A miniature detection system based on magnetic particle imaging

Abstract

This invention relates to a miniature detection system based on magnetic particle imaging, belonging to the field of medical inflammatory imaging technology. This invention is a miniature and simple device for magnetic particle imaging for fingertip detection. It uses a microcontroller as the control terminal, a receiving coil that is closer to the imaging aperture, and low-diameter driving and receiving coils. By improving the signal-to-noise ratio and reducing background interference signals, it effectively improves experimental efficiency and the sensitivity of the detection system, and greatly enhances portability.

Description

Technical Field

[0001] This invention relates to the field of medical inflammatory imaging technology, and more specifically to a miniature detection system based on magnetic particle imaging. Background Technology

[0002] Currently, autoimmune diseases, including lupus and systemic sclerosis, have complex pathogenic factors. Due to the unclear pathogenesis and strong heterogeneity of clinical manifestations, they not only cause difficulties and delays in clinical diagnosis and treatment, but also pose a great challenge to the study of their pathogenesis. At present, the diagnosis of lupus and systemic sclerosis is mainly based on a combination of typical clinical manifestations (such as skin involvement and Raynaud's phenomenon), positive serological results, and medical imaging.

[0003] Optical imaging is now widely used in the biomedical field. Among them, microcirculation detectors, as a new type of optoelectronic instrument, can non-invasively detect capillaries in the human extremities and can be used as an early auxiliary diagnostic tool for diseases including autoimmune diseases, hypertension, and cardiovascular and cerebrovascular diseases. Although optical molecular imaging has the advantage of high resolution, there are physical limitations in the depth of penetration of optical signals into biological tissues during the propagation process, and it cannot provide detection information at the biomolecular level.

[0004] Recent studies have revealed that magnetic nanoparticle imaging (MPI) possesses numerous advantages, including high spatiotemporal resolution, high sensitivity, and no limitations on tissue penetration depth. This provides a new solution to address the aforementioned challenges. Currently, it is widely used in cell tracking, angiography, and inflammation imaging. However, MPI also suffers from unavoidable signal interference in whole-body imaging, and there is a lack of development of miniaturized detection devices that can reduce the detection area and improve the signal-to-noise ratio and sensitivity. Summary of the Invention

[0005] In view of the above problems, the present invention provides a miniature detection system based on magnetic particle imaging, a miniature and simple device for magnetic particle imaging of fingertip detection. It uses a microcontroller as the control terminal, uses a receiving coil that is closer to the imaging aperture, and uses a low-diameter driving coil and receiving coil. By improving the signal-to-noise ratio and reducing background interference signals, it effectively improves experimental efficiency and the sensitivity of the detection system, and greatly improves portability.

[0006] On the one hand, the present invention provides a miniature detection system based on magnetic particle imaging, comprising: a signal acquisition module, a control module, a signal generation module, and a signal receiving module;

[0007] The signal acquisition module includes a receiving coil, a driving coil, and a permanent magnet;

[0008] The inner ring of the receiving coil is attached to the end of the limb being tested, and is used to collect the induced voltage signal emitted by the end of the limb being tested.

[0009] The driving coil is circumferentially arranged around the outer ring of the receiving coil and does not contact the outer ring of the receiving coil, and is used to construct a driving field;

[0010] The driving field is used to drive a point without a magnetic field through the end of the object being measured, thereby changing the magnetization intensity of magnetic particles near the point without a magnetic field; imaging holes are provided at the upper and lower ends of the outer coil of the receiving coil; as... Figure 2 ;

[0011] The driving field is a sinusoidal excitation magnetic field or a pulsed square wave excitation magnetic field;

[0012] The permanent magnet is circumferentially connected to the outer ring of the drive coil and contacts the outer ring of the drive coil to create a selective field;

[0013] Furthermore, the selected field is a static gradient magnetic field, used to drive all magnetic particles except those near the field-free point until saturation is achieved; for example... Figure 2 ;

[0014] Preferably, the permanent magnet is a neodymium iron boron permanent magnet; the permanent magnet constitutes a static gradient magnetic field;

[0015] The driving coil is a Helmholtz coil, and the driving coil constitutes an excitation magnetic field;

[0016] Preferably, the ratio of the magnetic field strength of the static gradient magnetic field to that of the excitation magnetic field is 3-6:10-20;

[0017] Furthermore, the permanent magnet forms a static gradient magnetic field of 3-6 T / m, and the driving coil forms a sinusoidal excitation magnetic field or a pulsed square wave excitation magnetic field of 10-20 mT.

[0018] Furthermore, the permanent magnet forms a static gradient magnetic field of 4T / m, and the driving coil forms a sinusoidal excitation magnetic field of 15mT.

[0019] In the technical solution of this invention, a permanent magnet is set to form a static gradient magnetic field of 4T / m, and a driving coil is set to form a sinusoidal excitation magnetic field of 15mT, which significantly improves the effective signal of the magnetic field and further improves the signal quality and sensitivity of the receiving coil.

[0020] In one embodiment of the present invention, the object limb is the fingertip of a human body;

[0021] A cylindrical receiving coil is obtained by winding Litz wire around a coil frame using a forward and reverse winding method.

[0022] Furthermore, the cylindrical receiving coil has a diameter of 15mm and a height of 20mm;

[0023] The method of using forward and reverse winding involves winding the Litz wire 40 turns around the coil frame.

[0024] The present invention uses a forward and reverse winding method to wind Litz wire 40 turns on the coil frame. This winding method significantly reduces background noise while improving the signal-to-noise ratio and sensitivity.

[0025] The control module includes a microcontroller and an RGB display screen; it is used for system startup, interruption, real-time signal monitoring, and data storage.

[0026] One side of the microcontroller is connected to one side of the RGB display screen; the other side of the microcontroller is connected to the ADDA chip.

[0027] The signal generation module includes a digital-to-analog converter, a bandpass filter, and a power amplifier; one side of the digital-to-analog converter is connected to one side of the bandpass filter, and the other side of the bandpass filter is connected to one side of the power amplifier;

[0028] The signal generation module is used to generate a sinusoidal current or a pulsed square wave to apply a uniform excitation magnetic field to the drive coil.

[0029] The signal receiving module includes a low-noise amplifier, a band-stop filter, and an analog-to-digital converter; one side of the low-noise amplifier is connected to one side of the band-stop filter, and the other side of the band-stop filter is connected to one side of the analog-to-digital converter.

[0030] The signal receiving module is used to process and transmit the induced voltage signal collected by the receiving coil; the analog-to-digital converter outputs the induced voltage signal collected by the receiving coil as a digital signal.

[0031] Preferably, the permanent magnet is a neodymium iron boron permanent magnet; the permanent magnet constitutes a static gradient magnetic field;

[0032] The driving coil is a Helmholtz coil, and the driving coil constitutes a sinusoidal excitation magnetic field or a pulsed square wave excitation magnetic field;

[0033] In one embodiment of the present invention, the driving coil forms a sinusoidal excitation magnetic field, the receiving coil collects a nonlinear response voltage signal, the nonlinear response voltage signal is used to obtain the spatial resolution of magnetic particle imaging (MPI) based on the Langevin function in X space, the image is reconstructed based on the spatial resolution of the magnetic particle imaging (MPI), and the detection image of the sinusoidal excitation magnetic field is output.

[0034] In one embodiment of the present invention, the driving coil forms a pulsed square wave magnetic field, the receiving coil collects the induced voltage signal, and the induced voltage signal is analyzed and imaged using the inverse Laplace transform to obtain a detection image of the pulsed square wave magnetic field.

