraveled longitudinal qualitative and quantitative modulations of fiber tracts ; it disentangled some fibers which appeared to "cross" the compact structure of the cortico-spinal tract.
1863. Real-Time MR Diffusion Tensor and Q-Ball Imaging Using Kalman Filtering
Fabrice Poupon1, 2, Alexis Roche1, 2, Jean-François Mangin1, 2, Cyril Poupon1, 2
1CEA,NeuroSpin, Saclay, France; 2IFR49, Saclay, France
Magnetic resonance diffusion imaging has become an established technique for inferring structural anisotropy of tissues and mapping the white matter connectivity of human brain. We developed a method to process diffusion tensor and Q-ball imaging in real-time. The basic idea is to use a Kalman filtering framework to fit either the linear tensor or Q-ball model incrementally, thus updating the model estimate after the acquisition of any new diffusion-weighted volume during ongoing scans.
1864. Comparison Between Q-Ball Reconstructions Using Radial Basis Function and Spherical Harmonic Basis
Chun-Hung Yeh1, Kuan-Hung Cho2, Ching-Po Lin1, 3
1Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan; 2Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan; 3Institute of Neuroscience, National Yang-Ming University, Taipei, Taiwan
A systematical comparison between q-ball imaging (QBI) reconstruction using radial basis function (RBF) and spherical harmonic basis (SHB) is performed in this study. For both reconstruction methods, the accuracy in defining fiber orientations is assessed using a diffusion phantom model of 45¢X fiber crossing. The results show that both RBF QBI and SHB QBI are capable of resolving crossing fibers, while the separation angles may be underestimated using an insufficient b-value. We propose that b-value is the predominant factor to determine the intrinsic angular resolution in QBI.
1865. Multi-Shelled Q-Ball Imaging: Moment-Based Orientation Distribution Function
Eizou Umezawa1, Mayo Yoshikawa2, Kana Ohno3, Emi Yoshikawa4, Kojiro Yamaguchi1
1Fujita Health University, Toyoake, Japan; 2NGK Insulators, Ltd., Nagoya, Japan; 3Gifu Public Health Center, Kakamigahara, Japan; 4Kyushu Koseinenkin Hospital, Kitakyusyu, Japan
We propose a method that calculates an orientation distribution function (ODF) based on the moments of the probability density function of diffusion displacement. The method is based on q-ball imaging and an idea of "q-space imaging using small magnetic field gradient" that have been proposed in our previous work. The ability of the ODF to identify fiber crossing is also investigated by numerical simulation. The results imply the possibility that the moment-based ODF can reduce the number of data acquisition measurements in keeping higher ability to identify fiber crossing.
1866. Splines on the Sphere Q-Ball Imaging
Nader Metwalli1, 2, John D. Carew, 3, Xiaoping P. Hu1
1Georgia Institute of Technology / Emory University, Atlanta, Georgia, USA; 2Cairo University, Cairo, Egypt; 3Georgia Institute of Technology, Atlanta, Georgia, USA
We present splines on the sphere as a method of modeling raw high angular resolution diffusion imaging (HARDI) data with the added feature of smoothing of the diffusion data in the 3D diffusion space. With an extension to Q-Ball imaging (QBI), Splines on the Sphere QBI (S2QBI) resultant orientation distribution functions (ODFs) are of better quality than their QBI counterparts without compromising angular directionality which will be beneficial in QBI-based fiber tracking applications.
Arterial Spin Labelling Methods
Hall D Wednesday 13:30-15:30
1916. Comparison of Continuous Arterial Spin Labeling Perfusion MRI at 7T and 3T
S. Lalith Talagala1, T-Q Li1, H. Merkle1, S. Wang1, J. Bodurka1, P. van Gelderen1, J Duyn1
1National Institutes of Health, Bethesda, Maryland, USA
This work compares continuous ASL (CASL) perfusion data at 7T and 3T on the same subjects using the same protocol. Good quality 7T CASL data, which compared very well with 3T data, were obtained from all subjects. The measured perfusion signal (range 1.3-1.6%) was similar at the two field strengths. The intrinsic SNR of the difference signal was 55-95% better at 7T compared to 3T. However, the temporal SNR of the difference signal (range 0.7-1.6) was similar at both fields. Results indicate that 7T CASL data may be further improved by optimization of labeling efficiency and reduction of signal fluctuations.
Robert Trampel1, Thies H. Jochimsen2, Toralf Mildner2, Carol Docherty2, Harald E. Möller2, Robert Turner2
1Max Planck Institute for Human Cognitive and Brain Sciences , Leipzig, Germany; 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
Perfusion imaging using magnetically labeled water is capable of measuring cerebral blood flow. As the signal-to-noise ratio increases with the main magnetic field strength B0 perfusion measurements at 7 T are expected to be more sensitive. For the quantification of perfusion, however, a reliable determination of the inversion efficiency α is required. A numerical method for predicting α under various conditions is demonstrated. At 7 T the specific absorption rate (SAR) limits the application of radio-frequency (RF) pulses. Therefore, we especially investigated whether it is possible to achieve sufficient inversion efficiencies in CASL experiments at high B0 and low B1 field strengths.
1918. Human Brain Perfusion MRI at 7T Using a Segmented True FISP ASL Method
Elan J. Grossman1, Ke Zhang1, Jing An2, Yulin Ge1, Jian Xu3, Qun Chen1
1New York University, New York, New York, USA; 2Siemens Medical China, Beijing, People's Republic of China; 3Siemens Medical USA, Malvern, Pennsylvania, USA
Ultra-high field (7T) MR imaging should benefit ASL methods due to increased SNR and longer T1 relaxation times. Here we assess the use of true FISP ASL as a feasible alternative to EPI-based methods of perfusion imaging at 7T. Preliminary results show that this sequence is capable of measuring local tissue perfusion in human brain at 7T with high spatial resolution and without the distortion artifacts commonly identified with EPI-based methods of ASL, although banding artefacts associated with true FISP imaging can sometimes degrade image quality.
1919. Hippocampal Blood Flow and Vascular Reserve: TrueFisp ASL at 3T
Henry Rusinek1, Miroslaw Brys, Remigiusz Switalski, Francois Haas, Kellyanne Mcgorty, Mony de Leon, Qun Chen
1NYU School of Medicine, New York, New York, USA
We have developed and tested a protocol based on segmented true FISP to measure regional cerebral blood flow (rCBF) in the hippocampal region of 12 young normal volunteers. The measurements were repeated during the carbon dioxide challenge achieved with a rebreathing technique. Baseline rCBF were 79.4±16.7 ml/100g/min in the right and 84.3±21.9 in the left hippocampus. During CO2 challenge, rCBF increased to 96.2±19.2 in the right and 98.5±22.9 in the left hippocampus. The technique is relatively quick and easily repeatable, which may be of particular importance in research on Alzheimer’s disease, epilepsy, and other neurological disorders of medial temporal lobe.
