JPH03272751A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To reduce color noise for obtaining clear color 2-D blood flow images by providing a control means by which the amplification in an amplifying means is controlled in accordance with the magnitude of a fault image to the amplifying means. CONSTITUTION:A ultrasonic diagnosis device comprises a system controller 7 for controlling respective parts of the device, and when the fault image of a first rate from a wave detector 26 is input into a delay-time adjusting part 5, the fault image echo is delayed by the control signal being input from a system controller 7, and a delay output is outputted into a gain controller 6. And, a color gain is controlled in inverse proportion to the magnitude of the fault image echo, and it is outputted into a MTI calculating part 4 so that MTI filters 43, 44 detect the movement of blood flow by the phase change, and after clatter has been removed, the blood-flow information from an average speed calculating part 46, a dispersion calculating part 47, and a power calculating part 48 together with a B-mode image information is scanned and converted in a DSC 8 to be outputted to a color monitor 11 via a color processing circuit 9 and a D/A converter 10 for obtaining color displays. As a result, unnecessary color noise can be reduced, and clear color 2-D blood images can be obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention particularly relates to ultrasonic diagnosis in which blood flow information within a subject is determined from Doppler information of ultrasound echoes and is displayed in two dimensions. Regarding equipment.

(Prior art) Ultrasonic diagnostic methods use anatomical information, typically represented by B-mode images, movement information of in-vivo organs, typically represented by M-mode images, and the Doppler effect, typically represented by blood flow imaging. Functional information associated with the movement of moving objects within a living body is used for diagnosis. Further, typical methods for scanning inside a living body with ultrasound 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) equipped with multiple ultrasonic transducers, a plurality of ultrasonic transducers is regarded as one unit, and this one unit of ultrasonic vibration The ultrasonic beam is transmitted by exciting the beam. For example, the position of the transmitting point of the ultrasonic beam is electronically shifted by sequentially shifting the pitch by one oscillator and excitation so that the position of each unit of element changes one after another. Then, so that the ultrasound beam is focused as a beam, the excited ultrasound transducers are shifted in excitation timing between those located in the center of the beam and those located on the sides, and the ultrasonic transducers generated thereby The reflected ultrasound waves are focused (electronically focused) using the phase difference between the sound waves generated by the vibrator. Then, the reflected ultrasound is received by the same vibrator that was excited and converted into an electrical signal, and the echo information from each transmitted and received wave is formed, for example, as a tomographic image.
Display the image on a V monitor, etc.

In addition, in the case of sector scanning, the excitation timing of each transducer is set so that the transmission direction of the ultrasonic beam sequentially changes in a fan shape for each pulse of the ultrasonic beam for one unit of excited ultrasonic transducers. It is changed depending on the desired direction, and the subsequent processing is basically the same as the linear electronic scanning described above.

On the other hand, in the imaging method, in addition to the B mode in which signals associated with ultrasonic transmission and reception are combined to form a tomographic image, an M mode image based on 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 diagnosis of 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 associated with the movement of a moving object within a living body and visualizing it, and this will be explained below. That is, the 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 object. Specifically, by transmitting ultrasonic rate pulses to a living body and obtaining the frequency deviation due to the Doppler effect from the phase change of the reflected wave echo, we can obtain motion information of a moving object at the depth position where the echo was obtained. I can do it.

According to this ultrasonic Doppler method, it is possible to know the direction of the flow of blood at a position in the living body and the state of the flow, whether it is turbulent or regular.

Next, a device to which this ultrasonic Doppler method is applied will be explained. First, in order to obtain blood flow information from ultrasound reception signals,
The ultrasonic probe is driven by a transmitting circuit to repeatedly transmit ultrasonic waves in a certain direction a predetermined number of times, and the received signal is detected by a quadrature phase detection circuit to separate Doppler shift signals caused by blood cells and clutter components. We get a signal consisting of This signal is converted into a digital signal, clutter components are removed by a filter, and the Doppler shift signal due to blood flow is frequency analyzed by a high-speed frequency analysis circuit to obtain a color Doppler image in real time. variance of deviation,
Obtain the average intensity of the Doppler shift, etc. In addition, a color flow mapping image of blood flow velocity is obtained using an autocorrelator built into the frequency analysis circuit, and two-dimensional blood flow information is displayed on a TV monitor.

(Problems to be Solved by the Invention) However, the conventional ultrasonic diagnostic apparatus for observing two-dimensional blood flow information has the following problems. An FFT image obtained by applying a range gate to one point on one scanning line on an ultrasound image and frequency-analyzing only the blood flow information at this point to obtain blood flow velocity is as shown in FIG. 6.

This FFT image contains noise in addition to blood flow signals. Such an FFT image contains noise as shown in the figure, and even if the noise and the blood flow signal are displayed overlapping, the blood flow signal can be distinguished from the noise based on the continuity of the blood flow signal.

However, when displaying blood flow information in blood vessels in color overlaid on a tomographic image as shown in Fig. 7, conventionally, color flow mapping images were obtained along the ultrasound transmission and reception direction as shown in Fig. 8. color gain G. was set as a constant value. In other words, color noise is likely to occur because the color gain is set to a constant amplification factor even in areas where tomographic image information exists and color information does not exist. When this color noise is near a blood vessel or overlaps a blood vessel, it is difficult to distinguish between the color noise and a thin blood vessel based on the diagnostic form as shown in FIG.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ultrasonic diagnostic apparatus that reduces color noise and obtains clear color two-dimensional blood flow images.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention takes the following measures. The present invention provides a means for obtaining a tomographic echo and detecting a Doppler shift signal due to blood flow based on a transmission signal obtained by transmitting and receiving ultrasound to and from a subject, and an amplification system for amplifying the detected signal. means for frequency-analyzing the obtained signal to obtain blood flow information such as mean velocity 1 variance of blood flow and power; and means for displaying this blood flow information as a two-dimensional blood flow image together with the tomographic image. In the ultrasonic diagnostic apparatus, the amplifying means inputs the Doppler shift signal and the tomographic image echo and amplifies the Doppler shift signal, and the amplification unit inputs the Doppler shift signal and the tomographic image echo, and performs the amplification according to the size of the tomographic image echo. Features include a control means for controlling the amplification factor in the means (Function) By taking such a means, the following effects are exhibited. The amplification factor for obtaining a two-dimensional blood flow image is set according to the size of the tomographic image echo, so during the period when the Doppler shift signal exists, the amplification factor (color gain) is increased and the Doppler shift signal is The amplification factor (color gain) can be lowered during a period in which no signal is present, that is, in a portion where the tomographic echo is large. This makes it possible to reduce unnecessary color noise and obtain a clear color two-dimensional blood flow image.

(Example) Hereinafter, specific examples of the present invention will be described.

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 in which color gain is varied according to the position of blood vessels on an ultrasound image, and FIG. - A diagram for explaining the action of the time adjustment unit 5, FIG. 4 is a diagram showing an ultrasound raster, and FIG. 5 is a diagram showing a plurality of ultrasound rasters on an ultrasound image.

The ultrasonic diagnostic device includes an ultrasonic probe 1. Sector electronic scanning section 2. Doppler detection section 3. MTI calculation unit 4° delay time adjustment unit 5. The gain controller 6 has a system controller 7 as a control means for controlling each part of the device. The device also includes a DSC (digital scan converter) 8° color processing circuit 9. It has a D/AIO, a color monitor 11, and a VTR 12.

The ultrasonic probe 1 includes a plurality of piezoelectric transducers, and these transducers transmit and receive ultrasonic pulses to and from a subject.

The sector electronic scanning section 2 includes an oscillator 21. Dayley line 22. Pulsar 23. Preamplifier 24 Adder 25. It is configured to include a detector 26.

The oscillator 21 is used to obtain one ultrasound raster for a color Doppler image in a certain direction as shown in FIG.
A plurality of rate pulses 1 to N as shown in FIG. 5 are output to the delay line 22.

As shown in FIG. 4, a plurality of pixel points 1 to M are set on each ultrasonic rask.

A transmission delay line (not shown) in the delay line 22 gives a predetermined delay time to each transducer in order to converge the ultrasonic beam in a predetermined direction with respect to the rate pulse input from the oscillator 21, This delayed rate pulse is output to the pulser 23. Pulsar 23 is
Each vibrator of the ultrasound probe 1 is repeatedly driven a predetermined number of times based on the plurality of delayed rate pulses.

That is, the ultrasound probe 1 is driven to transmit by the pulser 23, and the ultrasound pulses transmitted from the ultrasound probe 1 to a living body (not shown) are accompanied by a Doppler shift due to blood flow flowing inside the living body. This becomes a received signal and is received by the same transducer of the ultrasound probe 1.

