Joint Annual Meeting ISMRM-ESMRMB 2014 10-16 May 2014 Milan, Italy



1438-1463 RF Design & Mapping
1464-1519 Acquisition Methods
1520-1530 Spectroscopic Acquisition
1531-1545 Non-Cartesian Imaging
1546-1572 Image Reconstruction
1573-1596 Image Processing & Analysis

Motion Correction

1615-1648 Artifacts Correction
1649-1674 Fat Suppression, Separation & Quantification
1675-1683 Imaging Metal Implants
1684-1698 Elastography

RF Design & Mapping

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

Joint Design of Continuous Excitation k-space Trajectory and RF pulse for 3D Tailored Excitation
Hao Sun1, Jeffrey A. Fessler1, Douglas C. Noll2, and Jon-Fredrik Nielsen2
1Electrical Engineering and Computer Science, the University of Michigan, Ann Arbor, MI, United States, 2Biomedical Engineering, the University of Michigan, Ann Arbor, MI, United States

In 3D tailored RF pulse design, one typically predetermines a k-space (gradient) trajectory and then designs the corresponding RF waveforms for a target excitation pattern. Recently, the KT-points method was proposed as an approach for jointly designing the trajectory and RF pulses for 3D flip-angle homogenization (B1 shimming). KT-points models the 3D pulse design as a sparse approximation problem and selects sparse phase encoding locations by either a greedy approach or a simple inverse Fourier transform ignoring transmit coil sensitivity and field inhomogeneity. However, with only a few discrete phase encoding locations, it is difficult to approximate a non-smooth target excitation pattern in 3D. Also, it is relatively inefficient to traverse 3D k-space by discrete gradient blips with no RF transmission along those blips. In this work, we extend the KT-points method to a joint optimization of the continuous k-space trajectory and the RF waveform by: (1) applying local minimization to further optimize those KT points, and (2) efficiently ordering those points and generating a fast gradient waveform to traverse those points. We evaluate our proposed joint design with and without local minimization, and compare them with a recently proposed continuous nonselective spiral (SPINS) trajectory for 3D cubic excitation.

Multi-slice ultrafast spatiotemporal encoding (SPEN) MRI by new two dimensional excitation pulses
Rita Schmidt1 and Lucio Frydman1
1Chemical Physics, Weizmann Institute of Science, Rehovot, Israel

Two-dimensional (2D) excitation pulses are often used for localization in spectroscopic imaging and for in-plane region-of-interest delineation in MRI. Recent research has shown that these RF manipulations can also be based on spatiotemporal encoding (SPEN) principles. SPEN is a spatiotemporal manipulation that has also been used for single-shot ultrafast MRI. Fast volumetric SPEN MRI acquisitions, however, are still challenged. The present work merges the benefits of both 2D SPEN-based excitation and 2D SPEN single-shot acquisitions, demonstrating a multi-slice ultrafast sequence. Experiments testing these ideas were demonstrated on phantom as well as on brain volunteer imaging experiments at 3 T.

1440.   Nonlinear-Phase Multiband 90°-180° RF Pair With Reduced Peak Power
Kangrong Zhu1, Adam B. Kerr1, and John M. Pauly1
1Electrical Engineering, Stanford University, Stanford, CA, United States

Multiband RF pulses are central to the signal excitation in simultaneous multislice acquisitions. The peak amplitude has been a limiting factor in multiband RF design, especially in multiband spin-echo pulse design. In this work, nonlinear-phase multiband pulses, which have reduced peak power compared to linear-phase pulses, are designed. A pair of 90°-180° nonlinear-phase multiband pulses are applied to generate a linear-phase echo. An additional reference phase is applied to each individual excited band to further reduce the peak power of the multiband pulse.

1441.   A Robust and Low-Power Adiabatic T2 Preparation for Cardiovascular Imaging at High Magnetic Field
Ruud B van Heeswijk1,2, Kieran R O'Brien2,3, Jean Delacoste1,2, and Matthias Stuber1,2
1Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland, 2Center for Biomedical Imaging (CIBM), Lausanne, Switzerland,3Radiology, University of Geneva, Geneva, Switzerland

An adiabatic T2 Preparation module (T2Prep) at high magnetic field normally requires too much energy to allow it to be combined with bSSFP imaging. Numerically optimized adiabatic pulses were therefore used to design a T2Prep for cardiovascular imaging at high magnetic field. The energy efficiency of this optimized T2Prep was established at 3T and compared to standard adiabatic T2Prep. Finally, T2-prepared bSSFP cardiovascular imaging and coronary MRA were demonstrated in healthy volunteers.

1442.   MultiPINS: PINS + MultiBand hybrid RF pulse with reduced SAR for SMS Imaging at Ultra High Field Strength
Cornelius Eichner1,2, Robert Turner2, Lawrence L Wald1, and Kawin Setsompop1
1Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany

Simultaneous Multi Slice (SMS) acquisition enables increased temporal resolution and acquisition speed. However, at ultra high field strengths, SAR constraints of SMS RF pulses can enforce slower acquisition speed. We propose a novel MultiPINS RF pulse design that combines PINS and MultiBand pulses to achieve lower SAR. Slice profiles and off-resonance behavior of this pulse were evaluated using Bloch simulations. The MultiPINS pulse achieves similar slice profiles, but significantly reduced energy transmission and peak RF voltage. In-vivo high-resolution Blipped-CAIPI SMS diffusion MRI data with 3x multiband acceleration were acquired at 7T to show the usefulness of this new pulse design.

1443.   Multi-dimensional Susceptibility Conditioned RF Pulse (SCOPE) Design: A Spokes Approach
Wei Feng1, Yang Xuan2, and E Mark Haacke3
1Radiology, Wayne State University, Detroit, Michigan, United States, 2Radiology, Wayne State University, MI, United States, 3Wayne State University, MI, United States

A novel multi-dimensional spokes RF pulse design method is proposed to compensate for bulk susceptibility-induced phase variations. Under the small flip angle regime, there is a Fourier relationship between the excitation pattern and the RF and gradient waveforms, which traverses the excitation k-space. The conventional spokes pulse design approach is modified such that the cost function incorporates both magnitude and phase constraints inside the desired region of interest (ROI) based on susceptibility field map, while the phase is allowed to vary arbitrarily outside the ROI. Numerical Bloch simulations and imaging experiments were performed for 1D, 2D and 3D pulse design applications. It is shown that the proposed method is viable and could have significant potential in susceptibility-related imaging applications.

1444.   Design of a Variable-Rate Selective Dual-Band FOCI Pulse for Spin Labeling
Fabian Zimmer1, Frank G Zöllner1, and Lothar R Schad1
1Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany

For pulsed arterial spin labeling (ASL) the quality of the slice-selective inversion is decisive because of the inherent low perfusion contrast. Commonly, adiabatic inversion pulses are used. However, the adiabatic condition has to be fulfilled, leading to a compromise between the maximum available coil voltage and profile quality, i.e. pulse parameters. Especially the high RF power demand of adiabatic dual-band inversion pulses normally leads to inversion profiles that are unusable for ASL. We present a dual-band FOCI inversion pulse with reduced RF power requirements that conserves the high quality of a single-band FOCI pulse.

1445.   Implementation of a self-refocused adiabatic spin echo pulse-pair modulated using the power independent of the number of slices (PINS) technique for simultaneous B1-insensitive multi-slice imaging
Rebecca Emily Feldman1, Haisam Islam2, and Priti Balchandani1
1Translational and Molecular Imaging Institute, Icah School of Medicine at Mount Sinai, New York, New York, United States, 2Bioengineering, Stanford University, California, United States

High field MR can be challenging due to limited slice coverage, B1-inhomogeneity. Adiabatic pulses can limit sensitivity to B1-inhomogeneity, however adiabatic pulses deposit quadratic phase that is difficult to refocus and are SAR intensive. Similarly, simultaneous multi-slice imaging can accelerate image acquisition at high fields but RF pulses created as the superposition of multiple slice RF pulses can rapidly exceed safe SAR limits. Using a 'Power Independent of Number of Slices' (PINS) technique, multiple slices can be excited simultaneously at lower power. We implemented a adiabatic PINS refocusing pulse with a matched phased PINS excitation pulse.

1446.   A General Numerical VERSE RF Pulse Design Framework
Nii Okai Addy1 and Dwight G Nishimura1
1Electrical Engineering, Stanford University, Stanford, CA, United States

A recent method for a flexible, numerical spiral imaging trajectory design can be adapted to RF pulse design. With this general framework, various VERSE RF pulses can be designed in one or multiple dimensions. This work presents results for slab-selection and spiral excitation.

1447.   Variable-rate design of quieter slice-select pulses
Christopher J. Hardy1, Seung-Kyun Lee1, and Michael J. Wittbrodt1
1GE Global Research, Niskayuna, NY, United States

Slice-select pulses can be made quieter by derating them, i.e. by reducing gradient slew rate and/or amplitude (along with RF bandwidth), but this increases minimum echo time. The variable-rate principle is used here to design slice–select pulses with improved acoustic signature and with identical slice profiles on-resonance, without lengthening pulse duration.

1448.   RF pulse design for low SAR simultaneous multislice (SMS) excitation using optimal control
Christoph Stefan Aigner1, Christian Clason2, Armin Rund2, and Rudolf Stollberger1
1Institute of Medical Engineering, Graz University of Technology, Graz, Austria, 2Institute for Mathematics and Scientific Computing, University of Graz, Graz, Austria

Optimal control (OC) is a flexible framework for the design of RF pulses with arbitrary slice profiles, even in the presence of relaxation effects and field inhomogeneities, and is therefore well suited for simultaneous multislice (SMS) imaging. We demonstrate the ability of this approach to generate RF pulses with arbitrary (large) flip angles, slice thickness, slice gaps and slice numbers. The results for two and three slices of 4mm thickness are validated on a 3T MR scanner and indicate the applicability of the proposed method.

1449.   RF Pulse Design using Linear and Nonlinear Gradient Fields: A Multi-Dimensional k-Space Approach
Emre Kopanoglu1, Leo K. Tam1, and Robert Todd Constable1
1Dept. Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut, United States

The effect of using nonlinear gradient fields (NLGFs) on excitation fidelity is studied, specifically on a multi-dimensionally selective excitation scheme. For this purpose, three nonlinear and two linear gradient fields (LGFs) are used. Two-dimensionally selective RF pulses are designed utilizing more than two fields simultaneously, using a multi-dimensional k-space approach. Using simulations, it is shown that increasing the number of k-space dimensions beyond the number of spatial coordinates may yield excitation profiles with lower error, compared to the target profile. It is also shown that, NLGFs may improve excitation fidelity, even for profiles that are more compatible with LGFs.

1450.   Homogeneous neuroimaging at 7 tesla with short tailored radiofrequency pulses using high permittivity dielectric bags
Joep Wezel1, Maarten Versluis1, Andrew Webb1, Matthias van Osch1, and Peter Börnert1,2
1C.J. Gorter center for high field MRI, Radiology, Leiden University Medical Center, Leiden, Netherlands, 2Philips Research Europe, Hamburg, Germany

Neuroimaging at 7 tesla is complicated by the high degree of B1-inhomogeneity within the brain. Spezialized RF pulses that take the B1 distribution into account can compensate for the inhomogeneous field. These pulses are generally longer than the regular pulses, leading to increased sensitivity to B0 deviations. To counter this trend we apply high permittivity dielectric pads that reduce the severity of the flip angle voids. This potentially leads to the design of shorter RF pulses to compensate for the remainder of the inhomogeneities. We have simulated three pulse lengths with and without the bags and verified this in-vivo.

1451.   Variable Density 2D Spiral Excitation with Self Compressed Sensing
Wenwen Jiang1,2, Michael Lustig3, John Pauly4, and Peder E.Z. Larson5
1Graduate Group in Bioengineering, University of California, Berkeley, Berkeley, California, United States, 2University of California, San Francisco, San Francisco, California, United States, 3Electrical Enigneering and Computer Science, University of California, Berkeley, California, United States, 4Electrical Enigneering, Stanford University, California, United States, 5Radiology and Biomedical Imaging, University of California, San Francisco, California, United States

2D spiral excitation pulses are potentially valuable for bolus tracking and reduced FOV imaging. But 2D excitation pulses are usually long, given the FOV and resolution requirements, which results in off-resonance blurring of the spatial profile. Subsampled spiral trajectories could shorten the duration of the pulse but resulting in aliasing sidelobes in the excitation profile. In analogy to the subsampled data acquisition, subsampled excitation profiles can be designed to produce incoherent sidelobes. These can be further reduced by the fact that spin-echoes square the linear excitation dramatically shrinking the sidelobes. With the design of appropriate variable density spiral trajectories, this method will effectively suppress aliasing sidelobes while resulting in shorter excitation pulses.

Optimization of fast k-space trajectories for 3D spatially selective parallel excitations
Mathias Davids1,2, Bastien Guérin2, Lothar R. Schad1, and Lawrence L. Wald2,3
1Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Mannheim, BW, Germany, 2Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 3Harvard-MIT, Division of Health Sciences and Technology, Cambridge, MA, United States

The k-space trajectory, in addition to the RF, possesses powerful degrees of freedom to enhance 3D parallel selective excitations. A novel approach on rapidly designing arbitrarily shaped time-optimal trajectories was used to simultaneously optimize the trajectory and RF pulse. The trajectory was defined by shape parameters that were optimized for a cubic ROI and brain only excitation. Two trajectories were optimized – a 3D Cross and a 3D Concentric Shells trajectory – with durations of less than 7 ms each. The excitation RMSE could be reduced by up to 60% in an eight channel 7T setup, yielding applicable 3D selective excitation pulses.

1453.   On variant strategies to solve the Magnitude Least Squares optimization problem in parallel transmission RF pulse design and under strict SAR and power constraints
Nicolas Boulant1, Andres Hoyos-Idrobo1, Pierre Weiss2, Aurelien Massire1, and Alexis Amadon1
1Neurospin, CEA, Saclay, Ile de France, France, 2ITAV, CNRS, Toulouse, Midi-Pyrénées, France

Despite the importance of the magnitude least squares problem in parallel transmission pulse design and the availability of other powerful numerical optimization methods, this problem has been faced almost exclusively with the so-called variable exchange method. Here, we investigate various two stage strategies and incorporate directly the SAR and power constraints. Different schemes such as sequential quadratic programming, interior point methods, semi-definite relaxation and magnitude squared least squares relaxations are studied in the small and large flip angle regimes with B1 and DB0 maps obtained in-vivo on a human brain at 7 Tesla.

1454.   Local and global SAR constrained large tip angle 3D kt points parallel transmit pulse design at 7 T
Filiz Yetisir1, Bastien Guerin2, Lawrence L. Wald2,3, and Elfar Adalsteinsson1,3
1Dept. of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 2Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 3Harvard-MIT Division of Health Sciences Technology, Cambridge, MA, United States

Explicit SAR constraints have been proven useful for slice selective small tip angle pulse design. We propose a nonselective pulse design method that explicitly constrains local SAR and RF peak amplitude at large tip angle and demonstrate that when local SAR is controlled directly rather than via control of peak RF voltage, safer pulses with better excitation profiles are obtained. Our method is more practical than Tikhonov regularized strategies since it only requires one run to ensure that all the limits (SAR and RF) are satisfied.

1455.   3DREAM – A Three-Dimensional Variant of the DREAM Sequence
Daniel Brenner1, Desmond H. Y. Tse2, Eberhard D. Pracht1, Thorsten Feiweier3, Rüdiger Stirnberg1, and Tony Stöcker1
1German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, 2INM-4, Research Centre Jülich GmbH, Jülich, Germany, 3Siemens AG, Healthcare Sector, Erlangen, Germany

A 3D variant of the DREAM sequence, with a spiral phase encode view ordering, is utilized for B1 mapping at 7T. Together with short non-selective preparation and imaging RF pulses this enables whole volume B1 mapping of the human head in 15s or even a single shot - which only lasts 3s – at negligible SAR levels (1%). Good agreement is found with a reference AFI dataset with degraded quality in a low tip angle regime due to the low SNR of the STE* image.

1456.   Optimization of Amplitude-Modulated Pulses for Bloch-Siegert Based B1 Mapping
Qi Duan1, Peter van Gelderen1, Souheil J. Inati2, and Jeff H. Duyn1
1AMRI, LFMI, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States, 2FMRIF, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, United States

This abstract investigates fast simultaneous B0/B1+ mapping by Bloch-Siegert shift via lowering the off-resonance frequency of this pulse, as theoretical analysis indicated that the sensitivity of Bloch-Siegert based B1+ mapping can be substantially improved when irradiating closer to resonance. Using optimized irradiation pulse shape and gradient crushers to minimize direct excitation effects, in vivo experiments on human brain at 7T confirmed the improved sensitivity available with this approach operating with peak B1+ much larger than the frequency offset. This improved sensitivity translated into an 80% reduction in B1+ estimation errors, without increasing tissue heating.

1457.   Toward B1 estimation using coil locators
Parnian Zarghamravanbakhsh1, Christopher Ellenor1, John M Pauly1, and Greig Scott1
1Electrical engineering, Stanford university, Stanford, CA, United States

We propose a method to predict B1 filed using coil geometry and location in imaging coordinate system without doing B1 mapping. Most of B1 mapping are done without any assumption about the coil geometry and location. Coils location are found by placing markers on coil conductors, then by acquiring three sets of 1D projections to localize the markers ,coil plane can be detected. Having known the coil location and geometry, B1 field distribution can be obtained by computational analysis .To validate the method, we compare simulated with measured results. Field prediction can be used in auto-calibration and RF pulse design.

1458.   Lowering the B1 Threshold for BEAR B1 Mapping
Kalina V Jordanova1, Dwight G Nishimura1, and Adam B Kerr1
1Electrical Engineering, Stanford University, Stanford, California, United States

We redesign the BEAR B1 mapping method to use HSn pulses, which have lower adiabatic thresholds. By optimizing the HSn pulse parameters, we can reliably acquire B1maps for lower nominal peak B1 than with the original BEAR method. We validate the performance of BEAR with HSn pulses via simulation and in vivo at 3T, with average errors from the original BEAR method of less than 3%. This method will be useful for reliably acquiring B1 maps for lower B1 values.

1459.   Decoupled RF-Pulse Phase Sensitive B1 Mapping
Daniel J. Park1, Neal K. Bangerter1,2, and Glen R. Morrell2
1Department of Electrical and Computer Engineering, Brigham Young University, Provo, Utah, United States, 2Department of Radiology, University of Utah, SLC, Utah, United States

B1 mapping mapping is an important component of quantitative MRI and parallel transmission. Although many B1 mapping methods have been introduced and analyzed, there is no clear superior method. One method, the Bloch-Siegert shift method, has potential for improved B1 mapping of parallel transmit arrays through separation of excitation and the B1 encoding pulse. We introduce a modification to the Phase Sensitive (PS) method that allows similar improvement by decoupling the compound excitation pulse in the PS method. We introduce a brief Monte Carlo based statistical analysis (mean bias and standard deviation) which illustrates the potential of this method.

1460.   Reduced-FOV Lumbar Spine T1lower case Greek rho MR Imaging Using High-Low EP-2DRF Excitation Pulse
Qinwei Zhang1, Yi-Xiang J Wang1, Heather Ting Ma2, Queenie Chan3, and Jing Yuan1,4
1Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, 2Harbin Institute of Technology Shenzhen Graduate School, Shenzhen, Guangdong, China, 3Philips Healthcare, Hong Kong, Hong Kong, 4CUHK Shenzhen Research Institute, Shenzhen, Guangdong, China

T1ρ imaging has been proved to be a sensitive biomarker for disc degeneration while suffering from long scan time. Large field of view and respiratory motion further adversely affect the mapping results. We proposed a 2DRF pulse with novel high-low EP excitation trajectory to realize reduced field of view (rFOV) T1ρ imaging in lumbar spine region on a 3T clinical scanner. The scan time was halved and motion artifact was eliminated. Good consistency between rFOV and full FOV T1ρ maps was observed. The proposed 2DRF has potential to be used for high-resolution spine T1ρ imaging in routine clinical scan.

1461.   Correction of 2D RF Pulses
Yuval Zur1
1GE Healthcare, Tirat Carmel, Israel

Two dimensional (2D) RF pulses with EPI excitation trajectory are extremely sensitive to system imperfections such as eddy currents and waveform distortions. These imperfections cause stop band excitation and pass band saturation. A method to correct these 2D RF pulses is presented. The correction is done by adding a phase to even sub pulses and gradient blips to the oscillatory excitation gradient. The added phase and the area of the blips are determined by a calibration done at system installation. The method was applied successfully to spectral spatial RF pulses at oblique and non oblique slice orientations.

1462.   Characterizing the Inherent and Noise-Induced Errors in Actual Flip Angle Imaging
M Louis Lauzon1,2 and Richard Frayne1,2
1Radiology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, 2Seaman Family MR Research Centre, Calgary, AB, Canada

The flip angle term in an image can be determined using the TR-interleaved AFI (actual flip angle imaging) sequence. AFI makes an approximation, which leads to an inherent bias (a measure of accuracy). Noise propagation, however, produces an uncertainty bias and an increase in the variance (a measure of precision). Here, we analytically and numerically determine the accuracy/precision of the inherent and noise-induced errors of the cosine of the flip angle as a function of various acquisition parameters, and provide an overall error.

1463.   Shaped Saturation with RF Power Efficient 2D Spatially Selective Spiral Design in Parallel Transmission
Rainer Schneider1,2, Jens Haueisen2, and Josef Pfeuffer1
1MR Application Development, Siemens Healthcare, Erlangen, Bavaria, Germany, 2Institute of Biomedical Engineering and Informatics, TU Ilmenau, Ilmenau, Thuringia, Germany

Shaped saturation human in-vivo experiments were realized for the first time on the basis of multidimensional spatially selective RF pulses in parallel transmission. For this purpose, a variable-density 2D spiral trajectory design was introduced, which offers inherent RF power efficiency by incorporating the a-priori information of the target pattern and available B1 magnitude. The design was evaluated in sagittal head and t-spine experiments, saturating different patterns at 3T. The proposed approach was shown to offer up to 32% improved spatial accuracy and saturation performance under given RF hardware and SAR constraints.


Acquisition Methods

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

An SSFP Signal Equation with Finite RF Pulses and Exchanging Water Pools
Tobias C Wood1, Samuel A Hurley2, Gareth J Barker1, and Steven C R Williams1
1Neuroimaging, King's College London, Institute of Psychiatry, London, London, United Kingdom, 2Medical Physics, University of Wisconsin, Wisconsin, United States

We present an SSFP signal equation that includes finite RF pulse lengths and exchanging components, and then use this to calculate Myelin Water Fraction maps using mcDESPOT.

1465.   Fat-suppressed Alternating-SSFP for Whole-Brain fMRI Using a Short Spatial-Spectral Pulse
Tiffany Jou1, Steve Patterson2, John M. Pauly1, and Chris Bowen2
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada

Alternating-SSFP (alt-SSFP) suppresses banding artifacts and allows for whole-brain fMRI in a single run by using RF catalyzation to alternate between RF phase-cycling steady states. However, bright fat signal remains a problem because of the short TR used. Without an effective fat suppression technique, artifacts like fat chemical shift and off-resonance signal instability result. Our goal was to design a spectral-spatial (SPSP) pulse short enough to be used for alt-SSFP fMRI, with reduced fat chemical shift artifacts and improved temporal SNR (tSNR) time-courses. In this study, we propose our SPSP fat-suppression method as the first practical implementation of alt-SSFP and demonstrate good BOLD sensitivity in both breath-hold and visual paradigms.

1466.   A Comparative Study of the Uhrig Dynamic Decoupling (UDD) and CPMG Pulse Sequences
Jonathan Phillips1 and Sophie Schirmer2
1Institute of life Science, College of Medicine, Swansea University, Swansea, Wales, United Kingdom, 2Physics Department, Swansea University, Swansea, Wales, United Kingdom

It has been suggested that the UDD sequence, originally developed to extend the lifetime of qubits in quantum computing, may be used as an imaging sequence to extend the coherence lifetime in tissues to elucidate different tissue structures. We performed phantom studies to investigate these claims. We find evidence of lifetime extension although the interpretation of the images is complicated by steady state effects i.e. banding. However, the sequence may elucidate three-dimensional structure near tissue boundaries as well enhancing fat-water contrast at large repetition times.

1467.   On the feasibility of hybrid acquisition in SPACE
Guobin Li1, Maxim Zaitsev1, Matthias Weigel2, Esther Meyer3, Dominik Paul3, Jan Korvink4,5, and Jürgen Hennig1
1University Medical Center Freiburg, Freiburg, Baden-Württemberg, Germany, 2Radiological Physics, University of Basel Hospital, Switzerland, 3Siemens Healthcare, Germany, 4Department of Microsystems Engineering — IMTEK, University of Freiburg, Germany, 5Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Germany

SPACE employs non-selective RF pulses to achieve short echo spacing in the imaging with long echo trains. However, the use of non-selective RF pulses results in a single slab acquisition in SPACE imaging. In typical SPACE protocols, the duration of the echo train is only about 20% of the TR, which means 80% of the time is purely for waiting. In order to improve the time utilization ratio, in this work, we investigate the feasibility of acquiring a second contrast in the waiting time of the TR in single slab SPACE imaging. Some preliminary results of the hybrid imaging are shown.

1468.   FIESTA-flex : removing banding artifacts and allowing flexible contrast in FIESTA
Bing Wu1 and Yongchuan Lai1
1GE healthcare, Beijing, Beijing Municipality, China

A new pulse sequence named FIESTA-flex is proposed. Comparing to FIESTA(bSSFP), it removes the banding artifacts and allows flexibility image contrast at the sacrifice of signal level compared to FIESTA. In vivo feasibility studies have been performed, and qualitative inspection agrees with theoretical expectation.

1469.   Optimization of Flip angle and TR schedules for MR Fingerprinting
Maxwell L Wong1, Eric Z.C. Wu2, and Eric C Wong3
1UC San Diego, La Jolla, California, United States, 2University of Southern California, California, United States, 3Department of Radiology and Psychiatry, UCSD, La Jolla, California, United States

In this study, we simulate and attempt to optimize parameters for MR Fingerprinting. We looked for ways to characterize flip angle and TR schedules that produce the best estimated T1, T2 and frequency maps. This was done using frequency filters applied to random schedules, and comparison to DESPOT1 and DESPOT2 to assess the effectiveness of MRF. We confirmed higher sensitivity of MRF compared to DESPOT, and identified frequency characteristics in the flip angle schedules that were beneficial.

1470.   A Serial Artificial Neural Network Model for TrueFISP Sequence Design
Nahal Geshnizjani1, Kenneth A. Loparo1, Dan Ma2, Debra McGivney3, Vikas Gulani2,3, and Mark A. Griswold2,3
1Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, Ohio, United States, 2Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 3Radiology, University Hospitals of Cleveland and Case Western Reserve University, Cleveland, Ohio, United States

The purpose of this work is to design a system that is able to extract basic MR sequence parameters such as FA and TR from TrueFIsp signal evolutions. Artificial Neural Networks are used as the main tool because of their ability to be trained and learn and then solve complicated mathematical equations. We use an efficient method to predict FAs of TrueFISP signal evolutions one excitation at a time using the magnetization preceding and following the excitation. ANNs are trained by arbitrary initial magnetizations and random flip angles.

