JPS6382634A - Ultrasonic blood flow imaging apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention detects blood flow information within a subject using the Doppler effect of ultrasound, and displays this blood flow information in color. The present invention relates to an ultrasonic blood flow imaging device that displays two-dimensional images.

(Prior technology) By using Doppler ultrasound and tomographic images together, blood flow information and tomographic images (B-mode images) are obtained with one probe, and the blood flow information is displayed in color in real time by superimposing it on the tomographic images. An ultrasonic blood flow imaging device based on the above is known. The operating principle for measuring blood flow velocity using such an ultrasonic blood flow imaging device is as follows.

That is, when an ultrasonic pulse is transmitted to a blood flow flowing in a living body, which is a subject, the center frequency fc of this ultrasonic beam becomes a sound wave due to the flowing blood cells. At this time, the frequency ic,+ is expressed as the following equation (7), and the blood flow velocity ■
It is shown in a form that reflects the

2vcos θ f・　Y□−＋.

to Here, V: blood flow velocity; θ: angle that the ultrasound beam makes with the blood vessel, C: Speed of sound.

Therefore, by detecting the Doppler shift f, it is possible to obtain the blood flow velocity ■.

In order to display the blood flow velocity V obtained in this way as a two-dimensional image, the following method is used. First of all, the 9th
As shown in the figure, from the ultrasound probe 1 to the subject, A and B
, C, . . . to perform sector scanning by sequentially transmitting ultrasonic pulses in the directions, the ultrasonic blood flow imaging apparatus configured as shown in FIG. 10 performs scan control of the ultrasonic pulses.

When an ultrasound pulse is first transmitted in the A direction, the echo signal that is Doppler-shifted and reflected by the blood flow inside the subject is received by the same probe 1, converted into an electrical signal, and then sent to the receiving circuit. Sent to 2.

Next, a Doppler shift signal is detected by the phase detection circuit 3, and this Doppler shift signal is captured at each of, for example, 256 sample points (SP) provided in the direction of the ultrasound pulse. The Doppler shift signal captured at each sample point is frequency-analyzed by a frequency analyzer 4, and the analysis result is A/D converted and sent to an OSC (digital scan converter). blood flow images are displayed in real time as two-dimensional images.

Similar operations are repeated for each of the directions B, C, . . . , and blood flow images corresponding to each scanning direction are displayed.

By the way, in such a conventional ultrasonic blood flow imaging device, the spatial resolution (depending on the number of scanning lines n), concentration resolution (depending on the number of sampling points m), display viewing angle, and real-time performance (the number of frames FN) of the obtained image are ) etc. have the following relationship, n X m X 1 / f r
X F H= 1)r: There is a relationship in which if an attempt is made to improve any one of the ultrasonic repetition frequencies, the others will deteriorate.

In the current apparatus, the viewing angle θ is selected to be 45° to 60°, and the number of claims FN is selected to be approximately 4 to 30, but this has the disadvantage that resolution deteriorates. If you try to improve the resolution, you will need to scan multiple times in one beam direction, which will take a long time.

(Problems to be Solved by the Invention) As described above, the conventional ultrasonic blood flow imaging apparatus has a problem in that it is difficult to display a blood flow image with excellent resolution.

The present invention has been made in response to the above problems, and an object of the present invention is to provide an ultrasonic blood flow imaging device that can display blood flow images with excellent resolution in a short time.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention includes an ECG circuit that detects a heartbeat and outputs a trigger signal synchronized with the heartbeat, and an ECG circuit that detects a heartbeat and outputs a trigger signal synchronized with the heartbeat. a control circuit that outputs a color Doppler scan signal at the set viewing angle based on the control of the EGC circuit and the wind scan circuit; and a control circuit that scans the viewing angle multiple times. and means for adding and averaging the blood flow information obtained.

(Function) At any viewing angle set by the wind scan circuit, blood flow information of a specific time phase is obtained by synchronizing the heartbeat, and by averaging, this blood flow information is displayed in color as a secondary image in real time. Can be done. Therefore, a blood flow image with excellent resolution can be displayed in a short time.

