bedpostx spherical coordinate reference axes #94
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Lestropie
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Jun 5, 2024
- FSL bedpostx command fibre orientations stored as spherical coordinates are confirmed to use the "bvec" reference frame. - Enforcing azimuth angle to obey the right hand rule about the zenith axis would necessitate direct modification of image intensities from bedpostx outputs to store. Therefore it would be preferable to instead define the sign of the azimuth angle based on the direction of the second reference axis. Closes #95. Closes #94.
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Ideally, conversion of a
bedpostxoutput to BIDS compliance would only require basic image manipulation operations such as concatenation. I need to check the outputs ofbedpostxon datasets with different orientations to see exactly how they encode those polar angles. If they don't conform to the ISO standard, then we will either need to define a third reference axis system over and above['ijk', 'xyz']to support those data directly, or unambiguously define the mathematical transformations required to get frombedpostxto BIDS and back again.I have recently acquired a dataset that's ideal for this purpose: 24 combinations of slice encoding direction / slice order / phase encoding direction. So I can run
bedpostxon all 24, then attempt conversion to scanner-space 3-vectors and check the result inmrview.The text was updated successfully, but these errors were encountered: