JP2013198664A - Evaluation image creating apparatus, evaluation device, program, and method for creating evaluation image - Google Patents

Abstract

An image forming apparatus for evaluation capable of evaluating the quality of a radiographic image capturing apparatus with high accuracy is provided.
A first base member having a configuration corresponding to the first base member is obtained by acquiring a first image taken by a radiographic imaging device as an evaluation target for a first base member having radiation transparency (S205). A second image obtained by photographing a phantom provided with a predetermined evaluation pattern made of a member having a radiation shielding property equal to or greater than a predetermined threshold value with a radiographic imaging device is acquired (S213), A first selected from a plurality of images including the first radiographic image and the moved or deformed first radiographic image by moving at least one of the second radiographic images relative to the other or deforming the first radiographic image. A plurality of evaluation images can be obtained by combining the image and a second image selected from a plurality of images including the second radiation image and the moved second radiation image a plurality of times. To create a (S217).
[Selection] Figure 10

Description

  The present invention relates to an evaluation image creation device that generates an evaluation image for evaluating the quality of a radiographic imaging device, an evaluation device including the evaluation image creation device, a program used in the evaluation image device, and The present invention also relates to an evaluation image creating method for generating an evaluation image for evaluating the quality of a radiographic imaging device.

  When manufacturing and selling a radiographic imaging apparatus, it is evaluated in advance whether or not radiographic images can be captured with a certain quality or more for each manufactured product. Some countries stipulate that they cannot be sold if they do not meet the predetermined evaluation criteria. Further, after the radiation image capturing apparatus is delivered, periodic quality control is performed, and it is evaluated whether or not a certain level of quality is ensured for the radiation image capturing apparatus.

  When evaluating the quality of a radiographic imaging apparatus for mammography, a low-contrast resolution test is performed for quality control of the apparatus. In general, this test is performed using a radiographic image obtained by photographing with a radiographic apparatus in which a dedicated phantom is manufactured.

  For example, in the European guidelines for quality assurance in breast (hereinafter referred to as “Euref”), each diameter is measured using a phantom (CDMAM phantom) in which a plurality of gold disks having different diameters and thicknesses are arranged. The recommended method is to test how thick a disc can be taken with respect to the disc. Particularly in European countries, a quality control standard for mammography radiographic imaging devices has been established with reference to the above-mentioned Euref method. Note that the method of Euref is disclosed in Non-Patent Document 1. A method for displaying a radiation image obtained by photographing the CDMAM phantom is disclosed in Patent Document 1.

US Patent 7,729,524 B2 Specification

"Evaluation of software for reading images of the CDMAM test object to assess digital mammography systems" in Proceedings of SPIE, Vol. 6913, 69131C-1

  However, in the case of using the CDMAM phantom as disclosed in Patent Document 1 and Non-Patent Document 1, there is a variation in evaluation in each of a plurality of captured radiographic images, so that detection accuracy becomes a problem. Sometimes. Non-Patent Document 1 discloses a technique for reducing this variation in evaluation. However, since the disk size is as small as 0.1 mm in diameter and 1 μm in thickness, detection accuracy is still achieved even if the variation in evaluation is reduced. May not be enough.

  Therefore, as a method of increasing the detection accuracy, a solution of increasing the number of radiographic images used for evaluation can be considered, but in this case, in order to obtain sufficient detection accuracy, from a statistical viewpoint Since hundreds to thousands of radiographic images are required, there is a problem that the amount of work for photographing the number of radiographic images and the amount of work for inspecting the photographed radiographic images are not realistic. It was.

  The present invention has been made in view of the above problems, and provides an evaluation image creating apparatus, an evaluation apparatus, a program, and an evaluation image creating method capable of evaluating the quality of a radiographic imaging apparatus with high accuracy. Objective.

  In order to achieve the above object, an image forming apparatus for evaluation according to claim 1 is a first radiation obtained by photographing a first base member having radiolucency with a radiographic imaging apparatus to be evaluated. A first evaluation unit configured to acquire an image and a second base member having a configuration corresponding to the first base member are provided with a predetermined evaluation pattern made of a member having a radiation shielding property equal to or higher than a predetermined threshold. Second acquisition means for acquiring a second radiographic image obtained by imaging the acquired phantom with the radiographic imaging device, and moving at least one of the first radiographic image and the second radiographic image with respect to the other Or a first image selected from a plurality of images including the first radiation image and the moved or deformed first radiation image by deforming the first radiation image. And a creation means for creating a plurality of evaluation images by performing a plurality of times of combining a second image selected from a plurality of images including the second radiation image and the moved second radiation image. ing.

  According to the apparatus of claim 1, the first radiographic image obtained by imaging the radiographic first base member with the radiographic imaging device to be evaluated is acquired by the first acquisition means. Is done.

  Here, in the present invention, a predetermined evaluation pattern comprising a member having a radiation shielding property equal to or higher than a predetermined threshold value on the second base member having a configuration corresponding to the first base member by the second acquisition unit. A second radiographic image obtained by imaging the phantom provided with the radiographic imaging device is acquired, and at least one of the first radiographic image and the second radiographic image is applied to the other by the creating unit A first image selected from a plurality of images including the first radiation image and the moved or deformed first radiation image by moving or deforming the first radiation image, and the second radiation image and movement A plurality of evaluation images are created by performing combining a plurality of times with a second image selected from a plurality of images including the second radiation image.

  Thus, according to the apparatus of claim 1, at least one of the radiation image (first radiation image) of the first base member or the radiation image (second radiation image) of the phantom is moved with respect to the other, Alternatively, a plurality of evaluation images can be obtained by synthesizing one of the radiation images of the first base member and one of the radiation images of the phantom in a plurality of combinations after deforming the radiation image of the first base member. As a result, the quality of the radiation image capturing apparatus can be evaluated with high accuracy.

  In addition, this invention is based on the 3rd radiographic image obtained by image | photographing the said phantom with the said radiographic imaging apparatus for the radiographic imaging apparatus made into the said evaluation object like invention of Claim 2. In the radiographic imaging apparatus for which the pre-evaluation process to be evaluated is completed, the imaging conditions for capturing the first radiographic image and the imaging conditions for capturing the second radiographic image are set as signals of the third radiographic image. It may be determined so that a radiation image having the same or substantially the same noise ratio can be acquired. Thereby, since a plurality of images for evaluation can be easily created, detection accuracy can be easily improved.

In particular, in the invention described in claim 2, as in the invention described in claim 3, the imaging conditions for capturing the first radiation image and the imaging conditions for capturing the second radiation image are The radiation exposure dose under the imaging conditions when capturing the third radiation image is q, the radiation exposure dose when capturing the second radiation image is α × q, and the second radiation image is captured. If the radiation exposure dose under the current imaging conditions is β × q, each exposure dose may be determined so that α and β satisfy the following conditions.
Thereby, since a plurality of images for evaluation can be easily created, detection accuracy can be easily improved.

  Further, according to the present invention, as in the invention described in claim 4, the creation unit is provided with the evaluation pattern and the phantom, and includes a member having a radiation shielding property equal to or higher than a predetermined threshold, In addition, at least one of the first radiographic image and the second radiographic image is included so that a position specifying pattern for specifying the position of the evaluation pattern is included in a synthesis region of the first image and the second image. May be moved relative to the other, or the first radiation image may be deformed. Thereby, a plurality of evaluation images can be created without reducing the accuracy of evaluation.

  Further, according to the present invention, as in the invention described in claim 5, the pixel value of the pixel corresponding to each pixel of the second image of the first image is subtracted from the pixel value of each pixel of the second image. A value obtained by adding the average value of the pixel values of each pixel of the first image to the difference may be used as the pixel value of each pixel of the composite image. Thereby, a plurality of evaluation images can be easily created.

  Further, according to the present invention, as in the invention described in claim 6, the first acquisition unit acquires a plurality of the first radiation images obtained by a plurality of times of imaging, and the second acquisition unit includes a plurality of You may make it acquire two or more said 2nd radiographic images obtained by imaging | photography. Thereby, more images for evaluation can be created.

  In the present invention, as in the invention described in claim 7, when the radiation image is moved by the creating means, the first image is the first radiation image, and the first radiation image is the first direction. A radiographic image moved to, a radiographic image obtained by moving the first radiographic image in a second direction different from the first direction, and a radiographic image selected from the radiographic image obtained by rotating the first radiographic image, The second image, the second radiation image, a radiation image obtained by moving the second radiation image in the first direction, a radiation image obtained by moving the first radiation image in the second direction, and the second A single radiographic image selected from the rotated radiographic images may be used. Thereby, a plurality of evaluation images can be easily created.

