Ce,
you could create an image, that is '1' in your ROI and '0' elsewhere.
Multiply that image with a threshholded version of your spmT image. The
sum of all voxelvalues gives you the number of activated voxels in your
ROI.Also multiply your '0/1'-image with the original t-Image. You can
the read this image with standard SPM tools into matlab and have access
to the few voxel-values that you are interrested in.
Best,
Peter
Am 22.05.2012 10:47, schrieb Ce Mo:
>
> Dear all,
>
> I have 2 questions regarding voxel sizes and ROI.
>
> Suppose I have a spheric ROI with a radius of 10 mm centered around a
> MNI coordinate, say [x1,y1,z1].
>
> I am interested in how many voxels there are in this ROI and above
> all, their individual values.
>
> The intuitive thought is to find all these voxels based on the
> distances between the sphere center and the candidate voxels the MNI
> coordinates. However, I am not so sure whether I should take voxel
> sizes into consideration, and more importantly, whether this approach
> is feasible.
>
> Or is there anybody who has better ideas?
>
> Moreover, I understand that softwares such as Marsbar can be used to
> extract the mean parameter (beta) value, I suppose that will be to sum
> all the values of the voxels within that ROI and then divide it by the
> number of voxels to obtain the mean value. However, I wonder whether
> there are any additional scaling so that the extracted mean can be
> interpreted as percent signal change.
>
> Many thanks and best regards,
>
> Ce
>
|