TRADITIONAL POSTER - ismrm

Poster Sessions
1081. Functional Magnetic Resonance Imaging Using PROPELLER EPI
Martin Krämer 1 , Thies Halvor Jochimsen 1 , Marc Roth 1 , Jürgen Rainer Reichenbach 1
1 Medical Physics Group, Department of Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany
A method to improve spatial and temporal resolutions in fMRI using PROPELLER-EPI. First results are shown which demonstrate that a sliding window
reconstruction of high resolution long-axis propeller (LAP) data is suitable for simple fMRI experiments. Additionally the results achieved by the LAP
measurements are compared to the standard 64x64 EPI sequence which is usually used in fMRI. From there it is shown that the activation maps created from
the LAP scans are better localized along the cortex.
1082. Passband BSSFP: Functional Contrast Compared to GRE-EPI and SE-EPI at 3T.
Pål Erik Goa 1 , Anders Kristoffersen 1 , Michael H. Chappell 2 , Rob H. Tijssen 3 , Asta K. Håberg 4 , Karla L.
Miller 3
1 Dept. of Medical Imaging, St. Olavs University Hospital, Trondheim, Norway; 2 Dept. of Circulation and Medical Imaging,
Norwegian University of Science and Technology (NTNU), Trondheim, Norway; 3 FMRIB Centre, Oxford University, Oxford, Oxon,
United Kingdom; 4 Dept. of Neuromedicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
The functional contrast in passband balanced steady-state free precession (pbSSFP) with 3D segmented EPI readout is compared to that of GRE-EPI and SE-
EPI at 3T. For pbSSFP, TR is varied from 6.5 ms to 45 ms. Standard flickering checkerboard paradigm is used. We find that the best functional contrast is
obtained at TR = 33 ms with corresponding EPI-factor of 40. At this TR, the functional contrast in pbSSFP is approximately half that of GRE-EPI and twice
that of SE-EPI with otherwise comparable scan parameters. False detections due to banding artefacts are present in pbSSFP.
1083. Isotropic Sub-Millimeter FMRI in Humans at 7T
Robin Martin Heidemann 1 , Dimo Ivanov 1 , Robert Trampel 1 , Joeran Lepsien 1 , Fabrizio Fasano 2 , Josef
Pfeuffer 3 , Robert Turner 1
1 Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 2 Fondazione Santa Lucia, Rome, Italy; 3 Siemens
Healthcare Sector, Erlangen, Germany
For isotropic high resolution fMRI at ultra-high field strength, susceptibility effects and T2* decay must be properly addressed. A combination of reduced
FOV imaging (zoomed imaging) and parallel imaging is optimized here, achieving acceleration factors of up to 5.5. The high acceleration reduces distortions
and image blurring, while incurring no other image artifacts. With this approach, high quality single-shot EPI acquisitions can be obtained with an isotropic
resolution of 0.65 mm and sufficient coverage for e.g. fMRI in the visual cortex of the human brain.
1084. Automatic Functional and Anatomical Registration for FMRI Using Optimized 3D Flyback Echo
Planar Imaging
Thomas Sushil John 1 , Michael Lustig 2,3 , John Mark Pauly 2
1 Electrical Engineering , Stanford University, Stanford, CA, United States; 2 Electrical Engineering, Stanford University, Stanford, CA,
United States; 3 Electrical Engineering and Computer Science, UC Berkeley, Berkeley, CA, United States
Echo planar imaging (EPI) is the most widely used method for functional MRI. However, functional images are often distorted because EPI is highly
sensitive to field inhomogeneities, eddy currents, and gradient delays. Functional and neuro-anatomical registration is complicated by these distortions and
by the fact that functional and anatomical images are usually obtained with different imaging sequences. This work investigates the use of an optimized 3D
flyback EPI trajectory with echo time shifting to obtain functional and anatomical images that have minimal distortions and are inherently co-registered.
1085. Recovery of Signal Using Spiral-In K-Space Trajectories: Phase Coherence or Intensity Displacement?
Kimberly Brewer 1,2 , James Rioux 1,2 , Martyn Klassen 3 , Chris Bowen 1,4 , Steven Beyea 1,4
1 Institute for Biodiagnostics (Atlantic), National Research Council of Canada, Halifax, Nova Scotia, Canada; 2 Physics and
Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada; 3 Robarts Research Institute, University of Western
Ontario, London, Ontario, Canada; 4 Physics and Atmospheric Science, Radiology and Biomedical Engineering, Dalhousie University,
Halifax, Nova Scotia, Canada
Spiral pulse sequences are commonly used in fMRI, and spiral-in is known to be considerably better than spiral-out at signal recovery in regions with strong
susceptibility field gradients. Previously proposed theories in the literature do not address the probability of signal displacement or fully explain all of the
differences in signal recovery between spiral-out and spiral-in. In the current work we demonstrate that the difference in image intensity is not due to
differences in signal displacement between spiral-in and spiral-out, but rather the increased phase coherence of the displaced pixels when using spiral-in.
1086. Mitigating the Effects of Motion in EPI Time Series
John M. Ollinger 1 , Andrew L. Alexander 1
1 Waisman Laboratory for Brain Imaging, University of Wisconsin, Madison, WI, United States
A model for image variance due to motion is developed and validated. It can be used minimize motion effects by optimizing EPI sequence parameters. In
general, variance is minimized by minimizing the partial derivative of the steady-state magnetization along the slice axis. In particular, sidelobes contribute
much of the noise at high flip angles; an optimum flip angle exists for a specified degree of motion and can be computed; and inter-slice gaps increase
variance due to motion rather than decrease it.