JP6066629B2 - X-ray detector and X-ray imaging apparatus - Google Patents

Description

  The present invention relates to an X-ray detector and an X-ray imaging apparatus, and more particularly to a technique for detecting a defective element of an X-ray detector.

  Description will be made using a medical X-ray CT apparatus as a conventional technique. The X-ray CT apparatus calculates an X-ray absorption coefficient from an X-ray transmission image (hereinafter referred to as projection data) of a subject taken from a plurality of directions, and obtains a tomographic image (hereinafter referred to as a reconstructed image) of the subject. It is a device to obtain. Widely used in the fields of medicine and non-destructive inspection, in recent years, in particular, in the medical field, the number of X-ray detectors in the direction of the rotation axis is increasing. As a result, a wide range can be photographed in one rotation, and the photographing time can be shortened.

  As a result of the increase in the number of detection elements, the possibility that a failed detection element (hereinafter referred to as a defective element) is increased as the number of detection elements increases. The defective element is caused by a failure or manufacturing failure of a photodiode that changes light into an electric signal or a readout circuit. It may exist immediately after the manufacture of the device or may occur with the use of the device, and exhibits various unexpected behaviors in terms of sensitivity, input / output characteristics, output level, noise level, and the like.

  When a defective element is generated, if it is used as it is, an artifact is generated in the reconstructed image, which hinders diagnosis and causes a problem. Further, there may be a case where an effective image is not obtained by diagnosis and the exposure becomes invalid for the subject. In order to prevent these, check the position of the defective element and the presence / absence of the defective element, and if necessary, replace the entire detector or a part of it, estimate the output value of the defective element using the output of the element around the defective element, etc. I do.

  As a method for examining the position of a defective element and the presence / absence of occurrence, for example, Patent Document 1 discloses image data (hereinafter referred to as air data) obtained by irradiating X-rays in the absence of a subject, or irradiating X-rays. A method using image data (hereinafter referred to as “offset data”) obtained without using the image data is disclosed. By using air data, it is possible to investigate defects in the sensitivity characteristics, input / output characteristics, output level, noise level, etc. of the detection element when X-rays are incident. Further, by using the offset data, it is possible to check the output level and noise level when no X-ray is incident. These images need to be acquired prior to imaging of the subject, and in particular, it is desirable to perform these images immediately before imaging in order to detect defective elements that have occurred with the use of the apparatus.

  However, when obtaining air data to check the position and occurrence of defective elements, it is necessary to irradiate X-rays from the X-ray tube. It is necessary to have the customer wait at the service, which reduces the workability of the inspection. In addition, if the number of air data acquisitions is reduced once a day or week to improve workability, it will take time from data acquisition to imaging, so even if a defective element occurs, it can be detected immediately. Therefore, there is a high possibility that artifacts and invalid exposure will occur. Furthermore, since X-rays are irradiated, the life of the X-ray tube is shortened due to degradation of filaments and the like. On the other hand, if only offset data is used, an abnormality in sensitivity characteristics and input / output characteristics with respect to X-rays cannot be detected, so that the detection accuracy decreases.

  As one method for solving such a problem, Patent Document 2 discloses that a light emitting element and a driving circuit are separately provided, and a defective element is detected by irradiating light from the light emitting element to a scintillator and detecting it with a photodiode. A remote failure analysis system for a line CT apparatus is disclosed. This system detects defects including abnormalities in light transmission from the scintillator to the photodiode, abnormalities in the sensitivity and input / output characteristics of the photodiode and readout circuit, abnormalities in the readout operation, etc. it can. Furthermore, even when a subject such as immediately before X-ray imaging is on the bed, a defective element can be detected without giving an invalid exposure to the subject.

JP 2009-261842 A Japanese Patent Laid-Open No. 9-24044

  According to the method described in Patent Document 1, there is a problem that X-ray exposure is necessary for detecting a defective element, and invalid exposure that is not used for imaging occurs. Further, according to the system described in Patent Document 2, since the collimator is arranged on the X-ray incident surface of the scintillator, there is a problem that a sufficient amount of light cannot be irradiated on the entire detector surface. That is, the collimator becomes a shield against the light from the light source, creating a shadow on the detector surface, and there is a problem that the light cannot reach the entire surface of the detector. As described above, a detector element that does not reach light has a problem that defective elements cannot be detected, including abnormalities such as light transmission, sensitivity, input / output characteristics, and readout operation.

  Moreover, since the shadow of the collimator generated as described above varies depending on the position on the detector, there is a problem that light cannot be uniformly irradiated. Therefore, the problem that the precision which detects a defective element changes with positions of a detector has arisen. Further, in determining the defective element, it is necessary to provide a different determination value for each detection element, or to perform a correction process in order to use the same determination value. This may cause an increase in processing, an increase in work man-hours and labor, an increase in the amount of software, and the like.

  The present invention has been made in view of the above problems, and provides an X-ray detector and an X-ray imaging apparatus capable of detecting a defective element on the entire detector surface without causing invalid exposure unnecessary for imaging. For the purpose.

  In order to solve the above-described problems, an X-ray detector according to the present invention detects X-rays and X-ray detectors arranged in a matrix form to detect X-rays according to the detected X-ray intensity. Light emission disposed opposite to each of the detection substrate, an X-ray collimator disposed on the X-ray detection surface side of the X-ray detection substrate, and limiting the incident direction of the X-ray, and the X-ray detection element The X-ray detection element generates a charge corresponding to the light emitted from the light emitting unit.

  Further, an X-ray imaging apparatus according to the present invention uses the X-ray detector, a data acquisition apparatus that collects an electric signal from the X-ray detector, and an electric signal acquired by the data acquisition apparatus, A defect element determination unit that determines the presence / absence of an element and the position of the defect element, and a control device that performs operation control of the X-ray detector and the light irradiation unit, wherein the light irradiation unit is a light source , The defective element imaging control for obtaining the electrical signal from the X-ray detector, the data collection device creates defective element detection data from the electrical signal, the defective element determination unit, A defect element is detected based on the defect element detection data, and defect element position data representing the position of the defect element is created.

According to the present invention, it is possible to provide an X-ray detector and an X-ray imaging apparatus capable of detecting defective elements on the entire detector surface without causing invalid exposure unnecessary for imaging.

Schematic of the X-ray CT apparatus according to this embodiment Overall perspective view of the X-ray detector 104 according to the first embodiment. Cross-sectional view of the X-ray detector 104 according to the first embodiment (cross-sectional view seen from the arrow AA 'at the cross-sectional position 114 in FIG. 2) Flow chart showing the flow of processing from raw data to display of reconstructed image Flowchart showing the flow of processing for creating the defective element map 142 Explanatory drawing for demonstrating an example of the defective element map 142 It is sectional drawing which shows the other example of the X-ray detector which concerns on 1st embodiment (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 3), Comprising: (a) is X in a photoelectric conversion board | substrate. An X-ray detector 104a having a light source on an incident surface (an adjacent surface to a scintillator substrate) of light generated by converting a line is shown, and (b) is generated by converting X-rays on a photoelectric conversion substrate. An X-ray detector 104b having a light source on the surface opposite to the incident surface of the incident light (surface adjacent to the scintillator substrate) is shown. Cross-sectional view of the X-ray detector 104c according to the second embodiment (cross-sectional view as seen from the arrow AA 'at the cross-sectional position 114 in FIG. 2) Sectional drawing which shows X-ray detector 104d which concerns on the other example of 2nd embodiment (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2) Sectional drawing which shows X-ray detector 104e which concerns on the other example of 2nd embodiment (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2) Sectional drawing which shows X-ray detector 104f which concerns on the other example of 2nd embodiment (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2) Sectional drawing which shows X-ray detector 104g which concerns on the other example of 2nd embodiment (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2) Sectional drawing which shows X-ray detector 104h which concerns on the other example of 2nd embodiment (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2) It is sectional drawing (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2) which shows the X-ray detector 104i which concerns on other examples of 2nd embodiment, Comprising: (a) is a whole figure of a cross section. , (B) is an enlarged view of the periphery of the defective element detection light source 122 (within the chain line in FIG. 14 (a)). Sectional drawing which shows an example of the X-ray detector 104j which concerns on 3rd embodiment (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2) It is sectional drawing (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2) which shows the X-ray detector 104k which concerns on the other example of 3rd embodiment, Comprising: (a) is a whole figure of a cross section. , (B) is an enlarged view of the vicinity of the defective element detection light source 122 (within the chain line in FIG. 16 (a)). Sectional drawing which shows an example of the X-ray detector 104l which concerns on 4th embodiment (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2) Sectional drawing which shows an example of the X-ray detector 104m which concerns on 5th embodiment (sectional drawing seen from arrow AA 'in the cross-sectional position 114 of FIG. 2)

