JP2020039083A - Radiation detector - Google Patents

Abstract

To provide a radiation detector capable of accurately detecting a start time of radiation incidence and shortening a detection time.SOLUTION: The radiation detector includes: a substrate 2a; a plurality of control lines 2c1 provided on the substrate and extending in a first direction; a plurality of data lines 2c2 intersecting in the first direction; a plurality of detection units 2b1, each having a thin film transistor 2b2 electrically connected to a corresponding control line and data line, for detecting radiation; a thin film transistor control circuit; a signal detection circuit for reading image data from the plurality of detection units when the thin film transistor is on; and an incident radiation detector 7 for determining a start time of radiation incidence on the basis of a plurality of pieces of image data constituting a first radiation image and a plurality of pieces of image data selected from a second radiation image taken immediately before the first radiation image, or, on the basis of a plurality of pieces of interpolation data created from a plurality of pieces of selected image data.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a radiation detector.

  One example of the radiation detector is an X-ray detector. The X-ray detector includes, for example, an array substrate having a plurality of photoelectric conversion units, and a scintillator provided on the plurality of photoelectric conversion units and converting X-rays into fluorescence. The photoelectric conversion unit is provided with a photoelectric conversion element for converting fluorescence from the scintillator into electric charges, a thin film transistor for switching between accumulation and release of electric charges, a storage capacitor for accumulating electric charges, and the like.

Generally, an X-ray detector reads out image data as follows. First, X-ray incidence is recognized based on a signal input from the outside. Next, after a predetermined time has elapsed, the thin film transistor of the photoelectric conversion unit from which reading is performed is turned on, and the stored charge is read as image data.
However, in this case, since the start of the operation of the X-ray detector depends on an external signal, there is a problem that the processing time becomes longer due to a time lag or the like.

Here, when a thin film transistor which is a semiconductor element is irradiated with X-rays, current flows between the drain electrode and the source electrode even when the thin film transistor is off. The drain electrode of the thin film transistor is electrically connected to the data line.
Therefore, the thin film transistor is turned off, and the X-ray incidence is determined based on the difference between the value of the current flowing through the data line when the X-ray is irradiated and the value of the current flowing through the data line when the X-ray is not irradiated. Techniques for detecting the start time have been proposed.

  However, the value of the current flowing through the data line when the thin film transistor is off is extremely small. Further, if a large amount of X-rays are irradiated on the human body, there is a bad effect on health, and therefore the X-ray irradiation amount on the human body can be suppressed to the minimum necessary. Therefore, in the case of an X-ray detector used for medical treatment, the intensity of the incident X-ray becomes very weak, and the value of the current flowing through the data line when the thin film transistor is in the off state is further reduced. Therefore, even if the value of the current flowing through the data line is detected when the thin film transistor is in the off state, it may be difficult to accurately detect the start of X-ray incidence.

Therefore, a technique has been proposed in which the thin film transistor of the photoelectric conversion unit that performs reading is turned on, and the start of X-ray incidence is detected using the read image data. However, since the number of thin film transistors is very large, the amount of data (the amount of read image data) used for detection at the start of X-ray incidence becomes enormous. Therefore, the detection time at the start of X-ray incidence may be long.
Therefore, development of a radiation detector capable of accurately detecting the start of radiation incidence and shortening the detection time has been desired.

JP 2014-526178 A Japanese Patent No. 6302122

  The problem to be solved by the present invention is to provide a radiation detector capable of accurately detecting the start of radiation incidence and shortening the detection time.

  A radiation detector according to an embodiment includes a substrate, a plurality of control lines provided on the substrate, extending in a first direction, and a plurality of control lines provided on the substrate, extending in a second direction intersecting the first direction. A plurality of data lines, and thin film transistors provided side by side in the first direction and the second direction, each of which is electrically connected to the corresponding control line and the corresponding data line. A plurality of detection units that detect directly or in cooperation with a scintillator, a control circuit that switches an on state and an off state of the thin film transistor, and when the thin film transistor is in an on state, image data is output from each of the plurality of detection units. A signal detection circuit to be read; a plurality of image data constituting a first radiographic image; and a second radiograph taken immediately before the first radiographic image. A plurality of image data selected from a plurality of image data forming a line image, or a plurality of the image data forming the first radiation image; and the selected plurality of images An incident radiation detector that determines a start time of the radiation based on a plurality of interpolation data created from the data. The plurality of selected image data is provided along each of the plurality of detection units provided along each of the plurality of selected control lines, and each of the plurality of selected data lines. The image data is read from at least one of the plurality of detection units.

