Magnetic nanoparticle concentration omnibearing scanning method based on zero field line

Abstract

The invention relates to a magnetic nanoparticle concentration omnibearing scanning method based on a zero field line, and the method comprises the following steps: S1, selecting a method for detecting the concentration of magnetic nanoparticles according to the magnetization characteristics of the magnetic nanoparticles; s2, determining to adopt a zero field line device to generate a zero field line so as to detect the concentration of the magnetic nanoparticles; s3, a zero field line device capable of generating a zero field line is built through a plurality of coil combinations; s4, an existing model is improved, and coil configuration is adjusted to achieve omni-directional detection; and S5, verifying whether the performance of the new model meets actual requirements or not. The method can solve the problem that errors exist when the zero field line is controlled to rotate in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of medical imaging, and particularly to an all-round scanning method for the concentration of magnetic nanoparticles based on zero field lines. Background Art

[0002] Magnetic Particle Imaging (MPI) is an emerging medical imaging technology mainly used for real-time and high-resolution detection and imaging of the distribution of magnetic nanoparticles in the body. MPI is highly sensitive to magnetic nanoparticles, can provide high-resolution imaging, and is suitable for early disease detection and precise diagnosis. Different from CT and PET, MPI does not use ionizing radiation and has higher safety, making it suitable for long-term monitoring and repeated examinations. In addition, MPI can monitor dynamic processes in real time, such as blood flow and drug distribution, and MPI is not limited by tissue depth and is suitable for deep tissue imaging. With its advantages of high sensitivity, radiation-free and real-time imaging, MPI has broad application prospects in the fields of medical imaging, scientific research and drug development. With the progress of nanotechnology and imaging technology, MPI is expected to become an important medical diagnostic tool.

[0003] However, MPI still faces some challenges and problems in practical applications. Its imaging quality depends on the uniformity of the magnetic field, but it is difficult to achieve a completely uniform magnetic field in practice, which affects the imaging accuracy. The signal processing of MPI is complex, and efficient algorithms are required to extract and reconstruct images, and the optimization of algorithms still needs to be improved. Summary of the Invention

[0004] The purpose of the present invention is to provide an all-round scanning method for the concentration of magnetic nanoparticles based on zero field lines, which can solve the problem of errors in controlling the rotation of zero field lines in the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: an all-round scanning method for the concentration of magnetic nanoparticles based on zero field lines, including the following steps:

[0006] Step S1: Select a method for detecting its concentration according to the magnetization characteristics of magnetic nanoparticles;

[0007] Step S2: Study the method of generating a zero field region, and determine to use a zero field line device to generate zero field lines for magnetic nanoparticle concentration detection;

[0008] Step S3: Build a zero field line device capable of generating zero field lines through a combination of multiple coils;

[0009] Step S4: Improve the existing model and adjust the coil configuration to achieve all-round detection;

[0010] Step S5: Verify whether the performance of the new model meets the actual requirements.

[0011] Further, step S1 specifically includes the following steps:

[0012] Step S11: Generate a specific zero magnetic field region based on the non-linear characteristic that the magnetization characteristic of magnetic nanoparticles obeys the Langevin equation.

[0013] Step S12: Detect the particle concentration in the zero magnetic field region through a particle concentration detection device.

[0014] Further, in step S11, the Langevin equation is specifically:

[0015] L(a) = coth(a) - 1 / a

[0016] The magnetization characteristic of the magnetic nanoparticles is expressed by the following formula:

[0017] M(W) = φM d coth(μ0M d V / (k B T)W) - 1 / μ0M d V / (k B T)W

[0018] where M represents the magnetization magnetic field strength generated by the magnetic nanoparticles, W represents the excitation magnetic field strength, φ represents the volume fraction of the magnetic nanoparticles, μ0 represents the magnetic permeability in vacuum, M d represents the magnetic domain magnetization strength, V represents the volume of the magnetic nanoparticles, k B represents the Boltzmann constant, and T represents the temperature of the magnetic nanoparticles.

