WO2023028786A1

WO2023028786A1 - Method for designing nonlinear gradient coil, and nonlinear spatial coding method

Info

Publication number: WO2023028786A1
Application number: PCT/CN2021/115464
Authority: WO
Inventors: 郑海荣; 王海峰; 梁栋; 刘新; 刘聪聪
Original assignee: 深圳先进技术研究院
Priority date: 2021-08-30
Filing date: 2021-08-30
Publication date: 2023-03-09

Abstract

The present application is applicable to the field of nuclear magnetic resonance. Provided are a method for designing a nonlinear gradient coil, and a nonlinear spatial coding method. By means of the solution, brand-new nonlinear gradient coils that are applicable to a nuclear magnetic resonance device which has an open structure are designed, and the nonlinear gradient coils are arranged on two flat panels of the nuclear magnetic resonance device. The nonlinear gradient coils on the two flat panels act jointly to generate a target magnetic field. The nonlinear gradient coils having open structures can be directly applied to the nuclear magnetic resonance device, which has an open structure, in a low field, such that a comfortable test environment is provided for a patient that suffers from claustrophobia. Nonlinear spatial coding is performed in the target magnetic field. Since the nonlinear gradient coils on the two flat panels act jointly to generate the target magnetic field, the robustness of the magnetic field is improved, such that the conversion efficiency for the formed magnetic field during the process of performing spatial coding is improved; and the spatial sensitivity of the surface coils is supplemented, such that a coding field of view becomes larger, thereby improving the imaging quality.

Description

A method for designing nonlinear gradient coils and a nonlinear spatial encoding method

technical field

The present application belongs to the field of nuclear magnetic resonance, and in particular relates to a method, device, device, storage medium for designing a nonlinear gradient coil, and a nonlinear space encoding method, device, device, and storage medium.

Background technique

In Magnetic Resonance Imaging (MRI) technology, the undersampled data is completed, and then the image is reconstructed by Fourier transform. However, in traditional parallel image reconstruction methods, linear gradient coils usually cannot maximize the inherent spatial encoding of surface coil contours. In order to improve the imaging speed, the number of channels of the RF receiving coil is usually increased, but the higher the number of channels of the RF receiving coil, the coil will be over-coupled, and the decoupling will become more difficult in the process of designing the coil, resulting in a decrease in the signal-to-noise ratio of the received signal , the signal-to-noise ratio of the reconstructed image decreases. Not only that, the more channels the coil has, the more expensive it is, which is not good for inclusive medical care in low-income areas.

Therefore, in order to solve the above problems, an NSC gradient imaging method with nonlinear spatial coding (Nonlinear Spatial Coding, NSC) gradient coding is proposed. NSC gradient coding is to improve the efficiency of MRI gradient conversion and the resolution of spatial transformation while keeping the number of coil channels unchanged. Although the existing NSC gradient imaging method can compensate for the encoding space of the linear gradient magnetic field, the design of the existing NSC gradient coil is very stressful for patients with claustrophobia, and most NSC gradient imaging studies mainly focus on concentrated in the high field. Therefore, there is an urgent need for a nonlinear gradient coil and nonlinear spatial encoding method suitable for low field.

technical problem

One of the purposes of the embodiments of the present application is to provide a method, device, device, storage medium for designing nonlinear gradient coils, and a nonlinear spatial encoding method, device, device, and storage medium to solve the problem that traditional NSC gradient imaging is only applicable to High field, causing problems for claustrophobic patients unable to perform the test.

technical solution

The first aspect of the embodiments of the present application provides a method for designing a nonlinear gradient coil, the nonlinear gradient coil is used in a nuclear magnetic resonance device with an open structure, and the method includes:

Setting a target magnetic field, the target magnetic field includes several target matrix points, the target magnetic field is generated by the nonlinear gradient coil, and the nonlinear gradient coil is arranged on two planar plates of the nuclear magnetic resonance equipment;

determining current elements corresponding to the first planar plate and the second planar plate, the first planar plate corresponding to the second planar plate;

determining current density distributions corresponding to the first planar plate and the second planar plate respectively according to the current elements corresponding to the first planar plate and the second planar plate, and each of the target matrix points;

According to the respective current density distributions corresponding to the first planar plate and the second planar plate, the distributions of the nonlinear gradient coils respectively corresponding to the first planar plate and the second planar plate are respectively determined.

Optionally, said setting the target magnetic field includes:

determining the direction of each of said target matrix points;

According to the direction of each of the target matrix points, determine the distribution form of the several target matrix points;

The target magnetic field is determined according to the distribution form of the several target matrix points.

Optionally, the determining the current elements corresponding to the first plane plate and the second plane plate includes:

determining respective corresponding positions of the first planar plate and the second planar plate;

According to the corresponding positions of the first plane plate and the second plane plate, respectively corresponding current elements of the first plane plate and the second plane plate are determined.

Optionally, according to the current elements corresponding to the first plane plate and the second plane plate, and each of the target matrix points, determine the respective current elements of the first plane plate and the second plane plate Corresponding current density distribution, including:

respectively determining the magnetic field generated by each of the current elements at each of the target matrix points;

According to the magnetic field generated by each of the current elements at each of the target matrix points, the respective current density distributions corresponding to the first planar plate and the second planar plate are determined.

The second aspect of the embodiments of the present application provides a nonlinear spatial coding method, including:

determining a nonlinear gradient magnetic field, the nonlinear gradient magnetic field is generated by a nonlinear gradient coil, and the nonlinear gradient coil is arranged on two planar plates of the nuclear magnetic resonance equipment;

In the nonlinear gradient magnetic field, controlling the nuclear magnetic resonance equipment to perform nuclear magnetic resonance scanning on the target scanning part, and obtaining multiple echo signals corresponding to the target scanning part;

A nuclear magnetic resonance image corresponding to the target site is generated according to the plurality of echo signals.

Optionally, in the nonlinear gradient magnetic field, controlling the nuclear magnetic resonance equipment to perform nuclear magnetic resonance scanning on the target scanning site to obtain multiple echo signals corresponding to the target scanning site, including:

The magnetic field center of the nonlinear gradient magnetic field is moved to obtain a plurality of echo signals corresponding to the target scanning part.

Optionally, the moving the magnetic field center of the nonlinear gradient magnetic field to obtain multiple echo signals corresponding to the target scanning site includes:

controlling the current on and off of the nonlinear gradient coil through a preset controller;

According to the current on and off of the nonlinear gradient coil, the magnetic field center of the nonlinear gradient magnetic field is moved to obtain the plurality of echo signals.

The third aspect of the embodiment of the present application provides a device for designing a nonlinear gradient coil, including:

The first determination unit is used to set a target magnetic field, the target magnetic field includes several target matrix points, the target magnetic field is generated by the nonlinear gradient coil, and the nonlinear gradient coil is arranged on the nuclear magnetic resonance equipment on two flat boards;

A second determining unit, configured to determine current elements corresponding to the first plane plate and the second plane plate, the first plane plate corresponding to the second plane plate;

A third determination unit, configured to determine the first plane plate and the second plane plate according to the respective current elements corresponding to the first plane plate and the second plane plate, and each of the target matrix points The corresponding current density distribution;

A fourth determining unit, configured to determine the nonlinear gradient coils corresponding to the first planar plate and the second planar plate respectively according to the current density distributions corresponding to the first planar plate and the second planar plate Distribution.

A fourth aspect of the embodiments of the present application provides a nonlinear spatial encoding device, including:

A processing unit, configured to determine a nonlinear gradient magnetic field, the nonlinear gradient magnetic field is generated by a nonlinear gradient coil, and the nonlinear gradient coil is arranged on two plane boards of the nuclear magnetic resonance equipment;

A control unit, configured to control the nuclear magnetic resonance equipment to perform nuclear magnetic resonance scanning on the target scanning part in the nonlinear gradient magnetic field, and obtain a plurality of echo signals corresponding to the target scanning part;

A generating unit, configured to generate a nuclear magnetic resonance image corresponding to the target site according to the plurality of echo signals.

The fifth aspect of the embodiment of the present application provides a device for designing a nonlinear gradient coil, including a memory, a processor, and a computer program stored in the memory and operable on the processor, wherein the When the processor executes the computer program, the steps of the method for designing a nonlinear gradient coil as described in the first aspect are realized.

