Dear Bruce and others,
We have just ran into strange ICV volumes.
For all our 100+ subjets, the total icv is around 1500cm3 (around 1300-1700).
For the new group (only 7 subjects) the average ICV is around 1200 (ranging from 900-1500).
This is almost microcephalia, but they are normal.
If we take a look at the brainseg volume or brain mask volumes they are larger than the total ICV (for e.g. subject 5 has brainmaskvol: 1440; brainseg vol: 1021; ICV 1036)
This is not right. It's kind'a strange that someone has bigger brain than skull :)
I was using freesurfer 4.5 for both groups.
Do you have any idea what did I miss?
Thanks,
Gergo
2011/10/3 Bruce Fischl fischl@nmr.mgh.harvard.edu
The stuff outside the pial surface won't affect things, which is one of the reasons we prefer the surface-based measured of cortical morphometry.
Similarly, we don't use the surface-based stuff in the hippocampus, so you should be all set (since many of the cortical assumptions aren't valid there)
cheers Bruce
On Mon, 3 Oct 2011, Gergely Orsi wrote:
Dear Freesurfers!!
I've encountered two strange segmentation "errors", if they are errors at all.
Please see the attached fs.png:
You can see that there are excess pial tissues on the superior part of the brain. The pial surface is defined correctly and the excess pial tissue is outside the red line yet it is coloured pink. My question, is :
Does this have any impact on the results?
The second is related to the hippocampus.
Please see the attached fs2.png:
The pial surface around the hippocampus looks a bit weird. It actually discards 1/3 of the hippocampus (it is outside the red line).
Do you have any suggestions regarding the two problems.
I'm using FS 4.5 on several 64bit linux distributions.
-- Gergely Orsi biologist - research associate Diagnostic Center of Pécs H-7623 Pécs, Rét str. 2. Tel.: 0036-70-3174676 E-mail: gergo.orsi@gmail.com
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