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Mapping Cortical Development Using Diffusion Tensor Imaging

Mapping Cortical Development Using Diffusion Tensor Imaging. Jeff Neil, MD, PhD Departments of Neurology, Radiology and Pediatrics. MR Imaging. Detect signal from 1 H of H 2 O, which is present at a concentration of approximately 100 M.

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Mapping Cortical Development Using Diffusion Tensor Imaging

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  1. Mapping Cortical Development Using Diffusion Tensor Imaging Jeff Neil, MD, PhD Departments of Neurology, Radiology and Pediatrics

  2. MR Imaging • Detect signal from 1H of H2O, which is present at a concentration of approximately 100 M. • In conventional imaging, signal intensity (greyscale) is related to MR relaxation properties of 1H2O such as T1 or T2 relaxation times. • Water in grey matter has different T1 and T2 relaxation times than water in white matter or CSF.

  3. Water motion in white matter Parallel to axons Perpendicular to axons

  4. Hindered Diffusion (diffusion ellipsoid) without hindrance with hindrance WILSON

  5. Ellipsoid Image Pierpaoli and Basser, Toward a Quantitative Assessment of Diffusion Anisotropy, Magn. Reson. Med, 36, 893-906 (1996)

  6. Information available through DTI -- Dav • Related to the overall size of the ellipsoid. • Values for Dav change with brain maturation. • Values of Dav change dynamically after injury (useful for early detection of injury).

  7. Diffusion MR Imaging of Stoke Five hours after onset right hemiparesis and aphasia DWI T2W Courtesy of Jonathan Lewin, Case Western Reserve/UH of Cleveland

  8. Information available through DTI -- Aσ s av • Related to the shape of the ellipsoid • Independent of Dav (normalized) • Zero for a sphere, positive for other shapes • Sensitive to myelination and cortical development

  9. Normal Adult Brain (A maps) Diffusion Tensor Imaging (As)

  10. Information available through DTI – Orientation of λ1 • Useful for following white matter tracts

  11. Diffusion Tracking of Geniculo-Calcarine Tracts Conturo et al. Tracking neuronal fiber pathways in the living human brain PNAS96, 10422-10427 (1999).

  12. I. Diffusion Anisotropy in Cortical Grey Matter – Human Studies McKinstry et al. Radial organization of developing human cerebral cortex revealed by non-invasive water diffusion anisotropy MRI, Cereb Cortex, 12, 1237-1243 (2002).

  13. Background • Nonzero values for diffusion anisotropy have been described occurring transiently during the cerebral cortical development: • Cat [Baratti et al. Proc ISMRM, 5th Annual Meeting and Exhibition, Vancouver 504 (1997)] • Pig [Thornton et al. Magn Reson Imaging15, 433-440 (1997)]. • We measured cerebral cortical anisotropy values from premature newborn infants.

  14. Whisker Plot: 26 Weeks GA

  15. Whisker Plot: 35 Weeks GA

  16. Diffusion Anisotropy: Cerebral Cortex

  17. M. Marin-Padilla J Comp Neurol321, 223 (1992)

  18. Cortical Anisotropy Conclusions • Cerebral cortex in infants less than 36 weeks gestational age (GA) has nonzero anisotropy values. • Cortical A values decrease with increasing GA (rank sum = -0.94, p < 0.01) and are consistent with zero after 36 weeks GA. • Changes in diffusion anisotropy reflect changes in underlying cortical architecture. • Diffusion anisotropy measures may have a role in assessing cortical development and its response to injury.

  19. II. Diffusion Anisotropy in Cortical Grey Matter – Preliminary Baboon Data

  20. Experimental Design • Evaluated immersion-fixed tissue supplied by the Southwest Foundation in San Antonio (Drs. Jackie Coalson, Brad Yoder, Don McCurnin). • Specimens available from 90 days (20 weeks) through 182 days (40 weeks). • 450 mm3 spatial resolution. • 40 q or b values • Bayesian probability theory for model selection and parameter estimation (Drs. Chris Kroenke, G. Larry Bretthorst).

  21. No Constant Diffusion + C Model Selection No Signal Constant Isotropic Oblate Prolate DTI

  22. Model Selection

  23. Anisotropy Maps 90 128 182 146 0.0 0.2 0.4 0.6

  24. D Ellipsoid Map

  25. Whisker Plot

  26. Baboon Study Conclusions • Anisotropy features of fixed baboon brain are remarkably similar to those of live premature infants. • Models for cortical anisotropy tend to be fairly simple (axisymmetric, prolate, include “constant”). • Similar information can be obtained from human infants using fewer b or q values (i.e., with shorter scan times than for baboon tissue). • Studies of tissue from injured baboons (and humans) are under way.

  27. Terrie E. Inder, MD, PhD Chris Kroenke, PhD G. Larry Bretthorst, PhD Robert C. McKinstry, MD, PhD Amit Mathur, MD Jeff Miller, MD I. Alpay Ozcan, DSc Georgia Schefft, CPNP Shelly I. Shiran, MD Joshua S. Shimony, MD, PhD Avi Z. Snyder, MD, PhD C. Robert Almli, PhD NS37357

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