Table 3.
Human-Engineered Radiomic Features (RADHE) and Their Descriptions
| Image Feature | Feature Description | Reference |
|---|---|---|
| Volume (mm3) (S1) | Volume of lesion | [3] |
| Effective diameter (mm) (S2) | Greatest dimension of a sphere with the same volume as the lesion | |
| Surface area (mm2) (S3) | Lesion surface area | |
| Maximum linear size (mm) (S4) | Maximum distance between any 2 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 | [36] |
| 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 | [5] |
| 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 post-contrast time point | |
| Signal enhancement ratio (K7) | Ratio of initial enhancement to overall enhancement | |
| Volume of most enhancing voxels (mm3) (K8) | Volume of the most enhancing voxels | |
| Total rate variation (1/s2) (K9) | How rapidly the contrast will enter and exit from the lesion | |
| Normalized total rate variation (1/s2) (K10) | How rapidly the contrast will enter and exit from the lesion | |
| Maximum enhancement-variance (E1) | Maximum spatial variance of contrast enhancement over time | [37] |
| 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 | |