Electronic Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the video presentation.
Artifacts & Correction - Eddy Currents & B0 Homogeneity
Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 129

14:00 4564.   Correcting High Order Eddy Current Induced Distortion for Diffusion Weighted Echo Planar Imaging 
Dan Xu1, Joe K. Maier2, Kevin F. King1, Bruce D. Collick2, Hong Huang2, Tony M. Linz2, and Gaohong Wu2
1Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States, 2GE Healthcare, Waukesha, WI, United States

Eddy currents of high spatial order can generate slice and diffusion direction dependent distortions in diffusion weighted echo planar imaging (DW-EPI). In this paper, we propose two complementary methods to correct such distortions: The first method modifies gradient waveform amplitudes and receiver frequency on a slice-by-slice basis in the pulse sequence using predicted high order eddy current (HOEC) field, and the second method corrects the distorted images by image-domain post processing. Body diffusion results show that the proposed methods are capable of significantly reducing HOEC induced distortions for DW-EPI.

14:30 4565.   A 3D eddy current model for the prediction of geometric image distortions in Stejkal-Tanner diffusion weighted EPI 
Kieran R O'Brien1,2, Nils Kickler2, Francois Lazeyras1, Rolf Gruetter2, Thorsten Feiweier3, and Gunnar Krueger4
1Department of Radiology, Université de Genève, Geneva, Switzerland, 2Laboratory for functional and metabolic imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 3Siemens Healthcare Sector, Erlangen, Germany, 4Advanced Clinical Imaging Technology, Siemens Suisse SA, Lausanne, Switzerland

The current correction methods available to remove geometric image distortions seen in eddy current (EC) sensitive diffusion weighting (DW) echo planar imaging involve time intensive EC field measurements or have limited reliability at high b-values (>1000s/mm2). We propose a 3D-EC field measurement “tune-up” scan to model and to predict the 0th/1st order ECs originating from the applied DW-gradients. After 0th and 1st order distortion correction, EC induced spatial misalignments are visibly reduced and the image quality becomes comparable to the currently clinically preferred twice refocused spin echo scheme.

15:00 4566.   Efficient correction of static and dynamic (including eddy current) field inhomogeneity in DTI data 
Erik B Beall1, Wanyong Shin1, Kecheng Liu2, Ken E Sakaie1, Mingyi Li1, Dominic Holland3, Anders M Dale4, and Mark J Lowe1
1Imaging Institute, Cleveland Clinic, Cleveland, OH, United States, 2Siemens Medical Solutions USA, Inc, Malvern, PA, United States, 3Neurosciences, University of California, San Diego, La Jolla, CA, United States, 4Radiology, University of California, San Diego, La Jolla, CA, United States

White matter diffusion MRI is affected by both static field inhomogeneity and dynamic field distortions from eddy currents induced by the diffusion gradients. A recent method providing robust image unwarping using forward and reverse phase-encode direction EPI scans is applied to DTI data acquired with paired forward/reverese phase-encode volumes, for every volume. In this way, dynamic displacement maps due to both static inhomogeneity and dynamic eddy current artifacts can be calculated for every volume. We present results showing that this method produces improved image quality in both twice and single refocus spin-echo DTI.

Silvia De Santis1,2, Shani Ben Amitay3, Yaniv Assaf3, and Derek K Jones1
1CUBRIC, School of psychology, CARDIFF University, United Kingdom, 2Physics department, Sapienza University, Rome, Italy, 3Tel Aviv University, Israel

We propose a simple procedure for eddy currents correction based on a linear model for the distortions as a function of gradient amplitude. The model was first test on a tetradecane phantom and then applied to human brain. The procedure was demonstrated to improve the fit quality when a CHARMED data analysis is performed. Furthermore, the corrections can be combined with a model for motion-induced distortions to further improve the data quality.

Tuesday May 10th
  13:30 - 15:30 Computer 129

13:30 4568.   Automatic Geometric Distortion Correction for Single-Shot Echo Planar Imaging 
Thomas Benner1, Andre J. W. van der Kouwe1, Caterina Mainero1, Dominic Holland2, and Anders M. Dale2
1Radiology, Athinoula A. Martinos Center, Charlestown, MA, United States, 2Multimodal Imaging Laboratory, University of California, San Diego, La Jolla, CA, United States

Single-shot EPI suffers from spatial and intensity distortions caused by B0 field inhomogeneities. For comparison with anatomical MRI scans, undistorted images are highly desirable. We demonstrate a fully automatic version of a method to correct geometric distortions as implemented on Siemens MRI scanners. The method involves a displacement mapping scan based on two EPI scans with opposed phase encoding polarities together with a fast nonlinear alignment procedure. Results show better match of unwrapped data to the anatomical data as demonstrated in BOLD and DTI scans. The method has also been implemented in other EPI scans like PACE and ASL.

14:00 4569.   Distortion Correction of Single-Shot Spin-Echo EPI of the Liver at 3T 
Kevin M Koch1, Dominic Holland2, Dan Xu1, Ajit Shankaranarayanan3, and Anders Dale2
1Global Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States, 2Department of Neurosciences, University of California, San Diego, United States, 3Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States

A variety of techniques and algorithms have been proposed for distortion correction of EPI in the brain. However, EPI is also commonly used for diffusion imaging in other parts of the body. Correction of susceptibility-induced image distortions is a greater challenge in many of these anatomic regions. Here, we investigate the capability of a reversed-gradient-polarity acquisition and algorithm in correcting single-shot spin echo images of the human liver at 3T. Significant improvements in liver shape and positioning are demonstrated using the presented methods.

14:30 4570.   Point Spread Function Map for Distortion Correction with Double EPI Readout Acquisition Strategy at 3T 
Yu Cai1, Qingwei Liu2, Mark Woods1, Craig Hamilton3, and Hongyu An2
1Advanced Imaging Research Center, Oregon Health & Science University, Portland, Oregon, United States, 2University of North Carolina atg Chapel Hill, 3Wake Forest University

The current Point Spread Function (PSF) mapping technique uses an extra 2-3 min of scan time to acquire a PSF map for echo planar imaging (EPI) distortion correction, based on prevalent EPI acquisition parameters used in fMRI studies. However, when a subject moves during scanning the PSF map may not for the most appropriate method of distortion correction. A dual EPI readout train acquisition strategy has been developed that improves the performance of PSF map correction. This strategy embeds the PSF acquisition into the gradient echo EPI acquisition without increasing scan time synchronizes with the EPI acquisition.

