Magnetic resonance guided radiotherapy system and method

Abstract

The embodiment of the invention provides a magnetic resonance guided radiotherapy system and method. The method comprises the following steps: acquiring a first navigation signal and a second navigation signal acquired by magnetic resonance equipment in magnetic resonance scanning of a target object, the first navigation signal being acquired by the magnetic resonance equipment at a first time before radiotherapy ray emission, and the second navigation signal being acquired by the magnetic resonance equipment at a second time before radiotherapy ray emission; the second navigation signal is acquired by the magnetic resonance equipment at a second time after emission of radiotherapy rays; based on the first navigation signal and the second navigation signal, determining whether a first motion amplitude of the target object from the first time to the second time is greater than a threshold value; and determining whether emission of radiotherapy rays needs to be stopped based on a determination result of whether the first motion amplitude is greater than a threshold.

Description

Technical Field

[0001] This specification relates to the field of medical technology, and particularly to a magnetic resonance guided radiotherapy system and method. Background Art

[0002] Magnetic resonance guided radiotherapy has great clinical value in radiotherapy for tumors throughout the body, especially for soft tissue tumors. An integrated magnetic resonance guided radiotherapy device can, during treatment, detect in real time the target area (which can also be referred to as the region of interest) that needs to receive radiotherapy through magnetic resonance imaging (MRI), distinguish tumors from normal tissues, and greatly improve the accuracy of radiotherapy. Real-time imaging based on MRI plays a very crucial role in magnetic resonance guided radiotherapy devices. Real-time imaging can timely capture the position changes of tumor tissues and dynamically adjust the radiotherapy plan to achieve precise radiotherapy for tissues.

[0003] Therefore, there is a need to provide an efficient and accurate magnetic resonance guided radiotherapy system and method. Summary of the Invention

[0004] One embodiment of this specification provides a magnetic resonance guided radiotherapy method. The method includes: obtaining a first navigation signal and a second navigation signal collected by a magnetic resonance device during a magnetic resonance scan of a target object, where the first navigation signal is collected by the magnetic resonance device at a first time before radiotherapy rays are emitted, and the second navigation signal is collected by the magnetic resonance device at a second time after radiotherapy rays are emitted; determining, based on the first navigation signal and the second navigation signal, whether a first movement amplitude of the target object from the first time to the second time is greater than a threshold; and determining whether to stop emitting radiotherapy rays based on a determination result of whether the first movement amplitude is greater than the threshold.

[0005] One embodiment of this specification provides a magnetic resonance guided radiotherapy system. The system includes an obtaining module configured to obtain a first navigation signal and a second navigation signal collected by a magnetic resonance device during a magnetic resonance scan of a target object, where the first navigation signal is collected by the magnetic resonance device at a first time before radiotherapy rays are emitted, and the second navigation signal is collected by the magnetic resonance device at a second time after radiotherapy rays are emitted; a first determination module configured to determine, based on the first navigation signal and the second navigation signal, whether a first movement amplitude of the target object from the first time to the second time is greater than a threshold; and a second determination module configured to determine whether to stop emitting the radiotherapy rays based on a determination result of whether the first movement amplitude is greater than the threshold.

[0006] One embodiment of this specification provides a magnetic resonance-guided radiotherapy system, which includes at least one storage device for storing computer instructions; and at least one processor for executing the computer instructions to implement the magnetic resonance-guided radiotherapy method.

[0007] Some additional features of this application can be described below. Through the study of the following description and the corresponding drawings, or the understanding of the production or operation of the embodiments, some additional features of this application are obvious to those skilled in the art. The features of this application can be realized and obtained by practicing or using various aspects of the methods, means, and combinations described in the following detailed examples. Brief Description of the Drawings

[0008] This specification will further illustrate by way of exemplary embodiments, which will be described in detail through the drawings. These embodiments are not restrictive. In these embodiments, the same numbers represent the same structures, where:

[0009] Figure 1 is a schematic diagram of an application scenario of an exemplary magnetic resonance-guided radiotherapy system shown in some embodiments of this specification;

[0010] Figure 2 is a schematic diagram of an exemplary magnetic resonance-guided radiotherapy system shown in some embodiments of this specification;

[0011] Figure 3 is a schematic diagram of an exemplary process for generating real-time magnetic resonance images of a scanned object shown in some embodiments of this specification;

[0012] Figure 4 is a schematic diagram of an exemplary MRI pulse sequence for performing an MRI scan of a scanned object shown in some embodiments of this specification;

[0013] Figure 5 is for determining a time factor according to some embodiments of this specification of an exemplary process schematic diagram;

[0014] Figure 6 is a schematic diagram of an exemplary process for determining the spatial factor Uj shown in some embodiments of this specification;

[0015] Figure 7 is a schematic diagram of an exemplary process for generating real-time magnetic resonance images of a scanned object shown in some embodiments of this specification;

[0016] Figure 8 is a schematic diagram of an exemplary process for generating real-time magnetic resonance images of a scanned object shown in some embodiments of this specification;

[0017] Figure 9 It is a schematic diagram of an exemplary process for generating real-time magnetic resonance images of a scanned object as shown in some embodiments of this specification;

[0018] Figure 10 It is a schematic diagram of an exemplary process for magnetic resonance-guided radiotherapy as shown in some embodiments of this specification;

[0019] Figure 11 It is a schematic diagram of an exemplary MRI pulse sequence for performing MRI scans of a target object as shown in some embodiments of this specification;

[0020] Figure 12 It is a schematic diagram of an exemplary process for generating a first magnetic resonance image during magnetic resonance-guided radiotherapy as shown in some embodiments of this specification;

[0021] Figure 13 It is a schematic diagram of an exemplary process for generating a second magnetic resonance image during magnetic resonance-guided radiotherapy as shown in some embodiments of this specification;

[0022] Figure 14 It is a schematic diagram of an exemplary process for generating a third magnetic resonance image during magnetic resonance-guided radiotherapy as shown in some embodiments of this specification;

[0023] Figure 15 It is a schematic diagram for magnetic resonance-guided radiotherapy as shown in some embodiments of this specification. Detailed implementation manners

[0024] To more clearly illustrate the technical solutions of the embodiments of this specification, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some examples or embodiments of this specification. For those of ordinary skill in the art, without creative efforts, this specification can also be applied to other similar scenarios based on these drawings. Unless obvious from the language context or otherwise stated, the same reference numerals in the figures represent the same structure or operation.

[0025] It should be understood that the "system", "device", "unit" and / or "module" used herein is a method for distinguishing different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the said words can be replaced by other expressions.

[0026] As shown in this specification and the claims, unless the context clearly indicates otherwise, words such as "a", "an", "one", and / or "the" are not specifically singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. A method or device may also include other steps or elements.

[0027] Flowcharts are used in this specification to illustrate the operations performed by the system according to the embodiments of this specification. It should be understood that the operations before or after do not necessarily need to be executed precisely in sequence. On the contrary, the steps can be processed in reverse order or simultaneously. At the same time, other operations can also be added to these processes, or one or more steps can be removed from these processes.

[0028] MRI is widely used in radiotherapy guidance. To meet the requirements of radiotherapy guidance, MRI needs to have a certain degree of real-time performance to capture the position changes of tumor tissues in a timely manner and dynamically adjust the radiotherapy plan to achieve precise radiotherapy for tissues. In recent years, some spatiotemporal imaging with partially separable functions techniques have been proposed to achieve accelerated imaging. It makes full use of the low-rank characteristics in dynamic magnetic resonance images and transforms the reconstruction process of dynamic MRI into a process of separately solving the spatial basis and the temporal basis.

[0029] This application proposes a magnetic resonance-guided radiotherapy technology based on spatiotemporal imaging with partially separable functions to improve the real-time performance of MRI during the radiotherapy guidance process. In some embodiments, this application uses additional motion detection devices (such as optical cameras, radars, etc.) to detect the motion of the target object. In some embodiments, this application acquires navigation signals based on spatiotemporal imaging with partially separable functions and detects the motion of the target object based on the navigation signals, thereby improving the accuracy and timeliness of motion detection and further improving the accuracy of radiotherapy guidance.

[0030] The real-time MRI technology used in this application refers to a technology that can generate magnetic resonance images (i.e., real-time magnetic resonance images) with a short delay. For example, magnetic resonance images can be generated before the completion of MRI scanning. That is to say, during the MRI scanning process, real-time magnetic resonance images can be generated based on the already acquired MRI data while continuously acquiring new MRI data. Another example is that the time delay between the acquisition of MRI signals and the generation of corresponding magnetic resonance images based on the acquired MRI signals can be shorter than a certain threshold (such as 30 milliseconds, 40 milliseconds, 50 milliseconds, 1 second, 2 seconds). The magnetic resonance images obtained using the real-time MRI technology disclosed in this application can be called real-time magnetic resonance images.

[0031] Figure 1 It is a schematic diagram of the application scenario of the exemplary magnetic resonance-guided radiotherapy system 100 shown in some embodiments of the present application. As shown in the figure, the magnetic resonance-guided radiotherapy system 100 may include a medical device 110, a network 120, a terminal 130, a processing device 140, and a storage device 150. The components of the magnetic resonance-guided radiotherapy system 100 can be connected in various ways. For example, as Figure 1 shown, the medical device 110 can be connected to the processing device 140 through the network 120. Another example is that the medical device 110 can be directly connected to the processing device 140 (as shown by the bidirectional arrow in the dashed line connecting the medical device 110 and the processing device 140). Still another example is that the storage device 150 can be directly or through the network 120 connected to the processing device 140. Still another example is that the terminal devices (e.g., 131, 132, 133, etc.) can be directly connected to the processing device 140 (as shown by the bidirectional arrow in the dashed line connecting the terminal 130 and the processing device 140) or through the network 120.

[0032] The medical device 110 may include an MRI scanner 111 and a radiotherapy device 112. The MRI scanner 111 may be configured to scan an object (or a part of the object) to obtain image data, such as an MRI signal (also referred to as an MR signal) associated with the object. For example, the MRI scanner 111 may obtain a plurality of MRI signals by applying an MRI pulse sequence to the object. In the present application, "object" and "body" may be used interchangeably. Merely by way of example, the body may include a patient, an artificial object, etc. Another example is that the body may include a specific part of a patient, an organ and / or tissue. For example, the body may include the head, brain, neck, body, shoulder, arm, chest, heart, stomach, blood vessel, soft tissue, knee, foot, etc., or any combination thereof.

[0033] In some embodiments, the MRI scanner 111 may be configured to guide the radiotherapy device 112 to perform radiotherapy on an object. The MRI scanner 111 may be configured to obtain image data of the object before radiotherapy, during radiotherapy, and / or after radiotherapy. In some embodiments, the MRI scanner 111 may be configured to obtain real-time image data of the target object before and during radiotherapy. The real-time image data can be used to track the movement of the target region (which can also be referred to as the region of interest) that needs to receive radiotherapy and / or one or more organs at risk near the target region (e.g., physiological movement, rigid movement, etc.), so that the implementation of radiotherapy can be adjusted to adapt to the movement of the target object.

[0034] In some embodiments, the radiotherapy device 112 can be used to emit therapeutic rays to a target area of an object to perform radiotherapy on the target area. In some embodiments, the radiotherapy device 112 can include a Linear Accelerator (Linac), an X-ray therapy machine, etc.

[0035] The network 120 can include any suitable network that facilitates the exchange of information and / or data of the magnetic resonance-guided radiotherapy system 100. In some embodiments, one or more components of the magnetic resonance-guided radiotherapy system 100 (e.g., the medical device 110, the terminal 130, the processing device 140, or the storage device 150) can transmit information and / or data to one or more other components of the magnetic resonance-guided radiotherapy system 100 via the network 120. For example, the processing device 140 can obtain the signal of the RF pulse from the MRI scanner 111 via the network 120. In some embodiments, the network 120 can be a wired network, a wireless network, or any combination thereof.

[0036] The terminal 130 includes a mobile device 131, a tablet computer 132, a laptop computer 133, etc., or any combination thereof. In some embodiments, the mobile device 131 can include a smart home device, a wearable device, a smart mobile device, a virtual reality device, an augmented reality device, etc., or any combination thereof. In some embodiments, the terminal 130 can remotely operate the medical device 110 and / or the processing device 140. In some embodiments, the terminal 130 can operate the medical device 110 and / or the processing device 140 through a wireless connection. In some embodiments, the terminal 130 can receive information and / or instructions input by a user and send the received information and / or instructions to the medical device 110 or the processing device 140 via the network 120. In some embodiments, the terminal 130 can receive data and / or information from the processing device 140. In some embodiments, the terminal 130 can be a part of the processing device 140. In some embodiments, the terminal 130 can be omitted.

[0037] The processing device 140 can process the data and / or information obtained from the medical device 110, the terminal 130, and / or the storage device 150. For example, after the radiotherapy ray is emitted, the processing device 140 can, based on the signal collected by the MRI scanner 111, determine in real time whether to stop emitting the ray and generate a magnetic resonance image in real time. In some embodiments, the processing device 140 can be a single server or a server group. The server group can be centralized or distributed. In some embodiments, the processing device 140 can be local or remote.

[0038] The storage device 150 may store data and / or instructions. In some embodiments, the storage device 150 may store data obtained from the medical device 110, the terminal 130, and / or the processing device 140. For example, the storage device 150 may store real-time magnetic resonance images. In some embodiments, the storage device 150 may store data and / or instructions that the processing device 140 may execute or use to execute the exemplary methods described in this application. In some embodiments, the storage device 150 may be connected to the network 120 to communicate with one or more components of the magnetic resonance-guided radiotherapy system 100 (e.g., the medical device 110, the processing device 140, the terminal 130, etc.). One or more components of the magnetic resonance-guided radiotherapy system 100 may access the data or instructions stored in the storage device 150 via the network 120. In some embodiments, the storage device 150 may be directly connected to or communicate with one or more components of the magnetic resonance-guided radiotherapy system 100 (e.g., the medical device 110, the processing device 140, the terminal 130, etc.). In some embodiments, the storage device 150 may be part of the processing device 140.

[0039] It should be noted that the application scenario 100 is provided for illustrative purposes only and is not intended to limit the scope of this specification. Those of ordinary skill in the art can make various modifications or changes according to the description of this specification. For example, the application scenario 100 may further include an input device and / or an output device. Also, for example, the application scenario 100 may implement similar or different functions on other devices. However, these changes and modifications will not deviate from the scope of this specification.

[0040] Figure 2 is a schematic diagram of an exemplary magnetic resonance-guided radiotherapy system 200 shown according to some embodiments of this specification.

[0041] As Figure 2 shown, in some embodiments, the magnetic resonance-guided radiotherapy system 200 may include an acquisition module 201, a first determination module 202, a generation module 203, a second determination module 204, and a third determination module 205. In some embodiments, the functions corresponding to the magnetic resonance-guided radiotherapy system 200 may be executed by the processing device 140. For example, the acquisition module 201, the first determination module 202, the generation module 203, the second determination module 204, and the third determination module 205 may be modules in the processing device 140.

[0042] The acquisition module 201 is configured to acquire relevant information of the magnetic resonance-guided radiotherapy system 100. For example, the acquisition module 201 can acquire the pre-radiotherapy MRI signal, which is acquired during the first imaging stage of the MRI scan of the scanned object. As another example, the acquisition module 201 can acquire the during-radiotherapy MRI signal, which is acquired during the second imaging stage after the first imaging stage. For the relevant descriptions of acquiring the pre-radiotherapy MRI signal and the during-radiotherapy MRI signal, reference can be made to Figure 3 Steps 301 and 302 in it, which will not be elaborated here. As another example, the acquisition module 201 can acquire the first navigation signal and the second navigation signal acquired by the magnetic resonance device during the magnetic resonance scan of the target object. The first navigation signal is acquired by the magnetic resonance device at the first time before the radiotherapy ray is emitted. The second navigation signal is acquired by the magnetic resonance device at the second time after the radiotherapy ray is emitted. For the relevant descriptions of acquiring the first navigation signal and the second navigation signal, reference can be made to Figure 10 Steps 1001 and 1002 in it, which will not be elaborated here.

[0043] In some embodiments, the first determination module 202 is configured to determine an initial time factor and an initial space factor based on the pre-radiotherapy MRI signal. For the relevant descriptions of determining the initial time factor and the initial space factor, reference can be made to Figure 3 Step 303 in it, Figure 12 Step 1202 in it, Figure 13 Step 1302 in it, or Figure 14 Step 1402 in it, which will not be elaborated here. The first determination module 202 is configured to determine multiple time factors or / and multiple updated space factors. For the relevant descriptions of determining multiple time factors or / and multiple updated space factors, reference can be made to Figure 3 Step 304 in it, which will not be elaborated here.

[0044] In some embodiments, the generation module 203 is configured to generate a magnetic resonance image of the target object. For example, the generation module 203 is configured to generate multiple real-time magnetic resonance images within the second imaging stage. For the relevant descriptions of generating multiple real-time magnetic resonance images within the second imaging stage, reference can be made to Figure 3 Step 305 in it, which will not be elaborated here. In some embodiments, the generation module 203 is configured to generate multiple magnetic resonance images during the MRI scan (for example, Figure 12 The first magnetic resonance image in it, Figure 13 The second magnetic resonance image in it, Figure 14 The third magnetic resonance image in it). For the relevant descriptions of generating the first magnetic resonance image, the second magnetic resonance image, and the third magnetic resonance image, reference can be made to Figures 12 - 14 , which will not be elaborated here.

[0045] In some embodiments, the second determination module 202 is configured to determine whether a first movement amplitude of the target object from a first time to a second time is greater than a threshold value based on the first navigation signal and the second navigation signal. For the relevant description of determining whether the first movement amplitude of the target object from the first time to the second time is greater than the threshold value, reference may be made to Figure 10 step 1003 in it, which will not be elaborated here.

[0046] In some embodiments, the second determination module 203 is configured to determine whether to stop emitting the radiotherapy ray based on the determination result of whether the first movement amplitude is greater than the threshold value. For the relevant description of determining whether to stop emitting the radiotherapy ray, reference may be made to Figure 10 step 1004 in it, which will not be elaborated here.

[0047] It should be understood that Figure 2 the system and its modules shown can be implemented in various ways. For example, in some embodiments, the system and its modules can be implemented by hardware, software, or a combination of software and hardware.

[0048] It should be noted that the above description of the system and its modules is only for convenience of description and as an illustration, and does not limit this specification to the scope of the exemplified embodiments. It can be understood that for those skilled in the art, after understanding the principle of the system, they may, without departing from this principle, make any combination of the various modules, or form a subsystem and connect it to other modules. For example, in some embodiments, Figure 2 the above modules disclosed in it can be different modules in a system, or a module can implement the functions of two or more of the above modules. For example, the various modules can share a storage module, or each module can have its own storage module respectively. Such deformations are all within the protection scope of this specification.

[0049] Figure 3 is a schematic diagram of an exemplary process for generating real-time magnetic resonance images of a scanned object according to some embodiments of this specification. In some embodiments, one or more steps of process 300 can be implemented in Figure 1 the application scenario 100 shown or executed by the Figure 2 MRI system 200 shown. For example, process 300 can be executed by a module in the processing device 140.

[0050] As described in the present application, the scanning object can be biological or non-biological. For example, the scanning object can include patients, artificial objects, etc. As another example, the scanning object can include specific parts, organs, tissues, and / or physical points of a patient. By way of example only, the scanning object can include the head, brain, neck, body, shoulders, arms, chest, heart, stomach, blood vessels, soft tissues, knees, feet, etc., or combinations thereof.

[0051] As previously described, a real-time magnetic resonance image refers to a magnetic resonance image obtained using real-time imaging techniques. For example, a real-time magnetic resonance image can be generated based on the acquired data while the MRI scan is still being performed. As another example, the time delay between the generation of the real-time magnetic resonance image and the acquisition of the corresponding MRI signal can be shorter than a certain threshold. In some embodiments, process 300 can be executed during the radiotherapy of the scanning object to generate a real-time magnetic resonance image of the scanning object, so as to track the movement of the internal organs of the scanning object and guide radiotherapy. Specifically, before radiotherapy is performed, the processing device 140 can instruct a magnetic resonance device (such as Figure 1 the MRI scanner 111 therein) to start an MRI scan of the target object. The MRI scan will continue throughout the radiotherapy process to monitor the state of the target object in real time. The MRI scan of the target object can include a first imaging stage and a second imaging stage. The first imaging stage is the imaging stage before the radiotherapy device 112 emits radiotherapy rays (i.e., before radiotherapy starts). The second imaging stage is the imaging stage after the radiotherapy device 112 emits radiotherapy rays (i.e., after radiotherapy starts).

[0052] As Figure 3 shown, process 300 can include the following steps.

[0053] Step 301, obtain pre-radiotherapy MRI signals, which are acquired during the first imaging stage of the MRI scan of the scanning object. In some embodiments, step 301 can be executed by the processing device 140 or the acquisition module 201.

[0054] Step 302, obtain during-radiotherapy MRI signals, which are acquired during the second imaging stage after the first imaging stage. In some embodiments, step 302 can be executed by the processing device 140 or the acquisition module 201.

[0055] In some embodiments, the MRI scan of the scanning object can include a first imaging stage and a second imaging stage after the first imaging stage. The first imaging stage can be regarded as a training stage or a preparation stage for collecting basic data, which can serve as the basis for real-time imaging in the second imaging stage. The basic data can include data determined based on the pre-radiotherapy MRI signals, such as an initial time factor (referred to as ), conversion coefficients and initial spatial factors (called U0).

[0056] In some embodiments, the second imaging stage may include a plurality of second imaging sub-stages. Each second imaging sub-stage may be considered as a real-time imaging stage for collecting real-time image data (data determined based on the MRI signal during radiotherapy collected in the second imaging sub-stage), which may be used to generate a real-time image corresponding to the second imaging sub-stage. For example, the processing device 140 may obtain the MRI signal during radiotherapy (M1, M2, ..., M n ), where each M represents an MRI signal collected during radiotherapy in a second imaging sub-stage, the subscript of M (i.e., 1 to n) represents the number of the second imaging sub-stage, and n represents the number of the second imaging sub-stage. n ) in the time T i Acquisition of MRI signal M during radiotherapy i , where each T represents a time in the time series. T can be a short time period (e.g., 20 milliseconds, 100 milliseconds, 150 milliseconds, etc.), and each time T corresponds to a second imaging substage described in step 302, that is, the MRI signal M during radiotherapy can be acquired in a second imaging substage, i can represent any one of the subscripts of T and M (i.e., 1 to n), i can be an integer greater than 0 and less than or equal to n, and n can be an integer greater than 1.

[0057] In some embodiments, the basic data may be determined before the second imaging stage. For example, there may be a time interval between the first imaging stage and the second imaging stage for determining the basic data based on the pre-radiotherapy MRI signal. Alternatively, the second imaging stage may start immediately after the first imaging stage, i.e., there is no time interval between the first imaging stage and the second imaging stage. In this case, the basic data may be determined in the second imaging stage, i.e., the basic data is determined while the MRI signal during radiotherapy is being acquired.

[0058] In some embodiments, the durations of the first imaging phase and the second imaging sub-phase can be manually set by a user (e.g., an engineer) based on experience, or default set by the application scenario 100 of the MRI system. Optionally, the durations of the first imaging phase and the second imaging phase can be determined by the processing device 140 according to actual needs (e.g., requirements for the total scan time, imaging quality, etc.). Merely by way of example, the first imaging phase can last for 30 seconds, 40 seconds, 60 seconds, etc., and the second imaging sub-phase can last for, for example, 20 milliseconds, 100 milliseconds, 150 milliseconds, etc. In some embodiments, the second imaging phase can be much shorter than the first imaging phase. For example, the first imaging phase can be greater than 60 seconds while the second imaging sub-phase can be less than 1 second. In this case, sufficient and accurate basic data can be acquired in the first imaging phase, and real-time imaging can be achieved in the second imaging phase.

[0059] In some embodiments, during an MRI scan, the MRI device can apply an MRI pulse sequence to a scan object and acquire MRI signals from the scan object. The MRI signals acquired in the first imaging phase can be referred to as pre-radiotherapy MRI signals, and the MRI signals acquired in the second imaging phase can be referred to as during-radiotherapy MRI signals. The MRI pulse sequence can be any type of MRI pulse sequence, such as a spin echo sequence, a gradient echo sequence, a diffusion sequence, an inversion recovery sequence, etc. In some embodiments, the processing device 140 can acquire the pre-radiotherapy MRI signals and the during-radiotherapy MRI signals from an MRI scanner or a storage device used to store the pre-radiotherapy MRI signals and the during-radiotherapy MRI signals.

[0060] In some embodiments, the processing device 140 can acquire the pre-radiotherapy MRI signals and the during-radiotherapy MRI signals from an MRI scanner used to perform the MRI scan of the scan object or a storage device that stores the pre-radiotherapy MRI signals and the during-radiotherapy MRI signals.

[0061] In some embodiments, the pre-radiotherapy MRI signals can include pre-radiotherapy navigation signals and pre-radiotherapy imaging signals, and the during-radiotherapy MRI signals can include during-radiotherapy navigation signals. In some embodiments, the during-radiotherapy MRI signals can further include during-radiotherapy imaging signals.

[0062] The navigation signal, which can also be referred to as an auxiliary signal, includes high temporal resolution data related to at least one temporal variation dimension of the scanned object. The at least one temporal variation dimension can include any dimension reflecting the characteristics or dynamic information of the scanned object that changes over time. In some embodiments, the at least one temporal variation dimension of the scanned object can include a dimension related to elapsed time. In some embodiments, the at least one temporal variation dimension of the scanned object can include one or more dimensions related to other information, such as cardiac motion, respiratory motion, T1 relaxation, T2 relaxation, chemical exchange saturation transfer (CEST), contrast agent dynamics, T1ρ contrast, molecular diffusion, etc.

[0063] In some embodiments, the pre-radiotherapy navigation signal and the in-radiotherapy navigation signal can correspond to the same subset of the k-space (e.g., the k-space includes one or more k-space lines), which can be acquired by repeatedly sampling the subset of the k-space at a high sampling frequency. For example, the pre-radiotherapy navigation signal and the in-radiotherapy navigation signal can correspond to the same k-space line in the k-space, and can be obtained by repeatedly sampling the k-space line using a high sampling frequency. As used herein, a high sampling frequency refers to a sampling frequency higher than a threshold frequency. The threshold frequency can be a default value, or manually determined by the user, or determined by the processing device 140 based on data analysis. For example, the threshold frequency can be determined according to at least one temporal variation dimension to be analyzed. Merely as an example, the temporal variation dimension can be related to the respiratory motion of the scanned object, and the respiratory cycle of the scanned object is close to 0.75 seconds. To capture the dynamic information related to the respiratory motion of the scanned object, the sampling frequency may need to be greater than the threshold frequency of 1 / 0.75 Hertz (Hz). As another example, the threshold frequency can be determined according to actual requirements (e.g., accuracy requirements), experience, data models, etc.

[0064] The imaging signal can include high spatial resolution data related to at least one spatial variation dimension of the scanned object. Exemplary spatial variation dimensions can involve the phase encoding direction, the frequency encoding direction, etc., or any combination thereof. In some embodiments, the pre-radiotherapy imaging signal and the in-radiotherapy imaging signal can be obtained by sampling different k-space lines in the k-space in a pseudo-random trajectory acquisition manner.

