JP2015019788A - X-ray measurement apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an exposure dose of an analyte in X-ray measurement.SOLUTION: An X-ray measurement apparatus 10 measures at least one of bone density and fat/muscle percentage by folded-scanning a measurement space 22 with an X-ray with the different energy from the energy EL after setting a measurement condition by previously scanning the measurement space 22 with an X-ray with the energy EL. The folded-scanning speed and the measurement object region are set by the previous scanning, and the measurement object region is irradiated with the X-ray in the repeat scanning. When bone density measurement is performed, the X-ray with the energy EH larger than the energy EL is used in the folded-scanning. When fat/muscle percentage measurement is performed, the X-ray with the energy EVL smaller than the energy EL is used in the folded-scanning.

Description

  The present invention relates to an X-ray measurement apparatus, and more particularly to an apparatus that performs measurement using a plurality of types of X-rays having different energies.

  Bone density is used as an evaluation value for diagnosing osteoporosis and the like, and X-ray measurement apparatuses that measure the bone density are widely used. The X-ray measurement apparatus detects X-rays emitted from an X-ray generator and transmitted through a subject with an X-ray detector, and measures the bone density of the subject based on the detection result. As a method of measuring bone density by the X-ray measurement apparatus, there is a dual energy X-ray absorption measurement (DXA). In this measurement method, the absorption rate for the subject is obtained for each of two types of X-rays having different energies, and the bone density is measured from the absorption rate.

  An X-ray measurement apparatus using the DXA method is also used for measuring body fat percentage and muscle percentage. Body fat percentage is defined as the ratio of fat weight to body weight, and muscle percentage is defined as the ratio of muscle weight to body weight. Body fat percentage and muscle percentage are often measured as evaluation values for health care.

  Patent Document 1 below describes an X-ray bone density measuring device. In this apparatus, a bone density distribution and a body fat percentage distribution are obtained, and a composite image is generated in which the bone density distribution is represented by gradations of the first color and the body fat percentage is represented by gradations of the second color. Is done. Patent Document 2 describes an X-ray measurement apparatus that measures the amount of bone mineral. In this apparatus, when scanning an X-ray beam, the X-ray generator is provided with an X-ray shutter that avoids X-ray irradiation to a portion that does not need to be irradiated for bone mineral content measurement. . Patent Document 3 describes an X-ray bone density measuring system that selectively displays a single energy image obtained by X-rays of one kind of energy and a dual energy image obtained by the DXA method. .

JP 2004-147863 A JP 2004-113408 A JP-A-9-262228

  When bone density is measured by the DXA method, or when body fat percentage or muscle percentage is measured, two types of X-rays having different energies are scanned on the subject. Some conventional X-ray measurement apparatuses emit two types of X-rays over the entire area of the subject. In such an apparatus, two types of X-rays are irradiated outside the region to be measured in the subject, and unnecessary X-rays are irradiated to the subject.

  An object of the present invention is to reduce the exposure dose of a subject in X-ray measurement.

  The present invention includes an X-ray generation unit that generates a plurality of types of X-rays having different energies, an X-ray detection unit that detects X-rays, and a control unit that controls the X-ray generation unit, and the control unit The first X-ray is generated by the X-ray generation unit and the subject is scanned with the first X-ray, and the first X-ray is detected based on the X-ray detected by the X-ray detection unit. A first calculation unit for obtaining a first detection value distribution according to scanning of the line, a specifying unit for specifying a measurement target region included in the subject based on the first detection value distribution, and the first X-ray, Is based on the X-ray detected by the X-ray detection unit and the second scanning unit that generates the second X-ray having different energy in the X-ray generation unit and scans the measurement target region with the second X-ray. A second calculation unit for obtaining a second detection value distribution according to the scanning of the second X-ray, and the first detection Based on the distribution and the second detection value distribution, wherein comprises a measurement unit for performing measurements on the measurement target region, and wherein the.

  According to the present invention, the X-ray scanning of the subject is performed separately in the first X-ray scanning by the first scanning unit and the second X-ray scanning by the second scanning unit. This simplifies the control of generating and scanning X-rays. Further, the second X-ray scan is performed on the measurement target region. Therefore, the X-ray scanning range is limited, and the exposure dose of the subject is reduced. In addition, since the measurement target area is specified based on the first detection value distribution obtained by scanning with the first X-ray, the measurement result is used effectively.

  The control part in this invention is comprised by a processor, for example. The processor operates according to a program and forms each component included in the control unit.

The X-ray measurement apparatus according to the present invention preferably includes a mode selection unit that selects either the bone measurement mode or the soft tissue measurement mode, and when the bone measurement mode is selected,
The specifying unit specifies a bone region as the measurement target region, the second scanning unit sets the energy of the second X-ray larger than the energy of the first X-ray, and the measurement unit sets the measurement target region When the soft tissue measurement mode is selected and the soft tissue measurement mode is selected, the specifying unit specifies a soft tissue region as the measurement target region, and the second scanning unit includes the second X-ray energy. Is set smaller than the energy of the first X-ray, and the measurement unit performs measurement related to fat or muscle in the measurement target region.

  Further, in the X-ray measurement apparatus according to the present invention, preferably, the specifying unit distinguishes and specifies a bone region and a soft tissue region as the measurement target region, and the second scanning unit detects the bone region. For scanning, the energy of the second X-ray is set larger than the energy of the first X-ray, and for scanning the soft tissue region, the energy of the second X-ray is set smaller than the energy of the first X-ray, The measurement unit performs measurement related to bone mineral in the bone region, and performs measurement related to fat or muscle in the soft tissue region.

  According to such an invention, the measurement regarding the bone mineral is performed using the first X-ray and the second X-ray having higher energy than the energy of the first X-ray. And the measurement regarding fat or muscle is performed using the 1st X-ray and the 2nd X-ray whose energy is smaller than the energy of the 1st X-ray. Thus, measurement is performed using X-rays having appropriate energy for each region, and measurement accuracy is improved.

  In the X-ray measurement apparatus according to the present invention, preferably, the second scanning unit causes the X-ray generation unit to scan the second X-ray at a speed or tube current corresponding to the first detection value distribution.

  According to such an invention, the scanning speed of the second X-ray or the tube current of the X-ray generation unit is determined according to the thickness of the subject. As a result, X-rays are detected with appropriate intensity, and measurement accuracy is improved.

  ADVANTAGE OF THE INVENTION According to this invention, the exposure amount of the subject in a X-ray measurement can be reduced.

1 is a perspective view of an X-ray measurement apparatus according to an embodiment of the present invention. 1 is a side view of an X-ray measurement apparatus according to an embodiment of the present invention. It is a flowchart which shows the process which a control part performs. It is a flowchart of the process which a control part performs in the case of bone density measurement. It is a figure which shows notionally the X-ray image area | region where the measurement object area | region was set. It is a flowchart of the process which a control part performs in the case of a fat and muscle rate measurement. It is a figure which shows notionally the X-ray image area | region where the measurement object area | region was set. It is a flowchart of the process which a control part performs in the case of a bone and soft tissue measurement. It is a figure which shows notionally the X-ray image area | region where each measurement object area | region of a bone density and a fat / muscle rate was set.

  FIG. 1 shows a perspective view of an X-ray measuring apparatus 10 according to an embodiment of the present invention and a bucky table 18 used therewith. The X-ray measurement apparatus 10 includes a main body unit 12 that generates X-rays 20, an arm unit 14 that detects the X-rays 20, and a support column 16 that supports the arm unit 14 above the main body unit 12. A space surrounded by the main body 12, the support column 16, and the arm 14 forms a measurement space 22 in which the subject is arranged. A subject is received in the measurement space 22 from the side where the support column 16 does not exist in the positive y-axis direction.

  The X-ray measurement apparatus 10 is arranged so that the main body 12 enters under the table base of the bucky table 18. In the measurement space 22, the subject is laid on the Bucky table 18 leaving a margin on the front side of FIG. 1. The X-ray measurement apparatus 10 emits bone density, body fat percentage, muscle percentage (hereinafter referred to as body fat) based on the detected value of the X-ray 20 emitted from the main body section 12 and transmitted through the subject and detected by the arm section 14. Measure the combined amount of fat and muscle ratio as fat / muscle ratio).

  Here, an embodiment in which the X-ray measuring apparatus 10 and the Bucky table 18 are separated from each other is taken, but the upper surface of the main body 12 of the X-ray measuring apparatus 10 is a Bucky table on which the subject lies, The measurement device 10 and the bucky table may be integrated.

  FIG. 2 schematically shows a side surface of the X-ray measurement apparatus 10. In this side view, the internal configuration of the main body 12 and the arm 14 is shown. The X-ray measurement apparatus 10 includes an X-ray generator 26 housed in a main body housing 24 and an X-ray detector 30 housed in an arm housing 28. The X-ray generator 26 is transported in the horizontal direction inside the main body portion 12, and the X-ray detector 30 is transported in the horizontal direction inside the arm portion 14. As the X-ray generator 26, for example, one that generates X-rays having a planar beam shape parallel to the zx plane is used. The beam shape may be a divergent shape whose width increases as the distance from the X-ray generator 26 increases.

  The DXA method is used to measure bone density and fat / muscle rate. In the measurement space 22 of the X-ray measurement apparatus 10, a subject diagnostic space 34 in which the subject 32 is arranged and a reference measurement space 36 that does not allow the presence of the subject 32 are defined. When the X-ray generator 26 and the X-ray detector 30 are located at the reference positions P1 and Q1, respectively, a reference measurement space 36 is interposed between the X-ray generator 26 and the X-ray detector 30. In this case, X-rays emitted from the X-ray generator 26 are detected by the X-ray detector 30 without passing through the subject 32. In a state where the X-ray generator 26 and the X-ray detector 30 are arranged at the reference positions P1 and Q1, respectively, the detected value of the X-ray detected by the X-ray detector 30 is acquired as reference data.

