KR102550262B1 - Apparatus of ultrasound imaging using random interference and method of the same - Google Patents

Abstract

One embodiment of the present disclosure is an ultrasound imaging apparatus using random interference, comprising: a probe including a transducer array of a plurality of transducer elements; and generating random sequences for each of the plurality of transducer elements, transmitting ultrasound signals corresponding to the random sequences through the transducer array, and corresponding to the transmitted ultrasound signals through the transducer array. and a processor configured to receive echo signals corresponding to the random sequences and to generate an ultrasound image corresponding to the received echo signals using transmission matrices corresponding to the random sequences.

Description

Ultrasonic imaging apparatus and method using random interference {APPARATUS OF ULTRASOUND IMAGING USING RANDOM INTERFERENCE AND METHOD OF THE SAME}

The present disclosure relates to an ultrasound imaging apparatus and method using random interference.

Ultrasound imaging is a widely used and preferred diagnostic imaging technique, which transmits an ultrasound signal through a transducer, acquires an echo signal of the transmitted ultrasound signal, and analyzes the acquired echo signal to produce an image of a region of interest. technology that creates

The resolution of ultrasound imaging is spatially variable and depends on parameters such as the frequency of the transmitted signal, the beam width, the aperture size, and the transmit focal depth. Since these parameters limit the ability to focus ultrasound, there are physical limitations on the final resolution. Similar to optical imaging, the resolution of ultrasound imaging is defined by the diffraction limit. The theoretical spatial resolution of ultrasound imaging for a single cycle pulse is half the wavelength of an acoustic wave. However, the best axial and lateral resolutions are several orders of magnitude below the diffraction limit due to high ultrasonic attenuation and speckle noise. Achieving resolution beyond these limits would greatly help improve the accuracy of medical diagnosis.

1 is a diagram showing an example of a conventional ultrasound imaging method.

Referring to FIG. 1 , one example of a conventional ultrasound imaging method is an ultrasound imaging method using beamforming. This means that at least some of the transducers among a plurality of transducers included in the transducer array constructively interfere at a specific point within the Region of Interest (ROI) or Region of View, and at other points. In [0041] , an ultrasonic wave with destructive interference is transmitted, an echo signal corresponding to the transmitted ultrasonic wave is received, and an image of a specific point is generated by measuring the intensity of the received echo signal. In addition, an image of the region of interest may be generated by sequentially performing such ultrasonic transmission and reception processes at every point in the region of interest. Ultrasound imaging using such beamforming has low temporal resolution and low image quality due to diffraction because each point of the region of interest is sequentially scanned.

2 is a diagram for explaining axial resolution and lateral resolution in ultrasound imaging.

Referring to FIG. 2, lateral resolution refers to resolution in a direction perpendicular to the ultrasonic wave transmitted from the transducer or resolution in a direction parallel to the wavefront of the ultrasonic wave transmitted from the transducer array, and axial resolution refers to the resolution transmitted from the transducer array. It means the resolution in the direction parallel to the ultrasonic wave being transmitted or the resolution in the direction perpendicular to the wavefront of the ultrasonic wave transmitted from the transducer array.

In a conventional ultrasound system, the highest lateral resolution is as much as one wavelength (λ) of a transmission pulse, and when using a universal ultrasound having a frequency range of 3 to 15 MHz, the lateral resolution is 0.5 mm to 0.1 mm. In addition, the highest axial resolution is as much as two wavelengths (2λ) of the transmission pulse, and when using a universal ultrasonic wave with a frequency range of 3-15 MHz, the axial resolution is 1.0 mm to 0.2 mm.

An object of the present disclosure is to provide a high-resolution ultrasound imaging apparatus and method using random interference.

One embodiment of the present disclosure is an ultrasound imaging apparatus using random interference, comprising: a probe including a transducer array of a plurality of transducer elements; and generating random sequences for each of the plurality of transducer elements, transmitting ultrasound signals corresponding to the random sequences through the transducer array, and corresponding to the transmitted ultrasound signals through the transducer array. and a processor for receiving echo signals corresponding to the random sequences and generating an ultrasound image corresponding to the received echo signals using transmission matrices corresponding to the random sequences.

The processor may generate the random sequences by uniformly selecting a predetermined number of elements from −1 or 1.

The processor may generate a random sequence electrical signal by convolutional multiplying the random sequences with a half-cycle sine wave, and transmit the ultrasound signals corresponding to the random sequence electrical signal through the transducer array.

The processor may simultaneously transmit the corresponding ultrasound signals using at least one or more of the plurality of transducer elements included in the transducer array.

The processor may simultaneously transmit the corresponding ultrasound signals using all of the plurality of transducer elements included in the transducer array.

The processor may receive the echo signals using at least one of the plurality of transducer elements included in the transducer array.

Each of the transmission matrices may correspond to each receiving element used to receive the echo signals, and each column may include spatial impulse responses received by the corresponding receiving element.

The processor may individually generate ultrasound images for each receiving element using a corresponding echo signal and a corresponding transmission matrix, and may generate a final ultrasound image by calculating an average of the individually generated ultrasound images.

를 풀이하여 제i 수신 엘리먼트에 대응하는 제i 초음파 이미지 f_i를 생성하며, G_i는 상기 제i 수신 엘리먼트에 대응하는 제i 전송 행렬이고, p_i는 상기 제i 수신 엘리먼트에서 수신한 제i 에코 응답이고, N_R은 상기 수신 엘리먼트들의 개수이고, ε는 정칙화(regularization) 파라미터일 수 있다.The process is an optimization problem

to generate an ith ultrasound image f _i corresponding to the ith receiving element, G _i is an ith transmission matrix corresponding to the ith receiving element, and p _i is the ith received by the ith receiving element. Echo response, N _R may be the number of the receiving elements, and ε may be a regularization parameter.

