JP2014079406A - Bone density measurement adapter - Google Patents

Abstract

An object of the present invention is to easily measure bone density without using a large-scale facility.
A container includes a side wall and a bottom film. The side wall 30 has a cylindrical shape whose diameter increases along the X-ray beam shape downward. The side wall 30 is formed of a material that shields X-rays. A bottom film 32 is provided in the lower opening formed by the side wall 30. The bottom film 32 is made of a deformable material that transmits X-rays. When the bone density measuring adapter 18 is provided on the subject 24, the bottom membrane 32 is deformed according to the shape of the subject 24 and is in close contact with the subject 24. The bone density measuring adapter 18 contains a soft tissue equivalent liquid 34 in such an amount that a horizontal liquid level is formed. With such a configuration, a state equivalent to a state in which bone is surrounded by soft tissue having a constant thickness is formed, and bone density can be easily measured.
[Selection] Figure 3

Description

  The present invention relates to an adapter for measuring bone density, and more particularly to an adapter for measuring the bone density of a subject using X-rays.

  As a bone disease of the human body, there is osteoporosis in which the content of bone mineral decreases and bone strength decreases. In recent years, the number of patients has increased in many countries. Since osteoporosis is a disease in which subjective symptoms are difficult to appear, periodic diagnosis is desired. As a device for diagnosing bone such as osteoporosis, a bone density measuring device for measuring bone density by X-ray is widely used. The bone density measuring device detects X-rays emitted from an X-ray generator and transmitted through a subject with an X-ray detector, and measures the bone density of the subject based on the detection result.

  The bone density measuring apparatus measures the bone density by dual energy X-ray absorption measurement (DXA), QCT (QCT: Quantitative Computed Tomo-graph), single energy X-ray absorption measurement. There is a method (SXA: Single X-ray Abstractometry).

  The DXA method acquires X-ray image data of a subject for each of two types of X-rays having different energies, calculates bone mineral distribution data from these X-ray image data, and calculates bone density based on the bone mineral distribution data. Is. The QCT method acquires X-ray image data of a subject together with a reference object called a phantom. The bone density is measured based on the data corresponding to the phantom included in the X-ray image data and the data corresponding to the bone included in the X-ray image data. The SXA method calculates the bone density based on the level of X-ray transmitted through the bone in the soft tissue, the level of X-ray transmitted only through the soft tissue, and the geometrical relationship of each progression path of these X-rays. It is what you want. In the SXA method, in general, in order to establish a necessary measurement condition, measurement is performed in a state where a test site such as a hand or a foot is immersed in a measurement liquid.

  Patent Document 1 describes an apparatus for obtaining the bone mineral content using the SXA method. This apparatus includes a water tank for holding a liquid material, and measures the amount of bone mineral in a state in which the test site is immersed in the liquid material. Patent Document 2 describes a phantom used in the QCT method. This phantom is enclosed in a bag together with a material similar to the tissue of the subject. A material similar to the tissue of the subject is filled in the bag without any gaps. Patent Document 3 describes a calibration phantom. This calibration phantom is made of a radiopaque material, is composed of a plurality of portions with different transparency, and is X-rayed together with the subject. Then, the bone density is obtained based on the comparison between the bone image on the X-ray image and the calibration phantom image.

JP 2008-206560 A Japanese National Patent Publication No. 8-503637 Special table 2008-509737 gazette

  In a bone density measuring apparatus based on the SXA method, generally, measurement is performed in a state where a test site is immersed in a liquid. Therefore, there is a problem that the facility becomes large, such as providing a water tank for storing the liquid and immersing the test site in the liquid.

  An object of the present invention is to easily measure bone density without using a large-scale facility.

  The present invention is provided on a subject made of bone and soft tissue, has a bottom surface that is in close contact with the subject, and includes a container containing a liquid as a soft tissue equivalent substance therein, A horizontal liquid surface is formed, and bone density measurement X-rays pass through the subject and the liquid.

  According to such a configuration, a horizontal liquid surface is formed in the container with the bottom surface of the container being in close contact with the subject. As a result, when the liquid in the container and the subject are integrated from the viewpoint of the propagation medium and the lower surface of the subject can be regarded as a horizontal plane, this is equivalent to a state where the bone is surrounded by soft tissue having a constant thickness. A state can be formed. Therefore, the condition for measuring the bone density can be established by a simple operation of providing the bone density measuring adapter on the subject.

