KR101509447B1 - Display pixel based focusing method using quadrature sampling in photoacoustic imaging and apparetus thereof - Google Patents

Abstract

The present invention relates to a pixel-unit focusing apparatus for a photoacoustic signal, comprising: a rectangular-wave demodulator for generating in-phase and quadrature-phase components through quadrature demodulation sampling of a received photoacoustic signal; The beamformer includes a beam former that is beam-focused to a pixel point. By using quadrature demodulation sampling, the in-phase and quadrature phase components are obtained before beam focusing, and the amount of computation can be reduced by focusing each component on a pixel point.

Description

[0001] The present invention relates to a method of constructing a pixel-unit image of a photoacoustic and ultrasound image,

The present invention relates to a pixel-unit image forming method and apparatus for photoacoustic and ultrasound images, and more particularly, to a pixel-by-pixel focusing unit, a photoacoustic imaging system, Pixel-unit focusing method, and recording medium therefor.

In a typical ultrasonic and photoacoustic image, a plurality of scan lines are formed in an image region in a radial direction, and an envelope of a received focused signal is detected. The detected envelope signal is displayed on the screen through a scan conversion process based on a two-dimensional interpolator. However, the image forming method based on the scanning line converter has a disadvantage in that the side lobe generated in the radial direction affects the interpolation process and blurring artifacts generated in the interpolator degrade the image quality.

The prior art related to this is "an ultrasound imaging system and method for receiving and focusing at a point corresponding to pixels of a display device (Application No.: 10-2000-0007236) ".

The first problem to be solved by the present invention is to provide a pixel-by-pixel focusing device for concentrating photoacoustic signals on a pixel-by-pixel basis through quadrature demodulation sampling.

A second problem to be solved by the present invention is to provide a photoacoustic imaging system that concentrates photoacoustic signals pixel by quadrature demodulation sampling.

A third problem to be solved by the present invention is to provide a pixel-by-pixel focusing method of concentrating photoacoustic signals on a pixel-by-pixel basis through quadrature demodulation sampling.

It is another object of the present invention to provide a computer-readable recording medium storing a program for causing a computer to execute the above-described method.

According to an aspect of the present invention, there is provided an orthogonal demodulator for generating an in-phase component and a quadrature-phase component through quadrature demodulation sampling of a received photoacoustic signal. And a beam former for beam-focusing each of the generated in-phase component and quadrature-phase component to a pixel point.

According to an embodiment of the present invention, the apparatus may further include a phase compensator for compensating for a phase difference between signals generated according to a receive focusing delay time in each channel.

According to another embodiment of the present invention, the apparatus may further include a delay time calculator for calculating the reception focusing delay time.

According to another aspect of the present invention, there is provided an orthogonal demodulator for generating an in-phase component and a quadrature-phase component through quadrature demodulation sampling of a received photoacoustic signal. A beam former for beam-forming each of the generated in-phase component and quadrature-phase component to pixel points; A phase compensator for compensating for a phase difference between signals caused by a receive focusing delay time in each channel; An envelope detector for detecting an envelope of the beam converged signal; An image processor for generating a video signal using the beam converged signal; And a display for displaying the processed image.

According to a third aspect of the present invention, there is provided a method for generating a quadrature phase signal, comprising: generating an in-phase component and a quadrature phase component through quadrature demodulation sampling of a received photoacoustic signal; And focusing the generated in-phase component and the quadrature-phase component to pixel points.

According to another aspect of the present invention, there is provided a computer-readable recording medium having recorded thereon a program for causing a computer to execute the above-described pixel-unit focusing method.

According to the present invention, by using quadrature demodulation sampling, the amount of computation can be reduced by obtaining inphase and quadrature components before beam focusing and then focusing them on pixel points using each component. Also, according to the present invention, it is possible to provide the same ultrasound and photoacoustic image as the existing pixel-unit focusing method by eliminating the phase error generated in the beam focusing.