1920. Effects of CBV and Capillary Permeability on ASL Signal
Changwei Wesley Wu1, 2, Jyh-Horng Chen2, Yihong Yang1
1National Institute on Drug Abuse, Baltimore, Maryland, USA; 2National Taiwan University, Taipei, Taiwan
Although the arterial spin labeling (ASL) has been utilized to measure cerebral blood flow (CBF) for decades, none of the existing models considered the effects of cerebral blood volume (CBV) change on CBF quantification. In this study, the contributions of CBV and capillary permeability on the pulsed ASL signal were investigated using a two-compartment (2-comp) model. Results show that these physiological effects might induce up to 8% ASL signal change. CBV effect might have more influence on the estimated perfusion in animal models, while permeability might have more effect on human subjects.
1921.
Reliability and Reproducibility of Perfusion MRI in Elderly
Control Subjects
Li Jiang1, 2, Mina Kim1, 2, BettyAnn Chodkowski1, Manus J. Donahue1, 2, James J. Pekar1, 2, Peter C.M. Van Zijl1, 2, Marilyn Albert2
1Kennedy Krieger Institute, Baltimore, Maryland, USA; 2Johns Hopkins Medical Institution, Baltimore, Maryland, USA
Intraclass correlation coefficients (ICC) and within-subject variation coefficients (WSC) were used to estimate reliability and reproducibility of pulsed arterial spin labeling (ASL) MRI. Twelve elderly healthy subjects were scanned four times during one year. The first two scans were processed by two raters, the results of which showed high reliability (ICC>0.96) and reproducibility (WSC <0.01). However, over the total period of one year, reliability reduced (ICC = 0.59~0.68) while the reproducibility still remained high (WSC < 0.08). It was also found that the coefficient of random noise increased to greater than 0.24, which limited the reliability of perfusion measurements.
Sina Aslan1, Jinsoo Uh1, Perry Mihalakos1, Binu Thomas1, Carol Tamminga1, Hanzhang Lu1
1UT Southwestern Medical Center, Dallas, Texas, USA
CBF and CBV are important physiological parameters associated with neuronal activity measured by ASL and VASO MRI, respectively. In this study, we provide a reference aCBV for normal humans during resting state in four major cerebral lobes: temporal>occipital> parietal>frontal, 4.46±0.55 > 3.89±0.76 > 3.07±0.45 > 2.85 ± 0.46, respectively. Additionally, the relationship between CBF and CBV was examined using exponential model, CBV=0.778*CBF0.497. These results suggest CBV values could be used as a reference biomarker to provide prognosis and diagnosis. Furthermore, CBV can be calculated when CBF is known by using exponential model.
1923. Effects of Pulsatile Flow on Arterial Input Function and CBF Quantification in Continuous ASL
Tsukasa Nagaoka1, Xiaodong Zhang1, Robbie Champion1, Govind Nair1, Yoji Tanaka1, Thimothy Q. Duong1
1Emory University, Atlanta, Georgia, USA
CBF is quantified by arterial input function (AIF) and the regional distribution of the tracer. However, AIF on ASL is calculated assuming an arbitrarily shaped AIF without considering pulsatile flow profiles. In this study, we simulated the effect of different flow profiles on the AIF. This model was applied to the arterial ASL signals obtained at different post-labeling delays with and without diffusion gradients in anesthetized monkey. We estimated the potential errors in CBF quantification due to flow dynamics over wide ranges of physiological and MRI measurement parameters.
1924. Distribution of Arterial Transit Times Investigated by MATISSE
Toralf Mildner1, Karsten Müller1, Stefan Hetzer1, Robert Trampel1, Wolfgang Driesel1, Derek V.M. Ott1, D. Yves von Cramon, 12, Harald E. Möller1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 2Max Planck Institute for Neurological Research, Cologne, Germany
Mapping of Arterial Transit times by Intravascular Signal SElection (MATISSE) is introduced as an approach to map the distribution of arterial transit times, �a, in the human brain. The method is based on a smooth modulation of the efficiency of CASL between subsequent repetitions, and on the application of a short repetition time. Under these conditions, the difference in �a between two brain regions can be measured directly by evaluating the phase shift between the corresponding perfusion-weighted time series. CASL was performed by a separate labeling coil at the neck. The smooth modulation of the efficiency of CASL was achieved by changing the frequency offset of the labeling radiofrequency stepwise from repetition to repetition. It is demonstrated that MATISSE yields whole-brain � a difference maps which are consistent with respect to the vascular territories of the human brain.
1925.
Comparison Between Pseudo-Continuous and Separate Labeling
Coil in Continuous Arterial Spin
Labeling
Hesamoddin Jahanian1, Tiffany M. Love1, Gregory R. Lee2, Luis Hernandez-Garcia1
1University of Michigan, Ann Arbor, USA; 2Case western reserve University, Cleveland, USA
Perfusion based functional MRI through Arterial Spin Labeling (ASL) has remarkable potential as a tool to study brain function because of its quantifiable nature and close relation to neuronal activity. Many techniques have been developed to increase the sensitivity of ASL perfusion MRI. Continuous labeling techniques (CASL) offer SNR advantages over pulsed labeling techniques (PASL). In this study, we compare two continuous labeling schemes in terms of their success in improving the SNR and their activation detection efficiency in vivo: flow driven adiabatin inversion using a separate labeling coil (Double coil CASL)and pseudo-continuous inversion (pCASL).
1926.
Simultaneous Quantification of Cerebral Blood Flow and
In-Vivo T2 and T2* of Cerebral Blood Using
Continuous Arterial Spin
Labeling
Guangping Dai1, Jie Lu2, 3, Yasu Egi2, Eng H. Lo2, Young Ro Kim1
1A.A. Martinos Center/MGH, Charlestown, Massachusetts, USA; 2Neuroprotection Research laboratory/MGH, Charlestown, Massachusetts, USA; 3Xuanwu Hospital, Beijing, People's Republic of China
A new pulse sequence has been developed for quantifying in vivo intravascular blood oxygenation level dependence (BOLD) signal using continuous arterial spin labeling (CASL). Specifically, we have measured in-vivo T2 or T2* values of rat cerebral blood using the TE dependence of cerebral blood flow (CBF) signals obtained by CASL. With the transition of inhaled gas from air and 100% oxygen, we have demonstrated that our measurement scheme can be used for reliably quantifying the CBF and in vivo T2 and T2* changes of cerebral blood.
1927. Quantitative Perfusion Imaging Using Q2TIPS-FAIR PROPELLER EPI
Huan Tan1, Craig A. Hamilton1, Robert A. Kraft1
1Wake Forest University School of Medicine, Winston-Salem, USA
Perfusion imaging of the brain is greatly affected by subject motion and off-resonance effects. PROPELLER is an advanced imaging technique that is less sensitive to both motion artifacts and magnetic field inhomogeneity. We have implemented the Q2TIPS-FAIR PROPELLER EPI sequence that produced quantitative cerebral blood flow maps with improved image quality and spatial resolution.
