Berlin - 2007

WMSG Annual Meeting
Monday 21 May 2007, 18:30
Hall 4/5 ICC-Berlin
Berlin, Germany

Board Members in Attendance: Greg Stanisz, Charles Guttman, Roland Henry, Corree Laule, Egill Rostrop, Stefan Ropele, Thor Bjarnason
Total number of voting members present: 30 (Quorum reached)
Total number non-voting members present: 84

Meeting was called to order at 7:05pm

1.0    Procedural Items

1.1    Adoption of current agenda
Moved/Second: Irene Vavasour / Corree Laule
Motion carried.
1.2    Approval of minutes from May 10th, 2006
Moved/Second: Joe McGowan / Nancy Lobaugh
Motion carried.
1.3    Items resulting from the previous minutes
No items were brought to the attention of the executive.

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