A zero-inertia magnetic flux concentrating ring and magnetic field line-free magnetic particle imaging system and method

Abstract

The present invention belongs to the field of magnetic particle imaging, and specifically relates to a zero-inertia magnetic focusing ring magnetic particle imaging system and method without magnetic field lines, aiming to solve the problems of low magnetic field gradient, high complexity of magnetic field control, and limited imaging space. The present invention includes: the current of the gradient magnetic field coil group is generated by the magnetic field control and imaging module, output through the signal acquisition and output module, and amplified by the gradient power amplifier module. The current of the axial excitation magnetic field coil is generated by the magnetic field control and imaging module, output through the signal acquisition and output module, and amplified by the excitation power amplifier module. The signals received by the multi-axis detection coil are filtered and amplified by the signal processing unit, and then input to the imaging module by the magnetic field control and imaging module for algorithm reconstruction. The present invention not only significantly improves the magnetic field gradient and control accuracy, but also realizes the imaging space of the axial cross-section.

Description

Technical Field

[0001] The present invention belongs to the field of magnetic particle imaging, and particularly relates to a zero-inertia magnetic focusing ring magnetic field line-free magnetic particle imaging system and method. Background Art

[0002] Magnetic Particle Imaging (MPI) is a non-invasive imaging technique that uses superparamagnetic nanoparticles (usually ferrite or ferrate nanoparticles) as tracers. When these particles are exposed to an external excitation magnetic field, they generate specific non-linear magnetic response signals that can be captured by an MPI device and converted into an image of the particle distribution through imaging algorithms.

[0003] In an MPI device, a gradient coil module generates a high-intensity static magnetic field, and an excitation coil module generates a high-frequency dynamic excitation magnetic field. The static magnetic field is used to create field-free points (FFPs) or field-free lines (FFLs) and other field-free regions, while the dynamic excitation magnetic field moves the FFP or FFL within the scanning area to image the entire area.

[0004] During the MPI imaging process, by dynamically moving the field-free region through the object being scanned, magnetic particles can be excited to generate signals. These signals are then captured by the receiving system and used to reconstruct the distribution map of magnetic nanoparticles within the imaging region. Different from the point-like FFP, an FFL refers to a line in the magnetic field along which the magnetic field strength is zero or close to zero. In an MPI device using the FFL mode (FFL-MPI), the signal response of magnetic particles is generated by the magnetic particles along this line rather than concentrated at a single point. Therefore, the FFL technology can cover a larger volume area in each excitation, thereby improving the imaging speed and is a key research direction for the future.

[0005] In FFL-MPI, the generation and movement of FFL are crucial steps for achieving full-area imaging. By precisely controlling and moving the FFL, the entire scanned area can be gradually scanned, and sufficient data can be collected to reconstruct the image of the entire area. Currently, the methods for generating and moving FFL are mainly divided into inertial mechanical movement type and zero-inertia scanning type. In the mechanical movement method, the generation of FFL is achieved through permanent magnets or electromagnets, etc.; the movement of FFL is realized physically, usually relying on an external motor and a rotating structure. This method is intuitive and simple, but it has great limitations in terms of speed and smoothness, seriously affecting the imaging speed and quality. In addition, the use of mechanical components may lead to higher maintenance requirements and lower system durability, especially at high usage frequencies. Different from the mechanical movement type, the zero-inertia electric scanning type directly controls the position and movement of FFL by using the electromagnetic field change generated by a current-carrying coil, without any mechanical components, and can move the FFL quickly and precisely, providing a higher imaging speed and improved spatial resolution. The electromagnetic control in the electric scanning type allows for extremely precise adjustment of the FFL position, which is particularly important for high-resolution imaging. And by adjusting the parameters of the electromagnetic field, the shape, size, and movement path of the FFL can be flexibly controlled, thus providing customized solutions for specific imaging requirements.

[0006] Existing electric scanning type FFL-MPI technologies face many problems, including low magnetic field gradient, high complexity of magnetic field control, and limited imaging space, etc.

[0007] Based on this, the present invention proposes a zero-inertia magnetic field-free line magnetic particle imaging system and method with a magnetic field concentrating ring. Summary of the Invention

[0008] To solve the above problems in the prior art, namely the problems of low magnetic field gradient, high complexity of magnetic field control, and limited imaging space, the present invention proposes a zero-inertia magnetic field-free line magnetic particle imaging system and method with a magnetic field concentrating ring.

