KR20110110471A - Ultrasound diagnostic system and method for forming elastic image - Google Patents

Abstract

 The present invention relates to an ultrasound diagnosis system and method for forming an elastic image, wherein when a force is not applied to an object, an ultrasound transmission pulse is transmitted to form a first received signal with the reflected ultrasound signal, and when a force is applied to the object. An ultrasonic reception signal forming step of transmitting the same ultrasonic transmission pulse to form a second reception signal with the reflected ultrasonic signal; After estimating the phase difference between the first received signal and the second received signal, the second received signal is moved in a direction in which the estimated phase difference decreases to form a third received signal, and the first received signal and the estimated phase difference And processing the displacement using the third received signal shifted by. Accordingly, in the process of forming an elastic image for ultrasound diagnosis, it is possible to calculate a displacement to more accurately obtain a correlation between two received signals when a force is applied to an object such as a soft tissue of the human body and when it is not applied. This eliminates the need for complicated configuration of additional devices and prevents unnecessary calculations and computation time from increasing.

Description

Ultrasound Diagnostic System and Method for Forming Elastic Image

The present invention relates to an ultrasound diagnosis system and method, and more particularly, an autocorrelation is calculated after making an RF signal of an ultrasound into a complex signal using a Hilbert transform when calculating displacement for forming an elastic image. The present invention relates to an ultrasonic diagnostic system and method for forming a new elastic image to enable accurate displacement calculation.

Recently, a lot of researches in the field of ultrasound medical imaging is elastic imaging. This technique is used to image the rigidity of tissues by ultrasound measurement. For example, tumors that occur in soft tissues, such as the breast or prostate, are harder than the surrounding tissues. Therefore, breast cancer can be examined by palpation. A technique for imaging and diagnosing such a process using an ultrasound medical imaging system is known as an ultrasound diagnosis system using ultrasound elastic imaging.

The process of acquiring the data for the elastic image is obtained by applying an ultrasonic pulse to the soft tissue before and after the deformation while applying a force to the soft tissue to deform the shape, and then comparing the ultrasound data before and after the deformation to the size of the tissue movement. That is, by measuring the displacement. Hard tissues have relatively small movements, but soft tissues have relatively large movements. Therefore, what is important for the accuracy of diagnosis in elastic imaging method depends on how precisely this displacement can be measured.

In general, the elastic imaging method compares a first received signal in a state where no force is applied to an object and a second received signal in a state where a force is applied. Since the first received signal is a reflected ultrasound signal from an uncompressed object and the second received signal is a reflected ultrasound signal from a compressed object, the second received signal is a compressed form of the first received signal. In order to compare the first reception signal with the second reception signal, the size of the object, more specifically, the distance between the reflectors in the object must be restored to the same condition, so the second reception signal must be extended.

In the elastic imaging method, since pulses of the same waveform are transmitted into the human body when no force is applied or when a force is applied, when the second reception signal is extended, the distance between the reflectors is restored to its original state, but the width of the transmission pulse is also increased. There is a problem in that the estimation adversely affects the correlation between the first received signal and the second received signal, which causes a decrease in the precision of the displacement measurement.

In order to solve this problem, for example, the registration announcement of the Republic of Korea Patent Registration No. 10-0898946 "Ultrasound diagnosis system and method for forming the elastic image", the first reception by transmitting the first transmission pulse when the stress is not applied to the target When the signal is obtained and the subject is under stress, the second transmission pulse is different from the first transmission pulse to obtain a second reception signal, and then the displacement of the object using the first reception signal and the second reception signal. A technique for calculating is proposed. However, this increases the price of the equipment because a mechanism having a complicated configuration must be additionally configured to transmit different types of transmission pulses when the force is applied and the force is not applied. In this case, the first transmission pulse and the second transmission pulse are determined by applying the compression rate or the average compression rate of the object, and the compression rate or the average compression rate is a unilateral estimated value or the first received signal and the second received signal using the same transmission pulse. Since the compression rate or the average compression rate varies depending on the object, the time taken for the formation of the elastic image is increased.

Therefore, in the process of forming an elastic image for ultrasound diagnosis, the conventional apparatus can be used to calculate displacement so that the correlation between two received signals when a force is applied to an object such as a soft tissue of the human body and when it is not applied can be obtained more precisely. There is still an urgent need for an ultrasound diagnostic system and method for forming a new elastic image that does not need to be additionally complicated and does not increase the diagnostic time.

The present invention has been invented to improve and supplement the ultrasound diagnostic system and method for forming the conventional elastic image described above and to provide various additional advantages. In the process of forming an elastic image for ultrasound diagnosis, the present invention enables displacement calculation to more accurately obtain a correlation between two received signals when a force is applied to an object such as a soft tissue of a human body and when it is not applied. It is an object of the present invention to provide an ultrasonic diagnostic system and method for forming a new elastic image that does not need to additionally configure the device of the complex and does not increase unnecessary calculation amount or calculation time.

This object is achieved by an ultrasound diagnostic system and method for forming an elastic image provided according to the present invention.

According to an aspect of the present invention, an ultrasound diagnosis system for forming an elastic image includes transmitting an ultrasound transmission pulse when a force is not applied to an object to form a first received signal with a reflected ultrasound signal, and applying a force to the object. An ultrasonic reception signal forming unit for transmitting the same ultrasonic transmission pulse to form a second reception signal with the reflected ultrasonic signal when applied; After estimating the phase difference between the first received signal and the second received signal, the second received signal is moved in a direction in which the estimated phase difference decreases to form a third received signal, and the first received signal and the estimated phase difference And a processor configured to calculate a displacement using the third received signal moved by.

The subject is preferably a soft tissue of human or animal.

In one embodiment, the first to the third received signal used by the processor 60 to calculate the displacement is a complex signal generated by using a Hilbert transform signal of the RF data format, which is ultrasonically received data. to be.

In addition, the ultrasound diagnostic method for forming an elastic image provided according to another aspect of the present invention, when the force is not applied to the object to form a first received signal with the ultrasound signal reflected by transmitting the ultrasound transmission pulse, the force on the object An ultrasonic reception signal forming step of transmitting the same ultrasonic transmission pulse when the applied signal is formed to form a second received signal with the reflected ultrasonic signal; After estimating the phase difference between the first received signal and the second received signal, the second received signal is moved in a direction in which the estimated phase difference decreases to form a third received signal, and the first received signal and the estimated phase difference And processing the displacement using the third received signal shifted by.

In an embodiment, the processing may further include generating the first to third received signals as a complex signal using a Hilbert converter from a RF data format signal that is ultrasonic reception data.

Ultrasound system and method for forming an elastic image according to the present invention having the above-described configuration, in the process of forming the elastic image for ultrasound diagnosis, two received signals when and when applying a force to an object, such as soft tissues of the human body It is possible to calculate the displacement to obtain the correlation between them more precisely, but it does not need to additionally configure the conventional apparatus and provides an effect such that unnecessary calculation amount or calculation time is not increased.

1 is a block diagram schematically showing a functional configuration of an ultrasonic diagnostic system for forming a general elastic image.
2 is a flow chart showing a displacement calculation model employed in the ultrasound diagnostic system for forming an elastic image according to the present invention.
Figure 3 is a graph showing the shape of the signal used in the displacement calculation employed in the ultrasound diagnostic system for forming an elastic image according to the present invention.

Hereinafter, with reference to the accompanying drawings illustrating the present invention with a specific example as follows.

1, there is shown a schematic configuration of an ultrasonic diagnostic system 100 for forming an elastic image capable of executing the ultrasonic diagnostic method for forming an elastic image according to an embodiment of the present invention.

The ultrasound diagnosis system 100 is a component for forming an ultrasound reception signal, and includes a transmission pulse forming unit 10, a probe 20, a frame data forming unit 30, a storage unit 40, and a preprocessor ( 50). When the ultrasonic reception signal is formed by these, an operation for processing the ultrasonic reception signal to form an ultrasonic image is performed, which is processed by the processor 6 and the post processor 70. The ultrasound image formed by the post processor 70 may be represented as an image by the display 80.

