Open magnetic particle imaging method and system based on magnetic field spin encoding

Abstract

The present application belongs to the technical field of magnetic particle imaging, and particularly relates to an open magnetic particle imaging method and system based on magnetic field rotation coding, aiming to solve the problems of limited imaging resolution, insufficient imaging depth, excessive power consumption and the inability of MPS to image in the prior art single-sided MPI imaging. The present application: uses a bar-shaped permanent magnet or a coil to create a stable and controllable static magnetic field environment, drives the static magnetic field to rotate by means of a mechanical mechanism, changes the distribution form of the spatial static magnetic field and completes the coding operation, increases the number of independent equations to be solved, and then generates a system matrix, constructs a matrix equation capable of accurately solving the magnetic particle concentration distribution, solves the matrix equation, and successfully reconstructs the magnetic particle image of the target object. The present application is applied to a single-sided MPI device, effectively increases the imaging depth, improves the resolution and reduces the power consumption; and is applied to an MPS device, has imaging capability and expands the application range.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biomedical imaging, and particularly relates to an open magnetic particle imaging method and system based on magnetic field rotation encoding. BACKGROUND

[0002] As a frontier non-invasive tomographic imaging technology, magnetic particle imaging (MPI) has attracted widespread attention in the medical field since its inception in 2005 due to its unique imaging principle. MPI technology uses the static gradient field of the magnetic field to construct a magnetic field free point (FFP) or a magnetic field free line (FFL), and moves the magnetic field free area with the help of a driving field. The excitation coil excites the magnetic particles to generate a nonlinear response signal, thereby realizing accurate imaging of the internal structure of the living body.

[0003] Currently, based on the principle of nonlinear response of magnetic particles, two types of open devices, single-sided MPI and MPS, have been derived:

[0004] Single-sided MPI: The imaging device is placed on the same side of the measured object, and the device structure is simple and easy to move, which has obvious advantages in real-time imaging during surgery. However, due to the attenuation of the magnetic field gradient, the imaging resolution and imaging depth are limited, and there is a lack in meeting the needs of large field of view imaging of the human body. Some devices have high power consumption, which limits their application in more scenarios.

[0005] MPS: It is used to evaluate the properties of magnetic particles and does not have imaging function itself. However, since it does not need to generate FFP, the device can obtain more magnetic nanoparticle signals at the same position, and has high sensitivity in detecting weak magnetic particle signals. Due to the lack of imaging function, the application range is limited.

[0006] In the field of magnetic resonance imaging (MRI), spatial encoding relies on precisely controlled magnetic field gradients to locate the position of the signal source in the body. The MRI system can construct a high spatial resolution gradient magnetic field, apply a linearly varying magnetic field in different spatial directions, distinguish and track signals at different anatomical positions in the body, and realize spatial encoding and reconstruction of images.

[0007] In view of the above problems of the prior art, the present application aims to propose an open magnetic particle imaging method and system based on magnetic field rotation encoding, and apply it to single-sided MPI and MPS devices to innovate the technical performance of single-sided MPI and MPS devices. SUMMARY

[0008] In order to solve the above problems in the prior art, i.e. the problems of limited imaging resolution and insufficient imaging depth of existing single-sided MPI, high power consumption, and the inability of MPS to image, the present application proposes, in a first aspect, an open magnetic particle imaging system based on magnetic field rotation encoding, which comprises:

[0009] a static magnetic field generating component configured to generate a static magnetic field, the static magnetic field generating component being a bar-shaped permanent magnet or a coil;

[0010] an excitation coil configured to pass a sinusoidal alternating current to generate an excitation magnetic field, the excitation magnetic field driving magnetic particles to oscillate to generate a signal;

[0011] a compensation coil configured to generate a magnetic field identical to the excitation magnetic field generated by the excitation coil;

[0012] a receiving coil arranged in pair with the excitation coil and configured to receive the signal of the magnetic particles;

[0013] a compensation receiving coil arranged in pair with the compensation coil and reversely connected to the receiving coil, and configured to offset a direct current feed signal generated by the excitation magnetic field.

