The present invention concerns an inverse treatment planning system comprising: at least a data bus system (102) a memory (106) coupled to the data bus system (102) wherein the memory (106) comprises a computer usable program code and a processing unit (104) coupled to the data bus system (102) wherein the processing unit (104) is configured to execute the computer usable program code to pre compute (10) a set of individual dose shots (a) each individual dose shot having a predetermined location inside and/or outside a target area a size and a shape associate (40) a weight (¾) to each individual dose shot (a) based on one or more constraints (20) characterised in that the processing unit (104) executes the computer usable program code to find (30) the sparsest subset of individual dose shots so as to satisfy said one or more constraints (20).
