The present invention relates to a radiotherapy planning system (100) for determining a solution (101) corresponding to a fluence profile. The invention proposes to use a Pareto frontier navigator (140) to select the best plan from a set of various auto planned solutions. An interactive graphical user interface (400) is provided to the planner to navigate among convex combinations of auto planned solutions. This proposed Pareto plan navigation can be considered as a further optional refinement process which can be applied to find the best plan in those cases where auto generated solutions are not fully satisfying the planner s requirements. The navigation tool (400) moves locally through a set of auto generated plans and can potentially simplify the planner s decision making process and reduce the whole planning time on complex clinical cases from several hours to minutes.
