An electronic linear accelerator for an x-ray intratreatment radiotherapy apparatus

Abstract

The application provides an electron linear accelerator for X-ray intracourse radiotherapy equipment, which comprises an electron gun, a beam accelerating module and an X-ray conversion module arranged in sequence along the propagation direction of electrons, and a microwave generation and transmission system connected with the beam accelerating module; the beam accelerating module comprises a first cavity, a coupling cavity, a second cavity and a drift tube connected in sequence, and the first cavity is connected with the electron gun to receive an electron beam; the coupling cavity couples the microwave energy of the first cavity and the second cavity; the X-ray conversion module comprises a conversion target and a source applicator arranged in sequence, and the conversion target is connected with the beam accelerating module to receive the electron beam and emit X-rays. The electron linear accelerator of the application sets a coupling cavity between the first cavity and the second cavity of the beam accelerating module, only needs to feed power into the second cavity, reduces the volume of the beam accelerating module, and facilitates the adjustment of the phase and electric field amplitude between the cavities for realizing beam acceleration.

Description

Technical Field

[0001] This invention belongs to the field of medical accelerators, and particularly relates to an electronic linear accelerator for use in X-ray intraoperative radiotherapy equipment. Background Technology

[0002] Treatment methods for tumors include surgery, radiotherapy, chemotherapy, hormone therapy, and targeted therapy. In clinical treatment principles, surgery has the highest priority. However, during surgery, incomplete removal of the tumor or residual cancer cells in the tumor bed can lead to tumor recurrence. To reduce the recurrence rate, a combination of surgery and radiotherapy, known as intraoperative radiotherapy (IRT), has been developed. IRT is defined as radiation therapy performed during surgery. Typically, after surgical removal of the tumor, a single high-dose irradiation is administered to the tumor bed and unresectable areas to inhibit tumor growth or prevent recurrence. Internationally, IRT equipment technology has developed rapidly and is highly mature, primarily in Europe and the United States. It is widely used for breast cancer, pancreatic cancer, gastrointestinal tumors, brain tumors, head and neck tumors, skin cancer, and spinal metastases, applicable to a wide range of cases and a large patient population. Typical electron beam IRT equipment is represented by the United States and Italy, including Mobetron, LIAC, and Novac-7. X-ray IRT equipment includes Zeiss's Intrabeam from Germany and iCAD's Xoft Axxent from the United States. However, the progress of intraoperative radiotherapy technology in China has been slow. Currently, there is a mobile electron beam intraoperative radiotherapy system developed by Hunan Huachuang Medical Technology Co., Ltd. in China, but there is no prototype of X-ray intraoperative radiotherapy equipment yet.

[0003] The Intrabeam system from the German company Zeiss uses a 50kV high voltage to accelerate electrons to 50keV. Considering the safety and stability of the equipment, this invention uses microwaves to accelerate electrons, which can reduce the high voltage of the equipment to below 10kV.

[0004] In the invention patent application "An Electron Linear Accelerator for X-ray Intraoperative Radiotherapy Equipment" (application number 202510006880.1, hereinafter referred to as Prior Art 1), two cavities, two input couplers, one power divider, one microwave power source, and one electron gun are used to achieve an output electron beam energy of 50keV for the beam acceleration module. However, due to the large size of the power divider, the beam acceleration module is also large. Furthermore, the phase difference between the two cavities cannot be adjusted after processing, and the electric field amplitude of the two cavities cannot be adjusted either, which is not conducive to using this scheme in X-ray intraoperative radiotherapy equipment. Summary of the Invention

[0005] The purpose of this invention is to provide an electronic linear accelerator for X-ray intraoperative radiotherapy equipment, so as to reduce the volume of the beam acceleration module and facilitate the adjustment of phase and electric field amplitude between the beam acceleration cavities, thereby making it suitable for X-ray intraoperative radiotherapy equipment.

[0006] To achieve the above objectives, the present invention provides an electron linear accelerator for X-ray intraoperative radiotherapy equipment, comprising an electron gun, a beam acceleration module, and an X-ray conversion module arranged sequentially along the electron propagation direction, and a microwave generation and transmission system connected to the beam acceleration module to provide microwave power thereto; the beam acceleration module includes a first cavity, a coupling cavity, a second cavity, and a drift tube connected sequentially, the first cavity being connected to the electron gun to receive the electron beam; the electron gun is used to generate an electron beam that is injected into the first cavity; the first cavity is used to accelerate the electron beam; the coupling cavity is used to couple the microwave energy of the first cavity and the second cavity; the second cavity is used to optimize the electron beam energy spectrum; the drift tube is used to make the electron beam distribution more uniform; the X-ray conversion module includes a conversion target and an emitter arranged sequentially, the conversion target being connected to the beam acceleration module to receive the electron beam and emit X-rays.

[0007] A bellows is provided on the coupling cavity. The bellows is serrated and expandable, so that the length of the coupling cavity is adjustable.

[0008] When the electron beam is accelerated by the beam acceleration module, the phase difference between the first cavity and the second cavity is 90 degrees.

[0009] The first cavity and the coupling cavity, and the coupling cavity and the second cavity are connected through a coupling hole.

[0010] An energy switch is provided on the coupling hole between the coupling cavity and the second cavity. The energy switch is used to adjust the size of the coupling hole, thereby changing the electric field of the second cavity and obtaining electron beams of different energies.

[0011] The microwave generation and transmission system includes a microwave power source, an isolator, and a directional coupler connected in sequence. The directional coupler is connected to a second cavity to inject microwave power into the second cavity.

[0012] The coupling degree between the second cavity and the directional coupler is between 1 and 1.3.

[0013] The conversion target is connected to two dose detectors.

[0014] The electron linear accelerator also includes a control system, which is connected to the electron gun, microwave power source, directional coupler, and dose detector.

[0015] The drift tube is 5-20cm in length, and a solenoid is fitted over the drift tube.

[0016] The linear accelerator for X-ray intraoperative radiotherapy equipment of the present invention features a coupling cavity between the first and second cavities of the beam acceleration module. This coupling cavity replaces the power divider in the prior art, thus eliminating the need for a power divider and requiring only power to be fed into the second cavity. Because the beam acceleration module of the present invention does not require a power divider, its overall size is significantly reduced, facilitating the adjustment of phase and electric field amplitude between the beam acceleration cavities and adapting to the requirements of X-ray intraoperative radiotherapy equipment for the beam acceleration module. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the electron linear accelerator for X-ray intraoperative radiotherapy equipment of the present invention;

[0018] Figure 2 This is a three-dimensional structural diagram of the cavity portion of the beam acceleration module of the electronic linear accelerator for X-ray intraoperative radiotherapy equipment of the present invention. Detailed Implementation

[0019] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0020] like Figure 1 As shown, the electron linear accelerator for X-ray intraoperative radiotherapy equipment of the present invention includes an electron gun 10, a beam acceleration module 20, and an X-ray conversion module 30 arranged sequentially along the electron propagation direction, and a microwave generation and transmission system 40 connected to the beam acceleration module 20 to provide microwave power thereto. The electron gun 10, X-ray conversion module 30, and microwave generation and transmission system 40 are all connected to a control system 50, enabling the control system 50 to acquire and adjust the parameters of the electron gun 10, X-ray conversion module 30, and microwave generation and transmission system 40.

[0021] The beam acceleration module 20 includes a first cavity 21, a coupling cavity 22, a second cavity 23, and a drift tube 24 connected in sequence. The first cavity 21 is connected to the electron gun 10 to receive the electron beam. The first cavity 21 is used to accelerate the electron beam; the coupling cavity 22 is used to couple the microwave energy of the first cavity 21 and the second cavity 23; the second cavity 23 is used to optimize the electron beam energy spectrum; and the drift tube is used to make the electron beam distribution more uniform, resulting in a more uniform dose distribution after target firing.

[0022] Therefore, compared to the existing technology where the first cavity and second cavity are used to feed microwave power separately through a power divider, the present invention uses a coupled cavity to achieve energy coupling between the first cavity and the second cavity, thus eliminating the need for a power divider.

[0023] In this embodiment, the length of the drift tube 24 is 5-20 cm, and a solenoid 25 is fitted over the drift tube 24. The solenoid 25 focuses the electron beam so that it does not diverge excessively laterally within the drift tube 24.

[0024] In this embodiment, the cavity wall of the coupling cavity 22 is made of a corrugated tube with a serrated shape and is expandable, making the length of the coupling cavity 22 adjustable. Therefore, by changing the length of the coupling cavity, the present invention can adjust the cavity spacing between the first cavity 21 and the second cavity 23, thereby changing the phase difference between the two cavities.

[0025] In this embodiment, the microwave frequency received by the second cavity 23 is 9.3 GHz, and the phase difference between the first cavity 21 and the second cavity 23 is 90 degrees (π / 2). When the electron beam is accelerated by the beam acceleration module, the phase difference between the first cavity 21 and the second cavity 23 is adjusted to 90 degrees, so that the first cavity 21 accelerates the electrons, and the second cavity 23 performs electron beam energy spectrum optimization. The energy spectrum optimization effect is good. At a phase difference of 90 degrees, the faster electrons fall into the deceleration field region, where the electric field slightly decelerates them, consuming excess kinetic energy and reducing their speed. The slower electrons fall into the acceleration field region, where the electric field slightly accelerates them to make up for the speed gap. The fast and slow electrons move closer to the middle, and the electrons are compressed into a cluster longitudinally on the time axis (longitudinal beaming). The speed difference between electrons is greatly reduced, and the originally wide initial energy spectrum is narrowed, achieving energy spectrum pre-optimization. In addition, a solenoid 25 is added to the drift tube 24 to play a focusing role. Finally, the number of electrons at the exit of the beam acceleration module 20 is greater, and the capture rate is higher.

[0026] The first cavity 21 and the coupling cavity 22, as well as the coupling cavity 22 and the second cavity 23, are connected by a coupling hole 26. The coupling hole 26 serves as a microwave energy communication channel between the first cavity 21, the coupling cavity 22, and the second cavity 23. After microwaves are fed into the second cavity 23, the radio frequency electromagnetic field is transmitted across the cavity to the adjacent coupling cavity 22 and the first cavity 21 via the coupling hole 26. This enables the three resonant cavities—the first cavity 21, the coupling cavity 22, and the second cavity 23—to resonate at the same frequency, establishing a unified standing wave radio frequency electromagnetic field throughout the accelerating cavity and providing an accelerating electric field for electrons.

[0027] An energy switch 27 is provided on the coupling aperture 26 between the coupling cavity 22 and the second cavity 23. This energy switch 27 is used to adjust the size of the coupling aperture 26, thereby changing the magnitude of the electric field in the second cavity 23. The change in the electric field magnitude leads to a change in the final output energy of the beam acceleration module, ultimately resulting in electron beams of different energies. In this embodiment, the energy switch 27 has a baffle. The size of the coupling aperture is adjusted by adjusting the insertion length of the baffle into the coupling aperture 26, thereby adjusting the magnitude of the electric field amplitude in the second cavity. The ratio of the electric field amplitudes of the first cavity 21 to the second cavity 23 is 1:(0.06-0.11). The function of the second cavity is to optimize the energy spectrum; a very high field strength is not required. The specific value of the electric field amplitude ratio is obtained through beam dynamics calculations. After adjusting the field distribution using the energy switch, the field distribution can be measured using a perturbation method. Using a vector network analyzer and a perturbation body, the ratio of the electric field amplitudes of the first cavity 21 to the second cavity 23 can be measured.

[0028] The microwave generation and transmission system 40 includes a microwave power source 41, an isolator 42, and a directional coupler 43 connected in sequence. The directional coupler 43 is connected to a second cavity 23 to inject microwave power into the second cavity 23. The microwave power source 41 provides microwave power to the beam acceleration module 20; the isolator 42 isolates microwaves reflected back to the microwave power source 41, providing protection; the directional coupler 43 feeds microwave energy into the beam acceleration module 20; and the conversion target 31 is connected to two dose detectors 51, which are used to detect the dose of X-rays.

