Modulating intensity of radiation beam

A modulator for use in a radiation system, said radiation system being capable of irradiating a target from a plurality of orientations, wherein the orientations are associated with directional radiation beams respectively collimated into radiation fields, comprising:

• a plurality of displaceable radiation attenuating elements arranged in at least one row, said radiation attenuating elements being configured to attenuate portions of a radiation beam inside the radiation field according the position of the radiation attenuating elements, and wherein each radiation attenuating element is respectively attached to a substantially radiolucent member;
• and
• a driver operable to store motion profiles and to respectively drive said radiation attenuating elements in directions generally perpendicular to the radiation beam via the substantially radiolucent members, wherein the respective motions of the radiation attenuating elements are according to corresponding motion profiles, and wherein a motion profile relates position and/or velocity of said radiation attenuating elements to time and/or irradiation level.