JPS61228835A - 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 relates to an ultrasonic diagnostic device, particularly an ultrasonic diagnostic device that transmits ultrasonic waves into a living body, receives the transmitted waves or reflected waves, and measures and displays characteristic distributions within the living body. The present invention relates to an improved ultrasonic diagnostic device that can perform

[Prior Art] The pulse echo method is often used in ultrasound diagnostic devices that transmit ultrasound waves into a living body and measure the echo signals to display tomographic images of the inside of the living body. Generally, dynamic focusing is performed using an array type transducer to transmit a sharp ultrasonic beam to each point in the depth direction.

That is, by dividing the depth direction into multiple regions, transmitting and receiving ultrasound so as to focus on each region, and measuring the ultrasound reflected waves for each region, a tomographic image of the inside of the body can be obtained over a wide range. Furthermore, by increasing the number of divided regions within a certain range, a more precise tomographic image of the inside of the body can be displayed.

However, if the number of divided regions is increased, the ultrasonic beam must be made even sharper, and the number of times the ultrasonic waves are transmitted and received increases by the number of divided regions, so it takes time to form a tomographic image of one cross section. Therefore, it has been proposed to apply the synthetic aperture technique, which is well known in the fields of radar and sonar applications, to ultrasonic diagnostic equipment.

This synthetic aperture method involves transmitting and receiving ultrasonic waves inside a living body by repeatedly transmitting and receiving while moving the transmitting/receiving position, storing the received signal including the phase, and then converting the received waveform so that each point in the living body is focused. This is a method of synthesizing to obtain an image signal at each point, and an explanation of the waveform synthesis is shown in FIG.

In the figure, T1. T2. T3...T is a transducer, and when ultrasonic pulses are sequentially transmitted from this transducer, the received waveforms received by the same transducer are Ul (t), U2
(t), U3 (t)-Un (t). At this time, the vibrator T1. T2. T
3. - Focus on point F which is Ql, Q2゜Q3...Qntri from To, and when measuring this point, move it by the time τi required for the ultrasonic wave to go back and forth between each transducer and point 1. The summed waveform S (t) is obtained. That is, it is expressed as τj -2Ri/C (C: speed of sound), which corresponds to adding the amplitudes on the hyperbola f in the figure, and a large amplitude can be obtained. Regarding other points P, T1. T2. The data on T3... (uzt) corresponding to the positional relationship between the point P and the point P becomes the amplitude on the hyperbola p, and when these are added, these amplitudes cancel each other out and become smaller.

Therefore, if the focus is focused on point F, the received waves of LJi(t) will be added in the same phase and the amplitude will become large, so if the position of this focus is sequentially changed, a high-resolution tomographic image can be obtained. is understood.

However, depending on the position of the point F other than the focal point mentioned above, the received signals may be added in the same phase, which means that virtual sound wave interference occurs when each waveform of the focal point F is added, and it looks like an ultrasonic beam. This method has the disadvantage of causing a phenomenon that appears to be radiated by radiation, a phenomenon generally referred to as a sidelobe, which poses a problem of deteriorating the image quality of tomographic images.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to remove side lobes in an ultrasonic diagnostic apparatus using a synthetic aperture method and to display a good image of characteristic distribution in a living body. The purpose of the present invention is to provide an ultrasonic diagnostic device that can perform

[Configuration of the Invention] In order to achieve the above object, the present invention provides a transceiver that transmits ultrasonic waves into a living body and receives a plurality of transmitted waves or reflected waves from within the living body, and a transceiver that transmits the plurality of received signals. A logarithmic amplifier that performs nonlinear amplification, a memory that separately stores the plurality of nonlinearly amplified received signals, and a signal at a desired focal position in the living body from the stored plurality of received signals by adjusting the phase and synthesizing the signals. The ultrasonic diagnostic apparatus includes a computing unit that performs calculations, and is characterized in that a plurality of ultrasonic reception signals are each nonlinearly amplified and stored, and then synthesized to measure and display a characteristic distribution within a living body.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

The characteristic feature of the present invention is that it is equipped with a logarithmic amplifier that nonlinearly amplifies the received ultrasound signal, so it is possible to remove sidelobes that occur in ultrasound diagnostic equipment that uses the synthetic aperture method. This sidelobe removal will be explained based on the following.