FIG. 2 is a schematic perspective view illustrating an X-ray detector. It is a block diagram of an X-ray detector. FIG. 3 is a circuit diagram of an array substrate. 6 is a timing chart illustrating reading of image data. FIG. 3 is a block diagram illustrating a configuration of an incident X-ray detection unit. (A) is a schematic diagram for showing the area of the X-ray image to be determined. (B) is a schematic diagram for representing the region of the X-ray image to be compared. (C) is a schematic diagram showing the data amount of the area. (A) is a schematic diagram for showing the area of the X-ray image to be determined. (B) is a schematic diagram for representing the region of the X-ray image to be compared. (C) is a schematic diagram showing the data amount of the area. (A) is a schematic diagram for showing the area of the X-ray image to be determined. (B) is a schematic diagram for representing the region of the X-ray image to be compared. (C) is a schematic diagram showing the data amount of the area. (A) is a schematic diagram for showing the area of the X-ray image to be determined. (B) is a schematic diagram for representing the region of the X-ray image to be compared. (C) is a schematic diagram showing the data amount of the area. (A) is a schematic diagram for showing the area of the X-ray image to be determined. (B) is a schematic diagram for representing the region of the X-ray image to be compared and the intensity of the incident X-ray. (A) is a schematic diagram for showing the area of the X-ray image to be determined. (B) is a schematic diagram for representing the region of the X-ray image to be compared.

Hereinafter, embodiments will be described with reference to the drawings. In each of the drawings, similar components are denoted by the same reference numerals, and detailed description will be omitted as appropriate.
The radiation detector according to the present embodiment can be applied to various radiations such as γ-rays in addition to X-rays. Here, as an example, a case where X-rays are used as a typical radiation will be described. Therefore, by replacing “X-ray” in the following embodiment with “other radiation”, the present invention can be applied to other radiation.

The X-ray detector 1 exemplified below is an X-ray flat sensor that detects an X-ray image that is a radiation image. The X-ray flat sensor is roughly classified into a direct conversion method and an indirect conversion method.
The direct conversion type X-ray detector is provided with a photoelectric conversion film made of, for example, amorphous selenium. In the direct conversion type X-ray detector, X-rays incident from the outside are absorbed by the photoelectric conversion film and directly converted into signal charges.
The indirect conversion type X-ray detector includes, for example, an array substrate having a plurality of photoelectric conversion units and a scintillator provided on the plurality of photoelectric conversion units and converting X-rays into fluorescent light (visible light). ing. In an indirect conversion type X-ray detector, X-rays incident from the outside are converted into fluorescent light by a scintillator. The generated fluorescence is converted into signal charges by the photoelectric conversion unit.

In the following, the indirect conversion type X-ray detector 1 is illustrated as an example, but the present invention can also be applied to a direct conversion type X-ray detector.
That is, the X-ray detector only needs to have a detection unit that converts X-rays into electrical information. The detection unit may detect X-rays directly or in cooperation with a scintillator, for example.
Since a known technique can be applied to the basic configuration of the direct conversion type X-ray detector, detailed description is omitted.

In the following, as an example, a wired X-ray detector 1 that performs data communication via wiring is illustrated. However, the present invention relates to a wireless X-ray detector that performs data communication without using wiring. Can also be applied.
Further, the X-ray detector 1 can be used for, for example, general medical treatment. However, the use of the X-ray detector 1 is not limited to general medical care.

FIG. 1 is a schematic perspective view illustrating the X-ray detector 1.
In FIG. 1, the bias line 2c3 and the like are omitted.
FIG. 2 is a block diagram of the X-ray detector 1.
FIG. 3 is a circuit diagram of the array substrate 2.
As shown in FIGS. 1 to 3, the X-ray detector 1 includes an array substrate 2, a signal processing unit 3, an image processing unit 4, a scintillator 5, a memory 6, and an incident X-ray detection unit 7. .

The array substrate 2 converts the fluorescent light converted from the X-rays by the scintillator 5 into an electric signal.
The array substrate 2 includes a substrate 2a, a photoelectric conversion unit 2b, a control line (or gate line) 2c1, a data line (or signal line) 2c2, a bias line 2c3, a wiring pad 2d1, a wiring pad 2d2, a protective layer 2f, and the like. .
In the present embodiment, the photoelectric conversion unit 2b serves as a detection unit that detects X-rays in cooperation with the scintillator 5.
Note that the numbers of the photoelectric conversion units 2b, the control lines 2c1, the data lines 2c2, the bias lines 2c3, and the like are not limited to those illustrated.

The substrate 2a has a plate shape and is made of a light-transmitting material such as non-alkali glass.
A plurality of photoelectric conversion units 2b are provided on one surface of the substrate 2a. The photoelectric conversion unit 2b is provided in an area defined by the control line 2c1 and the data line 2c2. The plurality of photoelectric conversion units 2b are provided side by side in the direction in which the control line 2c1 extends (corresponding to an example of a first direction) and the direction in which the data line 2c2 extends (corresponding to an example of a second direction). . The plurality of photoelectric conversion units 2b are arranged in a matrix. Note that one photoelectric conversion unit 2b corresponds to one pixel (pixel) in the X-ray image.

Each of the plurality of photoelectric conversion units 2b is provided with a photoelectric conversion element 2b1 and a thin film transistor (TFT: Thin Film Transistor) 2b2.
Further, as shown in FIG. 3, a storage capacitor 2b3 to which the charge converted in the photoelectric conversion element 2b1 is supplied can be provided. The storage capacitor 2b3 has, for example, a rectangular plate shape and can be provided below the thin film transistor 2b2. However, depending on the capacitance of the photoelectric conversion element 2b1, the photoelectric conversion element 2b1 can also serve as the storage capacitor 2b3.

