Your analysis seems appropriate given your data. In practice although CBF around 60 ml/100g/min is expected in grey matter, the low spatial resolution of ASL data means that you will have quite a lot of partial volume effects with white matter that has a much lower CBF. Thus when you take a mean over an ROI or over the whole brain mean values of CBF often come out lower 30-40 ml/100g/min seem fairly usual from the literature. The only thing I can think of that you might want to look out for is the TR of your M0 image - if this is the same as the rest of your data (4 s) then you might want to correct for it - oxford_asl will do this automatically if you supply the TR value.
Michael
> On 21 Nov 2015, at 06:48, Shan(Hannah) Luo <[log in to unmask]> wrote:
>
> Dear FSL experts,
>
> I am currently running ASL analysis using BASIL. Based on the ASL white paper, it is expected that the mean CBF ranges from 60-100 ml/100g/min. I looked at CBF in a couple of region of interests and found out the mean CBF in each individual region ranges from 10-30 ml/100g/min, which makes the mean overall CBF much greater than 100. I am wondering whether you could give me some guidance why it is the case. This is how I did the ASL analysis:
>
>
> asl_file --data=pASL11_mcf --ntis=1 --iaf=tc --diff --mean=diffpASL11
>
> fslmaths ASL -Tmean mASL
>
> bet mASL mASL_brain
>
> oxford_asl -i diffpASL11 -o CBF11MC --tis 1.8 --bolus 0.7 -s mprage_brain.nii.gz -c M0 --regfrom mASL_brain --spatial
>
> I attached my pASL protocol and also CBF values from one region (the Ventral Striatum) as an example. Your thoughts/input are very much appreciated.
>
> Also for data presentation, it is better to present CBF in a certain region of interest or CBF in a ROI/overall CBF?
> <Bin_Accum50_ASL_ROI_output.txt><Siemens Imaging protocol for ASL.pdf>
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