  Further, according to the present invention, as in the invention described in claim 8, the radiographic imaging device to be evaluated is based on a third radiographic image obtained by imaging the phantom with the radiographic imaging device. In the radiographic imaging apparatus in which the pre-evaluation process to be evaluated is completed, and when the evaluation result obtained by the pre-evaluation process does not satisfy a predetermined condition, the creation unit The first radiation image may be acquired, the second acquisition unit may acquire the second radiation image, and the generation unit may generate the plurality of evaluation images. Thereby, based on the evaluation result of a prior evaluation process, the quality of a radiographic imaging apparatus can be evaluated with high precision as needed.

  On the other hand, in order to achieve the above object, an evaluation device according to claim 9 is characterized in that the evaluation image creation device according to any one of claims 1 to 8 and the plurality of evaluations created by the creation means. Evaluation means for evaluating the radiographic imaging device to be evaluated based on the image for use.

  Therefore, according to the method described in claim 9, since it operates in the same manner as the invention described in claim 1, the quality of the radiographic imaging apparatus is evaluated with high accuracy as in the invention described in claim 1. be able to.

  In order to achieve the above object, an evaluation device according to claim 10 is based on the evaluation image creation device according to claim 2 or 8 and the plurality of evaluation images created by the creation means. Evaluation means for evaluating the radiographic imaging device to be evaluated, and conversion means for converting an evaluation result by the evaluation means into an evaluation result obtained by the preliminary evaluation process.

  Therefore, according to the method of the tenth aspect, since it operates in the same manner as the invention according to the first aspect, the quality of the radiographic imaging apparatus is evaluated with high accuracy as in the case of the first aspect. be able to.

  On the other hand, in order to achieve the above object, a program according to claim 11 is obtained by photographing a first base member having radiation transparency with a radiation image photographing apparatus as an evaluation object. A predetermined evaluation pattern comprising a first acquisition means for acquiring one radiation image, and a second base member having a configuration corresponding to the first base member and a member having a radiation shielding property equal to or higher than a predetermined threshold value. Second acquisition means for acquiring a second radiographic image obtained by imaging the provided phantom with the radiographic imaging device; and at least one of the first radiographic image and the second radiographic image with respect to the other A plurality of images including the first radiographic image and the moved or deformed first radiographic image by moving or deforming the first radiographic image; A plurality of evaluation images are created by combining a selected first image and a second image selected from a plurality of images including the second radiation image and the moved second radiation image a plurality of times. Function as creation means.

  Therefore, according to the program of the eleventh aspect, since the computer can be operated in the same manner as the first aspect of the invention, the quality of the radiographic imaging apparatus can be improved as in the case of the first aspect of the invention. It can be evaluated with high accuracy.

  On the other hand, in order to achieve the above-described object, the evaluation image creating method according to claim 12 is obtained by photographing a first base member having radiation transparency with a radiographic imaging device to be evaluated. A first acquisition step for acquiring a first radiographic image; and a predetermined evaluation pattern comprising a member having a radiation shielding property equal to or higher than a predetermined threshold for a second base member having a configuration corresponding to the first base member. A second acquisition step of acquiring a second radiographic image obtained by imaging the phantom provided with the radiographic imaging device; and at least one of the first radiographic image and the second radiographic image with respect to the other A plurality of images including the first radiographic image and the moved or deformed first radiographic image. A plurality of evaluation images are created by combining a selected first image and a second image selected from a plurality of images including the second radiation image and the moved second radiation image a plurality of times. And a creation step.

  Therefore, according to the evaluation image creating method according to the twelfth aspect, since it operates in the same manner as the invention according to the first aspect, the quality of the radiographic imaging apparatus is improved as in the case of the first aspect. The accuracy can be evaluated.

  According to the present invention, there is an effect that the quality of the radiographic apparatus can be evaluated with high accuracy.

It is a lineblock diagram showing the whole evaluation system composition concerning an embodiment. It is a perspective view which shows the external appearance of the phantom of the evaluation system which concerns on embodiment. (A) is a front view which shows the phantom of the evaluation system which concerns on embodiment, (B) is sectional drawing in the AA cross section of the phantom of the evaluation system which concerns on embodiment. It is a photograph which shows an example of the phantom generally used. It is a perspective view which shows the external appearance of the base member of the evaluation system which concerns on embodiment. It is a notch perspective view which shows the external appearance of the electronic cassette made into evaluation object in the evaluation system which concerns on embodiment. It is a cross-sectional schematic diagram which shows the structure of the 3 pixel part of the radiation detector provided in the electronic cassette made into evaluation object in the evaluation system which concerns on embodiment. It is a block diagram which shows the principal part structure of the electric system of the electronic cassette made into evaluation object in the evaluation system which concerns on embodiment. It is a flowchart which shows the flow of a process of the 1st evaluation processing program which concerns on embodiment. It is a flowchart which shows the flow of a process of the 2nd evaluation processing program which concerns on embodiment. It is a flowchart which shows the flow of a process of the synthesized image generation process program which concerns on embodiment. It is a figure with which it uses for description of the calculation method of the evaluation value in the evaluation system which concerns on embodiment. It is a figure which shows an example of the phantom image in the evaluation system which concerns on embodiment. It is a figure which shows an example of the solid image in the evaluation system which concerns on embodiment. (A) is the schematic which combines with a phantom image after translating a solid image in the main direction (short direction of a base part; X-axis direction shown to FIG. 3 (A)) in the evaluation system which concerns on embodiment. (B) is a parallel image of the solid image in the evaluation system according to the embodiment is translated in the sub-direction (longitudinal direction of the base portion; the Y-axis direction shown in FIG. 3A) and then combined with the phantom image. It is a schematic diagram, (C) is a synthesized image obtained by translating a solid image in the main direction and then synthesized with a phantom image in the evaluation system according to the embodiment, and (D) is an evaluation system according to the embodiment. 3 is a composite image obtained by translating the solid image in the sub-direction and combining it with the phantom image. (A) is a figure which shows the relationship between the position and height in the phantom of the evaluation system which concerns on embodiment, (B) shows the relationship between the position and output signal in the phantom image of the evaluation system which concerns on embodiment. FIG. In the evaluation system which concerns on embodiment, it is a table | surface which shows the specific value of coefficient (alpha) and coefficient (beta) as an example. (A) thru | or (C) is a figure which shows another example of the method of moving or deform | transforming a solid image in the evaluation system which concerns on embodiment.

  Hereinafter, the evaluation system according to the present embodiment will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram showing an overall configuration of an evaluation system 1 according to the present embodiment.

  As shown in FIG. 1, an evaluation system 1 according to the present embodiment is a system for evaluating the quality of a radiographic imaging device, and includes an imaging control device (hereinafter referred to as “console”) 2 and radiation (this embodiment). In the embodiment, a radiation generator 3 that generates X-rays X, a radiation image capturing device (hereinafter referred to as “electronic cassette”) 4 that captures a radiation image with the radiation X generated by the radiation generator 3, and an electronic cassette. 4, a base member 6 for evaluating the quality of the electronic cassette 4, and an evaluation device 7 for performing a process for evaluating the quality of the electronic cassette 4. In the evaluation system 1 according to the present embodiment, the evaluation is performed using the electronic cassette 4 as an evaluation target. However, the evaluation is not limited to this, and an evaluation can be performed using any radiographic imaging apparatus as an evaluation target.

  The console 2 is connected to the radiation generator 3 via the communication cable 8. Further, the console 2 includes an exposure switch (not shown), and the radiation generation apparatus 3 exposes the subject to the radiation X based on the operation of the exposure switch. The console 2 acquires the exposure timing of the radiation X by the radiation generator 3. As a means for the console 2 to acquire the timing of exposure, even if an exposure synchronization signal is acquired from the radiation generation device 3, the operation content is monitored when the exposure switch is operated by monitoring the state of the exposure switch. You may get Further, the console 2 controls the electronic cassette 4 in accordance with the acquired exposure timing, and acquires imaging data.

  The electronic cassette 4 generates image data indicating a radiation image from the incident radiation X, and transmits the generated image data to the console 2 by wireless communication. The console 2 is configured to be capable of wireless communication with the electronic cassette 4 and performs various controls on the electronic cassette 4 by communicating with a predetermined wireless communication method and transmitting a control signal.

  FIG. 2 is a perspective view showing an appearance of the phantom 5 of the evaluation system 1 according to the present embodiment. 3A is a front view showing the phantom 5 of the evaluation system 1 according to this embodiment, and FIG. 3B is a cross-sectional view taken along the line AA of the phantom 5 of the evaluation system 1 according to this embodiment. FIG. 2 and 3, the disk 11 and the lattice pattern 12 are described in a simplified manner for easy understanding of the disk 11 and the lattice pattern 12 described later provided in the phantom 5.

