CN114403842B

CN114403842B - Magnetic particle imaging equipment

Info

Publication number: CN114403842B
Application number: CN202210086820.1A
Authority: CN
Inventors: 李檀平; 贾广; 胡凯; 黄力宇; 苗启广; 张艺飞
Original assignee: Xi'an Tiance Zhinao Electronic Technology Co ltd
Current assignee: Xi'an Tiance Zhinao Electronic Technology Co ltd
Priority date: 2022-01-25
Filing date: 2022-01-25
Publication date: 2024-07-30
Anticipated expiration: 2042-01-25
Also published as: CN114403842A

Abstract

The invention discloses a magnetic particle imaging device, comprising: the signal generating unit is used for generating an induced voltage signal under the action of a nonlinear and non-uniform excitation magnetic field; the signal generating unit comprises an upper flat plate and a lower flat plate which are opposite; an exciting coil and a receiving coil are arranged in the upper flat plate and the lower flat plate; the driving scanning unit drives the exciting coil and the receiving coil in the upper and lower flat plates to do circular motion; each time the circular motion direction is opposite; each circular motion comprises a plurality of data acquisition points; the magnetic field excitation unit is used for applying the same alternating current to the excitation coils in the upper plate and the lower plate at each data acquisition point in each circular motion to generate a nonlinear and non-uniform excitation magnetic field; and the data acquisition and imaging unit is used for acquiring the induced voltage signals generated on the receiving coils of the upper plate and the lower plate at each data acquisition point in each circular motion so as to acquire target acquisition data and perform magnetic particle imaging. The invention realizes the magnetic particle imaging with low power consumption, large visual field and high resolution.

Description

Magnetic particle imaging equipment

Technical Field

The invention belongs to the technical field of medical imaging, and particularly relates to magnetic particle imaging equipment.

Background

In clinical diagnosis and detection, how to accurately and objectively locate tumors and other targets has been an international research hotspot and a challenging problem. The existing medical imaging technology such as electronic computed tomography (Computed Tomography, CT for short), magnetic resonance imaging (Magnetic Resonance Imaging, MRI for short), single photon emission computed tomography (Single-Photon Emission Computed Tomography, SPECT for short) and the like have the problems of large harm, poor positioning, low precision and the like. In recent years, a brand new imaging mode based on a tracer, and a magnetic particle imaging technology (MAGNETIC PARTICLE IMAGING, abbreviated as MPI) is proposed.

By using a tomography technology, MPI can accurately locate tumors or other targets by detecting the spatial concentration distribution of superparamagnetic iron oxide nanoparticles (SPIOs) harmless to human bodies, and has the characteristics of two/three-dimensional imaging, high space-time resolution and high sensitivity. Furthermore, MPI does not show anatomical structures and has no background signal interference, so the intensity of the signal is directly proportional to the concentration of the tracer, which is a new method with potential for medical applications. The magnetic core size of the magnetic particles is in the range of 10 nm-60 nm, and high-frequency harmonic signals are generated along with the change of an excitation magnetic field. The magnetic particle imaging generates a magnetic field free region through a selection field, the free region is moved through a focusing field, the excitation field excites magnetic particles in the free region, high-frequency harmonic signals emitted by the magnetic particles are collected through a receiving coil, and a spatial distribution image of the concentration of the magnetic particles in a human body is obtained through an image reconstruction algorithm. Existing magnetic particle imaging techniques require detection of magnetic particle concentration information at specific points or lines within the human body each time. In order to obtain a signal of a specific point or line, a gradient coil needs to be used to generate a small free magnetic field area, which may be a point area (free magnetic field point) or a line (free magnetic field line). The magnetic particles in the free region of the magnetic field can be excited by the excitation magnetic field to contribute to the signal, while the magnetic particles outside the free region of the magnetic field are bound by the strong magnetic field and cannot be excited by the excitation magnetic field to not contribute to the signal. The signal acquired each time only originates from a magnetic field free region at a specific position, and the signal intensity depends on the concentration of magnetic particles in the magnetic field free region. Magnetic particle imaging uses a point-by-point scanning or a line-by-line scanning mode for imaging. The change of position of the free region of the magnetic field is required by means of a focusing field or an excitation field, or by means of a mechanical movement. The locus of the magnetic field free region is usually a lissajous curve, and is generated by alternating magnetic fields in orthogonal directions. The lissajous curve covers the whole imaging field of view, and an image of the whole field of view is obtained through interpolation.

However, the existing magnetic particle imaging apparatus has the following problems:

(1) And the power consumption is large: the existing magnetic particle imaging equipment forms a magnetic field free region (point or line) in the middle of a selection field and a focusing field by constructing the selection field, and moves the magnetic field free region in the focusing field, so that the magnetic field free point is required to be small enough, the magnetic field free line is required to be thin enough, and large power consumption devices are required to generate enough current to generate a large gradient magnetic field.

(2) The spatial resolution is low: the image resolution of the current medical imaging scanning technology can basically reach 0.5mm, and the image resolution of the current magnetic particle imaging technology can only reach 5mm under the field of view of 20 cm.

(3) Reconstructing image blur: the relaxation effect of the magnetic particles causes a hysteresis and a delay in the movement of the free region of the magnetic field, resulting in blurring of the reconstructed image.

(4) The field of view is small: the imaging field size of the existing magnetic particle imaging technology is determined by a composite magnetic field formed by overlapping an excitation field and a selection field, and the ratio of the intensity of the excitation magnetic field and the gradient of the selection field is usually used as the imaging field. At present, magnetic particle imaging is mainly applied to mouse imaging, the imaging field of view is 1 cm-3 cm, the required excitation magnetic field intensity is 15 mT-30 mT, the scanning field of view of a human body is usually 20 cm-50 cm, and the high excitation magnetic field intensity is required, so that the imaging is difficult to realize.

(5) It is difficult to extend to clinical body scanning: in order to meet the magnetic particle imaging of human body size, a strong selection field and excitation field are required, resulting in large power consumption and very difficult realization. Meanwhile, the image space resolution of the existing magnetic particle imaging technology is too low or the visual field is too small, so that the requirements of clinical diagnosis are difficult to meet. All existing magnetic particle imaging techniques are difficult to extend to clinical body scanning.

Disclosure of Invention

In order to solve the above-mentioned problems in the prior art, the present invention provides a magnetic particle imaging apparatus. The technical problems to be solved by the invention are realized by the following technical scheme:

the embodiment of the invention provides a magnetic particle imaging device, which comprises a signal generating unit, a driving scanning unit, a magnetic field exciting unit and a data acquisition and imaging unit, wherein,

The signal generating unit is used for generating an induced voltage signal under the action of a nonlinear and non-uniform excitation magnetic field; the signal generating unit comprises an upper flat plate structure and a lower flat plate structure which are opposite in position, and an imaging target is positioned between the upper flat plate structure and the lower flat plate structure; the upper flat plate structure and the lower flat plate structure are respectively internally provided with an exciting coil and a receiving coil, the positions of the exciting coil and the receiving coil in the upper flat plate structure and the lower flat plate structure are opposite, and the positions of the two receiving coils are opposite;

The driving scanning unit respectively drives the exciting coil and the receiving coil in the upper flat plate structure and the lower flat plate structure to do one or more circular motions by taking the corresponding projection positions of the imaging target on the plane where the exciting coil and the receiving coil are located as the center; the circular movement directions of the exciting coil and the receiving coil in the upper flat plate structure and the lower flat plate structure are opposite each time; a plurality of data acquisition points are included in each circular motion process;

The magnetic field excitation unit is used for applying alternating current in the same direction to the excitation coils in the upper plate structure and the lower plate structure to generate different nonlinear and non-uniform excitation magnetic fields at each data acquisition point in each circular motion one or more times; the current amplitude applied by the exciting coil in the upper flat plate structure is gradually increased or decreased each time, and the current amplitude applied by the exciting coil in the lower flat plate structure is correspondingly gradually decreased or increased;

The data acquisition and imaging unit is used for respectively acquiring the induced voltage signals generated on the receiving coils in the upper flat plate structure and the lower flat plate structure at each data acquisition point in each circular motion so as to acquire corresponding target acquisition data, and performing magnetic particle imaging on the imaging target according to the target acquisition data.

