CN117788630A - Super-resolution magnetic particle imaging method and system based on pulse square wave excitation - Google Patents
Super-resolution magnetic particle imaging method and system based on pulse square wave excitation Download PDFInfo
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Abstract
The invention belongs to the technical field of biomedical imaging, in particular relates to a super-resolution magnetic particle imaging method and system based on pulse square wave excitation, and aims to solve the problem that the resolution of the existing pulse magnetic particle imaging is still low. The method comprises the following steps: forming a single-pixel super-resolution system matrix; collecting magnetic particle signals of an object to be imaged as first signals; correcting the first signal and intercepting magnetic particle signals of a rising section and a leveling section of the waveform of the corrected first signal as a second signal; integrating the second signal with time, and filling grids according to the position of the free point of the magnetic field of the focusing field to obtain a preliminary reconstructed image; acquiring a non-zero pixel of the preliminary reconstructed image and intercepting a level segment of a signal corresponding to the non-zero pixel as a third signal; and decomposing the third signal into particle signals under different bias fields by combining a single-pixel super-resolution system matrix, so as to obtain a super-resolution magnetic particle reconstructed image. The invention improves the resolution of the existing pulse magnetic particle imaging.
Description
Technical Field
The invention belongs to the technical field of biomedical imaging, and particularly relates to a super-resolution magnetic particle imaging method and system based on pulse square wave excitation.
Background
The magnetic particle imaging can quantitatively image the concentration distribution of the magnetic particles, and is applied to the scenes such as vascular imaging, cell tracking, tumor marking and the like. Magnetic particle imaging typically uses a sinusoidal magnetic field to excite magnetic particles to produce a corresponding lower response signal that follows a Langmuir function. However, the sinusoidal excitation of magnetic particle signals is often affected by relaxation effects, especially on large particle sizes, which severely affects the spatial resolution of the magnetic particle imaging.
Pulsed magnetic particle imaging produces an exponentially decaying signal based on relaxation in the square wave plateau by applying a pulsed square wave excitation to the magnetic particles, decoupling the magnetic particle signal from the relaxation by integrating the signal over the time domain. The special excitation method of pulsed magnetic particle imaging allows for the use of larger size magnetic particles whose magnetization response function is generally steeper, thus potentially producing higher resolution magnetic particle images. However, pulsed magnetic particle imaging does not break through the langevin function predicted magnetic particle imaging resolution, but only approximates the predicted resolution.
In summary, the resolution of pulse magnetic particle imaging is still low. Based on the method and the system, the super-resolution magnetic particle imaging method and the system based on pulse square wave excitation are provided, and the super-resolution reconstruction is carried out on the magnetic particle signals under the pulse square wave, so that a magnetic particle reconstruction image with higher resolution can be obtained.
Disclosure of Invention
In order to solve the above problems in the prior art, that is, in order to solve the problem that the resolution of the existing pulsed magnetic particle imaging is still low, the first aspect of the present invention proposes a super-resolution magnetic particle imaging method based on pulse square wave excitation, which is applied to a magnetic particle imaging device; the magnetic particle imaging device comprises a gradient magnetic field, an excitation magnetic field with bias pulse and a focusing field, and the method comprises the following steps:
s100, closing the gradient magnetic field, opening the excitation magnetic field with bias pulse and setting a waveform; collecting time domain signals of magnetic nano particles with unit content in a set peak range of a direct current bias field with a bias pulse excitation magnetic field; correcting the time domain signal, intercepting the level segment of the waveform of the corrected time domain signal and forming a single-pixel super-resolution system matrix according to columns;
s200, opening the gradient magnetic field, setting a gradient range, closing the bias magnetic field with the bias pulse excitation magnetic field, opening the focusing field and setting corresponding parameters; after setting, collecting magnetic particle signals of an object to be imaged as first signals; the corresponding parameters include amplitude and frequency;
s300, correcting the first signal and intercepting magnetic particle signals of a rising section and a leveling section of the waveform of the corrected first signal as a second signal; integrating the second signal with time, and filling grids according to the free point position of the magnetic field of the focusing field to obtain a preliminary reconstructed image;
s400, acquiring a non-zero pixel in the preliminary reconstructed image and intercepting a level-keeping section of a signal corresponding to the non-zero pixel as a third signal; decomposing the third signal into particle signals under different bias fields by combining the single-pixel super-resolution system matrix; retaining the decomposed offset 0 particle signals, discarding other offset particle signals, and performing time domain integration on the offset 0 particle signals to serve as new pixel values to replace the pixel values of the primary reconstructed image;
s500, repeating S400 until all non-zero pixels in the primary reconstructed image are decomposed and replaced, and further obtaining a super-resolution magnetic particle reconstructed image.
In some preferred embodiments, the waveform comprises a square wave, a gradient wave.
In some preferred embodiments, when setting the waveform of the excitation magnetic field with bias pulse, parameters corresponding to the waveform include duty cycle, peak value and frequency.
In some preferred embodiments, the single-pixel super-resolution system matrix does not need to be acquired again after changing the scanning mode or adjusting the scanning parameters.
In some preferred embodiments, the third signal is decomposed into particle signals under different bias fields in combination with the single-pixel super-resolution system matrix by:
the equation is constructed:
wherein,representing a single-pixel super-resolution system matrix, +.>Representing the signal distribution at different biases, +.>Representing a third signal;
solving the constructed equation, and further obtaining particle signals under different bias fields; the method adopted in the decomposition comprises an ART method and an ADMM method.
In a second aspect of the present invention, a super-resolution magnetic particle imaging system based on pulse square wave excitation is provided, the system comprising: a gradient coil pair, a focusing coil set, an excitation coil and a receiving-compensating coil set;
the gradient coil pair comprises a first gradient coil and a second gradient coil; the first gradient coil and the second gradient coil are symmetrically and coaxially arranged; the gradient coil pair is used for generating a variable gradient field;
the focusing coil group comprises a first focusing coil group and a second focusing coil group; the first focusing coil group comprises a first Helmholtz coil and a second Helmholtz coil; the first Helmholtz coil and the second Helmholtz coil are symmetrically and coaxially arranged, and the axes of the coils in the first focusing coil group are orthogonal to the axes of the coils in the gradient coil pair; the first focusing coil group is used for generating a focusing field for exciting a parallel direction;
the second focusing coil group comprises a third Helmholtz coil and a fourth Helmholtz coil; the third Helmholtz coil and the fourth Helmholtz coil are symmetrically and coaxially arranged; the coils in the second focusing coil group are coaxial with the coils in the gradient coil pair; the third helmholtz coil is located inside the first gradient coil; the fourth helmholtz coil is located inside the second gradient coil; the second focusing coil group is used for generating an excitation vertical focusing field;
the exciting coil is arranged on the inner side of the second focusing coil group; the excitation coil is coaxial with coils in the second focusing coil group; the exciting coil is used for generating excitation of a set waveform;
the receiving-compensating coil is arranged on the inner side of the exciting coil; the receiving-compensating coil is coaxially arranged with the exciting coil; a receiving coil in the receiving-compensating coil for receiving the magnetic particle response signal; and the compensation coil in the receiving-compensation coil is used for compensating interference caused by excitation.
In some preferred embodiments, the super-resolution magnetic particle imaging system based on pulse square wave excitation further comprises:
the control module is used for controlling the gradient coil pair, the focusing coil group and the exciting coil to generate corresponding magnetic fields;
the power supply module is used for supplying corresponding currents to the gradient coil pair, the focusing coil group and the exciting coil under the control of the control module;
the signal receiving module comprises the receiving-compensating coil, a low-pass filter, a signal amplifier and an acquisition card; a receiving coil in the receiving-compensating coil for receiving the magnetic particle response signal; the compensating coil in the receiving-compensating coil is used for compensating interference caused by excitation; the low-pass filter is used for filtering magnetic particle response signals above the set megahertz so as to prevent aliasing filtering; the signal amplifier is used for amplifying and matching the filtered magnetic particle response signals to the input range of the acquisition card; the acquisition card is used for performing digital-to-analog conversion on the amplified magnetic particle response signals;
the time domain signal correction module comprises a time domain signal decoupling submodule and an exponential decay noise subtracting submodule; the time domain signal decoupling submodule is used for removing distortion caused by a low-pass filter and a signal amplifier in the signal receiving module, namely, performing hardware link decoupling on the signal after the analog-digital conversion of the acquisition card; the exponential decay noise-reducing submodule is used for reducing noise of signals after decoupling of the hardware link;
the image super-resolution reconstruction module comprises an image preliminary reconstruction module and an image single-pixel super-resolution reconstruction module; the image primary reconstruction module is used for carrying out primary reconstruction on the magnetic particle signals output by the time domain signal correction module to obtain a primary reconstruction image; the image single-pixel super-resolution reconstruction module is used for performing super-resolution reconstruction by combining a pre-constructed single-pixel super-resolution system matrix based on the preliminary reconstructed image, so as to obtain a super-resolution magnetic particle reconstructed image.
