JP2008132033A - X-ray imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray imaging apparatus with which an inclination of a flat panel detector (FPD) to an optical axis of X rays is recognized by a simple constitution in the X-ray imaging apparatus in which the FPD is not mechanically supported by an X-ray generator. <P>SOLUTION: The X-ray imaging apparatus 0 is equipped with the X-ray generator 2 for irradiating a subject P with X rays and the FPD 3 for obtaining image data in accordance with the incident dose of the X rays transmitting the subject P, and the FPD 3 is not mechanically supported by a main body 1. The X-ray imaging apparatus 0 is equipped with an emission limiting means (a spot forming diaphragm 7) for emitting spot-like X rays to the FPD 3, a storage means (a storage part 14) for storing image data formed on the FPD 3 by the spot-like irradiation of the X rays, an inclination calculating means (an inclination calculating part 15) for calculating the inclination of the FPD 3 to the optical axis 2A of the X rays, and an informing means (a monitor 5) for informing of the inclination. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention detects whether or not a flat detector is arranged perpendicular to the optical axis of an X-ray in an X-ray imaging apparatus in which the flat detector is not mechanically supported by the X-ray generator. It is related with the X-ray imaging device which can do.

  Conventionally, in industrial fields such as non-destructive inspection and medical fields such as medical examinations, radiation (typically, X-rays) is irradiated on the inspection object or subject, and radiation transmitted through the inspection object or subject is observed. An X-ray imaging apparatus that detects an intensity distribution and obtains a fluoroscopic image of an inspection object or a subject is widely used. In such an apparatus, in recent years, a flat panel detector (FPD) is used as a detector for detecting X-rays. This FPD has an extremely wide dynamic range, and has an advantage that a photographed fluoroscopic image can be confirmed immediately.

  Incidentally, X-ray imaging apparatuses in the medical field are not limited to those installed at fixed points such as a fluoroscopic room in a hospital, but those that can move are known. Such mobile devices can be broadly classified into operations and round trips. In a surgical X-ray imaging apparatus, an X-ray generator and an FPD are supported via a C arm or the like, and the relative positions of the two are defined. On the other hand, in the round-trip X-ray imaging apparatus, the FPD and the apparatus main body are connected only by a cable, and the FPD is not supported with respect to the X-ray generator.

  Here, when imaging is performed with an apparatus in which the FPD is not supported by the X-ray generator, such as an X-ray imaging apparatus for round trips, the FPD should be appropriately arranged, particularly with respect to the optical axis of the X-ray. It is important to place the FPD vertically. When the FPD is arranged to be inclined with respect to the optical axis, the obtained fluoroscopic image is distorted in the direction in which the FPD is inclined. Further, in this apparatus, since the FPD is manually arranged, the degree of distortion of the fluoroscopic image changes every time the FPD is arranged, so that the image reproducibility is lowered and there is a possibility that accurate diagnosis of the subject is hindered. In addition, when the scattered radiation removal grid plate is used, a false image may be generated if the FPD is inclined with respect to the optical axis.

  As mentioned above, it is difficult to place the FPD vertically with respect to the optical axis of the X-ray with this device, despite the fact that the FPD placement state is important. It is also difficult to do. For example, when performing a large amount of imaging in a short time in an ICU (intensive care unit), it is not possible to take time to align the FPD, and the FPD angle with respect to the optical axis every time the FPD is placed on the subject. May change significantly. Therefore, the image reproducibility of the fluoroscopic image is poor, and there is a risk of misdiagnosis when the taken fluoroscopic image is used for diagnosis.

  In order to solve such a problem, for example, in the radiation imaging apparatus of Patent Document 1, an attitude sensor is provided for both the radiation source (X-ray generator) and the cassette (including the film in the cassette, the X-ray detector). And the positional relationship between the X-ray generator and the X-ray detector is grasped by this attitude sensor. Based on this positional relationship, the optical axis of the X-ray and the X-ray detector can be arranged vertically.

JP 2000-23955 A

  However, in the radiation imaging apparatus disclosed in Patent Document 1, the attitude sensor must be mounted on the X-ray detector. In particular, when an FPD is used as an X-ray detector, the FPD has a complicated internal structure, and it is difficult to secure a space for mounting an attitude sensor and a substrate for controlling the sensor. It is complicated. In addition, in this apparatus, since an attitude sensor must be provided in both the X-ray detector and the X-ray generator, the cost increases.

  Therefore, a main object of the present invention is to grasp the inclination of the flat detector with respect to the optical axis of the X-ray with a simple configuration in an X-ray imaging apparatus in which the flat detector is not mechanically supported with respect to the X-ray generator. An object of the present invention is to provide an X-ray imaging apparatus capable of performing the above.

The present invention includes an X-ray generator that irradiates a subject with X-rays, and a flat detector that acquires image data corresponding to an incident dose of X-rays that have passed through the subject. The X-ray imaging apparatus is not supported by the X-ray. This X-ray imaging apparatus has the following configuration.
I. Irradiation limiting means for performing spot-like X-ray irradiation on a flat detector
II. Storage means for storing image data formed on a flat panel detector by spot-like X-ray irradiation
III. Inclination calculating means for calculating the inclination of the flat detector with respect to the optical axis of the X-ray based on the image data
IV. Notification means for notifying the inclination

  According to the configuration of the present invention, it is possible to confirm how much the flat detector is inclined with respect to the optical axis of the X-ray. Therefore, if the inclination of the flat detector exceeds a predetermined value, for example, exceeds the value of the inclination considered to be unsuitable for imaging from past experience, readjustment of the positional relationship between the flat detector and the X-ray generator Can be determined to be necessary. On the other hand, if the inclination of the flat detector is equal to or less than a predetermined value, it can be determined that this inclination is acceptable.

  The present invention will be described in detail below.

  The X-ray imaging apparatus of the present invention includes all those in which a flat panel detector (FPD) is not mechanically supported by the X-ray generator, and is typically an X-ray imaging apparatus for round trips. Etc. On the contrary, “Mechanically supported with respect to the X-ray generator” means that the FPD is controlled in its arrangement state by some mechanical support means, and the positional relationship between the FPD and the X-ray generator is changed. Points that can be grasped.

[FPD]
The FPD provided in the apparatus of the present invention can transmit acquired image data to the main body of the X-ray imaging apparatus by wired connection using a cable or wireless connection using a communication apparatus. In addition, the FPD can transmit information about the FPD itself, for example, information about the center of the FPD, the X axis of the FPD, the Y axis, and the like to the main body. The information of the FPD itself is used when calculating the inclination of the FPD with respect to the optical axis of the X-ray described in detail later.

