Traditional Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Artifacts & Correction: Phase Processing & SWI

Wednesday May 11th
Exhibition Hall  13:30 - 15:30

2663.   Improved forward calculation for phase artifacts removal in susceptibility mapping  
Saifeng Liu1, Jaladhar Neelavalli2, Weili Zheng3, and Ewart Mark Haacke2,4
1School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada, 2The Magnetic Resonance Imaging Institute for Biomedical Research, Detroit, Michigan, United States,3Biomedical Engineering, Wayne State University, Detroit, Michigan, United States, 4Academic Radiology, Wayne State University, Detroit, Michigan, United States

The forward calculation enables us to predict and remove the background field variation. However, it becomes insufficient when the eddy currents are considerable. We proposed to add an polynomial fitting to the forward calculation. With this new method, the background filed variation can be properly fitted and most of the phase artifacts were removed. This allows us to use a high-pass filter with smaller size to reduce the error in susceptibility mapping.

2664.   Matching Pursuit Iterative Dipole Based Filter of Background Fields in Phase Imaging 
José P. Marques1,2, Yves Wiaux3,4, and Rolf Gruetter1,5
1Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, 2Department of Radiology, University of Lausanne, Lausanne, Vaud, Switzerland, 3Signal Processing Laboratory 5, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 4Medical Image Processing Laboratory, University of Geneva, Geneva, Switzerland, 5Department of Radiology, University of Lausanne and Geneva, Switzerland

In this abstract a fast iterative method to filter the large background phase shifts of susceptibility origin in phase imaging is presented. The algorithm is based on the matching pursuit iterative methodology to solve the ill posed inverse problem of finding a susceptibility distribution outside that can explain the field inside the region of interest. The algorithm is demonstrated both in synthetic and in vivo brain data acquired at 7T.

2665.   Reducing Artifacts in SWI based MR Venography - Post Processing Technique to Compensate for the Signal Loss 
Se Rim Park1, Ung Jang1,2, and Dosik Hwang1,2
1School of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea, Republic of, 2Yonsei University

IN SWI MR venography, long echo time might be desired for high contrast. However, longer echo time eventually introduces artifacts mainly caused because of unexpected macroscopic field inhomogeneity, especially around the orbito-frontal cortex. In order to correct the image, for the first step, local inhomogeneity is directly calculated after the signal acquisition, and Local Field Gradient (LFG) map is created. Then each signal is corrected to certain degree according to this LFG value so that the optimum image is restored.

2666.   CAMPUS: A Catalytic Multiecho Phase Unwrapping Scheme 
Wei Feng1, Jaladhar Neelavalli1, and E.M. Haacke1
1Wayne State University, Detroit, MI, United States

Susceptibility weighted imaging (SWI) utilizes phase information at long echo time (TE). However, due to long TE, phase aliasing inevitably occurs. For the purpose of SWI, phase wraps can be removed by conventional region growing methods or homodyne filtering. Region growing phase unwrapping methods are not always reliable and conventional homodyne highpass filtering induces undesired artifacts. We propose a new pixel-wise catalytic multiecho phase unwrapping scheme (CAMPUS) that is not based on region growing and does not require filtering. It is suited for multiecho gradient echo imaging with short inter-echo spacing, which is exploited to unwrap the multiecho phase data.

2667.   On the impact of regularization and kernel type on SHARP-corrected GRE phase images 
Ferdinand Schweser1,2, Karsten Sommer1,3, Marie Atterbury1,4, Andreas Deistung1, Berengar Wendel Lehr1, and Jürgen R. Reichenbach1
1Medical Physics Group, Dept. of Diagnostic and Interventional Radiology 1, Jena University Hospital, Jena, Germany, 2School of Medicine, Friedrich Schiller University of Jena, Jena, Germany,3School of Physics and Astronomy, Friedrich Schiller University of Jena, Jena, Germany, 4Dept. of Physics, Brown University, Providence, RI, United States

In this study we investigated the impact of regularization and kernel type used with the SHARP method based on a numerical brain model. Furthermore, we present the smallest possible kernel, which allows overcoming one of the major pitfalls of SHARP, i.e. the missing values at the edges of the brain.

Traditional Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Artifacts & Corrections: Imaging Near Metal

Thursday May 12th
Exhibition Hall  13:30 - 15:30

2668.   Investigations on Imaging Near Metal with Combined 3D UTE-MAVRIC 
Michael Carl1, Jiang Du2, and Kevin Koch3
1Global Applied Science Laboratory, GE Healthcare, San Diego, CA, United States, 2University of California, San Diego, United States, 3Global Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States

We investigated the potential combination of 3D UTE with MAVRIC to image short T2 tissues surrounding orthopedic implants with reduced susceptibility artifacts. Phantom experiments were performed containing a stainless steel plate immersed in agarose gel and imaged at 3T. Our studies show that these two techniques may be combined to harvest their respective advantages.

2669.   Predicting Pileup Artifacts Around Magnetized Spheres in SWIFT Images 
Robert O'Connell1, Steen Moeller2, Curt Corum2, Djaudat Idiyatullin2, and Michael Garwood2
1University of Minnesota, Minneapolis, MN, United States, 2University of Minnesota

Magnetic materials cause T2* shortening and frequency shifts in MRI. With conventional techniques, magnetized objects give rise to signal voids, whereas with SWIFT the signal voids are surrounded by ‘pileup’ artifacts. The pileup artifacts arise from the displaced signals from off-resonance spins. By knowing how the signals are displaced, it should be possible to return them to their correct positions in image space, correcting the image distortion. This work used an analytic method to derive a predictive equation for the pileup artifact. The equation was then verified through simulation and experimental measurement of titanium balls.

2670.   MRI Artifacts due to Ingestion of Iron Supplements 
Jennifer Stoneburgh1, Ali Fatemi-Ardekani2, Barry Smith3, and Michael D Noseworthy4,5
1Electrical and Computer Engineering, McMaster University, Hamilton, Ontario, Canada, 2Medical Physics, McMaster University, Hamilton, Ontario, Canada, 3Department of Diagnostic Imaging, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada, 4Biomedical Engineering; Electrical and Computer Engineering, McMaster University, Hamilton, Ontario, Canada, 5Brain Body Institute, St. Joseph's Healthcare, Hamilton, Ontario, Canada

It is common MRI knowledge that iron causes rapid MR signal dephasing and artifacts. Meanwhile, many people take iron nutritional supplements for low iron status. We describe here how ingestion of a standard "over the counter" iron supplement, too soon before an MRI scan, can result in artifacts. Based on steady state imaging results and analytical measurement using a volume magnetic susceptibility balance our results demonstrate that patients should not ingest iron containing vitamin supplements prior to an abdominal MRI scan.

