CN115120221B - Magnetic nanoparticle imaging system and method based on Brownian relaxation coding - Google Patents
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Abstract
The invention belongs to the technical field of biomedical imaging, in particular relates to a magnetic nanoparticle imaging system and method based on Brownian relaxation coding, and aims to solve the problems that the existing magnetic nanoparticle imaging equipment depends on a gradient magnetic field generated by a high-power coil or a permanent magnet, and is large in size and not portable. The invention comprises the following steps: a pre-magnetizing coil, a driving coil and a receiving coil for performing pre-magnetizing, brownian relaxation excitation and induced magnetization change of the magnetic nanoparticles in a semi-saturated state; the rotating module is used for rotating the driving coil along the tangential direction of the field of view to realize space coding; the coil rotation control module is used for controlling the driving coil to alternately emit an alternating magnetic field; the fault scanning module is used for controlling the imaging target or the electromagnetic coil module to axially move along the field of view; and the signal acquisition and image reconstruction module is used for acquiring the induced voltage signals and performing magnetic nanoparticle imaging reconstruction. The invention has low power consumption and simple structure, and can be used in portable bedside MPI equipment.
Description
Technical Field
The invention belongs to the technical field of biomedical imaging, and particularly relates to a magnetic nanoparticle imaging system and method based on Brownian relaxation coding.
Background
The magnetic nanoparticle is a nano-scale particle with superparamagnetism, and is widely studied and applied as a novel medical imaging tracer agent in clinical problems such as tumor detection, magnetic particle thermotherapy, targeted drug delivery and the like in recent years.
Conventional magnetic nanoparticle imaging (MPI) generally requires the addition of three magnetic fields to achieve spatial encoding and field-of-view scanning. Firstly, a static gradient magnetic field is utilized to generate a magnetic Field Free Region (FFR), and magnetic nano particles outside the FFR are in a saturated state and cannot change the magnetization intensity; then, a high-frequency alternating magnetic field is utilized to drive FFR to move and simultaneously drive magnetic nano particles in FFR to rotate so as to cause the change of magnetization, which is generally called a driving field; due to the risks in terms of magnetic stimulation, etc., there is a limit to the amplitude of the high frequency drive field, and thus the field of view (FOV) of the drive field is limited. To solve this problem, a low frequency alternating magnetic field, commonly referred to as a focusing field, is added to move the FFR to a specific position, thereby achieving the purpose of increasing the FOV. The rotation mechanism of the magnetic nano-particles mainly comprises two kinds of Neille relaxation and Brownian relaxation, the Neille relaxation represents the inversion of the polarity of the crystal lattice inside the magnetic nano-particles in popular terms, and the Brownian relaxation represents the physical rotation of the magnetic nano-particles.
In summary, the conventional MPI method relies on FFR generated by gradient magnetic fields for spatial encoding, and spatial resolution is positively correlated with the magnetic field gradient size. It is therefore often necessary to generate a sufficiently large gradient magnetic field with high power coils and even permanent magnets in practice, which inevitably results in the disadvantages of large volumes, portability and high costs of conventional MPI scanners like other medical imaging devices (e.g. magnetic resonance, CT).
Recent studies have shown that MPI can be applied to early diagnosis of stroke. It is well known that the success rate of cerebral stroke treatment is closely related to the diagnosis time. Compared with the traditional fixed diagnosis device, the portable diagnosis device can greatly advance the diagnosis process, and gains more time for treatment.
In view of the foregoing, there is a further need in the art for a lightweight, portable MPI method and apparatus. To this end, the present invention provides a portable, brownian relaxation encoding-based magnetic nanoparticle imaging system and method that does not require the generation of static gradient magnetic field encoding.