[X-ray generator]
The X-ray generator provided in the apparatus of the present invention is an apparatus that includes an X-ray tube that generates X-rays and emits X-rays in a predetermined direction. This X-ray generator may be provided with a known movable diaphragm for limiting the X-ray irradiation area.

[Irradiation limiting means]
The apparatus of the present invention further includes irradiation limiting means at the X-ray irradiation port portion of the X-ray generator. The irradiation limiting means is made of a shielding member that blocks X-rays, and limits the irradiation of the subject and the FPD with X-rays. This shielding member may be composed of, for example, a single plate-like member, and restricts X-ray irradiation by being inserted in front of the X-ray irradiation port. In addition, the shielding member may be composed of a plurality of plate-like members like a movable diaphragm. In this case, X-ray irradiation can be restricted by arranging plate members in four directions around the optical axis and inserting (closing) the plate members in the center direction.

  The shielding member is formed with at least two minute irradiation ports penetrating the shielding member. When a shielding member is constituted by a plurality of plate-like members and these plate-like members are closed, when the plate-like members overlap, the minute irradiation port is provided so as to penetrate the overlapped plate-like members. In any case, the surface of the shielding member facing the X-ray irradiation port and the opening end surface of each minute irradiation port on the surface facing the FPD are formed flush with each other.

  Most of the X-rays emitted from the X-ray generator are shielded by the shielding member by this irradiation limiting means, and do not reach the FPD. However, a minute irradiation port is formed in the shielding member, and X-rays passing through the minute irradiation port are detected by FPD. That is, the irradiation limiting means is means for performing spot-like X-ray irradiation on the FPD.

  The number of minute irradiation ports is not particularly limited as long as it is two or more. However, it is preferable that the plurality of minute irradiation ports be arranged on a circle centering on the X-ray irradiation center which is the intersection of the shielding member and the optical axis of the X-ray. For example, in the case of two minute irradiation ports, the minute irradiation ports are provided at point-symmetric positions with the irradiation center in between. When three or more micro irradiation ports are provided, each micro irradiation port is arranged at the apex of a regular polygon whose center of gravity coincides with the X-ray irradiation center. Such an arrangement facilitates calculation of the FPD inclination as will be described later.

  The shape of the minute irradiation port is not particularly limited. For example, a circle or a regular polygon is suitable. However, it is preferable that the shapes of all the minute irradiation ports are the same. Thus, by unifying the shape of each minute irradiation port, it becomes easy to calculate the inclination of the FPD as will be described later.

[Memorization means]
In the FPD, image data having a plurality of spot images is detected by X-rays irradiated in a spot shape by the irradiation limiting means. The storage means can store this image data. The stored image data is used to calculate the inclination of the FPD with respect to the optical axis of the X-ray as will be described later. The storage means can store not only image data having a spot image but also a normal fluoroscopic image of the subject.

[Slope calculation means]
The inclination calculation means is means for calculating the inclination of the FPD with respect to the optical axis of the X-ray from the image data having the photographed spot image. The inclination calculating means further compares the size of each spot image to select a minimum spot image and a maximum spot image, and forms a spot image from the minimum spot image and the maximum spot image. Feature amount extraction means for extracting a feature quantity based on the above, and comparison means for applying the extracted feature quantity to a correlation between a preset feature quantity and the slope of the FPD to obtain the slope of the FPD.

  In order to compare the size relationship of the spot images by the selection means, it is necessary to calculate the size of the spot image. The size of the spot image can be calculated from the number of detection elements in the FPD.

  The feature amount based on the form of the spot image includes the length of a specific portion of the spot image. Here, when the FPD is inclined with respect to the optical axis of the X-ray, the spot image has a shape extending in the direction in which the FPD is inclined. For example, if the shape of the micro-irradiation port is circular, and the FPD is tilted, the shape of the spot image formed on the FPD is approximately oval. Of these egg-shaped spot images, the maximum length of the FPD in the X-axis direction and the Y-axis direction may be used as the feature amount. In addition, the contour shape of the spot image may be used as the feature amount.

  By applying the extracted feature quantity to the correlation between the preset feature quantity and the slope of the FPD, the slope of the FPD corresponding to the feature quantity can be obtained. Examples of the correlation include a table that shows the inclination of the corresponding FPD in the X-axis direction and the Y-axis direction when the extracted feature value is applied. For example, when using the maximum length of the FPD in the X-axis direction and Y-axis direction as the feature value, the maximum spot image for the minimum spot image length in the FPD X-axis direction and Y-axis direction Find the length ratio. Then, when both the ratio value in the X-axis direction and the ratio value in the Y-axis direction are applied, the correlation of how many times the FPD is inclined with respect to the X-axis direction and the Y-axis direction is used. Find the slope of the FPD. Further, when the contour shape of the spot image is used as the feature amount, a correlation is used in which the FPD inclination is known when both the contour shape of the minimum spot image and the contour shape of the maximum spot image are applied.

[Notification method]
The notifying means may be means for visually notifying the FPD inclination (inclination information) with respect to the optical axis of the X-ray, or may be means for notifying audibly. In the former case, for example, the tilt may be displayed on a monitor provided in the apparatus of the present invention. In the latter case, the inclination may be notified by an audio device or the like. Of course, both may be used in combination.

  Further, the notifying unit may notify the user with the inclination emphasized when the inclination exceeds an allowable range. For example, a warning display (bold, enlarged, red, flashing, etc.) or an alarm sound (siren, voice guidance, etc.) is issued to the effect that the inclination exceeds the allowable range.

  According to the apparatus of the present invention, since the inclination of the FPD is notified, the arrangement state of the FPD can be confirmed before imaging the subject. As a result, an opportunity to readjust the positional relationship between the FPD and the X-ray generator can be obtained. For example, the positional relationship between the FPD and the X-ray generator can be readjusted by actually moving the X-ray generator itself and changing the X-ray irradiation direction based on the inclination of the FPD. As a result, the FPD can be brought into a state without inclination before the subject is actually imaged.

