JPH08332184A - Osteoporosis diagnostic method - Google Patents

Abstract

PURPOSE: To diagnose the progressing condition of osteoporosis by estimating the bone density and the modulus of elasticity of the bone. CONSTITUTION: Ultrasonic impulses Ai are first shot without pressing a transducer 1 to a living body and at this time, the echoes returned from the front end face of the transducer 1 and the boundary with air are received and measurement data are extracted. Next, the transducer 1 is pressed to the living body and while the transducer is oscillated and moved within a prescribed angle range toward the bone Mb, the ultrasonic impulses Ai are shot and the surface echoes Ae1 returned from the surface of the living body and the bone echoes Ae2 returned from the surface of the bone Mb are received and the normal measurement data are extracted. The acoustic impedance of the bone of the testee M is thereafter calculated in accordance with the extracted preliminary measured data and the normal measurement data. The acoustic impedance of the bone Mb is expressed by the square root of the [modulus of elasticity ×density] of the bone Mb. The modulus of elasticity (increases) decreases as well when the bone density increases (decreases) and, therefore, a good index in judging the bone density and the modulus of elasticity of the bone are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an osteoporosis diagnosing method for diagnosing osteoporosis by applying an ultrasonic wave impulse to a bone tissue of a predetermined part of a human body.

[0002]

2. Description of the Related Art Osteoporosis is a disease in which calcium in bones escapes to form squashes, which easily deforms or breaks with a small shock. As one of means for diagnosing osteoporosis, conventionally, a method for diagnosing by ultrasonic waves as described in JP-A-2-104337 is known. In this diagnostic method using ultrasonic waves, it is assumed that the speed of sound in bone tissue is empirically proportional to the bone density, and an ultrasonic pulse is emitted toward the bone tissue of the subject, and the ultrasonic pulse that has passed through the bone tissue. To measure the speed of sound in bone tissue. Then, it is diagnosed that the osteoporosis is progressing as the speed of sound in the bone tissue is slower.

[0003]

Strictly speaking, the speed of sound in bone tissue is not proportional to bone density but is given by the square root of [bone elastic modulus / bone density]. Moreover, since the elastic modulus increases as the bone density increases, the sound velocity cannot respond sensitively to the increase in the bone density, and the correlation coefficient between the sound velocity and the bone density is never high. Therefore, it is difficult to reliably judge the progress of osteoporosis by the conventional diagnosis method based on the sound velocity information. On the other hand, there is an opinion that osteoporosis can be diagnosed based on the condition of bone elasticity.

The present invention has been made under such a background, and it is an object of the present invention to provide an osteoporosis diagnosing method capable of accurately estimating the states of bone density and bone elastic modulus to surely diagnose the progress of osteoporosis. Has an aim.

[0005]

In order to solve the above-mentioned problems, the invention according to claim 1 delays the return of an echo from a predetermined part until the transmission reverberation on the ultrasonic wave transmission / reception surface of the ultrasonic transducer subsides. A method for diagnosing osteoporosis using an ultrasonic wave transmitter / receiver formed by joining ultrasonic wave delay spacers, wherein the ultrasonic vibration is performed by exposing the tip surface of the ultrasonic wave delay spacer to an air atmosphere. Ultrasonic impulse is emitted from the ultrasonic wave transmitting / receiving surface of the child, at this time,
A first step of receiving the first echo reflected at the interface between the ultrasonic delay spacer and air and returning to the ultrasonic transmission / reception surface to extract pre-measurement data; The tip surface is applied to the living body, the normal line of the ultrasonic wave transmitting / receiving surface is directed to the bone, and while oscillating within a predetermined angle range with respect to the normal line of the bone, ultrasonic impulses are intermittently emitted, at this time. , The second echo reflected on the surface of the living body and returned to the ultrasonic wave transmitting / receiving surface, and the third echo reflected on the surface of the bone and returning to the ultrasonic wave transmitting / receiving surface are sequentially received and main measurement data is obtained. The second step of extracting
Calculating the reflection coefficient at the interface between the soft tissue of the living body and the bone or the acoustic impedance of the bone, based on the pre-measurement data extracted in the step and the main measurement data extracted in the second step. It is characterized in that the condition of the bone density or the bone elastic modulus is estimated from the reflection coefficient or the acoustic impedance of the bone calculated in the third step to diagnose osteoporosis.

The invention according to claim 2 is the osteoporosis diagnosing method according to claim 1, wherein the first step is performed in advance in a factory, and is extracted in the first step at the time of factory shipment. The pre-measured data stored is stored in a non-volatile memory, and when diagnosing osteoporosis by the ultrasonic transmitter / receiver, using the pre-measured data read from the non-volatile memory, It is characterized in that the reflection coefficient or the acoustic impedance of bone is calculated.

[0007]

In the configuration of the present invention, in the first step, the ultrasonic wave transmitting / receiving W surface of the ultrasonic transducer is exposed to the air atmosphere and is not yet applied to the living body. Then, the first echo reflected by the interface between the ultrasonic delay spacer and the air and returning to the ultrasonic wave transmitting / receiving surface is received, and the pre-measurement data such as the echo level is extracted. In the second step, the tip surface of the ultrasonic delay spacer is applied to the living body,
Ultrasonic impulses are fired at the bone. And
The second echo reflected on the surface of the living body and returning to the ultrasonic wave transmitting / receiving surface, and the third echo reflected on the bone surface and returning to the ultrasonic wave transmitting / receiving surface are sequentially received, and the second, third The main measurement data such as the echo level and echo arrival time difference are extracted. In the third step, the reflection coefficient at the interface between the soft tissue of the living body and the bone or the acoustic impedance of the bone is calculated based on the pre-measurement data and the main measurement data extracted in the first and second steps, respectively. It Then, the state of the bone density or the bone elastic modulus is estimated from the calculated reflection coefficient or the acoustic impedance of the bone to diagnose osteoporosis.

