The present invention relates to a method for calculating loads deposited (1) by an ionizing radiation, for example to be used by a radiotherapy therapeutic treatment device. The method of the invention comprises at least one first step (2) of calculating a function of the distribution of the load in the meshes of a mesh phantom. The method of the invention comprises a second step (3) of calculating the load deposited in a voxel assembly, the value of the deposited load for one voxel being given by the function of the distribution of the load particular to the mesh to which the voxel belongs. The invention can be used in particular for radiotherapy by intensity modulation.
