CN112657072A - Ultrahigh-dose-rate proton treatment device based on linear accelerator and scanning method - Google Patents
Ultrahigh-dose-rate proton treatment device based on linear accelerator and scanning method Download PDFInfo
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Abstract
The invention provides an ultrahigh dose rate proton treatment device based on a linear accelerator, which comprises a proton linear accelerator, a proton beam group distribution system, a full-energy static superconducting treatment bracket and a proton beam group scanning system which are sequentially connected, wherein the proton linear accelerator provides a pulse proton beam with switchable energy, the repetition frequency is at least 1 kilohertz, and the outlet mean flow strength is at least 30 microamperes; the distribution system and the scanning system have the same structure and deflect the proton beam based on a radio frequency deflection structure and a low level system; the full-energy static superconducting therapeutic stent is based on a plurality of groups of superconducting coil units corresponding to different irradiation angles. The invention also provides a corresponding scanning method. The device can realize the repetition frequency of 1 kilohertz, and the distribution and scanning system is based on a low level system and a radio frequency deflection structure, thereby realizing beam solid angle distribution and single-layer ultrafast scanning and switching, enabling a single treatment flow to cover the required number of scanning and energy layers, and rapidly completing the whole-area scanning within the specified time.
Description
Technical Field
The invention belongs to the technical field of particle radiotherapy, and particularly relates to an ultrahigh-dose-rate proton treatment device and a scanning method.
Background
FLASH therapy (FLASH), a proton therapy technology with ultrahigh dose rate (i.e. average dose rate not less than 300Gy/s), is the most advanced technology in the field of current radiotherapy, and can greatly reduce the damage of irradiation dose to normal tissues on the premise of not reducing the treatment effect of the irradiation dose to a target. Proton therapy has the characteristics of remarkable treatment effect and wide application range in numerous radiotherapy means, is a treatment technology which is popularized in a large range in Europe and America and China, shows very attractive prospect in recent years, and thus research and development of the proton flash therapy technology are actively promoted. The current proton treatment technology is mainly based on a cyclotron and a synchrotron, has the characteristics of slow proton energy switching or low pulse dose rate, and the treatment time for completing the irradiation treatment course is far from meeting the technical requirements of ideal flash treatment.
Therefore, there is a need for a device design for proton therapy (FLASH therapy) with ultra-high dose rate to meet the technical requirements of ideal FLASH therapy (FLASH), which can achieve an average dose rate of not less than 300Gy/s, an irradiation time of not more than 100ms, and compress several tens of original treatment procedures into a single therapy, wherein the therapeutic dose within 100ms per therapy reaches 30 Gy.
Disclosure of Invention
The invention aims to provide an ultrahigh-dose-rate proton treatment device and a scanning method based on a linear accelerator, so as to realize transient ultrahigh-dose-rate proton treatment.
In order to achieve the above object, the present invention provides an ultrahigh dose rate proton treatment apparatus based on a linear accelerator, comprising: a proton linac providing pulsed proton beams switchable between a plurality of energy points in an energy interval of 70MeV to 235MeV and having a repetition rate of at least 1 khz, a beam exposure time of at least 10 microseconds, and an exit average fluence of at least 30 microamps; an ultrafast proton beam mass distribution system, comprising: 2 sets of power source systems configured to provide pulsed microwave power; the radio frequency structure system is connected with the 2 sets of power source systems and comprises a waveguide structure and a radio frequency deflection structure which are sequentially connected; the radio frequency deflection structure is provided with two independent and mutually orthogonal polarization directions, two independent and orthogonal microwave electromagnetic fields are generated through pulse microwave power of 2 sets of power source systems, and two independent and orthogonal transverse deflection forces are provided for the proton beam through the microwave electromagnetic fields, so that the proton beam deflects under the action of the transverse deflection force; and 2 sets of low level systems respectively connected with the 2 sets of power source systems, and the low level systems are set to independently control the power level of the pulse microwave power of the corresponding power source systems; wherein a low level system of the ultrafast proton beam splitting system causes the proton beam to be emitted at different beam splitting angles by varying a power level of the pulsed microwave power; the beam distribution angle is a solid angle and is synthesized by a pitch angle and an azimuth angle; the full-energy static superconducting treatment bracket is based on a plurality of groups of superconducting coil units, and each group of superconducting coil units respectively corresponds to a plurality of beam distribution angles of one azimuth angle and one treatment visual field of an object to be scanned; and at least one ultrafast proton beam cluster scanning system having the same structure as the ultrafast proton beam cluster distributing system; the ultrafast proton beam scanning system is arranged at the downstream of each group of superconducting coil units, and the low-level system scans an object to be scanned by changing the power level of pulse microwave power, so that different proton beams are uniformly and orderly emitted to different transverse positions of the object to be scanned along with time.
The ultrafast proton beam distribution system is set to enable proton beams of different energy points to be emitted to the full-energy static superconducting therapy support at beam distribution angles of the same azimuth angle and different pitch angles, and the proton beams are emitted to the full-energy static superconducting therapy support at beam distribution angles of different azimuth angles.
The beam distribution angle switching frequency of the ultrafast proton beam distribution system is at least 1 kilohertz, and the corresponding beam distribution angle is maintained for at least 10 microseconds.
Each group of superconducting coil units are set to receive proton beams emitted to multiple different energy points of the full-energy static superconducting treatment support at beam distribution angles with the same azimuth angle and different pitch angles, and the proton beams are guided by deflection of multiple beam tracks, so that the proton beams are converged on the same beam track at the outlet of each superconducting coil unit; the number of beam tracks of each group of superconducting coil units is the same as that of the energy points, and the number of the beam tracks is 91.
The number of the ultrafast proton beam group scanning systems is equal to that of the superconducting coil units of the full-energy static superconducting treatment bracket and is fixedly arranged at the downstream of each group of the superconducting coil units, or the number of the superconducting coil units is smaller than that of the superconducting coil units of the full-energy static superconducting treatment bracket and is switchably arranged at the downstream of each group of the superconducting coil units.
The number of the superconducting coil units is at least 12, and the superconducting coil units are uniformly distributed in the 360-degree range of the object to be scanned to form the full-energy static superconducting treatment bracket.
The proton linear accelerator comprises a 10MeV injector, an energy increasing section of a drift tube linear accelerator and a high-gradient accelerator, wherein the high-gradient linear accelerator comprises 16 accelerating structures with the gradient of at least 50MV/m on the same axis, and each accelerating structure corresponds to 6 energy levels respectively.
On the other hand, the invention provides an ultrahigh-dose-rate proton scanning method based on a linear accelerator, which comprises the following steps:
s0: providing the ultrahigh dose rate proton treatment device based on the linear accelerator, respectively switching the proton linear accelerator and the ultrafast proton beam group distribution system of the ultrahigh dose rate proton treatment device to an energy point of a first scanning layer and a beam distribution angle corresponding to the energy point, then performing preparation work, and performing step S1 after the preparation work is completed;
s1: the proton linear accelerator is used for emitting proton beams at an energy point of a scanning layer, the beam distribution angle of the ultrafast proton beam mass distribution system is maintained, and the low level system of the ultrafast proton beam mass scanning system changes the power level of pulse microwave power according to a preset rule in the process so as to perform single-layer scanning on an object to be scanned, so that different proton beams are uniformly and orderly emitted to different transverse positions of the object to be scanned along with time;
s2: after the single-layer scanning is completed, the proton linear accelerator and the ultrafast proton beam cluster distributing system are respectively switched to an energy point corresponding to the next scanning layer and a beam distribution angle corresponding to the energy point according to a scanning start instruction of the next scanning layer, then preparation is performed, and the process returns to step S1 after the preparation is completed.
In step S1, the ultrafast proton beam bunch scanning system includes a first power source system and a second power source system, and the power level of the pulsed microwave power is changed according to a preset rule, including:
s11: controlling the power level of the first power source system to be unchanged and continuously switching the power level of the second power source system along the first direction;
s12: stepping the power level of the first power source system once under the condition of controlling the power level of the second power source system to be unchanged;
s13: controlling the power level of the first power source system to be constant and continuously switching the power level of the second power source system in the opposite direction of the first direction; subsequently, step S2 is repeated;
s14: the steps S11-S13 are repeated until the single-layer scan is completed.
The cycle time corresponding to steps S1-S2 is at most 1 millisecond, the time for scanning a single layer of the object to be scanned is at most 10 microseconds, and the beam irradiation time of the proton linac is at least 10 microseconds.
The ultrahigh dose rate proton treatment device based on the linear accelerator is based on the combination of the proton linear accelerator, the ultrafast proton beam group distribution system, the static full-energy treatment bracket and the ultrafast proton beam group scanning technology, can greatly improve the treatment dose rate of the proton treatment device, and realizes the irradiation dose rate not lower than 300 Gy/s; meanwhile, the ultrahigh-dose-rate proton treatment device can realize the repetition frequency of 1 kilohertz, so that the treatment time does not exceed 100 milliseconds, and the dose transmission of not less than 30Gy can be completed within 100 milliseconds; the ultrafast proton beam cluster distribution and ultrafast proton beam cluster scanning system is based on a low level system and a radio frequency deflection structure with orthogonal polarization directions, and realizes the rapid controllable switching of beam distribution angles and the single-layer scanning with extremely high speed, so that the proton beam clusters are accurately, orderly and uniformly transmitted to a scanning layer, the scanning layer switching is rapidly completed, a single treatment flow can cover the required energy layer number and multiple illumination fields, and finally the full-area scanning is rapidly completed within the specified time, so that the treatment requirements of proton FLASH therapy (FLASH) are met.
