JP5009744B2 - X-ray measuring device for forearm - Google Patents

Description

  The present invention relates to a forearm X-ray measuring apparatus, and more particularly to a bone density measuring apparatus for measuring the density of a forearm bone.

  A bone density (bone mineral content) measuring device is used for diagnosing bone properties, particularly osteoporosis. The bone density measuring device is a kind of X-ray measuring device, and various devices according to a target biological tissue (forearm, lumbar vertebra, heel, etc.) have been put into practical use.

  The measurement of bone density on the forearm is clinically performed at a predetermined site on the rib. Specifically, the forearm length is defined as the length between the proximal reference elbow head (capillary epiphysis) and the distal reference ulnar styloid process, and the forearm length is internally divided at a predetermined ratio. The position is the measurement site on the rib. The ratio includes 1/3, 1/6, 1/10, and the like. The measurement site is generally at a position displaced from the center of the rib to the wrist side. The proximal reference and the distal reference are defined as sites that can be easily identified from outside the body from the viewpoint of objectivity and reproducibility of the measurement. In order to measure bone density at an appropriate site, the position of each reference needs to be accurately recognized by the apparatus.

  The forearm bone density measuring device described in Patent Document 1 is provided with a plurality of slits into which the elbow pads are inserted, and the position of the elbow head is automatically recognized from the insertion position. On the other hand, the position of the ulnar styloid process is specified by manually adjusting the irradiation position of the light beam (laser light), specifically, the point where the position of the light spot matches the ulnar styloid process, The position of the ulnar styloid process is recognized. If the proximal reference and the distal reference can be specified, the measurement site for the rib can be specified. In addition, there is Japanese Patent Application No. 2006-196734 as an application related to this subject.

Japanese Patent No. 2735507

  However, in the conventional method, the placement surface on which the forearm is placed is inevitably enlarged. That is, it is necessary to form the mounting surface widely with a size that covers the entire forearm, in other words, it is necessary to secure a space for providing a plurality of slits for inserting the elbow pads on the mounting surface. Therefore, it is conceivable to provide a mechanism for sliding the elbow rest like a caliper so that the elbow rest can be positioned beyond the placement surface. However, in this case, if the position of the sliding elbow rest cannot be detected or recognized accurately, the accuracy of specifying the elbow head position is lowered, and consequently the positioning accuracy of the measurement site is lowered. Although it is possible to provide a high-accuracy position detector to detect the slide position, there arises a problem that the number of parts is increased and the apparatus configuration is thereby complicated. In addition, in the case of manual adjustment of the light beam, there is a problem that it is troublesome and takes time.

  An object of the present invention is to provide a forearm X-ray measuring apparatus capable of accurately specifying a measurement site with a simple configuration.

  Another object of the present invention is to provide a forearm X-ray measurement apparatus that does not require a complicated operation such as adjustment of a light beam by visual observation from outside the body.

  The present invention relates to an elbow rest applied to an elbow head forming a proximal reference in the forearm on the mounting surface, a slide mechanism for sliding the elbow rest in the X direction which is the forearm length direction, and the X direction of the elbow rest An X-ray marker that slides in the X direction in accordance with the sliding movement of the X-ray, a X-ray generator that irradiates the forearm on the placement surface with X-rays, and an X-ray transmitted through the forearm An X-ray detector that detects a line and outputs detection data; and a data processing unit that calculates a bone density of a predetermined measurement site in the forearm based on the detection data. The data processing unit includes: an image forming unit that forms a transmission image including a forearm image and an X-ray marker image based on the detection data; an X-direction position of the X-ray marker image; and the X-ray marker. X direction of the elbow rest And positional relationship, and the X-direction position of a predetermined portion forming a distal reference in the forearm, said calculating means for calculating the measurement site, to the forearm X-ray measuring apparatus which comprises a based on.

