Magnetic particle imaging system and method based on flexible receiving coil array

Abstract

The invention belongs to the technical field of magnetic particle imaging, particularly relates to a magnetic particle imaging system and method based on a flexible receiving coil array, and aims to solve the problems that an existing rigid receiving coil is poor in biological surface adaptability and low in signal-to-noise ratio for micro geometric texture imaging. According to the structure, a receiving coil array adheres to the surface of an object to be measured, the receiving coil array and a compensation coil array are distributed on the two sides of a flexible substrate, the receiving coil array is used for receiving magnetic nanoparticle signals, and the partitioned small compensation coil array is used for conducting feed-through interference and electromagnetic interference compensation on a receiving coil; the reconstruction method comprises the following steps: sequentially carrying out Fourier transform on the collected receiving signals, extracting in-phase third harmonics and superposing to obtain processed signals, interpolating to construct a sinogram for Cartesian coordinate distribution, and reconstructing the three-dimensional particle concentration distribution of a measured object by a filtering back projection method. A flexible receiving coil array strategy is adopted, an adaptive reconstruction method is provided, and the imaging signal-to-noise ratio is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedical imaging, and particularly relates to a magnetic particle imaging system and method based on a flexible receiving coil array. Background Art

[0002] Magnetic particle imaging technology has experienced rapid development and has been preclinically verified in the fields of stem cell tracking, cancer imaging, and magnetic hyperthermia, showing good potential for clinical applications.

[0003] Magnetic particle imaging uses magnetic nanoparticles with strong magnetic moments as tracers and has the technical advantage of high sensitivity. However, in the existing magnetic particle imaging system architecture, the receiving coil usually exhibits rigid characteristics, with its shape and size being fixedly set. The sensitivity map covers the entire imaging field of view, providing the ability to image the entire field of view. For small-sized or special-shaped objects to be measured, due to a certain distance interval between the receiving coil and the object to be measured, the electromagnetic conversion efficiency is limited, so that the current receiving coil has a low signal-to-noise ratio for imaging micro geometric textures; in contrast, the flexible receiving coil has good shape adaptability and can be wrapped on the surface of the imaging object, with a high filling factor, which helps to reduce signal noise and improve image quality.

[0004] However, currently, global receiving coils and rigid coils are commonly used in the field of magnetic particle imaging technology, and there is a lack of relevant technologies for flexible receiving coils.

[0005] The present invention aims to propose a magnetic particle imaging system and method based on a flexible receiving coil array to provide a solution for high-quality magnetic particle imaging. Summary of the Invention

[0006] To solve the above problems in the prior art, that is, the existing receiving coil exhibits rigid characteristics, there is a certain distance interval from the object to be measured, and the electromagnetic conversion efficiency is limited, so that the current receiving coil has a low signal-to-noise ratio for imaging micro geometric textures, which in turn leads to low quality of the reconstructed image. In the first aspect of the present invention, a magnetic particle imaging system based on a flexible receiving coil array is proposed. The system includes: A fourth coil configured to excite magnetic nanoparticles to generate a magnetization response; A driving coil pair configured to generate a uniform alternating magnetic field to drive the movement of the magnetic free line; the driving coil pair includes two pairs of electromagnetic coils, respectively serving as the second coil pair and the third coil pair; the two electromagnetic coils in the second coil pair are symmetrically arranged on the upper and lower sides outside the fourth coil; the two electromagnetic coils in the third coil pair are symmetrically arranged on the left and right sides outside the fourth coil; A first magnet group configured to generate a magnetic field free line at the center of the imaging field of view; the first magnet group includes 4 magnet units, with two magnet units as a group, symmetrically arranged on the upper and lower sides of the drive coil pair respectively; the 2 magnet units in each group are placed side by side. A flexible receiving coil array configured to receive the magnetization response signal of magnetic nanoparticles; the flexible receiving coil array includes a receiving coil array layer, a support substrate layer, and a compensation coil array layer; the receiving coil array layer is a uniform planar array for receiving the magnetization response signal, there are M receiving coils in the uniform planar array, one side of the receiving coil adheres to the inner side of the support substrate layer, and the other side adheres to the surface of the object to be measured, the compensation coil array layer is a segmented uniform planar array for compensating the feedthrough interference and electromagnetic interference of the receiving coil, the segmented uniform planar array is N compensation coils arranged within the coverage range of each receiving coil, one side of the compensation coil adheres to the outer side of the support substrate layer, and the other side is away from the object to be measured, and the compensation coil array has a total of M×N coils.

