Dear Jürgen,
that looks like a really helpful paper - thank you!
What I'm still unsure about: is the only difference between the images obtained using
a) New Segment with modulation (mwrc1*) --> smoothing
b) New Segment (rc1) --> create custom template with DARTEL --> spatial normalization to DARTEL template with option 'Preserve amount' and smoothing
really just the template the individual images are registered to (standard template in case a), population specific template in case b) )?
(Similarly, only the template used for registration should distinguish the images obtained via:
a_i) New Segment without modulation (wrc1*) --> smoothing
b_i) New Segment (rc1) --> create custom template with DARTEL --> spatial normalization to DARTEL template with option 'Preserve concentration' and smoothing
, right?)
Thanks for your valuable help!
Best,
Ulrike
Am 06.08.2014 um 10:59 schrieb Jürgen Hänggi:
> Dear Ulrike
>
> There is a paper about this issue that might help deciding which version
> should be used.
>
> http://www.ncbi.nlm.nih.gov/pubmed/16806978
>
> Cheers
> Jürgen
>
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> Division Neuropsychology
> Institute of Psychology
> University of Zurich
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> Am 04.08.14 09:57 schrieb "Ulrike Kuhl" unter <[log in to unmask]>:
>
>> Dear SPM-experts,
>>
>> I use SPM8 to do a VBM analysis. I am quite new to the VBM approach and
>> have a conceptual question regarding the process with modulated and
>> non-modulated images.
>>
>> In my VBM analysis I want to include a comparison of the grey matter
>> density as well grey matter volume between two groups. If I read the
>> manual correctly, I have two options:
>>
>> a) I produce modulated (mwc*, conveying volume information) as well as
>> non-modulated (wc*, conveying information about relative concentration of
>> grey matter) images using the 'New Segment' module. Those need to be
>> smoothed and then, I can already do stats on them.
>>
>> b) I can make the analysis using the DARTEL module. For grey matter
>> analysis I use the rc1* files produced during 'New Segment' to create the
>> custom template. Only in the ensuing normalization procedure I can then
>> specify via the 'Preserve amount' (= modulation) or 'Preserve
>> concentration' (= no modulation) option what I want. The result is then
>> used for stats.
>>
>> First of all: Are both procedures as I described them correct? I got a
>> bit confused regarding the DARTEL procedure: If I produce modulated and
>> non-modulated images using 'New Segment', can't I also use these files
>> (wc* and mwc*) as the basis for DARTEL (i.e. producing separate templates
>> for the modulated and the non-modulated case, and do normalization
>> accordingly)?
>>
>> Second of all: Is one 'better' than the other? I see that registration
>> using DARTEL yields advantages as the custom template used for
>> registration is based on the data I have such that group-specific
>> anatomical variations will be accounted for. I did not quite understand
>> where spatial normalization comes into play in the a) option: are the
>> resulting images normalized and in MNI space (and if so, which template
>> was used for registration)?
>>
>> Thirdly: Is there any general opinion on what to use?
>>
>> I'm very grateful for any suggestions that help me to get these things
>> clear.
>>
>> Best regards,
>> Ulrike
>
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