2671.   3D MRI impression of metal implant scan abutment in dental implantology 
Andreas Johannes Hopfgartner1, Julian Boldt2, Kurt Rottner2, Ernst Jürgen Richter2, and Peter Michael Jakob3
1Experimental Physics 5, University of Würzburg, Würzburg, Bavaria, Germany, 2Prosthodontics, Dental School, University of Würzburg, Würzburg, Bavaria, 3Experimental Physics 5, University of Würzburg, Würzburg, Bavaria

Artifacts induced from dental alloys are potential pitfall in dental MRT. Depending on the imaging sequence and the material used, susceptibility as well as eddy current artifacts are more or less distinct. In dental implantology, a titanium implant is inserted into the jaw bone. For virtual modeling of a fixed partial denture, the orientation of the in situ implant must be recorded along with the neighboring teeth, enabling the dental technician to model a well-fitting restoration. This is achieved by affixing a scan abutment with a defined shape that can be detected by pattern-recognition in the scan results. Despite the presence of a metal body in immediate vicinity, the unit consisting of PEEK screw, scan abutment and implant can be measured in MRI and yield a dataset containing the required information for further modeling of a fixed partial denture by a dental technician. A method to minimize and extrude disturbing metal artifacts is given in this work.

2672.   Metal-induced artifacts in computed tomography and magnetic resonance imaging: comparison of biodegradable magnesium alloy versus titanium and stainless steel control 
Gustav Andreisek1, Thomas Frauenfelder1, and Roger Luechinger2
1Department of Radiology, University Hospital Zurich, Zurich, ZH, Switzerland, 2Institute for Biomedical Engineering, University and ETH Zurich, Zurich, ZH, Switzerland

Our aim was to evaluate metal artifacts induced by biodegradable magnesium alloys – a new class of degradable biomaterials - at CT and MR imaging at 1.5T in comparison to standard titanium and stainless steel controls. It was shown that biodegradable magnesium alloys show less metal induced artifacts at CT and MR imaging than the controls.

Traditional Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Artifacts & Motion: Correction

Monday May 9th
Exhibition Hall  14:00 - 16:00

2673.   Validation of DC Self-Navigation for Breath-hold Period Identification in Contrast-Enhanced 3D Radial Liver Perfusion Imaging 
Debra E. Horng1,2, Ethan K. Brodsky1,2, and Scott B. Reeder1,2
1Radiology, University of Wisconsin-Madison, Madison, WI, United States, 2Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

Quantitative perfusion imaging of liver tumors requires acquisitions that occur over alternating periods of breathing and breath-holding. Knowledge of the time range when the liver is not moving is necessary for accurate perfusion modeling. In this work, we describe the use of DC phase and DC magnitude signal measured every TR from a 3D-radial contrast enhanced acquisition to identify breath-holding periods. Results demonstrate excellent agreement with respiratory bellows, which were used as the reference standard.

2674.   In-vivo Tagged-MR based Motion Correction in combined MR-PET 
Se Young Chun1,2, Timothy G Reese2,3, Bastien Guerin1,2, Ciprian Catana2,3, and Georges El Fakhri1,2
1Division of Nuclear Medicine & Molecular Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States, 2Radiology, Harvard Medical School, Boston, MA, United States, 3Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States

Motion artifacts in PET becomes a key problem affecting image quality. Combined MR-PET provides a new opportunity to improve PET image quality with accurately estimated motion from simultaneously acquired tagged MR without increased radiation dose. Here we report progress in our in-vivo motion correction study, showing results from a free-breathing primate that demonstrates the feasibility of PET motion correction in simultaneous MR-PET. Our tagged MR based motion correction methods significantly reduced motion artifacts and noise as compared to no motion correction or gating. They achieved image qualities comparable to those of gating method with much longer (8x) acquisition.

2675.   Respiratory gating with measurement time constraints applied to MRI with continuously moving table 
Matthias Honal1, and Tobias Baumann2
1Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany, 2Department of Radiology, University Medical Center Freiburg, Germany

The application of respiratory gating for MRI with continuously moving table is difficult. Due to the variability of the breathing motion over time the coverage of the complete k-space in the available measurement time which is fixed by the table motion cannot be guaranteed. In this study a variant of respiratory gating is proposed that acquires the required k-space data in a limited time as consistently as possible with respect to motion. Compared to acquisitions without motion correction blurring artifacts are reduced thereby significantly improving the diagnostic image quality.

2676.   Virtual Template Registration for DCE-MRI Renography 
Michael Hofer1, Gernot Reishofer2, Stephen Keeling3, Michael Riccabona4, Manuela Aschauer5, and Rudolf Stollberger6
1Institute of Medical Engineering, University of Technology, Graz, Austria, 2Department of Radiology, Medical University, Graz, Austria, 3Institute for Mathematics and Scientific Computing, Karl Franzens University Graz, Austria, 4Department of Pediatric Radiology, Medical University Graz, Austria, 5Department of Radiology, Medical University Graz, Austria, 6Institute of Medical Engineering, University of Technology Graz, Austria

For the non-invasive assessment of renal perfusion and functional parameters it is important to get tissue specific data (e.g. renal cortex, renal medulla). To overcome the problem of intensity variations, an image registration procedure was implemented which derives a virtual template image series that keeps the underlying signal time course intact. The algorithm is evaluated for a synthetic kidney phantom and in vivo DCE-MRI data. It is seen that the algorithm is robust against signal changes due to the uptake of contrast media. Our results indicate that for pixel-by-pixel evaluation of the renal blood flow, registration is mandatory.