1471.   Field Assessment for Matrix Gradient coils using SVD
Sebastian Littin1, Feng Jia1, Hans Weber1, Frederik Testud1, Anna Welz1, and Maxim Zaitsev1
1Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany

Singular Value Decomposition (SVD) is a very usefull tool to asses encoding fields from matrix gradient coils.

1472.   Automated Gradient Conversion Algorithm for Acoustic-Noise Reduction in MRI
David Manuel Grodzki1 and Bjoern Heismann1,2
1Magnetic Resonance, Siemens Healthcare, Erlangen, Bavaria, Germany, 2Pattern Recognition Lab, Friedrich-Alexander-University of Erlangen-Nuremberg, Erlangen, Bavaria, Germany

Acoustic noise is one of the main reasons for patient discomfort during an MRI examination. High noise levels are caused by fast-switching gradients during the scan. By reducing the gradient switching and optimizing gradients, significant acoustic-noise reductions can be achieved. In this work, we present an automated gradient conversion algorithm that optimizes the gradient shape of any incoming sequence on the fly. Noise reductions of up to 12 dB(A) were reached. Incorporating further careful protocol adaptions, further noise reduction of up to 10 dB(A) was achieved, without sacrificing diagnostic image quality.

1473.   An easily controllable spread spectrum using chirp radio frequency pulse and its application in compressed sensing MRI
Xiaobo Qu1, Ying Chen1, Xiaoxing Zhuang1, Zhiyu Yan1, Di Guo2, and Zhong Chen1
1Department of Electronic Science, Xiamen University, Xiamen, Fujian, China, 2School of Computer and Information Engineering, Xiamen University of Technology, Xiamen, Fujian, China

To accelerate imaging, compressed sensing MRI (CS-MRI) suggests performing randomly undersampling to reduce the coherence between the encoding matrix and the sparsity bases. Spread spectrum (SS) is recently introduced to improves the reconstruction by reducing this coherence. But SS is achieved via a second order shim coil which limits modulation intensity and is not convenient to be operated. In this work, we propose a chirp radio frequency (RF) pulses to easily control the spread intensity by choosing a proper bandwidth and apply in CS. Simulation on the sampled data implies that the reconstruction error reduces if a proper bandwidth is provided.

1474.   Reduced FOV excitation using a SPSP pulse and a static second-order shim gradient
Haisam Islam1 and Gary Glover2
1Bioengineering, Stanford University, Stanford, CA, United States, 2Radiology, Stanford University, Stanford, CA, United States

The use of a spatial-spectral pulse in the presence of a static non-linear shim gradient has been proposed for reduced FOV excitation, in particular for exciting thin disc-shaped regions at isocenter. In this work, we extend the method to excite regions at an arbitrary locations and of arbitrary slice thicknesses, allowing for accelerated 2D or 3D high-resolution imaging.

1475.   The Effect of 2D Excitation Profile on T1 Measurement Accuracy Using the Variable Flip Angle Method
Bryant T. Svedin1,2 and Dennis L. Parker1
1Utah Center for Advanced Imaging Research, Radiology, University of Utah, Salt Lake City, Utah, United States, 2Physics, University of Utah, Salt Lake City, Utah, United States

Measurements of T1 using the Variable Flip Angle method are subject to errors introduced by inaccuracy in the flip angle used. Simulations were performed to test the effects of the slice excitation profile on the dependence of the measured signal on flip angle. Excitation profiles for several TBP and T1 values were simulated using the steady state flash equation. Calculated T1 values are compared with the true values.

1476.   Volume-Selective Thin Slice Thickness EPI for Whole Brain fMRI: Comparison with Z-Shimming EPI
Xiaodong Guo1
1Brain Research Imaging Center, The University of Chicago, Chicago, IL, United States

The slice thickness of slices in a small region of the human brain, where large MRI signal loss was experienced due to susceptibility difference at the air-tissue interfaces, was set to half the thickness of slices located at other regions where the static magnetic field was homogeneous. The MRI signal loss was dramatically recovered. Compared with z-shimming technique, images acquired by this volume-selective thin slice thickness technique have lesser temporal signal to noise ratio. However, thin slice thickness technique worked better for slices close to brain stem which cover amygdala and hippocampus areas.

1477.   Enhanced Slice Resolution by Staggered Acquisitions with Z-Deblurring
Thomas Depew1 and Qing-San Xiang1,2
1Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada, 2Radiology, University of British Columbia, Vancouver, BC, Canada

High resolution 3D MRI is becoming increasingly desirable for many research and clinical applications. However, certain MRI pulse sequences (such as EPI) can only be performed in multi-slice mode, typically with inadequate through-plane resolution. We present a technique that allows scalable through-plane resolution enhancement for multi-slice acquisitions. The method employs multi-slice acquisitions staggered along Z refined with novel deblurring algorithms. Isotropic resolution in 3D is achievable when sufficient data are available.

1478.   An interleaved multi-shot scheme involving self-refocused single-scan SPEN that is immune to in-plane movement and phase shifts
Rita Schmidt1, Amir Seginer1, and Lucio Frydman1
1Chemical Physics, Weizmann Institute of Science, Rehovot, Israel

Recent studies have shown the benefits of a single-shot spatiotemporal encoding (SPEN): reducing magnetic field inhomogeneity distortions and delivering chemical shift information. The present work demonstrates that SPEN can also exhibit substantial motion immunity, even when executed in interleaved multi-shot schemes. Shots of SPEN data can be co-processed to generate full FOV images without requiring extra reference scans. Since no aliasing is involved, a phase correction from SPEN shots can be estimated, resolving ghost-free SPEN images, and eliminating transient phase shifts or in-plane movement between shots. Preliminary tests confirm the advantages on phantom and human scans, including functional MRI experiments.

1479.   SALSAS: Spectral Spatial Excitation Combined with Z-Shimming to Mitigate Through-Plane Signal Loss in Single-Slice and Multiband Gradient Echo Imaging
Anuj Sharma1, Manus Donahue2,3, V. Andrew Stenger4, and William A. Grissom1,2
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 2Radiology, Vanderbilt University, TN, United States, 3Psychiatry, Vanderbilt University, TN, United States, 4Medicine, University of Hawaii, HI, United States

An SNR-efficient method to mitigate signal loss artifacts in single-slice and simultaneous multi-slice long echo time gradient echo acqisitions is presented. Signal improvement comes from the use of spectral spatial pulses to selectively excite regions that are refocused with Z-shim. Scan time is minimized by treating the different z-shim acquisitions as additional slices in a multi-slice stack. Phantom and in-vivo experiments at 7T and 3T demonstrate the effectiveness of the proposed method in reducing signal loss artifacts in both single-slice and multiband exams.

1480.   Ultrafast in vivo imaging by SPatiotemporal ENcoding (SPEN) for Bruker MRI systems
Tangi Roussel1 and Lucio Frydman1
1Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel

Since 2010, ultrafast NMR is applied for MRI giving birth to several ultrafast single-shot SPatio-temporally ENcoded (SPEN) imaging sequences. Besides important scan time reduction, SPEN experiments are especially robust regarding high-field artifacts such as B0 inhomogeneities and susceptibility effects. Zooming abilities are also built-in into this kind of experiments. In this paper, we present a SPEN method developed for Bruker MRI systems. The method includes single-shot single-slice, multi-slice SPEN and RASER sequencing options; all with an online reconstruction and fully integrated in Bruker Paravision as a “method”.

1481.   Respiratory motion based dynamic keyhole reconstruction for real-time thoracic MRI
Danny Kyejun Lee1, Sean Pollock1, Peter Greer2, Taeho Kim1, and Paul Keall1
1Radiation Physics Laboratory, Sydney Medical School, The University of Sydney, Camperdown, NSW, Australia, 2The University of Newcastle, NSW, Australia

The dynamic keyhole method using respiratory signals has been demonstrated to reconstruct MR images with the considerably small amount of central phase encoding lines, linked to real-time thoracic imaging with minimal image intensity loss on tumor. These results suggest that the dynamic keyhole method could be a desirable technique for image-guided radiation therapy and MRI-guided radiotherapy that require real-time MR monitoring in thoracic region.

1482.   Non-rigid continuous motion correction in abdominal imaging
Xingfeng Shao1, Xucheng Zhu1, Feiyu Chen2, and Kui Ying3
1Department of Engineering Physics, Tsinghua University, Beijing, China, 2Department of Biomedical Engineering, Tsinghua University, Beijing, China, 3Department of Engineering physics, Tsinghua University, Beijing, China

In abdominal imaging, non-rigid and continuous motion artifacts can be introduced because of breathe and intestinal peristalsis movement. To reduce this kind of motion artifacts, we use COCOA to detect and discard motion corrupted data under PROPELLER trajectory, then use SPIRiT to reconstruct the k-space. To evaluate our method, simulated data was generated by adding non-rigid continuous motion to a reference image. After applying both proposed method and traditional COCOA to the simulated data, results show that simulated motion can be effectively reduced with our method comparing to traditional COCOA. Conclusion can be made that combining COCOA with PROPELLER and SPIRiT can effectively reduce non-rigid continuous motion in abdominal imaging, which is better than traditional COCOA.

1483.   Robust 3D SPACE imaging freely stopped by patient motion
Guobin Li1, Maxim Zaitsev1, Martin Büchert1, Esther Meyer2, Dominik Paul2, Jan Korvink3,4, and Jürgen Hennig1
1University Medical Center Freiburg, Freiburg, Baden-Württemberg, Germany, 2Siemens Healthcare, Germany, 3Department of Microsystems Engineering — IMTEK, University of Freiburg, Baden-Württemberg, Germany, 4Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Baden-Württemberg, Germany

3D turbo spin echo sequences (e.g. SPACE) suffer from long acquisition times and are therefore prone to motion artifacts. Two features are introduced into SPACE imaging: a) integrated motion detection, which judges whether a patient’s movement is tolerable or not, and stops the acquisition immediately when unacceptable motion is detected; b) a dedicated sampling strategy, which optimizes the image quality in cases that an acquisition is interrupted. Comprehensive in vivo experiments have been conducted to evaluate the performance of the method.

1484.   A novel MRI data processing strategy for the reduction of abdomen motion artifacts
Yajun Ma1, Wentao Liu1, Yang Fan1, Huanjie Li1, and Jia-Hong Gao1
1MRI Research Center and Beijing City Key Lab for Medical Physics and Engineering, Peking University, Beijing, Beijing, China

Date processing techniques such as multiple average methods and COCOA have been developed recently for motion artifacts reducing. They employed convolution of k-space data to reduce localized data inconsistencies. These data processing techniques can be incorporated with other techniques, such as respiratory gating, navigator echoes.And then, better image quality is obtained. And they can also be used alone for free breath imaging. A new data processing strategy is introduced in this work to optimize the date convolution procedure and take care of different motion characters exist in multi-coil images to protect the image SNR.

1485.   Multi-slice imaging of the abdomen during free breathing using a radial self-gating technique
Judith Biermann1, Martin Krämer1, and Jürgen R Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, TH, Germany

To perform multi-slice multi-echo abdominal imaging during free breathing a radial golden angle self-gating technique was used applying 1D projection navigators in an automatically added slice. 1D navigators were utilized to generate a breathing trigger signal through correlation analysis. Since each time point of the trigger signal is directly related to a radial readout in all slices, respiratory phases could be excluded from image reconstruction for obtaining breathing corrected images. Image blurring caused by respiratory motion was highly reduced.

Self-Gated Fat-Suppressed Cardiac Cine MRI
R Reeve Ingle1, Juan M Santos2, William R Overall2, Bob S Hu1,3, and Dwight G Nishimura1
1Electrical Engineering, Stanford University, Stanford, California, United States, 2HeartVista, Inc., Menlo Park, California, United States, 3Palo Alto Medical Foundation, Palo Alto, California, United States

A technique for fat-suppressed self-gated cardiac cine imaging is demonstrated, which enables cardiac cine imaging without the need for external electrocardiogram (ECG) gating. Fat suppression is achieved using an alternating repetition time (ATR) balanced steady-state free precession (bSSFP) pulse sequence. By redesigning the slice-select rephaser gradients, one-dimensional projection navigators can be acquired during the unused short TR interval. Volunteer and patient results are presented and compared with ECG-gated ATR and bSSFP acquisitions.

1487.   Accurate And Reliable PC-MRI Sequence To Investigate Complex Dynamic Of Cerebro-Spinal Fluid in the Brain.
Malek I Makki1, Christoph Ruegger2, Cyrille Capel3, Catherine Gondry-Jouet4, and Olivier Baledent5
1MRI Research Center, University Children Hospital of Zurich, Zurich, Switzerland, 2Neonatalogy, University Hospital of Zurich, Zurich, Switzerland, 3Neurosurgery, University Hospital, Amiens, France, 4Radiology, University Hospital, Amiens, France, 5Image Processing, University Hospital, Amiens, France

An accurate CSF flow measurement through the pontine cistern is difficult to achieve because of blood flow artifacts from the basilar artery and surrounding vessels. We developed a dedicated PCMRI sequence with pre-saturation double sided bands to suppress signal from blood with no compromise neither on SNR nor on spatio-temporal resolution and validated this on 18 patients with hydrocephalus. We compared the results of the developed sequence in the pontine cistern and foramen of Magendi which is free of blood flow artifact and demonstrated its accuracy and reliability to measuring the stroke volume and the minimum and maximum flow.

1488.   Multi-contrast inversion-recovery EPI (MI-EPI) functional MRI at 7 T
Ville Renvall1,2, Thomas Witzel1,2, Marta Bianciardi1,2, and Jonathan R. Polimeni1,2
1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, 2Department of Radiology, Harvard Medical School, Boston, MA, United States

Multi-contrast inversion-recovery EPI (MI-EPI) was implemented on a 7T system and was used to study brain activations simultaneously using T1-, BOLD-, and multiple inversion-recovery-time-signal changes following visual stimulation at a 3-s sampling period. The different contrast images yielded similar activation maps, with extent of activation roughly proportional to the signal levels, but less activation with CSF suppressed rather than gray matter suppressed contrasts. T1 values were found to significantly increase during visual stimulation concordant with blood volume increases and/or inflow effects.

1489.   7D velocity phase imaging with zoomed simultaneous multi-slice EPI reveals respiration driven motion in brain and CSF
Liyong Chen1,2, Alexander Beckett1,2, Ajay Verma3, and David Feinberg1,2
1Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States, 2Advanced MRI Technologies, LLC, Sebastopol, California, United States,3Biogen Idec, MA, United States

A new highly efficient velocity imaging technique is developed with simultaneous multi-slice EPI and zoomed spatial resolution which enables real-time measurement of CSF and brain velocity. Application of this 7D imaging technique to normal subjects revealed respiratory synchronous motion modulating cardiac waveforms in brain parenchyma and CSF. The brain pulsations may play a role in clearance of interstitial fluid in the brain.

1490.   The gray-white contrast in spin-echo imaging at 7 T
Robert Trampel1, Jochen Schmidt1, Laurentius Huber1, Andreas Schäfer1, and Robert Turner1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

Although the contrast between gray and white matter obtained by spin-echo and turbo spin-echo techniques is usually referred to as “T2-weighted”, transverse relaxation mechanisms contribute hardly at all to the contrast between those brain tissue types. We found that gray-white contrast in spin-echo brain images at 7T arises mainly from proton density and T1 relaxation, depending on TR. Magnetization transfer has a somewhat smaller influence, while the influence of T2 variations in tissue is negligible.

1491.   Simultaneous T1 and T2* weighted 3D Anatomical Imaging using a Dual-Echo Sequence
Won-Joon Do1, Paul Kyu Han1, Seung Hong Choi2, and Sung-Hong Park1
1Department of Bio and Brain Engineering, Korean Advanced Institute of Science and Technology, Daejeon, Korea, 2Seoul National University Hospital, Seoul, Korea

In this study we implemented a new dual-echo sequence for simultaneous acquisition of T1 and T2* weighted 3D Anatomical images. An echo-specific K-space reordering scheme was used to separately satisfy T1 and T2* contrast for the two echoes, which was determined to be 30 and 10-20 for the first echo and second echo, respectively. The results showed that the proposed method enables us to acquire both 3D T1 and T2* weighted images with scan time of ~3 min and a reasonable spatial coverage and resolution. The technique may be helpful for accelerating routine clinical studies requiring T1 and T2* acquisitions.

1492.   On the application of simultaneous dual contrast weighting using double echo 2in1-RARE in healthy subjects and multiple sclerosis patients
Katharina Fuchs1, Fabian Hezel1, Sabrina Klix1, Ralf Mekle2, Jens Wuerfel3,4, and Thoralf Niendorf1,5
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck Center for Molecular Medicine, Berlin, Germany, 2Medical Metrology, Physikalisch Technische Bundesanstalt, Berlin, Germany, 3Institute of Neuroradiology, University Medicine Goettingen, Germany, 4NeuroCure Clinical Research Center, Charité - University Medicine Berlin, Germany,5Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max-Delbrueck Center, Berlin, Germany

2in1-RARE is a RARE variant which is simultaneously sensitive to T2* and proton density contrast. This is achieved by strictly separating spin echo and stimulated echo magnetization within a RARE echo train. The performance of 2in1-RARE is elucidated using point spread function assessment. 2in1-RARE traits for T2* mapping are validated against conventional mulit-echo gradient echo acquisitions. The applicability of dual contrast weighted double echo 2in1-RARE is demonstrated for brain imaging using susceptibility weighted imaging, T2* mapping and proton density weighted imaging in healthy subjects and multiple sclerosis patients.

1493.   High resolution neuro-imaging with reduced SAR using radial GRASE
Melisa Okanovic1,2, Martin Blaimer2, Felix Breuer2, and Peter Michael Jakob2,3
1Comprehensive Heart Failure Center, University Hospital of Wuerzburg, Wuerzburg, Bavaria, Germany, 2Magnetic Resonance Bavaria (MRB), Wuerzburg, Bavaria, Germany, 3Department of Experimental Physics 5, University of Wuerzburg, Wuerzburg, Bavaria, Germany

For high resolution images of the human brain a hybrid sequence with a radial readout is presented. In this technique gradient refocused echoes replace refocusing radio-frequency pulses up to a certain level. This offers a significant SAR-reduced imaging compared to a turbo-spin-echo technique with the same echo-train-length. The radial k-space acquisition and a view-sharing technique (KWIC) for the reconstruction, allow several arbitrary T2-weighted images. High resolution in-vivo human brain images are presented.

1494.   Accuracy of VIBE and TSE for High Resolution Imaging of the Mandibular Nerve
Jakob Kreutner1, Andreas J. Hopfgartner2, Julian Boldt3, Kurt Rottner3, Ernst J. Richter3, Peter M. Jakob1,2, and Daniel Haddad1
1MRB-Research Center Magnetic-Resonance-Bavaria, Würzburg, Germany, 2Experimental Physics 5, University of Würzburg, Würzburg, Germany, 3Prosthodontics, Dental School, University of Würzburg, Würzburg, Germany

Recent studies have shown the accuracy of a VIBE sequence in visualizing the mandibular canal compared to X-ray based methods. In order to increase resolution without unnecessarily lengthen acquisition time a small field of view is needed. This can be achieved by using regional saturation bands in VIBE or local look technique in TSE sequences to avoid aliasing artifacts. Since TSE offers higher SNR and in combination with local look technique is more comfortable to set up, we compared both methods by calculating the surface difference of the mandibular canal.

1495.   Neuroimaging with INSIDIR: Integrated Single Inversion and Double Inversion Recovery
Andrew L Alexander1 and Steven R Kecskemeti1
1Waisman Center, University of Wisconsin, Madison, WI, United States

An efficient 3D brain imaging pulse sequence was developed with a pair of inversion pulses that simultaneously acquire both single inversion recovery (SIR) and double inversion recovery (DIR) image data. Sampling was performed using a spoiled gradient echoes with a 3D radial k-space readout. A sliding window reconstruction was used to generate multiple image volumes with different single and double inversion times. The SIR volumes included a nulled gray matter frame and a nulled white matter frames and also more standard T1-weighted contrast. The DIR sampling yielded a gray matter specific map with nulling of both white matter and CSF.

1496.   Transverse Relaxation Amplified by Chemical Exchange (TRACE): A New Method for Mapping Molecular Integrity of Cartilage
Anup Singh1, Ravi Prakash Nanga1, Mohammad Haris1,2, Kejia Cai1,3, Felik Kogan1, Hari Hariharan1, and Ravinder Reddy1
1Radiology, University of Pennsylvania, Philadelphia, PA, United States, 2Research Branch, Sidra Medical and Research Center, Doha, Qatar, 3Radiology, University of Illinois at Chicago, Chicago, IL, United States

Objective of current study was to develop a new method for mapping molecular integrity of cartilage based upon Transverse Relaxation Amplified by Chemical Exchange (TRACE). This simple and time efficient method provides a quantitative index of macromolecular content of cartilage and is less sensitive to fluid changes associated with pathological conditions of the tissue. The method was tested in chondroitin sulfate (CS) phantoms with different concentrations and pH as well as on human knee cartilage at 3T and 7T whole body MR scanners.

1497.   Apparent Exchange Rate (AXR) Mapping Using Diffusion MRI: an in vitro and in vivo Feasibility Study on Breast Cancer
Samo Lasic1, Savannah C. Partridge2, Cheng-Liang Liu2, Stina Oredsson3, Lao Saal4, Daniel Topgaard5, Markus Nilsson6, and Karin Bryskhe1
1CR Development AB, Lund, Sweden, 2Dept. of Radiology, University of Washington, Seattle Cancer Care Alliance, Seattle, United States, 3Department of Biology, Lund University, Lund, Sweden, 4Department of Oncology, Lund University Hospital, Lund, Sweden, 5Center for Chemistry and Chemical Engineering, Lund University, Lund, Sweden, 6Lund University Bioimaging Center, Lund University, Lund, Sweden

A feasibility study of filter exchange imaging (FEXI) for detection of apparent exchange rate (AXR) was performed on breast cancer cell lines and on a breast tumour patient in vivo. Results suggest that different breast cancer types could be distinguished with FEXI based on their AXR values. The AXR could be determined for the tumour ROI, while in normal tissue the AXR was outside the experimental range. Low SNR did not allow voxel based data analysis. Further optimization of FEXI will be required before FEXI can be evaluated in a larger group of breast cancer patients.

1498.   Magnetization Transfer from Inhomogeneously Broadened Lines (ihMT): Qualitative Evaluation of ihMT Specificity toward Myelinated Structures
Valentin Prevost1, Olivier M. Girard1, Gopal Varma2, David C. Alsop2, and Guillaume Duhamel1
1CRMBM UMR 7339, CNRS/Aix-Marseille Université, Marseille, France, 2Radiology Departement, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States

A previously reported new MT approach able to specifically image the inhomogenous component of the MT spectrum, and referred as inhomogeneous MT (ihMT), appeared to be sensitive to tissue with myelin. The present study proposed a qualitative investigation of ihMT specificity toward myelin by comparison with DTI and myelin stained images.

1499.   High-Resolution Perfusion-Weighted Imaging without Tagging Pulses
Hyunseok Seo1, Yeji Han1, and HyunWook Park1
1Electrical Engineering, KAIST, Daejeon, Daejeon, Korea

In this abstract, a novel isotropic perfusion-weighting approach is proposed, where bi-polar gradients are used instead of the tagging pulses to obtain a high-resolution PW image with radial trajectory. By using a pair of spin-echo (SE) images acquired with single and double bi-polar gradients from multi-directions, anisotropic characteristics of the cerebral perfusion are also considered. Computer simulations were performed to evaluate the relation between the proposed method and the cerebral perfusion. MR experiment results from in-vivo brain imaging show that the proposed method produces a high-resolution PW image.

1500.   Estimation of the arterial input function using accelerated dual-contrast EPIK: a multi-modality MR-PET study
Liliana Caldeira1, Seong Dae Yun1, Nuno A da Silva1, Christian Filss1, and N Jon Shah1,2
1Institute of Neuroscience and Medicine - 4, Research Centre Jülich GmbH, Jülich, Germany, 2Department of Neurology, RWTH Aachen University, Aachen, Germany

The arterial input function (AIF) is essential for quantification in MRI and PET imaging. The ground truth for AIF estimation is arterial cannulation. Alternatively, the AIF can be estimated using MRI and/or PET images, but a reasonable temporal resolution of dynamic image series is necessary (<2s). In PET imaging, high temporal resolution is limited (>5s). Here, we propose a method to acquire data for the AIF based on an EPI with keyhole (EPIK) sequence. The EPIK sequence combines both high temporal resolution and high spatial resolution. Furthermore, dual-contrast EPIK (DC-EPIK) can also be acquired to provide additional information.

1501.   Selective MRA for portal venography using Beam Saturation pulse
Takashi Nishihara1, Hiroyuki Itagaki1, Kuniaki Harada1, Masatomo Yokose1, Oka Kuniharu1, and Tetsuhiko Takahashi1
1MRI System Division, Hitachi Medical Corporation, Kashiwa, Chiba, Japan

In order to visualize the blood flow in portal vein, we investigate use of a 2D beam excitation pre-saturationpulse (hereafter Beam Sat pulse) with the flow phantom and healthy volunteer.@As a result, the Beam Sat pulse is able to saturate the portal vein selectively. When combined with unenhanced portal venography, the Beam Sat pulse seems to visualize additional information about the blood flow in portal vein.

1502.   Improving sensitivity and specificity for RS fMRI using multiband multi-echo EPI at 7T
Rasim Boyacioglu1, Jenni Schulz1, Peter Koopmans2, Markus Barth1,3, and David Norris1,3
1Radboud University, Donders Institute, Nijmegen, Netherlands, 2FMRIB Centre, University of Oxford, Oxford, United Kingdom, 3Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany

Recently we have implemented a multiband (MB) multi-echo (ME) sequence to investigate the potential improvement in sensitivity at 7T for resting state (RS) fMRI. In this study we investigated various approaches for cleaning ME and MB ME RS fMRI data to fully exploit the rich temporal information of MB ME data. With two different analysis strategies we have showed that MB acquisition improves functional connectivity compared a standard ME sequence after the removal of non-BOLD related artifactual signals.

1503.   Multiband spin- and gradient-echo (SAGE) fMRI
Heiko Schmiedeskamp1, Eric Peterson1, Julian Maclaren1, Rafael O'Halloran1, Thomas Christen1, Samantha J Holdsworth1, Eric Aboussouan1, William A Grissom2, and Roland Bammer1
1Department of Radiology, Stanford University, Stanford, CA, United States, 2Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

The combined acquisition of gradient-echo and spin-echo fMRI signals facilitates the differentiation between simultaneously acquired BOLD signal changes with distinct contrast mechanisms at the expense of increased repetition time or decreased slice coverage. To facilitate combined gradient-echo and spin-echo fMRI while maintaining whole-brain coverage without prolonging TR, we propose utilizing multiband RF excitation in simultaneous multi-echo spin- and gradient-echo (SAGE) EPI acquisitions for fMRI, and we present preliminary results using a breath-hold task as proof-of-principle for stimulus-based multiband SAGE fMRI experiments.

