CN113625208B - Three-dimensional magnetic particle imaging system and method based on multi-channel excitation and detection - Google Patents
Three-dimensional magnetic particle imaging system and method based on multi-channel excitation and detection Download PDFInfo
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Abstract
The invention belongs to the technical field of biomedical imaging, and particularly relates to a three-dimensional magnetic particle imaging system and method based on multi-channel excitation and detection, aiming at solving the problems of low imaging speed and low imaging precision caused by heating of an electromagnetic coil in the existing magnetic particle imaging technology. The invention comprises the following steps: a multi-channel excitation coil group for exciting the magnetic particles in different directions; a multi-channel detection coil group for detecting response voltage signals of the magnetic particles at different spatial positions and different angles; an AC power supply set for supplying power to the multi-channel exciting coil set; a channel control unit for switching the exciting coils in different directions in the exciting coil group and exciting the magnetic particles in different directions; the signal conditioning unit is used for amplifying and filtering the response voltage signal detected by the multi-channel detection coil group; and the image reconstruction unit is used for carrying out digital signal processing and three-dimensional magnetic particle image reconstruction according to the amplified and filtered response voltage signal. The magnetic particle imaging method is high in magnetic particle imaging speed and high in accuracy.
Description
Technical Field
The invention belongs to the technical field of biomedical imaging, and particularly relates to a three-dimensional magnetic particle imaging system and method based on multi-channel excitation and detection.
Background
Magnetic particles are nano-scale particles with superparamagnetism, and are widely researched and applied as a novel medical imaging tracer agent in clinical problems of tumor detection, magnetic particle thermotherapy, targeted drug delivery and the like in recent years.
The traditional magnetic particle imaging method needs to control a gradient magnetic field with high field strength to encode the whole imaging field. For three-dimensional imaging, the encoding process can be very lengthy, affecting the real-time performance of the imaging. In addition, the electromagnetic coil can generate heat due to the long continuous working time, which causes measurement errors and further influences the imaging precision.
In general, there is still a need in the art for a three-dimensional magnetic particle imaging system and method with faster imaging speed and compatible imaging precision.
Disclosure of Invention
In order to solve the problems in the prior art, namely the problems that the imaging speed of the existing magnetic particle imaging technology is low and the imaging precision is low due to the heating of an electromagnetic coil, the invention provides a three-dimensional magnetic particle imaging system based on multi-channel excitation and detection, which comprises a multi-channel excitation coil group, a multi-channel detection coil group, an alternating current power supply group, a channel control unit, a signal conditioning unit and an image reconstruction unit;
the multi-channel exciting coil group comprises a plurality of exciting electromagnetic coils with different exciting directions and is used for exciting magnetic particles along different directions;
the multi-channel detection coil set comprises a plurality of detection coil arrays, and each detection coil array in the plurality of detection coil arrays comprises a plurality of detection electromagnetic coils which are used for detecting response voltage signals of magnetic particles at different spatial positions and different angles;
the alternating current power supply set is used for supplying power to the multi-channel exciting coil set;
the channel control unit is used for switching the exciting coils in different directions in the exciting coil group to excite the magnetic particles in different directions;
the signal conditioning unit is used for amplifying and filtering the response voltage signal detected by the multi-channel detection coil group;
and the image reconstruction unit is used for carrying out digital signal processing and three-dimensional magnetic particle image reconstruction according to the amplified and filtered response voltage signal.
In some preferred embodiments, the alternating current power supply group comprises a multi-channel signal generator and a power amplifier;
the multi-channel signal generator is used for generating a current waveform required by the electrified coil group; the current waveform is one of sine wave, triangular wave and pulse square wave;
the power amplifier is used for amplifying the current waveform generated by the multi-channel signal generator to a set size and supplying power to the multi-channel exciting coil group based on the amplified current waveform.
In some preferred embodiments, the three-dimensional magnetic particle imaging system further comprises a display unit;
and the display unit is used for displaying the three-dimensional magnetic particle image reconstructed by the image reconstruction unit.
In some preferred embodiments, the excitation electromagnetic coils of the multi-channel excitation coil set surround the imaging field of view of the three-dimensional magnetic particle imaging system;
taking the center of the imaging view field as an origin of a three-dimensional coordinate system, and respectively placing excitation electromagnetic coils of the multi-channel excitation coil set in a z-axis negative direction, a z-axis positive direction, an x-axis positive direction and an x-axis negative direction of the three-dimensional coordinate system; the direction is the main magnetic field direction generated by the exciting coil, and an object to be imaged enters an imaging field of view along the y-axis direction.
