ELECTRONIC POSTER - ismrm

14:30 4031. Monte-Carlo Simulation Software Dedicated to Diffusion Weighted MR
Experiments in Neural Media
Chun-Hung Yeh 1,2 , Denis Le Bihan 1 , Jing-Rebecca Li 1 , Jean-Francois Mangin 1 , Ching-
Po Lin 2 , Cyril Poupon 1
1 NeuroSpin, I2BM, CEA, Gif-sur-Yvette, France; 2 National Yang-Ming University, Taipei, Taiwan
We develop a novel Monte-Carlo simulation tool dedicated to DW MR experiments by combining a Brownian dynamics simulator
capable of simulating water diffusion in arbitrary geometries reproduced using meshes with a DW signal integrator emulating various
MR pulse sequences. Complicated configurations mimicking neural tissue components (e.g. neurons) can be emulated, as well as
tissue features (e.g. membrane permeability) and basic diffusion mechanisms in different compartments. This framework allows to
bridge the gap between elementary processes and the resulting DW signal, providing a better understanding of the features observed in
DW-MRI (e.g. ADC), and to optimize acquisition schemes for different applications.
15:00 4032. Comparison of Spin Echo and Steady-State Free Precession Sequences for Diffusion
Tractography of Whole, Ex-Vivo Human Brains
Karla L. Miller 1 , Gwenaelle Douaud 1 , Saad Jbabdi 1 , Timothy EJ Behrens 1 , Jennifer A.
McNab 2
1 FMRIB Centre, Oxford University, Oxford, Oxon, United Kingdom; 2 AA Martinos Center, Massachusetts
General Hospital, Charlestown, MA, United States
Despite its popularity, there is relatively little data validating diffusion tensor imaging and tractography against gold-standard
histology or dissection methods. Diffusion imaging of whole, ex-vivo human brains could provide this link by allowing comparison in
the same tissue. We present results obtained using diffusion-weighted spin echo (DW-SE) and steady-state free precession sequences
(DW-SSFP), each with 6 hours scan time on a clinical scanner. Both methods are able to track the corticospinal tract and corpus
callosum. However, tractography of DW-SSFP data produces better quality tracking due to the lower uncertainty on principal tract
direction.
Wednesday 13:30-15:30 Computer 58
13:30 4033. Effect of Diffusion Time and B-Value on Quantitative DTI
Edward S. Hui 1,2 , Steve H. Fung 2,3 , Ed X. Wu 1,4
1 Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, Hong
Kong; 2 Department of Radiology Research, The Methodist Hospital Research Institute, Houston, TX, United
States; 3 Department of Radiology, Weill Medical College of Cornell University, New York, United States;
4 Department of Electrical & Electronic Engineering, The University of Hong Kong, Hong Kong, Hong Kong
Diffusion-weighted (DW) signal attenuation depends on not only the diffusion gradient strength but also the separation between the
two diffusion gradients (i.e., diffusion time Δ). In this study, the effect of Δ and diffusion weighting factor b-value was examined and
documented for conventional DTI by acquiring DW signals with various b-values at different Δ from normal adult rat brains in vivo.
14:00 4034. Combined T1- And DTI Weighted Contrast for High Resolution Human Brain
Mapping Using 3D MPRAGE
marzieh Nezamzadeh 1,2 , Gerald B. Matson, 23 , Yu Zhang 1,2 , Michael W. Weiner 1,2 , Norbert
Schuff 1,2
1 radiology, University of California San Francisco, san francisco, CA, United States; 2 Center for Imaging of
Neurodegenerative Diseases, CIND, VA medical center, San Francisco, san francisco, CA, United States;
3 Pharmaceutical Chemistry, University of California San Francisco, san francisco, CA, United States
Previously, magnetization-prepared rapid gradient-echo (MPRAGE) has been combined with diffusion encoding to achieve diffusion
tensor imaging (DTI). However, an incorporation of DTI contrast in 3D-MPRAGE has not been shown before on human brain data.
Furthermore, a combination of T1 and DTI weighted contrast should benefit assessment of gray/white matter boundaries, which has
important implications for accurately imaging brain atrophy. The overall goal of this study was to develop multiple contrast high
resolution MRI. Specifically, we show the incorporation of DTI contrast, e.g. fractional anisotropy (FA) and mean diffusivity (MD),
into T1-weighted 3D-MPRAGE using simulations and experimental results from human brain at 4T.
14:30 4035. Effects of B-Matrix Correction on Fiber Tractography in High Resolution DTI with
Short-Axis Propeller EPI
Murat Aksoy 1 , Samantha Jane Holdsworth 1 , Stefan Tor Skare 1,2 , Roland Bammer 1
1 Department of Radiology, Stanford University, Stanford, CA, United States; 2 Karolinska Institute, Stockholm,
Sweden
Due to the prolonged acquisition time in DTI, the likelihood of patient motion increases. It is essential to correct for motion to assure
the diagnostic quality and accuracy of tensor orientation in DTI. For interleaved sequences, such as Short-Axis Propeller-EPI, patient
motion causes the b-matrix to vary between different parts of k-space. It was previously shown that correction of motion artifacts in
this case requires non-linear methods. In this study, we investigated the effects of b-matrix correction on fiber tractography with high
resolution DTI. Results showed that b-matrix correction is necessary to get accurate fiber tracts in moving subjects.