JPH09224934A - Osteoporosis diagnostic device - Google Patents

Abstract

(57) [Abstract] [Problem] To measure a bone density and elastic modulus to easily perform a highly reliable diagnosis. First, an ultrasonic pulse is repeatedly emitted obliquely toward a predetermined cortical bone of a subject, a surface wave is excited on the surface of the cortical bone, and the leaked wave is received. The received signal is converted into a digital signal by the A / D converter 8,
The leak wave level is detected by the CPU 11. CPU
Reference numeral 11 extracts the maximum leaky wave level and calculates the sound velocity in the cortical bone based on the propagation time corresponding to the maximum leaky wave level. Next, ultrasonic pulses are repeatedly radiated toward the cortical bone, the echo from the cortical bone is received, the A / D converter 8 converts the echo into a digital echo signal, and the CPU 11
To detect the echo level. The CPU 11 extracts the maximum echo level and calculates the acoustic impedance of the cortical bone based on this maximum echo level. The density and elastic modulus of the cortical bone are calculated from the speed of sound in the cortical bone and the acoustic impedance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention radiates an ultrasonic pulse toward a predetermined cortical bone of a subject and measures an echo level from the surface of the cortical bone to measure an ultrasonic reflex type ultrasonic wave. The present invention relates to an osteoporosis diagnostic device.

[0002]

2. Description of the Related Art In recent years, with the advent of an aging society, a bone disease called osteoporosis has become a problem. this is,
It is a disease that causes calcium to escape from bones and becomes scuffed and easily broken with a slight shock, which is one of the causes of so-called bedridden elderly people. The physical diagnosis of osteoporosis is mainly performed by precisely measuring the bone density with a diagnostic device using X-rays such as DXA, but the physical diagnosis with X-rays requires a large-scale device. In addition, there is a troublesome problem in that it is subject to various restrictions from the viewpoint of preventing radiation exposure damage.

[0003] As a simple device that does not cause such inconveniences at all, diagnostic devices using ultrasonic waves have begun to spread. A diagnostic device that uses ultrasonic waves measures the speed of sound and attenuation when the ultrasonic waves propagate through bone tissue,
If the bone density or the elastic modulus of the bone is estimated and a low estimated value can be obtained, it can be considered that it is because calcium has escaped from the bone, and thus osteoporosis is diagnosed. For example, in the diagnostic apparatus described in Japanese Patent Application Laid-Open No. 2-104337, an ultrasonic pulse is emitted from one ultrasonic transducer toward a bone tissue of a subject, which is a measurement site, and an ultrasonic pulse transmitted through the bone tissue is emitted. By receiving the wave with the other ultrasonic transducer, the sound speed in the bone tissue is measured, and the lower the sound speed in the bone tissue, the more the diagnosis of osteoporosis is progressing. This is because the diagnosing device operates on the assumption that, in experience, the speed of sound in bone tissue is proportional to bone density and elastic modulus of bone.

[0004]

However, the rationale for the fact that the speed of sound is proportional to bone density and elastic modulus of bone is uncertain. Strictly speaking, the speed of sound in bone tissue is Is not proportional to the elastic modulus of
Bone density]. Moreover, since the elastic modulus of bone and the bone density contribute to the speed of sound in such a way that the elastic modulus of bone increases as the bone density increases, the speed of sound in the bone tissue increases as the bone density increases. It cannot respond sensitively, and the correlation coefficient between sound speed and bone density in bone tissue is never high. In addition, the rationale for linking bone density with ultrasonic attenuation is uncertain. Therefore, in order to obtain a highly reliable diagnosis from the conventional diagnostic device that diagnoses osteoporosis by estimating the bone density and the elastic modulus of the bone from the measurement results of the sound velocity and the attenuation of the ultrasonic wave in the bone tissue, It was impossible.

The present invention has been made in view of the above-mentioned circumstances, and is of an ultrasonic reflection type capable of performing a more reliable diagnosis than the conventional one, even though it is a simple type with no fear of radiation exposure. It is an object to provide an osteoporosis diagnostic device.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 applies an ultrasonic transducer to a skin surface covering a predetermined cortical bone of a subject,
The ultrasonic wave pulse is repeatedly emitted toward the cortical bone under the skin while changing the orientation of the transmitting / receiving surface of the ultrasonic transducer within a predetermined solid angle range including the orientation of the normal line of the cortical bone surface. Then, each time one pulse is emitted, the echo returning from the cortical bone surface is received by the ultrasonic transducer, the received signal is converted into a digital signal by an analog / digital converter, and the digitized echo signal is converted. An ultrasonic reflex-type osteoporosis diagnostic device for diagnosing osteoporosis by performing signal processing using an echo level detecting means for detecting an echo level from the input echo signal, and a plurality of the detected echo levels. The maximum echo level extraction means for extracting the maximum echo level from among Acoustic impedance calculation means for calculating the acoustic impedance of cortical bone, sonic velocity measurement means for applying an ultrasonic pulse to a predetermined cortical bone of a subject, and measuring the sound velocity of the ultrasonic pulse in the cortical bone, and the sonic velocity measurement Based on the acoustic velocity of the cortical bone measured by means and the acoustic impedance of the cortical bone calculated by the acoustic impedance calculation means, a bone density calculation means for calculating the density of the cortical bone, the bone It is characterized in that osteoporosis is diagnosed using the density of the cortical bone calculated by the density calculating means as an index.

According to a second aspect of the present invention, the ultrasonic transducer is applied to the skin surface covering a predetermined cortical bone of the subject, and the direction of the transmitting / receiving surface of the ultrasonic transducer is determined by the method of the cortical bone surface. The ultrasonic pulse is repeatedly emitted toward the cortical bone under the skin while changing variously within a predetermined solid angle including the direction of the line, and an echo returning from the surface of the cortical bone with each pulse emission. Is received by the ultrasonic transducer, the received signal is converted into a digital signal by an analog / digital converter, and signal processing is performed using the digitized echo signal to diagnose osteoporosis. An osteoporosis diagnostic device, comprising: echo level detection means for detecting an echo level from the input echo signal; and a plurality of detected echo levels. Maximum echo level extraction means for extracting the maximum echo level from among the above, based on the extracted maximum echo level, acoustic impedance calculation means for calculating the acoustic impedance of the cortical bone, predetermined cortical bone of the subject An ultrasonic pulse is applied to, and a sound velocity measuring means for measuring the sound velocity of the ultrasonic pulse in the cortical bone,
Based on the acoustic velocity of the cortical bone measured by the sound velocity measuring means and the acoustic impedance of the cortical bone calculated by the acoustic impedance calculating means, an elastic modulus calculating means for calculating the elastic modulus of the cortical bone. It is characterized in that osteoporosis is diagnosed using the elastic modulus of the cortical bone calculated by the elastic modulus calculating means as an index.

The invention according to claim 3 is the osteoporosis diagnosing device according to claim 1 or 2, wherein the acoustic impedance calculating means is based on the maximum echo level extracted by the maximum echo level extracting means. Then, the ultrasonic reflection coefficient of the cortical bone with respect to the soft tissue of the subject is calculated, and the acoustic impedance of the cortical bone is calculated based on the calculated ultrasonic reflection coefficient.

[0009] The invention described in claim 4 is the first invention.
The osteoporosis diagnostic apparatus according to 2 or 3, wherein the sound velocity measuring means measures the sound velocity of a surface wave propagating on the cortical bone surface by injecting an ultrasonic pulse obliquely into a predetermined cortical bone of the subject. Based on the sound velocity of the sound wave and the sound velocity of the surface wave measured by the sound wave velocity measuring means, the sound velocity of the longitudinal wave in the cortical bone is calculated as the sound velocity of the ultrasonic pulse. It is characterized by becoming.

[0010] The invention according to claim 5 is based on claim 1,
2. The osteoporosis diagnostic device according to 2, 3, or 4, wherein the surface wave sound velocity measuring means obliquely applies an ultrasonic pulse to the cortical bone under the skin while being applied to the skin surface covering a predetermined cortical bone of the subject. From the ultrasonic wave transducer for generating a surface wave propagating on the surface of the cortical bone and a known distance from the ultrasonic transducer for wave transmission, and receives the surface wave or its leaky wave. An ultrasonic transducer for receiving waves, and the ultrasonic pulse is input from the ultrasonic transducer for transmitting waves toward the cortical bone, and then the surface wave propagates on the surface of the cortical bone to generate the surface wave or the surface wave thereof. And a measuring unit for measuring a propagation time required for the leaky wave to be received by the receiving ultrasonic transducer.

Further, the invention according to claim 6 is the osteoporosis diagnostic device according to claim 5, wherein the ultrasonic transducers for transmitting and receiving waves have one end surface joined to an ultrasonic transducer. It is characterized in that it has an ultrasonic coupler in which the other end surface which comes into contact with the skin of the subject intersects with each other in a wedge shape.

[0012]

In the configuration of the present invention, ultrasonic pulses are repeatedly emitted from the ultrasonic transducer toward a predetermined cortical bone of the subject, and echoes returning from the surface of the cortical bone are emitted by the ultrasonic transducer with each pulse emission. Then, the acoustic impedance of the cortical bone is calculated based on the received signal. On the other hand, a pair of injection and receiving ultrasonic transducers on the skin surface covering the cortical bone so that the directions of the transmitting surface and the receiving surface form respective predetermined angles with respect to the predetermined cortical bone surface of the subject. The ultrasonic wave pulse is placed and the ultrasonic pulse is injected obliquely from the input ultrasonic transducer toward the cortical bone to generate a surface wave, and the ultrasonic pulse propagating near the surface of the cortical bone is received. The sound velocity of the surface wave of the ultrasonic pulse propagating on the cortical bone surface is measured by receiving the ultrasonic wave and measuring the time for the ultrasonic pulse to propagate between the input and receiving ultrasonic transducers. Then, the sound velocity of the longitudinal wave is calculated based on the sound velocity of the surface wave. Then, based on the calculated acoustic impedance of the cortical bone and the sound velocity of the longitudinal wave, the density of the cortical bone is calculated from the relation of [bone density] = [acoustic impedance] / [speed of sound],
The elastic modulus of the cortical bone is calculated from the relationship of [elastic modulus of bone] = [acoustic impedance] × [speed of sound], and osteoporosis is diagnosed using the density or elastic modulus of the cortical bone as an index.

According to the structure of the present invention, the density of cortical bone indicating the degree of clogging of the composition of cortical bone, or the elastic modulus of cortical bone, which is a measure of the fracture resistance of bone, is determined based on the received echo. Based on the calculated acoustic impedance of the cortical bone and the longitudinal wave velocity of the ultrasonic pulse in the cortical bone measured by the sound velocity measuring means, directly and accurately calculated, using the density or elastic modulus of the cortical bone as an index. Because it diagnoses osteoporosis,
A more reliable diagnosis can be performed. Also, X
Since no line is used, it is possible to easily perform a safe measurement without fear of radiation exposure.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The description will be specifically made using an embodiment. First Embodiment FIG. 1 is a block diagram showing an electrical configuration of an osteoporosis diagnostic device according to a first embodiment of the present invention, FIG. 2 is an external view of the device, and FIG. 3 is a usage state of the device. The schematic diagram shown in FIG.
FIG. 5 is a schematic diagram showing a usage state of the device, FIG. 5 is a flow chart showing an overall processing flow (main routine) of the device, and FIG. 6 is a processing flow of the device when measuring a sound velocity of an ultrasonic pulse. FIG. 7 is a flow chart showing a (sonic velocity measurement subroutine), FIG. 7 is a flow chart showing a processing flow (acoustic impedance calculation subroutine) of the device when calculating the acoustic impedance of cortical bone, and FIG. 8 is an explanation of the operation of the device. FIG. 9 is a diagram used and FIG. 9 is a diagram used to explain the operation of the apparatus.

In the osteoporosis diagnostic apparatus of this example, as shown in FIGS. 1 to 4, every time an electric pulse signal is input at a predetermined cycle, in response to this, a predetermined cortex of the subject, which is the measurement site, is responded to. An echo measurement in which an ultrasonic pulse Ai is emitted toward the bone Mb and an echo (hereinafter referred to as a bone echo) Ae returning from the surface Y of the cortical bone Mb is received and converted into a received signal (electrical signal). Ultrasonic transducer (hereinafter simply referred to as echo measurement transducer)
1 and a pair of ultrasonic transducers for emitting or receiving ultrasonic pulses, each time an electric pulse signal is input in a predetermined cycle, in response thereto, an ultrasonic pulse Ai is applied. An ultrasonic pulse Bi is obliquely emitted from one ultrasonic transducer toward a predetermined cortical bone Mb of the subject in the same region as the region to excite a surface wave Bs propagating on the surface of the cortical bone Mb and to generate a cortex. Ultrasonic waves returning from the surface Y of the bone Mb (hereinafter referred to as leakage wave) Be
Ultrasonic transducer for sonic velocity measurement (hereinafter, simply referred to as sonic velocity measurement transducer) 2 for receiving a wave by another ultrasonic transducer and converting it into a received signal (electrical signal), an echo measurement transducer 1 and a sonic velocity measurement An electric pulse signal is supplied to the transducer 2 for processing, the received signal output from the transducer 1 for echo measurement is processed to extract the bone echo level which is the amplitude of the reflected wave from the cortical bone Mb, and the bone echo level is extracted. On the other hand, the acoustic impedance is calculated based on the above, and the received signal output from the sound velocity measurement transducer 2 is processed to measure the propagation time of the surface wave Bs propagating on the surface Y of the cortical bone Mb, and this propagation time is measured. The sound velocity of the longitudinal wave is calculated based on the above, and the density and the elasticity of the cortical bone Mb are calculated from the acoustic impedance and the sound velocity of the longitudinal wave. To calculate the rate, which is and a device body 3 for diagnosis of osteoporosis.

Here, in the acoustic impedance calculation mode for obtaining the acoustic impedance of the cortical bone Mb, the echo measuring transducer 1 and the apparatus main body 3 are used for measuring the acoustic velocity in the acoustic velocity measuring mode for obtaining the acoustic velocity of the longitudinal wave in the cortical bone Mb. The transducer 2 and the device body 3 operate. The echo measuring transducer 1 and the device body 3 are connected to each other by the sound velocity measuring transducer 2 and the device body 3 by cables C1 and C2, respectively.

The echo measuring transducer 1 is
The ultrasonic vibrator 1a having electrode layers on both sides of a disk-shaped thickness vibration type piezoelectric element such as lead titan zirconate (PZT) is mainly constituted, and one electrode surface of the ultrasonic vibrator 1a (super An ultrasonic wave delay spacer 1b such as polyethylene bulk is fixed to the transmission / reception surface of the sound wave pulse Ai in order to remove the effect of transmission reverberation. The ultrasonic delay spacer 1b can be omitted when the transmission reverberation does not affect the reception of the bone echo Ae. Here, in order to perform a highly accurate measurement, the ultrasonic pulse Ai, which can be regarded as a plane wave from the transmitting and receiving surface of the transducer 1 for echo measurement, can be emitted toward the cortical bone Mb, and can be regarded as a plane wave. Since it is desirable that the echo Ae returns to the transmitting / receiving surface, it is preferable that the transmitting / receiving surface is as wide as possible as the echo measuring transducer 1 (in this example, the transmitting / receiving surface diameter D is 15 [mm]).
Set to). From the same viewpoint, the cortical bone Mb, which is the measurement site, has a large flatness with a large radius of curvature, for example,
It is preferable to select cortical bone Mb such as tibia.

The sonic velocity measuring transducer 2 includes a transmitting ultrasonic transducer (hereinafter referred to as a transmitting unit) 21 that emits an ultrasonic pulse Bi and a receiving ultrasonic transducer (hereinafter, referred to as a transmitting wave) 21 that receives a leakage wave Be. Called the wave receiver)
22 and a connecting portion 23 connecting the wave transmitting portion 21 and the wave receiving portion 22. The wave transmission unit 21 has an ultrasonic wave coupler 21b such as a wedge-shaped polyethylene bulk on the wave transmission surface of the ultrasonic wave oscillator 21a having the same configuration as the ultrasonic wave oscillator 1a, and the wave receiving unit 22 has the ultrasonic wave oscillator 22a. Ultrasonic couplers 22b such as wedge-shaped polyethylene bulks are joined to the wave-receiving surface. The connecting portion 23 is made of a flexible member having a predetermined length (for example, about 100 [mm]). The ultrasonic coupler 21b includes a bonding surface S1 bonded to the ultrasonic transducer 21a and a contact surface S contacting the skin surface X.
2 and the ultrasonic transducer 21a is joined to the joint surface S1 and the contact surface S2 is in contact with the skin surface X,
The ultrasonic pulse Bi emitted from the transmitting unit 21 is the cortical bone M.
In order to excite the surface wave Bs that is incident on b at a critical angle and propagates in the vicinity of the surface Y of the cortical bone along the surface Y, the joint surface S1
And the contact surface S2 form a predetermined angle.

The ultrasonic coupler 22b is an ultrasonic transducer 22.
It has a joint surface S3 joined to a and a contact surface S4 brought into contact with the skin surface X, and the ultrasonic transducer 22a is joined to the joint surface S3, and the contact surface S4 is attached to the skin surface X. Leaky wave Be generated by leaking the surface wave Bs propagating along the surface Y in the vicinity of the cortical bone surface Y to the soft tissue Ma side in the contact state.
So that the contact surface S3 and the contact surface S4 form a predetermined angle. The ultrasonic pulse Bi is the soft tissue M.
The condition that the surface wave Bs is generated when the light enters the cortical bone Mb at the incident angle θi from the a side is that the sound velocity in the soft tissue Ma is V
a and the sound velocity of the surface wave is Vs, [sin θi = Vs
/ Va], and the incident angle θi at this time is the critical angle. Here, the cortical bone Mb to be measured is selected to be substantially the same as the part that radiates the ultrasonic pulse Ai from the echo measurement transducer 1, but is a part having a large radius of curvature and good flatness. It is desirable that this flatness is a portion where the flatness is maintained for a certain length. This reduces noise such as echoes from the soft tissue Ma and captures desired ultrasonic waves,
This is because the wave transmitter 21 and the wave receiver 22 need to be separated by a predetermined distance or more. From this point as well, cortical bone Mb such as tibia
It is preferable to select

The apparatus main body 3 includes a pulse generator 4, a matching circuit 5, an amplifier 6, a waveform shaper 7, an A / D converter 8, a ROM 9, a RAM 10, and a CPU (central processing unit). 11, a level meter 12, a display unit 13, and a timing circuit 14 are roughly configured. Pulse generator 4
Is connected to an echo measurement transducer 1 (sound velocity measurement transducer 2) via a cable C1 (cable C2) and repeatedly generates an electric pulse signal having a center frequency of approximately 2.5 MHz at a predetermined cycle (for example, 100 msec). And transmits it to the echo measurement transducer 1 (sound velocity measurement transducer 2). In addition, in the sound velocity measurement mode, in addition to the above operation, the timing start signal Ta is supplied to the timing circuit 14 at the same timing as the transmission of this electric pulse signal to the sound velocity measurement transducer 2.

The period of this electric pulse signal is set to be sufficiently longer than the leak wave arrival time Ts described later. The matching circuit 5 enables transmission / reception of signals with maximum energy efficiency between the device main body 3 and the echo measurement transducer 1 (sound velocity measurement transducer 2) connected via the cable C1 (cable C2). , Impedance matching is performed. Therefore, in the acoustic impedance calculation mode, the received wave signal is transmitted by the ultrasonic transducer 1a of the echo measurement transducer 1 to the bone echo Ae.
Every time the wave is received, it is output from the echo measuring transducer 1 and input to the amplifier 6 via the matching circuit 5 without energy loss. In the sound velocity measuring mode, similarly, the sound velocity measuring transducer 2 When the ultrasonic transducer 22a of receives the leaky wave Be, the received signal is
It is input to the amplifier 6 without loss of energy.

The amplifier 6 amplifies the received signal input via the matching circuit 5 with a predetermined amplification degree and then inputs it to the waveform shaper 7. The waveform shaper 7 is composed of a band-pass filter having an LC structure, performs a filtering process on the received signal amplified by the amplifier 6, and linearly shapes the noise to remove a noise component, and then the A / D converter 8 To enter. A /
The D converter 8 includes a sample hold circuit (not shown), a sampling memory (SRAM), and the like, and in accordance with a sampling start request from the CPU 11, the output signal of the waveform shaper 7 (an analog received signal whose waveform has been shaped) is input. Is sequentially sampled at a predetermined frequency (for example, 12 MHz) into a digital signal (hereinafter referred to as a bone echo signal in the acoustic impedance calculation mode and a leaky wave signal in the sound velocity measurement mode), and the obtained bone is obtained. The echo signal (leakage wave signal) is temporarily stored in its own sampling memory and then sent to the CPU 11.

The ROM 9 stores a processing program executed by the CPU 11 for diagnosing osteoporosis in addition to the operating system (OS). This processing program is a procedure for detecting a bone echo level (leakage wave level) by taking in a bone echo signal (leakage wave signal) from the A / D converter 8 for each one pulse and one echo. Procedure for extracting the maximum bone echo level (maximum leaky wave level) from the bone echo level (leakage wave level) of the subject, and the ultrasonic reflection of the cortical bone Mb with respect to the soft tissue Ma of the subject based on the extracted maximum bone echo level The procedure for calculating the coefficient R, the procedure for calculating the acoustic impedance Zb of the cortical bone Mb of the subject based on the calculated ultrasonic reflection coefficient R, and the cortical bone based on the leaky wave arrival time Ts corresponding to the maximum leaky wave level A procedure for calculating the sound velocity Vl of the longitudinal wave in Mb, a procedure for calculating the bone density ρ of the cortical bone Mb of the subject based on the acoustic impedance Zb and the sound velocity Vl of the longitudinal wave, and A procedure for calculating the elastic modulus E of the cortical bone Mb of the subject based on the acoustic impedance Zb and the sound velocity Vl of the longitudinal wave is described.

In this processing program, the sound velocity Vl of the longitudinal wave in the cortical bone Mb of the subject is given by the equation (1).

Vl = αL / (Ts−2Tp) (1) α: Sound velocity of longitudinal waves propagating in cortical bone Mb and cortical bone surface Y
Ratio of the surface wave Bs propagating in the sound wave to the sound velocity (known) L: Distance on the cortical bone surface Y when the surface wave Bs propagates on the cortical bone surface Y (known) Tp: The ultrasonic pulse Bi is the ultrasonic coupler 21b And the time required to pass through the soft tissue Ma or the time required for the leaky wave Be to pass through the soft tissue Ma and the ultrasonic coupler 22b (known).

The acoustic impedance Zb of the subject's cortical bone Mb is given by equation (2).

## EQU00002 ## Zb = Za (R + 1) / (1-R) (2) Za: Acoustic impedance of soft tissue Ma (known) Here, the surface Y of the cortical bone Mb is a substantially flat surface, and from the echo measurement transducer 1. The emitted ultrasonic pulse Ai is also a plane wave, and when it can be considered that the wavefront is substantially parallel to the surface Y of the cortical bone Mb (that is, the ultrasonic pulse Ai
Is incident on the surface Y of the cortical bone Mb substantially vertically), the ultrasonic reflection coefficient R of the cortical bone Mb with respect to the soft tissue Ma of the subject.
Is represented by equation (3). By the way, the bone echo level becomes maximum when the ultrasonic pulse Ai is incident on the surface Y of the cortical bone Mb substantially perpendicularly. Therefore, the maximum bone echo level extracted by this example is, as described below,
Since the ultrasonic pulse Ai is obtained when the ultrasonic pulse Ai is incident on the surface Y of the cortical bone Mb substantially perpendicularly, the ultrasonic reflection coefficient R calculated from the extracted maximum bone echo level is the ultrasonic wave given by the equation (3). It matches the reflection coefficient R. therefore,
By transforming equation (3), equation (2) is obtained.

## EQU00003 ## R = (Zb-Za) / (Zb + Za) (3)

Then, the sound velocity Vl of the longitudinal wave calculated from the equation (1) and the acoustic impedance Z calculated from the equation (2).
From b and b, the bone density ρ of the cortical bone Mb of the subject is obtained by equation (4), and the elastic modulus E of the cortical bone Mb of the subject is obtained by equation (5).

(4) ρ = Zb / Vl (4)

[Equation 5] E = Zb · Vl (5)

The RAM 10 has a working area in which a work area of the CPU 11 is set and a data area for temporarily storing various data. In the data area, a bone echo level detected this time (current bone echo level) or , Leak wave level detected this time (leak wave level this time), maximum bone echo level (maximum leak wave level) extracted from the bone echo levels detected so far (leak wave level)
The data memory area that stores the data, the bone echo waveform received this time (current bone echo waveform), the leak wave waveform received this time (current leak wave waveform), and the maximum bone echo level (maximum leak wave level) are detected. The waveform memory area that stores the bone echo waveform (maximum bone echo waveform) or leaky wave waveform (maximum leaky waveform) received when Has been done.