[0019] Further, in step S12, the particle concentration detection device is composed of an excitation coil and a receiving coil, where the excitation magnetic field is used to excite the magnetic nanoparticles to generate a magnetic field, and the receiving coil is used to receive and record the change of the external magnetic field.

[0020] Further, step S2 specifically includes the following steps:

[0021] Step S21: The zero field region includes zero field lines and zero field points. Analyze the advantages, disadvantages and applicability of the zero field lines and zero field points.

[0022] Step S22: Select the zero field line with a larger zero field range and higher applicability to establish a zero field region model; A zero field line refers to a straight line with a non-zero width in a magnetic field space where the internal magnetic field is almost zero through various means such as a charged coil.

[0023] Further, step S3 specifically includes the following steps:

[0024] Step S31: Configure four multi-turn charged circular coils.

[0025] Step S32: Arrange the four circular coils at the four vertices of a rectangle in a plane with the center of the circle as the reference. The normal directions of the four circular coils are the same and are respectively on the same straight line as the two parallel sides of the rectangle.

[0026] Step S33: There are two circular coils on the left and right respectively after the circular coils are placed. Control the current directions of the circular coils on the same side on the left and right to be the same, and the current directions of the circular coils on the opposite sides to be opposite.

[0027] Step S34: Arrange according to the above method, and the magnetic field within the normal line with a non-zero width at the center point of the rectangle is almost zero, that is, the zero-field line.

[0028] Furthermore, change the circular coils to rectangular coils to generate a more stable magnetic field.

[0029] Furthermore, the specific steps of step S4 are as follows:

[0030] Step S41: Use eight rectangular coils to construct two zero-field line devices that can generate zero-field lines.

[0031] Step S42: Adjust the coil positions so that the two zero-field lines intersect perpendicularly.

[0032] Step S43: Improve the existing model to obtain a new model.

[0033] Furthermore, in step S43, the specific implementation method of the new model is as follows:

[0034] Step S431: Select eight rectangular coils of a set size.

[0035] Step S432: Simulate a cuboid with a square bottom surface in a plane.

[0036] Step S433: Take the center points of the eight rectangular coils as the vertices of the cuboid.

[0037] The placement direction of the rectangular coils is as follows: For the four coils at the bottom, their normal directions respectively face the diagonal directions of the vertices where they are located, and the sides of the coils are parallel to each other. The other four coils at the top are also placed in this way, and the overall model placement is completed.

[0038] Step S434: Energize the rectangular coils. The current directions of the rectangular coils on the diagonal are the same, and the current directions of the rectangular coils at the top and bottom are opposite. The currents on different diagonals can control the rotation direction of the zero-field line, and a variable current is introduced subsequently.

[0039] Furthermore, the specific steps of step S5 are as follows:

[0040] Step S51: Obtain zero-field lines in any direction within the plane where two zero-field line devices' coils intersect by changing the current magnitudes of the coils of the two zero-field line devices;

[0041] Step S52: Change the current ratio of the coils on both sides of the plane where the zero-field lines perpendicularly intersect to change the detection plane position, thereby completing the detection of the magnetic nanoparticle concentration anywhere within the region;

[0042] Step S53: Control the scanning region to change automatically, and apply specific variable currents to the two zero-field line devices respectively to achieve stable rotational and translational scanning within the region.

[0043] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an all-round scanning method for magnetic nanoparticle concentration based on zero-field lines. This method adjusts the positions of the zero-field lines generated by the two zero-field line devices, making the zero-field lines generated by each device the same under the same parameters, facilitating the calculation of the rotation angle. Moreover, the up-and-down translation of the coil can be completed without an externally added driving coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a flowchart of the method according to an embodiment of the present invention;

[0045] Figure 2 It is a diagram of a novel coil position model according to an embodiment of the present invention;

[0046] Figure 3 It is a magnetic field distribution diagram generated by a single group of coils according to an embodiment of the present invention;

[0047] Figure 4 It is a diagram showing the generation of zero-field lines according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0049] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0050] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0051] Figure 1This is the flowchart of the method for this embodiment. This embodiment provides a method for omnidirectional scanning of the concentration of magnetic nanoparticles based on zero field lines, and the specific implementation steps are as follows.

