Patent Number: 
Section: claims

1. A collimator for use in shaping a beam directed along a central axis, comprising:a first assembly, rotatable about said central axis, and having a first and a second jaw movable toward each other and toward said central axis; anda second assembly, positioned between said first assembly and a treatment zone, said second assembly being rotatable about said central axis independently from the rotation of the first assembly about said central axis, and having a third and a fourth jaw movable toward each other and toward said central axis, said third and fourth jaw each having a plurality of independently controllable elements disposed thereon that are individually operable to move toward said central axis,wherein each of said first and said second assemblies and said plurality of independently controllable elements are controllably positionable independently of each other to shape said beam. 2. The device of claim 1, wherein each of said jaws is formed of a radiation attenuating material. 3. The device of claim 1, wherein each of said jaws is formed of a material which has x-ray transmission characteristics of less than or equal to an average of one (1) percent. 4. The device of claim 1, wherein said first assembly is rotatable about said central axis from −180 degrees to +180 degrees. 5. The device of claim 1, wherein said second assembly is rotatable about said central axis from −180 degrees to +180 degrees. 6. The device of claim 1, wherein each of said plurality of elements includes a tongue and groove section for mating with another of said plurality of elements. 7. The device of claim 1, wherein said beam is an X-ray beam. 8. The device of claim 1, wherein said beam is an electron beam. 9. The device of claim 1, wherein said beam has a mixed modality of both X-rays and electrons. 10. A radiation therapy system, comprising:a beam generation device, directing a beam along an axis;a treatment head coupled to a control device, said treatment head having a first and a second radiation blocking device, said first and second radiation blocking devices independently rotatable by said control device about said axis to selectively shape said beam, said second radiation blocking device further comprising:a first jaw and a second jaw, each jaw comprising a plurality of elements disposed thereon that are individually positionable by said control device to move toward each other and toward said axis;wherein each of said first jaw, said second jaw, and said plurality of elements are independently positionable by said control device. 11. The radiation therapy system of claim 10, wherein said second radiation blocking device is positioned between said beam generation device and a treatment table. 12. A radiation therapy system, comprising:a control device, storing radiation treatment data defining a desired treatment plan;a beam generation device, controllable by said control device to deliver a beam along an axis towards a treatment zone;a first radiation blocking device, controllable by said control device to rotate about said axis; anda second radiation blocking device, positioned between said first radiation blocking device and said treatment zone, controllable by said control device to rotate about said axis independently of said first radiation blocking device, said second radiation blocking device comprising a first jaw and a second jaw, each jaw comprising a plurality of independently controllable elements disposed thereon that are individually operable to move toward each other and toward said central axis;wherein said first and said second radiation blocking devices are rotatable about said axis and at least one of said elements are independently controllable to shape said beam according to said radiation treatment data. 13. A radiation therapy method, comprising:establishing a treatment plan;rotating a first and a second radiation blocking device about an axis to produce a portal shape, said second radiation blocking device comprising a pair of jaws independently rotatable of said first radiation blocking device and having a plurality of elements disposed thereon that are individually movable toward each other and toward said axis;adjusting a position of at least one of said plurality of elements to adjust said portal shape according to said treatment plan; anddirecting a radiation beam along said axis toward a treatment zone, said radiation beam shaped by said first and second radiation blocking devices and said plurality of elements of said second radiation blocking device. 14. The radiation therapy method of claim 13, wherein said first and second radiation blocking devices are oriented to conform said portal shape to a shape of said treatment zone. 15. The radiation therapy method of claim 13, wherein said first and second radiation blocking devices are oriented to minimize the effective penumbra of said radiation beam created as said beam passes said first and second radiation blocking devices. 16. The radiation therapy method of claim 13, wherein said first and second radiation blocking devices are oriented to minimize the undulation of said radiation beam created as said beam passes said first and second radiation blocking devices. 17. The radiation therapy method of claim 13, further comprising:further adjusting at least one of said first and second radiation blocking devices after directing said beam. 18. The collimator of claim 1, at least one of said plurality of elements having a top segment, a bottom segment and a tongue-and-groove segment disposed therebetween, to minimize beam leakage and beam edge penumbra of the beam. 19. The radiation therapy system of claim 10, at least one of said plurality of elements having a top segment, a bottom segment and a tongue-and-groove segment disposed therebetween, to minimize beam leakage and beam edge penumbra of the beam. 20. The radiation therapy system of claim 12, at least one of said plurality of elements having a top segment, a bottom segment and a tongue-and-groove segment disposed therebetween, to minimize beam leakage and beam edge penumbra of the beam. 21. The radiation therapy method of claim 13, at least one of said plurality of elements having a top segment, a bottom segment and a tongue-and-groove segment disposed therebetween, to minimize beam leakage and beam edge penumbra of the beam. 22. The collimator of claim 1, wherein said elements are formed to move in an arc toward said central axis, a shape of said arc selected to maintain an end of each of said elements to match a beam edge divergence from a radiation source. 23. The radiation therapy system of claim 10, wherein said elements are formed to move in an arc toward said central axis, a shape of said arc selected to maintain an end of each of said elements to match a beam edge divergence from a radiation source. 24. The radiation therapy system of claim 12, wherein said elements are formed to move in an arc toward said central axis, a shape of said arc selected to maintain an end of each of said elements to match a beam edge divergence from said beam generation device. 25. The method of claim 13, wherein said elements are formed to move in an arc toward said central axis, a shape of said arc selected to maintain an end of each of said elements to match a beam edge divergence from a source of said radiation beam.