KR101298935B1 - Method and apparatus of producing ultrasound images and photoacoustic images - Google Patents

Method and apparatus of producing ultrasound images and photoacoustic images Download PDF

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Publication number
KR101298935B1
KR101298935B1 KR1020120038496A KR20120038496A KR101298935B1 KR 101298935 B1 KR101298935 B1 KR 101298935B1 KR 1020120038496 A KR1020120038496 A KR 1020120038496A KR 20120038496 A KR20120038496 A KR 20120038496A KR 101298935 B1 KR101298935 B1 KR 101298935B1
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South Korea
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image
ultrasonic
ultrasound
signal
interest
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KR1020120038496A
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Korean (ko)
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유양모
강지운
장진호
송태경
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서강대학교산학협력단
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/52—Devices using data or image processing specially adapted for diagnosis using ultrasonic, sonic or infrasonic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/8979—Combined Doppler and pulse-echo imaging systems
    • G01S15/8984—Measuring the velocity vector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52085—Details related to the ultrasound signal acquisition, e.g. scan sequences

Abstract

PURPOSE: A method and a device of generating an ultrasound image and a photoacoustic image are provided to obtain an image with improved spatial resolution, contrast, and a low noise level for the ultrasound image and the photoacoustic image by estimating an optimal ultrasound speed to be used for image restoration. CONSTITUTION: A method of generating an ultrasound image and a photoacoustic image includes a step of emitting a laser pulse to a target (200); a step of generating the photoacoustic image by receiving an ultrasound signal when the target absorbs the emitted laser pulse, and the ultrasound signal is generated (210); a step of estimating an optimal ultrasound speed from the generated photoacoustic image (220); a step of emitting an ultrasound pulse to the target (230); a step of performing beam convergence and orthogonal demodulation for the received ultrasound signal from the target by using the estimated optimal ultrasound speed (240); and a step of generating the ultrasound image by using an orthogonal demodulation performing result (250). [Reference numerals] (200) Emit a laser pulse to a target; (210) Generate a photoacoustic image by receiving an ultrasound signal when the target absorbs the emitted laser pulse, and the ultrasound signal is generated; (220) Estimate an optimal ultrasound speed from the generated photoacoustic image; (230) Emit an ultrasound pulse to the target; (240) Perform beam convergence and orthogonal demodulation for the received ultrasound signal from the target by using the estimated optimal ultrasound speed; (250) Generate an ultrasound image by using an orthogonal demodulation performing result; (260) Generate a fusion image by using the photoacoustic image and the ultrasound image; (AA) Start; (BB) End

Description

Method and apparatus for generating ultrasound images and photoacoustic images {Method and apparatus of producing ultrasound images and photoacoustic images}

The present invention relates to a method for generating an ultrasound image and an optoacoustic image, and more particularly, an improved image can be obtained more efficiently by performing an optimal ultrasound velocity estimation process only once, and a shortening sequence for estimating an optimum ultrasound velocity is provided. Accordingly, the present invention relates to a method and an apparatus for generating an ultrasound image and an optoacoustic image capable of obtaining a faster frame rate image.

Conventional ultrasound and optoacoustic imaging systems perform beam focusing and signal processing by fixing the speed of ultrasonic waves. However, since the speed of the ultrasound varies depending on the medium in the human body, an error occurs between the actual speed and the assumed speed. In particular, in the case of fat, the ultrasonic traveling speed is about 1450 m / s, which has a lot of error with the assumed ultrasonic traveling speed. This error reduces the effect of focusing on beam focusing and cannot provide a high resolution image.

Therefore, the actual ultrasonic velocity through the medium is required when generating high resolution ultrasound and photoacoustic images. However, in the related art, the ultrasonic speed is estimated after generating the ultrasound image, and the ultrasonic speed is estimated after generating the photoacoustic image, thereby causing an unnecessary estimation process and a low frame rate.

Therefore, the first problem to be solved by the present invention is to obtain an image with improved spatial resolution, contrast and low noise level for both the photoacoustic and ultrasonic images by estimating the optimal ultrasonic velocity and using it for image reconstruction. It is to provide an ultrasound image and a photoacoustic image generating method that can be.

