A fast simulation method for large-scale three-dimensional ultrasound array data

Abstract

The present invention belongs to the field of ultrasonic imaging, and specifically relates to a method for rapid simulation of large-scale three-dimensional ultrasonic array data, including: step 1, geometric modeling of ultrasonic imaging system; step 2, ultrasonic wave propagation path simulation; step 3, array element directivity modeling; step 4, calculating path propagation time and path propagation attenuation; step 5, constructing path transfer function, and generating ultrasonic array simulation data. Compared with conventional numerical simulation methods, the present invention consumes less computer hardware resources, has the advantages of fast calculation speed and strong versatility, and can be quickly applied to data simulation of large-scale ultrasonic arrays such as annular or spherical.

Description

Technical Field

[0001] The invention belongs to the field of ultrasonic imaging, and in particular relates to a large-scale three-dimensional ultrasonic array data rapid simulation method. Background Art

[0002] The 3D ultrasound array simulation data simulation technology can greatly improve the efficiency of the 3D ultrasound imaging system design and imaging algorithm development. The simulation data obtained through array simulation is an important basis for the optimization of ultrasound imaging system design.

[0003] For large-scale ultrasonic imaging equipment such as Ultrasound Computed Tomography (USCT), the number of sensor array elements is as high as 2304, and the three-dimensional imaging space is large. The conventional k-Wave or other finite element numerical simulation methods consume a lot of computing resources. Ordinary computers and even high-performance servers cannot perform full-scale simulation calculations of the array elements. Even if simulation calculations can be performed, the simulation time is as long as several days or even more than ten days, which cannot be applied in actual engineering simulations. Summary of the invention

[0004] In order to solve the problem of limited hardware resources in large-scale ultrasonic array simulation calculations, the present invention proposes a simulation method for quickly generating three-dimensional ultrasonic array data based on the idea of ​​ray tracing. The method is based on the simulation of the propagation path of ultrasonic waves, considers the directivity of the transmitting and receiving points, calculates the propagation time and attenuation of all paths, and uses them as the offset and signal strength to obtain the transfer function of the path, and finally constructs the array receiving signal after propagation through the medium.

[0005] A large-scale three-dimensional ultrasound array data rapid simulation method, comprising:

[0006] Step 1, geometric modeling of the ultrasound imaging system;

[0007] Step 2, simulating the ultrasonic wave propagation path;

[0008] Step 3, modeling the array element directivity;

[0009] Step 4, calculate the path propagation time and path propagation attenuation;

[0010] Step 5: construct a path transfer function and generate ultrasound array simulation data.

[0011] Furthermore, the step 1 comprises:

[0012] It is assumed that the three-dimensional ultrasonic imaging device is composed of N transducer array elements, which are distributed in a hemispherical shape in space, and each transducer array element is configured to both transmit and receive ultrasonic signals. When there is a geometric body of any shape in the imaging space, the transducer sequentially transmits ultrasonic signals at a certain time interval, thereby obtaining ultrasonic array data;

[0013] The transducer is assumed to be a point source according to the spatial coordinates, so as to establish a three-dimensional geometric model of the imaging system, and the mathematical expression of the geometric body is obtained by setting the parameters of the geometric body.

[0014] Furthermore, in step 1, the shape of the geometric body is set to an ellipsoid, a cube, or a sphere.

[0015] Furthermore, the step 2 comprises:

[0016] According to the known coordinates of the transmitting point and the receiving point, the analytical expression of the straight ray of the sound wave propagation path is constructed:

[0017] P=O+tD

[0018] Among them, O is the starting point coordinate, P is the end point coordinate, D is the unit normal, and t is the line segment distance;

[0019] Assuming that there are a certain number of points inside the geometric body, when the sound line propagates to these points, the propagation direction changes. These points are connected to the transmitting point and the receiving point respectively, generating the scattering path of the sound line;

[0020] Halton sequence is used in combination with geometric space expression to generate random scattering points in a three-dimensional space with a fixed shape, and the number of scattering points is used to simulate geometric bodies of different densities.

[0021] Furthermore, the step 3 comprises:

[0022] By judging the direction of the propagation path and the directivity angle, the paths that are not within the directivity angle range are removed.

[0023] Furthermore, the step 4 comprises:

[0024] Set the geometry attenuation coefficient to μ m , the propagation speed of ultrasonic wave in the geometric body is c m , the medium attenuation is μ w , the propagation speed of ultrasonic wave in the medium is c w , assuming that the transmitting array element is E t , the receiving array element is E r After directivity judgment, there are N propagation paths between these two points, of which N is the direct path. d The number is 1 or 0, the number of scattering paths is N sN-1 or N, where N=N d +N r , calculate the propagation time and attenuation corresponding to each propagation between the transmitting array element and the receiving array element, and form the path propagation time vector T and the path attenuation vector A:

[0025] T=[T1,T2,...,T N ];

[0026] A=[A1,A2,...,A N ];

[0027] T n (n=1,2,...,N) is the propagation time through the nth path, A n (n=1,2,...,N) is the propagation attenuation through the nth path. After path calculation, the distance through the geometric body on the nth path is obtained as L mn , the distance through the medium is L wn , the ray propagation intensity satisfies the law of exponential decay, then,

[0028]

[0029] T n =L mn / c m +L wn / c w ,n=1,2...,N

[0030] According to the number of array elements, the path propagation time and path propagation attenuation corresponding to all transmitting and receiving array elements are calculated according to the above steps.

[0031] Furthermore, the step 5 comprises:

[0032] According to the calculation results of the path propagation time and path propagation attenuation of the transmitting and receiving array element pair, the attenuation of each propagation path is offset according to the propagation time to form the path transfer function h. All propagation paths between the same transmitting and receiving array element pair are traversed and the path transfer function H is accumulated:

[0033] H=∑h

[0034] Convolving with the transmitted signal s(t) yields the simulated data R(t):

[0035] R(t)=H*s(t)

[0036] The total number of array elements is M. All transmit and receive pairs are traversed and the above steps are repeated to finally obtain the complete array simulation data R MM (t):

[0037] R MM(t) = {R ij (t),1≤i,j≤M}.

[0038] The application scenarios of the present invention include:

[0039] 1) In an environment without high-performance servers or other computing resources or when computing resources are very limited, simulation data of large-scale arrays can be calculated on conventional computers, which is very practical.

[0040] 2) Evaluate the performance of the existing ultrasound imaging system by simulating the imaging system, obtaining simulation data, calculating evaluation indicators such as spatial resolution and maximum imaging range, and evaluating the imaging performance of the system.

[0041] 3) Optimize the existing ultrasound imaging system. For example, if the number of ultrasound transducer array elements is too many or too few, simulation can be used to change the number of array elements, change the spatial distribution of the array, change the design of the transmitted pulse waveform, and analyze whether the system imaging performance is improved after the design parameters are changed from the simulation data.

[0042] 4) Design a new imaging system. Obtain simulation data according to the new imaging system parameters to verify the rationality and feasibility of the imaging system changes.

[0043] 5) Develop three-dimensional imaging algorithms and quickly generate simulation data based on algorithm requirements to provide data support for the verification and optimization of imaging algorithms.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] Compared with conventional numerical simulation methods, the present invention consumes less computer hardware resources, has the advantages of fast calculation speed and strong versatility, and can be quickly applied to data simulation of large-scale ultrasonic arrays such as annular or spherical arrays. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of the present invention;

[0047] Figure 2 This is a schematic diagram of USCT array element distribution;

[0048] Figure 3 It is a schematic diagram of ellipsoid geometry;

[0049] Figure 4 The direct path and scattering path models of ultrasonic waves. In the figure, the left side is the direct path model, and the right side is the scattering path model. T represents the transmitting point, R represents the receiving point, A and B represent the two intersection points of the line connecting the transmitting and receiving points and the geometric body, respectively, and S represents the scattering point.

[0050] Figure 5 Calculation process for path propagation time and attenuation. DETAILED DESCRIPTION

[0051] The present invention will be further described below in conjunction with the accompanying drawings.

[0052] See also Figure 1-5 , a large-scale three-dimensional ultrasound array data rapid simulation method, comprising the following steps:

[0053] Step 1: Geometric modeling of ultrasound imaging system

[0054] like Figure 2 As shown in the figure, the three-dimensional ultrasound imaging device USCT consists of 2304 transducer array elements, which are distributed in a hemispherical shape in space. Each transducer array element can both transmit and receive ultrasonic signals. When there are objects of any shape in the imaging space, the transducers transmit ultrasonic signals in sequence at a certain time interval to obtain ultrasonic array data.

