JP6261536B2 - Joint sound measurement system - Google Patents

Description

  The present invention relates to a joint sound measurement system.

Conventionally, diagnosis of knee osteoarthritis (hereinafter, also referred to as OA) has been performed mainly using an X-ray image. OA is an inflammation caused by abrasion or deformation of articular cartilage due to wear.
However, since cartilage is not shown in the X-ray image, it is necessary to make a diagnosis by estimating the state of the cartilage from the distance between the bones, and there is a problem in diagnosis accuracy.
Furthermore, there are MRI (Nuclear Magnetic Resonance Imaging) diagnosis and diagnosis using an arthroscope as methods for highly accurate diagnosis. However, since a large apparatus is required and the burden on the patient is large, early diagnosis and There was a problem that it was difficult to use for engraftment diagnosis.

On the other hand, measurement by joint sound (VAG (Vibroarthrography)) has been proposed as a diagnostic technique for OA.
VAG is caused by bending and stretching exercises, adding to the chondrocytes with their own weight as a load, and rubbing the chondrocytes existing at the ends of the femur, tibia and patella in the knee organ Non-invasive evaluation of articular cartilage condition by detecting joint sound as a vibration signal using an acceleration sensor or microphone installed outside the body, and the signal intensity of a specific frequency component increases or decreases depending on the presence or absence of OA disease It is a diagnostic method. In the present invention, the vibration sensor is a general term for sensors that detect vibration, such as an acceleration sensor, an acoustic sensor, and a microphone.

For example, Patent Document 1 discloses a biological acoustic sensor attached on the skin near the joint of the examinee, an angle sensor that detects a bending / extension angle near the joint, and a motion acceleration associated with the flexion / extension of the joint of the examinee. A diagnostic system is described that includes a weight meter to detect, an acoustic sensor for a living body, an angle sensor, and a diagnostic device that diagnoses arthropathy based on the detection result of the weight meter.
Further, this Patent Document 1 describes performing diagnosis based on the characteristics of frequency spectrum characteristics by performing signal processing such as frequency analysis such as fast Fourier transform (FFT) on the detection signal of the bioacoustic sensor. ing.

  In Patent Document 2, an accelerometer attached to one side of the joint and an accelerometer attached to the other side of the joint and a timing difference between vibrations generated by the two accelerometers are detected. The joint shock buffering tissue deterioration state is evaluated by a difference in timing of vibration generated by the two accelerometers when a force is applied to one side in a state where both side portions of the joint are in a linear relationship. It is described.

In such diagnosis of OA by VAG, in order to reduce the possibility of misdiagnosis and perform more accurate diagnosis, it is necessary to acquire a signal with few artifacts due to various noises.
In general, when removing a noise component from an acoustic signal, it is conceivable to perform software signal processing such as using a filter.
Non-Patent Document 1 describes that FFT is performed on data corresponding to a range of 25 ° to 75 ° of data from an acoustic sensor in order to suppress the influence of noise.

WO2011 / 096419 JP 2012-183294 A

6th Int'l Conf. Generic Evolutionary Computing, 2012 (T.F. Lee et al.)

However, in the case of the diagnosis by VAG, the vibration signal is measured while attaching and accelerating the acceleration sensor, which is a vibration sensor, on the surface of the subject (on the skin). Noise is generated due to fluctuations in the sensor cable, vibration due to friction between the skin and the sensor, vibration due to friction between the fixing band for fixing the acceleration sensor and the sensor, and the like.
It was found that noise caused by these was difficult to remove by software-like signal processing such as using a filter, or by dividing the range of the signal to be used by the bending angle. For this reason, it has been found that there is a problem that it is difficult to measure accurate numerical values of joint sounds due to the influence of artifacts caused by these noises, and it is difficult to perform more accurate diagnosis.

  An object of the present invention is to solve such problems of the prior art, and can perform a non-invasive diagnosis of knee osteoarthritis and measure a highly accurate vibration signal. It is possible to provide a joint sound measurement system capable of more accurate diagnosis.

As a result of intensive studies to achieve the above object, the present inventor has detected at least one of two or more vibration sensors and two or more vibration sensors that detect a vibration associated with the bending and stretching motion of the inspection object and output a vibration signal. A first substance layer having an acoustic impedance close to that of a living body, disposed on the surface of the first vibration sensor to be inspected, and two or more vibration sensors other than the first vibration sensor A vibration transmission suppressing layer that is disposed on a surface on the inspection object side of the second vibration sensor that is at least one of the above, and suppresses the vibration accompanying the bending and stretching movements from being transmitted to the second vibration sensor. It has been found that the above problems can be solved.
That is, the present invention provides the following (1) to (12).

