JP2004113696A - Bone salt quantity measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain the two-dimensional distribution of the quantity of a bone salt properly without relying on the height adjustment of a bed in a bone salt quantity measuring apparatus. <P>SOLUTION: An X-ray generator 16 and an X-ray detector 22 are moved relatively to the bed 12 by a moving mechanism not illustrated to scan a subject 24 with the X-ray beams 18 in parallel. As shown in figures (a) and (b), the operation conditions of the moving mechanism are altered according to the heights A<SB>0</SB>and A<SB>1</SB>of the bed 12. In other words, the pitches between the adjacent scan lines of the respective X-ray beams 18 are altered to proper pitches P<SB>0</SB>and P<SB>1</SB>so that the X-ray beam passage areas are adjusted to match the adjacent scan lines on a measuring reference surface 15 assumed for the lumber vertebrae 26 to be measured of the subject 24 placed on the bed 12. Otherwise, the X-ray beam passage areas can be adjusted between the adjacent scan lines by altering the angle θ of expansion of the X-ray beams 18 or by altering the effective detection aperture of the X-ray detector 22. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for measuring bone mineral density, and more particularly to an apparatus for measuring a bone mineral density of a subject placed on a bed.
[0002]
[Prior art]
2. Description of the Related Art As shown in, for example, Patent Literature 1, a conventional bone mineral density measurement device includes a bed on which a subject is placed, and an X-ray generation unit and an X-ray detection unit provided up and down via the bed. The X-ray generation unit and the X-ray detection unit are driven in a horizontal direction integrally by the scanning device, sequentially scan the subject on the bed with X-rays, and transmit the X-rays transmitted through the bones of the subject. The amount of bone mineral is measured by detecting.
[0003]
[Patent Document 1]
JP-A-10-192265
[0004]
[Problems to be solved by the invention]
In a medical institution such as a hospital, an X-ray room as a radiation control area is equipped with relatively large X-ray equipment and an X-ray bed for mounting a subject and imaging various parts. ing. The bone mineral density measurement device is also installed in the radiation control area, and depending on the circumstances of the medical institution, is installed in the same X-ray room as the X-ray imaging device. Since the bone mineral density measurement device also has a dedicated bed, if two beds are installed in the X-ray room, the room is inevitably crowded or the installation itself becomes impossible.
[0005]
In such a case, it is only necessary that the bed of the bone mineral amount measurement device can also be used as the bed for radiography, but as described below, the value of the bone mineral amount measurement is affected by the bed height, and it is difficult to use the bed as it is. It is. This will be described with reference to FIGS.
[0006]
In FIG. 7, the bone mineral amount measuring device is configured such that a lower unit 14 provided with an X-ray generator 16 therein and an upper unit 20 provided with an X-ray detector 22 are integrally movable. Then, the bed 12 and the bone mineral measuring device are assembled so that the bed is arranged between the lower unit 14 and the upper unit 20. A subject 24 is placed on the bed 12. The X-ray generator 16 irradiates the lumbar vertebra 26 of the subject 24 with the X-ray beam 18 spread in a fan shape, and the X-ray transmitted through the subject 24 is detected by the X-ray detector 22.
[0007]
In order to accurately measure the amount of bone mineral in the lumbar vertebra, an X-ray beam is scanned from the second lumbar vertebra to the fourth lumbar vertebra in the case of a plurality of bones, for example, a human body. That is, the X-ray generator 16 and the X-ray detector 22 are integrated, and the pitch P ₀ X-ray beam is sequentially scanned along a scan line set for each pitch feed, and a plurality of lumbar vertebrae are sequentially irradiated with X-rays.
