CN107789749B - Charged particle beam deflection device and treatment system - Google Patents
Charged particle beam deflection device and treatment system Download PDFInfo
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- CN107789749B CN107789749B CN201711184455.3A CN201711184455A CN107789749B CN 107789749 B CN107789749 B CN 107789749B CN 201711184455 A CN201711184455 A CN 201711184455A CN 107789749 B CN107789749 B CN 107789749B
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1001—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy using radiation sources introduced into or applied onto the body; brachytherapy
- A61N5/1028—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy using radiation sources introduced into or applied onto the body; brachytherapy using radiation sources applied onto the body
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1077—Beam delivery systems
- A61N5/1081—Rotating beam systems with a specific mechanical construction, e.g. gantries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/70—Arrangements for deflecting ray or beam
- H01J29/72—Arrangements for deflecting ray or beam along one straight line or along two perpendicular straight lines
- H01J29/76—Deflecting by magnetic fields only
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1001—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy using radiation sources introduced into or applied onto the body; brachytherapy
- A61N2005/1019—Sources therefor
- A61N2005/1024—Seeds
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N2005/1085—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy characterised by the type of particles applied to the patient
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N2005/1085—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy characterised by the type of particles applied to the patient
- A61N2005/1089—Electrons
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N2005/1092—Details
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N2005/1092—Details
- A61N2005/1097—Means for immobilizing the patient
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Abstract
The invention relates to a charged particle beam deflection device, which comprises a first deflection magnet positioned at the inlet end of a charged particle beam deflection track, a second deflection magnet positioned at the downstream side of the first deflection magnet and a third deflection magnet positioned at the outlet end of the charged particle beam deflection track; the first deflection magnet and the third deflection magnet are both suitable for forming a uniform magnetic field in at least part of the deflection track of the charged particle beam; the second deflection magnet is suitable for forming a gradient magnetic field in the deflection track of the partial charged particle beam; wherein, the magnetic deflection unit has edge angle between the inlet and the outlet of the deflection magnet, and the magnetic field falling index of the gradient magnetic field is less than 0. Thus, when the dispersion eliminating function is good, the electron beam before the target has good focusing characteristic, thereby improving the quality of the particle beam after the target shooting. A treatment system is also provided.
Description
Technical Field
The invention relates to the field of medical instruments, in particular to a charged particle beam deflection device and a treatment system.
Background
With the development of precision radiotherapy technology, Image Guide Radiation Therapy (IGRT) technology is gradually applied clinically. By using the IGRT technology, on one hand, before the patient receives treatment, the irradiation position of the patient can be verified in an imaging mode, and after the irradiation position is confirmed to be correct, treatment irradiation is carried out, so that the positioning error is reduced. On the other hand, the change of the tumor can be tracked in real time in the treatment process, and the treatment condition is adjusted according to the change of the tumor position, so that the irradiation field can closely follow the target area, and the accurate treatment is realized.
Generally, particle therapy systems are used for generating a high-energy particle beam, which comprises a radiation source for generating a charged particle beam, an acceleration tube for accelerating the charged particle beam, a deflection magnet for deflecting the accelerated charged particle beam, and a target for converting the charged particles into X-rays (other well-known components of particle therapy systems are not listed here). The accelerated charged particle beam changes the traveling direction under the action of the deflection magnet, and the deflected charged particle beam bombards the target or the scattering foil to form required X rays and electron beams, so that the lying patient can be treated. Particle therapy systems are generally bulky, and since the energy spectrum of a charged particle beam has a certain width, dispersion occurs after electromagnetic deflection, so that a magnetic deflection system is required to have a good function of dispersion elimination.
At the same time, in order to ensure the quality of the treatment beam or imaging beam, it is required that the pre-target particle beam also has good focusing properties.
Disclosure of Invention
Accordingly, there is a need for a charged particle beam deflection apparatus and a treatment system that combine a good dispersion eliminating function and a good focusing characteristic.
