JP3218224B2 - Ultrasonic tissue evaluation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic tissue evaluation apparatus for evaluating the state of a living tissue using ultrasonic waves.

[0002]

2. Description of the Related Art In recent years, ultrasonic waves are radiated to a living body (for example, heel), and the speed (hereinafter referred to as sound speed) of the ultrasonic wave in the living tissue (for example, calcaneus) at that time, Ultrasonic tissue evaluation devices that measure the degree of attenuation and evaluate and diagnose the state of the ecological tissue are becoming widespread. Further, there has been proposed an apparatus for evaluating tissues such as bones by using ultrasonic waves and X-rays in combination.

As is well known, in such tissue evaluation using ultrasonic waves, if an air layer intervenes on the path from the transmitting ultrasonic transducer to the receiving ultrasonic transducer, the ultrasonic Since reflection and attenuation occur, it is impossible to accurately measure and evaluate the speed of sound and the degree of attenuation. For this reason, conventionally, the subject and the ultrasonic vibrator were immersed in a measuring tank containing an acoustic matching material such as water, and the ultrasonic wave was transmitted and received in such a state to perform the measurement.

[0004] However, such a method of placing the subject in the acoustic matching material has a problem that the subject may feel uncomfortable and hygiene management becomes complicated. In view of this, the present applicant has disclosed in Japanese Patent Application No. 6-7010 that the ultrasonic vibrator is covered with a cover member called a matching material storage portion, and the inside of the matching material storage portion is filled with an acoustic matching material. We have proposed an apparatus for transmitting and receiving ultrasonic waves by bringing a living body contact surface into contact with a subject. According to this device, the living body contact surface of the matching material storage portion can easily come into contact with the surface of the subject, and the air layer can be prevented from intervening in the ultrasonic wave propagation path.

However, even when such an apparatus is used, the characteristics of the acoustic matching material change due to the environment in which the measurement is performed, particularly, changes in temperature and atmospheric pressure, and as a result, the evaluation value of the tissue such as the speed of sound in the tissue of the subject. Effect and cause errors.

That is, conventionally, ultrasonic waves are transmitted and received in a state where a subject is placed between ultrasonic transducers facing each other, and the propagation time of ultrasonic waves between the ultrasonic transducers is obtained. By dividing the distance between the ultrasonic transducers at that time, the sound velocity in the tissue of the subject was obtained. in this case,
The thickness of the acoustic matching material layer interposed between the subject and the ultrasonic transducer and the time required for the ultrasonic wave to propagate through the acoustic matching material layer are included in the values used for calculating the speed of sound. In other words, if the characteristics of the acoustic matching material change even for the same subject, the required value of the sound velocity differs. Along with this, the values of other evaluation values calculated using the sound speed also fluctuated due to changes in the characteristics of the acoustic matching material.

For example, when castor oil or the like is used as an acoustic matching material, the temperature of castor oil is 1 ° C. near room temperature.
If it changes, the speed of sound in castor oil will change by about 3 m / s. Therefore, in the case where the thickness of the castor oil layer as the acoustic matching material is about 4 cm and the thickness of the living tissue to be evaluated is about 6 cm, if the temperature of the castor oil changes by 1 ° C. For the sound velocity measurement results of
An error of about 2 m / s occurs.

Further, the acoustic matching material inside the matching material housing may contain gas, and when the atmospheric pressure of the measurement environment changes, the gas expands and contracts. The degree of deformation when pressed is changed by the atmospheric pressure, and changes the average thickness of the acoustic matching material layer.

Further, the thickness of the acoustic matching material layer changes due to leakage of the acoustic matching material due to aging. Further, in the conventional device, the living body contact surface of the matching material storage part is formed of a thin film such as a polyurethane sheet having excellent ultrasonic permeability and high flexibility. Of the acoustic matching material layer also changes because the degree of crushing of the living body contact surface changes even if the subject is pressed with the same pressure.

Generally, the sound velocity in the acoustic matching material is not the same as the sound velocity in the tissue of the subject. Therefore, if the average thickness of the acoustic matching material layer changes, even if the same subject is measured, the sound velocity measurement result will not be obtained. Change, resulting in measurement errors.

[0011]

SUMMARY OF THE INVENTION The present invention provides a method for obtaining an accurate and stable evaluation value in an ultrasonic tissue evaluation apparatus.
An object is to allow a vibrator to be pressed against a subject or the like at a predetermined pressure.