[0008]
FIGS. 7A and 7B show how the irradiation of the lumbar spine 26 with the X-ray beam is affected when the operating conditions of the bone mineral amount measuring device are the same and the bed height is different. FIG. The height of the bed 12 is based on the floor 9. Now, paying attention to the irradiation of the X-ray beam at the position of the lumbar vertebra, the pitch feed P ₀ When the overlapping of the boundaries of the passing areas of the adjacent X-ray beams 18 between the adjacent scanning lines when the scanning is performed, the bed height A shown in FIG. ₀ In, the passing areas of the adjacent X-ray beams 18 exactly coincide with each other at the boundary, and there is no overlap. On the other hand, the bed height A in FIG. ₁ In the above, the bed height A earlier ₀ Due to the higher height, the passage areas of the adjacent X-ray beams 18 overlap at the boundary, and overlap occurs.
[0009]
FIGS. 8A and 8B show X-ray imaging data 100a and 100b corresponding to FIGS. 7A and 7B, respectively. The X-ray imaging data 100a and 100b include the X-ray imaging data 102a and 102b on the first scanning line, the X-ray imaging data 104a and 104b on the second scanning line, and the X-ray imaging data on the third scanning line. It consists of imaging data 106a and 106b. In the case of (a), at the position of the lumbar vertebra, the passing areas of the adjacent X-ray beams 18 between the adjacent scanning lines are aligned at the boundary, so that the imaging data 108a, 110a, 112a, 114a faithful to the outer shape of each lumbar vertebra is obtained. . On the other hand, in the case of (b), since the overlapping portions 120 and 122 occur in the passage areas of the adjacent X-ray beams 18 between the adjacent scanning lines at the position of the lumbar vertebra, the imaging data 108b which is not always true to the outer shape of each lumbar vertebra , 110b, 112b, 114b.
[0010]
In the opposite case, that is, the height of the bed 12 is the bed height A in (a). ₀ If it is lower than the above, a gap is generated in the passage area of the adjacent X-ray beam 18 between the adjacent scanning lines at the position of the lumbar vertebra, resulting in imaging data that is not always faithful to the outer shape of each lumbar vertebra.
[0011]
As described above, in the bone mineral amount measuring device, the overlap or gap occurs in the imaged data depending on the height of the bed, and the fidelity of the data differs. Therefore, in order to properly obtain the two-dimensional distribution of the bone mineral density, it is necessary to use a bed having an appropriate bed height suitable for the bone mineral density measuring device.
[0012]
In this way, a bed other than a bed of an appropriate bed height suitable for the bone mineral density measuring device, for example, another existing bed such as a bed for X-ray photography, is used as it is as a bed for the bone mineral density measuring device or When used together, the two-dimensional distribution of bone mineral density is affected by the bed height, and accurate measurement of bone mineral density may be difficult. In addition, in order to adjust each bed height to an appropriate bed height only by mechanical adjustment, for example, an accurate jack-up mechanism or the like is required, which increases costs.
[0013]
An object of the present invention is to solve the problem of the related art and to provide a bone mineral amount measuring apparatus capable of appropriately obtaining a two-dimensional distribution of bone mineral amount without adjusting the height of a bed. Another object of the present invention is to provide a bone mineral amount measuring device that utilizes an existing bed when performing bone mineral amount measurement and that can obtain a two-dimensional distribution of bone mineral amount properly, regardless of bed height adjustment. To provide.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a bone mineral density measuring apparatus according to the present invention is a bone mineral density measuring apparatus used in combination with a bed on which a subject is placed, and has a fan-shaped spread X in a pitch feed direction orthogonal to a beam scanning direction. An X-ray generator that forms a X-ray beam, an X-ray detector that is arranged to face the X-ray generator via the bed, and detects X-rays transmitted through the subject; A mechanism for moving relatively to the subject, by sequentially scanning the X-ray beam along a scan line in the beam scanning direction set for each pitch feed position in the pitch feed direction A scanning mechanism that executes a parallel scan, a data analysis unit that analyzes a two-dimensional distribution of bone mineral density based on a group of X-ray detection data obtained by the parallel scan, and the bed A control unit that changes operating conditions of the bone mineral density measurement device in accordance with the height of the bed so that a two-dimensional distribution of the bone mineral density is appropriately obtained regardless of the height. Features.
