CN115797493B - Magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling - Google Patents
Magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling Download PDFInfo
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Abstract
The invention belongs to the technical field of magnetic particle imaging, in particular relates to a magnetic field free line magnetic particle imaging method, a system and equipment based on sparse sampling of a one-dimensional system matrix, and aims to solve the problems that an existing magnetic particle imaging method based on a densely sampled system matrix is low in correction efficiency, a post-processing model of the magnetic particle imaging method based on the sparse sampling system matrix is relatively complex and imaging efficiency is low. The method comprises the following steps: setting an initial angle, a rotation angle sequence and the imaging field of view, and measuring a one-dimensional system matrix in the gradient direction of a free line of a magnetic field under the initial angle; establishing an observation vector sequence; constructing a linear equation set sequence and solving to obtain a one-dimensional projection reconstruction result sequence; reconstructing a magnetic particle image of the target object based on the one-dimensional projection reconstruction result sequence. The invention greatly reduces the correction difficulty, does not need a post-processing model, and improves the imaging efficiency.
Description
Technical Field
The invention belongs to the technical field of magnetic particle imaging, and particularly relates to a magnetic field free line magnetic particle imaging method, system and equipment based on one-dimensional system matrix sparse sampling.
Background
Magnetic particle imaging is a new generation of medical imaging modalities proposed by the teachings of Gleich and Weizenecker. Based on the nonlinear magnetization response of the magnetic nanoparticles, the magnetic particle imaging can realize the in-vivo noninvasive three-dimensional tomography of organisms, and is verified by a large number of pre-clinical experiments, and has potential to be applied to critical clinical problems such as cardiovascular and cerebrovascular monitoring, magnetocaloric therapy, cell tracking and the like. The magnetic particle imaging can be divided into two imaging modes based on a magnetic field free point and a magnetic field free line according to the shape of a selected field, compared with the magnetic field free point, the magnetic field free line can detect signals of magnetic nano particles on a linear region at a time, the detection range is larger, the imaging sensitivity is higher, and the imaging method is a hot spot research direction in recent years.
The reconstruction process from the detected magnetic nanoparticle signal to the particle concentration space distribution image is a key link of magnetic particle imaging, and the reconstruction method commonly adopted in the technical field at present comprises the following steps: x-space method and system matrix method. The research shows that compared with the X space method, the system matrix method can more accurately measure and model the imaging system, and has higher reconstruction quality.
Turkish research team proposed and manufactured open magnetic field free line magnetic particle imaging devices in 2020, reconstructed using a system matrix method. In correcting the system matrix, an imaging field of view having a size of 34 mm long and 18 mm wide was set, and the particle response spectrum at each pixel point was measured using 2 mm by 2 mm samples. The team adopts a mode of rotating magnetic field free lines, takes 3 degrees as a step angle, rotates 60 angles altogether, measures a system matrix with the size of 17 times 9 once under each rotation angle, and finally combines the system matrix under all angles into a system matrix for constructing a linear equation set in an imaging model. This is a method for free line magnetic particle imaging of magnetic fields based on the system matrix method, which is commonly used in the current technical field. The measurement mode belongs to dense sampling and is relatively accurate, but the system matrix correction process is complex in operation, time-consuming, large in data storage quantity, high in calculation complexity in reconstruction and difficult to use for real-time imaging.
Aiming at the problem of high complexity of system matrix correction, the sparse sampling system matrix correction method based on technologies such as compressed sensing, data interpolation, deep learning super-resolution network and the like further appears, and the sparse sampling points in a two-dimensional or three-dimensional space are used for carrying out data post-processing according to a magnetic particle imaging principle to recover a densely sampled system matrix so as to reconstruct an image. However, the post-processing models of the methods are relatively complex, and particularly the deep learning method requires a large data volume and is seriously dependent on a hardware system for data measurement, so that the method is difficult to popularize at present.