  According to the above configuration, it is only necessary to bring the elbow head into contact with the elbow head by the sliding motion of the elbow pad, so there is no need to provide a plurality of slits on the placement surface as in the conventional method, and the elbow head is temporarily placed. Even if it protrudes from the surface, the position can be easily and accurately specified. Therefore, the mounting surface can be reduced in size. The elbow rest position is indirectly specified as the position of the X-ray marker that slides with the elbow rest position. In this case, the positional relationship between the position of the elbow rest and the X-ray marker needs to be known (preferably fixed distance). The position of the X-ray marker can be specified by image analysis. That is, a transmission image is formed by transmission of X-rays to the forearm, and the position of the X-ray marker can be easily specified from the position of the X-ray marker image in the transmission image. Therefore, it is not necessary to provide a complicated mechanism for specifying the position. The transmission image may be a simple X-ray transmission image, but is a difference image (an image reflecting bone density) between an image by irradiation with high energy X-rays and an image by irradiation with low energy X-rays. desirable. If the latter image is an image serving as a basis for bone density calculation, it is not necessary to repeat scanning of the X-ray beam, so that the measurement time can be shortened. In order to identify an X-ray marker image in image analysis, it is desired that the X-ray marker has an X-ray absorption (transmission) characteristic different from that of bone or soft tissue, and it is separated from bone or soft tissue. It is desirable to slide the area. Although the proximal reference is automatically recognized as described above, several modes can be considered as a method for recognizing the distal reference. First, there is a method of specifying a distal reference (generally an ulnar styloid process) by image analysis. In this case, the burden on the user can be greatly reduced. Second, a method of displaying a transmission image and allowing the user to designate the position of the distal reference on the screen is conceivable. In this case, user operation is required, but it is only necessary to specify one point on the image. Therefore, the operation is performed more than when the position of the laser beam is adjusted stepwise by repeatedly pressing (input) the button as in the past. The burden can be reduced. In particular, in the past, it was necessary to specify the position of the distal reference such as the ulna-shaped protrusion from outside the body through the skin. However, if the identification is performed based on the image, high-precision identification based on the actual bone morphology Can be done.

  Preferably, the scale mechanism includes a positioning unit that contacts the forearm on the placement surface to position the forearm in the Y direction, and the X-ray of the placement surface is determined by positioning the forearm in the Y direction. An offset area where the forearm does not exist is set in the irradiation area, and the slide motion path of the X-ray marker is included in or passes through the offset area. According to this configuration, it is possible to eliminate the possibility that the X-ray marker overlaps the living tissue in the transmission image and the identification accuracy is lowered.

  Preferably, in the X-ray marker, the detection target portion particularly slides in the space below the placement surface. According to this configuration, the operability is improved because the X-ray marker does not get in the way. Preferably, the slide mechanism includes a rod member that holds and slides the elbow rest, and the X-ray marker is connected to the rod member. According to this configuration, since the positional relationship between the elbow pads and the X-ray markers is fixed, the position of the elbow pads can be specified with high accuracy.

  Preferably, the calculation means includes means for calculating the position of the ulnar styloid process which is a predetermined part as the distal reference by image processing of the transmission image. According to this configuration, the user burden can be greatly reduced. Preferably, the display includes a display for displaying the transmission image, and a position input unit for allowing the user to specify the position of the ulnar styloid process, which is a predetermined site as the distal reference, on the transmission image. According to this configuration, simple and accurate coordinate designation is possible by visual judgment.

Desirably, a plurality of X-ray markers having different X-ray transmission characteristics are provided as the X-ray markers. According to this configuration, for example, the X-ray detection area (effective area) is small,
It is possible to cope with a case where the X-ray marker protrudes from the effective area. That is, a plurality of X-ray markers may be provided so as to be separated from each other, and at least one X-ray marker may belong to the effective area regardless of the forearm length. In the case where a left arm slide mechanism and a right arm slide mechanism are provided, an X-ray marker may be provided for each. In that case, it is desirable to make the X-ray absorption characteristics different for those X-ray markers, but if they can be discriminated from the measurement situation (for example, when only one of them enters the effective area), the X-ray absorption characteristics are different. The absorption characteristics may be matched.

