Magnetic resonance system and scanning method based on magnetic resonance system

Abstract

The embodiment of the invention discloses a magnetic resonance system and a scanning method based on the magnetic resonance system, and the method comprises the steps: obtaining a numerical distribution diagram determined based on the magnetic resonance system for at least one scanning parameter; determining a sensitive area, related to the implant, of the object to be scanned; determining a first numerical value corresponding to the sensitive area in the numerical value distribution diagram; acquiring a limit value of the at least one scanning parameter of the implant limited by the object to be scanned; adjusting a limit value of the at least one scanning parameter based on the first value; and; and scanning the object to be scanned by using the adjusted limit value of the at least one scanning parameter.

Description

Technical Field

[0001] Embodiments of the present invention generally relate to medical imaging technologies, and in particular, to a magnetic resonance (MR) system and a scanning method based on the magnetic resonance system. Background Art

[0002] Magnetic resonance imaging technology has been widely applied in the field of medical diagnosis. A magnetic resonance system generally includes a main magnet, a radio frequency system, a gradient system, and a computer system. Among them, the main magnet is used to generate a main magnetic field, and an object to be scanned is positioned in the main magnetic field space to receive magnetic resonance scanning. The radio frequency system is used to generate radio frequency pulses to excite the object to be scanned to generate magnetic resonance signals. The gradient system is used to generate a gradient field superimposed on the main magnetic field so that the magnetic resonance signals have encoding information. The magnetic resonance signals with encoding information are converted into digital image signals, and are processed by a computer for signal processing to reconstruct a medical image of the object to be scanned.

[0003] Generally, corresponding scanning parameters are selected to perform magnetic resonance scanning based on different clinical diagnosis requirements. These parameters may involve magnetic field, gradient, radio frequency, reconstruction method, etc. For an object to be scanned wearing an implant, when setting the scanning parameters, it is also necessary to refer to the corresponding implant safety manual, which stipulates the safety limits of the scanning parameters that its implant product can adapt to when performing magnetic resonance scanning. This limit is usually determined by the implant manufacturer according to the characteristics of its own implant product, combined with the magnetic resonance simulation environment, simulation environment, separate (or single) gradient field or radio frequency field environment, or the comprehensive parameters of the products of each magnetic resonance product manufacturer.

[0004] In addition, for the magnetic resonance scanning of patients wearing implants, industry standards have gradually been formed. For example, the standard "AAMI / ISO TIR10974" formulated by the Association for the Advancement of Medical Instrumentation (AAMI) in the United States stipulates the safety limits of various scanning parameters for implants.

[0005] The implant safety manual or standard stipulates safety limits for different implants, which may be instructive for performing safe scans. However, if the safety limits are too low, it may lead to an inability to obtain images that meet the clinical diagnosis requirements. Moreover, for patients wearing multiple implants, doctors usually do not know how to set appropriate scanning parameters so that they can obtain images that meet the clinical diagnosis requirements and avoid safety problems during the scanning process. Summary of the Invention

[0006] On the one hand, the present invention provides a scanning method based on a magnetic resonance system, which includes: for at least one scanning parameter, obtaining a numerical distribution map determined based on the magnetic resonance system; determining a sensitive area related to an implant of an object to be scanned; determining a first value corresponding to the sensitive area in the numerical distribution map; obtaining a limit value of the at least one scanning parameter limited by the implant of the object to be scanned; adjusting the limit value of the at least one scanning parameter based on the first value; and scanning the object to be scanned by applying the adjusted limit value of the at least one scanning parameter.

[0007] On the other hand, the present invention provides a magnetic resonance scanning system, which includes a magnetic resonance component and a controller. The controller is used to control the magnetic resonance component to scan an object to be scanned and execute the magnetic resonance scanning method of the above aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, in which like reference numerals represent like parts throughout the drawings, wherein:

[0009] Figure 1 A block diagram of a magnetic resonance scanning system showing some embodiments is presented;

[0010] Figure 2 A schematic diagram for setting safety limit values of scanning parameters in a safety manual for an implant is shown;

[0011] Figure 3 An example of an object to be scanned wearing multiple implants is shown;

[0012] Figure 4 A flowchart of a scanning method based on a magnetic resonance system according to some embodiments of the present invention is shown;

[0013] Figure 5 An example of a body model and adding implant identification in the body model is shown;

[0014] Figure 6 An example of edge information of implant identification is shown;

[0015] Figure 7 A flowchart of a scanning method based on a magnetic resonance system according to some other embodiments of the present invention is shown;

[0016] Figure 8 An example of a numerical distribution map and a body model is shown;

[0017] Figure 9 A flowchart of a scanning method based on a magnetic resonance system according to some other embodiments of the present invention is shown;

[0018] Figure 10 A flowchart of a scanning method based on a magnetic resonance system according to some other embodiments of the present invention;

[0019] Figure 11 A flowchart of a scanning method based on a magnetic resonance system according to some other embodiments of the present invention;

[0020] Figure 12 A block diagram of a magnetic resonance system not according to some embodiments of the present invention. Detailed implementation manners

[0021] To help those skilled in the art to accurately understand the subject matter claimed by the present invention, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following detailed description of these specific embodiments, the present specification does not describe some well-known functions or structures in detail to avoid unnecessary details from affecting the disclosure of the present invention.

[0022] Unless otherwise defined, technical terms or scientific terms used in the claims and the specification should have the ordinary meaning understood by those of ordinary skill in the art to which the present invention pertains. The terms "first", "second" and similar terms used in the present specification and the claims do not denote any order, quantity or importance, but are only used to distinguish different components. The terms "a" or "an" and the like do not denote a limitation of quantity, but mean that there is at least one. The terms "comprising" or "including" and the like mean that the elements or items appearing before "comprising" or "including" cover the elements or items listed after "comprising" or "including" and their equivalent elements, and do not exclude other elements or items. The terms "connected" or "coupled" and the like are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections. In addition, it should be understood that the reference to "one embodiment", "some embodiments" or "embodiments" of the present disclosure is not intended to be construed as excluding the existence of additional embodiments that also include the recited features.

[0023] The "modules", "units" and the like described herein may be implemented in a software, hardware or a combination of software and hardware manner. For example, according to certain aspects of the embodiments of the present invention, the "modules" described herein may be implemented as computer program modules or circuit modules.

[0024] The "image" described herein may include the displayed image, or may also include the data forming the displayed image.

[0025] Reference Figure 1, which shows an exemplary magnetic resonance scanning system 100 according to some embodiments of the present invention. The operator workstation 110 is used to control the operation of the MRI system 100. The operator workstation 110 includes an input device 114, a control panel 116, and a display 118. The input device 114 can be a joystick, keyboard, mouse, trackball, touch-activated screen, voice control, or any similar or equivalent input device. The control panel 116 can include a keyboard, touch-activated screen, voice control, buttons, sliders, or any similar or equivalent control device. The operator workstation 110 is coupled to and communicates with a computer system 120, and provides an interface for the operator to plan magnetic resonance scans, display images and graphical user interfaces, perform image processing, and store data and images.

[0026] The computer system 120 includes a plurality of modules that communicate with each other via an electrical and / or data connection module 122. The connection module 122 can be a wired communication link, an optical fiber communication link, a wireless communication link, etc. The computer system 120 can include a central processing unit (CPU) 124, a memory 126, and an image processor 128. In some embodiments, the image processor 128 can be replaced by image processing functions running in the CPU 124. The computer system 120 can be connected to an archival media device, permanent or backup memory, or a network. The computer system 120 can be coupled to and communicate with a separate MRI system controller 130.

[0027] The MRI system controller 130 includes a set of modules that communicate with each other via an electrical and / or data connection module 132. The connection module 132 can be a direct wired communication link, an optical fiber communication link, a wireless communication link, etc. In an alternative embodiment, the modules of the computer system 120 and the MRI system controller 130 can be implemented on the same computer system or multiple computer systems. The MRI system controller 130 can include a CPU 131, a sequence pulse generator 133 that communicates with the operator workstation 110, a transceiver (or RF transceiver) 135, a gradient controller 136, a memory 137, and an array processor 139.

[0028] The object 170 for MR scanning can be positioned within the cylindrical imaging volume 146 of the magnetic resonance assembly 140 via a scanning bed, a camera (or other auxiliary positioning means), etc. One or more implants may be worn on the body of the object 170. The MRI system controller 130 controls the scanning bed to travel along the Z-axis direction of the magnetic resonance system to transfer a predetermined part of the object 170 to be scanned into the imaging volume 146. The magnetic resonance assembly 140 includes a superconducting magnet having superconducting coils 144, a radio frequency coil assembly, and a gradient coil assembly 142. The superconducting coils 144 have a magnet bore to form the cylindrical imaging volume 146. The superconducting coils 144 provide a static uniform longitudinal magnetic field B throughout the cylindrical imaging volume 146 during operation. 0 . The radio frequency coil assembly may include a body coil 148 and a surface coil 149, which can be used to transmit and / or receive radio frequency signals.

[0029] The MRI system controller 130 can receive commands from the operator workstation 110 to indicate the scan sequence to be executed during the MRI scan. The above "scan sequence" refers to a combination of pulses with specific intensities, shapes, and timings, etc., applied during the execution of a magnetic resonance imaging scan. These pulses typically may include, for example, radio frequency pulses and gradient pulses. Multiple scan sequences can be pre-stored in the computer system 120 to enable the indication of a sequence suitable for clinical detection requirements via the operator workstation. The clinical detection requirements may include, for example, the imaging site, imaging function, imaging effect, scan safety, etc. The sequence pulse generator 133 of the MRI system controller 130 operates based on the indicated sequence to send instructions describing the timings, intensities, and shapes of the radio frequency pulses and gradient pulses in the sequence to operate the system components that execute the sequence.

[0030] The radio frequency pulses in the scan sequence sent by the pulse generator 133 can be generated via the transceiver 135 and amplified by the radio frequency power amplifier 162. The amplified radio frequency pulses are provided to the body coil 148 via the transmit / receive switch (T / R switch) 164. The RF body coil 148 then provides a transverse magnetic field. As a non-limiting example, at least a part of the radio frequency transmission link is constituted by the transmit part in the transceiver 135, the radio frequency power amplifier 162, the T / R switch 164, etc. This transverse magnetic field is substantially perpendicular to B throughout the cylindrical imaging volume 146. 0 , and this transverse magnetic field is used to excite the excited nuclei in the scanned object to generate MR signals.

[0031] The intensity of this radio frequency pulse (or radio frequency field intensity) B1 can be set based on different imaging application settings. Generally, the larger the radio frequency field intensity B1, the greater the transmitted radio frequency power. A part of the energy carried by the radio frequency pulse is released in the form of heat and absorbed by the human body. Over time, this energy is deposited in the scanned part of the human body, causing an increase in the local or whole-body temperature of the human body. The energy that can be absorbed by the human body per unit weight per unit time is defined as SAR (specific absorption rate), and different SAR values are usually set for different parts of the human body. When a patient wears an implant, more radio frequency energy may accumulate at the implant, thus posing a safety hazard to the patient's body. Therefore, it may be necessary to set limits for the radio frequency field intensity B1 and SAR for the implant to avoid safety problems. The limit of this radio frequency field intensity B1 can be to limit any one of the radio frequency field peak value, radio frequency field average value, or radio frequency field root mean square value (B1+rms).

[0032] The gradient pulses in the scan sequence sent by the pulse generator 133 can be generated via the gradient controller 136 and act on the gradient driver 150, which includes G x 、G y and G z amplifiers, etc. G x 、G y and G z Each of the G

[0033] gradient amplifiers is used to excite the corresponding gradient coils in the gradient coil assembly 142 (for example, the gradient coils respectively arranged along the X-axis, Y-axis, and Z-axis of the magnetic resonance system) to generate a gradient magnetic field superimposed on the main magnetic field, forming a magnetic field gradient for spatially encoding MR signals during MR scanning.

[0034] During the magnetic resonance scanning process, the superimposed gradient fields need to be switched quickly, so that the magnetic field intensity changes with time. The rate of change of this magnetic field intensity with time is the magnetic field change rate (dB / dt), and another related parameter is the maximum gradient slew rate. Too rapid a change in the magnetic field may cause the implant in the patient's body to be displaced, bringing safety problems. Therefore, when there is an implant in the object to be scanned, it may be necessary to limit the value of the magnetic field change rate.

