CN106037638A - Conductivity magnetoacoustic tomography device and method without influences of thermoacoustic effect - Google Patents

Conductivity magnetoacoustic tomography device and method without influences of thermoacoustic effect Download PDF

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CN106037638A
CN106037638A CN201610325093.4A CN201610325093A CN106037638A CN 106037638 A CN106037638 A CN 106037638A CN 201610325093 A CN201610325093 A CN 201610325093A CN 106037638 A CN106037638 A CN 106037638A
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thermoacoustic
signal
sample
effect
magnetoacoustic
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CN106037638B (en
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刘志朋
周晓青
殷涛
张顺起
马任
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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 discloses a conductivity magnetoacoustic tomography device and a conductivity magnetoacoustic tomography method without the influences of the thermoacoustic effect, wherein the influences of a thermoacoustic-effect sound source to sound signals during the magnetoacoustic coupling imaging are considered. The generation of magnetoacoustic-coupling-effect signals is realized in a manner that an alternating stimulating magnetic field is loaded to a steady-state magnetic field, and synchronous vibration is generated due to the effect of lorentz force. The thermoacoustic-effect signals are generated in a manner that the alternating stimulating magnetic field acts to a biological tissue, and the electromagnetic waves are absorbed so that thermal expansion is generated, namely, the vibration is generated. According to the method, one set of imaging device is adopted for realizing the detection for the signals with two effects and the sample conductivity imaging, a sample is placed in a static magnetic field, a pulsed excitation magnetic field with adjustable amplitude and frequency is applied under the two conditions including application of the static magnetic field and no application of the static magnetic field, and the collection for the magnetoacoustic-effect signals and the thermoacoustic-effect signals is realized. The collected signals are processed, the influences of the thermoacoustic effect to the magnetoacoustic-effect signals are eliminated, the reestablishment of the conductivity distribution of the sample is realized, and the conductivity reestablishment accuracy is improved to a certain extent.

Description

A kind of electrical conductivity magnetosonic imaging device removing thermoacoustic effect impact and formation method
Technical field
The present invention relates to a kind of electrical conductivity magnetosonic imaging device and formation method.Particularly relate to a kind of removal thermoacoustic effect The electrical conductivity magnetosonic imaging device of impact and formation method.
Background technology
Tumor tissues is when the change having not occurred form, and its electrical characteristics have occurred that change, if can extract Pathological changes electrical property change information in early days, the early discovery for disease provides probability.Therefore, noinvasive, safety, knot are constituted The imaging technique that picture and functional imaging combine increasingly receives significant attention.
Magnetosonic imaging is the method for new bio tissue electrical characteristics imaging.Magnetosonic imaging is by foreign current excitation tissue Internal charged ion, simultaneously under the effect of magnetostatic field, is converted to acoustical signal by organization internal electrical conductivity information.Thermoacoustic signal It is to be entered as organization internal produces faradic current, Joule heat exciting acoustical signal by alternating magnetic field, extracts from acoustical signal Heat absorption coefficients distributed intelligence carries out electrical characteristics imaging to tissue.
The vibration that the acoustical signal obtained in the magnetosonic imaging of existing apparatus causes from not only Lorentz force, also originates In the thermoacoustic effect sonic vibration without steady magnetic field, only pulsed magnetic field action.Therefore, the so-called magnetosonic that sonic transducer receives Signal 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 base In the electrical conductivity algorithm for reconstructing of lorentz force density divergence sound source design, do not account for the thermoacoustic effect sound source shadow to acoustical signal Ring, feature description and the 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 be to provide a kind of can be to the removal thermoacoustic effect of electrical conductivity accurate reconstruction The electrical conductivity magnetosonic imaging device of impact and formation method.
The technical solution adopted in the present invention is: a kind of electrical conductivity magnetosonic imaging device removing thermoacoustic effect impact, bag Include, couplant groove, be respectively arranged with in described couplant groove: for supporting the pallet of sample, be connected to the end of described pallet The motor that end rotates for driving pallet, is separately positioned on the first sonic transducer and the rising tone transducing of described sample both sides Device, 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, and being arranged above of described sample is swashed Encouraging coil, described excitation coil connects exciting bank, described excitation coil be arranged above static magnet.
