JP2019132727A - Radiation inspection device and radiation inspection method - Google Patents

Abstract

To provide a radiation inspection device capable of improving the detection accuracy of a hole and foreign matter regardless of the existence position of the hole and foreign matter and to provide a radiation inspection method.SOLUTION: The radiation inspection device includes a radiation source 2 which emits radiation, a stage 4 which is located in the irradiation range of the radiation source 2 and on which a specimen 1 can be placed, a detector 3 which is located on a side opposite to the radiation source 2 across the stage 4 and detects the radiation transmitted through the specimen 1, a processing device 6 which images the two-dimensional see-through information of the specimen 1 obtained from the detector 3, and a display device 7 which displays an image obtained by the processing device 6. The processing device 6 includes an arithmetic part 62 which calculates a ratio between two transmission data in which the position of the specimen 1 is different, to generate a two-dimensional ratio image. The display device 7 displays the ratio image generated by the arithmetic part 62.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a radiation inspection apparatus that detects radiation transmitted through a subject and forms an image of the subject.

  A radiation inspection apparatus that performs non-destructive inspection of a subject by irradiating the subject with radiation represented by X-rays and detecting and imaging a two-dimensional distribution of radiation attenuated by passing through the subject. Are known. For example, it is possible to find a void called a void existing inside the subject, or a foreign substance on the surface or inside of the subject, by this radiological examination apparatus.

  However, voids and foreign materials are generally very small and have a low contrast with the surroundings. For this reason, it is not easy to detect a hole or a foreign object by just looking at the perspective image. Therefore, a technique using a difference image is known in order to improve the detection accuracy.

  The difference image is an image obtained by taking a difference in pixel value between two fluoroscopic images picked up by slightly shifting the position of the same subject. The pixel value indicating the subject that is the background of the hole or foreign object is substantially the same between the two fluoroscopic images. Therefore, in the difference image, the subject as a background is canceled out, and an image in which holes and foreign matters are conspicuous is obtained. By referring to the difference image, the accuracy of detecting holes and foreign matters is improved.

Japanese Patent No. 3545073

  However, it has been found that, in the method using the difference image, the detection accuracy changes depending on where in the subject the same hole or foreign substance exists. The reason is that if the thickness of the subject, that is, the transmission distance of the radiation is different, the transmission distance of the subject as the background changes, so that the radiation transmission intensity of the thin part and the radiation transmission intensity of the thick part are This is because the change is reflected in the difference image. In particular, when a hole or a foreign object exists in a thick part of the subject, the radiation transmission intensity of the part is lower than that in the case where the same hole or a foreign object exists in a thin part of the subject, and thus appears on the difference image. Contrast was also low, and the detection accuracy was uneven.

  An object of the present embodiment is to provide a radiation inspection apparatus and a radiation inspection method capable of improving the detection accuracy of holes and foreign matters regardless of the positions of the holes and foreign matters in order to solve the above-described problems. And

  In order to achieve the above object, a radiation inspection apparatus according to the present embodiment includes a radiation source that irradiates radiation, a stage that is located in an irradiation range of the radiation source and on which a subject can be placed, and the stage. A detector that is positioned on the opposite side of the radiation source and detects the radiation that has passed through the subject; a processing device that images the two-dimensional perspective information of the subject obtained from the detector; A display device that displays an image obtained by the processing device, wherein the processing device calculates a ratio of the two pieces of fluoroscopic information at different positions of the subject and generates a two-dimensional ratio image. And the display device displays the ratio image generated by the calculation unit.

  The radiation inspection method according to the present embodiment is a radiation detection method using a radiation inspection apparatus having a radiation source, a detector, and a display device, and detects the radiation irradiated by the radiation source and transmitted through the subject. A first acquisition step of detecting with a detector and acquiring first fluoroscopic information; a movement step of moving the subject after the first acquisition step; and irradiation with the radiation source after the movement step The second acquisition step of detecting the radiation transmitted through the subject moved in the moving step by the detector and acquiring second fluoroscopic information, the first fluoroscopic information, and the second fluoroscopic information It has a calculation step of calculating a ratio with fluoroscopic information and generating a two-dimensional ratio image, and a display step of displaying the ratio image on the display device.

  The radiation inspection method according to the present embodiment is a radiation detection method using a radiation inspection apparatus having a radiation source and a flat panel detector having a gain correction value setting mode for correcting sensitivity variation of each pixel. An activation step for activating the gain correction value setting mode; a gain correction acquisition step for detecting a radiation irradiated by the radiation source and transmitted through the subject by the flat panel detector; and acquiring a gain correction value; A moving step for moving the specimen, and a fluoroscopic image acquiring step for detecting the radiation transmitted through the subject moved in the moving step by the flat panel detector and acquiring a fluoroscopic image. To do.

It is a figure which shows an example of a structure of the radiation inspection apparatus which concerns on 1st Embodiment. It is a flowchart which shows an example of operation | movement of the radiation inspection apparatus which concerns on 1st Embodiment. It is the figure which showed the test object from which thickness differs with respect to the permeation | transmission direction of a radiation, and shows the test object which has a void | hole inside. It is the figure which showed the test object from which thickness differs with respect to the permeation | transmission direction of a radiation, and shows the test object in which the foreign material exists on the surface. It is the figure which showed the test object from which thickness differs with respect to the permeation | transmission direction of a radiation, and shows the test object in which a foreign material exists. It is a figure which shows an example of a structure of the radiation inspection apparatus which concerns on 2nd Embodiment. It is a figure for demonstrating gain correction. It is a functional block diagram of a flat panel detector. It is a figure for demonstrating the gain correction | amendment in the state which put the test object on the stage. It is a flowchart which shows an example of operation | movement of the radiation inspection apparatus which concerns on 2nd Embodiment.

(First embodiment)
Hereinafter, the radiation inspection apparatus according to the first embodiment will be described in detail with reference to the drawings.

(Constitution)
FIG. 1 is a diagram illustrating an example of a configuration of a radiation inspection apparatus according to the present embodiment. The radiation inspection apparatus irradiates the subject 1 with radiation, detects the radiation transmitted through the subject 1, and forms a fluoroscopic image in the subject 1 based on the detection result. The radiation inspection apparatus includes a radiation source 2, a detector 3, a stage 4, a moving mechanism 5, a processing device 6, and a display device 7.

  The radiation source 2 irradiates the subject 1 with a radiation beam 22. The radiation is, for example, X-rays. The radiation beam 22 is a bundle of radiation that expands into a pyramid shape with the focal point 21 as an apex, and is a result of the radiation that expands into a cone shape being narrowed down by a collimator. The radiation source 2 is, for example, an X-ray tube. In a typical X-ray tube, a filament and a target such as tungsten are opposed to each other in a vacuum. The filament irradiates electrons, and the electrons are accelerated by the tube voltage between the filament and the target, travel toward the target, hit the target, and irradiate X-rays. This electron flow is a tube current, and the tube current is opposite to the electron flow.

  The detector 3 is arranged opposite to the focal point 21 of the radiation source 2. The detector 3 includes, for example, an image intensifier (II) and a camera, or a flat panel detector (FPD). I. I. Expands the scintillator surface made of cesium iodide or the like, which emits light when excited by radiation, in a two-dimensional manner, and converts the two-dimensional distribution of incident radiation into a fluorescent image, while multiplying the luminous intensity of the fluorescent image. The camera images a fluorescent image by arranging image sensors such as a CCD and a CMOS in parallel. The FPD has, for example, a photodiode and a TFT switch along the scintillator surface. The photodiode converts the fluorescence image into electric charge and accumulates it, and the TFT switch outputs the electric charge accumulated in the photodiode when an ON signal is given.

  That is, the detector 3 detects a two-dimensional distribution of the radiation intensity attenuated according to the radiation transmission path, and outputs transmission data proportional to the radiation intensity. The transmission data is a radiation intensity, a charge amount indicating the radiation intensity, or a luminance value indicating the radiation intensity, and is digitized to, for example, 256 gradations.

  The stage 4 is a mounting table for the subject 1. The stage 4 is interposed between the radiation source 2 and the detector 3, directs the placement surface toward the radiation source 2, and the placement surface expands perpendicular to the optical axis of the radiation beam. The position of the stage 4 is variable with respect to the radiation source 2 and the detector 3 by a moving mechanism 5.

