JPH0722580B2 - Bone evaluation device - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a bone assessment device that provides new information regarding bone quality useful in diagnosing bone disorders.

[0002]

2. Description of the Related Art With the rapid increase in the aging population, the number of people with bone diseases such as osteoporosis and osteomalacia is increasing.
There is a strong demand for the diagnosis and prevention. Bones
In terms of its composition, it is roughly divided into bone mineral (amount of minerals such as calcium) and matrix (intercellular substance of bone tissue).

Here, "osteoporosis" generally refers to a condition in which the ratio of bone matrix to bone mineral is normal, but the amount of bone itself has decreased, and "osteomalacia" generally refers to bone mineralization disorder. It refers to a condition in which only bone mineral is reduced by. In other words, even if it is called a bone disease, the composition of bone in the pathological condition is not uniform. In any case, when the strength of the bone is weakened, a bone fracture may occur, and an elderly person may become so-called bedridden.

Conventionally, a bone mineral content measuring device has been used for diagnosing bone diseases. This bone mineral content measuring device irradiates a subject with X-rays from outside the body, and analyzes the bone mineral content (mineral content such as calcium) from the attenuation rate at that time. In the conventional bone mineral density measuring device, the bone mineral density (g / cm ² ) per unit area is calculated.

Then, osteoporosis or the like is diagnosed based on the calculated amount of bone mineral.

[0006]

However, it is said that "bone strength" does not depend only on the amount of bone mineral. The amount of bone mineral is certainly the main factor that determines the strength of the bone, but besides that, the bone stiffness, elasticity, and structure (for example, the formation structure of the quality material that is a component of the matrix) and the like Strength depends on.

That is, even if the amount of bone mineral is large, the rigidity of the bone is poor and the bone fracture is likely to occur. On the other hand, even if the amount of the bone mineral is small, the bone stiffness is high and the bone fracture is hard to occur.

[0008] In summary, in order to know the risk of fracture,
It is not enough to evaluate the bone mineral content alone, and it is necessary to know the “bone strength” itself based on the bone composition and structure.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a bone evaluation apparatus capable of obtaining a new evaluation value for bone which indicates the strength of the bone.

[0010]

[Means for Solving the Problems]

(A) Principle of the present invention In the present invention, the bone density ρ obtained based on the amount of bone mineral is ρ
And the propagation velocity V of the sound wave (ultrasound) in the bone is used to calculate an “evaluation value” that indicates the strength of the bone.

The propagation velocity V of ultrasonic waves is a function of the bone density ρ and the elastic modulus E in the propagation direction in an anisotropic medium such as bone. That is, if expressed by a general formula, V = k · (E / ρ) ^1/2 (1).

Here, k is a constant, and the bone density ρ is the bone mineral density BMD (g / c) measured by a conventional bone mineral density measuring device.
m ² ) divided by the bone thickness d (cm). The ultrasonic propagation velocity V is measured by transmitting and receiving ultrasonic waves.

Therefore, the elastic modulus (Young's modulus) E is as follows.

E = k ′ · V ² · ρ (where ρ = BMD / d, k ′ = k ⁻² ) (2) Here, the elastic modulus E is the bone such as tensile strength and rigidity. In other words, the value of E is considered to indicate the risk of fracture.

Therefore, in the present invention, the E is defined as a bone evaluation value. Various calculation formulas are known for the elastic modulus of bone, and other definition formulas can be used as the index value of bone strength, but in any case, the elastic modulus is defined as E.

(B) Means for Solving the Problem In order to achieve the above object, the present invention is based on the above principle and the ultrasonic velocity V in the bone is transmitted and received by transmitting and receiving ultrasonic waves to and from the bone evaluation site of the subject. Measuring speed, a bone density measuring means for irradiating the bone evaluation site with X-rays to measure bone density, and a bone for calculating an evaluation value defined by the ultrasonic speed and the bone density. And an evaluation value calculating means.

