SCANNING SYSTEM

• US 20150231411A1
• Filed: 02/20/2014
• Published: 08/20/2015
• Est. Priority Date: 02/20/2014
• Status: Active Grant

• Current Assignee: Mevion Medical Systems Incorporated
• Original Assignee: Mevion Medical Systems Incorporated
• Inventors: O'Neal, Charles D. III, Molzahn, Adam C.
• Granted Patent: US 9,661,736 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61N 2005/1085 characterised by the type of particles applied to the patient
• CPC Class Codes: A61N 2005/1087 Ions; Protons
• CPC Class Codes: A61N 5/103 Treatment planning systems
• CPC Class Codes: A61N 5/1043 Scanning the radiation beam, e.g. spot scanning or raster scanning
• CPC Class Codes: A61N 5/1048 Monitoring, verifying, controlling systems and methods
• CPC Class Codes: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam
• CPC Class Codes: A61N 5/1065 Beam adjustment
• CPC Class Codes: A61N 5/1067 in real time, i.e. during treatment
• CPC Class Codes: A61N 5/1071 for verifying the dose delivered by the treatment plan
• CPC Class Codes: A61N 5/1081 Rotating beam systems with a specific mechanical construction, e.g. gantries
• CPC Class Codes: H05H 13/02 Synchrocyclotrons, i.e. frequency modulated cyclotrons
• CPC Class Codes: H05H 13/04 Synchrotrons
• CPC Class Codes: H05H 2007/002 for modifying beam trajectory, e.g. gantries
• CPC Class Codes: H05H 2007/004 for modifying beam energy, e.g. spread out Bragg peak devices
• CPC Class Codes: H05H 2007/048 for modifying beam trajectory, e.g. gantry systems
• CPC Class Codes: H05H 7/04 Magnet systems , e.g. undulators, wigglers free-electron laser H01S3/0903; Energisation thereof

Abstract

An example particle therapy system includes: a particle accelerator to output a beam of charged particles; and a scanning system to scan the beam across at least part of an irradiation target. An example scanning system includes: a scanning magnet to move the beam during scanning; and a control system (i) to control the scanning magnet to produce uninterrupted movement of the beam over at least part of a depth-wise layer of the irradiation target so as to deliver doses of charged particles to the irradiation target; and (ii) to determine, in synchronism with delivery of a dose, information identifying the dose actually delivered at different positions along the depth-wise layer.

Claims

1. A particle therapy system comprising:

a particle accelerator to output a beam of charged particles; and

a scanning system to scan the beam across at least part of an irradiation target, the scanning system comprising;

a scanning magnet to move the beam during scanning, where a position of the beam corresponds to a current of the scanning magnet; and

a control system (i) to control the current in order to produce uninterrupted movement of the beam across at least part of an irradiation target to deliver doses of charged particles, (ii) for positions at which the particle beam delivers dose, to store information identifying a location and an amount of dose delivered, (iii) to compare a cumulative dose delivered at each position to a target cumulative dose, and (iv) if the cumulative dose does not match the target cumulative dose at specific positions, control the current in order to move the beam so as to deliver additional dose to the specific positions.

2. The particle therapy system of claim 1, wherein the particle accelerator is configured to output pulses of charged particles in accordance with a radio frequency (RF) cycle, the pulses of charged particles forming the beam;

and

wherein movement of the beam across the at least part of an irradiation target is not dependent upon the RF cycle.

3. The particle therapy system of claim 2, wherein the control system is configured to measure the cumulative dose delivered at each position;

and

wherein measuring is substantially synchronous with the RF cycle.

4. The particle therapy system of claim 2, wherein the control system is configured to measure the cumulative dose delivered at each position;

and

wherein measuring is substantially synchronous with delivery of dose at each position.

5. The particle therapy system of claim 1, wherein the information comprises an amount of dose delivered at each position and at least one of:

a location of each position within the irradiation target or a magnet current corresponding to each position within the irradiation target.

6. The particle therapy system of claim 1, wherein the location corresponds to three-dimensional coordinates within the irradiation target.

7. The particle therapy system of claim 1, wherein the particle therapy system further comprises:

memory to store a treatment plan that identifies, for each position, a target cumulative dose of the particle beam, the treatment plan omitting information about individual doses delivered to individual positions during scanning.

8. The particle therapy system of claim 1, wherein the scanning system further comprises:

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

wherein the control system is configured to control movement of at least part of the degrader into, or out of, a path of the beam in order to affect the energy of the beam and thereby set a layer of the irradiation target to which charged particles are to be delivered.

9. The particle therapy system of claim 8, wherein the particle accelerator comprises an ion source to provide plasma from which pulses in the beam are extracted;

and

wherein, during at least part of the movement of the degrader, the ion source is deactivated.

10. The particle therapy system of claim 8, wherein the particle accelerator comprises:

an ion source to provide plasma from which pulses in the beam are extracted; and

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

wherein, during at least part of the movement of the degrader, the voltage source is deactivated.

11. The particle therapy system of claim 10, wherein, during the at least part of the movement of the degrader, the particle source is deactivated at a same time that the voltage source is deactivated.

12. The particle therapy system of claim 1, wherein the particle accelerator is a variable-energy particle accelerator;

and

wherein the control system is configured to set an energy level of the particle accelerator prior to scanning.

13. The particle therapy system of claim 1, wherein the particle accelerator is a variable-energy particle accelerator;

and

wherein the control system is configured to set an energy level of the particle accelerator during scanning.

14. The particle therapy system of claim 1, wherein, for a position at which the particle beam delivers dose, each individual delivery of dose is a percentage of the total cumulative dose.

15. The particle therapy system of claim 14, wherein the percentage is less than 100% of the total cumulative dose.

16. The particle therapy system of claim 14, wherein the percentage is about 100% of the total cumulative dose.

17. The particle therapy system of claim 1, wherein the scanning magnet has an air core.

18. The particle therapy system of claim 1, wherein the scanning magnet has a ferromagnetic core.

19. A particle therapy system comprising:

a particle accelerator to output a beam of charged particles; and

a scanning system to scan the beam across at least part of an irradiation target, the scanning system comprising;

a scanning magnet to move the beam during scanning; and

a control system (i) to control the scanning magnet to produce uninterrupted movement of the beam over at least part of a depth-wise layer of the irradiation target so as to deliver doses of charged particles to the irradiation target; and

(ii) to determine, in synchronism with delivery of a dose, information identifying the dose actually delivered at different positions along the depth-wise layer.

20. The particle therapy system of claim 19, wherein the particle accelerator is configured to output pulses of charged particles in accordance with a radio frequency (RF) cycle, the pulses of charged particles forming the beam;

and

wherein movement of the beam is not dependent upon the RF cycle.

21. A particle therapy system comprising:

a particle accelerator to output a beam of charged particles; and

a scanning system to scan the beam across at least part of an irradiation target, the scanning system comprising;

a scanning magnet to move the beam during scanning, where a position of the beam corresponds to a current of the scanning magnet; and

an open loop control system (i) to control the current to produce uninterrupted movement of the particle beam across at least part of a layer of an irradiation target, (ii) to record, in synchronism with delivery, doses of the particle beam delivered to the irradiation target and at least one of;

coordinates at which the doses were delivered or magnet currents at which the doses were delivered, and (iii) to compensate for deficiencies in the recorded doses relative to corresponding target cumulative doses.

22. The particle therapy system of claim 21, wherein the particle accelerator 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 for 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 towards the scanning system; 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 20T and the magnetic field bump is at most 2 Tesla; and

wherein the uninterrupted movement of the particle beam across the at least part of the layer of the irradiation target is not dependent upon the RF frequency.

23. The particle therapy system of claim 21, wherein the scanning magnet comprises an air core;

and

wherein the particle therapy system further comprises;

a gantry on which the particle accelerator and the scanning system are mounted, the gantry being configured to move the particle accelerator and the scanning system around the irradiation target;

wherein the current of the scanning magnet is adjusted based on a position of the gantry.

24. The particle therapy system of claim 21, wherein the particle accelerator is a synchrocyclotron.

25. The particle therapy system of claim 21, wherein uninterrupted movement of the particle beam occurs across an entirety of the layer.

26. The particle therapy system of claim 21, wherein uninterrupted movement of the particle beam occurs across less than an entirety of the layer.

27. The particle therapy system of claim 21, further comprising:

a current sensor associated with the scanning magnet;

wherein recording coordinates at which the doses were delivered comprises sampling an output of the current sensor and correlating the output to coordinates;

wherein the particle therapy system further comprises an ionization chamber between the scanning magnet and the irradiation target; and

wherein recording doses of the particle beam delivered to the irradiation target comprises sampling an output of the ionization chamber for each dose.