(Embodiment) Fig. 1 is a block diagram showing an ultrasonic blood flow imaging apparatus according to an embodiment of the present invention, in which 1) is an ultrasonic probe that transmits and receives ultrasonic pulses to and from a subject, and 12 is a sector electronic scanning device. In the analog section, preamplifier 13, pulser 14, oscillator 15, delay line 16, adder 17, detector 18
It consists of 19 beams, S, C, (digital
(scan converter), 20 is a color processing circuit, 21
2 is a D/A converter, 22 is a VTR, and 23 is a color monitor.

One of the signals output from the adder 17 is sent to the detector 18
, line 37, and is sent to S, C, and 19, and is provided for displaying a tomographic image (B-mode image). The other one is sent to line 39 and below, and is used to display a blood flow image. The signal (Doppler signal) applied from line 39 is split into two and applied to mixers 24a and 24b, respectively. Each mixer 24a.

24b also receives the reference signal f from the oscillator 15 by means of a 90° phase shifter 25. are added to each other with a phase difference of 90° to perform multiplication. As a result, the low-pass filter 26a
, 26b are input with the Doppler shift signal fd and the (2Jo+Ja) signal, and the low-pass filters 26a, 26 . The high frequency component is removed by b, and only the Doppler shift signal f4 is obtained.

This becomes a phase detection output signal for a blood flow image.

Figures 2 (a) to (C) show each signal waveform, (
a+ is a transmission pulse transmitted from the ultrasound probe 1) to the subject, (bl is a received pulse (received echo) reflected from the subject, and (C) is a phase detection output.

The above phase detection output signal contains not only blood flow information but also unnecessary reflected signals (referred to as clutter) from slow-moving objects such as the heart wall, so this clutter must be removed. Therefore, the phase detection output is MTI (Moving
(Target Indicator) is added to the calculation unit 27.

This MTI calculation section 27 is an A/D converter 28a.

28b, MTI filters 29a and 29b, an autocorrelator 30, an average velocity calculation section 31, a variance calculation section 32, and a power calculation section 33. This MTI is called a moving target indicating device, and is a technology that is used in radar and detects only moving targets using the Doppler effect. For example, the moving target is an airplane, and the fixed target (clutter) is the ground, weather (raindrops or clouds), or angels (a group of birds, etc.).

In contrast, in the present invention, the moving target is a blood cell, and the clutter is a blood vessel wall or the like. Since the speed of the moving target, which is a blood cell, is relatively slow, the MTI filters 29a, 2
The characteristics of 9b are very important. Figure 3 shows this MTI
An example of the configuration of a filter is shown. 1/Z represents the root delay, Σ represents the adder, and K represents the coefficient. FIG. 4 shows the characteristics of the MTI filter, with the vertical axis representing the response (dB) and the horizontal axis representing the frequency (kHz).

By changing the coefficients 2 to , various characteristics as shown in the figure can be obtained. Also, depending on the speed of the moving target, the cutoff frequency of the filter may be set to, for example, 200, 400, etc.
It can be changed to 600 (llz).

The autocorrelator 30 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.

The average velocity calculation unit 31 calculates the average Doppler shift frequency factor 7 based on the following equation.

The variance calculation unit 32 calculates the variance σ2 based on the following equation.

The power calculating section 33 calculates the power P based on the following equation.

This power P is proportional to the intensity of scattered echoes from blood cells, but echoes from moving objects that are below the cutoff frequency of the MTI filter are excluded.

The value calculated for each point is input to S, C, 19, and after interpolating the data, it is converted into color information by a color processing circuit 20. (2) In the case of -σ2 display, the direction of blood flow is shown in red light for flow approaching the probe and blue light for flow away from the probe. In addition, the magnitude of the average speed is displayed as brightness, and the speed dispersion is displayed as hue (mixed with green).

The ECG circuit 34 generates an ECG (electrocardiographic waveform) signal as shown in FIG. 5(al), and also generates an ECG (electrocardiographic waveform) signal as shown in FIG. Generate a trigger signal.

The wind scan circuit 36 has a variable resistor V as shown in FIG.
R, a DC bias-to-digital converter (ON), and a counter C0IN, and by adjusting the position of VR, the start position P1 for scanning ultrasonic pulses as shown in FIG. 7 is set. A viewing angle θz (P+ to P, l) within a range narrower than the viewing angle θ1 of the tomographic image is set.The viewing angle θ2 is determined by a wind scan circuit described later.

