Multi-resolution magnetic particle imaging method and system based on magnetic field free line parallel excitation

Abstract

The invention belongs to the field of magnetic particle imaging, particularly relates to a multi-resolution magnetic particle imaging method and system based on magnetic field free line parallel excitation, and aims to solve the problem that high-resolution and high-sensitivity image reconstruction cannot be realized at the same time. The method comprises the following steps: generating a magnetic field free line; moving the magnetic field free line to a target position; the alternating current of the excitation coil is started to generate a single-frequency excitation field, and a voltage signal induced by the receiving coil is collected; extracting amplitudes of different orders of harmonic waves as single pixel values; and mapping the single pixel values corresponding to the harmonic waves of different orders to the spatial positions of the magnetic field free lines until all spatial positions are scanned, thereby obtaining a multi-resolution image. According to the method, multi-resolution images can be obtained simultaneously through single scanning, multi-parameter repeated scanning and additional registration fusion are not needed, and the measurement efficiency is greatly improved. Meanwhile, the multi-resolution image can provide complementary information of structure positioning and concentration quantification, and clinical diagnosis can be guided.

Description

Background Art

[0002] Magnetic particle imaging (MPI) is a promising molecular imaging technology that can perform highly sensitive quantitative visualization of super magnetic particles (SPIONs) in vivo. Generally, high-resolution MPI images provide fine structural information, which is convenient for accurate positioning of tracer positions; high-sensitivity MPI images have a high detection limit and can quantify tracers in low-concentration areas. However, resolution and sensitivity indicators are mutually constrained and difficult to achieve at the same time. One is the classic MPI system, which usually selects certain scanning parameters when reconstructing the image, and usually only obtains a single-resolution image. The other is a multi-resolution image obtained by multiple scans with different parameters. It will face repeated scanning processes, and different scanning parameters will cause image offsets, and additional alignment is required. This method is very time-consuming and labor-intensive.

[0003] Based on this, the present invention proposes a multi-resolution magnetic particle imaging method and system based on parallel excitation of magnetic field free lines. Summary of the invention

[0004] In order to solve the above-mentioned problem in the prior art, namely, the problem that the existing magnetic particle imaging technology is difficult to achieve high-resolution and high-sensitivity image reconstruction simultaneously due to the use of fixed scanning parameters, the present invention provides a multi-resolution magnetic particle imaging method and system based on parallel excitation of magnetic field free lines.

[0005] In a first aspect of the present invention, a multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines is proposed, the method comprising the following steps: Step S1, constructing a magnetic field environment by means of an excitation coil, a receiving coil, and orthogonally arranged selection and focusing coils, and generating a magnetic field free line parallel to the excitation field direction; Step S2, planning the scanning path of the magnetic field free line by the control platform, driving the input current of the selection and focusing coil to move the magnetic field free line to the target position; Step S3, after the free line of the magnetic field moves to the target position, the AC current of the excitation coil is turned on to generate an excitation field of a single frequency, and the voltage signal induced by the receiving coil is collected at the same time; Step S4, processing the collected voltage signal through a multi-channel digital lock-in amplifier, and extracting the amplitudes of harmonics of different orders as single pixel values ​​based on a multi-harmonic signal mapping strategy of the nonlinear response of magnetic particles; Step S5, mapping the single pixel values ​​corresponding to the harmonics of different orders to the spatial positions of the magnetic field free lines to generate a multi-resolution image; Step S6, check whether all spatial positions have been scanned, if so, directly output the multi-resolution image, otherwise jump to step S2 to step S5 until all spatial positions have been scanned.

[0006] Furthermore, the direction of the alternating excitation field generated by the excitation coil is parallel to the direction of the magnetic field free line, and the selection and focusing coil is used to dynamically adjust the spatial position of the magnetic field free line.

[0007] Furthermore, the scanning path of the magnetic field free line is planned by the control platform, specifically: The imaging area is planned as discrete spatial points through the control platform, and the input current of the selection and focusing coil is driven to move the magnetic field free line to cover the entire field of view in a point-by-point scanning manner, wherein the target position of the magnetic field free line of each scan is the area where the corresponding spatial point is located.

