JPH0438942A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To enable amplification to almost the same intensity even for reflected signals obtained from all possible depths by setting a gain curve in such a manner that the more a rising rate increases, the greater the depth at which the reflection signal of an ultrasonic pulse is obtained to amplify the reflected signal, with the determination of a gain of a preamplifier based on the gain curve. CONSTITUTION:An ROM 8 of a gain control circuit 4 has a gain curve set as comprising two straight lines that gives a low increase rate at a less depth and a high increase rate at a larger depth When an echo signal is supplied to preamplifiers 3-3, a gain value is read out corresponding to a depth at which the echo signal is obtained and a gain value of the preamplifiers 3-3 is set through a D/A converter 9. Thereafter, the echo signals are amplified by the gain and delayed with delay circuits 6-6 to be added in an adder 7. The results are sent to a display system to be shown as ultrasonic image. This enables adjustment to almost the same intensity for echo signals obtained at all possible depths.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Application Field) The present invention relates to an ultrasound diagnostic method in which an echo signal received by an ultrasound probe is amplified and then post-processed to generate an ultrasound image. Regarding equipment.

(Prior Art) Ultrasonic diagnostic apparatuses are currently widely known as one of the methods for non-invasively examining tomographic images of soft tissue of a living body.

Ultrasonic diagnostic equipment emits ultrasonic pulses from the end face of an ultrasonic probe into a living body, and receives reflected waves from the pulses reflected between living tissues, that is, locations where there is a difference in acoustic impedance, as echo signals. , based on which an ultrasound image of the inside of a living body is generated.

At this time, the echo signal obtained between living tissues is attenuated as the distance (in other words, the depth) from the emission position of the ultrasound pulse to the reflection position where the echo signal is obtained increases, so the received echo signal is attenuated at the reflection position. must be amplified according to the depth.

For this reason, conventionally, a gain value that increases linearly with increasing depth is set in advance, and the echo signal is amplified using this gain value, so that the intensity of the echo signal obtained at each depth is the same. It was adjusted so that

(Problem to be solved by the invention) However, in reality, the attenuation rate of an echo signal with respect to distance does not change according to a single linear function, and the attenuation rate increases as the distance increases. Another drawback is that it is not possible to accurately adjust the intensity of the echo signal.

Therefore, if the increase rate of the gain value is set so that the strength of the echo signal obtained at a short distance is suitable, the sensitivity of the echo signal obtained at a long distance will not be the same; If the amplification factor of the gain value is set so that the intensity of the echo signal obtained is suitable, the output of the preamplifier and subsequent circuit will be saturated by the echo signal obtained at a short distance, making it impossible to obtain a clear ultrasound image. There was a problem.

This invention was made in order to solve such conventional problems, and its purpose is to provide ultrasonic diagnostics that can precisely adjust the intensity of echo signals obtained at any depth. The goal is to provide equipment.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention emits an ultrasonic pulse generated by a wave transmitting circuit and also emits a reflected signal of the ultrasonic pulse by a subject. In an ultrasonic diagnostic apparatus that has a receiving ultrasound probe, a reflected signal obtained by the ultrasound probe is amplified by an amplifier, and then post-processed to generate an ultrasound image, the reflected signal from the subject is The present invention is characterized in that it includes a gain storage means for storing a gain curve in which the increase rate increases as the depth obtained increases, and a gain adjustment means for adjusting the gain of the amplifier based on the stored gain curve. .

(Function) With the configuration as described above, a gain curve having a larger rate of increase as the depth at which a reflected signal by an ultrasonic pulse is obtained is stored in the gain storage means.

Then, when the reflected signal is captured from the ultrasound probe,
The reflected signal is amplified based on the gain curve stored in the gain storage means.

Therefore, the reflected signal can be amplified to a nearly constant intensity regardless of the depth at which the foul signal is obtained.

(Example) FIG. 1 is a block diagram showing an embodiment of the present invention.

As shown in the figure, the ultrasonic diagnostic apparatus in this embodiment includes a plurality of balsas 1 to 1 that oscillate high-frequency pulses, converts the high-frequency pulses into ultrasonic pulses, emits them to a subject, and emits the high-frequency pulses to a subject. an ultrasonic probe 2 that receives echo signals reflected by and converts them into electrical signals, a plurality of preamplifiers 3 to 3 that amplifies the echo signals converted to electrical signals, and a gain that adjusts the gain of each preamplifier 3 to 3. It has a control circuit 4.

Further, this ultrasonic diagnostic apparatus includes a rate circuit 5 for determining a time shift of an echo signal due to a difference in the emission position of ultrasonic pulses in the ultrasonic probe 2, and each preamplifier 3 to
Delay circuits 6 to 6 correct the time deviation of the echo signal amplified in step 3 based on the output of the rate circuit 5, and add the echo signals corrected in time by the delay circuits 6 to 6. The adder 7 is provided for outputting to a display system which is a subsequent stage circuit.