In the configuration of the present invention, a transmission reverberation is generated each time an ultrasonic impulse is emitted, but since the ultrasonic delay spacer is provided on the transmitting / receiving surface, the first, second, and second beams returning from the surface of the living body. The echo No. 3 is received without overlapping the transmission reverberation. In addition, the ultrasonic wave transmitter / receiver is applied to the living body, the normal line of the ultrasonic wave transmitter / receiver surface is directed to the bone, and the ultrasonic impulses are intermittently emitted while swinging within a predetermined angle range with respect to the bone normal line. Therefore, it is easy to extract the maximum level of the third echo. The maximum level of the third echo is received when the normal line of the bone and the normal line of the ultrasonic wave transmitting / receiving surface coincide with each other, and thus the vertically reflected bone echo is vertically incident on the transmitting / receiving surface. When
In this case, since the reflection coefficient and the acoustic impedance of the bone can be calculated using a very simple formula, the processing can be speeded up.

According to the structure of the present invention, the acoustic impedance of bone or the reflection coefficient at the interface between the soft tissue of the living body and the bone can be measured. Since the acoustic impedance of bone is expressed by the square root of [elastic modulus x density] of the bone, when the elastic modulus increases with the increase of bone density, these synergistic effects are received, resulting in a remarkable response. Increase to. Conversely, when bone density decreases and elastic modulus decreases, the acoustic impedance becomes
Under these synergistic effects, there is a sensitive response and a marked decrease. Therefore, the acoustic impedance of bone is a good index for determining the bone density and the bone elastic modulus. Therefore, the operator can reliably estimate the progress of osteoporosis from the value of the acoustic impedance of the bone output by the output means. For example, if the acoustic impedance is
When the average value of the age group is extremely small, it can be seen that osteoporosis is aggravated. Further, usually, even if the reflection coefficient at the interface between the soft tissue and the bone of the living body that can be regarded as a monotonically increasing function of the acoustic impedance of the bone is used as an index of the bone density or the bone elastic modulus, the same effect as described above can be obtained. You can In addition, the first step is performed in advance in the factory,
If the obtained results are written in a non-volatile memory such as a ROM before shipment, the processing can be speeded up.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a device (osteoporosis diagnostic device) used for carrying out an osteoporosis diagnostic method according to an embodiment of the present invention.
2 is an external view of the device, FIG. 3 is a diagram showing a usage state of the device, FIG. 4 is a diagram showing a state of osteoporosis diagnosis by the device, FIG. 5 and FIG. Figure 6
FIG. 7 is a flowchart showing an operation processing procedure (same osteoporosis diagnosing method) of the apparatus, and FIG. 7 is a diagram for explaining an operation of the apparatus. As shown in FIGS. 1 to 4, the apparatus used for carrying out the osteoporosis diagnosing method of this example is a subject M.
The ultrasonic impulse Ai with good directivity is emitted toward the bone Mb, which is the measurement site of
An ultrasonic transducer that receives waves and converts them into received signals (electrical signals) (hereinafter simply referred to as transducers)
1 and an electric signal of a half-wave impulse is input to the transducer 1, and the received signals (electrical signals) of various echoes supplied from the transducer 1 are processed to obtain the acoustic impedance of the bone Mb which is an index of osteoporosis diagnosis. It is roughly composed of a device main body 2 for providing information and a cable 3 for connecting them.

In the osteoporosis diagnosing method of this example which is carried out by using the above-mentioned device, first, before the main measurement for extracting the echo information from the human body, the pre-measurement is carried out, and
After this measurement, the calculation process of the acoustic impedance (acoustic impedance density: N · s / m ³ ) Zz of the bone Mb is performed. Here, the pre-measurement is a pre-measurement performed prior to the main measurement in order to obtain auxiliary data necessary for calculating the acoustic impedance Zz of the bone Mb. In this pre-measurement, the transducer 1 is used. The ultrasonic impulse Ai is emitted in a state where it is not exposed to the human body and is exposed to the air atmosphere. At this time, echo information at the interface between the tip surface of the transducer 1 and the air is extracted. However, for convenience of explanation, the osteoporosis diagnosing method of this example will be described in detail later. First, each part of the apparatus will be described.

Although not shown, the transducer 1 is an ultrasonic transducer 1a formed by laminating electrode layers (not shown) on both sides of a disk-shaped thickness vibration type piezoelectric element made of lead titanium zirconate (PZT). Ultrasonic wave transmission / reception surface X (hereinafter,
The ultrasonic wave delay spacer 1b is joined to the transmitting and receiving surface). The ultrasonic wave delay spacer 1b receives the echoes Ae1, from the surfaces Y and Z of the soft tissue Ma and the bone Mb composed of skin, muscle, fat, etc. while the transmission reverberation An remains.
This is a member for delaying the arrival of these echoes Ae1 and Ae2 so that Ae2 does not return to the wave transmission / reception surface X, and for example, polyethylene bulk is used. here,
As the ultrasonic transducer 1a, the echo Ae in a plane wave state is used.
Since it is preferable to receive 1 and Ae2 from the viewpoint of measurement sensitivity, it is preferable to use as large as possible a transmitting / receiving surface X so that the emitted ultrasonic impulse Ai can propagate toward the bone Mb in a state close to a plane wave.

