JP2009145266A - X-ray measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for recognizing the enlarged state of an X-ray image in an X-ray measuring device using an X-ray beam spreading like a fan. <P>SOLUTION: An X-ray generator 10 generates X-rays (X-ray beams) 11 spreading like a fan, and an X-ray detector 12 detects the X-rays 11 generated by the X-ray generator 10. An X-ray image forming section 20 forms image data of the X-ray image based on the detection result of the X-rays 11. A measuring pedestal 14 moves along a route of the X-rays (X-ray beams) 11 from generation to detection, and positions an analyte 40. A reference object is disposed fixedly on the measuring pedestal 14. A control section 30 recognizes the enlarged state of the X-ray image varying according to the position of the measuring pedestal 14, based on the size of the reference object on the X-ray image obtained from the detection result of the X-rays 11 transmitting through the reference object, and the actual size of the reference object. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an X-ray measurement apparatus, and more particularly to an X-ray measurement apparatus that uses an X-ray beam that spreads in a fan shape.

  In an X-ray measuring apparatus such as a bone density measuring apparatus using the DXA method (Dual X-ray Absorptiometry), high energy X-rays and Energy X-rays are alternately irradiated at a constant cycle. As the X-ray beam to be scanned, a pencil-shaped beam or the like is known, but using an X-ray beam spreading in a fan shape can secure a wider area that can be measured by one beam irradiation.

  However, the fan-shaped X-ray beam is irradiated from the X-ray generator toward the X-ray detector so as to gradually expand the size (spread) of the beam. The size of the subject detected by the X-ray detector changes depending on the distance between the subject and the X-ray detector. For example, the X-ray image of the subject is smaller when the measurement table is closer to the X-ray detector than when the measurement table on which the subject is placed is far from the X-ray detector.

  As described above, when an X-ray beam that spreads in a fan shape is used, the size of the X-ray image of the subject, that is, the enlargement ratio, changes according to the movement of the measurement table on which the subject is placed. If an X-ray image is formed without considering the change in the enlargement ratio, for example, the balance of the aspect ratio of the X-ray image may be lost during image display. Therefore, measurement in consideration of the expansion situation such as the expansion ratio is desired.

  Incidentally, Patent Document 1 describes a technique for correcting a patient's body thickness and the like using a detection result of an X-ray of a reference object attached to a patient. However, the technique described in Patent Document 1 cannot confirm the state of enlargement of the X-ray image of the subject in consideration of the shape of the X-ray beam and the position of the measurement table.

Japanese Patent Laid-Open No. 2004-154569

  The present invention has been made in view of the above-described background art, and an object of the present invention is to provide a technique for confirming an enlarged state of an X-ray image in an X-ray measurement apparatus using an X-ray beam spreading in a fan shape. It is in.

  In order to achieve the above object, an X-ray measurement apparatus according to a preferred aspect of the present invention includes an X-ray generator that generates a fan-shaped X-ray beam, and an X-ray beam that is generated by the X-ray generator. A line detection unit, an image forming unit that forms an X-ray image based on the detection result of the X-ray beam, a measurement table that moves along the X-ray beam path from generation to detection, and positions the subject; For comparison between the reference object fixed on the table and the size of the reference object on the X-ray image obtained from the detection result of the X-ray beam transmitted through the reference object and the actual size of the reference object And a control unit for confirming an enlargement state of the X-ray image that changes in accordance with the position of the measurement table.

  In a preferred aspect, the reference object is formed of a flat metal and is fixed to a measurement table via a connecting member. In a preferred aspect, the reference material is formed of a spherical metal.

  In a preferred aspect, the reference object is fixed to the measurement table with an adjustment distance corresponding to the distance between the measurement target site in the subject and the measurement table.

  In a preferred aspect, the control unit extracts a detection portion that has passed through the reference object based on a count value of X-rays that is a detection result of the X-ray beam, whereby the size of the reference object on the X-ray image is detected. It is characterized by specifying.

  In a preferred aspect, the image forming unit adjusts the balance of the aspect ratio of the X-ray image in accordance with an enlarged state of the X-ray image.

  According to the present invention, it is possible to confirm an enlarged state of an X-ray image in an X-ray measuring apparatus using an X-ray beam spreading in a fan shape.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 shows a preferred embodiment of an X-ray measuring apparatus according to the present invention, and FIG. 1 is a functional block diagram showing the overall configuration thereof. Each unit in the X-ray measurement apparatus in FIG. 1 is controlled by the control unit 30.

