Source: http://www.patentsencyclopedia.com/app/20110174984
Timestamp: 2017-10-18 13:30:28
Document Index: 713003535

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 application number: 20110174984
1. An apparatus for extracting a circulating charged particle beam from a synchrotron, said synchrotron having a center, said apparatus comprising: an extraction material; at least a one kilovolt direct current field applied across a pair of extraction blades; and a deflector, wherein the circulating charged particle beam passes through said extraction material resulting in a reduced energy charged particle beam, wherein the reduced energy charged particle beam passes between said pair of extraction blades, and wherein the direct current field redirects the reduced energy charged particle beam through said deflector, wherein said deflector yields an extracted charged particle beam.
4. The apparatus of claim 1, wherein said extraction material comprises any of: beryllium; lithium hydride; and carbon.
8. The apparatus of claim 1, further comprising an intensity controller controlling intensity of the extracted charged particle beam via a feedback control.
9. The apparatus of claim 8, wherein an induced current results from the circulating charged particle beam passing through said extraction material, wherein the induced current comprises a feedback input to said intensity controller.
10. The apparatus of claim 8, wherein said intensity controller alters an applied radio frequency inducing betatron oscillation on the circulating charged particle beam.
11. The apparatus of claim 1, further comprising at least one turning magnet.
12. The apparatus of claim 11, wherein said turning magnet comprises a magnetic field concentrating first magnet, wherein said first magnet comprises: a gap through which the circulating charged particle beam circulates; a first cross-section diameter not in contact with said gap; and a second cross-sectional diameter proximate said gap, wherein said second cross-section diameter is less than seventy percent of said first cross-sectional diameter, wherein a magnetic field passing through said first cross-sectional diameter concentrates in said second cross-sectional diameter before crossing said gap.
13. A method for extracting a circulating charged particle beam from a synchrotron, comprising the steps of: transmitting the circulating charged particle beam through an extraction material, said extraction material yielding a reduced energy charged particle beam; applying at least five hundred volts across a first pair of blades; and passing the reduced energy charged particle beam between said first pair of blades, wherein said first pair of blades redirect the reduced energy charged particle beam to a deflector, wherein said deflector yields an extracted charged particle beam.
14. The method of claim 13, wherein said extraction material consists essentially of atoms having six or fewer protons.
15. The method of claim 13, wherein said extraction material comprises any of: beryllium; lithium hydride; and carbon.
16. The method of claim 15, wherein said extraction material comprises a foil of about forty to sixty microns thickness.
17. The method of claim 13, further comprising the step of: inducing betatron oscillation using a second pair of blades, wherein the circulating charged particle beam passes between said second pair of blades prior to said step of transmitting.
18. The method of claim 13, further comprising the step of: controlling intensity of the extracted charged particle beam with an intensity controller using a feedback control.
19. The method of claim 18, wherein an induced current results from the circulating charged particle beam passing through said extraction material, wherein the induced current comprises a feedback input to said step of controlling intensity.
20. The method of claim 19, wherein said intensity controller alters duration of an applied radio frequency inducing altered trajectory of the circulating charged particle beam.
21. A method for extracting a circulating charged particle beam from a synchrotron, comprising the steps of: transmitting the circulating charged particle beam through an extraction material, said extraction material yielding a reduced energy charged particle beam; applying a field of at least five hundred volts across a pair of extraction blades; passing the reduced energy charged particle beam between said pair of extraction blades, wherein said field redirects the reduced energy charged particle as an extracted charged particle beam.
22. The method of claim 21, further comprising the step of: prior to said step of transmitting, inducing betatron oscillation on the circulating charged particle beam, wherein said step of inducing occurs at a selected energy level of the circulating charged particle beam, wherein the betatron oscillation increases average radius of curvature of the circulating charged particle beam until said step of transmitting yields the reduced energy charged particle beam, wherein said step of inducing at said selected energy level yields an energy controlled extracted charged particle beam.
23. The method of claim 22, further comprising the step of: controlling intensity of the energy controlled extracted charged beam with an intensity controller.
24. The method of claim 23, wherein said step of controlling comprises the steps of: inputting a feedback signal to said intensity controller, said step of transmitting yielding emitted electrons in the process of the circulating charged particle beam striking said extraction material, wherein the emitted electrons are converted to said feedback signal; comparing said feedback signal to an irradiation plan intensity; adjusting betatron oscillation with said intensity controller until said feedback signal proximately equals said irradiation plan intensity, wherein said energy controlled extracted charged particle beam comprises an independent intensity control.
25. The method of claim 21, further comprising the steps of: inducing a change in radial movement of the circulating charged particle beam: (1) after acceleration of the charged particle beam to a selected energy and (2) prior to said step of transmitting the circulating charged particle beam through said extraction material; and controlling intensity of said extracted charged particle beam using an electron flow resultant from the charged particle beam transmitting through said extraction material.
