Visualization of Fibers at Risk for Neuronal Tract Injury in Early MS by Streamtube Diffusion Tracto - PowerPoint PPT Presentation

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Visualization of Fibers at Risk for Neuronal Tract Injury in Early MS by Streamtube Diffusion Tracto

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Title: Visualization of Fibers at Risk for Neuronal Tract Injury in Early MS by Streamtube Diffusion Tracto


1
Visualization of Fibers at Risk for Neuronal
Tract Injury in Early MS by Streamtube Diffusion
Tractography at 3 TeslaJack H Simon 1David E
Miller 1Mark Brown 1John R Corboy 1Jeffrey L
Bennett 1Song Zhang 2 David H Laidlaw 2
1University of Colorado Health Sciences Center
2Brown University
Supported by the National MS Society (RG
3307-A-1), GE Medical Systems, and the National
Science Foundation (CCR-0086065).
2
Background Neuronal Tract Degeneration in Early
MS
  • Axonal injury in inflammatory MS Lesions
  • Trapp et al 1998 Ferguson et al 1997
  • Empty myelin cylinders 2 to and distant from
    focal lesion
  • Bjartmar et al 2001
  • Major axonal loss (and atrophy) in corpus
    callosum
  • Evangelou et al 2000
  • Neuronal Tract Degeneration Patterns in Early MS

Bjartmar et al 2001
Transcallosal Bands
Corticospinal Tract Degeneration
Simon et al Neurology 2001
Simon et al Neurology 2000
3
Goals/Question
  • Develop a process to identify and then
    interrogate neuronal fibers that are anatomically
    related to focal demyelinating lesions
  • Can we detect and measure neuronal fiber
    injury/degeneration in vivo ?

4
Strategy
  • Earliest MS
  • Identify focal lesions at the time of a CIS
  • Identify fibers transiting the focal lesion and
    reaching a distant structure (corpus callosum)
  • Interrogate fibers (in corpus callosum) by MRI
    distant from focal lesion
  • MTR, Diffusion tensor (ltDgt FA)
  • Longitudinal MRI follow-up

5
3T Pulse Parameters
  • Diffusion Tensor Imaging
  • Echo-planar
  • B-value 1000, 25 gradient directions
  • Axial plane - 3 sets of overlapping slices
  • 5.1 mm thick with 1.7mm shifts
  • FOV 28 x 28 cm, matrix 160 x160, 2 excitations
  • TR/TE 6075/69.8-minimum
  • Magnetization Transfer Imaging
  • 3D gradient-echo
  • MT pulse
  • Fermipulse applied middle 30 of the phase
    encode steps (SAR)
  • Pulse width of 8 ms
  • Peak B1 field of 9.24 µT, flip angle of 670
  • 1200 Hz from the center frequency
  • TR/TE/flip angle 50/2.4(fr)/15
  • FOV 22x22, matrix 256 x192, one excitation
  • Sagittal plane
  • 3 mm partitions

6
Patient Characteristics
7
Outline of Streamtube Tractography Strategy
Calculate Diffusion tensor - non-linear
approach
  • Generate streamtubes and streamsurfaces
  • Westin et al 2002 Zhang et al 2003
  • coherent white matter tracts fastest diffusion,
    principal eigenvector
  • Terminate streamtube
  • low linear diffusion data boundary curvature
  • 500,000 streamtubes
  • Cull 1 length anisotropy redundancy
  • 2,000 streamtubes
  • Cull 2 - seed points within the 3D coordinates
    of T2-lesions
  • Cull 3 - intersection with corpus callosum.

Register data sets- affine transformations
optimized by mutual information algorithm
Visualize in optimal projection quantitative
analyses
8
Visualization -Streamtubes Streamsurfaces
Segmentation Registration
  • AAMI (Analysis Application for Medical Imaging)
  • David E. Miller - University of Colorado HSC
  • Visualization Tools
  • Song Zhang and David Laidlaw - Brown University

9
Streamtubes culled to lesion Streamsurfaces not
utilized
10
Streamtubes culled to lesion corpus callosum
11
Case 1
Streamtubes and Streamsurfaces
Culled to Lesion
Culled to lesion corpus callosum
12
Case 2
Culled to Lesion
Culled to Lesion Corpus Callosum
13
Case 2
14
Case 3
Culled to lesion corpus callosum
15
Fibers at Risk (FAR)
Case 1 Registration of culled streamtubes to
sagittal representation of corpus callosum
16
CIS 1
CIS 2
CIS 3
17
Conclusions
  • Viable strategy and methodology to identify a new
    class of tissue called fibers at risk (FAR)
  • NAWM
  • AAWM
  • FAR
  • FAR makes up a formidable percentage of corpus
    callosum with minimal overlap with AAWM
  • Strategy applicable to any neuronal tract
  • Future studies to determine injury profile over
    time, factors associated with more severe
    neuronal tract injury
  • Assay of MS neurodegeneration to evaluate
    treatment ?

18
Supported by The National Multiple Sclerosis
Society (RG 3307-A-1)GE Medical Systems (3T
diffusion tensor MRI)National Science Foundation
(CCR-0086065)University of Colorado 3T Research
Instrument (ONDCP)University of Colorado Brain
Imaging Research Laboratory (BIRL) Rebecca Leek
and MaryJoel Meyer BIRL and Brain Imaging Center
for Drug Abuse Research Deb Singel
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