Dear Rosalia,
> Is it possible to run voxel based morphometry without modulating (DARTEL)
> and making co-variation with TIV when doing T-test?
Yes, it is definitely "possible". Whether it is a good idea depends on
the question you are trying to answer in your analysis. :-)
In general, the modulated images are going to more closely reflect
gray matter volume, which is typically what is of interest, and is (in
my mind) easiest to interpret.
Including TIV as a covariate (or accounting for it during the
modulation step) is probably a good idea in general for explaining
variability in your data. However, it is definitely not equivalent to
performing an analysis on modulated images.
These references may also be of some help:
Barnes J, Ridgway GR, Bartlett J, Henley SMD, Lehmann M, Hobbs N,
Clarkson MJ, MacManus DG, Ourselin S, Fox NC (2010) Head size, age and
gender adjustment in MRI studies: a necessary nuisance? NeuroImage
53:1244-1255.
Buckner RL, Head D, Parker J, Fotenos AF, Marcus D, Morris JC, Snyder
AZ (2004) A unified approach for morphometric and functional data
analysis in young, old, and demented adults using automated
atlas-based head size normalization: reliability and validation
against manual measurement of total intracranial volume. NeuroImage
23:724-738.
Best regards,
Jonathan
--
Dr. Jonathan Peelle
Center for Cognitive Neuroscience and
Department of Neurology
University of Pennsylvania
3 West Gates
3400 Spruce Street
Philadelphia, PA 19104
USA
http://jonathanpeelle.net/
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