  As described above, according to the present invention, the measurement site can be accurately identified with a simple configuration. Alternatively, the reference position can be specified without requiring a complicated operation such as adjustment of the light beam.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIGS. 1 to 3 are views showing an appearance of a bone density measuring device 10 which is an X-ray measuring device for forearm, FIG. 1 is a perspective view, FIG. 2 is a right side view, and FIG. 3 is a front view. It is. The bone density measuring device 10 includes a main body 12 in which a device for measuring bone density is housed, and a pedestal on which the main body 12 is placed, and supports the leg by tilting it at a predetermined height position and a predetermined angle. 14 and. In the case of this embodiment, the inclination is, for example, 10 °. Of course, the tilt angle may be variable. The leg 14 is provided with a plurality of casters 16 with a stop function.

  The main body 12 includes a base 20 whose upper surface is a mounting table 18 on which the forearm is placed, an arm 22 that covers the upper portion of the base 20 so that the forearm is positioned between the base 20 and the base 20. And a wall portion 24 that stands and supports the arm portion 22. A top plate 26 made of a material capable of transmitting X-rays is disposed at substantially the center of the mounting table 18. Further, a grip 28 that is gripped by the hand of the forearm to be inspected at the time of measurement is disposed immediately next to the top plate 26. An elbow pad 30 </ b> L that contacts the elbow of the forearm is provided on the rod 34 </ b> L that penetrates the rod support portion 32. The grip 28 is positioned on the right side of the top plate 26 in FIGS. 1 to 3, but may be positioned on the left side. That is, FIGS. 1 to 3 show a state for measuring the left arm. When measuring the right arm, the positional relationship between the grip 28 and the elbow rest to be used is reversed.

  FIG. 4 is a plan view in which a part of the arm portion 22 is omitted so that the configuration on the mounting table 18 can be seen. A pair of contact pads 36 are provided on the left and right sides of the rod support portion 32 to contact the side surfaces of the forearm and perform positioning in the back direction (Y direction perpendicular to the longitudinal direction when the longitudinal direction of the forearm is the X direction). ing. Further, FIG. 4 shows an elbow pad 30R and a rod 34R for the right arm in addition to the elbow pad 30L and the rod 34L for the left arm. The right arm elbow rest 30R is used as a grip fitting when measuring the left arm. The two rods 34L and 34R are slidable independently in the X direction.

  FIG. 5 is a block diagram showing a configuration relating to a measurement unit provided inside the main body 12. An X-ray generator 38 and a power supply 40 that supplies power to the X-ray generator 38 are accommodated in the base 20 of the main body 12. The X-ray generator 38 irradiates fan beam-shaped X-rays spreading in the Y direction, and the irradiated X-rays are detected by an array-type detection unit 42 housed in the arm unit 22. The detection unit 42 includes a detection element array that forms a one-dimensional array corresponding to the shape of the fan beam. Instead, a two-dimensional array type detector may be used. The X-ray generator 38 and the detection unit 42 are coupled by a bracket 44 and move integrally in the main body 12 in the X direction (left and right direction in FIG. 4). The X-ray beam shape may be a pencil beam or a cone beam in addition to a fan beam. The direction in which the X-ray generator 38 can be moved is determined according to the beam shape.

  Two-dimensional X-ray data can be collected by irradiating fan beam-shaped X-rays with the X-ray generator 38 and moving and scanning them in the X direction while being detected by the detector 42. This data is taken into the control unit 46, predetermined processing is executed, and bone density is calculated. Specifically, irradiation of high energy X-rays and low energy X-rays is repeated over the entire measurement area (effective area), thereby forming a first transmission image and a second transmission image, and a predetermined subtraction calculation for them. As a result, a transmission image (bone density image) in which the bone component is represented by excluding the soft tissue component is formed. Such a two-dimensional image is displayed as necessary, and data of a predetermined partial region (measurement site in the rib) in such a two-dimensional image is extracted, and based on this, bone mineral content is obtained as an average surface density. That is, the bone density is calculated. In determining the measurement site, it is first necessary to determine the distance (forearm length) from the elbow head as the proximal reference to the ulnar styloid process as the distal reference. Although specified, in the present embodiment, the position of the elbow rest is indirectly detected as the position of the X-ray marker that moves together with the elbow rest as described later. As will be described later, the distal reference is specified by the user on the screen or specified by image analysis. When the forearm length is calculated in this way, the position where the forearm length is internally divided at a predetermined ratio is determined as the center position of the measurement site. The measurement site is defined as a region having a certain width in the X direction centered on the center position in the rib.