[0014] In some preferred embodiments, the static magnetic field generating component is arranged with a mechanical device provided with a central axis, the mechanical device driving the static magnetic field generating component to rotate around the central axis to change the spatial magnetic field distribution of the static magnetic field and to encode;

[0015] the central axis coincides with the center of the imaging field of view.

[0016] In some preferred embodiments, the mechanical device drives the static magnetic field generating component to rotate around the central axis at N equidistantly selected angles within a range of 0° to 360°.

[0017] In some preferred embodiments, the compensation receiving coil has the same structure and electrical parameters as the receiving coil.

[0018] In a second aspect, the present application provides an open magnetic particle imaging method based on magnetic field rotation encoding, based on the magnetic particle imaging system based on magnetic field rotation encoding, the system comprising:

[0019] Step 1: obtaining a phantom of MxM pixel sites;

[0020] For each selected pixel site, the static magnetic field generating component is rotated around the phantom at N preset angles, and then time domain data of all pixel sites of the phantom at each preset angle are obtained;

[0021] performing Fourier transform on the time domain data to extract K harmonic data, each harmonic generating an NxM 2 system matrix S;

[0022] Step 2: Place the target object at the center of the imaging field of view, rotate the magnetic field generator component in the same way as when acquiring the time domain data in Step 1, collect the time domain signal, perform Fourier transform on each time domain signal, and extract the harmonic data as the measured harmonic data;

[0023] Step 3: Based on the system matrix and the measured harmonic data, solve the system matrix equation to obtain the magnetic particle concentration distribution, and then reconstruct the magnetic particle image of the target object.

[0024] In some preferred embodiments, the selected pixel sites of the M×M pixel site phantom include: all pixel sites in the phantom are sequentially filled with magnetic particles, while the remaining pixel sites are without magnetic particles;

[0025] The selection of pixel sites for the M×M pixel site phantom also includes: selecting pixel sites in the phantom that are at different distances from the center of the phantom and filling them with magnetic particles in sequence, while the remaining pixel sites are not filled with magnetic particles.

[0026] In some preferred embodiments, the geometric center of the phantom of the M×M pixel site includes: the center point corresponding to the M×M pixel array and the center point not corresponding to the M×M pixel array.

[0027] In some preferred embodiments, the temporal data of all pixel sites of the phantom at each preset angle are obtained by the following method:

[0028] For each selected pixel location, the static magnetic field generating component rotates around the phantom by N preset angles. At each angle, the receiving coil receives magnetic particle signals and collects N×P time-domain signals, i.e., time-domain data; where P is the number of selected pixel locations.

[0029] In some preferred embodiments, the system matrix equation is: S×c =b, where S is the system matrix, b is the measured harmonic data, and c is the magnetic particle concentration distribution;

[0030] The matrix equation solving method includes the kaczmarzReg regularized iterative algorithm.

[0031] In some preferred embodiments, the harmonic order extracted from the measured harmonic data is the same as the harmonic order corresponding to the system matrix; each harmonic in the measured harmonic data generates an N×1 matrix.

[0032] The beneficial effects of this invention are:

[0033] 1) Drawing upon the mature principles of magnetic resonance imaging (MRI), a stable and controllable static magnetic field environment is created using bar permanent magnets or coils. A mechanical mechanism drives the rotation of this static magnetic field, cleverly altering its distribution and encoding. This process effectively increases the number of independent equations available for solving, generating a system matrix and constructing a matrix equation capable of accurately solving for the magnetic particle concentration distribution. By solving this matrix equation, the magnetic particle image of the target object is successfully reconstructed. This not only significantly improves the accuracy of the reconstruction results but also helps overcome the depth limitations of traditional imaging techniques, obtaining clearer and more comprehensive imaging effects.

[0034] 2) Applied to single-sided magnetic particle imaging (MPI) equipment, compared to the traditional imaging approach using FFR encoding, this imaging-based design significantly simplifies the equipment structure, greatly improves sensitivity, and effectively increases imaging depth, providing an innovative solution for achieving high-quality magnetic particle imaging. Furthermore, applying this technology to magnetic particle energy dispersive spectrometers (MPS) successfully endows the MPS equipment, which originally only had magnetic particle characteristic assessment capabilities, with imaging capabilities, expanding its application scope. Attached Figure Description

[0035] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0036] Figure 1 This is a schematic diagram of the design of the single-sided MPI of the open magnetic particle imaging system based on magnetic field rotation encoding of the present invention.

[0037] Figure 2 This is a schematic diagram of the mechanical structure of the open magnetic particle imaging system based on magnetic field rotation encoding of the present invention.

[0038] Figure 3 This is a schematic diagram of the MPS device, which is an open magnetic particle imaging system based on magnetic field rotation encoding according to the present invention.

[0039] Figure 4 This is a static magnetic field distribution map of the open magnetic particle imaging method and system based on magnetic field rotation encoding of the present invention.

[0040] Figure 5 This is a schematic diagram of the mechanical device of the 3×3 phantom of the open magnetic particle imaging method and system based on magnetic field rotation coding of the present invention, which drives the static magnetic field generating component to rotate around the central axis.

[0041] Figure 6 This is a flowchart of the steps of the open magnetic particle imaging method based on magnetic field rotation coding of the present invention.

[0042] AppendixFigure 1 In the middle, 1. Excitation coil; 2. Receiving coil; 3. Static magnetic field generating component; (attached) Figure 2 In the middle, 4. Magnet slot; 5. Sliding ring; 6. MPS equipment; (Attached) Figure 3 In the diagram, 7 is the imaging space, i.e. the position to be measured, such as a mouse or a phantom; 8 and 10 are identical excitation coils; 9 and 11 are identical receiving coils. Detailed Implementation

[0043] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0044] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] To more clearly illustrate the open magnetic particle imaging system based on magnetic field rotation encoding of this invention, the following will be combined with... Figures 1 to 6 The steps in the embodiments of the present invention will be described in detail below.

[0046] The first embodiment of the present invention is an open magnetic particle imaging system based on magnetic field rotation coding, the system comprising:

[0047] A static magnetic field generating component is configured to generate a static magnetic field, wherein the static magnetic field generating component is a bar permanent magnet or a coil;

[0048] An excitation coil is configured to receive a sinusoidal alternating current to generate an excitation magnetic field, which drives magnetic particles to oscillate and generate a signal.

[0049] A compensation coil is configured to generate a magnetic field that is the same as the excitation magnetic field generated by the excitation coil.

[0050] A receiving coil, paired with the excitation coil, is used to receive magnetic particle signals;

[0051] A compensation receiving coil is paired with the compensation coil and reverse-connected to the receiving coil. It is configured to cancel the DC feedthrough signal generated by the excitation magnetic field, so that the receiving coil retains only the magnetic particle signal generated by the magnetic particle oscillation.

[0052] Figure 1 presents a design schematic of a single-sided MPI, while Figure 3 shows a design schematic of an MPS device. Regarding the layout of the compensation coil and the compensation receiving coil, a brief explanation is provided below: the compensation coil is generally symmetrically distributed with the excitation coil, and the compensation receiving coil is usually symmetrically distributed with the receiving coil. The compensation receiving coil is paired with the compensation coil, and the receiving coil is paired with the excitation coil. Figure 3 For example, 8 and 10 are identical excitation coils; one can be used as the excitation coil and the other as the compensation coil. Similarly, 9 and 11 are identical receiving coils; one can be used as the receiving coil and the other as the compensation receiving coil. Given that this type of arrangement is quite common in the field, its details will not be elaborated upon here.

[0053] In this embodiment, the static magnetic field generating component is equipped with a mechanical device. This mechanical device has a central axis, and it drives the static magnetic field generating component to rotate around this central axis, changing and encoding the spatial magnetic field distribution of the static magnetic field. The spatial magnetic field distribution can be visually presented through a static magnetic field distribution diagram. (See [reference]). Figure 3 The figure shows the distribution of the static magnetic field generated by the static magnetic field generating component at different depths Z, i.e., Z = -10mm, -20mm, -30mm, -40mm, and -50mm; see also Figure 4 The diagram shows a phantom with 3×3 pixel sites in rows and columns, 12 angles, and 30° angle intervals, with a mechanical device driving a static magnetic field generating component to rotate around the central axis.

[0054] The mechanical device drives the static magnetic field generating component to rotate around the central axis at N angles with equal intervals within the range of 0° to 360°.

[0055] The central axis coincides with the center of the imaging field of view;

[0056] The structure and electrical parameters of the compensation receiving coil are the same as those of the receiving coil;

[0057] The structure and electrical parameters of the compensation coil are the same as those of the excitation coil;

[0058] The mechanical structure is a general-purpose structure capable of being driven to rotate; see [link / reference]. Figure 2 This is one embodiment of a mechanical structure, including a magnet slot and a sliding ring. A static magnetic field generating component is placed in the magnet slot, and the sliding ring is fixed on the MPS. The sliding ring allows the permanent magnet to rotate around the MPS.

[0059] In this way, by using a biased static magnetic field, the magnetization state of magnetic particles varies at different spatial locations, allowing for differentiated encoding. This not only retains the high sensitivity advantage of MPS devices but also endows them with imaging capabilities. Specifically, MPS devices, which were originally only used to evaluate the characteristics of magnetic particles, can now reconstruct images reflecting the internal structure of objects by capturing and analyzing the spatial distribution information of magnetic particles. This technological breakthrough has enabled MPS devices to demonstrate unprecedented potential in detecting weak magnetic particle signals for imaging, opening up new directions for the development of medical imaging technology.

[0060] It should be noted that the open magnetic particle imaging system based on magnetic field rotation coding provided in the above embodiments is only an example of the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the modules or steps in the embodiments of the present invention can be further decomposed or combined. For example, the modules in the above embodiments can be merged into one module, or further divided into multiple sub-modules to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only for distinguishing the various modules or steps and are not considered as an improper limitation of the present invention.

[0061] Based on the principles of MRI imaging, the second embodiment of the open magnetic particle imaging method based on magnetic field rotation coding of the present invention, builds upon the first embodiment of the open magnetic particle imaging system based on magnetic field rotation coding, as detailed below. Figure 6 The system includes:

[0062] Step 1: Obtain the phantom of the M×M pixel site;

[0063] For each selected pixel location, the static magnetic field generating component rotates around the phantom by N preset angles to obtain time-domain data of all pixel locations of the phantom at each preset angle. It should be noted that, as described in the referenced system, when the static magnetic field generating component rotates to generate a static magnetic field, the excitation coil and the compensation coil also work together. When the receiving coil receives the magnetic particle signal, the compensation receiving coil also works together to obtain time-domain data of all pixel locations of the phantom at each preset angle.

[0064] Perform a Fourier transform on the time-domain data to extract the Kth harmonic data, generating an N×M harmonic data for each harmonic. 2 The system matrix S;

[0065] Step 2: Place the target object at the center of the imaging field of view, rotate the magnetic field generator component in the same way as when acquiring the time domain data in Step 1, collect the time domain signal, perform Fourier transform on each time domain signal, and extract the harmonic data as the measured harmonic data;

[0066] Step 3: Based on the system matrix and the measured harmonic data, solve the system matrix equation to obtain the magnetic particle concentration distribution, and then reconstruct the magnetic particle image of the target object;

[0067] In this embodiment, the selected pixel sites of the M×M pixel site phantom include: all pixel sites in the phantom are sequentially filled with magnetic particles, and the remaining pixel sites are not filled with magnetic particles. The data of each site is directly collected by sequentially filling each site with magnetic particles, which is also known as the full site filling method.

[0068] In addition to full-site filling, a simplified filling method can also be used. In an M×M pixel phantom, pixels at different distances from the phantom's center are sequentially filled with magnetic particles, while the remaining pixels are left unfilled. Figure 5 Taking a 3×3 phantom as an example, the selectable sites include the diagonal pixel sites, edge center pixel sites, and center pixel sites of the phantom. Since these sites are centrally symmetrically distributed, there is no need to fill and collect them one by one. The information of all 9 sites can be obtained by calculation. This simplified method can effectively reduce the number of magnetic particle filling steps and data acquisition steps, and improve efficiency.

[0069] The geometric center of the phantom at the M×M pixel site includes two cases: the center point corresponding to the center point of the M×M pixel array, and the center point not corresponding to the center point of the M×M pixel array.

[0070] The method for obtaining the temporal data of all pixel sites of the phantom at each preset angle is as follows:

[0071] For each selected pixel location, the static magnetic field generating component rotates around the phantom by N preset angles. At each angle, the receiving coil receives magnetic particle signals and collects N×P time-domain signals, i.e., time-domain data; where P is the number of selected pixel locations.

[0072] The system matrix equation is: S×c =b, where S is the system matrix, b is the measured harmonic data, and c is the magnetic particle concentration distribution.

[0073] The matrix equation solving method includes the kaczmarzReg regularized iterative algorithm. It should be noted that this matrix equation solving method is a common reconstruction method in MPI, as detailed in the literature (Rahmer J, Weizenecker J, Gleich B, et al. Signal Encoding in Magnetic Particle Imaging: Properties of the System Function [J]. BMC Medical Imaging, 2009, 9 (1): 1–21).

[0074] The harmonic order extracted from the measured harmonic data is the same as the harmonic order corresponding to the system matrix; each harmonic in the measured harmonic data generates an N×1 matrix.

[0075] To ensure data reliability, the receiving coil receives magnetic particle signals at each angle, performs multiple repeated measurements, and calculates the final result using the average value. This reduces the impact of noise, equipment stability, and operational errors on the results.

[0076] The following uses a phantom with M×M as a 3×3 pixel location as an example to illustrate the imaging steps and methods:

[0077] A 3×3 pixel phantom is obtained by 3D printing and placed in the center of the imaging field of view. (In practical applications, the pixel array can be expanded to the size of M×M, and the phantom site is M×M. The larger M is, the higher the pixel count is theoretically, and the clearer the image will be.)

[0078] Nine pixels in a 3×3 array are arranged in three rows and three columns with equal spacing. The center of the array corresponds to the center of the phantom. To obtain the magnetic particle concentration at the nine pixel sites, at least nine equations need to be established.

[0079] Pixels at different distances from the phantom center are selected and sequentially filled with magnetic particles; the remaining pixels are left unfilled. In a 3×3 phantom array, the nine filling points of the phantom are at three different distances from the phantom center (i.e., P = 3): 0 unit length, 1 unit length, ... Each unit length is filled with magnetic particles sequentially at a diagonal pixel site, an edge center pixel site, and a center pixel site, while leaving the remaining 8 sites without magnetic particles.

[0080] See Figure 5To improve the accuracy of the solution within the imaging field of view, for each selected pixel location, the static magnetic field generating component rotates around the phantom by N preset angles, and the receiving coil receives magnetic particle signals at each angle; all pixel locations are traversed to obtain the time-domain data of all pixel locations of the phantom at each preset angle; specifically, an equation can be listed for each angle the bar permanent magnet or coil rotates, and the rotation is designed to be 12 angles (i.e., N is 12), starting from 0 degrees and ending at 330 degrees, that is, the interval between each two signal acquisitions is 30 degrees;

[0081] For each selected partial pixel location, the permanent magnet or coil is rotated, and a signal is collected at each of the 12 angles, so a total of 12×9 (N=12) time-domain signals are collected;

[0082] Based on 12 rotation angles and 9 points, after performing a Fourier transform on the time-domain data at these 12 angles, a total of k×12×9 data points composed of k harmonics can be obtained. Each harmonic can generate a 12×9 (N×M) harmonic. 2 =12×3×3) system matrix. In practical applications, more harmonics can be selected, which can increase the number of equations, make the solution process more accurate, and improve the image reconstruction effect. If k harmonics are selected, a 12k×9 matrix can be generated.

[0083] Place the target object at the center of the imaging field of view;

[0084] The static magnetic field generating component rotates around the target object by N preset angles (here set to 12 times, 30 degrees each time). At each angle, the receiving coil receives magnetic particle signals and obtains the time domain data of the target object at each preset angle, obtaining a total of 12 time domain data.

[0085] Fourier transform is performed on the time-domain data to extract harmonic data b with the same harmonic order as the system matrix. This b represents the measured magnetic particle signal for each harmonic. Each harmonic generates an N×1 matrix (specifically, each harmonic generates a 12×1 matrix). This is used to change the spatial magnetic field distribution of the static magnetic field and encode it. The number of rows in the matrix is ​​determined by the number of rotation angles of the static magnetic field generating component. In practical applications, more harmonics can be selected, which can increase the number of equations, make the solution process more accurate, and improve the image reconstruction effect. If k harmonics are selected, a 12k×1 matrix can be generated.

[0086] Based on the system matrix and the measured harmonic data, the system matrix equation is solved to obtain the magnetic particle concentration distribution, and then the magnetic particle image of the target object is reconstructed.

[0087] The system matrix equation is S×c =b, where S is the system matrix, b is the measured harmonic data, and c is the magnetic particle concentration distribution.

[0088] The matrix equation solving method includes the kaczmarzReg regularized iterative algorithm.

[0089] Although the steps in the above embodiments are described in the above order, those skilled in the art will understand that in order to achieve the effect of this embodiment, different steps do not need to be executed in such an order. They can be executed simultaneously (in parallel) or in a reverse order. These simple variations are all within the protection scope of this invention.

[0090] Existing single-sided MPI devices include an excitation coil, a receiving coil, a driving coil, and a permanent magnet array. The permanent magnet array generates magnetic field free points (FFPs) by producing a static gradient field. During imaging, only the magnetic particle signals at the FFP points are acquired, and this characteristic is used for spatial encoding. The driving coil, based on paired coils, scans the target area by changing the position of the FFPs generated by the permanent magnet array. The excitation coil generates an excitation magnetic field covering the entire imaging area to induce a response in the magnetic particles. The receiving coil receives the signals generated by the magnetic particles due to the excitation. Generally, a larger magnetic field gradient results in higher imaging resolution. However, the magnetic field gradient decreases with increasing distance, leading to reduced resolution at distant locations, or even failure to image. Furthermore, the method of generating FFPs and changing their positions only enables signals from magnetic particles within the FFPs at any given time, limiting the imaging effect. Therefore, this invention provides a single-sided MPI magnetic particle imaging device based on magnetic field rotation encoding, aiming to overcome the bottlenecks of existing technologies and optimize imaging performance.

[0091] The third embodiment of the present invention is a single-sided MPI magnetic particle imaging device based on magnetic field rotation encoding, in which a static magnetic field generating component replaces the permanent magnet array; it is set on one side of the object to be imaged, and the static magnetic field generating component is a strip permanent magnet or a coil used to generate a static magnetic field;

[0092] A mechanical structure is provided, which is configured to be used in conjunction with the static magnetic field generating component. The mechanical structure has a central axis, and is capable of rotating the bar permanent magnet or the coil around the central axis. A magnetization model based on the Langevin function is used to modify the received magnetic particle signal to achieve spatial encoding. Here, the magnetization model based on the Langevin function is a classical theoretical framework for describing the magnetization behavior of materials in an externally applied magnetic field, and is particularly suitable for the analysis of the non-hysteretic magnetization characteristics of paramagnetic materials and some ferromagnetic materials. The standard expression of the Langevin function is: L(x) = coth(x) - 1 / x, where L(x) represents the function value, x represents the independent variable, and coth(x) represents the hyperbolic cotangent function. An open magnetic particle imaging method based on magnetic field rotation encoding is implemented to solve the problems of limited sensitivity and insufficient imaging depth in unilateral MPI imaging.

[0093] Compared with the method for generating FFP, it is less dependent on the magnetic field for generating FFP, has high sensitivity, and basically all magnetic particles in the entire region can generate signals.

[0094] By adjusting the size of the bar permanent magnet or the magnitude of the current in the bias coil, and combining different imaging field-of-view sizes, a bias magnetic field gradient intensity that can effectively meet the imaging requirements is designed. This takes into account the advantages of MPI devices compared to traditional imaging modalities in terms of imaging resolution and no radiation damage. At the same time, drawing on the imaging idea of MPS, compared with traditional MPI devices, it has a simpler structure, higher sensitivity, and greater imaging depth. In addition, compared with previous MPI devices, since this design uses a rotatable static magnetic field generating component, only one power amplifier is needed to amplify the sinusoidal alternating current and then apply it to the excitation coil, which reduces power consumption while improving imaging sensitivity and expanding the imaging field of view, achieving a better imaging effect.

[0095] Existing MPS devices include an excitation coil, a receiving coil, a compensation coil that is exactly the same as the excitation coil, and a compensation receiving coil that is exactly the same as the receiving coil. The signal received by the receiving coil is: magnetic particle signal + excitation signal; the signal received by the compensation receiving coil is: excitation signal; the two are connected in reverse, that is, subtracted, to obtain the magnetic particle response signal.

[0096] Since the MPS device does not have a magnetic field selection, it does not have the ability to encode, and can only be used to obtain the concentration of magnetic particles in the entire range, rather than the concentration of magnetic particles at each position, and cannot form images.

[0097] Based on this, the present invention provides an MPS magnetic particle imaging device based on magnetic field rotation encoding, aiming to break through the bottleneck of the existing technology so that the MPS device can form images.

[0098] The MPS magnetic particle imaging device based on magnetic field rotation encoding according to the fourth embodiment of the present invention adds the following:

[0099] A static magnetic field generating component, which is a bar permanent magnet or a coil, is used to generate a static magnetic field.

[0100] A mechanical structure, configured in conjunction with the static magnetic field generating component, is provided with a central axis, enabling the bar permanent magnet or coil to rotate around the central axis; it alters and encodes the spatial magnetic field distribution of the static magnetic field; it is combined with the excitation coil, receiving coil, compensation coil, and compensation receiving coil included in the aforementioned existing MPS equipment, and executes an open magnetic particle imaging method based on magnetic field rotation encoding, enabling the MPS equipment to perform imaging.

[0101] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of the device described above and related instructions can be referred to the corresponding process in the foregoing system embodiments, and will not be repeated here.

[0102] Those skilled in the art will recognize that the modules and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. The programs corresponding to the software modules and method steps can be placed in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. To clearly illustrate the interchangeability of electronic hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the invention.

[0103] The terms “first”, “second”, etc., are used to distinguish similar objects, not to describe or indicate a specific order or sequence.

[0104] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.

[0105] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. Open magnetic particle imaging system based on magnetic field spin encoding, characterized in that, The system comprises: a bias static magnetic field generating component configured to generate a static magnetic field, the bias static magnetic field generating component being a bar-shaped permanent magnet or a coil; the bias static magnetic field generating component being arranged on one side of an object to be imaged; the bias static magnetic field generating component rotating at a plurality of preset rotation angles; an excitation coil configured to pass a sinusoidal alternating current to generate an excitation magnetic field, the excitation magnetic field driving magnetic particles to oscillate to generate a signal; a compensation coil configured to generate a magnetic field identical to the excitation magnetic field generated by the excitation coil; a receiving coil arranged in pairs with the excitation coil, for receiving the magnetic particle signal; a compensation receiving coil arranged in pairs with the compensation coil and reversely connected with the receiving coil, configured to offset the direct current feed signal generated by the excitation magnetic field; the bias static magnetic field generating component rotating at the plurality of preset rotation angles by a mechanical device arranged in pairs with the bias static magnetic field generating component, the mechanical device being provided with a central axis, the mechanical device driving the static magnetic field generating component to rotate around the central axis, changing the spatial magnetic field distribution of the static magnetic field and encoding; the central axis coinciding with the center of the imaging field of view; the mechanical device driving the static magnetic field generating component to rotate around the central axis in the range of 0° to 360°, continuously selecting N angles at equal intervals; the structure and electrical parameters of the compensation receiving coil being identical to those of the receiving coil.

2. Open magnetic particle imaging method based on magnetic field spin encoding, open magnetic particle imaging system based on magnetic field spin encoding according to claim 1, characterized in that The method comprises: Step 1: obtaining an M×M pixel site phantom; for each selected pixel site, the static magnetic field generating component rotates around the phantom at N preset angles, thereby obtaining the time domain data of all pixel sites of the phantom at each preset angle; the bias static magnetic field generating component is arranged on one side of the object to be imaged; Fourier transforming the time domain data, extracting Kth harmonic data, each harmonic generating an NXM 2 system matrix S; Step 2: placing the target object at the center of the imaging field of view, rotating the bias static magnetic field generating component according to the rotation mode when obtaining the time domain data in step 1, collecting time domain signals, and performing Fourier transform on each time domain signal to extract harmonic data as the actually measured harmonic data; Step 3: based on the system matrix and the actually measured harmonic data, solving the system matrix equation to obtain the magnetic particle concentration distribution, and then reconstructing the magnetic particle image of the target object.

3. Open magnetic particle imaging method based on magnetic field rotation encoding according to claim 2, characterized in that, The selected pixel sites of the M×M pixel site phantom include: all pixel sites in the phantom, sequentially filling magnetic particles, and the remaining pixel sites without magnetic particles; The selected pixel sites of the M×M pixel site phantom also include: selecting pixel sites in the phantom with different distances from the center of the phantom to sequentially fill magnetic particles, and the remaining pixel sites without magnetic particles.

4. Open magnetic particle imaging method based on magnetic field rotation encoding according to claim 3, characterized in that, The geometric center of the M×M pixel site phantom includes: the center point corresponding to the M×M pixel array, and the center point not corresponding to the M×M pixel array.

5. Open magnetic particle imaging method based on magnetic field rotation encoding according to claim 4, characterized in that, The method for obtaining the time domain data of all pixel sites of the phantom at each preset angle is as follows: for each selected pixel site, the static magnetic field generating component rotates around the phantom at N preset angles, and at each angle, the receiving coil receives the magnetic particle signal to collect N×P time domain signals, i.e. time domain data; wherein P is the number of selected pixel sites.

6. The open magnetic particle imaging method based on magnetic field rotation encoding of claim 2, wherein, The system matrix equation is Sxc=b, wherein S is a system matrix, b is measured harmonic data, and c is a magnetic particle concentration distribution. The matrix equation solving method comprises a kaczmarzReg regularization iterative algorithm.

7. The open magnetic particle imaging method based on magnetic field rotation encoding of claim 2, wherein, The measured harmonic data is extracted with the same harmonic order as the harmonic order corresponding to the system matrix, and each harmonic in the measured harmonic data generates an Nx1 matrix.

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