Filter for improving X-ray irradiation uniformity

Abstract

The utility model discloses a filter for improving X-ray irradiation uniformity, which comprises a filter support, a wedge-shaped filter and a bell-shaped filter, the wedge-shaped filter is arranged above the filter support, and the bell-shaped filter is arranged below the filter support; the thickness of the wedge-shaped filter piece in the cathode direction is larger than that in the anode direction, and the middle of the face, away from the filter support, of the bell-shaped filter piece protrudes outwards to form an arch-shaped structure with the middle thickness larger than that of the two sides. According to the application, the heel effect and the distance influence of irradiation on a plane are solved at the same time in a manner of combining the filters, and the irradiation dose rate uniformity of the irradiated plane is improved; different filter sheet combinations can be designed according to different irradiation cone angle requirements through a detachable connection mode, and rapid positioning and replacement of the filter sheets are realized through a modular structure; on the premise that irradiation uniformity is guaranteed, the effects of fast irradiation of a small number of samples and simultaneous irradiation of a large number of samples can be achieved, and different requirements for single-time treatment capacity and treatment speed of irradiated objects are met.

Description

Technical Field

[0001] The present application relates to the field of irradiation technology, and in particular to a filter for improving the uniformity of X-ray irradiation. Background Art

[0002] Irradiation technology is a processing method that uses high-energy radiation such as electron beams, gamma rays, and X-rays to ionize the irradiated material, thereby meeting different needs. Irradiation technology can be applied to food to inhibit germination, delay or accelerate ripening, kill insects, and sterilize. Figure 1 When X-rays are used for irradiation, a reflection X-ray tube is the most common X-ray source. It uses electrons emitted by a cathode (101) to bombard an anode (102) at high speed, so that part of the electron energy is emitted in the form of X-rays.

[0003] To ensure irradiation effectiveness while avoiding negative local effects caused by excessive irradiation doses, irradiation applications require uniformity of absorbed dose to the irradiated object. For example, GB 18524-2016 stipulates that the dose nonuniformity for food irradiation should not exceed 2. Another example is YY / T 1834-2022, which mandates that the absolute deviation of absorbed dose uniformity for X-ray blood irradiation equipment should be ≤30% when the sample container is fully loaded.

[0004] There are two main factors that limit the uniformity of X-rays produced by reflection X-ray tubes on a plane: the heel effect and the distance effect.

[0005] The heel effect is related to the absorption of radiation in the anode, e.g. Figure 3 As shown, the average location of X-ray generation is not on the anode surface, but within the anode. This causes the path of the third ray 303 emitted toward the cathode to be shorter within the anode than the path of the first ray 301 emitted toward the anode, resulting in a higher irradiation dose rate toward the cathode. This is known as the heel effect. To counteract the heel effect, patents CN105161392A and CN112205991A both employ a wedge-shaped filter design, achieving a nearly uniform irradiation dose rate across all angles.

[0006] The radiation dose rate generated by a point X-ray source is inversely proportional to the square of the distance from the source to the irradiated point. This results in a maximum dose rate at the plane projection of the electron focal point (the location of the second ray 302), and a decreasing dose rate as one moves outward. Prior art papers have hypothesized that this high-center, low-end dose rate curve is Gaussian, and based on this, designed a parabolic filter, significantly improving the uniformity of the radiation within a few millimeters.

[0007] The aforementioned technologies all address filter improvements in imaging fields like CT, but fail to consider the need to irradiate larger planar areas within a wider cone angle range, a crucial means of improving radiation utilization during irradiation. The use of wedge-shaped filters to offset the heel effect only addresses the angular uniformity of the radiation, without considering the effect of distance on the plane. Articles examining the effect of distance only address the uniformity of the radiation within extremely small cone angles, without addressing the potential for optimizing radiation energy utilization by adjusting the cone angle and filter thickness to comprehensively consider single-shot processing volume and processing speed, depending on the needs of different irradiated samples. Utility Model Content

[0008] To this end, the present application provides a filter for improving the uniformity of X-ray irradiation, so as to solve the problem in the prior art that it is difficult to simultaneously eliminate the heel effect and the distance effect, resulting in uneven X-ray irradiation dose rate on a plane.

