CN110680320B - Magnetic induction imaging method and system - Google Patents
Magnetic induction imaging method and system Download PDFInfo
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- CN110680320B CN110680320B CN201911023031.8A CN201911023031A CN110680320B CN 110680320 B CN110680320 B CN 110680320B CN 201911023031 A CN201911023031 A CN 201911023031A CN 110680320 B CN110680320 B CN 110680320B
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- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/0522—Magnetic induction tomography
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0033—Features or image-related aspects of imaging apparatus classified in A61B5/00, e.g. for MRI, optical tomography or impedance tomography apparatus; arrangements of imaging apparatus in a room
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0033—Features or image-related aspects of imaging apparatus classified in A61B5/00, e.g. for MRI, optical tomography or impedance tomography apparatus; arrangements of imaging apparatus in a room
- A61B5/004—Features or image-related aspects of imaging apparatus classified in A61B5/00, e.g. for MRI, optical tomography or impedance tomography apparatus; arrangements of imaging apparatus in a room adapted for image acquisition of a particular organ or body part
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0033—Features or image-related aspects of imaging apparatus classified in A61B5/00, e.g. for MRI, optical tomography or impedance tomography apparatus; arrangements of imaging apparatus in a room
- A61B5/004—Features or image-related aspects of imaging apparatus classified in A61B5/00, e.g. for MRI, optical tomography or impedance tomography apparatus; arrangements of imaging apparatus in a room adapted for image acquisition of a particular organ or body part
- A61B5/0042—Features or image-related aspects of imaging apparatus classified in A61B5/00, e.g. for MRI, optical tomography or impedance tomography apparatus; arrangements of imaging apparatus in a room adapted for image acquisition of a particular organ or body part for the brain
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2576/00—Medical imaging apparatus involving image processing or analysis
- A61B2576/02—Medical imaging apparatus involving image processing or analysis specially adapted for a particular organ or body part
- A61B2576/026—Medical imaging apparatus involving image processing or analysis specially adapted for a particular organ or body part for the brain
Abstract
The application discloses a magnetic induction imaging method and system. The method comprises the following steps: the alternating current provided by the signal generating device for the signal transmitting device is utilized to generate an excitation magnetic field around the target biological tissue, the excitation magnetic field enables the target biological tissue to generate an induction magnetic field and/or a scattered field magnetic field which can be detected by the signal detecting device, a three-dimensional image of the target biological tissue can be generated according to the detection result and displayed by the image display device, thereby realizing magnetic induction imaging, on one hand, the three-dimensional imaging device does not need to be contacted with the target biological tissue, has no wound and is not needed to be pasted with any electrode on the target biological tissue, on the other hand, the three-dimensional imaging and displaying can be realized, the imaging information is more comprehensive, in practical application, the three-dimensional imaging device can realize more accurate detection on various diseases such as cerebral apoplexy, lung cancer, breast cancer and the like by collecting the three-dimensional imaging of the diseased target biological tissue, such as brain, and can be monitored continuously.
Description
Technical Field
The application relates to the technical field of magnetic induction imaging, in particular to a magnetic induction imaging method and system.
Background
At present, cerebral apoplexy seriously harms the health and the life quality of middle-aged and old people in China, and brings heavy economic and medical burdens to families and society of patients. The early discovery and early diagnosis are key factors for realizing the timely rescue and treatment of the cerebral apoplexy.
In the related art, medical imaging technologies such as X-ray computed tomography and Computed Tomography (CT) are currently conventional medical imaging technologies for stroke. However, X-ray computed tomography and CT generate ionizing radiation harmful to human health, and continuous, real-time monitoring of the development process of cerebral edema cannot be achieved.
Compared with the conventional stroke detection technology, magnetic induction imaging is expected to become a safe and effective routine or auxiliary stroke detection means due to the advantages of no wound, non-invasion, no ionizing radiation, high contrast, easiness in general investigation and the like, and the method is widely concerned by scholars at home and abroad. However, the current magnetic induction imaging technology cannot realize three-dimensional imaging, and the detection effect is not good.
Disclosure of Invention
It is an object of the present application to provide a magnetic induction imaging method and system to solve the problems in the related art.
The purpose of the application is realized by the following technical scheme:
a magnetic induction imaging method is applied to a magnetic induction imaging system, wherein the magnetic induction imaging system comprises a control device, a signal generation device, a signal detection device and an image display device which are respectively connected with the control device, and a signal transmitting device connected with the signal generation device; the signal transmitting device comprises a first magnetic induction coil as an excitation coil, wherein the first magnetic induction coil is in a first preset number; the signal detection device comprises a second preset number of second magnetic induction coils serving as detection coils; the magnetic induction imaging method performed by the control device includes:
controlling the signal generating device to generate an electromagnetic wave signal and outputting the electromagnetic wave signal to the signal transmitting device in the form of alternating current;
controlling the signal transmitting device to scan target biological tissue, and generating an excitation magnetic field around the target biological tissue through the alternating current so that the target biological tissue generates an induction magnetic field and/or a stray magnetic field under the action of the excitation magnetic field;
controlling the signal detection device to scan the target biological tissue and detect the induction magnetic field and/or the stray magnetic field;
and generating a three-dimensional image of the target biological tissue according to the detected induction magnetic field and/or stray field magnetic field, and sending the three-dimensional image to the image display device for displaying.