[0015]
According to the above configuration, when the bed height is not an appropriate bed height suitable for the bone mineral amount measuring device, the operating condition of the bone mineral amount measuring device is changed according to the bed height. Therefore, a two-dimensional distribution of the amount of bone mineral can be properly obtained without depending on the height of the bed.
[0016]
Further, it is preferable that the control unit changes the operation condition such that the X-ray beam passage areas are aligned between adjacent scan lines on a measurement reference plane assumed for the subject.
[0017]
Here, that the X-ray beam passage areas are aligned between adjacent scanning lines ideally means that the X-ray beam passage areas exactly coincide with each other in the range in which the two-dimensional distribution of bone mineral density can be appropriately obtained. However, it is sufficient that they substantially match on the X-ray imaging data. According to the above configuration, when the bed height is not an appropriate bed height that is suitable for the bone mineral amount measuring device, the operating condition of the bone mineral amount measuring device is changed according to the bed height, and the adjacent scan is performed. The X-ray beam passage areas between the lines are aligned. Therefore, it is possible to obtain a two-dimensional distribution of an appropriate amount of bone mineral without any overlap or gap without adjusting the height of the bed.
[0018]
Further, it is preferable that the change of the operating condition is to change a pitch between adjacent scan lines in the parallel scan. With the above configuration, the pitch between adjacent scanning lines is changed to make the X-ray beam passage areas between adjacent scanning lines uniform. Changing the pitch between adjacent scanning lines can be easily realized by changing the operating conditions of the X-ray beam scanning mechanism already provided. Therefore, the two-dimensional distribution of the amount of bone mineral can be properly obtained regardless of the height of the bed by a simple method of changing the pitch.
[0019]
Further, it is preferable that the change of the operation condition is to change a spread angle of the X-ray beam. With the above configuration, the spread angle of the X-ray beam is changed to make the X-ray beam passage areas between adjacent scanning lines uniform. Therefore, the two-dimensional distribution of the amount of bone mineral can be properly obtained regardless of the height of the bed while the setting of the spread angle of the X-ray beam of the X-ray generator is changed.
[0020]
Further, in the bone mineral density measurement device according to the present invention, the X-ray detector includes a plurality of X-ray detection elements arranged in the beam scanning direction, and the X-ray detection data group includes the plurality of X-rays. A plurality of X-ray detection data obtained by a plurality of X-ray detection elements belonging to an effective detection aperture among the detection elements, wherein the change of the operating condition is based on the size of the effective detection aperture for the plurality of X-ray detection elements. It is preferable to change the length.
[0021]
With the above configuration, the size of the effective detection aperture is changed for the plurality of X-ray detection elements of the X-ray detector to make the X-ray beam passage areas between adjacent scanning lines uniform. For example, when overlap occurs, the effective detection aperture is narrowed so that the X-ray beam passage areas between adjacent scan lines do not overlap. The change of the effective detection aperture can be performed by electronic processing of a plurality of X-ray detection elements, and can be performed without requiring other mechanical processing. Therefore, the two-dimensional distribution of the amount of bone mineral can be properly obtained regardless of the height of the bed by the electronic processing.
[0022]
Further, the change of the operating condition includes changing the pitch between the adjacent scanning lines, changing the spread angle of the X-ray beam, and changing the size of the effective detection aperture for the plurality of X-ray detection elements of the X-ray detector. In addition to performing these operations independently, it is also possible to combine two or more of these operating conditions.
[0023]
Further, the bone mineral density measuring device according to the present invention, in a bone mineral density measuring device used in combination with a bed on which a subject is placed, forms an X-ray beam spread in a fan shape in a pitch feed direction orthogonal to a beam scanning direction. An X-ray generator, an X-ray detector arranged to face the X-ray generator via the bed, and detecting X-rays transmitted through the subject; the X-ray generator and the X-ray detector A mechanism for moving a measurement unit composed of a measuring device relative to the subject, along a scan line in the beam scanning direction set for each pitch feed position in the pitch feed direction. A scanning mechanism for executing a parallel scan by sequentially scanning an X-ray beam, and a system for changing a pitch between adjacent scan lines in the parallel scan according to the height of the bed. Characterized in that it comprises a part, a.
