CN117598728A - Planar multi-focus acoustic lens and acoustic lens device for medical diagnosis and treatment - Google Patents

Planar multi-focus acoustic lens and acoustic lens device for medical diagnosis and treatment Download PDF

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CN117598728A
CN117598728A CN202410093187.8A CN202410093187A CN117598728A CN 117598728 A CN117598728 A CN 117598728A CN 202410093187 A CN202410093187 A CN 202410093187A CN 117598728 A CN117598728 A CN 117598728A
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sound field
acoustic lens
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CN117598728B (en
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陈剑
张梦茹
华友龙
吴施伟
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Zhejiang University ZJU
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    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/42—Details of probe positioning or probe attachment to the patient
    • A61B8/4272—Details of probe positioning or probe attachment to the patient involving the acoustic interface between the transducer and the tissue
    • A61B8/4281—Details of probe positioning or probe attachment to the patient involving the acoustic interface between the transducer and the tissue characterised by sound-transmitting media or devices for coupling the transducer to the tissue

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Abstract

The invention discloses a planar multi-focus acoustic lens for medical diagnosis and treatment and an acoustic lens device. The upper surface and the lower surface of the planar multi-focus acoustic lens are both planar, a polymer cavity is formed between the bottom surface of the polymer structure surrounded by the side wall surface structure and the planar polymer structure, and a liquid filling structure is formed after filling liquid into the polymer cavity; the top surface of the polymer structure is a flat surface, the bottom surface of the polymer structure is a concave-convex surface, and the top surface and the bottom surface of the flat polymer structure are both flat surfaces; the polymer structure is mainly formed by closely arranging and connecting a plurality of microstructure units in an array, wherein the thickness of each microstructure unit is different, and the concave-convex distribution of the bottom surface forms the concave-convex surface of the polymer structure. The invention can be used for generating a multi-focus sound field under the skin of a diagnosis and treatment object by the sound field modulated by the acoustic lens, realizes the detection or treatment of a discrete target area, is completely planar, and has the advantages of high sound field coupling efficiency, thinner thickness, simple structure, low price and high detection efficiency.

Description

Planar multi-focus acoustic lens and acoustic lens device for medical diagnosis and treatment
Technical Field
The invention relates to a medical ultrasonic acoustic lens technology, in particular to a planar multi-focus acoustic lens for medical diagnosis and treatment and a medical acoustic lens device.
Background
Biomedical ultrasound is one of important novel subjects for realizing disease diagnosis and treatment by taking ultrasound as a carrier and utilizing biological effects of ultrasound by means of engineering technical means such as signal processing technology, electronic science and the like. Based on the ultrasonic wave effect, medical ultrasonic imaging-diagnosis technologies such as B ultrasonic, ultrasonic guidance, ultrasonic radiography and the like are developed, and acoustic parameter characterization such as acoustic impedance and acoustic attenuation of biological tissues can be realized by utilizing a medical ultrasonic probe based on a pulse-echo mode. Compared with industrial nondestructive detection, the complexity of biological tissues enables echo signals to carry more abundant information, for example, detection of parts such as prostate and mammary gland can be realized based on the elastic coefficient extracted by the echo signals; based on harmonic components, nonlinear characteristics of tissue organisms can be obtained, and pathological diagnosis of endocardium, liver cirrhosis focus and the like can be realized. At present, the application of medical ultrasonic equipment is also gaining more and more attention, and the characteristics of noninvasive, real-time, repeatable and wide application objects of ultrasonic detection are that the ultrasonic detection becomes an indispensable means for preoperative and intraoperative clinical detection, so that the ultrasonic detection becomes one of 5 technologies of medical image examination.
Meanwhile, the ultrasound itself carries huge energy, and the high-power driven ultrasound has thermal effect, and medical researches show that the low-dose thermal effect can promote metabolism of human body functions, promote blood circulation, accelerate wound healing and the like. At present, the incidence rate of tumors at home and abroad is improved year by year, and for the treatment of tumors, besides the traditional operation, new diagnosis and treatment technology is layered endlessly, and besides the laparoscopic operation, the minimally invasive treatment also has a very good effect in clinical application, but the minimally invasive treatment based on the technologies of radio frequency, microwave or freezing and the like still belongs to an invasive method, and bleeding or tumor puncture metastasis can be caused. Invasive high intensity focused ultrasound (High Intensity Focusing Ultrasonic, HIFU) ablation therapy has gained increasing attention for the last 20 years. With the increase of ultrasonic excitation power, high-precision sound beams are propagated in human tissues and focused on a target area, huge carried energy can cause rapid heating of local areas, and the generated high-temperature thermal effect can cause rapid heating of the tissues and further cause irreversible coagulation necrosis. Since 1942 Lynn proposed the assumption of non-invasive surgery in vivo in vitro and performed injury experiments on animal brain cells and obtained obvious effects, medical treatment based on HIFU ultrasound was gradually developed, and it was proved that the treatment has the advantages of only damaging the tissue of the targeted area, but not damaging the surrounding tissues, etc.
However, most of the existing ultrasonic medical diagnosis and treatment technologies realize the focusing of the sound energy of the target area through the cambered surface multi-array element probe, and the sound energy is difficult to perfectly attach when contacting with most areas of the human body, so that the sound energy coupling is insufficient, and the sound energy utilization rate is reduced. Meanwhile, most of the existing medical focusing probes are focused in a single focus, and diagnosis and treatment efficiency is low under the condition of a plurality of discrete target areas. In addition, the characteristics of multiple array elements, cambered surfaces and the like all lead to high price and long preparation period of the existing ultrasonic medical probe.
Therefore, aiming at the defects of insufficient coupling between the medical ultrasonic focusing probe and the skin surface of a patient, complex structure, large thickness, single focus and the like of the focusing ultrasonic probe, a planar ultrasonic surface acoustic lens capable of realizing perfect surface lamination is urgently sought to realize medical diagnosis and treatment with higher acoustic energy utilization rate. Therefore, how to design the focusing acoustic lens to realize multi-focus sound field modulation in the axial direction or on the same plane can effectively improve the medical diagnosis and treatment efficiency and finally realize multi-plane tomography.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a planar multi-focus acoustic lens for medical diagnosis and treatment and a medical acoustic lens device. After the ultrasonic wave is modulated by the planar multi-focus acoustic lens, a multi-focus sound field is realized on a diagnosis and treatment object, the upper surface and the lower surface of the planar multi-focus acoustic lens are both planes, and in the use process, the upper surface and the lower surface of the planar multi-focus acoustic lens can be respectively and tightly attached to the ultrasonic transducer and the surface skin of the diagnosis and treatment object.
The invention adopts the technical scheme that:
1. a planar multi-focus acoustic lens apparatus:
the upper surface and the lower surface of the planar multi-focus acoustic lens are both planar;
the planar multi-focus acoustic lens comprises a polymer structure, a side wall surface structure, a flat polymer structure and a liquid filling structure;
the outer edge of the bottom surface of the polymer structure is provided with a downward annular bulge serving as a side wall surface structure, the bottom surface of the side wall surface structure and the upper surface of the flat polymer structure are closely arranged, so that a polymer cavity is formed between the bottom surface of the polymer structure surrounded by the side wall surface structure and the upper surface of the flat polymer structure, and a liquid filling structure is formed after filling liquid into the polymer cavity; the top surface of the polymer structure is a flat surface, the bottom surface of the polymer structure is a concave-convex surface, the top surface and the bottom surface of the flat polymer structure are both flat surfaces, and the flat surface of the polymer structure is parallel to the flat surface of the flat polymer structure.
Specifically, the thickness of the flat polymer structure and the thickness of the side connecting wall surface are uniformly distributed, and in order to reduce the attenuation and reflection effects of the polymer structure on the incident sound waves, the thinner the polymer structure, the better the rigidity is kept.
The planar multi-focus acoustic lens can be integrally prepared by a 3D printing technology.
The polymer structure is mainly formed by closely arranging and connecting a plurality of cuboid microstructure units with different thicknesses along two orthogonal directions of a plane in an array manner, or is mainly formed by concentrically arranging and closely arranging and connecting a plurality of annular microstructure units with different thicknesses along the radial direction from inside to outside; the top surfaces of the microstructure units are positioned on the same plane, and the thickness of each microstructure unit is different to form the thickness distribution of the whole microstructure unit, so that the concave-convex distribution of the bottom surfaces of the microstructure units forms the concave-convex surface of the polymer structure.
In specific implementation, the thicknesses of the microstructure units in each cuboid are the same throughout, and the thicknesses of the microstructure units can be the same along one direction of a plane, namely the thicknesses of the microstructure units passing through the same straight line along the direction are the same, but the thicknesses of the microstructure units on different straight lines along the direction are different, so that the concave-convex surfaces of the polymer structure are distributed symmetrically on two sides as a whole, and a plane type multifocal acoustic lens with a central symmetrical structure is formed.
The thicknesses of the cuboid-shaped microstructure units along the two directions of the plane are different, and the planar multifocal acoustic lens with the asymmetric structure is formed.
In the specific implementation, the thickness of each annular microstructure unit is the same everywhere, and the thicknesses of a plurality of annular microstructure units are different, so that the whole concave-convex surface of the polymer structure is distributed in a central symmetry way, and the planar multi-focus acoustic lens with a central axis symmetrical structure is formed.
Thickness of individual microstructure units of the polymer structureh ug Operating frequency with the planar multi-focal acoustic lensfSound velocity of target sound field distribution and polymer structurec u Sound velocity of filling liquidc w And the like. In specific implementation, after processing preset parameters, the first step is obtainedgThickness dimension of individual microstructure unitsh ug Width dimension of individual microstructure units in the processwRemain unchanged.
The position and the transverse resolution of each focus in the multi-focus focusing sound field realized by the planar multi-focus acoustic lens are respectively preset according to the target plane and the detection precision.
For a focal plane/target plane with a plane distance l to z=0, a target sound field with a precision σ is detected, and a focused sound field distribution on the focal plane/target plane is expressed as a target sound field as:
P i0 (x,y,z=l)=A×e^(-((x-x 0 ) 2 +(y-y 0 ) 2 /σ 2 ))
wherein P is i0 (x, y, z=l) is the focal plane/target plane focused sound field distribution of z=l,x,y,zrespectively two axes representing the focal plane and an axis perpendicular to the focal plane, AFor the maximum of the acoustic energy distribution, generally 1,lthe distance of the focal plane perpendicular to the origin of the coordinate system, i.e. the focal length,σin order to detect the accuracy of the measurement,x 0 、y 0 respectively with focus on focal planexA shaft(s),yAn axis coordinate value.
The individual microstructure element thickness distribution in the polymer structure is set in the following manner:
1) Presetting a plurality of target planes and only one focus on each target plane aiming at a polymer structure, wherein the focuses on the target planes are in the same axial direction, and generating a target sound field according to all the set target planes and all the focuses;
in the above case, preferably, the microstructure units are arranged in a ring shape, and the plurality of ring-shaped microstructure units are concentrically arranged and are closely arranged and connected to each other in a radial direction sequentially outwards.
2) With the detection of axial direction aszShaft to establishxyzCoordinate system, and set upxyzThe origin of the coordinate system,xyztwo orthogonal axes are arranged on a plane perpendicular to the detection axial direction in the coordinate systemxShaft and method for producing the sameyA shaft; iteratively obtaining a sound field distribution in the following mannerPPhase distribution of a phase detectorφ：
In particular, a parallel plane is arranged between the top surface of the polymer structure and the concave-convex surface or is arranged on the top surface of the polymer structure xyzThe origin of the coordinate system.