[0035] As described above, the RF body coil 148 and the RF surface coil 149 can be used to transmit radiofrequency pulses and / or receive MR signals from the scanned object. The MR signals emitted by the nuclei excited within the scanned object can be sensed and received by the RF body coil 148 or the RF surface coil 149 and sent back to the preamplifier 166 through the T / R switch 164. The T / R switch 164 can be controlled by a signal from the MRI system controller 130 to electrically connect the radiofrequency power amplifier 162 to the RF body coil 148 during the transmit mode and connect the preamplifier 166 to the RF body coil 148 during the receive mode. The T / R switch 164 can also enable the RF surface coil 149 to be used in the transmit mode or the receive mode.

[0036] In some embodiments, the MR signals sensed and received by the RF body coil 148 or the RF surface coil 149 and amplified by the preamplifier 166 are demodulated, filtered, and digitized in the receive portion of the transceiver 135 and transmitted as an array of raw k-space data to the memory 137 in the MRI system controller 130.

[0037] The reconstructed magnetic resonance images can be obtained by transforming / processing the stored raw k-space data. For each image to be reconstructed, the data is rearranged into separate k-space data arrays, and each of these separate k-space data arrays is input to the array processor 139, which is operated to transform the data into an array of image data.

[0038] The array processor 139 uses a transformation method, most commonly the Fourier transform, to create an image from the received MR signals. These images are transferred to the computer system 120 and stored in the memory 126. In response to commands received from the operator workstation 110, the image data can be stored in long-term memory or can be further processed by the image processor 128 and transferred to the operator workstation 110 for presentation on the display 118.

[0039] In various embodiments, the components of the computer system 120, the MRI system controller 130 can be implemented on the same computer system or multiple computer systems. It should be understood that Figure 1 the illustrated MRI system 100 is for illustration. A suitable MRI system can include more, fewer, and / or different components.

[0040] The MRI system controller 130 and the image processor 128 may respectively or jointly include a computer processor and a storage medium, on which a program for performing predetermined data processing to be executed by the computer processor is recorded. For example, programs for implementing scanning processing (such as scanning parameter setting, scanning control flow, imaging sequence), image reconstruction, image processing, etc. may be stored on the storage medium. Specifically, a scanning method based on a magnetic resonance system according to any embodiment of the present invention may be stored on the storage medium. The above storage medium may include, for example, ROM, floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, or non-volatile memory card.

[0041] As Figure 2 shown, for some implants, such as the Deep Brain Stimulation (DBS) of Boston Scientific Corporation, different limits of the root mean square value of the radio frequency field (B1+rms) are set for different human body regions A, B, C, D in its safety manual, and different limits of SAR are also set for the different human body regions A, B, C, D. Based on the positioning information of the scanned object in the magnetic resonance system, if the system center (ISO center) is positioned in region A, or region A is aligned with the ISO center of the magnetic resonance system, it is recommended to apply the parameter limits of region A. Correspondingly, if region B is aligned with the ISO center, it is recommended to apply the limit parameters of region B. For region D, no limit is set, so when the ISO center is positioned in region D, scanning can be performed in the normal mode.

[0042] However, the ISO center may be positioned between adjacent regions, resulting in doctors being unsure which set of limits to choose. When using the most stringent limits, such as those of region A, it may lead to unsatisfactory image quality.

[0043] There are also some implant safety manuals that only specify relatively stringent parameter limits without more refined analysis based on the region to be scanned. For example, the safety manual of the Biomet Spine Simulator Manual of BIOMET company specifies that the limit of the spatial gradient field strength is 250 gauss / cm, the limit of the magnetic field change rate is 20 tesla / second, and for a 25-minute scanning time, the limit of SAR is 1.1 watt / kg. The stringent limits may make some scanning sequences unavailable or result in unsatisfactory image quality. When the region of interest to be scanned is far from the implant, applying higher limits may be more compatible with image quality and safety. However, doctors may use more conservative parameter settings because they are unsure how to set the limits.

[0044] When the scanned object wears multiple implants, choosing the most stringent implant safety limits can maximize the avoidance of safety problems, but this may result in the inability to perform normal scanning.Figure 3 An example is shown where a subject to be scanned wears multiple implants, including a brain stimulator 310 and a cardiac pacemaker 320. According to the corresponding safety manual, the limits for the brain stimulator 310 are: SAR less than or equal to 0.2 W / kg (watts per kilogram), B1rms (B1) less than or equal to 1.6 μT (microtesla), and the limits for the cardiac pacemaker 320 are: SAR less than or equal to 2 W / kg, B1rms (B1) less than or equal to 2.8 μT. For safety considerations, the safety limits of the brain stimulator 310 may be selected during magnetic resonance scanning, however this may lead to image problems.

[0045] The inventors of the present application have found that implant manufacturers or standard associations usually analyze the safety of scanning parameters based on theoretical values, simple magnetic resonance simulation environments, single or separate gradient field or radio frequency field environments, or comprehensive parameters of magnetic resonance products from multiple manufacturers. However, due to the differences between actual magnetic resonance products and the above analyses, there may be room for adjustment of some parameter limits.

[0046] Figure 4 A flowchart 400 of a scanning method based on a magnetic resonance system according to an embodiment of the present invention is shown. In step 410, for at least one scanning parameter, a numerical distribution map determined based on the magnetic resonance system is obtained. The at least one scanning parameter may be a parameter whose value range is restricted by implants, for example, it may include one or more of radio frequency field intensity B1 (such as B1+rms), SAR (wherein it may include whole body SAR value, head SAR, and SAR of other body parts), spatial gradient field intensity (SpatialGradient), maximum gradient slew rate (Max Slew Rate), and magnetic field change rate (dB / dt), etc. The numerical distribution map of the at least one scanning parameter is determined based on the magnetic resonance system. For example, it can be obtained by actual measurement, simulation, monitoring, etc. of the magnetic resonance system currently performing magnetic resonance scanning on the subject to be scanned. Among them, the values of the scanning parameters can be distributed in the magnetic field space coordinates of the magnetic resonance system to form a numerical array or a color temperature map. The numerical distribution map may be pre-stored in the magnetic resonance system, or obtained in real time when performing the scanning method of the embodiment of the present invention. The numerical distribution map may include, for example, a radio frequency field map, a SAR distribution map, magnetic field change rate maps of different gradient axes, a spatial gradient field map, etc.

