Hi,
>Does it matter what order the T2-weighted images with and without diffusion weighting are assembled in the 4D file?
Nope, not really. But watch out to which volume you register by default.
You should ecc the volumes from all the directions you acquired data for. In your case, a 4D-file of the 25 directions with diffusion and the one with none (or the least) diffusion weighting is fine. The latter is obtained by the lowest b-value (e.g. zero).
Cheers-
Andreas
-----Ursprüngliche Nachricht-----
Von: FSL - FMRIB's Software Library [mailto:[log in to unmask]] Im Auftrag von Hoang Tran
Gesendet: Mittwoch, 5. Januar 2005 01:34
An: [log in to unmask]
Betreff: Re: [FSL] Eddy current correction
Does it matter what order the T2-weighted images with and without diffusion weighting are assembled in the 4D file?
For images with diffusion, does it matter which direction is used or should all directions be used? I have diffusion weighted images in 25 directions and I wondering if I need to create a 4D file with 2 sets of images (with and without diffusion) or 26 sets of images (25 directions with diffusion and 1 without diffusion).
Lastly, when you mention that the reference volume is the one with the least diffusion weighting, do you mean the image where the b-value is the least?
Thank you in advance for your time and help.
Cheers,
Hoang Tran
Neurobehavioral Research, Inc.
201 Tamal Vista Blvd.
Corte Madera, California 94925
415.927.6627 (Office)
415-924-2903 (Fax)
[log in to unmask]
On Tue, 4 Jan 2005 09:23:34 +0000, Tim Behrens <[log in to unmask]>
wrote:
>Hi -
>The input to eddycorrect should be the T2-weighted images with and
>without diffusion weighting. They should be organised in a 4D file. For
>best registration, the reference volume should be the volume with the
>least difusion weighting.
>
>No - you cannot use a high res reference volume at this stage. The
>purpose of this stage is to get all the spin-echo volumes in the same
>space. You can then use the "Registration" Tab to register this space
>to a high-res space.
>
>Hope this helps
>
>T
>
>
>On Sat, 25 Dec 2004, Philipp Sämann wrote:
>
>> Hello,
>>
>> just starting to use the eddy_current function:
>> What is the format (i.e. order) of the input image?
>> What images are suitable as reference volume for the affine
>> registration: just b0-weighted images? Could also high(er) resolution
>> images, as T2-SE
be
>> used?
>>
>> Thanks in advance,
>> Philipp
>>
>
>--
>-----------------------------------------------------------------------
>----
----
>Tim Behrens
>Centre for Functional MRI of the Brain
>The John Radcliffe Hospital
>Headley Way Oxford OX3 9DU
>Oxford University
>Work 01865 222782
>Mobile 07980 884537
>-----------------------------------------------------------------------
>----
----
|