KR20150124479A - Module for Processing Ultrasonic Signal Based on Spatial Coherence and Method for Processing Ultrasonic Signal - Google Patents

Abstract

The present invention relates to a space-coherent fundamental ultrasonic signal processing module and a method of processing an ultrasonic signal by the same, and more particularly, to a space coherence foundation which makes it possible to obtain an improved ultrasonic image by processing a reflected ultrasonic signal based on reflector or medium characteristics An ultrasonic signal processing module and a method of processing an ultrasonic signal by the module. An ultrasonic signal processing module for receiving an ultrasonic signal reflected from the inside of a human body to form an image includes a transducer including a plurality of receiving elements for receiving the reflected ultrasonic signal; An RF signal processor for processing the signal received by the transducer; A spatial coherence calculating unit for calculating spatial coherence from the received ultrasonic signal; A label unit for applying a value according to an area characteristic of a site to be imaged based on the value processed in the spatial consistency calculation unit; A filter unit for modifying the singularity of the label unit; And image enhancement filters that enhance the image by applying filter characteristics differently according to spatial consistency.

Description

TECHNICAL FIELD [0001] The present invention relates to a spatial coherence-based ultrasound signal processing module and an ultrasonic signal processing method using the same,

The present invention relates to a space-coherent fundamental ultrasonic signal processing module and a method of processing an ultrasonic signal by the same, and more particularly, to a space coherence foundation which makes it possible to obtain an improved ultrasonic image by processing a reflected ultrasonic signal based on reflector or medium characteristics An ultrasonic signal processing module and a method of processing an ultrasonic signal by the module.

Various types of diagnosis methods and treatment methods using the characteristics of ultrasonic waves transmitted to the human body as a medium are known. Ultrasonic imaging technology, which is a representative form of medical ultrasound technology, refers to a technique that enables diagnosis by detecting the distance between the ultrasonic transducer and the interface between the medium inside the human body and the echo signal and displaying it as an image. Ultrasound association diagnosis technology can be divided into A-mode imaging technology, M-mode imaging technology, B-mode imaging technology and D-mode (Doppler-mode) imaging technology.

The B-mode imaging technology, which is one of the ultrasound imaging technologies, has been developed around a beam-forming method and a signal processing technique for forming an ultrasonic beam suitable for a human body by a plurality of ultrasonic array elements. In order to form an ultrasound image in the B-mode imaging technology, a beam former for amplifying and collecting signals received from the respective ultrasonic array elements is used, and RF data (Radio Frequency Data) transmitted from a beam former is demodulated So that an envelope envelope can be obtained. Then, the envelope data is converted into synthesized image data by the scan converter, and the ultrasound image is displayed on the monitor by the video processor.

In the process of obtaining the received data to form the ultrasound image, the signal scattered back from the small reflectors has a characteristic of non-uniform amplitude in the process of focusing in the ultrasound focusing system, so that a unique noise image called a speckle . These speckle noises are superimposed on the long-term images of the human body, making it difficult to diagnose the detailed areas. Therefore, removing the Speckle noise from the image is an important factor for improving the image quality of the ultrasound image.

The image processing for removing the speckle noise utilizes the difference between the speckle noise and the characteristics of the desired video signal. In general, noise has a high frequency component, so low-pass filtering of ultrasound images reduces speckle noise. However, since high-frequency components such as long-term boundaries in the image, which require high resolution, are also removed, such regions are also eliminated.

The prior art has a disadvantage in that the characteristics of the entire image vary depending on the characteristics of the applied filter. It is disclosed that the image formation of the target or the formation of the ultrasonic beam is performed based on the delay characteristic in relation to the improvement of the ultrasonic image quality or the improvement of the ultrasonic beam formation.

The present invention proposes a method for improving the quality of a new ultrasound image which is different from the method or technology disclosed in the prior art or the known art, and calculates the correlation of the received ultrasound signals of each individual element in the array transducer, It is aimed to improve the image by reducing the speckle noise by using it as an indicator to distinguish whether the signal of the point is reflected from the organ or the speckle noise.

