JP5938860B2 - Radiography apparatus and tomographic image correction method - Google Patents

Description

  The present invention utilizes a radiation imaging apparatus that performs radiation imaging based on a projection image obtained by detecting radiation emitted from a radiation irradiation means and transmitted through an object by a radiation detection means, and a calibration phantom. The present invention relates to a tomographic image correction method for correcting a tomographic image of an object.

  An X-ray inspection apparatus will be described as an example of the radiation imaging apparatus. Conventionally, as shown in FIG. 8, this type of X-ray inspection apparatus includes a stage S on which an object O is placed and an X-ray tube T ( Radiation irradiating means) and an X-ray detector D (radiation detecting means). The stage S is a rotation stage having a rotation mechanism, and rotationally drives the rotation stage around the axis of the rotation axis Ax.

  Note that X-ray inspection objects include mounting substrates, through-holes / patterns / solder joints of multilayer substrates, electronic components before mounting such as integrated circuits (ICs) placed on pallets, metal There are castings such as video decks.

  In particular, when performing X-ray inspection by tomography of an object having a very fine structure such as a Ball Grid Array (BGA) or wiring, it is necessary to perform imaging with a large enlargement ratio. However, in order to increase the enlargement ratio, it is necessary to photograph a radiation source typified by an X-ray tube close to the object. Therefore, if the object has a wide shape on a plane, the X-ray tube and the object May interfere with each other. As a result, the enlargement rate cannot be increased so much to avoid interference.

  Therefore, as shown in FIG. 9, the rotation stage S and the X-ray tube T and the X-ray detector D are arranged in an axial direction inclined by a fixed angle (lamino angle) with respect to the rotation axis Ax for rotationally driving the rotation stage S. It arrange | positions (for example, refer patent document 1). In the case of FIG. 9, the X-ray tube T is fixedly arranged, and the rotary stage S is rotationally driven around the axis of the rotary axis Ax. At the time of data acquisition, the X-ray detector D detects X-rays irradiated from the X-ray tube T and transmitted through the object O from an oblique direction inclined by the lamino angle, and on the detection surface of the X-ray detector D based on the detection. A projected image is obtained. A projection image is acquired from a plurality of angles by acquiring a projection image each time the rotary stage S is rotationally driven.

  Thus, by arranging the X-ray tube and the X-ray detector in the oblique direction inclined by the lamino angle and photographing from the oblique direction, it is possible to bring the X-ray tube and the rotation stage and consequently the object close to each other. There is an advantage that a projection image with a high magnification can be obtained without interference between the ray tube and the object. However, since there is a restriction on the degree of freedom of the drive system, it is difficult to obtain a projected image of an object from an arbitrary position, and there is a drawback that the application is limited to CT (Computed Tomography).

  Therefore, for example, as shown in FIG. 10, there is known a method for realizing photographing from an oblique direction with an apparatus having no special rotation mechanism in the stage S (see, for example, Patent Documents 2 to 4). In FIG. 10, the stage S together with the object O is translated (moves straight) in a plane perpendicular to the rotation axis Ax (horizontal plane in FIG. 10) so as to draw a circular orbit, and the same rotation is synchronized with the movement of the stage S. By rotating the X-ray detector D around the axis of the axis Ax, a plurality of projection images are acquired, and further, a tomographic image is acquired based on the plurality of projection images.

  As described above, the relative geometric relationship among the X-ray tube, the object, and the X-ray detector at the time of imaging in FIG. 10 is the same as in FIG. 9 (the object and the rotary stage are driven to rotate around the axis of the rotation axis Ax In this case, the images are taken in an oblique direction by synchronously driving them so as to be the same as in FIG. In the case of FIG. 10, unlike FIG. 9, the direction of the stage S can be fixed.

  However, as shown in FIG. 10, in the method of photographing from an oblique direction by operating the stage and the X-ray detector, the stage and the X-ray detector have a drive mechanism independent of each other, which is ideal. In order to obtain a scanning scan trajectory for tomography, a mechanism and control capable of high-accuracy positioning and synchronization are required, which is expensive.

  Therefore, even if there is a deviation between the actual scanning trajectory and the ideal scanning trajectory, the calibration phantom is imaged under specific tomographic conditions, and the geometric deviation from the ideal scanning trajectory at that time is a parameter for correcting There is a method of correcting the deviation by calculating as (physical quantity) (see, for example, Patent Documents 4 and 5).

JP 2005-106515 A JP 2010-2221 A JP 2006-162335 A Japanese Patent No. 4415762 JP 2010-204060 A

  However, when imaging is performed by changing the geometric tomographic conditions (for example, the enlargement ratio and the lamino angle) by the method shown in FIG. 10, it is desirable to use correction parameters in accordance with the respective imaging conditions. Therefore, it is difficult to cope with an arbitrary imaging condition by using a correction parameter for a specific tomographic condition acquired in advance. Further, it is inconvenient for the user to install a calibration phantom each time the shooting condition is changed and to correct the deviation (calibration).

  The present invention has been made in view of such circumstances, and a radiation imaging apparatus capable of easily setting and changing arbitrary imaging conditions and calculating correction parameters for each imaging condition, and An object is to provide a tomographic image correction method.

In order to achieve such an object, the present invention has the following configuration.
That is, the radiation imaging apparatus of the present invention includes a stage on which an object is placed and advances straight in the X direction and the Y direction, and a radiation irradiating means and a radiation detecting means arranged so as to face each other with the stage interposed therebetween. A radiation imaging apparatus that performs radiation imaging based on a projection image obtained by detecting radiation emitted from the radiation irradiation means and transmitted through the object by the radiation detection means, wherein at least radiation The stage is configured so that a calibration phantom having a plurality of markers can be mounted at the time of imaging, and the radiation detection means is tilted with the object and the calibration phantom placed on the stage, and then around the central axis Driving means for driving the stage to draw a circular orbit in synchronization with the rotational driving of the radiation detecting means; and A parameter calculating means for calculating the parameters of the correction based on the image of the plurality of markers which are correlated in the projection image of a plurality of frames of Tadashiyo phantom, based on the projection image and the parameters of the plurality of the object, And a tomographic image calculating means for calculating a tomographic image of the object and reconstructing it using the parameters suitable for the imaging conditions when the object was imaged at the time of the calculation.