A charged particle beam deflection device including a magnetic deflection unit for deflecting the accelerated charged particle beam by a preset angle, the magnetic deflection unit including a first deflection magnet at an entrance end of the charged particle beam deflection trajectory, a second deflection magnet at a downstream side of the first deflection magnet, and a third deflection magnet at an exit end of the charged particle beam deflection trajectory;
the first deflection magnet and the third deflection magnet are both suitable for forming a uniform magnetic field in at least part of the charged particle beam deflection track;
the second deflection magnet is suitable for forming a gradient magnetic field in part of the charged particle beam deflection track;
wherein, the entrance and the exit of the magnetic deflection unit have edge angles, and the magnetic field falling index of the gradient magnetic field is less than 0.
The charged particle beam deflection device is provided with two uniform field deflection magnets and one gradient field deflection magnet, and the magnetic deflection system has higher acceptance of transverse and longitudinal beams on the premise of realizing the effect of achromatic dispersion. The entrance and the exit of a deflection magnet in the magnetic deflection unit are respectively provided with a certain edge angle, so that the transverse focusing of the charged particle beam can be ensured; the magnetic field falling index of the gradient field magnetic pole is less than 0, and the radial focusing of the charged particle beam can be ensured. Therefore, the electron beam in front of the target can obtain a small section and good axial symmetry while taking good dispersion elimination function into consideration, so that the quality of the particle rays after the target is hit is improved, the quality of the X rays after the target is further improved, the design of the equalizer is facilitated, and the penumbra of the equalized X rays is small. In addition, in both electronic and photonic treatment modes, consideration of beam flow non-rotational symmetry in treatment planning can be simplified, which is beneficial to improving treatment accuracy.
In one embodiment, the first and third deflection magnets each include a uniform field pole pair for forming a uniform magnetic field, and the second deflection magnet includes a gradient field pole pair for forming a gradient magnetic field.
In one embodiment, the cross section curve of the magnetic pole surface of the gradient field magnetic pole in the direction perpendicular to the charged particle beam current direction is a hyperbola.
In one embodiment, the first deflection magnet, the second deflection magnet, and the third deflection magnet share a pair of magnetic induction coils.
In one embodiment, the entrance edge angle of the first deflecting magnet is 30-45 degrees;
the range of the outlet edge angle of the third deflection magnet is 30-45 degrees.
In one embodiment, an energy selecting mechanism is further arranged in the gradient magnetic field of the second deflection magnet to allow the energy spectrum with a preset width to pass through.
In one embodiment, a beam spot correction device is further disposed between the third deflection magnet and the target, and the beam spot correction device is configured to generate a quadrupole magnetic field.
In one embodiment, the beam spot correction device is disposed at an exit end of the charged particle beam deflected within the uniform magnetic field of the third deflection magnet.
A therapeutic system, comprising:
a rotating frame capable of rotating around a rotating shaft;
a charged particle beam emitting device for generating a charged particle beam and accelerating the charged particle beam, wherein the advancing direction of the charged particle beam forms a first angle relative to the axial direction of the rotating shaft;
a charged particle beam deflecting device for deflecting the accelerated charged particle beam by a second angle;
the sum of the first angle and the second angle is 270 degrees;
the charged particle beam deflection device is a charged particle beam deflection device as described above.
In one embodiment, the treatment system further comprises a target for receiving the charged particle beam emitted from the charged particle beam deflection device, and the charged particle beam bombards the target to generate the treatment ray or the imaging ray.
In one embodiment, the first angle is in a range of 7 degrees to 17 degrees.
In one embodiment, the charged particle beam emitting device comprises an electron gun and an accelerating tube communicating with the electron gun and located between the electron gun and the charged particle beam deflecting device;
wherein the accelerating tube is a standing wave accelerating tube.
