Radiotherapy apparatus and microwave source therefor

Abstract

The present application provides a microwave source for use in a radiotherapy device. The microwave source can include an anode block and one or more cathodes. The cathode in the microwave source can include a cathode support element having at least two grooves. The at least two grooves can axially surround a periphery of the cathode support element. The microwave source can include a cathode heater having at least one filament. A first portion of the at least one filament can be wound in a first direction on the cathode support element and received by a first portion of the at least two grooves, and a second portion of the at least one filament can be wound in a second direction on the cathode support element and received by a second portion of the at least two grooves.

Description

[0001] Case Analysis

[0002] This case is a divisional application of Chinese patent application entitled "Radiotherapy apparatus and microwave source thereof", filed on December 23, 2019, with application number "2019800106416". Technical Field

[0003] This application generally relates to radiotherapy equipment, and more specifically, to microwave sources used in radiotherapy equipment. Background Technology

[0004] Radiation therapy is widely used in cancer treatment and also helps in the assessment of other health conditions. Radiation therapy is typically performed using radiation therapy equipment (such as linear accelerators). In radiation therapy equipment, a microwave source, consisting of an anode and a cathode, is configured to generate microwave pulses (or radio frequency pulses) to control the generation of a radiation beam (such as X-rays). The microwave source is a crucial component of radiation therapy equipment. In some cases, the cathode of the microwave source is easily damaged due to frequent deformation of the cathode heater, and such failures often affect the normal operation of the radiation therapy equipment. Therefore, it is desirable to develop high-quality microwave sources suitable for use in radiation therapy equipment. Summary of the Invention

[0005] In a first aspect of this application, a cathode for a microwave source can be provided. The cathode may include a cathode support element having at least two grooves and a cathode heater including at least one filament. The at least two grooves may axially surround the cathode support element. A first portion of at least one filament may be wound around the cathode support element in a first direction and received by the first portions of the at least two grooves, and a second portion of at least one filament may be wound around the cathode support element in a second direction and received by the second portions of the at least two grooves.

[0006] In some embodiments, at least one first portion and at least one second portion of a filament may be substantially parallel, and when at least one filament is powered by a power source, the directions of the current in the first and second portions of the at least one filament may be opposite.

[0007] In some embodiments, the first portions of at least two grooves and the second portions of at least two grooves may be axially spaced around the periphery of the cathode support element.

[0008] In some embodiments, the depth of at least two grooves may be greater than or equal to the diameter of at least one filament, and the width of the grooves may be greater than or equal to the diameter of the filament.

[0009] In some embodiments, the diameter of the filament can be in the range of 0.4 mm to 0.8 mm.

[0010] In some embodiments, at least one filament may be made of a high-melting-point and conductive material.

[0011] In some embodiments, at least one filament may include at least one of tungsten, molybdenum, rhenium, or iridium.

[0012] In some embodiments, the cathode support element may be made of an insulating material.

[0013] In some embodiments, the cathode support element may include at least one of plastic, rubber, glass, and ceramic.

[0014] In some embodiments, the cathode may include a thermionic emitter that releases electrons when heated by a cathode heater.

[0015] In a second aspect of this application, a microwave source may be provided. The microwave source may include an anode block and a cathode located at the center of the anode block. In some embodiments, the cathode may include a cathode support element having at least two grooves and a cathode heater including at least one filament. The at least two grooves may axially surround the cathode support element. A first portion of at least one filament may be wound around the cathode support element in a first direction and received by the first portions of the at least two grooves, and a second portion of at least one filament may be wound around the cathode support element in a second direction and received by the second portions of the at least two grooves. In some embodiments, the first portion and the second portion of at least one filament may be substantially parallel, and when at least one filament is powered by a power source, the directions of the current in the first and second portions of the at least one filament may be opposite.

[0016] In a third aspect of this application, a radiotherapy apparatus may be provided. The radiotherapy apparatus may include a linear accelerator. The linear accelerator may include an electron generator for emitting electrons along a beam path, a microwave source for generating microwaves, and an accelerating tube for accelerating electrons emitted by the electron generator in response to the microwaves. The microwave source may include an anode block and a cathode located at the center of the anode block. The cathode may include a cathode support element having at least two recesses and a cathode heater including at least one filament. The at least two recesses may axially surround the cathode support element. A first portion of at least one filament may be wound along a first direction on the cathode support element and received by the first portions of the at least two recesses, and a second portion of at least one filament may be wound along a second direction on the cathode support element and received by the second portions of the at least two recesses.

[0017] In some embodiments, at least one first portion and at least one second portion of a filament may be substantially parallel, and when at least one filament is powered by a power source, the directions of the current in the first and second portions of the at least one filament may be opposite.

[0018] In a fourth aspect of this application, a microwave source may be provided. The microwave source may include an anode block and a plurality of cathodes. When one of the cathodes is movably positioned at the center of the anode block, microwaves of a specific frequency can be generated in response to the resonance effect caused by the anode block and the cathodes.

[0019] In some embodiments, at least two of the plurality of cathodes may have different diameters.

[0020] In a fifth aspect of this application, a radiotherapy apparatus may be provided. The radiotherapy apparatus may include a linear accelerator. The linear accelerator may include an electron generator for emitting electrons along a beam path and a microwave source for generating microwaves. The microwave source may include an anode block and a plurality of cathodes. When one of the cathodes is movably positioned at the center of the anode block, microwaves of a specific frequency can be generated in response to the resonance effect caused by the anode block and the cathodes.

[0021] In some embodiments, the radiotherapy device may include an acceleration tube that accelerates electrons emitted by an electron generator in response to microwaves of a specific frequency.

