Hi, Why not use a measurement of brain size rather than “eTIV”?
cheers, -MH
-- Michael Harms, Ph.D.
----------------------------------------------------------- Conte Center for the Neuroscience of Mental Disorders Washington University School of Medicine Department of Psychiatry, Box 8134 660 South Euclid Ave.Tel: 314-747-6173 St. Louis, MO 63110Email: mharms@wustl.edu
On 2/21/16, 6:06 AM, "freesurfer-bounces@nmr.mgh.harvard.edu on behalf of Angela Favaro" <freesurfer-bounces@nmr.mgh.harvard.edu on behalf of angela.favaro@unipd.it> wrote:
there is a mistake in the graph, hippocampal volume is TIV2 I apologize for that!
Angela Favaro angela.favaro@unipd.it ha scritto:
Hi Bruce, please find attached the graph of the correlation between the two time point. I did not find outliers or failures. However the discrepancy between TIVs is particularly high in few cases. Obviously these data are those before running longitudinal streaming This is a sample of adolescents with low body weight (anorexia nervosa). In my previous study (on young adults with low weight) I found no correlation between TIV and body weight and high correlations between fs estimated TIV and manually segmented TIV (r=0.94 in the whole sample and r=0.93 in the underweight sample (n=38)). Do you think that the young age can be a factor? or patients who are more acutely underweight? Thank you for any suggestion
Angela
Bruce Fischl fischl@nmr.mgh.harvard.edu ha scritto:
Hi Angel
the time1/time2 correlation of eTIV is pretty worrisome. Are you sure that there aren't outliers/failures in that set?
Bruce
On Sun, 14 Feb 2016, angela.favaro@unipd.it wrote:
Dear Freesurfer experts, I have a question about eTIV (FS 5.3) which I use as a covariate where appropriate. Is it in some way influenced by the presence of brain atrophy? I have a new sample of subjects in a longitudinal study: at time 1 they have some atrophy (due to low body weight) that improves in time 2 (4 months). I observed that eTIV-time1 is slightly correlated with weight (r=0.3) whereas no correlation is present at time 2. The correlation between eTIV-time1 and eTIV-time2 is somewhat lower than expected (r=0.53) and is lower than correlation between SegBrain_Vol_1 and SegBrain_Vol_2 (0.65).
Do you suggest in these cases to perform manual segmentation to obtain TIV? or is there any other method (in freesurfer) to obtain an estimate of TIV not influenced by brain atrophy? What about using BrainMask_to_TIV?
Thank you for any suggestion
Angela
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