  In addition, the apparatus of the present invention may be provided with appropriate image data creation means for creating image data (proper image data) having substantially no inclination based on the calculated inclination of FPD. When obtaining appropriate image data by image processing, it is possible to obtain a fluoroscopic image of the subject suitable for diagnosis without physically re-adjusting the positional relationship between the FPD and the X-ray generator. Can be done. When the FPD is tilted so as not to be dealt with by image processing, the notification means may prompt the readjustment of the positional relationship between the FPD and the X-ray generator.

  The X-ray imaging apparatus of the present invention may further include a center calculating unit that calculates an irradiation center that is an intersection of the FPD and the optical axis of the X-ray using the calculated inclination of the FPD. When spot image data (corrected spot image data) corrected to a state having substantially no inclination is obtained for image data having a spot image (spot image data), the spot image of this data is It arrange | positions reflecting the arrangement | positioning state of a micro irradiation opening. Accordingly, when the plurality of minute irradiation ports are arranged at the positions of the vertices of the regular polygon, the center position of the regular polygon formed by the arrangement of the plurality of spot images becomes the irradiation center.

  The corrected spot image data may be obtained by performing spot imaging again after actually re-adjusting the arrangement state of the FPD and the X-ray generator, or by using appropriate image data creating means. It may be obtained by creating appropriate image data for the data.

  If the irradiation center in the FPD is known, the arrangement state of the FPD can be calculated in addition to the inclination of the FPD with respect to the optical axis of the X-ray. The FPD arrangement states that can be calculated are: [1] Relative displacement between the center of the FPD and the irradiation center (deviation information), [2] FPD rotation with respect to the X-ray optical axis (rotation information), [3 Since the distance (distance information) from the X-ray generator to the FPD is mentioned, the X-ray imaging apparatus of the present invention capable of calculating such information will be described below.

[1] X-ray imaging apparatus of the present invention capable of calculating deviation information This apparatus is configured to calculate a deviation amount between a center of an FPD and an irradiation center based on a positional relationship between the irradiation center and the center of the FPD. Calculation means is provided. The FPD center position information only needs to be transmitted by the FPD itself to the device body, and even if the FPD is not mechanically supported by the X-ray generator, it is transmitted by a cable or wireless device that connects the FPD and the device body. can do. Note that if the center of the FPD and the irradiation center deviate significantly, the X-ray irradiation region may protrude from the FPD, and a fluoroscopic image of the subject may not be obtained.

[2] X-ray imaging apparatus of the present invention capable of calculating rotation information This apparatus is based on the positional relationship between at least one spot image of corrected spot image data and the X-axis and Y-axis of the FPD passing through the irradiation center. And a rotation amount calculating means for calculating the rotation amount of the FPD with respect to the optical axis of the X-ray. As specific means for calculating the amount of rotation, there are typically a method using one spot image and a method using two or more spot images, which will be described sequentially.

“2-1 Using a single spot image”
First, an arbitrary spot image is selected, and the center of this spot image is obtained. Next, with respect to the center of the spot image, a distance from the X axis and the Y axis passing through the irradiation center is obtained. Here, when the X axis and the Y axis are orthogonal to each other and the four spot images are arranged in a regular square shape, the shortest distance from the X axis to the center of the spot image and the center of the spot image from the Y axis When the shortest distance to is equal, the FPD is not rotating. When this distance is different, the rotation amount of the FPD may be obtained from the difference in distance.

  Further, an arbitrary spot image is selected, a straight line connecting the center of the spot image and the irradiation center is obtained, and an angle formed by the straight line and the X axis or the Y axis is obtained. When using the four spot images in the previous stage, when the angle formed is 45 °, the FPD is not rotating.

“2-2 Using two or more spot images”
First, out of a plurality of spot images arranged in a polygonal shape, two spot images at the positions of adjacent vertices are selected, and a straight line connecting the centers of the two spot images is obtained. Next, the angle formed by this straight line and the X axis or Y axis of the FPD is obtained. Here, when the X axis and the Y axis are orthogonal coordinate systems and the four spot images are arranged in a regular square, the angle formed by these is the amount of rotation of the FPD.

[3] X-ray imaging apparatus of the present invention capable of calculating distance information This apparatus is configured to detect the size of a spot image when the FPD is not inclined with respect to the optical axis of the X-ray, and the X-ray generator and FPD. Distance calculating means for calculating the distance between the X-ray generator and the FPD from the size of the spot image of the appropriate image data based on the correlation with the distance between them. Here, since the spot image is a projection image of the minute irradiation port, the size of the spot image is proportional to the square of the distance. Therefore, as the correlation, for example, a graph in which the vertical axis indicates the size of the spot image and the horizontal axis indicates the distance between the X-ray generator and the FPD can be used.

[4] Other X-ray imaging devices As other X-ray imaging devices, all the above-mentioned means are provided, and "FPD tilt information", "FPD rotation information", "FPD deviation information", "FPD An X-ray imaging apparatus that can calculate all four pieces of numerical information of “distance information” may be used. In the case of this device, it is preferable to visually notify the four pieces of numerical information so that all of them can be confirmed collectively. With such a configuration, the arrangement relationship between the X-ray generator and the FPD can be easily adjusted. In addition, in this apparatus, when there is a clear hindrance to fluoroscopic imaging, for example, when the malfunction occurs such that the irradiation area protrudes from the FPD because the center position of the FPD and the optical axis are significantly displaced, The above numerical information may be displayed with emphasis (bold, enlarged, red, flashing, etc.), or an alarm sound (siren, voice guidance, etc.) may be emitted.

  The numerical information described above may be combined with a fluoroscopic image of the subject and displayed. The numerical information may be printed at the corners of the photograph when the fluoroscopic image is printed. By printing numerical information, it is possible to know the conditions at the time of shooting, that is, the FPD arrangement state at the time of shooting, so refer to the FPD arrangement state when comparing fluoroscopic images taken under different conditions Thus, the possibility of misdiagnosis can be reduced.

  Further, when the positional relationship between the X-ray generator and the FPD is corrected by moving the X-ray generator itself based on the numerical information, the numerical information changes so as to reflect the amount of movement of the X-ray generator. Anyway. Specifically, a sensor is provided in the movable part of the X-ray generator so as to detect how much and in what direction the X-ray generator is moved. For example, if there is a large lateral deviation between the center position of the FPD and the optical axis, the X-ray generator is moved to the left and right to reduce this deviation, and the X-ray irradiation direction is moved. Make the number actually decrease. Of course, in this example, since the X-ray irradiation direction is moved, there is a high possibility that information such as the FPD inclination will change in addition to the information on the deviation, so that all the changed information should be reflected. Is preferred. In addition, if it is an X-ray imaging device for round trips, if a sensor that detects the amount of movement of the main body is provided on the cart that allows the main body to travel, the device can also be moved for the “distance between the X-ray generator and the FPD” The amount can be reflected. In this way, according to the configuration reflecting the direction of the X-ray generator and the amount of movement of the main body itself, a more accurate fluoroscopic image can be obtained than by correcting the distortion of the fluoroscopic image by image correction. In addition, since it is not necessary to perform spot imaging again, there is no need to increase the exposure dose of the subject.

