Source: http://www.google.com/patents/US8188688?dq=6819670
Timestamp: 2014-12-18 07:02:43
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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 US8188688 - Magnetic field control method and apparatus used in conjunction with a ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsThe invention comprises a charged particle beam acceleration, extraction, and/or targeting method and apparatus used in conjunction with charged particle beam radiation therapy of cancerous tumors. Novel design features of a synchrotron are described. Particularly, turning magnets, edge focusing magnets,...http://www.google.com/patents/US8188688?utm_source=gb-gplus-sharePatent US8188688 - Magnetic field control method and apparatus used in conjunction with a charged particle cancer therapy systemAdvanced Patent SearchPublication numberUS8188688 B2Publication typeGrantApplication numberUS 12/545,815Publication dateMay 29, 2012Filing dateAug 22, 2009Priority dateMay 22, 2008Also published asUS8614554, US8637818, US20090309520, US20120209052, US20120242257Publication number12545815, 545815, US 8188688 B2, US 8188688B2, US-B2-8188688, US8188688 B2, US8188688B2InventorsVladimir BalakinOriginal AssigneeVladimir BalakinExport CitationBiBTeX, EndNote, RefManPatent Citations (110), Non-Patent Citations (23), Referenced by (6), Classifications (8), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetMagnetic field control method and apparatus used in conjunction with a charged particle cancer therapy systemUS 8188688 B2Abstract The invention comprises a charged particle beam acceleration, extraction, and/or targeting method and apparatus used in conjunction with charged particle beam radiation therapy of cancerous tumors. Novel design features of a synchrotron are described. Particularly, turning magnets, edge focusing magnets, concentrating magnetic field magnets, winding and control coils, flat surface incident magnetic field 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 reduces required operating power, and allow continual acceleration of protons in a synchrotron even during a process of extracting protons from the synchrotron.
1. An apparatus for acceleration of charged particles in a charged particle beam path, comprising:
a synchrotron, said synchrotron comprising:
a first magnet, said first magnet comprising an incident surface;
a non-magnetic isolating layer, said isolating layer comprising a first side and a second side;
a first magnetic penetration layer, said first magnetic penetration layer comprising a first foil, said first foil comprising an inner surface and an outer surface; and
a second magnet, said second magnet comprising an exiting surface, said incident surface of said first magnet affixed to said first side of said isolating layer, said second side of said isolating layer affixed to said inner surface of said first foil, said charged particle beam path positioned between said outer surface of said first foil and said exiting surface.
2. The apparatus of claim 1, said synchrotron further comprising:
a second magnetic penetration layer, said second magnetic penetration layer comprising a second foil, said second foil comprising an inner side and an outer side, said inner side of said second foil affixed to said outer surface of said first foil.
3. The apparatus of claim 2, wherein both said first foil and said second foil each comprise a thickness of less than about 0.2 millimeters, wherein all of said first foil inner surface, said first foil outer surface, said second foil inner side, and said second foil outer side comprise a surface finish of less than about five micron polish.
4. The apparatus of claim 2, said synchrotron further comprising:
a return yoke, wherein a magnetic field runs sequentially through said first magnet, said non-conductive isolating layer, said first magnetic penetration layer, said second magnetic penetration layer, said charged particle beam path, said second magnet, said yoke, and back to said first magnet.
5. The apparatus of claim 1, wherein said charged particle beam path comprises a vacuum path with cross dimensions of less than about three centimeters by about eight centimeters.
6. The apparatus of claim 1, wherein said isolating layer comprises a non-conductive material, wherein said isolating material comprises a thickness of less than about one millimeter.
7. The apparatus of claim 1, wherein the charged particles circulate in said charged particle beam path during use.
8. The apparatus of claim 1, wherein said synchrotron further comprises:
a radio-frequency cavity system comprising a first pair of blades for inducing betatron oscillation of the charged particles;
an extraction foil yielding slowed charged particles from the charged particles having sufficient betatron oscillation to traverse said foil, wherein the slowed charged particles pass through a second pair of blades having an extraction voltage directing the charged particles out of said synchrotron through an extraction magnet.
9. A method for turning charged particles in a charged particle beam path, comprising the step of:
accelerating the charged particles with a synchrotron, said synchrotron comprising:
a first magnet generating a magnetic field, said first magnet comprising an incident surface;
a non-magnetic isolating layer, said isolating layer comprising a first side and a second side, said non-magnetic isolating layer comprising a thickness of at least 0.05 millimeters;
a first magnetic penetration layer, said first magnetic penetration layer comprising a first foil, said first foil comprising an inner surface and an outer surface;
a second magnet, said second magnet comprising an exiting surface, said incident surface of said first magnet affixed to said first side of said isolating layer, said second side of said isolating layer affixed to said inner surface of said first foil, said charged particle beam path positioned between said outer surface of said first foil and said exiting surface; and
generating a magnetic field using said first magnet; and
blending said magnetic field using said thickness of said non-magnetic isolating layer provides to even out non-uniform properties of said magnetic field, wherein said magnetic field turns said charged particles in said charged particle beam path.
evening said magnetic field using a second magnetic penetration layer, said second magnetic penetration layer comprising a second foil, said second foil comprising an inner side and an outer side, said inner side of said second foil affixed to said outer surface of said first foil, wherein a surface polish of said outer side of said second foil evens said magnetic field.
11. The method of claim 10, wherein both said first foil and said second foil each comprise a thickness of less than about 0.2 millimeters, wherein all of said first foil inner surface, said first foil outer surface, said second foil inner side, and said second foil outer side comprise a surface finish of less than about five micron polish.
circulating said magnetic field sequentially through said first magnet, said non-conductive isolating layer, said first magnetic penetration layer, said second magnetic penetration layer, said charged particle beam path, said second magnet, said yoke, and back to said first magnet.
circulating said charged particles in said charged particle beam path, wherein said magnetic field axially crosses said charged particle beam path.
inducing a betatron oscillation of the charged particles using a radio-frequency cavity system comprising a first pair of blades;
traversing the charged particles across an extraction foil yielding slowed charged particles from the charged particles having sufficient betatron oscillation to traverse said foil;
passing the slowed charged particles through a second pair of blades having an extraction voltage; and
extracting the charged particles passing through said second pair of blades out of said synchrotron through an extraction magnet.
controlling a magnetic field in a bending magnet of said synchrotron, said bending magnet comprising:
a tapered iron based core adjacent said charged particle beam path, said core comprising a surface polish of less than about ten microns roughness; and
a focusing geometry comprising:
a first cross-sectional distance of said iron based core forming an edge of said first magnet; and
a second cross-sectional distance of said iron based core not in contact with said charged particle beam path, wherein said second cross-sectional distance is at least fifty percent larger than said first cross-sectional distance, said first cross-sectional distance running parallel said second cross-sectional distance.
extracting the charged particles from said synchrotron;
controlling an energy of the charged particles; and
controlling an intensity of the charged particles,
wherein said step of controlling said energy and said step of controlling said intensity both occur prior to the charged particles passing through a Lamberson extraction magnet in said synchrotron during said step of extracting.
rotating a platform, said charged particle beam path passing above at least a portion of said platform, wherein said platform rotates through at least one hundred eighty degrees during an irradiation period; and
delivering the charged particles above said platform in said charged particle beam path, wherein said step of delivering the charged particles occurs in greater than four rotation positions of said rotatable platform.
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;
wherein said field redirects the reduced energy charged particle beam as an extracted charged particle beam.
19. An apparatus for acceleration of charged particles in a charged particle beam path, comprising:
a first magnet, said first magnet comprising an incident surface; and
a first foil, said first foil comprising an inner side and an outer side, said inner side of said first foil affixed with a first adhesive layer to said incident surface, said charged particle beam path proximate said outer side of said foil.
20. The apparatus of claim 19, wherein said first foil of said first magnetic penetration layer comprises a thickness of less than about 0.2 mm thickness, wherein both said inner side of said foil and said outer side of said foil comprise an average surface roughness of less than about three micrometers.
21. The apparatus of claim 20, further comprising a gap isolating material, wherein said gap isolating layer comprises a non-conductive electric isolating layer, wherein said gap isolating material comprises a non-magnetic material, wherein said gap isolating material comprises an outer surface finish of about zero to three microns, said gap isolating material positioned between said incident surface of said first magnet and said inner side of said first foil.
a second foil, said second foil comprising a first side and a second side, said first side of said second foil affixed to said outer side of said first foil with a second adhesive layer.
23. The apparatus of claim 19, wherein said first foil comprises a nickel alloy.
a second magnet, said second magnet comprising an exiting surface,
wherein said charged particle beam path is positioned between said outer side of said first foil and said second magnet.
25. The apparatus of claim 19, wherein said synchrotron further comprises:
exactly four ninety degree turning sections, wherein each of said four ninety degree turning sections further comprises at least four magnets proximate said charged particle beam path, said at least four magnets comprising a total of at least eight beveled focusing edges.
26. The apparatus of claim 19, said synchrotron further comprising:
wherein the charged particles beam pass through said extraction material resulting in a reduced energy charged particle beam,
is a continuation-in-part of U.S. patent application Ser. No. 12/425,683 filed Apr. 17, 2009, now U.S. Pat. No. 7,939,809, 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. 21, 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 1. Field of the Invention
This invention relates generally to treatment of solid cancers. More particularly, the invention relates to magnetic field control elements used in conjunction with charged particle cancer therapy beam acceleration, extraction, and/or targeting methods and apparatus.
