JP5460482B2 - Radiation imaging apparatus and method, and program - Google Patents

Description

  The present invention relates to a radiation imaging apparatus, a radiation imaging method, and a radiation that perform alignment of a plurality of radiographic images using marker images included in a series of a plurality of radiographic images acquired by imaging a subject together with the markers. It relates to the shooting program.

  In recent years, in an X-ray imaging apparatus, in order to observe the affected area in more detail, an X-ray tube is moved to irradiate a subject with X-rays from different angles, and the acquired images are added to obtain a desired Tomosynthesis imaging capable of obtaining an image in which a tomographic plane is emphasized has been proposed. In tomosynthesis imaging, depending on the characteristics of the imaging device and the required tomographic image, the X-ray tube is moved in parallel with the X-ray detector, or moved in a circle or ellipse arc, and the subject is exposed at different irradiation angles. A plurality of photographed images obtained by photographing are acquired, and these photographed images are reconstructed to generate a tomographic image.

  When such tomosynthesis imaging is performed, when reconstructing a plurality of captured images acquired by imaging, it is necessary to align the captured images. For this reason, at the time of tomosynthesis imaging, a marker is attached to the subject or an imaging stage on which the subject is placed, and a plurality of captured images including the marker image are acquired by imaging the marker together with the subject ( Patent Document 1). By photographing the marker together with the subject in this way, it is possible to reconstruct a tomographic image while aligning the plurality of photographed images with reference to the marker image included in each of the plurality of photographed images.

  By the way, when performing imaging using radiation such as X-rays, image quality performance due to harmful effects on the human body caused by irradiating a part that is not necessary for observation of the subject and scattered light from the part unnecessary for observation In order to prevent a decrease in image quality, it is possible to perform imaging using an irradiation field stop that limits the irradiation area (irradiation field) of the radiation on the subject so that the radiation is irradiated only on a necessary portion of the subject. Many. When performing tomosynthesis imaging using the irradiation field diaphragm in this way, the end of the irradiation field is detected to prevent the irradiation field from protruding from the X-ray detector for detecting the X-rays. There has been proposed a method for detecting the approach to the end of the instrument and appropriately adjusting the position of the X-ray detector when approached (see Patent Document 2). In the technique described in Patent Document 2, a marker attached to a subject is used to detect the proximity of the end of the irradiation field with the end of the X-ray detector. In addition, when performing surgery, there is also a method of tracking the position of a medical instrument with a marker attached to the medical instrument, and setting the position of the X-ray source and the X-ray irradiation range so that the marker is within the X-ray image. It has been proposed (see Patent Document 3).

JP 2002-531209 A JP 2009-11645 A Special table 2007-530122

  As described above, when using a marker at the time of tomosynthesis imaging, it is necessary to arrange the marker so that the marker image is included in all of the plurality of acquired images. In particular, when imaging is performed using an irradiation field stop, it is necessary to arrange the marker so that the marker image is included in an irradiation field region narrower than the detection range of the X-ray detector. However, in order to appropriately place the marker, the relationship between the position of the X-ray source, the position of the X-ray detector and the marker position, and further the relationship between the irradiation field and the marker position when the irradiation field stop is used, Since it is necessary to consider each of the multiple shootings, the workload is very large. Here, the method of the above-mentioned Patent Document 2 detects the approach between the end of the irradiation field and the end of the X-ray detector using a marker, and does not perform imaging so that the marker is included. . Moreover, although the method of the said patent document 3 is image | photographed so that a marker may be included, it is performed in order to track a medical instrument.

  The present invention has been made in view of the above circumstances, and acquires a plurality of radiation images by photographing a subject together with a marker, and performs alignment of the plurality of radiation images using marker images included in the plurality of radiation images. In this case, it is an object to reduce the work load when arranging the markers.

A radiation imaging apparatus according to the present invention includes a radiation source for irradiating a subject with radiation together with at least one marker,
Detecting means for detecting radiation transmitted through the subject;
The radiation source is moved relative to the detection means, and the subject is irradiated with the radiation at a plurality of radiation source positions by the movement of the radiation source, and a plurality of radiation sources corresponding to the plurality of radiation source positions, respectively. Image acquisition means for acquiring a captured image;
Arrangement information acquisition means for acquiring arrangement information indicating the arrangement position of the marker;
And determining means for determining whether or not the marker is arranged based on the acquired range of the captured image and the arrangement information in the detecting means.

  “Capturing a subject together with a marker” means that when a marker is placed on a photographing stand on which a marker is attached or a subject is placed and the subject is irradiated with radiation, the marker is also irradiated with radiation. Means that.

  “Move the radiation source relative to the detection means” means both when the detection means is fixed and only the radiation source is moved, and when both the detection means and the radiation source are moved in synchronization. including.

  The radiographic apparatus according to the present invention may further include notification means for notifying the determination result.

  In this case, the notification means may be means for further notifying information indicating the movement direction of the marker when the determination result is a determination result indicating that the marker is not properly arranged.

  Further, in the radiographic apparatus according to the present invention, the determination means performs the determination based on information on a source position near an end in at least the movement range of the plurality of source positions that are relatively moved. It is good.

  In this case, a tomographic angle based on a predetermined reference point on a reference plane that defines a range for acquiring the plurality of captured images, a corresponding point corresponding to the reference point on the detection plane of the detection unit, and the detection plane An arithmetic means for calculating information on the radiation source position based on the shortest distance to the radiation source and the number of imaging times may be further provided.

