CONTROLLING INTENSITY OF A PARTICLE BEAM

• US 20140094638A1
• Filed: 09/27/2013
• Published: 04/03/2014
• Est. Priority Date: 09/28/2012
• Status: Active Grant

• Current Assignee: Mevion Medical Systems Incorporated
• Original Assignee: Mevion Medical Systems Incorporated
• Inventors: Gall, Kenneth P., Zwart, Gerrit Townsend, Van der Laan, Jan, Molzahn, Adam C., O'Neal, Charles D. III, Sobczynski, Thomas C., Cooley, James
• Granted Patent: US 9,723,705 B2
• Time in Patent Office: Days
• US Class Current: 600/1
• CPC Class Codes: A61N 2005/1087 Ions; Protons
• CPC Class Codes: A61N 5/1077 Beam delivery systems
• CPC Class Codes: H05H 13/02 Synchrocyclotrons, i.e. frequency modulated cyclotrons
• CPC Class Codes: H05H 2007/082 Ion sources, e.g. ECR, duoplasmatron, PIG, laser sources
• CPC Class Codes: H05H 2007/122 by electromagnetic means, e.g. RF cavities
• CPC Class Codes: H05H 7/02 Circuits or systems for supplying or feeding radio-frequency energy radio-frequency generators H03B
• CPC Class Codes: H05H 7/12 Arrangements for varying final energy of beam

Abstract

In an example, a synchrocyclotron includes a particle source to provide pulses of ionized plasma to a cavity; a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly; and an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator. The particle source is configured to control pulse widths of the ionized plasma in order to control an intensity of the beam of particles. This example synchrocyclotron may include one or more of the following features, either alone or in combination.

Claims

1. A synchrocyclotron comprising:

a particle source to provide pulses of ionized plasma to a cavity;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly; and

an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator;

wherein the particle source is configured to control pulse widths of the ionized plasma in order to control an intensity of the beam of particles.

2. The synchrocyclotron of claim 1, wherein the particle source is configured to activate for a period of time in response to a control signal, where the particle source generates a pulse of ionized plasma when activated.

3. The synchrocyclotron of claim 1, wherein the particle source is configured to generate pulses of ionized plasma periodically.

4. The synchrocyclotron of claim 3, wherein the particle beam is output for a duration of about 0.1 μ

s to 100 μ

s.

5. The synchrocyclotron of claim 3, wherein the particle beam is output for a duration of about 0.1 μ

s to 100 μ

s about every 2 ms.

6. The synchrocyclotron of claim 1, wherein the particle source comprises cathodes to provide voltage to ionize hydrogen to produce the ionized plasma, the cathodes being unheated by an external source.

7. A proton therapy system comprising:

the synchrocyclotron of claim 1; and

a gantry on which the synchrocyclotron is mounted, the gantry being rotatable relative to a patient position;

wherein protons are output essentially directly from the synchrocyclotron to the patient position.

8. A synchrocyclotron comprising:

a particle source to provide pulses of ionized plasma to a cavity, the particle source comprising cathodes to provide voltage to ionize hydrogen to produce the ionized plasma;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly; and

an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator;

wherein a voltage associated with the cathodes is controllable in order to control an intensity of the beam of particles.

9. The synchrocyclotron of claim 8, wherein the cathodes are unheated by an external source.

10. The synchrocyclotron of claim 8, wherein the voltage is controllable such that increasing the voltage increases an intensity of the beam of particles and such that decreasing the voltage decreases the intensity of the beam of particles.

11. A proton therapy system comprising:

the synchrocyclotron of claim 8; and

a gantry on which the synchrocyclotron is mounted, the gantry being rotatable relative to a patient position;

wherein protons are output essentially directly from the synchrocyclotron to the patient position.

12. A synchrocyclotron comprising:

a particle source to provide pulses of ionized plasma to a cavity, the particle source comprising cathodes to provide voltage to ionize hydrogen to produce the ionized plasma;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly; and

an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator;

wherein the particle source is controllable to adjust an amount of the hydrogen between the cathodes in order to control an intensity of the beam of particles.

13. The synchrocyclotron of claim 12, wherein the cathodes are unheated by an external source.

14. The synchrocyclotron of claim 12, wherein the amount of hydrogen is adjustable such that increasing the amount of hydrogen increases an intensity of the beam of particles and such that decreasing the amount of hydrogen decreases the intensity of the beam of particles.

15. A proton therapy system comprising:

the synchrocyclotron of claim 12; and

a gantry on which the synchrocyclotron is mounted, the gantry being rotatable relative to a patient position;

wherein protons are output essentially directly from the synchrocyclotron to the patient position.

16. A synchrocyclotron comprising:

a particle source to provide pulses of ionized plasma to a cavity;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly; and

an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator;

wherein the voltage source is controllable to control the RF voltage rate in order to control an intensity of the beam of particles.

17. The synchrocyclotron of claim 16, wherein the particle source comprises cathodes to provide voltage to ionize hydrogen to produce the ionized plasma, the cathodes being unheated by an external source.

18. The synchrocyclotron of claim 16, wherein a magnitude of the RF voltage is adjustable such that increasing the magnitude increases an intensity of the beam of particles and such that decreasing the magnitude decreases the intensity of the beam of particles.

19. A proton therapy system comprising:

the synchrocyclotron of claim 16; and

a gantry on which the synchrocyclotron is mounted, the gantry being rotatable relative to a patient position;

wherein protons are output essentially directly from the synchrocyclotron to the patient position.

20. A synchrocyclotron comprising:

a particle source to provide pulses of ionized plasma to a cavity;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly, the RF voltage sweeping between a maximum frequency and a minimum frequency; and

an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator;

wherein the particle source is controllable to provide pulses of the ionized plasma at specific frequencies proximate to a decrease from the maximum frequency of the RF voltage to the minimum frequency of the RF voltage.