[0017]

According to the above construction, the speed of the ultrasonic waves in the bone is obtained by transmitting and receiving the ultrasonic waves by the bone speed measuring means, and the bone density is measured by the X-ray irradiation by the bone density measuring means. The bone evaluation value calculation means calculates a bone evaluation value from the above two measured values.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an explanatory view of the principle of the bone evaluation apparatus according to the present invention. In FIG. 1, the subject 10 is
It is roughly divided into bone 12 and soft tissue 14. An X-ray generator 16 that generates X-rays is arranged near the subject 10, and an X-ray detector 18 that detects X-rays that have passed through the subject 10 is arranged.

Further, in the vicinity of the subject 10, a transducer 20 for transmitting ultrasonic waves and a transducer 22 for receiving ultrasonic waves are provided in the vicinity of the X-ray generator 16 and the X-ray detector 18. It is arranged. When the thickness d is measured, both the vibrators 20 and 22 function as a wave transmitter / receiver vibrator.

The bone density measuring section 24 supplies a drive signal to the X-ray generator 16 and receives a detection signal from the X-ray detector 18 to measure the bone density of the bone 12. The bone density ρ is sent to the evaluation value calculation unit 26.

The velocity measuring unit 28 supplies a drive signal to the oscillator 20, while receiving a received signal from the oscillator 22, and calculates the propagation velocity V of the ultrasonic wave in the bone 12. The speed V is sent to the evaluation value calculator 26.

The evaluation value calculator 26 executes the above-mentioned second equation to calculate the evaluation value E based on the bone density ρ and the speed V. Then, the E is output and displayed on, for example, a display device. Therefore, based on the magnitude of the evaluation value, it is possible to know the risk of bone fracture or the like, or to diagnose osteoporosis or the like.

By the way, bone is composed of cancellous bone and cortical bone due to its structure, and it is said that the cancellous bone has a metabolic rate about 8 times faster than that of cortical bone. Therefore, it is considered that the decrease in bone mass or the decrease in bone strength appears first in the cancellous bone.
Therefore, in evaluating the bone, it is preferable to measure, for example, the calcaneus or the lumbar spine, which has a large proportion of the cancellous bone, and the diagnostic accuracy can be improved. Therefore, in the bone evaluation device according to the present invention described below, the calcaneus is the measurement target.

FIG. 2 shows an overall external view of the bone evaluation apparatus of this embodiment. This bone evaluation device is roughly divided into
It is composed of a measuring device 30 and a control device 32.

As shown in the figure, the control device 32 is composed of a computer or the like, and is connected to the measuring device 30 by a cable 34.

In the measuring device 30, a plurality of casters is provided on the lower surface side of the carriage 36, while the carriage 36 is provided.
A chair 38 and a measurement unit 44 are arranged on the upper surface of the. The measurement unit 44 includes a water tank 46, and a footrest 48 is arranged in the water tank 46.

When the measurement is to be performed, the examinee 40 wears the chair 3
Sit on 8 and place the foot 42a on the footrest 48 arranged in the water tank 46, and in that state, X-ray irradiation and ultrasonic wave transmission / reception are performed.

The outer wall of the water tank 46 is made of, for example, an acrylic plate or the like. The reason why the foot 42a is put in the water tank 46 in this way is that water has an X-ray attenuation rate and a sound velocity almost equal to those of the soft tissue of the living body, and is separated from the soft tissue by such a configuration to measure the bone mineral content. In addition, the ultrasonic measurement of only the bone can be easily performed regardless of the shape of the soft tissue.

As shown in the figure, in the measuring unit 44, two ultrasonic transducers 50a and 50b supported by arms 52a and 52b are arranged to face each other via a foot 42a. The X-ray generator and the X-ray detector are not shown in FIG.

FIG. 3 is a perspective view showing the main part of the measuring unit 44. In addition, the water tank 46 is shown with the dashed-dotted line in the figure.

At one end of the substrate 54, the arm 5 described above is provided.
2a is arranged, and an X-ray generator 56 is arranged. A collimator and a filter are arranged at the X-ray irradiation port of the X generator 56.

On the other hand, the arm 52 is provided at the other end of the substrate 54.
b is arranged and X composed of a semiconductor detector or the like
A line detector 58 is arranged. Therefore, the X-ray is irradiated from the outside of the water tank 46, passes through the inside of the water tank and passes through the foot, and then is measured outside the water tank.