In some preferred embodiments, the first gradient coil and the second gradient coil are each helmholtz coils; the exciting coil is a solenoid; the receiving-compensating coil is a three-section gradient solenoid.
In some preferred embodiments, the first gradient coil and the second gradient coil are energized with opposite currents, and the polarities of the magnetic fields generated are opposite when the currents are non-zero.
The invention has the beneficial effects that:
the invention improves the resolution of the existing pulse magnetic particle imaging.
The pulse square wave excitation can enable the magnetic particles to generate exponentially decaying signals based on relaxation, under the action of different bias fields, the decaying speeds are different, and the signals with different decaying speeds are nonlinear, so according to the characteristics, the method further decomposes the response signals of the sum in the non-magnetic field point at one time according to the different bias fields, extracts the signals with the bias of 0 to replace the original sum signals, and can super-resolve the reconstructed image of the magnetic particles, further improve the resolution of magnetic particle imaging, and realize high-resolution imaging of any magnetic particle distribution.
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 super-resolution magnetic particle imaging method based on pulse square wave excitation according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a super-resolution magnetic particle imaging system based on pulse square wave excitation according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a single pixel super-resolution matrix according to an embodiment of the present invention;
reference numerals:
in fig. 2: 1. a first gradient coil; 2. a second gradient coil; 3. a first helmholtz coil; 4. a second helmholtz coil; 5. a third helmholtz coil; 6. a fourth helmholtz coil; 7. an exciting coil; 8. a receive-compensation coil.
Detailed Description
For the purpose of making the objects, technical solutions and advantages 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, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. 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, for convenience of description, only the portions related to the present invention are shown in the drawings.
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 super-resolution magnetic particle imaging method based on pulse square wave excitation is applied to magnetic particle imaging equipment; the magnetic particle imaging device comprises a gradient magnetic field, an excitation magnetic field with bias pulse and a focusing field, and comprises the following steps as shown in fig. 1:
s100, closing the gradient magnetic field, opening the excitation magnetic field with bias pulse and setting a waveform; collecting time domain signals of magnetic nano particles with unit content in a set peak range of a direct current bias field with a bias pulse excitation magnetic field; correcting the time domain signal, intercepting the level segment of the waveform of the corrected time domain signal and forming a single-pixel super-resolution system matrix according to columns;
s200, opening the gradient magnetic field, setting a gradient range, closing the bias magnetic field with the bias pulse excitation magnetic field, opening the focusing field and setting corresponding parameters; after setting, collecting magnetic particle signals of an object to be imaged as first signals; the corresponding parameters include amplitude and frequency;
s300, correcting the first signal and intercepting magnetic particle signals of a rising section and a leveling section of the waveform of the corrected first signal as a second signal; integrating the second signal with time, and filling grids according to the free point position of the magnetic field of the focusing field to obtain a preliminary reconstructed image;
s400, acquiring a non-zero pixel in the preliminary reconstructed image and intercepting a level-keeping section of a signal corresponding to the non-zero pixel as a third signal; decomposing the third signal into particle signals under different bias fields by combining the single-pixel super-resolution system matrix; retaining the decomposed offset 0 particle signals, discarding other offset particle signals, and performing time domain integration on the offset 0 particle signals to serve as new pixel values to replace the pixel values of the primary reconstructed image;
s500, repeating S400 until all non-zero pixels in the primary reconstructed image are decomposed and replaced, and further obtaining a super-resolution magnetic particle reconstructed image.
In order to more clearly describe the super-resolution magnetic particle imaging method based on pulse square wave excitation, each step in one embodiment of the method of the present invention is described in detail below with reference to the accompanying drawings.
S100, closing the gradient magnetic field, opening the excitation magnetic field with bias pulse and setting a waveform; collecting time domain signals of magnetic nano particles with unit content in a set peak range of a direct current bias field with a bias pulse excitation magnetic field; correcting the time domain signal (the invention is preferably realized by inputting the frequency domain data of the signal into the inverse function of the frequency response function of the receiving link), intercepting the level segment of the waveform of the corrected time domain signal and forming a single-pixel super-resolution system matrix by columns;
in this embodiment, the preferred waveform is a square wave or a trapezoidal wave, and the parameters of the waveform include duty cycle, peak value, and frequency (the preferred square wave of the present invention is a duty cycle of 50%, peak value of 7 mT, and frequency of 1 kHz).
