JP3356356B2 - X-ray equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray source in which an X-ray source and an X-ray television camera rotate while moving about the same center.
According to the radiography device , in particular, accurately correct the distortion of the image,
Those concerning the suitable X-ray imaging apparatus for obtaining three-dimensional reconstruction images of high resolution.

[0002]

2. Description of the Related Art Recently, as an X-ray imaging apparatus, for example, Society of Photo-Optical Instrumentation Engineers (Society of Photo)
-Optical Instrumentation Engineers) Collection of Papers, SPIE, 1897 (1993)
Pp. 90-98 have been developed. In this cone-beam CT apparatus, a two-dimensional X-ray detector is used as the X-ray detector, and the X-ray is a cone beam. X using one-dimensional X-ray detector
Compared to a line CT apparatus, it is possible to obtain three-dimensional image data having a high spatial resolution in a short time and having an isotropic spatial resolution. In the above document, an X-ray television camera including an X-ray image intensifier and a television camera is used as a two-dimensional X-ray detector. However, in such a cone beam CT apparatus or the like, X
Due to the spherical shape of the X-ray incident surface of the X-ray image intensifier and the influence of geomagnetism on the electron orbit, images obtained by photographing have large pincushion distortion and relatively small S There is a geometric distortion such as a character distortion.

Conventional techniques for correcting this distortion include, for example, Japanese Patent Laid-Open No. 2-10636 and Japanese Utility Model Laid-Open No. 5-283.
There is one described in JP-A-16. JP-A-2-10636
In the technique described in Japanese Patent Application Laid-Open Publication No. H10-209, an amount of a change in a pincushion-like distortion characteristic caused by a change in a distance between an X-ray tube and an X-ray image intensifier is determined by an electrode provided near an output fluorescent film of the X-ray image intensifier. Are controlled to cancel each other. The technique described in Japanese Utility Model Laid-Open No. 5-28316 does not suppress the distortion of an image itself obtained by photographing, but corrects the obtained image by an electronic method. The sample point is manually input with a digitizer or a mouse, etc., and the pincushion distortion characteristic curve obtained from the distortion amount at the sample point is approximated by the least square method, and the approximate expression is calculated for all points of the image having pincushion distortion. To correct pincushion distortion.

However, according to the technique described in Japanese Patent Application Laid-Open No. Hei 2-10636, the electrode potential is changed every time the distance between the X-ray tube and the X-ray image intensifier is changed or when the electronic visual field is expanded. Adjustment is time consuming and time consuming. In addition, actual opening Hei 5-28316
According to the technique described in Japanese Patent Application Laid-Open No. H11-207, since the sample points are manually input using a digitizer, a mouse, or the like, it is difficult to accurately measure the amount of distortion, and automation is difficult. Therefore, these conventional techniques cannot efficiently measure and correct distortion when performing imaging at a plurality of positions (rotational movement positions) as in a cone beam CT apparatus or the like. Furthermore, it is difficult for these conventional techniques to accurately correct distortion over the entire image. Therefore, it is difficult to combine images captured multiple times or to reconstruct a three-dimensional image using a cone-beam CT apparatus. Thus, it cannot be applied to processing that requires accurate distortion correction.

[0005]

The problems to be solved are that the conventional technique cannot easily and automatically measure an accurate distortion amount, and cannot perform an accurate distortion correction. An object of the present invention is to solve these problems of the prior art,
An object of the present invention is to provide an X-ray imaging apparatus capable of reducing the time and labor required for distortion correction, and enabling highly accurate and efficient reconstruction of a three-dimensional image.

[0006]

In order to achieve the above object, an X-ray imaging apparatus according to the present invention rotates an X-ray source and an X-ray television camera by a predetermined angle unit about the subject, and scans the subject. In an X-ray imaging apparatus for imaging, a distortion measurement chart in which markers indicating differences in the degree of X-ray absorption are arranged in an orthogonal lattice is substantially linear in a marker image measured at any one rotation angle position. The sequence of the marker is
Means for fixing the distortion measurement chart to the X-ray input surface of the X-ray television camera at a position corresponding to a reference line parallel and perpendicular to the signal reading direction of the X-ray television camera; Based on the comparison of the coordinates of the image with the ideal image coordinates of each marker when there is no distortion,
A position correspondence table 14a for associating each coordinate of the actual image with each integer coordinate in each pixel of the ideal image.
And a main processing unit 15 that corrects an image obtained from the subject 12 at the time of imaging the subject by referring to the position correspondence table 14a of the corresponding rotation angle. have a door, distortion measurement chart is X
X-ray transparency arranged at equal intervals on a metal plate that is radiopaque
Holes are provided as markers, and the pre-processing unit is a strain gauge
Of the image in the field of view actually obtained by shooting the measurement chart
Based on the coordinates of each marker,
Find coordinates and include actual markers, including markers outside the field of view.
ー The coordinate position of the image and the coordinate position of the ideal marker image
Is compared .

