Offline discussion with @tgbugs and @lzehl about the general organization of pulse sequences: Start problem is that T1 and T2 are, in the physical sense not pulse sequences (e.g., https://radiopaedia.org/articles/mri-pulse-sequences-1 does not even list it under pulse sequences, and this quote "The MR signal intensity (S) produced using a spin echo sequence is proportional to the proton density (ρH), TR, T1, TE and T2, described by the equation S ∝ ρH [1-eTR/T1]e-TE/T2 4.")

Generic pulse sequences and contrast as separate parameter or have all combinations? - @tgbugs: rather split them

contrast agents (given to specimen or quality of the specimen) vs. weighting/contrast (algorithm that produces the contrasted image, hopefully making sense but theoretically could be applied to any kind of data) vs. pulse sequences (machine settings and which coil(s) were used and such, physically available data)

examples:
contrast agent: oxygenated hemoglobin vs. deoxygenated hemoglobin
pulse sequence: radio echo sequence, etc.
MRI parameter weighting: T1, T2, T2star, proton-density, diffusion-weighted?, more?

Additionally some MRI technique should be reconsidered:
functional MRI:
fMRI as superclass for BOLD fMRI (blood oxygenation level dependent), VASO fMRI (vascular space occupancy) and ASL fMRI (arterial spin labeling)
This is related to #128 (MRI as superclass with structural MRI and functional MRI)

diffusion-weighted imaging:
is a protocol and not a single technique, should probably be sMRI + diffusion-weighted + some pulse sequence; what to do about these complex processes? should the "endpoint" be registered or not?

To Do:

• split weighting and sequences
• fix fMRI techniques

To Discuss:

• solution for the last point about complex processes

also related to openMetadataInitiative/bids2openminds#92