  The X-ray measurement apparatus 10 conveys the X-ray generator 26 and the X-ray detector 30 while facing each other in the conveyance ranges R1 and R2 in FIG. In the transport ranges R1 and R2, the left ends are set as reference positions P1 and Q1, respectively, and the right ends are set as folding positions P2 and Q2, respectively. The transport ranges R1 and R2 sandwich the reference measurement space 36 and the subject diagnosis space 34. The X-ray generator 26 moves between the reference position P1 and the folding position P2. The X-ray detector 30 moves between the reference position Q1 and the folding position Q2.

  The X-ray measurement apparatus 10 performs generation of X-rays by the X-ray generator 26 and detection of X-rays by the X-ray detector 30 while conveying the X-ray generator 26 and the X-ray detector 30. As a result, the X-ray measurement apparatus 10 scans the subject arrangement space 22 with X-rays, and acquires a detection value of the X-rays that have passed through the subject arrangement space 22. The X-ray measurement apparatus 10 obtains the distribution of the absorption rate with respect to the subject 32 based on the detection value acquired for the subject arrangement space 22 and the reference data. Here, the distribution of the absorptance refers to the distribution of the absorptance on the horizontal plane (yz plane) for X-rays passing upward through the subject space 22. The absorption rate is defined as a value obtained by dividing the value indicated by the reference data by the X-ray detection value detected by the X-ray detector 30. The smaller the detected value of X-rays detected by the X-ray detector 30, the greater the absorption rate. It can also be said that the absorptance distribution is a distribution corresponding to the reciprocal of the detected value of the X-ray detected by the X-ray detector 30. The X-ray measurement apparatus 10 obtains the absorption rate distribution for each of two types of X-rays having different energies by the operation described later, and measures the bone density, fat / muscle rate, and the like from the respective absorption rate distributions.

  A specific configuration of the X-ray measurement apparatus 10 will be described. A control device 38 is connected to the X-ray measurement apparatus 10. The control device 38 is configured by a computer such as a personal computer, for example. The control device 38 includes a control unit 40, an operation panel 42, and a display 44. The operation panel 42 as an operation unit includes a keyboard, a mouse, a drag ball, a lever, and the like. The control unit 40 includes a processor, a memory, and the like, and operates according to a program stored in advance. The control device 38 may be integrated with the X-ray measurement device 10 or may be configured individually.

  The main body housing 24 accommodates the generator transport rail 46 and the generator drive mechanism 48 in addition to the X-ray generator 26. The generator transport rail 46 is fixed to the main body housing 24 so that its longitudinal direction is horizontal. The X-ray generator 26 is attached to the generator transport rail 46 with the X-ray radiation direction facing upward. The generator driving mechanism 48 gives a driving force to the X-ray generator 26 based on the control of the control unit 40. The X-ray generator 26 moves along the generator transport rail 46 by the driving force applied from the generator driving mechanism 48. As a result, the X-ray generator 26 moves in the horizontal direction. The generator drive mechanism 48 may be a mechanism that conveys a belt or chain attached to the X-ray generator 26 by a motor.

  As the X-ray generator 26, an X-ray tube or the like that generates X-rays is used. The control unit 40 controls the tube voltage or tube current of the X-ray tube to change the generated X-ray energy, radiation amount (intensity), and the like. The top plate 50 of the main body housing 24 is made of a material that transmits X-rays, and X-rays are emitted upward from the X-ray generator 26 via the top plate 50. Further, the X-ray generator 26 is provided with a shutter 52 that is opened and closed by the control unit 40. The shutter 52 is formed of a material that shields X-rays such as a lead plate. When shielding X-rays, the X-ray emission port in the X-ray generator 26 is closed, and when emitting X-rays, the X-ray emission port is opened. In the following description, it is assumed that the shutter 52 is open unless otherwise specified. Further, instead of the shutter 52, a filter that attenuates X-rays may be used.

  In addition to the X-ray detector 30, the arm unit housing 28 houses the detector transport rail 54 and the detector driving mechanism 56. The detector transport rail 54 is fixed to the arm housing 28 so that the longitudinal direction thereof is the horizontal direction. The X-ray detector 30 is attached to the detector transport rail 54 with the X-ray detection direction facing downward. The detector driving mechanism 56 applies a driving force to the X-ray detector 30 based on the control of the control unit 40. The X-ray detector 30 moves along the detector transport rail 54 by the driving force applied from the detector driving mechanism 56. As a result, the X-ray detector 30 moves in the horizontal direction. Similarly to the generator drive mechanism 48, the detector drive mechanism 56 may employ a mechanism that conveys a belt or chain attached to the X-ray detector 30 by a motor. The bottom plate 58 of the arm housing 28 is formed of a material that transmits X-rays. X-rays emitted from the main body 12 toward the arm 14 are transmitted by the X-ray detector 30 via the bottom plate 58. Detected.

