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Hi Thomas


1) our scanner already calulates the FA maps. Is it possible to use this
maps instead of running the dtifit?


Sure, it is probably the same method for calculating the tensors anyway (least squares). 
The advantage of dtifit, though, is that you can use it after preprocessing your data (eddy_correct, brain extraction).


2) I am trying to run dtifit. As indicated i use 3D sequence for - not
diff-weighted images-and also diffusion data with 12 direction as INPUT.

After 27 slides dtifit crashes and i cant find out why (already read the
FAQ).
 Errormessage: Error: terminate called after throwing an instance of
'NEWMAT::IncompatibleDimensionException'. 

Try running bedpost_datacheck on your directory containing the diffusion data, this might tell you if there is something wrong.
The usual problems are: bvecs/bvals incompatible with the data dimensions. Or the data not in 4D format. 



I got the same when i use a normal 2D sequence like t2_haste.
Can somebody tells me where is the problem?

Thanks a lot for your help.

Thomas

Cheers,


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Saad Jbabdi, 
Postdoctoral Research Assistant,  
Oxford University FMRIB Centre

FMRIB, JR Hospital, Headington, Oxford  OX3 9DU, UK
+44 (0) 1865 222545  (fax 222717)
[log in to unmask]    http://www.fmrib.ox.ac.uk/~saad
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