T. Norimine, et. al. �Particle Therapy System Apparatus�, U.S. Pat. Nos. 7,060,997 (Jun. 13, 2006); T. Norimine, et. al. �Particle Therapy System Apparatus�, 6,936,832 (Aug. 30, 2005); and T. Norimine, et. al. �Particle Therapy System Apparatus�, 6,774,383 (Aug. 10, 2004) each describe a particle therapy system having a first steering magnet and a second steering magnet disposed in a charged particle beam path after a synchrotron that are controlled by first and second beam position monitors.
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.
There exists in the art of particle beam treatment of cancerous tumors in the body a need for efficient control of magnetic fields used in the control of charged particles in a synchrotron of a charged particle cancer therapy system. Further, there exists in the art of particle beam therapy of cancerous tumors a need for reduced power supply requirements, reduced construction costs, and reduced size of the synchrotron. 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. 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.
SUMMARY OF THE INVENTION The invention comprises a charged particle beam acceleration, extraction, and/or targeting method and apparatus used in conjunction with charged particle beam radiation therapy of cancerous tumors.
FIG. 3 illustrates straight and turning sections of a synchrotron
FIG. 8 illustrates magnetic field concentration in a turning magnet;
FIG. 9 illustrates correction coils in a turning magnet;
FIG. 10 illustrates a magnetic turning section of a synchrotron;
FIG. 11 illustrates a magnetic field control system;
FIG. 12 presents magnetic field control elements;
FIG. 13 illustrates magnetic field control elements;
FIG. 14 illustrates a charged particle extraction system;
FIG. 15 illustrates 3-dimensional scanning of a proton beam focal spot, and
FIG. 16 illustrates 3-dimensional scanning of a charged particle beam spot.
DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to treatment of solid cancers. More particularly, the invention relates to magnetic field control elements used in conjunction with charged particle cancer therapy beam acceleration, extraction, and/or targeting methods and apparatus.
Novel design features of a synchrotron are described. Particularly, turning or bending magnets, edge focusing magnets, magnetic field concentration magnets, winding and correction coils, flat magnetic filed 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.
By increasing the fields appropriately as the particles gain energy, the charged particles path can be held constant as they are accelerated. This allows the vacuum container for the particles to be a large thin torus. In practice it is easier to use some straight sections between the bending magnets and some turning sections giving the torus the shape of a round-cornered polygon. A path of large effective radius is thus constructed using simple straight and curved pipe segments, unlike the disc-shaped chamber of the cyclotron type devices. The shape also allows and requires the use of multiple magnets to bend the particle beam.
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 or turning 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 250 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 optionally 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. Use of the above listed elements is further described, infra. Protons are delivered with control to the patient interface module 170 and to a tumor of a patient.
In one example, the charged particle irradiation includes a synchrotron having: a center, straight sections, and turning sections. The charged particle beam path runs about the center, through the straight sections, and through the turning sections, where each of the turning sections comprises a plurality of bending magnets. Preferably, the circulation beam path comprises a length of less than sixty meters, and the number of straight sections equals the number of turning sections. Preferably no quadrupoles are used in or around the circulating path of the synchrotron.
In one illustrative embodiment, the synchrotron 130, which is also referred to as an accelerator system, has four straight elements and four turning sections. Examples of straight sections 310 include the: inflector 240, accelerator 270, extraction system 290, and deflector 292. Along with the four straight sections are four ion beam turning sections 320, which are also referred to as magnet sections or turning sections. Turning sections are further described, infra.
Referring now to FIG. 5, an example of a single magnet turning section 410 is expanded. The turning section includes a gap 510. Preferably, the charged particles run through the gap. The gap is a section of a charged particle beam path through which charged particles are accelerated in the synchrotron 130. The gap is preferably a flat gap, allowing for a magnetic field across the gap that is more uniform, even, and intense. A magnetic field enters the gap through a magnetic field incident surface and exits the gap through a magnetic field exiting surface. The gap 510 runs in a vacuum tube between two magnets or between two magnet halves. The gap is controlled by at least two parameters: (1) the gap 510 is kept as large as possible to minimize loss of protons and (2) the gap 510 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 510 allows for a compressed and more uniform magnetic field across the gap. The gap preferably has a first dimension of less than about three centimeters and a second dimension of less than about eight centimeters. 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.
As described, supra, a larger gap size requires a larger power supply. For instance, if the gap size doubles in vertical size, then the power supply requirements increase by about a factor of four. The flatness of the gap is also important. For example, the flat nature of the gap allows for an increase in energy of the extracted protons from about 250 to about 330 MeV. More particularly, if the gap 510 has an extremely flat surface, then the limits of a magnetic field of an iron magnet are reachable. An exemplary precision of the flat surface of the gap 510 is a polish of less than about five microns and preferably with a polish of about one to three microns. Unevenness in the surface results in imperfections in the applied magnetic field. The polished flat surface spreads unevenness of the applied magnetic field.