The sixth aspect of the embodiments of the present application provides a nonlinear spatial coding device, including a memory, a processor, and a computer program stored in the memory and operable on the processor, wherein the processing When the computer executes the computer program, the steps of designing a nonlinear spatial coding method as described in the first aspect above are realized.

The seventh aspect of the embodiments of the present application provides a computer-readable storage medium, the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the design non-trivial features described in the above-mentioned first aspect are implemented. The steps of the linear gradient coil method, and the steps of realizing the nonlinear spatial encoding method as described in the second aspect above.

The eighth aspect of the embodiments of the present application provides a computer program product, when the computer program product is run on the device for designing nonlinear gradient coils, the device is made to execute the method for designing nonlinear gradient coils described in the first aspect above A step of. Or when the computer program product runs on the nonlinear spatial encoding device, the device is made to execute the steps of the nonlinear spatial encoding method described in the second aspect above.

Beneficial effect

Compared with the prior art, the embodiment of the present application has the beneficial effects that: in this solution, according to the preset target magnetic field, the current elements corresponding to the first plane plate and the second plane plate are determined respectively; according to the first plane plate and the The corresponding current elements of the second plane plate determine the current density distribution corresponding to the first plane plate and the second plane plate respectively; then according to the current density distribution corresponding to the first plane plate and the second plane plate, a new A nonlinear gradient coil suitable for a nuclear magnetic resonance device with an open structure, where the nonlinear gradient coil is arranged on two planar plates of the nuclear magnetic resonance device. The nonlinear gradient coils on the two planar plates work together to generate the target magnetic field. The nonlinear gradient coil with an open structure can be directly applied in a low-field open-structure nuclear magnetic resonance device, providing a comfortable testing environment for patients suffering from claustrophobia.

Nonlinear spatial encoding is performed in the target magnetic field. Since the nonlinear gradient coils on the two planar plates work together to generate the target magnetic field, the robustness of the magnetic field will be improved, and the formed magnetic field will be transformed during the process of spatial encoding. The efficiency is improved, and the spatial sensitivity of the surface coil is supplemented, so that the encoding field of view becomes larger and the imaging quality is improved.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings that need to be used in the embodiments or exemplary technical descriptions. Obviously, the accompanying drawings in the following descriptions are only for this application. For some embodiments, those skilled in the art can also obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic flowchart of a method for designing a nonlinear gradient coil provided by an exemplary embodiment of the present application;

Fig. 2 is a schematic diagram of a nuclear magnetic resonance device with an open structure provided by an exemplary embodiment of the present application;

Fig. 3 is a schematic diagram of a nonlinear gradient coil provided by an exemplary embodiment of the present application;

Fig. 4 is a schematic diagram of distribution of target matrix points provided by an exemplary embodiment of the present application;

Fig. 5 is a schematic diagram of the actual spatial distribution of two planar panels provided by an exemplary embodiment of the present application;

Fig. 6 is a schematic diagram of a magnetic field generated by a current element provided by an exemplary embodiment of the present application;

Fig. 7 is a schematic diagram of the actual spatial distribution of the nonlinear gradient coil provided by an exemplary embodiment of the present application;

Fig. 8 is a schematic diagram of the spatial distribution of nonlinear gradient coils provided by an exemplary embodiment of the present application;

Fig. 9 is a schematic diagram of magnetic field verification provided by an exemplary embodiment of the present application;

Fig. 10 is a schematic flowchart of a nonlinear spatial coding method provided by an exemplary embodiment of the present application;

Fig. 11 is a schematic diagram of a nuclear magnetic resonance system provided by an exemplary embodiment of the present application;

Fig. 12 is a schematic diagram of a device for designing a nonlinear gradient coil provided by an embodiment of the present application;

Fig. 13 is a schematic diagram of a nonlinear spatial encoding device provided by an embodiment of the present application;

Fig. 14 is a schematic diagram of a device for designing a nonlinear gradient coil provided by another embodiment of the present application;

Fig. 15 is a schematic diagram of a nonlinear spatial encoding device provided by another embodiment of the present application.

Embodiments of the present invention

In order to make the purpose, technical solution and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application, and are not intended to limit the present application.

In Magnetic Resonance Imaging (MRI), parallel imaging methods exploit the spatial encoding provided by the spatial sensitivity of independent radio frequency coils and then perform image reconstruction from undersampled k-space data. Among them, k-space is the dual space of ordinary space under Fourier transform, which is mainly used in the imaging analysis of magnetic resonance imaging.

Since the image reconstructed from the undersampled k-space data has aliasing artifacts, it is necessary to complement the accelerated undersampled data in order to eliminate the aliasing artifacts.

There are mainly two methods for supplementing the under-collected data in k-space that are commonly used. One is to complement missing pixels in the image domain, such as sensitivity encoding (SENSE); the other is to complement missing data in k-space with the help of coil sensitivity, such as generalized automatic calibration space parallel acquisition (GRAPPA).

The performance of parallel imaging is generally evaluated using the noise amplification factor (g-factor), the lower the g-factor, the lower the signal-to-noise ratio of the reconstructed image. Parallel imaging methods that optimize coil sensitivity orthogonality and explore undersampled non-Cartesian k-space trajectories within a given region of interest (ROI) can improve the signal-to-noise ratio of reconstructed images. For radially distributed surface coils, radially symmetric gradient coils have higher spatial sensitivity of complementary coils than linearly varying gradient magnetic fields, thereby reducing the data necessary for imaging at a given resolution.

The encoding method that uses a radially symmetric nonlinear gradient magnetic field to compensate the Linear Spatial Coding (LSC) magnetic field is called Nonlinear Spatial Coding (NSC) gradient imaging. For example, non-bijective curved gradient magnetic field (PatLoc) parallel imaging, O-space (O-space) imaging, null-space (Null-space) imaging, and fast rotating NSC space acquisition (FRONSAC) imaging. However, these imaging methods require too many receiving coils with too many channels due to the high acceleration factor, which leads to excessive coupling of the coils. The multi-channel receiving coils are not only highly coupled between the coils, but also the high coil price is a limitation for the universality of the nuclear magnetic resonance system. Disadvantages.

Therefore, in order to solve the above problems, an NSC gradient imaging method with NSC gradient encoding is proposed. In MRI, since the gradient magnetic field and the radio frequency magnetic field are based on different physical principles, they will not interfere with each other, further making it possible for the gradient encoding magnetic field and the radio frequency magnetic field to be independently defined and modified.

In traditional MRI, spatial encoding generally uses a linear gradient magnetic field transformation to change the phase part of the Fourier transform. In NSC gradient coding, faster gradient conversion and faster spatial transformation resolution will be achieved.

In PatLoc NSC gradient-field imaging, using conformal mapping based multipolar encoding fields of real and imaginary components reduces peripheral nerve stimulation during gradient climb by using arbitrary orthogonal NSC encoding fields with the potential to increase peripheral resolution Advantage.

In O-space imaging, the performance of parallel imaging is optimized using a linear combination of multiple spherical harmonics to form a gradient shape appropriate to the spatial information contained in the coil profile.

Compared with the O-space method, Null-space is more general, and the encoding gradient in Null-space is directly based on the coil sensitivity design. Its redesigned encoding gradient magnetic field is the spatial position where the magnetic field is 0 across the sensitivity distribution of the receiving coil, using a combination of linear and high-order spherical harmonic encoding fields for spatial encoding, and the fields derived from the coil sensitivity distribution map form a set of Projected gradients with different spatial patterns that are complementary to the spatial encoding provided by the receive coil array, and the number of different projected gradients used is equivalent to the number of phase-encoded gradients used in conventional parallel imaging.

In the rapidly rotating NSC FRONSAC imaging method, standard linear trajectories are applied on two linear gradient channels, and then a rotating gradient magnetic field is generated using sinusoidal gradient waveforms on two second-order encoding domains (gx and gy), and other normal encoding processes remain unchanged .