1) M.A.Lediju, G.E.Trahey, B.C. Bram and J.J.Dahl, "Short-Lag Spatial Coherence of Backscattered Echos: Imaging Characteristics," IEEE Transaction of Ultrasonic, Ferroelectronics, and Frequency Control, vol. 58, no. 7, pp. 1377-1388, 2011. 2) P. Perona and J. Malik, "Scale-space and edge detection using anisotropic diffusion," in Proceedings of IEEE Computer Society workshop on Computer Vision, pp.

It is an object of the present invention to provide an ultrasonic image processing apparatus and a method of processing the ultrasonic image by performing filtering on image formation data obtained by a general ultrasonic image acquisition signal processing method according to spatial correlation between received signals transmitted from the ultrasonic element and application of region property weights, And to provide a space coherent fundamental ultrasonic signal processing module and an ultrasonic signal processing method therefor.

According to a preferred embodiment of the present invention, an ultrasonic signal processing module for receiving an ultrasonic signal reflected from the inside of a human body to form an image includes a transducer composed of a plurality of receiving elements for receiving the reflected ultrasonic signal; An RF signal processor for processing the signal received by the transducer; A spatial coherence calculating unit for calculating spatial coherence from the received ultrasonic signal; A label unit for applying a value according to an area characteristic of a site to be imaged based on the value processed in the spatial consistency calculation unit; A filter unit for modifying the singularity of the label unit; And image enhancement filters that enhance the image by applying filter characteristics differently according to spatial consistency.

According to another preferred embodiment of the present invention, the type or filter value of the filter unit or image enhancement filter is a user-defined parameter.

According to another preferred embodiment of the present invention, a delay function is provided for giving a delay time function to each receiving element of the receiving element to obtain a signal focused on a specific point.

According to another preferred embodiment of the present invention, there is provided a method of processing an ultrasonic signal, comprising the steps of: receiving ultrasound reflected from a diagnostic object in a human body; Converting a received ultrasound signal into RF data by applying a delay time to each receiving element to obtain a convergence signal corresponding to a specific point; Calculating space coherence with respect to the RF data and weighting the RF data according to characteristics of the diagnosis object; Filtering the singularities for the characteristic; And enhancing the image by applying different characteristics of the filter according to the spatial consistency.

The signal processing module according to the present invention has an advantage that a quality-enhanced ultrasonic image can be obtained by differently filtering the signal obtained based on spatial coherence according to the characteristics of the peripheral region. Also, the signal processing method according to the present invention has the advantage that the speckle is reduced in the B-mode image.

1 is a block diagram schematically showing an embodiment of a process of a method of processing an ultrasonic signal according to the present invention.
2 schematically shows an embodiment of a process of processing a signal in each step in the ultrasonic signal processing method according to the present invention.
FIG. 3 shows an embodiment of a spatial consistency calculation unit that can be applied to the ultrasonic signal processing method according to the present invention.
4 illustrates an embodiment of an ultrasonic signal processing module according to the present invention.
5 shows an embodiment of a method of processing an ultrasonic signal according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the accompanying drawings, but the present invention is not limited thereto. In the following description, components having the same reference numerals in different drawings have similar functions, so that they will not be described repeatedly unless necessary for an understanding of the invention, and the known components will be briefly described or omitted. However, It should not be understood as being excluded from the embodiment of Fig.

Generally, speckle noise is reduced by applying a low-pass filter to an ultrasound image in which an envelope is detected by using a characteristic of having a high frequency component in a signal processing for removing speckle noise and improving image quality. However, in the ultrasound image, the speckle is reduced due to the same filter applied to the portion having high frequency components such as the boundary of the organ, but other information is also lost.

According to the present invention, the characteristic of the filter is applied using the difference between the characteristics of the desired image signal and the speckle noise in the region where the signal is to be obtained. The transmitted ultrasound reflects a signal when the reflector meets the reflector and exhibits different reflection characteristics depending on the size of the reflector with respect to the wavelength of the ultrasonic wave. Since the organs inside the human body are sufficiently larger than the wavelength, the reflected signals are highly correlated signals that are received by the receiving elements when they are received by the ultrasonic element. However, since the signal that returns from the region where small reflectors are scattered is scattered compared with the ultrasonic wave, the signals are differently inputted when they are incident on the elements of the transducer. Therefore, by calculating the correlation of the signals input to each element of the transducer, it becomes possible to distinguish whether the signal is from a human organ or from a small reflector. In the present invention, speckle is reduced and image quality is improved by separating the long-term domain and the speckle domain according to the degree of correlation of the received signal and applying an adaptive filtering technique.