26. The method of claim 25, wherein energy control of said extracted charged particle beam is independent of intensity control of said extracted charged particle beam.
[0001] This application: [0002] is a continuation of U.S. patent application Ser. No. 12/425,683, which claims: the benefit of: [0003] U.S. provisional patent application No. 61/055,395 filed May 22, 2008; [0004] U.S. provisional patent application No. 61/137,574 filed Aug. 1, 2008; [0005] U.S. provisional patent application No. 61/192,245 filed Sep. 17, 2008; [0006] U.S. provisional patent application No. 61/055,409 filed May 22, 2008; [0007] U.S. provisional patent application No. 61/203,308 filed Dec. 22, 2008; [0008] U.S. provisional patent application No. 61/188,407 filed Aug. 11, 2008; [0009] U.S. provisional patent application No. 61/209,529 filed Mar. 9, 2009; [0010] U.S. provisional patent application No. 61/188,406 filed Aug. 11, 2008; [0011] U.S. provisional patent application No. 61/189,815 filed Aug. 25, 2008; [0012] U.S. provisional patent application No. 61/208,182 filed Feb. 23, 2009; [0013] U.S. provisional patent application No. 61/201,731 filed Dec. 15, 2008; [0014] U.S. provisional patent application No. 61/208,971 filed Mar. 3, 2009; [0015] U.S. provisional patent application No. 61/205,362 filed Jan. 12, 2009; [0016] U.S. provisional patent application No. 61/134,717 filed Jul. 14, 2008; [0017] U.S. provisional patent application No. 61/134,707 filed Jul. 14, 2008; [0018] U.S. provisional patent application No. 61/201,732 filed Dec. 15, 2008; [0019] U.S. provisional patent application No. 61/198,509 filed Nov. 7, 2008; [0020] U.S. provisional patent application No. 61/134,718 filed Jul. 14, 2008; [0021] U.S. provisional patent application No. 61/190,613 filed Sep. 2, 2008; [0022] U.S. provisional patent application No. 61/191,043 filed Sep. 8, 2008; [0023] U.S. provisional patent application No. 61/192,237 filed Sep. 17, 2008; [0024] U.S. provisional patent application No. 61/201,728 filed Dec. 15, 2008; [0025] U.S. provisional patent application No. 61/190,546 filed Sep. 2, 2008; [0026] U.S. provisional patent application No. 61/189,017 filed Aug. 15, 2008; [0027] U.S. provisional patent application No. 61/198,248 filed Nov. 5, 2008; [0028] U.S. provisional patent application No. 61/198,508 filed Nov. 7, 2008; [0029] U.S. provisional patent application No. 61/197,971 filed Nov. 3, 2008; [0030] U.S. provisional patent application No. 61/199,405 filed Nov. 17, 2008; [0031] U.S. provisional patent application No. 61/199,403 filed Nov. 17, 2008; and [0032] U.S. provisional patent application No. 61/199,404 filed Nov. 17, 2008; and [0033] priority to PCT patent application serial No.: PCT/RU2009/00015, filed Mar. 4, 2009, [0034] all of which are incorporated herein in their entirety by this reference thereto.
[0036] This invention relates generally to treatment of solid cancers. More particularly, the invention relates to a charged particle beam extraction method and apparatus used in conjunction with radiation treatment of cancerous tumors.
[0039] A tumor is an abnormal mass of tissue. Tumors are either benign or malignant. A benign tumor grows locally, but does not spread to other parts of the body. Benign tumors cause problems, because of their spread, as they press and displace normal tissues. Benign tumors are dangerous in confined places, such as the skull. A malignant tumor is capable of invading other regions of the body. Metastasis is cancer spreading by invading normal tissue and spreading to distant tissues.
[0041] Several forms of radiation therapy exist for cancer treatment, including: brachytherapy, traditional electromagnetic X-ray therapy, and proton therapy. Each are further described, infra.
[0043] The second form of traditional cancer treatment using electromagnetic radiation includes treatment using X-rays and gamma rays. An X-ray is high-energy, ionizing, electromagnetic radiation that is used at low doses to diagnose disease or at high doses to treat cancer. An X-ray or Rontgen ray is a form of electromagnetic radiation with a wavelength in the range of 10 to 0.01 nanometers (nm), corresponding to frequencies in the range of 30 PHz to 30 EHz. X-rays are longer than gamma rays and shorter than ultraviolet rays. X-rays are primarily used for diagnostic radiography. X-rays are a form of ionizing radiation and as such can be dangerous. Gamma rays are also a form of electromagnetic radiation and are at frequencies produced by sub-atomic particle interactions, such as electron-positron annihilation or radioactive decay. In the electromagnetic spectrum, gamma rays are generally characterized as electromagnetic radiation having the highest frequency, as having highest energy, and having the shortest wavelength, such as below about 10 picometers. Gamma rays consist of high energy photons with energies above about 100 keV. X-rays are commonly used to treat cancerous tumors. However, X-rays are not optimal for treatment of cancerous tissue as X-rays deposit their highest dose of radiation near the surface of the targeted tissue and delivery exponentially less radiation as they penetrate into the tissue. This results in large amounts of radiation being delivered outside of the tumor. Gamma rays have similar limitations.