  In the bone density measuring adapter according to the present invention, preferably, the container has a bottom membrane formed of a deformable material and having the bottom surface.

  According to such a configuration, the bottom film naturally deforms in accordance with the shape of the subject. Therefore, the bottom surface of the container can be brought into close contact with the subject regardless of the shape of the surface of the subject.

  In the bone mineral density measuring adapter according to the present invention, preferably, the container has a side wall that shields X-rays.

  According to such a configuration, unnecessary X-rays emitted from the container in the lateral direction are reduced.

  In the bone density measuring adapter according to the present invention, preferably, the bone density measuring X-ray has a beam shape that spreads in a traveling direction, and the container has a side wall that is shaped along the beam shape. Have

  X-ray beam shapes include, for example, a cone shape and an angular guess shape. According to such a configuration, the volume of the container can be reduced without hindering the progress of X-rays, and the container can be reduced in size and weight.

  In the bone mineral density measuring adapter according to the present invention, preferably, the bottom surface of the container has a part through which X-rays pass and a part through which X-rays are shielded.

  According to such a configuration, it is possible to limit the amount of X-rays that do not contribute to bone density measurement without hindering the progress of X-rays that contribute to bone density measurement. Thereby, the amount of X-rays emitted from the container to the subject is limited, and the exposure amount of the subject is reduced.

  In the bone mineral density measuring adapter according to the present invention, preferably, the container is held by a subject as the subject.

  According to such a configuration, a device for supporting the bone density measuring adapter is not necessarily required. For example, it is possible to use the bone density measuring adapter in close contact with the site where bone density is measured, and the subject holds the bone density measuring adapter with both hands.

  The bone mineral density measuring adapter according to the present invention preferably includes at least one X-ray attenuation reference object accommodated in the container.

  According to such a configuration, the X-ray attenuation reference object can be X-rayed together with the subject, and bone diagnosis can be performed based on a comparison between the imaged image and the bone image. Therefore, it is not necessary to separately measure the X-ray attenuation reference object.

  According to the present invention, bone density can be easily measured without using a large-scale facility.

It is a figure which shows the bone density measuring system which concerns on embodiment of this invention. It is a perspective view of the adapter for bone density measurement concerning the embodiment of the present invention. It is sectional drawing of the adapter for bone density measurement which concerns on embodiment of this invention. It is a figure which shows the state which stuck the adapter for bone density measurement to the test object. It is a figure which shows a measurement state typically. It is a figure which shows typically the measurement image shown by measurement X-ray data. It is the figure which replaced the soft tissue equivalent liquid in the adapter for bone density measurement with the soft tissue. It is a figure which shows the adapter for a bone density measurement which used each part of each of the lid | cover and the bottom membrane as the X-ray transmissive area | region, and made each remaining area | region of the lid | cover and the bottom membrane the X-ray shielding area. It is a figure which shows the adapter for bone density measurement which made the container the square cylinder shape. It is a figure which shows the adapter for a bone density measurement provided with the X-ray attenuation reference | standard object. It is a figure showing a bone density measuring system provided with a mechanism holding a bone density measuring adapter.

  FIG. 1 shows a bone density measuring system according to an embodiment of the present invention. This figure shows a state in which the bone density of the lumbar spine of the subject 24 is measured. The bone density measuring system includes a bucky table 10, an X-ray generator 12, an X-ray detector 14, a control unit 16, and a bone density measuring adapter 18.

  The bucky table 10 includes a measurement table 20 that transmits X-rays and a table leg 22 that supports the measurement table 20. An X-ray generator 12 is provided above the Bucky table 10 with a space in which the subject 24 lies. Below the measuring table 20 of the bucky table 10, an X-ray detector 14 is provided at a position facing the X-ray generator 12. The X-ray detector 14 has a horizontal detection surface 15 on which a plurality of X-ray detection elements are arranged. Each X-ray detection element detects an X-ray and outputs a pixel value, whereby X-ray two-dimensional distribution data based on the X-ray that has reached the detection surface 15 is generated. The X-ray detector 14 outputs the X-ray two-dimensional distribution data to the control unit 16.

