Radiation imaging apparatus, evaluation method of radiation imaging apparatus, and program

Abstract

To enable predicting a life of a radiation imaging apparatus on the basis of acquired image information.SOLUTION: A radiation imaging apparatus comprises: acquisition means that acquires an image from imaging means which has a plurality of pixels detecting a radiation; estimation means that estimates a deterioration degree of the radiation imaging apparatus on the basis of the image acquired by the acquisition means; and prediction means that predicts a life of the radiation imaging apparatus on the basis of transition prediction of the deterioration degree of the radiation imaging apparatus obtained by the estimation means.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a radiation imaging apparatus, a method for evaluating a radiation imaging apparatus, and a program.

Background Art

[0002] There is a radiation imaging apparatus in which a scintillator, a drive circuit, and a readout circuit are arranged on a sensor substrate in which pixels having a photoelectric conversion element such as a PIN diode and a switch element such as a thin film transistor (TFT) are formed in a two-dimensional matrix. Such a radiation imaging apparatus is used not only for medical purposes but also for industrial purposes such as inspection of electronic components and inspection of piping. When the radiation imaging apparatus is used for a long time, the image quality of the captured image deteriorates due to deterioration of the switch element caused by the irradiated radiation, and it becomes necessary to replace the radiation imaging apparatus. In industrial applications, in order to reduce the downtime of the entire apparatus, it is required to replace the radiation imaging apparatus at an appropriate timing before the end of its life. Patent Document 1 discloses a method for determining the life of a radiation imaging apparatus by measuring the threshold voltage of a switch element in the radiation imaging apparatus.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method described in Patent Document 1, it is possible to determine whether the timing at which the threshold voltage of the switch element is measured is the life of the radiation imaging apparatus, but it is not possible to predict when the life of the radiation imaging apparatus will come in the future. Therefore, it is difficult to replace the radiation imaging apparatus at an appropriate timing before the end of its life. An object of the present invention is to enable prediction of the life of a radiation imaging apparatus based on acquired image information.

Means for Solving the Problems

[0005] The radiation imaging apparatus according to the present invention includes an acquisition unit that acquires an image from an imaging unit having a plurality of pixels for detecting radiation, an estimation unit that estimates the degree of deterioration of the radiation imaging apparatus based on the image acquired by the acquisition unit, and a prediction unit that predicts the lifespan of the radiation imaging apparatus based on the predicted transition of the degree of deterioration of the radiation imaging apparatus obtained by the estimation unit.

Effect of the Invention

[0006] According to the present invention, the lifespan of a radiation imaging apparatus can be predicted based on the acquired image information.

Brief Description of the Drawings

[0007]

Figure 1

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Modes for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The radiation imaging apparatus in each of the embodiments described below can be applied, for example, to an X-ray imaging apparatus that takes X-ray image data of a subject using X-rays. Further, not limited to the X-ray imaging apparatus, the radiation imaging apparatus in each of the embodiments can also be applied to a radiation imaging apparatus that takes a radiation image of a subject using radiation such as α-rays, β-rays, γ-rays, particle beams, and cosmic rays.

[0009] (First Embodiment) FIG. 1 is a diagram showing a configuration example of a radiation imaging system to which the radiation imaging apparatus in the present embodiment is applied. FIG. 1 shows an inspection system 100 that inspects electronic components and the like using radiation as an example of the radiation imaging system.

[0010] The radiation generator 101 irradiates radiation in a conical shape in the direction (-z direction) from the radiation generator 101 toward the radiation imaging apparatus 105 in FIG. 1. The radiation control device 102 supplies a high voltage necessary for radiation generation and a signal for controlling radiation generation and stop to the radiation generator 101.

[0011] The movable stages 104 and 106 can move the positions of the subject 103, which is the object to be inspected, and the radiation imaging apparatus 105 with respect to two axes in the x direction and the y direction, respectively. For example, while the movable stage 104 on which the subject 103 is placed and the movable stage 106 to which the radiation imaging apparatus 105 is attached perform circular motion in the xy plane, the radiation imaging apparatus 105 can continuously acquire images and perform oblique CT imaging. In this example, the subject 103 and the radiation imaging apparatus 105 are configured to move by the movable stages 104 and 106. However, not limited to this configuration, any other configuration may be used as long as radiation irradiation and image acquisition can be performed while changing the relative positions of the radiation generator 101, the subject 103, and the radiation imaging apparatus 105.

[0012] The radiation imaging device 105 includes a sensor substrate 111 that detects radiation, a readout circuit 112 that reads information from the sensor substrate 111, a drive circuit 113 that controls the drive of the sensor substrate 111, and a power supply unit 114 that supplies power to these components. The sensor substrate 111 is an example of an imaging means. The sensor substrate 111 has a conversion element that converts radiation or light into electric charge and a switch element connected to the conversion element, and a plurality of pixels for detecting radiation are arranged in a matrix. An electrical signal corresponding to the electric charge accumulated in the conversion element is output via the switch element.