2677.   Bias Correction for Respiration Detection in Radial 3D Gradient-Echo Imaging 
Robert Grimm1, Kai Tobias Block2, Berthold Kiefer2, and Joachim Hornegger1,3
1Pattern Recognition Lab, Department of Computer Science, University of Erlangen-Nuremberg, Erlangen, Germany, 2Siemens Healthcare MR, Erlangen, Germany, 3Erlangen Graduate School in Advanced Optical Technologies (SAOT)

Radial k-space sampling is a promising technique for abdominal imaging due to the high motion robustness and the embedded information on the respiration phase. However, these self-gating signals are often corrupted by high-frequency variations from an angle-dependent bias, caused by inaccurate gradient timings. Here, we present a novel filtering scheme to estimate and correct the bias without compromising temporal resolution. After correction, the variance of the signal can be used to assess the quality of the gating signal for different slices. The approach is evaluated with volunteer data acquired under irregular breathing patterns, and results from gated reconstructions are shown.

2678.   Continuous Fat Suppression during Respiratory Triggering 
Alto Stemmer1, and Berthold Kiefer1
1Healthcare Sector, Siemens AG, Erlangen, Germany

Slices acquired at the beginning of the acquisition period of a respiratory triggered sequence may suffer from insufficient fat suppression, if a spectral selective saturation or inversion pulse is used for fat suppression. The proposed reason is the interruption of fat steady state during inspiration while the sequence waits on the next trigger. In this work the sequence of fat suppression modules is continued in the trigger pauses. This maintains the steady state and results in consistent fat suppression in all slices.

2679.   Mouse cardiac MRI: comparison of prospective synchronization using optical and ECG signals with a retrospective technique 
Raphaël Sablong1, Adrian Rengle1, Audrey Pouzin1, and Olivier Beuf1
1CREATIS, CNRS UMR 5220, Inserm U1044, INSA-Lyon, Université Lyon 1, Villeurbanne, France

An optical-based device designed to synchronize MRI acquisition on small animals was developed using a transmit-receive pair of optical fibers. The suitability of the developed device was assessed on ten mice and compared with ECG-gated and a retrospective technique (IntraGate). MR images of mice heart depict low visible motion artifacts with all three investigated methods and no significant SNR differences were found on images acquired or processed with these different methods. However, depending on device used, the triggering point does not correspond to the same instant of the cardiac cycle inducing a time shift between image series acquired with the devices. Full fiber optical-based signal derived from heart and respiratory motion was suitable for prospective triggering for heart MR imaging. The fiber optic device performed as well as the ECG. The optical fiber-based device could be an attractive alternative to commercially available triggering devices for small animal MRI, when retrospective method is inappropriate, in difficult environments such as small volume available and fast gradients switching.

2680.   Two degree-of-freedom (DOF) MRI-compatible motion generation system for MRI motion compensated algorithms evaluation 
Slavisa Jovanovic1,2, Laure Rousselet1,2, Lucas Albouy1,2, Pierre-André Vuissoz1,2, Cédric Pasquier3,4, and Jacques Felblinger1,2
1Imagerie Adaptative Diagnostique et Interventionnelle, Nancy-Université, Nancy, France, 2U947, INSERM, Nancy, France, 3CIT801, INSERM, Nancy, France, 4CIC-IT,CHU-Nancy, Nancy, France

Physiological motions can impair MR image quality by generating artifacts. To overcome or decrease artifact generation in MR images, synchronization or image processing techniques taking into account these motions must be employed. In order to validate either new motion sensors or motion correction algorithms in MRI environment before their use in clinics, a reproducible motion generation system is needed. Most of the solutions we find in literature are limited to a small range of applications and basic motion types. Within this framework, we present a dynamic fully MRI-compatible motion generation platform which was developed to evaluate the influence of its generated motion on MR image quality of phantoms and to assess image processing algorithms used for motion artifacts removal. As an initial test, we evaluate a motion correction algorithm GRICS by imposing on its inputs a known 2D motion generated with the developed mobile platform.

2681.   Motion Degradation in 3D µMRI of Trabecular Bone: Relevance to Quantitative Analysis of Clinical Data 
Yusuf A Bhagat1, Chamith S Rajapakse1, Jeremy F Magland1, Michael J Wald1, Hee K Song1, Mary B Leonard2, and Felix W Wehrli1
1Laboratory for Structural NMR Imaging, University of Pennsylvania, Philadelphia, PA, United States, 2Nephrology, The Children's Hospital of Philadelphia, United States

Subtle subject movement during high-resolution µMR scanning of trabecular bone (TB) causes blurring rendering the data unreliable for quantitative analysis. Images that were visually free of motion artifacts from two groups of 10 healthy individuals each differing in age were selected. We then applied retrospectively derived translational motion trajectories as phase shift to the k-space data of these 20 subjects. Motion induction affected all TB structural parameters. The significant difference in structural parameter group means of the motion-free images was lost upon motion degradation. The results underscore the importance of subject movement and its correction for TB structure analysis.

2682.   Characterisation of Motion-Induced Field Distortions in Spectroscopic Imaging With Prospective Motion Correction 
Thomas Lange1, Daniel Nicolas Splitthoff1, Maxim Zaitsev1, and Julian Maclaren1
1Department of Radiology, University Medical Center Freiburg, Freiburg, Germany

Prospective motion correction based on an optical tracking system in combination with retrospective phase correction has recently been proposed for spectroscopic imaging in the human brain and has been validated for in-plane motion. In this work, the method is assessed for through-plane motion, focussing on the characterisation of motion-induced field distortions in the VOI and evaluating the potential for real-time shimming. Through-plane motion causes stronger spectral degradation compared to in-plane motion, particularly in the frontal cortex close to the nasal cavities. For rotational motion, the field distortions may contain large second-order components, which are hard to correct in real time.

2683.   A Practical Tracking System to Avoid Motion Artifacts 
Michael Herbst1, Julian Maclaren1, Jan Gerrit Korvink2,3, and Maxim Zaitsev1
1Medical Physics, University Medical Center Freiburg, Freiburg, Germany, 2Dept. of Microsystems Engineering - IMTEK, University of Freiburg, Freiburg, Germany, 3Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany

Monitoring head motion is becoming a popular way to prevent motion artifacts in brain imaging. However, previously-described systems all have major practical problems. We present a new method that uses ‘optical-tracking-tape’, consisting of bend-sensitive optical fibre. The tape is attached to the head of the subject and used to identify motion for real-time data rejection. In comparison with other systems a major advantage of the tape is the setup time (3minutes). No time consuming calibration step is necessary and no direct line of sight on the patients head is required, which makes the system usable even with a enclosed headcoils.