1504.   MARTINI and GRAPPA - When Speed is Taste
Tom Hilbert1,2, Tobias Kober1,3, Tilman J. Sumpf4, Zhengguo Tan4, Jens Frahm4, Pavel Falkovskiy1,3, Heiko Meyer5, Rolf Bendl6,7, Jean-Philippe Thiran2, Reto Meuli8, and Gunnar Krueger1,8
1Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Switzerland, 2Signal Processing Laboratory (LTS5) École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 3CIBM - AIT, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 4Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany, 5Siemens Healthcare, Erlangen, Germany, 6Division of Medical Physics in Radiation Oncology, DKFZ Heidelberg, Heidelberg, Germany, 7Department of Medical Informatics, Heilbronn University, Germany, 8Centre Hospitalier Universitaire Vaudoise and Univ. of Lausanne, Lausanne, Switzerland

In this work we investigate the combination of Model-based Accelerated RelaxomeTry by Iterative Nonlinear Inversion (MARTINI) with Generalized Autocalibrating Partially Parallel Acquisition (GRAPPA) to further accelerate and improve the reconstruction quality of T2 maps. GRAPPA is used to interpolate missing k-space lines of two-fold subsampled blocks of the MARTINI scheme prior to the MARTINI reconstruction. Images from an analytical phantom and in-vivo datasets are investigated. Resulting T2 maps of nominal 10-fold accelerated whole brain exams (1:40 minutes scans) are qualitatively and quantitatively compared to the reconstruction of the fully sampled and conventional 5-fold accelerated MARTINI datasets.

Jenni Schulz1, Rasim Boyacioglu1, and David G Norris1,2
1Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, Netherlands, 2Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany

3D-TOF-MRA is commonly used for imaging intracranial vessels. This NCE-MRA technique is based on inflow enhancement suppressing stationary tissue. Unfortunately, it suffers from time-inefficiency. This problem can be overcome by exciting multiple slabs simultaneously which can be reconstructed with a fast low resolution 3D-FLASH reference scan. Acquisition time will be decreased by a factor almost equal to the number of simultaneously excited slabs. The obtained results are comparable to the reference and CNR is maintained which leads to an increase in CNR efficiency. Furthermore, by reducing the thickness of the slabs in the multislab multiband acquisition, in-flow contrast is improved.

1506.   Accelerated 3D EPI using 2D blipped-CAIPI for high temporal and/or spatial resolution
Benedikt A Poser1,2, Dimo Ivanov1, Stephan A Kannengiesser3, Kamil Uludag1, and Markus Barth2,4
1Faculty of Psychology and Neuroscience, Maastricht University, 6200MD Maastricht, Netherlands, 2Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, Netherlands, 3MR Applications Development, Siemens AG, Healthcare Sector, Erlangen, Germany, 4Erwin L Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany

2D CAIPIRINHA greatly improves volumetric parallel imaging reconstructions by making optimal use of the available coil sensitivities and distributing the image alias over the reduced FOV. We demonstrate blipped-CAIPIRINHA in 3D EPI, where CAIPIRINHA’s ability to freely distribute the undersampling capability between the two phase-encoding directions creates the flexibility to: (a) use maximum through-plane acceleration to achieve very short TR, (b) use maximum in-plane acceleration to shorten EPI echo train for high-spatial resolution and minimal geometric distortion, or (c) any trade-off between the two. Each case is demonstrated with a total undersampling factor 16.

1507.   Constrained Source Space Imaging: Rapid Point Measurement of fMRI Paramaters
Karl Landheer1 and Simon Graham1
1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

A novel technique to rapidly measure fMRI parameters has been improved upon. Our technique uses a modified PRESS sequence to excite three arbitrarily positioned voxels. SENSE is then used to reconstruct each of the four voxel’s time-dependent signal. A minimum TR of 73 ms was achieved, and showed to provide good agreeance between a single voxel measurement. This technique provides access to T2, T2* and centre frequency, all which can be used to monitor functional activity through the BOLD response. This technique will be used to measure very fast brain activity for mental chronometry in the future.

1508.   In Vivo Compressed Sensing fMRI using Conventional Gradient-recalled Echo and EPI Sequences
Xiaopeng Zong1, Juyoung Lee2, Alexander Poplawsky3, Seong-Gi Kim3,4, and Jong Chul Ye2
1Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 2Korea Advanced Institute of Science & Technology, Daejon, Korea, 3University of Pittsburgh, PA, United States, 4Dept. of Biological Sciences, SKKU, Suwon, Korea

Compressed sensing (CS) may be useful for accelerating data acquisitions in high-resolution fMRI. Most of the existing CS-fMRI studies have been conducted with synthesized experiments where fully sampled k-space data were retrospectively down-sampled. However, it is difficult to determine pulse sequence-dependent artifacts as well as potential advantages of improved temporal resolutions using retrospective analyses. Here, we systematically investigated the properties of CS-fMRI using computer simulations and in vivo experiments of rat forepaw and odor stimulations with 2-dimensional gradient-recalled echo (GRE) and echo planar imaging sequences. Our results show that CS improves the statistical performance of fMR with negligible image artifacts.

1509.   Phase Encoded Acquisition with Compressed sEnsing
Marc Rea1, Xavier Boullier2, Ian Young3, and Donald McRobbie1
1Radiological Sciences Unit, Imperial College Healthcare NHS Trust, London, United Kingdom, 2Bioengineering, Imperial College, London, London, United Kingdom, 3Electrical Engineering, Imperial College London, London, United Kingdom

This work investigates the combination of Single Point Imaging (SPI) with Compressed Sensing reconstruction for the reduction of artefacts near passive metal implants, enabling the benefits of SPI to be utilised with much reduced acquisition times.

1510.   Extracting MRI Sequence Response Kernels from Generalized Extended Phase Graph Simulations
Cristoffer Cordes1 and Matthias Günther1,2
1Fraunhofer MEVIS, Bremen, Bremen, Germany, 2MR-Physics and Spectroscopy, Faculty 1, Universität Bremen, Bremen, Germany

To further investigate the potential of the Extended Phase Graph algorithm, the reconstruction chain has been applied to the signal components created by Extended Phase Graph simulations. The resulting images can then be used as convolution kernels to simulate the sequence response to the parameter map of an object or to extract information about parameter sensitivity and influence from a sequence. An algorithm has been developed and utilized to generate images from object parameter maps to compare simulation results to measured images and to extract contrast information from a pulse sequence.

1511.   Murine Cardiac Imaging Methods at 4.7T
Matthew Firth1, Marco Mingarelli1, Hugh Seton1, and Dana Dawson1
1University of Aberdeen, Aberdeen, United Kingdom

We describe a gradient echo based imaging technique for fast murine cardiac gated cine imaging. Using relatively low strength gradients at 4.7T we have obtained a multi-slice, multi-frame cine with full ventricular coverage in just over 5 mins. These images were analysed to assess ventricular function and the results compared with images using a slower technique which acquired a single line of k-space per R–wave. There was no significant difference between the calculated left ventricular volumes and the “Fast” technique led to a reduction in flow artefacts.

Noel D. Montgomery1, Goldie R.E. Boone2, and Jack L. Lancaster2
1Human Effectiveness Directorate, Bioeffects Division, Radio Frequency Radiation Bioeffects Branch, Air Force Research Laboratory, 711 Human Performance Wing, JBSA Fort Sam Houston, Texas, United States, 2Research Imaging Institute, UT Health Science Center San Antonio, San Antonio, TX, United States

Spin Echo and Echo Planar imaging of resected nervous tissue presents a specific challenge due to susceptibility differences between tissue and air, and due to high signal from encapsulating media. The researchers developed an encapsulation method for brain tissue that minimized susceptibility artifacts in echo planar images and preserved contrast in spin echo images.

1513.   Imaging Battery for Brain Quantification
M. Ethan MacDonald1,2, M. Louis Lauzon2,3, and Richard Frayne2,3
1Biomedical Engineering, University of Calgary, Caglary, AB, Canada, 2Seaman Family Magnetic Resonance Research Centre, Hotchkiss Brain Institute, Foothills Medical Centre, Calgary, AB, Canada, 3Radiology and Clinical Neurosciences, University of Calgary, Calgary, AB, Canada

In this work combined methodologies for rapidly acquiring parametric maps of the brain are described. Several parameters in the brain, including: T1, T2, T2*, magnetic susceptibility and proton density are calculated, in addition to several machine distortion parameters, including: B0 and B1 field inhomogeneity, and coil profiles. The protocol time used to produce these images was less than 26 minutes, and resulted in whole brain coverage with 1 mm^3 isotropic resolution. Collection of these key physiological and machine distortion parameters will allow for advanced simulation of the MR system.

1514.   RARE Sequence Optimization Parameters for 19F MRI studies of Labeled Neuronal Stem Cells at 11.7 T
Alfonso Mastropietro1,2, Annette Tennstadt2, Nadine Henn2, Andreas Beyrau2, Maria Grazia Bruzzone3, Giuseppe Baselli4, and Mathias Hoehn2,5
1Scientific Direction Unit, Fondazione IRCCS Istituto Neurologico C. Besta, Milan, Italy, 2In-vivo NMR lab, Max Planck Institute for Neurological Research, Cologne, Germany,3Neuroradiology Unit, Fondazione IRCCS Istituto Neurologico C. Besta, Milan, Italy, 4Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy, 5Department of Radiology, Leiden Medical School, Leiden, Netherlands

Aim of this work is to perform a punctual optimization of RARE parameters for 19F MRI studies of labeled neuronal stem cells. This approach is based on relaxation times estimation and numerical simulations. The optimization approach was evaluated in different biological environments at 11.7T MRI scanner.A correct optimization strategy increases the sensitivity of 19F MRI technique.

1515.   Maximally Spaced Projection Sequencing for Uniform Acquisition of Electron Paramagnetic Resonance Imaging Projections
Gage Redler1, Boris Epel1, and Howard J Halpern1
1Radiation and Cellular Oncology, University of Chicago, Chicago, IL, United States

Uniform projection acquisition in electron paramagnetic resonance oxygen imaging reduces artifacts from changes during imaging, enables useful real-time reconstruction, and allows post-factum temporal resolution adjustment. A novel uniform acquisition method is presented as an alternative to the commonly used golden ratio (GR) method. The GR method allows acquisition of arbitrary numbers of projections, maintaining approximate uniformity throughout and for subsets of arbitrary size. In some cases, arrival at a pre-defined final projection set is necessary, which is impossible using the GR method. The maximally spaced projection sequencing method presented enables acquisition of arbitrary projection sets, maintaining approximate uniformity throughout acquisition.

1516.   e-Incubator: MRI Compatible Mini-Incubator
Huihui Xu1, Vahid Khalilzad-Shargi1, Karin wartella1, and Shadi F Othman1
1University of Nebraska - Lincoln, Lincoln, Nebraska, United Kingdom

There is a crucial need to assess ex vivo constructs. MRI helps fulfill this role, but specimens allocated to a test tube for imaging cannot be returned to incubators, therefore, are wasted due to transfer incubation in a less than optimal growth environment. We present a standalone, miniature MRI-compatible incubator, termed the e-incubator, which uses a microcontroller to automatically sense and regulate physiological conditions for tissues and allow concurrent tissue culture and evaluation. The e-incubator offers an innovative scheme to study multiple applications, including underlying mechanisms related to the structural and functional changes of tissues due to growth and maturation.

1517.   MR Microscopy and DTI of Organotypic Hippocampal Slice Cultures
Katharina Göbel1, Jochen Leupold1, Bibek Dhital1,2, Pierre LeVan1, Marco Reisert1, Johannes Gerlach3, Robert Kamberger4, Carola Haas3, Jürgen Hennig1, Dominik von Elverfeldt1, and Jan G. Korvink4
1Medical Physics, Dept. of Radiology, University Medical Center Freiburg, Freiburg, Germany, 2German Cancer Consortium (DKTK), Heidelberg, Germany, 3Dept. of Neurosurgery, Experimental Epilepsy Research, University Medical Center Freiburg, Freiburg, Germany, 4Dept. of Microsystems Engineering (IMTEK), Technical Faculty, University of Freiburg, Freiburg, Germany

Organotypic hippocampal slice cultures are a well established neuronal culture system that combines the advantages of cell culturing with a neuronal network tightly reflecting the in vivo state. They are frequently used to study morphological, molecular and electrophysiological changes associated with epilepsy. Our aim is to investigate these changes during epileptogenesis, particularly using high spatial resolution MR microscopy and DTI which allows continuous monitoring near the cellular level. High resolution MR images of fixed mouse hippocampi were obtained ex vivo and directly compared to histology. First trials in 2D DTI give notion of the structural composition of the hippocampus.

1518.   New strategy of improving the image quality of respiratory-gated Projection Acquisition using 3D k-space spiral trajectory
Jinil Park1, Chanhee Lee1, Soon Ho Yoon2, Jin Mo Goo2, and Jang-Yeon Park1
1School of Biomedical Engineering, Konkuk University, Chung-ju, Chungcheongbuk-do, Korea, 2Department of Radiology, Seoul National University College of Medicine, Seoul, Korea

A new and simple strategy of improving the image quality of respiratory-gated PA data was proposed here when using a 3D spiral trajectory to fill in k-space. Based on the gradient-view generation algorithm we upgraded. show that increasing the number of interleaves can practically be a good and easy way to avoid streak artifacts as well as blurring due to the non-uniformity of k-space trajectory when filling in 3D k-space with a spiral trajectory. Considering the wide use of a 3D k-space spiral trajectory with interleaves, this method would be useful in practice.

1519.   Respiratory-Resolved Fat-Suppressed Cardiac Cine MRI
R Reeve Ingle1, Michael V McConnell1,2, Juan M Santos3, William R Overall3, Bob S Hu1,4, and Dwight G Nishimura1
1Electrical Engineering, Stanford University, Stanford, California, United States, 2Cardiovascular Medicine, Stanford University, Stanford, California, United States,3HeartVista, Inc., Menlo Park, California, United States, 4Palo Alto Medical Foundation, Palo Alto, California, United States

A free-breathing, fat-suppressed cardiac cine pulse sequence is proposed, allowing multiple respiratory and cardiac phases to be simultaneously resolved. Fat suppression is achieved using an alternating repetition time balanced steady-state free precession sequence. By redesigning the slice-select rephasing gradients, a 1D navigator readout is acquired during the unused short TR interval and used to track respiratory motion. This technique allows data from a single free-breathing scan can to be displayed in a standard “cardiac-cine” format for a fixed respiratory phase, or in a “respiratory-cine” format for a fixed cardiac phase.


Spectroscopic Acquisition

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

1520.   Compressed Sensing Based J-Resolved Spectroscopic Imaging in Obstructive Sleep Apnea
Manoj Kumar Sarma1, Rajakumar Nagarajan1, Paul Michael Macey2, Ravi Aysola3, and M. Albert Thomas1
1Radiological Sciences, UCLA School of Medicine, Los Angeles, CA, United States, 2School of Nursing, UCLA School of Medicine, Los angeles, CA, United States, 3Division of Pulmonary and Critical Care Medicine, UCLA School of Medicine, Los Angeles, CA, United States

Obstructive sleep apnea syndrome (OSAS) is a common sleep disturbance affecting the adult population leading to numerous health problems. Chronic intermittent hypoxic episodes, hypercapnia and transient blood pressure elevation in OSAS may damage neural structures and induce cerebral metabolic changes. Even though many structural imaging studies have shown brain tissue changes in OSAS, only a limited number of MRS based studies can be found so far. In this study, we investigated neurochemical changes in multiple brain regions of OSAS patients using compressed sensing (CS) based Echo-planar J-resolved spectroscopic imaging (EP-JRESI) and quantify the metabolites using prior knowledge fitting (ProFit) algorithm.

1521.   Comparing Group Sparse Reconstruction of 4D EP-COSI data with Compressed Sensing, Total Variation, and Maximum Entropy Reconstruction
Brian L Burns1, Neil Wilson2, and M Albert Thomas1,2
1Department of Biomedical Engineering, UCLA, Los Angeles, CA, United States, 2Department of Biomedical Physics, UCLA, Los Angeles, CA, United States

Scan times for the 4D EP-COSI pulse sequence can be 20-40 minutes depending on scan parameters. To reduce these scans times to clinically acceptable levels non-uniform under-sampling of the phase encoded dimensions coupled with non-linear reconstruction can be used to accelerate acquisition. This work compares the reconstruction results of 4X and 8X phantom data from Compressed Sensing, Total Variation, and Maximum Entropy with Group Sparse reconstruction, a variant of Compressed sensing that used a mixed 1-1,2 regularizer. Group Sparse reconstruction with overlapping groupings is shown to provide qualitatively and quantitatively superior results to other methods tested.

1522.   Comparison of semi-LASER localized Brain MRS at 3T and 7T using 32-channel head coils
Subechhya Pradhan1, Susanne Bonekamp1, Joseph Gillen1, Laura Rowland2, S. Andrea Wijtenburg2, Richard A.E. Edden1, and Peter B Barker1
1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States, 2Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland, United States

MRS is expected to benefit from moving to high field strengths such as 7T. However, there are also technical challenges associated with high fields, such as increased B0 and B1 field inhomogeneities. Therefore, it is important to compare 7T measurements to those at lower field. In this study, SNR, linewidths and Cramer-Rao lower bounds are compared between 3T and 7T MRS in 3 brain regions of 4 healthy subjects. Measurements made with near identical methodology at both field strengths, including 32-channel head coils and semi-LASER localization. Improvements at 7T were found in all metrics examined, and were consistent with expectations.

1523.   Partial Volume Correction for 23Na MRI of Human Brain
Sebastian C. Niesporek1, Stefan H. Hoffmann1, Moritz C. Berger1, and Armin M. Nagel1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

The tissue sodium (23Na) concentration is of great interest in biomedical research. However the 23Na nucleus has a low MR sensitivity and fast relaxation times which requires larger voxel sizes in 23Na MRI. Thus, partial volume effects reduce the accuracy of concentration measurements. In this work, a partial volume correction method was transferred to 23Na MRI, optimized and tested in phantom measurements and simulations as wells as in 23Na MRI of the human brain. The study showed good correction capability for phantom and in-vivo data.

1524.   3D-Dictionary-Learning-CS Reconstruction of Radial 23Na-MRI-data
Nicolas G.R. Behl1, Christine Gnahm1, Peter Bachert1, and Armin M. Nagel1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

3D-dictionary-learning-CS is applied for the reconstruction of radial 23Na-MRI-data. The dictionary used for the sparsifying transform consists of 3D-blocks learnt on the gridding-reconstruction of the data. A K-SVD algorithm is used to learn the dictionary and the corresponding representation, the self-consistency of the actual image and the raw-data is enforced through a conjugate gradient algorithm. The performance of the reconstruction algorithm is verified with simulated data (2mm isotropic), phantom 23Na-data (1.5mm isotropic) and in-vivo 23Na-data (2mm isotropic), showing significant noise reduction compared to the corresponding gridding reconstructions, as well as increased SSIM and reduced RMSE.

1525.   Anatomically weighted 2nd order Total Variation reconstruction of 23Na MRI using 1H prior information
Christine Gnahm1, Nicolas G.R. Behl1, Armin Biller2, Peter Bachert1, and Armin M. Nagel1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Department of Neuroradiology, University Hospital Heidelberg, Heidelberg, Germany

23Na MRI is still hampered by low signal-to-noise ratio (SNR) and long acquisition times. We present an iterative reconstruction method using a priori information from high-SNR high-resolution 1H MRI through anatomically weighted 2nd order Total Variation regularization (AnaWeTV). By anatomical weighting, intensity variations in the 23Na image are promoted at positions with high confidence of tissue boundaries. In simulated brain images, it is shown that the total sodium concentration in small lesions that are known a priori can be determined more precisely. Furthermore, we find a 2.2 fold SNR increase over gridding in 23Na MRI of a MS patient.

1526.   A fast method for 31P localised MRS in vivo
Fabio Ginnari Satriani1, Emiliano Surrentino1, Alessandro Ricci1, and Rossella Canese1
1Cell Biology and Neurosciences Dept, Istituto Superiore di Sanità, Rome, Italy

31P MRS offers a powerful approach to non-invasively measure extracellular pH (pHe) and intracellular/extracellular pH gradient in vivo. 31P MRS techniques require long acquisition times.The exogenous cell-impermeant 31P reporter 3-aminopropyl phosphonate (3-APP) used for pHe evaluation should be retained within the tumor for the entire duration of the measurements. This condition is not always fulfilled in highly vascularised tumors. We here propose a new technique for fast 31P MRS in highly vascularised tumours by improving the localization of the surface coil (positioned on superficial tumours) with a saturation band which dephases the signal arising from the mouse body.

1527.   NMR signal acquisition in the Doubly Tilted Rotating Frame
Denis Grenier1, Anne-Laure Perrier1, Hervé Saint-Jalmes2, and Olivier Beuf1
1CREATIS, CNRS UMR 5220, INSERM U1044, INSA-Lyon, Université de Lyon, Villeurbanne, France, 2PRISM, LTSI, INSERM U1099, Université Rennes 1, Rennes, France

In this work we investigate the feasibility of the acquisition of an NMR signal during a strong RF irradiation. By acquiring the signal during the RF excitation, dipolar interaction can be canceled, leading to a solid state spectroscopy technique suited for in vivo physiologically sound applications.

1528.   Amplitude-modulated continuous wave excitation
Kelvin J. Layton1, Bahman Tahayori1, James Korte1, Iven M. Y. Mareels1, Peter M. Farrell1, and Leigh A. Johnston1
1Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, Victoria, Australia

The response of the magnetization to amplitude-modulated continuous wave RF excitation is investigated with theory and experiments. Proof-of-concept measurements of the steady-state magnetization waveform demonstrate substantial frequency components at harmonics of the modulation frequency, emphasizing the nonlinear nature of the spin system. Experiments are in excellent agreement with theoretical expressions derived from the Bloch equations. Furthermore, experiments show that the steady-state magnetization is relatively large when the amplitude of the field matches the modulation frequency, establishing a secondary resonance condition not previously observed in magnetic resonance systems.

Rajakumar Nagarajan1, Neil Wilson1, and M.Albert Thomas1
1Radiological Sciences, University of California Los Angeles, LOS ANGELES, CA, United States

Conventional three-dimensional MRSI is time-consuming because it involves a large number of phase encodings. Echo-planar spectroscopic imaging (EPSI) approaches have been used to reduce the long acquisition time required for multiple spatial encoding steps, In our study, we have implemented non-uniform undersampling (NUS) with compressed sensing (CS) reconstruction to a three dimensional (3D) EPSI in order to accelerate the data acquisition. We propose that by 2X nonuniform undersampling along phase encodings, the 3D EPSI acquisition time could be significantly reduced without sacrificing the spectral quality with more metabolite detection in the prostate phantom.

1530.   Fast high-resolution J-resolved correlation spectroscopy in inhomogeneous fields
Hao Chen1, Zhiyong Zhang1, Shuhui Cai1, and Zhong Chen1
1Department of Electronic Science, Xiamen University, Xiamen, Fujian, China

The inhomogeneity of magnetic fields always affects the quality of NMR spectra and hampers the spectral assignment. To circumvent this influence, a new NMR acquisition scheme based on spatial encoding technique and intermolecular zero-quantum coherence is proposed to achieve a high-resolution 3D NMR spectrum in a few minutes without the peaks broadening caused by field inhomogeneity. Both homonuclear correlation and J-resolved information can be obtained from this spectrum. The new scheme may be useful for the study of biological tissues.


Non-Cartesian Imaging

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

1531.   Floating slice whole-body MRI using a continuous moving bed, golden angle radial acquisition, and compressed sensing reconstruction
David S Smith1,2, Saikat Sengupta1,2, and E. Brian Welch1,2
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, 2Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

We present results from a rapid, whole-body, free-breathing MR imaging protocol that uses a continuous moving bed coupled with a golden angle radial acquisition and a compressed sensing reconstruction to achieve high image quality and artifact reduction despite an equivalent undersampling factor of 7.0. Additionally, the use of a golden angle radial acquisition allows slice positions and thicknesses to be determined after data collection, allowing the reconstructed images to be tailored to the clinical application so as to minimize through-slice signal averaging effects in regions of interest or control the balance of SNR and spatial resolution.

1532.   Radial CAIPI-CS for simultaneous multi-slice cardiac perfusion imaging
Ganesh Adluru1, Liyong Chen2, and Edward V.R. DiBella1
1Radiology, University of Utah, Salt lake city, Utah, United States, 2Advanced MRI Technologies, Sebastopol, CA, United States

Myocardial perfusion imaging is an invaluable tool to diagnose and study coronary artery disease. Complete coverage of the heart without sacrificing temporal or spatial resolution is desired. Many approaches aim to achieve the desired goal by undersampling k-space data for each time frame and using sophisticated reconstruction algorithms like compressed sensing. Another complementary approach to increase coverage without compromising spatio-temporal resolution is simultaneous multi-slice imaging in which multiple slices are simultaneously excited with phase modulation and acquired simultaneously. Here we combine CAIPI, a simultaneous multi-slice method, with compressed sensing for radial myocardial perfusion and present promising results.

Sagar Mandava1, Zhitao Li1, and Ali Bilgin1,2
1Electrical and Computer Engineering, University of Arizona, Tucson, AZ, United States, 2Biomedical Engineering, University of Arizona, Tucson, AZ, United States

A novel view ordering scheme for radial multi-band RF encoded acquisitions is presented. This view ordering enables sliding window reconstructions for arbitrary window positions and lengths. This flexible view ordering scheme combined with sparsity regularized reconstructions paves the way for rapid time resolved simultaneous multi-slice MRI.

Retrospective Reconstruction of Cardiac Cine Images from Golden-Ratio-Radial MRI using 1D Navigators
Martin Krämer1, Karl-Heinz Herrmann1, Judith Biermann1, and Jürgen R Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, TH, Germany

To perform cardiac cine imaging a single slice is repeatedly acquired with radial readouts rotated by an angle based on the golden ratio. Performing correlation analysis between interspersed 1D navigator projections, time points corresponding to the same cardiac motion phases were automatically identified and used for retrospective combination of radial readouts from multiple data windows. Analysis of the 1D navigator data provided a detailed correlation function revealing cardiac motion over time. Imaging results were comparable to images reconstructed based on a temporally synchronized ECG showing low artifact level and good image quality in terms of CNR.

1535.   A Preconditioned ADMM Strategy for Field-Corrected Non-Cartesian MRI Reconstruction
Joshua D. Trzasko1, Armando Manduca1, Yunhong Shu1, John Huston III1, and Matt A Bernstein1
1Mayo Clinic, Rochester, MN, United States

Sparse reconstruction of non-Cartesian MRI data remains computationally challenging since multiple “gridding” operations must be executed at each iteration of the reconstruction. Recently, an efficient alternating-direction-method-of-multiplier (ADMM) strategy was proposed for sparse MRI reconstruction. For non-Cartesian MRI, the data fidelity sub-problem must also be solved iteratively. If off-resonance effects are accounted for, standard circulant preconditioners cannot be used to accelerate this task. In this work, we show that an algebraic reformulation of the ADMM scheme enables the use of simple but effective diagonal PCs for non-Toeplitz models, and demonstrate their practical benefit for undersampled SWIRLS 3D CE-MRA.

