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TOPIC: coordinate space for gradient directions

coordinate space for gradient directions 9 years 1 month ago #217

  • gadde
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Hi,

Can someone tell me what the conventions are for the gradient directions in the .dts file? Are they in image coordinates (i.e. 1 0 0 means diffusion along the fastest axis in the data, 0 0 1 along the slowest), or in ITK coordinates (which I guess is LPS-positive, meaning 0.707 0.707 0 points between left and posterior), or something else?

Also, what is the effect of AffineTransform in the .dts file? I understand it has an effect, as I've been playing around with the values, but wasn't sure of its intended use. Does every point in the calculated fibers merely get multiplied by that transform before it is saved? If so, is 1 0 0 0 1 0 0 0 1 0 0 0 the equivalent of a no-op? (I assume DTI Track reads and uses orientation info from the input image file)

Thank you!

-syam
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Re: coordinate space for gradient directions 9 years 1 month ago #221

  • ocommowick
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Hi,

Unfortunately, I think you are talking about medinria 1.X series and we do not support this anymore, for the simple reason that almost all original developers of this version are now working elsewhere or changed projects.

That being said I think (but we have known bugs on it that we are investigating) that the gradients should be in real coordinates for medinria 2.x.

Hope this little answer helps a bit.
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