Points F and P in the living body are sufficiently far from the oscillator,
T1. T2. Since the lines connecting T3/Tn to points F and P can be considered parallel, the direction of point P is θ from the direction of point F as shown in the figure.
Consider the case in the corner direction. If the sidelobe signal from point P when focused on point F has the waveform shown in the second figure on the left, the received waves received by each vibrator are shifted by time τ. The time τ is expressed as d τ = -sin θ (d: distance between transducers, C: speed of sound), and in the formula C τ - 2 d sin θ that is modified from this, when C τ is an integral multiple of the wavelength λ (C τ - λ )
The received waves interfere. The direction angle θ- of the point P at this time is expressed as -λ θ--are sin'(-) (1: integer) d.

That is, when point P is in the θ-force direction, the reflected waves from point P are added in the same phase (FIG. 2C), resulting in a large amplitude and a side rope appears, and is strongest in the case of ■-1.

Next, consider the side 0-p in the case of -1 (in the θ1 direction).

If the directivity of each transducer is r(θ), in the conventional device, each received waveform is added linearly, so the side rope in the θ1 direction is nar, where the amplitude is a1 and the number of transducers is n. (θ1) ... (1)
This directivity r(θ) is expressed as θ=
0 and is usually normalized to r(0)=1, so the main lobe at point F is nar(0) −na...(
2).

The linearly amplified received wave signal is generally amplified again using a logarithmic amplifier and displayed as an image.
If the amplifier input signal ■ is smaller than the noise level ■δ, the output is treated as 0, and only if it is larger, the input signal is logarithmically amplified. The amplifier output ■
. Expressed as a formula, βlog(v,/δ)...δ×v・v−0−・δ<lv, I−βlog(IV・1/δ)…δ≧v.

(β: constant) becomes.

Therefore, if we logarithmically amplify the side lobe (1) equation and the main lobe (2) equation described above, we can substitute the equation (3) for δ<v- in the equation V-δ1oo(vH/δ). This difference can be expressed as δlog (na/δ)−δlog (nar(θ
1)/δ)-δ+oa (1/r(θ)) ・
...(4), and this equation (4) represents the difference between the main lobe level and the id lobe level.

In contrast, in the apparatus according to the present invention, each vibrator output is logarithmically amplified separately and added. In other words, the sidelobe signal before being added is ar(θ1
), and the main rope signal is a (ir(0) −
1), so if we logarithmically amplify this using equation (3), we get
βlog (ar (θ1)/δ) and βtoo(a/δ
). Then, if these signals are added, the side lobe level is nalog(ar(θ1/δ)) and the main lobe level is n1O(J(a/δ)), so the difference between them is n βIog(a/δ) = nβlog(ar(θ1)/δ) −βtoo (1/r(θ1))0...(5
).

Therefore, when comparing equations (4) and (5), βloa
(1/r(θ1)) ) βtoo (1/V (θ1)) (+”+ O<r(θ)<1), and the difference between the main lobe level and the side lobe level between the conventional device and the present invention is A big distance arises.

That is, it is understood that according to the present invention, it is possible to increase the difference between the main lobe level and the side lobe level, and thereby the side lobe signal can be effectively removed.

FIG. 3 shows a preferred embodiment of the invention.

The ultrasonic transmitter/receiver 10 includes an array transducer 12, a multiplexer 14 for controlling vibration of the array transducer, and an oscillator 1.
6 is provided, and the electrical signals obtained from the oscillator 16 under the control of the controller 18 are supplied to the multiplexer 14 via the driver 20, and the electrical signals are sequentially converted into ultrasound waves and transmitted into the living body. be done. Further, reflected waves from inside the living body are received by each of the vibrators, and each wave received by each vibrator is logarithmically amplified by a logarithmic amplifier 22.