The transmission pulse forming unit 10 forms the same ultrasonic pulse both when no force is applied to the object and when a force (stress) is applied. This ultrasound pulse is a broadband ultrasound pulse for B-mode ultrasound imaging. The subject may include a medium in soft tissues of a human or animal and reflectors such as tumors and the like.

The probe 20 transmits the ultrasonic pulses formed by the transmission pulse forming unit 10 to the object as ultrasonic transmission signals, respectively, and receives the first ultrasonic wave when no force is applied to the object based on the ultrasonic echo signal input from the object. A second ultrasonic wave reception signal when a force is applied to the signal and the object is formed.

The frame data forming unit 30 focuses the first ultrasound signal and the second ultrasound signal formed by the probe 20 to form corresponding frame data. This frame data has an RF data format.

The storage unit 40 stores frame data in frame order. In this case, the frame data formed by the first ultrasonic signal is stored as the first frame data, and the frame data formed by the second ultrasonic signal is stored as the second frame data.

The preprocessing unit 40 extracts the first and second frame data stored in the storage unit 40 and processes the first and second frame data as first and second received signals. The first received signal and the second received signal have an RF signal format. In the preprocessor 40, the extracted first and second received signals may be subjected to, for example, log compression to increase amplitude, or to perform filtering to reduce an error due to noise.

The processor 60 calculates a displacement from the preprocessed RF received signals, that is, the first received signal and the second received signal, and calculates the strain of the object based on the displacement. The displacement calculation process according to the invention can be performed by this processor 60.

The post-processing unit 70 may form elastic image data after normalizing the strain calculated by the processor 60 and processing such as filtering to reduce noise.

The display unit 80 may display elastic image data input from the post processor 70.

As described above, the ultrasonic diagnostic system according to an embodiment of the present invention, when the force is not applied to the object, such as soft tissue of the human body formed in the ultrasonic receiving signal forming unit (10, 20, 30, 40, 50), the ultrasonic transmission pulse Is an ultrasound diagnostic system that forms an elastic image using a first received signal by the reflected ultrasound signal and a second received signal by the reflected ultrasound signal by transmitting the same ultrasound transmit pulse when a force is applied to the object. .

In particular, the present invention, in order to enable more accurate displacement calculation in the displacement calculation process of the processor 60, the process of making the first and second received signal into a complex signal using a Hilbert transducer and the signal by moving the correlation Increasing process. That is, according to the present invention, after estimating the phase difference between the first received signal and the second received signal, the second received signal is moved in a direction in which the estimated phase difference decreases to form a third received signal, and then the first received signal. The displacement is calculated using the received signal and the third received signal moved by the estimated phase difference.

The most important process in the elastic imaging method is the process of measuring the magnitude, or displacement, of the movement before and after deformation of the soft tissue by comparing the ultrasound data obtained from the soft tissue before and after the deformation while applying the force to the soft tissue to deform the shape. Therefore, an important algorithm in the calculation for obtaining an elastic image is an algorithm for measuring displacement, which is the magnitude of motion.

The present invention has the feature of using radio frequency (RF) data as it is. RF data refers to ultrasonically received data that has not been processed such as complex signal processing. In general, when creating an ultrasound image, RF data is processed to generate complex signal IQ data (In-phase, Quadrature-phase component data) lowered to a low frequency band, and then the ultrasound signal is formed using the complex signal IQ data. do. Conventionally, in calculating the displacement in the elastic imaging method, it is common to calculate the displacement using IQ data, which is a complex signal for forming an ultrasound image.

Unlike the related art, according to the present invention, RF data before processing for an ultrasound image is used as it is. In other words, it is not complex signal to make an ultrasound image, but a new complex signal optimized for displacement calculation, that is, a complex signal made by using the Hilbert transform, and then the complex signal made by the Hilbert transform is used and the autocorrelation ( Displacement is calculated through autocorrelation. This enables more accurate displacement calculation than the conventional method using a complex signal for ultrasound imaging.

