Perpendicular magnetization based isotropic x-space magnetic particle imaging device and method

Abstract

The present application relates to the vertical magnetization-based isotropic X-space magnetic particle imaging device and method, the imaging device includes scanning coil, excitation coil and vertical receiving coil, the magnetic particle in the magnetic field-free region generates the magnetic particle signal under the excitation of excitation coil magnetic field, and the vertical receiving coil receives the vertical magnetization response signal;Scanning coil drives the magnetic field-free region to traverse the imaging plane region where the object to be imaged is located, then determines the scanning track grid according to the scanning coil current, compensates according to the excitation coil current, obtains the initial image containing the corresponding relationship between the instantaneous signal and the track grid position, and reconstructs the initial image to obtain the isotropic concentration distribution image of the object to be imaged.The present application only uses a pair of mutually perpendicular excitation-receiving coils, solves the direct coupling problem of the MPI device, simultaneously utilizes the vertical magnetization signal combined with the improved X-space reconstruction method, realizes the isotropic reconstruction and real-time reconstruction.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of imaging technology, and particularly relates to an isotropic X-space magnetic particle imaging device and method based on vertical magnetization. BACKGROUND

[0002] Magnetic particle imaging (MPI) uses magnetic nanoparticles as contrast agents, and under the action of an external excitation magnetic field and a detection magnetic field, a nonlinear response signal of the magnetic nanoparticles is detected, so that a distribution image of the magnetic nanoparticles in space is reconstructed.

[0003] The X-space method is a direct reconstruction method, and according to an analytical relationship between a signal and an image, an image is reconstructed in real time without complex calibration. However, the resolution and other parameters of the result of the existing X-space reconstruction method are low, and additional processing is required to reach the level of system matrix reconstruction. Since only a one-way Cartesian imaging trajectory is used for scanning, the reconstruction result obtained by the existing X-space reconstruction method is spatially anisotropic, which will cause a light and dark change artifact in the field of view, and therefore additional anisotropy calibration is required.

[0004] The existing anisotropy calibration methods mainly include the following three kinds: the first solution is to use a Lissajous trajectory for scanning, which produces better image quality than a Cartesian trajectory; however, the Lissajous trajectory requires more hardware and consumes more resources, increasing the difficulty and cost of hardware design, and using multi-channel acquisition also increases the imaging time cost. The second solution is to extend a one-way Cartesian trajectory to a two-way Cartesian trajectory, which switches the excitation direction after the first scan and performs a second scan, and the images obtained by the two scans are combined by post-processing to obtain an isotropic reconstruction image; since multiple scans are required to switch the excitation direction, the imaging time cost is also increased. The third solution is to use deconvolution and deep learning to improve the anisotropy resolution, however, these algorithms often rely on trained models and can only produce better results on specific data, and have insufficient generalization ability.

[0005] On the other hand, in an MPI device, the excitation coil has a direct coupling effect on the receiving coil, which seriously pollutes the particle signal and is not conducive to high-quality image reconstruction. SUMMARY

[0006] In order to solve the above problems in the prior art, the application provides an isotropic X-space magnetic particle imaging device and method based on vertical magnetization. The technical problems to be solved by the application are solved by the following technical solutions:

[0007] The application provides a vertical magnetization-based isotropic X-space magnetic particle imaging device, which comprises an X-space MPI device coil module, a signal acquisition and processing module, an image reconstruction module and a device power supply module.

[0008] The X-space MPI device coil module comprises a permanent magnet pair, a scanning coil group, an excitation coil and a vertical receiving coil.

[0009] The middle region of the X-space MPI device coil module is the imaging plane region of the object to be imaged, the permanent magnet pair forms a magnetic field-free region in the middle of the imaging plane region, the scanning coil group drives the magnetic field-free region to scan the object to be imaged, the excitation coil and the vertical receiving coil are arranged perpendicularly to each other, the excitation coil excites magnetic particles to generate a magnetic particle signal, and the vertical receiving coil receives the vertical component of the magnetic particle signal and outputs a vertical magnetization response signal.

[0010] The signal acquisition and processing module is used for acquiring and amplifying the vertical magnetization response signal and outputting the vertical magnetization response signal to the image reconstruction module, the image reconstruction module performs reconstruction processing on the received vertical magnetization response signal to obtain a reconstruction result, and the device power supply module is used for generating a driving waveform signal and an excitation waveform signal to drive the scanning coil group and the excitation coil respectively.

[0011] In an embodiment of the application, the permanent magnet pair comprises a first permanent magnet and a second permanent magnet.

[0012] The first permanent magnet, the second permanent magnet and the vertical receiving coil are arranged in parallel along the y-axis, and the first permanent magnet and the second permanent magnet have opposite polarities.

[0013] In an embodiment of the application, the scanning coil group comprises a first scanning coil group and a second scanning coil group.

[0014] The first scanning coil group comprises a first Helmholtz drive coil and a second Helmholtz drive coil, and the first Helmholtz drive coil, the second Helmholtz drive coil and the vertical receiving coil are arranged in parallel along the y-axis.

