JPH084590B2 - Ultrasonic Doppler diagnostic device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic Doppler diagnostic apparatus for measuring and displaying motion information (for example, velocity) of a moving body (for example, blood flow) in a living body.

[0002]

2. Description of the Related Art An ultrasonic wave is transmitted into a living body while an ultrasonic probe is in contact with the surface of the living body, and a reflected wave reflected by a moving body in the living body undergoing Doppler shift is received. There is known an ultrasonic Doppler diagnostic apparatus for measuring and displaying velocity information of the moving body.

Japanese Examined Patent Publication (Kokoku) No. 62-44494 discloses an ultrasonic Doppler diagnostic apparatus using the autocorrelation method. In such an apparatus, the received signal is quadrature-detected and then
The autocorrelation calculation is executed to find the average frequency of the Doppler shift, and the velocity is calculated from the average frequency.

Also, for example, Japanese Patent Publication No. 2-16139 discloses a similar ultrasonic Doppler diagnostic apparatus. In such an apparatus, dispersion (deviation) of velocity (Doppler shift frequency) is calculated from the result of autocorrelation. ing.

When performing a functional diagnosis of the heart or the like, there is a demand for displaying the Doppler signal spectrum at a certain site, rather than simply displaying the blood flow velocity at that site. Here, the Doppler signal spectrum is obtained by plotting the Doppler shift frequency on the horizontal axis and the intensity of the received signal on the vertical axis, and is also simply called a spectrum.

In the conventional ultrasonic Doppler diagnostic apparatus,
The said spectrum was calculated | required by frequency analysis calculation, such as FFT, and it was displayed by various display forms. As the display form, along with the display of the two-dimensional tomographic image and the two-dimensional Doppler image, the spectrum itself is supplementarily displayed, or the horizontal axis indicates time and the vertical axis indicates frequency. There is a device that displays the change over time in the spectrum while expressing the value as the brightness.

[0007]

However, the calculation for the spectrum analysis is complicated, and when the spectrum is displayed along with the display of the two-dimensional tomographic image and the two-dimensional Doppler image, the Doppler signal is not captured. Since it takes time and the processing becomes slow, there is a problem that the real time property of image display is deteriorated.

Accordingly, there has been a demand for an ultrasonic Doppler diagnostic apparatus capable of displaying a spectrum without deteriorating the real-time property of image display.

The present invention has been made in view of the above conventional problems, and an object thereof is to provide an ultrasonic Doppler diagnostic apparatus capable of easily estimating the spectrum of a received signal.

[0010]

In order to achieve the above object, the present invention is a super-display for detecting the Doppler shift frequency from a reception signal obtained by transmitting and receiving an ultrasonic pulse and displaying the motion information of the motion reflector. In the sound wave Doppler diagnostic device, an average power calculation unit that calculates an average power of the received signal per unit time based on the amplitude of the received signal, an average frequency calculation unit that calculates an average frequency of the Doppler shift from the received signal, Variance calculating means for computing the variance of the Doppler shift from the received signal, by specifying the normalized Gaussian distribution by the average frequency and the variance, by correcting the normalized Gaussian distribution based on the obtained average power Spectrum estimating means for calculating an estimated spectrum of the received signal.

[0011]

According to the above construction, the average frequency calculation means and the dispersion calculation means calculate the average frequency of the Doppler shift and the dispersion of the Doppler shift. On the other hand, the average power of the received signal is calculated by the average power calculation means. The spectrum estimating means specifies a normalized Gaussian distribution that is a predetermined function by the obtained average frequency and variance, and then corrects the normalized Gaussian distribution based on the average power to determine the spectrum of the received signal. Estimate and obtain the estimated spectrum.