1536.   A Method for Reducing the Convolution Kernel Size Used in k-Space Channel Combination for Non-Cartesian Acquisitions
Philip J Beatty1,2
1Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada, 2Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

An improved method of k-space channel combination for non-Cartesian acquisitions is described. With the proposed method, it is possible to simultaneously grid and perform channel combination in k-space using small width (4x4) convolution kernels for 2D non-Cartesian imaging. Enabling good image quality with small convolution kernels could lead to very fast non-Cartesian multi-channel image reconstruction.

1537.   Accelerated Spiral Gridding Reconstruction using Vectorization
Weiran Deng1 and V. A. Stenger1
1University of Hawaii, John A. Burns School of Medicine, Honolulu, HI, United States

This abstract presents a method that uses the vectorized parallelism in the modern CPUs to accelerate the reconstruction of images acquired using non-Cartesian trajectories such as spiral. Modern CPUs have SSE (Stream SIMD Extension) and AVX (Advanced Vectorization Extension) features, which are designed to improve the performance of the applications that have inherent parallel structures. We show that data acquired using spiral can be re-arranged and reconstructed using this approach. The reconstruction speed is four to five times faster than the conventional approach that uses multiple threads.

1538.   Self-calibrated gradient delay correction for golden angle radial MRI
David S Smith1,2 and E Brian Welch1,2
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, 2Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

We present a model for k-space trajectory shifts due to independent timing delays in gradient channels. We use this model to successfully detect and correct for gradient delays in 3D golden angle radial MRI data without the need for additional data collection, calibration, or hardware measurements. The method can also be used for 2D radial or other non-Cartesian trajectories with only slight modifications.

1539.   Compressed Sensing Reconstructed Radial bSSFP with Asymmetric Views for Free-breathing Cardiac Cine MRI
Hasan Ertan Cetingul1, Peter Speier2, Michaela Schmidt2, Qiu Wang1, and Mariappan S. Nadar1
1Imaging and Computer Vision, Siemens Corporation, Corporate Technology, Princeton, NJ, United States, 2Siemens AG, Healthcare Sector, Erlangen, Germany

2D unsegmented real-time bSSFP cine MRI is used for non-invasive assessment of the cardiac function without breath-hold. bSSFP requires short inter-pulse distance repetition time (TR) for robustness against B0 field inhomogeneities and flow. In Cartesian bSSFP the TR is reduced by partial Fourier in the readout direction, i.e., the early part of the echo is omitted. We develop CS reconstructed radial bSSFP with asymmetric views for free-breathing cardiac cine MRI. This technique can speed up acquisition and stabilize bSSFP signals by reducing TR by about 12% with only minor degradation in image quality compared to the conventional full echo schemes.

1540.   GRAPPA-based simultaneous multislice reconstruction using concentric ring k-space
Alan Chu1 and Douglas C. Noll1
1Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States

A GRAPPA-based reconstruction method for non-Cartesian simultaneous multislice (SMS) imaging is presented. The method is non-iterative, decreasing image reconstruction time relative to iterative SENSE-based methods for non-Cartesian SMS. A concentric ring k-space trajectory is used, along with z-gradient blipping, to enhance the accuracy of GRAPPA weight calibration and subsequent slice separation. Preliminary results suggest good potential for use in fMRI or DTI experiments.

1541.   Automated Design of Time-Optimal SWIRLS-like trajectory Additionally Optimized for Sampling Uniformity
Thomas W Polley1, YunHong Shu2, Joshua D Trzasko1, and Matt A Bernstein2
1Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States, 2Radiology, Mayo Clinic, Rochester, MN, United States

We demonstrate an automated design algorithm for a 3D non-Cartesian trajectory inspired by SWIRLS. In addition to being automated, the resulting trajectory maximizes the uniformity of sampling density through the k-space volume. Phantom and volunteer acquisitions demonstrate its feasibility and image quality improvement over the default SWIRLS trajectory for a fixed scan time. The algorithm takes as inputs the FOV, resolution, and hardware gradient limitations, and may be efficient enough to be done in real time. This would allow it to be more easily implemented in a variety of clinical and research situations.

1542.   A Chaotic K-space Trajectory for CS-MRI
Ya Li1, Ran Yang1, and Zhongping Zhang2
1Sun Yat-sen University, Guangzhou, Guangdong, China, 2GE Healthcare, Guangzhou, Guangdong, China

In general, the CS-MRI process carries out two main operations: undersampling in the k-space, which meets the incoherence condition, and the reconstruction of the image, which meets the sparsity or compressibility condition. To meet the incoherence condition, the basic theory of compressed sensing requires acquisition of randomized set of measurements. For MRI scanner, however, random sampling would yield longer sampling trajectory because of the MR hardware constraints, and requires bigger changes in amplitudes and polarity of MR gradients those making it infeasible practically. Here we introduce a chaotic k-space trajectory for CS-MRI, which is a good candidate k-space trajectory of incoherent-like sampling scheme.

1543.   Sampling pattern design for 2D compressed sensing using a multilevel variable-density spiral trajectory
Li Zhao1 and Craig H. Meyer1,2
1Biomedical Engineering, University of Virginia, Charlottesville, VA, United States, 2Radiology, University of Virginia, Charlottesville, VA, United States

Compressed sensing has demonstrated notable acceleration in 3D and dynamic imaging, but it is limited by sample pattern design in 2D imaging. The flexibility of variable-density spiral trajectories gives them unique advantages for optimal sampling pattern design for 2D compressed sensing. This study demonstrates that these trajectories can be used to implement a theoretically optimal multilevel random sampling pattern. Simulations and experiments using this sampling pattern yield high acceleration rates with good fidelity with a single-channel 2D acquisition.

1544.   An improved algorithm for trajectory correction in radial MRI
Guido Buonincontri1, Carmen Methner2, Thomas Krieg2, T Adrian Carpenter1, and Stephen J Sawiak1
1Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom, 2Department of Medicine, University of Cambridge, Cambridge, United Kingdom

Radial acquisitions can suffer from trajectory errors leading to reduced image quality. We present a new method of trajectory correction that uses all spokes of a radial acquisition, including B0 correction, and compare it to an existing method that uses a two-spoke pre-scan calibration, demonstrating this in the mouse heart. We also compared the quality of navigator signals obtained from the radial data with each technique. The typical shading artifacts seen in radial scans were significantly reduced with our method. Furthermore, modulation of navigator signals due to the acquisition angle was significantly reduced with the new technique.

1545.   Image based correction of radial trajectory shifts
Judith Biermann1, Martin Krämer1, and Jürgen R Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany

When performing MR imaging with radial trajectories time delays of readout gradients cause severe artifacts in the reconstructed images. A correction algorithm was implemented using only the acquired data without additional calibration or template measurements. Radial data were shifted along their readout direction by applying a range of discrete readout shifts. By analyzing the reconstructed image for each shift, a corrected image was obtained fully automatically. The proposed method was tested in phantom and in vivo data and proved its reliability.


Image Reconstruction

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

1546.   Joint Reconstruction of DCE Abdominal Images
Nadine Gdaniec1, Andrea J. Wiethoff2,3, Peter Börnert4, Mariya Doneva4, Ivan Pedrosa3,5, and Alfred Mertins1
1Institute for Signal Processing, University of Luebeck, Luebeck, Luebeck, Germany, 2Philips Research North America, Briarcliff Manor, New York, United States, 3Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, Texas, United States, 4Philips Research Laboratories, Hamburg, Germany, 5UT Southwestern Medical Center, Dallas, Texas, United States

An abdominal dynamic contrast enhanced (DCE) examination typically consists of a series of images acquired with the same imaging sequence. The resulting images represent the same anatomy, but differ due to contrast agent arrival and wash-out. The contrast agent injection can make it more difficult for the patient to hold their breath properly, resulting in severe artifacts after contrast injection. Data are acquired with a modified adaptive sampling pattern, which implies higher undersampling for shorter breath-holds. The post-contrast images should, therefore, benefit from a joint reconstruction of pre- and post-contrast images, which is evaluated in this work.

1547.   ESPReSSo: A Compressed Sensing partial k-space acquisition and reconstruction
Thomas Küstner1,2, Sergios Gatidis1, Christian Würslin1, Nina Schwenzer1, Bin Yang2, and Holger Schmidt3
1Department of Radiology, Universtity of Tübingen, Tübingen, Germany, 2Institute of Signal Processing and System Theory, University of Stuttgart, Stuttgart, Germany,3Department of Preclinical Imaging & Radiopharmacy, Universtity of Tübingen, Tübingen, Germany

For a clinical feasible Motion Correction setup in a PET/MR system, one should have accurate and sharp images which are acquired as fast as possible. Compressed Sensing promises high acquisition accelerations, whilst penalizing image quality with regard to sharpness. In order to sample the high frequencies denser, we propose a new subsampling scheme which reduces the sampled k-space region to a smaller subset. The k-space reduction has to be corrected for during the Compressed Sensing reconstruction process which uses a combined FOCUSS and POCS algorithm. The framework is called ESPReSSo (comprEssed Sensing PaRtial SubSampling).

1548.   Motion Corrected 3D Liver undersampled MRI
Felipe Yanez1,2 and Pablo Irarrazaval1,2
1Department of Electrical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile, 2Biomedical Imaging Center, Pontificia Universidad Católica de Chile, Santiago, Chile

We propose a new reconstruction technique tailored for free-breathing dynamic 3D liver MRI by estimating the motion between frames to correct inconsistencies in k-space data. Our approach produced results that demonstrate it is feasible to achieve a 10x speedup in acquisition time and remove motion artifacts without diminishing image quality. The proposed method produced gains up to 3 dB with respect of traditional CS framework.

1549.   Novel Sampling Strategies for Sparse MR Image Reconstruction
Qiu Wang1, Michael Zenge2, Hasan Ertan Cetingul1, Edgar Mueller2, and Mariappan S Nadar1
1Imaging and Computer Vision, Siemens Corporation, Corporate Technology, Princeton, NJ, United States, 2MR Application & Workflow Development, Siemens AG, Healthcare Sector, Erlangen, Germany

Compressed sensing or sparsity based MR reconstruction takes advantage of the fact that the image is compressible in a specific transform domain, and enables reconstruction based on under-sampled k-space data thereby reducing the acquisition time. One requirement for the compressed sensing theory to work is the data acquisition in k-space to be incoherent. Although many random sampling schemes theoretically meet such requirements good enough, the MR physics or even the pathophysiology of a patient might impose additional constraints which have to be taken into account. This is considered the coherence barrier. In the current work, we formulate a sampling strategy that promises to achieve asymptotic incoherence, thus breaking the coherence barrier. Please notice that both the data acquisition and the reconstruction which have been used are investigational prototypes which experience continuous development. Nonetheless, experimental results in a phantom and a volunteer demonstrate a significant improvement of the spatial resolution with an increasing sub-sampling rate and a constant data acquisition time accordingly.

1550.   Data-driven Cartesian sampling design for Compressed Sensing MRI
Frank Zijlstra1, Jaco J.M. Zwanenburg1, Max A. Viergever1, and Peter R. Seevinck1
1Image Sciences Institute, UMC Utrecht, Utrecht, Netherlands

We propose a novel, data-driven method for optimizing Cartesian undersampling patterns for Compressed Sensing. The method iteratively adds sampling points based on CS reconstructions of a training set. The performance of the proposed optimized sampling patterns are evaluated against the commonly used Variable Density undersampling methods. Our method shows improvements in both the Normalized Root Mean Square Error and the mean Structural Similarity index. The method generalizes to any reconstruction method that allows Cartesian undersampling in any number of dimensions and would enable optimization of patterns for a combination of CS and parallel imaging.

1551.   Elastic Net Formulation for MRI Reconstruction
Angshul Majumdar1 and Rabab Ward2
1Indraprastha Institute of Information Technology, New Delhi, Delhi, India, 2Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada

This work proposes to employ elastic-net for MRI reconstruction. The elastic net favours grouping effect among the stree-structured wavelet coefficients and thereby yields better reconstruction than straighforward sparse reconstruction. We propose generalization of the standard elastic net formulation by introducing an analysis prior elastic net. The results from our generalization yields better results than state-of-the-art techniques in MRI reconstruction.

1552.   Faster SPEED Imaging with Ghost Location Information from Central k-Space
Zhaoyang Jin1 and Qing-San Xiang2
1Institute of Information and Control, Hangzhou Dianzi University, Hangzhou, Zhejiang, China, 2Radiology Department, University of British Columbia, Vancouver, BC, Canada

Skipped phase encoding and edge deghosting (SPEED) is an effective method for scan time reduction. Previously, three interleaved datasets along PE direction were acquired to separate the overlapped ghosts by solving a least-square problem. This study reveals that overlapped ghosts can be separated by using only two interleaved k-space datasets since the ghost order index (n1, n2) can be readily calculated from central k-space data. Results from phantom and in vivo data demonstrated feasibility of the proposed method, leading to further acceleration of SPEED imaging.

1553.   Achieving Greater SPEED with Iterations between Object and K-space
Qing-San Xiang1
1Radiology, University of British Columbia, Vancouver, British Columbia, Canada

Skipped Phase Encoding and Edge Deghosting (SPEED) can accelerate MRI with a single coil. Previously, SPEED sparsely sampled 3 interleaved datasets with skip size N and relative offsets along PE, and resolved aliasing ghosts by solving linear equations pixel-by-pixel. In this study, it is demonstrated that SPEED can be performed with only 1 dataset, similar to that used in GRAPPA except from only one receiver coil, achieving greater acceleration. The new algorithm imposes partial knowledge of the data in both reciprocal Fourier domains, and finds a global answer through straightforward iterations between Object and K-space (iOK).

1554.   Application of Low-Rank Matrix-Completion Reconstruction Combined with Segmentation and Parallel Imaging in Lower Extremities Perfusion Imaging
Jieying Luo1, Taehoon Shin2, Tao Zhang1, Joseph Y. Cheng1, Bob S. Hu3, and Dwight G. Nishimura1
1Electrical Engineering, Stanford University, Stanford, California, United States, 2University of Maryland, Baltimore, Maryland, United States, 3Palo Alto Medical Foundation, Palo Alto, California, United States

Perfusion imaging in the lower extremities remains challenging due to the requirements of large volumetric coverage and high temporal resolution. A low-rank matrix-completion reconstruction method has been proposed for highly accelerated dynamic contrast-enhanced perfusion imaging. In this work, an improved reconstruction method that combines low-rank matrix-completion reconstruction with image-based segmentation and parallel imaging is developed and tested in vivo. The proposed method can recover perfusion dynamics with less temporal blurring, and is promising for quantitative perfusion imaging in the lower extremities.

1555.   Compressed Sensing with Self-Validation
Yudong Zhu1
1Zhu Consulting, Scarsdale, NY, United States

Compressed sensing offers a capacity for accelerating data acquisition while keeping aliasing and noise effects subdued. Theories and experiences however are yet to establish a more robust guidance on random sampling, sparse model and non-linear solver, to help manage the challenge of using the technology in diagnostic MR. In this work we took a new angle and investigated the feasibility of introducing self-validation into compressed sensing MR. The goal is to assist fidelity assessment and improvement in practice with validation tests that can be automatically performed on any specific imaging instance itself, without requiring additional data or comparison references.

1556.   Subjective quality assessment of under-sampled compressed sensing and parallel imaging MRI reconstructions
Mohammad Kayvanrad1,2, Amy Lin3, Rohit Joshi3, Jack Chiu3, and Terry Peters1,2
1Biomedical Engineering, University of Western Ontario, London, Ontario, Canada, 2Robarts Research Institute, University of Western Ontario, London, Ontario, Canada,3Medical Imaging, University of Western Ontario, London, Ontario, Canada

While the quality of under-sampled MRI reconstructions is commonly evaluated based on quantitative metrics, such as the error with respect to the fully-sampled reference, such quantitative measures do not necessarily correlated with the subjective quality as perceived by radiologists and other expert end users. Therefore, unless accompanied by subjective measurements, quantitative quality metrics will be of limited clinical impact. This abstract presents the results of our experiments aimed towards subjective quality assessment of under-sampled MRI reconstructions for specific clinical applications. Particularly, it is shown that the advantages of different reconstructions greatly depend on the underlying clinical application.

1557.   Reproducibility and Consistency of the Fast 3D-MERGE Imaging Using CS Reconstruction
Hao Li1, Li Dong2, Bo Li3, Bin Chen3, and JUE ZHANG1,3
1Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, Beijing, China, 2Radiology, Beijing Anzhen Hospital, Beijing, Beijing, China, 3College of Enigneering, Peking University, Beijing, Beijing, China

High-resolution 3D-MERGE technique based black-blood imaging has been reported to quantitatively measure carotid atherosclerotic plaque morphology and tissue composition, and receive more and more clincial concerns. However, it brings about relative long time consuming due to the use of motion-sensitized preparation, which can increase the probability of motion artifacts due to swallowing, respiration or neck movements. In our previous research, compressed sensing (CS) is used to improve temporal resolution by reconstructing images from a dramatically small number of data without introducing severe image artifacts[1]. The purposes of this study are: (1) to determine the reproducibility of the fast 3D-MERGE imaging using CS reconstruction. (2) to determine the consistency of this method when using different CS acceleration factors.

1558.   ROICS-PI:Combination of Region of Interest Compressed Sensing and Parallel Imaging for Arbitrary k-space Trajectories to Achieve Highly Accelerated MRI
Amaresha Shridhar Konar1, Divya Jain1, Shamshia Tabassum1, Rajagopalan Sundaresan2, Ramesh Venkatesan2, and Sairam Geethanath1
1Medical Imaging Research Center, Dayananda Sagar Institutions, Bangalore, Karnataka, India, 2GE Healthcare, Bangalore, Karnataka, India

Compressed Sensing (CS) and Parallel Imaging (PI) are widely used to reduce MRI scan time and their combination yields better performance than used individually. The proposed method implements the combination of Region of Interest Compressed Sensing (ROICS) and SENSitivity Encoding (SENSE) which applies weighted CS to a particular ROI and the resulting output is then reconstructed using SENSE for arbitrary k-space. Proposed method performs better compared to PI and CS+PI for 6 channel brain data as validated qualitatively through images and quantitatively as determined by Peak Signal to Noise Ratio (PSNR) parameter by comparing with existing methods.

1559.   Incoherence Parameter Analysis for Optimized Compressed Sensing with Nonlinear Encoding Gradients
Leo K. Tam1, Gigi Galiana1, Haifeng Wang1, Emre Kopanoglu1, Andrew Dewdney2, Dana C. Peters1, and R. Todd Constable1
1Diagnostic Radiology, Yale University, New Haven, CT, United States, 2Siemens Healthcare AG, Erlangen, Bavaria, Germany

Incoherence in compressed sensing is known to be important, but is there new understanding to be gained beyond the canonical method of selecting k-space coefficients in a psuedo-random manner. The incoherence parameter is studied, which dictates the largest subset of vectors in the sparse domain that may be exactly recovered via convex optimization with an L1 norm constraint. Incoherence parameter maps, showing the pairwise incoherence at each pixel are presented. The incoherence parameter is optimized using nonlinear encoding gradients, and experiments with a 3T Siemens Trio are presented that show an optimized incoherence parameter leads to reduced MSE.

1560.   Patch-based dictionaries for parallel MRI reconstruction
Jose Caballero1, Anthony N. Price2,3, Daniel Rueckert1, and Joseph V. Hajnal2,3
1Department of Computing, Imperial College London, London, United Kingdom, 2Division of Imaging Sciences and Biomedical Engineering Department, King's College London, London, United Kingdom, 3Centre for the Developing Brain, King's College London, London, United Kingdom

Acceleration of Magnetic Resonance (MR) acquisitions through partially parallel imaging using array coils is limited by noise amplification. Compressed sensing regularization has de-noising properties that can mitigate this effect. Recent results on dictionary learning have shown that using overcomplete patch-based frames and adapting them to the object can have a notable impact on reconstruction by finding sparser representations and adjusting to the natural features of the object. However, these results have not yet been tested for parallel MR. Here we propose an algorithm to exploit overcomplete and adaptive frames for SPIRiT reconstruction and demonstrate its superiority to traditional wavelet regularization.

1561.   Fast and Simple Patch-Based Sparse Reconstruction Exploiting Local Image Correlations
Alicia W Yang1,2, Li Feng1,2, Daniel K Sodickson1, and Ricardo Otazo1
1Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, 2Sackler Institute for Biomedical Sciences, New York University, New York, NY, United States

A patch-based sparse image reconstruction method based on local image correlations is proposed for compressed sensing. The method divides the image into non-overlapping blocks and sparsity is enforced in each block separately by thresholding the Principal Component Analysis (PCA) representation of a series of small patches within the block. The method exploits correlations directly in the image without the need of an analytical transform and it is reference-less and computationally efficient, removing the need to search for similar patches in the whole image. We tested the performance of the method to reconstruct undersampled 2D and 3D MSK images.

1562.   Patch based low rank constrained reconstruction for diffusion MRI
Ganesh Adluru1, Yaniv Gur2, Jeffrey Anderson1, and Edward V.R. DiBella1
1Radiology, University of Utah, Salt lake city, Utah, United States, 2SCI Institute, University of Utah, Salt lake city, Utah, United States

Standard diffusion imaging is limited when evaluating regions with crossing fibers. Higher order diffusion acquisitions with multiple b-values and multiple diffusion directions can reveal crossing fiber information; however it takes a long time to acquire such data. Acceleration techniques including compressed sensing can be applied to reduce the readout time by undersampling k-space and using constraints that exploit redundancies to remove the undersampling artifacts. Here we test a patch-based low rank constraint that exploits redundancies in terms of patches across diffusion directions for undersampled diffusion data. Promising results are presented in a multi-shell acquisition in a stroke patient.

1563.   Interactive Hip Joint Cartilage Segmentation
Pavel Dvorak1,2, Wolf Dieter Vogl3, and Vladimir Juras4
1Institute of Scientific Instruments of the ASCR, v.v.i., Brno, Czech Republic, 2Department of Telecommunications, Brno University of Technology, Brno, Czech Republic,3Computational Image Analysis and Radiology Lab, Department of Radiology, Medical University of Vienna, Vienna, Austria, 4MR Centre of Excellence, Department of Radiology, Medical University of Vienna, Vienna, Austria

This work deals with hip joint cartilage segmentation, which is an important task in joint diseases diagnosis. Since the manual segmentation, commonly used nowadays, is a tedious and lengthy task, this work brings new idea into its automation and simplification of the medical expert work. Nevertheless, the proposed method still preserve the medical expert interaction to enable manual corrections.

1564.   Reconstructing 3D dynamics based on complementary 2D acquisitions: a preliminary case study on speech imaging
Xiaoguang Lu1, Peter Speier2, Hasan Cetingul1, Marie-Pierre Jolly1, Michaela Schmidt2, Mariappan Nadar1, Frank Sauer1, and Edgar Mueller2
1Corporate Technology, Siemens Corporation, Princeton, New Jersey, United States, 2Siemens AG, Erlangen, Germany

We describe a general method for reconstructing a sequence of volumes representing 3D dynamics of a target anatomy, e.g., cardiac, tongue, vocal tract, or moving joint, based on densely acquired complementary 2D slices. Speech dynamics imaging is used as a case study for demonstration. Preliminary results have shown promise.

1565.   Improved k-t GRAPPA for Phase Contrast Cine MRI by using Modified Artificial Sparsity
Aiqi Sun1, Rui Li1, Bida Zhang2, Chun Yuan1,3, and Feng Huang4
1Department of Biomedical Engineering & Center for Biomedical Imaging Research, School of Medicine, Beijing, Beijing, China, 2Philips Research Asia Shanghai, Shanghai, China,3Department of radiology, University of Washington, Seattle, WA, United States, 4Philips Healthcare, Gainesville, FL, United States

The previous studies have shown phase-contrast cine MRI is a powerful tool for studying flow-related physiology and pathophysiology. However, the additional scans for encoding the flow velocity information increase the total scan time and limit the achievable spatial and temporal resolutions within a clinically acceptable duration. Among kinds of k-t reconstruction algorithms exploiting spatiotemporal correlation, k-t GRAPPA has the advantage of self-calibration, but degrades the temporal resolution when acceleration factor is high. Here we propose an artificial sparse scheme using static tissue elimination scheme to improve the temporal resolution preservation of k-t GRAPPA for blood flow measurements of thoracic aorta.

1566.   Highly Accelerated Cardiac Cine Imaging Using a Combination of k-t Group Sparse and SPIRiT
Feiyu Chen1, Feng Huang2, Dan Zhu1, Haikun Qi1, Kui Ying3, and Huijun Chen1
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing, China, 2Philips Healthcare, Gainesville, FL, United States,3Department of Engineering Physics, Tsinghua University, Beijing, China

In this research, we proposed a k-t GS-SPIRiT method to combine k-t group sparse and parallel imaging, which can result in images better than each individual method in cardiac cine image.

1567.   k-t ESPIRiT for Accelerating Proton Resonance Frequency Shift MR temperature mapping
Chen Guang Peng1, Dan Zhu2, Fei Yu Chen2, and Kui Ying1
1Physics and Engineering, Tsinghua University, Beijing, Beijing, China, 2Biomedical Engineering,Tsinghua University, Beijing, Beijing, China

We proposed k-t ESPIRiT for dynamic imaging, and applied it to PRFS thermometry. Accurate sensitivity maps computed from k-t ESPIRiT enables a phase preservation in image reconstruction, which is the prerequisite for the widely used PRFS on thermometry. Experimentally, we compare the proposed method with k-t FOCUSS on phantom under high under-sampled factor. We demonstrated that phase map reconstructed from K-t ESPIRiT is more accurate than k-t FOCUSS, and that temperature estimation of k-t ESPIRiT is closer to the reference. Therefore, k-t ESPIRiT performs better than k-t FOCUSS on PRFS acceleration.

1568.   Highly Accelerated Dynamic Parallel MRI Exploiting Constrained State-Space Model with Low Rank and Sparsity
Suhyung Park1 and Jaeseok Park1
1Department of Brain and Cognitive Engineering, Korea University, Seoul, Seoul, Korea

Fast magnetic resonance imaging (MRI) techniques [1-4], which lead to signal recovery from incomplete data, have been introduced in dynamic imaging to improve spatiotemporal resolution without apparent loss of image quality. In this respect, we propose a novel, highly accelerated dynamic parallel MRI reconstruction method exploiting a constrained state space model with low rank and sparsity while jointly estimating spatiotemporal kernels and missing signals in k-t space in an iterative fashion. Spatiotemporal kernels stacked across multiple time frames are estimated using the low rank constraint due to the nature of smoothly varying spatiotemporal correlation in k-t space during calibration, while the solution is projected onto the reconstructed k-t space with the sparsity constraint imposed on the estimated dynamic images in x-f space.

