Table 2.

Radiomic feature names and descriptions. Size features (designated by abbreviations S1, S2, S3, and S4) are included for reference, but the statistical analysis was not performed using these features.

Image feature	Feature description	Reference
Volume (${\mathrm{mm}}^3$) (S1)	Volume of lesion	[12]
Effective diameter (mm) (S2)	Greatest dimension of a sphere with the same volume as the lesion
Surface area (${\mathrm{mm}}^2$) (S3)	Lesion surface area
Maximum linear size (mm) (S4)	Maximum distance between any two voxels in the lesion
Sphericity (G1)	Similarity of the lesion shape to a sphere
Irregularity (G2)	Deviation of the lesion surface from the surface of a sphere
Surface area/volume (1/mm) (G3)	Ratio of surface area to volume
Margin sharpness (M1)	Mean of the image gradient at the lesion margin
Variance of margin sharpness (M2)	Variance of the image gradient at the lesion margin
Variance of radial gradient histogram (M3)	Degree to which the enhancement structure extends in a radial pattern originating from the center of the lesion
Contrast (T1)	Location image variations	[13]
Correlation (T2)	Image linearity
Difference entropy (T3)	Randomness of the difference of neighboring voxels’ gray-levels
Difference variance (T4)	Variations of difference of gray-levels between voxel-pairs
Energy (T5)	Image homogeneity
Entropy (T6)	Randomness of the gray-levels
Inverse difference moment (homogeneity) (T7)	Image homogeneity
Information measure of correlation 1 (T8)	Nonlinear gray-level dependence
Information measure of correlation 2 (T9)	Nonlinear gray-level dependence
Maximum correlation coefficient (T10)	Nonlinear gray-level dependence
Sum average (T11)	Overall brightness
Sum entropy (T12)	Randomness of the sum of gray-levels of neighboring voxels
Sum variance (T13)	Spread in the sum of the gray-levels of voxel-pairs distribution
Sum of squares (variance) (T14)	Spread in the gray-level distribution
Maximum enhancement (K1)	Maximum contrast enhancement	[14]
Time to peak (s) (K2)	Time at which the maximum enhancement occurs
Uptake rate (1/s) (K3)	Uptake speed of the contrast enhancement
Washout rate (1/s) (K4)	Washout speed of the contrast enhancement
Curve shape index (K5)	Difference between late and early enhancement
Enhancement at first postcontrast time point (K6)	Enhancement at first postcontrast time point
Signal enhancement ratio (K7)	Ratio of initial enhancement-to-overall enhancement
Volume of most enhancing voxels (${\mathrm{mm}}^3$) (K8)	Volume of the most enhancing voxels
Total rate variation ($1/{\mathrm{s}}^2$) (K9)	How rapidly the contrast will enter and exit from the lesion
Normalized total rate variation ($1/{\mathrm{s}}^2$) (K10)	How rapidly the contrast will enter and exit from the lesion
Maximum enhancement-variance (E1)	Maximum spatial variance of contrast enhancement over time
Enhancement-variance time to peak (s) (E2)	Time at which the maximum variance occurs
Enhancement variance-increasing rate (1/s) (E3)	Rate of increase of the enhancement-variance during uptake
Enhancement-variance decreasing rate (1/s) (E4)	Rate of decrease of the enhancement-variance during washout