[Operation / Effect] According to the radiation imaging apparatus of the present invention, the stage is configured so that the calibration phantom can be mounted (going straight in the X direction and the Y direction) during radiography having at least a plurality of markers . With the object and calibration phantom placed on the stage, the radiation detection means tilts and rotates around the central axis, and the stage is driven to draw a circular orbit in synchronization with the rotational drive of the radiation detection means. Radiography. Then, the parameter calculation means calculates correction parameters based on the images of a plurality of markers associated with the projection images of the plurality of frames of the calibration phantom , and based on the projection images and parameters of the plurality of objects, The tomographic image calculation means reconstructs using parameters suitable for the imaging conditions when the object is imaged at the time of the calculation. By configuring the stage so that at least a calibration phantom having a plurality of markers can be mounted at the time of radiography, the object and the calibration phantom are simultaneously placed on the stage at the time of radiography even if the imaging conditions are changed. be able to. Therefore, the troublesomeness of re-installing the calibration phantom each time the shooting conditions are changed can be eliminated, and any shooting conditions can be easily changed and corrected for each shooting condition. Each parameter can be calculated.
Here, the above-described tomographic image in the present invention is a three-dimensional tomographic image including a plurality of tomographic images, and of course includes a case of a single tomographic image.

The tomographic image correction method according to the present invention is a tomographic image correction method for correcting a tomographic image of an object using a calibration phantom having a plurality of markers , wherein the object and the calibration phantom are A placement step of placing on a stage that goes straight in the direction Y and the Y direction, and a center axis after the radiation detection means tilts with the object and the calibration phantom placed on the stage in the placement step First, a projection image of the object based on the radiation transmitted through the object is collected in a state where the object rotates around and the stage is driven to draw a circular orbit in synchronization with the rotational drive of the radiation detection means. In a state where the object and the calibration phantom are placed on the stage in the projection image collecting step and the placing step, the radiation detection means is tilted and around the central axis. A second stage of collecting a projection image of the calibration phantom based on the radiation transmitted through the calibration phantom in a state where the stage is driven to draw a circular orbit in synchronization with the rotational drive of the radiation detection means; Parameter calculation for calculating correction parameters based on the images of the plurality of markers associated with each other in the projection images of the plurality of frames of the calibration phantom collected in the projection image collection step and the second projection image collection step And a tomographic image of the object based on the projection image of the plurality of objects collected in the first projection image collection process and the parameter calculated in the parameter calculation process, and at the time of the calculation A tomographic image calculation step for reconstructing using the parameters suitable for imaging conditions when imaging the object, By performing the process, it is characterized in that to correct the tomographic image of the object by using the calibration phantom.

[Operation / Effect] According to the tomographic image correction method according to the present invention, in the placing step, the calibration phantom having the object and the plurality of markers is placed on a stage that goes straight in the X and Y directions. Then, the radiation detection means tilts and rotates around the central axis, and the stage is driven so as to draw a circular orbit in synchronization with the rotational drive of the radiation detection means, and radiation imaging is performed. In this state, in the first projection image collection step, the projection image of the object based on the radiation transmitted through the object is collected, while in the second projection image collection step, the calibration based on the radiation transmitted through the calibration phantom. Collect phantom projection images. The order of the first / second projection image collection process is not particularly limited, and the second projection image collection process may be performed after the first projection image collection process, or conversely, the second projection image collection process. The first projection image collection step may be performed later, or the first / second projection image collection step may be performed in parallel as will be described later.

Further, in the parameter calculation step, a correction parameter is calculated based on the images of a plurality of markers associated with each other in the projection images of the plurality of frames of the calibration phantom collected in the second projection image collection step, and the first projection The tomographic image calculation step calculates a tomographic image of the object based on the projection images of the plurality of objects collected in the image acquisition step and the parameters calculated in the parameter calculation step, and images the object at the time of the calculation. Reconfiguration is performed using parameters suitable for the shooting conditions. By performing these steps, the tomographic image of the object is corrected using the calibration phantom. By placing the object and the calibration phantom on the stage in this way and performing these steps, the object and the calibration phantom can be simultaneously placed on the stage during radiography even if the imaging conditions are changed. Can do. Therefore, the troublesomeness of re-installing the calibration phantom each time the shooting conditions are changed can be eliminated, and any shooting conditions can be easily changed and corrected for each shooting condition. Each parameter can be calculated.

  In the tomographic image correction method according to the present invention described above, when the object also serves as a calibration phantom, both the first projection image collection step and the second projection image collection step are performed simultaneously to collect the projection image of the object. In addition, a projection image of a calibration phantom shared by the object may be collected. Alternatively, similarly to the above-described radiographic apparatus according to the present invention, in the tomographic image correction method according to the present invention described above, the stage may be configured so that at least a calibration phantom can be mounted during radiography.

  In the radiation imaging apparatus and tomographic image correction method according to the present invention described above, the stage may be configured so that the calibration phantom can be mounted by embedding a marker in the stage to form a calibration phantom. Alternatively, the stage may be configured so that a calibration phantom made of the marker can be mounted by installing a pattern as a marker on the stage. Moreover, you may combine both.

  In the tomographic image correction methods according to these inventions described above, the projection image of the calibration phantom is collected in the second projection image collection step under the same imaging conditions as when the projection image of the object is collected in the first projection image collection step. When the parameters under the imaging conditions are calculated in the parameter calculation step and the imaging conditions are changed, the projection image of the object is collected in the first projection image collection step under the changed imaging conditions, and the changed Preferably, the projection image of the calibration phantom is collected in the second projection image collection step under the photographing condition, and the parameter under the photographing condition after the change is calculated in the parameter calculation step. Under the same shooting conditions, each projection image is collected in the first / second projection image collecting step to calculate parameters, and when the shooting conditions are changed, the first / second projection image collecting step is performed under the changed shooting conditions. By collecting the projection images and calculating the parameters, it is possible to easily calculate the correction parameters under any photographing condition.

  In addition, the above-described tomographic image correction methods according to these inventions include a parameter storage step of writing and storing the parameters calculated in the parameter calculation step in a storage medium for each imaging condition, and storing parameters suitable for a certain imaging condition. If not, the projection image of the calibration phantom is collected in the second projection image collection step under the shooting condition, the parameter under the shooting condition is calculated in the parameter calculation step, and is suitable for the calculated shooting condition. Preferably, the parameters are written and stored in a storage medium in the parameter storage step, and in the tomographic image calculation step, the tomographic image of the object is calculated and reconstructed using the parameters under each imaging condition. If the parameter is stored in the past in the storage process and already exists in the storage medium, the tomographic image of the object is calculated and reconstructed using the parameter, and only when the parameter is not in the storage medium, the imaging conditions at that time In the first / second projection image collection step, each projection image is collected, parameters are calculated, and reconstruction is performed. By doing this, there is no need to re-shoot under the same shooting conditions (collection of projection images / calculation of parameters), and there is no need to go back in the past to check for past shooting conditions. The time can be shortened without bothering the user for these.

