Hi, Cyril,
For a long scan with BOLD, ICA could be a good tool for analyzing the
data. It is data driven so that no canonical HRF modeling is required. For
group level ICA, you can try "GIFT" (Calhoun et al 2001, HBM), "sogICA"
(Esposito et al, 2005, NeuroImage), or the tensor PICA (Beckman and Smith,
2005, NeuoImage).
ASL has a superiority of immunity to the baseline MR signal drift, so it
is a good method for long time scan. To consider the hemodynamic response
discrepancy, you may still need ICA or SVM for data analysis. If you are
interested in understanding the temporal response, BOLD may a better choice
because the temporal resolution is higher than ASL, and you can try some
data analysis methods like Chen et al, 2004, IEEE tmi, 23: 85-98.
So to answer your question: ASL itself can not "answer" that, you need an
appropriate data analysis method.
Hope this could help!
Cheers
Ze
-----Original Message-----
From: cyril pernet [mailto:[log in to unmask]]
Sent: Friday, February 02, 2007 4:41 AM
To: zewang
Subject: Re: [SPM] scan pauses - off list
Hi Ze
> I guess the following two would be very comprehensive:
> 1. Aguirre et al, 2005, Int Rev Neurobiology, 66, 213-236.
> 2. Aguirre et al, 2002, NeuroImage, 15, 488-500.
> To get whole brain coverage, you could use parallel imaging or just
increase
> the slice thickness. Generally we can get 14 slices using 64x64 EPI
readout.
> Our site has years of experiences of processing ASL data using SPM or
Voxbo.
> We can share the experiences and a set of batch scripts for SPM2.
>
As I said in the SPM e-mail thanks - I'll probably not do ASL before a
year .. (you know some stuffs going on).
But anyway just to get your feeling about that: I'm working with
patients (dyslexics mainly) and many times I observed relative
activations/deactivations .. I believe (but still cannot prove) that the
hemodynamic of some subjects in some specific locations is not canonical
- I can obviously use non parametric stats or FIR models to look at the
data. But what I'm really interested in is to know if the deactivations
are related to less activation than baseline or to a real deactivation
.. (and keeping in mind that some guys really have strange hemodynamic
curves once plotted by hand). Do you think ASL can 'easily' answer that?
cheers
cyril
--
Pernet Cyril, PhD
Center for Cognitive Neuroimaging
Voice Neurocognition Laboratory
Department of Psychology
58 Hillhead Street
University of Glasgow
Glasgow G12 8QB
Scotland
[log in to unmask]
http://vnl.psy.gla.ac.uk/
tel: +44 (0)141 330 4965
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