15:00 4571.   Improved PSF Mapping Acceleration Technique for EPI Geometric Distortion Correction at 7 Tesla 
Myung-Ho In1, and Oliver Speck1
1Biomedical Magnetic Resonance, Otto-von-Guericke-University, Magdeburg, Germany

We propose an improved acceleration of the point spread function (PSF)data acquisition which acquires PSF data for EPI distortion correction with a new reduced sampling pattern in PSF dimension. Reduction of the PSF FOV and resolution are combined to an inhomogeneous sampling pattern. Fold-over effects caused by the high FOV reduction are resolved with by additional lines in k-space center. The results show that distortions in EPI can be corrected robustly and without loss of quality. The advantages of the proposed method for the geometric distortion correction in EPI are demonstrated in human brain in vivo at 7.0 Tesla.

Wednesday May 11th
  13:30 - 15:30 Computer 129

13:30 4572.   3D Magnetic Susceptibility Correction with Application to Diffusion-Weighted Imaging 
Anh Tu Van1, and Bradley P Sutton2
1Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 2Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States

To achieve a realistic scan time in vivo and mitigate the undersampling due to the rigid-body-motion-induced phase errors, 3D diffusion-weighted imaging usually has long readout duration leading to severe magnetic susceptibility artifacts even when a spin echo acquisition is used. The current study proposes to correct for the magnetic susceptibility artifacts in 3D diffusion-weighted imaging by incorporating the 3D field map information in the 3D encoding matrix and solving the inverse problem iteratively. In vivo results show the effectiveness of the proposed method in minimizing the magnetic susceptibility artifacts and improving the delineation of white matter structures in diffusion-weighted imaging.

14:00 4573.   Distortion correction of multi-coil diffusion-weighted EPI using the phase-based method: PLACE 
Sofia Chavez1, Elizabeth Ramsay1, Masoom Haider1,2, Qing-San Xiang3, and Greg Stanisz1,4
1Imaging Research, Sunnybrook Research Institute, Toronto, ON, Canada, 2Department of Radiology, University of Toronto, Toronto, ON, Canada, 3Department of Radiology, University of British Columbia, Vancouver, B.C., Canada, 4Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

It has been shown that the B0 inhomogeneity distortion occuring in single-coil EPI diffusion weighted images (DWIs) can be corrected using PLACE, a phase-based method. In this work, a method is presented which combines the multi-coil data for the two images required for PLACE while preserving the useful phase information. It is shown that although the inter-coil phase relation is not known, the phase relation between the two EPI acquisitions is coil independent for b=0. Phase difference images are produced for each coil and then complex averaging yields the distorted phase ramp. PLACE can use this to correct magnitude DWIs.

14:30 4574.   A correction of amplitude variation using navigators in an interleave-type multi-shot EPI at 7T 
Dae-Hun Kang1, Se-Hong Oh1, Jun-Young Chung1, Young-Bo Kim1, Seiji Ogawa1, and Zang-Hee Cho1
1Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea, Republic of

In this paper, we propose the technique to compensate amplitude variations on k-space comparing the energy of navigators of segments in interleave-type multi-shot EPI with variable flip angle

15:00 4575.   Dynamic Correction of Artifacts due to Susceptibility Effects and Time-Varying Eddy Currents in DTI 
Trong-Kha Truong1, Nan-kuei Chen1, and Allen W Song1
1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States

DTI is vulnerable to variations of the static magnetic field caused by susceptibility effects as well as eddy currents induced by the diffusion gradients. Their dependence on space, time, and/or diffusion direction causes distortions, blurring, and misregistration, leading to errors in the derivation of the diffusion tensor. Existing correction methods assume that the eddy currents remain constant within the readout window or decay monoexponentially, which is known not to be the case. Here, we propose a novel dynamic correction method that measures their exact time dependence and can effectively and efficiently correct for both susceptibility- and eddy current-induced artifacts.

Thursday May 12th
  13:30 - 15:30 Computer 129

13:30 4576.   Dynamic Distortion Correction of SE EPI data using Phase Maps from Simultaneously-Acquired GE-EPI data 
jack harmer1, Susan Francis1, and Richard Bowtell1
1SPMMRC, The University of Nottingham, Nottingham, Nottinghamshire, United Kingdom

EPI acquisitions are highly susceptible to image distortions due to the presence of B0-field inhomogeneities. A powerful approach which can be used to correct dynamically varying distortions in GE fMRI time series involves exploiting the phase of the EPI data in conjunction with a single reference field-map. We show that this dynamic distortion correction can be applied to SE data by modifying a SE-EPI sequence to acquire a GE-image before the 180 RF pulse and then using the phase of the GE-EPI data to monitor field variation. This method has been tested on SE-EPI data acquired at 7T.

14:00 4577.   Dynamic Phase Echo-Planar Imaging - Detection and Correction of Dynamic Off-Resonance 
Josef Pfeuffer1, Dingxin Wang2, and Christina Triantafyllou3
1MR Application Development, Siemens Healthcare, Erlangen, D, Germany, 2US R&D, Siemens Healthcare, Minneapolis, MN, United States, 3McGovern Institute for Brain Research, MIT, Cambridge, MA, United States

Dynamic B0-off-resonance, caused by subject physiology (respiration), leads to dynamic image artifacts in fast imaging sequences such as pixel shifts in PE direction for blipped EPI. Image phase EPI can be used for distortion correction in a static or dynamic mode using field maps or techniques such as PLACE. Our goal was to investigate the effects of global frequency drifts on dynamic phase EPI, secondly to employ navigator methods to robustly correct for these effects and evaluate remaining image phase EPI stability. The phase temporal SD could be significantly reduced in all sessions and was demonstrated also for all different orientations.

14:30 4578.   Dynamic Fieldmap Estimation for Respiration Correction based on single shot 3D images 
Benjamin Zahneisen1, Thimo Grotz1, Maxim Zaitsev1, and Juergen Hennig1
1University Hospital Freiburg, Freiburg, Germany

The aim of this work is to estimate dynamic changes of precession frequencies (off-resonance map) from dynamic changes of the image phase of a reconstructed time series. The dynamic changes are measured relative to a reference time point. Feeding back the dynamic off-resonance map to the reconstruction results in a ~64% reduction of respiration fluctuations in the signal time series compared to ~40% for the DORK-method. The approach provides a spatial map of the off-resonances and therefore allows one to restrict the calculation of the field map to a ROI and exclude unwanted regions that also influence the object’s phase.

15:00 4579.   Recovering fine-scale features in spiral imaging with piecewise linear off resonance correction (PLORC) 
Travis Benjamin Smith1, and Krishna S Nayak1
1Electrical Engineering, University of Southern California, Los Angeles, CA, United States

Spiral trajectories are often used to create fine-resolution images with time-efficient acquisitions. The long readout durations necessary to achieve this efficiency makes spiral imaging susceptible to blurring artifacts from off resonance. Point spread function blurring limits the effective resolution achieved in the images and negates some of the benefit of spiral acquisitions. We present a piecewise linear off resonance correction (PLORC) method for accurately deblurring spiral images. The proposed algorithm is computationally similar to standard frequency-segmented methods but is capable of recovering finer image details.

Electronic Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the video presentation.
Pulse Sequences - Corrections

Tuesday May 10th
Exhibition Hall  13:30 - 15:30 Computer 130

Xue Feng1, Sameul William Fielden1, Hao Tan1, and Craig H Meyer1,2
1Biomedical Engineering, University of Virginia, Charlottesville, Virginia, United States, 2Radiology, University of Virginia, Charlottesville, Virginia, United States

Spiral-in/out bSSFP differs from spiral-out bSSFP in that it has a symmetric spiral-in gradient in front of a spiral-out gradient. This yields TE=TR/2 and leads to nulling of the 0th and 1st gradient moments via symmetry, which saves time compared to a flow-compensated spiral rewinder. However, eddy currents and other gradient imperfections of the gradient system affect the fidelity of the k-space trajectory and cause blurring and distortion in reconstructed images. In this abstract we compare cardiac spiral-in/out bSSFP images reconstructed using a k-space trajectory calculated using a single gradient delay model to those reconstructed using a model that incorporates gradient delays and eddy currents calibrated for each physical axis. We compare each of these to measured trajectories. In addition, we measured B0 eddy currents and analyzed their effect in spiral-in/out bSSFP imaging. Using estimated trajectory corrects most of the infidelity in k-space trajectory and improves the image quality. B0 eddy currents, however, have little effect on the reconstructed images.

14:00 4581.   UTILE – A fast combined UTE-DIXON four class attenuation correction technique for PET/MR 
Jochen Franke1,2, Hank Donker3, Felix Mottaghy4, Christiane Kuhl3, Fabian Kiessling2, and Volkmar Schulz1,2
1Molecular Imaging Systems, Philips Research Europe, Aachen, North Rhine-Westphalia, Germany, 2Experimental Molecular Imaging, University of Aachen (RWTH), Aachen, North Rhine-Westphalia, Germany, 3Diagnostic and Interventional Radiology, University Hospital Aachen, Aachen, North Rhine-Westphalia, Germany, 4Nuclear Medicine, University Hospital Aachen, Aachen, North Rhine-Westphalia, Germany

The focus of this work is on the emerging methodology of magnetic resonance (MR)-based attenuation correction (MRAC) of positron emission tomography (PET) raw data. We propose a new MR sequence, comprising the functionality of ultrashort echotime (UTE) and the Dixon technique within a single examination. This UTE triple-echo (UTILE) sequence paired with a dedicated post-processing is capable to derive a truly MR-based attenuation map (µ-map) accounting for four compartments: soft tissue, adipose tissue, cortical bone and air.

14:30 4582.   An accelerating method for FSE phase correction 
Weiwei Zhang1, and Yongchuan Lai1
1GE Healthcare, Beijing, Beijing, China, People's Republic of

In this study, an accelerating phase correction method is introduced to reduce the pre-scan time for Fast Spin Echo pulse sequence (FSE). Compared with traditional phase correction method using an iterative approach with several shots data acquisition, this new method compresses all data acquisition within one shot.

15:00 4583.   STAGES: Dynamic Shimming by Nonlinear Phase Preparation and K-Space Parcellation in Steady-State MRI 
Walter RT Witschey1, Christian A. Cocosco1, Daniel Gallichan1, Gerrit Schultz1, Hans Weber1, Anna Masako Welz1, Jürgen Hennig1, and Maxim Zaitsev1
1Medical Physics, University Medical Center Freiburg, Freiburg i. Breisgau, Germany

A method is presented to dynamically shim a single spatially encoded volume in steady-state sequences. Nonlinear phase preparation is used to temporally disperse gradient echoes originating from different positions within a volume. These echoes are locally shimmed using a k-space parcellation algorithm. Simulations and experiments are performed to eliminate bSSFP stop band artifacts along the direction of phase encoding.

Electronic Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the video presentation.
Artifacts & Correction: Motion I

Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 131

14:00 4584.   External Calibration Parallel Imaging for Improved Motion Correction Capabilities with T1 FLAIR PROPELLER 
James H Holmes1, Philip J Beatty2, Howard A Rowley3, Zhiqiang Li4, Ajeetkumar Gaddipati5, Xiaoli Zhao5, Reed F Busse6, and Jean H Brittain1
1Global Applied Science Laboratory, GE Healthcare, Madison, WI, United States, 2Global Applied Science Laboratory, GE Healthcare, Toronto, ON, Canada, 3Radiology, University of Wisconsin-Madison, 4MR Engineering, GE Healthcare, Phoenix, AZ, 5MR Engineering, GE Healthcare, Waukesha, WI, 6MR Research, GE Healthcare, Waukesha, WI

While the mask data is much less sparse, it does allow removal of unaliasing over all regions of the legs that have pre-contrast signal.

14:30 4585.   Measuring Effect of Embedded Navigators on MEMPRAGE Tissue Contrast 
M. Dylan Tisdall1,2, Martin Reuter1,3, and Andre van der Kouwe1,2
1Athinoula A. Martinos Center for Biomedical Imaging, Masschusetts General Hosptial, Charlestown, MA, United States, 2Radiology, Harvard Medical School, Brookline, MA, United States, 3Neurology, Harvard Medical School, Brookline, MA, United States


15:00 4586.   Motion-insensitive structural MRI based on Repeated Imaging with Echo-planar Navigation and Acceleration (RIENA): Demonstrated with susceptibility-weighted imaging in the presence of frequent intra-scan tremors 
Nan-kuei Chen1
1Brain Imaging and Analysis Center, Duke University Medical Center, Durham, NC, United States

Here we report a novel strategy to remove MRI motion artifacts. Our new approach, termed Repeated Imaging with Echo-planar Navigation and Acceleration (RIENA), can generally be applied to various structural MRI. In this abstract we demonstrate the application of RIENA to remove motion artifacts in susceptibility-weighted imaging, even in the presence of frequent intra-scan tremors. The developed RIENA technique has higher scan efficiency than conventional sequences (e.g., SPGR), making it possible to acquire multiple images within the same scan time. Using the embedded EPI navigator, the intra-scan motion can be characterized and removed effectively, before multiple acquired images are combined.

