Patent ID: 7945023

Claim:
A radiotherapy system comprising: a radiation source operable to produce a radiation beam towards a target; an orientation changer operable to change a relative position of said radiation source with respect to said target; and a multileaf attenuator comprising attenuating leaves comprising respective spatially varying attenuation properties and a positioner in communication with the orientation changer, each of said attenuating leaves having a leaf length, leaf thickness, leaf center and leaf direction, wherein the leaf direction is a line intersecting the leaf center along the leaf thickness, wherein said radiation beam comprises one or more beam segments, wherein a beam segment is the part of the beam intercepted by one of said attenuating leaves, and wherein said target comprises one or more target segments, wherein a target segment is that part of said target that intercepts a corresponding one of said beam segments, wherein each of said attenuating leaves is operative to modulate an intensity of a corresponding beam segment by selective attenuation of the leaf thickness along the leaf length, and wherein said positioner is operable to vary at least one of a leaf center position and a leaf direction relative to said radiation source in accordance with positions of the corresponding target segment and said radiation source, and wherein the radiation source is stationary, and wherein said orientation changer is operable to rotate said radiation about a rotational axis which is generally vertical, and the radiation beam is generally horizontal.