JPH02134145A - Ultrasonic diagnosis device - Google Patents

Abstract

PURPOSE:To ensure satisfactory S/N of an image and to ensure a good image by correlative outputting by multiplication of an ultrasonic input signal input from a radio receiving circuit and an ultra sonic radio transmission signal input from an ultrasonic probe to decrease noise component contained in the ultrasonic input signal between a radio receiving circuit and a frequency analyzing circuit. CONSTITUTION:Correlation means 7 is disposed between an A/D converter 4 and a frequency analyzing circuit 5, and an ultrasonic radio transmission signal h(t) from an ultrasonic probe 1, and a phase detection signal r(t) obtained by phase detecting a received input signal by an orthogonal phase detection circuit 3 are input to the above means to calculate the correlation between these signals h(t).r(t). In the correlation means 7, as h(t) and r(t+r) are synchronized in respect of time and similar to each other in waveform, they have the substantially same spectrum distribution on the spectrum, are calculated in such a manner that the band displaying signal image blood current information is intensified and most of white noise n(t) outside the above band, that is, in a comparatively wide band is removed by the sum of products of r(t) and h(t+r).

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention provides a method for obtaining blood flow information as functional information associated with the movement of a moving object within a living body by using ultrasonic transmission and reception and the Doppler effect. The present invention relates to an ultrasonic diagnostic device that images images.

(Prior art) Ultrasonic diagnostic methods use anatomical information, typically represented by B-mode images, motion information of in-vivo organs, typically represented by N1-mode images, and Doppler, typically represented by blood flow imaging. Functional information associated with the movement of a moving object within a living body using this effect is used for diagnosis. Further, typical methods for scanning inside a living body using ultrasound waves include electronic scanning and mechanical scanning. Here, the electronic scanning method will be explained.

In the case of linear electronic scanning using an array-type ultrasonic probe (probe) consisting of multiple ultrasonic transducers arranged in parallel, multiple ultrasonic transducers are treated as one unit, and this one unit of ultrasound This is a method in which a vibrator is excited and an ultrasonic beam is transmitted. For example, this is scanning in which the position of the transmitting point of the ultrasonic beam is shifted at an electric reservation by sequentially shifting the pitch by one oscillator and exciting the position of one unit of element in turn. .

The ultrasonic transducers that are excited so that the ultrasonic waves are focused as a beam are shifted in excitation timing between those located in the center of the beam and those located on the sides. The reflected ultrasonic waves are focused (electronic focus) using the phase difference between each generated sound wave. The reflected ultrasonic waves are received by the same vibrator used for excitation and converted into electrical signals, and the echo information from each transmitted and received wave is formed, for example, as a tomographic image, and the image is displayed on a cathode ray tube or the like.

In addition, in the case of sector electronic scanning, the excitation timing of each transducer is set so that the transmission direction of the ultrasound beam changes sequentially into a fan shape for each pulse of the ultrasound beam for one unit of excited ultrasound transducers. is changed in accordance with a desired direction, and the subsequent processing is essentially the same as the linear electronic scanning method described above.

In addition to the above-mentioned linear and sector electronic scanning, there is also mechanical scanning in which a transducer (probe) is attached to a scanning mechanism and ultrasonic scanning is performed by moving the scanning mechanism.

On the other hand, in the imaging method, in addition to the B-mode image in which the signals underlying ultrasound transmission and reception are combined to form a tomographic image, the M-mode image by fixed scanning in the same direction is typical.

This M-mode image displays temporal changes in the ultrasound transmitting/receiving site, and is particularly suitable for diagnosing moving organs such as the heart.

Further, the ultrasonic Doppler method, of which blood flow imaging is a typical example, is a method of obtaining functional information based on the movement of a moving object within a living body and visualizing it, and this will be explained in detail below. This ultrasonic Doppler method utilizes the ultrasonic Doppler effect in which when an ultrasonic wave is reflected by a moving object, the frequency of the reflected wave shifts in proportion to the moving speed of the moving object. Specifically, when an ultrasonic rate pulse (or continuous pulse) is transmitted into a living body and the phase change of the reflected wave echo causes a frequency shift due to the Doppler effect, the movement at the depth position where the echo was obtained It is possible to obtain information on the movement of objects.

According to this ultrasound Doppler method, it is possible to know the state of blood flow at a certain position in the living body, such as the direction of blood flow, whether the flow is turbulent or regular, the flow pattern, and the velocity value. can.

Next, an apparatus to which the ultrasonic Doppler method is applied will be explained. FIG. 6 is a block diagram showing a conventional ultrasonic diagnostic apparatus. FIG. 7 is a diagram showing ultrasonic transmission and reception signals, (a) is a diagram showing the transmission signal h (t), and (b) is a diagram showing the reception signal rl.
(t), (C) is a diagram showing the received signal r2 (t), (d) is a diagram showing the signal r3 (t) obtained by phase detection of the received signal rl (t), (e) is the received signal r2
A diagram showing the signal r4 (t) obtained by phase detection of (t), (f) is the temporal movement r5 at a certain pixel depth.
(t), and (g) a diagram showing the temporal movement r6 (t) at other pixel depths. First, in order to obtain blood flow information from the ultrasonic reception signals rl (t) and r2 (t), the ultrasonic probe l and the transmitting/receiving circuit 2 are
The ultrasonic transmission signal h (t) is repeatedly transmitted a predetermined number of times in a certain direction, and the received ultrasonic reception signal rl is
(t), r2 (t) are detected by the quadrature phase detection circuit 3 to obtain a phase detection signal r3 (t), r4 Ct), that is, a signal consisting of a Doppler shift signal due to blood cells and a clutter component. We obtain signals r5 (t) r8 (t) indicating temporal movement in depth. This signal is converted into a digital signal by an A/D conversion circuit 4, clutter components are removed by a filter, and the Doppler shift component signal due to blood cells is subjected to frequency analysis by a high-speed frequency analysis circuit 5 in order to obtain a color Doppler image in real time, for example. Then, the average value of the Doppler shift, the variance value of the Doppler shift, the average intensity of the Doppler shift, etc. are obtained. Further, an autocorrelator or the like built in the frequency analysis circuit 5 obtains a blood flow velocity color flow mapping image and displays it on the TV monitor 6.

(Problem to be Solved by the Invention) However, in the conventional ultrasonic diagnostic apparatus, the reception 1゛7ζ signal rl which receives the signals scattered from the blood cells in the living body.
(t) and r2 (t) are considerably attenuated and become weak signals. Furthermore, this multiplier signal rl
(t) and r2 (t) are amplified by the amplifier in the quadrature phase detection circuit 3, but the internal noise of the amplifier is also amplified and output, resulting in an insufficient S/N ratio of the image. There was a problem.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ultrasonic diagnostic apparatus that can ensure a sufficient image S/N and a good image even if the received signal is weak and the phase detection signal contains noise. It's about doing.

[Configuration of the Invention (Means for Solving the Problems) The present invention has taken the following measures in order to solve the above problems and achieve the objectives. The present invention transmits an ultrasound transmission signal from an ultrasound probe to blood flow in a circulatory tissue in a living body,
In an ultrasound diagnostic apparatus, the scattered ultrasound scattered from the blood flow is received by a wave receiving circuit, a Doppler shift component is detected by a phase detection circuit, and the frequency is analyzed by a frequency analysis circuit to display blood flow information. , by multiplying the ultrasonic reception signal input from the wave reception circuit and the ultrasonic transmission signal input from the ultrasonic probe between the wave reception circuit and the frequency analysis circuit, the ultrasonic reception signal is A correlation means is provided for outputting correlation so as to reduce noise components included.

(Effects) By taking such measures, the following effects are achieved. When the ultrasonic reception signal and the ultrasonic transmission signal are multiplied by the correlation means, only the vicinity of the signal component band of the ultrasonic reception signal and the ultrasonic transmission signal is multiplied and output. That is, since the noise contained in the ultrasonic reception signal is white noise with a relatively wide band, noise in bands other than the signal component band is significantly reduced by multiplication.

Therefore, since the noise output by the correlation means is significantly reduced, the S/N ratio of the color flow mapping image can be improved, and a good two-dimensional image can be obtained.