15:30 4587.   Comparison of MR-Navigator and Optical Tracking Methods for Adaptive Motion Correction 
Kazim Z Gumus1, Brian Keating1, Brian Andrews-Shigaki2, Brian Armstrong3, Anders Dale4, and Thomas M Ernst1
1John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, United States, 2Department of Military & Emergency Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States, 3Electrical Engineering and Computer Science, University of Wisconsin-Milwaukee, Milwaukee, WI, United States,4Department of Radiology, University of California, San Diego, La Jolla, CA, United States

This study compares two methods to track head motion in real-time, MRI-based PROMO (PROspective Motion Correction) and optical-based Retro Grate Reflector (RGR) tracking system. A volunteer performed head rotations about the scanner X- and Z- axes while being tracked with PROMO and simultaneously with RGR. High resolution MP-RAGE images immediately before and after the scan were realigned with SPM to provide a “gold standard”. Tracking with RGR and PROMO differed from SPM registration up to 2mm and 2°. The possible causes of the non-negligible errors are presented. This study highlights the need for an independent method to evaluate tracking systems for adaptive MRI motion correction.

Tuesday May 10th
  13:30 - 15:30 Computer 131

13:30 4588.   Motion-Corrected Single Shot Fast Spin-Echo MRI using Prospective Motion Tracking and Retrospective Super-Resolution Volume Reconstruction 
Ali Gholipour1, Martin Polak1, Andre van der Kouwe2, Erez Nevo3, and Simon K Warfield1
1Computational Radiology Laboratory, Children's Hospital Boston, and Harvard Medical School, Boston, MA, United States, 2Martinos Center for Biomedical Imaging, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, United States, 3Robin Medical, Inc., Baltimore, MD, United States

We have developed a novel motion-robust T2-weighted MRI scheme based on single-shot fast spin echo imaging, real-time sensor-based prospective motion tracking, and retrospective super-resolution volume reconstruction. This technique has a simple setup as it requires the attachment of a single miniature magnetic field sensor to the subject head and is platform independent. Quantitative evaluation results obtained for phantom and volunteer subject experiments show the efficacy of the developed technique. This technique enables motion robust imaging, and may enable a reduction in the use of sedation in imaging newborns, children and adults who cannot hold still in the scanner.

14:00 4589.   Combined Real-Time Prospective Motion Correction and Concurrent Field Monitoring 
Maximilian Haeberlin1, Lars Kasper1, Christoph Barmet1, Signe Johanna Vannesjö1, Sebastian Kozerke1, and Klaas Paul Pruessmann1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

We propose to rigidly mount small, long-lifetime NMR probes to the object in order to concurrently monitor field evolutions in the object frame of reference and perform real-time motion correction without extra scan sequences. In particular, a mere 1ms rephasing gradient is enough to accurately resolve the slice select direction. We show that concurrently monitored acquisitions subject to motion can be reconstructed when calibration-based reconstructions fail and that performing the experiment in the object frame of reference can heavily alleviate image co-registration.

14:30 4590.   Impact of Motion on Parallel Transmission 
Roland Bammer1, Bei Zhang2, Weiran Deng3, Graham C Wiggins2, Andy V. Stenger3, and Daniel K. Sodickson2
1Radiology, Stanford University, Stanford, CA, United States, 2Radiology, New York University Langone Medical Center, New York, New York, United States, 3JABSOM, University of Hawaii, Honolulu, HI, United States

Due to the sequential nature of MRI, patient motion affects not only signal reception and encoding but also parallel transmit MRI (pTx). An obvious challenge is when pose changes happen between the measurement of coil sensitivities & the design of the corresponding RF waveforms and the point in time when RF pulses are actually played out on the system (as the patient might be exposed to an entirely different B1+ field). This will ultimately affect one’s pTx approach to fully handle unwanted aliasing in the excited region, as well as impair the outcome of pTx-based B1+ mitigation and B1+-shimming approaches. The purpose of this simulation study was to demonstrate pTx’s sensitivity to motion and how desired excitation patterns can potentially be degraded by patient motion.

15:00 4591.   Correction of Subject Motion in Quantitative T2*-Mapping 
Joerg Magerkurth1,2, Steffen Volz2, Marlies Wagner1, Alina Jurcoane1, Sandra Anti2, Elke Hattingen1, and Ralf Deichmann2
1Institute of Neuroradiology, Goethe University Frankfurt, Frankfurt/Main, Germany, 2Brain Imaging Center (BIC), Goethe University Frankfurt, Frankfurt/Main, Germany

A method for the correction of artifacts induced by subject motion in quantitative T2* maps is presented, based on scan repetition with reduced spatial resolution and weighted averaging of both raw data sets, choosing the weighting factor individually for each k-space line to eliminate motion affected contributions. The technique is tested on healthy volunteers performing deliberate head movement during the scan. The method can be implemented on any clinical scanner allowing for multiple gradient echo imaging with modulus and phase data export.

Wednesday May 11th
  13:30 - 15:30 Computer 131

13:30 4592.   DTI with prospective motion correction and reacquisition in a clinical subject population 
Thomas Benner1, Andre J. W. van der Kouwe1, and A. G. Sorensen1
1Radiology, Athinoula A. Martinos Center, Charlestown, MA, United States

Subject motion is a major source of image artifacts in DTI, causing misalignment of images, blurriness and erroneous values in the derived maps. A method that combines prospective motion correction with reacquisition of image data affected by motion is tested in a clinical subject population. Results show that motion tracking works well as does detection of images with artifacts. The corrected data is free of artifacts that are visible in the uncorrected images.

14:00 4593.   Combined Prospective Rigid-Body Motion Correction with Retrospective Non-Rigid Distortion Correction for EPI 
Melvyn B Ooi1, Roland Bammer1, and Truman R Brown2
1Radiology, Stanford University, Stanford, CA, United States, 2Radiology, Medical University of South Carolina, Charleston, SC, United States

Despite rigid-body realignment to compensate for head motion during an EPI time-series scan, non-rigid-body image deformations remain due to changes in the effective shim within the brain as the head moves through the B0 field. The current work presents a combined prospective + retrospective motion correction solution. Prospective rigid-body correction, where the scan-plane orientation is dynamically updated to track with the subject's head, is performed using an active marker setup. A retrospective distortion correction algorithm that uses the complex EPI-data is then applied to unwarp the remaining non-rigid image deformations caused by motion-induced shim changes.