[0013] Further, the radiation imaging device 105 includes a control unit 115 that controls the sensor substrate 111, the readout circuit 112, the drive circuit 113, and the power supply unit 114, and a storage unit 116 that stores two-dimensional map information (defective pixel map) of defective pixels and the like, which will be described later. The control unit 115 can control various operations such as the imaging operation in the radiation imaging device 105 and cause the radiation imaging device 105 to perform various operations. The control unit 115 can also perform image processing such as forming image information based on the output information from the readout circuit 112.

[0014] The inspection system 100 may also include a computer 107 for controlling and processing the acquired information. The computer 107 can control the radiation control device 102, the movable stages 104 and 106, and the radiation imaging device 105, and cause the radiation imaging device 105 to perform various operations such as the imaging operation. The computer 107 can also save the image obtained by the radiation imaging device 105 and reconstruct an oblique CT image.

[0015] FIG. 2 is a diagram showing an example of the hardware configuration of the control unit 115 and the storage unit 116 of the radiation imaging device 105. The radiation imaging device 105 includes a CPU 201, a ROM 202, a RAM 203, a storage device 204, an input unit 205, a communication unit 206, and a bus 207. The CPU 201, the ROM 202, the RAM 203, the storage device 204, the input unit 205, and the communication unit 206 are communicably connected via the bus 207.

[0016] The CPU (Central Processing Unit) 201 reads out the control program stored in the ROM (Read Only Memory) 202, executes various processes, and controls various operations in the radiation imaging apparatus 105. The RAM (Random Access Memory) 203 is used as a temporary storage area such as the main memory and work area of the CPU 201. The storage device 204 is, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores various data and various programs. The input unit 205 receives input of image data and measurement data such as time and dose. The communication unit 206 performs communication processing with an external device such as the computer 107.

[0017] For example, when the CPU 201 reads out a program stored in the ROM 202 or the storage device 204 and executes the read program, the various functions shown in FIG. 3 described later and the processes of the flowchart described later are realized.

[0018] FIG. 3 is a diagram showing a functional configuration example of the control unit 115 and the storage unit 116 of the radiation imaging apparatus 105. The radiation imaging apparatus 105 includes an image acquisition unit 301, an estimation unit 302, a storage unit 303, a time measurement unit 304, a dose measurement unit 305, and a prediction unit 306. The image acquisition unit 301, the estimation unit 302, the time measurement unit 304, the dose measurement unit 305, and the prediction unit 306 are realized by, for example, the control unit 115. The storage unit 303 is realized by the storage unit 116.

[0019] The image acquisition unit 301 acquires an image output from the sensor substrate 111 that detects radiation. The estimation unit 302 estimates the degree of deterioration of the radiation imaging apparatus 105 (sensor substrate 111) based on the image acquired by the image acquisition unit 301. As an evaluation index regarding the degree of deterioration of the radiation imaging apparatus 105, the estimation unit 302 estimates, for example, the amount of change (shift amount) of the threshold voltage of the switching element related to the sensor substrate 111, the number of defective pixels, the average image output, etc. as the amount of deterioration. The degree of deterioration (amount of deterioration) of the sensor substrate 111 estimated by the estimation unit 302 is stored in the storage unit 303.

[0020] The irradiation time measuring unit 304 measures the irradiation time of radiation in the radiation imaging apparatus 105. Further, the dose measuring unit 305 measures the cumulative dose of the radiation irradiated to the radiation imaging apparatus 105. The irradiation time of the radiation measured by the irradiation time measuring unit 304 and the cumulative dose of the radiation measured by the dose measuring unit 305 are stored in the storage unit 303. Note that, in the prediction of the transition of the degree of deterioration (amount of deterioration) in the prediction unit 306, the irradiation time measuring unit 304 may not be provided if the prediction of the transition of the degree of deterioration (amount of deterioration) with respect to time is not performed. Similarly, in the prediction of the transition of the degree of deterioration (amount of deterioration) in the prediction unit 306, the dose measuring unit 305 may not be provided if the prediction of the transition of the degree of deterioration (amount of deterioration) with respect to the cumulative dose is not performed.

[0021] The prediction unit 306 performs a prediction regarding the lifespan of the radiation imaging apparatus 105 (sensor substrate 111) based on information such as the degree of deterioration (amount of deterioration) of the radiation imaging apparatus 105 (sensor substrate 111) stored in the storage unit 303. The prediction unit 306 includes a transition calculation unit 307 and a determination unit 308. The transition calculation unit 307 predicts the transition of the degree of deterioration (amount of deterioration) based on information such as the degree of deterioration (amount of deterioration) of the radiation imaging apparatus 105 (sensor substrate 111) estimated by the estimation unit 302 and stored in the storage unit 303. The determination unit 308 determines the lifespan of the radiation imaging apparatus 105 (sensor substrate 111) based on the prediction result of the degree of deterioration (amount of deterioration) by the transition calculation unit 307 and a determination threshold value. The determination unit 308 determines, for example, that the time when the degree of deterioration (amount of deterioration) predicted by the transition calculation unit 307 exceeds a predetermined determination threshold value is the lifespan of the radiation imaging apparatus 105 (sensor substrate 111).

