Scripts for ASL-CBF preprocessing and analysis

AFNI Message Board
1

Dear all,

My ongoing study involves the acquisition of Spiral-ASL MRI as well as EPI-BOLD and T1-MPRAGE. I’m using some of the standard tools to preprocess and analyze the data from the two latter sequences, but I would like to explore also the AFNI capability to handle the ASL data.

I would very much appreciate any idea or script that could help me. I also can provide further details as needed. My e-mail is vpereira@alumni.unav.es

Thank you!

-victor

2

Hi Victor,

did you find any useful script since then ? I’m facing the same issue and would appreciate some feedback from the AFNI community.

The best,

Antonio.

3

I’ve helped a few people with ASL processing, and there seem to be a variety of approaches. BTW, Francois Lalonde, here at NIH is my principal go-to person for questions about ASL analysis. There are couple parts people are interested in - motion correction and difference datasets. Differences are computed a few different ways, and I’ve included one way below. Note, I haven’t actually tried this particular way for real data, but you may use this as a starting example. Proceed with caution…

extract evens

3dbucket -prefix evens.nii.gz myASLdset.nii’[0…$(2)]’

extract odds

3dbucket -prefix odds.nii.gz myASLdset.nii’[1…$(2)]’

motion correct evens

3dvolreg -prefix odds_mc.nii.gz -1Dmatrix_save odds ‘odds.nii.gz’

motion correct odds by applying evens’ transformation to odds

assumes no motion between even and odds but doesn’t add micro-motion differences

to be introduced.

This causes an extra interpolation if going to standard space separately

3dAllineate -prefix evens_mc.nii.gz -1Dmatrix_apply odds.aff12.1D -master ‘evens.nii.gz’

calculate differences

use odds, evens and even+1 (the next even) to average

3dcalc -a odds_mc.nii.gz -b evens_mc.nii.gz -c evens_mc.nii.gz’[1…$]’
-expr ‘a-(b+c)/2’ -prefix ASL_diff.nii.gz

consider putting a TR in seconds into the dataset (~2*TRorig)

3drefit -TR 4s ASL_diff.nii.gz