KR101393512B1 - Method for estimating speed of ultrasonic waves, method and apparatus for ultrasonic imaging using the estimated speed thereof - Google Patents

Abstract

A method for estimating an ultrasound velocity, and a method and an apparatus for ultrasound imaging using the same are disclosed. A method of estimating an ultrasonic velocity according to an exemplary embodiment includes obtaining an ultrasound image for the entire medium using one reference velocity and identifying boundaries of a plurality of medium layers constituting the medium from the obtained image, Selecting at least two regions of interest (ROIs) for adjacent different ones of the separated media layers, and using the ultrasound velocity and depth in the selected region of interest, To obtain a differential ultrasonic velocity.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating an ultrasound velocity and an ultrasound imaging method using the same,

The present invention relates to an ultrasound image processing technique, and more particularly, to a method for estimating an ultrasound velocity suitable for a medium composed of a complex medium layer, and a method and apparatus for imaging an ultrasound image using the estimated ultrasound velocity.

Ultrasound imaging is an ultrasound-based imaging technology that is well known for medical ultrasound imaging technology that can visualize the size, structure, and lesion of muscles and internal organs. Generally, ultrasound imaging uses the principle of pulse-echo. A piezoelectric crystal is provided in an ultrasonic probe or a transducer for generating an ultrasonic signal to irradiate a target medium to be photographed and sensing a signal reflected therefrom, As shown in FIG. When an instantaneous voltage is applied to the piezoelectric crystal, the crystal vibrates to generate ultrasonic waves.

When a short pulse of ultrasound is irradiated into the human body, it proceeds through the medium in the tissue at a constant rate until it meets a specific reflection surface. If the irradiated ultrasonic wave hits the reflecting surface, a part of the ultrasonic beam is reflected in the direction of the origin, which is called an echo. The interaction between the ultrasonic wave and the medium appears in the form of reflection, refraction, absorption, etc., of which reflection is the basis of ultrasound image formation. That is, the generation of echoes occurs at the interface (ultrasonic interface) between media having different properties, and even with a very small difference in density, such an interface can be formed. The water, blood cells, fat, hepatocytes, bile, bile duct wall, connective tissue, or fibrous tissue that constitute the human body have different densities, and the ultrasonic interface is formed due to the difference in density. Here, the property of the medium means the acoustic impedance of the medium, and can be determined by the product of the density and the sound velocity. That is, the greater the difference in acoustic resistance, the greater the degree of reflection of the ultrasonic waves.

On the other hand, the echo reflected at the ultrasonic interface in the medium receives the sound wave through a process similar to that of the transducer generating the ultrasonic wave. That is, the echo vibrates the transducer, and the transducer converts the vibration into an electrical signal. Then, the electrical signal thus converted can be converted into a digital image through an apparatus such as an ultrasonic scanner. The following non-patent references provide an overview of ultrasound imaging technology in the medical field.

 A Study on the Development of Medical Ultrasound Imaging Technology, Jong Soo Choi, Chung - Ang University, 1985.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is therefore an object of the present invention to provide an ultrasound diagnostic system and a method for correcting an ultrasound image, In order to overcome the technical limitations that can be set, the difference between the ultrasonic wave velocity and the actual ultrasonic wave velocity is caused by the ultrasonic wave velocity.

According to an aspect of the present invention, there is provided a method of estimating an ultrasonic velocity of a medium, comprising: obtaining an ultrasound image of the entire medium using a reference velocity; Identifying each of the medium layers by identifying a boundary of a plurality of medium layers constituting the medium from the obtained image; And selecting at least two regions of interest (ROIs) for the adjacent different medium layers from among the separated medium layers, using the ultrasonic velocity and the depth in the selected ROI, And obtaining a differential ultrasonic velocity for the ultrasonic wave.

In the method of estimating the ultrasonic velocity according to an exemplary embodiment, the step of obtaining the differential ultrasonic velocity may include calculating a difference between the depths of the two medium layers in the medium layer located second in the depth direction of the medium Selecting a region of interest; And calculating the ultrasonic velocity in the medium layer located first in the depth direction of the medium and the ultrasonic velocity in the medium layer located in the second medium by using a relation based on the medium contribution in the two selected regions of interest . The method for estimating the ultrasonic velocity may further include the steps of selecting a region of interest for a medium layer positioned third after the depth of the medium and calculating an ultrasonic velocity in the medium layer, And obtaining the differential ultrasonic velocity at each of the plurality of ultrasonic waves.

