JPH02142547A - Ultrasonic measuring device - Google Patents

Abstract

PURPOSE:To determine the acoustic characteristic in an examined body by adding and averaging a plurality of receiving signals close in point of time and space when a probe wave pulse is laid on the particle acceleration positive and negative peak positions of a pump wave pulse and determining two spectrum distributions corresponding to the codes of the particle acceleration peak positions followed by comparing. CONSTITUTION:A delay control part 13 of a control driving part 4 controls pulse drivers 11 and 12 so that a probe wave pulse is laid on the particle acceleration positive and negative peak positions of a pump wave pulse. The pump wave pulse and probe wave pulse are scattered corresponding to the change of acoustic quality in an examined body 10, and partly reached to a second ultrasonic exchanger 2, where they are converted into receiving signals, then converted into a digital signal in an A/D exchanger 21, and stored in a memory 22. The output of adding and averaging part 25, 26 picks up the range targeted in window characteristic parts 29, 30 and calculates the spectrum P<+>-(omega) of the receiving signal in frequency analyzing parts 31, 32. The frequency fx providing the P+ or -(omega) ratio of 1 is determined in a calculating part 33, and the acoustic characteristic depending on the frequency is determined and displayed on a display part 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention transmits ultrasonic waves into a subject, receives reflected waves from the subject, and determines whether the propagation characteristics within the subject affect the characteristics of the received ultrasound. The present invention relates to an ultrasonic measuring device that measures the ultrasonic characteristics of a subject using changes in the ultrasonic characteristics.

2. Description of the Related Art Conventionally, an example of a method for obtaining acoustic information inside a subject using ultrasound is an ultrasound diagnostic apparatus.

The mainstream of these ultrasonic diagnostic devices is one that uses a pulse reflection method that transmits ultrasonic waves into a living body and obtains information about the inside of the living body using reflected waves from the living body. This pulse reflection method usually collects and displays in-vivo information two-dimensionally from the reflected echo intensity from interfaces with different acoustic impedances, that is, amplitude values and ultrasound propagation times. It is something that gives you an image. However, in recent years, ultrasonic diagnostic equipment that mainly determines the shape of in-vivo tissues has become
There is a growing desire to obtain information not only on the shape but also on the quality of in-vivo tissue. Such information regarding the quality of in-vivo tissues can be obtained, for example, by measuring the magnitude of attenuation of ultrasound, the speed of sound, etc., which have specific values in various organs in the in-vivo.

As an ultrasonic measuring device that measures the attenuation coefficient of this ultrasonic wave, for example, ultrasonic imaging: UT, T
RASONICIMAGING, Vol. 5,
No.2.

1983, pp. 117-135 is known. The conventional ultrasonic measuring device will be described below with reference to FIG.

In FIG. 5, 101 is an ultrasonic transducer that transmits ultrasonic waves to the subject 102 and receives reflected waves from the subject 102, 103 is a pulse driver that drives the ultrasonic transducer 101, and 104 is a pulse driver that drives the ultrasonic transducer 101. A receiving circuit that amplifies the received signal of the ultrasonic transducer 101, 105 a frequency analyzer that performs frequency analysis from the output of the receiving circuit 104, 106 a frequency analyzer 10
This is a calculation unit that performs calculations from the output of 5.

First, the operation of the above conventional example will be explained.

First, a drive pulse sent out from the pulse driver 103 is applied to the ultrasonic transducer 101, and the ultrasonic transducer 101 generates an ultrasonic pulse. The generated ultrasound pulses propagate through the subject 102 and are successively scattered in accordance with the acoustic properties of the tissue, and some of them travel backwards along the propagation path, that is, the acoustic scanning line, and reach the ultrasound transducer 101. and is converted into a received signal.

During this process, the ultrasound pulse is influenced by the ultrasound attenuation characteristics and ultrasound scattering characteristics of the living tissue. The received signal is amplified by the receiving circuit 104, and the center frequency is determined by the frequency analyzer 105. To find the center frequency, use a zero-cross counter or fast-to-J transform method (FFT).
There is a method using etc.

This center frequency is a value that depends on the propagation distance and the attenuation coefficient of the ultrasonic wave. The calculation unit 106 calculates the attenuation coefficient of the ultrasonic wave from the center frequency output of the frequency analyzer 105. In the above description, it is assumed that there is no influence of the ultrasonic scattering coefficient of the subject 102.

Problems to be Solved by the Invention However, in the conventional configuration as described above, the subject 102
, the ultrasound scattering state changes considerably even if the location of the same tissue is slightly different, but since it is greatly influenced by this ultrasound scattering characteristic,
When determining the ultrasonic attenuation characteristics specific to 2, there was a problem in that the error became large.

The present invention solves the above-mentioned problems of the conventional technology by canceling the scattering characteristics of the ultrasonic propagation path for a subject that has various attenuation characteristics and sound speed characteristics depending on the tissue of a living body. It is an object of the present invention to provide an ultrasonic measuring device that can accurately measure the ultrasonic attenuation characteristics of a specific region.

Means for Solving the Problems In order to achieve the above object, the present invention includes a first ultrasonic transducer that sends out a pump wave pulse, and a second ultrasonic transducer that sends out a probe wave pulse having a higher frequency than the pump wave pulse. an ultrasonic transducer that performs fan-shaped scanning of the first and second ultrasonic transducers, and a probe wave pulse that drives the first and second ultrasonic transducers in a phase controlled manner. a control drive unit that superimposes the signal on the positive and negative peak positions of the particle acceleration of the pump wave pulse, a memory that stores the received signal that is the output of the second ultrasonic transducer, and a memory that stores the received signal that is the output of the second ultrasound transducer; An averaging section that performs addition separately; a weighting characteristic section that stores weighting values used when performing weighted addition in this averaging section; a window characteristic section that extracts an arbitrary section of the output of the averaging section; and this window characteristic. The frequency analyzer calculates the spectrum of the received signal using the data extracted by the frequency analyzer, and the arithmetic unit calculates the acoustic characteristics of the subject from the output of the frequency analyzer.

Alternatively, the ultrasonic transducer scanning section may perform linear scanning instead of fan-shaped scanning for the first and second ultrasonic transducers.

For production The present invention has the following effects due to the above configuration.

In other words, when a probe wave pulse is superimposed on the positive and negative particle acceleration peak positions of the pump wave pulse, multiple received signals temporally and spatially close are averaged, and the signal corresponds to the sign of the particle acceleration peak position of the pump wave pulse. By determining and comparing the two spectral distributions, the acoustic characteristics within the object are determined by canceling out the complex scattering characteristics of the object.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIGS. 1(a), (b), and (C) show an ultrasonic measuring device according to an embodiment of the present invention, FIG. 1(a) is an overall functional block diagram, and FIG. 1(b) is a control drive unit. FIG. 2C is a functional block diagram of the signal processing section.

In FIG. 1(a), ■ is a first ultrasonic transducer that sends out a pump wave pulse that is a first ultrasonic pulse in a low frequency band, and 2 is a second ultrasonic transducer that has a higher frequency than the first ultrasonic pulse. A second ultrasonic transducer 3 transmits a probe wave pulse which is an ultrasonic pulse of 4 is a control drive unit that drives the first ultrasonic transducer 1 and the second ultrasonic transducer 2 in phase control, and this control drive unit 4 is shown in FIG. 1(b). 1st as shown in
a pulse driver 11 that drives the second ultrasonic transducer 1; a pulse driver 12 that drives the second ultrasonic transducer 2; and delay control that controls the difference in pulse generation timing between the pulse drivers 11 and 12. It consists of a section 13. In FIG. 1(a), 5 is a receiving circuit that amplifies the received signal that is the output of the second ultrasonic transducer 2, and 6 is a signal processing section that performs signal processing on the output of the receiving circuit 5. The processing section 6 is configured as shown in FIG. 1(C).

In FIG. 1(C), 21 is an A/D converter that converts the received signal output from the receiving circuit 5 into a digital signal;
22 is a memory for storing the output of the A/D converter 21;
23 is a write address generation section that generates a write address for the memory 22; 24 is a read address generation section that generates a read address for the memory 22; 25, 2
Reference numeral 6 denotes an arithmetic averaging unit that adds the outputs of the memory 22; 27 a weighting characteristic unit that provides a weighting value to the arithmetic averaging unit 25;
Reference numeral 28 denotes a weighting characteristic section that provides a weighting value to the averaging section 26; 29 a window characteristic section that extracts the output of the averaging section 25 in an arbitrary section; 30 a window characteristic section that extracts the output of the averaging section 26 in an arbitrary section; 31 32 is a frequency analysis unit that calculates the spectrum of the received signal based on the data extracted by the window characteristic unit 30; 33 is the frequency Analysis department 31
, 32, which calculates the ultrasonic attenuation characteristic, which is the acoustic characteristic of the subject 10. In FIG. 1(a), 6 is a delay controller 13 of the control drive unit 4 (see FIG. 1(b)).
), the A/D converter 21 of the signal processing section 6 (see Fig. 1 (C
); reference numeral 8 designates a display unit that displays the output of the signal processing unit 6; reference numeral 9 designates a main control unit that controls the entire system; and reference numeral 10 designates a subject.

