Dear Kai
Unless you have special reasons for making the acquisition triggered I
would suggest that you instead sample the cardiac data and use
retrospective correction instead? The most popular method for this is
called RETROCOR, and it can be implemented as a part of a GLM. Since
the T1 relaxation involves an exponential function where T1 is the
time constant, the relaxation can only be described in a GLM, if you
know what the T1 value is, or if you make a regressor per TR-value.
Hope this helps
Torben
Torben Ellegaard Lund
Assistant Professor, PhD
The Danish National Research Foundation's Center for Functionally
Integrative Neuroscience (CFIN)
Aarhus University
Aarhus University Hospital
Building 30
Noerrebrogade
8000 Aarhus C
Denmark
Phone: +4589494380
Fax: +4589494400
http://www.cfin.au.dk
[log in to unmask]
@article{Glover2000,
Author = {G. H. Glover and T. Q. Li and D. Ress},
Journal = {Magn Reson Med},
Month = {7},
Pages = {162--7},
Title = {Image-based method for retrospective correction of
physiological motion effects in {fMRI}: {RETROICOR}},
Volume = {44},
Year = {2000}}
On 14/03/2008, at 17.18, Kai Lutz wrote:
> Dear List,
>
> currently we are setting up an experiment with scans triggered by
> cardiac signals leading to TR times in a range between ~2.8 and 4
> sec. Has anyone already implemented an algorithm to correct for
> differences in T1 relaxation and would be willing to publish and
> share with the community? Or do you rather think this can be solved
> by incorporating additional regressors (based on TR) into the design
> matrix?
>
> Any ideas are much appreciated!
>
> Cheers,
> Kai
>
> --
> Dr. Kai Lutz
> Neuropsychology
> Institute for Psychology
> University of Zurich
> Binzmühlestrasse 14 /Box 25
> CH-8050 Zürich
> Switzerland
|