[0009] In the first aspect of the present invention, a zero-inertia magnetic field-free line magnetic particle imaging system with a magnetic field concentrating ring includes:

[0010] A magnetic field control and imaging module, used to generate the first current required for the gradient magnetic field coil group and the second current required for the axial excitation magnetic field coil;

[0011] A signal acquisition and output module, used to receive the first current and the second current, and respectively send them to the excitation power amplifier module and the gradient power amplifier module;

[0012] The excitation power amplifier module and the gradient power amplifier module are respectively used for amplifying the first current and the second current;

[0013] Gradient magnetic field coil group, which is used to receive the amplified first current, generate a gradient magnetic field and a magnetic field-free line, and control the vector direction of the magnetic field-free line and the position of the imaging plane;

[0014] Axial excitation magnetic field coil, which is used to receive the amplified second current, drive the magnetic field-free line to move along the radial direction of the imaging plane, and excite the magnetic nanoparticles on the imaging plane to generate a non-linear response signal;

[0015] Multi-axis detection coil, which is used to receive the non-linear response signal, and after signal filtering and amplification by the signal processing unit, the filtered and amplified signal is transmitted by the signal acquisition and output module, returned to the magnetic field control and imaging module, and reconstructed through a preset algorithm to achieve magnetic particle imaging.

[0016] Further, the gradient magnetic field coil group is composed of at least two pairs of gradient magnetic field coils arranged in a circle. Each pair of gradient magnetic field coils is composed of two gradient magnetic field coils symmetrically distributed along the axial direction, and each gradient magnetic field coil pair is composed of two radially symmetric gradient magnetic field coils;

[0017] Each pair of gradient magnetic field coils is used to generate a magnetic field-free line in a different direction;

[0018] The current directions of the two gradient magnetic field coils in each gradient magnetic field coil pair are the same. Among the two gradient magnetic field coils distributed along the axial direction, the current directions of the adjacent two gradient magnetic field coils are opposite;

[0019] An imaging plane is formed between the two gradient magnetic field coils symmetrically distributed along the axial direction.

[0020] Further, when two pairs of gradient magnetic field coils are set, for different pairs of gradient magnetic field coils, the distance from any point on the edge line of the end face of each gradient magnetic field coil to the same point on the axis is equal.

[0021] Further, multiple pairs of gradient magnetic field coils are arranged in multiple layers with the axis as the center line, from the inside to the outside. Each layer includes a pair of two gradient magnetic field coils distributed along the axial direction;

[0022] In adjacent two layers, the outer gradient magnetic field coil is wrapped outside the inner gradient magnetic field coil;

[0023] When the number of layers is 2, the two pairs of gradient magnetic field coils are arranged vertically;

[0024] When the number of layers is greater than 2, the adjacent two layers of gradient magnetic field coils are set at an interval of a set angle ;

[0025] wherein, the set angle , and n is the number of layers.

[0026] Further, by controlling the current ratio of the current applied to the gradient magnetic field coils of different layers, the rotation angle of the zero magnetic field line in the imaging plane is controlled, so as to realize the control of the vector direction of the zero magnetic field line.

[0027] Further, by controlling the current ratio of the current applied to the two pairs of gradient magnetic field coils symmetrically distributed along the axial direction, the imaging plane is controlled to move along the axial direction of the gradient magnetic field coils.

[0028] Further, the axial excitation magnetic field coil is coaxially arranged inside the innermost layer of the gradient magnetic field coil.

[0029] Further, the multi-axis detection coil is a multi-group of saddle-shaped coils coaxially arranged inside the excitation magnetic field coil, and the multi-group of saddle-shaped coils are evenly distributed along the circumferential direction of the imaging plane.

[0030] Further, each gradient magnetic field coil in the gradient magnetic field coil group is wound with litz wire, copper wire or hollow copper tube coil.