When the photoelectric conversion element 2b1 also serves as the storage capacitor 2b3 (when the storage capacitor 2b3 is omitted), charge is stored and released in the photoelectric conversion element 2b1. In this case, by turning on the thin film transistor 2b2, charge is released from the photoelectric conversion unit 2b, and by turning off the thin film transistor 2b2, charge is accumulated in the photoelectric conversion unit 2b.
When the storage capacitor 2b3 is provided, when the thin film transistor 2b2 is turned off, a constant charge is stored in the storage capacitor 2b3 from the bias line 2c3, and when the thin film transistor 2b2 is turned on, the charge stored in the storage capacitor 2b3 is released. Is done.
In the following, a case where the storage capacitor 2b3 is provided is illustrated as an example.

The photoelectric conversion element 2b1 can be, for example, a photodiode or the like.
The thin-film transistor 2b2 performs switching of charge accumulation and discharge to the storage capacitor 2b3. The thin film transistor 2b2 has a gate electrode 2b2a, a drain electrode 2b2b, and a source electrode 2b2c. Gate electrode 2b2a of thin film transistor 2b2 is electrically connected to corresponding control line 2c1. The drain electrode 2b2b of the thin film transistor 2b2 is electrically connected to the corresponding data line 2c2. That is, the thin film transistor 2b2 is electrically connected to the corresponding control line 2c1 and the corresponding data line 2c2. Source electrode 2b2c of thin film transistor 2b2 is electrically connected to corresponding photoelectric conversion element 2b1 and storage capacitor 2b3. The anode side of the photoelectric conversion element 2b1 and the storage capacitor 2b3 are electrically connected to the corresponding bias line 2c3 (see FIG. 3).

  A plurality of control lines 2c1 are provided in parallel with each other at predetermined intervals. The control line 2c1 extends, for example, in the row direction. One control line 2c1 is electrically connected to one of the plurality of wiring pads 2d1 provided near the periphery of the substrate 2a. One of a plurality of wirings provided on the flexible printed circuit board 2e1 is electrically connected to one wiring pad 2d1. The other ends of the plurality of wirings provided on the flexible printed circuit board 2e1 are electrically connected to a control circuit 31 provided in the signal processing unit 3, respectively.

  A plurality of data lines 2c2 are provided in parallel with each other at a predetermined interval. The data line 2c2 extends, for example, in a column direction crossing the row direction. One data line 2c2 is electrically connected to one of a plurality of wiring pads 2d2 provided near the periphery of the substrate 2a. One of a plurality of wirings provided on the flexible printed circuit board 2e2 is electrically connected to one wiring pad 2d2. The other ends of the plurality of wirings provided on the flexible printed circuit board 2e2 are electrically connected to the signal detection circuits 32 provided in the signal processing unit 3, respectively.

As shown in FIG. 3, the bias line 2c3 is provided between the data line 2c2 and the data line 2c2 in parallel with the data line 2c2. A bias power supply (not shown) is electrically connected to the bias line 2c3. A bias power supply (not shown) can be provided, for example, in the signal processing unit 3 or the like. The bias line 2c3 is not always necessary, and may be provided as needed. When the bias line 2c3 is not provided, the anode side of the photoelectric conversion element 2b1 and the storage capacitor 2b3 are electrically connected to ground instead of the bias line 2c3.
The control line 2c1, the data line 2c2, and the bias line 2c3 can be formed using, for example, a low-resistance metal such as aluminum or chrome.

  The protection layer 2f covers the photoelectric conversion unit 2b, the control line 2c1, the data line 2c2, and the bias line 2c3. The protective layer 2f includes, for example, at least one of an oxide insulating material, a nitride insulating material, an oxynitride insulating material, and a resin material.

The signal processing unit 3 is provided on the array substrate 2 on the side opposite to the scintillator 5 side.
The signal processing unit 3 includes a control circuit 31 and a signal detection circuit 32.
The control circuit 31 switches between the on state and the off state of the thin film transistor 2b2.

As shown in FIG. 2, the control circuit 31 has a plurality of gate drivers 31a and a row selection circuit 31b.
The control signal S1 is input to the row selection circuit 31b from the image processing unit 4 or the like. The row selection circuit 31b inputs the control signal S1 to the corresponding gate driver 31a according to the scanning direction of the X-ray image.
The gate driver 31a inputs the control signal S1 to the corresponding control line 2c1.
For example, the control circuit 31 sequentially inputs the control signal S1 for each control line 2c1 via the flexible printed circuit board 2e1. The thin film transistor 2b2 is turned on by the control signal S1 input to the control line 2c1, and the charge (image data S2) from the photoelectric conversion unit 2b (storage capacitor 2b3) can be received.

  The signal detection circuit 32 reads out the charge (image data S2) from each of the plurality of photoelectric conversion units 2b (the storage capacitor 2b3) when the thin film transistor 2b2 is in the ON state. Further, the signal detection circuit 32 sequentially converts the read image data S2 (analog signal) into a digital signal.

The read image data S2 is temporarily stored in the memory 6.
The plurality of image data sets S2 are also input to the base image memory 72 of the incident X-ray detection unit 7. At this time, a plurality of image data S2 selected based on selection conditions described later can be input to the base image memory 72. The selection of the plurality of image data S2 can be performed by, for example, the image processing unit 4.