14:30 4594.   Inherent Correction of Motion-Induced Phase Errors in Multishot Spiral Imaging using Iterative Phase Cycling 
Trong-Kha Truong1, Nan-kuei Chen1, and Allen W Song1
1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States

Spiral imaging is a promising alternative to EPI for DTI because of its efficient k-space coverage and low sensitivity to flow artifacts. Multishot acquisitions are typically required to achieve a high resolution while minimizing off-resonance effects. However, shot-to-shot phase variations induced by motion in the presence of diffusion gradients lead to severe artifacts. Variable-density spiral trajectories can be used to correct for such artifacts, but result in a longer scan time. Here, we propose a novel iterative phase cycling method that can effectively and efficiently correct for motion-induced phase errors in multishot spiral imaging without requiring any additional navigator.

15:00 4595.   Retrospective Registration-Based Motion Correction with Interleaved Radial Trajectories 
Ashley Gould Anderson III1, Julia Velikina1, Oliver Wieben1,2, and Alexey Samsonov2
1Medical Physics, University of Wisconsin, Madison, Wisconsin, United States, 2Radiology, University of Wisconsin, Madison, Wisconsin, United States

A retrospective approach to motion correction that takes advantage of the self-navigation properties inherent to radial acquisitions is introduced. This technique requires no additional navigator echoes or external motion detection schemes. Consistent subsets of data are determined retrospectively using multi-coil center of mass analysis and co-registered to estimate motion parameters. Avoiding a priori assumptions about when motion-free periods occur improves scan efficiency and potentially correction accuracy, allowing robust correction of 2D and 3D rigid body motion. The technique is demonstrated with applications to 3D cranial imaging.

Thursday May 12th
  13:30 - 15:00 Computer 131

13:30 4596.   Non-iterative navigator-based approach: advances towards real time 3D motion correction 
Junmin Liu1,2, and Maria Drangova1,2
1Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada, 2Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada

This abstract presents a non-iterative navigator-based motion correction technique applied to spherical navigator (SNAV) data acquired using multi-element RF coils. The method is based on the pre-rotated SNAV (preRot-SNAV) technique where rotation is determined by identifying the best match template from a set of pre-rotated baseline SNAVs. Three different methods for combining the raw data were evaluated. In vivo results demonstrate the feasibility and practicality of using the preRot-SNAV in conjunction with multi-element RF coil acquisition. The results confirm that the preRot-SNAV technique is a viable, accurate approach for use in real time 3D motion correction.

14:00 4597.   Comparison of k-space based parallel imaging approaches for reducing non-rigid motion induced ghosting 
Suchandrima Banerjee1, Philip J Beatty2, and Ajit Shankaranarayanan1
1Global Applied Science Laboratory, GE Healthcare, Menlo Park, California, United States, 2Global Applied Science Laboratory, GE Healthcare, Toronto, Canada

Non-rigid motion such as coughing, swallowing or flow can cause ghosting artifacts that severely compromise image quality, especially in anatomies such as the spine. Self -navigated trajectories such as radial and PROPELLER can minimize these artifacts, but majority of imaging applications rely on Cartesian imaging. In recent years, there has been lot of work on extending parallel imaging (PI) methods to eliminate motion ghosts. In this work we analyze the differences between two previously proposed PI based motion correction methods through simulation and invivo spine studies, and present some method modifications to improve the motion correction ability.

14:30 4598.   Combined prospective-retrospective motion correction for high-resolution brain imaging 
Julian Maclaren1, Kuan Lee1, Chaiya Luengviriya2,3, Michael Herbst1, Oliver Speck2, and Maxim Zaitsev1
1Medical Physics, Dept. of Radiology, University Medical Center Freiburg, Freiburg, Germany, 2Dept. of Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany, 3Dept. of Physics, Kasetsart University, Thailand

Subject motion is a major limiting factor in high-resolution imaging of the brain. By updating the imaging volume continuously during imaging, prospective motion correction offers a solution to this problem; however, navigator data must be extremely precise if the reconstructed images are to be free of artifacts. This work presents a combined prospective-retrospective approach, which corrects for motion prospectively, but then estimates navigator errors after imaging and corrects for these retrospectively. Simulations and in vivo experiments demonstrate the effectiveness of the method.

Electronic Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the video presentation.
Artifacts & Correction: Motion II

Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 132

14:00 4599.   Phase Correction in Multi-Breath-Hold MRI with Tracking Using Information Entropy 
Yuji Iwadate1, and Hiroyuki Kabasawa1
1Global Applied Science Laboratory, GE Healthcare, Hino, Tokyo, Japan

The multi-breath-hold approach with slice/slab tracking enables high resolution abdominal MRI, but artifacts derived from nonuniform receive coil sensitivity still remains. We developed a novel technique to reduce residual motion artifacts using information entropy as a cost function to optimize correction phase. This method remarkably reduced artifacts in phantom and volunteer studies without explicit knowledge of coil sensitivity.

14:30 4600.   Comparison of Algorithms for Prediction of Respiratory Motion 
Tejas Nair1, and H Michael Gach1
1Research Imaging, Nevada Cancer Institute, Las Vegas, NV, United States

MRI techniques that have long acquisition deadtimes and are highly sensitive to motion (e.g., subtraction techniques like arterial spin labeling) can greatly benefit from predictive motion correction. Two Kalman filter based prediction models [the constant velocity (CV) and the interacting multiple model (IMM)] and a weighted fourier linear combiner (WFLC) algorithm were evaluated for respiratory motion prediction. The CV model, IMM and WFLC predicted organ motion 1 s into the future with a root mean square error of >6.6 mm, >5.3 mm and >1.5 mm, respectively. The CV model is computationally the fastest algorithm followed by IMM and WFLC.

15:00 4601.   Advantages of digital vs analog accelerometer-based sensor for respiratory motion correction 
Laure Rousselet1,2, Slavisa Jovanovic1,2, Cédric Pasquier3,4, and Jacques Felblinger1,2
1IADI, Nancy-Université, Nancy, France, 2U947, INSERM, Nancy, France, 3CIT 801, INSERM, Nancy, France, 4CIC-IT, CHU de Nancy, Nancy, France

Physiological motions influence considerably MRI image quality of moving organs by generating artifacts. To reduce their influence, information about the motion of imaged organs is needed. This information is often obtained by using motion sensors. In MRI environment, pneumatic belts are most often used for motion monitoring despite the fact that they only deliver average motion information, which is not suitable for motion compensated tools. An alternative to these sensors are already proposed accelerometer-based sensors having fixed motion signal acquisition parameters and making it less adapted for smaller respiratory motions. In this study a solution for this problem was proposed.

