JP2006271437A - X-ray bone density measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent or reduce the unnecessary exposure of a subject to X rays in the transition period for the energy shift in a bone density measuring apparatus for measuring the bone density by applying high-energy X rays and low-energy X rays alternately to the subject. <P>SOLUTION: The period t1 in a gate signal (A) is the measuring time and the period t2 is the non-measuring time. The application voltage of an X-ray generator varies in the period t2 as indicated in (B). In the method of this embodiment as indicated in (D), a shield member is inserted on an X-ray beam path in the period t2, by which the exposure of the subject can be reduced. Accordingly, a rotating filter plate or a rotating filter drum can be used as a filter unit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an X-ray bone density measuring apparatus, and more particularly to an exposure reduction technique.

  In a bone density measuring device using the DXA method (Dual X-ray Absorptiometry), high-energy X-rays and low-energy X-rays are generated at regular intervals as the X-ray beam scans the living body. Are alternately illuminated. X-ray energy can be varied by switching the voltage of the X-ray generator (tube voltage switching method). A filter unit is used to adjust the spectrum and intensity for each X-ray. Specifically, one or a plurality of filter members are inserted on the path of the X-ray beam during irradiation with high energy X-rays and irradiation with low energy X-rays.

  In the above-described tube voltage switching method, the X-ray energy becomes unstable during the voltage transition period, so that period is generally excluded from the measurement. That is, for example, X-ray detection is performed only during a period in which the gate signal is HI (a period in which X-rays of each energy can be stably irradiated), and X-ray irradiation is performed in a period in which the detection gate signal is LOW. However, in reality, X-ray detection is not performed.

  In the following Patent Document 1, when an X-ray beam is zigzag scanned, a shutter is inserted on the X-ray beam path in an unmeasured period such as an acceleration period or a deceleration period other than the steady scanning speed, which is unnecessary in the living body. An apparatus for preventing exposure is described. Patent Documents 2 and 3 disclose a bone density measuring device having a drum-shaped filter mechanism.

JP 2004-113408 A JP-A-10-85208 JP-A-9-108206

  In a conventional X-ray bone density measuring apparatus, when high-energy X-rays and low-energy X-rays are alternately irradiated at a constant short period, X-rays are also emitted during an X-ray energy switching period (unstable transition period). Is being irradiated. Therefore, it is desired to reduce unnecessary exposure as much as possible. Patent Document 1 describes a technique that avoids unnecessary irradiation by using a shutter in a non-measurement period such as an acceleration / deceleration period. However, the document describes the exposure reduction at the time of switching the X-ray energy level. Not listed.

  An object of the present invention is to reduce unnecessary exposure during X-ray energy transfer when the X-ray energy is periodically switched.

  Another object of the present invention is to realize a compact filter mechanism that can easily switch filters.

(1) The present invention provides an X-ray generator that alternately and repeatedly generates high-energy X-rays and low-energy X-rays, and X-ray detection provided at a position irradiated with an X-ray beam from the X-ray generator. A filter unit having a detector, a mounting table for positioning a subject on the path of the X-ray beam, a plurality of filter members, and a filter selection mechanism for selecting a filter member to be inserted on the path of the X-ray beam And the plurality of filter members are shielded to be inserted on the path of the X-ray beam in each transition period between the irradiation period of the high energy X-ray and the irradiation period of the low energy X-ray. And a filter member for use.

  According to the above configuration, at least one or particularly preferably both of the transition period from the high energy X-ray to the low energy X-ray and the transition period from the low energy X-ray to the high energy X-ray, A shielding filter member is temporarily inserted on the path. That is, unnecessary X-ray irradiation to the subject can be prevented or reduced during a period other than the measurement period. The transition period is generally short and the shielding effect in that unit may be small, but since it is repeated, a significant exposure reduction effect can be obtained as a whole measurement. In addition, the generation of scattered X-rays during an unstable transition period can be prevented or reduced. As a shielding filter member, it is desirable to use a member having a high X-ray shielding ability such as lead or tungsten. However, even a member having a low X-ray shielding ability is increased in thickness to obtain the same effect. It is possible.