[0031] On the other hand, the present invention proposes a zero-inertia magnetic field-free line magnetic particle imaging method, based on a zero-inertia magnetic field-free line magnetic particle imaging system, and the method includes the following steps:

[0032] Step S1, build the zero-inertia magnetic field-free line magnetic particle imaging system, and apply a first current and a second current to the gradient magnetic field coil group and the axial excitation magnetic field coil;

[0033] Step S2, generate a gradient magnetic field and a zero magnetic field line on the imaging plane based on multiple groups of gradient magnetic field coils with perpendicular magnetic field directions;

[0034] Step S3, according to the control strategy of the rotation and translation of the zero magnetic field line, adjust the magnitude of the current applied to the magnetic field gradient coil, so that the zero magnetic field line moves on the imaging plane;

[0035] Step S4, generate an excitation magnetic field based on the axial excitation magnetic field coil, so that the zero magnetic field line moves rapidly in the imaging plane and excites the magnetic particle response;

[0036] Step S5, control the current ratio of the current applied to the two pairs of gradient magnetic field coils symmetrically distributed along the axial direction, and control the imaging plane to move along the axial direction of the gradient magnetic field coils;

[0037] Step S6, collect the non-linear response signals of the magnetic particles based on the multi-axis detection coil, and after filtering and amplification, perform magnetic particle imaging using the reconstruction algorithm preset in the magnetic field control and imaging module.

[0038] Advantages of the present invention:

[0039] The present invention innovatively solves the problems of low magnetic field gradient, high complexity of magnetic field control, and limited imaging space in the prior art by adopting a pair of gradient magnetic field coils arranged at a set angle with at least two groups. This unique magnetic field structure not only significantly improves the magnetic field gradient and control accuracy, but also realizes the imaging space of the axial tomographic plane, providing the same imaging plane as traditional tomographic imaging technologies such as CT. In addition, this design also provides a more unified imaging area for multimodal fusion imaging devices, expanding its application scope and practicability. Brief Description of the Drawings

[0040] Other features, objects, and advantages of the present application will become more apparent by reading the detailed description of the non-limiting embodiments with reference to the following drawings:

[0041] Figure 1 is a schematic three-dimensional structure diagram of the first embodiment of the present invention;

[0042] Figure 2 is a schematic magnetic field diagram of generating a magnetic field without magnetic field lines in the first implementation manner of the first embodiment of the present invention;

[0043] Figure 3 is a schematic diagram of the structure and tomographic imaging area in the first implementation manner of the first embodiment of the present invention;

[0044] Figure 4 is a schematic diagram of the structure and tomographic imaging area in the second implementation manner of the first embodiment of the present invention when n is 2;

[0045] Figure 5 is a schematic diagram of the structure and tomographic imaging area in the second implementation manner of the first embodiment of the present invention when n is 3;

[0046] Figure 6 is a simulated magnetic field distribution diagram of the rotating FFL generated by two pairs of gradient magnetic fields in the first implementation manner of the first embodiment of the present invention;

[0047] Figure 7 is a simulated magnetic field distribution diagram of the rotating FFL generated by the fully enclosed two-pair gradient magnetic field in the second implementation manner of the first embodiment of the present invention;

[0048] Figure 8 is a simulated magnetic field distribution diagram of the rotating FFL generated by the double-group three-pair gradient magnetic field in the third implementation manner of the first embodiment of the present invention;

[0049] Figure 9 is an X-axis magnetic field distribution diagram of the gradient magnetic field simulation in the present invention;

[0050] Figure 10 is a schematic flowchart of the second embodiment of the present invention. Detailed implementation manners

[0051] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention, rather than limiting the invention. Additionally, it should be noted that for the sake of description, only parts related to the invention are shown in the accompanying drawings.

[0052] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and embodiments.

[0053] As Figure 1 shown, the first embodiment of the present invention provides a zero-inertia magnetic field concentrating ring magnetic particle imaging system without magnetic field lines, including:

[0054] A magnetic field control and imaging module 1, configured to generate a first current required for a gradient magnetic field coil group 6 and a second current required for an axial excitation magnetic field coil 7;

[0055] A signal acquisition and output module 2, configured to receive the first current and the second current, and respectively send them to an excitation power amplifier module 3 and a gradient power amplifier module 4;

[0056] The excitation power amplifier module 3 and the gradient power amplifier module 4 are respectively configured to amplify the first current and the second current;

[0057] The gradient magnetic field coil group 6 is configured to receive the amplified first current, generate a gradient magnetic field and multiple magnetic field lines without magnetic fields, and control the vector direction of the magnetic field lines without magnetic fields and the position of the imaging plane;

[0058] The axial excitation magnetic field coil 7 is configured to receive the amplified second current, drive the magnetic field lines without magnetic fields to move along the radial direction of the imaging plane, and excite magnetic nanoparticles on the imaging plane to generate a non-linear response signal;

[0059] The multi-axis detection coil 5 is configured to receive the non-linear response signal, perform signal filtering and amplification through a signal processing unit, and after the filtering and amplification, the signal is transmitted by the signal acquisition and output module 2, returned to the magnetic field control and imaging module 1, and reconstructed through a preset algorithm to achieve magnetic particle imaging.

