Hi Bruce, this is true, but I noticed that many papers used TIV as a covariate. In addition, in my samples (both pathological and healthy) there is a moderate positive correlation between gyrification and TIV (and brain volume). For the hemispheric overall gyrification index the correlation is 0.3-0.35 with TIV and 0.35-0.4 with total brain volume. I think that in pathological samples with possible brain atrophy, this is a way to control for a possible bias effect. Am I wrong?
Thank you Angela > Hi Angela > > gyrification is the ratio of areas and hence dimensionless, so I would > think it wouldn't be much affected by TIV. > > cheers > Bruce > > > On Sun, 21 Feb 2016, angela.fav...@unipd.it wrote: > >> In the case of a gyrification analysis, does correction for total brain >> volume make sense? >> >> Angela >> >> Inviato dal mio dispositivo Huawei >> >> -------- Messaggio originale -------- >> Oggetto: Re: [Freesurfer] eTIV question >> Da: Bruce Fischl >> A: Freesurfer support list >> CC: >> >> >> yes, it's a somewhat different and more conservative test. I >> guess you >> could check the talairach transforms of some of your subjects >> with eTIVs >> that don't make sense (or change the most over time) to try to >> see why >> this is happening. Or take Mike's suggestion and test a >> different (but >> probably still interesting) hypothesis >> >> On Sun, 21 Feb 2016, Angela Favaro wrote: >> >> > Hi, thank you >> > I think this would test something different: 'how much a brain >> area is >> > atrophic controlling for the average brain atrophy' and not >> 'how much >> > a brain area is atrophic controlling for the individual >> differences in >> > head size'. Doesn't it? >> > >> > Angela >> > >> > >> > "Harms, Michael" ha scritto: >> > >> >> 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: mha...@wustl.edu >> >> >> >> >> >> >> >> >> >> On 2/21/16, 6:06 AM, "freesurfer-boun...@nmr.mgh.harvard.edu >> on behalf of >> >> Angela Favaro" >> angela.fav...@unipd.it> wrote: >> >> >> >> there is a mistake in the graph, hippocampal volume is TIV2 >> >> I apologize for that! >> >> >> >> Angela Favaro 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 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.fav...@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 >> >>>>> >> >>>>> >> >>>>> _______________________________________________ >> >>>>> Freesurfer mailing list >> >>>>> Freesurfer@nmr.mgh.harvard.edu >> >>>>> >> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer >> >>>>> >> >>>>> >> >>>>> >> >>>> _______________________________________________ >> >>>> Freesurfer mailing list >> >>>> Freesurfer@nmr.mgh.harvard.edu >> >>>> >> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer >> >>>> >> >>>> >> >>>> The information in this e-mail is intended only for the >> person to whom >> >>>> it is >> >>>> addressed. If you believe this e-mail was sent to you in >> error and >> >>>> the e-mail >> >>>> contains patient information, please contact the Partners >> Compliance >> >>>> HelpLine at >> >>>> http://www.partners.org/complianceline . 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