Patent Number: 
Section: claims

1. A radiation method, comprising:moving a filter to a first position relative to a radiation source to obtain a first set of image data, the filter having an axis, a first cross sectional shape at a first point along the axis, and a second cross sectional shape at a second point along the axis, the first cross sectional shape being the same as the second cross sectional shape, wherein the filter has end portions that are thicker than a mid portion, the end portions being fixed in position relative to each other, and wherein the filter is made from a material that is partially transparent to radiation; andmoving the filter to a second position relative to the radiation source to obtain a second set of image data;wherein the filter is moved to the first position relative to the radiation source based on a first gantry position of the radiation source; andwherein the radiation source is capable of movement within a plane, and the filter is moved by a positioner to the first position in a direction that is parallel to the plane. 2. The method of claim 1, further comprising rotating the radiation source from the first gantry position to a second gantry position. 3. The method of claim 2, wherein the filter is at the first position when the radiation source is at the first gantry position, and the filter is at the second position when the radiation source is at the second gantry position. 4. The method of claim 2, wherein the acts of moving are performed in synchronization with a rotation of the radiation source. 5. The method of claim 1, wherein the filter is moved relative to the radiation source in a back-and-forth manner. 6. The method of claim 1, wherein the filter is moved to the second position in response to a change in the first gantry position. 7. The radiation method of claim 1, wherein the radiation source is configured to move along a circular path or partial circular path that lies within the plane. 8. An apparatus for modulating an intensity of a radiation beam generated by a radiation source, comprising:a filter made from a material that is partially transparent to radiation, the filter having end portions that are thicker than a middle portion, wherein the end portions are fixed in position relative to each other; anda positioner secured to the filter, the positioner configured to move the filter relative to the radiation source based on a gantry position of the radiation source;wherein the radiation source is capable of movement within a plane, and the positioner is configured to move the filter in a direction that is parallel to the plane. 9. The apparatus of claim 8, wherein the filter has a configuration such that the radiation beam filtered therethrough and passed through an object can be used to create an image having a first region and a second region, the first region having a poorer image quality relative to that of the second region. 10. The apparatus of claim 1, wherein the first region of the image corresponds to one of the end portions of the filter, and the second region of the image corresponds to the middle portion of the filter. 11. The apparatus of claim 1, wherein the second region contains an image of a target region. 12. The apparatus of claim 8, wherein the filter does not include a moveable leaf. 13. The apparatus of claim 8, wherein the filter has an axis, a first cross sectional shape at a first point along the axis, and a second cross sectional shape at a second point along the axis, the first cross sectional shape being the same as the second cross sectional shape. 14. The apparatus of claim 13, wherein the axis of the filter is parallel to an axis of a bore of a radiation machine. 15. The apparatus of claim 13, wherein the axis of the filter is parallel to a longitudinal axis of a patient support. 16. The apparatus of claim 8, wherein a first radiation transmitted through the middle portion of the filter and through a middle portion of an object has an intensity that is higher than an intensity of a second radiation transmitted through one of the end portions of the filter and through a side portion of the object. 17. The apparatus of claim 8, wherein the end portions and the middle portion form a U-shape. 18. The apparatus of claim 8, wherein the filter is configured to filter radiation directed towards an object, the filter having an attenuation profile that does not complement an attenuation pattern of the object. 19. The apparatus of claim 8, wherein the filter is configured to filter radiation directed towards an object such that radiation exciting the object has an intensity that is non-uniform. 20. The apparatus of claim 8, wherein the positioner is configured to move the filter relative to the radiation source based also on a position of an object to which the radiation beam is being directed. 21. The apparatus of claim 8, wherein the positioner is configured to move the filter relative to the radiation source in a back-and-forth manner. 22. The apparatus of claim 8, wherein the positioner is configured to move the filter relative to the radiation source in synchronization with a rotation of the radiation source. 23. The apparatus of claim 8, further comprising the radiation source, wherein the radiation source is located next to a gantry opening, the opening having an axis. 24. The apparatus of claim 23, wherein at least a portion of the filter has a cross sectional shape that is uniform along a direction of the axis. 25. The apparatus of claim 23, wherein the positioner is configured to move the filter relative to the radiation source in a direction that forms an angle with the axis. 26. The apparatus of claim 8, wherein the radiation source is configured to move along a circular path or partial circular path that lies within the plane. 