[0045] Proton therapy works by aiming energetic ionizing particles, such as protons accelerated with a particle accelerator, into a target tumor. These particles damage the DNA of cells, ultimately causing their death. Cancerous cells, because of their high rate of division and their reduced ability to repair damaged DNA, are particularly vulnerable to attack on their DNA.
[0046] Due to their relatively enormous size, protons scatter less easily than X-rays in tissue and there is very little lateral dispersion. Hence, the proton beam stays focused on the tumor shape without much lateral damage to surrounding tissue. All protons of a given energy have a certain range, defined by the Bragg peak, and the dosage delivery to tissue ratio is maximum over just the last few millimeters of the particle's range. The penetration depth depends on the energy of the particles, which is directly related to the speed to which the particles were accelerated by the proton accelerator. The speed of the proton is adjustable to the maximum rating of the accelerator. It is therefore possible to focus the cell damage due to the proton beam at the very depth in the tissues where the tumor is situated. Tissues situated before the Bragg peak receive some reduced dose of radiation and tissues situated after the peak receive no radiation.
[0051] Injection
[0115] Y. Muramatsu, et. al. "Medical Particle Irradiation Apparatus", U.S. Pat. No. 7,030,396 (Apr. 18, 2006); Y., Muramatsu, et. al. "Medical Particle Irradiation Apparatus", U.S. Pat. No. 6,903,356 (Jun. 7, 2005); and Y., Muramatsu, et. al. "Medical Particle Irradiation Apparatus", U.S. Pat. No. 6,803,591 (Oct. 12, 2004) all describe a medical particle irradiation apparatus having a rotating gantry, an annular frame located within the gantry such that is can rotate relative to the rotating gantry, an anti-correlation mechanism to keep the frame from rotating with the gantry, and a flexible moving floor engaged with the frame is such a manner to move freely with a substantially level bottom while the gantry rotates.
[0130] There exists in the art of particle beam treatment of cancerous tumors in the body a need for efficient extraction of charged particles from a synchrotron of a charged particle therapy system. Further, there exists a need for extraction of charged particles at a specified energy, time, and/or intensity to yield a charged particle beam for efficient, precise, and accurate in-vivo treatment of a solid cancerous tumor with minimization of damage to surrounding healthy tissue in a patient.
[0131] The invention comprises a charged particle beam extraction method and apparatus used in conjunction with charged particle beam radiation therapy of cancerous tumors.
[0132] FIG. 1 illustrates sub-system connections of a particle beam therapy system;
[0133] FIG. 2 illustrates a synchrotron;
[0134] FIG. 3 illustrates a turning magnet within the synchrotron;
[0135] FIG. 4 illustrates a particle beam extraction system;
[0136] FIG. 5 illustrates a particle beam intensity control system;
[0137] FIG. 6 demonstrates beam acceleration;
[0138] FIG. 7 demonstrates beam intensity; and
[0139] FIG. 8A illustrates charged particle treatment of a tumor in a patient and FIG. 8B illustrates 3-dimensional scanning of the charged particle beam.
[0140] The invention comprises a charged particle beam extraction method and apparatus used in conjunction with charged particle beam radiation therapy of cancerous tumors.
[0141] Accurate and precise delivery of protons to a tumor in body tissue is critical in charged particle beam therapy. Herein, extraction of a charged particle beam from a synchrotron is described as part of a charged particle cancer tumor therapy system. The system uses a radio-frequency (RF) cavity system to induce betatron oscillation of a charged particle stream. Sufficient amplitude modulation of the charged particle stream causes the charged particle stream to hit a material, such as a foil. The foil decreases the energy of the charged particle stream, which decreases a radius of curvature of the charged particle stream in the synchrotron sufficiently to allow a physical separation of the reduced energy charged particle stream from the original charged particle stream. The physically separated charged particle stream is then removed from the system by use of an applied field and deflector. The extraction system is further described, infra.
[0142] Charged Particle Beam Therapy
[0143] 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. The techniques described herein are equally applicable to any charged particle beam system.
[0144] Referring now to FIG. 1, a charged particle beam system 100 is illustrated. A charged particle beam, preferably comprises a number of subsystems including any of: a main controller 110; an injection system 120; a synchrotron 130 that typically includes: (1) an accelerator system 132 and (2) an extraction system 134; a targeting/delivery system 140; a patient interface module 150; a display system 160; and/or an imaging system 170.