[0024]
Further, the bone mineral density measuring device according to the present invention, in a bone mineral density measuring device used in combination with a bed on which a subject is placed, forms an X-ray beam spread in a fan shape in a pitch feed direction orthogonal to a beam scanning direction. An X-ray generator, an X-ray detector arranged to face the X-ray generator via the bed, and detecting X-rays transmitted through the subject; the X-ray generator and the X-ray detector A mechanism for moving a measurement unit composed of a measuring device relative to the subject, along a scan line in the beam scanning direction set for each pitch feed position in the pitch feed direction. A scanning mechanism that performs a parallel scan by sequentially scanning the X-ray beam, and a control unit that changes a spread angle of the X-ray beam according to the height of the bed. That.
[0025]
Further, the bone mineral density measuring device according to the present invention, in a bone mineral density measuring device used in combination with a bed on which a subject is placed, forms an X-ray beam spread in a fan shape in a pitch feed direction orthogonal to a beam scanning direction. An X-ray generator, means for detecting the X-rays transmitted through the subject, the X-ray generator being opposed to the X-ray generator via the bed, and comprising a plurality of X-rays arranged in the beam scanning direction. An X-ray detector constituted by a detection element; and a mechanism for moving a measurement unit constituted by the X-ray generator and the X-ray detector relative to the subject, wherein the pitch feed A scanning mechanism for performing a parallel scan by sequentially scanning the X-ray beam along a scanning line in the beam scanning direction set for each pitch feed position in a direction, and a height of the bed. A control unit that changes the size of the effective detection aperture for the plurality of X-ray detection elements, and a plurality of X-ray detection elements belonging to the effective detection aperture among the plurality of X-ray detection elements. A data analysis unit that analyzes a two-dimensional distribution of bone mineral density based on the plurality of pieces of detected data.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same elements as those in FIG. 7 are denoted by the same reference numerals. Also, in the following, a bed for radiography is described as a bed used in combination with the bone mineral amount measuring device, but this is merely an example and may be another existing bed, Any bed other than a bed having an appropriate bed height suitable for the measuring device can be widely applied.
[0027]
FIG. 1 is a diagram showing a bone mineral density measuring device 10 used in combination with a bed 12 of an X-ray imaging apparatus 40 in an X-ray room. The X-ray imaging apparatus 40 includes a rail 42, a shaft 44 having a telescopic mechanism, and an X-ray source 46, and the X-ray imaging bed 12 is installed on the floor 9 of the X-ray room. When using the bone mineral density measuring device 10, the X-ray source 46 can be raised sufficiently by using the telescopic mechanism of the shaft 44 and retracted to a position sufficiently far from the bed 12 by using the rail 42. Note that, in the directions shown in the figure, the short direction of the bed 12 is the X direction, the long direction is the Y direction, and the vertical direction is the Z direction.
[0028]
An X-ray bed 12 arranged on the floor 9 in the X-ray room includes a table including a frame and legs, and an acrylic plate supported by a frame above the table. The acrylic plate transmits X-rays. A photographing cassette (book portion) 13 is provided below the acrylic plate, and can be slid in the Y direction by a slide mechanism (not shown).
[0029]
The bone mineral density measuring device 10 used in combination with the bed 12 is roughly divided into a lower unit 14, an upper unit 20, and a connecting unit 21. When combined with the bed 12, the lower unit 14 is located below the bed 12, and the upper unit 20 is located above the bed 12. An X-ray generator is provided inside the lower unit 14, and an X-ray detector is provided inside the upper unit 20.
[0030]
FIG. 2 is a block diagram of the bone mineral density measuring device 10. As will be described in more detail below, the bone mineral density measuring device 10 uses the B. Changing the pitch P between adjacent scanning lines in the moving mechanism 50; B. changing the spread angle θ of the X-ray beam in the X-ray generator 16; The operating conditions for the effective detection aperture N × ΔD in the X-ray detector 22 are changed. These three changes in operating conditions may be used alone, or two or more operating conditions may be used in combination.