  The X-ray detector 30 uses a conversion device such as an electron tube that converts X-rays into electrical energy, or a photodiode that operates with respect to the X-ray wavelength. For example, the X-ray detector 30 arranges a plurality of conversion devices over a plurality of columns, with the horizontal direction (z-axis positive direction) being the column direction perpendicular to the transport direction, and outputs detection values from the plurality of conversion devices. The configuration is as follows. Further, the X-ray detector 30 may be configured to output a detection value at each detection point by linearly scanning one conversion device in the z-axis direction.

  In this configuration, the X-ray generator 26 is housed in the main body housing 24 and the X-ray detector 30 is housed in the arm housing 28. The X-ray detector 30 may be housed in the main body housing 24 by being housed in the arm housing 28.

  Specific processing executed by the control unit 40 will be described. FIG. 3 shows a flowchart of processing executed by the control unit 40. In this process, the measurement space 22 is pre-scanned with X-rays of energy EL and measurement conditions are set, and then the measurement space 22 is scanned back with X-rays of energy different from the energy EL to obtain bone density and fat / muscle rate. Is measured. When performing bone density measurement, X-rays having an energy EH larger than the energy EL are used in the return scanning. When measuring fat / muscle ratio, X-rays of energy EVL smaller than energy EL are used in the return scanning.

  The X-ray measurement apparatus 10 executes a measurement mode designated by the user among a bone density measurement mode, a fat / muscle ratio measurement mode, and a bone / soft tissue measurement mode. The bone density measurement mode is a measurement mode in which only bone density measurement is performed. The fat / muscle rate measurement mode is a measurement mode in which only fat / muscle rate measurement is performed. The bone / soft tissue measurement mode is a measurement mode in which both bone density measurement and fat / muscle ratio measurement are performed.

  First, it is assumed that the X-ray generator 26 and the X-ray detector 30 are at predetermined initial positions on the generator transport rail 46 and the detector transport rail 54, respectively. Further, the X-ray beam shape is assumed to be a divergent plane parallel to the zx plane.

  The control unit 40 displays the measurement mode options on the display 44, and waits for a measurement mode designation operation (S101). When there is a measurement mode designation operation on the operation panel 42, the control unit 40 reads mode designation information from the operation panel 42 (S102).

  The control unit 40 controls the generator driving mechanism 48 to convey the X-ray generator 26 from the initial position to the reference position P1 (S103). In addition, the control unit 40 controls the detector driving mechanism 56 to convey the X-ray detector 30 from the initial position to the reference position Q1 (S103). As a result, a state in which the subject 32 is not interposed between the X-ray generator 26 and the X-ray detector 30 is formed.

  In this state, the control unit 40 causes the X-ray generator 26 to generate X-rays of energy EL, and obtains a detection value in the X-ray detector 30 as reference data AL (S104). The reference data AL represents a detection value at any one of the positions arranged in the z-axis direction on the detection surface of the X-ray detector 30.

  The control unit 40 controls the generator drive mechanism 48 and the detector drive mechanism 56, and conveys the X-ray generator 26 and the X-ray detector 30 while making the X-ray generator 26 and the X-ray detector 30 face each other. The paper is conveyed rightward (y-axis positive direction) over the ranges R1 and R2 (S105). As a result, the X-ray generator 26 moves from the reference position P1 to the folding position P2, and the X-ray detector 30 moves from the reference position Q1 to the folding position Q2.

  While the X-ray generator 26 and the X-ray detector 30 are being transported, the control unit 40 causes the X-ray generator 26 to generate X-rays of energy EL, and the X-ray detector 30 detects X-rays of energy EL. Get the detection value detected in. In this way, the preceding scanning with respect to the measurement space 22 is performed.

  The control unit 40 acquires the detection value group acquired for the X-rays of the energy EL over the transport range R2 as the detection X-ray data BL (S106).

  The control unit 40 determines the return conveyance speed based on the detected X-ray data BL (S107). For example, the control unit 40 obtains an average value of the detection value group indicated by the detected X-ray data BL as an evaluation value, and when the evaluation value is greater than a predetermined threshold value TH, the folding conveyance speed is set to vH, and the evaluation value is a threshold value. When it is equal to or lower than TH, the return conveyance speed is set to vL. Here, the return conveyance speed vH is higher than the return conveyance speed vL. Further, the control unit 40 may store in advance a table that defines the relationship between the evaluation value and the conveyance speed, and execute a process of determining the conveyance speed associated with the evaluation value as the return conveyance speed. In this table, it is assumed that the larger the evaluation value is, the higher the conveyance speed is associated with. The evaluation value is a value representing a tendency of the magnitude of each detection value indicated by the detection X-ray data BL in addition to the average value of the detection value group indicated by the detection X-ray data BL, for example, a median value and a predetermined offset to the average value. Or a value obtained by adding

  The control unit 40 displays an X-ray image (bone image) based on the detected X-ray data BL on the display 44 (S108).