[0007] In some preferred embodiments, the system further includes a data acquisition and processing circuit configured to receive the magnetization response signal, filter, amplify, perform analog-to-digital conversion and process the signal to generate a magnetic particle image. It further includes a mechanical structure and a mechanical controller; the mechanical structure includes a magnet support structure for supporting and fixing the first magnet group, the drive coil pair, and the fourth coil. The mechanical controller is used to drive the first magnet group to rotate, including the rotation angle and speed of the rotation.

[0008] In some preferred embodiments, the fourth coil includes a solenoid coil and a Helmholtz-type coil. Both pairs of electromagnetic coils in the drive coil pair are Helmholtz-type coils.

[0009] In some preferred embodiments, the magnet units in the first magnet group include permanent magnets, electromagnetic coils, and superconducting magnets.

[0010] In some preferred embodiments, the N compensation coils are connected in series in the same phase, and after being connected in series in the same phase, they are connected in series in the opposite phase with the corresponding receiving coil. The sum of the inductances of the N compensation coils is equal to the inductance of the receiving coil, and the diameter of the compensation coil is smaller than that of the receiving coil.

[0011] In some preferred embodiments, the support substrate layer (800) has a support substrate with a preset thickness, and the thickness of the support substrate is h, where 2mm < h < 4mm.

[0012] In a second aspect of the present invention, a magnetic particle imaging method based on a flexible receiving coil array is proposed. Based on the magnetic particle imaging system based on a flexible receiving coil array described above, it is characterized in that the method includes the following steps: S1. A first magnet group is used to generate a magnetic field free line, and the gradient of the magnetic field free line is ; the imaging field of view radius is ; Currents are applied to the second coil pair and the third coil pair respectively to generate a uniform alternating magnetic field to drive the magnetic field free line to move along a predetermined trajectory, and the predetermined trajectory movement is a discrete Cartesian movement; A current is passed through the fourth coil to generate a magnetic field to excite magnetic nanoparticles; S2. The flexible receiving coil array is attached to the object to be measured to receive the magnetization response signals of the magnetic nanoparticles. Specifically, M receiving coils arranged in an array in the flexible receiving coil array are used to receive the magnetization response signals of M magnetic nanoparticles; S3. Fourier transform is performed on each of the magnetization response signals to convert them into frequency domain signals, and the in-phase and quadrature phases are distinguished; The in-phase third harmonics in all the frequency domain signals are extracted and superimposed to obtain a processed signal; The spatial distribution of the processed signal is interpolated from the polar coordinate mode to the Cartesian coordinate distribution to form a sinogram; S4. The mechanical controller drives the first magnet group to rotate, and corresponding sinograms are obtained in the manner of S1 - S3 at each angle; The rotation angle sequence is: ; S5. Based on all the obtained sinograms, a filtered backprojection method is used to reconstruct the three-dimensional particle concentration distribution of the object to be measured, and then the reconstructed magnetic particle image is obtained.

[0013] In some preferred embodiments, the current applied to the second coil pair is: ; The current applied to the third coil pair is: ; Among them, the current sequence is: , and the phase sequence is: ; The current passed through the fourth coil is .

[0014] In some preferred embodiments, the filtered backprojection method includes a filtered backprojection method with a Cosine filter kernel.