1569.   Real-time cardiac MRI using manifold sensing
Sunrita Poddar1, Sajan Goud Lingala2, and Mathews Jacob1
1Electrical and Computer Engineering, University of Iowa, Iowa City, Iowa, United States, 2Biomedical Engineering, University of Iowa, Iowa City, Iowa, United States

This work enables free-breathing un-gated cardiac MR imaging from highly under-sampled k-space data. It eliminates the need for multiple breath-holds to evaluate cardiac function, thus increasing patient comfort. We consider that the images live on a 2D manifold (parameterized by cardiac and respiratory phases) embedded in higher dimensional space. K-space data of images that lie close on the manifold are combined for reconstruction. The proposed approach does not require cardiac and respiratory gating or manual self-gating and can be automated for routine clinical use. This scheme can work for a range of existing k-space trajectories, including golden angle radial sequences.

1570.   Acceleration of Perfusion MRI using Adaptive Artificial Sparsity
Xiaoying Cai1, Feng Huang2, Kui Ying3, Chun Yuan4, and Huijun Chen4
1Biomedical Engineering, University of Virginia, Charlottesville, Virginia, United States, 2Philips Healthcare, Gainesville, FL, United States, 3Department of Engineering Physics, Tsinghua University, Beijing, China, 4Center for Biomedical Imaging Research, Beijing, China

We proposed a new framework for reconstruction of accelerating perfusion imaging. By prediction intensity change of perfusion images using pre-contrast image and adaptive weights , the sparsity of dynamic images was strengthened, which benefits the following regular imaging reconstruction (k-t GRAPPA, k-t PCA or k-t SLR). The framework was tested with black blood vessel wall imaging data. The results showed that our new framework could result in better image reconstruction and improved kinetic parameter fitting for all tested reconstruction methods when acceleration factors were high.

1571.   K-t PCA GROWL: Sequential Combination of Partially Parallel Imaging and K-t PCA
Haikun Qi1, Feng Huang2, Xiaoying Cai1, Dan Zhu1, Feiyu Chen1, Chun Yuan1,3, and Huijun Chen1
1Center for Biomedical Imaging Research, Tsinghua University, Beijing, Beijing, China, 2Philips Healthcare, Florida, United States, 3Department of radiology, University of Washington, Seattle, WA, United States

When multichannel coil is used for data acquisition, partially parallel imaging can be combined with k-t PCA to improve reconstruction accuracy. In this study, a sequential combination of partially parallel imaging and k-t PCA, which is called k-t PCA GROWL (GRAPPA Operator for Wider readout Line) is proposed. Compared with k-t PCA and k-t PCA/SNESE on artificially undersampled cardiac cine data, the proposed method resulted in the lowest error level. K-t PCA GROWL is a more efficient and more accurate scheme to combine k-t PCA and parallel imaging, and is promising in high spatiotemporal resolution dynamic MRI.

1572.   An Extended Matrix Method for Analysis of Restricted Diffusion in Multi-Compartment Tissue With Semi-Permeable Nuclear Membranes
Gregory Duane1,2, Yanwei Wang1, Blake R. Walters1, and Jae K. Kim1
1Thunder Bay Regional Research Institute, Thunder Bay, Ontario, Canada, 2University of Colorado, Boulder, Colorado, United States

The impulse-propagator (matrix) method is extended to a multi-compartment idealized cell geometry describing nucleus, cytoplasm, and extracellular fluid, with semi-permeable membranes. The R matrices now represent propagation between compartments as well as intra-compartment propagation, with an approximate adjustment of the latter. Results are compared with those of Monte Carlo simulations. For biologically realistic nuclear membrane permeability, there are quantitative differences with the Monte Carlo results, but the contrast between signals for cases of large and small nuclei is qualitatively similar to the Monte Carlo contrast. The extended matrix method appears adequate to optimize q values for sensitivity to nucleus size.


Image Processing & Analysis

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

1573.   Discontinuity Preserving Convex Image Registration Model for MRI of the Lung
Ketut Fundana1, Oliver Bieri2, and Philippe C. Cattin1
1Medical Image Analysis Center, University of Basel, Basel, Switzerland, 2Radiological Physics, University Hospital of Basel, Basel, Switzerland

Imaging the structure and function of the human lungs is of importance for early detection of lung diseases. With the new development of steady state free precession (SSFP) imaging concepts in combination with dedicated image registration methods for fast functional and morphological MRI, it is expected that we are able to study the lung functions. We propose a novel method for image registration of the lung MRI sequences by using a convex optical flow model. The model is based on combined local and global optical flow method and regularized by an anisotropic total variation (TV) norm. The anisotropy derived from the structure tensor in order to take into account local variations at each point and to preserve the discontinuities of the motion fields. Qualitative and quantitative evaluations are done to show the robustness of the method.

1574.   Correlation of MRI and externally visible findings by external fiducial markers
Bridgette Webb1, Andreas Petrovic1, and Eva Scheurer1,2
1Ludwig Boltzmann Institute for Clinical Forensic Imaging, Graz, Styria, Austria, 2Institute of Forensic Medicine, Medical University Graz, Graz, Styria, Austria

To improve the correlation of externally visible lesions in skin and subcutaneous fatty tissue with MRI findings, external strand-shaped markers were developed and tested. The visibility of the markers in photography and MRI, and quality of the final registration were investigated. Visualization of the markers and internal soft tissue damage was possible using a combination of sequences. Using manual feature detection followed by an affine transformation, MR images were registered to photographs documenting external and internal damage. Selected points in the registered MR images and photographs were used to evaluate the registration, giving an overall RMSE of 1.05 mm (95%CI[0.46;1.42]).

1575.   An alternative approach for the automatic prediction of therapy response from MRI data sets in small cohorts of experimental High Grade Gliomas
Ania Benítez1,2, Gerardo Peláez-Brioso1,2, Alexandra Borges3, Pilar López-Larrubia1, Sebastián Cerdán1, and Manuel Sánchez-Montañés2
1Instituto de Investigaciones Biomédicas "Alberto Sols", Madrid, Madrid, Spain, 2Computer Science and Engineering, Escuela Politécnica Superior, Universidad Autónoma de Madrid, Madrid, Madrid, Spain, 3Instituto Português de Oncologia Centro de Lisboa, Lisboa, Portugal

MRI is presently one of the most important non-invasive methods to investigate and diagnose High Grade Gliomas (HGG) with the automatic classification of medical images into different pathological categories or grades playing an important role. A common problem to both approaches is many times, the small size of individual observations, while the data set from each individual is very large. We propose here an interesting protocol to predict therapy response in an animal HGG model, from the MRIs obtained during the first two days of anti-VGEF treatment. This approach in combination with LDA predicts therapy response outperformimg the classical approaches.

1576.   Legal Majority Age Determination from MR Images of the Radius Bone
Darko Stern1, Thomas Ebner1, Eva Scheurer2,3, and Martin Urschler1,2
1Institute for Computer Graphics and Vision, Graz University of Technology, Graz, Styria, Austria, 2Ludwig Boltzmann Institute for Clinical Forensic Imaging, Graz, Styria, Austria, 3Medical University of Graz, Graz, Styria, Austria

In forensic practice determination of legal majority age is getting an increasing interest, e.g. for dealing with asylum seekers without proper identification. Traditional methods based on X-ray investigations of bone ossifications have the drawback of exposure to harmful ionizing radiation. MR based techniques overcome this limitation. Together with detection, automatic feature extraction and age estimation based on machine learning, MR may eventually become a powerful tool in this context. A first step in this direction is presented, by investigating age estimation based on the ossification of the wrist radius bone in an automatic fashion.

1577.   Application of a fussed lasso logistic regression classifier to the study of corpus callosum thickness in early Alzheimer's disease
Babak A Ardekani1, Sang Han A Lee1, Donghyun Yu2, Johan Lim2, and Alvin H Bachman1
1The Nathan S. Kline Institute for Psychiatric Research, Orangeburg, New York, United States, 2Statistics, Seoul National University, Seoul, Korea

We describe a multi-atlas-based method for corpus callosum segmentation and a fused Lasso logistic regression (FLLR) classifier that is able to differentiate patients with very mild/mild AD from normal controls (NC) using their CC thickness profile. We evaluated this technique using data from 196 individuals (98 AD and 98 NC) in the OASIS database. The FLLR classification accuracy was estimated to be 84% using cross-validation. Furthermore, the FLLR method highlights regions of the CC that are significantly thinner in AD relative to NC. The FLLR model presented can be extended to include other imaging or chemical biomarkers of AD.

1578.   Improved subcortical segmentation using multiple MR modalities
Eelke Visser1, Gwenaëlle Douaud1, and Mark Jenkinson1
1FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom

Automated segmentation of subcortical structures is typically performed using T1-weighted volumes. However, not all of these structures' boundaries are clearly visible with T1 contrast. We describe a multimodal segmentation method that integrates information from different contrasts: in this case T1-weighted, T2-weighted and FA volumes. Since the images contain complementary information, the method does not need to rely heavily on prior shape knowledge obtained from training data. We show that, in specific areas, the method performs considerably better than FIRST, a segmentation method that only uses T1-weighted volumes.

1579.   Distributed Computing on Gadgetron: A new paradigm for MRI reconstruction
Hui Xue1, Peter Kellman1, Souheil Inati2, Thomas Sorensen3, and Michael Schacht Hansen1
1Magnetic Resonance Technology Program, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States, 2National Mental Health Institute, National Institutes of Health, Bethesda, Maryland, United States, 3Department of Computer Science, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark

Although non-linear reconstruction has shown potential for shortening acquisition times, its clinical usage is often hampered by the lengthy reconstruction time. To speedup non-linear reconstruction and enable its clinical usage, we have extended previously published Gadgetron framework to support cloud computing. With this extension (named GT-Plus), any number of Gadgetron processes can run cooperatively across multiple computers. GT-Plus framework was deployed on Amazon EC2 cloud and NIH’s Biowulf system. We demonstrate that with the GT-Plus cloud, a multi-slice free-breathing myocardial cine imaging with the whole ventricular coverage can be completed within 1min, including data acquisition and reconstruction.

1580.   CPU, GPU and MIC performance: a comparison of modern reconstruction hardware
Eric A. Borisch1, Paul T. Weavers1, and Stephen J. Riederer1
1Mayo Clinic, Rochester, MN, United States

A comparison of the relative performance of multiple hardware options (CPU, GPU, MIC) available for accelerating reconstruction software performance is provided. The performance results were obtained during the process of implementing of a computationally intensive MR acceleration prescription-optimizing calculation across multiple hardware generations. Implications for purchasing and development activities where computational throughput as well as development time must be balanced are discussed.

Michael Oluwaseun Dada1, Simona Baroni2, and Bamidele Omotayo Awojoyogbe1
1Department of Physics, Federal University of Technology, Minna, Niger State, Nigeria, 2Invento Laboratory, Molecular Biotechnology Center (MBC), Torino, Turin, Italy

Field-cycling magnetic resonance imaging (FC MRI) allows switching of the magnetic field during an imaging scan1. FC MRI has been very successful in relaxometry studies and there arises the need to offer more theoretical supports to the rich experimental results available in NMR laboratories. These theories are expected to offer new ways of interpreting the results for new discoveries. In view of this, we have developed a methodology based on the time – independent Bloch NMR flow equations for calculating the transverse magnetization in terms of the applied RF field. The results obtained in the study is useful for spectroscopic studies and 3D mapping of tissues

1582.   Example based brain MRI synthesis
Qing He1, Snehashis Roy1, Amod Jog2, and Dzung L Pham1
1Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, Maryland, United States, 2Dept. of Computer Science, The Johns Hopkins University, Baltimore, Maryland, United States

An example based brain MRI synthesis method is proposed. No physical simulation of the image acquisition is involved and the synthesis is purely based on an example MR image. Patch based regression is used to predict the image based on anatomical models constructed from segmentation fusion. Results show that the synthetic images generated by our method are more realistic looking than those from the physics based methods.

1583.   Noise Estimation in Spiral Imaging
Sudarshan Ragunathan1, Dinghui Wang1, Zhiqiang Li1, and James G Pipe1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, United States

Current methods estimating noise content in an image require either multiple acquisitions or selecting an appropriate background region of the image. This work does not require either, and provides an estimate of the noise by eliminating signal content from a single dataset acquired by spiral or similar trajectories. The signal elimination was achieved by appropriate modification of the sampling density correction (SDC) weights. The modified weights was input to a gridding algorithm to obtain a noise image.

1584.   Bayesian Estimation of Signal Amplitude from Magnitude Data
Ken Sakaie1
1Imaging Institute, The Cleveland Clinic, Cleveland, OH, United States

Magnitude reconstruction leads to biased signal at low signal-to-noise ratio (SNR). The Rician distribution describes the signal magnitude given an underlying value from signal amplitude. However, one typically wants the opposite: the underlying amplitude given the measured magnitude. We show how to derive this latter, inverse Rician, distribution and demonstrate some of its properties.

1585.   Hotelling Observer Efficiency Image Quality Metric for Compressed Sensing MRI
Christian G. Graff1
1Division of Imaging and Applied Mathematics, U.S. Food and Drug Administration, Silver Spring, MD, United States

To facilitate dynamic and quantitative MR imaging there is significant interest in accelerated data acquisitions. Less data are acquired, which is often compensated for through iterative reconstruct techniques such as compressed sensing. These techniques involve non-linear regularization that complicates image analysis and challenges the validity of traditional image quality metrics such as pixel SNR. Here we develop the concept of Hoteling-SNR efficiency which quantifies the task-specific efficiency of compressed sensing reconstructions relative to a fully-sampled acquisition, measuring the tradeoff between image acquisition speed and clinical utility, overcoming inherent limitations of prior image quality metrics when analyzing compressed sensing techniques.

1586.   Intensity normalization for improved MR images analysis
Florent Lalys1, Sushmita Datta1, Léorah Freeman1, Stacey S. Cofield2, Gary R. Cutter2, Fred D. Lublin2, Jerry S. Wolinsky1, and Ponnada A. Narayana1
1University of Texas Health Science Center at Houston, Houston, Texas, United States, 2University of Alabama at Birmingham, Birmingham, Alabama, United States

Intensity normalization (IN) is a critical step in image processing, and particularly in MR image segmentation. The IN technique described by Nyul et al. has been routinely used in numerous studies, but never critically evaluated on large cohorts or optimized for specific applications. In this study we significantly improved this IN method by identifying an optimal set of parameters, and verified it on a large cohort of multiple sclerosis patients. Our findings support implementing different parameters than those used in the majority of published studies.

1587.   Image-based estimation method for field inhomogeneity map in brain EPI image
Seiji Kumazawa1, Takashi Yoshiura2, Hiroshi Honda2, and Fukai Toyofuku1
1Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, Fukuoka, Fukuoka, Japan, 2Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Fukuoka, Japan

EPI suffers from geometrical distortion due to magnetic field inhomogeneity. Our purpose was to develop an image-based method for estimating the magnetic field map based on the distorted EPI image and T1WI which requires no additional acquisitions. Our method synthesizes the distorted image to match the measured EPI image through the generating process of EPI image by changing the magnetic field. To evaluate the performance of our method, we applied it to simulation data. Our preliminary results demonstrate that the magnetic field inhomogeneity in EPI image can be estimated by our method without any additional acquisitions for estimation of the field map.

EPI distortion correction for quantitative imaging of the mouse brain at ultrahigh magnetic field
Xuan Vinh To1, Xin Hong1, Irvin Teh2, Jian Rui Soh1, and Kai-Hsiang Chuang1
1Lab of Molucular Imaging, Singapore Bioimaging Consortium, Singapore, Singapore, Singapore, 2A*STAR - NUS Clinical Imaging Research Centre, Singapore, Singapore

Echo Planar Imaging (EPI) is an ultrafast acquisition technique widely used in fMRI, diffusion imaging and perfusion imaging but suffers from geometric and intensity distortions, especially in ultrahigh field strength used in small animal imaging. In this study we compared several distortion correction methods. We found using a pair of reference EPI images acquired with opposite phase encoding directions to calculate an unwrapping field provides the most accurate, robust and efficient distortion correction for the mouse brain.

1589.   Improved algorithm for 3D non-contrast pulmonary MRA
Chia-Ling Chang1, Tzu-Cheng Chao1,2, Maria Alejandra Duràn-Mendicuti3, Ming-Ting Wu4,5, and Bruno Madore3
1Department of Computer Science and Information Engineering, National Cheng-Kung University, Tainan, Taiwan, 2Institute of Medical Informatics, National Cheng-Kung University, Tainan, Taiwan, 3Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States, 4Department of Radiology, Kaohsiung Veteran General Hospital, Kaohsiung, Taiwan, 5School of Medicine, National Yang-Ming University, Taipei, Taiwan

In an emergency room context, there is a need for a reliable non-contrast enhanced pulmonary MR angiography method to help handle the large number of patients with suspicion for pulmonary embolism and contra-indication for CT angiography. A promising method was previously introduced whose main weakness might have been the presence of discontinuities at the junction between the several slabs used to cover the chest volume. The present work aimed at alleviating this problem, thus making the overall approach more generally applicable. Through a specially-tailored registration algorithm as well as intensity-correction strategies, such discontinuities have been considerably suppressed here.

1590.   Prior-based Initialization for Automated Analysis of 3D MRE
Bogdan Dzyubak1, Armando Manduca2, Kevin J. Glaser3, and Richard L. Ehman3
1Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States, 2Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States, 3Radiology, Mayo Clinic, Rochester, Minnesota, United States

Our clinical implementation of liver magnetic resonance elastography (MRE), used for noninvasively staging hepatic fibrosis, has recently been extended to analyze wave propagation in 3D using a fast EPI-based acquisition. This produces images with severe intensity inhomogeneity, low edge contrast, and fat suppression, which make fully automated processing, such as that developed for 2D GRE-based MRE, extremely challenging. A new method that does not depend on global intensity values and is able to find large liver areas to initialize liver segmentation despite severe intensity inhomogeneity has been developed and evaluated in clinical images produced by the standard 3D MRE sequence.

1591.   High-quality Multi-contrast Susceptibility-Weighted Venography using Tissue-dependent Denoising Method
Tae-joon Eo1 and Dosik Hwang1
1School of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea

This study demonstrates that the proposed denoising method can reduce noise effectively on both the phase and magnitude data. The magnitude and phase data were simultaneously denoised by neighboring complex decaying signals using the tissue relaxation property. Consequently, the resulting SW venographies showed substantial improvement.

1592.   Sorted Compressed Sensing in MRI
Felipe Yanez1,2 and Pablo Irarrazaval1
1Pontificia Universidad Católica de Chile, Santiago, Chile, 2École Normale Supérieure, Paris, France

To improve the traditional Compressed Sensing (CS) framework for image reconstruction, we propose a CS technique with variable regularization parameter, which penalizes the pixels of the recovered image according to their magnitude. Herein, we present quantitative susceptibility map (QSM) reconstructions in in-vivo data, where the Sorted Compressed Sensing (SCS) technique produced results that demonstrate it is feasible to reconstruct high quality images. The proposed method produced gains up to 5-6 dB with respect of traditional CS.

1593.   3D GlObally Optimal Surface estimation (3D-GOOSE) algorithm for fat and water separation
Chen Cui1, Xiaodong Wu1,2, John D. Newell3, and Mathews Jacob1
1Electrical and Computer Engineering, University of Iowa, Iowa City, IA, United States, 2Radiation Oncology, University of Iowa, Iowa City, IA, United States, 3Radiology, University of Iowa, Iowa City, IA, United States

We introduce a robust algorithm to resolve the ambiguities in fat-water decomposition by utilizing the smoothness of the field-map in three spatial dimensions. Many current methods are still sensitive to local minima effects. We had recently introduced a novel graph cut algorithm termed as GlObally Optimal Surface Estimation (GOOSE) that is guaranteed to provide the global minimum, which was observed to considerably improve the performance on challenging datasets. However, GOOSE was restricted to two dimensional and hence not capable of exploiting the field smoothness between slices. This work is to extend GOOSE to 3-D therefore to further improve the robustness.

1594.   Water Fat Separation with Multiple-Acquisition bSSFP
Michael Anthony Mendoza1, Raul Villalpando1, Danny Park1, Daniel Gardner1, Kevin Perkins1, and Neal Bangerter1
1Electrical Engineering, Brigham Young University, Provo, Utah, United States

Motivated by the need for reliable and uniform water fat separation, which is used to improve medical diagnosis, we present a novel technique for water fat decomposition. This technique combines the advantages of balanced steady-state free precession (bSSFP) MRI with Dixon reconstruction to produce water fat decomposition with high SNR in a short imaging time, while simultaneously reducing banding artifacts that traditionally degrade image quality. This algorithm utilizes four phase-cycled bSSFP acquisitions at specific echo times to generate “in-phase” and “out-of-phase” images. Linear combinations of the strongest signals from these images are used to produce separate water and fat images.

1595.   Texture Analysis of Muscle 3-Point Dixon Fat-Fraction: Changes Over 1 Year
Christopher D J Sinclair1,2, Jasper M Morrow1, Arne Fischmann3, Michael G Hanna1, Mary M Reilly1, Tarek A Yousry1,2, and John S Thornton1,2
1MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, United Kingdom, 2Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom, 3University of Basel Hospital, Basel, Switzerland

Fat-water quantification is a promising method for sensitively measuring changes in muscle in upcoming clinical trials in neuromuscular diseases. In this work we applied texture analysis to 3-point Dixon fat fraction maps to assess fat-infiltration in the hamstring muscles in 17 patients with the representative condition inclusion body myositis, measured twice at a 1 year interval. Mean fat-fraction, contrast, homogeneity run length image texture measures all changed significantly over 1 year. There were no equivalent texture parameter changes in a healthy volunteer group over this period, demonstrating the promise of muscle fat-fraction texture analysis for measuring longitudinal fat-infiltration in neuromuscular conditions.

1596.   Quantitative comparison of abdominal adipose tissue volume segmentation on MR images acquired with body and phase array coils.
Sunil K. Valaparla1,2, Qi Peng3, Oscar S. E. Nateras1, Feng Gao1, Timothy Q. Duong1, and Geoffrey D. Clarke1,2
1Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States, 2Radiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States, 3Department of Radiology, Albert Einstein College of Medicine, Bronx, NY, United States

Excessive body fat, particularly visceral adipose tissue (VAT) correlates with diabetes and cardiovascular diseases. This study compared 3T breath-hold MRI T1W water-saturated (WS) and 2pt Dixon fat (DF) MRI with body and phase array coils in the application of subcutaneous (SAT), (VAT), inter-muscular (IMAT) adipose tissue volumetric assessment using semi–automated fuzzy c-means (FCM) clustering algorithm. Results indicate strong concordance and correlation between the SAT, VAT and IMAT calculated from different acquisitions. These methods can be used interchangeably along with FCM algorithm to effectively assess body fat for large-scale clinical imaging studies.


Motion Correction

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

1597.   Tracking Discrete Off-resonance markers with Three Spokes (trackDOTS) – a new motion tracking methodology
José P. Marques1, Daniel Gallichan2, and Rolf Gruetter2,3
1CIBM, Department of Radiology, University of Lausanne, Lausanne, Vaud, Switzerland, 2LIFMET, École Polytechnique Fédérale de Lausanne, Vaud, Switzerland, 3CIBM, Department of Radiology, University of Lausanne and Geneva, Vaud, Switzerland

In this work we evaluate the possibility to perform motion tracking of a subjects head by using small MR markers containing a liquid which is off-resonance in respect to water. TrackDOTS is able to determine the position of various MR markers with 3 orthogonal k-space readouts by constructing receive coil modes that limit the sensitivity to regions of the various markers. The methodology was demonstrated in vivo showing high correlation between the motion parameters obtained using conventional MR image co-registration and the proposed methodology.

1598.   Slice-by-slice prospective hardware motion correction in EPI and simultaneous multislice sequences
Paul Wighton1, M. Dylan Tisdall1, Erez Nevo2, Kawin Setsompop1, Stephen F Cauley1, Himanshu Bhat3, Thomas Benner4, Dara S Manoach5, and André van der Kouwe1
1Radiology, MGH, Charlestown, MA, United States, 2Robin Medical, Baltimore, MD, United States, 3Healthcare Sector, Siemens, Charlestown, MA, United States, 4Healthcare Sector, Siemens AG, Erlangen, Germany, 5Psychiatry, MGH, Charlestown, MA, United States

Recent research has shown that head motion can cause spurious group differences in functional as well as structural connectivity analyses. We examine slice-by-slice prospective hardware motion correction in EPI sequences (BOLD and 3x simultaneous multislice BOLD) in order to mitigate such differences. Our method incurs a 7.8% and 15.9% penalty to tSNR due motion in the BOLD and 3xSMS-BOLD sequences respectively, compared to 38.5% and 23.8% tSNR penalty respectively in the next best methods. Additionally, we observe that susceptibility due to motion has as large an effect as the motion itself.

1599.   Predictive Filtering for Improved Robustness in Prospective Motion Correction
Brian Keating1, Aditya Singh1, Benjamin Zahneisen1, Linda Chang1, and Thomas Ernst1
1Department of Medicine, University of Hawaii, Honolulu, HI, United States

System latencies can reduce the efficacy of prospective motion correction (PMC) with external optical tracking, especially during fast movements (50mm/s or 50°/s range). We integrated a Kalman filter into a prospectively corrected gradient echo (GRE) sequence in order to estimate the velocity and acceleration of the head from lagged optical tracking data. The latency was accounted for by extrapolating forward in time before each prospective update. In addition, conjugate gradient-based retrospective motion correction was performed in Matlab to correct for residual tracking errors. GRE images show reduced motion artifacts when predictive filtering is used as compared to standard PMC.

1600.   Prospective motion correction of 3D EPI data for functional MRI using optical tracking.
Nick Todd1, Oliver Josephs1, Martina Callaghan1, and Nikolaus Weiskopf1
1Wellcome Trust Centre for Neuroimaging, London, United Kingdom

An approach to using the XPACE camera system for prospective motion correction of MRI data was implemented for a 3D echo-planar imaging pulse sequence. The method uses a high frame rate camera to track the six degrees-of-freedom movement of a marker that is attached to the patient. This information is fed to the scanner host computer to dynamically update the imaging gradients necessary for rigid body realignment of the data to be acquired. The PMC method was tested for the application of acquiring 3D EPI data for functional MRI studies where high SNR and temporal stability are of paramount importance.

1601.   Comparison of BOLD censoring motion metrics when you know the motion (SimPACE)
Erik Beall1 and Mark Lowe1
1Imaging Institute, Cleveland Clinic, Cleveland, OH, United States

Censoring methods have gained a lot of attention recently, but, given the importance of head motion artifact in fMRI and fcMRI, more evaluation is necessary. Accurate identification of corrupted volumes, which we evaluate here, is a critical dependency. First we distinguish between intravolumetric (realistic) and volumetric (unrealistic) motion and point out that metrics reported to-date assume volumetric . We simulate intravolume and volumetric motion with a novel acquisition (SimPACE), and compare the true and false positive rates of several motion metrics. We report that volumetric metrics generally perform poorly, with negative implications for censoring and global signal regression.