(1) two or more vibration sensors that detect vibrations associated with the bending and stretching movements of the inspection object and output vibration signals;
A first material layer having an acoustic impedance equal to or higher than that of a living body, disposed on a surface of the first vibration sensor that is at least one of the two or more vibration sensors, on the inspection object side;
Of the two or more vibration sensors, the second vibration sensor, which is at least one other than the first vibration sensor, is arranged on the surface on the inspection object side, and vibrations accompanying bending and stretching motions are transmitted to the second vibration sensor. A joint sound measurement system having a vibration transmission suppressing layer that suppresses vibration.
(2) The joint sound measurement system according to (1), wherein the vibration transmission suppression layer is a layer made of a material having an acoustic impedance lower than that of a living body.
(3) The joint sound measurement system according to (1), wherein the vibration transmission suppression layer is a layer made of a material having a compression modulus of 270 kPa or less.
(4) It has a difference signal calculation unit that calculates a difference signal between the first vibration signal output from the first vibration sensor and the second vibration signal output from the second vibration sensor. The joint sound measurement system according to any one of (3).
(5) The joint sound measurement according to any one of (1) to (4), wherein one of the first vibration sensors and one of the second vibration sensors are attached to the inspection object at positions close to each other. system.
(6) The joint sound measurement system according to (5), wherein the distance between the first vibration sensor and the second vibration sensor when attached to the inspection object is 20 mm or less.
(7) The joint sound measurement system according to any one of (1) to (6), including two vibration sensors, one first vibration sensor and one second vibration sensor.
(8) The joint sound measurement system according to any one of (1) to (7), wherein the acoustic impedance of the first material layer is 1.35 × 10 ^{6 to} 47 × 10 ⁶ kg / (m ² · sec). .
(9) The joint sound measurement system according to any one of (1) to (8), wherein the acoustic impedance of the second material layer is less than 1.35 × 10 ⁶ kg / (m ² · sec).
(10) The joint sound measurement system according to any one of (4) to (9), further including a frequency analysis unit that performs frequency analysis on the difference signal and outputs the analysis signal.
(11) The joint sound measurement system according to (10), wherein the frequency analysis unit performs fast Fourier transform.
(12) The joint sound measurement system according to any one of (1) to (11), wherein the vibration sensor is a piezoelectric acceleration sensor.

  According to the present invention, there is provided a joint sound measurement system capable of non-invasively diagnosing knee osteoarthritis, measuring a highly accurate vibration signal, and enabling more accurate diagnosis. can do.

It is a block diagram which shows notionally an example of a structure of the joint sound measuring system of this invention. FIG. 2A is a side view schematically showing a state where the acceleration sensor is attached, and FIG. 2B is a cross-sectional view schematically showing a state where the acceleration sensor is attached. FIG. 3A is a graph conceptually showing the signal detected by the first acceleration sensor, and FIG. 3B is a graph conceptually showing the signal detected by the second acceleration sensor. is there.

Hereinafter, a joint sound measurement system of the present invention will be described in detail based on a preferred first embodiment shown in the accompanying drawings.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

FIG. 1 conceptually shows an example of a joint sound measurement system of the present invention by a block diagram, and FIG. 2A shows a schematic diagram of a state in which an acceleration sensor of the joint sound measurement system is attached to an inspection object. .
The joint sound measurement system 10 shown in FIGS. 1 and 2 includes a first acceleration sensor 12a, a first material layer 14 provided on a surface of the first acceleration sensor 12a on the inspection object side, and a second acceleration sensor. 12b, a vibration transmission suppression layer 15 provided on the surface of the second acceleration sensor 12b on the inspection object side, a difference signal calculation unit 16 connected to the first acceleration sensor 12a and the second acceleration sensor 12b, The frequency analysis unit 18, the determination unit 20, the display unit 22, the control unit 24, and the operation unit 26 are included.
In the illustrated example, the difference signal calculation unit 16, the frequency analysis unit 18, the determination unit 20, the display unit 22, the control unit 24, and the operation unit 26 constitute the measurement apparatus main body 13.
The acceleration sensors 12a to 12d are a kind of vibration sensor in the present invention.

As shown in FIG. 2A, in the joint sound measurement system 10, the first acceleration sensor 12a and the second acceleration sensor 12b are attached to the skin near the knee joint of the test object (subject). Yes, it is connected to the measuring apparatus body 13 by cable Cb or wirelessly. In the illustrated example, the first acceleration sensor 12a and the second acceleration sensor 12b are each fixed to the subject To by the fixing band Bd.
Here, in the joint sound measurement system 10 of the present invention, the first acceleration sensor 12a has the first material layer 14 on the surface on the subject To side, and the surface on the subject To side of the second acceleration sensor 12b. Since the vibration transmission suppression layer 15 is provided on the first acceleration sensor 12a, the first material layer 14 is disposed between the first acceleration sensor 12a and the subject To, and vibration transmission suppression is performed between the second acceleration sensor 12b and the subject To. Layer 15 is installed.
The first acceleration sensor 12a and the second acceleration sensor 12b have basically the same configuration except that the type of layers installed between the subject and the subject is different. When it is not necessary to distinguish the acceleration sensor 12a and the second acceleration sensor 12b, the acceleration sensor 12 will be collectively described.