The invention has the beneficial effects that:

The magnetic particle imaging equipment provided by the invention has the advantages that the exciting coils and the receiving coils in the upper plate structure and the lower plate structure move along different circumferences, each circumferential movement process comprises a plurality of data acquisition points, the current amplitude applied by the exciting coils in the upper plate structure is gradually increased or decreased at each data acquisition point, the current amplitude applied by the exciting coils in the corresponding lower plate structure is correspondingly gradually decreased or increased, and the generated nonlinear and non-uniform exciting magnetic field can be linearly decreased and then linearly increased along the axial components of the exciting coils and is distributed in a V shape.

Based on the nonlinear and nonuniform excitation magnetic field, the invention carries out nonlinear and nonuniform magnetic field excitation on magnetic particles in the whole space where an imaging target is located, all the magnetic particles in the whole space can contribute to the induction voltage on a receiving coil, a magnetic field free region is not required to be arranged, and the position of the magnetic field free region is not required to be changed; wherein the exciting coil and the receiving coil in the upper plate structure and the lower plate structure do one or more circular motions by taking the projection position of the imaging target on the plane where the exciting coil and the receiving coil are positioned as the center, applying different currents to the exciting coils in the upper flat plate structure and the lower flat plate structure, wherein the different currents are equivalent to the non-linear and non-uniform excitation of the exciting coils and the receiving coils in the upper flat plate structure and the lower flat plate structure in a plurality of different space postures and a plurality of different magnetic field distribution states; when the exciting coil and the receiving coil in the upper plate structure and the lower plate structure are in a certain space attitude, the current in the exciting coil is changed, so that the V-shaped magnetic field distribution is shifted in position along the axial direction of the exciting coil, and one-dimensional space coding is realized; when the exciting coil and the receiving coil in the upper plate structure and the lower plate structure are in different space attitudes, the magnetic field strength sensed by the magnetic particles at the same position is also different, so that two-dimensional full-space coding is realized.

Based on the scanning mode, the magnetic particle imaging equipment provided by the invention does not need to set a magnetic field free region for magnetic particle imaging; the position of the free region of the magnetic field is not required to be changed; the signals acquired each time are formed by superposing signals generated after all magnetic particles in the whole space are excited, and the imaging visual field is not limited by the size of a free region and the moving range of a magnetic field as in the prior art, so that the imaging visual field can be matched with the size of a human body. Moreover, the coil required for constructing the gradient field and the power consumption consumed correspondingly can be omitted without arranging a magnetic field free region, and the equipment scale and the power consumption are reduced.

In addition, compared with the mode of almost taking the resolution of an imaging image as a step to execute scanning in the prior art, the scanning step related in the invention comprises the step of current amplitude adjustment and the step between adjacent data acquisition points in circular motion, the scanning time required for executing scanning based on the step is far smaller than that of the prior art, the timeliness is higher, the relaxation effect of magnetic particles can be effectively lightened, the imaging result is clearer, and the imaging of the magnetic particles with high resolution is realized.

In summary, the present invention does not need to use the selection field and the focusing field in the existing magnetic particle imaging technology, and each point in the whole imaging space is a free region of the magnetic field and can be excited by the magnetic field, i.e. the signals acquired each time are overlapped by the signals of the magnetic nanoparticles at all points in the whole space. The magnetic particle concentration distribution image of the imaging target is reconstructed by carrying out space coding on the whole space, so that the magnetic particle imaging with low power consumption, large visual field and high resolution is realized. Such a low power, large field of view, high resolution magnetic particle imaging device can be extended to clinical body scanning.

The present invention will be described in further detail with reference to the accompanying drawings and examples.

Drawings

FIG. 1 is a schematic diagram of a magnetic particle imaging apparatus according to an embodiment of the present invention;

Fig. 2 is a schematic diagram of a signal generating unit according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a data acquisition and imaging unit in a magnetic particle imaging apparatus according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of another data acquisition and imaging unit in a magnetic particle imaging apparatus according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a signal correction subunit in a data acquisition and imaging unit according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a further data acquisition and imaging unit in a magnetic particle imaging apparatus according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of the effect of the relaxation convolution correction process provided by the embodiment of the present invention;

FIG. 8 is a schematic structural diagram of an imaging target carrying device in a magnetic particle imaging apparatus according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of a system matrix according to an embodiment of the present invention;

Fig. 10a to 10c are schematic diagrams of two-dimensional magnetic particle concentration space reconstruction effects corresponding to image reconstruction under three conditions by using the magnetic particle imaging apparatus provided by the embodiment of the present invention.

Reference numerals illustrate:

A 10-signal generating unit; 20-driving a scanning unit; 30-a magnetic field excitation unit; 40-a data acquisition and imaging unit; 101-an upper plate structure; 102-a lower plate structure; 103-a fixed support; 104-exciting the coil; 105-receiving coils; 401-a signal processing subunit; 402-a signal feature extraction subunit; 403-a one-dimensional data reconstruction subunit; 404-a two-dimensional data reconstruction subunit; 405-a signal corrector subunit; 406-relaxation deconvolution subunits; 4051-a first signal correction module; 4052—a magnetic field correction module; 4053-a second signal correction module.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but embodiments of the present invention are not limited thereto.

Example 1

In order to solve the problems of large power consumption, low spatial resolution, blurred reconstructed image, small field of view, difficulty in expanding to clinical human body scanning and the like of the conventional magnetic particle imaging device, referring to fig. 1, an embodiment of the present invention provides a magnetic particle imaging device, which includes: a signal generating unit 10, a driving scanning unit 20, a magnetic field exciting unit 30, and a data acquisition and imaging unit 40, wherein,

A signal generating unit 10 for generating an induced voltage signal under the action of a non-linear, non-uniform excitation magnetic field; the signal generating unit 10 includes an upper plate structure 101 and a lower plate structure 102 which are opposite in position, with an imaging target located between the upper plate structure 101 and the lower plate structure 102; the upper plate structure 101 and the lower plate structure 102 are respectively internally provided with an exciting coil 104 and a receiving coil 105, the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 are opposite, and the positions of the two receiving coils 105 are opposite;

The scanning unit 20 is driven to drive the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 respectively, and the imaging target performs one or more circular motions with the corresponding projection positions of the planes of the exciting coil 104 and the receiving coil 105 as the center; each time the circumferential movement directions of the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 are opposite; a plurality of data acquisition points are included in each circular motion process;

A magnetic field excitation unit 30 for applying an alternating current in the same direction to the excitation coils 104 in the upper plate structure 101 and the lower plate structure 102, respectively, one or more times at each data acquisition point in each circular motion to generate different nonlinear, non-uniform excitation magnetic fields; wherein, each time the current amplitude applied by the exciting coil 104 in the upper plate structure 101 is gradually increased or decreased, the current amplitude applied by the exciting coil 104 in the lower plate structure 102 is correspondingly gradually decreased or increased;

The data acquisition and imaging unit 40 is configured to acquire the induced voltage signals generated on the receiving coils 105 in the upper plate structure 101 and the lower plate structure 102 at each data acquisition point in each circular motion, respectively, so as to acquire corresponding target acquisition data, and perform magnetic particle imaging on the imaging target according to the target acquisition data.