[0015] Advantages of the present invention: 1) By using a flexible receiving coil array to wrap the object to be measured and receive the magnetization response signal of magnetic nanoparticles, a compensation coil is arranged outside the flexible substrate to achieve the effect of compensating the receiving coil. Four compensation coils in the compensation coil array layer correspond to the receiving coils in the receiving coil array layer, are connected in series in phase with each other, are connected in series in antiphase with the corresponding receiving coils, and the coils are closely attached in an asymmetric mode, further avoiding the direct feedthrough interference of the receiving coil and improving the compensation effect; 2) Perform Fourier transform on the received signal to extract the in-phase third harmonic superposition to obtain the processed signal, then interpolate it into a Cartesian coordinate distribution to form a sine diagram, and finally use the filtered back-projection method to reconstruct the three-dimensional particle concentration distribution of the object to be measured, further reducing interference and improving the imaging signal-to-noise ratio; In summary, the problem that the existing receiving coil shows rigid characteristics, has a certain distance interval from the object to be measured, and the electromagnetic conversion efficiency is limited, so that the current receiving coil has a low signal-to-noise ratio for imaging of tiny geometric textures is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects, and advantages of the present application will become more apparent: Figure 1 It is a component diagram of a magnetic particle imaging system based on a flexible receiving coil array according to the present invention.

[0017] Figure 2 It is a magnetic field distribution diagram of the components of a magnetic particle imaging system based on a flexible receiving coil array according to the present invention 。

[0018] Figure 3 It is a magnetic induction line distribution diagram of the first magnet group of a magnetic particle imaging system based on a flexible receiving coil array according to the present invention.

[0019] Figure 4 It is a schematic structural diagram of a flexible receiving coil array layer and a compensation coil array layer of a magnetic particle imaging system based on a flexible receiving coil array according to the present invention.

[0020] Figure 5 It is a schematic three-layer arrangement structure diagram of a flexible receiving coil array of a magnetic particle imaging system based on a flexible receiving coil array according to the present invention.

[0021] Figure 6 It is a magnetic field free line movement trajectory diagram of a magnetic particle imaging method based on a flexible receiving coil array according to the present invention.

[0022] Figure 7 It is a step flow chart of a magnetic particle imaging method based on a flexible receiving coil array according to the present invention.

[0023] In the accompanying drawings, 101-104: Four magnet units of the first magnet group 1; 201-202: Two electromagnetic coils of the second coil pair of the drive coil; 301-302: Two electromagnetic coils of the third coil pair of the drive coil; 401: Fourth coil; 500: Imaging field of view; 600: Receiver coil layer in the flexible receiver coil array; 601: One coil unit in the receiver coil array; 700: Compensation coil layer in the flexible receiver coil array; 701: One coil unit in the compensation coil array; 800: Flexible support substrate in the flexible receiver coil array; 901-904: Four moving positions and scanning trajectories of the magnetic field free line driven by the second coil pair of 201-202 and the third coil pair of 301-302. Detailed implementation manners

[0024] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention and not to limit the invention. Additionally, it should be noted that, for the sake of description, only parts related to the relevant invention are shown in the accompanying drawings.

[0025] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and embodiments.

[0026] For a clearer description of a magnetic particle imaging system based on a flexible receiver coil array according to the present invention, the following is combined with Figures 1 to 6 Each step in the embodiments of the present invention will be described in detail.