The CPU 11 executes the above-mentioned various processing programs stored in the ROM 9 using the RAM 10 to control the pulse generator 4 and the A / D converter 8 and other parts of the apparatus, and 1 pulse 1 pulse The bone echo signal (leakage wave signal) is taken from the A / D converter 8 for each echo (leakage wave) to detect the bone echo level (leakage wave level). Level), in the acoustic impedance calculation mode, the ultrasonic reflection coefficient R of the cortical bone Mb with respect to the soft tissue Ma of the subject is calculated based on the extracted maximum bone echo level value, and the calculated ultrasonic wave is calculated. The acoustic impedance Zb of the cortical bone Mb of the subject is calculated based on the reflection coefficient R, while in the sound velocity measurement mode, the leak corresponding to the maximum leak wave level is obtained. The sound velocity Vl of the longitudinal wave in the cortical bone Mb is calculated based on the arrival time of the leaky wave, and the acoustic impedance Zb and the sound velocity Vl of the longitudinal wave obtained in both modes are calculated.
Based on the above, the bone density ρ of the cortical bone Mb and the elastic modulus E of the cortical bone Mb of the subject are calculated to diagnose osteoporosis.

The level meter 12 is controlled by the CPU 11 and the current bone echo level (current leak wave level) stored in the RAM 10 is used as the deflection of the liquid crystal pointer pattern 12a shown by the broken lines in FIGS. The maximum bone echo level (maximum leaky wave level) detected up to (this time) is simultaneously displayed as the deflection of the liquid crystal pointer pattern 12b shown by the solid line in the figure. Further, the display 13 is composed of a CRT display or a liquid crystal display, etc., and under the control of the CPU 11, the maximum bone echo level (measured value), the maximum leaky wave level (measured value), the leaky wave arrival time Ts (measured value), Sound wave reflection coefficient R (calculated value), acoustic impedance Zb (calculated value), sound velocity Vl (measured value) of longitudinal waves in cortical bone Mb, bone density ρ (calculated value), elastic modulus E
(Calculated value), current bone echo waveform, maximum bone echo waveform, current leak wave waveform, maximum leak wave waveform, etc. are displayed on the screen.

The clock circuit 14 is used in the sound velocity measurement mode, and reaches the leak wave until the leak wave Be returns to the wave receiving surface after the ultrasonic pulse Bi is emitted from the wave sending surface of the sound velocity measuring transducer 2. Measure the time Ts. The clock circuit 14 is composed of a clock generator (not shown) and a counter circuit (not shown). Each time the pulse generator 4 supplies the clock start signal Ta, the clock circuit 14 starts clocking and the A / D converter 8 outputs an end signal. When receiving the, the time measurement is ended. Then, the time count value is held until it is reset, and the held time count value is C as the leakage wave arrival time Ts upon request.
It is given to PU11.

Next, with reference to FIGS. 3 to 9, the operation of this example (mainly the processing flow of the CPU 11 at the time of osteoporosis diagnosis) will be described. First, a cortical bone Mb such as a tibia having a large radius of curvature over a predetermined range, close to the surface of the skin, and a relatively thick bone is selected as a measurement site. As a result, the measurement accuracy is improved, noise is less mixed, and stable measurement with good reproducibility becomes possible. When the device is powered on, the CPU 11 performs presetting of each part of the device, initial setting of counters, various registers, and various flags (step SP10 (FIG. 5)),
Since the CPU 11 waits until the sound velocity measurement start switch is pressed (step SP11), the operator at this point, as shown in FIG. 3, the surface of the soft tissue Ma that covers the cortical bone Mb that is the measurement site of the subject ( The ultrasonic gel G is applied to the surface X of the skin, the transducer 2 for measuring the sound velocity is applied to the surface X of the skin through the ultrasonic gel G, and the transmitting / receiving surface is the cortical bone Mb.
Turn the measurement start switch on while facing to. When the sound velocity measurement start switch is turned on (step SP1
1), this osteoporosis diagnostic device enters the sound velocity measurement mode, and proceeds to the sound velocity measurement subroutine (step SP1).
2), the CPU 11 writes "1" in the measurement continuation flag to set the measurement continuation flag, and thereafter starts the measurement operation according to the processing procedure shown in FIG.

The CPU 11 first sets the pulse generator 4 to 1
A pulse generation command is issued (step SP20). When the pulse generator 4 receives the one-pulse generation command from the CPU 11, the pulse generator 4 converts the electric pulse signal into the sonic velocity measurement transducer 2
And also supplies the clock start signal Ta to the clock circuit 14 at the same timing as the transmission of this electric pulse signal. The sound velocity transducer 2 is a pulse generator 4
When an electric pulse signal is supplied from the transmitting unit 21, the transmitting unit 21 obliquely emits an ultrasonic pulse Bi toward the cortical bone Mb of the subject at a predetermined angle. On the other hand, the timing circuit 14 starts timing at the same time as receiving the timing start signal Ta from the generator 4. As shown in FIG. 3, the ultrasonic pulse Bi emitted from the sound velocity measuring transducer 2 has a soft tissue Ma.
Surface waves Bs propagating in the cortical bone Mb at a critical angle and propagating on the cortical bone surface Y are generated. This surface wave B
s propagates on the cortical bone surface Y while leaking to the soft tissue Ma side, propagates over a predetermined distance L, and then leaks the leaky wave B.
e is captured by the wave receiving portion 22 of the sound velocity measuring transducer 2. The leaky wave Be is received by the ultrasonic transducer 22a and then converted into a received signal corresponding to the waveform and amplitude of the ultrasonic wave. The received signal generated is
It is input to the apparatus main body 3 (matching circuit 5) via the cable C2, amplified by the amplifier 6 with a predetermined amplification degree, linearly shaped by the waveform shaper 7, and then input to the A / D converter 8. It

The CPU 11 sends a 1-pulse generation command to the pulse generator 4 (step SP20), and after the leak wave Be is received by the ultrasonic transducer 22a of the sound velocity measuring transducer 2, the A / D converter. A sampling start instruction is issued to 8 (step SP21). When the A / D converter 8 receives the sampling start command from the CPU 11, the A / D converter 8 waveform-shapes the waveform from the waveform shaper 7, and then receives the received signal for one leaky wave from the cortical bone Mb at a predetermined frequency ( For example, it is sampled at 12 MHz) and converted into a digital signal, and the obtained N sample values (digital signal for one leaky wave) are temporarily stored in its own sampling memory. On the other hand, an end signal is sent to the time counting circuit 14 to end the time counting. After that, N sample values stored in the sampling memory are sequentially transmitted to the CPU 11 in response to a transfer request from the CPU 11. The CPU 11 sequentially fetches N sample values from the A / D converter 8 and stores them as a leak waveform of this time in the waveform memory area of the RAM 10, and then extracts the largest value from the N sample values. Thus, the current leaky wave level (amplitude of the current leaky wave) is detected, and the detection result is stored in the data memory area of the RAM 10. On the other hand, when the leaky wave signal Ea is read, the leaky wave arrival time is read from the time counting circuit 14, and the read current leaky wave arrival time is also stored in the data memory area of the RAM 10. (Step SP22). The current leaky wave level stored in the RAM 10 is displayed as a deflection of the liquid crystal pointer pattern 12a on the level meter 12 and the current leaky wave arrival time is displayed on the display 13 as shown by the broken line in FIG. (Step SP23).

Next, the CPU 11 reads the current leak wave level and the maximum leak wave level from the data memory area in the RAM 10, and determines whether the value of the current leak wave level is larger than the value of the maximum leak wave level. Is determined (step SP24). This is the first time judgment, and the maximum leakage wave bone level value remains the initial setting value "0".
11 determines that the value of the current leaky wave level is larger than the value of the maximum leaky wave level, and rewrites the value of the maximum leaky wave level stored in the data memory area of the RAM 10 to the value of the current leaky wave level, Further, the maximum level leaky wave arrival time corresponding to the maximum leaky wave level is rewritten to the current leaky wave arrival time, and further, the maximum leaky wave waveform stored in the waveform memory area of the RAM 10 is rewritten to the current leaky wave waveform (step SP25). Then, the updated maximum leaky wave waveform and the maximum level leaky wave arrival time are displayed on the display 13, and the updated maximum leaky wave level is displayed on the level meter 12 as shown by the solid line in FIG. It is displayed as a shake of the liquid crystal pointer pattern 12b (step SP26).

