CN105816156A - Magneto-acoustic conductivity imaging device combining thermo-acoustic effect signal and imaging method - Google Patents

Magneto-acoustic conductivity imaging device combining thermo-acoustic effect signal and imaging method Download PDF

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CN105816156A
CN105816156A CN201610325568.XA CN201610325568A CN105816156A CN 105816156 A CN105816156 A CN 105816156A CN 201610325568 A CN201610325568 A CN 201610325568A CN 105816156 A CN105816156 A CN 105816156A
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signal
thermoacoustic
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electrical conductivity
acoustic
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CN105816156B (en
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刘志朋
李俊霖
殷涛
马任
周晓青
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Institute of Biomedical Engineering of CAMS and PUMC
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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
    • A61B5/0093—Detecting, measuring or recording by applying one single type of energy and measuring its conversion into another type of energy
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • 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 
    • A61B5/053—Measuring electrical impedance or conductance of a portion of the body
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7225—Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7235—Details of waveform analysis
    • A61B5/725—Details of waveform analysis using specific filters therefor, e.g. Kalman or adaptive filters
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/08—Detecting organic movements or changes, e.g. tumours, cysts, swellings
    • A61B8/0833—Detecting organic movements or changes, e.g. tumours, cysts, swellings involving detecting or locating foreign bodies or organic structures
    • A61B8/085—Detecting organic movements or changes, e.g. tumours, cysts, swellings involving detecting or locating foreign bodies or organic structures for locating body or organic structures, e.g. tumours, calculi, blood vessels, nodules
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/52—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/5207—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of raw data to produce diagnostic data, e.g. for generating an image
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/52—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/5215—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data
    • A61B8/5238—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data for combining image data of patient, e.g. merging several images from different acquisition modes into one image
    • A61B8/5261—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves involving processing of medical diagnostic data for combining image data of patient, e.g. merging several images from different acquisition modes into one image combining images from different diagnostic modalities, e.g. ultrasound and X-ray

Abstract

The invention provides a magneto-acoustic conductivity imaging device combining a thermo-acoustic effect signal and an imaging method. According to the device, the influences of a thermo-acoustic effect sound source on a sound signal in magneto-acoustic coupling imaging are taken into account. A magneto-acoustic coupling effect signal is generated through the steps that an alternating excitation magnetic field is loaded in a steady magnetic field, and the magnetic fields are subjected to the action of Lorentz force to generate synchronous vibration. The thermo-acoustic effect signal is generated through the step that vibration is generated by thermal expansion which is caused when electromagnetic waves are absorbed at biological tissue through the action of the alternating excitation magnetic field. According to the method, detecting on the signals with the two effects and sample conductivity imaging are achieved only through one set of the imaging device, a sample is placed in a static magnetic field, a pulsed excitation magnetic field with the adjustable amplitude value and frequency is applied under the condition that the static magnetic field is applied and the condition that the static magnetic field is not applied, and then collection of the magneto-acoustic effect signal and the thermo-acoustic effect signal is achieved. According to the device and the method, conductivity information reflected by the thermo-acoustic signal and conductivity information reflected by the magneto-acoustic signal are integrated, and a conductivity distribution image of the biological tissue is precisely rebuilt.

Description

The electrical conductivity magnetosonic imaging device of a kind of combination thermoacoustic effect signal and formation method
Technical field
The present invention relates to a kind of magnetosonic imaging device and formation method.Particularly relate to electrical conductivity magnetosonic imaging device and the formation method of a kind of combination thermoacoustic effect signal.
Background technology
Tumor tissues is when the change having not occurred form, and its electrical characteristics have occurred that change, if pathological changes electrical property change information in early days can be extracted, the early discovery for disease provides probability.Therefore, the imaging technique that noinvasive, safety, structure imaging and functional imaging combine increasingly receives significant attention.
Magnetosonic imaging is the method for new bio tissue electrical characteristics imaging.Magnetosonic imaging is the charged ion by foreign current excitation organization internal, simultaneously under the effect of magnetostatic field, organization internal electrical conductivity information is converted to acoustical signal.Thermoacoustic signal is to be entered as organization internal produces faradic current, Joule heat exciting acoustical signal by alternating magnetic field, extracts heat absorption coefficients distributed intelligence tissue is carried out electrical characteristics imaging from acoustical signal.
