A method of magnetic particle driven imaging

Abstract

The application discloses a kind of magnetic particle drive imaging method and system, it is related to magnetic particle imaging and magnetic particle drive technical field, it solves the problem that magnetic drive cannot be realized with magnetic imaging in same equipment;The method comprises: adjusting gradient field and uniform field to obtain superimposed field;The angle difference of each field in superimposed field is adjusted to control magnetic drive force;The direction of magnetic drive force is controlled by controlling the overall rotation of dipole ring in superimposed field relative to ground;The angle difference of dipole ring is adjusted, the uniform field is set to zero, and the gradient field forms a magnetic field free region in superimposed field;Adjust dipole ring, change the size and direction of uniform field, so that the magnetic field free region moves and scans along the preset trajectory, covers the entire imaging area;Receive magnetic particle signal and process image reconstruction operation, complete magnetic imaging;Magnetic drive and magnetic imaging are realized in same equipment, without using electromagnetic coil, reduce the influence of system heat output and electromagnetic coil vibration on reconstruction.

Description

Technical Field

[0001] This invention relates to the fields of magnetic particle imaging and magnetic particle actuation technology, and in particular to a method for magnetic particle actuation imaging. Background Technology

[0002] Magnetic particle imaging (MPI) technology utilizes the nonlinear response of magnetic nanoparticles in the free region of a high-gradient magnetic field to obtain the distribution and concentration of magnetic nanoparticles in biological organisms. It features high temporal resolution, high spatial resolution, and high sensitivity. Furthermore, MPI does not display anatomical structures and is free from ionizing radiation and interference signals from tissues. The intensity of the received signal is directly proportional to the concentration of the tracer, making it a promising new imaging method for medical applications.

[0003] Magnetic drive refers to a non-contact driving technology that uses an external magnetic field to adjust or change the spatial position or shape of magnetic materials. It has broad application prospects in fields such as magnetic separation, magnetic targeting, and magnetically controlled soft robots. Magnetic drive methods include utilizing magnetic torque induced by a magnetic field, gradient magnetic force, or a combination of both. Among these, combining magnetic torque and gradient magnetic force decouples steering and driving, offering a simpler and more flexible implementation and control mode.

[0004] In current technologies, most MPI devices use electromagnets or a combination of electromagnets and permanent magnets, with the permanent magnets providing the gradient field. Due to limitations in current and power, the magnetic field strength that electromagnets can generate is limited, making it impossible to achieve imaging with larger gradients. In a large imaging field of view, the limited magnetic field strength results in low spatial resolution. Furthermore, the electromagnetic field requires a large current to drive it, generating significant heat over prolonged use. Moreover, no current technology can simultaneously perform magnetic actuation and magnetic imaging. Summary of the Invention

[0005] This invention provides a magnetic particle-driven imaging method, which solves the problem in the prior art that magnetic drive and magnetic imaging cannot be implemented in the same device. It enables magnetic drive and magnetic imaging to be performed in the same device without the need for electromagnetic coils, thereby reducing the impact of system heat generation and electromagnetic coil vibration on reconstruction.

[0006] In a first aspect, embodiments of the present invention provide a method for magnetic particle-driven imaging, the method comprising:

[0007] Adjusting the angle difference of multiple Halbach quadrupole rings changes the gradient field, and adjusting the angle difference of multiple Halbach dipole rings changes the uniform field;

[0008] The uniform field and the gradient field are superimposed to obtain a superimposed field; wherein the intensity of the uniform field in the superimposed field is greater than the intensity of the gradient field.

[0009] The angle difference between the uniform field and / or the gradient field in the superimposed field is adjusted to control the magnetic driving force in the superimposed field;

[0010] The direction of the magnetic driving force is controlled by rotating the plurality of Halbach dipole rings in the superimposed field as a whole relative to the ground.

[0011] Adjusting the angle difference of the plurality of Halbach dipole rings, the uniform field is set to zero, the gradient field intensity is adjusted to the maximum, and the gradient field forms a magnetic field free region in the superimposed field;

[0012] Adjusting the angle difference of the multiple Halbach dipole rings changes the intensity of the uniform field. Rotating the multiple Halbach dipole rings relative to the ground changes the direction of the uniform field. The uniform field is superimposed on the gradient field, causing the free region of the magnetic field to move and cover the entire imaging area.

[0013] It receives magnetic particle signals, performs signal processing and image reconstruction operations, and completes magnetic imaging.