Next, the CPU 11 looks at the measurement continuation flag in the RAM 10 (step SP27), and if the measurement continuation flag is set (when the content of the measurement flag is "1"), the CPU 11 determines that the measurement is continued. After making a determination and repeating the above-described 1-pulse emission and 1-leakage wave reception (steps SP20 to SP23), RA is again performed in step SP24.
The current leaky wave level and the maximum leaky wave level are read from the data memory area in M10, and it is determined whether the value of the current leaky wave level is larger than the value of the maximum leaky wave level. If the result of this determination is that the leaky wave level at this time is not greater than the maximum leaky wave level, the update processing is not performed and the process directly goes to step SP27 to see the measurement continuation flag.
The content of the measurement continuation flag is kept at "1" unless the operator presses the measurement end switch, and the CPU 11 receives the above-mentioned 1 pulse emission 1 leakage wave reception (steps SP20 to SP2).
3), maximum bone echo level extraction work (step SP2
4 to step SP27) are repeated.

While the CPU 11 repeats the above-described processing (steps SP20 to SP27), the operator changes the sound velocity measuring transducer 2 to the skin surface X as shown in FIG.
The contact part 23 toward the measurement site cortical bone Mb.
With a constant length, the contact surface S2 of the ultrasonic coupler 21b
While the contact surface S4 of the ultrasonic coupler 22b is placed on the same plane, the contact surfaces S2, S4 are tilted to the front, rear, left and right,
The wave transmitter 21 and the wave receiver 22 are simultaneously moved to search for a direction in which the liquid crystal pointer patterns 12a and 12b of the level meter 12 are maximally swung, that is, a direction in which the maximum leak wave level is detected. At this time, it is confirmed that the directions of the contact surfaces S2 and S4 are not significantly deviated by referring to the data of the leaky wave arrival time measured on the screen of the display 13 each time. If the connecting portion 23 is slightly twisted or slightly bent, the directions of the contact surfaces S2 and S4 are finely adjusted to find the direction in which the maximum leak wave level is detected.
Here, in order to avoid directly receiving an echo reflected by the ultrasonic wave Bi emitted from the transmitting unit 21 from the cortical bone surface Y, the corrugated bone surface Y and the skin surface Wave and other soft tissue M that undergoes multiple reflections with X
A predetermined length is selected for the length of the connecting portion 23 in order to sufficiently attenuate unnecessary waves in the measurement of this example propagating in a. At this time, in the direction in which the maximum leaky wave level is detected, the ultrasonic pulse Bi is incident on the cortical bone Mb at a critical angle to excite the surface wave Bs and surely receive the leaky wave Be. Conceivable. Therefore, the leaky wave arrival time Ts for the maximum level leaky wave arrival time corresponding to this maximum leaky wave level is obtained.

The operator presses the measurement end switch when judging that the maximum leak wave level can be extracted by looking at the shake of the liquid crystal pointer patterns 12a and 12b of the level meter 12. When the measurement end switch is pressed, the CPU 11
Resets the content of the measurement continuation flag to "0" and lowers the measurement continuation flag by interrupt processing. When the measurement continuation flag is cleared, the CPU 11 causes the next 1 and subsequent 1
The pulse emission is stopped (step SP27). After this,
The CPU 11 uses the maximum level leakage wave arrival time (leakage wave arrival time T stored in the data memory area of the RAM 10).
s), the cortical bone Mb stored in the ROM 9
The sound velocity Vl is calculated according to the processing procedure for calculating the sound velocity Vl of the medium longitudinal wave (that is, the equation (1)) (step SP28), and the calculated value is displayed on the screen of the display 13 (step SP29).

Next, returning to the main routine, the CPU 11
Waits until the acoustic impedance measurement start switch is pressed (step SP13 (FIG. 5)).
The operator, as shown in FIG. 4, is the surface of the soft tissue Ma that covers the cortical bone Mb that is the measurement site of the subject (the surface X of the skin).
Then, the ultrasonic gel G is applied to the surface, the transducer 1 for echo measurement is applied to the surface X of the skin through the ultrasonic gel G, and the acoustic impedance measurement start switch is turned on with the transmitting / receiving surface facing the cortical bone Mb. . When the acoustic impedance measurement start switch is turned on (step SP1
3) The apparatus for diagnosing osteoporosis of this example enters the acoustic impedance calculation mode, proceeds to the acoustic impedance calculation subroutine (step SP14), and the CPU 11 writes "1" in the measurement continuation flag to set the measurement continuation flag, and then Thus, the measurement operation is started according to the processing procedure shown in FIG.

The CPU 11 first sets the pulse generator 4 to 1
A pulse generation command is issued (step SP40). When the pulse generator 4 receives the one-pulse generation command from the CPU 11, the pulse generator 4 transmits an electric pulse signal to the echo measuring transducer 1. When receiving the electric pulse signal from the pulse generator 4, the echo measurement transducer 1 emits an ultrasonic pulse Ai toward the cortical bone Mb of the subject (which can be regarded as a plane wave during the short distance handled). To do. As shown in FIG. 8, the emitted ultrasonic pulse Ai is partially reflected on the surface X of the skin, and the rest is injected from the surface X of the skin into the soft tissue Ma and propagates toward the cortical bone Mb. Then, a part is reflected on the surface Y of the cortical bone Mb to become a bone echo Ae, a part is absorbed by the cortical bone Mb, and the rest is transmitted through the cortical bone Mb.

The bone echo Ae follows a path opposite to that of the incident ultrasonic wave Ai, and is again received by the ultrasonic transducer 1a of the echo measuring transducer 1. Therefore, in the echo measurement transducer 1, after the ultrasonic pulse Ai is emitted, first, the transmission reverberation An, then the echo (hereinafter, referred to as a surface echo) As from the surface X of the skin is slightly delayed, and the bone is delayed. The echo Ae is received by the ultrasonic transducer 1a and converted into a received signal corresponding to the waveform and amplitude of the ultrasonic wave. The generated received signal is input to the device body 2 (matching circuit 5) via the cable C1,
The signal is amplified by the amplifier 6 with a predetermined amplification degree, linearly shaped by the waveform shaper 7, and then input to the A / D converter 8.

After sending the one-pulse generation command to the pulse generator 4 (step SP40), the CPU 11 receives the transmission reverberation An by the ultrasonic transducer 1a of the echo measuring transducer 1, and then the surface echo As. After the wave is received, a sampling start command is issued to the A / D converter 8 at the time when the bone echo Ae returns to the transmitting / receiving surface of the ultrasonic transducer 1a of the echo measuring transducer 1 (step SP41). The A / D converter 8 is
When a sampling start command is received from the CPU 11, the waveform is shaped by the waveform shaper 7, and then the input cortical bone Mb is input.
The received signal for one echo from the
2MHz) and convert it to a digital signal.
The obtained N sample values (digital signals for one echo) are temporarily stored in its own sampling memory. After that, N sample values stored in the sampling memory are sequentially transmitted to the CPU 11 in response to a transfer request from the CPU 11. The CPU 11 sequentially takes in N sample values from the A / D converter 8 and stores them as the present bone echo waveform in the waveform memory area of the RAM 10, and then extracts the largest value from the N sample values. As a result, the current bone echo level (amplitude of the current bone echo) is detected, and the detection result is stored in the data memory area of the RAM 10 (step SP42). The current bone echo level stored in the RAM 10 is displayed on the level meter 12 as a shake of the liquid crystal pointer pattern 12a as shown by the broken line in FIG. 4 (step SP43).

Next, the CPU 11 reads the current bone echo level and the maximum bone echo level from the data memory area in the RAM 10 and determines whether the value of the current bone echo level is larger than the value of the maximum bone echo level. It is determined (step SP44). Now, it is the first judgment, and the value of the maximum bone echo level remains the initial setting value "0".
The CPU 11 determines that the value of the current bone echo level is larger than the value of the maximum bone echo level, and rewrites the value of the maximum bone echo level stored in the echo data memory area of the RAM 10 with the value of the current bone echo level. Further, the maximum bone echo waveform stored in the waveform memory area of the RAM 10 is rewritten to the current bone echo waveform (step SP45). Then, the updated maximum bone echo waveform is displayed on the display 13 and the updated maximum bone echo level is displayed on the level meter 12 as the deflection of the liquid crystal pointer pattern 12b as shown by the solid line in FIG. Yes (step SP46).

Next, the CPU 11 looks at the measurement continuation flag in the RAM 10 (step SP47), and if the measurement continuation flag is set (when the content of the measurement flag is "1"), the CPU 11 determines that the measurement is continued. After making a judgment and repeating the above-described one-pulse emission and one-echo reception (steps SP40 to SP43), RA is again set in step SP44.
The current bone echo level and the maximum bone echo level are read from the data memory area in M10, and it is determined whether or not the value of the current bone echo level is larger than the value of the maximum bone echo level. If the result of this determination is that the current bone echo level is not higher than the maximum bone echo level this time, the update processing is not performed and the process directly jumps to step SP47 to see the measurement continuation flag. The content of the measurement continuation flag is kept at "1" unless the operator presses the measurement end switch.
1 is the above-mentioned 1 pulse emission 1 echo reception (step SP
40-SP43) and the maximum bone echo level extraction operation (steps SP44-SP47) are repeated.