[0145] An exemplary method of use of the charged particle beam system 100 is provided. The main controller 110 controls one or more of the subsystems to accurately and precisely deliver protons to a tumor of a patient. For example, the main controller 110 obtains 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 a proton into a synchrotron 130. The synchrotron typically contains at least an accelerator system 132 and an extraction system 134. The main controller preferably controls the proton beam within the accelerator system, such as by controlling speed, trajectory, and 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. 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.
[0146] Herein, the main controller 110 refers to a single system controlling the charged particle beam system 100, to a single controller controlling a plurality of subsystems controlling the charged particle beam system 100, or to a plurality of individual controllers controlling one or more sub-systems of the charged particle beam system 100.
[0147] Synchrotron
[0148] Herein, the term synchrotron is used to refer to a system maintaining the charged particle beam in a circulating path; however, cyclotrons are alternatively used, albeit with their inherent limitations of energy, intensity, and extraction control. 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.
[0149] Referring now to FIG. 2, an illustrative exemplary embodiment of one version of the charged particle beam system 100 is provided. The number, position, and described type of components is illustrative and non-limiting in nature. In the illustrated embodiment, the injection 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, dipole magnets, or circulating magnets 250 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. In one embodiment, the first axis control 142 allows for about 100 mm of vertical or y-axis scanning of the proton beam 268 and the second axis control 144 allows for about 700 mm of horizontal or x-axis scanning of the proton beam 268. A nozzle system 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. All of the above listed elements are optional and may be used in various permutations and combinations. The above listed elements are further described, infra.
[0150] Ion Beam Generation System
[0151] An ion beam generation system generates a negative ion beam, such as a hydrogen anion or H.sup.- beam; preferably focuses the negative ion beam; converts the negative ion beam to a positive ion beam, such as a proton or H.sup.+ beam; and injects the positive ion beam 262 into the synchrotron 130. Portions of the ion beam path are preferably under partial vacuum.
[0152] Synchrotron
[0153] 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 280.
[0154] Circulating System
[0155] The synchrotron 130 preferably comprises a combination of straight sections and ion beam turning sections. Hence, the circulating path of the protons is not circular in a synchrotron, but is rather a polygon with rounded corners.
[0156] In one illustrative embodiment, the synchrotron 130, which as also referred to as an accelerator system, has four straight elements and four turning sections. Examples of straight sections include the: inflector 240, accelerator 270, extraction system 290, and deflector 292. Along with the four straight sections are four ion beam turning sections, which are also referred to as magnet sections or turning sections. For example, a turning section is a set of about 2, 4, 6, or 8 turning magnets 250. Turning sections are further described, infra.
[0157] Referring still to FIG. 2, an exemplary synchrotron is illustrated. In this example, protons delivered along the initial proton beam path 262 are inflected into the circulating beam path with the inflector 240 and after acceleration are extracted via a deflector 292 to the beam transport path 268. In this example, the synchrotron 130 comprises four straight sections and four bending or turning sections 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.
[0158] Additional description of the first bending or turning section between injector magnet 240 and inflector/deflector system 290 is provided. Additional turning sections are (1) from the inflector/deflector system 290 to the Lamberson extraction magnet 292; (2) from the Lamberson extraction magnet 292 to the accelerator 270; and (3) from the accelerator 270 to the injector magnet 240. Each of the turning sections preferably comprise multiple magnets, such as about 2, 4, 6, 8, 10, or 12 magnets. In this example, four turning magnets or circulating magnets 250 in the first turning section 920 are used to illustrate key principles, which are the same regardless of the number of magnets in a turning section.
[0159] Turning Magnet Focusing Geometry
[0160] Referring now to FIG. 3, a cross section of a single turning magnet 250 is provided. The turning section includes a gap 310 through which protons circulate. The magnet assembly has a first magnet 320 and a second magnet 330. A magnetic field induced by coils runs between the first magnet 320 to the second magnet 330 across the gap 310. Return magnetic fields run through a first yoke 322 and second yoke 332. The magnetic field is created using a first winding coil 350 and a second winding coil 360. Isolating or concentrating gaps 340, such as air gaps, isolate the iron based yokes from the gap 310. The gap 310 is approximately flat to yield a uniform magnetic field across the gap 310. As illustrated, the first magnet 320 preferably contains an initial cross sectional distance 370 of the iron based core. The contours of the magnetic field are shaped by the magnets 320, 330 and the yokes 322, 332 from a first cross sectional distance or area 374 to a second cross sectional distance or area 376. For example, the first cross-sectional distance is about 15 cm and the second cross-section distance is about 10 cm. In a second example, the second cross section distance is less than seventy percent of the first cross-section distance. In these examples, the core tapers to a second cross sectional distance 372 with an angle theta, θ. As described, supra, the magnetic field in the magnet preferentially stays in the iron based core as opposed to the isolating gaps 340. As the cross-sectional distance decreases from the initial cross sectional distance 370 to the final cross-sectional distance 372, the magnetic field concentrates. The angle theta results in an amplification of the magnetic field in going from the longer distance 370 to the smaller distance 372. The concentration of the magnetic field is illustrated by representing an initial density of magnetic field vectors in the initial cross section 370 to a concentrated density of magnetic field vectors in the final cross section 372. The concentration of the magnetic field due to the geometry of the turning magnets results in fewer winding coils 350, 360 being required and also a smaller power supply to the winding coils 350, 360 being required.