[0060] Wherein, the gradient magnetic field coil group is composed of at least two pairs of gradient magnetic field coils arranged in a circumferential manner, each pair of gradient magnetic field coils is composed of two gradient magnetic field coils symmetrically distributed along the axial direction, and each gradient magnetic field coil pair is composed of two gradient magnetic field coils radially symmetric;

[0061] Each pair of the gradient magnetic field coils is configured to generate a magnetic field line without magnetic fields in a different direction;

[0062] The current directions of the two gradient magnetic field coils in each pair of gradient magnetic field coils are the same. Among the two pairs of gradient magnetic field coils distributed along the axial direction, the current directions of two adjacent gradient magnetic field coils are opposite;

[0063] An imaging plane is formed between two pairs of gradient magnetic field coils that are symmetrically distributed along the axial direction.

[0064] The present invention provides several specific structures of the gradient coil group 6:

[0065] Such as Figure 3 shown, the first embodiment: when there are two pairs of gradient magnetic field coils, for different pairs of gradient magnetic field coils, the distance from any point on the edge line of the end face of each gradient magnetic field coil to the same point on the axis is equal. Specifically, the gradient coil group includes:

[0066] Coil 111, coil 112, coil 113, coil 114, coil 121, coil 122, coil 123 and coil 124; coil 111, coil 112, coil 113, coil 114 are the first pair of gradient magnetic field coils; coil 121, coil 122, coil 123 and coil 124 are the second pair of gradient magnetic field coils;

[0067] Coil 111 and coil 112 are two radially symmetric gradient magnetic field coils; coil 113 and coil 114 are two radially symmetric gradient magnetic field coils; coil 121 and coil 122 are two radially symmetric gradient magnetic field coils; coil 123 and coil 124 are two radially symmetric gradient magnetic field coils.

[0068] The pair of gradient magnetic field coils formed by coil 111 and coil 112 and the pair of gradient magnetic field coils formed by coil 113 and coil 114 are symmetrically distributed along the axial direction of the gradient magnetic field coil. The axial direction can be referred to as Figure 3 the direction of the X-axis in.

[0069] Among them, Figure 3 In the left figure, the current directions of coil 111 and coil 113 are opposite, and the current directions of coil 112 and coil 114 are opposite, that is, the generated magnetic field directions are opposite. And the current directions of coil 111 and coil 112 are the same, and the current directions of coil 113 and coil 114 are the same, that is, the generated magnetic field directions are the same. This group of two pairs of coils generates a magnetic field-free line in the Y direction of the imaging plane 131 due to the action of the magnetic field. Its current direction and magnetic field direction are as shown in the left figure of Figure 2 in.

[0070] Similarly, Figure 3In the left figure, the current directions of coil 121 and coil 123 are opposite, and the current directions of coil 122 and coil 124 are opposite, that is, the generated magnetic field directions are opposite. And the current directions of coil 121 and coil 122 are the same, and the current directions of coil 123 and coil 124 are the same, that is, the generated magnetic field directions are the same. This set of two pairs of coils generates a magnetic field-free line in the Z direction of the imaging plane 131 due to the action of the magnetic field, and its current direction and magnetic field direction are as shown in the right figure of Figure 2 below.

[0071] As shown in the right figure of Figure 3 , it is a schematic diagram of the generation of a magnetic field-free line in the imaging plane 131. The rotation of the FFL in the imaging plane 131 can be controlled by the current ratio of the first set of gradient magnetic field coil pairs to the second set of gradient magnetic field coil pairs, that is, the magnetic field magnitude ratio. The generated rotational FFL magnetic field distribution diagram is as shown in Figure 6 . The rotation angle can be calculated by the formula , where is the current of the first set of gradient magnetic field coil pairs, and is the current of the second set of gradient magnetic field coil pairs.

