High-resolution ultrasonic imaging system in scattering medium based on diffraction acoustic gratings and applications thereof

Abstract

The application provides a high-resolution ultrasonic imaging system in scattering medium based on a diffraction acoustic grating and an application thereof, wherein a plane wave emitted by an ultrasonic transducer is converted into a diffraction illumination mode plane wave by a diffraction acoustic grating device, evanescent waves carrying subwavelength information of an imaging object are transmitted to a far field, and the subwavelength information of the imaging object is reconstructed based on amplitude information collected by the diffraction illumination through a high-resolution ultrasonic reconstruction algorithm. The application can improve the resolution of ultrasonic imaging in a scattering medium, and reduce the complexity of the ultrasonic imaging system and operation complexity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of biomedical ultrasound imaging, and particularly relates to a high-resolution ultrasound imaging system in scattering medium based on diffraction acoustic grating and application thereof. BACKGROUND

[0002] Ultrasound imaging has a wide range of applications in medical diagnosis and industrial detection. However, due to the existence of diffraction limit, the imaging depth and imaging resolution of ultrasound imaging are greatly limited. At the same time, due to the complexity of biological tissues faced by ultrasound imaging, it is also a challenging work to image the objects behind the complex medium or unwanted obstacles. Therefore, it is crucial to realize the collection and reconstruction of sub-wavelength information carried by evanescent waves disturbed by complex medium with simple operation.

[0003] However, in traditional ultrasound imaging, in order to improve the imaging resolution, it is generally necessary to rely on phased array for active wavefront adjustment. For example, plane wave imaging or focused imaging method relying on beam forming and synthetic aperture method, they all need a large number of channels for wavefront control; the lens based on acoustic metamaterial has a large thermal viscosity loss, which makes the acoustic transmission rate very low; the method of using superlens structure to convert evanescent wave component into propagating wave can reduce the thermal viscosity loss, but it needs to sacrifice the field of view.

[0004] In addition, the design of underwater ultrasonic frequency band superlens is difficult to realize due to the complexity of physical problems and preparation difficulties. The transmitted signal is acoustic wave information, and evanescent wave carries sub-wavelength information of the imaging object required for imaging. However, evanescent wave is a component that can only propagate along the surface of the object and the amplitude decays exponentially in the vertical interface direction, so it is difficult to capture evanescent wave in the far field, that is, a certain distance away from the imaging object. The method based on time reversal technology can convert evanescent wave into propagating wave by using random sub-wavelength scattering array, but it needs to be operated in the near field of the object, which limits its application scenario to some extent.

[0005] In optics, there has been significant development in the method of using scattered light to image objects in complex media, but for unknown transmission matrix, the wavefront shaping method needs complex optical system design; relying on photoacoustic imaging can use the random optical speckle pattern generated by strongly scattering medium for super-resolution imaging, but photoacoustic imaging devices usually have high complexity and manufacturing cost, which limits the popularization and popularization of the device to a certain extent.

[0006] Patent No. CN201711232982.7 discloses a kind of based on SOFI's ultrahigh resolution plane wave ultrasonic imaging method: under the intervention of ultrasonic contrast agent (microbubble), ultrasonic plane wave imaging is carried out to imaging object, obtains a group of plane wave ultrasonic images at different time;Filtering operation is carried out to all the plane wave ultrasonic images obtained, to remove the noise contained in plane wave ultrasonic image;Based on the ultrasonic plane wave data of imaging region only containing single microbubble, the lateral standard deviation δx and longitudinal standard deviation δy are calculated by measuring lateral half width FHWMx and longitudinal half width FHWMy, generate point spread distribution model;Finally, with the filtered dynamic ultrasonic plane wave image as input data, the SOFI image of second order (or high order) balanced is calculated.The method not only can greatly improve the spatial resolution of ultrasonic plane wave imaging, but also can improve the time resolution of ultrasonic imaging, suitable for fast ultrahigh resolution ultrasonic imaging.

[0007] Patent No. CN201811287534.1 relates to a total variation regularization constrained ultrasonic imaging synchronous algebraic iterative reconstruction method, which is used for ultrasonic tomography and includes: obtaining projection attenuation measurement values required for reconstruction;Constructing a coefficient matrix, considering the proportion of overlapping area of projection path and field pixel and the geometric position of overlapping area relative to field pixel;Using synchronous algebraic reconstruction method for imaging preprocessing;Building regularization weighted least square method framework and taking total variation regularization as regularization term, taking synchronous algebraic iterative reconstruction method as algebraic term, and carrying out inverse problem iterative reconstruction calculation;Iterate until residual error meets the requirement.

