JP2021183036A - Sound speed measurement method and apparatus for ultrasonic wave - Google Patents

Abstract

To provide a sound speed measurement method for a lateral ultrasonic wave which can be used for estimating the shear elasticity.SOLUTION: A sound speed measurement method for an ultrasonic wave according to the present invention comprises: the first step of emitting an ultrasonic wave at an incident angle exceeding a critical angle of a longitudinal wave through a soft tissue 6b to a long bone 1b by using a transmitter 2b of the ultrasonic wave within a plane including a long axis of the long bone 1b of a human body; the second step of receiving the ultrasonic wave propagated in the long bone 1b, propagated in the soft tissue 6b and leaked out from the surface of a living body with a receiver 3b and converting the ultrasonic wave into an electric signal; and the third step of measuring the sound speed of the transverse wave in the ultrasonic wave propagated in the long bone 1b on the basis of the electric signal received at plural positions having different distances with respect to the transmitter 2b in a direction in parallel with the long axis of the long bone 1b with the receiver 3b.SELECTED DRAWING: Figure 15

Description

The present invention relates to a method and an apparatus for measuring the speed of sound of ultrasonic waves propagating in the body load direction for a long bone under a load such as a femur or a radius.

A method of measuring bone density by ultrasonic waves has been put into practical use for preventive diagnosis of osteoporosis. Among them, in the calcaneal ultrasonic measurement method, the bone mass is estimated from the average sound velocity of the longitudinal wave ultrasonic waves passing through the heel, but the strength and elasticity of the bone cannot be evaluated. In order to evaluate the elasticity of long bones such as the femur, it is necessary to measure the speed of sound of ultrasonic waves propagating in the body load direction (long axis) of the long bones through the soft tissue of the skin.

The method of measuring the speed of sound of ultrasonic waves propagating through long bones and measuring the strength and elasticity of bones from the speed of sound is called the AT (Axial Transmission) method, and is being developed for practical use in Europe. (See Non-Patent Document 1).

"Current Status and Issues of Bone Evaluation Technology Using Ultrasound" Journal of the Acoustical Society of Japan, Vol. 68, No. 6 (issued in 2012) P293-299

On the other hand, in order to evaluate bone, it is necessary to estimate the strength against torsional and shear loads in addition to the strength against compressive loads. In the conventional AT method described above, since the sound velocity of the longitudinal wave mainly related to the compressive stress was measured among the ultrasonic waves, only the compressive elasticity could be estimated and could not be used for the estimation of the shear elasticity.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the AT method and to provide a method and apparatus for measuring the sound velocity of transverse wave ultrasonic waves that can be used for estimating shear elasticity.

In order to achieve the above object, the method for measuring the sound wave of ultrasonic waves according to the present invention is:
First, in a plane including the long axis of the long bone of the human body, the long bone is irradiated with ultrasonic waves at an incident angle exceeding the critical angle of the longitudinal wave through the soft tissue using an ultrasonic transmitter. Steps and
The second step of transmitting the ultrasonic waves propagating through the long bone and further propagating through the soft tissue and leaking from the surface of the living body by a wave receiver and converting them into an electric signal.
The ultrasonic wave propagates through the long bone based on the electric signals received by the wave receiver at a plurality of positions parallel to the long axis of the long bone and at different distances from the transmitter. It is characterized by including a third step of measuring the speed of sound of a transverse wave among ultrasonic waves.

Here, a B-mode image is generated in which the time axis of the luminance signal of the electric signal output from the receiver is the horizontal axis and the position where the receiver receives the ultrasonic waves of the transverse wave is the vertical axis. , It is preferable to calculate the sound velocity of the ultrasonic wave of the transverse wave from the inclination of the B mode image.

Further, it is preferable that the transmitter is composed of a single transducer and generates ultrasonic waves by applying a pulsed drive signal of one sine wave or several waves.

The transmitter and receiver are composed of a plurality of transducers arranged in a direction parallel to the long axis of the long bone, one of which is used as a transducer and the other transducer is received. It is preferable to use it as a vessel.

