I am following the recipe from John for a longitudinal study using SPM12b:
For each subject
- Run the SPM12b pairwise longitudinal registration to generate the subject average and Jacobian determinants (jd)
- Segment the subject average, generating c1, rc1, rc2
- Use ImCalc to compute c1.*jd (possibly dividing the result by the time difference to give the rate of atrophy)
- Run Dartel, aligning the rc1 and rc2 images from all subjects together
- Normalise and smooth the c1.*jd images
- Run stats
I have a question abut adding in the time difference to get the rate of atrophy. I already added in the time difference during the longitudinal registration. Does this mean it is already accounted for in the jd images? In which case do I need to add this again to get the rate of atrophy?
Thanks
Becky
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