2684.   Error evaluation and data correction for the outlier signals in Q-ball Imaging: comparison of orientation distribution function 
Yen-Wei Cheng1, Ming-Choung Chou2, Nai-Yu Cho3, Cheng-Yu Chen3, and Hsiao-Wen Chung1
1Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, 2Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan,3Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan

Corrupted signals in diffusion-weighted images due to hardware instability and physiological-related fluctuations are observed in Q-ball imaging. We proposed two suitable methods to restore the lost signals in DWIs and reduce the ODF errors in this study. The corrupted signals were replaced by its repeated scan to get the gold standard. The mean ODF errors between damaged QBI and gold standard QBI before correction were 2.32%. However, the mean ODF errors were reduced to 0.51% and 0.45% after correction by symmetrical compensation method and neighboring interpolation method. Therefore, we concluded that neighboring interpolation was suitable adjunct for QBI data processing.

Traditional Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Artifacts & Correction: B0 Estimation & Distortion Correction

Tuesday May 10th
Exhibition Hall  13:30 - 15:30

2685.   Improved Frequency Selective Fat Suppression using Tissue Susceptibility Matched Pyrolytic Graphite Foams 
Gary Chiaray Lee1,2, Caroline Jordan3,4, Pamela Tiet2, Carlos Ruiz2, Brian Hargreaves3, and Steven Conolly1,2
1Berkeley/UCSF Bioengineering Joint Graduate Group, Berkeley, CA, United States, 2Bioengineering, UC Berkeley, Berkeley, CA, United States, 3Radiology, Stanford University, 4Bioengineering, Stanford University

Magnetic susceptibility differences at air and tissue boundaries produce B0 field inhomogeneities near the skin and air cavities in the body, may cause significant imaging artifacts, including intravoxel dephasing, and distortion. These artifacts can result in unreliable chemically selective fat suppression, which exploit the 3.5 ppm chemical shift between fat and water. We have developed susceptibility matching pyrolytic graphite-embedded foams that are safe for patient use in MRI. Here we demonstrate significantly improved in vivo susceptibility matching in the hand and neck, improved frequency selective fat suppression in fat phantoms, and that the foams do not adversely affect SNR.

2686.   Accurate B0 mapping with sparse TE stepping and k-space energy spectrum analysis 
Pei-Hsin Wu1, Nan-Kuei Chen2, and Hsiao-Wen Chung1,3
1Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, Taiwan, 2Brain Imaging and Analysis Center, Duke University Medical Center, Durham, NC, United States,3Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan

We proposed an improved multi-TE approach for accurate B0 mapping with phase unwrapping along the TE dimension, using sparse TE spacing for shorter acquisition time. The k-space energy spectrum analysis method was used for an initial estimation of the phase evolution as a function of TE, following which the accurate phase values were derived on a pixel-by-pixel basis from the multi-TE data. Experimental results in the human brain using four TE values with 9 msec spacing suggested that our approach yielded accurate B0 maps in good agreement with those obtained from 37 TE values at 0.752 msec spacing.

2687.   Off-Resonance Artifact Correction with Convolution in k-space (ORACLE) 
Wei Lin1, Feng Huang1, George R Duensing1, and Arne Reykowski1
1Invivo Corporation, Philips Healthcare, Gainesville, FL, United States

A rapid off-resonance artifact correction method is proposed based on data convolution in k-space (ORACLE). The acquired k-space is divided into segments based on their readout time, and a convolution kernel is applied to each segment to render artifact-free data. ORACLE does not require a separate B0 mapping scan, therefore reducing the scan time and eliminating the need to align the B0 map with the actual imaging data. Phantom and in vivo brain scans demonstrate the successful application to radial, spiral and EPI datasets.

2688.   Frequency Filtered SENSE Shimming for B0 inhomogeneity detection 
Daniel Nicolas Splitthoff1, and Maxim Zaitsev1
1Dept. of Radiology, Medical Physics, Unversity Medical Center Freiburg, Freiburg, Germany

Recently the generalised non-linear SENSE Shimming (SSH) method was introduced, which can be used for estimating B0 inhomogeneities. The approach uses a reference image and tries to explain the time curve of a Free Induction Decay (FID) based on a model including relaxation and inhomogeneities. Due to the usage of the FID the method was up to now restricted to axial slices. We here introduce the concept of frequency filtered FIDs which enables the method to be used with an arbitrary slice orientation. Results from an in vivo measurement are shown.

2689.   Correcting B0 Induced Signal Loss Using Echo Planar Imaging Reference Data 
Dan Xu1, Joe K. Maier2, Kevin F. King1, and Gaohong Wu2
1Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States, 2GE Healthcare, Waukesha, WI, United States

B0 inhomogeneity can lead to significant signal loss especially for slices far off isocenter and/or pulse sequences with spectral spatial fat suppression pulses. Collecting B0 map on a per-subject basis is impractical because of the prolonged scan time. In this paper, we propose a method to estimate and correct the per-slice B0 offset using the freely available echo planar imaging (EPI) reference data. Spin echo EPI results on a phantom show that the method can increase the signal for slices 15 cm away from isocenter from 37% to over 75% as compared to signal at the isocenter slice.

2690.   Shim Navigators for Accurate Detection of the B0 Magnetic Field Inhomogeneities Using Reference MGE Images 
Iulius Dragonu1, Daniel Nicolas Splitthoff1, Nicoleta Baxan1, Paul Freitag2, Jürgen Hennig1, and Maxim Zaitsev1
1Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freibug, Baden-Wuerttemberg, Germany, 2Bruker Biospin, Ettlingen, Baden-Wuerttemberg, Germany

The B0 magnetic field may change during the experiment for several reasons: physiological motion, such as breathing, subject motion and hardware imperfections, such as passive shim element heating. Changes in B0 homogeneities can lead to unwanted signal fluctuations in EPI time course acquisitions. As suggested previously, shim navigators may allow the detection of magnetic field evolution. It has been demonstrated that the phase of a projection is not necessarily proportional to the B0 field inhomogeneities along the direction of that projection. In this work, we propose a method for detection of zero- and first-order in plane shims (f0, A11 and B11) based on shim navigators and reference multi gradient echo images.

