Apparatus and method for tracking position of radioactive source

Abstract

Provided in the embodiments of this specification are an apparatus and method for tracking the position of a radioactive source. The apparatus for tracking the position of a radioactive source (400) comprises: at least one incident window (410), the incident window (410) being arranged on a filtering apparatus (330) of a radioactive source (310); and a detector (420), configured for receiving rays passing through the incident window (410) so as to determine an change in the position of the radioactive source (310) on the basis of the received rays.

Description

Device and method for tracking position of radioactive source Cross-references

[0001] This application claims priority to Chinese application No. 202311620640.8 filed on November 29, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This specification relates to the field of medical devices, and in particular to a position tracking device and method for a radioactive source and a computed tomography device. Background Art

[0003] In computed tomography (CT) imaging equipment, the position of the radiation source serves as the most fundamental reference system for CT image reconstruction. The stability of the radiation source's position fundamentally guarantees CT image quality. In an ideal CT device, the radiation source is a point-shaped source with a defined position, meaning its position remains fixed. However, in practice, due to limitations in the mechanical structure and operating principle, the position of the radiation source can shift during continuous radiation emission. Generally, with optimal manufacturing processes and control, the positional shift of the radiation source in a CT device can be minimized, making its impact negligible. However, in CT devices with higher image quality requirements, the positional accuracy of the radiation source is extremely demanding.

[0004] Based on this, it is necessary to provide a device and method for tracking the position of a radiation source. When the mechanical design cannot meet the high stability requirements of the radiation source position, the CT equipment can be corrected accordingly by tracking the position of the radiation source, thereby improving the imaging quality of the CT equipment. Summary of the Invention

[0005] One or more embodiments of the present disclosure provide a device for tracking the position of a radioactive source. The device includes at least one incident window disposed on a filtering device of the radioactive source; and a detector configured to receive radiation passing through the incident window and determine a change in the position of the radioactive source based on the received radiation.

[0006] In some embodiments, the detector is further configured to receive rays passing through the target object to obtain scanning data of the target object.

[0007] In some embodiments, the incident window is a through hole, a concave structure, or a convex structure on the filtering device.

[0008] In some embodiments, the structure of the incident window satisfies at least one of the following conditions: the edge thickness of the incident window is different from the center thickness of the incident window; the thickness of the incident window changes smoothly from the edge to the center; or the size of the incident window is such that the difference between the attenuation degree of the rays passing through the incident window and the attenuation degree of the rays passing through other positions outside the incident window of the filtering device is within a preset range.

[0009] In some embodiments, the position tracking device includes at least one first entrance window arranged on the filtering device, and the size of the first entrance window is determined based on a first distance between the radiation source and the filtering device, and a second distance between the radiation source and the detector.

[0010] In some embodiments, a projection of the ray passing through the first incident window onto the receiving area of ​​the detector is located in an edge area of ​​the receiving area.

[0011] In some embodiments, the first incident window is in the shape of a hemisphere, a cone, or a spherical sector.

[0012] In some embodiments, the at least one first incident window is arranged on the filtering device along a first direction; the position tracking device also includes at least one second incident window arranged on the filtering device along a second direction, and the first direction is perpendicular to the second direction.

[0013] In some embodiments, the position tracking device includes a plurality of second incident windows spaced apart along the second direction on the filtering device.

[0014] In some embodiments, the entrance window is disposed at the top or bottom of the filtering device.

[0015] In some embodiments, the detector includes a plurality of detector modules, and a projection of the ray passing through the incident window on a receiving area of ​​the detector is located in a central area of ​​an edge detector module among the plurality of detector modules.

[0016] In some embodiments, the shape of the filtration device comprises a bow-tie structure, and / or the material of the filtration device comprises at least one of aluminum, tin, and Teflon.

[0017] One or more embodiments of the present disclosure provide a position tracking device for a radioactive source. The device includes: a shielding structure having at least one incident window disposed thereon; a detector configured to receive radiation passing through the incident window to determine a position change of the radioactive source based on the received radiation; and a detector configured to receive radiation passing through a target object to obtain scan data of the target object.

[0018] In some embodiments, the shielding structure includes at least one third incident window arranged along a first direction, and / or at least one fourth incident window arranged along a second direction, and the first direction is perpendicular to the second direction.

[0019] In some embodiments, the structure of the incident window satisfies at least one of the following conditions: the edge thickness of the incident window is different from the center thickness of the incident window; the thickness of the incident window changes smoothly from the edge to the center; or the size of the incident window is such that the difference between the attenuation degree of the rays passing through the incident window and the attenuation degree of the rays passing through other positions outside the incident window of the filtering device is within a preset range.

[0020] In some embodiments, the detector includes a plurality of detector modules, and a projection of the ray passing through the incident window on a receiving area of ​​the detector is located in a central area of ​​an edge detector module among the plurality of detector modules.

[0021] One or more embodiments of the present specification provide a computed tomography (CT) imaging device. The CT imaging device includes: a radiation source for emitting radiation; a filtering device for absorbing low-energy radiation from the radiation and uniformly hardening the energy distribution of radiation passing through a target object and the filtering device; at least one incident window provided on the filtering device; and a detector for receiving radiation passing through the target object and the incident window. The radiation received by the detector through the incident window is used to determine a position change of the radiation source.

[0022] In some embodiments, the computed tomography apparatus further comprises at least one first entrance window disposed on the filtering device along a first direction, and / or at least one second entrance window disposed on the filtering device along a second direction, wherein the first direction is perpendicular to the second direction.

[0023] One or more embodiments of the present disclosure provide a method for tracking the position of a radioactive source. The method includes: using a detector to receive radiation emitted by a radioactive source that passes through an incident window; determining an offset distance of the response intensity of the radiation; and determining a change in the position of the radioactive source based on the offset distance, a third distance between the radioactive source and the incident window, and a fourth distance between the incident window and the detector.

[0024] In some embodiments, determining the offset distance of the response intensity of the ray includes: determining whether the incident window is blocked; in response to the presence of blockage, determining a target incident window from two or more incident windows, the target incident window being an unblocked incident window; and determining the offset distance based on the response intensity of the ray passing through the target incident window. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present application will be further described in the form of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, like numbers represent like structures, wherein:

[0026] FIG1A is a schematic structural diagram of a conventional computed tomography imaging device according to some embodiments of the present specification;

[0027] FIG1B is a schematic diagram of an exemplary radiation source offset according to some embodiments of the present specification;

[0028] FIG1C is a schematic diagram of an exemplary detector response intensity offset according to some embodiments of the present specification;

[0029] FIG2 is a schematic diagram of an application scenario of a device for tracking the position of a radioactive source according to some embodiments of this specification;

[0030] FIG3A is a schematic structural diagram of a computed tomography imaging device according to some embodiments of this specification;

[0031] FIG3B is a structural diagram of an incident window according to some embodiments of this specification;

[0032] FIG3C is a structural diagram of an incident window according to some other embodiments of this specification;

[0033] 4A to 4E are schematic structural diagrams of devices for tracking the position of a radiation source according to some embodiments of this specification;

[0034] 5A to 5H are schematic structural diagrams of devices for tracking the position of a radiation source according to other embodiments of this specification;

[0035] 6A and 6B are schematic diagrams of exemplary detector response distributions according to some embodiments of the present specification;

[0036] FIG7 is a schematic diagram of exemplary radiation source offset according to other embodiments of the present specification;

[0037] 8A and 8B are schematic diagrams of exemplary detector response intensity offsets according to other embodiments of this specification;

[0038] 9A and 9B are schematic structural diagrams of devices for tracking the position of a radiation source according to other embodiments of this specification; and

[0039] FIG10 is a flowchart illustrating an exemplary method for tracking the position of a radiation source according to some embodiments of this specification. DETAILED DESCRIPTION

[0040] To more clearly illustrate the technical solutions of the embodiments of this application, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are merely examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without inventive effort. Unless otherwise apparent from the context or otherwise noted, the same reference numerals in the figures represent the same structure or operation.