The imaging mechanism described above is called NSC gradient imaging. This imaging method was first proposed in 2008, and various more optimized NSC gradient encoding imaging methods have subsequently emerged. However, no matter whether the O-space encoding method based on the second-order harmonic (Z2) magnetic field is used, or the PatLoc NSC gradient magnetic field is realized by changing the current direction in the current loop, the most fundamental hardware structure is similar to the loop used in traditional MRI. Shaped or cylindrical gradient coils generally realize the generation of sinusoidal or Z2 magnetic fields by controlling the current in the cylindrical gradient coils, and then modify the traditional linear gradient magnetic field to realize spatial encoding.

In traditional MRI systems, the spatial structure of gradient coils is generally designed to be columnar or ring-shaped. Inserting columnar gradient coils into the main magnet forms a relatively closed test environment, which poses great pressure to claustrophobic patients. In MRI reconstruction, parallel imaging technology is one of the main image reconstruction algorithms, through complementing the under-sampled data, and then using Fourier transform to reconstruct the image.

However, in traditional parallel image reconstruction methods, linear gradient coils usually cannot maximize the inherent spatial encoding of surface coil contours. In order to increase the imaging speed, the number of channels of the radio frequency receiving coil is generally increased, the number of equations to be solved is increased, and the acceleration factor is increased. However, at the same time, the higher the number of channels of the RF receiving coil, the excessive coupling of the coil will be caused, and the decoupling will become more difficult in the process of designing the coil, resulting in a decrease in the signal-to-noise ratio of the received signal and a decrease in the signal-to-noise ratio of the reconstructed image. Not only that, the more channels the coil has, the more expensive it is, which is not good for inclusive medical care in low-income areas.

Therefore, in order to solve the above problems, an NSC gradient imaging method with nonlinear spatial coding (Nonlinear Spatial Coding, NSC) gradient coding is proposed. NSC gradient coding is to improve the efficiency of MRI gradient conversion and the resolution of spatial transformation while keeping the number of coil channels unchanged. Although the existing NSC gradient imaging method can compensate for the encoding space of the linear gradient magnetic field, the existing NSC gradient coil design method is still mainly circular or cylindrical in order to maintain versatility, which is difficult for claustrophobic patients. There is a lot of pressure, and most studies of NSC gradient imaging have focused on high fields. NSC gradient magnetic fields and coils suitable for low-field applications have not been designed, mainly with insertable NSC gradient coils.

In view of this, the present application designs a brand-new nonlinear gradient coil suitable for nuclear magnetic resonance equipment with an open structure, and the nonlinear gradient coil is arranged on two plane boards of the nuclear magnetic resonance equipment. The nonlinear gradient coils on the two planar plates work together to generate the NSC gradient magnetic field. The nonlinear gradient coil with an open structure can be directly applied in a low-field open-structure nuclear magnetic resonance device, providing a comfortable testing environment for patients suffering from claustrophobia. And this nonlinear gradient coil can be controlled by an external controller, that is, the on-off current of different nonlinear gradient coil units on the two plane boards can be controlled by the external controller, and then the magnetic field center of the NSC gradient magnetic field can be moved to realize a new coding strategy. This does not exist in traditional NSC gradient encoding. This encoding strategy can cancel the linear gradient magnetic field and linear gradient coil, making the composition of MRI equipment simpler and lower in cost.

At the same time, nonlinear spatial encoding is carried out in the target magnetic field. Since the nonlinear gradient coils on the two planar plates work together to generate the target magnetic field, this will improve the robustness of the magnetic field and make the formed magnetic field perform spatial encoding. In the process, the conversion efficiency is improved, and the spatial sensitivity of the surface coil is supplemented, so that the encoding field of view becomes larger and the imaging quality is improved.

Please refer to FIG. 1 . FIG. 1 is a schematic flowchart of a method for designing a nonlinear gradient coil provided by an exemplary embodiment of the present application. The implementation subject of the method for designing a nonlinear gradient coil provided in this application is a device for designing a nonlinear gradient coil. The device may be a nuclear magnetic resonance device, and may also include but not limited to mobile terminals such as smart phones, tablet computers, computers, personal digital assistants (Personal Digital Assistant, PDA), and desktop computers, and may also include various types of servers. The method for designing a nonlinear gradient coil as shown in Figure 1 may include: S101-S104, specifically as follows:

S101: Set a target magnetic field, the target magnetic field includes several target matrix points, the target magnetic field is generated by the nonlinear gradient coil, and the nonlinear gradient coil is arranged on two plane boards of the nuclear magnetic resonance equipment.

The target magnetic field refers to a pre-determined spatial region in an actual nuclear magnetic resonance equipment, where the size and distribution of the magnetic field should meet given requirements. It can be understood that the target magnetic field is the magnetic field required for final nonlinear spatial encoding. Before the nonlinear gradient coil is designed, the target magnetic field is a self-defined magnetic field that needs to be generated by the nonlinear gradient coil. That is to predefine what kind of magnetic field the final designed nonlinear gradient coil needs to generate, and this magnetic field is the target magnetic field.

The final designed nonlinear gradient coil is used in the NMR equipment with open structure. Please refer to FIG. 2 . FIG. 2 is a schematic diagram of a nuclear magnetic resonance equipment with an open structure provided by an exemplary embodiment of the present application. As shown in FIG. 2 , the structure of the nuclear magnetic resonance equipment provided in this embodiment is an open structure, which can also be understood as an open structure. Exemplarily, the opening mode of the nuclear magnetic resonance equipment is not limited. For example, the structure of the nuclear magnetic resonance equipment may be a semi-open structure with the left side open and the right side closed, a semi-open structure with the right side open and the left side closed, and a top side open and the bottom side closed. Semi-open structure, semi-open structure with open bottom and closed top, etc. The description here is only for illustration and not for limitation.

Optionally, the structure of the nuclear magnetic resonance equipment may be a U-shaped open structure. For example, the structure of the nuclear magnetic resonance equipment can be U-shaped open on the left and closed on the right, U-shaped open on the right and closed on the left, U-shaped open on the top and closed on the bottom, U-open on the bottom and closed on the top, etc. As shown in Figure 2, the nuclear magnetic resonance equipment has a U-shaped open structure on the left and a closed structure on the right. The flat panel is arranged on the left U-shaped panel of the nuclear magnetic resonance equipment. The description here is only for illustration and not for limitation.

The nuclear magnetic resonance equipment is provided with a flat plate, and a nonlinear gradient coil is arranged on the flat plate. Exemplarily, the plane plate is arranged on the open side of the nuclear magnetic resonance equipment. As shown in Fig. 2, the nuclear magnetic resonance equipment has a semi-open structure with the left side open and the right side closed, and the plane plate is arranged on the left side of the nuclear magnetic resonance equipment.

The number of plane plates can be one or more. When there is only one plane plate, it can be arranged above the open side of the nuclear magnetic resonance equipment, or below the open side of the nuclear magnetic resonance equipment. When there are multiple plane plates, they are correspondingly arranged above and below the open side of the nuclear magnetic resonance equipment according to the number of plane plates. As shown in FIG. 2 , two planar plates are correspondingly arranged above and below the open side of the nuclear magnetic resonance equipment.

The nonlinear gradient coils arranged on the plane plate are used to generate a nonlinear gradient magnetic field, and the nonlinear gradient magnetic field is used for nonlinear space encoding.

Optionally, the plane plate includes a first plane plate and a second plane plate, and the first plane plate is parallel to the second plane plate. As shown in FIG. 2 , the two plane boards provided on the nuclear magnetic resonance equipment are respectively a first plane board and a second plane board. The positions of the first plane board and the second plane board are not limited. For example, the plane board on the upper left of the nuclear magnetic resonance equipment is the first plane board, and the bottom plane is the second plane board; or the plane board on the upper left side of the nuclear magnetic resonance equipment is the second plane board, and the bottom is the first plane board.

Exemplarily, when the structure of the nuclear magnetic resonance equipment is a U-shaped open structure, and the plane plate on the upper left of the nuclear magnetic resonance equipment is the first plane plate, and the lower left is the second plane plate, the first plane plate is arranged on the nuclear magnetic resonance equipment. Under the U-shaped panel on the upper left, the second flat panel is arranged on the U-shaped panel on the lower left of the nuclear magnetic resonance equipment. Correspondingly, when the structure of the nuclear magnetic resonance equipment is a U-shaped open structure, and the plane plate on the upper left of the nuclear magnetic resonance equipment is the second plane plate, and the lower left side is the first plane plate, the second plane plate is arranged on the upper left of the nuclear magnetic resonance equipment Under the square U-shaped panel, the first flat panel is arranged on the lower left U-shaped panel of the nuclear magnetic resonance equipment. The description here is only for illustration and not for limitation.