The acceleration sensor 12 is a sensor that detects a joint sound accompanying the bending and stretching motion of the subject as vibration and outputs a vibration signal.
As the acceleration sensor 12, various known acceleration sensors such as a piezoelectric type, a capacitance type, a servo type, a bubble type, a heat detection method, and a mechanical displacement measurement method can be used. Among these, the piezoelectric acceleration sensor is preferable in terms of a range of acceleration components that can be detected and a frequency range that can be detected.

The attachment position of the first acceleration sensor 12a is not particularly limited, and may be determined as appropriate according to the number of acceleration sensors, the method of bending and stretching the subject, and the like.
As an example, the first acceleration sensor 12a is preferably attached to the position of the lateral condyle of the tibia, the position of the medial condyle of the tibia, the position of the patella, the position of the tibia, and the like.

The mounting position of the second acceleration sensor 12b is not particularly limited, but the noise component detected by the first acceleration sensor 12a and the noise component detected by the second acceleration sensor 12b can be more approximated. In view of the above, it is preferable that the first acceleration sensor 12a is attached in the vicinity.
Specifically, the second acceleration sensor 12b is preferably attached at a position where the distance from the first acceleration sensor 12a is within 20 mm, and more preferably within 5 mm.

In the illustrated example, the configuration includes two acceleration sensors. However, the configuration is not limited to this, and may be three or more.
When three or more acceleration sensors are provided, at least one is the first acceleration sensor 12a, and at least one other than the first acceleration sensor 12a may be the second acceleration sensor 12b. In that case, it is preferable that the number of the 1st acceleration sensors 12a and the number of the 2nd acceleration sensors 12b are the same.
For example, in the case of having four first acceleration sensors 12a, it is preferable to have four second acceleration sensors 12b respectively corresponding to the four first acceleration sensors 12a.
By having the second acceleration sensor 12b corresponding to each of the first acceleration sensors 12a, the difference signal calculation unit 16 described later and the vibration signal output from the first acceleration sensor 12a and the second acceleration sensor 12b. It is preferable in that the difference signal with the vibration signal output from can be calculated, and a highly accurate vibration signal can be obtained.

  Each of the acceleration sensors 12 supplies the detected vibration signal to the measurement apparatus main body 13 via a signal reception unit (not shown) of the measurement apparatus main body 13 and supplies it to the difference signal calculation unit 16. The signal reception unit may include an AD conversion unit that AD converts the vibration signal output from the acceleration sensor 12 and an amplification unit that amplifies the signal. Further, a signal processing unit that performs various known signal processing may be provided between the signal receiving unit and the difference signal calculating unit 16.

The first material layer 14 is a layer provided on the surface of the first acceleration sensor 12a on the subject To side.
That is, as shown in FIG. 2A, the first material layer 14 is placed between the first acceleration sensor 12a and the subject To when the first acceleration sensor 12a is attached to the subject To. Is done.

The first material layer 14 is a layer for suitably propagating the vibration in the subject To to the first acceleration sensor 12a. Therefore, the first substance layer 14 is a layer made of a material having an acoustic impedance value equal to or higher than the acoustic impedance of the living body, and preferably made of a material that is equal to or higher than the acoustic impedance of the living body and equal to or lower than the acoustic impedance of the metal.
Specifically, the acoustic impedance of the first material layer 14 is preferably in the range of 1.35 × 10 ^{6 to} 47 × 10 ⁶ kg / (m ² · sec), and 1.36 × 10 ^{6 to} 47 × 10 ^6. The range of kg / (m ² · sec) is more preferable, and the range of 1.37 × 10 ⁶ to 15 × 10 ⁶ kg / (m ² · sec) is particularly preferable.
As a material of the first substance layer 14 having such an acoustic impedance, for example, a polymer material such as urethane gel is cross-linked to form a three-dimensional network structure, and a solvent such as water is formed therein. A gel that has absorbed and swollen can be used. Specifically, as such a gel, an ultrasonic gel used in an ultrasonic examination such as a urethane gel such as Sonagel (manufactured by Takiron), Gel Fine (Osaki Medical Co., Ltd.), Cavigel (Makeup Co., Ltd.), etc. Can be used. Alternatively, PVDF (polyvinylidene fluoride) or the like can be used as the material of the first substance layer 14.

  The thickness of the first material layer 14 is preferably 1 mm to 20 mm, and more preferably 1 mm to 10 mm, from the viewpoint of suitably propagating vibrations from within the subject To to the first acceleration sensor 12a.

  When the first acceleration sensor 12a is fixed in direct contact with the skin of the subject To, an air layer is formed between the first acceleration sensor 12a and the skin, and vibration occurs at the interface with the air. Is reflected and returned to the body, there is a possibility that vibration from within the subject To may not be sufficiently transmitted to the first acceleration sensor 12a. On the other hand, by providing the first material layer 14 made of a material having an acoustic impedance value that is greater than or equal to the acoustic impedance of the living body and less than or equal to the acoustic impedance of the metal between the first acceleration sensor 12a and the subject To, It is possible to suppress the formation of an air layer between the first acceleration sensor 12a and the skin, thereby sufficiently transmitting vibration in the subject To to the first acceleration sensor 12a.

