JPS6241020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic measuring device, and in particular, when obtaining a tomographic image of a specimen using reflected ultrasound waves, the tomographic image of a deep position can also be The present invention relates to an ultrasonic measurement device that can be used in an ultrasonic diagnostic device that can display images with approximately the same brightness as a tomographic image.

FIG. 1 shows a block system diagram of an example of a general ultrasonic diagnostic apparatus. In the figure, reference numeral 1 indicates a specimen, with which a probe 2 is acoustically contacted. The probe 2 is driven by the output signal of the transmission amplifier 4 under the control of the scanning control section 3 and emits ultrasonic waves into the specimen 1 . The ultrasonic waves emitted from the probe 2 are as shown in Fig. 2.
Boundaries 1a, 1b, 1 with different acoustic impedances
c and 1d due to impedance mismatching, and the reflected waves are sequentially received by the probe 2 starting from the shallowest position, where they are subjected to acoustic-to-electrical conversion. The reflected wave reception signal taken out from the probe is
After being amplified by a receiving amplifier 5, it is supplied to a logarithmic amplifier 6.

In the logarithmic amplifier 6, since the amount of attenuation of the ultrasonic wave within the specimen 1 is approximately proportional to its propagation path length, the amount of attenuation of the reflected wave from the boundary 1a closest to the surface of the specimen 1 shown in FIG. 2 is small. On the other hand, in view of the fact that the amount of attenuation of the reflected wave from the boundary 1d located deep in the sample 1 is large, the input/output characteristics of the logarithmic amplifier 6 are, for example,
As shown by the broken line in the figure, the characteristics have been selected to logarithmically amplify and output the input received signal voltage of 1V or less. In FIG. 3, a _i +b _i , c _i , and d _i are the received signal input voltages at the boundaries 1a, 1b, 1c, and 1d, respectively;
a _p , b _p , c _p , and d _p indicate the output voltages of the logarithmic amplifier 6 at that time.

The received signal that has passed through the logarithmic amplifier 6 is rectified by a rectifier circuit 7 and then supplied to a display 8, where the reflected position is displayed by brightness modulation on a predetermined scanning line based on the output of the scan control section 3. Thereafter, ultrasonic waves are emitted intermittently from the probe 2 at a predetermined period in the same manner as described above, and the ultrasonic emission direction is scanned according to the output signal of the scanning circuit 9, and the display 8 is accordingly scanned. Displaying the current reflection position by brightness modulation on another scanning line is repeated, and the tomographic image of the specimen 1 is displayed on the display 8.

However, in the above device, the number of logarithmic conversion digits of the logarithmic amplifier 6 was conventionally constant (for example, about 4 digits) regardless of the received signal level, so even if logarithmic amplification is performed, the reflected wave reception signal from a deep position is The output level is low, and the image at a deep position is displayed darkly.On the other hand, the output level of the reflected wave reception signal from a shallow position is high, and the image at a shallow position is displayed brightly, and the brightness of the image varies depending on the depth. The drawback was that the image quality changed.

An object of the present invention is to display images of reflected waves from shallow positions with low attenuation as wide as possible by changing the number of logarithmic conversion digits of a logarithmic amplifier according to the amount of attenuation of reflected waves. death,
Further, it is an object of the present invention to provide an ultrasonic diagnostic apparatus that can display an image of a reflected wave from a deep position with a large amount of attenuation with approximately the same brightness as an image from a shallow position.

The present invention emits ultrasonic waves into a specimen, receives the reflected waves, performs acoustic-to-electrical conversion, and logarithmically amplifies the received signal using a logarithmic amplifier, and uses this logarithmically amplified signal to provide tomographic information of the specimen. an ultrasonic measuring device for obtaining the ultrasonic waves, which comprises means for partially or entirely changing the logarithmic conversion characteristics of the logarithmic amplifier according to the amount of attenuation of the ultrasonic waves within the specimen, and is supplied to a display device. The above drawbacks are eliminated by keeping the signal level at a substantially constant level regardless of the amount of attenuation within the specimen, and each embodiment thereof will be described with reference to the drawings from FIG. 4 onwards.

FIG. 4 shows a block system diagram of the first embodiment of the essential parts of the apparatus of the present invention. In the figure, a received signal taken out from the receiving amplifier 5 shown in FIG. 1 enters an input terminal 10 and is branched into a plurality of systems. The number of branches may be any number as required, but in this case, the received signal is divided into four branches and the received signal is passed through the variable gain amplifiers 11 ₁ , 11
₂ , ₁₁₃ , and ₁₁₄ , respectively. The respective gains of these variable gain amplifiers 11 ₁ to 11 ₄ are determined by the controller 12 , counter 13 , memory 14 and
Each of the DA converters 15 ₁ to 15 ₄ is variably controlled independently of each other by output control signals from a control circuit. That is, the counter 13 is supplied with the output of the controller 12 and increments by 1, and the counting output is applied to the memory 14 as an address designation signal. Data stored in the memory 14 is read out by the output of the controller 12. memory 1
4 stores in advance data for appropriately changing the gains A ₁ to _{A 4} of the variable gain amplifiers 11 ₁ to 11 ₄ each time the address increases by 1. memory 1
For example, the lower 4 bits of the 16 bits of 4 are digital-to-analog converted by DA converters 15 ₁ to 15 ₄ , respectively, and then applied to the gain control terminals of variable gain amplifiers 11 ₁ to 11 ₄ . , whose gain is variably controlled.

For example, immediately after emitting ultrasonic waves until a reflected wave from a relatively shallow position is received, the gain of variable gain device 11 ₁ is 0 dB, and that of variable gain device 11 ₂ is 0 dB.
20dB, that of 11 ₃ is 40dB, that of 11 ₄ is
60dB, while the logarithmic amplifier 6 ₁
Assuming that the input/output characteristics of each of the variable gain amplifiers 11 ₁ to 11 are as shown in _FIG .
₄ , the output signal voltages passing through the logarithmic amplifiers ₆₁ to ₆₄ , respectively, and the input signal voltages at the input terminal 10 are as shown in FIG.
₁ , ₂ , ₃ and ₄ , respectively. Here, ₁ , ₂ , ₃ and ₄ are the above input signal voltages and logarithmic amplifiers ₆₁ , ₆₂ , _63, respectively.
A characteristic diagram of the output signal voltage and the output signal voltage of ₆₄ is shown.

The respective output signals of the logarithmic amplifiers ₆₁ to ₆₄ are added and synthesized by an adder 16, and then sent to the output terminal 1.
7 to the rectifier circuit 7 shown in FIG. Therefore, the characteristics of the input signal voltage at the input terminal 10 and the output signal voltage at the output terminal 17 at this time are as shown by _a in ^FIG . The characteristic is that the output voltage increases linearly.

As a result, the received signal from a relatively shallow position is at a much higher level than the noise level of the amplifier, etc., and the number of digits of logarithmic conversion is increased to 4 digits, as shown by _a in Figure 6A. Therefore, images can be displayed with a wide dynamic range from large signal levels to small signal levels.

Next, during the period from when the reflected wave from a relatively shallow position is received until the reflected wave from a relatively deep position is received, the variable gain unit 1
Each gain of 1 ₁ , 11 ₂ , 11 ₃ , 11 ₄ is
Assuming that the voltages are varied to 30 dB, 40 dB, 50 dB, and 60 dB, the characteristics of the input signal voltage and the output signal voltage of the logarithmic amplifiers _{61 to 64} are shown in FIG.
₂ , ' ₃ , and ' ₄ . Therefore, the input signal at the input terminal 10 is extracted from the output terminal 17 with logarithmic amplification characteristics as shown by _b in FIG. 6B. In other words, during this reception period, the slope of the logarithmic transformation is large, and the reflected wave from a relatively deep position has a large attenuation amount, but the received signal of the reflected wave is logarithmically amplified as shown by _b in Figure 6B. By imparting characteristics to the signal level and making it approximately the same level as the signal level during the first reception period, the signal is supplied to the rectifier circuit 7 shown in FIG. An image created by reflected waves from a relatively deep position is displayed with about the same brightness as the image created by .

Next, after the period in which the reflected waves from the above-mentioned relatively deep position are received, the reception period until the next ultrasonic wave is emitted is carried out by the variable gain amplifiers 11 ₁ , 11
For example, the gains of ₂ , 11 ₃ , and 11 ₄ are all
Variably controlled to 60dB. As a result, the input signal voltage at the input terminal 10 and the logarithmic amplifiers 6 ₁ , 6 ₂ , 6
The output signal voltages ₃ , 6, _and 4 all have the same characteristics as shown in Figure 6C as ' ₁ , ' ₂ , ' ₃ , and ' _4, respectively, and the input/output characteristics are logarithmic as shown in Figure 5. The input/output characteristics are the same as those of the amplifiers 6 ₁ to 6 ₄ . Therefore, the input/output characteristics of the input terminal 10 and the output terminal 17 during this reception period are as shown in FIG.
As ^shown in _c , the output signal voltage is constant at 4 V for an input signal voltage of 10 ^-3 V or higher;
For an input signal voltage of ~10 ^-3 V, the output signal voltage increases linearly, and the slope of logarithmic conversion becomes steep.