  The X-ray generator 10 irradiates the subject 40 placed on the measurement table 14 with X-rays 11. The X-ray 11 is preferably a two-dimensional fan beam that gradually spreads in a fan shape with the X-ray generator 10 side as a vertex toward the X-ray detector 12 side. However, the X-ray 11 may be, for example, a beam that spreads three-dimensionally in a conical shape.

  In the present embodiment, an X-ray image showing bones and the like in the subject 40 is formed, and the bone density (bone density and bone mineral content) in the subject 40 is calculated. The bone density is measured using, for example, the DXA method (Dual X-ray Absorptiometry). Incidentally, in the DXA method, two types of X-rays 11 of high energy X-rays and low energy X-rays are used. For example, the control unit 30 alternately changes the high energy X-rays and the low energy X-rays with respect to the X-ray generation tube provided in the X-ray generator 10 by changing only the tube voltage while keeping the tube current constant. To generate.

  The X-ray detector 12 is constituted by a single X-ray sensor or a plurality of X-ray sensors, and detects the X-ray 11 generated from the X-ray generator 10 and transmitted through the subject 40. A detection signal related to the X-ray 11 detected by the X-ray detector 12 is output to the X-ray image forming unit 20 and the signal processing unit 22.

  The X-ray image forming unit 20 forms image data of an X-ray image that reflects a bone in the subject 40 based on the detection signal of the X-ray 11. A known technique is used to form the image data. An X-ray image corresponding to the image data formed in the X-ray image forming unit 20 is displayed on the display unit 26.

  The signal processing unit 22 performs signal processing for calculating the bone density (bone density, bone mineral content) in the subject 40 with respect to the detection signal of the X-ray 11. Then, the bone density calculation unit 24 calculates the bone density in the subject 40 based on the signal processing result by the signal processing unit 22. A well-known technique is also used for calculating the bone density. The calculation result of the bone density is displayed on the display unit 26.

  In the present embodiment, when the subject 40 is irradiated with X-rays 11 and detected, the magnification of the X-ray image is adjusted by moving the measurement table 14 and positioning the subject 40. Is possible. Then, the magnification of the X-ray image is calculated using a reference object provided on the measurement table 14.

  FIG. 2 is a diagram for explaining an enlargement ratio calculation process using the reference object 50. FIG. 2A shows a state in which the fan beam of the X-ray 11 generated from the X-ray generator 10 is detected by the X-ray detector 12. The X-ray generator 10 and the X-ray detector 12 A reference object 50 is provided on the measurement table 14 disposed therebetween. The reference object 50 is formed of a member having a low X-ray transmittance. The reference object 50 is made of metal, for example.

  The measurement table 14 is moved along the path of the X-ray (X-ray beam) 11 from generation to detection to position a subject (not shown). That is, the subject placed on the measurement table 14 is positioned by moving the measurement table 14 along the Z-axis direction in the figure. Since the reference object 50 is fixedly provided on the measurement table 14, the reference object 50 also moves along the Z-axis direction as the measurement table 14 moves.

  As shown in FIG. 2A, in the present embodiment, the X-ray (X-ray beam) 11 gradually moves toward the X-ray detector 12 with the X-ray tube focus of the X-ray generator 10 as the apex. The fan beam spreads along the Y-axis direction in the figure. For this reason, the X-ray 11 that passes through the reference object 50 fixed on the measurement table 14 also gradually spreads along the Y-axis direction toward the X-ray detector 12 as shown by the alternate long and short dash line in the figure. Therefore, as shown in FIG. 2A, a reference object image 50I that is an image of the reference object 50 detected by the X-ray detector 12 is displayed larger than the actual reference object 50.

  Therefore, in the present embodiment, the enlargement ratio of the X-ray image that changes in accordance with the position of the measurement table 14 is calculated based on a comparison between the size of the reference object image 50I and the actual size of the reference object 50. For example, “magnification ratio = Li / Lr” is calculated from the actual length Lr of the reference object 50 in the Y-axis direction and the length Li of the reference object image 50I in the Y-axis direction.

  For example, when the magnification is 2, the ratio of the distance D1 from the X-ray generator 10 to the measurement table 14 and the distance D2 from the measurement table 14 to the X-ray detector 12 is D1: D2 = The measurement table 14 is arranged at a position of D1: D2 = 1: 1 along the Z-axis direction. The magnification of the X-ray image and the position of the measurement table 14 are confirmed by, for example, the control unit (reference numeral 30 in FIG. 1).