The second problem to be solved by the present invention is to obtain an improved image more efficiently because the optimal ultrasonic velocity estimation process is required only once, and to reduce the sequence of estimating the optimal ultrasonic velocity, It is to provide an ultrasound image and an optoacoustic image generating apparatus that can be obtained.

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.

The present invention comprises the steps of firing a laser pulse to the object of interest to achieve the first object; Receiving the ultrasound signal to generate an optoacoustic image when the emitted laser pulse is absorbed by the object of interest to generate an ultrasound signal; Estimating an optimum ultrasonic velocity from the generated photoacoustic image; Irradiating ultrasonic pulses to the object of interest; Performing beam focusing and quadrature demodulation on the ultrasonic signals received from the object of interest using the estimated optimal ultrasonic velocity; And generating an ultrasound image by using the result of performing the quadrature demodulation.

The method may further include generating a fusion image using the generated photoacoustic image and the ultrasound image. In this case, the fusion image may be generated by averaging luminance values of pixels of the photoacoustic image and pixels of the ultrasound image.

According to an embodiment of the present disclosure, estimating the optimal ultrasonic speed may include generating the optoacoustic image for a plurality of ultrasonic speeds, generating a lateral spatial spectrum from the optoacoustic image, and determining a predetermined side. The ultrasonic speed when the magnitude of the signal component at the directional frequency is the largest may be estimated as the optimal ultrasonic speed.

According to another embodiment of the present disclosure, the estimating of the optimal ultrasonic speed may include estimating the ultrasonic speed corresponding to the smallest phase difference among the differences between the channel data phases of the plurality of ultrasonic speeds as the optimal ultrasonic speed. Can be. At this time, the difference between the channel data phase is preferably calculated by the dispersion of the channel data phase.

In addition, the present invention, to achieve the first object, the step of irradiating the ultrasonic pulse of interest; If the irradiated ultrasonic pulse is reflected from the object of interest, receiving the reflected ultrasonic signal to generate an ultrasonic image; Estimating an optimum ultrasound velocity from the generated ultrasound image; Firing a laser pulse onto the object of interest; When the emitted laser pulse is absorbed by the object of interest to generate an ultrasonic signal, performing beam focusing and quadrature demodulation on the ultrasonic signal received from the object of interest using the estimated optimal ultrasonic velocity; And generating an optoacoustic image by using the result of performing the quadrature demodulation. In this case, the method may further include generating a fusion image using the generated photoacoustic image and the ultrasound image.

The present invention to achieve the second object, the laser generator for emitting a laser pulse to the target of interest; An ultrasonic pulse generator for radiating ultrasonic pulses to the target of interest; A transducer for receiving the ultrasonic signal generated by the laser generator and the ultrasonic signal generated by the ultrasonic pulse generator; A beamformer for beam focusing the ultrasonic signals received by the transducer; A quadrature demodulator for quadrature demodulating the beam focused ultrasound signal; An envelope detector for detecting an envelope from the quadrature demodulation result; A log compression unit configured to log-compress the detected envelope signal; A scanline converting unit converting the coordinate position of the log-compressed envelope signal into the coordinate position of the image display apparatus; And an ultrasonic velocity estimator for estimating an optimal ultrasonic velocity from the ultrasonic image or the photoacoustic image generated by the scan line converter, wherein the ultrasonic velocity estimator uses the ultrasonic velocity estimated from the ultrasonic image to beam the photoacoustic image. An ultrasound image and an optoacoustic image generating apparatus may be used for focusing and quadrature demodulation, or using the ultrasound velocity estimated from the photoacoustic image for beam focusing and quadrature demodulation of the ultrasound image.

In order to solve the above other technical problem, the present invention provides a computer-readable recording medium that records a program for executing the above-described method for generating the ultrasound image and photoacoustic image in a computer.

According to the present invention, an image having an improved spatial resolution, contrast, and low noise level can be obtained for both an optoacoustic image and an ultrasound image by estimating an optimal ultrasonic velocity and using the image for reconstruction.