  Further, in the tomographic image correction methods according to these inventions described above, the second projection image collection is performed for each frame other than the deleted predetermined number of frames in a state where the predetermined number of frames are deleted from all the frames required for radiography. In the process, projection images of the calibration phantoms are collected, and parameters are calculated for each frame in the parameter calculation process. The tomographic image correction method is based on the calculated parameters for each of the predetermined number of deleted frames. It is preferable to provide a parameter interpolation step for interpolating parameters, and to calculate parameters for all frames by interpolating the parameters in the parameter interpolation step. The parameters are calculated with the frames deleted, and the parameters for the deleted frames are interpolated based on the calculated parameters, thereby shortening the shooting (collection image / parameter calculation) time for the deleted frames. can do.

  According to the radiation imaging apparatus and the tomographic image correction method according to the present invention, the object and the calibration phantom can be simultaneously placed on the stage even when the imaging conditions are changed. Therefore, the troublesomeness of re-installing the calibration phantom each time the shooting conditions are changed can be eliminated, and any shooting conditions can be easily changed and corrected for each shooting condition. Each parameter can be calculated.

It is a schematic block diagram of the X-ray inspection apparatus which concerns on an Example. It is a block diagram of the X-ray inspection apparatus which concerns on an Example. It is a schematic plan view of an example in which an object also serves as a calibration phantom. It is the schematic of an example which comprises a stage so that a calibration phantom can be mounted at least at the time of radiography, (a) is a schematic perspective view at the time of embedding a marker in a stage, and is used as a calibration phantom, (b) is the schematic cross section FIG. It is the schematic of another example which comprises a stage so that a calibration phantom can be mounted at least at the time of radiography, (a) is a schematic perspective view of the calibration phantom when a pattern is set as a marker on the surface (upper surface) of the stage FIG. 4B is a schematic perspective view when a pattern is set as a marker on the back surface (lower surface) of the stage. It is a flowchart which shows a series of processes until it calculates a parameter from the projection image of a calibration parameter. It is a flowchart which shows a series of processes of the tomographic image correction method which concerns on an Example. It is the schematic of the conventional imaging | photography. It is the schematic of the conventional diagonal imaging | photography. It is the schematic of the conventional diagonal imaging | photography when a stage is moved in parallel and an X-ray detector is rotationally driven synchronizing with the movement of a stage.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an X-ray inspection apparatus according to the embodiment, and FIG. 2 is a block diagram of the X-ray inspection apparatus according to the embodiment. In the present embodiment, an X-ray inspection apparatus will be described as an example of a radiation imaging apparatus.

  As shown in FIG. 1, an X-ray inspection apparatus 1 includes a stage 2 on which an object O is placed, and an X-ray tube 3 and an X-ray detector arranged so as to face each other with the stage 2 interposed therebetween. 4 is provided. The X-ray detector 4 is not particularly limited, as exemplified by an image intensifier (II), a flat panel X-ray detector (FPD: Flat Panel Detector), and the like. In the present embodiment, a flat panel X-ray detector (FPD) will be described as an example of the X-ray detector 4. The stage 2 corresponds to the stage in the present invention, the X-ray tube 3 corresponds to the radiation irradiation means in the present invention, and the X-ray detector 4 corresponds to the radiation detection means in the present invention.

  The FPD is composed of a plurality of detection elements arranged vertically and horizontally corresponding to pixels, and the detection elements detect X-rays and output detected X-ray data (charge signals) as X-ray detection signals. In this way, the X-rays irradiated from the X-ray tube 3 and transmitted through the object O are detected by the X-ray detector 4 made of FPD and output an X-ray detection signal, and the pixel value based on the X-ray detection signal Are arranged in correspondence with the pixels to obtain a projection image projected on the detection surface of the X-ray detector 4.

Other, X-ray inspection apparatus 1, as shown in FIG. 1, tilting the detector rotation mechanism 5 for rotating the X-ray detector 4 around arrow R _1, the X-ray detector 4 in the arrow R ₂ direction And a detector tilting mechanism 6 to be operated. The detector tilting mechanism 6 includes an arcuate guide portion 6a that supports the X-ray detector 4 and a rotation motor (not shown). When the rotation motor is driven to rotate, X-ray detection is performed along the guide portion 6a. vessel 4 is tilted in the arrow _{R 2} direction.

Detector rotation mechanism 5 is made of a rotary motor (not shown), a rotary motor that rotationally drives the guide portion 6a of the detector tilt mechanism 6 around the arrow R _1, the guide portion 6a in the supported X-ray detector vessel 4 is also rotated about arrow R _1. In this embodiment, the detector rotation mechanism 5 rotates the X-ray detector 4 around the arrow R ₁ in synchronization with the drive of the stage 2. In particular, the detector rotation mechanism 5 moves the X-ray detector 4 to the arrow so that X-rays emitted from the X-ray tube 3 pass through the target point of the object O and are detected at the center of the radiation detector 4. for rotating about the R _1.

  In addition, as shown in FIG. 2, the X-ray inspection apparatus 1 includes a stage drive mechanism 7 that drives the stage 2 straightly in an orthogonal coordinate system X, Y, and Z (see FIG. 1), and a calibration phantom Ph ( A parameter calculation unit 8 that calculates a correction parameter (physical quantity) based on the projection image of FIG. 3 to FIG. 5; a parameter storage unit 9 that writes and stores the parameter calculated by the parameter calculation unit 8; Based on the projection images and parameters of the plurality of objects O, the tomographic image calculation unit 10 that calculates and calculates the tomographic images of the object O, the controller 11 that performs overall control thereof, and the tomographic image calculation unit 10 And an image output unit 12 for outputting the tomographic image (display output on a monitor or print output on a printer). The stage drive mechanism 7 including the detector rotation mechanism 5 and the detector tilt mechanism 6 described above corresponds to the drive means in the present invention, the parameter calculation unit 8 corresponds to the parameter calculation means in the present invention, and the parameter storage unit. 9 corresponds to the storage medium in the present invention, and the tomographic image calculation unit 10 corresponds to the tomographic image calculation means in the present invention.

  The stage drive mechanism 7 includes an X-axis rectilinear motor (not shown) that linearly drives the stage 2 in the X direction (here, horizontal drive), and a Y-axis rectilinear motor that linearly drives the stage 2 in the Y direction (here, horizontal drive) ( And a Z-axis rectilinear motor (not shown) that drives the stage 2 straightly in the Z direction (in this case, driving up and down). In this embodiment, the controller 11 moves the stage 2 so that the composition of the trajectories by the respective X-axis rectilinear motors and Y-axis rectilinear motors is a circular trajectory and is synchronized with the rotational drive of the X-ray detector 4 by the detector rotation mechanism 5. Drive.