[0022] Hereinafter, an example will be described in which the threshold voltage of the switching element of the pixel included in the sensor substrate 111 is used as the amount of deterioration of the radiation imaging apparatus 105, and a determination regarding the lifespan of the radiation imaging apparatus 105 is made based on the prediction of the transition of the threshold voltage. FIG. 4 is a flowchart showing an example of the lifespan prediction process of the radiation imaging apparatus 105 in the first embodiment.

[0023] In step S401, the radiation imaging apparatus 105 performs a threshold voltage measurement operation. In this threshold voltage measurement operation, the image acquisition unit 301 acquires an output image from the sensor substrate 111 that has pixel values corresponding to the threshold voltages of the switch elements of the pixels included in the sensor substrate 111. In step S402, the radiation imaging apparatus 105 performs a threshold voltage calculation operation. In this threshold voltage calculation operation, the estimation unit 302 calculates the threshold voltage for each pixel based on the image acquired in step S401, and creates a two-dimensional map (threshold voltage map) in which the threshold voltages are recorded for each pixel coordinate.

[0024] The measurement and calculation of the threshold voltage in steps S401 and S402 can be executed, for example, by the method described in Patent Document 1. The measurement and calculation of the threshold voltage by the method described in Patent Document 1 will be described with reference to FIGS. 5(A) and 5(B).

[0025] FIG. 5(A) is a diagram for explaining a configuration example of the sensor substrate 111. A plurality of pixels 501 for detecting radiation are arranged in a matrix on the sensor substrate 111. In FIG. 5(A), only some of the pixels 501 are shown on the sensor substrate 111 for simplicity of explanation, but an actual sensor substrate has more pixels. For example, in the case of a 17×17 inch sensor substrate, about 2800 rows×about 2800 columns of pixels can be arranged on the sensor substrate.

[0026] Each of the pixels 501 has a conversion element 503 that converts radiation or light into electric charges, and a switch element 502 connected to the conversion element. An electric signal corresponding to the electric charges accumulated in the conversion element 503 is output through the switch element 502. The switch element 502 is a transistor such as a TFT (thin film transistor), and has a gate electrode, a source electrode, a drain electrode, and a channel layer. From the viewpoint of increasing the speed and improving the image quality of the radiation imaging apparatus, an oxide semiconductor, for example, an amorphous oxide semiconductor such as IGZO or IZO, can be used for the channel layer of the TFT.

[0027] The conversion element 503 is an indirect conversion element or a direct conversion element, and converts the irradiated radiation into electric charges. The indirect conversion element has a wavelength converter that converts radiation into light, and a photoelectric conversion element that converts the light into electric charges. The direct conversion element is a photoelectric conversion element that can directly convert radiation into electric charges. Here, as an example of the indirect conversion element, a PIN diode made of amorphous silicon (a-Si) as the main material will be used for explanation.

[0028] The conversion element 503 has an individual electrode for extracting a signal, a common electrode to which a bias potential is supplied, and a photoelectric conversion layer made of a-Si sandwiched therebetween. The photoelectric conversion layer is a PIN diode such that the side closer to the individual electrode is n+-type and the side closer to the common electrode is p+-type. The individual electrode of the conversion element 503 is connected to the source electrode of the switch element 502, and the common electrode of the conversion element 503 is connected to a common bias line Vs. A bias potential from a bias power supply (not shown) is supplied to the bias line Vs. In FIG. 5(A), the bias line Vs extends in the column direction, but it may extend in the row direction.

[0029] The gate electrodes, which are the control electrodes of the respective switch elements 502 of the pixels in the k-th row (k = 0 to Y - 1), are commonly connected to a drive line Vg(k) corresponding to the row of the drive circuit 113. By the drive circuit 113 supplying a drive signal to the switch element 502 via the drive lines Vg(0), Vg(1), ···, the conduction state of the switch element 502 is controlled. Also, the drain electrodes of the respective switch elements 502 of the pixels in the j-th column (j = 0 to X - 1) are commonly connected to a signal line Sig(j) corresponding to the column of the readout circuit 112. The source electrodes of the respective switch elements 502 are connected to the individual electrodes of the conversion element 503 of the pixel in which the switch element 502 is arranged.

[0030] In the threshold voltage measurement operation in step S401, by driving and controlling the sensor substrate 111 configured as shown in FIG. 5(A) as shown in FIG. 5(B) under the control etc. from the control unit 115, an image having a pixel value corresponding to the threshold voltage can be obtained.

[0031] First, during the period from time T51 to time T52, a reset process is executed. During the reset process, the reference potential Vref is supplied to the drain electrode of the switch element 502 via the signal lines Sig(0), Sig(1), ···. Then, the potential of the drive line Vg(k) is sequentially set to the conduction potential Von, and the unnecessary charges (such as dark charges due to the dark current of the conversion element) accumulated in the conversion element 503 are discharged to the readout circuit 112 to reset the conversion element 503. As a result, the amount of charge accumulated in the conversion element 503 becomes almost zero, and the conversion element 503 is in a reset state. Note that since the purpose of this process is to discharge unnecessary charges, the formation of the two-dimensional image in the control unit 115 may not be performed. After the reset process, the potential of the drive line Vg(k) is set to the potential Voff1 that turns off the switch element 502.

