External Email - Use Caution        

Dear FreeSurfer users/experts,

I have two questions related to the manual of segmentHA_T2.sh pipeline
written on the FreeSurfer's website, which I would like to apply to ADNI
data. I couldn't find any solutions to that elsewhere. Regarding the data,
T1s have a resolution of 1.2 x 1.05 x 1.05 and T2s have a limited FoV on
Hippocampus/Amygdala with a voxel size of 0.4 x 2 x 0.4.

I have two questions:

   1.  What value should I set for USE_T1? According to the manual on
   FreeSurfer's website:


*"Using the main T1 is advised when the additional scan is of comparable
   resolution as the T1, or when the additional scan does not cover the whole
   hippocampal region - in that case, the T1 information will be critical to
   segment the hippocampal regions outside the field of view of the additional
   volume. Using the additional scan in isolation is advised when it is of
   higher resolution than the T1 while covering the whole hippocampi and
   amygdalae." *Based on this text and ADNI's high-resolution T2, what
   should I set USE_T1 to?
   2. Regarding the additional scan, it is written that:
*"In this case, the only requirement is that the additional scan is
   coarsely aligned to the main T1 scan." *What does it mean by "coarsely
   aligned"? Should I linearly register the T2 to T1? However, visualizing the
   T1 and T2 images overlaid on top of each other reveals that they are
   somewhat aligned, as both T1 and T2 were acquired in the same session;
   however, they are not as aligned as one would expect after a rigid
   transformation.


Looking forward to your comments.

Best,
Amir
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