  When measuring the bone density, the subject 24 is laid on his / her back on the measuring table 20 of the bucky table 10. A subject as the subject 24 holds the bone density measuring adapter 18 in close contact with the abdomen and holds it with both hands. The bone density measuring adapter 18 is used to establish bone density measuring conditions, and a specific configuration will be described later.

  When the subject 24 is laid on the measurement table 20 and a gap is formed between the back side of the subject 24 and the measurement table 20, a liquid equivalent to the soft tissue of the subject 24 is enclosed. The liquid bag thus formed may be inserted into the gap.

  The X-ray generator 12 emits X-rays having a divergent beam shape such as a cone shape or a pyramid shape downward. X-rays radiated from the X-ray generator 12 pass through the bone density measuring adapter 18, the subject 24 and the measurement table 20 and reach the detection surface 15 of the X-ray detector 14. The X-ray detector 14 generates X-ray two-dimensional distribution data and outputs it to the control unit 16. The control unit 16 measures the bone density of the subject 24 based on the X-ray two-dimensional distribution data.

  Next, a specific configuration of the bone density measuring adapter 18 will be described. 2 and 3 are a perspective view and a cross-sectional view of the bone density measuring adapter 18, respectively. The bone density measuring adapter 18 includes a container 26 and a lid 28. The container 26 contains a soft tissue equivalent liquid 34. The soft tissue equivalent liquid 34 is a liquid whose X-ray transmission characteristics are equivalent to the soft tissue 40 of the subject 24. However, the perspective view of FIG. 2 shows a state in which the soft tissue equivalent liquid 34 is not accommodated in order to show the internal structure. For the soft tissue equivalent liquid 34, for example, water is used.

  The container 26 includes a side wall 30 and a bottom film 32. The side wall 30 has a cylindrical shape whose diameter increases along the X-ray beam shape downward. The side wall 30 is formed of a material that shields X-rays. Examples of the X-ray shielding material include X-ray shielding glass such as lead glass and metal. Alternatively, the side wall 30 may be formed of a material that transmits X-rays such as plastic resin, and a layer formed of the X-ray shielding material may be provided in the side wall 30 or on the wall surface.

  A bottom film 32 is provided in the lower opening formed by the side wall 30. The bottom film 32 is made of a deformable material that transmits X-rays, such as rubber. When the bone density measuring adapter 18 is provided on the subject 24, the bottom membrane 32 is deformed according to the shape of the subject 24 and is in close contact with the subject 24.

  The lid 28 is formed of a plastic resin or the like that transmits X-rays, and is detachable from the opening of the container 26. The container 26 and the lid 28 may be detachable by a screw structure. By attaching the lid 28 to the container 26, leakage of the soft tissue equivalent liquid 34 is avoided.

  The bone density measuring adapter 18 contains a soft tissue equivalent liquid 34 in such an amount that a horizontal liquid level is formed. That is, air is mixed in the bone density measuring adapter 18 in a state where the lid 28 is attached to the container 26.

  According to such a configuration, as shown in FIG. 4, the bottom film 32 is deformed along the surface of the subject 24 even if the surface of the subject 24 is not flat. The bottom surface of the bone density measuring adapter 18 is in close contact with the subject 24 in a state where the soft tissue equivalent liquid 34 is filled in the container 26. As a result, the soft tissue equivalent fluid 34 and the soft tissue of the subject 24 are integrated from the viewpoint of the propagation medium, and a suitable condition for measuring the bone density is formed. Moreover, since the side wall 30 shields X-rays, unnecessary X-rays emitted from the container 26 in the lateral direction are reduced, and the exposure dose of the subject is reduced. Further, the side wall 30 has a cylindrical shape with a diameter increasing toward the lower side along the X-ray beam shape. Thereby, the volume of the container 26 can be reduced without hindering the progress of X-rays, and the container 26 is reduced in size and weight.

  Here, an example in which the bottom film 32 is formed of a deformable material has been described, but the bottom film 32 may be replaced with a plate formed of a rigid material. In this case, the bottom surface of the bone density measuring adapter is brought into close contact with the subject as the subject is deformed.