The processor assumes that the ultrasound images individually acquired by each receiving element are the same, generates a single relational expression between the echo signals and the transmission matrices, and generates a final ultrasound image through an inverse matrix operation in the relational expression. can do.

을 생성하고, 역행렬 연산을 이용한 수학식

을 풀이하여 상기 최종 초음파 이미지 f를 생성하며, G_i는 상기 제i 수신 엘리먼트에 대응하는 제i 전송 행렬이고, p_i는 상기 제i 수신 엘리먼트에서 수신한 제i 에코 응답이고, N_R은 상기 수신 엘리먼트들의 개수일 수 있다.The processor is the single relational expression

, and the equation using the inverse matrix operation

The final ultrasound image f is generated by solving , G _i is an i th transmission matrix corresponding to the i th receiving element, p _i is an i th echo response received by the i th receiving element, and N _R is the It may be the number of receiving elements.

The processor may output the generated ultrasound image through a display.

According to various embodiments of the present disclosure, even if the transducer array transmits an ultrasound signal only once, an image of the entire region of interest may be obtained, and ultrasound imaging with high temporal resolution may be performed.

In addition, according to various embodiments of the present disclosure, as an image is obtained using a spatial impulse response at each point in the region of interest, compared to the conventional ultrasound imaging method using beamforming, the axial direction Ultrasound imaging with high resolution and lateral resolution is possible.

1 is a diagram showing an example of a conventional ultrasound imaging method.
2 is a diagram for explaining axial resolution and lateral resolution in ultrasound imaging.
3 is a block diagram illustrating an ultrasound imaging apparatus 100 according to an exemplary embodiment of the present disclosure.
4 is an operation flowchart illustrating an ultrasound imaging method using random interference according to an embodiment of the present disclosure.
5 is a diagram illustrating an ultrasound imaging method using random interference according to an embodiment of the present disclosure.
FIG. 6 is an operational flowchart illustrating an example of generating an ultrasound image shown in FIG. 4 ( S407 ).
FIG. 7 is an operation flowchart illustrating an example of generating an ultrasound image shown in FIG. 4 ( S407 ).
8 is a diagram showing one of spatial points in a region of interest.
9 is a diagram showing examples of random sequence electrical signals and examples of spatial response.
10 to 12 are views illustrating echo signals according to a pair of a transmission element (Tx) and a reception element (Rx).
13 is a diagram showing results of ultrasound imaging simulation using beamforming and ultrasound imaging simulation results according to an embodiment of the present disclosure.
14 is a diagram showing results of ultrasound imaging simulation using beamforming and ultrasound imaging simulation results according to an embodiment of the present disclosure.
FIG. 15 is a diagram showing intensity profiles for the simulation shown in FIG. 14 .
16 is a diagram comparing the number of receiving elements to be used for ultrasound imaging and the quality of the results according to an embodiment of the present disclosure.
17 is a diagram showing ultrasound imaging results using beamforming for a silicon phantom and ultrasound imaging results according to an embodiment of the present disclosure.
18 is a diagram showing ultrasound imaging results using beamforming for a silicon phantom and ultrasound imaging results according to an embodiment of the present disclosure.

Hereinafter, the embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings, but the same or similar elements are given the same reference numerals regardless of reference numerals, and redundant description thereof will be omitted. The suffixes 'module' and 'unit' for the components used in the following description are given or used together in consideration of ease of writing the specification, and do not have meanings or roles that are distinct from each other by themselves. In addition, in describing the embodiments disclosed in this specification, if it is determined that a detailed description of a related known technology may obscure the gist of the embodiment disclosed in this specification, the detailed description thereof will be omitted. In addition, the accompanying drawings are only for easy understanding of the embodiments disclosed in this specification, the technical idea disclosed in this specification is not limited by the accompanying drawings, and all changes included in the spirit and technical scope of the present disclosure , it should be understood to include equivalents or substitutes.

Terms including ordinal numbers, such as first and second, may be used to describe various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another.

It is understood that when a component is referred to as being 'connected' or 'connected' to another component, it may be directly connected or connected to the other component, but other components may exist in the middle. It should be. On the other hand, when a component is referred to as being 'directly connected' or 'directly connected' to another component, it should be understood that no other component exists in the middle.

3 is a block diagram illustrating an ultrasound imaging apparatus 100 according to an exemplary embodiment of the present disclosure.

Referring to FIG. 3 , an ultrasound imaging apparatus 100 according to an embodiment of the present disclosure may include a probe 110, a display 120, a memory 130, a power supply 140, a processor 150, and the like. can

The probe 110 means a module including a transducer for transmitting ultrasound and receiving an echo signal corresponding thereto in the ultrasound imaging method.

The probe 110 includes a transducer array 111 , and the transducer array 111 may include a plurality of transducer elements 112 . A plurality of transducer elements 112 included in the transducer array 111 may be arranged in a row at regular intervals. Each of the transducer elements 112 may include a transmitting element 112a and a receiving element 112b.

An ultrasonic transducer or transducer may refer to a component capable of converting an electrical signal into an ultrasonic signal and conversely converting an ultrasonic signal into an electrical signal. The transducer may be composed of an array of a plurality of transducer elements 112 to configure the transducer array 111, and each transducer element 112 may mean a unit transducer in the transducer array 111. can

In one embodiment, each transducer element 112 may be a piezoelectric transducer element, in which case each transducer element 112 may be a single piezoelectric crystal.

