Hi, Zia 1- The name "Right-Hippocampus" is misleading you. The hippocampal subfields segmentation is atlas based. And the atlas was generated from expert manual segmentation. The problem is that the most posterior part of hippocampal tail is too small to allow a precise segmentation. So they know it was part of hippocampus but not being able to discriminate the subfields in this portion they named as hippocampus. This name in manual segmentation was preserved in FreeSurfer's automated process. So in this list Rigth-Hippocapus does not mean the whole right hippocampus. It is just the portion of the right hippocampus not segmented in subfields. You can see more details at https://surfer.nmr.mgh.harvard.edu/pub/articles/VanLeemputHippocampus2009.pd... . There you can read:
Towards the tail of the hippocampus, the manual delineations no longer discern between the different subfields, but rather lump everything together as simply ‘‘hippocampus,’’
In my own data I renamed this to "right hippocampal tail complement" just to avoid this confusion.
2- Yes, just divide the "volumeInVoxels" value by eight to get the volume in cubic milimeters.
Marcos.
Em Qui, 2014-07-10 às 19:55 +0000, Zia, Mohammad escreveu:
Hi,
Freesurfer reported the following hippocampal volumes for a subject
volumeInVoxels: right_CA1: 2652.3 right_CA2_3: 7245.11 right_CA4_DG: 3967.28 right_fimbria: 423.555 right_hippocampal_fissure: 191.897 right_presubiculum: 3598.99 right_subiculum: 4868.1 Right-Hippocampus: 3258.77
I have two questions about it
1. I don’t understand why the right_subiculum volume is more than the Right-Hippocampus volume. 2. Since the voxel size for the volumes is 0.5^mm, do we have to divide these volumes by 8 to convert them to voxel size 1^mm so that we can do direct comparison with other freesurfer stats volume (for example the volumes in rh.aparc.stats)?Thanks --Mohammad Zia
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