Ignore image & different number of repetitions

[Jennie Chen]

Hi everyone, I'm eager to try ExploreASL on my ASL data as it seems to many of the published best practices, but I'm using a C2P multi-PLD 3D-pCASL sequence that has the following image order:

M0, discard, (PLD1-label, PLD1-control)x2, (PLD2-label, PLD2-control)x2, (PLD3-label, PLD3-control)x2, (PLD4-label, PLD4-control)x3 , (PLD5-label, PLD5-control)x3

I'd like to discard the 2nd volume as it isn't useful for the quantification. Is it possible to specify this in the context field of StudyPar.json? I tried leaving empty ' ' for the 2nd volume but the import module throws an error about it. 

For the different number of repetitions, I just wrote out the actual PLDs for each volume, would this work?

"PostLabelingDelay":[0,0,0.5,0.5,0.5,0.5,0.9,0.9,0.9,0.9,1.3,1.3,1.3,1.3,1.7,1.7,1.7,1.7,1.7,1.7,2.2,2.2,2.2,2.2,2.2,2.2]

Thanks so much!

Jennie

[Jan Petr]

Hi Jennie,

Glad to hear that. Yes, ExploreASL should be perfectly able to handle such cases. 

You did specify it correctly for PLD. for the discard volume, you have to fill the aslcontext in study par for all volumes, for the discard volume, just fill control or label, it doesn’t matter. Currently, BIDS has no definition for that, but we’re working on it. So to discard the second volume write

“DummyScanPositionInASL4D”:2

Check 

https://exploreasl.github.io/Documentation/1.12.0_Beta/ProcessingParameters/

Let me know if you have any further questions  

Best

Jan

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