The apparatus main body 2 includes a pulse sending section 4, a matching circuit 5, an amplifier 6, a waveform shaper 7, an A / D converter 8, a clock circuit 9, and a CPU (central processing unit) 10.
, ROM 11, RAM 12, and level meter 13
And a display unit 14. Pulse sending unit 4
Is connected to the transducer 1 via a matching circuit 5, generates an electric signal of a half-wave impulse having a center frequency of about 2.5 MHz at a predetermined cycle, and transmits it to the transducer 1 intermittently. The matching circuit 5 is connected to the transducer 1 via the cable 3 and exchanges signals between the transducer 1 and the apparatus main body 2 with maximum energy efficiency. The amplifier 6 amplifies the output signal of the matching circuit 5 with a predetermined amplification degree, and then inputs it to the waveform shaper 7. Wave shaper 7
Is composed of a detection circuit (not shown) and a low-pass filter (LPF). The output signal of the amplifier 6 (amplified received signal) is subjected to detection processing and filter processing to shape the waveform, and then the A / D converter. Enter in 8.

The A / D converter 8 is provided with a level detection circuit, a sample hold circuit, etc., which are not shown, and detects the level of the output signal of the waveform shaper 7 (various wave reception signals) and is necessary. The arrival time and the like are also detected according to That is, at the time of pre-measurement, an echo reflected by the open end surface of the transducer 1 (the end surface of the ultrasonic delay spacer 1b when only in contact with air but not in contact with the human body) and returning (hereinafter referred to as open echo Ae0 Is extracted, and the received signal of the extracted opening-time echo Ae0 is input to the CPU 10 as a digital opening-time echo signal E0. Further, at the time of the main measurement, an echo Ae1 (hereinafter referred to as a surface echo) returning earlier from the surface Y of the soft tissue Ma (hereinafter also referred to as a skin surface) and an echo Ae2 (hereinafter referred to as a surface echo) returning later from the bone surface Z. Bone echo) are sequentially extracted, and the received signals of the surface echo Ae1 and the bone echo Ae2 extracted as a pair are converted into a digital surface echo signal E1 and a bone echo signal E2, respectively, and converted into digital. When the surface echo signal E1 and the bone echo signal E2 are sequentially input to the CPU 10 and the surface echo Ae1 is extracted,
The surface echo extraction signal ET is generated and given to the timing circuit 9. Here, as is clear from the above description, the digital open echo signal E0 is the open echo Ae returning from the open end face of the transducer 1 during the pre-measurement.
A digital surface echo signal E1 having a level value of 0 (opening echo level) is the surface echo Ae1 when the surface echo Ae1 returns to the transmitting / receiving surface X during the main measurement.
The level value of 1 (surface echo level) is the digital bone echo signal E2, and the level value of the bone echo Ae2 (bone echo level when the bone echo Ae2 returns to the transmitting / receiving surface X in this measurement is ) Are shown respectively. The clock circuit 9 is composed of a clock generator (not shown) and a counting circuit, and resets the counting circuit each time the surface echo extraction signal ET is supplied from the A / D converter 8 during the main measurement. After the start, the elapsed time (count value) is given to the CPU 10.

The CPU 10 executes the pre-measurement time processing program, the main measurement time processing program, and the acoustic impedance calculation program stored in the ROM 11 by using the RAM 12, so that the bone M serving as an index for osteoporosis diagnosis is detected.
The calculation processing of the acoustic impedance Zz of b is performed. Specifically, the CPU 10 first controls the pulse sending unit 4, the A / D converter 8 and the like in accordance with the description of the pre-measurement time processing program to extract a predetermined number of open echo levels E0 and extract them. An average value of a predetermined number of open echo levels E0 is obtained, and then the pulse sending unit 4, the A / D converter 8 and the like are controlled according to the description of the measurement processing program to obtain the surface echo level E1 and the bone echo level. E2 is sequentially extracted, and at the time of extraction of the bone echo level E2,
The elapsed time is read from the clock circuit 9 and the echo arrival time difference Tn is measured. Then, the maximum bone echo level E2max is extracted from the many extracted bone echo levels E2.
Here, the echo arrival time difference Tn is the surface echo Ae1
Means a delay in arrival of the bone echo Ae2 when the arrival time is set to the reference time, and the echo arrival time difference Tn
The value obtained by multiplying by the sound velocity in the soft tissue Ma corresponds to twice the thickness of the soft tissue Ma, that is, the way in which ultrasonic waves travel back and forth in the soft tissue Ma. Thereafter, the CPU 10 follows the acoustic impedance calculation program, the average value of the open echo level E0 obtained by the pre-measurement, the maximum bone echo level E2max obtained by the main measurement, the surface echo level E1max paired with this, The acoustic impedance Zz of the bone Mb is calculated based on the echo arrival time difference Tn at this time.

The ROM 11 calculates a pre-measurement processing program that describes a processing procedure to be executed by the CPU 10 during pre-measurement, a main measurement processing program that describes a processing procedure to be executed by the CPU 10 during main measurement, and the acoustic impedance Zz of the bone Mb. The acoustic impedance calculation program for performing the operation is stored. The RAM 12 has a working area in which a work area of the CPU 10 is set, and a data area for temporarily storing various data. In this data area, a predetermined number of open echo levels E0 extracted during pre-measurement are stored. Pre-measurement data memory area, average value data memory area that stores the average value of the echo level E0 when opened, the surface echo level E1, the bone echo level E2 that were extracted this time, and the echo arrival time difference Tn at this time are stored during the main measurement This time, the extracted data memory area, the maximum bone echo level E2max extracted from the bone echo levels E2 extracted so far, the surface echo level E1max paired with this, and the echo arrival time difference Tn at this time
A maximum value extraction data memory area for temporarily storing, etc., and a measurement status flag or the like indicating a status such as whether it is during pre-measurement or whether it is during main measurement are set. In this example, when the content of the measurement status flag is “0”, it indicates the status of measurement completion, when it is “1”, it indicates that the pre-measurement is in progress, and when it is “2”, , Indicates that it is during the main measurement.