  Measurement of bone density by the SXA method will be described with reference to FIGS. FIG. 5 schematically shows the measurement state. The bone 38 shown in FIG. 5 is the spine, and a cross section perpendicular to the longitudinal direction of the spine of the subject 24 is shown. In the bone density measuring adapter 18, a horizontal liquid level 36 is formed by the soft tissue equivalent liquid 34. The X-ray generator 12 emits X-rays including the bone 38 of the subject 24 and the surrounding soft tissue 40 in a beam 42. That is, the X-ray generator 12 passes through the bone density measuring adapter 18, then passes through only the soft tissue 40 and reaches the X-ray detector 14, and after passing through the bone density measuring adapter 18. The soft tissue 40, the bone 38, and the soft tissue 40 are transmitted through the subject 24 in this order, and X-rays that reach the X-ray detector 14 are emitted.

  In the measurement, first, a reference state in which the subject 24 is not laid and only the measurement table 20 is interposed between the X-ray generator 12 and the X-ray detector 14 is formed. The X-ray generator 12 emits X-rays in this reference state. The control unit 16 stores the X-ray two-dimensional distribution data output from the X-ray detector 14 as reference X-ray data.

  Next, the subject 24 is laid on the back on the measurement table 20, and a measurement state in which the bone density measuring adapter 18 is in close contact with the subject 24 is formed. The X-ray generator 12 emits X-rays in this state. The control unit 16 stores the X-ray two-dimensional distribution data output from the X-ray detector 14 as measured X-ray data.

  FIG. 6 schematically shows a measurement image indicated by the measurement X-ray data. In the measurement image, the region based on the X-rays transmitted through the bone 38 (bone region 44) has a smaller pixel value than the region based on the X-rays transmitted only through the soft tissue 40 (soft tissue region 46). In FIG. 6, the bone region 44 is more densely spotted than the soft tissue region 46, and the pixel value of the bone region 44 is smaller than the pixel value of the soft tissue region 46.

According to the SXA method, the pixel value of the pixel PB included in the bone region 44 is L _B , the pixel value of the reference X-ray data corresponding to the position of the pixel PB is L _B0 , and the position coordinate of the pixel PB is χ _B (x, z), the pixel value of the pixel PA included in the soft tissue region 46 is L _A , the pixel value of the reference X-ray data corresponding to the position of the pixel PA is L _A0 , and the position coordinate of the pixel PA is χ _A (x, z) In this case, the bone density at the position of the pixel PB is expressed by a bone density calculation function B _d to be described later using L _B , L _B0 , χ _B , L _A , L _A0, and χ _A as variables.

Therefore, the control unit 16 determines the bone density based on the bone density calculation function B _d for each pixel included in the bone region 44 with the pixel PA as a fixed pixel. Specifically, it is determined whether or not each pixel included in the measurement image is a pixel in the bone region 44. If the pixel to be determined is a pixel in the bone region 44, the bone density calculation function Based on B _d , the bone density for that pixel is determined. Here, the determination of whether each pixel of the measurement image indicates the bone region 44 is performed, for example, when the pixel value is less than a predetermined threshold, the pixel value is determined to be a pixel of the bone region 44. Is equal to or greater than a predetermined threshold, it is determined by determining that the pixel is in the soft tissue region 46.

  Based on such processing, the control unit 16 obtains the bone density for each of all the pixels in the bone region 44. The average value of all the bone densities obtained in the bone region 44 is set as the bone density obtained for the subject 24.

Next, an example of a bone density calculation function B _d, will be described together with the measurement principles of the SXA method. FIG. 7 shows a view in which the soft tissue equivalent liquid 34 accommodated in the bone density measuring adapter 18 is replaced with a soft tissue 40. The measurement table 20 is assumed to be sufficiently thin, and the reference X-ray data and the measurement X-ray data are acquired approximately on the upper surface of the measurement table 20.

From the point Q of the X-ray generator 12, X-rays having a diverging beam shape are emitted downward. An xy coordinate plane is defined with a point on the measurement table 20 immediately below the point Q as an origin O. Point A indicates a point included in the soft tissue region on the measurement image. The X-ray 47A emitted from the point Q in the X-ray generator 12 reaches the point A through the point C on the liquid surface 36 of the soft tissue equivalent liquid 34. The angle θ ₁ is an angle formed by the traveling direction of the X-ray 47A and the vertical direction. Point B indicates a point included in the bone region on the measurement image. The X-ray 47 </ b> B emitted from the point Q in the X-ray generator 12 reaches the point B through the point D on the liquid surface 36 of the soft tissue equivalent liquid 34. The angle θ ₂ is an angle formed by the traveling direction of the X-ray 47B and the vertical direction. Pixels at points A and B in FIG. 7 correspond to the pixels PA and PB in FIG. 6, respectively.