The first planar plate and the second planar plate are respectively provided with corresponding nonlinear gradient coils. That is, the position and order of the nonlinear gradient coils arranged on the first plane board correspond to the positions and order of the nonlinear gradient coils arranged on the second plane board. For example, 16 nonlinear gradient coils are sequentially arranged on the first plane, and correspondingly, 16 nonlinear gradient coils are also sequentially arranged on the second plane. The description here is only for illustration and not for limitation.

Optionally, the shape of the plane plate is not limited. That is, the shape of the planar plate can be any shape. For example, the shape of the planar plate can be square, rectangular, circular, triangular, etc.

Generally, the shapes of the first planar plate and the second planar plate correspond to each other, but this is not meant to be limited thereto. For example, the shape of the first flat plate is square, the shape of the second flat plate is circular; the shape of the first flat plate is rectangular, the shape of the second flat plate is circular, etc., are all possible. It is worth noting that no matter what the shape of the planar plate is, it must be ensured that the nonlinear gradient coils disposed on it can be completely disposed on the planar plate.

For ease of understanding, please refer to FIG. 3 , which is a schematic diagram of a nonlinear gradient coil provided by an exemplary embodiment of the present application. Figure 3 (a) is a schematic diagram of the arrangement of a nonlinear gradient coil provided by an exemplary embodiment of the present application, and the nonlinear gradient coil in Figure 3 (a) is only one of the nuclear magnetic resonance equipment The nonlinear gradient coils arranged on the plane plate correspond to the nonlinear gradient coils arranged on the other plane plate.

Exemplarily, in a nuclear magnetic resonance device with an open structure, there are 16 pairs of nonlinear gradient coils on two plane boards. Among them, there are 16 nonlinear gradient coils shown in (a) of FIG. 3 . The diagram (b) in FIG. 3 is a schematic diagram of the power-on sequence of a nonlinear gradient coil provided by an exemplary embodiment of the present application. Exemplarily, these 16 non-linear gradient coils are arranged neatly in order from t1 to t16, and the black arrows in (b) in Fig. The power-on sequence of the circuit signal. The arrangement and power-on sequence of the nonlinear gradient coils can be adjusted according to the actual situation, which is only an example and not limited here.

Exemplarily, the target magnetic field can be set by the target field method. In this example, in order to generate the target magnetic field, it is necessary to design a nonlinear gradient coil with a special shape, and this design method is called the target field method.

Exemplarily, the target magnetic field may include a non-bijective gradient magnetic field, a second-order harmonic (Z2) magnetic field, and the like. In this example, based on spherical harmonics, the second-order harmonic (Z2) magnetic field is selected as the target magnetic field.

S102: Determine current elements corresponding to the first planar plate and the second planar plate, where the first planar plate corresponds to the second planar plate.

Exemplarily, the required target magnetic field is finally generated by the joint action of the current elements on the two planar plates. Therefore, a number of current cells on the first plane board and a number of current cells on the second plane board are preset. The positions of the first plane board and the second plane board correspond, and correspondingly, the number and layout of the preset current cells on each plane board also correspond.

S103: According to the respective current elements corresponding to the first planar plate and the second planar plate, and each target matrix point, determine the respective current density distributions corresponding to the first planar plate and the second planar plate.

Exemplarily, when setting the target magnetic field, several target matrix points are defined, and each current element on the first plane plate and the second plane plate will generate a magnetic field at these target matrix points, according to each current element at The magnetic field generated by each target matrix point can calculate the corresponding current density distribution of the first plane plate and the second plane plate.

S104: According to the respective current density distributions corresponding to the first planar plate and the second planar plate, respectively determine distributions of nonlinear gradient coils corresponding to the first planar plate and the second planar plate.

The current density distribution represents the uniform distribution of the original current elements, and there is a certain difference from the actual spatial distribution, that is, it cannot represent the spatial distribution of the coil winding, so the actual coil wiring estimation is required.

Exemplarily, in order to express the spatial distribution of the current more vividly, and also provide a reference for the later winding, this example is based on the current density distribution corresponding to the first planar plate and the second planar plate, and uses a scalar current function to represent the current The actual spatial distribution, the equipotential line distribution of the current flow function obtained by solving represents the actual spatial part of the winding, that is, the distribution of the nonlinear gradient coils corresponding to the first planar plate and the second planar plate respectively.

In the above embodiments, a brand-new nonlinear gradient coil suitable for nuclear magnetic resonance equipment with an open structure is designed, and the nonlinear gradient coil is arranged on two planar plates of the nuclear magnetic resonance equipment. The nonlinear gradient coils on the two planar plates work together to generate the NSC gradient magnetic field. The nonlinear gradient coil with an open structure can be directly applied in a low-field open-structure nuclear magnetic resonance device, providing a comfortable testing environment for patients suffering from claustrophobia.

Optionally, in some possible implementations of the present application, the above S101 may include S1011-S1013, specifically as follows:

S1011: Determine the direction of each target matrix point.

S1012: Determine the distribution form of several target matrix points according to the direction of each target matrix point.

S1013: Determine the target magnetic field according to the distribution form of several target matrix points.

In this example, based on spherical harmonics, the Z2 magnetic field is selected as the NSC gradient magnetic field (ie, the target magnetic field). Exemplarily, several target matrix points are defined in advance, and it is assumed that the direction of each target matrix point faces the Z direction.

For ease of understanding, please refer to FIG. 4 , which is a schematic diagram of distribution of target matrix points provided by an exemplary embodiment of the present application. Figure 4 (a) shows the spatial distribution of the defined 15×15 target matrix points. The direction of each target matrix point is towards the Z direction, and (b) in Figure 4 shows the specific distribution form of these target matrix points in space and the spatial distribution of the formed magnetic field.

Exemplarily, these target matrix points are described by mathematical formulas as:

G _Z2 (x, z) = G _Z2 × (x ² , z ² ), (1)

The value of G _Z2 is predefined as 1, and 225 target matrix points form the distribution form in the above formula (1).

Optionally, in some possible implementations of the present application, the above S102 may include S1021-S1022, specifically as follows:

S1021: Determine respective corresponding positions of the first plane board and the second plane board.

S1022: Determine current elements corresponding to the first planar plate and the second planar plate according to respective corresponding positions of the first planar plate and the second planar plate.

After determining the target magnetic field, design the location where the nonlinear gradient coil is located. Since the nonlinear gradient coils are arranged on two corresponding planar plates, the positions where the nonlinear gradient coils are designed are the corresponding positions of the first planar plate and the second planar plate.

Exemplarily, the spatial distance between the first plane board and the second plane board is predefined. For example, the spatial distance between the first planar plate and the second planar plate is predefined as 5 cm (centimeter), that is, the distance between the first planar plate and the second planar plate is 5 cm from the target magnetic field.

For ease of understanding, please refer to FIG. 5 , which is a schematic diagram of the actual spatial distribution of two planar panels provided by an exemplary embodiment of the present application. As shown in FIG. 5 , where plate a represents the first plane plate, plate b represents the second plane plate, and the dots in the middle represent the defined target magnetic field.

A number of current cells are respectively defined on the first plane board and the second plane board. It is worth noting that the first plane board corresponds to the second plane board, and the number of current cells defined therein also corresponds. For example, 51×51 current cells are respectively defined on the first plane board and the second plane board. For a more refined simulation result, more and denser current elements may be defined, which is only an example and not limited here.

Optionally, in some possible implementations of the present application, the above S103 may include S1031-S1032, specifically as follows:

S1031: Determine the magnetic field generated by each current element at each target matrix point respectively.

S1032: According to the magnetic field generated by each current element at each target matrix point, determine the respective current density distributions corresponding to the first planar plate and the second planar plate.

