HK1143296A - Bone density meter - Google Patents

Description

Bone densitometer

Cross Reference to Related Applications

This application is based on and claims priority from prior japanese patent application No. JP2008-275945, having a filing date of 2008, month 10, and day 27, which is incorporated herein by reference in its entirety.

Technical Field

The present invention relates to a bone densitometer that uses light to measure bone density.

Background

A method of detecting bone density of a measured object such as a human or the like using light is known in the art. Japanese patent application publication No. JP2008-155011 discloses a bone densitometer. The bone densitometer includes a light emitting unit, a light receiving unit, a variation trend calculation device, and a density calculation device. The light emitting unit emits light onto the object to be measured to vary the intensity of the light. The light receiving unit receives reflected light of the emitted light from the object to be measured. The variation tendency calculation means calculates a variation tendency from the intensity of the reflected light. The density calculating device calculates the bone density of the object according to the variation trend. In this way, the bone densitometer in the related art evaluates and measures the bone density according to the intensity change of the reflected light by changing the intensity of the light emitted from the light emitting unit.

However, the prior art bone densitometer, when used for measuring, for example, bone density at a site where subcutaneous tissue is thick, may not reach the bone due to insufficient output of the light emitting unit, and in such a case, it is difficult to accurately detect the bone density.

Disclosure of Invention

The present invention relates to providing a bone densitometer that more accurately measures bone density using light.

One aspect of the present invention is a bone densitometer for measuring bone density of a user. The bone densitometer includes a light emitting unit that emits light toward a body surface of a user. The light receiving unit receives light emitted from the light emitting unit toward a body surface, which propagates through a body part including a bone. The bone density calculating unit measures bone density based on the amount of light received by the light receiving unit. The light emitting unit emits light toward a portion of the body surface where subcutaneous tissue is thin. The light receiving unit receives light propagating through a portion of a body where subcutaneous tissue is thin.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

Drawings

The invention, together with its objects and advantages, may best be understood by making reference to the following description of the presently preferred embodiment taken in conjunction with the accompanying drawings in which:

fig. 1 is a schematic view showing a preferred embodiment of the bone densitometer of the present invention.

Fig. 2 is a side schematic view showing the bone densitometer of fig. 1.

Fig. 3 is a schematic diagram showing the electrical connections of the bone densitometer of fig. 1.

Fig. 4A is a schematic graph showing the relationship between bone density and light-receiving amount.

Fig. 4B is a schematic graph showing the light reception amount in logarithmic terms.

Fig. 5 is a schematic graph showing the relationship between the light-receiving amount and the subcutaneous tissue.

Fig. 6A and 6B are schematic views showing a bone densitometer according to another embodiment of the present invention.

Fig. 7 is a schematic view showing a bone densitometer according to another embodiment of the present invention.

Fig. 8A and 8B are schematic views showing a bone densitometer according to another embodiment of the present invention.

Fig. 9A and 9B are schematic views showing a bone densitometer according to another embodiment of the present invention.

Fig. 10 is a schematic view showing a bone densitometer according to another embodiment of the present invention.

Fig. 11 is a schematic view showing a bone densitometer according to another embodiment of the invention.

Fig. 12 is a schematic view showing a bone densitometer according to another embodiment of the present invention.

Fig. 13 is a schematic view showing a bone densitometer according to another embodiment of the present invention.

Fig. 14 is a schematic view showing a bone densitometer according to another embodiment of the present invention.

Detailed Description

In the drawings, like numbering represents like elements throughout.

The preferred embodiments of the bone densitometer of the present invention will now be described with reference to the accompanying drawings.

Figure 1 schematically illustrates a bathroom scale 10 provided with a bone densitometer. The bathroom scale 10 includes a box-like platform 11 on which a user stands. The platform 11 has an upper surface 11 a. A footrest 12 is formed on an upper surface 11a of the platform 11. The operation unit 13 is detachably mounted to the front of the platform 11. The power switch 14 is provided on the rear side (lower side) of the stage 11. A load sensor (not shown), such as a load cell, is disposed in the stage 11. The bathroom scale 10 of the present embodiment can also be used as a weight scale.