When the incident X-ray detector 7 determines that X-rays are incident, the image processor 4 forms an X-ray image based on the plurality of image data S2 stored in the memory 6.
The details of the selection of the plurality of image data sets S2, the operation of the incident X-ray detector 7, and the like will be described later.
The image processing unit 4, the memory 6, and the incident X-ray detection unit 7 may be integrated with the signal processing unit 3.

The scintillator 5 is provided on the plurality of photoelectric conversion elements 2b1, and converts incident X-rays into fluorescent light. The scintillator 5 is provided so as to cover a region (effective pixel region) on the substrate 2a where the plurality of photoelectric conversion elements 2b1 are provided.
The scintillator 5 can be formed using, for example, cesium iodide (CsI): thallium (Tl), or sodium iodide (NaI): thallium (Tl). In this case, if the scintillator 5 is formed by using a vacuum evaporation method or the like, the scintillator 5 composed of an aggregate of a plurality of columnar crystals is formed.

Further, the scintillator 5 can also be formed using, for example, gadolinium oxysulfide (Gd ₂ O ₂ S). In this case, a matrix-shaped groove can be formed so that the square-column-shaped scintillator 5 is provided for each of the plurality of photoelectric conversion units 2b. The interior of the groove may be filled with an atmosphere (air) or an inert gas such as a nitrogen gas for preventing oxidation. Further, the inside of the groove may be in a vacuum state.

In addition, a reflection layer (not shown) can be provided so as to cover the surface side (the X-ray incident surface side) of the scintillator 5 in order to improve the efficiency of use of fluorescence and improve sensitivity characteristics.
Further, in order to prevent the characteristics of the scintillator 5 and the characteristics of the reflective layer from deteriorating due to the water vapor contained in the air, a moisture-proof portion (not shown) that covers the scintillator 5 and the reflective layer can be provided.

The memory 6 is electrically connected between the signal detection circuit 32 and the image processing unit 4. The memory 6 temporarily stores the image data S2 converted into a digital signal. The memory 6 stores a plurality of image data S2 constituting an X-ray image to be determined whether or not X-rays have entered.
The memory 6 can also store information on the photoelectric conversion unit 2b (detection unit) used when determining the start of X-ray incidence. That is, the memory 6 can store the image data S2 read from each of the plurality of photoelectric conversion units 2b and information on the photoelectric conversion unit 2b used when determining the start of X-ray incidence. it can. Information on the photoelectric conversion unit 2b (conditions for selecting the photoelectric conversion unit 2b) used when determining the start of X-ray incidence will be described later. The conditions for selecting the photoelectric conversion unit 2b may be stored in the base image memory 72.

The incident X-ray detector 7 is electrically connected to the memory 6. The incident X-ray detection unit 7 can be electrically connected to the memory 6 via the signal detection circuit 32 and the like.
The incident X-ray detection unit 7 captures a plurality of pieces of image data S2 constituting an X-ray image to be determined (corresponding to an example of a first radiation image) and an image captured immediately before the X-ray image to be determined. The start of X-ray incidence is determined based on a plurality of image data S2 selected from a plurality of image data S2 constituting an X-ray image (corresponding to an example of a second radiation image).
Further, the incident X-ray detection unit 7 performs X-ray based on a plurality of image data S2 constituting an X-ray image to be determined and a plurality of interpolation data created from the selected plurality of image data S2. It is also possible to determine the start time of the incident.
The details of the incident X-ray detector 7 will be described later.

Here, the X-ray detector 1 can form an X-ray image as follows, for example.
First, the control circuit 31 turns off the thin film transistor 2b2. When the thin film transistor 2b2 is turned off, a constant charge is stored in the storage capacitor 2b3 via the bias line 2c3. Next, when X-rays are irradiated, the scintillator 5 converts the X-rays into fluorescent light. When the fluorescent light enters the photoelectric conversion element 2b1, charges (electrons and holes) are generated by the photoelectric effect, and the generated charges are combined with the stored charges (heterogeneous charges) to reduce the stored charges. . Next, the control circuit 31 sequentially turns on the thin film transistors 2b2. The signal detection circuit 32 reads out the charge (image data S2) stored in each storage capacitor 2b3 via the data line 2c2 according to the sampling signal. Then, the signal detection circuit 32 sequentially converts the read image data S2 (analog signal) into a digital signal. The image data S2 converted into a digital signal is stored in the memory 6. The image processing unit 4 forms an X-ray image based on the image data S2 stored in the memory 6. The data of the composed X-ray image is output from the image processing unit 4 to an external device or the like.

FIG. 4 is a timing chart illustrating the reading of the image data S2.
FIG. 4 shows a case where n control lines 2c1 and m data lines 2c2 are provided.
First, the sampling signal 21 is input to the signal detection circuit 32 from the image processing unit 4 or the like. As shown in FIG. 4, when the sampling signal 21 is turned on, the signal detection circuit 32 starts sampling the data lines (1) to (m). The sampling signal 21 is turned off after a predetermined period has elapsed.