Taking the second plane plate (plate b) as an example, calculate each current in the second plane plate by the Biot Savart theorem (the Biot Savart theorem describes the magnetic field excited by the current element at any point P in space) The magnetic field formed by the element at the target matrix point. The magnetic field formed by each current element at the target matrix point can be calculated by the formula, as follows:

In the above formula (2),

Represents the current element, r represents the distance (the distance between the current element and the specified target matrix point),

Indicates the current element

The magnetic induction intensity corresponding to the specified target matrix point,

The direction of is determined by the current element.

For a small section of current element, the magnetic induction intensity generated at a distance r is the integral of the current element L (the length of the current element is L), as shown in the following formula (3), specifically as follows:

For ease of understanding, please refer to FIG. 6 , which is a schematic diagram of a magnetic field generated by a current element provided by an exemplary embodiment of the present application. Shown in Figure 6 is the magnetic field generated by a current element of length L at a distance r.

Since the magnetic field direction of the current element of length L is consistent at a distance r, the above formula (3) can be converted into a scalar form, as shown in the following formula (4), specifically as follows:

In the above formula (4), θ ₁ and θ ₂ are the included angles in FIG. 6 . The magnetic induction intensity generated by each current element on each plane plate at the target matrix point can be calculated by calculating Biot Savart's theorem. Since the calculated magnetic induction is in scalar form, in order to facilitate subsequent calculations, each obtained magnetic induction is multiplied by a direction vector to convert it into a vector form.

The target magnetic field designed in this application is the NSC coded magnetic field represented by the Z2 NSC gradient magnetic field. When the target magnetic field is known, the relationship between the target magnetic field and the current element can be listed through the magnetic field distribution calculated by the previous current element. ,details as follows:

B _t =B _E ×I _C , (5)

Among them, B _t represents the target magnetic field, that is, the Z2 magnetic field designed in this application, B _E represents the magnetic induction intensity distribution generated by the current element defined on the first plane plate and the second plane plate at the position of the target magnetic field, and the current used is the unit Current, I _C represents the current weighting coefficient, it can be understood that I _C is the quantity to be calculated in this application.

According to the above formula (3), it can be seen that there is a linear relationship between the current and the magnetic induction intensity, so the B _E can be weighted and summed by _IC to obtain the designed target magnetic field, and each current element can be obtained by solving the above formula (6). The magnitude of the current carried by the upper plate can then be used to obtain the magnitude of the current in all current elements on the first plane plate and the second plane plate, and finally the distribution of the actual current can be obtained through calculation. In this application, the magnetic induction intensity generated by each target matrix point is the result of the joint action of the corresponding current elements on the first plane plate and the second plane plate respectively.

Optionally, since the solution process without any constraints rarely occurs in practical problems, in this example an additional constraint item is added so that the magnetic field generated by the current element is 0 outside the target magnetic field. Tikhonov Regularization (Tikhonov Regularization, TR), also known as ridge regression, is the most common method of regularization in ill-posed problems. In the example, the Tikhonov regularization optimization algorithm is introduced to solve it. Tychonov regularization can be commonly understood as, for a certain equation, when the solution does not exist or the solution is not unique, it is a so-called ill-conditioned problem. Through some adjustments or other methods, the ill-conditioned problem can also get a unique solution .

Exemplarily, it can be solved by the following formula:

After integrating the above formula (7), we get:

I _C ＝(B _E ^T ·B _E +Γ ^T Γ) ^-1 B _E ^T ·B _t , (8)

Through the above formulas (8) and (9), I _C can be solved, and then the corresponding current density distributions on the first plane plate and the second plane plate can be obtained. Since the current density distribution represents the uniform distribution of the original current elements, there is a certain difference from the actual spatial distribution, that is, it cannot represent the spatial distribution of the coil winding, so the actual coil wiring estimation is required.

In order to express the current spatial distribution more vividly and provide reference for the later winding, this example is based on the current density distribution corresponding to the first plane plate and the second plane plate, and uses a scalar current function to represent the actual spatial distribution of the current. The distribution of the equipotential lines of the current flow function obtained through the solution represents the space part of the actual winding, that is, the distribution of the nonlinear gradient coils corresponding to the first planar plate and the second planar plate respectively are obtained.

Exemplarily, a method based on flow function design is introduced, and the flow function of current can be calculated by the following formula.

S=-∫J _x d _Z , (11)

In this example, the scalar current flow function is used to represent the actual spatial distribution of the current, and the equipotential line distribution of the obtained current flow function represents the space part of the actual winding, thereby solving the problem of vector representation of the current density. When designing the coil, after the current density distribution is calculated, it can be integrated (accumulated and summed) to obtain the final flow function S.

Then the distribution diagram of the actual nonlinear gradient coil is derived by the following formula, the formula is as follows:

Wherein, I ₀ =(S _max -S _min )/n, and the spatial distribution of the current equipotential lines can be derived through the above formula (12). S _max represents the maximum value on each current element, S _min represents the minimum value on each current element, n represents the series of equipotential lines on the plane plate, and m represents the number of current equipotential lines.

For ease of understanding, please refer to FIG. 7 , which is a schematic diagram of the actual spatial distribution of the nonlinear gradient coils provided by an exemplary embodiment of the present application. Specifically, what is shown in FIG. 7 is the actual spatial distribution of a pair of nonlinear gradient coils.

Please refer to FIG. 8 . FIG. 8 is a schematic diagram of spatial distribution of nonlinear gradient coils provided by an exemplary embodiment of the present application. The nonlinear gradient coil designed for the first time in this example is based on a 0.5T magnetic resonance system, so the spatial distribution of the final nonlinear gradient coil is shown in Figure 8. The length and width are equal to 200mm, and the line width is designed to be 2mm. In this example, the geometric parameters of the two corresponding nonlinear gradient coils are identical, but the current directions inside are different.

Please refer to FIG. 9 , which is a schematic diagram of magnetic field verification provided by an exemplary embodiment of the present application. Exemplarily, the present application also verifies the Z2 magnetic field. Using the spatial distribution of the current contours designed in the previous stage, the coil was actually fabricated, and the actually fabricated coil is shown on the left side of Figure 9.

Pass the rated current value of 1A to the coil, use a gauss meter to measure the magnetic induction intensity distribution of the central axis (the red line on the left side of Figure 9), and compare the measured value with the theoretical value, as shown on the right side of Figure 9. The shorter curves shown on the right side of Figure 9 are theoretical values and the longer curves are measured values. Although there are some errors, the errors are mainly distributed far away from the 0 magnetic field area, and the error between the measured and theoretical values of the magnetic field in the 0 magnetic field area that plays a major role is small, so the magnetic field has little influence on the encoding process.

In the above implementation, a new nonlinear gradient coil suitable for nuclear magnetic resonance equipment with an open structure is designed based on the target field method, and the nonlinear gradient coil is arranged on two plane boards of the nuclear magnetic resonance equipment. The nonlinear gradient coils on the two planar plates work together to generate the target magnetic field. The generated target magnetic field is gridded by the current to generate the distribution of the current in the actual space sink, and finally the spatial layout of the nonlinear gradient coils on the two planes is obtained, and the obtained nonlinear gradient coils on the two planes are applied to an open In the magnetic resonance system of the structure, the actual hardware system can be obtained. The nonlinear gradient coil with an open structure can be directly applied in a low-field open-structure nuclear magnetic resonance device, providing a comfortable testing environment for patients suffering from claustrophobia. It avoids excessive discomfort for patients with claustrophobia, increases the test friendliness of MRI equipment, and brings better experience to users.

Please refer to FIG. 10 . FIG. 10 is a schematic flowchart of a nonlinear spatial coding method provided by an exemplary embodiment of the present application. The execution body of the nonlinear spatial encoding method provided in this application is a nonlinear spatial encoding device. The device may be a nuclear magnetic resonance device, and may also include but not limited to mobile terminals such as smart phones, tablet computers, computers, personal digital assistants (Personal Digital Assistant, PDA), and desktop computers, and may also include various types of servers. The nonlinear spatial coding method as shown in Figure 1 may include: S201-S203, specifically as follows:

S201: Determine a nonlinear gradient magnetic field, the nonlinear gradient magnetic field is generated by a nonlinear gradient coil, and the nonlinear gradient coil is arranged on two plane plates of the nuclear magnetic resonance equipment.