While the CPU 11 repeats the above-described processing (steps SP40 to SP47), the operator indicates the arrow W in FIG.
As shown by, the echo measurement transducer 1 is applied to the surface X of the skin, and is directed toward the cortical bone Mb at the measurement site.
Sometimes a circle or a spiral is drawn like the precession motion of a top, and sometimes it is shaken back and forth and left and right like a seesaw to change the direction of the echo measuring transducer 1 and change the angle, while the liquid crystal of the level meter 12 is changed. Pointer patterns 12a, 12
A direction in which b is maximally swung, that is, a direction in which the maximum bone echo level is detected is searched for. The maximum deflection of the liquid crystal pointer patterns 12a and 12b of the level meter 12 is shown in FIG.
As shown in (a), when the normal line of the cortical bone Mb and the normal line of the transmitting / receiving surface of the echo measurement transducer 1 coincide with each other, therefore, the wavefront of the plane wave ultrasonic pulse Ai and the surface Y of the cortical bone Mb. Are substantially parallel to each other (that is, when the plane-wave ultrasonic pulse Ai is substantially vertically incident on the surface Y of the cortical bone Mb).

The reason is that, when the two normals coincide with each other, the bone echo Ae reflected vertically on the surface Y of the cortical bone Mb, as shown in FIG.
Since it returns perpendicularly to the wave transmission / reception surface, the wave front of the bone echo Ae is also aligned substantially parallel to the wave transmission / reception surface, and the phase shift of the bone echo Ae due to the difference in the reception position on the wave transmission / reception surface is minimized This is because the received signal has few peaks and troughs canceling each other, and therefore the bone echo Ae having the maximum bone echo level is received. On the other hand, when the normals do not match, the wavefront of the bone echo Ae is not uniform on the transmitting / receiving surface as shown in (b) of the figure, so that the received signal has peaks and troughs that cancel each other. Get smaller. Therefore, when the operator changes the angle of the echo measuring transducer 1 in the vicinity of the normal line of the cortical bone Mb and the bone echo level becomes maximum, the echo measuring transducer 1 transmits / receives the cortical bone Mb to the transmitting / receiving surface. Bone echo A reflected almost vertically on the surface Y
You can think of e coming back.

Here, it is important that the diagnostic apparatus of this example needs to extract the bone echo Ae of the vertical reflection in order to improve the diagnostic accuracy.
This is because the equation (2) for deriving the acoustic impedance Zb of the cortical bone Mb is, as described above, the bone echo A of the substantially vertical reflection.
This is because the expression holds for e. However, it is not difficult to extract the vertically reflected bone echo Ae, and the liquid crystal pointer pattern 12a,
It is possible to easily find the bone echo Ae of the vertical reflection while looking at the shake of 12b. That is, when the disagreement between the normal line of the cortical bone Mb and the normal line of the transmitting / receiving surface is extremely large, the liquid crystal pointer patterns 12a, 12 of the level meter 12 are displayed.
Since b is sensitively shaken, it is possible to recognize a great discrepancy between both normals. On the other hand, when both normals come close to each other, the bone echo level is stable even if the direction of the transmitting / receiving surface of the echo measurement transducer 1 is slightly displaced. LCD pointer pattern 12
Since the shakes of a and 12b settle down, it can be confirmed that both normals match.

When the operator judges that the maximum bone echo level can be extracted by looking at the shake of the liquid crystal pointer patterns 12a and 12b of the level meter 12, he depresses the measurement end switch. When the measurement end switch is pressed, the CPU1
1 rewrites the content of the measurement continuation flag to "0" by the interrupt processing and lowers the measurement continuation flag. When the measurement continuation flag is cleared, the CPU 11 causes the next 1 and subsequent 1
The pulse emission is stopped (step SP47). And
The maximum bone echo level stored in the echo data memory area of the RAM 10 is read out and displayed on the display 13 (step SP48). After that, the CPU 11 executes the reflection coefficient calculation routine, so that the RAM 10
From the maximum bone echo level Ve stored in the echo data memory area and the complete echo level V0 previously stored in the ROM 9, the soft tissue Ma and the cortical bone Mb of the subject.
The ultrasonic reflection coefficient R at the interface with and is calculated (step SP
49), the calculated value is displayed on the screen of the display 13 (step SP50).

Here, the ultrasonic reflection coefficient R is derived from the ratio [R = Ve / V0] between the perfect echo level V0 at the time of perfect vertical reflection and the maximum bone echo level Ve, and the perfect echo level V0 is Although it can be calculated theoretically, the ultrasonic pulse Ai is emitted toward the sky, and at this time, an ultrasonic delay spacer (dummy block) such as polyethylene bulk is emitted.
It can also be obtained by receiving the open echo returning from the front end surface of 1b by the ultrasonic transducer 1a and measuring the open echo level. Next, the CPU 11
Executes the acoustic impedance calculation routine to substitute the value of the ultrasonic reflection coefficient R given by the reflection coefficient calculation routine into the equation (2), and the acoustic impedance Zb [kg / m ² sec] of the cortical bone Mb. Is calculated (step S
P51), and the calculation result is displayed on the screen of the display 13 (step SP52).

Next, returning to the main routine, the CPU 11
By executing the bone density calculation routine, in the sound velocity measurement mode, the sound velocity Vl [m / sec] of the longitudinal wave in the cortical bone Mb calculated in step SP28 (FIG. 6), and in the acoustic impedance calculation mode, SP51
Acoustic impedance Z of cortical bone Mb calculated in (FIG. 7)
Substituting b [kg / m ² sec] into equation (4), the density ρ [kg / m ³ ] in the cortical bone Mb is calculated (step SP15 (FIG. 5)), and this calculation result is displayed. The screen is displayed on the container 13 (step SP16). Further, the CPU 11 executes the elastic modulus calculation routine to calculate the sound velocity Vl [m / sec] of the longitudinal wave in the cortical bone Mb and the acoustic impedance Zb [kg / m ² sec] of the cortical bone Mb. Substituting into equation (5), the elastic modulus E [N / m ² ] of the cortical bone Mb is calculated (step SP1
7) Then, the calculation result is displayed on the display 13 (step SP18).

According to the above configuration, the density ρ of the cortical bone Mb, which indicates the degree of clogging of the composition of the cortical bone Mb, and the elastic modulus E of the cortical bone Mb, which is a measure of the breaking resistance of the cortical bone Mb, are calculated as acoustic impedance. Mode, the acoustic impedance Zb of the cortical bone Mb calculated based on the received echo
And in the sound velocity measurement mode, based on the longitudinal wave velocity of the ultrasonic waves in the measured cortical bone, directly and accurately calculated,
Since the osteoporosis is diagnosed using the density ρ and the elastic modulus E of the cortical bone Mb as an index, the diagnosis can be performed with higher reliability. Further, since X-rays are not used, safe measurement can be easily performed without fear of radiation exposure.

Further, when measuring the echo in the acoustic impedance calculation mode, when the normal line of the bone and the normal line of the transmitting / receiving surface reach substantially the same level, the echo level is stable even if the direction of the transmitting / receiving surface is slightly displaced. Since (the deflection of the liquid crystal pointer patterns 12a and 12b of the level meter 12 is settled), the bone echo level at the time of vertical reflection, that is, the maximum bone echo level can be easily extracted, and measurement data with good reproducibility can be obtained. . Similarly, when measuring a leaky wave in the sound velocity measurement mode, the contact surface S2 of the coupler 21b and the contact surface S4 of the ultrasonic coupler 22b are substantially parallel to the cortical bone surface Y, and the ultrasonic pulse Bi is In a state in which the leaky wave Be is incident on the cortical bone Mb at a critical angle and is close to the positional relationship in which the leaky wave Be is reliably received, the leaky wave level is also stable, so that the maximum leaky wave level can be easily extracted.

In addition, the level meter 12 displays the current bone echo level (current leak wave level) every moment, and the maximum bone echo level (maximum leak wave level) is also fixedly displayed unless it is updated. Therefore, the search for the maximum bone echo level (maximum leaky wave level) becomes easier. Therefore, the acoustic impedance Zb of the cortical bone Mb
Also, the sound velocity Vl of the longitudinal wave in the cortical bone Mb can be accurately obtained. Therefore, the density ρ and the elastic modulus E of the cortical bone Mb are
Can also be calculated accurately.