[0161] Turning Magnet Correction Coils
[0162] Still referring to FIG. 3, optional correction coils 380, 390 are illustrated that are used to correct the strength of one or more turning magnets. The correction coils 380, 390 supplement the winding coils 350, 360. 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 350, 360. The smaller operating power applied to the correction coils 380, 390 allows for more accurate and/or precise control of the correction coils. The correction coils 380, 390 are used to adjust for imperfection in the turning magnets 250. Optionally, separate correction coils are used for each turning magnet allowing individual tuning of the magnetic field for each turning magnet, which eases quality requirements in the manufacture of each turning magnet.
[0163] The winding coils preferably cover 1, 2, or 4 turning magnets 250. 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 310 or at or near the magnet core or yoke. The sensors are part of a feedback system to the correction coils, which is optionally run by the main controller. Thus, the system preferably stabilizes the magnetic field in the synchrotron elements 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.
[0164] Turning Magnets Beveled Edges
[0165] The ends of a single bending or turning magnet are preferably beveled. Beveling the edge of the turning magnet 250 focuses the proton beam. Multiple turning magnets provide multiple magnet edges that each have edge focusing effects in the synchrotron 130. For example, if four magnets are used in a turning section of the synchrotron, then for a single turning section there are eight possible edge focusing effect surfaces, two edges per magnet. The eight focusing surfaces yield a smaller cross-sectional beam size, which allows the use of a smaller gap. For a synchrotron 130 having four turning sections, where each turning sections has four turning magnets and each turning magnet has two focusing edges, a total of thirty-two focusing edges exist for each orbit of the protons in the circulating path of the synchrotron 130. Similarly, if 2, 6, or 8 magnets are used in a given turning section, or if 2, 3, 5, or 6 turning sections are used, then the number of edge focusing surfaces expands or contracts according to equation 1.
[0166] where TFE is the number of total focusing edges, NTS is the number of turning sections, 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.
[0167] In various embodiments of the system described herein, the synchrotron has any combination of: [0168] 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; [0169] at least about 16 and preferably about 24, 32, or more edge focusing edges per orbit of the charged particle beam in the synchrotron; [0170] only 4 turning sections where each of the turning sections includes at least 4 and preferably 8 edge focusing edges; [0171] an equal number of straight sections and turning sections; [0172] exactly 4 turning sections; [0173] at least 4 focusing edges per turning section; [0174] no quadrupoles in the circulating path of the synchrotron; [0175] a rounded corner rectangular polygon configuration; [0176] a circumference of less than 60 meters; [0177] a circumference of less than 60 meters and 32 edge focusing surfaces; and/or; [0178] 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.
[0179] Proton Beam Extraction
[0180] Referring now to FIG. 4, an exemplary proton extraction process from the synchrotron 130 is illustrated. For clarity, FIG. 4 removes elements represented in FIG. 2, such as the turning magnets, which allows for greater clarity of presentation of the proton beam path as a function of time. Generally, protons are extracted from the synchrotron 130 by slowing the protons. As described, supra, the protons were initially accelerated in a circulating path 264, which is maintained with a plurality of turning magnets 250. The circulating path is referred to herein as an original central beamline 264. The protons repeatedly cycle around a central point in the synchrotron 280. The proton path traverses through an RF cavity system 410. To initiate extraction, an RF field is applied across a first blade 412 and a second blade 414, in the RF cavity system 410. The first blade 412 and second blade 414 are referred to herein as a first pair of blades.
[0181] In the proton extraction process, an RF voltage is applied across the first pair of blades, where the first blade 412 of the first pair of blades is on one side of the circulating proton beam path 264 and the second blade 414 of the first pair of blades is on an opposite side of the circulating proton beam path 264. The applied RF field applies energy to the circulating charged-particle beam. The applied RF field alters the orbiting or circulating beam path slightly of the protons from the original central beamline 264 to an altered circulating beam path 265. Upon a second pass of the protons through the RF cavity system, the RF field further moves the protons off of the original proton beamline 264. For example, if the original beamline is considered as a circular path, then the altered beamline is slightly elliptical. The applied RF field is timed to apply outward or inward movement to a given band of protons circulating in the synchrotron accelerator. Each orbit of the protons is slightly more off axis compared to the original circulating beam path 264. Successive passes of the protons through the RF cavity system are forced further and further from the original central beamline 264 by altering the direction and/or intensity of the RF field with each successive pass of the proton beam through the RF field.
