Fig. 2.

3D box-counting for computation of the FD. An example of the 3D box-counting algorithm that uses an automated selection of the fractal scaling window through the fractalbrain toolkit⁵⁹. N(s) is the average number of 3D cubes of side s needed to fully enclose the brain structure computed using 20 uniformly distributed random offsets to the grid origin. The regression line within the optimal fractal scaling window, whose slope (sign changed) is the FD, is depicted in red.