1928. PASL Filtering: A Method of Improving Clinical Perfusion Imaging
Huan Tan1, Joseph A. Maldjian1, Jonathan H. Burdette1, Andrew R. Deibler1, Jeffrey M. Pollock1, Robert A. Kraft1
1Wake Forest University School of Medicine, Winston-Salem, USA
Arterial spin labeled MR imaging is a powerful method for quantitatively measuring cerebral perfusion. We have implemented ASL as a routine part of the clinical MR evaluation, acquiring 3500 cases over a 10-month period. In a small, but significant number of these cases, the data is uninterpretable, largely due to excess patient motion and system instability. We have implemented a post processing filter which can recover the perfusion signal in many of these previously uninterpretable cases.
1929.
A Systematic Approach to Optimizing Background Suppression
for Arterial Spin Labeling Perfusion
Imaging
Nasim Maleki1, Weiying Dai2, David C. Alsop2
1University of Toronto, Toronto, Canada; 2Beth Israel Deaconess Medical Ctr, Boston, Massachusetts, USA
In this paper a systematic approach to optimizing background suppression for pulsed and continuous perfusion imaging is reported. We describe an algorithm to solve a nonlinear optimization problem with bounds on the pulse timings in order to decrease the background static signal for a broad range of T1s. Results of the optimization were added to pseudo-continuous ASL sequence and validated both in phantoms and in brain perfusion imaging in healthy subjects. Greater than 100 fold decrease in background signal intensity was successfully achieved such that the ASL signal change exceeded the residual signal from static tissue.
1930. Comparison of Pulsed Arterial Spin Labeling Sequences Using Different Absolute Quantification Methods
Mustafa Cavusoglu1, Kamil Ugurbil1, 2, Kamil Uludag1
1Max-Planck-Institute for biological Cybernetics, Tuebingen, Germany; 2Radiology, Minnesota, USA
Three different ASL schemes (Q2TIPS, FAIR-QUIPSSII and PICORE-QUIPSSII with asymmetric BASSI pulses) were compared measuring absolute cerebral blood flow (CBF) in the human brain at 3T. Signal-to-noise ratios (SNR), magnetization difference between control and tag images and three different absolute CBF quantification schemes were evaluated. For identical sequence parameters and voxels, it was found that a) FAIR-QUIPSSII has the highest SNR b) FAIR-QUIPSSII yields slightly higher CBF values c) absolute CBF values depend on the quantification scheme utilized. One possible explanation for the findings is that effective labeling efficiency and physiological noise contamination are different for the tagging procedures used.
1931. Variable-Density Spiral Improves Quality of Multi-Shot Arterial Spin Labeling Perfusion Images
Eric Scott Paulson1, Douglas Edward Prah1, Kathleen Marie Schmainda1
1Medical College of Wisconsin, Milwaukee, USA
By oversampling the center of k-space with each interleaf, variable-density spirals offer increased immunity against motion as well as facilitate self-navigated phase correction. We demonstrate here that variable-density spiral readouts improve the quality of multi-shot ASL perfusion images in brain.
1932. Quantification of Retinal Blood Flow Using a Pseudo-Continuous Arterial Spin Labeling Technique
Nasim Maleki1, Weiying Dai2, 3, David C. Alsop2, 3
1University of Toronto, Toronto, Canada; 2Beth Israel Deaconess Medical Ctr, Boston, Massachusetts, USA; 3Harvard Medical School, Boston, Massachusetts, USA
Measurement of perfusion to the retina has implication in the assessment of many important disorders of retinal vascular supply and growth which could lead to blindness. In this paper, we applied a pseudo-continuous arterial spin labeling technique to quantify the blood flow of the retina using multiple delay times, 3 Tesla imaging, and 8-channel phased array head coil on healthy subjects. The results of this study establish the feasibility of imaging and quantification of blood flow to the retina with contrast free MRI in humans and may also provide a unique window for the study of choroidal blood flow control and pathology.
ENT: Tumors, Anatomy & Functional
Hall D Wednesday 13:30-15:30
and During Early Treatment with Chemoradiation Predict Therapeutic Response?
Ann D. King1, Hua Zhou1, 2, Brian K H Yu1, David K W Yeung1, Frankie Mo1, Gary M K Tse3, Alex C. Vlantis1, Anil T. Ahuja1
1The Chinese University of Hong Kong, Shatin, Hong Kong; 2First Affiliated Hospital of Zhejiang University, Hangzhou, People's Republic of China; 3Prince of Wales Hospital, Shatin, Hong Kong
Diffusion-weighted imaging (DWI) is a MR technique that has been shown to be useful in the characterization of lesions. We investigated the usefulness of this technique in predicting treatment response in 31 patients with squamous cell carcinoma (SCC). ADC values from DWI of SCC decrease early in the course of treatment but the pre treatment ADC value and early change in ADC values does not seem to be able to predict tumor response.
1998.
Squamous Cell Carcinoma of the Head and Neck: Can 1H MRS
Pre-Treatment and During Early Treatment
with Chemoradiation Predict
Therapeutic Response?
Ann D. King1, David K. Yeung1, Hua Zhou1, 2, Brian K H Yu1, Frankie Mo1, Gary M K Tse3, Alex C. Vlantis1, Anil T. Ahuja1
1The Chinese University of Hong Kong, Shatin, Hong Kong; 2First Affiliated Hospital of Zhejiang University, Hangzhou, People's Republic of China; 3Prince of Wales Hospital, Shatin, Hong Kong
In vivo 1H MR spectroscopy has been shown to be useful in the characterization of tumors, including those in the head and neck. Whether this technique may be useful to predict treatment response following chemoradiation treatment is not known. We employed this technique to examine 39 patients with squamous cell carcinoma (SCC) and to compare spectroscopy results with tumor response assessed at 6 weeks after treatment. Our results showed that this technique has limited use to predict treatment response in patients with SCC.
1999. The Evaluation of Radiation-Induced Changes in Water Content of the Parotid Gland Using MRI
Antonetta Christina Houweling1, C A.T. van den Berg1, T Dijkema1, J M. Roesink1, C H. J. Terhaard1, C. P. J. Raaijmakers1
1University Medical Center Utrecht, Utrecht, Netherlands
The radiation-induced changes in water content of the parotid glands of five healthy subjects and three radiotherapy patients was evaluated with MR sialography and a multi-point Dixon technique. With MR sialography, the major ductal system of the parotid gland was visualized nicely. The water and fat content were successfully visualized using the multi-point Dixon technique. Radiation-induced changes in water content and the ductal system were not observed. However, the fat content appeared to change after radiotherapy.
