Table 1.

List of shape descriptors and their definition.

Descriptors	Definition
Length (mm)	$\frac{1}{n}\sum _{i=1}^{i=n}\sum _{t=1}^{t=m_i-1}{\Vert v_i(t)-v_i(t+1)\Vert }_2$
Span (mm)	$\frac{1}{n}{\sum }_{i=1}^{i=n}{\Vert v_i(1)-v_i\left(m_i\right)\Vert }_2$
Diameter (mm)	$2\sqrt{\frac{\mathit{\text{volume}}}{\pi \times \mathit{\text{length}}}}$
Radius (mm)	$\frac{1.5}{N_e}{{\sum }^{\text{}}}_{i=1}^{i=N_e}{\Vert E_i-\overline{E_i}\Vert }_2$
Surface Area (mm2 )	$N_s\times \mathit{\text{voxel spacin}}{g}^2$
Volume (mm3)	$N\times \mathit{\text{voxel volume}}$
Trunk Volume (mm3)	$N_t\times \mathit{\text{voxel volume}}$
Curl	$\frac{\mathit{\text{length}}}{\mathit{\text{span}}}$
Elongation	$\frac{\mathit{\text{length}}}{\mathit{\text{diameter}}}$
Irregularity	$\frac{\mathit{\text{surface area}}}{\pi \times \mathit{\text{diameter}}\times \mathit{\text{length}}}$
Irregularity of the end surface	$\frac{\pi \times \mathit{\text{radiu}}{s}^2}{\mathit{\text{area of the end surface}}}$

Bundle: trajectory form = {v_i(t)|i = 1, 2, 3, … n}, voxelized form = {V_i|i = 1, 2, 3, … N}

End surface: voxelized form = {E_i|i = 1, 2, 3, … N_e}, where E_i are voxel coordinates.

N_t is the number of “trunk bundle” voxels.

N_s is the number of tract surface voxels.