CN102085096A - Injection current type magnetoacoustic coupling imaging device - Google Patents

Abstract

The invention relates to the technical field of acquiring electrical characteristic information of biological tissues. In order to provide a current injection type magnetoacoustic coupling imaging device and provide conditions for the experiment of injection current type magnetoacoustic coupling imaging, the technical solution adopted in the present invention is to include: a central control unit, an excitation unit, a constant magnetic field unit, a medium Phantom, motor-driven scanning unit, detection processing unit, and data storage and display unit, the central control unit is connected with other units to provide synchronization and control signals for other units; the excitation unit generates arbitrary waveform excitation pulses for the medium phantom signal; the constant magnetic field unit provides a constant magnetic field to the medium unit; the acoustic signal generated by the medium phantom is scanned, received and converted into an electrical signal by the motor-driven scanning unit; The display unit performs storage and display. The invention is mainly applied to the acquisition of electrical characteristic information of biological tissues.

Description

Injection current magnetoacoustic coupling imaging device

technical field

The invention relates to the technical field of acquiring electrical characteristic information of biological tissues, in particular, to an injection current type magnetoacoustic coupling imaging device.

Background technique

The information of electrical properties of biological tissue is helpful to understand the electrophysiological properties of tissue, thus providing a basis for early diagnosis of diseases. Due to the low spatial resolution of electrical impedance technology imaging, magnetoacoustic coupling imaging overcomes the above shortcomings, and has the advantages of high contrast of functional parameters of electrical impedance imaging and high spatial resolution of ultrasonic imaging. The advantage of relatively simple reconstruction algorithm has become a new research hotspot in the field of functional imaging.

According to different excitation methods, magnetoacoustic coupling imaging can be divided into two types: current injection type and inductive type. Due to the inductive magnetoacoustic coupling, the induced current generated by the magnetic field coupling is used for excitation, and the imaging detector is easily disturbed by the magnetic field, which will have a great impact on the detection of the signal. The injection magnetoacoustic coupling avoids the energy conversion through the magnetic field, thereby avoiding the interference of the detector by the magnetic field.

There are many research institutions at home and abroad to study this method. However, the current research is mainly in the stage of theoretical models and simulations, and the current experiments only stay in the research of relatively simple neural current detection in biological tissues, and the imaging experiments using this principle have not been carried out in depth.

Contents of the invention

In order to overcome the deficiencies of the existing technology, an injection current type magnetoacoustic coupling imaging device is provided, which provides conditions for the experiment of injection current type magnetoacoustic coupling imaging, so as to provide more in-depth research on the theoretical research and experiment of this method, as well as the future To lay the foundation for medical clinical application, the technical solution adopted by the present invention is that the injection current magnetoacoustic coupling imaging device includes: a central control unit, an excitation unit, a stable and constant magnetic field unit, a motor-driven scanning unit, a detection processing unit, data storage and The display unit and the central control unit are connected with other units to provide synchronization and control signals for other units; the excitation unit generates an arbitrary waveform excitation pulse signal for the measured organism; the constant magnetic field unit provides a constant magnetic field for the medium unit; The acoustic signal generated by the living body is scanned by the motor-driven scanning unit to drive the sensor, received and converted into an electrical signal; the electrical signal is processed by the detection processing unit, and stored and displayed by the data storage and display unit.

The central control unit includes a computer, a GPIB interface, and a LabVIEW virtual instrument operating platform. The central control unit is connected with other units through the GPIB interface, and the central control unit provides synchronization and control signals for other units.

The excitation unit is composed of a function generator and a power amplifier, and is used to provide an excitation pulse signal with an arbitrary waveform.

The constant magnetic field unit provides a constant magnetic field, including an electromagnet, a DC power supply, a magnetic field sensor, and a magnetic field testing device.

The measured biological medium is connected to the excitation unit through electrodes to realize excitation.

The motor-driven scanning unit realizes the scanning of the sensor to the experimental phantom, and the motor-driven scanning unit is composed of a stepping motor driver and a stepping motor.

The detection processing unit receives the acoustic signal generated by the excitation of the measured biological medium, and performs amplification and filtering processing, and the data acquisition card triggers the acquisition signal synchronously, and uses the data processing module for processing, and finally forms an output. The detection processing unit It is composed of acoustic sensor, low noise amplifier, filter and data acquisition card.

The data storage and display unit is driven by a synchronous signal to complete data storage and display, and the data storage and display unit is composed of a disk array and an oscilloscope.

The present invention has the following technical effects: since the present invention adopts a central control unit, an excitation unit, a constant magnetic field unit, a motor-driven scanning unit, a detection processing unit, and a data storage and display unit structure, the present invention can realize the Apply current stimulation, measure the sound wave signal generated by the measured object, and form an image display; in addition, the present invention also has the characteristics of accurate and reliable testing.