Drawings
Fig. 1 is a schematic structural diagram of an ultrahigh dose rate proton treatment apparatus based on a linear accelerator according to an embodiment of the present invention.
Fig. 2 is a layout structure diagram of a proton linac of the linac-based ultra-high dose rate proton treatment apparatus shown in fig. 1.
Fig. 3 is a functional schematic diagram of an ultrafast proton beam mass distribution system of the linac-based ultra-high dose rate proton therapy apparatus shown in fig. 1.
Fig. 4 is a schematic structural diagram of an ultrafast proton beam cluster distributing system according to a first embodiment of the present invention.
Fig. 5 is a schematic structural diagram of an ultrafast proton beam cluster distributing system according to a second embodiment of the present invention.
Fig. 6 is a schematic structural diagram of a superconducting coil unit of a full-energy static treatment stent of the ultrahigh-dose-rate proton treatment apparatus based on a linear accelerator shown in fig. 1.
Fig. 7 is a schematic diagram of an ultrafast proton beam bunch scanning system of the linac-based ultra-high dose rate proton therapy apparatus, as shown in fig. 1.
Fig. 8 is a timing diagram of the ultra-high dose rate proton scanning method based on the linear accelerator of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
As shown in fig. 1, the ultra-high dose rate proton treatment apparatus based on a linear accelerator according to the present invention includes a proton linear accelerator 100, an ultrafast proton beam cluster distribution system 200, a full-energy static superconducting treatment support 300, and a plurality of ultrafast proton beam cluster scanning systems 400, which are connected in sequence. The ultra-high dose rate proton treatment device based on the linear accelerator combines a proton linear accelerator technology, an ultra-fast beam distribution technology based on a radio frequency technology, a full-energy superconducting treatment bracket technology, an ultra-fast beam scanning technology based on the radio frequency technology and an ultra-fast low level control technology to complete a brand-new overall design, is used for realizing the irradiation dose rate not lower than 300Gy/s, and completes the dose transmission not lower than 30Gy within 100 milliseconds so as to meet the requirements of FLASH therapy (FLASH).
Fig. 2 shows the layout structure of the proton linear accelerator 100, in which the diamond shape is a focused magnetic structure. The proton linear accelerator 100 comprises a 714MHz 10MeV injector 110, a 2856MHz drift tube linear accelerator (DTL) energy-increasing section 120 and a 2856MHz high gradient accelerator 130, wherein the distance between the 10MeV injector 110 and the DTL energy-increasing section 120 is 6m, the distance between the DTL energy-increasing section 120 and the high gradient accelerator 130 is 13m, and the gradient of the high gradient accelerator 130 is at least 50 mV/m.
The 10MeV injector 110 consists of a 2.45GHz ECR ion source 111, a radio frequency quadrupole field (RFQ)112, and a heavy ion drift tube linear accelerator (IH-DTL) 113. The distance between the ion source 111 and the radio frequency quadrupole field (RFQ)112 is 2 meters. The ion source 111 is arranged to provide a pulsed proton beam having an energy of 50keV and a fluence of not less than 20 milliamperes; the Radio Frequency Quadrupole (RFQ)112 and the heavy ion drift tube linear accelerator (IH-DTL)113 both use the klystron 14 of 8MW as a power source, are set to capture and accelerate the pulsed proton beam, and output the pulsed proton beam with energy of 10MeV, pulse intensity of not less than 5 milliamperes, and average intensity of not less than 50 microamperes after capture and acceleration.
The DTL energization stage 120 includes 3 drift tube linear accelerator (DTL) units 121 located on the same axis. The DTL energization segment 120 adopts an 8MW klystron 14 as a power source, and is configured to accelerate the pulsed proton beam, so that the pulsed proton beam realizes a fixed energy of 70MeV, and the minimum energy requirement of proton therapy is met, and the pulse current intensity of the pulsed proton beam is not lower than 5 milliamperes, and the average current intensity is not lower than 50 microamperes.