[0014] In conjunction with the first aspect, in one possible implementation, the plurality of Halbach quadrupole rings are nested together, and the plurality of Halbach dipole rings are nested together; the plurality of Halbach quadrupole rings and the plurality of Halbach dipole rings are placed coaxially.

[0015] In conjunction with the first aspect, in one possible implementation, adjusting the angular difference between the uniform field and / or the gradient field in the superimposed field to control the magnetic driving force in the superimposed field includes:

[0016] First, under the condition that the intensity of the uniform field is greater than the saturation magnetization, the relative rotation of the plurality of Halbach quadrupole rings in the superimposed field is controlled to obtain the changing angle difference in the gradient field;

[0017] Then, the changing gradient field is obtained through the changing angle difference in the gradient field;

[0018] The magnetic driving force in the superimposed field is then controlled by the changing gradient field.

[0019] In conjunction with the first aspect, in one possible implementation, adjusting the angular difference between the uniform field and / or the gradient field in the superimposed field to control the magnetic driving force in the superimposed field further includes:

[0020] First, under the condition that the intensity of the uniform field is less than the saturation magnetization, the relative rotation of the plurality of Halbach dipole rings in the superimposed field is controlled to obtain the changing angle difference in the uniform field;

[0021] Then, by using the changing angle difference in the uniform field, the changing uniform field is obtained;

[0022] The magnetic driving force in the superimposed field is then controlled by the changing uniform field.

[0023] In conjunction with the first aspect, in one possible implementation, adjusting the angular difference between the uniform field and / or the gradient field in the superimposed field to control the magnetic driving force in the superimposed field further includes:

[0024] First, under the condition that the intensity of the uniform field is less than the saturation magnetization, the angle difference of the multiple Halbach dipole rings in the superimposed field is adjusted to obtain a varying uniform field.

[0025] By adjusting the angle difference of the multiple Halbach quadrupole rings in the superimposed field, a changing gradient field is obtained;

[0026] The magnetic driving force in the superimposed field is then controlled by the changing gradient field and the changing uniform field.

[0027] In conjunction with the first aspect, in one possible implementation, controlling the direction of the magnetic driving force by controlling the overall rotation of the plurality of Halbach dipole rings in the superimposed field relative to the ground specifically includes:

[0028] The controller controls the motor to rotate the multiple Halbach dipole rings as a whole, thereby changing the direction of the uniform field and obtaining a superimposed field with changing direction.

[0029] The direction of the magnetic driving force can be controlled based on the superimposed field of the directional change.

[0030] In conjunction with the first aspect, in one possible implementation, the receiving of magnetic particle signals, the performance of signal processing and image reconstruction operations, and the completion of magnetic imaging specifically include:

[0031] The object to be tested is placed in the free region of the magnetic field from above, and magnetic particle signals are received.

[0032] Scan along a preset trajectory to obtain the acquired signal;

[0033] The acquired signals are then processed to obtain processed signals;

[0034] The processed signal is used to reconstruct the image using a predetermined reconstruction method to obtain the final imaging result.

[0035] In conjunction with the first aspect, in one possible implementation, the number of the plurality of Halbach quadrupole rings and the plurality of Halbach dipole rings are both two.

[0036] Secondly, embodiments of the present invention provide a magnetic particle-driven imaging system, which includes: a field strength generation module, a superimposed field module, a magnetic driving force magnitude control module, a magnetic driving force direction control module, a magnetic field free zone formation module, a signal acquisition module, and an imaging module.

[0037] The field strength generation module includes a gradient field generation module and a uniform field generation module. The gradient field generation module is used to adjust the angle difference of multiple Halbach quadrupole rings to change the gradient field, and the uniform field generation module is used to adjust the angle difference of multiple Halbach dipole rings to change the uniform field.

[0038] The superposition module is used to superimpose the uniform field and the gradient field to obtain a superimposed field; and to adjust the intensity of the gradient field so that the magnetization direction of the superimposed field is the driving field direction.

[0039] The magnetic driving force control module is used to adjust the angle difference between the uniform field and / or the gradient field in the superimposed field, so as to control the magnetic driving force in the superimposed field.

