LAUSR

Purpose An overview of the photon dose calculation algorithm is given according to the classification in type “a” (no lateral electron transport included), type “b” (with lateral electron transport estimation), type “c” (true Monte Carlo simulations or Boltzmann transport equation solvers). Methods Performances of the different algorithms for common clinical treatment sites were presented: prostate, head and neck, breast and lung, planned with conformal technique. To better focus on the heterogeneities, different phantom studies were proposed. Finally, the overview focused on the most critical case of small treatment fields on low density tissue. Results The dose calculation models belonging to type “a” (pencil beam based) presented quite high inaccuracies in the small fields and low density regions, while type “b” were more congruent in the clinical situations with the type “c”, where Monte Carlo is considered the benchmark for dose estimation. This congruence is lowered for the critical clinical case of e.g. a stereotactic lung treatment. Additional point of discussion, especially for type “c” algorithms, concerned the report of the estimated dose as dose to medium, or dose to water in different human tissues. Conclusions The clinical use of a dose calculation system should be correlated with the degree of accuracy of the algorithm in each specific clinical situation.