The level meter 13 is controlled by the CPU 10 and the bone echo level E2 of the current extraction stored in the current extraction data memory area of the RAM 12 (the current level 13a of the bone echo Ae2) and the maximum value extraction data memory of the RAM 12 are stored. The maximum bone echo level E2max (maximum level 13b of bone echo Ae2) stored in the area is simultaneously displayed by the liquid crystal pointer pattern. Display 14
Is a CRT display or a liquid crystal display, and displays a display indicating that the pre-measurement is completed, the acoustic impedance Zz of the bone Mb calculated by the CPU 10, and a result in the middle of calculation.

Next, with reference to FIGS. 3 to 7, the operation processing procedure (osteoporosis diagnosis method) of this example will be described.
In order to diagnose osteoporosis using the apparatus having the above-described configuration, the bone Mb having a shape and site where a plane wave bone echo Ae2 is easily obtained is selected as a measurement target. For example, the heel or the patella and the like have little curvature and are close to the skin, and the bone echo Ae2 that can be regarded as a plane wave is easily obtained, and therefore, it is suitable as a measurement target. When the power of the device is turned on after selecting the bone Mb to be measured, the CPU 10 first executes step SP10.
In FIG. 5, each part of the device is initialized.
The initialization includes clearing various data memory areas set in the RAM 12, resetting measurement status flags, and initializing various variables that are initial settings of peripheral circuits. As a result, the contents of the pre-measurement data memory area, average value data memory area, pre-measurement extraction number data memory area, current extraction data memory area, maximum value extraction data memory area, and measurement status flag set in the RAM 12 are as follows: Both are initially set to the state of "0". After completing the initialization of each part of the apparatus, the CPU 10 waits for the start of pre-measurement in step SP11.

Here, when the operator turns on the measurement start switch with the tip surface of the transducer 1 not in contact with the human body (subject M) and only in contact with air, the CPU 10 causes the CPU 10 to measure the measurement status flag. After rewriting the content of 1 to “1”, the pre-measurement operation is started according to the processing procedure of steps SP12 to SP17. CP
In step SP12, the U10 sends the pulse transmission unit 4
Is controlled to generate an electric signal of a half-wave impulse in a predetermined cycle, and the transducer 1 is intermittently sent out. Each time the transducer 1 receives an electric signal of a half-wave impulse from the pulse sending unit 4, it emits an ultrasonic impulse Ai having good directivity from the wave transmission / reception surface X of the ultrasonic transducer 1a. The emitted ultrasonic impulse Ai travels in the ultrasonic delay spacer 1b in the direction normal to the transmitting / receiving surface X,
It reaches the open end face of the ultrasonic delay spacer 1b, which is only in contact with air. The ultrasonic impulse Ai reaching the open end surface is
It almost does not go out into the air, and most of it is reflected vertically by the open end face and becomes an echo Ae0 at the time of opening. The open echo Ae0 travels backward in the ultrasonic delay spacer 1b and is received by the wave transmission / reception surface X of the ultrasonic transducer 1a (note that when the open echo Ae0 is received, it is transmitted. Reverberation An is quiet).

The transducer 1 has various echoes A
When n and Ae0 are received, they are converted into received signals (electrical signals), and the received signals generated by the conversion are sent to the apparatus main body 2 (matching circuit 5) via the cable 3. The amplifier 6 is
The received signal output from the matching circuit 5 is amplified by a predetermined amplification degree and then input to the waveform shaper 7. The waveform shaper 7
The output signal of the amplifier 6 is detected and filtered to be waveform-shaped, and then input to the A / D converter 8. CPU10
Controls the A / D converter 8 to detect the level of the output signal of the waveform shaper 7 to extract the open echo Ae0 and convert the extracted received signal into a digital open echo signal E0. It is converted (step SP13). Next, the open echo signal E0 obtained by digital conversion is A / D
A predetermined number of preset data are taken in from the converter 8 and a RAM
The pre-measurement data memory area 12 is sequentially stored as the open echo level E0 (step SP14, 1).
5). When a predetermined number of open echo levels E0 are fetched (in the case of "YES" in step SP15), the CPU 1
0 reads out the entire contents of the pre-measurement data memory area, calculates the average value of the echo level E0 at opening, stores the calculation result in the average value data memory area, and controls the display 14 to perform the pre-measurement. Is displayed (steps SP16 and SP17).

When the operator knows from the screen display of the display device 14 that the pre-measurement is completed, the operator starts the main measurement from this. That is, as shown in FIG. 3, the operator applies an ultrasonic coupling material 15 such as water or jelly to the surface (skin surface) Y of the soft tissue Ma covering the bone Mb to be measured, and After the sound waves are easily injected into the body of the subject M, the transducer 1 is brought into close contact with the skin surface Y from above the ultrasonic coupling material 15, and the wave transmission / reception surface X is directed toward the bone Mb to be measured. Turn on the measurement start switch again.

When the measurement start switch is turned on again (step SP18 (FIG. 6)), the CPU 10 rewrites the content of the measurement status flag to "2", and then the processing from step SP19 to SP25. Follow the procedure to start the main measurement operation. In step SP19, the CPU 10 controls the pulse sending unit 4 to generate an electric signal of a half-wave impulse at a predetermined cycle, and the transducer 1
To be sent intermittently. Each time the transducer 1 receives an electric signal of a half-wave impulse from the pulse transmitter 4,
An ultrasonic impulse Ai having good directivity is emitted from the wave transmission / reception surface X of the ultrasonic transducer 1a toward the bone Mb of the subject M.
The emitted ultrasonic impulse Ai travels in the ultrasonic delay spacer 1b in the direction normal to the transmitting / receiving surface X, and as shown in FIG. 4, the interface Y between the ultrasonic delay spacer 1b and the soft tissue Ma (strictly speaking, At the interface between the ultrasonic delay spacer 1b and the ultrasonic coupling material 15, as shown in FIG.
A part of the light is reflected to become a surface echo Ae1, and the rest enters the soft tissue Ma. Of these, the surface echo Ae1 travels in the opposite direction in the ultrasonic delay spacer 1b and is received by the wave transmission / reception surface X of the ultrasonic transducer 1a (note that the surface echo Ae1).
At the time when e1 is received, the transmission reverberation An is quiet). On the other hand, the ultrasonic impulse Ai that has entered the soft tissue Ma propagates toward the bone Mb to be measured while being attenuated due to the interaction with the molecules constituting the soft tissue Ma.
Then, on the bone surface Z, a part is reflected and the bone echo A
It becomes e2, and the rest enters the bone Mb and is partially absorbed and partially penetrated. Among these, the bone echo Ae2 follows the reverse path, enters the ultrasonic wave delay spacer 1b again, and is received by the wave transmission / reception surface X of the ultrasonic transducer 1a.