[0072] By controlling the current ratio between two gradient magnetic field coil pairs symmetrically distributed along the axial direction, the movement of the imaging plane along the axial direction of the gradient magnetic field coil is controlled. And by controlling the coil current ratio of coil 111, coil 112 and coil 113, coil 114, the FFL in the y-axis direction can be translated along the x-axis, and by controlling the coil current ratio of coil 121, coil 122 and coil 123, coil 124, the FFL in the z-axis direction can be translated along the x-axis. The combination of the two can achieve the translation of the entire rotation scanning plane along the x-axis direction. In addition, the combined control of the two sets of coils can also achieve the omnidirectional rotation and movement of the rotation scanning plane.

[0073] The second embodiment of the present invention is: multiple sets of the gradient magnetic field coil pairs are arranged in multiple layers from the inside to the outside with the axis as the center line, and each layer includes a set of two gradient magnetic field coil pairs distributed along the axial direction;

[0074] In adjacent two layers, the outer gradient magnetic field coil is wrapped outside the inner gradient magnetic field coil;

[0075] When the number of layers is 2, the two layers of gradient magnetic field coil pairs are vertically arranged;

[0076] When the number of layers is greater than 2, the gradient magnetic field coil pairs of each adjacent two layers are arranged at an interval of a set angle ;

[0077] wherein, the set angle , and n is the number of layers.

[0078] As shown in Figure 4As shown, when the number of layers is 2: In this embodiment, the gradient magnetic field coil group includes coil 211, coil 212, coil 213, coil 214, coil 221, coil 222, coil 223, and coil 224; among them, coil 211, coil 212, coil 213, and coil 214 are inner layer coils; coil 221, coil 222, coil 223, and coil 224 are outer layer coils;

[0079] Among the inner layer coils, coil 211, coil 212, coil 213, and coil 214 are the first group of gradient magnetic field coil pairs in the inner layer, and coil 221, coil 222, coil 223, and coil 224 are the second group of gradient magnetic field coil pairs in the outer layer;

[0080] Specifically, when the number of layers is 2, the first group of gradient magnetic field coil pairs in the inner layer and the second group of gradient magnetic field coil pairs in the outer layer are vertically distributed in a two-layer fully wrapped manner. Since they are not in the same layer, the coil winding range will increase, and the generated magnetic field magnitude will also double. Therefore, it is a better solution. Figure 4 In the left figure, the current directions of coil 211 and coil 213 are opposite, and the current directions of coil 212 and coil 214 are opposite, that is, the generated magnetic field directions are opposite.

[0081] And the current directions of coil 211 and coil 212 are the same, and the current directions of coil 213 and coil 214 are the same, that is, the generated magnetic field directions are the same. Due to the action of the magnetic field, this group of two pairs of coils generates magnetic field-free lines in the Y direction of the imaging plane 231. Similarly, Figure 4 In the left figure, the current directions of coil 221 and coil 223 are opposite, and the current directions of coil 222 and coil 224 are opposite, that is, the generated magnetic field directions are opposite. And the current directions of coil 221 and coil 222 are the same, and the current directions of coil 223 and coil 224 are the same, that is, the generated magnetic field directions are the same. Due to the action of the magnetic field, this group of two pairs of coils generates magnetic field-free lines in the Z direction of the imaging plane 231.

[0082] As Figure 4 shown in the right figure, it is a schematic diagram of the generation of magnetic field-free lines in the imaging plane 231. The rotation of the magnetic field-free lines in the imaging plane 231 can be controlled by the current ratio of the inner layer coil to the outer layer coil, that is, the magnetic field magnitude ratio. The generated magnetic field distribution diagram of the rotating magnetic field-free lines is as Figure 7 shown, and the rotation angle can be obtained by the formula , where is the magnetic field generated by the inner layer coil, is the magnetic field generated by the outer layer coil. is the current of the inner layer coil, is the current of the outer layer coil, , is the equivalent proportionality coefficient of the actual magnetic field and current, which needs to be calibrated according to the actual coil size. By controlling the current ratio of the inner coil, the FFL in the y-axis direction can be translated along the x-axis, and by controlling the current ratio of the outer coil, the FFL in the z-axis direction can be translated along the x-axis. The combined proportional control of the two sets of coils can achieve the translation of the entire rotation scanning plane along the x-axis direction. In addition, the combined control of the two sets of coils can also achieve the omnidirectional rotation and movement of the rotation scanning plane.

