A method for estimating a radiation dose and distribution for a target volume is provided. The method includes receiving a simulated dose array (606) describing a plurality of simulated dose values for a plurality of voxels in the target volume, generating an energy deposition coefficient function for the plurality of voxels (608), and obtaining a raw fluence array based at least on the simulated dose array and the energy deposition coefficient function (612). The method also includes generating an adjusted fluence array (613) based on the raw fluence array and at least one adjustment criteria, and generating an adjusted dose array (622) for the target volume based on the adjusted fluence array and the energy deposition coefficient function.