Margin strength descriptors
Average radial gradient	〈Gr(M)〉
Radial gradient index (RGI)	〈Gr(M)〉/〈|G(M)|〉
Relative RGI	RGI/max(RGI)
Margin Strength 1	〈|G(M)|〉/(〈GV(M)〉 − 〈GV(ℜa)〉)
Margin Strength 2	std(|G(M)|)/(〈GV(M)〉 − 〈GV(ℜa)〉)
Radial gradient variation	std(Gr(M))
Shape descriptors
Irregularity	c*ℜ1/3/M1/2 where c is a constant
Compactness	∑ (ℜ ∩ ℜs)/∑ ℜs
Ellipsoid semi-axes minimum to maximum ratio	min(h1,h2,h3)/max(h1,h2,h3) where hi (i = 1,2,3) are the semi-axes of an ellipsoid fit to ℜ
Standard deviation of margin to center distance [mm]	std(|dM|)
Relative standard deviation of margin to center distance	std(|dM|)/〈|dM|〉
average margin alignment: average cosine of polar angle along margin	〈cos(〈(G,r)) (M)〉
Margin volume (mm3)	∑ M
Histogram descriptors
Average region gray value (HU)	〈GV(ℜ)〉
Region contrast (HU)	〈GV(ℜ))〉 − GV(∼ℜ & ℜa)〉
Standard deviation of region gray values (HU)	std(GV(ℜ))〉
Standard deviation of gray values along margin (HU)	std(GV(M))