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are given to the procedures having the same functions and the same processing contents, and the description thereof will not be repeated. In the following, an example in which the X-ray detector to which the present invention is applied is mounted on an X-ray CT apparatus used in medicine will be described. However, the present invention is not limited to the X-ray CT apparatus and detects and transmits X-rays. The present invention is generally applicable to an X-ray imaging apparatus that obtains an image. Further, the present invention can also be applied to industrial X-ray CT apparatuses and X-ray imaging apparatuses used in the field of nondestructive inspection.

  Hereinafter, the schematic configuration of the X-ray CT apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram of an X-ray CT apparatus according to the present embodiment.

  As shown in FIG. 1, the X-ray CT apparatus 1 according to this embodiment includes an X-ray source 100, an X-ray limiting device 116, an X-ray detector 104, a detector container 151, a signal acquisition device 118, and a central processing unit 105. , Display device 106, input device 119, control device 117, gantry rotating unit 101, and couch top plate 103. A plurality of X-ray detectors 104 are arranged in an arc shape with the X-ray source 100 as the center in the detector container 151, and are mounted on the gantry rotating unit 101 together with the X-ray source 100. Here, FIG. 1 shows a case where eight X-ray detectors 104 are installed in the detector container 151 for the sake of simplicity, but in an actual apparatus, for example, about 40. It is.

  Although not shown, the X-ray source 100 includes an X-ray tube and a high-voltage generator that applies a high voltage to the X-ray tube, and the X-ray tube 100 irradiates the X-ray 100a.

  The X-ray diaphragm device 116 limits the irradiation range (denoted as an irradiation field) of the X-rays 100 a irradiated from the X-ray source 100. The X-ray diaphragm 116 is provided on the subject 102 side in the X-ray source 100.

  The gantry rotating unit 101 is configured in a substantially disk shape having an opening 101a for inserting the bed top plate 103. The X-ray source 100, the X-ray diaphragm 116, and the X-ray detector 104 are mounted to face each other, and the X-ray source 100, the X-ray diaphragm 116, and the X-ray detector 104 are mounted on the bed top. The plate 103 is rotated along the rotation direction 108 around the rotation axis direction 107.

  The signal collection device 118 collects the electrical signal output from the X-ray detection device 104 and outputs it to the central processing unit 105.

  The central processing unit 105 is configured by an arithmetic / control device such as a CPU. The storage unit 109 stores various data used for processing of the central processing unit 105, such as offset data, coefficients used for L0G conversion processing, sensitivity X-ray distribution data, and defect element maps. The central processing unit 105 corrects the electrical signal acquired from the signal collection device 118 using various data stored in the storage unit 109, performs a reconstruction calculation, and generates a reconstructed image of the subject.

  The display device 106 includes an image monitor including a CRT or a liquid crystal panel, and displays a reconstructed image of the subject.

  The input device 119 includes a device that accepts an input operation by an examiner, such as a keyboard, a mouse, and a trackball.

  The couch top 103 is placed with the subject 102 and is moved back and forth along the rotation axis direction 107 by a couch driving device (not shown).

  The X-ray detection apparatus 104 detects the X-ray 100a that has passed through the subject 102, and outputs an electrical signal indicating an electric charge corresponding to the transmitted X-ray intensity.

  Next, the flow of imaging processing for acquiring a reconstructed image using the X-ray CT apparatus 1 will be described. First, when there is an input to start photographing from the input device 119, a defective element is detected. This method will be described in detail below.

  Thereafter, X-rays are emitted from the X-ray source 100. The X-ray is limited in the irradiation field by the X-ray limiting device 116, is irradiated toward the subject 102 placed on the bed top plate 103, and the X-ray transmitted through the subject 102 is detected by the X-ray detector 104. The The X-ray detector 104 calculates the amount of charge corresponding to the incident X-ray for each of the two-dimensionally arranged X-ray detection elements in the rotation direction (coincidence with the channel direction) and the rotation axis direction (coincidence with the slice direction). Can be obtained. Details of the structure of the X-ray detector 104 will be described later.

  By rotating the gantry rotation unit 101 in the rotation direction 108, imaging is repeated while changing the X-ray irradiation angle with respect to the subject 102, and projection data for 360 degrees is acquired. Shooting is performed for a plurality of views, for example, every 0.4 degrees.

  The charge obtained in this manner is collected by the signal collecting device 118 and converted into a digital signal to create raw data. Next, the raw data is subjected to image processing by the central processing unit 105 to generate projection data. Next, reconstruction is performed to create a reconstructed image of the X-ray absorption coefficient distribution of the subject 102. Then, the display device 106 displays the reconstructed image.

<First embodiment>
Next, the X-ray detector according to the first embodiment of the present invention and defective element correction using the same will be described with reference to FIGS. The X-ray detector according to the first embodiment is characterized in that the defective element detection light source 122 is mounted on the photoelectric conversion substrate 125. FIG. 2 is an overall perspective view of the X-ray detector 104 according to the first embodiment. FIG. 3 is a cross-sectional view of the X-ray detector 104 according to the first embodiment (a cross-sectional view as viewed from the arrow AA ′ at the cross-sectional position 114 of FIG. 2). FIG. 4 is a flowchart showing a process flow from raw data to display of a reconstructed image. FIG. 5 is a flowchart showing a flow of processing for creating the defective element map 142. FIG. 6 is an explanatory diagram for explaining an example of the defect element map 142. 7 is a cross-sectional view showing another example of the X-ray detector according to the first embodiment (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 3), and (a) is a photoelectric conversion. The example which provided the light source in the incident surface (adjacent surface with a scintillator board | substrate) of the light produced | generated by converting the X-ray in a board | substrate is shown, (b) is produced | generated by converting the X-ray in a photoelectric conversion board | substrate. An example in which a light source is provided on a surface opposite to the incident surface of the incident light (surface adjacent to the scintillator substrate) is shown. 2, 3, and 7, the X-ray detectors 104, 104 a, and 104 b have eight X-ray detection elements in the channel direction 108 and eight X-ray detection elements in the slice direction 107. However, the present invention is not limited thereto.

  As shown in FIG. 2, the X-ray detector 104 according to the first embodiment includes an X-ray collimator 120 that limits the direction of incident X-rays, a scintillator element substrate 126 that changes incident X-rays to light, and a scintillator element. A photoelectric conversion substrate 125 that converts light generated on the substrate 126 into an electric signal, and a wiring substrate 124 having a wiring circuit that guides the electric signal generated on the photoelectric conversion substrate 125 to the outside are provided. A photoelectric conversion substrate 125 is stacked and bonded onto the wiring substrate 124. Further, the scintillator element substrate 126 is laminated on the photoelectric conversion substrate 125 and bonded thereto.

  The X-ray collimator 120 shown in FIG. 2 is a two-dimensional collimator. For example, a collimator plate 113 made of a metal having a large X-ray absorption rate such as tungsten, molybdenum, or lead has a gap between the channel direction 108 and the slice direction 107. The collimator plate 113 is bonded to each other at a contact point, and is fixed to the X-ray incident surface of the scintillator element substrate 126.

  As shown in FIG. 3, the scintillator element substrate 126 has eight scintillator elements 128 that absorb X-rays and generate light along the slice direction 107, and a reflective material 129 that reflects the light enters X-rays. The reflector 135 is provided between the scintillator elements 128 so as to reflect the light. The gap 152 between the adjacent collimator plates 113 faces the scintillator element 128 via the reflector 129, and the collimator plate 113 faces the reflector 135 between the scintillator elements via the reflector 129. Is done. In FIG. 3, nine collimator plates 113 are arranged along the slicing direction 107, and eight gaps 152 are formed between adjacent collimator plates 113, and one of the collimator plates 113 and the gaps 152 is assigned a reference numeral. Reference numerals for the remaining collimator plate 113 and the gap 152 are abbreviated. Further, one or two of the scintillator elements 128 and the reflective material 135 are given reference numerals, and the reference numerals are omitted for the remaining ones. The same applies to FIG.

  The photoelectric conversion substrate 125 is arranged in a matrix (two-dimensional) so that the photodiode elements 127 that convert light into electrical signals and the defective element detection light source 122 that emits light are in one-to-one correspondence with the scintillator elements 128. . That is, since each scintillator element 128 is arranged facing one photodiode element 127 and one defect element detection light source 122, in FIG. 3, eight photodiode elements 127 and eight defects are arranged along the slice direction. An element detection light source 122 is disposed. The photodiode element 127 and the defective element detection light source 122 are arranged on the incident surface (adjacent to the scintillator substrate) of the light generated by converting the X-rays on the photoelectric conversion substrate 125, and On the surface, the photodiode element 127 and the defective element detection light source 122 are arranged flush with each other with almost no step. Here, “almost flush with no level difference” does not interfere with the case where the substrates are arranged flush with each other and the substrate including the defective element detection light source 122 and another substrate that contacts the substrate. The purpose is to allow a level difference. The same is true for the following description. Although not shown in FIG. 3, the configuration is the same along the channel direction 108.

  A side surface of the photoelectric conversion substrate 125 in the scintillator element 128 (surface opposite to the X-ray incident surface in the scintillator element 128) and a side surface of the scintillator element substrate 126 in the photodiode element 127 (generated by converting X-rays in the photodiode element 127) The light incident surface) is bonded with an adhesive capable of transmitting light generated by the scintillator element 128 to realize an X-ray detection element. Further, the adhesive can transmit light emitted from the defective element detection light source 122. Therefore, the light emitted from the defective element detection light source 122 can travel between the defective element detection light source 122 and the scintillator element 128. However, the photodiode element 127 is an example here, and it goes without saying that various light receiving elements are possible.

  With such a structure, among the X-rays irradiated from the X-ray source 100, the X-ray transmitted through the subject reaches the scintillator element substrate 126 through the gap 152 and generates an output for each X-ray detection element. On the other hand, since the X-rays scattered by the subject 102 or the like have a scattering angle, most of them collide with the collimator plate 113 and are absorbed and scattered, and do not reach the scintillator element substrate 126 and are not detected. Furthermore, such a structure is also realized in the channel direction 108. That is, the X-ray detection elements are two-dimensionally arranged.

  Next, a flow of processing from raw data to display of a reconstructed image performed by the central processing unit 105 will be described with reference to FIG. The central processing unit 105 performs various correction processes in the series of processes. For example, offset correction for correcting the zero level of the X-ray detector 104, air correction for correcting the sensitivity distribution of the X-ray detector 104 and X-ray irradiation distribution, and defective element correction for estimating the output value of the defective element are performed. . However, the correction processing shown in FIG. 4 is an example and does not limit the present invention. For example, there are cases where these correction orders are different, when other corrections are applied, or when there is no at least one of offset correction, air correction, and defective element correction. Further, instead of correcting the defective element, for example, the generation of the defective element is displayed on the display device 106. Alternatively, as described above, information on the generation of the defective element may be transmitted to the outside of the apparatus manufacturer or the like. . Hereinafter, it demonstrates along each step of FIG.

(Step S1)
The central processing unit 105 first performs offset correction on the raw data 143 received from the signal collecting unit 118 (S1). This correction is realized by, for example, subtracting the offset data 140 created and saved in the storage device 109 in advance of the actual shooting from the raw data. The offset data 140 is zero-level data, and is generated by, for example, acquiring raw data for a plurality of views in advance without irradiating X-rays, and performing an averaging process on the view direction.

(Step S2)
Next, the central processing unit 105 performs LOG conversion (S2). The LOG conversion is, for example, a conversion represented by the following expression (1), where X is a value before conversion and Y is a value after conversion. Here, the constant coefficients a and b (110) are determined in advance and stored in the storage device 109.

(Step S3)
Next, the central processing unit 105 performs air correction (S3). This correction is realized, for example, by subtracting the sensitivity / X-ray distribution data 141 created and saved in the storage device 109 in advance of the main imaging from the raw data after the LOG conversion 131. Sensitivity / X-ray distribution data 141 is the same as in the case of actual data for raw data obtained in advance for a plurality of views by irradiating X-rays from the X-ray tube 100 in the absence of the subject 102, for example. After the offset correction (S1) and LOG conversion (S2) are performed, it is created by performing an averaging process for the view direction.

(Step S4)
Next, the central processing unit 105 performs defect element correction (S4). This correction 133 may be realized by the central processing unit 105 being stored as a program in a hard disk or a medium of a computer, or may be realized by an electric circuit. This correction is performed on the defective element described in the defective element map 142. As an interpolation method, for example, an average value of output values of adjacent normal elements is used. However, this is only an example and does not limit the present invention, and various methods can be applied.

(Steps S5 and S6)
Next, the central processing unit 105 performs reconstruction processing using the projection data 144 to create a reconstructed image 145 (S5) and displays it on the display device 106 (S6).

  Next, a method for detecting defective elements will be described. The X-ray detector 104 shown in FIG. 3 has a defective element detection light source 122 that irradiates visible light onto an incident surface (a surface adjacent to the scintillator substrate) of light generated by converting X-rays in the photoelectric conversion substrate 125. Have The defect element detection light source 122 is, for example, a GaN (gallium nitride) LED element. The defective element detection light source 122 is optically connected to the scintillator element 128, and the irradiated light is incident on the scintillator element 128. Since the periphery of the scintillator element 128 is covered with the reflective material 129 and the reflective material 135, the light is reflected and at least part of the light reaches the photodiode device 127. At this time, by reading from the photodiode element 127, the light from the defective element detection light source 122 is detected by the photodiode element 127 in the same manner as the light generated in the scintillator element 128 when X-rays are detected. Output can be produced. Therefore, as in the case of irradiation with X-rays, an output is generated if it is a normal X-ray detection element, and no output is generated if it is a defective element. Therefore, a normal element and a defective element can be discriminated from an image obtained by reading this signal with the X-ray detector 104 (hereinafter referred to as optical image raw data).

  According to the X-ray detector 104 of FIG. 3, the defective element detection light source 122 can be provided for each X-ray detection element without shielding the X-rays incident on the X-ray detection element. The light from the defective element detection light source 122 can enter the scintillator element 128 without being shielded. Therefore, with this structure, light can be delivered to all X-ray detection elements with good uniformity.

  Next, an example of a flow of a method for detecting a defective element from the optical image raw data 143 and creating a defective element map will be described with reference to FIG.

  Next, an example of defective element detection processing will be described with reference to FIGS. Prior to the start of the processing in FIG. 5, signals are collected by the signal collection device 118 while irradiating light from the defective element detection light source 122 in all the X-ray detectors 104 mounted on the X-ray CT apparatus 1. Thus, the optical image raw data 143 is obtained. At this time, data for a plurality of views is obtained. Using this optical image raw data 143, the position of the defective element is detected. In the following, description will be given in the order of each step in FIG.

(Step S11)
The central processing unit 105 performs the offset correction (S1) described above on the optical image raw data 143 using the offset data 140 (S11).

(Step S12)
The central processing unit 105 performs addition averaging processing of the optical image raw data 143a after offset correction of a plurality of views at each X-ray detection element to generate optical image data 147 (S12). Here, the reason why the optical image raw data 143 is obtained for a plurality of views and averaged by the addition averaging process 138 is to reduce the fluctuation of the value due to noise. However, these processes are examples, and one or both of the offset correction (S11) and the addition averaging process (S12) may not be performed.

