JP3472376B2 - Ultrasonic bone evaluation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic bone evaluation apparatus for evaluating and diagnosing bones using ultrasonic waves.

[0002]

2. Description of the Related Art The number of people with bone diseases such as osteoporosis and osteomalacia is increasing along with the rapid increase in the aging population, and a method for diagnosis and prevention thereof is required.

As a device for evaluating and diagnosing bones, there has conventionally been a device for measuring bone mineral content using X-rays. In recent years, however, in addition to this, ultrasonic waves are transmitted to the living body to evaluate and evaluate bone tissue. An ultrasonic bone evaluation device for diagnosis has been proposed. As such a bone evaluation device, for example, US Pat. No. 3,847,1 is used.
There is a device proposed in No. 41. This device is a device for evaluating a calcaneus of a person, and an ultrasonic wave is transmitted to the heel to obtain a sound velocity of the ultrasonic wave that penetrates the calcaneus, and this sound velocity is used as an evaluation value of the calcaneus.

[0004]

The evaluation values obtained by these conventional methods are so-called macroscopic values such as the speed of sound in the bone and the amount of bone mineral.

[0005] In general, bone is composed of cortical bone that covers the outside and cancellous bone inside the cortical bone.
As shown in FIG. 3, a hard trabecular bone 1 that relatively absorbs elastic waves
10 and a bone marrow 120 which is present between the trabecular bone 110 and which is soft and has relatively good transmission of elastic waves.
When the amount of bone decreases due to aging or the like, the trabecular bone 110 becomes thin or disappears, and thus it is considered that the distance between the trabecular bones 110 becomes large. The microscopic structure of bone cannot be directly known from the speed of sound and the amount of bone mineral in the bone.

In response to such a situation, in recent years, there has been a demand for an apparatus capable of directly evaluating the microscopic structure of bone in order to comprehensively evaluate the bone.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a new type of ultrasonic bone evaluation apparatus capable of obtaining an evaluation value relating to the microscopic structure of bone. .

[0008]

In order to achieve the above-mentioned object, an ultrasonic bone evaluation apparatus according to the present invention is provided with a transmitting means for transmitting an ultrasonic wave to a subject, and a transmitting means for transmitting the ultrasound. The receiving means for receiving the ultrasonic wave, the frequency analyzing means for frequency-analyzing the received signal to obtain the received signal spectrum, and the inside of the subject based on the periodicity of the peak in the obtained received signal spectrum. And an evaluation value calculation means for calculating an evaluation value regarding the bone.

Further, the ultrasonic bone evaluation apparatus according to the present invention is
The frequency analysis means obtains the received signal spectrum by performing a Fourier transform on the received signal, and the evaluation value calculation means further performs a Fourier transform on the received signal spectrum and appears in a secondary spectrum obtained as a result. The evaluation value is obtained based on the position of the peak.

[0010]

First, the principle of the present invention will be described.

When an ultrasonic wave containing many frequency components such as a pulse wave is irradiated to a subject including cancellous bone as shown in FIG. 3 and a transmitted ultrasonic wave is received, the received signal obtained is The spectrum is as shown in FIG. As can be seen from FIG. 4, periodic peaks shown by R in the figure are observed in the spectrum of the received signal.

Such periodicity of the spectrum is considered to reflect the microscopic structure of cancellous bone. That is,
The cancellous bone acts as a kind of filter for ultrasonic waves, and the effect of this filter reflects the microscopic structure of the cancellous bone, particularly the distance between trabecular bones. According to the ultrasonic wave propagation characteristics of trabecular bone and bone marrow, ultrasonic waves with a wavelength matching the trabecular space are more likely to pass through.Therefore, in the spectrum of the received signal, the intensity of the frequency component corresponding to the wavelength that easily passes through the cancellous bone. Is higher. Therefore, when the trabecular space in the cancellous bone is narrow, components with a relatively short wavelength, that is, relatively high frequencies, are well transmitted, so that the spectrum of the received signal contains harmonics with a high frequency as the fundamental frequency. The components appear strongly and they form periodic peaks. Therefore, when the trabecular bone is dense, the period of the peak of the spectrum of the received signal becomes large. On the other hand, when the trabecular spacing of the cancellous bone becomes large, the wavelength of the ultrasonic waves that are often transmitted becomes large (that is, the frequency becomes small), so the period of the peak appearing in the received signal spectrum becomes small.