In the method of estimating the ultrasonic velocity according to an embodiment, the number of the ROIs to be selected is proportional to the number of the separated medium layers.

In the method of estimating the ultrasonic velocity according to an embodiment, the boundary of the medium layer may be obtained by obtaining an ultrasound image at a plurality of velocities with respect to the entire medium, and using an absolute velocity of the boundary, Is identified by calculating the distance.

In the method of estimating the ultrasonic velocity according to an embodiment, when the slope of the boundary of the medium layer is equal to or greater than a threshold value, a cumulative ultrasonic velocity is estimated by dividing a receiver, which collects a beam reflected from the medium, into sub- And compensating for the slope of the boundary by estimating the contribution of each medium to the ultrasonic propagation path.

According to another aspect of the present invention, there is provided a method of capturing an ultrasound image of a medium, the method comprising: acquiring an ultrasound image of the entire medium using one reference speed; Identifying each of the medium layers by identifying a boundary of a plurality of medium layers constituting the medium from the obtained image; Selecting at least two regions of interest for adjacent different medium layers among the divided medium layers and obtaining a differential ultrasonic velocity for each of the medium layers using the ultrasonic velocity and depth in the selected region of interest step; And irradiating ultrasound corresponding to each of the medium layers using the obtained differential ultrasound velocity and focusing the beam reflected from the medium to acquire an ultrasound image.

In the method of photographing the ultrasound image according to another embodiment, the step of acquiring the differential ultrasound velocity may include acquiring the differential ultrasound velocity of the ultrasound image at a second depth in the medium layer located second in the depth direction of the medium Selecting a region of interest; Calculating an ultrasonic velocity at a first medium layer located in the depth direction of the medium and an ultrasonic velocity at the second medium layer using a relation based on the medium contribution in the selected two regions of interest; And selecting an area of interest with respect to a medium layer located third and subsequent to the depth direction of the medium and calculating an ultrasonic velocity in the medium layer by repeating the steps of obtaining a differential ultrasonic velocity in the plurality of medium layers Step.

The present invention also provides a computer-readable recording medium having recorded thereon a program for causing a computer to execute a method of estimating an ultrasonic velocity of a medium described above and a method of photographing an ultrasound image using the method.

According to another aspect of the present invention, there is provided an apparatus for photographing an ultrasound image of a medium according to another embodiment of the present invention, comprising: a beamformer for collecting an ultrasound image by focusing a reflected beam on a medium; A processing unit having at least one processor to control an ultrasonic wave velocity irradiated to the medium and reconstruct an ultrasound image acquired through the beam former; And a display unit for outputting the restored ultrasound image, wherein the processing unit obtains an ultrasound image for the whole medium through the beam former using one reference speed, The method comprising the steps of: identifying each of the medium layers by identifying boundaries of a plurality of medium layers constituting the medium layer; selecting at least two regions of interest for adjacent different medium layers of the divided medium layers; And the depth are used to obtain a differential ultrasonic velocity for each of the medium layers.

In the apparatus for photographing the ultrasound image according to another embodiment, the processing unit may select two ROIs having different depths from each other in the medium layer located second in the depth direction of the medium among the divided medium layers, Calculating an ultrasonic velocity in a first medium layer located in the depth direction of the medium and an ultrasonic velocity in the second medium layer using a relation based on the medium contribution in the selected two regions of interest, The region of interest is selected for the medium layer positioned third after the depth direction of the medium, and the process of calculating the ultrasonic velocity in the medium layer is repeated to acquire the differential ultrasonic velocity in the plurality of medium layers.

In the apparatus for photographing the ultrasound image according to another embodiment, the number of the ROIs to be selected is proportional to the number of the divided medium layers.

According to another embodiment of the present invention, in the apparatus for photographing the ultrasound image, the region of interest may be selected by a user visually recognizing a medium layer divided in the ultrasound image obtained for the entire medium, .

In the apparatus for photographing the ultrasound image according to another embodiment, the boundary of the medium layer may be obtained by obtaining an ultrasound image at a plurality of speeds with respect to the entire medium, and using the speed at which the boundary is clear, Is identified by calculating the distance.

In the apparatus for photographing the ultrasound image according to another embodiment, when the slope of the boundary of the medium layer is equal to or larger than the threshold value, the processing section divides the receiver of the beam former, which focuses the beam reflected from the medium, And compensating the slope of the boundary by estimating a cumulative ultrasonic velocity and estimating a contribution of each medium to each ultrasonic propagation path.

In an apparatus for photographing an ultrasound image according to another embodiment of the present invention, the beam former may include a beam reflected from the medium using ultrasound irradiated to each of the medium layers according to the differential ultrasonic velocity controlled through the processing unit And the processing unit acquires an ultrasound image from the focused beam and displays the obtained ultrasound image through the display unit.

Embodiments of the present invention can estimate the ultrasound propagation speed optimized for different tissues inside the human body by classifying the medium layer constituting the medium and acquiring the differential ultrasonic velocity for each medium layer in the region of interest selected therefrom , And the image quality, resolution, and signal sensitivity over the entire region of the ultrasound image can be improved by taking an ultrasound image of the complex medium using the obtained differential ultrasound velocity.

Fig. 1 is a diagram illustrating the ultrasonic wave propagation speed of each tissue in the human body.
FIG. 2 is a diagram for explaining and comparing ultrasound images according to the progress speed of ultrasonic waves in a composite medium.
3 is a flowchart illustrating a method of estimating an ultrasonic velocity for a medium according to an embodiment of the present invention.
FIG. 4 is a flowchart illustrating a process of acquiring a differential ultrasonic velocity for each of the medium layers in the ultrasonic velocity estimation method of FIG. 3 according to an embodiment of the present invention.
5 is a diagram illustrating a geometric modeling concept for calculating the ultrasonic propagation speed inherent in each medium layer in a composite medium.
6 is a block diagram illustrating an apparatus for photographing an ultrasound image according to another embodiment of the present invention.
FIG. 7 is a diagram illustrating an ultrasound image captured according to an ultrasound velocity estimation method according to embodiments of the present invention.

Prior to describing the embodiments of the present invention, the characteristics of the ultrasound diagnostic imaging field and the problems therefrom are briefly introduced, and the technical means employed by the embodiments of the present invention are sequentially presented to solve the problems .

As described above, in the conventional ultrasound imaging system, ultrasound waves fixed at a specific traveling speed are used in the reception beam focusing and signal processing processes. That is, in the medical ultrasound imaging apparatus, an ultrasound image is photographed and restored by using an average value for the entire human body tissue or an ultrasound velocity for one region of interest (ROI) in the image as a reference value.

However, as shown in FIG. 1 illustrating the ultrasonic propagation speed of each tissue in the human body, tissues and cells in the human body have different ultrasonic propagation rates due to their unique characteristics of the medium. In other words, there is a great difference in the speed of ultrasonic wave propagation between the respective tissues. When the ultrasound image is restored by performing the reception beam focusing at the ultrasonic wave propagation speed fixed to the same value due to such characteristics, the ultrasound velocity set to a fixed value, And the difference in the progress speed, which causes a problem of deteriorating the quality of the ultrasound image. This is because the conventional ultrasonic imaging method described above uses only a fixed value of the ultrasonic velocity, while the tissues constituting the human body have various values of the ultrasonic wave propagation velocity. Accordingly, it is possible to obtain a relatively good quality ultrasound image for the set region of interest, but the resolution of the ultrasound image is degraded for other regions having different tissue characteristics.

FIG. 2 is a diagram for explaining and comparing ultrasound images according to the progress speed of ultrasonic waves in a composite medium, wherein [A] illustrates the result of imaging an ultrasound image using a fixed ultrasound propagation velocity (1540 m / s) , And [B] illustrate the results of imaging an ultrasound image using the ultrasound propagation velocity (1590 m / s) for one specific ROI1. Experiments were performed to compare the images according to the ultrasonic propagation velocity used for focusing the receive beam on the two media, phantom and gel pad, which have different ultrasonic propagation velocities of 1540m / s and 1610m / s, and [A] and [B ] Note that both use only one ultrasonic propagation velocity.

(1590m / s) estimated in one specific region of interest (ROI1) compared to the [A] image using a fixed ultrasound propagation velocity (1540m / s) at the time of beam focusing [B] It can be confirmed that the resolution of the image is improved. However, it can be seen that the resolution of the [B] image using the estimated value is also improved at the depth to which the ROI belongs, while the resolution is still deteriorated at other depths.

From the above experimental results, it can be seen that when an ultrasound image is imaged using a single ultrasonic propagation velocity in a complex medium composed of a medium layer having various medium characteristics, it is impossible to acquire an image having good resolution in all the medium layers . Therefore, the embodiments of the present invention described below are based on the problems described above, and it is intended to use a plurality of differential ultrasonic velocities instead of using one ultrasonic wave propagation velocity. That is, embodiments of the present invention estimate the ultrasound propagation velocity optimized for each medium layer constituting the complex medium, and apply the estimated accumulated ultrasound velocity to the entire image individually using the estimated ultrasound propagation velocity, To improve the quality of ultrasound images.

