Patent Number: 
Section: claims

1. A medical apparatus comprising:a beam deflector having an electromagnet configured to provide a first magnetic field for deflecting a particle beam;a current control configured to adjust a current of the electromagnet in correspondence with an energy level associated with an accelerator, wherein the energy level associated with the accelerator comprises an energy level of an electric field in the accelerator or an energy level of the particle beam; anda permanent magnet configured to provide a second magnetic field, wherein the permanent magnet is implemented as a part of the beam deflector;wherein the first magnetic field and the second magnetic field form a total magnetic field that is variable to have at least a first magnetic field value and a second magnetic field value;wherein the medical apparatus is configured to adjust the total magnetic field in response to the electric field in the accelerator or the energy level of the particle beam; andwherein the medical apparatus is configured to provide the total magnetic field with the first magnetic field value when the electric field in the accelerator or the energy level of the particle beam has a first value, and wherein the medical apparatus is also configured to provide the total magnetic field with the second magnetic field value when the electric field in the accelerator or the energy level of the particle beam has a second value. 2. The apparatus of claim 1, wherein the permanent magnet comprises a rare earth magnet. 3. The apparatus of claim 1, wherein the electromagnet comprises a coil surrounding the permanent magnet. 4. The apparatus of claim 1, further comprising an accelerator for providing the particle beam, the accelerator having an energy switch configured to change the energy level of the particle beam. 5. The apparatus of claim 4, wherein the energy switch is configured to change the energy level of the particle beam within a duration that is less than one second. 6. The apparatus of claim 4, wherein the accelerator comprises a fixed-field alternating gradient (FFAG) accelerator, or a non-scaling fixed-field alternating gradient (NS-FFAG) accelerator. 7. The apparatus of claim 1, further comprising an ion chamber, wherein the ion chamber comprises a dosimetry circuit. 8. The apparatus of claim 7, wherein the control is also configured to adjust a parameter in the dosimetry circuit in correspondence with the energy level associated with the accelerator. 9. The apparatus of claim 1, wherein the electromagnet comprises a laminated steel. 10. The apparatus of claim 1, wherein the current control is configured to increase the current of the electromagnet in correspondence with an increase in the energy level associated with the accelerator. 11. The apparatus of claim 1, wherein the current control is configured to decrease the current of the electromagnet in correspondence with a decrease in the energy level associated with the accelerator. 12. The apparatus of claim 1, wherein the electromagnet comprises a pretzel magnet. 13. The apparatus of claim 1, further comprising a beam output coupled to the beam deflector, wherein the beam output is moveable to deliver treatment energy from a plurality of gantry angles that includes at least a first gantry angle and a second gantry angle. 14. The apparatus of claim 13, further comprising an energy adjuster configured to adjust the treatment energy so that the treatment energy has a first energy level when the beam output is at the first gantry angle, and a second energy level when the beam output is at the second gantry angle. 15. The apparatus of claim 14, wherein the energy adjuster is configured to adjust the treatment energy in a continuous manner. 16. The apparatus of claim 14, wherein the energy adjuster is configured to adjust the treatment energy in a discrete manner. 17. The apparatus of claim 13, further comprising an energy adjuster configured to adjust the treatment energy so that the treatment energy has a first energy level when the beam output is at the first gantry angle, and a second energy level when the beam output is at the first gantry angle. 18. The apparatus of claim 13, wherein the beam output is configured to deliver the treatment energy without using any flattening filter. 19. The medical apparatus of claim 1, wherein the current control is configured to adjust the current of the electromagnet such that a trajectory of the particle beam remains the same regardless of the energy level of the electric field in the accelerator or the energy level of the particle beam. 20. A medical apparatus comprising:an accelerator configured to provide a particle beam;an energy switch configured to change an energy level of the particle beam within a duration that is less than one second; anda target configured to receive the particle beam, wherein the target is a component of the medical apparatus;wherein the accelerator is configured to provide the particle beam directly onto the target without using a beam deflector at an end of the accelerator; andwherein the medical apparatus further comprises a beam output coupled to the accelerator, wherein the beam output is moveable to deliver treatment energy from a plurality of gantry angles that includes at least a first gantry angle and a second gantry angle. 21. The apparatus of claim 20, further comprising an energy adjuster configured to adjust the treatment energy so that the treatment energy has a first energy level when the beam output is at the first gantry angle, and a second energy level when the beam output is at the second gantry angle. 22. The apparatus of claim 21, wherein the energy adjuster is configured to adjust the treatment energy in a continuous manner. 23. The apparatus of claim 21, wherein the energy adjuster is configured to adjust the treatment energy in a discrete manner. 24. The apparatus of claim 20, wherein the beam output is configured to deliver the treatment energy without using any flattening filter. 25. The apparatus of claim 20, wherein the accelerator comprises a fixed-field alternating gradient (FFAG) accelerator, or a non-scaling fixed-field alternating gradient (NS-FFAG) accelerator. 26. The apparatus of claim 20, further comprising an ion chamber, wherein the ion chamber comprises a dosimetry circuit. 27. The apparatus of claim 26, further comprising a control configured to adjust a parameter in the dosimetry circuit in correspondence with the energy level of the particle beam. 28. A treatment method, comprising:configuring a medical system for delivering a first treatment beam having a first energy level;delivering the first treatment beam by the medical system towards a patient that is on a patient support;configuring the medical system for delivering a second treatment beam having a second energy level; anddelivering the second treatment beam by the medical system towards the patient; wherein the act of configuring the medical system for delivering the second treatment beam comprises changing an energy that is associated with an accelerator by an energy switch, and adjusting a current of an electromagnet by a current control in correspondence with the energy associated with the accelerator;wherein the first treatment beam is delivered towards the patient from a first gantry angle, and the second treatment beam is delivered towards the patient from the first gantry angle. 29. The method of claim 28, wherein the medical system comprises an ion chamber, wherein the ion chamber comprises a dosimetry circuit, and wherein the method further comprises adjusting a parameter in the dosimetry circuit in correspondence with the energy associated with the accelerator. 30. The method of claim 28, wherein the act of configuring the medical system, and the act of delivering are performed so that the first treatment beam transitions to the second treatment beam in a continuous manner. 31. The method of claim 28, wherein the act of configuring the medical system, and the act of delivering are performed so that the first treatment beam and the second treatment beam are delivered in a discrete manner.