[0040] The magnetic driving force direction control module is used to control the direction of the magnetic driving force by controlling the overall rotation of the plurality of Halbach dipole rings in the superimposed field relative to the ground;

[0041] The magnetic field free region forming module is used to adjust the angle difference of the multiple Halbach dipole rings, set the uniform field to zero, adjust the angle difference of the multiple Halbach quadrupole rings, and maximize the gradient field intensity. The gradient field forms a magnetic field free region in the superimposed field.

[0042] The signal acquisition module is used to adjust the angle difference of the Halbach dipole ring and the rotation angle relative to the ground, change the size and direction of the uniform field, and make the free region of the magnetic field scan along a preset trajectory to cover the entire imaging area.

[0043] The imaging module is used to receive magnetic particle signals, perform signal processing and image reconstruction operations, and complete magnetic imaging.

[0044] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention employs a magnetic particle-driven imaging method, which includes: adjusting the angle difference of multiple Halbach quadrupole rings to generate a gradient field, and adjusting the angle difference of multiple Halbach dipole rings to generate a uniform field. This condition is easy to achieve, and it is easy to rotate the magnetic field direction and change the field strength. The uniform field and the gradient field are superimposed to obtain a superimposed field. The gradient field strength is adjusted to a minimum so that the magnetization direction of the superimposed field is the driving field direction. The angle difference between the uniform field and / or the gradient field in the superimposed field is adjusted to control the magnetic driving force in the superimposed field. The direction of the magnetic driving force is controlled by controlling the overall rotation of multiple Halbach dipole rings in the superimposed field relative to the ground. By adjusting the angle difference of multiple Halbach dipole rings, the uniform field is set to zero, and the gradient field forms a magnetic field free region in the superimposed field. Adjusting the multiple Halbach dipole rings changes the magnitude and direction of the uniform field, causing the uniform field and gradient field to superimpose and move the magnetic field free region. By adjusting the angle difference of the Halbach dipole rings and the rotation angle relative to the ground, the magnetic field free region is scanned along a preset trajectory, covering the entire imaging area. Magnetic particle signals are acquired, and signal processing and image reconstruction are performed to complete magnetic imaging. This method solves the problems of existing magnetic imaging devices easily overheating and the inability to implement magnetic drive and magnetic imaging in the same device. It enables magnetic drive and magnetic imaging to be performed in the same device without the need for electromagnetic coils, reducing the impact of system heat generation and electromagnetic coil vibration on reconstruction. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments of the present invention or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart of the method steps for magnetic particle-driven imaging provided in an embodiment of the present invention;

[0047] Figure 2A A schematic diagram of a Halbach quadrupole ring model provided in an embodiment of the present invention when the angle difference between the two Halbach quadrupole rings is 0°;

[0048] Figure 2B A schematic diagram of a Halbach dipole ring model provided in an embodiment of the present invention when the angle difference between the two Halbach dipole rings is 0°;

[0049] Figure 2CThis is a schematic diagram showing the coaxial placement of two Halbach quadrupole rings and two Halbach dipole rings provided in an embodiment of the present invention;

[0050] Figure 3A The spatial gradient magnetic field distribution diagrams in the x and z directions when the angle difference of the Halbach quadrupole rings is 0° are provided for embodiments of the present invention.

[0051] Figure 3B The spatial gradient magnetic field distribution diagrams in the x and z directions are provided for an embodiment of the present invention when the angle difference of the Halbach quadrupole ring is 90°.

[0052] Figure 4A The magnetic field distribution diagrams in the x and z directions when the Halbach dipole ring angle difference is 0° are provided for embodiments of the present invention.

[0053] Figure 4B The magnetic field distribution in the x and z directions when the Halbach dipole ring angle difference is 180° is provided in this embodiment of the invention.

[0054] Figure 5A A uniform field spatial distribution diagram provided for an embodiment of the present invention;

[0055] Figure 5B This is a gradient field spatial distribution diagram provided in an embodiment of the present invention;

[0056] Figure 5C The spatial distribution diagram of the superimposed field provided in the embodiments of the present invention;

[0057] Figure 6 The structural design diagram provided for an embodiment of the present invention. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0059] Existing permanent magnet array-based magnetic particle imaging devices overcome the shortcomings of electromagnetic coils in MPI imaging, enabling high-gradient MPI imaging and improving spatial resolution. The permanent magnet MPI system, with its high gradient field and array superposition capabilities, can further enhance the imaging field of view.

[0060] This invention provides a method for magnetic particle-driven imaging, such as... Figure 1 As shown, the method includes the following steps S101 to S107.

