WO2017056780A1 - Measurement device, measurement method, and measurement program - Google Patents

Abstract

[Problem] To provide a measurement device, a measurement method, and a measurement program, whereby it is possible to obtain an evaluation indicator which takes measurement site dependency into account. [Solution] The measurement device according to the present invention is characterized by being provided with a transmission/reception unit for transmitting ultrasonic waves into a living body including cortical bone and receiving a resultant echo signal, an acoustic characteristic value calculating unit for calculating acoustic characteristic values relating to the cortical bone corresponding to each position from the echo signal obtained in a plurality of positions along a peripheral direction of the cortical bone substantially orthogonal to a long-axis direction of the cortical bone, and an evaluation index generating unit for generating an evaluation index indicating a state of the cortical bone on the basis of the acoustic characteristic values calculated by the acoustic characteristic value calculating unit.

Description

Measuring apparatus, measuring method, and measuring program

The present invention relates to a measuring apparatus, a measuring method, and a measuring program for measuring an acoustic characteristic value such as a sound speed inside a living body of a measurement subject from the outside using ultrasonic waves.

2. Description of the Related Art Conventionally, there is known a sound velocity measuring device that measures an acoustic characteristic value such as the sound velocity of a cortical bone by transmitting an ultrasonic wave to the cortical bone and receiving an echo signal reflected by the cortical bone. It is known that the speed of sound of cortical bone is related to the soundness of bone, and bone evaluation can be performed by measuring the speed of sound of cortical bone (for example, Patent Document 1, Patent Document 2, and Patent). Reference 3).

JP 2010-246692 A JP 2013-013567 A JP 2014-050589 A

In the conventional measurement method, it is not possible to obtain an evaluation index that takes into account the dependence depending on the measurement site (for example, the change in sound speed due to the change in the measurement site).

Therefore, an object of the present invention is to provide a measuring apparatus, a measuring method, and a measuring program capable of obtaining an evaluation index in consideration of the dependency of a measurement site.

The measuring apparatus includes a transmission / reception unit that transmits ultrasonic waves to the inside of a living body including cortical bone and receives echo signals thereof, and a plurality of measuring units that are substantially orthogonal to the long axis direction of the cortical bone and are along the circumferential direction of the cortical bone Based on the acoustic characteristic value calculated by the acoustic characteristic value calculation unit, an acoustic characteristic value calculation unit that calculates an acoustic characteristic value for the cortical bone corresponding to each position from the echo signal obtained at the position, And an evaluation index generation unit that generates an evaluation index indicating the state of the cortical bone.

Thus, the measuring device calculates an acoustic characteristic value that depends on the measurement site at each position. The acoustic characteristic value is, for example, a sound speed or an ultrasonic absorption coefficient. The measuring device generates an evaluation index based on the calculated acoustic characteristic value. Therefore, the measuring apparatus can obtain an evaluation index considering the measurement site dependency.

According to the present invention, it is possible to obtain an evaluation index considering the dependency of the measurement site.

FIG. 1A is a block diagram showing the main configuration of the measurement system, and FIG. 1B is a functional block diagram of the analysis unit 63. It is a figure which shows the mounting aspect of the measurement equipment. It is sectional drawing which shows the output mode of the ultrasonic wave of the probe with respect to a tibia. It is a flowchart which shows operation | movement of a measuring apparatus. It is the figure which showed the example of a display of an evaluation parameter | index. It is a figure which shows the relationship between sound velocity and apatite orientation which is a bone quality parameter | index.

FIG. 1A is a block diagram showing the main configuration of a measurement system including the measurement apparatus of the present invention. FIG. 2 is a view showing a mounting mode of the measuring device 1. FIG. 3 is a cross-sectional view illustrating an ultrasonic output mode of the probe 2 with respect to the tibia (cortical bone).

