ELECTRONIC POSTER - ismrm

Thursday 13:30-15:30 Computer 56
13:30 4005. Evidence for Microscopic Diffusion Anisotropy in Spinal Cord Tissue Observed
with DWV Imaging on a Whole-Body MR System
Marco Lawrenz 1 , Martin Koch 1 , Jürgen Finsterbusch 1
1 Department of Systems Neuroscience, University Medical Center, Hamburg-Eppendorf, Hamburg, Germany
Double-wave-vector diffusion-weighted imaging is able to detect microscopic diffusion anisotropy in macroscopically isotropic
samples. So far, corresponding experiments were performed on NMR systems with high performance gradient coils (>=300mT/m).
Here, experiments are presented that provide evidence for the observation of the anisotropy effect on a standard whole-body MR
system.
14:00 4006. Numerical Simulations of Double-Wave-Vector Diffusion-Weighting Experiments
with Multiple Concatenations at Short Mixing Times
Jürgen Finsterbusch 1,2
1 Department of Systems Neuroscience , University Medical Center Hamburg-Eppendorf, Hamburg, Germany;
2 Neuroimage Nord, University Medical Centers Hamburg-Kiel-Lübeck, Hamburg-Kiel-Lübeck, Germany
Double-wave-vector diffusion-weighting experiments where two diffusion weighting periods are applied successively in a single
acquisition are a promising tool to investigate tissue microstructure, e.g. cell or compartment sizes. However, for the long gradient
pulse durations required on whole-body MR systems the underlying signal modulation with the angle between the two wave vectors
may be small which hampers the detectability of the effect. Here, it is shown that multiple concatenations of the two diffusion
weightings in a single experiment can yield considerably higher signal modulations than expected theoretically because shorter
gradient pulses are sufficient to achieve the desired diffusion weighting.
14:30 4007. Multiple Echo Multi Shot (MEMS) Diffusion Sequence
Sergio Uribe 1,2 , César Galindo 3 , Cristian Tejos, 2,4 , Pablo Irarrazaval, 2,4 , Steren
Chabert 3
1 Radiology Department, Pontificia Universidad Catolica de Chile, Santiago, Chile; 2 Biomedical Imaging
Center, Pontificia Universidad Catolica de Chile, Santiago, Chile; 3 Biomedical Engineering Department,
Universidad de Valparaiso, Valparaiso, Chile; 4 Electrical Engineering Department, Pontificia Universidad
Catolica de Chile, Santiago, Chile
T2 and diffusion measurements are usually acquire in different scans. In this work we propose a multi echo multi shot diffusion
sequence that allows us obtaining T2 and mean diffusivity from a single scan. The multi shot approach enable short echo times for
both echoes. This characteristic makes this sequence suitable to be applied in tissues with short T2. Result of in vivo experiments
show an excellent correlation of T2 and mean diffusivity of the muscle compare to standard scans.
15:00 4008. Extension of the Double Wave Vector Experiments at Long Mixing Times to
Multiple Concatenations
Marco Lawrenz 1 , Jürgen Finsterbusch 1
1 Department of Systems Neuroscience, University Medical Center, Hamburg-Eppendorf, Hamburg, Germany
An extension of the tensor approach to the double wave-vector experiment for multiple concatenations is presented aiming at the
examination of microscopic anisotropy in tissue for fully restricted diffusion. A detailed analysis of the generalized tensor expression
to the fourth order does not only hold for the characterization of arbitrary pores in an idealized environment but can still derive a
microscopic anisotropy measure on the pore size level with sufficient accuracy for timing parameters compatible to whole-body MR
systems. Monte Carlo simulations confirm the theoretical considerations.
Tractography
Hall B Monday 14:00-16:00 Computer 57
14:00 4009. Fast Normalization of Probabilistic Tractography
Stephen Edward Jones 1,2 , Kenneth Sakaie
1 Neuroradiology, Cleveland Clinic, Cleveland, OH, United States
Numerical computation of track density using probabalistic DWI can be inefficient, particularly for distant points. We present a
method that uses a partial differential equation approach (Laplace's equation) to solve the special isotropic case of probablistic
tracking. This provides a rapid solution for any two points within the brain, with arbitrary accuracy. This solution can be coupled with
anisotropic probablistic tracking to obtain scalar measures of connectivity.
14:30 4010. A Minimal Model, Data-Driven Approach to Tractography
Angela Downing 1 , Daniel Rueckert 2 , A David Edwards, 1,3 , Jo V. Hajnal 1
1 Robert Steiner MRI Unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith
Hospital, Imperial College London, London, United Kingdom; 2 Visual Information Processing Group,
Department of Computing, Imperial College London, London, United Kingdom; 3 Department of Paediatrics,