[0008] Furthermore, based on the multi-harmonic signal mapping strategy of the nonlinear response of magnetic particles, the amplitudes of harmonics of different orders are extracted as single pixel values, specifically: A set of sine wave reference signals are input to each digital lock-in amplifier, and their reference frequencies are , n is an integer and n ≥1; The original voltage signal induced by the receiving coil is synchronously demodulated with each reference frequency signal to separate the harmonic components of the corresponding order; The amplitude of each harmonic component is measured by a digital lock-in amplifier, and the amplitude is used as a single pixel value at a corresponding spatial position.

[0009] In another aspect of the present invention, a multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines is proposed, based on a multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines, the system includes a magnetic field coil subsystem, a control platform subsystem and a matching circuit subsystem; The magnetic field coil subsystem includes at least one group of excitation coils for generating an alternating excitation field parallel to the magnetic field free line, at least one group of receiving coils for inducing nonlinear response signals of magnetic particles, and multiple groups of selection and focusing coils for generating and dynamically adjusting the spatial position of the magnetic field free line; wherein the receiving coil and the excitation coil are coaxially arranged, and the coaxial opening direction of the receiving coil and the excitation coil is orthogonal to the opening direction of the selection and focusing coil; The control platform subsystem includes a computer for planning the magnetic field free line scanning path and sending control instructions and parsing the received signal, a signal generator for generating analog signals for driving the excitation coil according to the computer instructions, and a data acquisition card for converting the analog signals of the receiving coil into digital signals; The matching circuit subsystem includes multiple power amplifiers and signal conditioning circuits for amplifying the excitation signal and enhancing the detection capability of the magnetic particle response signal.

[0010] Furthermore, the selection and focusing coils are two groups of Maxwell coil pairs, which are used to simultaneously generate and move the positions of the free lines of the magnetic field.

[0011] Furthermore, an alternating current is passed through the excitation coil to generate an alternating excitation field.

[0012] Furthermore, the signal generator and the data acquisition card are synchronously managed through a unified clock signal to ensure the timing consistency of the excitation field output and the received signal acquisition.

[0013] Furthermore, in the multiple groups of selection and focusing coils, the axis directions of every two adjacent selection and focusing coils are perpendicular.

[0014] Further, the signal conditioning circuit includes: an impedance matching circuit, a bandpass circuit, a low-pass filter circuit and a low-noise amplifier; Each power amplifier is used to receive an analog excitation signal from a signal generator, directly send it to each selection and focusing coil, and send it to the excitation coil through an impedance matching circuit and a bandpass circuit; The analog signal generated by the receiving coil is sent to the data acquisition card through a low-pass filter circuit and a low-noise amplifier.

[0015] Beneficial effects of the present invention: Synchronous acquisition of multi-resolution images: By extracting the amplitudes of harmonics of different orders (such as high-order harmonics corresponding to high-resolution images, and low-order harmonics corresponding to high-sensitivity images), a series of resolution and sensitivity combinations can be simultaneously acquired in a single scan, breaking through the single imaging mode limitation of traditional MPI due to fixed parameters.

[0016] Imaging efficiency is significantly improved: The parallel excitation of magnetic field free lines combined with dynamic scanning path planning avoids the multiple repeated scans required to obtain images of different resolutions in traditional methods, greatly reducing the operation complexity and time cost, and is especially suitable for real-time monitoring of dynamic biological processes.

[0017] Multimodal data are naturally aligned: The generated multi-resolution images are based on signal decoupling of the same scanning process, with completely consistent spatial positions. They can be directly fused without additional alignment, providing complementary information for structural positioning and concentration quantification.