Drawings
FIG. 1 is a schematic diagram of a treatment system according to an embodiment of the present invention;
FIG. 2 is a schematic view of a magnetic deflection unit of the charged particle beam deflection apparatus shown in FIG. 1;
FIG. 3 is a schematic structural view of another view angle of the magnetic deflection unit of the charged particle beam deflection apparatus shown in FIG. 1;
FIG. 4 is a diagram of the beam envelope of a therapeutic beam deflected by the charged particle beam deflector of FIG. 1 in the charged particle beam deflector;
FIG. 5 is a beam envelope before and after correction by the beam spot correction device of the imaging beam deflected by the charged particle beam deflector shown in FIG. 1;
FIG. 6 is a diagram of a pre-target beam spot before being corrected by the beam spot correction device for an imaging beam deflected by the charged particle beam deflector shown in FIG. 1;
fig. 7 is a diagram of a pre-target beam spot corrected by the beam spot correction device for the imaging beam deflected by the charged particle beam deflector shown in fig. 1.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Before describing the charged particle beam deflection apparatus in detail, the related contents of the charged particle beam deflection will be described first, so as to better understand the technical solutions of the charged particle beam deflection apparatus and the treatment system in the present invention.
In the present embodiment, the charged particles are exemplified by electrons, and the charged particle beam emitting device is exemplified by a charged particle beam emitting device, but the scope of the invention is not limited thereto. Since the charged particle beam for treatment is mainly of MV grade, the charged particle beam generated from the electron gun needs to be accelerated by the accelerating tube to obtain an electron beam with high energy level to meet the treatment or imaging requirements. Generally, the accelerating tube is long and arranged horizontally, and accordingly, the electron beam emitted from the accelerating tube is also in a horizontal transmission direction, and the treatment couch is also generally arranged horizontally, so that the magnetic deflection device is required to deflect the charged particle beam emitted from the accelerating tube, thereby deflecting the traveling direction of the charged particle beam to a direction pointing to the treatment couch, and further treating or imaging the patient lying on the treatment couch.
Since the energy spectrum of the charged particle beam in the accelerating tube has a certain width, it is scattered (dispersed) after the deflection process, and thus the magnetic deflection system is required to have a good function of dispersion elimination. The applicant of the present application finds, through research, that the chromatic dispersion phenomenon is related to factors such as the energy spectrum width and the structure and arrangement of the deflection magnet, and at present, the structural difference of the treatment system in the market for solving the chromatic dispersion problem is large according to the difference between the type of the accelerating tube and the frame structure.
The invention provides a novel charged particle beam deflection device and a treatment system, which are used for simultaneously achieving a good dispersion elimination function and ensuring that an electron beam in front of a target has a good focusing characteristic, so that the quality of a particle beam after targeting is improved.
As shown in FIG. 1, a treatment system 100 according to an embodiment of the present invention includes a base 20, a rotating gantry 30, an irradiation head 40, and a treatment couch 50. In this embodiment, the treatment system 100 is a roller-type treatment system having an aperture 31 defined in the rotating gantry 30.
The rotating gantry 30 is rotatably disposed on the base 20 and is capable of rotating around a rotation axis, and the irradiation head 40 is connected to the rotating gantry 30 to rotate with the rotating gantry 30 and is opposite to the treatment couch 50. The irradiation head 40 is used for irradiating the emergent imaging rays or therapeutic rays on the patient, and the rotating frame 30 can drive the irradiation head 40 to rotate so as to adjust the angle of the irradiation head 40 relative to the human body lying on the therapeutic bed 50, thereby adjusting the ray distribution irradiated on the human body.
The rotating gantry 30 is provided with a charged particle beam emitting device 60, and the irradiation head 40 is provided with a charged particle beam deflecting device 10 and a target 70. The charged particle beam emitting device 60 is used to generate a charged particle beam and accelerate the charged particle beam, and the charged particle beam deflecting device 10 is used to deflect the accelerated charged particle beam and direct it to the treatment couch 50. The target 70 is used for receiving the charged particle beam emitted from the charged particle beam deflection device 10, and the charged particle beam bombards the target 70 to generate a therapeutic ray or an imaging ray. Optionally, the target material 70 is a moving target to switch between imaging, therapy, or other modes.