[0012]

According to the present invention, there is provided an ultrasonic tissue evaluation apparatus for evaluating a living tissue using ultrasonic waves, the apparatus comprising at least one ultrasonic wave transmitting and receiving apparatus for transmitting and receiving ultrasonic waves. A vibrator unit, the vibrator unit,
A vibrator unit moving mechanism for moving the vibrator unit to make contact with the object, wherein the vibrator unit moving mechanism is configured such that a force for bringing the vibrator unit into contact with the object is limited to a predetermined value, It is characterized by having a limiting means for limiting a force for moving the vibrator unit.

Further, the present invention is an ultrasonic tissue evaluation apparatus for evaluating a living tissue using ultrasonic waves, wherein at least one vibrator unit for transmitting and receiving ultrasonic waves and moving the vibrator unit are provided. A vibrator unit moving mechanism, wherein the vibrator unit moving mechanism is rotated by a driving force from the driving force generating means to move the vibrator unit, and to drive the vibrator unit. A feed screw, and a torque limiter provided between the driving force generating means and the feed screw, for limiting a driving force transmitted from the driving force generating means to the feed screw to a predetermined value. I do.

The present invention is also directed to an ultrasonic tissue evaluation apparatus for evaluating a living tissue using ultrasonic waves, comprising: a pair of transducer units for transmitting and receiving ultrasonic waves; A vibrator unit moving mechanism for changing a distance, wherein the vibrator unit moving mechanism includes a driving force generating means for generating a driving force, and a driving force generating means for moving the pair of vibrator units. A feed screw rotated by a driving force, a torque limiter provided between the driving force generating means and the feed screw, and limiting a driving force transmitted from the driving force generating means to the feeding screw to a predetermined value; It is characterized by including.

In a preferred aspect of the present invention, the feed screw has a forward screw portion and a reverse screw portion whose winding directions are opposite to each other, and one vibrator unit is mounted on the forward screw portion. A screw receiver for supporting the other vibrator unit is engaged with the screw receiver for support, and a screw receiver for supporting the other vibrator unit is engaged with the reverse screw portion.

[0016]

FIG. 1 is a schematic view showing an example of a mechanical configuration of an ultrasonic tissue evaluation apparatus (hereinafter, abbreviated as an apparatus) according to the present invention. In FIG. 1, a pair of transducer units 10a and 10b are connected to respective ultrasonic transducers 12a and 12a.
2b are arranged so that the vibration surfaces face each other. The vibrating surfaces of the ultrasonic vibrators 12a and 12b are provided with vibrator covers 14a and 14b made of a thin film such as a polyurethane sheet having excellent flexibility and ultrasonic permeability. The inner space surrounded by the child covers 14a and 14b is filled with liquid acoustic matching materials 16a and 16b such as castor oil. Ultrasonic transducer 12
a, 12b from the rear end of the cord 20a, 20b respectively
These cords 20a and 20b are connected to a vibrator control unit (not shown). Further, the ultrasonic transducers 12a and 12b and the transducer covers 14a and 14b
Are stored in the transducer cases 18a and 18b. The vibrator cases 18a and 18b are supported by arms 22a and 22b, respectively.

At the lower ends of the arms 22a and 22b, screw receiving portions 24a and 24b for passing the feed screw 30 are provided. When the feed screw 30 rotates, the arms 22a and 22b move, and as a result, vibrate. Child unit 10
a and 10b move. Since the feed screw 30 is a reverse screw at the center,
When the feed screw 30 is turned in one direction, the pair of vibrator units 10a and 10b perform an operation of moving away from or approaching each other. Therefore, at the time of examination, the subject can be sandwiched between the pair of transducer units 10a and 10b by rotating the feed screw 30 in a predetermined direction. The feed screw 30 is rotated by turning the handle 34. Since the handle 34 is connected to the feed screw 30 via the torque limiter 32, the feed screw 30 is not pinched by a force greater than a certain force during the examination. Has become. The arm 22a is provided with a laser length measuring device 26, and the arm 22b is provided with a reflecting plate 28, by which the distance between the vibrating surfaces of the ultrasonic vibrator can be measured.

FIG. 2 is a block diagram showing the overall configuration of this device. 2, the same members as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the figure, an ultrasonic transducer 12a is connected to a transmission amplifier 40 as a transmitting ultrasonic transducer. Also, the ultrasonic transducer 12b serves as a receiving ultrasonic transducer as a receiving ultrasonic transducer.
It is connected to the. The receiving amplifier 42 is connected to an A / D converter 44. A transducer control unit 52 in the control unit 50 controls the transmission amplifier 40 to transmit an ultrasonic pulse from the transmission ultrasonic transducer 12a,
The digital signal is received from the D converter 44, and a predetermined process is performed on the received signal.