Then collecting time domain signal of magnetic nano particles with unit content under bias field of direct current of-7 mT to 7 mT, correcting the signal, cutting square wave leveling section, and recording as、/>…/>It is formed into single-pixel super-resolution system matrix according to columns +.>As shown in fig. 3, it is noted that: />. The single-pixel super-resolution system matrix is formed by combining time domain magnetic particle signals of pulse excitation magnetic field leveling segments under different bias fields; acquisition by applying different bias fields with the gradient fields turned off; in addition, single pixel super resolution system matrixThe hardware is decoupled through signal correction, and re-acquisition is not needed after the scanning mode is replaced or the scanning parameters are adjusted.
S200, opening the gradient magnetic field, setting a gradient range, closing the bias magnetic field with the bias pulse excitation magnetic field, opening the focusing field and setting corresponding parameters; after setting, collecting magnetic particle signals of an object to be imaged as first signals; the corresponding parameters include amplitude and frequency;
in this embodiment the gradient field is switched on and the gradient range is preferably set to 0.2T/m-4T/m. The bias field with bias pulse excitation field is turned off, the focus field is turned on and the focus field amplitude is preferably set to 3 mT-60 mT, at a frequency of DC-10Hz. Magnetic particle signals with unknown concentration distribution of an object to be imaged are acquired under the excitation of a pulse excitation magnetic field, the whole imaging visual field is traversed under the action of a focusing field, and the imaging time is preferably 1 s.
S300, correcting the first signal and intercepting magnetic particle signals of a rising section and a leveling section of the waveform of the corrected first signal as a second signal; integrating the second signal with time, and filling grids according to the free point position of the magnetic field of the focusing field to obtain a preliminary reconstructed image;
s400, acquiring a non-zero pixel in the preliminary reconstructed image and intercepting a level-keeping section of a signal corresponding to the non-zero pixel as a third signal; decomposing the third signal into particle signals under different bias fields by combining the single-pixel super-resolution system matrix; retaining the decomposed offset 0 particle signals, discarding other offset particle signals, and performing time domain integration on the offset 0 particle signals to serve as new pixel values to replace the pixel values of the primary reconstructed image;
s500, repeating S400 until all non-zero pixels in the primary reconstructed image are decomposed and replaced, and further obtaining a super-resolution magnetic particle reconstructed image.
In this embodiment, the method of decomposing the third signal into particle signals under different bias fields in combination with the single-pixel super-resolution system matrix includes:
the equation is constructed:
wherein,representing a single-pixel super-resolution system matrix, +.>Representing the signal distribution at different biases, +.>Representing the third signal.
Solving the constructed equation, and further obtaining particle signals under different bias fields; the method adopted in the decomposition comprises an ART method and an ADMM method.
Bias the decomposed signal at 0cAnd replacing the original pixel value in the primary reconstructed image by the corresponding pixel value, and obtaining a super-resolution magnetic particle reconstructed image after all the pixel values are replaced.
The invention is divided into two working phases, wherein the first working phase (S100) is single-pixel super-resolution system matrix acquisition, the second working phase (S200-S500) is signal acquisition reconstruction phase, and the two phases are completed by using a super-resolution magnetic particle imaging device based on pulse square wave excitation.
A super-resolution magnetic particle imaging system based on pulse square wave excitation according to a second embodiment of the present invention, as shown in fig. 2, includes: a gradient coil pair, a focusing coil set, an excitation coil and a receiving-compensating coil set;
the gradient coil pair comprises a first gradient coil and a second gradient coil; the first gradient coil and the second gradient coil are symmetrically and coaxially arranged; the gradient coil pair is used for generating a variable gradient field;
in the present embodiment, the first gradient coil 1 and the second gradient coil 2 are both preferably helmholtz coils; the first gradient coil 1 and the second gradient coil 2 form a gradient coil pair to generate a variable gradient field (preferably 0-4T/m in the invention); the first gradient coil 1 and the second gradient coil 2 are electrified with opposite currents, and when the currents are not zero, the polarities of the generated magnetic fields are opposite, so that magnetic fields at the central positions of the first gradient coil 1 and the second gradient coil are mutually offset to generate a magnetic field-free region, magnetic particles are saturated outside the magnetic field-free region and do not generate a responsive voltage signal under the action of a pulse excitation field, and magnetic particles in the magnetic field-free region generate a signal in response to the excitation field. In fig. 2, the crosses indicate the winding direction of the coil, the coil is wound from the position without the crosses, and the position with the crosses is wound (i.e., the "crosses" indicate the winding direction is wound from the paper surface, and the position without the crosses indicates the winding direction is wound from the paper surface). The winding of the 1, 2 gradient coils in fig. 2 is reversed, while the other coil pairs are forward.