[0022] Some of the additional features of this application will be described in the following description. Some of these additional features will be apparent to those skilled in the art from the study of the following description and the accompanying drawings, or from an understanding of the production or operation of the embodiments. The features of this application can be implemented and achieved through the practice or use of various methods, means, and combinations of the specific embodiments described below. Attached Figure Description

[0023] This application will be further described through exemplary embodiments. These exemplary embodiments will be described in detail with reference to the accompanying drawings. These embodiments are non-limiting exemplary embodiments, in which the same numbers in the figures denote similar structures, wherein:

[0024] Figure 1 These are schematic diagrams of exemplary radiotherapy systems according to some embodiments of this application;

[0025] Figure 2 This is a schematic diagram of exemplary components of a linear accelerator according to some embodiments of this application;

[0026] Figure 3A This is a cross-sectional view of an exemplary microwave source according to some embodiments of this application;

[0027] Figure 3B These are different forms of the anode block in a microwave source as shown in some embodiments of this application;

[0028] Figure 3C This is an exemplary outline of the cathode in a microwave source according to some embodiments of this application;

[0029] Figure 4 This is a cross-sectional view of the cathode according to some embodiments of this application;

[0030] Figure 5A and Figure 5B These are two exemplary forms of filament arrangement shown in some embodiments of this application;

[0031] Figure 6 This is a cross-sectional view of a cathode support element according to some embodiments of this application;

[0032] Figure 7 This is a cross-sectional view of a filament wound around a cathode support element according to some embodiments of this application;

[0033] Figure 8 This is a cross-sectional view of an exemplary microwave source according to some embodiments of this application;

[0034] Figure 9 Cross-sectional views of an exemplary microwave source shown according to some embodiments of this application; and

[0035] Figure 10A and Figure 10B This is a schematic diagram showing different cathodes located in the same anode block according to some embodiments of this application. Detailed Implementation

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. However, those skilled in the art should understand that this application can be implemented without these details. In other instances, to avoid unnecessarily obscuring some aspects of this application, well-known methods, procedures, systems, components, and / or circuits have been described in a highly generalized manner. It will be apparent to those skilled in the art that various changes can be made to the disclosed embodiments, and the general principles defined in this application can be applied to other embodiments and application scenarios without departing from the principles and scope of this application. Therefore, this application is not limited to the embodiments shown, but conforms to the broadest scope consistent with the scope of the claims.

[0037] The terminology used in this application is for describing specific exemplary embodiments only and does not limit the scope of this application. The singular forms “a,” “an,” and “the” used in this application may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that, as in this specification, the terms “comprising” and “including” indicate only the presence of the stated features, integrals, steps, operations, components, and / or parts, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, components, parts, and / or combinations thereof.

[0038] It should be understood that the terms “system,” “engine,” “unit,” “module,” and / or “block” used herein are methods for distinguishing different components, elements, parts, sections, or components at different levels in ascending order. However, other expressions that achieve the same purpose may be used instead of these terms.

[0039] Generally, the terms “module,” “unit,” or “block” as used herein refer to a collection of logical or software instructions embodied in hardware or firmware. The modules, units, or blocks described herein may be implemented as software and / or hardware and may be stored in any type of non-transitory computer-readable medium or other storage device. In some embodiments, software modules / units / blocks may be compiled and linked into an executable program. It will be appreciated that software modules may be invoked from other modules / units / blocks or from themselves, and / or may be invoked in response to detected events or interrupts. Software modules / units / blocks configured to execute on a computing device may be provided on computer-readable media (e.g., optical discs, digital video discs, flash drives, disks) or any other tangible media, or as a digital download (which may initially be stored in a compressed or installable format and require installation, decompression, or decryption prior to execution). The software code herein may be stored, in part or in whole, in the storage device of the computing device performing the operation and applied in the operation of the computing device. Software instructions may be embedded in firmware, such as erasable programmable read-only memory (EPROM). It will also be recognized that hardware modules / units / blocks can be included in connected logical components, such as gates and flip-flops, and / or can be included in programmable units, such as programmable gate arrays or processors. The modules / units / blocks or computing device functions described herein can be implemented as software modules / units / blocks, but can be represented in hardware or firmware. Generally, the modules / units / blocks described herein refer to logical modules / units / blocks that can be combined with other modules / units / blocks or divided into submodules / subunits / subblocks, regardless of their physical composition or storage. This description can apply to a system, an engine, or a portion thereof.

[0040] It should be understood that when a unit, engine, module, or block is referred to as being "on," "connected to," or "coupled to" another unit, engine, module, or block, it may be directly on, connected to, coupled to, or communicate with the other unit, engine, module, or block, or there may be intermediate units, engines, modules, or blocks, unless the context clearly indicates otherwise. In this application, the term "and / or" may include any one or more of the relevant listed items or a combination thereof.

[0041] These and other features, characteristics, functions and operating methods of related structural elements, as well as component assembly and manufacturing economics, will become more apparent from the following description of the accompanying drawings, which form part of this application specification. However, it should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of this application. It should also be understood that the drawings are not drawn to scale.

[0042] Unless otherwise stated, the following description pertains to a medical device including a microwave source (e.g., a magnetron) provided with exemplary embodiments. However, it should be understood that this is for illustrative purposes only and is not intended to limit the scope of this application. The microwave source disclosed herein can also be applied to other applications (e.g., microwave ovens, particle accelerators, etc.). By way of example only, the medical device may include a radiotherapy device, such as an image-guided radiotherapy (IGRT) device. An IGRT device may include an imaging component (e.g., an MRI device, a PET device, or a CT device) and a radiotherapy component (e.g., a linear accelerator).

[0043] The various embodiments provided herein relate to microwave sources comprising an anode block and one or more cathodes. In some embodiments, a microwave source (e.g., a single-cathode microwave source) may include an anode block and a cathode located at the center of the anode block. In some embodiments, a microwave source (e.g., a multi-cathode microwave source) may include an anode block and multiple cathodes. The multiple cathodes may share the same anode block. In some embodiments, one of the multiple cathodes may be movably positioned at the center of the anode block. The diameters of the multiple cathodes may be different. Microwaves with a specific frequency can be generated in response to the resonance effect caused by the anode block and the cathodes. For example, when a first cathode is positioned in the anode block, a first microwave with a first frequency can be generated due to the resonance effect caused by the anode block and the first cathode. As another example, when a second cathode is positioned in the anode block, a second microwave with a second frequency can be generated due to the resonance effect caused by the anode block and the second cathode. The first frequency and the second frequency may be different. Different microwave powers can be output. Compared to a single-cathode microwave source, a multi-cathode microwave source can output variable microwave power and / or frequency by combining the anode block and the cathodes among the multiple cathodes.

[0044] In some embodiments, the microwave source may include a specific cathode design to extend the cathode's lifespan. For example, the cathode heater may include at least one filament configured in a double-helix structure (e.g., a double-helix filament). The at least one filament may be received by at least two grooves on a cathode support element. A first portion and a second portion of the at least one filament may be substantially parallel. When the at least one filament is powered, the current in the first and second portions of the at least one filament flows in opposite directions, which can reduce filament deformation caused by the attraction between adjacent helical segments of a conventional single-helix filament. Furthermore, the use of grooves facilitates filament fixation, thereby reducing filament deformation. The lifespan of the filament can be extended.