[0031]
In the figure, an X-ray generator 16 is a device that generates X-rays of necessary energy. The X-ray generator 16 is provided with a beam collimator, and can set the directivity of the emitted X-ray beam 18. Here, an explanation will be given on the assumption that an X-ray beam 18 emitted upward from the X-ray generator 16 and spread in a fan shape at an angle θ in the YZ plane in FIG. 1 is used. As such an X-ray beam, a so-called fan beam can be used, and a pencil beam can also be treated as a fan-shaped spread X-ray beam although the value of the angle θ is small. The value of the angle θ can be changed by, for example, changing the condition of the beam collimator under the control of the control unit 58 described later. The details will be described in the section B below.
[0032]
The X-ray detector 22 is a device that arranges detection elements sensitive to X-rays in an array and detects X-rays transmitted through the subject 24. For example, an array element in which a plurality of detection elements are arranged in a line is used. FIG. 3 is a diagram illustrating an effective detection aperture of the X-ray detector 22 by taking an example of an array element in which a plurality of detection elements 23 are arranged in a line in the Y direction. In this case, when the two-dimensional distribution of bone mineral density is measured using N detection elements, N × ΔD is the effective detection aperture of the X-ray detector 22 when the size of the detection elements in the arrangement direction is ΔD. For example, assuming that N = 10, detection is performed by the detection elements of 10 channels. The effective detection aperture can be changed under the control of the control unit 58. The details will be described in the section C below.
[0033]
The moving mechanism 50 scans the subject 24 with the X-ray beam 18 by moving the measuring unit 52 composed of the X-ray generator 16 and the X-ray detector 22 integrally with respect to the bed 12. It is a mechanism to make it. The movement, that is, the scanning of the subject 24 with the X-ray beam 18 is performed as shown in FIG.
[0034]
FIG. 4 is a diagram schematically showing the state of scanning of the X-ray beam 18 as the locus of the center point of the X-ray beam 18 on the surface of the bed 12, that is, the XY plane shown in FIG. The position of the lumbar vertebra 26 to be scanned is also shown for reference. As shown in the figure, the X-ray beam 18 has scanning lines 70 a, 70 b, and 70 provided in the X direction at each pitch feed position different by a pitch P, with the X direction as the beam scanning direction and the Y direction as the pitch feeding direction. Scanning is sequentially performed along 70c. That is, the X-ray beam 18 scans the region of the subject 24 necessary for the bone mineral density measurement by dividing the scanning path into a plurality of scanning paths by parallel scanning. The pitch P between adjacent scanning lines can be changed by the control unit 58. The details will be described in the section A below.
[0035]
Returning to FIG. 2 again, the data processing unit 54 processes the X-ray detection data obtained by the X-ray detector 22. The data analysis unit 56 analyzes the two-dimensional distribution of the bone mineral density based on the data-processed X-ray detection data output from the data processing unit 54 and calculates the value of the bone mineral density. For example, a function of calculating the bone mineral density of the subject by calculating the bone mineral density for each measurement point at each measurement point from the X-ray detection data from the detection element of the X-ray detector, and calculating and displaying the total. Have.
[0036]
The control unit 58 controls each element of the bone mineral density measuring device 10. For example, a general computer can be used. Information regarding the height of the bed 12 is input to the control unit 58 manually or automatically from a measuring instrument (not shown). The control unit 58 controls the pitch P between adjacent scanning lines in the moving mechanism 50, the spread angle θ of the X-ray beam in the X-ray generator 16, the effective detection aperture in the X-ray detector 22, based on information on the height of the bed 12. Control is performed to change the operating condition for N × ΔD. As the information on the height of the bed 12, the height A from the floor 9 to the upper surface of the bed 12 can be used. In addition, the difference ΔA between the measurement reference plane assumed for the lumbar vertebra 26 to be measured of the subject 24 placed on the bed 12 and the upper surface of the bed 12 can be added to the information on the height of the bed 12. .