In the present embodiment, the long axis direction of the tibia 201 is the X direction, the direction in which the probe 2 is moved among the directions orthogonal to the direction is the Y direction, and the ultrasonic wave is output from the probe 2 among the directions orthogonal to the long axis direction. This direction is referred to as the Z direction. However, as shown in FIG. 3, the major axis direction of the tibia 201 may be slightly inclined with respect to the X direction (substantially parallel).

The information processing apparatus 3 corresponds to the measurement apparatus of the present invention, and is composed of, for example, a personal computer. The information processing device 3 is connected to the probe 2, the position detection unit 5 of the measurement device 1, and the display 8.

Further, the information processing apparatus 3 includes a transmission / reception unit 4, a signal processing unit 6, and an operation unit 7. The signal processing unit 6 functionally includes a signal generation unit 61, a control unit 62, and an analysis unit 63.

The operation unit 7 includes a mouse or a keyboard, and receives an operation from a user (measurer). The operation unit 7 receives, for example, an operation related to transmission setting or an operation for starting measurement. The control unit 62 of the signal processing unit 6 sets a transmission frequency, a pulse width, an input voltage, or the like according to an operation related to transmission setting received by the operation unit 7. The control unit 62 inputs the set contents to the signal generation unit 61. The signal generator 61 generates an ultrasonic signal under the input setting conditions. The transmission / reception unit 4 outputs the ultrasonic signal generated by the signal generation unit 61 to the probe 2 and transmits the ultrasonic wave from the probe 2.

The transmission / reception unit 4 converts the echo signal received by the probe 2 into a digital signal and outputs it to the analysis unit 63.

The probe 2 is fixed to the measuring device 1. As shown in FIG. 2, the measurement device 1 is attached to a user's limb. The measurement device 1 includes a first fixing mechanism 20, a second fixing mechanism 30, and a coupling mechanism 50.

The first fixing mechanism 20 has an opening 21. The opening 21 is fitted with a characteristic bone (for example, a rough surface of a tibial bone) located proximal to the subject's tibia (side closer to the trunk). The second fixing mechanism 30 has an opening 31. The opening 31 is fitted with a characteristic bone (for example, an ankle or an endometrium) located distal to the subject's tibia (the side far from the trunk). Thereby, the measuring equipment 1 is fixed to the limb (for example, leg) of the person to be measured.

The connecting mechanism 50 connects the first fixing mechanism 20 and the second fixing mechanism 30. The coupling mechanism 50 has a slide portion that slides the first fixing mechanism 20 and the second fixing mechanism 30 with respect to the coupling mechanism 50. The connecting mechanism 50 can expand and contract the interval between the first fixing mechanism 20 and the second fixing mechanism 30 by expanding and contracting the slide portion in the long axis direction (X direction). As a result, the measuring device 1 is adapted to be worn on the extremities in accordance with the length of the tibia 201 of the measurement subject in the long axis direction.

Further, the coupling mechanism 50 has a support holder 153 that supports the probe holding mechanism 40. The support holder 153 is formed in a staircase shape. In addition, the coupling mechanism 50 has a slide rail that allows the support holder 153 to move up and down. Thereby, the position of the probe holding mechanism 40 in the Z direction (axial direction perpendicular to the XY plane) can be adjusted.

The probe holding mechanism 40 holds the probe 2 so as to be in contact with a predetermined part of the tibia 201. The probe holding mechanism 40 can change an attachment angle around an attachment pin 155 that is an attachment location with the coupling mechanism 50.

An opening 401 is formed at the center of the probe holding mechanism 40. The probe 2 is brought into contact with the skin of the measurement subject through the opening 401. The ultrasonic transducer provided in the probe 2 outputs ultrasonic waves from the opening 401 to the tibia 201. Further, in this example, the opening 401 has a rectangular shape having a long axis in the Y direction in plan view, and can move the probe 2 in the Y direction.

