Grid structure and method for filtering scattered X-rays

Abstract

The invention belongs to the technical field of X-ray imaging, and particularly relates to a grid structure and method for filtering scattered X-rays, the grid structure comprises a scintillator array and a grid partition plate arranged between scintillator units, and the grid partition plate is made of a high-density material. The core is that the grid ratio (H / L) of the grid is greater than or equal to 8: 1 and less than or equal to 20: 1, and the grid density is greater than or equal to 80 line pairs / cm and less than or equal to 150 line pairs / cm. Through the design of high grating ratio and high density, space filtering is carried out by utilizing a geometric channel, scattered X-rays in disordered directions are effectively blocked, and meanwhile, original rays are allowed to pass through. According to the method, energy filtering is indirectly realized, and low-energy scattering photons are preferentially absorbed. The method can significantly suppress image fog noise, improves image contrast and signal-to-noise ratio, and can be widely applied to various X-ray detection systems.

Description

Technical Field

[0001] This invention relates to the field of X-ray imaging technology, and more specifically to a grid structure and method for X-ray detectors that can effectively filter scattered X-rays to improve imaging quality. Background Technology

[0002] X-ray inspection technology is widely used in medical diagnosis, industrial non-destructive testing, and security inspection. Its basic principle is based on the difference in X-ray absorption by different materials when X-rays penetrate an object, forming an image of its internal structure. However, when the X-ray beam interacts with the object, the Compton scattering effect occurs. In this effect, incident X-ray photons undergo inelastic collisions with the outer electrons of atoms in the material, causing the photon energy to decrease and its propagation direction to change. These scattered photons are randomly oriented and uniformly illuminate the detector, forming a layer of "haze noise" on the image background.

[0003] This fog noise severely reduces image contrast, blurring details that should be clearly distinguishable. While some anti-scattering grids exist to overcome this problem, they often suffer from low filtering efficiency, complex structures, or excessive radiation doses to the human body. Summary of the Invention

[0004] Objective of the Invention: The objective of this invention is to overcome the shortcomings of existing technologies and provide a novel gate structure and method that efficiently filters scattered rays while preserving useful imaging signals as much as possible, and has a reasonable structure.

[0005] Technical solution: Firstly, a grid structure for filtering scattered X-rays includes: A scintillator array consists of multiple scintillator units used to convert X-rays into visible light; A gate separator is disposed between the scintillator units. The gate separator is made of a high-density material and has a high absorption rate for X-rays. The ratio of the height (H) of the gate separator to the channel width (L) between adjacent gate separators is defined as the gate ratio (r), i.e.: The gate ratio r is greater than or equal to 8:1; the number of gate spacers arranged per unit distance is defined as the gate density, and the gate density is greater than or equal to 80 line pairs / cm.

[0006] In a further embodiment, the gate ratio r is in the range of 8:1 and less than or equal to 20:1, that is: 8:1≤r≤20:1.

[0007] In a further embodiment, the gate density is in the range of 80 line pairs / cm and less than or equal to 150 line pairs / cm, that is: 80 line pairs / cm ≤ gate density ≤ 150 line pairs / cm.

[0008] In a further embodiment, the high-density material is tungsten, lead, tantalum, or an alloy thereof.

[0009] In a further embodiment, the extension direction of the gate separator is configured to match the fan-beam equal-angle optical path of the primary X-ray beam emitted from the X-ray source, such that the direction of the channel converges at the focal point of the X-ray source.

[0010] In a further embodiment, the gate structure is applied to an X-ray array detector or an X-ray flat panel detector. Secondly, a method for filtering scattered X-rays using the gate structure described above includes the following steps: A mixed beam of radiation, comprising primordial rays and scattered X-rays, is incident onto the gate structure; Spatial filtering is achieved through the geometric channel formed by the gate separator: primary rays that are substantially aligned with the channel direction are allowed to pass through the channel and reach the scintillator unit, while scattered X-rays that deviate from the channel direction are blocked and absorbed by the gate separator.

[0011] In a further embodiment, energy filtering is performed concurrently with spatial filtering: the gate separator preferentially absorbs low-energy X-ray photons scattered at large angles by the Compton effect, thereby indirectly increasing the average energy of X-rays penetrating the channel.