  The parameter calculation unit 8 calculates correction parameters based on the projection image of the calibration phantom Ph (see FIGS. 3 to 5), and writes the calculated parameters in the parameter storage unit 9 for each shooting condition. To do. When correcting the tomographic image of the object O, the parameters stored in the parameter storage unit 9 are read out, and the read parameters are used. The parameter storage unit 9 is composed of a storage medium represented by a RAM (Random Access Memory) or the like.

  The tomographic image calculation unit 10 calculates a tomographic image of the target object O based on the projection images of the plurality of target objects O and the above-described parameters, and parameters suitable for the imaging conditions when the target object O is captured at the time of the calculation. Reconfigure using The controller 11 comprehensively controls each part constituting the X-ray inspection apparatus 1, and in particular, a rotation motor (not shown) of the detector rotation mechanism 5, a rotation motor (not shown) of the detector tilting mechanism 6, and a stage drive mechanism. 7 X-axis / Y-axis / Z-axis rectilinear motors (not shown) are respectively controlled. Although the X-ray tube 3 is at a fixed position in FIG. 1, the controller 11 may control the X-ray tube 3 so that the X-ray tube 3 can be tilted according to the tilt of the X-ray detector 4. The parameter calculation unit 8, the tomographic image calculation unit 10, and the controller 11 described above are configured by a central processing unit (CPU) and the like.

  As shown in FIG. 1, by arranging the X-ray tube 3, the object O, and the X-ray detector 4, the X-ray tube 3 and the X-ray detector 4 are inclined in the oblique direction inclined by the lamino angle, as in FIG. 10. And can be taken from an oblique direction. Then, the X-ray tube 3 and the stage 2 and thus the object O can be brought close to each other, and a high-magnification projection image can be obtained without the X-ray tube 3 and the object O interfering with each other. Each time the stage 2 is driven, a projection image is acquired to acquire a projection image from a plurality of angles, and the tomographic image calculation unit 10 shown in FIG. 2 calculates and calculates a tomographic image based on the plurality of projection images. To do.

  Next, the calibration phantom Ph will be described. The calibration phantom Ph has a marker and has a structure in which the same position of the marker can be extracted as a feature point from the marker in the projection image obtained when the calibration phantom Ph is radiographed. This will be described with reference to FIGS. FIG. 3 is a schematic plan view of an example in which the object also serves as a calibration phantom, and FIG. 4 is a schematic diagram of an example in which the stage can be mounted so that the calibration phantom can be mounted at least during radiography. FIG. 4A is a schematic perspective view when a marker is embedded in a stage to form a calibration phantom, FIG. 4B is a schematic sectional view thereof, and FIG. 5 is equipped with a calibration phantom at least during radiography. FIG. 5A is a schematic perspective view of a calibration phantom when a pattern is set as a marker on the surface (upper surface) of the stage. FIG. (B) is a schematic perspective view of the calibration phantom when the pattern is set as a marker on the back surface (lower surface) of the stage.

  To place the object O (see FIGS. 1 and 3) and the calibration phantom Ph simultaneously on the stage 2 (see FIGS. 1, 2, 4 or 5) at the time of radiography, as shown in FIG. Thus, the object O is roughly divided into a technique in which the calibration phantom Ph is also used and a technique in which the stage 2 is configured so that the calibration phantom Ph can be mounted at least during radiography as shown in FIG. 4 or FIG.

  As shown in FIG. 3, as an example in which the object O also serves as the calibration phantom Ph, for example, when the object O is a BGA, a marker M is placed on one of the spherical substances (Ball) in the object O To do. By installing the marker M, the calibration object phantom Ph composed of the marker M can be used as the object O, and it is not necessary to prepare a calibration phantom different from the object O. At this time, the first / second projection image collecting step may be performed simultaneously at the position of the marker M in the object O, or the first projection image collecting step may be performed at a position other than the marker M in the object O. Also good.

  As an example of configuring the stage 2 so that the calibration phantom Ph can be mounted at least during radiography, the calibration phantom is placed on the stage 2 as shown in the schematic perspective view of FIG. 4A and the schematic cross-sectional view of FIG. Embed Ph. In general, since the stage 2 is made of a material having a high radiation transmittance, the marker is made of a material (for example, lead) having a low radiation transmittance to be distinguished from the stage 2. In the case of FIG. 4, the marker is formed of a spherical material having a low radiation transmittance, and the spherical material embedded in the stage 2 is defined as a calibration phantom Ph.

  In addition to FIG. 4, as another example of configuring the stage 2 so that the calibration phantom Ph can be mounted at least during radiation imaging, a marker made of a pattern is placed on the stage 2 as shown in the schematic perspective view of FIG. In this way, by setting the marker, the stage 2 is configured so that the calibration phantom Ph including the marker can be mounted. It should be noted that the marker in FIG. 5 is also included in the concept of a marker because the intersection of the pattern can be a feature point.

  A marker may be placed on any surface of the stage 2. For example, a marker may be placed on the surface (upper surface) of the stage 2 as shown in FIG. 5A, or a marker is placed on the back surface (lower surface) of the stage 2 as shown in FIG. 5B. May be. Moreover, you may install a marker on both the front and back of the stage 2 combining FIG. 5 (a) and FIG.5 (b). You may install a marker in other surfaces (a side surface, a front surface, or a back surface).

  The following formula (1), which will be described later, is a general calculation formula representing perspective projection from a three-dimensional space to a two-dimensional image. In the case of using the equation (1), when correcting the tomographic image of the object O (see FIGS. 1 and 3) using 11 parameters consisting of 12 elements, they are arranged in a three-dimensional manner. If there are six or more markers with known relative coordinates, the parameters can be directly calculated by algebraic calculation. Therefore, as shown in the schematic plan view of FIG. 4A, six (or more) calibration phantoms Ph are three-dimensionally embedded and arranged in the stage 2.

  When correcting the tomographic image of the object O (see FIGS. 1 and 3) using the eleven parameters described above, if there is a constraint that some of the parameters are fixed values, the marker There are also conditions under which correct parameters can be calculated even if is a two-dimensional arrangement. Therefore, as shown in FIGS. 3 and 5, the markers may be arranged two-dimensionally.

  About the marker which consists of a pattern, you may install by providing a groove | channel or protrusion in the stage 2, and you may install a pattern by sticking a substance different from the stage 2. FIG. The pattern is a lattice shape in FIG. 5, but is not limited to the lattice shape. For example, it may be composed of a dot pattern.

  4 and 5, the calibration phantom Ph is mounted over the entire stage 2, but the calibration phantom Ph may be mounted at the end of the stage 2 so as not to interfere with photographing. 3 to 5 may be combined with each other.