A bone densitometer 20 is provided at the rear of the footrest 12 for measuring bone density, particularly at the heel K of the user. Referring to fig. 2, the bone densitometer 20 includes a light emitting unit 21 for emitting light toward the heel K of the user and a light receiving unit 22 for receiving light emitted from the light emitting unit 21 as reflected light after propagating through the body part of the user including bones. The light emitting unit 21 is composed of a Light Emitting Diode (LED) having a center wavelength of 800 nm. The light receiving unit 22 is constituted by a photodiode. The wavelength of light emitted from the light emitting unit 21 may vary in the range of 500nm to 2500 nm. Light having a wavelength in this range is highly transmissive to the user's body, e.g., bone or subcutaneous tissue. Light having a wavelength near 500nm is visible, thereby making the user aware that the bathroom scale 10 is operating.

The microprocessor 23 is disposed under the light emitting unit 21 and the light receiving unit 22, and is electrically connected to the light emitting unit 21 and the light receiving unit 22. The microprocessor 23 controls the light emitting unit 21 and the light receiving unit 22. For example, as shown in fig. 3, the light receiving unit 22 is connected to a calculation unit 23a, and the calculation unit 23a is provided in the microprocessor 23 and functions as a bone density calculation unit. The calculation unit 23a calculates or measures the bone density from the output (light amount) from the light receiving unit 22.

Referring to fig. 1, the operation unit 13 includes a measurement start button 13a and a display 13 b. The measurement start button 13a is used to indicate the start of bone density measurement, and the display 13b is used to display various kinds of information. The operation unit 13 is connected to the stage 11 by a connection line (not shown). The connecting line is wound in an extensible manner on a reel (not shown) placed inside the platform 11. The display 13b displays the bone density measurement result obtained by the calculation unit 23a of the microprocessor 23, so that the user can easily view the measurement result.

In a state where the sole of the user rests on the footrest 12, the user presses the measurement start button 13a of the operation unit 13 to operate the bathroom scale 10. When the bathroom scale 10 is operated, the microprocessor 23 drives the light emitting unit 21 and the light receiving unit 22 almost simultaneously. The light emitting unit 21 emits light toward the heel K. The light propagates in the user's body while passing through the subcutaneous tissue K1 of the heel K, the heel bone K2 (refer to fig. 3), and other parts are scattered and reflected before being received by the light receiving unit 22. Subsequently, the calculation unit 23a of the microprocessor 23 calculates the bone density of the heel bone K2 based on the amount of light received by the light receiving unit 22. The display 13b of the operation unit 13 displays the bone density measurement result. When the user's feet rest on the platform 11, the user's weight is applied to the platform 11. This stabilizes the state of subcutaneous tissue and bone density. Further, the foot of the user blocks external light to increase the accuracy of the measurement.

The relationship between the bone density and the light-receiving amount and the relationship between the emitted light and the subcutaneous tissue will be described below with reference to fig. 4 and 5.

The inventors of the present invention made a simulation experiment to examine the relationship between the bone density and the light receiving amount. Bone phantoms (bone phantoms) of four basic compounds, polyurethane (polyurethane), were prepared. Hydroxyapatite was the major component of bone and was added to four bone phantoms in amounts of 100, 200, 300 and 400mg/cm3, respectively. The bone phantom is used to detect the relationship between the bone density and the amount of light received by the light receiving unit 22. The results shown in fig. 4A clearly show that the amount of light decreases exponentially as the bone density increases. Further, when the light quantity is expressed logarithmically, the relationship between the bone density and the light quantity has a strong correlation (the correlation coefficient r is equal to 0.99) represented by a straight line L, as shown in fig. 4B. Thus, it is apparent that the bone density can be measured from the amount of light received by the light receiving unit 22.