In some preferred embodiments, the detection coil arrays of the multi-channel detection coil group are arranged in one-to-one correspondence with the excitation electromagnetic coils of the multi-channel excitation coil group;
each detection coil array is arranged on one side, close to the imaging view field, of each corresponding excitation electromagnetic coil and is used for detecting response voltage signals generated by magnetic particles at different spatial positions in a multi-angle mode.
In some preferred embodiments, the plurality of exciting electromagnetic coils with different exciting directions generate exciting magnetic fields by only one exciting electromagnetic coil at a certain time;
when any exciting electromagnetic coil generates an exciting magnetic field, all the detection coil arrays simultaneously detect magnetization response voltage signals generated by magnetic particles, the detection coil arrays in the same direction as the exciting magnetic field are used for detecting magnetization response voltage signals in the main magnetic flux direction generated by the magnetic particles, and the detection coil arrays perpendicular to the exciting magnetic field are used for detecting magnetization response voltage signals in the leakage magnetic flux direction generated by the magnetic particles.
In another aspect of the present invention, a three-dimensional magnetic particle imaging method based on multi-channel excitation and detection is provided, and based on the above three-dimensional magnetic particle imaging system based on multi-channel excitation and detection, the three-dimensional magnetic particle imaging method includes:
step S10, high-frequency pulse current is sequentially input to different excitation electromagnetic coils, a pulse magnetic field in a specific direction is generated in an imaging view field of the three-dimensional magnetic particle imaging system, and magnetic particles are excited to generate magnetization response voltage signals in different directions;
a step S20 of detecting, for each excitation electromagnetic coil, a magnetization response voltage signal in a main magnetic flux direction generated by magnetic particles by a detection coil array parallel to the excitation electromagnetic coil, and a magnetization response voltage signal in a leakage magnetic flux direction generated by magnetic particles by a detection coil array perpendicular to the excitation electromagnetic coil;
step S30, filtering the detected direct current component in the response voltage signal through a digital filtering technology, and performing fast Fourier transform on the detection signal to obtain a frequency spectrum sequence of the response voltage signal;
and step S40, constructing a measuring matrix of the multi-channel excitation electromagnetic coil and the detecting coil, and calculating the spatial distribution of the magnetic particle concentration by combining the frequency spectrum sequence of the response voltage signal to realize the reconstruction of the three-dimensional magnetic particle image.
In some preferred embodiments, the high-frequency pulse current has a waveform of a pulse square wave with a narrow pulse width.
In some preferred embodiments, the multi-channel excitation electromagnetic coil and detection coil measurement matrix is constructed by:
step S411, based on the preset resolution of the three-dimensional magnetic particle reconstructed image, dividing the imaging field of view of the three-dimensional magnetic particle imaging system into n reconstruction units;
step S412, putting the magnetic particle sample of the object to be imaged into the imaging field of view of the three-dimensional magnetic particle imaging system, traversing n reconstruction units: for each reconstruction unit, acquiring a group of frequency spectrum sequences by the method corresponding to the steps S10-S30 of the three-dimensional magnetic particle imaging method based on multi-channel excitation and detection; the group of frequency spectrum sequences form a one-dimensional vector with the length of m;
step S413, combining n groups of frequency spectrum sequences corresponding to n reconstruction units to obtain a measurement matrix of the multi-channel excitation electromagnetic coil and the detection coil; the first column of the measurement matrix is a first group of frequency spectrum sequences, the nth column is an nth group of frequency spectrum sequences, and the size of the measurement matrix is m rows and n columns.
In some preferred embodiments, the three-dimensional magnetic particle image is reconstructed by:
step S421, establishing a three-dimensional magnetic particle image reconstruction equation:
F＝AC
a is a measurement matrix of a multi-channel excitation electromagnetic coil and a detection coil, F is a frequency spectrum sequence obtained by detection of the multi-channel detection coil group, and C is a three-dimensional magnetic particle reconstruction image;
and S422, solving the three-dimensional magnetic particle reconstructed image C according to the image reconstruction equation to realize the reconstruction of the three-dimensional magnetic particle image.