[0015] The second scanning coil group comprises a third Helmholtz drive coil and a fourth Helmholtz drive coil, and the third Helmholtz drive coil, the fourth Helmholtz drive coil and the excitation coil are arranged in parallel along the x-axis.

[0016] In an embodiment of the application, the signal acquisition and processing module comprises a low-noise amplification module, a synchronous acquisition card and a current sampling module.

[0017] The low-noise amplification module inputs the vertical magnetization response signal and performs amplification processing, and the amplified vertical magnetization response signal is output to the synchronous acquisition card; the current sampling module samples the scanning coil current of the scanning coil group and the excitation coil current of the excitation coil respectively, and outputs to the synchronous acquisition card; the synchronous acquisition card acquires the amplified vertical magnetization response signal, the scanning coil current and the excitation coil current respectively, and outputs the acquisition result to the image reconstruction module.

[0018] In an embodiment of the present application, the image reconstruction module comprises a data calculation module and an image display module.

[0019] The data calculation module performs reconstruction processing according to the acquisition result of the synchronous acquisition card to obtain a concentration distribution image of the object to be imaged; and the image display module performs visualization processing on the concentration distribution image to obtain a reconstruction result.

[0020] The present application also provides a kind of isotropic X-space magnetic particle imaging method based on vertical magnetization, comprising:

[0021] S100: drive the non-magnetic field region to traverse the imaging plane region and scan the object to be imaged, excite magnetic particles to generate magnetic particle signals, and obtain vertical magnetization response signals according to the magnetic particle signals;

[0022] S200: form a scanning track of the non-magnetic field region according to the scanning coil current, and perform grid discretization processing on the scanning track to obtain a discrete grid containing position information;

[0023] S300: compensate the instantaneous vertical magnetization response signal according to the excitation coil current, and sequentially map the compensated vertical magnetization response signal to the corresponding position of the discrete grid in time sequence to obtain an initial image;

[0024] S400: perform pixel-by-pixel operation reconstruction processing on the initial image to obtain a concentration distribution image of the object to be imaged, and the concentration distribution image of the object to be imaged is isotropic.

[0025] In an embodiment of the present application, the vertical magnetization response signal is:

[0026]

[0027] wherein s(t) is the vertical magnetization response signal; t is the receiving time of the vertical magnetization response signal; B(X) is the sensitivity of the vertical receiving coil; m is the magnetic moment of the magnetic particle; and p(X) is the spatial concentration distribution of the magnetic particle. is the moving speed of the field-free region; X is a vector of the x-coordinate and the y-coordinate of the imaging plane region, X=(x,y) T ; x is the x-coordinate of the imaging plane region; y is the y-coordinate of the imaging plane region;

[0028] h(X) is a multi-dimensional point spread function (PSF), and is:

[0029]

[0030] wherein G is a magnetic field gradient; L is a Larmor equation; is a derivative of the Larmor equation.

[0031] In an embodiment of the present application, the S200 comprises:

[0032] S201: determining an x-direction scan coil current and a y-direction scan coil current according to a moving direction of the field-free region in the imaging plane region driven by a scan coil;

[0033] S202: synthesizing a scan trajectory according to a current relationship of the x-direction scan coil current and the y-direction scan coil current;

[0034] S203: performing grid discretization on the scan trajectory, wherein each discrete grid corresponds to a pixel, and obtaining position information of the discrete grid.

[0035] In an embodiment of the present application, the initial image is:

[0036]

[0037] wherein IMG xy (X(t)) is the initial image.

[0038] In an embodiment of the present application, the S400 comprises:

[0039] S401: processing each pixel in the initial image according to a processing mode of first x-integration and then y-derivation, and obtaining a first image IMG xx (X(t)), which is:

[0040]

[0041] S402: processing each pixel in the initial image according to a processing mode of first y-integration and then x-derivation, and obtaining a second image IMG yy (X(t)), which is:

[0042]

[0043] S403: add the first image and the second image to obtain a concentration distribution image of the object to be imaged as:

[0044] IMG(X(t))≈IMG xx (X(t))+IMG yy (X(t))。

[0045] Compared with the prior art, the present application has the beneficial effects that:

[0046] 1. The isotropic X-space magnetic particle imaging device based on perpendicular magnetization of the present application uses excitation-receiving coils perpendicular to each other to measure the magnetization response signal in the vertical direction, solves the problem of direct coupling of coils in the MPI device, enables the receiving coil to detect a purer magnetic particle signal to obtain a higher signal-to-noise ratio, further uses only one pair of excitation-receiving coils perpendicular to each other, can perform isotropic resolution reconstruction on the magnetic particle signal data without repeated scanning, is conducive to reducing the complexity of the design of the hardware, saves the time cost of scanning and imaging, and is conducive to real-time and rapid imaging.

[0047] 2. The reconstruction method of the isotropic X-space magnetic particle imaging device based on perpendicular magnetization of the present application effectively utilizes the magnetization response signal in the vertical direction and is organically combined with the improved X-space algorithm, the improved X-space algorithm performs real-time reconstruction on the image, the reconstruction result is isotropic, the real-time reconstruction of the image is realized through the excitation-receiving coils perpendicular to each other through the reconstruction method, and the reconstruction quality of the image is improved.