[0065] The pre - radiotherapy navigation signal, pre - radiotherapy imaging signal, during - radiotherapy navigation signal, and during - radiotherapy imaging signal can be acquired through any suitable sampling pattern. For illustrative purposes, the ways of acquiring the pre - radiotherapy navigation signal and pre - radiotherapy imaging signal are described below. The during - radiotherapy navigation signal can be acquired in a manner similar to that for acquiring the pre - radiotherapy navigation signal, and the during - radiotherapy imaging signal can be acquired in a manner similar to that for acquiring the pre - radiotherapy imaging signal. In some embodiments, the pre - radiotherapy navigation signal and pre - radiotherapy imaging signal can be acquired through radial sampling. The pre - radiotherapy navigation signal can correspond to radial lines in k - space having a constant angle (such as 0°, 10°, 20°, 30°, 100°, 180°, etc.). Merely by way of example, the radial lines at a constant angle in k - space can be sampled repeatedly at a fixed time interval to acquire the pre - radiotherapy navigation signal. The pre - radiotherapy imaging signal can correspond to at least two radial lines in k - space having different read - out angles. In some embodiments, the processing device 140 can acquire the pre - radiotherapy imaging signal by sampling at least two radial lines in k - space according to the golden - angle radial sampling mechanism. By adopting the golden - angle radial sampling mechanism, multiple radial lines evenly distributed in and covering k - space can be obtained in a relatively short time, which can improve the scanning efficiency and reduce the computational amount and computational time. It should be understood that any other read - out angle (such as a randomly set read - out angle) can be used to sample the pre - radiotherapy imaging signal according to actual needs (e.g., based on requirements regarding scanning time and / or imaging quality).

[0066] In some embodiments, the pre - radiotherapy navigation signal and pre - radiotherapy imaging signal can be acquired through Cartesian sampling. The pre - radiotherapy navigation signal can correspond to the same Cartesian line in k - space. The pre - radiotherapy imaging signal can correspond to different Cartesian lines in k - space. In some embodiments, the pre - radiotherapy navigation signal can correspond to the Cartesian line passing through the center of k - space in k - space. In some embodiments, the pre - radiotherapy imaging signal can be obtained through Cartesian sampling, while the pre - radiotherapy navigation signal can be obtained by repeatedly sampling a specific radial line or spiral line in k - space.

[0067] During the MRI scan of the scanned object, the pre-radiotherapy navigation signal and the pre-radiotherapy imaging signal can be acquired in any sampling order. In some embodiments, the pre-radiotherapy navigation signal and the pre-radiotherapy imaging signal can be alternately acquired during the MRI scan of the scanned object. For example, a first number of imaging signals can be acquired after or before each readout of a second number of navigation signals. The first number and the second number can be any positive integers, such as 1, 2, 3, 5, 10, etc. In some embodiments, the first number and the second number can be set according to actual needs. For example, the sampling frequency of the pre-radiotherapy navigation signal needs to be greater than a threshold frequency and / or sufficient pre-radiotherapy imaging signals need to be acquired for image reconstruction. In some embodiments, the ratio of the first number to the second number can be related to the type of the scanned object to be imaged. For example, for imaging of a patient's heart, the ratio of the first number to the second number can be equal to 1:1. As another example, for imaging of organs other than the heart (e.g., arm, knee), the ratio of the first number to the second number can be equal to 10:1. In some embodiments, the pre-radiotherapy navigation signal can have no phase encoding. The pre-radiotherapy navigation signal can be used to estimate a time factor related to at least one time-varying dimension. The phase encoding of the pre-radiotherapy imaging signal can conform to a certain rule (e.g., random Gaussian distribution).

[0068] Merely by way of example, Figure 4 is a schematic diagram of an exemplary MRI pulse sequence for performing an MRI scan of a scanned object as shown in some embodiments of the present specification. As Figure 4 shown, 4 pre-radiotherapy imaging signals can be acquired after each readout of a pre-radiotherapy navigation signal. In this case, the ratio of the number of pre-radiotherapy imaging signals acquired in step 301 to the number of pre-radiotherapy navigation signals can be 4:1. The pre-radiotherapy navigation signal has no phase encoding and repeats periodically. The phase encoding of the pre-radiotherapy imaging signal conforms to a random Gaussian distribution.

[0069] In some embodiments, the navigation signal and the imaging signal each have a preset readout direction. The readout direction can be the default setting of the system, or set by the user, or determined by the processing device 140 according to the actual situation. For example, when there is physiological movement in the target area to receive radiotherapy, the readout direction of the navigation signal is related to the movement direction of the target area. The movement direction of the target area can refer to the direction in which the movement amplitude (or movement displacement) of the target area is relatively large during the physiological movement process. In some embodiments, the readout direction of the navigation signal can be parallel or substantially parallel to a movement direction of the target area. For example, for respiratory movement, whose movement direction is the head-to-foot direction, the readout direction of the navigation signal can be parallel or substantially parallel to the head-to-foot direction of the target area.

[0070] In some embodiments, the readout direction of the imaging signal is the direction with higher imaging efficiency. For example, if the MRI scan (e.g., liver scan) is a transverse scan, the readout direction of the imaging data is the left-right direction of the target object. For another example, if the MRI scan is a coronal scan, the readout direction of the imaging data is the up-down direction of the target object.

[0071] Step 303: Based on the pre-radiotherapy MRI signal, determine an initial time factor (referred to as ) and an initial spatial factor (referred to as U0). In some embodiments, step 303 may be executed by the processing device 140 or the first determination module 202.

[0072] In some embodiments, step 303 is executed simultaneously with step 302 or before step 302.

[0073] In some embodiments, the time factor may include one or more time basis functions related to natural time. In some embodiments, each time basis function may be related to the time variation dimension of the scanned object. In some embodiments, the time factor may include one or more cardiac time basis functions related to the cardiac motion of the scanned object, one or more respiratory time basis functions related to the respiratory motion of the scanned object, one or more T1 recovery time basis functions related to the T1 relaxation of the scanned object, etc., or any combination thereof. The time basis function related to the time variation dimension can reflect the dynamic information along the time variation dimension and includes high-time-resolution information.

[0074] In some embodiments, the processing device 140 may determine a conversion coefficient T and an initial time factor based on the pre-radiotherapy navigation signal The conversion coefficient T can represent the relationship between the time factor and the navigation signal. In some embodiments, the pre-radiotherapy navigation signal may be filled into the K-space to obtain a first K-space matrix. The processing device 140 may determine the conversion coefficient T and the initial time factor based on the first K-space matrix For example, the processing device 140 may determine the conversion coefficient T and the initial time factor according to the singular value decomposition (SVD) algorithm Merely by way of example, the first K-space matrix may be referred to as K1. The first K-space matrix K1 can be expressed as wherein, an element in the first K-space matrix K1 represents the k-space data collected by a specific coil channel at a certain moment. For example, k(k c ,t1) represents the data of the k-space collected by the coil channel k at the moment t1 cThe acquired k-space data. The processing device 140 can perform SVD on the first K-space matrix K1 according to formula (1) to determine the conversion coefficient T and the initial time factor where U k represents the projection coefficient matrix, represents the initial time factor (e.g., the time factor represented by at least one time factor matrix), and D represents the singular value matrix. The conversion coefficient T can be determined based on the projection coefficient matrix U k and the singular value D matrix. For example, the conversion coefficient T can be (U k D) or where, represents the conjugate transpose matrix of the projection coefficient matrix U k and D -1 represents the inverse matrix of the singular value matrix D.

[0075] Furthermore, the processing device 140 can determine the initial spatial factor U0 based on the initial time factor and the pre-radiotherapy imaging signal. The spatial factor of the scanned object can include high-spatial-resolution information along the spatially varying dimension. For example, the spatial factor can reflect the relationship between the pixel information of the scanned object in the image domain and the spatial information of the scanned object in the physical domain. In some embodiments, the spatial factor can be represented as a base image including high-spatial-resolution information. Different spatial factors can be represented as base images including different high-spatial-resolution information.

[0076] In some embodiments, the processing device 140 can construct an optimization function related to the initial spatial factor U0. The optimization function can combine the pre-radiotherapy imaging signal and the initial time factor The processing device 140 can also determine at least one spatial factor by solving the optimization function. For example, the processing device 140 can determine the initial spatial factor U0 of the scanned object according to the first optimization function shown in formula (2): where, represents the optimal spatial factor determined by solving formula (2), U0 represents the initial spatial factor of the scanned object (e.g., the spatial factor represented by at least one spatial factor matrix), c represents the number of coil channels of the MRI device, d h represents the k-space data obtained by filling the pre-radiotherapy imaging signal acquired by the h-th coil channel into the k-space, Ω represents the downsampling operator (which can be omitted in some cases), F represents the Fourier transform operator, h represents the coil channel number, S hdenotes the coil sensitivity map corresponding to the h-th coil channel, and Φ0 represents the initial time factor of the scanned object (e.g., the time factor represented by at least one time factor matrix).

[0077] For another example, the processing device 140 may determine the initial spatial factor U0 of the scanned object according to the second optimization function shown in formula (3): where λ represents the regularization parameter, TV(U tr ) represents the 3D total variation, and λ||TV(U tr )||1 represents the constraint term related to at least one spatial factor matrix of the scanned object (which can be omitted in some cases).

[0078] Step 304, determine multiple time factors and / or multiple updated spatial factors. In some embodiments, step 303 may be executed by the processing device 140 or the first determination module 202.

[0079] In some embodiments, each time factor among the multiple time factors may correspond to a second imaging sub-stage. In some embodiments, for each time factor, the processing device 140 may determine the time factor based on the latest radiotherapy MRI signal acquired before determining this time factor, where the latest radiotherapy MRI signal acquired before determining this time factor may represent the radiotherapy MRI signal acquired from after the radiotherapy MRI signal for determining the previous time factor is acquired until the time factor is determined, which corresponds to a second imaging sub-stage. That is to say, whenever the radiotherapy MRI signal of a second imaging sub-stage is acquired, the time factor corresponding to this second imaging sub-stage may be determined based on the acquired radiotherapy MRI signal. Merely as an example, the radiotherapy MRI signal may include the radiotherapy MRI signal (M1, M2,..., M n ) described in step 302. The processing device 140 may determine the time factor n (which may also be referred to as the first time factor) based on the radiotherapy MRI signal (M1, M2,..., M ). The time factor may be determined based on the radiotherapy MRI signal M i , where may represent any one of the time factors , and M i may represent the latest radiotherapy MRI signal acquired before determining the time factor . In some embodiments, the time factor may be based on the radiotherapy MRI signal M iIt is determined within a first time period. For example, the first time period can be 40 milliseconds, 50 milliseconds, 100 milliseconds, 150 milliseconds, etc. In this case, the second imaging sub-phase as described above can last for the first time period (e.g., 50 milliseconds). More about determining the time factor can be found elsewhere in this application (e.g., Figure 5 and its description).

[0080] In some embodiments, each updated spatial factor can be determined based on the in - radiotherapy MRI signals obtained before determining the updated spatial factor. Optionally, the updated spatial factor can be determined based on at least a portion of the pre - radiotherapy MRI signals and the in - radiotherapy MRI signals obtained before determining the updated spatial factor. Merely as an example, the processing device 140 can determine the spatial factors (U1, U2,..., U n ) based on the in - radiotherapy MRI signals (M1, M2,..., M m ), where U represents the spatial factor, the subscript of U (i.e., 1 to m) represents the number of the spatial factor, m represents the number of spatial factors, and m can be less than or equal to n. The spatial factor U j can be determined based on the in - radiotherapy MRI signals (M1, M2,..., M t ), where j represents any one of the subscripts of the spatial factor (i.e., 1 to m) (i.e., U j can represent any one of the spatial factors (U1, U2,..., U m ), 1 < t < m, j can be an integer greater than 0 and less than or equal to m, and M t is the latest in - radiotherapy MRI signal obtained before determining the spatial factor U j , and t represents the subscript of the latest in - radiotherapy MRI signal obtained before determining the spatial factor U j . In some embodiments, the spatial factor U j can be determined based on the in - radiotherapy MRI signals (M1, M2,..., M t ) within a second time period. The second time period can be, for example, 400 milliseconds, 500 milliseconds, 1 second, etc. More about determining the spatial factor U j can be found elsewhere in this application (e.g., Figure 6 and its description).

[0081] In some embodiments, the processing device 140 may monitor the body movement of the scanned object during the second imaging phase. The processing device 140 may obtain the movement information of the scanned object. In some embodiments, the movement information of the scanned object may include the body movement amplitude of the scanned object from the first imaging phase to a second imaging sub-phase during the second imaging phase. The body movement amplitude of the scanned object from the first imaging phase to the second imaging sub-phase may be represented by the body movement amplitude of the scanned object from the first moment of the first imaging phase to the second moment of the second imaging sub-phase. The first moment may be any moment of the first imaging phase, and the second moment may be any moment of the second imaging sub-phase. For example, the first moment may be the starting moment of the first imaging phase, and the second moment may be the ending moment of the second imaging sub-phase. For another example, the first moment may be the ending moment of the first imaging phase, and the second moment may be the ending moment of the second imaging sub-phase. In some embodiments, the interval between the first moment and the second moment may be greater than the time threshold. The first moment, the second moment, and the time threshold may be manually set by a user (e.g., an engineer) according to actual needs, or be default set by the application scenario 100 of the MRI system.

[0082] In some embodiments, the movement information of the scanned object may be determined based on a first image captured by the image acquisition device at the first moment and a second image captured at the second moment. The image acquisition device may be any suitable device capable of capturing image data of the scanned object located within the field of view of the image acquisition device. For example, the image acquisition device may include a camera (e.g., a digital camera, an analog camera, a depth camera, a structured light camera, etc.), a red-green-blue (RGB) sensor, an RGB-depth (RGB-D) sensor, a lidar, etc., or any combination thereof. For example, the processing device 140 may obtain the first image and the second image. The processing device 140 may determine the movement information of the scanned object by analyzing the positions of the scanned object in the first image and the second image.

