Multi-color magnetic particle imaging method and system based on magnetic field free line projection decoding

Abstract

The present invention belongs to the field of biomedical imaging, and specifically relates to a multi-color magnetic particle imaging method and system based on magnetic field free line projection decoding. The method aims to solve the problem that the existing technology has no method for using magnetic field free lines to perform relaxation-based multi-color imaging, resulting in low imaging efficiency and quality. The method of the present invention comprises: placing N types of magnetic nanoparticles at the center of the imaging field of view for scanning, and using time-frequency analysis to obtain the central spectrum line of the time-frequency spectrum; scanning the imaging object, collecting the voltage response signal and performing time-frequency analysis to obtain the time-frequency spectrum; constructing and solving a system of linear equations to obtain various unknown quantities; discretely rotating the magnetic field free lines by P angles to obtain the content distribution of the N types of magnetic nanoparticles at each angle; constructing sinusoidal diagrams of the N types of magnetic nanoparticles, performing back-projection reconstruction to obtain a multi-color image, and superimposing them to obtain a reconstructed image. The present invention realizes relaxation-based multi-color imaging using magnetic field free lines, improving imaging efficiency and quality.

Description

Technical Field

[0001] The present invention belongs to the field of biomedical imaging, and in particular relates to a multi-color magnetic particle imaging method and system based on magnetic field free line projection decoding. Background Art

[0002] Magnetic particle imaging, as an emerging biomedical imaging technology, has developed rapidly in recent years. Magnetic nanoparticles, as tracers, can be metabolized by the human body and have good biosafety. Furthermore, magnetic nanoparticles can be functionalized and have improved biocompatibility through surface modification. Under the excitation magnetic field of a magnetic particle device, particles of different shapes, sizes, and surface modifications exhibit different magnetization signal characteristics. Multicolor magnetic particle imaging technology uses the differences in the magnetic properties of different types of particles to image their concentration distributions separately, and visualize them as different colors for differentiation. For example, in a vascular intervention scenario, particle 1 is injected into the blood, and particle 2 is coated on the catheter. Multicolor magnetic particle imaging displays the concentration distributions of the two particles separately, providing visual guidance for catheter positioning.

[0003] Magnetic particle imaging achieves spatial encoding by constructing magnetic field-free points or magnetic field-free lines, driving the movement of point-like or linear low-field regions. There are two main technical approaches to multi-color magnetic particle imaging: one is based on a multi-color system matrix, measuring the system matrix of multiple particles by solving a system of linear equations for imaging. However, the calibration process is cumbersome, and the inverse problem of the multi-color system matrix is somewhat ill-posed. The other is based on relaxation characteristics, eliminating the need for prior calibration and utilizing particle magnetization signals to analyze relaxation times for imaging. Currently, relaxation-based multi-color magnetic particle imaging technology primarily relies on magnetic field-free points for point-by-point scanning and imaging. Compared to point-like low-field regions, linear scanning based on magnetic field-free lines has the potential to provide higher magnetic particle detection sensitivity. However, due to the complex nature of magnetic field-free lines, which rely on multi-angle projection, no technology currently exists for relaxation-based multi-color imaging using magnetic field-free lines.

[0004] Based on this, the present invention proposes a multi-color magnetic particle imaging method and system based on magnetic field free line projection decoding, which performs calibration-free multi-color analysis of the projection signals of multiple particles through projection decoding, providing a multi-color imaging effect with higher sensitivity. Summary of the Invention

[0005] In order to solve the above-mentioned problems in the prior art, that is, to solve the problem that the prior art currently lacks a method for performing relaxation-based multi-color imaging using magnetic field free lines, which leads to low imaging efficiency and quality, the first aspect of the present invention proposes a multi-color magnetic particle imaging method based on magnetic field free line projection decoding, the method comprising:

[0006] S100, placing N types of magnetic nanoparticles contained in the object to be imaged at the center of the imaging field of a magnetic field free line magnetic particle imaging device for scanning, and after scanning, using time-frequency analysis to obtain a central spectral line of the time-frequency spectrum as a characteristic vector of the N types of magnetic nanoparticles;

[0007] S200, placing the object to be imaged in the imaging field of the magnetic field free line magnetic particle imaging device, scanning the object to be imaged using a set driving trajectory and collecting a voltage response signal; performing time-frequency analysis on the voltage response signal to obtain a time-frequency spectrum;