The operation will be described in more detail. First, when the start of the inspection is instructed, the transducer control unit 52 transmits a trigger to the transmission amplifier 40. Upon receiving this trigger, the transmission amplifier 40 supplies a predetermined negative pulse to the ultrasonic vibrator 12a, whereby an ultrasonic pulse is emitted from the ultrasonic vibrator 12a. The ultrasonic pulse is transmitted through the subject or the like, and then received by the ultrasonic transducer 12b.
The weak reception signal is subjected to predetermined amplification by the reception amplifier 42. The amplified received signal is digitized by the A / D converter 44 and sent to the transducer control unit 52 in the control unit 50. The vibrator control unit 52 obtains a predetermined measurement value based on the digitized received signal. In particular, the propagation time measuring section 54 in the transducer control section 52 determines the ultrasonic propagation time (hereinafter, abbreviated as propagation time) between the ultrasonic transducers required for measuring the speed of sound in the tissue of the subject. The transducer control unit 52 obtains the degree of attenuation of the ultrasonic wave in addition to the propagation time.

The control unit 50 has a length measuring unit control unit 56 in addition to the transducer control unit 52. The length measuring device control unit 56 controls the laser length measuring device 26 to
The distance between the vibrating surfaces 2a and 12b (hereinafter, referred to as the inter-vibrator distance) is measured.

Further, the control unit 50 includes a sound speed calculation processing unit 58.
And a memory 60. Propagation time measurement unit 54
The ultrasonic wave propagation time between the ultrasonic transducers obtained by the above and the inter-vibrator distance obtained by the length measuring device control unit 56 are input to the sound speed calculation processing unit 58. The sound speed calculation processing unit 58 performs a calculation process necessary for obtaining a sound speed in the subject tissue.
The memory 60 stores measurement values obtained in steps such as a preparatory measurement step which will be described in detail later, and these measurement values are used when the sound speed calculation processing unit 58 calculates the sound speed in the subject tissue. Can be

The sound speed and the degree of attenuation of the ultrasonic wave obtained by the control unit 50 in this manner are used as evaluation values for evaluating the tissue of the subject.

Hereinafter, as an application example using such an apparatus, an example of the measurement of sound velocity in the tissue of a subject will be described with reference to the flowchart of FIG. This example is hereinafter referred to as a first application example.

The processing of the first application example is roughly divided into three steps: a preparation measurement step, an actual measurement step, and a sound velocity calculation step in the tissue.

First, in the preparation measurement step, the operator
By turning the handle 34, the pair of transducer units 10a and 10b are brought closer to each other, and the transducer covers 14a and 14b are brought into contact with each other. Then, the vibrator covers are pressed together until the torque limiter 32 operates (S1).
02). FIG. 4 shows the state of the device at this time.
As will be described later, when the subject is sandwiched between the transducer units in the actual measurement process, the subject is sandwiched between the transducer unit pairs until the torque limiter 32 operates, as in S102. Thereby, the vibrator covers 14a in the preparation measurement step and the actual measurement step
14b, that is, the acoustic matching members 16a, 16
It can be considered that the thickness of the layer b is substantially equal. Next, in this state, the propagation time t _{1 of the} ultrasonic wave between the ultrasonic transducers 12a and 12b is measured (S104). That is, first, an ultrasonic pulse is transmitted from the transmitting ultrasonic transducer 12a, the pulse is received by the receiving ultrasonic transducer 12b, and the propagation time measuring unit 54 determines the propagation time t _{1 of the} ultrasonic wave based on these. Measure. Propagation time t measured in this preliminary measurement step
₁ indicates the time required for the ultrasonic wave to propagate through the acoustic matching layer. This measured value is stored in the memory 60 via the sound speed calculation processing unit 58.

Next, in the actual measurement step, the operator turns the handle 34 to widen the inter-vibrator distance, places the subject between the pair of vibrator units, and, as shown in FIG. The subject 70 is sandwiched between the vibrator units 10a and 10b until the actuator 32 operates (S10).
6). Next, in the state where the subject 70 is sandwiched, the propagation time t _{2 of the} ultrasonic wave is measured in the same manner as in the preparation measurement step, and at the same time, the distance between the transducers is measured using the laser length measuring device 26 at this time. L ₂ is measured (S108).

In the sound velocity calculation process in the tissue, first, S
The propagation time t ₂ in the actual measurement step obtained in 108 and the propagation time t in the preparation measurement step stored in the memory 60
With ₁ and, ultrasound determined by following equation transmission time t required for transmitting a subject 70 (1) (S110).

