Patent Number: 
Section: claims

1. A multiple layer multileaf collimator capable of improving resolution for coverage of a target during radiation therapy, the multiple layer multileaf collimator comprising: a first layer of multiple elongated radiation blocking leaves supported by a first frame for individual leaf positioning in a first direction; and  a second layer of multiple elongated radiation blocking leaves supported by a second frame for individual leaf positioning in a second direction, the second direction offset at a desired angle x, where 0xc2x0xe2x89xa6xxe2x89xa690xc2x0, relative to the first direction to achieve an arrangement of the first layer and second layer that ranges from parallel to perpendicular through rotation of the second layer relative to the first layer, wherein the individual leaves of the first and second layers conform more closely with a target shape to improve resolution. 2. The multiple layer multileaf collimator of  claim 1  wherein the second layer is positioned above the first layer. claim 1 3. The multiple layer multileaf collimator of  claim 2  wherein the second layer provides leakage coverage for the multiple elongated radiation blocking leaves of the first layer. claim 2 4. The multiple layer multileaf collimator of  claim 1  wherein the desired angle comprises an angle of about 90xc2x0. claim 1 5. The multiple layer multileaf collimator of  claim 1  further comprising a plurality of motor means with the first and second frames for the individual leaf positioning of the first and second layers. claim 1 6. The multiple layer multileaf collimator of  claim 1  wherein the first layer further comprises two opposing arrays of elongated radiation blocking leaves. claim 1 7. The multiple layer multileaf collimator of  claim 1  wherein the second layer further comprises two opposing arrays of elongated radiation blocking leaves. claim 1 8. A radiation emitting device with improved resolution coverage for a target during radiation therapy, the radiation emitting device comprising: a radiation source for providing a radiation beam; and  a collimator for shaping the radiation beam, the collimator comprising a first layer of multiple elongated radiation blocking leaves supported by a first frame for individual leaf positioning in a first direction, and a second layer of multiple elongated radiation blocking leaves supported by a second frame for individual leaf positioning in a second direction, the second direction offset at a desired angle x, where 0xc2x0xe2x89xa6xxe2x89xa690xc2x0, relative to the first direction to achieve an arrangement of the first layer and second layer that ranges from parallel to perpendicular through rotation of the second layer relative to the first layer, wherein the individual leaves of the first and second layers conform more closely with a target shape to improve resolution. 9. The radiation emitting device of  claim 8  wherein the second layer is positioned above the first layer. claim 8 10. The radiation emitting device of  claim 9  wherein the second layer provides leakage coverage for the multiple elongated radiation blocking leaves of the first layer. claim 9 11. The radiation emitting device of  claim 8  wherein the desired angle comprises an angle of about 90xc2x0. claim 8 12. The radiation emitting device of  claim 8  further comprising a plurality of motor means with the first and second frames for the individual positioning of the multiple elongated radiation blocking leaves of the first and second layers. claim 8 13. The radiation emitting device of  claim 8  wherein the first layer further comprises two opposing arrays of elongated radiation blocking leaves. claim 8 14. The radiation emitting device of  claim 8  wherein the second layer further comprises two opposing arrays of elongated radiation blocking leaves. claim 8 15. A method for improving resolution of coverage of a target during radiation therapy by a radiation emitting device, the method comprising: providing a first pair of opposing multiple elongated radiation blocking leaves in a first plane within a collimator of the radiation emitting device; and  providing a second pair of opposing multiple elongated radiation blocking leaves in a second plane within the collimator, the second pair being rotatable to within a desired angular offset relative to the first pair to achieve an arrangement of the first pair and second pair that ranges from parallel to perpendicular, wherein the first and second pairs more closely conform with a target shape while avoiding leakage between the multiple elongated radiation blocking leaves. 16. The method of  claim 15  wherein the second pair is rotatable to within approximately 0xc2x0 and 90xc2x0 of the first pair. claim 15 17. The method of  claim 15  wherein the first plane is below the second plane. claim 15