[0061] S101 generates a gradient field by adjusting the angle difference of multiple Halbach quadrupole rings, and generates a uniform field by adjusting the angle difference of multiple Halbach dipole rings. For example... Figure 2A As shown, the two Halbach quadrupole rings are nested together, as follows: Figure 2B As shown, the two Halbach dipole rings are nested within each other; as Figure 2C As shown, two Halbach quadrupole rings are placed coaxially with two Halbach dipole rings, and the two Halbach quadrupole rings are located inside the two Halbach dipole rings.

[0062] Two nested Halbach quadrupole rings generate a variable gradient field, and two nested Halbach dipole rings generate a variable uniform field. For example... Figure 6 As shown, four permanent magnet arrays are placed coaxially, with each array corresponding to a motor for control. The operating plane is located at the center of the device, perpendicular to the axis, and the object being measured enters the operating area from above.

[0063] Compared to existing technologies that can generate uniform and gradient fields, the magnet configuration provided by this invention offers a uniform magnetic field strength distribution and facilitates rotation of the magnetic field direction and alteration of the field strength. Traditional permanent magnet pairs cannot change the uniform field strength; the Helmholtz coil pair + rotating ring scheme has high power consumption and a less uniform magnetic field distribution than the current scheme.

[0064] The parameters of the magnetic drive system are set according to the magnetization characteristics of magnetic particles. The initial gradient information and the magnitude of the uniform field are calculated, and the system layout is adjusted. Multiple Halbach quadrupole ring permanent magnet arrays are adjusted to make the magnetic field gradient in space lower. Multiple Halbach dipole ring permanent magnet arrays are adjusted to make the uniform field intensity in space higher. The uniform field and gradient field are superimposed, with the uniform field intensity stronger than the gradient field intensity, and the main direction of the magnetic field in space is the same as that of the uniform field.

[0065] When a particle is magnetized by a uniform field, the direction of the magnetic force on the particle is the same as that of the uniform field, and the magnitude of the force is related to the gradient intensity.

[0066]

[0067]

[0068] in, Let ρ represent the magnetic moment of a particle under the influence of a uniform field, ρ represent the particle density, V represent the particle volume, χ represent the magnetic susceptibility, and μ0 represent the free permeability. It represents the magnetic flux density in space.

[0069] When the magnetic field strength in space is greater than the saturation magnetization M of the particle sat The magnetic moment can be represented by the saturation magnetization.

[0070]

[0071]

[0072] in, B represents the change in magnetic flux density in space. dr G represents the uniform magnetic flux density. qr This represents the gradient distribution of the gradient field. Represents a unit vector.

[0073] S102, the uniform field and the gradient field are superimposed to obtain the superimposed field; the gradient field intensity is adjusted to the minimum so that the magnetization direction of the superimposed field is the driving field direction, such as... Figure 3A The image shows the spatial gradient magnetic field distribution in the x and z directions when the quadrupole ring angle difference is 0°. Figure 3B The diagram shows the spatial gradient magnetic field distribution in the x and z directions when the angle difference between the four-pole rings is 90°. It also illustrates how adjusting the angle difference between multiple Halbach dipole rings can generate a uniform field, such as... Figure 4A The image shows the magnetic field distribution in the x and z directions when the angle difference of the Halbach dipole rings is 0°. Figure 4B The diagram shows the magnetic field distribution in the x and z directions when the angle difference of the Halbach dipole rings is 180°.

[0074] S103 adjusts the angle difference between the uniform field and / or gradient field in the superimposed field to control the magnetic driving force in the superimposed field, such as... Figure 5A The image shows a spatial distribution diagram of a uniform field; as shown. Figure 5B This is a spatial distribution map of the gradient field; such as... Figure 5C This is a spatial distribution diagram of the superimposed field.

[0075] One possible implementation of step S103 is to adjust the gradient field in the superimposed field, specifically including the following steps:

[0076] (1) First, under the condition that the intensity of the uniform field is greater than the saturation magnetization, multiple Halbach quadrupole rings in the superimposed field are controlled to rotate in opposite directions to obtain the changing angle difference α in the gradient field.