In addition, according to the present invention, since the optimal ultrasonic velocity estimation process is required only once, an improved image can be obtained more efficiently, and a faster frame rate image can be obtained by shortening a sequence for estimating the optimal ultrasonic velocity. .

Furthermore, according to the present invention, since there is a biological tissue in which the optimum ultrasound velocity estimation in the ultrasound image and the optimum ultrasound velocity estimation in the optoacoustic image are relatively favorable to each other, an image having an improved resolution using the ultrasound image and the photoacoustic image can be obtained. You can get it.

1 is a block diagram of an ultrasound image and an optoacoustic image generating device according to an exemplary embodiment of the present invention.
2 is a flowchart illustrating a method of generating an ultrasound image and an optoacoustic image according to an exemplary embodiment of the present invention.
3 is a flowchart illustrating a method of generating an ultrasound image and an optoacoustic image according to another exemplary embodiment of the present invention.
Figure 4 shows a sequence used in the ultrasound image and photoacoustic image generating apparatus according to the present invention.
FIG. 5 shows reconstructed ultrasound and optoacoustic fusion images at respective ultrasound velocities according to the ultrasound velocities.
FIG. 6 illustrates the spatial resolution at each ultrasonic velocity for the ultrasound image and the optoacoustic image.
7 shows light absorption coefficients of various biological tissues.

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.

The present invention estimates the average optimal ultrasonic velocity of a human body to be observed using photoacoustic or ultrasonic data in order to apply a non-uniform variation of ultrasonic velocity in an image to be used for both photoacoustic and ultrasonic image restoration. That's how.

Ultrasound image and optoacoustic image generation method according to an embodiment of the present invention comprises the steps of firing a laser pulse to the target of interest; Receiving the ultrasound signal to generate an optoacoustic image when the emitted laser pulse is absorbed by the object of interest to generate an ultrasound signal; Estimating an optimum ultrasonic velocity from the generated photoacoustic image; Irradiating ultrasonic pulses to the object of interest; Performing beam focusing and quadrature demodulation on the ultrasonic signals received from the object of interest using the estimated optimal ultrasonic velocity; And generating an ultrasound image by using the quadrature demodulation result.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred 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.

The configuration of the invention for clarifying the solution to the problem to be solved by the present invention will be described in detail with reference to the accompanying drawings based on the preferred embodiment of the present invention, the same in the reference numerals to the components of the drawings The same reference numerals are given to the components even though they are on different drawings, and it is to be noted that in the description of the drawings, components of other drawings may be cited if necessary. 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.

In addition, in the entire specification, when a part is referred to as being 'connected' to another part, it may be referred to as 'indirectly connected' not only with 'directly connected' . In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, "comprises" or "comprising" excludes the presence or addition of one or more other components, steps, operations, or elements other than the components, steps, operations, or elements mentioned. I never do that.

The present invention relates to a technique for applying a single ultrasonic velocity estimation result to both photoacoustic and ultrasonic imaging techniques in performing photoacoustic and ultrasonic fusion medical imaging. This is based on the ultrasonic propagation of the same medium, which will have the same optimal ultrasonic velocity for optoacoustic and ultrasonic imaging techniques. Through this, it is possible to obtain the effect of reducing the burden of estimating the optimal imaging ultrasonic speed by half, and obtain the optimal image quality for the photoacoustic and ultrasonic speed.

1 is a block diagram of an ultrasound image and an optoacoustic image generating device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the ultrasound image and photoacoustic image generating apparatus according to the present embodiment may include a laser generator 100, an ultrasonic pulse generator 110, a transducer 120, an operation controller 130, and an ADC 140. ), A beamformer 150, a quadrature demodulator 160, a back end processor 170, an ultrasonic velocity estimator 180, and a fusion image generator 190.

The ultrasound image and photoacoustic image generating apparatus according to an embodiment of the present invention is a system capable of selectively performing both ultrasound and laser transmission in a system capable of receiving ultrasonic waves, and estimates an optimum sound velocity with an ultrasonic reflection signal by ultrasonic transmission. In the case of SSC-US (Sound speed correction method based on ultrasound), the optical sound signal generated by the laser transmission to estimate the optimal sound wave speed will be referred to as SSC-PA (Sound speed correction method based on photoacoustic).