The transmission element 112a may refer to a function in which the transducer element 112 converts an electrical signal into an ultrasonic signal and transmits the ultrasonic signal. The receiving element 112b may refer to a function of receiving an ultrasonic signal reflected by the transducer element 112 and converting the received ultrasonic signal into an electrical signal.

The transducer array 111 generates ultrasonic signals under the control of the processor 150 . However, according to embodiments, the probe 110 may include a separate processor (not shown) for generating ultrasound, and in this case, the transducer array 111 controls the processor (not shown) in the probe 110. An ultrasonic signal can be generated by Also, a processor (not shown) in the probe 110 may be referred to as an ultrasonic generator or an ultrasonic generator controller, and may be controlled by the processor 150 .

The display 120 may output an image by converting the ultrasound image data generated by the processor 150 into R, G, B signals, gray scale signals, black and white signals, and the like.

The memory 130 may store various types of programs and application data necessary for controlling or operating the ultrasound imaging apparatus 100 .

The memory 130 may store an ultrasonic signal transmitted through the probe 110 and an ultrasonic signal or echo signal received through the probe 110 . The transmitted ultrasound signal or the received ultrasound signal may be temporarily stored in the memory 130 .

The memory 130 may store transmission matrices used to generate ultrasound images from echo signals. Transmission matrices are matrices including spatial impulse responses within a region of interest (ROI) for generating an ultrasound image, and a detailed description thereof will be described later.

The power supply 140 may supply power to the ultrasound imaging apparatus 100 .

The processor 150 may control overall operations of the ultrasound imaging apparatus 100 .

The processor 150 may generate and transmit an ultrasound signal through the probe 110 by generating and transmitting an ultrasound signal generation command to the probe 110 . A detailed description of this will be given later.

The processor 150 may generate an ultrasound image by analyzing an electrical signal (hereinafter referred to as a response signal) corresponding to the echo signal obtained from the probe 110 . To this end, the processor 150 may generate an ultrasound image using a response signal and a transmission matrix obtained from the probe 110 .

The processor 150 may output the generated ultrasound image through the display 120 .

In an embodiment, two or more components of the ultrasound imaging apparatus 100 may be combined into one component, or one component may be subdivided into two or more components. In addition, the functions performed in each block are for explaining an embodiment of the present disclosure, and the specific operation or device does not limit the scope of the present disclosure.

4 is an operation flowchart illustrating an ultrasound imaging method using random interference according to an embodiment of the present disclosure.

Referring to FIG. 4 , the processor 150 of the ultrasound imaging apparatus 100 generates random sequences for each transducer element 111 (S401).

The processor 150 generates a random sequence to be used for generating an ultrasound signal in the transducer array 111 or each transducer element 112 to transmit the random sequence ultrasound signal through the probe 110 .

A random sequence is used to generate a random sequence ultrasound signal.

Random sequences are generated corresponding to each transducer element 112, and therefore, random sequences corresponding to each transducer element 112 are not identical to each other. However, since each random sequence is randomly generated, random sequences corresponding to different transducer elements 112 may be identical to each other, although there is a low probability.

The processor 150 may generate random sequences having a predetermined length. That is, random sequences corresponding to each transducer element 112 may be generated to have the same length even if they are not identical to each other.

The processor 150 may generate a random sequence by (uniformly) selecting each element from a binary set {-1, 1} while having a predetermined length. For example, processor 150 generates a random sequence w ₁ =(-1, -1, -1, -1, 1, 1, -1, 1, -1, 1, -1, 1) of length 13. can do.

The processor 150 generates random sequences corresponding to each transducer element 112, and the random sequences generated thereby may be equally used during ultrasound imaging or when determining a transmission matrix for ultrasound imaging. That is, the random sequence means that the pattern is randomly determined, and does not mean that the pattern continuously and randomly changes each time ultrasound imaging is attempted or over time. If a first random sequence corresponding to the first transducer element is generated, the first transducer element may repeatedly transmit ultrasonic signal pulses corresponding to the first random sequence. Accordingly, random sequences generated corresponding to each transducer element 112 may not be changed unless a separate setting is changed.

Then, the processor 150 transmits ultrasound signals corresponding to the random sequences through the transducer array 111 (S403).

The processor 150 generates a random sequence electrical signal corresponding to the generated random sequence and transmits the corresponding random sequence electrical signal to each transducer element 112, thereby corresponding to the random sequence electrical signal (random sequence). It can generate and transmit ultrasonic signals.

Then, the processor 150 may generate a random sequence electrical signal by multiplying the generated random sequence with a half-cycle sine wave as shown in [Equation 1] to [Equation 3] below.

In [Equation 1] to [Equation 3], w _j (t) is a random sequence electrical signal corresponding to the j-th transducer element 112, N _w is the length of the random sequence, and w _j,n is the n-th element of the random sequence w _j corresponding to the j-th transducer element 112 and has a value of -1 or 1. And, A is the amplitude, f _c is the nominal frequency of the fundamental signal of the half-cycle sine wave, and 2T is the period of the fundamental signal. For example, the random sequence electrical signal shown in (a) of FIG. 9 is the random sequence w ₁ =(-1, -1, -1, -1, 1, 1, -1, 1, -1, 1, -1 , is an electrical signal corresponding to 1).

As described above, in terms of the transducer element 112 performing a function of converting a random sequence electrical signal into a (random sequence) ultrasonic signal and transmitting the converted ultrasonic signal, the transducer element 112 is a transmission transformer. It may be referred to as a reducer element or a transmission element 112a.

Each transducer element 112 starts transmitting the generated ultrasonic signal at the same time point, and since all random sequence electrical signals corresponding to each transducer element 112 have the same length, all transducer elements 112 may transmit its own ultrasonic signal during the same period. As such, all transducer elements 112 may simultaneously transmit their respective random sequence ultrasound signals, thereby generating an unfocused incident ultrasound wavefront of random interference.

