Hi Tina,
I think weighting by surface area is a reasonable approach.
cheers Bruce On Wed, 22 Dec 2010, tina roostaei wrote:
Dear all,
I have access to a dataset of freesurfer segmentation products (i.e. cortical volume, surface area, cortical thickness average and standard deviation) for a number of patients. I wanted to merge the data of some segmented parts (e.g. to compute a general cortical thickness average for the inferior frontal gyrus using the pars orbitalis, pars opercularis and pars triangularis data). I wanted to know if it is right to compute the average cortical thickness using the following formula: Average cortical thickness= [(part 1 cortical thickness*part 1 surface area) + (part 2 cortical thickness*part 2 surface area) + ÿÿ]/ (part 1 surface area + part 2 surface area + ÿÿ) BTW, I also checked whether the cortical volume equals ÿÿsurface area*average cortical thicknessÿÿ, to see if I could use the following formula instead: Average cortical thickness= (part 1 cortical volume + part 2 cortical volume + ÿÿ)/ (part 1 surface area + part 2 surface area + ÿÿ) But it simply proved wrong.
Any suggestion is greatly appreciated.
Thanks in advance. Tina