Table 2.
Examples of 2D and 3D shape-based features with their description [23]
| 2D | Measure |
|---|---|
| Mesh Surface | The sum of all areas defined for each triangle in the mesh |
| Pixel Surface | The surface area of a single pixel multiplicated by the number of pixels in the region of interest |
| Perimeter | The sum of all perimeters of each line in the mesh circumference |
| Perimeter to Surface ratio | The ratio of the Perimeter to the Mesh Surface |
| Sphericity | The ratio of the perimeter of the tumor region to the perimeter of a circle with the same surface area as the tumor region and therefore a measure of the roundness of The shape of the tumor region relative to a circle |
| Spherical Disproportion | The ratio of the perimeter of the tumor region to the perimeter of a circle with the same surface area as the tumor region, and by definition, the inverse of Sphericity |
| Maximum 2D diameter | The largest pairwise Euclidean distance between tumor surface mesh vertices |
| Major and Minor Axis Length | The largest and the second-largest axis length of the region of interest-enclosing ellipsoid and is calculated using the largest principal component |
| The inverse ratio of the major and minor principal axis lengths that could be viewed as the extent to the section is circle-like (not elongated) than it is 1 dimensional line (maximally elongated) | |
| 3D | Measure |
| Compactness 1 and 2 | A measure of how compact the shape of the tumor is relative to a sphere (most compact) |
| Spherical disproportion | The ratio of the surface area of the tumor region to the surface area of a sphere with the same volume as the tumor region, and by definition, the inverse of Sphericity |
| Sphericity | A measure of the roundness of the shape of the tumor region relative to a sphere |
| Mesh Volume | the sum of all volumes defined for each face in the triangle mesh of the region of interest |
| Voxel Volume | The volume of a single voxel multiplicated by the number of voxels in the region of interest |
| Surface Area | the sum of all areas of each triangle in the mesh |
| Surface Area to Volume Ratio | The ratio of the Surface Area to the Mesh Volume |
| Maximum 3D diameter | The largest pairwise Euclidean distance between tumor surface mesh vertices |
| Major, Minor and Least Axis Length | Respectively, the largest, the second-largest and the smallest axis length of the region of interest-enclosing ellipsoid, calculated using the largest principal component |
| Elongation | The inverse ratio of the major and minor principal axis lengths that could be viewed as the extent to which a volume is longer than it is wide, i.e., is eccentric |
| Flatness | The inverse ratio of the major and least axis lengths that could be viewed as the extent to which a volume is flat relative to its length |