[0035] Furthermore, the expression for the detected image of the sinusoidal excitation magnetic field is:

[0036]

[0037] Where A(t) is the signal vector received by the sinusoidal excitation magnetic field at time t, t = 1, 2, 3…T, where T represents the total number of times; B1 is the sensitivity matrix; m is the magnetic moment of a single magnetic particle in the sinusoidal excitation magnetic field; n is the magnetic particle density when the instantaneous position is a point without a magnetic field; c(x) is the point spread function PSF, i.e., the real space convolution function, which is generated by dividing the slewing rate of the driving field by other constants, and x represents the actual spatial position vector; x s (t) represents the instantaneous position s of the point without magnetic field at time t, where s denotes instantaneous; G is the invertible gradient matrix; E sat The magnetic field vector required for saturation.

[0038] The spatial resolution expression for the magnetic particle imaging (MPI) is:

[0039]

[0040]

[0041] in, Let be the spatial resolution of the magnetic particle imaging at time t; Δx be the full width at half maximum (FWHM) of the point spread function matrix (PSF); Msat be the saturation magnetization of the magnetic particle; r be the diameter of the magnetic particle; and k be the magnetic particle diameter. B is Boltzmann constant, T is temperature, and μ0 is vacuum permeability.

[0042] The expression for the pulsed square wave magnetic field detection image is:

[0043]

[0044] Among them, M z (d) represents the magnetic field strength recovered by the magnetic particle, d represents the radius of the magnetic particle, δ represents the magnetic moment of the magnetic particle, L(·) represents the Langevin function, and W0 represents the amplitude of the flat phase of the magnetic field; W α W represents the magnetic field strength along the imaging aperture α direction. β α is the magnetic field strength in the direction of the imaging aperture β; α is the unit vector of the horizontal coordinate in space, and β is the unit vector of the vertical coordinate in space.

[0045] Preferably, the control module uses a ZYNQ-7010 control system as the microcontroller, which is connected to the signal generation module and the signal receiving module respectively to realize system startup, interruption, and data transmission and storage. An RGB LCD touchscreen is used to realize real-time monitoring of system signals, such as... Figure 3 .

[0046] Preferably, the signal receiving module uses an AD9280 chip to achieve analog-to-digital conversion, with a sampling rate of millions of times per second and a single sampling time of 5ms for the detection system.

[0047] On the other hand, based on the above detection system, the present invention provides a detection method based on magnetic particle imaging, comprising the following steps:

[0048] S1: Move the end of the object to be measured into the imaging aperture of the receiving coil;

[0049] S2: The control module sends a start signal, and the signal generation module processes the encoded digital signal through a digital-to-analog converter, a bandpass filter, and a power amplifier before outputting it to the drive coil, so that the drive coil is subjected to a uniform sinusoidal excitation magnetic field.

[0050] S3: In the sinusoidal excitation magnetic field, the imaging aperture acquires signals to obtain the original induced voltage signal. The original induced voltage signal is sequentially converted into a corresponding digital signal by the low-noise amplifier, band-stop filter and analog-to-digital converter of the signal receiving module, and the corresponding digital signal is input into the control module for data storage.

[0051] S4: Repeat steps S2-3 twice to obtain the digital signal corresponding to the original induced voltage signal each time, and input it into the control module for data storage;

[0052] The detection system is interrupted after the data storage contains three digital voltage signals.

[0053] S5: The digital signals corresponding to the three original induced voltage signals are reconstructed using X-space magnetic particle imaging (MPI) to output a detection image of the sinusoidal excitation magnetic field.

[0054] Another embodiment of the present invention further includes: S2: The control module sends a start signal, and the signal generation module processes the encoded digital signal through a digital-to-analog converter, a bandpass filter and a power amplifier and outputs it to the drive coil, so that a uniform pulse square wave excitation magnetic field is applied to the drive coil;

[0055] S3: In the pulsed square wave excitation magnetic field, the imaging aperture acquires signals to obtain the original induced voltage signal. The original induced voltage signal is sequentially converted into a corresponding digital signal by the low noise amplifier, band-stop filter and analog-to-digital converter of the signal receiving module, and the corresponding digital signal is input into the control module for data storage.

[0056] S4: Repeat steps S2-3 twice to obtain the digital signal corresponding to the original induced voltage signal each time, and input it into the control module for data storage;

[0057] The detection system is interrupted after the data storage contains three digital voltage signals.