  The moving mechanism 5 moves the stage 4 linearly and moves up and down. The linear movement directions are the X-axis direction and the Y-axis direction. The X-axis direction is one direction along a plane in which the stage 4 extends. The Y-axis direction is a direction orthogonal to the X-axis direction along a plane in which the stage 4 extends. The ascending / descending direction is the Z-axis direction. The Z-axis direction is orthogonal to the stage 4, in other words, the direction in which the Z-axis direction is in contact with or separated from the radiation source 2.

  The processing device 6 controls the radiation source 2, the detector 3, and the moving mechanism 5, causes the subject 1 to be imaged, and generates an image in the subject 1. The processing device 6 is a so-called computer and a driver circuit connected to the computer by a signal line, and the computer part includes a storage such as a CPU, HDD or SSD, and a RAM. The storage stores a program, the program is expanded in the RAM, the data is temporarily stored in the RAM, the CPU processes the program, the driver circuit is, for example, a motor driver, and each unit according to the processing result of the CPU To supply power.

  The processing device 6 generates a ratio image as an image in the subject 1. The ratio image is an image generated by calculating the ratio of two transmission data obtained by photographing the same subject 1 while shifting the position, and the ratio value of the two transmission data is expressed in two shades. It is shown on the dimension plane. Even if the holes or foreign matters are the same, the position of the subject 1 is different, so that a pair of images appear as images of the holes or foreign matters on the specific image. The processing device 6 includes a storage unit 61, a calculation unit 62, and a shooting control unit 63.

  The imaging control unit 63 includes a driver circuit, controls the moving mechanism 5 to shift the position of the subject 1, and irradiates a radiation beam before and after the movement to obtain two transmission data. The storage unit 61 includes a storage, and stores transmission data of the subject 1 obtained before shifting the position.

  The calculation unit 62 includes a CPU, calculates a ratio of two transmission data having different positions of the subject 1, and generates a two-dimensional ratio image. For example, the calculation unit 62 calculates the ratio between the luminance value of the subject 1 stored in the storage unit 61 and the luminance value of the subject 1 at a position where the subject 1 is slightly moved, at the same coordinates. Find in pixels. And the calculating part 62 produces | generates the ratio image which consists of ratio of a two-dimensional luminance value by calculating | requiring the said ratio in each pixel extended on the mounting surface of the detector 3. FIG.

  The display device 7 is a monitor such as a liquid crystal display or an organic EL display. The display device 7 displays the ratio image obtained by the calculation unit 62 on the screen.

(Operation)
The operation of such a radiation inspection apparatus is shown in the flowchart of FIG. First, the subject 1 is placed on the stage 4 (step S1). Then, the subject 1 on the stage 4 is imaged with radiation (step S2). That is, the radiation source 22 irradiates the subject 1 with the radiation beam 22, and the radiation transmitted through the subject 1 is detected by the detector 3. At this time, here, the detector 3 converts the incident radiation intensity into a charge amount proportional to the intensity, and further sets a discrete pixel value according to the charge amount. The detector 3 outputs a two-dimensional distribution of pixel values to the processing device 6 as transmission data. Then, the processing device 6 stores the input transmission data in the storage unit 61 (step S3).

  Next, the subject 1 is slightly moved by moving the stage 4 by the moving mechanism 5 (step S4). Here, the “slightly moving” distance is, for example, a distance about the size of the hole V or the foreign matter F (see FIGS. 3 and 4), and preferably less than the size of the hole V or the foreign matter F. When an image having the same width as the moving distance is displayed on the display device 7, the observer can clearly grasp this image. For example, if the size of the foreign substance F to be detected is 100 μm, the distance is smaller than 100 μm.

  After moving the subject 1 slightly in this way, the subject 1 on the stage 4 is imaged with radiation (step S5). That is, the radiation source 22 irradiates the subject 1 with the radiation beam 22, and the radiation transmitted through the subject 1 is detected by the detector 3. The detector 3 outputs the transmission data to the processing device 6.

  And the calculating part 62 calculates the ratio of the transmission data memorize | stored in the memory | storage part 61, and the transmission data obtained from the detector 3 by step S5 in the pixel of the same coordinate, and produces | generates a ratio image ( Step S6). The calculation unit 62 outputs the generated ratio image to the display device 7 and displays the ratio image on the screen (step S7).