Next, embodiments of the present invention will be described in detail with respect to each of the above units.

As can be seen from the above, the conventional magnetic particle imaging apparatus forms a free region (dot or line) of a magnetic field in the middle of a selection field by constructing the selection field and a focusing field, and moves the free region of the magnetic field by changing the size of the focusing field to realize, for example, a point-by-point scan. However, in order to improve the image resolution, the magnetic particle imaging mode through selecting a field and a focusing field needs to have a sufficiently small magnetic field free point and a sufficiently thin magnetic field free line, so that a large power consumption device is needed to generate a sufficiently large current to generate a large gradient magnetic field, and the power consumption problem is brought, so that the magnetic particle imaging is more difficult to expand to clinical human body scanning. Based on this problem, the embodiment of the present invention proposes a mode of co-acting by the signal generating unit 10, the driving scanning unit 20, and the magnetic field exciting unit 30 to generate a non-linear and non-uniform exciting magnetic field, under the effect of which an induced voltage signal can be generated without constructing a selection field and a focusing field and taking any point in space as a free region of the magnetic field. Specifically:

The signal generating unit 10 includes an upper plate structure 101 and a lower plate structure 102 which are opposite in position, with an imaging target located between the upper plate structure 101 and the lower plate structure 102; the upper plate structure 101 and the lower plate structure 102 are respectively internally provided with an exciting coil 104 and a receiving coil 105, the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 are opposite, and the positions of the two receiving coils 105 are opposite. The exciting coil 104 is used for generating a nonlinear and non-uniform exciting magnetic field under the action of the magnetic field exciting unit 30; the receiving coil 105 is used for receiving the magnetic flux change caused by the magnetization response of the magnetic nanoparticles under the action of a nonlinear and non-uniform excitation magnetic field, and generating corresponding induced voltage signals for magnetic particle imaging. Wherein the imaging target carries magnetic particles.

Referring to fig. 2, a schematic diagram of a signal generating unit 10 is shown in an exemplary embodiment of the present invention: the upper plate structure 101 and the lower plate structure 102 are cylindrical plates; excitation coil 104 and receiving coil 105 within corresponding upper plate structure 101 and lower plate structure 102: the excitation coil 104 comprises a circular Huo Mhuo-z coil and the receiving coil 105 comprises a circular Huo Mhuo-z coil. The upper plate structure 101 and the lower plate structure 102 according to the embodiment of the present invention may be fixed in position by a fixing support 103, as shown in fig. 2, but are not limited to being fixed by the fixing support 103, and are not limited to being fixedly arranged, and the positions of the upper plate structure 101 and the lower plate structure 102 in the horizontal or vertical direction may be adjusted by a mechanical control manner.

The signal generating unit 10 according to the embodiment of the present invention generates a signal including a plurality of induced voltage signals generated by a plurality of nonlinear, non-uniform excitation magnetic fields. In the process of generating signals, the driving scanning unit 20 drives the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 respectively, one or more circular motions are performed by taking the projection positions of the imaging target on the plane corresponding to the exciting coil 104 and the receiving coil 105 as the center, the multiple circular motions form spiral movements from inside to outside, and each movement is equivalent to regulating and controlling the spatial postures of the exciting coil 20 and the receiving coil 30. Each time the corresponding upper plate structure 101 and the lower plate structure 102 have opposite circular motion directions of the exciting coil 104 and the receiving coil 105, for example, the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 perform spiral movement from inside to outside anticlockwise, and the exciting coil 104 and the receiving coil 105 in the lower plate structure 102 perform spiral movement from inside to outside clockwise. Multiple data acquisition points are included during each circular motion. For example, the upper plate structure 101 moves circumferentially 256 times, and 256 data acquisition points are formed in each circumferential movement, so that the upper plate structure 101 can form 256 x 256 data acquisition points, different nonlinear and non-uniform excitation magnetic fields act on each data acquisition point, the corresponding lower plate structure 102 moves circumferentially 256 times, and 256 data acquisition points are formed in each circumferential movement, so that the lower plate structure 102 can form 256 x 256 data acquisition points, and different nonlinear and non-uniform excitation magnetic fields act on each data acquisition point.

The driving scanning unit 20 according to the embodiment of the present invention may be respectively built in the upper plate structure 101 and the lower plate structure 102; the exciting coil 104 and the receiving coil 105 in the corresponding upper plate structure 101 and lower plate structure 102 are respectively fixed on the driving scanning unit 20, and the driving scanning unit 20 respectively drives the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 to do one or more circular motions with the projection position as a center point. The driving scanning unit 20 may also be electrically connected to the upper plate structure 101 and the lower plate structure 102 independently, which may also achieve that the driving scanning unit 20 drives the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 to do one or more circular motions with the projection position as the center point.

The driving scan unit 20 according to an embodiment of the present invention may include: a hardware driving module and a software control module; the hardware driving module drives the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 to do one or more circular motions by taking the projection position as a center point under the control of the software control module.

In practical applications, the software control module may be a control program running on a computer; the hardware drive module may include a rotary instrument and an electrical drive unit that may drive the rotary instrument for movement and that is electrically connected to the software control module. The rotary apparatus may include a mechanical arm and a mechanical structure for fixing the positions of the exciting coil 104 and the receiving coil 105, where the mechanical structure is driven by the mechanical arm to move. In the embodiment of the present invention, a computer integrated in the magnetic particle imaging apparatus may be referred to as a central control computer, and functions implemented by the central control computer are not limited to the software control modules described herein, and will be described one by one.

Whereas for the structural features of the signal generating unit 10, a non-linear, non-uniform excitation magnetic field acting at each data acquisition point is generated by the magnetic field excitation unit 30, specifically:

When the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 are in a certain spatial posture, alternating current in the same direction is applied to the exciting coil 104 in the upper plate structure 101 and the lower plate structure 102 one or more times at each data acquisition point in each circular motion respectively to generate a nonlinear and non-uniform exciting magnetic field; each time the amplitude of the current applied by the excitation coil 104 in the upper plate structure 101 is stepped up or down, the amplitude of the current applied by the excitation coil 104 in the lower plate structure 102 is correspondingly stepped down or up. For each data acquisition point, when the same-directional alternating current is respectively applied to the exciting coils 104, the axial components of the exciting magnetic field generated between the exciting coils 104 of the upper plate structure 101 and the lower plate structure 102 will all present a V-shaped distribution state that the axial components of the exciting coils 104 are linearly reduced and then linearly increased, or a V-shaped distribution state that the axial components of the exciting magnetic field are linearly increased and then linearly reduced, and then the V-shaped distribution and the V-shaped distribution are collectively called as V-shaped distribution, so that the magnetic field distribution is shifted in position along the axial direction of the exciting coils 20, thereby realizing one-dimensional space coding.