[0077] (2) Then, by using the changing angle difference in the gradient field, the changing gradient field is obtained. The changing gradient field is expressed as:

[0078]

[0079] Where α1 and α2 represent the rotation angles of multiple Halbach quadrupole rings; G q1 G represents the gradient distribution of a gradient field in multiple Halbach quadrupole rings; q2This represents the gradient distribution of another gradient field in a plurality of Halbach quadrupole rings;

[0080] When G q1 =G q2 =G qp When α1=α and α2=-α, the changing gradient field is expressed as:

[0081]

[0082] Magnetic driving force is expressed as:

[0083]

[0084] Where ρ represents particle density; V represents particle volume; M sat This represents the saturation magnetization of a particle.

[0085] At this point, the magnitude of the magnetic driving force is proportional to the magnetic field gradient, and the magnitude of the magnetic field gradient is only related to the angle difference of the Halbach quadrupole rings.

[0086] (3) Then, the magnetic driving force in the superimposed field is controlled by changing the gradient field.

[0087] One possible implementation of step S103 is to adjust the uniform field in the superimposed field, specifically including the following steps:

[0088] (1) First, under the condition that the intensity of the uniform field is less than the saturation magnetization, multiple Halbach dipole rings in the superimposed field are controlled to rotate in opposite directions to obtain the changing angle difference β in the uniform field.

[0089] (2) Then, by varying the angle difference within the uniform field, the varying uniform field is obtained. The magnetic flux density of the varying uniform field is expressed as:

[0090]

[0091] Where β1 and β2 represent the rotation angles of multiple Halbach dipole rings, respectively; B d1 B represents the magnetic flux density of a uniform field in a plurality of Halbach dipole rings; d2 This represents the magnetic flux density of another uniform field in a plurality of Halbach dipole rings;

[0092] When B d1 =B d2 =B dp When β1=β and β2=-β, the magnetic flux density of the changing uniform field is expressed as:

[0093]

[0094] Magnetic driving force is expressed as:

[0095]

[0096] Where ρ represents particle density; V represents particle volume; χ represents magnetic susceptibility; and G represents gradient field strength.

[0097] At this point, the magnitude of the magnetic driving force is proportional to the magnetic flux density, which is related to the rotation angle of the Halbach dipole ring.

[0098] (3) Then, the magnetic driving force in the superimposed field is controlled by changing the uniform field.

[0099] One possible implementation of step S103 is to adjust the uniform field and gradient field in the superimposed field, specifically including the following steps:

[0100] (1) First, under the condition that the intensity of the uniform field is less than the saturation magnetization, multiple Halbach dipole rings in the superimposed field are rotated in opposite directions to obtain the changing angle difference β in the uniform field. At the same time, multiple Halbach quadrupole rings in the superimposed field are rotated in opposite directions to obtain the changing angle difference α in the gradient field.

[0101] (2) A changing uniform field and a gradient field are used to obtain a changing magnetic driving force.

[0102] Magnetic driving force is expressed as:

[0103]

[0104] Where ρ represents particle density; V represents particle volume; χ represents magnetic susceptibility; G represents gradient field strength; β represents the rotation angle of the Halbach dipole ring; and α represents the rotation angle of the Halbach quadrupole ring.

[0105] S104 controls the direction of the magnetic driving force by controlling the overall rotation of multiple Halbach dipole rings in the superimposed field relative to the ground.

[0106] Method for controlling the direction of magnetic drive: Without changing the magnitude of the magnetic drive force, the direction of the uniform field is changed by controlling the overall rotation of the two dipole rings, thereby controlling the direction of the magnetic drive force.

[0107] (1) The controller controls the motor to rotate multiple Halbach dipole rings as a whole, thereby changing the direction of the uniform field and obtaining a superimposed field with changing direction. The magnetic flux density in space is expressed as:

[0108]

[0109] Among them, B dr G represents the magnetic flux density of a changing uniform field.qr Represents the changing gradient field;

[0110]

[0111]

[0112] Where β1 and β2 represent the rotation angles of multiple Halbach dipole rings, respectively; α1 and α2 represent the rotation angles of multiple Halbach quadrupole rings, respectively; and θ represents the angle of rotation of multiple Halbach dipole rings as a whole.

[0113] (2) The direction of the magnetic driving force can be controlled based on the superposition of the directional changes in the superimposed field. When B d1 =B d2 =B, β1=β, β2=-β, and G q1 =G q2 =G, α1=α, α2=-α,

[0114]

[0115]

[0116] Magnetic driving force is expressed as:

[0117]

[0118]

[0119] Where ρ represents particle density; V represents particle volume; M sat G represents the saturation magnetization of the particle; G represents the gradient distribution of the gradient field when the gradient fields formed by multiple Halbach quadrupole rings are equal.