T = t ₂ −t ₁ (1) That is, in the first application example, since the torque limiter 32 is used, the pressure applied to the vibrator cover and the acoustic matching material layer is measured in the preparation measurement step and the actual measurement step. Since the process becomes substantially equal, the degree of collapse of the vibrator cover can be considered to be substantially equal in both processes, and therefore, the thickness of the acoustic matching material layer can be considered to be substantially equal in both processes. Therefore, the ultrasonic propagation time t ₁ in the acoustic matching material layer obtained in the preparation measurement step can be used as it is as the ultrasonic propagation time in the acoustic matching material layer in the actual measurement step. Therefore, by subtracting the ultrasonic wave propagation time t ₁ in the acoustic matching material layer from the ultrasonic wave propagation time t ₂ between the ultrasonic transducers 12a and 12b, it is necessary for the ultrasonic waves to pass through the subject tissue. Time t can be determined.

In this application example, using the transmission time t and the inter-vibrator distance L ₂ in the actual measurement process obtained in the above-mentioned S108, the sound velocity in the tissue of the subject is calculated from the following equation (2). V is obtained (S112).

V = L ₂ / t (2) As described above, in the first application example, the influence of the propagation time t ₁ in the acoustic matching material layer was eliminated in the calculation of the sound velocity V in the tissue of the subject. In addition, a more accurate sound velocity V in the subject tissue can be obtained without being affected by a change in sound velocity in the acoustic matching material layer due to a temperature change.

Further, as a modified example of the first application example, there is the following method. That is, in S104 of the preparation measurement step in the flowchart of FIG. 3, while measuring the propagation time t _{1 of the} ultrasonic wave between the ultrasonic transducers,
The laser measurement device 26 measures the transducer distance L _1.
Then, in S112 of the in-tissue sound speed calculation step, the sound speed V in the tissue of the subject is obtained using the following equation (2a).

V = (L ₂ −L ₁ ) / t (2a) In this case, the inter-vibrator distance L ₁ measured in the preparatory measurement step can be regarded as indicating the thickness of the acoustic matching material layer. And the distance L ₂ between the transducers measured in the actual measurement process.
By subtracting from, the thickness of only the subject tissue can be obtained. The thickness (L ₂ −
By dividing L ₁ ) by the time t required for the ultrasonic wave to pass through only the subject tissue, a more accurate sound velocity V in the subject tissue can be obtained.

As described above, in this modified example, the sound velocity in the subject tissue is obtained based on the thickness of the subject tissue alone and the time when the ultrasonic wave passes only through the subject tissue. Since the influence is completely eliminated, an accurate sound velocity V in the subject tissue can be obtained without being affected by a change in the sound speed in the acoustic matching material layer or a change in the thickness of the acoustic matching material layer. .

The first application example and its modification have been described above. Velocity of sound in subject tissue determined in this application example
Is used as an evaluation value of the subject tissue by itself, but can be used in combination with another evaluation value of the subject tissue to newly obtain another evaluation value. For example,
As proposed by the present applicant in Japanese Patent Application No. 4-127551, the elastic modulus of bone is used in combination with X-ray measurement, by combining the amount of bone mineral determined by X-ray measurement with the sound velocity determined in this application example. This elastic modulus can be used as an evaluation value of the bone.

In this application example, a laser length measuring device is used as a means for measuring the inter-vibrator distance. However, the present invention is not limited to this. For example, a mechanical length measuring device such as an encoder may be used.

Although the preparatory measurement step, the actual measurement step, and the sound velocity calculation step in the tissue have been described here as a series of flows,
Preparation measurement process and actual measurement process (and sound velocity calculation process in the tissue)
It is not always necessary to continue. The preparation measurement process is
It may be performed every time a test is performed on the subject, or may be performed periodically, such as once a day or once a week, and the measured value may be stored to obtain the sound velocity during the actual test of the subject. Alternatively, the calculation may be performed using the stored measurement values.

Next, a description will be given of a second applied example of the method of measuring the speed of sound in tissue using the apparatus according to the present invention. This second application example considers the temperature change of the acoustic matching materials 16a and 16b,
It is intended to obtain a more accurate sound velocity in the tissue. The device used in this second application example has basically the same configuration as that of the first application example shown in FIG.

If the state where the subject is sandwiched between the pair of vibrator units continues for a long time in the actual measurement step, the temperature of the acoustic matching members 16a and 16b becomes larger than the temperature in the preparation measurement step due to the influence of the temperature of the subject itself. May change. In such a case, the speed of sound in the acoustic matching material differs between the preparatory measurement step and the actual measurement step. When used as the time to pass through the layer, an error occurs in the required sound speed in the subject tissue.