27. A radiation method, comprising:moving a filter to a first position relative to a radiation source to obtain a first set of image data, wherein the filter is made from a material that is partially transparent to radiation, the filter having end portions that are thicker than a middle portion, wherein the end portions are fixed in position relative to each other; andmoving the filter to a second position relative to the radiation source to obtain a second set of image data;wherein the filter is moved to the first position relative to the radiation source based on a first gantry position of the radiation source, and the filter is moved to the second position relative to the radiation source based on a second gantry position of the radiation source; andwherein the radiation source is capable of movement within a plane, and the filter is moved by a positioner to the first position in a direction that is parallel to the plane. 28. The method of claim 27, wherein the filter is configured to filter radiation directed towards an object, the filter having an attenuation profile that does not complement an attenuation pattern of the object. 29. The method of claim 27, wherein the filter is configured to filter radiation directed towards an object such that radiation exciting the object has an intensity that is non-uniform. 30. The method of claim 27, wherein the acts of moving the filter comprise moving the filter relative to the radiation source in a back-and-forth manner. 31. The method of claim 27, wherein the acts of moving the filter are performed in synchronization with a rotation of the radiation source. 32. The radiation method of claim 27, wherein the radiation source is configured to move along a circular path or partial circular path that lies within the plane. 33. An apparatus for modulating an intensity of a radiation beam generated by a radiation source that is configured to move within a plane, comprising:a filter made from a material that is partially transparent to radiation; anda positioner secured to the filter, the positioner configured to move the filter relative to the radiation source in a direction based on a gantry position of the radiation source, wherein the direction is parallel to the plane;wherein the filter has end portions that are thicker than a middle portion, the end portions being incapable of movement relative to each other. 34. The apparatus of claim 33, wherein the filter has a center portion, a first end portion, and a second end portion, the first and the second end portions having respective thicknesses that are larger than a thickness of the center portion. 35. The apparatus of claim 34, wherein the thickness of each of the first and the second end portions is selected such that an intensity of the radiation beam exiting a patient is approximately uniform. 36. The apparatus of claim 34, wherein the thickness of each of the first and the second end portions is selected such that an intensity of the radiation beam exiting a patient is substantially non-uniform. 37. The apparatus of claim 33, further comprising a processor for controlling an operation of the positioner. 38. The apparatus of claim 37, wherein the processor is configured to cause the filter to move relative to the radiation source in a back-and-forth manner. 39. The apparatus of claim 37, wherein the processor is configured to cause the filter to move relative to the radiation source in synchronization with a rotation of a gantry to which the radiation source is mounted. 40. The apparatus of claim 33, further comprising a processor programmed to transmit a signal for instructing the positioner to move the filter based on a relative position between the radiation source and an object that is being imaged. 41. The apparatus of claim 33, wherein the filter has an attenuation profile that does not complement an attenuation pattern of an object that is being imaged. 42. The apparatus of claim 33, wherein the radiation source is configured to move in a circular path or partial circular path that lies within the plane. 43. A computer program product that includes a medium, the medium having a set of instruction, an execution of which by a processor causes a process to be performed, the process comprising:sending a signal to move a filter in a direction relative to a radiation source based on a gantry position of the radiation source, the radiation source configured to move within a plane, wherein the direction is parallel to the plane;wherein the filter has end portions that are thicker than a middle portion, the end portions being incapable of movement relative to each other. 44. The computer program of claim 43, wherein the signal is for causing the filter to move relative to the radiation source in synchronization with the gantry position of the radiation source. 45. The computer program product of claim 43, wherein the process further comprises sending another signal to move the filter in another direction that is opposite to the direction. 46. The computer program product of claim 43, wherein the radiation source is configured to move along a circular path or partial circular path that lies within the plane. 47. The method of claim 1, wherein the first set of image data comprises an image having a first region and a second region, the first region having a poorer image quality relative to that of the second region.