Specifically, the charged particle beam emitting device 60 includes an electron gun 62 and an accelerating tube 64 communicating with the electron gun 62 and located between the electron gun 62 and the charged particle beam deflecting device 10, the electron gun 62 is used for generating a charged particle beam, and the charged particle beam is accelerated to a required velocity in the accelerating tube 64 to meet the energy level requirement for imaging or therapy. The charged particle beam deflection means 10 is located downstream in the direction of propagation of the charged particle beam emitted by the accelerating tube 64, and the path of the deflected charged particle beam is substantially parallel to the irradiation head 40 and directed to the couch 50. The target 70 is located downstream of the charged particle beam emitted by the charged particle beam deflection device 10 to be bombarded to generate therapeutic or imaging radiation.
It is understood that the arrangement of the base 20, the rotating gantry 30, the irradiation head 40, and the couch 50 of the treatment system 100 may be other, and is not limited herein.
It is understood that the accelerating tube 64 may be a traveling wave accelerating tube or a standing wave accelerating tube, and in this application, for the purpose of verifying the technical effect achieved by the technical solution, a standing wave accelerating tube that obtains a spectrum with a larger width is used, but this is not to be understood as only a standing wave accelerating tube.
In one embodiment, the rotating gantry 30 is a drum type, that is, the traveling direction of the charged particle beam forms a first angle with respect to the axial direction of the rotating shaft of the rotating gantry 30, the charged particle beam deflecting device 10 deflects the accelerated charged particle beam by a second angle, and the sum of the first angle and the second angle is 270 degrees. As shown in fig. 2, in a preferred embodiment, the first angle is 12 degrees and the second angle is 258 degrees, i.e. the angle of the accelerating tube 64 with respect to the horizontal plane is 12 degrees, and the magnetic deflecting unit deflects the charged particle beam emitted from the accelerating tube 64 by 258 degrees.
In particular, the accelerating tube 64 is disposed non-horizontally, i.e. at an angle to the horizontal plane, so that the proceeding direction of the charged particle beam forms a first angle with respect to the axial direction of the rotating shaft of the rotating gantry 30, thereby reducing the size of the rotating gantry 30, the size of the whole device, and the cost, and is particularly suitable for a drum-type therapeutic system. However, the applicant has found that in order to ensure the accuracy of the charged particle beam entering the deflection orbit after acceleration, and the X-ray formed after targeting is easy to be uniform, the penumbra is small, the axial symmetry is good, and the first angle does not have any angle to achieve the desired effect, and as a preferred embodiment, the first angle is in the range of 7 degrees to 17 degrees.
In one embodiment, the treatment system 100 further comprises a primary collimator (not shown) and a secondary collimator (not shown), which are in turn located downstream of the target 70 along the propagation path of the charged particle beam exiting the magnetic deflection system. Specifically, the primary collimator and the secondary collimator cooperate to generate a radiation field with a profile, and the profile of the therapeutic radiation emitted from the radiation head 40 is adjusted to make the profile of the range of the radiation irradiated on the tumor substantially the same as the shape of the tumor. The primary collimator is used for adjusting the range of the radiation field and providing the maximum radiation field range, and the secondary collimator is used for adjusting the shape profile of the radiation field.
Further, an ionization chamber (not shown) is disposed between the primary collimator and the secondary collimator for measuring the dose of the imaging radiation exiting from the primary collimator to ensure the quality of the imaging or measuring the energy of the treatment radiation to ensure effective and accurate treatment.
As shown in fig. 2, the charged particle beam deflecting device 10 includes a magnetic deflection unit for deflecting the accelerated charged particle beam by a preset angle, the magnetic deflection unit including a first deflection magnet 12 at an entrance end of the charged particle beam deflection trajectory, a second deflection magnet 14 at a downstream side of the first deflection magnet 12, and a third deflection magnet 16 at an exit end of the charged particle beam deflection trajectory. The first deflection magnet 12 and the third deflection magnet 16 are each adapted to form a uniform magnetic field within at least part of the charged particle beam deflection track; the second deflection magnet 14 is adapted to form a gradient magnetic field within the portion of the charged particle beam deflection track;
the inlet and the outlet of the magnetic deflection unit are respectively provided with an edge angle, and the magnetic field falling index of the gradient field magnetic pole is less than 0.