[0052] Step S1: Select a method for detecting the concentration of magnetic nanoparticles according to their magnetization characteristics.

[0053] Step S2: Determine to use a zero field line device to generate zero field lines for detecting the concentration of magnetic nanoparticles.

[0054] Step S3: Build a zero field line device that can generate zero field lines by combining multiple coils in a set manner.

[0055] Step S4: Improve the existing model and adjust the coil configuration to achieve omnidirectional detection.

[0056] Step S5: Verify whether the performance of the new model meets the actual requirements.

[0057] In this embodiment, the specific implementation steps of step S1 are as follows.

[0058] Step S11: Based on the non-linear characteristic that the magnetization characteristic of magnetic nanoparticles obeys the Langevin equation, generate a specific zero magnetic field region.

[0059] The specific Langevin equation is:

[0060] L(a) = coth(a) - 1 / a

[0061] The magnetization characteristic of the magnetic nanoparticles is expressed by the following formula:

[0062] M(W) = φM d coth(μ0M d V / (k B T)W) - 1 / μ0M d V / (k B T)W

[0063] Among them, M represents the magnetization magnetic field strength generated by the magnetic nanoparticles, W represents the excitation magnetic field strength, φ represents the volume fraction of the magnetic nanoparticles, μ0 represents the magnetic permeability in vacuum, M d represents the magnetic domain magnetization strength, V represents the volume of the magnetic nanoparticles, k B represents the Boltzmann constant, and T represents the temperature of the magnetic nanoparticles.

[0064] According to this characteristic equation, it can be known that the magnetic nanoparticles will generate a magnetization magnetic field under the influence of the excitation magnetic field in the region with a lower magnetic field, and this reaction is more obvious in the zero magnetic field region.

[0065] Step S12: Detect the particle concentration in the zero magnetic field region through a particle concentration detection device.

[0066] The particle concentration detection device is composed of an excitation coil and a receiving coil, where the excitation magnetic field is used to excite magnetic nanoparticles to generate a magnetic field, and the receiving coil is used to receive and record changes in the external magnetic field.

[0067] In this embodiment, the specific implementation steps of step S2 are as follows.

[0068] Step S21: The zero-field region includes zero-field lines and zero-field points. Analyze the advantages, disadvantages, and applicability of zero-field lines and zero-field points.

[0069] Step S22: Select a zero-field line with a larger zero-field range and higher applicability to establish a zero-field region model; a zero-field line refers to a straight line with a non-zero width within a magnetic field space where the magnetic field inside the line is almost zero through various means such as a charged coil.

[0070] In this embodiment, the specific implementation steps of step S3 are as follows.

[0071] Step S31: Configure four multi-turn charged circular coils.

[0072] Step S32: Arrange the four circular coils at the four vertices of a rectangle in a plane with the center of the circle as the reference. The normal directions of the four circular coils are the same and are respectively on the same straight line as two parallel sides of the rectangle.

[0073] Step S33: There are two circular coils on the left and right after the circular coils are placed. Control the current directions of the circular coils on the same side on the left and right to be the same, and the current directions of the circular coils on the opposite sides to be opposite.

[0074] Step S34: Arrange according to the above method to obtain that the magnetic field inside the normal line with a non-zero width at the center point of the rectangle is almost zero, that is, the zero-field line.

[0075] In this embodiment, the circular coils are changed to rectangular coils to generate a more stable magnetic field.

[0076] In this embodiment, the specific implementation steps of step S4 are as follows.

[0077] Step S41: Use eight rectangular coils to construct two zero-field line devices that can generate zero-field lines.

[0078] Step S42: Adjust the coil positions so that the two zero-field lines intersect perpendicularly.