  As shown in FIG. 2, the phantom 5 includes a plate-like base portion 10. The base portion 10 is formed of a member having transparency of the radiation X, has a predetermined thickness (in this embodiment, for example, 0.5 mm), and the size of the radiation imaging apparatus to be evaluated. It is formed in a predetermined size according to the above.

  Further, as shown in FIGS. 2 and 3, a plurality of disk-like discs 11 formed of metal and having different diameters or thicknesses are formed on one surface of the base portion 10 such that the thickness direction of the disc 11 is the same. The base portion 10 is provided so as to coincide with the thickness direction. The plurality of disks 11 are formed as an evaluation pattern used for evaluating the quality of the electronic cassette 4. That is, when the phantom 5 is imaged with the electronic cassette 4, the diameter of each of the plurality of disks 11 having the same diameter and different thicknesses in the captured radiographic image can be recognized. The quality of the electronic cassette 4 is evaluated by inspecting the disk 11.

  In addition, the member which forms the disk 11 should just be a member more than the threshold value by which the shielding property of the radiation X was predetermined, In this embodiment, the point which is easy to process into a thin shape, a point which is hard to rust, and a contrast level | step difference are included. Considering the point that it is easy to form (that is, the transmittance changes according to the change in thickness), the plurality of disks 11 are made of gold.

  In the present embodiment, a plurality of disks 11 are affixed to one surface of the base portion 10. However, the present invention is not limited to this, and a plurality of disks 11 disposed at predetermined positions when photographing the phantom 5 are used. It is sufficient that the disk 11 can be recognized by the captured image, and a plurality of disks 11 may be embedded in the base unit 10.

  Further, as shown in FIGS. 2 and 3, a predetermined lattice pattern 12 is drawn with a film on the surface of the base portion 10 on which the plurality of disks 11 are formed. The grid pattern 12 is formed as a position specifying pattern for specifying the position of the disk 11 when evaluating the quality of the electronic cassette 4. As shown in FIG. 3A, each of the plurality of disks 11 is formed within a minimum unit frame of one of the lattices in the lattice-like pattern 12, and when the phantom 5 is photographed with the electronic cassette 4. In the captured radiographic image, the positions of the plurality of disks 11 are specified using the grid pattern 12 as a position reference. Therefore, the grid pattern 12 only needs to be recognizable in the radiographic image obtained by photographing the phantom 5, and the material forming the grid pattern 12 blocks the radiation X generated from the radiation generator 3 more than a certain level. Any material can be used.

  As shown in FIG. 3, in the phantom 5, the disk 11 having the same thickness in one direction (for example, the X-axis direction shown in FIG. 3) on the surface on which the lattice-like pattern 12 of the base 10 is drawn Are arranged so as to gradually increase, and the disks 11 having the same diameter in one direction (for example, the Y-axis direction shown in FIG. 3) different from the one direction on the surface are gradually increased in thickness. They are arranged so that

  FIG. 4 is a photograph showing an example of a commonly used phantom. An example of a radiographic image obtained by imaging a phantom (radial image shown in FIGS. 12 to 14 to be described later) is a radiographic image obtained by imaging the phantom shown in FIG.

  FIG. 5 is a perspective view showing an appearance of the base member 6 of the evaluation system according to the present embodiment. As shown in FIG. 5, the base member 6 is composed of a member similar to the base portion 10 of the phantom 5, that is, a member having radiation X permeability. The base member 6 is formed with a predetermined thickness (in this embodiment, for example, 20 mm) and a size. However, the base member 6 is different from the phantom 5 in that the base part 10 is not provided with the metal disk-like disk 11 and the lattice-like pattern 12.

  When acquiring a radiographic image, the base member 6 is disposed on the upper side and the lower side of the phantom 5 (hereinafter referred to as “configuration St”), and the X-ray equivalent to the phantom 5 is provided on the base member 6. Shooting is performed using a configuration in which a base member 6 'having a thickness having transmittance is added (hereinafter referred to as "configuration Beta").

  The evaluation device 7 acquires the radiation image of the configuration St captured by the electronic cassette 4 or both of the radiation image of the configuration St and the radiation image of the configuration Beta from the console 2 and uses the acquired radiation image. The quality of the electronic cassette 4 is evaluated. The evaluation device 7 includes a CPU (Central Processing Unit) 7a that executes an evaluation processing program to be described later, a RAM (Random Access Memory) 7b that is a work area when the CPU performs processing, the evaluation processing program, and the evaluation processing program. ROM (Read Only Memory) 7c for storing information necessary for executing the operation, an input unit 7d for inputting information by a user operation, and a storage unit 7e for storing radiation images and evaluation results acquired from the console 2 Yes.

  FIG. 6 is a cutaway perspective view showing the appearance of the electronic cassette 4 to be evaluated in the evaluation system 1 according to the present embodiment.

  As shown in FIG. 6, the electronic cassette 4 includes a housing 20. In order to reduce the weight of the electronic cassette 4, the housing 20 is made of, for example, carbon fiber (carbon fiber), aluminum, magnesium, bionanofiber (cellulose microfibril), or a composite material. Inside the housing 20, a radiation detector 21 and a lead plate 22 are sequentially stacked in this order along the radiation X irradiation direction. Further, on one end side inside the housing 20, a case 23 for housing the cassette control unit and the power supply unit is disposed at a position that does not overlap the radiation detector 21 in the radiation X irradiation direction.

  FIG. 7 is a schematic cross-sectional view showing the configuration of the three pixel portions of the radiation detector 21 provided in the electronic cassette 4 to be evaluated in the evaluation system 1 according to the present embodiment. Other pixel portions have the same configuration and are not shown.

  As shown in FIG. 7, in the radiation detector 21, a signal output unit 25, a sensor unit 26, and a scintillator (phosphor film) 27 are sequentially stacked on an insulating substrate 24. A plurality of signal output units 25 and sensor units 26 are arranged on the substrate 24. The scintillator 27 is formed on the upper part of the sensor unit 26 (the side not facing the substrate 24) via a transparent insulating film 28, and a phosphor that emits light by converting radiation X such as X-rays into light is formed. Is. In the radiation detector 21, the incident radiation X is converted into light by the scintillator 27.

  The wavelength range of the light emitted from the scintillator 27 is preferably the visible light range (wavelength 360 nm to 830 nm). In order to enable monochrome imaging with the radiation detector 3, the wavelength range of green is included. More preferably.

  Specifically, the phosphor used in the scintillator 27 preferably contains cesium iodide (CsI) when imaging using X-rays as the radiation X, and the emission spectrum upon X-ray irradiation is 420 nm to 700 nm. It is particularly preferable to use CsI (Tl) (cesium iodide to which thallium is added). Note that the emission peak wavelength of CsI (Tl) in the visible light region is 565 nm.

  The sensor unit 26 includes an upper electrode 29a, a lower electrode 29b, and a photoelectric conversion film 30 disposed between the upper and lower electrodes. The photoelectric conversion film 30 is made of an organic photoelectric conversion material that generates charges by absorbing light emitted from the scintillator 27.

Since the upper electrode 29a needs to make the light generated by the scintillator 27 incident on the photoelectric conversion film 30, it is preferable that the upper electrode 29a is made of a conductive material that is transparent at least with respect to the emission wavelength of the scintillator 27. It is preferable to use a transparent conductive oxide (TCO) having a high transmittance for visible light and a small resistance value. Although a metal thin film such as Au can be used as the upper electrode 29a, the TCO is preferable because the resistance value tends to increase when an attempt is made to obtain a transmittance of 90% or more. For example, ITO, IZO, AZO, FTO, SnO ₂ , TiO ₂ , ZnO _{2 and the} like can be preferably used, and ITO is most preferable from the viewpoint of process simplicity, low resistance, and transparency. Note that the upper electrode 29a may have a single configuration common to all pixels, or may be divided for each pixel.

  The photoelectric conversion film 30 includes an organic photoelectric conversion material, absorbs the light emitted by the scintillator 27, and generates a charge corresponding to the absorbed light. Thus, the photoelectric conversion film 30 including the organic photoelectric conversion material has a sharp absorption spectrum in the visible range, and electromagnetic waves other than light emitted by the scintillator 27 are hardly absorbed by the photoelectric conversion film 30, and the radiation X Can be effectively suppressed as a result of being absorbed by the photoelectric conversion film 30.

  The organic photoelectric conversion material constituting the photoelectric conversion film 30 is preferably such that its absorption peak wavelength is closer to the emission peak wavelength of the scintillator 27 in order to absorb light emitted by the scintillator 27 most efficiently. Ideally, the absorption peak wavelength of the organic photoelectric conversion material matches the emission peak wavelength of the scintillator 27. However, if the difference between the two is small, the light emitted by the scintillator 27 can be sufficiently absorbed. Specifically, the difference between the absorption peak wavelength of the organic photoelectric conversion material and the emission peak wavelength of the scintillator 27 with respect to the radiation X is preferably within 10 nm, and more preferably within 5 nm.