Description of drawings

Fig. 1 is a system structure diagram of the present invention.

Figure 2 is the excitation unit of the present invention.

Fig. 3 is the constant magnetic field unit of the present invention.

FIG. 4 is a motor-driven scanning unit of the present invention.

Figure 5 is the tested biological medium of the present invention.

Fig. 6 is the detection processing unit of the present invention.

Fig. 7 is the data storage and display unit of the present invention.

Fig. 8 is the working process of the system of the present invention.

in,

1: Central control unit

2: Excitation unit

3: Steady magnetic field unit

4: Measured biological medium

5: Motor-driven scanning unit

6: Detection processing unit

7: Data storage display unit

8: Function Generator

9: Power Amplifier

10: Electromagnet

11: DC power supply

12: Magnetic field sensor

13: Magnetic field testing device

14: electrode

15: Stepper motor driver

16: stepper motor

17: Acoustic sensor

18: Low noise amplifier

19: filter

20: Data acquisition card

21: Data processing module

22: disk array

23: Oscilloscope.

Detailed ways

The injection current magneto-acoustic coupling imaging device includes: a central control unit, an excitation unit, a constant magnetic field unit, a motor-driven scanning unit, a detection processing unit, and a data storage and display unit.

The central control unit is realized by a computer, a GPIB interface, and a LabVIEW virtual instrument operating platform. The central control unit is connected with each subunit through a GPIB interface, and the central control unit provides synchronization and control signals for other units.

The excitation unit provides an arbitrary waveform excitation pulse signal. The excitation unit is composed of a function generator and a power amplifier. In the experiment, the pulse waveform of the excitation unit is selected or programmed to generate sinusoidal pulses, rectangular pulses, Gaussian pulses or other arbitrary waveforms with a pulse width of μs-ms level to achieve cm-level resolution, and the output voltage range is 100mV-100V.

The constant magnetic field unit provides a constant magnetic field, including an electromagnet, a DC power supply, a magnetic field sensor, and a magnetic field testing device. The constant magnetic field unit is used to provide a static magnetic field for magnetoacoustic coupling effect. The magnetic induction intensity of the magnetic field generated by the constant magnetic field unit is 1mT-1T, and can be detected in real time.

The tested biological medium can be selected according to the purpose of the experiment.

The measured biological medium is connected to the excitation unit through electrodes to realize excitation.

The motor-driven scanning unit realizes the scanning of the sensor to the experimental phantom, and the motor-driven scanning unit is composed of a stepping motor driver and a stepping motor. The scanning step angle is 1.8°, and the scanning range is 360°.

The detection processing unit receives the acoustic signal generated by the excitation of the measured biological medium, and performs amplification and filtering processing, and the data acquisition card performs synchronous trigger acquisition signal, and uses the data processing module to process, and finally forms an output. The detection processing unit is composed of an acoustic sensor, a low noise amplifier filter, a data acquisition card, and a data processing module. The detection processing unit has a detection accuracy of 10-3 Pa and a bandwidth of 1 MHz.

The data storage and display unit is driven by a synchronous signal to complete data storage and display. The data storage and display unit is composed of a disk array and an oscilloscope. The storage capacity of the storage display unit can reach 1TB.

The specific working process of the current injection type magnetoacoustic coupling imaging experimental system is as follows:

When the system is working, the central control unit communicates with each sub-unit through the GPIB interface, and sends commands to other sub-units,

1. Each subunit starts.

2. The central control unit sets the parameters of each sub-unit.

3. The excitation signal is output by the excitation unit, which is injected into the biological medium to be measured through the electrodes. Under the condition of the constant magnetic field provided by the constant magnetic field unit, the acoustic signal can be excited and generated.

4. The detection processing unit receives the signal.

5. The detection processing unit detects and processes the signal, including amplification and filtering.

6. The data storage and display unit is used for data storage and real-time display.

7. If the scanning is not over, the motor drives the scanning unit to drive the stepping motor to move a certain angle, and repeat the working steps of 3-6; if the scanning is over, the whole system ends.

In order to further understand the invention content, characteristics and effects of the present invention, the following examples are given, and detailed descriptions are as follows in conjunction with the accompanying drawings:

Please refer to Figure 6. The basic principle of magneto-acoustic coupling imaging is to inject current into the dielectric phantom through the electrodes for the dielectric phantom placed in a steady magnetic field. The sound waves vibrate, and at the same frequency as the injected electrical current. At this time, the acoustic wave response can be detected by using the acoustic wave transducer outside the medium phantom, combined with the corresponding image reconstruction algorithm, the image of the distribution of the electrical properties (such as conductivity) of the medium phantom can be reconstructed. Biological tissue is a dielectric, and the electrical properties of different biological tissues and the same tissue will change under the condition of disease. The magneto-acoustic coupling imaging method aims to obtain information on the electrical properties of biological tissues, so as to realize early functional diagnosis.