  The filter unit preferably has one or a plurality of filter members (selective insertion type filter members) selectively inserted on the path of the X-ray beam, and further, if necessary, the path of the X-ray beam. It has one or a plurality of filter members (fixed insertion type filter members) that are fixedly inserted above. Those filter members are provided between the X-ray generator and the subject. Furthermore, an X-ray shutter that closes before and after the start of measurement may be provided on the path, or an X-ray shutter that closes during the acceleration / deceleration period outside the measurement area may be provided. Good. Such an X-ray shutter and the shielding filter member are preferably provided separately, but may be integrated. The latter can be realized by controlling the filter selection mechanism. The switching of the X-ray energy can be realized preferably by switching the applied voltage of the X-ray generator tube, but the above configuration can be applied to other systems if the same problem occurs.

  Preferably, in the X-ray generator, the high-energy X-rays and the low-energy X-rays are alternately generated by switching the applied voltage to the X-ray generator tube included in the X-ray generator, , Which corresponds to a period during which the applied voltage transitions between high and low, during which period the shielding filter member is inserted on the path of the X-ray beam, and X-ray irradiation to the subject is intermittently limited. .

  Desirably, a gate signal generating means for generating a gate signal for specifying each irradiation period of the high energy X-ray and the low energy X-ray and each of the transition periods, and the X signal in synchronization with the gate signal. Control means for periodically switching the voltage applied to the line generating tube and periodically switching the filter member inserted on the path of the X-ray beam by the filter selection mechanism. According to this configuration, switching of the filter member and switching of the applied voltage are performed in synchronization with each other at an appropriate timing.

  Preferably, the plurality of filter members include an adjustment filter member and the shielding filter member, and the filter unit is provided so that the X-ray beam passes through a position shifted from a rotation center. The adjustment filter member and the shielding filter member are arranged in a circumferential direction, and the filter selection mechanism is a mechanism for rotating the filter plate. Preferably, the plurality of filter members include a first adjustment filter member, a second adjustment filter member, and the shielding filter member, and the first adjustment filter member includes the first adjustment filter member. The filter unit is fixedly arranged on a path of the X-ray beam, and the filter unit is a rotating plate provided so that the X-ray beam passes through a position shifted from a rotation center, A filter member, an opening, and the shielding filter member provided therebetween have a filter plate arranged in a circumferential direction, and the filter selection mechanism is a mechanism for rotating the filter plate. . According to this configuration, the shielding filter member is provided in at least one or particularly preferably both of the transition portion from the second adjustment filter member to the opening and the transition portion from the opening to the second adjustment filter portion. Provided. Since the filter member and the like can be selected simply by rotating the filter plate, the configuration can be simplified and the control is simple. As the adjustment filter member, a member for adjusting an X-ray energy spectrum, a member for adjusting an X-ray energy level, and the like can be used. The number of adjustment filter members (and openings) on the filter plate can be arbitrarily set according to the rotational speed and the applied voltage switching period.

  Preferably, the plurality of filter members include an adjustment filter member and the shielding filter member, and the filter unit is a rotating drum provided so that a rotation center axis intersects the X-ray beam. The adjustment filter member and the shielding filter member have a filter drum arranged in a circumferential direction, and the filter selection mechanism is a mechanism for rotating the filter drum. Preferably, the plurality of filter members include a first adjustment filter member, a second adjustment filter member, and the shielding filter member, and the first adjustment filter member includes the first adjustment filter member. The filter unit is fixedly arranged on the path of the X-ray beam, and the filter unit is a rotating drum provided so that a rotation center axis intersects the X-ray beam, and the second adjustment filter member and And an opening and a shielding filter member provided between them, each having a filter drum arranged in a circumferential direction, and the filter selection mechanism is a mechanism for rotating the filter drum. According to this configuration, the shielding filter member is provided in at least one or particularly preferably both of the transition portion from the second adjustment filter member to the opening and the transition portion from the opening to the second adjustment filter portion. Provided. Since the filter member and the like can be selected simply by rotating the filter drum, the configuration can be simplified and the control is simple. Furthermore, since it is not a disk type, the installation scale can be reduced. It is desirable that the filter drum is a hollow drum having no shaft member in the center. In such a configuration, both ends of the filter member are pivotally supported. As the filter member, it is desirable to use a single cylinder type, but it is also possible to use a double cylinder type.