The substrate 54 is supported by the moving mechanism 60. The moving mechanism 60 is roughly classified into a Z-direction elevating unit that elevates and lowers the substrate 54 in the Z direction in the drawing,
In the figure, it is configured with an X-direction moving unit that moves the substrate 54 in the X-direction. Each unit includes motors 62 and 64 and feed screws 66 and 68. By rotating the feed screws 66 and 68 by the motors 62 and 64, the substrate 54 is freely moved in the X direction and the Z direction in the drawing. Can be made.

As shown in FIG. 3, the X-ray 100 is irradiated as a thin beam, and the ultrasonic wave 102 is transmitted / received on the line connecting the ultrasonic transducers 50a and 50b. The central axes of the X-ray 100 and the ultrasonic wave 102 are close to each other.

FIG. 4 is a block diagram showing the configuration of the measuring device 30. The X-ray measurement control unit 70 controls the generation and detection of X-rays, and the X-ray measurement control unit 7 thereof.
The drive signal 104 output from 0 is the X-ray controller 72.
Is transmitted to the X-ray generator 56 via the. Here, the X-ray control device 72 determines the drive voltage and the like of the X-ray generator 56. On the other hand, the X-ray detection signal 106 output from the X-ray detector 58 that detects X-rays is amplified by the amplifier 74 and then input to the counting circuit 76. The counting circuit 76 obtains the intensity of X-rays by counting pulses, and the counting circuit 76 sends a signal 108 indicating the counting rate C to the X-ray measurement control unit 70. The signal 108 indicating the count rate C is further sent to the control device 32.

The ultrasonic measurement control section 78 controls the transmission and reception of ultrasonic waves, and the first transmission / reception unit 8
0 and the second transmission / reception unit 82 are controlled. Each transmission / reception unit 80, 82 is composed of a transmission circuit and a reception circuit. That is, the first transmission / reception unit 80 sends a transmission drive signal to the ultrasonic transducer 50a, and
The received signal from the ultrasonic transducer 50a is received. The second transmission / reception unit 82 includes the first transmission / reception unit 8
Similar to 0, the ultrasonic transducer 50b supplies the transmission drive signal and receives the reception signal.

The received signal 109 output from the transmitting / receiving units 80 and 82 is converted into a digital value by the A / D converter 84, and then sent to the ultrasonic measurement control section 78. Then, the ultrasonic measurement control unit 78 measures the fixed times t1, t2, and t3, which will be described later, and outputs the respective time values to the control device 32.

The scanning controller 86 controls the up-and-down movement and back-and-forth movement of the substrate 54, and outputs drive signals to the motors 62 and 64. These control units 70, 78, 86
Are controlled by the control device 32.

FIG. 5 is a block diagram showing a specific structure of the control device 32. Counting rate C indicating the intensity of X-rays
Is input to the BMD calculation circuit 88 that calculates the bone mineral content (BMD). The calculation result B is the bone density calculation circuit 9
0 and sent to the main controller 92. The bone density calculation circuit 90 calculates the bone density ρ per unit volume by dividing the bone mineral content B by the bone thickness d, and outputs the calculation result to the evaluation value calculation circuit 94.

On the other hand, the thickness calculation circuit 96 calculates the bone thickness d based on t2 and t3, as will be described later, and the calculation result d is the bone density calculation circuit 9 described above.
0, the speed calculation circuit 98, and the main controller 92.

Here, the velocity calculation circuit 98 calculates the velocity V of the ultrasonic wave in the bone based on t1 and d, as will be described later, and the calculation result V is the evaluation value calculation. It is output to the circuit 94 and the main controller 92.

The evaluation value calculation circuit 94 executes the calculation of the above-mentioned second equation based on the bone density ρ and the speed V, and calculates the evaluation value E. The evaluation value E is output to the CRT 110. On the other hand, in this embodiment, the evaluation frequency calculation circuit 1
12 is provided, and the bone evaluation frequency H is calculated based on the evaluation value E and sent to the CRT 110.