Optionally, the controlling the signal emitting device to scan the target biological tissue includes: controlling at least one excitation coil in the signal transmitting device to apply an alternating current to the target biological tissue;
the controlling the signal detection device to scan the target biological tissue and detect the induced magnetic field and/or the stray magnetic field includes: controlling at least three detection coils with the same distance to the target biological tissue in the signal detection device to move to different vertical distances along the vertical direction, and detecting the induction magnetic field and/or the stray magnetic field under different vertical distances to obtain a first detection result; controlling at least three detection coils with the same distance to the target biological tissue in the signal detection device to move to different horizontal distances along the horizontal direction, and detecting the induction magnetic field and/or the stray magnetic field under different horizontal distances to obtain a second detection result;
generating a three-dimensional image of the target biological tissue from the detected induced and/or stray magnetic fields, comprising:
and comparing the induced magnetic field and/or the stray magnetic field detected by each detection coil in the first detection result, and comparing the induced magnetic field and/or the stray magnetic field detected by each detection coil in the second detection result to generate a three-dimensional image of the target biological tissue.
Optionally, the comparing the induced magnetic field and/or the stray field magnetic field detected by each of the detection coils in the first detection result and the comparing the induced magnetic field and/or the stray field magnetic field detected by each of the detection coils in the second detection result to generate the three-dimensional image of the target biological tissue includes:
establishing an intensity model of the target biological tissue according to the following formula:
wherein j is the imaginary part of the complex number,
omega-2 pi f is the working angular frequency, f is the imaging system working frequency, mu0Is the permeability of free space, σ is the electrical conductivity of the target biological tissue,0is the dielectric constant of the free space and,ris the dielectric constant of the target biological tissue,r＝′r-jσ/ω0，′ris the real part of the relative dielectric constant of the target biological tissue,
as a result of the total magnetic field,
establishing an internal magnetic field induction model of the target biological tissue according to the following formula:
wherein the content of the first and second substances,
for an incident magnetic field, G is the Green function,
as a position vector from the field source point to the scattered magnetic field,
is a position vector, k, from a field source point to a point within said target biological tissue0Is the wave number in free space and is,
in order to obtain the density of the magnetic current,
μris the magnetic permeability of the target biological tissue,
in order to induce the current density,
as a result of the total electric field,
establishing an external magnetic field induction model of the target biological tissue according to the following formula:
wherein the content of the first and second substances,
in order to scatter the magnetic field,
is a unit vector from the field source point to any point in the field,
r is the distance from the field source point to any point in the scattering field;
taking an internal magnetic induction model and an external magnetic field induction model of the target biological tissue as nonlinear models of the target biological tissue;
comparing the induction magnetic field and/or the stray field magnetic field detected by each detection coil in the first detection result pairwise at the same vertical distance, and obtaining information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue according to the difference obtained by comparison;
obtaining information capable of reflecting a first depth distribution of the target biological tissue through the information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue obtained at different vertical distances:
Dn＝sncos(θn) (4)
wherein, thetanFor measuring the measuring or radiation angle of the coil n to the target object, DnIn order to be the depth information,
comparing the induction magnetic field and/or the stray field magnetic field detected by each detection coil in the second detection result pairwise at the same horizontal distance, and obtaining information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue according to the difference obtained by comparison;
obtaining information capable of reflecting a second depth distribution of the target biological tissue through the information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue obtained at different horizontal distances:
extracting corresponding change values and curves from the nonlinear observation model according to the first depth distribution information and the second depth distribution information of the target biological tissue, and reconstructing a three-dimensional image of the target biological tissue according to the change values:
optionally, the reconstructing a three-dimensional image of the target biological tissue includes:
calculating two detection coils in each detection coil on the same horizontal plane
The echo magnetic field of (2):
wherein x represents a complex conjugate of the complex number,<>representing mean time, echo magnetic field signal
Sequentially calculating the sum of the echo magnetic fields of every two detection coils to obtain the total echo magnetic field of all the detection coils, and when the number of the detection coils is NRWhen is not equal to NRIs a natural number and NRNot less than 3, total echo magnetic field is NR(NR-1) sum of echo magnetic field signals of the detection coils;
carrying out inverse Fourier transform on the total echo magnetic field of each detection coil to obtain a two-dimensional image of a target object in any shape;
and comparing and superposing the total echo magnetic fields of the detection coils at different vertical heights to obtain a three-dimensional image of the target biological tissue.