[0029] Figure 2 A three-dimensional structural diagram of the cavity portion of the beam acceleration module of the electron linear accelerator for X-ray intraoperative radiotherapy equipment of the present invention is shown, that is, the vacuum portion of each component is shown. It can be seen that the cavity portion 210 of the first cavity is connected to the cavity portion 220 of the coupling cavity through the cavity portion 260 of the coupling hole, the cavity portion 220 of the coupling cavity is connected to the cavity portion 230 of the second cavity through the cavity portion 260 of the coupling hole, and the cavity portion 430 of the directional coupler is connected to the cavity portion 230 of the second cavity.

[0030] In this embodiment, the coupling degree between the second cavity 23 and the directional coupler 43 is between 1 and 1.3. The microwave generation and transmission system 40 is configured to generate microwave power of 20kW to 30kW to inject into the second cavity 13, thereby forming a microwave field within the beam acceleration module 20.

[0031] The X-ray conversion module 30 includes a conversion target 31 and an applicator 32 arranged in sequence. The conversion target 31 is connected to the beam acceleration module 20 to receive the electron beam and emit X-rays. The electron beam emitted by the electron gun 10 passes through the first cavity 21, coupling cavity 22, second cavity 23, and drift tube 24, outputting an electron beam with an energy of 50 keV. The electron beam, after passing through the conversion target 31, generates X-rays, which are then distributed by the applicator 32 to create a dose distribution tailored to different tumor shapes.

[0032] The control system 50 is simultaneously connected to the electron gun 10, the microwave power source 41, the directional coupler 43, and the dose detector 51. The control system 50 is used to receive and control signals from these system components.

[0033] The operation of the control system 50 is as follows:

[0034] 1. Directional Coupler 43: Collects signals of incident microwave power and reflected microwave power from the directional coupler 43, and then monitors the output power of microwave power source 41 and the fault status of cavity microwave standing wave / reflection.

[0035] 2. Dosimeter 51: Collects two independent real-time X-ray dose rate and cumulative dose sampling signals from two dosimeters 51 to collect the emitted X-ray dose data of the conversion target 31 and provide closed-loop feedback of the actual output dose.

[0036] 3. Microwave power source 41: Send power adjustment signals and start / stop control signals to microwave power source 41 to regulate the microwave output power and power on / off;

[0037] 4. Electron gun 10: Sends filament power signal and high voltage pulse trigger control signal to electron gun 10 to control the start and stop of electron beam emission.

[0038] Therefore, the control system 50 can receive and control signals from the electron gun 10, microwave power source 41, directional coupler 43, and dose detector 51.

[0039] Experimental results:

[0040] Example 1: When the ratio of the electric field amplitude of the first cavity to that of the second cavity is 1:0.06, the final output average energy is 44.6 keV, the energy of the highest particle number in the energy spectrum is 52.2 keV, and the electron capture rate reaches 43.57%, which meets the requirements of X-ray intraoperative radiotherapy equipment.

[0041] Example 2: When the ratio of the electric field amplitude of the first cavity to that of the second cavity is 1:0.08, the final output average energy is 44.44 keV, the energy of the highest particle number in the energy spectrum is 51.1 keV, and the electron capture rate reaches 42.80%, which meets the requirements of X-ray intraoperative radiotherapy equipment.

[0042] Example 3: When the ratio of the electric field amplitude of the first cavity to that of the second cavity is 1:0.11, the final output average energy is 44.17 keV, the energy of the highest particle number in the energy spectrum is 50.1 keV, and the electron capture rate reaches 41.78%, which meets the requirements of X-ray intraoperative radiotherapy equipment.

[0043] Comparative Example 1: Using the scheme in Existing Technology 1, the final output average energy is 44keV, the energy of the highest number of particles in the energy spectrum is 50.2keV, and the electron capture rate only reaches 25%.

[0044] In summary, comparing the embodiments and the comparative examples, the capture rate of the present invention is above 41%, which is at least 67% higher than that of the comparative example (25%).

[0045] The electron linear accelerator for X-ray intraoperative radiotherapy equipment of the present invention provides a coupling cavity between the first and second cavities of the beam acceleration module. This coupling cavity replaces the power divider in the prior art, thus eliminating the need for a power divider and requiring only a coupler to feed power into the second cavity. Because the beam acceleration module of the present invention does not require a power divider, its overall size is significantly reduced, facilitating the adjustment of phase and electric field amplitude between the beam acceleration cavities and meeting the requirements of X-ray intraoperative radiotherapy equipment for the beam acceleration module.