Therefore, in the second application example, as shown in FIG. 6, a matching member temperature sensor 19 for measuring the temperature of the acoustic matching member 16a is provided in the vibrator unit 10a, and the acoustic matching member measured by this is used. Using the temperature of 16a, a more accurate sound velocity in the subject tissue is obtained. The device configuration used in the second application example is almost the same as that of the first application example except for the matching material temperature sensor 19. The control unit 50 in FIG. 2 controls the matching material temperature sensor 19, and uses the measured temperature in the calculation processing in the sound speed calculation processing unit 58. Detailed calculation processing will be described later. Such a matching material temperature sensor may be provided on at least one of the pair of transducer units.

Next, the procedure of measuring the sound velocity in the tissue in the second application example will be described with reference to the flowchart of FIG.

First, as in the first applied example, the operator performs a pair of vibrator units 10a, 10a in the preparatory measurement step.
By turning the handle 34 so that the inter-vibrator distance b becomes shorter, the vibrator covers 14a and 14b of the vibrator unit are aligned until the torque limiter 32 operates (S2).
02). Then, generate the ultrasonic pulses from the ultrasonic transducer 12a in this state, it receives the pulses on the other side of the ultrasonic transducer 12b, measures the propagation time t ₁ of the ultrasound between the ultrasound transducers. Furthermore, this time the transducer distance L ₁ measured by a laser measuring device 26 to measure the temperature d ₁ of the acoustic matching material at matching material temperature sensor 19 (S204).

Then, using the measurement result in the preparatory measurement step, the sound velocity V ₁ in the acoustic matching material layer in the preparatory measurement step is obtained by the following equation (3) (S206).

V ₁ = L ₁ / t ₁ (3) Next, in the actual measuring step, the distance between the transducers is once widened by turning the handle 34, the subject is placed between the transducer units, and the handle 34 is again turned on. Is turned to bring the transducer units closer to each other, and the subject is sandwiched until the torque limiter 32 operates (S208). Then, in this state, the propagation time t _{2 of the} ultrasonic wave in this state, the distance L ₂ between the transducers, and the temperature d _{2 of the} matching material in the same manner as in the preparatory measurement step.
Is measured (S210).

In order to obtain a more accurate sound velocity in the tissue of the subject, it is necessary to know the sound velocity in the acoustic matching material in the actual measurement step. This sound velocity V _{2 is obtained} by the following equation (S212). ).

V ₂ = V ₁ + a (d ₂ −d ₁ ) (4) In the equation (4), the constant a is the amount of change in the speed of sound in the acoustic matching material layer per 1 ° C. of temperature change. The unit of the constant a is given, for example, in m / s · deg. When the matching material is castor oil, the constant a has a value of about −3 to −4.

Next, in the in-tissue sound velocity calculation step, the measured values in the preparation measurement step and the actual measurement step and the sound velocity V ₂ of the acoustic matching material in the actual measurement step obtained in S212 are used. Find the speed of sound inside.

First, a time t required for an ultrasonic wave to pass through a subject tissue is determined by the following equation (5) (S21).
4).

T = t ₂ −L ₁ / V ₂ (5) That is, the distance L ₁ indicating the thickness of the acoustic matching material layer is divided by the sound velocity V ₂ of the acoustic matching material in the actual measurement step.
Ultrasound seek time required to transmit the acoustic matching material layer in the actual measuring step, which ultrasound by subtracting from the propagation time t ₂ between the ultrasonic transducers are required to transmit only the subject tissue Time t can be determined.

Then, the sound velocity V in the tissue of the subject is determined by using the above equation (2a) (S216).

As described above, according to the second application example, it is possible to eliminate the error caused by the temperature difference of the acoustic matching material between the preparatory measurement step and the actual measurement step, and to obtain a more accurate sound velocity V in the subject tissue. it can.

Next, a third application example of the method for measuring the speed of sound in a tissue using the device according to the present invention will be described. In the first and second application examples described above, in the preparatory measurement step, measurement was performed by bringing the transducer covers of the pair of vibrator units into contact with each other. The measurement is performed with a reference body having substantially the same thickness sandwiched between the transducer units. An acrylic block or the like is used as the reference body. The device used in the third application example has basically the same configuration as that of the first application example shown in FIG. Hereinafter, this application example will be described with reference to the flowchart in FIG.

First, in the preparatory measurement step, the operator
A reference body 80 is provided between the pair of vibrator units 10a and 10b.
Put. Then, by turning the handle 34, the transducer units are brought closer to each other, and the reference body 80 is sandwiched. At this time, the handle is turned until the torque limiter 32 operates, and the reference body 80 is sandwiched with a predetermined pressure (S302). FIG. 9 shows this state. As shown in FIG. 9, the vibrator units 10a and 10b are pressed against the reference body 80 at a predetermined pressure (that is, the pressure at the time of measuring the object), and the vibrator covers 14a and 14b are almost at the same time as at the time of measuring the object. It is in equal collapse. A reference body temperature sensor 82 is attached to the surface of the reference body 80, and the temperature of the reference body 80 is measured as needed. The setting of the reference body 80 at a predetermined position at this time is automatically performed by a reference body setting mechanism (not shown). Of course, the configuration may be such that the operator himself performs the setting manually.