Described exciting bank include be connected for producing the signal generator of pumping signal and for described The power amplifier that is amplified of pumping signal, 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 a kind of electrical conductivity magnetosonic imaging device for removing thermoacoustic effect impact, 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) by the dual pathways preamplifier of high cmrr respectively by the first sonic transducer and rising tone transducer Gather magnetoacoustic signals and the thermoacoustic signal of sample to be tested；
3) to magnetoacoustic signals and thermoacoustic signal digitized processing；
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 magnetosonic Thermoacoustic signal in signal, isolates single magnetoacoustic signals；
6) using magnetosonic sound source based on Lorentz force as source item, the acoustic pressure wave equation of magnetosonic sound source is set upSingle magnetoacoustic signals weight is utilized again based on time backprojection algorithm Build the electrical conductivity of sample to be tested, obtain sample distribution of conductivity image.
Step 2) in when detecting magnetoacoustic signals, loading under conditions of magnetostatic field, applying the arteries and veins of adjustable amplitude and frequency Impulse is encouraged and is acted 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, remove static magnet by moveable support, be not loaded with magnetostatic field Under the conditions of, the pulse excitation applying adjustable amplitude and frequency acts on excitation coil, uses the super of mid frequency 200～500kHz Sonic transducer gathers the thermoacoustic signal of sample to be tested.
A kind of electrical conductivity magnetosonic imaging device removing thermoacoustic effect impact of the present invention and formation method, it is considered to thermoacoustic is imitated Answer the impact of sound source, detect two kinds of sound sources and propagate to the acoustical signal of body surface sensing station, resolve thermoacoustic effect sound source to magnetosonic The impact that imaging electrical conductivity is rebuild, removes the impact that in the acoustical signal that sensor receives, heat effect sound source produces, isolates list One Lorentz force acoustical signal, uses original lorentz force density divergence sound source theory to rebuild conductivity imaging and then from acoustical signal Obtain electrical conductivity information more accurately, reduce the adverse effect of thermoacoustic effect, improve conductivity imaging quality.
Accompanying drawing explanation
Fig. 1 is the structural representation that the present invention removes the electrical conductivity magnetosonic imaging device of thermoacoustic effect impact；
Fig. 2 is the formation method flow chart that the present invention removes the electrical conductivity magnetosonic imaging device of thermoacoustic effect impact.
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
A kind of electrical conductivity magnetosonic imaging dress removing thermoacoustic effect impact on the present invention below in conjunction with embodiment and accompanying drawing Put and formation method is described in detail.
A kind of electrical conductivity magnetosonic imaging device removing thermoacoustic effect impact of the present invention and formation method, it is contemplated that magnetosonic The impact on acoustical signal of the thermoacoustic effect sound source in coupling imaging.The generation of magnetosonic coupling effect signal, is by steady magnetic Load alternating excitation magnetic field in Chang, acted on by Lorentz force and produce what once per revolution vibration realized.Thermoacoustic effect signal is to pass through The excitation field of alternation acts on biological tissue, and electromagnetic wave absorption causes the vibration that thermal expansion produces.The method of the present invention only makes Realize the detection of two kinds of effect signals of magnetosonic and thermoacoustic with a set of imaging device and separate.Sample is placed on pallet, is adding Magnetostatic field and under the conditions of being not added with magnetostatic field two kinds, treats side sample and applies adjustable amplitude and the pulse excitation magnetic field of frequency, respectively Realize magnetoacoustic signals and the collection of thermoacoustic effect signal of sample.The signal gathered is processed by algorithm for design of the present invention, goes Fall the thermoacoustic effect impact on magnetoacoustic signals, it is achieved sample distribution of conductivity is rebuild, and improves electrical conductivity weight to a certain extent The accuracy built.
As it is shown in figure 1, a kind of electrical conductivity magnetosonic imaging device removing thermoacoustic effect impact of the present invention, including, coupling Agent groove 1, is respectively arranged with in described couplant groove 1: for supporting the pallet 2 of sample 3, be connected to the bottom of described pallet 2 For the motor 4 driving pallet 2 to rotate, the first sonic transducer 9 and the rising tone that are separately positioned on described sample 3 both sides change Energy device 10, wherein, the input of described motor 4 connects by driving that computer 6 controls by running through the wire of couplant groove 1 Galvanic electricity road 5, the signal output part of described first sonic transducer 9 and rising tone transducer 10 is all connected with dual pathways preamplifier 8 Signal input part, the signal output part of described dual pathways preamplifier 8 connects computer 6, described sample by capture card 7 3 be arranged above excitation coil 12, described excitation coil 12 connects exciting bank 11, and described exciting bank 11 includes Be connected puts for producing the signal generator 111 of pumping signal and the power for being amplified described pumping signal Big device 112, the excitation coil 12 described in outfan connection of described power amplifier 112.The top of described excitation coil 12 is also Traversing carriage 14 is provided with static magnet 13.