Specifically, the first deflection magnet 12 and the third deflection magnet 16 each have a uniform magnetic field formed in at least a partial region corresponding to the charged particle beam deflection trajectory, and the second deflection magnet 14 has a gradient magnetic field formed in at least a partial region corresponding to the charged particle beam deflection trajectory. Further, the areas of the uniform magnetic field and the gradient magnetic field are related to the size of the charged particle beam, and generally, the larger the size of the charged particle beam, the larger the areas of the uniform magnetic field and the gradient magnetic field are.
In practical applications, the charged particle beam is deflected by the magnetic field formed by the first deflection magnet 12, enters the magnetic field formed by the second deflection magnet 14 for deflection, is deflected by the magnetic field formed by the third deflection magnet 16, and is finally emitted. The first deflection magnet 12 and the third deflection magnet 16 have a uniform magnetic field formed in at least a partial region corresponding to the charged particle beam deflection trajectory, and the gradient pole face curve of the second deflection magnet 14 is not approximated. On the premise of meeting the deflection angle, the position coordinate and the angle coordinate of the charged particles positioned at the outlet of the deflection track can be independent of the energy dispersion of the charged particles positioned at the inlet of the deflection track, namely, the dispersion elimination treatment can be realized.
Specifically, the first and third deflecting magnets 12 and 16 each include a uniform field pole pair formed with a uniform magnetic field, and the second deflecting magnet includes a gradient field pole pair formed with a gradient magnetic field. The cross section curve of the magnetic pole surface of the gradient field magnetic pole in the direction vertical to the charged particle beam is a hyperbola, and the cross section curve is influenced by factors such as a central magnetic field, a magnetic field gradient, a magnetic pole center gap and the like. The section curve of the magnetic pole surface of the gradient field magnetic pole in the direction vertical to the charged particle beam current direction is not subjected to approximate treatment, namely is a hyperbolic curve, and the dispersion elimination treatment can be realized. However, in the prior art, the method is limited by the arrangement structure of the magnets, and for convenience of processing, the sectional curve of the magnetic pole surface of the gradient field magnetic pole in the direction perpendicular to the beam current direction of the charged particles is approximately replaced by a multi-segment broken line, so that the achromatic effect is poor.
Meanwhile, the applicant of the application also finds that the magnetic deflection system has larger acceptance of transverse and longitudinal beams on the premise of realizing the effect of achromatic dispersion. That is, the cross-sectional size and divergence angle of the charged particle beam are large, and the energy spectrum and the beam cluster length of the charged particle beam are long. When the energy spectrum width of the accelerating tube 64 is high, for example, when the accelerating tube 64 is a standing wave accelerating tube, the entrance and the exit of the magnetic deflection unit have certain edge angles respectively, which can ensure the transverse focusing of the charged particle beam; the magnetic field falling index of the gradient field magnetic pole is less than 0, and the radial focusing of the charged particle beam can be ensured.
Specifically, the entrance edge angle of the first deflection magnet is equal to the exit edge angle of the third deflection magnet, and for convenience of description, the edge angle is defined as α, when the edge angle α is positive, the charged particle beam is focused laterally and focused radially, and when the edge angle α is negative, the charged particle beam is focused laterally and focused radially.
Therefore, when the good dispersion eliminating function and the wide energy spectrum are considered, the electron beam in front of the target is ensured to obtain a small section and good axial symmetry, so that the quality of the particle rays after the target is shot is improved, the quality of the X rays after the target is improved, the design of the equalizer is facilitated, and the penumbra of the X rays after the equalization is small. In addition, in both electronic and photonic treatment modes, consideration of beam flow non-rotational symmetry in treatment planning can be simplified, which is beneficial to improving treatment accuracy.
It should be noted that the lateral direction in the lateral acceptance of the charged particle beam is the lateral direction in the broad sense of the beam, that is, "lateral direction" and "longitudinal direction" in the direction perpendicular to the beam advancing direction are collectively referred to as the lateral direction, and further, the "lateral direction" refers to the radial direction in the bending plane of the beam. And the lateral direction in the lateral focusing of the charged particle beam is the lateral direction in the beam narrow sense.