Next, transmission and reception of ultrasonic waves are performed in this state.
The propagation time t _{1 of the} ultrasonic wave between the ultrasonic transducers is measured. Further, the temperature r of the reference body 80 at this time is measured by the reference body temperature sensor 8.
2 is measured (S304).

[0054] Then, using the measurement results, determine the sound velocity V _s of the reference body 80 during the preparatory measurement step by the following equation (6) (S306).

V _s = αr + β (6) In equation (6), α is the temperature gradient of the sound velocity V _s in the reference body 80, and β is its intercept, that is, the sound velocity at the reference temperature (for example, 0 ° C.). It is. Α and β are determined in advance by experiments or the like. The sound velocity V _s in the reference body thus determined is temporarily stored in the memory 60 (see FIG. 2).

Next, the operator turns the handle 34 to widen the inter-vibrator distance, removes the reference body 80, places the subject between the vibrator units, and turns the handle 34 again to turn the vibrator. The units are brought closer to each other, and the subject 70 is sandwiched until the torque limiter 32 operates (S308).

Then, in this state, the transmission and reception of the ultrasonic wave are performed to measure the propagation time t _{2 of the} ultrasonic wave, and at the same time, the distance L ₂ between the transducers is measured using the laser length measuring device 26 (S 310). .

[0058] In tissue sound velocity calculation step, the measurements at the preparatory measurement step and the actual measurement step, by using the sound velocity V _s of the reference body obtained in S306, the sound velocity in the subject tissue as follows Ask for.

First, the time t required for the ultrasonic wave to pass through only the subject is determined using the following equation (7) (S31).
2).

T = t ₂ − {t ₁ − (L _s / V _s )} (7) In the equation (7), L _s is the thickness of the reference body 80 and is a known value. Therefore, in the equation (7), L _s / V _s indicates the time required for the ultrasonic wave to pass through the reference body 80. Therefore, Δt ₁ − (L _s /
V _s )｝ indicates the time required for the ultrasonic wave to pass through the acoustic matching material layer. By subtracting this from the propagation time t _{2 of the} ultrasonic wave between the transducers, the ultrasonic wave The time t required to penetrate the tissue can be determined.

Using the ultrasonic transmission time t in the tissue of the subject thus obtained, the sound velocity in the tissue of the subject is obtained by the aforementioned equation (2), as in the first application example.

As described above, in the third applied example, as in the first applied example, the influence of the propagation time t ₁ in the acoustic matching material layer was excluded in the calculation of the sound velocity V in the subject tissue. In addition, a more accurate sound velocity V in the subject tissue can be obtained without being affected by a change in sound velocity in the acoustic matching material layer due to a temperature change. Further, in the preparatory measurement step, the reference body 80 having substantially the same thickness as the subject is sandwiched between the vibrator units to measure the propagation time and the like, so that the vibration between the preparatory measurement step and the actual measurement step The difference in the distance between the children is the reference body 8
Since it is smaller than the case where 0 is not used (for example, the first application example), it becomes possible to use a laser length measuring device having a small effective length measuring range, and it is possible to reduce the cost of the entire apparatus.

As a modification of the third application example, there is the following method. That is, in S304 in the flowchart of FIG. 8, at the same time when measuring the propagation time t ₁ of the ultrasound between the ultrasound transducers, to measure the transducer distance L ₁ by the laser length measuring machine 26. Then, in S314 of the in-tissue sound speed calculation step, the sound speed V in the tissue of the subject is obtained by using the following equation (8).

V = {L ₂ − (L ₁ −L _s )} / t (8) In the equation (8), (L ₁ −L _s ) represents the thickness of the acoustic matching material layer. by subtracting this from the L _2, the thickness of the subject tissue only is required. By dividing the thickness of the subject tissue alone by the time t required for the ultrasonic wave to pass through only the subject tissue, a more accurate sound velocity V in the subject tissue can be obtained. As described above, in this modified example, the influence of the acoustic matching material layer is completely eliminated in the calculation of the sound velocity, and thus the influence of the change in the sound speed in the acoustic matching material layer, the change in the thickness of the acoustic matching material layer, and the like. , It is possible to obtain an accurate sound velocity V in the subject tissue.

