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Hi Joe and Andreas, Thank you for your very helpful responses. I did mean cortico-cortical connections within a single hemisphere, rather than between the hemispheres (although this will also be useful). The areas we are interested in are ~2-3cm apart within the cortex of a single hemisphere. Apart from possibly not having sufficient SNR in our data, I wonder if I have the curvature threhsold set incorrectly, and therefore I'm not allowing very acute angle tracts to be detected? Is there a more appropriate threshold you would advise for this? Thank you, Elaine -----Original Message----- From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf Of Joseph Devlin Sent: 10 October 2005 18:59 To: [log in to unmask] Subject: Re: cortex to cortex tractography Dear Elaine, I've done quite a bit of cortico-cortical tracing within hemisphere with Fdt and so far it seems to work well. By that I mean that I can usually find paths that I believe should exist between two different cortical regions. I often get false paths due to various artifacts (e.g. dti resolution sometimes means that paths jump sulci), but with a little care, it's generally easy to identify and stop such paths from happening. Having said all that, we use 60 direction data and tend to average several acquisitions to increase SNR. Also, I'm looking for fairly strong paths. When I've looked for weaker ones, or ones penetrating larger fibre bundles (e.g. the acoustic radiation), this often fails. So in principle Fdt should be fine for cortico-cortical connections, but it does depend heavily on the specific path(s) you're interested in and the quality of the data you have. Cheers, Joe ----------- Joseph T. Devlin, Ph. D. FMRIB Centre, University of Oxford Headley Way, Headington Oxford, OX3 9DU, UK Phone: +44-(0)1865-222-494 Fax: +44-(0)1865-222-494 Email: [log in to unmask]