[0045] Figure 1 This is a schematic diagram of an exemplary radiotherapy system according to some embodiments of this application. For example... Figure 1 As shown, the radiotherapy system 100 may include a radiotherapy device 110, a network 120, one or more terminals 130, a processing device 140, and a storage device 150.

[0046] Radiotherapy device 110 can deliver a radiation beam to a target object (e.g., a patient or phantom). In some embodiments, radiotherapy device 110 may include a linear accelerator (also referred to as a “linac”) 111. The linear accelerator 111 can generate and emit a radiation beam (e.g., an X-ray beam) from a treatment head 112. The radiation beam may pass through one or more collimators of a specific shape (e.g., a primary collimator and / or a multi-leaf collimator (MLC)) before entering the target object. In some embodiments, the radiation beam may include electrons, photons, or other types of radiation. In some embodiments, the energy of the radiation beam may be in the megavolt range (e.g., >1 MeV), and therefore may be referred to as a megavolt beam. Treatment head 111 may be coupled to gantry 113. Gantry 113 may rotate clockwise or counterclockwise about, for example, a gantry rotation axis 114. Treatment head 112 may rotate with gantry 113. In some embodiments, radiotherapy device 110 may include an imaging element 115. Imaging element 115 can receive a radiation beam passing through a target object and generate images of the patient and / or phantom based on the received radiation beam before, during, and / or after a radiation therapy or correction procedure. Imaging element 115 may include analog detectors, digital detectors, etc., or combinations thereof. Imaging element 115 can be connected to gantry 113 in any connection manner, including an expandable housing. Therefore, rotation of gantry 113 can coordinate the rotation of treatment head 112 and imaging element 115. In some embodiments, the radiotherapy apparatus 110 may also include a treatment bed 116. Treatment bed 116 can support the patient during radiation therapy or imaging, and / or support the phantom during a correction procedure of the radiotherapy apparatus 110. Treatment bed 116 can be adjusted to suit different application scenarios.

[0047] Network 120 may include any suitable network that facilitates the exchange of information and / or data between the radiotherapy system 100 and the radiotherapy system 100. In some embodiments, one or more components of the radiotherapy system 100 (e.g., radiotherapy device 110, terminal 130, processing device 140, storage device 150, etc.) may exchange information and / or data with one or more other components of the radiotherapy system 100 via network 120. For example, processing device 140 may obtain planning data from terminal 130 via network 120. Network 120 may be and / or include public networks (e.g., the Internet), private networks (e.g., local area networks (LANs), wide area networks (WANs)), wired networks (e.g., Ethernet networks, wireless networks (e.g., 802.11 networks, Wi-Fi networks), cellular networks (e.g., LTE networks), Frame Relay networks, virtual private networks (“VPNs”), satellite networks, telephone networks, routers, hubs, switches, server computers, and / or any combination thereof. By way of example only, network 120 may include cable networks, wired networks, fiber optic networks, telecommunications networks, intranets, wireless local area networks (WLANs), metropolitan area networks (MANs), public switched telephone networks (PSTNs), Bluetooth, etc. TM Network, ZigBee TM A network, a near-field communication (NFC) network, or any combination thereof. In some embodiments, network 120 may include one or more network access points. For example, network 120 may include wired and / or wireless network access points such as base stations and / or internet exchange points, through which one or more components of the radiotherapy system 100 may connect to network 120 to exchange data and / or information.

[0048] Terminal 130 enables interaction between the user and the radiotherapy system 100. Terminal 130 may include mobile devices 131, tablet computers 132, laptop computers 133, etc., or any combination thereof. In some embodiments, mobile device 131 may include smart home devices, wearable devices, smart mobile devices, virtual reality devices, augmented reality devices, etc., or any combination thereof. In some embodiments, smart home devices may include smart lighting devices, smart appliance control devices, smart monitoring devices, smart TVs, smart cameras, walkie-talkies, etc., or any combination thereof. In some embodiments, wearable devices may include wristbands, shoes and socks, glasses, helmets, watches, clothing, backpacks, smart accessories, etc., or any combination thereof. In some embodiments, mobile terminals may include mobile phones, personal digital assistants (PDAs), gaming devices, navigation devices, point-of-sale (POS) devices, laptops, tablets, desktop computers, etc., or any combination thereof. In some embodiments, virtual reality devices and / or augmented reality devices include virtual reality helmets, virtual reality glasses, virtual reality goggles, augmented reality helmets, augmented reality glasses, augmented reality goggles, etc., or any combination thereof. For example, virtual reality devices and / or augmented reality devices may include Google Glass. TM Oculus Rift TM HoloLens TM Gear VR TM In some embodiments, terminal 130 may be part of processing device 140.

[0049] Processing device 140 can process data and / or information obtained from radiotherapy device 110, one or more terminals 130, and / or storage device 150. In some embodiments, processing device 140 can perform one or more radiotherapy operations. For example, processing device 140 can process planning data (e.g., from a treatment planning system (TPS)) and determine motion parameters that can be used to control the movement of multiple components in radiotherapy device 110. In some embodiments, processing device 140 can be a computer, a user console, a single server, or a group of servers, etc. The server group can be centralized or distributed. In some embodiments, processing device 140 can be local or remote. For example, processing device 140 can access information and / or data stored in radiotherapy device 110, terminals 130, and / or storage device 150 via network 120. As another example, processing device 140 can be directly connected to radiotherapy device 110, terminals 130, and / or storage device 150 to access stored information and / or data. In some embodiments, processing device 140 can be implemented on a cloud platform. As an example only, a cloud platform may include private cloud, public cloud, hybrid cloud, community cloud, distributed cloud, internal cloud, multi-layer cloud, etc., or any combination thereof.

[0050] Storage device 150 may store data, instructions, and / or any other information. In some embodiments, storage device 150 may store data obtained from terminal 130 and / or processing device 140. In some embodiments, storage device 150 may store data and / or instructions that processing device 140 may execute or use to execute the exemplary methods described in this application. In some embodiments, storage device 150 may include mass storage, removable storage, volatile read-write memory, read-only memory (ROM), etc., or any combination thereof. Exemplary mass storage may include disks, optical disks, solid-state drives, etc. Exemplary removable storage may include flash drives, floppy disks, optical disks, memory cards, compact disks, magnetic tapes, etc. Exemplary volatile read-write memory may include random access memory (RAM). Exemplary RAM may include dynamic random access memory (DRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), static random access memory (SRAM), thyristor random access memory (T-RAM), and zero-capacitance random access memory (Z-RAM), etc. Exemplary ROMs may include mask read-only memory (MROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), optical disc read-only memory (CD-ROM), and digital multifunction disk read-only memory, etc. In some embodiments, the storage device 150 may operate on a cloud platform. By way of example only, the cloud platform may include private cloud, public cloud, hybrid cloud, community cloud, distributed cloud, internal cloud, multi-tiered cloud, etc., or any combination thereof.

