JP5027711B2 - Radiation imaging apparatus and method, and program - Google Patents

Description

  The present invention relates to a radiographic image capturing apparatus, method, and program, and in particular, a plurality of images obtained by capturing a long radiation image using an FPD (flat panel detector) while changing the radiation field. The present invention relates to a technique that enables long composition with high accuracy when connecting two images.

  2. Description of the Related Art Conventionally, a radiographic imaging apparatus that irradiates a subject with radiation such as X-rays, detects the transmitted radiation, acquires a radiographic image, and provides for diagnosis is widely known. In this radiographic imaging apparatus, a radiation detector that detects radiation transmitted through a subject is known using a radiation film or a storage phosphor sheet that accumulates radiation energy.

  In radiographic imaging for medical diagnosis, long imaging is performed in order to grasp and diagnose the entire subject at once for the entire spine and the entire length of the lower limb.

  In conventional long shooting, a long radiation film is stored in a long dedicated cassette for shooting, or a plurality of stimulable phosphor sheets are arranged so as to partially overlap each other. It was housed in a cassette and shot.

  For example, in order to prevent the loss of images, the ends of two adjacent phosphorescent phosphor sheets are photographed so as to overlap each other, and the read image data is synthesized without excess or deficiency by image processing. There is known a CR (Computed Radiography) system capable of obtaining the image (see, for example, Patent Document 1).

  Thus, in the case of taking a long image by combining images captured on a plurality of stimulable phosphor sheets, a plurality of stimulable phosphors are used in order to synthesize a plurality of images accurately and stably. It is preferable to record an image after placing a positioning marker in advance between the sheets. By identifying markers such as lower limbs, the markers that serve as alignment marks can be attached to the outside of the cassette or embedded inside the cassette, and the marker imaged together with the subject image. Even in difficult regions, the stability of the image composition process can be improved.

  In recent years, as an X-ray detector for detecting an X-ray transmission image of a subject generated by X-ray irradiation by an X-ray tube, an extremely large number of X-ray detection elements using a semiconductor or the like are used as an X-ray detection surface. A flat panel X-ray detector (FPD, flat panel detector) arranged vertically and horizontally is used.

  For example, in long imaging using FPD, it is known that partial images at a plurality of positions of a subject are obtained by moving the FPD, and a long overall image is obtained by connecting them. (For example, see Patent Document 2 or Patent Document 3).

In the method using the FPD, as in the system using the stimulable phosphor sheet, in order to synthesize the image with high accuracy and stability, a marker serving as an alignment mark is arranged in advance. It is preferable to record and record. Further, the body movement of the subject can be confirmed by photographing and recording the marker together with the subject.
Japanese Patent Laid-Open No. 2000-257661 JP 2004-358254 A JP-T-2006-500126

  However, in the long shooting using the FPD, unlike the CR system in which a plurality of stimulable phosphor sheets are arranged and a plurality of partial images are obtained in one shot, the position of one panel is moved and shot. Therefore, in order to capture and record the alignment marker at a desired position in the image (in the overlapping area between the partial images), it is necessary to place the marker at an appropriate position every time the image is captured. There is a problem that it is bothersome and takes a long time.

  The present invention has been made in view of such circumstances, and in long shooting using an FPD, the marker can be easily used without having to adjust the position of a marker serving as a marker when combining a plurality of images. It is an object of the present invention to provide a radiographic image capturing apparatus, method, and program that can improve the convenience of long imaging.

In order to achieve the above-mentioned object, the invention according to claim 1 is directed to a radiation detector by moving a radiation detector so that a part of each part overlaps, taking a plurality of images, and synthesizing the overlapping parts. A radiographic imaging device for obtaining an image of a subject longer than the maximum field of view of the radiation source, a radiation source for emitting radiation, and a radiation detector for detecting radiation emitted from the radiation source and transmitted through the subject, , is formed by radiolucent material, said a partition disposed between the detector and the object, are formed by material having a high radiation attenuation coefficient, so that the mark in the synthesis of the image, opposition Markers arranged along an elevation, imaging condition setting means for setting an imaging range and the position of the radiation source as imaging conditions, and radiation emitted from the radiation source based on the set imaging conditions Wherein the projection position on the plane including the movable range of the radiation detector of the marker, the imaging and different imaging conditions for each, using the information relating to the location of the known the marker that is not based on imaging geometrically by Based on the calculated projection position and the calculated projection position, individual positions for moving the radiation detector for taking a plurality of images and the position of the radiation source or the radiation irradiation direction corresponding thereto are determined. There is provided a radiographic imaging apparatus comprising: a determination unit; and a control unit that controls the radiation source and the radiation detector based on the determination by the determination unit.