[0008] S300, constructing a characteristic matrix based on the characteristic vectors of the N types of magnetic nanoparticles as an augmented matrix, using the spectral lines of the time-frequency spectrum as constant terms, and the content distribution of the N types of magnetic nanoparticles at each spectral line as an unknown quantity, constructing and solving a system of linear equations to obtain each unknown quantity;

[0009] S400, using the angle corresponding to the magnetic field free line during the first scan of the object to be imaged as the initial angle, discretely rotating the magnetic field free line through P angles, performing scanning at each angle to obtain a voltage response signal, and obtaining the content distribution of N types of magnetic nanoparticles at each angle according to the methods of S200 and S300; wherein P is a positive integer;

[0010] S500, constructing sinusoidal graphs of N types of magnetic nanoparticles based on the content distributions of N types of magnetic nanoparticles at P angles; back-projecting and reconstructing the sinusoidal graphs of the N types of magnetic nanoparticles to obtain multi-color images, and superimposing them to obtain a reconstructed image.

[0011] In some preferred embodiments, the magnetic field free line magnetic particle imaging device uses one-dimensional scanning when scanning the N types of magnetic nanoparticles contained in the object to be imaged.

[0012] In some preferred embodiments, the feature vector , is a vector with a complex field length of M, .

[0013] In some preferred embodiments, the set driving trajectory is a driving trajectory of a triangle wave superimposed on a sine wave.

[0014] In some preferred embodiments, a feature matrix is constructed based on the feature vectors of the N kinds of magnetic nanoparticles, and the method is as follows: the feature vectors of the N kinds of magnetic nanoparticles are Concatenate by rows to get the feature matrix.

[0015] In some preferred embodiments, based on the content distribution of N types of magnetic nanoparticles at P angles, a sinusoidal graph of N types of magnetic nanoparticles is constructed by:

[0016] The content distribution of N kinds of magnetic nanoparticles at P angles ,according to k Index fill column position, according to p The index fills the row position, building the n A sine diagram, according to n Index to construct N sinograms.

[0017] In some preferred embodiments, the back-projection reconstruction method includes a filtered back-projection method using Ram-Lak as a filter.

[0018] In some preferred embodiments, after constructing the sinusoidal graphs of the N types of magnetic nanoparticles in S500 , the method further includes: assigning color maps to the sinusoidal graphs of the N types of magnetic nanoparticles respectively.

[0019] In a second aspect of the present invention, a multi-color magnetic particle imaging system based on magnetic field free line projection decoding is proposed, the system comprising:

[0020] a one-dimensional scanning module configured to place N types of magnetic nanoparticles contained in the object to be imaged at the center of the imaging field of the magnetic field free line magnetic particle imaging device for scanning, and after scanning, use time-frequency analysis to obtain the central spectral line of the time-frequency spectrum as the characteristic vector of the N types of magnetic nanoparticles;

[0021] an imaging object scanning module configured to place the object to be imaged in the imaging field of view of the magnetic field free line magnetic particle imaging device, scan the object to be imaged using a set driving trajectory and collect a voltage response signal; perform time-frequency analysis on the voltage response signal to obtain a time-frequency spectrum;

[0022] an equation system construction module configured to construct a characteristic matrix based on the characteristic vectors of the N types of magnetic nanoparticles as an augmented matrix, use the spectral lines of the time-frequency spectrum as constant terms, use the content distribution of the N types of magnetic nanoparticles at each spectral line as an unknown quantity, construct a linear equation system and solve it to obtain each unknown quantity;

[0023] a content distribution acquisition module configured to use the angle corresponding to the magnetic field free line during the first scan of the object to be imaged as an initial angle, discretely rotate the magnetic field free line by P angles, scan at each angle to obtain a voltage response signal, and obtain the content distribution of N types of magnetic nanoparticles at each angle according to the methods of S200 and S300; wherein P is a positive integer;

[0024] The image reconstruction module is configured to construct a sinusoidal graph of N types of magnetic nanoparticles based on the content distribution of N types of magnetic nanoparticles at P angles; back-project the sinusoidal graphs of the N types of magnetic nanoparticles to reconstruct a multi-color image, and superimpose the images to obtain a reconstructed image.

[0025] In some preferred embodiments, the system further comprises a color mapping module;

[0026] The color mapping module is configured to assign a color map to the reconstructed images of N types of magnetic nanoparticles.

[0027] Beneficial effects of the present invention:

[0028] The present invention realizes relaxation-based multi-color imaging by utilizing magnetic field free lines, thereby improving imaging efficiency and quality.

[0029] This invention enables efficient, calibration-free imaging of a wide range of magnetic particles. Compared to traditional methods, this not only simplifies the imaging process, avoiding tedious calibration steps and the challenges of ill-posedness associated with the matrix inversion problem of multicolor systems, but also significantly improves the sensitivity of magnetic particle detection by utilizing magnetic field free lines for linear scanning. This method is particularly suitable for applications requiring high-sensitivity imaging, providing a more advanced and reliable solution for multicolor magnetic particle imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present application will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings.

[0031] Figure 1 This is a flow chart of a multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to an embodiment of the present invention;

[0032] Figure 2 This is a simplified flowchart of a multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to an embodiment of the present invention;

[0033] Figure 3 It is a schematic diagram of collecting characteristic vectors for the first magnetic nanoparticle according to an embodiment of the present invention;

[0034] Figure 4 is a schematic diagram of an object to be imaged comprising three different magnetic nanoparticles and different spatial concentration distributions according to an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of a magnetic field free line performing one-dimensional scanning by translating at a certain angle in a two-dimensional plane according to an embodiment of the present invention;

[0036] Figure 6 In one embodiment of the present invention, a free line of a magnetic field is scanned in one dimension at a certain angle to obtain a projection;

[0037] Figure 7 This is a schematic diagram of a magnetic field free line rotating at multiple angles according to an embodiment of the present invention;

[0038] Figure 8 This is a schematic diagram of the back-projection reconstruction results of three magnetic nanoparticle sinusoidal images according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0040] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the relevant invention are shown in the accompanying drawings.

[0041] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0042] A multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to the first embodiment of the present invention is as follows: Figure 1 As shown, the following steps are included:

[0043] S100, placing N types of magnetic nanoparticles contained in the object to be imaged at the center of the imaging field of a magnetic field free line magnetic particle imaging device for scanning, and after scanning, using time-frequency analysis to obtain a central spectral line of the time-frequency spectrum as a characteristic vector of the N types of magnetic nanoparticles;

[0044] S200, placing the object to be imaged in the imaging field of the magnetic field free line magnetic particle imaging device, scanning the object to be imaged using a set driving trajectory and collecting a voltage response signal; performing time-frequency analysis on the voltage response signal to obtain a time-frequency spectrum;

[0045] S300, constructing a characteristic matrix based on the characteristic vectors of the N types of magnetic nanoparticles as an augmented matrix, using the spectral lines of the time-frequency spectrum as constant terms, and the content distribution of the N types of magnetic nanoparticles at each spectral line as an unknown quantity, constructing and solving a system of linear equations to obtain each unknown quantity;

[0046] S400, using the angle corresponding to the magnetic field free line during the first scan of the object to be imaged as the initial angle, discretely rotating the magnetic field free line through P angles, performing scanning at each angle to obtain a voltage response signal, and obtaining the content distribution of N types of magnetic nanoparticles at each angle according to the methods of S200 and S300; wherein P is a positive integer;

[0047] S500, constructing sinusoidal graphs of N types of magnetic nanoparticles based on the content distributions of N types of magnetic nanoparticles at P angles; back-projecting and reconstructing the sinusoidal graphs of the N types of magnetic nanoparticles to obtain multi-color images, and superimposing them to obtain a reconstructed image.

[0048] In order to more clearly illustrate the multi-color magnetic particle imaging method based on magnetic field free line projection decoding of the present invention, the following is combined with the attached Figure 2 Each step in an embodiment of the method of the present invention is described in detail.

