KR101631466B1 - Ultrasonic Image Processing Apparatus For Obtaining Image Of Nonuniform Scatterers And Method Using The Same - Google Patents

Abstract

The present invention relates to an apparatus and a method for processing ultrasound images for obtaining a non-uniform scatterer image, which remove a side lobe signal from an ultrasound signal received through an array transducer, and identify the distribution of a non-uniform scatterer by binarizing each pixel in the scatterer image from which side lobes have been removed through comparison with a critical value, thereby contributing to accurate diagnosis of lesion groups. The apparatus according to the present invention comprises: the array transducer for receiving, through individual receiving elements, ultrasound signals reflected by a scatterer in human tissue; an ultrasound focusing unit for delaying focus to chronologically align the signals received from each of the receiving elements on the array transducer; an image processing unit for removing side lobes from a summation signal, which is a product of adding all of the individual signals that have been focus-delayed by the ultrasound focusing unit, and synthesizing a scatterer image from which the side lobes have been removed; a binarizing unit for comparing, with the critical value, the image brightness of each pixel in the scatterer image from which the side lobes have been removed by the image processing unit; and a scatter image display unit for displaying the scatterer image which has been binarized by the binarizing unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an ultrasound image processing apparatus,

The present invention relates to an ultrasound image processing apparatus and method for acquiring a non-uniform scattering body image, and more particularly, to an ultrasound image processing apparatus and method for acquiring a non-scattering body image by removing a side lobe signal from an ultrasound signal received through an array transducer, The present invention relates to an ultrasound image processing apparatus and method for acquiring a non-uniform scattering object image, which can contribute to accurate diagnosis of a lesion by grasping the distribution of non-uniform scattering bodies through a process of binarizing compared to a threshold value.

The medical ultrasound image transmits ultrasound to the human body and displays the magnitude of the reflected signal from the human body in brightness to image. These reflected signals are useful for observing the anatomical shape of the internal organs of the human body, mainly because the media of different characteristics occur at the interface of adjacent tissues.

It is difficult to diagnose lesions accurately by general ultrasound imaging, which visualizes and displays the boundary of the tissue, because the boundary of the tissue is unclear in lesions such as cancer or tumor. Cancer and tumors are caused by the production of new cells, which can change the density of cells. In order to detect changes in these tissues, it is necessary to grasp the scattering body distribution in human tissues. In other words, imaging the distribution of non-uniform scattering bodies in the soft tissues or lesions of the human body can improve the accuracy of the lesion diagnosis.

The medical ultrasound image depends on the frequency used and the characteristics of the transducer. In addition, since a coherent image is obtained, when scatterers such as soft tissues are distributed unevenly, image noise called speckle is generated and the resolution is lowered. Therefore, speckle is removed from the ultrasound image, and ultrasound signals There is a need for an ultrasound image processing technique capable of acquiring a scatterer image obtained by visualizing the distribution of scatterers present in a human body during image processing.

none

none

An object of the present invention is to provide an ultrasonic diagnostic apparatus and an ultrasonic diagnostic apparatus which remove a side lobe component from an ultrasound signal received through a transducer, perform a binarization process for selecting a lavender image from which side lobes have been removed, And to provide an apparatus and a method for processing an ultrasound image for acquiring a nonuniform scattering object image capable of quantifying and displaying the density of an image occupied by a strong scattering body.

An apparatus for processing an ultrasound image for acquiring a non-uniform scattering body image according to an embodiment of the present invention includes an array transducer for receiving ultrasound signals reflected from a scattering body of a human body in respective receiving elements; An ultrasonic focusing unit for focusing and delaying the signals received by the receiving elements of the array transducers in order to temporally align the received signals; An image processing unit for removing side lobes from the sum signal obtained by summing the signals delayed and focused by the ultrasonic focusing unit and synthesizing scatterer images from which side lobes have been removed; A binarizing unit for binarizing the image brightness and threshold value for each pixel of the scatterer image from which the side lobes are removed in the image processing unit; And a scatterer image display unit for displaying the scatterer image binarized by the binarization unit.