15:30 4602.   Real Time Velocity-Based Navigator triggering in the abdomen: Initial results 
Gabriele Beck1, Jeroen Stout1, Vincent Denolin2, Kenneth Coenegrachts3, and Gwenael Herigault1
1Philips Healthcare, Best, Netherlands, 2Philips Healthcare Benelux, Brussels, Belgium, 3Department of Radiology, AZ St.-Jan, Brugge, Belgium

In Respiratory Triggering, prior knowledge of the optimal trigger delay time or level is typically needed to adjust the acquisition window to the end expiration phase. End expiration patterns however often varies throughout the scan with the consequence that trigger moments are missed or acquisitions are performed in between inspiration and expiration states showing image blurring and prolonged scan time. A novel Navigator triggering method is presented that relies on the real-time analysis of breathing states and velocities to detect the calm end expiration phase. The method provides improved scan efficiency and image sharpness in abdominal imaging as compared to conventional triggering techniques.

Tuesday May 10th
  13:30 - 15:30 Computer 132

13:30 4603.   Motion Artifact Removal by Retrospective Resolution Reduction (MARs) 
Candice Bookwalter1, Nicole Seiberlich1, Mark Griswold1,2, and Vikas Gulani1
1Department of Radiology, University Hospitals Case Medical Center, Cleveland, OH, United States, 2Department of Biomedical Engineering, Case Western Reserve Univeristy, Cleveland, OH, United States

Motion artifacts in MR images often obscure important clinical information especially due to breathing in abdominal imaging. Assuming that a patient can hold their breath at the beginning of an acquisition but may later fail, there will be a transition between data uncorrupted and corrupted by motion. In this study, the transition is identified by employing a centric ordered 3D VIBE acquisition and a novel, automatic, retrospective algorithm called Motion Artifact Removal by Retrospective Resolution Reduction (MARs). Volunteer and patient data is presented demonstrating images uncorrupted by motion artifact but with slightly lower resolution than initially desired.

14:00 4604.   Improvements of respiratory motion recording: optical belt vs pneumatic belt 
Laure Rousselet1,2, Julien De jonckheere3, François Narbonneau4, Slavisa Jovanovic1,2, Cédric Pasquier5,6, and Jacques Felblinger1,2
1IADI, Nancy-Université, Nancy, France, 2U947, INSERM, Nancy, France, 3CIC-IT 807, INSERM, Lille, France, 4Multitel, Mons, Belgium, 5CIT 801, INSERM, Nancy, France,6CHU de Nancy, Nancy, France

MR acquisitions have to be synchronized with respiration to avoid motion artifacts. Pneumatic belts are the most current tool for this purpose. However, these belts suffer from signal drifts and leaks in pneumatic system. To correct these shortcomings an optical sensor in form of belt has been developed using optical fiber Bragg grating sensor (FBG). This optical sensor is well correlated with the classical pneumatic belt but has the advantage of being more stable during breath hold. In addition, these sensors offer also the possibility of measuring a local deformation which could be used in different points.

14:30 4605.   Multiple-region affine motion correction using localized coil sensitivities 
Ghislain Vaillant1, Christian Buerger1, Graeme Penney1, Claudia Prieto1, and Tobias Schaeffter1
1Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom

Respiratory motion compensation is still a major challenge in cardiac and abdominal MRI. We propose the use of multiple affine motion correction in regions selected by localized coil sensitivities of a 32-channel coil array. The approach was validated in simulations by investigating the influence of the registration and the selectivity of the coil elements on the image quality. The feasibility was tested in-vivo on a healthy volunteer. Multiple region-affine motion compensation reduces artefacts in the reconstructed image in comparison to the non-corrected and a global affine correction scheme.

15:00 4606.   Subject specific respiratory motion in Cardiac MR 
Ian Hamilton Burger1, and Ernesta Meintjes1
1MRC/UCT Medical Imaging Research Unit, Department of Human Biology, University of Cape Town, Cape Town, Western Cape, South Africa

Due to great inter subject variation in the relationship between the motion of the diaphragm and the heart correcting for this is a major challenge in cardiac MR. By acquiring a subject specific model makes correction much more accurate. We have developed a technique to acquire a subject specific model describing the relationship between the motion of the diaphragm and that of the heart to enable improved slice following in cardiac MR.

Wednesday May 11th
  13:30 - 15:30 Computer 132

13:30 4607.   A first step towards multi slices fast spin echo cine imaging of the heart in free breathing using GRICS 
Pierre-André Vuissoz1,2, Marine Beaumont3,4, Gabriela Hossu3,4, Damien Mandry1,4, and Jacques Felblinger1,3
1Imagerie Adaptative Diagnostique et Interventionnelle, Nancy-Université, Nancy, France, 2U947, INSERM, Nancy, France, 3CIT801, INSERM, Nancy, France, 4CHU-Nancy, Nancy, France

Generalized Reconstruction by Inversion of Coupled Systems (GRICS) aims at correcting motion artifacts. Since this approach alleviates the breath hold constraint of functional cardiac MRI, cardiac cine imaging using fast spin echo (FSE) sequences should become possible. In this preliminary study, a stack of fat saturated free breathing multi slices FSE cine imaging of the heart has been acquired on one healthy volunteer. The reconstructed cine images display new contrast with T2 weighting and fat saturation. Functional parameters of the left ventricle were computed from manual segmentation clinical software.

14:00 4608.   Free-breathing cardiac black blood imaging using 1D navigator driven reconstruction 
Maelene Lohezic1,2, Brice Fernandez1,2, Damien Mandry2,3, Jacques Felblinger2,4, and Pierre-André Vuissoz2,5
1Global Applied Science Laboratory, GE Healthcare, Nancy, France, 2IADI Lab., Nancy-Université, Nancy, France, 3CHU de Nancy, Nancy, France, 4CIT801, INSERM, Nancy, France, 5U947, INSERM, Nancy, France

High resolution black-blood imaging is difficult to obtain due to long acquisition time incompatible with breath hold. Free-breathing approaches use either respiratory self gating techniques based on navigators or motion compensated reconstruction. We propose here to combine both approaches by using respiratory motion compensated reconstruction driven by 1D navigators. Results are comparable to those obtained when the reconstruction is driven by external sensors, without the need for additional recording hardware, and further improved when both sources of motion information are taken into account. Results have been obtained on 256x256 acquisitions but can be extended to higher resolutions.