  As a result, a specific ratio image of the contrast between the holes V and the foreign matter F can be obtained regardless of the positions where the holes V and the foreign matter F exist, so that the accuracy of detecting the holes V and the foreign matter F can be improved. . The principle of improving the detection accuracy of the holes and foreign matters will be described with reference to FIGS.

(Function)
3 and 4 are views showing the subject 1 having different thicknesses with respect to the radiation transmission direction. The subject 1 in FIG. 3 has a void V therein, and the subject 1 in FIG. Foreign matter F exists on the surface. If the radiation intensity that passes through the subject 1 and enters the arbitrary pixel of the detector 3 is I _A, and the radiation intensity that enters the pixel when the subject 1 does not exist is I ₀ , the radiation intensity I _A Can be expressed as in equation (1).

μ_Ａは、被検体１の線減弱係数であり、ｔ_Ａは、放射線が被検体１を透過する透過距離、すなわち被検体１の厚みである。

μ _A is a linear attenuation coefficient of the subject 1, and t _A is a transmission distance through which radiation passes through the subject 1, that is, a thickness of the subject 1.

As shown in FIG. 3, the radiation intensity I ₁ transmitted through only the background portion I where the thickness of the subject 1 is thin can be expressed as in Equation (2), and the radiation transmitted through the background portion I and the hole V. Intensity I _{1 + V} can be expressed as in equation (3).

ｔ_１は、背景部分Ｉの透過距離であり、ｔ_Ｖは、空孔Ｖの透過距離である。

t ₁ is the transmission distance of the background portion I, and t _V is the transmission distance of the hole V.

Therefore, from the formulas (2) and (3), the radiation intensity ratio I _{1 + V} / I ₁ is as shown in the formula (4).

On the other hand, the radiation intensity I ₂ transmitted only through the thick background portion II of the subject 1 can be expressed as in Equation (5), and the radiation intensity I _{2 + V} transmitted through the background portion II and the hole _V is It can be expressed as equation (6).

ｔ_２は、背景部分ＩＩの透過距離であり、ｔ_Ｖは、空孔Ｖの透過距離である。

t ₂ is the transmission distance of the background portion II, and t _V is the transmission distance of the hole V.

Therefore, from the formulas (5) and (6), the radiation intensity ratio I _{2 + V 1} / I ₂ is as shown in the formula (7).

As is clear from the above formulas (4) and (7), the radiation intensity ratios I _{1 + V} / I ₁ and I _{2 + V} / I ₂ are equal. That is, the ratio of the radiation intensity transmitted through the background portion and the hole V to the radiation intensity transmitted only through the background portion of the subject 1 is not affected by the thickness of the subject 1 serving as the background, and the subject 1 a linear attenuation coefficient mu _a, a unique value determined by the transmission distance t _V vacancy V. Therefore, by calculating the ratio of the radiation intensity when passing through the hole V and the radiation intensity when not passing through the hole V and generating an image reflecting the ratio, the presence or absence of the hole V Can be detected.

In addition, as shown in FIG. 4, when the foreign substance F exists on the surface of the subject 1, similarly, the radiation intensity ratios I _{1 + F} / I ₁ and I _{2 + F} / I ₂ having different thicknesses are equal. That is, the radiation intensity I _{1 + F} transmitted through the background portion I and the foreign substance F where the thickness of the subject 1 is thin can be expressed as in the equation (8), and the background portion II and the foreign matter F where the thickness of the subject 1 is thick. The transmitted radiation intensity I _{2 + F} can be expressed as in Equation (9).

μ_Ｆは異物Ｆの線減弱係数であり、ｔ_Ｆは異物Ｆの透過距離、すなわち異物Ｆの厚みである。

μ _F is a linear attenuation coefficient of the foreign matter F, and t _F is a transmission distance of the foreign matter F, that is, a thickness of the foreign matter F.

  Therefore, from the expressions (2), (5), (8), and (9), the ratio of the radiation intensity in each of the background portions I and II is as shown in the expression (10).

As is clear from the equation (10), the ratio of the radiation intensity transmitted through the background portion and the foreign substance F to the radiation intensity transmitted only through the background portion of the subject 1 depends on the thickness of the subject 1 serving as the background. without becomes a linear attenuation coefficient mu _F of the foreign matter F, a unique value determined by the transmission distance t _F of the foreign matter F. Therefore, the presence / absence of the foreign matter F is detected by calculating the ratio of the radiation intensity when passing through the foreign matter F and the radiation intensity when not passing through the foreign matter F and generating an image reflecting the ratio. be able to.

Further, as shown in FIG. 5, when the foreign substance F exists inside the subject 1, the ratios I _{1 + F} / I ₁ and I _{2 + F} / I ₂ of the radiation intensities having different thicknesses are the same. That is, the radiation intensity I _{1 + F} transmitted through the background portion I and the foreign substance F where the thickness of the subject 1 is thin can be expressed as in the equation (11), and the background portion II and the foreign matter F where the thickness of the subject 1 is thick. The transmitted radiation intensity I _{2 + F} can be expressed as in Equation (12).

μ_Ａは、被検体１の線減弱係数であり、ｔ_１は、放射線が被検体１の背景部分Ｉを透過する透過距離、すなわち被検体１の背景部分Ｉの厚みである。ｔ_２は、放射線が被検体１の背景部分ＩＩを透過する透過距離、すなわち被検体１の背景部分ＩＩの厚みである。μ_Ｆは異物Ｆの線減弱係数であり、ｔ_Ｆは異物Ｆの透過距離、すなわち異物Ｆの厚みである。

μ _A is a linear attenuation coefficient of the subject 1, and t ₁ is a transmission distance through which radiation passes through the background portion I of the subject 1, that is, the thickness of the background portion I of the subject 1. t ₂ is the transmission distance through which the radiation passes through the background portion II of the subject 1, that is, the thickness of the background portion II of the subject 1. μ _F is a linear attenuation coefficient of the foreign matter F, and t _F is a transmission distance of the foreign matter F, that is, a thickness of the foreign matter F.

  Therefore, from the expressions (2), (5), (11), and (12), the ratio of the radiation intensity in each of the background portions I and II is as shown in the expression (13).

As is clear from the equation (13), the ratio of the radiation intensity transmitted through the background portion and the foreign substance F to the radiation intensity transmitted only through the background portion of the subject 1 depends on the thickness of the subject 1 serving as the background. Instead, it is a unique value determined by the linear attenuation coefficient μ _{A of} the subject, the linear attenuation coefficient μ _F of the foreign substance F, and the transmission distance t _F of the foreign substance F. Therefore, the presence / absence of the foreign matter F is detected by calculating the ratio of the radiation intensity when passing through the foreign matter F and the radiation intensity when not passing through the foreign matter F and generating an image reflecting the ratio. be able to.

  That is, in this radiation inspection apparatus, the stage 4 is moved slightly, and the ratio of transmission data before and after the movement is calculated, so that the radiation intensity and the hole V or foreign matter when passing through the hole V or foreign matter F are calculated. The ratio with the radiation intensity when not passing through F is calculated.

  The stage 4 is moved slightly because, for example, the ratio between the radiation intensity transmitted through only the background portion II of the subject 1 and the radiation intensity transmitted through the background portion I and the hole V or the foreign substance F. This is to avoid becoming. However, the movement is such that the pixel area where the ratio of the radiation intensity when passing through the hole V or the foreign substance F and the radiation intensity when not passing through the hole V or the foreign substance F is calculated can be grasped on the image. desirable. Specifically, it is desirable that the slight movement amount is, for example, about three times the pixel pitch of the detector 3 at the position where the hole V or the foreign substance F exists. Here, the pixel pitch of the detector 3 at the position where the hole V or the foreign object F exists is the pixel pitch of the detector 3, the distance FDD between the focal point 21 and the radiation input surface of the detector 3, the focal point 21 and the sky. It is a value divided by the ratio FDD / FOD to the distance FOD to the position where the hole V or the foreign substance F exists.

  The moving mechanism 5 desirably moves the subject 1 in a direction in which the subject 1 has translational symmetry. The direction having translational symmetry is a direction in which the transmission data changes little before and after the subject 1 moves. Therefore, this radiation inspection apparatus is particularly effective for the subject 1 such as a cylindrical battery having an internal structure in which an anode foil and a cathode foil are wound. In this battery, each cross section orthogonal to the axis has the same structure, and the cylinder axis direction is a direction having translational symmetry.