Disclosure of Invention
In order to solve the above problems in the prior art, that is, the existing magnetic nanoparticle imaging device relies on a gradient magnetic field generated by a high-power coil or a permanent magnet, and has large volume and portability, the invention provides a magnetic nanoparticle imaging system based on Brownian relaxation coding, which comprises:
The electromagnetic coil module comprises at least one pre-magnetizing coil along the axial direction of the field of view, at least one driving coil along the radial direction of the field of view and at least one receiving coil along the axial direction of the field of view, and is used for performing semi-saturation pre-magnetizing, brownian relaxation excitation and induced magnetization intensity change of the magnetic nanoparticles;
the rotating module is used for rotating the at least one driving coil along the radial direction of the field of view along the tangential direction of the field of view to realize space coding along the tangential direction of the field of view;
The coil rotation control module is used for controlling the at least one driving coil along the radial direction of the field of view to alternately emit an alternating magnetic field;
The fault scanning module is used for controlling the imaging target or the electromagnetic coil module to axially move along the visual field so as to perform three-dimensional fault scanning of the imaging target;
and the signal acquisition and image reconstruction module is used for acquiring the induced voltage signal of the at least one receiving coil along the axial direction of the field of view in the three-dimensional tomography process of the imaging target and carrying out magnetic nanoparticle imaging reconstruction based on the induced voltage signal.
In some preferred embodiments, the at least one pre-magnetizing coil along the axial direction of the field of view generates a uniform pre-magnetizing field in the fault plane of the field of view after direct current or low-frequency alternating current is introduced, so as to enable the magnetic nano particles in the field of view to be in a semi-saturated magnetization state.
In some preferred embodiments, the at least one driving coil along the radial direction of the field of view generates an alternating magnetic field with a gradient along the radial direction of the field of view after high-frequency alternating current is introduced, so as to excite Brownian relaxation of the magnetic nanoparticles in a semi-saturated magnetization state, and generate physical rotation.
In some preferred embodiments, the at least one receiving coil along the axial direction of the field of view is used to induce axial macroscopic magnetization changes resulting from the rotation of the magnetic nanoparticles.
In some preferred embodiments, the half-saturated magnetization state is:
The macroscopic magnetization direction of the magnetic nano particles is aligned along the axial direction of the field of view and is consistent with the externally applied magnetic field, and the magnetic nano particles can rotate along with the externally applied magnetic field under the incomplete magnetic saturation state.
In some preferred embodiments, the at least one pre-magnetizing coil generates a pre-magnetizing field that is a uniform magnetic field with a magnetizing direction aligned axially along the field of view.
In some preferred embodiments, the at least one drive coil along the radial direction of the field of view is one or more drive coils disposed at an angle along the radial direction of the field of view and evenly distributed around the periphery of the field of view.
In another aspect of the present invention, a magnetic nanoparticle imaging method based on the brownian relaxation encoding is provided, and a magnetic nanoparticle imaging system based on the brownian relaxation encoding is provided, where the magnetic nanoparticle imaging method includes:
a uniform pre-magnetizing field is axially configured along the view field, so that magnetic nano particles in the view field reach a half-saturation magnetizing state, and the magnetizing directions are axially aligned along the view field;
a driving magnetic field with gradient is arranged along the radial direction of the field of view, so that magnetic nano particles in the field of view deflect along the radial direction of the field of view, and the maximum deflection angle position is obtained along the radial direction of the field of view;
Changing the size of an axial pre-magnetizing field of the field of view, so that the position of the maximum deflection angle is moved, radial coding along the radial direction of the field of view is realized, and the change of magnetization intensity from the axial direction is induced through at least one receiving coil along the axial direction of the field of view, so that a first induced voltage signal is generated; the magnetic field coil is driven in a tangential direction along the visual field, and the change of magnetization intensity from the axial direction is induced by at least one receiving coil along the axial direction of the visual field, so that a second induced voltage signal is generated; moving the imaging target or the electromagnetic coil module along the axial direction of the field of view, and inducing magnetization change from the axial direction through at least one receiving coil along the axial direction of the field of view to generate a third induced voltage signal;
And respectively extracting second harmonic components of the first induced voltage signal, the second induced voltage signal and the third induced voltage signal, and respectively projecting the amplitudes of the second harmonic components to radial encoding tracks to realize magnetic nanoparticle imaging reconstruction.