[0049] S100, placing N types of magnetic nanoparticles contained in the object to be imaged at the center of the imaging field of a magnetic field free line magnetic particle imaging device for scanning, and after scanning, using time-frequency analysis to obtain a central spectral line of the time-frequency spectrum as a characteristic vector of the N types of magnetic nanoparticles;

[0050] In this embodiment, the number of magnetic nanoparticles to be imaged is N, which are respectively recorded as the first magnetic nanoparticles , the second magnetic nanoparticle ,...,Nth magnetic nanoparticle ; After being placed in an imaging device, they are scanned in one dimension and subjected to time-frequency analysis to obtain the central spectrum line of the time-frequency spectrum, i.e., the characteristic vectors of various types of magnetic nanoparticles (specifically, the time-frequency spectrum is obtained by using a time-frequency analysis method including but not limited to short-time Fourier transform, and the central spectrum line is extracted. The signal of the magnetic nanoparticles is specifically generated by the intermodulation mechanism of the magnetic nanoparticles driven by the excitation magnetic field, and the M intermodulation signals are extracted to construct the characteristic vector), recorded as the first eigenvector , the second eigenvector ,...,Nth eigenvector , where the eigenvector , is a vector with a complex field length of M, requiring The signal of the magnetic nanoparticles is specifically generated by the intermodulation mechanism of the magnetic nanoparticles driven by the excitation magnetic field, and M is the number of intermodulation harmonic signals.

[0051] S200, placing the object to be imaged in the imaging field of the magnetic field free line magnetic particle imaging device, scanning the object to be imaged using a set driving trajectory and collecting a voltage response signal; performing time-frequency analysis on the voltage response signal to obtain a time-frequency spectrum;

[0052] In this embodiment, a driving trajectory of a triangle wave superimposed on a sine wave is preferably used to scan the object to be imaged and collect the voltage response signal.

[0053] S300, constructing a characteristic matrix based on the characteristic vectors of the N types of magnetic nanoparticles as an augmented matrix, using the spectral lines of the time-frequency spectrum as constant terms, and the content distribution of the N types of magnetic nanoparticles at each spectral line as an unknown quantity, constructing and solving a system of linear equations to obtain each unknown quantity;

[0054] In this embodiment, the method for constructing the feature matrix is: concatenating the feature vectors of N types of magnetic nanoparticles in rows: ,in .

[0055] Use the feature matrix A as the augmented matrix and use the spectral lines of the time spectrum in S200 as the constant terms (Specifically: the spectral line vector extracts the same frequency point as the magnetic nanoparticle feature vector, , , is the number of spectral lines, indicating the dimension of the one-dimensional projection of the magnetic field free line), and the content distribution of N kinds of magnetic nanoparticles at each spectral line is taken as the unknown quantity ( , ), and solve each spectral line in turn The linear equations ,get .

[0056] S400, using the angle corresponding to the magnetic field free line during the first scan of the object to be imaged as the initial angle, discretely rotating the magnetic field free line through P angles, performing scanning at each angle to obtain a voltage response signal, and obtaining the content distribution of N types of magnetic nanoparticles at each angle according to the methods of S200 and S300; wherein P is a positive integer;

[0057] In this embodiment, the magnetic field free line is discretely rotated by P angles, each angle is scanned to obtain a voltage response signal, and the content distribution of N types of particles at each angle is obtained according to steps S200 and S300. .

[0058] S500, constructing sinusoidal graphs of N types of magnetic nanoparticles based on the content distributions of N types of magnetic nanoparticles at P angles; back-projecting and reconstructing the sinusoidal graphs of the N types of magnetic nanoparticles to obtain multi-color images, and superimposing them to obtain a reconstructed image.

[0059] In this embodiment, based on the content distribution of N types of magnetic nanoparticles at P angles, a sinusoidal graph of N types of magnetic nanoparticles is constructed as follows:

[0060] The content distribution of N kinds of magnetic nanoparticles at P angles ,according to k Index fill column position, according to pThe index fills the row position, building the n A sine diagram, according to n The index constructs N sinusoidal graphs and assigns N color maps.

[0061] The constructed sinusoidal images of N particles are reconstructed by back-projection (the present invention preferably adopts the filtered back-projection method with Ram-Lak as the filter) to obtain a multi-color image. , and assign the same N colors as the corresponding sinusoidal graph for visualization.

[0062] In order to facilitate a further understanding of the present invention, specific examples are given below.