[0032] Next, at time T52, the potentials of the drive lines Vg(0), Vg(1), ··· of all rows are switched from the potential Voff1 to the potential Voff2. The potential Voff2 is a negative potential weaker than the potential Voff1 (Voff1 < Voff2 < Vref), but the switch element 502 is maintained in the non-conductive state. As a result, in each switch element 502, the gate-source voltage becomes smaller compared to the case when the potential is Voff1. For this reason, although it is in the non-conductive state, it can be in a weaker non-conductive state than when the normal switch element 502 is off.

[0033] Thereafter, at time T53, the bias potential Vs is changed from the potential Vs1 to the potential Vs2 (Vs2 < Vs1). At this time, a potential difference of (Vs2 - Vs1) transiently occurs in the pixel electrode, and the charge Q = C1 × (Vs2 - Vs1) is given to the conversion element 503. Here, C1 is the capacitance of the depleted conversion element 503. Thereafter, the potential of the individual electrode of the conversion element 503 also changes from Vref to Vref + (Vs2 - Vs1). At this time, the gate-source voltage Vgs of the switch element 502 is as shown in the following formula 1.

[0034] Vgs = Voff2 - Vref - (vs2 - Vs1) …(Formula 1) Here, the values of Vs1, Vs2, Voff2, and Vref are appropriately set so that Vgs > V0. V0 is the threshold voltage of the switch element 502. The gate-source voltage Vgs here is set to a value smaller than that during signal readout in the normal shooting operation. That is, the conduction state of the switch element 502 becomes a weaker conduction state than the conduction state during signal readout in the normal shooting operation.

[0035] When this weak conduction state is maintained, a part of the charge Q applied to the conversion element 503 due to the change in the bias potential Vs gradually flows out to the readout circuit 112 as a leakage current flowing through the switch element 502. The state is maintained as it is without changing the potential of the drive line and the bias potential for only the time when the leakage current of the switch element 502 settles to almost 0. Then, when the potential of the individual electrode of the conversion element 503 becomes (Voff2 - V0), the leakage current of the switch element 502 becomes almost 0. At this time, the amount of residual charge Q' remaining in the conversion element 503 is as shown in the following formula 2. Q’ = C1×(Vref - Voff2 + V0) …(Formula 2) When the threshold voltage V0 of the switch element 502 is different for each pixel, the value of the amount of residual charge Q' is also different for each pixel. Therefore, the charge amount Q' is obtained for each pixel.

[0036] At time T54 after the time when the leakage current of the switch element 502 settles to almost 0 has elapsed since time T53, the potentials of the drive lines Vg(0), Vg(1), ··· of all rows are returned from the potential Voff2 to the potential Voff1. Then, the conduction potential Von is sequentially applied to the drive line Vg(k), the switch element 502 is turned on, and the charge Q' remaining in the conversion element 503 of each row is sequentially transferred to the readout circuit 112. The image acquisition unit 301 acquires the image data based on the charge amount transferred from the conversion element 503 to the readout circuit 112.

[0037] The estimation unit 302 acquires the value of the charge amount Q' based on the image data acquired as described above. Then, the estimation unit 302 calculates the threshold voltage V0 corresponding to each pixel based on the above-described formula 2 from the acquired value of the charge amount Q', and creates a two-dimensional map (threshold voltage map) in which the threshold voltage is recorded for each pixel coordinate.

[0038] Note that the measurement and calculation of the threshold voltage in steps S401 and S402 are not limited to the methods described above. For example, it may be executed using a method of directly measuring the current-voltage characteristics of the switching element or other known methods.

[0039] Returning to FIG. 4, in step S403, the radiation imaging apparatus 105 performs a saving operation, and the estimation unit 302 saves the threshold voltage map created in step S402 in the storage unit 303.

[0040] In step S404, the radiation imaging apparatus 105 performs a threshold voltage transition prediction operation. In this threshold voltage transition prediction operation, the transition calculation unit 307 of the prediction unit 306 refers to a plurality of threshold voltage maps stored in the storage unit 303, and predicts the transition of the threshold voltage of the switch element 502 for each pixel. For example, the transition calculation unit 307 refers to a plurality of threshold voltage maps for each time series stored in the storage unit 303, and creates a prediction line of the transition of the threshold voltage with respect to time for each pixel. The transition calculation unit 307 performs the prediction of the threshold voltage transition using an approximation curve. For example, as shown in FIG. 6(A), a prediction line of the threshold voltage transition may be created using linear approximation, or may be created by approximating with a curve. Further, considering the dependency of the dose rate stored in the storage unit 303 on the change rate of the threshold voltage, a prediction line may be created. Subsequently, the transition calculation unit 307 sets the total number of pixels whose threshold voltage exceeds a predetermined range as D, and calculates the time transition of the number of pixels D from the prediction line as shown in FIG. 6(B). The predetermined range can be a predetermined range such as about +1V to -3V according to the characteristics of the switch element. As the threshold voltage map used for prediction, all the threshold voltage maps acquired in the past may be used, or the threshold voltage maps for the last several times may be used. Furthermore, not limited to the prediction line of the transition of the threshold voltage with respect to time, a prediction line of the transition of the threshold voltage with respect to the cumulative radiation dose may be created.