The invention has the beneficial effects that:
the invention relates to a three-dimensional magnetic particle imaging system based on multi-channel excitation and detection, wherein a channel control unit controls excitation electromagnetic coils in different excitation directions to excite magnetic particles in different directions respectively, a response voltage signal generated by each excitation electromagnetic coil is detected by a detection coil, and three-dimensional magnetic particle image reconstruction is performed based on the response voltage signal, so that the time of controlling a gradient magnetic field with high field intensity to spatially encode the whole imaging field in the traditional magnetic particle imaging method is saved, the problem of low imaging precision caused by heating of the electromagnetic coils is avoided, and the magnetic particle imaging speed is high and the imaging precision is high.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:
FIG. 1 is a schematic diagram of a multi-channel excitation coil set and a multi-channel detection coil set of an embodiment of a multi-channel excitation and detection-based three-dimensional magnetic particle imaging system of the present invention;
FIG. 2 is a flow chart of the three-dimensional magnetic particle imaging method based on multi-channel excitation and detection.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the related invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
The invention relates to a three-dimensional magnetic particle imaging system based on multi-channel excitation and detection, which comprises a multi-channel excitation coil set, a multi-channel detection coil set, an alternating current power supply set, a channel control unit, a signal conditioning unit and an image reconstruction unit, wherein the multi-channel excitation coil set is connected with the multi-channel detection coil set;
the multichannel exciting coil group comprises a plurality of exciting electromagnetic coils with different exciting directions and is used for exciting magnetic particles along different directions;
the multi-channel detection coil set comprises a plurality of detection coil arrays, and each detection coil array in the plurality of detection coil arrays comprises a plurality of detection electromagnetic coils which are used for detecting response voltage signals of magnetic particles at different spatial positions and different angles;
the alternating current power supply set is used for supplying power to the multi-channel exciting coil set;
the channel control unit is used for switching the exciting coils in different directions in the exciting coil group to excite the magnetic particles in different directions;
the signal conditioning unit is used for amplifying and filtering the response voltage signal detected by the multi-channel detection coil group;
and the image reconstruction unit is used for carrying out digital signal processing and three-dimensional magnetic particle image reconstruction according to the amplified and filtered response voltage signal.
In order to more clearly describe the three-dimensional magnetic particle imaging system based on multi-channel excitation and detection of the present invention, the following describes the modules in the embodiment of the present invention in detail with reference to fig. 1.
The three-dimensional magnetic particle imaging system based on multi-channel excitation and detection in the first embodiment of the invention comprises a multi-channel excitation coil set, a multi-channel detection coil set, an alternating current power supply set, a channel control unit, a signal conditioning unit and an image reconstruction unit, wherein the modules are described in detail as follows:
as shown in fig. 1, a schematic diagram of a multi-channel excitation coil set and a multi-channel detection coil set according to an embodiment of a multi-channel excitation and detection-based three-dimensional magnetic particle imaging system of the present invention includes: excitation coil sets 1, 2, 3, 4, detection coil sets 5, 6, 7, 8, and an imaging Field Of View (FOV).
The multi-channel excitation coil set comprises a plurality of excitation electromagnetic coils with different excitation directions and is used for exciting the magnetic particles along different directions.
In the embodiment shown in fig. 1, the multi-channel excitation coil includes a first excitation coil 1, a second excitation coil 2, a third excitation coil 3, and a fourth excitation coil 4; the direction of a main magnetic field generated by the first exciting coil 1 is a negative z-axis direction, the direction of a main magnetic field generated by the second exciting coil 2 is a positive z-axis direction, the direction of a main magnetic field generated by the third exciting coil 3 is a positive x-axis direction, and the direction of a main magnetic field generated by the fourth exciting coil 4 is a negative x-axis direction.
The excitation electromagnetic coil of the multi-channel excitation coil group surrounds the imaging field of view of the three-dimensional magnetic particle imaging system:
taking the center of the imaging view field as the origin of the three-dimensional coordinate system, and respectively placing the excitation electromagnetic coils of the multi-channel excitation coil set in the negative direction of the z axis, the positive direction of the x axis and the negative direction of the x axis of the three-dimensional coordinate system; the direction is the main magnetic field direction generated by the exciting coil, and the object to be imaged can enter the FOV of the imaging field of view along the y-axis direction.
