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Hi,
Upon further examination of pathstats.byvoxel.txt and pathstats.overall.txt,
I have 2 more questions.
Since my previous 3 questions still have not been answered, I'm including
them here
so that they are all in one place. The 2 new questions are 4) and 5), my
previous 3
questions are appended after.
4) I have noticed that the averages of AD, RD, MD and FA in
pathstats.byvoxel.txt
are exactly the same as the *_Avg_Center in pathstats.overall.txt.
According to the tutorial, *_Avg_Center in pathstats.overall.txt is
the "average over highest-probability path only" and the
AD, RD, MD and FA in pathstats.byvoxel.txt is the value at the
"position on the maximum a posteriori path".
Does it mean that "highest-probability path only" and "position on the
maximum a posteriori path" are the same or one of them should be changed to
the other one?
5) Are the averages of AD_Avg, RD_Avg, MD_Avg and FA_Avg in
pathstats.byvoxel.txt
suppose to match *_Avg(average over the entire support of the path
distribution)
in pathstats.overall.txt?
When I removed the duplicate points in pathstats.byvoxel.txt, the averages
of
AD_Avg, RD_Avg, MD_Avg and FA_Avg come very close to the value of *_Avg in
pathstats.overall.txt
I don't think I can calculate the averages by including the duplicate
points in 4)
but removing them in 5). Either including them in both or not at all.
Questions from my previous email.
1) There are duplicate points in pathstats.byvoxel.txt, is it normal?
I didn't try it on all 42 tractcs. For the few I've looked at, they all
have duplicate points.
I used the default setting in the config file to run trac-all.
2) When I do along-tract statistical analysis, sig.mgh and z.mgh are 1D
files.
When embed the sig.mgh and z.mgh statistical maps from the analysis into
the template .trk
(*.display.trk, which is 3D), it seems to me that sig.mgh and z.mgh don't
have enough information to give *.display.trk the voxel values for the
*.overlay.trk. There is no one-to-one voxel corresponding between sig.mgh
and *.display.trk. What am I missing? Or what's the embedding process do?
3) When I convert .trk(*.overlay.trk, for example) to nii.gz or ascii using
dmri_trk2trk or
mri_convert the voxel values of the .trk file don't get converted into the
.nii.gz or ascii file,
only the x,y,z coordinates are converted. Is there a way to get the voxels
values of the .trk file
when converting to .nii.gz or ascii format?
Thanks,
King-Wai
--
King-Wai Chu, Ph.D.
Program Analyst
Mental Illness Research, Education and Clinical Center (MIRECC, VISN3)
James J. Peters Dept. of Veterans Administration Medical Center (OOMH)
130 W. Kingsbridge Road
Bronx, NY 10468