[0063] First of all, Figure 3-Figure 8 Meaning of the digital codes: 100-imaging field of view; 201-the first magnetic nanoparticle; 202-the second magnetic nanoparticle; 203-the third magnetic nanoparticle; 300-magnetic field free line; 301-position 1 of the magnetic field free line; 302-position 2 of the magnetic field free line during translation; 303-position 3 of the magnetic field free line during translation; 304-rotation position 1 of the magnetic field free line; 305-rotation position 2 of the magnetic field free line; 306-rotation position 3 of the magnetic field free line; 307-rotation position 4 of the magnetic field free line; 400-grayscale projection superposition of the object to be imaged; 401-grayscale projection of the first particle; 402-grayscale projection of the second particle; 403-grayscale projection of the third particle; 501-back-projection reconstructed image of the first particle; 502-back-projection reconstructed image of the second particle; 503-back-projection reconstructed image of the third particle.

[0064] The object to be imaged contains N = 3 different magnetic nanoparticles with different spatial distributions, such as Figure 4 As shown, the three kinds of magnetic nanoparticles are respectively recorded as the first particle, the second particle and the third particle. Before imaging, a single sample of the three kinds of particles is placed at the center of the imaging field of view 100, and the magnetic field free line is driven to perform a one-dimensional scan to obtain the voltage signal of the magnetic nanoparticle response, as shown in FIG. Figure 3 As shown, the first particle is placed at the imaging center and scanned, as shown in FIG. Figure 5 As shown in the figure, the magnetic field free line performs a one-dimensional scan by translating at the current angle. The trajectory of the magnetic field free line is a triangle wave superimposed on a sine wave. The triangle wave has an amplitude of 30 mT, using only half the cycle from the negative peak to the positive peak, and a frequency of 1 Hz. The sine wave has an amplitude of 4 mT and a frequency of 3000 Hz. The gradient of the magnetic field free line is 1.5 T / m. The magnetic field free line can cover a maximum field of view with a diameter of 40 mm, that is, 100 mm has a diameter of 40 mm.

[0065] After scanning the three single particle samples and obtaining the voltage response signals, time-frequency analysis is performed (this embodiment uses short-time Fourier transform as the time-frequency analysis method, but other time-frequency analysis methods such as wavelet transform, Hilbert-Huang transform, etc. can also be used in general) to obtain the time-frequency spectrum, and the central spectral line vector of the time-frequency spectrum is extracted as the characteristic vector of the corresponding magnetic nanoparticle. In this embodiment, the voltage response signal is subjected to short-time Fourier transform to obtain the time-frequency spectrum, and the extracted characteristic vector is .

[0066] The characteristic vectors of the three magnetic nanoparticles obtained are spliced row by row to construct a characteristic matrix , .Will Figure 5 The magnetic field free line in the initial angle is set to p = 1, and rotated at equal intervals of P = 15. At the initial angle, after a one-dimensional scan, the voltage signal of the magnetic nanoparticle response is obtained and the response vector is obtained after short-time Fourier transform. , In this embodiment, the one-dimensional projection signal of the object to be imaged is segmented into K=25 pixels by short-time Fourier transform. A linear equation system is constructed:

[0067] (1)

[0068] Solve K linear equations to obtain the distribution of magnetic nanoparticle content of the object to be imaged at the current angle. Further, the response vector at the initial angle is recorded as , the content distribution of magnetic nanoparticles is recorded as .like Figure 7 As shown, the rotating magnetic field free line is adjusted to multiple angles. , then the linear relationship between the magnetic nanoparticle content distribution and the response voltage signal at each angle is:

[0069] (2)

[0070] In particular, the linear equations under the initial angle can be expressed as: Solve the K=25 linear equations at the initial angle to obtain the content distribution of magnetic nanoparticles at the current angle, such as Figure 6 As shown in the figure on the right. Figure 6 The left figure is the projection distribution of the superposition of 3 magnetic nanoparticle signals. As a comparison, after solving The overlay projection can be interpreted as Figure 6 The decoding result is shown in the figure on the right. The solution of formula (2) . The vector It represents the content of the first particle at the kth position obtained by magnetic field free line scanning at angle p. represents the content of the nth particle at the kth position obtained by magnetic field free line scanning at angle p. In this embodiment, .

[0071] After solving the linear equations at all rotation angles and all positions, the obtained , respectively construct the sinusoidal graphs of the first to third particles. The specific method is to Fill the values to the kth row and pth column of the nth sinusoidal graph.

[0072] After constructing the sinusoidal graphs of the three particles, the concentration distribution images of the three magnetic nanoparticles are reconstructed by the back projection method and superimposed to obtain the reconstructed image I. In this embodiment, the filtered back projection method with Ram-Lak as the filter is used (other parameter filtered back projection methods can also be used in general). The reconstruction result is shown in FIG. Figure 8 As shown, 501 to 503 are 、 、 , further assigning three different color maps for visualization can show the concentration distribution of three types of magnetic nanoparticles.

[0073] A multi-color magnetic particle imaging system based on magnetic field free line projection decoding according to a second embodiment of the present invention includes:

[0074] a one-dimensional scanning module configured to place N types of magnetic nanoparticles contained in the object to be imaged at the center of the imaging field of the magnetic field free line magnetic particle imaging device for scanning, and after scanning, use time-frequency analysis to obtain the central spectral line of the time-frequency spectrum as the characteristic vector of the N types of magnetic nanoparticles;

[0075] an imaging object scanning module configured to place the object to be imaged in the imaging field of view of the magnetic field free line magnetic particle imaging device, scan the object to be imaged using a set driving trajectory and collect a voltage response signal; perform time-frequency analysis on the voltage response signal to obtain a time-frequency spectrum;

[0076] an equation system construction module configured to construct a characteristic matrix based on the characteristic vectors of the N types of magnetic nanoparticles as an augmented matrix, use the spectral lines of the time-frequency spectrum as constant terms, use the content distribution of the N types of magnetic nanoparticles at each spectral line as an unknown quantity, construct a linear equation system and solve it to obtain each unknown quantity;

[0077] a content distribution acquisition module configured to use the angle corresponding to the magnetic field free line during the first scan of the object to be imaged as an initial angle, discretely rotate the magnetic field free line by P angles, scan at each angle to obtain a voltage response signal, and obtain the content distribution of N types of magnetic nanoparticles at each angle according to the methods of S200 and S300; wherein P is a positive integer;

[0078] The image reconstruction module is configured to construct a sinusoidal graph of N types of magnetic nanoparticles based on the content distribution of N types of magnetic nanoparticles at P angles; back-project the sinusoidal graphs of the N types of magnetic nanoparticles to reconstruct a multi-color image, and superimpose the images to obtain a reconstructed image.

[0079] In addition, the system further comprises a color mapping module; the color mapping module is configured to assign a color map to the reconstructed images of the N types of magnetic nanoparticles.

[0080] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working process and related instructions of the system described above can refer to the corresponding process in the aforementioned method embodiment and will not be repeated here.

[0081] It should be noted that the multi-color magnetic particle imaging system based on magnetic field free line projection decoding provided in the above embodiment is merely illustrated by the division of the above functional modules. In actual 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 embodiment can be combined into a single 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 merely for the purpose of distinguishing the modules or steps and are not to be considered as improper limitations of the present invention.

[0082] An electronic device according to a third embodiment of the present invention comprises: at least one processor; and a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor, the instructions being executed by the processor to implement the above-mentioned multi-color magnetic particle imaging method based on magnetic field free line projection decoding.

[0083] A fourth embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions are used to be executed by the computer to implement the above-mentioned multi-color magnetic particle imaging method based on magnetic field free line projection decoding.

[0084] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process and related instructions of the electronic device and computer-readable storage medium described above can refer to the corresponding process in the aforementioned method example and will not be repeated here.

[0085] Those skilled in the art should be able to appreciate that the modules and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two, and the programs corresponding to the software modules and method steps can be placed in random access memory (RAM), internal 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. In order to clearly illustrate the interchangeability of electronic hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0086] The terms "first", "second", etc. are used to distinguish similar objects, rather than to describe or indicate a particular order or sequence.