In some preferred embodiments, the maximum deflection angle position is the maximum deflection angle position existing in the process of decreasing the deflection angle of the corresponding field-of-view radial magnetic nano particles after gradually increasing when the ratio of the driving magnetic field amplitude and the pre-magnetizing magnetic field amplitude is gradually decreasing.
In some preferred embodiments, the greater the deflection angle, the greater the induced change in the axial magnetization of the field of view, the stronger the received signal.
The invention has the beneficial effects that:
(1) The magnetic nanoparticle imaging system based on Brownian relaxation coding provided by the invention is based on Brownian relaxation effect of magnetic nanoparticles, and magnetic nanoparticles in the radial direction of a field of view are excited by a driving magnetic field with gradient to rotate to different degrees, so that space coding is realized, and high-precision magnetic nanoparticle imaging reconstruction is rapidly and efficiently carried out according to induced voltage signals obtained in the coding process.
(2) The magnetic nanoparticle imaging system based on Brownian relaxation coding does not need extra high gradient fields to carry out space coding, overcomes the defects of large volume and portability of the traditional MPI equipment, can realize space coding and signal excitation simultaneously by only one driving coil and one pre-magnetizing coil, has lower power consumption and simpler structure compared with the traditional method, and can be used for developing the portable and bedside MPI equipment.
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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 accompanying drawings in which:
FIG. 1 is a schematic diagram of the composition of a magnetic nanoparticle imaging system based on Brownian relaxation encoding of the present invention;
FIG. 2 is a schematic flow diagram of an imaging method of an embodiment of a magnetic nanoparticle imaging system based on Brownian relaxation encoding in accordance with the present invention.
Detailed Description
The 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 application and are not limiting of the application. It should be noted that, for convenience of description, only the portions related to the present application are shown in the drawings.
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
The invention discloses a magnetic nanoparticle imaging system based on Brownian relaxation encoding, which comprises:
The electromagnetic coil module comprises at least one pre-magnetizing coil along the axial direction of the field of view, at least one driving coil along the radial direction of the field of view and at least one receiving coil along the axial direction of the field of view, and is used for performing semi-saturation pre-magnetizing, brownian relaxation excitation and induced magnetization intensity change of the magnetic nanoparticles;
the rotating module is used for rotating the at least one driving coil along the radial direction of the field of view along the tangential direction of the field of view to realize space coding along the tangential direction of the field of view;
The coil rotation control module is used for controlling the at least one driving coil along the radial direction of the field of view to alternately emit an alternating magnetic field;
The fault scanning module is used for controlling the imaging target or the electromagnetic coil module to axially move along the visual field so as to perform three-dimensional fault scanning of the imaging target;
and the signal acquisition and image reconstruction module is used for acquiring the induced voltage signal of the at least one receiving coil along the axial direction of the field of view in the three-dimensional tomography process of the imaging target and carrying out magnetic nanoparticle imaging reconstruction based on the induced voltage signal.
In order to more clearly illustrate the magnetic nanoparticle imaging system based on Brownian relaxation encoding of the present invention, an embodiment of the present invention is described in detail below with reference to FIG. 1.
The magnetic nanoparticle imaging system based on Brownian relaxation encoding of the first embodiment of the invention comprises an electromagnetic coil module, a rotating module, a coil rotation control module, a tomography module and a signal acquisition and image reconstruction module, wherein the detailed descriptions of the modules are as follows:
The electromagnetic coil module comprises at least one pre-magnetizing coil along the axial direction of the field of view, at least one driving coil along the radial direction of the field of view and at least one receiving coil along the axial direction of the field of view, and is used for performing semi-saturation pre-magnetizing, brownian relaxation excitation and induction magnetization change of the magnetic nanoparticles.
At least one pre-magnetizing coil along the axial direction of the field of view, after being electrified by direct current or low-frequency alternating current, generates a uniform pre-magnetizing field in the fault plane of the field of view, and is used for enabling the magnetic nano particles in the field of view to be in a half-saturated magnetization state.
