Re: [HCP-Users] Inter-subject vertex:voxel correspondence

[Hacker, Carl]

Yes, the resampling and registration guarantees a bijective mapping. However, like Matt said, the correctness of the mapping (that the same vertex index corresponds to the same gyral feature across subjects) is  of course dependent on the quality of the surface registration. Carl From: hcp-users-boun...@humanconnectome.org [hcp-users-boun...@humanconnectome.org] on behalf of Glasser, Matthew [glass...@wusm.wustl.edu] Sent: Thursday, September 25, 2014 9:19 AM To: Matthew George Liptrot; hcp-users@humanconnectome.org Subject: Re: [HCP-Users] Inter-subject vertex:voxel correspondence As one goes from subcortical to cortical structures, it progressively becomes more difficult to achieve an accurate volume-based alignment, which is why we don’t try to and instead use surface models (where the alignment problem is easier).  On the surface, we use a standard mesh approach so that a given vertex number is aligned by the registration to correspond to the same neuroanatomical location across subjects (and the accuracy of this depends on the information made available to the registration algorithm).   I’m not sure I understand the rest of your question (because I don’t know what surjective and bijective mean).  Perhaps you can restate the question a little more plainly? Thanks, Matt. From: Matthew George Liptrot <matthew.lipt...@di.ku.dk> Date: Thursday, September 25, 2014 at 9:00 AM To: "hcp-users@humanconnectome.org" <hcp-users@humanconnectome.org> Subject: [HCP-Users] Inter-subject vertex:voxel correspondence Hi, I am a novice at handling surfaces, and at using the Connectome Workbench/commandline, so apologies if the following is obvious. We want to be able to perform connectivity analysis of subjects (both HCP and our own) using diffusion tractography. In order to directly compare the resultant (voxel-to-voxel) connectivity matrices across subjects, we would like to have a one-to-one correspondence between the tractography seed voxels in each subject. I presume that the best way to do this would be to first select the desired set of (inter-subject matched) seed points upon the aligned surface meshes already provided (BIG thanks!) by the HCP and then convert them to the (nearest) voxel? (I realise that this may be a surjective mapping). Are there functions/commands within the Connectome Workbench that can do this? Or are there more sensible approaches to achieving this? Also, in [1], it states that the ‘standard grayordinate space’ (in CIFTI format) is used for achieving bijective inter-subject correspondence of the WM surface vertices and the subcortical voxels. However, I’m a bit confused how this bijective correspondence is maintained during the resampling from the 164K to the 32K meshes i.e. does the adaptive barycentric surface resampling method guarantee that the 32K-to-32K mappings are also bijective? 1.Glasser MF, Sotiropoulos SN, Wilson JA, Coalson TS, Fischl B, et al. (2013) The minimal preprocessing pipelines for the Human Connectome Project. NeuroImage 80: 105–124. doi:10.1016/j.neuroimage.2013.04.127. Cheers, M@ --  Matthew George Liptrot Department of Computer Science University of Copenhagen &  Section for Cognitive Systems Department of Applied Mathematics and Computer Science Technical University of Denmark http://about.me/matthewliptrot _______________________________________________ HCP-Users mailing list HCP-Users@humanconnectome.org http://lists.humanconnectome.org/mailman/listinfo/hcp-users   The materials in this message are private and may contain Protected Healthcare Information or other information of a sensitive nature. If you are not the intended recipient, be advised that any unauthorized use, disclosure, copying or the taking of any action in reliance on the contents of this information is strictly prohibited. If you have received this email in error, please immediately notify the sender via telephone or return mail. _______________________________________________ HCP-Users mailing list HCP-Users@humanconnectome.org http://lists.humanconnectome.org/mailman/listinfo/hcp-users   The materials in this message are private and may contain Protected Healthcare Information or other information of a sensitive nature. If you are not the intended recipient, be advised that any unauthorized use, disclosure, copying or the taking of any action in reliance on the contents of this information is strictly prohibited. If you have received this email in error, please immediately notify the sender via telephone or return mail. _______________________________________________ HCP-Users mailing list HCP-Users@humanconnectome.org http://lists.humanconnectome.org/mailman/listinfo/hcp-users