Small animal radiotherapy system guided by single-projection CT (Computed Tomography) in real time

Abstract

The invention discloses a single-projection CT real-time guided small animal radiotherapy system, and the system comprises an X-ray radiation source which emits X-rays to a radiation bin; the X-ray attenuation and uniformization device is used for uniformly attenuating the X-rays to an energy degree which can be detected by the X-ray flat panel detector in real time so as to prevent the X-ray flat panel detector from generating detection saturation; the X-ray flat panel detector is used for detecting the X-rays attenuated by the X-ray attenuation and uniformization device to obtain detection data; the three-dimensional image reconstruction algorithm module is used for forming a DR image according to the detection data; inputting the DR image into a pre-trained deep neural network to generate a 3D image of the small animal; when the 3D image shows that the target radiation area of the small animal deviates, the guiding device adjusts the relative position of the small animal and the X-ray radiation source, so that the X-ray emitted by the X-ray radiation source can irradiate the target radiation area, and the purpose of precise radiotherapy is achieved.

Description

Technical Field

[0001] This invention belongs to the field of radiotherapy equipment, specifically relating to a small animal radiotherapy system guided by single-projection CT (computed tomography). Background Technology

[0002] Cancer is the second leading cause of death after cardiovascular disease. Radiation therapy is a treatment that most cancer patients undergo. It uses high-energy ionizing radiation to kill cancer cells, thus treating tumors. Along with surgery and chemotherapy, it is considered one of the three major methods of cancer treatment. Currently, the main particles used in radiation therapy include X-rays, gamma rays, electrons, protons, and heavy ions. X-ray radiation therapy is the most commonly used method in hospitals. Radiation therapy is one of the most widely used cancer treatments; approximately half of all cancer patients require radiation therapy at some stage of their disease.

[0003] Small animal radiotherapy research holds significant importance in oncology, radiobiology, and therapeutic technology innovation. By conducting radiotherapy experiments on small animals, researchers can simulate the radiotherapy process for human tumors, explore the effects of radiotherapy on different types of tumors, assess radiobiological mechanisms, discover new treatment methods, and validate their clinical feasibility. These studies help elucidate tumor responses to radiotherapy, optimize dosing regimens, improve treatment precision, and reduce side effects on normal tissues, thereby advancing radiotherapy technology and providing a scientific basis for personalized treatment and the clinical application of new therapies.

[0004] Existing small animal radiotherapy systems typically require CBCT (cone-beam computed tomography) to locate the tumor before the radiotherapy experiment and to ensure that the small animal does not move during the radiotherapy process. However, in practice, even when the small animal is anesthetized, it is difficult to prevent it from moving, and this movement will cause deviations in the radiation area. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a small animal radiotherapy system guided by single-projection CT in real time.

[0006] The technical problem to be solved by this invention is achieved through the following technical solution: A single-projection CT real-time guided small animal radiotherapy system includes: a radiation chamber, an X-ray radiation source, an X-ray attenuation and homogenization device, an X-ray flat panel detector, a three-dimensional image reconstruction algorithm module, and a guidance device; wherein, The X-ray radiation source is used to emit X-rays into the radiation chamber to provide radiotherapy to the small animals inside the radiation chamber. The X-ray attenuation and homogenization device is located inside the radiation chamber and is used to attenuate the X-rays uniformly to an energy level that can be detected in real time by the X-ray flat panel detector, so as to prevent the X-ray flat panel detector from becoming saturated. The X-ray flat panel detector is located inside the radiation chamber and is used to detect X-rays after they have been attenuated by the X-ray attenuation and homogenization device, and to obtain detection data. The three-dimensional image reconstruction algorithm module is used to form a DR image based on the detection data; and input the DR image into a pre-trained deep neural network so that the deep neural network generates a 3D image of the small animal based on the DR image. When the 3D image indicates a deviation from the target radiation area of ​​the small animal, the guiding device adjusts the relative position of the small animal and the X-ray radiation source so that the X-rays emitted by the X-ray radiation source can irradiate the target radiation area.

[0007] Optionally, the system further includes: a radiation dose calibration module; The radiation dose calibration module is used to calculate the radiation dose applied to the small animal based on the detection data and using a preset radiation dose calibration formula. The radiation dose calibration formula is as follows: ; in, The detection data, For the small animal's first i X-ray attenuation coefficient corresponding to the type of tissue For the small animal's first i The thickness of the tissue The expression is an exponential function, where SSD is the distance from the X-ray radiation source to the target radiation region, and A is the attenuation coefficient of the X-ray attenuation and homogenization device. This refers to the radiation dose.