[0087] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0088] Thus far, the technical solutions of the present invention have been described in conjunction with 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 may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A multi-color magnetic particle imaging method based on magnetic field free line projection decoding, characterized in that: The method comprises the following steps: S100, placing N types of magnetic nanoparticles contained in the object to be imaged at the center of the imaging field of a magnetic field free line magnetic particle imaging device for scanning, and after scanning, using time-frequency analysis to obtain a central spectral line of the time-frequency spectrum as a characteristic vector of the N types of magnetic nanoparticles; S200, placing the object to be imaged in the imaging field of the magnetic field free line magnetic particle imaging device, scanning the object to be imaged using a set driving trajectory and collecting a voltage response signal; performing time-frequency analysis on the voltage response signal to obtain a time-frequency spectrum; S300, constructing a characteristic matrix based on the characteristic vectors of the N types of magnetic nanoparticles as an augmented matrix, using the spectral lines of the time-frequency spectrum as constant terms, and the content distribution of the N types of magnetic nanoparticles at each spectral line as an unknown quantity, constructing and solving a system of linear equations to obtain each unknown quantity; S400, using the angle corresponding to the magnetic field free line during the first scan of the object to be imaged as the initial angle, discretely rotating the magnetic field free line through P angles, performing scanning at each angle to obtain a voltage response signal, and obtaining the content distribution of N types of magnetic nanoparticles at each angle according to the methods of S200 and S300; wherein P is a positive integer; S500, constructing sinusoidal graphs of N types of magnetic nanoparticles based on the content distributions of N types of magnetic nanoparticles at P angles; back-projecting and reconstructing the sinusoidal graphs of the N types of magnetic nanoparticles to obtain multi-color images, and superimposing them to obtain a reconstructed image.

2. The multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to claim 1, characterized in that: The magnetic field free line magnetic particle imaging device adopts one-dimensional scanning when scanning the N kinds of magnetic nanoparticles contained in the object to be imaged.

3. The multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to claim 1, characterized in that: The feature vector , is a vector of length M in the complex field, .

4. The multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to claim 1, characterized in that: The set driving trajectory is a driving trajectory of a triangle wave superimposed on a sine wave.

5. The multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to claim 1, characterized in that: A characteristic matrix is constructed based on the characteristic vectors of the N types of magnetic nanoparticles, and the method is as follows: The characteristic vectors of the N magnetic nanoparticles Concatenate by rows to get the feature matrix.

6. The multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to claim 5, characterized in that: Based on the content distribution of N kinds of magnetic nanoparticles at P angles, a sinusoidal graph of N kinds of magnetic nanoparticles is constructed as follows: The content distribution of N kinds of magnetic nanoparticles at P angles ,according to k Index fill column position, according to p The index fills the row position, building the n A sine diagram, according to n Index to construct N sinograms.

7. The multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to claim 1, characterized in that: The back-projection reconstruction method includes a filtered back-projection method using Ram-Lak as a filter.

8. The multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to claim 1, characterized in that: After constructing the sinusoidal graphs of the N types of magnetic nanoparticles in S500 , the method further includes: assigning color maps to the sinusoidal graphs of the N types of magnetic nanoparticles respectively.

9. A multi-color magnetic particle imaging system based on magnetic field free line projection decoding, characterized in that: The system includes: a one-dimensional scanning module configured to place N types of magnetic nanoparticles contained in the object to be imaged at the center of the imaging field of the magnetic field free line magnetic particle imaging device for scanning, and after scanning, use time-frequency analysis to obtain the central spectral line of the time-frequency spectrum as the characteristic vector of the N types of magnetic nanoparticles; an imaging object scanning module configured to place the object to be imaged in the imaging field of view of the magnetic field free line magnetic particle imaging device, scan the object to be imaged using a set driving trajectory and collect a voltage response signal; perform time-frequency analysis on the voltage response signal to obtain a time-frequency spectrum; an equation system construction module configured to construct a characteristic matrix based on the characteristic vectors of the N types of magnetic nanoparticles as an augmented matrix, use the spectral lines of the time-frequency spectrum as constant terms, use the content distribution of the N types of magnetic nanoparticles at each spectral line as an unknown quantity, construct a linear equation system and solve it to obtain each unknown quantity; a content distribution acquisition module configured to use the angle corresponding to the magnetic field free line during the first scan of the object to be imaged as an initial angle, discretely rotate the magnetic field free line by P angles, scan at each angle to obtain a voltage response signal, and obtain the content distribution of N types of magnetic nanoparticles at each angle according to the methods of S200 and S300; wherein P is a positive integer; The image reconstruction module is configured to construct a sinusoidal graph of N types of magnetic nanoparticles based on the content distribution of N types of magnetic nanoparticles at P angles; back-project the sinusoidal graphs of the N types of magnetic nanoparticles to reconstruct a multi-color image, and superimpose the images to obtain a reconstructed image.

10. The multi-color magnetic particle imaging system based on magnetic field free line projection decoding according to claim 9, characterized in that: The system also includes a color mapping module; The color mapping module is configured to assign a color map to the reconstructed images of N types of magnetic nanoparticles.

Images