  Thereby, the projection position of the marker on the radiation detector is calculated based on the condition setting at the time of photographing, and the marker is photographed and recorded in the overlapping region between the plurality of photographed images based on the projection position of the marker. Since the detection system and the imaging system are controlled in this way, it is not necessary to adjust the marker position for each shooting during long shooting, and the length using the alignment marker when combining multiple images It is possible to improve the convenience of measuring the scale.

According to a second aspect of the present invention , a plurality of the markers are arranged at predetermined intervals in the vertical direction of the partitions along the partition surface. According to a third aspect of the present invention, the determining means further calculates a radiation irradiation range at each position where the radiation detector is moved, and a diaphragm disposed between the radiation source and the subject. The opening is determined, and the control means further controls the diaphragm based on the determination by the determining means. Accordingly, the present invention can be applied to a case where three or more images are captured and connected by switching the projection position and the radiation irradiation direction. In addition, this makes it possible to perform long shooting efficiently.

Further, as shown in claim 4, the determination means further determines the number of the plurality of images necessary to cover the imaging range of the subject and the position of the radiation detector in imaging each image. The image is determined so as to include the marker above and below the X-ray irradiation range of each radiation detector at each position of the radiation detector, the projected position of the marker on the radiation detector, Calculate based on the size, the size of the area where each image overlaps, and the interval of the marker projected on the radiation detector, and determine the X-ray irradiation direction from the calculated X-ray irradiation range, An opening of a diaphragm arranged between the radiation source and the subject is determined from an angular width of the X-ray irradiation range viewed from the radiation source, and the control means further includes: And controlling the iris based on the constant. Thereby, by calculating the X-ray irradiation range of each radiation detector and controlling the aperture, it is possible to prevent irradiation to an extra range unrelated to imaging and to reduce the exposure dose.

Similarly, in order to achieve the above object, the invention according to claim 5 , the radiation detector is moved so that a part of each part overlaps, and a plurality of images are taken and combined at the overlapping part. A radiographic imaging method for obtaining an image of a subject longer than the length of the maximum field of view of the radiation detector by detecting radiation emitted from a radiation source and transmitted through the subject, an imaging range, and the radiation source A step of setting the position as an imaging condition, and the image formed of a substance having a large radiation attenuation coefficient along a partition surface formed of a radiation transmissive material and disposed between the subject and the detector Including a step of arranging a marker that serves as a marker when combining the radiation detector, and a movable range of the marker by the radiation emitted from the radiation source based on the set imaging condition. A projection position on the surface, the a different imaging condition for each shooting, a step of geometrically determined using the information relating to the location of the known the marker that is not based on shooting, on the basis of the calculated projection position Determining an individual position to move the radiation detector for taking a plurality of images and a position or radiation direction of the radiation source corresponding to the position, and based on the determination by the determination means, And a step of controlling the radiation detector. A radiographic imaging method comprising:

  Thereby, the projection position of the marker on the radiation detector is calculated based on the condition setting at the time of photographing, and the marker is photographed and recorded in the overlapping region between the plurality of photographed images based on the projection position of the marker. Since the detection system and the imaging system are controlled in this way, it is not necessary to adjust the marker position for each shooting during long shooting, and the length using the alignment marker when combining multiple images It is possible to improve the convenience of measuring the scale.

According to a sixth aspect of the present invention, in the step of arranging the markers, a plurality of the markers are arranged at predetermined intervals in the vertical direction of the screen. Similarly, in order to achieve the object, the invention described in claim 7 provides a program that causes a computer to execute the radiographic imaging method described in claim 5 or 6 .