1 is a block diagram illustrating a pixel-unit focusing device according to an embodiment of the present invention.
2 is a block diagram illustrating an imaging system in accordance with an embodiment of the present invention.
FIG. 3 illustrates envelope detection in the pixel-unit focusing device according to the embodiment of the present invention.
4 illustrates quadrature demodulation and phase compensation of a pixel-unit focusing apparatus according to an embodiment of the present invention.
5 is a block diagram illustrating an image system according to another embodiment of the present invention.
6 is a flowchart of a pixel-by-pixel focusing method according to an embodiment of the present invention.
7 is a flowchart of a pixel-by-pixel focusing method according to another embodiment of the present invention.

Prior to the description of the concrete contents of the present invention, for the sake of understanding, the outline of the solution of the problem to be solved by the present invention or the core of the technical idea is first given.

A pixel-by-pixel convergence apparatus for a photoacoustic signal according to an embodiment of the present invention includes an orthogonal demodulator for generating an in-phase component and a quadrature-phase component through quadrature demodulation sampling of a received photoacoustic signal, And a beam former that beams each component to a pixel point.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art, however, that these examples are provided to further illustrate the present invention, and the scope of the present invention is not limited thereto.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which: It is to be noted that components are denoted by the same reference numerals even though they are shown in different drawings, and components of different drawings can be cited when necessary in describing the drawings. In the following detailed description of the principles of operation of the preferred embodiments of the present invention, it is to be understood that the present invention is not limited to the details of the known functions and configurations, and other matters may be unnecessarily obscured, A detailed description thereof will be omitted.

1 is a block diagram illustrating a pixel-unit focusing device according to an embodiment of the present invention.

The pixel-unit focusing apparatus 100 according to an embodiment of the present invention includes a quadrature demodulating unit 110 and a beam former 120. A phase compensation unit 130, a delay time calculating unit 140, and an analog receiving unit 150. [

The pixel-unit focusing device 100 may be used to receive a photoacoustic signal or an ultrasonic signal and focus the image signal on a pixel-by-pixel basis. Hereinafter, the pixel-unit focusing device 100 will be described using a photoacoustic signal. The pixel-unit focusing device of the ultrasonic signal corresponds to the pixel-unit focusing device of the photoacoustic signal and the object thereof is only the difference between the photoacoustic signal and the ultrasonic signal, and other configurations correspond.

The quadrature demodulation unit 110 generates the in-phase component and the quadrature-phase component through the quadrature demodulation sampling of the received photoacoustic signal.

More specifically, the received photoacoustic signal includes an in-phase component and a quadrature-phase component. Accordingly, the photoacoustic signal is received and quadrature demodulation sampling is performed on the photoacoustic signal to generate the in-phase component and the quadrature-phase component of the photoacoustic signal, respectively.

The beam former 120 beams each of the generated in-phase component and the quadrature-phase component to the pixel point.

More specifically, each of the in-phase component and the quadrature-phase component generated by the orthogonal demodulation unit 110 is beam-focused on a pixel point. It is possible to eliminate the problem that the image quality is deteriorated by the blurring artifacts generated in the image forming method based on the scanning line converter by direct beam focusing on the pixel points in pixel units without the scanning line converter.

The phase compensator 130 compensates the phase difference between signals generated according to the reception focusing delay time in each channel.

More specifically, since a time delay occurs due to reception focusing between received optical signals, each channel compensates the phase difference between signals caused by the reception focusing delay time.

The delay time calculation unit 140 calculates a reception focusing delay time.

More specifically, the receive-focusing delay time is calculated so that the phase compensator 130 can compensate for the phase difference between signals. The phase compensation unit 130 compensates for the phase difference between signals using the reception focusing delay time calculated by the delay time calculation unit 140. [

The analog receiving unit 150 filters and amplifies the photoacoustic signal.

More specifically, since the received photoacoustic signal contains noise, the analog receiving unit 150 filters the noise included in the photoacoustic signal and amplifies the photoacoustic signal. The analog receiving unit 150 may include the orthogonal demodulation unit 110 and may be implemented separately.

A series of processes of the pixel-unit focusing device 100 according to the embodiment of the present invention will be described in detail with reference to FIG. 3 to FIG.

2 is a block diagram illustrating an imaging system in accordance with an embodiment of the present invention.