At least one pre-magnetizing coil along the axial direction of the field of view, the pre-magnetizing magnetic field generated is a uniform magnetic field with the magnetizing direction aligned along the axial direction of the field of view.
At least one driving coil along the radial direction of the field of view, after being electrified by high-frequency alternating current, generates an alternating magnetic field with gradient along the radial direction of the field of view, and is used for exciting the Brownian relaxation of the magnetic nano particles in a semi-saturated magnetization state to generate physical rotation.
The at least one drive coil along the radial direction of the field of view is one or more drive coils disposed at an angle along the radial direction of the field of view and evenly distributed around the periphery of the field of view.
At least one receiving coil along the axial direction of the field of view is used for inducing the axial macroscopic magnetization change generated by the rotation of the magnetic nano particles.
As shown in fig. 1, a schematic diagram of the magnetic nanoparticle imaging system based on the brownian relaxation encoding according to the present invention is shown, 1 represents at least one pre-magnetizing coil along the axial direction of the field of view, 2 represents at least one driving coil along the radial direction of the field of view, 3 represents at least one receiving coil along the axial direction of the field of view, 4 represents the radial direction, 5 represents the tangential direction, the vertical straight direction is the axial direction, and FOV represents the scan field of view of the driving field.
A semi-saturated magnetization state refers to an external magnetic field of insufficient strength to bring the magnetic nanoparticles into a fully saturated state, but macroscopic magnetization directions are aligned axially along the field of view and coincident with the external magnetic field. In the semi-saturated magnetization state, the magnetic nanoparticles can still rotate with the applied magnetic field.
The rotating module is used for rotating the at least one driving coil along the radial direction of the field of view along the tangential direction of the field of view to realize space coding along the tangential direction of the field of view;
The coil rotation control module is used for controlling the at least one driving coil along the radial direction of the field of view to alternately emit an alternating magnetic field;
The fault scanning module is used for controlling the imaging target or the electromagnetic coil module to axially move along the visual field so as to perform three-dimensional fault scanning of the imaging target;
and the signal acquisition and image reconstruction module is used for acquiring the induced voltage signal of the at least one receiving coil along the axial direction of the field of view in the three-dimensional tomography process of the imaging target and carrying out magnetic nanoparticle imaging reconstruction based on the induced voltage signal.
As shown in fig. 2, the magnetic nanoparticle imaging method based on the brown relaxation coding according to the second embodiment of the present invention is based on the magnetic nanoparticle imaging system based on the brown relaxation coding, and the magnetic nanoparticle imaging method includes:
step S10, uniformly pre-magnetizing fields are axially configured along the view field, so that the magnetic nano particles in the view field reach a half-saturated magnetization state, and the magnetization directions are axially aligned along the view field.
And S20, configuring a driving magnetic field with gradient along the radial direction of the field of view, so that the magnetic nano particles in the field of view deflect along the radial direction of the field of view, and acquiring the maximum deflection angle position in the radial direction of the field of view.
And S30, changing the size of the field axial pre-magnetization field, so that the position of the maximum deflection angle is moved, and radial coding along the radial direction of the field is realized.
The deflection angle is related to the ratio of the drive field amplitude to the pre-magnetization field amplitude in the field space, where there is a maximum deflection angle position in the radial direction of the field.
The presence of a maximum deflection angle position means that the deflection angle of the corresponding magnetic nano particles in the radial direction gradually increases and then decreases along the radial direction along with the gradual decrease of the ratio of the amplitude of the driving field to the amplitude of the pre-magnetizing field, and the maximum deflection angle position exists. The larger the deflection angle, the larger the axial magnetization change caused, and the stronger the received signal.
Step S40, the magnetization change from the axial direction is induced by at least one receiving coil along the axial direction of the field of view, and an induced voltage signal is generated.
And S50, after the second harmonic component of the induced voltage signal is extracted, projecting the amplitude of the second harmonic component to the radial encoding track to realize one-dimensional radial imaging.