The scattering unit image analyzing unit may include a scattering unit image analyzing unit for quantifying a strong scattering member corresponding to a pixel whose image brightness is greater than a threshold value in the binarized image obtained by the binarizing unit, And provides the scatterer image display unit with information on the total number of the aggregated pixels, and the scatterer image display unit displays the provided pixel aggregation information as a numerical value or a percentage .

The image processing unit may further include a sidelobe calculator for calculating a sidelobe signal using the spatial frequency of the sidelobe signal included in the signal delayed by the ultrasonic focusing unit and the number of receiving elements, And subtracts the size of the side lobe signal calculated by the side lobe calculating unit from the summation signal obtained by summing the signals delayed by the focusing so as to remove the side lobe.

A method of processing an ultrasound image for acquiring a non-uniform scattering body image according to an embodiment of the present invention includes receiving signals from ultrasound signals reflected from a scattering body of a human body tissue by a receiving element of each array transducer; A signal focusing step of focusing and delaying the received signals received in the signal receiving step in order to temporally align the received signals; Calculating a size of the side lobe signal using the spatial frequency of the side lobe signal contained in the ultrasound signal focused and delayed in the signal focusing step and the number of receiving elements; An image processing step of subtracting the calculated size of the side lobe signal from the sum signal obtained by summing the signals delayed by the focusing and removing the side lobe and synthesizing the scatterer image using the summation signal from which the side lobe is removed; A binarization step of binarizing the image brightness and the threshold value for each pixel of the scattered image synthesized in the image processing step; And a display step of displaying the binarized scatterer image.

The analyzing step may include an analyzing step of counting the number of pixels whose image brightness is greater than a threshold value in binarization by the binarization unit of the binarized scatterer image, and information on the total number of the aggregated pixels to the image display unit And a display step of displaying pixels aggregated together with the binarized image in numerical value or percentage.

According to the present invention, image brightness and threshold value are compared for each pixel of a scatterer image from which side lobes have been removed, and binarization and image display are performed to easily confirm the distribution characteristics of scatterers present in the human tissue. Also, in the binarization process, the density of the scatterer image can be easily confirmed by collecting the pixels of the strong scatterer having the image brightness greater than the threshold value and displaying them together with a numerical value or a percentage. Therefore, the accuracy of the lesion diagnosis can be improved even when the boundary of the tissue is unclear, such as cancer or tumor, which has been difficult to diagnose due to the presence of speckle in the conventional ultrasound image.

1 is a block diagram of an ultrasound image processing apparatus for acquiring a non-uniform scattering body image according to the present invention.
FIG. 2 is a view showing a scattering body distribution in an ultrasonic sound field region, in which (a) is a scattering body distribution existing in the main lobe region and the side lobe region, (b) is a scattering body distribution in the region where the side lobe is removed and the width of the main lobe is narrowed to be.
3 is a view for explaining sound field characteristics of a general ultrasonic focusing system.
FIG. 4 is a view showing a state in which a signal incident at the angle of FIG. 3 appears on a transducer.
5 is a view for explaining a process for removing a side lobe in an ultrasonic signal according to the present invention.
6 (a) is an ultrasound image of a general scatterer, (b) is an image obtained by removing side lobes from the scatterer image, and (c) is a scatterer image obtained by binarizing the image obtained by removing the side lobes.
7 is a flowchart illustrating an ultrasound image processing method for acquiring a non-uniform scattering body image according to the present invention.

Hereinafter, an ultrasound image processing apparatus and method for acquiring a non-uniform scattering body image according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1, the present invention includes an array transducer 10, an ultrasonic focusing unit 20, a side lobe calculating unit 30, an image processing unit 40, a binarization unit 50, a scatterer image display unit 60 ).

The array transducer 10 is constructed by linearly arranging a plurality of receiving elements for transmitting ultrasonic waves to the inside of a human body tissue and receiving signals reflected from a tissue of the human body. In this embodiment, 128 receiving elements are linearly arranged (I.e., the number of channels is 128), it is not necessary to specifically limit the number of receiving elements.

The ultrasonic focusing unit 20 forms a scanning line for forming an ultrasound image from a channel signal received from each channel (receiving element) of the array transducer. The signals reflected from scatterers (i.e., reflectors or image points) existing in the tissue of the human body arrive at different times for each receiving element due to the arrangement position of the receiving elements. In this way, By applying a time delay to each of the channel signals, a focusing delay is performed that temporally aligns the channel signals as if they arrived at the same time.