(Step S13)
The central processing unit 105 performs a defective element determination process on the optical image data 147 to determine whether it is a defective element (S13). In the defective element determination process, for example, a threshold value 149 determined in advance and recorded in the storage device 109 is used to determine whether the element is a defective element. At this time, for example, an element having a threshold value of 149 or less is determined to be insensitive or extremely small, and is regarded as a defective element. The result of the presence or absence of defective elements and their positions are recorded in the storage device 109 using the format of the defective element map 142.

  An example of the defective element map 142 is shown in FIG. FIG. 6 is for the X-ray detector 104 having 8 × 8 X-ray detection elements, and the position of the matrix corresponds to the X-ray detection elements and the numbers indicate whether they are defective elements. That is, the vertical position of the matrix represents the number of the X-ray detection element in the direction of the slice 107 of the X-ray detector 104, the horizontal position represents the number of the direction of the channel 108, and when the number is 1, it is a defective element. , 0 represents a normal element. In the defect element map 142 of FIG. 6, the elements in the second channel, the third slice, and the eighth channel, the seventh slice are defective. However, the number of X-ray detection elements, the position of defective elements, and the display method are merely examples, and do not limit the present invention.

  According to the present embodiment, it is possible to detect a defective element using the light emitted from the defective element detection light source 122 without irradiating the X-ray from the X-ray source 100. In particular, with this structure, the entire scintillator element substrate 126 can be irradiated with light with good uniformity. In addition, the light emitted from the defective element detection light source 122 and reaching the scintillator element 128 reaches the photodiode to generate an electrical signal and is read out similarly to the light generated by absorbing the X-rays in the scintillator element 128. Therefore, defective elements including abnormal transmission of light from the scintillator to the photodiode, abnormal sensitivity of the photodiode, and abnormal signal reading and operation in the readout circuit of the X-ray detector 104 and the signal collecting device 118 Can be evaluated. Therefore, it is possible to detect a defective element with high accuracy, and it is possible to prevent occurrence of artifacts in the reconstructed image and invalid X-ray irradiation to the subject. Further, since X-rays are not irradiated, there is no fear of shortening the life of the X-ray tube. Furthermore, since light is used without irradiating X-rays, various timings such as immediately before imaging, for example, when the X-ray generator is not irradiating X-rays, a predetermined time interval is set, or the input device Can be performed at the time before receiving the X-ray after receiving the input signal instructing the X-ray irradiation, and can be performed even when the subject is in the imaging room. In addition, the defective element can be detected effectively. Further, since the defective element detection light source 122 can be provided without shielding the X-rays incident on the X-ray detection element, the influence on the projection data and the reconstructed image is small.

  As a modification of the present embodiment, the central processing unit 105 determines whether a defective element capable of correcting a defect or whether the X-ray detector 104 should be replaced based on the defective element map. May be provided. This defective element determination unit determines that the X-ray detector 104 should be replaced, for example, in a position where very high correction accuracy is required to suppress artifacts or in a state where the accuracy decreases. The method is performed, for example, when the defective element map is updated. In the defective element map, for example, when the element located at the reconstruction center is defective or when two or more defective elements are adjacent to each other, X It is determined that the line detector 104 has been replaced, and the content is displayed on the display device 106. In other cases, the defective element correction in step S4 of FIG. 4 is performed. By performing the defective element determination in this way, it is possible to prevent an artifact that occurs when the defective element cannot be corrected sufficiently.

  Further, the X-ray CT apparatus 1 may include means for exchanging information with the outside (for example, an apparatus manufacturer). As a result, when it is determined that the X-ray detector 104 should be replaced, it is possible to automatically contact the apparatus maker and the like so that the replacement can be performed quickly.

  In the present embodiment, visible light is used as light emitted from the defective element detection light source 122, but this does not limit the present invention. At least a part of the light may pass through the scintillator element 128, and the photodiode element 127 may be various kinds of light having sensitivity. For example, visible light having a long wavelength such as red or near infrared light may be used. Such light has higher transmittance of the reflective material 129 and the scintillator element 128 than visible light having a short wavelength. In addition, in the photodiode element 127 made of crystalline silicon and the like, the sensitivity increases as the wavelength is increased to about 900 nm. Therefore, there is an advantage that a large output can be obtained by using visible light or near infrared light having a long wavelength. .

  In the present embodiment, the light emitted from the defect element detection light source 122 and transmitted through the scintillator element 128 and scattered / refracted is detected by the photodiode element 127, but the light is absorbed in the scintillator element 128. Light of different wavelengths may be emitted and detected by the photodiode element 127. As an example, the scintillator element 128 made of, for example, GOS (gadolinium oxysulfide) is irradiated with ultraviolet light (first wavelength light) from the defect element detection light source 122, for example. At this time, GOS absorbs ultraviolet rays and generates visible light (second wavelength light). This light includes at least light having the same wavelength as light generated by absorbing X-rays. Since the photodiode element 127 has sensitivity, it can be detected. Therefore, it can be used for defective element detection. However, it goes without saying that the irradiated light can have various wavelengths shorter than the emitted wavelength, and the scintillator element 128 can have various materials other than GOS. By irradiating the ultraviolet light from the defective element detection light source 122 and converting it to visible light and causing the photodiode element 127 to detect it, it becomes easy to detect a defect of the scintillator element 128, for example, a decrease in sensitivity or a loss from the substrate.

  In the present invention, the case where the defective element detection light source 122 is provided for each X-ray detector 104 is described as an example, and the present invention is not limited thereto. One defective element detection light source 122 may be provided across a plurality of X-ray detectors 104.

  For example, as in the X-ray detector 104a in FIG. 7A, one defect exists on the light incident surface (adjacent surface to the scintillator substrate) of the photoelectric conversion substrate 125 generated by converting the X-rays. The element detection light source 122 may be disposed so as to face the two scintillator elements 128 across the reflector 135.

  Further, like the X-ray detector 104b of FIG. 7B, the surface opposite to the light incident surface (adjacent surface to the scintillator substrate) generated by converting the X-rays in the photoelectric conversion substrate 125, That is, one defective element detection light source 122 may be arranged on the surface of the wiring board so as to face the two scintillator elements 128 across the reflective material 135. In this case, each photodiode element 127 can be formed larger than that in FIG. In FIG. 7B, the width of each photodiode element 127 is formed to be approximately the same as that of the scintillator element 128.

  In the present embodiment, the case where the X-ray collimator 120 is a two-dimensional collimator is described, but it may be a one-dimensional collimator. Moreover, although the case where it implement | achieved by adhere | attaching the collimator board 113 by the contact was described, this is an example and this invention is not limited and there may be various cases. For example, a resin mixed with metal powder may be molded and cured, or a metal plate may be processed by etching or the like to realize a lattice collimator.

  In the present embodiment, the case where the defective element is detected immediately before imaging of the subject 102 using X-rays is described as an example, and the present invention is not limited thereto. For example, immediately after the apparatus is turned on or immediately before the power is turned off, before or after acquiring warm-up or correction data for the X-ray tube or CT apparatus, or during the acquisition (when X-rays are not irradiated), X It may be performed immediately after imaging of the subject 102 using a line. Furthermore, the central processing unit 105 has a function of measuring time, and may be performed when a certain time elapses after the power-on transition, the last X-ray irradiation, or periodically every certain time. The certain time described here is constant, for example, one hour, for example. However, it may not be constant. Furthermore, it is possible to combine these plural cases. Also in this case, as described above, a means for exchanging information with the defective element determination unit and the outside may be provided. At this time, the defective element determination unit determines that the X-ray detector 104 needs to be replaced. When this occurs, the contents can be automatically communicated to a device maker or the like, and the X-ray detector 104 in which the defective element is generated can be replaced sufficiently before the time for imaging.

  In this way, by performing defective element detection other than immediately before imaging of the subject 102 using X-rays, the subject 102 is caused to wait or imaging is stopped due to a defective element being generated and imaging cannot be performed. Can be prevented.

  In the present embodiment, as shown in FIG. 5, the case where the defect element map 142 is updated from the optical image raw data 143 obtained by irradiating light from the defect element detection light source 122 is described. There is no limitation to the present invention. For example, after the optical image data 147 is generated by performing the processing of FIG. 5, when it is determined that there is a defective element by performing the defective element determination 148, an image is acquired by separately irradiating X-rays, and from this image The defective element map may be updated. By doing so, it is possible to prevent a normal element from being erroneously detected as a defect in the optical image raw data 143 in the case of a failure of the defective element detection light source 122 or the like.

  In the present embodiment, the case where the defect element map 142 is updated only with the optical image raw data 143 obtained by irradiating light from the defect element detection light source 122 is described as an example, and the present invention is limited. It is not a thing. Furthermore, it goes without saying that a defective element may be detected using other air data or offset data, and the defective element map 142 may be updated. In particular, the offset data can be acquired immediately before X-ray imaging of the subject or periodically, and when the light from the defective element detection light source 122 is not irradiated before and after the optical image raw data 143 is acquired. It is desirable to acquire and use it for the detection of defective elements.

  In the present embodiment, the case where the defective image is detected by obtaining the optical image raw data 143 using one kind of light is described as an example, and the present invention is not limited thereto. For example, a plurality of light amounts may be used. The amount of light can be realized by changing the amount of current to the light source, for example. At this time, in the defective element determination in step S4 of FIG. 4, the determination is performed on the optical image raw data 143 obtained with the respective light amounts using the threshold values 149 provided for the respective light amounts. Alternatively, in the defective element determination in step S4, the input / output characteristics of each element are calculated from the plurality of optical image raw data 143, the inclination value, the amount of deviation of the data value from the obtained input / output characteristics, The defective element may be determined using a deviation amount of each input / output characteristic from the average input / output characteristic. By determining defective elements using multiple sensitivities and input / output characteristics obtained in such a wide input range, it is possible to detect defective elements with high accuracy, generating artifacts in the reconstructed image, It becomes possible to further prevent invalid X-ray irradiation to the specimen.

  Furthermore, a defective element may be detected using a plurality of optical image raw data 143 obtained with light having different wavelengths by providing a light source for irradiating light with a plurality of wavelengths to the defective element detection light source 122. Such a light source can be realized, for example, by providing a plurality of types of LEDs at one light irradiation point.

  Further, although the case of a GaN (gallium nitride) based LED element has been described as the defective element detection light source 122, this is an example and does not limit the present invention. In the case of an LED element made of ZnO (zinc oxide) or other materials, a light emitting element using amorphous silicon or porous silicon, and various other light emitting elements may be used.

  In the present embodiment, the optical image raw data 143 is subjected to offset correction as shown in step S11 of FIG. 5 and addition average processing in step S12 to generate optical image data 147, and defective elements are detected. However, this is only an example and does not limit the present invention. Further, air correction may be added. At this time, air data captured using X-rays may be used for air correction. Alternatively, the above-described air data creation procedure may be applied to the light image raw data 143 captured in the past to create reference data, which may be used as air data. Furthermore, other corrections may be added.

  Further, in the present embodiment, as a defective element determination method, as shown in step S13 of FIG. 5, the case where the output value is determined as a defective element by comparing with the threshold value 149 is described as an example. The present invention is not limited and various methods are conceivable. For example, the average value and the standard deviation in the image may be obtained, and the defect may be determined when the output value is smaller or larger than the magnification determined by the standard deviation from the average value. Here, the determined magnification is, for example, 5 times. Further, the previously captured optical image data 147 may be stored, and a difference image with the optical image data 147 may be stored, and an element that has changed more than the threshold value 149 may be determined as a defect.

  In the present invention, the case of an indirect detection type X-ray detector in which X-rays are converted into light by the scintillator element 128 and the light is converted into electric charge by a photodiode is described as an example. It goes without saying that the present invention may be applied to a direct detection type X-ray detector that directly converts X-rays into electric charges.

<Second embodiment>
In the X-ray detector according to the second embodiment, the defective element detection light source 122 is produced on the defective element detection light source substrate 136 which is a substrate different from the photoelectric conversion substrate, and the X-ray collimator 120 has an X-ray incident side. Or, it is different from the X-ray detector according to the first embodiment in that it is located on the opposite side to the X-ray incident side. Hereinafter, the X-ray detector according to the second embodiment will be described with reference to FIGS. FIG. 8 is a cross-sectional view of the X-ray detector 104c according to the second embodiment (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2). FIG. 9 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an X-ray detector 104d according to another example of the second embodiment. FIG. 10 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an X-ray detector 104e according to another example of the second embodiment. FIG. 11 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an X-ray detector 104f according to another example of the second embodiment. FIG. 12 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an X-ray detector 104g according to another example of the second embodiment. FIG. 13 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an X-ray detector 104 h according to another example of the second embodiment. FIG. 14 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an X-ray detector 104 i according to another example of the second embodiment, in which (a) is a cross-sectional view. It is a general view, (b) is an enlarged view of the periphery of the defective element detection light source 122.

  As shown in FIG. 8, the defect element detection light sources 122 are two-dimensionally arranged so as to face each scintillator element 128, and each defect element detection light source 122 faces the scintillator element 128. Irradiate light. Here, the defective element detection light source 122 is, for example, an LED element, and is preferably small in order to reduce attenuation of X-rays. Further, the defect element detection light source 122 may be located at the center of the X-ray detection element or may be located near the end of the X-ray detection element near the collimator plate 113. In FIG. 8, eight photodiode elements 127 are arranged along the channel direction, but reference numerals are given to one of them, and the remaining ones are omitted. The same applies to FIG. 9 and subsequent figures.

  A method for detecting a defective element in the X-ray detector 104 of this embodiment will be described. At this time, first, similarly to the first embodiment, light is irradiated from the defective element detection light source 122. At least part of this light needs to pass through the scintillator element 128 and through the reflector 129 as in the first embodiment. Therefore, the reflective material 129 is provided with a thickness such that the transmittance is, for example, 0.5% or more. At this time, at least part of the light passes through the scintillator element substrate 126 and reaches the photodiode 127.

  Here, the reflective material 129 transmits a part of the light from the defect element detection light source 122, but at the same time, sufficient reflection for the light from the scintillator element is also realized. This is because, for example, a light emitting element such as an LED is used for the defective element detection light source 122, and even if the light is reflected, scattered, or absorbed by the reflective material 129, the photodiode element 127 has a sufficient amount. This is because light can be incident. This is possible because the reflectance of the reflecting material 129 is different for the light from the scintillator element and the light from the light source 122 for detecting a defective element. The difference in reflectance is caused by the difference in the incident angle of light reaching the reflecting material 129 (the angle formed by the normal line of the reflecting material 129 and the incident direction of light). That is, the light emitted in the scintillator element is incident on the reflector 129 at various angles because the scintillator element is disposed in contact with the reflector 129, and there are many lights having a particularly large incident angle. To do. Since light having such a large incident angle has a substantial transmission path length of the reflector 129 as compared with a case where the incident angle is small, reflection and absorption are likely to occur and the transmittance is small. On the other hand, the light from the defective element detecting light source 122 is arranged right above the reflecting element 129 so that most of the light reaching the reflecting material 129 has a small incident angle and is uniform. ing. Therefore, it is easier to transmit the reflective material 129 than the light from the scintillator element. Therefore, the reflectance with respect to the light from the defective element detection light source 122 is smaller than the reflectance with respect to the light from the scintillator element. Here, the incident angle means the incident angle of light with respect to the normal vector of the X-ray incident surface of the reflector 129.

  Simultaneously with this light irradiation, as in the first embodiment, a signal is read from the photodiode 127 to obtain optical image raw data 143, a defective element is detected, and a defective element map is created.