14:30 4609.   Association of several motion sensors for free breathing reconstruction method 
Laure Rousselet1,2, Slavisa Jovanovic1,2, Maélène Lohezic2,3, Marina Filipovic1,2, Cédric Pasquier4,5, and Jacques Felblinger1,2
1IADI, Nancy-Université, Nancy, France, 2U947, INSERM, Nancy, France, 3Global Applied Science Lab., GE Healthcare, Nancy, France, 4CIT 801, INSERM, Nancy, France,5CIC-IT, CHU de Nancy, Nancy, France

New MR compatible sensors based on acceleration measurements have been developed. They are associated with a microcontroller to easily adjust amplification parameters to the respiration of each volunteer. Motion information extracted from these sensors has been included in a free-breathing reconstruction technique, GRICS. It is based on a non rigid motion model linearly constrained by physiological signals, initially pneumatic respiratory belts. The combination of motion information extracted from different sources (accelerometers and pneumatic belts) improves the quality of GRICS reconstructed images. Moreover, resulting images are comparable with images acquired in breath hold.

15:00 4610.   Motion Correction using Coil Arrays (MOCCA) for Free-Breathing Cardiac Cine MRI 
Peng Hu1, Susie Hong2, Mehdi H Moghari2, Beth Goddu2, Lois Goepfert2, Thomas H Hauser2, Warren J Manning2, and Reza Nezafat2
1Beth Israel Deaconess Medical Center, Boston, MA, United States, 2Beth Israel Deaconess Medical Center

We present a free-breathing motion compensation technique based on coil arrays (MOCCA) and evaluate its application in free-breathing respiratory self-gated cardiac cine MRI. The proposed method was tested on a cohort of healthy adult subjects and patients for subjective image quality and objective blood-myocardium border sharpness, and was compared with breath-hold cine MRI with regard to left and right ventricular volumes and ejection fraction measurements. Our data indicate that the proposed MOCCA method provides significantly improved image quality and sharpness compared to free-breathing cine without respiratory self-gating, and provides similar volume measurements compared with standard breath-hold cine MRI.

Thursday May 12th
  13:30 - 14:00 Computer 132

13:30 4611.   Assessment of Accuracy and Reproducibility of ECG, Pulse Oximetry and Phonocardiogram Gating of Cardiac MRI at 7T 
Tobias Frauenrath1, Thibaut de Geyer d´Orth1, and Thoralf Niendorf1,2
1Berlin Ultrahigh Field Facility, MDC Berlin, Berlin, Germany, 2Charité Campus Buch, Humboldt-University, Experimental and Clinical Research Center (ECRC), Berlin, Germany

At (ultra)high magnetic fields the artifact sensitivity of ECG recordings increases. This bears the risk of R-wave mis-registration which has been consistently reported for ECG triggered CMR at 7.0T. Realizing the constraints of conventional ECG, acoustic cardiac triggering (ACT) has been proposed. The clinical ACT has not been carefully examined yet. For this reason, this work scrutinizes the suitability, accuracy and reproducibility of ACT for CMR at 7.0T. For this purpose, the trigger reliability and trigger detection variance are examined together with an qualitative and quantitative assessment of image quality of the heart at 7.0T.

Electronic Posters : Pulse Sequences, Reconstruction & Analysis
Click on to view the abstract pdf and click on to view the video presentation.
Artifacts & Correction: Non-Motion

Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 133

14:00 4612.   PROPELLER-EPI-DWI with oblique N/2 ghost correction using 2D linear phase correction and interlaced Fourier transform reconstruction 
Hing-Chiu Chang1,2, Chun-Jung Juan3, Tzu-Chao Chuang4, and Hsiao-Wen Chung2,3
1Global Applied Science Laboratory, GE Healthcare, Taipei, Taiwan, 2Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan,3Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, 4Electrical Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan

The PROPELLER-EPI has been shown useful for diffusion applications with reduced geometric distortion. A 2D phase correction with double-FOV reference image can be applied for oblique ghost reduction in each blade prior to PROPELLER-EPI reconstruction. We demonstrate the feasibility of an alternative method without the need for 2D fitting and determination of 2D margin, using double-FOV reference to estimate linear phase along two dimensions, and then combined with interlaced Fourier transform (FT) to reduce the oblique N/2 ghost. Its insensitivity to very low-resolution double-FOV reference is particularly suitable for RPOPELLER-EPI where low-resolution blades are combined to reconstruct high-resolution images.

14:30 4613.   A Generalized Phase Correction Technique for EPI-PROPELLER 
Novena Rangwala1,2, and Xiaohong Joe Zhou2,3
1Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States, 2Center for Magnetic Resonance Research, University of Illinois Medical Center, Chicago, Illinois, United States, 3Departments of Radiology, Neurosurgery and Bioengineering, University of Illinois Medical Center, Chicago, Illinois, United States

A technique is proposed to reduce ghosts arising from constant, linear, and “oblique” phase errors in EPI-PROPELLER with an arbitrary (oblique) imaging plane. Phase correction parameters for each blade of EPI-PROPELLER were calculated from three reference scans acquired along each of the three orthogonal axes. This technique was validated on a phantom and human volunteers. The results showed a reduction of the Nyquist ghosts by at least 80% in both long- and short-axis EPI-PROPELLER images.

15:00 4614.   EPI Ghost Correction with LTI k-space Trajectory Estimation 
Nii Okai Addy1, Holden H Wu1,2, and Dwight G Nishimura1
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Cardiovascular Medicine, Stanford University, Stanford, CA, United States

Blipped echo planar imaging is very sensitive to timing errors resulting from MR gradient system imperfections causing ghosting artifacts to appear in images with no correction. Using a linear time-invariant model for the gradient system, trajectories achieved on the scanner can be estimated. This provides a general trajectory independent solution to correct for ghosting artifacts without an additional reference scan.

15:30 4615.   Two-dimensional phase cycled reconstruction for inherent correction of EPI Nyquist artifacts 
Nan-kuei Chen1, Alexandru V Avram1, and Allen W Song1
1Brain Imaging and Analysis Center, Duke University Medical Center, Durham, NC, United States

Here we report an inherent and 2D phase correction technique to effectively remove EPI Nyquist artifacts, without needing any reference scan. A series of images are first generated by cycling through different possible values of 2D phase errors. An image with the lowest artifact level is then identified based on the background energy level. In comparison to traditional 1D correction methods, the developed 2D phase correction method is significantly more effective, particularly for oblique-plane EPI or in the presence of cross-term eddy current. The developed method can generally be applied to single-shot and segmented EPI, with or without parallel acceleration.