[0051] In some embodiments, storage device 150 may be connected to network 120 to communicate with one or more other components of radiotherapy system 100 (e.g., processing device 140, terminal 130, etc.). One or more components of radiotherapy system 100 may access data or instructions stored in storage device 150 via network 120. In some embodiments, storage device 150 may be directly connected to or communicate with one or more other components of radiotherapy system 100 (e.g., processing device 140, terminal 130, etc.). In some embodiments, storage device 150 may be part of processing device 140. In some embodiments, processing device 140 may be connected to or communicate with radiotherapy device 110 via network 120 or at the back end of processing device 140.

[0052] Figure 2 This is a schematic diagram of exemplary components of a linear accelerator (linac) according to some embodiments of this application. In some embodiments, Figure 2The linear accelerator 200 shown can be implemented on a radiotherapy device (e.g., radiotherapy device 110). Figure 2 As shown, the linear accelerator 200 may include a power supply 202, a modulator 204, an electron generator 206, a microwave source 208, an accelerating tube 210, and a treatment head 212. In some embodiments, the power supply 202 may be used to provide the high voltage (e.g., 45 kV) required for proper modulator operation. In some embodiments, the power supply 202 may include an AC circuit for providing an alternating current voltage (ACV). In some embodiments, the power supply 202 may include a DC circuit for providing a direct current voltage (DCV). The modulator 204 may be used to simultaneously provide high-voltage pulses (e.g., DC pulses) to the electron generator 206 and the microwave source 208. The electron generator 206 (e.g., an electron gun or electron emitter) may generate electrons that are injected into the accelerating tube 210. For example, the electron generator 206 may generate electrons over an angular range and emit electrons along a beam path. The electron beam may be injected into the accelerating tube 210. Using microwaves of one or more frequency ranges, electrons in the accelerator tube 210 may be accelerated within one or more kinetic energy ranges. Accelerated electrons can be directed to the treatment head 212 to generate a radiation beam. For example, accelerated electrons can strike a target (e.g., an X-ray target) to generate a radiation beam (e.g., an X-ray beam). The radiation beam can pass through one or more collimators of a specific shape (e.g., a primary collimator and / or a multi-leaf collimator (MLC)) to form a collimated radiation beam. The collimated radiation beam can irradiate a target object (e.g., a lesion on a subject) to perform radiotherapy.

[0053] In some embodiments, microwave source 208 can be configured to generate microwaves within one or more frequency ranges. Microwave source 208 can be considered as an oscillator that converts DC pulses from modulator 204 into microwave pulses. In some embodiments, microwave source 208 can be a magnetron or a klystron. In some embodiments, microwave source 208 can include a magnetron consisting of a cathode and an anode block (also referred to as a single-cathode magnetron). In some embodiments, microwave source 208 can include a magnetron consisting of multiple cathodes and an anode block (also referred to as a multi-cathode magnetron). Multiple cathodes can share the same anode block. Through different arrangements of the cathodes and anode blocks, microwave source 208 can output different microwave powers.

[0054] In some embodiments, the microwave source 208 may be a magnetron. In the magnetron, the cathode may be heated by a cathode heater. The cathode heater may include at least one filament. Electrons released from the cathode may be accelerated toward the anode block by the action of a pulsed DC electric field. The anode block may contain at least two resonant cavities. In some embodiments, at least one electromagnet may be placed around the anode block. A static magnetic field may be applied perpendicular to the cross-section of the at least two resonant cavities. Due to the influence of the magnetic field, the released electrons may move toward the resonant cavities in a complex spiral pattern. When the resonant cavities begin to resonate at a certain resonant frequency (e.g., 3000 MHz), a resonance effect (or resonance phenomenon) may occur. The resonant cavities can then emit microwaves. The microwaves may be transmitted to the accelerating tube 210 via a transmission waveguide. Electrons in the accelerating tube 210 may be accelerated by the microwave energy. Further description of the microwave source components can be found elsewhere in this application (e.g., Figure 3A-9 (and its description).

[0055] Figure 3A This is a cross-sectional view of an exemplary microwave source (e.g., a magnetron) shown according to some embodiments of this application. Figure 3A As shown, the microwave source 300 may include an anode block 310 and a cathode 320 located at the center of the anode block 310. The anode block 310 and the cathode 320 may be coaxial. In some embodiments, the anode block 310 may be made into a cylindrical metal block (e.g., a copper block). The anode block 310 may include at least two resonant cavities 312. The number of resonant cavities may vary for different microwave sources. In some embodiments, the number of resonant cavities may be between 8 and 20. For illustrative purposes only, the anode block 310 includes eight resonant cavities 312, i.e., eight cylindrical holes around the cathode 320. An interaction space may be formed between the anode block 310 and the cathode 320, such as an open space between the anode block 310 and the cathode 320. In the interaction space, electric and magnetic fields interact to exert a force on electrons. The magnetic field is typically provided by a permanent magnet mounted around the microwave source 300 so that the magnetic field is parallel to the axis of the cathode. Electrons released from the cathode 320 can propagate outward in the interaction space. The released electrons can be accelerated toward the anode block 310 by the action of a pulsed DC electric field. Due to the effect of the magnetic field, electrons can move toward the resonant cavity 312 in a complex spiral pattern. In some embodiments, the resonant cavity 312 can exist in various shapes, such as, but not limited to, a semi-circular cavity, a circular cavity, a square cavity, a rectangular cavity, a fan-shaped cavity, or any combination thereof.

[0056] Figure 3B These are different forms of the anode block in a microwave source according to some embodiments of this application. For example... Figure 3BAs shown, anode block 310a may include at least two hole and groove type resonant cavities 312a, anode block 310b may include at least two groove type resonant cavities 312b, and anode block 310c may include at least two blade type resonant cavities 312c. The resonant cavities are typically radially distributed.

