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Because if a streamline hits a tile all three of the vertices that make up the tile are being incremented.

Peace,

Matt.

From: Longchuan Li <[log in to unmask]>
Reply-To: FSL - FMRIB's Software Library <[log in to unmask]>
Date: Friday, August 1, 2014 at 9:17 AM
To: <[log in to unmask]>
Subject: Re: [FSL] A question about tracking between volume-based and surface-based ROIs

Hi, Matt

Thank you for the information! Could you please elaborate a little bit more why it will have 3 times higher connectivity by counting on tiles than on the voxels?

Thanks

Longchuan


On Thursday, July 31, 2014 10:04 PM, Matt Glasser <[log in to unmask]> wrote:


That’s how it works for samples being sent out, but apparently on the surface it is counting-based on tile/triangle hits rather than vertex hits, so the connectivity will be 3x higher than it would be for the volume.  I think this was going to be made optional at some point.

Peace,

Matt.

From: Longchuan Li <[log in to unmask]>
Reply-To: FSL - FMRIB's Software Library <[log in to unmask]>
Date: Thursday, July 31, 2014 at 8:23 PM
To: <[log in to unmask]>
Subject: [FSL] A question about tracking between volume-based and surface-based ROIs

Hi, FSL experts

I have been using surface-based tractography for connectivity analyses and so far it works really well. However, I have a question regarding the connectivity between a volume-based ROI (say, Amgydala) and surface-based ROI (say STS). Am I right that for both types of ROIs, when I sent 5000 samples per voxel/vertex, the total number of samples sent will be 5000*N, where N is either the number of voxels for Amygdala or the number of vertices for STS ROI? Is there any way that the connectivity analyses may bias toward either volume-based ROIs over surface-based ROIs or vice versa?

Many thanks

Longchuan