The vibration that the acoustical signal obtained in the magnetosonic imaging of existing apparatus causes from not only Lorentz force, also derives from the thermoacoustic effect vibration without steady magnetic field, only pulsed magnetic field action.Therefore, the so-called magnetoacoustic signals that sonic transducer receives is the superposition of the acoustical signal that both sound sources produce, owing to both sound sources are all relevant to electrical conductivity, currently used electrical conductivity algorithm for reconstructing based on the design of lorentz force density divergence sound source, do not account for the impact on acoustical signal of the thermoacoustic effect sound source, feature description and image reconstruction result to acoustical signal, there are differences with the acoustical signal being an actually-received and distribution of conductivity.
Summary of the invention
The technical problem to be solved is to provide electrical conductivity magnetosonic imaging device and the formation method of a kind of combination thermoacoustic effect signal being capable of accurate reconstruction biological tissue distribution of conductivity image.
nullThe technical solution adopted in the present invention is: the electrical conductivity magnetosonic imaging device of a kind of combination thermoacoustic effect signal，Including，Couplant groove，It is respectively arranged with in described couplant groove: for supporting the pallet of sample，It is connected to the bottom of described pallet for the motor driving pallet to rotate，It is separately positioned on the first sonic transducer and the rising tone transducer of described sample both sides，Wherein，The input of described motor connects by computer-controlled drive circuit by running through the wire of couplant groove，The signal output part of described first sonic transducer and rising tone transducer is all connected with the signal input part of dual pathways preamplifier，The signal output part of described dual pathways preamplifier connects computer by capture card，Described sample be arranged above excitation coil，Described excitation coil connects exciting bank，The top of described excitation coil is provided with static magnet also by traversing carriage.
Described exciting bank include be connected for producing the signal generator of pumping signal and for the power amplifier that described pumping signal is amplified, the outfan of described power amplifier connect described in excitation coil.
Described static magnet is the top being arranged on described excitation coil by the traversing carriage that can move.
The formation method of the electrical conductivity magnetosonic imaging device of a kind of combination thermoacoustic effect signal, comprises the steps:
1) in excitation coil, sample to be tested is acted on by the pulsed sinusoidal driving voltage of exciting bank output frequency 1MHz；
2) gathered magnetoacoustic signals and the thermoacoustic signal of sample to be tested respectively by the first sonic transducer and rising tone transducer by the dual pathways preamplifier of high cmrr；
3) filtering and noise reduction process is carried out to after the sound signal digital collected；
4) use Time-Frequency Analysis Method that thermoacoustic signal is carried out frequency-domain analysis, obtain the frequency domain characteristic of thermoacoustic signal；
5) design wave digital lowpass filter according to the frequency domain characteristic of thermoacoustic signal, utilize wave digital lowpass filter to remove the thermoacoustic signal in magnetoacoustic signals, isolate single magnetoacoustic signals；
6) using magnetosonic sound source based on Lorentz force as source item, magnetosonic source acoustic pressure wave equation is set upSingle magnetoacoustic signals is utilized to rebuild the electrical conductivity of sample to be tested based on time backprojection algorithm again；
7) using thermoacoustic sound source based on Joule heat as source item, the acoustic pressure wave equation in thermoacoustic source is set upThe electrical conductivity of thermoacoustic signal reconstruction sample to be tested is utilized again based on time backprojection algorithm；
8) fusion steps 6) magnetoacoustic signals that utilizes that obtains rebuilds the electrical conductivity of sample to be tested and step 7) electrical conductivity utilizing thermoacoustic signal reconstruction sample to be tested that obtains, obtain sample distribution of conductivity image.
Step 2) in when detecting magnetoacoustic signals, loading under conditions of magnetostatic field, the pulse excitation applying adjustable amplitude and frequency acts on excitation coil, uses the ultrasonic transducer of mid frequency 1MHz to gather the magnetoacoustic signals of sample to be tested；
Step 2) in detect thermoacoustic signal time, static magnet is removed by moveable support, under conditions of being not loaded with magnetostatic field, the pulse excitation applying adjustable amplitude and frequency acts on excitation coil, uses the ultrasonic transducer of mid frequency 200～500kHz to gather the thermoacoustic signal of sample to be tested.
The electrical conductivity magnetosonic imaging device of a kind of combination thermoacoustic effect signal of the present invention and formation method, it is considered to the impact of thermoacoustic effect sound source, it is thus achieved that magnetosonic and two kinds of sound sources of thermoacoustic propagate to the acoustical signal of body surface sensing station.Utilize two kinds of sound sources to set up acoustic pressure wave equation respectively for source item, solve the acoustical signal feature obtaining two kinds of sound sources, separately design the reconstruction electrical conductivity algorithm of magnetoacoustic signals and thermoacoustic signal, to tissue conductivities accurate reconstruction.Merge electrical conductivity information and the electrical conductivity information of magnetoacoustic signals reflection of hot reflected acoustic signal, realize accurate reconstruction biological tissue distribution of conductivity image further.
Accompanying drawing explanation
Fig. 1 is the structural representation that the present invention combines the electrical conductivity magnetosonic imaging device of thermoacoustic effect signal；
Fig. 2 is the formation method flow chart that the present invention combines the electrical conductivity magnetosonic imaging device of thermoacoustic effect signal.
In figure
1: couplant groove 2: pallet
3: sample 4: motor
5: drive circuit 6: computer
7: capture card 8: dual pathways preamplifier
9: the first sonic transducers 10: rising tone transducer
11: exciting bank 12: excitation coil
13: static magnet 14: traversing carriage
Detailed description of the invention
Below in conjunction with embodiment and accompanying drawing, electrical conductivity magnetosonic imaging device and the formation method of a kind of combination thermoacoustic effect signal of the present invention are described in detail.
The electrical conductivity magnetosonic imaging device of a kind of combination thermoacoustic effect signal of the present invention, it is contemplated that the impact on acoustical signal of the thermoacoustic effect sound source in magnetosonic coupling imaging.The generation of magnetosonic coupling effect signal, is by loading alternating excitation magnetic field in steady magnetic field, is acted on by Lorentz force and produce what once per revolution vibration realized.Thermoacoustic effect signal is that the excitation field by alternation acts on biological tissue, and electromagnetic wave absorption causes the vibration that thermal expansion produces.The present invention only uses a set of imaging device to realize signal detection and the sample conductivity imaging of two kinds of effects, is included in the detection of magnetoacoustic signals under magnetic field conditions and without thermoacoustic signal detection under magnetic field conditions.Sample is placed on pallet, under the conditions of adding magnetostatic field and being not added with magnetostatic field two kinds, applies the pulse excitation magnetic field of adjustable amplitude and frequency, it is achieved magnetoacoustic signals and the collection of thermoacoustic effect signal.The signal gathered is respectively processed by algorithm for design, merges the sample electrical conductivity information of two kinds of effect reflected acoustic signals, it is achieved sample boundary and the distribution of internal conductance rate are rebuild, and improve the accuracy that electrical conductivity is rebuild to a certain extent.
nullAs shown in Figure 1，A kind of electrical conductivity magnetosonic imaging device of the combination thermoacoustic effect signal of the present invention，Including，Couplant groove 1，It is respectively arranged with in described couplant groove 1: for supporting the pallet 2 of sample 3，It is connected to the motor 4 that the bottom of described pallet 2 rotates for driving pallet 2，It is separately positioned on the first sonic transducer 9 and the rising tone transducer 10 of described sample 3 both sides，Wherein，The input of described motor 4 connects, by running through the wire of couplant groove 1, the drive circuit 5 controlled by computer 6，The signal output part of described first sonic transducer 9 and rising tone transducer 10 is all connected with the signal input part of dual pathways preamplifier 8，The signal output part of described dual pathways preamplifier 8 connects computer 6 by capture card 7，Described sample 3 be arranged above excitation coil 12，Described excitation coil 12 connects exciting bank 11，Described exciting bank 11 include be connected for producing the signal generator 111 of pumping signal and for the power amplifier 112 that described pumping signal is amplified，The excitation coil 12 described in outfan connection of described power amplifier 112.Described excitation coil 12 be arranged above static magnet 13.