[0012] In a further embodiment, the method enhances the filtering effect on scattered X-rays by increasing the gate ratio and gate density, thereby improving the detector's imaging signal-to-noise ratio and image contrast.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. High-efficiency spatial filtering: Through the design of high grid ratio and high grid density, a high and narrow channel is formed, which performs strict geometric screening of photon incident angle, effectively distinguishes and blocks scattered photons with random directions generated by Compton scattering, while efficiently transmitting primordial rays used for imaging, thereby significantly improving image contrast and signal-to-noise ratio.

[0014] 2. Indirect energy filtering: This structure preferentially absorbs low-energy, large-angle scattered photons, which enhances the energy spectrum hardness of the effective signal and helps improve image quality.

[0015] 3. Significantly improves image performance: The dual filtering mechanisms mentioned above work together to effectively suppress image fog, significantly improve image contrast and signal-to-noise ratio, and make details clearer.

[0016] 4. High structural practicality: This structure can be widely used in X-ray array detectors and flat panel detectors, and is compatible with fan-beam optical paths, with good engineering feasibility and application prospects. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] A grid structure and method for filtering scattered X-rays includes a scintillator array and a grid separator. The scintillator array consists of multiple scintillator units for converting X-rays into visible light. The grid separator is disposed between the scintillator units and is made of a high-density material with high absorption rate for X-rays, such as tungsten, lead, tantalum, or alloys thereof.

[0020] like Figure 1 As shown, the key innovation of this invention lies in the optimized design of the gate geometry parameters. The gate ratio (r) is defined as the ratio of the height (H) of the gate separator to the channel width (L) between adjacent gate separators. This invention requires that the gate ratio r be greater than or equal to 8:1, preferably within the range of 8:1 and less than or equal to 20:1, i.e., 8:1 ≤ r ≤ 20:1. Simultaneously, the number of gate spacers arranged per unit distance is defined as the gate density. This invention requires that the gate density be greater than or equal to 80 line pairs / cm, preferably within the range of 80 line pairs / cm and less than or equal to 150 line pairs / cm, i.e., 80 line pairs / cm ≤ gate density ≤ 150 line pairs / cm.

[0021] In one embodiment, such as Figure 1 As shown, in order to adapt to the fan-beam X-ray source, the extension direction of the grid partition can be configured to match the fan-beam isoangular optical path of the primary X-ray beam emitted by the X-ray source, so that the direction of the channel converges at the focal point of the X-ray source.

[0022] In one embodiment, such as Figure 1 As shown, by adjusting the grid ratio and grid density, a trade-off can be struck between anti-scattering performance and system flux (and the required radiation dose). For example, in medical CT where extremely high image quality is required, a higher grid ratio (e.g., 20:1) and density (e.g., 120 line pairs / cm) can be used; while in dose-sensitive applications, the parameters can be appropriately reduced.

[0023] The present invention also provides a method for filtering scattered X-rays using the above-described gate structure, comprising the following steps: subjecting a mixed beam of X-rays containing primary X-rays and scattered X-rays to the gate structure; performing spatial filtering through a geometric channel formed by the gate separator, allowing primary X-rays substantially aligned with the channel direction to pass through the channel and reach the scintillator unit, while blocking and absorbing scattered X-rays deviating from the channel direction.

[0024] This method also achieves energy filtering, because in Compton scattering, photons scattered at large angles lose more energy (according to the Compton displacement formula). The energy of the scattered photon can be derived. With the energy of the incident photon The relationship between and scattering angle θ ( (This is the rest energy of an electron), and the formula shows that the energy is relatively low. The high gate ratio and high-density gate structure of this invention can efficiently filter out these low-energy photons scattered at large angles, thereby indirectly increasing the average energy of X-rays in the penetration channel and further optimizing image quality.

[0025] Working principle: Compton effect: When an incident photon collides inelastically with the outer electron of a target atom, the incident photon transfers some of its energy to an orbital electron, ejecting it as a free electron (Compton electron). At the same time, the photon's own direction of motion and energy change.

[0026] Primary X-rays: originate from the focal point of the X-ray tube, and their flight direction is definite, pointing to various parts of the detector; Scattered photons: the generation of scattered photons does not originate from the X-ray source itself, but occurs during the interaction between X-rays and matter. The main source is the Compton effect, and their flight direction is random and distributed in all directions.

[0027] Gate ratio (r): The ratio of the gate height (H) to the width (L) between the two gates, i.e., r = .

[0028] To improve the signal-to-noise ratio (SNR) of X-ray imaging, it is necessary to eliminate scattered photons (noise) with erratic orientation caused by the Compton effect as much as possible, while preserving the original emission line (signal) with the correct orientation used for image formation to the greatest extent possible. Physically, scattered photons and original emission lines are essentially the same X-ray photons and cannot be distinguished by their intrinsic properties alone; the only difference is their direction of motion. Based on this directional difference, the gate structure employs a geometric path filtering method to differentiate them.

[0029] This invention employs two filtering methods: spatial filtering (direct effect) and energy filtering (indirect effect). Spatial filtering (direct effect) utilizes the good directionality of the original emission line and the random direction of scattered photons, forming a tall and narrow channel through a high grid ratio (e.g., 16:1). Only the original emission line (primary X-ray) that is substantially aligned with the channel direction is allowed to pass through. Any scattered photon deviating from this direction, even at a small angle, has a very high probability of striking the grid and being absorbed. The higher the grid ratio, the stricter the angle screening, and the more significant the descattering effect.

[0030] Energy filtering is based on the relationship between the photon scattering angle and energy loss in Compton scattering, derived from the Compton displacement formula. The energy of the scattered photon can be derived. With the energy of the incident photon The relationship between and scattering angle θ ( (This is the rest energy of an electron). This formula shows that photons scattered at large angles have lower energy, while those scattered at small angles have higher energy. The gate structure can efficiently filter out the photons scattered at large angles, which are precisely those with the lowest energy, thus indirectly improving image quality.

[0031] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A grating stage structure for filtering scattered X-rays, characterized by, The application relates to a grid structure for X-ray imaging, comprising: a scintillator array composed of a plurality of scintillator units for converting X-rays into visible light; a grid spacer arranged between the scintillator units, the grid spacer being made of a high-density material and having a high absorption rate for X-rays; The ratio of the height (H) of the gate spacer to the width (L) of the channel between adjacent gate spacers is defined as the gate ratio (r), i.e.: The gate ratio r is greater than or equal to 8:1; and the number of gate spacers arranged in a unit distance is defined as the gate density, which is greater than or equal to 80 lines per centimeter.

2. A grating-level structure for filtering scattered X-rays according to claim 1, wherein, the grid ratio r is in the range of 8:1 and less than or equal to 20:1, i.e. 8:1<=r<=20:

1.

3. A grating-level structure for filtering scattered X-rays according to claim 1, wherein, the grid density is in the range of 80 lines per centimeter and less than or equal to 150 lines per centimeter, i.e. 80 lines per centimeter<=grid density<=150 lines per centimeter.

4. The grating-level structure of claim 1, wherein, the high-density material is tungsten, lead, tantalum or an alloy thereof.

5. The grating-level structure of claim 1, wherein, the extension direction of the grid spacer is configured to match the equiangular fan-beam path of the primary beam emitted by the X-ray source, so that the directions of the channels converge at the focal point of the X-ray source.

6. The grating-level structure of claim 1, wherein, the grid structure is applied to an X-ray array detector or an X-ray flat panel detector.

7. A method of filtering scattered x-rays using the grid structure of any one of claims 1-6, wherein, The application further relates to a method for X-ray imaging, comprising the following steps: incident of a mixed beam containing primary rays and scattered X-rays to the grid structure; spatial filtering by the geometric channels formed by the grid spacer: the primary rays substantially consistent with the channel direction are allowed to pass through the channels to reach the scintillator units, while the scattered X-rays deviating from the channel direction are blocked and absorbed by the grid spacer.

8. The method of claim 7, wherein, at the same time of the spatial filtering, energy filtering is performed: the grid spacer preferentially absorbs large-angle scattered low-energy X-ray photons generated by the Compton effect, thereby indirectly increasing the average energy of the X-rays penetrating the channels.

9. The method of claim 7, wherein, The method enhances the filtering effect of the scattered X-rays by increasing the grid ratio and the grid density, thereby improving the imaging signal-to-noise ratio and image contrast of the detector.

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