On the other hand, while the sampling signal 21 is on, the control signal S1 is input from the image processing unit 4 to the control line (1) via the control circuit 31. When the control signal S1 is turned on, the thin film transistor 2b2 electrically connected to the control line (1) is turned on. The control signal S1 turns off after a predetermined period has elapsed.
The signal detection circuit 32 sequentially reads out the image data S2 from the data line (1) to the data line (m) when the thin film transistor 2b2 is on.
Thereafter, the above procedure is performed for the control lines (2) to (n).
The image data S2 read as described above is stored in the memory 6. The image data S2 read when the thin film transistor 2b2 is in the on state becomes image data S2 of n rows and m columns.

In FIG. 4, the sampling signal 21 is turned on before the control signal S1 is turned on, but the control signal S1 and the sampling signal 21 may be turned on at the same time, or the control signal S1 may be turned on. , The sampling signal 21 may be turned on.
In FIG. 4, the sampling signal 21 is turned off after the control signal S1 is turned off. However, the control signal S1 and the sampling signal 21 may be turned off simultaneously, or the control signal S1 may be turned off. Before turning off, the sampling signal 21 may be turned off.

Here, a general X-ray detector recognizes that X-rays have entered the X-ray detector as described below, and starts an imaging operation.
First, based on a signal from an external device such as an X-ray source, it is recognized that the X-ray has entered the X-ray detector. Next, after a lapse of a predetermined time, the thin film transistor 2b2 of the photoelectric conversion unit 2b from which reading is performed is turned on, and the stored charge is read. That is, in the case of a general X-ray detector, it does not mean that the X-ray is actually incident on the X-ray detector. Therefore, it is necessary to provide a predetermined time between the time when a signal is input from the external device and the time when the reading operation is started. As a result, a time lag occurs, and the processing time becomes longer.

  Here, when the thin film transistor 2b2, which is a semiconductor element, is irradiated with X-rays, a current flows between the drain electrode 2b2b and the source electrode 2b2c even when the thin film transistor 2b2 is off. The drain electrode 2b2b of the thin film transistor 2b2 is electrically connected to the data line 2c2. Therefore, the start of X-ray incidence is detected based on the difference between the value of the current flowing through the data line 2c2 when the X-ray is irradiated and the value of the current flowing through the data line 2c2 when the X-ray is not irradiated. can do. If the start time of X-ray incidence can be directly detected, no time lag or the like occurs, so that it is possible to suppress an increase in processing time.

However, the value of the current flowing through the data line 2c2 when the thin film transistor 2b2 is off is extremely small. Further, if a large amount of X-rays are irradiated on the human body, there is a bad effect on health, and therefore the X-ray irradiation amount on the human body can be suppressed to the minimum necessary. Therefore, in the case of an X-ray detector used for medical treatment, the intensity of the incident X-ray becomes extremely weak, and the value of the current flowing through the data line 2c2 when the thin film transistor 2b2 is in the off state is further reduced. .
As a result, if the start of X-ray incidence is detected based on the value of the current flowing through the data line 2c2 when the thin-film transistor 2b2 is in the off state, it becomes difficult to accurately detect the start of X-ray incidence. There is a risk.

  Therefore, the X-ray detector 1 according to the present embodiment is provided with the incident X-ray detector 7. When X-rays enter the X-ray detector 1, the value of the image data S2 changes according to the intensity of the incident X-rays. For example, when X-rays enter, the value of the image data S2 decreases (the X-ray image becomes brighter). For this reason, the incident X-ray detection unit 7 compares the plurality of image data S2 constituting the captured X-ray image (the X-ray image to be determined) with the X-ray image captured immediately before the X-ray image (comparison By comparing the data with a plurality of image data sets S2 constituting the target X-ray image, the start of X-ray incidence can be detected.

FIG. 5 is a block diagram for illustrating the configuration of the incident X-ray detector 7.
As shown in FIG. 5, the incident X-ray detector 7 includes a first selector 71, a base image memory 72, a second selector 73, a subtraction circuit 74, a comparison / counter circuit 75, and a determination circuit 76. ing.

  The first selector 71 extracts image data S2 to be determined from a plurality of image data S2 stored in the memory 6. The extraction of the image data S2 can be performed based on, for example, the address information of the photoelectric conversion unit 2b from which the image data S2 to be determined has been read.

  The base image memory 72 stores a plurality of image data S2 in the X-ray image to be compared. The X-ray image to be compared can be an X-ray image taken immediately before the X-ray image to be determined (a plurality of image data sets S2 stored in the memory 6). In this case, the base image memory 72 can store the image data S2 read from the selected photoelectric conversion unit 2b. The plurality of image data sets S2 stored in the base image memory 72 can be selected by, for example, the image processing unit 4. The details of the plurality of image data sets S2 stored in the base image memory 72 will be described later.

The second selector 73 extracts image data S2 corresponding to the image data S2 extracted by the first selector 71 from the plurality of image data S2 stored in the base image memory 72.
The subtraction circuit 74 calculates a difference between the image data S2 extracted by the first selector 71 and the image data S2 extracted by the second selector 73.

The comparison / counter circuit 75 calculates, for example, whether the number of times the value calculated by the subtraction circuit 74 exceeds a predetermined range exceeds a threshold value.
The determination circuit 76 can determine that the X-ray has entered the X-ray detector 1 when the comparison / counter circuit 75 determines that the threshold has been exceeded.
The threshold value used for this determination can be set in advance by performing an experiment or a simulation.