[0018] System stability and compatibility optimization: The orthogonal coil layout and magnetic field free line generation mechanism reduce magnetic field distortion interference, combined with multi-channel parallel signal processing design to avoid the influence of electromagnetic noise when switching parameters of traditional systems, and improve imaging reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 It is a schematic flow chart of a multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines of the present invention; Figure 2 It is a schematic diagram of multi-resolution image simulation in the multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines of the present invention; Figure 3 It is a schematic diagram of the connection relationship of the multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines of the present invention; Figure 4 It is a structural schematic diagram of a magnetic field coil subsystem in a multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines of the present invention. DETAILED DESCRIPTION

[0020] 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 is also necessary to explain that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0021] 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.

[0022] The present invention provides a multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines, the method comprising the following steps: Step S1, constructing a magnetic field environment by means of an excitation coil, a receiving coil, and orthogonally arranged selection and focusing coils, and generating a magnetic field free line parallel to the excitation field direction; Step S2, planning the scanning path of the magnetic field free line by the control platform, driving the input current of the selection and focusing coil to move the magnetic field free line to the target position; Step S3, after the free line of the magnetic field moves to the target position, the AC current of the excitation coil is turned on to generate an excitation field of a single frequency, and the voltage signal induced by the receiving coil is collected at the same time; Step S4, processing the collected voltage signal through a multi-channel digital lock-in amplifier, and extracting the amplitudes of harmonics of different orders as single pixel values ​​based on a multi-harmonic signal mapping strategy of the nonlinear response of magnetic particles; Step S5, mapping the single pixel values ​​corresponding to the harmonics of different orders to the spatial positions of the magnetic field free lines to generate a multi-resolution image; Step S6, check whether all spatial positions have been scanned, if so, directly output the multi-resolution image, otherwise jump to step S2 to step S5 until all spatial positions have been scanned.

[0023] In order to more clearly explain the multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines of the present invention, the following is combined with Figure 1 Each step in the embodiment of the present invention is described in detail.

[0024] A multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines according to the first embodiment of the present invention includes steps S1 to S5, each of which is described in detail as follows: Step S1, constructing a magnetic field environment by means of an excitation coil, a receiving coil, and orthogonally arranged selection and focusing coils, and generating a magnetic field free line parallel to the excitation field direction; Among them, the direction of the alternating excitation field generated by the excitation coil in this embodiment is parallel to the direction of the magnetic field free line, and the selection and focusing coil is used to dynamically adjust the spatial position of the magnetic field free line. More specifically, the receiving coil and the excitation coil are coaxially arranged, and the coaxial opening direction of the receiving coil and the excitation coil is orthogonal to the opening direction of the selection and focusing coil.

[0025] Step S2, planning the scanning path of the magnetic field free line by the control platform, driving the input current of the selection and focusing coil to move the magnetic field free line to the target position; In this embodiment, the imaging area is planned as discrete spatial points by the control platform, and the current of the selection and focusing coil is driven to move the magnetic field free line to cover the entire field of view in a point-by-point scanning manner, wherein each discrete point corresponds to the target position of the magnetic field free line, and the current control of the selection and focusing coil satisfies the following relationship: ; in, y and z Indicates the distance between the FFL position and the center of the field of view in the corresponding direction, which is determined by the focusing field parameters in two directions. and control, and is the gradient field parameter, by adjusting and Move the magnetic field free line to any target position within the field of view; Step S3, after the free line of the magnetic field moves to the target position, the AC current of the excitation coil is turned on to generate an excitation field of a single frequency, and the voltage signal induced by the receiving coil is collected at the same time; Step S4, processing the collected voltage signal through a multi-channel digital lock-in amplifier, and extracting the amplitudes of harmonics of different orders as single pixel values ​​based on a multi-harmonic signal mapping strategy of the nonlinear response of magnetic particles; Specifically, a set of sine wave reference signals are input to each digital lock-in amplifier, and their reference frequencies are ,n is an integer and n ≥1; The original voltage signal induced by the receiving coil is synchronously demodulated with each reference frequency signal to separate the harmonic components of the corresponding order; The amplitude of each harmonic component is measured by a digital lock-in amplifier, and the amplitude is used as a single pixel value at a corresponding spatial position.