A magnetic induction imaging system comprises a control device, a signal generation device, a signal detection device, an image display device and a signal transmitting device, wherein the signal generation device, the signal detection device and the image display device are respectively connected with the control device; the signal transmitting device comprises a first magnetic induction coil as an excitation coil, wherein the first magnetic induction coil is in a first preset number; the signal detection device comprises a second preset number of second magnetic induction coils serving as detection coils; the control device is adapted to perform a magnetic induction imaging method as defined in any one of the above.
Optionally, media are disposed between the target biological tissue and each magnetic induction coil, and between each magnetic induction coil.
Optionally, each of the excitation coils is uniformly distributed on a circular ring centered on the target biological tissue; the detection coils are evenly distributed on a circular ring centered on the target biological tissue.
Optionally, the detection coil and the excitation coil are both located on the same side or both sides of the target biological tissue;
and/or the heights of the detection coil and the excitation coil are the same or different;
and/or the detection coil and the excitation coil are parallel to each other;
and/or the detection coil and the excitation coil coincide with each other;
and/or the detection coil and the excitation coil are both at a preset angle with respect to the target biological tissue.
Optionally, the signal transmitting device is connected to the signal generating device through a multi-channel switch circuit board; the signal detection device is connected with the control device through the multi-channel switch circuit board.
Optionally, the magnetic induction coil is a solenoid coil, a helmholtz coil, a patch coil, or an antenna.
This application adopts above technical scheme, has following beneficial effect:
the magnetic induction imaging system is provided with a signal generating device capable of generating electromagnetic waves, a signal transmitting device, a control device, a signal detecting device and an image display device, wherein an alternating current provided for the signal transmitting device by the signal generating device is utilized to generate an excitation magnetic field around a target biological tissue, the excitation magnetic field enables the target biological tissue to generate an induction magnetic field and/or a scattered field magnetic field, the induction magnetic field can be detected by the signal detecting device, a three-dimensional image of the target biological tissue can be generated according to a detection result and displayed by the image display device, so that the magnetic induction imaging is realized, on one hand, the scheme does not need to be in contact with the target biological tissue, has no wound, does not need to paste any electrode on the target biological tissue, on the other hand, can realize the three-dimensional imaging and display, has more comprehensive imaging information, and is practical, the detection of various diseases such as cerebral apoplexy, lung cancer, breast cancer and the like can be more accurate by collecting diseased target biological tissues such as three-dimensional imaging of positions of brain, lung, breast and the like, the detection effect is improved, and continuous monitoring can be carried out.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a magnetic induction imaging method according to an embodiment of the present application.
FIG. 2 is a block diagram of a magnetic induction imaging system according to an embodiment of the present application.
Fig. 3 is a schematic diagram of a geometric arrangement of magnetic induction coils in a magnetic induction imaging system according to another embodiment of the present application.
Fig. 4 is a schematic diagram of a detection coil height adjustment provided in another embodiment of the present application.
FIG. 5(a) is a diagram of a simulation of a system including a skull model and coils according to another embodiment of the present application.
FIG. 5(b) is a three-dimensional image of a three-dimensional skull model provided in another embodiment of the present application.
FIG. 5(c) is a three-dimensional reconstructed image of a three-dimensional skull model provided by another embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail below. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without making any creative effort, shall fall within the protection scope of the present application.
Examples
Referring to fig. 1, fig. 1 is a flowchart of a magnetic induction imaging method according to an embodiment of the present application.
Referring to fig. 2, fig. 2 is a structural diagram of a magnetic induction imaging system according to an embodiment of the present application.
As shown in fig. 1, the present embodiment provides a magnetic induction imaging method, which is applied to a magnetic induction imaging system, as shown in fig. 2, the magnetic induction imaging system includes a control device 201, a signal generation device 202, a signal detection device 203, an image display device 204, and a signal transmission device 205 connected to the signal generation device, which are respectively connected to the control device; the signal transmitting device comprises a first magnetic induction coil as an excitation coil, wherein the first magnetic induction coil is in a first preset number; the signal detection device comprises a second preset number of second magnetic induction coils serving as detection coils; the magnetic induction imaging method executed by the control device comprises the following specific steps:
and step 11, controlling the signal generating device to generate an electromagnetic wave signal and outputting the electromagnetic wave signal to the signal transmitting device in the form of alternating current.
The signal generating means may be a vector network analyser of the type Keysight E5061B which can generate radio frequency signals in the frequency range 5Hz-3 GHz.
And 12, controlling the signal transmitting device to scan the target biological tissue, and generating an excitation magnetic field around the target biological tissue through the alternating current so that the target biological tissue generates an induction magnetic field and/or a stray magnetic field under the action of the excitation magnetic field.
In the implementation, alternating current is applied to one excitation coil, the sine alternating current generates an excitation magnetic field around the target biological tissue, eddy current is generated when the excitation magnetic field passes through the target biological tissue under the action of electromagnetic induction, and the eddy current generates an induction magnetic field and/or a scattered field magnetic field. The respective excitation coils can be controlled in turn.
And step 13, controlling the signal detection device to scan the target biological tissue, and detecting the induction magnetic field and/or the stray magnetic field.