The vibration transmission suppressing layer 15 is a layer provided on the surface of the second acceleration sensor 12b on the subject To side.
That is, as shown in FIG. 2A, the vibration transmission suppressing layer 15 is installed between the second acceleration sensor 12b and the subject To when the second acceleration sensor 12b is attached to the subject To. Is done.

The vibration transmission suppression layer 15 is a layer for suppressing the vibration from within the subject To from propagating to the second acceleration sensor 12b.
As the vibration transmission suppressing layer 15, a layer made of a material having a value far from both the acoustic impedance of the living body and the acoustic impedance of the second acceleration sensor 12 b, that is, a value less than the acoustic impedance of the living body is used. Can do. By using a layer made of a material having an acoustic impedance lower than that of the living body as the vibration transmission suppressing layer 15, vibration transmitted from within the subject To can be interfaced between the vibration transmission suppressing layer 15 and the subject To. Alternatively, the second acceleration is suppressed by reflecting the vibration at the interface between the vibration transmission suppressing layer 15 and the second acceleration sensor 12b to prevent the vibration from the subject To from being transmitted to the second acceleration sensor 12b. The sensor 12b is prevented from detecting vibration from within the subject To.

The acoustic impedance of the vibration transmission suppressing layer 15 made of a material having an acoustic impedance less than that of the living body is preferably less than 1.35 × 10 ⁶ kg / (m ² · sec), and 1.2 × 10 ⁶ kg / (m ² · sec) or less is preferable, and 1.1 ×× 10 ⁶ kg / (m ² · sec) or less is particularly preferable.

The material of the vibration transmission suppressing layer 15 having such an acoustic impedance is not particularly limited, and a silicone gel, an air layer, or the like can be used.
When an air layer is used as the vibration transmission suppressing layer 15, a spacer or the like is disposed between the second acceleration sensor 12 b and the skin of the subject To, and the second acceleration sensor 12 b and the skin are connected. What is necessary is just to set it as the structure fixed so that it may not contact directly.

  Further, as the vibration transmission suppressing layer 15, a layer made of a material having a compression elastic modulus of 270 kPa or less can be used. By using a layer made of a material having a low compressive modulus as the vibration transmission suppressing layer 15, the vibration transmitted from within the subject To is absorbed, and the vibration is suppressed from being transmitted to the second acceleration sensor 12b. Thus, the second acceleration sensor 12b is prevented from detecting vibration.

In view of more suitably absorbing vibration, the compression elastic modulus of the vibration transmission suppressing layer 15 is preferably 270 kPa, and more preferably 160 kPa.
Examples of the material of the vibration transmission suppressing layer 15 having such a compression elastic modulus include silicone gel and filler-containing silicone gel.

  In addition, as a material of the vibration transmission suppression layer 15, a substance having an acoustic impedance less than the acoustic impedance of the living body and having a compressive elastic modulus of 270 kPa or less may be used.

  In addition, the thickness of the vibration transmission suppressing layer 15 is 1 mm to 40 mm from the viewpoint of preferably suppressing vibrations from within the subject To from propagating to the second acceleration sensor 12b and not generating extra noise. Is preferable and 1 mm to 10 mm is more preferable.

Here, the first acceleration sensor 12a having the first material layer 14 between the subject To and the second acceleration sensor 12b having the vibration transmission suppressing layer 15 between the subject To and the subject To are detected. The vibration signal will be described with reference to FIG.
FIG. 2B is a cross-sectional view schematically showing a state where the acceleration sensor is attached to the subject.
First, the case of the first acceleration sensor 12a in which the first material layer 14 having an acoustic impedance close to that of the living body is provided between the subject To and the subject To will be described. In the subject To, the joint sound generated by rubbing the knee cartilage with bending and stretching motion propagates through the subject To and reaches the first material layer 14. At this time, since the acoustic impedance value of the first material layer 14 is between the acoustic impedance of the subject To and the acoustic impedance of the first acceleration sensor 12a, the joint sound generated in the subject To The vibration is absorbed by the first material layer 14 without being reflected at the interface between To and the first material layer 14 or reflected at the interface between the subject To and the first acceleration sensor 12a. Therefore, the first material layer 14 is propagated and reaches the first acceleration sensor 12a.
Therefore, the first acceleration sensor 12a can detect the joint sound generated in the subject To.
Here, as described above, the acceleration signal is attached to the surface of the subject and the vibration signal is measured while performing bending and stretching movements. Noise due to vibration due to vibration, vibration due to friction between the fixing band for fixing the acceleration sensor and the sensor, and the like are generated. Therefore, the first acceleration sensor 12a detects the joint sound including these noises and outputs it as a vibration signal V1 as shown in the graph of FIG.