[0048] The above description is only a summary of the technical scheme of the present application, in order to more clearly understand the technical means of the present application, the content of the specification can be implemented, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is the structure block diagram of the isotropic X-space magnetic particle imaging device based on perpendicular magnetization provided by the embodiment of the present application;

[0050] Figure 2 is the signal transmission flow chart of the isotropic X-space magnetic particle imaging device based on perpendicular magnetization provided by the embodiment of the present application;

[0051] Figure 3 is the structure sectional view of the X-space MPI device coil module provided by the embodiment of the present application;

[0052] Figure 4 is the reconstruction method flow chart of the isotropic X-space magnetic particle imaging device based on perpendicular magnetization provided by the embodiment of the present application;

[0053] Figure 5 is a schematic diagram of the receiving coil sensitivity direction and the excitation magnetic field direction in the same direction provided by the embodiment of the application;

[0054] Figure 6 is a schematic diagram of the receiving coil sensitivity direction and the excitation magnetic field direction in the perpendicular direction provided by the embodiment of the application;

[0055] Figure 7 is a schematic diagram of the result of the y integration first and x derivation later of the PSF xy

[0056] Figure 8 is a schematic diagram of the result of the x integration first and y derivation later of the PSF xy

[0057] Figure 9 is a schematic diagram of the isotropic result of the PSF provided by the embodiment of the application;

[0058] Figure 10 is a schematic diagram of the "MPI" letter phantom provided by the embodiment of the application;

[0059] Figure 11 is a schematic diagram of the result of the reconstruction of the phantom by the reconstruction method using only the x axis same direction excitation receiving provided by the embodiment of the application;

[0060] Figure 12 is a schematic diagram of the result of the reconstruction of the phantom by the reconstruction method using only the y axis same direction excitation receiving provided by the embodiment of the application;

[0061] Figure 13 is a schematic diagram of the result of the reconstruction of the phantom by the reconstruction method of the isotropic X space magnetic particle imaging device based on the perpendicular magnetization provided by the embodiment of the application.

[0062] ​​Icon: 1 - imaging plane area; 2 - no magnetic field area; 100 - magnetic particle phantom delivery module; 200 - X-space MPI device coil module; 210 - permanent magnet pair; 211 - first permanent magnet; 212 - second permanent magnet; 220 - scan coil group; 221 - first scan coil group; 2211 - first Helmholtz drive coil; 2212 - second Helmholtz drive coil; 222 - second scan coil group; 2221 - third Helmholtz drive coil; 2222 - fourth Helmholtz drive coil; 230 - excitation coil; 240 - vertical receiving coil; 300 - signal acquisition and processing module; 310 - low-noise amplification module; 320 - synchronous acquisition card; 330 - current sampling module; 400 - image reconstruction module; 410 - data calculation module; 420 - image display module; 500 - device power supply module; 510 - signal generator; 520 - power amplifier; 530 - excitation coil impedance matching module. DETAILED DESCRIPTION

[0063] In order to further illustrate the technical means and effects taken by the present application to achieve the predetermined object, a vertical magnetization-based isotropic X-space magnetic particle imaging device and method according to the present application are described in detail below in conjunction with the drawings and specific embodiments.

[0064] The foregoing and other technical contents, features and effects of the present application can be clearly presented in the detailed description of the specific embodiments below in conjunction with the drawings. Through the description of the specific embodiments, the technical means and effects taken by the present application to achieve the predetermined object can be understood more deeply and specifically. However, the accompanying drawings are provided for reference and illustration only, and are not intended to limit the technical solutions of the present application.

[0065] Embodiment One

[0066] Please refer to Figure 1 , Figure 2 and Figure 3 , Figure 1 is a structural block diagram of the vertical magnetization-based isotropic X-space magnetic particle imaging device provided by the embodiments of the present application; Figure 2 is a signal transmission flowchart of the vertical magnetization-based isotropic X-space magnetic particle imaging device provided by the embodiments of the present application; Figure 3 is a structural cross-sectional view of the X-space MPI device coil module provided by the embodiments of the present application.

[0067] As shown in the figure, the vertical magnetization-based isotropic X-space magnetic particle imaging device of the present embodiment includes an X-space MPI device coil module 200, a signal acquisition and processing module 300, an image reconstruction module 400 and a device power supply module 500.

[0068] In the embodiment, the X-space MPI device coil module 200 comprises: a pair of permanent magnets 210, a scanning coil group 220, an excitation coil 230, and a vertical receiving coil 240.

[0069] The X-space MPI device coil module 200 has a middle region as an imaging plane region 1 of the object to be imaged, and the pair of permanent magnets 210 forms a magnetic field-free region 2 in the middle of the imaging plane region 1. The normal direction of the imaging plane region 1 is along the z-axis and is located on the xoy plane, and the xoy plane has an orthogonal relationship between the x-axis, the y-axis, and the z-axis. The scanning coil group 220 receives a driving waveform signal to drive the magnetic field-free region 2 to move in the imaging plane region 1 and scan the object to be imaged in the imaging plane region 1. Meanwhile, the excitation coil 230 receives an excitation waveform signal to generate an excitation magnetic field. The magnetic particles are excited by the excitation magnetic field, and the magnetic particles in the magnetic field-free region 2 generate a magnetic particle signal by induction. The excitation coil 230 and the vertical receiving coil 240 are arranged perpendicular to each other, the vertical receiving coil 240 receives the vertical component of the magnetic particle signal, and outputs a vertical magnetization response signal.

