Patent Number: 
Section: claims

1. A method for modulating an energy of a particle beam, comprising:providing a first modulator that is located closer to a particle source than a nozzle;providing a second modulator that is located closer to the nozzle than the particle source;operating the first modulator when an energy of the beam is desired to be decreased; andoperating the second modulator when the energy of the beam is desired to be increased. 2. The method of claim 1, further comprising rotating the nozzle relative to a target region, wherein the operation of the first modulator is synchronized with the rotation of the nozzle. 3. The method of claim 2, wherein the operation of the second modulator is synchronized with the rotation of the nozzle. 4. The method of claim 1, wherein the act of operating the first modulator comprises inserting one or more blocks into a path of the particle beam. 5. The method of claim 4, further comprising:determining an amount of energy to be adjusted for the particle beam; andselecting the one or more blocks based on the determined amount of energy to be adjusted. 6. The method of claim 5, wherein the act of selecting the one or more blocks comprises performing a table lookup based on the determined amount of energy to be adjusted. 7. The method of claim 5, wherein the act of selecting the one or more blocks comprises performing a direction calculation. 8. The method of claim 1, wherein the act of operating the second modulator comprises removing one or more blocks from a path of the particle beam. 9. The method of claim 8, further comprising:determining an amount of energy to be adjusted for the particle beam; andselecting the one or more blocks based on the determined amount of energy to be adjusted. 10. The method of claim 9, wherein the act of selecting the one or more blocks comprises performing a table lookup based on the determined amount of energy to be adjusted. 11. The method of claim 1, further comprising providing a shield for protecting a patient from being irradiated by neutrons generated as a result of the operation of the second modulator. 12. The method of claim 1, further comprising cooling a component of the first modulator. 13. The method of claim 1, further comprising cooling a component of the second modulator. 14. The method of claim 1, wherein the first modulator comprises a plurality of blocks, the plurality of blocks having respective thicknesses that form a logarithmic pattern. 15. The method of claim 1, wherein the second modulator comprises a plurality of blocks, the plurality of blocks having respective thicknesses that form a logarithmic pattern. 16. The method of claim 1, wherein the first modulator comprises a first solid block, and the second modulator comprises a second solid block. 17. An energy modulator for use with a collimator and a particle source that provides a beam of particles, comprises:a first solid block moveable between a first position and a second position, wherein when the first solid block is at the first position, it is out of a path of the beam, and wherein when the first solid block is at the second position, it is in the path of the beam; anda second solid block moveable relative to the first block, wherein the second block and the first block are offset from each other in a direction of the beam;wherein the first block has a first energy absorption characteristic, and the second block has a second energy absorption characteristic that is different from the first energy absorption characteristic; andwherein the first solid block and the second solid block are located upstream from the collimator. 18. The energy modulator of claim 17, wherein the first solid block has a first thickness, and the second solid block has a second thickness that is different from the first thickness. 19. The energy modulator of claim 17, wherein the first solid block has a thickness, and the second solid block has a thickness that is two times the thickness of the first solid block. 20. The energy modulator of claim 17, wherein the first solid block is made from a first material, and the second block is made from a second material that is different from the first material. 21. The energy modulator of claim 17, wherein the first solid block is made from a first material and has a first thickness, and the second solid block is made from a second material and has a second thickness, the second material being different from the first material, and the second thickness being different from the first thickness. 22. The energy modulator of claim 17, wherein the first solid block is made from a material that is at least partially transparent to the beam. 23. The energy modulator of claim 17, further comprising a third solid block, wherein the first, second, and third solid blocks are offset relative to each other in a direction of the beam. 24. The energy modulator of claim 23, wherein the first solid block has a first thickness in a direction of the beam, the second solid block has a second thickness in the direction of the beam, and the third solid block has a third thickness in the direction of the beam; andwherein the first thickness, the second thickness, and the third thickness are different from each other. 25. The energy modulator of claim 24, wherein the third solid block has a thickness that is four times the thickness of the first solid block, and the second solid block has a thickness that is two times the thickness of the first solid block. 26. The energy modulator of claim 24, wherein the first thickness, the second thickness, and the third thickness form a non-linear pattern. 27. The energy modulator of claim 17, further comprising a positioner for moving the first solid block. 28. The energy modulator of claim 17, wherein a surface of the first solid block is perpendicular to the beam. 29. The energy modulator of claim 17, further comprising a mounting structure to which the first and the second solid block are slidably mounted. 30. The energy modulator of claim 29, wherein the mounting structure is mounted to a particle delivery system having the particle source, a particle transport system, and a nozzle. 31. The energy modulator of claim 30, wherein the mounting structure is mounted to the particle delivery system such that the mounting structure is closer to the particle source than the nozzle. 32. The energy modulator of claim 17, wherein the first solid block is made from a first material, the second solid block is made from a second material, and the second material has a Z value that is less then a Z value of the first material. 33. The energy modulator of claim 17, further comprising a cooling system coupled to the first solid block, the second solid block, or both. 34. The energy modulator of claim 17, further comprising an energy sensor, and a control coupled to the energy sensor, wherein the control is configured to adjust a position of the first solid block based on a feedback signal provided by the energy sensor. 35. The energy modulator of claim 17, wherein the particle source comprises a proton source. 36. The energy modulator of claim 17, wherein the first solid block and the second solid block are operable to attenuate the beam before the beam reaches the collimator. 37. The energy modulator of claim 17, further comprising a first end coupled to the particle source, and a second end coupled to a beam transport component. 38. The energy modulator of claim 37, wherein the first end is directly coupled to the particle source. 39. A method for modulating an energy of a particle beam, comprising:determining information regarding a desired particle beam energy;providing a set of at least three solid blocks, wherein the at least three solid blocks in the set are offset from each other in a direction of the beam, and are located upstream from a collimator;selecting one or more of the solid blocks from the set to be placed in a path of the beam based on the determined information; andplacing the selected one or more of the solid blocks in the path of the beam. 40. The method of claim 39, wherein the particle beam comprises a proton beam. 41. The method of claim 39, wherein each of the at least three solid blocks in the set has a thickness that is different from the remaining solid blocks in the set. 42. The method of claim 41, wherein one of the solid blocks in the set has a thickness that is two times a thickness of another one of the solid blocks in the set. 43. The method of claim 39, wherein the solid blocks in the set are at least partially transparent to the beam. 44. The method of claim 39, wherein each of the solid blocks has two surfaces that are parallel to each other. 45. The method of claim 39, wherein one of the solid blocks has a Z value that is different from a Z value of another one of the solid blocks. 46. The method of claim 39, further comprising cooling the selected one or more of the solid blocks. 47. The method of claim 46, wherein one of the solid blocks is cooled using liquid, and another one of the solid blocks is cooled using convection. 48. The method of claim 39, wherein the act of determining the information regarding the desired particle beam energy comprises obtaining the information from a treatment plan. 49. The method of claim 39, wherein the act of determining the information regarding the desired particle beam energy comprises:measuring an energy of a delivered beam; anddetermining a difference between the measured energy and a desired energy, wherein the information comprises the determined difference. 50. The method of claim 39, further comprising using the selected one or more of the solid blocks to attenuate the beam before the beam reaches the collimator. 51. The method of claim 50, wherein the set of at least three solid blocks is a part of an energy modulator having a first end and a second end, the first end coupled to a particle source, the second end coupled to a beam transport component; andwherein the method further comprises passing the beam to the transport component after the selected one or more of the solid blocks has been used to attenuate the beam. 52. The method of claim 51, wherein the first end of the energy modulator is directly coupled to the particle source.