  When the determination circuit 76 determines that the X-ray has entered the X-ray detector 1, the image processing unit 4 forms an X-ray image using the plurality of image data S2 stored in the memory 6. I do. When the determination circuit 76 determines that X-rays are not incident on the X-ray detector 1, the plurality of image data sets S2 stored in the base image memory 72 are deleted. Further, predetermined image data S2 is extracted from the plurality of image data S2 stored in the memory 6 and stored in the base image memory 72 based on selection conditions described later. Thereafter, the plurality of image data sets S2 stored in the memory 6 are deleted. The extraction and storage of the image data S2 and the deletion of the image data S2 can be performed by, for example, the image processing unit 4.

As described above, the incident X-ray detector 7 determines whether X-rays have entered based on the image data S2 read when the thin film transistor 2b2 is in the ON state. In this case, if the thin film transistor 2b2 is in the ON state, the resistance is low, and the value of the current flowing through the data line 2c2 (the value of the read image data S2) is large. Therefore, it becomes easy to accurately detect the start of X-ray incidence.
Further, as described above, in the case of the X-ray detector 1 used for medical treatment, the intensity of the incident X-ray becomes very weak. However, if the start of X-ray incidence is detected using the image data S2 obtained when the thin-film transistor 2b2 is in the ON state, the start of X-ray incidence can be accurately detected.

  In this case, when the temperature of the X-ray detector 1 changes, the value of the image data S2 may change. Therefore, when detecting the start of X-ray incidence, a plurality of image data S2 constituting an X-ray image to be determined and a plurality of image data S2 constituting an X-ray image taken immediately before the X-ray image are detected. It is preferable to use the image data S2. By doing so, it is possible to suppress a change in the value of the image data S2 due to a temperature change of the X-ray detector 1.

Next, the plurality of image data S2 stored in the base image memory 72 will be further described.
In a comparative example illustrated below, when detecting the start of X-ray incidence, the value of image data S2 read from all photoelectric conversion units 2b (the value of image data S2 in the entire region of the X-ray image) is detected. Values) are compared.
FIG. 6A is a schematic diagram illustrating an area 101 of an X-ray image to be determined.
FIG. 6B is a schematic diagram illustrating the region 102 of the X-ray image to be compared.
FIG. 6C is a schematic diagram showing the data amount 103 of the area 102.
In the detection at the start of X-ray incidence according to the comparative example, as shown in FIGS. 6A and 6B, the values of the image data S2 in all regions of the X-ray image are compared.
However, the number of photoelectric conversion units 2b is very large. For example, the number of photoelectric conversion units 2b may reach several million. Therefore, when comparing the values of the image data S2 in the entire region of the X-ray image, the amount of data 103 to be compared becomes enormous as shown in FIG.
As the amount of data 103 to be compared increases, the detection time increases. In the case of the X-ray detector 1 used for medical treatment, if the irradiation time of X-rays is prolonged, there is an adverse effect on health, so the irradiation time of X-rays is preferably shortened. Therefore, if the detection time is long, the X-ray incidence determination may not be completed within the X-ray irradiation period. That is, when the detection time is long, there is a possibility that the start of X-ray incidence cannot be detected.
Further, the plurality of image data sets S2 constituting the X-ray image to be compared may need to be rewritten because they change due to environmental changes such as temperature. Further, in order to prevent malfunctions due to sudden noises such as vibrations and external electromagnetic waves, and self-noises caused by drive circuits, it is necessary to take measures such as taking several X-ray images and averaging the image data S2. There are cases. For this reason, there may be a problem that a large-capacity base image memory 72 is required, that the averaging process takes a long time, and that the cost increases and the processing time becomes longer.

  Therefore, the incident X-ray detection unit 7 according to the present embodiment detects the start of X-ray incidence based on the image data S2 read from the selected photoelectric conversion unit 2b. In this way, the amount of data to be compared can be reduced, so that the detection time can be shortened. The image data S2 read from the selected photoelectric conversion unit 2b is stored in the base image memory 72.

FIG. 7A is a schematic diagram illustrating an area 101 of an X-ray image to be determined.
FIG. 7B is a schematic diagram for illustrating the region 102a of the X-ray image to be compared.
Note that the region 102a is a region where the selected plurality of photoelectric conversion units 2b are provided.
FIG. 7C is a schematic diagram illustrating the data amount 103a of the area 102a.

  As shown in FIG. 7B, the area 102a can be an area along the selected control lines 2c1. The plurality of control lines 2c1 can be selected, for example, at a predetermined pitch dimension. By doing so, the data amount 103a to be compared can be reduced as shown in FIG. If the number of the selected control lines 2c1 is too small, the detection accuracy may be deteriorated. If the number of the selected control lines 2c1 is too large, the detection time may not be shortened. Therefore, it is preferable that the number, the pitch size, and the like of the plurality of control lines 2c1 are appropriately determined by performing experiments and simulations.