Hereinafter, a displacement calculation algorithm using autocorrelation according to the present invention will be introduced. The displacement is converted into an analytic signal using a Hilbert transducer to use the phase information of the received ultrasonic RF signal. The displacement of the two signals was calculated after calculating the phase difference by calculating the autocorrelation. The signal model with displacement can be modeled with a global pass filter with linear delay (see Figure 2).

로 표현할 수 있고, 시간 축에서 τ만큼 이동된 후의 신호

를 힐버트 필터링(Hilbert filtering)하여 얻은 복소 RF 신호는 다음 수학식 1과 같다. The ultrasonic signal that is the reference in the displacement calculation

Signal after moving by τ on the time axis

The complex RF signal obtained by Hilbert filtering is represented by Equation 1 below.

은 제1 수신신호,

는 제2 수신신호,

는 포락선이며,

는 중심주파수이며, τ는 시간 지연,

는 기저 대역 신호의 위상에 해당한다. 일반적인 인체에서의 초음파 신호는 감쇄에 의하여 중심주파수가 깊이에 따라서 낮아진다. 이를 모델링하기 위하여 중심주파수 편이를

라고 하고 이를 고려하면 수학식 1은 다음 수학식 2와 같이 수정될 수 있다.here,

Is the first received signal,

Is the second received signal,

Is the envelope,

Is the center frequency, τ is the time delay,

Corresponds to the phase of the baseband signal. In general, the ultrasonic signal in the human body decreases as the center frequency decreases due to attenuation. In order to model this, the center frequency shift

In consideration of this, Equation 1 may be modified as in Equation 2 below.

The phase difference between the two signals is obtained from Equation 3 below from the autocorrelation calculation.

는 위상을 구하는 함수이며

는 상관도를 계산하는 함수이다. 수학식 3에서 시간 지연

가 작을 경우 기저 신호의 위상항은 테일러 급수의 1차 전개를 하면 다음 수학식 4와 같이 근사된다.here

Is a function to find the phase

Is a function that calculates the correlation. Time delay in equation (3)

If is small, the phase term of the base signal is approximated by Equation 4 when the first order expansion of the Taylor series is performed.

Therefore, the displacement becomes as shown in Equation 5 below.

가 큰 경우 비교하고자 하는 깊이에서 두개의 신호의 모양이 달라져 비상관도가 큰 데이터를 이용하여 계산하게 되므로 계산 오차가 커진다. 이를 극복하기 위하여 본 발명에 따르면, 도 3에서와 같이 두 신호, 즉 제1 수신신호와 제2 수신신호 사이의 변위

를 추정한 뒤 위상차가 줄어드는 방향으로 신호를 먼저 이동시킨 제3 수신신호

를 형성한 후, 제1 수신신호와 이 제3 수신신호를 이용하여 다시 변위를 계산한다. 압축 후의 신호 즉 제2 수신신호의

에 위상차를 줄이기 위해 인접한 이전의 윈도우에서 구한 변위값을 추정값 δ로 사용한다. 위상차가 줄어드는 방향으로 이동시킨 압축 후의 복소 신호 즉 제3 수신신호는 다음 수학식 6과 같이 된다.Figure 3 is a graph showing the movement of the signal in the displacement calculation considering the uncorrelated diagram. Displacement calculations that do not consider uncorrelation will only calculate the phase difference of the data in the window at the same location before and after the movement. Thus displacement

If is large, the shape of the two signals is different at the depth to be compared, and the calculation error is increased because the data is calculated using large uncorrelated data. In order to overcome this, according to the present invention, the displacement between two signals, that is, the first received signal and the second received signal, as shown in FIG.

The third received signal which first moved the signal in the direction of decreasing phase difference after estimating

After forming, the displacement is calculated again using the first received signal and the third received signal. Of the signal after compression, that is, the second received signal

In order to reduce the phase difference, the displacement value obtained from the previous adjacent window is used as the estimated value δ. The complex signal after compression, ie, the third received signal, shifted in the direction in which the phase difference decreases is expressed by the following equation (6).

