A system and method are disclosed for determining the radiation dose distribution created by a set of radioactive seeds (20) placed in a volume (30). The method includes three stages. Stage T01 comprises preliminary steps that allow one to obtain the unit radiation dose distribution created by one seed and the individual attenuations created by its neighboring seeds when said neighboring seeds are assumed to be positioned at the nodes of a three-dimensional periodic lattice. Steps of stage T02 load some results of the preliminary steps, said results being used by steps of stage T03 that actually determine the dose distribution created by a set of seeds (20). The invention also relates to an apparatus, a program and a computer readable medium adapted for the execution of this method.
