1. NA-MIC National Alliance for Medical Image Computing http://na-mic.org Cortical Thickness Analysis Delphine Ribes (Internship UNC 2005/2006) Guido Gerig

2. National Alliance for Medical Image Computing http://na-mic.org Slide 2 Project ? ? ? ? ? ? Measure Cortical Thickness by using the Danielsson Distance Transform White matter Boundary Grey Matter exterior boundary Cortical Thickness ?

3. National Alliance for Medical Image Computing http://na-mic.org Slide 3 Just another cortical thickness method … Given imperfect, somewhat noisy tissue images Perfect, topologically correct surface cannot be obtained Not necessary to inflate cortex Display on wm and gm surfaces Separate measure of thickness inside folds and on outer cortex Choice: “Engineering method” based on Euclidean distance transform Good enough to collect statistics across cortical areas, not precise measurements at each voxel

4. National Alliance for Medical Image Computing http://na-mic.org Slide 4 Cortical Thickness Pipeline : Brain Seg Image Danielsson Distance Map Vector Map Distance Maps White and Grey

5. National Alliance for Medical Image Computing http://na-mic.org Slide 5 Danielsson DT Danielsson’s DT: propagates a vectorial information, the location of the nearest pixel of the set S

6. National Alliance for Medical Image Computing http://na-mic.org Slide 6 Vector Map Grey matter Distance map White matter Danielsson distance transform of white matter At each grey matter voxel, we “know” the distance to the white matter => At each grey matter voxel, store vector to the closest point

7. National Alliance for Medical Image Computing http://na-mic.org Slide 7 Distance Maps White and Grey White matter Boundary Grey Matter exterior boundary Vector Map Problem :  Each grey matter voxel points to white matter surface  Gray matter surface in folds is not known Solution :  At each wm surface point, choose the grey matter voxel distance with maximum distance Method : Maximum Operator => For each white Matter point, find the furthest grey Matter point

8. National Alliance for Medical Image Computing http://na-mic.org Slide 8 Example Result : Mean: 5,02 mm White Distance Map Grey Distance Map Danielsson Distance Map 0 White matter Grey matter

9. National Alliance for Medical Image Computing http://na-mic.org Slide 9

10. National Alliance for Medical Image Computing http://na-mic.org Slide 10 Results differ: Reason is that thickness within folds is spatially limited!!!

11. National Alliance for Medical Image Computing http://na-mic.org Slide 11 Only thickness of outer cortex but not inside folds: Values match validation sphere!

12. National Alliance for Medical Image Computing http://na-mic.org Slide 12

13. National Alliance for Medical Image Computing http://na-mic.org Slide 13 Traveling Phantom Validation: Duke QC study (Cecil Charles)

14. National Alliance for Medical Image Computing http://na-mic.org Slide 14

15. National Alliance for Medical Image Computing http://na-mic.org Slide 15 Full Brain Cortical Thickness as fct of Age: N=22 Full brain cortical thickness as function of age shows peak at around 12 years of age.

16. National Alliance for Medical Image Computing http://na-mic.org Slide 16 Summary: Procedure Cortical thickness for full brain and for individual lobes Tissue Segmentation Lobe Parcellation Distance gray matter surface to white matter boundary

17. National Alliance for Medical Image Computing http://na-mic.org Slide 17 Web download of tool and manual at www.ia.unc.edu/dev

18. National Alliance for Medical Image Computing http://na-mic.org Slide 18 Status Tool fully written in ITK Toolkit available on UNC website and compiled on UNC dashboard Visualization with NA-MIC MeshVisu (Oguz) Comprehensive manual, very easy to use Might go very well with Slicer3 EMS (needs tissue segmentation and parcellation)