When the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 are in different spatial attitudes, the magnetic field strength sensed by the magnetic particles at the same position is also different, thereby realizing two-dimensional full-space encoding.

The current applied by the magnetic field excitation unit 30 is preferably, but not limited to, a cosine-oscillating alternating current. At this time, since the curve of the magnetic field strength with the applied magnetic field is a symmetrical curve, only half a period of scanning is required. For example, the alternating current applied by the embodiment of the invention is cosine-oscillating alternating current, and each time the current amplitude is adjusted, the alternating current is subjected to half of a cosine oscillation period. It is understood that the cosine oscillation period refers to an oscillation period of the cosine alternating current, and the current amplitude refers to a maximum value of the alternating current in the oscillation period.

And each plane perpendicular to the axial direction of the excitation coil 104 is an equipotential surface. Further, by increasing or decreasing the current of the excitation coil 104 in the upper plate structure 101 while decreasing or increasing the current of the excitation coil 104 in the lower plate structure 102, the "V" -shaped magnetic field distribution causes a positional shift in the axial direction of the excitation coil 104, whereby one-dimensional to two-dimensional spatial encoding can be achieved.

Meanwhile, for each data acquisition point, the embodiment of the present invention applies the same-directional alternating current to the exciting coils 104 in the upper plate structure 101 and the lower plate structure 102 for multiple times to generate nonlinear and non-uniform exciting magnetic fields, for example, 256 different same-directional alternating currents are applied to each data acquisition point, so that the exciting coils 104 in the upper plate structure 101 and the lower plate structure 102 generate 256×256 nonlinear and non-uniform exciting magnetic fields respectively, and generate 256×256 induction voltage signals under the action of each nonlinear and non-uniform exciting magnetic field. 256×256 induced voltage signals generated by the upper plate structure 101 and the lower plate structure 102 are used for image reconstruction.

In practice, the current excitation means 30 may be a digital ac power supply. The digital ac power source may be integrated with a communication interface to communicate with the central control computer via a communication bus to apply various magnitudes of current to the excitation coil 104 under the control of the central control computer. In another implementation, the current excitation device 30 may include a waveform generator and its corresponding front-end controller, the waveform generator applying various magnitudes of current to the excitation coil 104 under the control of the front-end controller. It will be appreciated that the front end controller is also under the control of the central control computer. Specifically, the waveform generator is used for increasing the voltage of the commercial power, rectifying the increased alternating voltage into direct current, and then obtaining alternating current at a specific frequency through frequency conversion, wherein the specific frequency is preferably 3.0 KHz-35 KHz. The front-end controller pre-drives a scanning sequence issued by the central control computer, and then power drives the scanning sequence; the power drive mainly distributes current to the exciting coil under the high voltage control of the variable frequency output. In addition, the magnitude of the current applied to the excitation coil 104 may be fed back to the pre-drive by a feedback loop, thereby forming a closed loop control.

Compared with the existing magnetic particle imaging technology, the embodiment of the invention can realize non-linear and non-uniform magnetic field excitation on the magnetic particles in the whole space of the imaging target by adopting the mode of coacting the flat plate structure 10, the driving scanning unit 20 and the magnetic field excitation unit 30 only at certain positions opposite to the imaging target, and signals generated after excitation are superposed to form an induced voltage signal generated by the receiving coil 102 without setting a magnetic field free region.

After the signal generating unit 10, the driving scanning unit 20 and the magnetic field exciting unit 30 jointly act to generate induced voltage signals, the data acquisition and imaging unit 40 respectively acquires the induced voltage signals generated on the receiving coils 105 in the upper plate structure 101 and the lower plate structure 102 at each data acquisition point in each circular motion so as to acquire corresponding target acquisition data, and performs magnetic particle imaging on an imaging target according to the target acquisition data. Referring to fig. 3, the data acquisition and imaging unit 40 according to the embodiment of the present invention includes a signal processing subunit 401, a signal feature extraction subunit 402, a one-dimensional data reconstruction subunit 403, and a two-dimensional data reconstruction subunit 404, specifically:

The signal processing subunit 401 is configured to perform analog-to-digital conversion processing on the induced voltage signals generated on the receiving coils 105 in the upper plate structure 101 and the lower plate structure 102 for each data acquisition point in each circular motion, respectively. The analog-to-digital conversion processing of the generated sensing signal includes an analog signal processing section and a digital signal processing section: the analog signal processing section includes sequentially performing low noise amplification processing, reception mixing processing, high frequency filtering processing, low frequency filtering processing, and ADC conversion processing on the induced voltage signal generated on the reception coil 105; the digital signal processing section includes performing fourier transform processing, spectrum analysis processing, and fundamental frequency reduction processing on the signal output from the analog signal processing section in order to complete analog-to-digital conversion processing of the final signal processing subunit 401. Wherein, each process in the analog signal processing part and the digital signal processing part is a relatively conventional signal processing mode, and will not be described in detail herein.

A signal feature extraction subunit 402, configured to extract corresponding target acquisition data from the induced voltage signal after the analog-to-digital conversion processing; the target acquisition data includes peak amplitude or 3 times fundamental harmonic components of the signal. The embodiment of the invention prefers that the peak amplitude or 3 times fundamental frequency harmonic component of the signal is used for reconstructing an image, and the theoretical basis on which the magnetic particle imaging is realized based on the peak amplitude or 3 times fundamental frequency harmonic component of the signal is as follows: the shape and size of the magnetization curve are also different according to the magnitude of the excitation magnetic field intensity, and the shape and size of the signal peak are also different. Taking the example of the alternating current applied by the magnetic field excitation unit 30 as cosine oscillation, the inventor finds that the signal peak u _peak generated by the magnetic particles under excitation thereof is proportional to the intensity a of the excitation magnetic field, is proportional to the concentration c of the magnetic particles, and the 3-times fundamental frequency harmonic component u ₃ is in a nonlinear relation with the intensity a of the excitation magnetic field, and is proportional to the concentration c of the magnetic particles, using an excitation magnetic field H (t) = -Acos (2pi ft) corresponding to the cosine oscillation alternating current. Equation (1) and equation (2) show a simple demonstration of this theoretical basis:

Where u _peak(i_n) represents the peak amplitude of the corresponding signal when current i _n is applied, N represents the number of data sampling points in the imaging region, f represents the frequency, m represents the magnetic moment of a single magnetic particle, μ ₀ represents the vacuum permeability, K _B denotes the boltzmann constant, T ^P denotes the absolute temperature of the imaging target, Δv denotes the volume size of the voxels of the data sample points, a (i _n,r_n) denotes the excitation magnetic field strength at the r _n th data sample point of the imaging region under the action of a corresponding non-linear, non-uniform excitation magnetic field when a current i _n is applied, s (r _n) denotes the spatial sensitivity of the r _n th data sample point receiving coil 105 in the imaging region, c (r _n) denotes the magnetic particle concentration at the r _n th data sample point in the imaging region, g (i _n,r_n) denotes the component of the target acquisition data of the generated signal at the r _n th data sample point of the imaging region under the action of a corresponding non-linear, non-uniform excitation magnetic field when a current i _n is applied.

Where u ₃(i_n) represents the 3-fold fundamental frequency harmonic component of the corresponding signal when current i _n is applied, Δv represents the volume size of the voxel of the data sample point, f (a (i _n,r_n)) represents the frequency corresponding to the excitation magnetic field of the data sample point at the r _n th data sample point in the imaging region under the action of the corresponding nonlinear, nonuniform excitation magnetic field when current i _n is applied, s (r _n) represents the spatial sensitivity corresponding to the r _n th data sample point receiving coil in the imaging region, c (r _n) represents the concentration of the magnetic particles at the r _n th data sample point in the imaging region, g (i _n,r_n) represents the component of the target acquisition data of the generated signal distributed at the r _n th data sample point in the imaging region under the action of the corresponding nonlinear, nonuniform excitation magnetic field when current i _n is applied.

Therefore, the peak amplitude of the signal and the 3 times fundamental frequency harmonic component are determined by the magnetic field intensity A and the magnetic particle concentration c together, so that the embodiment of the invention can select the peak amplitude of the signal or the 3 times fundamental frequency harmonic component to be used for one-dimensional data reconstruction, and can also select the peak amplitude of the signal and the 3 times fundamental frequency harmonic component to be used for one-dimensional data reconstruction together.

The one-dimensional data reconstruction subunit 403 is configured to reconstruct one-dimensional magnetic particle concentration spatial distribution data of the corresponding data acquisition point in each circular motion according to the peak amplitude and/or the 3 times fundamental frequency harmonic component of the signal and the system matrix. The system matrix is used for representing the spatial distribution corresponding to the target acquisition data of signals generated by magnetic particles with unit concentration under the action of a nonlinear and non-uniform excitation magnetic field. In the embodiment of the invention, in one-dimensional data reconstruction, the peak amplitude and/or 3 times fundamental frequency harmonic component of a signal related to the magnetic particle concentration c are utilized for data reconstruction. The specific data reconstruction process can be represented by the following formula:

c＝g^-1u (3)

In the formula (3), I ₀,i₁,…,i_N+1 denotes currents of N different magnitudes applied to the excitation coils 104 in the upper and lower plate structures 101 and 102, and r ₀,r₁,…,r_N+1 denotes N data sampling points dividing an imaging region where an imaging target is located. Where u represents the target acquisition data corresponding to each data acquisition point in each circular motion, where element u (i _n) represents the target acquisition data acquired upon application of current i _k to the excitation coil 104, the meaning of the remaining elements, and so on. Because the target acquisition data of the embodiment of the invention comprises peak amplitude and/or 3 times fundamental frequency harmonic component of the signal, in the corresponding one-dimensional data reconstruction, when the peak amplitude of the signal is adopted for reconstruction, the value of u (i _n) is u _peak(i_n corresponding to the formula (1), and when the 3 times fundamental frequency harmonic component of the signal is adopted for reconstruction, the value of u (i _n) is u ₃(i_n corresponding to the formula (2); g represents a system matrix, which is a known quantity, wherein g (i _n,r_n) represents components of target acquisition data of generated signals distributed at r _n data sampling points of an imaging region under the action of a corresponding nonlinear and non-uniform excitation magnetic field of magnetic particles with unit concentration when current i _n is applied, the meaning of the remaining elements is the same; c represents the reconstructed one-dimensional magnetic particle concentration spatial distribution data, wherein each element contained in the reconstructed one-dimensional magnetic particle concentration spatial distribution data is the magnetic particle concentration at each data sampling point in the imaging region, and c (r _n) represents the magnetic particle concentration at the r _n data sampling point in the imaging region.

In practical application, if the system matrix g is not very large, the reconstruction of the magnetic particle concentration c can be directly realized by performing inversion on the system matrix g and then performing multiplication on the inverted system matrix g ^-1 and the target acquisition data u according to the formula (3). If the system matrix g is huge and direct inversion is difficult, the elements in the magnetic particle concentration c can be used as the variable x to be solved, and a set of equations u(i_n)＝g(i_n,r₀)x+g(i_n,r₁)x+…+g(i_n,r₁)x,n∈[0,N-1], are constructed and solved in an iterative mode, so that the reconstruction of the magnetic particle concentration c is realized according to a solving result. Among them, iterative methods such as common algebraic reconstruction, joint algebraic reconstruction, maximum likelihood expectation maximization algorithm or ordered subset expectation maximization algorithm, etc.

And when imaging is carried out by utilizing peak amplitude and 3 times fundamental frequency harmonic components, respectively adopting a formula (3) for imaging, and fusing the two obtained imaging results. Specifically, each time target acquisition data is extracted from the induced voltage signal, the peak amplitude and 3 times fundamental frequency harmonic component of the signal are extracted. And then imaging by using peak amplitude and 3 times fundamental frequency harmonic components of the signals respectively to obtain two imaging results. Then, the two imaging results are fused, namely, the two imaging images are fused, so that the reconstruction effect is further improved. Specific image fusion methods may include weighted fusion of pixels at the same position between images, other commonly used image fusion methods, and the like.

It should be noted that, the existing magnetic particle imaging (MAGNETIC PARTICLE IMAGING, abbreviated as MPI) system also uses a system matrix to perform magnetic particle imaging, but is different from the system matrix proposed in the embodiment of the present invention: each element in a system matrix adopted by the existing magnetic particle imaging system comprises a group of Fourier components of signals generated by a magnetic particle sample with known concentration at a certain data sampling point in an imaging area, namely, subharmonics of the signals generated at the data sampling point; in the embodiment of the invention, each element of the system matrix is the peak amplitude and/or 3 times fundamental frequency harmonic component of a signal generated by magnetic particles with unit concentration at a certain data sampling point in an imaging area, which is different from the system matrix adopted by the existing MPI system.

A two-dimensional data reconstruction subunit 404, configured to reconstruct two-dimensional magnetic particle concentration spatial distribution data of the imaging target according to the one-dimensional spatial distribution data of each data acquisition point in each circular motion by using a filtered back projection method. Among them, the method of filtered back projection reconstruction is commonly used in CT imaging reconstruction, and the mathematical principle behind the method is Ladong transformation. The method for reconstructing the magnetic particle concentration distribution image by using the filtered back projection reconstruction method in the embodiment of the invention is basically the same as the method, so that the description is not repeated here.

In order to further improve the magnetic particle imaging accuracy, the embodiment of the present invention firstly performs correction processing on the signal before performing feature extraction, and adds a signal correction subunit 405, referring to fig. 4, the data acquisition and imaging unit 40 further includes a signal correction subunit 405; a signal corrector unit 405 for performing correction processing on the induced voltage signal after the analog-to-digital conversion processing. The inventors have found in the course of implementing the present invention that correction can be performed using the signal peak area and full width at half maximum information included in the target acquisition data. Specifically:

When the target acquisition data includes a signal peak area of the signal, referring to fig. 5, the signal correction subunit 405 includes a first signal correction module 4051, and the first signal correction module 4051 is configured to correct a peak amplitude and a full width at half maximum of the signal in the target acquisition data according to the signal area. The inventors analyzed that the signal peak area of the signal was independent of the magnetic field strength and was proportional to the magnetic particle concentration. Therefore, the peak area of the signal acquired each time is actually a conservation amount, provided that the concentration distribution of the magnetic particles of the imaging target remains unchanged, in the process of applying different current amplitudes to a single data acquisition point or in the process of changing the data acquisition point and even changing the circular motion. Considering that the magnetic particle concentration distribution of the actual imaging target is unchanged in a short time and possibly changed in a long time, the first signal correction module 4051 of the embodiment of the invention corrects the target acquisition data according to the signal peak area by taking the data acquisition point as a unit, so that the finally extracted target acquisition data can be better and more accurate.