The phase difference between the pre-compression signal, i.e., the first received signal and the moved compression signal, i.e., the third received signal, is expressed by the following equation (7) from the correlation calculation.

가 되므로 수학식 7은 다음 수학식 8과 같이 된다.This is the first approximation of Taylor series

Equation 7 is as follows.

는 다음과 같이 계산한다. 먼저

를

만큼 이동시킨 신호를 구하면 수학식 9와 같이 표현될 수 있다.In Equation 8, frequency shift

Calculate as first

To

Obtaining the shifted signal can be expressed as in Equation (9).

When the phase is calculated by obtaining the autocorrelation as follows, Equation 9 is expressed by Equation 10.

를 이용하여 수학식 10을 간략화하면 다음 수학식 11과 같이 된다.Taylor series approximation again

By simplifying the equation (10) by using the following equation (11).

Becomes In summary, the equation 12 is obtained.

Substituting this in Equation 8 can be expressed as Equation 13.

가 되면, 수학식 13은 아래 수학식 14로 근사된다.if

Equation 13 is approximated by Equation 14 below.

Therefore, equation (8) is finally approximated by equation (15).

After estimating the phase difference between the first and second received signals before and after applying a force to the object, a third received signal obtained by moving the second received signal in a direction in which the estimated phase difference decreases is formed, and the Next, when the displacement is calculated using the first and third received signals, the correlation between the signals may be increased and the decoration may be reduced, thereby calculating a more precise displacement.

In the above, the present invention has been described through specific embodiments, but those skilled in the art can refer to and combine various features described in the present disclosure, and various and modified construction methods are possible. Therefore, it is intended that the scope of the present invention should not be limited to the described embodiments, but should be interpreted by the appended claims.

As described above, the present invention can be widely used in the field of ultrasonic diagnostics for the detection of tumors occurring in soft tissues of the human body such as breast or prostate.

10: transmit pulse forming unit
20: probe
30: frame data forming unit
40: storage unit
50: preprocessing unit
60: processor
70: post-processing unit
80 display unit
100: ultrasound diagnostic system

Claims (6)

An ultrasound diagnostic system for forming elastic images,
When the force is not applied to the object, an ultrasonic transmission pulse is transmitted to form a first received signal with the reflected ultrasonic signal, and when the force is applied to the object, the same ultrasonic transmission pulse is transmitted to transmit the second received signal with the reflected ultrasonic signal. An ultrasonic receiving signal forming unit (10, 20, 30, 40, 50) to form;
After estimating the phase difference between the first received signal and the second received signal, the second received signal is moved in a direction in which the estimated phase difference decreases to form a third received signal, and the first received signal and the estimated phase difference The processor 60 for calculating the displacement using the third received signal moved by
Ultrasonic diagnostic system for forming an elastic image, characterized in that it comprises a. The ultrasound diagnostic system of claim 1, wherein the subject is a soft tissue of human or animal. The method according to claim 1, wherein the first to third received signal used by the processor 60 to calculate the displacement is a complex signal generated by using a Hilbert transform signal of the RF data format that is the ultrasonic reception data Ultrasonic diagnostic system for forming an elastic image, characterized in that. Ultrasonic diagnostic method for forming elastic images,
When the force is not applied to the object, an ultrasonic transmission pulse is transmitted to form a first received signal with the reflected ultrasonic signal, and when the force is applied to the object, the same ultrasonic transmission pulse is transmitted to transmit the second received signal with the reflected ultrasonic signal. Forming an ultrasonic receiving signal;
After estimating the phase difference between the first received signal and the second received signal, the second received signal is moved in a direction in which the estimated phase difference decreases to form a third received signal, and the first received signal and the estimated phase difference A processing step of calculating displacement using the third received signal shifted by
Ultrasound diagnostic method for forming an elastic image, characterized in that it comprises a. The ultrasound diagnostic method of claim 4, wherein the object is soft tissue of a human or animal. 5. The elastic image of claim 4, wherein the processing further comprises generating the first to third received signals as a complex signal using a Hilbert transformer from a signal having an RF data format, which is ultrasonic reception data. Ultrasound diagnostic method for shaping.

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