As shown in FIG. 2, the gain control circuit 4 includes a ROM 8 in which a function between the depth of the subject (not shown) and the gain value in each preamplifier 3 to 3 is stored, and the gain outputted from the ROM 8 is converted into an analog. each preamplifier 3~3
It has a D/A converter 9 for supplying data to the D/A converter 9.

Next, the operation of this embodiment will be explained.

When a high frequency pulse is emitted from each pulser 1 to 1, the ultrasonic probe 2 converts the high frequency pulse into an ultrasonic pulse and emits it to the subject.

FIG. 3(A) shows the propagation process of the emitted ultrasonic pulse, in this case propagating from the body surface to muscles, fat, and internal organs.

At points where the acoustic impedance changes, such as the boundary between muscle and fat, or the boundary between fat and internal organs, reflections of the ultrasound pulse occur, so this reflected wave is captured by the ultrasound probe 2 as an echo signal. It will be done.

As a result, as shown in FIG. 3(B), for example, an echo signal whose amplitude attenuates as the depth of the reflection position becomes deeper is obtained, and this echo signal is transmitted to the preamplifiers 3 to 3 corresponding to the oscillated balsas 1 to 1. supplied to

Furthermore, the ROM of the gain control circuit 4 shown in FIG.
8, as shown in FIG. 3(C), a gain curve consisting of two straight lines is set such that the increase rate is low at shallow depths and high at deep depths. Then, when the echo signal is supplied to the preamplifiers 3 to 3, a gain value corresponding to the depth at which this echo signal was obtained is read out, and the gain value of the preamplifier 3 to 3 is set via the D/A converter 9. be done.

Thereafter, the echo signal is amplified by this gain value, delayed by delay circuits 6 to 6, and combined by an adder 7, and then sent to a display system and displayed as an ultrasound image.

In this way, in this embodiment, a gain curve is set in advance in the ROM 8 of the gain control circuit 4 so that the gain curve has a low increase rate at a short distance point and a high increase rate at a far distance point, and Since the obtained echo signal is amplified based on this gain curve, it is possible to adjust the intensity of the echo signals obtained at any depth to be approximately the same.

As a result, problems such as insensitivity of echo signals obtained at long distances or saturation of echo signals obtained at short distances are eliminated, and highly accurate ultrasound images can be obtained.

In this embodiment, a gain curve consisting of two straight lines as shown in FIG. 3(C) is set in the ROM 8, but the present invention is not limited to this. It is obvious that a gain curve consisting of three or more straight lines that increases in value or a gain curve in which the gain increases in a parabolic manner may be set.

FIG. 4 is a block diagram showing another embodiment of the gain control circuit 4 shown in FIG. 1.

The figure shows a non-inverting amplifier using an operational amplifier 10, and when diode D is OFF, that is, Vs≦(R,/
R2) ・When VB holds true, the amplification degree A of the operational amplifier 10 is A =
(Rt/R,), and when diode D is ON, that is, Vg
> (R+/R2) "When VB is established, the amplification degree A is A-(1/Rs)+(1/R+)l" Rt
becomes.

Therefore, if you adjust the magnitude of the control signal ■5,
Since the magnitude of the amplification degree A can be switched in two stages, the gain curve shown in FIG. 3(C) can be easily obtained.

[Effects of the Invention] As explained above, in the present invention, a gain curve is set in which the rate of increase increases as the depth at which the reflected signal of the ultrasonic pulse is obtained increases, and the gain of the preamplifier is determined based on this gain curve. and amplifies the reflected signal.

Therefore, reflected signals obtained from all depths can be amplified to approximately the same intensity, resulting in the effect that highly accurate ultrasound images can be obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing the internal structure of a gain control circuit, and Fig. 3 is a block diagram showing an internal structure of a gain control circuit.
Figure (A) is an explanatory diagram showing the propagation process of an ultrasonic pulse, and Figure (B) is a waveform diagram of an echo signal due to this ultrasonic pulse.
FIG. 4C is a diagram showing a gain curve for amplifying the echo signal, and FIG. 4 is a configuration diagram showing another embodiment of the gain control circuit. 1-1...Pulsa 2...Ultrasonic probe 3-3...
・Preamplifier 4...gain control circuit

Claims (1)

[Scope of Claims] An ultrasonic probe that emits an ultrasonic pulse generated by a wave transmitting circuit and receives a reflected signal of the ultrasonic pulse from a subject, and includes a reflected signal obtained by the ultrasonic probe. In an ultrasound diagnostic apparatus that generates an ultrasound image by amplifying it with an amplifier and then post-processing it, a gain memory stores a gain curve in which the increase rate increases as the depth at which the reflected signal from the subject is obtained increases. An ultrasonic diagnostic apparatus comprising: means for adjusting the gain of the amplifier based on the stored gain curve.