[0037]
The change of the operating condition of the bone mineral density measuring device, which can appropriately obtain a proper two-dimensional distribution of the bone mineral density without adjusting the height of the bed, will be described separately. In the following, the bed height under the condition that the passing areas of the adjacent X-ray beams between the adjacent scanning lines are aligned at the boundary on the measurement reference plane assumed for the lumbar vertebra to be measured is defined as the standard bed height A. ₀ And Also, standard bed height A ₀ Pitch between adjacent scan lines for operating conditions under ₀ , The spread angle of the X-ray beam is θ ₀ , The effective detection aperture is N ₀ × ΔD.
[0038]
A. Changing the pitch P between adjacent scan lines
FIG. 5 shows the two-dimensional bone mineral density by changing the operating condition of the moving mechanism 50 by the control unit 58 and changing the pitch P between the adjacent scanning lines to align the X-ray beam passage areas between the adjacent scanning lines. It is a figure explaining the method of obtaining a distribution appropriately. (A) and (b) show that the height of the bed 12 from the floor 9 is A ₀ , A ₁ However, depending on the height, the pitch between adjacent scanning lines is also P ₀ , P ₁ Is changed. Other operating conditions are standard bed height A ₀ Do not change as it is the condition used in. The pitch between adjacent scan lines is such that, even if the height of the bed changes, the adjacent scan line is adjacent to the measurement reference plane 15 assumed for the lumbar vertebra 26 to be measured of the subject 24 placed on the bed 12. An appropriate pitch is set so that the matching X-ray beam passage areas are aligned at the boundary.
[0039]
Proper pitch P when adjacent X-ray beam passage areas exactly coincide with each other at the boundary ₁ Can be determined from equation (1) as a function of bed height. That is, the height from the floor 9 to the upper surface of the bed 12 is A ₁ , The height from the floor 9 to the concentration point of the X-ray beam 18 is B, the distance from the concentration point of the X-ray beam 18 to the X-ray detector 22 is L, and the effective detection aperture of the X-ray detector 22 is N ₀ × ΔD, when the distance from the upper surface of the bed 12 to the measurement reference surface 15 is ΔA,
(Equation 1)
P ₁ = N ₀ × ΔD × (A ₁ −B + ΔA) / L (1)
It becomes.
[0040]
B. Change of spread angle θ of X-ray beam
FIG. 6 shows that the control unit 58 changes the operating conditions of the X-ray generator 16 and changes the spread angle θ of the X-ray beam in the X-ray generator 16 to align the X-ray beam passage areas between adjacent scanning lines. FIG. 4 is a diagram for explaining a method for properly obtaining a two-dimensional distribution of bone mineral density. (A) and (b) show that the height of the bed 12 from the floor 9 is A ₀ , A ₁ , But the spread angle θ of the X-ray beam depends on its height. ₀ , Θ ₁ Is changed. Other operating conditions are standard bed height A ₀ Do not change as it is the condition used in. Even if the height of the bed changes, the divergence angle of the X-ray beam is adjacent to the lumbar vertebra 26 as the measurement target of the subject 24 placed on the bed 12 and is adjacent to the lumbar vertebra 26 in the adjacent scanning line. An appropriate spread angle is set so that the matching X-ray beam passage area is aligned at the boundary.
[0041]
Proper spread angle θ when adjacent X-ray beam passage areas exactly coincide with each other at the boundary ₁ Can be determined from equation (2) as a function of bed height. That is, similarly to the expression (1), the height from the floor 9 to the upper surface of the bed 12 is A ₁ , The height from the floor 9 to the concentration point of the X-ray beam 18 is B, the distance from the concentration point of the X-ray beam 18 to the X-ray detector 22 is L, and the standard bed height is A ₀ , The standard X-ray beam spread angle is θ ₀ As
(Equation 2)
tan (θ ₁ / 2) =
(A ₀ −B + ΔA) × tan (θ ₀ / 2) / (A ₁ −B + ΔA) (2)
It becomes.