[0041] In step S405, the radiation imaging apparatus 105 performs a lifetime determination operation. In this lifetime determination operation, the determination unit 308 of the prediction unit 306 determines the lifetime of the radiation imaging apparatus 105 based on the prediction result of the threshold voltage transition by the transition calculation unit 307. The determination unit 308 determines the time (time T61 shown in FIG. 6(B)) when the number of pixels D predicted by the transition calculation unit 307 in step S404 exceeds the allowable value Dmax, which is a predetermined reference value (determination threshold), as the lifetime of the radiation imaging apparatus 105. The allowable value Dmax may be set within a range that can ensure an image quality that does not affect the electronic component inspection. For example, it may be set to 0.01% of the total number of pixels of the sensor substrate 111.

[0042] In step S406, the radiation imaging device 105 performs a notification operation to notify the user of the time when the radiation imaging device 105 reaches its lifespan as determined in step S405. As a method for notifying the lifespan of the radiation imaging device 105, the computer controlling the radiation imaging device 105 may be notified of the time when it reaches its lifespan, or a lifespan gauge may be displayed on a display device or the like of the radiation imaging system 100.

[0043] The radiation imaging device 105 can perform the lifespan prediction process shown in FIG. 4 again according to arbitrary conditions. For example, it may be performed when an arbitrary predetermined period has elapsed since the previous lifespan prediction process was performed, or before and after calibration (update of the sensitivity map) is performed on the radiation imaging device 105.

[0044] The above-described lifespan prediction process may be automatically performed by the radiation imaging device 105 according to arbitrary conditions without an instruction from outside the radiation imaging device 105. For example, the radiation imaging device 105 may perform the lifespan prediction process at a timing controlled by the computer of the radiation imaging system 100 or at a timing instructed by the user.

[0045] According to the first embodiment, the threshold voltage of the switch element 502 is used as the amount of deterioration of the radiation imaging device 105, the transition of the threshold voltage of the switch element 502 calculated based on the acquired image is predicted, and the lifespan of the radiation imaging device 105 is determined based on the prediction result. Thereby, the lifespan of the radiation imaging device 105 can be predicted based on the acquired image. By making it possible to predict the lifespan of the radiation imaging device 105, for example, it becomes possible to replace the radiation imaging device 105 at an appropriate timing before it reaches its lifespan.

[0046] In addition, when creating the threshold voltage map by calculating values for each region including a plurality of pixels instead of for each pixel, the radiation imaging apparatus 105 can perform the life prediction process in the same manner as in the above-described example. When performing the process for each region, in the threshold voltage transition prediction operation in step S404, the transition calculation unit 307 of the prediction unit 306 may create a prediction curve of the transition of the threshold voltage with respect to time for each region using the representative value (average value, maximum value, minimum value, median value, etc.) of the threshold voltage in the region. Further, in the life determination operation in step S405, the determination unit 308 of the prediction unit 306 may determine a region where the representative value of the threshold voltage in the region exceeds a predetermined range as a defective region, and determine the life of the radiation imaging apparatus 105 with the total number of defective regions as the number of defects D. At this time, the allowable value Dmax used in the life determination operation may be the maximum allowable value determined for the total number of defective regions. Furthermore, the life of the radiation imaging apparatus 105 may be determined using only a part of the acquired image, that is, the degree of deterioration (amount of deterioration) in a specific region of the pixel region. For example, the life of the radiation imaging apparatus 105 may be determined based only on the degree of deterioration (amount of deterioration) in the central region of the pixel region.

[0047] (Second Embodiment) In the second embodiment described below, the point that the number of defective pixels is used as the amount of deterioration of the radiation imaging apparatus 105 is different from the first embodiment described above. Note that the configurations of the radiation imaging system 100 and the radiation imaging apparatus 105 in the second embodiment are the same as those in the first embodiment described above, and thus the description thereof is omitted.

[0048] Hereinafter, an example will be described in which the number of defective pixels is used as the amount of deterioration of the radiation imaging apparatus 105, and a determination regarding the life of the radiation imaging apparatus 105 is made based on the prediction of the transition of the number of defective pixels. FIG. 7 is a flowchart showing an example of the life prediction process of the radiation imaging apparatus 105 in the second embodiment.

[0049] In step S701, the radiation imaging apparatus 105 performs an image acquisition operation, and the image acquisition unit 301 acquires an output image from the sensor substrate 111 having pixel values corresponding to the irradiated radiation dose. In step S702, the radiation imaging apparatus 105 performs a defective pixel number calculation operation. In this defective pixel number calculation operation, the estimation unit 302 calculates the number of defective pixels based on the image acquired in step S701. The estimation unit 302 extracts defective pixels based on a predetermined criterion from the image acquired in step S701, and calculates the number of defective pixels. In step S703, the radiation imaging apparatus 105 performs a storage operation, and the estimation unit 302 stores the number of defective pixels calculated in step S702 in the storage unit 303.

[0050] In step S704, the radiation imaging apparatus 105 performs a defective pixel number transition prediction operation. In this defective pixel number transition prediction operation, the transition calculation unit 307 of the prediction unit 306 refers to a plurality of pieces of information regarding the number of defective pixels stored in the storage unit 303, and predicts the transition of the number of defective pixels. The transition calculation unit 307 creates, for example, a prediction line of the transition of the number of defective pixels with respect to time by referring to a plurality of time-series pieces of information regarding the number of defective pixels stored in the storage unit 303. The transition calculation unit 307 performs the prediction of the transition of the number of defective pixels using an approximation curve. For example, as shown in FIG. 8, a prediction line of the transition of the number of defective pixels may be created using linear approximation, or may be created by approximating with a curve. Further, as the information regarding the number of defective pixels used for the prediction, all the information acquired in the past may be used, or the information for the most recent several times may be used. Further, not limited to the prediction line of the transition of the number of defective pixels with respect to time, a prediction line of the transition of the number of defective pixels with respect to the cumulative radiation dose may be created.

[0051] In step S705, the radiation imaging apparatus 105 performs a lifetime determination operation. In this lifetime determination operation, the determination unit 308 of the prediction unit 306 determines the lifetime of the radiation imaging apparatus 105 based on the prediction result of the transition of the number of defective pixels by the transition calculation unit 307. The determination unit 308 determines the time (time T81 in the example shown in FIG. 8) when the total number D of defective pixels predicted by the transition calculation unit 307 in step S704 exceeds the allowable value Dmax, which is a predetermined reference value (determination threshold value), as the lifetime of the radiation imaging apparatus 105. The allowable value Dmax may be set within a range that can ensure an image quality that does not affect the electronic component inspection. For example, it may be set to 0.01% of the total number of pixels of the sensor substrate 111.

[0052] In step S706, the radiation imaging apparatus 105 performs a notification operation and notifies the user of the time that is the lifetime of the radiation imaging apparatus 105 determined in step S705. As a method for notifying the lifetime of the radiation imaging apparatus 105, the time that is the lifetime may be notified to the computer that controls the radiation imaging apparatus 105, or a lifetime gauge may be displayed on a display device or the like of the radiation imaging system 100.

[0053] Note that in the above description, an example of calculating the number of defective pixels from a radiation image is shown, but the number of defective pixels may be calculated using a dark image that does not receive a signal. The radiation imaging apparatus 105 can perform the lifetime prediction process shown in FIG. 7 again according to arbitrary conditions. Further, the above-described lifetime prediction process may be automatically performed by the radiation imaging apparatus 105 according to arbitrary conditions without an instruction from the outside of the radiation imaging apparatus 105.

[0054] According to the second embodiment, the number of defective pixels is used as the amount of deterioration of the radiation imaging apparatus 105, the transition of the number of defective pixels calculated based on the acquired image is predicted, and the lifetime of the radiation imaging apparatus 105 is determined based on the prediction result. Thereby, the lifetime of the radiation imaging apparatus 105 can be predicted based on the acquired image. By making it possible to predict the lifetime of the radiation imaging apparatus 105, for example, it becomes possible to replace the radiation imaging apparatus 105 at an appropriate timing before the lifetime.

[0055] (Third Embodiment) In the third embodiment described below, the point that the image average output of the radiation image is used as the amount of deterioration of the radiation imaging device 105 is different from the first and second embodiments described above. Note that the configurations of the radiation imaging system 100 and the radiation imaging device 105 in the third embodiment are the same as those in the first embodiment described above, and thus the description thereof is omitted.

[0056] Hereinafter, an example in which the average output of the radiation image is used as the amount of deterioration of the radiation imaging device 105, and a determination regarding the life of the radiation imaging device 105 is made based on the prediction of the transition of the image average value will be described. FIG. 9 is a flowchart showing an example of the life prediction process of the radiation imaging device 105 in the third embodiment.

[0057] In step S901, the radiation imaging device 105 performs an image acquisition operation, and the image acquisition unit 301 acquires an output image from the sensor substrate 111 having pixel values corresponding to the irradiated radiation dose. The irradiation dose of the radiation is preferably the same as the irradiation dose in the life prediction process performed in the past. In step S902, the radiation imaging device 105 performs an image average value calculation operation. In this image average value calculation operation, the estimation unit 302 calculates the average value of the image based on the image acquired in step S901. In step S903, the radiation imaging device 105 performs a storage operation, and the estimation unit 302 stores the image average value calculated in step S902 in the storage unit 303.