  Examples of organic photoelectric conversion materials that can satisfy such conditions include quinacridone-based organic compounds and phthalocyanine-based organic compounds. For example, since the absorption peak wavelength in the visible region of quinacridone is 560 nm, if quinacridone is used as the organic photoelectric conversion material and CsI (Tl) is used as the material of the scintillator 27, the difference in peak wavelength can be made within 5 nm. Thus, the amount of charge generated in the photoelectric conversion film 30 can be substantially maximized.

  The electromagnetic wave absorption / photoelectric conversion site in the radiation detector 21 can be composed of an organic layer including a pair of electrodes 29a and 29b and an organic photoelectric conversion film 30 sandwiched between the electrodes 29a and 29b. More specifically, this organic layer is a part that absorbs electromagnetic waves, a photoelectric conversion part, an electron transport part, a hole transport part, an electron blocking part, a hole blocking part, a crystallization preventing part, an electrode, and an interlayer contact improvement. It can be formed by stacking or mixing parts.

  The organic layer preferably contains an organic p-type compound or an organic n-type compound. The organic p-type semiconductor (compound) is a donor organic semiconductor (compound) mainly represented by a hole-transporting organic compound and refers to an organic compound having a property of easily donating electrons. More specifically, an organic compound having a smaller ionization potential when two organic materials are used in contact with each other. Accordingly, any organic compound can be used as the donor organic compound as long as it is an electron-donating organic compound.

  An organic n-type semiconductor (compound) is an acceptor organic semiconductor (compound) mainly represented by an electron-transporting organic compound and refers to an organic compound having a property of easily accepting electrons. More specifically, the organic compound having the higher electron affinity when two organic compounds are used in contact with each other. Accordingly, as the acceptor organic compound, any organic compound can be used as long as it is an electron-accepting organic compound.

  The material applicable as the organic p-type semiconductor and the organic n-type semiconductor and the configuration of the photoelectric conversion film 30 are described in detail in Japanese Patent Application Laid-Open No. 2009-32854, and thus the description thereof is omitted. The photoelectric conversion film 30 may be formed by further containing fullerenes or carbon nanotubes.

  The thickness of the photoelectric conversion film 30 is preferably as large as possible in terms of absorbing light from the scintillator 13. However, when the thickness is more than a certain level, the photoelectric conversion film 30 is generated in the photoelectric conversion film 30 by a bias voltage applied from both ends of the photoelectric conversion film 30. Since electric field strength is reduced and charges cannot be collected, the thickness is preferably 30 nm to 300 nm, more preferably 50 nm to 250 nm, and particularly preferably 80 nm to 200 nm.

  In the radiation detector 21 shown in FIG. 7, the photoelectric conversion film 30 has a single-sheet configuration shared by all pixels, but may be divided for each pixel. Moreover, the photoelectric conversion film 30 does not need to contain an organic photoelectric conversion material.

  The lower electrode 29b is composed of a thin film divided for each pixel. The lower electrode 29b can be made of a transparent or opaque conductive material, and aluminum, silver, or the like can be suitably used. Moreover, the thickness of the lower electrode 29b can be 30 nm or more and 300 nm or less, for example.

  In the sensor unit 26, by applying a predetermined bias voltage between the upper electrode 29a and the lower electrode 29b, one of charges (holes, electrons) generated in the photoelectric conversion film 30 is moved to the upper electrode 29a. And the other can be moved to the lower electrode 29b. In the radiation detector 21 of the present embodiment, a wiring is connected to the upper electrode 29a, and a bias voltage is applied to the upper electrode 29a via this wiring. The polarity of the bias voltage is determined so that electrons generated in the photoelectric conversion film 29 move to the upper electrode 29a and holes move to the lower electrode 29b, but this polarity is opposite. May be.

  The sensor unit 26 constituting each pixel only needs to include at least the lower electrode 29b, the photoelectric conversion film 30, and the upper electrode 29a. In order to suppress an increase in dark current, the electron blocking film 31 and the hole blocking film are used. It is preferable to provide at least one of 32, but it is particularly preferable to provide both.

  The electron blocking film 31 can be provided between the lower electrode 29b and the photoelectric conversion film 30, and when a bias voltage is applied between the lower electrode 29b and the upper electrode 29a, electrons are transferred from the lower electrode 29b to the photoelectric conversion film 30. It is possible to suppress the dark current from increasing due to the injection of.

  An electron donating organic material can be used for the electron blocking film 31. The material used for the electron blocking film 31 may be selected according to the material of the adjacent electrode, the material of the adjacent photoelectric conversion film 30, and the like. The electron affinity is 1.3 eV or more from the work function (Wf) of the adjacent electrode material. Those having a large (Ea) and an Ip equivalent to or smaller than the ionization potential (Ip) of the material of the adjacent photoelectric conversion film 30 are preferable. The material applicable as the electron donating organic material is described in detail in Japanese Patent Application Laid-Open No. 2009-32854, and thus the description thereof is omitted.

  The thickness of the electron blocking film 31 is preferably 10 nm or more and 200 nm or less, more preferably 30 nm or more and 150 nm or less, and particularly preferably, in order to reliably exhibit the dark current suppressing effect and prevent a decrease in the photoelectric conversion efficiency of the sensor unit 26. It is 50 nm or more and 100 nm or less.

  The hole blocking film 32 can be provided between the photoelectric conversion film 30 and the upper electrode 29a. When a bias voltage is applied between the lower electrode 29b and the upper electrode 29a, the hole blocking film 32 is transferred from the upper electrode 29a to the photoelectric conversion film 30. It is possible to suppress the increase in dark current due to the injection of holes.

  An electron-accepting organic material can be used for the hole blocking film 32. The thickness of the hole blocking film 12 is preferably 10 nm or more and 200 nm or less, more preferably 30 nm or more and 150 nm or less, and particularly preferably, in order to surely exhibit the dark current suppressing effect and prevent a decrease in photoelectric conversion efficiency of the sensor unit 26. Is from 50 nm to 100 nm. The material used for the hole blocking film 32 may be selected according to the material of the adjacent electrode, the material of the adjacent photoelectric conversion film 30, and the like. Ionization is 1.3 eV or more from the work function (Wf) of the material of the adjacent electrode. A material having a large potential (Ip) and an Ea equivalent to or larger than the electron affinity (Ea) of the material of the adjacent photoelectric conversion film 30 is preferable. Since the material applicable as the electron-accepting organic material is described in detail in Japanese Patent Application Laid-Open No. 2009-32854, description thereof is omitted.

  In the case where the bias voltage is set so that holes move to the upper electrode 29a and electrons move to the lower electrode 29b among the charges generated in the photoelectric conversion film 30, the electron blocking film 31 and the hole blocking are set. What is necessary is just to arrange | position reversely the position with the film | membrane 32. FIG.

  In the substrate 24, the signal output unit 25 described above is formed on the surface of each pixel facing the lower electrode 29b. The signal output unit 25 corresponds to the lower electrode 29b, a capacitor 33 that accumulates the charges transferred to the lower electrode 29b, and a field effect thin film transistor (Thin) that converts the charges accumulated in the capacitor 33 into an electric signal and outputs the electric signal. Film Transistor, hereinafter simply referred to as a thin film transistor) 34 is formed. The region in which the capacitor 33 and the thin film transistor 34 are formed has a portion that overlaps the lower electrode 29b in a plan view. With this configuration, the signal output unit 25 and the sensor unit 26 in each pixel are thick. There will be overlap in the vertical direction. In order to minimize the plane area of the radiation detector 21 (pixel), it is desirable that the region where the capacitor 33 and the thin film transistor 34 are formed is completely covered by the lower electrode 29b.

  The capacitor 33 is electrically connected to the corresponding lower electrode 29b through a wiring made of a conductive material penetrating an insulating film 35 provided between the substrate 24 and the lower electrode 29b. Thereby, the electric charge collected by the lower electrode 29b can be moved to the capacitor 33.

  In the thin film transistor 34, a gate electrode, a gate insulating film, and an active layer (channel layer) (not shown) are stacked, and a source electrode and a drain electrode are formed on the active layer at a predetermined interval. In addition, the substrate 24 is provided with an insulating layer for ensuring insulation, a gas barrier layer for preventing permeation of moisture and oxygen, an undercoat layer for improving flatness or adhesion to electrodes, and the like. May be.

  As described above, the substrate 24, the insulating film 35, the lower electrode 29 b, the electron blocking film 31, the photoelectric conversion film 30, the hole blocking film 32, the upper electrode 29 a, and the transparent insulating film 28 are sequentially stacked, so that the TFT substrate is obtained. A sensor substrate 36 is formed. Note that at least one of the electron blocking film 31 and the hole blocking film 32 may not be provided if unnecessary.

