I've got some files on my computer with gradient directions for the
Siemens Sonata & Trio. For the standard 12 gradient directions it gives:
1.0, 0., 0.5
0., 0.5, 1.0
0.5, 1.0, 0.
1.0, 0.5, 0.
0., 1.0, 0.5
0.5, 0., 1.0
1.0, 0., -0.5
0., -0.5, 1.0
-0.5, 1.0, 0.
1.0, -0.5, 0.
0., 1.0, -0.5
-0.5, 0., 1.0
Hope this helps,
Marcel.
Kingsley, Peter wrote:
>
> HweeLing:
>
> How many directions did you acquire? If this is the standard 12
> directions that Siemens used to use, you could check out S Naganawa et
> al, Eur Radiol 14:234-238 (2004). They give 12 directions for a 3T
> Trio. There are some obvious errors in their list, and I am not sure
> the order is correct, but according to them the directions are
>
> 1, 0, 0.5
> 1, 0.5, 1 [should be 0, 0.5, 1?]
> 0.5, -1, 0 [equivalent to -0.5, 1, 0 below]
> 1, 0.5, 0
> 0, 1, 0.5
> 0.5, 0, 1
> 1, 0, -0.5
> 0, -0.5, 1
> -0.5, 1, 0 [equivalent to 0.5, -1, 0 above][should be 0, 1, -0.5?]
> 1, -0.5, 0
> 0, 1, -0.5
> -0.5, 0, 1
>
> This (modified) scheme is not "balanced", and therefore not ideal, but
> should make no difference for calculating FA. The authors of that
> paper may be able to help you ( [log in to unmask] ). If you
> acquired more than 12 directions, then you will have to find an answer
> somewhere else.
>
> You might have better luck on the ISMRM Diffusion email list; if you
> are not a member of that list, maybe you can find a colleague who is a
> member and can post it for you.
>
> -----
> Peter B. Kingsley, MRI Physicist [log in to unmask]
> Department of Radiology / MRI
> North Shore University Hospital
> 300 Community Drive, Manhasset, NY 11030, USA
> Tel (516) 562-2842 Fax (516) 562-3561
>
>
> -----Original Message-----
> From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]
> On Behalf Of Lee HL
> Sent: Tuesday, April 25, 2006 10:51 AM
> To: [log in to unmask]
> Subject: [SPM] Diffusion tensor imaging
>
> Hi all,
> I understand that this is not the most ideal place to ask about diffusion
> tensor imaging. I have posted this question to the vendor recently, but
> there was no reply. So, I thought I would get a quick response from a
> bigger imaging community.
> I was wondering if anyone out there would know how to extract the
> diffusion
> tensor weighting directions from the standard Siemens DTI sequence on a
> Allegra 3T?
> I need this information to pre-process the DTI data to extract the
> fractional anisotropy values.
> Thanks!
>
> --
> Best regards,
> HweeLing Lee
>
> Research Scientist
> Cognitive Neuroscience Laboratory
> Singapore Health Services
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--
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Marcel Zwiers, PhD [log in to unmask]
Room 2.38 +31-(0)24-3668495
MR methods group www.ru.nl/fcdonders
F.C. Donders Centre for Cognitive Neuroimaging
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