The high gradient linear accelerator 130 is composed of 16 accelerating structures 131 with gradient of at least 50MV/m (i.e. high gradient) on the same axis, and each accelerating structure 131 is connected with a low level system 132 through an 8MW klystron 14 (i.e. power source), so as to be driven independently by the power source and controlled independently by the low level system. The low-level system is configured to control the feed power output by the corresponding power source to be switchable between 6 power levels, so that each acceleration structure corresponds to 6 energy levels, and thus, the high-gradient linear accelerator 130 can realize that the proton beam current is switchable between 91 energy points in the energy interval of 70MeV to 235MeV through 16 acceleration structures in total. In the energy switching process of the output proton beam, the energy of the proton beam approaches from a high energy point to a low energy point, which corresponds to fig. 2, that is, the power level is sequentially switched point by point from the downstream acceleration structure to the upstream acceleration structure. The focusing magnetic structure of the accelerating structure adopts a permanent magnet type, and the magnetic field intensity is unchanged, so that the focusing range covers 70MeV to 235 MeV; meanwhile, the low-level system can realize microsecond-level response speed, so that the working repetition frequency of the proton linear accelerator 100 is at least 1 kilohertz, the emission time length of a single proton beam is at least 1 microsecond, and finally, the maximum equivalent dose of 60Gy can be output within 100 milliseconds, thereby providing guarantee for realizing 30Gy flash therapy dose of a subsequent terminal.
Thus, the proton linac 100 provides pulsed proton beams switchable between 91 energy points in an energy interval of 70MeV to 235MeV, the repetition frequency of the proton linac 100 (i.e., the frequency of the switched energy points) being at least 1 khz, and the pulse length (i.e., beam irradiation time) for emitting a single proton beam being at least 10 microseconds. The average flow intensity at the outlet of the proton linac 100 is not less than 30 microamperes, and the sustained operation time of the proton linac 100 is not less than 100 milliseconds.
The ultrafast proton beam mass distribution system 200 is located downstream of the proton linac 100 and upstream of the full-energy static superconducting therapy stent 300, which serves as a critical pivotal connection. As shown in fig. 3, the ultrafast proton beam distribution system 200 may complete solid angle distribution of proton beams based on a polarization direction variable rf deflection cavity technology, so that the proton beams may be transmitted to the subsequent full-energy static superconducting therapy support 300 at different azimuth angles and pitch angles according to requirements.
Fig. 4 and 5 show ultrafast proton beam mass distribution systems 200 of two embodiments of a full-energy static treatment rack of a linac-based ultra-high dose rate proton treatment apparatus according to the present invention, which includes a power source system, and a radio frequency structural system and a low level system 31 connected to the power source system, wherein the low level system 31 is connected to the power source system through a cable.
The number of power source systems is 2 sets, which are arranged to provide pulsed microwave power. Each power source system corresponds to one polarization direction, and specifically comprises: the microwave signal source 11, the solid-state amplifier 12 and the klystron 15 are connected in sequence, and the trigger signal source 13 is directly connected with the solid-state amplifier 12 and connected with the klystron 15 through the modulator 14. Wherein the microwave signal source 11 is configured to provide a continuous microwave signal with a power of one milliwatt; the trigger signal source 13 is configured to output a time control signal to control the operating time of the solid-state amplifier 12 and the modulator 14; the solid-state amplifier 12 is arranged to amplify the continuous microwave signal to a pulsed microwave signal of a hundred watt level power in dependence on the time control signal; the modulator 14 is arranged to generate a corresponding direct-current high-voltage signal of tens of kilovolts on the basis of the time control signal; the klystron 15 is configured to convert the pulse microwave signal into megawatt pulse microwave power according to the direct current high voltage signal and output the megawatt pulse microwave power.
The radio frequency structure system is connected with 2 sets of power source systems and comprises a waveguide structure 21, a radio frequency deflection structure 22 and a high-power load 23 which are connected in sequence. The rf structure system is connected to the power source system through the waveguide structure 21, and the waveguide structure 21 plays a role of microwave transmission to transmit the pulsed microwave power provided by the klystron 15, i.e. the power source system, to the rf deflection structure 22. The rf deflection structure 22 has two independent and mutually orthogonal polarization directions, and is configured to generate two independent and orthogonal microwave electromagnetic fields by the pulse microwave power of 2 sets of power source systems, and provide two independent and orthogonal transverse deflection forces (i.e., kicking forces) to the proton beam by the microwave electromagnetic fields, so that the proton beam deflects a beam distribution angle under the action of the transverse deflection force and is emitted to the full-energy static superconducting therapy stent 300 by vector superposition of the two independent and orthogonal transverse deflection forces; the high power load 23 is arranged to absorb the remaining pulsed microwave power.
The number of the low-level systems 31 is 2, the low-level systems are respectively connected with 2 power source systems, the power levels of the pulse microwave powers of the corresponding power source systems are independently controlled, and the proton beam is emitted to the full-energy static superconducting therapy support 300 at different beam distribution angles through the output powers of different pulse microwave powers. Specifically, the low-level system 31 is connected to the solid-state amplifier 12 of the power source system, and is configured to output a power control signal to the corresponding solid-state amplifier 12 to control the amplification factor of the solid-state amplifier 12, so as to independently control the power level of the pulse microwave power corresponding to the solid-state amplifier, and enable the proton beam at different times to be emitted to the full-energy static superconducting therapy stent 300 at different beam distribution angles according to different power levels of the pulse microwave power.