Thereby, the measurement position of the probe 2 attached to the probe holding mechanism 40 can be adjusted to a desired position according to the operation of the measurer. Particularly, in the probe holding mechanism 40, the opening 401 is set so that the vicinity of the center position of the tibia 201 in the long axis direction (for example, when the limb is a leg, the center position of the leg tip and the knee) is the measurement site. . The central position of the tibia 201 in the long axis direction is easy to measure because the soft tissue is relatively thin and is flat in the horizontal direction.

In addition, the measuring device 1 has a built-in position detector 5. The position detector 5 is composed of an encoder, for example, and detects the position of the probe 2 in the Y direction. More specifically, the measurer slides the probe 2 in the horizontal direction (Y direction) using the probe holding mechanism 40 of the measurement device 1, and more specifically, the cortical bone substantially perpendicular to the long axis direction of the tibia 201. Are measured at a plurality of positions along the peripheral direction (hereinafter, for the sake of simplicity, the horizontal direction). Thereby, the information processing apparatus 3 acquires the position information of the probe 2 while performing transmission of an ultrasonic wave and reception of an echo signal at each position. An example of the position detection unit 5 is not limited to an encoder, and may be, for example, a method of detecting a position by photographing a probe with a camera (for example, a method disclosed in Japanese Patent Application Laid-Open No. 2014-050589). . Further, the probe holding mechanism 40 and the position detection unit 5 are not essential components in the present invention. For example, a measurer may hold the probe 2 by hand and perform measurement at each position and input position information.

The analysis unit 63 includes an acoustic characteristic value calculation unit 631 and an evaluation index generation unit 632 as shown in FIG. The acoustic characteristic value calculation unit 631 processes the received echo signal and calculates an acoustic characteristic value related to the tibia 201. The evaluation index generation unit 632 generates an evaluation index indicating the state of cortical bone. The evaluation index is, for example, the position distribution of the acoustic characteristic value. Examples of acoustic characteristic values include ultrasonic absorption coefficient or sound speed.

The ultrasonic absorption coefficient indicates the degree of absorption attenuation when an ultrasonic wave having a specific frequency (for example, 1 MHz) propagates through a unit distance, and is expressed in units such as dB / cm @ 1 MHz. In particular, when transmitting an ultrasonic pulse signal having a wide band (for example, the band is 2 MHz to 4 MHz) and receiving it between two points, calculating the spectrum ratio of the received pulse signal, the value of the ratio with respect to the frequency change A change (inclination) BUA (Broadband Ultrasound Absorption) is calculated. The BUA depends on the bone microstructure. Therefore, it is preferable that the analysis unit 63 calculates the position distribution of the BUA as the ultrasonic absorption coefficient.

The speed of sound is the speed SOS (Speed of Sound) at which sound waves propagate through the cancellous bone. In particular, cSOS (cortical speed of sound), which is the speed at which ultrasound propagates in the cortical bone in the long axis direction, has a strong correlation with the apatite orientation, which is a nanoscale bone quality index of minerals as shown in FIG. r = 0.889, p <0.001) is observed. The horizontal axis of the graph of FIG. 6 is an index indicating the apatite orientation (defined as the ratio of diffraction intensity from the (002 plane) and (310) planes of the apatite crystal in the bone in the X-ray diffractometer), and the vertical axis is cSOS.

The evaluation index generation unit 632 calculates the position distribution of the cSOS, for example, as the bone quality evaluation index. In the following description, an example of calculating cSOS will be described.

CSOS is determined as follows. First, as shown in FIG. 3, the probe 2 has a transmitting transducer 2A and a plurality of receiving transducers 2B arranged in the long axis direction. Each of the plurality of wave receiving vibrators 2B receives a leaky surface wave such as a leaky surface pseudo longitudinal wave.

The leaky surface wave is incident on the tibia 201 after the ultrasonic wave obliquely transmitted from the transmitting transducer 2A to the tibia 201 propagates in the soft tissue 250, propagates in the tibia 201, The light is again radiated into the soft tissue 250 and reaches the plurality of receiving transducers 2B.