[0047] In step 420, a sensitive area related to the implant of the subject to be scanned is determined. The sensitive area may be the area where the implant is located, or an area with a lower safety limit.

[0048] In some embodiments, the sensitive area may be determined with reference to the implant safety manual. For example, when a plurality of limit areas are specified in an implant safety manual (such as Figure 2If it is as shown in (e.g., area A), the sensitive area can be the area with the most stringent limit value. Another example is that when parameter limit values are set for multiple implants in multiple implant safety manuals respectively, the sensitive area can be the area with the most stringent limit value among the areas where the multiple implants are located (e.g., Figure 3 area 330 where the brain stimulator 310 is located in ). Still another example is that if the implant safety manual does not divide the limit value areas but only stipulates the parameter limit values, the area where the corresponding implant is located in the object to be scanned can be determined as the sensitive area.

[0049] In step 430, a first value corresponding to the sensitive area is determined in the numerical distribution map. As described above, the values of the scanning parameters in the numerical distribution map can be distributed in the magnetic field spatial coordinates of the magnetic resonance system, and thus can correspond to the spatial position information of the magnetic resonance system. When the object to be scanned is undergoing magnetic resonance scanning, it is positioned in the magnetic field space of the magnetic resonance. Therefore, the position information of the object to be scanned and the numerical distribution map can be matched through the spatial coordinates of the magnetic resonance system, so that the value corresponding to the sensitive area of the object to be scanned can be determined in the numerical distribution map. This will be described in detail below in combination with Figure 8 step 430.

[0050] In step 440, the limit value of the at least one scanning parameter of the implant restricted by the object to be scanned is obtained. The limit value obtained in this step can be the only limit value of the scanning parameter, or the "most stringent limit value" among multiple limit values, e.g., Figure 2 the limit value corresponding to area A in or Figure 3 the limit value corresponding to the brain stimulator 310 in .

[0051] In step 450, the limit value of the at least one scanning parameter is adjusted based on the first value.

[0052] In step 460, the adjusted limit value is applied to scan the object to be scanned.

[0053] Generally, the radiofrequency field and the main magnetic field of the magnetic resonance system are not completely uniform but vary compared to the system center (ISO center). When setting the system parameters, the above-mentioned safety limit values are applied to the system center instead of the area where the implant is located. When determining the safety limit values, it is usually assumed that the sensitive area is located at the system center. However, during actual scanning, the area where the implant is located or the above-mentioned sensitive area may be far from the system center. In the embodiments of the present invention, by obtaining the actual parameter value distribution map of the magnetic resonance system and determining the value corresponding to the actual sensitive area therein to adjust the safety limit values, more accurate safety limit values can be obtained.

[0054] Figure 5FIG. 500 is a flowchart of a scanning method based on a magnetic resonance system according to other embodiments of the present invention, which further includes step 510 and step 520. In step 510, a body model of an object to be scanned is obtained. In step 520, the position information of the body model relative to the magnetic resonance system is determined based on the positioning information of the object to be scanned in the magnetic resonance system. Specifically, a corresponding part to be scanned can be determined in the body model and its center can be aligned with the system center, so that the position information of the body model relative to the magnetic resonance system is determined, and this position information also corresponds to the numerical distribution map of the magnetic resonance system. As Figure 5 shown, step 420 may specifically include: determining a sensitive area in the body model.

[0055] Optionally, the sensitive area includes the area where the implant of the object to be scanned is located. When there are multiple implants, the sensitive area includes the area where the implant with the strictest limit on at least one scanning parameter is located.

[0056] In step 420, the sensitive area where the implant is located can be determined by adding an implant identifier in the body model, which may specifically include step 421 and step 422. In step 421, an implant identifier is added to the body model based on the implant information of the object to be scanned. In step 422, the area where the implant of the object to be scanned is located is determined based on the added implant identifier, and this area where the implant is located is used as the sensitive area.

[0057] This will be described in detail below in combination with Figure 6 how to obtain the body model and determine the sensitive area in the body model. Figure 6 FIG. shows an example of the body model 610. In some embodiments, the body model 610 can be obtained based on the optical image of the object to be scanned. For example, the object to be scanned positioned on the scanning bed can be photographed by an optical camera to obtain a two-dimensional or three-dimensional optical image of the object to be scanned. This optical image can be directly used as the body model of the object to be scanned, or can be used as the body model after appropriate calibration. Alternatively, the optical image can be used to register a pre-stored standard body model to obtain a personalized body model adapted to the body type of the object to be scanned.

[0058] The body model can be a three-dimensional model with a human-like structure. For example, it can include, but is not limited to, the torso, limbs, head, brain, heart, liver, spleen, stomach, bones, etc., to facilitate adding implant markers at more accurate positions. The body model can have a more simplified structure. For example, it can only include the outer contour, and the user can add implant markers to the simplified body model based on their own knowledge of the human body structure. The body model can be obtained by matching with the object to be scanned. This "matching" can include being consistent or similar to the object to be scanned in terms of height, weight, body proportion, gender, age, etc. In an example of the present invention, implant markers can be added to the body model 610 through a graphical user interface.

[0059] Implants of different types and models may have different shapes, structures, and sizes. Implant markers representing different implants can be pre-stored in the magnetic resonance system. The implant markers can have a shape and structure similar to the actual implant products, enabling the operator to quickly select a suitable implant marker according to the implant information of the object to be scanned (such as one or more of implant type, model, size, body part, etc.) and add it to the body model. As Figure 6 shown, implant markers 622 and 624 added to the body model 610 are shown. Implant marker 622 represents a brain stimulator, for example, and implant marker 624 represents a cardiac pacemaker, for example. The implant markers 622 and 624 can include one or more of electrodes, wires, a casing, etc.