Further, the ultrasonic sound velocity measuring device according to the present invention that achieves the above object is
A transmitter that irradiates the long bone with ultrasonic waves at an angle exceeding the critical angle of the longitudinal wave through the soft tissue in the plane including the long axis of the long bone of the human body.
A receiver that propagates through the long bones, further propagates through the soft tissue, receives ultrasonic waves leaked from the surface of the living body, and converts them into electrical signals.
The ultrasonic wave propagates through the long bone based on the electric signals received by the wave receiver at a plurality of positions parallel to the long axis of the long bone and at different distances from the transmitter. It is characterized by being provided with a sound velocity measuring means for measuring the sound velocity of a transverse wave among ultrasonic waves.

Here, it is preferable that a water bag is attached to the sound wave irradiation surface of the transmitter and the sound wave reception surface of the receiver.

According to the ultrasonic sound wave measuring method according to the present invention, the sound velocity of transverse wave ultrasonic waves, which is closely related to the shear elasticity of bones, can be measured separately from longitudinal waves, which is difficult with the conventional AT method. It can be used to estimate elasticity. Therefore, it can be a powerful means for improving the level of preventive diagnosis of osteoporosis.

It is a front view (a) and a side view (b) which show the positional relationship between a long bone and a transmitter and a receiver in the simulation which concerns on Embodiment 1 of this invention. It is a figure which shows an example of the waveform of the ultrasonic wave which was irradiated from a transmitter, propagated through a long bone, and then converted into an electric signal by a receiver. It is a figure which shows the B mode image generated based on the received signal of a receiver in the simulation which concerns on Embodiment 1. FIG. It is a graph which plotted the sound wave velocity of the ultrasonic wave calculated from the B mode image of FIG. It is a front view (a) and a side view (b) which show the positional relationship between a long bone and a transmitter and a receiver in another simulation which concerns on Embodiment 1. FIG. It is a graph (No. 1) plotting the sound wave velocity of the ultrasonic wave in the simulation performed by the configuration of FIG. It is a graph (No. 2) plotting the sound wave velocity of the ultrasonic wave in the simulation performed by the configuration of FIG. It is a figure which shows the positional relationship between a long bone, a transmitter, and a receiver in the experiment which concerns on Embodiment 2 of this invention. It is a figure which shows the B mode image generated based on the received signal of a receiver in the experiment which concerns on Embodiment 2. FIG. It is a graph which plotted the sound wave velocity of the ultrasonic wave calculated from the B mode image of FIG. It is a figure which shows the positional relationship between a long bone, a transmitter, and a receiver in another experiment which concerns on Embodiment 2. FIG. It is a figure which shows the B mode image generated based on the received signal of a receiver in the experiment which adopted the configuration shown in FIG. It is a graph (No. 1) in which the sound velocity of the ultrasonic wave calculated from the B mode image of FIG. 12 is plotted. It is a graph (No. 2) plotting the sound wave velocity of the ultrasonic wave calculated from the B mode image of FIG. It is a figure which shows the schematic structure of the ultrasonic sound velocity measuring apparatus which concerns on Embodiment 3 of this invention. It is a block diagram which shows the structure of the sound velocity measuring means of the sound velocity measuring apparatus which concerns on Embodiment 3. FIG. It is a figure which shows the other structure of the receiver in Embodiment 3. FIG.

Hereinafter, the method and apparatus for measuring the sound wave velocity of ultrasonic waves according to the embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
Through simulation, the inventors can detect the transverse wave separated from the longitudinal wave among the ultrasonic waves propagating in the long bones such as the femoral bone and the radius, and based on the result, the sound velocity of the separated transverse wave can be detected. We have found that it can be measured. In this embodiment, the contents of the simulation and the method of measuring the sound velocity of the transverse wave ultrasonic wave will be described.