2691.   R2* estimation in the presence of fat and macroscopic B0 field variations 
Diego Hernando1, Catherine DG Hines1, and Scott B Reeder1,2
1Radiology, University of Wisconsin, Madison, WI, United States, 2Medical Physics, University of Wisconsin, Madison, WI, United States

Quantitative, non-invasive estimation of R2* is an important biomarker of hepatic iron overload. Unfortunately, estimates of R2* may be confounded by the presence of fat, as well as the signal dephasing that occurs from macroscopic magnetic field gradients caused by external susceptibility. In this work, we propose a method that uses the complex signal for estimation of R2*, correcting for the presence of fat and macroscopic field variations. Phantom and liver imaging results are shown to illustrate the proposed method.

2692.   Single-scan T2* measurements with alternating compensation gradients for linear background gradients 
Yoonho Nam1, Hahnsung Kim1, and Dong-Hyun Kim1
1Electrical & Electronic Engineering, Yonsei University, Seoul, Korea, Republic of

Accurate measurement of T2* values, excluding the effects of macroscopic field inhomogeneity, is required in many applications. Macroscopic field inhomogeneity induces additional signal decay and leads to underestimated T2* values. Using compensation gradients in slice-selection direction, so called z-shim method, is an effective technique to restore additional signal loss due to macroscopic field inhomogeneity. Therefore, T2* measurements by using these compensation gradients raise the accuracy of T2* values. However, it requires additional scan time for different compensation gradients. In this study, we propose a post-processing technique with alternating compensation gradients in a single scan for accurate T2* measurement.

2693.   MR-based Field-of-View Extension: Compensation of Field Imperfections 
Jan Ole Blumhagen1,2, Ralf Ladebeck1, Matthias Fenchel1, Jürgen Kampmeier1, and Klaus Scheffler2
1Magnetic Resonance, Siemens Healthcare, Erlangen, Bavaria, Germany, 2Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland

Recently, the potential impact of a limited MR-based field-of-view (FoV) in whole-body MR/PET attenuation correction has been shown. In MR/PET the tissue attenuation map can be calculated from the MR images. However, the FoV restriction may cause a truncation of the MR data for bigger patients and therefore can bias the PET data reconstruction. In this work, we will show exemplarily for 2DFT spin-echo sequences a method that offers an extended FoV in the transversal plane of up to 600mm using a gradient field that compensates B0 inhomogeneities.

2694.   MR-based Field-of-View Extension: Gradient and B0 Correction Post-Processing 
Jan Ole Blumhagen1,2, Ralf Ladebeck1, Matthias Fenchel1, Jürgen Kampmeier1, and Klaus Scheffler2
1Magnetic Resonance, Siemens Healthcare, Erlangen, Bavaria, Germany, 2Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland

Several studies demonstrated rectification of static-field inhomogeneities inside a field-of-view (FoV) of less than 500mm using phantom-based or patient-based post-processing methods. However, in whole-body MR/PET a distortion-free MR image using an axial FoV up to 600mm would improve the human attenuation correction. Furthermore, an extended FoV can be useful in image-guided radio-surgery and biopsy. In this work we will show exemplarily for 2D spin-echo that significant distortion reduction using post-processed B0 correction can be achieved for an axial FoV up to 600mm.

2695.   EPI Distortion Correction Using Magnitude Difference Map 
Hao Lv1, and Yong Chuan Lai1
1MR Engineering, GE Healthcare, Beijing, Beijing, China, People's Republic of

In this study, a novel method using signal Magnitude Difference map (MD map) is proposed to correct EPI distortion. Compared with existing methods, it gives more robust & effective correction while only minimal sequence modification is needed.

2696.   Dynamic unwarping of multi echo EPI data 
Eelke Visser1,2, Benedikt A. Poser3, Markus Barth1,4, and Marcel P. Zwiers1,2
1Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, Netherlands, 2Department of Cognitive Neuroscience, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands, 3Department of Medicine, Queen's Medical Center, Honolulu, Hawaii, United States, 4Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany

Inhomogeneities of the main magnetic field are known to cause considerable geometric distortion of EPI-acquired data. Accelerated acquisition reduces the problem, but does not eliminate it. We calculate field maps directly from the phase maps of the first two echoes in a multi echo EPI acquisition and use these to correct the residual distortions. The resulting geometrical fidelity yields a significant improvement in the co-registration to undistorted data.

2697.   First in vivo results using decoupled projection based shimming 
Daniel Nicolas Splitthoff1, and Maxim Zaitsev1
1Dept. of Radiology, Medical Physics, Unversity Medical Center Freiburg, Freiburg, Germany

It is well known that Echo Planar Imaging (EPI) suffers strongly from geometric distortions caused by B0 inhomogeneities. As a remedy it has for example been suggested to correct for the distortions in the image processing, based on prescans. Nevertheless such approaches relay on the assumption that the field inhomogeneities due not change during the measurement, which is not necessarily the case. We here present an improved version of projection based real time linear shim detection and correction, that takes into account the cross talk between axes, when the orthogonality is broken due to inhomogeneous magnetisation distributions. The applicability of the method is shown in in vivo correction of motion induced shim changes.

2698.   A Novel Correction Method for Distortion Correction in EPI at Ultra High Field MRI using PSF Mapping Technique 
Se-Hong Oh1, Jun-Young Chung1, Myung-Ho In2, Maxim Zaitsev3, Oliver Speck2, Young-Bo Kim1, and Zang-Hee Cho1
1Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea, Republic of, 2Department of Biomedical Magnetic Resonance, Institute for Experimental Physics, Otto-von-Guericke University Magdeburg, Magdeburg, Germany, 3Department of Radiologic Research, Medical Physics, University Hospital of Freiburg, Freiburg, Germany

