ELECTRONIC POSTER - ismrm

14:30 4957. A Study of Wideband MR Imaging: SNR and CNR
Edzer Lienson Wu 1,2 , Jyh-Horng Chen, 23 , Tzi-Dar Chiueh 3
1 Biomedical Engineering, National Taiwan University, Taipei, Taiwan; 2 Interdisciplinary MRI/MRS Lab,
Taipei, Taiwan; 3 Electrical Engineering, National Taiwan University, Taipei, Taiwan
Most of the MR image accelerating methods suffer from degradation of acquired images, which is often correlated with the degree of
acceleration. However, Wideband MRI is a novel technique that transcends such flaws. In this study we demonstrate that Wideband
MRI is capable of obtaining images with identical quality as conventional MR images in terms of SNR, CNR (contrast-to-noise ratio)
and image sharpness, while using only half the total scan time (Wideband factor W=2) of normal MRI sequence.
15:00 4958. High Fidelity Imaging Using Frequency Sweep Encoding
Jun Shen 1
1 NIMH, Bethesda, MD, United States
Recently Frydman et al proposed a mechanism for directly forming images in k space using frequency sweep encoding. It relies on the
quadratic dependence of magnetization phase on position. In combination with EPI-type readout, this method has found applications
in single-shot spin-echo imaging. Its sequential excitation of magnetization may also be used for novel image contrast generation.
Fidelity of images directly formed in k space, however, is significantly degraded. Here we show that fidelity of this type of images can
be restored and we also extend this method to susceptibility-weighted imaging.
Non-Cartesian Imaging Methods
Hall B Monday 14:00-16:00 Computer 117
14:00 4959. Fast Regridding Using LSQR on Graphics Hardware
Gerald Buchgraber 1 , Florian Knoll 2 , Manuel Freiberger 2 , Christian Clason 3 , Markus
Grabner 1 , Rudolf Stollberger 2
1 Institute for Computer Graphics and Vision, Graz University of Technology, Graz, Austria; 2 Institute of
Medical Engineering, Graz University of Technology, Graz, Austria; 3 Institute of Mathematics and Scientific
Computing, University of Graz, Graz, Austria
Iterative image reconstruction methods have become increasingly popular for parallel imaging or constrained reconstruction methods,
but the main drawback of these methods is the long reconstruction time. In the case of non-Cartesian imaging, resampling of k-space
data between Cartesian and non-Cartesian grids has to be performed in each iteration step. Therefore the gridding procedure tends to
be the time limiting step in these reconstruction strategies. With the upcoming parallel computing toolkits (such as CUDA) for
graphics processing units image reconstruction can be accelerated in a tremendous way. In this work, we present a fast GPU based
gridding method and a corresponding inverse-gridding procedure by reformulating the gridding procedure as a linear problem with a
sparse system matrix.
14:30 4960. A General Trajectory Tester
Lawrence Frank 1,2 , Greg Balls 1 , Souheil Inati 3 , Leslie Greengard 4
1 Radiology, UCSD, La Jolla, CA, United States; 2 Radiology, VASDHS, San Diego, CA, United States; 3 Dept of
Psychology, NYU, New York; 4 Courant Institute, NYU, New York, United States
We present a software platform called the General Trajectory Tester (GTT) that allows users to input arbitrary 3D k-space trajectories,
in an arbitrary number of interleaves, which are then used to sample and reconstruct a known 3D analytical phantom. The GTT can
also simulate diffusion weighting, including arbitrary diffusion angular encoding schemes for DTI, multiple b-values, eddy current
and motion induced artifacts and self-navigation, and so is a natural platform to test efficient DTI acquisition and self-navigation
schemes.
15:00 4961. Nonlinear Inverse Reconstruction for Real-Time MRI of the Human Heart Using
Undersampled Radial FLASH
Martin Uecker 1 , Shuo Zhang 1 , Jens Frahm 1
1 Biomedizinische NMR Forschungs GmbH, Max-Planck-Institut für biophysikalische Chemie, Göttingen,
Germany
A previously proposed algorithm for autocalibrated parallel imaging simultaneously estimates image content and coil sensitivities by
inverting a nonlinear equation. Here, this algorithm is extended to non-Cartesian encodings and applied to real-time MRI. The method
takes advantage of a convolution-based technique to simplify the implementation on a graphical processing unit (GPU) for reduced
reconstruction times. The method is validated for real-time MRI of the human heart at 3 T using RF-spoiled radial FLASH. The
results demonstrate artifact-free reconstructions for acquisitions with only 65 – 85 spokes corresponding to imaging times of 130 –
170 ms.
15:30 4962. Improved BPE Reconstruction Using FOCUSS
Hisamoto Moriguchi 1 , Yutaka Imai 1
1 Radiology, Tokai University, Isehara, Kanagawa, Japan
Bunched Phase Encoding (BPE) is a new type of fast data acquisition method in MRI that takes advantage of zigzag k-space
trajectories. A primary disadvantage of BPE is that images reconstructed using matrix inversion methods are sometimes affected by
high levels of noise. In this study, a novel framework to reduce SNR loss in BPE reconstruction is presented. In this technique, high