On the other hand, the case of the second acceleration sensor 12b in which the vibration transmission suppressing layer 15 is provided between the subject To and the subject To will be described.
The joint sound generated by rubbing the cartilages of the knee in the subject To propagates through the subject To and reaches the vibration transmission suppressing layer 15. However, when the acoustic impedance of the vibration transmission suppression layer 15 is less than the acoustic impedance of the subject To, the joint sound is generated at the interface between the subject To and the vibration transmission suppression layer 15 or between the vibration transmission suppression layer 15 and the second. Is reflected at the interface with the acceleration sensor 12b. Alternatively, when the vibration transmission suppression layer 15 is a material having a low compression modulus, the vibration transmission suppression layer 15 is absorbed in the vibration transmission suppression layer 15. Therefore, since the joint sound does not reach the second acceleration sensor 12b, the second acceleration sensor 12b does not detect the joint sound generated in the subject To.
Here, as described above, the acceleration signal is attached to the surface of the subject and the vibration signal is measured while performing bending and stretching movements. Noise due to vibration due to vibration, vibration due to friction between the fixing band for fixing the acceleration sensor and the sensor, and the like are generated. Since these noises do not propagate from the subject To to the second acceleration sensor 12b via the vibration transmission suppression layer 15, the second acceleration sensor 12b detects these noises, and FIG. As shown in the graph conceptually shown in FIG. 3B, the vibration signal V2 resulting from only the noise component is output.

  The difference signal calculation unit 16 of the measurement apparatus body 13 is a part that calculates a difference between the vibration signal V1 supplied from the first acceleration sensor 12a and the vibration signal V2 supplied from the second acceleration sensor 12b. The difference signal calculation unit 16 calculates a difference signal V3 that is a difference between the vibration signal V1 and the vibration signal V2.

As described above, the vibration signal V1 output from the first acceleration sensor 12a is not only the component caused by the joint sound generated by rubbing the cartilage of the knees in accordance with the bending / extending movement, but also the acceleration sensor itself accompanying the bending / extending movement. Is a signal including noise components due to fluctuations in the sensor cable, vibration due to friction between the skin and the sensor, vibration due to friction between the fixing band for fixing the acceleration sensor and the sensor, and the like.
On the other hand, the vibration signal V2 output from the second acceleration sensor 12b is a signal including only noise components without detecting joint sounds.
Therefore, the difference signal calculation unit 16 takes the difference between the vibration signal V1 including the noise component and the vibration signal V1 including the noise component and the vibration signal V2 including only the noise component, thereby removing the noise component. The differential signal V3 including only the component to be obtained can be obtained.

As described above, in the diagnosis by VAG (Vibroarthrography), an acceleration sensor is attached to the surface of the subject (on the skin) and the vibration signal is measured while performing bending and stretching movements. There is a problem that noise is generated due to fluctuations in the vibration, vibration due to friction between the skin and the sensor, vibration due to friction between the fixing band for fixing the acceleration sensor and the sensor, and the like.
It was found that noise caused by these was difficult to remove by software-like signal processing such as using a filter, or by dividing the range of the signal to be used by the bending angle. For this reason, it has been found that there is a problem that it is difficult to measure accurate numerical values of joint sounds due to the influence of artifacts caused by these noises, and it is difficult to perform more accurate diagnosis.

  On the other hand, in the joint sound measurement system of the present invention, two acceleration sensors are used, and one acceleration sensor has a first substance having an acoustic impedance higher than that of a living body between the subject and the subject. The layer 14 is installed, and the other acceleration sensor is provided with a vibration transmission suppression layer 15 that suppresses transmission of vibration caused by joint sounds, and the difference between the vibration signals output from these acceleration sensors is determined. As a result, it is possible to obtain a differential signal with few artifacts including only the component caused by the joint sound from which the noise component is removed. By performing a diagnosis using this difference signal, a more accurate diagnosis can be performed.

  Further, in the diagnosis of OA by VAG, in order to rub the chondrocytes of the knee, exercises such as bending and stretching movements and swinging legs are necessary. Therefore, it is possible to estimate the noise components associated with these movements in advance and subtract a certain noise component to remove the noise components, but it is very difficult to perform the same movement every time. The accuracy cannot be increased. On the other hand, in the present invention, even if the same movement cannot be performed every time, the noise component is detected simultaneously with the measurement of the joint sound, so that a highly accurate signal can be obtained.

  In addition, when it has three or more acceleration sensors and has the some 1st acceleration sensor 12a and the some 2nd acceleration sensor 12b, the difference signal calculation part 16 is each 1st acceleration sensor 12a. And the second acceleration sensor 12b closest to each first acceleration sensor 12a as a set, and the difference between the vibration signal V1 and the vibration signal V2 may be obtained in each set.

Further, when the difference signal calculation unit 16 obtains the difference between the vibration signal V1 and the vibration signal V2, the difference signal calculation unit 16 may obtain the difference by weighting each vibration signal.
For example, weighting is performed according to the relationship between the attachment positions of the first acceleration sensor 12a and the second acceleration sensor 12b, the distance between the first acceleration sensor 12a and the second acceleration sensor 12b, and the like. May be requested.

  The difference signal calculation unit 16 supplies the obtained difference signal V3 to the frequency analysis unit 18.