Echo-planar imaging (EPI) is one of the fastest and most widely used MRI pulse sequences in the field of MRI. Compared to conventional imaging sequence, EPI is more prone to a variety of artifacts. A prominent EPI artifact is geometric distortion due to strong magnetic field inhomogeneity and susceptibility. Recently, a number of different approaches have been proposed for correcting the distortion in EPI, one of them is the point spread function (PSF) mapping method. PSF distortion correction techniques are now extensively used and are successful in the low field strength MRI such as 1.5T or 3.0T. These techniques, however, are still unable to correct distortions in UHF MRI. Especially in UHF MR, EPI image has both compressed and stretched geometric distortions depending on the B1 field inhomogeneity and local susceptibility. The shift map obtained in the non-distortion (x-s) has more information over compressed area. However, the ¡°PSF shift map¡± obtained in the distortion plane or direction (x-y) has more information in stretched area. Therefore, to correct both compressed and stretched region, shift map with more information is selectively applied method is needed. To combine both method we propose a PSF mapping method, which takes into account both the distortion and the non-distortion dimensional correction schemes, instead of previously employed singular method where either non-distortion or distortion dimensional correction are used. By combining the distortion and non-distortion dimensional correction scheme, we can correct more accurately the geometric distortion

2699.   View Angle Tilting in Echo Planar Imaging for Distortion Correction 
Sinyeob Ahn1, and Xiaoping Hu1
1Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States

Distortion caused by field inhomogeneity is prominent along the phase-encode (PE) direction in echo planar imaging (EPI). This work describes a method for correcting image distortion along the PE direction using a view angle tilting (VAT) technique in spin-echo EPI (SE-EPI). SE-EPI-VAT utilizes the addition of gradient blips along the slice-select direction, concurrently applied with the PE gradient blips, producing an additional phase. This phase offsets an unwanted phase by field inhomogeneity, resulting in the correction of distortion. The proposed method is simple and requires no post-processing. It was validated by a phantom and human brain imaging.

Traditional Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.

Wednesday May 11th
Exhibition Hall  13:30 - 15:30

2700.   Evaluation of image quality improvement using wavelet denoising based on Stein's Unbiased Risk Estimate (SURE) 
Tao Zhang1, Peng Lai2, Shreyas Vasanawala3, Robert Herfkens3, Kedar Khare4, Luca Marinelli4, Kevin F King5, and Anja Brau2
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States, 3Radiology, Stanford University, Stanford, CA, United States, 4GE Global Research Center, Niskayuna, NY, United States, 5GE Healthcare, Waukesha, WI, United States

Low SNR in MRI images can usually be found in cases with parallel imaging and acquisitions with high spatial resolution. Image denoising methods can increase SNR. But some of them will introduce artifacts such as image blurring. In this work, wavelet denosing based on Stein’s Unbiased Risk Estimate (SURE) was evaluated on various MRI applications. Comparisons on overall image quality and image sharpness were carried out on these applications. Based on the evaluation results from radiologists, wavelet denoising based on SURE can effectively increase SNR without introducing image blurring.

2701.   Controlled Denoising for fMRI using Adaptive Overcomplete Dictionaries 
Rajesh Venkataraman1, Steen Moeller2, and Essa Yacoub2
1University of Minnesota, Minneapolis, Minnesota, United States, 2University of Minnesota

The abstract describes an algorithm to control the level of denoising using knowledge of intrinsic noise and parallel imaging g-factor for application towards functional MRI

2702.   A Simple Fast Method of Gibbs Ringing Artifact and Noise Reduction with Edge Enhancement Using Low-pass, Band-pass, and High-pass K-Space Windowing Functions 
Leping Zha1, Tsutomu Hoshino1, and Yuichi Yamashita2
1Toshiba Medical Research Institute USA, Inc., Vernon Hills, Illinois, United States, 2Toshiba Medical Systems Corporation, Nasu, Tochigi, Japan

The existing Gibbs ringing reduction methods either blurs out fine details in the images or tend to produce piece-wise constant profile images of unnatural looking for MR. A new simple, fast, and rather straightforward method based on multiplying the k-space data with low-pass, band-pass, and high-pass windowing functions, and combining the results in image space simultaneously and effectively reduces ringing artifacts and noise, and enhance edges and fine details. The key components in the algorithm include optimized matching windowing functions and fast fuzzy edge extraction based on band-pass spatial frequency selection.

2703.   Three dimensional restoration of cardiac magnetic resonance diffusion weighted images based on sparse denoising 
Lijun Bao1, Wanyu Liu2, Changwei Hu1, Xiaobo Qu3, Shuhui Cai1, and Zhong Chen1
1Department of Physics, Xiamen University, Xiamen, Fujian, China, People's Republic of, 2Departments of Automatic Measurement and Control, Harbin Institute of Technology, Harbin, China, People's Republic of, 3Department of Communication Engineering, Xiamen University, Xiamen, Fujian, China, People's Republic of

There are spatial correlations between adjacent layers in cardiac DWI sequence due to the organ consistency, and each DWI contains repetitive structures. Therefore, sparsity could arise from self-similarity of cardiac DWIs. A 3D restoration method based on structure adaptive sparse denoising (SAP-SPDN) is proposed. Experimental results demonstrate that SAP-SPDN algorithm has a good performance in denoising images with high structural redundancy. It can achieve a trade-off between image contrast and smoothness in denoising.

Traditional Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Fat & Water

Thursday May 12th
Exhibition Hall  13:30 - 15:30

2704.   Accelerated Water-Fat Imaging Using Restricted Subspace Fieldmap Estimation 
Samir D Sharma1, Houchun H Hu1, and Krishna S Nayak1
1Electrical Engineering, University of Southern California, Los Angeles, CA, United States

Water-fat separation based on multi-echo methods play an important role in several clinical applications because they reliably separate water and fat signals in the presence of B0-field inhomogeneity. However, multi-echo methods require longer scan times as compared to single-echo imaging. An accelerated imaging technique is desirable to reduce the length of these methods. This work proposes a new approach for water-fat separation from undersampled data acquisitions. The typical voxel-independent model is generalized to consider estimation of water, fat, field map, and R2* images directly from the undersampled k-space data. Unlike previous works, region-growing is not used for field map estimation.

2705.   Joint Inhomogeneitiy Estimation for Water-fat Separation with Multi-peak Fat Modeling 
Wenmiao Lu1, and Yi Lu2
1Electrical & Electronic Engineering, Nanyang Technological University, Singapore, SG, Singapore, 2Electrical and Computer Engineering, University of Illinois, Urbana Champaign, Urbana, IL, United States

Key to the success of phase-sensitive water-fat separation lies in robust estimation of field inhomogeneities. This work describes a novel field map estimation technique that systematically incorporates field map smoothness and a priori likelihood of field map values via belief propagation algorithm, which perform joint estimation of field inhomogeneities across 2D image grid.