[0083] In some embodiments, the movement information of the scanned object may be determined based on a navigation signal. For more descriptions on determining movement information based on a navigation signal, please refer to Figure 10 , which will not be elaborated herein.

[0084] In some embodiments, the movement information of the scanned object may be determined by other means. For example, the movement information of the scanned object may be determined based on the distance information from the body surface of the scanned object to a reference position, where microwave technology or ultrasonic technology may be used to collect the distance information. In some embodiments, the processing device 140 may determine the maximum movement amplitude of the scanned object from the first imaging phase to the second imaging sub-phase, and designate the maximum movement amplitude of the scanned object as the final movement amplitude of the scanned object from the first imaging phase to the second imaging sub-phase.

[0085] In some embodiments, in response to determining that the body movement amplitude of the scanned object exceeds the amplitude threshold, which indicates that the scanned object has significant movement from the first imaging stage to the second imaging sub-stage, the processing device 140 may determine the next spatial factor in the spatial factors (U1, U2,..., U m ). That is to say, the current spatial factor needs to be updated. In some embodiments, in response to determining that the body movement amplitude of the scanned object does not exceed the amplitude threshold, which indicates that the scanned object has no significant movement from the first imaging stage to the second imaging sub-stage, that is to say, the current spatial factor does not need to be updated.

[0086] Step 305, generate a plurality of real-time magnetic resonance images within the second imaging stage. In some embodiments, step 303 may be executed by the processing device 140 or the generation module 203.

[0087] As described above, the second imaging stage may include a plurality of second imaging sub-stages. Each real-time magnetic resonance image may correspond to a second imaging sub-stage. The real-time magnetic resonance image may reflect the real-time state of the scanned object in the corresponding second imaging sub-stage. For example, the real-time magnetic resonance image may be generated with a very small delay within a very short time (e.g., shorter than a preset time period) after collecting the MRI signal during radiotherapy in the second imaging sub-stage. As another example, the real-time magnetic resonance image may be generated before completing the MRI scan (e.g., while still performing MRI signal acquisition). In some embodiments, the real-time magnetic resonance image of the scanned object may be a two-dimensional (2D) image, a three-dimensional (3D) image, etc.

[0088] In some embodiments, each real-time magnetic resonance image may be generated based on the latest determined time factor and the initial spatial factor, or each real-time magnetic resonance image may be generated based on the latest determined time factor and the latest determined spatial factor. In some embodiments, each time a time factor is determined, a real-time magnetic resonance image may be generated based on one of the initial spatial factor or the latest determined spatial factor and the time factor. Each real-time magnetic resonance image may reflect the state of the scanned object in the corresponding second imaging sub-stage. Merely as an example, the processing device 140 may generate real-time magnetic resonance images (A1, A2,..., A n ), where A represents the real-time magnetic resonance image, and the subscript of A (i.e., 1 to n) represents the number of the real-time magnetic resonance image, which corresponds to the number of the second imaging sub-stage, and n represents the number of real-time magnetic resonance images. The real-time magnetic resonance image A i may reflect the state of the scanned object in the second imaging sub-stage corresponding to time T i , where A i may represent the real-time magnetic resonance image (A1, A2,..., A nAny one of i can be generated based on a time factor and an initial spatial factor U0, or the real-time magnetic resonance image A i can be generated based on a time factor and the spatial factor that was most recently determined before time T i . In some embodiments, if the initial spatial factor U0 has not been updated before time T i (or when generating the real-time magnetic resonance image A i ), the initial spatial factor U0 can be used to generate the real-time magnetic resonance image A i . If the initial spatial factor U0 has been updated before time T i (or when generating the real-time magnetic resonance image A i ), the last updated spatial factor can be used to generate the real-time magnetic resonance image A i .

[0089] For illustrative purposes, an exemplary method for generating the real-time magnetic resonance image A i will be described below. In some embodiments, the real-time magnetic resonance image A i of the scanned object can be represented by a multi-dimensional tensor, which can be determined based on a time factor and an initial spatial factor U0. For example, when the time factor and the initial spatial factor U0 are available, the processing device 140 can generate the real-time magnetic resonance image A i of the scanned object by determining the product of at least one time factor matrix and at least one spatial matrix factor. At least one time factor matrix can include the time factor and at least one spatial matrix factor can include the initial spatial factor U0. Merely by way of example, the processing device 140 can generate the real-time magnetic resonance image A i of the scanned object according to formula (4): where A i represents the multi-dimensional tensor for representing the real-time magnetic resonance image of the scanned object, represents the time factor represented in the form of at least one time factor matrix, and U0 represents the initial spatial factor represented in the form of at least one spatial matrix factor.

[0090] In some embodiments, the processing device 140 can generate the real-time magnetic resonance image A i of the scanned object corresponding to a specific time variation dimension based on the time factor matrix and the spatial factor matrix corresponding to the specific time variation dimension.For example, the processing device 140 can generate a real-time magnetic resonance image of the heart by determining the product of a spatial factor matrix and a time factor matrix including time factors related to heart motion. The time factor matrix related to heart motion can include time factors related to heart motion.

[0091] In some embodiments, the processing device 140 can generate a real-time magnetic resonance image A of the scanned object based on the time factor initial spatial factor U0 and the core tensor. The core tensor can control the interaction between at least one time factor matrix and at least one spatial factor matrix. For example, the processing device 140 can generate a real-time magnetic resonance image A of the scanned object by determining the product of at least one time factor matrix including time factors i , at least one spatial factor matrix including the initial spatial factor U0, and the core tensor. In some embodiments, the core tensor can be determined based on the pre-radiotherapy navigation signal. i In some embodiments, during the real-time imaging process of the scanned object, the processing device 140 only needs to determine the value of the time factor

[0092] . Further, the real-time magnetic resonance image A can be generated based on the time factor i and the initial spatial factor U0. The generation of the real-time magnetic resonance image A involves simple calculations, thus having a short image output delay. In some cases, the calculation of the basic data can be performed immediately after the acquisition of the pre-radiotherapy MRI signal (e.g., before the second imaging stage or simultaneously with the acquisition of the in-radiotherapy MRI signal). In this way, the delay in image generation in the second imaging stage can be further reduced. i In some embodiments, the processing device 140 can generate a real-time magnetic resonance image A based on the time factor

[0093] and the spatial factor determined most recently before time T . In some embodiments, generating the real-time magnetic resonance image A i based on the time factor i and the spatial factor determined most recently before time T can be similar to generating the real-time magnetic resonance image A i of the scanned object based on the time factor i and the initial spatial factor U0 as described above. By way of example only, the processing device 140 can generate the real-time magnetic resonance image A of the scanned object according to formula (5) i : i : where A​i A multi-dimensional tensor representing a real-time magnetic resonance image of a scanned object A time factor represented by at least one time factor matrix, U i A spatial factor determined most recently before time T, represented by at least one spatial factor matrix i The most recently determined spatial factor

[0094] As described above, during the real-time imaging process of the scanned object, in addition to the time factor the processing device 140 can also determine the most recent spatial factor U i value. The processing device 140 can further generate a real-time magnetic resonance image A based on the time factor and the most recently determined spatial factor U i In some embodiments, the real-time magnetic resonance image A can be improved by monitoring the body movement of the scanned object and updating the current spatial factor when the scanned object has significant body movement i to improve the imaging quality of the real-time magnetic resonance image A (e.g., by reducing motion artifacts). i

[0095] In some embodiments, real-time magnetic resonance images corresponding to at least two second imaging sub-stages can generate a dynamic image. The dynamic image can reflect the dynamic information of the scanned object along the time variation dimension. For example, the dynamic image can reflect the heart movement of the heart during one cardiac cycle and include at least two real-time magnetic resonance images of the heart corresponding to at least two cardiac phases in the cardiac cycle.

[0096] Generally, a magnetic resonance image can be generated after the MRI scan is completed, and the delay time from the start of the MRI scan to the generation of the magnetic resonance image is about dozens of seconds or even several minutes. According to some embodiments of the present application, the pre-radiotherapy MRI signal can be collected and processed during the first imaging stage to obtain specific basic data (e.g., initial time factor, conversion coefficient, and initial spatial factor). After the radiotherapy MRI signal is collected during the second imaging sub-stage in the second imaging stage, at least a part of the basic data can be updated, and a real-time magnetic resonance image of the scanned object corresponding to the second imaging sub-stage can be generated based on the updated basic data. Since the second imaging sub-stage is relatively short and the radiotherapy MRI signal is relatively small, the generation of the real-time magnetic resonance image only involves simple calculations (e.g., matrix multiplication and / or matrix division), so real-time imaging can be achieved during the second imaging stage.

[0097] ​It should be noted that the above description of process 300 is for illustration and example only, and does not limit the scope of application of this specification. For those skilled in the art, various modifications and changes can be made to process 300 under the guidance of this specification. However, these modifications and changes are still within the scope of this specification. In some embodiments, process 300 can be completed through one or more additional steps not described and / or without one or more of the above steps. For example, process 300 can include an additional step of transmitting real-time magnetic resonance images to a terminal device (e.g., the doctor's terminal 130) for display.

[0098] Figure 5 is a schematic diagram of an exemplary process for determining a time factor according to some embodiments of this specification. In some embodiments, the process 500 shown can be used to implement Figure 5 the step 304 described above. Figure 3 Step 501, based on the pre-radiotherapy MRI signal, determine the conversion coefficient T. In some embodiments, step 501 can be executed by the processing device 140 or the first determination module 202.

[0099] As described elsewhere in this application, the conversion coefficient T can represent the relationship between the navigation signal and the time factor. In some embodiments, the processing device 140 can determine the conversion coefficient T based on the pre-radiotherapy navigation signal in a manner similar to that described in steps 301 - 302.

[0100] Step 502, based on the conversion coefficient T and the in-radiotherapy MRI signal M

[0101] i , determine the time factor In some embodiments, step 502 can be executed by the processing device 140 or the first determination module 202.

[0102] As described elsewhere in this application, the in-radiotherapy MRI signal M i can include the in-radiotherapy navigation signal collected at time T i i . The processing device 140 can determine the time factor

[0103] i In some embodiments, the processing device 140 can fill the in-radiotherapy navigation signal of the in-radiotherapy MRI signal M into the K-space to obtain a second K-space matrix. The processing device 140 can determine the value of the time factor based on the second K-space matrix and the conversion coefficient T. For example, the processing device 140 can determine the time factor according to formula (6).Value: Wherein, K2 represents the second K-space matrix, represents the conversion coefficient T determined in step 501.

[0104] In some embodiments, the processing device 140 may update the value of the conversion coefficient T based on the pre-radiotherapy navigation signal and a reference navigation signal acquired after the pre-radiotherapy navigation signal (e.g., at least a part of the in-radiotherapy navigation signal). For example, the processing device 140 may perform SVD on the pre-radiotherapy navigation signal and at least a part of the in-radiotherapy navigation signal to determine the updated conversion coefficient T * . Compared with the original conversion coefficient, since the updated conversion coefficient T * is determined based on more navigation signals, the updated conversion coefficient T * can have higher accuracy, thereby improving the accuracy of the generated real-time magnetic resonance image A i .

[0105] The processing device 140 may determine the time factor * based on the in-radiotherapy navigation signal and the updated conversion coefficient T For example, the processing device 140 may determine the time factor according to formula (7) Wherein, K2 represents the second K-space matrix, represents the updated conversion coefficient T * .

[0106] Figure 6 is a schematic diagram of an exemplary process for determining the spatial factor U j shown in some embodiments of this specification. In some embodiments, Figure 6 the process 600 shown can be used to implement Figure 3 the step 304 described above.

[0107] Step 601, based on the in-radiotherapy MRI signals (M1, M2,..., M t ), determine the second time factor In some embodiments, step 601 may be executed by the processing device 140 or the first determination module 202.

[0108] In some embodiments, Figure 5 the method for determining the time factor is described, and the processing device 140 may determine the second time factor in a similar method For example, the processing device 140 may use the in-radiotherapy MRI signals (M1, M2,..., Mt ) The navigation signals during radiotherapy are filled into the k-space to obtain a third k-space matrix. In some embodiments, the processing device 140 may fill the MRI signals during radiotherapy (M1, M2,..., M t ) The navigation signals during radiotherapy and at least a part of the navigation signals before radiotherapy are filled into the k-space to obtain a third k-space matrix. The processing device 140 may determine a second time factor based on the conversion coefficient T and the third k-space matrix Optionally, the processing device 140 may update the value of the conversion coefficient T based on at least a part of the navigation signals during radiotherapy (M1, M2,..., M t ) during radiotherapy and the navigation signals before radiotherapy. The processing device 140 may determine a second time factor based on the updated conversion coefficient and the third k-space matrix

[0109] Step 602: Based on the second time factor and the MRI signals during radiotherapy (M t-1 ,..., M t ), determine a spatial factor U j , where M t is the latest MRI signal during radiotherapy acquired before determining U j . In some embodiments, step 602 may be performed by the processing device 140 or the first determination module 202

[0110] In some embodiments, the processing device 140 may determine a reference spatial factor based on the second time factor and the MRI signals during radiotherapy (M t-1 ,..., M t ). Where M t-1 is the latest MRI signal during radiotherapy acquired after determining U j-1 , that is, M t-1 is the MRI signal during radiotherapy acquired in the latest second imaging sub-stage after the MRI signals during radiotherapy used to determine U j-1 are acquired. The processing device 140 may further determine the spatial factor U j-1 based on the spatial factor U j and the reference spatial factor. As described elsewhere in the present application, the MRI signals during radiotherapy may include the imaging signals during radiotherapy. The processing device 140 may determine a reference spatial factor based on the second time factor and the imaging signals during radiotherapy in the MRI signals during radiotherapy (M t-1 ,..., M t ). For example, the reference spatial factor may be determined by solving the third optimization function of the above formula (2) or formula (3). In the third optimization function, d hDenote the K-space data corresponding to the radiotherapy imaging signals (M t-1 ,...,M t ) acquired by the h-th coil channel. Φ0 can be replaced by the second time factor . Other coefficients can be the same as those in formula (2) or formula (3). The processing device 140 can determine the spatial factor U j-1 based on the reference spatial factor and the previously determined spatial factor U j . For example, the processing device 140 can use the sum of the reference spatial factor and the previously determined spatial factor U j-1 as at least one updated spatial factor.