  Preferably, the X-ray beam has a fan beam shape that spreads in a fan shape, and a rotation center axis of the filter drum coincides with a spreading direction of the X-ray beam. According to this configuration, even if the X-ray beam spreads in the lateral direction, the passage path to the filter member can be made substantially constant at each of the spread positions. It is also possible to perform electrical correction for each X-ray sensor in the X-ray detector.

  As described above, according to the present invention, unnecessary exposure during X-ray energy transfer can be reduced when the X-ray energy is periodically switched. Or according to this invention, the compact filter mechanism which can switch a filter simply is realizable.

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

  FIG. 1 shows a preferred embodiment of a bone density measuring apparatus according to the present invention, and FIG. 1 is a perspective view thereof. The bone density measuring device shown in FIG. 1 is a device that measures the bone density of the human body, particularly at the forearm, but the present invention can also be applied when measuring other sites.

  A forearm portion of the subject is placed on the mounting table 10. In the state where the rod-shaped member 12 is gripped, the forearm portion is positioned on the mounting table 10, and the X-ray beam 20 is scanned in this state. The X-ray beam 20 is a pencil beam in the example shown in FIG. 1, but may be a fan beam spreading in a so-called fan shape. Or you may have another beam form.

  The measurement unit 14 includes an X-ray generator 16 and an X-ray detector 18, and the measurement unit 14 is transported by a transport mechanism. When the X-ray beam 20 having a fan beam shape is used, the measurement unit 14 is one-dimensionally scanned in the longitudinal direction of the subject. On the other hand, when the X-ray beam 20 having a pencil beam shape is used, the measurement unit 14 is used. Is zigzag scanned. In any case, bone density is measured over a two-dimensional measurement region.

  In the example shown in FIG. 1, the X-ray generator 16 is provided in the apparatus main body, while the X-ray detector 18 is accommodated in a measurement head 17 provided above the mounting table 10. Specifically, the X-ray generator 16 is mounted on the lower end portion of the transport frame 24, and the measurement head 17 is provided on the upper end portion of the transport frame 24. As described above, the X-ray detector 18 is accommodated in the measurement head 17. The transport frame 24 is mechanically transported to scan the X-ray beam 20 as described above. A mechanism for this is not shown. Note that an X-ray generator may be provided above the mounting table 10, while an X-ray detector may be provided below the mounting table 10.

  A filter unit 22 is provided between the X-ray generator 16 and the mounting table 10. The structure of the filter unit 22 will be described in detail later with reference to FIG. 2 and the like. The filter unit 22 has a rotating filter plate in the example shown in FIG. In another embodiment described later in FIGS. 6 to 8, a rotating filter drum is used as the filter unit in place of the rotating filter plate. In any case, an appropriate bone density measurement can be performed by selectively inserting an appropriate filter member on the path of the X-ray beam. In that case, unnecessary exposure can be effectively reduced by the filter unit, and scattered X-rays can be effectively reduced.

  FIG. 2 is a block diagram showing the overall configuration of the bone density measuring apparatus shown in FIG. An X-ray generator 16 is provided below the subject 30 with the subject 30 interposed therebetween, and an X-ray detector 18 is provided above the subject 30. In the example shown in FIG. 1, the subject 30 is a forearm, but the subject 30 may be a torso or a leg.

