JP2000126179A - Ultrasonic doppler diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a smoothing processing by a simple constitution while archfact related to smoothing is prevented from being generated. SOLUTION: A mean speed operated by means of a self-correlating tool is displayed on a complex plane by means of a rectangular coordinate convertor 30. After weighting based on the amplitude A of a signal is performed on each component on the complex plane, smoothing processing is performed on each component. Then, polar coordinate conversion is eventually performed to obtain a mean flow speed signal 102 smoothed in the depth direction. The window width for the smoothing processing is variably set in accordance with the range of display and the site of diagnosis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ultrasonic Doppler diagnostic apparatus, and more particularly to a smoothing process for improving image quality.

[0002]

2. Description of the Related Art In an ultrasonic Doppler diagnostic apparatus, ultrasonic waves are transmitted and received by an ultrasonic probe, and a received signal obtained thereby is converted into a complex signal by a quadrature detector. Thereafter, the complex signal is input to a high-pass filter for removing a component of a low-speed moving body (for example, a heart wall), and the complex signal output from the filter is input to an autocorrelator. The autocorrelator performs an autocorrelation operation between a plurality of received signals (complex signals) obtained by transmitting and receiving ultrasonic pulses in the same direction a plurality of times, thereby obtaining an average blood flow velocity (average flow velocity). Is a known circuit that computes A so-called color Doppler image can be formed by expressing the average speed at each portion in the scanning plane by coloring.

[0003] By the way, when a blood flow or the like in a blood vessel is expressed in a color Doppler image, the image may be a blocky image near a blood vessel wall, and there is a demand for smoothing the image. Therefore, conventionally, an FIR type smoothing unit 18A as shown in FIG. 4 is used.

This circuit is a circuit for performing smoothing along a depth direction between an autocorrelator and a display processing circuit (DSC). Each of the input speed data 100 is delayed by each of the delay elements 50 to 56, and for each of a predetermined number of speed data, using the multipliers 66 to 74 and the adder 76,
Weighted addition is performed. However, in order to prevent artefacts related to smoothing, the circuit of FIG. 4 includes circuits 58 to 64 and 80 for determining folding and correcting them so that artifacts do not occur. Note that the artifact related to smoothing is, for example, a signal near an angle of 0 degree when two positive and negative signals are present across a 180-degree axis on a complex coordinate system, when these signals are averaged. That means.

[0005] For example, speed information of five points is represented by V _-2 (-
π ≦ V ₋₂ ≦ π), V ₋₁ (−π ≦ V ₋₁ ≦ π), V ₀ (−π
≦ V ₀ ≦ π), V ₁ (−π ≦ V ₁ ≦ π), V ₂ (−π ≦ V ₂
≦ π), and the weighting coefficients used in the smoothing process are ω ₋₂ , ω ₋₁ , ω ₀ , ω ₁ , ω ₂ (however, ω ₋₂ + ω ₋₁ + ω ₀₎
+ Ω ₁ + ω ₂ = 1), and the finally output speed information is V (−π ≦ V ≦ π). Here, the aliasing corrector 58
F (V ₀ , V _i ) (where i
= −2, −1, 0, 1, 2), the following is obtained.

[0006]

(Equation 1) Here, assuming that the added value after the aliasing correction is θ ₀ , it is as follows.

[0007]

(Equation 2) The average information V finally output is as follows.
That is, the return final determiner 80 makes the following determination.

[0008]

(Equation 3) Therefore, when a higher-order filter for the smoothing process is used, the window width of the smoothing, that is, the number of data required for the smoothing becomes as large as several to several tens, and the return determination is performed for each of these data. Performing the smoothing process becomes very complicated and increases the circuit scale. For this reason, there is a situation in which an upper limit is imposed on the window width of the smoothing process.

