TRADITIONAL POSTER - ismrm

Poster Sessions
1678. Effects of Susceptibility Distortion and Phase Encoding Direction on Tract Consistency in Diffusion
Tensor Imaging
Mustafa Okan Irfanoglu 1,2 , Lindsay Walker 2 , Carlo Pierpaoli 2
1 Department of Radiology, The Ohio State University, Columbus, OH, United States; 2 NICHD, National Institutes of Health,
Bethesda, MD, United States
The distortions on phase-encoding direction of diffusion weighted images due to magnetic susceptibility and concomitant fields greatly affect the quality and
consistency of tractography using on diffusion sequences. In this work, data from a healthy population were acquired in both Right-Left and Anterior-
Posterior phase encoding directions and the effects of these distortions and EPI distortion correction were analyzed on specific fiber bundles. Results indicate
tracts are greatly affected by these distortions and consistency and quality of the tracts are improved with correction and that this correction process should
be part of typical diffusion sequences acquired for tractography purposes.
1679. On the Importance of Appropriate Fibre Population Selection in Diffusion Tractography
Jonathan D. Clayden 1 , Chris A. Clark 1
1 Institute of Child Health, University College London, London, Greater London, United Kingdom
While a lot of recent research in diffusion MRI has focussed on estimating the orientations of multiple fibre populations within image voxels, little attention
has been given to the problem of how to effectively use this information in tractography. Typically a tractography algorithm selects a fibre direction to
follow based on continuity, but we show here that a alternative approach based on prior knowledge gives substantially more robust results. Our technique is
fully automated and uses a reference tract to inform the process.
1680. Quantitative Comparison of Automatic and Manual Tract Segmentation Methods
Susana Muñoz Maniega 1 , James D. Bridson 2 , Wei Jie Jensen Ang 2 , Paul A. Armitage 1 , Catherine Murray 3 ,
Alan J. Gow 3 , Mark E. Bastin 4 , Ian J. Deary 3 , Joanna M. Wardlaw 1
1 Clinical Neurosciences, University of Edinburgh, Edinburgh, United Kingdom; 2 Medicine and Veterinary Medicine, University of
Edinburgh, Edinburgh, United Kingdom; 3 Psychology, University of Edinburgh, Edinburgh, United Kingdom; 4 Medical Physics,
University of Edinburgh, Edinburgh, United Kingdom
We compare probabilistic neighbourhood tractography (PNT), an automatic tract segmentation method, with a well accepted tractography method using
manual seed placement and multiple region-of-interest (ROI) constraints. Tracts were segmented in the same data set using both methods and mean values of
FA and MD compared. Mean differences between PNT and ROI methods were ≤10%, comparable with the reproducibility obtained when ROI are manually
placed by different operators. PNT segmentation showed a reasonable agreement with the more conventional ROI tract segmentation method, with the
advantage of removing operator dependency.
1681. A New Combined Distance Measure for the Clustering of Fiber Tracts in Diffusion Tensor Imaging
(DTI)
Christian Ros 1 , Daniel Güllmar 1 , Juergen R. Reichenbach 1
1 Medical Physics Group, Institute for Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany, Jena,
Thuringia, Germany
In recent years various fiber tractography methods have been evolved. Although these resulting tractograms offers plenty of information, they are rarely used
in clinical routine due to the fact that processing is often time-consuming and an experienced operator is essential to obtain good results. To overcome this
limitations cluster analysis can be employed to partition fiber tracts into clusters through comparison of tract-specific features or similarity measures. The
aim of this study was to develop a new combined similarity measure that combines a shape based distance measure with other distance measures.
1682. Visualizing and Exploring Tractograms Via Two-Dimensional Connectivity Maps
Radu Jianu 1 , Cagatay Demiralp 1 , David H. Laidlaw 1
1 Brown University, Providence, RI, United States
We introduce a circular graph visualization of tract projections in a framework that uses two-dimensional map representations for exploring connectivity in
the brain. Expert feedback indicates that it can be useful for understanding connectivity densities and configurations.
1683. Visualization of Intrarenal Water Transport by Diffusion Tensor Tractography
Michael Pedersen 1 , Anders B. Lødrup 1 , Kristian Karstoft 1 , Eva A. Nielsen 2 , Mette K. Hagensen 2 , Peter A.
Nielsen 2 , Andreas Stavropoulos 3 , Bente Jespersen 4 , Steffen Ringgaard 1 , Morten Smerup 2
1 MR Research Center, Aarhus University Hosptial, Aarhus, Denmark; 2 Institute of Clinical Medicine, Aarhus University Hosptial,
Aarhus, Denmark; 3 Dept. of Periodontology, Aarhus University, Aarhus, Denmark; 4 Department of Nephrology, Aarhus University
Hospital, Aarhus, Denmark
The aim of this study is to investigate if DTI can be used for imaging the principal route of free water in the kidney, and we hypothesize that this route can
act as an indirect representation of the segments of nephrons going centripetally from the renal parenchyma to the collecting ducts. The orientation of
medullary diffusion anisotrophy was visualized using a proposed DTI tractography method