[0008] Optionally, the X-ray attenuation and homogenization device includes: a metal filter; the metal filter is thicker in the middle and thinner at the edges; the attenuation coefficient of X-rays is controlled by changing the material and thickness of the metal filter.

[0009] Optionally, the X-ray flat panel detector collects X-rays for 50ms every 1s to form a detection data, and the imaging device generates a 3D image frame based on each detection data from the X-ray flat panel detector; the deviation is detected by comparing the newly generated 3D image with the previous 3D image frame.

[0010] Optionally, the deep neural network includes: a representation network, a generation network, and a transformation module; The Representation network is used to extract high-dimensional features of the 2D image from the DR image; The Generation network is used to convert the high-dimensional features of the 2D image into high-dimensional features of the 3D image; The Transformation module is used to map the high-dimensional features of the 3D image into a 3D image.

[0011] Optionally, the system further includes: an air-cooling device and a water-cooling device; The air-cooling device includes a fan and a shielded enclosure; the X-ray radiation source is located in the shielded enclosure, the fan blows air into the shielded enclosure to dissipate heat, and the shielded enclosure is provided with ventilation openings to allow heat to be discharged from the shielded enclosure. The water cooling device includes: a circulating cooling water tank, water pipes, and a water pump; the circulating cooling water tank contains cooling water; the water pipes connect the circulating cooling water tank and the water pump, and are wound around the X-ray radiation source several times; the water pump is used to achieve circulating water supply; the circulating cooling water tank, water pipes, and water pump work together to dissipate heat from the X-ray radiation source.

[0012] Optionally, the guiding device includes: a small animal moving platform; the small animal moving platform is located in the radiation chamber; The shielding enclosure is divided into two layers; the upper layer houses the X-ray radiation source and the fan; the lower layer houses the X-ray attenuation and homogenization device, the X-ray flat panel detector, and the radiation chamber.

[0013] Optionally, the system further includes: an anesthesia device; the side wall of the radiation chamber is provided with curved gas anesthesia tube openings; The anesthesia device is connected to the interior of the radiation chamber through the gas anesthesia tube, enabling real-time anesthesia of small animals undergoing radiotherapy.

[0014] The single-projection CT real-time guided small animal radiotherapy system provided by this invention uses an X-ray flat panel detector and the rays generated by the radiotherapy itself to perform 3D imaging to locate the target radiation area of ​​the small animal. During the radiotherapy process, the movement of the small animal is monitored in real time and corrections are made to achieve the purpose of precise radiotherapy.

[0015] The present invention further introduces a radiation dose calibration module into the system, which recalculates the radiation dose of each radiotherapy experiment using the values ​​of the CT detector, providing more accurate guidance for subsequent result analysis.

[0016] The present invention further uses air-cooling and water-cooling devices in the system. By combining air cooling and water cooling, the temperature of the X-ray radiation source is rapidly reduced, and its operating time is extended.

[0017] The present invention further uses a filter that is thick in the middle and thin at the edges to attenuate the X-ray energy to the same level, so that the radiation energy of the target radiation area has a high uniformity.

[0018] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a single-projection CT real-time guided small animal radiotherapy system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another single-projection CT real-time guided small animal radiotherapy system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a deep neural network used in an embodiment of the present invention; Figure 4 Experimental results show the uniformity of radiant energy irradiated onto the irradiated area with and without using a filter and with different filters.

[0020] Figure label: 1. X-ray radiation source; 2. Light outlet; 3. Fan; 4. Water pipe; 5. Small animal; 6. First translation stage; 7. Second translation stage; 8. X-ray flat panel detector; 9. Anesthesia device; 10. Circulating cooling water tank; 11. Computer. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0022] Current small animal radiotherapy equipment involves anesthetizing the animal with liquid and placing it directly into a lead box for radiotherapy. If the animal wakes up and moves, this movement cannot be observed during the radiotherapy process; it can only be detected after the experiment has ended. A typical small animal radiotherapy experiment takes approximately 3-5 minutes. If the animal moves even slightly during the radiotherapy, it is difficult to ensure the accuracy of the experiment.