The multi-channel detection coil set comprises a plurality of detection coil arrays, and each detection coil array in the plurality of detection coil arrays comprises a plurality of detection electromagnetic coils which are used for detecting response voltage signals of magnetic particles at different spatial positions and different angles.
In the embodiment shown in fig. 1, the multi-channel detection coil set includes a first coil array 5, a second coil array 6, a third coil array 7 and a fourth coil array 8; each coil array is composed of a plurality of small electromagnetic coils and is used for detecting response signals generated by the magnetic particles at different spatial positions in a multi-angle mode.
The detection coil array of the multi-channel detection coil group and the excitation electromagnetic coils of the multi-channel excitation coil group are correspondingly arranged one by one:
each detection coil array is arranged on one side, close to the imaging view field, of each corresponding excitation electromagnetic coil and is used for detecting response voltage signals generated by magnetic particles at different spatial positions in a multi-angle mode.
The alternating current power supply set comprises a multi-channel signal generator and a power amplifier, and is used for supplying power to the multi-channel exciting coil set:
and the multi-channel signal generator is used for generating a current waveform required by the electrified coil group, and the current waveform is one of sine wave, triangular wave and pulse square wave.
And the power amplifier is used for amplifying the current waveform generated by the multi-channel signal generator to a set size and supplying power to the multi-channel exciting coil group based on the amplified current waveform.
And the channel control unit is used for switching the exciting coils in different directions in the exciting coil group to excite the magnetic particles in different directions.
And the signal conditioning unit is used for amplifying and filtering the response voltage signals detected by the multi-channel detection coil group.
And the image reconstruction unit is used for carrying out digital signal processing and three-dimensional magnetic particle image reconstruction according to the response voltage signal after amplification and filtering processing.
The three-dimensional magnetic particle imaging system further comprises a display unit for displaying the three-dimensional magnetic particle image reconstructed by the image reconstruction unit.
A plurality of excitation electromagnetic coils with different excitation directions, wherein only one excitation electromagnetic coil generates an excitation magnetic field at a certain time:
when any exciting electromagnetic coil generates an exciting magnetic field, all the detection coil arrays simultaneously detect magnetization response voltage signals generated by magnetic particles, the detection coil arrays in the same direction as the exciting magnetic field are used for detecting magnetization response voltage signals in the main magnetic flux direction generated by the magnetic particles, and the detection coil arrays perpendicular to the exciting magnetic field are used for detecting magnetization response voltage signals in the leakage magnetic flux direction generated by the magnetic particles.
In the embodiment shown in fig. 1, only one excitation electromagnetic coil is controlled to generate an excitation magnetic field at a certain time, all the detection coil arrays simultaneously detect the magnetization response signals generated by the magnetic particles, the detection coil array in the same direction as the excitation magnetic field is used for detecting the magnetization response signals generated by the magnetic particles in the main magnetic flux direction, and the detection coil array perpendicular to the excitation magnetic field is used for detecting the magnetization response signals generated by the magnetic particles in the leakage magnetic flux direction. Specifically, when the excitation solenoid 1 is controlled to excite the magnetic particles in the FOV, the excitation solenoids 2, 3, 4 are stopped, the detection coil arrays 5, 6 detect the magnetization response signal in the main magnetic flux direction generated by the magnetic particles, and the detection coil arrays 7, 8 detect the magnetization response signal in the leakage magnetic flux direction generated by the magnetic particles; then, the excitation solenoid 2 is switched to excite the magnetic particles in the FOV, the excitation solenoids 1, 3, 4 stop operating, the detection coil arrays 7, 8 detect the magnetization response signal in the main magnetic flux direction generated by the magnetic particles, and the detection coil arrays 5, 6 detect the magnetization response signal in the leakage magnetic flux direction generated by the magnetic particles; then, the exciting electromagnetic coil 3 and the exciting electromagnetic coil 4 are sequentially switched to be excited, and the detection coil operates on the same principle.