[0041] It should be understood that the terms "system," "device," "unit," and / or "module" used herein are a method for distinguishing different components, elements, parts, portions, or assemblies at different levels. However, if other terms can achieve the same purpose, the terms may be replaced by other expressions.

[0042] As used in this application and the claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not intended to refer to the singular but may include the plural. Generally speaking, the terms "comprises" and "include" only indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list. A method or apparatus may also include other steps or elements.

[0043] In the description of this specification, it should be understood that the terms "first," "second," "third," "fourth," etc. are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include at least one of such features. In the description of this specification, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0044] In this specification, unless otherwise specified or limited, terms such as "connected" and "fixed" should be interpreted broadly. For example, the term "connected" can refer to a fixed connection, a removable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; and can refer to internal communication between two components or an interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of these terms in this specification based on the specific circumstances.

[0045] Figure 1A is a schematic diagram of the structure of a traditional computed tomography device according to some embodiments of the present specification; Figure 1B is a schematic diagram of an exemplary radiation source offset according to some embodiments of the present specification; and Figure 1C is a schematic diagram of an exemplary detector response intensity offset according to some embodiments of the present specification.

[0046] As mentioned above, in the practical application of CT equipment, due to limitations in the mechanical structure and operating principle, the position of the radiation source may shift during continuous radiation emission. For applications with lower image quality requirements, through better manufacturing processes and control, the positional shift of the CT equipment's radiation source can be minimized, thus negligible. However, in CT equipment with higher image quality requirements, the positional accuracy of the radiation source is extremely high. When the mechanical design cannot meet the high stability requirements of the radiation source's focal position, tracking and confirming the radiation source position and making corresponding corrections to the CT system based on positional changes can improve the imaging quality of the CT equipment.

[0047] A radiation source is typically point-shaped and is therefore also referred to as a focal source. In some embodiments, as shown in FIG1A , a reference detector 130 and a small hole device 120 are added to the optical path between a focal source (Spot) 110 and a detector (also referred to as a measurement detector) 140. Using the principle of small hole imaging, radiation emitted by the focal source 110 passes through the small hole device 120 and is imaged on the reference detector 130. Based on the imaging data of the focal source 110 collected by the reference detector 130, an algorithm can be used to calculate the offset position of the focal source 110. For example, as shown in FIG1B , when the focal source 110 deviates (to the left as indicated by the dashed line in the figure), its offset is projected onto the reference detector 130 through the small hole device 120. The changes in the response of the reference detector 130 between different channels reflect the offset of the focal source 110 (for example, as shown in FIG1C , when the focal source 110 deviates to the left, the response intensity distribution on the reference detector 130 shifts from the solid line 151 to the dashed line 152 on the right). The vertical distance from the focal source 110 to the pinhole device 120 is h, the vertical distance from the pinhole device 120 to the reference detector 130 is H, and the distance of the focus offset projected on the reference detector 130 is D. According to the triangle similarity principle, the actual offset distance of the focal source 110 can be obtained as d = h / H×D.

[0048] However, in this type of CT equipment, the provision of an independent reference detector and pinhole device increases the difficulty of designing the radiation source end, making the mechanical and software and hardware structures of the CT equipment more complicated.

[0049] The embodiments of this specification provide a device and method for tracking the position of a radioactive source. These methods employ at least one incident window provided on a filter device of the radioactive source. The structure of the filter device is utilized to ensure that the attenuation of radiation passing through the incident window is greater or less than that of radiation passing through locations other than the incident window of the filter device. A measurement detector is used to receive radiation passing through the incident window, thereby determining changes in the position of the radioactive source based on the received radiation. This solution eliminates the need for additional detectors (such as reference detectors) or additional pinhole devices, simplifying the design of the CT device while effectively tracking the position of the radioactive source.

[0050] FIG2 is a schematic diagram of an application scenario of a device for tracking the position of a radioactive source according to some embodiments of this specification.

[0051] In some embodiments, as shown in FIG2 , the location tracking system 200 includes an imaging device 210, a processing device 220, a terminal device 230, a storage device 240, and a network 250. The connection relationships between the components in the location tracking system 200 are variable. In some embodiments, as shown in FIG2 , the imaging device 210 is connected to the processing device 220 via the network 250. For another example, the imaging device 210 is directly connected to the processing device 220 (as indicated by the dashed double-headed arrow connecting the imaging device 210 and the processing device 220 in FIG2 ). For another example, the storage device 240 is connected to the processing device 220 directly or via the network 250. As an example, the terminal device 230 can be directly connected to the processing device 220 (as indicated by the dashed double-headed arrow connecting the terminal device 230 and the processing device 220 in FIG2 ) or can be connected to the processing device 220 via the network 250.

[0052] The imaging device 210 is used to scan a target object or a portion thereof within its detection area and generate an image related to the target object or a portion thereof. In some embodiments, the target object is biological or non-biological. For example, the target object includes a patient, an artificial object, etc. In some embodiments, the target object includes a specific part of the body, such as the head, chest, abdomen, etc., or any combination thereof. In some embodiments, the target object includes a specific organ, such as the heart, esophagus, trachea, bronchi, stomach, gallbladder, small intestine, colon, bladder, ureter, uterus, fallopian tube, etc., or any combination thereof. In some embodiments, the target object includes a region of interest (ROI), such as a tumor, a nodule, etc.

[0053] In some embodiments, the imaging device 210 includes one or a combination of X-ray equipment, computed tomography (CT) equipment, three-dimensional (3D) CT, four-dimensional (4D) CT, single photon emission computed tomography (SPECT) equipment, positron emission tomography (PET) equipment, etc.

[0054] In some embodiments, the imaging device 210 is a CT device.

[0055] FIG3A is a schematic structural diagram of an exemplary computed tomography imaging device according to some embodiments of the present specification.

[0056] In some embodiments, as shown in FIG3A , a computed tomography (CT) device 300 includes a radiation source 310, a detector 320, and a filter 330. The radiation source 310 is used to emit radiation. For example, during CT imaging, the radiation source 310 (e.g., an X-ray tube) is used to emit radiation (e.g., X-rays 213) toward a target object (e.g., target object 212). The detector 320 is used to receive radiation emitted from the radiation source 310 (e.g., radiation that passes through the target object, radiation that passes through the entrance window) to obtain photon energy data corresponding to the radiation. The filter 330 is used to absorb low-energy radiation and to uniformly distribute the energy of radiation that passes through the target object and the filter 330. For example, when the X-rays 213 emitted by the radiation source 310 reach the filter 330, the filter 330 absorbs the low-energy radiation and uniformly distributes the energy of the radiation. After the X-rays 213 pass through the filter device 330 and reach the target object 212, the low-energy rays are absorbed by the filter device 330 and the energy distribution of the rays is uniformed, which not only reduces the human body's absorption dose of the rays, but also makes the rays received by the detector 320 uniform. It can also effectively reduce the effective dose on the skin surface in the edge area of ​​the human body and reduce the damage of the rays to the human body.

[0057] In some embodiments, the detector 320 has any reasonable detector parameters. The detector parameters include detector material, detector arrangement, number of detectors in each row, number of detector channels, etc. For example, the detector includes one or more rows of detector modules, and each row of detector modules includes multiple detector units. For another example, the material of the detector includes high-speed rare earth ceramics, artificial gemstones, solid chromium tungstate, scintillating crystal GOS, etc. The channel of the detector refers to an electronic device that converts the analog signal generated by the detector into a digital signal and transmits it to a reconstruction computer (such as the processing device 220). Each channel represents a physical path for signal transmission. The number of channels refers to the maximum number of rows of specific detectors used to obtain data during one acquisition process. Generally, the total number of rows of detectors is greater than or equal to the number of channels used.