Therefore, the acoustic characteristic value calculation unit 631 calculates the ultrasonic wave from the distance x between the plurality of receiving transducers 2B and the time difference t between the reception of the leaky surface wave by each receiving transducer 2B. CSOS (= x / t), which is the speed of propagation in the major axis direction, is calculated. Note that the acoustic characteristic value calculation unit 631 may correct the value of the distance x by detecting the surface of the tibia 201. For example, when the angle between the surface of the probe 2 and the surface of the tibia 201 is inclined by θ, the distance x1 between the receiving transducers 2B is expressed as x1 = x · cos θ. Therefore, cSOS is represented by cSOS = x · cos θ / t.

And since the bone microstructure of the tibia 201 differs depending on the position of the tibia 201 in the Y direction, cSOS and BUA are also a plurality of the tibia 201 substantially perpendicular to the long axis direction of the tibia 201 along the Y direction of the tibia 201. It changes according to the position (position change in the Y direction). Therefore, in the measurement system of the present embodiment, the measurer performs measurement at each position while sliding the probe 2 in the “peripheral direction (including Y direction)” using the probe holding mechanism 40 of the measurement device 1. The evaluation index generation unit 632 acquires the position information of the probe 2 from the position detection unit 5 and inputs the cSOS (or BUA) at each position calculated by the acoustic characteristic value calculation unit 631.

The operation of the analysis unit 63 will be described with reference to the flowchart of FIG. First, as described above, the transmission / reception unit 4 transmits ultrasonic waves from the probe 2 (S101). Further, the transmission / reception unit 4 receives an echo signal (S102). The position detection unit 5 detects the position (position in the Y direction) of the probe 2 (S103).

Then, the acoustic characteristic value calculation unit 631 calculates cSOS at each position by the method shown in FIG. 3 (S104). The measurement at each position is performed a plurality of times. The evaluation index generation unit 632 aggregates the calculated cSOS at each position and outputs it as a distribution (S105). This distribution is an example of an evaluation index indicating the state of cortical bone.

FIG. 5 is a diagram illustrating an example of a display mode of the evaluation index displayed on the display device 8. In the display example of the figure, information on the measurement subject (Patient ID), cSOS value, icon image (Measuring) indicating that the measurement is being performed, and icon image (STOP) indicating that the measurement is stopped are displayed on the upper left. An echo image is displayed in the lower left.

The icon image (Measuring) indicating that the measurement is in progress changes to, for example, an icon image “START” for instructing the start of measurement after the measurement is completed. When the measurer operates the operation unit 7 and presses down the icon image “START”, the measurement is started.

The cSOS at each position calculated by the analysis unit 63 is displayed as a distribution chart as shown in the lower right graph of FIG. The horizontal axis of the lower right graph in the figure shows the position in the Y direction, the left side of the horizontal axis is the outside of the tibia 201, and the right side is the inside of the tibia 201. The vertical axis is cSOS.

The evaluation index generation unit 632 outputs the calculated cSOS value to the display 8 as a distribution chart as shown in FIG. The evaluation index generation unit 632 displays an echo image based on the level of the echo signal received by the transmission / reception unit 4 as shown in the lower left of FIG.

Returning to the flowchart of FIG. 4, the evaluation index generation unit 632 determines whether or not the number of measurements at each position is equal to or greater than a reference value (S106). If it is not greater than the reference value, the process is repeated from the transmission of the ultrasonic wave. When it is determined that the evaluation index generation unit 632 is equal to or greater than the reference value, the evaluation index generation unit 632 notifies the measurer (S107). The notification is performed, for example, by displaying an image on the display 8. For example, as shown in the upper right of FIG. 5, a histogram indicating the number of measurements at each position is displayed on the display 8, and the histogram is highlighted, for example, when the number of measurements at each position exceeds a reference value. . The measurement at each position may be performed once, but in order to improve the reliability and reproducibility of the measurement, it is preferable to perform a predetermined number of measurements or more. Therefore, the information processing device 3 performs notification when the number of measurements becomes equal to or greater than the reference value. Note that the notification may be performed by sound, for example. When sound is output when the number of measurements exceeds the reference value, the measurer can measure while looking at the measurement site of the subject by listening to the sound without looking at the screen of the display 8. it can.