It should be noted that the edge angle of the deflection magnet refers to an angle between a normal line of an edge plane of the deflection magnet and an incident beam, that is, an angle between the edge plane of the deflection magnet and a charged particle beam radius at the entrance and exit. By setting a reasonable edge angle, the transverse focusing of the charged particle beam can be ensured, and the matched transmission of the beam current is realized.
It is to be understood that achieving an evanescent function does not imply a complete evanescent dispersion, e.g. for a small energy dispersive charged particle beam, it may be achieved that the dispersion has a small impact on the beam envelope.
In one embodiment, the first deflection magnet 12, the second deflection magnet 14, and the third deflection magnet 16 share a common pair of magnetic coils. Further, the pair of magnetic induction coils are arranged along the extending direction of the deflection orbit of the charged particle beam for generating a magnetic field, the pair of uniform field magnetic poles of the first deflection magnet 12 and the pair of uniform field magnetic poles of the third deflection magnet 16 are respectively acted on the magnetic field to form a uniform field, and the gradient field magnetic poles of the second deflection magnet 14 are acted on the magnetic field to form a gradient magnetic field. Specifically, each of the first deflection magnet 12, the second deflection magnet 14, and the third deflection magnet 16 has a support portion for supporting the pair of magnetic induction coils, and the deflection trajectory of the charged particle beam is arranged so as to pass through the magnetic poles, that is, the magnetic poles are located on both sides of the deflection trajectory of the charged particle beam, thereby deflecting the charged particle beam.
In one embodiment, the entrance edge angle of the first deflection magnet 12 ranges from 30 to 45 degrees; the exit edge angle of the third deflection magnet 16 ranges from 30 to 45 degrees. It should be understood that the entrance and exit of the deflection magnet in the magnetic deflection unit have a certain edge angle, respectively, to ensure the lateral focusing of the charged particle beam, and the beam spot size requirement on the target 70 is different for different applications. Therefore, the edge angle of the entrance and exit of the deflection magnet can be adjusted within this range according to the actual situation, thereby satisfying the requirements and obtaining better lateral focusing.
In one embodiment, an energy selection mechanism is also provided within the gradient magnetic field of the second deflection magnet 14 to allow a predetermined width of the energy spectrum to pass. Further, the energy selecting mechanism is arranged between the gradient field magnetic pole pair. Specifically, the energy selection mechanism comprises an energy selection slit allowing the energy spectrum with the preset width to pass through. In particular embodiments, the energy selection mechanism may allow a spectrum of ± 9.5% width to pass through. Thus, a wider energy spectrum can be obtained than the prior art, thereby meeting the requirements of diversified treatment or imaging rays.
Although not wishing to be bound by theory, applicants have discovered in their studies that the symmetry of the pre-target electron beam spot under imaging conditions is more demanding than the symmetry of the pre-target electron beam spot under treatment conditions due to the greater difference in the imaging beam and treatment beam parameters. Therefore, in order to adjust the symmetry of the electron beam spot, the design of a subsequent equalizer is facilitated, the treatment technology is simplified, and the quality of the particle ray is improved. Referring to fig. 3, in one embodiment, a beam spot correction device 18 is further disposed between the third deflection magnet 16 and the target 70, and the beam spot correction device 18 is used for generating a quadrupole magnetic field to adjust the rotational symmetry of the electron beam spot. Further, the beam spot correction device 18 includes a correction coil provided at an exit end of the charged particle beam deflected at the uniform magnetic field of the third deflection magnet 16. Specifically, the correction coil is a maxwell coil pair.
It should be understood that, during the process of emitting the charged particles from the deflection orbit, the parameters such as initial lateral displacement, velocity direction, etc. have a certain deviation from the ideal design values, and therefore, the rotational symmetry of the electron beam in front of the target is not good. The beam spot correction device 18 in the present application has a multipole gradient magnetic field in a direction perpendicular to the particle beam traveling direction, through which the charged particle beam passes to adjust the traveling trajectory of the charged particles, thereby correcting the rotational symmetry of the charged particle beam before the target.
