Hi All,
Thanks for that useful discussion about the left-right flipping issue. I have a follow-up
question.
I have data for which I confirmed that the left, posterior, inferior corner had the lowest values
and were all positive (voxel [1 1 1] was off screen). This means, I think, that my data are
right handed and therefore the defaults.analyze.flip value should be set to 0. The raw images I
was loading in and checking for LPI voxel values were .mnc files. I also confirmed that the
analyzed results had the low value voxels in the LPI corner.
However, after analyzing the data, I am finding language activation bilaterally, but stronger on
the right (i.e. on the right in the glass brain). The subjects are children, and the task was
somewhat difficult for them so it is remotely possible, though not likely, that these results are
accurate. More likely, however, I am making some mistake and the images are either not right
handed or there is some other kind of problem.
If anyone has any suggestions for how I can further test to be sure that my data are indeed right
handed and/or can spot where I'm making a mistake either in setting the default to 0, or in
reading the results, that would be much appreciated.
Best,
Juliana
On Fri, 13 May 2005 14:28:04 +0000
John Ashburner <[log in to unmask]> wrote:
>> after John's emails I'd like to be sure about a couple of things.
>> 1- What matters for flipping is the handness of storage, is that correct?
>
> Yes.
>
>> 2- Data stored in Right hand system needs not to be flipped, while Left
>> hand stored data need to be flipped.?
>
> Yes.
>
>> 3- To tell the handnees of the actual
>> data, John suggested to look at voxel (1,1,1) for axial images. Now if
>> voxel (1,1,1) is LPI my data are right hand and need not to be flipped in x
>> dimension. is that correct?
>
> Yes.
>
>> If voxel (1,1,1) is RPI data need to be flipped
>> in x dimension. is that correct?
>
> Yes.
>
>> thanks for any help
>
> That was easy.
>
> best regards,
> -John
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