Hi Kaveh,
Sorry, the doc is wrong. In multiple masks mode, probtrackx retains samples that pass through at least one of the other masks (not all of them).
The other difference with waypoints is that in multiple masks mode, each mask plays the role of a seed then one of the waypoints. The results from seeding from all the masks are then summed.
Cheers,
Saad.
On 17 Feb 2010, at 15:53, Kaveh Mehdiani wrote:
> Dear FSL - Team,
>
> i'm trying to figure out the differences between the seed specifications
> "multiple masks" and "waypoint masks".
>
> According to the FDT documentation site the
>
> Multiple masks
> Generates a connectivity distribution between a mask image and all the other
> mask images in a list of images, retaining only those tracts that pass
> through all the other images. Output is the sum of the connectivity
> distributions from each of the seed masks.
>
> whereas the
>
> Waypoint masks
> Use inclusion masks in the tractography. Tracts that do not pass through ALL
> these masks will be discarded from the calculation of the connectivity
> distribution.
>
> Unfortunately both specifications seems equal to me although the results
> using them totally differs.
> Maybe you can help me out.
>
> Thanks
>
> Kaveh
>
--
Saad Jbabdi
University of Oxford, FMRIB Centre
JR Hospital, Headington, OX3 9DU, UK
(+44)1865-222466 (fax 717)
www.fmrib.ox.ac.uk/~saad
|