Then, the processor 150 receives echo signals through the transducer array 111 (S405).

The ultrasonic signal transmitted from the transducer array 111 is transmitted to the region of interest (ROI) of the medium, and the ultrasonic signals are reflected or scattered by a scatterer in the region of interest to the transducer array 111. can be passed back. Also, each transducer element 112 included in the transducer array 111 may receive the reflected ultrasonic signal or echo signal and convert the received ultrasonic signal or echo signal into an electrical signal. The received ultrasonic signal and echo signal may refer to the ultrasonic signal itself, but may also refer to an electrical signal converted from the ultrasonic signal unless otherwise specified.

As described above, in terms of the transducer element 112 performing a function of receiving an ultrasonic signal and converting the received ultrasonic signal into an electrical signal, the transducer element 112 is a receiving transducer element or a receiving element ( 112b).

Echo signals received by each transducer element 112 are not identical to each other. This is because the transducer array 111 includes a plurality of transducer elements 112, and as each transducer element 112 is spatially disposed in a different position, a difference occurs in the path along which the ultrasonic signal moves. am. The ultrasonic signal travels along the path of the transmitting element 112a, the scattering body in the region of interest, and the receiving element 112b. If either of the transmitting element 112a or the receiving element 112b is different, the path is different. Scatterers on the path may vary. Therefore, a difference in path results in a difference in waveform as well as a time difference or time delay between several echo signals.

The reason why the ultrasonic imaging apparatus 100 transmits a random sequence ultrasonic signal through each transducer element 112 is that spatial responses in individual point scatterers in the region of interest are different from each other. To make it mutually incoherent. When a random sequence ultrasonic signal propagates in a medium, energy is reflected from tissue or the like, and in this case, each scattering body has a unique impulse response.

Then, the processor 150 generates ultrasound images corresponding to the received echo signals using transmission matrices corresponding to the random sequences (S407).

A column of each transmission matrix is composed of an impulse response (spatial impulse response) corresponding to each spatial point in the region of interest.

Each transmit matrix corresponds one to each receive element 112b. That is, the first transmission matrix corresponding to the first receiving element is composed of spatial impulse responses obtained from the first receiving element. Also, a first column of the first transmission matrix may be a spatial impulse response at the first receiving element with respect to a first spatial point within the ROI. However, since there are a plurality of transmitting elements 112a, a spatial impulse response at the first receiving element for a first spatial point is the sum of echo signals for individual ultrasonic signals transmitted from the plurality of transmitting elements 112a. It may mean a normalized signal. In addition, since each transmission element 112a is spatially disposed at a different location, the propagation path of the ultrasonic signal is different, and a time difference due to a path difference may exist. Accordingly, the spatial impulse response may be obtained by adding a delay according to a path difference to the echo signals of the individual ultrasound signals transmitted from the plurality of transmitting elements 112a, summing them, and normalizing them.

Since each column of the transmission matrix corresponding to a specific receiving element 112b is composed of spatial impulse responses for each spatial point in the ROI of the corresponding receiving element 112b, the echo signal received by the corresponding receiving element 112b can be expressed as a linear combination of spatial impulse responses for each spatial point. And, the weight of this linear combination may mean a weight or intensity for each spatial point in the region of interest.

Equation 4 above is a relationship between the ith echo signal p _i received at the ith receiving element, the ith transmission matrix G _i corresponding to the ith receiving element, and the ith image f _i measured at the ith receiving element. indicates i is an index of the receiving element 112b, and is a natural number less than or equal to N _R , the total number of receiving elements 112b. When the number of samples for the ultrasound signal and the echo signal is M and the number of spatial points or point scatterers in the region of interest is N _S , the ith echo signal _pi has a size of M is a 1-dimensional vector, the ith transfer matrix Gi is a 2-dimensional matrix of size MХN _S , and the ith image f _i is a 1-dimensional vector of size N _S .

When the total number of receiving elements 112b is N _R , the total number of N _R images can be expressed as in [Equation 5].

The processor 150 may generate a final ultrasound image by converting an average of ultrasound images corresponding to each receiving element 112b into a 2D image. However, a detailed method of generating an image using [Equation 4] and [Equation 5] described above will be described later.

The processor 150 may permanently or temporarily store the generated ultrasound image in the memory 130 .

Then, the processor 150 outputs the generated ultrasound image through the display 120 (S409).

The processor 150 may output the generated ultrasound image in real time. Here, outputting an image in real time may mean generating an image corresponding to the ultrasonic signal after transmitting the ultrasonic signal, and outputting the converted image without a separate waiting time. Therefore, since it takes time for the ultrasonic signal to propagate in the process of transmitting the ultrasonic signal through the probe 110 and receiving the corresponding echo signal, a corresponding delay may occur. In addition, if time is required for image conversion, a corresponding amount of delay may occur.

At least some of the steps shown in FIG. 4 may be performed in parallel.

5 is a diagram illustrating an ultrasound imaging method using random interference according to an embodiment of the present disclosure.

Referring to FIG. 5 , the probe 110 includes a plurality of transducers 112, and each transducer 112 generates random sequence ultrasound signals (generated based on random sequence electrical signals 511_1 and 511_2). 512_1 and 512_2) are transmitted. The transmitted ultrasound signals 512_1 and 512_2 cause constructive and destructive interference within the region of interest.

Also, each transducer 112 receives an echo signal 541 corresponding to the transmitted ultrasonic signals 512_1 and 512_2. Each transducer 112 may individually receive echo signals, and FIG. 5 shows only the echo signal 541 received by one receiving transducer 521 for convenience of explanation. The echo signal 541 corresponding to the receiving transducer 521 may be sampled and expressed as a vector p.