The logarithmically amplified received wave signal is then supplied to the orthogonal detector 24, where hologram conversion is performed. That is, ``The electric signal output from the oscillator 16 is supplied to the multiplier 28.30 via the transfer device 26, and the amplified received signal is multiplied by a cosine wave and a sine wave having the center frequency of the transmitted ultrasonic wave,
If this is input to low-pass filters 32 and 34 and the carrier wave is removed, a signal (hologram) having information on the amplitude and phase of the received signal is obtained.

In this embodiment, the logarithmic amplifier is placed before the quadrature detector 24, but it can also be placed after the quadrature detector 24, as shown in FIG. 4(C). Of course, it goes without saying that it must be placed before the memory 40.

The hologram obtained in this way is transferred to the A/D converter 3.
At step 6.38, the signal is A/D converted and supplied to the memory 40, where it is temporarily stored. Generally, in an A/D converter or a digital memory, the larger the fluctuation range of the input signal, the larger the number of bits of the A/D converter and the larger the memory capacity. However, in the apparatus according to the present invention, the amplitude variation range of the hologram described above is compressed by using the logarithmic amplifier 22, and signal recording or processing becomes easy.

Next, the hologram recorded in the memory 40 is transferred to a multiplier 42.
．． 44, the above-mentioned cosine wave and sine wave are multiplied again, and an adder 46 reproduces the received wave signal before orthogonal detection. The output of the adder 46 is input to the arithmetic unit 48, and by moving the received signals of each transducer by an appropriate time interval and performing an addition operation, information at each focal point within the living body can be obtained, and the tomographic image inside the living body is an image. An image is formed on the TV monitor 52 via the memory 50.

Furthermore, if the content of the area of the memory 40 corresponding to each transducer is controlled to be repeatedly updated, the latest hologram is always stored, and the TV monitor 52 displays a tomographic image based on the updated new information as appropriate. It becomes possible to display.

In this example, the transmitted and received signals are transmitted and received using the same transducer, but the ultrasonic waves can also be received by a transducer different from the transducer that transmitted them, or by mechanically scanning a pair of transducers. It is possible to transmit and receive ultrasonic waves, and the same effect can be obtained even if the received ultrasonic waves are not only reflected waves from inside the living body but also transmitted waves.

[Effect of the invention 1 As explained above, according to the present invention, since the ultrasonic transmitted waves or reflected waves in the living body received by each transducer are nonlinearly amplified and recorded, synthetic aperture technology can be used to The side loops that occur when combining images at each focal point within a living body are removed, making it possible to obtain highly accurate tomographic images of the living body through transmitted and received waves, making it possible to provide useful information for disease diagnosis. .

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the synthetic aperture method, Fig. 2 is an explanatory diagram of the side rope, Fig. 3 is an explanatory diagram showing a preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention, and Fig. 4 is an explanatory diagram of the logarithmic amplifier. It is an explanatory diagram of arrangement. 10... Transmitter/receiver 12... Array transducer 18... Controller 22... Logarithmic amplifier 40... Memory 48... Arithmetic unit 52... TV monitor.

Claims (2)

[Claims] (1) In an ultrasound diagnostic device that transmits an ultrasonic pulse beam into a living body, receives and amplifies transmitted waves or reflected waves, and displays them, the ultrasound is transmitted into a living body and multiple transmitted waves or reflected waves are generated from within the living body. a logarithmic amplifier that nonlinearly amplifies each of the plurality of received signals; a memory that separately stores the plurality of nonlinearly amplified received signals; an arithmetic unit that adjusts the phase of each signal at a desired focal position and performs a synthesis operation;
An ultrasonic diagnostic apparatus characterized by measuring and displaying an in-vivo characteristic distribution by nonlinearly amplifying and storing a plurality of ultrasonic reception signals and then composing them. (2) In the device according to claim (1), a single transmitter/receiver is moved to sequentially repeat the transmission of ultrasonic waves, while at the same time sequentially receiving the transmitted ultrasonic waves while moving;
An ultrasonic diagnostic apparatus characterized in that the plurality of received signals are stored and then synthesized.