JPS61290939A - Ultrasonic sonic speed measuring 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 [Technical Field of the Invention] The present invention relates to a device that forms an ultrasonic beam that intersects within a subject, such as a living body, and measures the speed of sound based on the propagation time of the beam.

[Technical background of the invention and its problems] In the field of ultrasonic diagnostic technology, tomographic images of a living body are mainly obtained by scanning pulsed ultrasound inside a living body and displaying the intensity of reflected waves from inside the living body. The B-mode display was used to diagnose the shape of internal organs and the presence of foreign substances such as cancer based on the B-mode display. In other words, diagnosis was performed based on information about the morphology inside the body.

However, recently there has been a growing demand for this B-mode device to obtain ultrasound information not on the morphology of living tissues but on the properties of the tissues themselves and to use this information for diagnosis.

As a technology to meet these demands, the directivity of the ultrasound beam between the transmitting transducer and the receiving transducer is crossed within the body, and the reflected waves from the directional intersection within the body are detected, thereby changing the process from ultrasound generation to reflected wave detection. Until the end II
A method (hereinafter also referred to as sound velocity measurement using the crossed beam method) has been proposed in which the speed of sound in living tissue is detected by measuring the propagation time (hereinafter referred to as propagation time).

The sound velocity measurement using this crossed beam method will be explained in more detail with reference to FIG. In the figure, 10 is a linear array type ultrasonic probe (transducer) formed by arranging a plurality of ultrasonic transducers in an array, and the transducer surface is placed on the body surface 11 of the living body. Here, among the plurality of transducer groups, the left end transducer group 21 is used for transmission, and the right end transducer group 22 on the opposite side is used for reception, and a desired delay is given to each when transmitting and receiving. The transmission beam BMz and the reception beam BM2 scan so as to intersect at a part 25 of the living tissue, and the time (propagation The speed of sound is determined by calculating the time) and substituting this into the formula for calculating the speed of sound.

By the way, since the ultrasound beam has a finite beam width,
The intersection area has a finite area as shown by the hatched portion 25 in FIG. For this reason, the waveform received by the reception transducer 22 has a temporal lag corresponding to the width of the intersection area 25, as shown in FIG. 5<a>. In the case of the conventional sound velocity measurement, by determining the arrival time of the peak value in the flooring,
Alternatively, by determining the time of the part where the center of gravity is located, this was measured as the propagation time.

However, in vivo, ultrasound generally becomes more attenuated as propagation progresses. Therefore, the magnitude of this attenuation will affect the distribution of reflected signals from the intersection area 25. That is, if there was no attenuation, a waveform like the broken line P1 shown in FIG. 5(b) would be obtained, but in reality, due to attenuation, the received waveform is reduced overall as shown by the solid line P2. If the propagation time is measured using the peak value or the center of gravity based on this, an error will occur.

This error will change depending on the degree of attenuation,
As a result, a large error will be given to the measured sound velocity value of the living tissue.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an ultrasonic sound velocity measuring device that corrects the influence of attenuation of ultrasonic waves within a subject.

[Summary of the Invention] In order to achieve the above object, the present invention arranges transmitting and receiving transducers at two spatially different points on a subject to form beams that intersect at a desired site within the subject. In the apparatus for measuring the speed of sound based on the propagation time from transmission to reception of the beam, the device includes means for detecting attenuation of the crossed beams, and a correction signal is created based on the output of the attenuation detecting means. The present invention is characterized in that it includes a means for correcting the received signal using the correction signal.

[Embodiments of the invention] Hereinafter, the present invention will be specifically explained with reference to Examples.

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus to which the ultrasonic sound velocity measuring apparatus of the present invention is applied. FIG. 10 shows a first wave transmitter that transmits and receives ultrasonic waves from different angles toward a desired site within the subject 1. Second ultrasonic wave transmitting/receiving means (ultrasonic probe: hereinafter referred to as "transducer") 21, 22. The ultrasonic probe 13 is equipped with this first. Second probe 1
1 and 12; 14 is a drive circuit for driving the first . A receiving circuit that amplifies the echo signal detected by the second probe 11, 12; 15 is a data capturing means that captures the echo component from this receiving circuit 14 for a predetermined time width; 16 is this data capturing means 15; and operation 1 of the drive circuit 13
17 is a frequency analysis means for frequency analysis of the output of the data acquisition means 15;
Reference numeral 18 denotes a storage means for storing the analysis result of the frequency analysis means 17 as necessary, and 19 stores the received waveform based on the analysis result of the frequency analysis means 17 which is inputted through the storage means 18. Calculating means calculates the propagation time t by determining the peak value, and calculates the speed of sound C based on this propagation time t, and 20 is a display means for displaying the calculation results.

The transmission/reception control means 16 performs control such as scanning the transmission beam BM1 using the one transducer 21 for transmission, and control that operates the other transducer 22 so as to receive the reflected beam BM2 at this time. At the same time, the transducer 21 used for the transmission is immediately switched to this transducer 21.
Control is performed so that the reflected beam BM3 from the intersection 25 can be received.

An attenuation detection means 23 is provided, and inputs the received signal obtained to the receiving circuit 14 at the timing when the reflected beam BM3 based on the transmitted beam BM1 is received by the transducer 21, thereby causing the ultrasonic beam BM to
Attenuation is detected from the change in the amplitude of step 3.

Further, a correction signal creating means 24 is provided, which inputs the attenuation information detected by the attenuation detecting means 23, that is, the slope of the waveform amplitude, creates a signal having an opposite slope, and inputs the signal to the calculating means 19. It looks like this.