[0023] To address the problem of inaccurate target radiation areas during small animal radiotherapy experiments, which leads to unnecessary ionizing radiation to non-target areas and affects experimental results, this invention provides a single-projection CT real-time guided small animal radiotherapy system, such as... Figure 1As shown, the system includes: a radiation chamber, an X-ray radiation source 1, an X-ray attenuation and homogenization device, an X-ray flat panel detector 8, a three-dimensional image reconstruction algorithm module, and a guidance device.

[0024] The radiation chamber is equipped with a platform for placing small animals (5).

[0025] X-ray radiation source 1 is used to emit X-rays into the radiation chamber to provide radiotherapy to the small animals 5 inside.

[0026] In practice, see Figure 2 The X-ray radiation source 1 includes a housing and an X-ray tube located within the housing. The housing has an exit port 2 through which the X-rays radiated by the X-ray tube are emitted.

[0027] The X-ray attenuation and homogenization device, located inside the radiation chamber, is used to uniformly attenuate X-rays to an energy level that can be detected in real time by the X-ray flat panel detector 8, thus preventing the X-ray flat panel detector 8 from becoming saturated. Here, the X-ray attenuation and homogenization device can be a metal filter, but it is not limited to this.

[0028] In one implementation, the small animal radiotherapy system provided by the present invention may further include an X-ray beam confinement device located at the light outlet 2 and made of lead plate. For small animal radiotherapy experiments, only the tumor area and a part of the area surrounding the tumor area need to be radiotherapy, and the X-rays generated at other locations are absorbed by the beam confinement device made of lead plate.

[0029] The X-ray flat panel detector 8, located inside the radiation chamber, is used to detect X-rays after they have been attenuated by the X-ray attenuation and homogenization device, and to obtain detection data. Here, the X-ray flat panel detector 8 is the same as or similar to the X-ray flat panel detector 8 used in existing DR equipment, and will not be described in detail in this embodiment of the invention.

[0030] In practice, an X-ray flat panel detector 8 can be installed at the bottom of the radiation chamber.

[0031] The 3D image reconstruction algorithm module is used to generate DR images based on the detection data; the DR images are input into a pre-trained deep neural network so that the deep neural network generates a 3D image of the small animal 5 based on the DR images.

[0032] In practice, this 3D image reconstruction algorithm module is a code program module deployed in computer 11. This imaging module contains a pre-trained deep neural network, see [link to documentation]. Figure 3 This deep neural network includes: a Representation network, a Generation network, and a Transformation module; The Representation Network is used to extract high-dimensional features of 2D images from DR images; specifically, it can obtain high-dimensional features of 2D images by performing convolutional pooling and other processing on the DR images. Generation networks are used to convert high-dimensional features of 2D images into high-dimensional features of 3D images. The Transformation module is used to map high-dimensional features of a 3D image into a 3D graph.

[0033] The number of convolutional layers, kernel size, and convolutional image size in this deep neural network are all adjustable options, allowing for optimal results through training. This deep neural network can be pre-trained using a training sample set.

[0034] Specifically, the training sample set includes multiple training samples, each consisting of a sample DR image and a sample 3D image. During training, the sample DR image is input into the deep neural network, which predicts and outputs the corresponding 3D image. The sample 3D image serves as ground truth information for the sample DR image, used to monitor the accuracy of the 3D image predicted by the deep neural network. Specifically, during training, each iteration uses a loss function to calculate the difference in tumor region location between the 3D image predicted by the deep neural network and the sample 3D image; that is, it does not need to focus on the overall imaging resolution. This continues until, after multiple iterations, the deep neural network can accurately output a 3D image with clear tumor boundaries based on the sample DR image.

[0035] After the 3D image reconstruction algorithm module generates a 3D image of the small animal 5, the experimenters can monitor whether the small animal 5 has moved through the 3D image. When the 3D image shows a deviation from the target radiation area of ​​the small animal 5, the guiding device adjusts the relative position of the small animal 5 and the X-ray radiation source 1 so that the X-rays emitted by the X-ray radiation source 1 can accurately irradiate the target radiation area of ​​the small animal 5.

[0036] For example, the guiding device may include: a small animal movement platform located in the radiation chamber; see, for example, [link to relevant documentation]. Figure 2 The small animal moving platform includes a first translation stage 6 and a second translation stage 7, which are used to move the small animal 5 along the X and Y directions, respectively, and the X and Y directions are perpendicular to each other. When the 3D image shows a deviation from the target radiation area of ​​the small animal 5, the first translation stage 6 and / or the second translation stage 7 are moved by a motor to move the target radiation area of ​​the small animal 5 back to its original position.