  The frequency analysis unit 18 is a part that performs frequency analysis on the difference signal V3 supplied from the difference signal calculation unit 16 and outputs an analysis signal A.

The frequency analysis performed by the frequency analysis unit 18 is not particularly limited as long as it is a mathematical process for obtaining the frequency characteristics of the divided signals. Specifically, fast Fourier transform (FFT), wavelet transform, time-frequency method, statistical analysis method, etc. can be used.
In particular, frequency analysis by FFT is preferable from the viewpoint of low processing load and low calculation cost.

In the diagnosis of knee osteoarthritis (OA), the joint sound of an OA patient uses higher power in a predetermined frequency band (for example, a frequency band of 50 Hz to 100 Hz) than that of a healthy person. And make a diagnosis.
That is, a frequency analysis such as FFT is performed on the vibration signal of the knee joint sound to obtain an analysis signal A representing the relationship between the power value and the frequency, and the power in the frequency band of 50 Hz to 100 Hz of the analysis signal A is obtained. Diagnosis can be made by comparing the values with those of healthy individuals.

  Here, in the present invention, the frequency analysis is performed on the difference signal V3 from which the noise component is removed by taking the difference between the vibration signal V1 and the vibration signal V2. Therefore, analysis can be performed using accurate numerical values of joint sounds, and more accurate diagnosis is possible.

  In addition, when there are a plurality of sets of the first acceleration sensor 12a and the second acceleration sensor 12b, and the difference signal calculation unit calculates a plurality of difference signals, the frequency analysis unit 18 outputs a difference signal to each difference signal. On the other hand, an analysis signal may be obtained by performing frequency analysis.

  The frequency analysis unit 18 supplies the obtained analysis signal A to the determination unit 20.

The determination unit 20 is a part that determines whether or not the analysis signal A supplied from the frequency analysis unit 18 is OA.
Specifically, for example, the determination unit 20 compares the power value of a predetermined frequency band in the analysis signal A with the reference power value and exceeds the reference power value. If the analysis signal A is equal to or less than the reference power value, it is determined to be normal.

  Note that a plurality of sets of first acceleration sensors 12a and second acceleration sensors 12b are provided, the difference signal calculation unit 16 calculates a plurality of difference signals, and the frequency analysis unit 18 calculates a plurality of analysis signals. In such a case, the determination unit 20 may obtain the average value of the analysis signal, compare whether the average value of the analysis signal exceeds the reference power value, and perform the above determination. Alternatively, the above determination may be performed for each analysis signal, and a determination result having the largest determination result may be employed.

  Note that when two or more sets of acceleration sensors are used to obtain a plurality of difference signals, ideally, the same determination result can be obtained from all the difference signals. However, due to the influence of the mounting position of the acceleration sensor 12 and noise. The determination result may vary. On the other hand, by obtaining a plurality of differential signals using two or more sets of acceleration sensors, it is possible to reduce the influence of the attachment position of the acceleration sensor 12 and noise, etc., and to determine more accurately.

The determination unit 20 may perform determination based on a plurality of different reference power values to determine the degree of OA symptoms.
For example, based on three reference power values, if the power value of the predetermined frequency band of the analysis signal A is higher than the highest reference power value, it is determined to be severe and less than the highest reference power value If it is higher than the second highest reference power value, it is judged as medium, and if it is lower than the second highest reference power value and higher than the third highest reference power value, it is judged as mild. If it is equal to or lower than the third highest reference power value, it may be determined as normal.
The determination unit 20 supplies the determination result to the display unit 22.

  The display unit 22 includes, for example, a display device such as an LCD, and displays the determination result supplied from the determination unit 20 under the control of the control unit 24.

The control unit 24 is a part that controls each unit of the joint sound measurement system 10 based on a command input from the operation unit 26 by the operator.
In addition, the control unit 24 supplies various types of information input by the operator using the operation unit 26 to necessary parts. For example, when the operation unit 26 is input with information on the start and end of measurement, information on weighting used in the difference signal calculation unit 16, information on a reference power value used in the determination unit 20, etc. Such information is supplied to each part of the joint sound measurement system as necessary.

The operation unit 26 is for an operator to perform an input operation, and can be formed from a keyboard, a mouse, a trackball, a touch panel, or the like.
Further, the operation unit 26 has an input function for the operator to input various types of information as necessary. For example, the operation unit 26 has an input function for inputting measurement start and end information, weighting information used by the difference signal calculation unit 16, reference power value information used by the determination unit 20, and the like. ing.

  In the joint sound measurement system, the difference signal calculation unit 16, the frequency analysis unit 18, the determination unit 20, the control unit 24, and the like are based on a CPU (Central Processing Unit) and an operation program for causing the CPU to perform various processes. For example, a PC (personal computer) may be used. However, in the present invention, these parts may be constituted by digital circuits.