[0070] In an optional embodiment, the signal acquisition and processing module 300 is configured to acquire and amplify the vertical magnetization response signal and output the vertical magnetization response signal to the image reconstruction module 400. The image reconstruction module 400 is configured to perform reconstruction processing on the received vertical magnetization response signal to obtain a reconstruction result. The device power supply module 500 is configured to generate a driving waveform signal and an excitation waveform signal to drive the scanning coil group 220 and the excitation coil 230, respectively, to form a scanning coil current and an excitation coil current in the scanning coil group 220 and the excitation coil 230.

[0071] In an optional embodiment, the isotropic X-space magnetic particle imaging device based on vertical magnetization further comprises a magnetic particle phantom delivery module 100 configured to deliver the object to be imaged to the imaging plane region 1. The magnetic particle phantom delivery module 100 can be a mechanical translation stage or a guide rail.

[0072] In the embodiment, the pair of permanent magnets 210 comprises a first permanent magnet 211 and a second permanent magnet 212. The first permanent magnet 211, the second permanent magnet 212, and the vertical receiving coil 240 are arranged in parallel along the y-axis. The first permanent magnet 211 and the second permanent magnet 212 have opposite polarities. According to the principle of magnetic field vector superposition, the pair of permanent magnets with opposite polarities generates a magnetic field-free region 2 in the center of the imaging plane region 1. When the magnetic particles are in the region, they are in a non-saturated magnetization state and will generate a magnetic particle signal under the excitation of an external magnetic field.

[0073] In the embodiment, the scanning coil group 220 comprises a first scanning coil group 221 and a second scanning coil group 222.

[0074] The first scanning coil group 221 includes a first Helmholtz drive coil 2211 and a second Helmholtz drive coil 2212; the first Helmholtz drive coil 2211, the second Helmholtz drive coil 2212 and the vertical receiving coil 240 are arranged in parallel along the y-axis.

[0075] The second scanning coil group 222 includes a third Helmholtz drive coil 2221 and a fourth Helmholtz drive coil 2222; the third Helmholtz drive coil 2221, the fourth Helmholtz drive coil 2222 and the excitation coil 230 are arranged in parallel along the x-axis.

[0076] In an optional embodiment, the first scanning coil group 221 and the second scanning coil group 222 are arranged orthogonally, and a driving waveform signal is input into the two pairs of scanning coil groups 220, the driving waveform signal being a low-frequency sinusoidal alternating current, so that the magnetic field-free region 2 moves in the imaging plane region 1 to realize scanning of the object to be imaged.

[0077] In an optional embodiment, the signal acquisition and processing module 300 includes a low-noise amplification module 310, a synchronous acquisition card 320 and a current sampling module 330; the low-noise amplification module 310 inputs and amplifies the vertical magnetization response signal, and the amplified vertical magnetization response signal is output to the synchronous acquisition card 320; the current sampling module 330 samples the scanning coil current of the scanning coil group 220 and the excitation coil current of the excitation coil 230 respectively, and outputs to the synchronous acquisition card 320; the synchronous acquisition card 320 acquires the amplified vertical magnetization response signal, the scanning coil current and the excitation coil current respectively, and outputs the acquisition results to the image reconstruction module 400.

[0078] In an optional embodiment, the current sampling module 330 is used to sample the scanning coil current on one hand and to sample the excitation coil current on the other hand; the sampled scanning coil current and excitation coil current are input to the synchronous acquisition card 320 for analog-to-digital conversion, and the converted digital signals are input to the image reconstruction module 400 for reconstruction processing of the concentration distribution image of the object to be imaged.

[0079] In an optional embodiment, the image reconstruction module 400 includes a data calculation module 410 and an image display module 420; the data calculation module 410 performs reconstruction processing to obtain the concentration distribution image of the object to be imaged according to the acquisition results of the synchronous acquisition card 320; and the image display module 420 performs visualization processing on the concentration distribution image to obtain the reconstruction result.

[0080] In an optional embodiment, the device power supply module 500 includes a signal generator 510, a power amplifier 520 and an excitation coil impedance matching module 530.

[0081] The signal generator 510 generates a scanning driving signal and an excitation driving signal respectively, the scanning driving signal is amplified by the power amplifier 520 and then output to drive the wave signal to the scanning coil group 220, and the excitation driving signal is amplified by the power amplifier 520 and then output to the excitation coil impedance matching module 530 for impedance matching, and the excitation coil impedance matching module 530 outputs the excitation wave signal to the excitation coil 230.