  A power supply 32 is connected to the X-ray generator 16, and a voltage applied by the power supply 32 is controlled by the control unit 34. That is, the X-ray generator 16 has a function of generating high energy X-rays and a function of generating low energy X-rays, and energy switching is performed by an X-ray generator tube provided in the X-ray generator 16. This is done by switching the applied voltage to. That is, the X-ray energy can be switched between high and low by switching the voltage applied by the power supply 32 between high and low.

  The X-ray detector 18 is constituted by a single X-ray sensor or a plurality of X-ray sensors. The X-ray detection signal is input to the signal processing unit 46, and the signal processing unit 46 performs signal processing for calculating bone density. Incidentally, the calculation of the bone density may be performed by the signal processing unit 46 or may be performed by the control unit 34. In the present embodiment, bone density is calculated according to the DXA method described above. The calculation result is displayed on the display unit 50. An input unit 48 is connected to the control unit 34, and the user can set operation conditions by using the input unit 48. The control unit 34 controls the operation of each component shown in FIG. 2, and particularly has a function of generating a gate signal which will be described later with reference to FIG. 5. The operation of each component is synchronized with the gate signal. I have control. The operation of the transport mechanism 36 is controlled by the control unit 34, and the transport mechanism 36 transports the measurement unit shown in FIG.

  In the configuration example illustrated in FIG. 2, the filter unit 22 includes a filter plate 41, a filter driving unit 44, and a first filter member 45. Here, the 1st filter member 45 is comprised, for example with aluminum etc., is fixedly provided on the path | route of an X-ray beam, and the effect | action is always exhibited. That is, the first filter member 45 is provided for adjusting the energy spectrum or the energy level for both high energy X-rays and low energy X-rays.

  As will be described later with reference to FIG. 4, the filter plate 41 is configured as a rotating disk, and includes a plurality of second filter members 64 alternately arranged along the circumferential direction, and a plurality of openings. Have. The gap between each second filter member 64 and each opening is provided with a shielding member as a third filter member. The entire filter plate 41 is constituted by a shielding member 62 except for the second filter member 64 and the opening. Here, the 2nd filter member 64 functions as a filter corresponding to a low energy X-ray, for example, is constituted by a copper member. The shielding member is made of a member such as lead and copper, for example. The shielding member is preferably composed of a member having a high degree of attenuation of X-rays. In addition to lead as described above, a member such as tungsten can be used, or a member having a low degree of attenuation of X-rays is made thick. As a result, a shielding effect may be obtained.

  The filter drive part 44 drives the rotating shaft in the filter plate 41, and rotates the filter plate 41 at a fixed speed. The operation is controlled by the control unit 34. The X-ray beam is transmitted to a position shifted from the center in the filter plate 41.

  Reference numeral 38 denotes a shielding member as a shutter, and the shutter 38 is made of a member such as lead or tungsten. The shutter drive unit 46 drives the shutter 38 forward and backward, and the shutter 38 is inserted on the path of the X-ray beam before or after the start of the bone density measurement. Further, for example, when measuring the bone density, the shutter 38 is inserted into the path of the X-ray beam during a period such as an acceleration period and a deceleration period when a zigzag scan is performed. Thereby, unnecessary exposure in the subject 30 can be prevented. Further, in the present embodiment, the shielding member is inserted in order to reduce unnecessary exposure even during the transition period in which the X-ray energy is switched, and this will be described later with reference to FIGS. To do.

  FIG. 3 shows a filter plate 52 as a conventional example. The rotating shaft 58 is provided with a pair of sector plates 54 extending in the horizontal direction, and the sector plates 54 are each configured as an energy spectrum adjusting member such as copper. A gap 56 between the two sector plates 54 is an opening.

  The opening 56 is inserted on the X-ray beam path during irradiation with high energy X-rays, while the sector plate 54 is inserted on the X-ray beam path during irradiation with low energy X-rays. The protrusion 54A provided on the outer edge of the sector plate 54 is a marker for detecting the rotation angle and the like.