[0007]

In the present invention, (i) a chart in which markers are arranged in an orthogonal grid in a matrix is used as a distortion measurement chart. Then, at least one of the images (strain measurement images) photographed at each predetermined angle using the strain measurement chart.
On the sheet, the strain measurement chart is fixed so that the substantially linear marker array and the reference lines parallel and perpendicular to the signal reading direction of the X-ray television camera almost coincide with each other.
The fixed distortion measurement chart is photographed in this manner, and the actual image coordinate position of each marker is compared with the ideal image coordinate position of each marker when obtained without distortion from the distortion measurement chart. By performing image distortion measurement, simple image distortion measurement becomes possible. Further, based on the distortion measurement result of the image, a position correspondence table used to correct the distortion measurement image to an ideal image without distortion is created for each predetermined angle, but in this position correspondence table,
Since the coordinate position (real number) of the distortion measurement image is associated with the position coordinate of the integer value in an ideal image-side pixel unit, the interpolation calculation in creating the position correspondence table is simplified. (Ii) By fixing the distortion measurement chart so that one of the markers of the distortion measurement chart is located at the center of the field of view of the X-ray television camera with small distortion, the marker array and the X-ray television camera are fixed. Can be easily improved. Also,
(Iii) X-ray transmissive holes arranged in a square lattice are provided as markers on a flat plate made of an X-ray opaque material to form a strain measurement chart. The marker can be easily prepared, and individual markers can be easily identified. (Iv)
By mounting the X-ray television camera so that the signal reading direction of the X-ray television camera is parallel or perpendicular to the orbital plane of the rotational movement of the X-ray television camera and the X-ray source, it is easy to create a position correspondence table. Become. Also,
(V) Even for positions outside the markers of the distortion measurement chart located at the outermost periphery of the visual field, by creating a position correspondence table, distortion correction can be performed up to the visual field boundary of the captured image, and X-ray The field of view of the imaging device can be extended to a maximum range determined by the detector size. Also, (vi) the marker (virtual marker) of the distortion measurement chart outside the field of view,
By obtaining coordinates on the strain measurement image and creating a position correspondence table for converting all the same markers and the same virtual markers in the strain measurement images obtained at each rotation angle into the same position coordinates, the X-ray imaging apparatus The field of view can be easily enlarged, and the accuracy of correction can be increased. In addition, (vii) for captured images at each rotation angle used for image reconstruction of a cone beam CT device,
By creating a position correspondence table using the distortion measurement chart and performing correction using this position correspondence table, accurate distortion correction can be performed for all measurement data having different distortions at each rotation angle, and a three-dimensional reconstructed image can be obtained. Image quality can be improved.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the configuration according to the present invention of the X-ray imaging apparatus of the present invention. This embodiment is a cone beam CT apparatus that uses an X-ray as a cone beam, and includes an imaging control apparatus 1, an X-ray tube 2, an X-ray grid 3, and an X-ray grid.
X-ray image intensifier 4, X-ray television camera 5, image collecting / processing device 6, rotating plate 7, couch top 8, rotating plate driving mechanism 9, top driving mechanism 10, rotating plate angle measuring mechanism 11, image display It is constituted by the device 13 and the like. The X-ray image intensifier 4 and the X-ray television camera 5 constitute an X-ray detector. The X-ray detector and the X-ray tube 2 are fixed to a rotating plate 7 and rotate around a bed 8. The couch top 8 is positioned horizontally, and the subject is assumed to be in a supine position as a standard imaging position. Note that the X-ray television camera 5 uses a high-resolution imaging tube as an imaging device.

