[Mristudio-users] Gradient Table

[Naama Barnea-Goraly]

We are using VB15. Like Susumu said, the Siemens scanner recalculates  
the gradient table slightly per each subject, and the revised table is  
in the header (but it is not obvious). You can get that information  
from the header using MRIconvert (you still have to edit it to  
dtistudio format).

Naama


On Apr 29, 2010, at 5:17 AM, susumu mori wrote:

> Hi Mark,
>
> If you are using the standard Siemens 12-orientation scheme or other  
> pre-defined tables available in the scanner, we have a file that  
> contains all tables. It seems that Siemens Mosaic/Dicom contains  
> some gradient orientation information, but we still haven't  
> completely figured out how to use them. There are several important  
> points you need to know.
>
> 1) Here is the usual 12 orientations in DtiStudio format (you can  
> cut&paste);
> 0: 0, 0, 0
> 1:  1.000000, 0.414250, -0.414250
> 2:  1.000000, -0.414250, -0.414250
> 3:  1.000000, -0.414250, 0.414250
> 4:  1.000000, 0.414250, 0.414250
> 5:  0.414250, 0.414250, 1.000000
> 6:  0.414250, 1.000000, 0.414250
> 7:  0.414250, 1.000000, -0.414250
> 8:  0.414250, 0.414250, -1.000000
> 9:  0.414250, -0.414250, -1.000000
> 10:  0.414250, -1.000000, -0.414250
> 11:  0.414250, -1.000000, 0.414250
> 12:  0.414250, -0.414250, 1.000000
>
> 2) Some old operating system uses different types of the tables. So  
> the current table may not work. If you find a problem with the above  
> table, please let us know.
>
> 3) If you are using another pre-defined table, please refer to the  
> attached file. This lists all the tables in VB13 (and after, I  
> believe). You need to convert the format to DtiStudio format. If you  
> look at the 20-orientation scheme in the file, you can find that I  
> converted the Siemens format to the DtiStudio format.
>
> 4) Unless you are using VB15, the gradient table needs to be  
> recalculated when you use oblique-plane imaging. VB15 does it  
> automatically and you don't have to worry. With older operating  
> systems, you need to click "Rotate Gradient if Applicable" checkbox  
> in the initial parameter input window of DtiStudio.
>
> Susumu
>
> 2010/4/29 wgh0805 <wgh0805 at 126.com>
> Dear all:
>
>   I have the data of Siemens DICOM ,but I can not find the gradient  
> table for it. How can I find it?
> Thanks ,
>
> Mark
>
>
>
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Naama Barnea-Goraly M.D.
Instructor
Center for Interdisciplinary Brain Sciences Research
Stanford University Division of Child and Adolescent Psychiatry
401 Quarry Rd. MC 5795
Stanford University School of Medicine
Stanford, CA  94305-5795
Phone: (650) 736-1874, fax: (650) 724-4794


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