  FIG. 4 shows a filter plate 41 according to this embodiment. The filter plate 41 has a body configured as a circular shielding plate 62, and the shielding plate 62 has a member such as lead or tungsten as described above. Furthermore, you may have members, such as copper. Two openings 66 are formed in the shielding plate 62 along the circumferential direction. Each opening 66 is circular in the example shown in FIG. The shielding plate 62 is provided with two second filter members 64 along the circumferential direction. In the shielding plate 62, the part where the second filter member 64 is provided is an opening. Accordingly, when the filter plate 41 is observed along the circumferential direction, the openings 66 and the second filter members 64 are alternately arranged such as the openings 66, the second filter members 64, the openings 66, and the second filter members 64. It is arranged. However, a shielding member constituting the shielding plate 62 is provided between them. Specifically, members such as lead and tungsten are provided in the four gaps 62A generated between the opening 66 and the second filter member 64. That portion functions as a third filter member, that is, exhibits a function of shielding X-rays in the transition period in the irradiation interval of high energy X-rays and low energy X-rays. The protrusion 62B is a marker for optically detecting the rotation angle of the filter plate 41, for example.

  FIG. 5 shows an operation example of the above-described bone density measuring apparatus. (A) shows a gate signal generated by the controller 34 shown in FIG. Here, the period t1 indicates an X-ray irradiation period (a high energy X-ray irradiation period and a low energy X-ray irradiation period), and t2 indicates a non-measurement period that exists intermittently between them. For example, t1 is 3.3 ms and t2 is 1.7 ms. (B) shows the waveform of the voltage applied to the X-ray generator. Here, LO indicates a low voltage, and HI indicates a high voltage. In the period t2, the voltage is changed, that is, the voltage is changed from the low voltage to the high voltage, or the voltage is changed from the high voltage to the low voltage. During these periods, the voltage is unstable.

  According to the conventional method as shown in FIG. 3, the operation is as shown in (C). If f1 is defined as a filter action by an opening and f2 is defined as a filter action by the above-mentioned sector-shaped filter member, f1 and f2 are alternately switched. It can be pointed out that the switching of the filter action is performed during this transition period, and irradiation continues during that period, causing unnecessary exposure to the subject. Further, since the filter action is suddenly switched during the transition period, there is a concern about generation of scattered X-rays and the like.

  (D) shows the system of this embodiment. Here, f1 shows a filter action corresponding to the opening 66 shown in FIG. 4, f2 shows a filter action equivalent to the second filter member 64 shown in FIG. 4, and f3 shows a shielding plate 62. The shielding action by the shielding member which comprises, ie, the 3rd filter member, is shown. For example, f1 is a shielding action by aluminum, f2 is a shielding action by copper and aluminum, and f3 is a shielding action by lead, copper and aluminum. That is, in the configuration example shown in FIGS. 1 and 2, the first filter member is always inserted, and the action of aluminum is always working.

  According to the method shown in (D), in the transition period t2, as shown by f3, the shielding member is inserted on the path of the X-ray beam, and the X-ray irradiation in that period is blocked. As described above, there is an advantage that unnecessary exposure can be prevented or problems such as scattered X-rays can be prevented. Although the period t2 is a short time, it occurs repeatedly and periodically, and therefore, it is expected that a slight exposure will be a constant exposure amount as a whole. The configuration according to the present embodiment is recognized as having extremely high practical value in that such exposure dose can be eliminated. In addition, all the specific examples of each member mentioned above are examples, and various members can be used as long as the same operation as described above is obtained. In that case, not only a single member but also a plurality of members may be combined to form a desired filter member.

  Therefore, according to this embodiment, combined with the use of the shutter shown in FIG. 2, there is an advantage that the exposure dose in a series of steps of bone density measurement can be reduced as much as possible. In the configuration example shown in FIG. 4, the shapes of the opening 66 and the second filter member 64 can be appropriately determined according to the shape of the X-ray beam. For example, the shape thereof may be an arc shape. Further, the weight of the shielding plate 62 can be reduced by excluding portions that do not substantially function. That is, it is only necessary to provide a member that exhibits a desired filter action at least in a region through which the X-ray beam passes.