In this embodiment, the simulation is performed based on the time domain finite difference method generally called the FDTD (Finite-difference time-domain method) method. FIG. 1 shows the positional relationship between the virtual long bone 1 used in the simulation, the transmitter 2 that emits ultrasonic waves, and the receiver 3 that receives ultrasonic waves and converts them into electrical signals. 1 (a) is a front view, and FIG. 1 (b) is a side view.

The long bone 1 is assumed to be a human radius, and has a length of 63 mm, an outer diameter of 12 mm, a thickness of 1.6 mm, and a density of 1.81 × 10 ³ kg / m ³ . Further, as the ultrasonic wave transmitter 2 and the receiver 3, a transducer manufactured by a disk-shaped piezoelectric vibrator is used, and 1 MHz, 1 wave pulsed ultrasonic wave US is radiated from the transmitter. The propagation distance of the ultrasonic US from the transmitter 2 and the receiver 3 to the long bone 1 was set to 25 mm, respectively.

The long bone 1, the transmitter 2 and the receiver 3 are immersed in water 4, which is a sound wave propagation medium. Assuming that the longitudinal direction of the annular long bone 1 is the longitudinal direction and the direction from the central axis to the outside is the radial direction, in the transmitter 2, the ultrasonic radiation surface is predetermined with respect to the radial direction of the long bone 1. It is arranged at an angle (hereinafter referred to as "incident angle") θ. Similarly, the ultrasonic receiving surface of the receiver 3 is also arranged at an angle θ with respect to the radial direction of the long bone 1. The angle θ is adjustable.

In the air layer 5 having a width of 3 mm and a length of 14 mm arranged above the central portion of the long bone 1, the ultrasonic waves radiated from the transmitter 2 and propagated in the water 4 are the receivers 3. It is installed in order to avoid being mixed in with the received signal as noise.

Further, the wave receiver 3 can scan, that is, move in a direction parallel to the long axis of the long bone 1 (indicated by an arrow), and as described later, propagates the long bone 1 and then into the water 4. The emitted ultrasonic waves are received while changing their positions. Then, as will be described later, the speed of sound of the ultrasonic wave propagating through the long bone 1 can be measured from the B mode image created based on the received signal.

FIG. 2 shows an example of an ultrasonic waveform that is irradiated from a transmitter 1, propagates through a long bone 1, and then converted into an electric signal by a receiver 3. The pulsed ultrasonic wave output from the transmitter 1 contains longitudinal and transverse wave components, and vibration components in various modes while propagating through the long bone 1 and before being received by the receiver 3. Are mixed to obtain the waveform shown in FIG. FIG. 2 shows a signal waveform received by the receiver in the experiment described later, but a waveform having the same shape is generated in the simulation and is output as a received signal from the receiver 3.

FIG. 3 shows a B-mode image generated based on the signal received by the receiver 3. In FIG. 3, the horizontal axis indicates the time when the signal waveform shown in FIG. 2 is converted into a brightness signal and displayed, and the vertical axis indicates the direction in which the receiver 3 is parallel to the long axis of the long bone 1. Shows the relative position when scanned (moved) to.

In the figure, the white straight line surrounded by the broken line indicates that the peak position of the luminance signal shifts as the receiver 3 moves, and by finding the slope of this straight line, the long bone 1 is propagated. It is possible to measure the speed of sound of ultrasonic waves.

In FIG. 3, (a) is a B-mode image when the incident angle θ = 15 °, (b) is θ = 30 °, (c) is θ = 45 °, and (d) is θ = 60 °. Further, FIG. 4 plots the slope of a straight line calculated from the B-mode images of FIGS. 3A to 3D, that is, the speed of sound of ultrasonic waves on a graph having the incident angle θ as the horizontal axis and the speed of sound as the vertical axis. It is a thing.

As shown in FIG. 4, when the incident angle is small (θ = 15 °, 30 °), the longitudinal wave with a high propagation velocity and the transverse wave with a slow propagation velocity are mixed, so that the variation in the speed of sound is large, but the incident When the angle becomes large (θ = 45 °, 60 °), the speed of sound shows an almost constant value. It is considered that this is because when the critical angle (22 ° to 25 °) of the longitudinal wave ultrasonic wave is exceeded, the propagation of the longitudinal wave disappears and only the transverse wave propagates in the long bone.