Described static magnet 13 is the top that the traversing carriage 14 by moving is arranged on described excitation coil 12, such that it is able to realize loading magnetostatic field and being not loaded with the different condition of magnetostatic field.Move static magnet by moveable support, under conditions of loading magnetostatic field, sample to be tested is applied adjustable amplitude and the pulse excitation magnetic field of frequency, it is achieved the collection of magneto-acoustic effect acoustical signal.Move static magnet by moveable support, under conditions of being not loaded with magnetostatic field, sample to be tested is applied adjustable amplitude and the pulse excitation magnetic field of frequency, it is achieved the collection of thermoacoustic effect acoustical signal.
First sonic transducer 9 and rising tone transducer 10 are staggered relatively, receive acoustical signal simultaneously, and the mid frequency of the first sonic transducer 9 and rising tone transducer 10 designs according to the requirement of sample electrical conductivity reconstruction information.When measuring biological tissue, the first sonic transducer 9 mid frequency is elected as with driving pulse with 1MHz frequently, and rising tone transducer 10 mid frequency elects 200～500kHz as.
A kind of formation method of the electrical conductivity magnetosonic imaging device of the combination thermoacoustic effect signal of the present invention, theoretical foundation be:
According to magnetosonic coupling effect acoustic pressure wave equation:
▿ 2 p ( r , t ) - 1 c s 2 ∂ 2 ∂ t 2 p ( r , t ) = ▿ · ( J ( r , t ) × B 0 ) - - - ( 1 )
Wherein, (r, is t) that magnetosonic couples acoustical signal to p, and J is electric current density, is electrical conductivity according to Ohm's law J=σ E, σ, B0For magnetostatic field, csFor the velocity of sound in medium.
According to thermoacoustic coupling effect acoustic pressure wave equation:
▿ 2 p ( r , t ) - 1 c s 2 ∂ 2 ∂ t 2 p ( r , t ) = - β C p ∂ ( σ | E ( r , t ) | 2 ) ∂ t - - - ( 2 )
Wherein, (r, is t) that thermoacoustic couples acoustical signal to p, and β is thermal coefficient of expansion, CpFor normal pressure thermal capacitance.
From equation (1), can reflect electrical conductivity boundary position information in magnetosonic coupling acoustical signal, from equation (2), thermoacoustic effect acoustical signal can embody internal conductance rate distributed intelligence.
As shown in Figure 2, a kind of formation method of the electrical conductivity magnetosonic imaging device of the combination thermoacoustic effect signal of the present invention, the signal gathered is processed, design the sample electrical conductivity information of corresponding algorithm fusion magnetosonic and two kinds of reflected acoustic signals of thermoacoustic, realize sample boundary and the distribution of internal conductance rate is rebuild, i.e. by merging electrical conductivity information and the electrical conductivity information of magnetoacoustic signals reflection of hot reflected acoustic signal, realize accurate reconstruction biological tissue distribution of conductivity image further.Specifically include following steps:
1) in excitation coil, sample to be tested is acted on by the pulsed sinusoidal driving voltage of exciting bank output frequency 1MHz；
2) gathered magnetoacoustic signals and the thermoacoustic signal of sample to be tested respectively by the first sonic transducer and rising tone transducer by the dual pathways preamplifier of high cmrr；
When detecting magnetoacoustic signals, under conditions of loading magnetostatic field, the pulse excitation applying adjustable amplitude and frequency is applied to excitation coil, uses the ultrasonic transducer of mid frequency 1MHz to gather the magnetoacoustic signals of sample to be tested.
When detecting thermoacoustic signal, static magnet is removed by moveable support, under conditions of being not loaded with magnetostatic field, the impulse action applying adjustable amplitude and frequency gathers the thermoacoustic signal of sample to be tested to excitation coil, the ultrasonic transducer of employing mid frequency 200～500kHz.