To this end, embodiments of the present invention provide a method for selecting a plurality of regions of interest for different depths of a lower layer medium for a plurality of media separated in the depth direction, And the optimum average ultrasonic velocity at all depths can be estimated by progressively repeating the ultrasonic velocity estimation for the lower layer media.

Hereinafter, embodiments of the present invention for solving the above-mentioned technical problems will be described in detail with reference to the drawings. In the following description and the accompanying drawings, detailed description of well-known functions or constructions that may obscure the subject matter of the present invention will be omitted. It is to be noted that the same components are denoted by the same names and reference numerals as possible throughout the drawings.

FIG. 3 is a flowchart illustrating a method of estimating an ultrasonic velocity for a medium according to an embodiment of the present invention, including the following steps.

In step 310, the present embodiment acquires an ultrasound image for the whole medium using one reference speed. Here, one reference speed may be determined by the average ultrasonic wave propagation speed for the entire medium or the ultrasonic wave propagation speed in a specific region of interest, and may be a specific value preset for the convenience of implementation. The process of acquiring an ultrasound image using one reference speed corresponds to a process of acquiring a conventional ultrasound image, and therefore, a detailed description thereof will be omitted.

In step 320, the present embodiment identifies each of the medium layers by identifying the boundaries of a plurality of medium layers constituting the medium from the image obtained in step 310. [ Various methods may be used to determine the boundary between the multi-media layers, but here an example is presented.

Since the boundary between the upper and lower layer is most clearly visualized when the value of the ultrasonic velocity at which the receiving beam focusing is performed is similar to the value of the ultrasonic velocity of the uniform upper layer medium, By reconstructing the image at a speed, it is possible to invert the absolute distance using the speed at which the boundary is clear, or to estimate the distance between boundaries. That is, the boundary of the medium layer can be identified by obtaining an ultrasound image at a plurality of velocities with respect to the entire medium, and calculating an absolute distance to the boundary using a velocity at which the boundary is clear. Furthermore, it is a matter of course that various outline recognition techniques utilized in the field of image processing technology can be utilized to distinguish the medium layer.

In operation 330, the embodiment may select at least two regions of interest (ROI) for adjacent medium layers among the medium layers classified through operation 320, And a differential ultrasonic velocity for each of the medium layers is obtained using the velocity and the depth. That is, in an image composed of different medium layers, the accumulated ultrasonic wave propagation velocity is estimated by selecting a plurality of regions of interest that are divided into a boundary between the medium layers and a depth direction in the lower layer medium.

In this case, the number and position of the ROIs to be set are increased in proportion to the number of the medium layers separated from each other. At least one ROI is selected for all the medium layers to be used as the representative ultrasound velocity of each medium layer . However, according to the implementation method of the ultrasonic velocity estimation method, it is possible to estimate the ultrasonic velocity without setting the region of interest for the first medium layer.

Meanwhile, the region of interest may be input by selecting a user visually recognizing a medium layer divided in the ultrasound image obtained for the entire medium by the display means.

In step 330, in estimating the ultrasonic wave propagation velocity, the ultrasonic wave propagation velocity of each medium can be calculated through a proportional equation modeling the depth direction position of the ROI and the medium thickness, I will describe it again through 5.

Through the above process, the embodiment of the present invention can estimate the differential ultrasonic velocity for each of the medium layers constituting the complex medium.

In step 340, the ultrasound image for the entire medium can be reconstructed by applying the ultrasound propagation velocity that varies according to the depth to be used for focusing the beam using the estimated ultrasound velocity of each medium layer. That is, the ultrasonic wave corresponding to each of the medium layers is irradiated using the differential ultrasonic velocity obtained in step 330, and the beam reflected from the medium is focused to acquire the ultrasonic image. The process of reconstructing one ultrasound image using a beam-forming technique of a beam (echo) reflected from the medium is out of the essence of the present invention, and thus a detailed description thereof will be omitted.

FIG. 4 is a flowchart specifically illustrating a process of obtaining a differential ultrasonic velocity for each of the medium layers in the ultrasonic velocity estimation method of FIG. 3 according to an embodiment of the present invention. Referring to FIG. 3, Describe the details of the process.

In FIG. 4, a method of calculating the ultrasonic velocity for each of the medium layers by using the relational expression for the adjacent medium layers divided in the depth direction is adopted. First, the principle will be briefly described with reference to FIG.

FIG. 5 is a diagram illustrating a geometric modeling concept for calculating the ultrasonic wave propagation velocity inherent to each medium layer in a complex medium, and FIG. 5 is a graph illustrating the geometric modeling concept for calculating the ultrasonic wave propagation velocity of each medium layer through the estimated ultrasonic wave propagation velocity value in each region of interest Model. If the boundary of the medium layer is inclined, if the slope is small, the modeling is performed assuming a straight line (which means a straight line perpendicular to the depth direction of the medium). However, if the slope of the boundary of the medium is excessively large and the error becomes large, this assumption may be difficult to utilize. Therefore, when the slope of the boundary of the medium layer is equal to or greater than the threshold value, the cumulative ultrasonic velocity is estimated by dividing the receiver, which collects the beam reflected from the medium, into sub-apertures, and the contribution of each medium to each ultrasonic propagation path is estimated, It is desirable to compensate for the slope of the boundary.

In estimating the optimal cumulative ultrasonic velocity using the representative ultrasonic velocity values of each medium, there is a difference in the number of samples for the depth information of the same boundary depending on what kind of ultrasound velocity is actually restored, have. Therefore, in reconstructing an image according to each ultrasonic velocity, it is necessary to estimate the optimal accumulated ultrasonic velocity using the number of samples corresponding to the physical distance between the medium layers.

Referring to FIG. 5, the contribution ratio of each medium layer is constructed by using the thickness of the medium layer and the thickness of the medium layer, which are divided in the depth direction, and the ultrasonic wave propagation speed in each medium layer is calculated. By setting the region of interest in the medium layer, the ultrasonic velocity of each medium layer can be obtained. When the proportional expression is used, the ultrasonic velocity of each medium layer can be calculated by selecting at least one region of interest in each medium layer except for the first upper layer in the selection of the region of interest. However, it is necessary to select at least two regions of interest for the medium layer located at the second upper layer in contact with the receiver in the image. For example, in FIG. 5, two ROIs having no ROI selected at Layer 1, two ROIs having different depths at Layer 2, and one ROI at Layer 3 can be selected.

In the above example, when a region of interest is selected for a uniform medium, the estimated ultrasonic velocity in each region of interest can be expressed by Equation 1 below.

는 각 관심 영역에서 추정된 초음파 속도를 나타내고,

는 첫 번째 매질 층(Layer 1)의 두께를 나타내고,

는 트랜스듀서(Transducer)부터 각 관심 영역까지의 깊이를 나타내며,

는 각 매질 층(Layer 1 및 Layer 2)의 초음파 속도를 나타낸다.In Equation (1)

Represents the estimated ultrasonic velocity in each region of interest,

Represents the thickness of the first medium layer (Layer 1)

Represents the depth from the transducer to each region of interest,

Represents the ultrasonic velocity of each medium layer (Layer 1 and Layer 2).

과

에 대한 수학식 1을 전개하여 각 매질 층의 속도에 해당하는

를 산출하면 다음의 수학식 2와 같다.ideal

and

1 < / RTI > for < RTI ID = 0.0 >

The following equation (2) is obtained.

를 표현하는 나머지 변수들은 모두 알려진 값이거나, 알 수 있는 값이므로 최초의 2개의 매질 층(Layer 1 및 Layer 2)에서의 초음파 속도가 획득된다. 물론, 이상의 수학식들이 제시하고 있는 바와 같이 각 관심 영역에서의 각 매질 층의 기여도를 비례식으로 구성하지 않고, 하나의 매질 층에 하나씩의 관심 영역을 설정함으로써 평균 최적 초음파 속도를 산출할 수도 있다.In Equation 2,

Are known values or are known values, the ultrasonic velocity at the first two medium layers (Layer 1 and Layer 2) is obtained. Of course, as shown in the above equations, it is also possible to calculate the average optimum ultrasonic velocity by setting one region of interest in one medium layer without constituting the contribution of each medium layer in each region of interest proportionally.

If the ultrasonic velocity of each medium layer is obtained through the above calculation process, an adaptive optimal accumulated ultrasonic velocity to be used for focusing the receiving beam of the image can be generally expressed as Equation (3).