The transducer 1 has various echoes A.
When n, Ae1, and Ae2 are sequentially received, they are converted into received signals (electrical signals), and the received signals generated by the conversion are sent to the apparatus main body 2 (matching circuit 5) via the cable 3. The amplifier 6 amplifies the received signal output from the matching circuit 5 with a predetermined amplification degree and then inputs the amplified signal to the waveform shaper 7. The waveform shaper 7 detects and filters the output signal of the amplifier 6 to shape the waveform, and then inputs the signal to the A / D converter 8.

Here, the CPU 10 controls the A / D converter 8 to detect the level of the output signal of the waveform shaper 7, the arrival time, and the like, and returns the surface echo Ae1 returning earlier and the returning after a delay. The incoming bone echoes Ae2 are sequentially extracted, and the received signals of the surface echoes Ae1 and bone echoes Ae2 extracted in pairs are converted into digital surface echo signals E1 and bone echo signals E2 (step SP20). A / D
When the surface echo Ae1 is extracted, the converter 8 generates a surface echo extraction signal ET and supplies it to the time counting circuit 9. C
The PU 10 takes in a pair of the surface echo signal E1max and the bone echo signal E2 from the A / D converter 8 and reads the elapsed time from the timing circuit 9 at the time of taking in the bone echo signal E2, and echoes at this time. After measuring the arrival time difference Tn, the surface echo level E1 extracted this time,
As a bone echo level E2 and an echo arrival time difference Tn, R
After storing in the currently extracted data memory area of AM12 (step SP21), the level meter 13 is controlled,
The bone echo level E2 (the current level 13a of the bone echo Ae2) extracted this time and the maximum bone echo level E2max (the maximum level 13b of the bone echo Ae2) stored in the maximum value extraction data memory area of the RAM 12 are displayed on the liquid crystal pointer pattern. Are simultaneously displayed by (step SP22).

Next, the CPU 10 proceeds to step SP23, reads the bone echo level E1 of this time extraction from the currently extracted data memory area in the RAM 12, and also reads the maximum bone echo level E2m from the maximum value extracted data memory area.
By reading ax, it is determined whether or not the bone echo level extracted this time is higher than the maximum bone echo level E2max. When the result of this determination is "YES", that is, when the bone echo level E2 of this time extraction is larger than the maximum bone echo level E2max, the processing proceeds to step SP24, and the stored contents (maximum bone extraction data memory area) After rewriting the echo level E2max etc. with the stored content of the bone data memory area extracted this time (bone echo level E2 etc. extracted this time),
Go to step SP25. On the other hand, when the result of the determination in step SP23 is "NO", that is, when the bone echo level E2 extracted this time is smaller than the maximum bone echo level E2max, the process directly jumps to step SP25. In step SP25, the CPU 10 looks at the measurement status flag in the RAM 12 and determines whether or not to continue the measurement. When the content of the measurement status flag is "2", it means that the measurement is continued, so the CPU 10 returns to step SP19 and repeats the above-described processing (steps SP19 to SP25). In addition,
Until the operator presses the measurement end switch, the content of the measurement status flag is kept at "2".

While the CPU 10 repeats the above-described processing (steps SP19 to SP25), the operator operates the arrow R in FIG.
, The transducer 1 is applied to the skin surface Y and is directed toward the bone Mb to be measured, and sometimes a circle is drawn like a precession motion of a coma and sometimes a back and forth like a seesaw. Aiming for a state in which the liquid crystal pointer pattern of the level meter 13 swings to the maximum while swinging left and right in an oblique direction.
When the liquid crystal pointer pattern of the level meter 13 swings to the maximum, as shown in FIG.
Of the plane wave ultrasonic wave Ai.
When it is vertically incident on the bone surface Z (ultrasound impulse Ai
When the wave fronts of are aligned substantially parallel to the bone surface Z).

The reason is that when the two normals coincide with each other, the bone echo Ae2 vertically reflected by the bone surface Z is vertically incident on the transmitting / receiving surface X and returns as shown in FIG. The wave front of the echo Ae2 is also aligned substantially parallel to the transmission / reception surface X, and therefore, the bone echo Ae due to the difference in the receiving position.
This is because the phase shift of 2 is minimized, so that the received signal has less cancellation of peaks and troughs, and therefore the maximum level of bone echo Ae2 is received. On the other hand, when the normals do not match, the wavefront of the bone echo Ae2 is not uniform on the transmitting and receiving wavefront X, as shown in FIG. , Get smaller. Here, the important thing is, of the bone echo Ae2,
I want to extract the bone echo Ae2 that returns with vertical reflection.
It means that This is because the mathematical formula applied to the algorithm described below is a formula that holds when the bone echo Ae2 is substantially vertical reflection for the sake of accuracy and simplification of calculation. However, bone echo A reflected vertically on the bone surface Z
Since the received signal of e2 has the maximum level as described above, the bone echo Ae2 of the maximum level is extracted with reference to the level meter 13 in order to extract the bone echo Ae2 of the vertical reflection. Note that the liquid crystal pointer pattern of the level meter 13 changes sensitively when the normal line of the bone Mb and the normal line of the transmitting / receiving surface X are extremely dissimilar, but changes when both normal lines substantially match. Because it becomes dull
The vertical reflection bone echo Ae2 can be extracted easily and with good reproducibility. On the other hand, the surface echo Ae1 is the ultrasonic transducer 1
Since the wave transmission / reception surface X of a and the tip surface of the ultrasonic delay spacer 1b are set to have a parallel relationship with each other, vertical reflection is always performed as shown in FIGS.