[0111] In some embodiments, since the second imaging sub-phase is relatively short and the amount of radiotherapy imaging signals acquired is relatively small, the accuracy of the reference spatial factor determined based on the radiotherapy imaging signals is relatively low. The processing device 140 can determine the reference spatial factor based on the radiotherapy imaging signals and other reference imaging signals acquired before the radiotherapy imaging signals. For example, the reference imaging signals can include a part of the pre-radiotherapy imaging signals. To reduce the calculation time of the reference spatial factor (e.g., the time for solving the third optimization function), on the premise that the accuracy of the determined reference spatial factor meets the requirements, only a small number of reference imaging signals can be used to determine the reference spatial factor.

[0112] In some embodiments, the processing device 140 can determine the spatial factor U j without determining the reference spatial factor. For example, the spatial factor U j can be determined by solving the fourth optimization function of the above formula (2) or formula (3). In the fourth optimization function, d h denotes the K-space data corresponding to the pre-radiotherapy imaging signals and the radiotherapy imaging signals (M1, M2,..., M t ) acquired by the h-th coil channel. Φ0 can be replaced by the second time factor . Other coefficients can be the same as those in formula (2) or formula (3). Compared with the third optimization function, the fourth optimization function is constructed based on the original pre-radiotherapy imaging signals and the radiotherapy imaging signals (M1, M2,..., M t ), and solving the fourth optimization function requires more data. Compared with directly determining the spatial factor U j , the method of determining the spatial factor U j by determining the reference spatial factor and adding it to the previously determined spatial factor can improve the efficiency of determining the spatial factor, save computing resources, and thus improve the real-time performance of imaging.

[0113] In some embodiments, the processing device 140 may be based on the MRI signals (M1, M2, ..., M t ) of the radiotherapy imaging signal, and updating the coil sensitivity map of the plurality of coils used to collect the MRI signal before radiotherapy and the MRI signal during radiotherapy. The processing device 140 may further be based on the second time factor MRI signals during radiotherapy (M1, M2, ..., M t ) and the updated coil sensitivity map to determine the spatial factor U j For example, in the third or fourth optimization function above, S h The updated coil sensitivity map corresponding to the hth coil channel may be represented. The coil sensitivity map of the coil may reflect the distribution of the response degree of the coil relative to different parts of the scanned object (i.e., the ability to receive MRI signals from different parts of the scanned object). As an example only, for each coil, the processing device 140 may generate a coil image based on the imaging signal during radiotherapy acquired by the coil. The processing device 140 may determine the updated coil sensitivity map of different coils based on the coil image. In some embodiments, the updated coil sensitivity map may be determined based on a combination of the pre-radiotherapy imaging signal and the during-radiotherapy imaging signal.

[0114] According to some embodiments of the present application, the time factor can be determined based on the navigation signal and the conversion coefficient T in radiotherapy. Further, we can use the time factor and the initial spatial factor U0 to generate a real-time magnetic resonance image of the scanned object. Because the value of the time factor can be determined based on a small amount of data, and, in some embodiments, the conversion coefficient T can be determined in advance (for example, before the end of the first and second imaging sub-stages), the real-time magnetic resonance image of the second imaging stage can be generated by simple calculations (for example, matrix multiplication and / or matrix division). In this way, the efficiency of generating real-time magnetic resonance images can be improved, and real-time imaging with low latency (for example, close to zero seconds) can be achieved. In the case where the body movement amplitude of the scanned object from the first imaging stage to the second imaging stage is small or the scanned object has no body movement, the generated real-time magnetic resonance image of the scanned object can have the desired accuracy and meet the use requirements.

[0115] According to some embodiments of the present application, the real-time magnetic resonance image of the scanned object can be based on the time factor and spatial factors (U1,U2,...,U m ) is generated by monitoring the body motion of the scanned subject and determining the spatial factors (U1, U2, ..., U m) can improve the imaging quality of the generated real-time magnetic resonance image. In addition, the value of the spatial factor can be determined by determining a reference spatial factor and adding it to the previously determined spatial factor to improve the efficiency of determining the spatial factor, thereby improving the efficiency of generating the real-time magnetic resonance image of the scanned object, and low-latency (e.g., less than 100 milliseconds) real-time imaging can be achieved.

[0116] In addition, significant movement of the scanned object may also cause changes in the coil sensitivity map of the coil. According to some embodiments of the present application, if significant movement of the scanned object is detected, the coil sensitivity map of the coil can be updated, and the value of the spatial factor can be determined based on the imaging signal during radiotherapy and the updated coil sensitivity map. In this way, the real-time magnetic resonance image of the scanned object obtained based on the temporal factor and the spatial factor can have the desired accuracy.

[0117] Figure 7 is a schematic diagram of an exemplary process 700 for generating a real-time magnetic resonance image of a scanned object as shown in some embodiments of the present specification. As Figure 7 shown, the MRI scan of the scanned object may include a first imaging stage and at least two second imaging sub-stages after the first imaging stage (e.g., Figure 7 the second imaging sub-stages L1 and L2 shown). In the first imaging stage, the pre-radiotherapy MRI signal can be acquired. Then, based on the acquired pre-radiotherapy MRI signal, the initial temporal factor conversion coefficient T and the initial spatial factor U0 can be determined. In each of the at least two second imaging sub-stages, the in-radiotherapy MRI signal can be acquired. In some embodiments, the initial temporal factor conversion coefficient T and the initial spatial factor U0 can be determined before the second imaging sub-stage L1. Alternatively, the time period for determining the initial temporal factor conversion coefficient T and the initial spatial factor U0 may at least partially overlap with the second imaging sub-stage L1. Then, for each second imaging sub-stage, the temporal factor can be determined based on the acquired in-radiotherapy MRI signal, and based on the temporal factor and the initial spatial factor, a real-time magnetic resonance image of the scanned object can be generated. For example, for the second imaging sub-stage L1, the temporal factor can be determined based on the acquired in-radiotherapy MRI signal M1, and based on the temporal factor and the initial spatial factor U0, a real-time magnetic resonance image A1 of the scanned object can be generated.

[0118] Figure 8 is a schematic diagram of an exemplary process 800 for generating a real-time magnetic resonance image of a scanned object as shown in some embodiments of the present specification. As Figure 8As shown, the MRI scan of the scan object may include a first imaging stage and at least two second imaging sub-stages after the first imaging stage (e.g., Figure 8 the second imaging sub-stages P1 and P2 shown). In the first imaging stage, pre-radiotherapy MRI signals may be acquired. Then, based on the acquired pre-radiotherapy MRI signals, an initial time factor conversion coefficient T, and an initial spatial factor U0 may be determined. In each of the at least two second imaging sub-stages, during-radiotherapy MRI signals may be acquired. In some embodiments, the initial time factor conversion coefficient T, and the initial spatial factor U0 may be determined before the second imaging sub-stage P1. Alternatively, the time period for determining the initial time factor conversion coefficient T, and the initial spatial factor U0 may at least partially overlap with the second imaging sub-stage P1. Then, for each second imaging sub-stage, a time factor may be determined based on the acquired during-radiotherapy MRI signals, and a latest spatial factor may be determined based on the time factor and the during-radiotherapy MRI signals. Finally, a real-time magnetic resonance image of the scan object may be generated based on the time factor and the latest spatial factor. For example, for the second imaging sub-stage P1, based on the acquired during-radiotherapy MRI signal M1, a time factor may be determined. Further, a spatial factor U1 may be determined based on the acquired during-radiotherapy MRI signal M1 and the time factor . Finally, a real-time magnetic resonance image A1 of the scan object may be generated based on the time factor and the spatial factor U1.

[0119] Figure 9 is a schematic diagram of an exemplary process 900 for generating a real-time magnetic resonance image of a scan object according to some embodiments of this specification. As Figure 9 shown, the MRI scan of the object may include a first imaging stage and a second imaging stage after the first imaging stage. In the first imaging stage, pre-radiotherapy MRI signals may be acquired. Then, based on the acquired pre-radiotherapy MRI signals, an initial time factor and an initial spatial factor U0 may be determined.

[0120] In the second imaging stage, during-radiotherapy MRI signals (M1, M2,..., M n ) may be acquired, where M i is acquired at time T n in the time series (T1, T2,..., T i ). A first time factor n and spatial factors (U1, U2,..., U may be determined based on the during-radiotherapy MRI signals (M1, M2,..., M m), where m is less than or equal to n. Specifically, whenever an in - radiotherapy MRI signal is acquired at a time in the time series (T1, T2,..., T n ), a corresponding first time factor can be determined based on the acquired in - radiotherapy MRI signal. For example, after the in - radiotherapy MRI signal is acquired at time T i , based on the acquired in - radiotherapy MRI signal M i , the first time factor can be determined

[0121] For each of the spatial factors (U1, U2,…, U m ), the spatial factor can be determined based on the in - radiotherapy MRI signals obtained before determining this spatial factor. For example, based on the in - radiotherapy MRI signals (M1, M2,..., M i ), the spatial factor U1 can be determined. In some embodiments, for the spatial factor U j , the second time factor can be determined based on the in - radiotherapy MRI signals obtained before determining the spatial factor U j . Then, the spatial factor U j can be determined based on the corresponding second time factor . For example, as Figure 9 shows, the second time factor can be determined based on the in - radiotherapy MRI signals (M1, M2,..., M i ). The spatial factor U1 can be determined based on the second time factor .

[0122] During the process of the second imaging stage, real - time magnetic resonance images (A1, A2,..., A n ) can be generated. A real - time magnetic resonance image can reflect the state of the scanned object at a certain time in the time series (T1, T2,..., T n ). For example, A i can reflect the state of the scanned object at time T i . Each of the real - time magnetic resonance images (A1, A2,..., A n ) can be generated based on the latest determined time factor and the initial spatial factor U0, or each of the real - time magnetic resonance images (A1, A2,..., A n ) can be generated based on the latest determined time factor and the latest determined spatial factor. For example, as Figure 9 shows, the real - time nuclear magnetic resonance image A i can be generated based on the time factor and the initial spatial factor U0. Another example, the real - time magnetic resonance image A i+1 can be generated based on the time factor and the newly determined spatial factor U1 are generated.

[0123] In some embodiments, the processing device 140 may execute process 900 through multiple threads. For example, process 900 may be executed through a first thread and a second thread. The first thread and the second thread may run simultaneously. In some embodiments, the processing device 140 may obtain MRI signals (e.g., pre-radiotherapy MRI signals, in-radiotherapy MRI signals (M1, M2,..., M n )) through the first thread, determine time factors (e.g., the initial time factor time factor ), and generate real-time magnetic resonance images (e.g., real-time magnetic resonance images (A1, A2,..., A n )) through the first thread. The processing device 140 may determine spatial factors (e.g., the initial spatial factor U0, spatial factors (U1, U2,..., U m )) through the second thread. The second thread may also be configured to feedback the determined spatial factors to the first thread.

[0124] For example, the acquisition of in-radiotherapy MRI signals (M1, M2,..., M n ), the determination of the first time factor , and the generation of real-time magnetic resonance images (A1, A2,..., A n ) may be executed through the first thread. The determination of spatial factors (U1, U2,..., U m ) may be executed through the second thread. The second thread may be further configured to feedback the determined spatial factors (U1, U2,..., U m ) to the first thread. In some embodiments, the first thread may also be configured to determine a second time factor and feedback the determined second time factor to the second thread. The spatial factor U t may be determined through the second thread based on the in-radiotherapy MRI signals (M1, M2,..., M ) and the second time factor j .

[0125] Determining the time factor and the real-time magnetic resonance image involves relatively little computational effort (e.g., only involves the calculation of the corresponding navigation signal), can be highly efficient and requires fewer computational resources. However, determining each spatial factor involves a large amount of computational effort (e.g., involves the calculation of the corresponding navigation signal, imaging signal, etc.), which may require more computational resources. The first thread for determining the time factor and the real-time magnetic resonance image and the second thread for determining the spatial factor can run independently, which can ensure the calculation of the time factor and the real-time magnetic resonance image is not affected by the calculation of the spatial factor, thereby achieving real-time imaging. In some embodiments, a specific resource allocation strategy can be adopted to preferentially execute the first thread. If there are sufficient computational resources, the second thread can be executed. If the computational resources are insufficient, only the first thread is executed. This can ensure the continuity of real-time imaging and prevent the user from experiencing stuttering when viewing the real-time magnetic resonance image.

[0126] Figure 10 is a schematic diagram of an exemplary process for magnetic resonance-guided radiotherapy according to some embodiments of this specification. In some embodiments, the process Figure 10 shown in 1000 can be executed to detect the movement of a target object based on MRI signals (navigation signals and imaging signals) acquired during magnetic resonance scanning and generate a real-time image of the target object to achieve radiotherapy guidance. In some embodiments, process 1000 can be executed by processing device 140 or Figure 2 the first or more modules shown. For example, process 1000 can be executed by a module of processing device 140. As Figure 10 shown, process 1000 can include the following steps.

[0127] Step 1001, obtain a first navigation signal acquired by a magnetic resonance device during magnetic resonance scanning of a target object. In some embodiments, step 1001 can be executed by processing device 140 or acquisition module 201.