  The detected X-ray data BL has a tendency that the value in the soft tissue region is larger than the value in the bone region, and the value in the air region is larger than the value in the soft tissue region. Therefore, the control unit 40 specifies a bone region and a soft tissue region based on the detected X-ray data BL (S109). That is, the control unit 40 refers to the detection value group indicated by the detected X-ray data BL, and identifies a region having a value within a predetermined range for identifying a bone region as a bone region. In addition, the control unit 40 refers to the detection value group indicated by the detected X-ray data BL, and identifies a region having a value within a predetermined range for identifying the soft tissue region as the soft tissue region.

  The control unit 40 performs measurement according to the mode designation information read in step S102 among bone density measurement, fat / muscle ratio measurement, or bone / soft tissue measurement (S110). Hereinafter, each of bone density measurement, fat / muscle ratio measurement, and bone / soft tissue measurement will be specifically described.

  FIG. 4 shows a flowchart of processing executed by the control unit 40 in bone density measurement. The control unit 40 sets the measurement target region 62 based on the bone region and the soft tissue region specified in step S109 (S201).

  FIG. 5 conceptually shows the X-ray image region 60 in which the measurement target region 62 is set. The X-ray image area 60 corresponds to the X-ray image displayed on the display 44 in step S108. However, this area is an arithmetic area and does not necessarily have to be displayed on the display 44.

  The left end of the X-ray image region 60 corresponds to the reference positions P1 and Q1 (y = 0), and the right end of the X-ray image region 60 corresponds to the folding positions P2 and Q2 (y = d). The X-ray image region 60 includes four lumbar vertebrae 64 and a soft tissue region 66 surrounding these lumbar vertebrae 64.

  The control unit 40 sets, as the measurement target region 62, a region including the soft tissue region 66 surrounding the bone region in addition to the bone region specified in step S109. In FIG. 5, a range represented by y1 ≦ y ≦ y2 is set as the measurement target region 62. The reason for including the soft tissue region 66 in the measurement target region 62 is that the ratio of the attenuation constant of the energy EH to the X-ray and the attenuation constant of the energy EL to the X-ray is measured for the soft tissue, and this measured value is based on the DXA method. This is for use in bone density measurement. When a predetermined fixed value is used as the ratio of these attenuation constants, the soft tissue region 66 may not be included in the measurement target region 62.

  The control unit 40 controls the generator drive mechanism 48 and the detector drive mechanism 56, and conveys the X-ray generator 26 and the X-ray detector 30 while making the X-ray generator 26 and the X-ray detector 30 face each other. It is conveyed in the y-axis negative direction over the ranges R1 and R2 (S202). The conveyance speed at this time is the folding conveyance speed determined in step S107. As a result, the X-ray generator 26 moves from the folding position P2 to the reference position P1, and the X-ray detector 30 moves from the folding position Q2 to the reference position Q1.

  The control unit 40 causes the X-ray generator 26 to generate X-rays of energy EH while the X-ray generator 26 and the X-ray detector 30 are being conveyed (S202).

  In addition, when the X-ray generator 26 is transported to a position corresponding to the measurement target region 62, the control unit 40 opens the shutter 52 and sets the X-ray generator to a position corresponding to a region other than the measurement target region 62. If 26 is being conveyed, the shutter 52 is closed (S202). That is, the control unit 40 closes the shutter 52 when the X-ray generator 26 and the X-ray detector 30 are located in the range of y> y2, and opens the shutter 52 when located in the range of y1 ≦ y ≦ y2. . When the X-ray generator 26 and the X-ray detector 30 are in the range of 0 <y <y2, the shutter 52 is closed again. Furthermore, the control part 40 acquires the detected value detected by the X-ray detector 30 about the X-ray of energy EH. In this way, the return scanning with respect to the measurement space 22 is performed.

  The control unit 40 acquires, as detection X-ray data BH, a detection value group acquired for X-rays of energy EH over the measurement target region 62 (S203). In addition, when the X-ray generator 26 and the X-ray detector 30 reach the reference positions P1 and Q1 and stop, respectively, the control unit 40 opens the shutter 52 and sets the detection value detected by the X-ray detector 30. Obtained as reference data AH (S204). The reference data AH indicates a detection value at a position where the reference data AL is acquired among the positions arranged in the z-axis direction on the detection surface of the X-ray detector 30.

  Based on the detected X-ray data BH and the reference data AH, the control unit 40 obtains the absorptance distribution data CH for the X-rays of energy EH (S205). Further, the control unit 40 obtains the absorption rate distribution data CL for the X-rays of the energy EL based on the detected X-ray data BL and the reference data AL (S206).