2000. High Resolution MRI of the Parotid Gland and Duct at 7 Tesla
Oliver Kraff1, 2, Jens M. Theysohn1, 2, Stefan Maderwald1, 2, Stefan Kruszona1, Mark E. Ladd1, 2, Elke R. Gizewski1, 2, Susanne C. Ladd1, 2
1Erwin L. Hahn Institute for MRI, Essen, Germany; 2University Hospital Essen, Essen, Germany
Most examinations of gland diseases are still performed with X-ray sialography. MR imaging at ultra high fields (7T) offers an increase in SNR and hence spatial resolution as well as new image contrasts which might be able to replace conventional sialography in the future. Our study aimed to optimize different PD and T2 weighted GRE and TSE sequences at 7T for high resolution MRI of the parotid gland and duct. The final imaging protocol at 7T provides a non-invasive examination within 20 minutes as well as excellent image contrast and resolution of the parotid duct and branches.
2001. Motion Corrected 3D High Resolution Larynx Imaging with a Two-Coil Array
Joëlle Karine Barral1, Edward J. Damrose1, Dwight George Nishimura1
1Stanford University, Stanford, California , USA
Laryngeal cancer is usually treated with radiotherapy and chemotherapy to preserve speech and swallowing abilities. However, if the cartilage has been invaded, this treatment is ineffective and partial or total laryngectomy is required. The latter has a dramatic impact on the quality of life of the patient. If cartilage invasion is detected early, partial laryngectomy, with preservation of speech and swallowing, can be performed in lieu of total laryngectomy. A 3D trajectory is investigated to get coverage of the larynx at high resolution in less than 5 minutes with motion correction, and a two-coil array is proposed, which better fits the larynx geometry.
2002. Real-Time MRI of Swallowing in Upright Position
Juan Manuel Santos1, Kim Butts Pauly1, Gerald R. Popelka1, John M. Pauly1
1Stanford University, Stanford, USA
Swallowing disorders are difficult to study because they have multiple etiologies and involve the careful coordination of many different oral structures. These oral structures are not readily visible in their natural state, nor are their mechanics completely understood We have adapted the RTHawk real-time system to the SP 0.5 T GE interventional MRI scanner allowing a person to be scanned in an upright position. Swallowing function can then be studied in a natural position with continuous real-time imaging.
2003. Application of Compressed Sensing to 3D Imaging of the Vocal Tract for Speech MRI
Yoon-Chul Kim1, Jon-Fredrik Nielsen1, Shrikanth Narayanan1, Dani Byrd2, Krishna S. Nayak1
1Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California , USA; 2Department of Linguistics, University of Southern California, Los Angeles, California , USA
Three-dimensional (3D) MRI of the vocal tract during speech production has the potential to provide full anatomical information of the vocal tract shaping, but it requires prohibitively long scan time. In order to reduce scan time and achieve reconstructed image quality comparable to the image from fully sampled data, we apply the principle of compressed sensing MRI to 3D imaging of the vocal tract. Sustained unvoiced English fricative consonants were tested to demonstrate the effectiveness of the method with an acceleration factor of 3.
2004. MR Evaluation in Patients with Congenital Dysosmia
Hui You1, Feng Feng2, Jian-Feng Liu2, Xue-Yan Wu2, Jian Wang, Zhengyu King
1Peking Union Medical College Hospital, Beijing, People's Republic of China; 2Peking Union Medical College Hospital, People's Republic of China
To study the MR imaging findings of congenital dysosmia, 47 patients with congenital dysosmia including 39 patients with Kallmann syndrome and 8 with isolated dysosmia, and 21 age-matched normal volunteers underwent high-resolution MRI examination. All the patients had abnormal findings in olfactory bulbs and tracts. And the pituitary gland was smaller and the stalk was thinner in patients with Kallmann syndrome than volunteers. MR can readily depict the malformation of olfactory bulbs and tracts in congenital dysosmic patients.
2005. Field-Corrected Dynamic Imaging of the Velopharyngeal Musculature During SwallowCharles A. Conway1, Youkyung Song1, David P. Kuehn1, Bradley P. Sutton1
1University of Illinois at Urbana-Champaign, Urbana, USA
Real-time dynamic MRI of swallowing is particularly difficult because field inhomogeneity due to air-tissue interfaces changes as the anatomy moves. The aim of this study is to reconstruct dynamic field-corrected images, allowing us to gain temporal resolution by lengthening readouts without paying the penalty of additional image distortion. This method has been applied to a spiral FLASH sequence for imaging the velopharyngeal musculature during swallow with 61 ms temporal resolution. Scans of healthy adults demonstrate the ability of MRI to compete with traditional methods of clinical swallowing evaluation including endoscopy and X-ray fluoroscopy.
2006. Magnetic Resonance Imaging in Orthodontics: Three-Dimensional Localization of Impacted Teeth
Olga Tymofiyeva1, Kurt Rottner1, Florian Schmid1, Ernst-Juergen Richter1, Peter Michael Jakob1
1University of Wuerzburg, Wuerzburg, Germany
Impacted teeth are teeth that are unable to erupt properly and remain under the gum. They often become infected or damage neighbouring teeth. Information about three-dimensional positioning of impacted teeth is invaluable in orthodontic diagnosis and treatment planning. The purpose of this study was to assess the feasibility of MRI of three-dimensional localization of impacted teeth in children and adults. MRI yielded a clear separation between impacted teeth and the surrounding tissue, and the position and angulation of impacted teeth in all three spatial dimensions could be assessed.
2007. In Vivo Caries Imaging Using Contrast-Enhanced Dental MRI
Olga Tymofiyeva1, Kurt Rottner1, Florian Schmid1, Ernst-Juergen Richter1, Peter Michael Jakob1
1University of Wuerzburg, Wuerzburg, Germany
For diagnosis of carious lesions and estimation of their extension X-ray imaging has been routinely used in clinical practice. However, the technique only provides two-dimensional projections, which yields only limited information regarding localization and size of the lesion. In this article the first in vivo demonstration of carious lesion visualization and quantification using contrast-enhanced dental MRI is presented. Advantages of this innovative technique for caries diagnostic include the three-dimensionality of lesion visualization and quantification, the possibility to determine relative position of the lesion in relation to the pulp and absence of ionizing radiation.
Pediatric Brain: Metabolic, Leukodystrophy
Hall D Wednesday 13:30-15:30
Stephan Gruber1, Margareta Holub2, Wolfgang Bogner1, Andreas Stadlbauer3, Martin Krssak2, Olaf Bodamer2
1Medical University of Vienna, Vienna, Austria; 2Medical University of Vienna, Austria; 3Landesklinikum St. Poelten, Austria
Fabry and Gaucher disease are rare, progressive, inherited disorders of glycosphingolipid metabolism that affect multiple organ systems. Aim of this studies was to investigate central nervous system involvement using MR spectroscopic imaging. Absolute metabolite values revealed no differences between Fabry- and Gaucher- (Type 1) patients and controls. Previous work reported increased Cho in a Gaucher Type 1 patient, which can be explained by using different echo time and inappropriate control group. In this study we found significantly decreasing NAA/Cho in all three goups measured (between 5 and 8% per decade) pointing out the importance of sex- and age-matched controls.