[0182] The RF voltage is frequency modulated at a frequency about equal to the period of one proton cycling around the synchrotron for one revolution or at a frequency than is an integral multiplier of the period of one proton cycling about the synchrotron. The applied RF frequency modulated voltage excites a betatron oscillation. For example, the oscillation is a sine wave motion of the protons. The process of timing the RF field to a given proton beam within the RF cavity system is repeated thousands of times with successive passes of the protons being moved approximately one micrometer further off of the original central beamline 264. For clarity, the approximately 1000 changing beam paths with each successive path of a given band of protons through the RF field are illustrated as the altered beam path 265.
[0183] With a sufficient sine wave betatron amplitude, the altered circulating beam path 265 touches a material 430, 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 40-60 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.
[0184] The thickness of the material 430 is optionally adjusted to created a change in the radius of curvature, such as about 1/2, 1, 2, 3, or 4 mm less than the last pass of the protons 265 or original radius of curvature 264. Protons moving with the smaller radius of curvature travel between a second pair of blades 414, 416. The second pair of blades 414, 416 is also referred to as a pair of extraction blades. In one case, the second pair of blades is physically distinct and/or are separated from the first pair of blades. In a second case, one of the first pair of blades is also a member of the second pair of blades. For example, the second pair of blades is the second blade 414 and a third blade 416 in the RF cavity system 410. A high voltage DC signal, such as about 0.5, 1, 2, 3, 4, or 5 kV, is then applied across the second pair of blades, which directs the protons out of the synchrotron through a deflector 292, such as a Lamberson magnet, into a transport path 268.
[0185] In a first example, protons are extracted from a synchrotron by slowing the protons with a foil. Initially, an RF signal is applied across a proton path, such as through two metal elements where one metallic element is on a first side of a cyclic proton path in the synchrotron and a second metallic element is on an opposite side of the proton path. An RF voltage is applied across the two metal elements. The applied voltage is modulated or frequency modulated to induce an oscillation in the path of the protons. The oscillation forces a portion of the proton beam through a foil. In this case, the foil is a beryllium material of about fifty microns in thickness. The electrons on the foil slow the protons resulting in a beam path having a smaller average diameter compared to protons repeatedly cycling in the synchrotron. The protons having the smaller average diameter beam path traverse a high DC voltage field, which directs the protons out of the synchrotron or into a Lamberson magnet directing the protons out of the synchrotron.
[0186] Still referring to FIG. 4, an exemplary synchrotron 130 is illustrated. A set of magnets control protons in the synchrotron in a repeated cyclic path 264 having a first radius of curvature. Protons in the first path traverse between a first pair of metal plates 412, 414 having an AC frequency voltage applied across the two metal plates. The AC voltage induces an oscillation on some of the protons causing them to pass through a foil material 430 that reduces the speed of the protons. The protons moving at a slower speed have a reduced radius of curvature path 266. The protons having the reduced radius of curvature then pass through a DC field, such as a high voltage field between a second pair of metal plates 414, 416, which directs the protons along a new path. The new path 266 optionally traverses another magnetic field, such as that of a Lamberson magnet, that directs the protons away from the synchrotron.
[0187] Generally, the extraction process takes a proton circulating in a synchrotron and slows the proton by passing the proton through a foil. The circulating proton has a first radius of curvature associated with the energy of the circulating proton and the applied magnetic fields of the turning magnets. The protons passing through the foil have less energy resulting in a second radius of curvature that is less than the first radius of curvature. Hence, the protons are extracted toward the center of the synchrotron relative to the circulating proton beam path. The smaller radius of curvature slowed protons, after passing through the foil, are kicked out of the synchrotron by application of a field between the second and third plates and via use of a deflector, such as a Lamberson deflector.
[0188] Intensity Control
[0189] Referring now to FIG. 5, typically when protons in the proton beam hit the material 430 electrons are given off. The resulting current is optionally measured and sent to the main controller 110 or to an intensity controller subsystem 540. The current is used as a measure of the circulating beam path intensity and is optionally used to control the RF cavity system. In one instance, when a current is measured beyond a threshold, the RF field modulation in the RF cavity system is terminated or reinitiated to establish a subsequent cycle of proton beam extraction. This process is repeated to yield many cycles of proton beam extraction from the synchrotron accelerator. In another instance, the current is used as a feedback control to control the intensity of the extracted particle beam.