[0058] S5: The digital signals corresponding to the three original induced voltage signals are analyzed and imaged using the inverse Laplace transform to obtain a detection image of the pulse square wave magnetic field.

[0059] Compared with the prior art, the present invention has at least the following beneficial effects:

[0060] (1) The present invention uses a positive and negative winding gradient coil that is closer to the size and structure of the limb end of the object being detected as the receiving coil, thereby getting closer to the region of interest (ROI) of the detection system and improving the signal quality and sensitivity of the receiving coil;

[0061] (2) The present invention uses a single-chip microcomputer as the control terminal, which effectively improves the experimental efficiency;

[0062] (3) This invention integrates the nonlinear response signal of magnetic particles and the spectral relaxation time analysis, which further improves the acquisition of effective signals.

[0063] (4) The present invention uses a low-diameter driving coil and receiving coil to build a miniature simple device based on magnetic particle imaging, which greatly improves portability. Attached Figure Description

[0064] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0065] Figure 1 This is a schematic diagram of the flowchart of the miniature detection system of the present invention;

[0066] Figure 2 This is a schematic diagram illustrating the configuration of the miniature detection system of the present invention.

[0067] Figure 3 This is a schematic diagram of the control module of the miniature detection system of the present invention. Detailed Implementation

[0068] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0069] A specific embodiment of the present invention, such as Figure 1-3 This invention discloses a miniature detection system based on magnetic particle imaging. To illustrate the effectiveness of the proposed method, a specific embodiment is provided below for detailed explanation of the above technical solution. The specific implementation steps are as follows:

[0070] On the one hand, the present invention provides a miniature detection system based on magnetic particle imaging, comprising: a signal acquisition module, a control module, a signal generation module, and a signal receiving module;

[0071] The signal acquisition module includes a receiving coil, a driving coil, and a permanent magnet;

[0072] The inner coil of the receiving coil is attached to the end of the limb being tested to collect the induced voltage signal emitted by the end of the limb. The driving coil is circumferentially arranged around the outer coil of the receiving coil, without contacting it, and is used to construct a driving field. The driving field is used to drive a point without a magnetic field through the end of the limb being tested, changing the magnetization intensity of magnetic particles near the point without a magnetic field. Imaging holes are provided at the upper and lower ends of the outer coil of the receiving coil. Figure 2 ;

[0073] The driving field is a sinusoidal excitation magnetic field or a pulsed square wave excitation magnetic field;

[0074] The permanent magnet is circumferentially connected to the outer ring of the drive coil and contacts the outer ring of the drive coil to create a selective field;

[0075] Furthermore, the selected field is a static gradient magnetic field, used to drive all magnetic particles except those near the field-free point until saturation is achieved; for example... Figure 2 ;

[0076] Preferably, the permanent magnet is a neodymium iron boron permanent magnet; the permanent magnet constitutes a static gradient magnetic field;

[0077] The driving coil is a Helmholtz coil, and the driving coil constitutes an excitation magnetic field;

[0078] Preferably, the ratio of the magnetic field strength of the static gradient magnetic field to that of the excitation magnetic field is 3-6:10-20;

[0079] Furthermore, the permanent magnet forms a static gradient magnetic field of 3-6 T / m, and the driving coil forms a sinusoidal excitation magnetic field or a pulsed square wave excitation magnetic field of 10-20 mT.

[0080] Furthermore, the permanent magnet forms a static gradient magnetic field of 4T / m, and the driving coil forms a sinusoidal excitation magnetic field of 15mT.

[0081] In the technical solution of this invention, a permanent magnet is set to form a static gradient magnetic field of 4T / m, and a driving coil is set to form a sinusoidal excitation magnetic field of 15mT, which significantly improves the effective signal of the magnetic field and further improves the signal quality and sensitivity of the receiving coil.

