Hi Cindy,
it depends on the bandwidth of the imaging sequence. We use multi-echo mprage to avoid this type of thing. Do the surfaces look accurate in these regions? I can imagine that it would affect thickness more than surface area. Have you checked which parameter dominates your volume change? I wouldn't think that it would be a bigger effect in one group than the other though.
cheers, Bruce
On Tue, 2 Mar 2010, Cindy Eckart wrote:
Dear FreeSurfers,
in the FreeSurfer cortical parcellation procedure, a volume measure is
calculated for the lateral orbitofrontal cortex and in my study population I indeed do find a significant group difference in the volumes of this region. However, there certainly is signal loss of the MR signal in the orbitofrontal region... However, I am not quite sure how much of the lateral orbitofrontal cortex is concerned by this phanomenon. Thus, my question: Is there any data how reliable the volume measurement of the FreeSurfer cortical parcellation might be in the lateral orbitofrontal cortex? Is there a way to check how much of this parcel is concered from signal loss in my own data? And do you have any experience how reasonable it may be to interpret a group difference in this region?
Thank you very much in advance!
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