[0058] In some embodiments, the filter device 330 is disposed between the radiation source 310 and the detector 320. In some embodiments, the filter device 330 has a bowtie-shaped structure. As shown in FIG4A , the filter device 330 includes a body 331. The upper end surface of the body 331 is provided with a concave structure 333 along its length (e.g., the X-direction in the figure), thereby forming a centrally symmetrical bowtie-shaped structure on the body 331. The concave structure 333 includes a central planar region 3331 and curved edge regions 3332 on either side of the central planar region 3331, i.e., the sidewalls of the concave structure are curved. In some embodiments, the body 331 is a cube or a rectangular parallelepiped. In some embodiments, the filter device 330 includes a bowtie filter. The filter device 330 is made of a low atomic number material (e.g., polytetrafluoroethylene (Teflon)), which can attenuate radiation (e.g., X-rays) passing through the filter device 330. As shown in FIG4A , since the edge arc region 3332 of the concave structure 333 of the filter device 330 is smooth and the central plane region 3331 and the edge arc region 3332 are also smoothly connected, the filter device 330 can uniformly change the attenuation degree of the rays passing through it.

[0059] It will be appreciated that the above description of the structure of the filter device 330 is provided for illustrative purposes only and is not intended to limit the scope of this specification. In some embodiments, the filter device 330 may be of any suitable structure, which is not limited by this specification. In some embodiments, the material of the filter device 330 includes at least one of aluminum, tin, and Teflon.

[0060] In some embodiments, the filter device 330 is provided with at least one entrance window, which is configured to attenuate radiation passing through the entrance window to a greater or lesser degree than radiation passing through locations other than the entrance window of the filter device 330. For example, as shown in FIG4A , the filter device 330 is provided with an entrance window 410. For more information about the entrance window, see FIG4A to FIG4E or FIG5A to FIG5H .

[0061] The processing device 220 processes data and / or information obtained from the imaging device 210, the terminal device 230, the storage device 240, or other components of the position tracking system 200. For example, the processing device 220 obtains data of a radiation source (e.g., radiation source 310) detected by a detector (e.g., detector 320) from the imaging device 210 (e.g., radiation emitted by the radiation source 310 and passing through an incident window and received by the detector 320) to determine an offset distance of the response intensity of the received radiation; thereby, the position change of the radiation source is determined based on the offset distance, a third distance between the radiation source and the incident window, and a fourth distance between the incident window and the detector.

[0062] In some embodiments, the processing device 220 and the imaging device 210 are integrated into one. For example, the processing device 220 is integrated into the imaging device 210, and the processing device 220 and the imaging device 210 work together to implement the methods and / or functions described in this specification.

[0063] In some embodiments, the processing device 220 includes an input device and / or an output device. The input device and / or the output device can be used to interact with the user (e.g., displaying a reconstructed image, etc.). In some embodiments, the input device and / or the output device include a display screen, a keyboard, a mouse, a microphone, etc., or any combination thereof.

[0064] The terminal device 230 can be connected to and / or communicate with the imaging device 210, the processing device 220, and / or the storage device 240. In some embodiments, the terminal device 230 includes a mobile device 231, a tablet computer 232, a laptop computer 233, or any combination thereof. In some embodiments, the terminal device 230 (or all or part of its functionality) is integrated into the processing device 220.

[0065] The storage device 240 can store data, instructions, and / or any other information. In some embodiments, the storage device 240 stores data (e.g., changes in the position of a radiation source, etc.) acquired from the imaging device 210, the processing device 220, or the terminal device 230. In some embodiments, the storage device 240 stores computer instructions for implementing radiation source position tracking.

[0066] In some embodiments, storage device 240 includes one or more storage components, each of which can be a standalone device or part of another device. In some embodiments, storage device 240 includes random access memory (RAM), read-only memory (ROM), mass storage, removable memory, volatile read-write memory, or any combination thereof. Exemplary mass storage includes magnetic disks, optical disks, solid-state disks, and the like. RAM includes dynamic RAM (DRAM), double data rate synchronous dynamic RAM (DDR SDRAM), static RAM (SRAM), thyristor RAM (T-RAM), and zero-capacitance RAM (Z-RAM). ROM includes mask ROM (MROM), programmable ROM (PROM), erasable programmable ROM (PEROM), electrically erasable programmable ROM (EEPROM), compact disc ROM (CD-ROM), and digital versatile disk ROM. In some embodiments, storage device 240 is implemented on a cloud platform.

[0067] The network 250 may include any suitable network capable of facilitating the exchange of information and / or data. In some embodiments, at least one component of the location tracking system 200 (e.g., the imaging device 210, the processing device 220, the terminal device 230, the storage device 240) exchanges information and / or data with at least one other component of the location tracking system 200 via the network 250.

[0068] It should be noted that the location tracking system 200 is provided for illustrative purposes only and is not intended to limit the scope of this specification. A person skilled in the art would be able to make various modifications or variations based on the description of this specification. For example, the location tracking system 200 may implement similar or different functions on other devices. However, such variations and modifications would not depart from the scope of this specification.

[0069] FIG3B is a structural diagram of an incident window according to some embodiments of the present specification; FIG3C is a structural diagram of an incident window according to some embodiments of the present specification; FIG4A to FIG4E are schematic structural diagrams of a position tracking device for a radioactive source according to some embodiments of the present specification; and FIG5A to FIG5H are schematic structural diagrams of a position tracking device for a radioactive source according to other embodiments of the present specification. Specifically, FIG4A, FIG5A, FIG5B, FIG5E, FIG5F, FIG5G, and FIG5H are schematic structural diagrams of the position tracking device for a radioactive source from a second viewing angle (Z direction), FIG4B and FIG4E are schematic structural diagrams of the position tracking device for a radioactive source from a first viewing angle (X direction), and FIG4C, FIG4D, FIG5C, and FIG5D are schematic structural diagrams of the position tracking device for a radioactive source from a Y viewing angle.

[0070] In some embodiments, as shown in FIG4A , a position tracking device 400 includes at least one incident window 410 and a detector 420. The structure of the detector 420 is the same as or similar to the detector 320 in FIG3A .

[0071] At least one entrance window 410 is disposed on a filter device (e.g., filter device 330) of a radiation source (e.g., radiation source 310) to attenuate a portion of the radiation that passes through the filter device. In some embodiments, the entrance window is configured such that the attenuation of radiation passing through the entrance window is greater or less than the attenuation of radiation passing through locations other than the entrance window of the filter device. In some embodiments, the entrance window is a through hole, a concave structure, or a convex structure on the filter device.

[0072] When radiation passes through a substance, its intensity varies depending on the thickness of the material it passes through. A filtering device can uniformly vary the attenuation of the radiation passing through it. By providing an entrance window on the filtering device, the thickness of the location where the entrance window is provided varies, causing the attenuation of radiation passing through the entrance window to vary compared to the attenuation of radiation passing through that location without the entrance window. This, in turn, causes the detector to respond differently to radiation passing through the entrance window and radiation passing through the area surrounding the entrance window on the filtering device. In some embodiments, the entrance window attenuates radiation passing through it to varying degrees, such that the attenuation of radiation passing through the entrance window is significantly greater or less than the attenuation of radiation passing through the surrounding area outside the entrance window. For example, the intensity of radiation passing through an entrance window with a concave structure or through-hole on the filtering device is significantly higher than the intensity of radiation passing through the area surrounding the entrance window on the filtering device. For another example, the intensity of radiation passing through an entrance window with a convex structure on the filtering device is significantly less than the intensity of radiation passing through other locations on the filtering device. In some embodiments, the region surrounding the incident window refers to an area on the filter device that is within a certain distance from the edge of the incident window. For example, the region surrounding the incident window refers to an area on the filter device that is less than 0.3 mm or 0.5 mm from the edge of the incident window. It will be understood that the response channels on the detector for rays passing through the region surrounding the incident window are adjacent to the response channels on the detector for rays passing through the incident window. For example, if the response channels on the detector for rays passing through the incident window are channels 11, 12, and 13, then channels 9, 10, 14, and 15 are the response channels on the detector for rays passing through the region surrounding the incident window.