Referring to FIG. 2, the scattering body distribution in the ultrasonic sound field region will be described.

In a general ultrasonic focusing system, a main lobe is formed on the basis of a scan line direction, and side lobes are formed on both sides of the main lobe due to leakage of an ultrasonic signal. As shown in FIG. 2 (a), the signals reflected by the non-uniform scatterers existing in the main lobe and the secondary lobe are irregularly added to the array transducer, resulting in speckle. In order to image the scattering body distribution in the human tissue, it is necessary to reduce the width of the main lobe of the ultrasonic wave and to remove the side lobes. Through this processing, only a minimum scattering body exists in the reduced local region in the ultrasonic transmitting and receiving sound field, It is possible to easily distinguish the signals reflected from the respective scatterers present in the local region by reducing the noise.

3, the sound field characteristics obtained in the image region of a general ultrasonic focusing system are such that a main lobe is formed on the basis of the direction of a scan line of each transducer, and a side lobe due to the leakage of the ultrasonic signal to both sides of the main lobe side lobes are formed.

Thus, when a signal enters the transducer in a direction having an arbitrary angle adjacent to the scanning line direction of the transducer, the receiving element is incident on the receiving element in a different phase. Therefore, a signal incident on an arbitrary incident angle is expressed by a signal having a specific frequency called a spatial frequency in a transducer. The spatial frequency can be expressed by the following equation (1) .

[Equation 1]

Where D is the size of the transducer, λ is the center frequency of the ultrasonic wave, and θ is the incident angle of the ultrasonic signal to the scan line.

In FIG. 4, the ultrasonic signal incident on the transducer at an angle corresponding to the number of the horizontal axis in the sound field characteristic of the ultrasonic focusing system shown in FIG. 3 is shown in the transducer. It can be seen that the signal is a signal forming the main lobe.

In addition, the signals incident on odd-numbered (3,5, 7, ...) angles (hereinafter referred to as "null directions") of the signals appearing on both sides of the main lobe are the number of cycles, , 6, 8, ...), the number of cycles is non-constant.

At this time, a signal incident in the null direction is a signal having a CPA (cycle per aperture) of an integer spatial frequency, and since the number of cycles is an integer as described above, Zero, so that no noise of the side lobe is formed in the image.

However, since the number of cycles is non-constant as described above, the signal incident on the side-by-side direction has a CPA with a spatial frequency of (integer +0.5) half cycle) component of the image is not removed.

Therefore, in the channel signal received by the tracer, the spatial frequency that forms the side lobe (the spatial frequency is 1.5 CPA for the first side lobe component and the 2.5 CPA for the second side lobe component) is removed The side lobe components can be removed from the ultrasound image.

Specifically, the spatial frequency of the known side lobe components (i.e., 1.5 CPA, 2.5 CPA, etc.) and the number of channels (i.e., the number of receiving elements ) To calculate the frequency component of the side lobe signal having the spatial frequency, and subtracting the frequency component of the side lobe signal in the process of summing the delayed channel signals to remove the side lobe component from the ultrasound image.

The detailed description of the method for removing the side lobe components in the ultrasound image is described in detail in the earlier filed patent application (filed by the present applicant No. 10-2014-0138034, filed in October 14, 2014) .

Generally, the waveform or the magnitude of the received signal at the transducer can be calculated using any known frequency estimation technique such as Fourier transform, and these frequency estimation methods are applicable to an integer multiple of the frequency corresponding to the inverse of the signal length The size of a frequency component which is not an integer multiple can not be accurately calculated because of a window effect due to finite length data.

In order to solve this problem, the side lobe calculator 30 according to the present invention extends the length of the side lobe signal corresponding to the side lobe component to a length capable of frequency estimation by calculation according to a predetermined method, A method of calculating the size of the corresponding side lobe signal is applied by using a frequency estimation method such as Fourier transform.

Here, the subsidiary lobe calculator 30 inserts zeros into at least one of the front end or the rear end of the side lobe signal to expand the signal length of the side lobe signal so that the spatial frequency becomes a positive integer closest to the spatial frequency.