The alternating magnetic field propagates through the space to all the other detection coils, and the detection coils can detect the alternating magnetic field. After the exciting coils are sequentially controlled, the detection coils are used for respectively detecting, and a group of complete measurement data can be obtained.
And step 14, generating a three-dimensional image of the target biological tissue according to the detected induction magnetic field and/or stray field magnetic field, and sending the three-dimensional image to the image display device for displaying.
The propagation of the magnetic field is influenced by the complex conductivity and the complex permittivity of the passing space, the amplitude and the phase difference of the scattered magnetic fields of different detection coils are compared pairwise, the information of the complex conductivity or the complex permittivity or the permeability of the space can be obtained, and a distribution image of the conductivity or the variation of the conductivity in the three-dimensional fault is reconstructed and obtained on the basis of the information. Wherein, during the measurement process, the radio frequency coil does not need to change position.
The magnetic induction imaging system is provided with a signal generating device capable of generating electromagnetic waves, a signal transmitting device, a control device, a signal detecting device and an image display device, wherein an alternating current provided for the signal transmitting device by the signal generating device is utilized to generate an excitation magnetic field around a target biological tissue, the excitation magnetic field enables the target biological tissue to generate an induction magnetic field and/or a scattered field magnetic field, the induction magnetic field can be detected by the signal detecting device, a three-dimensional image of the target biological tissue can be generated according to a detection result and displayed by the image display device, so that the magnetic induction imaging is realized, on one hand, the scheme does not need to be in contact with the target biological tissue, has no wound, does not need to paste any electrode on the target biological tissue, on the other hand, can realize the three-dimensional imaging and display, has more comprehensive imaging information, and is practical, the detection of various diseases such as cerebral apoplexy, lung cancer, breast cancer and the like can be more accurate by collecting diseased target biological tissues such as three-dimensional imaging of positions of brain, lung, breast and the like, the detection effect is improved, and continuous monitoring can be carried out.
The magnetic induction imaging method is also called a three-dimensional holographic imaging method.
In some embodiments, optionally, a medium is disposed between the target biological tissue and each magnetic induction coil, and between each magnetic induction coil. The medium may be saline, etc., and the dielectric properties of the medium are similar to those of adipose tissue, thereby reducing signal coupling and improving detection sensitivity.
The position relationship between the detection coil and the excitation coil is various, for example: the detection coil and the excitation coil may be both located on the same side or both sides of the target biological tissue; the heights of the detection coil and the excitation coil may be the same or different; the detection coil and the excitation coil may be parallel to each other; the detection coil and the excitation coil may coincide with each other; it is also possible that both the detection coil and the excitation coil are organized at a predetermined angle to the target biological tissue, and so on.
In some embodiments, optionally, each of the excitation coils is uniformly distributed on a circle centered on the target biological tissue, thereby forming a planar array; as shown in fig. 3, the magnetic induction coils 207 each serving as the detection coil are uniformly distributed on a circle centered on the target biological tissue 208, thereby forming a planar array. In addition, the distance or the height of each magnetic induction coil from the target biological tissue is the same. In the embodiment, the magnetic induction coils are regularly arranged, so that the detection sensitivity can be effectively improved, the image data acquisition time and the device cost are reduced, and the imaging quality is improved.
In fig. 3, the magnetic induction coil is disposed on a carrier 206.
The excitation coil and the detection coil may be the same coil or different coils, and if the excitation coil and the detection coil are the same coil, the excitation coil generates a magnetic field, and the detection coil detects the magnetic field change in and around the target biological tissue and the distribution state of the dielectric property and the electric conductivity.
In implementation, the number of the magnetic induction coils can be set according to actual needs, and the number of the excitation coils is the first preset number NTCan be NTNot less than 1, the number of the detection coils, i.e. the second preset number NRCan be NRNot less than 3, and the comparison can be carried out pairwise.
For example, the number of the magnetic induction coils is 16, the target biological tissue is taken as a center, the 16 magnetic induction coils are uniformly arranged in a circular ring shape around the target biological tissue, and each magnetic induction coil is used as an excitation coil to generate a magnetic field and also used as a detection coil to detect the magnetic field change and the distribution state of the electric conductivity in and around the target biological tissue.
Optionally, the magnetic induction coil is a solenoid coil, a helmholtz coil, a patch coil, an antenna, or the like, and the number of turns of the magnetic induction coil is limited by the operating frequency and the size of the coil.
The working frequency of the magnetic induction imaging system is single frequency, and the optimal frequency range is 1MHz-10 MHz.
In some embodiments, optionally, the signal transmitting device is connected to the signal generating device through a multi-channel switch circuit board; the signal detection device is connected with the control device through the multi-channel switch circuit board. The multi-channel switch can realize the connection of the magnetic induction coil under the control of the control device.
