Algorithm I.

Location optimization for axial points.

for each axial voxel av

initialize an axial point ap = av

repeat

compute the tensor scale at ap with eigenvectors

${\mathbf{i}}_1\left(a_p\right),{\mathbf{i}}_2\left(a_p\right),{\mathbf{i}}_3\left(a_p\right)$

compute local structure intercepts v2 and v3 at ap along ${\mathbf{i}}_2\left(a_p\right)$

and ${\mathbf{i}}_3\left(a_p\right)$

corresponding to the shorter semiaxes

reposition ap at the middle of the intercepts v2 and v3

until convergence of the axial point ap or a maximum of three

iterations