  FIG. 8 is a configuration diagram illustrating a main configuration of the electrical system of the electronic cassette 4 to be evaluated in the evaluation system 1 according to the present embodiment.

  As shown in FIG. 8, in the radiation detector 21 built in the electronic cassette 4, the gate line driver 40 is disposed on one side of two adjacent sides, and the signal processing unit 41 is disposed on the other side. Each gate wiring 42 of the sensor substrate 36 is connected to the gate line driver 40, and each data wiring 43 of the sensor substrate 36 is connected to the signal processing unit 41.

  Each thin film transistor 34 on the sensor substrate 36 is sequentially turned on in a row unit by a signal supplied from the gate line driver 40 via the gate wiring 42, and the electric charge read out by the thin film transistor 34 in the on state is converted into an electric signal. The data wiring 43 is transmitted and input to the signal processing unit 41. As a result, the charges are sequentially read out in units of rows, and a two-dimensional radiation image can be acquired.

  Although not shown, the signal processing unit 41 includes an amplification circuit and a sample hold circuit for amplifying an input electric signal for each data wiring 43, and the electric signal transmitted through the individual data wiring 43. Is amplified by the amplifier circuit and then held in the sample hold circuit. Further, a multiplexer and an A / D (analog / digital) converter are connected in order to the output side of the sample and hold circuit, and the electric signals held in the individual sample and hold circuits are sequentially (serially) input to the multiplexer. The digital image data is converted by an A / D converter.

  An image memory 44 is connected to the signal processing unit 41, and image data output from the A / D converter of the signal processing unit 41 is sequentially stored in the image memory 44. The image memory 44 has a storage capacity capable of storing a predetermined number of image data, and image data obtained by imaging is stored in the image memory 44 every time a radiographic image is captured.

  The image memory 44 is connected to the cassette control unit 45. The cassette control unit 45 includes a microcomputer, and includes a CPU 46, a memory 47 including a ROM and a RAM as recording media, and a non-volatile storage unit 48 formed of a flash memory or the like, and the electronic cassette 1 as a whole. Overall control of the operation.

  Further, a wireless communication unit 49 is connected to the cassette control unit 45. The wireless communication unit 49 is compatible with a wireless local area network (LAN) standard represented by IEEE (Institute of Electrical and Electronics Engineers) 802.11a / b / g, etc. Control transmission of various information. The cassette control unit 45 can wirelessly communicate with an external device such as a console via the wireless communication unit 49, and can transmit and receive various types of information to and from the external device.

  By the way, in the evaluation system 1 according to the present embodiment, when the evaluation device 7 evaluates the quality of the electronic cassette 4, first, as a first evaluation process as a pre-evaluation process, a plurality of images photographed under the same shooting conditions are used. Evaluation is performed using the radiation image of the configuration St of the sheet (for example, 8 sheets in the present embodiment), and the quality of the electronic cassette 4 is passed (a predetermined condition is satisfied) or rejected (a predetermined condition) Is not satisfied). When it is determined that the first evaluation process is unsuccessful, the evaluation device 7 further improves the quality of the electronic cassette 4 by performing an evaluation with a second evaluation process having a higher detection accuracy than the first evaluation process. The accuracy can be evaluated.

  In the second evaluation process, evaluation is performed using hundreds to thousands of radiation images (hereinafter, also referred to as “phantom images”) having a structure St photographed under the same imaging conditions. This is because the greater the number of shots, the better the detection accuracy. However, as described above, since it is practically difficult to capture several hundred to thousands of radiation images, in the present embodiment, a plurality of (eight in the present embodiment) sheets are used as the second evaluation process. While capturing radiographic images of the configuration St, a plurality of (in the present embodiment, four) radiographic images of the configuration Beta (hereinafter also referred to as “solid images”) are captured, and the solid images are moved to a plurality of types. By transforming (in this embodiment, the case where the image is moved) and combining any one of the phantom images and any one of the solid images, respectively, hundreds to thousands of images are combined. The radiation image of the sheet structure St is created in a pseudo manner, and the quality of the electronic cassette 4 is evaluated using this. In the calculation, a plurality of composite images obtained by moving or transforming the solid images by different methods as described above and combining the solid images with the phantom images are generated, so that the radiation images of hundreds to thousands of St images are formed. The same result as that obtained when shooting is obtained.

  For example, when the evaluation is performed using 48 radiation images of the configuration St, the variation coefficient σ indicating the variation in evaluation is σ = ± 8 to 10 for the disk 11 having a diameter of 0.1 mm and a thickness of 1 μm. % (See Non-Patent Document 1). The evaluation result varies depending on the exposure dose of radiation X, radiation quality, IP (radiation image conversion panel), characteristics of the reading device, characteristics of the radiation generation device 3, individual differences of the phantom 5, and the like. The difference in evaluation results due to these factors may be about 5% or less. Therefore, the evaluation accuracy when the number of radiographic images is 8 is insufficient, and the accuracy of the variation coefficient σ = ± 1% is required.

  However, in order to set the variation σ = ± 1%, it is necessary to evaluate 512 to 800 radiographic images, and an image acquisition time for acquiring this number of radiographic images is generally about 15 hours.

Therefore, in the present embodiment, in the second evaluation process, the following (1) to (3) are adopted as a method of setting the evaluation accuracy to variation σ = ± 1% while shortening the image acquisition time.
(1) Photographing is performed with an exposure dose larger than the exposure dose in the first evaluation process for the configuration (configuration St) in which the base member 6 is disposed on each of the upper side and the lower side of the phantom 5.
(2) In order to change the S / N (signal-to-noise ratio) improved by photographing with a large dose to a value equivalent to that at the time of the first evaluation process, a disk using an image obtained by adding a solid image to a phantom image 11 is detected.
(3) The image acquisition time is shortened by generating a plurality of moving solid images obtained by translating the solid images and synthesizing the moving solid images and the phantom images.

  In the second evaluation process, in order to improve the detection accuracy, the exposure dose of the radiation X of the configuration St is set to an exposure dose larger than the exposure dose of the radiation X of the first evaluation process. A solid image is added to the phantom image so that the S / N improved by increasing the exposure dose of the radiation X in the second evaluation process and taking the S / N equivalent to that in the first evaluation process. Detection is performed using the obtained image.

  In order to make the exposure dose in the second evaluation process larger than the exposure dose in the first evaluation process, the tube current in the second evaluation process is changed to the tube current in the first evaluation process with a constant exposure time. The exposure time in the second evaluation process is made larger than the exposure time in the first evaluation process with the tube current being constant, or the tube current and the exposure time in the second evaluation process are set in the first evaluation process. There is a method of making it larger than the tube current and the exposure time.

In the first evaluation process, the exposure dose of the configuration St was acquired as β × q in the image A acquired as the exposure dose of the configuration St as q and the phantom image acquired as the exposure dose of the configuration St as α × q. For the image B created by adding the solid images, the relational expression of α and β when the detection result of the disk 11 is equal between the image A and the image B is the following expression (2). A method for deriving the relational expression will be described later.

  Next, the operation of the evaluation system 1 according to this embodiment will be described.

  9 to 11 are flowcharts showing the processing flow of the evaluation processing program according to this embodiment. The CPU 7a of the evaluation device 7 performs a first evaluation process and a second evaluation process as the evaluation process. FIG. 9 is a flowchart showing the flow of processing of the first evaluation processing program for performing the first evaluation processing, and FIGS. 10 and 11 are flowcharts showing the flow of processing of the second evaluation processing program for performing the second evaluation processing. Each program is stored in advance in a predetermined area of a ROM 7c, which is a recording medium provided in the evaluation device 7. The CPU 7a performs the evaluation process program (the first evaluation process program and the second evaluation process) at a predetermined timing (in this embodiment, an instruction input for execution is performed from the input unit 7d of the evaluation device 7). (Including processing program).

  First, the first evaluation process will be described based on the flowchart shown in FIG. When the user starts the evaluation of the quality of the electronic cassette 4 by the evaluation system 1, for example, the configuration St is set at a predetermined position of the electronic cassette 4 (a position where the entire phantom 5 is included in the imaging region of the electronic cassette 4). Install.

  After the configuration St is installed in step S101, in step S103, the CPU 7a sets imaging conditions indicating the exposure dose and the like of the radiation X exposed to the configuration St and the electronic cassette 4. The photographing conditions at this time are the photographing conditions input by the user via the input unit 7d, the photographing conditions set in advance in the first evaluation processing program, or are incorporated as options in the first evaluation processing program in advance. The photographing conditions selected by the user via the input unit 7d among the existing photographing conditions may be used.