Japanese Patent Publication No. Hei 6-73523 discloses that
A configuration is disclosed in which calculated flow velocity information (instantaneous flow velocity) is developed on orthogonal coordinates, smoothing processing is performed for each component, and then flow velocity is obtained by polar coordinate conversion. However, in this configuration, the smoothing is performed in the time axis direction, and it is determined that the processing performed inside the conventional autocorrelator is only performed outside the conventional autocorrelator. That is, smoothing in the depth direction is not performed. Further, in this configuration, no consideration is given to the amplitude of the signal.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to realize smoothing along a depth direction with a simple configuration while preventing artifacts related to smoothing. is there.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a transmitting / receiving means for transmitting / receiving an ultrasonic wave, and converts a received signal obtained by transmitting / receiving the ultrasonic wave into a complex signal. A complex signal conversion unit, an autocorrelation operation unit that executes an autocorrelation operation on the complex signal, and outputs an average speed signal, and an orthogonal coordinate conversion unit that executes an orthogonal coordinate conversion on the average speed signal. For each component after the orthogonal coordinate transformation, smoothing processing means for performing a smoothing process along the depth direction, polar coordinate transformation means for performing a polar coordinate transformation on each component after the smoothing process, It is characterized by including.

[0012] According to the above configuration, the average velocity signal after auto-correlation (the signal averaged in the time axis direction) is subjected to orthogonal transformation on complex coordinates, and each component is processed in the depth direction. A smoothing process is performed (between a plurality of adjacent data). Then, polar coordinate conversion is performed on each component after the smoothing process, and thereby the component is returned to the original coordinate system.
In this configuration, since the smoothing process is performed for each component on the complex coordinate axis, it is not necessary to perform special aliasing correction. In other words, simply performing the smoothing process on the average speed signal,
Although artifacts related to smoothing are likely to occur as described above, according to the present invention, since smoothing processing can be performed for each component on a complex coordinate system, such artifacts related to smoothing can be avoided. Therefore, smoothing can be realized with a simpler configuration than before, while preventing artifacts.

Preferably, the apparatus further includes weighting means for weighting each component after the orthogonal coordinate conversion according to the magnitude of the amplitude of the received signal. According to this weighting,
More natural smoothing can be expected.

Preferably, a window width setting means for variably setting a window width of the smoothing process is included. According to this configuration, the degree of smoothing can be changed according to various situations, and a desired ultrasonic image can be formed. For example, the window width is variably set according to the display range and the diagnostic site.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a block diagram showing the overall configuration.

In FIG. 1, a probe 10 is, for example, an ultrasonic probe used in contact with the surface of a living body or inserted into a body cavity. The probe 10 has an array transducer composed of a plurality of transducers. An ultrasonic beam is scanned by electronically scanning (for example, electronic linear scanning and electronic sector scanning) the array transducer, thereby forming a scanning surface which is a two-dimensional data acquisition area. In the present embodiment, Doppler information is extracted on the scanning plane.

The transmission / reception circuit 12 supplies a transmission signal to an array vibrator provided in the probe 10, and amplifies, delays, and adds to a reception signal output from the probe 10. Is a circuit that executes

The quadrature detector 14 is a circuit that performs a known quadrature detection process on the received signal after the phasing addition, and converts the received signal into a complex signal. The quadrature detector 14 includes two mixers, and each mixer is supplied with a predetermined reference signal.

The autocorrelator 16 is a known circuit that calculates the average velocity of the moving tissue in the living body, specifically, the average flow velocity of the blood flow by performing an autocorrelation operation on the complex signal. In the present embodiment, transmission and reception of the ultrasonic pulse are performed a plurality of times for each direction in the scanning plane, and a plurality of reception signals (complex signals) in the same direction obtained thereby are obtained.
, The average flow velocity at each depth position on the beam axis is calculated.

The average speed signal 10 obtained in this way is
0 is input to the smoothing unit 18, which performs a smoothing process described later in detail. The smoothed average speed signal 102 is sent to the DSC (digital scan converter) 20. The DSC 20 has a coordinate conversion function, a data interpolation function, and the like. Image data corresponding to the average flow velocity is sent from the DSC 20 to the display 22, and a two-dimensional Doppler image or the like is displayed on the display 22.

By the way, although not shown in FIG. 1, a B-mode image (two-dimensional tomographic image) is formed based on the received signal, and the display 22 displays a two-dimensional Doppler image on the B-mode image. Are composited and displayed.

Next, a specific configuration example of the smoothing unit 18 shown in FIG. 1 will be described.

