JPH0775610B2 - Ultrasonic diagnostic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Table of Contents] Outline Industrial field of application Conventional technology (Figs. 6 and 7) Problems to be solved by the invention Means for solving problems (Fig. 1) Action Embodiment (a) Description of configuration of one embodiment (FIGS. 2 and 3) (b) Description of operation of one embodiment (FIG. 4) (c) Description of another embodiment (FIG. 5) (D) Description of another embodiment Effect of the invention [Outline] An ultrasonic diagnostic apparatus that obtains and displays blood flow information together with a B-mode image from an ultrasonic received wave. For the purpose of utilizing the received wave train, an ultrasonic wave transmission / reception unit that transmits / receives ultrasonic waves a plurality of times in each ultrasonic wave transmission / reception direction in B mode scanning, and B mode image information from the amplitude component of the ultrasonic reception wave is obtained. Frequency analysis of the obtained amplitude extraction unit and the data of the plurality of received waves in the same transmission / reception direction In an ultrasonic diagnostic apparatus having a frequency analysis unit for obtaining blood flow information and displaying blood flow information together with the B-mode image, m-th received wave data is obtained from other plural times received wave data in the transmission / reception direction. A data creation unit to be created is provided, and the frequency analysis unit performs frequency analysis using a plurality of received wave data in the same transmission / reception direction including the created received wave data.

[Industrial application field]

The present invention relates to an ultrasonic diagnostic apparatus that obtains and displays blood flow information from a received ultrasonic wave along with a B-mode image.

The ultrasonic diagnostic apparatus is non-invasive, non-invasive and simple, and is therefore indispensable for morphological diagnosis in medicine.

In a cardiovascular diagnostic device, in addition to morphological diagnosis, if blood flow information can be displayed in real time in two dimensions, regurgitation of valvular disease,
It is convenient because it can accurately diagnose abnormal blood flow such as stenotic jet flow and short-circuited blood flow in a short time.

Therefore, a color flow imaging ultrasonic diagnostic apparatus that two-dimensionally displays blood flow information together with a B-mode image has been developed.

In such an ultrasonic diagnostic apparatus, a technique for effectively utilizing received waves to obtain blood flow information is required.

[Conventional technology]

 6 and 7 are explanatory views of the prior art.

As shown in FIG. 6, the ultrasonic transmitting / receiving unit 1 scans the ultrasonic wave (hereinafter referred to as a probe) 1a with a sector electronic scanning unit 1b in a fan-shaped manner on the living body Bd under the control of the scanner control unit 1c. Then, the received wave RS is obtained.

The received wave RS is amplitude-detected by the wave detector 2 which is an amplitude extractor, and a B-mode signal is obtained.

On the other hand, the received wave RS is frequency-analyzed by the frequency analyzer 3 to obtain a blood flow signal.

In this frequency analysis unit 3, the Doppler detection unit 3a performs Doppler detection of the received wave RS by quadrature detection, and the Doppler shift frequency component of the received wave is given to the Doppler calculation unit 3b. Doppler calculation unit 3b
Then, MTI (Moving Target Ind), which is a high-pass filter,
icator) filter 30 removes components such as blood vessel walls and extracts frequency components of blood flow such as blood cells, and
Obtain a blood flow signal such as average Doppler shift frequency and power with a frequency analyzer such as 31.

In the display unit 4, the B-mode signal and the blood flow signal are input to the digital scan converter 40, and in the display CRT 41, for example, the B-mode image is black and white, and the flow approaching the probe 1a in the direction of blood flow is reddish, and is away from the probe. The flow is bluish,
In addition, the average speed and power are displayed in brightness.

In such an ultrasonic diagnostic apparatus, the band of the transmitted ultrasonic waves is wide, for example, centering on 3.5 MHz, and the Doppler frequency is 100 H.
Since it is as low as z-5kHz, Doppler frequency analysis cannot be performed sufficiently.

Therefore, as shown in FIG. 7, each scanning direction i, i + 1
.. are transmitted and received n times, and n received waves are obtained in one scanning direction to form a line spectrum, and frequency analysis is performed from a plurality of received wave data.

By the way, since various discontinuous layers such as the outer wall of an organ having a high reflectance are generally present in the living body, transmitted ultrasonic waves are
Multiple reflections are made between these walls, and the multiple reflection waves are superimposed on the received reflection liquid.

That is, as shown in FIG. 7, for example, the reception signal Ri (n− for the (n−1) th transmission in the i-th scanning line is transmitted.
1) is the transmitted wave component ai and the reflected wave components bi and ci.

This reflected wave component ci is received from the transmission point with a delay due to an echo from a position having a deep low resolution or the above-described multiple reflection, and is a noise when viewed from the reflected wave component bi.

After the reflected wave component ci is completely attenuated, the next transmission may be performed, but with this, the time required to transmit and receive the ultrasonic waves for one scan becomes long, and the dynamic state of the living body Bd cannot be accurately obtained.

Therefore, the transmission interval is set to T, and the next transmission is performed immediately after the necessary reflected wave component bi is received.

When the transmission interval is shortened in this way, the reflected wave component ci that becomes the previous noise is superimposed on the received wave Ri (n) of this time.

In this case, when the previous reflected wave component ci on the same scan line is superimposed, there is no problem because n received waves on the same scan line are analyzed by frequency analysis, but there is no problem when the scan line is switched. For the first received wave (Ri + 1 (1) in the figure, the scanning line i
The reflected wave component ci of is superposed on the second scan line of the (i + 1) th scan line.
This is different from the previous reflected wave component ci + 1 superimposed on the received waves Ri + 1 (2), (3), ...

Therefore, the first reception wave Ri (1) at which the scanning line is switched,
Ri + 1 (1) ... is the received wave Ri (2), Ri after the second time
It is considerably different in frequency from +1 (2) ..., which causes an error in frequency analysis.

As a method of solving this, in the "Ultrasonic Doppler blood flow meter" shown in the specification of Japanese Patent Application No. 175293 (filed on August 9, 1985), the first time of each scanning line is used. It was controlled not to use the received wave data.

[Problems to be solved by the invention]

By the way, the shorter the transmission / reception time of one B-mode scan, that is, each scanning line, the more accurately the dynamic state of the living body can be analyzed, and the more the number of received wave data in one scanning, the more accurate Frequency analysis is possible.

However, in the conventional technique, although ultrasonic waves are transmitted and received n times per scanning and n received wave trains are obtained,
Since one received wave train is discarded, in order to obtain n received wave trains per scan, (n + 1) times of transmission / reception must be performed, and the time required for one B-mode scan becomes long. However, there is a problem that the frame route is lowered.

On the contrary, if the transmission / reception is performed n times, only (n-1) received wave trains can be used for frequency analysis, which causes a problem that the analysis accuracy decreases.

An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of utilizing n reception wave trains for frequency analysis for transmission and reception of n times.

[Means for solving problems]

 FIG. 1 is an explanatory view of the principle of the present invention.

In FIG. 1 (A), the same components as those shown in FIG. 6 are designated by the same symbols, and 32 is a data creation circuit, which is used to convert m-th received wave data to other plural data in the transmission / reception direction. It is created from the received wave data of one time.

The frequency analysis unit 3 performs frequency analysis using a plurality of received wave data in the same transmission / reception direction including the created received wave data.

[Action]

There is a certain degree of correlation between the received wave data obtained in the same scanning direction.

Therefore, in the present invention, as shown in FIGS. 1B and 1C, at the beginning or the end of the received wave data in the scanning direction, it is created as estimated received wave data from a plurality of other received wave data, The received wave data is increased once.

For example, as shown in FIG. 1B, out of the reception wave data Ri (1) to Ri (1) of the i-th scanning line, Ri (1) is the second reception wave data Ri (2), Create from Ri (3).