Described static magnet 13 is the top that the traversing carriage 14 by moving is arranged on described excitation coil 12, from And can realize loading magnetostatic field and being not loaded with the different condition of magnetostatic field.Move static magnet by moveable support, adding Under conditions of carrying magnetostatic field, sample to be tested is applied adjustable amplitude and the pulse excitation magnetic field of frequency, it is achieved magneto-acoustic effect sound is believed Number collection.Move static magnet by moveable support, under conditions of being not loaded with magnetostatic field, sample to be tested is applied adjustable The pulse excitation magnetic field of amplitude and 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, the first sonic transducer 9 He simultaneously The mid frequency of rising tone transducer 10 designs according to the requirement of sample electrical conductivity reconstruction information.When measuring biological tissue, the One sonic transducer 9 mid frequency elect as and driving pulse with frequency 1MHz, rising tone transducer 10 mid frequency elect as 200～ 500kHz。
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, p (r, is t) that magnetosonic couples acoustical signal, 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), magneto-acoustic effect signal is caused by Lorentz force vibration sound source, can from equation (2) Seeing, thermoacoustic effect acoustical signal is caused by Joule heat sound source.Under the measuring condition of magnetosonic imaging, measured acoustical signal was both Comprise and vibrated, by Lorentz force, the magnetoacoustic signals caused, also comprise the thermoacoustic signal that thermoacoustic effect produces.
The formation method of a kind of electrical conductivity magnetosonic imaging device for removing thermoacoustic effect impact of the present invention, by going Except the thermoacoustic signal in magnetoacoustic signals is to realize accurate reconstruction tested sample distribution of conductivity image, as in figure 2 it is shown, 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) by the dual pathways preamplifier of high cmrr respectively by the first sonic transducer and rising tone transducer Gather magnetoacoustic signals and the thermoacoustic signal of sample to be tested；Wherein
When detecting magnetoacoustic signals, under conditions of loading magnetostatic field, the pulse excitation applying adjustable amplitude and frequency is made For excitation coil, the ultrasonic transducer of mid frequency 1MHz is used to gather the magnetoacoustic signals of sample to be tested；
When detecting thermoacoustic signal, move static magnet by moveable support, under conditions of being not loaded with magnetostatic field, execute The pulse excitation adding adjustable amplitude and frequency acts on excitation coil, uses the ultrasonic transducer of mid frequency 200～500kHz Gather the thermoacoustic signal of sample to be tested.
3) to magnetoacoustic signals and thermoacoustic signal digitized processing；
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 magnetosonic Thermoacoustic signal in signal, isolates single Lorentz force magnetoacoustic signals；
6) using magnetosonic sound source based on Lorentz force as source item, the acoustic pressure wave equation of magnetosonic sound source is set upSingle magnetoacoustic signals weight is utilized again based on time backprojection algorithm Build the electrical conductivity of sample to be tested, 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, by moving above couplant groove 1 Dynamic support 14 is placed the uniform magnetic field of static magnet 13 formation and is perpendicular to sample holding plane, and the first sonic transducer 9 and the rising tone change Sample 3 plane both sides can be symmetrically disposed in the horizontal direction by device 10；
2), during detection thermoacoustic signal, use the sine pulse voltage drive sample of 1MHz frequency, moved by traversing carriage 14 Walk static magnet 13 and remove the effect of homogeneous static magnetic field, with the rising tone transducer and the first of 1MHz of mid frequency 200-500kHz Sonic transducer gathers signal, uses dual pathways preamplifier 8 to receive signal, controls driven by motor by computer and is placed with sample The pallet 2 of 3 rotates, and makes the circumferentially scan mode pointwise of the first sonic transducer 9 and rising tone transducer 10 gather signal, it is thus achieved that each The thermoacoustic signal of sample 3 at collection point；
3), during detection magnetoacoustic signals, use the sine pulse voltage drive sample of 1MHz frequency, moved by traversing carriage 14 The underface of sound Magnet 13 to sample 3, the intensity arranging magnetostatic field is 1T, simultaneously with the second of mid frequency 200-500kHz First sonic transducer of sonic transducer and 1MHz gathers signal, uses dual pathways preamplifier to receive signal, passes through computer Control driven by motor is placed with the pallet 2 of sample 3 and rotates, and makes the first sonic transducer 9 and the rising tone transducer 10 circumferentially side of scanning Formula pointwise gathers signal, it is thus achieved that the magnetoacoustic signals of sample 3 at each collection point；
4) for the signal of each station acquisition, Time-frequency Analysis is used to remove in the magnetoacoustic signals that sensor receives Thermoacoustic effect impact, isolate single Lorentz force acoustical signal；
5) solving equation
▿ 2 p ( r , t ) - 1 c s 2 ∂ 2 ∂ t 2 p ( r , t ) = ▿ · ( J ( r , t ) × B 0 ) - - - ( 1 )
Obtain corresponding algorithm, by step 4) in obtain data input algorithm, sample distribution of 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 one sonic transducer should be consistent with driving pulse frequency.When measuring biological tissue, rising tone transducer 10 center Frequency elects 200～500kHz as.