  Next, a method for correcting a tomographic image will be described. There are known methods for calculating a tomographic image, and for example, it can be calculated by an FBP method (Filtered Back Projection method) or the like. At this time, if a parameter representing a geometric condition at the time of radiography is known, a tomographic image can be calculated using that parameter as a correction (calculation) parameter. Here, the following equation (1), which is a general equation representing perspective projection from a three-dimensional space to a two-dimensional image, is expressed by the following equation (1). Can be represented.

P ^to _W are three-dimensional homogeneous coordinates of feature points in the world coordinate system, and are represented by a transposed matrix, and thus are actually a matrix of 4 rows and 1 column. P ^to _in are two-dimensional homogeneous coordinates in the pixel coordinate system on the projection image. Since P ^to _in are also expressed as transposed matrices, they are actually 3 × 1 matrices.

  M is a matrix composed of external parameters, and is a transformation matrix from the world coordinate system to the camera coordinate system. R in M is a rotation matrix representing rotation of three degrees of freedom in a three-dimensional space, and is a matrix of 3 rows and 3 columns composed of three parameters. T in M is a “translation vector” representing a translation with three degrees of freedom in a three-dimensional space, and is a 3 × 1 vector composed of three parameters. Further, “0” in M is a zero vector of 1 row and 3 columns, and “1” in M is 1 row and 1 column. Therefore, M is a 4 × 4 matrix composed of 6 parameters (external parameters).

  The matrix A and the matrix P are matrices composed of internal parameters, and the matrix AP is a transformation matrix from the camera coordinate system to the pixel coordinate system. F in P is a parameter that represents a distance (SID: Source Image Distance) from the X-ray tube 3 (see FIG. 1), a so-called light source to the X-ray detector 4 (see FIGS. 1 and 2). And P is a 3 × 4 matrix.

K _x and k _y in A are parameters for scale conversion from the coordinate system in the real space to the pixel coordinate system, and “skew” in A is a parameter representing the distortion of the coordinate axes of the pixel coordinate system, and is orthogonal In the case of the coordinate system, it is “0”. Also, σ _x and σ _{y in A} are parameters representing the origin position of the pixel coordinate system. A is a 3 × 3 matrix. A matrix AP obtained by multiplying the matrix A and the matrix P is a matrix composed of six elements but has 5 degrees of freedom, so the matrix AP is a matrix of 3 rows and 4 columns composed of 5 parameters (internal parameters).

In the case of obtaining the geometric condition at the time of radiography using the above equation (1), a total of 11 parameters including 6 external parameters in the matrix M and 5 internal parameters in the matrix AP are obtained. The calculation of these 11 parameters is a camera calibration problem that is generally handled in the field of computer vision and the like, and a marker feature point in a projection image obtained when radiographing a calibration phantom. pixel coordinates ((1) P ^~ _in the _formula), 3-dimensional coordinates in the world coordinate system of the marker when the marker relative coordinates of the calibration phantom is known ((1) P ^~ _W in the formula) And can be calculated.

  In addition, since each coordinate system of a world coordinate system, a camera coordinate system, and a pixel coordinate system is well-known, the detailed description is abbreviate | omitted. Further, the above expression (1) of 11 parameters is merely an example. Therefore, when correcting a tomographic image, the above equation (1) is not necessarily used, and is not particularly limited as long as it is a well-known equation using a parameter representing a geometric condition at the time of photographing.

  As described above, if there are six or more feature points arranged three-dimensionally with known three-dimensional coordinates in one projection image, 11 parameters can be directly calculated by algebraic calculation. Can do. It is also possible to calculate parameters by a non-linear optimization method, and methods such as Bundle Adjustment are known.

  Further, as described above, if there is a constraint that some of the parameters are fixed values, the feature point arrangement is two-dimensional or the number of feature points in the projection image is less than six. There are also conditions under which correct parameters can be calculated. In order to satisfy the above condition, for example, as shown in FIG. 4 or FIG. 5, a substance having a low radiation transmittance and a stage 2 having a relatively high radiation transmittance may be used as the calibration phantom Ph. it can.

  Next, a process until a parameter is calculated from the projection image of the calibration phantom Ph acquired by the above method will be described with reference to FIG. FIG. 6 is a flowchart showing a series of processes until the parameter is calculated from the projection image of the calibration parameter.

(Step S1) Feature Point Extraction First, feature points are extracted from the projection image of the calibration phantom Ph, and the pixel coordinates of the feature points are stored. As the feature points, for example, the center of the sphere may be set as the feature point when the marker is spherical, and the intersection of the lattice pattern may be set as the feature point when the marker is the lattice pattern. It is preferable that a plurality of feature points exist in one projection image (the number depends on the number of parameters to be calculated), and feature points at the same point of the calibration phantom Ph are extracted from all the projection images.

(Step S2) Identification of Same Feature Points Next, the feature points of each frame extracted in step S1 are associated with the feature points representing the same points of the calibration phantom Ph between the projection images of the calibration phantom Ph. I do. As an association method, for example, it is conceivable to compare the feature points having the shortest distance on the projection image as the same feature point by comparing the projection images of the continuous frames. Also, the feature point position (feature point pixel) on the projected image in a certain frame is estimated from the trajectory on the image of the feature point known from the projected image obtained in the previous frame, and the same feature point is supported A method of attaching and identifying is also conceivable.

(Step S3) Parameter Calculation Next, a parameter is calculated from the associated feature point (identified feature point) group. When the three-dimensional coordinates of feature points are known and six or more feature points are arranged three-dimensionally, the parameters can be directly calculated by algebraic calculation as described above. Further, it can be calculated by nonlinear optimization such as Bundle Adjustment method. At this time, some parameters can be handled as fixed values, and the number of necessary feature points varies depending on the number of parameters that need to be calculated. Even when the three-dimensional coordinates of the feature points are unknown, if skew is 0, self-calibration can be performed by the nonlinear optimization method, and optimal variable parameters can be calculated. The parameter calculation at this time leaves scale indefiniteness for Euclidean reconstruction. Therefore, an appropriate scale conversion can be performed as necessary, or a desired scale can be obtained by restricting parameters.

  Next, the tomographic image correction method according to the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart illustrating a series of processes of the tomographic image correction method according to the embodiment.

  First, the object O (see FIGS. 1 and 3) and the calibration phantom Ph (see FIGS. 3 to 5) are placed on the stage 2 (see FIG. 1, FIG. 2, FIG. 4 or FIG. 5). . This placement corresponds to the placement step in the present invention.

(Step T1) Parameter stored?
Next, in order to perform reconstruction using parameters suitable for the photographing conditions when photographing the object O, the parameters (suitable parameters) under the photographing conditions are stored in the parameter storage unit 9 (see FIG. 2). For example, the controller 11 (see FIG. 2) determines whether it has already been stored. If a suitable parameter has already been stored in the parameter storage unit 9, the process proceeds to step T2. If a suitable parameter is not already stored in the parameter storage unit 9, the process proceeds to step T11 in order to calculate a parameter under the photographing condition.