(Embodiment) FIG. 1 is a schematic block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. Note that the parts explained in FIG. 6 are designated by the same reference numerals and detailed explanations will be omitted. In FIG. 1, the correlation means 7 is provided between the A/D converter 4 and the frequency analysis circuit 5, and the correlation means 7 is provided between the A/D converter 4 and the frequency analysis circuit 5, and is connected to The phase detection signal r whose phase is detected by the orthogonal t0 detection circuit 3
(t) and these signals h(t).

This is to calculate the correlation of r(t).

FIG. 2 is a diagram showing the operation of the correlation means 7, in which (a) shows the transmitted signal h (t), and (b) shows the transmitted signal h (t
), (C) is a diagram showing the phase detection signal r (t) delayed by τ with respect to the signal h (t), r to be correlated.
(t+τ) and noise N included in the phase detection signal r (t). This correlation means 7 uses the transmitted signal h(
t), the correlation function C(τ) C(r)=f r (t)Xh (t+r) dt is calculated based on the phase detection signal "(t).

FIG. 3 is a diagram showing the signal obtained by the correlation means 7, where (a) is the phase detection signal CI (
(b) is a diagram showing the phase detection signal C2 (τ) at a certain pixel depth, and (C) is a diagram showing the phase detection signal C3 (τ) at another pixel depth.

FIG. 4 is a block diagram showing details of the correlation means 7. The correlation means 7 includes a system response memory 11 (lla to llj) for storing the ultrasonic transmission signal h(1), and a phase detection signal shift register 12 (12a to 12j) for shifting the inputted phase detection signal r(t). ),
A multiplier 13 (13a...13j') that reads and multiplies the corresponding signals of the system response memory 11 and phase detection signal shift register 12, and the multiplication output of the previous multiplier 13 and the next multiplier 13. It is comprised of an adder 14 (14a...14h) that adds the multiplication output of .

FIG. 5 is a block diagram showing details of the frequency analysis circuit 5. As shown in FIG. The frequency analysis circuit 5 includes a Fourier transformer 21 that Fourier transforms the signal input from the correlation means 7. It is comprised of an average frequency/variance calculation circuit 22 that calculates and outputs the average frequency f and variance s2 based on the output of the Fourier transformer 21.

Next, the operation of the embodiment configured as described above will be explained with reference to the drawings. 1 and 2, an ultrasonic probe 1 receives an ultrasonic transmission signal f generated by a transmitter/receiver circuit 2.
(t), an ultrasonic pulse f(t)XhT(1) is emitted to a subject (not shown) in a pulse form, that is, according to an impulse function hT(t) (here, * represents a convolution integral). In this case, ultrasonic pulses are emitted at 3 to 8 rates in the same direction, and the ultrasonic pulses f (t)XhT (t)X are scattered by the object and subjected to Doppler shift.
A i ejθi and white noise n (t) are
A pulse-like impulse function hR(t
) is received by. Further, these signals are subjected to quadrature phase detection by a quadrature phase detection circuit 3. The output signal of the quadrature phase detection circuit 3 is a component containing Doppler shift components at various pixel depths of the subject. This signal containing the Doppler shift component is converted into an A/D converter 4.
After being subjected to /D conversion, it is sent to correlation means 7.

Then, to this correlation means 7, [n (L) +fT (t
), jθ1 XhT (t) + Σ Ase
The signal XhR(t)-r(t) is input. Then, first, the response h (B fT (t)
Based on XhT(t)xhR(1) and the received phase detection signal r(t) shown in FIG. 2(b), the correlation means 7
From the transmitted pulse h(t+τ) and r(t) which are temporally advanced only with respect to the ultrasonic transmitted pulse h(t), the correlation output C(τ) C(r)'=f r (t) xh (t+r)
dt-(1) is calculated.

Specifically, in the correlation means 7, in order to realize equation (1) in a digital system, the ultrasonic transmission signal h(i
A discrete correlation calculation that calculates the correlation output c (nΔt) from the phase detection signal r ((n+i)×Δt) is performed by (2) (where N is the system response (represents length). That is, the phase detection signal r (t) is input into the shift register 12 one after another, and is shifted to the right within the shift register 12 each time a phase detection signal is input. Now, the phase detection signal r mouth + 4 - r i (n + 4) Xh
When T) is input, the calculation is output as shown (k--N/2 to N/2-1)
. Further, the average frequency/variance calculation circuit 22 calculates the average frequency f+n, and the correlation means 7 outputs the variance 82. Next, the phase detection signal rl+
5 is input, the correlation means 7 inputs cl(n+1)
Δt) is output.