[0055] In the present invention, the transducer is assumed to be a point source according to the spatial coordinates, such as Figure 3 As shown, for the convenience of analysis, the shape of the object (geometric body) is set to an ellipsoid to establish a three-dimensional geometric model of the imaging system. In addition, it can also be set to a cube, a sphere, etc. By setting the geometric body parameters, such as the center coordinates, the axis length, etc., the mathematical expression of the geometric body can be obtained.

[0056] Step 2: Ultrasonic wave propagation path simulation

[0057] The sound propagation in the high frequency band usually adopts a ray model. The present invention is based on the idea of ​​ray tracing, analogizes the sound line to the light, and simulates the ultrasonic data by simulating the propagation path.

[0058] Given the coordinates of the transmitting and receiving points, construct the analytical expression of the straight ray of the sound wave propagation path:

[0059] P=O+tD

[0060] Among them, O is the starting point coordinate, P is the end point coordinate, D is the unit normal, and t is the line segment distance.

[0061] like Figure 4 As shown in the figure, the ultrasonic wave is emitted by the transmitting transducer, propagates through the medium, and reaches the receiving transducer. There are two main propagation paths: the first is the direct path. That is, starting from the transmitting point, it directly reaches the receiving point. Among all direct paths, some will pass through the geometric body, and some will not pass through the geometric body; the second is the scattered path. That is, the ultrasonic wave starts from the transmitting point and reaches the designated receiving point after being scattered by the phantom.

[0062] The present invention assumes that there are a certain number of points inside the geometric body. When the sound line propagates to these points, the propagation direction changes. These points are respectively connected to the transmitting point and the receiving point to generate a scattering path of the sound line. The low-discrepancy sequence can efficiently generate uniformly distributed random points in a high-dimensional space. The Halton sequence is used in the scattering path modeling and combined with the geometric body space expression to generate random scattering points in a three-dimensional space with a fixed shape, and the number of scattering points is used to simulate geometric bodies of different densities. The more scattering points, the greater the density of the geometric body.

[0063] Step 3: Array element directivity modeling

[0064] In the actual system, the transmission and reception of the transducer array elements are directional. In the ultrasonic propagation path model, the transmission and reception directivity are taken into consideration. By judging the direction of the propagation path and the directivity angle, the paths that are not within the directivity angle range are removed. In this way, the simulation data obtained is more in line with the actual situation.

[0065] Step 4: Calculate the path propagation time and path propagation attenuation

[0066] Based on the coordinate information of all array elements and geometric bodies, the propagation time and attenuation of all propagation paths of ultrasound are calculated. Since ultrasound propagates through different media, the density, attenuation coefficient, speed of sound and other physical parameters are different, so the propagation time and attenuation in different media are calculated separately. The specific process is as follows Figure 5 shown.

[0067] Set the geometry attenuation coefficient to μ m , the propagation speed of ultrasonic wave in the geometric body is c m , the medium attenuation is μ w , the propagation speed of ultrasonic wave in the medium is c w , the medium is water. Assume that the transmitting element is E t , the receiving array element is E r After directivity judgment, there are N propagation paths between these two points, of which N is the direct path. d The number is 1 or 0, the number of scattering paths is N s N-1 or N, where N=N d +N r . Calculate the propagation time and attenuation corresponding to each propagation path between the transmitting array element and the receiving array element to form the path propagation time vector T and the path attenuation vector A.

[0068] T=[T1,T2,...,T N ];

[0069] A=[A1,A2,...,A N ];

[0070] Tn (n=1,2,...,N) is the propagation time through the nth path, A n (n=1,2,...,N) is the propagation attenuation through the nth path. After path calculation, the distance through the geometric body on the nth path is obtained as L mn , the distance through the medium is L wn , the ray propagation intensity satisfies the law of exponential decay, then,

[0071]

[0072] T n =L mn / c m +L wn / c w ,n=1,2...,N

[0073] According to the number of array elements, the path propagation time and path propagation attenuation corresponding to all transmitting and receiving array elements are calculated according to the above steps.