According to the theory of electromagnetism, the interior of the medium is acted by the Lorentz force,

dF=Idl×B

Among them, l is the length unit, F is the Lorentz force, B is the static magnetic field, and I is the current injected into the dielectric phantom.

According to Ohm's law,

I=U/R

When the voltage provided by the excitation unit is constant, the current density distribution in the dielectric phantom is related to the dielectric parameters.

At the same time, it can be seen from the theory of electromagnetism and acoustics that the sound pressure is closely related to the steady and constant magnetic field, the current density inside the medium, and the electrical parameters of the medium phantom.

${<span\; class="notranslate">\; \&dtri;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\frac{{<span\; class="notranslate">\; \&PartialD;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; p</span>}}{{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; \&dtri;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; J</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; B</span>}<span\; class="notranslate">\; )</span>$

为超声在介质仿体中的传播速度，ρ₀为介质密度，β_s为绝热压缩系数，p为声压，J为电流密度，B为稳恒磁场。in,

is the propagation velocity of ultrasound in the medium phantom, _ρ0 is the medium density, _βs is the adiabatic compressibility coefficient, p is the sound pressure, J is the current density, and B is the steady magnetic field.

In summary, it can be deduced that, in the case of known steady magnetic field and excitation voltage, for a medium phantom whose conductivity parameter distribution is determined, the sound pressure is related to the conductivity, that is, the vibration sound source is located in the medium with conductivity The intensity at the changed interface is greater. The time-varying curve of the ultrasonic pulse signal detected by the transducer outside the medium phantom reflects the change of the internal conductivity of the medium along this propagation direction. Therefore, the position of the conductivity interface along the propagation direction can be obtained from the acoustic signal detected by the transducer located outside the dielectric phantom.

An injection current magnetoacoustic coupling imaging experiment system includes a central control unit, an excitation unit, a constant magnetic field unit, a medium phantom, a motor-driven scanning unit, a detection processing unit, and a data storage and display unit.

The central control unit is realized by a computer, a GPIB interface, and a LabVIEW virtual instrument operating platform. The central control unit is connected with each subunit through a GPIB interface, and the central control unit provides synchronization and control signals for other units.

The excitation unit is composed of a function generator and a power amplifier, the function generator model is Tektronix AFG3252, and the power amplifier model is HSA4104. The excitation unit provides an arbitrary waveform current pulse signal.

Parameter setting and output control of the function generator and power amplifier are performed by the central control unit. The output voltage signal forms an injection current in the phantom medium through the electrodes,

Existing studies have shown that the imaging resolution of MAT-MI is related to the pulse width, and it is proportional to the product of sound velocity and pulse width. A waveform with a large rate of change and a narrow pulse width should be used. Considering the imaging of a target (such as a tumor in the tissue) with a size of Δl in the medium, the transducer detects two signal pulses before and after the boundary of the imaging target, as shown in Figure 2, and the interval is set as Δt, and we have

Δl=c _s ·Δt

In order to achieve a millimeter-level imaging resolution, the pulse width of the pulse signal output by the excitation unit should be less than 1 μs. The excitation pulse can choose to use sinusoidal pulse or rectangular pulse.

The constant magnetic field unit provides a constant magnetic field, including an electromagnet, a DC power supply, a magnetic field sensor, and a magnetic field testing device. The electromagnet model is Yingpu SBV-380, which can reach a maximum magnetic induction of 2.4T. The model of the electromagnet DC power supply is Agilent-6684A, the model of the magnetic field sensor is Lakeshore HMNT-4E04-VR, and the model of the magnetic field testing device is Lakeshore 460.

The constant magnetic field unit is used to provide a static magnetic field for magnetoacoustic coupling effect. The DC power supply is controlled by the central control unit, and the magnetic field testing device is controlled at the same time, and the magnetic induction intensity is measured by the magnetic field sensor.

The size of the tested biological medium can be designed according to the purpose of the experiment. Animal tissues such as pork, or agar blocks with a certain percentage of salt added, or metal blocks such as copper blocks can be used for experiments.

The measured biological medium is connected to the excitation unit through electrodes to realize excitation. The electrodes are realized by copper or aluminum wires with a wire diameter of 0.5mm-1mm.

The motor-driven scanning unit is composed of a stepper motor driver and a stepper motor. When the system is working, the stepper motor driver drives the stepper motor to rotate at a specific angle, such as 1.8° for scanning, and the scanning range is 360°. While scanning, under the excitation of the excitation unit, the acoustic signal generated by the measured biological medium is received by the detection and processing unit. The model of the stepper motor is NI-NEMA23, and the model of the driver is P70530.

The detection processing unit is composed of an acoustic sensor, a low noise amplifier filter, a data acquisition card, and a data processing module.

The detection processing unit receives the acoustic signal generated by the excitation of the measured biological medium, and performs amplification and filtering processing, and the data acquisition card performs synchronous trigger acquisition signal, and uses the data processing module to process, and finally forms an output. The acoustic sensor model is Olympus V303, the low noise amplifier model is NF-SA230F5, the filter model is nf 3628, and the data acquisition card model is NI PXIe-5122. The data processing module can use the average superposition algorithm to perform more than 1000 superposition average calculations.

The data storage and display unit is composed of a disk array and an oscilloscope. The data storage and display unit is driven by a synchronous signal to complete data storage and display. The disk array model is NI-8262, and the oscilloscope model is Tektronix TDS2012B.

To sum up, the specific working process of the current injection type magnetoacoustic coupling imaging experimental system is as follows, see Figure 9:

When the system is working, the central control unit communicates with each sub-unit through the GPIB interface, and sends commands to other sub-units,

1. Each subunit starts.

2. The central control unit sets the parameters of each sub-unit.

3. The excitation is output by the excitation unit, injected into the dielectric body through the electrode, and the acoustic signal can be excited and generated under the condition of the constant magnetic field provided by the constant magnetic field unit.

4. The detection processing unit receives the signal.

5. The detection processing unit detects and processes the signal, including amplification and filtering.

6. The data storage and display unit is used for data storage and real-time display.

7. If the scanning is not over, the motor drives the scanning unit to drive the stepping motor to move a certain angle, and repeat the working steps of 3-6; if the scanning is over, the whole system ends.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above specific implementations, which are only illustrative and not restrictive. The central control unit in the present invention can also be completed using a single-chip microcomputer or a digital processing system. The display storage unit described in the present invention can also be composed of a liquid crystal display and a solid state hard disk. Under the enlightenment of the present invention, those skilled in the art can also make many forms without departing from the gist of the present invention and the scope of protection of the claims, and these all belong to the protection scope of the present invention.

Claims (8)

1. An injection current type magneto-acoustic coupling imaging device is characterized in that it comprises: a central control unit, an excitation unit, a stable and constant magnetic field unit, a motor-driven scanning unit, a detection processing unit, a data storage and display unit, a central control unit and The other units are connected to provide synchronization and control signals for other units; the excitation unit generates an arbitrary waveform excitation pulse signal for the measured organism; the constant magnetic field unit provides a constant magnetic field for the medium unit; the acoustic signal generated by the measured organism The motor drives the scanning unit to drive the sensor to scan, receive and convert it into an electrical signal; the electrical signal is processed by the detection processing unit, and stored and displayed by the data storage and display unit. 2. a kind of injection current type magneto-acoustic coupling imaging device according to claim 1, is characterized in that, described central control unit comprises computer, GPIB interface, LabVIEW virtual instrument operating platform, and described central control unit communicates with by GPIB interface The other units are connected, and the central control unit provides the synchronization and control signals of other units. 3. A magneto-acoustic coupling imaging device of injection current type according to claim 1, wherein the excitation unit is composed of a function generator and a power amplifier, and is used to provide excitation pulse signals with arbitrary waveforms. 4. A current-injection magnetoacoustic coupling imaging device according to claim 1, wherein the constant magnetic field unit provides a constant magnetic field, including an electromagnet, a DC power supply, and a magnetic field sensor, and a magnetic field test device. 5 . The magnetoacoustic coupling imaging device of injection current type according to claim 1 , wherein the measured organism is connected to the excitation unit through electrodes to realize excitation. 6 . 6. A kind of injection current type magneto-acoustic coupling imaging device according to claim 1, is characterized in that, described motor-driven scanning unit realizes the scanning of sensor to experimental phantom, and described motor-driven scanning unit is driven by stepping motor driver , composed of stepper motors. 7. A current injection magnetoacoustic coupling imaging device according to claim 1, characterized in that, the detection processing unit receives the acoustic signal generated by the excited organism to be measured, and performs amplification and filtering processing, and the data acquisition The card performs synchronous triggering to collect signals, processes them with a data processing module, and finally forms an output. The detection processing unit is composed of an acoustic sensor, a low-noise amplifier, a filter, and a data acquisition card. 8. A current injection magnetoacoustic coupling imaging device according to claim 1, wherein the data storage and display unit completes data storage and display under the drive of a synchronous signal, and the data storage and display The unit consists of a disk array and an oscilloscope.

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