Patent Number: 
Section: claims

1. A multi-leaf collimator comprising a plurality of leaves, each leaf being movable to allow a selected portion of radiation energy to be blocked, whereby a shape is defined by a portion of radiation energy which is incident at a target, and the shape is controlled by a positioning of the plurality of leaves,wherein at least some of the plurality of leaves comprise a leaf body which includes a first section and a second section, the first section being thicker than the second section and being provided with a drive screw adapted to move the leaf body. 2. The multi-leaf collimator of claim 1 wherein the drive screw is provided inside the first section of the leaf body. 3. The multi-leaf collimator of claim 1 whereinthe first section provides a first edge portion of the leaf body, the second section provides a second edge portion of the leaf body, andthe first edge portion of the leaf body is provided with an elongate recess adapted to slidably engage a support, the second edge portion of the leaf body is provided with an elongate step adapted to slidably engage the support. 4. The multi-leaf collimator of claim 1 wherein the first section of the leaf body has a cross-section in a trapezoidal shape. 5. The multi-leaf collimator of claim 1 wherein the at least some of plurality leaves are arranged such that a first section of a leaf body is adjacent to a second section of another leaf body. 6. The multi-leaf collimator of claim 1 wherein the plurality of leaves comprise a first set of leaves having a first greatest thickness and a second set of leaves having a second greatest thickness, said first greatest thickness is smaller than the second greatest thickness. 7. A multi-leaf collimator comprising a support and a plurality of leaves supported by the support, each leaf being movable to allow a selected portion of radiation energy to be blocked, whereby a shape is defined by a portion of radiation energy which is incident at a target, and the shape is controlled by a positioning of the plurality of leaves,wherein at least some of the plurality of leaves comprise a leaf body which includes a first edge portion and a second edge portion, the first edge portion of the leaf body being provided with an elongate recess slidably engaging the support, and the second edge portion of the leaf body being provided with an elongate step slidably engaging the support. 8. The multi-leaf collimator of claim 7 wherein the leaf body comprises a first section including the first edge portion and a second section including the second edge portion, and the first section is thicker than the second section. 9. The multi-leaf collimator of claim 8 wherein the first section of the leaf body is provided with a drive screw adapted to move the leaf body. 10. The multi-leaf collimator of claim 9 wherein the drive screw is provided inside the first section of the leaf body. 11. The multi-leaf collimator of claim 8 wherein the first section of the leaf body has a cross-section in a trapezoidal shape. 12. The multi-leaf collimator of claim 8 wherein the at least some of plurality leaves are arranged such that a first section of a leaf body is adjacent to a second section of another leaf body. 13. The multi-leaf collimator of claim 8 wherein the plurality of leaves comprise a first set of leaves having a first greatest thickness and a second set of leaves having a second greatest thickness, said first greatest thickness is smaller than the second greatest thickness.