[0074] Step 5: Construct path transfer function and generate ultrasound array data

[0075] According to the calculation results of the path propagation time and path propagation attenuation of the transmitting and receiving array element pair, the attenuation of each propagation path is offset according to the propagation time to form the path transfer function h. All propagation paths between the same transmitting and receiving array element pair are traversed and the path transfer function H is accumulated:

[0076] H=∑h

[0077] Convolving with the transmitted signal s(t) can obtain the simulated data R(t):

[0078] R(t)=H*s(t)

[0079] The total number of array elements is M. All transmit and receive pairs are traversed and the above steps are repeated to finally obtain the complete array simulation data R MM (t):

[0080] R MM (t) = {R ij (t),1≤i,j≤M}.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for rapid simulation of large-scale three-dimensional ultrasound array data, characterized in that: include: Step 1: geometric modeling of the ultrasound imaging system, including: It is assumed that the three-dimensional ultrasonic imaging device is composed of N transducer array elements, which are distributed in a hemispherical shape in space, and each transducer array element is configured to both transmit and receive ultrasonic signals. When there is a geometric body of any shape in the imaging space, the transducer sequentially transmits ultrasonic signals at a certain time interval, thereby obtaining ultrasonic array data; The transducer is assumed to be a point source according to the spatial coordinates, so as to establish a three-dimensional geometric model of the imaging system, and the mathematical expression of the geometric body is obtained by setting the parameters of the geometric body; Step 2, simulating the ultrasonic wave propagation path, including: According to the known coordinates of the transmitting point and the receiving point, the analytical expression of the straight ray of the sound wave propagation path is constructed: P=O+tD Among them, O is the starting point coordinate, P is the end point coordinate, D is the unit normal, and t is the line segment distance; Assuming that there are a certain number of points inside the geometric body, when the sound line propagates to these points, the propagation direction changes. These points are connected to the transmitting point and the receiving point respectively, generating the scattering path of the sound line; Halton sequence is used in combination with geometric space expression to generate random scattering points in a three-dimensional space with a fixed shape, and geometric bodies of different densities are simulated by the number of scattering points. Step 3: Modeling the array element directivity, including: By judging the direction of the propagation path and the directivity angle, the paths that are not within the directivity angle range are removed; Step 4, calculating the path propagation time and path propagation attenuation, including: Set the geometry attenuation coefficient to μ m , the propagation speed of ultrasonic wave in the geometric body is c m , the medium attenuation is μ w , the propagation speed of ultrasound in the medium is c w , assuming that the transmitting array element is E t , the receiving array element is E r After directivity judgment, there are N propagation paths between these two points, of which N is the direct path. d The number is 1 or 0, the number of scattering paths is N s N-1 or N, where N=N d +N r , calculate the propagation time and attenuation corresponding to each propagation between the transmitting array element and the receiving array element, and form the path propagation time vector T and the path attenuation vector A: T=[T1,T2,...,T N ]; <h2 style=";text-align:left;direction:ltr">A=[A1,A2,...,A<h2 style=";text-align:left;direction:ltr"> N <h2 style=";text-align:left;direction:ltr"> ]; T n (n=1,2,...,N) is the propagation time through the nth path, A n (n=1,2,...,N) is the propagation attenuation through the nth path. After path calculation, the distance through the geometric body on the nth path is obtained as L mn , the distance through the medium is L wn , the ray propagation intensity satisfies the law of exponential decay, then, T n =L mn / c m +L wn / c w ,n=1,2...,N According to the number of array elements, calculate the path propagation time and path propagation attenuation corresponding to all transmitting and receiving array elements according to the above steps; Step 5, constructing a path transfer function to generate ultrasound array simulation data, including: According to the calculation results of the path propagation time and path propagation attenuation of the transmitting and receiving array element pair, the attenuation of each propagation path is offset according to the propagation time to form the path transfer function h. All propagation paths between the same transmitting and receiving array element pair are traversed and the path transfer function H is accumulated: H=∑h Convolving with the transmitted signal s(t) yields the simulated data R(t): R(t)=H*s(t) The total number of array elements is M. All transmit and receive pairs are traversed and the above steps are repeated to finally obtain the complete array simulation data R MM (t): R MM (t)={R ij (t),1≤i,j≤M}。 2. A large-scale three-dimensional ultrasound array data rapid simulation method according to claim 1, characterized in that: In step 1, the geometry shape is set to an ellipsoid, a cube, or a sphere.

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