Still referring to FIG. 5, a portion of an optional second magnet turning section 420 is illustrated. The coils 520, 530 typically have return elements or turns at the end of one magnet, such as at the end of the first magnet turning section 410. The return elements 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 560 is preferably minimized. The second turning magnet is used to illustrate that the coils 520, 530 optionally run along a plurality of magnets, such as 2, 3, 4, 5, 6, or more magnets. Coils 520, 530 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 560 between two turning section magnets.
Referring now to FIGS. 6 and 7, two illustrative 90 degree rotated cross-sections of a single magnet turning section 410 is presented. The magnet assembly has a first magnet section or half 610 and a second magnet section or half 620. A magnetic field induced by coils, described infra, runs between the first magnet section 610 to the second magnet section 620 across the gap 510. The gap 510 includes a magnetic field incident surface 670 and a magnetic field exiting surface 680. Return magnetic fields run through a first yoke 612 and second yoke 622. The charged particles run through the vacuum tube in the gap. As illustrated, protons run into FIG. 6 through the gap 510 and the magnetic field, illustrated as a 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. 6. The magnetic field is created using windings through which a current flows about the core. A first coil makes up and a second coil makes up a second winding coil 660. Isolating gaps 630, 640, such as air gaps, isolate the iron based yokes 612, 622 from the gap 510. The gap is approximately flat to yield a uniform magnetic field across the gap, as described supra.
Referring again to FIG. 7, the ends of a single turning magnet are preferably beveled. Nearly perpendicular or right angle edges of a turning magnet 410 are represented by a dashed lines 674, 684. Preferably, the edge of the turning magnet is beveled at angles alpha, α, and beta, β, which is the off perpendicular angle between the right angles 674, 684 and beveled edges 672, 682. 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 410 at angle alpha focuses the proton beam.
Multiple turning magnets provide multiple magnet edges that each have edge focusing effects in the synchrotron 310. If only one turning magnet is used, then the beam is only focused once for angle alpha or twice for angle alpha and angle beta. However, by using smaller turning magnets, more turning magnets fit into the turning sections 320 of the synchrotron 310. For example, if four magnets are used in a turning section 320 of the synchrotron, then there are eight possible edge focusing effect surfaces, two edges per magnet. The eight focusing surfaces yield a smaller cross sectional beam size. This allows the use of a smaller gap 510.
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.
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. 6, the incident magnetic field surface 670 of the first magnet section 610 is further described. FIG. 6 is not to scale and is illustrative in nature. Local imperfections or unevenness in quality of the finish of the incident surface 670 results in inhomogeneities or imperfections in the magnetic field applied to the gap 510. Preferably, the incident surface 670 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. 8, additional magnet elements, of the magnet cross-section illustratively represented in FIG. 6, are described. The first magnet section 610 preferably contains an initial cross sectional distance 810 of the iron based core. The contours of the magnetic field are shaped by the magnets 610, 620 and the yokes 612, 622. The iron based core tapers to a second cross sectional distance 820. The magnetic field in the magnet preferentially stays in the iron based core as opposed to the gaps 630, 640. As the cross-sectional distance decreases from the initial cross sectional distance 810 to the final cross-sectional distance 820, the magnetic field concentrates. The change in shape of the magnet from the longer distance 810 to the smaller distance 820 acts as an amplifier. The concentration of the magnetic field is illustrated by representing an initial density of magnetic field vectors 830 in the initial cross section 810 to a concentrated density of magnetic field vectors 840 in the final cross section 820. The concentration of the magnetic field due to the geometry of the turning magnets results in fewer winding coils 650, 660 being required and also a smaller power supply to the coils being required.
EXAMPLE I In one example, the initial cross-section distance 810 is about fifteen centimeters and the final cross-section distance 820 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 670 of the gap 510, though the relationship is not linear. The taper 860 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.
Referring now to FIG. 9, an additional example of geometry of the magnet used to concentrate the magnetic field is illustrated. As illustrated in FIG. 8, the first magnet section 610 preferably contains an initial cross sectional distance 810 of the iron based core. The contours of the magnetic field are shaped by the magnet sections 610, 620 and the yokes 612, 622. In this example, the core tapers to a second cross sectional distance 820 with a smaller angle theta, θ. As described, supra, the magnetic field in the magnet preferentially stays in the iron based core as opposed to the gaps 630, 640. As the cross-sectional distance decreases from the initial cross sectional distance 810 to the final cross-sectional distance 820, the magnetic field concentrates. The smaller angle, theta, results in a greater amplification of the magnetic field in going from the longer distance 810 to the smaller distance 820. The concentration of the magnetic field is illustrated by representing an initial density of magnetic field vectors 830 in the initial cross section 810 to a concentrated density of magnetic field vectors 840 in the final cross section 820. The concentration of the magnetic field due to the geometry of the turning magnets results in fewer winding coils 650, 660 being required and also a smaller power supply to the winding coils 650, 660 being required.
