NA-MIC - Contrasting Tractography Method Conference Utah/UNC results Sylvain Gouttard Guido Gerig Casey Goodlett Santa Fe, October 1 st & 2 nd 2007

Overview Processing description:  DWI to tensors  ROIs  Tracking  Bundling / cleaning Results:  Fiber tracked  FA/MD analysis Conclusion

Original Data High resolution DWI with 59 images (8 B0's and 51 directions) size 256*256*81 resolution 0.9,0.9,1.7 Tensor field Tensor estimation using dtiestim: - Linear least square - B0 threshold = 500

ROIs 5 ROIs:  Arcuate  Cingulum  Fornix  Internal Capsule  Uncinate Original ROIs not appropriate for our tractography tool (need volumetric ROIs)‏ Had to specify target and source labels Split right and left

ROIs - Arcuate No editing

ROIs - Cingulum Original ROIsEdited ROIs

ROIs – Fornix Original ROIs Edited ROIs

ROIs – Internal Capsule Original ROIs Edited ROIs

ROIs - Uncinate Original ROIs Edited ROIs

Fiber tracking Fiber tracking done with the FiberTracking tool, based on Susumu Mori's tool. Input: tensor field & ROI Output: Streamlines Parameters:  min FA threshold 0.15  angle of max dev 0.35

Post processing – FiberViewer Clustering and cleaning bundle cleaning via clustering: Metrics for clustering:  fiber length  center of mass  Hausdorff Fiber cutting

Post processing - FiberViewer Diffusion statistics Diffusion statistics for each bundle: Definition of coordinate origin FA MD λ 1,2,3 diffusion val. geodesic distance 0+L-L

Specifications Computational resources:  2 Intel Xeon processors 2GHz  2G of RAM  linux Average execution time per case:  DWI -> tensors: <1min  Tractography: 2 < t < 10 min  Cleaning: 2 < t < 5 min (manual interaction)‏

Results – High resolution cases 10 cases ( dim:256*256*81 res:0.9,0.9,1.7 )‏ 5 ROIs ( Arcuate, Cingulate, Fornix, Int. Capsule, Uncinate )‏ We use the number of streamlines for comparison but know that it is limited

Fiber tracking example D00925 ; Internal capsule 19 fibers D00935 ; Internal capsule 740 fibers D00935 cleaned ; Internal capsule ; 545 fibers

Fiber tracking example D00920 ; Arcuate ; 29 fibers D00928 ; Arcuate ; 99 fibers

Fiber tracking example D00925 Cingulum 2 fibers D00917 ; Cingulum ; 175 fibers D00917 cleaned ; Cingulum ; 170 fibers

Fiber tracking example D00925 ; Fornix ; 3 fibers D00928 ; Fornix ; 77 fibers

Fiber tracking example D00936 Uncinate 1 fibers D00935 ; Uncinate ; 140 fibers D00935 cleaned ; Uncinate ; 100 fibers

Resulting data structure Origin plane manually placed Arc-length parameterization Diffusion values along fibers (FA, MD, λ's,GA) in excel format

FA-MD plots - Cingulum FA MD

FA-MD plots - Fornix FA MD Analysis: - 1 branch at a time? - 2 at the same time?

FA-MD plots – Internal capsule FA MD

FA-MD plots - Uncinate FA MD

Evaluation of preprocessing 2 cases with:  Orignal data (dim:256*256*81 res:0.9,0.9,1.7)‏  Eddy current correction (dim:256*256*81 res:0.9,0.9,1.7)‏  Eddy current correction and sub sampled (dim:144*144*81 res:1.6,1.6,1.7)‏ ‏ # of fibers

Evaluation of preprocessing Tensors filtered using MedINRIA tensor smoothing => Inconsistent results Internal Capsule: - Not filtered => 59 fib - Filtered => 179 fib Cingulum: - Not filtered => ~140 fib - Filtered => 0 fib Examples:

Summary / Problems ROIs: need redrawing to do tractography with our tools Noise level seems high w.r.t. to streamline tracking High variability across cases =>  subject specific?  scanning artefacts?  motion? distortion? ...

Summary / Problems (2)‏  Coordinate system inconsistency: ROIs are individually placed FiberViewer: origin plane manually set for statistics  Metric for comparison: number of fibers: does not describe quality

High resolution cases Percentage of fibers (with Left and Right)‏

High resolution cases Fiber tracked numbers

High resolution cases Fiber cleaned numbers

Results High resolution cases after cleaning

Results – High resolution cases 10 cases ( dim:256*256*81 res:0.9,0.9,1.7 )‏ 5 ROIs ( Arcuate, Cingulate, Fornix, Int. Capsule, Uncinate )‏

Results High resolution cases after cleaning