Table 2 Summary of quantitative imaging features
Type/order of statistics | Feature | Brief definition |
|---|---|---|
Morphological | Volume | Sum of voxels delineated multiplied by the volume of one voxel |
Pre-discretisation | SUVmax | Maximum uptake of FDG in the MTV |
Energy | Sum squared SUV values in the MTV | |
First order | Skewness | Measures symmetry of intensity histogram |
Kurtosis | Measures flatness of intensity histogram | |
Entropy | Measures randomness | |
Second order | Dissimilarity | Variation of grey level pairs (GLCM). Features were calculated for each unique direction and averaged with a distance setting of 1 |
Higher order | Grey-level non-uniformity | Distribution of zone counts for each intensity value (GLSZM) |
Zone percentage | Fraction of recorded zones compared to maximum possible | |
Coarseness | Measures spatial rate of change in intensity using a distance of 1 |