阅读说明：本技术 X射线探测阵列像素单元、制造工艺和双层能谱ct探测器 (X-ray detection array pixel unit, manufacturing process and double-layer energy spectrum CT detector ) 是由 李文 黄海波 吴小页 于 2021-09-03 设计创作，主要内容包括：本发明公开了一种X射线探测阵列像素单元、双层闪烁体阵列的制造工艺以及基于该像素单元的双层能谱CT探测器,像素单元包括顶层闪烁体像素、底层闪烁体像素、薄膜光过滤层和光敏阵列等,顶层和底层闪烁体阵列的子像素采用发射不同光谱的闪烁体材料加工而成,薄膜光过滤层对应每个闪烁体像素的光输出面,光敏阵列的像素分为两个独立的子像素区域,其输出信号分别对应顶层闪烁体像素和底层闪烁体像素的X光响应,可以有效地获得入射X射线的能谱信息。本发明的双层闪烁体阵列采用二维阵列加工工艺,探测器子模块的整合工艺采用与常规CT探测器相同的叠加装配工艺,不影响探测器的灵敏面积,能够有效保持成像的剂量效率以及控制探测器的成本。(The invention discloses an X-ray detection array pixel unit, a manufacturing process of a double-layer scintillator array and a double-layer energy spectrum CT detector based on the pixel unit, wherein the pixel unit comprises a top layer scintillator pixel, a bottom layer scintillator pixel, a thin film light filtering layer, a photosensitive array and the like, sub-pixels of the top layer scintillator array and the bottom layer scintillator array are processed by adopting scintillator materials emitting different spectrums, the thin film light filtering layer corresponds to a light output surface of each scintillator pixel, the pixels of the photosensitive array are divided into two independent sub-pixel areas, output signals of the two independent sub-pixel areas respectively correspond to X-ray responses of the top layer scintillator pixel and the bottom layer scintillator pixel, and energy spectrum information of incident X-rays can be effectively obtained. The double-layer scintillator array adopts a two-dimensional array processing technology, the integration technology of the detector sub-modules adopts the same overlapping assembly technology as that of the conventional CT detector, the sensitive area of the detector is not influenced, and the imaging dose efficiency and the cost of the detector can be effectively kept.)

1. An X-ray detection array pixel cell, characterized by: sequentially arranging a top layer scintillator pixel, a bottom layer scintillator pixel, a thin film light filtering layer and a photosensitive array pixel in the light incidence direction;

the top layer scintillator pixels and the bottom layer scintillator pixels form a double-layer scintillator array, are made of scintillator materials with different light-emitting spectrums and are used for converting incident X rays into visible light; light reflecting layers are arranged outside the top layer scintillator pixels and the bottom layer scintillator pixels;

the film light filter layer comprises two filter areas arranged on the same layer, namely a first filter area of the film light filter layer and a second filter area of the film light filter layer, which respectively correspond to the light-emitting spectrum areas of the top layer scintillator pixel and the bottom layer scintillator pixel;

the photosensitive array pixels are used for converting visible light generated by the scintillator pixels into electric signals, each photosensitive array pixel comprises a first photosensitive sub-pixel corresponding to a first filtering area of the thin film light filtering layer and a second photosensitive sub-pixel corresponding to a second filtering area of the thin film light filtering layer, and output signals of the first photosensitive sub-pixel and the second photosensitive sub-pixel respectively correspond to X-ray responses of the top layer scintillator and the bottom layer scintillator.

2. An X-ray detection array pixel cell according to claim 1, wherein: the first filtering area of the thin film light filtering layer and the first photosensitive array sub-pixel are equal in size, and the second filtering area of the thin film light filtering layer and the second photosensitive array sub-pixel are equal in size.

3. An X-ray detection array pixel cell according to claim 1, wherein: the top layer scintillator pixels and the bottom layer scintillator pixels are connected in a direct light coupling mode.

4. An X-ray detection array pixel cell according to claim 1, wherein: the combination of the top layer scintillator pixel and the bottom layer scintillator pixel adopts any one of ZnSe/GOS, BaF2/GOS, BaF2/CdWO4 and ZnSe/YAG.