In some embodiments, optionally, in step 12, controlling the signal emitting device to scan the target biological tissue may include: controlling at least one excitation coil in the signal transmitting device to apply an alternating current to the target biological tissue. The method comprises the following specific steps:
establishing an oxyz rectangular coordinate system of a region to be imaged where a target biological tissue is located, and determining the distance between the target biological tissue and an excitation coil and a detection coil, the position coordinate of the excitation coil, the position coordinate of the detection coil and the number N of image points.
And secondly, applying sinusoidal alternating current to the target biological tissue in any shape by at least one excitation coil, wherein the sinusoidal alternating current generates an excitation magnetic field around the target biological tissue, the excitation magnetic field can be regarded as a time harmonic electromagnetic field, and eddy current is generated due to the action of electromagnetic induction when the excitation magnetic field passes through the target biological tissue.
Eddy current by calculating magnetic potential vector
The acquisition step is carried out by the user,
where μ is permeability, ω is angular frequency, ω -2 π f, f is the emission frequency of the signal, σ is conductivity, JsIs the current density of the excitation coil.
Step three, N surrounding the target biological tissue or positioned at one side or two sides of the target biological tissueTThe exciting coils emit electromagnetic wave signals in specific frequency range and the detecting coils detect response magnetic field
Wherein r isiAs position coordinates of the excitation coil, rrFor detecting coilsThe position coordinates of (a).
Further, if N is presentTWhen the exciting coils are distributed in a uniform circular shape, exciting an incident field to each exciting coil in sequence, wherein the total incident field is NTThe sum of the incident fields excited by the excitation coils.
Step four, moving the target biological tissue out of the detected area, and detecting the incident magnetic field at the same detection position on the premise of keeping the emission source unchanged
Step five, the scattered field echo of the target biological tissue can be obtained by subtracting the measurement data of step three and step four, namely:
in step 13, the signal detection device is controlled to scan the target biological tissue and detect the induced magnetic field and/or the stray magnetic field, and the specific implementation manner may include: as shown in fig. 3, at least three detection coils in the signal detection device, which are located at the same distance from the target biological tissue, are controlled to move to different vertical distances along a vertical direction (arrow direction), and the induced magnetic field and/or the stray magnetic field is detected at different vertical distances, so as to obtain a first detection result; and controlling at least three detection coils which are arranged in the signal detection device and have the same distance with the target biological tissue to move to different horizontal distances along the horizontal direction, and detecting the induction magnetic field and/or the stray magnetic field under different horizontal distances to obtain a second detection result.
In the step 14, the generating a three-dimensional image of the target biological tissue according to the detected induced magnetic field and/or stray magnetic field may be implemented in a specific manner, including:
and comparing the induced magnetic field and/or the stray magnetic field detected by each detection coil in the first detection result, and comparing the induced magnetic field and/or the stray magnetic field detected by each detection coil in the second detection result to generate a three-dimensional image of the target biological tissue. The method comprises the following specific steps:
step one, establishing an intensity model of the target biological tissue according to the following formula:
wherein j is the imaginary part of the complex number,
omega-2 pi f is the working angular frequency, f is the imaging system working frequency, mu0Is the permeability of free space, σ is the electrical conductivity of the target biological tissue,0is the dielectric constant of the free space and,ris the dielectric constant of the target biological tissue,r＝′r-jσ/ω0，′ris the real part of the relative dielectric constant of the target biological tissue,
as a result of the total magnetic field,
is a position vector in an oxyz rectangular coordinate system.
Step two, establishing an internal magnetic field induction model of the target biological tissue according to the following formula:
wherein the content of the first and second substances,
for an incident magnetic field, G is the Green function,
from the field source point to the scattered magnetic fieldIs determined by the position vector of (a),
is a position vector, k, from a field source point to a point within said target biological tissue0Is the wave number in free space and is,
in order to obtain the density of the magnetic current,
μris the magnetic permeability of the target biological tissue,
in order to induce the current density,
as a result of the total electric field,
step three, establishing an external magnetic field induction model of the target biological tissue according to the following formula:
wherein the content of the first and second substances,
in order to scatter the magnetic field,
is a unit vector from the field source point to any point in the field,
r is the distance from the field source point to any point in the scattering field;
when no or negligible magnetic media is present, i.e. murWhen 1, the external induced magnetic field effect model is described as:
when the magnetic medium is not negligible, i.e. murWhen not equal to 1, the external induced magnetic field effect model is described as:
taking an internal magnetic induction model and an external magnetic field induction model of the target biological tissue as nonlinear models of the target biological tissue;
comparing the induction magnetic field and/or the stray field magnetic field detected by each detection coil in the first detection result in pairs at the same vertical distance, and obtaining information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue according to the difference obtained by comparison;
step six, obtaining information capable of reflecting the first depth distribution of the target biological tissue through the information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue obtained under different vertical distances:
Dn＝sncos(θn) (4)
wherein, as shown in FIG. 4, θnFor measuring the measuring or radiation angle of the coil n to the target object, DnIn order to be the depth information,
wherein, cos (θ)n) The calculation of (a) can refer to the existing technology, and is not described herein in detail.