Considering the effect of subcutaneous tissue, and in particular subcutaneous fat, on the emitted light, the inventors of the present invention examined the effect of subcutaneous tissue on bone density measurements using a simulation model. Here, four simulation models with subcutaneous fat thicknesses of 0mm, 5mm, 10mm and 20mm, respectively, were used. Fig. 5 shows the relationship between the bone density and the light-receiving amount for the four simulation models with approximately straight lines L1 to L4, respectively. Reference characters L1-L4 are drawn to approximate straight lines in order from the simulation model with the thinnest subcutaneous fat. As shown in fig. 5, when the thickness of subcutaneous fat is increased in the order of 0mm, 5mm, and 10mm, the change in the amount of light received with respect to the change in the bone density becomes small, that is, the inclination of the approximate straight line becomes small. Further, when a simulation model in which the thickness of subcutaneous fat (subcutaneous tissue) is 20mm greater than 10mm is used, the received amount of light no longer changes with the change in bone density. Accordingly, the amount of light received by the light receiving unit 22 is not substantially affected by the subcutaneous tissue, generally at a portion where the thickness of the subcutaneous tissue is equal to or less than 10mm (e.g., the heel of the present preferred embodiment). This allows quantitative measurement of bone density.

As described above, by measuring the bone density at the heel where the subcutaneous tissue thickness is equal to or less than 10mm, a further accurate measurement result can be obtained. In addition, the user can easily measure the bone density by simply standing on the platform 11.

The bone densitometer 20 of the preferred embodiment has the following advantages:

(1) the light emitting unit 21 emits light toward a portion of the human body surface where subcutaneous tissue is thin (in the present preferred embodiment, the heel K). The light receiving unit 22 receives light propagating through subcutaneous tissue in the body. This allows bone density to be measured at sites where the subcutaneous tissue (subcutaneous fat) is thin. Thus, the light emitted from the light emitting unit 21 easily reaches the bone, which suppresses the influence of the subcutaneous tissue on the light while ensuring the measurement of the bone density. In addition, the bone density was measured at the heel K of the sole. This also makes it easier to measure the weight of the user.

(2) The light emitting unit 21 emits light having a wavelength of 800nm, which is within a wavelength range of 500nm to 2500 nm. Therefore, the light used to measure bone density is light of a wavelength that is highly transmissive in the human body. In addition, light with a wavelength of approximately 500nm is emitted which is visible. Thus, emitting such light will let the user know that the bone densitometer 20 within the bathroom scale 10 is working.

It will be apparent to those skilled in the art that the present invention may be practiced in other embodiments that depart from the spirit or scope of the invention. In particular, it should be understood that the present invention may have the following embodiments.

In the preferred embodiment described above, the bone densitometer 20 is used in combination with a weight scale function in the bathroom scale 10. However, the bone densitometer 20 may not necessarily be used in combination with other functions, but may be a separate device.

Although not particularly specified in the above preferred embodiment, the bone densitometer 20 may further include, for example, a light shielding portion for shielding external light to prevent it from being mixed with the light emitted from the light emitting unit 21 and the light propagating in the body. For example, when the light shielding portion is adopted in the present embodiment, as shown in fig. 6A and 6B, a U-shaped light shielding wall 30 may be provided at the rear portion of the footrest 12 for each heel of the user to shield the periphery of the heel K. Preferably, the light-shielding wall 30 is a black elastomer made of urethane (urethane) or the like. The light-shielding wall 30 shields light required for bone density measurement from external light, for example, the light-shielding wall 30 prevents illumination light or the like from entering the heel K. This further ensures accurate bone density measurement.

Further, referring to fig. 7, the arch light shielding portion 31 is formed at a position on the upper surface 11a of the footrest 12 where the arch portion T of the foot can be placed, and the shape of the arch light shielding portion 31 matches the shape of the arch portion T of the foot. The light shielding portion 31 can prevent external light for illumination and the like from entering the heel K through a gap formed by the arcuate portion T. This further ensures the accuracy of the bone density measurement.