Next, the evaluation index generation unit 632 determines whether or not the measurement at all positions is completed (S108). When the measurement at all positions is not completed, the process is repeated from the transmission of the ultrasonic wave. If the evaluation index generation unit 632 determines that the measurement has been completed at all positions, the evaluation index generation unit 632 calculates the overall average cSOS (S109), and displays it on the display unit 8 (S110).

As described above, since the bone microstructure differs depending on the position in the Y direction (circumferential direction), the cSOS also changes according to the position change in the Y direction. Therefore, the analysis unit 63 averages the calculated cSOS at each position to calculate an average cSOS. The calculated average cSOS is displayed on the display 8 as shown in the upper left of FIG.

The evaluation index generation unit 632 first determines a representative value (for example, an average value or a median value) of cSOS at each position, and sets the average value (representative average value) of the representative values at each position as an average cSOS. Average cSOS is also an example of an evaluation index indicating the state of cortical bone.

The evaluation index generation unit 632 averages each representative value by unit length, and generates an evaluation index based on a representative value (unit length average value) averaged by the unit length. Also good. The average unit length is a value obtained by adding the representative values of cSOS at each position and dividing by the total length (L), as shown in the following formula. In this case, an average value that does not depend on the variation in the number of measurement samples at each position can be obtained.

In addition, it is preferable that the evaluation index generation unit 632 selectively uses an acoustic characteristic value within a predetermined range for calculating the average cSOS and does not employ a measurement result with a low reliability (a value outside the specified range). . For example, the specified range is preferably determined by statistical processing from the average value and standard deviation at each position. The value outside the specified range is, for example, a specifically large or small value among cSOS calculated at each position. Moreover, the measurement result when the amplitude of the echo signal is within a predetermined range is used, or the measurement result when the waveform of the leaky surface wave is a predetermined pattern (correlation with the reference is within the predetermined range) is used. It may be. In addition, it is preferable to set the specified range of each position after calculating the entire distribution. For example, in the example of FIG. 5, the lowest value of cSOS at a position of 3 mm is about 3700 (m / s), and the lowest value of cSOS at a position of 15 mm is also about 3700 (m / s). Both values are comparable. However, at the position of 3 mm, the value of 3700 (m / s) is close to the other measured values and thus falls within the specified range. On the other hand, at the position of 15 mm, the value of 3700 (m / s) is a value that is specifically smaller than other measured values, and thus is outside the specified range and is not used for calculating the average cSOS.

As described above, the analysis unit 63 detects the measurement position of the probe by the position detection unit 5 and calculates, for example, cSOS as an index having dependency on the measurement site at each position. In addition, the analysis unit 63 outputs an index having dependency on the measurement site such as cSOS as a position distribution, or calculates an average cSOS as a whole, thereby obtaining an evaluation index considering the measurement site dependency. Can be generated.

In the present embodiment, an aspect has been shown in which acoustic characteristic values are calculated at each position along the circumference of the cortical bone (Y direction) substantially orthogonal to the long axis direction (X direction) of the tibia. It is not necessary to measure each position in a direction that is exactly 90 ° with respect to the X direction. For example, even in a direction that is shifted by about 90 ± 10 ° with respect to the X direction (preferably a direction that is shifted by about 90 ± 3 °), it is possible to obtain an evaluation index that takes into account the site dependence of the acoustic characteristic value.