[0058] In step S904, the radiation imaging apparatus 105 performs an image average value transition prediction operation. In this image average value transition prediction operation, the transition calculation unit 307 of the prediction unit 306 refers to a plurality of pieces of information regarding the image average value stored in the storage unit 303 to predict the transition of the image average value. The transition calculation unit 307 creates, for example, a prediction line of the transition of the image average value with respect to time by referring to a plurality of time-series pieces of information regarding the image average value stored in the storage unit 303. The transition calculation unit 307 performs the transition prediction of the image average value using an approximation curve. For example, as shown in FIG. 10, a prediction line of the transition of the image average value may be created using linear approximation, or may be created by approximating with a curve. Further, as the information regarding the image average value used for prediction, all the information acquired in the past may be used, or the information for the most recent several times may be used. Further, not limited to the prediction line of the transition of the image average value with respect to time, a prediction line of the transition of the image average value with respect to the cumulative radiation dose may be created.

[0059] In step S905, the radiation imaging apparatus 105 performs a lifetime determination operation. In this lifetime determination operation, the determination unit 308 of the prediction unit 306 determines the lifetime of the radiation imaging apparatus 105 based on the prediction result of the transition of the image average value by the transition calculation unit 307. The determination unit 308 determines, as the lifetime of the radiation imaging apparatus 105, the time (time T101 shown in FIG. 10) when the image average value predicted by the transition calculation unit 307 in step S904 becomes equal to or less than the allowable value Dmin which is a predetermined reference value (determination threshold value).

[0060] In step S906, the radiation imaging apparatus 105 performs a notification operation and notifies the user of the time which is the lifetime of the radiation imaging apparatus 105 determined in step S905. As a method for notifying the lifetime of the radiation imaging apparatus 105, the time which is the lifetime may be notified to the computer that controls the radiation imaging apparatus 105, or a lifetime gauge may be displayed on a display device or the like included in the radiation imaging system 100.

[0061] 9 again in response to any condition. The radiation imaging apparatus 105 may automatically perform the above-described life prediction process in response to any condition, without being based on an instruction from outside the radiation imaging apparatus 105.

[0062] According to the third embodiment, the average image output is used as the amount of deterioration of the radiation imaging device 105, a transition of the average image output calculated based on an acquired image is predicted, and the life of the radiation imaging device 105 is determined based on the prediction result. This makes it possible to predict the life of the radiation imaging device 105 based on an acquired image. By being able to predict the life of the radiation imaging device 105, it becomes possible to replace the radiation imaging device 105 at an appropriate timing, for example, before the end of its life.

[0063] (Another embodiment of the present invention) The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiment is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for implementing one or more of the functions.

[0064] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

[0065] The disclosure of the present embodiment includes the following configurations, methods, etc. (Configuration 1) an acquisition means for acquiring an image from an imaging means having a plurality of pixels for detecting radiation; an estimation means for estimating a degree of deterioration of the radiation imaging device based on the image acquired by the acquisition means; A radiation imaging apparatus, characterized by comprising prediction means for predicting the lifespan of the radiation imaging apparatus based on the predicted transition of the degradation degree of the radiation imaging apparatus obtained by the estimation means. (Configuration 2) The prediction means includes calculation means for predicting the transition of the degradation degree from the degradation degree of the radiation imaging apparatus obtained by the estimation means, and determination means for determining the lifespan of the radiation imaging apparatus from the prediction result of the degradation degree by the calculation means and a determination threshold value. The radiation imaging apparatus according to Configuration 1, characterized by the above. (Configuration 3) The estimation means estimates the amount of change in the threshold voltage of the switching element included in the pixel based on the acquired image, The prediction means performs prediction of the transition regarding the amount of change in the threshold voltage of the switching element. The radiation imaging apparatus according to Configuration 1 or 2, characterized by the above. (Configuration 4) The estimation means estimates the number of defective pixels of the imaging means based on the acquired image, The prediction means performs prediction of the transition regarding the number of defective pixels. The radiation imaging apparatus according to Configuration 1 or 2, characterized by the above. (Configuration 5) The estimation means estimates the average image output of the imaging means based on the acquired image, The prediction means performs prediction of the transition regarding the average image output. The radiation imaging apparatus according to Configuration 1 or 2, characterized by the above. (Configuration 6) includes time measurement means for measuring the irradiation time of radiation, The prediction means performs prediction of the transition of the degradation degree of the radiation imaging apparatus with respect to the irradiation time. The radiation imaging apparatus according to any one of Configurations 1 to 5, characterized by the above. (Configuration 7) includes dose measurement means for measuring the cumulative dose of the irradiated radiation, The prediction means performs prediction of the transition of the degradation degree of the radiation imaging apparatus with respect to the cumulative dose. The radiation imaging apparatus according to any one of Configurations 1 to 5, characterized by the above. (Configuration 8) The radiation imaging apparatus according to any one of Configurations 1 to 7, wherein the prediction means predicts the degree of deterioration of the radiation imaging apparatus using an approximate curve. (Configuration 9) The radiation imaging apparatus according to any one of Configurations 1 to 8, wherein the prediction means predicts the trend of the degree of deterioration of the radiation imaging apparatus based on the results of the most recent several times among the degrees of deterioration of the radiation imaging apparatus obtained by the estimation means. (Configuration 10) The radiation imaging apparatus according to any one of Configurations 1 to 9, wherein the estimation means estimates the degree of deterioration of the radiation imaging apparatus based on the representative value for each region of the acquired image. (Configuration 11) The radiation imaging apparatus according to any one of Configurations 1 to 9, wherein the estimation means estimates the degree of deterioration of the radiation imaging apparatus using a part of the acquired image. (Method 1) An acquisition step of acquiring an image from an imaging means having a plurality of pixels for detecting radiation; An estimation step of estimating the degree of deterioration of the radiation imaging apparatus based on the image acquired in the acquisition step; An evaluation method for a radiation imaging apparatus, comprising a prediction step of predicting the lifespan of the radiation imaging apparatus based on the predicted trend of the degree of deterioration of the radiation imaging apparatus obtained in the estimation step. (Program 1) A program for causing a computer of a radiation imaging apparatus to execute an acquisition step of acquiring an image from an imaging means having a plurality of pixels for detecting radiation; an estimation step of estimating the degree of deterioration of the radiation imaging apparatus based on the image acquired in the acquisition step; and a prediction step of predicting the lifespan of the radiation imaging apparatus based on the predicted trend of the degree of deterioration of the radiation imaging apparatus obtained in the estimation step.