  In this way, similarly, it is possible to improve the convenience of long shooting using a positioning marker when combining a plurality of images.

  As described above, according to the present invention, the projection position of the marker on the radiation detector is calculated based on the condition setting at the time of photographing, and the plurality of images obtained by photographing the marker based on the projection position of the marker Since the detection system and the imaging system are controlled so as to capture and record in the overlapping area between them, there is no need to adjust the position of the marker for each shooting during long shooting, and when combining multiple images It is possible to improve the convenience of long shooting using the alignment marker.

  Hereinafter, a radiographic imaging apparatus and method, and a program according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing a first embodiment of a radiographic image capturing apparatus according to the present invention.

  As shown in FIG. 1, the radiographic imaging apparatus 10 of this embodiment mainly includes an X-ray source 12 that irradiates a subject M with X-rays, and a collimator 14 that narrows down X-rays emitted from the X-ray source 12. A flat panel X-ray detector (FPD, flat panel detector, hereinafter also referred to as a detection panel) 16 that detects X-rays transmitted through the subject M and outputs a detection signal, and the subject M maintains a posture during imaging A controller 18 (console) for setting and calculating various partitions necessary for photographing, and a partition 20 for combining the screen 18 and a marker 20 for combining a plurality of photographed images. ) 22.

  Although the detailed description of the X-ray source 12 is omitted, the X-ray source 12 has an X-ray tube that irradiates the subject M with X-rays, and the controller 22 controls the tube voltage and tube current applied to the X-ray tube. Then, the energy of the emitted X-ray is controlled.

  The FPD 16 has a light-receiving surface (panel surface) formed on a surface thereof in a flat plate shape, and the inclination can be changed so that the light-receiving surface is horizontal or vertical. X-rays that have passed through the specimen M are detected photoelectrically and an analog electrical signal is output. The output signal of the FPD 16 is converted into a digital signal and input to the control unit 22 or converted into a digital signal in the control unit 22 and subjected to image processing.

  The FPD 16 is installed so as to be movable along a support column 24 provided in parallel to the body axis of the subject M. In long shooting, shooting is performed by moving the FPD 16 so as to have the overlapping region 26, and one long image is obtained by combining the obtained plural images in the overlapping region 26.

  The screen 18 is used for supporting and fixing the posture of the subject M while taking a plurality of images in a state where the subject M is standing, for example, when taking a long picture of the entire spine. Is. The screen 18 is made of a radiation transmissive material.

  The marker 20 serves as a mark when a plurality of captured images are combined, and is arranged at an appropriate position of the partition 18 according to the subject M and the captured images. The marker 20 is formed, for example, in a shape of about 10 mm by using a substance having a large radiation attenuation coefficient such as a lead with a corner.

  FIG. 2 is an explanatory diagram showing the positional relationship between the X-ray source 12 and the FPD 16 when the radiographic image capturing apparatus 10 is used for long imaging.

  As described above, when an image longer than the length of the FPD 16 is captured, the X-ray irradiation direction from the X-ray source 12 is changed while moving the FPD 16 along the support column 24 so as to have the overlapping region 26. By doing so, long shooting is performed. By synthesizing the plurality of X-ray images obtained in this way in the overlapping region 26, one long image is obtained.

  FIGS. 2A and 2B show a case where the FPD 16 is moved to three different positions and the X-ray irradiation direction is switched three times for imaging. FIGS. 2C and 2D show a case where the FPD 16 is moved to two different positions and the X-ray irradiation direction is switched twice to perform imaging. 2A and 2C show the case where the distance from the X-ray source 12 to the FPD 16 is short, and FIGS. 2B and 2D show that the distance from the X-ray source 12 to the FPD 16 is long. Is the case.

  In either case, the marker 20 is projected onto the overlapping area 26 of the FPD 16. Furthermore, at this time, the imaging system and the detection system can be controlled so that the position of the marker 20 placed on the partition 18 can be fixed regardless of the position, height, or X-ray irradiation range of the X-ray source 12. This is desirable, but will be described in detail later.

  The marker 20 that serves as a marker when combining a plurality of photographed images is disposed on the partition 18, but may be embedded in the partition 18, detachable from the partition 18, and slidable. Also good.