[0073] In some embodiments, the shape of the incident window is hemispherical, spherical sector, etc.

[0074] In some embodiments, the incident window satisfies at least one of the following conditions: the edge thickness of the incident window is different from the center thickness; the thickness of the incident window changes smoothly from the edge to the center; the size of the incident window is such that the difference between the attenuation degree of the rays passing through the incident window and the attenuation degree of the rays passing through other positions outside the incident window of the filtering device (for example, the area surrounding the incident window on the filtering device) is within a preset range.

[0075] The thickness of a concave incident window refers to the depth of the incident window relative to the surface of the filter device (e.g., the central planar region 3331 or the curved edge region 3332 of the filter device). The thickness of a convex incident window refers to the height of the incident window relative to the surface of the filter device. The thickness of a through-hole incident window refers to the length, depth, or height of the hole in the incident window.

[0076] For example, taking one of the at least one incident window 410 shown in FIG3A as incident window 440, in conjunction with FIG3B , the edge points on either side of the edge of the concave incident window 440 are b and c, d is the midpoint of line segment bc, a is the midpoint of arc bc (the center point of incident window 440 and the point of greatest thickness in incident window 440), e and g are points on line segment bd, f and h are points on arc ab, and line segments ef and gh are parallel to line segment ad. r and s are the intersection points of the extensions of line segments ad and ef with the edge of the filtering device 330, respectively. It will be appreciated that line segments ad, ef, and gh can each represent the thickness of the incident window 440 at their respective locations. The edge thickness of the incident window 440 is different from the center thickness. Specifically, the lengths of line segments ad, gh, and ef decrease in sequence (i.e., the edge thickness of the incident window 440 is less than the center thickness). In some embodiments, the edge thickness ratio of the incident window is different from the center thickness ratio. Taking one of the at least one incident windows 410 shown in FIG3A as incident window 440 as an example, in conjunction with FIG3B , the ratio of the lengths of line segment ef to line segment fs is the edge thickness ratio of the incident window, and the ratio of the lengths of line segment ad to line segment ar is the center thickness ratio of the incident window. Since the length of line segment ad is greater than that of line segment ef, and the length of line segment ar is less than that of line segment ad to line segment ar (i.e., the edge thickness ratio and the center thickness ratio of the incident window are different). The thickness of the incident window 440 changes smoothly from the edge to the center. Specifically, the incident window 440 transitions smoothly from edge point b to center point a along arc line ab, so that the thickness of the incident window 440 changes smoothly from the edge to the center.

[0077] As another example, taking one of the at least one incident windows 410 shown in FIG3A as the incident window 450, in conjunction with FIG3C , the edge points on both sides of the edge of the incident window 450 with a raised structure are j and k, m is the midpoint of the line segment jk, i is the midpoint of the arc jk (the center point of the incident window 450, and also the point with the maximum thickness (such as the height of the projection) in the incident window 450), n and p are points on the line segment mk, o and q are points on the arc ik, and the line segments on and pq are parallel to the line segment im. It can be understood that the line segments on, pq, and im can respectively represent the thickness of the incident window 450 at their respective locations. The thickness of the edge of the incident window 450 is different from the thickness at the center. Specifically, the lengths of the line segments im, on, and pq decrease in sequence (i.e., the thickness of the edge of the incident window 450 is less than the thickness at the center). The thickness of the incident window 450 changes smoothly from the edge to the center. Specifically, the incident window 450 transitions smoothly from the edge point k to the center point i along the arc line ik, so that the protrusion height of the incident window 450 changes smoothly from the edge to the center.

[0078] The size of the entrance window includes the diameter and thickness of the entrance window. In some embodiments, when the diameter and thickness of the entrance window are both within the range of 1 mm to 3 mm, the difference between the attenuation degree of the ray passing through the entrance window and the attenuation degree of the ray passing through other positions outside the entrance window of the filter device (hereinafter referred to as the first difference) is within a preset range. Exemplarily, the preset range can be [-20%, -10%] ∪ [10%, 20%]. It can be understood that when the entrance window is a concave structure or a through hole on the filter device, the attenuation degree of the ray passing through the entrance window is weaker than the attenuation degree of the ray passing through other positions outside the entrance window of the filter device. In this case, the first difference is a negative value. When the entrance window is a convex structure on the filter device, the attenuation degree of the ray passing through the entrance window is greater than the attenuation degree of the ray passing through other positions outside the entrance window of the filter device. In this case, the first difference is a positive value.

[0079] In some embodiments, the difference in attenuation is characterized based on the difference in response between the detector channel corresponding to the entrance window and the detector channel corresponding to locations other than the entrance window of the filtering device (e.g., detector channels adjacent to the detector channel corresponding to the entrance window). In some embodiments, the response values ​​of different detector channels of the detector module (e.g., the detector channel corresponding to the entrance window and adjacent detector channels) to the radiation can be obtained and normalized to determine the difference in attenuation. For more information on the above embodiments, please refer to Figures 6A and 6B and the related descriptions.

[0080] In some embodiments of the present specification, setting the incident window to a hemispherical / spherical sector-shaped convex or concave structure can make the incident window meet the above conditions, so that the response curve of the detector presents a Gaussian distribution, which is beneficial to improving the accuracy of the position tracking results.

[0081] In some embodiments, position tracking device 400 includes at least one first entrance window disposed on the filtering device. In some embodiments, the at least one first entrance window is disposed on the filtering device along a first direction. The first direction is parallel to the horizontal plane. For example, as shown in FIG. 4A , at least one entrance window 410 includes a first entrance window 411 and a first entrance window 412 disposed on filtering device 330 along a first direction (the X direction in the figure).

[0082] In some embodiments, the size of the first entrance window (e.g., first entrance window 411 and first entrance window 412) is determined based on a first distance between the filtering device (e.g., filtering device 330) and the radiation source (e.g., radiation source 310), and a second distance between the radiation source and the detector (e.g., detector 320). In this embodiment, the size of the first entrance window primarily refers to the diameter or radius of the entrance window, or the width of the entrance window in the first direction. For example, assuming a detector channel of 1 mm, and a ratio of the first distance between the filtering device and the radiation source to the second distance from the radiation source to the detector of 1:9, the diameter of the first entrance window can be determined to be 1 mm based on the similarity theorem.

[0083] The detector 420 is configured to receive radiation that has passed through at least one incident window 410, so as to determine a position change of a radiation source (e.g., radiation source 310) based on the received radiation. It should be noted that when determining the position change of a radiation source based on radiation that has passed through an incident window, the radiation that has passed through the incident window may also pass through a target object (e.g., target object 212) after passing through the incident window. However, to ensure the accuracy of the determined position change of the radiation source, the radiation that has passed through the incident window generally does not pass through the target object.

[0084] In some embodiments, detector 420 is also used to receive radiation that has passed through the target object to acquire scan data of the target object. That is, detector 420 functions as both a reference detector and a measurement detector. It should be understood that radiation that has passed through the target object includes radiation that has passed through the target object without passing through the entrance window, as well as radiation that has passed through both the entrance window and the target object. While this may affect the determination of the position change of the radiation source, it does not affect the acquisition of scan data.

[0085] Due to the effect of the filter, after the radiation emitted by the radiation source is received by the detector, the detector's response will exhibit a relatively stable distribution across different channels. The provision of an entrance window on the filter ensures that the intensity of the radiation passing through different locations of the filter varies. Consequently, after the radiation emitted by the radiation source passes through the filter and is received by the detector, the distribution of the detector's response across different channels will vary significantly. For example, when the filter is not provided with an entrance window, the distribution of the detector's response across different channels exhibits a gentle curve. However, when the filter is provided with an entrance window with a concave or convex structure, the distribution of the detector's response across different channels exhibits a Gaussian distribution.

[0086] Figures 6A and 6B are schematic diagrams of exemplary detector response distributions according to some embodiments of this specification. Figure 6A is a distribution curve of detector response across different channels without an incident window, and Figure 6B is a distribution curve of detector response across different channels with an incident window.

[0087] In Figures 6A and 6B, the abscissa represents the detector channel number (25 channels are shown), and the ordinate represents the response value of each channel to the received radiation. As shown in Figure 6A, when there is no entrance window, due to the uniform effect of the filtering device (which uniformly hardens the energy distribution of the radiation), the distribution trend of the detector response across different channels approaches a straight line. As shown in Figure 6B, when the filtering device is equipped with an entrance window, due to the attenuation effect of the entrance window, the response values ​​of detector channels 10 to 15 corresponding to the location of the entrance window show a clear upward trend. The response of channels 10 to 15 (i.e., the protrusion between dashed lines 611 and 612 in Figure 6B) is also called the response intensity corresponding to the radiation from the entrance window.

[0088] Radiation emitted by the radiation source is projected onto the detector through the entrance window of the filter assembly, forming a Gaussian distribution curve between channels (as shown in Figure 6B). By fitting this curve, the channel corresponding to the centerline of the curve (such as the solid black line 620 in Figure 6B) can be determined, thereby determining the position of the corresponding radiation source (focal source). When the focal source shifts, its shift is projected onto the detector through the entrance window. Therefore, the change in the detector response between different channels can reflect the shift of the focal source. By calculating the centerline position of the detector response curve before and after the shift, the change in the radiation source's position can be determined.

[0089] It is worth noting that Figures 6A and 6B only show the response distribution of some channels of the detector, mainly the response distribution corresponding to the detector modules / detector units in the detector that receive rays passing through the incident window. In practice, the detector channel response distribution also includes the response distribution of other detector modules / detector units. For example, it is assumed that the detector (for example, detector 320, detector 420) includes 12 annular detector modules, each detector module includes 25 detector units. Due to the different positions of each detector module, different detector modules are used to receive rays at different positions. If detector module 3 receives rays passing through the incident window, Figure 6B is the response distribution corresponding to detector module 3, where each detector unit of detector module 3 corresponds to one channel.

[0090] Figure 7 is a schematic diagram illustrating exemplary radiation source offset according to some embodiments of the present disclosure. As shown in Figure 7 , when the radiation source deflects to the left (i.e., in the direction indicated by the arrow in the figure), the projection of the radiation emitted by it on the detector deflects to the right. Figures 8A and 8B are schematic diagrams illustrating exemplary detector response intensity offset according to some embodiments of the present disclosure. As shown in Figure 8A or 8B , when the radiation source deflects, the distribution of the detector response intensity (the convex portion of the curve in Figure 8A , or the concave portion of the curve in Figure 8B ) shifts from the center (black solid line 801 in Figure 8A , black solid line 803 in Figure 8B ) to the right (black dashed line 802 in Figure 8A , black solid line 804 in Figure 8B ). By fitting the two sets of response curves shown in Figure 8A or 8B and obtaining the channel corresponding to the centerline of the response intensity, the offset distance D of the response intensity can be obtained. Furthermore, based on the offset distance D, the third distance between the entrance window and the radiation source, and the fourth distance between the entrance window and the detector, the position change of the radiation source can be determined. For more details, please refer to the description in Figures 9A and 9B.

[0091] In some embodiments, a projection of the ray passing through the first incident window on the receiving area of ​​the detector is located at an edge area of ​​the receiving area.

[0092] The receiving area of ​​a detector refers to the area within which the detector receives radiation. For example, in FIG4A , the receiving area of ​​detector 420 is area P. The projection of the first entrance window on the receiving area of ​​the detector located at the edge of the receiving area means that the distance between the projection of the first entrance window on the receiving area of ​​the detector and the edge of the receiving area is less than a first threshold (e.g., the first threshold is 0.01 mm, 0.15 mm, or 0.02 mm). In some embodiments, the projection of the entrance window on the receiving area of ​​the detector is determined based on the projection of the radiation on the receiving area of ​​the detector. For example, in conjunction with FIG3A , after ray 215 passes through entrance window 410 and reaches receiving area P of detector 320, the distance between the intersection of ray 215 with receiving area P and the edge of receiving area P is 0.005 mm (assuming the first threshold is 0.01 mm, the aforementioned distance is less than the first threshold). Therefore, the projection of the entrance window on the receiving area of ​​the detector is determined to be located at the edge of the receiving area. In some embodiments, whether the projection of the first entrance window on the receiving area of ​​the detector is located at the edge of the receiving area is determined based on the detector channels covered by the projection of the first entrance window. For example, in combination with Figure 4A, if the channels close to the edge position in the detector module of the detector 420 for receiving rays passing through the incident window are channel 10, channel 11, channel 12, and channel 13, then by making the projection of the first incident window cover channel 10, channel 11, channel 12 and / or channel 13 of the detector, the projection of the first incident window in the receiving area of ​​the detector is located in the edge area of ​​the receiving area.

[0093] Since the target object is generally placed at the center of the CT device during scanning (for example, the volume center of the patient's target organ or the patient's volume center coincides or substantially coincides with the aperture center of the CT device), the edge areas of the detector's receiving area are generally not blocked by the target object. For example, as shown in FIG4A , when the target object is placed at the center of the CT device, areas P1 and P2 in the receiving area P of the detector 420 will not be blocked by the target object 212. Based on this, the position and size of the first incident window can be set so that the projection of the rays passing through the first incident window on the detector's receiving area is located within area P1 and / or area P2.

[0094] In some embodiments of the present specification, by making the projection of the incident window on the receiving area of ​​the detector located in the edge area of ​​the receiving area, it is possible to avoid the rays passing through the incident window from affecting the response of the detector module due to passing through the target object, thereby enabling real-time and accurate tracking of the position of the emission source during the scanning process, thereby improving the accuracy of the scanning results.

[0095] In some embodiments, the projection of the radiation passing through the first entrance window onto the receiving area of ​​the detector does not need to be located at the edge of the receiving area; it only needs to not affect the imaging of the region of interest (the area on the detector module covered by the target object). For example, the projection of the radiation passing through the first entrance window onto the receiving area of ​​the detector and the projection of the radiation passing through the target object onto the receiving area of ​​the detector can be located in different areas.

[0096] In some embodiments, the first incident window is a strip-shaped structure, and the long side of the strip-shaped structure is perpendicular to the first direction.

[0097] Exemplarily, as shown in FIG4B , the first incident window 413 is a strip structure, and the long side 413 - 1 of the first incident window 413 is parallel to the second direction (ie, the Z direction in the figure) and perpendicular to the first direction (ie, the X direction in the figure).

[0098] In some embodiments, the center of the long side of the strip structure is on the midline of the cross section of the filtration device along the second direction, wherein the cross section refers to a cross section of the filtration device parallel to the XZ plane.

[0099] Exemplarily, as shown in Figure 4C, taking the filtering device 330 as an example, which includes two first incident windows, the center 413-2 of the long side of the first incident window 413 is located on the center line 334 of the cross section of the filtering device 330 along the first direction, and the center 414-2 of the long side of the first incident window 414 is located on the center line 334 of the cross section of the filtering device 330 along the first direction.