The operation of the above configuration will be explained below.

First, the relationship between probe wave pulses and pump wave pulses will be explained. An example of the probe wave pulse is shown in FIG. 2(a), and an example of the pump wave pulse is shown in FIG. 2(b). FIG. 2(C) shows an example in which a probe wave pulse and a pump wave pulse are superimposed. These waveforms are under the control of the delay control section 13 of the control drive section 4. The center frequency of the pump wave pulse is, for example, Q, 3 MHz, and the center frequency of the probe wave pulse is, for example, 3 MH2, and these center frequencies are selected to have significantly different values. In FIG. 2(C), the center of gravity of the waveform of the probe wave pulse is superimposed at the timing when the particle velocity of the pump wave pulse is near zero and the particle acceleration thereof has a positive peak. When the wavelength of the pump wave pulse and the pulse length of the A1 probe wave pulse are t, it is desirable to set the relationship expressed by the following equation (1).

Zt<A (1) When the above equation (1) is satisfied, the modulation characteristics of the probe wave pulse can be easily analyzed.

Next, the manner in which each pulse shown in FIG. 2 propagates within the subject 10 will be explained in detail. It is known that even in the case of a peak ultrasonic output level used in a normal ultrasonic diagnostic apparatus, the waveform of the ultrasonic wave is distorted due to nonlinear propagation phenomena. The reason for this can be easily explained using the following equation (2).

△C-(1+B/2A)・U ・・・・・・(2)
Here, U is the particle velocity of the sound wave, B/A is the acoustic nonlinear parameter of the medium, and ΔC is the change in the sound velocity based on the nonlinear effect. The above equation (2) shows that when the direction of the particle velocity U of the sound wave coincides with the sound wave traveling direction, the sound speed change Δc? i increases,
In the opposite direction, it decreases, indicating that the waveform of the sound wave is distorted as a result. FIG. 3 shows the influence of this nonlinear propagation phenomenon on the waveform of the ultrasonic pulse. Figure 3(a) shows the distortion of the pump wave pulse accompanying propagation, and Figure 3(b) shows the distortion of the pump wave pulse accompanying propagation.
) shows a state in which the center frequency of the superimposed probe wave pulse is compressed as it propagates due to the distortion of the pump wave pulse shown in FIG. 3(a), and shifted to the higher frequency side. Conversely, if the probe wave pulse is superimposed at the peak position where the particle force velocity of the pump wave pulse is negative,
As it propagates, it is expanded and shifted to the lower frequency side. Therefore,
By taking the difference between when the center frequency shifts to the high frequency side and when it shifts to the low frequency side, it becomes possible to obtain a large amount of change in the center frequency based on the nonlinear effect. P+(ω) is the spectrum of the received signal of the probe wave pulse when the probe wave pulse is superimposed on the peak position where the particle acceleration of the pump wave pulse is positive, and the probe wave pulse is superimposed on the peak position where the particle acceleration of the pump wave pulse is negative. Assuming that the spectrum of the received signal of the probe wave pulse when superimposed is P-(ω), P+(ω) is expressed by the following equation (3).

P+(ω)=Hshi(ω)・S±(ω)・G(ω)・T(
ω) (3) In the above equation (3), )-I±(ω) is the modulated probe wave spectrum, and S±(ω) is the sample 1
0, G(ω) is the attenuation property associated with propagation after scattering, and T(ω) is the property of the probe wave pulse transducer. The following (4) is obtained by taking the ratio of the spectra P±(ω) of the two modulated received signals.

Spectrum of modulated probe wave pulse H-fflω
), if the scattering characteristic Sf(ω) within the object 10 does not change much, the above equation (4) can be approximated as the following equation (5).

In the above equation (5), the ratio of P+(ω) is the ratio of the subject l.

does not include the complex scattering characteristics S±(ω) in the spectrum, and is simply the ratio of the spectrum H±(ω) of the modulated probe wave pulse. The frequency at which the ratio of this spectrum H±(ω) is 1 is fX, l! - Then, it is analytically determined that this frequency fx is a value that depends on the attenuation characteristics of the object, the nonlinear parameter B/A value, etc. From the above, by calculating the frequency at which the ratio of the received signal spectrum P±(ω) of the modulated probe wave pulse is 1, the acoustic properties inside the subject can be determined.

Next, the process by which these received signals are processed will be explained.

The first ultrasonic transducer shown in FIG. 1(a)] and the second ultrasonic transducer 2 scan the object 1
0 mechanically or electronically fan-scanned. First, the delay control unit 13 of the control drive unit 3 shown in FIG. control device 12. The pump wave pulse and the probe wave pulse sent out from the first ultrasonic transducer 1 and the second ultrasonic transducer 2 propagate inside the object 10, while the probe wave pulse is affected by propagation distortion due to nonlinear phenomena. is generated and modulated. At the same time, the light is scattered one after another in response to changes in the acoustic quality within the subject 10, and a portion of it reaches the second ultrasonic transducer 2 and is converted into a received signal. This received signal is amplified with a good S/N ratio by a duplication circuit 5 and then inputted to a signal processing section 6. The output of the receiving circuit 5 is shown in Fig. 1(C).
The signal is converted into a digital signal by the A/D converter 21 in the signal processing unit 6 shown in FIG.

Next, the delay control unit 13 shown in FIG. 1(b) controls the pulse driver 11 and the pulse driver 12 so that the probe wave pulse is superimposed on the particle acceleration negative peak position of the pump wave pulse. The pump wave pulses and probe wave pulses sent out from the first ultrasonic transducer 1 and the second ultrasonic transducer 2 are transmitted one after another in response to changes in the acoustic quality within the subject 10, as described above. A part of the scattered light reaches the second ultrasonic transducer 2, where it is converted into a received signal, passed through the receiving circuit 5, and converted into a digital signal by the A/D converter 21 of the signal processing section 6. Write address generation section 2 in memory 22
It is stored in the position indicated by 3. By repeating this operation, the received signal is measured as shown in FIG. In Figure 4, the solid line shows the received signal when the probe wave pulse is superimposed on the peak position of the particle acceleration pressure of the pump wave pulse, and the broken line shows the received signal when the probe wave pulse is superimposed on the peak position of the negative particle acceleration of the pump wave pulse. Shows the received signal.

When calculating the ratio of spectra P±(ω) of received signals, received signals from the same location in time and space are required, but as shown in Fig. 4, the spectrum P of the received signals from the same location is There is no ±(ω). Therefore, by performing averaging processing on the received signal group shown in Fig. 4, the received signal spectrum P±
Find (ω). First, a plurality of received signals when the probe wave pulse is superimposed on the peak position of the particle acceleration pressure of the pump wave pulse, for example, 1+, 2+, 3+ shown in FIG.
, . . 8+ are read out from the memory 22 shown in FIG. Similarly, the received signals 1, 2, 3, . Transfer to. Next, the averaging section 25
, 26 add and average the eight received signals transferred from the memory 22.

However, when this averaging is performed, sound field correction is performed by weighting, for example, a Gaussian distribution such that the middle received signals 4 and 5 have peaks, and performing the averaging. The weighting values used at this time are stored in the weighting characteristic units 27 and 28 in advance. Next, the output of the averaging section 25 is sent to the window characteristic section 29, where the data corresponding to the depth of examination of the part to be calculated is extracted using a Hamming window, for example, and a region corresponding to 2α is extracted, and the frequency analysis section 31 The spectrum P+(0) of the received signal is calculated at . The window characteristic section 30 extracts the target area, and the frequency analysis section 32 calculates the spectrum p-(ω) of the received signal.The two spectra P+(ω) calculated by the frequency analysis sections 31 and 32 are as follows. In the calculation unit 33, P±(ω)
The frequency fx at which the ratio of 1 is 1 is determined, and the acoustic characteristics that depend on this frequency fx are determined and transferred to the display section 8 for display.