2.1 At a target sound field P of each target plane i0 Initial sound field distribution as each of the target planes;
2.2 According to the sound field distribution, obtaining the spatial spectrum distribution on the target plane after Fourier transformation in the following way, the firstiThe target planes arez=l i Is a plane of:
P i (k x ,z=l i )=∫P i (x,z=l i )e^(jk x x)dx
in the method, in the process of the invention,P i (k x ,z=l i ) Is the firstiThe spatial spectral distribution over the individual object planes,P i (x,z=l i ) Is the firstiThe sound field distribution over the target planes is calculated, for the first time,k x is thatxThe wave number in the axial direction,xis the coordinate axis perpendicular to the propagation direction of the sound wave,ithe ordinal number representing the object plane,jis an imaginary number, and is used for the purpose of calculating,j 2 = -1, d represents calculus, e represents natural constant, and a represents power of power, e.g. ejk x x) Representing ejk x xPower to power;
2.3 Processing according to a back propagation model based on the spatial spectral distribution on each object plane to obtain the position in the object planezWith zero axiszSound field distribution on acoustic lens plane of =0 asP(x,z=0) and phase distribution thereofφ(x,z=0), specifically:
2.3.1 First, the spatial spectrum distribution of each target planeP i (k x ,z=l i ) Multiplying the phase factors H respectivelyk x ,z=l i ) Then, the spatial spectrum distribution of the sound field of each target plane back-propagating to the acoustic lens plane with zero z-axis is obtainedP i (k x ,z=0)：
P i (k x ,z=0)=P i (k x ,z=l i )*H(k x ,z=l i )
H(k x ,z=l i )=e^(-jl i (k 0 2 -k x 2 ) 1/2 )
k 0 =2πf/c
In the method, in the process of the invention,P i (k x ,z=0) is the firstiSound field back propagation to be at the target plane zSpatial spectral distribution on an acoustic lens plane with zero axis H #k x ,z=l i ) As a phase factor of the sound field,l i is the firstiThe focal length corresponding to the respective object plane,k 0 the wave numbers of the sound field are excited for the ultrasonic transducer,ffor presetting the operating frequency, i.e. the frequency at which the ultrasonic transducer is excited to emit incident wavesThe rate of the product is determined by the ratio,cthe sound velocity under the superficial skin of the diagnosis and treatment object;
2.3.2 Then back-propagating the sound field for each target plane to be atzSpatial spectral distribution in an acoustic lens plane with zero axisP i (k x ,z=0) After the inverse Fourier transform is carried out, the sound field of each target plane is obtained and respectively positioned atzWith zero axiszSound field distribution of acoustic lens plane =0:
P i (x,z=0)=∫P i (k x ,z=0)e^(jk x x)dk x
in the method, in the process of the invention,P i (x,z=0) is the firstiThe sound fields of the target planes are respectively inzSound field distribution of an acoustic lens plane with zero axis;
2.3.3 Then, the sound fields for all target planes are respectively in the following formulaszSound field distribution for an acoustic lens plane with zero axisP i (k x ,zAfter fusion treatment, =0), the obtained product is inzSound field distribution on an acoustic lens plane with zero axisP(x,z=0) and phase distribution thereofφ(x,z=0)：
P(x,z=0)=P 1 (x,z=0)+P 2 (x,z=0)+…+P n (x,z=0)
φ(x,z=0)=arg(P(x,z=0))
Wherein arg () represents a phase distribution of sound pressure,nrepresenting the total number of target planes;
2.4 According to being atzWith zero axiszSound field distribution on acoustic lens plane =0 P(x,z=0) and phase distribution thereofφ(x,z=0) processing according to the forward propagation model to obtain a signal at the target planez=lIs of the forward sound field distribution of (a)P 1 ’(x,z=l) Specifically, it is：
2.4.1 First, remain inzSound field distribution on an acoustic lens plane with zero axisP(x,z=0) will be atzWith zero axiszAll magnitudes of the sound field distribution on the acoustic lens plane of =0 are replaced with 1, resulting in a new sound field distribution on the top surface of the planar multi-focal acoustic lens:
P’(x,z=0)=e^(jφ(x,z=0))
in the method, in the process of the invention,P’(x,z=0) is the new sound field distribution on the plane of a planar multi-focal acoustic lens,φ(x,z=0) is atzWith zero axiszPhase distribution of sound field distribution on acoustic lens plane=0;
2.4.2 Then, the obtained new sound field distribution on the plane of the planar multi-focus acoustic lensP’(x,z=0) forward propagation to each target planez=l i And respectively obtaining the forward sound field distribution of each target plane:
P i ’(x,z=l i )=∫(∫P’(x,z=0)e^(-jk x x)dx)*e^(jl i (k 0 2 -k x 2 ) 1/2 )*e^(jk x x)dk x
in the method, in the process of the invention,P i ’(x,z=l i ) Is the firstiForward sound field distribution for each target plane;
2.4.3 Finally, the phase distribution of the forward sound field distribution of each target plane is kept unchanged, and the amplitude distribution of the forward sound field distribution of each target plane is respectively replaced by the target sound field corresponding to the respective target planeP i0 (x,z=l i ) Obtaining new sound field distribution of each target plane:
P i (x,z=l i )=P i0 (x,z=l i )e^(-jφ i ’(x,z=l i ))
φ i ’(x,z=l i )=arg(P i ’(x,z=l i ))
In the method, in the process of the invention,φ i ’(x,z=l i ) Is the firstiThe phase distribution of the forward sound field distribution of the individual object planes,P i0 (x,z=l i ) Is the firstiThe target sound field distribution of the individual target planes,P i (x,z=l i ) Is the firstiNew sound field distribution for each target plane;
2.5 (2.4) distributing the new sound field of each target plane obtained in the step 2)P i (x,z=l i ) Returning to the processing of the step 2.2) as the sound field distribution of each target plane of the next iteration cycle, and continuously repeating the optimized iteration processing of the sound field distribution according to the steps 2.2) to 2.4) until the iteration number reaches the set maximum iteration number or the phase distribution on z=0 converges, ending the iteration, and setting the last iteration obtained in the step 2.3) at the end of the iterationzThe sound field distribution on the acoustic lens plane with zero axis isP(x,z=0) as final sound field distributionPAnd its phase distribution;
3) From the sound field distribution obtained beforePIs of the phase distribution of (a)φThe thicknesses of the microstructure units in the polymer structure of the planar multi-focus acoustic lens are obtained by combining the thicknesses of the planar multi-focus acoustic lens in the following manner, and the thicknesses are further used for manufacturing the planar multi-focus acoustic lens:
φ g =k u h ug +k w h wg
H = h ug+ h wg
in the method, in the process of the invention,k u the wavenumber for the polymer structure is that,k w the wave number for the liquid-filled structure,φ g is a phase distributionφMiddle (f)gThe phase value of the individual microstructure elements, h ug Is the firstgThickness of each microstructure unit, each microstructure unit is cube, and interval between adjacent microstructure units isw，h wg Is the firstgThe thickness of the filling liquid corresponding to each microstructure unit is H, and the thickness of the planar multi-focus acoustic lens is the same everywhere.
The individual microstructure element thickness distribution in the polymer structure is set in the following manner:
1) Presetting only one target plane and a plurality of focuses on the target plane aiming at a polymer structure, and generating a target sound field according to the set target plane and all focuses;
in the above case, preferably, the microstructure units are rectangular, and the plurality of rectangular microstructure units are arranged in a close array along two orthogonal directions of the plane.
2) Build-up with the probe axial direction as z-axisxyzCoordinate system, and set upxyzThe origin of the coordinate system,xyztwo orthogonal vertical axes are arranged on a plane perpendicular to the detection axial direction in the coordinate system and are an x axis and a y axis; iteratively obtaining a sound field distribution in the following mannerPPhase distribution of a phase detectorφ：
In practice, a parallel plane is taken between the top surface of the polymer structure and the concave-convex surface or the origin of the xyz coordinate system is set on the top surface of the polymer structure.
2.1 Taking the target sound field as an initial sound field distribution;
2.2 According to the sound field distribution, carrying out Fourier transform to obtain the spatial spectrum distribution on a target plane, wherein the target plane isz=lIs a plane of:
P 1 (k x ,k y ,z=l)=∫∫P 1 (x,y,z=l)e^(-j(k x x+k y y))dxdy
in the method, in the process of the invention,P 1 (k x ,k y ,z=l)、P 1 (x,y,z=l) The spatial spectrum distribution and the sound field distribution on the target plane are respectively,k x is thatxThe wave number in the axial direction,k y is thatyThe wave number in the axial direction,lfor the focal length corresponding to the target plane,x、ythe spatially distributed coordinates of the perpendicular acoustic wave propagation direction,jis an imaginary number, and is used for the purpose of calculating,j 2 = -1, d represents calculus, e represents natural constant, and a power of power, e.g. e (j (k) x x+k y y)) represents j (k) of e x x+k y y) power;
2.3 Processing according to a back propagation model based on the spatial spectral distribution on the target plane to obtain the positionzThe sound field distribution on the acoustic lens plane with axis zero z=0 isP(x,y,z=0) and phase distribution thereofφ(x,y,z=0), specifically:
first, the spatial spectrum distribution of the target planeP 1 (k x ,k y ,z=l) Multiplying by a phase factor Hk x ,k y ,z=l) Back-propagated to be atzSpatial spectral distribution of an acoustic lens plane with zero axisP(k x ,k y ,z=0), followed by an inverse fourier transform to obtain the phase-shift signalzSound field distribution on an acoustic lens plane with zero axisP(x,y,z=0) and phase distribution thereofφ(x,y,z=0)：
P(k x ,k y ,z=0)=P 1 (k x ,k y ,z=l)×H(k x ,k y ,z=l)
H(k x ,k y ,z=l)=e^(-jl(k 0 2 -k x 2 -k y 2 ) 1/2 )
P(x,y,z=0)=∫∫P(k x ,k y ,z=0)e^(j(k x x+k y y))dk x dk y
φ(x,y,z=0)=arg(P(x,y,z=0))
k 0 =2πf/c
In the method, in the process of the invention,P(k x ,k y ,z=0) is counter-propagating to atzWith zero axis zSpatial spectral distribution on acoustic lens plane =0,P(x,y,z=0) is atzSound field distribution on an acoustic lens plane with zero axis,φ(x,y,z=0) is atzThe phase distribution of the sound field distribution on the acoustic lens plane with zero axis,k 0 wave numbers exciting the sound field for the ultrasonic transducer; h (k) x ,k y Z=l) represents a phase factor, arg represents a phase distribution;cto diagnose the sound velocity of the superficial skin and the subsurface skin of the object,fthe working frequency is preset, namely the working frequency of the incident wave;
2.4 According to the sound field distribution in the acoustic lens plane with zero z-axisP(x,y,z=0) and phase distribution thereofφ(x,y,z=0) processing according to the forward propagation model to obtain a signal at the target planez=lIs of the forward sound field distribution of (a)P 1 ’(x,y,z=l) The method specifically comprises the following steps:
2.4.1 First, remain inzPhase distribution of sound field distribution on an acoustic lens plane with zero axisφ(x,y,z=0), will be atzAll amplitudes in the sound field distribution on the acoustic lens plane with zero axis are replaced by 1, and then a new sound field distribution on the top surface of the planar multi-focus acoustic lens is obtainedP’(x,y,z=0)：
P’(x,y,z=0)=e^(jφ(x,y,z=0))
2.4.2 Then, the new sound field distribution of the plane type multi-focus acoustic lens planeP’(x,y,z=0) forward propagation to the target planez=lObtaining the forward sound field distribution in the target planeP 1 ’(x,y,z=l) Phase distribution of a phase detectorφ 1 ’(x,y,z= l)：
P 1 ’(x,y,z=l)=∫∫(∫∫P’(x,y,z=0)e^(-j(k x x+k y y))dxdy)e^(jl(k 0 2 -k x 2- k y 2 ) 1/2 )e^(j(k x x+k y y))dk x dk y
φ 1 ’(x,y,z=l)=arg(P 1 ’(x,y,z=l))
2.4.3 Then, the phase distribution phi of the forward sound field distribution at the target plane is preserved 1 ' x, y, z=l, and replaces the amplitude distribution in the forward sound field distribution at the target plane z=l with the target sound field corresponding to the target planeP i0 (x,z=l i ) After the amplitude distribution in (3), a new sound field distribution P of the target plane is obtained 1 (x, y, z=l) and phase distribution thereofφ 1 (x, y, z=l), specifically expressed as:
P 1 (x,y,z=l)=P 10 (x,y,z=l)e^(jφ 1 ’(x,y,z=0))
φ 1 (x,y,z=l)=arg(P 1 (x,y,z=l))
wherein P is 1 (x, y, z=l) new sound field distribution for target plane, P 10 (x, y, z=l) is a target sound field distribution of the target plane;
2.5 (2.4) the new sound field distribution P of the target plane obtained in the step 2) 1 (x, y, z=l) returning to the process of step 2.2) as the sound field distribution of the next iteration cycle, and continuously repeating the optimized iteration process of the sound field distribution according to the steps 2.2) -2.4) until the iteration number reaches the set maximum iteration number or the phase distribution on z=0 converges, and ending the iterationAt the end of the iteration, the last iteration is in step 2.3)zWith zero axiszSound field distribution on acoustic lens plane of =0 asP(x,y,z=0) as final sound field distributionP；
3) From the sound field distribution obtained beforePIs of the phase distribution of (a)φThe thicknesses of the microstructure units in the polymer structure of the planar multi-focus acoustic lens are obtained by combining the thicknesses of the planar multi-focus acoustic lens in the following manner, and the thicknesses are further used for manufacturing the planar multi-focus acoustic lens:
φ g =k u h ug +k w h wg
H = h ug+ h wg
In the method, in the process of the invention,k u the wavenumber for the polymer structure is that,k w the wave number for the liquid-filled structure,φ g is a phase distributionφThe phase value of the g-th microstructure element,h ug for the thickness of the g-th microstructure unit, each microstructure unit is a cube, the interval between adjacent microstructure units is w,h wg the thickness of the filling liquid corresponding to the g-th microstructure unit is H, and the thickness of the planar multi-focus acoustic lens is the same as the thickness of each part of the planar multi-focus acoustic lens.