[0008] The present inventors are inspired by the super-resolution photoacoustic microscopy using blind structured illumination (Super-Resolution Photoacoustic Microscopy Using Blind Structured Illumination, Optica 4, 17 (2017), T. W. Murray, M. Haltmeier, T. Berer, E. Leiss-Holzinger, and P. Burgholzer.) which applies the blind-SIM algorithm (structured illumination blind deconvolution algorithm), the structured illumination microscopy using unknown speckle patterns (Structured Illumination Microscopy Using Unknown Speckle Patterns, Nature Photon 6, 312 (2012), E. Mudry, K. Belkebir, J. Girard, J. Savatier, E. Le Moal, C. Nicoletti, M. Allain, and A. Sentenac.) and the l 2,1 Inspired by the block-sparse analysis regularization of ill-posed problems via L2,1-minimization (Block-Sparse Analysis Regularization of Ill-Posed Problems via L2,1-Minimization, in 2013 18th International Conference on Methods & Models in Automation & Robotics (MMAR) (2013), pp. 520-523, M. Haltmeier.), the present application proposes a high-resolution ultrasonic imaging system in scattering medium based on diffraction acoustic grating, which can improve the resolution of ultrasonic imaging in complex medium while reducing the complexity of the ultrasonic imaging system. SUMMARY

[0009] To solve the above problems, the purpose of the present application is to provide a high-resolution ultrasonic imaging system in scattering medium based on diffraction acoustic grating, which can improve the resolution of ultrasonic imaging in complex medium while reducing the complexity of the ultrasonic imaging system.

[0010] Still another purpose of the present application is to provide the application of the high-resolution ultrasonic imaging system in scattering medium based on diffraction acoustic grating.

[0011] In order to achieve the above object, the application provides a high-resolution ultrasonic imaging system in scattering medium based on diffraction acoustic grating, which comprises an imaging object and an information collection device, and a large-size scattering body / obstacle and / or randomly distributed scattering medium exist in the ultrasonic wave propagation path between the imaging object and the information collection device, and further comprises an ultrasonic transducer and a diffraction illumination modulation module, the ultrasonic transducer can emit a plane wave, and the diffraction illumination modulation module comprises a diffraction acoustic grating device; wherein the ultrasonic transducer, the diffraction acoustic grating device, the imaging object and the information collection device are sequentially arranged along the plane wave propagation direction, the diffraction acoustic grating device can only move forward and backward along the plane wave propagation direction and modulate the plane wave, the modulated plane wave is converted into a plane wave in diffraction illumination mode, and the plane wave in diffraction illumination mode generates an evanescent wave carrying subwavelength information of the imaging object after passing through the imaging object, and meanwhile the information collection device captures corresponding ultrasonic signals.

[0012] Different diffraction illumination modes are obtained by moving the position of the diffraction acoustic grating device, so that ultrasonic signals carrying subwavelength information of the imaging object with different frequencies are obtained, the evanescent wave carrying subwavelength information of the imaging object is convolved, and the evanescent wave is converted into a propagating wave, so that the capture of far-field subwavelength information is realized.

[0013] Preferably, the single displacement distance and the maximum displacement distance of the diffraction acoustic grating device are determined based on the subwavelength size and distribution of the imaging object.

[0014] The moving interval of the diffraction acoustic grating device is controlled to realize the propagation control and optimization of detailed information.

[0015] Preferably, the diffraction illumination modulation module further comprises an acoustic grating displacement platform, the diffraction acoustic grating device is fixed on the acoustic grating displacement platform, and the diffraction acoustic grating device is controlled to move forward and backward along the plane wave propagation direction and modulate the plane wave by the acoustic grating displacement platform.

[0016] Preferably, the ultrasonic transducer emits a horizontal plane wave, the ultrasonic transducer, the diffraction acoustic grating device, the imaging object and the information collection device are sequentially arranged along the horizontal direction, and the diffraction acoustic grating device is vertically fixed on the acoustic grating displacement platform by a support.

[0017] The application further provides an application of the high-resolution ultrasonic imaging system in scattering medium based on diffraction acoustic grating.

[0018] The application provides a high-resolution ultrasonic imaging method based on the high-resolution ultrasonic imaging system of a scattering medium based on a diffraction acoustic grating, wherein the diffraction acoustic grating device converts a plane wave into a plane wave of different diffraction illumination modes at M random different positions, the generated evanescent wave carrying subwavelength information of an imaging object is convolved into a propagating wave, and the collected ultrasonic signal is a convolution of a point spread function (PSF) of the ultrasonic imaging system, a product of an illumination pattern and the imaging object, and is expressed by a formula as follows:

[0019] , …, M, (1)

[0020] In the formula (1), s m (x) represents a corresponding acoustic pressure amplitude value obtained by performing Fourier transform on an ultrasonic signal, h(x) represents a point spread function of the system, p m (x) represents a product of the illumination pattern i m (x) and the imaging object o(x), represents noise existing in the ultrasonic imaging system;

[0021] The product p m (x) of the illumination pattern i m (x) and the imaging object o(x) has joint sparsity, and the average energy density of the imaging object is uniform, subwavelength resolution of the imaging object is recovered from M diffraction illuminations by using a high-resolution ultrasonic imaging reconstruction algorithm, transmission intensity distribution information of the imaging object is obtained, and subwavelength information of the imaging object is reconstructed.

[0022] On the basis of high-resolution ultrasonic imaging, when there are large-size scattering bodies or obstacles and randomly distributed scattering media in a propagation path, high-resolution subwavelength information of the imaging object can be reconstructed based on disturbed signal distribution by using the high-resolution ultrasonic imaging reconstruction algorithm, and the application scene of the imaging method is expanded.

[0023] Preferably, a minimization equation of the high-resolution ultrasonic imaging reconstruction algorithm is as follows:

[0024] , (2)

[0025] In the formula (2), x i is a discrete coordinate in measurement, and a joint sparse term in the high-resolution ultrasonic imaging reconstruction algorithm is as follows:

[0026] l 2,1 -norm and

[0027] l 2 -norm Composition, wherein and is a regularization parameter that can be tuned within the algorithmic framework to optimize performance.

[0028] Based on the high-resolution ultrasound imaging reconstruction algorithm, the intensity information of the imaging object is iteratively optimized according to the objective function and the constraint condition based on the far-field amplitude information obtained under the diffraction illumination, and then the transmission intensity distribution information of the imaging object is inverted.

[0029] When there are large-size scatterers or obstacles in the propagation path that are not desired, and randomly distributed scattering media, the high-resolution ultrasound imaging reconstruction algorithm can reconstruct the high-resolution subwavelength information of the imaging object based on the disturbed signal distribution.

[0030] Preferably, the single displacement distance of the diffraction acoustic grating device is determined based on the detail scale required by the high-resolution ultrasound imaging reconstruction algorithm.

[0031] Based on the high-resolution ultrasound imaging reconstruction algorithm, the propagation control and optimization of the detail information are further realized.

[0032] The beneficial effects of the present application are:

[0033] 1. By constructing multiple different diffraction illumination modes, the evanescent wave carrying subwavelength information of the object can be converted into propagating waves, which can effectively reduce the difficulty of capturing subwavelength information of the imaging object, and further improve the imaging resolution.

[0034] 2. By simply moving the position of the diffraction acoustic grating device to obtain different diffraction illumination modes, different frequencies of ultrasonic signals carrying subwavelength information of the imaging object are obtained, which not only improves the resolution of ultrasonic imaging, but also reduces the complexity and operation difficulty of the high-resolution ultrasonic imaging system.

[0035] 3. On the basis of high-resolution ultrasonic imaging, when there are large-size scatterers or obstacles in the propagation path that are not desired, and randomly distributed scattering media, the high-resolution ultrasound imaging reconstruction algorithm can reconstruct the high-resolution subwavelength information of the imaging object based on the disturbed signal distribution, thereby expanding the application scenarios of the imaging method. BRIEF DESCRIPTION OF DRAWINGS

[0036] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings, in which:

[0037] Figure 1 is a schematic structural diagram of the high-resolution ultrasonic imaging system of the present application;

[0038] Figure 2 is an assembly diagram of the high-resolution ultrasonic imaging system of the first embodiment of the present application; is an assembly diagram of the high-resolution ultrasonic imaging system of the first embodiment of the present application;

[0039] Figure 3 This is a schematic diagram of the diffraction grating device and the imaging object according to Embodiment 1 of the present invention.

[0040] Figure 4 The ultrasound imaging reconstruction results, showing the comparison between images with and without diffraction chord illumination, demonstrate the correlation between different slit gaps Wi and mean square error MSE. This indicates that images with diffraction chord illumination can be reconstructed using high-resolution ultrasound imaging.