According to the present invention, the array transducer is used as an index for discriminating whether a signal of an image point is a signal returned from an organ or a speckle noise by calculating the consistency of received ultrasonic signals of individual discrete elements in the array transducer.

According to the present invention, an ultrasound imaging system performs image processing for existing ultrasound image processing to produce an ultrasound image, and calculates a correlation index of a point at which an image is to be obtained, thereby removing the speckle of the ultrasound image according to the correlation value To improve the quality of the image. Space coherence and spatial correlation are used herein in the same or similar sense.

This is explained in detail below.

1 is a block diagram schematically showing an embodiment of a process of a method of processing an ultrasonic signal according to the present invention.

(P11) of receiving ultrasound signals (Rx) reflected from a predetermined region transmitted to the human body and delayed by each of the transducer elements, in accordance with the present invention; (P12) calculating a spatial correlation degree based on a received ultrasound signal delayed in each of the ultrasonic elements of the transducer; Forming a spatial coherence matrix from the calculated spatial correlation map (P13); A step (P14) of calculating a label matrix according to characteristics of a reflection part in the human body in addition to the space coherence matrix; Detecting a singular point according to a surrounding region according to a label result and performing filtering (P15); And applying an adaptive filter to the image of the result of the filtered label to enhance the image (P16).

The method or apparatus according to the present invention is for improving the quality of a B-mode ultrasound image and a method for improving the quality of a B-mode image by adding an adaptive filtering process to the spatial coherence calculated additionally to the B- . However, the ultrasonic signal processing apparatus or the ultrasonic processing method according to the present invention can be applied to B-mode image formation for ultrasonic diagnosis, but it is not limited thereto. For example, an apparatus or method according to the present invention may be applied to obtain an image of a treatment site in a process for high intensity intensive ultrasound therapy. An apparatus or method according to the present invention may be applied for diagnosis or treatment of various modes.

The ultrasonic signal transmitted to the diagnosis part in the human body can be generated by a plurality of ultrasonic devices arranged in the transducer and can be formed into a beam forming ultrasonic signal so that a focus is formed at a predetermined part, It can be an ultrasonic signal that is not formed. A signal reflected at a predetermined portion in the human body can be received by the same ultrasonic element or an ultrasonic element disposed at a different position from the ultrasonic element for transmission. The arrangement of the ultrasonic elements for receiving the ultrasonic signals can be any structure known in the art and the time delay of the ultrasonic signals received in each element can be calculated.

The spatial correlation can be calculated according to the time delay of the received ultrasonic signal (P12). The spatial correlation can be calculated based on the time delay received at each ultrasonic element disposed in the transducer. The spatial correlation between the ultrasonic elements that are separated from each other by m (m is 0 or a natural number) can be calculated by the following equation (1).

≪ Formula 1 >

In Equation (1), r (m) represents the spatial correlation, N represents the total number of ultrasonic elements, N-m represents the size of the kernel, and si (n) represents data of the i-th ultrasonic element obtained at the depth n.

From equation (1), spatial correlation can be calculated for different devices and spatial coherence r can be summed with spatial correlation M. The spatial coherence r can be expressed by Equation 2 below.

&Quot; (2) "

In equation (2), r represents the spatial correlation and one scalar value is obtained for the sampling location where the in-body reflections are focused, and each sample location is stored in a two-dimensional array (matrix I) (P13).

When a two-dimensional matrix (matrix I) related to spatial consistency is calculated, the label characteristic according to the characteristic of the reflection region can be applied (P14). The label characteristic means the reflection characteristic of the ultrasonic signal. And may have different reflection characteristics depending on the density of the medium or the distribution of the medium. In case of a strong reflector having a sufficiently large size compared to the amplitude of ultrasonic wave, the spatial coherence value becomes large. In the case of a material such as blood cells, which is smaller in size than the ultrasonic wave, space coherence can be small due to ultrasonic scattering. Therefore, the characteristics of the region to obtain the ultrasound image can be calculated based on the calculated spatial coherence. Specifically, structural regions with strong reflectors such as bones or diaphragms have increased spatial consistency and less spatial consistency in homogeneous regions with small material such as soft tissue or blood vessels. These characteristics can be shown in spatial coherence, and the label value z can have a value of +1 for a dense structural region, a value of 1 for a dense homogeneous region, and a middle value between a structural region and a homogeneous region Can have a value between? 1 and 1 in the region corresponding to? 1 and can be expressed as shown in Equation 3 below.