When the operator determines that the maximum level of bone echo Ae2 has been extracted by looking at the degree of deflection of the pointer pattern on the level meter 13, he presses the measurement end switch.
When the measurement end switch is pressed, the CPU 10 rewrites the content of the measurement status flag to "0" by interrupt processing. The CPU 10 looks at the content of the measurement status flag at the time of next determination at step SP25. When the end of measurement is known, the pulse sending unit 4 is controlled to stop the transmission of the half-wave impulse (electrical signal) to the transducer 1. Then, the stored contents (maximum bone echo level E2max etc.) are read from the maximum value extraction data memory area and displayed on the display 14 (step SP26).

Thereafter, the CPU 10 causes the open echo level E0 stored in the pre-measurement data memory area,
Data stored in the maximum value extraction data memory area (maximum bone echo level E2max, surface echo level E1max paired therewith, and echo arrival time difference T at this time)
n) is used to execute the calculation process of the acoustic impedance Zz of the bone Mb. In this calculation process, first, the attenuation A (Tn) of the ultrasonic wave in the soft tissue Ma is calculated (step SP2
7), and then the soft tissue M from the obtained attenuation A (Tn) etc.
After calculating the reflection coefficient R at the interface between a and the bone Mb (step SP28), the acoustic impedance Zz of the bone Mb is calculated from the obtained reflection coefficient R and the like (step SP30).
It is performed in the procedure.

[1] Attenuation A due to soft tissue reciprocation of ultrasonic waves A
Calculation of (Tn) First, the CPU 10 reads the echo arrival time difference Tn from the maximum value extraction data memory area, substitutes the value of the read echo arrival time difference Tn [sec] into the equation (1), and calculates the soft tissue. The attenuation A (Tn) of ultrasonic waves in Ma is calculated (step SP27).

[0031]

[Equation 1]

Here, the degree of attenuation A (Tn) is the degree of attenuation that ultrasonic waves undergo when they reciprocate in the soft tissue Ma, that is, the ultrasonic waves propagate from the skin surface Y to the bone surface Z, It means the degree of attenuation that is reflected by Z and returns to the skin surface Y again (the smaller A (Tn), the larger the attenuation). The attenuation A (Tn) is a function of the echo arrival time difference Tn, and the relational expression can be obtained by experiment or simulation. Ultrasonic waves
First, the ultrasonic wave used in this example is not a perfect plane wave, but also contains a spherical wave component, and this spherical wave component diffuses acoustic energy (ultrasonic diffusion). Secondly, 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 can be obtained by calculation or experiment from the aperture of the transducer 1, the frequency of ultrasonic waves, the speed of sound of the soft tissue Ma, and the like. Further, the degree of attenuation due to ultrasonic wave absorption is reduced by lowering the frequency of ultrasonic waves. Even if the frequency is not sufficiently low, the typical absorption constant of soft tissue Ma (the ultrasonic wave attenuation rate per unit length is ) Can be used. The equation (1) that gives the attenuation A (Tn) of the ultrasonic wave is an empirical equation that holds when the use center frequency of the ultrasonic wave is set to 2.5 MHz and the aperture of the transducer 1 is set to 15 mm. .

[2] Calculation of Reflection Coefficient R at Interface between Soft Tissue Ma and Bone Mb Next, the CPU 10 determines the maximum bone echo level E2max and the surface echo level E1max paired with it from the maximum value extraction data memory area. Substituting into the expression (2) together with the attenuation A (Tn) read out and calculated using the expression (1),
A reflection coefficient R at the interface between the soft tissue Ma and the bone Mb when the ultrasonic wave is vertically incident on the bone Mb from the medium side of the soft tissue Ma is calculated (step SP28).

[0034]

[Equation 2]

However, h = -E2max / E0 s = -E1max / E0

Equation (2) is derived as follows. First, when the sound pressure of the ultrasonic impulse Ai incident from the medium of the ultrasonic delay spacer 1b to the air medium is Pi, the sound of the open echo Ae0 which is the reflected wave from the interface between the ultrasonic delay spacer 1b and the air. The pressure P (e0) is given by the equation (3).

[0037]

(Equation 3)

Here, Zx: acoustic impedance of the ultrasonic delay spacer 1b (known) Z0: acoustic impedance of air D0: ultrasonic wave when the ultrasonic wave vertically enters the air from the medium side of the ultrasonic delay spacer 1b. Reflection coefficient of sound pressure at the interface between the delay spacer 1b and the air By considering that Zx is approximately 10 ⁴ times Z0, it can be regarded as Z0 / Zx → 0. , Equation (4) is obtained.

## EQU00004 ## P (e0) =-Pi ... (4)

Next, when the sound pressure of the ultrasonic impulse Ai entering the soft tissue Ma of the human body from the medium of the ultrasonic delay spacer 1b is Pi, the ultrasonic delay spacer 1b and the soft tissue Ma are
Surface echo A which is a reflected wave from the interface (skin surface Y) of
The sound pressure P (e1) of e1 is given by the equation (5).

[0040]

(Equation 5)

Here, Zy: Acoustic impedance of soft tissue Ma D1: At the interface between the ultrasonic delay spacer 1b and the soft tissue Ma when the ultrasonic wave vertically enters the soft tissue Ma of the human body from the medium side of the ultrasonic delay spacer 1b. (6) is obtained by substituting the equation (4) into the equation (5).