The focusing coil group comprises a first focusing coil group and a second focusing coil group; the first focusing coil group comprises a first Helmholtz coil and a second Helmholtz coil; the first Helmholtz coil and the second Helmholtz coil are symmetrically and coaxially arranged, and the axes of the coils in the first focusing coil group are orthogonal to the axes of the coils in the gradient coil pair; the first focusing coil group is used for generating a focusing field for exciting a parallel direction;
the second focusing coil group comprises a third Helmholtz coil and a fourth Helmholtz coil; the third Helmholtz coil and the fourth Helmholtz coil are symmetrically and coaxially arranged; the coils in the second focusing coil group are coaxial with the coils in the gradient coil pair; the third helmholtz coil is located inside the first gradient coil; the fourth helmholtz coil is located inside the second gradient coil; the second focusing coil group is used for generating an excitation vertical focusing field;
in the present embodiment, the first helmholtz coil 3 and the second helmholtz coil 4 form a first focusing coil group for generating a focusing field for exciting parallel directions; the third Helmholtz coil 5 and the fourth Helmholtz coil 6 form a second focusing coil group, which is used for generating an excitation vertical focusing field; in the preliminary reconstruction, the focus field amplitude is used for spatial localization, preferably 3 mT-60 mT, and the frequency is preferably DC-10Hz.
The exciting coil is arranged on the inner side of the second focusing coil group; the excitation coil is coaxial with coils in the second focusing coil group; the exciting coil is used for generating excitation of a set waveform;
in this embodiment, the excitation coil 7 is preferably a solenoid for generating square wave or trapezoidal wave excitation (the present invention is preferably-7 mT to 7 mT dc biased square wave or trapezoidal wave excitation with a duty cycle of 50%, a peak value of 7 mT, and a frequency of 1 kHz).
The receiving-compensating coil is arranged on the inner side of the exciting coil; the receiving-compensating coil is coaxially arranged with the exciting coil; a receiving coil in the receiving-compensating coil for receiving the magnetic particle response signal; the compensating coil in the receiving-compensating coil is used for compensating interference caused by excitation;
in this embodiment, the receive-compensation coil 8 is preferably a three-segment gradient solenoid. In addition, in other embodiments, the solenoid 7, the receiving-compensating coil 8 do not necessarily need to be symmetrically arranged in practice.
The super-resolution magnetic particle imaging system based on pulse square wave excitation further comprises:
the control module is used for controlling the gradient coil pair, the focusing coil group and the exciting coil to generate corresponding magnetic fields;
in this embodiment, the control module outputs a corresponding control signal to the power supply module, and performs current output to control the generated magnetic field.
The power supply module is used for supplying corresponding currents to the gradient coil pair, the focusing coil group and the exciting coil under the control of the control module;
in this embodiment, the power supply module is composed of a power amplifier and an impedance matching circuit, and supplies current to coils in the gradient coil pair, the focusing coil group, and the excitation coil.
The signal receiving module comprises the receiving-compensating coil, a low-pass filter, a signal amplifier and an acquisition card; a receiving coil in the receiving-compensating coil for receiving the magnetic particle response signal; the compensating coil in the receiving-compensating coil is used for compensating interference caused by excitation; transmitting the compensated magnetic particle response signal to the low-pass filter; the low-pass filter is used for filtering magnetic particle response signals above the set megahertz so as to prevent aliasing filtering; the signal amplifier is used for amplifying and matching the filtered magnetic particle response signals to the input range of the acquisition card; the acquisition card is used for performing digital-to-analog conversion on the amplified magnetic particle response signals;
in this embodiment, the acquisition frequency of megahertz or more is set, preferably 1MHz or more.
The time domain signal correction module comprises a time domain signal decoupling submodule and an exponential decay noise subtracting submodule; the time domain signal decoupling submodule is used for removing distortion caused by a low-pass filter and a signal amplifier in the signal receiving module, namely, performing hardware link decoupling on the signal after the analog-digital conversion of the acquisition card; the exponential decay noise-reducing submodule is used for reducing noise of signals after decoupling of the hardware link;
the image super-resolution reconstruction module comprises an image preliminary reconstruction module and an image single-pixel super-resolution reconstruction module; the image primary reconstruction module is used for carrying out primary reconstruction on the magnetic particle signals (namely second signals) output by the time domain signal correction module to obtain a primary reconstructed image; the image single-pixel super-resolution reconstruction module is used for performing super-resolution reconstruction by combining a pre-constructed single-pixel super-resolution system matrix based on the preliminary reconstructed image, so as to obtain a super-resolution magnetic particle reconstructed image.