The laser generator 100 emits a short laser pulse to an object of interest (for example, human body or animal tissue). Laser energy is absorbed in the object of interest, which causes a sharp increase in temperature and thermal expansion. This thermal expansion generates ultrasonic waves, and the generated ultrasonic signals are received by the transducer 120.

The ultrasonic pulse generator 110 irradiates human or animals with ultrasonic pulses in the 2 MHz to 30 MHz band. Ultrasound images are constructed by using reflected waves generated at the interface between different media and scattered waves scattered by particles in the respective media.

According to an embodiment of the present invention, the ultrasonic pulse generator 110 in the reception dynamic focusing technique changes the time for transmitting the ultrasonic pulse from the transducer 120 at the time of transmitting the ultrasonic pulse, and all the same time at one focal point. By allowing to be added, the phases can be added in the same state.

The transducer 120 receives the ultrasonic waves generated by the laser generator 100 and the ultrasonic signals generated by the ultrasonic pulse generator 110 and transmits the ultrasonic signals to the ADC 140.

The operation controller 130 controls the operations of the laser generator 100 and the ultrasonic pulse generator 110. It is preferable that the laser pulse of the laser generator 100 and the ultrasound pulse of the ultrasonic pulse generator 100 are sequentially irradiated to the human body or the animal.

The ADC 140 converts the received analog ultrasonic signal into a digital ultrasonic signal.

The beamformer 150 performs beam focusing using a digital ultrasonic signal. Ultrasonic signals reflected from the focal point arrive at different times on the transducer 120. When the delay values are compensated by the time difference, the sum is matched with the phases of the ultrasonic signals from the focal point. Will have

In order to obtain a high resolution image during beam focusing, the variable time delay value given to the transducer 120 may be sampled at 16 times the center frequency of the transducer (f 0 ). However, in consideration of the performance of the ADC 140 and the size of the memory used for beam focusing, the sample may be sampled at a low sampling frequency and then interpolated to perform digital beam focusing with an effect of 16f 0 .

The quadrature demodulator 160 multiplies the cosine signal and the sine signal having a fundamental frequency f 0 component by the beam-focused ultrasonic signal r (n) to separate the in-phase component and the quadrature component.

As the ultrasonic signal passes through the medium, the ultrasonic wave is attenuated according to the type of the medium, the frequency of the ultrasonic wave, and the distance of the ultrasonic wave. That is, since the ultrasonic signal is a signal reflected from a deeper return, the center frequency of the signal decreases, so the phase value of the quadrature demodulator 160 should also change dynamically.

The separated in-phase and quadrature components are preferably passed through a low pass filter that removes harmonic components to obtain a baseband signal. In this case, since the reflected ultrasonic signal decreases not only the center frequency but also the bandwidth, the cutoff frequency of the low pass filter needs to be changed dynamically.

The back end processor 170 includes an envelope detector 171, a log compressor 172, and a scan line converter 173.

The envelope detection unit 171 detects an envelope from an in-phase component and a right angle component.

The log compression unit 172 performs log compression for nonlinear conversion of the detected envelope signal. Since the dynamic range of the signal passing through the envelope detector 171 is 60 dB or more while the dynamic range of the display device and the human eye is about 30 dB, the log compression unit 172 compresses the signal passed through the envelope detector 171.

The scan line converter 173 converts the coordinate position of the ultrasound data into an image representation coordinate position of a video display device or an image storage device which is generally used. In this case, the conversion process of the scan line converter 173 varies depending on the transducer used.

In the case of the linear transducer, the acquired ultrasound data and the pixel position of the image do not coincide, but since the coordinates of the ultrasound data generally coincide with the X-Y coordinate system, which is the coordinate system constituting the image, the pixel value of the image can be saved simply. However, in the case of the phased array transducer, since the coordinates of the acquired ultrasound data are made of R-θ coordinates instead of X-Y coordinates, they are inconsistent with the coordinates of the image. Therefore, scanning line transformation including coordinate transformation must be performed to construct an image.

The ultrasonic velocity estimator 180 estimates the ultrasonic velocity in the medium and transmits the ultrasonic velocity to the ultrasonic pulse generator 110, the beamformer 150, and the scan line converter 173.

The ultrasonic pulse generator 110 controls the transmission delay time of the ultrasonic pulse using the estimated ultrasonic speed, the beamformer 150 calculates the reception focus delay time using the estimated ultrasonic speed, and the scan line converter. 173 converts log-compressed data into scanline data using the estimated ultrasonic speed.

An example of the ultrasonic velocity estimation is as follows. After setting the region of interest (ROI), the signal component magnitude at a specific lateral frequency is analyzed through lateral spatial spectral analysis on the image data at each specific ultrasound velocity imaged by the imaging system. At this time, in order to improve the accuracy of the ultrasonic velocity estimation, various lateral frequencies are selectively selected to obtain the magnitude of the lateral frequency signal, and normalized to the baseband signal size so that the ratio with the high frequency signal can be compared. Thereafter, the focal velocity is calculated by accumulating the magnitude of the normalized lateral frequency, and the ultrasonic velocity having the highest focal velocity value is the optimal ultrasonic velocity.

As another example of the ultrasonic speed estimation, a difference between each channel data phase may be received for each ultrasonic speed, and the ultrasonic speed corresponding to the smallest phase difference among the differences between the received channel data phases may be estimated as the optimal ultrasonic speed. The difference between each channel data phase is preferably calculated by the variance of each channel data phase. The optimal ultrasonic velocity estimated by the ultrasonic velocity estimator 180 is preferably provided to the beamformer 150 and the quadrature demodulator 160.

The fusion image generator 190 generates a fusion image by using the generated photoacoustic image and the ultrasound image. For example, when the intensity value of an ultrasonic signal corresponding to a pixel of an image is equal to or less than a predetermined value, the ultrasound image is represented by gray scale, and when the magnitude value of the ultrasonic signal corresponding to a pixel of the image exceeds a predetermined value, light is emitted. Acoustic images can be expressed in color.

Meanwhile, the ultrasound speed may be estimated by selecting an image for which ultrasound speed is advantageous for each body tissue, and then the ultrasound speed estimated for generating another image may be used.

If the light absorption coefficient is significantly different from the surroundings, it is preferable to estimate the ultrasonic velocity from the photoacoustic image in the case of a point image such as microcalcification, cancer tissue blood vessel image or blood flow image.

On the other hand, in the case of a tissue having a large ultrasound reflection coefficient or a tissue having a large difference in acoustic signal impedance, for example, a plane image such as a liver or a carotid artery, it is desirable to estimate the ultrasound velocity from the ultrasound image. That is, since the ultrasonic reflection coefficient on the surface of the blood vessel of the carotid artery is large, the ultrasonic velocity estimation method using edge detection of the ultrasonic image is more effective than the ultrasonic velocity estimation method from the photoacoustic image.

Therefore, in the photoacoustic image, the signal sensitivity of the microcalcified tissue image is higher than that of the ultrasound image, and in the ultrasound image, the signal sensitivity of the liver image is higher than that of the photoacoustic image.

2 is a flowchart illustrating a method of generating an ultrasound image and an optoacoustic image according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the ultrasound image and optoacoustic image generating method according to the present exemplary embodiment includes steps that are processed in time series in the ultrasound image and optoacoustic image generating apparatus illustrated in FIG. 1. Therefore, although omitted below, the above descriptions of the apparatus for generating the ultrasound image and the photoacoustic image shown in FIG. 1 also apply to the method for generating the ultrasound image and the photoacoustic image according to the present embodiment.

In operation 200, the ultrasound image and the optoacoustic imaging apparatus emit short laser pulses to an object of interest (eg, human body or animal tissue). Laser energy is absorbed in the object of interest, which causes a sharp increase in temperature and thermal expansion. This thermal expansion generates ultrasonic waves, and the generated ultrasonic waves are received by the transducer 120.

In operation 210, the ultrasound image and the optoacoustic imaging apparatus generate an optoacoustic image through beamforming, quadrature demodulation, envelope detection, log compression, and scanning line conversion using the ultrasonic signal received by the transducer 120.

In operation 220, the ultrasound image and the optoacoustic imaging apparatus estimate an optimal ultrasonic speed from the generated optoacoustic image.

In operation 230, the ultrasound image and the optoacoustic imaging apparatus irradiate an ultrasound pulse to an object of interest.

In operation 240, the ultrasound image and the optoacoustic imaging apparatus perform beam focusing on the ultrasonic signals reflected from the object of interest using the estimated ultrasonic speed, and quadrature demodulate the beam focused data.

In operation 250, the ultrasound image and the optoacoustic imaging apparatus detect an envelope using an in-phase component and a right-angle component generated as a result of quadrature demodulation, and generate an ultrasound image through log compression and scan line transformation. In scanning line conversion, it is necessary to consider the ultrasonic velocity in the process of converting the post-processed data (time gain compensation or log compression) to a scale that is easy for human to see.

In operation 260, the ultrasound image and the optoacoustic imaging apparatus generate a fusion image using the generated photoacoustic image and the ultrasound image.

3 is a flowchart illustrating a method of generating an ultrasound image and an optoacoustic image according to another exemplary embodiment of the present invention.

Referring to FIG. 3, the method for generating an ultrasound image and an optoacoustic image according to the present exemplary embodiment includes steps that are processed in time series in the ultrasound image and the optoacoustic image generating apparatus illustrated in FIG. 1. Therefore, although omitted below, the above descriptions of the apparatus for generating the ultrasound image and the photoacoustic image shown in FIG. 1 also apply to the method for generating the ultrasound image and the photoacoustic image according to the present embodiment.

In operation 300, the ultrasound image and the optoacoustic imaging apparatus irradiate an ultrasound pulse to an object of interest.

In operation 310, the ultrasound image and the optoacoustic imaging apparatus generate an ultrasound image through beamforming, quadrature demodulation, envelope detection, log compression, and scanning line conversion by using the ultrasound signal received by the transducer 120.

In operation 320, the ultrasound image and the optoacoustic imaging apparatus estimate an optimal ultrasound velocity from the generated ultrasound image.

In operation 330, the ultrasound image and the photoacoustic imaging apparatus emit short laser pulses to an object of interest (eg, human body or animal tissue). Laser energy is absorbed in the object of interest, which causes a sharp increase in temperature and thermal expansion. This thermal expansion generates ultrasonic waves, and the generated ultrasonic waves are received by the transducer 120.

In operation 340, the ultrasound image and the optoacoustic imaging apparatus perform beam focusing and quadrature demodulation on the ultrasonic signals received by the transducer 120 using the estimated ultrasonic speed.

In operation 350, the ultrasound image and the optoacoustic imaging apparatus detect an envelope using the in-phase component and the right-angle component generated as a result of orthogonal demodulation, and generate an optoacoustic image through log compression and scanning line conversion.

In operation 360, the ultrasound image and the optoacoustic imaging apparatus generate a fusion image using the generated photoacoustic image and the ultrasound image.

Figure 4 shows a sequence used in the ultrasound image and photoacoustic image generating apparatus according to the present invention.

Referring to FIG. 4, SSC-PA and SSC-US, which are applied to both imaging techniques after calculating the optimum sound velocity for only an ultrasonic or optoacoustic single technique, are shown. In particular, the ultrasound image and the photoacoustic image generating apparatus according to the present invention can obtain an improved image more efficiently because the optimal ultrasonic velocity estimation process is required only once.

Looking at the sequence of sound speed correction method based on photoacoustic (SSC-PA), the laser pulses are first fired on the object of interest, and receive beamforming, quadrature demodulation, and backend processing are performed. Back-end processing includes envelope detection, log compression, and scan line conversion. Then, the optimal ultrasonic velocity is estimated using the photoacoustic image generated as a result of the backend processing.

Now, the ultrasonic pulse is irradiated to the object of interest. When the ultrasonic pulse is irradiated to the object of interest, it is preferable to irradiate the ultrasonic pulse after the ultrasonic signal is generated and received by the transducer. This is to prevent the ultrasonic signal generated by the laser pulse and the ultrasonic signal generated by the ultrasonic pulse from interfering with each other.

Looking at the sequence of the sound speed correction method based on ultrasound (SSC-US), first, the ultrasonic pulse is emitted to the target of interest, and the SSC-US performs reception beamforming, quadrature demodulation, and back-end processing similarly to the SSC-PA. Then, the optimum ultrasound velocity is estimated using the ultrasound image generated as a result of the backend processing.

Now, the laser pulse is emitted to the object of interest. When the laser pulse is irradiated to the object of interest, it is preferable to emit the laser pulse after the ultrasound signal is reflected and received by the transducer after the ultrasound signal is reflected.

Since SSC-US and SSC-PA only need to perform the optimal ultrasonic velocity estimation once, the performance can be improved in a shorter time. The method of obtaining the average optimal ultrasonic waves is performed by beam focusing for various ultrasonic velocities with stored radio-frequency (RF) channel data and then evaluating their focusing performance to convert the ultrasonic velocities that represent the maximum performance into the optimal ultrasonic velocities. There is a method of selection, and the selected ultrasonic velocity is used for image restoration. The time required for the estimation of the ultrasound velocity is proportional to the number of image reconstructions performed to find the optimum ultrasound velocity. In the present invention, since the optimal ultrasonic velocity estimation is performed only once, the image quality can be improved while reducing the number of image reconstructions.

Referring back to FIGS. 1 to 4, the transmission of energy for constituting the ultrasound image or the photoacoustic image is performed by the laser generator 100 and the ultrasound pulse generator 110, according to a predetermined sequence. The operation control unit 130 controls the transmission and the transducer 120 receives it. Since the optimal sound wave velocity estimation has various algorithms proposed as a method of applying the ultrasonic velocity satisfying the optimal performance parameter to the beamformer 150 using the signal in each signal processing step, a detailed description thereof will be omitted. .

In the ultrasonic and optoacoustic fusion systems according to the present invention, in order to estimate the optimum ultrasonic speed, the ultrasonic speed is estimated from the ultrasonic or optoacoustic single data rather than the optimal ultrasonic speed from the ultrasonic and optoacoustic images. Applies to both optoacoustic images.

FIG. 5 shows reconstructed ultrasound and optoacoustic fusion images at respective ultrasound velocities according to the ultrasound velocities. According to the image evaluation, it can be seen that the quality of the photoacoustic and ultrasonic images is the best at the ultrasonic speed of 1530m / s to 1540m / s.

FIG. 6 illustrates the spatial resolution at each ultrasonic velocity for the ultrasound image and the optoacoustic image.

Referring to FIG. 6, it can be seen that the same trend is shown, and particularly, the optimal performance is equally shown between 1530 m / s and 1540 m / s. Therefore, the optimal convergence image may be obtained by applying the velocity estimated in either the photoacoustic or ultrasonic imaging technique to both imaging techniques.

In order to quantitatively determine the spatial resolution of each image in FIG. 6, it can be seen that both techniques show the best performance in the expected interval. This is because sound waves in the photoacoustic image or sound waves in the ultrasonic image are both affected by the same nonuniformity as they pass through the same medium. Through this, it can be seen that the image quality of the ultrasonic and optoacoustic imaging technique can be improved by one estimation regardless of the optimal sound velocity estimation algorithm.

As shown in FIG. 6, since the section showing the optimal spatial resolution is the same in the photoacoustic and ultrasonic images, the present invention can implement the ultrasonic and optoacoustic fusion images more efficiently.

7 shows light absorption coefficients of various biological tissues.

The intensity of the ultrasonic waves generated by the photoacoustic effect is generated in proportion to the light absorption. Referring to the optical absorption coefficient shown in FIG. 7, it can be seen that biological tissues such as hemoglobin oxide (HbO 2), hemoglobin, melanin, and moisture have different absorption rates according to respective wavelengths. Since the light absorption coefficient is different for each living tissue, it is preferable to supplement the living tissue with a small light absorption coefficient by an ultrasonic imaging method.

