Thanks Bruce, this is going to be very helpful.

One thing I have not understood from the statistics freesurfer outputs is why average thickness is not exactly the ratio between volume and surface area. This is just a small curiosity though.

Best regards. Dorian On Jul 23, 2014 3:40 PM, "Bruce Fischl" fischl@nmr.mgh.harvard.edu wrote:

Hi Dorian

yes, that would work.

cheers Bruce

On Wed, 23 Jul 2014, Dorian P. wrote:

...

Hi all, A while ago I asked how can I calculate the average thickness of the

three

...

lateral temporal gyri, and Bruce kindly suggested to draw the label on fsaverage and use transforms to calculate it for each subject. I may try

to

...

do that, but given my time constrains and my level of knowledge of Freesurger I thought an alternative method:

Say for example I have the inferior, middle, and superior temporal gyrus with surface areas of 1000, 2000, and 3000. They also have an average thickness of 2, 3, and 4mm, respectively. Given that these thicknesses

are

...

distributed in those areas, I could weight each region accordingly and calculate the average thickness as:

( (1000*2) + (2000*3) + (3000*4) ) / (1000+2000+3000) = 20000/6000 = 3.33

Is this logic correct, and why yes or no?

Thank you in advance. Dorian TJU

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