And S60, driving the magnetic field coil in a tangential direction along the field of view, and repeating the steps S10-S50 to realize two-dimensional tomography.
And step S70, axially moving an imaging target or an electromagnetic coil module along the field of view, and repeating the steps S10-S60 to realize three-dimensional tomography.
And step S80, completing magnetic nanoparticle imaging reconstruction.
Although the steps are described in the above-described sequential order in the above-described embodiments, it will be appreciated by those skilled in the art that in order to achieve the effects of the present embodiments, the steps need not be performed in such order, and may be performed simultaneously (in parallel) or in reverse order, and such simple variations are within the scope of the present invention.
It will be clear to those skilled in the art that, for convenience and brevity of description, the specific operation of the system and the related description described above may refer to the corresponding process in the foregoing system embodiment, which is not repeated here.
It should be noted that, the magnetic nanoparticle imaging system and method based on the brown relaxation encoding provided in the foregoing embodiments are only exemplified by the division of the foregoing functional modules, and 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 embodiments of the present invention are further decomposed or combined, for example, the modules in the foregoing embodiments may be combined into one module, or may be further split into a plurality of sub-modules, so as to complete all or part of the functions described above. The names of the modules and steps related to the embodiments of the present invention are merely for distinguishing the respective modules or steps, and are not to be construed as unduly limiting the present invention.
An electronic device of a third embodiment of the present invention includes:
At least one processor; and
A memory communicatively coupled to at least one of the processors; wherein,
The memory stores instructions executable by the processor for execution by the processor to implement the above-described magnetic nanoparticle imaging method based on Brownian relaxation encoding.
A computer-readable storage medium of a fourth embodiment of the present invention stores computer instructions for execution by the computer to implement the above-described brown relaxation encoding-based magnetic nanoparticle imaging method.
It will be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process of the storage device and the processing device described above and the related description may refer to the corresponding process in the foregoing method embodiment, which is 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," and the like, are used for distinguishing between similar objects and not for describing a particular sequential or chronological order.
The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus/apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus/apparatus.
Thus far, the technical solution of the present invention has been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of protection of the present invention is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present invention, and such modifications and substitutions will be within the scope of the present invention.
Claims (10)
1. A magnetic nanoparticle imaging system based on brown relaxation encoding, the magnetic nanoparticle imaging system comprising:
The electromagnetic coil module comprises at least one pre-magnetizing coil along the axial direction of the field of view, at least one driving coil along the radial direction of the field of view and at least one receiving coil along the axial direction of the field of view, and is used for performing semi-saturation pre-magnetizing, brownian relaxation excitation and induced magnetization intensity change of the magnetic nanoparticles;
the rotating module is used for rotating the at least one driving coil along the radial direction of the field of view along the tangential direction of the field of view to realize space coding along the tangential direction of the field of view;
The coil rotation control module is used for controlling the at least one driving coil along the radial direction of the field of view to alternately emit an alternating magnetic field;
The fault scanning module is used for controlling the imaging target or the electromagnetic coil module to axially move along the visual field so as to perform three-dimensional fault scanning of the imaging target;
and the signal acquisition and image reconstruction module is used for acquiring the induced voltage signal of the at least one receiving coil along the axial direction of the field of view in the three-dimensional tomography process of the imaging target and carrying out magnetic nanoparticle imaging reconstruction based on the induced voltage signal.
2. The magnetic nanoparticle imaging system based on brown relaxation encoding according to claim 1, wherein the at least one pre-magnetizing coil along the axial direction of the field of view generates a uniform pre-magnetizing field in the fault plane of the field of view after being supplied with a direct current or a low frequency alternating current, so as to enable the magnetic nanoparticles in the field of view to be in a half-saturated magnetization state.
