JPS6125535A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention emits ultrasonic pulses into a living body, analyzes echo signals reflected from tissues in the living body, and determines the position of any tissue within the living body. Alternatively, the present invention relates to an ultrasonic diagnostic apparatus that measures the attenuation coefficient of ultrasound waves of the tissue and diagnoses diseases and the like.

[Prior art] Conventional diagnostic equipment using the general ultrasound echo method mainly visualizes the morphological information of the tissue based on the position of the echo signal reflected from the tissue in the living body and the amplitude information of that signal. Therefore, it was not possible to know in detail the characteristics of the organization itself.

On the other hand, it is known that ultrasonic waves propagating in a living body are attenuated depending on the tissue in which the ultrasonic wave is propagating, based on frequency dependence specific to the tissue. In other words, living organisms generally have a characteristic that the attenuation rate for high frequencies is larger than that for low frequencies. It is known that the attenuation characteristic α(f) is proportional to the frequency f as shown in the following equation.

α(f)・βf Here, β is an attenuation coefficient that varies depending on the tissue.

It has also been reported that this attenuation coefficient differs between abnormal tissue and normal tissue, and it has been strongly desired to accurately measure this attenuation coefficient for diagnosis of diseases and the like.

One method that has been proposed in the past for determining this attenuation coefficient is to determine the attenuation coefficient received between the front and rear of the measurement site based on the difference in the spectra of the echo signals obtained before and after the site to be measured. A disadvantage of this method is that the fine spectrum caused by the tissue structure within the measurement distance makes it difficult to measure the attenuation coefficient.

Therefore, a method has been proposed in which the center frequency of each spectrum is found without directly finding the difference between the spectra, and the attenuation coefficient is found from the difference in the center frequencies. This method has the advantage that the spectrum is less affected by the fine tissue structure mentioned above, but the value of the difference in center frequency is
It is necessary to convert it into a single coefficient value, and this conversion is generally difficult because it is related to the spectrum of the probe. However, if we assume that the spectrum is a Gaussian spectrum, the mathematical processing becomes significantly easier.
Its application was expected. However, in reality, it is extremely difficult to create a probe with such a Gaussian spectrum.

[Object of the Invention] The present invention is directed to the above-mentioned conventional JLL! The objective was to accurately calculate the attenuation coefficient of living tissue using a normal non-glass type probe with a spectrum of 1-1, using extremely simple calculations similar to those of a Gaussian spectrum. An object of the present invention is to provide an improved ultrasonic diagnostic device that can easily perform tissue diagnosis.

E. Structure of the Invention] In order to achieve the above object, the present invention uses the transfer characteristic of a probe determined in advance for an echo signal obtained from an arbitrary probe having a non-Gaussian spectrum. Then, by using so-called deconvolution processing to remove the spectrum unique to the probe and then converting it to a Gaussian spectrum, an echo signal equivalent to the echo signal obtained from a probe with a Gaussian spectrum is obtained. It is characterized by Therefore, according to the present invention, the attenuation characteristics of the tissue can be easily determined from the movement m of the center frequency of the Gaussian spectrum.

[Explanation of Examples] The present invention will be described in detail below based on the drawings.

Generally, in the ultrasonic echo method, as shown in Figure 1,
The sound radiated from the vibrator 10 is 1111 and 12 is 1=Il.
The pulse wave 5(t) reflected by the ai is reflected at a boundary surface with different acoustic impedance and is received by the vibrator 10. The reflection series corresponding to each boundary surface in the observed section of the object is expressed as r(B-
Assuming that the pulse wave s (B does not change) within the interval, the obtained echo signal e(t) is expressed as e('t)=r(t)''5(t)-11). However, the car represents convolution.If we express each function in capital letters after Fourier transform, equation (1) becomes E(r)=R(f)・5(f)...(2) It is expressed in the form of a product, therefore R(f ) f, 1LR(f)・E(
f) /5(f)...(3). This is generally called f-involution and is well known. Multiplying this by the Gaussian spectrum Gm gives E c (f) = R(f)・G(f)...(4)(
4) Find E c (f) in the equation. , 1R(r)l is l
When G(r) is sufficiently smaller than 1, the center frequency of G(f) approximately matches that of E c (f).

Next, there is attenuation like a living body! If the spectrum of the echo signal from inside II is expressed as E F (r), then E F
It can be expressed as (f)-R(f) 5(r)e-'' fΩ-(51. However, Q is the round trip distance for the ultrasonic pulse to return from the reflector.