Here, the critical angle of ultrasonic waves will be described. In living organisms, ultrasonic waves are transmitted to long bones via soft tissues such as fat and muscle. As an example, assuming that the speed of sound of a longitudinal wave in soft tissue is 1500 m / s and the speed of sound of a longitudinal wave in a long bone is 4000 m / s, the critical angle of the longitudinal wave is about 22 °. On the other hand, if the speed of sound of the transverse wave in the soft tissue is 1500 m / s and the speed of sound of the transverse wave in the long bone is 1800 m / s, the critical angle of the transverse wave is about 56 °.

Therefore, when an ultrasonic wave is incident on a long bone at an incident angle θ exceeding 22 °, the longitudinal wave of the ultrasonic wave does not propagate, and only the transverse wave propagates along the surface of the long bone. In reality, the critical angle is determined by the shape and sound field of the transmitter, the speed of sound in the soft tissue and the speed of sound in the long bone, and has a certain angular range.

In FIG. 4, as a reference, a part of the long bone sample is cut out, and the sound velocities of the longitudinal wave and the transverse wave measured by another method are shown by solid lines. The speed of sound of a transverse wave with an incident angle of 60 ° calculated by simulation shows a value substantially equal to the speed of sound of a transverse wave shown as a reference. Further, the incident angle of 45 ° is smaller than the critical angle of the transverse wave, but shows a value very close to the speed of sound shown as a reference.

From these results, when ultrasonic waves are incident on the long bone at an incident angle that exceeds the critical angle of the longitudinal wave, especially near or above the critical angle of the transverse wave, the sound velocity of the transverse wave ultrasonic wave propagating through the long bone. It turned out that it is highly possible to measure.

On the other hand, in the simulation shown in FIG. 1, the case where ultrasonic waves are directly applied to the long bone 1 without considering the presence of the soft tissue has been described, but in the human body, the long bone is exposed to the long bone via the soft tissue such as fat and muscle. Since ultrasonic waves are irradiated, it is doubtful whether the speed of sound of transverse wave ultrasonic waves can be accurately measured by the above-mentioned method.

Therefore, in FIG. 5, the same simulation was performed in the case where the circumference of the annular long bone 1 was covered with the tubular soft tissue 6. ^{Here, when the soft tissue was covered with a cylinder having a density of 1043 kg / m 3} similar to that of agar close to the human body, a simulation was performed under the same conditions as in FIG. 1, and the velocity of ultrasonic waves propagating through the long bone 1 was measured. .. The results are shown in FIGS. 6 and 7.

FIG. 6 is a graph showing the calculation result of the speed of sound when the circumference of the long bone 1 is covered with a soft tissue 6 having a thickness of 2.2 mm, and FIG. 7 is a graph showing the calculation result of the sound velocity when the circumference of the long bone 1 is covered with a soft tissue having a thickness of 4.0 mm. It is a graph which shows the calculation result of the sound velocity at the time.

In all the graphs, the same results as in the case without the soft tissue shown in FIG. 4 were obtained, and when the incident angle was large (θ = 45 °, 60 °), the speed of sound showed almost constant values. From this result, it was found that there is a high possibility that the sound velocity of the transverse wave can be measured by setting the incident angle to the long bone to a value exceeding the critical angle of the longitudinal wave and measuring the sound wave of the ultrasonic wave.

(Embodiment 2)
In this embodiment, an experiment in which ultrasonic waves are actually radiated under the same conditions as in the above simulation was performed, and it was confirmed that the sound velocity of transverse wave ultrasonic waves can be measured in the same manner in a living body. ..

First, the experimental results when ultrasonic waves are directly applied to the long bone 1 (that is, without soft tissue intervention) will be described. FIG. 8 shows the configuration of the sound velocity measurement adopted in this experiment. In the figure, the members having the same functions as those used in the above-mentioned simulation are designated by the same reference numerals, and alphabets are added to indicate the difference from the simulation. The same shall apply thereafter.