As shown in fig. 4, in the first embodiment, the number of the rf structure systems is 2 and independent, each rf structure system includes a set of waveguide structures 21, an rf deflecting structure 22 with a fixed polarization direction, and a high power load 23, which are connected in sequence, and each rf deflecting structure 22 is connected to a set of power source system. The 2 rf deflecting structures 22 in the 2 sets of rf structure systems are respectively an rf deflecting structure 22 with a horizontal polarization direction and an rf deflecting structure 22 with a vertical polarization direction (the polarization direction of the rf deflecting structure 22 is marked in the figure). Thus, the rf deflecting structure 22 has two independent and mutually orthogonal polarization directions. The rf deflection structure 22 in the horizontal polarization direction and the rf deflection structure 22 in the vertical polarization direction are located on the same axis, so that the proton beam passes through.
As shown in fig. 5, in the second embodiment, the number of the rf structure systems is 1, and the rf structure systems respectively include two groups of waveguide structures 21, one rf deflecting structure 22 with a variable polarization direction connected to the two groups of waveguide structures 21 at the same time, and two high-power loads 23 connected to the rf deflecting structure 22. The rf deflecting structure 22 is an rf deflecting structure 22 having both horizontal and vertical polarization directions (i.e. two independent and mutually orthogonal polarization directions), so that the rf deflecting structure 22 has two independent and mutually orthogonal polarization directions.
Therefore, the radio frequency structure system generates two independent and orthogonal microwave electromagnetic fields through the pulse microwave power of 2 sets of power source systems, and provides two independent and orthogonal transverse deflection forces for the proton beam through the microwave electromagnetic fields (the total deflection force is synthesized by the two orthogonal transverse deflection forces), so that the proton beam deflects a beam distribution angle under the action of the transverse deflection force and is emitted to the full-energy static superconducting treatment support 300; the low-level system independently controls the output power of the pulse microwave power of the corresponding power source system, so that different proton beam currents are emitted to the full-energy static superconducting therapy support 300 at different beam distribution angles through the output power of different pulse microwave powers. The beam distribution angle is a solid angle and is synthesized by a pitch angle and an azimuth angle; the pitch angle is determined by the energy of the proton beam, and the ultrafast proton beam distribution system 200 is configured to enable proton beams at different energy points to be emitted to the full-energy static superconducting therapy support 300 at the same azimuth angle and at different pitch angles, so that the proton beams converge on the same beam track at the outlet of the downstream full-energy static superconducting therapy support 300; the proton beam is emitted to the full-energy static superconducting therapy stent 300 at beam distribution angles of different azimuth angles.
According to the requirements of a typical treatment plan prescription, the beam distribution angle switching frequency (i.e., the frequency of the low-level system switching power level) of the ultrafast proton beam mass distribution system 200 is at least 1 khz, so that the proton beam distribution of at least 100 scan layers can be completed within 100ms, the energy points of the proton beam masses in each scan layer are the same, and the beam distribution angles are consistent; the corresponding beam distribution angle is maintained for at least 10 microseconds (the same energy point may correspond to 1-2 scanned layers of the object being scanned). According to the energy and prescription requirements of different scanning layers, the distribution system quickly completes the switching and preparation of beam distribution angles (azimuth angle and pitch angle), and the total time (namely a work repetition period) of the whole switching, preparation and beam distribution time is at most 1 millisecond.
The full-energy static superconducting therapy stent 300 of the present invention is based on a plurality of sets of superconducting coil units (see specifically [ Bottura L, felicin E, Rijk G D, et al. gatoroid: a novel toroidal winding for a hydro thermal [ J ]. Nuclear Instruments and Methods in Physics Research Section a algorithms Detectors and Associated Equipment,2020:164588 ]), each corresponding to a plurality of beam distribution angles (the number of beam distribution angles in one azimuth angle is plural) of one azimuth angle of the ultrafast proton beam distribution system 200, and one treatment field of view (e.g., front, side, back, etc. of the object to be scanned) of the object to be scanned. The magnetic field distribution of each set of superconducting coil units is specially designed without changing the magnetic field strength, and the superconducting coil units are arranged to receive proton beams of a plurality of different energy points emitted to the full-energy static superconducting treatment support 300 at beam distribution angles of the same azimuth angle and different pitch angles, and deflect and guide the proton beams of the plurality of different energy points by a plurality of beam tracks, so that the proton beams are converged on the same beam track at the outlet of the superconducting coil unit and then transmitted to the downstream ultrafast proton beam scanning system 400. In the present embodiment, the number of beam trajectories of each group of superconducting coil units is the same as the number of energy points, and is 91, and each beam trajectory is in an α shape as shown in fig. 6. As shown in fig. 6, the α orbit at the inside is correspondingly switched to the proton beam bunch at the low energy point, and the α orbit at the outside is correspondingly switched to the beam bunch at the high energy point, so that the design of the α -shaped orbit can effectively increase the treatment area space and enhance the flexibility of the treatment process. The multiple groups of superconducting coil units respectively receive proton beams emitted to the full-energy static superconducting therapy support 300 at different azimuth angle beam distribution angles, and respectively converge on respective beam tracks at the outlets of the superconducting coil units corresponding to the respective azimuth angles. In this embodiment, the number of the superconducting coil units may be 12 or more, and the multiple groups of superconducting coil units are uniformly distributed in the 360-degree range of the object to be scanned according to the azimuth direction of the beam distribution angle to combine into a complete full-energy static superconducting treatment support 300, so as to provide multiple treatment views. Because the treatment support is composed of a plurality of groups of superconducting coil units and receives the proton beam current distributed to different beam current distribution angles through the ultrafast proton beam group distribution system 200, the treatment support is in a static state and a non-magnetic Field change state, the treatment requirements of different scanning layers (Layer) and different treatment fields (Field) can be met without any mechanical rotation, and all the proton beam groups with 91 energy points from 70MeV to 235MeV are covered.
The ultrafast proton beam bolus scanning system 400 is located at the most downstream of the flash therapy apparatus, and the number of the ultrafast proton beam bolus scanning system 400 is equal to the number (i.e. multiple) of the sets of superconducting coil units of the full-energy static superconducting therapy stent 300, and the ultrafast proton beam bolus scanning system 400 is respectively and fixedly disposed at the downstream of the sets of superconducting coil units of the full-energy static superconducting therapy stent 300, so that one corresponding ultrafast proton beam bolus scanning system 400 exists in each therapy field. The principle of the ultrafast proton beam scanning system 400 is shown in fig. 7, which is also based on the deflection cavity technology with a variable polarization direction, so that different proton beams can be emitted to different lateral positions of an object to be scanned over time (which scanning layer of the object to be scanned the proton beams are emitted is controlled by an energy point, that is, controlled by the proton linear accelerator 100), and single-layer scanning can be completed within 10 microseconds.
The configuration of the ultrafast proton beam bolus scanning system 400 is identical to that of the ultrafast proton beam bolus dispensing system 200 described above (i.e., it also includes 2 sets of power source system, rf configuration system, and 2 sets of low level system). The ultrafast proton beam bolus scanning system 400 and the ultrafast proton beam bolus dispensing system 200 differ only in that: because the ultrafast proton beam group scanning system 400 is located at the most downstream of the ultrahigh dose rate proton treatment device based on the linear accelerator, the proton beam current of each ultrafast proton beam group scanning system 400 deflects a stereoscopic scanning angle under the action of two independent and orthogonal transverse deflection forces (i.e. deflection forces in the X and Y directions) and is emitted to an object to be scanned, the low-level system of each ultrafast proton beam group scanning system 400 is set to independently control the power level of the pulse microwave power of the corresponding power source system, so that the object to be scanned is scanned by changing the power level of the pulse microwave power, and different proton beam currents are emitted to different transverse positions of the object to be scanned uniformly and orderly through different stereoscopic scanning angles along with time.
Based on the ultrahigh-dose-rate proton treatment device based on the linear accelerator, the realized ultrahigh-dose-rate proton scanning method based on the linear accelerator comprises the following steps:
step S0: the proton linear accelerator 100 and the ultrafast proton beam distribution system 200 of the ultrahigh dose rate proton therapy apparatus based on the linear accelerator are respectively switched to an energy point of a first scanning layer and a beam distribution angle corresponding to the energy point, and then preparation work (i.e. automatic initialization work of an electronic device such as a low level system) is performed, and after the preparation work is completed, step S1 is performed to start scanning;
step S1: the proton linear accelerator 100 is used for emitting proton beams at an energy point of a scanning layer, and beam distribution angles of the ultrafast proton beam mass distribution system 200 are maintained, in the process, a low-level system of the ultrafast proton beam mass scanning system 400 changes the power level of pulse microwave power according to a preset rule so as to perform single-layer scanning on an object to be scanned, so that different proton beams are uniformly and orderly emitted to different transverse positions of the object to be scanned along with time;
in the step S1, the ultrafast proton beam bunch scanning system 400 includes a first power source system and a second power source system; changing the power level of the pulse microwave power according to a preset rule, which specifically comprises the following steps:
step S11: controlling the power level of the first power source system to be unchanged and continuously switching the power level of the second power source system along a first direction (the first direction is a power level amplification direction or a power level reduction direction), so that the proton beam continuously scans to the other end from the starting point in the X direction on a scanning layer of the object to be scanned;
step S12: under the condition of controlling the power level of the second power source system to be unchanged, stepping the power level of the first power source system once so as to stop the X-direction scanning of the proton beam on a scanning layer of the object to be scanned and step one line in the Y direction;
step S13: controlling the power level of the first power source system to be unchanged and continuously switching the power level of the second power source system along the opposite direction of the first direction so as to enable the proton beam to reversely scan on a scanning layer of the object to be scanned along the X direction; then, repeating the step S2 to make the proton beam stop scanning in the X direction on the scanning layer of the object to be scanned, and stepping one line in the Y direction;
step S14: the steps S11-S13 are repeated until the single-layer scan is completed. The control response speed of the low-level system of the ultrafast proton beam mass scanning system 400 is on the order of 10ns, and at most 1000 spot scans can be completed within 10 microseconds, meeting the prescription requirements in a typical treatment plan.