Disclosure of Invention
In order to solve the above problems in the prior art, that is, in order to solve the problems that the existing magnetic particle imaging method based on the densely sampled system matrix has low correction efficiency, the post-processing model of the magnetic particle imaging method based on the sparsely sampled system matrix is relatively complex, and the imaging efficiency is low, the invention provides a magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparsely sampling, which is applied to a magnetic field free line-based magnetic particle imaging device, and the method comprises the following steps:
step S100, setting an initial angle, a rotation angle sequence and an imaging field size of the magnetic particle imaging equipment based on the magnetic field free line, and measuring a one-dimensional system matrix A in the gradient direction of the magnetic field free line under the initial angle;
step S200, placing the target object to be imaged in the imaging field of the magnetic particle imaging equipment based on the free line of the magnetic field, rotating the free line of the magnetic field or the target object to be imaged according to the rotating angle sequence set in the step S100, and establishing an observation vector sequence;
step S300, a linear equation set sequence is constructed and solved by combining the system matrix A and the observation vector sequence, and a one-dimensional projection reconstruction result sequence is obtained;
and step S400, reconstructing a magnetic particle image of the target object based on the one-dimensional projection reconstruction result sequence.
In some preferred embodiments, the initial angle is an angle of the magnetic particle imaging device based on magnetic field free lines in a radial direction of the magnetic field free lines.
In some preferred embodiments, the rotation angle sequence is set up by:
rotating the magnetic field free line by N angles in an equidistant or unequal interval mode by the initial angle of 0 degrees and rotating the magnetic field free line by 180 degrees, so that the movement range of the magnetic field free line can cover all imaging fields; where N represents a set number.
In some preferred embodiments, the dimension of the observation vector in the sequence of observation vectors is equal to the number of rows of the system matrix a.
In some preferred embodiments, reconstructing a magnetic particle image of the target object based on the sequence of one-dimensional projection reconstruction results, the method comprising:
and converting the one-dimensional projection reconstruction result sequence into a Radon space to establish a sinogram, and reconstructing a magnetic particle image of the target object by using a back projection method.
In a second aspect of the present invention, a free line magnetic field magnetic particle imaging system based on one-dimensional system matrix sparse sampling is provided, the system comprising: the system comprises an initialization setting module, an observation vector sequence construction module, an equation set construction and solving module and an image reconstruction module;
the initialization setting module is configured to set an initial angle, a rotation angle sequence and an imaging field size of the magnetic particle imaging device based on the magnetic field free line, and measure a one-dimensional system matrix A in the gradient direction of the magnetic field free line under the initial angle;
the observation vector sequence construction module is configured to place a target object to be imaged in the imaging field of the magnetic particle imaging equipment based on the free magnetic field lines, rotate the free magnetic field lines or the target object to be imaged according to the rotation angle sequence set by the initialization setting module, and establish an observation vector sequence;
the equation set constructing and solving module is configured to combine the system matrix A and the observation vector sequence, construct a linear equation set sequence and solve the linear equation set sequence to obtain a one-dimensional projection reconstruction result sequence;
the image reconstruction module is configured to reconstruct a magnetic particle image of the target object based on the one-dimensional projection reconstruction result sequence.
In a third aspect of the present invention, an electronic device is provided, including: at least one processor; and a memory communicatively coupled to at least one of the processors; the memory stores instructions executable by the processor for execution by the processor to implement the magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling.
In a fourth aspect of the present invention, a computer readable storage medium is provided, where computer instructions are stored, where the computer instructions are used to be executed by the computer to implement the above-mentioned magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling.
The invention has the beneficial effects that:
the invention greatly reduces the correction difficulty, does not need a post-processing model, and improves the imaging efficiency.
According to the invention, aiming at projection imaging characteristics, one-dimensional sparse sampling is adopted, reconstruction is carried out through a projection imaging method, and a complex dense sampling process or a data post-processing process is avoided; a large volume of test sample can be used in one-dimensional sampling, and the sampling signal to noise ratio is higher; the reconstruction is performed based on the one-dimensional system matrix, the calculation speed is high, the real-time imaging is facilitated, and the method is concise in flow and beneficial to popularization.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments made with reference to the following drawings.
FIG. 1 is a flow chart of a magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling in accordance with one embodiment of the present invention;
FIG. 2 is a schematic diagram of a frame of a magnetic field free line magnetic particle imaging method based on sparse sampling of a one-dimensional system matrix according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a prior art comparison of one embodiment of the present invention with the sampling process of the present invention;
FIG. 4 is an exemplary diagram of a one-dimensional system matrix for measuring the direction of the free line gradient of a magnetic field at an initial angle in accordance with one embodiment of the present invention;
FIG. 5 is an exemplary diagram of rotating magnetic field free lines or rotating a target object to be imaged in accordance with one embodiment of the present invention;
FIG. 6 is a sinogram of an L-shaped object to be imaged in accordance with one embodiment of the present invention;
FIG. 7 is a schematic diagram of the reconstruction result of an L-shaped object to be imaged using a direct back projection method according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a reconstruction result of an L-shaped object to be imaged using a filtered back projection method according to an embodiment of the present invention;
fig. 9 is a schematic diagram of a computer system suitable for use in implementing the electronic device of an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The present application is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other.
The magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling is applied to a magnetic particle imaging device based on magnetic field free lines, as shown in fig. 1, and comprises the following steps:
step S100, setting an initial angle, a rotation angle sequence and an imaging field size of the magnetic particle imaging equipment based on the magnetic field free line, and measuring a one-dimensional system matrix A in the gradient direction of the magnetic field free line under the initial angle;
step S200, placing the target object to be imaged in the imaging field of the magnetic particle imaging equipment based on the free line of the magnetic field, rotating the free line of the magnetic field or the target object to be imaged according to the rotating angle sequence set in the step S100, and establishing an observation vector sequence;
step S300, a linear equation set sequence is constructed and solved by combining the system matrix A and the observation vector sequence, and a one-dimensional projection reconstruction result sequence is obtained;
and step S400, reconstructing a magnetic particle image of the target object based on the one-dimensional projection reconstruction result sequence.
In order to more clearly describe the magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling, each step in one embodiment of the method is described in detail below with reference to the accompanying drawings.
Step S100, setting an initial angle, a rotation angle sequence and an imaging field size of the magnetic particle imaging equipment based on the magnetic field free line, and measuring a one-dimensional system matrix A in the gradient direction of the magnetic field free line under the initial angle;
in this embodiment, an initial angle, a rotation angle sequence, and an imaging field size of the magnetic particle imaging apparatus based on the magnetic field free line are set, and a one-dimensional system matrix a in the gradient direction of the magnetic field free line at the initial angle is measured and stored.
In the present invention, it is preferable to set the angle of the magnetic particle imaging apparatus based on the magnetic field free line in the radial direction of the magnetic field free line as the initial angle. The rotation angle sequence rotates N angles at the initial angle of 0 degrees in an equidistant or unequal-interval mode, and rotates 180 degrees altogether, so that the movement range of the free line of the magnetic field can cover all imaging fields; where N represents a set number, 9 or more is preferably set in this embodiment, and may be set according to actual conditions in other embodiments. The range requirement of the one-dimensional system matrix A is not less than the imaging field length; an elongated large volume sample is used in measuring the system matrix. The manner of measuring the one-dimensional system matrix is not unique, and the nature of "one-dimensional" is that information of each column along the radial direction of the free line of the magnetic field can be measured, wherein "column" is a dimension of "one-dimensional", not "row", not "two-dimensional", not limited to the shape and position of the test simulation body, and can conform to the nature of "one-dimensional system matrix", as in six examples in 4 in the figure, and the one-dimensional system matrix in step S100 can be measured.
Step S200, placing the target object to be imaged in the imaging field of the magnetic particle imaging equipment based on the free line of the magnetic field, rotating the free line of the magnetic field or the target object to be imaged according to the rotating angle sequence set in the step S100, and establishing an observation vector sequence;
in this embodiment, the rotation process starts from 0 DEG, the free line of the rotating magnetic field or the object to be imaged (or referred to as the object under test) is rotated, and the observation vector sequence { b } is established 1 ,b 2 ,...,b N And the dimension of the observation vector in the observation vector sequence is equal to the number of rows of the system matrix A.
Step S300, a linear equation set sequence is constructed and solved by combining the system matrix A and the observation vector sequence, and a one-dimensional projection reconstruction result sequence is obtained;
in this embodiment, the mathematical description of the series of linear equations is:
when solving a linear equation set, a regularization method is used for reducing the system matrix morbidity, and in the method, a truncated singular value decomposition algorithm is preferably used for solving the linear equation set sequence to obtain a one-dimensional projection reconstruction result sequence { x } 1 ,x 2 ,...,x N In other embodiments, the objective function may be established by a regularization method, and an iterative algorithm may be used to solve, or an algebraic reconstruction technique such as SVD may be used to solve the linear system of equations.