  Based on the DXA method, the control unit 40 obtains a bone mineral distribution and a bone density image based on the absorption rate distribution data CH and CL (S207). Here, the distribution of the bone mineral is a distribution of the bone mineral on the yz plane, and the bone density image is an image representing the distribution of the bone mineral with each pixel value. Further, the control unit 40 calculates the bone mineral content by integrating the bone mineral distribution with respect to the yz plane (S207). Further, the bone density is obtained by dividing the amount of bone mineral by the area of the bone projected on the yz plane (S207). Here, the area of the bone is obtained, for example, as the area of a region where the value indicated by the detected X-ray data BL or BH is less than a predetermined value. Moreover, you may obtain | require as an area of the area | region where the value which absorptance distribution data CH or CL shows is more than predetermined value. The control unit 40 displays these measurement results on the bone mineral on the display 44 (S208). Specifically, for example, any one or more of a bone density image, a bone mineral content, and a bone density are displayed on the display 44 according to a user operation.

  FIG. 6 shows a flowchart of processing executed by the control unit 40 when measuring the fat / muscle ratio. The control unit 40 sets the measurement target region 62 based on the bone region and the soft tissue region specified in step S109 (S301).

  FIG. 7 conceptually shows the X-ray image region 60 in which the measurement target region 62 is set. For example, the control unit 40 sets, as the measurement target region 62, a region where the value indicated by the detected X-ray data BL is within a predetermined range on the y-axis negative direction side from the folding positions P2 and Q2.

  The control unit 40 performs return scanning with respect to the measurement space 22 (S302). This process corresponds to the process in step S202 in which the X-rays of energy EH are replaced with X-rays of energy EVL. That is, when the X-ray generator 26 and the X-ray detector 30 are located in the range of y1 ≦ y ≦ y2, the shutter 52 is opened, the measurement target region 62 is scanned with X-rays of energy EVL, and the measurement target region 62 X-rays transmitted through are detected by the X-ray detector 30.

  The control unit 40 acquires the detection value group acquired for the X-rays of energy EVL over the measurement target region 62 as detection X-ray data BVL (S303). In addition, when the X-ray generator 26 and the X-ray detector 30 reach the reference positions P1 and Q1 and stop, respectively, the control unit 40 opens the shutter 52 and sets the detection value detected by the X-ray detector 30. Obtained as reference data AVL (S304). The reference data AVL indicates a detection value at a position where the reference data AL is acquired among the positions arranged in the z-axis direction on the detection surface of the X-ray detector 30.

  Based on the detected X-ray data BVL and the reference data AVL, the controller 40 obtains the absorptance distribution data CVL for the X-rays of energy EVL (S305). Further, the control unit 40 obtains the absorption rate distribution data CL for the X-rays of the energy EL based on the detected X-ray data BL and the reference data AL (S306).

  Based on the DXA method, the control unit 40 obtains fat distribution and muscle distribution based on the absorption rate distribution data CL and CVL (S307). Here, the fat distribution is the distribution of fat on the yz plane, and the muscle distribution is the distribution of muscle on the yz plane. The control unit 40 obtains the fat weight by integrating the fat distribution with respect to the yz plane, and obtains the body fat percentage by dividing the fat weight by the body weight of the subject 32 input in advance from the operation panel 42 (S307). Further, the muscle distribution is integrated with respect to the yz plane to obtain the muscle weight, and the muscle ratio is obtained by dividing the muscle weight by the body weight of the subject 32 (S307). The control unit 40 displays these measurement results regarding fat and muscle on the display 44 (S308). Specifically, for example, any one or more of fat weight, body fat percentage, muscle weight, and muscle percentage are displayed on the display 44 in accordance with a user operation.

  FIG. 8 shows a flowchart of processing executed by the control unit 40 at the time of bone / soft tissue measurement. Based on the bone region and soft tissue region specified in step S109, the control unit 40 sets measurement target regions for each of the bone density and fat / muscle rate (S401).

  FIG. 9 conceptually shows an X-ray image region 60 in which a bone measurement target region 62-1 and a soft tissue measurement target region 62-2 are set. The control unit 40 sets the bone measurement target region 62-1 by the same process as step S201, and sets the soft tissue measurement target region 62-2 by the same process as step S301. Here, the range of y1 ≦ y ≦ y2 is set as the bone measurement target region 62-1 and the range of y3 ≦ y ≦ y4 is set as the soft tissue measurement target region 62-2.

  The control unit 40 controls the generator drive mechanism 48 and the detector drive mechanism 56, and conveys the X-ray generator 26 and the X-ray detector 30 while making the X-ray generator 26 and the X-ray detector 30 face each other. It is conveyed in the y-axis negative direction over the ranges R1 and R2 (S402). The conveyance speed at this time is the folding conveyance speed determined in step S107. As a result, the X-ray generator 26 moves from the folding position P2 to the reference position P1, and the X-ray detector 30 moves from the folding position Q2 to the reference position Q1.