The area of the peak value of the extracted signal specifically refers to the area under the time domain curve of the signal, and the integration processing can be performed on the data acquired in the time domain. Specifically: at each data acquisition point, acquiring a signal once when the current amplitude is changed once, and extracting the signal peak area of the signal; after the current amplitude adjustment process is finished, namely the scanning on the stop data acquisition point is finished, comparing the signal areas of all acquired signals, finding possible anomalies in the intangible magnetic field through the comparison result, and correcting the signals with the anomalies in the signal areas in various specific correction modes. For example, the current corresponding to the signal may be reapplied to the excitation coil 104, thereby re-acquiring; or correcting the abnormal signal by using signals adjacent in acquisition time, and the like.

When the target acquisition data further includes a full width half maximum of the signal, referring to fig. 5 again, the signal correction subunit 405 according to the embodiment of the present invention further includes a magnetic field correction module 4052 and a second signal correction module 4053, where the magnetic field correction module 4052 is configured to correct the nonlinear and non-uniform excitation magnetic field according to the full width half maximum of the signal; the second signal correction module 4053 is configured to correct the peak amplitude and the full width at half maximum of the signal in the target acquired data according to the full width at half maximum of the signal under the effect of the corrected nonlinear and non-uniform excitation magnetic field. The inventor finds that the full width at half maximum of the signal is irrelevant to the concentration of magnetic particles in the process of realizing the invention, but is inversely related to the strength of the excitation magnetic field; therefore, by uniformly comparing the full widths at half maximum of all the signals actually acquired, the stability of the excitation magnetic field can be checked according to the comparison result, and possible anomalies in the intangible magnetic field can be found out so as to ensure that the data on which the final reconstructed image depends are true and effective.

The full width at half maximum refers to the width of the corresponding time domain when the amplitude of the signal drops to half. Considering that the comparison efficiency is low in the unified comparison of the full width at half maximum of the signals acquired in the whole scanning process, the second signal correction module 4053 in the embodiment of the invention adopts a scheme of performing full width at half maximum comparison by taking the data acquisition points as units, and particularly, at each data acquisition point, the signal is acquired once when the current amplitude is converted once, and the full width at half maximum of the signal is extracted; when the current amplitude adjustment process is finished, namely after the scanning on the data acquisition point is finished, comparing the full width at half maximum of all acquired signals, and finding abnormal full width at half maximum from the full width at half maximum, thereby finding possible abnormality in the intangible magnetic field. For the found abnormal magnetic field condition, the position of the exciting coil 104 is corrected by the magnetic field correction module 4052, so that the accurate change of the exciting magnetic field is ensured, and the target acquisition data is corrected according to the full width at half maximum of the signal under the action of the corrected exciting magnetic field, so that the finally extracted target acquisition data can be more accurate.

The second signal correction module 4053 of the embodiment of the present invention is further configured to correct the system matrix according to the corrected nonlinear and non-uniform excitation magnetic field; the corrected system matrix is used for representing the spatial distribution corresponding to the target acquisition data of signals generated by the magnetic particles with unit concentration under the action of the corrected nonlinear and non-uniform excitation magnetic field. The system matrix of the embodiment of the invention is a spatial distribution corresponding to target acquisition data of signals generated by magnetic particles with unit concentration under the action of a nonlinear and non-uniform excitation magnetic field, which is obtained in advance through experiments, when the magnetic field is abnormal, the nonlinear and non-uniform excitation magnetic field is corrected, the corrected system matrix is measured in real time according to the corrected nonlinear and non-uniform excitation magnetic field, the data reconstruction is carried out according to the corrected system matrix, and the accuracy of the data reconstruction is improved.

Further, referring to fig. 6, the data acquisition and imaging unit 40 further includes a relaxation deconvolution subunit 406 according to an embodiment of the present invention; a relaxation deconvolution subunit 406, configured to perform deconvolution correction processing on the analog-to-digital conversion processed induced voltage signal under the effect of the corrected nonlinear and inhomogeneous excitation magnetic field; the signal corrector 405 is further configured to perform correction processing on the induced voltage signal after the deconvolution correction processing. Referring to fig. 7, signal degradation is typically caused by relaxation effects during data reconstruction. In the embodiment of the present invention, deconvolution processing is performed on the target acquired data by using the relaxation effect deconvolution subunit 406, so as to alleviate signal deformation caused by the relaxation effect of the magnetic particles, where the specific deformation mainly includes reduction of signal amplitude, and stretching, asymmetry, etc. of the time domain, as indicated by the circle in fig. 7. Through deconvolution operation, the target acquired data can be corrected, signal degradation is reduced, and finally extracted target features can be better and more accurate. After the deconvolution correction processing, the relevant correction and feature extraction processing is performed.

In practical applications, large-sized (30 nm to 100 nm) magnetic particles are more prone to relaxation effects, and therefore, if the magnetic particle size in the imaging target is large, signal deformation can be mitigated by adding the relaxation effect deconvolution subunit 406.

In practical applications, the data acquisition and imaging unit 40 may be a data acquisition device including an Analog-to-Digital Converter (ADC) integrated with an image imaging processing program module running on a central control computer. It should be understood that the central control computer in the embodiment of the present invention is not limited to a single entity computer, and in practice, the program modules for implementing the image imaging process and implementing the coil control, the current control, etc. may be integrated or divided according to the computing capability of the entity computer, which is not limited by the embodiment of the present invention.

In a medical application scenario, the central control computer of the magnetic particle imaging device provided by the embodiment of the invention can also be in interconnection communication with a radiology information system (Radiography Information System, RIS) and an image archiving and communication system (Picture ARCHIVE AND Communication System, PACS) through a DIGITAL IMAGING AND communication IN MEDICINE (DICOM) interface. The magnetic particle imaging device can be directly connected with a laser camera through a DICOM interface, so that a magnetic particle imaging result is subjected to laser printing.

Further, referring to fig. 8, the magnetic particle imaging apparatus according to the embodiment of the present invention further includes an imaging target carrying device for carrying an imaging target; a plurality of rectangular shielding coils are arranged in parallel in the imaging target bearing device; when the magnetic particle imaging equipment works, the shielding coils corresponding to the position of the imaging target are closed, and the rest shielding coils are electrified and opened. As shown in fig. 8, the thickened coil is a central region shielding coil corresponding to the imaging target, and the other coils are peripheral region shielding coils.

Here, the shielding coil has a main function of reducing external interference. For example, when the magnetic particle device is located in an environment where shielding effects are poor, opening the shielding coil may effectively saturate magnetic particles present in areas other than the non-imaging area such that only magnetic particles located within the imaging area are excited by the excitation coil 104. For example, when the magnetic particle imaging apparatus is used for scanning imaging of a human body, the imaging target carrier may be an examination couch. In addition, when the magnetic particle imaging apparatus is used for scanning imaging of an imaging target having an irregular shape, the imaging target carrying device may further include a structure for holding or fixing the imaging target. In practical application, the switch control of the shielding coil can be controlled independently, and linkage control can be realized through a central control computer and a scanning process.

When the output magnetic field is abnormal, a prompt device such as a display device and a sound alarm device can be included. Generally, the occurrence of magnetic field anomalies may be related to external disturbances; after the magnetic field abnormality is found, higher shielding measures such as opening shielding coils outside the imaging area can be adopted, the determination of the system matrix is carried out again, and then scanning imaging is carried out again.