Here, in the case of having a plurality of sets of the first acceleration sensor 12a and the second acceleration sensor 12b, the configuration may be such that the difference signal is obtained from the vibration signal output by the acceleration sensor in all the sets. In one set, the difference signal may be obtained from the vibration signal output from the acceleration sensor.
In addition, in the case of having a plurality of sets of the first acceleration sensor 12a and the second acceleration sensor 12b, the configuration may be such that frequency analysis is performed on all the differential signals obtained from each set of acceleration sensors. The frequency analysis may be performed on the difference signal obtained from at least one set of acceleration sensors.

Moreover, in the example shown in FIG. 1, it was set as the structure which displays the determination result of the determination part 20 on the display part 22, but it is not limited to this, The determination result of the determination part 20 is notified by an audio | voice etc. Also good.
In the example shown in FIG. 1, the determination unit 20 determines whether or not it is OA based on the analysis signal from the frequency analysis unit 18, and the determination result is displayed on the display unit 22. However, the present invention is not limited to this, and a graph of the analysis signal by the frequency analysis unit 18 may be displayed on the display unit 22. That is, only by displaying the analysis signal graph on the display unit 22, a doctor or the like may make a diagnosis by looking at the analysis signal graph.

In addition, the joint sound measurement system 10 of the present invention may include an angle sensor that detects an angle of bending and stretching of the knee (a bending and stretching angle) accompanying a bending and stretching motion of the subject.
The angle sensor is not particularly limited, and various known sensors such as an inclinometer that detects an inclination angle with respect to the horizontal direction, a rotation angle sensor such as a rotary encoder, a potentiometer, and a MEMS (Micro Electro Mechanical Systems) capacitance type angle sensor system. The angle sensor can be used. Among these, the MEMS capacitive type angle sensor is suitable in terms of angular resolution and response speed.

  In addition, the detection of the bending / extension angle by the angle sensor may be performed by detecting a state in which the knee is extended as 0 ° and a state in which the knee is bent by 90 ° as 90 °, or a state in which the knee is extended as 90 °, A state where the knee is bent by 90 ° may be detected as 0 °.

  In the example shown in FIG. 1, an acceleration sensor is used as the vibration sensor, but the present invention is not limited to this, and an electronic stethoscope, a device such as a microphone, or the like may be used.

  As described above, the joint sound measurement system of the present invention has been described in detail. However, the present invention is not limited to the above-described example, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

  The features of the present invention will be described more specifically with reference to the following examples.

[Example 1]
The first acceleration sensor 12a (MA3-04AD manufactured by Wako Tech Co., Ltd.) was fixed on the lateral condyle side of the subject's knee using the fixation band Bd.
A first material layer 14 made of urethane gel (Sonagel N0511 manufactured by Takiron Co., Ltd.) was placed between the first acceleration sensor 12a and the subject. The acoustic impedance of sonagel is 1.4 × 10 ⁶ kg / (m ² · sec).

Further, the second acceleration sensor 12b (MA3-04AD manufactured by Wako Tech Co., Ltd.) was fixed at a position 10 mm from the first acceleration sensor 12a by using the fixing band Bd.
Between the second acceleration sensor 12b and the subject, a gel tape made of silicone gel (gel chip GC-7 manufactured by Taika Co., Ltd.) was installed as the vibration transmission suppressing layer 15. The acoustic impedance of this silicone gel is 1.1 × 10 ⁶ kg / (m ² · sec). The compression elastic modulus is 40 kPa.

With the accelerometer attached, the subject stands in a chair, rises in 1 second, rests for 3 seconds, and then sits down in 1 second, with two outputs from two accelerometers. A signal was detected.
The output signal from each acceleration sensor is taken into the PC via the A / D conversion board, and the RMS (root mean square) average value (X direction, Y) of the time domain acceleration data obtained through the acceleration sensor Direction, Z direction), that is, vibration signals V1 and V2.

Next, the difference signal calculation unit 16 calculates the difference between the vibration signal V1 and the vibration signal V2 to obtain the difference signal V3.
Next, in the frequency analysis unit, the obtained difference signal V3 was subjected to FFT processing to obtain an analysis signal A representing the relationship between the power value and the frequency. The average value of the power values at 50 Hz to 100 Hz of the analysis signal A was obtained as the average signal P.
The above measurement was performed 10 times, 10 average signals P were obtained, and the average value, standard deviation σ, and variation rate of the 10 average signals P were obtained.
The variation rate is a value (%) obtained by dividing the standard deviation σ by the average value.

[Example 2]
The average signal P was obtained in the same manner as in Example 1 except that the material of the first substance layer 14 was changed to a PVDF sheet (TOMOB No. 9000-PVDF manufactured by NICHIAS). The average value of 10 average signals P, The standard deviation σ and the variation rate were obtained.
The acoustic impedance of the PVDF sheet is 4 × 10 ⁶ kg / (m ² · sec).

[Example 3]
The average signal P is obtained in the same manner as in Example 1 except that the distance between the first acceleration sensor 12a and the second acceleration sensor 12b is changed to 7 mm, the average value of the 10 average signals P, the standard Deviation σ and variation rate were obtained.