  For example, as shown in FIG. 3, the markers 20 are bonded and fixed to the surface of a long and narrow strip-shaped member 30 at a predetermined interval, and hooks 28 are attached to the top and bottom of the strip-shaped member 30 to You may make it attach to the frame member 19 so that attachment or detachment is possible.

  Next, an outline of a long image capturing method in the radiographic image capturing apparatus 10 of the present embodiment will be described. In addition, the long imaging | photography method demonstrated below is an example, Comprising: It is not limited to this.

  In performing long imaging, first, as preparation for imaging, normal X-ray imaging is usually performed via a control unit (console) 22 installed in a separate room from the imaging room in which the X-ray source 12 and the FPD 16 are installed. A shooting menu such as long shooting is selected. Although not shown in the drawing, a desired menu may be selected and input by touching the shooting menu displayed on the display screen (control panel) of the control unit 22 or may be input to the control unit 22. You may make it input using input means, such as a connected keyboard and a mouse | mouth.

  And the partition 18 and the marker 20 are arrange | positioned in the predetermined position of an imaging | photography room (illustration omitted). The screen 18 has a mechanism for fixing it at a predetermined position in the photographing room. For example, a configuration in which a stopper is inserted and fixed in the floor hole of the photographing room may be used, or a configuration in which the stopper is connected or integrated with the stand may be employed.

  Also, instead of setting the shooting menu after selecting the shooting menu in this way, the shooting menu and shooting mode may be controlled according to the setting state of the partition 18 and the like. . For example, the control unit 22 may detect that the partition 18 or the like has been set and automatically enter the long photographing mode.

  Further, when a long shooting menu is selected via the control unit 22, the partition 18 may be automatically set at a predetermined position in accordance with the selected menu. For example, as a screen of a projector, a form that is lifted or lowered during use, or a form in which the partition 18 moves to a predetermined position while automatically grasping the positional relationship between the stand and the X-ray source 12. Also good.

  By arranging the partition 18 at a predetermined position, the positional relationship (distance) with the X-ray source 12 is determined, but instead of moving the partition 18 in this way, the X-ray source 12 is moved horizontally and vertically. The distance between the X-ray source 12 and the partitions 18 and the FPD 16 may be set by setting the position of the X-ray source 12 so as to be movable in the direction.

  When preparation for imaging is completed, the subject (patient) is then entered into the imaging room and placed at a predetermined position before the screen 18. Then, an imaging range is set according to the height and width of the subject M, the imaging purpose, and the imaging site. Thus, the imaging conditions such as the imaging range and the position of the X-ray source 12 (relative position between the X-ray source 12 and the X-ray detector (FPD 16)) are set.

  Next, the X-ray irradiation range is set by adjusting the collimator 14 with respect to the imaging range. The control unit 22 calculates the irradiation range of the X-ray that irradiates the detection surface (panel surface) of the FPD 16 through the subject M positioned in front of the screen 18 from the position of the X-ray source 12 and the opening of the collimator 14. Sought by. Then, when the determination button on the control panel of the console is touched (pressed), the X-ray irradiation range is determined.

  Then, in the control unit 22, an imaging procedure such as a moving method of the FPD 16 (X-ray detection panel) when imaging a long image is set based on the set imaging conditions. For example, as a method of moving the FPD 16, first, the FPD 16 is arranged so that the top position of the FPD 16 coincides with the upper end of the X-ray irradiation range, and imaging is started. Control to move.

  The X-ray irradiation range is not calculated, but an irradiation field lamp is arranged in the vicinity of the X-ray source 12, the imaging room is darkened, and visible light is irradiated from the irradiation field lamp. The range of light striking the screen 18 after being squeezed by 14 may be obtained by visually confirming. The irradiation field lamp is not particularly limited as long as it can irradiate visible light. Usually, the irradiation field lamp is used in combination with a mirror so as to have a light irradiation field that matches the irradiation field of the X-ray source 12.

  Moreover, in the control part 22, based on the said imaging | photography procedure, the marker 20 arrange | positioned along the screen 18 surface on the detection surface (panel surface) of FPD16 by the X-rays irradiated from the X-ray source 12 is shown. A projection position is calculated.