Therefore, the present invention pays attention to the relationship between the periodicity of the received signal spectrum and the microscopic structure of the bone, obtains the periodicity of peak repetition in the received signal spectrum, and based on this, An evaluation value regarding the microscopic structure of is calculated.

That is, according to the structure of the present invention, the ultrasonic wave radiated from the transmitting means is transmitted through the bone and detected by the receiving means. The received signal at that time is analyzed by the frequency analysis means to obtain the spectrum of the received signal. The evaluation value calculation means detects the periodicity of the peak of the received signal spectrum, and calculates the bone evaluation value based on this periodicity.

More specifically, the evaluation value calculation means further performs Fourier transform on the received signal spectrum obtained by Fourier transforming the received signal to obtain a secondary spectrum. If the received signal spectrum has periodicity, a peak corresponding to the periodicity appears in the secondary spectrum. Therefore, the bone evaluation value is determined based on the position where the peak appears in the secondary spectrum.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ultrasonic bone evaluation device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an ultrasonic bone evaluation apparatus according to the present invention. In the figure, a pair of transducers 10a and 10b facing each other is fixed to a scanning unit (not shown). When inspecting a subject, the subject (for example, the heel) is placed between the transducers 10a and 10b.
100 is arranged to transmit / receive ultrasonic waves. At this time,
By driving the entire scanning unit through a scanning control unit (not shown), the pair of transducers 10a and 10b can sequentially scan the subject 100.

The vibrators 10a and 10b are connected to the transmission / reception units 12a and 12b, respectively. The transmission / reception units 12a and 12b are respectively provided with the vibrators 10a and 10b.
To the oscillator 10a,
The received signal from 10b is taken in. In this embodiment, both of the vibrators 10a and 10b are for both transmission and reception, and can be used properly. It should be noted that, in the present embodiment, an impulse-shaped ultrasonic pulse including many frequency components is transmitted from the transmitting-side transducer.

The transmission / reception units 12a and 12b generate transmission pulses and take in received signals under the control of the measurement controller 14. In addition, the transmission / reception units 12a, 1
2b is connected to the A / D converter 16 and is connected to the transducer 10a or 10 by the transmission / reception unit 12a or 12b.
The received signal fetched from b is digitized by the A / D converter 16 and then input to the arithmetic processing unit 18 via the measurement control unit 14.

FIG. 2 is a functional block diagram of the arithmetic processing unit 18. As shown in the figure, the arithmetic processing unit 18 includes a first Fourier transform unit 20, a second Fourier transform unit 22, and an evaluation value calculation unit 24. Have

The received signal digitized by the A / D converter 16 is first input to the first Fourier transform section 20. The first Fourier transform unit 20 obtains the spectrum of the received signal by Fourier transforming the received signal. The obtained received signal spectrum data is input to the second Fourier transform unit 22. The second Fourier transform unit 22
Fourier transform is further applied to the data of the received signal spectrum. That is, the second Fourier transform unit 22 views the received signal spectrum as a function of frequency and further frequency-analyzes the spectrum of the received signal itself. When there are periodic peaks in the received signal spectrum, the periodicity is detected by frequency analysis of the received signal spectrum itself.

FIG. 5 shows an example of a spectrum obtained by Fourier-transforming the received signal spectrum having the periodic peaks shown in FIG. In FIG. 5, the vertical axis represents intensity and the horizontal axis represents the frequency of the repetitive component appearing in the received signal spectrum. Hereinafter, the result of Fourier transform of the received signal spectrum will be referred to as a secondary spectrum.

As shown in FIG. 5, a characteristic peak A appears in the secondary spectrum of the received signal. This peak A is
It is considered that this is due to the repetition of peaks in the received signal spectrum. Therefore, the periodicity of the received signal spectrum can be detected from the peak of the secondary spectrum.