Comparing the induction magnetic field and/or the stray magnetic field detected by each detection coil in the second detection result pairwise at the same horizontal distance, and obtaining information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue according to the difference obtained by comparison;
step eight, obtaining information capable of reflecting a second depth distribution of the target biological tissue through the information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue obtained under different horizontal distances:
extracting corresponding change values and curves from the nonlinear observation model according to the first depth distribution information and the second depth distribution information of the target biological tissue, and reconstructing a three-dimensional image of the target biological tissue according to the change values:
in some embodiments, optionally, the reconstructing a three-dimensional image of the target biological tissue may include:
step one, calculating two detection coils in each detection coil on the same horizontal plane
The echo magnetic field of (2):
wherein x represents a complex conjugate of the complex number,<>representing mean time, echo magnetic field signal
Step two, calculating the sum of the echo magnetic fields of every two detection coils in sequence to obtain the total echo magnetic field of all the detection coils, and when the number of the detection coils is NRWhen is not equal to NRIs a natural number and NRNot less than 3, total echo magnetic field is NR(NR-1) sum of echo magnetic field signals of the detection coils;
performing inverse Fourier transform on the total echo magnetic field of each detection coil to obtain a two-dimensional image of the target object in any shape;
and step four, comparing and superposing the total echo magnetic fields of the detection coils at different vertical heights to obtain a three-dimensional image of the target biological tissue.
In step 13, the distance between the at least three detection coils and the target biological tissue is greater than one wavelength (far field) of the electromagnetic wave for detection.
It should be noted that, in the step 13, when the target biological tissue is non-magnetic and has conductivity, the scattering magnetic field of the target biological tissue at any one of the detection coils can be calculated by the formula (11), and the method can be used for monitoring various physiological and pathological characteristics of the organism, such as cerebral edema, cerebral apoplexy, diabetes, burn injury, and the like.
When the target biological tissue has both magnetic and electrical characteristics, the scattering magnetic field of the target biological tissue at any one detection coil can be calculated by the formula (12), and the method can be applied to detecting various physiological and pathological characteristics of the organism, such as tumor, breast cancer and the like.
In the scheme of the application, according to the method that the distances between the at least three detection coils and the target biological tissue are kept the same, the distance is gradually changed, and the difference of the electromagnetic properties detected by the at least two detection coils is synchronously calculated, so that the three-dimensional image of the target biological tissue is constructed.
A group of complete data is formed by calculating the difference distribution of the visible intensity of the target object obtained when the detection coil array is at different heights and comparing the difference of the visible intensity obtained when the detection coil array is at different heights in pairs, thereby realizing the reconstruction of the three-dimensional image. The spatial resolution of a three-dimensional image is affected by the type of coil, the shape of the coil, the scanning speed, and the scanning height. To quantitatively evaluate the imaging results, a scaling function formula may be applied to enhance image contrast.
In order to verify the three-dimensional holographic magnetic induction imaging method provided by the application, a three-dimensional simulation model is established below through an MATLAB platform and is used for simulating the electromagnetic field influence of different organisms when diseases occur. Fig. 5(a) is a simulation diagram of a system including a skull model 208 and magnetic induction coils 207. Fig. 5(b) is a three-dimensional skull model diagram, and fig. 5(c) is a three-dimensional reconstruction diagram of the three-dimensional skull model. The reconstructed image of the three-dimensional skull model can clearly show different tissues of the skull, including tumor cells. Experimental results show that the method can realize three-dimensional imaging, and compared with the traditional imaging algorithm, the method does not need a large amount of electromagnetic inverse operation, and saves time and cost.
Based on the same concept, another embodiment of the present application further provides a magnetic induction imaging system. The magnetic induction imaging system comprises a control device, a signal generation device, a signal detection device, an image display device and a signal transmitting device, wherein the signal generation device, the signal detection device and the image display device are respectively connected with the control device; the signal transmitting device comprises a first magnetic induction coil as an excitation coil, wherein the first magnetic induction coil is in a first preset number; the signal detection device comprises a second preset number of second magnetic induction coils serving as detection coils; the control device is adapted to perform a magnetic induction imaging method as defined in any one of the above.
Optionally, media are disposed between the target biological tissue and each magnetic induction coil, and between each magnetic induction coil.
Optionally, each of the excitation coils is uniformly distributed on a circular ring centered on the target biological tissue; the detection coils are evenly distributed on a circular ring centered on the target biological tissue.
Optionally, the detection coil and the excitation coil are both located on the same side or both sides of the target biological tissue;
and/or the heights of the detection coil and the excitation coil are the same or different;
and/or the detection coil and the excitation coil are parallel to each other;
and/or the detection coil and the excitation coil coincide with each other;
and/or the detection coil and the excitation coil are both at a preset angle with respect to the target biological tissue.
Optionally, the signal transmitting device is connected to the signal generating device through a multi-channel switch circuit board; the signal detection device is connected with the control device through the multi-channel switch circuit board.