The ultrasound image 551 may be generated from the echo signal 541 corresponding to the receiving transducer 521 by using the transmission matrix G 532 corresponding to the receiving transducer 521 . Each column of the transmission matrix G 532 corresponding to the receiving transducer 521 is composed of spatial impulse responses 531_1 and 531_N _S corresponding to each spatial point or point scatterer in the region of interest. The first spatial impulse response 531_1 denotes an impulse response to a first point in the region of interest and the receiving transducer 521, and the N _th spatial impulse response 531_NS _{531_N S} denotes a first point in the region of interest and an impulse response to the receiving transducer 521 . It means the impulse response to the transducer 521.

The echo signal 541 can be expressed as a linear combination of the spatial point impulse responses 531_1 and _{531_NS} , and such a linear relationship can be expressed as [Equation 4] and [Equation 5] above. . By solving this linear relationship, an ultrasound image 551 can be obtained.

FIG. 6 is an operational flowchart illustrating an example of generating an ultrasound image shown in FIG. 4 ( S407 ).

Referring to FIG. 6 , the processor 150 individually generates ultrasound images for each receiving element 112b (S601).

The receiving element 112b used to generate an ultrasound image may be all of the transducer elements 112 included in the transducer array 111, or may be some of the transducer elements 112 included in the transducer array 111. may be The receiving element 112b used to generate the ultrasound image may be determined by a user's setting or may be variously determined according to a predetermined setting value.

The processor 150 generates the ith ultrasound image f _i corresponding to the ith receiving element by solving the optimization problem of [Equation 6] below.

In [Equation 6] above, ε is a regularization parameter. Regularization parameters affect the quality of solutions of optimization problems. For example, the regularization parameter ε may be 3Х10 ^-3 .

Then, the processor 150 generates a final ultrasound image by calculating an average of each ultrasound image (S603).

When the processor 150 generates the ith ultrasound image f _i corresponding to the ith receiving element by solving the optimization problem of [Equation 6], the average of the generated ultrasound images is calculated as shown in [Equation 7] below. Thus, the final ultrasound image f _compound can be generated.

As described above, in [Equation 7], N _R is the number of receiving elements.

The final ultrasound image f _compound is expressed as a one-dimensional vector of size _NS representing the number of point scatterers in the region of interest, and by converting it into a two-dimensional vector, an ultrasound image that we generally observe can be obtained.

FIG. 7 is an operation flowchart illustrating an example of generating an ultrasound image shown in FIG. 4 ( S407 ).

Referring to FIG. 7 , the processor 150 assumes that the ultrasound images acquired by each receiving element 112b are the same, and generates a single relational expression between echo signals and transmission matrices (S701).

In the embodiment shown in FIG. 6, the processor 150 individually generates an ultrasound image for each receiving element 112b using a corresponding transmission matrix, and the ultrasound image generated corresponding to each receiving element 112b. The average of them was calculated to generate the final ultrasound image. However, even if different receiving elements 112b are used, since the object or region of interest to be actually measured is the same, it can be assumed that the same ultrasound image is acquired in all the receiving elements 112b. When this assumption is made, [Equation 5] can be expressed as [Equation 8] below.

Also, [Equation 8] can be expressed as a single relational expression between echo signals and transmission matrices as shown in [Equation 9] and [Equation 10] below.

As described above, in [Equation 9] and [Equation 10], p _i is a one-dimensional vector having a size of M, and G _i is a two-dimensional matrix having a size of MХN _S . Therefore, p _T is a one-dimensional matrix of size M*N _R , and G _T is a two-dimensional matrix of size (M*N _R )ХN _S .

Then, the processor 150 generates an ultrasound image through an inverse matrix operation in the generated relational expression (S703).

As shown in [Equation 9] and [Equation 10] above, since a single relational expression between the echo signals received by the plurality of receiving transducers 112b and the corresponding transmission matrices is generated, the processor 150 may generate an ultrasound image f through an inverse matrix operation.

The processor 150 multiplies the transpose matrix of the rearranged transmission matrix G _T to the left side of both sides in [Equation 10] as shown in [Equation 11] below, and the inverse matrix as shown in [Equation 12] below. An ultrasound image f may be calculated through operation.

8 is a diagram showing one of spatial points in a region of interest.

Referring to FIG. 8 , a plurality of spatial points 801 to be measured in ultrasound imaging are included in the ROI. Also, the transducer element 112 included in the probe 110 may transmit a random sequence ultrasound signal and receive the ultrasound signal reflected or scattered at a specific spatial point 801 again.

The positions of each transmitting element 112a, each receiving element 112b, and each spatial point 801 can be expressed as a vector with respect to an arbitrary reference point, and thus the propagation path of the ultrasonic wave transmitted from the probe 110 is a vector. can be expressed as

The position of the j-th transmission element (or the j-th transmission element) among the N _T transmission elements 112a is the vector r _j , the position of the i-th reception element (or the i-th reception element) among the N _R reception elements 112b. A location may be defined as a vector r _i , and a location of a k th spatial point (or k th spatial point) among the N _S spatial points 801 may be defined as a vector r _k . In this case, the propagation path of the ultrasonic wave transmitted from the j th transmitting element to the k th spatial point can be expressed as a vector r _k -r _j , and the propagation path of the ultrasonic wave scattered from the k th spatial point to the i th receiving element is It can be expressed as a vector r _i -r _k .

Each column of the ith transmission matrix G _i corresponding to the above-described ith receiving element is a spatial impulse response scattered at each spatial point and received at the ith receiving element. Specifically, the i-th transmission matrix G _i can be expressed as in [Equation 13], and the k-th column g _i,k of the i-th transmission matrix is an echo scattered at the k-th spatial point and received at the i-th receiving element. It's a signal.