Step S2: after the single-layer scanning is completed, the proton linear accelerator 100 and the ultrafast proton beam distributing system 200 of the ultrahigh dose rate proton therapy apparatus based on the linear accelerator are respectively switched to the energy point corresponding to the next scanning layer and the beam distributing angle corresponding to the energy point according to the scanning start instruction of the next scanning layer, and then preparation is performed, and after the preparation is completed, the process returns to step S1.
As shown in fig. 8, the cycle time of a complete single-layer scan is at most 1 millisecond (i.e., the repetition period is at least 1 khz), the cycle time including the irradiation preparation time, the energy switching time, and the beam irradiation time, corresponding to steps S1-S2; time for scanning the object to be scanned by a single layer (corresponding to steps S11-S14) toThe time of beam irradiation of the proton linac (i.e., the time of emitting a proton beam at an energy point of one scan layer, corresponding to step S1) is at least 10 microseconds, which is at most 10 microseconds. In the figure, Ei is the ith energy layer (i.e., the layer corresponding to the ith energy point), i is the ordinal number of the energy layer, and i is 1,2,3, …, M. The total number of energy layers M is less than the total number of scanning layers, so that some energy layers (e.g. E)m) Two passes of scanning are required corresponding to two scan layers. As shown in fig. 8, the present invention can complete a single FLASH (FLASH) treatment in 100 milliseconds with an ultrafast proton beam cluster scanning system 400, and in conjunction with the proton linac 100, up to 100 physical scans can cover all 91 proton energy layers (70MeV to 230 MeV). The 70MeV proton beam with the lowest energy can provide the average dose rate which is not less than 300Gy/s, so the proton beam with the higher energy can provide the dose rate which is more than 300Gy/s, and finally the irradiation dose which is not less than 30Gy can be realized in the equivalent target area of 10cm multiplied by 10cm within 100 milliseconds, thereby achieving the technical requirement of advanced FLASH therapy (FLASH).
While the above description is directed to the preferred embodiment of the present invention, it is not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention, for example, the number of ultrafast proton beam cluster scanning systems may be single or less than the number of superconducting coil units of the full-energy static superconducting therapy stent described above, and all or part of the beam cluster scanning systems may be rotationally moved in azimuth of the therapy stent and switchably disposed downstream of each set of superconducting coil units as needed. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.
Claims (10)
1. The utility model provides an ultra-high dose rate proton treatment device based on linear accelerator which characterized in that includes consecutive:
a proton linac providing pulsed proton beams switchable between a plurality of energy points in an energy interval of 70MeV to 235MeV and having a repetition rate of at least 1 khz, a beam exposure time of at least 10 microseconds, and an exit average fluence of at least 30 microamps;
an ultrafast proton beam mass distribution system, comprising:
2 sets of power source systems configured to provide pulsed microwave power;
the radio frequency structure system is connected with the 2 sets of power source systems and comprises a waveguide structure and a radio frequency deflection structure which are sequentially connected; the radio frequency deflection structure is provided with two independent and mutually orthogonal polarization directions, two independent and orthogonal microwave electromagnetic fields are generated through pulse microwave power of 2 sets of power source systems, and two independent and orthogonal transverse deflection forces are provided for the proton beam through the microwave electromagnetic fields, so that the proton beam deflects under the action of the transverse deflection force; and
2 sets of low level systems respectively connected with the 2 sets of power source systems are set to independently control the power level of the pulse microwave power of the corresponding power source system;
wherein a low level system of the ultrafast proton beam splitting system causes the proton beam to be emitted at different beam splitting angles by varying a power level of the pulsed microwave power; the beam distribution angle is a solid angle and is synthesized by a pitch angle and an azimuth angle;
the full-energy static superconducting treatment bracket is based on a plurality of groups of superconducting coil units, and each group of superconducting coil units respectively corresponds to a plurality of beam distribution angles of one azimuth angle and one treatment visual field of an object to be scanned; and
at least one ultrafast proton beam cluster scanning system having a structure identical to that of the ultrafast proton beam cluster distributing system; the ultrafast proton beam scanning system is arranged at the downstream of each group of superconducting coil units, and the low-level system scans an object to be scanned by changing the power level of pulse microwave power, so that different proton beams are uniformly and orderly emitted to different transverse positions of the object to be scanned along with time.