(effect)
As described above, the radiation inspection apparatus according to the present embodiment includes the radiation source 2 that irradiates radiation, the stage 4 that is located in the irradiation range of the radiation source 2 and on which the subject 1 can be placed, and the radiation across the stage 4. A detector 3 that is located on the opposite side of the source 2 and detects radiation transmitted through the subject 1; a processing device 6 that images the two-dimensional perspective information of the subject 1 obtained from the detector 3; And a display device 7 for displaying an image obtained by the device 6. The processing device 6 includes a calculation unit 62 that calculates a ratio of two transmission data having different positions of the subject 1 and generates a two-dimensional ratio image. The display device 7 is generated by the calculation unit 62. A ratio image was displayed.

  Accordingly, a ratio image of the inherent contrast between the holes and the foreign matters can be obtained regardless of the positions where the holes and foreign matters are present, so that the accuracy of detecting the holes and foreign matters can be improved. For example, when viewing a fluoroscopic image, the background portion other than the holes and foreign matters is substantially uniform in shade, and therefore the ratio of two pieces of transmission data with different positions of the subject 1 is calculated to obtain information on the background portion. Can be offset. On the other hand, the holes and foreign matters have unique values that do not depend on the X-ray transmission thickness of the background portion, so that they have a noticeable contrast and can be made conspicuous. Therefore, it is possible to improve the accuracy of detecting holes or foreign matters.

  In the present embodiment, the ratio of the transmission data output from the detector 3 is calculated. However, if the fluoroscopic information is derived from the two-dimensional distribution of the radiation intensity, regardless of the positions of the holes and the foreign matter, Since a specific ratio image of the contrast between the pores and the foreign matter is obtained, the accuracy of detecting the pores and the foreign matter can be improved. The perspective information includes, in addition to transmission data, a perspective image that can be displayed on the display device 7 by converting the pixel value of the transmission data into a luminance value such as a gray scale.

  Further, the radiation examination apparatus of the present embodiment has a moving mechanism 5 that moves the stage 4, and the moving mechanism 5 moves the subject 1 in a direction in which the subject 1 has translational symmetry. As a result, the fluoroscopic information of the background portion other than the holes and foreign matters can be made substantially the same before and after the movement of the subject 1 and can be canceled out, and the holes and foreign matters can be made conspicuous. As a result, the detection accuracy of holes and foreign matters can be improved.

(Second Embodiment)
(Constitution)
Next, a radiation inspection apparatus according to the second embodiment will be described in detail with reference to the drawings. The same configurations and functions as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 6 is a diagram illustrating an example of the configuration of the radiation inspection apparatus according to the second embodiment. As shown in FIG. 6, the radiation inspection apparatus of this embodiment includes a flat panel detector 8. The flat panel detector 8 has a gain correction value setting mode. The gain correction value setting mode is a mode for setting a gain correction value for correcting variation in sensitivity of each pixel. As shown in FIG. 7, the sensitivity of each pixel varies, and the value of fluoroscopic information, which is an output value, is different even when the incident radiation intensity is the same. Therefore, a gain correction value is obtained so that the value of the fluoroscopic information output from the flat panel detector 8 is output at each pixel, and the sensitivity is obtained by multiplying the detection amount of the flat panel detector 8 by the gain correction value. Make the correction to keep the constant. In order to make the output value of each pixel constant, for example, when the output value is normalized to 1, the gain correction value is the reciprocal of the detection amount of the flat panel detector 8, and as shown in FIG. Complementary relationship with

  FIG. 8 is a functional block diagram of the flat panel detector 8. As shown in FIG. 8, the flat panel detector 8 includes a gain correction acquisition unit 81, a storage unit 82, and a calculation unit 83, in addition to the X-ray detection unit 3a.

  The X-ray detection unit 3a is a radiation detection element of the flat panel detector 8, and includes a photodiode and a TFT switch along the scintillator surface.

  The gain correction acquisition unit 81 detects radiation transmitted through the subject 1 in a state where the subject 1 is placed on the stage 4, and acquires a gain correction value that makes each pixel value the same value. This gain correction value is a two-dimensional distribution, and the subject 1 is reflected. For example, as shown in FIG. 9, when the subject 1 is placed on the stage 4 and the radiation transmitted through the subject 1 is detected, the fluoroscopy information includes variations in sensitivity of each pixel and the thickness of the subject 1. A shape tailored to appears. The gain correction acquisition unit 81 acquires a gain correction value as the reciprocal of the fluoroscopic information. The storage unit 82 includes a storage, and stores the gain correction value acquired by the gain correction acquisition unit 81. The calculation unit 83 includes a CPU, and multiplies the fluoroscopic information obtained by the X-ray detection unit 3a by a gain correction value.

(Function)
FIG. 10 is a flowchart showing an example of the operation of the radiation inspection apparatus according to the present embodiment. As shown in FIG. 10, first, the gain correction value setting mode is activated (step S21). Next, the subject 1 is placed on the stage 4 (step S22). Then, the radiation irradiated from the radiation source 2 and transmitted through the subject 1 is detected by the flat panel detector 8, and the gain correction acquisition unit 81 acquires the gain correction value (step S23). Furthermore, the acquired gain correction value is stored in the storage unit 82 (step S24).

  Next, the gain correction value setting mode is ended (step S25), and the subject 1 is slightly moved by moving the stage 4 by the moving mechanism 5 (step S26). After slightly moving the subject 1, the examination mode is activated (step S27), and the subject 1 on the stage 4 is imaged with radiation (step S28). That is, the radiation source 22 irradiates the subject 1 with the radiation beam 22, and the radiation transmitted through the subject 1 is detected by the flat panel detector 8. The fluoroscopic information that is the detection result is output to the calculation unit 83.

  Then, the calculation unit 83 multiplies the two-dimensional luminance value obtained from the X-ray detection unit 3a in step S28 by the gain correction value stored in the storage unit 82 between pixels having the same coordinates. At this time, since the gain correction value is the reciprocal of the fluoroscopic information of the subject 1, this multiplication generates a ratio image (step S29). The calculation unit 83 outputs the generated ratio image to the display device 7 and displays the ratio image on the screen (step S30).

(effect)
The radiation inspection apparatus according to the present embodiment includes a flat panel detector 8, and the flat panel detector 8 acquires a gain correction value that makes each pixel value the same value while the subject 1 is placed on the stage 4. A gain correction acquisition unit 81 for storing, a storage unit 82 for storing gain correction values, and a calculation unit 83. The calculation unit 83 generates the ratio image by multiplying the fluoroscopic information obtained by moving the subject 1 to a position different from the time when the gain correction value is acquired and the gain correction value.

  Thereby, the output of the flat panel detector 8 is a ratio image as it is, and the configuration and time for calculating the ratio image can be reduced. That is, a gain correction value is acquired in a state where nothing is placed on the stage 4, and gain correction is performed by multiplying the gain correction value by the fluoroscopy information in a state where the subject 1 is placed on the stage 4. In the case of the conventional method of using the result as the output value of the flat panel detector 8, it is necessary to calculate the ratio between the fluoroscopic information obtained by the first imaging and the fluoroscopic information obtained by the second imaging with the position shifted.

  On the other hand, in the present embodiment, the gain correction value is acquired with the subject 1 placed on the stage 4, and therefore, the gain correction value includes variations in sensitivity of each pixel and the subject 1. The gain correction value is reflected, and is, for example, the reciprocal of the fluoroscopic information obtained by the first imaging in the first embodiment. For this reason, the result obtained by performing gain correction by multiplying the gain correction value by the fluoroscopic information obtained by imaging with shifted positions is the ratio image itself.

  Therefore, it is not necessary to actually calculate the ratio image, and by performing gain correction using a general flat panel detector having a gain correction function, substantially the same effect as calculating the ratio image can be obtained. Can do. In other words, the calculation unit 83 is substantially the same as the calculation unit 62, and the flat panel detector 8 stores the gain correction value acquired by the gain correction acquisition unit 81 in the storage unit 61. And a processing device 6.

  In addition, there is an advantage that a ratio image with a good SN can be obtained rather than gain correction using gain correction in which air in a state where nothing is placed on the stage 4 is transmitted. Further, in the conventional method using gain correction in which air in a state where nothing is placed on the stage 4 is transmitted, the same gain correction is continuously used even if the subject 1 changes. Is not reflected. In contrast, in this embodiment, every time the subject 1 changes, the gain correction value is acquired in a state where the subject 1 is placed on the stage 4, so that a ratio image that takes into account the temporal change of the flat panel detector 8 is also obtained. Therefore, the accuracy of detecting the holes V and the foreign matter F can be further improved.

