Abstract: Various embodiments of the present invention provide methods and systems for deterministic calculation of radiation doses, delivered to specified volumes within human tissues and organs, and specified areas within other organisms, by external and internal radiation sources. Embodiments of the present invention provide for creating and optimizing computational mesh structures for deterministic radiation transport methods. In general these approaches seek to both improve solution accuracy and computational efficiency. Embodiments of the present invention provide methods for planning radiation treatments using deterministic methods.