The image system 200 according to an exemplary embodiment of the present invention may generate a photoacoustic image or an ultrasound image in the same manner as the pixel-unit focusing apparatus 100. [ Hereinafter, an image system for generating a photoacoustic image will be described. The configuration of the ultrasound image system corresponds to the photoacoustic imaging system.

The photoacoustic imaging system 200 generates and displays an image using the beam converged signal in the pixel unit focusing device 100 of FIG. For this purpose, in addition to the orthogonal demodulating unit 110, the beam former 120, the phase compensating unit 130, the delay time calculating unit 140, and the analog receiving unit 150 of the pixel-unit focusing apparatus 100 of FIG. And may further include a detection unit 260, an image processing unit 270, and a display 280.

The envelope detector 260 detects an envelope of the beam converged signal.

More specifically, to generate a photoacoustic image, an envelope of a beam-focused signal is detected at a pixel point.

The image processor 270 generates a video signal using the beam converged signal.

More specifically, a beam is focused and a video signal that can be displayed using a signal that detects an envelope is generated. A B-mode image or a different type of image signal.

The display 280 displays the image generated by the image processing unit 270 and provides the photo-acoustic image to the user.

The envelope detection process of the envelope detector 260 will be described in detail with reference to FIGS. 3 to 4. FIG.

FIG. 3 illustrates envelope detection in a pixel-unit focusing apparatus according to an embodiment of the present invention, and FIG. 4 illustrates quadrature demodulation and phase compensation of a pixel-unit focusing apparatus according to an embodiment of the present invention.

)들이 필요하다. 상기 추가적인 빔포밍 포인트의 수는 직각 복조에 사용되는 유한 임펄스 응답 필터(a finite impulse response (FIR) filter)에 의해 결정된다. n번째 채널의 흡수체(absorber)로부터 수신된 고주파는 수학식 1과 같다.In the pixel-based convergence method, the dynamic receive beamforming directly converges the signal to each pixel point on the Cartesian coordinates to remove the blurring artifacts occurring in the scanning line converter. As shown in Fig. 3, along the virtual scanning line for detecting the envelope of each pixel point in the quadrature demodulation, an additional beam forming point

) Are needed. The number of additional beamforming points is determined by a finite impulse response (FIR) filter used for quadrature demodulation. The high frequency received from the absorber of the n-th channel is expressed by Equation (1).

[Equation 1]

는 광음향(PA, Photoacoustic) 신호의 포락선,

는 샘플링 주기,

는 각주파수,

는 위상, 및

은 트랜스듀서와 흡수체 사이의 거리와 초음파속도이다.here,

Is an envelope of a photoacoustic (PA) signal,

The sampling period,

Respectively,

Is the phase, and

Is the distance between the transducer and the absorber and the ultrasonic velocity.

The receive focusing delay time is applied to compensate for the phase difference between the absorbers for each channel, and the focusing delay time for the additional beam forming point is calculated as shown in equation (2).

&Quot; (2) "

은 n번째 위치하는 채널의 위치, c는 초음파 속도이다.here,

Is the position of the n-th channel, and c is the ultrasonic velocity.

에 동일한 상기 산출된 수신 집속 지연 시간을 적용하면, 빔포밍은 수학식 3과 같이 나타낼 수 있다.

The beamforming can be expressed by Equation (3). &Quot; (3) "

&Quot; (3) "

Here, N is the number of channels.

As shown in Equation (3), after performing beamforming along a virtual scanning line, baseband in-phase and quadrature-phase components for a pixel point can be calculated as shown in Equation (4).

&Quot; (4) "

은 L의 길이를 갖는 필터의 계수(the coefficient of low-pass FIR filter)이다.here,

Is the coefficient of the low-pass FIR filter.

The envelope detected from Equation (3) can be calculated as shown in Equation (5).

&Quot; (5) "

A block diagram of envelope detection using quadrature sampling (QS) and quadrature demodulation sampling for a complex baseband signal generated by demodulation of a high-frequency signal prior to an analog-to-digital converter (ADC) is shown in FIG.

The complex baseband signal received at the n < th > channel using quadrature demodulation sampling is expressed by Equation (6).

&Quot; (6) "

If the receive focusing delay time of Equation (2) is applied to Equation (6), the following Equation (7) can be obtained.