Therefore, in this embodiment, the evaluation value calculation unit 24
Receives the data of the secondary spectrum obtained by the second Fourier transform unit 22, detects the position T of the peak in the secondary spectrum, and outputs this as an evaluation value for bone. A large evaluation value indicates that the peak repetition frequency in the received signal spectrum is large, that is, the peak repetition period in the received signal spectrum is small, which indicates that the trabecular spacing is coarse. . On the contrary, a small evaluation value indicates that the trabecular spaces are close.

As described above, according to the present embodiment, by further frequency-analyzing the received signal spectrum, an evaluation value regarding the periodicity (that is, the interval between peaks) of the repetitive components included in the received signal spectrum is obtained. be able to. Since the peak spacing of the received signal spectrum reflects the trabecular spacing, the evaluation value is an index value for evaluating the trabecular spacing, which is one feature amount in the microscopic structure of bone.

In this embodiment, attention was paid to the repetition of peaks of the received signal spectrum, but this repetition of peaks does not appear unless the frequency band is considerably higher than 1 MHz. However, since the living body including bone itself has low transparency to high-frequency components, the level of this repeated portion is the received signal level of the relatively low-frequency component with high transparency (main lobe M of the spectrum in FIG. 4). It will be much lower than. Therefore, the repeated portion of the peak is easily affected by the noise of the circuit itself. Therefore, in the present embodiment, the ultrasonic pulse is transmitted to the subject many times, the received signal data is sampled, and addition processing (or addition averaging processing) is performed on the received signal data. Reduce the impact.

Further, since the peak repetition of the received signal spectrum appears in a frequency band much higher than the main lobe, data near the main lobe is basically unnecessary for detecting the periodicity of the peak. Therefore, as a method of reducing the influence of noise, increase the transmission power of the ultrasonic pulse by assuming that the received signal level near the main lobe may be saturated, and increase the received power in the high frequency region where peak repetition appears. There is also a way to increase the level.

In the embodiment described above, the secondary spectrum is obtained by Fourier transforming the received signal spectrum in order to detect the periodicity of the peak of the received signal spectrum. However, the present invention is not limited to this. It is also possible to detect peaks from the received signal spectrum itself, find the interval between the peaks, and use the peak interval as an evaluation value.

[0029]

As described above, according to the present invention,
By detecting the repeating periodicity of the peaks appearing in the received signal spectrum, it is possible to obtain an evaluation value regarding the trabecular spacing, which is one of the feature quantities indicating the microscopic structure of bone.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an ultrasonic bone evaluation apparatus according to the present invention.

FIG. 2 is a functional block diagram of an arithmetic processing unit of the ultrasonic bone evaluation apparatus according to the present invention.

FIG. 3 is a diagram for explaining the structure of cancellous bone.

FIG. 4 is a diagram showing a spectrum of a received signal when an ultrasonic wave transmitted through a bone is received.

FIG. 5 is a diagram showing a secondary spectrum obtained by further performing a Fourier transform on the received signal spectrum.

[Explanation of symbols]

10a, 10b vibrator, 12a, 12b transmitting / receiving unit, 14 measurement control unit, 16 A / D converter, 18
Arithmetic processing unit, 20 first Fourier transform unit, 22 second Fourier transform unit, 24 evaluation value calculation unit.

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Claims (2)

(57) [Claims] 1. A wave transmitting means for transmitting an ultrasonic wave to a subject, a wave receiving means for receiving an ultrasonic wave transmitted through the subject, and a received signal spectrum by frequency-analyzing the received signal. Ultrasonic bone evaluation, which comprises: a frequency analysis unit that calculates the evaluation value; and an evaluation value calculation unit that calculates an evaluation value of the bone in the subject based on the periodicity of peaks in the received signal spectrum that has been obtained. apparatus. 2. The ultrasonic bone evaluation device according to claim 1, wherein the frequency analysis unit obtains the received signal spectrum by performing a Fourier transform on the received signal, and the evaluation value calculation unit includes the evaluation value calculation unit. An ultrasonic bone evaluation apparatus, characterized in that the received signal spectrum is further subjected to Fourier transform, and the evaluation value is obtained based on the position of the peak appearing in the secondary spectrum obtained as a result.