2058. Quantitative Diffusion Tensor Imaging and T1 Relaxometry in Niemann-Pick C Disease
christabel ec Lee1, David M. Thomasson1, Nicole M. Yanjanin2, Eva H. Baker2, Forbes D. Porter2
1National Institutes of Health, Bethesda, Maryland, USA; 2National Institutes of Health, Bethesda, Maryland, USA
We imaged the brains of 14 patients with Niemann-Pick C disease using diffusion tensor imaging and T1 relaxometry to develop MR based quantitative measurements for the assessment of disease severity. We correlated patients’ symptom-based severity scores with fractional anisotropy (FA), apparent diffusion coefficient (ADC), and T1 relaxation time. For DTI, we found 8 different anatomical locations had statistically significant correlation to the symptom-based severity score, while for T1 relaxation, we found statistically significant correlations at 2 locations. We suggest DTI may be more sensitive than T1 relaxometry as a quantitative measurement for assessment of this disease.
2059. MRS Measurement of Disease Severity in Niemann-Pick Disease Type C
Eva H. Baker1, Nicole M. Yanjanin2, Forbes D. Porter2
1Clinical Center, NIH, Bethesda, Maryland, USA; 2National Institute of Child Health and Development, NIH, Bethesda, Maryland, USA
Niemann-Pick disease, type C is an autosomal recessive lipid storage disorder involving liver, spleen, lungs, and brain. Onset of symptoms is usually in childhood; rate of progression is variable, and patients can survive into adulthood. Neurologic findings follow a progressive degenerative course. Brain imaging findings are nonspecific; MRI is often normal. Seeking an MR-based measure of disease severity, we examined metabolite levels at 4 locations in the brain, and found statistically significant correlation between NAA+NAAG and symptom-based severity score at 2 locations in the cerebellum. Thus, NAA+NAAG levels could prove useful for monitoring disease progression and response to treatment.
2060. Quantitative T2 Mapping in a Niemann-Pick Type C Mouse Model
John Totenhagen1, Katherine Thome1, Christine Howison1, Robert P. Erickson1, Theodore P. Trouard1
1University of Arizona, Tucson, USA
Niemann-Pick Type C (NPC) disease is a fatal autosomal recessive neurodegenerative disorder with no current effective treatments. A quantitative measure of the progression and response to treatment of NPC disease is desired for evaluation of NPC therapies. In this work we have investigated quantitative T2 mapping in a mouse model of NPC disease. Mice were imaged with a radial FSE sequence and T2 maps created from individual radial datasets. Differences in T2 values were measured in white matter regions of NPC, transgenic NPC and control mice.
2061.
1H MR Spectroscopy of Creatine Deficiency Syndrome Caused by
a Novel Mutation
Monika Dezortova1, Filip Jiru1, Milan Hajek1, Vera Malinova2, Jan Petrasek1, Milan Jirsa1
1Institute for Clinical and Experimental Medicine, Prague, Czech Republic; 21st Faculty of Medicine, Charles University, Prague, Czech Republic
Two siblings (male and female) were repeatedly examined using 1H MR spectroscopic imaging. First, MR spectra showed significantly reduced creatine concentration only in the male, whereas other metabolites were in normal range. Creatine concentration calculated from female’s spectra was near the lower control limit. Initial hypothesis of creatine transporter deficiency was proved when, one year later, creatine supplementation did not improve clinical status of the male and another decrease in creatine was observed in his spectra. Our findings strongly indicated the diagnosis which was confirmed by finding a novel nonsense mutation del c.219C in exon 1 of the SLC6A8 gene.
2062. L-2-Hydroxyglutaric Aciduria: Pattern of MRI Abnormalities in 53 Patients
Marjan Elisabeth Steenweg1, N M. Verhoeven1, C Jakobs1, G S. Salomons1, M S. van der Knaap1
1VU University Medical Center, Amsterdam, Netherlands
L-2-hydroxyglutaric aciduria is a rare, inherited metabolic disorder. Affected individuals only have neurological manifestations. We studied the brain-MRI pattern associated with the disease. Using a standard protocol for reviewing the MR images we found a consistent pattern of signal abnormalities. The most severe white matter abnormalities were seen in the frontal, subcortical white matter. In addition, bilateral involvement of the globus pallidus, caudate nucleus, putamen, and dentate nucleus was almost invariably seen. Over time the white matter abnormalities showed antero-posterior and centripetal progression and atrophy of the cerebral white matter occurred.
2063. MRI Findings and Neuropathology in a Mouse Model of Maple Syrup Urine Disease
Jelena Lazovic1, Kathryn LaNoue2, Gregg Homanics3, William Zinnanti2
1California Institute of Technology, Pasadena, California , USA; 2Pennsylvania State University, Hershey, Pennsylvania, USA; 3University of Pittsburgh, Pittsburgh, Pennsylvania, USA
A mouse model of intermediate maple syrup urine disease (iMSUD) is introduced. Elevated to highly elevated T2-values were present in the striatum, thalamus, occipital lobes and cerebellum indicating irreversible injury. Immunohistochemistry revealed intense vacuolation similar to spongiform changes throughout these regions, accompanied by severe loss of neuronal processes. We propose that prominent vacuolation rather than dysmyelination are contributing to increased signal on T2-weighted images in the iMSUD mouse model. The MSUD associated neuropathology was minimized when animals were placed on low branched chain amino acids (BCAA) diet, indicating the importance of BCAA control to prevent MSUD related brain injury.
2064.
Effect of Standard Oral Aminoacid Mixtures on Cerebral
Phenylalanine Content and the Dynamics of
Blood-Brain-Barrier Dynamics
in PKU Patients
Roland Kreis1, Karin Zwygart1, Thomas Lutz2, Chris Boesch1, Joachim Pietz2
1University Berne, Berne, Switzerland; 2University of Heidelberg, Heidelberg, Germany
Phenylketonuria is normally treated with dietary protein restriction and supplementation with the other amino acids (AA). It was shown earlier that oral substitution with high loads of large neutral AA can hinder the entry of additional phenylalanine (Phe) into brain for several hours. We now show with MRS that the same short-term effect can be reached with commercial AA powder in realistic dosage and that regular AA supplementation leads to lowering of cerebral steady state Phe levels on the long run because of its modulating influence on the BBB transport, which is described with asymmetric Michaelis Menton kinetics.
