Dear Mona,
> I have some fMRI scans that i need to register to the subjects' t1
> brain and
> the standard brain. In some cases, the T1 brain was obtained from a
> different
> scan session than the functional data. How many degrees of freedom
> should I
> use, 6 or 7 DOFs? I tried both options, and did not see any visible
> difference in
> the registration.
I am assuming we are talking about the EPI->T1 registration here. I
would say that in principle the 6DOF registration should be the
"correct" one. The "theoretical" reason for why one would want to use
the 7DOF registration would be if one of the sequences were
geometrically miscalibrated so that the actual voxel size was
different from the tentative one.
However, if you have a reasonable brain coverage in both scans the
results will be very similar in the 2 cases (provided the geometry is
correct in both scans) and both options would give valid results.
Good luck Jesper
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