  While the X-ray generator 26 and the X-ray detector 30 are transported to a position corresponding to the measurement target region 62-2 of the soft tissue, the control unit 40 transmits X-rays of energy EVL to the X-ray generator 26. Is generated. While the X-ray generator 26 and the X-ray detector 30 are being transported to a position corresponding to the bone measurement target region 62-1, the X-ray generator 26 generates X-rays of energy EH ( S402). In addition, when the X-ray generator 26 is transported to a position corresponding to the measurement target areas 62-1 and 62-2, the control unit 40 opens the shutter 52, and the measurement target areas 62-1 and 62-2. When the X-ray generator 26 is being transported to a position corresponding to a region other than the shutter 52, the shutter 52 is closed (S402). That is, the control unit 40 closes the shutter 52 when the X-ray generator 26 and the X-ray detector 30 are located in the range of y> y4, and opens the shutter 52 when located in the range of y3 ≦ y ≦ y4. . When the X-ray generator 26 and the X-ray detector 30 are located in the range of y2 <y <y3, the shutter 52 is closed, and when the X-ray generator 26 and the X-ray detector 30 are located in the range of y1 ≦ y ≦ y2, the shutter 52 is opened. The control unit 40 closes the shutter 52 when the X-ray generator 26 and the X-ray detector 30 are located in the range of 0 <y <y1. In this way, the return scanning with respect to the measurement space 22 is performed.

  The control unit 40 acquires the detection value group acquired for the X-rays of energy EVL over the measurement target region 62-2 as detection X-ray data BVL (S403). Moreover, the control part 40 acquires the detection value group acquired about the X-ray of energy EH over the measurement object area | region 62-1 as detection X-ray data BH (S404).

  The control unit 40 opens the shutter 52 when the X-ray generator 26 and the X-ray detector 30 reach the reference positions P1 and Q1 and stop, respectively. In this state, the control unit 40 causes the X-ray generator 26 to generate X-rays with energy EH, and acquires the detection value in the X-ray detector 30 as the reference data AH (S405). The reference data AH indicates a detection value at any position among the positions arranged in the z-axis direction on the detection surface of the X-ray detector 30. Further, the control unit 40 causes the X-ray generator 26 to generate X-rays of energy EVL, and acquires the detection value in the X-ray detector 30 as reference data AVL (S406). The reference data AVL is acquired at the same position as the position where the reference data AH is acquired.

  The control unit 40 obtains the bone mineral distribution, the bone density image, the bone mineral content, and the bone density by the same processing as steps S205 to S207 (S407). That is, the absorptance distribution data CH is obtained based on the detected X-ray data BH and the reference data AH, the absorptance distribution data CL is obtained based on the detected X-ray data BL and the reference data AL, and the absorptance distribution data CH and These measurements are obtained based on CL.

  Further, the control unit 40 obtains fat distribution, muscle distribution, fat weight, body fat percentage, muscle weight, and muscle percentage by the same processing as steps S305 to S307 (S408). That is, the absorptance distribution data CL is obtained based on the detected X-ray data BL and the reference data AL, the absorptance distribution data CVL is obtained based on the detected X-ray data BVL and the reference data AVL, and the absorptance distribution data CL and These measurements are obtained based on the CVL.

  The control unit 40 causes the display 44 to display these measurement results regarding bone and soft tissue (S409). Specifically, for example, one or more of bone density images, bone mineral density, bone density, fat distribution, muscle distribution, fat weight, body fat percentage, muscle weight and muscle percentage, It is displayed on the display 44 according to the user's operation.

  The processing described here has the following advantages. The X-ray of energy EH and the X-ray of energy EL are used for the measurement of the amount of bone mineral, and the X-ray of energy EL and the X-ray of energy EVL are used for the measurement of fat / muscle ratio. As a result, measurement is performed with X-rays having an appropriate amount of energy for each of bone and soft tissue, and measurement accuracy is improved. That is, it is avoided that the measurement accuracy of the bone density decreases due to the energy of the X-ray being too small and the X-ray not passing through the bone. In addition, the difference between the intensity of X-rays transmitted through fat due to excessive X-ray energy and the intensity of X-rays transmitted through muscle is reduced, and the measurement accuracy of body fat percentage and muscle percentage is reduced. Is avoided.

  Further, X-ray scanning of energy EL, EH, and EVL is performed individually. This simplifies the control of generating and scanning X-rays.

  Further, the return scanning speed is set to a larger value as the evaluation value indicating the tendency of the size of each detected value indicated by the detected X-ray data BL is larger. As a result, the thicker the subject 32, the slower the X-ray folding scanning speed, and the X-ray can be detected with an appropriate intensity.

  In addition, the region that is not the measurement target region is irradiated with only the X-rays by the preceding scanning, and the X-rays by the folding scanning are shielded by the shutter 52. Thereby, the exposure dose of the subject is reduced.

  Further, in the bone / soft tissue measurement mode, when the bone measurement target region 62-1 and the soft tissue measurement target region 62-2 do not overlap, only two types of X-rays are irradiated to each measurement target region. is there. This avoids that the subject 32 is irradiated with all X-rays of energy EH, EL, and EVL.

  The setting of the measurement target region in each measurement mode may be performed by a user operation. In this case, the user refers to the X-ray image displayed on the display 44 in step S108, and sets the measurement target region by operating the operation panel 44. The measurement target area set according to the operation may be displayed on the display 44. The control unit 44 reads information for setting the measurement target region from the operation panel 44.