Tuesday May 10th
  13:30 - 15:30 Computer 133

13:30 4616.   Simulations of stent artifacts in MRI 
Yan Guo1, Jiangbo Chen1, and Xiaohua Jiang1
1Department of Electrical Engineering, Tsinghua University, Beijing, China, People's Republic of

This work proposes an approach to simulate the stent artifacts in MRI based on electromagnetic field analysis. Both static and RF field distributions with a sample stent in a uniform imaging sample are calculated using the commercial FEM software JMAG 10.0 (JRI Solution, Limited, Japan). The images with stent artifacts are simulated by an MRI simulator based on the calculated field distributions.

14:00 4617.   Frequency Adjustments in TIDE bSSFP Imaging to Compensate for Banding Artifacts Caused by Dental Braces 
Yin-Cheng Kris Huang1, Chun-Jung Juan2, and Te-Son Kuo1
1Department of Electrical Engineering, National Taiwan University, Taipei City, Taiwan, 2Department of Radiology, Tri-Service General Hospital, Taipei City, Taiwan

Metallic implants caused image artifacts like in-plane distortion and T2*-related signal loss. As discovered in our preliminary studies that when dental braces were present, there were banding artifacts in the resulted TIDE bSSFP images, while the in-plane distortion was much less severe than the TSE images. The signal loss is likely due to the inherent off-resonance suppression mechanism for the findings of continuous phase drifts rather than random phases. Therefore, we applied system frequency adjustment to validate this hypothesis, and also used post-processing methods to combine the images acquired at various system frequencies, in hope to obtain an artifact-minimized image.

14:30 4618.   Spiral imaging with view angle tilting for application to metal artifact correction 
Sang-Young Zho1, and Dong-Hyun Kim1,2
1Electrical and Electronic Engineering, Yonsei University, Shinchon-dong, Seoul, Korea, Republic of, 2Radiology, Yonsei University College of Medicine, Shinchon-dong, Seoul, Korea, Republic of

View angle tilting technique showed great reduction of image distortion from B0 inhomogeneity. With slice-encoding, namely SEMAC, enable MR imaging near metal object. One drawback is long scan time and diffuculty of applying on the high-field due to increased frequency range. To mitigate this problem, spiral sequence is considered and result showed VAT is applicable even on metal object.

15:00 4619.   MRI near metal objects: Investigating the effects of induced RF currents and currents induced by gradient switching on SE phase images using a simple model system 
Hanne Wojtczyk1, Petros Martirosian1, Verena Ballweg1, Hansjoerg Graf1, and Fritz Schick1
1Section on Experimental Radiology, University Hospital Tuebingen, Tuebingen, Baden-Wuerttemberg, Germany

In MRI near metals, electrical currents can be induced in the metals by RF pulses or by gradient switching (due to the imaging or concomitant gradient fields). The objective of the study was to systematically assess for the first time which effects both types of current have on SE phase images. A copper sheet was imaged in a coronal plane at 1.5 T using a SE sequence. The position of the sheet, phase encoding direction, bandwidth and transmit voltage were varied. For the measurements performed here, the SE phase images were dominated by effects from currents induced by gradient switching.

Wednesday May 11th
  13:30 - 15:30 Computer 133

13:30 4620.   Reducing artefacts in inversion recovery prepared MRI caused by varying heart rate through real-time adaptation of the inversion time 
Jedrzej Burakiewicz1, Christoph Kolbitsch1, Geoffrey David Charles-Edwards1,2, and Tobias Schaeffter1
1Division of Imaging Sciences, King's College London, London, United Kingdom, 2Guy's & St Thomas' NHS Foundation Trust, London, United Kingdom

Rapid changes of heart rate create ghosting artefacts in ECG-triggered inversion recovery prepared MRI. A method is proposed to reduce the artefacts by real-time inversion time adaptation. The correction scheme was theoretically described, simulated, implemented on a scanner and tested using phantom and healthy volunteer brain scans. Variation in signal strength - the cause of artefacts - was reduced from 15% to 2.5%. This suggests a promising, easy to implement correction scheme increasing image quality by reducing artefacts.

14:00 4621.   The Inner Lives of Voxels: Revisiting the basics for nonlinear gradient imaging 
Gigi Galiana1, Jason Stockmann2, Leo K. Tam2, and Robert Todd Constable1,2
1Diagnostic Radiology, Yale University, New Haven, CT, United States, 2Biomedical Engineering, Yale University, New Haven, CT, United States

This work examines the prototypical MR echo that would expected for a voxel of spins evolving in a strong quadratic (2z2-x2-y2) gradient field. This case is increasingly relevant given the growing interest in nonlinear imaging, and we report several surprising differences from the linear case, both in magnitude and phase of the echo. Furthermore, we show that neglecting these dynamics can lead to significant errors even in basic sequences, such as those routinely used for field mapping.

14:30 4622.   Partial Volume Corrections of Myelin Water Fraction values 
Sonya Bells1, Sean Deoni2,3, Ofer Pasternak4, and Derek K Jones1
1CUBRIC, School of Psychology, Cardiff, United Kingdom, 2School of Engineering, Brown University, Providence, Rhode Island, United States, 3Centre of Neuroimaging Sciences-Institute of Psychiatry, King's College, London, United Kingdom, 4Brigham and Women's Hospital, Harvard Medical School, Bostan, MA, United States

Multi-component relaxometry of fast- and slow-T1 and T2 has previously been used to quantify aspects of tissue microstructure in brain tissue, notably – the myelin water fraction (MWF). The myelin water content is estimated by attributing the short T2 relaxation component to the water trapped within the myelin sheath. However, the amount of partial volume contamination from cerebral spinal fluid (CSF) is unknown and until now. Here, We investigate the effects of partial volume contamination due to CSF and propose a novel approach to correcting the problem of partial volume errors in mapping myelin water content.

15:00 4623.   Post processing correction of ghosting artefacts in arterial input function determination for fast Dynamic Contrast Enhanced MRI 
Hendrik Laue1, Dennis Doelschel2, Felix Gremse2, Matthias Günther1, Fabian Kiessling2, and Heinz-Otto Peitgen1
1Fraunhofer MEVIS, Bremen, Bremen, Germany, 2Experimental Molecular Imaging, RWTH (University of Aachen), Aachen, Germany

Quantitative DCE-MRI requires fast sampling of the AIF. Fast aquisitions are prone to artifacts such as ghosting. We compared two methods correcting AIF measurements and compared the results on 10 Datasets. The first method removes affected timepoints by identifying increased signal outside the body. The second method splits the images and rejoins it so that the signal lost by the ghosting is recollected. Both methods yield an improvement. The first shows a strong improvement performs better but at the cost of about half of the time-points. The second is not as strong but conserves all time-points.