The nonlinear gradient magnetic field in this example is generated by a nonlinear gradient coil, which is the nonlinear gradient coil designed through the above S101-S104. The nonlinear gradient coil is arranged on two planar plates of the nuclear magnetic resonance equipment, and the nuclear magnetic resonance equipment is a nuclear magnetic resonance equipment with an open structure.

Using the above example, the Z2 magnetic field is used as a nonlinear gradient magnetic field. The nonlinear gradient magnetic field is generated by the joint action of the current elements distributed on the first plane plate and the second plane plate, so that the nonlinear gradient magnetic field obtained in this way has high robustness, and the controllable spatial range of the formed magnetic field is enlarged, and further Enlarges the coding field of view, thereby improving the quality of imaging.

S202: In the nonlinear gradient magnetic field, control the nuclear magnetic resonance equipment to perform nuclear magnetic resonance scanning on a target scanning part, and obtain a plurality of echo signals corresponding to the target scanning part.

The target scanning part to be scanned is determined, and in the nonlinear gradient magnetic field, the nuclear magnetic resonance equipment is controlled to perform nuclear magnetic resonance scanning on the target scanning part, and multiple echo signals corresponding to the target scanning part are obtained. Exemplarily, the magnetic field center of the nonlinear gradient magnetic field is moved to obtain a plurality of echo signals corresponding to the target scanning part.

S203: Generate an MRI image corresponding to the target site according to the multiple echo signals.

Exemplarily, based on the O-Space imaging method in the NSC gradient magnetic field, one of the most important magnetic fields Z2 NSC gradient magnetic field (non-linear gradient magnetic field) is designed. In O-Space imaging, the Z2 field is defined as follows:

Among them, G _Z2 represents the intensity of the Z2 spherical harmonic, and the unit is Hz/cm2, and x and y represent the center position of the Z2 gradient magnetic field.

The center of the magnetic field (CP) of the nonlinear gradient magnetic field is moved to achieve the effect of spatial encoding. The whole moving process is shown as follows:

Among them, G _X (x, y) = -G _Z2 x ₀ , G _Y (x, y) = -G _Z2 y ₀ , G _X and G _Y represent the encoding gradient along the x and y directions, and the unit is Hz/ cm,

The effect of CP movement on the signal in magnetic resonance is shown in the following formula:

It can be seen from the above equation (15) that the movement of the CP leads to a change in the phase of the signal, thereby achieving the effect of spatial encoding. Among them, S represents the original signal obtained,

Indicates the integral kernel.

In the discrete case, the above formula (15) can be transformed into:

s=Aρ, (16)

That is, in the discrete case, the integral kernel in the above formula (15) can be expressed as a projection matrix A _m,q,t ρ. Among them, the matrix row represents the time point t, CP represents the center of the magnetic field, m represents the position, q represents the coil, the matrix column corresponds to the voxel of the object (that is, the voxel corresponding to the target scanning part), the object ρ is vectorized, and comes from multiple CPs The echo signals of the nonlinear gradient coil and the encoding function are superimposed, yielding a single matrix equation. Since the encoding function does not take the form of a Fourier integrating kernel, the data will not have a k-space similar to that in LSC in conventional MR. Therefore, the k-space density compensation and regrid methods in non-Cartesian imaging in linear gradients are no longer used in NSC coding, and the final image can be obtained by directly solving ρ in formula (16) (that is, the NMR corresponding to the target part resonance image).

Exemplarily, the method for solving ρ may include a projection-based spatial domain algorithm and an echo-based frequency domain algorithm. The description here is only for illustration and not for limitation.

In the above embodiment, imaging is performed based on the nonlinear gradient magnetic field generated by the designed nonlinear gradient coil suitable for the nuclear magnetic resonance equipment with an open structure, and the spatial movement of the Z2 magnetic field can be realized without the need for a linear gradient encoding magnetic field, and then Implement spatial encoding. Since the encoding function does not use the form of the Fourier integral kernel, the data will not have a k-space similar to that in LSC in traditional magnetic resonance, and there is no need to complete the k-space data, thereby improving the imaging speed. And because the NSC spatial encoding process in MRI can be realized without the LSC gradient magnetic field, this can eliminate the linear gradient coil, greatly reduce the complexity of the system, and reduce the cost of the MRI system.

Optionally, in some possible implementations of the present application, the current on and off of the nonlinear gradient coil can be controlled by a preset controller; according to the current on and off of the nonlinear gradient coil, the magnetic field center of the nonlinear gradient magnetic field is moved to obtain A plurality of echo signals; according to the plurality of echo signals, a nuclear magnetic resonance image corresponding to the target site is generated.

Exemplarily, the present application provides a nuclear magnetic resonance system, which includes devices such as a programmable logic gate array (FPGA) controller, a power supply, a channel switching controller, and a power amplifier.

Please refer to FIG. 11 . FIG. 11 is a schematic diagram of a nuclear magnetic resonance system provided by an exemplary embodiment of the present application. The electrical signal (weaker signal) output by the power supply is input to the channel switching controller, the channel switching control signal input by the FPGA controller controls the channel switching sequence in the channel switching controller, and the multi-channel signal output by the channel switching controller is input into the power amplifier. The high-power signal output by the power amplifier is connected to the nonlinear gradient coil (16 pairs of nonlinear gradient coils are used as an example in the figure) to form a complete control loop and control the encoding process in the system. Due to the advantages of FPGA parallel computing, a faster signal processing process can be realized, thereby improving the imaging speed.

Exemplarily, a controller is provided in the nuclear magnetic resonance equipment, and the controller is used to control the current on and off of the nonlinear gradient coil on the plane board. Exemplarily, the controller may be a programmable logic gate array (FPGA) controller. The current on and off of the nonlinear gradient coil can be controlled by this controller.

Optionally, the nuclear magnetic resonance equipment includes a power supply, a channel switching controller, and a power amplifier; wherein, the power supply is electrically connected to the channel switching controller, the channel switching controller is electrically connected to the power amplifier, and the controller is electrically connected to the channel switching controller; The amplifier is electrically connected to the nonlinear gradient coil.

The power supply is used to output electrical signals and input the electrical signals to the channel switching controller; the controller is used to input the channel switch control signal to control the channel switching sequence in the channel switching controller; the channel switching controller is used to output the multi-channel The signal is input to the power amplifier; the power amplifier is used to connect the output power signal with the nonlinear gradient coil. That is, the line below the power amplifier is connected to the nonlinear gradient coil, and the output power signal is also input into the nonlinear gradient coil through this line.

Illustratively, the electrical signal (weaker signal) output by the power supply is input to the channel switching controller, the channel switching control signal input by the FPGA controller controls the channel switching sequence in the channel switching controller, and the multi-channel switching controller output input signal to the power amplifier. The high-power signal output by the power amplifier is connected to the nonlinear gradient coil (16 pairs of nonlinear gradient coils are used as an example in the figure) to form a complete control loop and control the encoding process in the system. Due to the advantages of FPGA parallel computing, a faster signal processing process can be realized, thereby improving the imaging speed.

In the above embodiments, since the FPGA can independently and parallelly control each unit of the matrix nonlinear gradient coil, and then only through the control form of the switch, the center of the nonlinear gradient magnetic field can be moved, and the phase change of the model in the control received signal can be realized. If the number of matrix nonlinear gradient coils and the switching speed are increased, such coils and corresponding encoding methods can greatly reduce the complexity and cost of the NMR system, and can effectively remove the noise formed by the gradient coils in the NMR.

Optionally, the nonlinear gradient coils in this application are designed based on the nuclear magnetic resonance equipment with an open structure (open structure) by using the target field method.

In the above embodiment, since the FPGA can independently and parallelly control each unit of the matrix nonlinear gradient coil, and only through the control form of the switch, the center of the Z2 field magnetic field can be moved, and the phase change of the model in the control received signal can be realized. If the number of matrix nonlinear gradient coils and the switching speed are increased, such coils and corresponding encoding methods can greatly reduce the complexity and cost of the NMR system, and can effectively remove the noise formed by the gradient coils in the NMR.