[0082] The perpendicular magnetization-based isotropic X-space magnetic particle imaging device provided in the embodiment of the application uses the excitation-receiving coil perpendicular to each other to measure the vertical magnetization response signal of the magnetic particle, solves the direct coupling problem of the coil of the MPI device, and enables the receiving coil to detect a purer magnetic particle signal to obtain a higher signal-to-noise ratio; further, only one pair of excitation-receiving coils perpendicular to each other is used, and the isotropic resolution reconstruction can be performed on the magnetic particle signal data without repeated scanning, which is beneficial to reducing the complexity of the design of the hardware and saving the time cost of scanning and imaging, and is beneficial to real-time and rapid imaging.

[0083] Embodiment two

[0084] Please refer to Figure 4 , Figure 4 The reconstruction method flowchart of the perpendicular magnetization-based isotropic X-space magnetic particle imaging device provided in the embodiment of the application.

[0085] As shown in the figure, the reconstruction method of the perpendicular magnetization-based isotropic X-space magnetic particle imaging device provided in the embodiment of the application comprises:

[0086] S100: driving the non-magnetic field region to traverse the imaging plane region to scan the object to be imaged, and simultaneously exciting the magnetic particle to generate a magnetic particle signal, and obtaining a vertical magnetization response signal according to the magnetic particle signal;

[0087] In this embodiment, the permanent magnet 210 generates a gradient field on the imaging plane region 1 to generate a zero magnetic field point (FFP), and a driving wave signal is input, the driving wave signal is an alternating current, two driving magnetic fields in different directions and with different frequencies are generated in the two pairs of orthogonally arranged annular first scanning coil groups 221 and second scanning coil groups 222, and the non-magnetic field region 2 is driven by the driving magnetic field to quickly scan in the xoy plane along a predetermined scanning track (controlled by the alternating current), and finally traverse the entire xoy plane.

[0088] The vertical magnetization response signal s(t) can be expressed as:

[0089]

[0090] Wherein, s(t) is the vertical magnetization response signal; t is the receiving time of the vertical magnetization response signal; B(X) is the sensitivity of the vertical receiving coil 240; m is the magnetic moment of the magnetic particle; p(X) is the spatial concentration distribution of the magnetic particle; is the moving speed of the field-free region 2; X is a vector X=(x, y) representing the imaging plane region 1 coordinate; T ; x is the x coordinate of the imaging plane region 1; y is the y coordinate of the imaging plane region 1; h(X) is a multi-dimensional point spread function (PSF), which can be expressed as:

[0091]

[0092] Wherein, G is the magnetic field gradient; L is the Larmor equation;

[0093] is the derivative of the Larmor equation, including four parts:

[0094]

[0095]

[0096]

[0097]

[0098] Wherein, E T and E N are matrices, or in other words, are scalar under a single element; W T and W N are tensors.

[0099] S200: Forming a scanning trajectory of the field-free region according to the scanning coil current, and performing grid discretization processing to obtain a discrete grid containing position information;

[0100] Wherein, S200 includes:

[0101] S201: According to the moving direction of the scanning coil driving the field-free region in the imaging plane region, respectively determining the x-direction scanning coil current and the y-direction scanning coil current;

[0102] In an optional embodiment, the direction of the scanning coil current is determined according to the moving direction of the field-free region 2 in the imaging plane region 1, such as the driving waveform signal passed through the third Helmholtz driving coil 2221 and the fourth Helmholtz driving coil 2222 to make the field-free region 2 move in the x-axis direction in the imaging plane region 1, and the scanning coil current collected by the current sampling module 330 is referred to as the x-direction scanning coil current.

[0103] Likewise, the driving waveform signal is passed through the scanning coil group 220 to drive the field-free region 2 to move in the imaging plane region 1, and if the field-free region 2 moves in the y-direction, the scanning coil current collected by the current sampling module 330 is referred to as the y-direction scanning coil current I y (t).

[0104] S202: Synthesizing the scanning trajectory according to the current relationship between the x-direction scanning coil current and the y-direction scanning coil current;

[0105] S203: Grid discretization is performed on the scanning trajectory, where each discrete grid corresponds to a pixel to obtain the position information of the discrete grid.

[0106] In an optional embodiment, each discrete grid corresponds to an imaging pixel to obtain the position information POS(x i ,y j ), i, j = 1 ~ N.

[0107] Wherein, N is the pre-defined number of pixel points in the x and y dimensions of the imaging plane region 1; x i is the x coordinate of the discrete grid pixel point; and y i is the y coordinate of the discrete grid pixel point.

[0108] S300: Compensating the instantaneous vertical magnetization response signal according to the excitation coil current, and sequentially mapping the compensated vertical magnetization response signal to the corresponding positions of the discrete grids in time sequence to obtain an initial image;

[0109] Further, the instantaneous velocity compensation is performed on s(t) to correspond the compensated signal s(t k ) to the spatial position at the same time t k , to obtain the initial image IMG xy (X(t)) of the particle distribution at the position, which is expressed as:

[0110]

[0111] At this time, the initial image IMG xy (X(t)) still has anisotropy and needs to be further reconstructed.

[0112] S400: According to the initial image, a pixel-by-pixel operation reconstruction process is performed to obtain a concentration distribution image of the object to be imaged, and the concentration distribution image of the object to be imaged is isotropic.