[0120] The direction of the magnetic driving force is related to the direction of the uniform field. Controlling the rotation of the Halbach dipole ring can change the direction of the magnetic driving force, while the magnitude of the force remains unchanged.

[0121] S105: Adjust the angle difference of multiple Halbach dipole rings to set the uniform field to zero, and adjust the angle difference of multiple Halbach quadrupole rings to maximize the gradient field, forming a free region of magnetic field in the superimposed field. That is, the angle difference of Halbach quadrupole rings 2α = 0°, and the angle difference of Halbach dipole rings 2β = 180°.

[0122] S106 adjusts the angle difference of multiple Halbach dipole rings to change the intensity of the uniform field. Rotating these rings relative to the ground changes the direction of the uniform field, thereby altering the position of the free region of the magnetic field within the superimposed field. By adjusting the magnitude and direction of the uniform field, the free region of the magnetic field is scanned along a preset trajectory, covering the entire imaging area.

[0123] S107 receives magnetic particle signals, performs signal processing and image reconstruction, and completes magnetic imaging. The specific steps for completing magnetic imaging are as follows:

[0124] (1) The receiving coil acquires the particle signal in the region of interest, which is then processed by the hardware circuit and converted by AD to obtain the electromagnetic signal;

[0125] (2) The electromagnetic signal is filtered and denoised to obtain a preprocessed signal;

[0126] (3) The preprocessed signal is reconstructed using a predetermined reconstruction method, and the missing data is filled in using an interpolation method to obtain the final two-dimensional imaging result.

[0127] Standalone MPI devices use a fixed gradient magnetic field, which cannot change the gradient magnitude, and the direction of the driving field intensity cannot be changed either, thus preventing the direction of magnetic drive and hindering the realization of magnetic drive functionality. This invention proposes a specially designed magnetic drive imaging scheme with an adjustable gradient field. Combined with variations in the intensity and direction of the uniform field, a magnetic drive mode can be achieved. Furthermore, this invention proposes a magnetic drive imaging scheme with both a gradient field and a uniform field, coupled with a signal excitation and receiving system, enabling two-dimensional magnetic particle imaging.

[0128] Within the same size or imaging space, permanent magnets can generate large gradient magnetic fields, resulting in high image resolution. Under the same magnetic field gradient conditions, permanent magnet arrays can construct MPI devices with a larger field of view. In driven imaging devices, the system can achieve magnetic drive functionality through the combination of gradient and uniform fields. In magnetic drive mode, magnetic particles can be driven to move along a specific direction, and the magnitude and timing of the driving force can be controlled to achieve movement at a specific location. Combined with the device's imaging mode, the spatial distribution of magnetic particles can be located, showing promising applications in special phantoms, mice, and other opaque test objects. The two modes work together to achieve guidance and positioning within the same device.

[0129] This invention comprises a multi-layered Halbach permanent magnet array, generating both gradient and uniform fields. In addition to MPI control mode, this invention proposes a scheme to achieve magnetic particle actuation by controlling the rotation of the permanent magnet array via a motor. Magnetic actuation facilitates thrombolysis, while the high magnetic field gradient of the permanent magnet system helps to overcome the blood-brain barrier, offering natural advantages in drug delivery. Furthermore, an external magnetic field can be used to drive magnetic microrobots, enabling swarm movement of these microrobots through magnetic field control. This allows the microrobots to converge at the thrombus site, performing local drug release and thrombolysis under high-frequency magnetic field control.

[0130] In a specific embodiment of this invention, a blocked blood vessel model is first placed into the system provided by this invention, and ferromagnetic material is injected. Through the superposition of external magnetic field strength and gradient, a magnetic driving force in a specific direction is generated on the magnetic particles. When the magnetic driving force is greater than the resistance of the blockage, the thrombus will dissolve. During this process, magnetic imaging can be used to locate the ferromagnetic material, thereby determining its current position and guiding the next step of the operation; alternatively, the location of the blockage can be determined, allowing for the use of other more effective methods. Ultimately, the goal of thrombus dissolution is achieved.

[0131] In a specific embodiment of the present invention, a method for driving a specific position is implemented: (x, y) = (rsinθ, rcosθ) is expressed in polar coordinates. Substituting this into the formula in S104, we obtain:

[0132]

[0133] According to the above formula, the magnetic particles can be driven to move based on the target point. This method is a combination of the first two control modes, allowing for faster adjustment of the magnetic driving force. It can only be used when the uniform field strength is less than the particle saturation magnetization.

