A system for estimating a dose from, and developing, a radiation therapy treatment plan, the system comprising: a memory configured to store machine-readable instructions; a processor communicatively coupled to the memory, the processor being operable to execute the instructions to: subdivide a representation of a volume of interest into a plurality of voxels, wherein the volume of interest corresponds to an organ at risk with respect to the radiation therapy plan, determine a first plurality of distances comprising, for each voxel of the plurality of voxels traversed by a first planned radiation field of a radiation beam, a distance between an origin of the first planned radiation field and the voxel; compute a plurality of metrics based on the first plurality of distances, a first plan parameter, and a first field parameter, wherein the first plan parameter comprises a prescription dose associated with a target volume traversed by the first planned radiation field; and sum the plurality of metrics corresponding to the plurality of voxels, wherein the summation of the plurality of metrics represents an estimated dose received by the volume of interest from the first planned radiation field; wherein the instructions are further configured to cause the processor to: employ said plurality of metrics to generate beam orientations for said radiation therapy treatment plan so that said beam orientations meet constraints for the organ at risk. a memory configured to store machine-readable instructions; a processor communicatively coupled to the memory, the processor being operable to execute the instructions to: subdivide a representation of a volume of interest into a plurality of voxels, wherein the volume of interest corresponds to an organ at risk with respect to the radiation therapy plan, determine a first plurality of distances comprising, for each voxel of the plurality of voxels traversed by a first planned radiation field of a radiation beam, a distance between an origin of the first planned radiation field and the voxel; compute a plurality of metrics based on the first plurality of distances, a first plan parameter, and a first field parameter, wherein the first plan parameter comprises a prescription dose associated with a target volume traversed by the first planned radiation field; and sum the plurality of metrics corresponding to the plurality of voxels, wherein the summation of the plurality of metrics represents an estimated dose received by the volume of interest from the first planned radiation field; wherein the instructions are further configured to cause the processor to: employ said plurality of metrics to generate beam orientations for said radiation therapy treatment plan so that said beam orientations meet constraints for the organ at risk. subdivide a representation of a volume of interest into a plurality of voxels, wherein the volume of interest corresponds to an organ at risk with respect to the radiation therapy plan, determine a first plurality of distances comprising, for each voxel of the plurality of voxels traversed by a first planned radiation field of a radiation beam, a distance between an origin of the first planned radiation field and the voxel; compute a plurality of metrics based on the first plurality of distances, a first plan parameter, and a first field parameter, wherein the first plan parameter comprises a prescription dose associated with a target volume traversed by the first planned radiation field; and sum the plurality of metrics corresponding to the plurality of voxels, wherein the summation of the plurality of metrics represents an estimated dose received by the volume of interest from the first planned radiation field; wherein the instructions are further configured to cause the processor to: employ said plurality of metrics to generate beam orientations for said radiation therapy treatment plan so that said beam orientations meet constraints for the organ at risk.