Radiation therapy system

Abstract

The system comprises a magnetic resonance imaging (MRI) device (310) configured for acquiring MRI data about a region of interest (ROI), and a radiotherapy device (300) configured for radiotherapy of at least a portion of the region of interest.

Description

[0001] Divisional Statement

[0002] This application is a divisional application of the Chinese application with the application number 201880060517.6, the application date of November 14, 2018, and the invention name of “Radiotherapy system”. TECHNICAL FIELD

[0003] The present application generally relates to radiotherapy systems, and more particularly, to image-guided radiotherapy systems incorporating radiotherapy and magnetic resonance imaging technologies. BACKGROUND

[0004] Currently, radiotherapy of tumors is affected by difficulties in tracking changes (e.g. motion) of the tumor between different treatment sessions. Today, various imaging technologies are available to provide real-time images of the tumor before or within each treatment session. For example, a magnetic resonance imaging (MRI) device can be used in conjunction with a radiotherapy device to provide MRI images of the tumor. The combination of the MRI device and the radiotherapy device forms a treatment device, which can encounter difficulties in arranging components of the MRI device (e.g. at least two main magnetic coils, at least two magnetic shielding coils) and the radiotherapy device (e.g. a linear accelerator) does not cause interference in a relatively compact space. Therefore, it can be desirable to provide a treatment device which provides high treatment quality and also has a compact structure. SUMMARY

[0005] In a first aspect of the present application, a radiotherapy system is provided. The system can include: a magnetic resonance imaging device configured to acquire magnetic resonance imaging data of a region of interest; and a radiotherapy device configured to radiotherapy at least a portion of the region of interest, the radiotherapy device comprising: a linear accelerator configured to accelerate electrons in an electron beam to generate a photon beam of the radiotherapy; a first shielding structure configured to provide magnetic shielding for the linear accelerator; the first shielding structure forms a semi-closed loop around an axis of the linear accelerator, the semi-closed loop comprising at least two plates arranged along a circumferential direction of the linear accelerator; or the radiotherapy device further comprises: two annular magnetic shielding layers, the first shielding structure is formed by at least two first magnetic shielding partitions connecting the two annular magnetic shielding layers.

[0006] In some embodiments, the linear accelerator is at least partially surrounded by the first shielding structure.

[0007] In some embodiments, the radiotherapy device further comprises: a target; and a beam deflection unit configured to deflect the electrons from the electron beam onto the target to generate the photon beam of the radiotherapy.

[0008] In some embodiments, the magnetic resonance imaging apparatus comprises: at least two main magnet coils; at least two magnetic shielding coils; and a toroidal cryostat, wherein the at least two main magnet coils and the at least two magnetic shielding coils are arranged coaxially along an axis of the toroidal cryostat, and the at least two magnetic shielding coils are arranged at a greater radius from the axis than the at least two main magnet coils.

[0009] In some embodiments, the toroidal cryostat further comprises: at least one outer wall and at least one inner wall coaxial with the axis; and a toroidal recess between the at least one outer wall and the at least one inner wall.

[0010] In some embodiments, the linear accelerator is at least partially located within the toroidal recess of the toroidal cryostat.

[0011] In some embodiments, the toroidal cryostat further comprises: at least one second shielding structure identical to the first shielding structure, the first shielding structure and the at least one second shielding structure being located at circumferential positions within the toroidal recess, respectively; the at least one second shielding structure comprises more than two second shielding structures, and the first shielding structure and the at least one second shielding structure are uniformly distributed within the toroidal recess.

[0012] In some embodiments, the two toroidal magnetic shielding layers are arranged along the axis of the toroidal cryostat and are parallel to each other.

[0013] In some embodiments, the radiation therapy apparatus further comprises an inner magnetic shielding layer and an outer magnetic shielding layer connected with the two toroidal magnetic shielding layers, and the first shielding structure is composed of the two toroidal magnetic shielding layers, the inner magnetic shielding layer, the outer magnetic shielding layer, and two first magnetic shielding partitions connecting the two toroidal magnetic shielding layers.

[0014] In some embodiments, the outer magnetic shielding layer comprises at least two slots, and at least one slot of the at least two slots is located at a position corresponding to one of the two first magnetic shielding partitions.

[0015] In some embodiments, the radiation therapy apparatus further comprises: at least one second shielding structure identical to the first shielding structure, the first shielding structure and the at least one second shielding structure being located at circumferential positions within the toroidal recess, respectively; the at least one second shielding structure comprises more than two second shielding structures, and the first shielding structure and the at least one second shielding structure are uniformly distributed within the toroidal recess.

[0016] Some of the attendant features will be described in the description that follows, and in part will be apparent from the description or can be learned by practice of the application. The features of the application can be realized and attained by means of the instrumentalities, methods, and combinations particularly pointed out in the following description and associated drawings. BRIEF DESCRIPTION OF DRAWINGS

[0017] The present application will be further described by way of example. These examples will be described in detail with reference to the accompanying drawings. These examples are non-limiting examples in which, in these examples, like numbers refer to like structures, wherein:

[0018] Figure 1 is a block diagram illustrating an exemplary radiation treatment system according to some embodiments of the present application;

[0019] Figure 2 is a flowchart illustrating an exemplary process for radiation treatment in a radiation treatment system according to some embodiments of the present application;

[0020] Figure 3A is illustrated an exemplary treatment device according to some embodiments of the present application;

[0021] Figure 3B is illustrated another exemplary treatment device according to some embodiments of the present application;

[0022] Figure 4A is shown an upper portion of a cross-sectional view of an exemplary treatment device viewed along the X direction according to some embodiments of the present application;

[0023] Figure 4B is shown an upper portion of a cross-sectional view of another exemplary treatment device viewed along the X direction according to some embodiments of the present application;

[0024] Figure 4C is shown an upper portion of a cross-sectional view of another exemplary treatment device viewed along the X direction according to some embodiments of the present application;

[0025] Figure 4D is shown an upper portion of a cross-sectional view of another exemplary treatment device viewed along the X direction according to some embodiments of the present application;

[0026] Figure 5A is shown an upper portion of a cross-sectional view of an exemplary treatment device viewed along the X direction according to some embodiments of the present application;

[0027] Figure 5B is shown an upper portion of a cross-sectional view of another exemplary treatment device viewed along the X direction according to some embodiments of the present application;

[0028] Figure 5C is shown an upper portion of a cross-sectional view of another exemplary treatment device viewed along the X direction according to some embodiments of the present application;

[0029] Figure 5DAn upper portion of a cross-sectional view of another exemplary treatment device is shown, according to some embodiments of the application, as viewed along the X direction;

[0030] Figure 6A An upper portion of a cross-sectional view of another exemplary treatment device is shown, according to some embodiments of the application, as viewed along the X direction;

[0031] Figure 6B An upper portion of a cross-sectional view of another exemplary treatment device is shown, according to some embodiments of the application, as viewed along the X direction;

[0032] Figure 7A An upper portion of a cross-sectional view of another exemplary treatment device is shown, according to some embodiments of the application, as viewed along the X direction;

[0033] Figure 7B An upper portion of a cross-sectional view of another exemplary treatment device is shown, according to some embodiments of the application, as viewed along the X direction;

[0034] Figure 8A A perspective view of an exemplary treatment device is shown, according to some embodiments of the application;

[0035] Figure 8B A perspective view of an exemplary treatment device is shown, according to some embodiments of the application;

[0036] Figure 9A A cross-sectional view of the treatment device described in Figure 8A is shown, according to some embodiments of the application, as viewed along the axial direction of the cryostat (i.e., the Z direction);

[0037] Figure 9B A cross-sectional view of the treatment device described in Figure 8B is shown, according to some embodiments of the application, as viewed along the axial direction of the cryostat (i.e., the Z direction);

[0038] Figure 10A Another cross-sectional view of the treatment device described in Figure 8A is shown, according to some embodiments of the application;

[0039] Figure 10B A cross-sectional view of the treatment device described in Figure 8B is shown, according to some embodiments of the application, as viewed along the Y direction;

[0040] Figure 11A A cross-sectional view of an exemplary treatment device is shown, according to some embodiments of the application, as viewed along the X direction;

[0041] Figure 11BAnother exemplary treatment device with two magnetic shielding structures viewed in the X direction is shown in accordance with some embodiments of the application;

[0042] Figure 12A An upper portion of a cross-sectional view of an exemplary treatment device viewed in the X direction is shown in accordance with some embodiments of the application;

[0043] Figure 12B An upper portion of a cross-sectional view of another exemplary treatment device viewed in the X direction is shown in accordance with some embodiments of the application;

[0044] Figure 12C An upper portion of a cross-sectional view of another exemplary treatment device viewed in the X direction is shown in accordance with some embodiments of the application;

[0045] Figure 13A An upper portion of a cross-sectional view of an exemplary treatment device viewed in the X direction is shown in accordance with some embodiments of the application;

[0046] Figure 13B An upper portion of a cross-sectional view of another exemplary treatment device viewed in the X direction is shown in accordance with some embodiments of the application;

[0047] Figure 13C An upper portion of a cross-sectional view of another exemplary treatment device viewed in the X direction is shown in accordance with some embodiments of the application;

[0048] Figure 14A A perspective view of an exemplary treatment device is shown in accordance with some embodiments of the application;

[0049] Figure 14B A perspective view of another exemplary treatment device is shown in accordance with some embodiments of the application;

[0050] Figure 15A A perspective view of a treatment device is shown in accordance with some embodiments of the application;

[0051] Figure 15B A perspective view of a treatment device is shown in accordance with some embodiments of the application;

[0052] Figure 15C A perspective view of another treatment device is shown in accordance with some embodiments of the application;

[0053] Figure 15D A perspective view of a treatment device is shown in accordance with some embodiments of the application;

[0054] Figure 16A A perspective view of an exemplary treatment device is shown in accordance with some embodiments of the application; and

[0055] Figure 16B A perspective view of a treatment device is shown in accordance with some embodiments of the present application. DETAILED DESCRIPTION

[0056] The following description is presented to enable any person skilled in the art to make and use the application, and is provided in the context of particular applications and their requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments and applications without departing from the principles and spirit of the application. Thus, the present application is not intended to be limited to the described embodiments but is to be accorded the widest scope consistent with the claims.

[0057] The terminology used in the present application is for the purpose of describing particular example embodiments only and is not intended to limit the scope of the present application. As used in the description of the application and the claims, the following terms are intended to have the following meanings, except to the extent otherwise indicated: "a," "an," and "the" are understood to mean one or more unless the context clearly indicates otherwise; "about" and "substantially" are understood to be approximate or nearly; "coupled" is understood to be electrically or mechanically connected, whether directly or through one or more intermediaries; and "associated with" is understood to mean in communication with or to have a bearing on.

[0058] These and other features, aspects, and advantages of the present application can become better understood with reference to the following description and appended claims, taken in conjunction with the accompanying drawings. However, it is to be understood that the appended drawings are only intended to aid in the description of the application. It is to be understood that the drawings are not drawn to scale.

[0059] Figure 1 is a block diagram illustrating an example radiotherapy system 100 in accordance with some embodiments of the present application. In some embodiments, the radiotherapy system 100 can be a multi-modality imaging system, including, for example, a positron emission tomography radiotherapy (PET-RT) system, a magnetic resonance imaging radiotherapy (MRI-RT) system, etc. For better understanding of the present application, the MRI-RT system can be described as an example of the radiotherapy system 100, and is not intended to limit the scope of the present application.

[0060] As Figure 1As shown, the radiation therapy system 100 can include a therapy device 110, one or more processing engines 120, a network 130, a storage device 140, and one or more terminal devices 150. In some embodiments, the therapy device 110, the one or more processing engines 120, the storage device 140, and / or the terminal devices 150 can be connected and / or communicate with each other through wireless connections (e.g., wireless connections provided by the network 130), wired connections (e.g., wired connections provided by the network 130), or any combination thereof.

[0061] The therapy device 110 can include a magnetic resonance imaging device (hereinafter referred to as “MRI device”). The MRI device can generate image data related to magnetic resonance imaging signals (hereinafter referred to as “MRI signals”) by scanning a subject or a portion of a subject. In some embodiments, the subject can include a body, a substance, an object, etc., or any combination thereof. In some embodiments, the subject can include a specific part of a body, a specific organ, or a specific tissue, such as a head, a brain, a neck, a body, a shoulder, an arm, a chest, a heart, a stomach, a blood vessel, soft tissue, a knee, a foot, etc., or any combination thereof. In some embodiments, the therapy device 110 can transmit the image data to the one or more processing engines 120, the storage device 140, and / or the terminal devices 150 via the network 130 for further processing. For example, the image data can be transmitted to the one or more processing engines 120 to generate MRI images, or can be stored in the storage device 140.

[0062] The therapy device 110 can also include a radiation therapy assembly (hereinafter referred to as “radiation therapy device”). The radiation therapy device can provide radiation therapy for a target region (e.g., a tumor). As used herein, the radiation can include particle radiation, photon radiation, etc. The particle radiation can include neutrons, protons, electrons, muons, heavy ions, alpha radiation, etc., or any combination thereof. The photon radiation can include X-rays, gamma rays, ultraviolet rays, laser light, etc., or any combination thereof. For illustrative purposes, the radiation therapy device associated with X-rays can be described as an example. In some embodiments, the therapy device 110 can generate a dose of X-rays to perform radiation therapy with the help of image data provided by the MRI device. For example, the image data can be processed to locate a tumor and / or determine a dose of X-rays.

[0063] The one or more processing engines 120 can process data and / or information acquired from the treatment device 110, the storage device 140, and / or the terminal device 150. For example, the one or more processing engines 120 can process image data and reconstruct at least one MRI image based on the image data. Also, the one or more processing engines 120 can determine a location of a treatment region and a radiation dose based on the at least one MRI image. Benefits that can be provided by MRI images include, for example, excellent soft tissue contrast, high resolution, geometric accuracy, which can allow precise localization of the treatment region. MRI images can be used to detect changes in the treatment region (e.g., tumor regression or metastasis) during determination of a treatment plan and during the time of performing treatment, such that the original treatment plan can be adjusted accordingly. The original treatment plan can be determined prior to the start of treatment. For example, the original treatment plan can be determined at least one day, or three days, or one week, or two weeks, or one month, etc. prior to the start of treatment.

[0064] In the original or adjusted treatment plan, the radiation dose can be determined based on, for example, synthetic electron density information. In some embodiments, the synthetic electron density information can be generated based on the MRI images.

[0065] In some embodiments, the one or more processing engines 120 can be a single processing engine that communicates with and processes data from the MRI device and the radiation treatment device of the treatment device 110. Alternatively, the one or more processing engines 120 can include at least two processing engines. One of the at least two processing engines can communicate with and process data from the MRI device of the treatment device 110, and another of the at least two processing engines can communicate with and process data from the radiation treatment device of the treatment device 110. In some embodiments, the one or more processing engines 120 can include a treatment planning system. The at least two processing engines can communicate with each other.

[0066] In some embodiments, the one or more processing engines 120 can be a single server or a group of servers. The group of servers can be centralized or distributed. In some embodiments, the one or more processing engines 120 can be located locally or remotely from the treatment device 110. For example, the one or more processing engines 120 can access information and / or data from the treatment device 110, the storage device 140, and / or the terminal device 150 via the network 130. For example, the one or more processing engines 120 can be directly connected to the treatment device 110, the terminal device 150, and / or the storage device 140 to access information and / or data. In some embodiments, the one or more processing engines 120 can be implemented on a cloud platform. The cloud platform can include a private cloud, a public cloud, a hybrid cloud, a community cloud, a distributed cloud, an intercloud, a multi-cloud, etc., or any combination thereof.

[0067] The network 130 can include any suitable network that can facilitate the exchange of information and / or data for the radiation therapy system 100. In some embodiments, one or more components of the radiation therapy system 100 (e.g., the therapy device 110, the one or more processing engines 120, the storage device 140, or the terminal device 150) can communicate with one or more other components of the radiation therapy system 100 via the network 130 to obtain information and / or data. For example, the one or more processing engines 120 can obtain image data from the therapy device 110 via the network 130. For another example, the one or more processing engines 120 can obtain user instructions from the terminal device 150 via the network 130. The network 130 can include a public network (e.g., the Internet), a private network (e.g., a local area network (LAN), a wide area network (WAN)), a wired network (e.g., an Ethernet network), a wireless network (e.g., an 802.11 network, a Wi-Fi network), a cellular network (e.g., a Long Term Evolution (LTE) network), a frame relay network, a virtual private network (VPN), a satellite network, a telephone network, routers, hubs, switches, server computers, and / or the like, or any combination thereof. In some embodiments, the network 130 can include one or more network access points. For example, the network 130 can 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 radiation therapy system 100 can connect to the network 130 to exchange data and / or information.

[0068] The storage device 140 can store data, instructions, and / or any other information. In some embodiments, the storage device 140 can store data acquired from the one or more processing engines 120 and / or the terminal device 150. In some embodiments, the storage device 140 can store data and / or instructions that the one or more processing engines 120 can execute or use to perform the example methods described in this application. In some embodiments, the storage device 140 can include a mass storage device, a removable storage device, a cloud-based storage device, a volatile read-and-write memory, a read-only memory (ROM), etc., or any combination thereof. An example mass storage device can include a magnetic disk, an optical disk, a solid-state disk, etc. An example removable storage device can include a flash drive, a floppy disk, an optical disk, a memory card, a compact disk, a magnetic tape, etc. An example volatile read-and-write memory can include a random access memory (RAM), which can include a dynamic random access memory (DRAM), a Double Data Rate synchronous DRAM (DDR SDRAM), a static RAM (SRAM), a thyristor RAM (T-RAM), and a Zero-Capacitor RAM (Z-RAM), etc. An example read-only memory can include a mask ROM (MROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a compact disk ROM (CD-ROM), and a digital versatile disk ROM, etc. In some embodiments, the storage device 140 can be implemented on a cloud platform as described elsewhere in this application.

[0069] In some embodiments, the storage device 140 can be connected to the network 130 to communicate with one or more other components of the radiation therapy system 100 (e.g., the one or more processing engines 120 or the terminal device 150). The one or more components of the radiation therapy system 100 can access data or instructions stored in the storage device 140 via the network 130. In some embodiments, the storage device 140 can be part of the one or more processing engines 120.

[0070] The terminal device 150 can be connected to and / or in communication with the treatment device 110, the one or more processing engines 120, and / or the storage device 140. For example, the one or more processing engines 120 can obtain a scan protocol from the terminal device 150. For another example, the terminal device 150 can obtain image data from the treatment device 110 and / or the storage device 140. In some embodiments, the terminal device 150 can include a mobile device 151, a tablet 152, a laptop 153, or the like, or any combination thereof. For example, the mobile device 151 can include a mobile phone, a personal digital assistant (PDA), a gaming device, a navigation device, a point-of-sale (POS) device, a laptop, a tablet, a desktop, or the like, or any combination thereof. In some embodiments, the terminal device 150 can include an input device, an output device, or the like. The input device can include alphanumeric and other keys that can be entered through a keyboard, a touch screen (e.g., with tactile or haptic feedback), voice input, eye tracking input, a brain monitoring system, or any other similar input mechanisms. Input information received through the input device can be sent to the one or more processing engines 120 via, for example, a bus, for further processing. Other types of input devices can include a cursor control device, such as a mouse, a trackball, or cursor direction keys, among others. The output device can include a display, a speaker, a printer, or the like, or any combination thereof. In some embodiments, the terminal device 150 can be part of the one or more processing engines 120.

[0071] This description is intended to be illustrative, and not to limit the scope of the application. Many alternatives, modifications, and variations will be apparent to those skilled in the art. Features, structures, methods, and other characteristics described herein can be combined in various ways to achieve yet other example embodiments. For example, the storage device 140 can be a data storage including a cloud computing platform, such as a public cloud, a private cloud, a community, a hybrid cloud, or the like. In some embodiments, the one or more processing engines 120 can be integrated into the treatment device 110. However, those variations and modifications do not depart from the scope of the present application.

[0072] Figure 2 is a flowchart of an example process 200 for applying radiation therapy by a radiation therapy system in accordance with some embodiments of the present application. In some embodiments, Figure 2 One or more operations of the process 200 shown in Figure 1 may be implemented in the radiation therapy system 100 shown in Figure 2 The process 200 shown in Figure 1One or more of the processing engines 120 shown in FIG. 1 can invoke and / or execute. For illustrative purposes, implementation of the process 200 in one or more of the processing engines 120 is described herein as an example. It should be noted that the process 200 can similarly be implemented in the terminal device 150.

[0073] At 202, the one or more processing engines 120 can acquire, via the MRI apparatus, magnetic resonance imaging (MRI) data regarding a region of interest (ROI). The MRI data can be MR signals received by RF coils from the subject. More detailed descriptions regarding the MR signals can be found elsewhere in the present application, e.g., FIG. 3 and its description.

[0074] In some embodiments, the ROI can refer to a treatment region associated with a tumor. The treatment region can be a region (e.g., body, matter, object) of the subject. In some embodiments, the ROI can be a specific part of the body, a specific organ, or a specific tissue, such as a head, a brain, a neck, a body, a shoulder, an arm, a chest, a heart, a stomach, a blood vessel, a soft tissue, a knee, a foot, etc., or any combination thereof.

[0075] At 204, the one or more processing engines 120 can reconstruct, based on the MRI data, an MRI image associated with at least a portion of the ROI. The MRI image can be reconstructed based on the MRI data to a distribution of atomic nuclei within the subject. Different kinds of image reconstruction techniques for the image reconstruction process can be employed. Exemplary image reconstruction techniques can include Fourier reconstruction, constrained image reconstruction, and regularized image reconstruction in MRI, etc., or variants thereof, or any combination thereof.

[0076] MRI images can be used to determine radiation treatment to a tumor. For example, one or more processing engines 120 can determine a location of a tumor and a radiation dose from the MRI images. In some embodiments, it can take at least a few minutes to reconstruct an MRI image representing a large imaging region. In some embodiments, to generate MRI images during a relatively short time period (e.g., every second), one or more processing engines 120 can reconstruct an initial image representing a smaller imaging region (e.g., at least a portion of a ROI) compared to the MRI image representing a large imaging region, and then combine the initial image with the MRI image representing a large imaging region. For example, one or more processing engines 120 can replace a portion of the MRI image representing a large imaging region that is related to the ROI with the initial image. The MRI image representing a large imaging region can include information of non-ROI (e.g., healthy tissue) near the ROI and the ROI. In some embodiments, the MRI image representing a large imaging region can be acquired and reconstructed prior to radiation treatment on the tumor. For example, the MRI image representing a large imaging region can be acquired in less than 1 day, or half a day, or 6 hours, or 3 hours, or 1 hour, or 45 minutes, or 30 minutes, or 20 minutes, or 15 minutes, or 10 minutes, or 5 minutes, etc., prior to a radiation source starting to emit a radiation beam for treatment. In some embodiments, the MRI image representing a large imaging region can be acquired from a storage device in the radiation treatment system 100, such as storage device 140.

[0077] At 206, one or more processing engines 120 can determine a parameter associated with a size of at least a portion of the ROI based on the MRI image. In some embodiments, the parameter associated with the size of at least a portion of the ROI can include a size of a cross-section of the tumor that has a largest area and is perpendicular to a direction of at least a radiation beam that irradiates the ROI. In some embodiments, the parameter associated with the size of at least a portion of the ROI can indicate a shape of the cross-section of the tumor. For example, the parameter associated with the size of at least a portion of the ROI can indicate that the shape of the cross-section of the tumor is circular, and further indicate a diameter of the circle. In some embodiments, to determine the parameter associated with the size of at least a portion of the ROI, one or more processing engines 120 can extract texture information from the MRI image, and determine texture features indicative of the ROI in the extracted texture information by identifying frequently. Then, one or more processing engines 120 can measure a size of a region including the texture features in the MRI image, and determine the parameter associated with the size of the ROI.

[0078] In 208, the one or more processing engines 120 can generate a control signal according to parameters associated with the size of at least a portion of the ROI. The control signal can be dynamically adjusted based on at least two MRI images taken at different points in time. In some embodiments, the control signal can include parameters related to the radiation treatment on the tumor. For example, the control signal can include the dose of X-rays and the duration of the radiation beam. For another example, the control signal can include parameters of a multi-leaf collimator (MLC) that determines the shape of the radiation beam projected on the subject. The MLC can include at least two separate high-atomic-number material (e.g., tungsten) leaves that independently move in and out of the path of the radiation beam. In some embodiments, the control signal can include parameters associated with the movement of one or more components of the radiation treatment device. For example, the control signal can include parameters associated with one or more positions of a radiation source of the radiation treatment device (e.g., in the treatment device 110, the radiation treatment device 300). For another example, the control signal can include parameters associated with the height or position of a platform of the radiation treatment apparatus (e.g., the position of the platform 308 of the treatment bed 330 along the axis of the magnet 302) to properly position the patient so that the treatment region (e.g., a cancerous tumor or lesion) in the patient can properly receive the radiation beam from the radiation treatment device.

[0079] In 210, the one or more processing engines 120 can send the control signal to the radiation treatment device to cause the radiation treatment device to apply the radiation treatment. During the radiation treatment, the radiation source of the radiation treatment device can rotate, and the dose of X-rays, the duration of the radiation beam from the radiation source, the shape of the MLC, and the position of the platform can be changed. In some embodiments, the radiation beam can be emitted only when the radiation source of the radiation treatment device rotates to certain angles (e.g., 60 degrees, 120 degrees, 180 degrees, 240 degrees, 300 degrees, 360 degrees). For example, intensity-modulated radiation therapy (IMRT) can be applied. The radiation source can intermittently stop rotating. The radiation source can rotate to a desired position, pause there, emit a radiation beam, and then resume rotating. In some embodiments, the radiation source can rotate continuously, and emit the radiation beam continuously or intermittently. In some embodiments, the radiation source can emit the radiation beam continuously while rotating.

[0080] In some embodiments, as described above, the treatment region (e.g., a region including a tumor) can be determined from image data acquired from the MRI device. Then, a radiation beam can be generated by a radiation source of the radiation treatment device to perform the radiation treatment of the treatment region. For example, the dose of the radiation beam and / or the position of the treatment region can be determined in real-time with the help of the MRI device.

[0081] It should be noted that the foregoing is provided for purposes of illustration and is not intended to limit the scope of the application. Various further changes and modifications of the application can be made based on the description and drawings without departing from the scope of the application. For example, operations 202 and 204 can be performed simultaneously.

[0082] Figure 3A An exemplary treatment device 110 according to some embodiments of the present application is illustrated. As shown, the treatment device 110 can include an MRI device 310, a radiation treatment device 300, and a treatment couch 330. In some embodiments, the MRI device 310 can generate MRI data as described in operation 202, and the radiation treatment device 300 can perform radiation treatment as described in operation 210. Figure 3A

[0083] The MRI device 310 can include a bore 301, a magnet 302, one or more gradient coils (not shown), and one or more radio frequency (RF) coils (not shown). The MRI device 310 can be configured to acquire image data from an imaging region. For example, the image data can relate to a treatment region associated with a tumor. In some embodiments, the MRI device 310 can be a permanent magnet MRI scanner, a superconducting electromagnet MRI scanner, or a resistive electromagnet MRI scanner, among others, depending on the type of the magnet 302. In some embodiments, the MRI device 310 can be a high-field MRI scanner, a mid-field MRI scanner, and a low-field MRI scanner, among others, depending on the strength of the magnetic field. In some embodiments, the MRI device 310 can be a closed-bore (cylindrical) type, an open-bore type, among others.

[0084] The magnet 302 can have a toroidal shape and can generate a static magnetic field B0. The magnet 302 can be of various types, including, for example, a permanent magnet, a superconducting electromagnet, a resistive electromagnet, among others. The superconducting electromagnet can include niobium, vanadium, technetium alloy, among others.

[0085] The one or more gradient coils can generate magnetic field gradients to the main magnetic field B0in the X, Y, and / or Z directions (or axes). In some embodiments, the one or more gradient coils can include X-direction (or axis) coils, Y-direction (or axis) coils, Z-direction (or axis) coils, among others. For example, the Z-direction coils can be designed based on a circular (Maxwell) coil design, the X-direction coils and the Y-direction coils can be designed based on a saddle-shaped (Golay) coil. As used herein, the X-direction can also be referred to as a readout (RO) direction (or frequency encoding direction), the Y-direction can also be referred to as a phase encoding (PE) direction, and the Z-direction can also be referred to as a slice selection encoding direction. In the present application, the readout direction and the frequency encoding direction can be used interchangeably.

[0086] ​By way of example only, the gradient magnetic fields can include a slice selection gradient field corresponding to the Z direction, a phase encoding (PE) gradient field corresponding to the Y direction, and a readout (RO) gradient field corresponding to the X direction, among others. Gradient magnetic fields in different directions can be used to encode spatial information of the MR signals. In some embodiments, the gradient magnetic fields can also be used to perform at least one function of flow encoding, flow compensation, flow dephasing, or any combination thereof.

[0087] One or more RF coils can transmit RF pulses to and / or receive MR signals from an object under examination (e.g., a body, a substance, an object). As used herein, RF pulses can include excitation RF pulses and refocusing RF pulses. In some embodiments, excitation RF pulses (e.g., 90 degree RF pulses) can cause magnetization vectors to move away from the direction of the main magnetic field B0. In some embodiments, refocusing pulses (e.g., 180 degree RF pulses) can rotate the rotation of dispersed spins about an axis in the transverse plane so that the magnetization vectors can rephase at a later time. In some embodiments, the RF coils can include RF transmit coils and RF receive coils. The RF transmit coils can transmit RF pulse signals that can excite nuclei in a subject to resonate at the Larmor frequency. The RF receive coils can receive MR signals emitted from the object. In some embodiments, the RF transmit coils and the RF receive coils can be integrated into a single coil, such as a transmit / receive coil. The RF coils can be one of various types, including, for example, quadrature (QD) orthogonal coils, phased array coils, and the like. In some embodiments, different RF coils 240 can be used to scan different parts of a body under examination, such as a head coil, a knee coil, a cervical spine coil, a thoracic spine coil, a temporomandibular joint (TMJ) coil, and the like. In some embodiments, the RF coils can be classified as volume coils and local coils according to their functions and / or sizes. For example, volume coils can include birdcage coils, transverse electromagnetic coils, surface coils, and the like. By way of further example, local coils can include solenoid coils, saddle coils, flexible coils, and the like.

[0088] The radiotherapy device 300 can include a drum 312 and a base 307. The drum 312 can have a ring shape. The drum 312 can be disposed around the magnet 302 and intersect the magnet 302 at a central region of the magnet 302 along an axis 311 of the bore 301. The drum 312 can house and support a radiation source configured to emit a radiation beam toward a treatment region in the bore 301. The radiation beam can be an X-ray beam, an electron beam, a gamma ray source, a proton ray source, etc. The drum 312, together with the radiation source mounted thereon, can be rotatable around the axis 311 of the bore 301 and / or a point called isocenter. By way of example only, the drum 312, together with the radiation source mounted thereon, can be rotated by any angle, such as 90 degrees, 180 degrees, 360 degrees, 450 degrees, 540 degrees, around the axis 311. The drum 312 can be further supported by the base 307.

[0089] It should be noted that the above is provided only for illustrative purposes and is not intended to limit the scope of the present application. Various changes or modifications can be made by those having ordinary skill in the art under the teachings of the present application. For example, the radiotherapy device 300 can further include a linear accelerator for accelerating electrons, ions, or protons, a dose detection device, a temperature control device (e.g., a cooling device), a multi-layer collimator, etc., or any combination thereof. However, such changes and modifications will not depart from the scope of the present application.

[0090] The treatment couch 330 can include a platform 308 and a base 309. In some embodiments, the platform 308 can be movable in a horizontal direction and into the bore 301 of the MRI device 310. In some embodiments, the platform 308 can be movable in two dimensions, three dimensions, four dimensions, five dimensions, or six dimensions. In some embodiments, the platform 308 can be movable according to changes (e.g., position changes) of a tumor estimated by real-time MRI images acquired during treatment, for example.

[0091] In some embodiments, a subject can be placed on the platform 308 and sent into the MRI device. In some embodiments, the subject can be a human patient. The human patient can be supine, prone, lying on a side of the platform 308.

[0092] During treatment, the drum 312 can be set to rotate around the magnet 302. In some embodiments, the magnet 302 can include a groove (not shown) at an outer wall thereof. The groove can be disposed around an entire circumference of the magnet 302. For example, the groove can have a ring shape around the magnet 302, thereby housing at least a portion of the drum 312. In some embodiments, the groove can be disposed around a portion of the circumference of the magnet 302. For example, the groove can have one or more arc shapes around the magnet 302.

[0093] In some embodiments, the radiation source can move along the entire rotational path within the groove. The radiation source can generate a radiation beam according to one or more parameters. Exemplary parameters may include parameters of the radiation beam, parameters of the radiation source, or parameters of the platform 308. For example, parameters of the radiation beam may include irradiation intensity, irradiation angle, irradiation distance, irradiation area, irradiation time, intensity distribution, etc., or any combination thereof. Parameters of the radiation source may include position, rotation angle, rotation speed, rotation direction, configuration of the radiation source, etc., or any combination thereof. In some embodiments, the generation of the radiation beam by the radiation source may take into account energy loss of the radiation beam, because, for example, a magnet 302 located in the path of the radiation beam may absorb at least a portion of the radiation beam. For example, the irradiation intensity of the radiation beam may be set to be greater than in the case of no energy loss, because, for example, absorption by the magnet 302 thus compensates for the energy loss, such that a particular intensity of the radiation beam may affect the treatment area (e.g., a tumor).

[0094] Figure 3B Another exemplary treatment device 110' according to some embodiments of this application is described. Figure 3A Compared to the treatment device 110 described herein, treatment device 110' can use a frame 306 instead of a roller 312. The frame 306 can be positioned on one side of the magnet 302. The treatment head 304 can be mounted on the frame 306 via a treatment arm 305. The treatment head 304 can accommodate a radiation source. The frame 306 allows the treatment head 304 to rotate about the axis 311 of the aperture 301.

[0095] like Figure 3B As shown, a groove 303 can be formed on the outer wall of the magnet 302 and has an annular shape. The groove 303 can accommodate at least a portion of the treatment head 304 and provide a path for rotation of the treatment head 304. This arrangement can reduce the distance between the treatment head 304 and the axis 311 of the aperture 301 along the radial direction of the magnet 302. In some embodiments, the reduced distance between the treatment head 304 and the axis 311 of the aperture 301 can cause an increase in the radiation dose that can reach the treatment area (e.g., a tumor), resulting in improved treatment efficiency. In some embodiments, the width of the groove 303 along the Z-direction (i.e., the axial direction of the magnet 302) can be no less than the width of the treatment head 304 along the Z-direction.

[0096] It should be noted that the description of the treatment device 110 above is provided for illustrative purposes only and is not intended to limit the scope of this application. Various changes and modifications can be made by those skilled in the art based on the description in this application. For example, the assembly and / or function of the treatment device 110 may vary or be altered depending on the specific embodiment. In some embodiments, the magnet 302 of the MRI device 310 may also rotate relative to the treatment head 304. For example, the radiotherapy device 300 and the MRI device 310 may rotate synchronously or asynchronously about the same axis (e.g., axis 311). However, these changes and modifications do not depart from the scope of this application.

[0097] Figure 4A The upper portion of a cross-sectional view of an exemplary treatment apparatus 400 viewed along the X-direction according to some embodiments of this application is shown. The treatment apparatus 400 may include an MRI apparatus configured to generate MRI data and a radiotherapy apparatus configured to apply radiotherapy.

[0098] like Figure 4A As shown, the MRI device may include at least two main magnetic coils 401, at least two magnetic shielding coils 402, and a cryostat 403.

[0099] At least two main magnetic coils 401 and at least two magnetic shielding coils 402 can be housed in a cryostat 403 and maintained in a superconducting state under certain conditions (e.g., when the two coils are immersed in the cooling medium in the cryostat 403).

[0100] The cryostat 403 may have a ring shape with a shaft 405 (e.g., Figure 3A (Axis 311 in the middle). When at least two main magnetic coils 401 transmit current along the first direction, the at least two main magnetic coils 401 can be arranged coaxially along axis 405 to generate a uniform magnetic field (e.g., main magnetic field B0) in a specific region (e.g., the region within the hole 301).

[0101] At least two magnetic shielding coils 402 may also be arranged coaxially along axis 405 at a radius greater than that of the at least two main magnetic coils 401 from axis 405. The at least two magnetic shielding coils 402 may carry current in a second direction opposite to the first direction. The at least two magnetic shielding coils 402 can help shield the magnetic field generated by the at least two main magnetic coils 401 on an area outside the MRI device.

[0102] like Figure 4AAs shown, the cryostat 403 can include two chambers (e.g., left chamber and right chamber for brevity). The two chambers can be located on opposite sides of the cryostat 403 along the axial direction (i.e., the direction of the shaft 405) and can be connected by a neck between the two chambers. The neck can have a smaller radial dimension than the two chambers. Each chamber can have an annular shape with different outer walls. In some embodiments, the outer walls can refer to the outermost surface of each chamber that has an annular shape. The two chambers and the neck can share the same inner wall, i.e., the inner wall of the cryostat 403. In some embodiments, the inner wall can refer to the innermost surface of each chamber that also has an annular shape. In some embodiments, each chamber can house at least one coil of the at least two main magnetic coils 401 and at least one coil of the at least two magnetic shielding coils 402. For example, at least one coil of the at least two main magnetic coils 401 can be disposed near the inner wall of the left chamber, and at least one coil of the at least two magnetic shielding coils 402 can be disposed near the outer wall of the left chamber. A gap 406 can be formed between the main magnetic coil disposed in the left chamber and the main magnetic coil disposed in the right chamber, allowing a radiation beam generated by the radiotherapy device to pass through. The two chambers can be in fluid communication with each other through the neck between them. The cryostat 403 can contain a cooling medium in which the at least two main magnetic coils 401 and the at least two magnetic shielding coils 402 are immersed to achieve a superconducting state.

[0103] The cryostat 403 can have a recess 408 at a radial position between the inner wall of the cryostat 403 and the outer wall of the different chambers of the cryostat 403. The recess 408 can have an opening 407 formed between the outer walls of the two chambers of the cryostat 403. When viewed in perspective, the recess 408 can have an annular shape. The annulus can have the same or different widths (i.e., dimensions in the axial direction) at different radial positions. The recess 408 can have a depth (i.e., the thickness of the annulus in the radial direction), which is defined as the distance in the radial direction from the opening 407 of the cryostat 403 to the outermost surface of the neck.

[0104] The recess 408 can be configured to house components of the radiotherapy device. As shown, the recess 408 can house a radiation source including a linear accelerator 409, a shielding structure 411, a collimator 412, a target 404, and a multileaf collimator (MLC) 410. Figure 4A

[0105] The linear accelerator 409 can be configured to accelerate charged subatomic particles or ions to high speeds. In some embodiments, the linear accelerator 409 can accelerate electrons using microwave technology. For example, the linear accelerator 409 can accelerate electrons in an electron beam having an energy group between 4 MeV and 22 MeV using high RF electromagnetic waves.​

[0106] The linac 409 can be mounted to a gantry or drum (e.g., gantry 306 or drum 312) that is capable of rotating about an axis 405 and can enable the emission of a radiation beam from any circumferential position. As shown, the gantry or drum can be rotated to a first position, and the linac 409 can be positioned above the axis 405. The linac 409 can include an acceleration waveguide (tube) having an axis that is perpendicular to the axis 405. The acceleration waveguide (tube) can provide a linear path for accelerating electrons along a beam path that is perpendicular to the axis 405. Figure 4A

[0107] The acceleration waveguide (tube) of the linac 409 can be at least partially surrounded by a shielding structure 411. In some embodiments, the shielding structure 411 can provide a cavity that is coaxial with the longitudinal axis of the tube of the linac 409, with at least one end being open to allow a radiation beam emitted from the linac 409 to pass through. In some embodiments, the shielding structure 411 can have any configuration. For example, the shielding structure 411 can include one annular space on the left side of the slot (i.e., the side near the left chamber) and one annular plate on the right side of the slot (i.e., the side near the right chamber) with a plate connecting the two rings. Alternatively, the rings can be replaced by separate arc segments. It should be noted that the shielding structure 411 can be of any shape, as long as at least one end of the shielding structure 411 is open for the radiation beam emitted from the linac 409 to pass through. Details regarding exemplary configurations of the shielding structure 411 can be found elsewhere in this application (e.g., in the description of the shielding structure 411 of the linac 109 of the radiation therapy system 100 of FIG. 1). Figure 8A-16B

[0108] In some embodiments, the shielding structure 411 can include at least two shielding layers. At least one of the at least two shielding layers can be used to reduce magnetic interference between one or more components of the MRI device and the radiation therapy device. For example, the shielding structure 411 can include a magnetic shielding layer configured to shield a magnetic field generated by the MRI device (e.g., a main magnet coil, a magnetic shield coil, a gradient coil) from affecting the electrons.

[0109] Additionally, at least one of the at least two shielding layers can be used to reduce RF and / or microwave interference between one or more components of the MRI device and the radiation therapy device. For example, the shielding structure 411 can include an electromagnetic shielding layer configured to shield RF signals generated by the MRI device (e.g., an RF coil) and microwaves generated by the radiation therapy device.

[0110] ​​The at least two shielding layers can be made of the same material and / or different materials. For example, both the electromagnetic shielding layer and the magnetic shielding layer can be made of a high magnetic permeability and magnetic susceptibility material (e.g., non-oriented silicon steel), or one of the electromagnetic shielding layer and the magnetic shielding layer is made of a high electrical conductivity and magnetic permeability material. In some embodiments, the at least two shielding layers can be magnetically and / or electrically isolated from each other with a suitable dielectric material (e.g., air or plastic) in between them.

[0111] Additionally or alternatively, at least one of the at least two shielding layers can be used to protect one or more components of the MRI device from radiation generated by the linear accelerator 409. For example, one of the at least two shielding layers can be made of a material capable of absorbing radiation generated by the radiation beam of the linear accelerator 409. Exemplary materials capable of absorbing radiation can include materials for absorbing photon radiation and / or materials for absorbing neutron radiation. Materials for absorbing photon radiation can include steel, aluminum, lead, tungsten, etc. Materials for absorbing neutron radiation can include boron, graphite, etc. It should be noted that in some embodiments, the shielding structure 411 can be made of only radiation absorbing materials without high magnetic permeability and magnetic susceptibility materials. In this way, the shielding structure 411 can provide radiation shielding for one or more components of the MRI device only.

[0112] The target 404 can be configured to receive accelerated charged subatomic particles or ions (e.g., an electron beam) to generate a radiation beam for radiation therapy. For example, the electron beam can collide with the target 404 to generate high-energy X-rays according to the Bremsstrahlung effect. In some embodiments, the target 404 can be located near an exit window of the linear accelerator 409 to receive the accelerated electron beam. In some embodiments, the target 404 can be made of a material including aluminum, copper, silver, tungsten, etc., or any combination thereof. Alternatively, the target 404 can be made of a composite material including tungsten and copper, tungsten and silver, tungsten and aluminum, etc., or any combination thereof.

[0113] The radiation beam from the target 404 can pass through the collimator 412 to form a beam having a specific shape (e.g., a cone beam). In some embodiments, the collimator 412 can include a primary collimator, a homogenizer, and at least one secondary collimator.

[0114] The MLC 410 can be configured to reshape the radiation beam. For example, the MLC 410 can adjust the irradiation shape, the irradiation area, etc., of the radiation beam. The MLC 410 can be placed at any location on the path of the radiation beam. For example, the MLC 410 can be placed close to the linear accelerator 409, as shown in FIG. 4A, or placed close to the target 404, as shown in FIG. 4B. Figure 4AThe radiation beam can further pass through a gap 406 between the neck of the cryostat 403 and the at least two main magnet coils after being reshaped by the MLC 410 to reach the treatment region. For example, the MLC 410 can be placed at a relatively long distance from the linac (e.g., as shown in FIG. 4B), such that the MLC 410 can be closer to, for example, a patient to be irradiated. Figure 6A

[0115] The MLC 410 can be held stationary with respect to the linac 409, thereby rotating with the linac 409 around the axis 405. The MLC 410 can include at least two separate high-atomic-number material (e.g., tungsten) leaves that independently move in and out of the path of the radiation beam in order to block it. As the at least two separate leaves move in and out, the shape of the radiation beam can change, forming different slot profiles of a tumor viewed from the axis of the radiation beam (i.e., the vertical dashed line 416 shown in FIG. 4A). Figure 4A In some embodiments, the MLC 410 can include one or more leaf layers. For example, the MLC 410 can have only one layer of leaves, and the height of the MLC 410 along the axis of the radiation beam can be between 7 and 10 centimeters. For another example, the MLC 410 can include two layers, and the height of the MLC 410 can be at least 15 centimeters.

[0116] Figure 4B An upper portion of a cross-sectional view of an exemplary treatment device 400’ viewed along the X direction is shown in accordance with some embodiments of the present application. As compared to the treatment device 400 described in Figure 4A At least a portion of the linac 409 of the treatment device 400’ can be located radially outside the groove 408 of the cryostat 403. As shown in Figure 4B the linac 409 and the shielding structure 411 around it along the axis of the radiation beam can protrude through the opening 407 formed by the outer wall of the cryostat 403. In some embodiments, the linac 409 and the shielding structure 411 can be supported by or mounted to a gantry or drum (e.g., the gantry 306 or the drum 312) that is capable of rotating around the axis 405.

[0117] Figure 4C An upper portion of a cross-sectional view of an exemplary treatment device 400” viewed along the X direction is shown in accordance with some embodiments of the present application. As compared to the treatment device 400 described in Figure 4A The cryostat 403’ of the treatment device 400” can have two separate cavities. As shown in Figure 4C ​As shown, the left chamber 403a and the right chamber 403b can be independent of each other, and thus no fluid communication is established between them. The cryostat 403' can have two different inner walls for the left chamber 403a and the right chamber 403b. Another opening 413 of the recess 408 can be formed between the two different inner walls. After reshaping by the MLC 410, the radiation beam can pass through the opening 413 and reach the treatment region.

[0118] Figure 4D An upper portion of a cross-sectional view of another exemplary treatment device 400"' viewed in the X direction is shown in accordance with some embodiments of the present application. As shown, the left chamber 403a and the right chamber 403b can be independent of each other, and thus no fluid communication is established between them. The cryostat 403' can have two different inner walls for the left chamber 403a and the right chamber 403b. Another opening 413 of the recess 408 can be formed between the two different inner walls. After reshaping by the MLC 410, the radiation beam can pass through the opening 413 and reach the treatment region. Figure 4C In contrast to the treatment device 400" described in the background section, at least a portion of the linear accelerator 409 of the treatment device 400"' can be located radially outside the recess 408 of the cryostat 403'. As shown, the linear accelerator 409 and the shielding structure 411 around it along the axis of the radiation beam can protrude out of the opening 407 formed by the outer wall of the cryostat 403'. In some embodiments, the linear accelerator 409 and the shielding structure 411 can be supported by or mounted to a gantry or a drum (e.g., the gantry 306 or the drum 312) that is capable of rotating around the axis 405. Figure 4D

[0119] It should be noted that the above description of the treatment device 400, 400', 400" or 400"' is provided for illustrative purposes only and is not intended to limit the scope of the present application. Various changes and modifications can be made to the present application based on the description provided herein by one of ordinary skill in the art. For example, the collimator 412 and the MLC 410 can be integrated to form a single collimator. As another example, the neck shown in the cryostat 403 can not form a complete ring. Specifically, the neck can be a discrete arc connecting the left chamber and the right chamber of the cryostat 403. Thus, the neck can intermittently appear in the path of the radiation beam to generate the radiation beam when the linear accelerator 409 rotates around the axis 405.

[0120] Figure 5A An upper portion of a cross-sectional view of an exemplary treatment device 500 viewed in the X direction is shown in accordance with some embodiments of the present application. As shown, the left chamber 403a and the right chamber 403b can be independent of each other, and thus no fluid communication is established between them. The cryostat 403' can have two different inner walls for the left chamber 403a and the right chamber 403b. Another opening 413 of the recess 408 can be formed between the two different inner walls. After reshaping by the MLC 410, the radiation beam can pass through the opening 413 and reach the treatment region. Figure 5A ​As shown, the treatment device 500 can include at least two main magnetic coils 501, at least two magnetic shielding coils 502, a cryostat 503 having a shaft, a target 504, a gap 506, an opening 507, a recess 508, a linac 509, an MLC 510, a shielding structure 511, a collimator 512, and a deflection unit 513. The at least two main magnetic coils 501, the at least two magnetic shielding coils 502, the cryostat 503, the target 504, the shaft 505, the gap 506, the opening 507, the recess 508, the MLC 510, and the collimator 512 can be similar to the at least two main magnetic coils 401, the at least two magnetic shielding coils 402, the cryostat 403, the target 404, the shaft 405, the gap 406, the opening 407, the recess 408, the MLC 410, and the collimator 412, the description of which is not repeated here.

[0121] Unlike the linac 409, the acceleration waveguide (tube) of the linac 509 can have an axis parallel to the shaft 505. Thus, the acceleration waveguide (tube) can provide a linear path for accelerating electrons along a beam path parallel to the shaft 505 (also referred to as “parallel beam pass”). The at least two main magnetic coils 501 and the at least two magnetic shielding coils 502 can generate a magnetic field parallel or substantially parallel to the shaft 505 (also referred to as “parallel magnetic field”). It should be appreciated that the parallel magnetic field can have minimal impact on the parallel beam pass. Thus, the linac 509 can help reduce the impact of the magnetic field generated by the MRI device on the electrons. Similarly, the acceleration waveguide (tube) of the linac 509 can be at least partially surrounded by the shielding structure 511. The shielding structure 511 can be continuously distributed along the direction of the shaft 505. In some embodiments, the shielding structure 511 can stretch along the direction of the shaft to cover both ends of the linac, which means that the shielding structure 511 can have a larger size along the direction of the shaft than the linac 509. The shielding structure 511 can be configured to further reduce the interference from the magnetic field generated by the MRI device.

[0122] The deflection unit 513 can be configured to deflect the accelerated electrons from the parallel beam path onto the target 504. In some embodiments, the deflected electrons can impact the target 504 perpendicularly, thus the deflection angle of the electrons can be 90 degrees or 270 degrees. In some embodiments, the deflection unit 513 can include one or more configured magnets for providing a deflection magnetic field to deflect the accelerated electrons.

[0123] As Figure 5AAs shown, both the linac 509 and the deflection unit 513 are disposed within the groove 508 between the opening 507 and the gap 506. In some embodiments, no magnetic shielding coils are disposed to "cover" the linac 509 and / or the deflection unit 513 along the radial direction of the cryostat 503. That is, there is no overlap between the axial position of the at least two magnetic shielding coils 502 and the axial position of the linac 509 and / or the deflection unit 513. Further, the cryostat 503 can have a continuous body (i.e., a body that provides continuous fluid communication) along the radial direction of the cryostat 503 that houses the at least two main magnetic coils 501 and the at least two magnetic shielding coils 502.

[0124] Figure 5B An upper portion of a cross-sectional view of an exemplary treatment device 500' viewed along the X direction is shown in accordance with some embodiments of the present application. As with the treatment device 500 described in Figure 5A In contrast to the treatment device 500 described in, at least a portion of the linac 509 of the treatment device 500' can be located outside of the groove 508 along the radial direction of the cryostat 503. As Figure 5B shown, the linac 509, the shielding structure 511, and the deflection unit 513 can at least partially protrude out of the opening 507 formed by the outer wall of the cryostat 503. In some embodiments, the linac 509 and the shielding structure 511 can be supported by or mounted to a gantry or drum (e.g., the gantry 306 or the drum 312) that is capable of rotating about the axis 505.

[0125] Figure 5C An upper portion of a cross-sectional view of another exemplary treatment device 500" viewed along the X direction is shown in accordance with some embodiments of the present application. As with the treatment device 500 described in Figure 5A In contrast to the treatment device 500 described in, the cryostat 503' of the treatment device 500" can have two separate cavities. As Figure 5C shown, the left and right cavities 503a and 503b can be independent of each other, and thus no fluid communication is established between them. The cryostat 503' can have two different inner walls for the left and right cavities 503a and 503b. Another opening 513 of the groove 508 can be formed between the two different inner walls. After reshaping by the MLC 510, the radiation beam can pass through the opening 513 and reach the treatment region.

[0126] Figure 5D An upper portion of a cross-sectional view of an exemplary treatment device 500"' viewed along the X direction is shown in accordance with some embodiments of the present application. As with the treatment device 500" described in Figure 5C In contrast to the treatment device 500" described in, at least a portion of the linac 509 of the treatment device 500"' can be located outside of the groove 508 along the radial direction of the cryostat 503'. AsFigure 5D As shown, the linac 509, the shielding structure 511, and the deflection unit 513 can at least partially protrude out of the opening 507 formed by the outer wall of the cryostat 503’. In some embodiments, the linac 509, the shielding structure 511, and the deflection unit 513 can be supported by or mounted to a gantry or a barrel (e.g., the gantry 306 or the barrel 312) that is capable of rotating around the axis 505.

[0127] It should be noted that the above description of the treatment device 500, 500’, 500”, or 500”’ is provided for illustrative purposes only and is not intended to limit the scope of the present application. Various changes and modifications can be made to the treatment device based on the description of the present application by one of ordinary skill in the art. For example, the collimator 512 and the MLC 510 can be integrated to form a single collimator. For another example, the neck shown in the cryostat 503 can not form a complete ring. Specifically, the neck can be a discrete arc connecting the left chamber and the right chamber of the cryostat 503. Thus, the neck can intermittently appear in the path of the radiation beam to generate the radiation beam when the linac 509 rotates around the axis 505.

[0128] Figure 6A An upper portion of a cross-sectional view of an exemplary treatment device 600 viewed along the X direction is shown in accordance with some embodiments of the present application. As shown, the treatment device 600 can include at least two main magnetic coils 601, at least two magnetic shielding coils 602, a cryostat 603 having an axis 605, a target 604, a first opening 607, a second opening 615, a recess 608, a linac 609, an MLC 610, a shielding structure 611, a collimator 612, and a deflection unit 613. The at least two main magnetic coils 601, the at least two magnetic shielding coils 602, the target 604, the axis 605, the first opening 607, the recess 608, the linac 609, the collimator 612, and the deflection unit 613 can be similar to the at least two main magnetic coils 501, the at least two magnetic shielding coils 502, the target 504, the axis 505, the opening 507, the recess 508, the linac 509, the collimator 512, and the deflection unit 513, which are not repeated here. Figure 6A

[0129] As compared to the MLC 510 shown in FIG. 6, the MLC 610 can be located at a position further away from the linac 609 along the radial direction, such that the MLC 610 can be closer to, for example, a treatment region to be irradiated. It should be noted that the closer the distance between the MLC and the treatment region, the more accurate the shape of the radiation beam irradiated on the treatment region can be controlled by the MLC. Figure 5A

[0130] ​​The cryostat 603 can have a recessed structure at the inner wall of the cryostat 603 to accommodate the MLC 610. Similar to the groove 608, the recessed structure can have a first opening 607 formed between the outer walls of the two chambers of the cryostat 603, the recessed structure can have a second opening 615 formed between the inner walls of the two chambers of the cryostat 603. The recessed structure can have a ring shape and can be coaxial with the groove 608. The recessed structure and the groove 608 can be separated by a neck portion of the cryostat 603. That is, the outermost surface of the neck portion forms the innermost boundary of the groove 608, and the innermost surface of the neck portion forms the outermost boundary of the recessed structure. The recessed structure can have a depth along the radial direction of the cryostat 603 that is greater than the height of the MLC 610 along the axis of the radiation beam. In some embodiments, one or more of the at least two main magnetic coils 601 (e.g., 601a) can be arranged around the recessed structure along the axis 605. The main magnetic coils 601a in the left / right chambers of the cryostat 603 and the remaining main magnetic coils can form a stepped structure. The main magnetic coils 601a can have a radius from the axis 605 that is greater than the radius of the remaining main magnetic coils from the axis 605. Further, a gap 606 can be formed between the main magnetic coils 601a, allowing the radiation beam to pass through. In some embodiments, no main magnetic coils are arranged around the groove along the axis 605, and thus, all of the main magnetic coils 601 can be arranged around the inner wall of the cryostat 603 and have the same radius as the axis 605.

[0131] Figure 6B An upper portion of a cross-sectional view of an exemplary treatment device 600’ viewed along the X direction is shown in accordance with some embodiments of the present application. As with the treatment device 600 described in the Figure 6A embodiments, at least a portion of the linear accelerator 609 of the treatment device 600’ can be located radially outside of the groove 608 of the cryostat 603. As shown, the linear accelerator 609, the shielding structure 611, and the deflection unit 613 can at least partially protrude out of the opening 607 formed by the outer wall of the cryostat 603. In some embodiments, the linear accelerator 609, the shielding structure 611, and the deflection unit 613 can be supported by or mounted to a gantry or drum (e.g., the gantry 306 or the drum 312) that is capable of rotating around the axis 605. Figure 6B

[0132] Figure 7A An upper portion of a cross-sectional view of another exemplary treatment device 600” viewed along the X direction is shown in accordance with some embodiments of the present application. As with the treatment device 600 described in the Figure 6A ​In comparison with the treatment device 600 described in the above, the cryostat 603' of the treatment device 600" can have two independent cavities. The concave structure of the cryostat 603' can be connected with the groove 608 to form a larger annular space around the axis 605. In this case, no part of the cryostat 603 is located in the path of the radiation beam.

[0133] In some embodiments, in order to achieve the synchronous rotation of the linear accelerator and the MLC, various mechanisms can be used. For example, in Figure 6A In the above, the sliding structure (e.g., a slide rail, not shown) can be installed on the MLC 610. When the linear accelerator 609 is rotated by the gantry or the drum as described above, the MLC 610 can be synchronously moved along the inner wall of the cryostat 603 by the sliding structure to keep fixed relative to the linear accelerator 609. The movement of the MLC 610 can be controlled according to the instructions generated by one or more processing engines 120. In addition, in Figure 7A In the above, the MLC 610 can be mechanically connected to the linear accelerator 609 by the rigid structure (e.g., two or more rods, one or more plates, not shown). In order to reduce the width of the groove 608 in the direction of the axis 605, the two or more rods can be arranged at different circumferential positions of the groove 608 relative to the linear accelerator 609. For example, the two or more rods can be located at the left and right sides of the linear accelerator 609 when viewed along the axis 605. It should be noted that the mechanism for achieving the synchronous rotation of the linear accelerator and the MLC is not limited to the above description, and any modification or adjustment can be made according to different scenarios. For example, in Figure 7A In the above, the MLC 610 can also be moved along the sliding structure to achieve the synchronous rotation with the linear accelerator 609.

[0134] Figure 7B An upper part of a cross-sectional view of an exemplary treatment device 600"' viewed in the X direction is shown according to some embodiments of the present application. In comparison with the treatment device 600" described in the above, Figure 7A In comparison with the treatment device 600" described in the above, at least a part of the linear accelerator 609 of the treatment device 600"' can be located outside the groove 608 in the radial direction of the cryostat 603'. As Figure 7B shown, the linear accelerator 609, the shielding structure 611 and the deflection unit 613 can at least partially protrude out of the opening 607 formed by the outer wall of the cryostat 603'. In some embodiments, the linear accelerator 609, the shielding structure 611 and the deflection unit 613 can be supported by or mounted to the gantry or the drum (e.g., the gantry 306 or the drum 312) which is capable of rotating around the axis 605.

[0135] It should be noted that the above description of the treatment device 600, 600', 600", or 600'" is provided for illustrative purposes only and is not intended to limit the scope of the present application. Various modifications and alterations can be made to the description of the present application by those skilled in the art. For example, the neck shown in the cryostat 603 can not form a complete ring. In particular, the neck can be a discrete arc connecting the left and right chambers of the cryostat 603. Thus, the neck can intermittently appear in the path of the radiation beam to produce the radiation beam as the linear accelerator 609 rotates about the axis 605.

[0136] As described elsewhere in this application, MRI devices and radiation therapy devices can interfere with and impair the proper operation of each other. By way of example only, the magnetic fields generated by the main magnet coil and the magnetic shield coil of an MRI device can interfere with the acceleration of the electron beam in the linear accelerator of a radiation therapy device. To prevent such interference, the above-described shielding structure can include at least a magnetic shield device to isolate the linear accelerator from the magnetic field. For brevity, the magnetic shield device should provide at least one passageway in the vicinity of the linear accelerator through which the magnetic field can more easily pass, such that the magnetic field can bypass the linear accelerator. In some embodiments, the magnetic shield device can include one or more magnetic shield structures made of a material having a high magnetic permeability and / or magnetic susceptibility. The one or more magnetic shield structures can include at least one magnetic shield plate or layer that is continuously distributed along the axial direction of the cryostat to provide a continuous passageway for the magnetic field to pass through. The one or more magnetic shield structures can surround or substantially surround the linear accelerator such that the magnetic field in the vicinity of the linear accelerator can be conducted through the one or more magnetic shield structures instead of the space in which the linear accelerator is located. As used herein, substantially surrounding can mean that one or more slots can be formed in the one or more magnetic shield structures, provided that there is at least one continuous path along the axis of the cryostat for the magnetic field to pass through. Further details regarding the configuration of the magnetic shield device can be described below.

[0137] Figure 8A A perspective view of an exemplary treatment device 800 according to some embodiments of the present application is shown.

[0138] As Figure 8A shown, the treatment device 800 can include a bore 801, an annular cryostat 803 having an axis 805, a recess 808, a linear accelerator 809, and a magnetic shield device. The cryostat 803, the axis 805, the recess 808, the linear accelerator 809 can be similar to the cryostat 403, 403', 503, 503', 603 or 603', the axis 405, 505, or 605, the recess 408, 508, or 608, the linear accelerator 409, 509, or 609, which are not described again here.

[0139] The magnetic shielding device may include at least two magnetic shielding structures, including, for example, magnetic shielding structure 811, magnetic shielding structure 831a, magnetic shielding structure 831b, etc. The linear accelerator 809 may be surrounded or substantially surrounded by the magnetic shielding structure 811. The magnetic shielding structure 811 may include a first plate located on one side of the linear accelerator 809 along the circumferential direction of the groove 808 and a second plate located on the opposite side of the linear accelerator 809 along the circumferential direction of the groove 808. The first and second plates may be symmetrical to each other with respect to the axis of the linear accelerator 809. The first and second plates may form a surrounding structure to surround and / or retain the linear accelerator 809. Each of the two plates may have a shape similar to the symbol "I," providing a continuous path along the axial direction (i.e., the direction of axis 805) of the cryostat 803 for the magnetic field to pass through. Because the two plates of the magnetic shielding structure 811 are made of a material with high magnetic susceptibility and / or permeability, the magnetic field can be conducted by the two plates and retained in the region formed between them, thereby achieving magnetic shielding of the linear accelerator 809. In some embodiments, each of the two plates may be arranged radially about axis 805, and at least one side of each of the two plates may point towards axis 805.

[0140] In some embodiments, the first plate and the second plate may be connected to each other on both sides of the linear accelerator 809 along the axial direction of the cryostat 803, thereby forming a closed loop around the linear accelerator 809. In some embodiments, the first plate and the second plate may be separated from each other on both sides of the linear accelerator 809 along the axial direction of the cryostat 803, thereby forming a semi-closed loop substantially around the linear accelerator 809. It should be noted that the configuration of the magnetic shielding structure 811 is not limited, and any other configuration (e.g., a hollow cylinder or other shapes with curved sides) may be used to achieve magnetic shielding.

[0141] Furthermore, the presence of the magnetic shielding structure 811 within the magnetic field of the MRI device may affect the magnetic field (e.g., causing distribution distortion and resulting in magnetic field inhomogeneity). To correct the magnetic field distortion caused by the magnetic shielding structure 811, similar magnetic shielding structures of the magnetic shielding device, including magnetic shielding structures 831a, 831b, etc., may also be placed within the recess 808. In some embodiments, all magnetic shielding structures may be identical to each other. For example, magnetic shielding structures 831a and 831b may be made of the same material and have the same structure as magnetic shielding structure 811. Magnetic shielding structures 811, 831a, 831b, etc., may be mounted on the gantry or roller (not shown) of the treatment device 800 to achieve synchronous rotation with the linear accelerator 809.

[0142] In some embodiments, the magnetic shielding structures 811, 831a, 831b, etc. can be placed at selected symmetrical circumferential positions around the axis 805. For example, all the magnetic shielding structures can be evenly distributed within the recess 808. Each magnetic shielding structure can correspond to an opposite or opposite counterpart. Each magnetic shielding structure and its counterpart can be symmetrical about the axis 805. As used herein, two magnetic shielding structures can be considered opposite or opposite if they are symmetrical about the axis 805.

[0143] Figure 8B A perspective view of an exemplary treatment device 800’ is shown in accordance with some embodiments of the present application. As compared to the treatment device 800 described in Figure 8A at least a portion of the linac 809 of the treatment device 800’ can be located radially outside of the recess 808 of the cryostat 803. As shown in Figure 8B the linac 809 and the magnetic shielding structures 811 surrounding the linac 809 can protrude out of the opening of the recess 808 formed by the outer wall of the cryostat 803. Similarly, the magnetic shielding structures 831a, 831b, etc. can also protrude out of the opening of the recess 808, thereby preserving the symmetry of the magnetic shielding structures with respect to the axis 805. In some embodiments, the linac 809 and all the magnetic shielding structures can be supported by or mounted to a gantry or drum (e.g., the gantry 306 or the drum 312) that is rotatable about the axis 805.

[0144] Figure 9A A cross-sectional view of the treatment device 800 viewed along the axial direction (i.e., the Z direction) of the cryostat is shown in accordance with some embodiments of the present application. The linac 809, the collimator 812, and the MLC 810 can be similar to the linac 409, 509, or 609, the collimator 412, 512, or 612, and the MLC 410, 510, or 610, and are not repeated here.

[0145] As shown in Figure 9A the magnetic shielding structures 811, 821, and 831a, 831b, 831c, 831d can be evenly distributed within the recess 808 and around the axis 805 of the bore 801. The distance between every two adjacent magnetic shielding structures can be the same. The magnetic shielding structure 821 can be the opposite or opposite counterpart of the magnetic shielding structure 811. The magnetic shielding structure 821 can be identical to the magnetic shielding structure 811 if the magnetic shielding structure 821 is rotated 180 degrees clockwise around the axis 805 to the position of the magnetic shielding structure 811. All the magnetic shielding structures can be fixed with respect to the linac 809, and thus can be rotated in synchronization with the linac 809.

[0146] Figure 9B A cross-sectional view of the therapy device 800’ viewed along the axial direction (i.e., Z direction) of the cryostat is shown in accordance with some embodiments of the present application. As Figure 8B indicated, at least a portion of the linac 809 of the therapy device 800’ can be located radially outside the groove 808 of the cryostat 803. Figure 9B

[0147] Figure 10A A cross-sectional view of the therapy device 800 viewed along the Y direction is shown in accordance with some embodiments of the present application.

[0148] Figure 10B A cross-sectional view of the therapy device 800’ viewed along the Y direction is shown in accordance with some embodiments of the present application.

[0149] It should be noted that the number of magnetic shielding structures in the magnetic shielding device is not limited. Any number of magnetic shielding structures can be used in the therapy device as long as the symmetry of the magnetic shielding structures is achieved. Figure 11A A cross-sectional view of an exemplary therapy device 1100 having two magnetic shielding structures viewed along the X direction is shown in accordance with some embodiments of the present application. As Figure 11A indicated, the therapy device 1100 can include at least two main magnetic coils 1101, at least two magnetic shielding coils 1102, a cryostat 1103 having an axis 1105, a groove 1108, a linac 1109, a first magnetic shielding structure 1111, a collimator 1112, a second magnetic shielding structure 1121, and a hole 1113. The at least two main magnetic coils 1101, the at least two magnetic shielding coils 1102, the cryostat 1103, the axis 1105, the groove 1108, the linac 1109, and the collimator 1112 can be similar to the at least two main magnetic coils 401, 501, or 601, the at least two magnetic shielding coils 402, 502, or 602, the cryostat 403, 403’, 503, 503’, 603, 603’, or 803, the axis 405, 505, 605, or 805, the groove 408, 508, 608, or 808, the linac 409, 509, 609, or 809, and the collimator 412, 512, 612, or 812, which are not repeated here.

[0150] ​The second magnetic shielding structure 1121 can be the opposite or opposite counterpart of the first magnetic shielding structure 1111 and can be configured to reduce field inhomogeneity caused by the presence of the first magnetic shielding structure 1111. The second magnetic shielding structure 1121 and the first magnetic shielding structure 1111 can form a symmetric structure within the magnetic field of the MRI apparatus. That is, the second magnetic shielding structure 1121 can be located within the recess 1108 and in the opposite position relative to the axis 1105 of the first magnetic shielding structure 1111. The second magnetic shielding structure 1121 can be made of the same material as the first magnetic shielding structure 1111 and have the same structure as the first magnetic shielding structure 1111. For example, if the second magnetic shielding structure 1121 is rotated 180 degrees around the axis 1105 to the position of the first magnetic shielding structure 1111, the second magnetic shielding structure 1121 can be identical to the first magnetic shielding structure 1111.

[0151] Figure 11B An exemplary treatment apparatus 1100' with two magnetic shielding structures viewed along the X direction is shown in accordance with some embodiments of the present application. As with the treatment apparatus 1100 described in Figure 11A At least a portion of the linac 1109 of the treatment apparatus 1100' can be located radially outside the recess 1108 of the cryostat 1103 as compared to the treatment apparatus 1100 described in Figure 11B As shown, the linac 1109, the first magnetic shielding structure 1111, and the second magnetic shielding structure 1121 can at least partially protrude out of the opening of the recess 1108 formed by the outer wall of the cryostat 1103. The first magnetic shielding structure 1111 and the second magnetic shielding structure 1121 can still be symmetric about the axis 1105. In some embodiments, the linac 1109, the first magnetic shielding structure 1111, and the second magnetic shielding structure 1121 can be supported by or mounted to a gantry or drum (e.g., the gantry 306 or the drum 312) that is capable of rotating about the axis 1105.

[0152] Figure 12A An upper portion of an exemplary treatment apparatus 1200 cross-sectional view viewed along the X axis direction is shown in accordance with some embodiments of the present application. As Figure 12AAs shown, the treatment device 1200 may include at least two main magnetic coils 1201, at least two magnetic shielding coils 1202, a cryothermal device 1203, a target 1204, a shaft 1205, a gap 1206, a groove 1208, a linear accelerator 1209, an MLC 1210, a magnetic shielding structure 1211, and a collimator 1212. At least two main magnetic coils 1201, at least two magnetic shielding coils 1202, a cryostat 1203, a target 1204, a shaft 1205, a gap 1206, a groove 1208, a linear accelerator 1209, an MLC 1210, and a collimator 1212 may be similar to at least two main magnetic coils 401, at least two magnetic shielding coils 402, a cryostat 403, 503, 603, 803, or 1103, a target 404, 504, or 604, a shaft 405, 505, 605, 805, or 1105, a gap 406, 506, or 606, a groove 408, 508, 608, 808, or 1108, a linear accelerator 409, 509, 609, 809, or 1109, and an MLC. 410, 510, 610 or 810, and collimators 412, 512, 612, 812 or 1112, and their descriptions will not be repeated here.

[0153] like Figure 12A As shown, the magnetic shielding structure 1211 may include a first side plate 1211a, a second side plate 1211b, an upper side plate 1211c, and a lower side plate 1211d. The first side plate 1211a and the second side plate 1211b may be placed on opposite sides of the linear accelerator 1209 along the axial direction of the cryostat 1203 (i.e., along the direction of axis 1205). The upper side plate 1211c and the lower side plate 1211d may be placed on opposite sides of the linear accelerator 1209 along the axial direction of the linear accelerator 1209. The first side plate 1211a, the second side plate 1211b, the upper side plate 1211c, and the lower side plate 1211d may form a closed loop around the linear accelerator 1209. If each plate is made of a material with high magnetic susceptibility and / or permeability, the magnetic field can bypass the linear accelerator 1209 and be conducted from one side of the cryostat 1203 to the other side of the cryostat 1203 along the axial direction of the cryostat 1203 by the upper plate 1211c and the lower plate 1211d (e.g., from left to right), thereby achieving magnetic shielding for the linear accelerator 1209. The lower plate 1211d may also be provided with at least one slot to allow the radiation beam generated by the linear accelerator 1209 to pass through.

[0154] Figure 12B The upper portion of a cross-sectional view of an exemplary treatment device 1200' viewed along the X direction according to some embodiments of this application is shown. Figure 12AAt least a portion of the linac 1209 of the treatment device 1200' can be located radially outside the recess 1208 of the cryostat 1203, in contrast to the treatment device 1200 described in Figure 12B As shown, the linac 1209 and the magnetic shielding structure 1211 can at least partially protrude out of the opening of the recess 1208 formed by the outer wall of the cryostat 1203. Specifically, the first side plate 1211a, the second side plate 1211b, and the upper side plate 1211c of the magnetic shielding structure 1211 can protrude out of the opening of the recess 1208. In some embodiments, the linac 1209 and the magnetic shielding structure 1211 can be supported by or mounted to a gantry or a barrel (e.g., the gantry 306 or the barrel 312) that is capable of rotating around the axis 1205.

[0155] Figure 12C An upper portion of a cross-sectional view of an exemplary treatment device 1200" viewed along the X direction is shown in accordance with some embodiments of the present application. In contrast to the magnetic shielding structure 1211 described in Figure 12A and the treatment device 1200' described in Figure 12B In contrast to the magnetic shielding structure 1211 of the treatment device 1200 described in and the treatment device 1200' described in the magnetic shielding structure 1211' of the treatment device 1200" can form a closed loop around the linac 1209, the collimator 1212, and the MLC 1210. As shown, Figure 12C the first side plate 1211a' and the second side plate 1211b' can extend at least along the radial direction from the innermost radial position of the MLC 1210 to the outermost radial position of the linac 1209. The lower side plate 1211d' can be located at the innermost side of the MLC 1210 and also provide at least one slot to allow the radiation beam generated by the linac 1209 to pass through. Thus, the magnetic shielding structure 1211' can provide magnetic shielding for the linac 1209 and the MLC 1210.

[0156] Figure 13A An upper portion of a cross-sectional view of an exemplary treatment device 1300 viewed along the X direction is shown in accordance with some embodiments of the present application. In contrast to the magnetic shielding structure 1211 described in Figure 12A In contrast to the side plates 1211a and 1211b of the magnetic shielding structure 1211 described in the side plates 1211a" and 1211b" of the magnetic shielding structure 1211" can both have slots. The slots can be of any shape, such as rectangular, elliptical, etc. It should be noted that the magnetic field can still be conducted by the upper side plate 1211c" and the lower side plate 1211d" provided that the slots are small enough to prevent the magnetic field from passing through the slots into the linac 1209.

[0157] Figure 13B An upper portion of a cross-sectional view of an exemplary treatment device 1300' viewed along the X direction is shown in accordance with some embodiments of the present application. In contrast to the magnetic shielding structure 1211 described in Figure 13AAt least a portion of the linac 1209 of the treatment device 1300’ can be located radially outside of the recess 1208 of the cryostat 1203, in contrast to the treatment device 1300 described in Figure 13B As shown, the linac 1209 and the magnetic shielding structure 1211” can at least partially protrude out of the opening of the recess 1208 formed by the outer wall of the cryostat 1203. Specifically, the first side plate 1211a”, the second side plate 1211b”, and the upper side plate 1211c” of the magnetic shielding structure 1211” can protrude out of the opening of the recess 1208. In some embodiments, the linac 1209 and the magnetic shielding structure 1211” can be supported by or mounted to a gantry or a barrel (e.g., the gantry 306 or the barrel 312) that is capable of rotating around the axis 1205.

[0158] Figure 13C An upper portion of a cross-sectional view of an exemplary treatment device 1300” viewed in the X direction is shown, according to some embodiments of the present application. The treatment device 1300” can include a hole 1301, a magnet 1302 (similar or identical to the “cryostat”), a linac 1309, and a magnetic shielding structure 1311”. The linac 1309, the hole 1301, and the magnet 1302 can be similar to the linac 409, 509, 609, 809, 1109, or 1209, the hole 301 or 801, and the magnet 302, which are not repeated here. Figure 13A Figure 13B In contrast to the treatment device 1300 described in Figure 13C As shown, the first side plate 1311a” and the second side plate 1311b” can extend at least radially from an innermost radial position of the MLC 1310 to an outermost radial position of the linac 1309. The lower side plate 1311d” can be located at the innermost side of the MLC 1310 and also provide at least one slot to allow the radiation beam generated by the linac 1309 to pass through.

[0159] Figure 14A A perspective view of an exemplary treatment device 1400 is shown, according to some embodiments of the present application. The treatment device 1400 can include a hole 1401, a magnet 1402 (similar or identical to the “cryostat”), a linac 1409, and a magnetic shielding device. The magnetic shielding device can include a first magnetic shielding layer 1421, a second magnetic shielding layer 1422, and at least two magnetic shielding septa (e.g., 1420a, 1420b, 1420c). The linac 1409, the hole 1401, and the magnet 1402 can be similar to the linac 409, 509, 609, 809, 1109, or 1209, the hole 301 or 801, and the magnet 302, which are not repeated here.

[0160] As shown, the first side plate 1411a” and the second side plate 1411b” can extend at least radially from an innermost radial position of the MLC 1410 to an outermost radial position of the linac 1409. The lower side plate 1411d” can be located at the innermost side of the MLC 1410 and also provide at least one slot to allow the radiation beam generated by the linac 1409 to pass through. Figure 14A ​As shown, the first magnetic shielding layer 1421 can be located between one chamber of the linear accelerator 1409 and the magnet 1402, and the second magnetic shielding layer 1422 can be located between the other chamber of the linear accelerator 1409 and the magnet 1402. The first magnetic shielding layer 1421 and the second magnetic shielding layer 1422 can have the same annular shape. The first magnetic shielding layer 1421 and the second magnetic shielding layer 1422 can be parallel to each other and coaxial with the aperture 1401. The outer diameter of the first magnetic shielding layer 1421 can be equal to or greater than the outer diameter of the magnet 1402. The inner diameter of the first magnetic shielding layer 1421 can be greater than or equal to the inner diameter of the magnet 1402. The difference between the outer and inner diameters of the ring can be greater than or equal to the longitudinal length of the linear accelerator 1409.

[0161] Each of at least two magnetic shielding partitions may be located between the first magnetic shielding layer 1421 and the second magnetic shielding layer 1422. Each of the at least two magnetic shielding partitions may connect the first magnetic shielding layer 1421 and the second magnetic shielding layer 1422. Every two adjacent magnetic shielding partitions (e.g., magnetic shielding partitions 1420e and 1420f) may form a magnetic shielding structure with a portion of the first magnetic shielding layer 1421 and a portion of the second magnetic shielding layer 1422. The linear accelerator 1409 may be located within one of the magnetic shielding structures. Each magnetic shielding structure may have opposite or opposite counterparts. Each magnetic shielding structure and its corresponding portion may be symmetrical about the axis of the aperture 1401.

[0162] At least two magnetic shielding partitions 1420 may be uniformly or non-uniformly distributed between the first magnetic shielding layer 1421 and the second magnetic shielding layer 1422. In some embodiments, the number of at least two magnetic shielding partitions 1420 may be a multiple of 2, forming an even number of magnetic shielding structures, thereby reducing field inhomogeneities caused by the presence of at least two magnetic shielding partitions 1420.

[0163] like Figure 14A As shown, the first magnetic shielding layer 1421, the second magnetic shielding layer 1422, and at least two magnetic shielding partitions can form a structure with... Figure 8AThe magnetic shielding structures described in the foregoing can be similar to the magnetic shielding structures described in the foregoing. For example, a portion of the first magnetic shielding layer 1421, a portion of the second magnetic shielding layer 1422, the magnetic shielding septum 1420f, and the magnetic shielding septum 1420e can form a magnetic shielding structure similar to the magnetic shielding layer 811. The magnetic shielding septum 1420f and the magnetic shielding septum 1420e can provide a continuous path along the axial direction of the magnet 1402 for the magnetic field to pass through. As another example, a portion of the first magnetic shielding layer 1421, a portion of the second magnetic shielding layer 1422, the magnetic shielding septum 1420a, and the magnetic shielding septum 1420b can form another magnetic shielding structure similar to the magnetic shielding layer 831a. As yet another example, a portion of the first magnetic shielding layer 1421, a portion of the second magnetic shielding layer 1422, the magnetic shielding septum 1420c, and the magnetic shielding septum 1420d can form another magnetic shielding structure similar to the magnetic shielding layer 831b.

[0164] Figure 14B A perspective view of an exemplary treatment device 1400’ is shown, in accordance with some embodiments of the present application. As compared to the treatment device 1400 described in the foregoing, at least a portion of the linac 1409 of the treatment device 1400’ can be located outside of a groove (not shown) along the radial direction of the magnet 1402. As shown in Figure 14A Figure 14B As shown, the linac 1409 and the magnetic shielding device can at least partially protrude out of the opening of the groove formed by the outer wall of the magnet 1402. In particular, the first magnetic shielding layer 1421, the second magnetic shielding layer 1422, and the at least two magnetic shielding septa (e.g., 1420a, 1420b, 1420c) can protrude out of the opening of the groove. In some embodiments, the linac 1409 and the magnetic shielding device can be supported by or mounted to a gantry or a barrel (e.g., the gantry 306 or the barrel 312) that is capable of rotating around the axis of the magnet 1402.

[0165] Figure 15A A perspective view of a treatment device 1500 is shown, in accordance with some embodiments of the present application. The treatment device 1500 can include a bore 1501, a linac 1509, and a magnetic shielding device. The magnetic shielding device can include at least two magnetic shielding septa (e.g., 1520a, 1520b, 1520c, 1520d, 1520e, 1520f), an inner magnetic shielding layer 1510, and an outer magnetic shielding layer 1530. The linac 1509 and the bore 1501 can be similar to the linac 809 and the bore 801, respectively, as shown in Figure 9A

[0166] As Figure 15A ​​As shown, the inner magnetic shielding layer 1510 and the outer magnetic shielding layer 1530 can be two hollow cylinders sharing a common axis. For example, when viewed along the axial direction of the hole 1501, the inner magnetic shielding layer 1510, the outer magnetic shielding layer 1530, and the hole 1501 can form concentric circles. The inner magnetic shielding layer 1510 and the outer magnetic shielding layer 1530 can be placed in a recess as described elsewhere in this application. The recess can be similar to recesses 408, 508, or 608 and can be configured to accommodate the linear accelerator 1509. The inner magnetic shielding layer 1510 can be located at the innermost side of the recess and have a smaller radius than the outer magnetic shielding layer 1530.

[0167] Each of at least two magnetic shielding septa (e.g., 1520a, 1520b, 1520c, 1520d, 1520e, 1520f) may be located between the inner magnetic shielding layer 1510 and the outer magnetic shielding layer 1530. For example, each of the at least two magnetic shielding septa may connect the outer surface of the inner magnetic shielding layer 1510 and the inner surface of the outer magnetic shielding layer 1530. The at least two magnetic shielding septa may be arranged radially around the aperture 1501. In some embodiments, each magnetic shielding septa may point towards the center of the aperture 1501. Every two adjacent magnetic shielding septa (e.g., magnetic shielding septa 1520a and magnetic shielding septa 1520b) may form a magnetic shielding structure with a portion of the inner magnetic shielding layer 1510 and a portion of the outer magnetic shielding layer 1530. The linear accelerator 1509 may be located within one of the magnetic shielding structures. Each magnetic shielding structure may have opposite or opposite counterparts. Each individual space and its counterpart may be symmetrical about the axis of the aperture 1501. The magnetic shielding structure formed by at least two magnetic shielding partitions can be the same or different. For example, at least two magnetic shielding partitions can be uniformly distributed between the inner magnetic shielding layer 1510 and the outer magnetic shielding layer 1530, thereby forming at least two uniform magnetic shielding structures.

[0168] like Figure 15A As shown, when the linear accelerator 1509 is located inside a magnetic shielding structure formed by a portion of an inner magnetic shielding layer 1510, a portion of an outer magnetic shielding layer 1530, a magnetic shielding partition 1520a, and a magnetic shielding partition 1520b, the magnetic field can be conducted by the inner magnetic shielding layer 1510, the outer magnetic shielding layer 1530, the magnetic shielding partition 1520a, and / or the magnetic shielding partition 1520b, and is aligned with the linear accelerator 1509 located therebetween, thereby achieving magnetic shielding for the linear accelerator 1509. In some embodiments, for transmitting a radiated beam emitted from the linear accelerator 1509, the inner magnetic shielding layer 1510 may have one or more openings in the transmission path of the radiated beam.

[0169] In some embodiments, two or more magnetic shielding layers similar to magnetic shielding layer 1421 may be added. Figure 15AThe magnetic shielding arrangement shown. For brevity, Figure 14A The first magnetic shielding layer 1421 and the second magnetic shielding layer 1422 described in the middle can be connected to the outer magnetic shielding layer 1530 at its outside and to the inner magnetic shielding layer 1510 at its inside. Each of the at least two magnetic shielding partitions can connect the first magnetic shielding layer 1421 and the second magnetic shielding layer 1422, forming a magnetic shielding structure, the cross-sectional view of which can be similar to Figure 12A The cross-sectional view shown in the middle. The diameter of the outer magnetic shielding layer 1530 can be equal to or smaller than the outer diameter of the magnet 1402. The diameter of the inner magnetic shielding layer 1510 can be equal to or greater than the inner diameter of the magnet 1402. The difference between the diameter of the outer magnetic shielding layer 1530 and the diameter of the inner magnetic shielding layer 1510 can be greater than or equal to the longitudinal length of the linac 1509.

[0170] Figure 15B A perspective view of a treatment device 1500’ is shown, in accordance with some embodiments of the present application. As compared to the treatment device 1500 described in the middle, Figure 15A As compared to the treatment device 1500 described in the middle, at least a portion of the linac 1509 of the treatment device 1500’ can be located outside of the groove (not shown) radially along the magnet 1502. As shown in the middle, Figure 15B The linac 1509 and the magnetic shielding device can at least partially protrude out of the groove formed by the outer wall of the magnet 1502, as shown in the middle. In particular, the outer magnetic shielding layer 1530 can have a larger radius than the radius of the magnet 1502. The at least two magnetic shielding partitions (e.g., 1520a, 1520b, 1520c, 1520d, 1520e, 1520f) can protrude out of the opening of the groove. In some embodiments, the linac 1509 and the magnetic shielding device can be supported by or mounted to a gantry or drum (e.g., the gantry 306 or the drum 312) that is capable of rotating around the axis of the magnet 1502.

[0171] Figure 15C A perspective view of a treatment device 1500” is shown, in accordance with some embodiments of the present application. As compared to the treatment device 1500’ described in the middle, Figure 15AThe magnetic shielding septa of the therapy device 1500” can have different configurations compared to the therapy device 1500 described in the background. Specifically, the magnetic shielding septa 1520a’ can have a shape of a strip or a rod. At least two parallel strips or rods can be used instead of the magnetic shielding septa 1520 having a plate shape. The at least two parallel strips or rods can connect the magnetic shielding layer 1521 between the linac 1509 and one chamber of the cryostat (not shown) and another magnetic shielding layer (not shown) between the linac 1509 and another chamber of the cryostat. It should be noted that the number of strips or rods at each circumferential location of the cryostat can be any suitable integer, such as 2, 3, 4, etc. The at least two parallel strips or rods can also provide a continuous passage along the axial direction of the bore 1501 for the magnetic field to pass through.

[0172] The magnetic shielding layer 1521 can also have at least two slots thereon. Each slot can have a rectangular, elliptical, etc. shape. Alternatively, the at least two slots can be directed towards the axis of the bore 1501. The at least two slots can help better dissipate the heat generated by the MRI device and / or the radiotherapy device. When slots are provided between the shield septa 1520a’ and the magnetic shielding septa 1520b’, the magnetic shielding structure can have a cross-section similar to that shown. Figure 13A

[0173] Figure 15D A perspective view of a therapy device 1500”’ according to some embodiments of the present application is shown. Compared to the therapy device 1500” described in the background, Figure 15C At least a portion of the linac 1509 of the therapy device 1500”’ can be located outside of a groove (not shown) in the radial direction of the magnet 1502’ compared to the therapy device 1500” described in the background. As shown in Figure 15D The linac 1509 and the magnetic shielding device can at least partially protrude out of the groove formed by the outer wall of the magnet 1502’. Specifically, the outer magnetic shielding layer 1530’ can have a larger radius than the magnet 1502’. The at least two magnetic shielding septa (e.g., 1520a’, 1520b’, 1520c’, 1520d’, 1520e’, 1520f’) can protrude out of the opening of the groove. In some embodiments, the linac 1509 and the magnetic shielding device can be supported by or mounted to a gantry or drum (e.g., the gantry 306 or the drum 312) that is capable of rotating around the axis of the magnet 1502’.

[0174] Figure 16A ​A perspective view of an exemplary therapeutic device 1600 according to some embodiments of this application is shown. The therapeutic device 1600 may include an aperture 1601, a linear accelerator 1609, and a magnetic shielding device. The magnetic shielding device may include at least two magnetic shielding partitions (e.g., 1620a, 1620b, 1620c, 1620d, 1620e, 1620f), an inner magnetic shielding layer 1610, and an outer magnetic shielding layer 1630. The inner magnetic shielding layer 1610, at least two magnetic shielding partitions (i.e., 1620a, 1620b, 1620c, 1620d, 1620e, 1620f), linear accelerator 1609, and aperture 1601 can be similar to the inner magnetic shielding layer 1510, at least two magnetic shielding partitions (i.e., 1520a, 1520b, 1520c, 1520d, 1520e, 1520f), linear accelerator 1509, and aperture 1501, and will not be described again here.

[0175] Unlike outer magnetic shielding layer 1530, outer magnetic shielding layer 1630 may not be continuous. For example... Figure 16A As shown, the outer magnetic shielding layer 1630 may have at least two slots at the contact surface between the outer magnetic shielding layer 1630 and at least two magnetic shielding partitions. The width of each slot in the circumferential direction may be equal to or greater than the thickness of the magnetic shielding partition. At least two slots can help to better dissipate heat generated by the MRI device and / or radiotherapy device. In addition, at least two slots can also be used for cable layout. In some embodiments, similar slots may also exist in the inner magnetic shielding layer 1610 for the same purpose.

[0176] Figure 16B A perspective view of a treatment device 1600' according to some embodiments of this application is shown. Figure 16A Compared to the treatment device 1600 described herein, at least a portion of the linear accelerator 1609 of the treatment device 1600' may be located radially outside the groove (not shown) of the magnet 1602. Figure 16B As shown, the linear accelerator 1609 and the magnetic shielding device can at least partially extend out of the groove formed by the outer wall of the magnet 1602. Specifically, the outer magnetic shielding layer 1630 can have a larger radius than the magnet 1602. At least two magnetic shielding baffles (e.g., 1620a, 1620b, 1620c, 1620d, 1620e, 1620f) can extend out from the opening of the groove. In some embodiments, the linear accelerator 1609 and the magnetic shielding device can be supported by or mounted to a frame or roller (e.g., frame 306 or roller 312) that is rotatable about the axis of the magnet 1602.

[0177] Having described the basic concepts, it is obvious to those of ordinary skill in the art after a reading of this application that the above-described embodiments of the application are merely illustrative and not restrictive. Modifications, improvements and changes can be suggested by persons skilled in the art and are to be incorporated into the spirit and scope of the application. Such modifications, improvements and changes are therefore intended to fall within the scope of the application as set forth in the claims.

[0178] Also, the use of "an" or "one" to describe elements, items or features can be understood as meaning one or more than one unless explicitly stated otherwise. Similarly, the use of "a" or "one" can be understood to convey the meaning specified individually to the several items, or the same meaning to all of the items. Also, the use of "one" or "another" to describe a feature or structure can be understood to convey that the feature or structure is either singular or more than one, as appropriate. The use of "another" therefore can be understood to convey a "second" or "third" such feature or structure, as appropriate.

[0179] Also, those skilled in the art will appreciate that the various aspects of the present application can be described in terms of a few preferred embodiments or examples, but that the application is not limited to the preferred embodiments or examples. Rather, the various aspects of the present application can be applied to any or all methods, machines, manufacture, compositions of matter, processes, operations, or items of manufacture where such aspects would be useful. Those skilled in the art will further appreciate that the technology taught herein can be embodied in a variety of forms, including, but not limited to, a computer program product, a process, a computer-substantiated system, or a combination of hardware and software components. Accordingly, the various aspects of the present application can be embodied in hardware and / or in software (including firmware, resident software, micro-code, etc.) that runs on hardware, and that works alone or in combination with other software.

[0180] In addition, unless explicitly stated otherwise, the process elements and sequence of processes described herein can be performed in any order other than the described order and / or the processes can be performed in parallel. Furthermore, examples of the terms "comprising", "including", containing", listed", "having" and the like are used herein to generally mean containing some examples of the specified element or elements but not excluding others. In some embodiments, these terms can mean "consisting essentially of. In some embodiments, these terms can mean "consisting of. Unless otherwise stated, the use of the negative "does not" to describe a process element should not be construed to -negative the existence of that element - but merely to indicate that more than one process element can exist. For example, the statement "a process does not include A" should not be construed to mean that the process excludes A, but rather that the process can or does not include A. In some embodiments, the use of the negative "does not" to describe a process element should be construed to mean that the process element does not exist. In some embodiments, the use of the negative "does not" to describe a process element should be construed to mean that the process element does not exist.

[0181] For the same reasons, it should be noted that, in order to simplify the presentation of the application and to help the understanding of one or more inventive embodiments, the preceding description of the embodiments of the application sometimes refers to a plurality of features belonging to one embodiment, figure or description of it. However, this presentation should not be interpreted in a way reflecting the intention of the application to claim a subject matter to be scanned requiring more features than those explicitly mentioned in each claim. On the contrary, the inventive subject matter should be provided with fewer features than the single embodiment described above.

[0182] Some embodiments use numerical values to describe components, quantities of attributes. It should be understood that such numerical values used in the description of embodiments are, in some examples, modified by the adjectives "about", "approximately", or "generally". Unless otherwise stated, "about", "approximately", or "generally" indicates that the described numerical value allows for a variation of ±20%. Accordingly, numerical values used in the specification and claims are approximations that can vary depending upon the desired characteristics of the individual embodiments. In some embodiments, numerical values used in the specification and claims are approximations that can vary depending upon the desired characteristics of the individual embodiments. In some embodiments, numerical values should be considered in the context of the number of significant digits used in the number and by applying common rounding techniques. Although the numerical ranges and parameters setting forth the broadest scope of the application in some embodiments are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values set forth in the specific examples are provided to be as precise as reasonably possible. However, some variations may

[0183] All patents, patent applications, publications, and other materials mentioned herein (e.g., treatises, books, specifications, publications, records, things, and / or the like) are hereby incorporated by reference in their entirety for all purposes, except to the extent that any such material is inconsistent with the express teachings of this document. In the event of inconsistent usages between this document and any such materials, the usage in this document should be considered more precise. In the event of inconsistent usages between this document and any such materials, the usage in this document should be considered more precise.

[0184] Finally, it should be understood that the embodiments described herein are meant as illustrations of the principles of the application. Other variations and modifications of the application can be made by persons of ordinary skill in the art without departing from the scope of the application. Therefore, nothing in this application should be construed as a limitation on the scope of the application, which is defined by the appended claims.

Claims

1. A radiation therapy system, comprising: A magnetic resonance imaging device, configured to acquire magnetic resonance imaging data of a region of interest; as well as A radiotherapy apparatus configured for radiotherapy of at least a portion of the region of interest, the radiotherapy apparatus comprising: A linear accelerator, configured to accelerate electrons in an electron beam to produce a photon beam for radiotherapy; and A first shielding structure is configured to provide magnetic shielding for at least one of the linear accelerator and one or more collimation assemblies, wherein... The first shielding structure is formed by a first magnetic shielding layer, a second magnetic shielding layer, and at least two first magnetic shielding partitions located between the first magnetic shielding layer and the second magnetic shielding layer, wherein the first magnetic shielding layer and the second magnetic shielding layer are parallel to each other and coaxial with the aperture of the radiotherapy device; and / or The first shielding structure is formed by an inner magnetic shielding layer, an outer magnetic shielding layer, and at least two first magnetic shielding partitions located between the inner magnetic shielding layer and the outer magnetic shielding layer, wherein the inner magnetic shielding layer has a smaller radius than the outer magnetic shielding layer.

2. The radiotherapy system according to claim 1, characterized in that, The linear accelerator is at least partially surrounded by the first shielding structure, and the at least two first magnetic shielding baffles are arranged radially around the aperture of the radiotherapy device.

3. The radiotherapy system according to claim 1, characterized in that, The radiotherapy device also includes: Target; and A beam deflection unit is configured to deflect the electrons from the electron beam onto the target to generate a photon beam for radiotherapy.

4. The radiotherapy system according to claim 1, characterized in that, The magnetic resonance imaging device includes: At least two main magnetic coils; At least two magnetically shielded coils; and A ring-shaped cryogenic thermostat, wherein at least two main magnetic coils and at least two magnetic shielding coils are arranged coaxially along the axis of the ring-shaped cryogenic thermostat, and the at least two magnetic shielding coils are arranged at a radius greater than that of the at least two main magnetic coils from the axis.

5. The radiotherapy system according to claim 4, characterized in that, The annular cryostat also includes: At least one outer wall and at least one inner wall coaxial with the shaft; and An annular groove located between the at least one outer wall and the at least one inner wall.

6. The radiotherapy system according to claim 5, characterized in that, The radiotherapy device also includes: At least one second shielding structure identical to the first shielding structure, wherein the first shielding structure and the at least one second shielding structure are respectively located at circumferential positions within the annular groove; The at least one second shielding structure includes more than two second shielding structures, and the first shielding structure and the at least one second shielding structure are evenly distributed within the annular groove.

7. The radiotherapy system according to claim 1, characterized in that, The outer magnetic shielding layer includes at least two slots, and at least one of the at least two slots is located at a position corresponding to one of the two first magnetic shielding partitions.

8. The radiotherapy system according to claim 5, characterized in that, The annular groove has an opening formed on at least one outer wall, and the linear accelerator is at least partially located within the annular groove of the annular cryostat.

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