Hi,
I am new to FSL and I apologise in advance if any of this sounds trivial . I am trying to analyse two sets of ASL data obtained from a simple finger taping experiment with two different inversion times.
Firstly which is the better method to use - Full perfusion modelling or simple subtraction ?
In the simple subtraction case does the phase need to be TR/2 ?
If I need ON OFF ON OFF instead of OFF ON OFF ON would I need to set the phase equal to rest period or activity period ( 29.3 secs in my experiment) in all the EVs to shift the model forwards ?
How would this change if I need to include TR/2 in the simple subtraction method ? Would it just be rest period + TR/2 ? So say the rest period is 29.3 secs , would the phase need to be set 29.3 +14.65 ~ 44 secs ?
Is there any way to view the subtracted images to see what they look like ?
I have used the Full perusion model approach and do not seem to get any activation when i view the zstat1 image(perfusion) but get activation in the ztat3 image (BOLD) . Strangely, when I used a wrong TR (3 secs instead of 2.93) I got a single cluster in the left motor area. I have run MELODIC and there seems to be a lot of noise. The Simple subtraction model gives me a good result in one case but random blobs in the other
I was wondering how I should choose the components to remove when using the MELODIC denoising option. I have around 35 components and in most of them the activations seem like artifacts except for one or two where the activations are in the left motor cortex(with a lot fo noise). Is there a 'rule' for selecting components to discard and retain ? Is there a limit to the number of components that can be discraded without causing any additional problems in the results ?
I have uploaded my data (link below) if anyone wants to have a look.
https://fileexchange.imperial.ac.uk/files/4da75154f9b/ASl_results.tar.gz
I would be extremely grateful if anyone could have a look and give me any tips.
Thanks in advance for any help
Ben
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