  In step S <b> 105, the CPU 7 a causes the radiation generator 3 to generate radiation X, exposes the radiation St to the configuration St under the set imaging conditions, and captures the radiation image of the configuration St by the electronic cassette 4. In step S107, the CPU 7a acquires radiation image information indicating the radiation image captured in step S105 from the electronic cassette 4 and stores it in the storage unit 7e.

  In step S109, the CPU 7a determines whether or not the required number of times (8 times in the present embodiment) of shooting (shooting in step S105) has been completed. When it is determined that the required number of shootings has not been completed, the CPU 7a repeats the processes of steps S105 to S109 until the predetermined number of shootings is completed. When the radiographic image capturing is repeated, the on / off state of the generation of the radiation X by the radiation generation device 3 may be switched, or the radiation is generated in the electronic cassette 4 while the generation of the radiation X by the radiation generation device 3 is continued. Depending on the exposure dose of X, the imaging of one radiation image may be terminated and the imaging of the next radiation image may be started.

  Here, the phantom 5 is provided with a plurality of minute disks 11 in units of μm, but each disk 11 is not necessarily formed in the shape as designed. When the shape of the disk 11 is different from the design among the phantoms 5, even if the phantom 5 can be photographed with high precision by the electronic cassette 4, the evaluation result using the phantom image is the same apparatus. Also varies from phantom to phantom.

  Therefore, the evaluation device 7 stores phantom correction data for correcting the shape of each disk 11 provided in the phantom 5 in the storage unit 7e in advance. The phantom correction data is recorded in advance on a recording medium such as a CDROM for each phantom as data for reducing the difference in evaluation results due to individual phantom differences. Further, in this recording medium, the position within the frame of the disk 11 existing in the frame, the diameter of the disk 11, corresponding to the position in the minimum unit frame delimited by the lattice pattern 12, Information indicating the thickness of the disk 11 is recorded as disk data. The storage unit 7e stores these data recorded on the recording medium.

  If it is determined in step S109 that the predetermined number of times of shooting has been completed, the CPU 7a acquires phantom correction data corresponding to the phantom 5 in step S111. In addition, the acquisition method in this case is not limited to the method of acquiring the phantom correction data from the storage unit 7e, and may be a method of acquiring from the storage medium or a method of acquiring from outside by telecommunications.

  In step S113, the CPU 7a uses the predetermined number (in this embodiment, eight) of the captured images stored in step S107 and the phantom correction data acquired in step S111 to store the electronic cassette 4. An evaluation value is calculated. The evaluation value at this time is calculated by a calculation method described below.

  FIG. 12 is a diagram for explaining an evaluation value calculation method. In the present embodiment, as shown in FIG. 12, in the radiation image of the phantom 5, in the region 12 a within the minimum unit frame delimited by the grid pattern 12, the minimum unit delimited by the grid pattern 12 is used. While shifting the search area (window) R having the same shape as the disk 11 existing in the frame by one pixel, the average value of the pixel values in the search area R is obtained at each position, and the search area R having the smallest average value is obtained. It is determined that the disk exists within this frame. When the disk 11 existing in the frame of the minimum unit delimited by the lattice pattern 12 is captured, the radiation X is blocked by the disk 11, so that the search region R having the smallest average value is the radiation of the phantom 5. This is because the image corresponds to the area 11 a corresponding to the disk 11.

  The CPU 7a compares the area determined as the disk existence area with the disk data stored in the storage unit 7a, and the search area R determined as the disk existence area is the disk 11 actually provided in the phantom 5. If the area matches (or substantially matches), it is determined as “1”, and if it does not match (or approximately matches), it is determined as “0”. Since the phantom 5 is provided with a plurality of discs 11 having different diameters and thicknesses, the probability that the disc 11 having the diameter and the thickness among the plurality of captured radiographic images is determined as “1” is predetermined. If it is equal to or greater than%, it is determined that the disk 11 having the diameter and the thickness is visible by sensory evaluation. The minimum disc 11 thickness that can be photographed for each diameter is derived as an evaluation value.

  When calculating the evaluation value of the electronic cassette 4, the CPU 7a determines whether or not the calculated evaluation value satisfies a predetermined criterion in step S115. The predetermined determination criterion may be input by the user via the input unit 7d and stored in the storage unit 7e, or may be set in advance by the first evaluation processing program.

  When it is determined in step S115 that the evaluation value satisfies a predetermined condition, in step S117, the CPU 7a passes the determination result of the electronic cassette 4 as a pass. In step S117, the CPU 7a stores information indicating the determination result in the storage unit 7e, and ends the evaluation processing program. Note that the information indicating the determination result may include information indicating the radiation image stored in step S107 and information indicating the evaluation value calculated in step S113. As described above, the evaluation value in this case may be a numerical value indicating the minimum thickness of the disk 11 that can be photographed for each diameter, and the contrast that can be expressed in the photographed image of the electronic cassette 4 is indicated as a percentage. It may be a numerical value, or both of them.

  On the other hand, when it is determined in step S115 that the evaluation value does not satisfy the predetermined condition, in step S121, the CPU 7a rejects the determination result of the electronic cassette 4. Then, the CPU 7a continues to perform the second evaluation process.

  Here, the second evaluation process will be described based on the flowchart shown in FIG.

  In the second evaluation process, first, in step S201, as in step S101, the user installs the configuration St in the electronic cassette 4. Note that if the configuration St is installed in the electronic cassette 4 in the first evaluation process and remains as it is, the process of step S101 may be omitted.

  After the configuration St is installed in step S201, in step S203, the CPU 7a sets shooting conditions for shooting of the configuration St in the electronic cassette 4. The shooting conditions of the configuration St at this time are set as follows based on the shooting conditions set in advance in the first evaluation processing program. When the exposure dose of radiation X under the imaging conditions set in advance in the first evaluation processing program (the exposure dose in step S103 of the first evaluation processing program) is q, the exposure dose of radiation X in step S203 Is set to α × q (α> 1). The larger the coefficient α, the better, and the maximum exposure dose that can be generated by the radiation generator 3 is set.

  When the imaging conditions are set, in step S <b> 205, the CPU 7 a causes the radiation generator 3 to generate the radiation X, irradiates the configuration St with the radiation X, and captures a phantom image with the electronic cassette 4. In step S207, the CPU 7a acquires radiation image information indicating the radiation image captured in step S205 from the electronic cassette 4 and stores it in the storage unit 7e of the evaluation device 7.

  In step S208, as in step S109, the CPU 7a determines whether the predetermined number of times (in this embodiment, eight times) of shooting (shooting in step S205) has been completed, and the predetermined number of times. Steps S205 to S208 are repeated until the shooting is completed.

  Next, in step S <b> 209, the user installs the configuration Beta on the electronic cassette 4. The user installs the configuration Beta at a predetermined position of the electronic cassette 4 (substantially the same position as the installation position of the configuration St). In the present embodiment, the CPU 7a determines that the configuration Beta is installed when the operation input through the input unit 7d is performed.

  After the configuration Beta is installed in step S209, in step S211, the CPU 7a sets shooting conditions for shooting the configuration Beta in the electronic cassette 4. The shooting conditions of the configuration Beta at this time are set as follows based on the shooting conditions set in advance in the first evaluation processing program, as in the case of setting the shooting conditions of the configuration St in step S203. When the exposure dose of radiation X under the imaging conditions set in advance in the first evaluation processing program (the exposure dose in step S103 of the first evaluation processing program) is q, the exposure dose of radiation X in step S211 Is set to β × q (β> 1). The coefficient β at this time is determined so as to satisfy the above formula (2).

  When the imaging conditions are set, in step S213, the CPU 7a causes the radiation generator 3 to generate the radiation X, irradiates the configuration Beta with the radiation X, and captures a radiographic image of the configuration Beta with the electronic cassette 4. In step S215, the CPU 7a acquires radiation image information indicating the radiation image captured in step S213 from the electronic cassette 4 and stores it in the storage unit 7e.

  In step S216, as in step S109, the CPU 7a determines whether or not the predetermined number of times (four times in this embodiment) of shooting (shooting in step S213) has been completed, and the predetermined number of times. Steps S213 to S216 are repeated until the shooting is completed.

  In step S217, the CPU 7a performs a composite image generation process for generating a composite image of the phantom image captured in step S205 and the solid image captured in step S213.

  Here, the composite image generation processing will be described based on the flowchart shown in FIG.

  The evaluation device 7 displays the solid image in the main direction (short direction of the base portion 10; the X-axis direction shown in FIG. 3A) and the sub-direction (longitudinal direction of the base portion 10; Y-axis shown in FIG. 3A). A plurality of radiation images are created as moving solid images, each of which is translated by a predetermined distance (1 mm in this embodiment) separately in each direction.