[0057] Figure 3C This is an exemplary outline of the cathode of a microwave source according to some embodiments of this application. Figure 3C As shown, the cathode 320 may include a hollow dumbbell-shaped structure. In some embodiments, the cathode 320 may consist of a hollow cylinder made of an emitting material (e.g., barium oxide) surrounding a cathode heater. For example, the cathode 320 may include a cathode heater and a thermionic emitter. The cathode heater may include at least one filament. The thermionic emitter may consist of a hollow cylinder made of an emitting material. In some embodiments, the cathode heater may be helically fixed to a cathode support element (e.g., a cathode rod). The cathode support element may be positioned within the hollow space of the thermionic emitter. When the cathode heater is heated by a power source, the external thermionic emitter releases electrons due to thermionic electrons generated by thermal radiation. These released electrons can move outward toward the anode block. As the electrons pass through the resonant cavity of the anode block, energy can be transferred to the resonant cavity, which may then resonate at a certain resonant frequency and radiate energy in the form of microwaves.

[0058] Figure 4 This is a cross-sectional view of the cathode in a microwave source according to some embodiments of this application. For example... Figure 4 As shown, the cathode 320 may include a cathode support element 402, a cathode heater 404, and a thermionic emitter 406.

[0059] In some embodiments, the cathode support element 402 can have various shapes, such as cylinders, cubes, cones, etc. The cross-sectional shape of the cathode support element 402 can be a regular shape (e.g., semicircular, circular, square, triangular, trapezoidal, etc.) or an irregular shape (e.g., irregular polygon). In some embodiments, the cathode support element 402 can be made of an insulating material. Exemplary insulating materials may include plastics, rubber, glass, ceramics, etc., or any combination thereof. In some embodiments, the insulating cathode support element 402 can be integrally formed to achieve high mechanical strength. A high-strength support element may help extend the service life of the cathode and ensure its reliability.

[0060] In some embodiments, the cathode support element 402 may include at least two recesses for receiving a cathode heater 404. In some embodiments, the cathode heater 404 may consist of at least one filament. When wound around the cathode support element 404, the at least one filament can be positioned within the at least two recesses. In this way, each helical segment (or each turn) of the at least one filament can be secured due to the use of the recesses. In some embodiments, the at least two recesses (e.g., Figure 6 The grooves 602a and 602b shown may be axially spaced along the circumference of the cathode support element 402. In some embodiments, each groove may accommodate a helical segment when the at least one filament 402 is wound on the cathode support element 404. For example, the depth of the groove may be greater than or equal to the diameter of the filament, and the width of the groove may be greater than or equal to the diameter of the filament. In some embodiments, the width of the groove may refer to the maximum width of the groove (e.g., the width of the opening of the groove).

[0061] In some embodiments, the filament may be made of a material having a high melting point (e.g., >1000°C) and being conductive. Exemplary filament materials may include tungsten, molybdenum, rhenium, iridium, and any combination thereof. In some embodiments, the filament diameter may range from 0.2 mm to 2.0 mm. In some embodiments, the filament diameter may range from 0.4 mm to 1.5 mm. In some embodiments, the filament diameter may range from 0.4 mm to 0.8 mm. In some embodiments, the filament diameter may be 0.5 mm. It should be noted that any suitable filament diameter can be designed, and there are no limitations in this application.

[0062] Figure 5A and 5B These are two exemplary forms of filament arrangement shown in some embodiments of this application. For example... Figure 5A As shown, the filament 510 can be arranged as a single-helix filament. The two leads of the filament 510 can be located at either end of the filament 510. The helical segment of the filament 510 extends in one direction, for example, from the first lead 512 to the second lead 514. In some embodiments, when the filament 510 is energized, the filament current in the filament 510 may be a unidirectional current (at any given moment), for example, the current from the first lead 512 to the second lead 514. The filament currents in adjacent helical segments (e.g., adjacent turns) are in the same direction, thus creating an attractive force. Due to this attractive force, adjacent helical segments may contract. After the filament 510 is de-energized, the contracted helical segments will recover once the attractive force disappears. Because the filament 510 contracts and recovers frequently, this deformation of the filament 510 may shorten the lifespan of the filament 510 and the cathode.

[0063] To address the aforementioned or similar problems that lead to reduced service life, the cathode heater may include at least one filament configured in a double-helix structure. For example... Figure 5B As shown, the filament 520 can be a double-helix filament. In the double-helix filament structure, the two leads of the filament 520, such as the first lead 522 and the second lead 524, can be arranged on the same side. In this case, the feed line electrically connected to the two leads can be led out from the same side. This facilitates the installation of the filament inside the microwave source to prevent excess feed lines from causing short circuits. The first portion of the filament 520 (e.g., the first continuous helical segment 523 connected to the first lead 522) can extend helically in a first direction parallel to the filament axis (e.g., axis 527 shown in partial enlarged view 521), configured in a first helical structure. The second portion of the filament 520 (e.g., the second continuous helical segment 525 connected to the second lead 524) can extend helically in a second direction parallel to the filament axis, configured in a second helical structure. The first and second directions can be opposite and point to both ends of the filament axis. In some embodiments, a first portion (e.g., a first continuous helical segment 523) and a second portion (e.g., a second continuous helical segment 524) of filament 520 can be operatively connected in a loop configuration as shown in FIG. 526. The helical segments of the first and second portions of filament 520 can be substantially interlaced and parallel. In some embodiments, as shown in FIG. 521, when filament 520 is energized, the corresponding currents of the first and second portions of filament 520 are in opposite directions. The interaction forces between the helical segments can be canceled out by the reverse currents. Compared to a single-helix filament 510, the attraction between adjacent helical segments can be avoided, thereby reducing filament deformation. In some embodiments, a double-helix filament can consist of a single filament (or a single coil). In some embodiments, a double-helix filament 520 can consist of two filaments (or two coils). For example, the first portion of filament 520 may include a first filament, and the second portion of filament 520 may include a second filament. A first end of the first filament may be designated as a first lead 522. A first end of the second filament may be designated as a second lead 524. The second end of the first filament can be electrically connected to the second end of the second filament according to the circuit configuration shown in 526.

[0064] In some embodiments, to reduce the deformation of the filament (e.g., filament 510 or 520), the filament may be spirally wound around a cathode support element having at least two grooves. Figure 6 The cathode support element shown in some embodiments of this application (e.g., Figure 4 The cross-sectional view of the cathode support element 404 shown is illustrated in the figure. Figure 6As shown, at least two grooves (e.g., a first groove 602a and a second groove 602b) can be provided on the cathode support element. The at least two grooves are axially spaced around the periphery of the cathode support element. In some embodiments, a first portion of the at least two grooves (e.g., the first groove 602a) can be formed by a first continuous spiral groove radially around the periphery of the cathode support element. A second portion of the at least two grooves (e.g., the second groove 602b) can be formed by a second continuous spiral groove radially around the periphery of the cathode support element. The first groove 602a and the second groove 602b are axially staggered. In some embodiments, a double-helix filament (e.g., ...) can be provided in the at least two grooves. Figure 5B The filament 520 is fixed in place and its deformation is reduced. For example, a first groove 602a can accommodate a first portion of the filament 520, and a second groove 602b can accommodate a second portion of the filament 520. In some embodiments, the grooves must be large enough to accommodate a coiled section of the first or second portion of the filament 520. For example, the depth of the groove (e.g., groove 602a or 602b) can be greater than or equal to the diameter of the filament (e.g., 0.4 mm to 0.8 mm), and the width of the groove can be greater than or equal to the diameter of the filament.

