Toronto - 2008

WMSG Annual Meeting
Monday 7 May 2008, 19:30
Room 701 A
Toronto, Canada

Board Members in Attendance: Greg Stanisz, Charles Guttman, Roland Henry, Derek Jones, Hugo Vrenken, Stefan Ropele, Ives Levesque
Exiting Board Members in Attendance: Corree Laule, Egill Rostrop, Thor Bjarnason
Total number of voting members present: 25 (Quorum reached)
Total number non-voting members present: 50

Meeting was called to order at 19:42pm

1.0    Welcome

1.1    Introduction of new members
1.1.1    Derek Jones, Hugo Vrenken (committee members)
1.1.2    Ives Levesque (student member)
1.1.3    Roland Henry (secretary)

1.2    Adoption of current agenda
Moved/Second: Roland Henry/Corree Laule
Motion carried.

1.3    Approval of minutes from May, 2007
Moved/Second: Charles Guttman/Roland Henry
Motion carried.

1.4    Items resulting from the previous minutes
No items were brought to the attention of the executive.
1.5    Statistics
1.5.1    WMSG Membership 2006 - 2008

2.0    Opening remarks (Greg Stanisz)

2.1    Welcome
2.2    Farewell and thank you to Victor Song
2.3    Introduction of new members:

2.3.1    Stefan Ropele (committee member)
2.3.2    Thor Bjarnason (student representative)

3.0    Debate: Does DTI Have a Chance Of Being Specific To White Matter   Pathologies?

3.1     “Definitely Unlikely” (Andy Alexander Ph.D., University of Wisconsin)

•    DTI is sensitive to microstructural changes
•    Diffusion has 4962 pubmed references – most number of references of all techniques looking at WM
•    Many applications and is extremely sensitive to myelin, axons, cell density, inflammation, ischemia
•    One can measure 3 principle axes to get mean diffusivity (average), normalized variance (anisotropy), perpendicular = myelin? parallell = axons?
•    Head injury example: FA appears normal

-    There are partial volume effects on anisotropy
-    Many shapes have FA=0.5
-    Decrease in FA can be caused by increase in Dperp or decrease in axial diffusivity
-    Crossing fibres mess up measures
-    Anisotropy doesn’t equal tensor shape (oblate or prolate)
-    Non-gaussian diffusion is non Gaussian, but the diffusion tensor assumes Gaussian diffusion
-    Other problem with DTI is SNR (at low SNR you over estimate anisotropy)

•    What about anatomical specificity?

-    More logical to compare apples to apples (example genu to genu). 19 studies found FA of genu to be on average 0.36 (0.5-0.9) stdev 0.1 – large variation!!!
-    Mean D range was 0.4 – 1 (0.58, stdev 0.16) 10-3mm/s2

•    Is DTI a marker of WM integrity?

-    170 pubmed hits
-    Many pathologies can cause decreases in FA (myelin, axons, glia, edema, inflammation), increases MD, increases in radial D and questionable for Dpara
-    Is Dperp related to myelin? There are animal studies – but model likely only works in homogeneous parallel WM

•    WM Tractography

-    Pretty pictures, but small errors can have large effects!
-    Tensor fields are heterogeneous
-    False branching can occur
-    Errors are cumulative
-    If tractograms look realistic, are they?

3.2    “Very Likely” (Christian Beaulieu Ph.D., University of Alberta)

•    DTI does have a chance!
•    Celery has high anisotropy!
•    Anisotropy and DTI

-    Some cases have same trace/ADC, while FA and Dperp/Dpara are different
-    DTI is not qualitative
-    FA decreases in a number of pathologies
-    One also sees increases in FA in development, hyper acute stroke, putamen in aging

•    Relationship to WM?

-    There are unmyelinated axons which give higher FA than myelinated (Beaulieu 1994) – Myelin Is not necessary
-    Gulani 2001 myelin deficient spinal cord in rat, got rid of all myelin and anisotropy decreased 20%
-    Song 2002 anisotropy decreased by 16-25%
-    Nair 2005
-    Tyszka 2006 pathology / DTI
-    Harsan 2007 development
-    Schmierer 2007

•    Myelin has more marked effects on mean diffusivity and ADC than FA

-    Concha 2006: callosomy reduction in parallel diffusion first, followed by increase in perpendicular diffusion
-    Concha 2005: epilepsy example
-    Alexander 2007!

•    DTI can detect and characterize myelin and axonal changes and can be specific:

-    One must compare things correctly
-    Investigate relative changes in eigenvalues
-    DTI signatures – anatomy reflected

4.0    Student Poster Award

4.1    Summary of finalists (Joe McGowan)

•    5 finalists were selected:

1596 – SungWon Chung (UCSF/Berkeley, USA) Effect of DTI Bootstrap Bias on the DTI Uncertainty Measurements and Probabilistic Tractography
1609 – Bennet Landman (Johns Hopkins, USA) A Window for High-Resolution Post-Mortem DTI: Mapping Contrast Changes in Neural Degeneration
2123 – SungWon Chung (UCSF/Berkeley, USA) Progressive White Matter Microstructural Changes Following Mild Traumatic Brain Injury Revealed by Bootstrap Analysis of Serial 3T Diffusion Tensor MRI
2412 – Ives Levesque (McGill, Canada) Characterization of myelin damage in multiple sclerosis using myelin water imaging: Insight from simulations on a four pool model of white matter
3712 – Istvan Csapo (Harvard Medical School, USA) Strategy and validation of large-scale MRI registration framework

•    Criteria for winner included was the work novel and useful and did the student do the work?

4.2    Announcement of winner (Thor Bjarnason, Nancy Lobaugh)

•    SungWon Chung: 1596
 

 5.0    Current Status of the Study Group (Greg Stanisz)

5.1    WMSG Membership 2006 & 2007

 5.2    WMSG Membership numbers from around the world (as of May 2007)

 6.0    2008 White Matter Study Group Workshop (Charles Guttmann)

•    Wiki: www.wmsg.org
•    Next WMSG workshop September 24-26, 2008 (Krakow) “Pathogenesis, Detection and Implications of White Matter Injury”
 

 7.0    Adjournment

Motion to adjourn.
Moved/Second: Corree Laule / Irene Vavasour
Motion carried.

Meeting adjourned at 8:55pm

Next meeting: May 2008, Toronto
 

2007 - Berlin

2006 - Seattle

2005 - Miami