Still referring to FIG. 9, optional correction coils 910, 920 are illustrated that are used to correct the strength of one or more turning magnets. The correction coils 920, 930 supplement the winding coils 650, 660. The correction coils 910, 920 have correction coil power supplies that are separate from winding coil power supplies used with the winding coils 650, 660. 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 650, 660. The smaller operating power applied to the correction coils 920, 920 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 410, 420, 430, 440.
Referring now to FIG. 10, an example of winding coils and correction coils about a plurality of turning magnets in an ion beam turning section is illustrated. The winding coils preferably cover 1, 2, or 4 turning magnets. In the illustrated example, a winding coil 1030 winds around two turning magnets 410, 420. Correction coils are used to correct the magnetic field strength of one or more turning or bending magnets. In the illustrated example, a first correction coil 1010 corrects a single turning magnet. Combined in the illustration, but separately implemented, a second correction coil 1020 corrects two turning magnets 410, 420. The correction coils supplement the winding coils. The correction coils have correction coil power supplies that are separate from winding coil power supplies used with the winding coils. 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. The smaller operating power applied to the correction coils allows for more accurate and/or precise control of the correction coils. More particularly, a magnetic field produced by the first correction coil 1010 is used to adjust for imperfection in a magnetic filed produced by the turning magnet 410 or the second correction coil 1020 is used to adjust for imperfection in the turning magnet sections 610, 620. 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.
Correction coils are preferably used in combination with magnetic field concentration magnets to stabilize a magnetic field in a synchrotron. For example, high precision magnetic field sensors 1050 are used to sense a magnetic field created in one or more turning magnets using winding elements. The sensed magnetic field is sent via a feedback loop to a magnetic field controller that adjusts power supplied to correction coils. The correction coils, operating at a lower power, are capable of rapid adjustment to a new power level. Hence, via the feedback loop, the total magnetic field applied by the turning magnets and correction coils is rapidly adjusted to a new strength, allowing continuous adjustment of the energy of the proton beam. In further combination, a novel extraction system allows the continuously adjustable energy level of the proton beam to be extracted from the synchrotron.
For example, one or more high precision magnetic field sensors 1050 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 510 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 110. The feedback system is controlled by the main controller 110 or a subunit or sub-function of the main controller 110. 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.
Optionally, the one or more high precision magnetic field sensors are used to coordinate synchrotron beam energy and timing with patient respiration. 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. A winding or correction coil covering multiple magnets reduces space between magnets as fewer winding or correction coil ends are required, which occupy space.
EXAMPLE II Referring now to FIG. 11, an example is used to clarify the magnetic field control using a feedback loop 1100 to change delivery times and/or periods of proton pulse delivery. In one case, a respiratory sensor 1110 senses the breathing cycle of the subject. The respiratory sensor sends the information to an algorithm in a magnetic field controller 1120, 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 breathing cycle, such as at the bottom of a breath. Magnetic field sensors 1130, such as the high precision magnetic field sensor 1050, are used as input to the magnetic field controller, which controls a magnet power supply 1140 for a given magnetic field 1150, such as within a first turning magnet 410 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 breathing 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 second with a fixed period.
EXAMPLE III Referring again to FIG. 10, an example of a winding coil 1030 that covers four turning magnets 410, 420, 430, 440 is provided. 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 1010 is illustrated that is used to correct the magnetic field for the first turning magnet 410. 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 1010 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 1030, as an independent coil is used for each turning section magnet. Alternatively, a multiple magnet correction coil 1020 is used to correct the magnetic field for a plurality of turning section magnets.
FIGS. 12 and 13 are not to scale and are illustrative in nature. FIGS. 12 and 13 are in an exploded view for clarity; the described layers are preferably joined or compressed together in the final apparatus and in use.