  Examples of the “reference plane that determines the range for acquiring the tomographic image” include the top surface of the imaging table on which the subject is placed, the detection surface of the detection means, and the surface closest to the detection means for the region of interest when the region of interest is set. Alternatively, any tomographic plane or the like in the subject can be used. The “region of interest” is a region having a particularly high degree of interest in diagnosis using an image, and is a region that is a target for acquiring a tomographic image in a subject. The region of interest is a three-dimensional region defined by a range in the depth direction of the subject (that is, a direction in which radiation travels) and a range in a plane orthogonal to the depth direction. It is also possible to set a region of interest as a two-dimensional region on the reference plane.

  The “tomographic angle” is an angle that faces two end portions that define a moving range of the radiation source from a reference point on the reference plane.

  Further, in the radiographic apparatus according to the present invention, the determination unit may be arranged at the source position near at least the end portion of the plurality of source positions using the source position information and the arrangement information. When the radiation source is located, the projection position of the marker on the plane including the detection surface of the detection unit is calculated, and it is determined whether or not the projection position is out of the captured image acquisition range of the detection unit. By doing so, it may be a means for determining the appropriateness of the arrangement of the markers.

  In the radiation imaging apparatus according to the present invention, the captured image acquisition range may be a detection range of the detection unit.

Further, in the radiographic apparatus according to the present invention, when further comprising an irradiation field stop means for limiting the irradiation range of the radiation on the subject,
The captured image acquisition range may be an irradiation range of the radiation in the detection unit.

  In the radiographic apparatus according to the present invention, the arrangement information acquisition unit may be configured to perform either pre-photographing before photographing for obtaining the plurality of photographed images or photographing a predetermined number of times in photographing for obtaining the plurality of photographed images. The arrangement information may be obtained based on a photographed image obtained by such photographing.

  The radiographic apparatus according to the present invention may further include image reconstruction means for generating a tomographic image of the subject by reconstructing the plurality of captured images.

A radiation imaging method according to the present invention includes a radiation source for irradiating a subject with radiation together with at least one marker,
Detecting means for detecting radiation transmitted through the subject;
The radiation source is moved relative to the detection means, and the subject is irradiated with the radiation at a plurality of radiation source positions by the movement of the radiation source, and a plurality of radiation sources corresponding to the plurality of radiation source positions, respectively. A radiation imaging method in a radiation imaging apparatus comprising an image acquisition means for acquiring a captured image,
Obtaining arrangement information indicating the arrangement position of the marker,
The adequacy of the marker arrangement is determined based on the captured image acquisition range and the arrangement information in the detection means.

  In addition, you may provide as a program for making a computer perform the radiography method by this invention.

  According to the present invention, the arrangement information indicating the arrangement of the marker is acquired, and the suitability of the arrangement of the marker is determined based on the captured image acquisition range and the arrangement information in the detection unit. Therefore, the operator does not need to adjust the marker position when the marker is properly arranged, and the marker is properly arranged only when the marker is not properly arranged. It is only necessary to arrange the markers so that the determination result is obtained. Therefore, it is possible to reduce the burden on the operator when placing the marker, thereby improving convenience when photographing the subject together with the marker.

  Further, when the determination result indicates that the marker is not properly arranged, the burden of the work for arranging the marker can be further reduced by notifying the information indicating the moving direction of the marker.

Schematic of an X-ray imaging apparatus to which the radiation imaging apparatus according to the first embodiment of the present invention is applied. Illustration for explaining tomosynthesis shooting Diagram for explaining calculation of movement range of X-ray tube The top view of the top plate of the imaging stand explaining the marker used in this embodiment and the arrangement position of the marker The flowchart which shows the process performed in 1st Embodiment. The figure for demonstrating acquisition of the arrangement information of the marker in 1st Embodiment The figure for demonstrating calculation of the projection position of a marker image The figure for demonstrating the determination result of the marker arrangement | positioning appropriateness in each radiation source position The figure for demonstrating the determination result of the marker arrangement | positioning appropriateness in each radiation source position The figure for demonstrating the determination result of the marker arrangement | positioning appropriateness in each radiation source position Figure showing the judgment result notification screen Figure showing the judgment result notification screen The figure for demonstrating calculation of the irradiation range of the X-ray of the x direction in 2nd Embodiment. The figure for demonstrating calculation of the irradiation range of the X-ray | X_line of the y direction in 2nd Embodiment. The figure for demonstrating calculation of the arrangement position of the marker in 3rd Embodiment The flowchart which shows the process performed in 3rd Embodiment The figure which shows the notification screen of the determination result in 3rd Embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of an X-ray imaging apparatus to which the radiation imaging apparatus according to the first embodiment of the present invention is applied. As shown in FIG. 1, an X-ray imaging apparatus 10 according to the first embodiment is for tomosynthesis imaging, and includes an X-ray tube 12 and a flat panel X-ray detector (hereinafter simply referred to as a detector). 14. The X-ray tube 12 moves along a straight line or an arc by the moving mechanism 16 and irradiates the subject 2 on the imaging table top 4 with X-rays at a plurality of positions on the moving path. In this embodiment, the X-ray tube 12 is moved in the direction of arrow A along a straight line. Note that the amount of X-ray irradiation to the subject 2 is controlled to be a predetermined amount by a control unit described later.