Further, as a configuration according to the present invention, a reference line 13a according to the present invention is provided parallel and perpendicular to the signal reading direction of the X-ray television camera 5, and the X-ray grid 3 is shown in detail in FIG. The strain measurement charts according to the present invention, in which markers indicating positions made of materials having different degrees of X-ray absorption as shown in FIG. In this installation, X
In a marker image obtained by photographing a strain measurement chart at an arbitrary rotation angle by the line detector and the X-ray tube 2, a marker array that is substantially straight is substantially coincident with the reference line 13a. Fix the strain measurement chart. And
The image collection / processing device 6 includes a pre-processing unit 14 that creates a position correspondence table 14a according to the present invention and a main processing unit 15 that performs image distortion correction based on the position correspondence table 14a.

The function of each of the above-described units will be described. The imaging control device 1 defines a movement sequence for rotating the rotating plate 7 to which the X-ray detector and the X-ray tube 2 are fixed, and also controls the X-ray tube 2
An X-ray generation and an imaging sequence for controlling the imaging operation of the X-ray detector are defined. The rotating plate driving mechanism 9 rotates the rotating plate 7 based on control from the imaging control device 1, and the rotating plate angle measuring mechanism 11 outputs rotation angle data of the rotating plate 7 by the rotating plate driving mechanism 9. The top driving mechanism 10 moves the couch top 8 based on the control from the imaging control device 1,
A fluoroscopic region of the subject 12 is set.

X-rays generated from the X-ray tube 2
2, and the scattered radiation is shielded by the X-ray grid 3,
The image is converted into a visible light image by the X-ray image intensifier 4 and is formed on the X-ray television camera 5 by an optical lens system (not shown). The X-ray television camera 5 converts the formed image into a video signal and inputs the video signal to the image collection / processing device 6. The X-ray television camera 5 has a standard scan mode in CT scan of 60 frames and a scan line number of 5
25 lines, 30 frames per second, 1050 scan lines
Shooting with books is also possible. As a high-resolution shooting mode, shooting at 3.75 frames per second and 2,100 scanning lines is also possible. In the standard scanning mode in the CT scan, 60 images are taken every second every 1.25 degrees,
Obtain 288 images in 4.8 seconds.

An image converted into a visible light image by the X-ray image intensifier 4 and formed on the X-ray television camera 5 has a pincushion type geometric shape due to the structure of the X-ray image intensifier 4. Severe distortion occurs. Further, due to the influence of geomagnetism on the electron trajectory of the X-ray image intensifier 4, the image reciprocates with the rotation of the X-ray tube 2 and the X-ray detector. Further, an S-shaped distortion is added. Therefore, in this embodiment, the image collection / processing device 6 corrects these geometric distortions. That is, the image collection / processing device 6 performs A / D conversion of the video signal from the X-ray television camera 5 and stores it in the internal frame memory together with the rotation angle data from the rotating plate angle measurement mechanism 11 to store each projected image. After performing correction of geometric distortion of the image and shading correction of the density level of the image, three-dimensional reconstruction is performed. In order to correct the geometric distortion of this image, first, a distortion measurement chart is fixed to the X-ray grid 3 and photographed at each rotation angle. At this time, one of the marker arrays of the image obtained by photographing the distortion measurement chart is fixed so as to substantially coincide with the reference line 13a at an arbitrary angle.

The image acquisition / processing device 6 first uses the pre-processing unit 14 to first obtain the actual position of each marker at each predetermined rotation angle obtained by photographing the strain measurement chart fixed to the X-ray grid 3. The coordinate position of the image is compared with the ideal image coordinate position of each marker when the substantially linear marker array is obtained without distortion from the distortion measurement chart at the position coincident with the reference line 13a. Next, based on the result of the comparison measurement, the actual coordinate position of the marker image obtained at each rotation angle corresponding to each coordinate position of the ideal marker image in pixel units is calculated. Then, a position correspondence table 14a for associating the calculated coordinate positions of the actual marker image with the coordinate positions of each pixel of the ideal image is created for each predetermined rotation angle.

Here, the distortion of each pixel is estimated from the distortion of each marker (grid point). That is, for each pixel after the distortion correction, the coordinate positions of the four lattice points surrounding the pixel on the distortion image are calculated by the above-described processing, and the target is obtained from the coordinates of these four lattice points by two-dimensional linear interpolation. The coordinates of the pixel on the distorted image are obtained. Then, the image collection / processing device 6 corrects an image obtained from the subject 12 by the main processing unit 15 with reference to the corresponding rotation angle position correspondence table 14a when the subject 12 is imaged.

