Zero-inertia magnetism gathering ring non-magnetic field line magnetic particle imaging system and method

Abstract

The invention belongs to the field of magnetic particle imaging, particularly relates to a zero-inertia magnetism gathering ring magnetic-field-free line magnetic particle imaging system and method, and aims to solve the problems of low magnetic field gradient, high magnetic field control complexity and limited imaging space. The current of a gradient magnetic field coil group is generated by a magnetic field control and imaging module, is output by a signal acquisition and output module, and is amplified and provided by a gradient power amplifier module. The current of the axial excitation magnetic field coil is generated by the magnetic field control and imaging module, is output by the signal acquisition and output module and is amplified and provided by the excitation power amplifier module, and a signal received by the multi-axis detection coil is filtered and amplified by the signal processing unit and then is input to the imaging module by the magnetic field control and imaging module for algorithm reconstruction. According to the invention, the magnetic field gradient and the control precision are obviously improved, and the imaging space of the axial fault plane is realized.

Description

Technical Field

[0001] The invention belongs to the field of magnetic particle imaging, and in particular relates to a zero-inertia magnetic concentrating ring magnetic field line 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 ferrite nanoparticles) as tracers. When these particles are exposed to an external excitation magnetic field, they generate specific nonlinear magnetic response signals that can be captured by the MPI device and converted into an image of the particle distribution through an imaging algorithm.

[0003] In the MPI device, the gradient coil module generates a high-intensity static magnetic field, and the excitation coil module generates a high-frequency dynamic excitation magnetic field. The static magnetic field is used to create a magnetic field-free area such as a magnetic field-free point (FFP) or a magnetic field-free line (FFL), while the dynamic excitation magnetic field moves the FFP or FFL within the scanning area to image the entire area.

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

[0005] In FFL-MPI, the generation and movement of FFL are key steps to achieve full-area imaging. By precisely controlling and moving the FFL, the entire scanned area can be scanned step by step, and sufficient data can be collected to reconstruct the image of the entire area. At present, the methods for generating and moving FFL are mainly divided into inertial mechanical movement and zero inertia scanning. In the mechanical movement method, the FFL is generated by permanent magnets or electromagnets; the movement of FFL is achieved by physical means, usually relying on external motors and rotating structures. This method is intuitive and simple, but it has huge limitations in speed and smoothness, which seriously affects 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. Unlike the mechanical movement method, the zero inertia electrical scanning method uses the changes in the electromagnetic field generated by the energized coil to directly control the position and movement of the FFL. Without any mechanical parts, the FFL can be moved quickly and accurately, providing higher imaging speed and improved spatial resolution. The electromagnetic control in the electrical scanning method allows the FFL position to be adjusted with extremely high precision, 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 needs.

[0006] The existing electronically scanned FFL-MPI technology faces many problems, including low magnetic field gradient, high complexity of magnetic field control and limited imaging space.

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

[0008] In order to solve the above problems in the prior art, namely, low magnetic field gradient, high magnetic field control complexity and limited imaging space, the present invention proposes a zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging system and method.

[0009] In a first aspect of the present invention, a zero-inertia magnetic field-free linear magnetic particle imaging system is provided, comprising: 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 first current and the second 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 first current and the second 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; 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.

[0010] Further, 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; 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.

[0011] Furthermore, 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.

[0012] Furthermore, 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.

[0013] Furthermore, by controlling the current ratio of the gradient magnetic field coils of different layers, the rotation angle of the magnetic field-free lines in the imaging plane is controlled, thereby achieving control of the vector direction of the magnetic field-free lines.

[0014] Furthermore, 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.

[0015] Furthermore, the axial excitation magnetic field coil is coaxially arranged inside the innermost gradient magnetic field coil.

[0016] Furthermore, 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.

[0017] Furthermore, each gradient magnetic field coil in the gradient magnetic field coil assembly is wound by litz wire, copper wire or hollow copper tube coil.

[0018] On the other hand, the present invention proposes a zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging method, based on a zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging system, 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.