^{In this experiment, two types of annular samples (Sample A :, outer diameter 11 mm, density 1.75 × 10 3} kg / m ^{3) with a} length of 63 mm and a thickness of 1.6 mm from the femoral bone of a cow were used as the long bone 1a. , Sample B :, outer diameter 12 mm, density 1.81 × 10 ³ kg / m ³ ) was cut out and used as a substitute for the human radius. On the other hand, for the transmitter 2a and the receiver 3a, a commercially available disk-shaped transducer was used as in the simulation.

In the simulation, an air layer 5 was interposed between the transmitter 2 and the receiver 3 in order to remove the influence of the ultrasonic waves propagating in the water, but in the present embodiment, the thickness is 3 mm instead. The plate-shaped sponge 5a of the above was arranged. In the simulation, the transmitter 2 was fixed and the receiver 3 was moved in the direction parallel to the long axis. However, in this experiment, the transmitter 2a was changed to the long bone 1a for ease of implementation. We adopted a configuration that moves in the direction parallel to the long axis of.

FIG. 9 shows a B-mode image created by the same method as in FIG. 3, and FIG. 10 shows a graph of the speed of sound created by the same method as in FIG. FIG. 9 is a B-mode image created for the sample A, and FIG. 10 is a graph of the speed of sound calculated for the samples A and B.

As can be seen from FIG. 10, as in the simulation results, when the incident angle is small (θ = 15 ° to 30 °), the variation in sound velocity is large, but when the incident angle is large (θ = 40 ° to 60 °). ), The speed of sound shows almost the same value. Further, when the incident angle was large (θ = 45 ° to 60 °), the sample A and the sample B having different sizes showed almost the same speed of sound. From this result, it was found that when the incident angle is set larger than the critical angle and the sound velocity of the ultrasonic wave propagating in the long bone is measured, the sound velocity of the transverse wave ultrasonic wave can be measured without being affected by the shape of the bone. ..

Next, the experimental results when the ultrasonic waves are irradiated with the soft tissue 6 intervening in the same manner as in FIG. 5 described above will be described. FIG. 11 shows the configuration of the sound velocity measurement adopted in this experiment. In this experiment, the above-mentioned sample A was used as the long bone 1a, and the soft tissue 6a was 4.0 mm and 7.0 mm thick agar (density 1043 kg / m ³ , sound velocity of longitudinal wave ultrasonic wave 1.75 × 10 ³ m). Using / s), a long agar with a rectangular cross section was placed on the long bone 1a. The configurations and functions of the transmitter 2a and the receiver 3a were the same as those shown in FIG.

FIG. 12 shows a B-mode image created by the same method as in FIG. 3, and FIGS. 13 and 14 show a graph of the speed of sound created by the same method as in FIG. 12 and 13 are B-mode images and a graph of the speed of sound when agar having a thickness of 4.00 mm is used as the soft tissue, and FIG. 14 is a graph of the speed of sound when agar having a thickness of 7.00 mm is used as the soft tissue. Is.

As can be seen from FIGS. 13 and 14, when the incident angle is small (θ = 15 °, 30 °), similar to the result of the simulation in which the annular long bone 1 is covered with the soft tissue 6 (FIGS. 6 and 7). Has a large variation in the speed of sound, but when the angle of incidence is large (θ = 45 °, 60 °), the speed of sound shows almost the same value. Further, when the incident angle was large (θ = 45 °, 60 °), there was almost no change in the speed of sound even if the thickness of the soft tissue 6a changed.

From the results of the above simulations and experiments, when the incident angle is set to a value exceeding the critical angle of longitudinal ultrasonic waves, the speed of sound of transverse wave ultrasonic waves propagating through long bones is affected by the bone density and soft tissue thickness. It turned out that it can be measured without.

(Embodiment 3)
Since the inventors have developed a device that embodies a method for measuring the sound velocity of transverse wave ultrasonic waves whose effect has been confirmed through simulations and experiments, the configuration and the functions of each part will be described below.

FIG. 15 shows the configuration of a sound velocity measuring device 100 that measures the sound velocity of ultrasonic waves propagating through a long bone. In the present embodiment, the living body 11 is attached to the forearm portion of a person placed on a horizontal table 10 from a transmitter 2b arranged above the forearm portion via a water bag 21 attached to a sound wave irradiation surface. A pulsed ultrasonic wave US is radiated toward. The ultrasonic US incident on the living body 11 propagates through the radius 1b, then enters the receiver 3b via the water bag 31 attached to the sound wave receiving surface, and is converted into an electric signal. The water bags 21 and 31 are filled with water.

In the present embodiment, the ultrasonic US is focused to increase the intensity of the ultrasonic wave applied to the living body 11 and the intensity of the received signal. However, if a signal having sufficient intensity can be obtained, It does not necessarily have to be focused. Further, not only a disk-shaped transducer but also a rectangular transducer may be used.

When a pulsed and MHz band drive signal is applied to the electrodes of the above-mentioned transducer, the piezoelectric vibrator expands and contracts, and this expansion and contraction generates a pulsed ultrasonic US.

The transmitter 2b and the receiver 3b have basically the same configuration, and the transducer of the receiver 3b propagates through the radius 1b and the soft tissue 6b, and receives the ultrasonic waves leaked from the living body 11. Generates an electrical signal with a strength corresponding to ultrasonic waves.

Although omitted in FIG. 15, the transmitter 2b is attached to a swivelable and vertically movable support and is swiveled in a plane including the long axis of the radius 1b to the radius 1b. On the other hand, it is held at a predetermined incident angle θ. Further, the water bag 21 is fixed by the support in a state of being pressed against the living body 11 by the moving mechanism in the vertical direction.

On the other hand, although not shown, the receiver 3b is attached to a support that can be swiveled and can move up and down like the transmitter 2b, and the support is configured to be movable in the horizontal direction. There is. The moving distance in the horizontal direction is read by the position sensor 7, which will be described later.

When measuring the sound wave velocity of ultrasonic waves, the turning angles of the transmitter 2b and the receiver 3b are maintained at predetermined values, and the receiver 3b is kept constant while the operator manually scans in the horizontal direction. The reception of ultrasonic waves is repeated at intervals (for example, 0.25 mm). Based on the received signal thus obtained, the above-mentioned B mode image is generated, and the sound velocity of the transverse wave ultrasonic wave propagating in the radius 1b is calculated from the image.

In the present embodiment, the transmitter 2b is fixed and the receiver 3b is scanned in a direction parallel to the long axis of the rib 1b, but the receiver 3b is fixed and the transmitter 2b. May be obtained by scanning in a direction parallel to the long axis to obtain an electric signal received at a plurality of positions having different distances with respect to the transmitter 2b.

Next, with reference to FIG. 17, the configuration of the sound velocity measuring means 8 for measuring the sound velocity of the ultrasonic wave propagating in the radius 1b based on the received signal of the receiver 3b and the function of each part will be described. The sound velocity measuring means 8 includes a control unit 80, an operation unit 81, a drive signal generation unit 82, a signal processing unit 83, a first storage unit 84, a B mode image data generation unit 85, a second storage unit 86, and a sound velocity calculation unit 87. It is composed of a third storage unit 88 and a display unit 89.

Among these components, the functions of the control unit 80, the B-mode image data generation unit 85, and the sound velocity calculation unit 87 are realized by a microprocessor (not shown). The microprocessor is composed of a CPU, a ROM, a RAM, and a non-volatile memory, and realizes the functions of the above parts by reading software (program) stored in the non-volatile memory and executing the software on the CPU.

Further, the functions of the first storage unit 84, the second storage unit 86, and the third storage unit 88 are realized by an external storage device such as a hard disk drive or a memory card.

In the present embodiment, the receiver 3b is manually moved in the horizontal direction and the position information is acquired by the position sensor 7, but the receiver 3b is moved by using the motor and the encoder is used. You may try to acquire the position information.