[0027] A magnetic particle imaging system based on a flexible receiver coil array according to the first embodiment of the present invention, see Figure 1 , the system includes: A first magnet group 1 configured to generate a magnetic field free line at the center 5 of the imaging field of view; the first magnet group 1 includes 4 magnet units, and the 4 magnet units are divided into two groups, and are symmetrically arranged on the upper and lower sides of the drive coil pair respectively; the 2 magnet units in each group are arranged side by side; In this embodiment, the four magnet units (or coil units) 101-104 of the first magnet group 1, including permanent magnets, electromagnetic coils, and superconducting magnets, are specifically arranged as follows: For the four magnet units, two are placed side by side on each of the upper and lower sides. Among them, magnet units 101 and 103 are a group and are arranged side by side on the upper side of the drive coil pair (on the same plane above the second coil pair 2, the third coil 3 pair, and the fourth coil 4, and parallel to the corresponding side coils in the second coil pair 2, i.e., 201-202), and magnet units 102 and 104 are a group and are placed side by side on the lower side of the drive coil pair (on the same plane below the second coil pair 2, the third coil 3 pair, and the fourth coil 4, and parallel to the corresponding side coils in the second coil pair 2, i.e., 201-202), configured to generate a magnetic field free line at the center 500 of the imaging field of view, and the current-carrying direction is as shown in the appendix Figure 3 shown, generating a magnetic field free line with a gradient G = 1.5 T / m at the center of the imaging field of view center 500, and the imaging field of view is set to ; The drive coil pair is configured to generate a uniform alternating magnetic field to drive the movement of the magnetic field free line; the drive coil pair includes two pairs of electromagnetic coils, which are respectively used as the second coil pair 2 and the third coil pair 3; the two electromagnetic coils in the second coil pair 2 are symmetrically arranged on the upper and lower sides outside the fourth coil 4; the two electromagnetic coils in the third coil pair 3 are symmetrically arranged on the left and right sides outside the fourth coil 4; In this embodiment, the two pairs of electromagnetic coils are the second coil pair 2 and the third coil pair 3, including Helmholtz-type coils and electromagnetic coils, which respectively include two electromagnetic coils 201-202 and 301-302. Among them, the electromagnetic coils 201-202 are symmetrically arranged on the upper and lower sides outside the fourth coil 4, and a sinusoidal alternating current is passed through to generate a uniform alternating magnetic field to drive the magnetic field free line to move in the vertical direction. The passed current sequence is , , , and one of the typical magnetic fields generated is as shown in the left figure of the appendix Figure 2 . Specifically, the electromagnetic coil of 201 is placed on the upper side of the imaging field of view center 5, and the electromagnetic coil of 202 is placed on the lower side of the imaging field of view center 5. The two electromagnetic coils of the third coil pair 3 are symmetrically arranged on the left and right sides outside the fourth coil 4, and a sinusoidal alternating current is passed through to generate a uniform alternating magnetic field to drive the magnetic field free line to move in the horizontal direction. The passed current sequence is , , , and one of the typical magnetic fields generated is as shown in the middle figure of the appendix Figure 2 . The peak value of the magnetic field intensity is 30 mT, and the frequency is 100 Hz. Specifically, the electromagnetic coil of 301 is arranged on the left side of the imaging field of view center 5, and the electromagnetic coil of 302 is arranged on the right side of the imaging field of view center 5; The fourth coil 4, including an electromagnetic coil 401 (which can be a solenoid coil or a Helmholtz-type coil), is configured to excite magnetic nanoparticles to generate a magnetization response, specifically by passing an alternating current , can be set, , to generate a 5 mT uniform alternating magnetic field to