However,

은 빔포밍이후 위상 에러를 발생시킨다.Since the focusing delay time differs between channels,

Generates a phase error after beamforming.

를 제거하기 위하여, 복소수 기저대역 신호의 위상을 보상한다. 상기 위상보상은 상기 복소수 기저대역 신호에

을 곱해줌으로써 수행될 수 있으며, 이는 다음 수학식 8과 같다.The phase error

To compensate for the phase of the complex baseband signal. The phase compensation may be performed on the complex baseband signal

, Which is expressed by the following equation (8). &Quot; (8) "

&Quot; (8) "

는 각 채널에서와 초점에서 다른 값을 갖는 동적 수신 집속 지연 시간에 의해 결정된다. 따라서, 동상신호와 직각위상 성분을 각각 생성하여 수신 집속을 수행하면, 포락선은 다음 수학식 9와 같이 검출될 수 있다.

Is determined by the dynamic receive focusing delay time at each channel and with different values in focus. Therefore, when the in-phase signal and the quadrature-phase component are respectively generated and reception focusing is performed, the envelope can be detected as shown in the following equation (9).

&Quot; (9) "

As described above, quadrature demodulation sampling can be performed in a dynamic receive focusing without phase errors. Since the in-phase and quadrature components can be obtained in the analog-to-digital converter, additional beam forming points for performing quadrature demodulation at each pixel point become unnecessary. Therefore, by using the quadrature demodulation sampling, the beam forming points in the pixel unit focusing can be reduced by the L factor. And L is the number of taps of the FIR filter used for the quadrature demodulation.

5 is a block diagram illustrating an image system according to another embodiment of the present invention.

First, the photoacoustic signal received through the ultrasound transducer is filtered and amplified through the analog receiver, and then the quantized data is converted into inphase and quadrature components. The converted signal is stored in the system and received and concentrated by using the respective components at the pixel points. At this time, each channel compensates the phase difference caused by the receiving focusing delay time. The beam-focused photoacoustic signal is displayed on the screen through various signal processing processes.

6 is a flowchart of a pixel-by-pixel focusing method according to an embodiment of the present invention.

Step 610 is a step of generating the in-phase component and the quadrature-phase component through the quadrature demodulation sampling of the received photoacoustic signal.

More specifically, in order to reduce the beam convergence amount of the received photoacoustic signal, the received photoacoustic signal is subjected to quadrature demodulation sampling to generate an in-phase component and a quadrature-phase component. The detailed description of this step corresponds to the detailed description of the orthogonal demodulation unit 110 of FIG. 1, and is replaced with a detailed description of the orthogonal demodulation unit 110 of FIG.

In step 620, the generated in-phase component and quadrature-phase component are beam-concentrated to pixel points.

More specifically, the in-phase component and the quadrature-phase component generated in operation 610 are integratedly focused on the pixel points. In step 610, the photoacoustic signal is divided into an in-phase component and a quadrature-phase component, and each component is beam-focused to a pixel point. A detailed description of this step corresponds to a detailed description of the beam former 120 of FIG. 1, and is replaced with a detailed description of the beam former 120 of FIG.

Step 630 is a step of calculating the reception focusing delay time.

More specifically, since the focusing delay time differs for each channel receiving the photoacoustic signal, a phase error occurs. Therefore, the reception focusing delay time is calculated to compensate for the phase error. The detailed description of this step corresponds to the detailed description of the delay time calculation unit 140 of FIG. 1, and is replaced with a detailed description of the delay time calculation unit 140 of FIG.

Step 640 is a step of compensating for a phase difference occurring in each channel due to the receiving focusing delay time.

More specifically, the phase error is compensated using the receive focusing delay time calculated in step 630. The detailed description of this step corresponds to the detailed description of the phase compensator 130 of FIG. 1 and is replaced with a detailed description of the phase compensator 130 of FIG.

7 is a flowchart of a pixel-by-pixel focusing method according to another embodiment of the present invention.

In operation 710, an envelope of the beam converged signal is detected.

More specifically, in step 620, an envelope of the beam converged signal is detected to generate an image signal from the beam converged signal. The detailed description of this step corresponds to the detailed description of the envelope detection unit 260 of FIG. 2, and is replaced with a detailed description of the envelope detection unit 260 of FIG.