[0083] As Figure 5 shown, when n is greater than 2, the present invention takes n = 3 as an example. In this embodiment, the three sets of gradient magnetic field coil groups respectively include an inner coil, an intermediate coil, and an outer coil;

[0084] Among them, the inner coil, that is, the first set of gradient magnetic field coil pairs, includes coils 311, 312, 313, and 314;

[0085] The intermediate coil, that is, the second set of gradient magnetic field coil pairs, includes coils 321, 322, 323, and 324;

[0086] The outer coil, that is, the third set of gradient magnetic field coil pairs, includes coils 331, 332, 333, and 334;

[0087] As Figure 5 shown, the three sets of coils are distributed in a three-layer fully wrapped manner, and the three sets of coils are arranged at an angle of 120° in sequence, that is, evenly distributed in the circumferential direction. The generated rotation-free magnetic field lines will be smoother, so it is a better solution.

[0088] Figure 5 In the left figure, the current directions of coils 311 and 313, and coils 312 and 314 are opposite, that is, the generated magnetic field directions are opposite. And the current directions of coils 311 and 312 are the same, and the current directions of coils 313 and 314 are the same, that is, the generated magnetic field directions are the same. This pair of two coils generates a magnetic field-free line in the A direction of the imaging plane 341 due to the magnetic field. Similarly, Figure 5 In the left figure, the current directions of coils 321 and 323 are opposite, and the current directions of coils 322 and 324 are opposite, that is, the generated magnetic field directions are opposite. And the current directions of coils 321 and 322 are the same, and the current directions of coils 323 and 324 are the same, that is, the generated magnetic field directions are the same. This pair of two coils generates a magnetic field-free line in the B direction of the imaging plane 341 due to the magnetic field, and the B direction is 120° different from the A direction.

[0089] Similarly, Figure 5In the left figure, the current directions of coil 331 and coil 333 are opposite, and the current directions of coil 332 and coil 334 are opposite, that is, the generated magnetic field directions are opposite. While the current directions of coil 331 and coil 332 are the same, and the current directions of coil 333 and coil 334 are the same, that is, the generated magnetic field directions are the same. This set of two pairs of coils generates magnetic field-free lines in the C direction of the imaging plane 341 due to the action of the magnetic field. The C direction is 120° different from both the B direction and the A direction.

[0090] As Figure 5 shown in the right figure, it is a schematic diagram of the generation of magnetic field-free lines in the imaging plane 341. The rotation of the magnetic field-free lines in the imaging plane 341 can be controlled by the current relationship of the inner layer coil, the middle layer coil, and the outer layer coil, that is, the magnetic field magnitude relationship. The generated magnetic field vector is on the x-axis and can be expressed as . The generated magnetic field vector forms a 120-degree angle with the x-axis and can be decomposed . The generated magnetic field vector forms a 240-degree angle with the x-axis and can be decomposed into . The magnetic field distribution diagram of the generated rotating magnetic field-free lines is as Figure 8 shown. The rotation angle can be obtained from the formula . Among them, is the current of the inner layer coil, is the current of the middle layer coil, is the current of the outer layer coil, is the equivalent proportional coefficient of the actual magnetic field and the current, which needs to be calibrated according to the actual coil size. By controlling the current ratio of coil 311, coil 312 and coil 313, coil 314, the FFL in the A-axis direction can be translated along the x-axis. By controlling the current ratio of coil 321, coil 322 and coil 323, coil 324, the FFL in the B-axis direction can be translated along the x-axis. By controlling the current ratio of coil 331, coil 332 and coil 333, coil 334, the FFL in the C-axis direction can be translated along the x-axis. The combined proportional control of the three groups of coils can achieve the translation of the entire rotation scanning plane along the x-axis direction. In addition, the combined control of the three groups of coils can also achieve the omnidirectional rotation and movement of the rotation scanning plane.

[0091] Figure 9 is the x-axis direction magnetic field distribution (Y = 0, Z = 0) diagram of the gradient magnetic field simulation in the present invention. It can be seen from the figure that the magnetic field is zero at the middle x = 0 position, that is, the projection position of the FFL plane on the x-axis. At this time, controlling the current of adjacent two pairs of coil pairs can control the forward and backward movement of the magnetic field-free along the x direction.