The calculation means 19, which receives the correction signal from the correction signal generation means 24, corrects the received waveform stored in the storage means 18 using the correction signal, calculates the peak value of the corrected received waveform, and calculates the peak value of the corrected received waveform. It is now ready to process. In addition to the above-mentioned functions, this calculation means 19 also has a function of averaging received data based on multiple transmission and reception scans to obtain a waveform with less scattered components (speckles), as will be described later. There is.

Next, the operation of the device will be explained.

FIG. 2 is an explanatory diagram of a scanning method using the linear array probe 10 in the device. In the present invention, as described above, in order to detect reflected waves from intersections, a part of the transducer group 21 constituting the array transducer is used as a transmitting transducer to generate a transmitting beam BMI,
Next, another part of the transducer group 22 is used as a receiving transducer to detect the reflected beam BM2 from the point 25 where the directivity intersects, and furthermore, the transducer group 21 used for the transmission is used as a receiving transducer to detect the reflected beam BM2 with the same directivity as the transmitting transducer. The reflected beam BM3 is received by the receiver.

The reflected waves received in this way are each sent to the receiving circuit 1.
4, the reflected beam BM2 in the cross direction is led to the data acquisition means 15, and the reflected beam BM3 in the transmission direction is dedicated to the attenuation detection means 23. The waveform input to the attenuation detection means 15 is such that the amplitude of the reflected wave changes over time as shown in FIG. 3(a).
However, if the waveform is detected only once, the speckle noise SP is included in the waveform, and accurate amplitude detection cannot be performed. The waveform shown in FIG. 3(b) is obtained by averaging the data. Then, the slope of the portion of this attenuated waveform corresponding to the width of the crossing area 25 is determined, and this data is used to create a correction signal in the next stage. The correction signal generating means 24 generates a desired correction signal, for example, correction data having a slope in the opposite direction to the slope, from the data corresponding to the slope of the attenuation waveform, and outputs the correction signal to the calculation means 19. On the other hand, the data acquisition means 15 receives the reflected wave BM2 from the intersection 25 based on the several tens of scans.
is taken in, the frequency of each reflected wave is analyzed by the frequency analysis means 17, and the frequency is temporarily stored in the storage means 18.

The calculation means 19 performs the following calculations. First, the data for each scan stored in the storage means 18 is sequentially taken in and averaged, and then the data is corrected based on the relationship between the data obtained by the averaging and the correction data. The data corrected in this way is shown in Figure 3 (C).
Indicated by JPt. A solid line P2 indicates data before correction. Time t at the peak point of this corrected data P1
seek. This time is the propagation time. Once the propagation time t is determined, the distance y between the transmitting and receiving points and
Since the crossing angle θ of the crossing beams is known, the sound speed C can be determined by the following equation (1).

(i=V/(t-sin θ) −(1) The above-mentioned sound speed C is displayed on the display means 20 by an appropriate method.The B-mode image based on the scanning method of FIG.
The received waveforms before and after the correction shown in FIG. 3(C) may be displayed simultaneously or sequentially on the display means 20.

As described above, even if the ultrasonic wave attenuates in the living body, its peak value or center of gravity is determined based on the waveform corrected by the correction data, so accurate measurement of propagation time t and sound speed C can be performed.

The present invention is not limited to the embodiments described above, and various modifications are possible.

For example, the attenuation detection means 23 and the correction signal creation means 24
A conversion table (storage means) having each function may be used. That is, the average attenuation factor in each part of the biological tissue is determined in advance, the corresponding correction data is stored, and the corresponding correction data is selected from the stored data using a tissue-specific drive signal from the transmission/reception control means 16. It may also be input to the calculation means.

[Effects of the Invention] According to the present invention described in detail above, it is possible to provide an ultrasonic sound speed measurement device that can improve the accuracy of sound speed measurement in a subject's internal tissue using the crossed beam method.

Therefore, tissue properties can be diagnosed more accurately based on the speed of sound.
In particular, it is effective in ensuring the possibility of application to liver cirrhosis, fatty liver, and bimanic liver diseases.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the device of the present invention, Fig. 2 is an ultrasonic scanning mode diagram for explaining its operation, and Fig. 3 (a).
~(C> is a waveform diagram of each part for explaining the operation of the device,
Fig. 4 is an explanatory diagram of the conventional ultrasonic scanning method, Fig. 5(a),
(b) is a waveform diagram for explaining problems with the conventional method. 10... Ultrasonic probe, 19... Calculating means, 21.
22... Transmission/reception transducer, 23... Attenuation detection means, 24... Correction signal creation means.

Claims (3)

[Claims] (1) Place transmitting and receiving transducers at two spatially different points on the subject, form beams that intersect at a desired location within the subject, and obtain the propagation time from transmission to reception of the crossed beams. , a device for measuring the speed of sound based on this, comprising means for detecting attenuation of the crossed beams, means for creating a correction signal based on the output of the attenuation detection means, and correcting the received signal using the correction signal. 1. An ultrasonic sound velocity measuring device, comprising: calculation means. (2) The ultrasonic sound speed measuring device according to claim 1, wherein the attenuation detecting means calculates the attenuation value based on a change in the amplitude of the scattered wave near the beam intersection depending on the distance. (3) The attenuation detection means and the correction signal creation means are comprised of storage means in which correction values corresponding to attenuation in each part of the living body are stored in advance. The ultrasonic sound velocity measuring device described above.