For example, since the signal corresponding to the first side lobe component shown in FIG. 3 or 4 has a spatial frequency of 1.5 CPA as shown in FIG. 5 (a), the signal length is extended And the spatial frequency is 2 CPA, the length of the channel signal becomes an integer multiple frequency signal. Therefore, the frequency component of the spatial frequency 2 CPA can be accurately calculated by the frequency estimation method such as Fourier transform.

Since the length of the actually received signal is D (that is, the number of receiving elements or the number of channels), the length of the signal corresponding to the first side lobe component is calculated by the following equation (2) The length can be extended.

[Equation 2]

In this case, as shown in FIG. 6 (c), the subsidiary lobe calculating unit 30 inserts zero in at least one of the front end or the rear end of the signal to adjust the extended signal length.

When the length of each side lobe signal is extended according to the above-described method, the side lobe calculating unit 30 calculates a frequency component of the side lobe component (that is, a waveform or a size of the side lobe signal) using a frequency estimation method such as Fourier transform, Can be calculated.

The image processing unit 40 forms a scanning line by subtracting the frequency component of each side lobe signal calculated by the side lobe calculating unit 30 in the process of summing signals delayed and focused by the ultrasonic focusing unit 20, Thereby synthesizing the scatterer image. In the embodiment, the image processing unit 40 subtracts the size of the corresponding side lobe signal obtained by calculating the waveform of each side lobe signal in the summation process of the delayed signals.

When the side lobes are removed as described above, the image processing unit 40 reduces the width of the main lobes as shown in FIG. 2B for the scattered body image from which the side lobes are removed. In the calculation process for reducing the side lobes, The effect of reducing the width of the main lobe can be increased. That is, the width variable weight is set in advance so that the width of the main lobe of the scatterer image can be narrowed, and the scatterer can be easily distinguished from the finally obtained scatterer image by synthesizing the scatterer image according to the variable weight.

The signal obtained by the scatterers existing in the main lobe region of the scatterer image formed in the image processor 40 contains a weak signal component and a strong signal component. For example, in the image shown in FIG. 6 (a), the image noise corresponding to the speckle appears before the side lobes are removed, but the speckle is reduced due to removal of the side lobe component in the image shown in FIG. 6 (b) . However, the strong signal component in the image of Fig. 6 (b) is useful information for the diagnosis of the lesion. However, since the weak signal component may interfere with the diagnosis of the lesion, it is necessary to remove the weak signal component.

In order to solve this problem, the binarization unit 50 compares the image brightness and the threshold value for each pixel of the scatterer image from which the side lobes are removed in the image processing unit 40, and binarizes the image brightness. That is, if the image brightness of the corresponding pixel is larger than the threshold value, it is determined to be white, and if the image brightness of the corresponding pixel is not greater than the threshold value, it is determined to be black. Here, the image brightness of each pixel can be divided into 0 to 255 levels, and the threshold value can be preset between 0 and 255 to display white or black according to the image brightness of the corresponding pixel.

Then, the image display unit 60 displays the binarized image by the binarization unit 50. [ For example, by using the above-described processing, a strong signal component reflected and received by a strong scatterer as shown in FIG. 6 (c) can be displayed as white and the other portion can be displayed as black.

The binarized image shown in Fig. 6 (c) is useful for visually confirming the distribution of the scattering body in the human tissue. In addition, if the number of pixels corresponding to the strong scattering body is quantified so as to know the density of the image occupied by the strong scattering body in the binarized image, it can be more useful for the user who diagnoses the lesion.

In order to solve this problem, the scattering unit image analyzing unit 70 compares the number of pixels whose image brightness is larger than the threshold value in binarization of the scatterer image in the binarization unit 50, And provides the information to the video display unit 60.

Then, the image display unit 60 can display a numerical value or a percentage based on the information about the pixels aggregated together with the binarized image, whereby the user who diagnoses the lesion can distribute the distribution of the strong scattering body through the binarized scatterer image It is possible to visually confirm the density of the image occupied by the strong scatterer as well as visually confirm it.

7 is a flowchart illustrating an ultrasound image processing method for acquiring a non-uniform scattering body image according to the present invention.

