Appendix A.
Radiomic features extracted from breast DCE-MRI images
| Image Feature | Description |
|---|---|
| Size [11] | |
| (S1) Volume (mm3) | Volume of lesion |
| (S2) Effective greatest dimension (mm) | Greatest dimension of a sphere with the same volume as the lesion |
| (S3) Surface area (mm2) | Lesion surface area |
| (S4) Maximum linear size (mm) | Maximum distance between any 2 voxels in the lesion |
| Shape [11] | |
| (G1) Sphericity | Similarity of the lesion shape to a sphere |
| (G2) Irregularity | Deviation of the lesion surface from the surface of a sphere |
| (G3) Surface area/volume (1/mm) | Ratio of surface area to volume |
| Morphology [11] | |
| (M1) Margin sharpness | Mean of the image gradient at the lesion margin |
| (M2) Variance of margin sharpness | Variance of the image gradient at the lesion margin |
| (M3) Variance of radial gradient histogram | Degree to which the enhancement structure extends in a radial pattern originating from the center of the lesion |
| Enhancement texture [10] | |
| (T1) Contrast | Location image variations |
| (T2) Correlation | Image linearity |
| (T3) Difference entropy | Randomness of the difference of neighboring voxels’ gray-levels |
| (T4) Difference variance | Variations of difference of gray-levels between voxel-pairs |
| (T5) Angular second moment (energy) | Image homogeneity |
| (T6) Entropy | Randomness of the gray-levels |
| (T7) Inverse difference moment | Image homogeneity |
| (T8) Information measure of correlation 1 | Nonlinear gray-level dependence |
| (T9) Information measure of correlation 2 | Nonlinear gray-level dependence |
| (T10) Maximum correlation coefficient | Nonlinear gray-level dependence |
| (T11) Sum average | Overall brightness |
| (T12) Sum entropy | Randomness of the sum of gray-levels of neighboring voxels |
| (T13) Sum variance | Spread in the sum of the gray-levels of voxel-pairs distribution |
| (T14) Sum of squares (variance) | Spread in the gray-level distribution |
| Kinetic curve assessment [12] | |
| (K1) Maximum enhancement | Maximum contrast enhancement |
| (K2) Time to peak (s) | Time at which the maximum enhancement occurs |
| (K3) Uptake rate (1/s) | Uptake speed of the contrast enhancement |
| (K4) Washout rate (1/s) | Washout speed of the contrast enhancement |
| (K5) Curve shape index | Difference between late and early enhancement |
| (K6) Enhancement at first postcontrast time point | Enhancement at first post-contrast time point |
| (K7) Signal enhancement ratio | Ratio of initial enhancement to overall enhancement |
| (K8) Volume of most enhancing voxels (mm3) | Volume of the most enhancing voxels |
| (K9) Total rate variation (1/s2) | How rapidly the contrast will enter and exit from the lesion |
| (K10) Normalized total rate variation (1/s2) | How rapidly the contrast will enter and exit from the lesion |
| Enhancement-variance kinetics [9] | |
| (E1) Maximum variance of enhancement | Maximum spatial variance of contrast enhancement over time |
| (E2) Time to peak at maximum variance (s) | Time at which the maximum variance occurs |
| (E3) Enhancement variance increasing rate (1/s) | Rate of increase of the enhancement-variance during uptake |
| (E4) Enhancement variance decreasing rate (1/s) | Rate of decrease of the enhancement-variance during washout |