[0100] In some embodiments of the present specification, for certain imaging devices, if only the focus position change in the X direction is of interest, the incident window in the filter device structure can be designed as a strip structure. Based on this, the projection of rays passing through the filter device on the detector is evenly distributed in the Z direction, which is beneficial to improving the accuracy of the calculation results of the focus position change in the X direction.

[0101] In some embodiments, the first entrance window is shaped like a hemisphere, a cone, or a spherical sector. For example, the first entrance window 411 and the first entrance window 412 shown in FIG4A are shaped like a hemisphere, a third of a sphere, three-quarters of a sphere, or a spherical sector. In some embodiments, the material of the entrance window is the same as or different from the material of the filtering device.

[0102] In some embodiments, as shown in Figure 4D, taking the filtering device 330 as an example, which includes two first incident windows, the center 411-2 of the shape of the first incident window 411 on the cross-section of the filtering device 330 is located on the center line 334 of the filtering device 330 along the first direction of the cross-sectional plane, and the center 412-2 of the shape of the first incident window 412 on the cross-sectional plane of the filtering device 330 is located on the center line 334 of the filtering device 330 along the first direction of the cross-sectional plane.

[0103] In some embodiments, the position tracking device further comprises at least one second incident window arranged on the filtering device along a second direction, wherein the second direction is perpendicular to the first direction.

[0104] Exemplarily, as shown in FIG4E , the position tracking device 400 includes at least one second incident window 430 disposed on the filtering device 330 along the second direction (ie, the Z direction in the figure).

[0105] In some embodiments, the position tracking device includes a plurality of second incident windows spaced apart along the second direction on the filtering device.

[0106] Exemplarily, as shown in FIG4E , the position tracking device 400 includes a second incident window 431 , a second incident window 432 , and a second incident window 433 spaced apart on the filtering device 330 along the second direction (ie, the Z direction in the figure).

[0107] In some embodiments, the distance between two adjacent second incident windows in the plurality of second incident windows is greater than a second threshold value. The second threshold value can be preset, for example, the second threshold value is 3 mm, 4 mm, or 5 mm.

[0108] In some embodiments, the entrance window is disposed on the top or bottom of the filter device, wherein the top of the filter device refers to the side of the filter device facing the radiation source, and the bottom of the filter device refers to the side of the filter device facing away from the radiation source.

[0109] In some embodiments, the entrance window is disposed within a concave structure (e.g., concave structure 333) at the top of the filtration device. In some embodiments, the entrance window is disposed within an arcuate region (arc-shaped region 3332) of the concave structure of the filtration device. For example, as shown in FIG4A , first entrance window 411 and first entrance window 412 are disposed within arcuate region 3332 of concave structure 333 of filtration device 330.

[0110] In some embodiments, the distance between the incident window (e.g., first incident window 411 and first incident window 412) and the radiation source is equal to or substantially equal to the distance between the radiation source and the filtering device. Correspondingly, the distance between the incident window and the detector is equal to or substantially equal to the distance between the filtering device and the detector.

[0111] In some embodiments, the incident window is disposed on the bottom surface of the filter device (eg, bottom 332 ). For example, as shown in FIG5A , the first incident window 415 and the second incident window 416 are disposed on the bottom surface of the filter device 330 .

[0112] In some embodiments, the incident windows are disposed on both the curved region and the bottom surface of the concave structure of the filter device. For example, as shown in FIG5B , first incident windows 411 and 412 are disposed within the curved region 3332 of the concave structure 333 of the filter device 330, and first incident windows 415 and 416 are disposed on the surface of the bottom 332 of the filter device 330.

[0113] In some embodiments, the shape of the incident window in the cross section of the filtering device (e.g., a cross section parallel to the XZ plane) includes an L-shape, a triangle, a rectangle, a circle, a sector, or a polygon. For example, as shown in FIG5C , the shape of the first incident window 417 and the first incident window 418 in the cross section of the filtering device 330 is L-shaped. For another example, as shown in FIG5D , the shape of the first incident window 419 and the first incident window 4110 in the cross section of the filtering device 330 is triangular.

[0114] In some embodiments, a detector (eg, detector 420 ) includes a plurality of detector modules, wherein each module has its own receiving area.

[0115] In some embodiments, the projection of the radiation passing through the incident window onto the receiving area of ​​the detector is located in the center region of the edge detector module. An edge detector module refers to a detector module located at an edge position among multiple detector modules. For example, as shown in FIG5E , detector 420 includes detector module 421, detector module 422, detector module 423, detector module 424, detector module 425, detector module 426, and detector module 427, wherein detector module 421 and detector module 427 are located at the edge positions on both sides of the multiple detector modules, respectively. Therefore, detector module 421 and detector module 427 are edge detector modules.

[0116] Exemplarily, as shown in FIG5E , the projection of the ray passing through the first incident window 411 on the receiving area of ​​the detector 420 is located in the central area of ​​the detector module 421 (the detector module 421 is one of the edge detector modules), and the projection of the ray passing through the first incident window 412 on the receiving area of ​​the detector 420 is located in the central area of ​​the detector module 427 (the detector module 427 is another edge detector module).

[0117] In some embodiments, the projection of the ray passing through the entrance window on the ray receiving area of ​​the corresponding detector module (for example, a detector module in the detector that can be used to receive the ray passing through the entrance window) covers 3 to 10 detector channels of the detector module. Taking the above-mentioned detector module having 26 channels (channel 0 to channel 25) as shown in Figure 6B as an example, the projection of the ray passing through the entrance window on the ray receiving area of ​​the corresponding detector module covers channels 10 to 15 (channels 10 to 15 belong to the central area of ​​the detector module). Taking into account the coverage range of the response intensity of the detector module and the accuracy of the fitting centerline, setting the coverage range of the projection of the ray passing through the entrance window on the ray receiving area of ​​the corresponding detector module to cover 3 to 10 detector channels can ensure the fitting accuracy and thereby improve the accuracy of the position tracking result of the radiation source.

[0118] In some embodiments, the maximum difference between the response value of a detector channel corresponding to an entrance window and the response value of an adjacent channel of the corresponding detector channel is within a preset range (e.g., 8% to 12%). For example, as shown in FIG6B , the differences between the response values ​​of channels 10 to 15 (with response values ​​of approximately 1.03, 1.06, 1.11, 1.06, and 1.03, respectively) and the response values ​​of an adjacent channel (for example, channel 9, with a response value of approximately 1.01) are 1.99%, 4.95%, 9.9%, 4.95%, and 1.99%, respectively. The maximum difference is 9.9%, which is within the preset range of 8% to 12%.

[0119] In some embodiments, the incident window is a through hole, a concave structure, or a convex structure on the filtering device. For example, as shown in FIG4A , the first incident window 411 and the first incident window 412 of the position tracking device 400 are two small concave structures on the filtering device 330. As another example, as shown in FIG5F , the first incident window 411 and the first incident window 412 of the position tracking device 400 are two small convex structures on the filtering device 330. As another example, as shown in FIG5G , the first incident window 4111 and the first incident window 4112 of the position tracking device 400 are two through holes on the filtering device 330.

[0120] In some embodiments, the size of the protruding structure is the same as or different from the size of the concave structure. For example, the diameter of the protruding structure shown in FIG5F is equal to the diameter of the concave structure shown in FIG4A.

[0121] It is understandable that when the incident window is a through hole or concave structure, when the radiation emitted by the radiation source passes through the through hole or concave structure and is projected onto the detector, the response of the detector channel covered by the through hole or concave structure is higher in intensity than the responses of other detector channels (as shown in FIG8A ). Conversely, when the incident window is a convex structure, when the radiation emitted by the radiation source passes through the convex structure and is projected onto the detector, the response of the detector channel covered by the convex structure is lower in intensity than the responses of other detector channels (as shown in FIG8B ).