  Further, a collimator (irradiation field stop) 6 is connected to the X-ray tube 12 so that the operator can set an X-ray range (irradiation range) irradiated to the subject 2. When setting the irradiation range using the collimator 6, visible light is irradiated to the subject 2 through the collimator 6 instead of X-rays. The visible light is emitted from an irradiation field lamp (not shown) provided in the collimator 6. Thus, the operator can set the X-ray irradiation range by adjusting the range of visible light irradiated on the subject 2 using the collimator 6. In this embodiment, a marker is arranged on the imaging table top 4 as will be described later, and imaging is performed so that the marker is included in the plurality of captured images together with the subject 2.

  The detector 14 is disposed so as to face the X-ray tube 12 with the imaging table top plate 4 on which the subject 2 is placed interposed therebetween in order to detect X-rays transmitted through the subject 2. The detector 14 is moved along a straight line or an arc as necessary by the moving mechanism 18 and detects X-rays transmitted through the subject 2 at a plurality of positions on the moving path. In the first embodiment, the detector 14 is moved in the direction of arrow B along a straight line.

  The X-ray imaging apparatus 10 includes an image acquisition unit 20 and a reconstruction unit 22. The image acquisition unit 20 moves the X-ray tube 12 along a straight line, irradiates the subject 2 with X-rays at a plurality of source positions by the movement of the X-ray tube 12, and detects X-rays transmitted through the subject 2 as a detector. 14 to obtain a plurality of captured images at a plurality of moving source positions. The reconstruction unit 22 reconstructs a plurality of captured images acquired by the image acquisition unit 20 to generate a tomographic image indicating a desired cross section of the subject 2. A method for reconstructing a tomographic image will be described below.

  As shown in FIG. 2, when the subject 2 is imaged at different irradiation angles from positions S1, S2,..., Sn with the X-ray tube 12, captured images G1, G2,. Shall. Therefore, for example, when an object (T1, T2) existing at different depths is projected from the radiation source position S1, it is projected onto the captured image G1 at positions P11, P12, and from the radiation source position S2, the object is projected. When (T1, T2) is projected, it is projected onto the captured image G2 at positions P21 and P22. As described above, when projection is repeatedly performed from different source positions S1, S2,..., Sn, the object T1 is projected to the positions of P11, P21,. The object T2 is projected onto the positions P12, P22,..., Pn2.

  When it is desired to emphasize the cross section where the object T1 exists, the photographed image G2 is moved by (P21-P11), the photographed image G3 is moved by (P31-P11), and the photographed image Gn is (Pn1). -P11) A tomographic image in which the structure on the cross section at the depth of the object T1 is emphasized is created by aligning and adding the images moved by the amount of P11. When it is desired to emphasize the cross section in which the object T2 exists, the captured image G2 is moved by (P22-P12), the captured image G3 is moved by (P32-P12),. Move by (Pn2-P12), align and add. In this way, an image in which a tomographic image at a desired position is emphasized is acquired by aligning and adding the captured images G1, G2,. Can do. In the present embodiment, since a marker is arranged on the imaging table top 4 and a plurality of captured images are acquired so that the marker is captured, the captured image includes a marker image. Therefore, alignment of each captured image G1, G2,..., Gn is performed based on the marker image.

  The X-ray imaging apparatus 10 includes an operation unit 24, a display unit 26, and a storage unit 28. The operation unit 24 includes a keyboard, a mouse, or a touch panel type input device, and receives an operation of the X-ray imaging apparatus 10 by an operator. It also accepts input of various information such as imaging conditions and information correction instructions necessary for performing tomosynthesis imaging. In the present embodiment, each unit of the X-ray imaging apparatus 10 operates in accordance with information input from the operation unit 24 by the operator. The display unit 26 is a display device such as a liquid crystal monitor. In addition to the captured image acquired by the image acquisition unit 20 and the tomographic image reconstructed by the reconstruction unit 22, a notification screen for determination results described later, messages necessary for operation, and the like Is displayed. The display unit 26 may include a speaker that outputs sound. The storage unit 28 stores various parameters for setting imaging conditions necessary for operating the X-ray imaging apparatus 10. Various parameters are stored in the storage unit 28 as standard values corresponding to the imaging region, and are corrected by an operator giving instructions from the operation unit 24 as necessary.

  Parameters for setting imaging conditions include the reference plane, the tomographic angle, the source distance, the number of shots, the shot interval, the tube voltage and tube current of the X-ray tube 12, the X-ray exposure time, and the like. . Of these parameters, the number of shots, the shot interval, the tube voltage and tube current of the X-ray tube 12, and the X-ray exposure time can be directly used as imaging conditions.

  FIG. 3 is a diagram for explaining various parameters. The reference plane is a plane that defines a range in which tomographic images are acquired. For example, the top plate surface of the imaging table top plate 4, the detection surface of the detector 14, or an arbitrary tomographic plane in the subject 2 can be used. In FIG. 3, a plane (hereinafter referred to as a center plane) that bisects the thickness of the subject 2 is used as a reference plane. The tomographic angle is an angle that faces two end portions that define the movement range of the X-ray tube 12 from the reference point B0 on the reference plane. Here, since the detection surface of the detector 14 and the movement path of the X-ray tube 12 are parallel, the distance closest to the detection surface of the detector 14 on the movement path of the X-ray tube 12 is the radiation source distance. To do. 3 and the following description, the direction parallel to the movement path of the X-ray tube 12 is the x direction, the direction perpendicular to the movement path of the X-ray tube 12 is the z direction, and the direction perpendicular to the paper surface is the y direction. To do.