[0134] When using the magnetic drive mode, it is necessary to adjust the gradient field to the minimum mode, i.e., the Halbach quadrupole ring angle difference 2α = 90°, and the uniform field to the strongest magnetic field mode, i.e., the Halbach dipole ring angle difference 2β = 0°.

[0135] Adjust the quadrupole rings to the target direction, gradually increase the angle difference between the quadrupole rings, and increase the magnitude of the magnetic field gradient in space until the particle moves. When the particle is driven to the designated position, decrease the angle difference between the quadrupole rings so that the magnetic field gradient in space is zero.

[0136] The present invention also provides a magnetic particle driven imaging system, which includes: a field strength generation module, a superimposed field module, a magnetic driving force magnitude control module, a magnetic driving force direction control module, a magnetic field free zone formation module, a signal acquisition module, and an imaging module.

[0137] The field strength generation module includes a gradient field generation module and a uniform field generation module. The gradient field generation module is used to adjust the angle difference of multiple Halbach quadrupole rings to generate a gradient field, and the uniform field generation module is used to adjust the angle difference of multiple Halbach dipole rings to generate a uniform field.

[0138] The superposition module is used to superimpose the uniform field and the gradient field to obtain the superimposed field; the gradient field intensity is adjusted to the minimum so that the magnetization direction of the superimposed field is the driving field direction.

[0139] The magnetic driving force control module is used to adjust the angle difference between the uniform field and / or gradient field in the superimposed field in order to control the magnetic driving force in the superimposed field.

[0140] The magnetic drive force direction control module is used to control the direction of the magnetic drive force by controlling the overall rotation of multiple Halbach dipole rings in the superimposed field relative to the ground.

[0141] The magnetic field free zone forming module is used to adjust the angle difference of multiple Halbach dipole rings, set the uniform field to zero, and form a magnetic field free zone in the superimposed field by the gradient field.

[0142] The signal acquisition module is used to adjust the Halbach quadrupole ring angle difference and the rotation angle relative to the ground, change the size and direction of the uniform field, and make the free region of the magnetic field scan along the preset trajectory to cover the entire imaging area.

[0143] The imaging module is used to receive magnetic particle signals, perform signal processing and image reconstruction operations, and complete magnetic imaging.

[0144] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for magnetic particle-driven imaging, characterized in that, include: The gradient field is changed by adjusting the angle difference of multiple Halbach quadrupole rings, and the uniform field is changed by adjusting the angle difference of multiple Halbach dipole rings; wherein the multiple Halbach quadrupole rings are nested with each other, and the multiple Halbach dipole rings are nested with each other; the multiple Halbach quadrupole rings and the multiple Halbach dipole rings are placed coaxially; the number of multiple Halbach quadrupole rings and the number of multiple Halbach dipole rings are both two; The uniform field and the gradient field are superimposed to obtain a superimposed field; the intensity of the gradient field is adjusted so that the magnetization direction of the superimposed field is the driving field direction. The angle difference between the uniform field and / or the gradient field in the superimposed field is adjusted to control the magnetic driving force in the superimposed field. This adjustment includes: first, under the condition that the intensity of the uniform field is greater than the saturation magnetization, controlling the relative rotation of the plurality of Halbach quadrupole rings in the superimposed field to obtain a changing angle difference in the gradient field; then, obtaining a changing gradient field through the changing angle difference in the gradient field; and finally, controlling the magnetic driving force in the superimposed field through the changing gradient field. The direction of the magnetic driving force is controlled by rotating the plurality of Halbach dipole rings in the superimposed field as a whole relative to the ground. By adjusting the angle difference of the plurality of Halbach dipole rings, the uniform field is set to zero, and the gradient field forms a magnetic field free region in the superimposed field; Adjusting the Halbach dipole ring angle difference and the rotation angle relative to the ground changes the magnitude and direction of the uniform field, causing the free region of the magnetic field to scan along a preset trajectory and cover the entire imaging area; It receives magnetic particle signals, performs signal processing and image reconstruction operations, and completes magnetic imaging.