2. The linac-based ultra-high dose rate proton treatment apparatus according to claim 1, wherein the ultrafast proton beam distribution system is configured such that proton beams of different energy points are emitted to the full-energy static superconducting therapy gantry at beam distribution angles of the same azimuth and different elevation angles, and proton beams are emitted to the full-energy static superconducting therapy gantry at beam distribution angles of different azimuth angles.
3. The linac-based ultra-high dose rate proton treatment apparatus according to claim 2, wherein the beam distribution angle switching frequency of the ultrafast proton beam mass distribution system is at least 1 khz, and the corresponding beam distribution angle has a hold time of at least 10 μ s.
4. The ultrahigh dose rate proton therapy device according to claim 2, wherein each set of superconducting coil units is configured to receive a plurality of proton beams of different energy points emitted to the full-energy static superconducting therapy support at beam distribution angles of the same azimuth angle and different pitch angles, and the proton beams are guided by deflection of a plurality of beam tracks, so that the proton beams converge on the same beam track at the outlets of the superconducting coil units; the number of beam tracks of each group of superconducting coil units is the same as the number of energy points.
5. The linac-based ultra-high dose rate proton therapy device according to claim 3, wherein the number of the ultrafast proton beam bunch scanning systems is equal to the number of the superconducting coil units of the full-energy static superconducting therapy stent and fixedly disposed downstream of each group of the superconducting coil units, or is less than the number of the superconducting coil units of the full-energy static superconducting therapy stent and switchably disposed downstream of each group of the superconducting coil units.
6. The linear accelerator-based ultrahigh dose rate proton treatment device according to claim 1, wherein the number of the superconducting coil units is at least 12, and multiple sets of superconducting coil units are uniformly distributed in a 360-degree range of an object to be scanned to form the full-energy static superconducting treatment stent.
7. The linac-based ultra-high dose rate proton therapy device according to claim 1, characterized in that the proton linac consists of a 10MeV injector, a drift tube linac energization section and a high gradient accelerator consisting of 16 accelerating structures with a gradient of at least 50MV/m on the same axis, each accelerating structure corresponding to 6 energy levels respectively.
8. An ultrahigh dose rate proton scanning method based on a linear accelerator is characterized by comprising the following steps:
step S0: providing the linac-based ultra-high dose rate proton treatment apparatus according to any one of claims 1 to 7, switching the proton linac and the ultrafast proton beam mass distribution system thereof to the energy point of the first scan layer and the beam distribution angle corresponding to the energy point, respectively, and then performing a preparation operation, and after the preparation operation is completed, performing step S1;
step S1: the proton linear accelerator is used for emitting proton beams at an energy point of a scanning layer, the beam distribution angle of the ultrafast proton beam mass distribution system is maintained, and the low level system of the ultrafast proton beam mass scanning system changes the power level of pulse microwave power according to a preset rule in the process so as to perform single-layer scanning on an object to be scanned, so that different proton beams are uniformly and orderly emitted to different transverse positions of the object to be scanned along with time;
step S2: after the single-layer scanning is completed, the proton linear accelerator and the ultrafast proton beam cluster distributing system are respectively switched to an energy point corresponding to the next scanning layer and a beam distribution angle corresponding to the energy point according to a scanning start instruction of the next scanning layer, then preparation is performed, and the process returns to step S1 after the preparation is completed.
9. The linac-based ultra-high dose rate proton scanning method according to claim 8, wherein in the step S1, the ultrafast proton beam bunch scanning system includes a first power source system and a second power source system, the power level of the pulsed microwave power is changed according to a preset rule, including:
step S11: controlling the power level of the first power source system to be unchanged and continuously switching the power level of the second power source system along the first direction;
step S12: stepping the power level of the first power source system once under the condition of controlling the power level of the second power source system to be unchanged;
step S13: controlling the power level of the first power source system to be constant and continuously switching the power level of the second power source system in the opposite direction of the first direction; subsequently, step S2 is repeated;
step S14: the steps S11-S13 are repeated until the single-layer scan is completed.
10. The linac-based ultra-high dose rate proton scanning method according to claim 8, characterized in that the cycle time corresponding to steps S1-S2 is at most 1 millisecond, the time for scanning a single layer of the object to be scanned is at most 10 microseconds, and the beam irradiation time of the proton linac is at least 10 microseconds.
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