Structural scans don't require a run-alias

[jan-petr]

Description

Runs are usually scantype-specific, e.g. mostly T1w & FLAIRs have a single run, and ASL can have multiple runs, e.g. SinglePLD and MultiPLD. For example, we can have directories "T1w-structural", "FLAIR-structural" and "ASL_SinglePLD", "ASL_MultiPLD", where "structural" was manually added. We then have scantypes T1w|FLAIR|ASL and runAliases "structural|SinglePLD|MultiPLD" See the example above. Ideally, we change the source data as least as possible. We probably just want to make a list of sessions per scantype, and sort it that way. So the session tokens are not only ASL_1 ASL_2 but also T1w_1 and FLAIR_1.

Tasks

• Allow an empty token for session (MultiPLD|SinglePLD|). Then if we detect an empty token, we give session 1 by default.
• Note that per BIDS, T1w and FLAIR can have sessions as well. We don't use them in ExploreASL processing but for dcm2BIDS they should be detected, so we need the option for 2 FLAIR or T1w sessions (not urgent though). This would be the typical case if a study has repeated a FLAIR when there was motion, and BIDS would then have two FLAIRs, and the user removes the FLAIR with the most motion, whereas the sourcedata should be kept intact (read-only). But this is really complicated and requires a complete rehaul and has to be moved to a new issue

How to test

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Release notes

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