where is node 0 and where is node 99? maybe not all LPI+ convention?

[emilyharriott]

Hi pyAFQ team! :)

I apologize if this is a basic question, but I am unable to find a consistent answer amongst the plethora of online resources, and so am hoping you might be able to help me.

Assuming all default settings -- for each tract, where is node 0? and where is node 99? And how might I be able to confirm that?
Especially with regard to the CST, I am finding inconsistent answers online. Maybe not every tract conforms to LPI+ orientation conventions?

Any guidance/resources/thoughts you might be able to share would be so greatly appreciated.

Thank you!
Emily

[arokem]

We believe this to be the authoritative guide to this topic: https://tractometry.org/pyAFQ/explanations/bundle_orientation.html.

But this only covers current versions. I also found your post here: https://neurostars.org/t/pyafq-where-is-node-0-and-where-is-node-99-maybe-not-all-lpi-convention/36351, which used an older version of pyAFQ, so maybe that is the source of the confusion.

If all else fails, you can use the method I describe here to empirically determine which way is up: https://neurostars.org/t/putting-mrtrix-tractography-into-pyafq/26780/7