Alternatively, the (n-1) th and nth received wave data Ri (n-
1), Ri (n) to (n + 1) th received wave data Ri
Create (n + 1).

The received wave data created in this way has a somewhat lower reliability than other received wave data, but if it is the first or last data, the analysis result does not change so much.

Thereby, the frame rate can be improved or the analysis result can be improved.

〔Example〕

(A) Description of Configuration of One Embodiment FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. 3 is a configuration diagram of a main part of the configuration of FIG.

In the figure, the same components as those shown in FIGS. 1 and 6 are designated by the same symbols.

The probe 1a is composed of 48 divided ultrasonic transducers, and is capable of electronic sector scanning.

The sector electronic scanning unit 1b is a delay circuit for electronic scanning.
10, a pulser 11 that outputs ultrasonic pulses for transmission, and 48 preamplifiers 12 that amplify the received wave from the probe 1a,
It includes 48 delay lines 13 that delay the output of the preamplifier 12 according to the scanning direction, and an adder 14 that adds the outputs of the delay lines 13 (48 outputs). The received wave signal RS is output as the output of the adder 14. It is a worm.

The scanner control unit 1C includes an oscillator, outputs the ultrasonic transmission timing signal ST to the pulsar 11 at a constant period T (see FIG. 7), and performs ultrasonic scanning every time the ultrasonic transmission timing signal ST is output n times. Delay circuit 1 for direction change signal SCS
0, the delay line 13 is applied to change the scanning direction by one step, and the ultrasonic wave (sin component) is transmitted to the quadrature detector 3a.
And outputs the cos component rotated by 90 degrees.

The detector 2 amplitude-detects the received wave signal RS and outputs the B-mode signal.
It outputs BS.

The quadrature detector 3a is a Doppler detector, which multiplies the received wave signal RS and the reference frequency f ₀ by a mixer to obtain the number of Doppler shift frequencies fd and high frequency components (2f ₀ + fd), and pass them through a low pass filter. , Only the shift frequency component fd is output, and two channels are provided for detecting the blood flow direction (positive / negative of the Doppler shift).

The Doppler calculation unit 3b includes a pair of A / D (analog / digital) converters 33a and 33b that convert the Doppler shift frequency component fd from the quadrature detector 3a from an analog amount into a digital value.
And a pair of data creation units 32a and 3a that create data respectively from the received wave data strings from the pair of A / D converters 33a and 33b.
2b and a high pass filter, a pair of high pass filters 30a, 30b for removing reflected wave components such as wall parts
And each data from the autocorrelation frequency detection unit 31 that detects the frequency by taking the autocorrelation (pulse pair) of the received data string from the high-pass filters 30a and 30b, the ultrasonic transmission timing signal ST, and the ultrasonic scanning direction change signal SCS. Creation unit 32a, 32
b, The autocorrelation frequency detection unit 31 has a timing control unit 34 that generates a timing signal.

The timing controller 34 and the data generator 32 are shown in FIG.
A and 32b will be described.

The timing control unit 34 is cleared by the ultrasonic scanning direction change signal SCS every time the scanning direction is changed, counts the ultrasonic transmission timing signal ST, and outputs the number of times of transmission in the same scanning direction, and the output of the counter 34a. Is α = 3
Comparator 34b that outputs a switching signal CS of "1" when
And a flip-flop 34c that delays the output of the counter 34a by an interval T of the transmission timing signal ST, and a flip-flop 3 that further delays the output of the flip-flop 34c by T.
With 4d.

The data creation units 32a and 32b have the same configuration, and the tap delay unit 320 that delays the received wave data from the A / D converter 33a or 33b by the transmission interval T, and the output of the tap delay unit 320 at the transmission interval T. A tap delay line 321, which delays only by, a multiplier 322 that multiplies the received wave data of the A / D converter 33a or 33b by a coefficient w ₁ , and a multiplier 323 that multiplies the output of the tap delay line 320 by a coefficient W ₂ . Adder 3 that adds the outputs of multipliers 322 and 323
24, and a switch 325 for switching and outputting the output of the tap delay line 321 and the output of the adder 324 according to the switching signal CS.

The data creation units 32a and 32b delay the received wave data by a transmission interval of 2T, and a changeover switch according to the changeover signal CS.
325 is a side (adder 324 side) and b side (tap delay line 321
Side) and change over.

Therefore, if the changeover switch 325 is connected to the b side,
If the received wave data delayed by T is output to the MTI filters 30a and 30b and is connected to the side a, the adder 324 uses the current received wave data and the received wave data delayed by T instead of the received wave data delayed by 2T. The received wave data created by the MTI filter 30
It is output to a and 30b.

(B) Description of Operation of One Embodiment FIG. 4 is an operation explanatory diagram of one embodiment of the present invention.

The scanner control unit 1c indicates the scanning direction to the delay circuit 10 and the delay line 13 by the scanning direction switching signal SCS,
The transmission timing transmission ST is given to the pulsar 11 at a predetermined interval T,
Cycle T (about 100-300) from the probe 1a to the specified scanning direction
The ultrasonic pulse is transmitted n times in μsec).

The signal reflected from the living tissue is the same probe 1a again.
Received by the preamplifier 12, delay line 13, adder
14 becomes the received wave signal RS.

The received wave signal RS is amplitude-detected by the detector 2 and is written in the digital scan converter 40 as a B-mode image signal BS.

In addition, the received wave signal RS is a quadrature detector 3a and the sin component and cos of the reference frequency (transmitted ultrasonic wave center frequency) f ₀ of the scanner controller 1c.
The components are multiplied and the Doppler shift frequency component fd is obtained from the low pass filter. This Doppler shift frequency component fd
Are converted into digital values by the A / D converters 33a and 33b, respectively, and become reception wave data strings.

The timing control unit 34 clears the counter 34a and counts the transmission timing signal ST by the scanning direction change signal SCS, and recognizes the number of times of transmission and reception in the same scanning direction.

Received wave data trains Ri (1), Ri (2), ... Of each time are input to the data creation units 32a, 32b, respectively, and delayed by 2 transmission intervals 2T by the tap delay units 320, 321.

The output Ri (n−2) ′ of the adder 324 is Ri (n−2) ′ = Ri (n−1) × W ₂ + Ri (n) × W ₁ (1).

Therefore, at the third transmission timing, when the count value k of the counter 34a becomes k = 3, the comparator 34b issues a switching signal CS of "1" to switch the changeover switch 325 to the a side, and the adder 324 The output Ri (n-2) 'is given to the MTI filters 30a and 30b.

At this time, since n = 3, Ri (1) ′ = Ri (2) × W ₂ + Ri (3) × W ₁ (2) is output from the equation (2).

This means that as shown in FIG. 4 (A), the first received wave data Ri (1) 'is created from the second received wave data Ri (2) and the third received wave data Ri (3). Will be done.

Therefore, to create data from two points Ri (2) and Ri (3),
It is estimated that Ri (1) 'is on the straight line of two points Ri (2) and Ri (3), and the equation (2) is expressed as the following equation.

Ri (1) ′ = 2 · Ri (2) −Ri (3) (3) Therefore, the coefficients W ₁ = 2 and W ₂ = −1 may be set.

At this time, the first actual received data Ri (1) is the output of the tap delay unit 321 and the changeover switch 325 is connected to the a side, so that the data is output to the MTI filter 30a as shown in FIG. 4 (B). If not, it is discarded and the above Ri (1) 'is output instead.

The switching signal CS is "0" except for the count value k = 3 of the counter 34a.
Therefore, the changeover switch 325 is connected to the b side, so 2
The reception data Ri (2) and the subsequent data after the first time is output following Ri (1) ', that is, 2T behind the corresponding transmission timing, as shown in FIG. 4 (B).