(Step T11) Tomography of the calibration phantom In order for the parameter calculation unit 8 (see FIG. 2) to calculate the parameters under the imaging conditions, the projection image of the calibration phantom Ph is collected under the imaging conditions, and the calibration is performed. A tomography of the phantom Ph is performed. Specifically, the X-ray detector 4 (see FIGS. 1 and 2) detects X-rays that have passed through the calibration phantom Ph with the object O and the calibration phantom Ph placed on the stage 2. Thus, the projection image of the calibration phantom Ph is acquired and collected.

  If the object O also serves as the calibration phantom Ph as shown in FIG. 3, the tomography of the calibration phantom in step T11 is the same as the tomography of the object in step T2 described later. Therefore, it is sufficient to proceed to step T11 (T2) regardless of the parameter storage at step T1. Step T11 corresponds to the second projection image collection step in this invention.

  When step T11 is completed, step T2 and step T12 are performed in parallel. If step T2, subsequent steps T3 and T4, step T12, and subsequent step T13 are completed before the calculation of the tomographic image in step T5, which will be described later, the start / end timing of step T2 and step T12 Is not particularly limited. Therefore, step T2 and step T12 may be started simultaneously, step T12 may be performed after the start of step T2, and step T2 may be performed after the start of step T12.

(Step T2) Tomographic imaging of the object The projection image of the object O is collected under the imaging conditions, and the tomographic imaging of the object O is performed. Specifically, as in step T11, the X-ray detector 4 detects X-rays transmitted through the object O while the object O and the calibration phantom Ph are placed on the stage 2, thereby detecting the object. Acquire and collect projection images of O. Step T2 corresponds to the first projection image collection step in this invention.

(Step T3) Is the parameter already calculated?
After performing tomographic imaging of the object O in step T2, for example, the controller 11 determines whether or not the parameter calculation unit 8 has already calculated parameters (suitable parameters) under the imaging conditions. If the parameter calculation unit 8 has already calculated a suitable parameter, the process proceeds to step T5. If the parameter calculation unit 8 has not calculated a suitable parameter, the process waits at step T4 until the parameter calculation is completed.

  In addition, if the parameter suitable at step T1 has already been stored in the parameter storage unit 9, step T3 is not necessarily performed. Even if the imaging conditions of the parameters already stored in the parameter storage unit 9 and the imaging conditions in the tomographic imaging of the object O in step T2 are not the same, if the following parameter interpolation is performed, the projection is not necessarily performed. There is no need to collect images / calculate parameters.

  That is, in a state where a predetermined number of frames are deleted from all the frames necessary for radiography, projection images of the calibration phantom Ph are collected for each frame other than the deleted predetermined number of frames in step T11. Then, parameters are calculated for each frame in step T12. This parameter includes parameters stored in the parameter storage unit 9 in the past.

  Based on the calculated parameters, the parameters for the deleted predetermined number of frames are interpolated. By interpolating the parameters by the parameter interpolation, the parameters for all frames are calculated. Since parameter interpolation is publicly known, a detailed description thereof will be omitted. This parameter interpolation corresponds to the parameter interpolation step in the present invention.

(Step T4) Wait until Completion of Parameter Calculation In order for the parameter calculation unit 8 to calculate a suitable parameter, the process waits at step T4 until the calculation is completed. If the calculation is completed, the process proceeds to step T5.

(Step T12) Parameter Calculation On the other hand, after performing tomography of the calibration phantom Ph in step T11, the parameter calculation unit 8 calculates parameters based on the projection image of the calibration phantom Ph. When the above steps S1 to S3 (see FIG. 6) are performed and the parameters are obtained using the above equation (1), the parameters are obtained as follows. That is, the coordinates of each feature point (x _in , y _{in in} P ^to _in of the pixel coordinate system) reflected on the projection image of the calibration phantom Ph, and the coordinates under the shooting conditions at the time (1) By substituting into the equation, the geometric condition at the time of shooting is obtained. By obtaining these geometric conditions, a maximum of 11 parameters (in this case, 6 external parameters and 5 internal parameters) are obtained. This step T12 corresponds to the parameter calculation step in the present invention.

(Step T13) Parameter storage The parameter calculated in step T12 is written and stored in the parameter storage unit 9. By performing steps T11 to T13, parameters under the photographing conditions are calculated and stored. When the parameters are stored, the process proceeds to step T5. This step T13 corresponds to the parameter storing step in the present invention.

(Step T5) Calculation of Tomographic Image When the parameters are obtained in step T4 or T13, the tomographic image calculation unit 10 (see FIG. 2) determines the tomographic image of the object O based on the projection images and parameters of the plurality of objects O. An image is calculated and reconstructed using parameters suitable for the shooting conditions when the object O is shot at the time of calculation. In this way, the tomographic image of the object O is corrected using the calibration phantom Ph. This step T5 corresponds to the tomographic image calculation step in this invention.

(Step T6) Display of Tomographic Image The tomographic image obtained by the tomographic image calculation unit 10 is displayed and output on the monitor of the image output unit 12 (see FIG. 2). The tomographic image obtained by the tomographic image calculation unit 10 may be printed out to the printer of the image output unit 12.

  The tomographic image is corrected by performing a series of steps T1 to T6 (including steps T11 to T13) shown in FIG.

  According to the X-ray inspection apparatus according to the present embodiment having the above-described configuration, the stage 2 is configured so that the calibration phantom Ph can be mounted at least during radiation imaging, as shown in FIG. 4 or FIG. Then, the parameter calculation unit 8 calculates a correction parameter based on the projection image of the calibration phantom Ph, and based on the projection image and parameters of the plurality of objects O, the tomographic image calculation unit 10 performs the calculation. When the object O is imaged, reconstruction is performed using parameters suitable for the imaging conditions. Thus, by configuring the stage 2 so that the calibration phantom Ph can be mounted at least during radiation imaging, the object O and the calibration phantom Ph are simultaneously placed on the stage 2 even when the imaging conditions are changed. be able to. Accordingly, it is possible to eliminate the conventional troublesomeness of re-installing the calibration phantom Ph every time the shooting conditions are changed, and it is possible to easily change the setting of arbitrary shooting conditions and perform correction under each shooting condition. The parameters can be calculated respectively.