And step S400, reconstructing a magnetic particle image of the target object based on the one-dimensional projection reconstruction result sequence.
In this embodiment, the one-dimensional projection reconstruction result sequence is converted into Radon space to create a sinogram, and a back projection method is used to reconstruct a magnetic particle image of the target object.
In addition, to further verify the effectiveness of the method of the present invention, an imaging procedure of an "L" shaped framework (or simply a proxy) is illustrated.
In the imaging process of the L-shaped imitation body, an open magnetic field free line magnetic particle imaging device is preferably adopted, wherein the device comprises four runway-type gradient coils, two Helmholtz type exciting coils and two Helmholtz type receiving coils, and two-dimensional scanning imaging is carried out by rotating a target object to be imaged. Specific references may be made to: top C, gungor A. Tomographic Field Free Line Magnetic Particle Imaging With anOpen-Sided Scanner Configuration [ J ]. IEEE transactions on medical imaging,2020, 39 (12): 4164-4173.
The middle planes of the upper and lower groups of gradient coils are set as X-Y planes, the magnetic field direction on the X-Y planes is set as Z-axis direction, and the geometric centers of the four gradient coils are set as the origin of coordinates to establish a coordinate system. The selection field gradient is set to be 1T/m, the excitation magnetic field is excited by single frequency, the frequency is 2500 Hz, and the magnetic field strength is 30mT. The workstation is used for writing Libview control software to control the two power amplifiers to supply power to the gradient coil and the exciting coil; rotating the measured object by using a rotating motor, wherein the step angle is set to be 3.6 degrees, the angle rotation sequence is 0 degrees along the radial direction of a free line of a magnetic field, and the equal angle is 3 degrees, and the step angle is clockwise by N=60 angles to 180 degrees; the three-axis displacement table is used for measuring a one-dimensional system matrix A of the gradient direction of the free line of the magnetic field, and the sampling process is shown in (c) of fig. 3.
The test simulants were rotated using a perimag particle, 3D printed "L" shaped scaffold, with a particle-filled diluent as the target object to be imaged, on a rotating motor table, as shown in fig. 5.
After the above setting is completed, the rotating motor is started according to a predetermined rotation angle sequence, and the observation vector sequence { b ] at each angle is measured 1 ,b 2 ,...,b N }. After the measurement is completed, a linear equation set sequence is established by using the system matrix A and the observation vector sequence.
Carrying out one-dimensional projection reconstruction on all linear equation sets by using a truncated singular value decomposition algorithm to obtain a result sequence { x } 1 ,x 2 ,...,x N }. The truncated singular value decomposition algorithm suppresses system noise interference by removing smaller singular values, achieving a certain regularization effect.
Will { x } 1 ,x 2 ,...,x N The sequence is converted into Radon space to build a sine diagram, as shown in FIG. 6, an "L" shaped simulation used for the testSinograms of a volume (i.e., a target object).
After constructing the sinogram, reconstructing an image of the "L" -shaped measured object (i.e., the target object) by using a direct back projection method, as shown in fig. 7, where (a) in fig. 7 is a standard reference of the "L" -shaped measured object, and (b) in fig. 7 is a result of reconstruction by using the method proposed by the present patent.
An image of an "L" type measured object is reconstructed by using a "Ram-Lak" filter back projection method, as shown in fig. 8, wherein (a) in fig. 8 is a standard reference of the "L" type measured object, and (b) in fig. 8 is a result of reconstruction by using the method proposed by the present invention.
A magnetic field free line magnetic particle imaging system based on sparse sampling of a one-dimensional system matrix according to a second embodiment of the present invention, as shown in fig. 2, includes: the system comprises an initialization setting module 100, an observation vector sequence constructing module 200, an equation set constructing and solving module 300 and an image reconstructing module 400;
the initialization setting module 100 is configured to set an initial angle, a rotation angle sequence and an imaging field size of the magnetic particle imaging device based on the magnetic field free line, and measure a one-dimensional system matrix a in a gradient direction of the magnetic field free line at the initial angle;
the observation vector sequence construction module 200 is configured to place a target object to be imaged in the imaging field of the magnetic particle imaging device based on the free line of magnetic field, rotate the free line of magnetic field or the target object to be imaged according to the rotation angle sequence set by the initialization setting module 100, and establish an observation vector sequence;
the equation set constructing and solving module 300 is configured to combine the system matrix a and the observation vector sequence, construct a linear equation set sequence, and solve the linear equation set sequence to obtain a one-dimensional projection reconstruction result sequence;
the image reconstruction module 400 is configured to reconstruct a magnetic particle image of the target object based on the one-dimensional projection reconstruction result sequence.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working processes and related descriptions of the above-described system may refer to corresponding processes in the foregoing method embodiments, which are not repeated herein.