  When the projection position of the marker 20 on the FPD 16 (detection panel) is calculated, the number of divisions when photographing a long image, the position (panel position) of the FPD 16 when photographing each division image, and the X-ray source Control information such as 12 irradiation angles (irradiation directions) is determined by the control unit 22.

  Further, the control unit 22 confirms the control amount of the X-ray source 12 in actual imaging such as the tube voltage and irradiation dose of the X-ray source 12 according to the imaging procedure set above, and if necessary. Changed.

  Next, a method for calculating the values of the above control amounts will be described with reference to the drawings.

  FIG. 4 is an explanatory diagram of a method for calculating values such as control amounts.

  As shown in FIG. 4, the setting information fixed to the apparatus and the setting information set for each photographing are stored in the memories 32 and 34 of the control unit 22, respectively. The control unit 22 reads necessary information from the memories 32 and 34 and calculates various values.

  Device fixed setting information stored in the database of the memory 32 includes the screen size panel of the panel surface of the FPD 16 (detection panel), the distance db between the screen and the detection panel, and the marker arrangement position expressed by the height from the floor. hm ′ (1), hm ′ (2),..., marker size marker, etc.

  The information set for each imaging stored in the memory 34 includes the X-ray source height hs, the distance da between the X-ray source and the detection panel, and the upper end ht of the imaging range on the surface on which the FPD 16 is arranged. And shooting range information [ht, hb] represented by the lower end hb.

  First, in step S10 of FIG. 4, the control unit 22 calculates the projection position of the marker 20 on the panel surface of the FPD 16. The projection position hm (i) on the panel surface of the i-th marker 20 from the top of the marker 20 arranged on the partition 18 (not shown in FIG. 4) is the distance da, the partition between the X-ray source and the detection panel. It is calculated by the following equation (1) from the distance db between the detection panels, the X-ray source height hs, and the marker arrangement position hm ′ (i) on the screen 18 surface.

hm (i) = (hm ′ (i) −hs) × da / (da−db) + hs (1)
Next, in step S20, the control unit 22 calculates and determines the number of divided long images necessary to cover the shooting range [ht, hb] and the position of the FPD 16 (detection panel) in each divided image shot. To do.

  Based on the marker projection position hm (i) calculated above and the screen size panel of the detection panel, the position (panel top position) hp (i) of the FPD 16 (detection panel) is calculated by the following equation (2). . At this time, the center of the FPD 16 (detection panel) is set to a midpoint between adjacent marker projection positions.

hp (i) = hm (i) + md / 2 + panel / 2 (2)
Here, i = 1, 2,..., Mn−1 (mn is the number of markers). Md represents the interval between the markers 20 projected on the detection panel, and this is calculated by the following equation (3) by the interval md ′ between the markers 20 arranged on the partition 18.

md = md ′ × da / (da−db) (3)
Further, the position of the panel top when i = mn is calculated by the following equation (4) instead of the above equation (2).

hp (mn) = hm (mn−1) −md / 2 + panel / 2 (4)
Next, in step S30, the control unit 22 calculates and determines the X-ray irradiation direction in the shot of each divided image.

  FIG. 5 is an explanatory diagram showing a method for calculating the X-ray irradiation direction.

  FIG. 5 shows a case where the X-ray irradiation direction from the X-ray source 12 with respect to the i-th FPD 16 (the position of the FPD 16 in the i-th imaging) is obtained.

  As shown in FIG. 5, the distance between the FPD 16 and the X-ray source 12 is da, the panel top position of the FPD 16 is hp (i), the length of the FPD 16 is panel, and the upper end (panel top) of the FPD 16 and the X-ray source 12 Is the direction connecting the X-ray source 12 (angle with respect to the floor surface) and θ is the direction to connect the lower end (panel bottom) of the FPD 16 and the X-ray source 12 (angle with respect to the floor surface). And At this time, the X-ray irradiation direction θ is set to a direction just between α and β, that is, θ = (α + β) / 2. Then, α and β are calculated as in the following formulas (5) and (6), respectively, and the X-ray irradiation direction θ to be calculated is calculated as in formula (7).