  By providing the photodiode element 127 and the defective element detection light source 122 on separate substrates as in this embodiment, it is possible to prevent one manufacturing process from affecting the manufacturing process of the other element. Further, even when the manufacturing process of the photodiode element 127 and the defective element detection light source 122 is difficult to achieve, it can be realized by separately manufacturing each. Furthermore, it is possible to manufacture with different materials suitable for each. Further, the defective element detection light source 122 can be easily provided, and the defective element detection light source 122 can be easily replaced in the event of a failure. Furthermore, in this structure, since light can be irradiated from directly above the scintillator element substrate 126, the transmission length of light that substantially passes through the reflecting material 129 can be minimized, and a large amount of light can be irradiated to the photodiode 127. .

  In the present embodiment, the collimator plate 113 preferably has a surface structure that reflects light from the defective element detection light source 122. Such a structure that reflects light can be realized, for example, by polishing the surface of the collimator plate 113, which is a metal plate, and performing a metallic luster treatment. Alternatively, a material or a structure that reflects light from the defective element detection light source 122 may be added to the collimator plate 113, for example, by spraying a highly reflective metal. At this time, since the amount of light reaching the scintillator element substrate 126 from the defective element detection light source 122 increases and many signals can be obtained from the X-ray detector 104, the output difference between the defective element and the normal element is The detection accuracy of defective elements can be improved by detecting defective elements.

  In the present embodiment, the case where a plurality of the defective element detection light sources 122 are two-dimensionally arranged so as to face the respective scintillator elements 128 in a one-to-one manner is described, but this is an example, and the present invention is limited. Not what you want. For example, a plurality of defect element detection light sources 122 may be arranged to face one scintillator element 128.

  Further, for example, as shown in FIG. 9, the defective element detection light source 122 may be a surface light source that emits light two-dimensionally. In the X-ray detector 104 d shown in FIG. 9, a defective element detection light source 122 composed of one surface light source is produced on a defective element detection light source substrate 136. Then, the defective element detection light source substrate 136 is placed on the X-ray incident side of the X-ray collimator 120 with the surface of the defective element detection light source substrate 136 on which the defective element detection light source 122 is disposed facing the X-ray collimator 120. Be placed. As the surface light source, a light source having good X-ray transparency is good, and for example, an organic EL or inorganic EL light source may be used.

  Further, as in the X-ray detector 104e shown in FIG. 10, a plurality of surface light sources are produced on the defective element detection light source substrate 136, and the defect element detection light source 122, which is one surface light source, is formed on the plurality of scintillator elements 128. It may be provided across.

  Furthermore, in this embodiment, the case where light is directly irradiated from the defective element detection light source 122 produced on the defective element detection light source substrate 136 is described, but this is an example, and the present invention is not limited thereto. . For example, like the X-ray detector 104f shown in FIG. 11, the defect element detection light source substrate 136 includes a light guide plate 163 and a light source 161, and the light guide plate 163 guides the light from the light source 161 to serve as a defect element detection light source. It may be realized. At this time, the light emitted from the light source 161 is guided by the light guide plate 163 along the optical path 137, and part of the light is reflected and scattered in the direction of the optical path 139 toward the respective scintillator elements 128. Irradiated. With such a light source, the light source 161 can be disposed at a position where the X-ray does not directly hit. Thereby, it is possible to prevent a shadow from being generated by the light source 161 and to reduce the X-ray dose to the scintillator element 128. Furthermore, the light source 161 can be disposed at a position where the X-ray does not hit directly, such as outside the X-ray incident range, and deterioration due to hitting the X-ray can be prevented.

  Further, for example, as in the X-ray detector 104g shown in FIG. 12, the defective element detection light source substrate 136 includes a light source substrate 162 on which the light source 161 is manufactured and a diffusion plate 160, and along the optical path 137, for example. The light emitted from the light source substrate 162 may be diffused and spread by the diffusion plate 160, and the light may be emitted in a direction in which the reflective material 129 exists. At this time, as shown in FIG. 12, the light source 161 can be disposed between the X-ray detection elements, that is, at a position facing the collimator plate 113, and prevents attenuation of X-rays incident on the X-ray detection elements. it can.

  The structure of the defective element detection light source substrate 136 composed of the light source substrate 162 and the diffusion plate 160 shown in FIG. 12 is an example, and the present invention is not limited thereto, and various structures may be possible. For example, in FIG. 12, the diffuser plate 160 and the light source substrate 162 are upside down, that is, the diffuser plate 160 is provided on the X-ray incident surface side, and the light source substrate 162 is provided on the reflector 129 side. There may be various cases such as a structure in which the light source substrate 162 and the diffusion plate 160 are integrated and the light source 161 is provided on the surface or inside of the diffusion plate 160.

  In the present embodiment, the case where the defective element detection light source substrate 136 is provided on the X-ray incident side of the X-ray collimator 120 is described, but this is an example and the present invention is not limited thereto. For example, it may be provided between the X-ray collimator 120 and the scintillator element substrate 126 as in the X-ray detector 104h shown in FIG.

  Furthermore, in this case, for example, as in the X-ray detector 104i shown in FIG. 14A, most of the light source 161 is provided at a position sandwiched between the collimator plate 113 and the reflecting material 135, and FIG. As shown, each scintillator element 128 may be configured to face the end of the light source 161 with a width w1. Thereby, deterioration of the light source 161 by X-rays can be prevented. Furthermore, the defect element detection light source substrate 136 may include the light guide plate 163 and the diffusion plate 160 described in the second embodiment. In this case, it is also possible to provide the light source 161 at a position between the collimator plate 113 and the reflecting material 135, and the deterioration of the light source 161 due to X-rays can be further prevented.

<Third embodiment>
The third embodiment differs from the second embodiment in that a defective element detection light source substrate 136 is provided between the scintillator element substrate 126 and the photoelectric conversion substrate 125. Hereinafter, the third embodiment will be described with reference to FIGS. 15 to 16. FIG. 15 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an example of the X-ray detector 104j according to the third embodiment. FIG. 16 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an X-ray detector 104k according to another example of the third embodiment. It is a general view, and (b) is an enlarged view of the periphery of the defective element detection light source 122 (within the alternate long and short dash point in FIG. 16 (a)).

  In the X-ray detector 104j shown in FIG. 15, the defective element detection light source 122 is flush with the adjacent surface of the defective element detection light source substrate 136 to the scintillator element substrate 126 on the surface of the adjacent surface with almost no step. It is formed as follows. Further, the defective element detection light source 122 and the defective element detection light source substrate 136 irradiate the scintillator element 128 with the light emitted from the scintillator element 128 or the defective element detection light source 122 when detecting the defective element. It is transparent to the light returned from. As such a defective element detection light source 122, for example, an organic EL element may be used.

  With such a structure, both X-ray detection and defective element detection can be achieved. That is, when X-rays are detected, the light generated by the X-rays detected by the scintillator element 128 passes through at least one of the defective element detection light source 122 and the defective element detection light source substrate 136 and passes through the photodiode element 127. Can be detected. When detecting a defect, light is emitted from the defective element detection light source 122 toward the photodiode element 127, and the light transmitted through the defective element detection light source substrate 136 is detected by the photodiode element 127. Alternatively, light is emitted from the defective element detection light source 122 toward the scintillator element 128. Part of this light is reflected by the reflectors 129, 135, etc., returns from the scintillator substrate 126 to the defective element detection light source substrate 136, and passes through at least one of the defective element detection light source 122 and the defective element detection light source substrate 136. Then, it reaches the photodiode element 127 and can be detected.

  In the third embodiment, the light from the defect element detection light source 122 is not attenuated by the reflecting material 129 as compared with the first embodiment and the second embodiment, so that the defect element can be detected with a small amount of light.

  On the other hand, in the X-ray detector 104j according to the present embodiment, the light emitted from the scintillator element 128 spreads in the defective element detection light source substrate 136 and enters the photodiode elements 127 other than the opposing photodiode elements 127. The fear increases. That is, there is a possibility that the crosstalk becomes high. Accordingly, the defective element detection light source substrate 136 is easy to transmit light in the vertical direction (direction from the scintillator element 128 toward the photodiode element 127), for example, like a fiber optic plate, and in the horizontal direction (direction in which crosstalk light spreads). It is desirable to use a material that does not allow light to pass through.

  In the present embodiment, the case where the defective element detection light source 122 is provided between the photodiode element 127 and the scintillator element 128 is described as an example, but the present invention is not limited thereto. For example, as in the X-ray detector 104k shown in FIG. 16A, a defective element is detected at a position facing between the scintillator elements 128, that is, a position facing the reflector 135 provided between the scintillator elements 128. The main part of the light source 122 may be provided, and as shown in FIG. 16B, the end of each scintillator element 128 may be opposed to the defective element detection light source 122 with a width w2. Thereby, attenuation of the light by the defective element detection light source 122 can be prevented. Furthermore, the defect element detection light source substrate 136 may include the light guide plate 163 and the diffusion plate 160 described in the second embodiment. In this case, it is also possible to provide the light source 161 at a position facing the reflective material 135 provided between the scintillator elements 128, and further attenuation of light by the defective element detection light source 122 can be further prevented.

  In the present embodiment, the case where the defective element detection light source 122 is formed on the surface adjacent to the scintillator element substrate 126 of the defective element detection light source substrate 136 is described as an example, and the present invention is limited. is not. For example, it may be fabricated on a surface adjacent to the photodiode element 127.

<Fourth embodiment>
The fourth embodiment differs from the second embodiment in that a defective element detection light source substrate 136 is provided between the wiring substrate 124 and the photoelectric conversion substrate 125. Hereinafter, a fourth embodiment will be described with reference to FIG. FIG. 17 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an example of the X-ray detector 104l according to the fourth embodiment.

  In the X-ray detector 104l shown in FIG. 17, defective element detection light sources 122 made of point light sources are arranged in a matrix on the surface adjacent to the photoelectric conversion substrate 125 of the defective element detection light source substrate 136. Furthermore, the photoelectric conversion substrate 125 is a silicon substrate having a thickness of, for example, several hundred μm or less, and transmits at least part of the light from the defective element detection light source 122.

  With such a structure, when light is emitted from the defective element detection light source 122, a part of the light can pass through the photoelectric conversion substrate 125 and be detected by the photodiode element 127, so that the defective element can be detected. Moreover, in this structure, since the gap between the photodiode element 127 and the scintillator element 128 can be optically connected without causing a gap due to the defective element detection light source substrate 136 as in the third embodiment, crosstalk can be suppressed. It becomes. Compared with the first and second embodiments, since the X-rays do not directly hit the defective element detection light source 122 or the defective element detection light source substrate 136, the incident X-rays are prevented from being attenuated and the defective elements are detected. Deterioration due to X-rays of the detection light source 122 and the defective element detection light source substrate 136 can be prevented.

  In the present embodiment, the case of the so-called surface irradiation type X-ray detector 104 in which the photodiode element 127 is manufactured on the surface on the scintillator element substrate 126 side in the photoelectric conversion substrate 125 is described, but this is an example. Needless to say, a so-called back-illuminated type produced on the opposite surface may be used. At this time, the defect element detection light source 122 and the photodiode element 127 face each other, and the light emitted from the defect element detection light source 122 is not attenuated by the defect element detection light source substrate 136. Element detection can be performed.

  In the present embodiment, the defect element detection light source 122 composed of point light sources is arranged in a matrix on the defect element detection light source substrate 136, but the defect element detection light source substrate 136 may include a surface light source.

<Fifth embodiment>
The fifth embodiment is different from the fourth embodiment in that the defective element detection light source substrate 136 is provided on the surface of the wiring substrate 124 opposite to the photoelectric conversion substrate 125. Hereinafter, a fifth embodiment will be described with reference to FIG. FIG. 18 is a cross-sectional view (a cross-sectional view seen from the arrow AA ′ at the cross-sectional position 114 in FIG. 2) showing an example of the X-ray detector 104m according to the fifth embodiment.

  In the X-ray detector 104m shown in FIG. 18, defective element detection light sources 122 made of point light sources are arranged in a matrix on the surface of the defective element detection light source substrate 136 facing the photoelectric conversion substrate 125. Then, the defective element detection light source substrate 136 is disposed on the back surface of the wiring substrate 124 (the surface opposite to the surface facing the photoelectric conversion substrate 125). At this time, the wiring substrate 124 needs to be a substrate that transmits light emitted from the defective element detection light source 122. This is because, for example, a method using a material that transmits light, such as glass, or a surface facing the photoelectric conversion substrate 125 from the back surface (corresponding to a surface facing the defective element detection light source substrate 136) on the wiring substrate 124. It can be realized by a method of providing a plurality of small holes penetrating between the two.

  In the present embodiment, the defect element detection light source 122 composed of point light sources is arranged in a matrix on the defect element detection light source substrate 136, but the defect element detection light source substrate 136 may include a surface light source.

<Other embodiments>
In the first to fifth embodiments, the case where the defective element detection light source 122 is provided at various positions is described. However, the present invention is not limited to this, and these are combined to form a plurality of positions. It may be provided.

  In the first to fifth embodiments, examples of medical X-ray CT apparatuses are described. However, the present invention is not limited to this, and the X-ray detector 104 described in the examples is mounted. Needless to say, it can be applied to any device. Examples include X-ray CT equipment for non-destructive inspection, X-ray cone beam CT equipment, dual energy CT equipment, X-ray image diagnostic equipment, X-ray imaging equipment, X-ray fluoroscopy equipment, mammography, digital subtraction equipment, nuclear There may be medical examination devices, radiotherapy devices, and the like. Further, an X-ray detector 104 may be installed which has an X-ray detector 104 and does not have an X-ray or radiation source. Furthermore, not only the X-ray detector, but also a photodetector for light of various wavelengths, a photodetector equipped with the photodetector, and an imaging device using light can be applied. At this time, the light may have any wavelength such as visible light, infrared light, ultraviolet light, and gamma rays.

  Furthermore, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention at the stage of implementation. Furthermore, the above embodiment includes various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed components. For example, some components may be deleted from all the components shown in the embodiment.

DESCRIPTION OF SYMBOLS 100 ... X-ray source 101 ... Gantry rotation part 102 ... Subject 103 ... Bed top plate 104 ... X-ray detector 105 ... Central processing unit 106 ... Display apparatus 107 ... Rotating-axis direction, slice direction 108 ... Rotating direction, Channel direction 109 DESCRIPTION OF SYMBOLS ... Storage device 110 ... Coefficient 113 ... Collimator plate 114 ... Sectional position 116 ... X-ray collimator 117 ... Control circuit 118 ... Signal collection device 119 ... Input device 120 ... X-ray collimator 122 ... Light source 124 for detecting defective elements 124 ... Wiring board 125 ... Photoelectric conversion board 126 ... Scintillator element board 127 ... Photodiode element 128 ... Scintillator element 129, 135 ... Reflector 130 ... Offset correction 131 ... LOG conversion 132 ... Air correction 133 ... Defect element correction 134: Reconstruction processing 136 ... Light source substrate for detecting defective elements 137, 139 ... Arrows indicating the traveling direction of light 138 ... Addition averaging processing 140 ... Offset data 141 ... Sensitivity / X-ray distribution data 142 ... Defect element map 143 ... Raw data 144 ... Projection data 145 ... Reconstructed image 147 ... Optical image data 148 ... Defect element determination 149 ... Threshold value 151 ... Detector container 152 ... Clearance 160 ... Diffuser plate 161 ... Light source 162 ... Light source substrate 163 ... Light guide plate

Claims (13)

An X-ray detection substrate in which X-ray detection elements that detect X-rays and generate charges according to the detected X-ray intensity are arranged in a matrix;
An X-ray collimator which is disposed on the X-ray incident surface side of the X-ray detection substrate and limits the incident direction of the X-ray;
A light irradiation unit having a light emitting unit disposed to face each of the X-ray detection elements;
A data collection device for collecting an electrical signal from the X-ray detection element;
A defective element determination unit that determines the presence / absence of a defective element of the X-ray detection element and the position of the defective element using an electrical signal acquired by the data collection device;
A central processing unit that processes the electrical signal acquired by the data collection device and creates a reconstructed image of the subject;
The X-ray detection element generates a charge corresponding to light emitted from the light emitting unit,
The light irradiation unit is disposed on an incident surface of the X-ray of the X-ray collimator,
An X-ray detector characterized by that. The x-ray detector of claim 1.
The X-ray detection substrate includes a scintillator substrate in which a plurality of scintillator elements that detect the X-rays and convert them into light are two-dimensionally arranged;
A photoelectric conversion substrate in which photoelectric conversion elements that convert light into electrical signals are two-dimensionally arranged,
The scintillator substrate is disposed on the photoelectric conversion substrate on the incident surface side of the light generated by converting the X-rays, with each scintillator element and each photoelectric conversion element facing each other.
The X-ray collimator is disposed on the X-ray incident surface side of the scintillator substrate,
The light emitting portion is arranged to face the scintillator elements,
An X-ray detector characterized by that. The x-ray detector of claim 1 .
The X-ray detector, wherein the light emitting unit is a surface light source that emits light two-dimensionally. The X-ray detector according to claim 3 .
The light emitting unit is configured to include a light source that emits light, and at least one of a light guide plate that guides light from the light source and a diffuser plate that diffuses light from the light source. Detector.   The x-ray detector of claim 1.
  The X-ray detection board has a two-dimensional arrangement of a scintillator board in which a plurality of scintillator elements that detect the X-rays and convert them into light are two-dimensionally arranged, and a photoelectric conversion element that converts light into an electrical signal. A photoelectric conversion substrate,
  An X-ray detector characterized by that. The x-ray detector of claim 5,
The light emitting unit emits light having a first wavelength different from that of the X-ray,
The scintillator element absorbs light of the first wavelength, and emits light of a second wavelength that is longer than the light of the first wavelength and the photoelectric conversion element is sensitive to. An X-ray detector characterized by that. The X-ray detector according to claim 6 .
The X-ray detector, wherein the light having the first wavelength is ultraviolet light. An X-ray detection substrate in which X-ray detection elements that detect X-rays and generate charges according to the detected X-ray intensity are arranged in a matrix;
An X-ray collimator which is disposed on the X-ray incident surface side of the X-ray detection substrate and limits the incident direction of the X-ray;
A light irradiation unit having a light emitting unit disposed to face each of the X-ray detection elements;
A data collection device for collecting an electrical signal from the X-ray detection element;
A defective element determination unit that determines the presence / absence of a defective element of the X-ray detection element and the position of the defective element using an electrical signal acquired by the data collection device;
A central processing unit that processes the electrical signal acquired by the data collection device and creates a reconstructed image of the subject;
The X-ray detection element generates a charge corresponding to light emitted from the light emitting unit,
The X-ray detection board has a two-dimensional arrangement of a scintillator board in which a plurality of scintillator elements that detect the X-rays and convert them into light are two-dimensionally arranged, and a photoelectric conversion element that converts light into an electrical signal. A photoelectric conversion substrate,
The scintillator substrate is disposed on the photoelectric conversion substrate on the incident surface side of the light generated by converting the X-rays, with each scintillator element and each photoelectric conversion element facing each other.
The X-ray collimator is disposed on the X-ray incident surface side of the scintillator substrate,
The light emitting unit is provided to face the scintillator element of the photoelectric conversion substrate.
An X-ray detector characterized by that. The x-ray detector of claim 8 ,
The light emitting unit is at least one of a light incident surface generated by converting the X-rays on the photoelectric conversion substrate and a surface opposite to the light incident surface generated by converting the X-rays. An X-ray detector comprising: An X-ray detection substrate in which X-ray detection elements that detect X-rays and generate charges according to the detected X-ray intensity are arranged in a matrix;
An X-ray collimator which is disposed on the X-ray incident surface side of the X-ray detection substrate and limits the incident direction of the X-ray;
A light irradiation unit having a light emitting unit disposed to face each of the X-ray detection elements;
A data collection device for collecting an electrical signal from the X-ray detection element;
A defective element determination unit that determines the presence / absence of a defective element of the X-ray detection element and the position of the defective element using an electrical signal acquired by the data collection device;
A central processing unit that processes the electrical signal acquired by the data collection device and creates a reconstructed image of the subject;
The X-ray detection element generates a charge corresponding to light emitted from the light emitting unit,
The X-ray detection board has a two-dimensional arrangement of a scintillator board in which a plurality of scintillator elements that detect the X-rays and convert them into light are two-dimensionally arranged, and a photoelectric conversion element that converts light into an electrical signal. A photoelectric conversion substrate,
The scintillator substrate is disposed on the photoelectric conversion substrate on the incident surface side of the light generated by converting the X-rays, with each scintillator element and each photoelectric conversion element facing each other.
The X-ray collimator is disposed on the X-ray incident surface side of the scintillator substrate,
The light emitting unit is disposed to face at least one of the scintillator element and the photoelectric conversion element,
The X-ray collimator includes a plurality of plate-like collimator blades, the plurality of collimator plates are arranged side by side at a gap between the collimator plates adjacent,
The light emitting unit is disposed at a position facing the gap,
An X-ray detector, wherein the scintillator element faces the light emitting unit. An X-ray detection substrate in which X-ray detection elements that detect X-rays and generate charges according to the detected X-ray intensity are arranged in a matrix;
An X-ray collimator which is disposed on the X-ray incident surface side of the X-ray detection substrate and limits the incident direction of the X-ray;
A light irradiation unit having a light emitting unit disposed to face each of the X-ray detection elements;
A data collection device for collecting an electrical signal from the X-ray detection element;
A defective element determination unit that determines the presence / absence of a defective element of the X-ray detection element and the position of the defective element using an electrical signal acquired by the data collection device;
A central processing unit that processes the electrical signal acquired by the data collection device and creates a reconstructed image of the subject;
The X-ray detection element generates a charge corresponding to light emitted from the light emitting unit,
The X-ray detection board has a two-dimensional arrangement of a scintillator board in which a plurality of scintillator elements that detect the X-rays and convert them into light are two-dimensionally arranged, and a photoelectric conversion element that converts light into an electrical signal. A photoelectric conversion substrate,
The scintillator substrate is disposed on the photoelectric conversion substrate on the incident surface side of the light generated by converting the X-rays, with each scintillator element and each photoelectric conversion element facing each other.
The X-ray collimator is disposed on the X-ray incident surface side of the scintillator substrate,
The light emitting unit is disposed to face at least one of the scintillator element and the photoelectric conversion element,
The X-ray collimator includes a plurality of plate-like collimator blades, the plurality of collimator plates is constructed by arranging side by side at a gap between the collimator plates adjacent,
The light emitting unit is disposed at a position facing the collimator plate,
An X-ray detector, wherein an end portion of the scintillator element faces the light emitting portion. An X-ray detector according to any one of claims 1 to 11 ,
A control device for controlling the operation of the X-ray detector and the light irradiation unit,
The control device performs defect element imaging control for obtaining the electrical signal from the X-ray detector while the light irradiation unit emits light,
The data collection device reads an electrical signal obtained by the defective element imaging,
The X-ray imaging apparatus, wherein the defective element determination unit detects defective elements based on an electrical signal obtained by the defective element imaging, and creates defective element position data representing a position of the defective element. The X-ray imaging apparatus according to claim 12 ,
An X-ray generator that emits X-rays, and an input device that inputs an instruction to irradiate X-rays from the X-ray generator;
The control device further performs operation control of the X-ray generation unit, and the defective element imaging is performed at a predetermined time interval while the X-ray generation unit is not irradiating X-rays, and An X-ray imaging apparatus, wherein the X-ray imaging apparatus is performed at least at a time before receiving the X-ray irradiation after receiving an input signal instructing the X-ray irradiation from the input apparatus.

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