Hi - please see the FDT manual - you need a bval entry for EVERY
diffusion image - i.e., as many entries as you have columns in your
bvecs file.
Steve.
On 20 Feb 2007, at 08:59, Eytan Raz wrote:
> Dear Doctor Tim Behrens,
> we are writing from the Neuroradiology Department of the
> University of
> Rome "La Sapienza".
> We are trying to use FSL-FDT on a Linux workstation.
> We use a Philips Intera 1.5 T with a 32 direction sequence and 2 "b
> values" (zero and 700)
> We could make Eddy current correction, but we have problem in
> performing
> DTIfit.
> We suspect that the problem is the way in which we wrote down the
> gradient
> directions (bvecs) or the b values (bvals).
> I attach them and write them here in the way we did: are them
> written in
> the correct way?
>
> BVALS
> 0 700
>
> BVECS
> 1.0000 0.0000 0.0000 -0.0424 0.1749 0.2323 0.3675 0.1902 -0.1168
> -0.2005 -0.4958 -0.0141 -0.7445 -0.7609 -0.1809 -0.6796 0.7771
> 0.9242
> 0.4685 0.8817 0.6904 0.2391 -0.0578 -0.5368 -0.9918 -0.9968 -0.8724
> -0.2487 0.1183 0.3376 0.5286 0.9969 0.0000
> 0.0000 1.0000 0.0000 -0.1146 -0.2005 -0.1626 0.0261 0.3744 0.8334
> 0.2527 0.1345 -0.6281 -0.1477 0.3204 0.9247 -0.4224 0.4707 -0.1036
> -0.7674 -0.1893 0.7062 0.7571 0.9837 0.8361 -0.1207 0.0709
> 0.4781
> 0.9335 0.9919 0.8415 0.8409 0.0550 0.0000
> 0.0000 0.0000 1.0000 -0.9925 -0.9639 -0.9590 -0.9296 -0.9076 -0.5402
> -0.9466 -0.8580 -0.7780 -0.6511 -0.5643 -0.3351 -0.5997 -0.4178
> -0.3677
> -0.4378 -0.4322 -0.1569 -0.6080 0.1703 -0.1135 -0.0423 -0.0379
> -0.1014
> 0.2581 -0.0471 0.4218 0.1163 -0.0571 0.0000
>
> Thank you very much for your attention.
> Eytan Raz, MD
>
> Policlinico Umberto I
> Viale dell' Universita', 30
> 00100 Roma
> Italy
>
> 1.0000 0.0000 0.0000 -0.0424 0.1749 0.2323 0.3675 0.1902
> -0.1168 -0.2005 -0.4958 -0.0141 -0.7445 -0.7609 -0.1809 -0.6796
> 0.7771 0.9242 0.4685 0.8817 0.6904 0.2391 -0.0578 -0.5368
> -0.9918 -0.9968 -0.8724 -0.2487 0.1183 0.3376 0.5286 0.9969
> 0.0000
> 0.0000 1.0000 0.0000 -0.1146 -0.2005 -0.1626 0.0261 0.3744
> 0.8334 0.2527 0.1345 -0.6281 -0.1477 0.3204 0.9247 -0.4224
> 0.4707 -0.1036 -0.7674 -0.1893 0.7062 0.7571 0.9837 0.8361
> -0.1207 0.0709 0.4781 0.9335 0.9919 0.8415 0.8409 0.0550
> 0.0000
> 0.0000 0.0000 1.0000 -0.9925 -0.9639 -0.9590 -0.9296 -0.9076
> -0.5402 -0.9466 -0.8580 -0.7780 -0.6511 -0.5643 -0.3351 -0.5997
> -0.4178 -0.3677 -0.4378 -0.4322 -0.1569 -0.6080 0.1703 -0.1135
> -0.0423 -0.0379 -0.1014 0.2581 -0.0471 0.4218 0.1163 -0.0571
> 0.0000
>
> 0 700
>
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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