[0042]

(Equation 6)

By rearranging equation (6), equation (7) giving the acoustic impedance Zy of the soft tissue Ma is obtained.

[0044]

(Equation 7)

However, s = P (e1) / P (e0) On the other hand, the ultrasonic impulse Ai is the ultrasonic delay spacer 1
The transmittance Txy of the sound pressure when the light is transmitted perpendicularly to the soft tissue Ma of the human body from the medium side of b is given by the equation (8).

[0046]

(Equation 8)

Further, the sound pressure transmittance Tyx when the ultrasonic impulse Ai is perpendicularly transmitted from the soft tissue Ma side of the human body to the medium of the ultrasonic delay spacer 1b is given by the equation (9).

[0048]

[Equation 9]

Therefore, when the sound pressure of the ultrasonic impulse Ai vertically incident on the soft tissue Ma of the human body from the medium of the ultrasonic delay spacer 1b is Pi, the ultrasonic impulse Ai injected into the soft tissue Ma becomes the soft tissue Ma. It is reflected vertically at the interface with the bone Mb (bone surface Z) and becomes a bone echo Ae2,
The sound pressure P (e2) when this bone echo Ae2 returns to the transmitting / receiving surface X of the ultrasonic transducer 1a perpendicularly again.
In consideration of the attenuation A (Tn) due to the reciprocation of the soft tissue Ma of the ultrasonic wave calculated from the expression (1), the expression (1
0). The reflection component when the ultrasonic wave enters the ultrasonic wave delay spacer 1b from the medium side of the soft tissue Ma and the attenuation component in the ultrasonic wave delay spacer 1b will be ignored.

[0050]

[Equation 10]

Where R is the reflection coefficient of the sound pressure at the interface between the soft tissue Ma and the bone Mb when the ultrasonic wave is vertically incident on the bone Mb from the medium side of the soft tissue Ma. Is used, equation (11) is obtained.

[0052]

[Equation 11]

By substituting equation (7) into equation (11) and rearranging, equation (12) giving the reflection coefficient R of the sound pressure at the interface between the soft tissue Ma and the bone Mb with respect to vertical incidence is obtained.

[0054]

(Equation 12)

However, h = -P (e2) / P (e0) s = -P (e1) / P (e0) Here, the bone echo Ae2 again reaches the transmitting / receiving surface X of the ultrasonic transducer 1a. Sound pressure P (e
2) corresponds to the maximum bone echo level E2max, and the sound pressure P (e0) of the open echo Ae0 is the ultrasonic delay spacer 1b.
Neglecting the attenuation of the ultrasonic waves inside, it corresponds to the open echo level E0 and similarly the sound pressure P (e of the surface echo Ae1
Since 1) corresponds to the surface echo level E1max which is paired with the maximum bone echo level E2max, the proviso of the formula (12) can be expressed by the formulas (13) and (14), respectively.

[0056]

(Equation 13)

[0057]

[Equation 14]

Therefore, the equation (2) giving the reflection coefficient R of the sound pressure at the interface between the soft tissue Ma and the bone Mb with respect to the normal incidence can be obtained.

Returning to the explanation of the flowchart of FIG. 6 again, the CPU 10 calculates the reflection coefficient R at the interface between the soft tissue Ma and the bone Mb using the equation (2) (step S).
P28), and the calculation result is displayed on the display 14 (step SP29).

[3] Calculation of acoustic impedance Zz of bone Mb After this, the CPU 10 causes the acoustic impedance Zz of bone Mb.
z is calculated using equation (15) (step SP30),
The calculation result is displayed on the display 14 (step SP3).
1).

[0061]

(Equation 15)

According to the above configuration, the ultrasonic delay spacer 1
b eliminates the influence of the transmission reverberation An and also considers the attenuation A (Tn) of the ultrasonic wave due to the round trip of the soft tissue, so that the acoustic impedance Zz of the bone Mb can be reliably measured. Since the acoustic impedance Zz of the bone Mb is represented by the square root of [elastic modulus × density] of the bone Mb, when the elastic modulus increases with an increase in bone density, these synergistic effects cause a sensitive response. And increase significantly. Conversely, bone Mb
The acoustic impedance Zz is significantly decreased in response to the above-mentioned synergistic effect when the density decreases and the elastic modulus decreases. Therefore, the acoustic impedance Zz of the bone Mb is a good index for determining the bone density. Therefore, the operator can reliably estimate the progress of osteoporosis from the value of the acoustic impedance Zz of the bone Mb displayed on the display unit 14. For example, when the acoustic impedance is significantly smaller than the average value of that age group, it is understood that the osteoporosis of the bone Mb is aggravated. In addition, according to the above configuration, the current level 13a of the bone echo Ae2 is displayed on the level meter 13, and the maximum level 13b of the bone echo Ae2 is also displayed, so that the maximum level can be easily searched. In addition, the bone echo A of the vertical reflection that changes slowly with respect to the displacement (vibration of the transducer 1)
Since e2 is used, measurement data can be easily extracted,
And it can be extracted with good reproducibility. In addition, since the RAM 12 is set with a currently extracted data memory area that stores only the currently extracted data and a maximum value extracted data memory area that stores only the maximum bone echo level and related data, it is inexpensive and has a small storage capacity. RAM can be used.

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, bones are not limited to humans. Similarly, the measurement site is not limited to the heel or the patella. Further, the ultrasonic transducer forming the transducer is not limited to the thickness vibration type, but may be the bending vibration type. The wave transmission / reception surface of the ultrasonic transducer is not limited to a large one. The center frequency used is 2.5M.
Not limited to Hz. Further, the expression (1) giving the attenuation degree A (Tn) is an example, and can be changed if the use center frequency of ultrasonic waves or the aperture of the transducer is changed. Also,
The output device that outputs the index (acoustic impedance) of the osteoporosis diagnosis is not limited to the display device, and a printer may be used. In addition, a time waveform display device (for example, a digital oscilloscope) may be provided to observe the echo waveform.