The main controller 92 controls the whole of the control device, and at the same time, the X-ray measurement controller 70,
The ultrasonic measurement control unit 78 and the scanning control unit 86 are controlled. The main controller 92 is connected to the input unit 114 including a keyboard.

Next, the operation of the bone evaluation apparatus of this embodiment will be described.

As shown in FIG. 2, when performing bone evaluation,
The subject 40 is seated on the chair 38, and the foot 42a is put in the water tank 46. After that, the operator commands the measurement execution from the input unit 114. Then, the main controller 92
The scan controller 86 shown in FIG. 4 is instructed to move to the initial position. As a result, the scan controller 86 causes the motor 62 to
And 64 are controlled to move the irradiation position of the X-ray and the ultrasonic wave to the initial position. After the position is set, the main controller 92 shown in FIG. 5 causes the X-ray measurement controller 7 shown in FIG.
X-ray measurement command is issued to 0.

Then, the drive signal 104 is sent from the X-ray measurement controller 70 to the X-ray generator 56 via the X-ray controller 72, and X-rays are emitted.

The X-ray transmitted through the foot 42a is detected by the X-ray detector 5
8, the detection signal 106 is input to the counting circuit 76 via the amplifier 74 and counting is performed. The signal C108 indicating the count value is the BMD shown in FIG.
It is sent to the arithmetic circuit 88 and the amount of bone mineral is calculated in the same manner as before,
The bone mineral content B is sent to the bone density calculation circuit 90.

After such X-ray measurement is performed, ultrasonic measurement is next performed.

When an ultrasonic measurement command is given from the main controller 92 to the ultrasonic measurement control unit 78 of FIG. 4, the ultrasonic measurement control unit 78 causes the first transmission / reception unit 80 to operate as shown in FIG. 6 (A). On the other hand, a pulse indicating a transmission command is output. At the same time, as shown in FIG. 6 (B), the ultrasonic measurement control unit 78 activates a counter provided therein. As a result, a drive signal is applied from the first transmitting / receiving unit 80 to the ultrasonic transducer 50a, whereby ultrasonic waves are transmitted to the foot 42a, and transmitted ultrasonic waves are received by the ultrasonic transducer 50b. Be waved. Figure 6
A received signal obtained by the received wave is shown in (C), and the received signal is the second transmission / reception unit 82 and the A / D.
It is sent to the ultrasonic measurement control unit 78 via the converter 84.

The ultrasonic measurement controller 78 reads the count value up to when the received pulse shown in FIG. 6C is obtained, and outputs the time information t1 indicated by the count value to the controller 32.

Next, thickness measurement is performed to measure the thickness of the bone (calcaneus).

Before explaining the operation in the thickness measurement, the principle of measuring the thickness of the bone (calcaneus) will be described. As shown in FIG. 7, in the present embodiment, ultrasonic waves are transmitted from one side of the calcaneus 200 by the ultrasonic transducer 50a, and ultrasonic waves reflected by the calcaneus 200 are also transmitted by the ultrasonic transducer 50a.
Is measured at. After that, also on the other side of the calcaneus 200, the same ultrasonic wave transmission and reflected wave reception are performed by the ultrasonic transducer 50b.

Since water has a sound velocity almost equal to that of soft tissue, the thickness d of the calcaneus 200 is determined by the ultrasonic wave transmission / reception period Δt on one side of the calcaneus 200 and the ultrasonic wave transmission / reception period Δt on the other side. Easily calculated. That is, since the sound velocity V _w of water is known, the thickness d is calculated by the following third equation.

D = L− (t2 + t3) · (V _w / 2) (3) where L is the distance between the transducers.

Therefore, in order to realize the above principle, when the thickness measurement command is issued from the main controller 92, the ultrasonic measurement control section 78, as shown in FIG. A transmission pulse is output to 80 to activate a counter provided therein as shown in FIG. As a result, a drive signal is output from the first transmitting / receiving unit 80 to the ultrasonic transducer 50a, the ultrasonic wave is transmitted, and then the reflected wave is received by the same ultrasonic transducer 50a. The received signal shown in FIG. 8C is sent to the ultrasonic measurement control unit 78 via the first transmission / reception unit 80 and the A / D converter 84. In this case, the ultrasonic measurement control unit 78 determines the received pulse in the received signal and obtains the transmission / reception period t2 from the number of pulses from the start of counting to the time when the received pulse is obtained. The t2 is sent to the control device 32.