As described above, in the X-ray imaging apparatus of the present embodiment, a distortion measurement chart in which markers are arranged in a vertical and horizontal orthogonal grid is used, and this distortion measurement chart is placed on the X-ray grid 3. The marker array of the distortion measurement image of the distortion measurement chart photographed at an arbitrary rotation angle is fixed so that the signal reading direction of the X-ray television camera 5 substantially matches, and the distortion measurement chart thus fixed is fixed. And comparing the actual image coordinate position of each marker as shown in FIG. 3 with the ideal image coordinate position of each marker when obtained from the distortion measurement chart without distortion. Since distortion measurement is performed, measurement of image distortion can be simplified.
Further, in the position correspondence table 14a created for each angle, the coordinate position (real number) of the strain measurement image shown in FIG. 3 is associated with the position coordinate of an integer value in an ideal image-side pixel unit. The interpolation calculation in creating the position correspondence table 14a is simplified.

FIG. 2 is a front view showing one embodiment of the configuration according to the present invention of the distortion measuring chart in FIG. In the strain measurement chart of the present embodiment, X-ray permeable holes 32 arranged in a square lattice at equal intervals in the vertical and horizontal directions are provided as markers on a metal flat plate 31 made of an X-ray opaque material. . By configuring the distortion measurement chart in this manner, a marker array can be easily created with high positional accuracy, and individual markers can be easily identified.

FIG. 3 is a front view showing a specific example of a distortion measurement image obtained by photographing the distortion measurement chart in FIG. In FIG. 3, the digital image 21 is obtained by converting the distortion measurement chart shown in FIG. 2 into the X-ray television camera 5 shown in FIG.
The X-ray tube 2 and the X-ray television camera 5 shown in FIG. 1 capture a strain measurement image at a certain angular position on a rotational orbit, and capture the strain measurement image on a digital memory. 3 schematically illustrates an example of an image. Generally, since the X-ray incidence surface of the X-ray image intensifier 4 in FIG. 1 is spherical, the pincushion type distortion is large. In addition, since the magnetic orbit of the X-ray image intensifier 4 of FIG.
The image rotates and reciprocates with the rotation of the tube 2 and the X-ray television camera 5. Further, although an S-shaped distortion is added, the distortion is relatively small, and the illustration thereof is omitted.

The horizontal direction of the pixel array of the digital image 21 is the same as the X-ray television camera signal reading direction 22. FIG. 3A shows that the marker array 23 of the strain measurement chart and the X-ray television camera signal reading direction 22 substantially coincide with each other at a certain angular position on the rotation orbit of the X-ray tube 2 and the X-ray television camera 5 in FIG. In this manner, the distortion measurement chart is fixed, and an image taken at that angular position is shown. FIG. 3B shows the condition of FIG. 1A from the condition of FIG.
3 shows an image (distortion measurement image) obtained by rotating the X-ray tube 2 and the X-ray television camera 5 at another angle.

As shown in FIG. 3A, by fixing the distortion measurement chart so that the signal reading directions of the X-ray television camera substantially coincide, distortion measurement of the captured image is simplified. That is, the image collection / processing device 6 in FIG.
Compares the coordinates of each marker of the digital image 21 (distortion measurement image) with the respective markers of an ideal image having no distortion from the distortion measurement chart in FIG. Is calculated, and correction data to be stored in the position correspondence table 14a of FIG. 1 is calculated. Here, first, correction data of each marker is calculated, and then correction data of a portion surrounded by four markers is calculated by, for example, four-point Lagrange interpolation or the like. Therefore, by arranging the markers vertically and horizontally in an orthogonal grid like the distortion measurement chart in FIG. 2, the interpolation becomes easy, and the creation of the position correspondence table 14a in FIG. 1 becomes easy.

Although the four-point Lagrangian interpolation cannot be performed outside the outermost peripheral marker of the digital image 21 in the visual field, it is estimated based on the correction data of each marker in the vicinity of the outermost peripheral. The correction data is also stored in the position correspondence table for the outside of the marker. In this way, even for positions outside the marker of the distortion measurement chart present at the outermost periphery of the visual field, by creating a position correspondence table, distortion correction can be performed up to the visual field boundary of the captured image, The field of view of the X-ray imaging device can be expanded to a maximum range determined by the detector size. Alternatively, the coordinates of the marker (virtual marker) outside the field of view are obtained based on the coordinates of each marker of the image in the field of view actually obtained by photographing the distortion measurement chart, and The coordinate position of the marker image is compared with the coordinate position of the ideal marker image, and a position correspondence table is created. As a result, the field of view of the X-ray imaging apparatus can be easily enlarged, and the accuracy of correction can be improved.