Substituting equation (5) into E([) of equation (3), and further adding Gaussian spectrum G('') to (6) in equation (4),
) to obtain the formula.

E F G fr)=R(r)e-a'ΩG (f)
- (6) Since G([) is Gaussian, it is assumed as in equation (7).

G(rl-exp((r4o)'/2a")-
(7) However, fo is the center frequency, and σ is the Gaussian component 4 used in statistics, t! - corresponds to the deviation. , substitute equation (7) into equation (6) to obtain equation (8).

E F G (fl- to R(f)exp[(f-(fo
→Δf)] '/2a2]...(8) However, it is assumed to be a constant. Also, 8[ is Δ[=α'Qσ2...(9) Substituting equation (7) into equation 6 (') of a(4) where Δ[=α'Qσ2...(9), the following equation is obtained.

[c(r)=R(f)eXI)((f-rO)'
/2(y 2) - (10) Comparing equation (10) with equation (8), we find that E F G
It can be seen that (r) also maintains a Gaussian spectrum. However, the difference is that the center frequency of the spectrum is shifted by Δf. That is, by finding the moving valve of this center frequency, the damping coefficient α can be obtained using equation (9).

A characteristic feature of the present invention is that it is possible to obtain a signal equivalent to the signal obtained from a Gaussian probe by deconvolution processing of the echo signal transmitted and received from a non-Gaussian probe. be.

Next, an example will be shown in which the deconpolicing process of the present invention is performed using a computer.

Figure 2 shows an echo waveform obtained from the surface of an acrylic plate placed in water, and Figure 3 shows its spectrum.

It is clear from the waveform in Figure 2 that this echo decays backward along the time axis, and is a non-Gaussian pulse waveform. The weighted waveform in Figure 4 is:
It shows a Gaussian pulse whose envelope is Gaussian and weighted.

Figure 5 is the spectrum of Figure 4, and the spectrum of the Gaussian pulse is also Gaussian, and Figure 4 is based on data obtained by processing actual waveforms, so
Although the shape is slightly uneven, it is understood that it shows a Gaussian shape. In other words, this shows the waveform and spectrum obtained by transmitting and receiving Gaussian pulses, and shows that it was possible to obtain an echo signal using Gaussian pulses, which is difficult in reality.

FIG. 6 shows a preferred embodiment of the ultrasonic diagnostic apparatus of the present invention.

The device of the embodiment has a suyayana 16 including a focus circuit that performs focusing adjustment of the vibrator 10 and a single fin circuit that performs electronic switching scanning of the vibrator 10, and an oscillator circuit 1.
When a trigger pulse that determines the transmission repetition period of ultrasonic pulses is input to the scanner 16 from 8, this scanner 16
excites the vibrator 10 in synchronization with the input of the trigger pulse.
III 111, ultrasonic pulse 5 (t
).

The ultrasonic pulse 5(t) emitted in this manner is successively reflected at each boundary surface having a different acoustic impedance while propagating inside the subject 12. Then, the reflection wave "-e(t)" is received by the vibrator 10~, where it is converted into a "-air signal", and is further transmitted through a focus circuit provided in the skyshaft 16, which is a characteristic feature of the present invention. The signal is input to a deconvolution circuit and a Gaussian weighting circuit 20, which are constituent elements.

In device a of the present invention, this circuit 20 includes a delay circuit that delays an echo signal and outputs it as a plurality of delayed signals delayed at regular intervals, and a weighting circuit that performs predetermined weighting processing on each delay circuit. includes a circuit and an adder that adds and outputs each weighted delay signal, and uses these circuits to perform deconvolution processing on the input echo signal e(t), and further performs Gaussian weighting processing. The obtained Gaussian echo signal is sent to the amplifier 22 and center frequency detector 30. It has specific power.

The Gaussian signal input to the amplifier 22 in this way is amplified by a predetermined amplification factor, and then sent to the detector 24.
The image is inputted to the memory 26 via the video signal, where it is stored as a video signal and then displayed on the CRT 28 as a diagnostic image.

On the other hand, the center frequency of the Gaussian signal is measured by the center frequency detector 30 from the Gaussian signal at the time corresponding to the designated depth, and is sent to the capital reduction coefficient calculator 32. Then, in the field generator 32, an attenuation coefficient is calculated from the difference with the center frequency measured in the non-attenuated state, and the memory 26G, l!
! ! and displayed on the CRT. The deconvolution circuit and Gaussian weight circuit 2 of the present invention are described below.
A preferred embodiment of 0 will now be described.