[0092] As a further explanation of the present invention, the axial excitation magnetic field coil 7 is coaxially arranged inside the innermost gradient magnetic field coil. Specifically:

[0093] The axial excitation magnetic field coil 7 is arranged in the aperture direction (legend x direction) and is wound by litz wire, copper wire or hollow copper tube coil. In this embodiment, it is preferably wound by litz wire, and its axis is consistent with the axis of the surrounding gradient magnetic field coil group 7. The magnetic field generated by the axial excitation magnetic field coil 7 is superimposed on the magnetic field generated by the above gradient coil, and the magnetic field-free lines are rapidly moved along the direction perpendicular to the magnetic field-free lines. Combining with the rotating magnetic field-free lines generated by the gradient magnetic field coil, the entire imaging plane can be covered, etc.

[0094] The multi-axis detection coil 8 is a plurality of sets of saddle-shaped coils coaxially arranged inside the excitation magnetic field coil, and the plurality of sets of saddle-shaped coils are evenly distributed along the circumferential direction of the imaging plane. Specifically:

[0095] One example is that two pairs of saddle-shaped coils are vertically arranged in the radial plane, and the axis of the formed coil pair is consistent with the axis of the surrounding axial excitation magnetic field coil 7 and gradient magnetic field coil group 6. Another more optimal example is that a plurality of sets of saddle-shaped coil pairs are sequentially and evenly distributed in the radial plane, and the axis of the formed coil pair is consistent with the axis of the surrounding axial excitation magnetic field coil 7 and gradient magnetic field coil group 6.

[0096] As Figure 10 shown, in the second embodiment of the present invention, a magnetic particle imaging method of a zero-inertia magnetic flux concentrating ring magnetic field-free line is proposed. Based on a zero-inertia magnetic flux concentrating ring magnetic field-free line magnetic particle imaging system of the first embodiment, the method includes the following steps:

[0097] Step S1, build the zero-inertia magnetic flux concentrating ring magnetic field-free line magnetic particle imaging system, and apply a first current and a second current to the gradient magnetic field coil group and the axial excitation magnetic field coil;

[0098] Step S2, generate a gradient magnetic field and magnetic field-free lines on the imaging plane based on a plurality of sets of gradient magnetic field coils with perpendicular magnetic field directions;

[0099] Step S3, according to the control strategy of the rotation and translation of the magnetic field-free lines, adjust the magnitude of the current applied to the magnetic field gradient coil to move the magnetic field-free lines on the imaging plane;

[0100] Step S4, generate an excitation magnetic field based on the axial excitation magnetic field coil to rapidly move the magnetic field-free lines in the imaging plane and stimulate the magnetic particle response;

[0101] Step S5, control the current ratio applied to the two gradient magnetic field coil pairs symmetrically distributed along the axial direction to control the movement of the imaging plane along the axial direction of the gradient magnetic field coil;

[0102] Step S6: Based on the multi-axis detection coil, collect the non-linear response signals of magnetic particles. After filtering and amplification, use the reconstruction algorithm preset in the magnetic field control and imaging module to perform magnetic particle imaging.

[0103] In the description of the present invention, the terms indicating directions or positional relationships such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0104] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0105] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, so that a process, method, article or device / equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes the elements inherent in these processes, methods, articles or devices / equipment.