5. An X-ray detection array pixel cell according to claim 1, wherein: and the combination of the top layer scintillator pixels and the bottom layer scintillator pixels adopts ZnSe/GOS, and the thicknesses of the top layer scintillator pixels and the top layer scintillator pixels are respectively 0.5mm and 1.0 mm.

6. An X-ray detection array pixel cell according to claim 5, wherein: the first filtering area of the thin film light filtering layer is a short-pass filtering layer and only allows photons with the wavelength being larger than or equal to 550nm to pass through, and the second filtering area of the thin film light filtering layer is a long-pass filtering layer and only allows photons with the wavelength being larger than 550nm to pass through.

7. An X-ray detection array pixel cell according to claim 1, wherein: the area ratio of the first filtering area of the film light filtering layer to the second filtering area of the film light filtering layer is 1: 1.

8. a process for manufacturing a bilayer scintillator array, comprising the steps of:

(1) the method comprises the following steps of (1) respectively polishing a top layer scintillator wafer and a bottom layer scintillator wafer serving as raw materials, and then bonding the top layer scintillator wafer and the bottom layer scintillator wafer through an optical coupling adhesive to obtain an integrated double-layer scintillator wafer;

(2) cutting a plurality of two-dimensional separation grooves from one end of a top scintillator wafer of the double-layer scintillator wafer, wherein the depth of each two-dimensional separation groove is greater than the design thickness of the double-layer scintillator array and smaller than the thickness of the double-layer scintillator wafer;

(3) filling a light reflection layer material from one end of a top layer scintillator wafer of the double-layer scintillator wafer and solidifying to form a light reflection layer covering the top layer scintillator wafer and separating adjacent pixels of the scintillator, wherein the distance between the adjacent pixels separated by the two-dimensional separation groove is equal to the size of the required pixel of the double-layer scintillator array;

(4) grinding the double-layer scintillator wafer subjected to the light reflection layer process from one end of the bottom layer scintillator wafer until the thickness of the bottom layer scintillator wafer is reduced to a preset thickness, and then polishing from one end of the bottom layer scintillator wafer to form a coupling surface with a thin film light filtering layer; and cutting along the two-dimensional separation groove to obtain the required double-layer scintillator array.

9. The manufacturing process of the double-layer scintillator array according to claim 8, characterized in that: the areas of the top layer scintillator wafer and the bottom layer scintillator wafer in the step (1) are determined by wafer raw materials and a production process;

in the step (2), the design thickness of the top layer scintillator wafer is the design thickness of the top layer scintillator pixels, and the thickness of the bottom layer scintillator wafer is larger than the design thickness of the bottom layer scintillator pixels;

in the step (4), the top end of the top layer scintillator wafer and the two-dimensional separation groove are covered and filled by the light reflection layer, and the bottom surface of the bottom layer scintillator wafer is the light output surface of the pixel.

10. A dual-layer spectral CT detector, characterized by: the double-layer energy spectrum CT detector minimum submodule is comprised, each minimum submodule comprises a plurality of X-ray detection array pixel units according to any one of claims 1 to 7, and a top layer scintillator array pixel serves as an incidence end of an X-ray.

Technical Field

The invention relates to the field of semiconductor photoelectric detectors, in particular to an X-ray detection array pixel unit, a double-layer scintillator array manufacturing process and a double-layer energy spectrum CT detector.

Background

The X-ray response signal acquired in conventional CT is proportional to the energy integral of all the X-rays of different energies detected by the detector, which does not contain any energy spectrum information of the X-rays. In recent years, rapidly developed energy spectrum CT is obtained, more image information than conventional CT is obtained by acquiring and distinguishing response signals of different energy X-rays, possibility is provided for density resolution optimization of images according to energy weight and realization of substance resolution of imaging objects, and image quality, dosage efficiency and clinical diagnosis accuracy are remarkably improved on the basis of conventional CT. The technology and application research of spectral CT has become an important development direction of CT medical imaging technology.