3) filtering and noise reduction process is carried out to after the sound signal digital collected；
4) use Time-Frequency Analysis Method that thermoacoustic signal is carried out frequency-domain analysis, obtain the frequency domain characteristic of thermoacoustic signal；
5) design wave digital lowpass filter according to the frequency domain characteristic of thermoacoustic signal, utilize wave digital lowpass filter to remove the thermoacoustic signal in magnetoacoustic signals, isolate single magnetoacoustic signals；
6) using magnetosonic sound source based on Lorentz force as source item, the acoustic pressure wave equation in magnetosonic source is set upSingle magnetoacoustic signals is utilized to rebuild the electrical conductivity of sample to be tested based on time backprojection algorithm again；
7) using thermoacoustic sound source based on Joule heat as source item, the acoustic pressure wave equation in thermoacoustic source is set upThe electrical conductivity of thermoacoustic signal reconstruction sample to be tested is utilized again based on time backprojection algorithm；
8) fusion steps 6) magnetoacoustic signals that utilizes that obtains rebuilds the electrical conductivity of sample to be tested and step 7) electrical conductivity utilizing thermoacoustic signal reconstruction sample to be tested that obtains, obtain sample distribution of conductivity image.
Example be given below:
1) sample to be tested 3 is fixed on below the excitation coil in device as shown in Figure 1, above couplant groove 1 by traversing carriage 14 place static magnet 13 formed uniform magnetic field be perpendicular to sample holding plane, the first sonic transducer 9 and rising tone transducer 10 are symmetrically disposed at sample 3 plane both sides in the horizontal direction；
2) during detection thermoacoustic signal, use the sine pulse voltage drive sample of 1MHz frequency, remove static magnet 13 by traversing carriage 14 and remove the effect of homogeneous static magnetic field, signal is gathered with the rising tone transducer of mid frequency 200-500kHz and first sonic transducer of 1MHz, dual pathways preamplifier 8 is used to receive signal, the pallet 2 being placed with sample 3 by computer control driven by motor is rotated, the circumferentially scan mode pointwise of the first sonic transducer 9 and rising tone transducer 10 is made to gather signal, it is thus achieved that the thermoacoustic signal of sample 3 at each collection point；
3) during detection magnetoacoustic signals, use the sine pulse voltage drive sample of 1MHz frequency, the underface of static magnet 13 to sample 3 is moved by traversing carriage 14, the intensity arranging magnetostatic field is 1T, gather signal with the rising tone transducer of mid frequency 200～500kHz and first sonic transducer of 1MHz simultaneously, dual pathways preamplifier is used to receive signal, the pallet 2 being placed with sample 3 by computer control driven by motor is rotated, the circumferentially scan mode pointwise of the first sonic transducer 9 and rising tone transducer 10 is made to gather signal, obtain the magnetoacoustic signals of sample 3 at each collection point；
4) the thermoacoustic signal using Time-Frequency Analysis Method to collect the second transducer 10 carries out frequency-domain analysis, obtains the frequency domain characteristic of thermoacoustic signal；Frequency domain characteristic design wave digital lowpass filter according to thermoacoustic signal, utilizes wave digital lowpass filter to remove the thermoacoustic signal in magnetoacoustic signals, isolates single magnetoacoustic signals；
5) solving equation
▿ 2 p ( r , t ) - 1 c s 2 ∂ 2 ∂ t 2 p ( r , t ) = - β C p ∂ ( σ | E ( r , t ) | 2 ) ∂ t - - - ( 2 )
Obtain the algorithm of thermoacoustic signal reconstruction electrical conductivity；By step 2) the thermoacoustic signal data that obtains input algorithm obtains the tested sample distribution of conductivity that thermoacoustic effect is rebuild；
6) solving equation
▿ 2 p ( r , t ) - 1 c s 2 ∂ 2 ∂ t 2 p ( r , t ) = ▿ · ( J ( r , t ) × B 0 ) - β C p ∂ ( σ | E ( r , t ) | 2 ) ∂ t - - - ( 3 )
Obtaining the acoustic pressure fluctuation non trivial solution that two kinds of sound sources cause, by step 4) the single magnetoacoustic signals data input algorithm that obtains obtains the tested sample distribution of conductivity rebuild under magneto-acoustic effect effect；
7) by step 5) and 6) the distribution of conductivity figure rebuild carries out location position and fusion, obtain the distributed image of sample conductivity variations border and interior location, improve accuracy and integrity that electrical conductivity is rebuild.
The method and step are equally applicable in the case of driving pulse is other frequencies, be not limited only to 1MHz.Now, the mid frequency of the first sonic transducer should be consistent with driving pulse frequency.When measuring biological tissue, rising tone transducer 10 mid frequency elects 200～500kHz as.

Claims (6)

  1. null1. the electrical conductivity magnetosonic imaging device combining thermoacoustic effect signal，Including，Couplant groove (1)，It is characterized in that，It is respectively arranged with in described couplant groove (1): be used for supporting the pallet (2) of sample (3)，It is connected to the motor (4) that the bottom of described pallet (2) is used for driving pallet (2) to rotate，It is separately positioned on the first sonic transducer (9) and the rising tone transducer (10) of described sample (3) both sides，Wherein，The input of described motor (4) connects, by running through the wire of couplant groove (1), the drive circuit (5) controlled by computer (6)，The signal output part of described first sonic transducer (9) and rising tone transducer (10) is all connected with the signal input part of dual pathways preamplifier (8)，The signal output part of described dual pathways preamplifier (8) connects computer (6) by capture card (7)，Described sample (3) be arranged above excitation coil (12)，Described excitation coil (12) connects exciting bank (11)，The top of described excitation coil (12) is provided with static magnet (13) also by traversing carriage (14).
  2. The electrical conductivity magnetosonic imaging device of a kind of combination thermoacoustic effect signal the most according to claim 1, it is characterized in that, described exciting bank (11) include be connected for producing the signal generator (111) of pumping signal and for power amplifier (112) that described pumping signal is amplified, the outfan of described power amplifier (112) connect described in excitation coil (12).
  3. The electrical conductivity magnetosonic imaging device of a kind of combination thermoacoustic effect signal the most according to claim 1, it is characterized in that, described static magnet (13) is the top that the traversing carriage (14) by moving is arranged on described excitation coil (12).
  4. 4. the formation method of the electrical conductivity magnetosonic imaging device of the combination thermoacoustic effect signal described in a claim 1, it is characterised in that comprise the steps:
    1) in excitation coil, sample to be tested is acted on by the pulsed sinusoidal driving voltage of exciting bank output frequency 1MHz；
    2) gathered magnetoacoustic signals and the thermoacoustic signal of sample to be tested respectively by the first sonic transducer and rising tone transducer by the dual pathways preamplifier of high cmrr；
    3) filtering and noise reduction process is carried out to after the sound signal digital collected；
    4) use Time-Frequency Analysis Method that thermoacoustic signal is carried out frequency-domain analysis, obtain the frequency domain characteristic of thermoacoustic signal；
    5) design wave digital lowpass filter according to the frequency domain characteristic of thermoacoustic signal, utilize wave digital lowpass filter to remove the thermoacoustic signal in magnetoacoustic signals, isolate single magnetoacoustic signals；
    6) using magnetosonic sound source based on Lorentz force as source item, magnetosonic source acoustic pressure wave equation is set upSingle magnetoacoustic signals is utilized to rebuild the electrical conductivity of sample to be tested based on time backprojection algorithm again；
    7) using thermoacoustic sound source based on Joule heat as source item, the acoustic pressure wave equation in thermoacoustic source is set upThe electrical conductivity of thermoacoustic signal reconstruction sample to be tested is utilized again based on time backprojection algorithm；
    8) fusion steps 6) magnetoacoustic signals that utilizes that obtains rebuilds the electrical conductivity of sample to be tested and step 7) electrical conductivity utilizing thermoacoustic signal reconstruction sample to be tested that obtains, obtain sample distribution of conductivity image.
  5. The formation method of the electrical conductivity magnetosonic imaging device of combination thermoacoustic effect signal the most according to claim 4, it is characterized in that, step 2) in detect magnetoacoustic signals time, under conditions of loading magnetostatic field, the pulse excitation applying adjustable amplitude and frequency acts on excitation coil, uses the ultrasonic transducer of mid frequency 1MHz to gather the magnetoacoustic signals of sample to be tested.
  6. The formation method of the electrical conductivity magnetosonic imaging device of combination thermoacoustic effect signal the most according to claim 4, it is characterized in that, step 2) in detect thermoacoustic signal time, static magnet is removed by moveable support, under conditions of being not loaded with magnetostatic field, the pulse excitation applying adjustable amplitude and frequency acts on excitation coil, uses the ultrasonic transducer of mid frequency 200～500kHz to gather the thermoacoustic signal of sample to be tested.
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