DESCRIPTION OF SYMBOLS 1 ... Measurement equipment 2 ... Probe 2A ... Transmitting transducer 2B ... Receiving transducer 3 ... Information processing device 4 ... Transmission / reception unit 5 ... Position detection unit 6 ... Signal processing unit 7 ... Operation unit 8 ... Display 20 ... first fixing mechanism 21 ... opening 30 ... second fixing mechanism 31 ... opening 40 ... probe holding mechanism 50 ... connecting mechanism 61 ... signal generating unit 62 ... control unit 63 ... analyzing unit 153 ... support holder 155 ... mounting pin 201 ... tibia (Cortical bone)
401 ... opening

Claims (12)

A transmission / reception unit for transmitting an ultrasonic wave to the inside of the living body including the cortical bone and receiving an echo signal thereof;
An acoustic characteristic value for calculating an acoustic characteristic value for the cortical bone corresponding to each position from the echo signals obtained at a plurality of positions along the circumferential direction of the cortical bone substantially orthogonal to the longitudinal direction of the cortical bone A calculation unit;
Based on the acoustic characteristic value calculated by the acoustic characteristic value calculation unit, an evaluation index generation unit that generates an evaluation index indicating the state of the cortical bone;
A measuring apparatus comprising: The measuring apparatus according to claim 1,
The acoustic characteristic value is calculated from an echo signal obtained by transmitting and receiving the ultrasonic wave a plurality of times at the same position. In the measuring apparatus according to claim 1 or 2,
The evaluation index generation unit determines a representative value of the acoustic characteristic value at each position, and generates the evaluation index based on a representative average value obtained by further averaging the determined representative value as a whole. Characteristic measuring device. In the measuring apparatus in any one of Claims 1 thru | or 3,
The evaluation index generation unit determines a representative value of the acoustic characteristic value at each position, and generates the evaluation index based on a unit length average value obtained by averaging the determined representative value by a unit length. A measuring apparatus characterized by: In the measuring apparatus in any one of Claims 1 thru | or 4,
The evaluation index generation unit selectively uses an acoustic characteristic value within a predetermined range among the acoustic characteristic values. In the measuring apparatus in any one of Claims 1 thru | or 5,
A measurement apparatus further comprising a position detection unit that detects the plurality of positions. The measuring apparatus according to any one of claims 1 to 6,
The measuring apparatus further comprising a display unit that displays each acoustic characteristic value in correspondence with the positional relationship. The measuring apparatus according to any one of claims 1 to 7,
The measuring device is characterized in that the sound velocity is a velocity at which an ultrasonic wave propagates through the cortical bone in the long axis direction. The measuring apparatus according to any one of claims 1 to 8,
The acoustic characteristic value is an ultrasonic absorption coefficient. The measuring apparatus according to any one of claims 1 to 9,
A measuring apparatus, comprising: a notification unit that performs notification when the number of measurements at each position is equal to or greater than a predetermined number. Sending ultrasonic waves to the inside of the living body including cortical bone and receiving the echo signal,
Calculating the acoustic characteristic values for the cortical bone corresponding to each position from the echo signals obtained at a plurality of positions along the circumferential direction of the cortical bone substantially orthogonal to the longitudinal direction of the cortical bone,
Based on the calculated acoustic characteristic value, an evaluation index indicating the state of the cortical bone is generated.
A measuring method characterized by the above. A transmission / reception step of transmitting an ultrasonic wave to the inside of the living body including the cortical bone and receiving an echo signal thereof;
An acoustic characteristic value for calculating an acoustic characteristic value for the cortical bone corresponding to each position from the echo signals obtained at a plurality of positions along the circumferential direction of the cortical bone substantially orthogonal to the longitudinal direction of the cortical bone A calculation step;
Based on the acoustic characteristic value calculated by the acoustic characteristic value calculating step, an evaluation index generating step for generating an evaluation index indicating the state of the cortical bone;
A measurement program for causing a computer to execute.

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