3. The magnetic nanoparticle imaging system based on the brown relaxation encoding according to claim 2, wherein the at least one driving coil along the radial direction of the field of view generates an alternating magnetic field with gradient along the radial direction of the field of view after being supplied with a high-frequency alternating current, so as to excite the brown relaxation of the magnetic nanoparticles in a half-saturated magnetization state, and generate physical rotation.
4. A magnetic nanoparticle imaging system based on broussing encoding according to claim 3, wherein the at least one receiving coil along the field of view is arranged to sense axial macroscopic magnetization changes resulting from rotation of the magnetic nanoparticles.
5. The magnetic nanoparticle imaging system based on broussing encoding of any one of claims 2 to 4, wherein the semi-saturated magnetization state is:
The macroscopic magnetization direction of the magnetic nano particles is aligned along the axial direction of the field of view and is consistent with the externally applied magnetic field, and the magnetic nano particles can rotate along with the externally applied magnetic field under the incomplete magnetic saturation state.
6. The magnetic nanoparticle imaging system based on brown relaxation encoding of claim 5, wherein the at least one pre-magnetizing coil generates a pre-magnetizing field that is a uniform magnetic field with magnetization directions aligned axially along the field of view.
7. The magnetic nanoparticle imaging system based on brown relaxation encoding of claim 1, wherein the at least one drive coil along the radial direction of the field of view is one or more drive coils evenly distributed placed at an angle around the periphery of the field of view along the radial direction of the field of view.
8. A magnetic nanoparticle imaging method based on brown relaxation encoding, characterized in that the magnetic nanoparticle imaging method based on the magnetic nanoparticle imaging system based on brown relaxation encoding according to any one of claims 1-7 comprises:
a uniform pre-magnetizing field is axially configured along the view field, so that magnetic nano particles in the view field reach a half-saturation magnetizing state, and the magnetizing directions are axially aligned along the view field;
a driving magnetic field with gradient is arranged along the radial direction of the field of view, so that magnetic nano particles in the field of view deflect along the radial direction of the field of view, and the maximum deflection angle position is obtained along the radial direction of the field of view;
Changing the size of an axial pre-magnetizing field of the field of view, so that the position of the maximum deflection angle is moved, radial coding along the radial direction of the field of view is realized, and the change of magnetization intensity from the axial direction is induced through at least one receiving coil along the axial direction of the field of view, so that a first induced voltage signal is generated; the magnetic field coil is driven in a tangential direction along the visual field, and the change of magnetization intensity from the axial direction is induced by at least one receiving coil along the axial direction of the visual field, so that a second induced voltage signal is generated; moving the imaging target or the electromagnetic coil module along the axial direction of the field of view, and inducing magnetization change from the axial direction through at least one receiving coil along the axial direction of the field of view to generate a third induced voltage signal;
And respectively extracting second harmonic components of the first induced voltage signal, the second induced voltage signal and the third induced voltage signal, and respectively projecting the amplitudes of the second harmonic components to radial encoding tracks to realize magnetic nanoparticle imaging reconstruction.
9. The method of claim 8, wherein the maximum deflection angle position is a maximum deflection angle position existing in a process that the deflection angle of the corresponding field radial magnetic nanoparticle is gradually increased and then decreased when the ratio of the driving magnetic field amplitude and the pre-magnetizing magnetic field amplitude is gradually decreased.
10. The method of magnetic nanoparticle imaging based on brown relaxation encoding of claim 9, wherein the larger the deflection angle, the larger the induced change in the axial magnetization of the field of view, and the stronger the received signal.
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| US9167983B2 (en) * | 2008-08-15 | 2015-10-27 | The University Of Houston System | Imaging method for obtaining spatial distribution of nanoparticles in the body |
| US10222438B2 (en) * | 2012-11-01 | 2019-03-05 | The Trustees Of Dartmouth College | System and apparatus for combined magnetic resonance imaging with magnetic spectroscopy of brownian motion and/or magnetic nanoparticle imaging |
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| CN114376550A (en) * | 2021-12-14 | 2022-04-22 | 西安电子科技大学青岛计算技术研究院 | Magnetic particle imaging system based on gradient field |
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