Table 4.

Definition of shape features

$\mathit{Solidity}=\frac{A}{A_{\mathit{Convex}}}$	$\mathit{Circularity}=\frac{4\pi A}{P_{\mathit{convex}}^2}$
$\mathit{Roughness}=1-\frac{P_{\mathit{convex}}}{P}$	$\mathit{Compactness}=\frac{P^2}{4\pi A}$
$\mathit{Second}\mathit{Moment}={\displaystyle \sum _i^A}\frac{d{\left(u,p_i\right)}^2}{A^2}$	$\mathit{Extent}=\frac{A}{A_{bb}}$
Radial Distance Standard Deviation = std(d(u, p i)| p i  P)	$\mathit{Eccentricity}=\sqrt{1-\frac{b^2}{a^2}}$

A area in pixels, P perimeter of the shape in pixels, convex convex hull of the nodule, bb bounding box of the nodule, a same major axis as an ellipse with the same second moment as the nodule, p _i pixel i of the nodule