A more sophisticated method for acquiring spectral data in CT applications uses a double-layer scintillator X-ray detector instead of the single-layer scintillator X-ray detector in conventional CT. The detector array in conventional CT is usually formed by splicing a plurality of detector modules along the X direction, and each detector module is precisely positioned by processing into an arc-shaped detector guide rail, so as to ensure that the distance between each module and the focal point of the tube is the same, as shown in fig. 1. The detector module is generally formed by arranging a plurality of detector minimum sub-modules in a Z direction perpendicular to an XY plane, one structure of the detector minimum sub-modules is shown in fig. 2 and comprises a collimator array, a scintillator array, a photosensitive array, an analog-to-digital conversion chip, a mounting block for accurate assembly and positioning and the like. The scintillator array and the photosensitive array are main devices for signal conversion and are composed of two-dimensional pixel arrays. A conventional signal conversion pixel unit of a CT detector is shown in fig. 3, in which a scintillator pixel converts incident X-rays into visible light, and a photosensitive array pixel converts the visible light generated by the scintillator pixel into an electrical signal, which is transmitted to a subsequent analog-to-digital conversion circuit through a signal connection of a substrate. The traditional CT detector adopts a single-layer scintillator array and an integral signal acquisition mode, and cannot distinguish energy spectrum information of incident X-rays. Compared with the structure of the traditional CT detector, the difference of the existing double-layer energy spectrum CT detector is mainly the more complicated signal conversion pixel structure, as shown in FIG. 4, each signal conversion pixel consists of two stacked scintillator sub-pixels and two side-coupled photosensitive array sub-pixels, and the top layer scintillator sub-pixels and the bottom layer scintillator sub-pixels are connected by a light reflection layer and realize the isolation of optical signals. The top layer scintillator sub-pixels mainly detect a low-energy part in incident X-rays, the bottom layer scintillator sub-pixels mainly detect a high-energy part in the incident X-rays, and energy spectrum information corresponding to the high-energy part and the low-energy part of the incident X-rays can be obtained in the imaging process by simultaneously reading signals of the two sub-pixels.

The existing double-layer energy spectrum CT detector adopts a side coupling design between a scintillator sub-pixel and a photosensitive array sub-pixel, and two main defects which cannot be avoided are determined: (1) the detector unit is formed by three-dimensional precise integration and assembly of physically-divided scintillator pixels and photosensitive array pixels, and the complex processing and assembly process is not beneficial to batch production and cost control of the detector; (2) in the incident direction of X-rays, the photosensitive array pixels occupy a certain sensitive area of the detector, thereby affecting the imaging dose efficiency.

Disclosure of Invention

The technical purpose is as follows: aiming at the defects in the prior art, the invention discloses an X-ray detection array pixel unit and a double-layer energy spectrum CT detector, which have novel signal conversion pixel structure design, and realize the reading of energy spectrum signals of the double-layer detector by using a two-dimensional array processing technology of a double-layer scintillator array and a two-dimensional area scintillator array and photosensitive array overlapping assembly technology used by a conventional CT detector, thereby effectively overcoming the main defects of the conventional double-layer energy spectrum CT detector.

The technical scheme is as follows: in order to achieve the technical purpose, the invention adopts the following technical scheme:

an X-ray detection array pixel cell, characterized by: the light source comprises a top layer scintillator pixel, a bottom layer scintillator pixel, a thin film light filtering layer and a photosensitive array pixel which are sequentially arranged in the light incidence direction;

the top layer scintillator pixels and the bottom layer scintillator pixels form a double-layer scintillator array, are made of scintillator materials which have obviously different luminescence spectra and can be clearly distinguished, and are used for converting incident X rays into visible light; the light signal sent by the top layer scintillator pixel enters the bottom layer scintillator pixel through the contact surface, and the bottom surface of the bottom layer scintillator pixel is a light output surface; light reflecting layers are arranged outside the top layer scintillator pixels and the bottom layer scintillator pixels;

the film light filter layer comprises two filter areas arranged on the same layer, namely a first filter area of the film light filter layer and a second filter area of the film light filter layer, which respectively correspond to the light emission spectra of the top layer scintillator and the bottom layer scintillator;

the photosensitive array pixels are used for converting visible light generated by the scintillator pixels into electric signals, each photosensitive array pixel comprises a first photosensitive sub-pixel corresponding to a first filtering area of the thin film light filtering layer and a second photosensitive sub-pixel corresponding to a second filtering area of the thin film light filtering layer, and output signals of the first photosensitive sub-pixel and the second photosensitive sub-pixel are respectively corresponding to X-ray responses of the top layer scintillator and the bottom layer scintillator.

Preferably, the size of the first filtering area of the thin film light filtering layer is equal to that of the first photosensitive array sub-pixel, and the size of the second filtering area of the thin film light filtering layer is equal to that of the second photosensitive array sub-pixel.

Preferably, the top layer scintillator pixels and the bottom layer scintillator pixels are connected in a direct optical coupling mode, so that light emitted by the top layer scintillator pixels can enter the bottom layer scintillator pixels.

Preferably, the combination of the top layer scintillator pixel and the bottom layer scintillator pixel adopts any one of ZnSe/GOS, BaF2/GOS, BaF2/CdWO4 and ZnSe/YAG.

Preferably, the combination of the top layer scintillator pixel and the bottom layer scintillator pixel adopts ZnSe/GOS, and the thicknesses of the top layer scintillator pixel and the top layer scintillator pixel are respectively 0.5mm and 1.0 mm.

Preferably, the first filtering area of the thin film light filtering layer is a short-pass filtering layer which only allows photons with the wavelength being larger than or equal to 550nm to pass through, and the second filtering area of the thin film light filtering layer is a long-pass filtering layer which only allows photons with the wavelength being larger than 550nm to pass through.

Preferably, the area ratio of the first filtering area of the thin film light filtering layer to the second filtering area of the thin film light filtering layer is 1: 1.

a process for manufacturing a bilayer scintillator array, comprising: the following steps are sequentially performed:

(1) the method comprises the following steps of (1) respectively polishing a top layer scintillator wafer and a bottom layer scintillator wafer serving as raw materials, and then bonding the top layer scintillator wafer and the bottom layer scintillator wafer through an optical coupling adhesive to obtain an integrated double-layer scintillator wafer;

(2) cutting a plurality of two-dimensional separation grooves from one end of a top layer scintillator wafer of the double-layer scintillator wafer, wherein the depth of each two-dimensional separation groove is greater than the design thickness of the double-layer scintillator array and smaller than the actual thickness of the double-layer scintillator wafer, and the distance between adjacent pixels separated by the two-dimensional separation grooves is equal to the size of the required double-layer scintillator array pixel;

(3) filling a light reflection layer material from one end of a top scintillator wafer of the double-layer scintillator wafer and curing to form a light reflection layer covering the top scintillator wafer and separating adjacent scintillator pixels;

(4) grinding the double-layer scintillator wafer subjected to the light reflection layer process from one end of the bottom layer scintillator wafer until the thickness of the bottom layer scintillator wafer is reduced to a preset thickness, and then polishing from one end of the bottom layer scintillator wafer to form a coupling surface with a thin film light filtering layer; and cutting along the two-dimensional separation groove to obtain the required double-layer scintillator.

Preferably, the areas of the top layer scintillator wafer and the bottom layer scintillator wafer in the step (1) are determined by wafer raw materials and production processes;

in the step (2), the design thickness of the top layer scintillator wafer is the design thickness of the top layer scintillator pixels, and the thickness of the bottom layer scintillator wafer is larger than the design thickness of the bottom layer scintillator pixels;

in the step (4), the top end of the top layer scintillator wafer and the two-dimensional separation groove are covered and filled by the light reflection layer, and the bottom surface of the bottom layer scintillator wafer is the light output surface of the pixel.

A dual-layer spectral CT detector, characterized by: the detector comprises a plurality of double-layer energy spectrum CT detector minimum sub-modules, each minimum sub-module comprises a plurality of X-ray detection array pixel units, and the top layer scintillator array pixels are used as incident ends of X-rays.

Has the advantages that: compared with the prior double-layer CT energy spectrum detector technology, the signal conversion pixel structure and the double-layer CT energy spectrum detector have the following technical characteristics and effects:

(1) the double-layer scintillator array is processed by two different scintillator materials, and under the irradiation of X rays, the two scintillator materials have different luminescence spectra which can be distinguished obviously and can be distinguished by a color filtering method; the top layer scintillator sub-pixels and the bottom layer scintillator sub-pixels are in a direct light coupling mode, and light emitted by the top layer scintillator sub-pixels can penetrate through the bottom layer scintillator sub-pixels to reach the light output surface.

(2) A thin film light filtering layer is arranged between the scintillator pixels and the photosensitive array pixels, and is divided into two different areas corresponding to the light output surface of each scintillator pixel and two photosensitive array sub-pixels respectively; the light filtering design of one area only allows the light-emitting spectrum of the top-layer scintillator to pass through, and the light filtering design of the other area only allows the light-emitting spectrum of the bottom-layer scintillator to pass through, so that the output signals of the two photosensitive array sub-pixels respectively correspond to the X-ray responses of the top-layer scintillator sub-pixels and the bottom-layer scintillator sub-pixels, and the energy spectrum information of incident X-rays is effectively provided.

(3) The existing double-layer CT detector adopts a physically-divided scintillator array and a photosensitive array, realizes signal reading of the double-layer detector through a complex three-dimensional integration process, and has the processing cost which is obviously higher than that of a two-dimensional array plane superposition assembly process adopted by a conventional CT detector; the double-layer CT detector adopts a two-dimensional continuous scintillator array, a photosensitive array and a pixelized thin film light filtering layer, the double-layer scintillator array adopts a two-dimensional array processing technology, the integration technology adopts the same plane superposition assembly technology as the conventional CT detector, and the processing cost similar to that of the conventional CT detector can be effectively kept.

(4) The existing double-layer CT detector adopts a scintillator array and photosensitive array side coupling mode, so that the photosensitive array can occupy a certain sensitive area of the detector in the X-ray incidence direction, thereby influencing the imaging dose efficiency; the double-layer CT detector uses the two-dimensional area scintillator array and photosensitive array overlapping assembly process used by the conventional CT detector, does not influence the sensitive area of the detector, and can effectively keep the imaging dosage efficiency.

Drawings

FIG. 1 is a schematic view of a CT detector array;

FIG. 2 is a schematic diagram of an embodiment of a detector minimum submodule;

FIG. 3 is a schematic diagram of a signal conversion pixel of a conventional single-slice CT detector;

FIG. 4 is a schematic structural diagram of a signal conversion pixel of a conventional dual-layer CT energy spectrum detector;

FIG. 5 is a schematic structural diagram of a signal conversion pixel of a dual-layer CT energy spectrum detector according to the present invention;

FIG. 6 is a luminescence spectrum of GOS and ZnSe scintillators;

FIG. 7 shows the transparency of GOS scintillators at different wavelengths;

FIG. 8 is a schematic diagram of a fabrication process for a bi-layer scintillator array;

fig. 9 is a schematic cross-sectional view of a 16x16 pixel bi-layer scintillator array.

Detailed Description

The invention provides a double-layer energy spectrum CT detector which is formed by processing a two-dimensional continuous double-layer scintillator array, a photosensitive array and a pixilated thin film light filter layer in the pixel structure design of the double-layer CT detector.

The dual layer scintillator array is fabricated using different top and bottom layer scintillator materials according to the process steps shown in fig. 8. Under the irradiation of X-rays, the scintillator materials of the scintillator sub-pixels of the top layer and the bottom layer have different luminescence spectra which can be distinguished obviously and can be distinguished by a color filtering method. The top layer scintillator sub-pixels and the bottom layer scintillator sub-pixels are in a direct light coupling mode, and light emitted by the top layer scintillator sub-pixels can penetrate through the bottom layer scintillator sub-pixels to reach the light output surface. A thin film light filtering layer is arranged between the scintillator pixels and the photosensitive array pixels, and is divided into two different regions corresponding to the light output surface of each scintillator pixel, wherein the light filtering design of one region only allows the light emitting spectrum of the top layer scintillator to pass through, and the light filtering design of the other region only allows the light emitting spectrum of the bottom layer scintillator to pass through.

As an example of the thin film light filtering layer, the function thereof may be realized by preparing a plurality of light transmitting films having different refractive indexes on a flexible or rigid transparent substrate, and by adjusting the thickness of each light transmitting film, a light filtering effect in a specific wavelength range may be realized. The different refractive index light-transmitting thin film materials include, but are not limited to, various combinations of Ag and SiO2, Ag and TiO2, and the like.

The photosensitive array pixel is divided into two sub-pixels which are read out independently, the areas of the sub-pixels correspond to two areas of the thin film light filtering layer respectively, and output signals of the two photosensitive array sub-pixels are transmitted to two channels of a subsequent analog-to-digital conversion circuit through the substrate to be read out simultaneously.

In the present invention, the double-layer scintillator array can be manufactured by the processing steps shown in fig. 8, including the following steps:

(1) polishing the top layer scintillator and the bottom layer scintillator wafer, and then bonding the top layer scintillator and the bottom layer scintillator wafer through an optical coupling adhesive to realize direct optical coupling, thereby obtaining an integrated wafer of the double-layer scintillator; the area of the wafer is determined by the wafer raw materials and the production process, and can be far larger than the size of a double-layer scintillator array used in the minimum submodule of the final detector; the thickness of the top layer scintillator wafer is the design thickness of the top layer scintillator pixels, and the thickness of the bottom layer scintillator wafer is larger than the design thickness of the bottom layer scintillator pixels, so that the required processing allowance is provided for the subsequent processing steps;

(2) according to the design thickness of a light reflection layer between pixels in a scintillator array, cutting and processing a two-dimensional separation groove between adjacent pixels from one end of a top layer scintillator on a double-layer scintillator wafer, wherein the depth of the groove is controlled to be larger than the design thickness of the double-layer scintillator array and smaller than the thickness of the double-layer scintillator wafer, so that the whole wafer is still connected by a bottom layer scintillator wafer which is not cut, and an integral structure is kept;

(3) filling a light reflection layer material from one end of the top layer scintillator according to the design and curing to form a light reflection layer covering the top layer scintillator and the adjacent pixels;

(4) and grinding the wafer subjected to the light reflection layer process from one end of the bottom layer scintillator until the thickness of the bottom layer scintillator is reduced to the design thickness of the scintillator pixel, and then polishing from one end of the bottom layer scintillator to form a coupling surface with the light filtering layer. The structural processing of the double-layer scintillator array is completed, and the double-layer scintillator array can be cut into the array size required by the minimum submodule of the detector and put into use.

As an example, fig. 9 is a cross-sectional schematic view of a cut 16x16 pixel bi-layer scintillator array, each bi-layer scintillator pixel consisting of a top layer scintillator pixel and a bottom layer scintillator pixel directly optically coupled, with the top of the top layer scintillator pixel and between adjacent scintillator pixels covered and separated by a light reflecting layer, and the bottom surface of the bottom layer scintillator pixel being the light output surface of the pixel.

As shown in fig. 5, in an embodiment of the pixel structure of the present invention, ZnSe (zinc selenide) and GOS (gadolinium oxysulfide) scintillator materials are used as the top layer and the bottom layer scintillator sub-pixels, respectively, and the thicknesses thereof are 0.5mm and 1.0mm, respectively. The emission spectra of these two scintillators under X-ray irradiation are shown in fig. 6, have different main light peak wavelengths, and are clearly distinguished on the spectra. The transparency curve of the GOS scintillator with a thickness of 1.0mm is shown in fig. 7, and the transparency is good in the luminescence spectrum region of the ZnSe scintillator, so that most of the luminescence photons of the ZnSe scintillator can reach the coupling surface with the light filter layer through the GOS scintillator.

Two areas of the light filtering layer are respectively designed into short-pass filtering layers with the cut-off wavelength of 550nm, and only photons with the wavelength less than 550nm are allowed to pass through; and a long pass filter layer that allows only photons with wavelengths greater than 550nm to pass through. Thus, the sub-pixels of the photosensitive array corresponding to the short-pass filter region read out signals from the sub-pixels of the GOS scintillator, the sub-pixels of the photosensitive array corresponding to the long-pass filter region read out signals from the sub-pixels of the ZnSe scintillator, and the two signals are read out simultaneously, so that information about the incident X-ray energy spectrum can be obtained.

The practical application of the present invention is not limited to a pair of scintillator material combinations of ZnSe/GOS, and any scintillator material combination satisfying the above-described characteristics is within the scope of the present invention, such as scintillator material combinations of BaF2/GOS, BaF2/CdWO4, ZnSe/YAG, etc. In addition, in the pixel structure shown in fig. 5, the two regions of the light filtering layer and the corresponding two photosensitive array sub-pixel areas are divided by a ratio of 50% -50%, and in practical application, the ratio can be optimally adjusted according to the relative magnitude of the signals.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.