In the above explanation, the first ultrasonic transducer 1 and the second ultrasonic transducer 2 are scanned in a fan shape by the ultrasonic transducer scanning unit 3, and the modulated received signal is measured as shown in FIG. However, the received signal when the probe wave pulse is superimposed on the peak position of the particle acceleration pressure of the pump wave pulse and the probe wave pulse is superimposed on the negative peak position of the particle acceleration pressure of the pump wave pulse at the same site without fan scanning. The received signal when superimposed on the position is stored in the memory 22, and then the first ultrasonic transducer 1 and the second ultrasonic transducer 2 are moved by a small angle by the ultrasonic transducer scanning unit 3, and the same process is performed. You may repeat the measurement. In this case, the weighting characteristics sections 27 and 28 have the same weighting value. In addition, only the received signal when the probe wave pulse is superimposed on the peak position of the particle acceleration pressure of the pump wave pulse during fan-shaped scanning is stored in the memory 22, and the probe wave pulse is pumped when the same position is next scanned in the fan-shaped manner. The received signal obtained when the wave pulse is superimposed on the negative particle acceleration peak position may be stored in the memory 22.

In this case as well, the weighting characteristics sections 27 and 28 have the same weighting value. Furthermore, first and second ultrasonic transducers l.

2 may be replaced with fan-shaped scanning and may be linearly scanned.

Effects of the Invention As described above, according to the present invention, the received signal when the probe wave pulse is superimposed on the peak position of the particle acceleration pressure of the pump wave pulse, and the probe at the negative peak position of the particle acceleration pressure of the pump wave pulse Obtain the distribution of the received signal when wave pulses are superimposed, extract multiple received signals, weight and average them, and calculate the acoustic characteristics of the object with high precision by frequency analysis and calculation of this output. can do.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (C) show an ultrasonic measuring device according to an embodiment of the present invention, FIG. 1(a) is an overall functional block diagram, and FIG. 1(b) is a control drive unit. Functional block diagram of
Figure 2 (C) is a functional block diagram of the signal processing section, and Figure 2 (a)
) is a diagram showing an example of a probe wave, FIG. 2(b) is a diagram showing an example of a pump wave pulse, FIG. Figure (a) shows the distortion of the pump wave pulse as it propagates.
Figure (b) shows a state in which the center frequency of the superimposed probe wave pulse is compressed as it propagates due to distortion of the pump wave pulse, and is shifted to the high frequency side. Figure 4 shows the received signal obtained by the present invention. FIG. 5 is a functional block diagram showing a conventional ultrasonic measuring device. 1.2... Ultrasonic transducer, 3... Ultrasonic transducer scanning unit, 4... Control drive unit, 5... Receiving circuit, 6...
Signal processing section, 7... Clock source, 8 - Display section, 9.
- Main control unit, 10... Subject, 11, 12 - Pulse driver, 13 - Delay control unit, 21... A/D
Converter, 22 memory, 23...-write address generation section, 24 read address generation section, 25.26... averaging section, 27, 28... weighting characteristic section, 29,
30... Window characteristic section, 31, 32... Frequency analysis section, 33 Arithmetic section. Patent applicant Yuki Iizuka Director of the Agency of Industrial Science and Technology

Claims (2)

[Claims] (1) a first ultrasonic transducer that sends out a pump wave pulse; a second ultrasonic transducer that sends out a probe wave pulse having a higher frequency than the pump wave pulse;
an ultrasonic transducer scanning unit that performs fan-shaped scanning of the ultrasonic transducer;
a control drive unit that drives the first and second ultrasonic transducers in phase control to superimpose the probe wave pulse on the positive and negative peak positions of particle acceleration of the pump wave pulse; and an output of the second ultrasonic transducer. a memory for storing received signals, an averaging section for separately adding the received signals stored in this memory, and a weighting characteristic section for storing weighting values used when performing weighted addition in the averaging section. , a window characteristic section that extracts the output of the averaging section in an arbitrary interval, a frequency analysis section that calculates the spectrum of the received signal from the data extracted by this window characteristic section, and a frequency analysis section that calculates the spectrum of the received signal from the output of this frequency analysis section. An ultrasonic measurement device comprising a calculation unit that calculates acoustic characteristics. (2) The ultrasonic measuring device according to claim 1, wherein the ultrasonic transducer scanning section performs linear scanning of the first and second ultrasonic transducers instead of fan-shaped scanning.