However, the k-th column g _i,k of the i-th transmission matrix denotes an echo signal scattered at the k-th spatial point and received at the i-th receiving element, which corresponds to the ultrasonic signals transmitted by the plurality of transmitting elements 112a. is a synthesized signal of the echo signal for Ultrasonic signals transmitted from different transmission elements 112a are scattered at the kth spatial point, and the propagation path to the ith receiving element is equal to r _i -r _k , and the kth spatial point is transmitted from the jth transmitting element to the ith receiving element. The propagation path to r _k -r _j is different. Accordingly, since the ultrasonic signals transmitted from the different transmission elements 112a have different propagation paths, there is a time difference in propagating each other. Accordingly, when determining each column of the transmission matrix, the processor 150 may sum and normalize the time-delayed echo signals by considering the time difference according to the difference in the propagation path of the ultrasonic signal.

9 is a diagram showing examples of random sequence electrical signals and examples of spatial response.

9(a) and (b) respectively show random sequence electrical signals corresponding to a random sequence having a length of 13, and a sine wave frequency f _c is 3 MHz. Accordingly, the random sequence electric signal or excitation signal shown in (a) and (b) of FIG. 9 has a length of 4.5 μs.

Specifically, the random sequence electrical signal shown in (a) of FIG. 9 is the random sequence w ₁ =(-1, -1, -1, -1, 1, 1, -1, 1, -1, -1, 1, -1, 1), and the random sequence electrical signal shown in (b) of FIG. 9 is a random sequence w ₂ = (-1, -1, -1, -1, 1, -1, 1, 1, 1, -1, 1, 1, 1) is an electrical signal generated in response to

9(c) and 9(d) show spatial responses at two spatial points r _k=1 and r _k=2 in the region of interest. Assuming that the middle position of the transducer array 111 of the probe 110 is the reference point (or origin), the coordinates of the first spatial point r _k=1 are (0.25mm, 0.55mm) and the second spatial point r _k The coordinates of ₌₂ are (-0.25mm, 0.55mm).

Specifically, (c) of FIG. 9 shows spatial responses at two spatial points when random sequence ultrasound signals are transmitted using only two transducer elements. As can be seen in (c) of FIG. 9 , when only two ultrasound signals are transmitted, it can be seen that spatial responses to two different spatial points are very similar. That is, the spatial resolution is low.

On the other hand, (d) of FIG. 9 shows spatial responses at two spatial points when random sequence ultrasound signals are transmitted using 128 transducer elements. As can be seen in (d) of FIG. 9, when many ultrasonic signals are transmitted, it can be seen that the spatial response of two adjacent spatial points differs greatly. That is, as more independent random sequence ultrasound signals are transmitted, correlation between spatial responses between adjacent spatial points may be reduced and spatial resolution may be increased.

10 to 12 are views illustrating echo signals according to a pair of a transmission element (Tx) and a reception element (Rx).

10 to 12, the transducer array 111 includes 128 transducer elements 112.

10 shows normalized echoes received by the first receiving element (i=1) to the tenth receiving element (i=10) when only the first transmitting element (j=1) is activated and transmits an ultrasonic signal. indicate signals. Referring to FIG. 10 , since the ultrasonic signal is transmitted only from the first transmitting element, it can be confirmed that echo signals received by different receiving elements have similar waveforms.

11 shows normalized echo signals received by the first receiving element (i = 1) when the first transmitting elements (j = 1) to the tenth transmitting elements (j = 10) are activated one by one and transmit ultrasonic signals. indicate Referring to FIG. 11 , since different ultrasonic signals are individually transmitted from different transmitting elements, it can be seen that echo signals received by the first receiving element have very different waveforms.

FIG. 12 shows that when 10 unit transmission elements from the 20th transmission element (j = 20) to the 110th transmission element (j = 110) are activated one by one to transmit ultrasonic signals, the first reception element (i = 1) receives the signal. represents normalized echo signals. Referring to FIG. 12 , as in FIG. 11 , since different ultrasonic signals are individually transmitted from different transmitting elements, it can be seen that echo signals received by the first receiving element have very different waveforms. Furthermore, referring to FIG. 12, since the activated transmission elements are spatially spaced apart from each other, there is a difference in the propagation path of the ultrasonic signal, and accordingly, it can be confirmed that a time difference (or time delay) occurs in each echo signal. .

The simulations of FIGS. 13 to 16 described later were performed using a transducer array 111 composed of 128 transducer elements 112, and each transducer element 112 had a width of 0.3 mm, a height of 4.5 mm, and a height of 0.03 mm. They are spaced at intervals of mm. The central frequency is 3 MHz and the sampling frequency is 40 MHz. The region of interest ranged from 35 mm to 55 mm in the axial direction and −10 mm to 10 mm in the lateral direction. A virtual grid with resolution d = 0.25 mm is set in the region of interest, and accordingly, the number of point scatterers is N _S = 6561. In addition, the acoustic properties of the phantom were set to be similar to those of the human body, and the speed of sound was set to c ₀ =1540 m/s.

13 is a diagram showing results of ultrasound imaging simulation using beamforming and ultrasound imaging simulation results according to an embodiment of the present disclosure.

13(a) shows a synthetic phantom including two adjacent point objects, the two adjacent points are located at a depth of 45 mm, and the two points are separated by 0.25 mm in the lateral direction.

FIG. 13(b) shows ultrasound imaging results using conventional beamforming for the phantom shown in FIG. was created by Referring to (b) of FIG. 13, two points are not distinguished from each other, and a sidelobe appears.