Obtaining the thickness of the planar multi-focus acoustic lens on a two-dimensional scaleh ug (x, z) orh ug After (x, y, z), the shape and size of the ultrasonic transducer selected in practical application can be changed in the iterative angular spectrometryzWith zero axiszAcoustic lens plane =0z=lAnd the size parameters of the plane are further used for obtaining square or round multi-focus acoustic lenses with different sizes.
Wavenumber of the polymer structurek u And wave number of liquid filled structurek w The calculation is carried out in the following ways:
k u =2πf/c u ，k w =2πf/c w
in the method, in the process of the invention,ffor the operating frequency of the incident wave,c u is the speed of sound of the polymer structure,c w is the speed of sound of the liquid filled structure.
The side wall surface structure is provided with a through hole as a liquid filling small hole, the axis of the liquid filling small hole is perpendicular to the central axis of the planar multi-focus acoustic lens, and the liquid filling small hole is used for inflow/outflow of filling liquid.
In operation, the filling liquid fills the polymer cavity through the liquid filling small hole. When the filling liquid needs to be replaced, the filling liquid is pumped out through the liquid filling small hole for replacement.
The polymer structure, the flat polymer structure and the side wall surface structure are all made of the same polymer material, and the polymer material is an epoxy-based metal polymer material which can be matched with a matching layer of an ultrasonic transducer and the impedance of water; the epoxy metal polymer material is preferably prepared from the following materials in percentage by mass of 0.5-1.5: 1 and an epoxy resin mixture.
The filling liquid is ethanol-glycerol mixed solution. Sound velocity of filling liquid prepared by mixing according to different proportionsc w Can take any value in the range of 1207-1904 m/s. The distribution condition of the focusing sound field realized by the planar multi-focus acoustic lens can be changed by changing the proportion of glycerol and ethanol solution in the filling liquid, and the focal length, the number, the focusing transverse dimension and the like of the focusing sound field are modulated, so that the sound field modulation freedom degree and the application potential of the planar multi-focus acoustic lens device are greatly improved.
2. A planar multi-focus acoustic lens apparatus:
according to the planar multi-focus acoustic lens, a planar multi-focus acoustic lens device can be prepared and used for performing diagnosis and treatment operations such as imaging detection, ablation treatment and the like on a diagnosis and treatment object.
The planar multi-focus acoustic lens device is used for moving on the surface skin of a diagnosis and treatment object to realize scanning, and comprises a double-opening flange structure, an ultrasonic transducer and a planar multi-focus acoustic lens; the double-opening flange structure is provided with a cavity, openings are formed in the upper end and the lower end of the double-opening flange structure, an ultrasonic transducer is detachably arranged on the upper part of the cavity, and the lower end of the ultrasonic transducer extends into the cavity; the lower part of the cavity is provided with a stepped groove, a planar multi-focus acoustic lens is embedded in the stepped groove, the top surface of the planar multi-focus acoustic lens is contacted with the lower end surface of the ultrasonic transducer, and the bottom surface of the planar multi-focus acoustic lens is contacted with the surface skin of a diagnosis and treatment object.
Any side surface of the planar multi-focus acoustic lens can be directly attached to the matching layer plane of the ultrasonic transducer, and mechanical vibration excited by the ultrasonic transducer is subjected to phase modulation and transmitted to the planar multi-focus acoustic lens. Meanwhile, the other side plane of the plane type multi-focus acoustic lens is perfectly attached to the surface skin of the diagnosis and treatment object, the modulated ultrasonic signals can be coupled to the body surface or the lower surface of the diagnosis and treatment object, and the multi-focus focusing sound field distributed along the axial direction or along the same plane is realized.
The ultrasonic transducer emits ultrasonic waves to the planar multi-focus acoustic lens along the detection axis as incident waves, the incident waves are incident to the polymer structure from the upper surface of the polymer structure, sequentially pass through the polymer structure, the liquid filling structure and the planar polymer structure, then are emitted to the surface skin and focused on at least one target plane to form a target sound field.
The target plane is a focal plane, is a plane parallel to the top surface of the polymer structure, and is a focal point where incident waves are focused after passing through the planar multi-focal-point acoustic lens, and the focal point is positioned on the target plane.
In particular, there may be multiple target planes and multiple focuses, and the multiple focuses may be distributed on different multiple target planes.
The target sound field is a multi-focus sound field and is a coaxial multi-focus sound field, a coplanar multi-focus sound field or a mixed multi-focus sound field formed by the coaxial multi-focus sound field and the coplanar multi-focus sound field. The coaxial multi-focus sound field means that all the multiple focuses are arranged at intervals along the same detection axial direction, and the coplanar multi-focus sound field means that all the multiple focuses are arranged at intervals on a plane perpendicular to the detection axial direction.
Further, a central axis symmetrical structure or a plane type multi-focus acoustic lens of a central symmetrical structure is used for realizing the coaxial multi-focus sound field; the planar multi-focus acoustic lens with an asymmetric structure is used for realizing a co-planar multi-focus acoustic field.
The planar multi-focus acoustic lens device also comprises a plurality of set screws and screw holes; the screw holes are uniformly formed in the outer wall of the upper end part of the double-opening flange structure, and each set screw penetrates through the corresponding screw hole to extend into the cavity and then is tightly connected to the side wall of the ultrasonic transducer, so that the ultrasonic transducer is fixedly arranged in the cavity, and the assembly and the fixation of the ultrasonic transducer are realized.
The interface between the ultrasonic transducer and the planar multi-focus acoustic lens is provided with a water layer, and the water layer is used for wetting and coupling the interface between the ultrasonic transducer and the planar multi-focus acoustic lens.
The annular groove is formed in the position, corresponding to the water layer, on the side wall of the stepped groove and used for storing water used for wetting the interface, and wet coupling is guaranteed all the time during operation. The upper surface of the opening flange structure is provided with two axial holes which are respectively used as a water inlet and a water outlet, and the two holes are communicated with the annular groove and are used for wetting coupling between the ultrasonic transducer and the planar multi-focus acoustic lens.
In a specific implementation, the liquid stored in the annular groove is mainly used for liquid coupling in the detection process, and is generally water; the filling of the small holes is mainly used for filling the liquid in the planar lens, and is a mixture of ethanol and glycerol.
When in use, filling liquid is filled into the filling small holes on the side wall of the planar multi-focus acoustic lens as a liquid filling structure. And then the whole planar multi-focus acoustic lens is assembled with the connecting flange through threads on the side wall and then is matched with a conventional ultrasonic probe for use, the probe needs to be in acoustic coupling with the acoustic lens, and the probe needs to be wetted through liquid, so that wetting liquid is filled through the water inlet and the water outlet.
The planar multi-focus acoustic lens is connected with the double-opening flange structure through threaded fit.
An ultrasonic couplant is arranged between the bottom surface of the planar multi-focus acoustic lens and the surface skin of the diagnosis and treatment object and is used for carrying out ultrasonic coupling in the scanning process.
The device can realize multi-focus focusing sound field in the diagnosis and treatment object, and can be finally used for diagnosis and treatment operations such as subsurface imaging detection, ablation treatment and the like of the diagnosis and treatment object. When the ultrasonic diagnosis and treatment device is used, the two side surfaces of the planar type multi-focus acoustic lens device can be respectively and directly attached to the ultrasonic transducer and the surface skin of a diagnosis and treatment object, and the assembled ultrasonic transducer-planar type multi-focus acoustic lens device can be horizontally moved along the surface skin of the diagnosis and treatment object without water immersion, so that the resolution and efficiency of medical ultrasonic diagnosis and treatment are greatly improved.
The planar multi-focus acoustic lens device provided by the invention has the following beneficial effects:
(1) The invention utilizes the polymer cavity structure with the height of the inner surface changed, and the cavity structure is completely filled with fluid to form a solid-liquid mixed structure, so that the phase modulation can be carried out on the incident plane wave sound field. The cavity structure realizes phase modulation at each microstructure unit by utilizing the sound velocity difference between the polymer material and the liquid filling material, so that the upper surface and the lower surface of the designed and prepared planar multi-focus acoustic lens device are planar. When the planar multi-focus acoustic lens is used for medical ultrasonic diagnosis and treatment, as the upper surface and the lower surface of the planar multi-focus acoustic lens are both planar, the two side surfaces can be respectively and directly and perfectly attached to the ultrasonic transducer and the surface skin of a diagnosis and treatment object, and further the on-site detection of the body surface and the subsurface of the non-water immersed diagnosis and treatment object can be realized.