[0082] In one embodiment of the present invention, the object limb is the fingertip of a human body;

[0083] A cylindrical receiving coil is obtained by winding Litz wire around a coil frame using a forward and reverse winding method.

[0084] Furthermore, the cylindrical receiving coil has a diameter of 15mm and a height of 20mm;

[0085] The method of using forward and reverse winding involves winding the Litz wire 40 turns around the coil frame.

[0086] The present invention uses a forward and reverse winding method to wind Litz wire 40 turns on the coil frame. This winding method significantly reduces background noise while improving the signal-to-noise ratio and sensitivity.

[0087] The control module includes a microcontroller and an RGB display screen; it is used for system startup, interruption, real-time signal monitoring, and data storage.

[0088] One side of the microcontroller is connected to one side of the RGB display screen; the other side of the microcontroller is connected to the ADDA chip.

[0089] The signal generation module includes a digital-to-analog converter, a bandpass filter, and a power amplifier; one side of the digital-to-analog converter is connected to one side of the bandpass filter, and the other side of the bandpass filter is connected to one side of the power amplifier;

[0090] The signal generation module is used to generate a sinusoidal current or a pulsed square wave to apply a uniform excitation magnetic field to the drive coil.

[0091] The signal receiving module includes a low-noise amplifier, a band-stop filter, and an analog-to-digital converter; one side of the low-noise amplifier is connected to one side of the band-stop filter, and the other side of the band-stop filter is connected to one side of the analog-to-digital converter.

[0092] The signal receiving module is used to process and transmit the induced voltage signal collected by the receiving coil; the analog-to-digital converter outputs the induced voltage signal collected by the receiving coil as a digital signal.

[0093] Preferably, the permanent magnet is a neodymium iron boron permanent magnet; the permanent magnet constitutes a static gradient magnetic field;

[0094] The driving coil is a Helmholtz coil, and the driving coil constitutes a sinusoidal excitation magnetic field or a pulsed square wave excitation magnetic field;

[0095] In one embodiment of the present invention, the driving coil forms a sinusoidal excitation magnetic field, the receiving coil collects a nonlinear response voltage signal, the nonlinear response voltage signal is used to obtain the spatial resolution of magnetic particle imaging (MPI) based on the Langevin function in X space, the image is reconstructed based on the spatial resolution of the magnetic particle imaging (MPI), and the detection image of the sinusoidal excitation magnetic field is output.

[0096] In one embodiment of the present invention, the driving coil forms a pulsed square wave magnetic field, the receiving coil collects the induced voltage signal, and the induced voltage signal is analyzed and imaged using the inverse Laplace transform to obtain a detection image of the pulsed square wave magnetic field.

[0097] Furthermore, the expression for the detected image of the sinusoidal excitation magnetic field is:

[0098]

[0099] Where A(t) is the signal vector received by the sinusoidal excitation magnetic field at time t, t = 1, 2, 3…T, where T represents the total number of times; B1 is the sensitivity matrix; m is the magnetic moment of a single magnetic particle in the sinusoidal excitation magnetic field; n is the magnetic particle density when the instantaneous position is a point without a magnetic field; c(x) is the point spread function PSF, i.e., the real space convolution function, which is generated by dividing the slewing rate of the driving field by other constants, and x represents the actual spatial position vector; x s (t) represents the instantaneous position s of the point without magnetic field at time t, where s denotes instantaneous; G is the invertible gradient matrix; E sat The magnetic field vector required for saturation.

[0100] The spatial resolution expression for the magnetic particle imaging (MPI) is:

[0101]

[0102]

[0103] in, Let be the spatial resolution of the magnetic particle imaging at time t; Δx be the full width at half maximum (FWHM) of the point spread function matrix (PSF); Msat be the saturation magnetization of the magnetic particle; r be the diameter of the magnetic particle; and k be the magnetic particle diameter. B is Boltzmann constant, T is temperature, and μ0 is vacuum permeability.