Referring now to FIG. 12, the magnetic field incident surface 670 of the first magnet, magnet half, or magnet section 610 is further described. The first magnet 610 terminates next to the gap 510, through which the protons circulate. Particularly, the flatness of the magnetic field incident surface is described. Imperfections in the surface quality of the magnetic field incident surface 670 of the first magnet 610 results in non-uniformity in the magnetic field across the gap 510. Imperfections in the magnetic field results in variations in control of the protons in the circulating path of the synchrotron. Poor control of protons in their circulating path results in defocused protons not fitting into a small gap 510. Hence, the gap size must be increased. An increase in the gap size results in increased power consumption requirements as the applied magnetic field must be stronger to span the larger gap. However, tight control of the magnetic field incident surface 670 of the first magnet 610 results in a smooth surface, which yields relatively smaller imperfections in the magnetic field applied across the gap, tighter focusing of the protons in the gap, a corresponding decrease in the required gap size, a corresponding decrease in the size of the magnets required, and a corresponding reduction in power supply requirements to the magnets. Hence, control of the flatness of the magnetic filed incident surface 670 of the first magnet 610 in each of the turning magnets is important and has multiple benefits in terms of size, reproducibility, and cost. While the gap surface is described in terms of the first turning magnet 610, the discussion applies to each of the turning magnets in the synchrotron. Similarly, while the gap 510 surface is described in terms of the magnetic field incident surface 670, the discussion additionally optionally applies to the magnetic field exiting surface 680. Several examples illustrate how desired flatness specifications are achieved.
In a first example, the magnetic field incident surface 670 of the first magnet 610 is machined flat, such as to within about a zero to three micron finish polish or less preferably to about a ten micron finish polish. The cost of machining the surface to the tighter zero to three micron finish roughness, such as average roughness, median roughness, mean roughness, or peak-to-peak roughness, is prohibitive to large scale production as the cost is high per synchrotron unit as each magnetic field incident, and optionally exiting, surface of each turning magnet of each synchrotron unit would have to be machined. The costs of machining a large piece of magnetically uniform material can reach $100,000 per piece, which is prohibitive to production.
In a second example, two layers are applied to the magnetic field incident surface 670 of the first magnet 610 to achieve the specified flatness. Referring now to FIG. 12, a first layer is a gap isolating material, which is preferably about one millimeter in thickness and is more preferably about one-half millimeter in thickness. The gap isolating material 1210 is preferably a non-conductive electric isolating layer. The gap isolating material 1210 is especially non-magnetic. The gap isolating material 1210 preferably has a surface finish of about zero to three microns. A second layer is preferably a first magnetic penetration layer 1220. The first magnetic penetration layer 1220 is preferably composed of a very thin piece of foil, such as about 0.1 mm thick. The first magnetic penetration layer 1220 has an inner surface and an outer surface. The foil is preferably a nickel alloy, a special steel, or iron. The foil is especially smooth, such as to about zero to three micron polish finish on both sides. A first adhesive layer 1215 and second adhesive layer 1225 are a glue or bonding agent. The first adhesive layer 1215 and second adhesive layer 1225 are optionally composed of the same material or are different materials. The adhesive layers 1215, 1225 primary purpose is to connect the gap isolating material 1210 and first magnetic penetration layer 1220 to the magnet 610.
Preferably, a compression force compresses together the inner surface of the first magnetic penetration layer 1220, the second adhesive layer 1225, the gap isolating material 1210, the first adhesive layer 1215, and the magnetic field incident surface 670 of the first magnet 610. The result is a new outer layer of the first magnet 610, which is the outer surface of the first magnetic penetration layer. The outer surface of the first magnetic penetration layer has a surface finish of about zero to three microns of roughness and is preferably electrically isolated from the first magnet 610. The outer surface of the first magnetic penetration layer 1220 preferably defines the surface of the gap 510. When more than one magnetic penetration layer is used, the magnetic penetration surface most remove from the first magnet 610 defines the edge of the gap 510.
The gap isolating material 1210 and flat outer surface of the first magnetic penetration layer 1220 improve the magnetic field properties of the applied magnetic field across the gap 510. First, iron in the magnet 610 has its own magnetic properties and iron has non-uniform properties. Instead of trying to make the iron uniform or using very expensive material for the magnet 610, the series of layers is used to make the magnetic field more uniform. The gap isolating material 1210 isolates residual magnetic properties of the magnet 610. The gap isolating material 1210 does not stop the magnetic properties of the magnet, but rather the isolating material enhances uniformity of the magnetic field in the gap 510 and makes the field more stable. Stated differently, the gap isolating material 1210 does not actually stop the magnetic properties of the magnet 610 from reaching the gap 510. Instead, the gap isolating material 1220 isolates and evens out the non-uniform properties of the iron core of the magnet 610. Essentially, the iron of the first magnet has its own magnetic properties and on a micro level is not uniform. The gap isolating material 1210 yields a distance to blend the imperfections in the magnetic field resulting from the iron inhomogeneities and yields a more stable and uniform magnetic field across the gap. The first magnetic penetration layer 1220, by being a very flat and high penetration material, spreads the unevenness of the applied magnetic field across the gap 510. Again, having a very flat and high penetration magnetic material next to the gap creates a uniform magnetic field across the gap, which leads to a smaller required gap, smaller required magnetic fields, and smaller required power supplies, as described supra.