  Next, another configuration example of the filter unit will be described with reference to FIGS. In the filter unit 70 shown in FIG. 6, a filter drum 80 is provided. Reference numeral 72 denotes an X-ray generator. The X-ray generator 72 includes an X-ray generator tube, a collimator, and the like. Further, an aluminum plate or the like as a first filter member is provided at the emission end.

  The filter drum 80 is rotatably supported by the frame 74. Specifically, one end 74 </ b> A of the frame 74 pivotally supports one end of the shaft 78 of the filter drum 80, and a drive unit 76 is attached to the other end of the frame 74. The other end of 78 is pivotally supported. The shaft member 78 is rotated by the drive of the drive unit 76, and the filter drum 80 is rotated accordingly. The filter drum 80 has three openings 88, one second filter member 86, and four shielding members 84 along the circumferential direction thereof. In the example shown in FIG. 6, the X-ray beam 82 has a fan beam shape, and the X-ray beam 82 passes through the second adjustment filter member 86 through an opening positioned below. On the other hand, in the example shown in FIG. 7, the X-ray beam 82 passes through the opening positioned below and the opening positioned above as it is. The operation will be described in detail with reference to FIG.

  FIG. 8 shows a schematic cross-sectional view of the rotating filter drum 80. As shown in (A) to (C), the filter drum 80 has three openings 88-1, 88-2, 88-3, one second filter member 86, and four along the circumferential direction. There are two shielding members 84-1, 84-2, 84-3, 84-4. Each member is made of the material described above.

  As shown in (A), at the time of irradiation with high energy X-rays, the X-ray beam incident from the opening 88-3 passes through the opening 88-1 and is irradiated to the subject. Next, as shown in (B), at the time of low-energy X-ray irradiation, the X-ray beam entered from the opening 82-2 positioned below, and the X-ray beam was positioned upward. The subject is irradiated through the second filter member 86. Furthermore, as shown in (C), in the above-described switching period of the tube voltage, that is, the transition period, both the shielding member 84-2 positioned below and the shielding member 84-4 disposed above are combined. The X-ray attenuation effect is exhibited. In this case, since the two shielding members 84-2 and 84-4 are arranged on the X-ray beam path, the shielding effect can be enhanced. However, if a sufficient shielding effect can be obtained by only one of them, the shielding member may be provided on only one of them.

  In any case, as the rotating drum 80 rotates at a constant speed, the filter actions as described above are obtained sequentially, and it is possible to sufficiently shield X-rays particularly during the transition period. Thus, it is possible to effectively reduce the exposure to the subject. The embodiment shown in FIGS. 6 to 8 has an advantage that the installation volume of the filter unit can be reduced because the rotary drum 80 is used.

  As shown in FIGS. 6 and 7, when an X-ray beam 82 having a fan beam shape is used, the spreading direction thereof coincides with the central axis of the filter drum 80. As a result, the filter action at each position in the lateral direction of the fan beam becomes substantially the same even when the filter drum 80 is rotated, so that the positional instability of the filter action can be eliminated. Incidentally, the inside of the filter drum 80 is hollow, and the shaft exists only at the end. The filter drum can also have a double cylindrical structure.

It is a perspective view which shows suitable embodiment of the bone density measuring apparatus which concerns on this invention. It is a block diagram which shows the whole structure of the bone density measuring apparatus shown in FIG. It is a figure which shows an example of the filter plate in a prior art example. It is a figure which shows an example of the filter plate in embodiment shown in FIG. 3 is a timing chart for explaining the operation of the apparatus shown in FIGS. 1 and 2. It is a figure which shows the structural example of the filter unit which concerns on other embodiment. It is a figure which shows the structural example of the filter unit which concerns on other embodiment. It is a figure for demonstrating the effect | action of the filter drum which concerns on other embodiment.