[0037] The single-projection CT real-time guided small animal radiotherapy system provided by this invention has an X-ray flat panel detector 8 installed at the bottom of the radiation chamber. X-rays are irradiated on the X-ray flat panel detector 8 to obtain a projection image (DR image) of the small animal 5. The system uses the rays required for the radiotherapy experiment for real-time guidance. The system uses a deep neural network to reconstruct the overall 3D image from the single-projection DR image for radiotherapy guidance. The system monitors the movement of the small animal 5 in real time during radiotherapy and makes corrections. If the target radiation area deviates from the preset position, the system uses a guiding device to move the target radiation area of ​​the small animal 5 back to its original position, so that the rays are always irradiated on the tumor area of ​​the small animal 5, ensuring that the tumor area receives precise radiation.

[0038] Currently, researchers conducting small animal radiotherapy experiments do not know the exact radiation dose received by the animals in each experiment. They can only determine the radiation dose based on prior EBT film or calibration data from the ionization chamber. However, the fixed anode tube suffers continuous damage to the anode target surface during the experiment. Furthermore, slight variations in the voltage generated by the high-voltage source and tube temperature can all lead to differences in the radiation dose from one experiment to another. Moreover, the location of the radiation dose calibration beforehand typically does not account for tissue attenuation in the small animal, resulting in a significant difference between the radiation dose received by the tumor area and the pre-calibrated dose, affecting the accuracy of the experiment.

[0039] To address the aforementioned issues, this invention employs an X-ray flat panel detector to receive radiation, fits the correspondence between detector values ​​and dose values, and accumulates the detector values ​​in each radiotherapy experiment.

[0040] Specifically, the system provided in this embodiment of the invention may further include a radiation dose calibration module. This radiation dose calibration module is used to calculate the radiation dose applied to the small animal 5 based on the detection data and using a preset radiation dose calibration formula.

[0041] The above radiation dose calibration formula is: ; in, To detect data, For the 5th small animal i X-ray attenuation coefficient corresponding to the type of tissue For the 5th small animal i The thickness of the tissue The expression is an exponential function, where SSD is the distance from X-ray source 1 to the target radiation region, and A is the attenuation coefficient of the X-ray attenuation and homogenization device. This refers to the radiation dose.

[0042] In practice, the conversion relationship between detector readings and radiation dose is established through prior experiments. During radiotherapy, the detector is intermittently activated to determine the radiation dose received by the small animal in the radiotherapy experiment. Therefore, by establishing the correspondence between detector readings and dose, the specific radiation dose received by the small animal in the radiotherapy experiment can be calculated, facilitating subsequent experimental analysis by researchers.

[0043] Specifically, EBT4 film was used to calibrate the X-ray tube's radiation dose. EBT series film is an internationally recognized method for measuring radiation dose. The film's transmittance decreases continuously with increasing cumulative radiation dose. After 24 hours, the transmittance of the film was scanned using an EPSON scanner. The radiation dose of the X-ray tube was obtained by analyzing the correlation between different transmittances and the actual dose. Simultaneously, the X-ray tube calibrated with the film was used to illuminate the detector. The detector readings increased continuously with increasing dose, thus allowing for the determination of the correlation between detector readings and radiation dose. Next, the attenuation relationship between radiation dose and distance was measured, and the tissue structure of small animals was modeled using Monte Carlo simulation. The tissue structure of the mice was divided into soft tissue, bone, water, and air, and the attenuation of X-rays of different energies for each part was calculated by density calculation. It can be approximated that the overall structure of the small animal (usually a mouse) changes proportionally with its volume. In each experiment, the overall model of the small animal and the location of the tumor were obtained through projection data. It is approximated that the radiation energy intensity of 50ms does not change in 1s. The detector value of 50ms is converted into the value of 1s. The detector values ​​of each experiment are accumulated, and the specific radiation dose received by the tumor area of ​​the small animal in each radiotherapy experiment is obtained by attenuation by distance and Monte Carlo simulation attenuation. A 3D dose distribution map of various parts of the mouse is obtained to provide more accurate guidance for subsequent analysis.

[0044] In one embodiment, the X-ray attenuation and homogenization device may include a metal filter that is thick in the middle and thin at the edges, and the attenuation coefficient of X-rays can be controlled by changing the material and thickness of the filter.

