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Quantitative Analysis of Diffusion Tensor Measurements along White Matter Tracts

Quantitative Analysis of Diffusion Tensor Measurements along White Matter Tracts. Isabelle Corouge. Postdoctoral fellow, Dept of Computer Science and Psychiatry, UNC-Chapel Hill. Gray matter. DT MRI. White matter. Diffusion Tensor MRI (DT MRI). Reveals white matter structure.

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Quantitative Analysis of Diffusion Tensor Measurements along White Matter Tracts

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  1. Quantitative Analysis of Diffusion Tensor Measurements along White Matter Tracts Isabelle Corouge Postdoctoral fellow, Dept of Computer Science and Psychiatry, UNC-Chapel Hill - 1 - October 7, 2005

  2. Gray matter DT MRI White matter Diffusion Tensor MRI (DT MRI) • Reveals white matter structure Courtesy of Susumu Mori, JHU - 2 - October 7, 2005

  3. Diffusion of water molecules Diffusion of Water Molecules From Beaulieu[02] • Isotropic vs Anistropic diffusion • Underlying structures of the tissues • Faster diffusion along fibers than perpendicular to them • Water diffusion anisotropy used to track fibers, estimate white matter integrity (v1, l1) • Tensor model (v2, l2) vi : principal directions of diffusion li: associated diffusivities (v3, l3) Isotropic Diffusion Anisotropic Diffusion - 3 - October 7, 2005

  4. Tensor field - 4 - October 7, 2005

  5. Mean diffusivity (MD) Fractional anisotropy (FA) Tensor shape Diffusion Properties Tensor size White matter Cerebrospinal fluid Highly directional diffusion Isotropic diffusion High Low 1 0 - 5 - October 7, 2005

  6. DTI Analysis in Clinical Study • One concept: Region-based Analysis • Co-registration of DTI • Registration of DTI of each subject with: • structural MRI • segmentation maps • lobe parcellation • user-defined ROIs • Statistical analysis per ROI Group 1 Group 2 - 6 - October 7, 2005

  7. Alternative Concept • Quantitative Analysis of Fiber Tracts • Fiber-tract oriented analysis • Measurements across/along fiber bundles with complex geometry • Statistics of diffusion properties (FA,MD) • Statistics of tensors (non-Euclidean metric) • Analysis scheme Tracking/ Clustering Selection FA FA along tract - 7 - October 7, 2005

  8. Fiber Tracking & Clustering into Bundles Fornix cluster Longitudinal fasciculus 6 clusters (2312 streamlines) - 8 - October 7, 2005

  9. Diffusion Properties: Adult vs Neonate FA FA: Mean ± σ Adult Neonate - 9 - October 7, 2005

  10. Diffusion Properties: Adult vs Neonate MD MD: Mean ± σ Adult Neonate - 10 - October 7, 2005

  11. Example: Early Brain Development Study • White Matter Diffusion Corpus Callosum • Extraction and clustering of genu and splenium bundles • Measurement of diffusion properties in cross-sections along the bundles • Selection of center and left/right off-center locations - 11 - October 7, 2005

  12. 21mm 21mm 21mm WM Diffusion of Neonates: Genu Tract • DTI properties measured at midsagittal position and +/- 21 mm - 12 - October 7, 2005

  13. White Matter Diffusion Corpus Callosum 280d GestAge at MRI 360d GestAge at MRI • Diffusion tensor representation at the midsagittal plane and off-center (24mm along bundles). • Tensors get “thinner” → less diffusivity across fibers → more structure, ev. marker for maturation • Genu shows change, but not splenium - 13 - October 7, 2005

  14. Tensor Statistics: Neonate to 1 year • Genu and splenium 1 year old Neonate MD MD Neonate FA FA 1 year old Neonate 1 year old - 14 - October 7, 2005

  15. Tensor Statistics: Neonate to 1 year Splenium Genu - 15 - October 7, 2005

  16. In Practice… the Tools ! FiberViewer FiberTracking - 16 - October 7, 2005

  17. Demo • Data: Brockton VA/Harvard • Case HUVA00102397 • Resampled to isotropic resolution (2x2x2mm3) • Tracts: cingulate, motor, genu, splenium,… - 17 - October 7, 2005

  18. Fiber Tracking and Fiber Viewer • Easy to use and easy to learn • Download: http://www.ia.unc.edu/dev • Online tutorial (same url) • Compatibility Slicer/FiberViewer - 18 - October 7, 2005

  19. The team Guido Gerig (UNC) Casey Goodlett (UNC) Weili Lin (UNC) Sampath Vetsa (UNC) Tom Fletcher (Utah) Xiadong Tao (GE) Rémi Jean Matthieu Jomier (France) Sylvain Gouttard (France) Clément Vachet (France) Software development ITK, VTK, Qt Julien Jomier (UNC) Acknowledgements - 19 - October 7, 2005

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