[0019] Beneficial effects of the present invention: The present invention innovatively solves the problems of low magnetic field gradient, high magnetic field control complexity and limited imaging space in the prior art by using at least two groups of gradient magnetic field coils arranged at set angles. 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 CT and other tomographic imaging technologies. In addition, this design also provides a more unified imaging area for multimodal fusion imaging equipment, expanding its application range and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 is a schematic diagram of the three-dimensional structure of the first embodiment of the present invention; Figure 2 is a schematic diagram of a magnetic field without magnetic field lines generated by a first implementation method in the first embodiment of the present invention; Figure 3 is a schematic diagram of the structure and tomographic imaging area of ​​the first implementation mode of the first embodiment of the present invention; Figure 4 is a schematic diagram of the structure and tomographic imaging area of ​​the second implementation mode of the first embodiment of the present invention when n is 2; Figure 5 is a schematic diagram of the structure and tomographic imaging area of ​​the second implementation mode of the first embodiment of the present invention when n is 3; Figure 6 is a simulated magnetic field distribution diagram of a rotating FFL generated by two pairs of level gradient magnetic fields in a first implementation mode of the first embodiment of the present invention; Figure 7 It is a simulated magnetic field distribution diagram of a rotating FFL generated by a fully wrapped two-pair gradient magnetic field in the second implementation manner of the first embodiment of the present invention; Figure 8 This is a simulated magnetic field distribution diagram of a rotating FFL generated by a double-group three-pair gradient magnetic field in the third implementation manner of the first embodiment of the present invention; Fig. 9 It is the X-axis magnetic field distribution diagram of the gradient magnetic field simulation in the present invention; Fig.10 It is a flowchart of the second embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] like Figure 1 As shown, the first embodiment of the present invention provides a zero-inertia magnetic field-free linear magnetic particle imaging system, comprising: A magnetic field control and imaging module 1, used to generate a first current required by the gradient magnetic field coil group 6 and a second current required by the axial excitation magnetic field coil 7; A signal acquisition and output module 2, used for receiving the first current and the second current, and sending them to the excitation power amplifier module 3 and the gradient power amplifier module 4 respectively; An excitation power amplifier module 3 and a gradient power amplifier module 4, respectively used for amplifying the first current and the second current; The gradient magnetic field coil assembly 6 is used to receive the amplified first current, generate a gradient magnetic field and a plurality of non-magnetic field lines, and control the vector direction of the non-magnetic field lines and the position of the imaging plane; The axial excitation magnetic field coil 7 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 nonlinear response signals; The multi-axis detection coil 5 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 2 and returned to the magnetic field control and imaging module 1. It is reconstructed through a preset algorithm to achieve magnetic particle imaging.

[0024] Wherein, 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; 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.

[0025] The present invention provides several specific structures of the gradient coil assembly 6: like Figure 3 As shown, in the first embodiment, when two groups of gradient magnetic field coil pairs are provided, in the gradient magnetic field coil pairs of different groups, any point on the edge line of the end surface of each gradient magnetic field coil is at an equal distance from the same point on the axis. Specifically, the gradient magnetic field coil group includes: Coil 111, coil 112, coil 113, coil 114, coil 121, coil 122, coil 123 and coil 124; coil 111, coil 112, coil 113 and coil 114 are a first group of gradient magnetic field coil pairs; coil 121, coil 122, coil 123 and coil 124 are a second group of gradient magnetic field coil pairs; Coil 111 and coil 112 are two radially symmetrical gradient magnetic field coils; coil 113 and coil 114 are two radially symmetrical gradient magnetic field coils; coil 121 and coil 122 are two radially symmetrical gradient magnetic field coils; coil 123 and coil 124 are two radially symmetrical gradient magnetic field coils.

[0026] The gradient magnetic field coil pair formed by coils 111 and 112 and the gradient magnetic field coil pair formed by coils 113 and 114 are symmetrically distributed along the axial direction of the gradient magnetic field coils. The axial direction can be seen in FIG. Figure 3 The direction of the X axis.

[0027] in, Figure 3 In the left figure, the current directions of coils 111 and 113 are opposite, and the current directions of coils 112 and 114 are opposite, that is, the directions of the generated magnetic fields are opposite. However, the current directions of coils 111 and 112 are the same, and the current directions of coils 113 and 114 are the same, that is, the directions of the generated magnetic fields are the same. Due to the effect of the magnetic field, this group of two pairs of coils generates magnetic field-free lines in the Y direction of the imaging plane 131. The current direction and magnetic field direction are as follows Figure 2 As shown in the left figure.

[0028] Likewise, Figure 3 In the left figure, the current directions of coils 121 and 123 are opposite, and the current directions of coils 122 and 124 are opposite, that is, the directions of the generated magnetic fields are opposite. However, the current directions of coils 121 and 122 are the same, and the current directions of coils 123 and 124 are the same, that is, the directions of the generated magnetic fields are the same. Due to the effect of the magnetic field, this group of two pairs of coils generates magnetic field-free lines in the Z direction of the imaging plane 131. The current direction and magnetic field direction are as follows Figure 2 As shown in the right figure.