&Quot; (3) "

In Equation (3), t1 and t2 represent threshold values for the homogeneous region and the structural region.

If a label value according to the region is applied, the presence of a singularity around the periphery can be detected. The presence of a singularity can be detected independently for the homogeneous region and the structural region, respectively. Depending on the detection result, filtering may be performed to eliminate the singularity (P15). The presence of a singular point in the homogeneous region is modified depending on whether the shape is shaped or not. If the shape has a constant area size and at the same time shows a certain shape, it is treated as a signal different from other peripheral areas. On the other hand, if the area does not have a certain size or has an irregular shape, it can be treated as noise. Uniformity in the size or shape of a certain region to be a reference can be determined according to the inspection region in the human body. For example, if a known shape exists in the inspection region and a similar signal is detected, it can be processed as an image signal. On the other hand, if the contrast ratio is not different from that of the surrounding area, it may be treated as noise and smoothed to have relevance to the surrounding area as described below. Unlike the structure region, the singular point is basically processed as an image signal and can be processed as a noise signal in consideration of the peripheral region and the contrast ratio.

Median filtering may be applied for filtering and median filtering may be any nonlinear digital filter known in the art for noise reduction and may be, for example, a linear Gaussian filter. Filtering for outliers The results can be represented by a two-dimensional matrix (matrix A) and applied by the image enhancement unit with the spatial correlation matrix for adaptive filtering for image enhancement.

Image enhancement may be an image determination step for an ultrasound signal to be displayed by the display unit and may have the function of improving the quality of the displayed image. The digital signal thus adaptively filtered according to the singularity is eventually processed and the image quality can be improved (16) and displayed on the display unit.

The image enhancement may include, for example, smoothing out the singularity to remove noise in the homogeneous region and processing the singularity to the image region as an image signal. Specifically, the matrix I obtained in the filtering step may be applied to the matrix I representing the spatial correlation, so that the matrix I may be modified. For example, a diffusion filter expressed by Equation 4 below can be applied to the B-mode image matrix I.

≪ Equation 4 &

In Equation (4), div denotes divergence and c denotes a diffusion coefficient.

The diffusion coefficient c can be expressed by the following equation (5).

≪ Eq. 5 &

In Equation 5, A represents the matrix A obtained in the filtering step, and m can be a user-defined parameter.

For example, the speckle corresponding to the noise in the B-mode image may be reduced by applying the matrix A representing the area attribute to the matrix I according to the spatial coherence. Subsequently, the signal with the enhanced image quality that has been subjected to the adaptive filtering is subjected to a scan conversion to be displayed on the display unit and an image with improved quality can be obtained.

The method of calculating spatial consistency and calculating or filtering the label values shown above is exemplary and the present invention is not limited to the embodiments shown.

A unit applied to a signal processing module according to the present invention will be described below.

2 schematically shows an embodiment of a process of processing a signal in each step in the ultrasonic signal processing method according to the present invention. And FIG. 3 illustrates an application of the spatial consistency calculation unit applicable to the ultrasonic signal processing method according to the present invention.

Fig. 2 (a) is a schematic block diagram of an embodiment of a signal processing procedure according to the present invention, and Fig. 2 (b) shows an embodiment of a signal processing procedure known for comparison. 3 (a) and 3 (b) show signal processing processes and known signal processing processes according to the present invention corresponding to the beam forming and spatial consistency calculation of FIGS. 2 (a) and 2 Respectively.