Explanation of symbols

  10 mounting table, 14 measurement unit, 16 X-ray generator, 18 X-ray detector, 20 X-ray beam, 22 filter unit, 41 filter plate, 80 filter drum.

Claims (8)

An X-ray generator that alternately and repeatedly generates high energy X-rays and low energy X-rays;
An X-ray detector provided at a position irradiated with an X-ray beam from the X-ray generator;
A mounting table for positioning a subject on a path of the X-ray beam;
A filter unit having a plurality of filter members and a filter selection mechanism for selecting a filter member to be inserted on the path of the X-ray beam;
Including
The plurality of filter members include a shielding filter member inserted on a path of the X-ray beam in each transition period between the high energy X-ray irradiation period and the low energy X-ray irradiation period. X-ray bone density measuring apparatus characterized by that. The apparatus of claim 1.
In the X-ray generator, the high-energy X-rays and the low-energy X-rays are alternately generated by switching the voltage applied to the X-ray generator tube of the X-ray generator,
Each of the transition periods corresponds to a period in which the applied voltage transitions between high and low, and in that period, the shielding filter member is inserted on the path of the X-ray beam, and X-ray irradiation to the subject is intermittent. Limited,
An X-ray bone density measuring apparatus characterized by the above. The apparatus of claim 2.
Gate signal generating means for generating a gate signal for specifying each irradiation period of the high energy X-ray and the low energy X-ray and each transition period;
Control means for periodically switching a voltage applied to the X-ray generation tube in synchronization with the gate signal, and periodically switching a filter member inserted on the path of the X-ray beam by the filter selection mechanism; ,
An X-ray bone density measuring apparatus comprising: The apparatus of claim 1.
The plurality of filter members include an adjustment filter member and the shielding filter member,
The filter unit is a rotating plate provided so that the X-ray beam passes through a position shifted from a rotation center, and the adjustment filter member and the shielding filter member are arranged in a circumferential direction. Having a filter plate,
The filter selection mechanism is a mechanism for rotating the filter plate;
An X-ray bone density measuring apparatus characterized by the above. The apparatus of claim 1.
The plurality of filter members include a first adjustment filter member, a second adjustment filter member, and the shielding filter member,
The first adjustment filter member is fixedly disposed on a path of the X-ray beam;
The filter unit is a rotating plate provided so that the X-ray beam passes through a position shifted from the rotation center, and is provided between the second adjustment filter member, the opening, and the second adjustment filter member. And the filter member for shielding, having a filter plate arranged in a circumferential direction,
The filter selection mechanism is a mechanism for rotating the filter plate;
An X-ray bone density measuring apparatus characterized by the above. The apparatus of claim 1.
The plurality of filter members include an adjustment filter member and the shielding filter member,
The filter unit is a rotating drum provided so that a rotation center axis intersects with the X-ray beam. The filter unit includes a filter drum in which the adjustment filter member and the shielding filter member are arranged in a circumferential direction. Have
The filter selection mechanism is a mechanism for rotating the filter drum.
An X-ray bone density measuring apparatus characterized by the above. The apparatus of claim 1.
The plurality of filter members include a first adjustment filter member, a second adjustment filter member, and the shielding filter member,
The first adjustment filter member is fixedly disposed on a path of the X-ray beam;
The filter unit is a rotating drum provided so that a rotation center axis intersects the X-ray beam, and the second adjustment filter member, an opening, and the above-described filter provided between them. A shielding filter member and a filter drum arranged in a circumferential direction,
The filter selection mechanism is a mechanism for rotating the filter drum.
An X-ray bone density measuring apparatus characterized by the above. The device according to claim 6 or 7,
The X-ray beam has a fan beam shape spreading in a fan shape,
The rotation center axis of the filter drum matches the spreading direction of the X-ray beam,
An X-ray bone density measuring apparatus characterized by the above.

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