[0113] Wherein, S400 includes:

[0114] S401: For each pixel in the initial image function, a processing mode of first integrating x and then deriving y is performed to obtain a first image;

[0115] In an optional embodiment, the initial image IMG xy (X(t)) of the object to be imaged collected is pixel-by-pixel operated, first integrating x and then deriving y to obtain a first image IMG xx (X(t)).

[0116] S402: For each pixel in the initial image, a processing mode of first integrating y and then deriving x is performed to obtain a second image;

[0117] In an optional embodiment, the initial image IMG xy (X(t)) of the object to be imaged collected is pixel-by-pixel operated, first integrating y and then deriving x to obtain a second image IMG yy (X(t)).

[0118] S403: The first image and the second image are added to obtain a concentration distribution image of the object to be imaged.

[0119] In an optional embodiment, the first image IMG xx (X(t)) and the second image IMG yy (X(t)) are added to obtain a concentration distribution image IMG(X(t)) of the object to be imaged reconstructed only by the vertical magnetization response signal, which is represented as:

[0120] IMG(X(t))≈IMG xx (X(t))+IMG yy (X(t))(5);

[0121]

[0122]

[0123] The concentration distribution image IMG(X(t)) of the object to be imaged obtained by the reconstruction process only by the vertical magnetization response signal is isotropic, which is specifically illustrated by the following process:

[0124] The point spread function (PSF) in the multi-dimensional X space reconstruction in the MPI is normalized, and the receiving coil sensitivity direction and the zero magnetic field point FFP are also normalized, so that the PSF formed by the receiving coil sensitivity in any direction and the excitation magnetic field can be obtained by the following formula:

[0125]

[0126] Wherein, d1 is the direction of the receiving coil sensitivity; d2 is the moving direction of the FFP;

[0127] Please refer to Figure 5 and Figure 6 , Figure 5 is the schematic diagram of the receiving coil sensitivity direction and the excitation magnetic field direction in the same direction provided by the embodiment of the application; Figure 6 is the schematic diagram of the receiving coil sensitivity direction and the excitation magnetic field direction perpendicular provided by the embodiment of the application.

[0128] As shown in the figure, the PSF xx represents the point spread function when the receiving coil sensitivity direction and the excitation magnetic field direction are both x-axis directions, and is expressed as:

[0129] PSF xx = E T (X)cos 2 θ + E N (X)sin 2 θ (9);

[0130] Wherein, θ is the included angle between the receiving coil sensitivity direction and the excitation magnetic field direction; H x is the component of the excitation magnetic field along the x-axis direction; H y is the component of the excitation magnetic field along the y-axis direction.

[0131] PSF yy represents the point spread function when the receiving coil sensitivity direction and the excitation magnetic field direction are both y-axis directions, and is expressed as:

[0132] PSF yy = E T (X)sin 2 θ + E N (X)cos 2 θ (10);

[0133] In one embodiment of the application, when the receiving coil sensitivity direction and the excitation magnetic field direction are in the same direction with the x-axis, and the other is in the same direction with the y-axis, the point spread function PSF xy is expressed as:

[0134] PSF xy = E T (X)sinθcosθ-E N (X)sinθcosθ (11);

[0135] where the coordinates (x, y, z) have been normalized by the gradient field (H x , H y , H z ), i.e. the present coordinates are equal in value to the magnetic field generated by the gradient field.

[0136] Again, cosθ and sinθ are brought into equations (9)-(11), then PSF xx , PSF yy and PSF xy are expressed as:

[0137]

[0138]

[0139]

[0140] First, PSF xy is integrated with respect to x, then differentiated with respect to y. According to the property of convolution, integration and differentiation on PSF are equivalent to integration and differentiation on image domain, then:

[0141]

[0142] where SE T is the function integrated with respect to E T ; SE N is the function integrated with respect to E N ; and l(x, y) is the residual of ∫PSF xy dx.

[0143] Further, the relationship among SE T , SE N and l(x, y) is:

[0144] SE T = ∫E T dx, SE N = ∫E N dx (16) ;

[0145]

[0146] Further, the function integrated is differentiated with respect to y:

[0147]

[0148] wherein r(x,y) is the remainder of the Taylor series, which can be expressed as:

[0149]

[0150] Combining equations (12)-(19), we have:

[0151]

[0152] wherein ε is an error term.

[0153] Similarly, we have:

[0154]

[0155] According to the theory of the multi-channel acquisition of isotropic resolution in MPI, the signal PSF xx and PSF yy are acquired by using the dual-channel and same direction excitation and reception, and the reconstruction image PSF of isotropic resolution is obtained by adding PSF xx and PSF yy , and is:

[0156]

[0157] Therefore, for the object to be imaged, the reconstruction method based on the vertical magnetization of the isotropic X-space magnetic particle imaging device of the embodiment is used to perform the reconstruction processing on the initial image IMG xy (X(t)), and through the reconstruction processing, the anisotropy of the initial image IMG xy (X(t)) is calibrated, and the concentration distribution image IMG(X(t)) of the object to be imaged, which is reconstructed only by the vertical magnetization response signal, is obtained, and has isotropy.

[0158] Please refer to Figure 7 , Figure 8 and Figure 9 , Figure 7 is a schematic diagram of the result of performing the y integration first and then the x derivation on PSF xy provided by the embodiment of the application; Figure 8 is a schematic diagram of the result of performing the x integration first and then the y derivation on PSF xy provided by the embodiment of the application; Figure 9 is a schematic diagram of the result of the isotropic resolution of PSF provided by the embodiment of the application.

[0159] As shown in the figure, using the vertical magnetization-based isotropic X-space magnetic particle imaging method of the embodiment of the present application, it can be seen that, compared with the method using only the same direction (x direction or y direction) excitation and reception, which is represented as only first derivation on x and then integration on y or only first derivation on y and then integration on x, the reconstructed image of the vertical magnetization-based isotropic X-space magnetic particle imaging method of the embodiment of the present application has obvious isotropic characteristics, and the imaging quality can be effectively improved.

[0160] Please refer to Figure 10 、 Figure 11 、 Figure 12 and Figure 13 , Figure 10 is a schematic diagram of the "MPI" letter phantom provided by the embodiment of the present application; Figure 11 is a result schematic diagram of the reconstruction of the phantom using the reconstruction method of the x-axis same direction excitation and reception provided by the embodiment of the present application; Figure 12 is a result schematic diagram of the reconstruction of the phantom using the reconstruction method of the y-axis same direction excitation and reception provided by the embodiment of the present application; Figure 13 is a result schematic diagram of the reconstruction of the phantom using the reconstruction method of the vertical magnetization-based isotropic X-space magnetic particle imaging device provided by the embodiment of the present application.

[0161] As shown in the figure, in order to verify the vertical magnetization-based isotropic X-space magnetic particle imaging method proposed by the embodiment of the present application, the following simulation experiment is set to illustrate:

[0162] The simulation experiment conditions are set as follows: the gradient field is GX=GY=2.5T / m; the excitation magnetic field is 10mT; the mechanical scanning is performed using the translation type; the simulation field of view is about 28mmx178mm;

[0163] Based on the above simulation experiment conditions, the two-dimensional space imaging is performed using the vertical magnetization-based isotropic X-space magnetic particle imaging method of the embodiment of the present application, wherein the phantom is "MPI" three letters; it can be seen that, compared with the method using only the same direction (x direction or y direction) excitation and reception, the vertical magnetization-based isotropic X-space magnetic particle imaging method of the embodiment of the present application can effectively improve the imaging quality.

[0164] The reconstruction method of the vertical magnetization-based isotropic X-space magnetic particle imaging device of the embodiment of the present application effectively utilizes the vertical magnetization response signal and is organically combined with the improved X-space algorithm, the improved X-space algorithm performs real-time reconstruction on the image, the reconstruction result is isotropic, the real-time reconstruction of the image is realized through the excitation-reception coils perpendicular to each other through the reconstruction method, and the reconstruction quality of the image is improved.

[0165] It is to be understood that the terminology used herein such as first and second, and the like, is only to distinguish one from another without prejudice to either and is not necessarily used in a sequence. Also, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion such that a vesicle or an apparatus that comprises a list of components does not include only those components but can include other components not expressly listed or inherent to such vesicle or apparatus. The terms "comprises", "comprising", or any other variations thereof, do not have the meaning of excluding other components not expressly listed. The term "connected" or "coupled" or any other variations thereof are not to be construed as being necessarily limited to a physical or mechanical connection or coupling, but can also include an electrical connection or coupling, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like, indicate orientations or positional relationships based on the orientations or positional relationships as shown in the drawings and are made only for the purpose of ease of description and illustration, and thus can not be construed as indicating or implying necessary or absolutely directional or positional relationships, and therefore should be understood as being open to other orientations or positional relationships.

[0166] The above description is further to the present application in connection with specific preferred embodiments, and cannot be deemed as limiting the specific implementation of the present application to these descriptions. For those skilled in the art, some simple deductions or substitutions can be made without departing from the concept of the present application, and all of these should be deemed as falling within the protection scope of the present application.

Claims

1. A perpendicular-magnetization-based isotropic X-space magnetic particle imaging device, characterized by, The application relates to an X-space MPI device coil module (200), a signal acquisition and processing module (300), an image reconstruction module (400) and a device power supply module (500). The X-space MPI device coil module (200) comprises a permanent magnet pair (210), a scanning coil group (220), an excitation coil (230) and a vertical receiving coil (240). The middle region of the X-space MPI device coil module (200) is an imaging plane region (1) of a to-be-imaged object, the permanent magnet pair (210) forms a magnetic field-free region (2) in the middle of the imaging plane region (1), the scanning coil group (220) drives the magnetic field-free region (2) to scan the to-be-imaged object, the excitation coil (230) and the vertical receiving coil (240) are arranged perpendicularly to each other, the excitation coil (230) generates an excitation magnetic field to excite magnetic particles to generate a magnetic particle signal, and the vertical receiving coil (240) receives a vertical component of the magnetic particle signal and outputs a vertical magnetization response signal. The signal acquisition and processing module (300) is used for acquiring and amplifying the vertical magnetization response signal and outputting the vertical magnetization response signal to the image reconstruction module (400), the image reconstruction module (400) performs reconstruction processing on the received vertical magnetization response signal to obtain an isotropic reconstruction result, and the device power supply module (500) is used for generating a driving waveform signal and an excitation waveform signal to drive the scanning coil group (220) and the excitation coil (230) respectively. The scanning coil group (220) comprises a first scanning coil group (221) and a second scanning coil group (222), the first scanning coil group (221) comprises a first Helmholtz drive coil (2211) and a second Helmholtz drive coil (2212), the first Helmholtz drive coil (2211), the second Helmholtz drive coil (2212) and the vertical receiving coil (240) are arranged in parallel along a y-axis, the second scanning coil group (222) comprises a third Helmholtz drive coil (2221) and a fourth Helmholtz drive coil (2222), and the third Helmholtz drive coil (2221), the fourth Helmholtz drive coil (2222) and the excitation coil (230) are arranged in parallel along an x-axis. The permanent magnet pair (210) comprises a first permanent magnet (211) and a second permanent magnet (212).