excite magnetic nanoparticles to generate a magnetization response, where a typical magnetic field generated is as shown in the right figure of the appendix Figure 2 , with a frequency of 100 Hz; See Figure 4 , Figure 5 , the flexible receiving coil array 6 is configured to receive the magnetization response signal of the magnetic nanoparticles; the flexible receiving coil array 6 includes a receiving coil array layer 600, a support base layer 800, and a compensation coil array layer 700; the receiving coil array layer 600 is a uniform planar array for receiving the magnetization response signal. There are M (shown as 9 in the figure) receiving coils in the uniform planar array, and the sub-field of view covered by each receiving coil is a block. One side of each receiving coil adheres to the inner side of the support base layer 800, and the other side adheres to the surface of the object to be measured. The compensation coil array layer 700 is a block-uniform planar array for compensating the feedthrough interference and electromagnetic interference of the receiving coils. The block-uniform planar array is N (shown as 4 in the figure) compensation coils arranged within the coverage range of each receiving coil, that is, within the block. The compensation coil array has a total of M×N coils (shown as 36 in total in the figure). One side of the compensation coil adheres to the outer side of the support base layer 800, and the other side is away from the object to be measured and faces the center of the imaging field of view; among them, the support base layer 800 is arranged between the coil array layer 600 and the compensation coil array layer 700 to isolate and support the positions of the coils. Among them, the receiving coils and compensation coils can be circular coils, and the support base layer can be a polyurethane (PU) base. The PU base has good flexibility, making the entire array receiving device flexible. This flexible receiving strategy enables the device to better fit different-shaped surfaces and has better adaptability and stability in scenarios such as energy reception or signal acquisition on wearable devices and the surfaces of irregular objects; hereby it is stated that the number M of receiving coils, the number N of compensation coils, and the distance between each receiving coil and compensation coil can be adaptively adjusted according to the actual needs of the object to be measured. Taking a small animal imaging device with an imaging field of view of 10 cm as an example, the thickness of the PU base layer is set to 1 mm, the size of the receiving coil is a 2 cm circular coil, a 5×5 array with a spacing of 1 mm is set as the uniform planar array, the sub-field of view of each block is 2 cm×2 cm, the compensation coil is a 1 cm circular coil, a 2×2 compensation coil array is arranged within each block, the spacing of the compensation coils is 0.5 mm, and the inductance of the receiving coil is equal to the sum of the inductances of the compensation coils in the corresponding block; In this embodiment, the N compensation coils are connected in series in the same phase. After being connected in series in the same phase, they are connected in series in the opposite phase with the receiving coil. The sum of the inductances of the N compensation coils is equal to the inductance of the receiving coil; the diameter of the compensation coil is smaller than that of the receiving coil, and the arrangement is denser, and they are evenly arranged within the respective sub-blocks; The support base layer 800 has a support base with a preset thickness. The thickness of the support base is h, where 2 mm < h < 4 mm; In this embodiment, it further includes a data acquisition and processing circuit, configured to receive the magnetization response signal, filter, amplify, perform analog-to-digital conversion and process the signal to generate a magnetic particle image; It further includes a mechanical structure and a mechanical controller. The mechanical structure includes a magnet support structure for supporting and fixing the first magnet group 1, the driving coil pair, and the fourth coil 4; The mechanical controller is used to drive the first magnet group 1 to rotate, including the rotation angle and speed of rotation, and rotate around the z-axis in an angular sequence.