[0065] Figure 7 A cross-sectional view of a filament wound around a cathode support element is shown. For example, a double-helix filament 520 is wound around a cathode support element 402. The double-helix filament 520 and the cathode support element 402 may be coaxial. Reference numeral 702 may indicate a circular cross-section of a first portion of the helical segment of the filament 520, and reference numeral 704 may indicate a circular cross-section of a second portion of the helical segment of the filament 520.

[0066] Figure 8 This is a cross-sectional view of an exemplary microwave source according to some embodiments of this application. For illustrative purposes only. Figure 8 The microwave source 800 shown may be a magnetron. The magnetron may be a tunable magnetron. The microwave source 800 may include an anode block 802, a cathode 804 located at the center of the anode block 802, a tuning element 806, a microwave output device 808, and a transmission waveguide 810. (As in combination...) Figure 3A and 3B As described, the anode block 802 may include at least two resonant cavities 802a. The resonant cavities 802a can be configured to... Figure 3B The holes and grooves shown are present. The cathode 804 can be movably positioned at the center of the anode block. (As shown in the diagram...) Figures 4 to 7As described, cathode 804 may include a cathode heater, a thermionic emitter surrounding the cathode heater, and a cathode support element. The cathode heater may include a double-helix filament. The double-helix filament may be helically wound around the cathode support element and received by at least two recesses on the cathode support element. Further descriptions of the anode block and cathode can be found elsewhere in this application (e.g., Figure 3A-7 (and its description), which will not be repeated here.

[0067] Tuning element 806 can be configured to adjust the resonant frequency of microwave source 800. The resonant frequency can be changed by altering the inductance or capacitance of the microwave source resonant cavity. In some embodiments, tuning element 806 can be inserted into the aperture of a hole or recessed cavity. Tuning element 806 can change the capacitance of the resonant cavity by altering the ratio of the surface area in the high-current region to the cavity volume. The resonant frequency of microwave source 800 can be increased or decreased by inserting or removing tuning element 806. For example, when tuning element 806 is inserted into an anode aperture, the capacitance of the cavity can be increased, thereby decreasing the resonant frequency. In some embodiments, microwave source 800 may include a plurality of tuning elements 806 operatively connected to each resonant cavity 802a. Only one tuning element 806 is shown for illustrative purposes only. In some embodiments, tuning element 806 may be made of a conductive material (e.g., copper, aluminum, or other metallic materials).

[0068] The microwave output unit 808 can be used to transmit microwaves generated by the microwave source 800. The microwaves can be transmitted into the transmission waveguide 810 (e.g., Figure 2 (The transmission waveguide shown). The transmission waveguide 810 can then transmit microwaves to an accelerating tube (e.g., accelerating tube 210) to provide kinetic energy to accelerate electrons in the accelerating tube.

[0069] Figure 9 This is a cross-sectional view of an exemplary microwave source according to some embodiments of this application. For example... Figure 9 As shown, the microwave source 900 can be a multi-cathode microwave source (e.g., a multi-cathode magnetron). The microwave source 900 may include an anode block 902 and multiple cathodes, such as a first cathode 904 and a second cathode 906. In some embodiments, the multiple cathodes may be movably positioned at the center of the anode block 902. For example, as... Figure 10A As shown, the first cathode 1004 is positioned at the center of the anode block 1002. Figure 10BAs shown, the second cathode 1006 is positioned at the center of the anode block 1002. In some embodiments, when one of the plurality of cathodes (e.g., the first cathode 904 or the second cathode 906) is movably positioned at the center of the anode block, microwaves of a specific frequency (e.g., a specific microwave power) can be generated in response to the resonance effect caused by the anode block and the cathode. Further description of the anode block and cathode can be found elsewhere in this application (e.g., Figure 3A-7 (and its description) have been found, and will not be repeated here.

[0070] In some embodiments, the diameters of the plurality of cathodes may be different. In some embodiments, at least two of the plurality of cathodes may have different diameters. For example, the first cathode may have a diameter of 18 mm and the second cathode may have a diameter of 22 mm. In some embodiments, the microwave source 900 may include a connector 908. The plurality of cathodes may be mechanically connected to each other via the connector 908. The connector 908 (e.g., a support rod) may be used to support and connect each cathode. In some embodiments, a cathode support element (e.g., a cathode support element 402) may be part of the connector 908. The connector 908 may be made of an insulating material. In some embodiments, the microwave source 900 may include a limiting member 910. One end of the connector 908 may be operatively connected to the limiting member 910. In some embodiments, the microwave source 900 may include a guide groove 912. The limiting member 910 may be disposed in the guide groove 912. In some embodiments, the limiting member 910 may be movable (e.g., slid) along the guide groove 912 to position a cathode among the plurality of cathodes. For example, when the limiting member 910 is moved to a first position, the first cathode 904 may be positioned at the center of the anode block 902. When the limiting member 910 moves to the second position, the second cathode 906 can be positioned at the center of the anode block 902, and the first cathode 904 can be removed. In some embodiments, the limiting member 910 can be driven by various driving devices. Exemplary driving devices may include hydraulic actuators, pneumatic actuators, and electric actuators. In some embodiments, the various driving devices may not interfere with the generation of microwaves.

[0071] The electronic efficiency of a microwave source (e.g., a magnetron) may depend on the ratio of the diameters of the cathode and anode blocks (also known as the "diameter ratio"). When the diameter ratio is within a specific range, the electronic efficiency is optimal, and the output power of the microwave source is maximized. For example, for an eight-cavity anode block, the magnetron's electronic efficiency may be optimal when the diameter ratio is in the range of 0.37–0.42. As another example, for a twelve-cavity anode block, the magnetron's electronic efficiency may be optimal when the diameter ratio is in the range of 0.50–0.58. And as yet another example, for a sixteen-cavity anode block, the magnetron's electronic efficiency may be optimal when the diameter ratio is in the range of 0.60–0.66.

