1. Process for determining the configuration or configurations of a stereotactic radiosurgery helmet (5), to which can be fitted a plurality of collimators (C.sub.f) focused on an irradiation isocenter, each helmet configuration subsequently corresponding to a shot (i) centered on a predetermined target point on a given target volume, characterized in that, on the basis: of optimization points (M.sub.p) chosen in relation to the target volume, of an expected irradiation dose (ED.sub.p) at each optimization point (M.sub.p), and of one (a single shot) or several (a series of successive shots) predetermined initial helmet configuration(s), the dose (D.sub.p) received at each optimization point (M.sub.p) is automatically optimized, through iterative dose calculation, by modifying, in the course of the successive iterations, the treatment time (TT.sub.i) of at least one shot (i), and the diameter (.phi..sub.i,f) of at least one collimator (C.sub.f) used for at least one shot (i), and by calculating, at each iteration, an objective function (OF) having as variables the differences between the calculated dose (D.sub.p) and the expected dose (ED.sub.p) for each optimization point (M.sub.p), iterative dose calculation being carried out automatically until the objective function (OF) satisfies a predetermined optimization criterion.