Please refer to FIG. 12 . FIG. 12 is a schematic diagram of an apparatus for designing a nonlinear gradient coil provided by an embodiment of the present application. The units included in the device are used to execute the steps in the embodiment corresponding to FIG. 1 . For details, please refer to the relevant descriptions in the corresponding embodiments in FIG. 1 . For ease of description, only the parts related to this embodiment are shown. Referring to Figure 12, the device includes:

The first determining unit 310 is configured to set a target magnetic field, the target magnetic field includes several target matrix points, the target magnetic field is generated by the nonlinear gradient coil, and the nonlinear gradient coil is arranged in the nuclear magnetic resonance equipment on the two planes;

The second determining unit 320 is configured to determine current elements corresponding to the first plane plate and the second plane plate, the first plane plate corresponding to the second plane plate;

The third determining unit 330 is configured to determine the first plane plate and the second plane plate according to the current elements corresponding to the first plane plate and the second plane plate and each of the target matrix points. The current density distribution corresponding to each panel;

The fourth determining unit 340 is configured to determine the nonlinear gradients corresponding to the first planar plate and the second planar plate respectively according to the current density distributions corresponding to the first planar plate and the second planar plate Distribution of coils.

Optionally, the first determining unit 310 is specifically configured to:

determining the direction of each of said target matrix points;

Optionally, the second determining unit 320 is specifically configured to:

Optionally, the third determining unit 330 is specifically configured to:

Please refer to FIG. 13 . FIG. 13 is a schematic diagram of a nonlinear spatial encoding device provided by an embodiment of the present application. Each unit included in the nonlinear spatial encoding device is used to execute each step in the embodiment corresponding to FIG. 10 . For details, please refer to the relevant descriptions in the corresponding embodiments in FIG. 10 . For ease of description, only the parts related to this embodiment are shown. Referring to Figure 10, the nonlinear spatial encoding device includes:

A processing unit 410, configured to determine a nonlinear gradient magnetic field, the nonlinear gradient magnetic field is generated by a nonlinear gradient coil, and the nonlinear gradient coil is arranged on two plane boards of the nuclear magnetic resonance equipment;

The control unit 420 is configured to control the nuclear magnetic resonance equipment to perform nuclear magnetic resonance scanning on the target scanning part in the nonlinear gradient magnetic field, and obtain a plurality of echo signals corresponding to the target scanning part;

The generating unit 430 is configured to generate an MRI image corresponding to the target part according to the plurality of echo signals.

Optionally, the control unit 420 is specifically configured to:

Optionally, the control unit 420 is further configured to:

Please refer to FIG. 14 . FIG. 14 is a schematic diagram of a device for designing a nonlinear gradient coil provided by another embodiment of the present application. As shown in FIG. 14 , the device 5 of this embodiment includes: a processor 50 , a memory 51 , and a computer program 52 stored in the memory 51 and operable on the processor 50 . When the processor 50 executes the computer program 52 , the steps in the above embodiments of the method for designing a nonlinear gradient coil are implemented, such as S101 to S104 shown in FIG. 1 . Alternatively, when the processor 50 executes the computer program 52, the functions of the units in the above-mentioned embodiments are implemented, for example, the functions of the units 310 to 340 shown in FIG. 12 .

Exemplarily, the computer program 52 may be divided into one or more units, and the one or more units are stored in the memory 51 and executed by the processor 50 to complete the present application. The one or more units may be a series of computer instruction segments capable of accomplishing specific functions, and the instruction segments are used to describe the execution process of the computer program 52 in the device 5 . For example, the computer program 52 may be divided into a first determining unit, a second determining unit, a third determining unit and a fourth determining unit, and the specific functions of each unit are as described above.

The device may include, but is not limited to, a processor 50 and a memory 51 . Those skilled in the art can understand that Fig. 14 is only an example of device 5, and does not constitute a limitation to the device, and may include more or less components than shown in the figure, or combine some components, or different components, such as the The aforementioned devices may also include input and output devices, network access devices, buses, and so on.

The so-called processor 50 can be a central processing unit (Central Processing Unit, CPU), and can also be other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), Off-the-shelf programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor, or the processor may be any conventional processor, or the like.

The storage 51 may be an internal storage unit of the device, such as a hard disk or memory of the device. The memory 51 can also be an external storage terminal of the device, such as a plug-in hard disk equipped on the device, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash memory card (Flash Card) etc. Further, the memory 51 may also include both an internal storage unit of the device and an external storage terminal. The memory 51 is used to store the computer instructions and other programs and data required by the terminal. The memory 51 can also be used to temporarily store data that has been output or will be output.

Please refer to FIG. 15 . FIG. 15 is a schematic diagram of a nonlinear spatial encoding device provided in another embodiment of the present application. As shown in FIG. 15 , the device 6 of this embodiment includes: a processor 60 , a memory 61 , and a computer program 62 stored in the memory 61 and operable on the processor 60 . When the processor 60 executes the computer program 62, the steps in the above embodiments of the nonlinear spatial coding method are implemented, such as S201 to S203 shown in FIG. 10 . Alternatively, when the processor 60 executes the computer program 62, the functions of the units in the above-mentioned embodiments can be realized, for example, the functions of the units 410 to 430 shown in FIG. 13 .

Exemplarily, the computer program 62 can be divided into one or more units, and the one or more units are stored in the memory 61 and executed by the processor 60 to complete the present application. The one or more units may be a series of computer instruction segments capable of performing specific functions, and the instruction segments are used to describe the execution process of the computer program 62 in the device 6 . For example, the computer program 62 may be divided into a processing unit, a control unit and a generating unit, and the specific functions of each unit are as described above.

The device may include, but is not limited to, a processor 60 and a memory 61 . Those skilled in the art can understand that FIG. 15 is only an example of the device 6, and does not constitute a limitation to the device. It may include more or less components than shown in the figure, or combine certain components, or different components, such as the The aforementioned devices may also include input and output devices, network access devices, buses, and so on.

The so-called processor 60 can be a central processing unit (Central Processing Unit, CPU), and can also be other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), Off-the-shelf programmable gate array (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor, or the processor may be any conventional processor, or the like.

The storage 61 may be an internal storage unit of the device, such as a hard disk or memory of the device. The memory 61 can also be an external storage terminal of the device, such as a plug-in hard disk equipped on the device, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash memory card (Flash Card) etc. Further, the memory 61 may also include both an internal storage unit of the device and an external storage terminal. The memory 61 is used to store the computer instructions and other programs and data required by the terminal. The memory 61 can also be used to temporarily store data that has been output or will be output.

The embodiment of the present application also provides a computer storage medium. The computer storage medium may be non-volatile or volatile. The computer storage medium stores a computer program. When the computer program is executed by a processor, the above-mentioned designs are realized. The steps in the embodiment of the nonlinear gradient coil method, and the steps for realizing each of the above nonlinear spatial encoding methods.

The present application also provides a computer program product, which, when the computer program product is run on the device, causes the device to execute the steps in the above-mentioned embodiments of the methods for designing nonlinear gradient coils, and implement the above-mentioned methods for each nonlinear space encoding method step.

The embodiment of the present application also provides a chip or an integrated circuit, the chip or integrated circuit includes: a processor, used to call and run a computer program from the memory, so that the device installed with the chip or integrated circuit executes the above-mentioned various design functions. The steps in the embodiment of the linear gradient coil method, and the steps for realizing the above-mentioned nonlinear spatial encoding methods.

An embodiment of the present application also provides a nonlinear spatial encoding system, which is used to manage at least one nuclear magnetic resonance equipment provided above.

Those skilled in the art can clearly understand that for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used for illustration. In practical applications, the above-mentioned functions can be assigned to different functional units, Completion of modules means that the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment may be integrated into one processing unit, or each unit may exist separately physically, or two or more units may be integrated into one unit, and the above-mentioned integrated units may adopt hardware It can also be implemented in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the protection scope of the present application. For the specific working process of the units and modules in the above system, reference may be made to the corresponding process in the foregoing method embodiments, and details will not be repeated here.

In the above-mentioned embodiments, the descriptions of each embodiment have their own emphases, and for parts that are not detailed or recorded in a certain embodiment, refer to the relevant descriptions of other embodiments.

Those skilled in the art can appreciate that the units and algorithm steps of the examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed by hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be regarded as exceeding the scope of the present application.

The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still implement the foregoing embodiments Modifications to the technical solutions recorded in the examples, or equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit of the technical solutions of the various embodiments of the application, and should be included in this application. within the scope of the application.