  The main body 12 is provided with a data processing unit that constitutes an image forming unit and a calculation unit, which are not shown. The data processing unit is composed of a microcomputer and other data processing units. The image forming unit forms the above-described two-dimensional transmission image for bone density calculation, and the calculation unit executes calculation for specifying the measurement site.

  FIG. 6 is a view showing a state where the left arm 48 is positioned on the mounting table 18. In this state, bone density measurement is performed. FIG. 6 also shows the bones of the forearm for illustrative purposes. The bone inside the arm, that is, the lower side of FIG. 6 is the radius 50, and the other is the ulna 52. The protrusion existing near the distal end of the ulna 52 is the ulnar styloid process 54, and the proximal end is the elbow head 56. With the left hand gripping the grip 28, the left arm 48 is positioned on the mounting table 18 by bringing the side surface of the left arm into contact with the two contact pads 36. As shown in the figure, since the grip 28 is positioned on the right side of the top plate 26, the distal end sides of the radius 50 and the ulna 52 are positioned on the top plate 26 that is the X-ray irradiation range. . In this state, the rod 34L is slid to bring the elbow rest 30L into contact with the elbow head 56.

  FIG. 7 is a perspective view showing details of the scale mechanism. The scale mechanism is composed of two elbow pads 30L and 30R and a slide mechanism that slides them in the X direction. The latter slide mechanism supports (holds) two rods 34L and 34R and slidably supports them. ) Rod support portion 32. The two elbow pads 30L and 30R also function as a mounting portion for the grip 28, and when one is used as an elbow pad, the other is used as a mounting portion for the grip 28. The grip 28 is formed with an engagement hole into which the elbow pads 30L and 30R are inserted. The elbow pads 30L and 30R to which the grip is attached are positioned at the most retracted position (origin position), and when the grip 28 is attached in this state, a sensor (not shown) is used. The attachment is detected (left / right identification), and the sliding movement of the rod connected to the elbow rest to which the grip 28 is attached is restricted. That is, only the other rods can slide independently.

  In the present embodiment, X-ray markers 100 and 102 are connected to the rods 34L and 34R in order to detect the positions of the elbow pads 30L and 30R. Specifically, the X-ray marker 100 is fixed to the rod 34L, and the X-ray marker 100 is fixed in the X direction even if the elbow rest 30L is positioned according to various arm lengths. It is determined to belong to an effective area (X-ray irradiation area). The X-ray marker 102 is fixed to the rod 34R under the same conditions. The X-ray markers 100 and 102 have an L shape, which is composed of a vertical portion and a horizontal portion. The upper end of the vertical part is connected to the rods 34L, 34R. The tip portions 100a and 102a of the horizontal portion slide under the top plate, and specifically slide within the effective area as viewed from above, and appear as marker images in a transmission image formed by beam scanning. This will be described later.

  FIG. 8 shows a configuration on the placement surface. The tip surfaces of the two pads 36 are brought into contact with the side surfaces of the arms, thereby forming an offset region 112 in which entry of the arms is restricted. That is, the Y direction end portion (the upper end portion in FIG. 8) in the effective area 110 functions as an area where the X-ray markers 100 and 102 can be observed without being shielded by the living body. In other words, it is possible to perform marker measurement by effectively using an empty space.