  The number of shots is the number of times of imaging while the X-ray tube 12 moves from end to end within the range of the tomographic angle. The shot interval is a time interval between shots.

  In FIG. 3 and the following description, the moving range of the X-ray tube 12 is s0, the distance between the X-ray tube 12 and the detection surface of the detector 14 (ie, the source distance) is sz, the tomographic angle is θ, and the detection is performed. The distance between the detection surface of the device 14 and the reference surface (that is, the center surface of the subject 2) is d0, and the distance between the detection surface of the detector 14 and the top surface of the imaging table top 4 is mz. In addition, as a predetermined reference point B0 on the reference plane, an intersection of a perpendicular passing through the center of gravity of the detector 14 and the reference plane is used.

  The X-ray imaging apparatus 10 includes a calculation unit 30. The calculation unit 30 calculates imaging conditions such as the movement range of the X-ray tube 12 according to the parameters stored in the storage unit 28.

  Here, referring to the relationship shown in FIG. 3, the moving range s0 of the X-ray tube 12 can be calculated from the source distance sz, the distance d0, and the tomographic angle θ. That is, if the intersection of the perpendicular passing through the reference point B0 and the movement path of the X-ray tube 12 is the origin O1, the distance between the reference plane and the X-ray tube 12 is sz-d0. The movement range s0 of the tube 12 is calculated as-(sz-d0) · tan (θ / 2) to (sz-d0) · tan (θ / 2). This determines the positions of both ends of the calculated movement range s0.

  Further, the calculation unit 30 equally divides the moving range s0 of the X-ray tube 12 by the number of shots, thereby calculating the position of the X-ray tube 12 in each radiographing (hereinafter referred to as a radiation source position). Thereby, as shown in FIG. 2, the source positions S1, S2,..., Sn of the X-ray tube 12 can be calculated.

  Moreover, the calculating part 30 calculates imaging | photography time and a radiation source travel speed as imaging | photography conditions. The shooting time can be calculated by the number of shots × shot interval. The radiation source traveling speed can be calculated from the moving range s0 / imaging time.

  Further, the X-ray imaging apparatus 10 includes a marker arrangement information acquisition unit 32 that acquires information (arrangement information H) of marker arrangement positions on the imaging table top 4. FIG. 4 is a plan view of a marker used in the present embodiment and the top plate of the photographing table for explaining the arrangement positions of the markers. As shown in FIG. 4, in the present embodiment, four circular markers M1 to M4 are used, and the operator 2 can overlap the subject 2 and the markers M1 to M4 in the X-ray irradiation direction. Four markers M <b> 1 to M <b> 4 are arranged on the imaging stand top plate 4. The markers M1 to M4 are made of a material such as lead having a high X-ray absorption rate. The size of the markers M1 to M4 is about 1 cm, and each has a hole with a unique shape. Thereby, each of the four markers M1 to M4 included in the captured image can be identified. In FIG. 4, the sizes of the markers M1 to M4 are shown enlarged. Further, the shape of the marker is not limited to a circle, and any known shape can be used. Also, the number of markers is not limited to four, and may be any number greater than or equal to one. The processing performed by the marker arrangement information acquisition unit 32 will be described later.

  In addition, the X-ray imaging apparatus 10 includes a determination unit 34 that determines the appropriateness of the arrangement of the markers M <b> 1 to M <b> 4 based on the captured image acquisition range and arrangement information H in the detector 14. The process performed by the determination unit 34 will be described later.

  Furthermore, the X-ray imaging apparatus 10 includes a control unit 36 for controlling each unit of the X-ray imaging apparatus 10. The control unit 36 controls each unit of the X-ray imaging apparatus 10 according to an instruction from the operation unit 24. Further, the control unit 36 determines the X-ray irradiation dose to the subject 2 based on the X-ray tube 12 based on the tube voltage and tube current of the X-ray tube 12 and the X-ray exposure time stored in the storage unit 28. Control.

  Next, processing performed in the first embodiment will be described. FIG. 5 is a flowchart showing processing performed in the first embodiment. Note that the first embodiment has a feature in the process of determining the appropriateness of the arrangement of the markers M1 to M4. Therefore, only the process will be described here. Acquisition of a plurality of captured images by tomosynthesis imaging and tomography Description of image reconstruction is omitted. In the first embodiment, it is assumed that only the X-ray tube 12 is moved and the detector 14 is not moved to perform tomosynthesis imaging. In addition, before the start of processing, the operator sets the X-ray irradiation range using the collimator 6 and confirms the positional relationship between the X-ray irradiation range and the detector 14 and the positional relationship with the subject 2. However, the markers M1 to M4 are arranged on the imaging table top plate 4. Further, an intersection of the straight line connecting the center of gravity of the detector 14 and the origin O1 and the imaging table top plate 4 is defined as an origin O2 that determines the coordinate position on the imaging table top plate 4. Further, the center of gravity of the detector 14 is set as an origin O3 that determines the coordinate position on the detector 14. In addition, the coordinate value in the z direction at the origin O3 is assumed to be zero. The origin O3 is also the origin of the captured image.

