[Mristudio-users] GE 15 gradient table

[miguel.burgaleta at uam.es]

Hi Susumu,

I'm sorry but what I was trying to mean is if I can trust the gradient  
table whose values come from the DICOM headers.

I have 2 gradient tables: one from the manufacturer (medium GE) and  
one from the DICOM headers. When I use the former I get wrong  
colormaps (I have validated this with other software), but when I use
the latter, the colormaps *seem* to be OK (red corpus callosum,  
symmetric colors).

So the question is: even if the CC is solid red and the colormap is  
symmetric, is it still possible that the gradient table is wrong?  
Since I am a beginner I am not able to see it just by looking at the  
colormap.

I know this is a basic question, perhaps beyond the scope of this  
list. So any help will be highly appreciated.

Thanks,
Miguel


Quoting susumu mori <susumu at mri.jhu.edu>:

> Hi Miguel,
>
> There are two possibilities;
>
> 1) your table is wrong.
> 2) your table format is wrong.
>
> I suspect #2. The table has to be rewritten to DtiStudio format, which is;
>
> 0: x, y, z
> 1: x, y, z
>
> Common mistakes are;
>
> 0; x, y, z (";" instead of ":")
> 1: x y z (missing ",")
> .
> .
> (there is no [0, 0, 0] in the table)
>
> When you have a long table, it is sometimes difficult to catch one mistake.
> In this case, please do the following;
>
>> Use your current table and load the images. You will get the problem you
> reported.
>> Close the window and choose "DtiMapping" again.
>> You will get the initial data input window, which still remembers all the
> parameters you specified last time, including the gradient table.
>> Closely inspect the gradient table. This time it contains the table which
> is NOT the one you typed in but the version interpreted by the software. If
> you made a mistake in the syntax, it is much easier to catch it in this
> version.
>
> I hope this will help.
>
> Susumu
>
> On Fri, Sep 25, 2009 at 7:07 PM, <miguel.burgaleta at uam.es> wrote:
>
>>
>> Dear DTIStudio group,
>>
>> I have a beginner's question regarding the gradient table that I
>> should use with my DTI. The scanner is a GE and I already have the
>> standard medium table from the manufacturer, but I get weird FA
>> colormaps when using it (non-symmetric, corpus callosum not red).
>> However, if I use a gradient table made by reading the DICOM headers
>> with dcm2nii, I get a gradient table that leads to symmetric, solid
>> red CC FA colormaps.
>>
>> I have read in this list before that this is a good criterion to make
>> sure that the gradient table is the right one, but also heard that it
>> could be incorrect too! So the question is how to make sure that the
>> gradient table is the right one?
>>
>> I appreciate your help.
>>
>> Miguel
>>
>>
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