Hi Sal - I apologize for the late response due to traveling.

With tracula we have certainly used 30 direction data. It shouldn't be a problem, since tracula fits the ball-and-stick model of diffusion of Behrens et al 2007, which has been shown to give reasonable results fitting 2 crossing fibers with 30 directions.

Hope this helps, a.y

On Mon, 18 Nov 2013, Salil Soman wrote:

Hi,

I hope all is well.

Was wondering if any of had heard of an explicit minimum number of DTI directions necessary for using odf / hardi modeling ? I have run a couple of data sets of 30 directions (+ 5 b0) through TRACULA, and have run this same data through diffusion toolkit using the hardi / odf model, with reasonable looking results. I was wondering if there was any specific reason why using these models with 30 directions would be considered in appropriate?

Thanks!

Sal