FIG. 8A is a schematic diagram illustrating an area 101 of an X-ray image to be determined.
FIG. 8B is a schematic diagram illustrating an area 102b of the X-ray image to be compared.
The region 102b is a region where the selected plurality of photoelectric conversion units 2b are provided.
FIG. 8C is a schematic diagram showing the data amount 103b of the area 102b.

  As shown in FIG. 8B, the area 102b can be an area along the selected data lines 2c2. The plurality of data lines 2c2 can be selected at a predetermined pitch size, for example. In this way, as shown in FIG. 8C, the data amount 103b to be compared can be reduced. If the number of the selected data lines 2c2 is too small, the detection accuracy may be deteriorated. If the number of the selected data lines 2c2 is too large, the detection time may not be shortened. Therefore, it is preferable that the number, the pitch size, and the like of the plurality of data lines 2c2 are appropriately determined by performing experiments and simulations.

FIG. 9A is a schematic diagram illustrating an area 101 of an X-ray image to be determined.
FIG. 9B is a schematic diagram illustrating the regions 102a and 102b of the X-ray image to be compared.
FIG. 9C is a schematic diagram illustrating the data amount 103c of the areas 102a and 102b.
As shown in FIG. 9B, the area 102a can be an area along the selected control lines 2c1. The area 102b can be an area along the selected data lines 2c2. The plurality of control lines 2c1 can be selected, for example, at a predetermined pitch dimension. The plurality of data lines 2c2 can be selected at a predetermined pitch size, for example. In this way, as shown in FIG. 9C, the data amount 103c to be compared can be reduced. If the number of the selected control lines 2c1 and the number of the data lines 2c2 are too small, the detection accuracy may be deteriorated. If the number of the selected control lines 2c1 and the number of the data lines 2c2 are too large, the detection time may not be shortened. Therefore, it is preferable that the number and pitch size of the plurality of control lines 2c1 and the number and pitch size of the plurality of data lines 2c2 are appropriately determined by performing experiments and simulations.

FIG. 10A is a schematic diagram illustrating an area 101 of an X-ray image to be determined.
FIG. 10B is a schematic diagram illustrating the region 102a of the X-ray image to be compared and the intensity of the incident X-ray.
As shown in the graph on the right side of FIG. 10B, the intensity of the incident X-ray tends to be strong in the central region of the X-ray image and weak in the peripheral region of the X-ray image. The amount of change in the intensity of incident X-rays tends to be small in the central region of the X-ray image and large in the peripheral region of the X-ray image.
Therefore, as shown in the left-side diagram of FIG. 10B, in the peripheral region of the X-ray image, it is preferable to reduce the pitch dimension of the selected control lines 2c1 or increase the number. . This makes it easier to improve the detection accuracy. Further, in the central region of the X-ray image, it is preferable to increase the pitch dimension of the selected control lines 2c1 or to reduce the number. In this case, the data amount can be reduced, so that the detection time can be easily reduced.

Note that the intensity of incident X-rays may vary depending on the environment in which the X-ray detector 1 is installed. In such a case, the pitch size and number of the selected control lines 2c1 can be changed according to the difference in the intensity of the generated incident X-rays.
Therefore, it is preferable that the number, the pitch size, and the like of the plurality of control lines 2c1 are appropriately determined by performing experiments and simulations.
In the above description, the intensity of incident X-rays in the direction in which the plurality of control lines 2c1 are arranged (the direction in which the plurality of data lines 2c2 extend) has been described. However, the direction in which the plurality of data lines 2c2 are arranged (the plurality of control lines 2c1 are not included). The same applies to the intensity of incident X-rays in the direction of extension. That is, at least one of the selection condition of the plurality of control lines 2c1 and the selection condition of the plurality of data lines 2c2 can be changed according to the change in the intensity of the incident X-ray.

FIG. 11A is a schematic diagram illustrating an area 101 of an X-ray image to be determined.
FIG. 11B is a schematic diagram illustrating an area 102a of the X-ray image to be compared. As shown in FIG. 11B, the area 102a from which the image data S2 is actually read can be an area along the selected control lines 2c1. Then, in the area 102c between the areas 102a and 102a, the interpolation data created based on the actually read image data S2 can be applied. For example, the interpolation data in the area 102c can be the same as the image data S2 in one of the two areas 102a sandwiching the area 102c. The interpolation data in the area 102c can be obtained by averaging or linearly interpolating the image data S2 of the two areas 102a sandwiching the area 102c. The interpolation data in the area 102c can be obtained by an approximate expression created based on the image data S2 of three or more areas 102a in the vicinity of the area 102c.

  In this case, the image data S2 actually read is stored in the memory 6, so that the amount of data stored does not increase. In addition, since the created interpolation data can be used, it is possible to compare all images and compare arbitrary areas. Therefore, the detection accuracy can be further improved.

  In the above, the creation of the interpolation data in the direction in which the plurality of control lines 2c1 are arranged (the direction in which the plurality of data lines 2c2 extend) has been described, but the direction in which the plurality of data lines 2c2 are arranged (the plurality of control lines 2c1 extend). The same applies to the creation of interpolation data in (direction). That is, interpolation data can be created using the image data S2 actually read in the area 102a or the image data S2 actually read in the area 102b.