α = arctan ((hp (i) −hs) / da) (5)
β = arctan ((hp (i) −hs−panel) / da) (6)
θ = (α + β) / 2
= {Arctan ((hp (i) -hs) / da) + arctan ((hp (i) -hs-panel) / da)} / 2 (7)
As described above, in the present embodiment, the projection position of the marker on the panel surface is calculated based on the imaging condition, and the FPD 16 and the X-ray source 12 are controlled based on the calculated projection position. The marker can be embedded at a desired position on the image without depending on the imaging range, the position (height) of the X-ray source, the distance between the X-ray source and the panel surface, etc. The stability of image composition can be improved.

  The marker arrangement interval md ′ on the partition 18 is determined as follows based on the minimum value min (da) of the distance between the panel surface and the X-ray source 12.

  First, since a marker as a marker for composition must be projected on the panel surface, if margin is taken into consideration when considering the marker size marker and error, max (md) <panel−margin, and the formula ( 3) From md = md ′ × da / (da−db) = md ′ / (1−db / da), max (md) = max (md ′ / (1−db / da)) < panel-margin.

  Here, when the marker position (marker interval) md ′ on the screen 18 is fixed, md ′ / (1−db / min (da)) <panel−margin. Thereby, the following formula (8) is established.

md '<(1-db / min (da)) x (panel-margin) (8)
For example, as shown in FIG. 6, when panel-margin = 40 [cm], db = 10 [cm], and min (da) = 100 [cm], md ′ <(1-10 / 100) × 40 [ cm] = 36 [cm].

  When the X-ray source 12 is closest to the FPD 16 (panel surface), the interval md between the markers 20 projected on the panel surface is the largest.

  Next, a second embodiment of the present invention will be described.

  The second embodiment is similar to the first embodiment in the apparatus configuration, but differs from the first embodiment in that the X-ray irradiation range is adjusted for each shot in order to reduce exposure. .

  FIG. 7 shows a calculation method of each control amount and the like including an adjustment method of the X-ray irradiation range for each shot for capturing each divided image.

  As shown in FIG. 7, as in the case of the first embodiment shown in FIG. 4, the setting information fixed to the apparatus and the setting information set for each photographing are stored in the memories 32 and 34 of the control unit 22, respectively. Has been. The control unit 22 reads necessary information from the memories 32 and 34 and calculates various values.

  The device-fixed setting information stored in the memory 32 includes the screen size panel of the panel surface of the FPD 16 (detection panel), the distance db between the screen and the detection panel, the marker arrangement position (height from the floor) hm ′ ( 1), hm ′ (2),..., Marker size marker, etc.

  Information set for each imaging stored in the memory 34 includes an X-ray source height hs, a distance da between the X-ray source and the detection panel, imaging range information [ht, hb], and the like.

  First, in step S110 in FIG. 7, the control unit 22 calculates the projection position of the marker 20 on the panel surface of the FPD 16. The calculation method is the same as in the first embodiment described above.

  Next, in step S120, the control unit 22 calculates and determines the number of long images divided to cover the shooting range [ht, hb] and the position of the FPD 16 (detection panel) in each divided image shot. To do.

  Next, in step S130, the control unit 22 calculates and determines the X-ray irradiation range and irradiation direction in each divided image shot.

  FIG. 8 is an explanatory diagram showing a method for calculating the X-ray irradiation range and irradiation direction.

  As shown in FIG. 8A, the top position (upper end) xtop (i) and the bottom position (lower end) xbottom (i) indicating the X-ray irradiation range P [xtop (i), xbottom (i)] on the FPD 16. Is calculated as follows.

  Here, it is assumed that each divided image includes markers 20 above and below, and the overlap area size is overlap.

  Then, the top position xtop (i) can be obtained by the following equation (9).

xtop (i) = hm (i) + md + marker / 2 + overlap / 2 (9)
Here, i = 1, 2,..., Mn−1 (mn is the number of markers).

  Further, the bottom position xbottom (i) can be obtained by the following equation (10).

xbottom (i) = hm (i) −marker / 2−overlap / 2 (10)
Note that md represents the interval between the markers 20 projected on the detection panel, and this is calculated by the above-described equation (3) by the interval md ′ between the markers 20 arranged on the partition 18.