In order to verify the effectiveness of the magnetic particle imaging apparatus proposed by the embodiments of the present invention, the following experiments are explained.

The exciting coils 104 in the upper plate structure 101 and the lower plate structure 102 are composed of a circular Huo Mhuo-inch coil, the diameter of each exciting coil 104 is 40cm, the thickness and the width are 5cm, the number of turns of each exciting coil 104 is 200 turns, the distance between the two exciting coils 104 is 50cm, a cosine alternating current in the same direction is applied, a cosine alternating magnetic field of 15 mT-30 mT is generated in an imaging target area, the frequency is 3.0 KHz-35 KHz, the applied cosine alternating current is 20A-40A, the magnetic field of an axial component is uniformly distributed along a transverse plane, the variation range of the magnetic field intensity in the visual field range of 20 cm-50 cm in the central area of the imaging target is less than 5%, and the equal magnetic field is ensured to be a plane instead of a curved surface. The current of the exciting coil 104 of each data acquisition point is changed 256 times, and the current of the exciting coil 104 in the upper plate structure 101 is increased from 20A to 0.78A each time, and the current is increased 256 times until 40A; the current to the excitation coil 104 in the lower plate structure 102 is reduced from 40A by a total of 256 times, each time by 0.78A, up to 20A, such that 256 independent changes in the shape and position of the "V" shaped magnetic field occur. The shape and position of the V-shaped magnetic field after each change are kept for a short time and kept for 0.017ms, the excitation magnetic field of half cosine oscillation (the oscillation frequency is 30 KHz) and signal acquisition are completed, then the next shape and position are changed, and the shape and position change of the V-shaped magnetic field for 256 times is completed, wherein 4.267ms is required. Correspondingly, after the follow-up data one-dimensional/two-dimensional reconstruction subunit performs data reconstruction, one-dimensional/two-dimensional magnetic particle concentration distribution information along the axial direction of the exciting coil is obtained.

The receiving coils 105 in the upper plate structure 101 and the lower plate structure 102 are each composed of a circular Huo Mhuo-z coil, and each receiving coil 105 has a diameter of 40cm and a thickness and width of 5cm. The distance between the two receiving coils 105 is 40cm, and the upper plate structure 101 and the lower plate structure 102 are respectively close to the exciting coils 104 in the axial direction.

The upper plate structure 101 is a cylindrical plate, the diameter of the plate is 120cm, the thickness of the plate is 40cm, the scanning unit 20 is driven to drive the exciting coil 104 and the receiving coil 105 to wind a central point of an imaging target, circular motion is carried out on a plane where the exciting coil 104 and the receiving coil 105 are located, anticlockwise spiral movement is carried out from inside to outside, and scanning of 256 circumference x 256 data sampling points is completed totally, and the scanning time is 4.66 minutes; similarly, the lower plate structure 102 is a cylindrical plate, the diameter of the plate is 120cm, the thickness of the plate is 100cm, the scanning unit 20 is driven to drive the exciting coil 104 and the receiving coil 105 to do circular motion around an imaging target taking a projection position corresponding to a plane where the exciting coil 104 and the receiving coil 105 are located as a center point, the inner side and the outer side do clockwise spiral motion, namely do opposite direction and opposite position motion with the coil in the upper plate, 256 circles are completed together, 256 sampling points are scanned, and the scanning time is 4.66 minutes. 256 times of circular motions are performed by the exciting coil 104 and the receiving coil 105, 256 data acquisition points are acquired in each circular motion, 256 times of different alternating currents are correspondingly applied to each data acquisition point, 256 times of 256 induced voltage signals are respectively obtained by the upper plate structure 101 and the lower plate structure 102, and image reconstruction is performed through the induced voltage signals obtained by the upper plate structure 101 and the lower plate structure 102.

In addition, the imaging target bearing device of the embodiment of the invention can comprise an inspection bed, and the inspection bed can be provided with buttons for controlling the height and the movement of the inspection bed. A plurality of shielding coils are arranged in the examination bed: the examination bed is internally provided with 15 shielding coils with the width of 10cm and the length of 30cm, the number of turns of the shielding coils is 200, and the direct current is 30 amperes. The shielding coils are arranged in parallel along the examination bed, and 2-5 shielding coils in the central area are closed during scanning, so that magnetic particles in the central area of an imaging target can be oscillated by the exciting coil 104 to generate an induced voltage signal, and shielding coils in other positions are opened to generate a 30mT nonlinear and non-uniform exciting magnetic field for saturating and restraining the magnetic particles in the peripheral area, thereby avoiding generating interference signals.

Based on the experimental conditions, the magnetic particle imaging device provided by the embodiment of the invention is adopted for image reconstruction, a system matrix adopted in the image reconstruction is shown in fig. 9, and the imaging effect is shown in fig. 10a to 10 c. Specifically:

In fig. 10a and 10b, the imaging target is a sample with magnetic particles distributed in a two-dimensional plane, the magnetic particles are distributed in the original image as shown in the figure, the white area is the area with magnetic particles, and the black area is the area without magnetic particles; it can be seen that the two-dimensional image reconstructed from the two-dimensional projections can clearly show the original magnetic particle distribution of the imaging target.

In fig. 10c, the imaging target is a patient's head, and the original image is a magnetic resonance image of the patient's head taken with a magnetic resonance apparatus; it can be seen that the magnetic resonance imaging comprises images of other tissues in the cranium and images of vascular tissues which are overlapped together; in the two-dimensional image reconstructed by the magnetic particle imaging device according to the two-dimensional projection, only vascular tissues with magnetic particle distribution are displayed.

In the magnetic particle imaging apparatus provided in the embodiment of the present invention, the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 move along different circles, each circular movement process includes a plurality of data acquisition points, at each data acquisition point, the current amplitude applied by the exciting coil 104 in the upper plate structure 101 gradually increases or decreases, and the current amplitude applied by the exciting coil 104 in the corresponding lower plate structure 102 correspondingly gradually decreases or increases, so that the generated nonlinear and non-uniform exciting magnetic field can linearly decrease first and then linearly increase along the axial component of each exciting coil 104, and is distributed in a V shape.

Based on the nonlinear and nonuniform excitation magnetic field, the embodiment of the invention performs nonlinear and nonuniform magnetic field excitation on the magnetic particles in the whole space where the imaging target is located, and all the magnetic particles in the whole space can contribute to the induced voltage on the receiving coil 105 without setting a magnetic field free region or changing the position of the magnetic field free region; the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 do one or more circular motions with the projection position of the imaging target on the plane where the exciting coil 104 and the receiving coil 105 are located as the center, and different currents are applied to the exciting coil 104 in the upper plate structure 101 and the lower plate structure 102, which is equivalent to that the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 perform nonlinear and non-uniform excitation in a plurality of different spatial postures and a plurality of different magnetic field distribution states; when the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 are in a certain space attitude, the current in the exciting coil 104 is changed, so that the V-shaped magnetic field distribution is shifted in position along the axial direction of the exciting coil 104, and one-dimensional space coding is realized; when the exciting coil 104 and the receiving coil 105 in the upper plate structure 101 and the lower plate structure 102 are in different spatial attitudes, the magnetic field strength felt by the magnetic particles at the same position is also different, thereby realizing two-dimensional full-space encoding.

Based on the scanning mode, the magnetic particle imaging equipment provided by the embodiment of the invention does not need to set a magnetic field free region for magnetic particle imaging; the position of the free region of the magnetic field is not required to be changed; the signals collected each time are formed by overlapping signals generated after all magnetic particles in the whole space are excited, and the imaging visual field is not limited by the size of a free region of a magnetic field and the moving range as in the prior art, so that the imaging visual field is not limited to small animals, such as mice, for imaging, and the imaging visual field can be matched with the size of a human body, such as a scanning visual field of 20 cm-50 cm which is generally required by human body scanning. Moreover, the coil required for constructing the gradient field and the power consumption consumed correspondingly can be omitted without arranging a magnetic field free region, and the equipment scale and the power consumption are reduced, so that the scanning field of view of at least 50cm of a human body can be realized when the magnetic field strength of the adopted excitation magnetic field is 15 mT-30 mT.

In addition, compared with the mode of almost taking the resolution of an imaging image as a step to execute scanning in the prior art, the scanning step related in the embodiment of the invention comprises the step of current amplitude adjustment and the step between adjacent data acquisition points in circular motion, the scanning time required for executing scanning based on the step is far smaller than that of the prior art, the timeliness is higher, the relaxation effect of magnetic particles can be effectively lightened, the imaging result is clearer, and the imaging of the magnetic particles with high resolution is realized.

In summary, the embodiment of the invention does not use the selection field and the focusing field in the existing magnetic particle imaging technology, and each point of the whole imaging space is a magnetic field free region and can be excited by a magnetic field, i.e. the signals acquired each time are overlapped by the signals of the magnetic nanoparticles at all points of the whole space. By spatially encoding the whole space, a magnetic particle concentration distribution image of an imaging target is reconstructed by using a system matrix and an image reconstruction method, and the magnetic particle imaging with low power consumption, large visual field and high resolution is realized. Such a low power, large field of view, high resolution magnetic particle imaging device can be extended to clinical body scanning.

The magnetic particle imaging device provided by the embodiment of the invention can be used in medicine, including but not limited to cardiovascular and cerebrovascular imaging, tumor imaging, stem cell tracking, erythrocyte labeling, immune cell labeling, inflammatory cell monitoring and other targeted imaging. Compared with the existing vascular imaging technology, the embodiment of the invention does not need digital subtraction for magnetic particle imaging and has less motion artifact. Compared with the existing PET and SPECT imaging technology, the embodiment of the invention provides the magnetic particle imaging equipment with higher sensitivity and image resolution, no ionizing radiation is generated, and the production and storage of the tracer are easier.

In the description of the present invention, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Further, one skilled in the art can engage and combine the different embodiments or examples described in this specification.

Although the application is described herein in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.

Claims

1. A magnetic particle imaging device is characterized by comprising a signal generating unit, a driving scanning unit, a magnetic field excitation unit and a data acquisition and imaging unit, wherein,

The magnetic field excitation unit is used for applying alternating current in the same direction to the excitation coils in the upper plate structure and the lower plate structure at each data acquisition point in each circular motion one or more times to generate different nonlinear and non-uniform excitation magnetic fields; the current amplitude applied by the exciting coil in the upper flat plate structure is gradually increased or decreased each time, and the current amplitude applied by the exciting coil in the lower flat plate structure is correspondingly gradually decreased or increased;

2. The magnetic particle imaging apparatus of claim 1, wherein the upper plate structure and the lower plate structure are each cylindrical plates;

corresponding excitation coils and receiving coils within the upper and lower plate structures, comprising:

the exciting coil comprises a round Huo Mhuo-z coil;

The receiving coil comprises a circular Huo Mhuo-z coil.

3. The magnetic particle imaging apparatus of claim 1, wherein the drive scanning unit is built in the upper plate structure and the lower plate structure, respectively;

and the exciting coil and the receiving coil in the upper flat plate structure and the lower flat plate structure are respectively fixed on the driving scanning unit.

4. The magnetic particle imaging apparatus of claim 1, wherein the data acquisition and imaging unit comprises a signal processing subunit, a signal feature extraction subunit, a one-dimensional data reconstruction subunit, and a two-dimensional data reconstruction subunit, wherein,

The signal processing subunit is used for respectively carrying out analog-digital conversion processing on the induced voltage signals generated on the receiving coils in the upper flat plate structure and the lower flat plate structure aiming at each data acquisition point in each circular motion;

The signal characteristic extraction subunit is used for extracting corresponding target acquisition data from the induced voltage signal after analog-digital conversion processing; the target acquisition data comprise peak amplitude values and/or 3 times fundamental frequency harmonic components of signals;

The one-dimensional data reconstruction subunit is used for reconstructing one-dimensional magnetic particle concentration space distribution data of corresponding data acquisition points in each circular motion according to the peak amplitude of the signal and/or 3 times fundamental frequency harmonic components and a system matrix; the system matrix is used for representing the spatial distribution corresponding to target acquisition data of signals generated by magnetic particles with unit concentration under the action of the nonlinear and non-uniform excitation magnetic field;

The two-dimensional data reconstruction subunit is used for reconstructing and obtaining the two-dimensional magnetic particle concentration spatial distribution data of the imaging target by utilizing a filtering back projection method according to the one-dimensional spatial distribution data of each data acquisition point in each circular motion.

5. The magnetic particle imaging apparatus of claim 4, wherein the data acquisition and imaging unit further comprises a signal correction subunit;

the signal correction subunit is used for correcting the induced voltage signal after the analog-to-digital conversion processing;

the signal characteristic extraction subunit is further used for extracting corresponding target acquisition data from the corrected induced voltage signals; the target acquisition data includes peak amplitudes and/or 3 times fundamental frequency harmonic components of the signal.

6. The magnetic particle imaging apparatus of claim 5, wherein the target acquisition data further comprises a signal peak area and a full width at half maximum of a signal;

The signal correction subunit comprises a first signal correction module, and the first signal correction module is used for correcting peak amplitude and half-value full width of a signal in the target acquisition data according to the signal area.

7. The magnetic particle imaging apparatus of claim 6, wherein the signal correction subunit further comprises a magnetic field correction module and a second signal correction module, wherein,

The magnetic field correction module is used for correcting the nonlinear and nonuniform excitation magnetic field according to the full width at half maximum of the signal;

The second signal correction module is used for correcting peak amplitude and full width at half maximum of the signals in the target acquisition data according to the full width at half maximum of the signals under the action of the corrected nonlinear and non-uniform excitation magnetic field.

8. The magnetic particle imaging apparatus of claim 7, wherein the second signal correction module is further configured to correct the system matrix based on the corrected non-linear, non-uniform excitation magnetic field;

The corrected system matrix is used for representing the spatial distribution corresponding to the target acquisition data of signals generated by the magnetic particles with unit concentration under the action of the corrected nonlinear and non-uniform excitation magnetic field.

9. The magnetic particle imaging apparatus of claim 7, wherein the data acquisition and imaging unit further comprises a relaxation deconvolution module;

The relaxation deconvolution module is used for carrying out deconvolution correction processing on the induced voltage signal after the analog-digital conversion processing under the action of the corrected nonlinear and non-uniform excitation magnetic field;

the signal correction subunit is further used for correcting the induction voltage signal after the deconvolution correction processing.

10. The magnetic particle imaging apparatus of claim 1, further comprising an imaging target carrying means for carrying the imaging target;

A plurality of rectangular shielding coils are arranged in parallel in the imaging target bearing device; when the magnetic particle imaging equipment works, the shielding coils corresponding to the position of the imaging target are closed, and the rest shielding coils are electrified and opened.