In a third example, three or more layers are applied to the magnetic field incident surface 670 of the first magnet 610 to achieve the specified flatness. Referring now to FIG. 13, a second magnetic penetration layer 1330 is added to the first magnetic penetration layer 1220 and the gap isolating material 1210 and the thicknesses of the layers are changed. Particularly, the gap isolating material 1210 retains the above described properties, but is preferably about one-quarter millimeter in thickness. The first magnetic penetration layer 1220 retains the same properties as described, supra. A second magnetic penetration layer 1330 is similar to or the same as the first magnetic penetration layer 1220. The first adhesive layer 1215, second adhesive layer 1225, and third adhesive layer 1335 are a glue or bonding agent. The second magnetic penetration layer 1330 is joined to the first magnetic penetration layer 1220 via the third adhesive layer 1335. The first magnetic penetration material layer 1220 is joined to the gap isolating material 1210 with the second adhesive layer 1225. The gap isolating material is joined to the magnetic field incident surface 670 of the first magnet 610 with the first adhesive layer 1215. The result is a new outer layer of the first magnet 610, which is the outer surface of the second magnetic penetration layer 1330. The use of multiple magnetic field penetration layers results in a flatter resulting outer surface of the first magnet 610 when the initial outer surface of the first magnet includes surface imperfections as the imperfections are reduced with each subsequently bonded layer.
An example further illustrates. A method or apparatus using a synchrotron for turning and/or acceleration of charged particles in a charged particle beam path is described. Preferably, the synchrotron includes: a first magnet having an incident surface, a non-magnetic isolating layer having a first side and a second side, a first magnetic penetration layer or foil having an inner surface and an outer surface, and/or a second magnet having an exiting surface. Preferably, the incident surface of the first magnet affixes directly or indirectly to the first side of said isolating layer and the second side of said isolating layer affixes directly or indirectly to the inner surface of the first foil, where the charged particle beam path is positioned between the outer surface of the first foil and the exiting surface. Optionally, the synchrotron further includes a second magnetic penetration layer or second foil having an inner side and an outer side where the inner side of the second foil affixes directly or indirectly to the outer surface of the first foil. The synchrotron uses a magnetic field to turn or bend the charged particles running in the charged particle beam path. The magnetic field runs through any of the first magnet, the non-conductive isolating layer, the first magnetic penetration layer, the second magnetic penetration layer, the charged particle beam path, the second magnet, the yoke, and back to the first magnet. Preferably, the magnetic field of the first magnet is blend out in the thickness of the non-magnetic isolating layer resulting in an evening of the non-uniform properties of the magnetic field in the first magnet. Preferably, the first and/or second magnetic penetration layer smooth out the incident surface of the first magnet. The high surface polish of the first and/or second magnetic penetration layer results in an even magnetic field running axially across the charged particle beam path and/or gap. The application of one or more isolation layers and/or one or more magnetic field penetration layers results in a magnetic surface with a surface polish that is finer that the surface polish of the incident surface of the first magnet. Alternatively stated, the incident surface of the first magnet has a surface roughness greater than a surface roughness of the outer surface of the outermost magnetic penetration layer next to the gap and/or charged particle beam path.
The examples above are illustrative in nature and are not limiting. The illustrated size of the layers are greatly exaggerated in thickness to clarify the key concepts. Roughness of the incident magnetic field surface layer 670 is exaggerated for clarity. The actual thicknesses of each of the described layers is optionally up to about three-quarters of a millimeter per layer. The second magnetic penetration layer 1210 is not necessarily the same material or thickness as the first magnetic penetration layer 1220. One or more magnetic penetration layers are optionally used without use of a gap isolating material. A gap isolating layer is optionally used without use of a magnetic penetration layer. Zero or more than one gap isolating material layer is optionally used. More than two magnetic penetration layers are optionally used, such as 3, 4, 5, 7, or 10 layers. The adhesive layers are optionally composed of the same material or are different materials.
A smaller gap 510 size requires a higher quality finish. The combination of the highly polished magnetic penetration layer and the magnetic field gap isolating material having a polished surface onto the magnet results in an outer magnet layer that is very flat. The very flat surface, such as 0-3 micron finish, allows for a smaller gap size, a smaller applied magnetic field, smaller power supplies, and tighter control of the proton beam cross-sectional area.
Referring now to FIG. 14, an exemplary proton extraction process from the synchrotron 130 is illustrated. For clarity, FIG. 14 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 1410. To initiate extraction, an RF field is applied across a first blade 1412 and a second blade 1414, in the RF cavity system 1410. The first blade 1412 and second blade 1414 are referred to herein as a first pair of blades.