[0190] Referring still to FIG. 5, a feedback loop is added to the extraction system described supra. When protons in the proton beam hit the material 430 electrons are given off resulting in a current. The resulting current is converted to a voltage and is used as part of a ion beam intensity monitoring system or as part of an ion beam feedback loop for controlling beam intensity. The voltage is optionally measured and sent to the main controller 110 or to the controller subsystem 410. More particularly, when protons in the charged particle beam path pass through the material 430, some of the protons lose a small fraction of their energy, such as about one-tenth of a percent, which results in a secondary electron. That is, protons in the charged particle beam push some electrons when passing through material 430 giving the electrons enough energy to cause secondary emission. The resulting electron flow results in a current or signal that is proportional to the number of protons going through the target material 430. The resulting current is preferably converted to voltage and amplified. The resulting signal is referred to as a measured intensity signal.
[0191] The amplified signal or measured intensity signal resulting from the protons passing through the material 430 is preferably used in controlling the intensity of the extracted protons. For example, the measured intensity signal is compared to a goal signal, which is predetermined in an irradiation of the tumor plan 560. The difference between the measured intensity signal and the planned for goal signal is calculated. The difference is used as a control to the RF generator. Hence, the measured flow of current resulting from the protons passing through the material 430 is used as a control in the RF generator to increase or decrease the number of protons undergoing betatron oscillation and striking the material 430. Hence, the voltage determined off of the material 430 is used as a measure of the orbital path and is used as a feedback control to control the RF cavity system. Alternatively, the measured intensity signal is not used in the feedback control and is just used as a monitor of the intensity of the extracted protons.
[0192] As described, supra, the photons striking the material 430 is a step in the extraction of the protons from the synchrotron 130. Hence, the measured intensity signal is used to change the number of protons per unit time being extracted, which is referred to as intensity of the proton beam. The intensity of the proton beam is thus under algorithm control. Further, the intensity of the proton beam is controlled separately from the velocity of the protons in the synchrotron 130. Hence, intensity of the protons extracted and the energy of the protons extracted are independently variable.
[0193] For example, protons initially move at an equilibrium trajectory in the synchrotron 130. An RF field is used to excite the protons into a betatron oscillation. In one case, the frequency of the protons orbit is about 10 MHz. In one example, in about one millisecond or after about 10,000 orbits, the first protons hit an outer edge of the target material 430. The specific frequency is dependent upon the period of the orbit. Upon hitting the material 430, the protons push electrons through the foil to produce a current. The current is converted to voltage and amplified to yield a measured intensity signal. The measured intensity signal is used as a feedback input to control the applied RF magnitude, RF frequency, or RF field. Preferably, the measured intensity signal is compared to a target signal and a measure of the difference between the measured intensity signal and target signal is used to adjust the applied RF field in the RF cavity system 1810 in the extraction system to control the intensity of the protons in the extraction step. Stated again, the signal resulting from the protons striking and/or passing through the material 430 is used as an input in RF field modulation. An increase in the magnitude of the RF modulation results in protons hitting the foil or material 430 sooner. By increasing the RF, more protons are pushed into the foil, which results in an increased intensity, or more protons per unit time, of protons extracted from the synchrotron 130.
[0194] In another example, a detector 550 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. Particularly, the measured intensity signal is compared to a desired signal from the irradiation plan 560 in a feedback intensity controller 540, which adjusts the RF field between the first plate 412 and the second plate 414 in the extraction process, described supra.
[0195] In yet another example, when a current from material 430 resulting from protons passing through or hitting material is measured beyond a threshold, the RF field modulation in the RF cavity system is terminated or reinitiated to establish a subsequent cycle of proton beam extraction. This process is repeated to yield many cycles of proton beam extraction from the synchrotron accelerator.
[0196] In still yet another embodiment, intensity modulation of the extracted proton beam is controlled by the main controller 110. The main controller 110 optionally and/or additionally controls timing of extraction of the charged particle beam and energy of the extracted proton beam.
[0197] The benefits of the system include a multi-dimensional scanning system. Particularly, the system allows independence in: (1) energy of the protons extracted and (2) intensity of the protons extracted. That is, energy of the protons extracted is controlled by an energy control system and an intensity control system controls the intensity of the extracted protons. The energy control system and intensity control system are optionally independently controlled. Preferably, the main controller 110 controls the energy control system and the main controller 110 simultaneously controls the intensity control system to yield an extracted proton beam with controlled energy and controlled intensity where the controlled energy and controlled intensity are independently variable. Thus, the radiation spot hitting the tumor is under independent control of: [0198] time; [0199] energy; [0200] intensity; [0201] x-axis position, where the x-axis represents horizontal movement of the proton beam relative to the patient; and/or [0202] y-axis position, where the y-axis represents vertical movement of the proton beam relative to the patient.
[0203] In addition, the patient is optionally independently translated and/or rotated relative to a translational axis of the proton beam at the same time.