(2) The planar polymer acoustic lens used in the invention has the advantages of convenient processing and low price, and can be rapidly prepared by 3D printing. Meanwhile, the material for preparing the cavity type polymer structure with the internal height change can be selected to be matched with the impedance of the ultrasonic transducer matching layer material, so that the transmissivity and the conversion rate of the sound field are greatly improved. In addition, the sound velocity of the liquid filling structure can be changed and the sound field modulation condition can be changed by changing the proportion of different proportions in the liquid filling material. The rapid switching of the focusing sound field is realized, and the operability and the reliability are higher.
(3) The ultrasonic transducer and the planar polymer acoustic lens are both of detachable structures, and the ultrasonic transducer or the planar polymer acoustic lens with proper parameters can be selected according to actual conditions.
Drawings
Fig. 1 is a schematic view of a planar multi-focal acoustic lens apparatus of embodiment 1 of the present invention, wherein (a) represents a side view and (b) represents a cross-sectional view;
fig. 2 is a schematic structural view of a planar multi-focal acoustic lens in the present invention, wherein (a) represents a sectional view and (b) represents a schematic dimensional view;
fig. 3 is an isometric view of a polymer structure in an embodiment of the present invention under different distributions, wherein (a) shows an isometric view of a planar multi-focal acoustic lens having a central symmetrical structure in embodiment 1, (b) shows an isometric view of a planar multi-focal acoustic lens having a two-sided symmetrical structure in embodiment 1, and (c) shows a three-dimensional view of a planar multi-focal acoustic lens having an asymmetrical structure in embodiment 2;
FIG. 4 is a flow chart of phase distribution optimization for a planar multi-focal acoustic lens of the present invention;
fig. 5 is a phase distribution diagram of an embodiment of a planar multi-focal acoustic lens of the present invention, wherein (a) represents the phase distribution diagram in embodiment 1 and (b) represents the phase distribution diagram in embodiment 2;
FIG. 6 is a multi-focal sound field profile achieved by the present invention based on planar multi-focal acoustic lens modulation, wherein (a) represents a co-axial multi-focal sound field profile and (b) represents a co-planar multi-focal sound field profile;
FIG. 7 is an acoustic energy distribution of a sound field modulated by a planar multi-focal acoustic lens, wherein (a) represents an axially normalized acoustic energy distribution of the co-axial multi-focal sound field, (b) represents a laterally normalized acoustic energy distribution of the co-planar multi-focal sound field, (c) represents an axially acoustic energy distribution of the co-axial multi-focal sound field, and (d) represents a laterally acoustic energy distribution of the co-planar multi-focal sound field;
fig. 8 is a schematic diagram of the diagnosis and treatment process of the present invention.
The ultrasonic transducer comprises a ultrasonic transducer body, a flange structure with two openings, a fastening screw body, a planar multi-focus acoustic lens body, a polymer structure, a side wall structure, a flat polymer structure, a liquid filling hole and a liquid filling hole, wherein the ultrasonic transducer body comprises the ultrasonic transducer body, the flange structure with two openings, the fastening screw body, the planar multi-focus acoustic lens body, the polymer structure and the liquid filling hole.
Detailed Description
The invention will be described in further detail with reference to the accompanying drawings and specific examples.
In order that those skilled in the art will better understand the technical solution of the present invention and will be able to implement it, the following detailed description of the present invention will be made with reference to the accompanying drawings and specific embodiments. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be understood that the terms "middle," "upper," "lower," "left," "right," "transverse," "longitudinal," "horizontal," "vertical," "axial," "mirror," "length," "width," "thickness," etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the technical solutions of the present invention and to simplify the description, and do not indicate or imply that the apparatus or device in question must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise indicated, and will not be described in detail herein.
In order to more clearly illustrate the embodiments of the present invention and the design thereof, the drawings required for the embodiments will be briefly described below. The drawings in the following description are only some of the embodiments of the present invention and other drawings may be made by those skilled in the art without the exercise of inventive faculty.
The acoustic lens comprises a polymer cavity structure with the inner height being changed and prepared by a 3D printing technology and a liquid filling structure for filling the cavity structure, wherein the polymer cavity structure and the liquid filling structure form a planar multi-focus acoustic lens based on a solid-liquid mixing structure. The surfaces of the upper side and the lower side of the planar multi-focus acoustic lens are flat surfaces, so that the upper flat surface and the lower flat surface of the planar multi-focus acoustic lens can be directly attached to the surface of the ultrasonic transducer and the surface skin of a diagnosis and treatment object respectively in actual operation.
The invention also uses a double-opening flange structure to directly assemble the planar multi-focus acoustic lens and the ultrasonic transducer into the planar multi-focus acoustic lens device, the device can generate an axial or same-plane multi-focus sound field in a diagnosis and treatment object, and then the assembled transducer-acoustic lens device can realize high-efficiency ultrasonic medical diagnosis and treatment by moving the assembled transducer-acoustic lens device along the surface skin of the diagnosis and treatment object. When scanning along the surface skin of the diagnosis and treatment object, scanning detection and imaging can be carried out on a plurality of discrete planes at the same time, so that the detection efficiency is greatly improved.
The finally determined and prepared planar multi-focus acoustic lens device can realize axial or same-plane multi-focus focusing sound field.
In the embodiment of the present invention, the planar type multi-focal-point acoustic lens apparatus is assembled as shown in fig. 1 (a) and (b). The planar multi-focus acoustic lens apparatus includes an ultrasonic transducer 1, a double-opening flange structure 2, a set screw 3, and a planar multi-focus acoustic lens 4.
The double-opening flange structure 2 is used for assembling the ultrasonic transducer 1 and the planar multi-focus acoustic lens 4, a hollow cavity is arranged in the double-opening flange structure, openings are formed in the upper end and the lower end of the double-opening flange structure, the ultrasonic transducer 1 is detachably arranged on the upper portion of the cavity, the ultrasonic transducer 1 is inserted from the opening above the double-opening flange structure 2, and the lower end of the ultrasonic transducer 1 is connected with the upper surface of the planar multi-focus acoustic lens 4 in a contact mode after extending into the cavity.
The inner wall of the lower part of the cavity is provided with a stepped groove as a limiting platform for positioning the planar multi-focus acoustic lens 4. A planar multi-focus acoustic lens 4 is embedded in the stepped groove.
Specifically, the opening direction of the stepped groove is downward.
Specifically, the top surface of the planar multi-focal acoustic lens 4 is disposed in planar contact with the lower end surface of the ultrasound transducer 1, i.e., the matching layer thereof, and the bottom surface of the planar multi-focal acoustic lens 4 is disposed in planar contact with the superficial skin of the subject.
In the embodiment of the present invention, the width of the flat polymer structure 43 is the same as the width of the polymer structure 41, and is slightly smaller than the width of the ultrasonic transducer 1.
Further, the outer wall of the upper end part of the double-opening flange structure 2 is uniformly provided with a plurality of screw holes, and each set screw 3 is abutted against the side wall of the ultrasonic transducer 1 after penetrating through the corresponding screw hole respectively through threads to extend into the cavity, so that the ultrasonic transducer 1 is assembled and fixed.
Further, the interface between the ultrasonic transducer 1 and the planar multi-focal acoustic lens 4 is provided with a water layer for wet coupling of the interface between the ultrasonic transducer 1 and the planar multi-focal acoustic lens 4. Grooves are formed in the side walls of the stepped grooves at positions corresponding to the interfaces and are used for storing water used for wetting and coupling, so that the interfaces of the ultrasonic transducer 1 and the planar multi-focus acoustic lens are in a wetting state;
further, two openings are formed in the upper surface of the opening flange structure 2 and serve as a water inlet and a water outlet respectively, and the two openings are communicated with the groove.
Further, the planar multi-focus acoustic lens 4 is connected with the double-opening flange structure 2 through screw thread matching.
Further, in the application process of the device, an ultrasonic couplant is arranged between the bottom surface of the planar multi-focus acoustic lens 4 in the device and the superficial skin of the diagnosis and treatment object, and is used for carrying out ultrasonic coupling in the scanning process.
The assembly process of the embodiment of the invention specifically comprises the following steps:
firstly, the planar multi-focus acoustic lens 4 is screwed with the lower end opening of the double-opening flange structure 2 through the screw threads on the side surface of the planar multi-focus acoustic lens 4, and is positioned by taking the stepped groove in the double-opening flange structure 2 as a limiting platform, so that the top surface of the planar multi-focus acoustic lens 4 is tightly connected with the bottom surface of the stepped groove.
Next, after the transmitting end of the ultrasonic transducer 1 is inserted into the upper end of the double-opening flange structure 2 from the upper end opening of the double-opening flange structure 2, the bottom surface of the transmitting end of the ultrasonic transducer 1 is in contact with the upper surface of the planar multi-focal acoustic lens 4.
Next, the ultrasonic transducer 1 is fixed using the set screw 3 on the double-opening flange structure 2.
It should be noted that, in order to allow sufficient contact and coupling between the ultrasonic transducer 1 and the planar multi-focal acoustic lens 4, the upper surface of the double-open flange structure 2 is vertically provided with two openings for water inlet and outlet, respectively, for supplementing the water required for wet coupling.
Then, the other side surface of the planar multi-focus acoustic lens 4 is directly attached to the superficial skin of the subject by an ultrasonic couplant for detection. The ultrasonic transducer 1 and the double-opening flange structure 2 are symmetrical to the axis of the ultrasonic transducer 1, the direction perpendicular to the upper and lower surfaces of the planar multi-focus acoustic lens 4 is denoted as the z direction, and the plane parallel to the upper and lower surfaces of the planar multi-focus acoustic lens 4 is denoted as the xoy plane.
In practical application, if the implemented multi-focus sound field is to be changed, only the assembled planar multi-focus acoustic lens 4 is required to be changed, simple and rapid assembly can be performed in a screwing mode, the sound field switching is rapid, and the applicability is strong.
Fig. 2 (a) is a cross-sectional view of a planar multi-focal acoustic lens 4 provided by the present invention. The sound field modulated by the planar multi-focus acoustic lens realizes multi-focus sound field on a diagnosis and treatment object. The upper and lower surfaces of the planar multi-focus acoustic lens 4 are both planar, and in the use process, the upper and lower surfaces of the planar multi-focus acoustic lens 4 can be respectively and tightly attached to the ultrasonic transducer 1 and the surface skin of a diagnosis and treatment object, so that on-site diagnosis and treatment under the non-water immersion condition is realized.
The planar multi-focal acoustic lens 4 includes a polymer structure 41, a side wall structure 42, a planar polymer structure 43, a liquid-filled structure 44, and a liquid-filled aperture 45. The polymer structure 41 and the flat polymer structure 43 are coaxially arranged at intervals up and down and are connected through the side wall surface structure 42, the polymer structure 41 and the flat polymer structure 43 are enclosed together to form a polymer cavity structure which is communicated with the inside and has different depths, namely, the polymer cavity structure with the height of the inside being changed, and the inside of the polymer cavity structure is filled with filling liquid to form the liquid filling structure 44. The side wall structure 42 is provided with a through hole as a liquid filling small hole 45, the axis of which is perpendicular to the central axis of the planar multi-focus acoustic lens for inflow/outflow of the filling liquid. In operation, the polymer cavity is filled with a fill fluid through the fluid-filled orifice 45. When the filling liquid needs to be replaced, the filling liquid is pumped out through the liquid filling small hole 45 for replacement.
Specifically, the top surface of the polymer structure 41 is a flat surface, and the bottom surface is a concave-convex surface, i.e., a surface concave-convex structure composed of microstructure units of different thicknesses; the top and bottom surfaces of the planar polymer structure 43 are planar surfaces.
