Anatomically realistic numerical brain phantom is built using MRI images. The phantom considers the frequency dispersive properties of the head biological tissues. To that end, a fourth-order Debye model is derived and included in the numerical model over the band from 0.5 GHz to 2.5 GHz, which is widely used in microwave-based head imaging as a reasonable compromise between penetration and resolution. The model is created using a combination of Matlab and CST Microwave Studio from MRI slices of a real patient. The head phantom is comprised of a three-dimensional grid of 256×256×128 cubic voxels where the size of each voxel is 1.1 mm× 1.1 mm× 1.1 mm.