2. The perpendicular-magnetization-based isotropic X-space magnetic particle imaging device of claim 1, wherein, The first permanent magnet (211), the second permanent magnet (212) and the vertical receiving coil (240) are arranged in parallel along the y-axis, and the first permanent magnet (211) and the second permanent magnet (212) have opposite polarities. The signal acquisition and processing module (300) comprises a low-noise amplification module (310), a synchronous acquisition card (320) and a current sampling module (330).

3. The perpendicular magnetic based isotropic X-space magnetic particle imaging device of claim 1, wherein, The low-noise amplification module (310) inputs the vertical magnetization response signal and performs amplification processing, and the amplified vertical magnetization response signal is output to the synchronous acquisition card (320). ​ The current sampling module (330) samples the scan coil current of the scan coil group (220) and the excitation coil current of the excitation coil (230) respectively and outputs to the synchronous acquisition card (320); The synchronous acquisition card (320) acquires the amplified vertical magnetization response signal, the scan coil current and the excitation coil current respectively and outputs the acquisition result to the image reconstruction module (400).

4. The perpendicular-magnetization-based isotropic X-space magnetic particle imaging device of claim 3, wherein, The image reconstruction module (400) comprises a data calculation module (410) and an image display module (420); The data calculation module (410) performs reconstruction processing according to the acquisition result of the synchronous acquisition card (320) to obtain a concentration distribution image of the object to be imaged; and the image display module (420) performs visual processing on the concentration distribution image to obtain a reconstruction result.

5. A method of X-space magnetic particle imaging based on perpendicular magnetization using the imaging device according to any one of claims 1 to 4, characterized in that, Comprise: S100: driving the non-magnetic field region to scan the object to be imaged in the imaging plane region, exciting magnetic particles to generate magnetic particle signals, and obtaining a vertical magnetization response signal according to the magnetic particle signals; S200: forming a scan trajectory of the non-magnetic field region according to the scan coil current, performing grid discretization processing on the scan trajectory, and obtaining a discrete grid containing position information; S300: compensating the instantaneous vertical magnetization response signal according to the excitation coil current, sequentially mapping the compensated vertical magnetization response signal to the corresponding positions of the discrete grid in time sequence, and obtaining an initial image; S400: performing pixel-by-pixel operation reconstruction processing on the initial image to obtain a concentration distribution image of the object to be imaged, and the concentration distribution image of the object to be imaged is isotropic.

6. The perpendicular-magnetization-based isotropic X-space magnetic particle imaging method of claim 5, wherein, The vertical magnetization response signal is: ； wherein, is a vertical magnetization response signal; is a reception time of the vertical magnetization response signal; is a sensitivity of the vertical receiving coil; is a magnetic moment of the magnetic particles; is a spatial concentration distribution of the magnetic particles; is a moving speed of the field-free region; is a vector of the imaging plane region plane coordinates ; is an x-coordinate of the imaging plane region; is a y-coordinate of the imaging plane region; For a multi-dimensional point spread function PSF, for: ； wherein is the magnetic field gradient; is the Larmor equation; is the derivative of the Larmor equation.

7. The perpendicular magnetic based isotropic X-space magnetic particle imaging method of claim 5, wherein, The S200 comprises: S201: determining the x-direction scan coil current and the y-direction scan coil current respectively according to the moving direction of the scan coil driving the non-magnetic field region in the imaging plane region; S202: synthesizing a scan trajectory according to the current relationship of the x-direction scan coil current and the y-direction scan coil current; S203: performing grid discretization on the scan trajectory, wherein each discrete grid corresponds to a pixel, and obtaining position information of the discrete grid.

8. The perpendicular magnetic based isotropic X-space magnetic particle imaging method of claim 5, wherein, The initial image is: ； wherein is the initial image.

9. The perpendicular-magnetization-based isotropic X-space magnetic particle imaging method of claim 8, wherein, The S400 comprises: S401: For each pixel in the initial image, process according to the processing mode of first integration derivation, obtain a first image : ； S402: For each pixel in the initial image, process according to the processing mode of first integration derivation, obtain a second image : ； S403: summing the first image and the second image to obtain the concentration distribution image of the object to be imaged, which is 。

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