Multicolor magnetic particle imaging method and system based on magnetic field free line projection decoding

Abstract

The invention belongs to the field of biomedical imaging, particularly relates to a multicolor magnetic particle imaging method and system based on magnetic field free line projection decoding, and aims to solve the problems of low imaging efficiency and quality caused by the absence of a relaxation-based multicolor imaging method by using a magnetic field free line in the prior art. The method comprises the following steps: respectively placing N kinds of magnetic nanoparticles in an imaging view center for scanning, and obtaining a time-frequency spectrum center spectral line by adopting time-frequency analysis; scanning an imaging object, acquiring a voltage response signal and performing time-frequency analysis to obtain a time-frequency spectrum; a linear equation set is constructed and solved, and all unknown quantities are obtained; discretely rotating the free line of the magnetic field by P angles, and obtaining the content distribution of N magnetic nanoparticles at each angle; and constructing a sinogram of the N magnetic nanoparticles, performing back projection reconstruction to obtain multicolor images, and superposing the multicolor images to obtain a reconstructed image. According to the invention, relaxation-based multicolor imaging is realized by using the free line of the magnetic field, and the imaging efficiency and quality are improved.

Description

Technical Field

[0001] The 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] As an emerging biomedical imaging technology, magnetic particle imaging has developed rapidly in recent years. Magnetic nanoparticles as tracers can be metabolized by the human body and have good biosafety. In addition, magnetic nanoparticles can be functionalized and have better biocompatibility through surface modification. Under the excitation magnetic field of the magnetic particle device, particles of different shapes, particle sizes and surface modifications show 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 distribution separately, and visualize them as different colors for distinction. 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 is used to display the concentration distribution of the two particles to provide visual guidance for catheter positioning.

[0003] Magnetic particle imaging constructs magnetic field free points or magnetic field free lines to drive the movement of point-shaped or linear low-field areas for spatial encoding. There are two main technical directions for multi-color magnetic particle imaging: one is based on a multi-color system matrix, which measures the system matrix of multiple particles by solving a set of linear equations for imaging, but the calibration process is cumbersome and the inverse problem of the multi-color system matrix has certain ill-posedness; the other is based on relaxation characteristics, without the need for advance calibration, and uses particle magnetization signals to analyze relaxation time for imaging. At present, relaxation-based multi-color magnetic particle imaging technology mainly relies on magnetic field free points for point-by-point scanning and imaging. Compared with point-shaped low-magnetic field areas, linear scanning based on magnetic field free lines has the potential to provide higher magnetic particle detection sensitivity. Due to the complex characteristics of magnetic field free lines that rely on multi-angle projection, there is currently no technology that uses magnetic field free lines for relaxation-based multi-color imaging.

[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 on 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 there is no method for performing relaxation-based multi-color imaging using magnetic field free lines in the prior art, 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: S100, placing N kinds of magnetic nanoparticles contained in the object to be imaged in the center of the imaging field of the magnetic field free line magnetic particle imaging device for scanning, and after scanning, using time-frequency analysis to obtain the central spectral line of the time-frequency spectrum as the characteristic vector of the N kinds 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 kinds of magnetic nanoparticles as an augmented matrix, taking the spectral lines of the time-frequency spectrum as constant terms, taking the content distribution of the N kinds of magnetic nanoparticles at each spectral line as an unknown quantity, constructing a linear equation system and solving it to obtain each unknown quantity; S400, taking the angle corresponding to the magnetic field free line when the object to be imaged is scanned for the first time as the initial angle, discretely rotating the magnetic field free line by P angles, scanning at each angle to obtain a voltage response signal, and obtaining the content distribution of N kinds 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 kinds of magnetic nanoparticles based on the content distribution of N kinds of magnetic nanoparticles at P angles; back-projecting and reconstructing the sinusoidal graphs of the N kinds of magnetic nanoparticles to obtain a multi-color image, and superimposing them to obtain a reconstructed image.

[0006] 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.

[0007] In some preferred embodiments, the feature vector , is a vector of length M in the complex field, .

[0008] In some preferred embodiments, the set driving trajectory is a driving trajectory of a triangle wave superimposed on a sine wave.

[0009] 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 rows to get the feature matrix.

[0010] In some preferred embodiments, 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, and the method is: The content distribution of N kinds of magnetic nanoparticles at P angles ,according to kIndex fills the column position, according to p The index fills the row position, constructing the n A sine graph, according to n Index to construct N sinograms.

[0011] In some preferred embodiments, the back-projection reconstruction method includes a filtered back-projection method using Ram-Lak as a filter.

[0012] In some preferred embodiments, after constructing the sinusoidal graphs of the N kinds of magnetic nanoparticles in S500, the method further includes: assigning color graphs to the sinusoidal graphs of the N kinds of magnetic nanoparticles respectively.

[0013] 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: A one-dimensional scanning module is configured to place N kinds of magnetic nanoparticles contained in the object to be imaged in 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 kinds of magnetic nanoparticles; An imaging object scanning module is 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 group construction module is configured to construct a characteristic matrix based on the characteristic vectors of the N kinds 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 kinds of magnetic nanoparticles at each spectral line as an unknown quantity, construct a linear equation group and solve it to obtain each unknown quantity; The content distribution acquisition module is configured to use the angle corresponding to the magnetic field free line when the object to be imaged is scanned for the first time as the 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 kinds of magnetic nanoparticles at each angle according to the method of S200 and S300; wherein P is a positive integer; The image reconstruction module is configured to construct a sinusoidal graph of N kinds of magnetic nanoparticles based on the content distribution of N kinds of magnetic nanoparticles at P angles; back-project the sinusoidal graph of the N kinds of magnetic nanoparticles to reconstruct a multi-color image, and superimpose them to obtain a reconstructed image.

[0014] In some preferred embodiments, 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.

[0015] Beneficial effects of the present invention: The present invention realizes relaxation-based multi-color imaging using magnetic field free lines, thereby improving imaging efficiency and quality.

[0016] The present invention can image a variety of magnetic particles efficiently and without calibration. Compared with the traditional method, the present invention not only simplifies the imaging process, avoids the cumbersome calibration steps and the challenge of ill-posedness caused by the inverse problem of the multi-color system matrix, but also significantly improves the sensitivity of magnetic particle detection by using the free lines of the magnetic field for linear scanning. It is particularly suitable for application scenarios that require high-sensitivity imaging, and provides a more advanced and reliable solution for the field of multi-color magnetic particle imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings.

[0018] Figure 1 It 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; Figure 2 It 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; Figure 3 It is a schematic diagram of collecting characteristic vectors of the first magnetic nanoparticle according to an embodiment of the present invention; Figure 4 is a schematic diagram of an object to be imaged including three different magnetic nanoparticles and different spatial concentration distributions according to an embodiment of the present invention; Figure 5 It is a schematic diagram of a magnetic field free line in an embodiment of the present invention being translated at a certain angle in a two-dimensional plane to perform one-dimensional scanning; Figure 6 In one embodiment of the present invention, a magnetic field free line is scanned in one dimension at a certain angle to obtain a projection; Figure 7 It is a schematic diagram of a magnetic field free line rotating at multiple angles according to an embodiment of the present invention; Figure 8 It 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

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0022] A multi-color magnetic particle imaging method based on magnetic field free line projection decoding according to a first embodiment of the present invention is as follows: Figure 1 As shown, the following steps are included: S100, placing N kinds of magnetic nanoparticles contained in the object to be imaged in the center of the imaging field of the magnetic field free line magnetic particle imaging device for scanning, and after scanning, using time-frequency analysis to obtain the central spectral line of the time-frequency spectrum as the characteristic vector of the N kinds 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 kinds of magnetic nanoparticles as an augmented matrix, taking the spectral lines of the time-frequency spectrum as constant terms, taking the content distribution of the N kinds of magnetic nanoparticles at each spectral line as an unknown quantity, constructing a linear equation system and solving it to obtain each unknown quantity; S400, taking the angle corresponding to the magnetic field free line when the object to be imaged is scanned for the first time as the initial angle, discretely rotating the magnetic field free line by P angles, scanning at each angle to obtain a voltage response signal, and obtaining the content distribution of N kinds 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 kinds of magnetic nanoparticles based on the content distribution of N kinds of magnetic nanoparticles at P angles; back-projecting and reconstructing the sinusoidal graphs of the N kinds of magnetic nanoparticles to obtain a multi-color image, and superimposing them to obtain a reconstructed image.

[0023] 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.

[0024] S100, placing N kinds of magnetic nanoparticles contained in the object to be imaged in the center of the imaging field of the magnetic field free line magnetic particle imaging device for scanning, and after scanning, using time-frequency analysis to obtain the central spectral line of the time-frequency spectrum as the characteristic vector of the N kinds of magnetic nanoparticles; In this embodiment, the number of magnetic nanoparticles to be imaged is N, which are respectively denoted 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 spectral 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 spectral 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 characteristic vector , the second eigenvector ,..., the 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.

[0025] 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; In this embodiment, it is preferred to use a driving trajectory of a triangle wave superimposed on a sine wave to scan the object to be imaged and collect a voltage response signal.

[0026] S300, constructing a characteristic matrix based on the characteristic vectors of the N kinds of magnetic nanoparticles as an augmented matrix, taking the spectral lines of the time-frequency spectrum as constant terms, taking the content distribution of the N kinds of magnetic nanoparticles at each spectral line as an unknown quantity, constructing a linear equation system and solving it to obtain each unknown quantity; In this embodiment, the method for constructing the feature matrix is: concatenating the feature vectors of N types of magnetic nanoparticles in rows: ,in .

[0027] Use the feature matrix A as the augmented matrix and use the spectral lines of the time-frequency spectrum in S200 as the constant term (Specifically: the spectral line vector extracts the frequency point that is the same as the characteristic vector of the magnetic nanoparticle, , , 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 .

[0028] S400, taking the angle corresponding to the magnetic field free line when the object to be imaged is scanned for the first time as the initial angle, discretely rotating the magnetic field free line by P angles, scanning at each angle to obtain a voltage response signal, and obtaining the content distribution of N kinds of magnetic nanoparticles at each angle according to the methods of S200 and S300; wherein P is a positive integer; 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 kinds of particles at each angle is obtained according to steps S200 and S300. .

[0029] S500, constructing sinusoidal graphs of N kinds of magnetic nanoparticles based on the content distribution of N kinds of magnetic nanoparticles at P angles; back-projecting and reconstructing the sinusoidal graphs of the N kinds of magnetic nanoparticles to obtain a multi-color image, and superimposing them to obtain a reconstructed image.

[0030] In this embodiment, 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, and the method is as follows: The content distribution of N kinds of magnetic nanoparticles at P angles ,according to k Index fills the column position, according to p The index fills the row position, constructing the n A sine graph, according to n The index constructs N sinusoidal graphs and assigns N color maps.

[0031] The constructed sinusoidal images of the N particles are back-projected and reconstructed (the present invention preferably uses a filtered back-projection method with Ram-Lak as a filter) to obtain a multi-color image. , and assign the same N colors as the corresponding sinusoidal graph for visualization.

[0032] In order to further understand the present invention, specific examples are given below.

[0033] First of all, Figure 3-Figure 8Meaning 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.

[0034] 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 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 one-dimensional scanning 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. Figure 5 As shown in the figure, the magnetic field free line performs one-dimensional scanning by translation at the current angle. The motion trajectory of the magnetic field free line is a triangle wave superimposed on a sine wave. The triangle wave amplitude is 30mT, and only half of the cycle from the negative peak to the positive peak of the triangle wave is used, with a frequency of 1Hz; the sine wave amplitude is 4mT, and the frequency is 3000Hz. The gradient of the magnetic field free line is 1.5T / m. The magnetic field free line can cover a field of view with a diameter of 40mm at most, that is, 100 has a diameter of 40mm.

[0035] 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 and Hilbert-Huang transform 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 .

[0036] The feature vectors of the three magnetic nanoparticles obtained were concatenated row by row to construct a feature matrix , .Will Figure 5The magnetic field free line in is set to the initial angle, that is, angle p=1, and rotated at equal intervals of angle 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 transformation. , 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: (1) 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 free lines of the rotating magnetic field are rotated to multiple angles , then the linear relationship between the magnetic nanoparticle content distribution and the response voltage signal at each angle is: (2) In particular, the linear equations at the initial angle can be written 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 shows the projection distribution of the superposition of the magnetic nanoparticle signals in 3. 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 represents the content of the first particle at the kth position obtained by scanning the magnetic field free line at angle p. represents the content of the kth position obtained by scanning the magnetic field free line at the nth particle at angle p. In this embodiment .

[0037] After solving the linear equations at all rotation angles and all positions, according to the obtained , respectively construct the sinusoidal graphs of the first to third particles. The specific method is to The values ​​are filled to the kth row and pth column of the nth sinusoidal graph.

[0038] 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 a reconstructed image I. In this embodiment, a filtering back projection method using Ram-Lak as a filter is used (other parameter filtering back projection methods can also be used in general). The reconstruction result is shown in FIG. Figure 8 As shown, 501 to 503 are respectively , , , and further assigning three different color maps for visualization can show the concentration distribution of the three types of magnetic nanoparticles.