  In the case of a configuration in which numerical information changes reflecting the amount of movement of the X-ray generator, a means for visually displaying the numerical information is attached in the vicinity of the X-ray generator, for example, the X-ray generator itself. Is preferred. According to this configuration, since the numerical information can be confirmed while manually moving the X-ray generator, the positional relationship between the X-ray generator and the FPD can be easily corrected.

  According to the X-ray imaging apparatus of the present invention, it can be confirmed whether the FPD is inclined with respect to the optical axis. Therefore, when the X-ray generator itself is moved in order to eliminate the FPD inclination with respect to the optical axis, it can be easily understood how much the X-ray generator should be moved in which direction. Alternatively, when obtaining a perspective image without inclination by image processing correction, it is easy to know what image processing correction should be performed.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to a following example at all, In the range which does not change the summary, it can change suitably and can implement.

<Example 1>
[overall structure]
In this example, a round trip X-ray imaging apparatus will be described as an example of the X-ray imaging apparatus. As shown in FIG. 1, the round-trip X-ray imaging apparatus 0 is an apparatus that performs X-ray imaging of a subject P by moving from a bed B to a hospital room where the subject P cannot be easily moved. . The apparatus 0 includes a main body 1, an X-ray generator 2 integrally provided on the main body 1 via a support portion 4 (for example, an arm having an extension mechanism), and a cable (not shown) on the main body 1. And an FPD (Flat Panel Detector) 3 connected to each other. X-rays irradiated from the X-ray generator 2 pass through the subject P and enter the FPD 3. The FPD 3 acquires image data of the subject P according to the incident amount of the X-ray. The acquired image data is subjected to image processing by a computer inside the main body 1 and displayed on the monitor 5 as a fluoroscopic image of the subject P.

  By the way, when the subject P is imaged using the X-ray imaging apparatus 0 of this example for round trips, as shown in FIG. 1, the FPD 3 is placed behind the subject P resting on a bed B or the like. And the X-ray generator 2 is arranged so as to face the FPD 3, and X-ray imaging is performed. At this time, the FPD 3 is manually arranged behind the subject P. Therefore, it is easy to arrange the FPD 3 in an inclined state with respect to the X-ray optical axis 2A, and it is impossible to know how much the FPD 3 is inclined. If imaging of the subject P is performed with the FPD3 tilted, the obtained fluoroscopic image of the subject P becomes a fluoroscopic image distorted in the tilted direction of the FPD3, and the diagnosis of the subject P may not be performed accurately. is there.

  Therefore, as shown in FIG. 2, the apparatus of this example forms a plurality of spot images on the FPD 3 as a configuration for knowing the inclination of the FPD 3 with respect to the optical axis 2A of the X-ray before imaging the subject P. A spot forming diaphragm (irradiation limiting means) 7 for the purpose, and an inclination calculating section (inclination calculating means) 15 for calculating the inclination of the FPD 3 from the spot image.

  In the X-ray imaging apparatus having the above configuration, the inclination of the FPD 3 with respect to the optical axis 2A obtained by the inclination calculation unit 15 can be known by the monitor (notification means) 5. Therefore, it is possible to know how much the FPD 3 is inclined with respect to the optical axis 2A before imaging the subject P, and to obtain an opportunity to correct the inclination of the FPD 3 based on this information.

  Hereinafter, each configuration of the X-ray imaging apparatus of this example will be described in detail, and then a procedure for calculating the FPD inclination will be described.

(Body)
The main body 1 is arranged on the carriage D and can be driven by the carriage D. The main body 1 also has a computer 10 that controls the round-trip X-ray imaging apparatus 0 and an operation panel CP that inputs X-ray intensity and irradiation time. The configuration of the computer 10 will be described later.

(X-ray generator)
The X-ray generator 2 is a device that irradiates the subject P with X-rays. The X-ray generator 2 has an X-ray tube 21 that receives power supply from the high-voltage generator 8 and generates X-rays, and can irradiate X-rays in one direction from the X-ray irradiation port 22. It can be done. By controlling the power supply amount and power supply time supplied to the X-ray generator 2 by the high-pressure generator 8, the X-ray intensity, the X-ray irradiation time, and the X-ray irradiation interval can be changed.

  A movable diaphragm 6 and a spot forming diaphragm 7 are provided in front of the X-ray irradiation port 22 of the X-ray generator 2 (position in the X-ray irradiation direction) to limit the X-ray irradiation range.

(Movable aperture)
The movable diaphragm 6 is configured to change the X-ray irradiation range of a general X-ray imaging apparatus, and is a configuration for determining the outer frame of the irradiation area. Specifically, the movable diaphragm 6 has a configuration in which four rectangular plates capable of shielding X-rays are arranged in a frame shape. Then, by changing the size of the opening surrounded by the frame, as shown in FIG. 5 (A), the irradiation range f of the X-ray irradiated to the subject, that is, the visual field size and the visual field position can be adjusted. it can.

(Spot formation aperture)
On the other hand, as shown in FIG. 3, the spot forming aperture 7 has a configuration in which four rectangular plate-shaped spot forming blades (shielding plates) 71 to 74 are arranged in four directions, like the movable aperture. Each of the spot forming blades 71 to 74 is formed with two through holes 71h to 74h, and when the four spot forming blades 71 to 74 are inserted (closed) in the central direction, they pass through. By overlapping the holes 71h to 74h, four minute irradiation ports 7h are arranged at the positions of the vertices of a regular square. Each minute irradiation port 7h has a circular shape and the same diameter. The center (center of gravity) of the regular square is made to coincide with the intersection of the optical axis of the X-ray and the shielding plate, that is, the irradiation center.

  The number of spot forming blades constituting the spot forming stop is not particularly limited. For example, as shown in FIG. 4A, four spot irradiation blades 75 may be provided with four minute irradiation ports 7h. Further, the number of minute irradiation ports 7h is not particularly limited as long as it is two or more. For example, there may be three as shown in FIG. The three minute irradiation ports 7h are arranged at the positions of the vertices of the regular triangle so that the center (center of gravity) of the regular triangle coincides with the irradiation center.