[0045] It is understandable that X-rays produced by an X-ray tube have a high energy intensity at the center and a low energy intensity at the edges. In tumor experiments, because the tumor area is relatively small, the radiation energy distribution is relatively uniform. However, in cell experiments, a large area of ​​cells needs to be irradiated. In this case, the radiation dose received by cells in the peripheral areas is significantly lower than that in the central area, causing deviations in the experimental results. Therefore, this embodiment of the invention uses a filter that is thicker in the middle and thinner at the edges to attenuate the radiation energy to a uniform level, ensuring a uniformity of more than 95% across the entire irradiation area. Figure 4The experimental results show the uniformity of radiant energy irradiated onto the radiation area when no filter is used and when filters of different thicknesses are used. It can be seen that the uniformity is better when a metal filter with a thicker middle and thinner edges is used.

[0046] In one embodiment, the X-ray flat panel detector 8 can collect X-rays every 50ms every 1s, forming a detection data set. The imaging device generates a 3D image frame based on each detection data set from the X-ray flat panel detector 8. In this way, by comparing the newly generated 3D image with the previous 3D image frame, it can be determined whether the target radiation area of ​​the small animal 5 has deviated.

[0047] In one embodiment, the system provided by the present invention may further include: an air-cooled device and a water-cooled device; The air-cooling device includes a fan 3 and a shielded enclosure; the X-ray radiation source is located in the shielded enclosure, the fan blows air into the shielded enclosure to dissipate heat, and the shielded enclosure is provided with ventilation openings to allow heat to be discharged from the shielded enclosure; the shielded enclosure is divided into two layers; the upper layer holds the X-ray radiation source and the fan; the lower layer holds the X-ray attenuation and homogenization device, the X-ray flat panel detector and the radiation chamber. The water cooling device includes: a circulating cooling water tank 10, a water pipe 4, and a water pump; the circulating cooling water tank 10 contains cooling water; the water pipe 4 connects the circulating cooling water tank 10 and the water pump, and is wrapped around the X-ray radiation source 1 several times; the water pump is used to achieve circulating water supply; the circulating cooling water tank 10, the water pipe 4, and the water pump work together to dissipate heat from the X-ray radiation source 1.

[0048] Understandably, the efficiency of X-ray tubes in generating X-rays is less than 1%, with the remaining energy being converted into heat. This results in a long cooling time required when conducting large-scale radiotherapy experiments on small animals. Furthermore, using only air cooling is inefficient and fails to achieve rapid heat dissipation. Therefore, this invention employs both air cooling and water cooling to rapidly reduce the tube temperature, enabling the small animal radiotherapy equipment to operate for extended periods.

[0049] In one embodiment, the system provided by this invention may further include an anesthesia device 9; the side wall of the radiation chamber is provided with a curved gas anesthesia tube; the anesthesia device is connected to the interior of the radiation chamber through the gas anesthesia tube to achieve real-time anesthesia of the small animal 5 undergoing radiotherapy.

[0050] In summary, the single-projection CT real-time guided small animal radiotherapy system provided in this embodiment of the invention utilizes the X-ray flat panel detector 8 and the radiation generated by the radiotherapy itself to perform 3D imaging, thereby locating the target radiation area of ​​the small animal 5. During radiotherapy, the system monitors the movement of the small animal 5 in real time and makes corrections accordingly, achieving precise radiotherapy and providing more accurate guidance for subsequent result analysis. The radiation dose for each radiotherapy experiment is recalculated using the CT detector values, providing more accurate guidance for subsequent result analysis. A combination of air cooling and water cooling rapidly reduces the temperature of the X-ray radiation source 1, extending its operating time. Using a filter that is thicker in the middle and thinner at the edges attenuates the X-ray energy to a uniform level, resulting in high uniformity of radiation energy in the target radiation area.

[0051] It should be noted that the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0053] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings and the disclosure in carrying out the claimed invention. In the description of the invention, the word "comprising" does not exclude other components or steps, "a" or "an" does not exclude a plurality, and "a plurality" means two or more, unless otherwise explicitly specified. Furthermore, while different embodiments may describe certain measures, this does not mean that these measures cannot be combined to produce good results.