In FIG. 2, the smoothing section 18 has an orthogonal coordinate converter 30, two smoothing processors 32 and 34, and a polar coordinate converter 36. The orthogonal coordinate converter 30 is a circuit that performs orthogonal coordinate conversion on the average speed signal 100, and specifically executes a process of representing the average speed on a complex plane. Specifically, co for φ as the average speed
Execute the calculation of sφ and sinφ. The two components obtained by such an operation are respectively applied to the smoothing processor 3
2, 34. These smoothing processors 32 and 3
Reference numeral 4 is an FIR filter having several to several tens taps. Of course, other filter configurations may be employed. For example, as the smoothing processors 32 and 34, the aliasing correctors 58 to 6 in the circuit shown in FIG.
4 and a circuit excluding the return final decision unit 80.

Therefore, according to the smoothing processors 32 and 34, it is possible to perform a smoothing process for each component on the complex plane, and more specifically, a plurality of adjacent ones in the depth direction on the ultrasonic beam. Speed data smoothing processing can be performed.

The polar coordinate converter 36 is a circuit for performing a polar coordinate conversion based on the two components after the smoothing. The average speed signal 102 smoothed in the depth direction by such a conversion is obtained.

Therefore, according to the circuit configuration shown in FIG. 2, since it is not necessary to perform aliasing correction and its determination as in the prior art, it is possible to prevent artifacts related to smoothing while using a very simple configuration in the depth direction. Along with a smoothing. Thereby, there is an advantage that the image quality of the ultrasonic image can be improved.

FIG. 3 shows another example of the structure of the smoothing section 18. As shown in FIG. In this configuration example, the rectangular coordinate converter 3
Multipliers 38 and 40 as weighting circuits are provided between 0 and the smoothing processors 32 and 34. The multipliers 38 and 40 are circuits for weighting each signal component based on the amplitude A104 calculated separately. That is,
This is a circuit for performing greater weighting when the amplitude A of the received signal is large.

Incidentally, it is desirable to provide a circuit for variably setting a smoothing window width which affects the degree of smoothing. The window width is set, for example, manually or automatically. In the latter case, it is desirable to automatically set the window width according to, for example, the display range. For example, when the display range becomes large, the window width in smoothing is set to be large. In addition, the window width may be set according to the diagnostic site such as the abdomen or the neck. In this case, the window width may be automatically set in accordance with such a diagnostic part when a mode setting corresponding to the diagnostic part is performed on an operation panel (not shown) of the ultrasonic diagnostic apparatus. Good.

[0030]

As described above, according to the present invention,
Smoothing along the depth direction can be realized with a simple configuration while preventing artifacts related to smoothing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 2 is a diagram illustrating a configuration example of a smoothing unit illustrated in FIG. 1;

FIG. 3 is a diagram illustrating another configuration of the smoothing unit illustrated in FIG. 1;

FIG. 4 is a diagram illustrating a configuration example of a conventional smoothing unit.

[Explanation of symbols]

10 probe, 12 transmitting / receiving circuit, 14 quadrature detector,
16 autocorrelator, 18 smoothing unit, 30 orthogonal coordinate converter, 32, 34 smoothing processor, 36 polar coordinate converter.

Claims (5)

[Claims] A transmitting / receiving means for transmitting / receiving an ultrasonic wave; a complex signal converting means for converting a received signal obtained by transmitting / receiving the ultrasonic wave into a complex signal; And an autocorrelation calculating means for outputting an average speed signal; an orthogonal coordinate conversion means for executing orthogonal coordinate conversion on the average speed signal; and for each component after the orthogonal coordinate conversion, along a depth direction. An ultrasonic Doppler diagnostic apparatus, comprising: a smoothing processing unit that performs a smoothing process by performing a smoothing process; and a polar coordinate conversion unit that performs a polar coordinate conversion process on each component after the smoothing process. 2. The ultrasonic Doppler diagnosis according to claim 1, further comprising weighting means for weighting each of the components after the orthogonal coordinate transformation according to the magnitude of the amplitude of the received signal. apparatus. 3. The ultrasonic Doppler diagnostic apparatus according to claim 1, further comprising a window width setting unit that variably sets a window width of the smoothing process. 4. The ultrasonic Doppler diagnostic apparatus according to claim 3, wherein said window width setting means sets a window width according to a display range. 5. The ultrasonic Doppler diagnostic apparatus according to claim 3, wherein said window width setting means sets a window width according to a diagnosis site.