Referring to FIGS. 2 and 3, the ultrasonic signal processing module includes transducers 31a to 31n including a plurality of piezoelectric elements for receiving the reflected ultrasonic signals. A delay signal processor (32a-32n) for delaying beam focusing of the signal received from the transducer (31a-31n); A spatial coherence calculating unit (33) for calculating spatial coherence from the reflected ultrasonic signal; And a filter unit 28 for filtering the signal processed by the delay signal processors 32a to 32n to remove the specificity of the value calculated in the spatial consistency calculation unit 33. [

The ultrasound signals reflected from the in-vivo diagnostic region T can be received by the ultrasonic elements 31a to 31n disposed in the transducer and transmitted from the diagnostic region T corresponding to the focal position to the respective ultrasonic elements 31a to 31b , And are received by the respective ultrasonic elements 31a to 31n. Each signal can be compensated for the delay time by the delay signal processors 32a through 32n. Such a process can be performed by the beam forming unit 21. The signal delay-compensated by the beam forming unit 21 is demodulated by the waveform detecting unit 22 to detect the amplitude and each of the ultrasonic signals can be synthesized.

2B and 3B, the signals processed by the delay signal processors 32a to 32n are combined into one signal by the waveform forming unit 36, and the envelope detector 22, And then converted to a signal representing the diagnostic region and transmitted to the scan converter 24. Processed by the post-processing processor 241 and transferred to the display unit 25 and displayed as an image. In contrast, in the signal processing module according to the present invention, spatial consistency can be calculated from the signals processed by the delay signal processors 32a to 32n.

Referring to Figs. 2 (A) and 3 (A), signals delay-compensated by the delay signal processors 32a through 32n are processed by the spatial consistency calculation unit 33 and used for image enhancement. Specifically, the spatial consistency calculation unit 33 may be composed of a correlation calculation unit 26, a label unit 27, and a filter unit 28. [ A correlation characteristic matrix A can be created in which the correlation matrix I is generated as described above in the correlation calculation unit 26 and weight values are given according to the crack region and the structure region in the label unit 27. [ The matrix I and the matrix A are then sent to the filter unit 28 and filtering may be done to remove singularities along the homogeneous and structural regions. (E.g., filter unit 28) may include such things as a median filter, an adaptive filter, or a diffusion filter. Correction values for each position of the diagnostic region T in the filter unit 28 can be made in the form of a two dimensional matrix and transmitted to the image enhancement unit 23. [ The image enhancement unit 23 may be time delay compensated to apply the adaptive filter according to the matrix through the filter unit 28 again for the waveform synthesized signal. The finally processed signal may then be transmitted to the scan converter 24 and displayed on the display unit 25. [ Such a series of processes is shown in Fig.

3, the label unit 27 may have a function of applying a weight according to the region characteristic of a region to be imaged. Then, the filter unit 28 searches for a singular point in the label unit 27 The characteristic of the filter may be changed based on the value calculated in the spatial consistency calculation unit 33 or the correlation calculation unit 26. In addition, the filter unit 28 or the image The value of the enhancement filter can be determined by the user based on the value calculated in the label unit 27 or the correlation calculation unit 26 and the characteristic of the diagnostic region. In other words, the filter value can be a user-defined parameter.

4 illustrates an embodiment of an ultrasonic signal processing module according to the present invention.

Referring to FIG. 4, the reflected ultrasound signals Rx may be received by the respective ultrasonic devices 411 to 41k of the transducer 41. The signal received at the ultrasonic element 411 can be converted into an electric signal to become RF data and the delay time can be compensated by the beam forming units 42a to 42k and transmitted to the detection unit 44. [ On the other hand, the signals of the beam forming units 42a to 42k are transmitted to the correlation unit 43 so that the spatial correlation of the mutual positions of the ultrasonic elements 411 to 41lk can be calculated. An envelope is made in the detection unit 44 so that a preliminary image signal for each position of the diagnostic region can be formed. The preliminary image signal does not substantially exhibit the characteristic of the diagnosis site and needs to be corrected. The label unit 441 indicates the characteristic of the area where the signal is received in the homogeneous region or the structure region, and the singularity is removed by the filter unit 442. And transmitted to the display unit 47 via the image enhancing unit 45 and the scan converter 46 for applying an adaptive filter according to the characteristics of the homogeneous region and the structural region to improve the image, and displayed as an image.