The preamplifier 24 amplifies the received signal and outputs it to the delay line 22. This day line 2
A reception delay line (not shown) in 2 gives a delay time to the received signal from each vibrator to restore the delay time given at the time of transmission.

Then, the adder 25 adds the signals of each vibrator. Furthermore, the detector 26 performs envelope detection on the signal for each root pixel among the signals output from the adder 25,
It is output to the DSC 8 as a tomographic echo (echo for obtaining a black and white B-mode image).

Further, the root tomographic image echo from the detector 26 is
It is input to the delay time adjustment section 5.

The delay time adjustment section 5 is controlled by a system controller 7.
The control signal from the detector 26 is controlled by the control signal input from the detector 26.
The second tomographic image echo is delayed by a time t1 as shown in FIG. 3, and this delayed tomographic image echo, that is, a delay output, is output to a gain controller 6, which will be described later. The reason why the tomographic echo is delayed by the time (t+to) is to synchronize it with the Doppler detection output (Doppler shift signal) output from the Doppler detection unit 3 to the gain controller 6, which will be described later.

On the other hand, the mixers 31 and 32 receive the received signals from the adder 25, that is, the rate pulses 1 to 1 as shown in FIG.
Input one received signal N times up to N times. 90° again
The phase shifter 33 receives the reference signal f from the oscillator 21. 90“
are input to the mixer 32 with different phases, and the mixer 3
Each is multiplied by 1.32. Then, the Doppler shift signal fd and the Doppler shift signal (2fo+fd) are input to the low-pass filter 34.35, and the high frequency components are removed by the low-pass filter 34.35 to produce the Doppler shift signal fd, that is, the blood flow image. Doppler detection output can be obtained. In addition to blood flow information, the Doppler detection output also includes unnecessary reflected signals (clutter components) from slow-moving objects such as the wall of the heart.

Note that the Doppler detection output is transmitted through a low-pass filter 34.3.
The tomographic image echo is delayed by a time (t+to) by a narrow band filter such as 5 and input to the gain controller 6. Furthermore, since the tomographic echo is a delayed output delayed by the time (t+'to) by the delay time adjustment section 5, the gain controller 6 includes a low-pass filter 34 as shown in FIG.
．． The Doppler detection output from 35 and the delay output are input synchronously. The reason why the Doppler detection output and the tomographic image echo are synchronized in this way is to prevent the tomographic image portions other than the blood vessels from being colored.

The gain controller 6 inputs the Doppler detection output and the tomographic echo, and performs the following processing. That is, the tomographic echoes are at times 1, -1, . It is almost zero during this period, and echo output is obtained during periods other than this period. Further, during the period, the Doppler detection output is obtained.

Therefore, the gain controller 6 generates a gain that is an inversion of the tomographic echo. That is, as shown in FIG. 2, along the ultrasound transmission direction, a relatively large gain (Go + G) is set in the blood vessel region (corresponding to the above-mentioned times t to t3), and a relatively large gain (Go + G) is set in the other regions. low gain G
. It is closed.

The gain controller 6 amplifies the Doppler detection output with a gain (Go +G,) from time t1 to t, and from time t1 to t.
Gain G at times other than . Amplify with.

In this way, the gain controller 6 controls the color gain in inverse proportion to the magnitude of the tomographic image echo, and outputs Doppler detection output in which only the blood vessel gain is particularly emphasized to the MTI calculation unit 4.

The MTI calculation unit 4 includes A/Ds 41, 42 . MTI filter 4B, 44. Autocorrelator 45. Average speed calculation unit 461
Distributed calculation unit 47. It is composed of a power calculation section 48. A/D converters 41, 42 convert the outputs of low-pass filters 34, 35 into digital signals, and the converted outputs are output to MTI filters 43, 44.

MTI is a technology used in radar.Movin
G Target Indicator is a method of detecting only moving targets using the Doppler effect. Therefore, the MTI filters 43 and 44 detect the movement of blood flow based on the phase change between the same pixels in the N rate pulses, and remove clutter.

Next, an autocorrelator 45 is used to perform frequency analysis on the signal from which clutter has been removed. This self-phase quantizer 45 is a type of frequency analysis method, and is used because it is necessary to perform two-dimensional multi-point frequency analysis in real time, and has the advantage that it requires fewer calculations than the FFT method.

The average velocity calculation unit 46 calculates the average Doppler shift frequency fd using the following equation.

fd-, I"f-5(f)df/J'S(f')df where S (n is the power spectrum.

The variance calculation unit 47 calculates the variance σ2 using the following equation.