It should be noted that, in the magnetic field free line magnetic particle imaging system based on one-dimensional system matrix sparse sampling provided in the foregoing embodiment, only the division of the foregoing functional modules is illustrated, in practical application, the foregoing functional allocation may be completed by different functional modules according to needs, that is, the modules or steps in the foregoing embodiment of the present invention are further decomposed or combined, for example, the modules in the foregoing embodiment may be combined into one module, or may be further split into a plurality of sub-modules, so as to complete all or part of the functions described above. The names of the modules and steps related to the embodiments of the present invention are merely for distinguishing the respective modules or steps, and are not to be construed as unduly limiting the present invention.
An electronic device of a third embodiment of the present invention includes at least one processor; and a memory communicatively coupled to at least one of the processors; wherein the memory stores instructions executable by the processor for execution by the processor to implement the one-dimensional system matrix sparse sampling-based magnetic field free line magnetic particle imaging method of the claims.
A computer readable storage medium of a fourth embodiment of the present invention stores computer instructions for execution by the computer to implement the above-described magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working processes of the electronic device, the computer readable storage medium and related descriptions of the electronic device and the computer readable storage medium described above may refer to corresponding processes in the foregoing method examples, which are not described herein again.
Reference is now made to FIG. 9, which is a block diagram illustrating a computer system suitable for use in implementing embodiments of the present systems, methods, and apparatus. The server illustrated in fig. 9 is merely an example, and should not impose any limitation on the functionality and scope of use of the embodiments of the present application.
As shown in fig. 9, the computer system includes a central processing unit (CPU, central Processing Unit) 901 which can execute various appropriate actions and processes according to a program stored in a Read Only Memory (ROM) 902 or a program loaded from a storage portion 908 into a random access Memory (RAM, random Access Memory) 903. In the RAM 903, various programs and data required for system operation are also stored. The CPU 901, ROM 902, and RAM 903 are connected to each other through a bus 904. An Input/Output (I/O) interface 905 is also connected to bus 904.
The following components are connected to the I/O interface 905: an input section 906 including a keyboard, a mouse, and the like; an output portion 907 including a Cathode Ray Tube (CRT), a liquid crystal display (LCD, liquid Crystal Display), and the like, and a speaker, and the like; a storage portion 908 including a hard disk or the like; and a communication section 909 including a network interface card such as a LAN (local area network ) card, a modem, or the like. The communication section 909 performs communication processing via a network such as the internet. The drive 910 is also connected to the I/O interface 905 as needed. A removable medium 911 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, or the like is installed as needed on the drive 910 so that a computer program read out therefrom is installed into the storage section 908 as needed.
In particular, according to embodiments of the present disclosure, the processes described above with reference to flowcharts may be implemented as computer software programs. For example, embodiments of the present disclosure include a computer program product comprising a computer program embodied on a computer readable medium, the computer program comprising program code for performing the method shown in the flowcharts. In such an embodiment, the computer program may be downloaded and installed from the network via the communication portion 909 and/or installed from the removable medium 911. When the computer program is executed by a Central Processing Unit (CPU) 901, the above-described functions defined in the method of the present application are performed. It should be noted that the computer readable medium described in the present application may be a computer readable signal medium or a computer readable storage medium, or any combination of the two. The computer readable storage medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples of the computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. In the present application, however, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, with computer-readable program code embodied therein. Such a propagated data signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination of the foregoing. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to: wireless, wire, fiber optic cable, RF, etc., or any suitable combination of the foregoing.
Computer program code for carrying out operations of the present application may be written in one or more programming languages, including an object oriented programming language such as Java, smalltalk, C ++ and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computer (for example, through the Internet using an Internet service provider).
The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present application. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The terms "first," "second," and the like, are used for distinguishing between similar objects and not for describing a particular sequential or chronological order.
The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus/apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus/apparatus.
