Dear Najmeh and Andreas
Thanks a lot for your messages, even though I must admit that I was hoping for a more straightforward and simple analysis ...
Another question: Is it possible to do the relCBF ASL "fit" in FSL?
I am asking because at least visually, the FA maps calculated in FSL DTIFIT outperform the FA maps calculated on the SIEMENS scanner. In the same line I am wondering as to whether or not the ASL relCBF maps in FSL might be better than the SIEMENS maps
Thanks a lot
Sven
On 19 mars 2012, at 12:36, Andreas Bartsch wrote:
> Hi Sven,
>
> if you do have M0 calibration scans you >could< try to calculate absolute
> perfusion values, merge these across sessions / subjects and use these as
> a 4D confound.
> However, usually the z-coverage of ASL is below that of the BOLD
> acquisitions, i.e. you may need to cut down your analysis to the partial
> volume of the ASL. Furthermore, if you don't have the calibration scans
> you are lost.
> You may consider to extract some reference ratios but I'm afraid there is
> no region where you could safely assume that caffeine has no effect upon
> it.
> Hth,
> Andreas
>
> Am 19.03.12 11:56 schrieb "HALLER Sven" unter <[log in to unmask]>:
>
>> Dear FSL expert
>>
>> I have a study aiming to assess the effect of caffeine on working memory
>>
>> I have a 2back working memory task. In a repeated measures design, each
>> subject performs 2 days (one with placebo, one with caffeine), and 2
>> 2back tasks each day (total of 2x2 fMRI EPI BOLD runs per subject).
>>
>> The problem is that caffeine has a direct vascular effect. To capture
>> this, each subject additionally has an ASL on each day. The idea is to
>> assess the global CBF changes in ASL, and to eliminate this effect from
>> the fMRI EPI BOLD analysis.
>>
>> I looked into the FEAT analysis, and there is in fact a perfusion
>> analysis. Yet if I understood correctly, this analysis is rather intended
>> for fMRI-like analysis of ASL instead of EPI data.
>>
>> Are there any suggestions how I could use the ASL data to extract
>> medication-related changes in CBF from the fMRI tasks??
>>
>> Your help is highly appreciated
>>
>> Sven
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