는 추정된 n번째 집속 점의 적응 최적 누적 초음파 속도를 나타내고,

는 트랜스듀서로부터 집속점까지의 깊이를 나타내고,

는 m번째 매질 층(layer)의 두께를 나타내며,

는 m번째 매질 층의 최적 평균 초음파 속도를 나타낸다.In Equation (3)

Denotes an adaptive optimal accumulated ultrasound velocity of the n-th focusing point,

Represents the depth from the transducer to the focal point,

Represents the thickness of the mth medium layer,

Represents the optimum average ultrasonic velocity of the mth medium layer.

Now, returning back to FIG. 4, let us outline each operation procedure proposed by the embodiment of the present invention.

In step 331, in this embodiment, two regions of interest having different depths from each other are selected in a medium layer located second in the depth direction of the medium among the medium layers divided through the step 320. [

In step 332, the ultrasound velocity at the first medium layer located in the depth direction of the medium and the second ultrasound velocity at the second medium region are calculated using the relational formula based on the medium contribution in the two ROIs selected in step 331 And the ultrasonic velocity in the medium layer is respectively calculated. Here, the relational expression based on the medium contribution can be calculated by using the estimated ultrasonic velocity for the selected region of interest, the thickness of the first positioned medium layer, and the depth from the irradiated point of the ultrasonic wave to the selected region of interest, The ultrasonic velocity of the ultrasonic wave can be expressed.

If the medium is composed of two medium layers, it is possible to obtain all unknowns (meaning ultrasonic velocity) for the entire medium layer through the above process. However, if the medium is composed of three or more medium layers, it is necessary to determine the unknowns for the remaining medium layer by the following procedure.

In step 333, the region of interest is selected for the medium layer located third and subsequent to the depth direction of the medium, and the process of calculating the ultrasonic velocity in the medium layer is repeated to calculate the difference Respectively. That is, an area of interest is set for the adjacent medium layer, and the ultrasonic velocity for the newly set ROI is calculated using the previously calculated ultrasonic velocity. By acquiring the ultrasonic velocity for the gradually adjacent medium layer, the ultrasonic velocity for the whole medium can be grasped.

Now, when the receiving beam focusing of the image is performed using the optimal accumulated cumulative ultrasonic velocity calculated through the above process, the image can be reconstructed at the ultrasound velocity optimized for each image depth, thereby improving the resolution and signal sensitivity of the entire image .

FIG. 6 is a block diagram illustrating an apparatus 610 for photographing an ultrasound image according to another embodiment of the present invention. The apparatus 610 corresponds to the ultrasound velocity estimation method and the ultrasound image acquisition method shown in FIG. ≪ / RTI > Therefore, we concentrate on the device characteristics, but avoid the redundancy of explanation and outline the operation of each configuration.

The transducer 10 converts the alternating current energy into a mechanical vibration of the same frequency using the piezoelectric effect, irradiates the medium 620 with the mechanical vibration, and obtains an electrical signal again from the reflected echo. The transducer 10 may generate channel data for each of a plurality of channels and transmit the channel data to the beamformer 20.

The beamformer 20 is configured to collect an ultrasound image by focusing the reflected beam after being irradiated to the medium 620. The beamformer 20 irradiates the medium layer with ultraviolet light in accordance with the differential ultrasonic velocity controlled through the processing section 30 The beam reflected from the medium 620 is focused using the ultrasonic waves irradiated to the medium 620.

The processing unit 30 controls the speed of the ultrasonic waves irradiated to the medium 620 and restores the ultrasound image obtained through the beam former 20. For this, the processing unit 30 acquires an ultrasound image for the entire medium through the beam former using one reference velocity, identifies the boundaries of a plurality of medium layers constituting the medium from the obtained image, Wherein at least two regions of interest are selected for adjacent ones of the divided medium layers and a difference value of the difference for each of the medium layers is calculated using the velocity and depth of the ultrasonic waves in the selected region of interest Acquire the ultrasound velocity. The processor 30 includes at least one processor for performing a series of operations defined above, and if necessary, a memory capable of storing temporary data calculated in the operation is utilized , A software code for defining an operation can be added.

More specifically, the processing unit 30 selects two regions of interest different in depth from each other in the medium layer located second in the depth direction of the medium among the divided medium layers, The ultrasonic velocity in the medium layer located first in the depth direction of the medium and the ultrasonic velocity in the medium layer located in the second medium are calculated using a relational formula based on the medium contribution, And the ultrasonic velocity in the medium layer is calculated to obtain the differential ultrasonic velocity in the plurality of medium layers. At this time, the relational expression based on the medium contribution is calculated by using the estimated ultrasonic velocity for the selected region of interest, the thickness of the medium layer positioned at the first region, and the depth from the irradiation point of the ultrasonic wave to the selected region of interest, It is preferable to express the ultrasonic velocity in the layer.