In the measurement of t3, the second
The transmitter / receiver unit 82 is operated to perform the measurement,
T3 is sent to the controller 32.

T2 and t3 obtained as described above are
It is sent to the thickness calculation circuit 96 of FIG. 5, the above-mentioned third equation is executed, the bone thickness d is obtained, and the thickness d is sent to the bone density calculation circuit 90 and the speed calculation circuit 98. As a result, the bone density calculation circuit 90 executes the following fourth equation.

Ρ = B / d (4) On the other hand, in the speed calculation circuit 98 to which t1 is input,
The following formula 5 is executed to obtain the speed V.

V = d / {t1− (t2 + t3) / 2} (5) Therefore, based on ρ and V thus obtained, the evaluation value calculation circuit 94 causes the evaluation value calculation circuit 94 to have the above-mentioned second equation, that is, E =
The evaluation value E is obtained by executing k · V ² · ρ.

After the above process is performed for one measurement site, the measurement point is moved under the control of the scan control unit 86, and the same process as above is repeated.

FIG. 9 shows the irradiation areas of X-rays and ultrasonic waves. In the figure, 300 is an X-ray irradiation area,
Reference numeral 2 denotes an ultrasonic wave transmission / reception region. Both regions are large enough to cover the calcaneus.

Here, since the ultrasonic transducer and the X-ray generator are arranged slightly displaced from each other, the regions 300 and 3 are provided.
02 is also set to be slightly deviated from each other.

The above-mentioned initial positions are A and A'in FIG. 9, where A is the initial position of X-ray irradiation and A'is the initial position of ultrasonic irradiation. Then, as described above, after the irradiation at this initial position is performed, the irradiation point is slightly shifted leftward or downward in the figure and the same irradiation / measurement is performed again, and such a process is performed. Repeatedly, the data is finally taken in in the area shown in FIG. After the X-ray irradiation, the X
It is also possible to match the regions 300 and 302 shown in FIG. 9 by moving the ultrasonic wave transmitting / receiving point to the point where the line is irradiated.

FIG. 10 shows a display example on the CRT 110. In the figure, 304 is the amount of bone mineral (BM
D) is a bone mineral density map showing the distribution, 306 is a thickness map showing the thickness d of the bone (calcaneus), 308 is a sound velocity map showing the sound velocity of ultrasonic waves in the bone, and 310 is 9 is an evaluation value map showing an evaluation value E obtained by the above calculation. Incidentally, reference numeral 312 in the drawing is a cursor.

Further, reference numeral 314 is an evaluation frequency indicating the degree of health of the bone in the portion designated by the cursor 312, which is calculated based on the evaluation value E as follows.

FIG. 11 shows a standard characteristic curve 322 showing a standard evaluation value E at each age. The displayed evaluation frequency 314 indicates how far the point specified by the age of the subject and the actually measured evaluation value E is from the standard characteristic curve 322. Specifically, the evaluation value actually measured is subtracted from the standard evaluation value at that age, and the difference is displayed as the evaluation frequency 314. Furthermore, the point data display 320 in FIG. 10 displays the amount of bone mineral, the thickness, the speed of sound, and the evaluation value at the measurement site specified by the cursor 312 as numerical values.

As described above, such a display is displayed on the CRT1.
When displayed on 10, multifaceted information about bones can be provided in correlation with each other, and meaningful information can be provided in diagnosing bone diseases such as osteoporosis.

In the embodiment described above, X is applied over the entire calcaneus.
Although line irradiation and ultrasonic wave transmission / reception were performed, the following modified examples can also be used. That is, as shown in the display example in FIG. 12, X-ray irradiation is first performed to display only the bone mineral content map 304 as in the above-described embodiment, and then,
The operator uses the cursor 312 to specify the part for which the evaluation value is to be obtained. Then, ultrasonic waves are transmitted / received only to the specified portion, and the transmission / reception periods t1, t
2, t3 are measured, and based on these data, the thickness of the calcaneus, the speed of sound in the calcaneus, and the evaluation value are calculated in the same manner as in the above embodiment, and these are displayed as the point data display 320. Further, together with this, the evaluation frequency display 314 is performed.

According to such a modification, it is not necessary to transmit and receive ultrasonic waves over the entire range, and there is an effect that the time required for measurement can be extremely shortened. Of course, the apparatus may be provided with a mode change-over switch or the like, and the above-mentioned embodiment or this modified example may be changed over according to the operator's request.

FIG. 13 shows a second embodiment of thickness measurement. In this embodiment, an array transducer 326 in which a plurality of ultrasonic transducers are linearly arranged is arranged, and as shown in FIG. 13, the array transducer 326 is directed in a direction orthogonal to the beam directions of X-rays and ultrasonic waves. By transmitting and receiving a plurality of ultrasonic waves at regular intervals, the thickness of the calcaneus 200 can be easily obtained from the content of the received signal of each vibrating element.

In the above embodiment, the velocity of the ultrasonic waves in the water was calculated as a known velocity. However, in order to further improve the accuracy, as shown in FIG. A pair of ultrasonic transducers 328a, 328
It is preferable to provide b.

[0073]

As described above, according to the bone evaluation apparatus of the present invention, it is possible to obtain an evaluation value defined by the speed of ultrasonic waves in the bone and the bone density. There is an effect that it is possible to provide meaningful information regarding the bone health degree indicating such as. Therefore, there is an effect that the accuracy of diagnosing bone-related diseases can be further improved.

[Brief description of drawings]

FIG. 1 is a principle explanatory view showing a measurement principle of the present invention.

FIG. 2 is an external view showing the external appearance of a bone evaluation device according to the present invention.

FIG. 3 is a perspective view showing a main part of a measurement unit.

FIG. 4 is a block diagram showing a configuration of a measuring device.

FIG. 5 is a block diagram showing a configuration of a control device.

FIG. 6 is a timing chart showing the timing of each signal in ultrasonic measurement.

FIG. 7 is a principle explanatory view showing a measurement principle of bone thickness.

FIG. 8 is a timing chart showing the timing of each signal in ultrasonic measurement.

FIG. 9 is a conceptual diagram showing irradiation areas of X-rays and ultrasonic waves.

FIG. 10 is an explanatory diagram showing a display example.

FIG. 11 is a standard characteristic diagram of evaluation values.

FIG. 12 is an explanatory diagram showing another display example.

FIG. 13 is an explanatory diagram showing a second embodiment of bone thickness measurement.

FIG. 14 is an explanatory diagram showing measurement of sound velocity in water.

Claims (3)

[Claims] 1. A velocity measuring means for measuring an ultrasonic velocity in a bone by transmitting and receiving ultrasonic waves to and from a bone evaluation site of a subject, and irradiating the bone evaluation site with X-rays to determine bone density. A bone evaluation device comprising: a bone density measuring unit for measuring; and a bone evaluation value calculating unit for calculating an evaluation value defined by the ultrasonic velocity and the bone density. 2. The bone evaluation device according to claim 1, wherein the evaluation value is defined based on a result of multiplying the square of the ultrasonic velocity by the bone density. 3. The bone evaluation device according to claim 2, wherein the speed measuring unit includes an ultrasonic transducer that transmits and receives ultrasonic waves to and from a bone evaluation site, and an ultrasonic wave reception from the ultrasonic transducer. A thickness calculator for calculating the bone thickness in the direction along the beam direction of the X-ray based on the signal, and a speed calculator for calculating the ultrasonic velocity by dividing the ultrasonic wave propagation time in the bone by the thickness. The bone density measuring means includes: an X-ray generator that irradiates a bone evaluation site with X-rays; an X-ray detector that detects transmitted X-rays that have passed through the bone evaluation site; and an X-ray detector. The bone evaluation device, comprising: a density calculator that calculates a bone density based on an X-ray detection signal from the bone and the thickness of the bone.