σ2. =ff2 ・5(f) d f/, l'5(f)
d f(fd)2 The power calculation unit 48 calculates the total power TP based on the following equation.
seek.

TP-fS(f)df This total power TP is proportional to the intensity of echoes scattered from the blood flow, but echoes from moving objects corresponding to frequencies below the cutoff frequency of the MTI filters 43 and 44 are excluded.

Further, blood flow information from the average velocity calculation unit 461, variance calculation unit 47, and power calculation unit 48 is input to the DSC 8,
The color processing circuit 9 converts it into color information. That is, in the case of V-σ2 display by the color processing circuit 9,
The flow approaching the ultrasonic probe 1 is converted into a red color, and the flow away from the probe 1 is converted into a front thread. Further, the magnitude of the average velocity is expressed by a difference in brightness, and the velocity dispersion is expressed by hue.

Thus, the blood flow information is scan-converted in the DSC 8 together with the B-mode image information, and the color processing circuit 9 and the D/A 1
0 to the color monitor 11, where the colors are expressed. It is also recorded on the VTR 12 as necessary.

As described above, according to this embodiment, the color gain for obtaining a color flow mapping image is controlled by the gain controller 6 in inverse proportion to the magnitude of the tomographic image echo, so that the period during which the Doppler shift signal exists is controlled by the gain controller 6. Medium (t+
At t3), the color gain can be increased, and the color gain can be lowered during a period in which no Doppler shift signal exists (a period other than t+-ts), that is, in a portion where the tomographic echo is large.

As a result, only blood vessels are emphasized, unnecessary color noise can be reduced in other parts, and a clear color two-dimensional blood flow image can be obtained.

Note that the present invention is not limited to the embodiments described above. In the above-described embodiment, a BDF image that displays a tomographic image (B-mode image) and a color Doppler image was explained.
For example, the present invention can be applied to a BDF image/FF image obtained by adding an FFT image to the BDF image. Further, in the embodiment described above, the color gain is set only to the blood vessels (Go 1 G,), and the portion other than the blood vessels is set to a fixed gain G. However, for example, the color gain may be varied for both blood vessels and parts other than blood vessels. In this case, the gain of the blood vessel may be controlled to be larger than the gain of the portion other than the blood vessel by controlling the variable ratio between the two. In short, it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, the amplification factor for obtaining a two-dimensional blood flow image is
Since it is set according to the size of the tomogram echo, the amplification factor (color gain) is
can be increased, and the amplification factor (color gain) can be lowered during a period in which no Doppler shift signal exists, that is, in a large portion of tomographic echoes. This makes it possible to reduce unnecessary color noise and provide an ultrasonic diagnostic apparatus that obtains clear color two-dimensional blood flow images.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the ultrasonic diagnostic apparatus according to the present invention, FIG. 2 is a diagram in which color gain is varied according to the position of blood vessels on an ultrasonic image, and FIG. 3 is a diagram showing the delay A diagram for explaining the action of the time adjustment section, FIG. 4 is a diagram showing a plurality of ultrasound rasters on an ultrasound image, FIG. 5 is a timing diagram of a plurality of rate pulses constituting one ultrasound raster, Figure 6 shows an FFT image containing noise, Figure 7
The figure shows a color Doppler image, and FIG. 8 is a diagram showing a conventional constant level color gain. 1... Ultrasonic probe, 2... Sector electronic scanning unit, 3
... Doppler detection unit, 4... MTI calculation unit, 5...
Delay time adjustment section, 6...gain controller, 7
...System controller, 8...DSC, 9...
- Color processing circuit, 10...D/A, 11...Color monitor, 2...VTR146...Average speed calculation section, 47...Dispersion calculation section, 48...Power calculation section.

Claims (1)

[Claims] means for obtaining a tomographic echo and detecting a Doppler shift signal due to blood flow based on a received signal obtained by transmitting and receiving ultrasound to and from a subject; and an amplification means for amplifying the detected signal; A means for frequency-analyzing the obtained signal to obtain blood flow information such as the average velocity, dispersion, and power of blood flow, and
In an ultrasonic diagnostic apparatus comprising means for displaying a dimensional blood flow image together with the tomographic image, the amplifying means inputs the Doppler shift signal and the tomographic image echo and amplifies the Doppler shift signal. An ultrasonic diagnostic apparatus comprising: a control means for controlling an amplification factor in the amplification means according to the magnitude of the tomographic echo.