The array transducer 10, in which a plurality of receiving elements are linearly arranged, transmits an ultrasonic wave to the inside of the human tissue and receives an ultrasonic signal reflected by a non-uniform scattering body existing inside the human tissue. The ultrasound focusing unit 20 forms a scanning line for forming an ultrasound image from the channel signals received by the receiving elements of the array transducer. At this time, the receiving elements arrive at different times, And applies a time delay to each of the plurality of generated channel signals to perform a focusing delay in which the channel signals are temporally aligned as if they arrived at the same time (S100).

The sub-lobe calculator 30 extends the length of the side lobe signal corresponding to the side lobe component to a length capable of frequency estimation by calculation according to a predetermined method, and performs a frequency estimation method such as Fourier transform And calculates the size of the corresponding side lobe signal. In this case, the subsidiary lobe calculating unit 30 inserts zeros into at least one of the front end or the rear end of the side lobe signal to extend the signal length of the side lobe signal so that the spatial frequency becomes a positive integer closest to the spatial frequency. Then, the subsidiary lobe calculating unit 30 calculates a frequency component of the corresponding side lobe component using a frequency estimation method such as Fourier transform. That is, the subsidiary lobe calculating section 30 calculates the size of the side lobe signal delayed in focusing.

The image processing unit 40 forms a scanning line by subtracting the frequency component of each side lobe signal calculated by the side lobe calculating unit 30 in the process of summing signals delayed and focused by the ultrasonic focusing unit 20, Thereby synthesizing scatterer images from which the side lobe components are removed (S200). If the side lobes are removed, the width of the main lobes of the scatterer image can be reduced according to a preset variable width weight.

The signal obtained by the scatterers present in the main lobe region of the scatterer image formed by the image processor 40 has a weak signal component and a strong signal component mixed therein (see Fig. 6 (a)). Therefore, it is necessary to selectively display scatterer images corresponding to strong scatterers useful for the diagnosis of lesions.

In order to solve this, the binarization unit 50 compares the image brightness and the threshold value for each pixel of the scatterer image from which the side lobes are removed in the image processing unit 40, and binarizes the image brightness. As shown in Fig. 6 (b), the binarized scattered image can be seen to have reduced speckle.

Specifically, if the image brightness of the corresponding pixel is greater than the threshold value, it is determined to be white, and if the image brightness of the corresponding pixel is not greater than the threshold value, it is determined to be black. Here, the image brightness of each pixel can be divided into 0 to 255 levels, and the threshold value can be preset between 0 and 255 to display white or black according to the image brightness of the corresponding pixel. The binarized scatterer image is provided to the image display unit 60 and the image display unit 60 displays the binarized scatterer image. For example, as shown in FIG. 6 (c), the binarized image can visually confirm the distribution of the scatterer existing in the human tissue, and thus the user diagnosing the lesion can easily confirm the distribution of the scatterer image S300).

In addition to the display process of the scatterer image, the scatterer image analyzer 70 compares the number of pixels corresponding to the strong scatterer so that the intensity of the image occupied by the strong scatterer in the binarized image can be known, And provides the image display unit 60 with information on the number of pixels. That is, the scatterer image analyzing unit 70 aggregates pixels of the strong scatterer whose image brightness is larger than the threshold value, and provides information on the total number of the aggregated pixels to the image display unit 60 (S400).

Then, the image display unit 60 displays the number of pixels counted for the strong scatterer as a numerical value or a percentage based on the information provided from the scatterer image analyzer 70 together with the binarized scatterer image (S500).

In the embodiments described above, the processing method of calculating the size of the side lobe signal included in the signal delayed by focusing and delaying the ultrasound signal is applied to remove the side lobe. However, it is not necessary to limit the method of removing the side lobes in the acquisition of the image of the non-uniform scattering body according to the present invention. As a known technique for reducing the speckle noise, the minimum variance beamforming method is applied, In this way, it is possible to utilize the heterogeneous scattering body images obtained through the binarization process for each pixel of the scattered body image with the side lobes removed to be used for the lesion diagnosis.

