Radiation transport calculations in treatment planning

This article reviews the role of radiation transport calculations in radiotherapy dose computation. The physical and mathematical principles underlying transport theory, as applied to electrons and photons, are discussed. Practical methods of solving the transport equation, with emphasis on Monte Carlo techniques, are reviewed. The contribution of analytic and Monte Carlo transport calculations to electron beam, photon beam, and brachytherapy treatment planning dosimetry is assessed. Currently, the most important roles of transport theory include using approximate solutions of the transport equation as theoretical foundations of dose computation algorithms, and using Monte Carlo simulation to calculate basic treatment planning data, characteristic of the treatment modality, which can serve as input to a dose computation algorithm.