When the correlation output is thus input into the frequency analysis circuit 5 shown in FIG.

As described above, according to this embodiment, in the correlation means 7, h
Since Ct> and r (with 10τ) are temporally synchronized and have similar waveforms, their spectral distributions on the spectrum are almost the same, and they are calculated so that the band that displays the signal image blood flow information is emphasized. , most of the white noise n(t) in a band other than this band, that is, a relatively wide band, is ``
It is removed by the sum of products of (t) and h(t+τ).

Therefore, the noise n (t) contained in the phase detection signal r (t) is significantly reduced, so the S/N ratio of the color flow mapping image can be improved, and as shown in Fig. 3, a good noise-free image can be obtained. An image is obtained.

Note that the present invention is not limited to the embodiments described above. In the above-mentioned embodiments, a color flow mapping image has been described, but it goes without saying that the present invention can also be applied to a pulsed Doppler apparatus.

Other examples of the correlation means 7 include a method of integrating the signal according to the burst length of the transmitted signal, and a method of implementing it using a digital filter (making the impulse response of the filter match the system function). Further, in the above-described embodiment, the correlation means 7 is provided at the rear stage of the phase detection circuit 3, but for example, the correlation means 7 is provided at the front stage of the phase detection circuit 3, and ultrasonic wave reception before detection by the phase detection circuit 3 is performed. signal(
Correlation may also be performed for high frequency signals).

It goes without saying that various other modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, an ultrasonic transmission signal is transmitted from an ultrasonic probe to a blood flow in a circulatory tissue in a living body, and scattered ultrasound waves scattered from the blood flow are received. In an ultrasonic diagnostic apparatus that receives waves by a circuit, detects Doppler shift components by a phase detection circuit, performs frequency analysis by a frequency analysis circuit, and displays blood flow information, there is a Correlation that outputs a correlation so as to reduce noise components included in the ultrasound reception signal by multiplying the ultrasound reception signal input from the reception circuit and the ultrasound transmission signal input from the ultrasound probe. Therefore, since the noise contained in the ultrasonic reception signal is white noise with a relatively wide band, noise in bands other than the signal component band is significantly reduced by multiplication. Therefore, since the noise output by the correlation means is significantly reduced, the S/N ratio of the color flow mapping image can be improved, and a good two-dimensional image can be obtained.
An ultrasonic diagnostic device that can obtain dimensional images can be provided.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of the ultrasonic diagnostic apparatus according to the present invention, FIG. 2 is a diagram showing the operation of the correlation means, FIG. 3 is a diagram showing signals obtained by the correlation means, and FIG. FIG. 4 is a diagram showing details of the correlation means, FIG. 5 is a diagram showing details of the frequency analysis circuit, FIG. 6 is a block diagram showing a conventional ultrasonic diagnostic device, and FIG. 7 is a diagram showing ultrasonic transmission/reception signals. It is. ■...Ultrasonic probe (probe), 2...Transmission/reception circuit, 3...Quadrature F0 detection circuit, 4...A/D conversion circuit, 5...Frequency analysis circuit, 6...TV monitor, 7
... Correlation means, 11 ... System response memory, 1
2... Shift register, 13... Multiplier, 14...
Adder, 21... Fourier transformer, 22... Average frequency/variance calculation circuit. Figure 6 Applicant's agent Patent attorney Takehiko Suzue Figure 7 (g) (f)

Claims (1)

[Claims] An ultrasonic transmission signal is transmitted from an ultrasound probe to the blood flow in the circulatory tissue of a living body, and the scattered ultrasound waves scattered from the blood flow are received by a wave receiving circuit and Doppler is detected by a phase detection circuit. In an ultrasonic diagnostic apparatus that detects a deviation component, performs frequency analysis using a frequency analysis circuit, and displays blood flow information, an ultrasonic reception signal is input from the reception circuit between the reception circuit and the frequency analysis circuit. and an ultrasonic transmission signal inputted from the ultrasonic probe to thereby reduce a noise component included in the ultrasonic reception signal. Diagnostic equipment.