  When the operation unit 24 receives an instruction to start processing by the operator, the control unit 36 starts processing, and the moving mechanism 16 moves the X-ray tube 12 to the origin O1 to perform pre-shot imaging for checking marker placement. To obtain a pre-shot image (step ST1). And marker arrangement information acquisition part 32 acquires arrangement information H showing the arrangement position of markers M1-M4 using a pre-shot image (Step ST2).

  FIG. 6 is a diagram for explaining acquisition of marker arrangement information in the first embodiment. In the present embodiment, four markers M1 to M4 are used. However, here, only acquisition of the arrangement information of the marker M1 will be described in order to simplify the description. In addition, it is assumed that the operator adjusts the collimator 6 so that the X-ray irradiation range A10 is within the detection range A1 of the detector 14 illustrated in FIG. The arrangement position of the marker M1 on the imaging table top plate 4 is (mx, my, mz) (unknown), and the position of the marker image in the pre-shot image is (px0, py0). The marker arrangement information acquisition unit 32 calculates the two-dimensional arrangement position (mx, my) of the marker M1 on the imaging table top plate 4 as the arrangement information H by the following equation (1).

mx = px0 × (sz−mz) / sz
my = py0 × (sz−mz) / sz (1)
sz is the source distance, and mz is the distance from the detection surface of the detector 14 to the top surface of the imaging table top 4 and is stored in the storage unit 28 as a parameter. The position of the marker image can be detected by performing pattern recognition processing on the pre-shot image. Therefore, the arrangement information H can be calculated by the above equation (1). In the present embodiment, four markers M1 to M4 are used. Since each of them has a unique hole, the marker images of the four markers M1 to M4 can be recognized separately. it can. In the present embodiment, since the shapes of the markers M1 to M4 are circular, the marker arrangement information acquisition unit 32 calculates the center position of the circle as the marker image position (px0, py0).

  The marker arrangement information acquisition unit 32 determines whether or not the arrangement information about all the markers M1 to M4 has been acquired (step ST3). If step ST3 is denied as in the case where the marker image of some markers is not included in the pre-shot image, the markers M1 to M4 are not properly arranged, so the marker arrangement is inappropriate. Information to that effect is output to the determination unit 34 (output of inappropriate placement information, step ST4), and the process proceeds to step ST8.

  When step ST3 is affirmed, the determination unit 34 uses the arrangement information H to calculate the projection position of the marker image when the X-ray tube 12 moves to all the radiation source positions in a series of imaging (step ST5). . FIG. 7 is a diagram for explaining the calculation of the projection position of the marker image. The coordinates of an arbitrary radiation source position Si (i = 1 to n) in the movement range s0 of the X-ray tube 12 are (sxi, syi, szi), and the arrangement position of the marker M1 on the imaging table top plate 4 is (mx, my). , Mz), the coordinates (sxi, syi, szi) are calculated by the calculation unit 30 and stored in the storage unit 28, and the arrangement position (mx, my, mz) is acquired by the marker arrangement information acquisition unit 32. Both are known. If the coordinates of the projection position of the marker when the X-ray tube 12 is located at the radiation source position Si is (pxi, pyi), the determination unit 34 calculates (pxi, pyi) by the following equation (2). FIG. 7 shows an example of calculating the coordinates (px1, py1) of the projection position of the marker M1 when the X-ray tube 12 is at the radiation source position S1.

pxi = mx− (sxi−mx) × mz / (szi−mz)
pyi = mx− (syi−my) × mz / (szi−mz) (2)
And the determination part 34 determines the appropriateness | suitability of marker arrangement | positioning by determining whether the projection position of the markers M1-M4 in all the radiation source positions Si is located in the detection range A0 of the detector 14 ( Step ST6), the determination result is output (step ST7). FIG. 8 and FIG. 9 are diagrams for explaining determination results of appropriateness of marker arrangement at all radiation source positions. 8 and 9 show the determination results of only the two markers M1 and M2, and the projection positions of the markers M1 and M2 at the respective radiation source positions Si are within the detection range A0 of the detector 14. ○, when not present is indicated by ×. The determination result of FIG. 8 shows that the projection positions of both the markers M1 and M2 are within the detection range A0 of the detector 14 at all the radiation source positions Si. On the other hand, the determination result of FIG. 9 shows that the projection position of the marker M1 is not within the detection range A0 at the source positions Sn-1 and Sn, and the projection position of the marker M2 is not within the detection range A0 at the source positions S1 and S2. It has become a thing. Therefore, when the determination result is that shown in FIG. 8, the determination unit 34 determines that the marker arrangement is appropriate. Conversely, when the determination result is that shown in FIG. 9, the determination unit 34 determines that the marker arrangement is inappropriate. Note that during actual imaging, the X-ray tube 12 does not accurately move along the calculated movement path, but moves with some error, so an error occurs in the actual marker projection position. Therefore, it is preferable to determine whether or not the marker projection position is within the detection range A0 with some error.

  The projection positions of the markers M1 to M4 are often out of the detection range A0 in many cases where the source position Si is near both ends of the movement range s0 of the X-ray tube 12. Accordingly, the determination unit 34 calculates the projection positions of the markers M1 to M4 only at a predetermined number of radiation source positions near both ends of the movement range s0 of the X-ray tube 12, and the projection positions of the markers M1 to M4 are calculated. You may make it determine whether it is located in detection range A0. Thereby, the calculation time can be shortened and the processing can be performed at high speed.