FIG. 7 shows a preferred embodiment of the recursive gay convolution circuit 20. One signal C ([) output from 16
is directly inputted to the delay circuit 34, and the result is a signal c (non-recursive deconvolution processing of H).

Here, the delay circuit 34 performs a predetermined ff delay process on the input echo (U signal C(+), and delays the echo signal e(t) at regular time intervals. Multiple delayed signals e(t-τ), e(+-2r)...
...It is weighted as 0 (tnτ) and output to the filter circuit 3G.

The weighting circuit 36 generates a plurality of weighting signals a1 corresponding to each delayed signal based on a signal from a control circuit (not shown).
．． a2...output ao Φmi ('I IJ A38
and a plurality of signal generators 40-1 and 40-2 for multiplying these weighted signals by each delay signal output from the delay circuit 34.
-40-n, and performs a predetermined weighting process on the delayed signal output from the delay circuit 34.

In this way, the weights (]1 and 1 are output from the weight number) circuit 36, respectively.
The image signal r (becomes 0) is crimped and deconpoliced at 3/12.

Therefore, the signal r(1) output from the adder 42 is expressed as follows: % formula % (11) It will be expressed as.

Here, when both sides of equation (11) are Fourier transformed, the following convolution form is expressed. Therefore, by comparing this equation (12) with the above-mentioned equation (3), the following relationship is obtained, and by performing an inverse Fourier transform on 1/S[) expressed by this equation (13), a can be found. can.

Therefore, by finding 1/5(f) and performing inverse Fourier transform on it, the a required for deconvolution is
can be obtained in advance, and by outputting a obtained in this way from the adder 38, the adder 42
The signal r(t) of the above equation (11) outputted from the echo signal e([) can be said to be the result of deconvolution processing of the echo signal e([).

Next, a method for converting this deconvolved signal into a Gaussian signal will be described. If the spectrum of a Gaussian signal is [C ket) and J, this is the above-mentioned (
It can be obtained by multiplying the Gaussian spectrum G(f) as shown in equation 4). Therefore, when calculating the weighting constant ar using equation (13), by calculating ai from equation (15), it is possible to perform both deconpolization and Gaussian weighting at - degrees. .

[Effects of the Invention] As explained above, according to the present invention, deconpolization processing is performed on echo signals obtained from a subject while using an ultrasound probe having a non-Gaussian spectrum. After removing the spectrum specific to the probe, a conversion process to a Gaussian spectrum is performed.As a result, it is possible to obtain an echo signal equivalent to that of a probe with a Gaussian spectrum. It becomes possible to easily obtain the information, and it becomes possible to steadily increase the information obtained by ultrasonic diagnosis.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the emitted ultrasonic waves and reflected echo signals of a general ultrasonic diagnostic device, Section 2.3.4
．． 5 is an explanatory diagram showing the principle of the present invention, and FIG. 6 is a preferred actual mPA of the ultrasonic diagnostic apparatus according to the present invention.
FIG. 7 is a block diagram showing a preferred embodiment of the involution circuit and weight circuit used in the present invention. 10... Vibrator 12... Subject 16... Scanner 20... Deconvoluted circuit and Gaussian weighting circuit 24... Detector 26... Memory 28... CRT 30... Center frequency detector 32... Attenuation coefficient calculator.

Claims (3)

[Claims] (1) In an ultrasonic diagnostic device that emits ultrasonic pulses from a non-Gaussian ultrasonic transducer into a living body, analyzes the echo signals from the tissues in the living body, and measures the attenuation coefficient of the desired tissue, the echo signals are deconvoluted. It includes a deconvolution circuit and a Gaussian weighting circuit that perform processing to remove the probe-specific spectrum and perform Gaussian weighting processing to convert the echo signal into a Gaussian pulse waveform. An ultrasonic diagnostic device characterized by accurately measuring. (2) In the device according to claim (1), the conversion to the Gaussian pulse waveform is performed simultaneously when the echo signal is directly input to the delay circuit and non-recursive or recursive deconvolution processing of the echo signal is performed. An ultrasonic diagnostic device characterized by: (3) In the apparatus described in either claim (1) or (2), the attenuation coefficient of the object is determined from the shift amount of the center frequency of the echo signal converted into a Gaussian type, and a tomographic image is An ultrasonic diagnostic device characterized by simultaneous display.