Claims (6)

1. remove an electrical conductivity magnetosonic imaging device for thermoacoustic effect impact, including, couplant groove (1), it is characterised in that institute It is respectively arranged with in the couplant groove (1) stated: be used for supporting the pallet (2) of sample (3), be connected to the bottom of described pallet (2) For the motor (4) driving pallet (2) to rotate, be separately positioned on described sample (3) both sides the first sonic transducer (9) and Rising tone transducer (10), wherein, the input of described motor (4) by run through couplant groove (1) wire connect by The drive circuit (5) that computer (6) controls, described first sonic transducer (9) and the signal output part of rising tone transducer (10) Being all connected with the signal input part of dual pathways preamplifier (8), the signal output part of described dual pathways preamplifier (8) passes through Capture card (7) connect computer (6), described sample (3) be arranged above excitation coil (12), described excitation coil (12) Connect exciting bank (11), described excitation coil (12) be arranged above static magnet (13).
A kind of electrical conductivity magnetosonic imaging device removing thermoacoustic effect impact the most according to claim 1, it is characterised in that Described exciting bank (11) include be connected for producing the signal generator (111) of pumping signal and for described The power amplifier (112) that is amplified of pumping signal, the outfan of described power amplifier (112) connect described in excitation Coil (12).
A kind of electrical conductivity magnetosonic imaging device removing thermoacoustic effect impact the most according to claim 1, it is characterised in that Described static magnet (13) is the top that the traversing carriage (14) by moving is arranged on described excitation coil (12).
4. for a formation method for the electrical conductivity magnetosonic imaging device removing thermoacoustic effect impact described in claim 1, It is characterized 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 by the first sonic transducer and rising tone transducer respectively by the dual pathways preamplifier of high cmrr The magnetoacoustic signals of sample to be tested and thermoacoustic signal；
3) to magnetoacoustic signals and thermoacoustic signal digitized processing；
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 magnetoacoustic signals In thermoacoustic signal, isolate single magnetoacoustic signals；
6) using magnetosonic sound source based on Lorentz force as source item, the acoustic pressure wave equation of magnetosonic sound source is set upSingle magnetoacoustic signals weight is utilized again based on time backprojection algorithm Build the electrical conductivity of sample to be tested, obtain sample distribution of conductivity image.
The formation method of the electrical conductivity magnetosonic imaging device of removal thermoacoustic effect the most according to claim 4 impact, it is special Levy and be, step 2) in when detecting magnetoacoustic signals, under conditions of loading magnetostatic field, apply the pulse of adjustable amplitude and frequency Incentive action, in excitation coil, uses the ultrasonic transducer of mid frequency 1MHz to gather the magnetoacoustic signals of sample to be tested.
The formation method of the electrical conductivity magnetosonic imaging device of removal thermoacoustic effect the most according to claim 4 impact, it is special Levy and be, step 2) in when detecting thermoacoustic signal, remove static magnet by moveable support, be not loaded with the bar of magnetostatic field Under part, the pulse excitation applying adjustable amplitude and frequency acts on excitation coil, uses the ultrasonic of mid frequency 200～500kHz Transducer gathers the thermoacoustic signal of sample to be tested.
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