[0009] In order to achieve the above objectives, this application provides the following technical solutions:

[0010] A filter for improving the uniformity of X-ray irradiation comprises a filter holder, a wedge-shaped filter and a bell-shaped filter, wherein the wedge-shaped filter and the bell-shaped filter are both mounted on the filter holder, the wedge-shaped filter is arranged above the filter holder, and the bell-shaped filter is arranged below the filter holder; the thickness of the wedge-shaped filter in the cathode direction is greater than the thickness in the anode direction, and the middle portion of the bell-shaped filter protrudes outward on a side facing away from the filter holder, forming an arched structure with a middle thickness greater than the thickness on both sides.

[0011] Optionally, the filter support is a hollow structure.

[0012] Optionally, the bell-shaped filter plate includes a connecting plate and a raised portion, and the connecting plate is a hollow structure.

[0013] Optionally, the wedge-shaped filter disc and the bell-shaped filter disc are both detachably connected to the filter bracket.

[0014] Optionally, the wedge-shaped filter disc and the bell-shaped filter disc are connected to the filter bracket via a quick lock, and the wedge-shaped filter disc, the connecting plate and the filter bracket are all provided with notches that cooperate with the quick lock.

[0015] Optionally, the connecting plate is provided with a countersunk screw hole that cooperates with the quick locker.

[0016] Optionally, the wedge-shaped filter is made of a high atomic number material.

[0017] Optionally, the bell-shaped filter is made of a low atomic number material.

[0018] Compared with the prior art, this application has at least the following beneficial effects:

[0019] 1. Wedge-shaped filters and bell-shaped filters address the heel effect and distance effect respectively. By combining these filters, both the heel effect and the distance effect on the plane of irradiation are simultaneously addressed, improving the uniformity of the irradiated dose rate across the plane. This also reduces design and manufacturing complexity and allows the use of different materials for the two filters.

[0020] 2. Through the detachable connection method, different filter combinations can be designed according to different irradiation cone angle requirements, and the positioning and replacement of filters can be achieved through the modular structure.

[0021] 3. The quick locking device can realize the rapid replacement of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more intuitively illustrate the prior art and the present application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be considered as limiting conditions for implementing the present application; for example, based on the technical concepts disclosed in this application and the exemplary drawings, those skilled in the art are capable of easily making routine adjustments or further optimizations to the addition / reduction / attribution division, specific shapes, positional relationships, connection methods, dimensional ratios, etc. of certain units (components).

[0023] Figure 1 A schematic diagram of the structure of a filter for improving X-ray irradiation uniformity provided in an embodiment of the present application;

[0024] Figure 2 A cross-sectional view of an embodiment of the present application;

[0025] Figure 3 This is a schematic diagram of the use of an embodiment of the present application.

[0026] Description of reference numerals:

[0027] 101. Cathode; 102. Anode; 201. Filter holder; 202. Wedge-shaped filter; 203. Bell-shaped filter; 204. Quick-lock; 205. Countersunk screw hole; 301. First ray; 302. Second ray; 303. Third ray; 400. Plane. DETAILED DESCRIPTION

[0028] The present application will be further described below in detail through specific embodiments in conjunction with the accompanying drawings.

[0029] In the description of this application: unless otherwise specified, the meaning of "plurality" is two or more. The terms "first", "second", "third", etc. in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (for example, they should not be understood as emphasizing the importance or order, etc.). Expressions such as "including", "comprising", "having", etc. also mean "not limited to" (certain units, components, materials, steps, etc.).

[0030] The terms such as "upper", "lower", "left", "right", "middle", etc. cited in this application are usually used to indicate the general relative position relationship for the convenience of intuitive understanding by referring to the drawings, and are not absolute limitations on the position relationship in the actual product.

[0031] A filter for improving the uniformity of X-ray irradiation, referring to Figure 1-Figure 3 The invention comprises a filter holder 201, a wedge-shaped filter 202, and a bell-shaped filter 203. Both the wedge-shaped filter 202 and the bell-shaped filter 203 are mounted on the filter holder 201, with the wedge-shaped filter 202 positioned above the filter holder 201 and the bell-shaped filter 203 positioned below the filter holder 201. The thickness of the wedge-shaped filter 202 is greater toward the cathode 101 than toward the anode 102. The middle portion of the bell-shaped filter 203, facing away from the filter holder 201, protrudes outward, forming an arched structure with a greater thickness in the middle than on either side. By combining the two filters, the heel effect and distance effect are addressed separately. Their combined use can simultaneously address both the heel effect and the distance effect on the irradiation plane 400, thereby improving the uniformity of the irradiation dose rate across the irradiated plane 400.

[0032] The basic principle of the filter is that when X-ray photons of a certain energy pass through an object, their intensity is reduced by atomic light effects, Rayleigh scattering, Compton scattering, etc., and generally follows the Lambert-Beer law. The relationship between the outgoing ray intensity I and the incident intensity I0, the thickness of the material passed through x, and the linear attenuation coefficient μ of the material is:

[0033] I / I0=exp[-μx]

[0034] Therefore, by forcing the radiation originally irradiating a high-dose-rate region to pass through thicker metal, the dose rate in that region can be reduced, thereby improving the uniformity of the radiation dose rate on a plane 400. The wedge-shaped filter 202 is used to compensate for differences in the radiation attenuation path within the anode 102, ensuring that the irradiation dose rate is the same at different angles θ at the same distance from the focal point.

[0035] The distances from the focus of the rays passing through the wedge filter 202 to the plane 400 are different at different locations. According to the inverse square law, the ratio of the irradiation dose rates of the second ray 302 and the third ray 303 at the intersection of the plane 400 is 1 / cos 2 (θ) Therefore, ray 303 needs to travel a path 2ln[1 / cos(θ)] / μ longer than ray 304 through bell-shaped filter 203. From the above calculations, it can be seen that when the cone angle corresponding to the irradiation range is fixed, changing the distance between plane 400 and the focal point does not affect the dose rate ratio between the center and the edge of the irradiation range, nor does it affect the structural design of bell-shaped filter 203. Therefore, for the same irradiation cone angle, only one type of bell-shaped filter 203 needs to be designed. Based on the same principle, only one type of wedge-shaped filter 202 needs to be designed for a fixed irradiation cone angle.

[0036] This method of improving dose rate uniformity makes the final irradiation dose rate tend to be the lowest dose rate within the irradiation area. Therefore, the larger the area to be irradiated, the higher the proportion of irradiation energy absorbed by the two filters in the high-dose rate area, and the lower the overall irradiation dose rate. This means that when using a fixed filter to irradiate an object with an area much smaller than the area for which it is designed to irradiate uniformly, excessive energy is wasted, irradiation speed is reduced, and irradiation costs are increased.

[0037] Therefore, to better meet the requirements of different irradiation cone angles, a wedge-shaped filter 202 and a bell-shaped filter 203 are detachably mounted on the filter holder 201. In this embodiment, a quick-locking device 204 is used to connect the three components to facilitate rapid positioning and replacement. Corresponding notches for the quick-locking device 204 are provided at corresponding locations on the filter holder 201, the wedge-shaped filter 202, and the bell-shaped filter 203. The bell-shaped filter 203 includes a connecting plate and a raised portion. The connecting plate is provided with a countersunk screw hole 205 for mounting the quick-locking device 204.

[0038] In other embodiments, various solutions such as positioning pins or clips may be used to achieve detachable connection between the filter holder 201 , the bell-shaped filter plate 203 , and the wedge-shaped filter plate 202 .

[0039] Specifically, the arched portion of the bell-shaped filter 203 is designed according to the aforementioned basic principle formula, and the hollow design of the connecting plate is used to avoid additional attenuation of radiation. Similarly, the filter holder 201 also adopts a hollow design. In addition to the notch that mates with the quick-lock 204, it also contains two through-holes for securing it to the radiation source.

[0040] To use, first secure the filter holder 201 to the radiation source, unlock the quick-lock 204, hold the bell-shaped filter 203, and insert the quick-lock 204 through the notch of the filter holder 201. Then, align the notch of the wedge-shaped filter 202 and place it in place, and finally tighten the quick-lock 204 by rotating it. To replace the filter, hold the bell-shaped filter 203 to unlock the quick-lock 204, then remove the wedge-shaped filter 202 and bell-shaped filter 203 with both hands, and then reinstall the appropriate filter combination.

[0041] In addition to the bell-shaped filter 203, an optional hollow connecting plate (not shown) is also provided. The side of this connecting plate facing away from the filter holder 201 is a flat structure, used for irradiating curved surfaces centered on the radiation source. It also has a notch that mates with the quick-lock 204, allowing for detachable connection to the filter holder 201. If the surface of the irradiated object is not flat but rather curved, similar to a CT image, the bell-shaped filter 203 can be replaced with a connecting plate without the bell-shaped protrusion. In this case, the filter's performance is similar to that of the traditional wedge-shaped filter 202.

[0042] The wedge-shaped filter 202 is preferably made of a high atomic number material similar to that of the anode 102 to correct spectral distortion. The bell-shaped filter 203 is preferably made of a low atomic number material (such as aluminum, magnesium, or other metals or alloys) that is easy to process and has a low linear attenuation coefficient, thereby reducing the processing accuracy requirements while maintaining the same uniformity.

[0043] In some embodiments, the irradiation ranges corresponding to different cone angles can be marked on the irradiated plane 400 to facilitate operators in selecting different filter combinations for different irradiated objects.

[0044] The implementation principle of the present embodiment is as follows: by combining filters, both the heel effect and the influence of irradiation distance on plane 400 are simultaneously addressed, thereby improving the uniformity of the irradiation dose rate across the irradiated plane 400. Compared to fixed filters, the detachable connection allows for the design of different filter combinations for varying irradiation cone angle requirements, while the modular structure enables rapid positioning and replacement of filters. Combined with these features, this filter can achieve both rapid irradiation of small samples and simultaneous irradiation of large numbers of samples while ensuring irradiation uniformity, meeting varying requirements for single-shot irradiation throughput and processing speed.

[0045] The technical features of the above embodiments can be combined arbitrarily (as long as there is no contradiction in the combination of these technical features). In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described; these embodiments that are not explicitly written should also be considered to be within the scope of this specification.

Claims

1. A filter for improving X-ray irradiation uniformity, characterized by: The invention comprises a filter support (201), a wedge-shaped filter disc (202) and a bell-shaped filter disc (203), wherein the wedge-shaped filter disc (202) and the bell-shaped filter disc (203) are both mounted on the filter support (201), the wedge-shaped filter disc (202) is arranged above the filter support (201), and the bell-shaped filter disc (203) is arranged below the filter support (201); the thickness of the wedge-shaped filter disc (202) in the direction of the cathode (101) is greater than the thickness in the direction of the anode (102), and the middle part of the bell-shaped filter disc (203) facing away from the filter support (201) protrudes outwards, forming an arched structure with a thickness in the middle greater than the thickness on both sides.

2. The filter for improving X-ray irradiation uniformity according to claim 1, characterized in that: The filter support (201) is a hollow structure.

3. The filter for improving X-ray irradiation uniformity according to claim 1, characterized in that: The bell-shaped filter plate (203) comprises a connecting plate and an arched portion, and the connecting plate is a hollow structure.

4. The filter for improving X-ray irradiation uniformity according to claim 3, characterized in that: The wedge-shaped filter disc (202) and the bell-shaped filter disc (203) are both detachably connected to the filter bracket (201).

5. The filter for improving X-ray irradiation uniformity according to claim 4, characterized in that: The wedge-shaped filter disc (202) and the bell-shaped filter disc (203) are connected to the filter bracket (201) via a quick lock (204); the wedge-shaped filter disc (202), the connecting plate and the filter bracket (201) are all provided with notches that cooperate with the quick lock (204).

6. The filter for improving X-ray irradiation uniformity according to claim 5, characterized in that: The connecting plate is provided with a countersunk screw hole (205) that matches the quick locker (204).

7. The filter for improving X-ray irradiation uniformity according to claim 1, characterized in that: The wedge-shaped filter (202) is made of a high atomic number material.

8. The filter for improving X-ray irradiation uniformity according to claim 1, characterized in that: The bell-shaped filter (203) is made of a low atomic number material.

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