  The two X-ray markers 100 and 102 may have different X-ray absorption characteristics. For example, you may comprise them with a different material and different thickness. If an X-ray absorption characteristic different from that of a living body (tissue, bone) is provided, marker extraction can be easily performed in image analysis. Of course, if the marker is observed only for specific coordinates in the Y direction, discrimination from the tissue becomes unnecessary. The two X-ray markers 100 and 102 may have the same X-ray absorption characteristics. In this case, basically, when one X-ray marker belongs to the effective area, it is assumed that the other X-ray marker is positioned outside the effective area. You may make it arrange | position two X-ray markers which have mutually different X-ray absorption characteristics mutually spaced apart with respect to one rod. According to this structure, there exists an advantage that it can measure beyond the measurement range of the elbow rest position by one X-ray marker. In other words, even if the slide amount increases according to the length of the arm (or even if the size of the effective area in the X direction is small), the position of the elbow rest can be reliably measured. In the present embodiment, the tip portion of the X-ray marker has a rectangular shape when viewed from above, but may have a sharp shape or the like in order to increase the accuracy of position identification by image analysis. Since the relationship (distance) between the X-direction position of the elbow rest and the X-direction position of the X-ray marker that moves with the elbow rest is known, the X-direction position of the elbow rest is indirectly specified using the relationship.

  In this embodiment, the position of the elbow head as the proximal reference is calculated as described above, while the position of the ulnar styloid process as the distal reference is specified by user designation on the image or specified by image analysis. Is done. In the former case, a transmission image is displayed. The transmission image may be a simple transmission image, but is preferably a difference image that is the basis of bone density calculation. On the transmission image, the position (X-direction position) of the ulnar styloid process is designated by the user using a pointing device. In the latter case, image analysis processing such as ulna / radius extraction processing and epiphysis specifying processing is performed on the transmission image, and the position of the ulnar styloid process (X-direction position) is automatically calculated.

  In FIG. 9, a transmission image 104 is shown, which includes a bone image 106 and a marker image 108. The bone image 106 includes an ulna image 110 and a rib image 112. The position Xr2 of the elbow head is specified based on the known length L1 from the position Xm of the marker image 108, while the position Xr1 of the ulnar styloid process is specified by user designation or by image analysis. Thereby, the forearm length L is calculated between them. The center position of the measurement site is determined as a position where the forearm length L is internally divided by a predetermined ratio a / b. It is represented by Xp. A region 116 having a constant width centered on the position Xp in the rib is a region for bone density calculation. Specifically, the data of the region 116 is extracted from the transmission image as the difference image, and the bone density is calculated by performing a predetermined calculation on the data. Of course, various methods are conceivable as a method for specifying the measurement site. In any case, since the position of the elbow rest is specified using the marker, it is not necessary to provide a complicated coordinate detection mechanism for the rod. In this sense, the configuration of the apparatus can be simplified and the position specifying accuracy can be increased. The position of the marker image can be calculated as the center position of the two edges in the X direction, but the right or left edge may be used as the marker position. Which X-ray marker is used can be easily identified by recognizing the grip attachment target or from the level of the X-ray marker image.

  Next, the operation will be described with reference to FIG. In S101, the forearm is placed on the placement surface. In S102, in this example, it is specified from the identification of the grip attachment target whether the target forearm is the left arm or the right arm. That is, which elbow rest, rod, and X-ray marker have been used are identified. In S103, the elbow rest is brought into contact with the elbow head, and in S104, the X beam is scanned in the X direction. Since the X beam is a fan beam that extends in the entire Y direction, beam scanning in the Y direction is unnecessary, and the entire effective area can be scanned only by beam scanning in the X direction. In beam scanning, irradiation with high energy X-rays and irradiation with low energy X-rays are alternately and repeatedly executed. Thereby, detection data obtained by irradiation with high energy X-rays and detection data obtained by irradiation with low energy X-rays are obtained. Two transmission images are formed based on the detection data, and a bone density calculation image as a difference image is generated by a predetermined difference calculation of the two transmission images. In S105, the position Xm of the marker image is calculated by image analysis. Thereby, the position Xr2 of the elbow head is specified. When the manual designation mode is recognized in S106, an image is displayed on the screen in S107, and the position Xr1 of the ulnar styloid process is specified by the user on the screen. On the other hand, when the automatic analysis mode is recognized in S106, the position Xr1 of the ulnar styloid process is specified by image analysis in S109. In S110, the forearm length L is calculated, and based on this, the center position Xp of the measurement site is calculated. Then, data corresponding to the measurement site is extracted from the bone density calculation image, and the bone density is calculated based on the data and displayed.

