Hi Hankee,

The eTIV or the ICV is a measure of the head size and with Freesurfer can be found within the aseg.stats file. There are several ways to utlize this for adjusting for head size for individual structures. For one, you can simply take the volume of a region (e.g. parahippocampal gyrus) and divide this by the eTIV/ICV measure and get an 'adjusted volume' and use this for all further statistical comparisons. Another way is to perform a linear regression with the eTIV/ICV measure for all subjects and the volumes of individual regions for all subjects, take the residuals, and utilize these as 'adjusted volume' measures for all further statistical comparisons.

Best,

rahul

hi,rahul Sorry,I have not heard about the eTIV or ICV,what does this letter stand for? and how to use eTIV or ICV to adjust head size? Thank you very much! best, hankee

hankee£¬duhanjian@sohu.com 2007-04-26 ----- Original Message ----- From: rahul To: duhanjian Sent: 2007-04-26, 23:18:32 Subject: (ÈðÐÇÌáʾ-´ËÓʼþ¿ÉÄÜÊÇÀ¬»øÓʼþ)Re: [Freesurfer] (no subject)

Hi Hankee,

You certainly can use the statistical information regarding the volume, thickness, and surface area of individual regions, such as the parahippocampal gyrus (as derived from the ?h.aparc.annot file), to compare between various groups of subjects. The only recommendation would be that if you are performing cross-sectional comparisons using the volumes of individual brain regions, you should use the eTIV or ICV measure to adjust for head size for individual subjects.

Best,

rahul

...

hi,I have question about the ?h.aparc file in stats directory. Can I use the parahippocample's gray matter volume or other brain structure's gray matter volume to do statistics analysis? For example,select 15 normal people and 15 AD disease patient,using FreeSurfer software to deal with them,when It is done, Can I compare the parahippocample's gray matter volume which located in /stats/lh.aparc file between patient group and normal group? Thank you!

hankee£¬duhanjian@sohu.com 2007-04-26 _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer