TRADITIONAL POSTER - ismrm

3068. Robust and Fast Evaluation of Orbital Navigator Data for Rigid Body Motion Estimation
Tim Nielsen 1 , Peter Boernert 1
1 Philips Research Europe, Hamburg, Germany
Poster Sessions
To overcome image artifacts induced by motion the use of navigator signals has been proposed, combined with either real-time correction of the data
acquisition or motion compensated reconstruction. The quality of the correction depends critically on the estimated motion derived from the navigator signal.
We present a fast, robust and precise algorithm to evaluate data from an orbital navigator trajectory and its application to motion compensated
reconstruction.
3069. Direct and Independent Estimation of B 0 Components Based on Raw EPI Data
Frederik Testud 1 , Iulius Dragonu 1 , Jürgen Hennig 1 , Maxim Zaitsev 1
1 Medical Physics, Department of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany
GE EPI is a widely used imaging technique, but is very sensitive to B 0 field inhomogeneities. To correct for temporal changes of B 0 , real-time measuring
methods are necessary, such as estimating gradient maps of B 0 from raw EPI data. Here a filter scheme is presented to calculate local B 0 gradients. The local
gradient in the readout direction is estimated independently from the gradient in the phase encoding direction by finding the contour lines of the gradients.
This method is compared with previously introduced raw data based techniques and shown to perform better or equally well.
3070. Rapid Retrospective Non-Rigid Motion Correction for Free-Breathing MRI
Yoshihiro Tomoda 1 , Yuji Iwadate 2 , Tetsuji Tsukamoto 2 , Yoshikazu Ikezaki 1
1 MR Engineering, GE Healthcare Japan, Hino, Tokyo, Japan; 2 MR Applied Science Laboratory, GE Healthcare Japan, Hino, Tokyo,
Japan
We proposed a new framework that enables not only non-rigid motion correction with 100% acceptance rate but also rapid reconstruction. As the first
investigation, we implemented the 1D non-rigid motion correction, called 1D MMFK, and confirmed the effectiveness with the simple linear expansion
model by numerical simulation and volunteer scan.
3071. Correction of Motion Artifacts Using a Genetic Algorithm
Stephan Witoszynskyj 1 , Alexander Rauscher 2
1 Department of Radiology , Medical University of Vienna, Vienna, Austria; 2 UBC MRI Research Centre, University of British
Columbia, Vancouver, BC, Canada
We present a genetic algorithm for correction of motion artifacts in MRI. Two types of genetic algorithms were investigated: the first used only "non-sexual"
multiplication and the second allowed "cross-over" between solutions. The algorithm corrects for translations by estimating correction factors for each k-
space line. Four different image metrics were studied: entropy, normalized-gradient-squared (NGS), signal in the background and local coherence in the
background. The best results were obtained by using the simple algorithm and NGS and entropy as metric. Since genetic algorithms are inherently
parallelizable our approach could benefit greatly from being implemented on computer clusters and GPUs.
3072. Less Can Be More: Reduction of Motion Artifacts by Ignoring Parts of the Acquired Dataset
Tim Nielsen 1 , Jinnan Wang 2,3 , Peter Boernert 1
1 Philips Research Europe, Hamburg, Germany; 2 Philips Research North America, Briarcliff Manor, NY, United States; 3 University of
Washington, Seattle, WA, United States
High resolution MR imaging of the carotids is an interesting technique for plaque characterization but image quality can be compromised by motion
artifacts. Effects of breathing and pulsation can be reduced by gated acquisition. Coping with non-periodic motion (e.g. swallowing) is still often challenging
in clinical practice and is considered as a major factor that contributes to the overall 20% failure rate in clinical scans. We present a method to reduce the
effects of sudden, non-periodic motion by exploiting data redundancy which is usually present in parallel imaging with multiple receive coils. The method
can be applied retrospectively without any navigator information.
3073. Fast Phase Based Registration for Robust Quantitative MRI
Anders Eklund 1,2 , Marcel Warntjes, 2,3 , Mats Andersson 1,2 , Hans Knutsson 1,2
1 Division of Medical Informatics, Department of Biomedical Engineering, Linköping University, Sweden; 2 Center for Medical Image
Science And Visualization (CMIV), Linköping University, Sweden; 3 Division of Clinical Physiology, Department of Medicine and
Health, Linköping University, Sweden
Quantitative magnetic resonance imaging has the major advantage that it handles absolute measurements of physical parameters. Quantitative MRI
can for example be used to estimate the amount of different tissue types in the brain, but other applications are possible. When quantitative MRI is
performed, a number of volumes are collected from the MR scanner. In order for the tissue quantification to work properly, the volumes have to be perfectly
aligned. The problem with the volumes is that they differ significantly in intensity. We present a method for fast registration of such volumes and prove that
it is more robust than the statistical parametric mapping (SPM) software.
3074. Navigator-Based Elliptical K-Space Reordering for Aortic 4D-Flow Imaging
Ashley Gould Anderson III 1 , Sebastian Gruhlke 2 , Oliver Wieben 1,3 , Michael Markl 2,4
1 Medical Physics, University of Wisconsin, Madison, WI, United States; 2 Medical Physics, University Hospital Freiburg, Freiburg,
Germany; 3 Radiology, University of Wisconsin, Madison, WI, United States; 4 Diagnostic Radiology, University Hospital Freiburg,
Freiburg, Germany
Respiratory motion causes significant artifacts during 4D-Flow imaging in the torso due to long scan time requirements. Respiratory gating based on
navigator signals or external measurements with bellows have been shown to reduce phase-related motion artifacts in long two- and three-dimensional free
breathing acquisitions. Moreover, real-time adaptive k-space reordering, i.e. phase encoding based on the current position in the respiration cycle, can
considerably improve navigator efficiency and thus reduce overall scan time. This work builds on proven respiratory gating and compensation methods by
extending them to include reordering in the 3D slice-select direction in addition to the phase-encoding direction.