No, the subcortical calculation sums the number of voxels. For voxels on the edge of a structure, there is a partial volume calculation based on the intensity of the voxel and the mean intensities of the adjacent structures. doug
On 01/16/2013 05:52 PM, KimMJ wrote: > > > ------------------------------------------------------------------------ > Dear Dr. Greve > > Thanks so much for your quick and clear response. > One additional question here. > Is this volume calculation method you have mentioned also applied to > volume measurement of subcortical GM structure (in addition to > cortical GM volume)? > > Thank you again > Kim > > > > Date: Tue, 15 Jan 2013 23:16:04 -0500 > From: gr...@nmr.mgh.harvard.edu > To: freesurfer@nmr.mgh.harvard.edu > Subject: Re: [Freesurfer] A question regarding volume calculation > > Hi Kim, yes it is surface area times thickness. A volume at each > vertex is computed as the average area of the triangles around the > vertex times the thickness at that vertex. The volume of a > parcellation is then the sum of the volumes of the vertices in that > parcellation. > doug > > > On 1/15/13 9:03 PM, KimMJ wrote: > > Dear experts > > > I'm currently preparing a paper using the results of automatic > volumetric segmentation of subcortical and cortical grey matter > structures from aseg.stats and aparc.stats files. > I have cited previous article by Desikan RS, et al (Neuroimage > 2006;31:968-980) for the cortical GM volumetric segmentation, and > Fischl B, et al (Neuron 2002;33:341-355) for the subcortical GM > volumetric segmentation. > At this point, my question is how volumes of these structures > calculated. Is this volume of each GM structure based on surface > area multiplied by cortical thickness? > > Apology for the newbie's question. > Thank you in advance for your help. > > Kim MJ > > > > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu <mailto:Freesurfer@nmr.mgh.harvard.edu> > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > > _______________________________________________ Freesurfer mailing > list Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer The > information in this e-mail is intended only for the person to whom it > is addressed. If you believe this e-mail was sent to you in error and > the e-mail contains patient information, please contact the Partners > Compliance HelpLine at http://www.partners.org/complianceline . If the > e-mail was sent to you in error but does not contain patient > information, please contact the sender and properly dispose of the e-mail. -- Douglas N. Greve, Ph.D. MGH-NMR Center gr...@nmr.mgh.harvard.edu Phone Number: 617-724-2358 Fax: 617-726-7422 Bugs: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html Outgoing: ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/ _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