2. The method for magnetic particle-driven imaging according to claim 1, characterized in that, The step of adjusting the angle difference between the uniform field and / or the gradient field in the superimposed field to control the magnetic driving force in the superimposed field further includes: First, under the condition that the intensity of the uniform field is less than the saturation magnetization, the relative rotation of the plurality of Halbach dipole rings in the superimposed field is controlled to obtain the changing angle difference in the uniform field; Then, by using the changing angle difference in the uniform field, the changing uniform field is obtained; The magnetic driving force in the superimposed field is then controlled by the changing uniform field.

3. The method for magnetic particle-driven imaging according to claim 1, characterized in that, The step of adjusting the angle difference between the uniform field and / or the gradient field in the superimposed field to control the magnetic driving force in the superimposed field further includes: First, under the condition that the intensity of the uniform field is less than the saturation magnetization, the angle difference of the multiple Halbach dipole rings in the superimposed field is adjusted to obtain a varying uniform field. By adjusting the angle difference of the multiple Halbach quadrupole rings in the superimposed field, a changing gradient field is obtained; The magnetic driving force in the superimposed field is then controlled by the changing gradient field and the changing uniform field.

4. The method for magnetic particle-driven imaging according to claim 1, characterized in that, The control of the direction of the magnetic driving force by controlling the overall rotation of the plurality of Halbach dipole rings in the superimposed field relative to the ground specifically includes: The controller controls the motor to rotate the multiple Halbach dipole rings as a whole, thereby changing the direction of the uniform field and obtaining a superimposed field with changing direction. The direction of the magnetic driving force can be controlled based on the superimposed field of the directional change.

5. The method for magnetic particle-driven imaging according to claim 1, characterized in that, The process of receiving magnetic particle signals, performing signal processing and image reconstruction to complete magnetic imaging specifically includes: The object to be tested is placed in the free region of the magnetic field from above, and magnetic particle signals are received. Scan along a preset trajectory to obtain the acquired signal; The acquired signals are then processed to obtain processed signals; The processed signal is used to reconstruct the image using a predetermined reconstruction method to obtain the final imaging result.

6. A system for magnetic particle-driven imaging, characterized in that, include: The system includes a field strength generation module, a superimposed field module, a magnetic driving force magnitude control module, a magnetic driving force direction control module, a magnetic field free zone formation module, a signal acquisition module, and an imaging module. The field strength generation module includes a gradient field generation module and a uniform field generation module. The gradient field generation module is used to adjust the angle difference of multiple Halbach quadrupole rings to change the gradient field, and the uniform field generation module is used to adjust the angle difference of multiple Halbach dipole rings to change the uniform field. The multiple Halbach quadrupole rings are nested within each other, and the multiple Halbach dipole rings are nested within each other. The multiple Halbach quadrupole rings and the multiple Halbach dipole rings are placed coaxially. The number of both the multiple Halbach quadrupole rings and the multiple Halbach dipole rings is two. The superposition module is used to superimpose the uniform field and the gradient field to obtain a superimposed field; and to adjust the intensity of the gradient field so that the magnetization direction of the superimposed field is the driving field direction. The magnetic driving force control module is used to adjust the angle difference between the uniform field and / or the gradient field in the superimposed field to control the magnetic driving force in the superimposed field. Adjusting the angle difference between the uniform field and / or the gradient field in the superimposed field to control the magnetic driving force in the superimposed field includes: first, under the condition that the intensity of the uniform field is greater than the saturation magnetization, controlling the relative rotation of the plurality of Halbach quadrupole rings in the superimposed field to obtain the changing angle difference in the gradient field; then, obtaining the changing gradient field through the changing angle difference in the gradient field; and finally, controlling the magnetic driving force in the superimposed field through the changing gradient field. The magnetic driving force direction control module is used to control the direction of the magnetic driving force by controlling the overall rotation of the plurality of Halbach dipole rings in the superimposed field relative to the ground; The magnetic field free region forming module is used to adjust the angle difference of the multiple Halbach dipole rings, set the uniform field to zero, adjust the angle difference of the multiple Halbach quadrupole rings, and maximize the gradient field intensity. The gradient field forms a magnetic field free region in the superimposed field. The signal acquisition module is used to adjust the angle difference of the Halbach dipole ring and the rotation angle relative to the ground, change the size and direction of the uniform field, and make the free region of the magnetic field scan along a preset trajectory to cover the entire imaging area. The imaging module is used to receive magnetic particle signals, perform signal processing and image reconstruction operations, and complete magnetic imaging.

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