[0029] like Figure 3 As shown in the right figure of , it is a schematic diagram of no magnetic field lines generated in the imaging plane 131. The current ratio of the first set of gradient magnetic field coil pairs and the second set of gradient magnetic field coil pairs, that is, the magnetic field ratio, can control the rotation of the FFL in the imaging plane 131. The generated rotating FFL magnetic field distribution diagram is shown in Figure 6 As shown, the rotation angle The formula ,in, is the current of the first set of gradient magnetic field coil pairs, is the current of the second set of gradient magnetic field coil pairs.

[0030] By controlling the current ratio between the 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 coil, and by controlling the coil current ratio of coils 111, coil 112 and coils 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 coils 121, coil 122 and coils 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 omnidirectional rotation and movement of the rotation scanning plane.

[0031] A second embodiment of the present invention is: a plurality of groups 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 group of two gradient magnetic field coil pairs distributed in 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.

[0032] like Figure 4 As 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; wherein 211, coil 212, coil 213, coil 214 are inner coils; coil 221, coil 222, coil 223 and coil 224 are outer coils; In the inner coil, coil 211, coil 212, coil 213, and coil 214 are the inner first group of gradient magnetic field coil pairs, and coil 221, coil 222, coil 223, and coil 224 are the outer second group of gradient magnetic field coil pairs; Specifically, when the number of layers is 2, the first inner group of gradient magnetic field coil pairs and the second outer group of gradient magnetic field coil pairs are two layers of fully wrapped vertical distribution. Since they are not in the same layer, the range of coils that can be wound will increase and the size of the magnetic field generated will double, so 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 directions of the generated magnetic fields are opposite.

[0033] The current directions of coils 211 and 212 are the same, and the current directions of coils 213 and 214 are the same, that is, the directions of the generated magnetic fields are the same. Due to the effect of the magnetic field, these two pairs of coils generate magnetic field-free lines in the Y direction of the imaging plane 231. Similarly, Figure 4 In the left figure, the current directions of coils 221 and 223 are opposite, and the current directions of coils 222 and 224 are opposite, that is, the directions of the generated magnetic fields are opposite. However, the current directions of coils 221 and 222 are the same, and the current directions of coils 223 and 224 are the same, that is, the directions of the generated magnetic fields are the same. Due to the effect 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.

[0034] like Figure 4 The figure on the right is a schematic diagram of the generation of magnetic field-free lines in the imaging plane 231. The current ratio of the inner coil to the outer coil, that is, the magnetic field ratio, can control the rotation of the magnetic field-free lines in the imaging plane 231. The magnetic field distribution diagram of the generated rotating magnetic field-free lines is shown in Figure 7 As shown, the rotation angle The formula ,in, is the magnetic field generated by the inner coil, is the magnetic field generated by the outer coil. is the current of the inner coil, is the current of the outer coil, , It is the equivalent proportional coefficient of the actual magnetic field and current, and 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 same proportional control of the two sets of coils can achieve the translation of the entire rotating scanning plane along the x-axis. In addition, the combined control of the two sets of coils can also achieve omnidirectional rotation and movement of the rotating scanning plane.

[0035] like Figure 5 As shown, when n is greater than 2, the present invention takes n as 3 as an example. In this embodiment, the three groups of gradient magnetic field coil groups include an inner coil, a middle coil and an outer coil respectively; The inner coil, that is, the first set of gradient magnetic field coil pairs, includes coil 311, coil 312, coil 313, and coil 314; The middle layer coil, that is, the second group of gradient magnetic field coil pairs includes coil 321, coil 322, coil 323, and coil 324; The outer coil, i.e., the third group of gradient magnetic field coil pairs, includes coil 331, coil 332, coil 333, and coil 334; like Figure 5As shown, three groups of coils are distributed in three layers of full wrapping, and the three groups of coils are arranged in sequence at an angle of 120°, that is, evenly distributed in the circumferential direction. The generated rotating magnetic field-free lines will be smoother, so it is a better solution.

[0036] Figure 5 In the left figure, the coil currents of coils 311 and 313, and coils 312 and 314 are in opposite directions, that is, the magnetic fields they generate are in opposite directions. However, the currents of coils 311 and 312 are in the same direction, and the currents of coils 313 and 314 are in the same direction, that is, the magnetic fields they generate are in the same direction. Due to the effect of the magnetic field, these two pairs of coils generate magnetic field-free lines in the A direction of the imaging plane 341. 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 directions of the generated magnetic fields are opposite. However, 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 directions of the generated magnetic fields are the same. Due to the effect of the magnetic field, this group of two pairs of coils generates magnetic field-free lines in the B direction of the imaging plane 341, and the B direction differs from the A direction by 120°.

[0037] Likewise, Figure 5 In the left figure, the current directions of coils 331 and 333 are opposite, and the current directions of coils 332 and 334 are opposite, that is, the directions of the generated magnetic fields are opposite. However, the current directions of coils 331 and 332 are the same, and the current directions of coils 333 and 334 are the same, that is, the directions of the generated magnetic fields are the same. Due to the effect of the magnetic field, this group of two pairs of coils generates magnetic field-free lines in the C direction of the imaging plane 341, and the C direction differs from the B direction and the A direction by 120°.

[0038] like Figure 5 The right figure is a schematic diagram of the generation of magnetic field-free lines in the imaging plane 341. The current relationship among the inner coil, the middle coil and the outer coil, that is, the magnetic field size relationship, can control the rotation of the magnetic field-free lines in the imaging plane 341. The generated magnetic field vector is on the x-axis and can be expressed as . The generated magnetic field vector is at an angle of 120 degrees to the x-axis and can be decomposed into . The generated magnetic field vector is 240 degrees to the x-axis and can be decomposed into The generated rotating magnetic field line distribution diagram is as follows Figure 8 As shown, the rotation angle The formula .in, is the current of the inner coil, is the current of the middle coil, is the current of the outer coil, is the equivalent proportional coefficient of the actual magnetic field and the current, and needs to be calibrated according to the actual coil size. By controlling the current ratio of coils 311, 312 and coils 313, 314, the FFL in the A-axis direction can be translated along the x-axis, by controlling the current ratio of coils 321, 322 and coils 323, 324, the FFL in the B-axis direction can be translated along the x-axis, and by controlling the current ratio of coils 331, 332 and coils 333, 334, the FFL in the C-axis direction can be translated along the x-axis. The three sets of coils can be controlled in the same proportion to achieve the translation of the entire rotating scanning plane along the x-axis. In addition, the combined control of the three sets of coils can also achieve omnidirectional rotation and movement of the rotating scanning plane.

[0039] Fig. 9 This is the x-axis 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 middle x=0 position is where the magnetic field is zero, that is, the projection position of the plane where the FFL is located on the x-axis. At this time, controlling the current of the two adjacent sets of coil pairs can control the magnetic field-free to move forward and backward along the x-direction.

[0040] As a further explanation of the present invention, the axial excitation magnetic field coil 7 is coaxially arranged in the innermost gradient magnetic field coil. Specifically: The axial excitation magnetic field coil 7 is arranged in the aperture direction (x direction in the figure), and is wound by litz wire, copper wire or hollow copper tube coil. In this embodiment, litz wire is preferably wound, 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-mentioned gradient coil, and the non-magnetic field line is quickly moved in a direction perpendicular to the non-magnetic field line. Combined with the rotating non-magnetic field line generated by the gradient magnetic field coil, the entire imaging plane can be covered.

[0041] The multi-axis detection coil 8 is a plurality of groups of saddle-shaped coils coaxially arranged in the excitation magnetic field coil, and the plurality of groups of saddle-shaped coils are evenly distributed along the circumferential direction of the imaging plane. Specifically: One example is that two pairs of saddle-shaped coils are arranged vertically in the radial plane, and the axis of the coil pair is consistent with the axis of the surrounding axial excitation magnetic field coil 7 and the gradient magnetic field coil group 6. Another more preferred example is that multiple groups of saddle-shaped coil pairs are evenly distributed in the radial plane, and the axis of the coil pair is consistent with the axis of the surrounding axial excitation magnetic field coil 7 and the gradient magnetic field coil group 6.

[0042] like Fig.10 As shown, the second embodiment of the present invention proposes a zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging method, which is based on a zero-inertia magnetic focusing ring magnetic field-free linear magnetic particle imaging system of the first embodiment. 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.

[0043] In the description of the present invention, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0044] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "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 a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or also includes elements inherent to such process, method, article, or apparatus / device.

[0046] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying 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 first current and the second 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 first current and the second 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; 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: 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; 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: 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 arranged 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.

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 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.

6. 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.

7. The zero-inertia magnetic focusing ring 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.

8. 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.

9. 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.

10. 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 9, 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.

Images