FIG. 13(c) shows ultrasound imaging results of the phantom shown in FIG. 13(a) according to an embodiment of the present disclosure. Referring to (c) of FIG. 13, it can be seen that the two points are very clearly distinguished and no other noise is included.

13(d) is a diagram comparing a radio frequency (RF) signal obtained from a single channel and a reconstructed signal according to an embodiment of the present disclosure. The original RF signal is the superposition of the impulse response for two points. Referring to (d) of FIG. 13 , it can be confirmed that the original RF signal and the reconstructed signal match according to an embodiment of the present disclosure.

13(e) is a diagram comparing intensity profiles at a point of 45 mm in the axial direction. Referring to (e) of FIG. 13 , it can be confirmed that the intensity profile according to an embodiment of the present disclosure clearly distinguishes the boundary between two points and matches the intensity image profile of the original image. On the other hand, the intensity profile according to focused B-mode ultrasound imaging using conventional beamforming cannot distinguish the boundary between two points at all.

14 is a diagram showing results of ultrasound imaging simulation using beamforming and ultrasound imaging simulation results according to an embodiment of the present disclosure.

14(a) shows the Shepp-Logan phantom. Referring to (a) of FIG. 14, the Shepp-Logan phantom includes a large number of scatterers having different intensities.

FIG. 14(b) shows ultrasound imaging results using conventional beamforming for the phantom shown in FIG. 14(a). Referring to (b) of FIG. 14 , the image is blurry and the inner circle is not visible.

FIG. 14(c) shows ultrasound imaging results of the phantom shown in FIG. 14(a) according to an embodiment of the present disclosure. Referring to (c) of FIG. 14 , the boundary line is clear in the image, and the inner circle is also clearly visible. Also, the contrast is similar to the original phantom image.

FIG. 15 is a diagram showing intensity profiles for the simulation shown in FIG. 14 .

Referring to FIG. 15 , it can be seen that the intensity profile according to an embodiment of the present disclosure is very similar to the original image at a point of 45 mm in the axial direction. On the other hand, the intensity profile according to focused B-mode ultrasound imaging using conventional beamforming cannot distinguish the boundary line from the original image at all, including side lobes.

16 is a diagram comparing the number of receiving elements to be used for ultrasound imaging and the quality of the results according to an embodiment of the present disclosure.

In the example shown in FIG. 16 , the transducer array 111 of the probe 110 includes 128 transducer elements 112 . That is, ultrasonic signals are transmitted using 128 transmitting elements 112a, and echo signals are received using at least some of the 128 receiving elements 112b.

(a) of FIG. 16 shows the original image of the Shepp-Logan phantom, and (b) to (e) of FIG. 16 receive an echo signal using at least one receiving element 112b and based on the received signal. shows the ultrasound image generated by The types and numbers of receiving elements 112b used for each image are shown in Table 1 below.

Name # of receiving element MSE PSNR [dB] SNR [dB] (a) Original phantom image - - - - (b) All elements of the array 128 0.0158 17.99 5.60 (c) Every ^3rd element 43 0.0162 17.90 5.51 (d) Every ^5th element 26 0.0164 17.86 5.47 (e) Elements in the inverval [30,98] 69 0.0120 19.21 6.81 (f) Elements in the inverval [40,88] 49 0.0119 19.23 6.84 (g) Every 2 ^nd element in the inverval [50,78] 15 0.0122 19.20 6.80 (h) single element One 0.0255 15.93 3.54

(b) of FIG. 16 shows an ultrasound image generated using all 128 receiving elements 112b, and it can be seen that details of the original image are well represented. 16(g) shows an ultrasound image generated using 15 receiving elements 112b located in the center of the transducer array 111, and an ultrasound image generated using all the receiving elements ((b in FIG. 16) )), MSE (Mean Squared Error) is lower, and PSNR (Peak Signal-to-Noise Ratio) and SNR (Signal-to-Noise Ratio) are further improved. This phenomenon can be explained by the acceptance angle of the transducer element 112. The effect of random interference is dependent on the number of random waves, and random interference is stronger in the center of the region of interest. Therefore, in order to provide better performance, an ultrasound image may be generated by selectively using some of the receiving elements 112b located in the center of the transducer array 111 instead of using all of the receiving elements 112b. Also, (h) of FIG. 16 shows an ultrasound image generated using only one receiving element 112, and although noise is included, it can be confirmed that the boundary line of the phantom is well represented. That is, even if only one receiving element 112b is used, an ultrasound image having significant quality can be generated.

The experiments of FIGS. 17 and 18 to be described later were performed using a transducer array 111 composed of 128 piezo-electric transducer elements 112, each transducer element 112 having a width of 0.3 mm and They are 4.5 mm high and are spaced at intervals of 0.03 mm. The central frequency is 3-12 MHz, the sampling frequency is 40 MHz, and the frequency of the transmitted ultrasonic signal is 3 MHz. The region of interest has an axial length of 60 mm and a lateral length of 40 mm. A virtual grid with resolution d = 0.25 mm is set in the region of interest, and accordingly, the number of point scatterers is N _S =38801.

17 is a diagram showing ultrasound imaging results using beamforming for a silicon phantom and ultrasound imaging results according to an embodiment of the present disclosure.

The silicone phantom used in FIG. 17 is made of a solid elastic hydrogel that mimics the properties of human tissue. The region of interest in this phantom contains eight 0.1 mm diameter nylon wires and a cyst, each nylon wire spaced 10 mm apart.

17(a) shows ultrasound imaging results using conventional beamforming having 128 scan lines for the silicon phantom described above. And, (b) of FIG. 17 shows ultrasound imaging results using random interference with respect to the above-described silicon phantom according to an embodiment of the present disclosure. Comparing the two ultrasound imaging results, the ultrasound imaging result using random interference can confirm a neat nylon wire without side lobes and significantly less speckle noise, in contrast to the ultrasound imaging result using conventional beamforming.

18 is a diagram showing ultrasound imaging results using beamforming for a silicon phantom and ultrasound imaging results according to an embodiment of the present disclosure.

The region of interest of the silicon phantom used in FIG. 18 contained 12 nylon wires with a diameter of 0.08 mm, and each nylon wire was spaced at intervals of 4 mm, 3 mm, 2 mm, 1 mm, 0.5 mm, and 0.25 mm in the axial and lateral directions, respectively. are spaced apart

18(a) shows the result of ultrasound imaging using conventional beamforming having 128 scan lines for the silicon phantom described above, and FIG. 18(c) shows the nylon wire of the image of FIG. 18(a). This is an enlarged image of the area. In addition, FIG. 18(b) shows ultrasound imaging results using random interference for the above-described silicon phantom according to an embodiment of the present disclosure, and FIG. 18(d) shows the image of FIG. 18(b). This is an enlarged image of the nylon wire area. Comparing the two ultrasound imaging results, it can be confirmed that the ultrasound imaging result using random interference represents the details of the nylon wire more clearly, compared to the ultrasound imaging result using conventional beamforming.

According to an embodiment of the present disclosure, the above-described method can be implemented as computer readable code on a medium on which a program is recorded. The computer-readable medium includes all types of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable media include Hard Disk Drive (HDD), Solid State Disk (SSD), Silicon Disk Drive (SDD), ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc. there is

Claims (14)

In the ultrasonic imaging device using random interference,
a probe comprising a transducer array of a plurality of transducer elements; and
generating random sequences for each of the plurality of transducer elements, transmitting ultrasound signals corresponding to the random sequences through the transducer array, and corresponding to the transmitted ultrasound signals through the transducer array; A processor for receiving echo signals and generating an ultrasound image corresponding to the received echo signals using transmission matrices corresponding to the random sequences
including,
The processor
generating a random sequence electrical signal by convolutional multiplying the random sequences with a half-cycle sine wave, and transmitting the ultrasonic signals corresponding to the random sequence electrical signal through the transducer array;
ultrasound imaging device. The method of claim 1,
The processor
An ultrasound imaging apparatus generating the random sequences by uniformly selecting a predetermined number of elements from -1 or 1. delete The method of claim 1,
The processor
The ultrasound imaging apparatus, wherein the corresponding ultrasound signals are simultaneously transmitted using at least one of the plurality of transducer elements included in the transducer array. The method of claim 4,
The processor
The ultrasound imaging apparatus of claim 1 , wherein the corresponding ultrasound signals are simultaneously transmitted using all of the plurality of transducer elements included in the transducer array. The method of claim 1,
The processor
and receiving the echo signals using at least one of the plurality of transducer elements included in the transducer array. The method of claim 1,
Each of the transfer matrices is
Corresponds to each receiving element used to receive the echo signals, and each column is composed of spatial impulse responses received by the corresponding receiving element. The method of claim 7,
The processor
The ultrasound imaging apparatus of claim 1 , wherein ultrasound images are individually generated for each receiving element using a corresponding echo signal and a corresponding transmission matrix, and a final ultrasound image is generated by calculating an average of the individually generated ultrasound images. The method of claim 8,
The processor
optimization problem

to generate an ith ultrasound image f _i corresponding to the ith receiving element, G _i is an ith transmission matrix corresponding to the ith receiving element, and p _i is the ith received by the ith receiving element. An echo response, N _R is the number of the receiving elements, and ε is a regularization parameter. The method of claim 7,
The processor
Assuming that the ultrasound images individually acquired by each receiving element are the same, a single relational expression between the echo signals and the transmission matrices is generated, and a final ultrasound image is generated through an inverse matrix operation in the relational expression. imaging device. The method of claim 10,
The processor
The above single relation

, and the equation using the inverse matrix operation

The final ultrasound image f is generated by solving , where G _T is a transmission matrix corresponding to the N _{R th} receiving element, p _T is an echo response corresponding to the N _{R th} receiving element, and N _R is the Repairman, Ultrasound Imaging Device. The method of claim 1,
display
Including more,
The processor
An ultrasound imaging device that outputs the generated ultrasound image through the display. In the ultrasound imaging method using random interference,
generating random sequences for each of a plurality of transducer elements included in the transducer array;
transmitting ultrasound signals corresponding to the random sequences through the transducer array;
receiving echo signals corresponding to the transmitted ultrasound signals through the transducer array; and
generating ultrasound images corresponding to the received echo signals using transmission matrices corresponding to the random sequences;
including,
Transmitting the ultrasonic signals
generating a random sequence electrical signal by convolutional multiplying the random sequences with a half-cycle sine wave, and transmitting the ultrasonic signals corresponding to the random sequence electrical signal through the transducer array;
ultrasound imaging method. A computer program stored in a computer readable medium recording an ultrasound imaging method using random interference, the method comprising:
generating random sequences for each of a plurality of transducer elements included in the transducer array;
transmitting ultrasound signals corresponding to the random sequences through the transducer array;
receiving echo signals corresponding to the transmitted ultrasound signals through the transducer array; and
generating ultrasound images corresponding to the received echo signals using transmission matrices corresponding to the random sequences;
including,
Transmitting the ultrasonic signals
generating a random sequence electrical signal by convolutional multiplying the random sequences with a half-cycle sine wave, and transmitting the ultrasonic signals corresponding to the random sequence electrical signal through the transducer array;
A computer program stored on a computer-readable medium.

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