2065. Directional Diffusivity as an MR Biomarker of Axonal Injury in Leukodystrophy
Tammie LS Benzinger1, Chin-I Chen, 2, Agus Priatna, Junqian Xu, Peng Sun1, Amy Lee, Anne Cross, Sheng-Kwei Song1, Soe Mar
1Washington University in Saint Louis, St. Louis, Missouri, USA; 2Wangang Municipal Hospital, Taipei, Taiwan
Luekodystropy represents a broad category of genetic white matter diseases, characterized by varying degrees of myelin and axonal damage, depending upon the subtype. Frequently, these patients present for MR imaging without a known diagnosis. Although leukodystrophies have a very classic appearance on MRI, identifying the correct genetic subtype, which is critical for prognosis, is currently difficult by MRI alone. Here, we use axial and radial directional diffusivity to estimate the degree of axonal versus myelin damage, thus allowing for more precise diagnosis and prognosis.
2066. Multi-Slice Spectroscopic Imaging of Late Infantile Metachromatic Leukodystrophy (MLD)
Lars G. Hanson1, Christine I. Dali2, Jens M. Fogh3
1Copenhagen University Hospital, Hvidovre, Denmark; 2Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark; 3Zymenex A/S, Roskilde, Denmark
Late infantile metachromatic leukodystrophy (MLD) is a fatal genetic disease leading to brain degeneration after the first year of life. Since treatments are being developed, it is important to be able to diagnose and monitor the disease in the early stages. Few spectroscopic studies of this rare condition exist and little is known about the progression and spatial distribution of metabolic changes. Four children in different stages of the disease were scanned with multi-slice echo planar spectroscopic imaging. An almost complete loss of white matter NAA signal was found in the later stages of the disease.
2067. Contrast-Enhanced Ex Vivo MR Reveals Inflammatory Zone in X-Linked Adrenoleukodystrohpy
Megan L. Blackwell1, W C. Hubbard, M Selig, Bruce R. Rosen1, Ann B. Moser, Florian S. Eichler
1Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
We demonstrate with luxol fast blue-enhanced MR microscopy a zone of macrophages and myelin debris at the leading edge of active demyelination. Both immunohistopathology and biochemistry helped to explain the distinct contrasts seen in LFB-enhanced MR images: inflammation on T2*-weighting and NAWM on T1-weighting. Thus, a single contrast agent is able to measure different biochemical parameters.Our findings support the conclusion that enhanced T2* susceptibility in ALD samples is in part due to compartmentalization of the LFB contrast agent. Our technique of contrast-enhanced ex vivo MR microscopy allows for the investigation of lipids and inflammation in the process of demyelination.
Hall D Wednesday 13:30-15:30
Daniel T. Franc1, Chris Kodl, Bryon Mueller, Ryan Muetzel, Elizabeth Seaquist, Kelvin O. Lim
1University of Minnesota, Minneapolis, USA
Tract-specific fractional anisotropy and regional cortical thickness measures were found to be reduced and correlated in patients with Type 1 diabetes.
Benjamin Schmitt1, Peter Bachert1
1German Cancer Research Center, Heidelberg, Germany
This study demonstrates a possibility to trace the energy metabolism in human brain tissue non invasively by means of proton NMR spectroscopy. We observed that it is possible to detect resolved glucose signals in the brain of a patient with type 1 diabetes on a commercial 3-T MR scanner. This technique does not require specific equipment and can therefore be easily included in clinical routine MR examinations at 3 Tesla.
2102.
Glucose Transport and Neurochemical Profile in the
Hippocampus of STZ-Induced Diabetic Rats Under
Hyper- And Euglycaemia
Studied by in Vivo 1H MRS at 9.4T
João MN Duarte1, 2, Rui A. Carvalho1, Rodrigo A. Cunha1, Rolf Gruetter2
1Center for Neuroscience and Cell Biology, Coimbra, Portugal; 2Laboratory for functional and metabolic imaging, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland
Diabetes mellitus accentuates the age-dependent decline of cognitive function which is related to reduction of hippocampal volume, a brain structure involved in learning and memory processing. In the present study, we measured the neurochemical profile and the kinetics of glucose transport in the hippocampus of streptozotocin (STZ)-induced diabetic rats using non-invasive 1H NMR spectroscopy. Our results show that chronic hyperglycemia does not alter brain glucose transport/content and that glycemia restoration immediately normalizes most neurochemical alterations.
2103. Cerebral H-MRS Correlates of Painless Diabetic Neuropathy
Rajiv Gandhi1, Dinesh Selvarajah1, Celia J. Emery1, Paul D. Griffiths2, Solomon Tesfaye1, Iain D. Wilkinson2
1Royal Hallamshire Hospital, Sheffield, UK; 2University of Sheffield, Sheffield, UK
Previous proton spectroscopy (H-MRS) studies have demonstrated abnormalities within the thalamus in patients with diabetic neuropathy (DN). It is unclear which parts of the brain’s sensory matrix are involved. A large 130 subject cohort was studied consisting subjects at different stages of DN plus controls without diabetes. Single voxel H-MRS was performed within the thalamus and somatosensory cortex at two TE’s. In subjects with painless DN, lower NAA/Cr was observed in the thalamus at long TE and lower NAA in the sensory cortex at short TE. There is spatial variation in H-MRS abnormalities in subjects with painless DN.
2104. Neurochemical Changes in Hippocampus of Developing Rats During Acute Hypoglycemia
Ivan Tkac1, Kathleen Ennis1, Raghavendra Rao1
1University of Minnesota, Minneapolis, Minnesota, USA
In vivo 1H NMR spectroscopy at 9.4 T was used to investigate neurochemical changes in hippocampus of 14-day-old rat pups during insulin induced hypoglycemia. Significant changes from homeostasis were observed for Asp, Glc, Gln, Glu, Lac, Cr and PCr. Time courses of individual metabolites revealed different mechanisms supporting energy production. When endogenous Glc resources ware exhausted, amino acids Gln, Glu became primary sources to feed TCA cycle through different anaplerotic pathways.
Hall D Wednesday 13:30-15:30
2146.
SPHARM Detects Hippocampal Subfield Pathology in Temporal
Lobe Epilepsy
Hosung Kim1, Mark Niethammer2, Boris C. Bernhardt1, Sylvain Bouix2, Neda Bernasconi1, Andrea Bernasconi1
1Montreal Neurological Institute and Hospital, Montreal, Canada; 2Harvard Medical School, Boston, Massachusetts, USA
Our purpose was to detect volume changes in the hippocampal subfields of patients with pharmacoresistant temporal lobe epilepsy (TLE) using SPHARM, a surface-based shape analysis method. We studied 95 TLE patients with unilateral hippocampal atrophy on MR volumetry and 46 controls. SPHARM applied to manual hippocampal labels measured a distance at each vertex between groups. In more than 40% of patients, we found a bilateral CA1 inward deformation more marked ipsilateral to the focus. These changes were negatively correlated with disease duration. Predominant CA1 atrophy with relative sparing of other subfields is in agreement with histopathological hippocampal sclerosis.