1602.   Subject-Motion Correction in HARDI Acquisitions: Choices and Consequences
Shireen Elhabian1, Yaniv Gur1, Joseph Piven2, Martin Styner2,3, Ilana Leppert4, G. Bruce Pike4,5, and Guido Gerig1
1Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah, United States, 2Psychiatry, University of North Carolina, North Carolina, United States,3Computer Science, University of North Carolina, North Carolina, North Carolina, United States, 4Neurology and Neurosurgery, Montréal Neurological Institute, Montréal, Quebec, Canada, 5Radiology, University of Calgary, Calgary, Canada

Diffusion weighted imaging (DWI) is known to be sensitive to motion originating from vibration, cardiac pulsation, breathing and subject movement, creating artifacts which require post-imaging correction. Users often do not fully understand the consequences of different choices for post-correction schemes for HARDI such as elimination versus alignment of affected DWIs with inherent choices of image interpolation, and how correction would affect ODF estimation, ability to resolve crossing fibers and final quantitative measures. We report about an experimental synthetic data platform and comparison with real data to systematically explore motion correction schemes under different scenarios to provide recommendations for best choices.

1603.   Motion Correction in Diffusion-Weighted Imaging using Intermediate Pseudo-Trace-Weighted Images
David Andrew Porter1 and Stefan Huwer1
1Healthcare Sector, Siemens AG, Erlangen, Germany

This paper introduces a new motion-correction technique for high-angular-resolution diffusion imaging studies. The method uses an optimized set of diffusion gradient vectors, which allows intermediate images to be calculated with a contrast that approximates to that of a trace-weighted image. The low contrast variation makes these intermediate images useful for motion tracking during the time series. Studies in healthy subjects suggest that the method delivers motion parameter estimates that are similar to those provided by interleaved low-b-value images. The temporal resolution can be optimized by using a sliding-window method, in which the intermediate image is updated after each diffusion-weighted volume.

1604.   Motion detection for 3D radial balanced SSFP sequences
Matthias Schloegl1, Clemens Diwoky1, and Rudolf Stollberger1
1Institute of Medical Engineering, Graz University of Technology, Graz, Austria

A novel method for intrinsic qualitative motion information detection for 3D radial balanced SSFP sequences is presented. Validation was performed for potential applications of correction for rigid head motion and self-gating cardiac CINE imaging. The comparison was carried out with low-resolution navigators and in the second case by comparison to the matched ECG signal. Results show that the method effectively captures motion variations or can serve as an ECG surrogate not requiring any additional external devices or internal navigators.

1605.   FID-guided retrospective motion correction based on autofocusing
Maryna Babayeva*1,2, Alexander Loktyushin*3, Tobias Kober2,4, Cristina Granziera5, Hannes Nickisch3, Rolf Gruetter1,6, and Gunnar Krueger2,4
1CIBM-AIT, École Polytechnique Fédérale de Lausanne and University of Lausanne, Lausanne, Switzerland, 2Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Switzerland, 3Max Planck Institute for Intelligent Systems, Tübingen, Germany, 4CIBM-AIT, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland,5Departments of Clinical Neurosciences, University Hospital Center (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland, 6Departments of Radiology, Universities of Lausanne and Geneva, Switzerland

This work investigates the possibility of using FID navigator signals to improve the performance of a recently proposed autofocusing-based retrospective motion correction technique. FID navigators were incorporated into an MPRAGE sequence and 3 subjects were scanned at 3T while performing head movements. The acquired data was retrospectively corrected for motion by exploiting the FID signals to constrain the unknown motion parameters. The results were compared against the reconstructions obtained from a non-FID-guided version of the algorithm, demonstrating that the use of FID navigators for retrospective motion correction leads to improvement in both image quality and computation time.

1606.   Comparison of Different Motion Correction Methods for PROPELLER MRI
Yilong Liu1, Zhe Liu2, Zhe Zhang1, Huailing Zhang3, and Hua Guo1
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, Beijing, China, 2Department of Biomedical Engineering, Cornell University, New York, United States, 3School of Information Engineering, Guangdong Medical College, Guangdong, China

Proper reference for motion estimation is critical for accurate and robust motion correction in PROPELLER MRI. In this work, single blade reference (SBR), combined blade reference (CBR), grouped blade reference (GBR) and Pipe et al¡¯s latest revised method in which no blade reference is required (NBR) are implemented and compared. Simulation results show that all methods above is accurate enough to generate a good image. For some special cases of in vivo imaging, SBR, CBR and GBR may fail to converge, while NBR still maintains relatively good performance, which indicates NBR is more robust.

1607.   Patient Motion: Small Annoyance or Call To Action?
Jalal B Andre1, Mahmud Mossa-Bosha1, Michael N. Hoff1, C. Patrick Smith2, and Wendy Cohen1
1Radiology, University of Washington, Seattle, WA, United States, 2Radiology, Harborview Medical Center, Seattle, WA, United States

Patient motion frequently degrades clinical MR examinations, but its prevalence remains unknown. We sought to assess the prevalence of significant patient motion in MR examinations of the neuroaxis by manually evaluating images sent to PACS. 55 of the 175 total neuroaxis MRI examinations completed in one calendar week were sent to PACS with at least some motion degradation (31.4%). We conservatively estimate that motion-related imaging costs approach $296,092.00/year at our institution. Since patient motion may be common in the global MR community, we suggest that attention be directed toward providing more practical solutions to this common problem.

1608.   Retrospective Motion Correction of T2* Maps Improves Interpretability of Brain Pathologies
Ulrike Nöth1, Steffen Volz1, Elke Hattingen2, and Ralf Deichmann1
1Brain Imaging Center (BIC), Goethe University Frankfurt/Main, Frankfurt/Main, Germany, 2Institute of Neuroradiology, University Hospital Frankfurt/Main, Frankfurt/Main, Germany

A method for reducing motion artefacts in quantitative T2* maps is presented, based on repeated acquisitions with reduced spatial resolution. Raw data are averaged with weighting factors individually chosen for each k-space line, so the influence of corrupted lines is strongly reduced. A study performed on healthy subjects performing pre-trained motion shows that corrupted lines are reliably detected and suppressed. In a study on tumour patients, pathological details visible in a T2-weighted reference image are replicated in the motion corrected T2* map, whereas the uncorrected T2* map yields artefacts that can easily be misinterpreted as additional lesions.

1609.   Collapsed FatNav - A 3D Motion Navigator Using the Chemical Saturation RF-pulse
Mathias Engström1,2, Magnus Mårtensson1,3, Ola Norbeck2, Enrico Avventi1, Axel Hartwig2, and Stefan Skare1,2
1Clinical Neuroscience, Karolinska Institutet, Stockholm, Stockholm, Sweden, 2Neuroradiology, Karolinska University Hospital, Stockholm, Stockholm, Sweden, 3EMEA Research and Collaboration, GE Applied Science Laboratory, GE Healthcare, Stockholm, Sweden

The chemical saturation pre-pulse is investigated as a source for rigid-body motion correction, utilizing three orthogonal, highly accelerated, EPI readouts.

1610.   Improved Reconstruction of Free-Breathing Abdominal PROPELLER MRI: A Preliminary Study
Dallas C Turley1, Michael Schär2, and James G Pipe1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ, United States, 2Philips Healthcare, Cleveland, OH, United States

Abdominal MRI presents many imaging challenges due to non rigid-body motion of respiration. Continuous data acquisition during free breathing is fastest and most comfortable for patients but respiratory motion must be corrected in order to obtain high quality images. In a T2-weighted free-breathing PROPELLER exam, instructing patients to pause 2-3 seconds after exhalation improved image sharpness without adding substantial patient discomfort. Respiratory motion was captured with bellows and the waveform was used as additional data to weight PROPELLER reconstruction in favor of blades collected during end-exhalation, reducing the effects of respiratory motion.

1611.   Slice-Localized Soft-Gating for Non-rigid Motion Correction in Free-Breathing 3D Cartesian MRI
Joseph Y. Cheng1,2, Tao Zhang1, Xinwei Shi1, Martin Uecker3, Marcus T. Alley2, John M. Pauly1, Michael Lustig3, and Shreyas S. Vasanawala2
1Electrical Engineering, Stanford University, Stanford, California, United States, 2Radiology, Stanford University, Stanford, California, United States, 3Electrical Engineering & Computer Sciences, University of California, Berkeley, California, United States

Soft-gating (or motion-based weighting) reconstruction can reduce motion artifacts in free-breathing MRI. However, the performance of this method depends on the accuracy of the motion-based weights. For respiratory motion, the degree of motion varies throughout space. For 3D Cartesian imaging, 1D spatial localization can be achieved by transforming the data into the hybrid (x,ky,kz)-space. Taking advantage of this, x-slice specific weights are derived and applied to correct for the varying non-rigid motion on a slice-by-slice basis. The proposed technique is applied to free-breathing abdominal imaging of pediatric patients. Improvement over no soft-gating and soft-gating with a single set of weights are shown.

1612.   Feasibility of entire cardiac MRI examinations during free breathing using GRICS motion correction
Freddy Odille1,2, Bailiang Chen1,2, Anne Menini1,2, Pauline Ferry1,2, Marine Beaumont2,3, Jacques Felblinger1,2, and Laurent Bonnemains1,2
1U947, Inserm, Nancy, France, 2IADI, Université de Lorraine, Nancy, France, 3CIC-IT 801, Inserm, Nancy, France

Cardiac MRI conventionally relies on a large number of breath holds. This is relatively inefficient as it results in a high scanner idle time and motion inconsistencies (misalignment between sequences). In this work we evaluate the feasibility and potential benefits of performing a whole cardiac examination during free-breathing using GRICS non-rigid motion correction. The approach was validated in 5 Duchenne muscular dystrophy patients with a cardiac protocol including free-breathing function (2D short-axis SSFP with whole heart coverage) and fibrosis assessment (post-contrast cine and 3D late enhancement). These preliminary results indicate diagnostic quality can be achieved along with good motion consistency.

1613.   Sensitivity of Modulated Refocusing Flip Angle Single-Shot Fast Spin Echo to Impulsive Cardiac-Like Motion
Daniel V Litwiller1, James H Holmes2, Manojkumar Saranathan3, Andreas M Loening3, James F Glockner4, Shreyas S Vasanawala3, and Ersin Bayram5
1Global MR Applications and Workflow, GE Healthcare, Rochester, MN, United States, 2Global MR Applications and Workflow, GE Healthcare, Madison, WI, United States,3Department of Radiology, Stanford University, Palo Alto, CA, United States, 4Department of Radiology, Mayo Clinic, Rochester, MN, United States, 5Global MR Applications and Workflow, GE Healthcare, Houston, TX, United States

Modulated refocusing flip angle single-shot fast spin echo (SSFSE) is of particular interest for pediatric and breath-held abdominal imaging. When low minimum refocusing flip angles are utilized with this technique in the presence of motion, however, as in the liver, images may suffer from signal loss due to cardiac motion. In this work, we characterize the empirical sensitivity of this modulated SSFSE technique to impulsive cardiac-like motion and validate our findings in vivo.

1614.   Robust automated Navigator tracker positioning for MRI liver scans
Takao Goto1, Shiro Ozaki2, Koji Uchida3, Hajime Kitagaki3, and Hiroyuki Kabasawa1
1Global MR Applications and Workflow, GE Healthcare, Hino-shi, Tokyo, Japan, 2Shimane University Hospital, Izumo-shi, Shimane, Japan, 3Department of Radiology, Shimane University Faculty of Medicine, Izumo-shi, Shimane, Japan

We present a robust method for automated positioning of a Navigator tracker for MRI liver scans. Our method detects the dome peak of the liver and uses it for Navigator tracker positioning. We used AdaBoost to extract liver dome shape following detection of the edges close to the liver dome and identify the dome peak. During application of our method to 118 volunteers and 53 patients, the tracker did not show any significant mistakes and performed slice tracking successfully. We expect our practical approach to assist the scanning operator and improve workflow.


Artifacts Correction

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

1615.   Method for B0 off-resonance mapping by non-iterative correction of phase errors
Junmin Liu1, David W Holdsworth1,2, and Maria Drangova1,2
1Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada,2Department of Medical Biophysics, Schulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada

Phase unwrapping techniques are conventionally used for B0 mapping. However, perfect unwrapped phase images are still very difficult to obtain. We present a novel non-iterative phase-unwrapping-based field mapping method. The method uses a raw fat-fraction map estimated from multi-echo magnitude images followed by histogram analysis of phase images to generate an accurate B0 map; both global and local phase errors are removed. The method is tested with a large number of data sets, including all cases from 2012 ISMRM Challenge.

1616.   Fast low-SAR B0-mapping along projections at high field using two-dimensional RF pulses
Olivier Reynaud1, Daniel Gallichan1, Benoit Schaller1, and Rolf Gruetter1
1CIBM, Lausanne, Switzerland

At 7T, conventional static field (B0) projection mapping techniques (FASTMAP, FASTESTMAP) suffer from elevated SAR and force long acquisition times (TA). Here the series of adiabatic pulses needed for pencil selection is replaced by a single 2D-RF pulse in the small tip angle regime. After in-vivo characterization of the selection profile, results (N=7, 6 VOIs) show no significant difference between the water spectral linewidths obtained with the conventional adiabatic (TA = 4 min) and the optimized 2D-RF FASTMAP sequence (TA = 42 s). In addition, SAR is reduced by two orders of magnitude without impact on shimming or spectrum quality.

1617.   Bilateral shimming of the breast at 7T
Vincent O. Boer1, Mariska P. Luttje2, Peter R. Luijten1, and Dennis W.J. Klomp1
1radiology, UMC Utrecht, Utrecht, Utrecht, Netherlands, 2radiotherapy, UMC Utrecht, Utrecht, Utrecht, Netherlands

Bilateral shimming of the breast puts higher restraints on shimming capabilities as compared to unilateral shimming. Where unilateral shimming can be performed well with 2nd order spherical harmonics, we show that up to fourth order spherical harmonics do not reach the same field homogeneity for bilateral shimming. A midplane shimcoil was designed and used to generate a locally varying field, which was able to compensate the fields in bilateral shimming to a degree beyond that possible with fourth order shimming.

1618.   Correction of B0 field fluctuations in the breast at 7 tesla by fitting a dipole field to field probe data – A simulation study
Tijl A. van der Velden1, Dennis W.J. Klomp1, Peter Luijten1, and Vincent O Boer1
1Radiology, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

Respiration causes motion of boundaries with large susceptibilities differences, such as the shoulders, the heart and the diaphragm. These motions can cause artefacts in a variety of MR scans. With field probes the field fluctuations caused by this motion can be observed. However, these probes measure the field outside the body. In this simulation study we suggest to fit a dipole to field probe measurements to translate field fluctuations from outside the body to field fluctuations inside the breast.

1619.   Off-resonance correction of 23Na spiral trajectories based on a 1H B0-map at 7T
Paul W. de Bruin1, Maarten J. Versluis1, Sebastian A. Aussenhofer1, Peter Börnert1,2, and Andrew G. Webb1
1Radiology Department, Leiden University Medical Center, Leiden, Netherlands, 2Innovative Technologies Research Laboratories, Philips Technologie GmbH, Hamburg, Germany

Off-resonance correction of spiral 23Na trajectories using a 1H B0-map is used to achieve a completely free modest increase in SNR which is beneficial for quantitative 23Na imaging.

1620.   Correction of B0 Phase Errors for Spiral-in/Spiral-out Acquisitions
Ryan K Robison1, Zhiqiang Li1, Michael Schär1,2, and James G Pipe1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, United States, 2Philips Healthcare, Cleveland, Ohio, United States

Spiral-in/spiral-out acquisitions can be affected by artifacts that manifest differently between the spiral-in and spiral-out portions of the acquisition. If uncorrected these artifacts will be accentuated in the final combined image. Time dependent phase errors from B0 eddy currents are one source of artifacts that manifest differently between spiral-in and spiral-out acquisitions. These phase errors were measured and corrected. The resulting images demonstrate improvements in apparent resolution.

1621.   High-accuracy off-resonance estimation from EPI, with application to volumetric navigators (vNavs) enabling real-time motion and frequency correction
M. Dylan Tisdall1,2 and André J. W. van der Kouwe1,2
1A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, United States, 2Radiology, Harvard Medical School, Boston, Massachusetts, United States

The phase-correction navigators of EPI sequences have previously be shown to enable real-time estimation and prospective correction of resonance frequency drift. In the present work we describe a novel algorithm that provides more accurate estimates than previous methods. We also demonstrate how a small modification to our EPI-based volumetric navigator (vNavs), allows us to use it not just for prospective motion correction, but also prospective frequency correction. Results from a vNav-enabled MPRAGE sequence are shown.

1622.   Joint Field Map and Metabolite Image Reconstruction Framework for Hyperpolarized 13C Spiral CSI
Ulrich Koellisch1,2, Rolf F. Schulte2, Markus Durst1,2, Axel Haase1, and Florian Wiesinger2
1IMETUM, Technical University München, Munich, Germany, 2GE Global Research, Munich, Germany

An algorithm for IDEAL spiral CSI reconstruction of hyperpolarized 13C metabolites is presented. It calculates field maps or CS frequencies and metabolite images with a joint estimation approach. The field maps gets estimated by a set of polynomials. The estimation of the CS-frequencies decreases the number of necessary excitations, because no extra spectra have to be recorded. The application of the off-resonance correction on in-vivo datasets has shown, that this approach increases the image quality due to a reduced amount of blurring in the metabolite maps.

1623.   Evaluation of dynamic off-resonance correction of respiratory instability in MRI signals for high-order spherical harmonic basis set and multivariate modeling of respiratory sources
Marta Bianciardi1, Jonathan R Polimeni1, Kawin Setsompop1, Cornelius Eichner1, Berkin Bilgic1, and Lawrence L Wald1
1Department of Radiology, A.A. Martinos Center for Biomedical Imaging, MGH, Harvard Medical School, Boston, MA, United States

Chest motion due to respiration produces off-resonance (OR) effects in the brain, resulting in signal-instability in both structural and functional MRI. Previous work performed dynamic OR-correction using a second-order spatial model, and a univariate temporal respiratory model. Aim of this work was to evaluate dynamic OR correction for increased degrees-of-freedom in both spatial and temporal domain. Our results demonstrate the benefits of higher order (up to the fifth) spatial models combined with the use of bivariate temporal modeling of respiratory effects. These findings show the expected dynamic capabilities of high-order shim-arrays at high magnetic field and on a whole-brain basis.

1624.   Simulation of Respiration-Induced B0 Shifts in the Heart
Anjali Datta1, Reeve Ingle1, Bob Hu1,2, and Dwight Nishimura1
1Electrical Engineering, Stanford University, Stanford, California, United States, 2Cardiology, Palo Alto Medical Foundation, Palo Alto, California, United States

Respiration-induced B0 variations are of interest because they may lead to off-resonance artifacts in free-breathing acquisitions and may contribute to variable image quality across patients. Using the XCAT1 4D computational phantom to generate susceptibility models, we simulate the main field map over the heart in several respiratory frames and in different anatomies to determine if B0 variations across the breathing cycle and between individuals may be significant. This work suggests that respiration induces spatially-variant B0 shifts in the heart and that the magnitude and distribution depend on the left ventricular long-axis orientation.

1625.   Dynamic Slice-Optimized Shimming in Continuous Moving bed MRI
Saikat Sengupta1,2, David Smith1,2, and E. Brian Welch1,2
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, 2Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

Continuous moving bed MRI (COMBI) is a high throughput imaging technique for rapid whole-body examination. A primary limitation of COMBI is that the frequency and B0 shims are typically optimized for only one body location. As a result, image quality and parameter quantification suffers from field variations along the extent of the body. In this abstract, we present slice-specific zeroth and first order dynamic B0 shimming in COMBI. Slice-optimized shimming is demonstrated on a 1.500 meter field of view phantom setup with significant field homogeneity gains throughout the full field of view over a static single station shim.

A Structured MRI Phantom with the Magnetic Susceptibility of Air
Simon Gross1, Christoph Barmet1,2, Thomas Schmid1, and Klaas Paul Prüssmann1
1Institute for Biomedical Engineering, ETH and University Zurich, Zurich, Switzerland, 2Skope Magnetic Resonance Technologies, Zurich, Switzerland

By doping epoxide-resins with paramagnetic substances, solid materials with widely adjustable magnetic susceptibility can be produced. With this method, we built an MR phantom whose susceptibility is matched to air (including the liquid filling). It has the unique properties of not affecting the magnetic field homogeneity, neither internally nor externally, turning it into a versatile tool for sequence development and quality assurance in MR imaging and spectroscopy. Furthermore, the excellent mechanical properties of this material allow the construction of NMR equipment and consumables that are invisible within the magnetic field.

1627.   Artifact Correction in Temporal Bone Imaging with GS-bSSFP
Michael N Hoff1, Greg J Wilson1, Qing-San Xiang2,3, and Jalal B Andre1
1Department of Radiology, University of Washington, Seattle, WA, United States, 2Department of Radiology, University of British Columbia, Vancouver, BC, Canada,3Department of Physics, University of British Columbia, Vancouver, BC, Canada

The geometric solution (GS) is clinically applied to correct artifacts in balanced steady state free precession (bSSFP) images of the temporal bone at 3T. Four phase cycled bSSFP brain images are acquired from a patient, and a pixel-by-pixel GS is computed in the complex plane and compared with a complex average of the images. The solution not only eliminates bSSFP banding and dependence on signal off-resonance, it also shows an insensitivity to motion. Further testing is planned in order to determine the GS’ capacity for correcting motion artifacts.

1628.   Homodyne Reconstruction for Single-Echo Dixon Imaging
Eric G. Stinson1, Joshua D. Trzasko1, and Stephen J. Riederer1
1Mayo Clinic, Rochester, Minnesota, United States

Dixon-based methods avoid errors by accounting for B0 inhomogeneities during the fat-water separation, but can extend scan time. Single-echo Dixon techniques avoid this limitation, but have yet to use partial Fourier sampling. Homodyne reconstruction for partial Fourier single-echo Dixon imaging is derived and experimentally demonstrated. The processing is performed within the framework of a phase constrained reconstruction and accomplishes fat-water separation and homodyne phase correction in a single step. Partial Fourier sampling with homodyne processing can reduce scan time by a factor of almost 2 and shows promise for time-resolved Dixon imaging for dynamic applications such as CE-MRA.

1629.   Robust Partial Fourier Parallel Imaging Using ESPIRiT and Virtual Conjugate Coils
Martin Uecker1 and Michael Lustig1
1Electrical Engineering and Computer Sciences, University of California, Berkeley, California, United States

ESPIRiT is a recently developed algorithm for auto-calibrated parallel MRI. It is based on an eigenvalue analysis of the calibration data. The present work describes an extension using virtual conjugate coils, which allows the estimation of sensitivity maps which include image phase. Such maps can be used in a phase-constrained SENSE reconstruction for acceleration with partial Fourier sampling. In contrast to other methods, high-frequency phase is not simply discarded but taken into account by a second eigenvector map in affected image regions. This map can be used in an extended soft-SENSE reconstruction which is robust against errors from high-frequency phase.

1630.   A phase constrained reconstruction method in compressed sensing
Guobin Li1, Maxim Zaitsev1, Esther Meyer2, Dominik Paul2, Jan Korvink3,4, and Jürgen Hennig1
1University Medical Center Freiburg, Freiburg, Baden-Württemberg, Germany, 2Siemens Healthcare, Germany, 3Department of Microsystems Engineering — IMTEK, University of Freiburg, Baden-Württemberg, Germany, 4Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Baden-Württemberg, Germany

Half Fourier acquisition has widely been used for a long time to shorten the measurement time in turbo spin echo sequences.The combination of half Fourier acquisition with compressed sensing has also been investigated. One drawback of typical Homodyne and POCS based methods is that they brutally replace the phase of the resulting images by an estimate. We introduce a relaxed phase constraint term in the regularized reconstruction, to encourage the phase consistency between the result and the estimation, instead of an overall phase replacement in the compressed sensing reconstruction with half Fourier acquisition.

1631.   Phase Correction for 3D Fast Spin Echo Imaging With Compressed Sensing
Weitian Chen1, Peng Lai1, and Yuval Zur2
1Global MR Applications & Workflow, GE Healthcare, Menlo Park, CA - California, United States, 2GE Healthcare, Haifa, Haifa, Israel

Fast spin echo imaging plays a central role in clinical imaging. Eddy current and other factors, however, can introduce phase error in FSE sequences, which causes the violation to CPMG condition and result in image artifacts. The existing phase correction method works well for 2D FSE, which assumes a linear phase error along readout direction. However, to extend this approach to 3DFSE, we may need assume a linear phase error along both readout and slice direction, which may not always be the case. Data acquisition with phase cycling can be used to address this problem at the cost of doubled scan time. In this work, we investigated compressed sensing acceleration of data acquisition for 3DFSE phase correction using phase cycling.

1632.   3D EPI Phase Maps for Real Time EPI Distortion Correction
A. Alhamud1, Paul A. Taylor1, André J.W. van der Kouwe2, and Ernesta M. Meintjes1
1Human Biology,MRC/UCT Medical Imaging Research Unit, University of Cape Town, Cape Town, Western Cape, South Africa, 2Massachusetts General Hospital, Charlestown, Massachusetts, United States

Single- or multi-shot Echo Planar Imaging (EPI) is the first choice for several imaging modalities such as diffusion tensor imaging (DTI) and functional MRI (fMR) etc, due to its ability to acquire images very rapidly. EPI is affected by several artifacts such as distortion from magnetic field inhomogeneity. Although several techniques have been reported for correcting the B0 homogeneity, these methods have some limitations and drawbacks. In this work we introduce a sophisticated method using the 3D EPI phase maps to correct TR-by-TR in real time the distortion in B0 for any imaging modality that implement EPI.

1633.   Distortion Correction in DW-EPI using an Extended PSF Method with a Reversed Gradient Approach
Myung-Ho In1, Oleg Posnansky1, Erik B. Beall2, Mark J. Lowe2, and Oliver Speck1,3
1Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany, Magdeburg, Germany, 2Radiology, Imaging Institute, Cleveland Clinic, Cleveland, OH, USA, OH, United States, 3Leibniz Institute for Neurobiology, Magdeburg, Germany, Magdeburg, Germany

In echo-planar imaging (EPI), compressed distortion is a more difficult challenge than local stretching as spatial information can be lost in strongly compressed areas. To resolve this problem, two EPIs with opposite phase-encoding (PE) polarity were acquired and combined after distortion correction. A modified point spread function (PSF) mapping and distortion correction method was developed. A single PSF reference acquisition was extrapolated to reverse PE (extended) for reverse PE correction and an improved weighted combination of the two distortion-corrected images that properly accounts for the differential loss of information in forward and reverse PE images.

1634.   EPI distortion correction using highly under-sampled point-spread function estimation based on Finite Rate of Innovation
Rita G. Nunes1,2 and Joseph V. Hajnal2,3
1Institute of Biophysics and Biomedical Engineering, Faculty of Sciences, University of Lisbon, Lisbon, Portugal, 2Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom, 3Centre for the Developing Brain, King's College London, London, United Kingdom

With the drive to higher B0 magnetic fields, geometric distortion correction of Echo Planar Images (EPI) becomes essential. Point Spread Function (PSF) mapping has been shown to be more robust than B0 field mapping, however previous attempts to accelerate acquisition, still required a minimum of 10 EPI repeats. We demonstrate that by using a pattern search approach it is possible to estimate the peak of the PSF at each voxel from as little as 2 EPI repeats, one of which is the EPI image itself. This would enable estimation of distortion maps to be incorporated in standard EPI preparation phases.