[0028] It should be noted that for the magnetic particle imaging system based on the flexible receiving coil array provided in the above embodiment, only the above division of each functional module is used as an example. In practical applications, the above functions can be allocated to different functional modules as needed, that is, the modules or steps in the embodiments of the present invention can be further decomposed or combined. For example, the modules in the above embodiment can be combined into one module, or further split into multiple sub-modules to complete all or part of the functions described above. For the names of the modules and steps involved in the embodiments of the present invention, they are only used to distinguish each module or step and are not regarded as an improper limitation of the present invention.

[0029] In the second aspect of the present invention, a magnetic particle imaging method based on a flexible receiving coil array is proposed. Based on the magnetic particle imaging system based on a flexible receiving coil array described above, the method includes the following steps: S1, using the first magnet group to generate a magnetic field free line, and the gradient of the magnetic field free line is ; the imaging field of view radius is ; Apply currents to the second coil pair 2 and the third coil pair 3 respectively to generate a uniform alternating magnetic field to drive the magnetic field free line to move along a predetermined trajectory. The predetermined trajectory movement is a discrete Cartesian movement, that is, a discrete Cartesian movement along the plane formed by the second and third coil pairs; as shown in the appendix Figure 6 shown, the movement mode is: taking the coordinate system in the appendix Figure 3 as a reference, the magnetic field free line scans along 901; adjust and in The sequence can rotate the scanning line of the magnetic field free line by an angle, and typical positions such as 902, 903, and 904 determine the trajectory density of the magnetic field free line scanning; Applying a current to the fourth coil 4 generates a magnetic field to excite the magnetic nanoparticles; In this embodiment, the ; The current applied to the second coil pair 2 is , and can be specifically set to ; The current applied to the third coil pair 3 is , and can be specifically set to ; Among them, the current sequence is: , and the phase sequence is: ; The current applied to the fourth coil 4 is , and can be specifically set to , generating a 5 mT uniform alternating magnetic field with a frequency of 100 Hz; S2, attaching the flexible receiving coil array 6 to the object to be measured to receive the magnetization response signal of the magnetic nanoparticles , and the flexible receiving coil array specifically uses M receiving coils arranged in an array to receive the magnetization response signals of M magnetic nanoparticles; In this embodiment, due to the vectorial nature of the magnetization of the magnetic nanoparticles, the receiving coils at symmetric positions on both sides of the particles will receive signals with the same amplitude but opposite phases. Directly superimposing these two signals will cancel each other out. Therefore, during implementation, the in-phase signals in the receiving coil array are extracted; due to the movable characteristics of the receiving coils, it is difficult to avoid reducing the compensation effect and generating relatively serious direct feedthrough interference. The compensation coil uses an asymmetric mode to closely adhere to the compensation coil while reducing the impact on sensitivity, achieving a better compensation effect to suppress direct feedthrough; S3, since the magnetization response signal is a time-domain signal and is easily interfered with, performing a Fourier transform on each magnetization response signal to convert it into a frequency-domain signal, represents the signal collected when the m-th receiving coil of the flexible receiving coil array 6 rotates to the angle and the magnetic field free line moves to the position; Extracting the in-phase third harmonics in all the frequency-domain signals and superimposing them to obtain the processed signal ; Since the spatial distribution of the signal after the superimposition process is as shown in the appendixFigure 6 As shown, it presents a polar coordinate mode and needs to be interpolated into a Cartesian coordinate distribution for subsequent processing. The processed signal The spatial distribution of is interpolated from the polar coordinate mode into a Cartesian coordinate distribution to form a sinogram, which can be used as the sinogram for the free line scan of the magnetic field; S4. The mechanical controller drives the first magnet group to rotate, and obtains the corresponding sinogram in the manner of steps 1-3 at each angle; the rotation angle sequence is: The rotation angle sequence is: ; S5. Based on all the obtained sinograms, the filtered backprojection method is used to reconstruct the three-dimensional particle concentration distribution of the object to be measured, and then the reconstructed magnetic particle image is obtained; In this embodiment, the filtered backprojection method includes the filtered backprojection method with Cosine as the filter kernel. Generally, other filter kernels and other filtered backprojection parameters can be used for image reconstruction, which can meet the technical method requirements involved in this patent.

[0030] Although the above steps are described in the above order in the above embodiments, those skilled in the art can understand that in order to achieve the effects 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 reversed order, and these simple changes are all within the protection scope of the present invention.

[0031] Those skilled in the art should be able to realize that the modules and method steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, computer software, or a combination of the two. The programs corresponding to the software modules and method steps can be placed in a random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, register, hard disk, removable disk, CD-ROM, or any other form of storage medium well-known in the technical field. To clearly illustrate the interchangeability of electronic hardware and software, the components and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in the form of 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.

[0032] Terms such as "first" and "second" are used to distinguish similar objects, rather than to describe or represent a specific order or sequence.

[0033] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, so that a process, method, article or apparatus / device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to these processes, methods, articles or apparatus / devices.

[0034] So far, the technical solution of the present invention has 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 magnetic particle imaging system based on a flexible receiving coil array, characterized in that: The system comprises: a fourth coil configured to excite the magnetic nanoparticles to generate a magnetization response; A driving coil pair, configured to generate a uniform alternating magnetic field to drive the magnetic field free line to move; the driving coil pair includes two pairs of electromagnetic coils, serving as a second coil pair and a third coil pair respectively; the two electromagnetic coils in the second coil pair are symmetrically arranged on the upper and lower sides outside the fourth coil; the two electromagnetic coils in the third coil pair are symmetrically arranged on the left and right sides outside the fourth coil; A first magnet group is configured to generate a magnetic field free line at the center of the imaging field of view; the first magnet group includes four magnet units, and the four magnet units are grouped in two and symmetrically arranged on the upper and lower sides of the driving coil pair; the two magnet units in each group are placed side by side; A flexible receiving coil array is configured to receive magnetization response signals of magnetic nanoparticles; the flexible receiving coil array comprises a receiving coil array layer, a supporting substrate layer and a compensating coil array layer; the receiving coil array layer is a uniform planar array for receiving magnetization response signals, there are M receiving coils in the uniform planar array, one side of the receiving coil is adhered to the inner side of the supporting substrate layer, and the other side is adhered to the surface of the object to be measured, the compensating coil array layer is a block uniform planar array for compensating for feedthrough interference and electromagnetic interference of the receiving coil, the block uniform planar array is N compensating coils arranged within the coverage range of each receiving coil, one side of the compensating coil is adhered to the outer side of the supporting substrate layer, and the other side is away from the object to be measured, and the compensating coil array has a total of M×N coils.