Claims

A method of designing a nonlinear gradient coil, wherein the nonlinear gradient coil is used in a nuclear magnetic resonance device with an open structure, the method comprising:

Setting a target magnetic field, the target magnetic field includes several target matrix points, the target magnetic field is generated by the nonlinear gradient coil, and the nonlinear gradient coil is arranged on two planar plates of the nuclear magnetic resonance equipment;

determining current elements corresponding to the first planar plate and the second planar plate, the first planar plate corresponding to the second planar plate;

determining current density distributions corresponding to the first planar plate and the second planar plate respectively according to the current elements corresponding to the first planar plate and the second planar plate, and each of the target matrix points;

According to the respective current density distributions corresponding to the first planar plate and the second planar plate, the distributions of the nonlinear gradient coils respectively corresponding to the first planar plate and the second planar plate are respectively determined.
The method according to claim 1, wherein said setting the target magnetic field comprises:

determining the direction of each of said target matrix points;

According to the direction of each of the target matrix points, determine the distribution form of the several target matrix points;

The target magnetic field is determined according to the distribution form of the several target matrix points.
The method according to claim 1, wherein said determining the respective current elements corresponding to the first planar plate and the second planar plate comprises:

determining respective corresponding positions of the first planar plate and the second planar plate;

According to the corresponding positions of the first plane plate and the second plane plate, respectively corresponding current elements of the first plane plate and the second plane plate are determined.
The method according to claim 1, wherein, according to the current elements corresponding to the first plane plate and the second plane plate, and each of the target matrix points, determining the first plane plate and the second plane plate The current density distribution corresponding to each of the second planar plates includes:

respectively determining the magnetic field generated by each of the current elements at each of the target matrix points;

According to the magnetic field generated by each of the current elements at each of the target matrix points, the respective current density distributions corresponding to the first planar plate and the second planar plate are determined.
A nonlinear spatial coding method, including:

determining a nonlinear gradient magnetic field, the nonlinear gradient magnetic field is generated by a nonlinear gradient coil, and the nonlinear gradient coil is arranged on two planar plates of the nuclear magnetic resonance equipment;

In the nonlinear gradient magnetic field, controlling the nuclear magnetic resonance equipment to perform nuclear magnetic resonance scanning on the target scanning part, and obtaining multiple echo signals corresponding to the target scanning part;

A nuclear magnetic resonance image corresponding to the target site is generated according to the plurality of echo signals.
The method according to claim 5, wherein, in the nonlinear gradient magnetic field, the nuclear magnetic resonance equipment is controlled to perform nuclear magnetic resonance scanning on the target scanning part, and a plurality of echo signals corresponding to the target scanning part are obtained ,include:

The magnetic field center of the nonlinear gradient magnetic field is moved to obtain a plurality of echo signals corresponding to the target scanning part.
The method according to claim 6, wherein said moving the magnetic field center of said nonlinear gradient magnetic field to obtain multiple echo signals corresponding to said target scanning site comprises:

controlling the current on and off of the nonlinear gradient coil through a preset controller;

According to the current on and off of the nonlinear gradient coil, the magnetic field center of the nonlinear gradient magnetic field is moved to obtain the plurality of echo signals.
A device for designing a nonlinear gradient coil, comprising:

The first determination unit is used to set the target magnetic field, the target magnetic field includes several target matrix points, the target magnetic field is generated by the nonlinear gradient coil, and the nonlinear gradient coil is arranged on two sides of the nuclear magnetic resonance equipment flat panel;

A second determining unit, configured to determine current elements corresponding to the first plane plate and the second plane plate, the first plane plate corresponding to the second plane plate;

A third determination unit, configured to determine the first plane plate and the second plane plate according to the respective current elements corresponding to the first plane plate and the second plane plate, and each of the target matrix points The corresponding current density distribution;

A fourth determining unit, configured to determine the nonlinear gradient coils corresponding to the first planar plate and the second planar plate respectively according to the current density distributions corresponding to the first planar plate and the second planar plate Distribution.
The device according to claim 8, wherein the first determining unit is specifically configured to:

determining the direction of each of said target matrix points;

According to the direction of each of the target matrix points, determine the distribution form of the several target matrix points;

The target magnetic field is determined according to the distribution form of the several target matrix points.
The device according to claim 8, wherein the second determining unit is specifically configured to:

determining respective corresponding positions of the first planar plate and the second planar plate;

According to the corresponding positions of the first plane plate and the second plane plate, respectively corresponding current elements of the first plane plate and the second plane plate are determined.
The device according to claim 8, wherein the third determining unit is specifically configured to:

respectively determining the magnetic field generated by each of the current elements at each of the target matrix points;

According to the magnetic field generated by each of the current elements at each of the target matrix points, the respective current density distributions corresponding to the first planar plate and the second planar plate are determined.
A nonlinear spatial encoding device, including:

A processing unit, configured to determine a nonlinear gradient magnetic field, the nonlinear gradient magnetic field is generated by a nonlinear gradient coil, and the nonlinear gradient coil is arranged on two plane boards of the nuclear magnetic resonance equipment;

A control unit, configured to control the nuclear magnetic resonance equipment to perform nuclear magnetic resonance scanning on the target scanning part in the nonlinear gradient magnetic field, and obtain a plurality of echo signals corresponding to the target scanning part;

A generating unit, configured to generate a nuclear magnetic resonance image corresponding to the target site according to the plurality of echo signals.
The device according to claim 12, wherein the control unit is specifically configured to:

The magnetic field center of the nonlinear gradient magnetic field is moved to obtain a plurality of echo signals corresponding to the target scanning part.
The apparatus of claim 12, wherein the control unit is further configured to:

controlling the current on and off of the nonlinear gradient coil through a preset controller;

According to the current on and off of the nonlinear gradient coil, the magnetic field center of the nonlinear gradient magnetic field is moved to obtain the plurality of echo signals.
A device for designing a nonlinear gradient coil, comprising a memory, a processor, and a computer program stored in the memory and operable on the processor, wherein, when the processor executes the computer program, it realizes:

Setting a target magnetic field, the target magnetic field includes several target matrix points, the target magnetic field is generated by the nonlinear gradient coil, and the nonlinear gradient coil is arranged on two plane boards of the nuclear magnetic resonance equipment;

determining current elements corresponding to the first planar plate and the second planar plate, the first planar plate corresponding to the second planar plate;

determining current density distributions corresponding to the first planar plate and the second planar plate respectively according to the current elements corresponding to the first planar plate and the second planar plate, and each of the target matrix points;

According to the respective current density distributions corresponding to the first planar plate and the second planar plate, the distributions of the nonlinear gradient coils respectively corresponding to the first planar plate and the second planar plate are respectively determined.
The apparatus of claim 15, wherein said processor, when executing said computer program, further implements:

determining the direction of each of said target matrix points;

According to the direction of each of the target matrix points, determine the distribution form of the several target matrix points;

The target magnetic field is determined according to the distribution form of the several target matrix points.
The apparatus of claim 15, wherein said processor, when executing said computer program, further implements:

determining respective corresponding positions of the first planar plate and the second planar plate;

According to the corresponding positions of the first plane plate and the second plane plate, respectively corresponding current elements of the first plane plate and the second plane plate are determined.
A nonlinear spatial coding device, comprising a memory, a processor, and a computer program stored in the memory and operable on the processor, wherein, when the processor executes the computer program, it realizes:

determining a nonlinear gradient magnetic field, the nonlinear gradient magnetic field is generated by a nonlinear gradient coil, and the nonlinear gradient coil is arranged on two planar plates of the nuclear magnetic resonance equipment;

In the nonlinear gradient magnetic field, controlling the nuclear magnetic resonance equipment to perform nuclear magnetic resonance scanning on the target scanning part, and obtaining multiple echo signals corresponding to the target scanning part;

A nuclear magnetic resonance image corresponding to the target site is generated according to the plurality of echo signals.
The nonlinear spatial encoding device according to claim 18, wherein, when the processor executes the computer program, it also realizes:

The magnetic field center of the nonlinear gradient magnetic field is moved to obtain a plurality of echo signals corresponding to the target scanning part.
A computer-readable storage medium storing a computer program, wherein the computer program implements the method according to any one of claims 1 to 7 when executed by a processor.