[0204] Timing
[0205] In yet another embodiment of the invention, the main controller 110 controls timing of extraction. For example, extraction is in synchronization with patient respiration or breathing. For instance, extraction is performed when the patient is at the bottom of a breath so that the proton beam is generated when the internal organs, bones, and structures of the patient are in reproducible positions or are in reproducible relative positions. Accurate and precise delivery of protons to a tumor in body tissue is critical in charged particle beam therapy. Complicating accurate and precise deliver is natural movement of the body. Movement of the body occurs on multiple levels, including: (1) general patient movement, such as walking; (2) standing, sitting, or lying position variation; and (3) relative movement of internal body parts, such as organs. All of these movements change with time. Hence, the method of timing extraction of the proton beam results in enhanced targeting, precision, and/or accuracy of the delivered proton beam to the tumor of the patient.
[0206] Proton Energy and Intensity Control
[0207] Referring now to FIGS. 6 and 7, proton energy and intensity capabilities of the proton delivery system are demonstrated. Referring now to FIG. 6, beam acceleration up to a maximum energy of 330 MeV is demonstrated. Further illustrated is a flexible repeated acceleration and retardation of the proton beam in one cycle. Particularly, in the first cycle from the first to fourth seconds, the beam is accelerated to 100 MeV, retarded to 50 MeV and accelerated once more to 150 MeV. In the next cycle starting at the fifth second, the proton energy is increased rapidly to 330 MeV where it is maintained for one second, which is needed for carrying out tomography. Referring now to FIG. 7, the corresponding beam intensity is provided for the two serial cycles of the synchrotron accelerator's work. From approximately the 11/2 to 31/2 second marks, the beam is directed to a certain irradiating point. Upon achieving the necessary dose value, the extraction is interrupted, the beam is moved to the next point and the extraction process is resumed from the 51/2 to 71/2 second marks. Combined, FIGS. 6 an d7 demonstrate independent control of energy and intensity. FIGS. 6 and 7 are demonstrative in nature. In real time operation, each of the above described processes optionally are generated at ten times the demonstrated rate.
[0208] Proton Beam Position Control
[0209] Referring now to FIG. 8, a beam delivery and tissue volume scanning system is illustrated. Presently, the worldwide radiotherapy community uses a method of dose field forming using a pencil beam scanning system. In stark contrast, FIG. 8 illustrates a spot scanning system or tissue volume scanning system. In the tissue volume scanning system, the proton beam 268 is controlled, in terms of transportation and distribution, using an inexpensive and precise scanning system. The scanning system is an active system, where the beam is focused into a spot focal point of about one-half, one, two, or three millimeters in diameter in the tumor 820. The focal point is translated to a momentary position 269 along two axes while simultaneously altering the applied energy of the proton beam, which effectively changes the third dimension of the focal point. For example, in the illustrated system in FIG. 8A, the spot is moved horizontally, is translated down a vertical axis, and then is moved again horizontally. In this example, current is used to control a vertical scanning system having at least one magnet. The applied current alters the magnetic field of the vertical scanning system to control the vertical deflection of the proton beam. Similarly, a horizontal scanning magnet system controls the horizontal deflection of the proton beam. The degree of transport along each axes is controlled to conform to the tumor cross-section at the given depth. The depth is controlled by changing the energy of the proton beam. For example, the proton beam energy is decreased, so as to define a new penetration depth, and the scanning process is repeated along the horizontal and vertical axes covering a new cross-sectional area of the tumor.
[0210] The system has five axes of control: x-axis, y-axis, energy, intensity, and time. The intensity control provided by the feedback current and the sub-controller 540 provides the fifth axis of intensity control. Combined, the five axes of control allow scanning or movement of the proton beam focal point over the entire volume of the cancerous tumor. The time at each spot and the direction into the body for each spot is controlled to yield the desired radiation does at each sub-volume of the cancerous volume while distributing energy hitting outside of the tumor.
[0211] The focused beam spot volume dimension is preferably tightly controlled to a diameter of about 0.5, 1, or 2 millimeters, but is alternatively several centimeters in diameter. Preferred design controls allow scanning in two directions with: (1) a vertical amplitude of about 100 mm amplitude and frequency up to 200 Hz; and (2) a horizontal amplitude of about 700 mm amplitude and frequency up to 1 Hz. More or less amplitude in each axis is possible by altering the scanning magnet systems.
[0212] In FIG. 8B, the proton beam goes along a z-axis controlled by the beam energy, the horizontal movement is an x-axis, and the vertical direction is a y-axis. The distance the protons move along the z-axis into the tissue, in this example, is controlled by the kinetic energy of the proton. This coordinate system is arbitrary and exemplary. The actual control of the proton beam is controlled in 3-dimensional space using two scanning magnet systems and by controlling the kinetic energy of the proton beam.
[0213] Although the invention has been described herein with reference to certain preferred embodiments, one skilled in the art will readily appreciate that other applications may be substituted for those set forth herein without departing from the spirit and scope of the present invention.
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