[0104] The expression for the pulsed square wave magnetic field detection image is:

[0105]

[0106] Among them, M z(d) represents the magnetic field strength recovered by the magnetic particle, d represents the radius of the magnetic particle, δ represents the magnetic moment of the magnetic particle, L(·) represents the Langevin function, and W0 represents the amplitude of the flat phase of the magnetic field; W α W represents the magnetic field strength along the imaging aperture α direction. β α is the magnetic field strength in the direction of the imaging aperture β; α is the unit vector of the horizontal coordinate in space, and β is the unit vector of the vertical coordinate in space.

[0107] Preferably, the control module uses a ZYNQ-7010 control system as the microcontroller, which is connected to the signal generation module and the signal receiving module respectively to realize system startup, interruption, and data transmission and storage. An RGB LCD touchscreen is used to realize real-time monitoring of system signals, such as... Figure 3 .

[0108] Preferably, the signal receiving module uses an AD9280 chip to achieve analog-to-digital conversion, with a sampling rate of millions of times per second and a single sampling time of 5ms for the detection system.

[0109] On the other hand, based on the above detection system, the present invention provides a detection method based on magnetic particle imaging, comprising the following steps:

[0110] S1: Move the end of the object to be measured into the imaging aperture of the receiving coil;

[0111] S2: The control module sends a start signal, and the signal generation module processes the encoded digital signal through a digital-to-analog converter, a bandpass filter, and a power amplifier before outputting it to the drive coil, so that the drive coil is subjected to a uniform sinusoidal excitation magnetic field.

[0112] S3: In the sinusoidal excitation magnetic field, the imaging aperture acquires signals to obtain the original induced voltage signal. The original induced voltage signal is sequentially converted into a corresponding digital signal by the low-noise amplifier, band-stop filter and analog-to-digital converter of the signal receiving module, and the corresponding digital signal is input into the control module for data storage.

[0113] S4: Repeat steps S2-3 twice to obtain the digital signal corresponding to the original induced voltage signal each time, and input it into the control module for data storage;

[0114] The detection system is interrupted after the data storage contains three digital voltage signals.

[0115] S5: The digital signals corresponding to the three original induced voltage signals are reconstructed using X-space magnetic particle imaging (MPI) to output a detection image of the sinusoidal excitation magnetic field.

[0116] Another embodiment of the present invention further includes: S2: The control module sends a start signal, and the signal generation module processes the encoded digital signal through a digital-to-analog converter, a bandpass filter and a power amplifier and outputs it to the drive coil, so that a uniform pulse square wave excitation magnetic field is applied to the drive coil;

[0117] S3: In the pulsed square wave excitation magnetic field, the imaging aperture acquires signals to obtain the original induced voltage signal. The original induced voltage signal is sequentially converted into a corresponding digital signal by the low noise amplifier, band-stop filter and analog-to-digital converter of the signal receiving module, and the corresponding digital signal is input into the control module for data storage.

[0118] S4: Repeat steps S2-3 twice to obtain the digital signal corresponding to the original induced voltage signal each time, and input it into the control module for data storage;

[0119] The detection system is interrupted after the data storage contains three digital voltage signals.

[0120] S5: The digital signals corresponding to the three original induced voltage signals are analyzed and imaged using the inverse Laplace transform to obtain a detection image of the pulse square wave magnetic field.