In this embodiment, the image preliminary reconstruction module firstly collects waveform diagrams of a pulse excitation field, a received signal and a focusing field at the same time, divides a coordinate according to a value of the focusing field, performs segmentation processing on the received signal according to the focusing field, and each segment of signal corresponds to one pixel; and then, integrating the rising edge (or the falling edge, preferably integrating the signals of the rising section and the leveling section) of the whole signal, taking the integrated value as the pixel value of the pixel point, taking the average value of the pixels if a plurality of sections of signals correspond to the same pixel, and obtaining an image after all the signals are assigned, namely the primary reconstructed image.
The image single-pixel super-resolution reconstruction module finds a non-zero pixel in the preliminarily reconstructed image, intercepts a level segment part of a signal corresponding to the pixel, and decomposes the signal into particle signals under different bias fields by using a single-pixel super-resolution system matrix, wherein the decomposition method comprises the following steps of:after signal decomposition, only the bias of 0 is kept +.>And replacing the corresponding value with the original pixel value, repeating the process until all pixels are subjected to one-time single-pixel super-resolution reconstruction, and obtaining an image which is a super-resolution magnetic particle reconstruction image finally. Namely, each non-zero pixel needs to carry out one single-pixel super-resolution iteration, and zero pixels do not need to be iterated; all the pixels needing non-zero are super-resolved by using a single-pixel super-resolution algorithm, and the obtained image is the super-resolved reconstructed image.
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 super-resolution magnetic particle imaging system based on pulse square wave excitation provided in the foregoing embodiment, only the division of the foregoing functional modules is illustrated, in practical application, the foregoing functional allocation may be performed 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 multiple 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.
A super-resolution magnetic particle imaging apparatus based on pulse square wave excitation 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; the memory stores instructions executable by the processor for execution by the processor to implement the pulse square wave excitation-based super-resolution magnetic particle imaging method described above.
A fourth embodiment of the present invention is a computer-readable storage medium storing computer instructions for execution by the computer to implement the pulse square wave excitation-based super-resolution magnetic particle imaging method described above.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working processes of the above-described super-resolution magnetic particle imaging apparatus based on pulse square wave excitation, computer readable storage medium and related descriptions may refer to corresponding processes in the foregoing method examples, and are not repeated herein.
Those of skill in the art will appreciate that the various illustrative modules, method steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the program(s) corresponding to the software modules, method steps, may be embodied in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. To clearly illustrate this interchangeability of electronic hardware and software, various illustrative components and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as electronic hardware or software depends upon the particular application and design constraints imposed on the solution. Those skilled in the art may implement the described functionality using different approaches for each particular application, but such implementation is not intended to be limiting.
The terms "first," "second," "third," and the like, are used for distinguishing between similar objects and not for describing a particular sequential or chronological order.
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 be within the scope of the present invention.
Claims (9)
1. A super-resolution magnetic particle imaging method based on pulse square wave excitation is applied to magnetic particle imaging equipment; the magnetic particle imaging equipment comprises a gradient magnetic field, an excitation magnetic field with bias pulse and a focusing field; characterized in that the method comprises the following steps:
s100, closing the gradient magnetic field, opening the excitation magnetic field with bias pulse and setting a waveform; collecting time domain signals of magnetic nano particles with unit content in a set peak range of a direct current bias field with a bias pulse excitation magnetic field; correcting the time domain signal, intercepting the level segment of the waveform of the corrected time domain signal and forming a single-pixel super-resolution system matrix according to columns;
s200, opening the gradient magnetic field, setting a gradient range, closing the bias magnetic field with the bias pulse excitation magnetic field, opening the focusing field and setting corresponding parameters; after setting, collecting magnetic particle signals of an object to be imaged as first signals; the corresponding parameters include amplitude and frequency;
s300, correcting the first signal and intercepting magnetic particle signals of a rising section and a leveling section of the waveform of the corrected first signal as a second signal; integrating the second signal with time, and filling grids according to the free point position of the magnetic field of the focusing field to obtain a preliminary reconstructed image;
s400, acquiring a non-zero pixel in the preliminary reconstructed image and intercepting a level-keeping section of a signal corresponding to the non-zero pixel as a third signal; decomposing the third signal into particle signals under different bias fields by combining the single-pixel super-resolution system matrix; retaining the decomposed offset 0 particle signals, discarding other offset particle signals, and performing time domain integration on the offset 0 particle signals to serve as new pixel values to replace the pixel values of the primary reconstructed image;
s500, repeating S400 until all non-zero pixels in the primary reconstructed image are decomposed and replaced, and further obtaining a super-resolution magnetic particle reconstructed image.