A three-dimensional magnetic particle imaging method based on multi-channel excitation and detection according to a second embodiment of the present invention is based on the above three-dimensional magnetic particle imaging system based on multi-channel excitation and detection, as shown in fig. 2, the three-dimensional magnetic particle imaging method includes:
step S10, high-frequency pulse current is input to different exciting electromagnetic coils in sequence, a pulse magnetic field in a specific direction is generated in an imaging view field of the three-dimensional magnetic particle imaging system, and magnetic particles are excited to generate magnetization response voltage signals in different directions;
a step S20 of detecting, for each excitation electromagnetic coil, a magnetization response voltage signal in a main magnetic flux direction generated by magnetic particles by a detection coil array parallel to the excitation electromagnetic coil, and a magnetization response voltage signal in a leakage magnetic flux direction generated by magnetic particles by a detection coil array perpendicular to the excitation electromagnetic coil;
step S30, filtering the detected direct current component in the response voltage signal through a digital filtering technology, and performing fast Fourier transform on the detection signal to obtain a frequency spectrum sequence of the response voltage signal;
and step S40, constructing a measuring matrix of the multi-channel excitation electromagnetic coil and the detecting coil, and calculating the spatial distribution of the magnetic particle concentration by combining the frequency spectrum sequence of the response voltage signal to realize the reconstruction of the three-dimensional magnetic particle image.
The flow of the three-dimensional magnetic particle imaging method based on multi-channel excitation and detection shown in fig. 2 is specifically described with reference to the composition of the multi-channel excitation coil set and the multi-channel detection coil set in fig. 1:
high-frequency pulse current is sequentially input to different exciting coils to excite magnetic particles to generate magnetization response signals in different directions: high-frequency pulse current is sequentially input to the first excitation coil 1, the second excitation coil 2, the third excitation coil 3 and the fourth excitation coil 4 by using an alternating current power supply, excitation magnetic fields in different directions are generated in the FOV, and magnetic particles are excited to generate magnetization response signals in different directions.
The waveform of the high-frequency pulse current is a pulse square wave with a narrow pulse width.
And detecting magnetization response signals in the main flux direction and the leakage flux direction generated by the magnetic particles by using the detection coil group: when one exciting electromagnetic coil in the exciting electromagnetic coil group excites the magnetic particles to generate a magnetization response signal, the magnetization response signal in the main magnetic flux direction generated by the magnetic particles is detected by using a detection coil array parallel to the exciting electromagnetic coil, and the magnetization response signal in the leakage magnetic flux direction generated by the magnetic particles is detected by using a detection coil array perpendicular to the exciting electromagnetic coil.
Filtering out direct current components in the detection signals through a digital filtering technology, and performing fast Fourier transform on the detection signals to obtain a frequency spectrum sequence of the detection signals: firstly, digital filtering is carried out on a detection signal of an upper computer, useless direct current components in the detection signal are filtered, fast Fourier transform is carried out on the detection signal, and a frequency spectrum sequence corresponding to the detection signal is obtained, wherein the detection signal is a response voltage signal acquired by a detection coil group.
And constructing a measuring matrix of the multi-channel excitation electromagnetic coil and the detecting coil, and calculating the spatial distribution of the magnetic particle concentration by using the frequency spectrum sequence and the measuring matrix to realize the reconstruction of the three-dimensional magnetic particle image.
The measuring matrix of the multi-channel exciting electromagnetic coil and the detecting coil is constructed by the following steps:
step S411, based on the preset resolution of the three-dimensional magnetic particle reconstructed image, the imaging field of view of the three-dimensional magnetic particle imaging system is divided into n reconstruction units. The reconstruction unit can be selected from square cells, rectangular cells and the like, and the shape of the reconstruction unit is not limited by the invention.
The size of the reconstruction unit corresponds to the resolution of the reconstructed image, and the higher the resolution is, the smaller the reconstruction unit is.
Step S412, putting the magnetic particle sample of the object to be imaged into the imaging field of view of the three-dimensional magnetic particle imaging system, traversing n reconstruction units: for each reconstruction unit, acquiring a group of frequency spectrum sequences by the method corresponding to the steps S10-S30 of the three-dimensional magnetic particle imaging method based on multi-channel excitation and detection; the set of spectral sequences constitutes a one-dimensional vector of length m.
Step S413, combining n groups of frequency spectrum sequences corresponding to n reconstruction units to obtain a measurement matrix of the multi-channel excitation electromagnetic coil and the detection coil; the first column of the measurement matrix is a first group of frequency spectrum sequences, the nth column is an nth group of frequency spectrum sequences, and the size of the measurement matrix is m rows and n columns.
The measurement matrix is a spectrum matrix which represents the mapping relation between the magnetic particle concentration space distribution and the spectrum sequence obtained by detection.
