top | Longitudinal Tutorial

Making white matter edits

For the longitudinal stream, it is recommended that you make wm.mgz edits to the base. This is because even though the long transfers manual wm edits from the cross, it still takes the surfaces from the base, and if the base surfaces did not improve, neither will the long. The only way to make corrections to the base surfaces themselves is to edit wm.mgz on the base. Therefore, making wm.mgz right on the base can save you a lot of time. Of course it is best to edit all stages (all cross time points and base), but often it is sufficient to edit only the base.

Were you able to find the area that needs intervention? Here is what we found. You can see below on the brainmask.mgz (left) that the pial surface is cutting through the wm. If you toggle to the wm.mgz (right), you can see that there are a few wm voxels missing.

This is at slice 169 for the base.
0185bm_169_before.jpg 0185wm_169_before.jpg

This happens also at the tip of the lh temporal lobe several slices away (slice 166).
0185bm_166_before.jpg 0185wm_166_before.jpg

Add wm voxels to connect the wm together in all the slices that need it. Here is what we did.
0185wm_169_after.jpg 0185wm_166_after.jpg

After you are satisfied with your edits, save the aux volume and rerun the base.

recon-all -base OAS2_0185 -autorecon2-wm -autorecon3

After that is done, check the surfaces on base using tkmedit.

tkmedit OAS2_0185_fixed brainmask.mgz -aux wm.mgz -surfs

This is what it should look like, slice 169 (left) and slice 166 (right).
0185bm_169_after.jpg 0185bm_166_after.jpg

When the surfaces are all corrected, you can recreate the long (make sure you remove the long directories before the rerun - or at the very least, remove the wm.mgz files in all the mri directories).

recon-all -long OAS2_0185_MR1 OAS2_0185 -all
recon-all -long OAS2_0185_MR2 OAS2_0185 -all

Inspect your output in tkmedit.

tkmedit OAS2_0185_MR1.long.OAS2_0185_fixed brainmask.mgz -aux wm.mgz -surfs
tkmedit OAS2_0185_MR2.long.OAS2_0185_fixed brainmask.mgz -aux wm.mgz -surfs

See here that the improved surfaces in the base also correct the surfaces in the long. Compare MR1.long slice 164 in the before (left) and after (right) images below.
0185_long1_163_before.jpg 0185_long1_163_after.jpg

The same improvement should have occurred with MR2.long.

Fstutorial/LongWMEdits (last edited 2011-05-24 15:57:39 by KhoaNguyen)