The control unit 80 controls the operation of each unit of the sound velocity measuring means 8 according to the data input from the operation unit 81. Although the control unit 80 and each component are connected by a control wiring, they are omitted in the figure in order to avoid complication.

The operation unit 81 is used by the operator to input data necessary for generating a B-mode image (for example, one movement distance of the receiver 3b), an image generation instruction, and the like, and is used by a keyboard or a button. It is configured.

The drive signal generation unit 82 generates the drive signal of the transmitter 2b, and in the present embodiment, the drive signal of one sine wave or several waves in the band of 1 to 10 MHz is repeatedly generated, and the transducer 24 It is applied between the electrodes.

The received signal of the ultrasonic wave generated by the receiver 3b is input to the signal processing unit 83. Although not shown, the signal processing unit 83 includes a noise reduction filter, a signal amplifier, and an A / D converter. After the noise reduction filter and the signal amplifier remove unnecessary noise and amplify the signal, A It is converted into a digital signal by the / D converter.

The sampling frequency of the A / D converter needs to be at least about 10 times the frequency included in the received ultrasonic waves, and is preferably 20 times or more the frequency of the received ultrasonic waves.

In the first storage unit 84, the received signal converted into a digital signal by the signal processing unit 83 is output from the position sensor 7 for each scan of the receiver 3b, and the position information of the receiver 3b and the drive signal generation unit are generated. It is stored together with the information of the occurrence time output from 82.

The storage of the received signal data in the first storage unit 84 is continued until the operator manually starts scanning the receiver 3b from the left end and finishes scanning at the right end in FIG. 15, and finally B The data for one screen of the mode is stored in the first storage unit 84.

The B-mode image data generation unit 85 reads out the data of the received signal for one screen stored in the first storage unit 84, and uses the STC (sensitivity time control) function for each received signal to attenuate the data due to the distance. After the correction, the envelope detection process is performed to generate B-mode image data. The generated B-mode image data is transferred to a display unit 89 composed of an LCD display or the like and displayed on the screen. The B-mode image data generated by the B-mode image data generation unit 85 is stored in the second storage unit 86.

The sound velocity calculation unit 87 reads out the data of the received signal for one screen stored in the second storage unit 86, and explains using FIG. 3, the slope of a straight line connecting the peak values of the luminance signal, that is, the ultrasonic wave. Calculate the speed of sound.

As shown in FIG. 3, the slope of the straight line of the peak value may be calculated by enclosing the target straight line by the operator with a broken line and using software to calculate the slope of the straight line. All the processing from the extraction to the calculation of the slope may be performed by using software.

The graph created by the sound velocity calculation unit 87 is displayed on the screen of the display unit 89 and stored in the third storage unit 88.

In the sound velocity measuring device shown in FIG. 15, the operator manually scans the receiver 3b to acquire the received signal for the B mode image, but the probe of the linear scanning ultrasonic diagnostic device As described above, a received signal for a B-mode image may be acquired by using a receiver in which a plurality of strip-shaped transducers cut out from a piezoelectric vibrator are arranged.

FIG. 17 shows a schematic configuration of a probe 3c in which a plurality of strip-shaped transducers are arranged and the functions of a transmitter and a receiver are integrated. The probe 3c is composed of a plurality of strip-shaped transducers 32 arranged parallel to the long axis direction of the radius 1b, and a damper 33 that supports them and suppresses the propagation of ultrasonic waves to the rear.

Of the transducers 32, the transducer 321 located at the center functions as a transmitter and emits ultrasonic US, and the other transducers 322 function as a receiver. Among the ultrasonic waves radiated from the transducer 321, the sound velocity of the transverse wave ultrasonic wave can be measured by the method described above from the received signal of the transducer 322 that has received the ultrasonic wave US whose incident angle exceeds the critical angle of the longitudinal wave. .. When using the probe 3c, it is necessary to apply a gel to the surface of the living body to prevent the reflection of ultrasonic waves.

