Martin,
The sequence says it is FAIR QII this means it is pASL and not pcASL. In which case your bolus duration is correct, but you need to select pASL (i.e. no —casl option on the command line) and your TI is the same as your PLD, i.e. 1.99.
If you do only have a pASL sequence and do not have pcASL then you should follow the pASL recommendations of the white paper - the critical thing is that you wont be able to achieve a bolus duration much longer than 700-800ms in practice.
If this sequence does not have background suppression then you might be able to use the control image for calibration.
Michael
On 17 Sep 2019, at 07:07, Martin M <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Hi, I am trying to "Translate" the MR sequence parameters of a "stock" siemens pcASL (see below/attached) to the inputs for asl_gui and I was looking for some input.
The basics of the sequence, which is attached in full, are as follows:
pcASL, TR 4,600ms, TE 16.18ms
1 average / 4 measurements
Perfusion mode FAIR QII
Bolus Duration 700ms
Inversion Time 1,990ms
Is it correct, then to enter the following in the GUI:
Bolus duration 0.700
PLD 1.29 (i.e., TI minus BD: 1,990 - 700)
That is (I do not have calibration or fieldmaps unfortunately..):
oxford_asl \
-i "asl_02.nii.gz" \
--ibf=rpt --iaf=tc --tis 1.99 --bolus 0.70 --casl \
--fslanat="MPRAGE-T1.anat" \
--wp --t1b 1.65 --alpha 0.85 --spatial --mc --artoff \
-o "asl_01_dir"
Finally, do i understand correctly that, following the WP, for the future I should set:
Bolus duration = 1,800ms
(PLD = 1,800 ms)
Inversion time (BD+PLD) = 3,6000ms?
thank you
martin
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<LIFUP_Sess01_ASL.pdf>
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Michael Chappell MEng DPhil
W: http://www.ibme.ox.ac.uk/qubic
T: +44 1865 617657
Associate Professor, Institute of Biomedical Engineering, University of Oxford.
http://www.ibme.ox.ac.uk
Director of Training, EPSRC-MRC CDT in Biomedical Imaging
http://www.onbicdt.ox.ac.uk
Governing Body Fellow, Wolfson College, Oxford.
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