  In each measurement mode, generation of X-rays at the start of measurement and interruption of X-rays at the end of measurement may be performed by the shutter 52. That is, the X-ray generator 26 may be set in advance in a state where X-rays are generated, and the shutter 52 may be opened and closed according to the start and end of measurement. As a result, generation of X-rays and interruption of X-rays are performed quickly. Further, instead of controlling the shutter 52, the control unit 40 may turn on and off the tube voltage or tube current of the X-ray tube.

  Furthermore, the tube current of the X-ray generator 26 in the return scan may be determined based on the detected X-ray data BL acquired in step S106. That is, the tube current may be increased as the value indicated by the detected X-ray data BL tends to be smaller. By such control, the thicker the subject 32 is, the greater the intensity of X-rays irradiated to the subject 32 is, and X-rays are detected with an appropriate intensity.

  Specifically, the smaller the evaluation value indicating the tendency of the magnitude of the value indicated by the detected X-ray data BL, such as the average value of the detected value group indicated by the detected X-ray data BL, is smaller. Increase the tube current. Even if the tube current is changed in this way, the X-ray energy does not change. Therefore, the attenuation constant in each tissue of the subject 32 is not affected, and the DXA method can be used for bone density measurement and fat / muscle rate measurement.

  In the above description, the control for starting the folding scan from the predetermined folding positions P2 and Q2 has been described. In addition to such control, the right end position of the soft tissue may be obtained based on the detected X-ray data BL, and X-ray scanning in the left direction may be started from the right end position of the soft tissue. In this case, after the preceding scanning is completed, the positions of the X-ray generator 26 and the X-ray detector 30 are transported to the right end position of the soft tissue at a speed higher than the X-ray scanning speed, and the return scanning is performed from this position. You can do that.

  10 X-ray measuring device, 12 body part, 14 arm part, 16 strut, 18 bucky table, 20 X-ray, 22 measurement space, 24 body part housing, 26 X-ray generator, 28 arm part housing, 30 X-ray Detector, 32 subject, 34 subject diagnostic space, 36 reference measurement space, 38 control device, 40 control unit, 42 operation panel, 44 display, 46 generator transport rail, 48 generator drive mechanism, 50 top plate, 52 Shutter, 54 Detector transport rail, 56 Detector drive mechanism, 58 Bottom plate, 60 X-ray image area, 62, 62-1, 62-2 Measurement target area, 64 Lumbar vertebra, 66 Soft tissue area.

Claims (4)

An X-ray generator that generates multiple types of X-rays with different energies;
An X-ray detector for detecting X-rays;
A control unit for controlling the X-ray generation unit,
The controller is
A first scanning unit that generates a first X-ray in the X-ray generation unit and scans the subject with the first X-ray;
A first calculation unit for obtaining a first detection value distribution according to the scanning of the first X-ray based on the X-ray detected by the X-ray detection unit;
A specifying unit that specifies a measurement target region included in the subject based on the first detection value distribution;
A second scanning unit that causes the X-ray generation unit to generate a second X-ray having energy different from that of the first X-ray, and scans the second X-ray with respect to the measurement target region;
A second calculation unit for obtaining a second detection value distribution according to the scanning of the second X-ray based on the X-ray detected by the X-ray detection unit;
A measurement unit that performs measurement on the measurement target region based on the first detection value distribution and the second detection value distribution;
An X-ray measurement apparatus comprising: The X-ray measurement apparatus according to claim 1,
A mode selection unit for selecting either the bone measurement mode or the soft tissue measurement mode;
When the bone measurement mode is selected,
The specifying unit specifies a bone region as the measurement target region,
The second scanning unit sets the energy of the second X-ray larger than the energy of the first X-ray,
The measurement unit performs measurement related to bone mineral in the measurement target region,
When the soft tissue measurement mode is selected,
The specifying unit specifies a soft tissue region as the measurement target region,
The second scanning unit sets the energy of the second X-ray to be smaller than the energy of the first X-ray,
The X-ray measurement apparatus, wherein the measurement unit performs measurement related to fat or muscle in the measurement target region. The X-ray measurement apparatus according to claim 1,
The specific part is:
As the measurement target region, a bone region and a soft tissue region are identified and specified,
The second scanning unit includes
For the scanning of the bone region, the energy of the second X-ray is set larger than the energy of the first X-ray,
For scanning the soft tissue region, the energy of the second X-ray is set smaller than the energy of the first X-ray,
The measuring unit is
An X-ray measurement apparatus, characterized in that measurement is performed on bone mineral in the bone region, and measurement is performed on fat or muscle in the soft tissue region. In the X-ray measuring device according to any one of claims 1 to 3,
The X-ray measurement apparatus, wherein the second scanning unit causes the X-ray generation unit to scan the second X-ray at a speed or tube current corresponding to the first detection value distribution.

Images