[0060] One of the regions where the implant marker is located in the body model (for example, corresponding to the most stringent safety limit) can be used as the sensitive region. In some embodiments, based on the added implant marker and the position information of the body model, the region where the implant is located can be automatically determined. For example, the region where the implant is located can be determined based on the edge position information of the implant marker. The region can be, for example, an annular cylindrical region defined by the edge information and the radius. As Figure 6 shown, the edge information can include, for example, the Z-axis coordinate information (Z start 、Z end ) of the two ends (such as D1 and D2) on the implant marker edge that are farthest apart in the Z-axis direction, and the radius information (R inner 、R outer ) of the two ends (such as D3 and D4) on the implant marker edge that are farthest apart in the X-axis (and / or Y-axis) direction. Among them, the radius information R inner 、R outer are the coordinate information of the endpoints D3 and D4 relative to the system center, respectively representing the distances between the endpoints D3 and D4 and the Z central axis (passing through the system center).

[0061] In an embodiment of the present invention, other computer-aided means may also be used to determine the region where the implant is located based on the added implant identifier.

[0062] In an embodiment of the present invention, by operating the body model, the sensitive region can be determined more accurately, and a more accurate adjusted value of the safety limit can be further obtained. However, after determining the positioning information of the object to be scanned in the magnetic resonance system based on the part to be scanned, the numerical regions corresponding to the sensitive region can be directly estimated in the radiofrequency field map and the SAR map of the magnetic resonance system respectively. Therefore, there is no need to operate the body model, simplifying the scanning process.

[0063] Figure 7 FIG. 700 shows a flowchart of a scanning method based on a magnetic resonance system according to other embodiments of the present invention, which includes Figure 4 the steps shown, and further includes step 710: determining a second value corresponding to the scanning center in the numerical distribution map. The scanning center may be a position coinciding with the system center. More specifically, in step 450, the limit value of the at least one scanning parameter may be adjusted based on the relationship between the first value and the second value. Further, the relationship may be a proportional relationship.

[0064] As described above, the position information of the body model relative to the magnetic resonance system can be determined based on the positioning information of the object to be scanned in the magnetic resonance system. In an embodiment of the present invention, the following steps may further be included: obtaining the position correspondence relationship between the body model and the numerical distribution map based on the pre-determined positioning information of the object to be scanned in the magnetic resonance system; wherein, the first value is determined based on the position correspondence relationship. The following will be described in conjunction with Figure 8 examples.

[0065] Figure 8An example of a numerical distribution diagram 810 and a body model 820 is shown. In the numerical distribution diagram 810, the numerical values distributed on the coordinate axes are represented by squares, for example, including a first numerical value 811 and a second numerical value 812. The second numerical value 812 is the parameter value at the system center, that is, this numerical value has zero coordinates. An area of interest 821 is determined in the body model 820, which corresponds to the part to be scanned of the object to be scanned. The center of the area of interest 821 is the scanning center, and its coordinate position is defined as the coordinate center of the magnetic resonance system, that is, the system center, for example, zero coordinates. A sensitive area 823 is also determined in the body model 820, which can be, for example, the area where the cardiac pacemaker is located. The safety manual of this cardiac pacemaker stipulates the safety limit values for magnetic resonance scanning. The numerical distribution diagram 810 has a numerical area 813, and its coordinate position corresponds to the coordinate position of the sensitive area 822. The first numerical value is the numerical value in the numerical area 811. In some embodiments, in order to ensure the safety of the scanning, the maximum numerical value is selected as the first numerical value in the numerical area 811. However, the first numerical value can also be determined by other means, for example, by performing mathematical operations on all or part of the numerical values in the numerical area 813 to determine the first numerical value 811.

[0066] As described above, the main magnetic field, radio frequency field, etc. of the magnetic resonance system are not completely uniform, resulting in the relevant parameter values in the space coordinates not being completely the same. Therefore, the first numerical value and the second numerical value may be different. Further, the first numerical value and the second numerical value may change in proportion. For example, when the second numerical value changes, the first numerical value changes in the same proportion as the second numerical value. Therefore, in step 450, specifically, the safety limit value (or the current limit value) in the safety manual can be adjusted based on this proportional relationship.

[0067] More specifically, the limit value of the at least one scanning parameter after adjustment is the product of the ratio between the second numerical value and the first numerical value and the limit value before adjustment. For example, the safety limit value in the manual can be adjusted by the following formula (1):

[0068]

[0069] where L scan-limit is the limit value of the at least one scanning parameter after adjustment, L manual-limit is the limit value set for the at least one scanning parameter in the safety manual, L 1 is the first numerical value, and L2 is the second numerical value.

[0070] Based on the numerical distribution map of the magnetic resonance system, the value at the system center is usually the maximum value, and the value at other positions decreases as the distance from the system center increases. Therefore, through the above method, it is possible to adjust the relatively strict safety limits in the manual to a larger limit range, bringing image quality that can better meet the clinical diagnosis requirements while achieving safe scanning.

[0071] Figure 9 FIG. 900 shows a flowchart of a scanning method based on a magnetic resonance system according to another embodiment of the present invention, which includes the following optional steps 910: Determine whether the current limit (e.g., specified in the safety manual) is too low. If so, adjust the current limit, that is, execute step 450. If not, execute step 920: Perform magnetic resonance scanning using the current limit. In step 910, it can be determined whether the limit is too low by performing simulation scanning, quality assessment, etc. using the current safety limit, or by asking the operator through human-computer interaction.

[0072] Take Figure 2 the safety limit method shown as an example for illustration. According to the safety limits for each region in the safety manual Figure 2 the safety limits for the "radiofrequency field intensity" and "SAR" of the scanning parameters in region A are the strictest. The B1 limit is 1.6 μT (microtesla), and the SAR limit is 0.2 W / kg. According to the embodiment of the present invention, the safety limits of these two parameters are adjusted through the following steps:

[0073] Determine the body region of the object to be scanned corresponding to region A as the sensitive region;

[0074] Obtain the body model of the object to be scanned and determine its position information relative to the magnetic resonance system;

[0075] Determine the sensitive region in the body model, for example, directly draw a region in the head position of the model that matches region A, or add corresponding implant markers (such as a brain stimulator) to determine the sensitive region;

[0076] Determine the numerical regions corresponding to the sensitive region in the radiofrequency field map and SAR distribution map of the magnetic resonance system respectively, and set the maximum value therein as the first value (e.g., 2.0 μT and 1.0 W / kg respectively);

[0077] Determine the second value corresponding to the scanning center in the radiofrequency field map and SAR distribution map respectively (e.g., 3.0 μT and 1.5 W / kg respectively);

[0078] Substitute the above first value and second value into the following formulas (2) and (3) to obtain the adjusted limit. Among them, B1 manual-limit is 1.6 μT, B12 is 3.0 μT, B1 1 is 2.0 μT, the adjusted B1 limit value B1 scan-limit is 2.4 μT; SAR manual-limit is 0.2 W / kg, SAR 2 is 1.5 W / kg, SAR 1 is 1.0 W / kg, the adjusted SAR limit value SAR scan-limit is 0.3 W / kg.

[0079]

[0080]

[0081] Optionally, at least one of the above scanning parameters may further include a magnetic field change rate or a maximum gradient switching rate, and the numerical distribution map may further include a distribution map of the magnetic field change rate of the magnetic resonance system. Specifically, the distribution map of the magnetic field change rate may also be a value distributed in the spatial coordinates of the magnetic resonance system.

[0082] Furthermore, the numerical distribution map may include a distribution map of the magnetic field change rate of one or more gradient axes of the magnetic resonance system. As described above, the magnetic resonance system may include X-axis, Y-axis, and Z-axis gradient coils, which can be individually turned on to generate gradient fields in their respective directions, or can be turned on simultaneously to generate an equivalent gradient field. Therefore, in the embodiments of the present invention, at least one of the X-axis dB / dt (magnetic field change rate map), Y-axis dB / dt map, Z-axis dB / dt map, and the spatial (or equivalent) dB / dt map formed by the X, Y, and Z axes can be used to adjust the safety limit value of the magnetic field change rate.

[0083] Figure 10 FIG. 1000 shows a flowchart of a scanning method based on a magnetic resonance system according to another embodiment of the present invention, including Figure 4 the steps shown, and further including step 101 and step 102. In step 101, reference information is obtained. In step 102, a second value of the magnetic field change rate corresponding to the sensitive area is determined from the reference information.

[0084] The reference information includes magnetic field change rate distribution information via one or more externally defined gradient axes. The magnetic field change rate distribution information includes the magnetic field change rate at defined spatial coordinates, and the defined spatial coordinate system corresponds to the magnetic field spatial coordinate system of the magnetic resonance system. Table (1) below shows an example of the magnetic field change rate distribution information defined externally, which is defined by a standards association. Specifically, it comes from the standard manual "AAMI / ISOTIR10974" of AAMI. In this embodiment, it is only cited as an example for description, and reference information in other forms, contents, or sources can also be applied to the examples of this embodiment.

[0085]

[0086] Table (1)

[0087] As shown in Table (1) above, in the magnetic field change rate distribution information, position information (Radial distance) is defined, which represents the dB / dt of the X-axis (dB x / dt), the dB / dt of the Y-axis (dB y / dt), the dB / dt of the Z-axis (dB z / dt), and the spatial dB / dt (dB m / dt) on the cylindrical surface with a radius of 5 - 30 cm centered on the Z-axis. Among them, the distribution values of the dB / dt of the X-axis (dB x / dt) and the dB / dt of the Y-axis (dB y / dt) in the spatial coordinates are the same, and based on this distribution information, it is considered that the distribution values on the same cylindrical surface are uniform. For example, the dB / dt of the X-axis on the cylindrical surface with a radius (or radial distance) of 5 cm is 58.0. And in this standard, at least a safety limit is set for the magnetic field change rate or the maximum gradient switching rate based on at least a part of this information. In the distribution map of the magnetic field change rate obtained by the magnetic resonance system, the distribution values on the same cylindrical surface may be different. For example, the dB / dt of the X-axis on the cylindrical surface with a radius (or radial distance) of 5 cm changes with the spatial position, that is, the value of the dB / dt of the X-axis on this surface may be multiple.

[0088] In the embodiments of the present invention, the safety limit of at least one of the magnetic field change rate and the maximum gradient switching rate is further adjusted by combining the reference information and the numerical distribution map (distribution map of the magnetic field change rate) of the magnetic resonance system itself.

[0089] Further, the numerical distribution map of the magnetic resonance system may include the distribution map of the magnetic field change rate of one or more gradient axes (such as the X-axis, Y-axis, Z-axis, and the spatial axes formed by the X / Y / Z three axes) of the magnetic resonance system, where there are values corresponding to the above-mentioned sensitive regions in the numerical distribution map of each gradient axis, that is, the first value.

[0090] In step 450, the limit value of the at least one scanning parameter may be adjusted based on the relationship between the first value and the second value. More specifically, the relationship is the proportional relationship between the second value and the first value. For example, formula (1) may be used to adjust the magnetic field change rate or the maximum gradient switching rate.

[0091] In the embodiments of the present invention, the magnetic field change rate distribution map on only one gradient axis and the reference information on the corresponding gradient axis may be used to adjust the magnetic field change rate or the maximum gradient switching rate of all or part of the gradient axes. For example, the first value used in formula (1) may come from the magnetic field change rate distribution map of the equivalent axis, and the second value may come from the value on the equivalent axis in the reference information.

[0092] However, optionally, in order to further improve the accuracy of the limit value adjustment, the magnetic field change rate distribution maps and reference information on multiple axes may also be used simultaneously to adjust the magnetic field change rate or the maximum gradient switching rate of all or part of the gradient axes.

[0093] Figure 11 The flowchart 1100 of the scanning method based on the magnetic resonance system according to another embodiment of the present invention is shown, where step 450 further includes steps 451 and 452. As described above, both the numerical distribution map and the external reference information may include the numerical (magnetic field change rate) distributions of one or more gradient axes. Therefore, the first value may include one or more first axis values, and each first axis value is: the maximum value determined in the numerical value region corresponding to the sensitive region in the magnetic field change rate distribution map of one gradient axis of the magnetic resonance system.

[0094] For example, in the magnetic field change rate distribution map of the X-axis, there are multiple values in the region corresponding to the sensitive region, and the maximum value is selected as the first axis value B of the X-axis X-implant , correspondingly, the first axis value of the Y-axis, the first axis value of the Z-axis, and the first axis value of the equivalent axis can be determined respectively in the magnetic field change rate distribution maps of the Y-axis, Z-axis, and equivalent axis, and are denoted as B Y-implant , B Z-implant and B M-implant .

[0095] Similarly, the second numerical value may include a plurality of second axis numerical values B corresponding to the sensitive region respectively determined from the magnetic field change rate distribution information of the defined one or more gradient axes X 、B Y 、B Z and B M . For example, if the region corresponding to the sensitive region in the above table (1) is the region where the Radial distance is 10 cm, then the second axis numerical values B X 、B Y 、B Z and B M are 63.7, 63.7, 79.3 and 108.7 respectively.

[0096] Then in step 451, the ratios of the one or more second axis numerical values to the corresponding one or more first axis numerical values are determined respectively to obtain one or more ratio values. For example,

[0097] In step 452, the limits of the magnetic field change rate or the maximum gradient slew rate of the one or more gradient axes of the magnetic resonance system are adjusted based on the one or more ratio values. For example, one ratio value can be used to adjust the parameter limits of multiple gradient axes, or multiple ratio values can be used to adjust the parameter limits of multiple corresponding gradient axes.

[0098] Specifically, in one embodiment, step 452 may further include the following steps:

[0099] Determine the minimum value of the one or more ratio values; and,

[0100] Adjust the limits of the magnetic field change rate of the one or more gradient axes of the magnetic resonance system based on the minimum value.

[0101] For example, the ratio value α may be the minimum value, which can be used to adjust the limits of the magnetic field change rate of all or part of the gradient axes of the magnetic resonance system.

[0102] Specifically, the adjusted limit is the product of the minimum value of the multiple ratio values and the limit before adjustment. For example, the magnetic field change rate and the maximum gradient slew rate of each gradient axis can be adjusted respectively based on the following formulas (4), (5):

[0103] dB / dt limit =Min(α,β,γ,δ)×dB / dt implant (3);

[0104] Max_Slew_Rate scan= Min(α, β, γ, δ) × Max_Slew_Rate implant (4);

[0105] wherein, dB / dt limit is the adjusted limit value of the magnetic field change rate, Min(α, β, γ, δ) is the minimum value among the multiple proportional values α, β, γ, δ, and dB / dt implant is the current limit value of the magnetic field change rate, such as the safety limit value defined in a safety manual or standard; Max_Slew_Rate scan is the adjusted limit value of the maximum gradient slew rate, and Max_Slew_Rate implant is the current limit value of the maximum gradient slew rate, such as the safety limit value defined in a safety manual or standard.

[0106] Adjusting the magnetic field change rate or the maximum gradient slew rate using the minimum value among the proportions corresponding to multiple axes can be applied to the limit value adjustment of all gradient axes, can largely ensure scanning safety, and can simplify the parameter setting process. However, in other embodiments, the limit value of the parameter (such as the magnetic field change rate or the maximum gradient slew rate) corresponding to each axis can also be adjusted based on each proportional value, that is, the parameter limit values of different axes are adjusted according to their respective proportions. For example, the magnetic field change rate of the X axis can be adjusted respectively through formulas (5), (6), (7), and (8):

[0107] dB x / dt limit = α × dB x / dt implant (5);

[0108] dB y / dt limit = β × dB y / dt implant (6);

[0109] dB z / dt limit = γ × dB z / dt implant (7);

[0110] dB m / dt limit = δ × dB m / dt implant (8);

[0111] wherein, dB x / dt limit , dB y / dt limit dBz / dt limit , dB m / dt limit are respectively the limits of dB / dt of the adjusted X-axis, the limits of dB / dt of the Y-axis, the limits of dB / dt of the Z-axis, and the limits of dB / dt of the equivalent axis, dB x / dt implant , dB y / dt implant , dB z / dt implant , dB m / dt implant are respectively the current limits of dB / dt for the X-axis, the current limits of dB / dt for the Y-axis, the current limits of dB / dt for the Z-axis, and the current limits of dB / dt for the equivalent axis.

[0112] Therefore, step 452 may optionally include: respectively adjusting the limits of the magnetic field change rate or the maximum gradient switching rate of the corresponding one or more gradient axes of the magnetic resonance system based on the one or more proportional values. For example, when it is necessary to adjust the above parameters of all or only some of the gradient axes, the adjustment can be made based on the corresponding proportional values without determining the minimum proportional value.

[0113] In this way, the limit values of the parameters of different axes can be adjusted respectively, and more accurate scanning parameters can be obtained.

[0114] In the embodiments of the present invention, in the cylindrical gradient space, the cylindrical surface close to the edge of the sensitive area is determined as the area corresponding to the sensitive area. For example, according to Figure 6 shown, the sensitive area can be defined as an annular cylinder of Z-axis coordinate information (Z start , Z start ), and radius information (R inner , R outer ), and the gradient space position of the magnetic resonance system can be described as a plurality of concentric cylinders with the Z-axis (passing through the center of the system) as the center and the radius changing. Then the area corresponding to the sensitive area is the area corresponding to the outer surface of the annular cylinder.

[0115] As Figure 12 shown, some embodiments of the present invention may further provide a magnetic resonance system 1200, which includes a magnetic resonance component 1210 and a controller 1220. Among them, the controller 1220 is used to control the magnetic resonance component 1210 to scan an object to be scanned (for example, the object to be scanned 16, and the object to be scanned 16 is wearing an implant (not shown in the figure)). The controller 1220 is also used to execute the magnetic resonance scanning method of any of the above embodiments.

[0116] The controller 1220 can communicate with at least a part of the computer system 120 and the MR system controller 130 in Figure 1 , or include at least a part of the computer system 120 and the MR system controller 130, or be integrated with at least a part of the computer system 120 and the MR system controller 130. The magnetic resonance component 1210 may further include Figure 1 part or all of the magnetic resonance component 140 in

[0117] In embodiments of the present invention, based on the self-parameters of the magnetic resonance system (such as the numerical distribution map of the parameters), the object to be scanned (such as the determined sensitive area), the current implant information (such as its safety limit), etc., the limit value of the scanning parameters that can better meet the clinical diagnosis requirements is determined. And by making numerical adjustments on the basis of the current safety limit value, the requirements of safe scanning can be met simultaneously.

[0118] Furthermore, when there are multiple safety limit values for the same scanning parameter, the strictest limit value is used to determine the new limit value to ensure the safety during the scanning process.

[0119] Although the present invention has been described in detail in connection with specific specific embodiments, those skilled in the art can understand that many modifications and variations can be made to the present invention. Therefore, it should be recognized that the intention of the claims is to cover all such modifications and variations within the true concept and scope of the present invention.

Claims

1. A scanning method based on a magnetic resonance system, comprising: For at least one scanning parameter, obtaining a numerical distribution map determined based on the magnetic resonance system; Determining a sensitive area related to an implant of the object to be scanned; Determining a first value corresponding to the sensitive area in the numerical distribution map; Obtaining the limit value of the at least one scanning parameter limited by the implant of the object to be scanned; Adjusting the limit value of the at least one scanning parameter based on the first value; and; Scanning the object to be scanned by applying the adjusted limit value of the at least one scanning parameter.

2. The method according to claim 1, wherein, further comprising: Obtaining a body model of the object to be scanned; and, Determining the position information of the body model relative to the magnetic resonance system based on the positioning information of the object to be scanned in the magnetic resonance system; wherein, determining a sensitive area related to an implant of the object to be scanned includes: determining the sensitive area in the body model.

3. The method according to claim 2, wherein, Determining a sensitive area related to an implant of the object to be scanned includes: In a plurality of predefined human body areas, determining a human body area with the most stringent limit value for the at least one scanning parameter; and, Determining the area corresponding to the human body area with the most stringent limit value in the body model as the sensitive area.

4. The method according to claim 1, wherein, The sensitive area includes: the area where the implant of the object to be scanned is located.

5. The method according to claim 4, wherein, The sensitive area includes: Among the multiple implants of the object to be scanned, the area where the implant with the most stringent limit value for the at least one scanning parameter is located.

6. The method according to claim 4, wherein, Determining the sensitive area in the body model includes: Adding an implant identifier in the body model based on the implant information of the object to be scanned; Determining the area where the implant of the object to be scanned is located based on the added implant identifier.

7. The method according to claim 6, wherein, Determining the area where the implant of the object to be scanned is located based on the added implant identifier includes: Determining the area where the implant is located based on the edge position information of the implant identifier.

8. The method according to claim 1, wherein, further comprising: Determining a second value corresponding to the scanning center in the numerical distribution map; wherein, adjusting the limit value of the at least one scanning parameter based on the first value includes: Adjusting the limit value of the at least one scanning parameter based on the relationship between the first value and the second value.

9. The method according to claim 7, wherein, The relationship is the proportional relationship between the first value and the second value.

10. The method according to claim 8, wherein, The adjusted limit value of the at least one scanning parameter is the product of the ratio between the first value and the second value and the limit value before adjustment.

11. The method according to claim 2, It is characterized in that further comprising: obtaining a position correspondence relationship between the body model and the numerical distribution map based on pre-determined positioning information of the object to be scanned in the magnetic resonance system; wherein, the first numerical value is determined based on the position correspondence relationship.

12. The method according to claim 1, it is characterized in that the at least one scanning parameter includes radio frequency field intensity or SAR, and the numerical distribution map includes a radio frequency field map or an SAR distribution map of the magnetic resonance system.

13. The method according to claim 1, it is characterized in that the first numerical value includes: the maximum numerical value among the numerical values corresponding to the sensitive region in the numerical distribution map.

14. The method according to claim 1, it is characterized in that the at least one scanning parameter includes magnetic field change rate or maximum gradient switching rate, and the numerical distribution map includes a distribution map of the magnetic field change rate of the magnetic resonance system.

15. The method according to claim 14, it is characterized in that further comprising: obtaining reference information, the reference information including externally defined magnetic field change rate distribution information, the magnetic field change rate distribution information including the magnetic field change rate in a defined spatial coordinate system, and the defined spatial coordinate system corresponding to the magnetic field spatial coordinate system of the magnetic resonance system; determining a second numerical value of the magnetic field change rate corresponding to the sensitive region in the reference information; wherein, adjusting the limit value of the at least one scanning parameter based on the first numerical value includes: adjusting the limit value of the at least one scanning parameter based on the relationship between the first numerical value and the second numerical value.

16. The method according to claim 15, it is characterized in that the numerical distribution map includes a distribution map of the magnetic field change rate of one or more gradient axes of the magnetic resonance system, and the reference information includes defined magnetic field change rate distribution information of one or more gradient axes.

17. The method according to claim 16, it is characterized in that the first numerical value includes one or more first axis numerical values, and each of the first axis numerical values is: the maximum numerical value determined in the numerical value region corresponding to the sensitive region in the distribution map of the magnetic field change rate of one gradient axis of the magnetic resonance system; the second numerical value includes one or more second axis numerical values respectively determined in the defined magnetic field change rate distribution information of one or more gradient axes and corresponding to the sensitive region; adjusting the limit value of the at least one scanning parameter based on the first numerical value includes: respectively determining the ratio of the one or more second axis numerical values to the corresponding one or more first axis numerical values to obtain one or more ratio values; and adjusting the limit value of the magnetic field change rate or the maximum gradient switching rate of the one or more gradient axes of the magnetic resonance system based on the one or more ratio values.

18. According to the method according to claim 17, it is characterized in that adjusting the limit value of the magnetic field change rate or the maximum gradient switching rate of the one or more gradient axes of the magnetic resonance system based on the one or more ratio values includes: Determine the minimum value of the one or more proportional values, Based on the minimum value, adjust the limit value of the magnetic field change rate or the maximum gradient switching rate of one or more gradient axes of the magnetic resonance system.

19. The method according to claim 17, Characterized in that, Based on the one or more proportional values, adjusting the limit value of the magnetic field change rate or the maximum gradient switching rate of the one or more gradient axes of the magnetic resonance system includes: Respectively based on the one or more proportional values, adjust the limit value of the magnetic field change rate or the maximum gradient switching rate of the corresponding one or more gradient axes of the magnetic resonance system.

20. A magnetic resonance system, Comprising: A magnetic resonance component; And, A controller for controlling the magnetic resonance component to scan an object to be scanned and executing the magnetic resonance scanning method according to any one of claims 1-19.

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