In addition, the number of ROIs selected through the processing unit 30 is proportional to the number of the divided medium layers, and the ROI is divided into the ultrasound images obtained for the entire medium by the display unit 40 to the processing unit 30 by selection of a user visually recognized. Further, the boundary of the medium layer can be identified by obtaining an ultrasound image at a plurality of velocities with respect to the entire medium 620, and calculating an absolute distance to the boundary using the velocity at which the boundary is clear.

If the inclination of the boundary of the medium layer is equal to or greater than the threshold value, the processing unit 30 divides the receiver of the beam former 20, which concentrates the beam reflected from the medium 620, into sub- (Not shown) for compensating the slope of the boundary by estimating the velocity and estimating the contribution of each medium to each ultrasonic propagation path.

Now, when the processing unit 30 restores the ultrasound image from the focused beam, the display unit 40 outputs the restored ultrasound image.

FIG. 7 is a diagram illustrating an ultrasound image photographed according to the ultrasound velocity estimation method according to the embodiments of the present invention, and shows the results of measurement in the same experimental environment as the conventional techniques of FIG. 2 described above.

The ultrasonic image of FIG. 7 adopting the ultrasonic velocity estimation method proposed by the embodiments of the present invention, when compared with the experimental result of FIG. 2, estimates the ultrasonic velocity of each medium layer through two regions of interest in different depth directions, And the cumulative ultrasonic velocity using the value is used for the reception beam focusing. Compared with FIG. 2, it can be seen that the resolution of the image is uniformly improved for all depths of the ultrasound image of FIG.

According to the embodiments of the present invention described above, the medium layer constituting the medium is distinguished and the differential ultrasonic velocity for each medium layer in the selected region of interest is obtained, whereby the ultrasonic wave propagation speed optimized for different tissues inside the human body And the image quality, resolution, and signal sensitivity can be improved over the entire region of the ultrasound image by taking an ultrasound image of the complex medium using the obtained differential ultrasound velocity. In other words, the ultrasound propagation velocity corresponding to each medium layer is calculated and the receive beam focusing is performed considering the change in the propagation speed of the ultrasonic wave generated in the course of passing through different medium layers, An image having an increased depth and a low noise level can be obtained. In addition, embodiments of the present invention can also be utilized for image processing in a 'photoacoustic imaging system' using a technique for estimating a differential speed for a medium layer of a hierarchical structure.

Meanwhile, the embodiments of the present invention can be embodied as computer readable codes on a computer readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored.

Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device and the like, and also a carrier wave (for example, transmission via the Internet) . In addition, the computer-readable recording medium may be distributed over network-connected computer systems so that computer readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present invention can be easily deduced by programmers skilled in the art to which the present invention belongs.

The present invention has been described above with reference to various embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

610: ultrasound imaging apparatus 620: medium
10: Transducer 20: Beamformer
30: processing section 40: display section

Claims (18)

