I have two groups of subjects
and would like to investigate task related signal chaneg in each group
seperately and to ultimately use an unpaired t-test to compare the two
I would like to limit my search to only a few regions of interest. I have
drawn the rois on the MRIcro standard image which has voxel sizes of 1x1x1
with a matrix of 181x217x181. Can I use these ROIs as pre-threshold
masking in the higher level FEAT analysis?
Does my ROI image need to have the same dimensions and voxel sizes as the
FSL standard? (2x2x2, 91 109 91)
What should my threshold be then when I use the pre-threshold masking?
voxel wise, cluster wise, uncorrected? I would guess voxel wise.
Also in regards to the resels issue. My ROIs have a large surface area and
should therefore limit the statistical power gained by limiting my search
volume. Is there some tradeoff I should make? Could I make nonspecific
"smooth blob" rois that encompass my regions of interest. An ideal ROI in
this case would then be a sphere, but what about cubes or 3-D ellipses?
Any pointers are greatly appreciated.
Department of Radiology
New Jersey Medical School
Biomedical Engineering Department
New Jersey Institute of Technology
Newark, NJ USA
(973) 676-1000 x1545