The method for reconstructing the magnetotactic particle image comprises the following steps:
step S421, establishing a three-dimensional magnetic particle image reconstruction equation as shown in formula (1):
F＝AC (1)
a is a measurement matrix of a multi-channel excitation electromagnetic coil and a detection coil, F is a frequency spectrum sequence obtained by detection of the multi-channel detection coil group, and C is a three-dimensional magnetic particle reconstruction image;
and S422, solving the three-dimensional magnetic particle reconstructed image C according to the image reconstruction equation to realize the reconstruction of the three-dimensional magnetic particle image.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process and related descriptions of the method described above may refer to the corresponding process in the foregoing system embodiment, and are not described herein again.
It should be noted that, the three-dimensional magnetic particle imaging system and method based on multi-channel excitation and detection provided by the above embodiment are only exemplified by the division of the above functional modules, and in practical applications, the above function distribution may be completed by different functional modules according to needs, that is, the modules or steps in the embodiments of the present invention are further decomposed or combined, for example, the modules in the embodiments 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 involved in the embodiments of the present invention are only for distinguishing the modules or steps, and are not to be construed as unduly limiting the present invention.
An apparatus of a third embodiment of the invention comprises:
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 above-described multi-channel excitation and detection-based three-dimensional magnetic particle imaging method.
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-mentioned three-dimensional magnetic particle imaging method based on multi-channel excitation and detection.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes and related descriptions of the storage device and the processing device described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
Those of skill in the art would appreciate that the various illustrative modules, method steps, and modules described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that programs corresponding to the software modules, method steps may be located in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a 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. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing or implying a particular order or sequence.
The terms "comprises," "comprising," or any other similar term are intended to cover a non-exclusive inclusion, such that a process, method, article, or 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.
So far, the technical solutions of the present invention have 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 the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.
Claims (9)
1. A three-dimensional magnetic particle imaging system based on multi-channel excitation and detection is characterized by comprising a multi-channel excitation coil set, a multi-channel detection coil set, an alternating current power supply set, a channel control unit, a signal conditioning unit and an image reconstruction unit;
the multi-channel exciting coil group comprises a plurality of exciting electromagnetic coils with different exciting directions and is used for exciting magnetic particles along different directions;
the multi-channel detection coil set comprises a plurality of detection coil arrays, and each detection coil array in the plurality of detection coil arrays comprises a plurality of detection electromagnetic coils which are used for detecting response voltage signals of magnetic particles at different spatial positions and different angles;
the alternating current power supply set is used for supplying power to the multi-channel exciting coil set;
the channel control unit is used for switching the exciting coils in different directions in the exciting coil group to excite the magnetic particles in different directions;
the signal conditioning unit is used for amplifying and filtering the response voltage signal detected by the multi-channel detection coil group;
the image reconstruction unit is used for carrying out digital signal processing and three-dimensional magnetic particle image reconstruction according to the amplified and filtered response voltage signal;
wherein, the exciting electromagnetic coils with different exciting directions only have one exciting electromagnetic coil to generate exciting magnetic fields at a certain time;
when any exciting electromagnetic coil generates an exciting magnetic field, all the detection coil arrays simultaneously detect magnetization response voltage signals generated by magnetic particles, the detection coil arrays in the same direction as the exciting magnetic field are used for detecting magnetization response voltage signals in the main magnetic flux direction generated by the magnetic particles, and the detection coil arrays perpendicular to the exciting magnetic field are used for detecting magnetization response voltage signals in the leakage magnetic flux direction generated by the magnetic particles.
2. The multi-channel excitation and detection based three-dimensional magnetic particle imaging system of claim 1, wherein the ac power pack comprises a multi-channel signal generator and a power amplifier;
the multi-channel signal generator is used for generating a current waveform required by the electrified coil group; the current waveform is one of sine wave, triangular wave and pulse square wave;
the power amplifier is used for amplifying the current waveform generated by the multi-channel signal generator to a set size and supplying power to the multi-channel exciting coil group based on the amplified current waveform.
3. The multi-channel excitation and detection based three-dimensional magnetic particle imaging system of claim 1, further comprising a display unit;
and the display unit is used for displaying the three-dimensional magnetic particle image reconstructed by the image reconstruction unit.