[0026] The harmonic component model is expressed by the following formula: ; in, is the frequency component (here regarded as PSF distribution), T is the excitation period, is the magnetization combination of excitation and reception in the x direction, is the excitation amplitude, is the local magnetic field in the excitation region, is the Chebyshev polynomial of the second kind.

[0027] The system function reflects the relationship between the spatial position of the SPIONs tracer and the frequency response. However, for MPI imaging with a single harmonic, the distribution of the point spread function (PSF) is equivalent to the spatial dependence of the frequency components in the system function. Mathematically, the spatial dependence of the frequency components can be modeled as a one-dimensional Chebyshev convolution in the direction of the magnetization combination and the driving field.

[0028] The frequency response model of the harmonic component is defined by the following formula: ; O x is the static bias field, n is the harmonic order, is the saturation magnetization of the magnetic particles.

[0029] Step S5, mapping the single pixel values ​​corresponding to the harmonics of different orders to the spatial positions of the magnetic field free lines to generate a multi-resolution image; The magnetic field free lines satisfy the requirement that the absolute values ​​of the gradients in the orthogonal directions are equal, that is: .

[0030] The image reconstruction module point spread function model can be described by the following formula: ; in, , represents the sensitivity calibration coefficient constant, which is determined by factors such as receiving sensitivity, gradient and particle characteristics.

[0031] like Figure 2As shown in FIG. 1 , it is a multi-resolution image simulation, showing the 1D simulation results of the 3rd, 4th, 5th, 6th and 11th order harmonics. In the MPI scan of the even harmonics 4th and 6th order, a certain bias field needs to be applied along the excitation direction.

[0032] The ideal PSF was simulated according to the mathematical model. Among them, the magnetization component and the 1D Chebyshev polynomial were convolved to obtain a 2D system function. Taking the center of the image as the reference point, the vertical direction represents the magnitude of the bias field applied along the free line of the magnetic field, and the horizontal direction represents the position. It can be observed that as the harmonic order increases, the PSF shrinks toward the center. This may be because the magnetization component has a more blurred convolution kernel far from the center, so that the fine structure of the higher-order Chebyshev polynomial is averaged close to 0.

[0033] In summary, the resolution of different harmonic orders in MPI is different. Moreover, as the harmonic order increases, the resolution of single harmonic MPI images increases.

[0034] Step S6, check whether all spatial positions have been scanned, if so, directly output the multi-resolution image, otherwise jump to step S2 to step S5 until all spatial positions have been scanned.

[0035] After jumping to step S2, switch to a new scanning position and start a new round of scanning from the spatial position selection.

[0036] Although the various steps in the above embodiment are described in the above-mentioned order, those skilled in the art can understand that in order to achieve the effect of this embodiment, different steps do not have to be executed in such an order. They can be executed simultaneously (in parallel) or in a reverse order. These simple changes are within the scope of protection of the present invention.

[0037] A multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines according to a second embodiment of the present invention is based on a multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines according to the first embodiment, the system comprising a magnetic field coil subsystem, a control platform subsystem and a matching circuit subsystem; The magnetic field coil subsystem includes at least one group of excitation coils for generating an alternating excitation field parallel to the magnetic field free lines, at least one group of receiving coils for inducing nonlinear response signals of magnetic particles, and multiple groups of selection and focusing coils for generating and dynamically adjusting the spatial positions of the magnetic field free lines; wherein the opening directions of the selection and focusing coils are orthogonal to the excitation coils and the receiving coils; and among the multiple groups of selection and focusing coils, the axial directions of every two adjacent selection and focusing coils are perpendicular.

[0038] The control platform subsystem includes a computer for planning the magnetic field free line scanning path and sending control instructions and parsing the received signal, a signal generator for generating analog signals for driving the excitation coil according to the computer instructions, and a data acquisition card for converting the analog signals of the receiving coil into digital signals; The matching circuit subsystem includes multiple power amplifiers and signal conditioning circuits for amplifying the excitation signal and enhancing the detection capability of the magnetic particle response signal.

