--randfib refers to initialization of streamlines only (i.e. the very first
step) and only affects voxels with more than one fiber reconstructed:
randfib==0, only sample from the strongest fiber
randfib==1, randomly sample from all fibers regardless of strength that are
above --fibthresh
randfib==2, sample fibers stronger than --fibthresh in proportion to their
strength (in my opinion, this is the best choice)
randfib==3, sample all fibers randomly regardless of whether or not they are
above --fibthresh
When I say fiber strength, I am referring to the proportion of the diffusion
signal explained by the fiber (this is also called the fsample or the volume
fraction).
Peace,
Matt.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Chris Lambert
Sent: Wednesday, October 06, 2010 9:32 AM
To: [log in to unmask]
Subject: [FSL] randfib clarification
Hello,
I just want to clarify these functions.
randfib==0: Default, (?)estimates the most likely fibre orientation at each
step
randfib==1: Sample initial fibres (i.e. seed) with f<fthresh, with random
probability
randfib==2: Sample initial fibres (i.e. seed) with f<fthresh, with equal
probability
randfib==3: Sample initial fibres (i.e seed) with f possibly >fthresh, with
random probability
Is this correct? What I'm wondering is what is your definition of "initial
fibres", and how far along the tractography does this randfib apply (every
step, first step, burn in??). Also is the definition of default correct?
Cheers!
- Chris
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