In FIG. 17, the number of transducers 32 is set to 9 for the sake of clarity, but tens to more than 100 transducers may be arranged depending on the scanning range. Further, the transducer 321 for the transmitter is not limited to the one located in the central portion, and a transducer located near the left and right end portions may be selected. Further, the receiver sensitivity can be improved by installing the transducer 322 for a receiver so that the sound wave receiving surface is slanted in accordance with the receiving direction of the ultrasonic wave.

As described above, by using the ultrasonic sound velocity measuring method according to the present invention, the sound velocity of lateral wave ultrasonic waves propagating in a long bone in a living body such as a femur or a radius can be adjusted to the bone density or the thickness of soft tissue. Since it can be measured without being affected, it can be an effective means for estimating the shear elasticity of long bones.

1, 1a, 1b long bones 2, 2a, 2b transmitter 3, 3a, 3b receiver 4 water 5 air layer 5a sponge 6, 6a, 6b soft tissue 7 position sensor 8 sound velocity measuring means 10 units 11 living body 21, 31 Water bag 22 Transmitter body 23, 33 Damper 24, 32 Transducer 100 Ultrasonic sound velocity measuring device

Claims (9)

First, in a plane including the long axis of the long bone of the human body, the long bone is irradiated with ultrasonic waves at an incident angle exceeding the critical angle of the longitudinal wave through the soft tissue using an ultrasonic transmitter. Steps and
The second step of transmitting the ultrasonic wave propagating through the long bone and further propagating through the soft tissue and leaking from the surface of the living body by a wave receiver and converting it into an electric signal.
The ultrasonic wave propagates through the long bone based on the electric signals received by the wave receiver at a plurality of positions parallel to the long axis of the long bone and at different distances from the transmitter. A method for measuring the speed of sound of an ultrasonic wave, which comprises a third step of measuring the speed of sound of a transverse wave among sound waves. A B-mode image is generated in which the time axis of the brightness signal of the electric signal output from the receiver is the horizontal axis and the position where the receiver receives the ultrasonic waves of the transverse wave is the vertical axis. The method for measuring the sound wave of an ultrasonic wave according to claim 1, wherein the sound wave of the transverse wave ultrasonic wave is calculated from the inclination of the mode image. The method for measuring the sound velocity of ultrasonic waves according to claim 1 or 2, wherein the transmitter is composed of a single transducer and generates ultrasonic waves by applying a pulsed drive signal of one sine wave or several waves. The method for measuring the sound wave velocity of an ultrasonic wave according to any one of claims 1 to 3, wherein the receiver is composed of a single transducer and can move in a direction parallel to the long axis of the long bone. The transmitter and receiver are composed of a plurality of transducers arranged in a direction parallel to the long axis of the long bone, one of which is used as a transducer and the other transducer is received. The method for measuring the sound velocity of ultrasonic waves according to claim 1 or 2, which is used as a device. A transmitter that irradiates the long bone with ultrasonic waves at an angle exceeding the critical angle of the longitudinal wave through the soft tissue in the plane including the long axis of the long bone of the human body.
A receiver that propagates through the long bones, further propagates through the soft tissue, receives ultrasonic waves leaked from the surface of the living body, and converts them into electrical signals.
The ultrasonic wave propagates through the long bone based on the electric signals received by the wave receiver at a plurality of positions parallel to the long axis of the long bone and at different distances from the transmitter. An ultrasonic sound velocity measuring device provided with a sound velocity measuring means for measuring the sound velocity of a transverse wave among sound waves. The ultrasonic sound velocity measuring device according to claim 6, wherein the receiver is composed of a single transducer and can move in a direction parallel to the long axis of the long bone. The ultrasonic sound velocity measuring device according to claim 7, wherein a water bag is attached to the sound wave irradiation surface of the wave transmitter and the sound wave receiving surface of the wave receiver, respectively. The transmitter and receiver are composed of a plurality of transducers arranged in a direction parallel to the long axis of the long bone, one of which is used as a transmitter and the other transducer is received. The ultrasonic sound velocity measuring device according to claim 6, which is used as a device.

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