Dear SPMers,
I encountered a problem using the SPM segmentation module in a DTI study in
which i need to determine WM volume of each subject.
I segmented a T1-weighted volume saving both WM volume in native space
(c2Img.*) and in normalized space (mwc2Img.*), but modulated in intensity.
I read that modulation is a process which multiplies the segmented
normalized volume of interest by the jacobian, to correct for effects of
volume change.
Given this, i determined the sum of all voxels' intensity for volume both in
native space and in normalized modulated space, and i was expecting for
these two values to be near equal.
On the contrary, i found that the sum of all voxels' intensity for the
normalized modulated space is less (about a half) than that of native space,
even setting all NaN of the modulated volume equal to 1.
Does anyone encounter the same problem? and which is the better value
(native or normalized modulated) for estimating WM volume?
Thank you for your time
Marta
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