(Other embodiments)
In the present specification, an embodiment according to the present invention has been described. However, this embodiment is presented as an example, and is not intended to limit the scope of the invention. The above embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. The embodiments and the modifications thereof are included in the scope of the invention and the scope of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  For example, in the first and second embodiments, the calculation units 62 and 83 are configured as computers, but may be configured by dedicated electronic circuits. The calculation unit 62 includes a logarithmic conversion circuit that performs logarithmic conversion of the perspective information, a difference circuit that calculates a difference between the two logarithmically converted perspective information, and an exponential conversion circuit that exponentially converts the value obtained by the difference circuit. It may be configured. Thereby, a ratio image can be generated at higher speed.

  In the first and second embodiments, the subject 1 is moved by the moving mechanism 5, but an operator may move it.

DESCRIPTION OF SYMBOLS 1 Subject 2 Radiation source 21 Focus 22 Radiation beam 3 Detector 3a X-ray detection part 4 Stage 5 Movement mechanism 6 Processing apparatus 61 Storage part 62 Calculation part 63 Imaging control part 7 Display apparatus 8 Flat panel detector 81 Gain correction acquisition part 82 Storage unit 83 Calculation unit

Claims (7)

A radiation source that emits radiation;
A stage that is located in the irradiation range of the radiation source and on which a subject can be placed;
A detector that is located on the opposite side of the radiation source across the stage and that detects radiation transmitted through the subject;
A processing device for imaging two-dimensional perspective information of the subject obtained from the detector;
A display device for displaying an image obtained by the processing device;
With
The processor is
Calculating a ratio of the two pieces of fluoroscopic information having different positions of the subject, and generating a two-dimensional ratio image,
The display device
Displaying the ratio image generated by the calculation unit;
Radiation inspection apparatus characterized by this. The stage moves so as to shift the position of the subject,
The radiation source emits radiation before and after moving the stage,
The detector detects each of the radiation transmitted through the subject before and after the movement of the stage;
The calculation unit calculates a ratio of the two pieces of fluoroscopic information before and after the movement of the stage;
The radiation inspection apparatus according to claim 1. The computing unit is
A logarithmic conversion circuit for logarithmically converting the fluoroscopic information;
A difference circuit for calculating a difference between the two logarithmically transformed fluoroscopic information;
An exponent conversion circuit that exponentially converts the value obtained by the difference circuit;
Having
The radiation inspection apparatus according to claim 1 or 2. A flat panel detector including the detector and the processing device;
The flat panel detector is
A gain correction acquisition unit for acquiring a gain correction value for making each pixel value the same value in a state where the subject is placed on the stage;
A storage unit for storing the gain correction value;
Further comprising
The arithmetic unit generates the ratio image by multiplying the fluoroscopic information obtained by moving the subject to a position different from when the gain correction value is acquired and the gain correction value,
The radiation inspection apparatus according to claim 1 or 2. A moving mechanism for moving the stage;
The moving mechanism moves the subject in a direction in which the fluoroscopic information changes little before and after the subject moves.
The radiation inspection apparatus according to any one of claims 1 to 4. A radiation detection method using a radiation inspection apparatus having a radiation source, a detector, and a display device,
A first acquisition step in which radiation detected by the radiation source and transmitted through the subject is detected by the detector, and first fluoroscopic information is acquired;
A moving step of moving the subject after the first acquiring step;
A second acquisition step of acquiring second fluoroscopic information by detecting, by the detector, radiation irradiated by the radiation source and transmitted through the subject moved in the movement step after the movement step;
A calculation step of calculating a ratio between the first perspective information and the second perspective information to generate a two-dimensional ratio image;
Displaying the ratio image on the display device; and
Having
A radiation inspection method characterized by the above. A radiation detection method using a radiation inspection apparatus having a radiation source and a flat panel detector having a gain correction value setting mode for correcting sensitivity variation of each pixel,
An activation step of activating the gain correction value setting mode;
A gain correction acquisition step of detecting radiation irradiated by the radiation source and transmitted through the subject by the flat panel detector, and acquiring a gain correction value;
A moving step of moving the subject;
A fluoroscopic image acquisition step of detecting radiation transmitted through the subject moved in the moving step by the flat panel detector and acquiring a fluoroscopic image;
Having
A radiation inspection method characterized by the above.

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