Next, a fourth application example of the method for measuring the speed of sound in tissue using the apparatus according to the present invention will be described. This fourth application example has an acoustic matching material 16 in addition to the configuration of the third application example.
Means for measuring the temperatures of the acoustic matching members 16a and 16b are provided, and a more accurate sound velocity in the tissue is determined in consideration of the temperature change of the acoustic matching members 16a and 16b. As the means for measuring the temperature of the acoustic matching material, the same device as the matching material temperature sensor 19 described in the second application example is used. Hereinafter, this application example will be described with reference to the flowchart in FIG.

First, the operator sandwiches the reference body 80 between a pair of transducer units (S402). In this state, transmission and reception of ultrasonic waves are performed, and the propagation time t _{1 of the} ultrasonic waves is measured. Further, at this time, the distance L ₁ between the transducer vibrating surfaces is measured by the laser length measuring device 26, and the temperature r of the reference body 80 is measured by the reference body temperature sensor 82. Further, the temperature d ₁ of the acoustic matching material is measured by the matching material temperature sensor 19 (S4).
04).

[0067] Using the measured values in these preparatory measurement step, first, determine the sound velocity V _s of the reference body when the using the above-described (6) (S406).

[0068] Then, by using the speed of sound V _s of the obtained reference body, seeking acoustic velocity V ₁ of the inside acoustic matching material in the preparation measuring step by the following equation (9) (S408).

V ₁ = (L ₁ −L _s ) / (t ₁ −L _s / V _s ) (9) Next, the operator sandwiches the subject 80 between the transducer units (S 410). Then, in this state, transmission and reception of the ultrasonic wave are performed to measure the propagation time t _{2 of the} ultrasonic wave, and further, the temperature d ₂ of the acoustic matching material and the distance L ₂ between the transducers are measured (S412).

Then, using these measured values, the sound velocity V ₂ in the acoustic matching material at the time of actual measurement is obtained by the above-mentioned equation (4) (S414).

Next, the time t required for the ultrasonic wave to pass through the subject tissue is determined according to the equation (10) (S41).
6).

T = t ₂ − (L ₁ −L _s ) / V ₂ (10) That is, the distance (L ₁ −L _s ) indicating the thickness of the acoustic matching material layer
Is divided by the temperature V ₂ of the acoustic matching material in the actual measurement step, thereby obtaining the time required for the ultrasonic wave to pass through the acoustic matching material layer in the actual measurement step, and this is calculated as the propagation time t ₂ between the ultrasonic transducers. The time t required for the ultrasonic wave to pass through only the subject tissue is obtained by subtracting from the above.

Then, the sound velocity V in the tissue of the subject is obtained by the aforementioned equation (8) as in the third application example (S41).
8).

As described above, also in the fourth applied example, the reference body 80
By using a laser measuring device, it is possible to employ a laser length measuring device having a small effective length measuring range, and the cost of the apparatus can be reduced.

In the third and fourth application examples described above, the example in which the reference body temperature sensor 82 is mounted on the surface of the reference body 80 has been described. However, the present invention is not limited to this. The temperature may be regarded as being equal to the room temperature, and the room temperature at that time may be measured and used as the temperature of the reference body 80. Further, in the fourth application example, the temperature measuring means of the reference body and the temperature measuring means of the acoustic matching material are provided separately. However, a single temperature measuring means having both of them may be provided.

[0076]

As described above, according to the present invention,
By providing the limiting means, the vibrator unit can be moved to an object (for example, a subject, the other vibrator unit of a pair, etc.)
Can be limited to a predetermined value.

According to the present invention, the vibrator unit is moved by rotating the feed screw with the driving force from the driving force generating means, and a torque limiter is provided between the driving force generating means and the feed screw. Therefore, the force when the vibrator unit is brought into contact with the object can be limited by the torque limiter.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a configuration of a mechanical part of an ultrasonic tissue evaluation apparatus according to the present invention.

FIG. 2 is a block diagram showing an overall configuration of an ultrasonic tissue evaluation apparatus according to the present invention.

FIG. 3 is a flowchart illustrating a first application example of the method of measuring the speed of sound in a tissue.

FIG. 4 is an explanatory diagram showing a state in which transducer covers are pressed together during a preparation measurement step.

FIG. 5 is an explanatory diagram showing a state where a subject is sandwiched between transducer units in an actual measurement process.

FIG. 6 is a schematic view showing a vibrator unit having a matching material temperature sensor.

FIG. 7 is a flowchart showing a second applied example of the method of measuring the speed of sound in a tissue.

FIG. 8 is a flowchart showing a third applied example of the method of measuring the speed of sound in a tissue.

FIG. 9 is an explanatory diagram showing a state where a reference body is sandwiched between transducer units in a preparatory measurement step of the third applied example.

FIG. 10 is a flowchart illustrating a fourth applied example of the method of measuring the speed of sound in a tissue.

[Explanation of symbols]

10a, 10b vibrator unit, 12a, 12b ultrasonic vibrator, 14a, 14b vibrator cover, 16a,
16b acoustic matching material, 18a, 18b vibrator case,
20a, 20b cord, 22a, 22b arm, 2
4a, 24b screw receiving portion, 26 laser length measuring device, 28
Reflector, 30 feed screw, 32 torque limiter, 34
Handle, 40 transmission amplifier, 42 reception amplifier, 4
4 A / D converter, 50 control unit, 52 oscillator control unit, 54 propagation time measurement unit, 56 length measurement unit control unit, 58
Sound speed calculation processing unit, 60 memories.

Continuation of the front page (56) References JP-A-5-237101 (JP, A) JP-A-4-183453 (JP, A) JP-A-6-174697 (JP, A) JP-A-2-104337 (JP) , A) Japanese Utility Model Application 57-197431 (JP, U) Japanese Utility Model Application 1-74084 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 8/00-8/15 G01N 29/00-29/28

Claims (4)

(57) [Claims] An ultrasonic tissue evaluation apparatus for evaluating a living tissue portion including a bone using ultrasonic waves, comprising a pair of transducer units for transmitting and receiving ultrasonic waves,
A vibrator unit including an ultrasonic vibrator and an acoustic matching material provided on a front surface of the ultrasonic vibrator; a vibrator unit moving mechanism for changing a distance between the pair of vibrator units; At the same time, the ultrasonic wave is transmitted and received in a state where the pair of vibrator units are directly pressed at a predetermined pressure or a predetermined reference body is held at a predetermined pressure, and the propagation time of the ultrasonic wave between the two units is measured. In the actual measurement step, the pair of transducer units transmit and receive ultrasonic waves with the living tissue portion including the bone at the predetermined pressure, and measure the ultrasonic propagation time between the two units. Control means for calculating a sound velocity of the living tissue portion or an evaluation value based on the sound velocity from the ultrasonic propagation times measured in the measurement step and the actual measurement step, respectively, the preparation measurement step and the actual measurement Limiting means for limiting the force by which the vibrator unit moving mechanism moves the vibrator unit, such that the force for bringing the vibrator unit into contact with the living tissue portion is limited to the same predetermined value. The vibrator unit moving mechanism comprises: a driving force generating means for generating a driving force; and a feed screw rotated by the driving force from the driving force generating means to move the pair of vibrator units. And a torque limiter that is provided between the driving force generating means and the feed screw and limits a driving force transmitted from the driving force generating means to the feed screw to a predetermined value. An ultrasonic tissue evaluation device characterized by including: 2. An ultrasonic tissue evaluation apparatus for evaluating a living tissue portion including a bone using ultrasonic waves, comprising: a pair of transducer units for transmitting and receiving ultrasonic waves; and a pair of transducer units facing each other. While the pair of
Anda transducer unit moving mechanism for changing the distance between the transducer unit, the transducer unit moving mechanism includes a driving force generating means for generating a driving force, while facing the pair of transducer units, wherein Pair of
In order changing the distance between the transducer unit, a feed screw rotated by the driving force from the driving force generating means, provided between said feed screw and said driving force generating means,
And a torque limiter for limiting a driving force transmitted from the driving force generating means to the feed screw to a predetermined value, wherein the driving force transmitted to the feed screw is limited to a predetermined value after the operation of the torque limiter. An ultrasonic tissue evaluation apparatus for transmitting and receiving ultrasonic waves in a state. 3. An ultrasonic tissue evaluation apparatus for evaluating a living tissue portion including a bone using ultrasonic waves, comprising: a pair of transducer units for transmitting and receiving ultrasonic waves; A vibrator unit moving mechanism for changing a distance, wherein the vibrator unit moving mechanism comprises: a driving force generating means for generating a driving force; and a driving force generating means for moving the pair of vibrator units. A feed screw that is rotated by the driving force of, and is provided between the driving force generating means and the feed screw,
And a torque limiter for limiting a driving force transmitted from the driving force generating means to the feed screw to a predetermined value, wherein the driving force transmitted to the feed screw is limited to a predetermined value after the operation of the torque limiter. An ultrasonic tissue evaluation apparatus for transmitting and receiving ultrasonic waves in a state. 4. The ultrasonic tissue evaluation apparatus according to claim 3, wherein the feed screw has a forward screw part and a reverse screw part whose winding directions are opposite to each other, and one of the forward screw parts is one. And a screw receiver supporting the other vibrator unit is engaged with the reverse screw portion.