Second Embodiment FIG. 10 is a block diagram showing the electrical configuration of an osteoporosis diagnostic apparatus according to a second embodiment of the present invention, and FIG. 11 is the same as the calculation of the acoustic impedance of cortical bone. It is a flow chart which shows a flow of processing (acoustic impedance calculation subroutine) of a device. This second embodiment is the same as the first embodiment described above.
A big difference from the embodiment is that in calculating the acoustic impedance Zb in the acoustic impedance calculation mode, the acoustic impedance Zb of the cortical bone Mb can be reliably measured by considering the attenuation of ultrasonic waves due to the round trip of the soft tissue Ma. And the ultrasonic reflection coefficient R in the first embodiment was calculated as the ratio [R = Ve / V0] between the perfect echo level V0 and the maximum bone echo level Ve, whereas the perfect echo level V0 was not used. The point is that the ultrasonic reflection coefficient R is calculated.

The apparatus main body 3a of the second embodiment has a structure shown in FIG.
As shown in FIG. 0, in addition to the operation of the first embodiment, the timing circuit 1 that also measures the time in the acoustic impedance calculation mode.
4a is provided. That is, the timing circuit 14a is
After the ultrasonic pulse Ai is emitted from the wave transmission / reception surface of the echo measuring transducer 1, the bone echo arrival time Te until the bone echo Ae returns to the wave transmission / reception surface is measured. Further, the processing program of this example uses the maximum bone echo level extracted by the same algorithm as in the first embodiment and the bone echo arrival time Te at this time to perform ultrasound of the cortical bone Mb with respect to the soft tissue Ma of the subject. Including the description of the procedure for calculating the reflection coefficient R, the CPU 11 executes the processing program to calculate the ultrasonic reflection coefficient R, and the acoustic impedance Zb is calculated based on the calculated ultrasonic reflection coefficient R. It In addition, except for this point, FIG.
10, the same components as those shown in FIG. 1 are designated by the same reference numerals in FIG. 10 to simplify the description.

In the acoustic impedance calculation mode,
The pulse generator 4a of the apparatus main body 3a of this example is the CPU 1
In response to a pulse generation command repeated from 1 to a predetermined cycle, an electric pulse signal having a center frequency of approximately 2.5 MHz is generated at a predetermined cycle and transmitted to the echo measuring transducer 1 and the electric pulse signal is transmitted. The timing start signal Tb is supplied to the timing circuit 14 at the same timing as. Here, the cycle of the electric pulse signal is set to be sufficiently longer than the bone echo arrival time Te. Timing circuit 14a
Is composed of a clock generator (not shown) and a counting circuit, and starts counting time each time the pulse generator 4a supplies a timing start signal Tb, and receives an end signal from the A / D converter 8a. Stop timing. Then, the time count value is held until it is reset, and the held time count value is given to the CPU 11 as a bone echo arrival time Te in response to a request.

Next, with reference to FIG. 11, the operation of this example (mainly the processing flow of the CPU 11 at the time of osteoporosis diagnosis) will be described. The process flow of this example is substantially the same as that described in the first embodiment except that the bone echo arrival time Te is measured from step SP40 to step SP48, and therefore the description thereof will be simplified. In this example, the CPU 11 executes A / A in step SP42.
While reading the bone echo signal Eb from the D converter 8a,
The bone echo arrival time Te is read from the timing circuit 14a, and the present bone echo signal Eb and the bone echo arrival time Te read
Is stored in the data memory area of the RAM 10. After the measurement is completed (step SP47, step SP4
8) First, the CPU 11 reads the bone echo arrival time Te from the data memory area by executing the ultrasonic wave attenuation degree calculation routine, and sets the value of the read bone echo arrival time Te [sec]. By substituting into the equation (6), the attenuation A (Te) of the ultrasonic wave in the soft tissue Ma of the subject is calculated (step SP481).

[0057]

(Equation 6) Here, the degree of attenuation A (Te) is the degree of attenuation that the ultrasonic wave receives before it reciprocates in the soft tissue Ma, that is, the ultrasonic wave propagates from the surface X of the skin to the surface Y of the cortical bone Mb. , A degree of attenuation that is reflected by the surface Y of the cortical bone Mb and returned to the surface X of the skin again (A (T
Smaller e) means greater damping). This attenuation A (T
e) is a function of the bone echo arrival time Te, and the relational expression is obtained by experiment or simulation. The first reason that ultrasonic waves are attenuated in the soft tissue Ma is
In addition, the ultrasonic wave used in this example includes not only a perfect plane wave but also a spherical wave component, and the spherical wave component diffuses acoustic energy (ultrasonic wave diffusion).
This is because the acoustic energy is converted into heat energy (ultrasonic absorption) by friction with the soft tissue Ma.

The degree of attenuation due to ultrasonic diffusion is determined by the aperture of the echo measuring transducer 1, the frequency of ultrasonic waves,
It can be obtained by calculation or experiment from the sound velocity of the soft tissue Ma. Also, the degree of attenuation due to ultrasonic absorption is
If the frequency of the ultrasonic wave is lowered, it becomes smaller. Even if the frequency is not sufficiently low, a typical absorption constant of the soft tissue Ma (attenuation rate of ultrasonic wave per unit length) can be used. The expression (6) that gives the attenuation A (Te) of the ultrasonic wave is an experiment that is established when the use center frequency of the ultrasonic wave is set to 2.5 MHz and the opening of the echo measurement transducer 1 is set to 15 mm. It is an expression.

Next, the CPU 11 reads out the maximum bone echo level Ve from the echo data memory area and substitutes it into the equation (7) together with the attenuation A (Te) calculated using the equation (6). Then, the ultrasonic reflection coefficient R at the interface between the soft tissue Ma and the cortical bone Mb when the ultrasonic wave is perpendicularly incident on the cortical bone Mb from the medium side of the soft tissue Ma is calculated (step SP49).

## EQU00007 ## R = Ve / P.Q.B.Vi.A (Te) (7) P: Echo when a unit electric signal (voltage, current, scattering parameter) is applied to the echo measurement transducer 1. Sound pressure of ultrasonic pulse Ai output from the transmitting / receiving surface of the measuring transducer 1 in a substantially vertical direction Q: Echo measuring transducer when an echo of unit sound pressure enters the transmitting / receiving surface of the echo measuring transducer 1 substantially vertically Received signal (electrical signal) output from 1
Amplitude B: product of amplitude amplification of amplifier 6 and amplitude shaper of waveform shaper 7 Vi: amplitude Ve of electric signal (voltage, current, scattering parameter) applied from the pulse generator 4 to the transducer 1 for echo measurement : Maximum bone echo level P, Q, B, and Vi are all functions of frequency, but here, the component at the center frequency (for example, 2.5 MHz) is used. Regarding P, Q, B and Vi,
These measured values and set values are written in the ROM 9.

Equation (7) is derived as follows. First, when an electric signal of amplitude Vi is applied from the pulse generator 4a to the echo measuring transducer 1, the ultrasonic pulse Ai of the sound pressure PVi is injected into the soft tissue Ma from the transmitting / receiving surface of the echo measuring transducer 1. The injected ultrasonic pulse Ai is attenuated in the soft tissue Ma,
(Consider the case of incidence perpendicularly to the surface Y of the cortical bone Mb), the light is reflected vertically on the surface Y of the cortical bone Mb, becomes a bone echo Ae, and returns vertically to the echo measurement transducer 1. . Therefore, the sound pressure P (e) of the bone echo Ae that has returned to the transmission / reception surface of the echo measurement transducer 1 considers the attenuation A (Te) of the ultrasonic wave due to the round trip of the soft tissue Ma obtained from the equation (6). Then, it is given by the equation (8).

[Equation 8] P (e) = P · Vi · R · A (Te) (8)

When the bone echo Ae having the sound pressure P (e) is received by the transmitting / receiving surface of the echo measuring transducer 1, the echo measuring transducer 1 outputs the received signal having the amplitude Q · P (e). Then, the received signal is amplified by the amplification degree B in the amplifier 6 (and the waveform shaper 7). And A /
After being digitally converted by the D converter 8a, the maximum bone echo level Ve (= B · Q · P) is taken in by the CPU 11.
(e)) is detected. Therefore, the maximum bone echo level Ve is given by equation (9).

[Equation 9] Ve = P · Vi · R · A (Te) · B · Q (9) If the equation (9) is solved for the ultrasonic reflection coefficient R, the equation (7) is obtained.
Is obtained. Returning to the explanation of the flowchart of FIG. 11 again, the CPU 11 calculates the ultrasonic reflection coefficient R at the interface between the soft tissue Ma and the cortical bone Mb using the equation (7) (step SP49), and then the calculation result. Is displayed on the display 13 (step SP50). After that, the CPU 11 calculates the acoustic impedance Zb (N · s / m ³ ) of the cortical bone Mb using the formula (2) (step SP51) and displays the calculation result on the display 13 (step SP52). Then, the process returns to the main routine.