  When i = mn, that is, for the last detection panel, the top position xtop (mn) can be obtained by the following equation (11), and the bottom position xbottom (mn) can be obtained by the following equation (12). .

xtop (mn) = hm (mn-1) + marker / 2 + overlap / 2 (11)
xbottom (mn) = hm (mn-1) -md-marker / 2-overlap / 2 (12)
Next, the X-ray irradiation direction and the aperture are calculated from the irradiation range P thus obtained.

  As shown in FIG. 8A, the angle between the X-ray source 12 and the floor surface in the direction connecting the top position of the irradiation range P is α, and the floor in the direction connecting the X-ray source 12 and the bottom position of the irradiation range P. The angle with the surface is β, and the X-ray irradiation direction θ is calculated as θ = (α + β) / 2 as an intermediate value between these angles.

  Then, α and β are calculated as the following equations (13) and (14), respectively.

α = arctan ((xtop (i) −hs) / da) (13)
β = arctan ((xbottom (i) −hs) / da) (14)
Therefore, the X-ray irradiation direction θ obtained from this is calculated as in the following equation (15).

θ = (α + β) / 2
= {Arctan ((xtop (i) -hs) / da) + arctan ((xbottom (i) -hs) / da)} / 2
... (15)
Next, the aperture width Δ of the collimator 14 is calculated from the angle width φ viewed from the X-ray source 12 in the irradiation range P as follows.

  That is, as shown in FIG. 8B, the angular width φ is calculated as the difference between α and β obtained above, and φ = α−β = arctan ((xtop (i) −hs) / da) −arctan ((xbottom (i) -hs) / da).

  Using this angular width φ, the aperture width Δ is obtained as follows: Δ = 2d × tan (φ / 2).

  In this way, every time each divided image is photographed, the irradiation range P and the aperture width Δ on the panel surface of the FPD 16 at that time are obtained and controlled to irradiate an extra range unrelated to photographing. Can be prevented and the exposure dose can be reduced.

  In order to reduce the exposure dose, it is desirable to appropriately control the aperture width in the non-longitudinal direction of the collimator 14.

  Normally, the direction of the collimator changes in conjunction with the change of the direction of the tube, so that when the angle of the tube is inclined with respect to the panel, the shape of the irradiation range on the panel surface becomes a trapezoid. This becomes more prominent as it becomes oblique.

  For example, it is desirable to set the appropriate irradiation range as follows. For example, by providing a mechanism in which the shape of the aperture of the aperture becomes a trapezoidal shape, the aperture shape may be appropriately controlled according to the irradiation direction within a plane orthogonal to the irradiation direction of the X-ray source, The collimator surface may be independent of the irradiation direction of the X-ray source, and the rectangular diaphragm may be appropriately controlled in a plane parallel to the panel surface.

  In the examples described so far, the imaging method for controlling the angle of the tube of the X-ray source has been described. However, the imaging method for controlling the diaphragm with the tube angle fixed, or the tube and the FPD. As a photographing method for moving the (panel surface) in parallel, the method of the above embodiment may be applied to this. That is, by calculating the projection position of the marker and determining the position of the detection panel and the X-ray irradiation direction based on the calculation result, control is performed so that the marker appears in the overlapping area of the detection panel where the marker moves.

  The control by the radiographic imaging apparatus in each embodiment of the present invention described above can be realized by, for example, a general personal computer system and a software program that operates on the personal computer system. The program is controlled to execute the functions as described above.

  The radiographic imaging apparatus, method, and program of the present invention have been described in detail above. However, the present invention is not limited to the above examples, and various improvements and modifications are made without departing from the gist of the present invention. Of course.