  FIG. 2B shows a state in which the measuring table 14 is moved upward (in the increasing direction of the Z axis in the drawing) from the position of FIG. As the measurement table 14 is moved upward and approaches the X-ray detector 12, the size of the reference object image 50I becomes smaller in FIG. 2B than in the case of FIG. For example, in the state of FIG. 2B, the enlargement ratio that is the ratio of the actual length Lr of the reference object 50 in the Y-axis direction to the length Li of the reference object image 50I in the Y-axis direction is 4/3. Suppose there was. In this case, the ratio of the distance D1 from the X-ray generator 10 to the measurement table 14 and the distance D2 from the measurement table 14 to the X-ray detector 12 is D1: D2 = 3: 1, and is in the Z-axis direction. Accordingly, the measurement table 14 is arranged at a position of D1: D2 = 3: 1.

  FIG. 3 is a diagram for explaining the process of detecting the size of the reference object image. FIG. 3 shows an example of the X-ray detection result detected by the X-ray detector (reference numeral 12 in FIG. 2). It is shown. The horizontal axis in FIG. 3 indicates the detection position. That is, the position on the Y-axis from one end to the other end in the Y-axis direction of the X-ray detector (reference numeral 12 in FIG. 2) is shown. In addition, the vertical axis in FIG. 3 indicates the X-ray count value (detection value) detected at each position on the Y-axis.

  The detection result in FIG. 3 corresponds to the X-ray measurement result in a state where only the reference object (reference numeral 50 in FIG. 2) is placed on the measurement table (reference numeral 14 in FIG. 2). At the detection position where there is no reference object, X-rays that have passed through air with high transmittance are detected, so the count value is relatively large. In FIG. 3, the count value CA is a count value of X-rays that have passed through air. On the other hand, the X-ray count value is extremely low at a detection position where a reference object having a low X-ray transmittance exists. In FIG. 3, an extremely low interval of the count value corresponds to the reference object.

  In the present embodiment, as the length of the reference object image (50I in FIG. 2), the length L of the section having an extremely low count value in FIG. 3 is measured. For example, the threshold value TH is calculated by multiplying the count value CA that has passed through air (for example, the average value of the air count value along the Y-axis direction) by 0.9, and the count value is equal to or less than the threshold value TH. The length L is measured. Of course, the threshold value TH may be determined by another calculation method.

  FIG. 4 is a diagram for explaining the structure of the reference object 50. In the present embodiment, the length of the reference object image is measured using the fact that the count value of the X-rays transmitted through the reference object 50 becomes extremely low (see FIG. 3). Therefore, the reference object 50 is formed of a member having a low X-ray transmittance. For example, the reference object 50 is formed of a metal such as tungsten.

  FIG. 4A shows an example in which the reference object 50 is formed of a flat metal and is fixed to the measurement table 14 via the connection member 52. The shape of the surface of the reference object 50 is a circle, an ellipse, a rectangle, or the like. The connection member 52 is formed of, for example, acrylic, and fixes the reference object 50 at a position separated from the measurement table 14 by a distance H.

  The distance H is an adjustment distance corresponding to the distance between the measurement target site in the subject and the measurement table 14. For example, when the lumbar vertebra in the subject is a measurement target region, the distance H is about 4.5 cm as the position from the position of the lumbar vertebra in the subject lying on the measurement table 14 to the surface of the measurement table 14. Set to By associating (preferably matching) the position of the reference object 50 with the position of the measurement target part, the enlargement ratio of the image relating to the measurement target part can be calculated more accurately.

  FIG. 4B shows an example in which the reference object 50 is formed of a spherical metal. In the example shown in FIG. 4B, the reference object 50 may be directly fixed to the measurement table 14, or may be fixed to the measurement table 14 through a connection member. When the reference object 50 is spherical, a distance H from the center of the sphere of the reference object 50 to the surface of the measurement table 14 is set as an adjustment distance.

  The shape of the reference object 50 shown in FIGS. 4A and 4B is merely an example. For example, the reference object 50 may be formed in another shape according to the measurement target site. . Further, since the reference object 50 is used for confirming the enlargement ratio and the position of the measurement table 14, the reference object 50 may be removed from the measurement table 14 after the confirmation. Of course, the reference object 50 may remain attached to the position of the measurement table 14 that does not interfere with the measurement of the subject.

  FIG. 5 is a diagram for explaining the balance adjustment of the aspect ratio according to the enlargement ratio of the X-ray image. FIG. 5 shows an example of an X-ray image corresponding to the image data formed in the X-ray image forming unit (reference numeral 20 in FIG. 1). Each image in FIGS. Shows a bone image (bone image 40I) which is a measurement target part in the subject. 5A shows an image before adjusting the aspect ratio balance, and FIG. 5B shows an image after adjusting the aspect ratio balance.