  Further, according to the tomographic image correction method according to the present embodiment, the object O and the calibration phantom Ph are placed on the stage 2 in the placing step. In that state, in the first projection image collection step (step T2 in FIG. 7), the projection image of the object O based on the X-rays transmitted through the object O is collected, while the second projection image collection step (FIG. 7, in step T11), projection images of the calibration phantom Ph based on the X-rays transmitted through the calibration phantom Ph are collected. As described above, the order of the first / second projection image collection process (steps T2, T11) is not particularly limited, and the second projection image collection process (step T11) is performed after the first projection image collection process (step T2). ), Or the first projection image collection step (step T2) after the second projection image collection step (step T11), or the first / second projection image collection step (step T11). Steps T2 and T11) may be performed in parallel.

  Further, in the parameter calculation step (step T12 in FIG. 7), a correction parameter is calculated based on the projection image of the calibration phantom Ph collected in the second projection image collection step (step T11), and the first projection image is obtained. In the tomographic image calculation step (step T5 in FIG. 7) based on the projection images of the plurality of objects O respectively collected in the collection step (step T2) and the parameters calculated in the parameter calculation step (step T12) A tomographic image of the object O is calculated, and reconstruction is performed using parameters suitable for the imaging conditions when the object O is imaged at the time of the calculation.

  By performing these steps (steps T1 to T6 including steps T11 to T13 in FIG. 7), the tomographic image of the object O is corrected using the calibration phantom Ph. As described above, the object O and the calibration phantom Ph are placed on the stage 2 and these steps are performed. Thus, even if the imaging conditions are changed, the object O and the calibration phantom Ph are simultaneously staged at the time of radiography. 2 can be mounted. Accordingly, it is possible to eliminate the conventional troublesomeness of re-installing the calibration phantom Ph every time the shooting conditions are changed, and it is possible to easily change the setting of arbitrary shooting conditions and perform correction under each shooting condition. The parameters can be calculated respectively.

  In the tomographic image correction method according to the present embodiment, as shown in FIG. 3, the object O also serves as the calibration phantom Ph, so that the first projection image collection step (step T2) and the second projection image collection step ( Step T11) may be performed at the same time to collect the projection image of the object O and to collect the projection image of the calibration phantom Ph shared by the object O. Alternatively, similarly to the X-ray inspection apparatus according to the present embodiment, in the tomographic image correction method according to the present embodiment, as shown in FIG. 4 or FIG. 2 may be configured.

  In the X-ray inspection apparatus and tomographic image correction method according to the present embodiment, the stage 2 is configured so that the calibration phantom Ph can be mounted by embedding a marker in the stage 2 as shown in FIG. May be. Alternatively, as shown in FIG. 5, the stage 2 may be configured so that a calibration phantom Ph including the marker can be mounted by installing a pattern as a marker on the stage 2. Moreover, you may combine both FIG. 4 and FIG.

  In the tomographic image correction method according to the present embodiment, preferably, as shown in the flowchart of FIG. 7, the first imaging image acquisition process (step T2) is performed under the same imaging conditions as when the projection image of the object O is acquired. The projection image of the calibration phantom Ph is collected in the two projection image collection step (step T11), and the parameters under the photographing conditions are calculated in the parameter calculation step (step T12). And if the said imaging condition is changed, while the projection image of the target object O is collected by the 1st projection image collection process (step T2) on the said imaging condition after the change, the 2nd projection image collection will be carried out on the said imaging condition after the change In the step (step T11), projection images of the calibration phantom Ph are collected, and the parameters under the changed imaging conditions are calculated in the parameter calculation step (step T12). Under the same shooting conditions, the projection images are collected in the first / second projection image collection step (steps T2, T11), the parameters are calculated, and if the shooting conditions are changed, the first / first shooting conditions are changed. By collecting each projection image and calculating the parameters in the two projection image collection steps (steps T2 and T11), it is possible to easily calculate parameters for correction under an arbitrary shooting condition.

  Further, in the tomographic image correction method according to the present embodiment, preferably, as shown in the flowchart of FIG. 7, the parameter calculated in the parameter calculation step (step T12) is stored for each imaging condition in the storage medium (the parameter in the present embodiment). A parameter storage step (step T13 in FIG. 7) for writing and storing in the storage unit 9) is provided. When a parameter suitable for a certain imaging condition is not stored (in FIG. 7, branching to “No” in step T1: when a suitable parameter is not already stored in the parameter storage unit 9), the second projected image in the imaging condition The projection image of the calibration phantom Ph is collected in the collecting step (step T11), and the parameters under the photographing conditions are calculated in the parameter calculating step (step T12). Then, the calculated parameters suitable for the imaging conditions are written and stored in the parameter storage unit 9 in the parameter storage step (step T13), and the parameters under the respective imaging conditions are used in the tomographic image calculation step (step T5). Then, a tomographic image of the object O is calculated and reconstructed.

  When the parameter is stored in the past in the storage step (step T13) and already exists in the parameter storage unit 9, the tomographic image of the object O is calculated and reconstructed using the parameter, and the parameter is stored in the parameter storage unit 9. Only when there is not, each projection image is collected in the first / second projection image collection step (steps T2 and T11) under the photographing conditions at that time, parameters are calculated, and reconstruction is performed. By doing this, there is no need to re-shoot under the same shooting conditions (collection of projection images / calculation of parameters), and there is no need to go back in the past to check for past shooting conditions. The time can be shortened without bothering the user for these.

  In the tomographic image correction method according to the present embodiment, it is preferable that the second projection image is generated for each frame other than the predetermined number of deleted frames in a state where the predetermined number of frames are deleted from all the frames necessary for radiography. Projection images of the calibration phantom Ph are collected in the collection step (step T11), and parameters are calculated for each frame in the parameter calculation step (step T12). The tomographic image correction method according to the present embodiment includes a parameter interpolation process for interpolating parameters in a predetermined number of deleted frames based on the calculated parameters, and by interpolating the parameters in the parameter interpolation process, Calculate parameters for all frames. The parameters are calculated with the frames deleted, and the parameters for the deleted frames are interpolated based on the calculated parameters, thereby shortening the shooting (collection image / parameter calculation) time for the deleted frames. can do.

  The present invention is not limited to the above-described embodiment, and can be modified as follows.

  (1) In the above-described embodiments, the X-ray inspection apparatus has been described as an example of the radiation imaging apparatus. However, if the apparatus performs radiography by acquiring tomographic images based on a plurality of projection images, radiation Is not limited to X-rays, and may be radiation other than X-rays (α rays, β rays, γ rays, etc.).

  (2) The object is not particularly limited. As described above, mounting boards, through holes / patterns / solder joints on multilayer boards, electronic parts before mounting such as integrated circuits (ICs) placed on pallets, castings of metals, moldings such as video decks What is necessary is just to perform radiography with respect to a target object, as exemplified by goods.