[0072] In some embodiments, the output power of a microwave source can be varied by changing the diameter ratio of the anode block to the cathode. In some embodiments, for a particular anode block, the diameter ratio can be varied by alternating cathodes with different diameters. For illustration only, a magnetron with a twelve-cavity anode block has a resonant frequency of 2998 MHz and a maximum output power of 3.4 MW. Assume the diameter of the anode block is 34 mm. The maximum output power of the magnetron can only be achieved when the diameter of the cathode is in the range of 17-19.72 mm. It is understood that when the diameter of the cathode is less than 17 mm or greater than 19.72 mm, the magnetron can output relatively low microwave power. By setting a fixed anode block and cathodes with different diameters, the magnetron can output variable microwave power. Variable microwave power can be used to generate radiation beams of different energies. For example, the diameter of the anode block 902 can be set to 34 mm, and the diameter of the first cathode 904 can be set to 18 mm. When the anode block 902 and the first cathode 904 are energized, the microwave source 900 can output maximum microwave power to accelerate electrons in the accelerating tube 210 to generate a therapeutic radiation beam. This therapeutic radiation beam can be used to eliminate tumor tissue from the target object. Alternatively, the diameter of the second cathode 906 can be set to 22 mm. When the anode block 902 and the second cathode 906 are energized, the microwave source 900 can output relatively lower microwave power to accelerate electrons in the accelerating tube 210 to generate an imaging radiation beam. For IGRT equipment, the imaging radiation beam can be used to image a region of interest (ROI) related to the target object. The radiotherapy procedure can be guided based on information related to the ROI (e.g., tumor region).

[0073] In some embodiments, the resonant frequency of a microwave source can be changed by alternating different cathodes. The resonant frequency of a microwave source can depend on the equivalent capacitance and inductance of the microwave source. For example, the resonant frequency... Where L represents inductance and C represents equivalent capacitance. For a fixed anode block, the larger the diameter of the cathode, the smaller the distance between the cathode and the anode block, and therefore the larger the equivalent capacitance becomes. The resonant frequency can be changed with the equivalent capacitance. In some embodiments, different resonant frequencies can be generated accordingly by switching cathodes of different diameters. Additionally, the tuning element of the microwave source (e.g., tuning element 806) can fine-tune the resonant frequency, for example, by ±5 MHz. By using the plurality of cathodes and tuning elements, the adjustable range of the microwave source's resonant frequency can be expanded. It is understood that the output frequency of the microwave can vary with the characteristics of the microwave source (e.g., resonant frequency). Specific microwave frequencies can be generated when different cathodes are applied.

[0074] The basic concepts have been described above. Obviously, for those skilled in the art who have read this application, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore, such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this application.

[0075] Furthermore, this application uses specific terms to describe its embodiments. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0076] Furthermore, those skilled in the art will understand that aspects of this application can be described and illustrated through several patentable types or situations, including any new and useful combination of processes, machines, products, or substances, or any new and useful improvements thereof. Accordingly, aspects of this application can be implemented entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. All of the above hardware or software can be referred to as a "unit," "module," or "system." Furthermore, aspects of this application can be embodied as computer products located on one or more computer-readable media, said products including computer-readable program code.

[0077] Computer-readable signal media may contain a propagated data signal containing computer program code, for example, on baseband or as part of a carrier wave. Such propagated signals can take many forms, including electromagnetic, optical, and any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can be connected to an instruction execution system, apparatus, or device to enable communication, propagation, or transmission of a program for use. The program code located on the computer-readable signal medium can be propagated through any suitable medium, including radio, cable, fiber optic cable, RF, and any combination of the above.

[0078] The computer program code required for the operation of each part of this application can be written in any one or more programming languages, including object-oriented programming languages ​​such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, Python, etc.; conventional procedural programming languages ​​such as C, Visual Basic, Fortran, Perl, COBOL, PHP, ABAP; dynamic programming languages ​​such as Python, Ruby, and Groovy; or other programming languages. This program code can run entirely on the user's computer, or as a standalone software package on the user's computer, or partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer through any network, such as a local area network (LAN) or wide area network (WAN), or connected to an external computer (e.g., via the Internet), or in a cloud computing environment, or used as a service such as Software as a Service (SaaS).

[0079] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this application are not intended to limit the order of the processes and methods of this application. Although some currently considered useful embodiments of the invention have been discussed in the foregoing disclosure through various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments of this application. For example, although the implementation of the various components described above can be embodied in a hardware device, it can also be implemented as a purely software solution, such as installed on an existing server or mobile device.

[0080] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, the method of the present application should not be construed as reflecting an intention that the claimed object to be scanned requires more features than expressly recited in each claim. Rather, the subject of the invention should possess fewer features than in any single embodiment described above.

[0081] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of scope in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0082] All patents, patent applications, patent application publications, and other materials (such as papers, books, specifications, publications, records, things, and / or similar items) mentioned herein are incorporated herein by reference in their entirety for all purposes, except for any prosecution documents relating to the foregoing, any foregoing documents that are inconsistent with or conflict with this document, or any foregoing documents that limit the broad scope of the claims sooner or later to this document. For example, if there is any inconsistency or conflict between the description, definitions, and / or use of terminology associated with any incorporated material and the terminology associated with this document, the terminology used in the description, definitions, and / or this document shall prevail.

[0083] Finally, it should be understood that the embodiments described in this application are merely illustrative of the principles of the embodiments of this application. Other variations may also fall within the scope of this application. Therefore, alternative configurations of the embodiments of this application are considered as examples and not limitations, and are regarded as consistent with the teachings of this application. Accordingly, the embodiments of this application are not limited to the embodiments explicitly described and illustrated in this application.

Claims

1. A cathode, comprising: a cathode support element having at least two grooves, the at least two grooves axially surrounding a circumference of the cathode support element; and a cathode heater comprising at least one filament, wherein a first portion of the at least one filament is wound in a first direction on the cathode support element and is accommodated by a first portion of the at least two grooves, and a second portion of the at least one filament is wound in a second direction on the cathode support element and is accommodated by a second portion of the at least two grooves; the first portion extends helically in the first direction to form a first helical structure, the second portion extends helically in the second direction to form a second helical structure, the first direction and the second direction being parallel to an axis of the filament; the first portion and the second portion form a double helical structure; and a first lead of the first portion and a second lead of the second portion are arranged on a same side relative to an axis of the double helical structure. the first portion of the at least one filament and the second portion of the at least one filament are substantially parallel, and directions of respective currents of the first portion and the second portion of the at least one filament are opposite when the at least one filament is powered by a power supply.