[0039] Next, combine Figure 3 and Figure 4 Further explanation of this system, specifically: In this embodiment, the receiving coil and the excitation coil are each provided in a group, and the selection and focusing coil is provided in four groups and is arranged around the excitation coil. The axial direction of the receiving coil and the excitation coil is the x-axis direction. Among the selection and focusing coils, the axial direction of two of them is the y-axis, and the axial direction of the other two selection and focusing coils is the z-axis. In other words, the receiving coil and the excitation coil are coaxially arranged, and the coaxial opening direction of the receiving coil and the excitation coil is orthogonal to the opening direction of the selection and focusing coil.

[0040] The selection and focusing coils are two groups of Maxwell coil pairs, which are used to simultaneously generate and move the positions of the magnetic field free lines.

[0041] The method for generating the alternating excitation field is as follows: an alternating current is introduced into the excitation coil to generate the alternating excitation field.

[0042] The receiving coil and the exciting coil are coaxially arranged from inside to outside, and the imaging field of view is arranged within the receiving coil.

[0043] The signal generator and the data acquisition card in this embodiment are synchronously managed through a unified clock signal to ensure the timing consistency between the excitation field output and the received signal acquisition.

[0044] The signal conditioning circuit includes: an impedance matching circuit, a bandpass circuit, a low-pass filter circuit and a low-noise amplifier; Each power amplifier is used to receive an analog excitation signal from a signal generator, directly send it to each selection and focusing coil, and send it to the excitation coil through an impedance matching circuit and a bandpass circuit; The analog signal generated by the receiving coil is sent to the data acquisition card through a low-pass filter circuit and a low-noise amplifier.

[0045] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process and related instructions of the system described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0046] It should be noted that the multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines provided in the above embodiment is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the modules or steps in the embodiments of the present invention can be decomposed or combined. For example, the modules in the above embodiment can be combined into one module, or further divided into multiple sub-modules to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only for distinguishing the modules or steps, and are not regarded as improper limitations of the present invention.

[0047] An electronic device according to a third embodiment of the present invention includes: at least one processor; and a memory communicatively connected to at least one of the processors; wherein, The memory stores instructions that can be executed by the processor, and the instructions are used to be executed by the processor to implement the above-mentioned multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines.

[0048] A computer-readable storage medium according to a fourth embodiment of the present invention stores computer instructions, and the computer instructions are used to be executed by the computer to implement the above-mentioned multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines.

[0049] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process and related instructions of the storage device and processing device described above can refer to the corresponding process in the aforementioned method embodiment and will not be repeated here.

[0050] Those skilled in the art should be able to appreciate that the modules and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented with electronic hardware, computer software, or a combination of the two, and the programs corresponding to the software modules and method steps can be placed in random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the technical field. In order to clearly illustrate the interchangeability of electronic hardware and software, the composition and steps of each example have been generally described in the above description according to the function. Whether these functions are performed in electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0051] The terms "first", "second", etc. are used to distinguish similar objects rather than to describe or indicate a particular order or sequence.

[0052] 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.

[0053] 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 multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines, characterized in that: The method comprises the following steps: Step S1, constructing a magnetic field environment by means of an excitation coil, a receiving coil, and orthogonally arranged selection and focusing coils, and generating a magnetic field free line parallel to the excitation field direction; Step S2, planning the scanning path of the magnetic field free line by the control platform, driving the input current of the selection and focusing coil to move the magnetic field free line to the target position; Step S3, after the free line of the magnetic field moves to the target position, the AC current of the excitation coil is turned on to generate an excitation field of a single frequency, and the voltage signal induced by the receiving coil is collected at the same time; Step S4, processing the collected voltage signal through a multi-channel digital lock-in amplifier, and extracting the amplitudes of harmonics of different orders as single pixel values ​​based on a multi-harmonic signal mapping strategy of the nonlinear response of magnetic particles; Step S5, mapping the single pixel values ​​corresponding to the harmonics of different orders to the spatial positions of the magnetic field free lines to generate a multi-resolution image; Step S6, check whether all spatial positions have been scanned, if so, directly output the multi-resolution image, otherwise jump to step S2 to step S5 until all spatial positions have been scanned.