[0041] Figure 5 This is a diagram showing the ultrasound imaging reconstruction result of Embodiment 2 of the present invention. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0043] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0044] Example 1

[0045] like Figure 1 and Figure 2 As shown, this embodiment provides a high-resolution ultrasonic imaging system in a scattering medium based on a diffraction grating. The entire system is located in underwater free space and includes four imaging objects with different slit spacing w1 and a hydrophone as an information acquisition device. It also includes an ultrasonic transducer and a diffraction illumination modulation module. The ultrasonic transducer can emit horizontal plane waves. The diffraction illumination modulation module includes a diffraction grating device and a grating displacement platform. The diffraction grating device is vertically fixed on the grating displacement platform by a bracket. The ultrasonic transducer, diffraction grating device, imaging object, and information acquisition device are arranged sequentially along the plane wave propagation direction. The grating displacement platform controls the diffraction grating device to move forward and backward and modulate the plane wave only along the plane wave propagation direction. The modulated plane wave is converted into a plane wave of diffraction illumination mode. After the plane wave of diffraction illumination mode passes through the imaging object, it generates an evanescent wave carrying subwavelength information of the imaging object. At the same time, the information acquisition device captures the corresponding ultrasonic signal.

[0046] In this embodiment, the single displacement distance and the maximum displacement distance of the diffraction acoustic grating device are determined based on the sub-wavelength size and distribution of the imaging object and the detail scale required by the high-resolution ultrasonic imaging reconstruction algorithm.

[0047] As shown in Figure 3 and Figure 4 , according to the high-resolution ultrasonic imaging method of the diffraction acoustic grating-based high-resolution ultrasonic imaging system of the scattering medium, the slit interval Wi is 0.2λ, 0.3λ, 0.4λ, 0.5λ, respectively, wherein the diffraction acoustic grating device converts the plane wave into a plane wave of different diffraction illumination modes at M random different positions, the generated evanescent wave carrying sub-wavelength information of the imaging object is convolved into a propagating wave, and the ultrasonic signal collected at this time is the convolution of the point spread function (PSF) of the ultrasonic imaging system, the illumination pattern and the imaging object, which is expressed as:

[0048] , …, M,

[0049] wherein s m (x) represents the corresponding sound pressure amplitude obtained by Fourier transforming the ultrasonic signal, h(x) represents the point spread function of the system, p m (x) represents the product of the illumination pattern i m (x) and the imaging object o(x), represents the noise existing in the ultrasonic imaging system;

[0050] The product p m (x) of the illumination pattern i m (x) and the imaging object o(x) has joint sparsity, and the average energy density of the imaging object is uniform, the sub-wavelength resolution of the imaging object is recovered from M diffraction illuminations using a high-resolution ultrasonic imaging reconstruction algorithm, the transmission intensity distribution information of the imaging object is obtained, and the sub-wavelength information of the imaging object is reconstructed, and the minimization equation of the high-resolution ultrasonic imaging reconstruction algorithm is:

[0051] ,

[0052] wherein, x i is the discrete coordinate in the measurement, and the joint sparse term in the high-resolution ultrasonic imaging reconstruction algorithm is composed of:

[0053] l 2,1 -norm and

[0054] l 2 -norm ​​The regularization parameter is adjustable in the algorithm framework to optimize performance.

[0055] As shown in Figure 4 The correlation between different slit gaps Wi and mean square error MSE is embodied, that is, the diffraction acoustic grating illumination image can be used for high-resolution ultrasonic reconstruction imaging of the imaging object.

[0056] The embodiment verifies that the application can realize high-resolution ultrasonic reconstruction imaging of the imaging object by simply moving the diffraction acoustic grating device.

[0057] Embodiment two

[0058] As shown in Figure 5 The embodiment provides a high-resolution ultrasonic imaging system in a scattering medium based on a diffraction acoustic grating, the entire system is located in an underwater free space, and three different scattering media exist in an ultrasonic wave propagation path between the imaging object and the information collection device, and other structures and methods are the same as those in embodiment one.

[0059] The slit intervals are 0.3 lambda, 0.4 lambda and 0.5 lambda respectively, and the far-field sound pressure amplitude is compared between the no acoustic grating illumination and the acoustic grating illumination of the application, as shown by i, h and g in Figure 5 .