As a result, during this reception period in which a reflected wave whose reflection position is extremely deep and the amount of attenuation is extremely large is received, the received signal is greatly amplified and output at approximately the same level as in the first reception period. So,
An image resulting from a reflected wave from a very deep position is displayed on the display 8 shown in FIG. 1 with approximately the same brightness as an image resulting from a reflected wave from a relatively shallow position.

As described above, according to this embodiment, as the attenuation of the reflected wave increases, that is, as the input signal voltage decreases, the slope of the logarithmic conversion increases as shown in FIG. By keeping the level always at a substantially constant level, images at deep positions can be displayed on the display 8 with the same brightness as images at shallow positions, regardless of the depth of the reflected position of the specimen 1.

Next, a second embodiment of the apparatus of the present invention will be described. FIG. 8 shows a block system diagram of the second embodiment of the main part of the apparatus of the present invention. In the figure, the same parts as in FIG. 1 are given the same numbers. Assume that the input/output characteristics of the logarithmic amplifier 6 are as shown in FIG. A correction amplifier 18 is provided after the logarithmic amplifier 6.
is provided, and its gain is variably controlled by the output signal of the memory 21. memory 21
The address is designated by the output of the counter 20 that counts the output of the controller 19, and the stored data at the designated address is read out in accordance with the output of the controller 19. Here, the read data of the memory 21 is transferred to the correction amplifier 18 as time passes.
It is said that this is data that changes the gain to an appropriate amount.

That is, since the input signal voltage of the logarithmic amplifier 6 becomes a small level as time passes within the ultrasound transmission cycle, first, the gain of the correction amplifier 18 is set to a predetermined value G for a certain period of time immediately after ultrasound transmission, and
After that, as time passes, the input signal voltage will be 2G when it is around 10 ^-2 V, and 2G when it is around 10 ^-3 V.
4G, the characteristics are controlled in the direction of the arrow as shown in FIG.

This allows the input signal voltage to be 1V, 10 ^-1 V,
In both cases of 10 ^-2 V and 10 ^-3 V, correction amplifier 1
The output signal voltages of 8 are shown in FIG. 9 by broken lines V ₁ , V ₂ , V ₃ ,
It is equal to about 1V as shown by _V4 . Therefore, in the case of this embodiment as well, the gain of the correction amplifier is controlled to be large as the input signal voltage decreases (as time passes), and as a result, regardless of the depth of the reflection position of the specimen 1, the image at a deep position is The image can also be displayed on the display 8 shown in FIG. 1 with the same brightness as an image at a shallow position. This embodiment has a smaller number of circuit components than the first embodiment, and can be constructed at low cost.

Note that the first embodiment and the second embodiment can also be used in combination.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of a general ultrasound diagnostic device, Figure 2 is a diagram showing ultrasound reflection positions (boundaries) within a specimen, and Figure 3 is the input/output characteristics of a logarithmic amplifier in a conventional device. FIG. 4 is a block system diagram showing a first embodiment of the essential parts of the device of the present invention; FIG. 5 is a diagram showing an example of the input/output characteristics of the logarithmic amplifier in FIG. 4; Figures A to C are diagrams showing the input/output characteristics of each part for explaining the operation of Figure 4, and Figure 7.
The figure shows the relationship between the input voltage and the number of logarithmic conversion digits of the device shown in FIG.
FIG. 9 is a diagram showing the input/output characteristics of each part of FIG. 8, and FIG. 10 is a diagram illustrating a method of controlling the gain of the correction amplifier in FIG. 9. 1...Specimen, 2...Probe, 6,6 ₁ to 6 ₄ ...
... Logarithmic amplifier, 8 ... Display, 10 ... Received signal input terminal, 11 ₁ to 11 ₄ ... Variable gain amplifier,
14, 21...memory, 16...adder, 17...
...output terminal, 18...correction amplifier.

Claims (1)

[Claims] 1. Ultrasonic waves are emitted into the specimen, the reflected waves are received, and the received signal obtained by acoustic-to-electrical conversion is logarithmically amplified by a logarithmic amplifier, and the logarithmically amplified signal is used to An ultrasonic measurement device for obtaining tomographic information, comprising: a plurality of logarithmic amplifiers; a variable gain amplifier provided before each of the logarithmic amplifiers and whose gain is variable; It includes a control circuit that performs variable control so that it increases as time passes or changes in a functional manner as appropriate depending on the object to be measured, and an adder that adds each output signal of the plurality of logarithmic amplifiers. An ultrasonic measuring device featuring: