JP2019174184A - Radiation detector and method for manufacturing the same - Google Patents

Abstract

To provide a radiation detector which can reduce the influence of scattering radiation and can improve the image characteristics.SOLUTION: An X-ray detector 1 includes: a photoelectric conversion substrate 2 for converting light into an electric signal; and a scintillator layer 31 in contact with the photoelectric conversion substrate 2 for converting the X-ray 51 entering from the outside into a light. The scintillator layer 31 is a fluorescent body including CsI as a halide and TI as an activator. When the region of the scintillator layer 31 where the X-ray 51 enters in the direction of the film thickness is the incident side region A, the region opposite to the incident side region A is the non-incident side region B, the center region of the scintillator layer 31 in the in-plane direction is the center part, and the surrounding region of the scintillator layer 31 in the in-plane direction is the surrounding part, the non-incident side region B includes the activator, the incident side region A does not include the activator, and the film thickness distribution in the incident side region A is larger in the center part than in the surrounding part.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a radiation detector having a scintillator layer that converts radiation into light and a method for manufacturing the same.

  Conventionally, as a radiation detector, an X-ray detector provided with a photoelectric conversion substrate that converts light into an electrical signal, and a scintillator layer that converts X-rays that are incident from the outside in contact with the photoelectric conversion substrate into light There is. In this X-ray detector, the light converted in the scintillator layer by incident X-rays reaches the photoelectric conversion substrate and is converted into electric charge. This electric charge is read out as an output signal and is output by a predetermined signal processing circuit or the like. It is converted into a digital image signal.

  When CsI which is a halide is used for the scintillator layer, since CsI alone cannot convert incident X-rays into visible light, the scintillator layer activates excitation of light for incident X-rays as in a general phosphor. Therefore, an activator is included. In the X-ray detector, since the peak wavelength of the light receiving sensitivity of the photoelectric conversion substrate exists in the visible light region in the vicinity of 400 nm to 700 nm, when CsI is used for the scintillator layer, the wavelength of the light excited by the incident X-ray is Tl in the vicinity of 550 nm is used as an activator.

  In addition, since X-rays generate scattered X-rays when they pass through the subject, the scattered X-rays cause effects such as deterioration in resolution and contrast. In many cases, X-ray detectors have an X-ray grid installed on the X-ray incident side in order to eliminate the influence of resolution and contrast deterioration due to scattered X-rays.

  However, when an X-ray grid is used in an X-ray detector, it is possible to improve the resolution and contrast of the detected X-ray image, but a photoelectric conversion substrate (active active) for the purpose of improving image characteristics It becomes difficult to cope with the miniaturization of the pixel electrode size and pixel electrode pitch of the matrix photoelectric conversion substrate), and it becomes impossible to prevent image quality deterioration due to the occurrence of moire.

  Furthermore, when using an X-ray grid in an X-ray detector, restrictions for obtaining an appropriate X-ray image (for example, SID (Source Image receptor Distance) which is the distance between the X-ray source and the X-ray detector) In addition, the influence of scattered X-rays generated from a structure or the like existing between the X-ray grid and the scintillator layer cannot be removed structurally.

Japanese Patent Laid-Open No. 2015-38458

  The problem to be solved by the present invention is to provide a radiation detector capable of reducing the influence of scattered radiation and improving image characteristics, and a method for manufacturing the same.

  The radiation detector of this embodiment includes a photoelectric conversion substrate that converts light into an electrical signal, and a scintillator layer that converts radiation incident on the photoelectric conversion substrate and incident from the outside into light. The scintillator layer is a phosphor containing CsI as a halide and Tl as an activator. The incident side of the radiation in the film thickness direction of the scintillator layer is the incident side region, the opposite side of the incident side region is the non-incident side region, the central region in the in-plane direction of the scintillator layer is the central portion, and the outer peripheral region is the peripheral portion In this case, the non-incident side region contains the activator, the incident side region does not contain the activator, and the film thickness distribution of the incident side region is in the relationship of the central portion> the peripheral portion.

It is a schematic sectional drawing of the 1st structural example of the radiation detector which shows one Embodiment. It is a schematic sectional drawing of the 2nd structural example of a radiation detector same as the above. It is a schematic sectional drawing of the 3rd structural example of a radiation detector same as the above. It is a schematic sectional drawing of the 4th structural example of a radiation detector same as the above. It is an equivalent circuit diagram of a radiation detector same as the above. It is a schematic diagram of the scintillator layer of the 1st structural example of a radiation detector same as the above. It is a schematic diagram of the scintillator layer of the 2nd structural example of a radiation detector same as the above. It is an X-ray image in which sensitivity spots have occurred. It is the X-ray image which corrected the sensitivity spot. It is an X-ray image at the time of use of an X-ray grid. It is an X-ray image when the X-ray grid is not used. It is a schematic diagram which shows the general formation method of a scintillator layer. It is a table | surface which shows the structure of the sample which performs a comparison. It is a schematic diagram which shows the imaging condition of a sample. (a) is a front view of a subject showing contrast measurement conditions, and (b) is a waveform diagram of a luminance level for obtaining a contrast ratio. It is a table | surface which shows the image characteristic of a sample. It is an X-ray image which calculates | requires uniformity (BU) about the sample 4. FIG. 3 is an X-ray image for obtaining uniformity (BU) for a sample 3;

  Hereinafter, an embodiment will be described with reference to the drawings.

  1 to 4 show first to fourth structural examples of the basic configuration of the radiation detector, and FIG. 5 shows an equivalent circuit diagram of the basic configuration.

  First, a first structural example of an X-ray detector (X-ray image detector) 1 as a radiation detector (radiation image detector) will be described with reference to FIGS. 1 and 5.

  As shown in FIG. 1, the X-ray detector 1 is an indirect X-ray planar image detector. The X-ray detector 1 includes a photoelectric conversion substrate 2 that is an active matrix photoelectric conversion substrate that converts visible light into an electrical signal.

  The photoelectric conversion substrate 2 includes a support substrate 3 as an insulating substrate formed of a rectangular flat plate-shaped glass having translucency. On the surface of the support substrate 3, a plurality of pixels 4 are two-dimensionally arranged in a matrix and spaced from each other. For each pixel 4, a thin film transistor (TFT) 5 as a switching element and a charge storage capacitor 6. A pixel electrode 7 and a photoelectric conversion element 8 such as a photodiode are formed.

  As shown in FIG. 5, on the support substrate 3, control electrodes 11 are wired as a plurality of control lines along the row direction of the support substrate 3. The plurality of control electrodes 11 are located between the respective pixels 4 on the support substrate 3 and are separated from each other in the column direction of the support substrate 3. These control electrodes 11 are electrically connected to the gate electrode 12 of the thin film transistor 5.

  On the support substrate 3, a plurality of readout electrodes 13 are wired along the column direction of the support substrate 3. The plurality of readout electrodes 13 are located between the respective pixels 4 on the support substrate 3 and are separated from each other in the row direction of the support substrate 3. The source electrode 14 of the thin film transistor 5 is electrically connected to the plurality of readout electrodes 13. The drain electrode 15 of the thin film transistor 5 is electrically connected to the charge storage capacitor 6 and the pixel electrode 7, respectively.

  As shown in FIG. 1, the gate electrode 12 of the thin film transistor 5 is formed in an island shape on the support substrate 3. An insulating film 21 is laminated on the support substrate 3 including the gate electrode 12. This insulating film 21 covers each gate electrode 12. On the insulating film 21, a plurality of island-shaped semi-insulating films 22 are laminated. These semi-insulating films 22 are made of a semiconductor and function as a channel region of the thin film transistor 5. Each of these semi-insulating films 22 is disposed to face each gate electrode 12 and covers each gate electrode 12. That is, each of these semi-insulating films 22 is provided on each gate electrode 12 via the insulating film 21.

  On the insulating film 21 including the semi-insulating film 22, island-shaped source electrodes 14 and drain electrodes 15 are formed, respectively. The source electrode 14 and the drain electrode 15 are insulated from each other and are not electrically connected. The source electrode 14 and the drain electrode 15 are provided on both sides of the gate electrode 12, and one end portions of the source electrode 14 and the drain electrode 15 are stacked on the semi-insulating film 22.

  As shown in FIG. 5, the gate electrode 12 of each thin film transistor 5 is electrically connected to the common control electrode 11 together with the gate electrodes 12 of other thin film transistors 5 located in the same row. Further, the source electrode 14 of each thin film transistor 5 is electrically connected to the common readout electrode 13 together with the source electrodes 14 of other thin film transistors 5 located in the same column.

  As shown in FIG. 1, the charge storage capacitor 6 includes an island-shaped lower electrode 23 formed on the support substrate 3. An insulating film 21 is laminated on the support substrate 3 including the lower electrode 23. The insulating film 21 extends from the gate electrode 12 of each thin film transistor 5 to the lower electrode 23. Further, an island-shaped upper electrode 24 is laminated on the insulating film 21. The upper electrode 24 is disposed to face the lower electrode 23 and covers each lower electrode 23. That is, each upper electrode 24 is provided on each lower electrode 23 via the insulating film 21. A drain electrode 15 is laminated on the insulating film 21 including the upper electrode 24. The other end of the drain electrode 15 is stacked on the upper electrode 24 and is electrically connected to the upper electrode 24.

On the insulating film 21 including the semi-insulating film 22, the source electrode 14 and the drain electrode 15 of each thin film transistor 5 and the upper electrode 24 of each charge storage capacitor 6, an insulating layer 25 is laminated and formed. Yes. The insulating layer 25 is formed of silicon oxide (SiO ₂ ) or the like, and is formed so as to surround each pixel electrode 7.

  A part of the insulating layer 25 is formed with a through hole 26 as a contact hole communicating with the drain electrode 15 of the thin film transistor 5. On the insulating layer 25 including the through hole 26, an island-shaped pixel electrode 7 is laminated. The pixel electrode 7 is electrically connected to the drain electrode 15 of the thin film transistor 5 through the through hole 26.

  On each pixel electrode 7, a photoelectric conversion element 8 such as a photodiode for converting visible light into an electric signal is laminated.

Further, a scintillator layer 31 that converts X-rays as radiation into visible light is formed on the surface of the photoelectric conversion substrate 2 on which the photoelectric conversion elements 8 are formed.
The scintillator layer 31 is a phosphor containing cesium iodide (CsI) as a halide and thallium (Tl) as an activator. The scintillator layer 31 is formed by depositing phosphors in a columnar shape on the support substrate 11. The scintillator layer 31 is formed in a columnar crystal structure in which a plurality of strip-shaped columnar crystals 32 are formed in the surface direction of the photoelectric conversion substrate 2.

  In addition, a reflection layer 41 is formed on the scintillator layer 31 so as to increase the utilization efficiency of visible light converted by the scintillator layer 31, and the scintillator layer 31 is removed from moisture in the atmosphere on the reflection layer 41. A protective layer 42 for protection is laminated and formed, and a protective cover 43 is disposed on the protective layer 42.

  In the X-ray detector 1 configured as described above, X-rays 51 as radiation incident on the scintillator layer 31 are converted into visible light 52 by the columnar crystals 32 of the scintillator layer 31.

  The visible light 52 reaches the photoelectric conversion element 8 of the photoelectric conversion substrate 2 through the columnar crystal 32 and is converted into an electric signal. The electric signal converted by the photoelectric conversion element 8 flows to the pixel electrode 7 and is transferred to the charge storage capacitor 6 connected to the pixel electrode 7 until the gate electrode 12 of the thin film transistor 5 connected to the pixel electrode 7 is driven. Move and hold and accumulate.

  At this time, when one of the control electrodes 11 is in a driving state, the thin film transistors 5 in one row connected to the control electrode 11 in the driving state are in a driving state.

  Electric signals stored in the charge storage capacitors 6 connected to the respective thin film transistors 5 in this driving state are output to the readout electrode 13.

  As a result, since signals corresponding to the pixels 4 in a specific row of the X-ray image are output, signals corresponding to the pixels 4 of all X-ray images can be output by the drive control of the control electrode 11, and this output signal Is converted into a digital image signal and output.

  Next, a second structural example of the X-ray detector 1 will be described with reference to FIG. The same reference numerals as those in the first structural example of the X-ray detector 1 are used, and the description of the same configuration and operation is omitted.

  The structure and operation of the photoelectric conversion substrate 2 are the same as those in the first structure example.

  A scintillator panel 62 is bonded onto the photoelectric conversion substrate 2 via a bonding layer 61. The scintillator panel 62 has a support substrate 63 that transmits X-rays 51, a reflection layer 41 that reflects light is formed on the support substrate 63, and a plurality of strip-like columnar crystals 32 are formed on the reflection layer 41. A scintillator layer 31 is formed, and a protective layer 42 that seals the scintillator layer 31 is laminated on the scintillator layer 31.

  In the X-ray detector 1 configured as described above, the X-ray 51 incident on the scintillator layer 31 of the scintillator panel 62 is converted into visible light 52 by the columnar crystal 32 of the scintillator layer 31.

  The visible light 52 reaches the photoelectric conversion element 8 of the photoelectric conversion substrate 2 through the columnar crystal 32 and is converted into an electric signal, and is converted into a digital image signal and output as described above.

  Next, a third structural example of the X-ray detector 1 will be described with reference to FIG. In the first structural example of the X-ray detector 1 shown in FIG. 1, the scintillator layer 31 does not form the columnar crystal 32, and the other configuration is the same.

  Next, a fourth structural example of the X-ray detector 1 will be described with reference to FIG. In the second structural example of the X-ray detector 1 shown in FIG. 2, the scintillator layer 31 does not form the columnar crystal 32, and the other configurations are the same.

  In the X-ray detector 1 having the structure shown in FIGS. 1 to 4, the scintillator layer 31 is a phosphor containing CsI that is a halide and Tl that is an activator, and further the film thickness of the scintillator layer 31. When the incident region of the X-ray 51 in the direction is A, the non-incident region is B, the central region in the in-plane direction of the scintillator layer 31 is the central portion C, and the outer peripheral region is the peripheral portion D, the following ( 1) It has the characteristics of (2), (3) and (4).

  (1): The non-incident side region B contains an activator, the incident side region A contains no activator, and the in-plane direction film thickness distribution of the incident side region A is such that the central portion C> the peripheral portion D. Become.

  (2): The scintillator layer 31 preferably has a strip-like columnar crystal 32, and the incident side region A occupies 5% to 50% of the film thickness of the scintillator layer 31.

  (3): The central portion C of the scintillator layer 31 is concentric or rectangular with respect to the center of the formation region of the scintillator layer 31, and occupies 50% or more of the formation region of the scintillator layer 31.

  (4): The concentration range of the activator in the non-incident side region B of the scintillator layer 31 is 0.1 mass% to 2.0 mass%.

  Here, in the X-ray detector 1 of the first structural example shown in FIG. 1, a schematic diagram of the scintillator layer 31 is shown in FIG. FIG. 7 shows a schematic diagram of the scintillator layer 31 in the X-ray detector 1 of the second structural example shown in FIG.

  As shown in FIG. 6 or FIG. 7, when the features (1) and (2) are imparted to the scintillator layer 31, the incident side region A does not contain an activator, and therefore absorbs X-rays 51 that do not contribute to light emission. This is an absorption layer for scattered X-rays generated when the X-rays 51 pass through the subject, and thus has the same effect as when an X-ray grid is used.

  In the X-ray detector 1, the intensity distribution of scattered X-rays generated when the X-rays 51 pass through the subject satisfies the central part C> the peripheral part D. Therefore, when a scattered X-ray absorption layer corresponding to the intensity of scattered X-rays at the center C is uniformly formed in the entire formation region of the scintillator layer 31, an X-ray image (Flat Field correction: none) shown in FIG. In addition, concentric sensitivity spots (shading) associated with the intensity distribution of scattered X-rays are generated.

  Normally, in the X-ray detector 1, flat field correction for correcting sensitivity spots as shown in FIG. 8 is applied to the X-ray image. However, when flat field correction is applied to the X-ray image, correction is performed. As a result, the noise component included in the X-ray image is also amplified. Therefore, as the sensitivity spot before correction increases, the S / N of the X-ray image after correction decreases and the dynamic range of the X-ray image also decreases. In other words, the better the uniformity of sensitivity distribution of the X-ray image {BU (Brightness Uniformity)}, the higher the quality of the X-ray image (high S / N, wide dynamic range).

  For this reason, if the characteristics of (1) and (2) are given to the scintillator layer 31, the central portion C> periphery is obtained by setting the film thickness distribution of the incident side region A of the scintillator layer 31 to the central portion C> the peripheral portion D. Since an absorption layer of scattered X-rays corresponding to the intensity distribution of scattered X-rays in the part D can be formed, sensitivity spots before correction can be reduced, and correction can be performed as in the X-ray image subjected to flat field correction shown in FIG. It is possible to reduce the S / N reduction and dynamic range reduction of the X-ray image later, and obtain a higher quality X-ray image (high S / N, wide dynamic range).

  Further, in the X-ray detector 1, when the features (1) and (2) are imparted to the scintillator layer 31, the incident-side region A has a structure in which each columnar crystal of the scintillator layer 31 has a strip-like columnar crystal structure. Therefore, the following effects I to III can be obtained with respect to the case where the X-ray grid is used.

  I: Since moire does not occur regardless of the pixel electrode size and pixel electrode pitch of the photoelectric conversion substrate (active matrix photoelectric substrate), the image quality of the X-ray image does not deteriorate. When the X-ray grid is used, moire is generated as shown in FIG. 10 and the image quality of the X-ray image is deteriorated. On the other hand, by not using the X-ray grid, moire is generated as shown in FIG. Does not occur and image quality deterioration of the X-ray image can be prevented.

  II: There are few restrictions (for example, restrictions (Source Image receptor Distance) etc. which are distances between the X-ray generation source 80 and the X-ray detector 1) for obtaining an appropriate X-ray image.

  III: Since there is no structure between the absorption layer (incident side region A) of the scattered X-rays and the non-incident side region B of the scintillator layer 31 that contributes to light emission, image characteristics (sensitivity, resolution) And the improvement efficiency of contrast etc. are good.

  Also, when the quality of the incident X-ray is soft {when the tube voltage of the X-ray generation source (X-ray tube) 80 is low}, the absorption of the incident X-ray by the subject increases, The effect becomes prominent, and a slight difference in the X-ray absorption rate of the structure (the reflective layer 41, the protective layer 42, the protective cover 43, etc.) existing on the scintillator layer 31 incident side of the X-ray 51 is observed in the X-ray image. In the X-ray detector 1, when the features (1) and (2) are added to the scintillator layer 31, unlike the case where an X-ray grid is used, the incident side region A is the X-ray of the scintillator layer 31. Because it is formed on the non-incident side than the structure existing on the incident side, even if the quality of incident X-rays is soft, it is possible to suppress minute X-ray image spots generated by the influence of scattered X-rays It becomes.

  For this reason, the X-ray detector 1 can improve the image characteristics (sensitivity, resolution, contrast, etc.) without using an X-ray grid.

  In addition, in the X-ray detector 1, when the features (1) and (2) are added to the scintillator layer 31, the central portion C of the scintillator layer 31 that is the feature (3) is a region 50 where the scintillator layer 31 is formed. If it occupies% or more, for example, the X-ray detector 1 suitable for diagnosis using an X-ray image can be provided.

  Further, in the X-ray detector 1, when the features (1) and (2) are imparted to the scintillator layer 31, the incident side region A does not contain an activator. Therefore, if the concentration range in the film thickness direction of the activator in the non-incident side region B, which is a feature of (4), is 0.1 mass% to 2.0 mass%, good image characteristics (sensitivity, resolution, etc.) are obtained. can get. More preferably, if the concentration range in the film thickness direction of the activator in the non-incident side region B is 1.6 mass% ± 0.4 mass%, the afterimage characteristics can be improved without deteriorating the image characteristics (sensitivity, resolution, etc.). It can also be improved.

  Next, FIG. 12 shows a schematic diagram of a general method for forming the scintillator layer 31 made of a phosphor containing Tl as an activator in CsI which is a halide.

  A substrate 72 (corresponding to the photoelectric conversion substrate 2 or the support substrate 63) is arranged in the vacuum chamber 71, and the evaporated particles from the CsI evaporation source 73 installed in the vacuum chamber 71 while rotating the substrate 72. The scintillator layer 31 is laminated by a vacuum vapor deposition method in which the vaporized particles 74a from the evaporation source 74 of 73a and TlI are vapor-deposited on the laminated surface of the substrate 72.

  At this time, in the formation process of the scintillator layer 31, if the supply of the evaporated particles 74 a from the TlI evaporation source 74 is cut off or stopped, an area not containing the activator is formed in an arbitrary area in the film thickness direction of the scintillator layer 31. It becomes possible to form.

  For this reason, the scintillator layer 31 of the present embodiment shuts off or stops the supply of the vaporized particles 74a from the TlI evaporation source 74 at the final stage or the initial stage of the formation process of the scintillator layer 31, and the CsI evaporation source 73. It is formed by controlling the supply distribution of the vaporized particles 73a. A shield or the like may be used to control the supply distribution of the evaporated particles 73a. Therefore, the incident side region A does not contain an activator, the non-incident side region B contains an activator, and the film thickness distribution in the in-plane direction of the incident side region A is set as a central portion C> a peripheral portion D. The non-incident side region B can be set to a predetermined activator concentration. The film thickness distribution in the in-plane direction of the non-incident side region B is substantially uniform.

Here, an embodiment of the X-ray detector 1 having the structure shown in FIG. 1 will be described. In this example, samples 1, 2, 3, and 4 were prepared in which the base material of the scintillator layer 31: CsI, the activator: Tl, the reflective layer 41: TiO _{2, the} protective cover 43: aluminum, and other configurations differed. did. FIG. 13 shows the configurations of Samples 1, 2, 3, and 4.

  Sample 1 has a configuration in which an activator is contained in the entire region of the scintillator layer 31 in the film thickness direction and there is no X-ray grid.

  Sample 2 is a configuration having an X-ray grid in the configuration of sample 1.

  Sample 3 is the present embodiment in which the features of (1) and (2) are imparted to the scintillator layer 31. The incident side region A does not contain an activator, and the non-incident side region B contains an activator. The film thickness distribution of the side region A is in the relationship of the central part C> the peripheral part D.

  In the configuration of sample 3, sample 4 has a film thickness distribution such that central portion C = peripheral portion D.

  Each of these four samples 1, 2, 3, and 4 is combined with the X-ray detector 1 to image a subject under specific imaging conditions, and image characteristics (sensitivity ratio, MTF ratio (resolution)) of the X-ray image, (Contrast ratio, moire). As for the imaging conditions, as shown in FIG. 14, a rectangular acrylic 82 in which a lead object 81 is arranged at the center is arranged between the X-ray generation source 80 and the X-ray detector 1. Furthermore, the X-ray irradiation conditions during measurement of sensitivity, MTF, and contrast ratio are 70 kV-0.0087 mGy, and the acrylic thickness is 60 mm. As for the contrast, as shown in FIG. 15A, the luminance on the luminance measurement line 83 passing through the subject 81 is measured, and as shown in FIG. A ratio H / L between the luminance level H and the luminance level L with the subject is obtained.

  And the result of having measured the image characteristic of the X-ray image about four samples 1, 2, 3, and 4 is shown in the table | surface of FIG. Note that the sensitivity ratio, the MTF ratio, and the contrast ratio are relative values based on the image characteristic of the sample 1 as a reference (1.00).

  As shown in FIG. 16, the sample 3 according to the present embodiment in which the features (1) and (2) are imparted to the scintillator layer 31 has a sensitivity ratio, an MTF ratio, and a contrast ratio in the same manner as the sample 2 having an X-ray grid. In addition, it has the effect of improving, and in addition to the use of an X-ray grid, there is no structurally moire and balanced image characteristics can be obtained.

  Further, FIG. 17 shows an X-ray image of Sample 4 (Flat Field Correction: None), and FIG. 18 shows an X-ray image of Sample 3 (Flat Field Correction: None). At this time, the X-ray irradiation condition is 70 kV-0.0087 mGy, and the image processing is a histogram average value ± 50%. The sensitivity of the central portion C is a, the sensitivity of the peripheral portion D (position 90% from the center of the diagonal length of the X-ray image) is b, and the sensitivity distribution of the X-ray image is uniform. When determining the brightness (Brightness Uniformity) (%) = b / a · 100, sample 4 was BU = 62% and sample 3 was BU = 72%. Therefore, the sample 3 according to this embodiment in which the features of (1) and (2) are imparted to the scintillator layer 31 can reduce the concentric sensitivity spots associated with the scattered X-ray intensity distribution with respect to the sample 4 as well. A higher quality X-ray image can be obtained.

  From the above, the non-incident side region B of the scintillator layer 31 contains the activator, the incident side region A does not contain the activator, and the film thickness distribution in the in-plane direction of the incident side region A is the central portion C. > By setting the peripheral portion D, it is possible to reduce the influence of scattered X-rays and improve image characteristics (sensitivity, resolution, contrast, etc.).

  Further, the scintillator layer 31 has strip-like columnar crystals 32, and the incident side region A occupies 5% to 50% of the film thickness of the scintillator layer 31, thereby further reducing the influence of scattered X-rays. Image characteristics (sensitivity, resolution, contrast, etc.) can be further improved.

  Further, the central portion C of the scintillator layer 31 is concentric or rectangular with respect to the center of the scintillator layer 31 formation region, and occupies 50% or more of the scintillator layer 31 formation region, for example, an X-ray image. It is possible to provide an X-ray detector 1 that is suitable for diagnosis using a sensor.

  Further, when the concentration range of the activator in the non-incident side region B of the scintillator layer 31 is 0.1 mass% to 2.0 mass%, good image characteristics (sensitivity, resolution, etc.) can be obtained.

  As described above, it is possible to provide the X-ray detector 1 having high performance and high reliability with excellent image characteristics (sensitivity, resolution, contrast, etc.).

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1 X-ray detector as a radiation detector 2 Photoelectric conversion substrate
31 Scintillator layer
51 X-ray as radiation A Incident side area B Non-incident side area C Center part D Peripheral part

Claims (5)

A photoelectric conversion substrate that converts light into an electrical signal;
A scintillator layer that contacts the photoelectric conversion substrate and converts radiation incident from the outside into light, and
The scintillator layer is
A phosphor containing CsI as a halide and Tl as an activator;
The incident side of the radiation in the film thickness direction of the scintillator layer is an incident side region, the opposite side to the incident side region is a non-incident side region, and the central region in the in-plane direction of the scintillator layer is a central portion and an outer periphery When the region is a peripheral portion, the non-incident side region contains the activator, the incident side region does not contain the activator, and the film thickness distribution of the incident side region is the central portion> the peripheral portion A radiation detector comprising: in a part relationship. The radiation detector according to claim 1, wherein the scintillator layer has a columnar crystal structure, and the incident side region occupies 5% to 50% of the film thickness of the scintillator layer. The radiation detector according to claim 1, wherein the central portion of the scintillator layer occupies 50% or more of a formation region of the scintillator layer. The radiation detector according to any one of claims 1 to 3, wherein a concentration range of the activator in the non-incident side region of the scintillator layer is 0.1 mass% to 2.0 mass%. A method for manufacturing a radiation detector comprising: a photoelectric conversion substrate that converts light into an electrical signal; and a scintillator layer that converts radiation incident from the outside in contact with the photoelectric conversion substrate;
The scintillator layer is a phosphor containing CsI which is a halide and Tl which is an activator, and the incident side of the radiation in the film thickness direction of the scintillator layer is an incident side region, and the opposite side to the incident side region is non-exposed. When the incident side region is the center region in the in-plane direction of the scintillator layer and the outer peripheral region is the peripheral portion, the non-incident side region contains Tl as an activator, and the incident side region The scintillator layer is formed by a vapor phase growth method using the CsI and the Tl as a material source so as not to contain an activator and the film thickness distribution of the incident side region has a relation of center portion> peripheral portion. A method of manufacturing a radiation detector.