[0079] Step S43: Some modifications are made to the existing model based on the perpendicular intersection so that the model can meet various transformation requirements to complete the scanning within the plane. Improve the existing model to obtain a new model. The new model is further modified based on the basic principle of the original model while ensuring that its function remains unchanged or has more ideal performance.

[0080] In step S43, the specific implementation method of the new model is as follows:

[0081] Step S431: Select eight rectangular coils of appropriate size. In this simulation experiment, rectangular coils with a side length of 12 mm, a height of 1 mm, and a thickness of 1 mm are selected.

[0082] Step S432: Simulate a cuboid with a square bottom surface in a plane; in this simulation experiment, a cuboid is used.

[0083] Step S433: Take the center points of the eight rectangular coils as the vertices of the cuboid.

[0084] Step S434: The placement direction of the rectangular coils is as follows: for the four coils at the bottom, their normal directions respectively face the diagonal directions of the corresponding vertices, and the sides of the coils are parallel to each other. The other four coils at the top are also placed in this way, and the overall model is placed.

[0085] Step S435: Energize the rectangular coils. The current directions of the rectangular coils on the diagonal are the same, and the current directions of the rectangular coils at the top and bottom are opposite. The currents on different diagonals can control the rotation direction of the zero-field line, and a variable current is input subsequently.

[0086] Figure 2 is the coil position model diagram in this embodiment. Figure 3 is the magnetic field distribution diagram generated by a single group of coils in this embodiment. Figure 4 is the zero-field line display diagram generated in this embodiment.

[0087] In this embodiment, the specific implementation steps of step S5 are as follows.

[0088] Step S51: Experimentally verify that the new model can normally generate zero-field lines.

[0089] Step S52: The combination of two coil groups generating FFLs can portably change the angle of the zero-field line. By changing the current magnitudes of the two coil groups, FFLs in any direction within the plane where the two FFLs intersect can be obtained.

[0090] Furthermore, in this experiment, current functions that increase and decrease with time are respectively added to the two groups of coils. After the FFL rotates one week, the current of the modified function value is input again. Therefore, it can be regarded as adding a periodic variation function.

[0091] Step S53: To achieve omnidirectional particle detection, it is not enough to detect a single plane. It is also necessary to change the position of the detection plane. By changing the current ratio of the coils on both sides of the plane where the above FFLs intersect perpendicularly, the position of the plane can be changed, thereby completing the detection of the magnetic nanoparticle concentration at any place within the region.

[0092] Furthermore, in this experimental example, after the entire current plane is scanned every once in a while, the ratio of the coil currents on both sides of the plane is changed, or a value is simply added or subtracted, so that the rotating plane changes. Multiple changes can cover the entire area.

[0093] Step S54: Control the scanning area to change automatically, and apply specific variable currents to the two sets of coils to achieve stable rotational and translational scanning within the area.

[0094] The all-round scanning method for the concentration of magnetic nanoparticles based on zero field lines provided by the present invention adjusts the positions of the two sets of coils generating FFL, so that the FFLs generated by each are the same when the parameters are the same, facilitating the calculation of the rotation angle. Moreover, the up-and-down translation of the coil can be completed without an external driving coil.

[0095] The above are only the preferred embodiments of the present invention, and the present invention is not limited to other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines, characterized in that: The following steps are involved: Step S1: selecting a method for detecting the concentration of magnetic nanoparticles according to the magnetization characteristics of the magnetic nanoparticles; Step S2: Determine to use a zero field line device to generate zero field lines for magnetic nanoparticle concentration detection; Step S3: constructing a zero field line device capable of generating a zero field line by combining multiple coils; Step S4: improving the existing model and adjusting the coil configuration to achieve omnidirectional detection; Step S5: Verify whether the performance of the new model meets the actual requirements.

2. The method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines according to claim 1, characterized in that: The step S1 specifically includes the following steps: Step S11: generating a specific zero magnetic field region based on the nonlinear characteristics of the magnetic nanoparticles obeying the Langevin equation; Step S12: Detect the particle concentration in the zero magnetic field region by a particle concentration detection device.

3. The method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines according to claim 2, characterized in that: In step S11, the Langevin equation is specifically: L(a)=coth(a)-1 / a The magnetization characteristics of the magnetic nanoparticles are expressed by the following formula: M(W)=φM d coth(μ0M d V / (k B T)W)-1 / μ0M d V / (k B T)W Where M represents the magnetizing magnetic field intensity generated by the magnetic nanoparticles, W represents the excitation magnetic field intensity, φ represents the volume fraction of the magnetic nanoparticles, μ0 represents the magnetic permeability in vacuum, and M d represents the magnetization intensity of the magnetic domain, V represents the volume of the magnetic nanoparticle, k B represents the Boltzmann constant, and T represents the temperature of the magnetic nanoparticles.

4. The method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines according to claim 2, characterized in that: In step S12, the particle concentration detection device is composed of an excitation coil and a receiving coil, wherein the excitation magnetic field is used to excite the magnetic nanoparticles to generate a magnetic field, and the receiving coil is used to receive and record changes in the external magnetic field.

5. The method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines according to claim 1, characterized in that: The step S2 specifically includes the following steps: Step S21: The zero field includes the zero field line and the zero field point, and the advantages, disadvantages and applicability of the zero field line and the zero field point are analyzed; Step S22: Select a zero field line with a larger zero field range and higher applicability to establish a zero field domain model; a zero field line refers to a straight line with a non-zero width in a space with a magnetic field, which is made almost zero in magnetic field through various means such as charged coils.

6. The method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines according to claim 1, characterized in that: The step S3 specifically comprises the following steps: Step S31: configuring four multi-turn charged circular coils; Step S32: Arrange four circular coils at four vertices of a rectangle in a plane with the center of the circle as a reference, wherein the normal directions of the four circular coils are the same and are respectively on the same straight line as the two parallel sides of the rectangle; Step S33: There are two circular coils on each side, and the current directions of the circular coils on the same side are controlled to be the same, while the current directions of the circular coils on the opposite sides are controlled to be opposite; Step S34: Arrange according to the above method, and obtain a normal line with a non-zero width at the center of the rectangle, and the magnetic field is almost zero, that is, the zero field line.

7. The method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines according to claim 6, characterized in that: The circular coil is changed to a rectangular coil to produce a more stable magnetic field.

8. The method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines according to claim 7, characterized in that: The step S4 specifically comprises the following steps: Step S41: using eight rectangular coils to construct two zero field line devices capable of generating zero field lines; Step S42: adjusting the coil position so that the two zero field lines intersect vertically; Step S43: Improve the existing model to obtain a new model.

9. The method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines according to claim 8, characterized in that: In step S43, the specific implementation method of the new model is: Step S431: Select eight rectangular coils of set size; Step S432: simulating a cuboid with a square bottom in a plane; Step S433: taking the center points of the eight rectangular coils as the vertices of the cuboid; Step S434: The rectangular coils are placed in the following direction: the normal directions of the four coils at the bottom are respectively oriented toward the diagonal directions of the vertices at which they are located, and the sides of the coils are parallel to each other. The other four coils at the top are also placed in this way, and the overall model is placed; Step S435: energize the rectangular coils. The current directions of the rectangular coils on the diagonals are the same, and the current directions of the rectangular coils at the top and bottom are opposite. The currents on different diagonals can control the rotation direction of the zero field line, and then a variable current is introduced.

10. The method for omnidirectional scanning of magnetic nanoparticle concentration based on zero field lines according to claim 1, characterized in that: The step S5 specifically comprises the following steps: Step S51: obtaining a zero field line in any direction within the plane where the two zero field lines intersect by changing the currents of the coils of the two zero field line devices; Step S52: changing the current ratio of the coils on both sides of the plane where the zero field lines intersect vertically to change the position of the detection plane, thereby completing the concentration detection of magnetic nanoparticles at any place in the area; Step S53: Control the scanning area to change automatically, and add specific variable currents to the two zero field line devices to achieve stable rotational translation scanning within the area.

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