Specifically, the concave-convex surface of the polymer structure 41 is formed by sequentially and tightly connecting a plurality of microstructure units with the same width and different thickness, each microstructure unit is concentrically arranged with the common axis of the polymer structure 41 and the plate-shaped polymer structure 43 as the center, and the microstructure units are distributed in a central axis symmetrical structure or a central symmetrical structure or an asymmetrical structure on the bottom surface of the polymer structure 41.
When the target modulated sound field is a coaxial multi-focal sound field, the planar multi-focal acoustic lens 4 is an axisymmetric structure (embodiment 1) or a center symmetric structure. When the target modulated sound field is a coplanar multifocal sound field, the planar multifocal acoustic lens 4 is of a non-axisymmetric structure (embodiment 2).
Further, the polymer structure 41, the side wall structure 42 and the plate polymer structure 43 are each selected from epoxy-based metal polymer materials matching the impedance of the water and the matching layer of the ultrasonic transducer 1.
Preferably, the epoxy-based metal polymer material is formed by mixing tungsten powder and epoxy resin, and the mass ratio of the tungsten powder to the epoxy resin is 0.5-1.5: 1.
Further, the filling liquid in the liquid filling structure 44 is formed by mixing ethanol and glycerin in a ratio which affects the thickness dimension of the planar multi-focal acoustic lens 4 by affecting the sound velocity in the filling liquid.
Fig. 2 (b) is a schematic dimensional diagram of the planar multi-focal acoustic lens 4 provided by the present invention. Wherein the thickness of the planar multi-focus acoustic lens 4 is H, and the width W is slightly larger than the width W of the ultrasonic transducer 1 T Set to w=0.9w T . To reduce acoustic wave reflection, the thickness of the side wall structures 42 and the planar polymer structure 43h s Andh d the rigidity should be as small as possible.
In addition, each microstructure element in the polymer structure 41 has a width w and a thickness wh ug Thickness of liquid filled structure 44h wg Are determined by the target sound field distribution.
Specifically, the thickness of each microstructure unit of the above-described flat plate type multi-focus acoustic lens 4h ug Is the sound velocity of the liquid filled structure 44 according to the incident frequency fc w And the target sound field distribution.
Further, when changing the target multi-focal acoustic field distribution, only the thickness h of each microstructure element of the polymer structure 41 needs to be re-optimized and determined ug The arbitrary multi-focus sound field of the target can be reproduced and realized.
Fig. 3 (a) and (b) are perspective views of planar multi-focal acoustic lenses 4 of different shapes for modulating the coaxial multi-focal acoustic field, respectively, the circular and directional transducers in fig. 3 (a) and (b) can be assembled with circular and square transducers, respectively, and point-like and line-like focusing can be achieved in the target acoustic field, respectively.
Fig. 3 (c) is a three-dimensional view of a planar multi-focal acoustic lens 4 for modulating a co-planar multi-focal acoustic field, which, when assembled with a transducer, achieves multi-focal focusing at a target focal plane.
Specific embodiments of the invention are as follows:
example 1:
in this embodiment, the plate-type multi-focal acoustic lens 4 and the apparatus thereof in this embodiment are used to realize a coaxial multi-focal sound field. The design process of the device is shown in fig. 4, and specifically comprises the following steps:
first, preset parameters
In this embodiment:
preset working frequency, i.e. the frequency of the incident wave isf=2.5 MHz；
The background sound field is water (sound velocityc 0 Wavelength=1500 m/sλ=c 0 /f=0.6 mm）；
The ratio of ethanol to glycerin in the filling liquid of the liquid filling structure 44 is 1:1 (Sound velocity isc w =1556 m/s with wave number ofk w =2πf/c w =1×10 4 ）；
The polymer materials used for the polymer structure 41, the flat polymer structure 43 and the side wall surface structure 42 have a mass ratio of 1:1 (sonic velocity is c u =2650 m/s, wavenumber isk u =2πf/c u =5.9×10 3 ；
The thickness of the flat polymer structure 43 ish d =0.2mm；
The side wall structure 42 has a thickness ofh s =0.4mm；
The plate-type multi-focal acoustic lens 4 has a width w=40 mm and a thickness h=3 mm.
In the polymer structure 41, each microstructure unit has a width ofw=0.8mm。
(II) sizing the plate-type multifocal acoustic lens 4
After processing the preset parameters in this step, the thickness dimensions of the individual microstructure elements of the polymer structure 41 and the liquid filling structures 44 at their corresponding positions in the plate-type multi-focus acoustic lens device 4 are obtainedh ug Andh wg . Further, both satisfy:
H=h ug+ h wg
where H is the thickness of the planar multi-focal acoustic lens 4,h ug to be the thickness of any microstructure element in the polymer structure 41,h wg the thickness of the liquid-filled structure 44 is at a location corresponding to any microstructure element.
The thickness H of the planar multi-focal-point acoustic lens 4 in this embodiment is preset to 3mm, and thus, only the thickness dimension of the polymer structure 41 is required to be determined before the multi-focal-point planar acoustic lens of the present invention is manufacturedh ug And (3) obtaining the product.
The size determination process of the plate-type multi-focal acoustic lens 4 in this embodiment is as shown in fig. 4, and specifically includes:
s1) presetting a target sound field focal length and target sound field distribution. In this process, the direction perpendicular to the upper and lower surfaces of the planar multi-focus acoustic lens 4 is zThe direction, the plane parallel to the upper and lower surfaces of the planar multi-focus acoustic lens 4 isxoyA plane. Since the three foci are all located on the axis, there is x 0 =0，y 0 =0, thus each focal planez=l i All have a target sound field distributionP i (x,y)。
S1.1) presetting a target sound field focal length and target sound field distribution.
Target sound field focal length: the three focus positions of the coaxial multi-focus sound field are all positioned on the axis, and the transverse resolutions of the three focuses are:
σ=0.8λ
in the method, in the process of the invention,σthe lateral resolution of the focus is used for representing the size of the focus; lambda is the wavelength of the background sound field;
the focal lengths of the three focuses are respectively:
l 1 =20 mm
l 2 =30 mm
l 3 =40 mm
target sound field distribution: to be used forz=l 1 、l 2 、l 3 As focal planes, and taking the plate type multi-focus acoustic lens 4 for realizing the axial multi-focus acoustic field into an axisymmetric structure, after the y axis is ignored, the target acoustic field distribution of each focal plane at the moment can be obtained respectively as follows:
P 10 (x,z=l 1 )=Ae^(-x 2 /σ 2 ))
P 20 (x,z=l 2 )=Ae^(-x 2 /σ 2 ))
P 30 (x,z=l 3 )=Ae^(-x 2 /σ 2 ))
in the method, in the process of the invention,P 10 (x,z=l 1 )、P 20 (x,z=l 2 )、P 30 (x,z=l 3 ) Respectively isz=l 1 、l 2 、l 3 The target sound field distribution in the focal plane, a being the maximum amplitude,xis the coordinate axis perpendicular to the propagation direction of the sound wave,zis the coordinate axis of the propagation direction of the sound wave,l 1 、l 2 、l 3 the distances between the first focal plane, the second focal plane and the third focal plane and the super surface are respectively, namely the focal lengths of the first focal point, the second focal point and the third focal point, and sigma is the transverse resolution of the focal points and is used for representing the focal point size.
S1.2) taking the target sound field distribution as initial sound field distribution, and obtaining the plane of the plate type multi-focus acoustic lens 4 according to iterative processingzPhase distribution on=0. The method comprises the following steps: taking the target sound field distribution as initial sound field distribution, firstly establishing a back propagation model and a forward propagation model according to the initial sound field distribution, and then sequentially aiming at the back propagation model and the forward propagation modelz=0 sumz=l i Repeatedly optimizing and iterating the sound field on the plane until the iteration number reaches the set maximum iteration number orzThe phase distribution on =0 converges, the resulting phase is atzSound field distribution on an acoustic lens plane with axis zero z=0P(x,z=0). Wherein the forward propagation direction is a direction away from the acoustic lens and the reverse propagation direction is a direction from the far field to the acoustic lens. In the present invention, the maximum number of iterations may be 20 or more.
In this embodiment, the maximum number of iterations is set to 60. At the position ofzWith zero axiszThe phase distribution on the acoustic lens plane of =0 is as in (a) of fig. 5As shown.
The process of step S1.2) is specifically as follows:
s1.2.1) taking the target sound field distribution of the three focal planes as the initial sound field distribution P of the three focal planes i (x, z=l i )。
S1.2.2) the spatial spectral distribution of the three focal planes is obtained from the initial sound field distribution of the three focal planes, respectively. Wherein, l 1 、l 2 、l 3 The spatial spectral distribution in the focal plane is:
P i (k x ,z=l i )=∫P i (x,z=l i )e^(-jk x x)dx
in the method, in the process of the invention,P i (k x ,z=l i ) Is thatz=l i The spatial spectral distribution in the plane is such that,P i (x,z=l i ) Is thatz=l i The distribution of the sound field over the plane,k x is thatxThe wave number of the direction is set,xis the coordinate axis perpendicular to the propagation direction of the sound wave,jis imaginary andj 2 = -1. And power of power, e represents natural constant, e (jk) x x) represents e (jk) x x) power to power.
S1.2.3) a back propagation model is constructed from the spatial spectral distribution of the three focal planes. The method comprises the following steps:
first, the spatial spectrum distribution of three focal planesP i (k x ,z=l i ) Multiplying by phase factor Hk x ,z=l i ) After that, three sound fields are obtained and are reversely propagated to the positionzWith zero axiszSpatial spectral distribution on acoustic lens plane =0P i (k x ,z=0)：
P i (k x ,z=0)=P i (k x ,z=l i )*H(k x ,z=l i )
H(k x ,z=l i )=e^(-jl i (k 0 2 -k x 2 ) 1/2 )
k 0 =2πf/c
In the method, in the process of the invention,P i (k x ,z=0) back-propagating for three sound fields to be inzWith zero axiszSpatial spectral distribution on acoustic lens plane =0,P i (k x ,z=l i ) Is the spatial spectrum distribution of three focal planes, H #k x ,z=l i ) Is the phase factor of the three sound fields,k 0 the wave numbers of the sound field are excited for the ultrasonic transducer 1,ffor a preset operating frequency, i.e. the frequency at which the ultrasonic transducer 1 excites the sound field,cis the sound velocity of the body surface and the subsurface of the diagnosis and treatment object.
Counter-propagating three sound fields to being inzWith zero axiszAfter performing inverse fourier transform on the spatial spectrum distribution on the acoustic lens plane of =0, three sound fields are obtained respectively in the positions of zWith zero axiszSound field distribution of acoustic lens plane =0:
P i (x,z=0)=∫P i (k x ,z=0)e^(jk x x)dk x
in the method, in the process of the invention,P i (x,z=0) is zero in the z-axis for three sound fields respectivelyzSound field distribution of acoustic lens plane =0,P i (k x ,z=0) back propagation of three sound fields to zero at z-axiszSpatial spectral distribution on acoustic lens plane=0.