Specifically, the beam spot correction device 18 includes two magnetic poles disposed opposite to each other and a pair of maxwell coils wound around the respective magnetic poles, and the maxwell coils are excited by a magnetic field. More specifically, the two oppositely arranged magnetic poles are arranged in an axisymmetric manner, and the charged particles continuously correct the advancing track under the action of the gradient magnetic field, so that when the charged particle beam exits the beam spot correction device 18, the beam spot is substantially coaxial with the axis of the beam spot correction device 18, and the rotational symmetry of the electron beam spot in front of the target is ensured. In particular, in some embodiments, the two pole surfaces are hyperboloid.
It is understood that in other embodiments, a permanent magnet may be disposed along the proceeding direction of the charged particle beam, and specifically, the permanent magnet may be in the form of a permanent magnet ferromagnetic ring, and the magnetic rings are arranged according to a certain rule, so as to achieve the aforementioned effect of modifying the rotational symmetry of the electron beam spot in front of the target.
It will be appreciated that the aperture of the good field region of the beam spot modification apparatus 18 should exceed the size of the charged particle beam to ensure accuracy of the modification. It should be noted that the good field region refers to a field region where the magnetic field distribution of the magnet meets the requirement.
It can be understood that the magnetic field gradient can be determined according to the energy required by the imaging beam, and specifically, the larger the energy is, the larger the magnetic field gradient is, which is not described herein.
In order to better understand the technical effects achieved by the technical solutions of the present application, the charged particle beam deflecting device 10 will be described in the following with reference to the accompanying drawings by using specific embodiments.
Fig. 4 shows a diagram of the beam envelope of the therapeutic beam in the charged particle beam deflection device 10; fig. 5 shows a beam envelope diagram of the imaging beam before and after correction by the beam spot correction device 18; fig. 6 shows a pre-target beam spot pattern of the imaging beam before being modified by the beam spot modification device 18; fig. 7 shows a pre-target beam spot pattern of the imaging beam after being corrected by the beam spot correction device 18.
In this embodiment, the rotating gantry 30 is a drum type, the traveling direction of the charged particle beam is 12 degrees with respect to the axial direction of the rotating shaft of the rotating gantry 30 (see fig. 2, the angle between the direction a and the horizontal direction is 12 degrees), and the angle at which the charged particle beam deflecting device 10 deflects the accelerated charged particle beam is 258 degrees.
As shown in fig. 4, the upper and lower black lines B, B' represent the envelopes of the charged particle beam in the transverse and radial directions, respectively, and the dotted lines represent the dispersion characteristics of the magnetic deflection system. At the exit position of the magnetic deflection system, i.e. the position of the target 70, the charged particle beam has substantially the same dimensions in the transverse and radial directions, indicating that the cross-section of the charged particle beam is rotationally symmetric.
As shown in fig. 5, a line C, C' indicates that the beam spot before the target is not rotationally symmetric when the beam spot correction apparatus 18 is not in operation. And line D, D' indicates that the beam spot before the target is rotationally symmetric after being corrected by the beam spot correction device 18. Meanwhile, as can be seen from a comparison of fig. 6 and 7, the beam spot before the target which is not corrected by the beam spot correcting device 18 is elliptical, and the beam spot which is corrected by the beam spot correcting device 18 is circular.