21. The synchrocyclotron of claim 20, wherein the particle accelerator is controllable to provide pulses of the ionized plasma between 132 MHz of RF voltage and 131 MHz of RF voltage from a decrease from a maximum frequency of about 135 MHz of the RF voltage.

22. The synchrocyclotron of claim 21, wherein the particle source comprises cathodes to provide voltage to ionize hydrogen to produce the ionized plasma, the cathodes being unheated by an external source.

23. A proton therapy system comprising:

the synchrocyclotron of claim 20; and

a gantry on which the synchrocyclotron is mounted, the gantry being rotatable relative to a patient position;

wherein protons are output essentially directly from the synchrocyclotron to the patient position.

24. A synchrocyclotron comprising:

a particle source to provide pulses of ionized plasma to a cavity;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly; and

an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator;

wherein the particle source is configured to selectively output pulses of the ionized plasma in order to control an intensity of the beam of particles.

25. The synchrocyclotron of claim 24, wherein the RF voltage sweeps periodically from a maximum frequency to a minimum frequency;

and

wherein selectively outputting the pulses comprises outputting pulses in certain ones of the RF voltage sweeps and not in others of the RF voltage sweeps.

26. The synchrocyclotron of claim 24, wherein the RF voltage sweeps periodically from a maximum frequency to a minimum frequency;

and

wherein selectively outputting the pulses comprises skipping pulse output in every N^th (N>

1) sweep.

27. The synchrocyclotron of claim 24, further comprising a controller for performing operations comprising:

determining the intensity of the beam of particles; and

selectively outputting the pulses based on the determined intensity.

28. A proton therapy system comprising:

the synchrocyclotron of claim 24; and

a gantry on which the synchrocyclotron is mounted, the gantry being rotatable relative to a patient position;

wherein protons are output essentially directly from the synchrocyclotron to the patient position.

29. A synchrocyclotron comprising:

a particle source to provide pulses of ionized plasma to a cavity;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly; and

an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator;

wherein the voltage source is configurable to vary a slope of the RF voltage in order to control an intensity of the beam of particles.

30. A proton therapy system comprising:

the synchrocyclotron of claim 29; and

a gantry on which the synchrocyclotron is mounted, the gantry being rotatable relative to a patient position;

wherein protons are output essentially directly from the synchrocyclotron to the patient position.

31. A synchrocyclotron comprising:

a particle source to provide pulses of ionized plasma to a cavity;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly, the voltage source comprising a first dee and a second dee, wherein at least one of the first dee and the second dee has a bias voltage applied thereto; and

an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator.

32. The synchrocyclotron of claim 31, wherein the first dee has first bias voltage applied thereto and the second dee has a second bias voltage applied thereto, the first bias voltage being different from the second bias voltage.

33. The synchrocyclotron of claim 31, wherein the first dee has the bias voltage applied thereto and the second dee is electrically grounded.

34. A proton therapy system comprising;

the synchrocyclotron of claim 31; and

a gantry on which the synchrocyclotron is mounted, the gantry being rotatable relative to a patient position;

wherein protons are output essentially directly from the synchrocyclotron to the patient position.

35. A particle therapy system comprising:

a synchrocyclotron to output a particle beam comprised of pulses; and

a scanning system for the synchrocyclotron to scan the particle beam across at least part of an irradiation target, the scanning system being configured to scan the particle beam in two dimensions that are angled relative to a longitudinal direction of the particle beam, the particle beam making a spot at the irradiation target;

wherein the synchrocyclotron is controllable to vary a width of the pulses so as to vary an intensity of the particle beam between different spots on the irradiation target during scanning.

36. The synchrocyclotron of claim 35, wherein the synchrocyclotron comprises a particle source, and wherein the particle source is controllable to activate for periods of time to generate pulses that vary in width.

37. The synchrocyclotron of claim 35, wherein the synchrocyclotron is configured to sweep between low and high voltages, and wherein a rate of the voltage sweep is controllable to vary a width of the pulses.

38. The synchrocyclotron of claim 35, wherein the synchrocyclotron comprises a particle source comprising first and second cathodes to generate a plasma stream from a gas, the pulses of particle beam being extractable from the plasma stream;

wherein the gas comprises a combination of hydrogen and less than 25% of a noble gas.

39. The synchrocyclotron of claim 35, wherein the gas comprises a combination of hydrogen and less than 10% of a noble gas.

40. The synchrocyclotron of claim 35, wherein the gas comprises a combination of hydrogen and helium.

41. The synchrocyclotron of claim 40, wherein the helium comprises less than 25% of a composition of the gas.

42. The synchrocyclotron of claim 41, wherein the helium comprises less than 10% of a composition of the gas.

43. The particle therapy system of claim 35, wherein the scanning system comprises:

a magnet to affect a direction of the particle beam to scan the particle beam in the two dimensions across at least part of the irradiation target; and

a degrader to change an energy of the beam prior to output of the particle beam to the irradiation target, the degrader being down-beam of the magnet relative to the synchrocyclotron.

44. The particle therapy system of claim 35, wherein the synchrocyclotron comprises:

a voltage source to provide a radio frequency (RF) voltage to a cavity to accelerate particles from a plasma column, the cavity having a magnetic field causing particles accelerated from the plasma column to move orbitally within the cavity;

an extraction channel to receive the particles accelerated from the plasma column and to output the received particles from the cavity; and

a regenerator to provide a magnetic field bump within the cavity to thereby change successive orbits of the particles accelerated from the plasma column so that, eventually, particles output to the extraction channel;

wherein the magnetic field is between 4 Tesla (T) and 20 T and the magnetic field bump is at most 2 Tesla.