In addition, as shown in fig. 8A, for example, the stage 11 may be provided with a groove 32 extending downward from the upper surface 11a thereof, the groove 32 serving to shield the light emitting unit 21 and the light receiving unit 22 from external light. When the foot is placed in the groove 32, the light emitting unit 21 and the light receiving unit 22 are shielded from external light. This allows the light required for bone density measurement to be shielded from external light, i.e. to be disturbing light. Thus, an accurate bone density measurement is further ensured. In this case, the protrusion 33 having a predetermined height is provided adjacent to the toes so that the measurement of the heel K is performed in a stable state. Further, referring to FIG. 8B, the shape of the recess 32 may be curved to conform to the shape of the heel K, such that the heel K may be comfortably positioned within the recess 32.

The light emitting unit 21 and the light receiving unit 22 may be disposed near the toes to measure the bone density at the toes, in which case a groove matched with the shape thereof is designed for each toe to measure the bone density at the toe.

As shown in fig. 9A and 9B, a protrusion 35 for each heel of the user may be provided on the upper surface 11a of the platform 11. The protrusion 35 may include a groove 32. A similar structure to the protrusions of fig. 9A and 9B may also be provided for the toes.

In a preferred embodiment, bone density is measured at the heel where the subcutaneous tissue is thin. However, bone density may also be measured at the toe a as shown in fig. 10 or at the arch T as shown in fig. 14. Or may also measure bone density at the loins, shoulder joints, elbows, lower legs, wrist joints, each finger joint, ankle joint, and the like.

Although not specifically mentioned above, in a preferred embodiment of the present invention, the bone densitometer may further include an ultrasonic device 40 and a computing unit 23a as shown in fig. 11. The ultrasonic device 40 serves as a measuring unit for measuring the thickness of subcutaneous tissue. The calculation unit 23a determines as a determination unit whether the thickness of the subcutaneous tissue is equal to or less than 10mm from the measurement result of the ultrasonic device 40. The bone densitometer may further include a notification unit 41, and the notification unit 41 provides notification of whether the thickness of the subcutaneous tissue is suitable for measurement through audio or a display according to the measurement result of the calculation unit 23 a. The ultrasonic device 40 includes, for example, a transmitter 40a and a receiver 40 b. In this case, the thickness of the subcutaneous tissue is measured, for example, from the time when the ultrasonic wave emitted from the transmitter 40a is reflected by the surface of the heel bone K2 (refer to fig. 3) and received by the receiver 40 b. In this structure, light is emitted by the light emitting unit 21 and received by the light receiving unit 22, while detecting a relatively thin portion of the subcutaneous tissue of 10mm or less. This ensures a more accurate measurement of bone density. In addition to using light or ultrasound, the thickness of the subcutaneous tissue can be measured by mechanically compressing it. In addition, the calculation unit 23a can start calculating the bone density when the thickness of the subcutaneous tissue is determined to be equal to or less than 10mm without issuing a notification indicating whether the thickness of the subcutaneous tissue is suitable for the bone density measurement.

In the preferred embodiment, the light receiving unit 22 is constituted by a single photodiode, but may be constituted by a plurality of light receiving elements (photodiodes). This suppresses the deviation of the bone density measurement value due to the error of the light receiving amount that may occur in the light receiving element. The light receiving element in the light receiving unit 22 is not limited to a photodiode, and may be a phototransistor. As long as the light receiving element can receive the light emitted by the light emitting unit 21.