From empirical facts, it is known that the spectrum of the received signal follows a Gaussian distribution. In the present invention, paying attention to this point, the Gaussian distribution normalized by the average frequency and the variance is first specified. Here, the average frequency and the variance are normally found in a general ultrasonic Doppler diagnostic apparatus, and it is possible to use the calculation result in the existing apparatus. Since the Gaussian distribution specified by the average frequency and the variance is normalized, an average power calculation means is provided to specify the height of the Gaussian distribution, and the average power calculated by this means is used. The estimated spectrum is finally obtained by correcting the Gaussian distribution.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

First, the overall configuration of the apparatus will be described with reference to FIG. 1, and then the spectrum estimation calculation will be described in detail.

In FIG. 1, an ultrasonic wave is transmitted to the inside of a living body by a probe 10, and a reflected wave reflected by a Doppler shift by a motion reflector such as a bloodstream is received by the probe 10. The reception signal output from the probe 10 is sent to a quadrature detector 14 for Doppler analysis and a detector 16 for forming a tomographic image via a transmitter / receiver 12.

The received signal detected by the detector 16 is converted into a digital signal by the A / D converter 18 and is sent to a two-dimensional DSC (digital scan converter) 20 as a black and white tomographic image signal.

On the other hand, the timing signal generator 22 shown in FIG. 1 outputs a transmission signal to the transceiver 12 and also outputs a reference signal for quadrature detection to the quadrature detector 14. .

In the quadrature detector 14, the transmitter / receiver 12
The received signal from the reference signal is mixed with the reference signal, and quadrature detection is executed. As a result, a so-called complex signal is obtained.

The received signal thus converted into a complex signal is converted into a digital signal in the A / D converter 24, and then the clutter removing filter 26 removes noise due to the low speed moving body.

In the autocorrelator 28, the autocorrelation between the received signals is calculated, and the autocorrelation result is sent to the average frequency / variance calculator 30. In the calculator 30, the average frequency f-and the variance σ of the Doppler shift frequency are calculated. ² is required. The autocorrelator 28 and the average frequency / dispersion calculator 30 may be, for example, Japanese Patent Publication No.
The one disclosed in JP-A-2-44494 or JP-B-2-16139 is used.

The calculated average frequency f and variance σ ² are
It is sent to the two-dimensional DSC 20. Then, in this two-dimensional DSC, a so-called B-mode tomographic image and a two-dimensional Doppler image are combined to form an image signal, which is the D / A converter 3.
At 2, the signal is converted into an analog signal and sent to the display 34. As a result, the display 34 displays an ultrasonic image in which the color Doppler image is superimposed on the tomographic image.

The above structure is almost the same as that of the conventional ultrasonic Doppler diagnostic apparatus.

In the ultrasonic Doppler diagnostic apparatus of this embodiment, the received signal output from the clutter removing filter 26 is sent to the average power calculator 36. As will be described later in detail, the average power calculator 36 calculates the average power of the received signal per unit time, and the calculated average power x ^{2 −} is the spectrum estimation calculator 38.
Have been sent to.

The spectrum estimation calculator 38 estimates the spectrum of the received signal from the three pieces of information of the above-mentioned average frequency, dispersion, and the above-mentioned average power, and its specific calculation will be detailed later. I will describe.

The estimated spectrum calculated by the spectrum estimation calculator 38 is the line scan DSC 40.
It is sent to the D / A converter 32 via the, and further sent to the display 34 as an analog signal. As a result, the ultrasonic image and the image showing the spectrum are displayed on the same screen.

The displayed spectrum is the spectrum of the received signal sampled at a certain position in the living body. Therefore, although not shown, a gate circuit or the like is provided in the average power calculator 36. ing.

Next, the operation of the average power calculator 36 will be described.

When the amplitude of the received signal (complex signal) input to the average power calculator 36 is defined as x (t), time t
The average power x ² ￣ from ₁ to t ₂ is calculated by the following first equation.

[Equation 1] Therefore, the average power x ^{2 −} shown by the above-mentioned first equation is output from the estimated power calculator 36 to the spectrum estimation calculator 38.

On the other hand, it is known from experience that the spectrum of the received signal follows a Gaussian distribution. In the ultrasonic diagnostic apparatus of this embodiment, the following calculation is performed assuming that the spectrum of the received signal has a Gaussian distribution. Is going. Here, the probability density function p (f) of the Gaussian distribution is expressed by the following second equation using the above-mentioned average frequency f and variance σ ² .

