TABLE 2
Formulas for Regional Heterogeneity Features
| Feature | Formula |
| Small-area emphasis |  |
| Large-area emphasis |  |
| Intensity variability |  |
| Size–zone variability |  |
| Zone percentage |  |
| High-intensity emphasis |  |
| Low-intensity small-area emphasis |  |
| High-intensity small-area emphasis |  |
| Low-intensity large-area emphasis |  |
| High-intensity large-area emphasis |  |
Ω = number of homogeneous areas within tumor; z = intensity size–zone matrix; M = discretization value; N = size of largest homogeneous area within tumor; z(i,j) = number of areas with intensity i and size j.