Figure 6.

Second-order GLCM textural features extraction, where the central voxel of interest is shown in blue and the 26-neighbors are shown in red. The spatial relationship in the neighborhood block is obtained at different angles of zero, $\frac{\mathsf{\pi }}{2}$, $\frac{\mathsf{\pi }}{4}$, and $\frac{3\mathsf{\pi }}{4}$.