2147. Abnormal Gyrification of the Cerebral Cortex in Mesial Temporal Lobe Epilepsy
Cathy Scanlon1, Lisa Ronan1, Colin Doherty2, Norman Delanty1, Mary Fitzsimons1
1Beaumont Hospital, Dublin 9, Ireland; 2St. James's Hospital, Dublin 6, Ireland
The aim of this project is to identify abnormalities of cerebral cortical gyrification in mesial temporal lobe epilepsy using advanced quantitative magnetic resonance image-based techniques. Our results demonstrate a statistically significant reduction in temporal lobe gyrification. The identification of brain morphological abnormalities in TLE may help to further elucidate the pathogenesis of this disease.
2148.
Simultaneous FMRI and Electrophysiology During Intracerebral
Stimulation of Partial Seizures in Rats
Dario J. Englot1, Asht M. Mishra1, Michael Purcaro1, Peter Herman1, Fahmeed Hyder1, Hal Blumenfeld1
1Yale University School of Medicine, New Haven, Connecticut, USA
fMRI could be a useful tool for studying partial limbic seizures because of its success with other seizure models. However given patient movement during temporal lobe seizures, human fMRI recordings in temporal lobe epilepsy are technically difficult. Therefore, animal models would be extremely valuable. Here we describe an anesthetized rat model where electrical stimulation of the hippocampus induces limbic seizures which mimic complex-partial temporal lobe seizures in humans. We achieved reliable EEG and fMRI data, simultaneously acquired, during intracerebral stimulation. The network of increased BOLD signal changes occurred within expected areas based on separate neurophysiologic studies.
2149. Decrypting Cryptogenic Partial Epilepsy Using White Matter Fractional Anisotropy Analysis
Simon Sean Keller1, Thomas Duning2, Christoph Kellinghaus2, Siawoosh Mohammadi2, Hagen Schiffbauer2, E Bernd Ringelstein2, Stefan Knecht2, Michael Deppe2
1University of Liverpool, Liverpool, UK; 2University of Muenster, Germany
In patients with electroclinical evidence of cryptogenic partial epilepsy (PE) without brain abnormalities on conventional MRI, we show reduced fractional anisotropy (FA) in multi-lobar regions symmetrically, and asymmetrical temporal lobe FA reduction consistent with the side of the epileptogenic focus. We suggest that diffusion tensor imaging analysis of FA may represent an effective method for lateralising a neuroanatomical abnormality underlying the epileptogenic zone during pre-surgical evaluation of PE.
2150.
Multimodal MRI Reveals Secondarily Generalized Seizure
Related Microstructural Brain Tissue
Abnormalities at 1.5 T
Jacobus F.A. Jansen1, M Eline Kooi1, Marielle C.G. Vlooswijk1, H J.M. Majoie1, Rianne P. Reijs1, Paul A.M. Hofman1, Klaas Nicolay2, Marc C.T.F.M. de Krom1, Albert P. Aldenkamp1, Walter H. Backes1
1Maastricht University Hospital, Maastricht, Netherlands; 2Eindhoven University of Technology, Eindhoven, Netherlands
Patients who have suffered a high number of secondarily generalized tonic-clonic seizures (SGTCS) frequently show cognitive comorbidity. We have investigated whether a high number of SGTCS accumulated over life is associated with microstructural and metabolic changes in brain tissue. Sixteen patients with localization-related epilepsy with SGTCS underwent multimodal quantitative MRI (1.5 T), comprising T2 relaxometry, DWI, and MRSI. SGTCS are associated with significant changes in microstructural brain tissue characteristics within the frontal lobes, but not in the temporal lobes. These frontal changes possibly explain the cognitive problems which are often observed in patients with many SGTCS. This knowledge may help in the development of treatment aimed at preventing decline in cognitive abilities.
2151. Voxel Based Morphometry of 3D FLAIR Imaging in Cryptogenic Intractable Focal Epilepsy
Kate J. Riney1, 2, Kling C. Chong2, J Helen Cross1, 2, Chris A. Clark1
1University College London Institute of Child Health, London, UK; 2Great Ormond Street Hospital for Children NHS Trust, London, UK
Fluid-attenuated inversion-recovery (FLAIR) magnetic resonance imaging has improved the detection of focal cortical dysplasia (FCD) which can underlie intractable focal epilepsy (IFE). Recently methods have been developed to allow the acquisition of 3D FLAIR volumes. Voxel based morphometry (VBM) is an objective method of assessing 3D volumetric imaging, performing a voxel-wise comparison between an individual brain and a control group. In this study we report on a method for performing VBM of 3D FLAIR and validate this technique through reliably detecting the FCD in 7/8 children with IFE and visible FCD. In addition we report that VBM of 3D FLAIR detected abnormality in 4/14 children with cryptogenic IFE and in 2/4 the VBM abnormality was subsequently found to represent FCD not seen on previous image reporting. For the children in whom FCD has been detected with VBM of 3D FLAIR, epilepsy surgery may now become a possible treatment option.
2152. Combined EEG, FMRI, and Cognitive Testing in Childhood Absence Epilepsy
Rachel Berman1, Michiro Negishi1, Marisa Spann1, Mi Hae Chung1, Michael Joseph Purcaro1, Edward J. Novotny1, R.Todd Constable1, Hal Blumenfeld1
1Yale University, New Haven, Connecticut, USA
Patients with childhood absence epilepsy (CAE) have repeated 5-10 s episodes of unresponsiveness, associated with a “spike-wave” discharge on electroencephalography. The fundamental mechanisms of altered brain function and impaired attention in CAE are not known. Our central hypothesis is that SWD cause dysfunction in specific networks important for attention, including the medial frontal cortex and thalamus. If confirmed, this may lead to regional therapies targeted at improving impaired attention in patients with CAE. We will, therefore, map abnormal function in CAE, between and during seizures, using simultaneous EEG-fMRI and test attentional vigilance with the continuous performance task (CPT).
2153. Short and Long Term MRI Abnormalities After Experimental Febrile Seizures
Jacobus F.A. Jansen1, Evi M.P. Lemmens1, Gustav J. Strijkers2, Jeanine J. Prompers2, M Eline Kooi1, Klaas Nicolay2, Govert Hoogland1, Walter H. Backes1
1Maastricht University Hospital, Maastricht, Netherlands; 2Eindhoven University of Technology, Eindhoven, Netherlands
Experimental febrile seizures (FS) are known to increase the risk for eventual temporal lobe epilepsy. Quantitative multimodal MRI may provide early markers of microstructural and metabolic changes. FS were induced in 9-day old rats by hyperthermia exposure. Hippocampal volumetry and 1H-MRS, and cerebral T2 relaxometry and DTI was applied in FS rats and controls (24h and 8w later). At 9 weeks histological analysis was performed. Hippocampal T2 elevations at 24 hours appeared to be transient. DTI abnormalities detected in the amygdala at 24 hours persisted up to 8 weeks. Hippocampal volume was not affected. Histological analysis showed increased hippocampal (fiber density and anisotropy) and amygdalar changes. Quantitative MRI is able to detect both transient and long-term FS induced abnormalities in the limbic system that reflect microstructural alterations. These long-term findings support the concept that early-life FS are related to epilepsy.