  First, in step S301, the CPU 7a creates a plurality of types of moving solid images by moving the pixel values of the respective pixels in the solid image so as to move in parallel in the main direction by a predetermined number of pixels. Note that the CPU 7a performs processing for generating the moving solid image for each solid image.

  In step S303, the CPU 7a generates a plurality of types of moving solid images by moving the pixel values of the pixels in the solid image so as to move in parallel in the sub-direction by a predetermined number of pixels. Note that the CPU 7a performs processing for generating the moving solid image for each solid image.

In step S305, the CPU 7a creates a composite image by combining any one of the phantom images with either the solid image or the moving solid image moved in step S301 or S303. The CPU 7a performs the process of creating the composite image so that all the phantom images are combined with all the solid images and the moving solid images. Also, the pixel value X _{i, j} when the phantom image and the solid image are combined includes the pixel value f _{i, j} of the phantom image, the pixel value b _{i, j of} the solid image, and the average value ba of the pixel values of the solid image. Then, it calculates | requires by following formula (3).
In addition, when the pixel value is linear, the logarithm is calculated.

  In the present embodiment, when the solid image is moved in the second evaluation process, the solid image is translated by a predetermined distance within a range in which the grid pattern 12 and the edge of the solid image do not overlap. When one solid image can be translated k times in the main direction and h times in the sub direction, the evaluation apparatus 7 translates one solid image k times in the main direction, By translating in the direction h times, k × h images can be created. Accordingly, (k × h + 1) solid images can be used from one solid image, including a solid image that is not translated (a solid image that has been captured). In addition, when m phantom images and n solid images are taken, all combinations of phantom images and solid images can be performed by selecting and combining one phantom image and one solid image multiple times. And a total of (m × (n × (k × h + 1)) composite images can be generated.

  Specifically, in the present embodiment, when the solid image is translated by 1 mm by 1 mm so that the grid pattern 12 and the edge of the solid image do not overlap, it can be translated by 6 mm in the main direction, and also in the sub direction. Similarly, when the translation is possible by ± 2 mm in the sub direction when the translation is performed in increments of 1 mm, in this case, the evaluation apparatus 7 translates one solid image six times in the main direction. 24 images can be created by translating the sub-direction four times (twice in the plus direction and twice in the minus direction). Therefore, 25 solid images can be created from one solid image, including a solid image that is not moved in parallel (a solid image that has been captured). Therefore, in this embodiment, since 8 phantom images and 4 solid images are taken, when combining each phantom image and 1 solid image in all combinations, a total of 800 (8 × (4 Sheet × 25 sheets)) can be generated.

  As described above, in the evaluation system 1 according to the present embodiment, for example, when evaluation is performed using eight phantom images in the first evaluation process and the evaluation is rejected, 800 composite images are used in the second evaluation process. By performing the evaluation, the quality of the electronic cassette 4 can be evaluated with high accuracy.

  FIG. 13 is a diagram illustrating an example of a phantom image in the evaluation system according to the present embodiment. FIG. 14 is a diagram illustrating an example of a solid image in the evaluation system according to the present embodiment.

  As shown in FIG. 13, it can be understood that the phantom image has been photographed to such an extent that the lattice-like pattern 12 is visible. In addition, although it is difficult to visually confirm the phantom image, some of the plurality of disks 11 are photographed. On the other hand, as shown in FIG. 14, it can be understood that an object that can be visually confirmed is not photographed in the solid image.

  FIG. 15A is a schematic diagram in which the solid image 5a is translated in the main direction and then combined with the phantom image 6a. FIG. 15B is a diagram in which the solid image 5a is translated in the sub direction. FIG. 15C is a synthesized image obtained by translating the solid image 5a in the main direction and then synthesized with the phantom image 6a, and FIG. This is a composite image obtained by translating the solid image 5a in the sub-direction and compositing with the phantom image 6a. As shown in FIGS. 15A and 15B, when the solid image 6a is translated with respect to the phantom image 5a and the phantom image 5a and the solid image 6a are combined, FIG. 15C and FIG. A radiation image as shown in D) is taken.

  In step S219, the CPU 7a calculates an evaluation value from the composite image generated in step S305 by the same method as in step S113.

  In step S221, the CPU 7a converts the evaluation value in the second evaluation process calculated in step S219 into the evaluation value in the first evaluation process using the conversion table stored in the storage unit 7e.

  Conversion as shown in the table below for converting the evaluation result of the second evaluation process into the evaluation result of the first evaluation process so that the evaluation result of the second evaluation process is equivalent to the evaluation result of the first evaluation process By creating a table in advance and storing it in the storage unit 7e, the evaluation result of the second evaluation process is converted into the evaluation result of the first evaluation process using this conversion table. This conversion table is created based on the photographing conditions in the first evaluation process, the detection values of the first evaluation process and the second evaluation process, and the like.

  As described above, the determination result of the second evaluation process has higher detection accuracy than the determination result of the first evaluation process. Therefore, even if it is determined that “if the first evaluation process, interpretation is possible up to amm with an error ± Δa”, the second evaluation process indicates that “this imaging apparatus has an error ± Δb (Δa <Δb) can be read ”. That is, the reliability of the thickness amm that can be interpreted by the second evaluation process with high detection accuracy is increased.

  In step S223, the CPU 7a stores information indicating the evaluation value converted in step S221 in the storage unit 7e. The information indicating the converted evaluation value may include information indicating the radiation image synthesized in step S217 and information indicating the evaluation value in the second evaluation process calculated in step S219. .

  Here, a method for determining the coefficient α and the coefficient β described above will be described.

  FIG. 16A is a diagram showing a relationship between the position and height in the phantom 5 of the evaluation system 1 according to this embodiment, and FIG. 16B is a diagram in the phantom image of the evaluation system 1 according to this embodiment. It is a figure which shows the relationship between a position and an output signal.

A method for deriving the result relational expression will be described. If you exposure with a dose q, the output O _n which is output to the signal processing unit 41,
It becomes.

Here, the noise is expressed as δOn. Quantum noise (in this embodiment, X-ray quantum noise) is dominant as the noise, and the quantum noise is represented by the right side of Expression (5). Further, the variation δy of the linear function y = f (x) is expressed by the following equation (6).

Let the exposure dose in the evaluation 1 of the configuration St be q. In addition, the exposure dose of the configuration St in evaluation 2 is α × q, and the exposure dose of the configuration Beta is β × q. A relational expression between α and β when the S / N of the composite image of the phantom image and the solid image of evaluation 2 is equal to the S / N of the image acquired in evaluation 1 is obtained. When the configuration St is exposed with an exposure dose of α × q, the reader output O _cd is
It becomes.

In addition, when the configuration Beta is exposed with an exposure dose of β × q, the reader output O _beta is
It becomes.

The output O _t output to the signal processing unit 41 shown in FIG. 16B in the area a <x <b of the disk 11 shown in FIG. 16A is as follows when O _cd and O _beta are added. It is expressed by equation (11).

From the above, in order to make the S / N of the composite image of the phantom image and the solid image of evaluation 2 equal to the S / N of the phantom image and the solid image acquired in evaluation 1,
Α and β may be determined so that

here,
So,
It is sufficient to determine α and β so that

  FIG. 17 is a table showing, as an example, specific values of the coefficient α and the coefficient β obtained from the equation (15) in the evaluation system 1 according to the present embodiment.

  In the evaluation system 1 according to the embodiment, when generating a composite image in the second evaluation process, a solid image is moved to generate a moving solid image. However, the present invention is not limited to this, and the phantom image may be moved. good. Similarly, in this case, when the phantom image is moved in the second evaluation process, the phantom image is moved by a predetermined distance within a range where the grid pattern 12 and the edge of the solid image do not overlap.

  18A to 18C are diagrams illustrating another example of a method for moving or deforming a solid image in the evaluation system 1 according to the embodiment. In the evaluation system 1 according to the embodiment, when generating a composite image, the solid image is translated in either the X-axis direction or the Y-axis direction. However, the present invention is not limited to this, and as illustrated in FIG. In addition, the solid image 6a may be translated with respect to the phantom image 5a in an oblique direction with respect to the X axis direction or the Y axis direction, and the solid image 6a may be rotated with respect to the phantom image 5a. Alternatively, the phantom image may be translated in the X-axis direction or the Y-axis direction obliquely with respect to the solid image, and the phantom image may be rotated with respect to the solid image. Similarly, in these cases, when the phantom image or the solid image is moved in the second evaluation process, the phantom image or the solid image is moved within a range in which the grid pattern 12 and the edge of the solid image do not overlap.