Further, as shown in fig. 12, the light receiving unit 22 may further include a first light receiving element 50 and a second light receiving element 51. The first light receiving element 50 is closer to the light emitting unit 21 than the second light receiving element 51. In this case, the calculation unit 23a serving as a bone density calculation unit calculates the bone density from the light amount ratio of the first light receiving element 50 and the second light receiving element 51. Specifically, the first light receiving element 50 and the second light receiving element 51 are disposed at different distances from the light emitting unit 21 to receive light propagating through different optical paths in the body. For example, the first light receiving element 50 is disposed at a position closer to the light emitting unit 21 to receive light (mainly subcutaneous tissue) propagated through a shallower portion of the human body. The second light receiving element 51 is disposed at a position distant from the light emitting unit 21 to receive light (mainly subcutaneous tissue and bone) propagated through a deeper part of the human body. The calculation unit 23a calculates the bone density from the ratio of the light amounts received by the first light receiving element 50 and the second light receiving element 51. This suppresses the influence of the skin color on the surface of the human body or the state of the subcutaneous tissue on the bone density measurement, and makes the bone density measurement more accurate.

Although not specifically mentioned above, in a preferred embodiment, the calculation unit 23a may measure the bone density of the soles of the left and right feet to calculate the difference in bone density between the left and right feet. Further, the display 13b may display the difference in bone density calculated by the calculation unit. The calculation unit 23a may also calculate an average value of bone densities obtained by soles of the left and right feet. In this case, the display 13b may also display the bone density average calculated by the calculating unit 23 a.

In a preferred embodiment, the display 13b displays (provides notification of) the results of the bone density measurement. Bone density measurements may also be provided via an audio output.

Although not specifically mentioned above, in a preferred embodiment, such as that shown in fig. 13, a load sensor 60 may be provided beneath the microprocessor 23. When the load cell 60 detects that the weight is greater than or equal to a predetermined value, bone density measurement starts. In this case, the measurement start button 13a of the operation unit 13 may be eliminated.

Although not specifically mentioned above, in a preferred embodiment, for example, the microprocessor 23 may include a memory (not shown) to store a database relating bone density to age, height and weight to calculate and display the bone age of the user. Further, the estimated bone density of the entire human body can be calculated from the plantar bone density.

The light emitting unit 21 and the light receiving unit 22 may not be necessarily provided on the stage 11. For example, the light emitting unit 21 and the light receiving unit 22 may be held on the body of the user so as to be in direct contact with the body of the user.

The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

Claims (8)

1. A bone densitometer for measuring bone density of a user, the bone densitometer comprising:

a light emitting unit that emits light toward a body surface of a user;

a light receiving unit that receives the light emitted from the light emitting unit toward a body surface, the light propagating through a body part including a bone;

a bone density calculation unit that measures bone density from light quantity received by the light receiving unit;

wherein the light emitting unit emits light toward a portion of the body surface where the subcutaneous tissue is thin, and the light receiving unit receives the light propagated through the portion of the body where the subcutaneous tissue is thin.

2. The bone densitometer of claim 1, wherein the light emitting unit emits light toward a sole of a foot of a person of the body surface.

3. The bone densitometer of claim 1, further comprising:

a determination unit for determining whether the thickness of the subcutaneous tissue of the body surface is equal to or less than 10 mm.

4. The bone densitometer of claim 1, wherein the light emitting unit emits light having a wavelength in the range of 500nm to 2500 nm.

5. The bone densitometer of claim 1, further comprising:

a light shielding portion shielding external light to prevent the external light from being mixed with light emitted from the light emitting unit and light propagating in a body.

6. The bone densitometer of claim 1, further comprising:

a platform for a person to stand on, the platform comprising an upper surface having a downwardly extending recess;

wherein the light emitting unit and the light receiving unit are disposed in the groove and avoid external light.

7. The bone densitometer of claim 1, wherein the light receiving unit includes a plurality of light receiving elements, and the bone density calculation unit determines bone density from light quantity received by each light receiving element.

8. The bone densitometer of claim 7, wherein:

the plurality of light receiving elements include a first light receiving element and a second light receiving element, the first light receiving element being positioned closer to the light emitting unit than the second light receiving element;

the bone density calculation unit determines bone density from a ratio of light quantities received by the first light receiving element and the second light receiving element.