Patent ID: 8637841

Claim:
A multileaf collimator comprising: a first set of a plurality of pairs of beam blocking leaves arranged adjacent one another, leaves of each pair in the first set being disposed in an opposed relationship and longitudinally movable relative to each other in a first direction; and a second set of a plurality of pairs of beam blocking leaves arranged adjacent one another, leaves of each pair in the second set being disposed in an opposed relationship and longitudinally movable relative to each other in a second direction generally parallel to the first direction; wherein the first and second sets of pairs of leaves are disposed in different planes, each of the first and second sets includes an inner first section of a plurality of pairs of leaves having a first cross section and an outer second section of a plurality of pairs of leaves having a second cross section, and the first cross section of the leaves in the first section of the first set is thinner than the first cross section of the leaves in the first section of the second set; and wherein the second section in each of the first and second sets includes a plurality of pairs of leaves at each side of the inner first section.