Therefore, the charged particle beam deflection device 10 and the treatment system 100 have the following advantages compared with the prior art:
1) the effect of dispersion elimination is realized, and the beam current acceptance of the transverse and longitudinal beams is higher;
2) the electron beam in front of the target has good focusing characteristic, and the beam spot with a small cross section and axial symmetry is obtained on the target in a treatment mode or an imaging mode, so that the quality of particle rays is improved, and the treatment or imaging effect is further improved;
3) the design of the equalizer is facilitated, the penumbra of the X-ray after equalization is small, the consideration of beam flow non-rotational symmetry in a treatment plan can be simplified no matter in an electronic treatment mode or a photon treatment mode, and the treatment precision is improved.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (11)
1. A charged particle beam deflection device including a magnetic deflection unit for deflecting an accelerated charged particle beam by a predetermined angle, the magnetic deflection unit including a first deflection magnet at an entrance end of the charged particle beam deflection trajectory, a second deflection magnet at a downstream side of the first deflection magnet, and a third deflection magnet at an exit end of the charged particle beam deflection trajectory;
the first deflection magnet and the third deflection magnet are both suitable for forming a uniform magnetic field in at least part of the charged particle beam deflection track;
the second deflection magnet is suitable for forming a gradient magnetic field in part of the charged particle beam deflection track;
wherein, the entrance and the exit of the magnetic deflection unit have edge angles, and the magnetic field falling index of the gradient magnetic field is less than 0;
and an energy selecting mechanism is also arranged in the gradient magnetic field of the second deflection magnet so as to allow the energy spectrum with preset width to pass through.
2. The charged particle beam deflection device according to claim 1, wherein the first deflection magnet and the third deflection magnet each comprise a uniform field pole pair for forming a uniform magnetic field, and the second deflection magnet comprises a gradient field pole pair for forming a gradient magnetic field.
3. The charged particle beam deflector of claim 2, wherein a cross-sectional curve of the magnetic pole faces of the gradient field poles in a direction perpendicular to the charged particle beam is hyperbolic.
4. The charged particle beam deflection device according to claim 1, wherein the first deflection magnet, the second deflection magnet, and the third deflection magnet share a pair of induction coils.
5. The charged particle beam deflection device according to claim 1, wherein the entrance edge angle of the first deflection magnet is 30 to 45 degrees;
the range of the outlet edge angle of the third deflection magnet is 30-45 degrees.
6. A charged particle beam deflection unit as claimed in any one of claims 1 to 5, wherein a beam spot correction device is further provided between said third deflection magnet and the target, said beam spot correction device being adapted to generate a quadrupole magnetic field.
7. The charged particle beam deflection device according to claim 6, wherein the beam spot correction device is provided at an exit end of the charged particle beam deflected within the uniform magnetic field of the third deflection magnet.
8. A treatment system, comprising:
a rotating frame capable of rotating around a rotating shaft;
a charged particle beam emitting device for generating a charged particle beam and accelerating the charged particle beam, wherein the advancing direction of the charged particle beam forms a first angle relative to the axial direction of the rotating shaft;
a charged particle beam deflecting device for deflecting the accelerated charged particle beam by a second angle;
the sum of the first angle and the second angle is 270 degrees;
the charged particle beam deflection device according to any one of claims 1 to 7.
9. The treatment system of claim 8, further comprising a target for receiving the charged particle beam emitted from the charged particle beam deflection device, the charged particle beam bombarding the target to produce a therapeutic or imaging ray.
10. The treatment system of claim 8, wherein the first angle is in a range of 7 degrees to 17 degrees.
11. The treatment system of claim 8, wherein the charged particle beam emitting device comprises an electron gun and an accelerating tube in communication with the electron gun and located between the electron gun and the charged particle beam deflecting device;
wherein the accelerating tube is a standing wave accelerating tube.
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| CN108744314B (en) * | 2018-06-25 | 2020-10-02 | 西安大医集团股份有限公司 | Radiotherapy apparatus |
| CN109613597B (en) * | 2018-11-30 | 2021-04-06 | 上海联影医疗科技股份有限公司 | Method and system for determining electron beam energy spectrum |
| TWI712436B (en) * | 2019-05-07 | 2020-12-11 | 禾榮科技股份有限公司 | Neutron beam generating device |
| EP4090421A4 (en) * | 2020-04-17 | 2023-01-18 | Shanghai United Imaging Healthcare Co., Ltd. | Systems and methods for controlling electron beam in radiotherapy |
| CN113921357B (en) * | 2021-09-30 | 2024-06-11 | 中国人民解放军国防科技大学 | Strong current diode and gradient magnetic field device based on gradient magnetic field |
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