  In the above embodiment, the elbow head position is specified by sliding the elbow rest, so even if the elbow head exists beyond the mounting table, the position can be specified accurately. is there. That is, there is an advantage that the apparatus can be downsized. Further, since the position of the elbow rest is specified by image analysis of the marker image, it is not necessary to incorporate a complicated detector in the slide mechanism, and the position specifying accuracy can be improved. In addition, since the user-specified or automatic designation method on the image is used to specify the position of the ulnar styloid process, manual positioning of the laser beam outside the body is unnecessary, and the entire actual bone is observed. The ulnar styloid process can be easily and accurately specified. The method according to the present embodiment can be applied to a forearm X-ray measuring apparatus other than the bone density measuring apparatus.

It is a perspective view which shows the external appearance of the bone density measuring apparatus of this embodiment. It is a right view which shows the external appearance of the bone density measuring apparatus of this embodiment. It is a front view which shows the external appearance of the bone density measuring apparatus of this embodiment. It is a top view of the bone density measuring device of this embodiment. It is a figure for demonstrating the function inside a main body. It is a top view of the bone density measuring device of this embodiment. It is a perspective view which shows a scale mechanism. It is a figure for demonstrating the function of a X-ray marker. It is a figure for demonstrating the calculation method of a measurement site | part. It is a flowchart for demonstrating operation | movement.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Bone density measuring device, 12 main body, 14 legs, 18 mounting base, 22 arm part, 28 grip, 30L, 30R elbow rest, 32 rod support part, 34L, 34R rod, 36 contact pad, 48 forearm, 50 rib , 52 ulna, 54 ulnar styloid, 56 olecranon, 100,102 X-ray marker.

Claims (7)

An elbow rest applied to an elbow head that is a proximal reference in the forearm on the placement surface, a slide mechanism that slides the elbow rest in the X direction that is the forearm length direction, and a sliding movement in the X direction of the elbow rest An X-ray marker that slides in the X direction with the scale mechanism;
An X-ray measurement unit comprising: an X-ray generator that irradiates the forearm on the placement surface with X-rays; and an X-ray detector that detects X-rays transmitted through the forearm and outputs detection data; ,
A data processing unit that calculates a bone density of a predetermined measurement site in the forearm based on the detection data;
The data processing unit
An image forming means for forming a transmission image including a forearm image and an X-ray marker image based on the detection data;
The measurement site is determined based on the X-direction position of the X-ray marker image, the positional relationship between the X-ray marker and the elbow rest in the X direction, and the X-direction position of a predetermined site that forms a distal reference in the forearm. Computing means for computing;
A forearm X-ray measuring apparatus comprising: The apparatus of claim 1.
The scale mechanism includes a positioning unit that contacts the forearm on the placement surface and positions the forearm in the Y direction,
By positioning the forearm in the Y direction, an offset area in which the forearm does not exist is set in the X-ray irradiation area of the placement surface,
The forearm X-ray measurement apparatus characterized in that the slide motion path of the X-ray marker is included in or passes through the offset area. The apparatus of claim 2.
The X-ray marker for forearm, wherein the X-ray marker slides in a space below the placement surface. The apparatus of claim 3.
The slide mechanism includes a rod member that holds and moves the elbow rest,
The X-ray measurement apparatus for forearm, wherein the X-ray marker is connected to the rod member. The apparatus according to any one of claims 1 to 4,
The forearm X-ray measurement apparatus characterized in that the calculation means includes means for calculating the position of an ulnar styloid process, which is a predetermined site as the distal reference, by image processing of the transmission image. The apparatus according to any one of claims 1 to 4,
A display for displaying the transparent image;
A position input device for allowing the user to specify the position of the ulnar styloid process that is a predetermined site as the distal reference on the transmission image;
A forearm X-ray measuring apparatus comprising: The apparatus of claim 1.
A forearm X-ray measuring apparatus, wherein a plurality of X-ray markers having different X-ray transmission characteristics are provided as the X-ray markers.

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