1 is a schematic configuration diagram showing a first embodiment of a radiographic imaging apparatus according to the present invention. It is explanatory drawing which shows the positional relationship of X-ray source and FPD at the time of carrying out long imaging using a radiographic imaging apparatus. It is explanatory drawing which shows the example of the attachment method of a marker. It is explanatory drawing which shows the calculation methods, such as each control amount. It is explanatory drawing which shows the method of calculating an X-ray irradiation direction. It is explanatory drawing which shows the specific example of a marker projection space | interval. The calculation method of each control amount etc. including the adjustment method of the X-ray irradiation range for every shot is shown. (A), (b) is explanatory drawing which shows the method of calculating an X-ray irradiation range and an irradiation direction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Radiological imaging device, 12 ... X-ray source, 14 ... Collimator, 16 ... Flat panel type X-ray detector (FPD), 18 ... Screen, 20 ... Marker, 22 ... Control part, 24 ... Strut, 26 ... Duplication region

Claims (7)

Radiographic imaging that obtains an image of a subject longer than the maximum field of view of the radiation detector by moving the radiation detector so that each part overlaps, taking a plurality of images and combining them at the overlapping part A device,
A radiation source that emits radiation;
A radiation detector that detects radiation emitted from the radiation source and transmitted through the subject;
A partition formed of a radiolucent material and disposed between the subject and the detector;
Is formed by material having a high radiation attenuation coefficient, so that the mark in the synthesis of the image, and a marker disposed along the collision elevation,
Imaging condition setting means for setting an imaging range and the position of the radiation source as imaging conditions;
The projection position of the marker on the plane including the movable range of the radiation detector by the radiation emitted from the radiation source based on the set imaging condition is different depending on the imaging condition and the imaging. Projection position calculating means for geometrically using information of the arrangement position of the known marker that is not known ;
Determining means for determining individual positions for moving the radiation detector for taking a plurality of images based on the calculated projection positions, and corresponding positions of the radiation sources or radiation irradiation directions;
Control means for controlling the radiation source and the radiation detector based on the determination of the determination means;
A radiographic imaging apparatus comprising:   The radiographic image capturing apparatus according to claim 1, wherein a plurality of the markers are arranged at predetermined intervals in the vertical direction of the partition along the partition surface. The determination means further calculates a radiation irradiation range at each position where the radiation detector is moved, determines an opening of a diaphragm arranged between the radiation source and the subject,
Wherein the control unit further radiographic imaging apparatus according to claim 1 or 2, wherein the controller controls the diaphragm based on the determination of the determining means.   The determining means further indicates the number of the plurality of images necessary to cover the imaging range of the subject and the position of the radiation detector in imaging each image, so that each image includes the marker above and below it. And the X-ray irradiation range of each radiation detector at each position of the radiation detector, the projection position of the marker on the radiation detector, the size of the marker, and the region where the images overlap. Calculated based on the size and the interval between the markers projected on the radiation detector, determines the X-ray irradiation direction from the calculated X-ray irradiation range, and determines the X-ray irradiation range from the radiation source. Determine the aperture of the diaphragm arranged between the radiation source and the subject from the angular width seen,
  The radiographic imaging apparatus according to claim 1, wherein the control unit further controls the diaphragm based on the determination of the determination unit. Radiographic imaging that obtains an image of a subject longer than the maximum field of view of the radiation detector by moving the radiation detector so that each part overlaps, taking a plurality of images and combining them at the overlapping part A method,
Detecting radiation emitted from a radiation source and transmitted through the subject;
Setting the imaging range and the position of the radiation source as imaging conditions;
A marker that serves as a marker for synthesizing the image formed of a substance having a large radiation attenuation coefficient is disposed along a partition surface formed of a radiation transmissive material and disposed between the subject and the detector. And a process of
The projection position of the marker on the plane including the movable range of the radiation detector by the radiation emitted from the radiation source based on the set imaging condition is different depending on the imaging condition and the imaging. Determining geometrically using no known information on the location of the marker ;
Determining an individual position for moving the radiation detector for taking a plurality of images based on the calculated projection position and a position of the radiation source or a radiation irradiation direction corresponding to the position;
Controlling the radiation source and the radiation detector based on the determination by the determining means;
A radiographic imaging method comprising: The radiographic imaging method according to claim 5, wherein the step of arranging the markers includes arranging a plurality of the markers at a predetermined interval in a vertical direction of the screen. A program causing a computer to execute the radiographic image capturing method according to claim 5 .

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