General experimental irradiation device for small and medium-sized animals

Abstract

This invention relates to a universal experimental irradiation device for small and medium-sized animals. The device includes a slowing shield, a variable-diameter collimator, and multiple replaceable positioning sleeves. The slowing shield has a beam passage hole, and several sets of snap-fit ​​bases are arranged in a circumferential array around the beam passage hole on its surface. The variable-diameter collimator is positioned at the beam passage hole, and its multiple shielding blades can be relatively converged or displaced to form an adjustable-diameter collimation outlet. The multiple positioning sleeves have different inner diameters, and the axial positions of the irradiation windows on the bottom side of each sleeve are different; at least one sleeve has an axial dimension larger than the diameter of the beam passage hole, spans across the beam passage hole, and is detachably connected to the snap-fit ​​bases via radially arranged claws. By replacing different sized sleeves and adjusting the collimator aperture, the device can be adapted to the irradiation needs of animals of different sizes and tumors in different anatomical locations, offering strong versatility and precise positioning.

Description

Technical Field

[0001] This invention relates to the field of radiation experiment technology, and specifically to an experimental irradiation device suitable for small and medium-sized animals. Background Technology

[0002] In the fields of radiotherapy and nuclear medicine research, boron neutron capture therapy, as a binary targeted radiotherapy method, relies on the nuclear reaction between thermal neutrons and boron drugs accumulated in tumor cells to produce high-energy alpha particles and lithium nuclei with a range only on the order of cell diameter. Because the slowing and scattering characteristics of thermal neutrons within biological tissues are extremely complex, the energy spectrum purity of the beam, collimation accuracy, and the spatial coupling state between the source and target ends during irradiation directly determine the therapeutic gain ratio.

[0003] In existing experimental irradiation procedures, researchers often need to conduct experiments on animals of different sizes on the same irradiation device one after another, from subcutaneous tumor-bearing models in mice to glioma models in rats, and then to deep abdominal tumor models in rabbits. Different experimental animals have huge differences in body size, weight, and anatomical structure, and their requirements for the inner diameter, length, and position of the irradiation window are different.

[0004] Existing irradiation devices are either only suitable for small rodents such as mice or medium-sized laboratory animals such as rabbits, lacking a universal irradiation device that can be easily adapted to multiple species through simple device changes. When an experiment requires switching from one animal to another, it is often necessary to replace the entire irradiation device and recalibrate the coordinates, which is cumbersome and introduces additional positioning errors.

[0005] For small experimental subjects such as mice, due to their limited physiological space, it is usually necessary to integrate a head or organ shielding structure in a specific position inside the positioning sleeve. In this case, in order to shorten the irradiation cycle and ensure that the target area obtains a neutron energy spectrum with extremely high flux, it is often necessary to provide an extraction beam with a larger diameter at the source end.

[0006] Conversely, when dealing with medium to large experimental subjects such as rabbits, since their irradiation field (irradiation window) is usually set to be large according to anatomical needs, if the source still outputs a large-diameter beam, a large number of neutrons will overflow from the edge of the window and produce violent secondary scattering in the animal's body, thereby accidentally damaging the healthy physiological tissues around the tumor.

[0007] Because laboratory animals such as mice, rats, and rabbits have significant differences in physiological size and tumor anatomical sites, single-function irradiation devices cannot achieve rapid switching between species while ensuring protective efficacy. Summary of the Invention

[0008] The purpose of this invention is to provide a universal experimental irradiation device for small and medium-sized animals, in order to solve the problem that existing irradiation devices cannot meet the requirements of universal adaptability when irradiating animals of different body sizes and tumor locations, resulting in poor versatility and inaccurate irradiation.

[0009] The technical solution of a universal experimental irradiation device for small and medium-sized animals according to the present invention is as follows:

[0010] A general-purpose experimental irradiation device for small and medium-sized animals includes a slowing shield plate with a beam-passing hole for a neutron beam to pass through. Several sets of snap-fit ​​bases are arranged in a circumferential array around the beam-passing hole on the surface of the slowing shield plate. The device also includes:

[0011] A variable-diameter collimator, disposed at the beam passage aperture, includes multiple relatively movable shielding blades. The shielding blades are relatively close together and far apart to form a collimation outlet with an adjustable aperture. Each of the shielding blades is made of neutron shielding material.

[0012] Multiple replaceable positioning sleeves, each with a claw at the bottom that can be detachably connected to the snap-fit ​​base, and an adjustment structure between the claw and the snap-fit ​​base for adjusting the installation position of the positioning sleeve;

[0013] Each set of snap-fit ​​bases is arranged opposite each other in the radial direction of the beam passage hole;

[0014] At least one of the positioning sleeves has an axial dimension larger than the diameter of the beam passage hole. The positioning sleeve with an axial dimension larger than the diameter of the beam passage hole spans across the beam passage hole, and its radial sides are detachably connected to the buckle bases on both radial sides of the beam passage hole via the claws.

[0015] The bottom of the positioning sleeve is also provided with an irradiation window corresponding to the collimation outlet, wherein the inner diameter of at least one positioning sleeve is smaller than the inner diameter of the other positioning sleeve, and the axial position of the bottom irradiation window of at least one positioning sleeve is different from the axial position of the bottom irradiation window of the other positioning sleeve.

[0016] The irradiation window and the collimation outlet are aligned axially, so that the neutron beam is sequentially incident on the animal target area inside the positioning sleeve through the collimation outlet and the irradiation window.

[0017] The adjustment structure includes an elongated hole disposed on the snap-fit ​​base and extending radially along the slowing shield plate. After the snap-fit ​​claw is engaged in the elongated hole, it can be moved radially to adjust the installation position of the positioning sleeve on the surface of the slowing shield plate.

[0018] Furthermore, the multiple shielding blades overlap and cooperate with each other to block the neutron beam in a non-collimated path through the overlapping surface between the shielding blades.

[0019] Furthermore, the variable diameter collimator also includes a drive linkage disk mounted on one side of the slowing shield plate. The drive linkage disk has multiple spiral curved grooves distributed along the circumference. Each shield blade has a transmission pin that is slidably inserted into the corresponding curved groove, so that the rotation of the drive linkage disk drives multiple shield blades to synchronously converge or move away. An adjustment lever is provided on the side of the variable diameter collimator, and the adjustment lever is connected to the drive linkage disk.

[0020] Furthermore, the shielding blades are made of polymer shielding material containing lithium-6 fluoride or boron-containing shielding material.

[0021] Furthermore, the variable diameter collimator has a large aperture mode and a small aperture mode:

[0022] In the large aperture mode, the shielding blades are far apart from each other, the aperture of the collimation outlet is increased, and the neutron beam diffuses to cover the installation positions of the multiple oscillating sleeves.

[0023] In the small aperture mode, the shielding blades converge with each other, the aperture of the collimation outlet decreases, and the neutron beam is focused on the animal target area within a single positioning sleeve.

[0024] Furthermore, the positioning sleeve is made of polyethylene material containing lithium-6 fluoride, and the positioning sleeve includes a lower cover and a movable upper cover hinged to the lower cover, with the irradiation window located at the bottom of the lower cover.

[0025] Furthermore, the positioning sleeve also includes an extension sleeve fitted to the axial end of the lower cover. The extension sleeve and the lower cover are slidably connected coaxially via a telescopic slide rail, so that the axial length of the positioning sleeve is adjustable.

[0026] Furthermore, the outer wall of the lower cover is provided with a ratchet knob for securing experimental animals, and a strap driven by the knob for retraction and extension. One end of the strap is connected to the ratchet knob, and the other end passes through the bottom wall of the lower cover, the hinge area between the lower cover and the movable upper cover, and the top of the movable upper cover in sequence before being fixed to the outer edge of the movable upper cover.

[0027] Furthermore, both the inner surfaces of the lower cover and the movable upper cover are fitted with sponge liners, and the outer circumferential surface of the sponge liners is provided with guide grooves for accommodating the straps.

[0028] The beneficial effects of this application are as follows: The standardized snap-fit ​​base and multi-specification modular sleeves enable rapid costume changes for mice, rats, and rabbits. The adjustable structure between the snap-fit ​​claw and the base automatically compensates for geometric deviations introduced by differences in sleeve length and window position, ensuring the uniqueness and repeatability of tumor target area spatial coordinates in multiple comparative experiments and guaranteeing the accuracy of treatment dosage planning.

[0029] To address the conflict between fixed aperture and the need for shielding different body sizes, a deep synergy between a variable-diameter collimator and a modular sleeve was achieved to compensate the source-end energy spectrum for the target-end animal. When irradiating mice, the collimator was adjusted to a large aperture to provide a high-flux beam. Combined with the internal shielding structure of the mouse sleeve, the irradiation cycle was shortened while protecting non-target organs, enabling batch irradiation experiments on mice. When irradiating rabbits, the collimator was adjusted to a small aperture to achieve precise focusing, preventing neutrons from escaping from the edge of the large opening in the sleeve and causing secondary scattering within the animal, significantly reducing damage to surrounding healthy tissues. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a specific embodiment of an experimental irradiation device for small and medium-sized animals according to the present invention;

[0031] Figure 2 This is a diagram showing the state of the collimation outlet in the present invention when it is in the large-hole state;

[0032] Figure 3 A diagram showing the bridging assembly state of the large swing sleeve used in the experimental irradiation device of the present invention.

[0033] Figure 4 This is a diagram showing the state of the collimation outlet in the present invention when it is in the small hole state;

[0034] Figure 5 This is a back view of the slowing shield plate in the present invention when the collimation outlet is in the large-hole state;

[0035] Figure 6 This is a cross-sectional view of the positioning sleeve;

[0036] Figure 7 A diagram showing the state of the activity with the top cover open;

[0037] Figure 8 for Figure 7 Enlarged view of a portion of point A in the middle;

[0038] Figure 9 This is a radial cross-sectional view of the positioning sleeve.

[0039] In the diagram: 1-Slowing shield; 11-Beam passage hole; 12-Snap-on base; 2-Variable diameter collimator; 21-Shielding blade; 22-Drive linkage disc; 23-Adjusting lever; 24-Collimation outlet; 3-Positioning sleeve; 31-Lower cover; 311-Claw; 312-Irradiation window; 32-Modible upper cover; 33-Hinge; 34-Extension sleeve; 35-Sponge liner; 351-Guide groove; 4-Ratchet knob; 41-Strap; 42-Unlocking pin; 43-Claw. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0042] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0043] In the description of this invention, the term "axial" refers to the emission direction of the neutron beam, and "radial" refers to the direction perpendicular to the axial direction. "Bottom side" refers to the side of the positioning sleeve 3 facing the slowing shield 1. "Front" refers to the direction closer to the slowing shield 1, and "rear" refers to the direction farther from the slowing shield 1. It should be noted that these directional terms are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0044] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0045] A specific embodiment of the experimental irradiation device for small and medium-sized animals according to the present invention is as follows: Figures 1 to 9 As shown, it mainly includes a slowing shield plate 1, a variable diameter collimator 2, and multiple replaceable positioning sleeves 3.

[0046] A moderating shield 1 is vertically positioned at the front end of the neutron beam. The moderating shield 1 is made of polyethylene material containing lithium-6 fluoride, and its thickness is determined according to the neutron moderating requirements. A circular beam passage hole 11 is formed at the center of the moderating shield 1, penetrating the moderating shield 1 axially. The axis of the beam passage hole 11 is the principal optical axis of the neutron beam. Several sets of snap-fit ​​bases 12 are arranged on the surface of the moderating shield 1, circumferentially around the beam passage hole 11. Each set of snap-fit ​​bases 12 is arranged in a circumferential array along the circumference of the beam passage hole 11, and each set includes two snap-fit ​​bases 12 arranged radially opposite each other. Preferably, there are six sets of snap-fit ​​bases 12, evenly distributed at 60° intervals around the circumference of the beam passage hole 11. The snap-fit ​​bases 12 are used for detachably mounting the positioning sleeve 3. When installing a large sleeve (such as a rabbit sleeve) with an axial dimension larger than the diameter of the beam passage hole 11, the sleeve spans across the beam passage hole 11, and its radial sides are detachably connected to one of the sets of snap-fit ​​bases 12 via claws 311.

[0047] A variable-diameter collimator 2 is mounted at the beam passage hole 11 of the moderation shielding plate 1. This collimator includes multiple shielding blades 21, a drive linkage disk 22, and an adjustment lever 23. The number of shielding blades 21 is six or eight, arranged in a circumferential overlapping pattern. Each shielding blade 21 is fan-shaped and made of a polymer shielding material containing lithium-6 fluoride or a boron-based shielding material to ensure effective absorption of neutrons in non-collimated paths. The multiple shielding blades 21 overlap and cooperate with each other, with adjacent blades partially overlapping radially. This overlapping area forms a labyrinthine shielding path, effectively blocking the neutron beam in non-collimated directions and preventing rays from leaking in a straight line from the gaps between the blades.

[0048] The drive linkage disk 22 is mounted on the surface of the slowing shielding plate 1, located on the same side or opposite side of the shielding blades 21. The drive linkage disk 22 has multiple spiral curved grooves distributed circumferentially, the number of which is the same as the number of shielding blades 21. Each shielding blade 21 is fixedly equipped with a transmission pin, which slides into the corresponding curved groove. When the drive linkage disk 22 rotates around its axis, the curved grooves drive each shielding blade 21 to move synchronously radially through the transmission pins—the blades converge towards the center during forward rotation and move away from the edge during reverse rotation, thus achieving continuous adjustment of the collimation outlet 24 aperture. The adjustment lever 23 is located on the side of the variable diameter collimator 2, one end of which is connected to the drive linkage disk 22. The experimenter can manually rotate the drive linkage disk 22 by moving the adjustment lever 23.

[0049] The variable-diameter collimator 2 has two operating modes: a large aperture mode and a small aperture mode. In the large aperture mode, the shielding blades 21 are spaced further apart, the aperture of the collimation outlet 24 is increased to its maximum opening, and the neutron beam is emitted in a diffused manner, which can cover the installation positions of multiple positioning sleeves 3, making it suitable for multi-sample parallel irradiation experiments.

[0050] In small aperture mode, the shielding blades 21 converge, reducing the aperture of the collimation outlet 24 and narrowing and focusing the neutron beam, making it suitable for precise irradiation experiments on deep tumors in single animals. The aperture of the collimation outlet 24 can be continuously adjusted between the maximum and minimum opening to meet the varying requirements for irradiation field size in different experimental scenarios.

[0051] The positioning sleeves 3 are made of polyethylene material containing lithium-6 fluoride, and there are three or more of them, each corresponding to a different size of experimental animal—for example, mouse sleeves, rat sleeves, and rabbit sleeves. The inner diameter of each sleeve is different. Each positioning sleeve 3 includes a lower cover 31 and a movable upper cover 32. The lower cover 31 is semi-cylindrical or U-shaped, and its axial length is the same as the total length of the sleeve. The movable upper cover 32 is connected to one edge of the lower cover 31 via a hinge 33 and can be flipped up and down around the hinge 33. When the lower cover 31 and the movable upper cover 32 are engaged, an inner cavity is formed between them to accommodate the experimental animal. A claw 311 is provided on the bottom side of the lower cover 31, and the claw 311 is detachably connected to the latching base 12 on the slowing shielding plate 1. The snap-fit ​​base 12 is an elongated hole structure extending radially along the slowing shield plate 1. After the claw 311 is engaged in the elongated hole, it can be moved radially to adjust the installation position of the positioning sleeve 3 on the surface of the slowing shield plate 1. This design allows the same sleeve to be finely adjusted radially according to experimental needs, ensuring that the irradiation window 312 of the sleeve is precisely aligned with the collimation outlet 24.

[0052] An irradiation window 312 is also provided on the bottom side of the lower cover 31. The irradiation window 312 extends axially through the bottom wall of the lower cover 31, and its shape is circular or rectangular, with a size adapted to the aperture range of the collimation outlet 24. The axial position of the irradiation window 312 varies for animals of different sizes—for example, the irradiation window 312 of the mouse sleeve is located near the front of the sleeve, corresponding to subcutaneous tumors on the back of the mouse; the irradiation window 312 of the rat sleeve is located in the middle of the sleeve, corresponding to the brain or abdomen of the rat; and the irradiation window 312 of the rabbit sleeve is located in the middle and rear of the sleeve, corresponding to deep abdominal tumors in the rabbit.

[0053] At least one of the positioning sleeves 3 has an axial dimension larger than the diameter of the beam passage 11. This sleeve (typically a rabbit sleeve) spans across the beam passage 11, and its radial sides are detachably connected to the snap-fit ​​bases 12 on both sides of the beam passage 11 via claws 311. This bridging fixing method allows the large sleeve to obtain double-sided support, making the fixation more stable, while ensuring that the irradiation window 312 on the bottom side of the sleeve can completely cover the beam passage 11, avoiding beam obstruction.

[0054] After the positioning sleeve 3 is installed in place by engaging with the latch base 12 via the claw 311, the bottom side plate of the positioning sleeve 3 is in contact with the plate surface of the slowing shield 1, and the irradiation window 312 is aligned axially with the collimation outlet 24. The neutron beam is sequentially incident on the animal target area inside the cavity of the positioning sleeve 3 through the collimation outlet 24, the beam passage hole 11, and the irradiation window 312. Since there is no air gap between the bottom side plate of the sleeve and the plate surface of the slowing shield 1, the neutron beam will not undergo additional scattering during its journey from the collimator outlet to the animal's body surface.

[0055] For larger laboratory animals (such as rabbits), the positioning sleeve 3 is also equipped with an extension sleeve 34. The extension sleeve 34 is fitted to the axial end of the lower cover 31, and the extension sleeve 34 and the lower cover 31 are slidably connected by coaxial nesting. By pulling the extension sleeve 34 to extend or retract axially, the axial length of the positioning sleeve 3 can be adjusted according to the animal's body length, so that animals of different body lengths can be fully accommodated in the inner cavity of the sleeve, and the head and tail are properly supported.

[0056] The fastening mechanism of the strap 41 includes a ratchet knob 4 and the strap 41. The ratchet knob 4 is located on the outer right side of the lower cover 31 and has a ratchet mechanism inside. It can only be rotated in one direction to tighten the strap 41, preventing the strap 41 from accidentally coming loose during the experiment. One end of the strap 41 is connected to the spool of the ratchet knob 4, and the other end extends from the knob, passing through the bottom wall of the lower cover 31, the hinge area between the lower cover 31 and the movable upper cover 32, and the top of the movable upper cover 32, finally being fixed to the outer edge of the movable upper cover 32. This path of the strap 41 allows the strap 41 to start from the bottom right side, go around to the left side, cross the top of the movable upper cover 32, and return to the right side, forming a right-bottom-left-top-right circular arrangement.

[0057] The unlocking pin 42 is located on the right outer wall of the lower cover 31, next to the ratchet knob 4. The inner end of the unlocking pin 42 abuts against the pawl 43. When the experimenter presses the unlocking pin 42, the unlocking pin 42 pushes the pawl 43 inward, causing the pawl 43 to overcome the spring force and lift off the tooth surface of the ratchet, allowing the ratchet to rotate freely and the strap 41 to be released. After releasing the unlocking pin 42, the pawl 43 automatically returns to the locked position abutting against the ratchet tooth surface under the action of the spring. Specifically, one side wall of the unlocking pin 42 has a wedge surface that fits against the pressing side of the pawl 43. When pressed to the left, the unlocking disappears, and the wedge surface pushes upward against the unlocking end of the pawl 43, thereby swinging the locking end of the pawl 43 outward, away from the ratchet, thus unlocking.

[0058] Both the lower cover 31 and the movable upper cover 32 have a sponge liner 35 attached to their inner surfaces. The sponge liner 35 is made of flexible foam material, and its outer circumference has a guide groove 351 corresponding to the path of the strap 41. The strap 41 is embedded in the guide groove 351 to prevent the strap 41 from shifting or sliding during tightening. When the strap 41 is tightened, the strap 41 generates a centripetal clamping force on the circumference of the sleeve, which smoothly presses the movable upper cover 32 against the sponge liner 35, completing the flexible and stress-free fastening of the experimental animal's torso.

[0059] During the experiment, the adjusting lever 23 is moved according to the experimental objective to adjust the variable diameter collimator 2 to the required aperture mode—large aperture mode for multi-sample parallel experiments, and small aperture mode for single-target precision irradiation experiments. Then, the experimenters select the appropriate inner diameter sleeve 3 according to the species of experimental animals. The sleeve 3 is installed on the snap-fit ​​base 12 of the moderating shielding plate 1 using the claws 311, and the sleeve position is finely adjusted along the radial elongated hole to ensure that the irradiation window 312 is precisely aligned axially with the collimation outlet 24.

[0060] The anesthetized experimental animal is placed inside the positioning sleeve 3, and the movable upper cover 32 is closed. The ratchet knob 4 is rotated clockwise, gradually tightening the strap 41. The strap 41 first presses the movable upper cover 32 towards the lower cover 31, ensuring a tight fit. As the strap 41 continues to tighten, the sponge liner 35 is compressed, and its elastic deformation evenly wraps and fixes the animal's torso within the U-shaped cavity. For large animals, the extension sleeve 34 can be pre-pulled to adjust the axial length of the sleeve, ensuring the animal is fully contained within. After fixation, the neutron source is activated for irradiation. Waste liquids (such as urine) generated during irradiation flow out of the sleeve along the drainage channel on the bottom wall of the cavity, preventing hydrogen-containing liquids from accumulating in the irradiation path and interfering with the neutron energy spectrum.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A general-purpose experimental irradiation device for small and medium-sized animals, comprising a slowing shield plate, wherein the slowing shield plate has a beam-passing hole for a neutron beam to pass through, and wherein a plurality of sets of snap-fit ​​bases are arranged in a circumferential array around the beam-passing hole on the surface of the slowing shield plate, characterized in that, Also includes: A variable-diameter collimator, disposed at the beam passage aperture, includes multiple relatively movable shielding blades. The shielding blades are relatively close together and far apart to form a collimation outlet with an adjustable aperture. Each of the shielding blades is made of neutron shielding material. Multiple replaceable positioning sleeves, each with a claw at the bottom that can be detachably connected to the snap-fit ​​base, and an adjustment structure between the claw and the snap-fit ​​base for adjusting the installation position of the positioning sleeve; Each set of snap-fit ​​bases is arranged opposite each other in the radial direction of the beam passage hole; At least one of the positioning sleeves has an axial dimension larger than the diameter of the beam passage hole. The positioning sleeve with an axial dimension larger than the diameter of the beam passage hole spans across the beam passage hole, and its radial sides are detachably connected to the buckle bases on both radial sides of the beam passage hole via the claws. The bottom of the positioning sleeve is also provided with an irradiation window corresponding to the collimation outlet, wherein the inner diameter of at least one positioning sleeve is smaller than the inner diameter of the other positioning sleeve, and the axial position of the bottom irradiation window of at least one positioning sleeve is different from the axial position of the bottom irradiation window of the other positioning sleeve. The irradiation window and the collimation outlet are aligned axially, so that the neutron beam sequentially passes through the collimation outlet and the irradiation window and enters the animal target area within the positioning sleeve. The adjustment structure includes an elongated hole disposed on the snap-fit ​​base and extending radially along the slowing shield plate. After the snap-fit ​​claw is engaged in the elongated hole, it can be moved radially to adjust the installation position of the positioning sleeve on the surface of the slowing shield plate.

2. The experimental irradiation apparatus for small and medium-sized animals according to claim 1, wherein The multiple shielding blades overlap and cooperate with each other to block the neutron beam in a non-collimated path through the overlapping surface between the shielding blades.

3. The experimental irradiation apparatus for small and medium-sized animals according to claim 2, wherein The variable diameter collimator also includes a drive linkage disk mounted on one side of the slowing shield plate. The drive linkage disk has multiple spiral curved grooves distributed along the circumference. Each shield blade has a transmission pin that is slidably inserted into the corresponding curved groove, so that the rotation of the drive linkage disk drives multiple shield blades to synchronously converge or move away. An adjustment lever is provided on the side of the variable diameter collimator, and the adjustment lever is connected to the drive linkage disk.

4. The experimental irradiation apparatus for small and medium-sized animals according to claim 1, wherein The shielding blades are made of polymer shielding material containing lithium-6 fluoride or boron-containing shielding material.

5. The experimental irradiation apparatus for small and medium-sized animals according to claim 1, wherein The variable diameter collimator has a large aperture mode and a small aperture mode: In the large aperture mode, the shielding blades are far apart from each other, the aperture of the collimation outlet is increased, and the neutron beam diffuses to cover the installation positions of the multiple oscillating sleeves. In the small aperture mode, the shielding blades converge with each other, the aperture of the collimation outlet decreases, and the neutron beam is focused on the animal target area within a single positioning sleeve.

6. The experimental irradiation apparatus for small and medium-sized animals according to claim 1, wherein The positioning sleeve is made of polyethylene material containing lithium-6 fluoride, and the positioning sleeve includes a lower cover and a movable upper cover hinged to the lower cover, with the irradiation window located at the bottom of the lower cover.

7. The experimental irradiation apparatus for small and medium-sized animals according to claim 6, wherein The positioning sleeve also includes an extension sleeve fitted to the axial end of the lower cover. The extension sleeve and the lower cover are slidably connected coaxially via a telescopic slide rail, so that the axial length of the positioning sleeve is adjustable.

8. The experimental irradiation apparatus for small and medium-sized animals according to claim 7, wherein The outer wall of the lower cover is provided with a ratchet knob for securing experimental animals and a strap driven by the knob for retraction and extension. One end of the strap is connected to the ratchet knob, and the other end passes through the bottom wall of the lower cover, the hinge area between the lower cover and the movable upper cover, and the top of the movable upper cover in sequence before being fixed to the outer edge of the movable upper cover.

9. The experimental irradiation apparatus for small and medium-sized animals according to claim 8, wherein Both the inner surfaces of the lower cover and the movable upper cover are fitted with sponge linings, and the outer circumferential surface of the sponge linings is provided with guide grooves for accommodating the straps.

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