1635.   Slice-specific frequencies can reduce ghosting artifacts in T2*-weighted single-shot EPI with GRAPPA
Jürgen Finsterbusch1,2
1Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, 2Neuroimage Nord, Hamburg-Kiel-Lübeck, Germany

In regions with magnetic field inhomogeneities, e.g. close to significant susceptibility differences as in the vicinity of major air cavities, T2*-weighted single-shot EPI with GRAPPA is susceptible to ghosting artifacts. To some extend, these artifacts seem to be related to the offset of the resonance frequency that is not handled appropriately by the GRAPPA reconstruction algorithm. Here, it is shown that with slice-specific frequencies for the data acquisition, i.e. the analog-to-digital converter’s demodulation frequency and phase settings, these artifacts can be reduced or even avoided.

1636.   Slice-specific navigator correction for multiband imaging
Steen Moeller1, An T Vu1, Edward Auerbach1, Kamil Ugurbil1, and Essa Yacoub1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States

The use of a slice specific navigator correction for both the SENSE/GRAPPA algorithm and the slice-GRAPPA algorithm is demonstrated and compared with high quality data from the Human Connectome project.

1637.   Slice-wise Nyquist Ghost Correction for Slice-Accelerated EPI
Eric Peterson1, Samantha Holdsworth1, Rafael O'Halloran1, Julian Maclaren1, Eric Aboussouan1, William Grissom2, and Roland Bammer1
1Radiology, Stanford University, Stanford, CA, United States, 2Biomedical Engineering, Vanderbilt, Nashville, TN, United States

When using slice-accelerated echo planar imaging (EPI), slice-wise Nyquist ghost correction requires extra scan time because it necessitates an additional pre-scan (reference scan) in addition to parallel imaging calibration. This work presents a method to perform slice-wise Nyquist ghost correction using the parallel imaging pre-scan. This obviates the Nyquist ghost correction pre-scan and also allows for Nyquist ghost correction before the parallel imaging is performed, which allows for standard parallel imaging reconstructions. More importantly, by not requiring an additional pre-scan scan, it allows for a faster, more streamlined scan session.

1638.   Improved ghost-correction in multi-shot EPI using PLACE and GESTE
W Scott Hoge1,2, Huan Tan3, Robert A Kraft4, and Jonathan R Polimeni2,5
1Brigham and Women's Hospital, Boston, Massachusetts, United States, 2Harvard Medical School, Boston, MA, United States, 3Department of Surgery (Neurosurgery), University of Chicago, Chicago, Illinois, United States, 4Virginia-Tech Wake Forest School of Biomedical Engineering, Winston-Salem, NC, United States, 5A.A. Martinos Center for Biomedical Imaging, MGH, Charlestown, MA, United States

This works seeks to further improve the correction of Nyquist ghosting in multi-shot (or segmented) echo planar imaging. EPI is vulnerable to static local field inhomogeneity and eddy current effects induced by the EPI readout, which results in Nyquist ghosting. Multi-shot EPI is further complicated by phase inconsistencies that often occur between the acquisition of each segment. PLACE and GESTE have been shown previously to provide superior ghost correction in single-shot EPI images. We demonstrate their further effectiveness in segmented EPI with in-vivo brain data acquired at 7T using a 32-channel head coil.

1639.   A comparison of the static and dynamic phase correction methods in timeseries EPI with parallel imaging
Wanyong Shin1, Sehong Oh1, and Mark J Lowe1
1Radiology, Cleveland Clinic, Cleveland, Ohio, United States

To correct Nyquist ghost artifacts in single-shot EPI, 2 or 3 lines of readout acquisition without a phase encoding gradient is commonly applied. While the phase correction information is updated for each measurement for timeseries of EPI, the phase shift could be corrected either by using single phase correction scan (called static here) or each phase correction scan (dynamic). In the abstract, we evaluated the performance of the dynamic and static phase correction in timeseries EPI. We found the static phase correction provides higher tSNR and less spatial variation of tSNR than the dynamic phase correction with parallel imaging technique.

1640.   Simultaneous Nyquist ghost and Geometric distortion correction based on reversed readout strategy in EPI
Victor B. Xie1,2, Adrian Tsang1,2, and Ed X. Wu1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, Hong Kong SAR, China, 2Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, Hong Kong SAR, China

Echo planar imaging (EPI) has been used in many applications such as fMRI and DWI. However, EPI images are prone to Nyquist ghost and geometric distortion.In this study, we proposed a new scheme based on reversed readout strategy to correct both Nyquist ghost and geometric distortion artifacts on EPI images simultaneously. We have demonstrated the proposed method can effectively remove Nyquist ghost and correct geometric distortion both in phantom and rat brain. This method may be paticularly suited for dynamic EPI protocols such as fMRI and dynamic contrast-enhanced MRI applications.

Referenceless Reconstruction of Spatiotemporally-Encoded Imaging Data
Amir Seginer1, Rita Schmidt1, Eddy Solomon1, Avigdor Leftin1, and Lucio Frydman1
1Chemical Physics Department, Weizmann Institute of Science, Rehovot, Israel

Single-shot sequences utilizing spatiotemporal encoding (SPEN) provide robust alternatives to single-shot EPI with similar acquisition durations and comparable resolution, provided that specialized super-resolved reconstruction algorithms are used in the image retrieval. Acquisition imperfections known to cause ghosting artifacts in EPI, can also give rise to artifacts in processed Hybrid-SPEN images. We demonstrate that these experiments, unlike EPI, do not require a reference scan to correct for these imperfections. A self-referencing algorithm based on the fact that under-sampling along the SPEN direction does not generate aliasing, but rather lower resolution images, is developed. The referenceless algorithm and sample results are presented.

1642.   Reception sensitivity inhomogeneity correction at ultra high field using a fast gradient echo sequence
Franck Mauconduit1, Aurélien Massire2, Nicolas Boulant2, Alexis Amadon2, and Alexandre Vignaud2
1Siemens Heathcare, Saint Denis, France, 2CEA, DSV, I2BM, Neurospin, LRMN, Gif-Sur-Yvette, Ile de france, France

UHF suffers from significant inhomogeneity artifacts originating from transmission RF and reception sensitivity coils. In vivo measurement approaches have been proposed earlier. Based on these approaches, we suggest a very short TR GRE sequence to reduce image unihomogeneity. On a Siemens 7T Magnetom scanner, a B1 field map (AFI) and a GRE sequence with minimal tissue contrast are acquired. Then the GRE sequence is low pass filtered and a post processing corrects reception sensitivities on an MPRAGE acquisition. Our result shows a significant improvement using a GRE sequence with TR=9ms and 10 sec acquisition therefore providing a fast correction method.

1643.   A simple method for cusp artifact removal by gradient optimization
weiwei zhang1, Bing Wu1, and Yongchuan Lai1
1GE Healthcare, Beijing, Beijing, China

In this abstract, we proposed an easy-to-implement method to eliminate cusp artifacts, or called annefact, by optimizing the pulse sequence design in FSE. The gradient polarities for excitation and refocusing RF slice selection are the same. However, the amplitudes of excitation and refocusing gradients are optimized individually so that location shift of excited spins by the two RF is minimized, whereas the annefact regions correspond to the two RF are separated. The former ensures no signal drop takes place. The latter ensures no cusp artifact is formed. This method requires no additional post-processing and hardware modification.

1644.   Spatiotemporally encoded single-shot MRI based on de-convolution reconstruction on 3.0 T human scanner
Jianfeng Bao1,2, Congbo Cai2, Zhong Chen2, and Jianhui Zhong1
1Department of Imaging Sciences, University of Rochester, Rochester, NY, United States, 2Department of Electronic Science, Xiamen University, Xiamen, Fujian, China

Spatiotemporally encoded (SPEN) imaging is an emerging ultrafast MRI method that can be used to obtain 2D image in a single shot, with much less sensitivity to B0 inhomogeneity compared with EPI. However, a super-resolved reconstruction method is needed to improve spatial resolution of the SPEN image. Recently, we have demonstrated that the de-convolution reconstruction method is superior to other existing methods in simulations and studies on 7 T small animal scanner. Here, we show that the de-convolution can obtain artifact-free and high resolution images on human brain at 3.0T. This emerging ultrafast MRI method may be applied to reduce artifacts caused by B0 inhomogeneity in fMRI and DTI images.

1645.   Non-Linear Correction of 3D R2* Maps with Fast through-Plane Gradient Mapping Computation
Chemseddine Fatnassi1,2, Gunnar Krueger2,3, Reto Meuli1, and Kieran O'Brien2,4
1Université de Lausanne/Centre Hospitalier Universitaire de Lausanne, Lausanne, Switzerland, 2CIBM - AIT, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 3Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Switzerland, 4Hôpitaux Universitaires de Genève, Genève, Switzerland

In 3D GRE, B0macro field gradients due to air/tissue interfaces lead to an apparent increase in the intravoxel dephasing and leads to large signal loss or inaccurate R2* estimation. If these B0macro are measurable, their influence can be removed. The algorithms normally assume the phase evolves linearly with time; however, in the presence of a large B0macro, this assumption is broken, Furthermore, the central difference approximation used to estimate gradient leads to edge artifacts at the brain's edges. To overcome these problems, we hypothesize a non-linear phase evolution including a fast computation of the through-plane gradient.

1646.   Image entropy-based phase correction for closely-spaced slices in simultaneous multi-slice imaging
Angus Z. Lau1,2, Elizabeth M. Tunnicliffe1, Damian J. Tyler1,2, and Matthew D. Robson1
1Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom, 2Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, United Kingdom

Blipped CAIPI acquisitions reduce g-factor noise amplification in simultaneous multi-slice (SMS) experiments by introducing inter-slice image shifts using through-plane phase encoding gradients during the image readout. For closely-spaced slices, large Gz blips result in N-fold image ghosts (where N is the SMS factor), which overlap with the desired multlband aliasing pattern. In this abstract, we introduce a simple deconvolution model and novel image entropy-based approach to correcting phase errors in a SMS scan. The method does not require an additional reference scan, and we anticipate that this development will enable SMS accelerated scans of the heart with closely spaced slices.

1647.   Deblurring in View angle tilting imaging
Min-Oh Kim1, Semin Kwak1, and Dong-Hyun Kim1
1Electrical and Electronic Engineering, Yonsei University, Seoul, Seoul, Korea

View angle tilting (VAT) technique was proposed to correct chemical shift artifact and in-plane field inhomogeneity artifact. In spite of its advantages, VAT suffers from blurring artifact. In this study, post-processing methods that can alleviate VAT blurring based on VAT signal equation are presented.

1648.   A technique to eliminate artifacts in 3D Fast Spin Echo Imaging
Yuval Zur1 and Weitian Chen2
1GE Healthcare, Tirat Carmel, Israel, 2GE Healthcare, Menlo Park, California, United States

3D Fast Spin Echo (3DFSE) with flip angle modulation is used for high resolution T2 weighted imaging due to high T2 contrast and the ability to reformat the data in any desirable plane. Unavoidable violations of the CPMG condition due to system imperfections generate artifacts. In this work we present a technique to overcome this problem using a post processing method applied in conjunction with a two excitations approach. The drawback of the method is that two excitations are required. However, in many applications this method is necessary in order to acquire reliable high quality images.


Fat Suppression, Separation & Quantification

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

1649.   A New Fat-suppressed Spin-Echo Imaging Using Hyperbolic-Secant Pulses
Yoojin Lee1, Jang Yeon Park2, Yeji Han3, ChangHyun Oh3, and HyunWook Park3
1Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 2School of Biomedical Engineering, Konkuk University, Chungju, Korea,3Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea

In this study, a new fat-suppressed spin-echo imaging technique using hyperbolic secant (HS) RF pulses for π/2 excitation and π refocusing in a conventional SE sequence is proposed. This technique utilizes the fact that non-linear phase profile across slice created by HS pulses is not compensated in the regions where the frequency offset exists. Phantom and in vivo experiments were performed at 3T to demonstrate this technique.

1650.   Shaped Fat Saturation with 2D Spatially Selective Multi-Frequency RF Pulse Design in Parallel Transmission
Rainer Schneider1,2, Jens Haueisen2, and Josef Pfeuffer1
1MR Application Development, Siemens Healthcare, Erlangen, Bavaria, Germany, 2Institute of Biomedical Engineering and Informatics, TU Ilmenau, Ilmenau, Thuringia, Germany

Shaped fat saturation was realized for the first time on the basis of multi-frequency optimization of multidimensional spatially selective RF pulses in parallel transmission. Shaped fat saturation pulses were optimized based on a target-driven variable-density 2D spiral trajectory and evaluated in phantom and human in-vivo experiments and compared to the commonly used Gaussian FATSAT pulse. The fat saturation performance of the proposed RF pulses was found to be similar to the FATSAT pulse, but allowed also for the simultaneous saturation of other frequency bands. Furthermore, less interference with the water band was observed.

1651.   Fat Suppression Using Random Encoding Pulse Sequences
Haifeng Wang1, Yihang Zhou2, Yuchou Chang3, and Dong Liang4
1Department of Diagnostic Radiology, Yale University, New Haven, CT, United States, 2Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, NY, United States, 3Barrow Neurological Institute, Phoenix, AZ, United States, 4Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China

Many methods of fat suppression are applied, but the cost is more computational time or sequence durations. In this abstract, a novel fat suppression method, named as Hybrid, is proposed to suppress the fat signal and enhance the image contrast. The method exploits non-Fourier random encoding pulse sequences to generate inhomogeneous B1 filed, thus the signal contrast of fat and other tissues has been changed comparing the conventional Fourier encoding method. The actual in vivo human knee experiments illustrate the proposed method augment the signal contrast of fat and other tissues, suppress more the fat signal than the conventional Fourier method, and has no growth of imaging time and decoding computational complexity.

1652.   Simultaneous Fat Saturation and Magnetization Transfer Preparation with Steady-state Incoherent Sequences
Feng Zhao1, Jeffrey A Fessler2, Jon-Fredrik Nielsen1, and Douglas C Noll1
1Biomedical Engineering, The University of Michigan, Ann Arbor, MI, United States, 2EECS, The University of Michigan, Ann Arbor, MI, United States

Combining fat saturation and magnetization transfer (MT) preparation is beneficial in many clinical applications. The use of both fat sat and MT with steady-state incoherent (SSI) sequences may be limited by long minimal TR. Also, the conventional fat sat is sensitive to field inhomogeneity. We investigated a multi-dimensional spectral-spatial fat sat pulse for SSI sequences, i.e., small-tip fast recovery imaging (STFR) and spoiled GRE, to produce B0 insensitive fat suppression and MT preparation simultaneously. The methods were applied to cartilage imaging or MR angiography in brain at 3T.

1653.   Water or Fat selective 3D-bSSFP imaging combined with banding artifact correction for MSK imaging at 3T
Emeline Julie Ribot1, Jean-Michel Franconi1, and Sylvain Miraux1
1CNRS/University Bordeaux, RMSB, Bordeaux, France

Musculo-skeletal MRI with fat signal suppression techniques are usually performed in 2D to shorten acquisition time and obtain sufficient signal and induce restrictions in echo time or flip angle values. Due to high SNR acquired in short acquisition time in 3D, bSSFP sequence was combined to a frequency-selective binomial pulse at 3T. Centering the frequency of this pulse to the resonance frequency of water or fat protons generated fat-free or water-free images, respectively. To remove banding artefacts, four images acquired at different resonance frequencies were summed using « Sum-Of-Square ». This new sequence allowed to obtain 3D high-resolution knee images without fat signal and banding artefacts.

1654.   Water or Fat selective 3D-bSSFP imaging combined with banding artifact correction on small-animal at 7T
Emeline Julie Ribot1, Didier Wecker2, Jean-Michel Franconi1, and Sylvain Miraux1
1CNRS/University Bordeaux, RMSB, Bordeaux, France, 2Bruker Biospin, France

To obtain fat-free MR images on small animals, several techniques have been developed. Low SNR, susceptibility arfetacts and echo time value restrictions limit their application at high magnetic field. 3D-bSSFP MR sequence, generating high signal in short acquisition time, was performed after a frequency-selective binomial pulse at 7T. Water-selective or fat-selective mouse whole-body 3D-bSSFP images were obtained with no banding artefacts due to the combination with « Sum-Of-Square » technique. Chemical shift artifact was removed allowing for better delineation and quantification of lymph node volumes. In addition, tumors growing in the renal sup-capsule were easily identified from abdominal fat.

1655.   Jointly-Processing Fast Spin-Echo Triple-Echo Dixon Images with a Two-Point Dixon Phase Correction Algorithm
Jong Bum Son1, John Hazle1, and Jingfei Ma1
1Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States

Fast spin echo triple-echo Dixon (fTED) acquires one in-phase (IP) and two out-of-phase (OP) images in a single acquisition without interleave. A two-point Dixon processing algorithm is then used to independently process two pairs of IP/OP images. A potential drawback is that any processing failure in each processing will lead to incomplete local or global water and fat separation. In this work, we proposed and developed a jointly-processed region growing based two-point Dixon phase correction algorithm. The proposed approach was capable of reconstructing uniformly separated water and fat images even when anatomic regions are separated by large signal-void.

1656.   Off-Resonance Correction in PROPELLER using Dixon Water-Fat Separation
Holger Eggers1, Michael Schär2,3, and James G. Pipe3
1Philips Research, Hamburg, Germany, 2Philips Healthcare, Cleveland, OH, United States, 3Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ, United States

Combinations of PROPELLER and Dixon methods have recently been proposed to achieve motion insensitive water-fat imaging. They perform the water-fat separation after the PROPELLER reconstruction so far. However, applying the water-fat separation to single blades instead potentially offers several advantages. In this work, the feasibility of this approach is demonstrated in abdominal T2-weighted TSE imaging. By exploiting the Cartesian k-space sampling in single blades, an off-resonance correction for image quality enhancement is shown to become simpler in this way.

1657.   Variable Bandwidth Turbo Spin-Echo Dixon Imaging
Holger Eggers1
1Philips Research, Hamburg, Germany

The echo shifts commonly applied in turbo spin-echo Dixon imaging for chemical shift encoding affect the signal-to-noise ratio in the resulting in-phase and water images not only directly through the noise propagation in the water-fat separation, but also indirectly through the turbo spin-echo sequence. In this work, an optimization of the signal-to-noise ratio is proposed under the constraint of a fixed spacing between successive refocusing pulses. On the example of dual-echo Dixon imaging, it is shown to lead to shorter optimal echo shifts and to suggest a variable readout gradient strength, bandwidth and sampling window length per echo shift, which permits enhancing the signal-to-noise ratio.

1658.   Fat-water separation in the abdomen during free-breathing by using stack-of-star (SOS) 3D radial TrueFISP Imaging
Riad Ababneh1, Thomas Benkert2, and Felix Breuer2
1Physics Department, Yarmouk University, Irbid, Jordan, 2Research Center Magnetic Resonance Bavaria, Würzburg, Bavaria, Germany

We used a stack-of-stars 3D radial acquisition with non-uniform fast Fourier transform (NUFFT) gridding to separate fat and water signals of different respiratory phases in free-breathing.

1659.   Iterative Field Map Extraction for Spiral Water-fat Imaging
Dinghui Wang1, Nicholas R. Zwart1, Zhiqiang Li1, Michael Schär1,2, and James G. Pipe1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ, United States, 2Philips Healthcare, Cleveland, OH, United States

Spiral water-fat imaging suffers from blurring caused by B0 inhomogeneity and chemical shift of fat. Long spiral readout is efficient but often results in blurred and erroneous B0 field map at the interface of water and fat, and/or in regions of rapidly varying B0. We propose two approaches to iteratively correct and refine the initial field map obtained from Dixon water-fat imaging. Both methods employ a previously presented approach that simultaneously separates and deblurs water and fat. In vivo experiment results have demonstrated the feasibility of both approaches.

1660.   Spiral CG Deblurring and Fat-Water Separation using a Multi-peak Fat Model
Nicholas Ryan Zwart1, Dinghui Wang1, and James Grant Pipe1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, United States

Blurring in spiral images can be caused by both field inhomogeneity and chemical shift. The method presented in this work addresses both by simultaneously separating fat-water signal and deblurring. A multi-peak fat model has been added to the previously presented algorithm, making the algorithm more robust while maintaining the same reconstruction time as the single-peak model.

1661.   Joint Water-fat Separation and Deblurring with Spiral In-out Sampling
Dinghui Wang1, Zhiqiang Li1, Ryan K. Robison1, Nicholas R. Zwart1, Michael Schär1,2, and James G. Pipe1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ, United States, 2Philips Healthcare, Cleveland, OH, United States

Spiral in-out is an efficient sampling scheme, especially for spin echo and T2* weighted sequences. Two images can be reconstructed from the spiral-in and spiral-out parts respectively. Based on a previous conjugate gradient method, we propose an iterative approach to simultaneously separate and deblur water and fat using these two images with known B0 inhomogeneity. Ringing artifacts can arise at sharp boudaries since different frequences at the k-space converge at various speeds. In-vivo data have confirmed that the ringing artifacts can be eliminated by the assumption that water and fat are in phase at time 0.

1662.   Analytical Three-point Water-fat Imaging with Multi-peak Fat Model
Dinghui Wang1 and James G. Pipe1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ, United States

We propose an analytical approach of three-point water-fat Dixon imaging with a known multi-peak fat model. This approach works with flexible even and uneven TE increments. By selecting appropriate TE points, spatial phase unwrapping can be avoided. This method solves the quadratic equations of water and fat. If the TE points are selected such that the magnitude of fat fluctuates significantly, a substantial portion of pure water and pure fat voxels can be identified according to the asymmetry between water and fat. The efficiency and robustness of the subsequent post-processing will thus be enhanced.

1663.   A Parallelizable Multi-threaded and Multi-leveled Region-Growing Based Algorithm for Phase Correction in MRI
Jingfei Ma1, Jong Bum Son1, and John Hazle1
1Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States

We present a parallelizable region growing algorithm for phase correction in MRI. An image is divided into sub-images in which region growing is independently initiated from seed pixels and temporarily halted at a pre-defined quality threshold. Results from different sub-images are compared and then merged to form consistent pixel islands. Finally, region growing is resumed from the pixel islands by gradually relaxing the quality threshold used for controlling the region growing process and merging the different pixel islands whenever possible. The algorithm is demonstrated for generating in vivo two-point Dixon images.

1664.   Assessing the Performance of Homodyne Combined with 2-point Dixon Reconstruction
Brady Quist1,2, Evan G. Levine1,2, Bruce L. Daniel1, Brian A. Hargreaves1, and Manojkumar Saranathan1
1Department of Radiology, Stanford University, Stanford, California, United States, 2Department of Electrical Engineering, Stanford University, Stanford, California, United States

The 2-point Dixon and Homodyne method each rely on certain assumptions of the underlying phase in the image to work correctly. Here we analyze a published method of combining both reconstruction techniques into one, effectively performing fat/water separation while regaining lost resolution from a partial k-space acquisition. New echo times with improved phase characteristics are proposed which are shown to reduce the artifact associated with the method. The Homodyne Dixon method along with the new echo time choice can enable improved temporal or spatial resolution in time-sensitive scans such as DCE or breath hold imaging.

1665.   A single point, echo time independent water/fat separation method
Sjoerd Crijns1, Bjorn Stemkens1, Alessandro Sbrizzi1,2, Jan Lagendijk1, Peter Luijten2, Nico van den Berg1, and Anna Andreychenko1
1Radiotherapy, UMC Utrecht, Utrecht, Utrecht, Netherlands, 2Radiology, UMC Utrecht, Utrecht, Utrecht, Netherlands

Dixon water/fat separation sequences usually need at least two images acquired at different TEs constrained to specific values, causing prolonged repetition and acquisition times and complicating application in dynamic imaging (e.g. DCE-MRI). We propose a single point water/fat separation method based on alternation of two RF pulses that introduces a spatial shift of fat with respect to water in the reconstructed image. We demonstrate the feasibility of this method and obtain in-phase water/fat separated images at an arbitrary echo time in a single acquisition.

1666.   An artifacts reducing approach for fat-water separation in spatiotemporally encoded single-shot MRI
Lin Chen1, Congbo Cai1, Shuhui Cai1, Jing Li1, Miao Zhang1, Ting Zhang1, and Zhong Chen1
1Department of Electronic Science, Xiamen University, Xiamen, Fujian, China

Separation of fat and water signals in MRI is very important for many clinical applications. Usual methods, such as Dixon and IDEAL, will lead to a long scan time. Spatiotemporally encoded (SPEN) single-shot MRI is an alternative method to separate fat and water in subsecond. For SPEN approach, super-resolved reconstruction is indispensable. However, existing algorithms will result in artifacts. In this abstract, compressed sensing is applied to the reconstruction to reduce the artifacts and improve the image quality. This reconstruction algorithm would benefit the application of SPEN single-shot MRI to fat-water separation.

1667.   Water Fat Separation from a Single Spatiotemporally Encoded Echo Using k-space Peaking and Joint Regularized Estimation
Ying Chen1, Congbo Cai1, Jianhui Zhong2, and Zhong Chen1
1Department of Electronics Science,Xiamen University, Xiamen, Fujian, China, 2Department of Imaging Sciences, University of Rochester, Rochester, New York, United States

This abstract proposed a high-resolution water fat separation algorithm using single spatiotemporally encoded echo. The overall field inhomogeneity in each spatiotemporally encoded signal line was evaluated; then spatial smoothness regularization was imposed to the signal equation set to estimate water and fat profiles in these lines; by evaluating the phase linearity of the output, the regions where intermingling may exist can be identified and were constrained with adaptive filtering regularization in the second estimation for better output. Experiment results show this technique can deliver more efficient water fat separation in many cases that is challenging or intractable for conventional methods.

1668.   MR Fingerprinting : Fat-Water separation imaging
Su-Chin Chiu1,2, Hsiao-Wen Chung2, Martin Buechert1, and Michael Bock1
1Radiology - Medical Physics, University Medical Center Freiburg, Freiburg, Germany, 2Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan

The MR fingerprinting (MRF) has recently been introduced to generate various quantitative parameter maps in a single image acquisition. In this study we extend MRF to apply it to fat/water separation. In addition to acquiring parameter maps of T1 and T2, fat and water fraction maps were created with a dedicated MRF pulse sequence and an orthogonal matching pursuit algorithm with 3 iterations. In a phantom experiment the fat/water separations shows a good agreement with data from an MR spectroscopic method.

1669.   Comparison of fat content measured by MRI water-fat separation, MR spectroscopy and chemical analysis on salmon
Julien Picaud1,2, Guylaine Collewet1, Giulio Gambarota3,4, and Jerome Idier2
1UR TERE, IRSTEA, Rennes, France, 2IRCCyN, CNRS, Nantes, France, 3UMR 1099, INSERM, Rennes, France, 4LTSI, Universite de Rennes 1, Rennes, France

The purpose of this study was to compare fat quantification on fish using MRI water/fat separation with localized spectroscopy (MRS) and with chemical analysis. 36 samples inside a wild salmon were used for MRI vs. MRS and 15 salmon cutlets for MRI vs. chemical analysis. MRI images and MRS spectra were acquired at 1.5T. We used GRE with 6 echoes and the VarPro reconstruction method proposed by Hernando (MRM 2010, 63-1). High correlations were found in both cases. Very good agreement was found between MRI and MRS while and overestimation of fat content was observed for MRI versus chemical analysis.