The control circuit 35 outputs a scan signal for color Doppler at the viewing angle θ2 to the sector electronic scanning device analog unit 12 under the control of the ECG circuit 34 and the wind scan circuit 36.

The operation of this embodiment will be explained below.

When performing a sector scan as shown in Fig. 7, first, A, B, C,
... is sequentially scanned in the direction of viewing angle θ1 to display the Ur layer image D1.

Next, a specific section (p.

to Pn) are set by operating the wind scan circuit 36, and scanning is performed at a viewing angle θ2 from P to the starting position until P, , and is repeated multiple times.

Here, the number of scans in the same direction is m, and the window (viewing angle θ2)
Let n be the scanning line and f be the ultrasound repetition frequency, then the time T to scan all of Pl to Pfi is T=nXmX - f'.Here, as an example, f1=4k1) 8,
If n-16, T=23ms.

If the number of scans within the same window is l, then Figure 5(C)
, one wind scan (p
, to pn ) 1-I is completed, and the wind scan (Pl to P, , ) x -2 is performed again at the next T2.

In this way, for example, wind scan is performed three times within the same field of view (P, to P,), and the average flow velocity at each point (x, y) obtained from this is
l vx+y+1' -z + vx+y+j 1)3
shall be.

Letting the average flow velocity of three times at each point be ■M+y, it becomes as follows. This vX+V value is performed by an averaging function in S and C19.

By determining the flow velocity by averaging in this way, in the case of Doppler blood flow detection, in addition to improving the S/N, there is also the effect of correcting the temporal deviation of blood flow due to heartbeat synchronization. Note that instead of this averaging, peak holding or the like may be used.

In FIG. 5(C), the fourth and subsequent time phases T4 and Ts
Now, by adjusting the VR shown in FIG. 6, the window (viewing angle) is moved as shown in FIG. 8, and scanning is now performed in the range of Q1 to Q7.

In this case as well, P to P. The average flow velocity can be determined in the same manner as in case ①X+V.

Note that the blood flow image obtained at TI in FIG. 5 and T1 in FIG. 2 is frozen. The blood flow velocity obtained at T2 is sequentially added (averaged) to the image created at T and displayed in real time. In FIGS. 7 and 8, D2 is a blood flow image.

If the value of the wind scan initial setting is fixed, the number of times of averaging will be equal to the heart rate during this period. If you want to cancel the addition, adjust the VR and change the initial setting value to Z (9th
), 0 is input as the blood flow information and no addition is performed.

The wind scan initial value marker may be the same as the M mode marker.

〔Effect of the invention〕

As described above, according to the present invention, blood flow information of a specific time phase is obtained by heartbeat synchronization and displayed as a two-dimensional image, so it is possible to display a blood flow image with excellent resolution in a short time. can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an ultrasonic blood flow imaging apparatus according to an embodiment of the present invention, FIG. 4 is a characteristic diagram of the MTr filter, FIG. 5(a) to tel are waveform diagrams for explaining the present invention, FIG. 8 and 8 are scan pattern diagrams showing the principle of the present invention, and FIGS. 9 and 10 are scan pattern diagrams and block diagrams showing conventional examples. 1) Probe, 12 Sector electron Scanning device analog section, 24a, 24b...Mixer, 26a. 26b...Low pass filter, 27...MTI performance section, 29a, 29b・MTI filter, 3
4-ECG circuit, N circuit. Figure 3 Figure 4 Figure 9 Figure 10

Claims (2)

[Claims] (1) Ultrasonic blood flow imaging equipment that displays a tomographic image based on the echo signals obtained by transmitting and receiving ultrasound pulses to and from a subject and displays a blood flow image superimposed on this tomographic image. An ECG circuit that detects and outputs a trigger signal in synchronization with the ECG circuit, and a wind scan circuit that can set any viewing angle within a range narrower than the viewing angle of the tomographic image.
A control circuit that outputs a color Doppler scan signal at the set viewing angle based on control of an ECG circuit and a wind scan circuit, and means for adding and averaging blood flow information obtained by scanning within the viewing angle a plurality of times. and,
An ultrasonic blood flow imaging device comprising: (2) The ultrasonic blood flow imaging apparatus according to claim 1, wherein the viewing angle setting operation in the wind scan circuit is performed manually.