2. A magnetic particle imaging system based on a flexible receiving coil array according to claim 1, characterized in that: The system further comprises a data acquisition and processing circuit configured to receive the magnetization response signal, filter, amplify, perform digital-to-analog conversion and process the signal to generate a magnetic particle image; It also includes a mechanical structure and a mechanical controller; the mechanical structure includes a magnet support structure for supporting and fixing the first magnet group, the driving coil pair and the fourth coil; The mechanical controller is used to drive the first magnet group to rotate, including the rotation angle and speed.

3. A magnetic particle imaging system based on a flexible receiving coil array according to claim 1, characterized in that: The fourth coil includes a solenoid coil and a Helmholtz coil; The two pairs of electromagnetic coils in the driving coil pair are both Helmholtz coils.

4. The magnetic particle imaging system based on a flexible receiving coil array according to claim 1, characterized in that: The magnet units in the first magnet group include permanent magnets, electromagnetic coils, and superconducting magnets.

5. The magnetic particle imaging system based on a flexible receiving coil array according to claim 1, characterized in that: The N compensation coils are connected in series in phase and then connected in series in anti-phase with the corresponding receiving coils. The sum of the inductances of the N compensation coils is equal to the inductance of the receiving coil and the diameter of the compensation coil is smaller than that of the receiving coil.

6. The magnetic particle imaging system based on a flexible receiving coil array according to claim 1, characterized in that: The supporting substrate layer has a supporting substrate of a preset thickness, and the thickness of the supporting substrate is h, wherein 2 mm <h<4mm。 7. A magnetic particle imaging method based on a flexible receiving coil array, based on a magnetic particle imaging system based on a flexible receiving coil array according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: S1, using the first magnet group to generate a magnetic field free line, the gradient of the magnetic field free line is ; The imaging field of view radius is ; Applying current to the second coil pair and the third coil pair respectively to generate a uniform alternating magnetic field to drive the magnetic field free line to move along a predetermined trajectory, wherein the predetermined trajectory motion is a discrete Cartesian motion; Passing current through the fourth coil to generate a magnetic field to excite the magnetic nanoparticles; S2, attaching the flexible receiving coil array to the object to be measured to receive the magnetization response signal of the magnetic nanoparticles, the flexible receiving coil array uses M receiving coils arranged in an array to receive the magnetization response signals of the M magnetic nanoparticles; S3, performing Fourier transformation on each magnetization response signal, converting it into a frequency domain signal, and distinguishing between in-phase and anti-phase; Extracting and superimposing in-phase third harmonics from all frequency domain signals to obtain processed signals; interpolating the spatial distribution of the processed signal from the polar coordinate mode to a Cartesian coordinate distribution to form a sinusoidal diagram; S4, the mechanical controller drives the first magnet group to rotate, and obtains the corresponding sine diagram at each angle according to the method of S1-S3; the rotation angle sequence is: ; S5, based on all acquired sinusoidal graphs, a filtered back-projection method is used to reconstruct the three-dimensional particle concentration distribution of the object under test, and then a reconstructed magnetic particle image is obtained.

8. The magnetic particle imaging method based on a flexible receiving coil array according to claim 7, characterized in that: The current flowing through the second coil pair is ; The current passing through the third coil pair is ; The current sequence is: , the phase sequence is: ; The current flowing through the fourth coil is .

9. The magnetic particle imaging method based on a flexible receiving coil array according to claim 7, characterized in that: The filtering back projection method includes a filtering back projection method using Cosine as a filtering kernel.

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