In order to match with this, the count value k of the counter 34a (that is, the number of ultrasonic wave transmission / reception in the same scanning direction) is set to the flip-flop.
The signals are delayed twice by 34c and 34d and given to the autocorrelation frequency detection unit 31.

Received wave data Ri (1) ′, Ri (2), ... In FIG.
Is input to the MTI filters 30a and 30b, low-frequency components such as walls are cut off, and then input to the autocorrelation frequency detection unit 31.

The autocorrelation frequency detection unit 31 calculates an average Doppler shift frequency and power from n received wave data in the same scanning direction, and writes it in the digital scan converter 40 as blood flow information.

The contents of the digital scan converter 40 are color-processed and displayed on the CRT 41.

Therefore, the blood flow is displayed in color on the CRT together with the B-mode image.

In this way, the first received data in each scan is replaced with the created received data, and the frequency analysis can be performed using the n received data for n times of ultrasonic transmission / reception.

(C) Description of Other Embodiments FIG. 5 is a configuration diagram of another embodiment of the present invention.

In this embodiment, the MTI filter has a data creating function.

As a MTI filter 30a (30b), 4-tap FIR (Finite
Inpulse Response) filter shall be used.

The 4-tap FIR filter 30a (30b) includes three tap delay units 300, 301, 302 and four multipliers 303, 304, 305, 306.
And an adder 307, and the output Z (l) is Z (l) = W ₃ Ri (l-3) + W ₂ · Ri (l-2) + W ₁ · Ri (l-1) + W ₀ · Ri (l) …… (4)

Therefore, when the number of taps is r for the n received data strings, (n-r + 1) data strings Z are output.

On the other hand, a 3-tap FIR filter 35a (35b) is provided in parallel, and the switching switch 325 is used to switch the 3-tap FIR filter 35a (35b).
The output of 5b) and the output of the 4-tap FIR filter 30a (30b) are selected.

The 3-tap FIR filter 35a (35b) includes two tap delay units 350 and 351, three multipliers 352, 353 and 354, and an adder 3
Is composed of a 55, the output Z (l) _{is, Z (l) = W 2} '· Ri (l-2) + W 1' · Ri (l-1) + W 0 '· Ri (l) ...... (5 ) Is.

The 4-tap MTI filter 30a (30b) has three (n-3) fewer filter outputs Zi, that is, Zi (4), Zi (5), ... Zi (for n received wave data Ri (n). n) is output.

According to the equation (4), the first output Zi (4) is Ri (1)
~ Created by Ri (4), the first received data Ri
It may be created with the 3-tap filter 35a (35b) without using (1).

That is, from the equation (5), Zi (4) = W ₂ ′ · Ri (2) + W ₁ ′ · Ri (3) + W ₀ ′ · Ri (4) (6)

The coefficients W ₂ ′, W ₁ ′ and W ₀ ′ are determined as follows.

By FIG. 4, 'because is created in the _{(3), W 3 · Ri (1)} ' Ri (1) = 2W 3 · Ri (2) -W 3 · Ri (3) ...... (7 ) Substituting this into Ri (l-3) of equation (4) with l = 4, Z (4) = 2W ₃ · Ri (2) −W ₃ · Ri (3) + W ₂ · Ri (2) + W ₁ · Ri (3) + W ₀ · Ri (4), which can be rearranged as follows: Z (4) = (2W ₃ −W ₂ ) · Ri (2) + (W ₁ −W ₃ ) · Ri (3 ) + W ₀ · Ri (4) …… (8)

By comparing this with the equation (6), and obtaining W ₂ ′, W ₁ ′ and W ₀ ′, Becomes

By thus determining the coefficients W ₂ ′, W ₁ ′ and W ₀ ′, the 3-tap FIR filter and the 4-tap MTI filter become equivalent.