(FPD)
The FPD 3 is a device that detects X-rays irradiated from the X-ray generator 2 and transmitted through the subject and outputs them as image data. The FPD 3 includes a plurality of X-ray detection elements arranged in a two-dimensional array. The X-rays incident on the FPD 3 can be converted into electric signals (image data) by these detection elements. The acquired image data can be transferred to the main body 1 via a cable. Of course, the FPD 3 and the main body 1 may be wirelessly connected. In addition, the FPD can transmit the FPD center position and the information of the FPD itself such as the X-axis and the Y-axis of the FPD.

(computer)
The computer 10 includes a control unit 11 that controls each device of the apparatus of the present example, an image data acquisition unit 12 that acquires image data from the FPD 3, and an image processing unit 13 that performs various image processes on the acquired image data. . Further, the computer 10 includes a storage unit 14 that stores acquired image data, a correlation used for calculation of inclination described later, and an inclination calculation unit 15 that calculates the inclination of the FPD 3 with respect to the optical axis 2A.

(Inclination calculator)
The inclination calculation unit 15 further includes a selection unit (selection unit) 151, a feature amount extraction unit (feature amount extraction unit) 152, and a comparison unit (comparison unit) 153, and image data including photographed spot images. Thus, the inclination of the FPD 3 with respect to the optical axis 2A of the X-ray is calculated.

  The selection unit 151 is configured to select the smallest spot image and the largest spot image by comparing the sizes of the spot images. The selection unit 151 can calculate the size of the spot image when comparing the sizes of the spot images. The size of the spot image is calculated from the number of detection elements of the FPD 3 that form the spot image.

  The feature amount extraction unit 152 is configured to extract a feature amount based on the form of the spot image from the minimum spot image and the maximum spot image. The feature quantity extraction unit 152 of this example extracts the maximum lengths of the FPD 3 in the X-axis direction and the Y-axis direction from the spot images as feature quantities. Here, since the shape of the minute irradiation port in this example is circular, when the FPD 3 is inclined, the shape of the spot image formed on the FPD 3 is approximately oval. Therefore, the maximum length of the FPD 3 in the X-axis direction and the Y-axis direction is extracted as a feature amount from the egg-shaped spot image.

  The comparison unit 153 is configured to compare the extracted feature amount with the correlation between the feature amount stored in the storage unit 14 and the FPD inclination. The correlation in this example is the slope of the corresponding FPD in the X-axis direction when the ratio of the maximum length of the maximum spot image and the maximum length of the minimum spot image in the X-axis direction and the Y-axis direction of the FPD is applied. It is a table that defines the inclination in the Y-axis direction. The table data used was obtained in advance by actual measurement. The table will be described in detail when the procedure for calculating the FPD inclination is described.

(Image processing unit)
The image processing unit 13 can perform various image processes on the image data acquired by the FPD 3. For example, brightness value correction for adjusting the brightness of image data, noise removal processing for removing noise in image data, binarization processing, and the like can be performed. In addition, image processing that can be used in a normal X-ray imaging apparatus, such as white balance adjustment and black-and-white reversal processing, can be performed.

  The image processing unit 13 further includes an inclination correction unit (appropriate image data creation unit). The tilt correction unit can correct the fluoroscopic image of the photographed subject P based on the tilt information of the FPD 3 with respect to the optical axis 2A of the X-ray calculated by the tilt calculation unit 15. Specifically, the fluoroscopic image distorted so as to extend in the direction in which the FPD 3 is tilted is corrected so as to be substantially the same as the non-distorted fluoroscopic image obtained when the FPD 3 is not tilted.

(Other)
In addition, the apparatus of this example has a speaker (notification means) (not shown). The speaker can notify the FPD3 tilt information by voice.

[Spot shooting]
When imaging the subject P using this apparatus 0, as shown in FIG. 1, the FPD 3 is placed behind the subject P that is resting on a bed B or the like, and is opposed to the FPD 3 An X-ray generator 2 is arranged to perform X-ray imaging. At this time, the FPD 3 is manually arranged behind the subject P. Therefore, it is difficult to arrange the FPD 3 perpendicular to the optical axis 2A of the X-ray, and if the subject P is imaged as it is, a fluoroscopic image distorted in the direction in which the FPD 3 is tilted is obtained. Therefore, in the apparatus 0 of the present invention, spot imaging is performed before imaging the subject P, and the inclination of the FPD 3 is obtained using image data obtained by this spot imaging.

  Spot imaging refers to irradiating X-rays from the X-ray generator 2 to the FPD 3 at a position facing the X-ray generator 2 through the spot forming diaphragm 7. An X-ray irradiation dose for spot imaging is preferably about 0.1 μGy because the exposure dose to the subject P can be reduced. The irradiation dose of 0.1 μGy is about 1/50 of the irradiation dose of X-rays used for standard X-ray imaging, and spot imaging is performed only on a limited irradiation area. The exposure is considered to be so small that it does not matter.

  FIG. 5 shows the X-ray irradiation state according to the arrangement of the spot forming diaphragm. However, in FIG. 5, the spot forming diaphragm 7 is illustrated as being composed of a single plate-like member. In a state where the spot forming diaphragm 7 is not inserted in front of the X-ray tube 21, a frame-shaped irradiation range f is formed by the movable diaphragm 6 (see FIG. 5A). On the other hand, in the state where the spot forming diaphragm 7 is inserted in front of the tube 21, as shown in FIG. 5B, the irradiated X-ray is shielded, and only the X-ray passing through the minute irradiation port 7h is examined. It passes through P and enters FPD3. Therefore, a spot image reflecting the shape of the minute irradiation port 7h of the spot forming diaphragm 7 can be acquired by this spot photographing. In this example, since the shape of the minute irradiation port 7h is circular, when the FPD 3 is inclined, the spot image has an oval shape. If the FPD 3 is not tilted at all, the spot image is circular.

  Next, the inclination of the FPD with respect to the optical axis of the X-ray is calculated using image data having the acquired spot image. Hereinafter, the calculation procedure will be described based on the flowchart of FIG.

[Step S10]
First, image data having a spot image is acquired by the image data acquisition unit. The obtained image data is binarized by the image processing unit and smoothed. By this processing, a spot image with a clear outline can be obtained, and the subsequent processing can be performed smoothly.

