Source: http://www.google.com/patents/US7943913?dq=5,581,513
Timestamp: 2016-08-25 06:32:14
Document Index: 658511028

Matched Legal Cases: ['application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61', 'application No. 61']

Patent US7943913 - Negative ion source method and apparatus used in conjunction with a charged ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsThe invention comprises a negative ion source method and apparatus used as part of an ion beam injection system, which is used in conjunction with multi-axis charged particle or proton beam radiation therapy of cancerous tumors. The negative ion source preferably includes an inlet port for injection...http://www.google.com/patents/US7943913?utm_source=gb-gplus-sharePatent US7943913 - Negative ion source method and apparatus used in conjunction with a charged particle cancer therapy systemAdvanced Patent SearchPublication numberUS7943913 B2Publication typeGrantApplication numberUS 12/567,901Publication dateMay 17, 2011Filing dateSep 28, 2009Priority dateMay 22, 2008Fee statusPaidAlso published asUS20100014639Publication number12567901, 567901, US 7943913 B2, US 7943913B2, US-B2-7943913, US7943913 B2, US7943913B2InventorsVladimir BalakinOriginal AssigneeVladimir BalakinExport CitationBiBTeX, EndNote, RefManPatent Citations (170), Non-Patent Citations (25), Referenced by (34), Classifications (12), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetNegative ion source method and apparatus used in conjunction with a charged particle cancer therapy system
US 7943913 B2Abstract
The invention comprises a negative ion source method and apparatus used as part of an ion beam injection system, which is used in conjunction with multi-axis charged particle or proton beam radiation therapy of cancerous tumors. The negative ion source preferably includes an inlet port for injection of hydrogen gas into a high temperature plasma chamber. In one embodiment, the plasma chamber includes a magnetic material, which provides a magnetic field barrier between the high temperature plasma chamber and a low temperature plasma region on the opposite side of the magnetic field barrier. An extraction pulse is applied to a negative ion extraction electrode to pull the negative ion beam into a negative ion beam path, which proceeds through a first partial vacuum system, through an ion beam focusing system, into the tandem accelerator, and into a synchrotron.
1. An apparatus for injecting a charged particle beam into an accelerator of an irradiation device, said irradiation device irradiating a tumor during use, said apparatus comprising:
a negative ion source, said negative ion source configured to produce negative ions in a negative ion beam path, said negative ion source comprising a magnetic field barrier across a gap separating a high energy plasma chamber from a low temperature plasma zone;
an ion beam focusing lens configured to focus the negative ions; and
a converting foil, said converting foil converting the negative ions into the charged particle beam.
a first ion generation electrode at a first end of said high energy plasma chamber; and
a second ion generation electrode at a second end of said high energy plasma chamber,
wherein application of a first high voltage pulse across said first ion generation electrode and said second ion generation electrode breaks hydrogen in said high energy plasma chamber into component parts.
a third ion generation electrode, wherein application of a second high voltage pulse across said second ion generation electrode and said third ion generation electrode extracts the negative ions from the low temperature plasma zone to form extracted negative ions in said negative ion beam path.
a magnet centrally located within said negative ion source;
a first ion generation electrode on a first side of said high energy plasma chamber;
a second ion generation electrode on a second side of said high energy plasma chamber; and
a magnetic field carrying outer wall running about parallel said magnet,
said magnet generating a magnetic field loop running through said first ion generation electrode, through said magnetic field carrying outer wall, through said second ion generation electrode, across said gap, and through said magnet.
coils wrapped around said high energy plasma chamber, said coils configured to carry a current during use producing the magnetic field barrier.
6. The apparatus of claim 1, said ion beam focusing lens further comprising:
a focusing electrode circumferentially surrounding the negative ion beam path; and
metal conductive paths at least partially blocking the negative ion beam path,
wherein electric field lines run between said focusing electrode and said metal conductive paths, and
wherein the negative ions encounter force vectors running up the electric field lines that focus the negative ions.
7. The apparatus of claim 1, wherein said converting foil provides a particle vacuum pressure seal between an ion beam formation side of said irradiation device and a synchrotron side of said irradiation device, wherein a first pump system operates to maintain a first vacuum in said ion beam formation side of said converting foil, wherein a second pump system operates to maintain a second vacuum in said synchrotron side of said irradiation device.
8. A method for injecting a charged particle beam into an accelerator of an irradiation device, said irradiation device irradiating a tumor during use, said method comprising the steps of:
generating negative ions in a negative ion source, said negative ion source comprising a magnetic field barrier separating a high energy plasma region from a low temperature plasma zone;
extracting the negative ions from said negative ion source;
focusing said negative ions using an ion beam focusing lens; and
converting the negative ions into the charged particle beam with a converting foil.
applying a first high voltage pulse across a first ion generation electrode at a first end of a high energy plasma region and a second ion generation electrode at a second end of said high energy plasma region,
wherein the first high voltage pulse breaks hydrogen in said high energy plasma region into component parts.
applying a second high voltage pulse across said second ion generation electrode and a third ion generation electrode to extract negative ions formed in the low temperature plasma zone resulting in formation of the negative ion beam.
11. The method of claim 8, further comprising the step of:
focusing the negative ion beam using electric field lines running between a first focusing electrode circumferentially surrounding the negative ion beam path and metal conductive paths at least partially blocking the negative ion beam path.
converting the negative ions into positively charged particles using a conversion foil, said conversion foil comprising a beryllium carbon film, wherein said carbon film comprises a thickness of about thirty to two hundred micrometers.
13. An apparatus for generating ions, said ions used in an irradiation device for treatment of a tumor during use, said apparatus comprising:
a negative ion source, said negative ion source comprising:
a second ion generation electrode at a second end of said high temperature plasma chamber;
means for generating a magnetic field barrier separating said high temperature plasma chamber from a low temperature plasma zone, wherein said magnetic barrier selectively passes elements of plasma in said high temperature plasma chamber to said low temperature plasma zone, wherein low energy electrons interact with atomic hydrogen to create hydrogen anions in said low temperature plasma zone; and
an electrode configured to apply a high voltage pulse across said low temperature plasma zone to extract the hydrogen anions from said negative ion source as a negative ion beam.
14. The apparatus of claim 13, wherein said means for generating a magnetic field barrier comprises a magnetic material generating said magnetic field barrier, said magnetic material at least partially located inside said high temperature plasma chamber.
an ion beam focusing lens, said ion beam focusing lens comprising:
metal conductive paths traversing the negative ion beam; and
a focusing electrode circumferentially surrounding the negative ion beam,
wherein the negative ion beam encounters force vectors running up the electric field lines, said force vectors focusing the negative ion beam.
a converting foil traversing the negative ion beam, said converting foil converting the negative ion beam into a positively charged ion beam, said converting foil forming a portion of a vacuum barrier between said negative ion source and a synchrotron portion of said irradiation device.
a converting foil partially blocking the negative ion beam, wherein said converting foil comprises a beryllium carbon film, wherein said carbon film comprises a thickness of about thirty to two hundred micrometers.
18. A method for generating ions, said ions used in an irradiation device for treatment of a tumor during use, said method comprising the steps of:
generating a magnetic field barrier between a high temperature plasma region and a low temperature plasma zone in a negative ion source; and
applying a high voltage pulse across the low temperature plasma zone, said pulse extracting the ions from said negative ion source.
converting the ions into positively charged particles at a converting foil, said converting foil forming a portion of a vacuum barrier between said negative ion source and a synchrotron.
controlling intensity of an extracted charged particle beam from said synchrotron using an induced current resulting from the charged particle beam passing through an extraction material.
imaging the tumor using an X-ray source located within about twenty millimeters of the extracted charged particle beam from said synchrotron,
rotating the patient on a rotatable platform to at least ten positions within a period of less than one minute during a single irradiation period of the tumor.
varying energy of the extracted charged particle beam simultaneous with changing both horizontal and vertical targeting of the extracted charged particle beam.
is a continuation-in-part of U.S. patent application Ser. No. 12/425,683 filed Apr. 17, 2009, which claims the benefit of:
U.S. provisional patent application No. 61/055,395 filed May 22, 2008; U.S. provisional patent application No. 61/137,574 filed Aug. 1, 2008; U.S. provisional patent application No. 61/192,245 filed Sep. 17, 2008; U.S. provisional patent application No. 61/055,409 filed May 22, 2008; U.S. provisional patent application No. 61/203,308 filed Dec. 22, 2008; U.S. provisional patent application No. 61/188,407 filed Aug. 11, 2008; U.S. provisional patent application No. 61/188,406 filed Aug. 11, 2008; U.S. provisional patent application No. 61/189,815 filed Aug. 25, 2008; U.S. provisional patent application No. 61/201,731 filed Dec. 15, 2008; U.S. provisional patent application No. 61/205,362 filed Jan. 12, 2009; U.S. provisional patent application No. 61/134,717 filed Jul. 14, 2008; U.S. provisional patent application No. 61/134,707 filed Jul. 14, 2008; U.S. provisional patent application No. 61/201,732 filed Dec. 15, 2008; U.S. provisional patent application No. 61/198,509 filed Nov. 7, 2008; U.S. provisional patent application No. 61/134,718 filed Jul. 14, 2008; U.S. provisional patent application No. 61/190,613 filed Sep. 2, 2008; U.S. provisional patent application No. 61/191,043 filed Sep. 8, 2008; U.S. provisional patent application No. 61/192,237 filed Sep. 17, 2008; U.S. provisional patent application No. 61/201,728 filed Dec. 15, 2008; U.S. provisional patent application No. 61/190,546 filed Sep. 2, 2008; U.S. provisional patent application No. 61/189,017 filed Aug. 15, 2008; U.S. provisional patent application No. 61/198,248 filed Nov. 5, 2008; U.S. provisional patent application No. 61/198,508 filed Nov. 7, 2008; U.S. provisional patent application No. 61/197,971 filed Nov. 3, 2008; U.S. provisional patent application No. 61/199,405 filed Nov. 17, 2008; U.S. provisional patent application No. 61/199,403 filed Nov. 17, 2008; and U.S. provisional patent application No. 61/199,404 filed Nov. 17, 2008; claims the benefit of U.S. provisional patent application No. 61/209,529 filed Mar. 9, 2009; claims the benefit of U.S. provisional patent application No. 61/208,182 filed Feb. 23, 2009; claims the benefit of U.S. provisional patent application No. 61/208,971 filed Mar. 3, 2009; and claims priority to PCT patent application serial No.: PCT/RU2009/00015, filed Mar. 4, 2009, all of which are incorporated herein in their entirety by this reference thereto. BACKGROUND OF THE INVENTION
This invention relates generally to treatment of solid cancers. More particularly, the invention relates to a negative ion source system used as part of an ion beam injection system, which is used in conjunction with charged particle cancer therapy beam acceleration, extraction, and/or targeting methods and apparatus.
Proton therapy systems typically include: a beam generator, an accelerator, and a beam transport system to move the resulting accelerated protons to a plurality of treatment rooms where the protons are delivered to a tumor in a patient's body.
F. Cole, et. al. of Loma Linda University Medical Center “Multi-Station Proton Beam Therapy System”, U.S. Pat. No. 4,870,287 (Sep. 26, 1989) describe a proton beam therapy system for selectively generating and transporting proton beams from a single proton source and accelerator to a selected treatment room of a plurality of patient treatment rooms.
H. Tanaka, et. al. “Charged Particle Accelerator”, U.S. Pat. No. 7,259,529 (Aug. 21, 2007) describe a charged particle accelerator having a two period acceleration process with a fixed magnetic field applied in the first period and a timed second acceleration period to provide compact and high power acceleration of the charged particles.
T. Haberer, et. al. “Ion Beam Therapy System and a Method for Operating the System”, U.S. Pat. No. 6,683,318 (Jan. 27, 2004) describe an ion beam therapy system and method for operating the system. The ion beam system uses a gantry that has vertical deflection system and a horizontal deflection system positioned before a last bending magnet that result in a parallel scanning mode resulting from an edge focusing effect.
V. Kulish, et. al. “Inductional Undulative EH-Accelerator”, U.S. Pat. No. 6,433,494 (Aug. 13, 2002) describe an inductive undulative EH-accelerator for acceleration of beams of charged particles. The device consists of an electromagnet undulation system, whose driving system for electromagnets is made in the form of a radio-frequency (RF) oscillator operating in the frequency range from about 100 KHz to 10 GHz.
K. Saito, et. al. “Radio-Frequency Accelerating System and Ring Type Accelerator Provided with the Same”, U.S. Pat. No. 5,917,293 (Jun. 29, 1999) describe a radio-frequency accelerating system having a loop antenna coupled to a magnetic core group and impedance adjusting means connected to the loop antenna. A relatively low voltage is applied to the impedance adjusting means allowing small construction of the adjusting means.
J. Hirota, et. al. “Ion Beam Accelerating Device Having Separately Excited Magnetic Cores”, U.S. Pat. No. 5,661,366 (Aug. 26, 1997) describe an ion beam accelerating device having a plurality of high frequency magnetic field inducing units and magnetic cores.
J. Hirota, et. al. “Acceleration Device for Charged Particles”, U.S. Pat. No. 5,168,241 (Dec. 1, 1992) describe an acceleration cavity having a high frequency power source and a looped conductor operating under a control that combine to control a coupling constant and/or de-tuning allowing transmission of power more efficiently to the particles.
T. Kobari, et. al. “Apparatus For Treating the Inner Surface of Vacuum Chamber”, U.S. Pat. No. 5,820,320 (Oct. 13, 1998) and T. Kobari, et. al. “Process and Apparatus for Treating Inner Surface Treatment of Chamber and Vacuum Chamber”, U.S. Pat. No. 5,626,682 (May 6, 1997) both describe an apparatus for treating an inner surface of a vacuum chamber including means for supplying an inert gas or nitrogen to a surface of the vacuum chamber with a broach. Alternatively, the broach is used for supplying a lower alcohol to the vacuum chamber for dissolving contaminants on the surface of the vacuum chamber.
H. Akiyama, et. al. “Charged-Particle Beam Irradiation Method and System”, U.S. Pat. No. 6,433,349 (Aug. 13, 2002) and H. Akiyama, et. al. “Charged-Particle Beam Irradiation Method and System”, U.S. Pat. No. 6,265,837 (Jul. 24, 2001) both describe a charged particle beam irradiation system that includes a changer for changing energy of the particle and an intensity controller for controlling an intensity of the charged-particle beam.
There exists in the art of particle beam therapy of cancerous tumors a need for efficiently generating a negative ion beam. There further exists in the art a need for extracting the negative ion, focusing the negative ion, converting the negative ion into a positive ion, and injecting the positive ion into a synchrotron. There further exists in the art of particle beam treatment of cancerous tumors in the body a need for reduced synchrotron power supply requirements, reduced synchrotron size, and control of synchrotron magnetic fields. Still further, there exists a need in the art to control the charged particle cancer therapy system in terms of specified energy, intensity, and/or timing of charged particle delivery. Yet still further, there exists a need for efficient, precise, and/or accurate noninvasive, in-vivo treatment of a solid cancerous tumor with minimization of damage to surrounding healthy tissue in a patient.
The invention comprises a negative ion source method and apparatus used as part of an ion beam injection system, which is part of a charged particle cancer therapy beam system.
FIG. 1 illustrates component connections of a particle beam therapy system;
FIG. 4 illustrates a negative ion beam source;
FIG. 5 illustrates a negative ion beam source;
FIG. 6 illustrates an ion beam focusing system;
FIG. 7 A-D illustrate electrodes about a negative ion beam path;
FIG. 10 illustrates bending magnets of a synchrotron;
FIG. 11 provides a perspective view of a bending magnet;
FIG. 12 illustrates a cross-sectional view of a bending magnet;
FIG. 13 illustrates a cross-sectional view of a bending magnet;
FIG. 14 illustrates magnetic field concentration in a bending magnet;
FIG. 15 illustrates correction coils in a bending magnet;
The invention relates generally to treatment of solid cancers. More particularly, the invention relates to a negative ion source system as part of an ion beam injection system used in conjunction with charged particle cancer therapy beam injection, acceleration, extraction, and/or targeting methods and apparatus.
Novel design features of a synchrotron are described. Particularly, a negative ion beam source with novel features in the negative ion source, ion source vacuum system, ion beam focusing lens, and tandem accelerator are described. Additionally, turning magnets, edge focusing magnets, magnetic field concentration magnets, winding and correction coils, flat magnetic field incident surfaces, and extraction elements are described that minimize the overall size of the synchrotron, provide a tightly controlled proton beam, directly reduce the size of required magnetic fields, directly reduce required operating power, and allow continual acceleration of protons in a synchrotron even during a process of extracting protons from the synchrotron. The ion beam source system and synchrotron are preferably computer integrated with a patient imaging system and a patient interface including breath monitoring sensors and patient positioning elements.
Used in conjunction with the injection system, imaging system, and breathing sensors; novel features of a synchrotron are described. Particularly, intensity control of a charged particle beam acceleration, extraction, and/or targeting method and apparatus used in conjunction with charged particle beam radiation therapy of cancerous tumors are described. More particularly, intensity control of a charged particle stream of a synchrotron is described. Intensity control is described in combination with turning magnets, edge focusing magnets, concentrating magnetic field magnets, winding and control coils, and extraction elements of the synchrotron. The synchrotron control elements allow tight control of the charged particle beam, which compliments the tight control of patient positioning to yield efficient treatment of a solid tumor with reduced tissue damage to surrounding healthy tissue. In addition, the system reduces the overall size of the synchrotron, provides a tightly controlled proton beam, directly reduces the size of required magnetic fields, directly reduces required operating power, and allows continual acceleration of protons in a synchrotron even during a process of extracting protons from the synchrotron.
Throughout this document, a charged particle beam therapy system, such as a proton beam, hydrogen ion beam, or carbon ion beam, is described. Herein, the charged particle beam therapy system is described using a proton beam. However, the aspects taught and described in terms of a proton beam are not intended to be limiting to that of a proton beam and are illustrative of a charged particle beam system. Any of the techniques described herein are equally applicable to any charged particle beam system.
Herein, the term synchrotron is used to refer to a system maintaining the charged particle beam in a circulating path. Further, the charged particle beam is referred to herein as circulating along a circulating path about a central point of the synchrotron. The circulating path is alternatively referred to as an orbiting path; however, the orbiting path does not refer a perfect circle or ellipse, rather it refers to cycling of the protons around a central point or region.
Referring now to FIG. 2, an illustrative exemplary embodiment of one version of the charged particle beam system 100 is provided. In the illustrated embodiment, an injector system 120 or ion source or charged particle beam source generates protons. The protons are delivered into a vacuum tube that runs into, through, and out of the synchrotron. The generated protons are delivered along an initial path 262. Focusing magnets 230, such as quadrupole magnets or injection quadrupole magnets, are used to focus the proton beam path. A quadrupole magnet is a focusing magnet. An injector bending magnet 232 bends the proton beam toward the plane of the synchrotron 130. The focused protons having an initial energy are introduced into an injector magnet 240, which is preferably an injection Lamberson magnet. Typically, the initial beam path 262 is along an axis off of, such as above, a circulating plane of the synchrotron 130. The injector bending magnet 232 and injector magnet 240 combine to move the protons into the synchrotron 130. Main bending magnets 250, dipole magnets, turning magnets, or circulating magnets are used to turn the protons along a circulating beam path 264. A dipole magnet is a bending magnet. The main bending magnets 250 bend the initial beam path 262 into a circulating beam path 264. In this example, the main bending magnets 250 or circulating magnets are represented as four sets of four magnets to maintain the circulating beam path 264 into a stable circulating beam path. However, any number of magnets or sets of magnets are optionally used to move the protons around a single orbit in the circulation process. The protons pass through an accelerator 270. The accelerator accelerates the protons in the circulating beam path 264. As the protons are accelerated, the fields applied by the magnets are increased. Particularly, the speed of the protons achieved by the accelerator 270 are synchronized with magnetic fields of the main bending magnets 250 or circulating magnets to maintain stable circulation of the protons about a central point or region 280 of the synchrotron. At separate points in time the accelerator 270/main bending magnet 250 combination is used to accelerate and/or decelerate the circulating protons while maintaining the protons in the circulating path or orbit. An extraction element of the inflector/deflector system 290 is used in combination with a Lamberson extraction magnet 292 to remove protons from their circulating beam path 264 within the synchrotron 130. One example of a deflector component is a Lamberson magnet. Typically the deflector moves the protons from the circulating plane to an axis off of the circulating plane, such as above the circulating plane. Extracted protons are preferably directed and/or focused using an extraction bending magnet 237 and extraction focusing magnets 235, such as quadrupole magnets along a transport path 268 into the scanning/targeting/delivery system 140. Two components of a scanning system 140 or targeting system typically include a first axis control 142, such as a vertical control, and a second axis control 144, such as a horizontal control. A nozzle system 146 is used for imaging the proton beam and/or as a vacuum barrier between the low pressure beam path of the synchrotron and the atmosphere. Protons are delivered with control to the patient interface module 150 and to a tumor of a patient.
Still referring to FIG. 3, the ion beam focusing system 350 includes two or more electrodes where one electrode of each electrode pair partially obstructs the ion beam path with conductive paths 372, such as a conductive mesh. In the illustrated example, three ion beam focusing system sections are illustrated, a two electrode ion focusing section 360, and a three electrode ion focusing section. In a given electrode pair, electric field lines, running between the conductive mesh of a first electrode and a second electrode, provide inward forces focusing the negative ion beam. Multiple such electrode pairs provide multiple negative ion beam focusing regions. Preferably the two electrode ion focusing section 360, first three electrode ion focusing section 370, and a second three electrode ion focusing section are placed after the negative ion source and before the tandem accelerator and/or cover a space of about 0.5, 1, or 2 meters along the ion beam path 319. Ion beam focusing systems are further described, infra.
Still referring to FIG. 3, the tandem accelerator 390 preferably includes a foil 395, such as a carbon foil. The foil is also referred to as a converting foil. The negative ions in the negative ion beam path 319 are converted to positive ions, such as protons, and the initial ion beam path 262 results. The foil 395 is preferably sealed directly or indirectly to the edges of the vacuum tube 320 providing for a higher pressure, such as about 10−5 torr, to be maintained on the side of the foil 395 having the negative ion beam path 319 and a lower pressure, such as about 10−7 torr, to be maintained on the side of the foil 390 having the proton ion beam path 262. Having the foil 395 physically separating the vacuum chamber 320 into two pressure regions allows for a system having fewer and/or smaller pumps to maintain the lower pressure system in the synchrotron 130 as the inlet hydrogen and its residuals are extracted in a separate contained and isolated space by the first partial vacuum system 330.
An example of the negative ion source 310 is further described herein. Referring now to FIG. 4, a cross-section of an exemplary negative ion source system 400 is provided. The negative ion beam 390 is created in multiple stages. During a first stage, hydrogen gas is injected into a chamber. During a second stage, a negative ion is created by application of a first high voltage pulse, which creates a plasma about the hydrogen gas to create negative ions. During a third stage, a magnetic field filter is applied to components of the plasma. During a fourth stage, the negative ions are extracted from a low temperature plasma region, on the opposite side of the magnetic field barrier, by application of a second high voltage pulse. Each of the four stages are further described, infra. While the chamber is illustrated as a cross-section of a cylinder, the cylinder is exemplary only and any geometry applies to the magnetic loop containment walls, described infra.
In the first stage, hydrogen gas is injected through an inlet port 442 into a high temperature plasma region 490. The injection port 442 is open for a short period of time, such as less than about 1, 5, or 10 microseconds to minimize vacuum pump requirements to maintain vacuum chamber 320 requirements. The high temperature plasma region is maintained at reduced pressure by the partial vacuum system 330. The injection of the hydrogen gas is optionally controlled by the main controller 110, which is responsive to imaging system 170 information and patient interface module 150 information, such as patient positioning and period in a respiration cycle.
In the second stage, a high temperature plasma region is created by applying a first high voltage pulse across a first electrode 422 and a second electrode 424. For example a 5 kV pulse is applied for about 20 microseconds with 5 kV at the second electrode 424 and about 0 kV applied at the first electrode 422. Hydrogen in the chamber is broken, in the high temperature plasma region 490, into component parts, such as any of: atomic hydrogen, H0, a proton, H+, an electron, e−, a hydrogen anion, and H−.
In the third stage, the high temperature plasma region 490 is at least partially separated from a low temperature plasma region 492 by a magnetic field or magnetic field barrier 430. High energy electrons are restricted from passing through the magnetic field barrier 430. In this manner, the magnetic field barrier 430 acts as a filter between, zone A and zone B, in the negative ion source. Preferably, a central magnetic material 410 is placed within the high temperature plasma region 490, such as along a central axis of the high temperature plasma region 490. Preferably, the first electrode 422 and second electrode 424 are composed of magnetic materials, such as iron. Preferably, the outer walls 450 of the high temperature plasma region, such as cylinder walls, are composed of a magnetic material, such as a permanent magnet, ferric, or iron based material, or a ferrite dielectric ring magnet. In this manner a magnetic field loop is created by: the central magnetic material 410, first electrode 422, the outer walls 450, the second electrode 424, and the magnetic field barrier 430. Again, the magnetic field barrier 430 restricts high energy electrons from passing through the magnetic field barrier 430. Low energy electrons interact with atomic hydrogen, H0, to create a hydrogen anion, H−, in the low temperature plasma region 492.
In the fourth stage, a second high voltage pulse or extraction pulse is applied at a third electrode 426. The second high voltage pulse is preferentially applied during the later period of application of the first high voltage pulse. For example, an extraction pulse of about 25 kV is applied for about the last 5 microseconds of the first creation pulse of about 20 microseconds. The potential difference, of about 20 kV, between the third electrode 426 and second electrode 424 extracts the negative ion, H−, from the low temperature plasma region 492 and initiates the negative ion beam 390, from zone B to zone C.
The magnetic field barrier 430 is optionally created in number of ways. Referring now to FIG. 5, an example of creation of the magnetic field barrier 430 using coils is provided. In this example, the elements described, supra, in relation to FIG. 4 are maintained with several differences. First, the magnetic field is created using coils 570. Isolating material 560 is provided between the first electrode 422 and the second electrode 424 and the cylinder walls 550 and/or central material 510 are optionally metallic. In this manner, the coils create a magnetic field loop through the first electrode 422, isolating material 560, outer walls 550, second electrode 424, magnetic field barrier 430, and the central material 510. Essentially, the coils 570 generate the a magnetic field in place of production of the magnetic field produced by the magnetic material 410. The magnetic field barrier 430 operates as described, supra. Generally, any manner that creates the magnetic field barrier 430 between the high temperature plasma region 490 and low temperature plasma region 492 is functionally applicable to the ion beam extraction system 400.
Referring now to FIG. 6, the ion beam focusing system 350 is further described. In this example, three electrodes are used. In this example, the first electrode 610 and third electrode 630 are both negatively charged and each is a ring electrode circumferentially enclosing or at least partially enclosing the negative ion beam path 319. The second electrode 620 is positively charged and is also a ring electrode circumferentially enclosing the negative ion beam path. In addition, the second electrode includes one or more conducting paths 372 running through the negative ion beam path 319. For example, the conducting paths are a wire mesh, a conducting grid, or a series of substantially parallel conducting lines running across the second electrode. In use, electric field lines run from the conducting paths of the positively charged electrode to the negatively charged electrodes. For example, in use the electric field lines 640 run from the conducting paths 372 in the negative ion beam path 319 to the negatively charged electrodes 610, 630. Two ray trace lines 650, 660 of the negative ion beam path are used to illustrate focusing forces. In the first ray trace line 650, the negative ion beam encounters a first electric field line at point M. Negatively charged ions in the negative ion beam 650 encounter forces running up the electric field line 671, illustrated with an x-axis component vector 672. The x-axis component force vectors 672 alters the trajectory of the first ray trace line to a inward focused vector 652, which encounters a second electric field line at point N. Again, the negative ion beam 652 encounters forces running up the electric field line 673, illustrated as having an inward force vector with an x-axis component 674, which alters the inward focused vector 652 to a more inward focused vector 654. Similarly, in the second ray trace line 660, the negative ion beam encounters a first electric field line at point O. Negatively charged ions in the negative ion beam encounter forces running up the electric field line 675, illustrated as having a force vector with an x-axis force 676. The inward force vectors 676 alters the trajectory of the second ray trace line 660 to an inward focused vector 662, which encounters a second electric field line at point P. Again, the negative ion beam encounters forces running up the electric field line 677, illustrated as having force vector with an x-axis component 678, which alters the inward focused vector 662 to a more inward focused vector 664. The net result is a focusing effect on the negative ion beam. Each of the force vectors 672, 674, 676, 678 optionally has x and/or y force vector components resulting in a 3-dimensional focusing of the negative ion beam path. Naturally, the force vectors are illustrative in nature, many electric field lines are encountered, and the focusing effect is observed at each encounter resulting in integral focusing. The example is used to illustrate the focusing effect.
Still referring to FIG. 6, optionally any number of electrodes are used, such as 2, 3, 4, 5, 6, 7, 8, or 9 electrodes, to focus the negative ion beam path where every other electrode, in a given focusing section, is either positively or negatively charged. For example, three focusing sections are optionally used. In the first ion focusing section 360, a pair of electrodes are used where the first electrode encountered along the negative ion beam path is negatively charged and the second electrode is positively charged, resulting in focusing of the negative ion beam path. In the second ion focusing section 370, two pairs of electrodes are used, where a common positively charged electrode with a conductive mesh running through the negatively ion beam path 319 is used. Thus, in the second ion focusing section 370, the first electrode encountered along the negative ion beam path is negatively charged and the second electrode is positively charged, resulting in focusing of the negative ion beam path. Further, in the second ion focusing section, moving along the negative ion beam path, a second focusing effect is observed between the second positively charged electrode and a third negatively charged electrode. In this example, a third ion focusing section is used that again has three electrodes, which acts in the fashion of the second ion focusing section, describe supra.
Referring now to FIG. 7, the central regions of the electrodes in the ion beam focusing system 350 are further described. Referring now to FIG. 7A, the central region of the negatively charged ring electrode 610 is preferably void of conductive material. Referring now to FIGS. 7B-D, the central region of positively charged electrode ring 620 preferably contains conductive paths 372. Preferably, the conductive paths 372 or conductive material within the positively charged electrode ring 620 blocks about 1, 2, 5, or 10 percent of the area and more preferably blocks about 5 percent of the cross-sectional area of the negative ion beam path 319. Referring now to FIG. 7B, one option is a conductive mesh 710. Referring now to FIG. 7C, a second option is a series of conductive lines 720 running substantially in parallel across the positively charged electrode ring 620 that surrounds a portion of the negative ion beam path 319. Referring now to FIG. 7D, a third option is to have a foil 730 or metallic layer cover all of the cross-sectional area of the negative ion beam path with holes punched through the material, where the holes take up about 90-99 percent and more preferably about 95 percent of the area of the foil. More generally, the pair of electrodes are configure to provide electric field lines that provide focusing force vectors to the negative ion beam when the ions in the negative ion beam translate through the electric field lines, as described supra.
In an example of a two electrode negative beam ion focusing system having a first cross-sectional diameter, d1, the negative ions are focused using the two electrode system to a second cross-sectional diameter, d2, where d1>d2. Similarly, in an example of a three electrode negative beam ion focusing system having a first cross-sectional diameter, d1, the negative ions are focused using the three electrode system to a third cross-sectional diameter, d3, where d1>d3. For like potentials on the electrodes, the three electrode system provides tighter or stronger focusing compared to the two-electrode system, d3<d2.
Referring now to FIG. 8, another exemplary method of use of the charged particle beam system 100 is provided. The main controller 110, or one or more sub-controllers, controls one or more of the subsystems to accurately and precisely deliver protons to a tumor of a patient. For example, the main controller sends a message to the patient indicating when or how to breath. The main controller 110 obtains a sensor reading from the patient interface module, such as a temperature breath sensor or a force reading indicative of where in a respiration cycle the subject is. The main controller collects an image, such as a portion of a body and/or of a tumor, from the imaging system 170. The main controller 110 also obtains position and/or timing information from the patient interface module 150. The main controller 110 then optionally controls the injection system 120 to inject hydrogen gas into a negative ion beam source 310 and controls timing of extraction of the negative ion from the negative ion beam source 310. Optionally, the main controller controls ion beam focusing the ion beam focusing lens system 350; acceleration of the proton beam with the tandem accelerator 390; and/or injection of the proton into the synchrotron 130. The synchrotron typically contains at least an accelerator system 132 and an extraction system 134. The synchrotron preferably contains one or more of: turning magnets, edge focusing magnets, magnetic field concentration magnets, winding and correction coils, and flat magnetic field incident surfaces, some of which contain elements under control by the main controller 110. The main controller preferably controls the proton beam within the accelerator system, such as by controlling speed, trajectory, and/or timing of the proton beam. The main controller then controls extraction of a proton beam from the accelerator through the extraction system 134. For example, the controller controls timing, energy, and/or intensity of the extracted beam. The controller 110 also preferably controls targeting of the proton beam through the targeting/delivery system 140 to the patient interface module 150. One or more components of the patient interface module 150 are preferably controlled by the main controller 110, such as vertical position of the patient, rotational position of the patient, and patient chair positioning/stabilization/control elements. Further, display elements of the display system 160 are preferably controlled via the main controller 110. Displays, such as display screens, are typically provided to one or more operators and/or to one or more patients. In one embodiment, the main controller 110 times the delivery of the proton beam from all systems, such that protons are delivered in an optimal therapeutic manner to the patient.
In one illustrative embodiment, the synchrotron 130, which as also referred to as an accelerator system, has four straight sections and four turning sections. Examples of straight sections 910 include the: inflector 240, accelerator 270, extraction system 290, and deflector 292. Along with the four straight sections are four ion beam turning sections 920, which are also referred to as magnet sections or turning sections. Turning sections are further described, infra.
Referring now to FIG. 9, an exemplary synchrotron is illustrated. In this example, protons delivered along the initial path 262 are inflected into the circulating beam path with the inflector 240 and after acceleration are extracted via a deflector 292 to a beam transport path 268. In this example, the synchrotron 130 comprises four straight sections 910 and four bending or turning sections 920 where each of the four turning sections use one or more magnets to turn the proton beam about ninety degrees. As is further described, infra, the ability to closely space the turning sections and efficiently turn the proton beam results in shorter straight sections. Shorter straight sections allows for a synchrotron design without the use of focusing quadrupoles in the circulating beam path of the synchrotron. The removal of the focusing quadrupoles from the circulating proton beam path results in a more compact design. In this example, the illustrated synchrotron has about a five meter diameter versus eight meter and larger cross-sectional diameters for systems using a quadrupole focusing magnet in the circulating proton beam path.
Referring now to FIG. 10, additional description of the first bending or turning section 920 is provided. Each of the turning sections preferably comprises multiple magnets, such as about 2, 4, 6, 8, 10, or 12 magnets. In this example, four turning magnets 1010, 1020, 1030, 1040 in the first turning section 20 are used to illustrate key principles, which are the same regardless of the number of magnets in a turning section 920. A turning magnet 1010 is a particular type of main bending or circulating magnet 250.
Referring now to FIG. 11, an example of a single magnet bending or turning section 1010 is expanded. The turning section includes a gap 1110. The gap 1110 is preferably a flat gap, allowing for a magnetic field across the gap 1110 that is more uniform, even, and intense. A magnetic field enters the gap 1110 through a magnetic field incident surface and exits the gap 1110 through a magnetic field exiting surface. The gap 1110 runs in a vacuum tube between two magnet halves. The gap 1110 is controlled by at least two parameters: (1) the gap 1110 is kept as large as possible to minimize loss of protons and (2) the gap 1110 is kept as small as possible to minimize magnet sizes and the associated size and power requirements of the magnet power supplies. The flat nature of the gap 1110 allows for a compressed and more uniform magnetic field across the gap 1110. One example of a gap dimension is to accommodate a vertical proton beam size of about 2 cm with a horizontal beam size of about 5 to 6 cm.
Still referring to FIG. 11, a portion of an optional second magnet bending or turning section 1020 is illustrated. The coils 1120, 1130 typically have return elements 1140, 1150 or turns at the end of one magnet, such as at the end of the first magnet turning section 1010. The turns 1140, 1150 take space. The space reduces the percentage of the path about one orbit of the synchrotron that is covered by the turning magnets. This leads to portions of the circulating path where the protons are not turned and/or focused and allows for portions of the circulating path where the proton path defocuses. Thus, the space results in a larger synchrotron. Therefore, the space between magnet turning sections 1160 is preferably minimized. The second turning magnet is used to illustrate that the coils 1120, 1130 optionally run along a plurality of magnets, such as 2, 3, 4, 5, 6, or more magnets. Coils 1120, 1130 running across turning section magnets allows for two turning section magnets to be spatially positioned closer to each other due to the removal of the steric constraint of the turns, which reduces and/or minimizes the space 1160 between two turning section magnets.
Referring now to FIGS. 12 and 13, two illustrative 90 degree rotated cross-sections of single magnet bending or turning sections 1010 are presented. The magnet assembly has a first magnet 1210 and a second magnet 1220. A magnetic field induced by coils, described infra, runs between the first magnet 1210 to the second magnet 1220 across the gap 1110. Return magnetic fields run through a first yoke 1212 and second yoke 1222. The charged particles run through the vacuum tube in the gap 1110. As illustrated, protons run into FIG. 12 through the gap 1110 and the magnetic field, illustrated as vector B, applies a force F to the protons pushing the protons towards the center of the synchrotron, which is off page to the right in FIG. 12. The magnetic field is created using windings. A first coil makes up a first winding coil 1250 and a second coil of wire makes up a second winding coil 1260. Isolating or concentrating gaps 1230, 1240, such as air gaps, isolate the iron based yokes from the gap 1110. The gap 1110 is approximately flat to yield a uniform magnetic field across the gap 1110, as described supra.
Still referring to FIG. 13, the ends of a single bending or turning magnet are preferably beveled. Nearly perpendicular or right angle edges of a turning magnet 1010 are represented by dashed lines 1374, 1384. The dashed lines 1374, 1384 intersect at a point 1390 beyond the center of the synchrotron 280. Preferably, the edge of the turning magnet is beveled at angles alpha, α, and beta, β, which are angles formed by a first line 1372, 1382 going from an edge of the turning magnet 1010 and the center 280 and a second line 1374, 1384 going from the same edge of the turning magnet and the intersecting point 1390. The angle alpha is used to describe the effect and the description of angle alpha applies to angle beta, but angle alpha is optionally different from angle beta. The angle alpha provides an edge focusing effect. Beveling the edge of the turning magnet 1010 at angle alpha focuses the proton beam.
TFE = NTS ⋆ M NTS ⋆ FE M eq . 2 where TFE is the number of total focusing edges, NTS is the number of turning section, M is the number of magnets, and FE is the number of focusing edges. Naturally, not all magnets are necessarily beveled and some magnets are optionally beveled on only one edge.
The inventors have determined that multiple smaller magnets have benefits over fewer larger magnets. For example, the use of 16 small magnets yields 32 focusing edges whereas the use of 4 larger magnets yields only 8 focusing edges. The use of a synchrotron having more focusing edges results in a circulating path of the synchrotron built without the use of focusing quadrupoles magnets. All prior art synchrotrons use quadrupoles in the circulating path of the synchrotron. Further, the use of quadrupoles in the circulating path necessitates additional straight sections in the circulating path of the synchrotron. Thus, the use of quadrupoles in the circulating path of a synchrotron results in synchrotrons having larger diameters or larger circumferences.
at least 4 and preferably 6, 8, 10, or more edge focusing edges per 90 degrees of turn of the charged particle beam in a synchrotron having four turning sections; at least about 16 and preferably about 24, 32, or more edge focusing edges per orbit of the charged particle beam in the synchrotron; only 4 turning sections where each of the turning sections includes at least 4 and preferably 8 edge focusing edges; an equal number of straight sections and turning sections; exactly 4 turning sections; at least 4 edge focusing edges per turning section; no quadrupoles in the circulating path of the synchrotron; a rounded corner rectangular polygon configuration; a circumference of less than 60 meters; a circumference of less than 60 meters and 32 edge focusing surfaces; and/or any of about 8, 16, 24, or 32 non-quadrupole magnets per circulating path of the synchrotron, where the non-quadrupole magnets include edge focusing edges. Referring now to FIG. 12, the incident magnetic field surface 1270 of the first magnet 1210 is further described. FIG. 12 is not to scale and is illustrative in nature. Local imperfections or unevenness in quality of the finish of the incident surface 1270 results in inhomogeneities or imperfections in the magnetic field applied to the gap 1110. Preferably, the incident surface 1270 is flat, such as to within about a zero to three micron finish polish, or less preferably to about a ten micron finish polish.
Referring now to FIG. 14, additional optional magnet elements, of the magnet cross-section illustratively represented in FIG. 12, are described. The first magnet 1210 preferably contains an initial cross-sectional distance 1410 of the iron based core. The contours of the magnetic field are shaped by the magnets 1210, 1220 and the yokes 1212, 1222. The iron based core tapers to a second cross-sectional distance 1420. The magnetic field in the magnet preferentially stays in the iron based core as opposed to the gaps 1230, 1240. As the cross-sectional distance decreases from the initial cross-sectional distance 1410 to the final cross-sectional distance 1420, the magnetic field concentrates. The change in shape of the magnet from the longer distance 1410 to the smaller distance 1420 acts as an amplifier. The concentration of the magnetic field is illustrated by representing an initial density of magnetic field vectors 1430 in the initial cross-section 1410 to a concentrated density of magnetic field vectors 1440 in the final cross-section 1420. The concentration of the magnetic field due to the geometry of the turning magnets results in fewer winding coils 1250, 1260 being required and also a smaller power supply to the coils being required.
In one example, the initial cross-section distance 1410 is about fifteen centimeters and the final cross-section distance 1420 is about ten centimeters. Using the provided numbers, the concentration of the magnetic field is about 15/10 or 1.5 times at the incident surface 1270 of the gap 1110, though the relationship is not linear. The taper 1460 has a slope, such as about 20 to 60 degrees. The concentration of the magnetic field, such as by 1.5 times, leads to a corresponding decrease in power consumption requirements to the magnets.
Still referring to FIG. 15, optional correction coils 1510, 1520 are illustrated that are used to correct the strength of one or more turning magnets. The correction coils 1520, 1530 supplement the winding coils 1250, 1260. The correction coils 1510, 1520 have correction coil power supplies that are separate from winding coil power supplies used with the winding coils 1250, 1260. The correction coil power supplies typically operate at a fraction of the power required compared to the winding coil power supplies, such as about 1, 2, 3, 5, 7, or 10 percent of the power and more preferably about 1 or 2 percent of the power used with the winding coils 1250, 1260. The smaller operating power applied to the correction coils 1510, 1520 allows for more accurate and/or precise control of the correction coils. The correction coils are used to adjust for imperfection in the turning magnets.
Referring now to FIG. 16, an example of winding coils and correction coils about a plurality of turning magnets in an ion beam turning section 920 is illustrated. One or more high precision magnetic field sensors are placed into the synchrotron and are used to measure the magnetic field at or near the proton beam path. For example, the magnetic sensors are optionally placed between turning magnets and/or within a turning magnet, such as at or near the gap 1110 or at or near the magnet core or yoke. The sensors are part of a feedback system to the correction coils. Thus, the system preferably stabilizes the magnetic field in the synchrotron rather than stabilizing the current applied to the magnets. Stabilization of the magnetic field allows the synchrotron to come to a new energy level quickly. This allows the system to be controlled to an operator or algorithm selected energy level with each pulse of the synchrotron and/or with each breath of the patient. The winding and/or correction coils correct 1, 2, 3, or 4 turning magnets, and preferably correct a magnetic field generated by two turning magnets. In the illustrated example, a correction coil winds around a single turning magnet 460. the illustrated example also shows a correction coil 1620 wrapped around two turning magnets 410, 420, to correct the magnetic field of the two turning magnets.
Referring now to FIG. 17, an example is used to clarify the magnetic field control using a feedback loop 1700 to change delivery times and/or periods of proton pulse delivery. In one case, a respiratory sensor 1710 senses the respiration cycle of the subject. The respiratory sensor sends the information to an algorithm in a magnetic field controller 1720, typically via the patient interface module 150 and/or via the main controller 110 or a subcomponent thereof. The algorithm predicts and/or measures when the subject is at a particular point in the respiration cycle, such as at the bottom of a breath. Magnetic field sensors 1730 are used as input to the magnetic field controller, which controls a magnet power supply 1740 for a given magnetic field 1750, such as within a first turning magnet 1010 of a synchrotron 130. The control feedback loop is thus used to dial the synchrotron to a selected energy level and deliver protons with the desired energy at a selected point in time, such as at the bottom of the breath. More particularly, the synchrotron accelerates the protons and the control feedback loop keeps the protons in the circulating path by synchronously adjusting the magnetic field strength of the turning magnets. Intensity of the proton beam is also selectable at this stage. The feedback control to the correction coils allows rapid selection of energy levels of the synchrotron that are tied to the patient's respiration cycle. This system is in stark contrast to a system where the current is stabilized and the synchrotron deliver pulses with a period, such as 10 or 20 cycles per second with a fixed period.
Referring again to FIG. 16, an example of a winding coil 1630 that covers two turning magnets 1010, 1020 is provided. Optionally, a first winding coil 1640 covers two magnets and a second winding coil covers another two magnets. As described, supra, this system reduces space between turning section allowing more magnetic field to be applied per radian of turn. A first correction coil 1610 is illustrated that is used to correct the magnetic field for the first turning magnet 1010. A second correction coil 1620 is illustrated that is used to correct the magnetic field for a winding coil 1630 about two turning magnets. Individual correction coils for each turning magnet are preferred and individual correction coils yield the most precise and/or accurate magnetic field in each turning section. Particularly, the individual correction coil 1610 is used to compensate for imperfections in the individual magnet of a given turning section. Hence, with a series of magnetic field sensors, corresponding magnetic fields are individually adjustable in a series of feedback loops, via a magnetic field monitoring system, as an independent coil is used for each turning section. Alternatively, a multiple magnet correction coil is used to correct the magnetic field for a plurality of turning section magnets.
While the gap surface is described in terms of the first turning magnet 1010, the discussion applies to each of the turning magnets in the synchrotron. Similarly, while the gap 1110 surface is described in terms of the magnetic field incident surface 1270, the discussion additionally optionally applies to the magnetic field exiting surface 1280.
With a sufficient sine wave betatron amplitude, the altered circulating beam path 265 touches or traverses a material 1830, such as a foil or a sheet of foil. The foil is preferably a lightweight material, such as beryllium, a lithium hydride, a carbon sheet, or a material of low nuclear charge. A material of low nuclear charge is a material composed of atoms consisting essentially of atoms having six or fewer protons. The foil is preferably about 10 to 150 microns thick, is more preferably 30 to 100 microns thick, and is still more preferably about 40 to 60 microns thick. In one example, the foil is beryllium with a thickness of about 50 microns. When the protons traverse through the foil, energy of the protons is lost and the speed of the protons is reduced. Typically, a current is also generated, described infra. Protons moving at a slower speed travel in the synchrotron with a reduced radius of curvature 266 compared to either the original central beamline 264 or the altered circulating path 265. The reduced radius of curvature 266 path is also referred to herein as a path having a smaller diameter of trajectory or a path having protons with reduced energy. The reduced radius of curvature 266 is typically about two millimeters less than a radius of curvature of the last pass of the protons along the altered proton beam path 265.
Because the extraction system does not depend on any change in magnetic field properties, it allows the synchrotron to continue to operate in acceleration or deceleration mode during the extraction process. Stated differently, the extraction process does not interfere with synchrotron acceleration. In stark contrast, traditional extraction systems introduce a new magnetic field, such as via a hexapole, during the extraction process. More particularly, traditional synchrotrons have a magnet, such as a hexapole magnet, that is off during an acceleration stage. During the extraction phase, the hexapole magnetic field is introduced to the circulating path of the synchrotron. The introduction of the magnetic field necessitates two distinct modes, an acceleration mode and an extraction mode, which are mutually exclusive in time.
In another example, a detector 1850 external to the synchrotron 130 is used to determine the flux of protons extracted from the synchrotron and a signal from the external detector is used to alter the RF field or RF modulation in the RF cavity system 1810. Here the external detector generates an external signal, which is used in a manner similar to the measured intensity signal, described in the preceding paragraphs.
Referring still to FIG. 19, the patient positioning system 1910 optionally includes a bottom unit 1912 and a top unit 1914, such as discs or a platform.
Referring now to FIG. 19A, the patient positioning unit 1910 is preferably y-axis adjustable 1916 to allow vertical shifting of the patient relative to the proton therapy beam 268. Preferably, the vertical motion of the patient positioning unit 1910 is about 10, 20, 30, or 50 centimeters per minute. Referring now to FIG. 19B, the patient positioning unit 1910 is also preferably rotatable 1917 about a rotation axis, such as about the y-axis, to allow rotational control and positioning of the patient relative to the proton beam path 268. Preferably the rotational motion of the patient positioning unit 1910 is about 360 degrees per minute. Optionally, the patient positioning unit rotates about 45, 90, or 180 degrees. Optionally, the patient positioning unit 1910 rotates at a rate of about 45, 90, 180, 360, 720, or 1080 degrees per minute. The rotation of the positioning unit 1917 is illustrated about the rotation axis at two distinct times, t1 and t2. Protons are optionally delivered to the tumor 1920 at n times where each of the n times represent different directions of the incident proton beam 269 hitting the patient 1930 due to rotation of the patient 1917 about the rotation axis.
Combined, the system allows for multi-axes control of the charged particle beam system in a small space with low or small power supply. For example, the system uses multiple magnets where each magnet has at least one edge focusing effect in each turning section of the synchrotron and/or multiple magnets having concentrating magnetic field geometry, as described supra. The multiple edge focusing effects in the circulating beam path of the synchrotron combined with the concentration geometry of the magnets and described extraction system yields a synchrotron having:
Imaging/X-Ray System
An X-ray is preferably taken just before treating the subject to aid in patient positioning. For positioning purposes, an X-ray of a large body area is not needed. In one embodiment, an X-ray of only a local area is collected. When collecting an X-ray, the X-ray has an X-ray path. The proton beam has a proton beam path. Overlaying the X-ray path with the proton beam path is one method of aligning the proton beam to the tumor. However, this method involves putting the X-ray equipment into the proton beam path, taking the X-ray, and then moving the X-ray equipment out of the beam path. This process takes time. The elapsed time while the X-ray equipment moves has a couple of detrimental effects. First, during the time required to move the X-ray equipment, the body moves. The resulting movement decreases precision and/or accuracy of subsequent proton beam alignment to the tumor. Second, the time required to move the X-ray equipment is time that the proton beam therapy system is not in use, which decreases the total efficiency of the proton beam therapy system.
Referring now to FIG. 21, an example of an X-ray generation device 2100 having an enhanced lifetime is provided. Electrons 2120 are generated at a cathode 2110, focused with a control electrode 2112, and accelerated with a series of accelerating electrodes 2140. The accelerated electrons 2150 impact an X-ray generation source 2148 resulting in generated X-rays that are then directed along an X-ray path 2270 to the subject 1930. The concentrating of the electrons from a first diameter 2115 to a second diameter 2116 allows the cathode to operate at a reduced temperature and still yield the necessary amplified level of electrons at the X-ray generation source 2148. In one example, the X-ray generation source is the anode coupled with the cathode 2110 and/or the X-ray generation source is substantially composed of tungsten.
Still referring to FIG. 21, a more detailed description of an exemplary X-ray generation device 2100 is described. An anode 2114/cathode 2110 pair is used to generated electrons. The electrons 2120 are generated at the cathode 2110 having a first diameter 2115, which is denoted d1. The control electrodes 2112 attract the generated electrons 2120. For example, if the cathode is held at about −150 kV and the control electrode is held at about −149 kV, then the generated electrons 2120 are attracted toward the control electrodes 2112 and focused. A series of accelerating electrodes 2140 are then used to accelerate the electrons into a substantially parallel path 2150 with a smaller diameter 2116, which is denoted d2. For example, with the cathode held at −150 kV, a first, second, third, and fourth accelerating electrodes 2142, 2144, 2146, 2148 are held at about −120, −90, −60, and −30 kV, respectively. If a thinner body part is to be analyzed, then the cathode 2110 is held at a smaller level, such as about −90 kV and the control electrode, first, second, third, and fourth electrode are each adjusted to lower levels. Generally, the voltage difference from the cathode to fourth electrode is less for a smaller negative voltage at the cathode and vise-versa. The accelerated electrons 2150 are optionally passed through a magnetic lens 2160 for adjustment of beam size, such as a cylindrical magnetic lens. The electrons are also optionally focused using quadrupole magnets 2170, which focus in one direction and defocus in another direction. The accelerated electrons 2150, which are now adjusted in beam size and focused strike an X-ray generation source 2148, such as tungsten, resulting in generated X-rays that pass through an optional blocker 2262 and proceed along an X-ray path 2170 to the subject. The X-ray generation source 2148 is optionally cooled with a cooling element 2149, such as water touching or thermally connected to a backside of the X-ray generation source 2148. The concentrating of the electrons from a first diameter 2115 to a second diameter 2116 allows the cathode to operate at a reduced temperature and still yield the necessary amplified level of electrons at the X-ray generation source 2148.
More generally, the X-ray generation device 2100 produces electrons having initial vectors. One or more of the control electrode 2112, accelerating electrodes 2140, magnetic lens 2160, and quadrupole magnets 2170 combine to alter the initial electron vectors into parallel vectors with a decreased cross-sectional area having a substantially parallel path, referred to as the accelerated electrons 2150. The process allows the X-ray generation device 2100 to operate at a lower temperature. Particularly, instead of using a cathode that is the size of the electron beam needed, a larger electrode is used and the resulting electrons 2120 are focused and/or concentrated into the required electron beam needed. As lifetime is roughly an inverse of current density, the concentration of the current density results in a larger lifetime of the X-ray generation device. A specific example is provided for clarity. If the cathode has a 15 mm radius or d1 is about 30 mm, then the area (π r2) is about 225 mm2 times pi. If the concentration of the electrons achieves a radius of 5 mm or d2 is about 10 mm, then the area (π r2) is about 25 mm2 times pi. The ratio of the two areas is about 9 (225π/25π). Thus, there is about 9 times less density of current at the larger cathode compared to the traditional cathode having an area of the desired electron beam. Hence, the lifetime of the larger cathode approximates 9 times the lifetime of the traditional cathode, though the actual current through the larger cathode and traditional cathode is about the same. Preferably, the area of the cathode 2110 is about 2, 4, 6, 8, 10, 15, 20, or 25 times that of the cross-sectional area of the substantially parallel electron beam 2150.
As a whole, the system generates an X-ray beam that lies in substantially the same path as the proton therapy beam. The X-ray beam is generated by striking a tungsten or equivalent material with an electron beam. The X-ray generation source is located proximate to the proton beam path. Geometry of the incident electrons, geometry of the X-ray generation material, and/or geometry of the X-ray beam blocker 262 yield an X-ray beam that runs either in substantially in parallel with the proton beam or results in an X-ray beam path that starts proximate the proton beam path an expands to cover and transmit through a tumor cross-sectional area to strike an X-ray detector array or film allowing imaging of the tumor from a direction and alignment of the proton therapy beam. The X-ray image is then used to control the charged particle beam path to accurately and precisely target the tumor, and/or is used in system verification and validation.
Referring now to FIG. 23, additional geometry of the electron beam path 2150 and X-ray beam path 2270 is illustrated. Particularly, the electron beam 2150 is shown as an expanded electron beam path 2152, 2154. Also, the X-ray beam path 2270 is shown as an expanded X-ray beam path 2272, 2274.
In this section, three examples of positioning systems 2400 are provided: (1) a semi-vertical partial immobilization system; (2) a sitting partial immobilization system; and (3) a laying position. Elements described for one immobilization system apply to other immobilization systems with small changes. For example, a head rest will adjust along one axis for a reclined position, along a second axis for a seated position, and along a third axis for a laying position. However, the headrest itself is similar for each immobilization position.
An optional camera is used with the patient immobilization system. The camera views the subject creating an video image. The image is provided to one or more operators of the charged particle beam system and allows the operators a safety mechanism for determining if the subject has moved or desires to terminate the proton therapy treatment procedure. Based on the video image, the operators optionally suspend or terminate the proton therapy procedure. For example, if the operator observes via the video image that the subject is moving, then the operator has the option to terminate or suspend the proton therapy procedure.
Respiration control is optionally performed by using the video display. As the patient breathes, internal and external structures of the body move in both absolute terms and in relative terms. For example, the outside of the chest cavity and internal organs both have absolute moves with a breath. In addition, the relative position of an internal organ relative to another body component, such as an outer region of the body, a bone, support structure, or another organ, moves with each breath. Hence, for more accurate and precise tumor targeting, the proton beam is preferably delivered at point a in time where the position of the internal structure or tumor is well defined, such as at the bottom of each breath. The video display is used to help coordinate the proton beam delivery with the patient's breathing cycle. For example, the video display optionally displays to the patient a command, such as a hold breath statement, a breathe statement, a countdown indicating when a breath will next need to be held, or a countdown until respiration may resume.
In a second partial immobilization embodiment, the patient is partially restrained in a seated position. The sitting restraint system has support structures that are similar to the support structures used in the semi-vertical positioning system, described supra with the exception that the seat support is replaced by a chair and the knee support is not required. The seated restraint system generally retains the adjustable support, rotation about the y-axis, camera, video, and respiration control parameters described in the semi-vertical embodiment, described supra.
In a third partial immobilization embodiment, the patient is partially restrained in a laying position. The laying restraint system has support structures that are similar to the support structures used in the sitting positioning system and semi-vertical positioning system, described supra. In the laying position, optional restraint, support, or partial immobilization elements include one or more of: the head support and the back, hip, and shoulder support. The supports preferably have respective axes of adjustment that are rotated as appropriate for a laying position of the patient. The laying position restraint system generally retains the adjustable supports, rotation about the y-axis, camera, video, and respiration control parameters described in the semi-vertical embodiment, described supra.
Positioning constraints include all elements used to position the patient, such as those described in the semi-vertical positioning system, sitting positioning system, and laying positioning system. Preferably, positioning constraints or support system elements are aligned in positions that do not impede or overlap the proton beam path 269. However, in some instances the positioning constraints are in the proton beam path 269 during at least part of the time of treatment of the patient. For instance, a positioning constraint element may reside in the proton beam path 269 during part of a time period where the patient is rotated about the y-axis during treatment. In cases or time periods that the positioning constraints or support system elements are in the proton beam path, then an upward adjustment of proton beam energy is preferably applied that increases the proton beam energy to offset the positioning constraint element impedance of the proton beam. This time period and energy is a function of rotational orientation of the patient. In one case, the proton beam energy is increased by a separate measure of the positioning constraint element impedance determined during a reference scan of the positioning constraint system element or set of reference scans of the positioning constraint element as a function of rotation about the y-axis.
Referring now to FIG. 25 another example of a head support system is described for positioning and/or restricting movement of a human head 1902 during proton therapy of a solid tumor in the head or neck. In this system, the head is restrained using 1, 2, 3, 4, or more straps or belts, which are preferably connected or replaceably connected to a back of head support element 2510. In the example illustrated, a first strap 2520 pulls or positions the forehead to the head support element 2510, such as by running predominantly along the z-axis. Preferably a second strap 2530 works in conjunction with the first strap 2520 to prevent the head from undergoing tilt, yaw, roll or moving in terms of translational movement on the x-, y-, and z-axes coordinate system. The second strap 2530 is preferably attached or replaceable attached to the first strap 2520 at or about: (1) a forehead position 2532; (2) as a position on one or both sides of the head 2534; and/or (3) at a position about the support element 2536. A third strap 2540 preferably orientates the chin of the subject relative to the support element 2510 by running dominantly along the z-axis. A fourth strap 2550 preferably runs along a predominantly y- and z-axes to hold the chin relative to the head support element 2510 and/or proton beam path. The third 2540 strap preferably is attached to or is replaceably attached to the fourth strap 2550 during use at or about a position by the chin 2542. The second strap 2530 optionally connects to the fourth strap 2550 at or about the support element 2510. The four straps 2520, 2530, 2540, 2550 are illustrative in pathway and interconnection. Any of the straps optionally hold the head along different paths around the head and connect to each other in separate fashion. Naturally, a given strap preferably runs around the head and not just on one side of the head. Any of the straps 2520, 2530, 2540, and 2550 are optionally used independently or in combinations or permutations with the other straps. The straps are optionally indirectly connected to each other via a support element, such as the head support element 2510. The straps are optionally attached to the head support element 2510 using hook and loop technology, a buckle, or fastener. Generally, the straps combine to control position, front-to-back movement of the head, side-to-side movement of the head, tilt, yaw, roll, and/or translational position of the head.
The straps are preferably of known impedence to proton transmission allowing a calculation of peak energy release along the z-axis to be calculated, such as an adjustment to the Bragg peak is made based on the slowing tendency of the straps to proton transport.
Monitoring Respiration
Preferably, the patient's respiration pattern is monitored. When a subject, also referred to herein as a patient, is breathing many portions of the body move with each breath. For example, when a subject breathes the lungs move as do relative positions of organs within the body, such as the stomach, kidneys, liver, chest muscles, skin, heart, and lungs. Generally, most or all parts of the torso move with each breath. Indeed, the inventors have recognized that in addition to motion of the torso with each breath, various motion also exists in the head and limbs with each breath. Motion is to be considered in delivery of a proton dose to the body as the protons are preferentially delivered to the tumor and not to surrounding tissue. Motion thus results in an ambiguity in where the tumor resides relative to the beam path. To partially overcome this concern, protons are preferentially delivered at the same point in each of a series of breathing cycles.
Preferably, one or more sensors are used to determine the respiration cycle of the individual. Two examples of a breath monitoring system are provided: (1) a thermal monitoring system and (2) a force monitoring system.
Respiration Control
Once the rhythmic pattern of the subject's breathing is determined, a signal is optionally delivered to the subject to more precisely control the breathing frequency. For example, a display screen is placed in front of the subject directing the subject when to hold their breath and when to breath. Typically, a breathing control module uses input from one or more of the breathing sensors. For example, the input is used to determine when the next breath exhale is to complete. At the bottom of the breath, the control module displays a hold breath signal to the subject, such as on a monitor, via an oral signal, digitized and automatically generated voice command, or via a visual control signal. Preferably, a display monitor is positioned in front of the subject and the display monitor displays at least breathing commands to the subject. Typically, the subject is directed to hold their breath for a short period of time, such as about one-half, one, two, or three seconds. The period of time the subject is asked to hold their breath is less than about ten seconds. The period of time the breath is held is preferably synchronized to the delivery time of the proton beam to the tumor, which is about one-half, one, two, or three seconds. While delivery of the protons at the bottom of the breath is preferred, protons are optionally delivered at any point in the breathing cycle, such as upon full inhalation. Delivery at the top of the breath or when the patient is directed to inhale deeply and hold their breath by the breathing control module is optionally performed as at the top of the breath the chest cavity is largest and for some tumors the distance between the tumor and surrounding tissue is maximized or the surrounding tissue is rarefied as a result of the increased volume. Hence, protons hitting surrounding tissue is minimized. Optionally, the display screen tells the subject when they are about to be asked to hold their breath, such as with a 3, 2, 1, second countdown so that the subject is aware of the task they are about to be asked to perform.
Proton Beam Therapy Synchronization with Respiration
A proton delivery control algorithm is used to synchronize delivery of the protons to the tumor within a given period of each breath, such as at the top or bottom of a breath when the subject is holding their breath. The proton delivery control algorithm is preferably integrated with the breathing control module. Thus, the proton delivery control algorithm knows when the subject is breathing, where in the breath cycle the subject is, and/or when the subject is holding their breath. The proton delivery control algorithm controls when protons are injected and/or inflected into the synchrotron, when an RF signal is applied to induce an oscillation, as described supra, and when a DC voltage is applied to extract protons from the synchrotron, as described supra. Typically, the proton delivery control algorithm initiates proton inflection and subsequent RF induced oscillation before the subject is directed to hold their breath or before the identified period of the breathing cycle selected for a proton delivery time. In this manner, the proton delivery control algorithm can deliver protons at a selected period of the breathing cycle by simultaneously or nearly simultaneously delivering the high DC voltage to the second pair of plates, described supra, which results in extraction of the protons from the synchrotron and subsequent delivery to the subject at the selected time point. Since the period of acceleration of protons in the synchrotron is constant or known for a desired energy level of the proton beam, the proton delivery control algorithm is used to set an AC RF signal that matches the breathing cycle or directed breathing cycle of the subject.
Multi-Field Irradiation
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