In operation 720, an image signal is generated using the beam converged signal.

More specifically, it is a step of generating a video signal using the envelope data detected in step 710. The detailed description of this step corresponds to the detailed description of the image processing unit 270 of FIG. 2, and is replaced with a detailed description of the image processing unit 270 of FIG.

Step 730 is a step of displaying the generated image. And provides the image generated in operation 720 to the user.

Embodiments of the present invention may be implemented in the form of program instructions that can be executed on various computer means and recorded on a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and specific embodiments and drawings. However, it should be understood that the present invention is not limited to the above- And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

100: Pixel-based focusing device
110: orthogonal demodulator
120: Beamformer
130: phase correction unit
140: delay time calculating unit
150:
200: Imaging system
260: envelope detection unit
270:
280: Display

Claims (20)

A quadrature demodulator for generating an in-phase component and a quadrature-phase component with respect to a pixel point through quadrature demodulation sampling of the received photoacoustic signal; And
And a beam former directly beam-assembling each of the generated in-phase component and quadrature-phase component to each of the pixel points on a pixel-by-pixel basis. The method according to claim 1,
And a phase compensator for compensating for a phase difference between signals generated according to a receive focusing delay time corresponding to each pixel point in each channel. 3. The method of claim 2,
And a delay time calculator for calculating the reception focusing delay time. The method according to claim 1,
And an analog receiving unit for filtering and amplifying the photoacoustic signal. A quadrature demodulator for generating an in-phase component and a quadrature-phase component with respect to a pixel point through quadrature demodulation sampling of the received photoacoustic signal;
A beam former for directly beam-forming each of the generated in-phase component and quadrature-phase component on a pixel-by-pixel basis;
An envelope detector for detecting an envelope of the beam converged signal;
An image processor for generating a video signal using the beam converged signal; And
And a display for displaying the generated image. 6. The method of claim 5,
And a phase compensator for compensating for a phase difference between signals generated according to a receive focusing delay time corresponding to each pixel point in each channel. The method according to claim 6,
And a delay time calculating unit for calculating the reception focusing delay time. A quadrature demodulator for generating an in-phase component and a quadrature component with respect to a pixel point through quadrature demodulation sampling of the received ultrasonic signal;
A beam former for directly beam-forming each of the generated in-phase component and quadrature-phase component on a pixel-by-pixel basis;
An envelope detector for detecting an envelope of the beam converged signal;
An image processor for generating a video signal using the beam converged signal; And
And a display for displaying the generated image. 9. The method of claim 8,
And an ultrasound transducer for receiving the ultrasound signal. 9. The method of claim 8,
And a phase compensator for compensating for a phase difference between signals generated according to a receive focusing delay time corresponding to each pixel point in each channel. Generating an in-phase component and a quadrature-phase component with respect to a pixel point through quadrature demodulation sampling of the received photoacoustic signal; And
And directly beam-combining each of the generated in-phase component and quadrature-phase component to each pixel point on a pixel-by-pixel basis. 12. The method of claim 11,
Compensating a phase difference occurring in accordance with a receiving focusing delay time corresponding to each pixel point in each channel. 13. The method of claim 12,
And calculating the reception focusing delay time. 12. The method of claim 11,
And detecting an envelope of the beam-focused signal. 12. The method of claim 11,
Further comprising the step of filtering and amplifying the photoacoustic signal. 15. The method of claim 14,
Generating a video signal using the beam focused signal; And
And displaying the generated image. A method of focusing a photoacoustic signal on a pixel-by-pixel basis. Generating an in-phase component and a quadrature-phase component with respect to a pixel point through quadrature demodulation sampling of the received ultrasound signal; And
And directly beam-combining the generated in-phase component and the quadrature-phase component to each of the pixel points on a pixel-by-pixel basis. 18. The method of claim 17,
And compensating for a phase difference occurring in accordance with a reception focusing delay time corresponding to each pixel point in each channel. 18. The method of claim 17,
Wherein the ultrasound signals are received through an ultrasound transducer. A computer-readable recording medium storing a program for causing a computer to execute the method according to any one of claims 11 to 19.

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