[Mrtrix-discussion] DWI Gradient Values

[Donald Tournier]

Hi Jesse,

A similar question came up on the mailing list just a couple of weeks ago,
for which I gave quite a detailed answer. I'd recommend you have a look
through it and see if it answers your question. It's archived here:
http://www.nitrc.org/pipermail/mrtrix-discussion/2013-April/000688.html

Hopefully that'll clarify everything for you, but don't hesitate to follow
up if you still have questions.
Cheers,

Donald.


On 12 April 2013 19:06, Jesse Ross-Jones <jesse.rj at gmail.com> wrote:

> Dear MRtrix Users,
>
> I am converting DICOM data from a Siemens Espree 1.5T machine for Fiber
> Tracking. Looking at the converted files I see that there is a difference
> between the raw gradients and the gradients once converted. I am interested
> to know where these differences come from. What pre processing steps are
> performed on the data during conversion?
>
> I have included the gradient values I have obtained from various software
> here as reference. I have also summarized my findings below.
>
> Your help in helping me to identify the source of these differences is
> much appreciated!!
>
> Best Regards
> Jesse
>
>
>    1.
>
>    *Raw Info of gradient*
>
>    File: RawDicomGradient.txt (The gradients are not sort as the output
>    of other tools)
>
>    0.000000 0.000000 0.000000
>    0.999977 0.006051 0.003027
>
>    -0.000006 -0.999982 0.006006
>
>    -0.024989 -0.653018 -0.756930
>
>    0.588672 0.769595 -0.247364
>
>
>
>    1.
>
>    *MRTrix (dcm2mif)*
>
>    *left->right\posterior->anterior\inferior->superior*
>
>    File:MRtrix.mif
>
>    dw_scheme: 0,0,0,0
>    dw_scheme: -0.999977,-0.00605102,0.00302703,1000
>    dw_scheme: 6.01e-006,0.999982,0.00600569,1000
>    dw_scheme: 0.0249894,0.653018,-0.75693,1000
>    dw_scheme: -0.588672,-0.769595,-0.247363,1000
>    2.
>
>    *3DSlicer (dcm2nrrd)*
>
>    *left-posterior-superior*
>
>    File:3DSlicer.dwi
>
>    DWMRI_gradient_0000:=0 0 0
>    DWMRI_gradient_0001:=-0.999977 -0.00605102 -0.00302703
>    DWMRI_gradient_0002:=-6.01148e-006 -0.999982 0.00600569
>    DWMRI_gradient_0003:=-0.0249893 -0.653018 -0.75693
>    DWMRI_gradient_0004:=-0.588672 -0.769595 0.247363
>    3.
>
>    *MRCron (dcm2nii)*
>
>    File:MRCron.txt
>
>    dw_scheme:0.000000 0.000000 0.000000
>    dw_scheme:0.999659 -0.004982 -0.025617
>    dw_scheme:-0.008158 0.962864 -0.269862
>    dw_scheme:-0.052384 0.418964 -0.906491
>    dw_scheme:0.587632 -0.807968 -0.043309
>
>
>    1. *MRIConverter (dcm2nii)*
>
>    File:MRIConverter.txt
>
>    dw_scheme:0.000000 0.000000 0.000000
>    dw_scheme:0.999660 -0.004982 -0.025588
>    dw_scheme:-0.008132 0.962882 -0.269799
>    dw_scheme:-0.052352 0.419028 -0.906463
>    dw_scheme:0.587622 -0.807974 -0.043334
>
>
>
>
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>
>


-- 
*Dr Jacques-Donald Tournier
*
Research Fellow

The Florey Institute of Neuroscience and Mental Health
Melbourne Brain Centre - Austin Campus
245 Burgundy Street
Heidelberg  Vic  3084
Ph:  +61 3 9035 7033
Fax:  +61 3 9035 7307
www.florey.edu.au
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