Optionally, the magnetic induction coil is a solenoid coil, a helmholtz coil, a patch coil, or an antenna.
It is understood that the same or similar parts in the above embodiments may be mutually referred to, and the same or similar parts in other embodiments may be referred to for the content which is not described in detail in some embodiments.
It should be noted that, in the description of the present application, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Further, in the description of the present application, the meaning of "a plurality" means at least two unless otherwise specified.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and the scope of the preferred embodiments of the present application includes other implementations in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present application.
It should be understood that portions of the present application may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes one or a combination of the steps of the method embodiments.
In addition, functional units in the embodiments of the present application may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. The integrated module, if implemented in the form of a software functional module and sold or used as a stand-alone product, may also be stored in a computer readable storage medium.
The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc.
In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and that variations, modifications, substitutions and alterations may be made to the above embodiments by those of ordinary skill in the art within the scope of the present application.
Claims (10)
1. A magnetic induction imaging method is characterized by being applied to a magnetic induction imaging system, wherein the magnetic induction imaging system comprises a control device, a signal generation device, a signal detection device and an image display device which are respectively connected with the control device, and a signal transmitting device connected with the signal generation device; the signal transmitting device comprises a first magnetic induction coil as an excitation coil, wherein the first magnetic induction coil is in a first preset number; the signal detection device comprises a second preset number of second magnetic induction coils serving as detection coils; the magnetic induction imaging method performed by the control device includes:
controlling the signal generating device to generate an electromagnetic wave signal and outputting the electromagnetic wave signal to the signal transmitting device in the form of alternating current;
controlling the signal transmitting device to scan target biological tissue, and generating an excitation magnetic field around the target biological tissue through the alternating current so that the target biological tissue generates an induction magnetic field and/or a stray magnetic field under the action of the excitation magnetic field;
controlling the signal detection device to scan the target biological tissue and detect the induced magnetic field and/or the stray magnetic field, wherein the method comprises the following steps: controlling at least three detection coils with the same distance to the target biological tissue in the signal detection device to move to different vertical distances along the vertical direction, and detecting the induction magnetic field and/or the stray magnetic field under different vertical distances to obtain a first detection result; controlling at least three detection coils with the same distance to the target biological tissue in the signal detection device to move to different horizontal distances along the horizontal direction, and detecting the induction magnetic field and/or the stray magnetic field under different horizontal distances to obtain a second detection result;
generating a three-dimensional image of the target biological tissue from the detected induced and/or stray magnetic fields, comprising: comparing the induced magnetic field and/or the stray magnetic field detected by each detection coil in the first detection result, and comparing the induced magnetic field and/or the stray magnetic field detected by each detection coil in the second detection result to generate a three-dimensional image of the target biological tissue;
after a two-dimensional image of the target biological tissue is generated, comparing and superposing total echo magnetic fields of the detection coils at different vertical heights to obtain a three-dimensional image of the target biological tissue;
comparing the induced magnetic field and/or the stray magnetic field detected by each detection coil in the first detection result pairwise at the same vertical distance, and obtaining information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue according to the difference obtained by comparison;
obtaining information capable of reflecting a first depth distribution of the target biological tissue through the information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue obtained at different vertical distances:
Dn＝sncos(θn) (4)
wherein Sn is the distance from the measuring coil n to any point in the target biological tissue;
wherein, thetanFor measuring the measuring or radiation angle of the coil n to the target object, DnIs the depth information of the target biological tissue,
wherein dD is the differential of the depth of the target biological tissue, and dz is the differential of z;
z represents a z-axis of spatial coordinate axes; p is sin θ cos Φ, q is sin θ sin Φ;
wherein P (x, y, z) is a point within the target biological tissue,
is the distance from the origin 0 to the point P, and theta represents the line connecting OP and
the angle between the axes, phi, denotes the point P (x, y, z) is at
The connecting line between the vertical point of the plane and the origin O
Angle between axes, Ai，AjRespectively indicate to be located at positions
The detection coil of (a) is,
denotes coil AiAnd AjThe distance between them;
comparing the induction magnetic field and/or the stray field magnetic field detected by each detection coil in the second detection result pairwise at the same horizontal distance, and obtaining information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue according to the difference obtained by comparison;
obtaining information capable of reflecting a second depth distribution of the target biological tissue through the information capable of reflecting the amplitude and the phase of the electromagnetic property distribution of the target biological tissue obtained at different horizontal distances:
wherein the content of the first and second substances,
a differential representing a reconstructed image of the target biological tissue;
znrepresenting a height of all the detection coil arrays from the target biological tissue;
zn-1represents another height of all detection coil arrays from the target biological tissue:
extracting corresponding change values and curves from a nonlinear observation model according to the information of the first depth distribution and the information of the second depth distribution of the target biological tissue, and reconstructing a three-dimensional image of the target biological tissue according to the change values:
wherein I represents a non-linear observation model of the visibility intensity of the target biological tissue;
h represents the vertical height of the detection coil reaching the bottom of the target biological tissue;
and sending the three-dimensional image to the image display device for display.
2. The magnetic induction imaging method according to claim 1 wherein said controlling said signal emitting device to scan a target biological tissue comprises: controlling at least one excitation coil in the signal transmitting device to apply an alternating current to the target biological tissue.
3. The magnetic induction imaging method according to claim 1, wherein the comparing the induced magnetic field and/or the stray magnetic field detected by each of the detection coils in the first detection result and the comparing the induced magnetic field and/or the stray magnetic field detected by each of the detection coils in the second detection result to generate the three-dimensional image of the target biological tissue comprises:
determining a non-linear model of the target biological tissue;
comparing the induced magnetic field and/or the stray field magnetic field detected by each detection coil in the first detection result and comparing the induced magnetic field and/or the stray field magnetic field detected by each detection coil in the second detection result according to the nonlinear model of the target biological tissue to generate a three-dimensional image of the target biological tissue;
wherein the determining a non-linear model of the target biological tissue comprises:
establishing an intensity model of the target biological tissue according to the following formula:
wherein s represents the vector position of the target biological tissue and σ(s) represents the electrical conductivity of the target biological tissue at the vector position s;
j is the imaginary part of the complex number,
omega-2 pi f is the working angular frequency, f is the imaging system working frequency, mu0Is the permeability of free space, σ is the electrical conductivity,0is the dielectric constant of the free space and,ris the dielectric constant of the target biological tissue,r＝′r-jσ/ω0，′ris the real part of the relative dielectric constant of the target biological tissue,
represents the sum of the incident magnetic field and the total magnetic field of the scattered magnetic field of the target biological tissue at any point on the direction vector s,
represents the sum of the incident magnetic field and the total magnetic field of the scattering magnetic field of the target biological tissue at any point on the direction vector s', and represents complex conjugate;
establishing an internal magnetic field induction model of the target biological tissue according to the following formula:
wherein the content of the first and second substances,
for an incident magnetic field, G is the Green function,
as a position vector from the field source point to the scattered magnetic field,
is a position vector, k, from a field source point to a point within said target biological tissue0Is the wave number in free space and is,
in order to obtain the density of the magnetic current,
μris the magnetic permeability of the target biological tissue,
in order to induce the current density,
as a result of the total electric field,
establishing an external magnetic field induction model of the target biological tissue according to the following formula:
wherein k is0Represents the wave number of free space; v represents the volume of the target biological tissue, G represents the Green's function,
is a position vector from the field source point to a point within the target organism,
is the position vector from the field source point to the scattered magnetic field; mu.srRepresents the permeability of the target biological tissue;
4. The magnetic induction imaging method according to claim 1 wherein the step of generating a two-dimensional image of the target biological tissue comprises:
calculating two detection coils in each detection coil on the same horizontal plane
The echo magnetic field of (2):
wherein x represents a complex conjugate of the complex number,<>representing mean time, echo magnetic field signal
Comprising any two detection coils
Phase delay and/or amplitude difference of (a);
sequentially calculating the sum of the echo magnetic fields of every two detection coils to obtain the total echo magnetic field of all the detection coils, and when the number of the detection coils is NRWhen is not equal to NRIs a natural number and NRNot less than 3, total echo magnetic field is NR(NR-1) sum of the echo magnetic field signals of the detection coils.
5. A magnetic induction imaging system is characterized by comprising a control device, a signal generation device, a signal detection device and an image display device which are respectively connected with the control device, and a signal transmitting device connected with the signal generation device; the signal transmitting device comprises a first magnetic induction coil as an excitation coil, wherein the first magnetic induction coil is in a first preset number; the signal detection device comprises a second preset number of second magnetic induction coils serving as detection coils; the control device is used for executing the magnetic induction imaging method as set forth in any one of claims 1-4.
6. The magnetic induction imaging system of claim 5, wherein a medium is disposed between the target biological tissue and each magnetic induction coil, and between each magnetic induction coil.
7. The magnetic induction imaging system of claim 5, wherein each of the excitation coils is uniformly distributed over an annulus centered on the target biological tissue; the detection coils are evenly distributed on a circular ring centered on the target biological tissue.
8. The magnetic induction imaging system of claim 5, wherein the detection coil and the excitation coil are both located on the same side or on both sides of the target biological tissue;
or, the heights of the detection coil and the excitation coil are the same or different;
or, the detection coil and the excitation coil are parallel to each other;
or, the detection coil and the excitation coil coincide with each other;
or, the detection coil and the excitation coil are both organized at a preset angle with the target biological tissue.
9. The magnetic induction imaging system of claim 5, wherein the signal emitting device is connected to the signal generating device via a multi-channel switch circuit board; the signal detection device is connected with the control device through the multi-channel switch circuit board.
10. The magnetic induction imaging system of claim 5, wherein the magnetic induction coil is a solenoid coil, a Helmholtz coil, a patch coil, or an antenna.
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