2154.
MRI Measurements After Status Epilepticus Can Be Used as an
Early Biomarker for the Hippocampal Injury
in the Rat Lithium-Pilocarpine
Model
ManKin Choy1, Rodney C. Scott1, David L. Thomas2, Ken K. Cheung2, David G. Gadian1, Mark F. Lythgoe, 12
1UCL-Institute of Child Health, London, UK; 2UCL, London, UK
Status epilepticus (SE) can cause hippocampal injury, with subsequent cognitive decline and development of temporal lobe epilepsy (TLE). We investigated these events using CBF, ADC and T2 in the lithium-pilocarpine rat model of SE and identified time-dependent MR changes that peaked on day 2. A strong relationship was identified between these peak changes and subsequent hippocampal volumes measured on day 21, which suggests that MRI measurements on day 2 after SE can be used as an early biomarker for the associated progressive hippocampal injury.
2155.
Perfusion MRI Changes During Status Epilepticus in the Rat
Pilocarpine Model
ManKin Choy1, Rodney C. Scott1, David L. Thomas2, Jack A. Wells2, Edward Proctor1, David G. Gadian1, Mark F. Lythgoe, 12
1UCL-Institute of Child Health, London, UK; 2UCL, London, UK
There is a known relationship between convulsive status epilepticus (SE) and hippocampal injury, although the reasons for particular hippocampal injury remain uncertain. Potential mechanisms of injury include excitotoxicity and ischaemia. During the early phase of seizures, CBF increases in the cortex to meet energy demand, but it remains uncertain whether similar changes occur in the hippocampus. We have used perfusion MRI to investigate SE and have identified a limited CBF response in the hippocampus during pilocarpine-induced SE, which may in part account for the selective vulnerability.
2156. A New Method to Quantify Language Lateralization in FMRI Using Whole Brain Analysis
Stephen E. Jones1, Shamseldeen Younes Mahmoud1, Mark J. Lowe1, Michael D. Phillips1
1CCF, Cleveland, Ohio, USA
We present a new method to quantify language lateralization from fMRI studies, which uses a whole brain histogram approach. Advantages include no need to a priori threshold, and higher sensitivity for small activations.
2157.
TLE is Associated with Reduced Folding of the Temporal
Neocortex
Boris Christian Bernhardt1, Hosung Kim1, Neda Bernasconi1, Andrea Bernasconi1
1Montreal Neurological Institute and Hospital, Montreal, Canada
Our purpose was to quantify the neocortical gyrification in temporal lobe epilepsy (TLE), and to investigate its relationship to underlying morphological parameters using MRI. We extracted skeletons of the temporal neocortex of 92 TLE patients and 33 controls. On the skeletons, we measured the fractal dimension (FD), total sulcal sulcal length (TL), and average sulcal depth. In the lateral temporal cortex, we observed a bilateral decrease of FD and TL in TLE with a left-sided seizure focus. FD was positively correlated to TL, but not to sulcal depth. A ”simplified” lateral temporal lobe may indicate a neurodevelopmental disruption in TLE.
Innovative Imaging of the Normal Brain
Hall D Wednesday 13:30-15:30
and Histopathology
Mario Alcides Miranda1, Luke A. Massey1, Harry G. Parkes1, So Po-Wah2, John S. Thornton1, Janis Holton1, Laura Mancini3, P Cheshire1, K Strand1, Andrew J. Lees1, Tamas Revesz1, Tarek A. Yousry1
1Institute of Neurology, UCL, London, UK; 2Imperial College School of Medicine, MRC Clinical Sciences Centre, Hammersmith Hospital, London, UK; 3Lysholm Department of Neuroradiology, London, UK
High resolution T2W MRI images at 9.4T of the midbrain targeted on the Substantia Nigra (SN) have been compared with histopathology samples. The detailed micro environment of the SN and the superior midbrain is described. The SN is seen as two layered band of tissue with a hypointense antero-lateral segment (par reticulata) and a hyperintense postero-medial component (pars compacta). This is probable the first MRI description of both segments of the SN (pars reticulata and compacta) that has been achieved.
2216. Susceptibility-Weighted Imaging (SWI) Delineates the Whole Length of the Optic Radiation
Nobuyuki Mori1, Yukio Miki1, Chikara Maeda1, Seiko Kasahara1, Shin-ichi Urayama1, Nobukatsu Sawamoto1, Hidenao Fukuyama1, Kaori Togashi1
1Kyoto University Graduate School of Medicine, Kyoto, Japan
This study examined whether low signal-intensity band (LSB) lateral to the lateral ventricles on 3T SWI represented the optic radiation (OR) by measuring profiles of LSB in 4 anatomical planes. Seven healthy volunteers entered. Comparison was also made with diffusion tensor tractography (DTT) of the OR. Measured profiles of the LSBs were consistent with the anatomical literature regarding the OR; even Meyerfs loops were clearly demarcated on SWI. DTT overlapped all LSBs posterior to the geniculate body, while at Meyerfs loop overlapped incompletely. Visualization of the whole length of the OR on SWI may have clinical relevance.
2217. Quantitative Cytoarchitectural Mapping of the Parahippocampal Region
Neda Bernasconi1, 2, Thomas Mansi2, Gheorghe Postelnicu1, Jean C. Augustinack1, Bruce Fischl1
1Athinoula Martinos Center, Massachusetts General Hospital, Harvard Medical School, Boston, USA; 2Montreal Neurological Institute, Montreal, Canada
Our purpose was to delineate cytoarchitectonic borders of parahippocampal region structures based on their laminar cortical pattern on ultra-high resolution MRI at 7T. We obtained ex-vivo 100 ?m isotropic images of the temporal lobe in three neurologically healthy subjects using a multiecho multi flip-angle sequence. The cortex was extracted by solving the Laplace Equation. This process generated streamlines between GM/CSF and GM/WM boundaries, and allowed computing laminar distribution of grey level intensities across the cortex. Applying multivariate statistics on laminar intensity profiles allowed distinguishing cytoarchitectonic borders between parahippocampal subregions that are currently invisible to conventional means of analysis.
2218. High-Resolution in Vivo MR Imaging of the Human Hippocampus at 7 Tesla
Zang-Hee Cho1, Kyoung Nam Kim1, Young-Bo Kim1, Kyongtae T. Bae2, Chan-Hong Moon2
1Gachon University of Medicine and Science, Incheon, Republic of Korea; 2University of Pittsburgh, Pittsburgh, Pennsylvania, USA
Volumetric atrophy of the hippocampus is associated with a wide range of neurodegenerative diseases (ND), such as Alzheimer¡¯s disease (AD), and has been thoroughly evaluated at 1.5 or 3 T magnetic f