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: greve@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.