The bone density calculation function B _d is expressed as the following (Equation 1) to (Equation 6).

μ _s is the soft tissue mass attenuation coefficient, ρ _s is the soft tissue weight density, μ _b is the bone mass attenuation coefficient, and ρ _b is the bone weight density, both of which are known values. L _B is the pixel value of the measured X-ray data at point B. L ₁ represents a virtual pixel value detected at the point B when it is assumed that the bone 38 does not exist in the subject 24 and only the soft tissue 40 exists, and is expressed by the following (Equation 2). Desired.

L _B0 is the pixel value of the reference X-ray data at point B. Further, the overlined BD is a distance between the point B and the point D, and is obtained based on (Equation 3) and (Equation 4).

(Equation 3) is an expression derived from the fact that the upper surface of the measurement table 20 and the liquid surface 36 of the soft tissue equivalent liquid 34 are horizontal, and the heights of the points C and D from the measurement table 20 are equal. By providing the bone density measuring adapter 18 on the subject 24, a horizontal liquid surface is formed by the soft tissue equivalent liquid 34, and the soft tissue equivalent liquid 34 and the soft tissue 40 of the subject 24 are the propagation medium. From this point of view, this condition is established. The overlined AC is the distance between point A and point C, and is obtained based on the following (Equation 4). Further, θ ₁ and θ ₂ are obtained from the following (Equation 5) and (Equation 6), respectively.

L _A is the pixel value of the measurement X-ray data at the point A, and L _A0 is the pixel value of the reference X-ray data at the point A.

d ₁ is the absolute value of the x coordinate value of the point A, that is, the distance between the point A and the origin O. D ₂ is the absolute value of the x coordinate value of the point B, that is, the distance between the point B and the origin O. h ₀ is the height of the point Q from the measurement table 20 and is a constant value.

Here will be described the physical significance of bone density calculation function B _d. The thickness β of the bone 38 along the direction of the straight line QB in FIG. 7 is defined as follows. That is, when assuming a soft tissue and bone having the same thickness β as a model, the ratio between the level of X-rays transmitted through the bone as the model and the level of X-rays transmitted through the soft tissue as the model is It is defined as the value of β that is equal to the ratio between the pixel value L _B and the pixel value L ₁ . Here, the pixel value L _B is a pixel value based on X-rays that have passed through the subject 24 in the order of the soft tissue 40, the bone 38, and the soft tissue 40, and the pixel value L ₁ is the travel path of such an X-ray. Are virtual pixel values obtained when it is assumed that there is no bone and only soft tissue exists. According to this definition, the ratio between the pixel value L _B and the pixel value L ₁ is as follows. As shown in the following (Equation 7), the attenuation ratio of the X-ray passing through the bone having the thickness β and the soft part having the thickness β It is expressed as a ratio to the attenuation ratio of X-rays transmitted through the tissue.

The bone density is obtained by multiplying the bone thickness β by its weight density ρ _s . That is, by solving (Equation 7) for β and multiplying by the weight density ρ _s , the bone density is obtained, and the equation representing this bone density is (Equation 1).

Pixel value L _B is obtained directly from the measured X-ray data. On the other hand, the pixel value L ₁ is obtained by applying the pixel values of the measurement X-ray data and the reference X-ray data to (Equation 2) to (Equation 6) based on the geometric relationship shown in FIG. .

  The relationships shown in (Equation 2) to (Equation 6) are established under the condition that the upper surface of the measurement table 20 and the liquid surface 36 of the soft tissue equivalent liquid 34 are horizontal. In the bone density measuring adapter 18 according to the embodiment of the present invention, an amount of soft tissue equivalent liquid is stored in the bone density measuring adapter 18 so as to form a horizontal liquid surface. That is, air is mixed in the bone density measuring adapter 18. As a result, as shown in FIG. 4, a horizontal liquid level 36 is formed in the container 26 even when the surface of the subject 24 is inclined. Therefore, a state equivalent to the state in which the bone 38 is surrounded by the soft tissue 40 having a constant thickness is formed, and the relationship shown in (Expression 2) to (Expression 6) is established, and the bone density can be easily measured. can do.

  As is clear from the measurement principle of the SXA method described above, the X-ray used for the measurement only needs to include at least the bone 38 of the subject 24 and the surrounding soft tissue 40. Therefore, when such a condition is satisfied, the lid 28 and the bottom membrane 32 of the bone density measuring adapter 18 may not be entirely formed of a material that transmits X-rays. That is, among the X-rays emitted from the X-ray generator 12, the X-ray corresponding to the vicinity of the outside of the beam shape that does not contribute to the bone density measurement, the lid 28 and the bottom membrane 32 of the bone density measuring adapter 18. You may shield by.

  For example, as shown in FIG. 8, with respect to the bottom film 32, a part of the region including the vicinity of the center may be the X-ray transmission region 48 and the remaining region may be the X-ray shielding region 50. Similarly, for the lid 28, a part of the region including the vicinity of the center may be the X-ray transmission region 52 and the remaining region may be the X-ray shielding region 54. Each X-ray transmission region is formed of a material that transmits X-rays such as plastic resin and rubber, and each X-ray shielding region is formed of an X-ray shielding material such as metal and X-ray shielding glass. The shape of each X-ray transmission region and each X-ray shielding region may be a shape adapted to the X-ray beam shape.

  According to such a configuration, it is possible to limit the amount of X-rays that do not contribute to bone density measurement without hindering the progress of X-rays that contribute to bone density measurement. Thereby, the amount of X-rays radiated from the container 26 to the subject 24 is limited, and the exposure amount of the subject is reduced.

  Further, the shape of the container of the bone density measuring adapter may be a square tube in addition to the cylinder. FIG. 9 shows an example in which the shape of the container 26 is a square cylinder. Also in this example, like the bone density measuring adapter 18 shown in FIG. 8, a part of the bottom membrane 32 is an X-ray transmission region 48 and the remaining region is an X-ray shielding region 50. . Furthermore, a partial area of the lid 28 is an X-ray transmission area 52 and the remaining area is an X-ray shielding area 54.

  An X-ray attenuation reference object may be provided in the container of the bone density measuring adapter. The X-ray attenuation reference material is formed of, for example, a plastic resin such as polyvinyl chloride (PVC), or a plastic resin in which a metal, a metal oxide, or the like is mixed, and attenuates transmitted X-rays. The X-ray attenuation reference object is X-rayed together with the subject, and the bone density and the like are measured based on a comparison between the taken image and a bone image.

  FIG. 10 shows an example in which a plurality of X-ray attenuation reference objects 56 having different sizes are provided. Each X-ray attenuation reference object 56 is formed in a spherical shape and is supported by a support bar 57 protruding from the side wall of the container 26. The support rod 57 is made of, for example, a material having an X-ray transmission characteristic equivalent to that of a soft tissue. Since each X-ray attenuation reference object 56 has a different diameter, the attenuation ratio with respect to X-rays is different. Therefore, the pixel of each X-ray attenuation reference object 56 in the X-ray image has a pixel value corresponding to its diameter. By making the diameters of the plurality of X-ray attenuation reference objects 56 different in stages, it becomes easy to measure bone density and the like based on the comparison between the pixel value of the bone and the pixel value of each X-ray attenuation reference object 56.

  In addition, since each X-ray attenuation reference object 56 is formed in a spherical shape, a pixel indicating that the X-ray attenuation is the largest in the X-ray image of each X-ray attenuation reference object 56 is the X-ray attenuation reference object 56. It corresponds to the X-ray transmitted through the center. Therefore, a pixel with the highest X-ray attenuation in the image of each X-ray attenuation reference object 56 is used as a reference pixel for bone diagnosis, so that highly accurate measurement is possible.

  Note that the X-ray attenuation reference object is not necessarily formed in a spherical shape. For example, the X-ray attenuation reference object may be formed in a rectangular parallelepiped. In this case, by arranging one of the six faces of the rectangular parallelepiped toward the X-ray arrival direction, a constant attenuation ratio with respect to the X-ray is obtained, and an image for comparison with the bone image in the X-ray image is obtained. It is done.

  In the above description, the example of measuring the bone density of the lumbar spine of the subject has been described. In the bone density measuring system according to the present embodiment, it is possible to measure the bone density of other measurement sites such as the femur in addition to the lumbar spine.

  Further, the X-ray generator 12 is not provided above the measurement table 20 and the X-ray detector 14 is not provided below the measurement table 20, but the X-ray detector 14 is provided above the measurement table 20. It is good also as a structure which provides the X-ray generator 12 below.

  Further, instead of the X-ray detector 14, an X-ray film may be used. In this case, each X-ray image corresponding to the above-described measurement X-ray data and reference X-ray data is taken with an X-ray film. Then, the brightness of each position on each X-ray image is digitized, and the bone density is measured using the digitized brightness of each position instead of each pixel value of the measured X-ray data and the reference X-ray data. I do.

  Further, the bone density measuring adapter may be held on the subject by mechanical means. FIG. 11 shows a bone density measuring system in which a mechanism for holding the bone density measuring adapter 18 is provided in the X-ray generator 12.

  A plurality of support columns 58 extending in the vertical direction are attached to the X-ray generator 12. A pressing plate 62 is attached to the lower end of each column 58 via a spring 60. The pressing plate 62 is made of a material that transmits X-rays, and the lower surface thereof is in contact with the upper surface of the lid of the bone density measuring adapter 18.

  The X-ray generator 12 is movable up and down. When the subject 24 is laid on the measurement table 20, the X-ray generator 12 is positioned upward in order to avoid the subject 24 coming into contact with the X-ray generator 12. Then, after the subject 24 is laid down, the X-ray generator 12 is moved downward. As a result, a state in which the bone density measuring adapter 18 and the subject 24 are sandwiched between the pressing plate 62 and the measuring table 20 is formed. Further, a downward force is applied to the bone density measuring adapter 18 through the pressing plate 62 by the elastic force of the spring 60, and the bottom surface of the bone density measuring adapter 18 is in close contact with the subject 24. As described above, the mechanism for holding the bone density measuring adapter 18 is provided in the X-ray generator 12, thereby reducing the burden on the subject.

  According to the bone density measuring adapter of the present invention, the soft tissue equivalent fluid and the soft tissue of the subject are integrated from the viewpoint of the propagation medium. Furthermore, a horizontal liquid level of the soft tissue equivalent liquid is formed in the container. As a result, a state equivalent to a state in which the bone is surrounded by the soft tissue having a constant thickness is formed, and the bone density can be easily measured by the SXA method or the like. The bone density measuring adapter according to the present invention may be used for various measuring methods that can measure bone density in such a state, such as the DXA method and the QCT method, in addition to the SXA method.

  DESCRIPTION OF SYMBOLS 10 Bucky table, 12 X-ray generator, 14 X-ray detector, 15 Detection surface, 16 Control part, 18 Bone density measuring adapter, 20 Measurement stand, 22 Table leg, 24 Subject, 26 Container, 28 Lid, 30 Side wall, 32 Base membrane, 34 Soft tissue equivalent fluid, 36 Fluid level, 38 Bone, 40 Soft tissue, 42 Beam, 44 Bone region, 46 Soft tissue region, 47A, 47B X-ray, 48, 52 X-ray transmission region, 50 , 54 X-ray shielding area, 56 X-ray attenuation reference object, 57 support rod, 58 strut, 60 spring, 62 pressure plate.

Claims (7)

A container provided on a subject made of bone and soft tissue, having a bottom surface in close contact with the subject, and containing a liquid as a soft tissue equivalent substance therein;
An adapter for measuring bone density, wherein a horizontal liquid surface is formed in the container, and bone density measuring X-rays pass through the subject and the liquid. The adapter for bone density measurement according to claim 1,
The bone density measuring adapter, wherein the container is formed of a deformable material and has a bottom membrane having the bottom surface. In the bone density measuring adapter according to claim 1 or 2,
The bone density measuring adapter, wherein the container has a side wall that shields X-rays. In the bone density measuring adapter according to any one of claims 1 to 3,
The bone density measurement X-ray has a beam shape that spreads in the traveling direction,
The bone density measuring adapter, wherein the container has a side wall shaped along the beam shape. The adapter for measuring bone density according to any one of claims 1 to 4,
The bone density measuring adapter, wherein the bottom surface of the container has a part through which X-rays pass and a part through which X-rays are shielded. In the bone density measuring adapter according to any one of claims 1 to 5,
An adapter for measuring bone density, wherein the container is held by a subject as the subject. In the bone density measuring adapter according to any one of claims 1 to 6,
An adapter for bone density measurement, comprising at least one X-ray attenuation reference object housed in the container.

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