Therefore, when l = 4, that is, when the count value k of the counter 34a in FIG. 3 is “4” (during the fourth ultrasonic wave transmission / reception), the changeover signal CS can be used to change over the changeover switch 325 to the side a. For example, the filter output Zi (4) obtained from Ri (2) to Ri (4) is obtained without using the first received data Ri (1).

After that, by returning the changeover switch to the b side, Ri
Zi (5), Ri (3) -Ri (6) by (2) -Ri (5)
Zi (6), ... Zi (n) is obtained.

This example does not actually create the reception data instead of the first reception data Ri (1), but 3 taps
Since the equation (3) is used when setting the coefficients of the FIR filter 35a (35b), it is nothing but the creation of Ri (1) 'indirectly by the equation (3).

(D) Description of another embodiment In the above-mentioned embodiment, two reception data Ri (2), Ri
The first-time data Ri (1) ′ is created from (3), but as another method, the first-time data is obtained from three data Ri (2), Ri (3), and Ri (4). Ri (1) 'may be created.

In this case, since there are three points, data can be created using a quadratic curve, and Ri (1) ′ = 3 · Ri (2) −2 · Ri (3) + Ri (4) instead of equation (3). …
... (10) should be used.

Also, as shown in FIG. 1 (C), instead of making Ri (1) ', R (1) is discarded and Ri (n-1) and Ri (n) are used, or Ri (n-2), The last received wave data Ri (n + 1) may be created from Ri (n-1) and Ri (n).
The number of data is increased, but it may be two.

Furthermore, the data creation units 32a and 32b and the MTI filter 30 shown in FIG.
a, 30b, timing controller 34, autocorrelation frequency detector 31
For digital processing, the processor may be configured to execute the program by executing the program instead of providing individual hardware.

Besides, I explained the MTI filter as FIR filter, but IIR
A filter may be used, and the frequency analysis is not limited to the autocorrelation method, and a well-known FFT method, zero-cross method, or the like may be used.

The embodiments of the present invention have been described above, but the present invention can be modified in various ways according to the gist of the present invention, and these modifications are not excluded from the present invention.

〔The invention's effect〕

As described above, the present invention has the following effects.

"Since the received wave data can be increased at least once, the number of ultrasonic wave transmissions in one scanning direction can be reduced, the frame rate can be significantly improved, and clear flow imaging can be obtained.

"If the number of ultrasonic waves transmitted in one scanning direction is the same, the number of data strings for analysis increases by one, the frequency analysis accuracy can be greatly improved, and highly accurate flow imaging can be performed.

"Since the received wave data string is created from another received wave data string with the MTI filter, it can be realized with a simple circuit.

[Brief description of drawings]

 FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention, FIG. 3 is a configuration diagram of a main part of the configuration of FIG. 2, and FIG. FIG. 5 is a block diagram of another embodiment of the present invention, and FIGS. 6 and 7 are explanatory views of the prior art. In the figure, 1 ... Ultrasonic wave transmitting / receiving section, 1a ... Probe, 2 ... Amplitude extraction section, 3 ... Frequency analysis section, 4 ... Display section, 32 ... Data creation section.

Claims (1)

[Claims] 1. An ultrasonic transmitting / receiving unit (1) for transmitting and receiving ultrasonic waves a plurality of times in each ultrasonic transmitting / receiving direction in B-mode scanning, and amplitude extraction for obtaining B-mode image information from the amplitude component of the ultrasonic received wave. And a frequency analysis unit (3) for frequency-analyzing the data of a plurality of received waves in the same transmission / reception direction to obtain blood flow information. In the ultrasonic diagnostic apparatus, a data creating unit (32) including an MTI filter that creates m-th received wave data from other received wave data in the transmission / reception direction is provided, and the frequency analysis unit (3) An ultrasonic diagnostic apparatus, wherein frequency analysis is performed using a plurality of received wave data in the same transmission / reception direction including the created received wave data.