Dear Victor,
On 31 May 2018, at 18:17, Víctor Costumero Ramos wrote:
> Dear Christian,
>
> Thank you very much for your quick response.
>
> I have a further question.
>
> for GM ROI analyses, I assume that TIV should be adjusted for group
> comparisons, right?
Correct. Same as for VBM, where after modulation the values from native
space.
>
> If so, which method would you recomend? the division of ROI values by
> TIV
> or to include TIV as covariate at group analyses?
There is a longer explanation why using TIV as covariate is the
preferred method here:
https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=SPM;c95da4bf.1707
The easiest way to use the ROI values in CAT12 is to use the function
„Analyze ROIs“. Here you can use an existing VBM design to apply
exactly that design (including all covariates) to your ROI data. Give it
a try…
Best,
Christian
>
> Best regards,
>
> Victor.
>
> 2018-05-31 16:21 GMT+02:00 Christian Gaser
> <[log in to unmask]>:
>
>> Dear Víctor,
>>
>> On Tue, 29 May 2018 19:01:57 +0200, Víctor Costumero Ramos <
>> [log in to unmask]> wrote:
>>
>>> Dear SPM experts
>>>
>>>
>>>
>>> I not completely understand what exactly does ROI analysis
>>> implemented in
>>> CAT12 toolbox. I would appreciate some clarification about that.
>>>
>>>
>>>
>>> The description of this analysis provided in Gaser et al., 2016 is
>>> as
>>> follows:
>>>
>>>
>>>
>>> "We used maximum probability tissue labels derived from the
>>> Neuromorphometric atlas (provided by Neuromorphometrics, Inc. (
>>> http://Neuromorphometrics.com <http://neuromorphometrics.com/>) to
>> estimate
>>> the sum of local gray matter inside the defined ROI's. The
>>> anatomical
>> atlas
>>> -which is defined in template space - was transformed to native
>>> subject
>>> space using the inverse non-linear deformations needed to spatially
>>> normalize images to template space."
>>>
>>>
>>>
>>> Does it means that the atlas is transformed to native subject space
>>> to
>>> label each voxel and then the voxel values within each label are
>>> summed?
>> Yes, exactly.
>>
>>>
>>>
>>>
>>> If so, what values are used for that sum? Those obtained after
>> segmentation
>>> (e.g. P1 images)?
>> The values in native space. For GM these are the p1* images. This is
>> to
>> ensure that data with minimal processing are used for ROI analysis
>> (interpolation, smoothing...).
>>
>> Best,
>>
>> Christian
>>
>>>
>>>
>>>
>>> Thanks in advance.
>>>
>>
>>
>>
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