Also, one of the markers may be positioned at the center of the field of view of the X-ray television camera 5 in FIG. 1 to fix the distortion measurement chart in FIG. In this case,
Accuracy of matching between the marker array and the signal reading direction of the X-ray television camera can be easily improved. Further, FIG.
The signal reading direction of the X-ray television camera 5 at
By mounting the X-ray television camera 5 so as to be parallel or perpendicular to the orbital plane of the rotational movement of the X-ray television camera 5 and the X-ray tube 2, it is possible to easily create the position correspondence table.

FIG. 4 is a flowchart showing an outline of a procedure for geometric distortion correction according to the present invention. The distortion correction process is
Pre-processing (processing by the pre-processing unit 14 in FIG. 1) for photographing the distortion measurement chart in FIG. 2 and creating a conversion table (position correspondence table) for correction, and main processing for correcting the captured image by table lookup (Processing by the main processing unit 15 in FIG. 1). In the pre-processing, first,
A distortion measurement chart in which markers are arranged is photographed for all angles at which the photographed image is measured, and a distortion measurement image shown in FIG. 3 is obtained (step 401). For each of the 288 distortion measurement images obtained by the CT scan (4.8 seconds) in the standard scanning mode, the positions of the markers arranged in an orthogonal lattice are detected (step 402), and the markers on the image without distortion are detected. (Step 403). At this time, the position correspondence table is set as shown in FIG. 5 so that the same marker obtained on all the distortion measurement images has the same coordinates of the integer value in pixel units. In the image after the distortion correction, the table is set such that the arrangement of the markers matches in the vertical direction and the horizontal direction of the image. Then, in this processing, for each imaging angle, the position correspondence table created in the pre-processing is looked up to correct the distortion of the image captured from the subject (step 404).

FIG. 5 is an explanatory diagram showing one embodiment of the configuration of the position correspondence table in FIG. 1 according to the present invention. As shown in FIG. 5, in the position correspondence table 14a created by the pre-processing unit 14 in FIG. 1, the point (x ′, y ′) on the distorted image with respect to the point (x, y) on the image after distortion correction. ) Is stored. The horizontal direction and the vertical direction of the position correspondence table 14a are the x coordinate and the y coordinate in increments of one pixel, respectively, and are the coordinates (Xi, Yj) (i: horizontal direction) of the marker on the image without distortion and the virtual marker. Grid point number,
j: grid point number in the vertical direction), stores the coordinates X′i, j of the marker and the virtual marker on the strain measurement image. By this processing, the position correspondence table 14a is created.

The values of the table other than the coordinates (Xi, Yj) of the marker, for example, the value x 'of (x, y) are interpolated using the values stored in the marker coordinates. The interpolation is, for example, linear interpolation by a four-point Lagrange method, and is obtained using four surrounding points. The creation of the position correspondence table 14a for the point y 'on the distorted image is the same as the creation of the above-described position correspondence table 14a for the point x' on the distorted image. By looking up the position correspondence table 14a created in this way, the main processing unit 15 of the image collection / processing device 6 in FIG. 1 corrects the distortion of the photographed image for each photographing angle.

As described above with reference to FIGS. 1 to 5, the X-ray imaging apparatus according to the present embodiment uses an X-ray television camera to provide a distortion measurement chart having a marker array arranged in a vertical and horizontal orthogonal lattice. Is fixed to the X-ray input surface, and a distortion measurement image is captured at each rotation angle position. At this time, the distortion measurement chart is fixed so that the marker arrangement and the signal reading direction of the X-ray television camera substantially coincide with at least one of the distortion measurement images. And in the image after distortion correction,
A position where each marker array completely matches the vertical and horizontal directions of the image, and all the same markers in the strain measurement image obtained at each rotation angle are converted into the same position coordinates of integer values in pixel units. A correspondence table is created, and geometric distortion is corrected for the captured image of the subject using the position correspondence table. As a result, distortion measurement in the X-ray imaging apparatus can be easily performed, and distortion correction can be performed with a small amount of calculation.

The present invention is not limited to the embodiment described with reference to FIGS. 1 to 5, but can be variously modified without departing from the gist thereof. For example, with respect to the attachment of the strain measurement chart, an example is shown in which the strain measurement chart is attached so as to overlap with the X-ray grid 3, but the X-ray grid 3 may be removed and replaced. Further, in the above-described embodiment, the measurement of the distortion measurement chart is performed for all the rotation angles at which the captured image is measured. However, the measurement may be performed only at a plurality of rotation angles, not at all the rotation angles. . It is also conceivable to measure the distortion correction chart at an angle other than the rotation angle at which the captured image is measured. In these cases, distortion measurement data of the rotation angle at which the captured image is measured is obtained by interpolation or the like using the distortion measurement images before and after the rotation angle at which the captured image is measured.

In the above embodiment, X is used as the marker.
X-ray permeable holes arranged in a square lattice at equal intervals in the vertical and horizontal directions were used on a top plate made of a radiopaque material. It can be used as a marker. Furthermore, in the above embodiment, the position of the marker on the distortion measurement image is stored in the table corresponding to the image without distortion, but the table that associates the marker position on the distortion measurement image with the marker position on the image without distortion is stored. Then, it can be used as a position correspondence table. For example, it is conceivable to store the position of a marker on an image without distortion in a table corresponding to the distortion measurement image.

[0028]

According to the present invention, in an X-ray imaging apparatus such as a cone beam CT apparatus, an accurate distortion amount can be easily and automatically measured, and more accurate distortion correction can be performed. In addition to reducing the time and labor required, it is possible to reconstruct a three-dimensional image with high resolution and high efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the configuration of an X-ray imaging apparatus according to the present invention.

FIG. 2 is a front view showing an embodiment of the configuration according to the present invention of the distortion measurement chart in FIG. 1;

FIG. 3 is a front view showing a specific example of a distortion measurement image obtained by photographing the distortion measurement chart in FIG. 2;

FIG. 4 is a flowchart showing an outline of a procedure of geometric distortion correction according to the present invention.

FIG. 5 is an explanatory diagram showing one embodiment of a configuration according to the present invention of the position correspondence table in FIG. 1;

[Explanation of symbols]

1: imaging control device, 2: X-ray tube, 3: X-ray grid,
4: X-ray image intensifier, 5: X-ray television camera, 6: image acquisition / processing device, 7: rotating plate, 8: bed top plate, 9: rotating plate drive mechanism, 10: top plate drive mechanism, 1
1: rotating plate angle measurement mechanism, 12: subject, 13: image display device, 13a: reference line, 14: pre-processing unit, 14a:
Position correspondence table, 15: main processing unit, 21: digital image, 22: X-ray television camera signal reading direction, 23: marker arrangement direction, 31: metal plate, 32: hole

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-261651 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 6/00-6/03

Claims (1)

(57) [Claims] 1. An X-ray imaging apparatus for imaging an object by rotating an X-ray source and an X-ray television camera around an object by a predetermined angle unit, wherein a marker indicating a difference in X-ray absorption degree is orthogonalized. The distortion measurement chart arranged in a lattice pattern, the marker array that is substantially linear in the marker image measured at any one rotation angle position is parallel and parallel to the signal reading direction of the X-ray television camera. Means for fixing the distortion measurement chart to an X-ray input surface of the X-ray television camera at a position coincident with a vertical reference line; and coordinates and distortion of an actual image of each marker of the distortion measurement chart are not present. A position correspondence table that associates each coordinate of the actual image with each coordinate of an integer value in each pixel of the ideal image based on a comparison result of the respective markers with ideal image coordinates. A pre-processing unit for creating the said with reference to the position correspondence table of the rotational angle of the to the time of photographing of a subject, said possess a present processing unit that corrects the image obtained from the subject, the strain Measurement chart is equally spaced on a radiopaque metal plate
X-ray permeable holes arranged at intervals are provided as the markers.
The pre-processing unit is configured to display the distortion measurement chart.
Each of the markers of the image in the field of view actually obtained by shooting
Based on the coordinates of, the coordinates of the marker outside the field of view
The actual marker, including the marker outside the field of view.
Car image coordinate position and ideal marker image coordinate position
An X-ray imaging apparatus characterized by performing comparisons with: