Need a fall-back for cases where no T1w images are available

[arokem]

Two kinds of use-cases:

• Acquisition protocols that don't include T1w.
• Individual cases within a protocol that don't have that data (e.g., when the quality of the T1 is not good. This is a thing in the HBN dataset).

One option is to register to the FS average brain.

[jyeatman]

One option would be to copy in an mni template or fsaverage brain if there is not T1 image. This will put the data in (roughly) the correct orientation

[arokem]

DIPY has a function to fetch MNI template brains: dipy.data.fetch_mni_template