Dear Lee,
On Sat, 2 Sep 2017 02:14:42 +0900, novice imaging <[log in to unmask]> wrote:
>Dear Prof. Gaser
>
>Thanks for the quick and valuable comments.
>I've just found mean thickness value in the cat_subject.xml or
>catreport_subject.pdf.
>
>Apologies for not specifying my study.
>I'm conducting cortical thickness analysis, not vbm.
>As far as I know, some researchers strongly recommend using mean global
>thickness as a nuisance covariate in cortical thickness analysis (from the
>FreeSurfer mailing lists).
You just have to keep in mind, that this will depend on your hypothesis. If you use global scaling with mean thickness you might artificially increase data with overall atrophy and this might be sometimes not what you want.
Best,
Christian
>
>Thank you again,
>
>Lee K.
>
>
>2017-08-31 16:40 GMT+09:00 Christian Gaser <[log in to unmask]>:
>
>> Dear LK,
>>
>> have you found that approach of using mean thickness values in the
>> literature? I am not sure whether this might be useful, because cortical
>> thickness is almost independent from TIV and overall brain size. If you use
>> mean thickness as nuisance variable it might happen that you artificially
>> increase the values for subjects that have a large atrophy (e.g.
>> Alzheimer's Dementia).
>>
>> Furthermore, there is no function in CAT12 to estimate the mean thickness
>> values, although this value is saved in the report folder in the xml-file
>> (look for <dist_thickness>).
>>
>> Best,
>>
>> Christian
>>
>> Best,
>>
>> Christian
>>
>> On Thu, 31 Aug 2017 00:05:07 +0900, novice imaging <
>> [log in to unmask]> wrote:
>>
>> >Dear Prof. Gaser and CAT12 experts
>> >
>> >I have the following queries;
>> >
>> >1) For between-group comparison of cortical thickness, is it better to
>> >include mean global thickness as a nuisance covariate?
>> >
>> >2) If so, how can I obtain mean global thickness for each subject?
>> >According to the manual, I've tried 'Extract ROI Data' --> 'Extract
>> >ROI-based surface values' --> 'ROI analysis', and got several csv files
>> >that contained information regarding the cortical thickness for each
>> >parcellated cortex (i.e., ROI_catROIs_aparc_a2009s_thickness.csv).
>> >However, I cannot find mean global thickness value for each subject.
>> >
>> >Thank you in advance for your comments.
>> >
>> >LK
>> >
>>
>>
>>
>
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