2706.   Feasibility of water-fat separation with diffusion weighted EPI 
Ken-Pin Hwang1,2, and Jingfei Ma2
1Global Applied Science Laboratory, GE Healthcare, Houston, TX, United States, 2Department of Imaging Physics, University of Texas M.D. Anderson Cancer Center, Houston, TX, United States

Fat suppression methods for EPI sequences are often prone to inconsistency or loss of SNR. It is observed that with parallel imaging, spatial shift of fat is small relative to the variation in background field. In this study, we evaluate the feasibility of applying water-fat separation to an echo shifting EPI sequence. Without diffusion weighting, successful water-fat separation was achieved without modifications to the algorithm. With diffusion weighting, water-fat separation was possible when phase variations from the coil sensitivity and the background field are first corrected. These phase error maps can be estimated from images acquired without diffusion weighting.

2707.   Two-point Dixon imaging with flexible echo times and a region growing-based postprocessing algorithm 
Jingfei Ma1
1Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, TX, United States

Water and fat separation using a two-point Dixon technique is possible with images obtained at flexible echo times. However, postprocessing has previously been based on a statistical iterative process and involved a specific fat signal model and empirical image thresholding. In this study, we propose an alternative strategy that includes a precalibration method for determining the complex fat signal variation with echo times and a fully automated region growing algorithm for phase correction. Successful application of the proposed strategy was demonstrated by phantom and in vivo images obtained using a 3D dual-echo acquisition with flexible echo times.

2708.   A networked GPU reconstructor within the clinical workflow for rapid fat quantification. 
Grzegorz Kowalik1,2, Jennifer Anne Steeden1,2, David Atkinson2, and Vivek Muthurangu1
1Centre for Cardiovascular MR, UCL Institute of Child Health, London, United Kingdom, 2Centre for Medical Image Computing, UCL Department of Medical Physics & Bioengineering, London, United Kingdom

Rapid imaging techniques and quantitative model fitting often require significant computation time that hinders clinical uptake. A good example is MRI fat water separation techniques. This work aims to provide a GPU accelerated image reconstruction platform to facilitate computationally intensive algorithms. Flexible networking architecture is used to accommodate bidirectional communication between an external reconstruction system and a scanner. The implementation uses affordable GPU card to provide a real time response. T2-IDEAL reconstruction, as an example of time-consuming algorithm, is implemented and tested in clinical environment. The adopted reconstruction framework allows rapid reconstruction and immediate assessment of the results.

2709.   Combining phase images from multi-channel RF coils using 3D phase offset maps derived from a dual-echo scan 
Simon Robinson1, Günter Grabner1, Stephan Witoszynskyj1, and Siegfried Trattnig1
1Department of Radiology, Medical University of Vienna, Vienna, Austria

We present a new, simple method for the combination of phase images from multi-channel coils without the need for a volume reference coil or prior processing such as spatial filtering. The method is based on the calculation and subtraction of 3D phase offsets for each channel which are derived from a dual-echo scan. This data comes either from the high resolution scan or is acquired in a separate, fast, low resolution scan. This second alternative is particularly computationally efficient, can be applied to single-echo high resolution data, and requires only a short (circa 30 s) additional measurement. Both method variants give near-perfect phase matching are compatible with parallel imaging.

Traditional Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the pdf of the poster viewable in the poster hall.
Fat-Water MRI

Monday May 9th
Exhibition Hall  14:00 - 16:00

2710.   Fat Fraction Bias Correction using Estimated T1 Values 
Issac Yiqun Yang1, Curtis Nathan Wiens2, Lanette Friesen-Waldner1, and Charles Andrew McKenzie1,2
1Medical Biophysics, University of Western Ontario, London, Ontario, Canada, 2Physics and Astronomy, University of Western Ontario, London, Ontario, Canada

Synopsis: Using small flip angles with IDEAL-SPGR acquisitions reduces T1 bias in fat fraction quantification at the cost of decreased SNR. Since the exact T1 values are unknown, bias correction using estimated T1s was investigated. Simulations were used to determine theoretical decrease in fat fraction bias using T1s of various deviations. Measurement of T1 bias in phantoms of various fat fractions demonstrated that fat fraction bias can be reduced with estimated T1s, even when those values are significantly different from the true T1. This suggests that using estimated T1s can be a simple but effective means of fat fraction bias correction.

2711.   Fat Water Classification of Symmetrically Sampled Two-Point Dixon Images Using Biased Partial Volume Effects 
Thobias Romu1,2, Olof Dahlqvist Leinhard2,3, Mikael F Forsgren3,4, Sven Almer4, Nils Dahlström3,5, Stergios Kechagias3, Fredrik Nyström3, Örjan Smedby2,3, Peter Lundberg1,2, and Magnus Borga2,6
1Department of Radiation Physics, Center for Surgery, Orthopedics and Oncology, Linköping University Hospital, Linköping, Sweden, 2Center for Medical Imaging Science and Visualization (CMIV), Linköping University, Sweden, 3Department of Medical and Health Sciences, Linköping University, Sweden, 4Department of Clinical and Experimental Medicine Faculty of Health Science, Linköping University, Sweden, 5Department of Radiology, Diagnostic Imaging Center, Linköping University Hospital, Sweden, 6Department of Biomedical Engineering, Linköping University, Sweden

Fat and water classification of symmetrically sampled two-point Dixon images is required for automatic post processing of the data after the phase sensitive reconstruction. The problem was resolved by analyzing the fat/water partial volume intensities which were biased due to the mean intensity difference between the two classes of signal. An evaluation was performed on pre and post Gd-EOB-DTPA injection volumes of the liver and whole-body datasets. A total of 905 tissue volumes were included in the evaluation. Visual classification was used as a golden standard. The result was a 100% success rate.