10: Array transducer 20: Ultrasonic focusing unit
30: a side-sheet calculating unit 40:
50: binarization unit 60: scatterer image display unit
70: Scattering body image analysis section

Claims (5)

An array transducer for receiving ultrasound signals reflected from a scattering body of a human tissue at respective receiving elements;
An ultrasonic focusing unit for focusing and delaying the signals received by the receiving elements of the array transducers in order to temporally align the received signals;
An image processing unit for removing side lobes from the sum signal obtained by summing the signals delayed and focused by the ultrasonic focusing unit and synthesizing scatterer images from which side lobes have been removed;
A binarizing unit for binarizing the image brightness and threshold value for each pixel of the scatterer image from which the side lobes are removed in the image processing unit;
A scattering unit image analyzing unit for aggregating the number of pixels whose brightness values are binarized by the binarization unit and whose brightness is larger than a threshold value and providing information about the total number of pixels to be aggregated; And
And a scatterer image display unit for displaying the scattered object images binarized by the binarization unit and the provided pixel aggregation information in numerical values or percentage, and a display unit for processing the ultrasound images. An array transducer for receiving ultrasound signals reflected from a scattering body of a human tissue at respective receiving elements;
An ultrasonic focusing unit for focusing and delaying the signals received by the receiving elements of the array transducers in order to temporally align the received signals;
A sub-lobe calculating unit for calculating a size of the side lobe signal using the spatial frequency of the side lobe signal included in the signal delayed by the ultrasonic focusing unit and the number of receiving elements;
An image processor for removing the side lobes by subtracting the size of the side lobes calculated by the side lobes calculating unit from the summation signal obtained by summing the signals delayed and focused by the ultrasonic focusing unit and synthesizing the scatterer images from which the side lobes have been removed;
A binarizing unit for binarizing the image brightness and threshold value for each pixel of the scatterer image from which the side lobes are removed in the image processing unit; And
And a scatterer image display unit for displaying the scatterer image binarized by the binarization unit. The apparatus for processing an ultrasound image for acquiring a heterogeneous scatterer image. An array transducer for receiving ultrasound signals reflected from a scattering body of a human tissue at respective receiving elements;
An ultrasonic focusing unit for focusing and delaying the signals received by the receiving elements of the array transducers in order to temporally align the received signals;
A sub-lobe calculating unit for calculating a size of the side lobe signal using the spatial frequency of the side lobe signal included in the signal delayed by the ultrasonic focusing unit and the number of receiving elements;
An image processor for removing the side lobes by subtracting the size of the side lobes calculated by the side lobes calculating unit from the summation signal obtained by summing the signals delayed and focused by the ultrasonic focusing unit and synthesizing the scatterer images from which the side lobes have been removed;
A binarizing unit for binarizing the image brightness and threshold value for each pixel of the scatterer image from which the side lobes are removed in the image processing unit;
A scattering unit image analyzing unit for aggregating the number of pixels whose brightness values are binarized by the binarization unit and whose brightness is larger than a threshold value and providing information about the total number of pixels to be aggregated; And
And a scatterer image display unit for displaying the scattered object images binarized by the binarization unit and the provided pixel aggregation information in numerical values or percentage, and a display unit for processing the ultrasound images. A signal receiving step of receiving ultrasound signals reflected from a scattering body of a human body tissue by a receiving element of each of the array transducers;
A signal focusing step of focusing and delaying the received signals received in the signal receiving step in order to temporally align the received signals;
Calculating a size of the side lobe signal using the spatial frequency of the side lobe signal contained in the ultrasound signal focused and delayed in the signal focusing step and the number of receiving elements;
An image processing step of subtracting the calculated size of the side lobe signal from the sum signal obtained by summing the signals delayed by the focusing and removing the side lobe and synthesizing the scatterer image using the summation signal from which the side lobe is removed;
A binarization step of binarizing the image brightness and the threshold value for each pixel of the scattered image synthesized in the image processing step;
And displaying the binarized image of the scatterer. The method of processing an ultrasound image for acquiring a non-uniform scatterer image. 5. The method of claim 4,
An analyzing step of counting the number of pixels whose image brightness is greater than a threshold value in binarizing the binarized scatterer image by the binarization step, and providing information on the total number of the aggregated pixels to the image display unit, And a display step of displaying pixels, which have been collected together with the image, in a numerical value or a percentage.

Images