  In steps S301 and S303, the solid image may be rotated instead of translated, and both the parallel movement and the rotational movement may be performed. Further, in step S301 and S303, not only the solid image but also the phantom image is translated or rotated, and when the phantom image and the solid image are combined in step S305, the moved phantom image and the moved solid image are displayed. And may be combined.

  As shown in FIG. 18B, a modified solid image 6b in which the solid image is deformed by moving the pixel value of each pixel of the solid image 6a in a different direction for each region where the pixel exists is generated. Thus, as shown in FIG. 18C, the deformed solid image 6b may be combined with the phantom image 5a. Note that the method for deforming a solid image is not limited to this method. That is, the solid image may be synthesized with respect to the entire area of the phantom image corresponding to the plurality of disks 11 and the grid pattern 12 of the phantom 5. Therefore, if this condition is satisfied, the solid image may be enlarged or reduced, or affine transformation may be performed.

  Also, in steps S301 and S303, the solid image is translated, rotated, or deformed to translate or rotate the phantom image, and when the phantom image and the solid image are combined in step S305, the moved phantom image A solid image that has been moved or deformed may be combined.

  In the evaluation system 1 according to the embodiment, eight phantom images are captured in the first evaluation process and the quality of the electronic cassette 4 is evaluated using the eight phantom images. However, the number of phantom images is limited to this. Alternatively, one phantom image may be taken and the quality of the electronic cassette 4 may be evaluated using one phantom image, or a plurality of phantom images may be taken and electronic using a plurality of phantom images. The quality of the cassette 4 may be evaluated.

  Moreover, in the evaluation system 1 which concerns on embodiment, although the evaluation apparatus 7 performs the 1st evaluation process and the 2nd evaluation process which were mentioned above, it is not limited to this, The console 2 performs a 1st evaluation process and a 2nd evaluation process. You may do it.

  DESCRIPTION OF SYMBOLS 1 ... Evaluation system, 2 ... Console, 3 ... Radiation generator, 4 ... Electronic cassette, 5 ... Phantom, 6 ... Base member, 7 ... Evaluation device, 7a ... CPU, 7b ... RAM, 7c ... ROM, 7d ... Input part , 7e ... storage unit, 8 ... external cable, 10 ... base unit, 11 ... disk, 11a ... area corresponding to the disk, 12 ... grid pattern, 12a ... area corresponding to the grid pattern, 20 ... housing , 21 ... Radiation detector, 22 ... Lead plate, 23 ... Case, 24 ... Substrate, 25 ... Signal output part, 26 ... Sensor part, 27 ... Scintillator, 28 ... Transparent insulating film, 29a ... Upper electrode, 29b ... Lower electrode , 30 ... photoelectric conversion film, 31 ... electron blocking film, 32 ... hole blocking film, 33 ... capacitor, 34 ... thin film transistor, 35 ... insulating film, 36 ... sensor substrate, 40 ... gate Line driver, 41 ... Signal processing unit, 42 ... Gate wiring, 43 ... Data wiring, 44 ... Image memory, 45 ... Cassette control unit, 46 ... CPU, 47 ... Memory, 48 ... Storage unit, 49 ... Wireless communication unit, X …radiation.

Claims (12)

First acquisition means for acquiring a first radiographic image obtained by imaging a radiographic first base member with a radiographic imaging device as an evaluation target;
Photographing a phantom in which a predetermined evaluation pattern made of a member having a radiation shielding property equal to or higher than a predetermined threshold is provided on the second base member having a configuration corresponding to the first base member by the radiation image capturing apparatus Second acquisition means for acquiring a second radiation image obtained by
At least one of the first radiographic image and the second radiographic image is moved with respect to the other, or the first radiographic image is deformed to convert the first radiographic image and the moved or deformed first radiographic image. A plurality of evaluations are performed by combining a first image selected from a plurality of images including a second image selected from a plurality of images including the second radiation image and the moved second radiation image a plurality of times. Creating means for creating an image,
An image creating apparatus for evaluation comprising: The radiographic image capturing apparatus to be evaluated is a radiographic image capturing apparatus for which a preliminary evaluation process for evaluating based on a third radiographic image obtained by capturing the phantom with the radiographic image capturing apparatus is completed,
A radiographic image having the same or substantially the same signal-to-noise ratio as that of the third radiographic image can be acquired with respect to the radiographing conditions for capturing the first radiographic image and the radiographic conditions for capturing the second radiographic image. The image creating apparatus for evaluation according to claim 1 defined. The imaging conditions for capturing the first radiographic image and the imaging conditions for capturing the second radiographic image are set to q as the radiation exposure dose in the imaging conditions for capturing the third radiographic image, When the radiation exposure dose when capturing the second radiation image is α × q and the radiation exposure dose under the imaging conditions when capturing the second radiation image is β × q, α and β are Each exposure dose was determined to satisfy the following conditions

The evaluation image photographing apparatus according to claim 2. The creation means includes the evaluation pattern, a position specifying pattern that is provided in the phantom and includes a member having a radiation shielding property equal to or higher than a predetermined threshold, and specifies a position of the evaluation pattern. At least one of the first radiographic image and the second radiographic image is moved relative to the other, or the first radiographic image is deformed so as to be included in a synthesis region of the first image and the second image. The evaluation image creating apparatus according to any one of claims 1 to 3. The difference between the pixel value of each pixel of the first image and the pixel value of the pixel corresponding to each pixel of the second image of the first image is subtracted from the average value of the pixels of the first image. The evaluation image creation apparatus according to any one of claims 1 to 4, wherein the added value is used as a pixel value of each pixel of the composite image. The first acquisition means acquires a plurality of the first radiation images obtained by a plurality of times of imaging,
The evaluation image creation apparatus according to any one of claims 1 to 5, wherein the second acquisition unit acquires a plurality of the second radiation images obtained by a plurality of times of imaging. When the radiation image is moved by the creating means,
The first image, the first radiographic image, the radiographic image obtained by moving the first radiographic image in the first direction, the radiographic image obtained by moving the first radiographic image in a second direction different from the first direction, And one radiation image selected from the rotated radiation images of the first radiation image,
The second image, the second radiation image, a radiation image obtained by moving the second radiation image in the first direction, a radiation image obtained by moving the first radiation image in the second direction, and the second The evaluation image creation apparatus according to claim 1, wherein the radiation image is a single radiation image selected from the rotated radiation images. The radiographic image capturing apparatus to be evaluated is a radiographic image capturing apparatus for which a preliminary evaluation process for evaluating based on a third radiographic image obtained by capturing the phantom with the radiographic image capturing apparatus is completed,
When the evaluation result obtained by the pre-evaluation process does not satisfy a predetermined condition, the creation unit acquires the first radiation image, and the second acquisition unit The evaluation image creation apparatus according to claim 1, wherein a second radiation image is acquired, and the creation unit creates the plurality of evaluation images. An evaluation image creating apparatus according to any one of claims 1 to 8,
Evaluation means for evaluating the radiographic imaging device to be evaluated based on the plurality of evaluation images created by the creation means;
Evaluation device with An image forming apparatus for evaluation according to claim 2 or 8,
Evaluation means for evaluating the radiographic imaging device to be evaluated based on the plurality of evaluation images created by the creation means;
Conversion means for converting the evaluation result by the evaluation means into the evaluation result obtained by the prior evaluation process;
Evaluation device with Computer
First acquisition means for acquiring a first radiographic image obtained by imaging a radiographic first base member with a radiographic imaging device as an evaluation target;
Photographing a phantom in which a predetermined evaluation pattern made of a member having a radiation shielding property equal to or higher than a predetermined threshold is provided on the second base member having a configuration corresponding to the first base member by the radiation image capturing apparatus Second acquisition means for acquiring a second radiation image obtained by
At least one of the first radiographic image and the second radiographic image is moved with respect to the other, or the first radiographic image is deformed to convert the first radiographic image and the moved or deformed first radiographic image. A plurality of evaluations are performed by combining a first image selected from a plurality of images including a second image selected from a plurality of images including the second radiation image and the moved second radiation image a plurality of times. Creating means for creating an image,
A program to make it function as. A first acquisition step of acquiring a first radiographic image obtained by imaging a radiographic first base member with a radiographic imaging device to be evaluated;
Photographing a phantom in which a predetermined evaluation pattern made of a member having a radiation shielding property equal to or higher than a predetermined threshold is provided on the second base member having a configuration corresponding to the first base member by the radiation image capturing apparatus A second acquisition step of acquiring a second radiation image obtained by
At least one of the first radiographic image and the second radiographic image is moved with respect to the other, or the first radiographic image is deformed to convert the first radiographic image and the moved or deformed first radiographic image. A plurality of evaluations are performed by combining a first image selected from a plurality of images including a second image selected from a plurality of images including the second radiation image and the moved second radiation image a plurality of times. A creation step for creating an image,
An image creation method for evaluation comprising: