--- Original Message ---
From : p.s.bjerkan@studmed.uio.no
To : freesurfer@nmr.mgh.harvard.edu
Date : 2008/05/16 ?????? ???? 1:55:05
Subject : [Freesurfer] Hippocampal volumes

Hi,

We have been using your exellent software for some time now. We work on
several studies and in one of them we now asess the hippocampus volume.
The information is gathered from the Freesurfer aseg.stats file. The data
for this group has been run in both versions 3.0 and 4.0. When comparing
results from these runs we find discrepant results.

We have four questions:

1) I assume that some degree of difference in outcome between the two FS
versions is to be expected. But how large a difference would you consider
"normal" or acceptable? Our differences seem to be quite large. I have
attached the outputs for lh. for two subjects with extensions fs3
(Freesurfer 3.0) and fs4 (Freesurfer 4.0).

2) I have inspected the subjects with the largest discrepancies and so far
it seems that it is v4.0 that is producing the errors. The tiffs attached
showing where I believe there are obvious errors (the fs4?s).

3) Is it possible to edit aseg results? (or is that only for the cortical
reconstructions?)

4) Can you give any advise on which of the data sets we should do
calculations on?

Have also attached a Excel-file with the volumes for all the subjects in
the study (average and STD on the bottom...). If this large variations is
to be expected, small changes in subject groups (about 3-5 per cent) could
be missed.

Thank you !

Petr_______________________________________________
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