4. The multi-channel excitation and detection based three-dimensional magnetic particle imaging system according to any one of claims 1-3, wherein the excitation electromagnetic coil of the multi-channel excitation coil set surrounds the imaging field of view of the three-dimensional magnetic particle imaging system;
taking the center of the imaging view field as an origin of a three-dimensional coordinate system, and respectively placing excitation electromagnetic coils of the multi-channel excitation coil set in a z-axis negative direction, a z-axis positive direction, an x-axis positive direction and an x-axis negative direction of the three-dimensional coordinate system; the direction is the main magnetic field direction generated by the exciting coil, and an object to be imaged enters an imaging field of view along the y-axis direction.
5. The multi-channel excitation and detection based three-dimensional magnetic particle imaging system according to any one of claims 1-3, wherein the detection coil arrays of the multi-channel detection coil set are placed in one-to-one correspondence with the excitation electromagnetic coils of the multi-channel excitation coil set;
each detection coil array is arranged on one side of each corresponding excitation electromagnetic coil close to an imaging field and used for detecting response voltage signals generated by magnetic particles at different spatial positions in a multi-angle mode.
6. A three-dimensional magnetic particle imaging method based on multi-channel excitation and detection, which is characterized in that based on the three-dimensional magnetic particle imaging system based on multi-channel excitation and detection as claimed in any one of claims 1-5, the three-dimensional magnetic particle imaging method comprises:
step S10, high-frequency pulse current is input to different exciting electromagnetic coils in sequence, a pulse magnetic field in a specific direction is generated in an imaging view field of the three-dimensional magnetic particle imaging system, and magnetic particles are excited to generate magnetization response voltage signals in different directions;
a step S20 of detecting, for each excitation electromagnetic coil, a magnetization response voltage signal in a main magnetic flux direction generated by magnetic particles by a detection coil array parallel to the excitation electromagnetic coil, and a magnetization response voltage signal in a leakage magnetic flux direction generated by magnetic particles by a detection coil array perpendicular to the excitation electromagnetic coil;
step S30, filtering the detected direct current component in the response voltage signal through a digital filtering technology, and performing fast Fourier transform on the detection signal to obtain a frequency spectrum sequence of the response voltage signal;
and step S40, constructing a measuring matrix of the multi-channel excitation electromagnetic coil and the detecting coil, and calculating the spatial distribution of the magnetic particle concentration by combining the frequency spectrum sequence of the response voltage signal to realize the reconstruction of the three-dimensional magnetic particle image.
7. The method according to claim 6, wherein the high-frequency pulse current has a waveform of a pulse square wave with a narrow pulse width.
8. The three-dimensional magnetic particle imaging method based on multi-channel excitation and detection as claimed in claim 6, wherein the measurement matrix of the multi-channel excitation electromagnetic coil and the detection coil is constructed by:
step S411, based on the preset resolution of the three-dimensional magnetic particle reconstructed image, dividing the imaging field of view of the three-dimensional magnetic particle imaging system into n reconstruction units;
step S412, putting the magnetic particle sample of the object to be imaged into the imaging field of view of the three-dimensional magnetic particle imaging system, traversing n reconstruction units: for each reconstruction unit, acquiring a set of spectrum sequences by a method corresponding to steps S10-S30 of the multi-channel excitation and detection based three-dimensional magnetic particle imaging method of claim 7; the group of frequency spectrum sequences form a one-dimensional vector with the length of m;
step S413, combining n groups of frequency spectrum sequences corresponding to n reconstruction units to obtain a measurement matrix of the multi-channel excitation electromagnetic coil and the detection coil; the first column of the measurement matrix is a first group of frequency spectrum sequences, the nth column is an nth group of frequency spectrum sequences, and the size of the measurement matrix is m rows and n columns.
9. The multi-channel excitation and detection based three-dimensional magnetic particle imaging method according to claim 8, wherein the three-dimensional magnetic particle image is reconstructed by:
step S421, establishing a three-dimensional magnetic particle image reconstruction equation:
F＝AC
a is a measurement matrix of a multi-channel excitation electromagnetic coil and a detection coil, F is a frequency spectrum sequence obtained by detection of the multi-channel detection coil group, and C is a three-dimensional magnetic particle reconstruction image;
and S422, solving the three-dimensional magnetic particle reconstructed image C according to the image reconstruction equation to realize the reconstruction of the three-dimensional magnetic particle image.
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