In the proton extraction process, an RF voltage is applied across the first pair of blades, where the first blade 1412 of the first pair of blades is on one side of the circulating proton beam path 264 and the second blade 1414 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.
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 effect of 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.
With a sufficient sine wave betatron amplitude, the altered circulating beam path 265 touches a material 1430, 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 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.
The thickness of the material 1430 is optionally adjusted to created a change in the radius of curvature, such as about �, 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. 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 1414 and a third blade 1416 in the RF cavity system 1410. A high voltage DC signal, such as about 1 to 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.
The benefits of the system include a multi-dimensional scanning system. Particularly, the system allows an energy and/or intensity change while scanning. Because the extraction system does not depend on any change 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. 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.
Referring now to FIG. 15, 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. 15 illustrates a spot scanning system or tissue volume scanning system. In the tissue volume scanning system, the proton beam 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. The focal point is translated 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. 15, the spot is translated up a vertical axis, is moved horizontally, and is then translated down a vertical axis. 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. Combined, the three 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.
In FIG. 15, the proton beam goes along a z-axis controlled by the beam energy, the horizontal movement is along an x-axis, and the vertical direction is along 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. The use of the extraction system, described supra, allows for different scanning patterns. Particularly, the system allows simultaneous adjustment of the x-, y-, and z-axes in the irradiation of the solid tumor. Stated again, instead of scanning along an x,y-plane and then adjusting energy of the protons, such as with a range modulation wheel, the system allows for moving along the z-axes while simultaneously adjusting the x- and or y-axes. Hence, rather than irradiating slices of the tumor, the tumor is optionally irradiated in three simultaneous dimensions. For example, the tumor is irradiated around an outer edge of the tumor in three dimensions. Then the tumor is irradiated around an outer edge of an internal section of the tumor. This process is repeated until the entire tumor is irradiated. The outer edge irradiation is preferably coupled with simultaneous rotation of the subject, such as about a vertical y-axis. This system allows for maximum efficiency of deposition of protons to the tumor, as defined using the Bragg peak, to the tumor itself with minimal delivery of proton energy to surrounding healthy tissue.
a small circumference system, such as less than about 50 meters; a vertical proton beam size gap of about 2 cm; corresponding reduced power supply requirements associated with the reduced gap size; an extraction system not requiring a newly introduced magnetic field; acceleration or deceleration of the protons during extraction; control of z-axis energy during extraction; and variation of z-axis energy during extraction. The result is a 3-dimensional scanning system, x-, y-, and z-axes control, where the z-axes control resides in the synchrotron and where the z-axes energy is variably controlled during the extraction process inside the synchrotron.
Referring now to FIG. 16, an example of a targeting system 140 used to direct the protons to the tumor with 3-dimensional scanning control is provided, where the 3-dimensional scanning control is along the x-, y-, and z-axes. Typically, charged particles traveling along the transport path 268 are directed through a first axis control element 142, such as a vertical control, and a second axis control element 144, such as a horizontal control and into a tumor 1101. As described, supra, the extraction system also allows for simultaneous variation in the z-axis. Thus instead of irradiating a slice of the tumor, as in FIG. 15, all three dimensions defining the targeting spot of the proton delivery in the tumor are simultaneously variable. The simultaneous variation of the proton delivery spot is illustrated in FIG. 16 by the spot delivery path 269. In the illustrated case, the protons are initially directed around an outer edge of the tumor and are then directed around an inner radius of the tumor. Combined with rotation of the subject about a vertical axis, a multi-field illumination process is used where a not yet irradiated portion of the tumor is preferably irradiated at the further distance of the tumor from the proton entry point into the body. This yields the greatest percentage of the proton delivery, as defined by the Bragg peak, into the tumor and minimizes damage to peripheral healthy tissue.
The 3-dimensional scanning system of the proton spot focal point, described supra, is preferably combined with a rotation/raster method. The method includes layer wise tumor irradiation from many directions. During a given irradiation slice, the proton beam energy is continuously changed according to the tissue's density in front of the tumor to result in the beam stopping point, defined by the Bragg peak, to always be inside the tumor and inside the irradiated slice. The novel method allows for irradiation from many directions, referred to herein as multi-field irradiation, to achieve the maximal effective dose at the tumor level while simultaneously significantly reducing possible side-effects on the surrounding healthy tissues in comparison with existing methods. For example, a multi-axis control comprises delivery of the charged particles at a set point in the breathing cycle and in coordination with rotation of the patient on a rotatable platform during said at least ten rotation positions of the rotatable platform. Preferably, the rotatable platform rotates through at least one hundred eighty and preferably about three hundred sixty degrees during an irradiation period of a tumor. Essentially, the multi-field irradiation system distributes dose-distribution at tissue depths not yet reaching the tumor.
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