[0054] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0055] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0056] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0057] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A small animal radiotherapy system guided by single-projection CT in real time, characterized in that, include: The system includes a radiation chamber, an X-ray radiation source, an X-ray attenuation and homogenization device, an X-ray flat panel detector, a three-dimensional image reconstruction algorithm module, and a guidance device; among these components... The X-ray radiation source is used to emit X-rays into the radiation chamber to provide radiotherapy to the small animals inside the radiation chamber. The X-ray attenuation and homogenization device is located inside the radiation chamber and is used to attenuate the X-rays uniformly to an energy level that can be detected in real time by the X-ray flat panel detector, so as to prevent the X-ray flat panel detector from becoming saturated. The X-ray flat panel detector is located inside the radiation chamber and is used to detect X-rays after they have been attenuated by the X-ray attenuation and homogenization device, and to obtain detection data. The three-dimensional image reconstruction algorithm module is used to form a DR image based on the detection data; and input the DR image into a pre-trained deep neural network so that the deep neural network generates a 3D image of the small animal based on the DR image. When the 3D image indicates a deviation from the target radiation area of ​​the small animal, the guiding device adjusts the relative position of the small animal and the X-ray radiation source so that the X-rays emitted by the X-ray radiation source can irradiate the target radiation area.

2. The single-projection CT real-time guided small animal radiotherapy system according to claim 1, characterized in that, The system also includes: a radiation dose calibration module; The radiation dose calibration module is used to calculate the radiation dose applied to the small animal based on the detection data and using a preset radiation dose calibration formula. The radiation dose calibration formula is as follows: ； in, The detection data, For the small animal's first i X-ray attenuation coefficient corresponding to the type of tissue For the small animal's first i The thickness of the tissue The expression is an exponential function, where SSD is the distance from the X-ray radiation source to the target radiation region, and A is the attenuation coefficient of the X-ray attenuation and homogenization device. This refers to the radiation dose.

3. The single-projection CT real-time guided small animal radiotherapy system according to claim 1, characterized in that, The X-ray attenuation and homogenization device includes: a metal filter; the metal filter is thicker in the middle and thinner at the edges; the attenuation coefficient of X-rays is controlled by changing the material and thickness of the metal filter.

4. The single-projection CT real-time guided small animal radiotherapy system according to claim 1, characterized in that, The X-ray flat panel detector collects X-rays for 50ms every 1s, forming a detection data. The three-dimensional image reconstruction algorithm module generates a 3D image frame based on each detection data from the X-ray flat panel detector. The deviation is detected by comparing the newly generated 3D image with the previous 3D image frame.

5. The single-projection CT real-time guided small animal radiotherapy system according to claim 1, characterized in that, The deep neural network includes: a representation network, a generation network, and a transformation module; The Representation network is used to extract high-dimensional features of the 2D image from the DR image; The Generation network is used to convert the high-dimensional features of the 2D image into high-dimensional features of the 3D image; The Transformation module is used to map the high-dimensional features of the 3D image into a 3D image.

6. The single-projection CT real-time guided small animal radiotherapy system according to claim 1, characterized in that, The system also includes: an air-cooling device and a water-cooling device; The air-cooling device includes a fan and a shielded enclosure; the X-ray radiation source is located in the shielded enclosure, the fan blows air into the shielded enclosure to dissipate heat, and the shielded enclosure is provided with ventilation openings to allow heat to be discharged from the shielded enclosure. The water cooling device includes: a circulating cooling water tank, water pipes, and a water pump; the circulating cooling water tank contains cooling water; the water pipes connect the circulating cooling water tank and the water pump, and are wound around the X-ray radiation source several times; the water pump is used to achieve circulating water supply; the circulating cooling water tank, water pipes, and water pump work together to dissipate heat from the X-ray radiation source.

7. The single-projection CT real-time guided small animal radiotherapy system according to claim 6, characterized in that, The guiding device includes: a small animal moving platform; the small animal moving platform is located in the radiation chamber; The shielding enclosure is divided into two layers; the upper layer houses the X-ray radiation source and the fan; the lower layer houses the X-ray attenuation and homogenization device, the X-ray flat panel detector, and the radiation chamber.

8. The single-projection CT real-time guided small animal radiotherapy system according to claim 7, characterized in that, The system also includes: an anesthesia device; the side wall of the radiation chamber is provided with curved gas anesthesia tube openings; The anesthesia device is connected to the interior of the radiation chamber through the gas anesthesia tube, enabling real-time anesthesia of small animals undergoing radiotherapy.

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