In this paper, we present work on the application of the Electron Dose Kernel discrete ordinates method (EDK-SN) to compute doses and account for material heterogeneities using high energy external photon beam irradiations in voxelized human phantoms. EDKs are pre-computed using photon pencil "beamlets" that lead to dose delivery in tissue using highly converged Monte Carlo. Coupling the EDKs to accumulate dose scaled by integral photon fluences computed using SN methods in dose driving voxels (DDVs) allows for the full charged particle physics computed dose to be accumulated throughout the voxelized phantom, and is the basis of the EDK-SN method, which is fully parallelized. For material heterogeneities, a density scaling correction factor is required to yield good agreement. In a fully voxelized phantom, all doses were in agreement with those determined by independent Monte Carlo computations. We are continuing to expand upon the development of this robust approach for rapid and accurate determination of whole body and out of field organ doses due to high energy x-ray beams.