[0042]
C. Change of effective detection aperture of X-ray detector
Next, the operating condition of the X-ray detector 22 is changed by the control unit 58 and the effective detection aperture of the X-ray detector 22 is changed, so that the boundary between the adjacent X-ray detection data between the adjacent scanning lines can be obtained. A method for preventing the overlap of the bone mineral density and appropriately obtaining the two-dimensional distribution of the bone mineral content will be described. Now, the pitch P between adjacent scanning lines used when the operating condition is a standard bed height is used. ₀ , X-ray beam spread angle θ ₀ , Effective detection aperture N of X-ray detector ₀ The bed height is set to the standard bed height A while keeping × ΔD ₀ Different bed height A ₁ , The X-ray detection data adjacent to each other between adjacent scanning lines overlap at the boundary. Assuming that the number of detection elements where X-ray detection data overlaps on the X-ray detector is n, an overlap area n × ΔD can be obtained from Expression (3).
[Equation 3]
n × ΔD = N ₀ × ΔD-P ₀ × L / (A ₁ −B + ΔA) (3)
The second term on the right side is an effective detection aperture on the X-ray detector when adjacent X-ray detection data does not overlap between adjacent scan lines. Therefore, the effective detection aperture is N ₀ × ΔD to (N ₀ By changing to (−n) × ΔD, duplication of X-ray detection data on the X-ray detector can be prevented. This change can be made for each detection element.
[0043]
In order to properly obtain the two-dimensional distribution of bone mineral density, in addition to changing the above three operating conditions alone, it is also possible to combine changes in a plurality of operating conditions. For example, the change of the spread angle θ of the X-ray beam and the change of the effective detection aperture N × ΔD or the change to the overlapping part processing in the data processing can be performed together. In addition, in that combination, in addition to using each of them in an equal relationship, a part that cannot be covered by a change in the main operation condition is mainly performed by changing one of the operation conditions, and another operation condition is subject to the other operation conditions. The conditions can be changed to supplement the details.
[0044]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the bone mineral amount measuring apparatus of this invention, the two-dimensional distribution of the bone mineral amount can be obtained appropriately regardless of the height adjustment of a bed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a bone mineral density measuring device used in combination with a bed of an X-ray imaging apparatus in an X-ray room.
FIG. 2 is a block diagram of a bone mineral density measuring device.
FIG. 3 is a diagram illustrating an effective detection aperture of an X-ray detector.
FIG. 4 is a diagram schematically showing a locus of a center point of an X-ray beam in a plane of a bed.
FIG. 5 is a diagram illustrating a method of appropriately obtaining a two-dimensional distribution of bone mineral density by changing a pitch P between adjacent scanning lines.
FIG. 6 is a diagram illustrating a method of appropriately obtaining a two-dimensional distribution of bone mineral content by changing the spread angle θ of the X-ray beam.
FIG. 7 is a diagram illustrating a state in which it is difficult to use the bed of the bone mineral amount measurement device as an X-ray imaging bed.
FIG. 8 shows X-ray imaging data corresponding to FIGS. 7A and 7B, respectively.
[Explanation of symbols]
9 floor, 10 bone mineral density measuring device, 12 bed, 14 lower unit, 15 measurement reference plane, 16 X-ray generator, 18 X-ray beam, 20 upper unit, 21 connecting unit, 22 X-ray detector, 24 subjects , 26 lumbar spine, 50 moving mechanism, 52 measuring unit, 54 data processing unit, 56 data analyzing unit, 58 control unit.