  Further, when aligning captured images when reconstructing a tomographic image, it is only necessary to detect a marker image that is common between captured images with adjacent radiation source positions. For this reason, as shown in FIG. 9, even if the projection position of the marker M2 is out of the detection range A0 at the radiation source positions S1 and S2, the two captured images acquired at the radiation source positions S1 and S2 are Since the marker image of the marker M1 is included, alignment can be performed using the marker image of the marker M1. Even if the projection position of the marker M1 is out of the detection range A0 at the radiation source positions Sn-1 and Sn, the two captured images acquired at the radiation source positions Sn-1 and Sn are the markers of the marker M2. Since the image is included, alignment can be performed using the marker image of the marker M2. Therefore, as shown in FIG. 9, when a marker image that is common between captured images acquired at adjacent radiation source positions can be detected, the marker arrangement may be determined to be appropriate. Note that, when making such a determination, as shown in FIG. 10, if a common marker image cannot be detected between captured images acquired at adjacent radiation source positions, it is determined that the marker arrangement is inappropriate. do it.

  Next, the control unit 36 notifies the determination result output by the determination unit 34 (step ST8), and ends the process. The notification may be performed only when the marker arrangement is inappropriate or may be performed when the marker arrangement is appropriate. Specifically, when the marker arrangement is inappropriate, as shown in FIG. 11, the notification screen 50 including a message such as “Inappropriate marker arrangement. Please move the marker” is displayed on the display unit 26. May be displayed. On the other hand, when the marker arrangement is appropriate, a notification screen including a message such as “the marker arrangement is appropriate” may be displayed. In addition, when step ST3 is denied and information indicating that the marker placement is inappropriate is output to the determination unit 34, for example, “the marker placement is inappropriate. Please move all markers. A notification screen including a message such as “

  Also, voice or beep sound may be used instead of or in addition to the display of the notification screen. Further, when the marker arrangement is inappropriate, as shown in FIG. 12, the projected image 52 of the virtual markers M1 to M4 can be discriminated from an appropriately arranged marker and an inappropriately arranged marker. May be displayed. In FIG. 12, a marker that is improperly arranged is indicated by hatching. However, a marker that is appropriately arranged and a marker that is improperly arranged are indicated by adding characters such as OK or NG. You may display so that identification is possible. In this case, an arrow 54 indicating the moving direction of the marker may be given to a marker that is improperly arranged. Thereby, since the operator can know which marker is improperly arranged and how to move the marker, the burden on the operator can be further reduced. In addition, when the marker arrangement is appropriate, notification to that effect may be performed.

  As described above, in the first embodiment, the suitability of the marker placement is determined and the determination result is notified, so that the operator can change the marker position when the marker is properly placed. There is no need to perform the adjustment work, and it is only necessary to arrange the markers so as to obtain a determination result that the markers are properly arranged only when the markers are not properly arranged. Therefore, it is possible to reduce the burden on the operator when placing the marker, thereby improving convenience when photographing the subject together with the marker.

  Next, a second embodiment of the present invention will be described. Since the configuration of the X-ray imaging apparatus according to the second embodiment is the same as the configuration of the X-ray imaging apparatus 10 according to the first embodiment, only the processing performed here will be described here, and the detailed configuration will be described. Description is omitted. In the first embodiment, whether or not the marker is positioned is determined according to whether or not the projected position of the marker is within the detection range A0 of the detector 14, but in the second embodiment, The difference from the first embodiment is that the suitability of the marker arrangement is determined according to whether the projection position of the marker is within the X-ray irradiation range. For this reason, in the second embodiment, the calculation unit 30 calculates the X-ray irradiation range A10i on the detection surface of the detector 14 at all the radiation source positions Si.

  FIG. 13 is a diagram for explaining calculation of the X-ray irradiation range A10 in the x direction in the second embodiment, and FIG. 14 is a diagram for explaining calculation of the X-ray irradiation range A10 in the y direction. The coordinates of an arbitrary radiation source position Si (i = 1 to n) in the movement range s0 of the X-ray tube 12 are (sxi, syi, szi), and the swing angle of the X-ray tube 12 at each radiation source position Si is α, x Assuming that the X-ray aperture angle by the collimator 6 in the direction is θx, and the X-ray aperture angle by the collimator 6 in the y direction is θy, the calculation unit 30 sets xmin and xmax, which define the X-ray irradiation range in the x direction, as follows: (3) and (4). The swing angle α can be calculated from the positional relationship between each radiation source position Si and the origin O3 of the detection surface of the detector 14, and the aperture angles θx and θy are input from the operation unit 24 by the operator as the setting values of the collimator 6. Can be obtained.

xmin = sxi−szi × tan (90−α−θx / 2) (3)
xmax = sxi−szi × tan (90−α + θx / 2) (4)
Moreover, the calculating part 30 calculates ymin and ymax which define the irradiation range of the X-ray of ay direction by the following formula | equation (5) and (6), respectively.

ymin = −szi × tan (θy / 2) (5)
ymax = szi × tan (θy / 2) (6)
In the second embodiment, the aperture amount of the collimator 6 may be constant regardless of the radiation source position Si, and the aperture amount of the collimator 6 may be increased as the radiation source position Si moves away from the origin. Good. Thereby, irrespective of the radiation source position, the size of the X-ray irradiation range can be made constant.

  Here, each of the X-ray apertures θx and θy using the collimator 6 is applied to a pre-shot image acquired by pre-shot, for example, an irradiation field recognition process as described in JP-A-10-275213. The irradiation field region (that is, the irradiation range) may be recognized to calculate using the recognized irradiation range and the distance from the detection surface of the detector 14 to the moving path of the X-ray tube. The technique described in Japanese Patent Laid-Open No. 10-275213 detects edge candidate points along a radial linear direction set for a predetermined point in a pre-shot image, and performs a Hough transform on these edge candidate points. Is used to obtain a predetermined number of reference candidate lines and recognize an area surrounded by these reference candidate lines as an irradiation field area.

  Here, in the second embodiment, the determination unit 34 determines whether or not the projection positions of the markers M1 to M4 at all the radiation source positions Si are located within the X-ray irradiation range A10i at each radiation source position Si. By determining, the appropriateness of marker arrangement is determined.

  In the second embodiment, as the X-ray tube 12 moves, the projection position of the marker image deviates only in the moving direction of the X-ray tube 12 (that is, the x direction). Therefore, the calculation unit 30 calculates only xmin and xmax that define the X-ray irradiation range in the x direction, and the determination unit 34 irradiates the projection position of the marker image only in the x direction of the X-ray irradiation range A10i. Whether or not the marker arrangement is appropriate may be determined based on whether or not it is located within the range A10i.

  Next, a third embodiment of the present invention will be described. Note that the configuration of the X-ray imaging apparatus according to the third embodiment is the same as the configuration of the X-ray imaging apparatus 10 according to the first embodiment, and therefore only the processing performed will be described here, and the detailed configuration will be described. Description is omitted. In the first embodiment, the marker arrangement information acquisition unit 32 acquires the arrangement information H representing the arrangement positions of the markers M1 to M4 using the pre-shot image. In the third embodiment, The difference from the first embodiment is that the arrangement information H representing the arrangement positions of the markers M1 to M4 is acquired using the captured image acquired by the first imaging of tomosynthesis imaging.

  FIG. 15 is a diagram for explaining the calculation of the marker arrangement position in the third embodiment. Here, only the calculation of the arrangement position of the marker M2 will be described in order to simplify the description. The coordinates of the first radiation source position S1 are (sx1, sy1, sz1), the arrangement position of the marker M2 on the imaging table top plate 4 is (mx, my, mz), and the position of the marker image in the first captured image. (Px0, py0). The marker arrangement information acquisition unit 32 calculates the two-dimensional arrangement position (mx, my) of the marker M2 on the imaging table top plate 4 as the arrangement information H by the following equation (7).

mx = px0 + (sx−px0) × mz / sz
my = py0 + (sy−py0) × mz / sz (7)
The coordinates (sx1, sy1, sz1) are calculated by the calculation unit 30 and stored in the storage unit 28, and mz is the distance between the detection surface of the detector 14 and the top plate surface of the imaging table top plate 4, and is a parameter. Is stored in the storage unit. Further, the position of the marker image can be detected by performing pattern recognition processing on the captured image, as in the first embodiment. Therefore, the arrangement information H can be calculated by the above equation (7).

  Next, processing performed in the third embodiment will be described. FIG. 16 is a flowchart showing processing performed in the third embodiment. When the operation unit 24 receives an instruction to start processing from the operator, the control unit 36 starts processing, and the moving mechanism 16 moves the X-ray tube 12 to the first radiation source position S1, and from the X-ray tube 12 to the subject 2 X-rays are emitted toward the camera to perform the first imaging, and a captured image is acquired (step ST11). And marker arrangement information acquisition part 32 acquires arrangement information H showing the arrangement position of markers M1-M4 using a photography picture (Step ST12).

  Next, the marker arrangement information acquisition unit 32 determines whether or not the arrangement information about all the markers M1 to M4 has been acquired (step ST13). If step ST13 is negative, since the markers M1 to M4 are not properly arranged, information indicating that the marker is improperly output is output to the determination unit 34 (arrangement inappropriate information output, step ST14). The process proceeds to step ST18.

  When step ST13 is affirmed, the determination unit 34 uses the arrangement information H to calculate the projection position of the marker image when the X-ray tube 12 moves to all the radiation source positions in a series of imaging (step ST15). . Since the calculation of the marker image projection position is performed in the same manner as in the first embodiment, detailed description thereof is omitted here.

  And the determination part 34 determines the appropriateness | suitability of marker arrangement | positioning by determining whether the projection position of the markers M1-M4 in all the radiation source positions Si is located in the detection range A0 of the detector 14 ( Step ST16), the determination result is output (step ST17). Next, the control unit 36 notifies the determination result output by the determination unit 34 (step ST18), and ends the process.

  Here, in the third embodiment, since the first photographed image is acquired, the projected images of the virtual markers M1 to M4 are superimposed on the first photographed image 58 as shown in FIG. The marker may be displayed so that a marker with an appropriate arrangement and a marker with an inappropriate arrangement can be identified. In this case, an arrow 60 indicating the movement direction may be given to a marker that is improperly arranged.

  In the third embodiment, the appropriateness of the marker arrangement is determined according to whether or not the projected position of the marker is within the detection range A0 of the detector 14, but the second embodiment is different from the second embodiment. Similarly, the suitability of marker placement is determined by determining whether or not the projection positions of the markers M1 to M4 at all the radiation source positions Si are located within the X-ray irradiation range A10i at each radiation source position Si. You may do it.

