[Mrtrix-discussion] Probabilistic part of SD_PROB

[René Besseling]

Dear Donald,

 

I was wondering what the real probabilistic part of SD_PROB is. The FOD
glyphs themselves do not contain any true probabilistic information: the
lobes of these glyphs have certain widths because they are only defined up
until a certain resolution (a certain number of spherical harmonics). The
width of a lobe is therefore not a pure measure for the uncertainty that a
fiber population is oriented in that direction. To draw a parallel with the
diffusion tensor model: if we assume the main eigenvector e_1 of the DT
gives the direction of the local fiber population, by bootstrapping we can
collect several e_1 estimates. If the direction of each e_{1,i} is given by
(\phi_i,\theta_i), we can uses these e_1 estimates to estimate
P(\phi_i,\theta_i). When doing fiber tracking, in every propagation step we
choose a certain local propagation direction (\phi_i,\theta_i) and we can
calculate the product of P(\phi_i,\theta_i) for all voxels i along the track
to get a measure of the track probability. How do this translate to fiber
tracking based on CSD based FOD glyphs?

 

Best regards,

 

René Besseling

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