Explanation of Reference Numerals

[0066] 100: Radiation imaging system 101: Radiation generator 102: Radiation control device 103: Subject 104, 106: Movable stage 105: Radiation imaging device 107: Computer 111: Sensor substrate 112: Readout circuit 113: Drive circuit 114: Power supply unit 115: Control unit 116: Memory unit 301: Image acquisition unit 302: Estimation unit 303: Memory unit 304: Time measurement unit 305: Dose measurement unit 306: Prediction unit 307: Transition calculation unit 308: Determination unit

Claims

1. An acquisition means for acquiring an image from an imaging means having a plurality of pixels for detecting radiation; An estimation means for estimating the degree of deterioration of the radiation imaging apparatus based on the image acquired by the acquisition means; A radiation imaging apparatus, comprising: a prediction means for predicting the life of the radiation imaging apparatus based on a prediction of the transition of the degree of deterioration of the radiation imaging apparatus obtained by the estimation means.

2. The prediction means includes: An arithmetic means for predicting the transition of the degree of deterioration from the degree of deterioration of the radiation imaging apparatus obtained by the estimation means; The radiation imaging apparatus according to claim 1, further comprising: a determination means for determining the life of the radiation imaging apparatus from the prediction result of the degree of deterioration by the arithmetic means and a determination threshold value.

3. The estimation means estimates the amount of change in the threshold voltage of the switching element included in the pixel based on the acquired image; The radiation imaging apparatus according to claim 1, wherein the prediction means performs a prediction of the transition regarding the amount of change in the threshold voltage of the switching element.

4. The estimation means estimates the number of defective pixels of the imaging means based on the acquired image; The radiation imaging apparatus according to claim 1, wherein the prediction means performs a prediction of the transition regarding the number of defective pixels.

5. The estimation means estimates the average image output of the imaging means based on the acquired image; The radiation imaging apparatus according to claim 1, wherein the prediction means performs a prediction of the transition regarding the average image output.

6. Having a time measurement means for measuring the irradiation time of radiation; The radiation imaging apparatus according to claim 1, wherein the prediction means performs a prediction of the transition of the degree of deterioration of the radiation imaging apparatus with respect to the irradiation time.

7. Having a dose measurement means for measuring the cumulative dose of the irradiated radiation; The radiation imaging apparatus according to claim 1, wherein the prediction means performs a prediction of the transition of the degree of deterioration of the radiation imaging apparatus with respect to the cumulative dose.

8. The radiation imaging apparatus according to claim 1, wherein the prediction means predicts the degree of deterioration of the radiation imaging apparatus using an approximate curve.

9. The radiation imaging apparatus according to claim 1, wherein the prediction means performs a prediction of the transition of the degree of deterioration of the radiation imaging apparatus based on the results of the most recent several times among the degrees of deterioration of the radiation imaging apparatus obtained by the estimation means.

10. The radiation imaging apparatus according to claim 1, wherein the estimation means estimates the degree of deterioration of the radiation imaging apparatus based on representative values for each region of the acquired image.

11. The radiation imaging apparatus according to claim 1, wherein the estimation means estimates the degree of deterioration of the radiation imaging apparatus using a part of the acquired image.

12. An acquisition step of acquiring an image from an imaging means having a plurality of pixels for detecting radiation; An estimation step of estimating the degree of deterioration of the radiation imaging apparatus based on the image acquired in the acquisition step; An evaluation method for a radiation imaging apparatus, comprising: a prediction step of predicting the lifespan of the radiation imaging apparatus based on a prediction of the change in the degree of deterioration of the radiation imaging apparatus obtained in the estimation step.

13. On a computer of a radiation imaging apparatus, An acquisition step of acquiring an image from an imaging means having a plurality of pixels for detecting radiation; An estimation step of estimating the degree of deterioration of the radiation imaging apparatus based on the image acquired in the acquisition step; A program for causing the computer to execute a prediction step of predicting the lifespan of the radiation imaging apparatus based on a prediction of the change in the degree of deterioration of the radiation imaging apparatus obtained in the estimation step.

Images