The selection conditions exemplified in FIGS. 7A to 11B can be appropriately selected or combined according to the model of the X-ray detector 1 and the required detection accuracy.
As described above, the selected plurality of image data S2 includes the plurality of photoelectric conversion units 2b provided along each of the selected plurality of control lines 2c1 and the selected plurality of data lines 2c2. Can be image data S2 read from at least one of the plurality of photoelectric conversion units 2b provided along each of.
The selected control lines 2c1 may be arranged at a predetermined pitch dimension.
The pitch dimension of the selected control lines 2c1 provided in the peripheral region of the substrate 2a in the direction in which the data lines 2c2 extend is the same as the selected plurality of control lines 2c1 provided in the central region of the substrate 2a in the direction in which the data lines 2c2 extend. It can be shorter than the pitch dimension of the control line 2c1.
The selected plurality of data lines 2c2 can be arranged at a predetermined pitch dimension.
The pitch dimension of the selected plurality of data lines 2c2 provided in the peripheral region of the substrate 2a in the direction in which the control lines 2c1 extend is the same as the selected plurality of data lines 2c2 provided in the central region of the substrate 2a in the direction in which the control lines 2c1 extend. It can be shorter than the pitch dimension of the data line 2c2.

Here, the plurality of image data S2 may include data that is not suitable for use in the determination. For example, the plurality of photoelectric conversion units 2b may include a photoelectric conversion unit 2b (also referred to as a defective pixel or the like) having a defect such as a short circuit or disconnection.
For example, the value of the image data S2 read from the defective photoelectric conversion unit 2b may always be higher than a predetermined threshold. Therefore, when the number of defective photoelectric conversion units 2b becomes too large, there is a possibility that an erroneous detection that X-rays are incident is possible even though X-rays are not incident.

The defect of the photoelectric conversion unit 2b mainly occurs when the array substrate 2 is manufactured. Therefore, if a product inspection of the array substrate 2 or a product inspection of the X-ray detector 1 is performed, it is possible to know which photoelectric conversion unit 2b has a defect. For example, if an X-ray image is taken without a subject (a dark image is taken) and the value of the image data S2 read from each of the plurality of photoelectric conversion units 2b is checked, it is found that any of the photoelectric conversion units 2b has a defect. You can know if there is.
Further, a short circuit or disconnection of the control line 2c1 and the data line 2c2 can be known by taking a dark image.

The position information (address information) of the photoelectric conversion unit 2b from which the inappropriate image data S2 detected in the product inspection or the subsequent inspection can be read can be stored in the memory 6, for example.
For example, the image processing unit 4 can exclude the corresponding image data S2 from the image data S2 stored in the base image memory 72 based on the position information.
In this way, the start of X-ray incidence can be detected with higher accuracy.

  While some embodiments of the present invention have been described above, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. These novel embodiments can be implemented in other various forms, and various omissions, replacements, changes, and the like can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and equivalents thereof. The above-described embodiments can be implemented in combination with each other.

  Reference Signs List 1 X-ray detector, 2 array substrate, 2a substrate, 2b photoelectric conversion unit, 2b1 photoelectric conversion element, 2b2 thin film transistor, 2b3 storage capacitor, 2c1 control line, 2c2 data line, 3 signal processing unit, 4 image processing unit, 5 scintillator , 6 memory, 7 incident X-ray detector, 71 first selector, 72 base image memory, 73 second selector, 74 subtraction circuit, 75 comparison / counter circuit, 76 determination circuit

Claims (5)

Board and
A plurality of control lines provided on the substrate and extending in a first direction;
A plurality of data lines provided on the substrate and extending in a second direction intersecting the first direction;
A thin film transistor that is provided side by side in the first direction and the second direction and that is electrically connected to the corresponding control line and the corresponding data line, respectively, and directs radiation directly or in cooperation with a scintillator; A plurality of detectors that operate and detect;
A control circuit for switching between an on state and an off state of the thin film transistor;
When the thin film transistor is on, a signal detection circuit that reads image data from each of the plurality of detection units,
A plurality of image data constituting a first radiation image; and a plurality of image data selected from a plurality of image data constituting a second radiation image taken immediately before the first radiation image. ,On the basis of the,
Alternatively, based on a plurality of the image data constituting the first radiation image and a plurality of interpolation data created from the selected plurality of image data, an incidence that determines a start time of the radiation is determined. A radiation detection unit;
With
The plurality of selected image data is provided along each of the plurality of detection units provided along each of the plurality of selected control lines, and each of the plurality of selected data lines. A radiation detector, which is image data read from at least one of the plurality of detection units.   The radiation detector according to claim 1, wherein the selected control lines are arranged at a predetermined pitch dimension.   The pitch dimension of the selected plurality of control lines provided in the peripheral region of the substrate in the second direction is the same as the selected plurality of control lines provided in the central region of the substrate in the second direction. The radiation detector according to claim 1, wherein the radiation detector is shorter than a line pitch dimension.   The radiation detector according to claim 1, wherein the plurality of selected data lines are arranged at a predetermined pitch dimension. The pitch dimension of the selected plurality of data lines is shorter than the pitch dimension of the selected plurality of data lines provided in a central region of the substrate in the first direction. A radiation detector according to one of the preceding claims.

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