Although there is an opinion that osteoporosis can be diagnosed from the condition of the bone elastic modulus, the acoustic impedance of the bone is expressed by the square root of [elastic modulus × density] of the bone, and therefore it also serves as an index of the bone elastic modulus. obtain. Further, instead of using the acoustic impedance of bone as an index of bone density or bone elastic modulus, a reflection coefficient at the interface between the soft tissue Ma and the bone Mb, which can be generally regarded as a monotonically increasing function of the acoustic impedance of bone, is used. The same effect as described above can be obtained as an index of bone density or bone elastic modulus. In addition, in the above-described embodiment, the pre-measurement (opening echo level E0 is performed every time osteoporosis is diagnosed.
However, instead of such pre-measurement, the open echo level E0 is extracted in advance at the factory stage, and the obtained result is written in a non-volatile memory such as a ROM. By doing so, the load on the CPU can be reduced, and the processing can be speeded up.

[0065]

As is apparent from the above description, according to the configuration of the present invention, the influence of the transmission reverberation is eliminated by the ultrasonic delay spacer, so that the acoustic impedance of bone can be reliably measured. In addition, since the bone echo (second echo) of vertical reflection, which changes slowly with respect to the displacement (vibration of the ultrasonic transducer), is used, the measurement data can be extracted easily and with good reproducibility. . Since the acoustic impedance of bone is expressed by the square root of [elastic modulus x density] of bone,
When the elastic modulus increases with the increase of bone density, it undergoes these synergistic effects, and therefore, it significantly increases in response to sensitivity. Conversely, when the bone density decreases and the elastic modulus decreases,
The acoustic impedance undergoes these synergistic effects and responds sensitively to a significant decrease. Therefore, the acoustic impedance of bone is a good index for determining the bone density and the bone elastic modulus. Therefore, the operator can reliably estimate the progress of osteoporosis from the value of the acoustic impedance of the bone displayed on the display. For example, if the acoustic impedance is significantly smaller than the average value for that age group,
It can be seen that the osteoporosis of the bone is getting worse. Further, instead of using the acoustic impedance of bone as an index of bone density or bone elastic modulus, normally, the reflection coefficient at the interface between the soft tissue and the bone of the living body, which can be regarded as a monotonically increasing function of the acoustic impedance of bone, is used. The same effect as described above can be obtained as an index of density or bone elastic modulus.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an apparatus (osteoporosis diagnostic apparatus) used for carrying out an osteoporosis diagnostic method according to an embodiment of the present invention.

FIG. 2 is a diagram showing an appearance of the same device.

FIG. 3 is a diagram showing a usage state of the apparatus.

FIG. 4 is a diagram showing how osteoporosis is diagnosed by the device.

FIG. 5 is a flowchart showing an operation processing procedure of the apparatus (the osteoporosis diagnosing method of the embodiment).

FIG. 6 is a flowchart showing an operation processing procedure of the device (the osteoporosis diagnosing method of the embodiment).

FIG. 7 is a diagram for explaining the operation of the same device.

[Explanation of symbols]

 1 Transducer (Ultrasonic Transducer) 1a Ultrasonic Transducer 1b Ultrasonic Delay Spacer 8 A / D Converter 9 Timing Circuit 10 CPU 11 ROM 12 RAM 14 Display (Output Means) Ai Ultrasonic Impulse Ma Soft Tissue Mb Bone X Transmitting / receiving surface (ultrasonic transmitting / receiving surface) Y Surface of soft tissue (skin surface) Z Bone surface Ae1 surface echo (second echo) Ae2 Bone echo (third echo)

Claims (2)

[Claims] 1. Osteoporosis is prevented by an ultrasonic wave transmitter / receiver formed by bonding an ultrasonic wave delay spacer for delaying the return of echoes from a predetermined site on the ultrasonic wave transmission / reception surface of an ultrasonic transducer until the transmission reverberation is calmed down. A method of diagnosing osteoporosis for diagnosing, wherein an ultrasonic impulse is emitted from an ultrasonic wave transmitting / receiving surface of the ultrasonic transducer while the tip surface of the ultrasonic wave delay spacer is exposed to an air atmosphere. A first step of receiving the first echo reflected at the interface between the delay spacer and the air and returning to the ultrasonic wave transmitting / receiving surface to extract pre-measurement data; and a tip surface of the ultrasonic delay spacer. To the living body, the normal line of the ultrasonic wave transmitting and receiving surface is directed to the bone, and while oscillating within a predetermined angle range with respect to the normal line of the bone, ultrasonic impulses are intermittently emitted, at this time, Living The second echo reflected on the surface and returned to the ultrasonic wave transmitting / receiving surface and the third echo reflected on the bone surface and returning to the ultrasonic wave transmitting / receiving surface are sequentially received to obtain the main measurement data. Second to extract
And the reflection coefficient or bone at the interface between the soft tissue of the living body and the bone based on the pre-measurement data extracted in the first step and the main measurement data extracted in the second step. And a third step of calculating the acoustic impedance of the bone, and diagnosing osteoporosis by estimating the condition of the bone density or the bone elastic modulus from the reflection coefficient or the acoustic impedance of the bone calculated in the third step. And a method for diagnosing osteoporosis. 2. The first step is performed in advance in a factory, and the pre-measurement data extracted in the first step at the time of factory shipment is stored in a non-volatile memory, 2. The reflection coefficient or the acoustic impedance of bone is calculated by using the pre-measurement data read from the non-volatile memory when diagnosing osteoporosis with the transceiver. Method for diagnosing osteoporosis in.