aslcontext.tsv dummy volumes

[nmrotstein]

Hi, I have an ASL dataset that I am hoping to convert to BIDS format (to eventually use with ASLPrep), but the sequence that our group is using is structured as an M0 volume, a dummy volume, and then 9 label-control pairs, and the current BIDS specification for the aslcontext.tsv file does not seem to have any option for indicating a dummy volume, just label/control/m0. Could an option for labeling dummy volumes (or an "other" or "ignore" option) potentially be added to the specification for aslcontext.tsv so that it is possible to convert this type of ASL sequence to valid BIDS format? Thank you!

[tsalo]

I don't really understand what a "dummy volume" is in this context, or why dummy volumes are included in the protocol, but this was also brought up by lucia_sanchez_aranda on NeuroStars (https://neurostars.org/t/plds-calibration-image-and-dummy-volumes-in-aslprep/26373), so it seems like multiple people are struggling with this.