In the embodiment shown in Figs. 3 and 4, the correlating unit, the label unit or the filter unit is presented as an independent configuration, but can be made as a single processor or a processing unit. The delay signal processor may also be composed of a single processor with a correlation unit, a label unit or a filter unit as well. The correlation unit, label unit or filter unit may also be made in hardware or software form.

As described above, the signal processing module or method according to the present invention does not improve the image quality through the enhancement of the contrast ratio of the image, but rather the improvement of the image quality such as speckle or blurring of the edge of the region caused by the region characteristic of the diagnostic region Thereby improving the quality of the ultrasound image or the B-mode ultrasound image. However, due to this, the sharpness of the image can be improved due to the enhancement of the contrast ratio of the ultrasonic image incidentally.

5 shows an embodiment of a method of processing an ultrasonic signal according to the present invention.

5, the ultrasonic signal processing method according to the present invention includes receiving a reflected wave from a diagnosis site (S51); Performs delay compensation on each of the received reflected waves (S52); Calculating (S53) spatial correlation from time delay data of the received reflected wave; Filtering the specificity among the correlation values (S54): applying a different adaptive filter according to the homogeneous region or the structure region with respect to the obtained correlation value (S55); and transmitting the enhanced image data to the scan converter Step S56.

The reception of the reflected wave may be performed by each receiving element disposed in the transducer. And the signal received by each receiving element may be delay compensated and converted to radio frequency (RF) data. Then, the spatial correlation can be calculated from the converted RF data (S53). The spatial correlation can be calculated according to the method described above and can be expressed, for example, in the form of a matrix. And a weight according to the region characteristic may be given as needed. Thereafter, the specificity filtering may be performed based on the spatial correlation (S54). The type of the filter can be determined based on the spatial correlation or according to the region characteristic, and the filter value can be a user-defined parameter. Thereafter, the image is enhanced by the adaptive filter (S55), and the improved image data can be obtained accordingly. Thereafter, the enhanced image data may be transmitted to the scan converter and displayed as an image (S56).

The filtering in the ultrasonic signal processing according to the present invention can be performed by various methods, and the present invention is not limited to the embodiments shown.

The signal processing module according to the present invention has an advantage that a quality of an image to be imaged is defined based on a value obtained based on spatial coherence and applied to an image enhancement signal processing so that an improved ultrasound image can be obtained. Also, the signal processing method according to the present invention has the advantage that the speckle is reduced in the B-mode image.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention . The invention is not limited by these variations and modifications, but is limited only by the claims appended hereto.

21: beam forming unit 22: waveform detecting unit
23: image preprocessing unit 24: scan converter
25: Display unit 26: Correlation calculation unit
27: label unit 28: filter unit
31a to 31n: Ultrasound elements 32a to 32n: RF signal processor
33: Space consistency calculating unit 36: Waveform forming unit
41: transducer 43: correlation unit
44: detection unit 45: preprocessing unit
46: scan converter 47: display unit

Claims (4)

An ultrasonic signal processing module for receiving an ultrasonic signal reflected from the inside of a human body to form an image,
A transducer including a plurality of receiving elements for receiving the reflected ultrasonic signals;
An RF signal processor for processing the signal received by the transducer;
A spatial coherence calculating unit for calculating spatial coherence from the received ultrasonic signal;
A label unit for applying a value according to an area characteristic of a site to be imaged based on the value processed in the spatial consistency calculation unit;
A filter unit for modifying the singularity of the label unit; And
An ultrasound signal processing module including an image enhancement filter for enhancing an image by applying filter characteristics differently according to spatial consistency. The ultrasound signal processing module of claim 1, wherein the type or filter value of the filter unit or the image enhancement filter is a user-defined parameter. The ultrasound signal processing module according to claim 1, comprising a delay function for giving a delay time function to each receiving element of the receiving element to obtain a signal focused on a specific point. Receiving ultrasound reflected from a subject in the human body;
Converting a received ultrasound signal into RF data by applying a delay time to each receiving element to obtain a convergence signal corresponding to a specific point;
Calculating space coherence with respect to the RF data and weighting the RF data according to characteristics of the diagnosis object;
Filtering the singularities for the characteristic; And
And enhancing the image by applying filter characteristics differently according to the spatial consistency.

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