Then, the three sound fields are respectively in the following formulaszWith zero axiszAcoustic lens plane =0Sound field distributionP i (k x ,zAfter treatment of =0), the product is inzWith zero axiszSound field distribution on acoustic lens plane =0P(x,z=0) and phase distribution thereofφ(x,z=0)：
P(x,z=0)=P 1 (x,z=0)+P 2 (x,z=0)+P 3 (x,z=0)
φ(x,z=0)=arg(P(x,z=0))
S1.2.4) is based on the sound field distribution P' on the acoustic lens plane with zero z=0 in the z-axisx,z=0) and phase distribution thereofφ(x,z=0) builds a forward propagation model. The method comprises the following steps:
first, the phase distribution of the sound field distribution on the sound lens plane with zero z=0 in the z axis is kept unchanged, and the amplitude distribution of the sound field distribution on the sound lens plane with zero z=0 in the z axis is replaced by 1, so as to obtain a new sound field distribution on the plane of the planar multi-focus sound lens 4:
P’(x,z=0)=e^(jφ(x,z=0))
in the method, in the process of the invention,P’(x,z=0) is the new sound field distribution in the plane of the planar multi-focal acoustic lens 4,φ(x,z=0) is the phase distribution of the sound field distribution on the acoustic lens plane with zero z=0 in the z-axis.
Then, the obtained new sound field distribution on the plane of the plane type multi-focus acoustic lens 4 P’(x,z=0) forward propagation to three focal planesz=l 1 、l 2 、l 3 And respectively obtaining the forward sound field distribution of three focal planes:
P i ’(x,z=l i )=P’(x,z=0)*e^(jl i (k 0 2 -k x 2 ) 1/2 )
in the method, in the process of the invention,P i ’(x,z=l i ) Is the forward sound field distribution of three focal planes,l i is the focal length of the three focal planes.
Finally, the phase distribution of the forward sound field distribution of the three focal planes is kept unchanged, and the amplitude distribution is replaced by the target sound field distribution P corresponding to each focal plane i0 (x,z=l i ) Obtaining new sound field distribution of three focal planes, and taking the new sound field distribution of the three focal planes as initial sound field distribution P of the next iteration cycle i (x,z=l i ) The method comprises the following steps:
P i (x,z=l i )=P i0 (x,z=l i )e^(-jφ i ’(x,z=l i ))
φ i ’(x,z=l i )=arg(P i ’(x,z=l i ))
in the method, in the process of the invention,φ i ’(x,z=l i ) Forward sound field distribution P for three focal planes i ’(x,z=l i ) Phase distribution, P i0 (x,z=l i ) Target sound field distribution for three focal planes, P i (x,z=l i ) The initial sound field distribution for the three focal planes of the next iteration loop.
S1.2.5) repeating the optimization iteration according to the steps S1.2.2-S1.2.4) until the iteration number reaches the set maximum iteration number or the phase distribution on z=0 converges, and ending the optimization iteration. The sound field distribution and its phase distribution on the sound lens plane with zero z=0 z axis obtained at the end of the iteration are taken as the final sound field distribution P (x, z=0) and its phase distribution on the sound lens plane with zero z=0 z axis.
S2) equally spacing the resulting sound field distribution P (x, z=0) in the acoustic lens planewSelecting the phase value of the g-th microstructure elementφ g Phase value phi of g-th microstructure unit g The relation with the thickness is:
P=e^(-jφ g )
φ g =k u h ug +k w h wg
h wg= H-h ug
wherein k is w 、k u The wave numbers of the filling liquid and the polymer material are respectively,φ g for the phase value of the g-th microstructure element, h ug Thickness of g-th microstructure unit, h wg The thickness of the liquid filling structure 43 is the thickness of the lower portion of the microstructure unit, and H is the thickness of the planar multi-focal acoustic lens 4.
S3) based on the cell spacing w=0.8 mm of the polymer structure 41 and the thickness h=3 mm of the planar multi-focal acoustic lens 4, the thickness H of each microstructure cell from inside to outside based on the axis can be obtained based on the phase distribution shown in fig. 5 (a) ug The method comprises the following steps of:
0.89mm、0.91mm、0.97mm、0.14mm、0.28mm、0.45mm、0.66mm、0.89mm、0.53mm、0.31mm、0.61mm、0.8mm、0.59mm、0.32mm、0.84mm、0.41mm、0.31mm、0.84mm、0.53mm、0.36mm、0.5mm、0.3mm、0.98mm、0.65mm。
it should be noted that the planar multi-focus acoustic lens for realizing axial multi-focus in the present embodiment has an axisymmetric structure, and thus the above parameter h ug The cylindrical focusing acoustic lens shown in (a) and (b) of fig. 1 can be prepared after rotation symmetry.
As shown in fig. 6 (a), when the planar multi-focal acoustic lens 4 of the above-described structural parameters is assembled with an ultrasonic transducer, the original plane wave sound field is modulated into a focused sound field of a plurality of focal points in the axial direction. It can be seen from fig. 7 (a) that focusing of the acoustic energy occurs at this point from the acoustic lenses 20 mm, 30 mm, 40 mm. And as shown in fig. 7 (b), the transverse dimensions of the focal sound field in the three planes are equal to about 0.8λ, which coincides with the target.
Example 2:
the flat type multi-focal acoustic lens apparatus in the present embodiment is used for the same plane multi-focal sound field. The size determining process of the present embodiment specifically includes the following steps:
first, preset parameters
The preset parameters of this embodiment are the same as those of the first embodiment.
Sizing of (two) plate-type multifocal acoustic lens 4
For the same plane multi-focus sound field, the coordinate values of each focus are (x 0 =x i ,y 0 =y i ) The sound field distribution of the object plane can thus be directly expressed as P (x, y, z=l) = Σp i (k x ,k y Z=0), which corresponds to iterative optimization using only one target planar sound field.
The steps of determining the size of the flat type multi-focal acoustic lens 4 in the present embodiment are specifically as follows:
s1) after a target sound field focal length and target sound field distribution are preset, taking the target sound field distribution as an initial sound field distribution, and obtaining the sound field distribution of a plane type multi-focus sound lens plane through iterative processing. In this process, the direction perpendicular to the upper and lower surfaces of the planar type multi-focal acoustic lens 4 is taken as the z direction, and the plane parallel to the upper and lower surfaces of the planar type multi-focal acoustic lens 4 is taken as the xoy plane.
S1.1) presetting a target sound field focal length and target sound field distribution
Target sound field focal length: the focal length of the target multi-focal plane is l=30mm；
The coordinates of the three focuses are (x) 1 ,y 1 )，(x 2 ,y 2 ) And (x) 3 ,y 3 )；
The lateral resolution of each of the three foci is σ=0.8λ.
Target sound field distribution: since the planar type multi-focal acoustic lens 4 for realizing the in-plane multi-focal sound field at this time is of an asymmetric structure, the focal coordinates at this time are set to (0, 0), (0, -9) and (0, 13) mm, respectively, for convenience of representation. At this time, the target sound field distribution P of the target focal plane 10 (x, y, z=l) is:
P 10 (x,y,z=l)=A(e^(-((x-x 1 ) 2 +(y-y 1 ) 2 )/σ 2 )+e^(-((x-x 2 ) 2 +(y-y 2 ) 2 )/σ 2 )+e^(-((x-x 3 ) 2 +(y-y 3 ) 2 )/σ 2 ))。
wherein x and y are respectively the space distribution coordinates perpendicular to the propagation direction of the sound wave, z is the coordinate axis of the propagation direction of the sound wave, A=1 is the maximum amplitude, and x 1 、x 2 、x 3 X-axis coordinates, y of three focuses respectively 1 、y 2 、y 3 Respectively are provided withThe y-axis coordinates of the three foci, σ is the lateral resolution of the foci, used to characterize the focus size.
S1.2) after a back propagation model and a forward propagation model are sequentially established according to the initial sound field distribution, repeatedly optimizing and iterating the sound fields on the z=0 and z=l planes according to the back and forward propagation models in sequence until the iteration number reaches the set maximum iteration number or the phase distribution on the z=0 converges, and finally obtaining the sound field distribution P (x, y, z=0) on the sound lens plane with the z axis of zero z=0. Wherein the forward propagation direction is a direction away from the acoustic lens and the reverse propagation direction is a direction from the far field to the acoustic lens. In this embodiment, the maximum number of iterations is set to 60. The phase distribution on the acoustic lens plane with zero z=0 in the z-axis is shown in fig. 5 (b).
The process of step S1.2) is specifically as follows:
s1.2.1) distributing the target sound field P 10 (x, y, z=l) as an initial sound field distribution P 1 (x,y,z=l i )。
S1.2.2) a spatial spectral distribution in the z=l plane is derived from the initial sound field distribution. The spatial spectral distribution on the z=l plane is:
P 1 (k x ,k y ,z=l)=∫P 1 (x,y,z=l)e^(-j(k x x+k y y))dxdy
wherein P is 1 (k x ,k y ,z=l)、P 1 (x, y, z=l) is the spatial spectral distribution and the sound field distribution in the z=l plane, k, respectively x Wavenumber in x-direction, k y The wave number in the y direction is l the focal length of the focal plane, x and y are the spatial distribution coordinates perpendicular to the propagation direction of the sound wave, j is imaginary and j 2 =-1。
S1.2.2) a back propagation model is constructed from the spatial spectral distribution in the z=l plane. The method comprises the following steps:
first, the spatial spectrum distribution P of the focal plane z=l 1 (k x ,k y Z=l) multiplied by a phase factor H (k x ,k y Z=l), a spatial spectral distribution P (k) is obtained that counter-propagates to the acoustic lens plane at zero z=0 in the z-axis x ,k y Z=0), then the sound field distribution P (x, y, z=0) and its phase distribution on the acoustic lens plane with zero z=0 z axis is obtained by inverse fourier transformφ(x, y, z=0). Wherein:
P(x,y,z=0)=∫∫P 1 (k x ,k y ,z=l)e^(-jl(k 0 2 -k x 2 -k y 2 ) 1/2 )e^(j(k x x+k y y))dk x dk y
φ(x,y,z=0)=arg(P(x,y,z=0))
wherein P is 1 (k x ,k y Z=l) is the spatial spectral distribution on focal plane z=l, P (x, y, z=0) is the sound field distribution on the acoustic lens plane with z axis zero z=0, phi (x, y, z=0) is the phase distribution on the acoustic lens plane with z axis zero z=0, k 0 The wave numbers of the sound field are excited for the ultrasonic transducer 1.
S1.2.3) a forward propagation model is constructed from the sound field distribution P (x, y, z=0) and the phase distribution phi (x, y, z=0) of the sound field on the acoustic lens plane at zero z=0. The method comprises the following steps:
first, the phase distribution of the sound field distribution in the sound lens plane with zero z=0 z axis is reserved, and the amplitude distribution of the sound field distribution in the sound lens plane with zero z=0 z axis is replaced by 1, so that the new sound field distribution in the plane type multi-focus sound lens 4 plane is obtained:
P’(x,y,z=0)=e^(jφ(x,y,z=0))
in the method, in the process of the invention,P’(x,y,z=0) is the new sound field distribution of the plane of the planar multi-focal acoustic lens 4,φ(x,y,z=0) is atzWith zero axiszPhase distribution of acoustic lens plane=0.
Then, the new sound field distribution of the plane type multi-focus acoustic lens 4 is performedP' forward propagation to focal plane (x, y, z=0)z=lObtaining a focal planez=lIs a forward sound field distribution P of (2) 1 ’(x,y,z=l)：
P 1 ’(x,y,z=l)=
∫∫(∫∫P’(x,y,z=0)×e^(-j(k x x+k x x))dxdy)×e^(jl(k 0 2 -k x 2 -k y 2 ) 1/2 )×e^(j(k x x+ k x x))dk x dk y
Wherein P is 1 'x, y, z=l is the forward sound field distribution of focal plane z=l, and P' (x, y, z=0) is the new sound field distribution of the plane of the planar multi-focal acoustic lens 4.