2. The method for super-resolution magnetic particle imaging based on pulse square wave excitation according to claim 1, wherein the waveform comprises square wave, gradient wave.
3. The super-resolution magnetic particle imaging method based on pulse square wave excitation according to claim 2, wherein when the waveform of the bias pulse excitation magnetic field is set, parameters corresponding to the waveform include duty ratio, peak value and frequency.
4. The pulse square wave excitation based super-resolution magnetic particle imaging method according to claim 1, wherein the single pixel super-resolution system matrix does not need to be acquired again after the scanning mode is replaced or the scanning parameters are adjusted.
5. The pulse square wave excitation-based super-resolution magnetic particle imaging method as claimed in claim 1, wherein the third signal is decomposed into particle signals under different bias fields in combination with the single-pixel super-resolution system matrix, and the method comprises the following steps:
the equation is constructed:
；
wherein,representing a single-pixel super-resolution system matrix, +.>Representing the signal distribution at different biases, +.>Representing a third signal;
solving the constructed equation, and further obtaining particle signals under different bias fields; the method adopted in the decomposition comprises an ART method and an ADMM method.
6. A super-resolution magnetic particle imaging system based on pulsed square wave excitation, the system comprising: a gradient coil pair, a focusing coil set, an excitation coil and a receiving-compensating coil set;
the gradient coil pair comprises a first gradient coil and a second gradient coil; the first gradient coil and the second gradient coil are symmetrically and coaxially arranged; the gradient coil pair is used for generating a variable gradient field;
the focusing coil group comprises a first focusing coil group and a second focusing coil group; the first focusing coil group comprises a first Helmholtz coil and a second Helmholtz coil; the first Helmholtz coil and the second Helmholtz coil are symmetrically and coaxially arranged, and the axes of the coils in the first focusing coil group are orthogonal to the axes of the coils in the gradient coil pair; the first focusing coil group is used for generating a focusing field for exciting a parallel direction;
the second focusing coil group comprises a third Helmholtz coil and a fourth Helmholtz coil; the third Helmholtz coil and the fourth Helmholtz coil are symmetrically and coaxially arranged; the coils in the second focusing coil group are coaxial with the coils in the gradient coil pair; the third helmholtz coil is located inside the first gradient coil; the fourth helmholtz coil is located inside the second gradient coil; the second focusing coil group is used for generating an excitation vertical focusing field;
the exciting coil is arranged on the inner side of the second focusing coil group; the excitation coil is coaxial with coils in the second focusing coil group; the exciting coil is used for generating excitation of a set waveform;
the receiving-compensating coil is arranged on the inner side of the exciting coil; the receiving-compensating coil is coaxially arranged with the exciting coil; a receiving coil in the receiving-compensating coil for receiving the magnetic particle response signal; and the compensation coil in the receiving-compensation coil is used for compensating interference caused by excitation.
7. The pulse square wave excitation based super-resolution magnetic particle imaging system of claim 6, further comprising:
the control module is used for controlling the gradient coil pair, the focusing coil group and the exciting coil to generate corresponding magnetic fields;
the power supply module is used for supplying corresponding currents to the gradient coil pair, the focusing coil group and the exciting coil under the control of the control module;
the signal receiving module comprises the receiving-compensating coil, a low-pass filter, a signal amplifier and an acquisition card; a receiving coil in the receiving-compensating coil for receiving the magnetic particle response signal; the compensating coil in the receiving-compensating coil is used for compensating interference caused by excitation; the low-pass filter is used for filtering magnetic particle response signals above the set megahertz so as to prevent aliasing filtering; the signal amplifier is used for amplifying and matching the filtered magnetic particle response signals to the input range of the acquisition card; the acquisition card is used for performing digital-to-analog conversion on the amplified magnetic particle response signals;
the time domain signal correction module comprises a time domain signal decoupling submodule and an exponential decay noise subtracting submodule; the time domain signal decoupling submodule is used for removing distortion caused by a low-pass filter and a signal amplifier in the signal receiving module, namely, performing hardware link decoupling on the signal after the analog-digital conversion of the acquisition card; the exponential decay noise-reducing submodule is used for reducing noise of signals after decoupling of the hardware link;
the image super-resolution reconstruction module comprises an image preliminary reconstruction module and an image single-pixel super-resolution reconstruction module; the image primary reconstruction module is used for carrying out primary reconstruction on the magnetic particle signals output by the time domain signal correction module to obtain a primary reconstruction image; the image single-pixel super-resolution reconstruction module is used for performing super-resolution reconstruction by combining a pre-constructed single-pixel super-resolution system matrix based on the preliminary reconstructed image, so as to obtain a super-resolution magnetic particle reconstructed image.