1670.   On the confounding effect of temperature on chemical shift-encoded fat quantification
Diego Hernando1, Samir D. Sharma1, Harald Kramer1,2, and Scott B. Reeder1,3
1Radiology, University of Wisconsin-Madison, Madison, WI, United States, 2Ludwig-Maximilians-University Hospital Munich, Munich, Germany, 3Medicine, University of Wisconsin-Madison, Madison, WI, United States

The proton resonance frequency (PRF) of water depends on temperature, whereas the PRF of triglycerides is temperature independent (aside from bulk susceptibility effects). This leads to a temperature dependence of the frequency shift between fat and water resonances, which may introduce errors in chemical shift-encoded (CSE) fat quantification methods that assume a known relative shift between the PRF of water and fat. In this work, we characterize the confounding effect of temperature on CSE fat quantification. Further, we demonstrate that a temperature-corrected spectral model of fat can be used to avoid these errors.

1671.   On the Effect of Fat Suppression via Chemically Selective Saturation (CHESS) Pulses on R2* Measurements in Patients with Transfusional Iron Overload
Axel Joachim Krafft1, Ralf B. Loeffler1, Xiao Bian1,2, Ruitian Song1, Beth M. McCarville1, Jane S. Hankins3, and Claudia M. Hillenbrand1
1Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN, United States, 2Rhodes College, Memphis, TN, United States, 3Hematology, St. Jude Children's Research Hospital, Memphis, TN, United States

Fat is a confounder in R2* based liver iron assessment as fat-water modulations in multi gradient echo imaging eventually affect the T2* evaluation. A simple solution could be the inclusion of fat suppression (FS) via chemically selective saturation (CHESS). However, decreasing T2* times as observed with increasing liver iron correspond to spectral profiles which overlap with the CHESS frequency band. This partial saturation potentially alters R2* leading to a biased iron evaluation. Here, the effect of CHESS FS on R2* is measured in 65 transfusional iron overload patients. A phenomenological model is presented to explain and correct the observed changes.

1672.   Signal Model Consistency Analysis of Different Protocols and Spectral Models in Multi Gradient Echo Liver PDFF and R2* Quantification
Mario A. Bacher1,2, Xiaodong Zhong3, Brian M. Dale4, Marcel D. Nickel2, Berthold Kiefer2, Mustafa R. Bashir5, Rudolf Stollberger1, and Stephan A.R. Kannengiesser2
1Institute of Medical Engineering, Technical University Graz, Graz, Austria, 2MR Applications Development, Siemens AG, Healthcare Sector, Erlangen, Germany, 3MR R&D Collaborations, Siemens Healthcare, Atlanta, GA, United States, 4MR R&D Collaborations, Siemens Healthcare, Cary, NC, United States, 5Department of Radiology, Duke University Medical Center, Durham, NC, United States

Multi gradient echo quantification of liver proton density fat fraction (PDFF) and transverse relaxation rate (R2*) was analyzed using model consistency metrics. Different acquisition protocols and fat spectral models as reconstruction parameters were compared. Data from twenty healthy volunteers showed no significant differences in PDFF for different protocols, but significant differences in PDFF and R2* for different protocols and spectral models. With respect to fitting error, the protocols were significantly different, whereas the spectral models were not significantly different from each other. Model consistency analysis is a useful tool for evaluating multi gradient echo imaging with advanced quantification

1673.   Fat Quantification with an Interleaved Bipolar Acquisition
Abraam S Soliman1,2, Curtis Wiens3, Trevor Wade2,4, Ann Shimakawa5, Terry M Peters1,2, and Charles A McKenzie1,4
1Biomedical Engineering, Western University, London, Ontario, Canada, 2Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada, 3Radiology, University of Wisconsin, Madison, Wisconsin, United States, 4Medical Biophysics, Western University, London, Ontario, Canada, 5Global MR Applied Science Laboratory, GE Healthcare, Menlo Park, California, United States

Chemical-shift based multi gradient echo sequences have been widely used for water/fat separation. Typically, 6 unipolar readout gradients are applied over multiple shots in order to achieve optimal echo-spacing. Although single shot bipolar readout acquisition can offer optimal echo-spacing with shorter scan time, phase errors can significantly corrupt water/fat separation. To overcome this problem, a new interleaved bipolar acquisition is proposed. Accurate fat quantification is demonstrated in phantom and in-vivo experiments compared to the well-established unipolar sequence. The proposed bipolar acquisition scheme offers accurate fat fraction maps with shorter acquisitions and higher SNR efficiency compared to unipolar sequences.

1674.   14 T NMR and 7 T MRI in vitro investigation of cold stimulation of abdominal WAT, inguinal WAT and BAT
Alexander Brunner1, Daniela Strzoda2, Karel D. Klika3, Mathies Breithaupt1, Vanessa Stahl1, Stephan Herzig2, and Armin M. Nagel1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Molecular Metabolic Control, German Cancer Research Center (DKFZ), Heidelberg, Germany, 3Molecular Structure Analysis, German Cancer Research Center (DKFZ), Heidelberg, Germany

Based on its unique thermogenic capacity, brown adipose tissue (BAT) shows very high potential to serve as a therapeutic node in the treatment of metabolic disorders, e.g., obesity. Recently, the BOLD effect T2*-weighted MRI during cold stimulation was used to detect cold-activated BAT in human individuals [1]. In this work, we compared 14 T NMR spectra and, for the first time, water fat fraction (WFF) [2], T1, T2 values measured in vitro by 7 T MRI between BAT, inguinal white adipose tissue (iWAT) and abdominal white adipose tissue (aWAT) in cold-stimulated mice and normal mice.


Imaging Metal Implants

Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

1675.   Polarized Multi-Channel Transmit MRI to Reduce B1-Shading near Metal Implants
Theresa Bachschmidt1,2, Peter Jakob2, Markus Vester1, Jürgen Nistler1, and Mathias Nittka1
1Siemens Healthcare, Erlangen, Germany, 2Experimental Physics 5, University of Würzburg, Würzburg, Germany

Susceptibility-induced artifacts in MR imaging of metal hip implants can be addressed by methods like SEMAC. Hence, B1 effects like shading and banding become more prominent at 3T. This work systematically analyzes B1 modulations and investigates a new approach to reduce those by means of B1 polarization, using state-of-the-art multi-channel transmit MRI systems. An analytical model is verified numerically and in phantom measurements. It is also used to predict and optimize signal intensity patterns for spin-echo based sequences and verified in vivo. This model helps to avoid signal loss or sharp transitions between hypo- and hyper-intense signal close to hip implants.

1676.   MAVRIC-SL with 3x2 parallel imaging and a hexagonally sampled calibration region
Bragi Sveinsson1, Valentina Taviani1, Kevin Koch2, Garry Gold1, and Brian Hargreaves1
1Radiology, Stanford University, Stanford, CA, United States, 2Applied Sciences Laboratory, General Electric, Waukesha, WI, United States

MAVRIC-SL is routinely used for clinical imaging close to metallic orthopedic devices. MAVRIC-SL collects multiple off-resonant 3D volumes acquired under a constant slab selection gradient. The collection of multiple 3D volumes presents challenges in maintaining short scan times. Previous work has demonstrated how hexagonal sampling can substantially reduce scan time when employing 2×1 parallel imaging. In this work, we demonstrate a variation of this method that allows hexagonal sampling in conjunction with 3×2 parallel imaging for more rapid imaging.

1677.   Quantified Estimates of Artifact Regions near Metal-on-Poly and and Metal-on-Metal Hip Replacements at 1.5T and 3T
Kevin Koch1, Adriana Kanwischer1, and Robert Peters1
1GE Healthcare, Milwaukee, WI, United States

An artifact quantification study is presented on metal-on-metal and metal-on-poly total hip replacements at 1.5T and 3T. Computational models and known theoretical performance limitations are used to quantify artifact volumes in 2D-FSE and 3D-MSI imaging approaches. Analysis of these results demonstrates the expected performance differences across different pulse sequences, joint replacement constructions, and field strengths. Simulated images are presented using an anatomic hip model to demonstrate practical clinical impact of the predicted artifacts.

Approach to characterize magnetic inhomogenities for development of MRI sequences near metallic prostheses
Matthew R. Smith1, Nathan S. Artz1, and Scott B. Reeder1,2
1Radiology, University of Wisconsin, Madison, Wisconsin, United States, 2Biomedical Engineering, University of Wisconsin, Madison, WI, United States

Metallic implants induce extremely large B0 field perturbations that cause severe signal distortion. The purpose of this work is to examine the theoretically induced field map perturbation using the digital representation of commercially available metallic joint prostheses. Simulations presented here demonstrate that both RF excitation and frequency encoding is highly problematic for these implants using current 3D-MSI methods at both field strengths. Fully phase encoded methods may help with the frequency-encoding distortion but not with RF excitation limitations.

1679.   On the Feasibility of Overcoming Frequency Encoding Limitations Near Metal Implants with Broadband Single-Point Imaging on Clinical MR Systems
Kevin Koch1 and Graeme McKinnon1
1GE Healthcare, Milwaukee, WI, United States

It has been established that all frequency encoded imaging acquisitions have encoding limitations that are reached near commonly encountered implants at 3T. Here, we present a study whereby the known limitations on clinical MR scanners are modeled in the context of broadband single-point imaging. The resolution, scan time, and T2* signal loss of such a clinically viable single-point-imaging implementation are discussed. It is shown that such an implementation may provide signal directly near metal implants that cannot be acquired via any conventional readout-driven sequence

1680.   Geometrically undistorted imaging of orthopedic implants using compressed sensing accelerated phase encoded imaging
Jetse S. van Gorp1, Chris J.G. Bakker1,2, Frank Zijlstra1, Jouke Smink3, Job G. Bouwman1, and Peter R. Seevinck1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands, 2Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands,3Philips Healthcare, Best, Netherlands

In this work 3D imaging was performed in the presence of a titanium hip implant using conventional frequency encoded and purely phase encoded spin-echo sequences. Phase encoded images were shown to avert geometric distortion and to improve image quality in the proximity of the implant compared to conventional images. The total acquisition time could be successfully decreased a factor six by undersampling k-space in all three phase encoded dimensions followed by compressed sensing reconstruction.

1681.   A hybrid multi-spectral approach for near metal imaging: combining the best of phase and frequency encoding
Jetse S. van Gorp1, Chris J.G. Bakker1, and Peter R. Seevinck1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands

In this work the feasibility of a new hybrid multi-spectral method is investigated using two orthopedic implants. The method combines on-resonance frequency encoded with off-resonance reduced field of view fully phase encoded images, to exploit the efficiency of frequency encoding and the geometrical accuracy of phase encoding. Hybrid images were compared to MAVRIC-type images, showing that the hybrid method was able to improve the image quality adjacent to metal implants. Large excitation bandwidths and a reduced field-of-view could be used for the phase encoded images, decreasing the number of necessary off-resonance acquisitions and reducing the acquisition time compared to solely phase encoded imaging.

1682.   Hybrid structure design for implants: dramatic reduction of the metal artifacts
Toru Yamamoto1, Yanhui Gao2, and Kazuhiro Muramatsu2
1Faculty of Health Sciences, Hokkaido University, Sapporo, Hokkaido, Japan, 2Department of Electrical and Electronic Engineering, Saga University, Saga, Japan

MR artifacts caused by implants are hindering proper diagnosis. Lowering the susceptibility of the material has been being developed, but even titanium is not enough for several diagnoses. To reduce these metal artifacts to a small area to enable diagnosis, we propose a new structural design of implants with hybrid of paramagnetic outer shell and diamagnetic inner core. The hybrid structure of paramagnetic and diamagnetic materials reduces the metal artifact of the implant dramatically. This structural design would be applied to various orthopedic implants.

1683.   Off-resonance Artifact Reduction Methods for Imaging with Electrodes
JaeJin Cho1, Yeji Han1, and HyunWook Park1
1Korea Advanced Institute of Science and Technology, Daejeon, Korea

This paper proposes the method that reduces the artifact caused by the electrode used in deep brain stimulation or electroencephalogram



Tuesday 13 May 2014
Traditional Poster Hall  10:00 - 12:00

1684.   Continuous vibration single shot magnetic resonance elastography for fast wave image acquisition
Florian Dittmann1, Sebastian Hirsch1, Jing Guo1, Jürgen Braun2, and Ingolf Sack1
1Institute of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany, 2Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany

We propose a single shot MRE sequence synchronized to continuous mechanical vibrations by adaptive measurement block shifting. As a result, measurement time is significantly reduced compared to former single shot MRE sequences without compromising SNR and data quality. The new sequence is demonstrated for high resolution elastography of the brain by applying 15 frequencies in the range from 25 to 60 Hz and multifrequency wave field inversion. For 7 slices, 8 wave dynamics and three field components data acquisition for 15 frequencies was accomplished within 9:40 min which is to our knowledge the fastest MRE sequence currently available.

1685.   Simultaneous Acquisition of the 3D Displacement Vector in Magnetic Resonance Elastography of the In Vivo Human Brain
Dieter Klatt1, Curtis L. Johnson2, Temel K. Yasar3, Joseph L. Holtrop2,4, Bradley P. Sutton2,4, Thomas J. Royston1, and Richard L. Magin1
1The Richard and Loan Hill Department of Bioengineering, The University of Illinois at Chicago, Chicago, Illinois, United States, 2Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 3Mechanical and Industrial Engineering, The University of Illinois at Chicago, Chicago, Illinois, United States,4Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States

SampLe Interval Modulation Magnetic Resonance Elastography (SLIM-MRE) enables the simultaneous acquisition of the 3D displacement vector through direction-dependent shifting of motion encoding gradients relative to the applied vibration. In this study, we have embedded a SLIM-MRE acquisition scheme into a multishot, variable-density spiral imaging sequence and have determined the cerebral mechanical properties of three volunteers. Our findings suggest that SLIM reduces MRE scan time and allows immediate co-registration of the three displacement components without compromising inversion results.

1686.   Magnetic Resonance Elastography with a Wireless Synchronization Pneumatic Vibration System
Tomokazu Numano1, Kazuyuki Mizuhara2, Yoshihiko Kawabata3, Toshikatsu Washio4, and Kazuhiro Homma4
1Radiological Sciences, Tokyo Metropolitan University, Arakawa, Tokyo, Japan, 2Mechanical Engineering, TOKYO DENKI UNIVERSITY, Adachi, Tokyo, Japan, 3Takashima Seisakusho Co.,Ltd, Hino, Tokyo, Japan, 4National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan

In this work a new MR Elastography (MRE) technique which can be performed on conventional MRI was developed. A wireless TR synchronization system consists of high-frequency radio receiver and a plain dipole antenna tuned to the RF excitation frequency was developed. The leak RF signal received via the dipole antenna, in the magnet room was available as the TR synchronization trigger then any electrical wiring from the MRI electronics is required. The fusion of the simple MRE sequence and the wireless synchronization pneumatic vibration system make it possible to construct the MRE system in any conventional MRI system.

Multi-Direction Excitation for Magnetic Resonance Elastography to Increase the Fidelity of Mechanical Properties
Aaron T Anderson1, Curtis L Johnson2, Joseph L Holtrop2,3, Elijah EW Van Houten4,5, Matthew DJ McGarry5, Keith D Paulsen5,6, Bradley P Sutton2,3, and John G Georgiadis1,2
1Mechanical Science & Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 2Beckman Institute for Advanced Science, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 3Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 4Département de Génie Mécanique, Université de Sherbrooke, Sherbrooke, QC, Canada, 5Thayer School of Engineering, Dartmouth College, Hanover, NH, United States, 6Dartmouth-Hitchcock Medical Center, Lebanon, NH, United States

Magnetic resonance elastography (MRE) has seen many advances in shear wave drivers, imaging techniques, and material property reconstruction but continues to have issue with specificity of properties within anisotropic microstructures due to the isotropic assumption. Sections within the brain with highly ordered structure behave very differently depending on the direction of applied shear, longitudinal compared to transverse. Adding multiple shaking directions, within the existing isotropic framework, shows promise of increasing the fidelity of all reconstructed material properties and throughout the brain. The increase in fidelity will help improve diagnosis of diseases affecting the microstructure of the brain.

1688.   Tabletop magnetic resonance elastography for the measurement of viscoelastic properties in soft tissue micro samples
Selcan Ipek-Ugay1, Michael Ledwig2, Toni Drießle2, Jing Guo3, Ingolf Sack3, and Jürgen Braun4
1Radiology, Charité-Universitätsmedizin Berlin, Berlin, Berlin, Germany, 2Pure Devices GmbH, Würzburg, Germany, 3Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany, 4Medical Informatics, Charité-Universitätsmedizin Berlin, Berlin, Germany

A tabletop magnetic resonance elastography (MRE) system was developed based on a 0.5T permanent magnet for the analysis of viscoelastic properties of tissue samples. The system allowed us the measurement of viscoelastic parameters in soft tissue samples in a frequency range of 500-1000 Hz. The data are in good agreement to published data acquired in a 7T-highfield superconducting magnet. Acquiring the same viscoelasticity information by low costs with little requirements for space and maintenance might support MRE developments towards mechanics based histopathology capable to links viscoelastic constants with the etiology and pathogenesis of diseases.

1689.   MR-Rheology - A feasibility study with phantoms
Anna-Lisa Kofahl1, Jakob Bindl1, Deniz Ulucay1, Sebastian Theilenberg1, Judith Wild1, Sylvia Napiletzki1, Alexandra Vohlen1, Jürgen Finsterbusch2, Bernd Weber3, Carsten Urbach1, and Karl Maier1
1HISKP, University of Bonn, Bonn, Germany, 2University Medical Center Hamburg-Eppendorf, Hamburg, Germany, 3Life & Brain GmbH, Bonn, Germany

The knowledge of the viscoelastic properties of the human brain tissue may aid in the diagnosis of diseases like Alzheimer’s disease, brain cancer or multiple sclerosis. A novel method to image the viscoelastic properties of the brain in vivo and non-invasively with a good spatial resolution is Magnetic Resonance Rheology (MR-R). MR-R uses an acceleration and creep experiment inside an MRI, where a motion encoding EPI sequence is used to measure the relaxation movement of the substance under investigation. To prove the feasibility of this novel method and to estimate its potential agar-phantoms with and without inclusions are investigated.

1690.   Magnetic Resonance Rheology of the human brain
Sebastian Theilenberg1, Jakob Bindl1, Anna-Lisa Kofahl1, Deniz Ulucay1, Judith Wild1, Alexandra Vohlen1, Sylvia Napiletzki1, Jürgen Finsterbusch2, Bernd Weber3, Carsten Urbach1, and Karl Maier1
1HISKP, University of Bonn, Bonn, Germany, 2University Medical Center Hamburg-Eppendorf, Hamburg, Germany, 3Life & Brain GmbH, Bonn, Germany

Magnetic Resonance Rheology is a novel method to image the viscoelastic properties of tissue in vivo using MRI phase images. By introducing a free fall over a small height the steady state of the brain tissue is disturbed, causing the tissue to move relative to the cranial bone. The exact trajectory of this motion is dependent on the local viscoelastic properties. Measuring these using a motion sensitive single-shot EPI sequence synchronized to the free fall creates a phase contrast. By varying the point in time of measurement the whole trajectory can be investigated.

1691.   Effects of Fiber Curvature on Anisotropic Inversions in Waveguide Elastography
Anthony Romano1, Varsha Viswanath2, Jing Guo3, Michael Scheel3, Sebastian Hirsch3, Jürgen Braun4, and Ingolf Sack3
1Physical Acoustics, The Naval Research Laboratory, Washington, DC, United States, 2Department of Biomedical Engineering, University of California at Davis, Davis, CA, United States, 3Department of Radiology, Charité-Universitätsmedizin, Berlin, Germany, 4Institute of Medical Informatics, Charité-Universitätsmedizin, Berlin, Germany

Previously, we introduced a method called Waveguide Elastography and implemented this to analyze the anisotropic stiffnesses of the Corticospinal Tracts of both healthy volunteers and patients suffering from ALS. In these previous studies, we inverted the Orthotropic equations of motion along the local tangent vectors of the fiber tracts. Here, we invert along the principal direction of fiber tracts while including the effects of curvature. It was observed that the effects of curvature in the calculation of the Laplacians bias the “inherent” stiffness in a similar fashion as wave velocities are altered by an index of refraction in ray theory.

1692.   Power-Law Multi-Frequency MRE Reconstruction
Elijah EW Van Houten1, Curtis L Johnson2, Aaron T Anderson2, Joseph L Holtrop2, Bradley P Sutton2, John G Georgiadis2, Matthew D McGarry3, John B Weaver3, and Keith D Paulsen3
1Univ. de Sherbrooke, Sherbrooke, QC, Canada, 2Univ. Illinois at Urbana-Champaign, IL, United States, 3Dartmouth College, NH, United States

A multi-frequency magnetic resonance elastography image reconstruction method is presented with power-law frequency dependency for the elastic properties. The method is based on a nonlinear inversion framework and uses a generalized Rayleigh damping model for the soft tissue elastic energy absorption. Comparative reconstructions in a healthy brain, based on three frequencies of excitation, show improved fidelity and definition within the power-law multi-frequency image. Structures such as the ventricles and the falx cerebri are clearly defined and possess material property values in line with expectations.

1693.   Remotely induced cerebral strain for enhanced safety and acceptance of MR elastography of the brain
Andreas Fehlner1, Sebastian Papazoglou1, Jing Guo1, Kaspar-Josche Streitberger1, Sebastian Hirsch1, Jürgen Braun2, and Ingolf Sack1
1Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany, 2Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany

A new driver for brain MRE is introduced which avoids the direct application of vibrations to the head without compromising sufficiently high extrinsic wave amplitudes needed for MRE. Waves are introduced into the cranial cavity by a chest cradle mounted to a piezo-based actuator which was placed at the end of the patient table. The new driver is particularly suited for low drive frequencies (25–40 Hz) which are capable to resolve anatomical details and provide viscoelastic parameters in agreement to previous work. The new method is demonstrated in ten healthy volunteers for 8 driving frequencies and two 3D views.

1694.   Waves as biosensor for microarchitecture
Simon A. Lambert1,2, Peter Nashölm3, Lauriane Juge1, Lynne Bilston4, Bojan Guzina5, Sverre Holm3, and Ralph Sinkus2
1INSERM U1149, 1- Center for research on inflammation, Université Paris 7, Clichy, Ile de france, France, 2Division of Imaging Sciences and Biomedical Engineering, KCL, BHF Centre of Excellence, london, London, United Kingdom, 3Informatics Department, University of Oslo, oslo, Norway, 4University of New South Wales, Neuroscience Research Australia, Randwick, Australia, 5University of Minnesota, Minneapolis, United States

Recently in vivo experiments using Multifrequency MRE (MMRE) have shown that the exponent of the power law derived from MMRE data fitting with a power law could be more sensitive to specific pathologies such as fibrosis, steatosis or even inflammation. However these works lack fundamental understanding of the relation existing between the tissue microstructure with its macroscopic nature. In this study we develop a full theoretical model of shear wave propagation at the microscopic scale in phantoms containing wave obstacles and demonstrate that shear waves are able to reveal at the macroscopic scale the hidden micro-architectural properties of the material.

1695.   3D Gradient Echo MRE of the Liver with CLEAR Parallel Image Reconstruction
Roger C Grimm1, Joshua D Trzasko1, Armando Manduca1, and Richard L Ehman1
1Mayo Clinic, Rochester, MN, United States

Clinical 2D GRE Elastography is acquired and processed as 2D data sets. Commonly, four slices of stiffness estimates can be obtained in four breath-holds. A true 3D wave field sample with 3D processing would provide a more accurate estimate of the tissue stiffness. The proposed 3D GRE sequence can provide similar slice throughput with four to six 3D processed images obtained in four breath-holds. Due to the nature of the acquisition, the GRE scans provide fewer artifacts compared to similar EPI scans. The CLEAR reconstruction algorithm is used to provide superior ghost reduction compared to ASSET while providing additional acceleration.

1696.   Magnetic Resonance Elastography of cysts and fluid filled cavities
Jing Guo1, Sebastian Hirsch1, Sebastian Papazoglou1, Kaspar-Josche Streitberger1, Andreas Fehlner1, Juergen Braun2, and Ingolf Sack1
1Department of Radiology, Charite - Universitaetsmedizin Berlin, Berlin, Berlin, Germany, 2Department of Medical Informatics, Charite - Universitaetsmedizin Berlin, Berlin, Germany

MRE can differentiate small lesions based on their stiffness or softness compared to surrounding healthy tissue. However, in tissue with fluid filled cavities the obtained elastograms are biased due to effects of the lesion's geometry to the refracted wave field, resulting an overestimation of stiffness values. We analyze this effect by numerical simulations and MRE data of phantoms and in vivo cysts in the abdomen and brain. Our results indicate severe overestimation of viscoelasticity in cysts unlike other fluid filled parts of the tissue. We show that this effect is a result of resonances in oscillating cavities with regular interfaces.

1697.   Displacement field normalization in MR-elastography: phantom validation and in vivo application
Marion Tardieu1, Marie Poirier-Quinot1, Ralph Sinkus2, Luc Darrasse1, and Xavier Maître1
1IR4M (UMR8081), CNRS, Univ Paris-Sud, Orsay, France, 2Imaging Sciences & Biomedical Engineering Division, King's College, London, United Kingdom

MR-elastography aims at characterizing the mechanical properties of living tissues by probing wave propagation therein. Displacement fields are recorded over a mechanical cycle by encoding the inferred motion along the three spatial directions. Thus the complex shear viscoelastic moduli can be computed after inversion of the wave equation. Patients' motion during the MR-acquisition usually results in unrestrained spatial transformations of the targeted organ. It may also yield unwanted mismatch of the components of the acquired displacement fields. Spatial normalization of the phase image along the magnitude image tackles the correcting linear or non-linear transformations but, as numerically showed recently, displacement field normalization is required to fully recover the phase information in MR-elastography and improve the parametric reconstruction. Here, we experimentally validate the approach by applying these corrections on a breast phantom after MR-elastography exams for arbitrary three-dimensional rotations. This double normalization scheme was advantageously applied on a brain MR-elastography data set where the subject had involuntary moved during the acquisition.

1698.   MR elastography of MPTP-induced Parkinson’s disease in the mouse
Ingolf Sack1, Barbara Steiner2, Charlotte Klein2, Elisabeth Hain2, Kerstin Riek3, Jing Guo3, and Jürgen Braun4
1Radiology, Charité-Universitätsmedizin Berlin, Berlin, Berlin, Germany, 2Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany, 3Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany, 4Medical Informatics, Charité-Universitätsmedizin Berlin, Berlin, Germany

Magnetic resonance elastography (MRE) was applied to a murine model of neurotoxin-induced Parkinson's disease and compared to histological findings. For the first time, a significant increase of cerebral elasticity was observed in response to disease. We found an increase in the storage modulus of the brain at day 6 after treatment with the neurotoxin MPTP which parallels the proliferation of new neurons predominantly in the hippocampal region. The results provide insight into the crucial role of neurons for the constitution of the viscoelastic matrix and motivate further applications of MRE in patients as a new biomarker for neurodegenerative diseases.