[0060] The embodiment verifies that on the basis of high-resolution ultrasonic imaging, when a large-size scattering body or obstacle that is not expected to exist in the propagation path and a complex condition of randomly distributed scattering media, high-resolution ultrasonic reconstruction imaging of the imaging object can be realized based on the disturbed signal distribution through a high-resolution ultrasonic imaging reconstruction algorithm.

[0061] The embodiments of the application are described in detail above in combination with the drawings, but the application is not limited to the above-described embodiments. Even if various changes are made to the application, if the changes belong to the scope of the claims of the application and equivalent technologies, they still fall within the protection scope of the application.

Claims

1. A high-resolution ultrasonic imaging system in a scattering medium based on a diffractive acoustic grating, comprising an imaging object and an information acquisition device, between which there are large-size scatterers / barriers and / or randomly distributed scattering media in the ultrasonic wave propagation path, characterized in that: The device further comprises an ultrasonic transducer and a diffraction illumination modulation module, the ultrasonic transducer is capable of emitting a plane wave; the diffraction illumination modulation module comprises a diffraction acoustic grating device; wherein the ultrasonic transducer, the diffraction acoustic grating device, the imaging object and the information acquisition device are sequentially arranged along the direction of the plane wave propagation, the diffraction acoustic grating device is capable of moving forward and backward along the direction of the plane wave propagation and modulating the plane wave, the modulated plane wave is converted into a plane wave of a diffraction illumination mode, and the plane wave of the diffraction illumination mode generates evanescent waves carrying subwavelength information of the imaging object after passing through the imaging object, while the information acquisition device captures corresponding ultrasonic signals.

2. The high-resolution ultrasonic imaging system in scattering media based on diffractive acoustic lattices of claim 1, wherein: The single displacement distance and the maximum displacement distance of the diffraction acoustic grating device are determined based on the subwavelength size and distribution of the imaging object.

3. The high-resolution ultrasonic imaging system in scattering media based on diffractive acoustic lattices of claim 2, wherein: The diffraction illumination modulation module further comprises an acoustic grating displacement platform, the diffraction acoustic grating device is fixed on the acoustic grating displacement platform, and the diffraction acoustic grating device is controlled to move forward and backward along the direction of the plane wave propagation and modulate the plane wave through the acoustic grating displacement platform.

4. The high-resolution ultrasonic imaging system in scattering media based on diffractive acoustic lattices of claim 3, wherein: The ultrasonic transducer emits a horizontal plane wave, the ultrasonic transducer, the diffraction acoustic grating device, the imaging object and the information acquisition device are sequentially arranged along the horizontal direction, and the diffraction acoustic grating device is vertically fixed on the acoustic grating displacement platform through a support.

5. A high-resolution ultrasound imaging method of a high-resolution ultrasound imaging system based on a diffractive acoustic grating-based scattering medium according to any one of claims 1-4, characterized in that: The diffraction acoustic grating device converts the plane wave into plane waves of different diffraction illumination modes at M random different positions, the generated evanescent waves carrying subwavelength information of the imaging object are convolved into propagating waves, at this time, the acquired ultrasonic signals are the convolution of the point spread function (PSF) of the ultrasonic imaging system, the illumination pattern and the imaging object, and the formula is expressed as: ， where s m (x) represents the corresponding sound pressure amplitude obtained by Fourier transforming the ultrasound signal, h(x) represents the point spread function of the system, p m (x) represents the product of the illumination pattern i m (x) and the imaged object o(x), and ε represents the noise present in the ultrasound imaging system; wherein illumination pattern i m (x) the product p of the imaging object o(x) m (x) has joint sparsity, and the average energy density of the imaging object is uniform, using a high-resolution ultrasound imaging reconstruction algorithm to recover sub-wavelength resolution of the imaging object from M diffraction illuminations, obtaining the transmission intensity distribution information of the imaging object, and reconstructing the sub-wavelength information of the imaging object.

6. A high-resolution ultrasound imaging method of a high-resolution ultrasound imaging system based on a diffractive acoustic grating-based scattering medium according to claim 5, characterized in that: The minimization equation of the high-resolution ultrasonic imaging reconstruction algorithm is: ， wherein x i are the discrete coordinates in the measurement, the joint sparsity term in the high-resolution ultrasound imaging reconstruction algorithm is given by: and comprise, wherein and are regularization parameters that are tunable within the algorithmic framework to optimize performance.

7. The high-resolution ultrasound imaging method of claim 5 or 6, characterized in that: The single displacement distance of the diffraction acoustic grating device is determined based on the required detail scale of the high-resolution ultrasonic imaging reconstruction algorithm.

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