Thus far, the technical solution of the present invention has been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of protection of the present invention is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present invention, and such modifications and substitutions will fall within the scope of the present invention.
Claims (8)
1. The magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling is applied to magnetic field free line-based magnetic particle imaging equipment, and is characterized by comprising the following steps of:
step S100, setting an initial angle, a rotation angle sequence and an imaging field size of the magnetic particle imaging equipment based on the magnetic field free line, and measuring a one-dimensional system matrix A in the gradient direction of the magnetic field free line under the initial angle; the one-dimensional system matrix A is a system matrix constructed by arranging a sampling point on each column of the free line of the magnetic field along the radial direction of the free line of the magnetic field and based on the detected signals on each sampling point;
step S200, placing the target object to be imaged in the imaging field of the magnetic particle imaging equipment based on the free line of the magnetic field, rotating the free line of the magnetic field or the target object to be imaged according to the rotating angle sequence set in the step S100, and establishing an observation vector sequence;
step S300, a linear equation set sequence is constructed and solved by combining the system matrix A and the observation vector sequence, and a one-dimensional projection reconstruction result sequence is obtained;
and step S400, reconstructing a magnetic particle image of the target object based on the one-dimensional projection reconstruction result sequence.
2. The one-dimensional system matrix sparse sampling based magnetic field free line magnetic particle imaging method of claim 1, wherein the initial angle is an angle of the magnetic field free line based magnetic particle imaging apparatus along a radial direction of a magnetic field free line.
3. The method for imaging free line magnetic particles of a magnetic field based on sparse sampling of a one-dimensional system matrix according to claim 2, wherein the rotation angle sequence is set by the following steps:
rotating the magnetic field free line by N angles in an equidistant or unequal interval mode by the initial angle of 0 degrees and rotating the magnetic field free line by 180 degrees, so that the movement range of the magnetic field free line can cover all imaging fields; where N represents a set number.
4. A magnetic field free line magnetic particle imaging method based on one-dimensional system matrix sparse sampling as claimed in claim 3, wherein the dimension of the observation vector in the sequence of observation vectors is equal to the number of rows of the system matrix a.
5. The method for imaging magnetic free line magnetic particles based on sparse sampling of a one-dimensional system matrix according to claim 1, wherein reconstructing a magnetic particle image of the target object based on the one-dimensional projection reconstruction result sequence comprises:
and converting the one-dimensional projection reconstruction result sequence into a Radon space to establish a sinogram, and reconstructing a magnetic particle image of the target object by using a back projection method.
6. A free line magnetic particle imaging system based on one-dimensional system matrix sparse sampling, based on the free line magnetic particle imaging method of one-dimensional system matrix sparse sampling according to any one of claims 1-5, characterized in that the system comprises: the system comprises an initialization setting module, an observation vector sequence construction module, an equation set construction and solving module and an image reconstruction module;
the initialization setting module is configured to set an initial angle, a rotation angle sequence and an imaging field size of the magnetic particle imaging device based on the magnetic field free line, and measure a one-dimensional system matrix A in the gradient direction of the magnetic field free line under the initial angle; the one-dimensional system matrix A is a system matrix constructed by arranging a sampling point on each column of the free line of the magnetic field along the radial direction of the free line of the magnetic field and based on the detected signals on each sampling point;
the observation vector sequence construction module is configured to place a target object to be imaged in the imaging field of the magnetic particle imaging equipment based on the free magnetic field lines, rotate the free magnetic field lines or the target object to be imaged according to the rotation angle sequence set by the initialization setting module, and establish an observation vector sequence;
the equation set constructing and solving module is configured to combine the system matrix A and the observation vector sequence, construct a linear equation set sequence and solve the linear equation set sequence to obtain a one-dimensional projection reconstruction result sequence;
the image reconstruction module is configured to reconstruct a magnetic particle image of the target object based on the one-dimensional projection reconstruction result sequence.
7. An electronic device, comprising:
at least one processor; and a memory communicatively coupled to at least one of the processors;
wherein the memory stores instructions executable by the processor for execution by the processor to implement the one-dimensional system matrix sparse sampling based magnetic field free line magnetic particle imaging method of any one of claims 1-5.
8. A computer readable storage medium storing computer instructions for execution by the computer to implement the one-dimensional system matrix sparse sampling based magnetic field free line magnetic particle imaging method of any one of claims 1-5.
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