[0039] A multi-color magnetic particle imaging system based on magnetic field free line projection decoding according to a second embodiment of the present invention comprises: A one-dimensional scanning module is configured to place N kinds of magnetic nanoparticles contained in the object to be imaged in 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 kinds of magnetic nanoparticles; An imaging object scanning module is 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 group construction module is configured to construct a characteristic matrix based on the characteristic vectors of the N kinds 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 kinds of magnetic nanoparticles at each spectral line as an unknown quantity, construct a linear equation group and solve it to obtain each unknown quantity; The content distribution acquisition module is configured to use the angle corresponding to the magnetic field free line when the object to be imaged is scanned for the first time as the 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 kinds of magnetic nanoparticles at each angle according to the method of S200 and S300; wherein P is a positive integer; The image reconstruction module is configured to construct a sinusoidal graph of N kinds of magnetic nanoparticles based on the content distribution of N kinds of magnetic nanoparticles at P angles; back-project the sinusoidal graph of the N kinds of magnetic nanoparticles to reconstruct a multi-color image, and superimpose them to obtain a reconstructed image.

[0040] In addition, the system also includes 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.

[0041] 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 system described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0042] It should be noted that the multicolor magnetic particle imaging system based on magnetic field free line projection decoding provided in the above embodiment is only illustrated by 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 decomposed or combined. For example, the modules in the above embodiment can be combined 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 modules or steps, and are not regarded as improper limitations of the present invention.

[0043] An electronic device according to the 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, and the instructions are used to be executed by the processor to implement the above-mentioned multi-color magnetic particle imaging method based on magnetic field free line projection decoding.

[0044] A computer-readable storage medium according to a fourth embodiment of the present invention 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.

[0045] Technicians in the technical field 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.

[0046] 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 with 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), 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 technical field. In order to clearly illustrate the interchangeability of electronic hardware and software, the composition and steps of each example have been generally described in the above description according to the function. 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 can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0047] The terms "first", "second", etc. are used to distinguish similar objects rather than to describe or indicate a particular order or sequence.

[0048] The term "comprise" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that includes a list of elements includes not only those elements but also other elements not expressly listed, or also includes elements inherent to such process, method, article, or apparatus / device.

[0049] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle 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 these changes or substitutions will fall within the protection scope 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 kinds of magnetic nanoparticles contained in the object to be imaged in the center of the imaging field of the magnetic field free line magnetic particle imaging device for scanning, and after scanning, using time-frequency analysis to obtain the central spectral line of the time-frequency spectrum as the characteristic vector of the N kinds 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 kinds of magnetic nanoparticles as an augmented matrix, taking the spectral lines of the time-frequency spectrum as constant terms, taking the content distribution of the N kinds of magnetic nanoparticles at each spectral line as an unknown quantity, constructing a linear equation system and solving it to obtain each unknown quantity; S400, taking the angle corresponding to the magnetic field free line when the object to be imaged is scanned for the first time as the initial angle, discretely rotating the magnetic field free line by P angles, scanning at each angle to obtain a voltage response signal, and obtaining the content distribution of N kinds 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 kinds of magnetic nanoparticles based on the content distribution of N kinds of magnetic nanoparticles at P angles; back-projecting and reconstructing the sinusoidal graphs of the N kinds of magnetic nanoparticles to obtain a multi-color image, and superimposing them to obtain a reconstructed image.

2. A 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 kinds of magnetic nanoparticles, and the method is as follows: The characteristic vectors of the N magnetic nanoparticles Concatenate 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 fills the column position, according to p The index fills the row position, constructing the n A sine graph, 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 kinds of magnetic nanoparticles in S500 , the method further includes: assigning color graphs to the sinusoidal graphs of the N kinds 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 is configured to place N kinds of magnetic nanoparticles contained in the object to be imaged in 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 kinds of magnetic nanoparticles; An imaging object scanning module is 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 group construction module is configured to construct a characteristic matrix based on the characteristic vectors of the N kinds 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 kinds of magnetic nanoparticles at each spectral line as an unknown quantity, construct a linear equation group and solve it to obtain each unknown quantity; The content distribution acquisition module is configured to use the angle corresponding to the magnetic field free line when the object to be imaged is scanned for the first time as the 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 kinds of magnetic nanoparticles at each angle according to the method of S200 and S300; wherein P is a positive integer; The image reconstruction module is configured to construct a sinusoidal graph of N kinds of magnetic nanoparticles based on the content distribution of N kinds of magnetic nanoparticles at P angles; back-project the sinusoidal graph of the N kinds of magnetic nanoparticles to reconstruct a multi-color image, and superimpose them 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 the N types of magnetic nanoparticles.

Images