2. The cathode of claim 1, wherein the first portion of the at least one filament and the second portion of the at least one filament are electrically connected.

3. The cathode of claim 1, wherein a magnitude of the current in the first portion of the at least one filament and the second portion of the at least one filament is equal.

4. The cathode of claim 1, wherein the at least two grooves are helically distributed along the circumference of the cathode support element; the first portion of the at least two grooves and the second portion of the at least two grooves are axially spaced along the circumference of the cathode support element.

5. The cathode of claim 1, wherein an anode block and the cathode of any one of claims 1-5.

6. A microwave source comprising:

7. A radiotherapy device comprising a linear accelerator, the linear accelerator comprising: an electron generator to emit electrons along a beam path; a microwave source to generate microwaves, wherein the microwave source comprises an anode block and a cathode located at a center of the anode block, the cathode comprising: a cathode support element having at least two grooves, the at least two grooves axially surrounding a circumference of the cathode support element; and a cathode heater comprising at least one filament, wherein a first portion of the at least one filament is wound in a first direction on the cathode support element and is accommodated by a first portion of the at least two grooves, and a second portion of the at least one filament is wound in a second direction on the cathode support element and is accommodated by a second portion of the at least two grooves; the first portion extends helically in the first direction to form a first helical structure, the second portion extends helically in the second direction to form a second helical structure, the first direction and the second direction being parallel to an axis of the filament; the first portion and the second portion form a double helical structure; and a first lead of the first portion and a second lead of the second portion are arranged on a same side relative to an axis of the double helical structure; and an acceleration tube to accelerate the electrons emitted by the electron generator in response to the microwaves.

8. A microwave source, comprising: ​ An anode block; A plurality of cathodes; Each of the plurality of cathodes comprises: a cathode support element having at least two grooves that axially surround a circumference of the cathode support element; and a cathode heater comprising at least one filament, wherein a first portion of the at least one filament is wound on the cathode support element in a first direction and is accommodated by a first portion of the at least two grooves, and a second portion of the at least one filament is wound on the cathode support element in a second direction and is accommodated by a second portion of the at least two grooves; the first portion extends helically in the first direction to form a first helical structure, the second portion extends helically in the second direction to form a second helical structure, the first direction and the second direction are parallel to an axis of the filament; the first portion and the second portion form a double helical structure; and a first lead of the first portion and a second lead of the second portion are arranged on a same side relative to an axis of the double helical structure; a limiting member connecting the plurality of cathodes; and a guide slot in which the limiting member is disposed; wherein the limiting member is movable along the guide slot to position one of the plurality of cathodes at a center of the anode block, and when the one of the plurality of cathodes is movably positioned at the center of the anode block, a microwave having a specific frequency is generated in response to a resonance effect caused by the anode block and the cathode.

9. The microwave source of claim 8, wherein, Diameters of at least two of the plurality of cathodes are different.

10. The microwave source of claim 8 or 9, wherein, Each of the plurality of cathodes comprises: a cathode support element having at least two grooves that axially surround a circumference of the cathode support element; and a cathode heater comprising at least one filament, wherein a first portion of the at least one filament is wound on the cathode support element in a first direction and is accommodated by a first portion of the at least two grooves, and a second portion of the at least one filament is wound on the cathode support element in a second direction and is accommodated by a second portion of the at least two grooves.

11. The microwave source of claim 10, wherein, The first portion of the at least one filament and the second portion of the at least one filament are substantially parallel, and when the at least one filament is powered by a power source, directions of respective currents of the first portion and the second portion of the at least one filament are opposite.

12. The microwave source of claim 10, wherein, The first portion of the at least two grooves and the second portion of the at least two grooves are axially spaced along the circumference of the cathode support element.

13. The microwave source of claim 10, wherein, A depth of a groove of the at least two grooves is greater than or equal to a diameter of one of the at least one filament, and a width of the groove is greater than or equal to the diameter of the filament.

14. The microwave source of claim 13, wherein, The diameter of the filament ranges from 0.4 millimeters to 0.8 millimeters.

15. The microwave source of claim 10, wherein, The at least one filament is made of a material having a high melting point and being conductive.

16. The microwave source of claim 15, wherein, The at least one filament comprises at least one of a tungsten, molybdenum, rhenium, or iridium filament.

17. The microwave source of claim 10, wherein, The cathode support element is made of an insulating material.

18. The microwave source of claim 17, wherein, The cathode support element comprises at least one of a plastic, a rubber, a glass, a ceramic element.

19. The microwave source of claim 10, wherein, The cathode further comprises: a thermionic electron emitter configured to release electrons when the thermionic electron emitter is heated by the cathode heater.

20. The microwave source of claim 8, further comprising: a connector for connecting each of the plurality of cathodes.

21. The microwave source of claim 20, further comprising: a limiting member connected to an end of the connector and configured to move the plurality of cathodes.

22. The microwave source of claim 21, wherein, The limiting member moves along a guide slot, such that a cathode of the plurality of cathodes is positioned at the center of the anode block.

23. A radiotherapy device comprising a linear accelerator, the linear accelerator comprising: an electron generator for emitting electrons along a beam path; and a microwave source for generating microwaves, wherein the microwave source comprises an anode block, a plurality of cathodes, a limiting member, and a guide slot, each of the plurality of cathodes comprising: a cathode support element having at least two grooves that surround the cathode support element in an axial direction; and a cathode heater comprising at least one filament, wherein a first portion of the at least one filament is wound on the cathode support element in a first direction and is received by a first portion of the at least two grooves, and a second portion of the at least one filament is wound on the cathode support element in a second direction and is received by a second portion of the at least two grooves; the first portion extends helically in the first direction to form a first helical structure, the second portion extends helically in the second direction to form a second helical structure, the first direction and the second direction are parallel to an axis of the filament; the first portion and the second portion form a double helical structure; and a first lead of the first portion and a second lead of the second portion are arranged on the same side relative to an axis of the double helical structure; the limiting member connects the plurality of cathodes; the limiting member is disposed within the guide slot; wherein the limiting member is movable along the guide slot to position a cathode of the plurality of cathodes at the center of the anode block, and when the cathode of the plurality of cathodes is movably positioned at the center of the anode block, microwaves having a specific frequency are generated in response to a resonance effect caused by the anode block and the cathode.

24. The radiotherapy device of claim 23, wherein, the linear accelerator further comprises: an acceleration tube for accelerating electrons emitted by the electron generator in response to the microwaves having the specific frequency.

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