[0046] Specifically, the electron linear accelerator for X-ray intraoperative radiotherapy equipment of the present invention has the following effects:

[0047] 1. This invention utilizes a coupling cavity to replace the power divider in the prior art, which can reduce the overall volume of the beam acceleration module by 2 / 3 while fully realizing the functions of X-ray intraoperative radiotherapy equipment.

[0048] 2. By using X-band microwaves to accelerate electrons, the existing 50kV high voltage of intraoperative X-ray radiotherapy equipment can be reduced to below 10kV while ensuring that the technical specifications are met, thereby improving the stability and safety of the equipment.

[0049] 3. By using a bellows, the length of the coupling cavity can be changed, thereby adjusting the phase difference between the two cavities. This results in a good energy spectrum distribution at the exit of the beam acceleration module, and the machining precision does not need to be too high, greatly reducing the complexity of machining.

[0050] 4. By utilizing an energy switch, the final beam acceleration module can output energy that is not uniform, allowing for different energy levels to be set for different tumors.

[0051] 5. Adding a solenoid to the drift tube allows the electron beam inside the drift tube to be focused, resulting in a smaller lateral beam spot at the drift tube exit and a higher capture rate.

[0052] 6. By replacing the power divider in the prior art 1 with a coupling cavity and adding the combined effect of structures such as bellows and energy switches, the capture rate percentage is increased by at least 67% compared to the solution in the prior art 1.

[0053] 7. By placing the applicator after the target conversion, different X-ray dose distributions can be formed for different tumors.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. An electron linear accelerator for use in X-ray intraoperative radiotherapy equipment, characterized in that, It includes an electron gun, a beam acceleration module, and an X-ray conversion module arranged sequentially along the direction of electron propagation, as well as a microwave generation and transmission system connected to the beam acceleration module to provide microwave power to it. The beam acceleration module includes a first cavity, a coupling cavity, a second cavity, and a drift tube connected in sequence. The first cavity is connected to the electron gun to receive the electron beam; the first cavity is used to accelerate the electron beam. The coupling cavity is used to couple the microwave energy of the first cavity and the second cavity; The second cavity is used to optimize the electron beam energy spectrum; the drift tube is used to make the electron beam current distribution more uniform. The X-ray conversion module includes a conversion target and an emitter arranged in sequence. The conversion target is connected to the beam acceleration module to receive an electron beam and emit X-rays.

2. The electron linear accelerator according to claim 1, characterized in that, A bellows is provided on the coupling cavity. The bellows is serrated and expandable, so that the length of the coupling cavity is adjustable.

3. The electron linear accelerator according to claim 2, characterized in that, When the electron beam is accelerated by the beam acceleration module, the phase difference between the first cavity and the second cavity is 90 degrees.

4. The electron linear accelerator according to claim 1, characterized in that, The first cavity and the coupling cavity, and the coupling cavity and the second cavity are connected through a coupling hole.

5. The electron linear accelerator according to claim 1, characterized in that, An energy switch is provided on the coupling hole between the coupling cavity and the second cavity. The energy switch is used to adjust the size of the coupling hole, thereby changing the electric field of the second cavity and obtaining electron beams of different energies.

6. The electron linear accelerator according to claim 1, characterized in that, The microwave generation and transmission system includes a microwave power source, an isolator, and a directional coupler connected in sequence. The directional coupler is connected to a second cavity to inject microwave power into the second cavity.

7. The electron linear accelerator according to claim 6, characterized in that, The coupling degree between the second cavity and the directional coupler is between 1 and 1.

3.

8. The electron linear accelerator according to claim 6, characterized in that, The conversion target is connected to two dose detectors.

9. The electron linear accelerator according to claim 8, characterized in that, It also includes a control system, which is connected to the electron gun, microwave power source, directional coupler, and dose detector.

10. The electron linear accelerator according to claim 1, characterized in that, The drift tube is 5-20cm in length, and a solenoid is fitted over the drift tube.

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