Likewise, the phase distribution φ of the forward sound field distribution preserving the focal plane z=l 1 ’(x,y,z=l)=arg(P 1 ' x, y, z=l), and replaces the amplitude with the target sound field distribution P of the focal plane 10 After (x, y, z=l), the new sound field distribution of the focal plane is taken as the initial sound field distribution P of the next iteration cycle 1 (x, y, z=l), i.e.:
P 1 (x,y,z=l)=P 10 (x,y,z=l)e^(jφ 1 ’(x,y,z=0))
wherein P is 1 (x, y, z=l) is the initial sound field distribution for the next iteration loop, P 10 (x, y, z=l) is the focal plane target sound field distribution, φ 1 ' where (x, y, z=l) is the phase distribution of the forward sound field distribution of focal plane z=l, j is an imaginary number and j 2 =-1。
S1.2.4) repeating optimization iteration of sound field distribution according to the steps S1.2.1-S1.2.3) until the iteration number reaches the set maximum iteration number or the phase distribution on z=0 converges, and ending the iteration. Taking the sound field distribution on the sound lens plane with the z axis of zero z=0 obtained at the end of iteration as the final sound field distribution Px,y,z=0)。
In this embodiment, about 60 iterations are performed, and finally, the sound field distribution P (x, y, z=0) on the acoustic lens plane with the z axis of zero z=0 is obtained, and the phase distribution thereof is shown in fig. 5 (b).
S2) selecting the phase value phi of the g-th microstructure element at equal intervals w for the sound field distribution P (x, y, z=0) on the obtained acoustic lens plane g Phase value of g-th microstructure unitφ g The relation with the thickness is:
P=e^(jφ g )
φ g =k u h ug +k w h wg
h wg= H-h ug
wherein k is w And k u Wavenumbers, phi, of filler fluid and polymer material, respectively g For the phase value of the g-th microstructure element, h ug Thickness of g-th microstructure unit, h wg The thickness of the liquid filling structure 43 is the thickness of the lower portion of the microstructure unit, and H is the thickness of the planar multi-focal acoustic lens 4.
S3) setting the Polymer Structure 41 Unit spacingwThe thicknesses h=0.8 mm and h=3 mm of the planar multi-focal acoustic lens 4, based on the phase distribution shown in (b) of fig. 5, can obtain the thicknesses H of the microstructure units of 50×50 pixels ug 。
It should be noted that the planar multifocal acoustic lens for achieving axial multifocal is of asymmetric structure, and thus the above parameter h ug It is necessary to confirm based on the phase value phi (x, y, z=0) at each pixel point.
As shown in fig. 7 (c), after the flat type multi-focal acoustic lens 4 prepared according to the above parameters is assembled with the ultrasonic transducer, the original plane wave sound field will be modulated to be a multi-focal sound field along the same plane. It can be seen from fig. 6 (b) that at this time, focusing of acoustic energy occurs at three points on a plane from the acoustic lens 30 mm, and coordinates of the three acoustic energy focusing points are (0, 0), (0, -9) and (0, 13) mm, respectively. And the transverse dimensions of the focal sound field in the three planes are approximately equal to 0.8λ, consistent with the target.
Example 3:
according to the steps, the number and the positions of focuses of any coplanar multifocal sound field can be preset. The preset focal plane l=30 mm has four focuses, which are respectively:
(-10, -5), (0, 10), (0, -15) and (13, 0) mm
As a result, as shown in fig. 7 (d), planar multi-focal acoustic holography can realize an arbitrary multi-focal sound field with a high degree of freedom.
As shown in fig. 8, when the planar multi-focus acoustic lens for medical diagnosis and treatment and the medical acoustic lens device are used for medical ultrasound diagnosis and treatment, the bottom surface of the acoustic lens device can be directly and perfectly attached to the superficial skin of a diagnosis and treatment object, and an ultrasound couplant is arranged between the bottom surface of the planar multi-focus acoustic lens and the superficial skin of the diagnosis and treatment object and used for ultrasound coupling in the diagnosis and treatment process.
In the diagnosis and treatment process, the acoustic lens can generate a multi-focus sound field under the body surface of a diagnosis and treatment object, and meanwhile, detection or treatment of a plurality of discrete target areas is realized, so that the efficiency of medical ultrasonic diagnosis and treatment is greatly improved.
In the foregoing embodiments, the descriptions of the embodiments are focused on, and for those portions of one embodiment that are not described in detail, reference may be made to the related descriptions of other embodiments.
The foregoing has described in detail the examples of the present application, wherein specific examples are employed to illustrate the principles and embodiments of the present invention, and the above examples are provided to assist in understanding the methods and core ideas of the present invention; meanwhile, as a person skilled in the art will have variations in the specific implementation method and application scope according to the idea of the present invention, the present disclosure should not be construed as limiting the present invention.
It should be noted that the above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and the switchable dual-function acoustic ultrasonic surface device based on the partition electrode provided by the present invention for realizing the focusing of acoustic energy and the bottle-shaped acoustic field not only can be used for the polymer ultrasonic surface mixed by the metal tungsten and the epoxy resin described by the present invention, but also can be replaced by any ultrasonic surface for focusing, so as to realize the dual functions of the focusing of acoustic energy and the bottle-shaped acoustic field by a single device.

Claims (10)

1. A planar multifocal acoustic lens for medical treatment, characterized in that:
the upper and lower surfaces of the planar multi-focus acoustic lens (4) are both planar;
the planar multi-focus acoustic lens (4) comprises a polymer structure (41), a side wall structure (42), a flat polymer structure (43) and a liquid filling structure (44);
the outer edge of the bottom surface of the polymer structure (41) is provided with annular protrusions serving as side wall structures (42), the bottom surfaces of the side wall structures (42) and the flat polymer structures (43) are closely arranged, so that a polymer cavity is formed between the bottom surfaces of the polymer structures (41) and the flat polymer structures (43) which are surrounded by the side wall structures (42), and a liquid filling structure (44) is formed after filling liquid into the polymer cavity; the top surface of the polymer structure (41) is a flat surface, the bottom surface is a concave-convex surface, the top surface and the bottom surface of the flat polymer structure (43) are both flat surfaces, and the flat surface of the polymer structure (41) is parallel to the flat surface of the flat polymer structure (43).
2. A planar multifocal acoustic lens for medical procedures as defined in claim 1, wherein: the polymer structure (41) is mainly formed by closely arranging and connecting a plurality of cuboid microstructure units along two orthogonal directions of a plane in an array manner, or is mainly formed by concentrically arranging and connecting a plurality of annular microstructure units along the radial direction from inside to outside in an array manner; the top surfaces of the microstructure units are in the same plane, and the thicknesses of the microstructure units are different, so that the concave-convex distribution of the bottom surfaces of the microstructure units forms a concave-convex surface of the polymer structure (41).
3. A planar multifocal acoustic lens for medical procedures as defined in claim 2, wherein:
the individual microstructure element thickness distribution in the polymer structure (41) is set in the following manner:
1) Presetting a plurality of target planes and only one focus on each target plane for a polymer structure (41), wherein the focuses on the target planes are in the same axial direction, and generating a target sound field according to all the set target planes and all the focuses;
2) With axial direction aszShaft to establishxyzCoordinate system, and set up xyzThe origin of the coordinate system is iteratively obtained as followsPPhase distribution of a phase detectorφ：
2.1 At a target sound field P of each target plane i0 Initial sound field distribution as each of the target planes;
2.2 Fourier transforming according to the sound field distribution to obtain the spatial spectrum distribution on the target plane according to the following mode:
P i (k x ,z=l i )=∫P i (x,z=l i )e^(jk x x)dx
in the method, in the process of the invention,P i (k x ,z=l i ) Is the firstiThe spatial spectral distribution over the individual object planes,P i (x,z=l i ) Is the firstiThe sound field distribution over the target planes is calculated, for the first time,k x is thatxThe wave number in the axial direction, ithe ordinal number representing the object plane,jis an imaginary number, d represents a calculus, e represents a natural constant, and a power;
2.3 Processing according to a back propagation model based on the spatial spectral distribution on each object plane to obtain the position in the object planezWith zero axiszSound field distribution on acoustic lens plane of =0 asP(x,z=0) and phase distribution thereofφ(x,z=0), specifically:
2.3.1 First, the spatial spectrum distribution of each target planeP i (k x ,z=l i ) Multiplying the phase factors H respectivelyk x ,z=l i ) Then, the spatial spectrum distribution of the sound field of each target plane back-propagating to the acoustic lens plane with zero z-axis is obtainedP i (k x ,z=0)：
P i (k x ,z=0)=P i (k x ,z=l i )*H(k x ,z=l i )
H(k x ,z=l i )=e^(-jl i (k 0 2 -k x 2 ) 1/2 )
k 0 =2πf/c
In the method, in the process of the invention,P i (k x ,z=0) is the firstiSound field back propagation to be at the target planezSpatial spectral distribution on an acoustic lens plane with zero axis H # k x ,z=l i ) As a phase factor of the sound field,l i is the firstiThe focal length corresponding to the respective object plane,k 0 wave numbers for exciting a sound field for the ultrasonic transducer (1),ffor the preset operating frequency to be a preset value, cis the sound velocity under the diagnosis and treatment object;
2.3.2 Then back-propagating the sound field for each target plane to be atzSpatial spectral distribution in an acoustic lens plane with zero axisP i (k x ,z=0) After the inverse Fourier transform is carried out, the sound field of each target plane is obtained and respectively positioned atzWith zero axiszSound field distribution of acoustic lens plane =0:
P i (x,z=0)=∫P i (k x ,z=0)e^(jk x x)dk x
in the method, in the process of the invention,P i (x,z=0) is the firstiThe sound fields of the target planes are respectively inzSound field distribution of an acoustic lens plane with zero axis;
2.3.3 Then, the sound fields for all target planes are respectively in the following formulaszSound field distribution for an acoustic lens plane with zero axisP i (k x ,zAfter fusion treatment, =0), the obtained product is inzSound field distribution on an acoustic lens plane with zero axisP(x,z=0) and phase distribution thereofφ(x,z=0)：
P(x,z=0)=P 1 (x,z=0)+P 2 (x,z=0)+…+P n (x,z=0)
φ(x,z=0)=arg(P(x,z=0))
Wherein arg () represents a phase distribution of sound pressure,nrepresenting the total number of target planes;
2.4 According to being atzWith zero axiszSound field distribution on acoustic lens plane =0P(x,z=0) and phase distribution thereofφ(x,z=0) processing according to the forward propagation model to obtain a signal at the target planez=lIs of the forward sound field distribution of (a)P 1 ’(x,z=l) The method specifically comprises the following steps:
2.4.1 First, remain inzSound field distribution on an acoustic lens plane with zero axisP(x,z=0) will be atzWith zero axiszAll magnitudes of the sound field distribution on the acoustic lens plane =0 are replaced with 1, resulting in a new sound field distribution on the top surface of the planar multifocal acoustic lens (4):
P’(x,z=0)=e^(jφ(x,z=0))
in the method, in the process of the invention,P’(x,z=0) is the new sound field distribution in the plane of the planar multifocal acoustic lens (4),φ(x,z=0) is atzWith zero axiszPhase distribution of sound field distribution on acoustic lens plane=0;
2.4.2 Then, the obtained new sound field distribution on the plane of the plane type multi-focus acoustic lens (4)P’(x,z=0) forward propagation to each target planez=l i And respectively obtaining the forward sound field distribution of each target plane:
P i ’(x,z=l i )=∫(∫P’(x,z=0)e^(-jk x x)dx)*e^(jl i (k 0 2 -k x 2 ) 1/2 )*e^(jk x x)dk x
in the method, in the process of the invention,P i ’(x,z=l i ) Is the firstiForward sound field distribution for each target plane;
2.4.3 Finally, the phase distribution of the forward sound field distribution of each target plane is kept unchanged, and the amplitude distribution of the forward sound field distribution of each target plane is respectively replaced by the target sound field corresponding to the respective target planeP i0 (x,z=l i ) Obtaining new sound field distribution of each target plane:
P i (x,z=l i )=P i0 (x,z=l i )e^(-jφ i ’(x,z=l i ))
φ i ’(x,z=l i )=arg(P i ’(x,z=l i ))
in the method, in the process of the invention,φ i ’(x,z=l i ) Is the firstiThe phase distribution of the forward sound field distribution of the individual object planes,P i0 (x,z=l i ) Is the firstiThe target sound field distribution of the individual target planes, P i (x,z=l i ) Is the firstiNew sound field distribution for each target plane;
2.5 (2.4) distributing the new sound field of each target plane obtained in the step 2)P i (x,z=l i ) Returning to step 2.2) processing as sound field distribution of each target plane of the next iteration loop, according toStep 2.2) to 2.4) continuously and repeatedly carrying out optimization iteration processing of sound field distribution, and when the iteration is finished, carrying out the last iteration in the step 2.3)zThe sound field distribution on the acoustic lens plane with zero axis isP(x,z=0) as final sound field distributionPAnd its phase distribution;
3) From the sound field distribution obtained beforePIs of the phase distribution of (a)φThe thickness of the individual microstructure units in the polymer structure (41) of the planar multi-focus acoustic lens (4) is obtained in combination with the thickness of the planar multi-focus acoustic lens (4) by:
φ g =k u h ug +k w h wg
H=h ug+ h wg
in the method, in the process of the invention,k u is the wavenumber of the polymer structure (41),k w the wave number for the liquid filled structure (44),φ g is a phase distributionφMiddle (f)gThe phase value of the individual microstructure elements,h ug is the firstgThe thickness of the individual microstructure elements, h wg is the firstgThe thickness of the filling liquid corresponding to each microstructure unit is H, and the thickness of the planar multi-focus acoustic lens (4).
4. A planar multifocal acoustic lens for medical procedures as defined in claim 2, wherein:
The individual microstructure element thickness distribution in the polymer structure (41) is set in the following manner:
1) Presetting only one target plane and a plurality of focuses on the target plane aiming at a polymer structure (41), and generating a target sound field according to the set target plane and all focuses;
2) Set up with the axial direction as the z-axisxyzCoordinate system, and set upxyzThe origin of the coordinate system is iteratively obtained as followsPPhase distribution of a phase detectorφ：
2.1 Taking the target sound field as an initial sound field distribution;
2.2 Fourier transforming according to the sound field distribution to obtain the spatial spectrum distribution on the target plane according to the following mode:
P 1 (k x ,k y ,z=l)=∫∫P 1 (x,y,z=l)e^(-j(k x x+k y y))dxdy
in the method, in the process of the invention,P 1 (k x ,k y ,z=l)、P 1 (x,y,z=l) The spatial spectrum distribution and the sound field distribution on the target plane are respectively,k x is thatxThe wave number in the axial direction,k y is thatyThe wave number in the axial direction,lfor the focal length corresponding to the target plane,x、ythe spatially distributed coordinates of the perpendicular acoustic wave propagation direction,jis an imaginary number, d represents a calculus, e represents a natural constant, and a power;
2.3 Processing according to a back propagation model based on the spatial spectral distribution on the target plane to obtain the positionzThe sound field distribution on the acoustic lens plane with axis zero z=0 isP(x,y,z=0) and phase distribution thereofφ(x,y,z=0), specifically:
First, the spatial spectrum distribution of the target planeP 1 (k x ,k y ,z=l) Multiplying by a phase factor Hk x ,k y ,z=l) Back-propagated to be atzSpatial spectral distribution of an acoustic lens plane with zero axisP(k x ,k y ,z=0), followed by an inverse fourier transform to obtain the phase-shift signalzSound field distribution on an acoustic lens plane with zero axisP(x,y,z=0) and phase distribution thereofφ(x,y,z=0)：
P(k x ,k y ,z=0)=P 1 (k x ,k y ,z=l)×H(k x ,k y ,z=l)
H(k x ,k y ,z=l)=e^(-jl(k 0 2 -k x 2 -k y 2 ) 1/2 )
P(x,y,z=0)=∫∫P(k x ,k y ,z=0)e^(j(k x x+k y y))dk x dk y
φ(x,y,z=0)=arg(P(x,y,z=0))
k 0 =2πf/c
In the method, in the process of the invention,P(k x ,k y ,z=0) is counter-propagating to atzWith zero axiszSpatial spectral distribution on acoustic lens plane =0,P(x,y,z=0) is atzSound field distribution on an acoustic lens plane with zero axis,φ(x,y,z=0) is atzThe phase distribution of the sound field distribution on the acoustic lens plane with zero axis,k 0 wave numbers for exciting the sound field for the ultrasonic transducer (1); h (k) x ,k y Z=l) represents a phase factor, arg represents a phase distribution;cas the sound velocity of the subject to be diagnosed,fthe working frequency is preset, namely the working frequency of the incident wave;
2.4 According to the sound field distribution in the acoustic lens plane with zero z-axisP(x,y,z=0) and phase distribution thereofφ(x,y,z=0) processing according to the forward propagation model to obtain a signal at the target planez=lIs of the forward sound field distribution of (a)P 1 ’(x,y,z=l) The method specifically comprises the following steps:
2.4.1 First, remain inzPhase distribution of sound field distribution on an acoustic lens plane with zero axisφ(x,y,z=0), will be atzAll of the sound field distributions on an acoustic lens plane with zero axis The amplitude values are replaced by 1, and then a new sound field distribution on the top surface of the planar multi-focus acoustic lens (4) is obtainedP’(x,y,z=0)：
P’(x,y,z=0)=e^(jφ(x,y,z=0))
2.4.2 Then, the new sound field distribution of the plane type multi-focus acoustic lens (4)P’(x,y,z=0) forward propagation to the target planez=lObtaining the forward sound field distribution in the target planeP 1 ’(x,y,z=l) Phase distribution of a phase detectorφ 1 ’(x,y,z=l)：
P 1 ’(x,y,z=l)=∫∫(∫∫P’(x,y,z=0)e^(-j(k x x+k y y))dxdy)e^(jl(k 0 2 -k x 2- k y 2 ) 1/2 )e^(j(k x x+k y y))dk x dk y
φ 1 ’(x,y,z=l)=arg(P 1 ’(x,y,z=l))
2.4.3 Then, the phase distribution phi of the forward sound field distribution at the target plane is preserved 1 ' x, y, z=l, and replaces the amplitude distribution in the forward sound field distribution at the target plane z=l with the target sound field corresponding to the target planeP i0 (x,z=l i ) After the amplitude distribution in (3), a new sound field distribution P of the target plane is obtained 1 (x, y, z=l) and phase distribution thereofφ 1 (x, y, z=l), specifically expressed as:
P 1 (x,y,z=l)=P 10 (x,y,z=l)e^(jφ 1 ’(x,y,z=0))
φ 1 (x,y,z=l)=arg(P 1 (x,y,z=l))
wherein P is 1 (x, y, z=l) new sound field distribution for target plane, P 10 (x, y, z=l) as the target planeA target sound field distribution;
2.5 (2.4) the new sound field distribution P of the target plane obtained in the step 2) 1 (x, y, z=l) returning to the process of step 2.2) as the sound field distribution of the next iteration cycle, and continuously repeating the optimized iteration process of the sound field distribution according to the steps 2.2) to 2.4), wherein the last iteration is obtained in the step 2.3) at the end of the iterationzWith zero axiszSound field distribution on acoustic lens plane of =0 as P(x,y,z=0) as final sound field distributionP；
3) From the sound field distribution obtained beforePIs of the phase distribution of (a)φThe thickness of the individual microstructure units in the polymer structure (41) of the planar multi-focus acoustic lens (4) is obtained in combination with the thickness of the planar multi-focus acoustic lens (4) by:
φ g =k u h ug +k w h wg
H=h ug+ h wg
in the method, in the process of the invention,k u is the wavenumber of the polymer structure (41),k w the wave number for the liquid filled structure (44),φ g is a phase distributionφThe phase value of the g-th microstructure element,h ug for the thickness of the g-th microstructure element, h wg the thickness of the filling liquid corresponding to the g-th microstructure unit is H, and the thickness of the planar multi-focus acoustic lens (4).
5. A planar multifocal acoustic lens for medical procedures as defined in claim 1, wherein: the side wall structure (42) is provided with a through hole as a liquid filling small hole (45), and the liquid filling small hole (45) is used for inflow/outflow of the filling liquid.
6. A planar multifocal acoustic lens for medical procedures as defined in claim 1, wherein: the polymer structure (41), the flat polymer structure (43) and the side wall surface structure (42) are all made of the same polymer material, and the polymer material is an epoxy-based metal polymer material; the filling liquid is ethanol-glycerol mixed solution.
7. A planar multi-focal acoustic lens apparatus comprising a planar multi-focal acoustic lens as claimed in any of claims 1-6, characterized in that: the planar multi-focus acoustic lens device is used for moving on the surface skin to realize scanning, and comprises a double-opening flange structure (2), an ultrasonic transducer (1) and a planar multi-focus acoustic lens (4); the double-opening flange structure (2) is provided with a cavity, openings are formed in the upper end and the lower end of the double-opening flange structure, an ultrasonic transducer (1) is detachably arranged on the upper part of the cavity, and the lower end of the ultrasonic transducer (1) stretches into the cavity; the lower part of the cavity is provided with a stepped groove, a planar multi-focus acoustic lens (4) is embedded in the stepped groove, the top surface of the planar multi-focus acoustic lens (4) is contacted with the lower end surface of the ultrasonic transducer (1), and the bottom surface of the planar multi-focus acoustic lens (4) is contacted with the surface skin of a diagnosis and treatment object.
8. A planar multi-focal acoustic lens assembly as claimed in claim 7, wherein:
the ultrasonic transducer (1) emits ultrasonic waves to the planar multi-focus acoustic lens (4) along the axial direction as incident waves, the incident waves are incident on the polymer structure (41), and the incident waves are emitted to the superficial skin after passing through the polymer structure (41), the liquid filling structure (44) and the planar polymer structure (43) in sequence and focused on at least one target plane to form a target sound field.
9. A planar multi-focal acoustic lens assembly as claimed in claim 7, wherein: the interface between the ultrasonic transducer (1) and the planar multi-focus acoustic lens (4) is provided with a water layer, and the water layer is used for wetting and coupling the interface between the ultrasonic transducer (1) and the planar multi-focus acoustic lens (4).
10. A planar multi-focal acoustic lens apparatus as claimed in claim 9, wherein:
the annular groove is formed in the position, corresponding to the water layer, on the side wall of the stepped groove, two axial holes are formed in the upper surface of the opening flange structure (2) and serve as a water inlet and a water outlet respectively, and the two holes are communicated with the annular groove.
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