[0121] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A miniature detection system based on magnetic particle imaging, characterized in that, include: Signal acquisition module, control module, signal generation module, and signal receiving module; The signal acquisition module includes a receiving coil, a driving coil, and a permanent magnet; the inner ring of the receiving coil is provided with an imaging hole that fits against the end of the limb being tested, for acquiring the induced voltage signal emitted by the end of the limb being tested; the driving coil is disposed on the outer ring of the receiving coil, for constructing a driving field; the permanent magnet is disposed on the outer ring of the driving coil, for constructing a selection field; the driving field is a sinusoidal excitation magnetic field or a pulsed square wave excitation magnetic field; The permanent magnet is used to construct a selection field; The control module is used for the system's startup, interruption, real-time signal monitoring, and data storage; The signal generation module is used to generate a sinusoidal current or a pulsed square wave to apply a uniform excitation magnetic field to the drive coil. The signal receiving module is used to process and transmit the induced voltage signal collected by the receiving coil; The expression for the detected image of the sinusoidal excitation magnetic field is: in, For a moment t The signal vector received by the sinusoidal excitation magnetic field, t =1,2,3… T , T Indicates the total number of moments; This is the sensitivity matrix; Let be the magnetic moment of a single magnetic particle in a sinusoidal excitation magnetic field; n be the magnetic particle density at the instantaneous position of a point without a magnetic field; and c(x) be the point spread function (PSF). Actual spatial position vector; For a moment t Instantaneous point without magnetic field s Location, s Indicates instantaneous time; It is an invertible gradient matrix; The magnetic field vector required for saturation; The expression for the pulsed square wave magnetic field detection image is: in, This represents the magnetic field strength recovered by the magnetic particles. d Indicates the radius of a magnetic particle. Let L(•) represent the magnetic moment of a magnetic particle, and let L(•) represent the Langevin function. w The independent variable of the Langevin function represents the energy ratio constant. W 0 represents the amplitude during the flat phase of the magnetic field; For imaging aperture Magnetic field strength in the direction, For imaging aperture Magnetic field strength in the direction; Let be the unit vector of the horizontal coordinate in space. The unit vector of the coordinates in the vertical direction of space.

2. The miniature detection system based on magnetic particle imaging according to claim 1, characterized in that, The permanent magnet is a neodymium iron boron permanent magnet; the permanent magnet forms a static gradient magnetic field; The driving coil is a Helmholtz coil, and the driving coil constitutes the excitation magnetic field.

3. A miniature detection system based on magnetic particle imaging according to claim 2, characterized in that, The ratio of the magnetic field strength of the static gradient magnetic field to that of the excitation magnetic field is 3-6:10-20.

4. A miniature detection system based on magnetic particle imaging according to claim 3, characterized in that, The permanent magnet forms a static gradient magnetic field of 3-6 T / m, and the driving coil forms a sinusoidal excitation magnetic field or a pulsed square wave excitation magnetic field of 10-20 mT.

5. A miniature detection system based on magnetic particle imaging according to claim 4, characterized in that, The driving coil forms a sinusoidal excitation magnetic field, and the receiving coil collects a nonlinear response voltage signal. The nonlinear response voltage signal is then used to obtain the spatial resolution of magnetic particle imaging (MPI) based on the Langevin function in X space. Based on the spatial resolution of the MPI, image reconstruction is performed, and the detection image of the sinusoidal excitation magnetic field is output.

6. A miniature detection system based on magnetic particle imaging according to claim 5, characterized in that, The driving coil forms a pulsed square wave magnetic field, and the receiving coil collects the induced voltage signal. The induced voltage signal is analyzed and imaged using the inverse Laplace transform to obtain a detection image of the pulsed square wave magnetic field.

7. A method for microscopic detection using the system according to any one of claims 1-6, characterized in that, include: S1: Move the end of the object to be measured into the imaging aperture of the receiving coil; S2: The control module sends a start signal, and the signal generation module processes the encoded digital signal through a digital-to-analog converter, a bandpass filter, and a power amplifier before outputting it to the drive coil, so that the drive coil is subjected to a uniform excitation magnetic field. S3: In the excitation magnetic field, the imaging aperture acquires signals to obtain the original induced voltage signal. The original induced voltage signal is sequentially converted into a corresponding digital signal by the signal receiving module, and the corresponding digital signal is input into the control module for data storage. S4: Repeat steps S2-3 multiple times to obtain the digital signal corresponding to the original induced voltage signal each time, and input it into the control module for data storage; The detection system is interrupted after the data storage contains multiple digital voltage signals. S5: The digital signals corresponding to the multiple original induced voltage signals are reconstructed by X-space magnetic particle imaging (MPI) or relaxed time analysis imaging is performed using inverse Laplace transform, and the detection image of the excitation magnetic field is output.

Images