Range, setup and dose calculation errors in IMPT and their interrelation

Abstract

Treatment plans optimized for intensity modulated proton therapy (IMPT) may be very sensitive to setup errors, range uncertainties and dose calculation errors. To mitigate the adverse effect of range and setup errors, uncertainty can be accounted for in the formulation of the IMPT optimization problem via stochastic or robust programming techniques. Dose calculation accuracy can be improved by applying Monte Carlo algorithms or pencil beam algorithms with sub-pencil beam decomposition. However, the costs for the improved accuracy are larger calculation times, especially in case of Monte Carlo. For two paraspinal cases, we show that dose calculation errors can lead to severe degradation of the dose distribution. We further demonstrate that there is an interrelation between different types of errors: a treatment plan which is made robust against range and setup errors, is typically less sensitive to dose calculation errors as well. © 2009 Springer-Verlag.