[Step S11]
Next, the inclination calculator calculates the sizes of the four spot images formed on the FPD. This size may be obtained from the number of FPD elements constituting the detected spot image.

[Step S12]
When the size of each spot image is obtained, the sizes are compared in the selection unit. When the sizes of the spot images are compared and the difference is not less than a predetermined value, the process proceeds to step S13. On the other hand, if the difference is less than the predetermined value, it is determined that the FPD is not inclined, and a notification to that effect is given (step S16).

  Here, if there is a defective spot image that cannot be used for the subsequent processing among the spot images for which the size is obtained, as will be described later, the subsequent processing is performed by excluding the defective spot image, Alternatively, spot imaging is performed again by changing the X-ray irradiation position. Of course, the notification means notifies that the defective spot image has been excluded, or notifies the user to reshoot. If the number of irradiation ports and the number of spot images do not match, it is considered that the X-ray irradiation area protrudes from the FPD, and re-imaging is prompted by the notification means.

  Among the photographed spot images, an extremely small spot image is formed because the irradiated X-rays are absorbed by these members due to, for example, the presence of a fixing bolt or a pacemaker at the fracture site in the subject. Conceivable. On the other hand, when an extremely large spot image exists, the other three spot images are considered to be defective spot images.

  Instead of comparing the size of the spot image, a defective spot image may be detected based on the contour shape of the spot image. Since the spot image is oval or circular reflecting the shape of the minute irradiation port, if the spot image is missing, it can be determined as a defective spot image.

[Step S13]
The selection unit selects the largest and smallest of the four spot images, and the feature amount extraction unit extracts the feature amounts of both spot images. The feature amount in this example is the length of the FPD in the X-axis direction and the length in the Y-axis direction of the spot image, and is the maximum of the lengths.

[Step S14]
The ratio of the length of the maximum spot image obtained in step S13 and the length of the minimum spot image is calculated. This ratio is (the length of the maximum spot image in the X-axis (Y-axis) direction / the length of the minimum spot in the X-axis (Y-axis) direction).

[Step S15]
The obtained ratio value is checked against a preset correspondence table. Specifically, a correspondence table showing (the FPD X-axis direction inclination, FPD Y-axis direction inclination) corresponding to (the ratio of FPD in the X-axis direction, the ratio of FPD in the Y-axis direction) is used. For example, when the ratio of the FPD in the X-axis direction is 1, and the ratio of the FPD in the Y-axis direction is 1.3, the inclination of the FPD in the X-axis direction is 0 ° and the inclination in the Y-axis direction is 5 °.

[Step S16]
The numerical value of the FPD inclination calculated in step S15 is displayed on the monitor and notified to the imaging technician. At this time, if the slope of the FPD is greater than or equal to a predetermined value, an alarm may be issued. Examples of alarms include enlarging numerical values, displaying them in red letters, and displaying them in blinking. At the same time, a warning sound may be emitted.

  If the slope of the FPD is clarified as a numerical value by the above-described procedure, it can be determined how much the fluoroscopic image data when the subject is imaged should be corrected. Therefore, appropriate image data for the subject can be created by the inclination correction unit of the image processing unit. The tilt information is stored in association with the fluoroscopic image, or if the fluoroscopic image is printed on a photograph, the tilt information can be used as a reference when diagnosing the subject. Lower.

  Of course, the X-ray generator may be manually moved to rearrange the X-ray generator and the FPD so that the FPD inclination becomes physically zero before imaging the subject. Here, if the sensor for detecting the orientation of the X-ray generator is provided, and the FPD inclination value changes according to the amount of movement of the X-ray generator, the FPD inclination can be easily reduced to zero. .

  If the image processing correction cannot be dealt with, an alarm can be issued to prompt the rearrangement of the X-ray generator and the FPD.

<Example 2>
In this example, not only the inclination of the FPD with respect to the optical axis of the X-ray but also the spot image (corrected spot image) after correcting this inclination is used to further calculate numerical information related to the arrangement state of the FPD. An X-ray imaging apparatus that notifies these pieces of information will be described. The numerical information about the FPD arrangement state other than “FPD tilt with respect to the optical axis of X-ray: tilt information” is “the amount of misalignment between the center of the FPD and the optical axis: misalignment information”, “FPD centered on the optical axis” Rotation amount: rotation information ”and“ distance between X-ray generator and FPD: distance information ”. Hereinafter, a configuration different from the configuration of the X-ray imaging apparatus according to the first embodiment will be mainly described. In the drawings, the same components as those of the first embodiment are denoted by the same reference numerals and the description thereof will be omitted.

(overall structure)
FIG. 7 is a functional block diagram of the X-ray imaging apparatus of this example. In addition to the configuration of the first embodiment, the X-ray imaging apparatus includes a preliminary monitor 51 in the X-ray generator 2 and a sensor in the carriage D. The sensor of the carriage D can detect information (movement information) on the movement amount and movement direction of the apparatus itself, and can output this information to the total calculation unit 100. As a sensor, it is possible to use a configuration that obtains movement information by detecting the rotation speed and direction of the wheel of the carriage D, or a configuration that obtains movement information using a light emitter and a light receiver such as an optical mouse. it can. A method of using this movement information will be described later.

  In addition, the computer 10 of this apparatus includes a total calculation unit 100 that calculates numerical information about the arrangement state of the FPD 3. In addition to the inclination calculation unit 15, the total calculation unit 100 calculates a rectangular center position formed by four spot images, that is, the position of the intersection of the optical axis 2A of the X-ray and the FPD 3, that is, the irradiation center. A center position calculation unit 16 is provided. Furthermore, the total calculation unit 100 calculates a shift amount calculation unit 17, a rotation amount calculation unit 18, and a distance calculation for calculating shift information, rotation information, and distance information, respectively, from the corrected spot image and the center position. Part 19. Then, the preliminary monitor 51 collectively notifies the calculated tilt information, deviation information, rotation information, and distance information.

  According to the configuration of this example, the accurate arrangement state of the FPD 3 can be grasped before the subject P is actually photographed. Therefore, when photographing the subject, the FPD and the X-ray generator are properly used. Can be readjusted.

  Hereinafter, a configuration different from the first embodiment will be described in detail.

[Center position calculator]
The center position calculation unit 16 (center calculation means) is a means for calculating a square center position formed by the spot image. Here, since the optical axis of the X-ray coincides with the irradiation central axis of the X-ray, calculating the center position means calculating the irradiation center.

  In order to calculate the center position, image data (corrected spot image) having a spot image in which the FPD 3 is not inclined with respect to the optical axis 2A of the X-ray is necessary. FIG. 8 shows a corrected spot image S. Four spot images S detected by the FPD are arranged at the vertices of a regular square, and each spot image S is circular. Accordingly, the center Sc of each spot image is obtained, and the intersection of the straight lines connecting the centers Sc at the diagonal positions becomes the irradiation center Ic.

  In the apparatus of this example, a corrected spot image necessary for calculating deviation information, rotation information, and distance information was obtained by image processing. The three pieces of numerical information may be obtained in any order based on the irradiation center obtained from the inclination of the FPD. By creating a corrected spot image by image processing, all information can be notified at once, and the FPD can be properly placed before the subject is actually imaged. Further, since spot photographing for obtaining a corrected spot image can be omitted, it is possible to save the trouble of photographing, and at the same time, it is preferable from the viewpoint of radiation protection.

[Deviation amount calculation unit]
The deviation amount calculation unit (deviation amount calculation means) 17 is configured to calculate a relative deviation amount (deviation information) between the center of the FPD 3 and the irradiation center. Specifically, as shown in FIG. 8, the deviation amount calculation unit 17 determines that the position of the irradiation center Ic from the position of the center Fc of the FPD is the horizontal axis (X axis) direction of the FPD and the vertical axis (Y axis). Calculate how far away you are in the direction. The calculated deviation information is displayed on the preliminary monitor 51 (see FIG. 7). At this time, if the amount of deviation exceeds the allowable value, the fact is notified as will be described later. For example, when the amount of deviation is extremely large, the X-ray irradiation range may protrude from the FPD, so that a fluoroscopic image taken in this state cannot be used for diagnosis of the subject.

[Rotation amount calculation unit]
The rotation amount calculation unit (rotation amount calculation means) 18 is configured to calculate the rotation amount (rotation information) of the FPD 3 around the optical axis 2A. The rotation amount calculation unit 18 calculates rotation information from the horizontal axis (X axis) or vertical axis (Y axis) information of the FPD 3 passing through the irradiation center and the spot image. The methods for calculating the rotation information can be roughly divided into two methods, which will be described sequentially.

"Method 1"
As method 1, as shown in FIG. 9, an arbitrary spot image S is selected from the four spot images, and the center Sc of the spot image S is a distance from the X axis and the Y axis passing through the irradiation center Ic. Ask for. Specifically, a distance dx of a straight line parallel to the X axis from the Y axis to the center Sc of the spot image S and a distance dy of a straight line parallel to the Y axis from the X axis to the center Sc of the spot image S are obtained. . When the obtained dx and dy are equal, it can be said that the FPD is not rotating. On the other hand, when dx and dy are different, the rotation amount of the FPD may be obtained from the difference between dx and dy.

  Also, as shown in the figure, an arbitrary spot image S is selected, a straight line connecting the irradiation center Ic and the center Sc of the spot image S is obtained, and this straight line is formed with the X axis (or Y axis). Find the angle α. When the angle α is 45 °, it can be said that the FPD is not rotating. Then, the amount of rotation of the FPD can be obtained by subtracting 45 ° from the formed angle α.

"Method 2"
As method 2, as shown in FIG. 10, the degree of inclination of two spot images S arranged in the horizontal direction (or vertical direction) with respect to the horizontal axis (or vertical axis) of the FPD is calculated. It is a technique. In this example, since the spot image S is arranged in a regular square shape, for example, an angle β formed by a straight line connecting the centers Sc of the two spot images S corresponding to the upper side of the square shape and the horizontal axis of the FPD is obtained. . This angle β is the amount of rotation of the FPD. Further, an angle formed by a straight line connecting the centers Sc of the two spot images S corresponding to the rectangular side edges and the vertical axis of the FPD may be obtained. In this case, the angle β formed is the amount of rotation of the FPD.

[Distance calculation unit]
The distance calculation unit (distance calculation means) 19 is configured to calculate the distance (distance information) between the X-ray generator 2 and the FPD 3. In order to calculate the distance information, first, the size of an arbitrary spot image is calculated. Next, the distance when the spot image is photographed is calculated based on a graph of a correlation between a preset size of the spot image when the FPD is not tilted and the distance.

  FIG. 11 shows the correlation graph described above. The horizontal axis of the graph shows the distance (cm) between the FPD and the X-ray tube, and the vertical axis shows the size of the spot image when the distance is 180 cm and the magnification is 1.0. Indicates the value (%) converted to. That is, if the magnification of the photographed spot image is 0.59, for example, the distance between the FPD and the X-ray tube is 100 cm.

As described above, the numerical information regarding the arrangement state of the FPD 3 calculated by the four calculating units 15, 17, 18, and 19 described above is displayed on the standby monitor 51 and the monitor 5 provided in the main body 1. FIG. 12 shows a state in which numerical information is notified by the preliminary monitor. A monitoring diagram for schematically grasping the position of the irradiation field region 502 with respect to the detection region 501 that is a region where X-rays can be detected by the FPD is displayed on the upper right of the screen of the preliminary monitor. The meanings of the words on the screen are as follows.
SID: Distance information θ: FPD X-axis tilt (tilt information)
φ: FPD Y-axis tilt (tilt information)
ω ... Rotation information X ... X-axis misalignment between FPD center position and irradiation center (deviation information)
Y: Deviation in the Y-axis direction between the FPD center position and irradiation center (deviation information)

  FIG. 12A shows a case where the amount of deviation between X and Y is relatively large, but all of the numerical information is within an allowable range. FIG. 12B shows a case where the inclination (inclination information) of the FPD in the X-axis direction exceeds an allowable value, and FIG. 12C shows a case where the amount of X deviation exceeds the allowable value. As shown in FIGS. 12 (B) and 12 (C), the apparatus of this example urges the radiographer to pay attention by enlarging and displaying numerical information exceeding the allowable value in red. Further, notification by a warning sound may be performed. Further, when at least one of the numerical information exceeds the allowable value, the subject may not be imaged unless the FPD arrangement state is readjusted.

  Further, in the apparatus of this example, the X-ray generator and the carriage are provided with sensors, and the numerical information on the preliminary monitor and the monitor reflects the amount of movement of the X-ray generator and the amount of movement of the carriage. It has been updated. Therefore, when at least one of the X-ray generator and the apparatus main body is moved, readjustment of the positional relationship between the X-ray generator and the FPD can be performed accurately, and before the subject is actually imaged, The positional relationship can be brought into an optimum state. Further, with the configuration in which numerical information is updated, it is not necessary to perform spot imaging again after readjustment of the arrangement state, and the exposure dose to the subject can be reduced.

  As described above, according to the X-ray imaging apparatus of this example, it is possible to optimally adjust the arrangement state of the X-ray generator and the FPD before imaging the subject.

  The X-ray imaging apparatus of the present invention can be suitably used particularly for a round-trip X-ray imaging apparatus.

FIG. 1 is an external view of the X-ray imaging apparatus described in the first and second embodiments. FIG. 2 is a functional block diagram of the X-ray imaging apparatus described in the first embodiment. FIG. 3 is a schematic configuration diagram of a spot forming diaphragm (irradiation limiting means) including four spot forming blades. FIG. 4 is a schematic configuration diagram of a spot forming diaphragm (irradiation limiting means) composed of a single spot forming blade, where (A) shows four micro irradiation ports and (B) shows three micro irradiation ports. Show things. FIGS. 5A and 5B are diagrams showing an X-ray irradiation state according to the arrangement of the spot forming diaphragm. FIG. 5A shows the case where the spot forming diaphragm is not inserted, and FIG. 5B shows the spot forming diaphragm inserted. Indicates the state. FIG. 6 is a flowchart showing a procedure for calculating the inclination of the FPD with respect to the optical axis of the X-ray. FIG. 7 is a functional block diagram of the X-ray imaging apparatus described in the second embodiment. FIG. 8 is an explanatory diagram showing a method for calculating the deviation between the X-ray irradiation center and the FPD center based on the spot image when the FPD is not inclined with respect to the optical axis of the X-ray. FIG. 9 shows a method for calculating the amount of rotation of the FPD around the optical axis of the X-ray based on the spot image when the FPD is not inclined with respect to the optical axis of the X-ray. It is explanatory drawing which shows the method (method 1) which uses a spot image. FIG. 10 shows a method for calculating the amount of rotation of the FPD around the optical axis of the X-ray based on the spot image when the FPD is not inclined with respect to the optical axis of the X-ray. It is explanatory drawing which shows the method (method 2) which uses a spot image. FIG. 11 is a graph showing the relationship between the size of the spot image and the distance between the X-ray generator and the FPD when the FPD is not inclined with respect to the optical axis of the X-ray. FIG. 12 is a diagram showing a state in which numerical information about the FPD arrangement state is notified by the preliminary monitor. FIG. 12A shows that the amount of deviation of the FPD is relatively large, but all of the numerical information is within the allowable range. This is the case. (B) shows the case where the inclination θ in the X-axis direction of the FPD exceeds the allowable value, and (C) shows the case where the amount of deviation of the FPD in the X-axis direction exceeds the allowable value.

Explanation of symbols

0 X-ray imaging device
1 Main unit 2 X-ray generator 21 X-ray tube 22 X-ray irradiation port 2A X-ray optical axis
3 FPD 4 Support section 5 Monitor 51 Spare monitor 6 Movable diaphragm
7 Spot forming aperture 7h Micro irradiation port
71,72,73,74,75 Spot forming blade 71h, 72h, 73h, 74h Through hole
8 High-pressure generator B Sleeper D Dolly CP Operation panel P Subject
10 computer
11 Control unit 12 Image data acquisition unit 13 Image processing unit 14 Storage unit
15 Inclination calculator 151 Selector 152 Feature extraction unit 153 Comparison unit
100 Total calculator
16 Center position calculation unit 17 Deviation amount calculation unit 18 Rotation amount calculation unit 19 Distance calculation unit
501 Detection area 502 Irradiation field area
S Spot image Sc Center of spot image Ic Irradiation center Fc Center of FPD

Claims (5)

An X-ray generator that irradiates the subject with X-rays, and a flat detector that acquires image data corresponding to the incident dose of X-rays that have passed through the subject. An X-ray imaging device not mechanically supported,
An irradiation limiting means comprising a shielding member for shielding X-rays, and having at least two minute irradiation ports penetrating the shielding member;
Storage means for storing image data (spot image data) having a plurality of spot images formed on a flat detector by X-rays passing through the minute irradiation port;
An inclination calculating means for calculating an inclination of the flat detector with respect to the optical axis of the X-ray irradiated to the subject based on the plurality of spot images;
Notification means for notifying the inclination,
The inclination calculating means includes
A selection means for comparing the size of each spot image and selecting the smallest spot image and the largest spot image;
Feature amount extraction means for extracting a feature amount based on the form of the spot image from the minimum spot image and the maximum spot image;
An X-ray imaging apparatus comprising: a comparison unit that obtains the inclination by applying the extracted feature quantity to a correlation between a preset feature quantity and the inclination of the flat detector.   The X-ray imaging apparatus according to claim 1, further comprising appropriate image data creating means for creating image data in a substantially non-tilted state based on the tilt. Center calculation means for calculating an irradiation center that is an intersection of the flat detector and the optical axis, from spot image data corrected to a substantially tilt-free state based on the tilt,
The displacement amount calculating means for calculating a relative displacement between the center of the flat detector and the irradiation center from the positional relationship between the irradiation center and the center of the flat detector is provided. The X-ray imaging apparatus described. Center calculation means for calculating an irradiation center that is an intersection of the flat detector and the optical axis, from spot image data corrected to a substantially tilt-free state based on the tilt,
A rotation amount calculating means for calculating the rotation amount of the flat detector with respect to the optical axis of the X-ray,
This rotation amount calculation means calculates the rotation amount from the positional relationship between at least one spot image of the corrected spot image data and the X axis and Y axis of the flat detector passing through the irradiation center. The X-ray imaging apparatus according to claim 1 or 2. Center calculation means for calculating an irradiation center that is an intersection of the flat detector and the optical axis, from spot image data corrected to a substantially tilt-free state based on the tilt,
A distance calculating means for calculating a distance between the X-ray generator and the flat panel detector;
This distance calculation means is based on the correlation between the size of the spot image when the flat detector is not inclined with respect to the optical axis of the X-ray and the distance between the X-ray generator and the flat detector. The X-ray imaging apparatus according to claim 1, wherein the distance is calculated from a spot image size of the corrected spot image data.

Images