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, etc. 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 recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, 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 not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device 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 .

The present invention is a technique belonging to an efficient image quality improvement technique of ultrasound and optoacoustic fusion medical imaging system.

100: laser generating unit 110: ultrasonic pulse generating unit
120: transducer 130: operation control unit
140: ADC 150: beamformer
160: right angle demodulator 170: back-end processing unit
180: ultrasonic velocity estimation unit 190: fusion image generator

Claims (11)

Firing a laser pulse onto the object of interest;
Receiving the ultrasound signal to generate an optoacoustic image when the emitted laser pulse is absorbed by the object of interest to generate an ultrasound signal;
Estimating an optimum ultrasonic velocity from the generated photoacoustic image;
Irradiating ultrasonic pulses to the object of interest;
Performing beam focusing and quadrature demodulation on the ultrasonic signals received from the object of interest using the estimated optimal ultrasonic velocity; And
And generating an ultrasound image using the quadrature demodulation result. The method according to claim 1,
And generating a fusion image using the generated photoacoustic image and the ultrasonic image. The method of claim 2,
And the fused image is generated by averaging luminance values of pixels of the photoacoustic image and pixels of the ultrasonic image. The method according to claim 1,
Estimating the optimal ultrasonic velocity,
Generating the optoacoustic image for a plurality of ultrasonic velocities, generating a lateral spatial spectrum from the optoacoustic image, and determining the ultrasonic velocity when the magnitude of the signal component at a predetermined lateral frequency is the largest. Ultrasonic image and optoacoustic image generation method characterized in that the estimation by the speed. The method according to claim 1,
Estimating the optimal ultrasonic velocity,
And an ultrasonic speed corresponding to the smallest phase difference among the differences between the channel data phases of the plurality of ultrasonic speeds as the optimal ultrasonic speed. 6. The method of claim 5,
And the difference between the channel data phases is calculated as a variance of the channel data phases. Irradiating an ultrasound pulse to a subject of interest;
If the irradiated ultrasonic pulse is reflected from the object of interest, receiving the reflected ultrasonic signal to generate an ultrasonic image;
Estimating an optimum ultrasound velocity from the generated ultrasound image;
Firing a laser pulse onto the object of interest;
When the emitted laser pulse is absorbed by the object of interest to generate an ultrasonic signal, performing beam focusing and quadrature demodulation on the ultrasonic signal received from the object of interest using the estimated optimal ultrasonic velocity; And
And generating an optoacoustic image using the result of performing the quadrature demodulation. The method of claim 7, wherein
And generating a fusion image using the generated photoacoustic image and the ultrasonic image. A laser generator for emitting a laser pulse to an object of interest;
An ultrasonic pulse generator for radiating ultrasonic pulses to the target of interest;
A transducer for receiving the ultrasonic signal generated by the laser generator and the ultrasonic signal generated by the ultrasonic pulse generator;
A beamformer for beam focusing the ultrasonic signals received by the transducer;
A quadrature demodulator for quadrature demodulating the beam focused ultrasound signal;
An envelope detector for detecting an envelope from the quadrature demodulation result;
A log compression unit configured to log-compress the detected envelope signal;
A scanline converting unit converting the coordinate position of the log-compressed envelope signal into the coordinate position of the image display apparatus; And
And an ultrasonic velocity estimator for estimating an optimal ultrasonic velocity from the ultrasonic image or the photoacoustic image generated by the scan line converter.
The ultrasonic velocity estimator uses the ultrasonic velocity estimated from the ultrasonic image for beam focusing and quadrature demodulation of the optoacoustic image, or uses the ultrasonic velocity estimated from the photoacoustic image for beam focusing and quadrature demodulation of the ultrasonic image. An ultrasound image and an optoacoustic image generating device. 10. The method of claim 9,
And an fusion image generator configured to generate a fusion image using the generated photoacoustic image and the ultrasonic image. A computer-readable recording medium having recorded thereon a program for executing the method of claim 1 on a computer.
KR1020120038496A 2012-04-13 2012-04-13 Method and apparatus of producing ultrasound images and photoacoustic images KR101298935B1 (en)

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