According to the above structure, in addition to the effects of the first embodiment described above, the attenuation A due to the reciprocal movement of the soft tissue Ma of the ultrasonic wave A
Since (Te) is also taken into consideration, the acoustic impedance Zb of the cortical bone Mb can be measured more accurately, so that the density ρ and elastic modulus E of the cortical bone Mb can also be calculated more accurately.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific structure is not limited to this embodiment, and there are design changes and the like within a range not departing from the gist of the present invention. Also included in the present invention. For example, in the above-described embodiment, first, the sound velocity V of the longitudinal wave in the cortical bone Mb is
After obtaining l, the acoustic impedance Zb of the cortical bone Mb
However, the order may be reversed.
In addition, a data input means such as a keyboard may be used to input the height, weight, sex, age, etc. of the subject into the apparatus main body in order to assist the diagnosis of osteoporosis. Further, the ultrasonic transducers forming the echo measuring transducer and the sound velocity measuring transducer are not limited to the thickness vibration type, but may be the bending vibration type. Similarly, the center frequency used is not limited to 2.5 MHz. Further, since the acoustic impedance of the soft tissue Ma is close to the acoustic impedance of water, the soft tissue Ma should be applied when applying the equation (2).
The acoustic impedance of water may be used instead of the acoustic impedance of.

[0064]

According to the configuration of the present invention, the density of cortical bone showing the degree of clogging of the composition of cortical bone, or the elastic modulus of cortical bone, which is a measure of the fracture resistance of the cortical bone, is converted into the received echo. Based on the acoustic impedance of the cortical bone calculated based on, and the longitudinal wave velocity of the ultrasonic pulse in the cortical bone measured by the sound velocity measuring means, directly and accurately calculated, the density or elastic modulus of this cortical bone Since osteoporosis is diagnosed as an index, it is possible to make a more reliable diagnosis. Further, since X-rays are not used, safe measurement can be easily performed without fear of radiation exposure.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an osteoporosis diagnostic apparatus according to a first embodiment of the present invention.

FIG. 2 is an external view of the device.

FIG. 3 is a schematic view showing a usage state of the apparatus.

FIG. 4 is a schematic diagram showing a use state of the device.

FIG. 5: Overall processing flow of the same device (main routine)
It is a flowchart which shows.

FIG. 6 is a flowchart showing a processing flow (sound velocity measurement subroutine) of the apparatus when measuring a sound velocity of an ultrasonic pulse.

FIG. 7 is a flowchart showing a processing flow (acoustic impedance calculation subroutine) of the apparatus when calculating acoustic impedance of cortical bone.

FIG. 8 is a diagram used for explaining the operation of the device.

FIG. 9 is a diagram used to explain the operation of the device.

FIG. 10 is a block diagram showing an electrical configuration of an osteoporosis diagnostic apparatus according to a second embodiment of the present invention.

FIG. 11 is a flowchart showing a processing flow (acoustic impedance calculation subroutine) of the apparatus when calculating acoustic impedance of cortical bone.

[Explanation of symbols]

1 Echo Measurement Transducer (Ultrasonic Transducer) 21 Wave Sending Part (Wave Sending Ultrasonic Transducer) 22 Receiving Part (Receiving Ultrasonic Transducer) 21a, 22a Ultrasonic Transducer 21b, 22b Ultrasonic Coupler Ai, Bi Ultrasonic pulse Ae Echo from cortical bone Bs Surface wave Be Leakage wave Ma Soft tissue Mb Cortical bone X Skin surface Y Cortical bone surface

Claims (6)

[Claims] 1. A predetermined three-dimensional shape including a direction of a transmitting / receiving surface of the ultrasonic transducer in a state where an ultrasonic transducer is applied to a skin surface covering a predetermined cortical bone of a subject, including a direction of a normal line of the cortical bone surface. The ultrasonic pulse is repeatedly emitted toward the cortical bone under the skin while changing variously within the angular range, and the echo returning from the cortical bone surface is received by the ultrasonic transducer at each pulse emission. An ultrasonic reflex type osteoporosis diagnostic device for diagnosing osteoporosis by converting a received signal into a digital signal by an analog / digital converter and performing signal processing using a digitized echo signal, Echo level detecting means for detecting an echo level from the echo signal, and a maximum echo level from the detected plurality of echo levels Maximum echo level extraction means for extracting, acoustic impedance calculation means for calculating the acoustic impedance of the cortical bone based on the extracted maximum echo level, and an ultrasonic pulse is applied to a predetermined cortical bone of the subject. And a sound velocity measuring means for measuring the sound velocity of the ultrasonic pulse in the cortical bone, a sound velocity in the cortical bone measured by the sound velocity measuring means and an acoustic impedance of the cortical bone calculated by the acoustic impedance calculating means. An osteoporosis diagnosing device comprising: a bone density calculating unit that calculates the density of the cortical bone based on the above, and diagnoses osteoporosis using the density of the cortical bone calculated by the bone density calculating unit as an index. . 2. The ultrasonic wave transducer is applied to the skin surface covering a predetermined cortical bone of a subject, and the direction of the transmitting / receiving surface of the ultrasonic transducer is a predetermined three-dimensional shape including the direction of the normal line of the cortical bone surface. The ultrasonic pulse is repeatedly emitted toward the cortical bone under the skin while changing variously within the angular range, and the echo returning from the cortical bone surface is received by the ultrasonic transducer at each pulse emission. An ultrasonic reflex type osteoporosis diagnostic device for diagnosing osteoporosis by converting a received signal into a digital signal by an analog / digital converter and performing signal processing using a digitized echo signal, Echo level detecting means for detecting an echo level from the echo signal, and a maximum echo level from the detected plurality of echo levels Maximum echo level extraction means for extracting, acoustic impedance calculation means for calculating the acoustic impedance of the cortical bone based on the extracted maximum echo level, and an ultrasonic pulse is applied to a predetermined cortical bone of the subject. And a sound velocity measuring means for measuring the sound velocity of the ultrasonic pulse in the cortical bone, a sound velocity in the cortical bone measured by the sound velocity measuring means and an acoustic impedance of the cortical bone calculated by the acoustic impedance calculating means. And an elastic modulus calculating means for calculating the elastic modulus of the cortical bone based on the above, and diagnosing osteoporosis using the elastic modulus of the cortical bone calculated by the elastic modulus calculating means as an index. Diagnostic device. 3. The acoustic impedance calculating means calculates and calculates an ultrasonic reflection coefficient of the cortical bone with respect to the soft tissue of the subject based on the maximum echo level extracted by the maximum echo level extracting means. The osteoporosis diagnostic device according to claim 1, wherein the acoustic impedance of the cortical bone is calculated based on the ultrasonic reflection coefficient. 4. The surface acoustic velocity measuring means for measuring the acoustic velocity of a surface wave propagating on a cortical bone surface by injecting an ultrasonic pulse obliquely into a predetermined cortical bone of a subject, A longitudinal wave sound velocity calculating means for calculating the sound velocity of the longitudinal wave in the cortical bone as the sound velocity of the ultrasonic pulse based on the sound velocity of the surface wave measured by the surface wave sound velocity measuring means. Item 1. The osteoporosis diagnostic device according to item 1, 2 or 3. 5. The surface wave sound velocity measuring means applies an ultrasonic pulse obliquely to the cortical bone under the skin in a state of being applied to the skin surface covering a predetermined cortical bone of the subject, and the cortical bone surface An ultrasonic transducer for transmitting a wave that generates a surface wave that propagates, a receiving ultrasonic transducer that is separated from the ultrasonic transducer for a known distance by a known distance, and receives the surface wave or a leak wave thereof, After an ultrasonic pulse is input from the ultrasonic transducer for wave transmission toward the cortical bone, the surface wave propagates on the surface of the cortical bone, and the surface wave or its leaky wave is the ultrasonic wave for reception. The osteoporosis diagnostic apparatus according to claim 1, 2, 3, or 4, further comprising: a measuring unit that measures a propagation time required for being received by the acoustic wave transducer. 6. The ultrasonic transducers for transmitting and receiving waves, wherein one end face joined to an ultrasonic transducer and the other end face abutting against the skin of the subject cross each other in a wedge shape. 6. A coupler is provided, which has a coupler.
The osteoporosis diagnostic device described.