[0128] As described above, before the radiotherapy device 112 emits radiotherapy rays, a magnetic resonance device (such as Figure 1 the MRI scanner 111 therein) can perform a first imaging phase to acquire navigation signals and imaging signals. The first navigation signal is acquired by the magnetic resonance device at a first time before the radiotherapy rays are emitted, and it can be used as a reference signal for detecting the movement of the target object. That is to say, the first navigation signal is the navigation signal acquired by the magnetic resonance device at a first time before the radiotherapy device 112 emits radiotherapy rays. The first time can be any time period or time point in the first imaging phase described above. That is to say, the first navigation signal can include any one or more navigation signals acquired during the first imaging phase (i.e., before the radiotherapy rays are emitted). For example, the first navigation signal can be the last acquired navigation signal during the first imaging phase.

[0129] In some embodiments, the first imaging stage includes a breath-holding time period during which the target object holds its breath, and the first time is within the breath-holding time period. In some embodiments, the target object maintains normal breathing during the first imaging stage, and the first time is a time period or a time point during which the target object maintains normal breathing.

[0130] Step 1002: Obtain a second navigation signal collected by the magnetic resonance device during the magnetic resonance scan of the target object. In some embodiments, step 1002 may be executed by the processing device 140 or the acquisition module 201.

[0131] The second navigation signal is collected by the magnetic resonance device at a second time after the radiotherapy ray is emitted. That is to say, the second navigation signal is the navigation signal collected by the magnetic resonance device at a second time after the radiotherapy device 112 emits the radiotherapy ray. The second time may be any time period or time point later than the first time in the second imaging stage described above. That is to say, the second navigation signal may be any one or more navigation signals collected during the second imaging stage (i.e., after the radiotherapy ray is emitted). In some embodiments, whenever the magnetic resonance device collects a new navigation signal at a certain time in the second imaging stage, the processing device 140 will use this navigation signal as the second navigation signal, and determine whether there is obvious movement (such as movement with an amplitude greater than the threshold) of the target object at this moment based on the first navigation signal and this second navigation signal.

[0132] Step 1003: Based on the first navigation signal and the second navigation signal, determine whether the first movement amplitude of the target object from the first time to the second time is greater than the threshold. In some embodiments, step 1003 may be executed by the processing device 140 or the second determination module 204.

[0133] In this specification, the movement amplitude of the target object refers to the movement amplitude or movement displacement of the target object.

[0134] In some embodiments, the first movement amplitude may be represented by the difference between the first navigation signal and the second navigation signal. The difference between the first navigation signal and the second navigation signal may be determined based on k-space data or based on image domain data. Correspondingly, the threshold may refer to the threshold corresponding to the difference between the navigation signals. In some embodiments, when the number of the first navigation signals and / or the number of the second navigation signals is multiple, the difference between the first navigation signal and the second navigation signal may be determined based on the average value of the first navigation signals and / or the average value of the second signals.

[0135] When the difference between the first navigation signal and the second navigation signal is less than or equal to a threshold value, the processing device 140 may determine that the first movement amplitude of the target object from the first time to the second time is less than or equal to the threshold value. When it is determined that the difference between the first navigation signal and the second navigation signal is greater than the threshold value, the processing device 140 may determine that the first movement amplitude of the target object from the first time to the second time is greater than the threshold value.

[0136] Since the navigation signal itself is the projection of the imaging data of the target object in a certain direction, it can reflect the occurrence of movement (such as the overall movement of the body). Therefore, based on the difference between the first navigation signal and the second navigation signal, the movement of the target object can be effectively detected.

[0137] In some embodiments, as described above, the navigation signal has a preset readout direction. When the readout direction of the navigation signal is substantially parallel to the movement direction of the target region, the navigation signal can more accurately reflect the movement of that region. However, the movement of some target regions (such as the heart) does not have a clear movement direction (different points on the heart have different movement directions), and the navigation signal with a preset readout direction cannot accurately detect the movement of this region. In order to more accurately detect the movement of the target region, in addition to the navigation signal, the magnetic resonance device may also be instructed to collect a reference navigation signal during the MRI scan. The navigation signal can be used for both motion detection and MRI imaging, while the reference navigation signal is only used for motion detection. The acquisition method of the reference navigation signal is similar to that of the navigation signal, but its readout direction is different from that of the navigation signal. For ease of description, the readout direction of the navigation signal (including the first navigation signal and the second navigation signal) is denoted as the first readout direction. The readout direction of the reference navigation signal is denoted as the second readout direction. The second readout direction is different from the first readout direction. For example, the second readout direction is perpendicular to the first readout direction. Merely as an example, if the target region includes the heart, the first readout direction is the head-foot direction of the target object, and the second readout direction is the front-back direction of the target object.

[0138] Merely as an example, Figure 11 is a schematic diagram of an exemplary MRI pulse sequence for implementing the MRI scan of a target object shown in some embodiments of this specification. As Figure 11 shown, after collecting a navigation signal for imaging, a reference navigation signal and three imaging signals can be collected.

[0139] When performing motion detection, the processing device 140 may determine whether the first motion amplitude of the target object is greater than a threshold value based on the first navigation signal, the second navigation signal, and the reference navigation signal. For example, the processing device 140 may obtain the first reference navigation signal and the second reference navigation signal collected by the magnetic resonance device. The first reference navigation signal is collected after the first time, and the second reference navigation signal is collected after the second time. The first reference navigation signal and the second reference navigation signal have a second readout direction. The second readout direction is different from the first readout direction. For example, the second readout direction is perpendicular to the first readout direction. It should be noted that the time difference between the collection time of the first reference navigation signal and the first time is small (less than the threshold value), so the first reference navigation signal can approximately reflect the state of the target object at the first time; the time difference between the collection time of the second reference navigation signal and the second time is small (less than the threshold value), so the second reference navigation signal can approximately reflect the state of the target object at the second time. For example, the magnetic resonance device may collect the first reference navigation signal immediately after collecting the first navigation signal, and collect the second reference navigation signal immediately after collecting the second navigation signal.

[0140] Further, the processing device may determine whether the first motion amplitude of the target object from the first time to the second time exceeds a threshold value based on the first navigation signal, the second navigation signal, the first reference navigation signal, and the second reference navigation signal. At this time, the first motion amplitude may be represented by the first difference between the first navigation signal and the second navigation signal, and the second difference between the first reference navigation signal and the second reference navigation signal. When both the first difference and the second difference are less than or equal to the threshold value, the processing device 140 may determine that the first motion amplitude of the target object from the first time to the second time is less than or equal to the threshold value. When it is determined that any one of the first difference and the second difference is greater than the threshold value, the processing device 140 may determine that the first motion amplitude of the target object from the first time to the second time is greater than the threshold value.

[0141] By using navigation signals and reference navigation signals with different readout directions, the accuracy of motion detection can be improved, thereby improving the accuracy of guiding radiotherapy.

[0142] Step 1004, based on the determination result of whether the first motion amplitude is greater than the threshold value, determine whether to stop emitting radiotherapy rays. In some embodiments, step 1004 may be executed by the processing device 140 or the third determination module 205.

[0143] In some embodiments, in response to determining that the first motion amplitude is less than or equal to the threshold value, the processing device 140 may determine that it is necessary to continue emitting radiotherapy rays and generate a first magnetic resonance image corresponding to the second time. For the description of generating the first magnetic resonance image, see Figure 12 its related description, which will not be elaborated here.

[0144] In some embodiments, in response to determining that the first movement amplitude is greater than a threshold, the processing device 140 may instruct the radiotherapy device to stop emitting the radiotherapy rays, and continue to monitor the movement of the target object based on the newly acquired navigation signal in the magnetic resonance scan. For example, the processing device 140 may obtain a third navigation signal acquired by the magnetic resonance device at a third time, where the third time is later than the second time. The third navigation signal may be any navigation signal acquired later than the second navigation signal. By way of example only, after determining that it is necessary to stop emitting the radiotherapy rays, each time the magnetic resonance device acquires a navigation signal, the processing device 140 will use this navigation signal as the third navigation signal. Further, the processing device 140 may further determine whether it is necessary to continue emitting the radiotherapy rays based on the third navigation signal.

[0145] Specifically, the processing device 140 may determine whether the second movement amplitude of the target object from the first time to the third time is greater than the threshold based on the first navigation signal and the third navigation signal. In some embodiments, the processing device 140 may determine whether the second movement amplitude is greater than the threshold in a manner similar to determining whether the first movement amplitude exceeds the threshold. For example, the second movement amplitude may be represented by the difference between the first navigation signal and the third navigation signal. As another example, the processing device 140 may determine whether the second movement amplitude of the target object is greater than the threshold based on the first navigation signal, the third navigation signal, and a reference navigation signal. In response to determining that the second movement amplitude is less than or equal to the threshold, the processing device 140 may instruct the radiotherapy device to continue emitting the radiotherapy rays, and generate a second magnetic resonance image corresponding to the third time in real time. For the description of generating the second magnetic resonance image, see Figure 13 its related description, which will not be elaborated here. When the second movement amplitude is less than or equal to the threshold, it indicates that the target object has returned to a position close to the first time, and radiotherapy can continue. By continuously detecting the movement of the target object and restarting radiotherapy when its movement amplitude returns below the threshold, the time of interrupted radiotherapy can be reduced, and the radiotherapy efficiency can be improved.

[0146] In some embodiments, in response to determining that the second movement amplitude is greater than a threshold, the processing device 140 may determine whether the third movement amplitude of the target object from the second time to the third time is greater than the threshold based on the second navigation signal and the third navigation signal. In some embodiments, the processing device 140 may determine whether the third movement amplitude is greater than the threshold in a manner similar to determining whether the first movement amplitude is greater than the threshold. For example, the third movement amplitude may be represented by the difference between the second navigation signal and the third navigation signal. As another example, the processing device 140 may determine whether the third movement amplitude of the target object is greater than the threshold based on the second navigation signal, the third navigation signal, and a reference navigation signal. In response to determining that the third movement amplitude is less than or equal to the threshold, the processing device 140 may instruct the radiotherapy device to continue emitting radiotherapy rays and generate a third magnetic resonance image corresponding to the third time in real time. For the description of generating the third magnetic resonance image, see Figure 14 its related description, which will not be elaborated here. When the second movement is greater than the threshold while the third movement amplitude is less than or equal to the threshold, it indicates that although the target object has not returned to a position close to the first time, the target object has maintained its position at the second time and has not continued to move. Therefore, radiotherapy can continue. In this way, the time of radiotherapy interruption is reduced and the radiotherapy efficiency is improved.

[0147] In some embodiments, only when the time difference between the second time and the third time exceeds a threshold time and the third movement amplitude is less than or equal to the threshold (that is, when the target object has maintained its position at the second time for a certain period), the processing device 140 will instruct the radiotherapy device to continue emitting radiotherapy rays. In some embodiments, after the target object has maintained its position at the second time for a certain period, the processing device 140 may determine whether the data volume of the MRI signals (including navigation signals and imaging signals) collected from the second time to the third time is sufficient for updating the time factor and the space factor. When the data volume is sufficient, the processing device 140 may use the period between the second time and the third time as a new first imaging stage, the period after the third time as a new second imaging stage, the navigation signals (such as the second navigation signal, the third navigation signal, etc.) in the new first imaging stage as a new first navigation signal (the reference signal for motion detection), and a certain navigation signal collected after the third navigation signal as a new second navigation signal. The processing device 140 may repeat process 1000 to continue monitoring the movement of the target object.

[0148] In some embodiments, the processing device 140 may determine the position information of the region of interest of the target object at the third time based on the third magnetic resonance image, and update the radiation parameters of the radiotherapy ray based on the position information of the region of interest at the third time. Exemplary radiation parameters include radiation angle, dose distribution, ray intensity, etc. Further, the processing device 140 instructs the radiotherapy device to continue emitting radiotherapy rays based on the updated radiation parameters. By adjusting the radiation parameters in a timely manner, the accuracy of radiotherapy can be improved.

[0149] In some embodiments, in response to determining that both the second movement amplitude and the third movement amplitude are greater than the threshold, indicating that the target object has neither returned to the position at the first time nor maintained the position at the second time, the processing device 140 may determine that it is necessary to continue interrupting the emission of radiotherapy rays and issue a prompt message to remind the target object to stop moving. After the target object stops moving for a certain period of time, the processing device 140 determines new radiation parameters based on the latest position information of the target object and instructs the radiotherapy device to continue emitting radiotherapy rays. In some embodiments, when the magnetic resonance device acquires a new navigation signal at a new moment, the processing device 140 may use it as the new second navigation signal, and determine whether the first movement amplitude of the target object is less than or equal to the threshold (i.e., whether it has returned to the position at the first time) based on the first navigation signal and the new second navigation signal, or determine whether the second movement amplitude of the target object is less than or equal to the threshold (i.e., whether it has maintained the new position) based on the new second navigation signal and the subsequently acquired third navigation signal. Only when the target object has returned to the position at the first time, or when the target object has maintained the new position for a certain period of time, will the processing device 140 determine that it is necessary to continue emitting radiotherapy rays.

[0150] According to process 1000, the present application detects the movement of the target object based on the navigation signal collected by the magnetic resonance device, which does not rely on an additional movement detection device and can reduce costs. Moreover, since the navigation signal can accurately reflect the movement of the target object, the present application can obtain accurate movement detection results based on the navigation signal, thereby improving the accuracy of guiding radiotherapy. Furthermore, since the navigation signal is collected quickly and the calculation amount is small, the present application can quickly obtain movement detection results based on the navigation signal, improving the efficiency of guiding radiotherapy.

[0151] It should be noted that the above description of process 1000 is only for illustration and example, and does not limit the scope of application of this specification. For those skilled in the art, various modifications and changes can be made to process 1000 under the guidance of this specification. However, these modifications and changes are still within the scope of this specification. In some embodiments, process 1000 can be completed through one or more additional steps not described and / or without one or more of the above steps. For example, process 1000 can include an additional step of transmitting the magnetic resonance image to a terminal device (e.g., the doctor's terminal 130) for display.

[0152] In some embodiments, other methods can be used to detect the movement of the target object to determine the movement amplitude of the target object. For example, additional motion detection devices (e.g., optical cameras, radars, etc.) can be used to detect the movement of the target object.

[0153] Figure 12 is a schematic diagram of an exemplary process 1200 for generating a first magnetic resonance image during a magnetic resonance-guided radiotherapy process according to some embodiments of this specification. In some embodiments, when it is determined that the first movement amplitude from the first time to the second time is less than the threshold, process 1200 can be executed. Process 1200 can be executed by the processing device 140 or Figure 2 the first or more modules shown. For example, process 1200 is executed by the third determination module 205 of the processing device 140. As Figure 12 shown, process 1200 can include the following steps.

[0154] Step 1201, obtain a first imaging signal collected by the magnetic resonance device before the radiotherapy ray is emitted. In some embodiments, step 1201 can be executed by the processing device 140 or the acquisition module 201.

[0155] As described above, before the radiotherapy device 112 emits the radiotherapy ray, the magnetic resonance device can execute a first imaging stage to collect a navigation signal and an imaging signal. The imaging signal collected in the first imaging stage is the first imaging signal (i.e., the pre-radiotherapy imaging signal). The processing device 140 can obtain the first imaging signal from the magnetic resonance device or a storage device for storing MRI signals (e.g., the storage device 150).

[0156] Step 1202, based on the first navigation signal and the first imaging signal, determine an initial time factor and an initial space factor. In some embodiments, step 1202 can be executed by the processing device 140 or the first determination module 202. In some embodiments, step 1202 is executed simultaneously with or before step 1002.

[0157] In some embodiments, step 1202 may be similar to step 303. For related descriptions, please refer to Figure 3 .

[0158] In some embodiments, the processing device 140 may determine a conversion coefficient and an initial time factor based on a first navigation signal. The conversion coefficient may represent the relationship between the time factor and the navigation signal. In some embodiments, the first navigation signal may be filled into the K-space to obtain a fourth K-space matrix. The processing device 140 may determine the conversion coefficient and the initial time factor based on the fourth K-space matrix. For example, the processing device 140 may determine the conversion coefficient and the initial time factor according to the singular value decomposition (SVD) algorithm. Merely as an example, the fourth K-space matrix may be referred to as K4. The fourth K-space matrix K4 may be expressed as where, an element in the fourth K-space matrix K4 represents the k-space data collected by a specific coil channel at a certain moment. For example, κ(k c , t1) represents the k-space data collected by the coil channel k c at the moment t1. The processing device 140 may perform SVD on the fourth K-space matrix K4 according to formula (8) to determine the conversion coefficient and the initial time factor: where, U k represents the projection coefficient matrix, represents the initial time factor (for example, the time factor represented by at least one time factor matrix), and D represents the singular value matrix. The conversion coefficient T may be determined based on the projection coefficient matrix U k and the singular value D matrix. For example, the conversion coefficient T may be (U k D) or where, represents the conjugate transpose matrix of the projection coefficient matrix U k , and D -1 represents the inverse matrix of the singular value matrix D.

[0159] In some embodiments, the first navigation signal only includes part of the navigation signals collected in the first imaging stage. The processing device 140 may determine the conversion coefficient T and the initial time factor based on the first navigation signal and other navigation signals collected in the first imaging stage The manner of determining the conversion coefficient T and the initial time factor based on the first navigation signal and other navigation signals is similar to the manner of determining the conversion coefficient T and the initial time factor based on the first navigation signal described above .

[0160] Further, the processing device 140 may determine an initial spatial factor U0 based on the initial time factor and the first imaging signal. In some embodiments, the processing device 140 may construct an optimization function related to the initial spatial factor U0. The optimization function may combine the first imaging signal and the initial time factor The processing device 140 may also determine at least one spatial factor by solving the optimization function. For example, the processing device 140 may determine the initial spatial factor U0 of the scanned object according to the fifth optimization function shown in formula (9): wherein, represents the optimal spatial factor determined by solving formula (9), U0 represents the initial spatial factor of the scanned object (for example, the spatial factor represented by at least one spatial factor matrix), c represents the number of coil channels of the MRI device, d h represents the K-space data obtained by filling the first imaging signal acquired by the h-th coil channel into the K-space, Ω represents the downsampling operator (which can be omitted in some cases), F represents the Fourier transform operator, h represents the coil channel number, S h represents the coil sensitivity map corresponding to the h-th coil channel, and Φ0 represents the initial time factor of the scanned object (for example, the time factor represented by at least one time factor matrix).

[0161] For another example, the processing device 140 may determine the initial spatial factor U0 of the scanned object according to the sixth optimization function shown in formula (10): wherein, λ represents the regularization parameter, TV(U tr ) represents the three-dimensional total variation, and λ||TV(U tr )||1 represents the constraint term related to at least one spatial factor matrix of the scanned object (which can be omitted in some cases).

[0162] Step 1203, in response to determining that the first motion amplitude is less than or equal to the threshold, determine a first updated time factor based on the second navigation signal. In some embodiments, step 1203 may be performed by the processing device 140 or the first determination module 202.

[0163] When the first motion amplitude is less than or equal to the threshold, it indicates that the target object has no obvious motion from the first time to the second time, and only the time factor needs to be updated, without updating the initial spatial factor U0.

[0164] In some embodiments, the processing device 140 may adopt a method similar to Figure 5 the method for determining the time factor described in Determine the first update time factor in the following manner. For example, the processing device 140 can fill the second navigation signal into the K-space to obtain the fifth K-space matrix. Further, the processing device 140 can determine the first update time factor by performing SVD on the fifth K-space matrix in a manner similar to that for determining the initial time factor in step 1202.

[0165] As another example, the processing device 140 can determine the first update time factor based on the fifth K-space matrix and the transformation coefficient U. For example, the processing device 140 can determine the first update time factor according to formula (11): where, represents the first update time factor, K5 represents the fifth K-space matrix, represents the transformation coefficient T determined in step 1202.

[0166] Step 1204: Generate the first magnetic resonance image of the target object based on the first update time factor and the initial spatial factor. The first magnetic resonance image corresponds to the second time. In some embodiments, step 1204 can be executed by the processing device 140 or the generation module 203.

[0167] The first magnetic resonance image can reflect the state of the target object at the second time. In some embodiments, the first magnetic resonance image can be a two-dimensional (2D) image, a three-dimensional (3D) image, etc.

[0168] In some embodiments, the first magnetic resonance image of the target object can be represented by a multi-dimensional tensor, and this tensor can be determined based on the first update time factor and the initial spatial factor U0. For example, when the first update time factor and the initial spatial factor U0 are available, the processing device 140 can generate the first magnetic resonance image A1 of the target object by determining the product of at least one time factor matrix and at least one spatial matrix factor. The at least one time factor matrix can include the first update time factor The at least one spatial matrix factor can include the initial spatial factor U0. Merely by way of example, the processing device 140 can generate the first magnetic resonance image A1 of the target object according to formula (12): where, A1 represents the multi-dimensional tensor used to represent the first magnetic resonance image of the target object, represents the first update time factor in the form of at least one time factor matrix, and U0 represents the initial spatial factor in the form of at least one spatial factor matrix.

[0169] In some embodiments, the processing device 140 may generate a first magnetic resonance image A1 of a target object corresponding to a specific time-varying dimension based on a time factor matrix and a spatial factor matrix corresponding to the specific time-varying dimension. For example, the processing device 140 may generate the first magnetic resonance image A1 of the heart by determining the product of the spatial factor matrix and a time factor matrix including time factors related to heart motion. The time factor matrix related to heart motion may include time factors related to heart motion.

[0170] According to process 1200, when it is determined that the first motion amplitude is less than or equal to the threshold, the first magnetic resonance image may be generated based on the first updated time factor and the initial spatial factor. The generation of the first magnetic resonance image involves simple calculations, thus having a short image generation delay, thereby improving the radiotherapy guidance efficiency. In some cases, the calculation of the basic data may be performed immediately after the acquisition of the first navigation signal (e.g., before the second imaging stage or simultaneously with the acquisition of the MRI signal during radiotherapy). In this way, the delay in generating the first magnetic resonance image can be further reduced, thereby further improving the radiotherapy efficiency.

[0171] Figure 13 FIG. 1300 is a schematic diagram of an exemplary process for generating a second magnetic resonance image during magnetic resonance-guided radiotherapy according to some embodiments of the present specification. In some embodiments, when it is determined that the first motion amplitude from the first time to the second time is greater than the threshold and the second motion amplitude from the first time to the third time is less than the threshold, process 1300 may be executed. In some embodiments, process 1300 may be executed by the processing device 140 or Figure 2 one or more of the illustrated modules. For example, process 1300 may be executed by the third determination module 205 of the processing device 140. As Figure 13 illustrated, process 1300 may include the following steps.

[0172] Step 1301, obtain a first imaging signal acquired by the magnetic resonance device before the radiotherapy ray is emitted. In some embodiments, step 1301 may be executed by the processing device 140 or the acquisition module 201.

[0173] Step 1301 may be similar to step 1201, and for related descriptions, please refer to Figure 12 , which will not be elaborated here.

[0174] Step 1302, based on the first navigation signal and the first imaging signal, determine an initial time factor and an initial spatial factor. In some embodiments, step 1302 may be executed by the processing device 140 or the first determination module 202.

[0175] Step 1302 may be similar to step 1202, and for related descriptions, please refer to Figure 12 , which will not be elaborated here.

[0176] Step 1303: In response to the second movement amplitude being less than or equal to the threshold, determine a second update time factor based on the third navigation signal. In some embodiments, step 1303 may be performed by the processing device 140 or the first determination module 202.

[0177] When the second movement amplitude is less than or equal to the threshold, it indicates that the target object has no obvious movement from the first time to the third time. Only the update of the time factor is required, and there is no need to update the initial spatial factor U0. In some embodiments, the processing device 140 may determine the second update time factor in a manner similar to determining the first update time factor. For a detailed description, please refer to step 1203. For example, the processing device 140 may fill the third navigation signal into the K-space to obtain a sixth K-space matrix, and perform SVD on the sixth K-space matrix to determine the second update time factor. Alternatively, the processing device 140 may determine the second update time factor based on the sixth K-space matrix and the conversion coefficient T.

[0178] Step 1304: Generate a second magnetic resonance image of the target object based on the second update time factor and the initial spatial factor. The second magnetic resonance image corresponds to the third time. In some embodiments, step 1304 may be performed by the processing device 140 or the generation module 203.

[0179] The second magnetic resonance image can reflect the state of the target object at the third time. The processing device 140 may determine the second magnetic resonance image in a manner similar to determining the first magnetic resonance image. For a detailed description, please refer to step 1204 and will not be elaborated here.

[0180] In some embodiments of this specification, when the target object returns to the position at the first time after movement, only the update of the time factor is required. At this time, the second magnetic resonance image can be generated based on the second update time factor and the initial spatial factor. The generation of the second magnetic resonance image involves simple calculations, resulting in a shorter image generation delay, thereby improving the radiotherapy guidance efficiency. In some cases, the calculation of the basic data can be performed immediately after collecting the first navigation signal (for example, before the second imaging stage or simultaneously with the acquisition of the MRI signal during radiotherapy). In this way, the delay in generating the second magnetic resonance image can be further reduced, thereby further improving the radiotherapy efficiency.

[0181] Figure 14It is a schematic diagram of an exemplary process 1400 for generating a third magnetic resonance image during a magnetic resonance-guided radiotherapy process shown in some embodiments of this specification. In some embodiments, when it is determined that both the first movement amplitude from the first time to the second time and the second movement amplitude from the first time to the third time are greater than a threshold, and the third movement amplitude from the second time to the third time is less than the threshold, process 1400 can be executed. In some embodiments, process 1400 can be executed by the processing device 140 or Figure 2 the first one or more modules shown. For example, process 1400 can be executed by the third determination module 205 of the processing device 140. As Figure 14 shown, process 1400 can include the following steps.

[0182] Step 1401, obtain a first imaging signal collected by the magnetic resonance device before the radiotherapy ray is emitted. In some embodiments, step 1401 can be executed by the processing device 140 or the acquisition module 201.

[0183] Step 1401 can be similar to step 1201, for related descriptions, please refer to Figure 12 , which will not be elaborated here.

[0184] Step 1402, based on the first navigation signal and the first imaging signal, determine an initial time factor and an initial space factor. In some embodiments, step 1402 can be executed by the processing device 140 or the first determination module 202.

[0185] Step 1402 can be similar to step 1202, for related descriptions, please refer to Figure 12 , which will not be elaborated here.

[0186] When the second movement amplitude is greater than the threshold and the third movement amplitude is less than the threshold, it indicates that the target object has moved and maintained at a new position. To improve the imaging accuracy, both the time factor and the space factor need to be updated through steps 1403 and 1404.

[0187] Step 1403, based on the third navigation signal, determine a second updated time factor. In some embodiments, step 1403 can be executed by the processing device 140 or the first determination module 202.

[0188] For a detailed description of the second updated time factor, please refer to step 1303, which will not be elaborated here.

[0189] Step 1404, based on the second imaging signal collected by the magnetic resonance device between the second time and the third time and the second updated time factor, determine an updated space factor. In some embodiments, step 1404 can be executed by the processing device 140 or the first determination module 202.

[0190] In some embodiments, the processing device 140 may employ the method for determining the spatial factor Uj described in Figure 6 to determine the updated spatial factor. For the relevant description, please refer to Figure 6 .

[0191] For example, the updated spatial factor may be determined by solving a seventh optimization function similar to the above formula (9) or formula (10). In the seventh optimization function, d h represents the k-space data corresponding to the second imaging signal acquired by the h-th coil channel. Φ0 may be replaced by a second update time factor, and other coefficients may be the same as those in formula (9) or formula (10). In some embodiments, the second imaging signals acquired between the second time and the third time include the imaging signal acquired at the second time, the imaging signal acquired at the third time, and the imaging signals acquired during the time period between the second time and the third time.

[0192] As another example, the processing device 140 may update the coil sensitivity maps of multiple coils for acquiring MRI signals based on the second imaging signal. The processing device 140 may further determine the updated spatial factor based on the second update time factor, the second imaging signal, and the updated coil sensitivity maps. For example, in the above seventh optimization function, S h may represent the updated coil sensitivity map corresponding to the h-th coil channel. The coil sensitivity map of a coil may reflect the distribution of the response degree of the coil with respect to different parts of the scanned object (i.e., the ability to receive MRI signals from different parts of the scanned object). Merely by way of example, for each coil, the processing device 140 may generate a coil image based on the second imaging signal acquired by the coil. The processing device 140 may determine the updated coil sensitivity maps of different coils based on the coil images. In some embodiments, the updated coil sensitivity maps may be determined based on a combination of the first imaging signal and the second imaging signal.

[0193] Step 1405: Generate a third magnetic resonance image of the target object based on the second update time factor and the updated spatial factor. The third magnetic resonance image corresponds to the third time. In some embodiments, step 1405 may be executed by the processing device 140 or the generation module 203.

[0194] The third magnetic resonance image may reflect the state of the target object at the third time. The processing device 140 may determine the third magnetic resonance image in a manner similar to that for determining the first magnetic resonance image. For the detailed description, please refer to step 1204 and will not be elaborated herein.

[0195] According to process 1400, when both the first and second movement amplitudes of the target object are greater than the threshold value and the third movement amplitude is less than the threshold value, it indicates that the target object has maintained its position at the second time. At this time, based on the second update time factor and the updated spatial factor, a third magnetic resonance image of the target object is generated, which can improve the imaging quality of the third magnetic resonance image, thereby improving the accuracy of radiotherapy.

[0196] In addition, significant movement of the scanned object (e.g., movement amplitude greater than the threshold) may also cause changes in the coil sensitivity map of the coil. According to some embodiments of the present application, if significant movement of the scanned object is detected, the coil sensitivity map of the coil can be updated, and the value of the updated spatial factor can be determined based on the second imaging signal and the updated coil sensitivity map. In this way, a more accurate updated spatial factor can be obtained, further improving the imaging quality of the third magnetic resonance image, thereby further improving the accuracy of radiotherapy.

[0197] Figure 15 is a schematic diagram for magnetic resonance-guided radiotherapy shown according to some embodiments of the present specification. As Figure 15 shown, the magnetic resonance device can acquire magnetic resonance signals before and during radiotherapy. The magnetic resonance signals include navigation signals and imaging signals.

[0198] The processing device 140 can determine an initial time basis and an initial spatial basis based on the magnetic resonance signals acquired before radiotherapy. Specifically, the processing device 140 can determine an initial time factor based on the first navigation signal acquired at the first time before radiotherapy. Further, the processing device 140 can determine an initial spatial factor based on the first navigation signal and the first imaging signal.

[0199] During radiotherapy, the processing device 140 can detect the movement of the target object in real time based on the navigation signal and guide the radiotherapy process in real time based on the detection result. Specifically, the processing device 140 can obtain the second navigation signal acquired at the second time during radiotherapy and determine whether the first movement amplitude of the target object from the first time to the second time is greater than the threshold value based on the first navigation signal and the second navigation signal. In response to determining that the first movement amplitude is less than or equal to the threshold value, the processing device 140 can instruct the radiotherapy device to continue emitting radiotherapy rays. At this time, the processing device 140 can determine a first update time factor based on the second navigation signal and generate a first magnetic resonance image corresponding to the second time based on the first update time factor and the initial spatial factor.

[0200] In response to determining that the first movement amplitude is greater than the threshold, the processing device 140 may instruct the radiotherapy device to stop emitting radiotherapy rays and obtain a third navigation signal collected at a third time. Further, based on the third navigation signal, it is determined whether to stop emitting radiotherapy rays. Specifically, the processing device 140 may determine whether the second movement amplitude of the target object from the first time to the third time is greater than the threshold based on the first navigation signal and the third navigation signal. In response to determining that the second movement amplitude is less than or equal to the threshold, the processing device 140 may instruct the radiotherapy device to continue emitting radiotherapy rays. At this time, the processing device 140 may determine a second update time factor based on the third navigation signal, and generate a second magnetic resonance image corresponding to the third time based on the second update time factor and the initial spatial factor.

[0201] In response to determining that the second movement amplitude is greater than the threshold, the processing device 140 may determine whether the third movement amplitude of the target object from the second time to the third time is greater than the threshold based on the second navigation signal and the third navigation signal. In response to determining that the third movement amplitude is less than or equal to the threshold, the processing device 140 may instruct the radiotherapy device to continue emitting radiotherapy rays. At this time, the processing device 140 may determine a second update time factor based on the third navigation signal, and further determine an updated spatial factor based on the second update time factor and the second imaging signal. Then, the processing device 140 may generate a third magnetic resonance image corresponding to the third time based on the second update time factor and the updated spatial factor. In response to determining that both the second movement amplitude and the third movement amplitude are greater than the threshold, indicating that the target object does not maintain its position at the second time, the processing device 140 may determine that it is necessary to continue terminating the emission of radiotherapy rays.

[0202] In some embodiments of this specification, the movement of the target object may be detected based on the navigation signal collected by the magnetic resonance device, so as to guide radiotherapy in real time. The beneficial effects that the embodiments of this specification may bring include but are not limited to: (1) In some embodiments, this application detects the movement of the target object based on the navigation signal collected by the magnetic resonance device, which does not rely on additional movement detection devices and can reduce costs; (2) Since the navigation signal can relatively accurately reflect the movement of the target object, this application can obtain accurate movement detection results based on the navigation signal, thereby improving the accuracy of guiding radiotherapy; (3) Since the navigation signal is collected quickly and has a small amount of calculation, this application can quickly obtain movement detection results based on the navigation signal, improving the efficiency of guiding radiotherapy; (4) Continuously detecting the movement of the target object based on the navigation signal, for different movement detection results, high-precision magnetic resonance images can be quickly generated to timely adjust the radiotherapy process, thereby improving the efficiency and accuracy of the radiotherapy process, and even realizing real-time guidance of the radiotherapy process.

[0203] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only an example and does not constitute a limitation to this specification. Although not explicitly stated here, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification, so such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this specification.

[0204] Meanwhile, this specification uses specific terms to describe the embodiments of this specification. Such as "one embodiment", "an embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of this specification. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.

[0205] In addition, unless clearly stated in the claims, the order of the processing elements and sequences, the use of numerical letters, or the use of other names in this specification is not used to limit the order of the processes and methods of this specification. Although some currently considered useful invention embodiments are discussed through various examples in the above disclosure, it should be understood that such details only serve the purpose of illustration. The appended claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that conform to the essence and scope of the embodiments of this specification. For example, although the system components described above can be implemented by hardware devices, they can also be implemented only through software solutions, such as installing the described system on existing servers or mobile devices.

[0206] Similarly, it should be noted that, in order to simplify the expression of the disclosure of this specification and thus help the understanding of one or more invention embodiments, in the previous description of the embodiments of this specification, sometimes multiple features are merged into one embodiment, drawing, or description thereof. However, this disclosure method does not mean that the features required by the object of this specification are more than those mentioned in the claims. In fact, the features of the embodiments are fewer than all the features of the individual embodiments disclosed above.

[0207] In some embodiments, numbers are used to describe components and the quantity of attributes. It should be understood that such numbers used in the description of embodiments are, in some examples, modified by the modifiers "about", "approximately", or "substantially". Unless otherwise specified, "about", "approximately", or "substantially" indicate that the said numbers allow a variation of ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may vary according to the characteristics required by individual embodiments. In some embodiments, the numerical parameters should consider the specified significant digits and adopt the method of retaining the general number of digits. Although the numerical ranges and parameters used in some embodiments of this specification to confirm the breadth of their scope are approximate values, in specific embodiments, such numerical settings are as precise as possible within the feasible range.

[0208] For each patent, patent application, patent application publication, and other materials cited in this specification, such as articles, books, specifications, publications, documents, etc., their entire contents are hereby incorporated into this specification by reference. This excludes the application history files that are inconsistent with or conflict with the content of this specification, and also excludes the files (currently or subsequently appended to this specification) that limit the broadest scope of the claims of this specification. It should be noted that if there are inconsistencies or conflicts between the descriptions, definitions, and / or uses of terms in the attached materials of this specification and the content described in this specification, the descriptions, definitions, and / or uses of terms in this specification shall prevail.

[0209] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, by way of example and not limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. A magnetic resonance-guided radiotherapy method, characterized in that, The method includes: Obtaining a first navigation signal and a second navigation signal collected by a magnetic resonance device during magnetic resonance scanning of a target object, where the first navigation signal is collected by the magnetic resonance device at a first time before radiotherapy ray emission, and the second navigation signal is collected by the magnetic resonance device at a second time after radiotherapy ray emission; Based on the first navigation signal and the second navigation signal, determining whether a first movement amplitude of the target object from the first time to the second time is greater than a threshold; Based on the determination result of whether the first movement amplitude is greater than the threshold, determining whether to stop emitting radiotherapy rays.

2. The method according to claim 1, wherein The method further includes: Obtaining a first imaging signal collected by the magnetic resonance device before radiotherapy ray emission; Based on the first navigation signal and the first imaging signal, determining an initial time factor and an initial space factor; In response to determining that the first movement amplitude is less than or equal to the threshold, determining a first updated time factor based on the second navigation signal; Based on the first updated time factor and the initial space factor, generating a first magnetic resonance image of the target object, where the first magnetic resonance image corresponds to the second time.

3. The method according to claim 1, characterized in that, The method further includes: In response to determining that the first movement amplitude is greater than the threshold, Instructing the radiotherapy device to stop emitting the radiotherapy rays; Obtaining a third navigation signal collected by the magnetic resonance device at a third time, where the third time is later than the second time; Based on the first navigation signal and the third navigation signal, determining whether a second movement amplitude of the target object from the first time to the third time is greater than the threshold; In response to determining that the second movement amplitude is less than or equal to the threshold, instructing the radiotherapy device to continue emitting the radiotherapy rays.

4. The method according to claim 3, characterized in that, The method further includes: Obtaining a first imaging signal collected by the magnetic resonance device before radiotherapy ray emission; Based on the first navigation signal and the first imaging signal, determining an initial time factor and an initial space factor; In response to the second movement amplitude being less than or equal to the threshold, determining a second updated time factor based on the third navigation signal; and Based on the second updated time factor and the initial space factor, generating a second magnetic resonance image of the target object, where the second magnetic resonance image corresponds to the third time.

5. The method according to claim 3, wherein In response to determining that the second movement amplitude is greater than the threshold, the method further includes: Based on the second navigation signal and the third navigation signal, determining whether a third movement amplitude of the target object from the second time to the third time is greater than the threshold; In response to determining that the third movement amplitude is less than or equal to the threshold, instructing the radiotherapy device to continue emitting the radiotherapy rays.

6. The method according to claim 5, characterized in that, In response to determining that the third movement amplitude is less than or equal to the threshold, the method further includes: Obtaining a first imaging signal collected by the magnetic resonance device before radiotherapy ray emission; Based on the first navigation signal and the first imaging signal, determining an initial time factor and an initial space factor; Based on the third navigation signal, determining a second updated time factor; Determine an updated spatial factor based on the second imaging signal and the second update time factor acquired by the magnetic resonance device between the second time and the third time; Generate a third magnetic resonance image of the target object based on the second update time factor and the updated spatial factor, where the third magnetic resonance image corresponds to the third time.

7. The method according to claim 6, wherein the instructing the radiotherapy device to continue emitting the radiotherapy rays in response to determining that the third movement amplitude is less than the threshold comprises: Determine position information of a region of interest of the target object at the third time based on the third magnetic resonance image; Update the radiation parameters of the radiotherapy rays based on the position information; Instruct the radiotherapy device to continue emitting the radiotherapy rays based on the updated radiation parameters.

8. The method according to claim 1, wherein The first navigation signal and the second navigation signal have a first readout direction, The determining whether a first movement amplitude of the target object from the first time to the second time is greater than a threshold based on the first navigation signal and the second navigation signal comprises: Obtain a first reference navigation signal and a second reference navigation signal acquired by the magnetic resonance device, where the first reference navigation signal is acquired after the first time and the second reference navigation signal is acquired after the second time, and the first reference navigation signal and the second reference navigation signal have a second readout direction different from the first readout direction; Determine whether a first movement amplitude of the target object from the first time to the second time is greater than a threshold based on the first navigation signal, the second navigation signal, the first reference navigation signal, and the second reference navigation signal.

9. A magnetic resonance guided radiotherapy system, comprising: An acquisition module configured to acquire a first navigation signal and a second navigation signal acquired by a magnetic resonance device during a magnetic resonance scan of a target object, where the first navigation signal is acquired at a first time before the emission of radiotherapy rays, and the second navigation signal is acquired at a second time after the emission of radiotherapy rays; A first determination module configured to determine whether a first movement amplitude of the target object from the first time to the second time is greater than a threshold based on the first navigation signal and the second navigation signal; A second determination module configured to determine whether to stop emitting the radiotherapy rays based on a determination result of whether the first movement amplitude is greater than the threshold.

10. A magnetic resonance guided radiotherapy system, comprising: At least one storage device for storing computer instructions; At least one processor for executing the computer instructions to implement the method according to any one of claims 1-8.

Images