  When forming the images in FIGS. 5A and 5B, for example, the X-ray detector 12 and the X-ray generator 10 shown in FIG. The X-ray detector 12 and the X-ray generator 10 are scanned along the X-axis direction with respect to the measurement table 14 on which the specimen is placed, and the scan line is moved stepwise along the Y-axis direction. By doing so, the X-ray detector 12 and the X-ray generator 10 are scanned two-dimensionally in the XY plane. As a result, an X-ray detection result is obtained from the XY plane shown in FIG. 5, and the images shown in FIGS. 5A and 5B are formed as X-ray images corresponding to the detection result.

  As described with reference to FIG. 2, the magnification of the X-ray image in the Y-axis direction changes according to the position of the measurement table 14 in the Z-axis direction. Therefore, there is a difference between the magnification in the Y-axis direction and the magnification in the X-axis direction. For example, an X-ray image is formed in a state where the magnification in the Y-axis direction is smaller than the magnification in the X-axis direction. Then, as shown in FIG. 5A, an X-ray image in which the bone image 40I is crushed in the Y-axis direction is formed.

  Therefore, in the present embodiment, the balance adjustment of the aspect ratio according to the enlargement ratio is performed. That is, when the enlargement ratio in the Y-axis direction is calculated by the control unit (reference numeral 30 in FIG. 1) by the method described with reference to FIG. 2, the X-ray image forming unit (FIG. 1) is calculated according to the calculation result. The balance of the aspect ratio is adjusted at 20). For example, the X-ray image is formed by adjusting the magnification in at least one of the X-axis direction and the Y-axis direction of the X-ray image so that the magnifications in the X-axis direction and the Y-axis direction are matched. As a result, as shown in FIG. 5B, the aspect ratio of the entire X-ray image is adjusted, and the bone image 40I corresponding to the actual bone aspect ratio (desirably coincident with the actual bone aspect ratio). Is formed.

  The preferred embodiment of the present invention has been described above. According to the X-ray measurement apparatus of FIG. 1 described above, it is possible to adjust the magnification of the X-ray image by moving the measurement table 14 according to the size of the subject 40, for example. For example, when the subject 40 is relatively small, the resolution can be improved by bringing the measurement table 14 closer to the X-ray generator 10 side to increase the magnification, and when the subject 40 is relatively large The measurement table 14 can be brought closer to the X-ray detector 12 side to reduce the enlargement ratio and increase the measurement area. Even when the enlargement ratio is changed, an X-ray image in which the balance of the aspect ratio is adjusted can be formed by adjusting the balance of the aspect ratio in accordance with the enlargement ratio.

  In addition, embodiment mentioned above, its effect, etc. are only illustrations in all the points, and do not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

It is a functional block diagram which shows the whole structure of the X-ray measuring apparatus which concerns on this invention. It is a figure for demonstrating the calculation process of the enlargement factor using a reference | standard thing. It is a figure for demonstrating the detection process of the magnitude | size of a reference | standard object image. It is a figure for demonstrating the structure of a reference | standard thing. It is a figure for demonstrating the balance adjustment of the aspect ratio according to an enlargement ratio.

Explanation of symbols

  10 X-ray generator, 12 X-ray detector, 20 X-ray image forming unit, 30 control unit.

Claims (6)

An X-ray generator for generating a fan-shaped X-ray beam;
An X-ray detector that detects an X-ray beam generated by the X-ray generator;
An image forming unit that forms an X-ray image based on the detection result of the X-ray beam;
A measuring stage that moves along the X-ray beam path from generation to detection to position the subject;
A reference object fixed to the measuring table;
Based on a comparison between the size of the reference object on the X-ray image obtained from the detection result of the X-ray beam transmitted through the reference object and the actual size of the reference object, X varies depending on the position of the measurement table. A control unit for confirming the expansion state of the line image;
Having
An X-ray measuring apparatus characterized by that. The X-ray measurement apparatus according to claim 1,
The reference object is formed of a flat metal and is fixed to a measurement table via a connection member.
An X-ray measuring apparatus characterized by that. The X-ray measurement apparatus according to claim 1,
The reference object is formed of a spherical metal.
An X-ray measuring apparatus characterized by that. The X-ray measuring apparatus according to claim 2 or 3,
The reference object is fixed to the measurement table by an adjustment distance corresponding to the distance between the measurement target site in the subject and the measurement table.
An X-ray measuring apparatus characterized by that. The X-ray measurement apparatus according to claim 4,
The control unit identifies the size of the reference object on the X-ray image by extracting a detection portion that has passed through the reference object based on an X-ray count value that is a detection result of the X-ray beam.
An X-ray measuring apparatus characterized by that. The X-ray measurement apparatus according to claim 5,
The image forming unit adjusts the balance of the aspect ratio of the X-ray image according to the enlargement state of the X-ray image;
An X-ray measuring apparatus characterized by that.

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