2712.   Simultaneous Quantification of Fat Fraction and Fatty Acid Composition Using MRI 
Pernilla Peterson1, and Sven Månsson1
1Medical Radiation Physics, Lund University, Malmö, Sweden

In this phantom study, a new reconstruction algorithm based on multi-echo imaging is introduced which uses theoretical knowledge of the chemical structure of fatty acids (FA) to simultaneously quantify the fat fraction (FF) and the FA composition. An iterative least squares approach was used to estimate the number of double bonds, number of methylene-interrupted double bonds, chain length and water and fat signals. From these estimates, FF and the fraction unsaturated FA (UF) were calculated. Both FF and UF were successfully quantified. These results clearly show that the investigated imaging technique enables simultaneous quantification of FF and FA composition.

2713.   Assessment of Accuracy, Repeatability, Reproducibility and Robustness of Fat Quantification in a Water-Fat Phantom 
Huanzhou Yu1, Catherine D.G. Hines2, Ann Shimakawa1, Charles A McKenzie3, Scott B Reeder4, and Jean H. Brittain5
1Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States, 2Departments of Radiology, Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, United States,3Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada, 4Departments of Radiology, Medical Physics, Biomedical Engineering, University of Wisconsin, Madison, WI, United States, 5Global Applied Science Laboratory, GE Healthcare, Madison, Wisconsin, United States

In this work, we assess the performance of an IDEAL-based fat quantification method in a water-fat phantom with fat-fractions ranging from 0 to 100%. Assessment of the ground truth in phantoms allows evaluation of accuracy. By repeating the scans on the same scanner and different scanners, precision including repeatability and reproducibility are also evaluated. Finally, robustness is studied by changing a variety of imaging parameters. We demonstrate that quantitative IDEAL is highly accurate, repeatable, reproducible and robust. It has potential to offer an accurate and precise MR imaging method to measure fat-fraction in a 0~100% range, independent of imaging parameters.

2714.   Mapping the Double Bonds in Triglyceride 
Mark Bydder1, Gavin Hamilton1, Michael S Middleton1, and Claude B Sirlin1
1University of California San Diego, San Diego, CA, United States

This study demonstrates the validity and feasibility of using chemical shift imaging to map the degree of saturation of triglycerides.

2715.   Noise Performance of Magnitude-based Water-Fat Separation is Sensitive to the Echo Times 
Huanzhou Yu1, Ann Shimakawa1, Diego Hernando2, Catherine D.G. Hines3, Charles A McKenzie4, Scott B Reeder5, and Jean H. Brittain6
1Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States, 2Departments of Radiology, University of Wisconsin, Madison, Wisconsin, United States, 3Departments of Radiology, Biomedical Engineering, University of Wisconsin, Madison, Wisconsin, United States, 4Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada,5Departments of Radiology, Medical Physics, Biomedical Engineering, University of Wisconsin, Madison, WI, United States, 6Global Applied Science Laboratory, GE Healthcare, Madison, Wisconsin, United States

Accurate fat-fraction quantification using chemical shift based water-fat separation methods requires correction of eddy-current induced phase errors that can lead to substantial errors at low fat-fraction estimates. The undesired phase modulation can be removed by magnitude-signal based water-fat separation methods. We show that noise performance of the magnitude-based reconstruction is sensitive to echo times. Some combinations of echo times may result in poor noise performance, demonstrated by both simulations and in-vivo scans. As a result, careful design of the acquisition is required to avoid poor SNR that may lead to inaccurate fat-fraction measurement when using magnitude-based methods.

2716.   Water fat opposed phase (WFOP) sequence is a robust fat suppression technique under the presence of B0 inhomogeneity in abdominal MRI at 3.0 T. 
Koji Fujimoto1, Tomohissa Okada1, Aki Kido1, Hiroshi Kusahara2, Andrew Wheaton3, Mitsue Miyazaki3, and Kaori Togashi1
1Diagnostic Imaging and Nueclear Medicine, Kyoto university, Kyoto, Kyoto, Japan, 2Toshiba Medical Systems Corporation, Otawara, Tochigi, Japan, 3Toshiba Medical Research Institute, USA, OH, United States

Robustness of water fat opposed phase (WFOP) sequence to B0/B1 inhomogeneity was evaluated at 3T quantitatively and qualitatively by comparing with CHESS, and SPAIR. Voxels with unsuppressed fat due to B0 inhomogeneity was fewest for WFOP, and the degree was well presented by inhomogeneity index. Image quality was rated best for SPAIR due to effects of B1 field inhomogeneity in WFOP and CHESS.

2717.   Fully Automated Quantification of Subcutaneous and Visceral Abdominal Adipose Tissue using Water and Fat Acquisition and Graph Cuts 
Vitali Zagorodnov1, Sarayu Parimal2, and Michael WL Chee2
1Nanyang Technological University, Singapore, Singapore, Singapore, 2Duke-NUS Graduate Medical School

We developed a fully automated algorithm for quantification of visceral (VAT) and subcutaneous (SAT) adipose tissue. Our algorithm is based on water and fat acquisition (Dixon sequences), and improves on previous work by utilizing fat-fraction images (for fat/non-fat separation) and graph cuts (for separation of VAT and SAT compartments). In our evaluation, the algorithm achieved excellent correlations with manual measurements, and outstanding reproducibility for both SAT and VAT (coefficient of variation 1.5% and 2.3% respectively).

2718.   Image-based weighted B0 shimming using a fast multi-echo DIXON technique: feasibility for abdominal imaging 
Arjan Willem Simonetti1, Gabriele Beck1, Hans Hoogduin2, Jeroen C.W. Siero3, and Gwenael Herigault4
1MR CTO, Philips Healthcare, Best, Netherlands, 2Brain Division University Medical Center Utrecht, Utrecht, Netherlands, 3Rudolf Magnus Institute, University Medical Center Utrecht, Utrecht, Netherlands, 4Clinical Science, Philips Healthcare, Best, Netherlands

Clinically acceptable fat suppression is a key element in abdominal MRI. B0 homogeneity plays an important role in achieving fat suppression, but is not always optimal using standard spectral-based B0 shimming approaches. We propose a new method that combines mDIXON and image-based weighted B0 shimming to achieve optimal fat suppression. mDIXON allows to generate 3D B0 maps as well as water and fat images which, when automatically segmented, can be used to tailor the cost function method employed in our shimming approach. Our results show that this method improves significantly fat suppression without impact on examination workflow and duration.