[Example 4]
The average signal P is obtained in the same manner as in Example 1 except that the distance between the first acceleration sensor 12a and the second acceleration sensor 12b is changed to 5 mm, the average value of the 10 average signals P, the standard Deviation σ and variation rate were obtained.

[Example 5]
The average signal P is obtained in the same manner as in Example 1 except that the distance between the first acceleration sensor 12a and the second acceleration sensor 12b is changed to 1 mm, the average value of the ten average signals P, the standard Deviation σ and variation rate were obtained.

[Example 6]
The average signal P is obtained in the same manner as in Example 1 except that the distance between the first acceleration sensor 12a and the second acceleration sensor 12b is changed to 11 mm, the average value of the 10 average signals P, the standard Deviation σ and variation rate were obtained.

[Example 7]
The average signal P is obtained in the same manner as in Example 1 except that the material of the vibration transmission suppressing layer 15 is changed to a silicone gel chip GC-1 manufactured by Taica, and the average value of 10 average signals P, the standard deviation σ, and The rate of change was determined.
The acoustic impedance of the gel chip GC-1 is 1.0 × 10 ⁶ kg / (m ² · sec), and the compression elastic modulus is 30 kPa.

[Example 8]
The average signal P is obtained in the same manner as in Example 1 except that the material of the vibration transmission suppressing layer 15 is changed to a silicone gel chip GC-2 manufactured by Taika, and the average value of the 10 average signals P, the standard deviation σ, and The rate of change was determined.
The acoustic impedance of the gel chip GC-2 is 1.2 × 10 ⁶ kg / (m ² · sec), and the compression elastic modulus is 151 kPa.

[Reference Example 1]
Except for detecting the vibration signal by the second acceleration sensor 12b, the vibration signal is detected only by the first acceleration sensor, and the frequency analysis is performed without calculating the difference signal. Thus, the average signal P was obtained, and the average value, standard deviation σ, and variation rate of the 10 average signals P were obtained.
The results are shown in Table 1.

As shown in Table 1 above, Examples 1 to 7, which are examples of the present invention, have smaller standard deviation and variation rate of the average signal P than the reference example 1, and the same signal every time. It can be seen that is detected. That is, it can be seen that the noise component can be properly removed. Therefore, more accurate diagnosis is possible by performing diagnosis using such a signal from which noise components have been appropriately removed.
From the above, the effect of the present invention is clear.

DESCRIPTION OF SYMBOLS 10 Joint sound measuring system 12a 1st acceleration sensor 12b 2nd acceleration sensor 13 Measurement apparatus main body 14 1st substance layer 15 Vibration transmission suppression layer 16 Differential signal calculation part 18 Frequency analysis part 20 Determination part 22 Display part 24 Control part 26 Operation part

Claims (12)

Two or more vibration sensors for detecting vibration associated with the bending and stretching movement of the inspection object and outputting a vibration signal;
A first material layer having an acoustic impedance equal to or higher than that of a living body, disposed on a surface of the first vibration sensor, which is at least one of the two or more vibration sensors, on the inspection object side;
Of the two or more vibration sensors, the second vibration sensor, which is at least one other than the first vibration sensor, is disposed on a surface on the inspection object side, and vibrations associated with the bending and stretching movements are the second vibration sensors. A joint sound measurement system comprising: a vibration transmission suppression layer that suppresses transmission to a vibration sensor.   The joint sound measurement system according to claim 1, wherein the vibration transmission suppression layer is a layer made of a material having an acoustic impedance lower than that of a living body.   The joint sound measurement system according to claim 1, wherein the vibration transmission suppression layer is a layer made of a material having a compression elastic modulus of 270 kPa or less.   The differential signal calculation part which calculates the differential signal of the 1st vibration signal output from the said 1st vibration sensor, and the 2nd vibration signal output from the said 2nd vibration sensor. The joint sound measurement system according to any one of the above.   The joint sound measurement according to any one of claims 1 to 4, wherein one of the first vibration sensors and one of the second vibration sensors are attached to the inspection object at positions close to each other. system.   The joint sound measurement system according to claim 5, wherein a distance between the first vibration sensor and the second vibration sensor when attached to the inspection object is 20 mm or less.   The joint sound measurement system according to claim 1, comprising two vibration sensors, one of the first vibration sensors and one of the second vibration sensors. 8. The joint sound measurement system according to claim 1, wherein an acoustic impedance of the first material layer is 1.35 × 10 ^{6 to} 47 × 10 ⁶ kg / (m ² · sec). 9. The joint sound measurement system according to claim 1, wherein an acoustic impedance of the second material layer is less than 1.35 × 10 ⁶ kg / (m ² · sec).   The joint sound measurement system according to claim 4, further comprising a frequency analysis unit that performs frequency analysis on the difference signal and outputs an analysis signal.   The joint sound measurement system according to claim 10, wherein the frequency analysis unit performs fast Fourier transform.   The joint sound measurement system according to claim 1, wherein the vibration sensor is a piezoelectric acceleration sensor.