  In the third embodiment, the marker arrangement information H is acquired using the captured image acquired at the radiation source position where the first imaging is performed. However, the marker arrangement information H is limited to the first radiation source position. Instead of this, a captured image acquired at an arbitrary source position in the initial stage of a series of imaging may be used.

  In the first to third embodiments, the marker arrangement information H is acquired using the pre-shot image or the first shot image. However, a sensor for detecting the marker position is provided on the shooting stand. The marker arrangement information H may be acquired by a sensor. Alternatively, the imaging platform on which the marker is arranged may be photographed with a digital camera or the like, and the marker arrangement information H may be acquired using the photographed image.

  In the first to third embodiments, only the X-ray tube 12 is moved. However, the X-ray tube 12 and the detector 14 may be moved in synchronization. In this case, the marker placement is determined by determining whether the projected position of the marker calculated at each radiation source position Si is located within the detection range A0 of the moved detector 14 or within the X-ray irradiation range A10i. What is necessary is just to determine the suitability of.

  In the first to third embodiments, tomosynthesis imaging is performed by placing the subject on the imaging stand in the upright position. However, even when tomosynthesis imaging is performed using the imaging stand in the standing position. Of course, the present invention can be applied.

2 subject 4 imaging table top plate 6 collimator 10 X-ray imaging apparatus 12 X-ray tube 14 detector 16, 18 moving mechanism 20 image acquisition unit 22 reconstruction unit 24 operation unit 26 display unit 28 storage unit 30 calculation unit 32 marker arrangement information Acquisition unit 34 Determination unit 36 Control unit

Claims (12)

A radiation source for irradiating the subject with radiation with at least one marker;
Detecting means for detecting radiation transmitted through the subject;
The radiation source is moved relative to the detection means, and the subject is irradiated with the radiation at a plurality of radiation source positions by the movement of the radiation source, and a plurality of radiation sources corresponding to the plurality of radiation source positions, respectively. Image acquisition means for acquiring a captured image;
Arrangement information acquisition means for acquiring arrangement information indicating the arrangement position of the marker;
A radiation imaging apparatus comprising: a determination unit that determines appropriateness of the arrangement of the marker based on an acquisition range of the captured image and the arrangement information in the detection unit.   The radiation imaging apparatus according to claim 1, further comprising notification means for notifying the determination result.   The said notification means is a means to further notify the information showing the moving direction of the said marker, when the said determination result is a determination result that the arrangement | positioning of the said marker is not appropriate. Radiography equipment.   2. The determination unit according to claim 1, wherein the determination unit is a unit that performs the determination based on information on a source position in the vicinity of an end in a moving range to be relatively moved among the plurality of source positions. 4. The radiographic apparatus according to any one of 3 above.   A tomographic angle based on a predetermined reference point on a reference plane that defines a range for acquiring the plurality of captured images, a corresponding point corresponding to the reference point on the detection plane of the detection means, and the radiation source from the detection plane The radiation imaging apparatus according to claim 4, further comprising a calculation unit that calculates information on the radiation source position based on the shortest distance to and the number of imaging times.   The determination means uses the information on the radiation source position and the arrangement information to determine the position of the marker when the radiation source is located at least at the radiation source position near the end of the plurality of radiation source positions. By calculating the projection position on the plane including the detection surface of the detection means, and determining whether the projection position is out of the captured image acquisition range of the detection means, it is determined whether or not the marker is properly arranged. 6. The radiation imaging apparatus according to claim 4, wherein the radiation imaging apparatus is a means for performing the above.   The radiation imaging apparatus according to claim 1, wherein the captured image acquisition range is a detection range of the detection unit. An irradiation field stop means for limiting the irradiation range of the radiation on the subject;
The radiation imaging apparatus according to claim 1, wherein the captured image acquisition range is an irradiation range of the radiation in the detection unit.   The arrangement information acquisition means is based on a photographed image obtained by any one of the pre-photographing before photographing for obtaining the plurality of photographed images or photographing a predetermined number of times in photographing for obtaining the plurality of photographed images. The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus is means for acquiring the arrangement information.   The radiation imaging apparatus according to any one of claims 1 to 9, further comprising image reconstruction means for generating a tomographic image of the subject by reconstructing the plurality of photographed images. A radiation source for irradiating the subject with radiation with at least one marker;
Detecting means for detecting radiation transmitted through the subject;
The radiation source is moved relative to the detection means, and the subject is irradiated with the radiation at a plurality of radiation source positions by the movement of the radiation source, and a plurality of radiation sources corresponding to the plurality of radiation source positions, respectively. A radiation imaging method in a radiation imaging apparatus comprising an image acquisition means for acquiring a captured image,
Obtaining arrangement information indicating the arrangement position of the marker,
A radiography method comprising: determining appropriateness of arrangement of the marker based on an acquisition range of the captured image and the arrangement information in the detection unit. A radiation source for irradiating the subject with radiation with at least one marker;
Detecting means for detecting radiation transmitted through the subject;
The radiation source is moved relative to the detection means, and the subject is irradiated with the radiation at a plurality of radiation source positions by the movement of the radiation source, and a plurality of radiation sources corresponding to the plurality of radiation source positions, respectively. A program for causing a computer to execute a radiation imaging method in a radiation imaging apparatus including an image acquisition unit that acquires a captured image,
A procedure for obtaining arrangement information indicating the arrangement position of the marker;
A program for causing a computer to execute a procedure for determining the appropriateness of arrangement of the marker based on the acquisition range of the captured image and the arrangement information in the detection means.

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