Dear Dawn. We have observed that the hippocampal volumes obtained from the subfield module are ~10% smaller than those from the main recon-all stream - but, in any case, very highly correlated. I believe that the discrepancy is due to the smaller voxel size in the analysis, and due to the fact that the subfield module does not include the alveus in the segmentation. Cheers, /Eugenio
Juan Eugenio Iglesias ERC Senior Research Fellow Translational Imaging Group University College London http://www.jeiglesias.com http://cmictig.cs.ucl.ac.uk/
On 3 Mar 2017, at 13:15, Dawn C. Matthews <dmatthews@admdx.commailto:dmatthews@admdx.com> wrote:
Eugenio and Freesurfer team,
Many thanks for responding to these questions. My question relates to hippocampal volume overestimation. I believe that a European team recently evaluated the performance of hippocampus segmentation using different automated segmentation methods including Freesurfer on more than 400 scans from several previous studies, and found that Freesurfer and FSL-FIRST may include tissue that is not part of the hippocampus. Liedlgruger et al, “Variability Issues in Automated Hippocampal Segmentation”, 2017, also reported that Freesurfer overestimated volumes vs. other methods tested. I wondered if version 6.0 addresses the overestimation issue? It appeared that the FS 6.0 release web page figure (which showed the hippocampal portion of an MRI at left, the 5.3 subfield segmentation in the middle, and the 6.0 subfield segmentation at right) showed that a portion of gray tissue superior to hippocampus was included in the 5.3 segmentation but not in the 6.0 version – was that an example of 5.3 overinclusion, addressed in 6.0?
Thank you again for your help and for the team’s continued advances.
Dawn
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