The present invention concerns an inverse treatment planning system. The system includes, at least a data bus system (102), a memory (106) coupled to the data bus system (102), and a processing unit (104) coupled to the data bus system (102). The processing unit (104) is configured to execute the instructions to pre-compute (10) a set of individual dose shots (aj), each individual dose shot having a predetermined location inside and/or outside a target area, a size and a shape. The processing unit also associates (40) a weight (sj) to each individual dose shot (aj), based on one or more constraints (20). The processing unit (104) further executes the instructions to find (30) the sparsest subset of individual dose shots, so as to satisfy said one or more constraints (20).