2. The multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines according to claim 1, characterized in that: The direction of the alternating excitation field generated by the excitation coil is parallel to the direction of the magnetic field free line, and the selection and focusing coil is used to dynamically adjust the spatial position of the magnetic field free line.

3. The multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines according to claim 1, characterized in that: The scanning path of the magnetic field free line is planned by the control platform, specifically: The imaging area is planned as discrete spatial points through the control platform, and the input current of the selection and focusing coil is driven to move the magnetic field free line to cover the entire field of view in a point-by-point scanning manner, wherein the target position of the magnetic field free line of each scan is the area where the corresponding spatial point is located.

4. The multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines according to claim 1, characterized in that: Based on the multi-harmonic signal mapping strategy of the nonlinear response of magnetic particles, the amplitudes of harmonics of different orders are extracted as single pixel values, specifically: A set of sine wave reference signals are input to each digital lock-in amplifier, and their reference frequencies are , n is an integer and n ≥1; The original voltage signal induced by the receiving coil is synchronously demodulated with each reference frequency signal to separate the harmonic components of the corresponding order; The amplitude of each harmonic component is measured by a digital lock-in amplifier, and the amplitude is used as a single pixel value at a corresponding spatial position.

5. A multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines, based on a multi-resolution magnetic particle imaging method based on parallel excitation of magnetic field free lines according to any one of claims 1 to 4, characterized in that: The system includes a magnetic field coil subsystem, a control platform subsystem and a matching circuit subsystem; The magnetic field coil subsystem includes at least one group of excitation coils for generating an alternating excitation field parallel to the magnetic field free line, at least one group of receiving coils for inducing nonlinear response signals of magnetic particles, and multiple groups of selection and focusing coils for generating and dynamically adjusting the spatial position of the magnetic field free line; wherein the receiving coil and the excitation coil are coaxially arranged, and the coaxial opening direction of the receiving coil and the excitation coil is orthogonal to the opening direction of the selection and focusing coil; The control platform subsystem includes a computer for planning the magnetic field free line scanning path and sending control instructions and parsing the received signal, a signal generator for generating analog signals for driving the excitation coil according to the computer instructions, and a data acquisition card for converting the analog signals of the receiving coil into digital signals; The matching circuit subsystem includes multiple power amplifiers and signal conditioning circuits for amplifying the excitation signal and enhancing the detection capability of the magnetic particle response signal.

6. A multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines according to claim 5, characterized in that: The selection and focusing coils are two groups of Maxwell coil pairs, which are used to simultaneously generate and move the positions of the magnetic field free lines.

7. The multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines according to claim 5, characterized in that: An alternating current is supplied to the excitation coil to generate an alternating excitation field.

8. The multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines according to claim 5, characterized in that: The signal generator and the data acquisition card are synchronously managed through a unified clock signal to ensure the timing consistency of the excitation field output and the received signal acquisition.

9. The multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines according to claim 5, characterized in that: In the multiple groups of selection and focusing coils, the axis directions of every two adjacent selection and focusing coils are perpendicular.

10. The multi-resolution magnetic particle imaging system based on parallel excitation of magnetic field free lines according to claim 5, characterized in that: The signal conditioning circuit includes: an impedance matching circuit, a bandpass circuit, a low-pass filter circuit and a low-noise amplifier; Each power amplifier is used to receive an analog excitation signal from a signal generator, directly send it to each selection and focusing coil, and send it to the excitation coil through an impedance matching circuit and a bandpass circuit; The analog signal generated by the receiving coil is sent to the data acquisition card through a low-pass filter circuit and a low-noise amplifier.

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