Claims (8)

In the bone mineral density measurement device used in combination with the bed on which the subject is placed,
An X-ray generator for forming an X-ray beam spread in a fan shape in a pitch feed direction orthogonal to the beam scanning direction;
An X-ray detector arranged to face the X-ray generator via the bed and detecting X-rays transmitted through the subject;
A mechanism for moving the X-ray beam relative to the subject, the X-ray beam along the scanning line in the beam scanning direction set for each pitch feed position in the pitch feed direction A scanning mechanism for performing a parallel scan by sequentially scanning;
A data analysis unit that analyzes a two-dimensional distribution of bone mineral density based on the X-ray detection data group obtained by the parallel scan,
A control unit that changes operating conditions of the bone mineral density measurement device according to the height of the bed so that a two-dimensional distribution of the bone mineral density is appropriately obtained regardless of the height of the bed,
An apparatus for measuring bone mineral density, comprising: The bone mineral density measurement device according to claim 1,
The bone mineral density measurement, wherein the control unit changes the operation condition such that an X-ray beam passage area is aligned between adjacent scan lines on a measurement reference plane assumed for the subject. apparatus. The bone mineral density measuring device according to claim 2,
The change of the operating condition is to change a pitch between adjacent scan lines in the parallel scan, wherein the bone mineral density measurement device is characterized in that: The bone mineral density measuring device according to claim 2,
The change of the operating condition is to change a divergence angle of the X-ray beam. The bone mineral density measuring device according to claim 2,
The X-ray detector includes a plurality of X-ray detection elements arranged in the beam scanning direction,
The X-ray detection data group is a plurality of X-ray detection data obtained by a plurality of X-ray detection elements belonging to an effective detection aperture among the plurality of X-ray detection elements,
The bone mineral density measuring device according to claim 1, wherein the change of the operating condition is to change a size of the effective detection aperture for the plurality of X-ray detection elements. In the bone mineral density measurement device used in combination with the bed on which the subject is placed,
An X-ray generator for forming an X-ray beam spread in a fan shape in a pitch feed direction orthogonal to the beam scanning direction;
An X-ray detector arranged to face the X-ray generator via the bed and detecting X-rays transmitted through the subject;
A mechanism for relatively moving a measurement unit including the X-ray generator and the X-ray detector with respect to the subject, the mechanism being set for each pitch feed position in the pitch feed direction. A scanning mechanism for performing a parallel scan by sequentially scanning the X-ray beam along a scanning line in a beam scanning direction;
A control unit that changes a pitch between adjacent scan lines in the parallel scan according to the height of the bed,
An apparatus for measuring bone mineral density, comprising: In the bone mineral density measurement device used in combination with the bed on which the subject is placed,
An X-ray generator for forming an X-ray beam spread in a fan shape in a pitch feed direction orthogonal to the beam scanning direction;
An X-ray detector arranged to face the X-ray generator via the bed and detecting X-rays transmitted through the subject;
A mechanism for relatively moving a measurement unit including the X-ray generator and the X-ray detector with respect to the subject, the mechanism being set for each pitch feed position in the pitch feed direction. A scanning mechanism for performing a parallel scan by sequentially scanning the X-ray beam along a scanning line in a beam scanning direction;
A control unit that changes a spread angle of the X-ray beam according to a height of the bed;
An apparatus for measuring bone mineral density, comprising: In the bone mineral density measurement device used in combination with the bed on which the subject is placed,
An X-ray generator for forming an X-ray beam spread in a fan shape in a pitch feed direction orthogonal to the beam scanning direction;
Means for detecting the X-rays transmitted through the subject, which are arranged opposite to the X-ray generator via the bed, and constituted by a plurality of X-ray detection elements arranged in the beam scanning direction. An X-ray detector,
A mechanism for relatively moving a measurement unit including the X-ray generator and the X-ray detector with respect to the subject, the mechanism being set for each pitch feed position in the pitch feed direction. A scanning mechanism for performing a parallel scan by sequentially scanning the X-ray beam along a scanning line in a beam scanning direction;
A control unit that changes the size of the effective detection aperture for the plurality of X-ray detection elements according to the height of the bed,
Based on a plurality of detection data obtained by a plurality of X-ray detection elements belonging to the effective detection aperture among the plurality of X-ray detection elements, a data analysis unit that analyzes a two-dimensional distribution of bone mineral density,
An apparatus for measuring bone mineral density, comprising:

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