A method for estimating an ultrasonic velocity for a medium,
Acquiring an ultrasound image for the entire medium using one reference speed;
Identifying each of the medium layers by identifying a boundary of a plurality of medium layers constituting the medium from the obtained image; And
Selecting at least two regions of interest (ROIs) for the adjacent different medium layers from among the separated medium layers, and using the ultrasonic velocity and the depth in the selected ROIs, Obtaining a differential ultrasound velocity. The method according to claim 1,
Wherein the step of obtaining the differential ultrasonic velocity comprises:
Selecting two regions of interest different in depth from each other in a medium layer located second in the depth direction of the medium among the divided medium layers; And
Calculating an ultrasonic velocity at a first medium layer located in the depth direction of the medium and an ultrasonic velocity at the second medium layer using a relation based on the medium contribution in the selected two regions of interest; ≪ / RTI > 3. The method of claim 2,
Obtaining a differential ultrasound velocity in a plurality of medium layers by repeating the process of selecting an area of interest with respect to a medium layer positioned third after the depth direction of the medium and calculating an ultrasonic velocity in the medium layer, ≪ / RTI > 3. The method of claim 2,
The relational expression based on the medium contribution,
The ultrasonic velocity in the medium layer is expressed using the estimated ultrasonic velocity for the selected region of interest, the thickness of the medium layer positioned at the first region, and the depth from the irradiation point of the ultrasonic wave to the selected region of interest. How to. The method according to claim 1,
Wherein the number of selected regions of interest is proportional to the number of the identified media layers. delete The method according to claim 1,
When the slope of the boundary of the medium layer is equal to or greater than the threshold value,
Compensating for the slope of the boundary by partitioning the receiver that is to reflect the beam reflected from the medium into sub-apertures, estimating the accumulated ultrasonic velocity, and estimating the contribution of each medium to each ultrasonic propagation path. A method of imaging an ultrasound image of a medium,
Acquiring an ultrasound image for the entire medium using one reference speed;
Identifying each of the medium layers by identifying a boundary of a plurality of medium layers constituting the medium from the obtained image;
Selecting at least two regions of interest for adjacent different medium layers among the divided medium layers and obtaining a differential ultrasound velocity for each of the medium layers using the velocity and depth of the ultrasonic waves in the selected region of interest step; And
Irradiating ultrasound corresponding to each of the medium layers using the obtained differential ultrasound velocity, and focusing the beam reflected from the medium to acquire ultrasound images. 9. The method of claim 8,
Wherein the step of obtaining the differential ultrasonic velocity comprises:
Selecting two regions of interest different in depth from each other in a medium layer located second in the depth direction of the medium among the divided medium layers;
Calculating an ultrasonic velocity at a first medium layer located in the depth direction of the medium and an ultrasonic velocity at the second medium layer using a relation based on the medium contribution in the selected two regions of interest; And
Obtaining a differential ultrasound velocity in a plurality of medium layers by repeating a process of selecting an area of interest with respect to a medium layer positioned third after the depth direction of the medium and calculating an ultrasonic velocity in the medium layer, ≪ / RTI > A computer-readable recording medium storing a program for causing a computer to execute the method according to any one of claims 1 to 5 and 7 to 9. An apparatus for photographing an ultrasound image,
A beamformer for focusing the reflected beam after being irradiated to the medium to obtain an ultrasound image;
A processing unit having at least one processor to control an ultrasonic wave velocity irradiated to the medium and reconstruct an ultrasound image acquired through the beam former; And
And a display unit for outputting the restored ultrasound image,
Wherein,
Acquiring an ultrasound image for the entire medium through the beam former using one reference velocity and identifying a boundary of a plurality of medium layers constituting the medium from the obtained image to separate each of the medium layers, At least two regions of interest are selected for adjacent different medium layers among the divided medium layers and a differential ultrasonic velocity for each of the medium layers is obtained by using the ultrasonic velocity and depth in the selected region of interest . 12. The method of claim 11,
Wherein,
Selecting two regions of interest having different depths from each other in the medium layer located second in the depth direction of the medium among the divided medium layers,
The ultrasonic velocity in the medium layer located first in the depth direction of the medium and the ultrasonic velocity in the medium layer located in the second medium are respectively calculated using a relation based on the medium contribution in the two selected regions of interest,
The region of interest is selected for the medium layer located third and subsequent to the depth direction of the medium, and the process of calculating the ultrasonic velocity in the medium layer is repeated to acquire the differential ultrasonic velocity in the plurality of medium layers Characterized in that. 13. The method of claim 12,
The relational expression based on the medium contribution,
The ultrasonic velocity in the medium layer is expressed using the estimated ultrasonic velocity for the selected region of interest, the thickness of the medium layer positioned at the first region, and the depth from the irradiation point of the ultrasonic wave to the selected region of interest. . 12. The method of claim 11,
Wherein the number of selected regions of interest is proportional to the number of the separated media layers. 12. The method of claim 11,
Wherein the region of interest comprises:
Wherein the medium layer separated in the ultrasound image obtained for the entire medium is input to the processing unit by a user who visually recognizes the medium layer through the display unit. delete 12. The method of claim 11,
When the slope of the boundary of the medium layer is equal to or larger than the threshold value,
A compensator for compensating a slope of the boundary by estimating a cumulative ultrasonic velocity by dividing a recipient of the beam former for focusing a beam reflected from the medium into sub-bores and estimating a contribution of each medium to each ultrasonic propagation path; ≪ / RTI > 12. The method of claim 11,
Wherein the beam former focuses a beam reflected from the medium using ultrasonic waves irradiated to each of the medium layers according to the differential ultrasonic velocity controlled through the processing unit,
Wherein the processing unit acquires an ultrasound image from the focused beam and displays the obtained ultrasound image through the display unit.

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