[Mristudio-users] test-retest

[Miguel Burgaleta]

Hi Susumu,

Thanks for your reply.

I find your suggestion very helpful! However, with that method I don't  
see how to separate the reproducibility of the tract from the rater  
reliability. If the tract in time 1 is different from that in time 2,  
we don't really know to what extent it is caused by small errors in  
the ROI placement, or by problems of reproducibility...

Another possibility would be to do tractography in time 1 twice, and  
once in time 2, so that we can look at the time1-time2 reproducibility  
relative to the time1-time1 reliability.

Also, can ROIs be transformed with Diffeomap as well (just like I  
suggested in my previous email)? That would help ensure that  
differences are due to reproducibility only.

Thanks,
Miguel


On Apr 1, 2011, at 12:15 AM, susumu mori wrote:

> Hi Miguel,
>
> You can do it using Diffeomap (or FSL or SPM). First do tractography
> in image 1 and 2 independently. Save the results as a 3D 1/0 mask in
> DtiStudio.
> Then run a rigid transformation between the image 1 and 2. You can do
> FA vs FA but b0 vs b0 could be easier because FA maps could have some
> random intense pixels outside the brain that may interfere with the
> rigid alignment. Save the transformation matrix and apply it to your
> 1/0 binary fiber mask image. Then you can superimpose the aligned #1
> and original #2 see the reproducibility. You can do all these very
> easily by DiffeoMap.
>
> Susumu
>
> On Wed, Mar 30, 2011 at 12:56 PM, Miguel Burgaleta
> <miguel.burgaleta at uam.es> wrote:
>>
>> Hi,
>>
>> We have a sample of DWI acquired twice for each subject, 1 month in
>> between, and would like to analyze the test-retest reproducibility of
>> a selection of tracts with DTIStudio. We would also like to see the
>> effect of outlier pixel rejection on the reproducibility. However, we
>> are not sure of how to proceed so that we control for the intra-rater
>> reliability.
>>
>> One option we thought of is to perform tractography at time 1, save
>> both binary tracts and ROIs, and then register each FA image in  
>> time 1
>> to its corresponding FA image in time 2, apply that transformation to
>> the ROIs and get the tract for time 2. Is this feasible with  
>> DTIStudio?
>>
>> If you know a better way to do this, please let me know.
>>
>> Best,
>> Miguel
>>
>>
>>
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