8. The pulse square wave excitation based super resolution magnetic particle imaging system of claim 7, wherein the first gradient coil and the second gradient coil are each helmholtz coils; the exciting coil is a solenoid; the receiving-compensating coil is a three-section gradient solenoid.
9. The super-resolution magnetic particle imaging system based on pulse square wave excitation according to claim 7, wherein the first gradient coil and the second gradient coil are supplied with opposite currents, and the polarities of the generated magnetic fields are opposite when the currents are not zero.
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Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20170084503A (en) * | 2016-01-12 | 2017-07-20 | 한국전자통신연구원 | Image reconstruction device, image reconstruction method of the same, and image system including the same |
| CN112037129A (en) * | 2020-08-26 | 2020-12-04 | 广州视源电子科技股份有限公司 | Image super-resolution reconstruction method, device, equipment and storage medium |
| CN113129403A (en) * | 2021-04-19 | 2021-07-16 | 中国科学院自动化研究所 | Magnetic particle imaging system matrix image reconstruction method and system based on forward model |
| CN114587328A (en) * | 2022-01-13 | 2022-06-07 | 西安电子科技大学 | Magnetic particle imaging method based on gradient field |
| CN115153488A (en) * | 2022-07-08 | 2022-10-11 | 北京航空航天大学 | Pulsed magnetic nanoparticle imaging system and method based on magnetic field modulation |
| CN115153490A (en) * | 2022-07-20 | 2022-10-11 | 北京航空航天大学 | Magnetic nanoparticle detection imaging device and method based on non-rotating field free line |
| CN116030155A (en) * | 2023-02-09 | 2023-04-28 | 中国科学院自动化研究所 | Magnetic particle imaging reconstruction method and system based on time-frequency double information |
| CN116503507A (en) * | 2023-06-26 | 2023-07-28 | 中国科学院自动化研究所 | Magnetic particle image reconstruction method based on pre-training model |
| CN116520214A (en) * | 2023-03-21 | 2023-08-01 | 西安电子科技大学 | Vertical magnetization-based rapid single-harmonic magnetic particle imaging device and method |
| CN116626563A (en) * | 2023-03-14 | 2023-08-22 | 中国科学院自动化研究所 | Gradient and visual field self-adaptive three-dimensional magnetic particle imaging device and method |
| CN116807440A (en) * | 2023-06-09 | 2023-09-29 | 西安电子科技大学 | Isotropic X-space magnetic particle imaging equipment and method based on vertical magnetization |
Patent Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20170084503A (en) * | 2016-01-12 | 2017-07-20 | 한국전자통신연구원 | Image reconstruction device, image reconstruction method of the same, and image system including the same |
| CN112037129A (en) * | 2020-08-26 | 2020-12-04 | 广州视源电子科技股份有限公司 | Image super-resolution reconstruction method, device, equipment and storage medium |
| CN113129403A (en) * | 2021-04-19 | 2021-07-16 | 中国科学院自动化研究所 | Magnetic particle imaging system matrix image reconstruction method and system based on forward model |
| CN114587328A (en) * | 2022-01-13 | 2022-06-07 | 西安电子科技大学 | Magnetic particle imaging method based on gradient field |
| CN115153488A (en) * | 2022-07-08 | 2022-10-11 | 北京航空航天大学 | Pulsed magnetic nanoparticle imaging system and method based on magnetic field modulation |
| CN115153490A (en) * | 2022-07-20 | 2022-10-11 | 北京航空航天大学 | Magnetic nanoparticle detection imaging device and method based on non-rotating field free line |
| CN116030155A (en) * | 2023-02-09 | 2023-04-28 | 中国科学院自动化研究所 | Magnetic particle imaging reconstruction method and system based on time-frequency double information |
| CN116626563A (en) * | 2023-03-14 | 2023-08-22 | 中国科学院自动化研究所 | Gradient and visual field self-adaptive three-dimensional magnetic particle imaging device and method |
| CN116520214A (en) * | 2023-03-21 | 2023-08-01 | 西安电子科技大学 | Vertical magnetization-based rapid single-harmonic magnetic particle imaging device and method |
| CN116807440A (en) * | 2023-06-09 | 2023-09-29 | 西安电子科技大学 | Isotropic X-space magnetic particle imaging equipment and method based on vertical magnetization |
| CN116503507A (en) * | 2023-06-26 | 2023-07-28 | 中国科学院自动化研究所 | Magnetic particle image reconstruction method based on pre-training model |
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