[0106] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A zero-inertia magnetic field-free magnetic particle imaging system, characterized in that: include: A magnetic field control and imaging module, used to generate a first current required by the gradient magnetic field coil group and a second current required by the axial excitation magnetic field coil; A signal acquisition and output module, used for receiving the second current and the first current, and sending them to an excitation power amplifier module and a gradient power amplifier module respectively; An excitation power amplifier module and a gradient power amplifier module, respectively used for amplifying the second current and the first current; A gradient magnetic field coil assembly, used for receiving the amplified first current, generating a gradient magnetic field and a magnetic field-free line, and controlling the vector direction of the magnetic field-free line and the position of the imaging plane; The gradient magnetic field coil group is composed of at least two groups of circumferentially arranged gradient magnetic field coil pairs, each group of gradient magnetic field coil pairs is composed of two gradient magnetic field coil pairs symmetrically distributed along the axial direction, and each gradient magnetic field coil pair is composed of two radially symmetrical gradient magnetic field coils; The plurality of groups of gradient magnetic field coil pairs are arranged in multiple layers from the inside to the outside with the axis as the center line, and each layer includes a group of two gradient magnetic field coil pairs distributed along the axial direction; In two adjacent layers, the gradient magnetic field coil of the outer layer is wrapped around the outer side of the gradient magnetic field coil of the inner layer; When the number of layers is 2, the two layers of gradient magnetic field coils are set vertically; When the number of layers is greater than 2, the gradient magnetic field coils of each adjacent layer are spaced at an angle of set up; The setting angle , n is the number of layers; An axial excitation magnetic field coil is used to receive the amplified second current, drive the magnetic field-free line to move radially along the imaging plane, and excite the magnetic nanoparticles on the imaging plane to generate a nonlinear response signal; The multi-axis detection coil is used to receive the nonlinear response signal and filter and amplify the signal through the signal processing unit. After filtering and amplification, the signal is transmitted by the signal acquisition and output module and returned to the magnetic field control and imaging module. It is reconstructed through a preset algorithm to realize magnetic particle imaging.

2. According to claim 1, a zero-inertia magnetic field-free magnetic field line magnetic particle imaging system is characterized in that: Each group of the gradient magnetic field coil pairs is used to generate a non-magnetic field line in a different direction; The currents flowing through the two gradient magnetic field coils in each gradient magnetic field coil pair are in the same direction, and the currents flowing through the two adjacent gradient magnetic field coils in the two gradient magnetic field coil pairs distributed along the axial direction are in opposite directions; An imaging plane is formed between two gradient magnetic field coil pairs symmetrically distributed along the axial direction.

3. The zero-inertia magnetic field-free linear magnetic particle imaging system according to claim 2, characterized in that: When two groups of gradient magnetic field coil pairs are provided, in different groups of gradient magnetic field coil pairs, any point on the edge line of the end surface of each gradient magnetic field coil is at the same distance from the same point on the axis.

4. The zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging system according to claim 2, characterized in that: By controlling the current ratio of the gradient magnetic field coils of different layers, the rotation angle of the magnetic field-free line in the imaging plane is controlled, thereby achieving control of the vector direction of the magnetic field-free line.

5. The zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging system according to claim 2, characterized in that: By controlling the current ratio between two gradient magnetic field coil pairs symmetrically distributed along the axial direction, the imaging plane is controlled to move along the axial direction of the gradient magnetic field coils.

6. The zero-inertia magnetic field-free linear magnetic particle imaging system according to claim 1, characterized in that: The axial excitation magnetic field coil is coaxially arranged inside the innermost gradient magnetic field coil.

7. The zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging system according to claim 1, characterized in that: The multi-axis detection coils are multiple groups of saddle-shaped coils coaxially arranged in the excitation magnetic field coil, and the multiple groups of saddle-shaped coils are evenly distributed along the circumferential direction of the imaging plane.

8. The zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging system according to claim 1, characterized in that: Each gradient magnetic field coil in the gradient magnetic field coil group is wound by litz wire, copper wire or hollow copper tube coil.

9. A zero-inertia magnetic focusing ring non-magnetic field linear magnetic particle imaging method, based on a zero-inertia magnetic focusing ring non-magnetic field linear magnetic particle imaging system according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: Step S1, constructing the zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging system, and supplying a first current and a second current to the gradient magnetic field coil group and the axial excitation magnetic field coil; Step S2, generating a gradient magnetic field and magnetic field-free lines on an imaging plane based on a plurality of groups of gradient magnetic field coils distributed vertically in the magnetic field direction; Step S3, according to the control strategy of rotation and translation of the magnetic field free lines, adjusting the magnitude of the current passed through the magnetic field gradient coil to make the magnetic field free lines move on the imaging plane; Step S4, generating an excitation magnetic field based on the axial excitation magnetic field coil, so that the magnetic field-free lines move rapidly in the imaging plane to stimulate the magnetic particles to respond; Step S5, controlling the current ratio of two gradient magnetic field coils symmetrically distributed along the axial direction, and controlling the imaging plane to move along the axial direction of the gradient magnetic field coils; Step S6, collecting the nonlinear response signals of the magnetic particles based on the multi-axis detection coil, filtering and amplifying, and performing magnetic particle imaging using a preset reconstruction algorithm in the magnetic field control and imaging module.

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