TRADITIONAL POSTER - ismrm

Poster Sessions
blurring and RF deposition. This is demonstrated in phantoms and the human brain at 3T using blipped-planar 2D-selective RF excitations. Thereby, the
unwanted side excitations were positioned in the dead corner between the slice stack and the image section in order to minimize the duration of the 2DRF
excitations without saturating neighbored sections.
Echo Planar Imaging: New Acquisition Approaches
Hall B Thursday 13:30-15:30
3039. An Effective Method to Increase Temporal or Spatial Resolution in Interleaved Echo Planar Imaging
Thomas Sushil John 1 , Dwight George Nishimura 2 , John Mark Pauly 2
1 Electrical Engineering , Stanford University, Stanford, CA, United States; 2 Electrical Engineering, Stanford University, Stanford, CA,
United States
A common solution to correct for ghosting in interleaved echo planar imaging (EPI) is to employ echo time shifting (ETS). Although ETS corrects for
ghosting in a robust, non-iterative, and automatic manner, it does so at the expense of increasing total scan time. In this work, a simple, yet effective scheme
to increase the efficiency of ETS is proposed. Using the proposed technique, shorter scan times are possible when the in-plane resolution is fixed.
Alternatively, the proposed scheme can acquire higher resolution images when total scan time is fixed.
3040. Non-Uniform Density EPI Acquisition Improves the SNR of Smoothed MR Images
Lars Kasper 1,2 , S. Johanna Vannesjö 1 , Maximimilian Häberlin 1 , Christoph Barmet 1 , Klaas Enno Stephan 2,3 ,
Klaas Paul Prüssmann 1
1 University and ETH Zurich, Institute for Biomedical Engineering, Zurich, Switzerland; 2 Institute for Empirical Research in
Economics, University of Zurich, Laboratory for Social and Neural Systems Research, Zurich, Switzerland; 3 Institute of Neurology,
University College London, Wellcome Trust Centre for Neuroimaging, London, United Kingdom
Smoothing MR-images is a common preprocessing step in areas like functional MRI to improve signal as well as noise characteristics of the images and
facilitate inter-subject comparison. We present how an EPI-acquisition scheme (1.5 mm resolution) whose density is specifically tailored to match an image
smoothing kernel improves the SNR of the finally smoothed images. Furthermore, this shows the opportunity to assign differing spatial properties to signal
and noise contributions within an MR image. Because these non-uniform trajectories differ from common MR gradient demands, we relied on actually
measured trajectories for our reconstructions, using an NMR field monitoring setup.
3041. Reducing the Effective Point Spread Function in Echo Planar Imaging Through the Use of Partial
Fourier Asymmetric Spin Echo Pulse Sequences
Andrew Scott Nencka 1 , Daniel L. Shefchik 1 , Eric S. Paulson 2 , Andrzej Jesmanowicz 1 , James S. Hyde 1
1 Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 2 Department of Radiation Oncology,
Medical College of Wisconsin, Milwaukee, WI, United States
Pulse sequences which acquire trains of echoes face an inherent limit in resolution due to intra-acquisition decay. In gradient echo sequences, often used in
functional studies, T2* decay leads to an increased point spread function in the phase encoding direction due to the lower effective bandwidth in that
direction during data acquisition. In this abstract, we illustrate that the desirable T2’ weighting associated with gradient echo sequences may be preserved
with an asymmetric spin echo, and that acquisitions on the ascending edge of the spin echo yield point spread functions which are reduced in the phase
encoding direction. This effect comes from the competing T2’ rephrasing and T2 decay leading up to the formation of the spin echo. Matching the effective
echo time on the ascending and descending sides of the spin echo can yield varying image contrast in vivo due to true T2 decay, thereby affecting the
perceived smoothness of the reconstructed image.
MRI Sequence Optimisation
Hall B Monday 14:00-16:00
3042. Optimized, Unequal Pulse Spacing in Multiple Echo Sequences Improves Refocusing in Magnetic
Resonance
Warren S. Warren 1 , Rosa Tamara Branca 2
1 Chemistry/CMBI, Duke University, Durham, NC, United States; 2 Chemistry, Duke University, Durham, NC, United States
A recent quantum computing paper analytically derived optimal pulse spacings for a multiple spin echo sequence which differ dramatically from the
conventional, equal pulse spacing of a Carr-Purcell-Meiboom-Gill (CPMG) sequence. Here we show that this “UDD sequence” has advantages for MR of
tissue, where diffusion in microstructured environments leads to fluctuating fields on a range of different timescales. Both in excised tissue and in a live
mouse tumor model, optimal UDD sequences produce different contrast than do CPMG sequences, with substantial enhancements in most regions. This
provides a new source of endogenous contrast and enhances sequences which are currently T2-limited.