[0030]

[Equation 2] The distribution of the power of the received signal is represented by the above second equation.

FIG. 2 shows the form of the function p (f). As shown in the figure, the distribution function is specified by the variance and the average frequency. The maximum value of the distribution function is the following third formula, and the maximum value is shown in FIG.

[0032]

(Equation 3) However, the function p (f) obtained by the above
Is a normalized one, so we need to adjust the height of the function peaks. Therefore, the correction of the function is executed using the relationship of the following fourth equation.

[0033]

[Equation 4] Here, x ^{2 −} on the left side is the average power obtained by the first expression, and P (f) included on the left side is the spectrum of the received signal. However, f _n represents the Nyquist frequency determined by the ultrasonic transmission repetition frequency.

Therefore, the second equation is established so that the above fourth equation is satisfied.
By correcting p (f) obtained by the formula, the estimated spectrum P (f) to be finally obtained can be obtained.

Specifically, the estimated spectrum P (f) is calculated by the following fifth equation.

[0036]

(Equation 5) The calculation of the second equation and the calculation of the fourth equation described above are performed by the spectrum estimation calculator 38 shown in FIG. The estimated spectrum output from the spectrum calculator 38 is subjected to scan conversion and interpolation processing in the line scan DSC 40, and the D / A converter 3 is operated as described above.
2 to the display 34.

FIG. 3 shows a display example of the estimated spectrum, and the mountain-shaped spectrum as shown in FIG. 3 may be displayed as it is together with the ultrasonic image. Alternatively, the spectrum may be displayed by expressing the power in luminance as shown in FIG. The horizontal axis in FIG. 4 is the time axis, and the vertical axis is the frequency.

As described above, in the ultrasonic toppler diagnostic apparatus of this embodiment, the received signal can be easily received based on the average frequency f and the variance σ ² used in the conventional general ultrasonic Doppler diagnostic apparatus. The effect is that the spectrum of can be estimated. Therefore, it is possible to display an image while maintaining real-time property without disturbing the original Doppler calculation. Here, the displayed spectrum of the received signal is
Of course, it is assumed that the spectrum has a Gaussian distribution, but even in that case, the width, height, or center position of the spectrum is obtained by each calculation, and is therefore close to the actual spectrum. It has become a thing. Various display examples of the spectrum can be applied, and in any case, the ultrasonic Doppler diagnostic apparatus of this embodiment has an effect that the spectrum can be estimated by a simple calculation.

In the present application, the average power is shown as the upper bar (-).

[0040]

As described above, according to the present invention,
The spectrum of the received signal can be specified by a simple calculation, and even when the spectrum is displayed, deterioration of real time property in displaying the ultrasonic image can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an ultrasonic Doppler diagnostic apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a Gaussian distribution.

FIG. 3 is an explanatory diagram showing a display example of an estimated spectrum.

FIG. 4 is an explanatory diagram showing a spectrum luminance display example.

[Explanation of symbols]

 28 Auto-correlator 30 Average frequency / dispersion calculator 36 Average power calculator 38 Spectrum estimation calculator

Claims (1)

[Claims] 1. An ultrasonic Doppler diagnostic apparatus for detecting a Doppler shift frequency from a received signal obtained by transmitting and receiving an ultrasonic pulse and displaying motion information of a motion reflector, wherein the received signal is based on the amplitude of the received signal. An average power calculating means for calculating an average power per unit time, an average frequency calculating means for calculating an average frequency of the Doppler shift from the received signal, a dispersion calculating means for calculating a dispersion of the Doppler shift from the received signal, A normalized Gaussian distribution is specified by the average frequency and the variance, and the positive Gaussian distribution is calculated based on the obtained average power.
An ultrasonic Doppler diagnostic apparatus comprising: a spectrum estimating unit that calculates an estimated spectrum of the received signal by correcting a normalized Gaussian distribution .