  (3) In the above-described embodiment, as shown in FIG. 1, the radiation irradiation means (X-ray tube 3 in the embodiment) and the radiation detection means (X-ray detector 4 in the embodiment) from the oblique direction inclined by the lamino angle. Are arranged and photographed from an oblique direction, but may be photographed from the direction as shown in FIG. 8 of the prior art, or may be photographed from the direction as shown in FIG.

  (4) In the embodiment described above, the driving means is the detector rotating mechanism 5, the detector tilting mechanism 6, and the stage driving mechanism 7 shown in FIG. 2, and the object O and the calibration phantom Ph are mounted on the stage 2. In this state, the radiation detection means (X-ray detector 4 in the embodiment) and the stage 2 are each driven, but the drive target is not limited to this. If at least one of the radiation irradiation means (X-ray tube 3 in the embodiment), the radiation detection means, and the stage is driven with the object and the calibration phantom placed on the stage, the radiation irradiation means and the radiation detection Only one of the means and the stage may be driven, or the radiation irradiating means, the radiation detecting means, and the stage may all be driven, or two of the radiation irradiating means, the radiation detecting means, and the stage may be driven. It may be driven.

DESCRIPTION OF SYMBOLS 2 ... Stage 3 ... X-ray tube 4 ... X-ray detector 5 ... Detector rotation mechanism 6 ... Detector tilting mechanism 7 ... Stage drive mechanism 8 ... Parameter calculation part 9 ... Parameter memory | storage part 10 ... Tomographic image calculation part M ... Marker Ph: Phantom for calibration O: Object

Claims (11)

A stage on which the object is placed and goes straight in the X and Y directions;
Radiation irradiating means and radiation detecting means arranged to face each other with the stage in between,
A radiation imaging apparatus that performs radiation imaging based on a projection image obtained by detecting radiation emitted from the radiation irradiation means and transmitted through the object by the radiation detection means,
Configure the stage so that a calibration phantom having a plurality of markers can be mounted at least during radiography,
In a state where the object and the calibration phantom are placed on the stage, the radiation detection means tilts and rotates around a central axis, and the stage rotates in a circular orbit in synchronization with the rotational drive of the radiation detection means. Driving means for driving to draw,
Parameter calculating means for calculating a correction parameter based on the images of the plurality of markers associated with each other in the projection image of the plurality of frames of the calibration phantom;
A tomogram that calculates a tomographic image of an object based on a plurality of projection images of the object and the parameters, and that is reconstructed using the parameters suitable for imaging conditions when the object is imaged at the time of the calculation A radiation imaging apparatus comprising: an image calculating unit. The radiographic apparatus according to claim 1,
A radiation imaging apparatus, wherein a stage is configured so that the calibration phantom can be mounted by embedding a marker in the stage to form the calibration phantom. The radiographic apparatus according to claim 1,
A radiation imaging apparatus, wherein a stage is configured so that the calibration phantom including the marker can be mounted by installing a pattern as a marker on the stage. A tomographic image correction method for correcting a tomographic image of an object using a calibration phantom having a plurality of markers ,
A placing step of placing the object and the calibration phantom on a stage that goes straight in the X direction and the Y direction;
In a state where the object and the calibration phantom are placed on the stage in the placing step, the radiation detecting means tilts and rotates around the central axis, and the stage synchronizes with the rotational drive of the radiation detecting means. A first projection image collecting step of collecting a projection image of the object based on radiation transmitted through the object in a state where the object is driven to draw a circular orbit;
In a state where the object and the calibration phantom are placed on the stage in the placing step, the radiation detecting means tilts and rotates around a central axis, and the stage is driven to rotate the radiation detecting means. A second projection image collecting step of collecting a projection image of the calibration phantom based on the radiation transmitted through the calibration phantom in a state where the circular orbit is driven synchronously;
A parameter calculating step of calculating correction parameters based on the images of the plurality of markers associated in the projection images of the plurality of frames of the calibration phantom collected in the second projection image collecting step;
A tomographic image of the object is calculated based on the projection images of the plurality of objects collected in the first projection image collection process and the parameters calculated in the parameter calculation process, and the object is calculated at the time of the calculation. A tomographic image calculation step for reconstructing using the parameters suitable for the imaging conditions when imaging
A tomographic image correction method comprising correcting the tomographic image of the object using the calibration phantom by performing these steps. The tomographic image correction method according to claim 4,
By combining the object with the calibration phantom,
Performing both the first projection image collection step and the second projection image collection step simultaneously to collect the projection image of the object, and to collect the projection image of the calibration phantom shared by the object. A characteristic tomographic image correction method. The tomographic image correction method according to claim 4,
A tomographic image correction method, wherein the stage is configured so that the calibration phantom can be mounted at least during radiation imaging. The tomographic image correction method according to claim 6,
A tomographic image correction method, wherein a stage is configured so that the calibration phantom can be mounted by embedding a marker in the stage to form the calibration phantom. The tomographic image correction method according to claim 6,
A tomographic image correction method characterized in that a stage is configured so that the calibration phantom comprising the marker can be mounted by installing a pattern as a marker on the stage. In the tomographic image correction method according to any one of claims 4 to 8,
The projection image of the calibration phantom is collected in the second projection image collection step under the same photographing condition as when the projection image of the object is collected in the first projection image collection step, and the parameter under the photographing condition is set. Calculated in the parameter calculation step,
When the imaging condition is changed, the projection image of the object is collected in the first projection image collection step under the changed imaging condition, and the calibration is performed in the second projection image collection step under the changed imaging condition. A tomographic image correction method, comprising: collecting projection images of an imaging phantom, and calculating the parameters under the changed imaging conditions in the parameter calculation step. In the tomographic image correction method according to any one of claims 4 to 9,
A parameter storage step of storing the parameter calculated in the parameter calculation step in a storage medium for each shooting condition;
When the parameter suitable for a certain photographing condition is not stored, the projection image of the calibration phantom is collected in the second projected image collecting step under the photographing condition, and the parameter under the photographing condition is calculated as the parameter Calculated in the process, parameters suitable for the calculated shooting conditions are written and stored in the storage medium in the parameter storage process,
A tomographic image correction method characterized in that in the tomographic image calculation step, a tomographic image of the object is calculated and reconstructed using parameters in each imaging condition. In the tomographic image correction method according to any one of claims 4 to 10,
In a state where a predetermined number of frames are deleted from all the frames required for radiography, the projection images of the calibration phantom are collected in the second projection image collection step for each frame other than the deleted predetermined number of frames. , Calculating the parameters for each frame in the parameter calculation step,
The tomographic image correction method includes:
A parameter interpolation step of interpolating parameters in the deleted predetermined number of frames based on the calculated parameters,
A tomographic image correction method, wherein parameters in all the frames are calculated by interpolating parameters in the parameter interpolation step.

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