[0122] In some embodiments, the thickness of the entrance window on the filtering device is in the range of 1 mm to 3 mm.

[0123] In some embodiments, the thickness of the incident window on the filtering device is determined based on the size of the incident window (e.g., diameter, side length, etc.). For example, the thickness of the incident window on the filtering device is proportional to the diameter or side length of the incident window (e.g., the length of the first incident window along the first direction, or the length of the second incident window along the second direction).

[0124] In some embodiments, the thickness of the entrance window on the filtering device is determined based on the shape of the entrance window. For example, when the entrance window is circular, the thickness of the entrance window on the filtering device is 1 mm. For another example, when the entrance window is triangular, the thickness of the entrance window on the filtering device is 2 mm.

[0125] In some embodiments, the thickness of the entrance window on the filter device (e.g., the depth of the concave structure or through-hole, or the height of the protrusion of the protrusion) is adjusted based on the actual offset of the radiation source. For example, the thickness of the entrance window on the filter device is proportional to the offset distance of the entrance window. For more information on the offset distance, see FIG. 7 and its related description.

[0126] It is worth noting that in this embodiment, the thickness of the incident window of the concave structure includes the vertical distance between the deepest part of the concave shape and the edge arc area of ​​the filtering device (for example, one of the at least one incident window 410 and the edge arc area 3332 of the filtering device 330) (for example, the distance from a to d shown in Figure 3B), or the average value of the depth of the concave shape at all reference points on the concave arc segment of the concave structure (for example, the average value of the vertical distances between all reference points on arc bc and line segment bc shown in Figure 3B). The thickness of the incident window of the convex structure includes the vertical distance between the highest point of the incident window convexity and the edge arc area of ​​the filtering device (for example, the distance from i to m shown in Figure 3C), or the average value of the convex height of all reference points on the convex arc segment (for example, the average value of the vertical distances between all reference points on arc jk and line segment jk shown in Figure 3C). The reference points refer to a preset number of points selected on the concave arc segment of the concave structure or the convex arc segment of the convex structure. The distances between adjacent reference points can be the same or different. For example, on the arc bc shown in FIG3B , taking the preset number as 20, the reference points include 20 points, and the distance between adjacent reference points is a random value between 0.01 mm and 0.05 mm.

[0127] In some embodiments, the inner wall of the incident window has a pattern, for example, a wave pattern, a ring pattern, etc.

[0128] In some embodiments, when position tracking device 400 includes two entrance windows disposed on the filtering device, the line connecting the two entrance windows is parallel to the bottom of the filtering device. For example, as shown in FIG4A , position tracking device 400 includes first entrance window 411 and first entrance window 412 disposed on filtering device 330, and line 4199 connecting first entrance window 411 and first entrance window 412 is parallel to bottom 332 of filtering device 330.

[0129] In some embodiments, the line connecting the two incident windows intersects with the extension line of the bottom of the filtering device. For example, as shown in FIG5H , the line 4198 connecting the first incident window 411 and the second incident window 412 intersects with the extension line of the bottom 332 of the filtering device 330.

[0130] In some embodiments, the distances between the two entrance windows and the two side edges of the filtering device are equal or unequal. For example, the minimum distance between the first entrance window 411 and one side edge of the filtering device 330 is equal to or greater than the minimum distance between the first entrance window 412 and the other side edge of the filtering device 330. For another example, as shown in FIG5H , the minimum distances between the first entrance window 411 and the first entrance window 412 and one side edge of the filtering device 330 are less than the minimum distance between the first entrance window 412 and the other side edge of the filtering device 330.

[0131] In some embodiments, as shown in FIG4A , two incident windows (a first incident window 411 and a second incident window 412 ) are respectively disposed at two edge arc regions (arc regions 3332 ) of the concave structure 333 of the filtering device.

[0132] In some embodiments of the present specification, by providing two incident windows, the position of the radiation source can still be accurately tracked even when one of the incident windows is blocked (eg, blocked by a target object).

[0133] In some embodiments, the position tracking device 400 includes two or more incident windows, i.e., the filtering device is provided with two or more incident windows. For example, as shown in FIG5B , the filtering device 330 of the position tracking device 400 is provided with four incident windows, i.e., a first incident window 411, a first incident window 412, a first incident window 415, and a first incident window 416.

[0134] 9A and 9B are schematic structural diagrams of devices for tracking the position of a radiation source according to other embodiments of this specification.

[0135] In some embodiments, as shown in FIG9A , a position tracking device 900 includes a shielding structure 910 , a filtering device 920 , and a detector 930 . Detector 930 has a structure that is the same as or similar to detector 320 or detector 420 .

[0136] In some embodiments, as shown in FIG9A , at least one incident window 940 is provided on the shielding structure 910 for attenuating part of the rays passing through the shielding structure 910. In some embodiments, the incident window is configured so that the attenuation degree of the rays passing through the incident window is greater or less than the attenuation degree of the rays passing through other positions outside the incident window. In some embodiments, the shape of the incident window is hemispherical, spherical sector, cylindrical, etc. In some embodiments, the incident window 940 is a through hole, a concave structure, or a convex structure on the shielding structure 910. In some embodiments, the structure of the at least one incident window 940 is the same as or similar to the at least one incident window 410. For more description of the at least one incident window 410, please refer to FIG4A to FIG4E or FIG5A to FIG5H and their related descriptions.

[0137] In some embodiments, the shielding structure includes at least one third incident window arranged along the first direction, and / or at least one fourth incident window arranged along the second direction. The first direction is perpendicular to the second direction. For example, as shown in FIG9A , the shielding structure 910 includes a third incident window 941 and a third incident window 942 arranged along the first direction (i.e., the X direction). For another example, as shown in FIG9B , the shielding structure 910 includes a fourth incident window 943, a fourth incident window 944, and a fourth incident window 945 arranged along the second direction (i.e., the Z direction).

[0138] In some embodiments, each of the at least one incident window 940 has a structure that is the same as or similar to the incident window 340 shown in FIG3B . Based on this, the structure of the incident window 940 satisfies at least one of the following conditions: the thickness at the edge of the incident window is different from the thickness at the center; the thickness of the incident window changes smoothly from the edge to the center; the size of the incident window is such that the difference between the attenuation degree of the ray passing through the incident window and the attenuation degree of the ray passing through other positions outside the incident window satisfies a preset condition (for example, the maximum value of the difference between the response value of the detector channel corresponding to the incident window and the response value of the adjacent channel of the corresponding detector channel (belonging to other positions outside the incident window) is within a preset range (for example, 8% to 12%)). For more information about this embodiment, please refer to FIG3B and its related description.

[0139] In some embodiments, the shielding structure 910 is a pinwheel-type structure, which includes two or more blades. Among them, at least two blades of the pinwheel-type structure may have different structures. For example, the at least two blades of the pinwheel-type structure have the same shape but different sizes (for example, side length and / or thickness), or the at least two blades of the pinwheel-type structure have different shapes, etc. In some embodiments, the position tracking device adjusts the blades used for position tracking according to the scanning situation (for example, the size of the target object, the offset distance of the radiation source). For example, when the target object is large, smaller windmill blades are used to avoid obstruction. For another example, when the offset distance of the radiation source is large, L-shaped or strip-shaped blades are used.

[0140] In some embodiments, detector 930 has a structure identical or similar to detector 420 shown in FIG5E . Accordingly, detector 930 includes multiple detector modules, and the projection of radiation passing through the incident window onto the receiving area of ​​detector 930 is located in the center region of an edge detector module among the multiple detector modules. For more information on this embodiment, please refer to FIG5E and its related description.

[0141] In some embodiments of the present specification, by providing a shielding structure in the position tracking device, the position change of the radiation source can be measured without modifying the structure of the filtering device or providing an additional detector (for example, a reference detector). This ensures the accuracy of the measurement of the position change of the radiation source while reducing the structural complexity of the position tracking device.

[0142] It should be noted that the above description of the position tracking device 400 and the position tracking device 900 is for illustration and purpose only and does not limit the scope of application of this specification. Those skilled in the art will appreciate that various modifications and alterations to the position tracking device 400 and the position tracking device 900 can be made under the guidance of this specification. However, such modifications and alterations are still within the scope of this specification.

[0143] FIG10 is a flowchart illustrating an exemplary method for tracking the position of a radiation source according to some embodiments of this specification.

[0144] In some embodiments, process 1000 is performed by position tracking device 400 or 900. The operational diagram of process 1000 presented below is illustrative. In some embodiments, the process may be completed using one or more additional operations not described above and / or one or more operations not discussed above. In addition, the order of the operations of process 1000 shown in FIG. 10 and described below is not intended to be limiting.

[0145] Step 1010: Receive radiation emitted by a radiation source and passing through an entrance window using a detector. The entrance window is provided on a filter or shielding structure of the radiation source and is configured such that the attenuation of radiation passing through the entrance window is greater or less than the attenuation of radiation passing through other locations outside the entrance window of the filter or shielding structure.

[0146] In some embodiments, after a radiation source (such as radiation source 310) emits radiation, a detector (such as detector 420, detector 320, or detector 930) can receive the radiation that passes through the incident window. In some embodiments, the detector can be used to receive the radiation that passes through the incident window emitted by the radiation source during non-operating time (i.e., idle time) of the position tracking system 200 (e.g., CT equipment), i.e., when there is no target object. For example, with reference to FIG3A , when the position tracking system 200 is not operating, the radiation source 310 emits X-rays, which pass through the filter 330 and are projected onto the detector 320, and the detector 320 receives the radiation that passes through the incident window. For another example, with reference to FIG9A , when the position tracking system 200 is not operating, the radiation source 310 emits X-rays, which pass through the shielding structure 910 and the filter 920 and are projected onto the detector 930, and the detector 930 receives the radiation that passes through the incident window.

[0147] Step 1020: Determine the offset distance of the response intensity of the ray.

[0148] The response intensity refers to the response value of the ray passing through the incident window in the detector channel, such as the convex part shown in Figure 6B or the concave part shown in Figure 8B. In combination with the above, the change in the response of the detector between different channels can reflect the offset process of the focal source. In some embodiments, the offset distance of the response intensity can be determined based on the corresponding detector response distribution curve before and after the radiation source is offset. In some embodiments, the channel corresponding to the center line of the response intensity (such as the black solid line in Figure 6B) can be obtained by fitting the response distribution curve of the detector. Further, the offset distance is determined based on the center line position of the response intensity before the offset and the center line position of the response intensity after the offset. Exemplarily, by fitting the two groups of response curves shown in Figure 8A (or Figure 8B) (the solid curve and the dotted curve in the figure), the channels corresponding to the center lines of the two groups of curves are respectively obtained, and the channel difference between the center lines of the two groups of curves is calculated to obtain the offset distance D of the response intensity.

[0149] In some embodiments, a detector response distribution curve corresponding to any incident window is selected to determine the offset distance.

[0150] In some embodiments, it is determined whether an incident window is obstructed. If obstructed, a detector response distribution curve corresponding to an unobstructed incident window is selected to determine the offset distance. Specifically, in response to the presence of obstruction, a target incident window is determined from two or more incident windows, the target incident window being the unobstructed incident window; and the offset distance is determined based on the response intensity of rays passing through the target incident window.

[0151] In some embodiments, whether the entrance window is obstructed is determined based on the response distribution curve of the detector. For example, if the response value of the radiation passing through the entrance window in the detector channel covered by the entrance window is lower or higher than a standard value (such as the response value corresponding to the unobstructed entrance window), then the entrance window is determined to be obstructed.

[0152] In some embodiments, a target entrance window is determined from a plurality of entrance windows based on a detector response distribution curve. For example, a response distribution curve is selected in which the response value of the detector channel covered by the entrance window is equal to its standard value, and the entrance window corresponding to the response distribution curve is determined as the target entrance window.

[0153] Step 1030 : Determine the position change of the radiation source based on the offset distance, the third distance between the radiation source and the incident window, and the fourth distance between the incident window and the detector.

[0154] In some embodiments, the third distance and the fourth distance refer to straight-line distances. The third distance between the entrance window and the radiation source refers to the vertical distance between the radiation source and the reference plane of the entrance window (a horizontal plane tangent to the inner wall of the entrance window), for example, the third distance is the vertical distance between the radiation source and the reference plane R of the entrance window 440 as shown in FIG3B . The fourth distance between the entrance window and the detector refers to the vertical distance between the reference plane of the entrance window and the detector, for example, the fourth distance is the vertical distance between the detector and the reference plane R of the entrance window 440 as shown in FIG3B .

[0155] In some embodiments, a third distance between the entrance window and the radiation source is determined based on the thickness of the filter device, the thickness of the entrance window, and the distance between the filter device and the radiation source. In some embodiments, a fourth distance between the entrance window and the detector is determined based on the thickness of the filter device, the thickness of the entrance window, and the distance between the filter device and the detector.

[0156] Because the entrance window is disposed on the filtering device, the height of the entrance window is the same as or substantially the same as the height of the filtering device. Therefore, in some embodiments, the third distance between the entrance window and the radiation source is equal to the distance between the filtering device and the radiation source. Correspondingly, the fourth distance between the entrance window and the detector is equal to the distance between the filtering device and the detector. The distance between the filtering device and the detector can be characterized based on the distance between the bottom of the filtering device and the detector (e.g., the distance between the bottom 332 of the filtering device 330 and the detector 420).

[0157] 7 , assuming that the third distance from the radiation source 310 to the incident window 440 is h, the fourth distance between the incident window 440 and the detector 420 is H, and the offset distance of the radiation source 310 reflected in the response intensity of the detector 420 is D, then according to the triangle similarity theorem, the actual offset distance (i.e., position change) of the radiation source is obtained as d = h / H×D.

[0158] In some embodiments, the scan data of the target object is corrected based on the position change of the radiation source, and reconstruction is performed based on the corrected data to obtain a scan image of the target object.

[0159] It should be noted that the above description of process 1000 is provided for illustrative purposes only and is not intended to limit the scope of this specification. A person of ordinary skill in the art may make various changes and modifications based on the description of this specification. However, such changes and modifications do not depart from the scope of this specification.

[0160] Some embodiments of this specification also provide a computer device, including a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that when the processor executes the computer program, it implements the method as described above (for example, process 1000).

[0161] Another aspect of this specification provides a computer-readable storage medium, which stores computer instructions. When a computer reads the computer instructions in the storage medium, the computer executes the method described above (for example, process 1000).

[0162] The beneficial effects that may be brought about by the embodiments of this specification include but are not limited to: (1) by arranging the incident window on the filtering device, there is no need to add an additional pinhole device, making the design of the CT device simpler; (2) by using a measuring detector to receive the rays passing through the incident window to track the position of the radiation source, there is no need to add an additional reference detector, which ensures effective position tracking while making the design of the CT device simpler; (3) by making the projection of the incident window on the receiving area of ​​the detector located at the edge area of ​​the receiving area, the imaging quality can be maintained while ensuring the tracking of the radiation source position; (4) by providing two incident windows, the inability to perform position tracking due to the incident window being blocked can be avoided, thereby improving the flexibility and applicability of position tracking.

[0163] While the basic concepts have been described above, it will be apparent to those skilled in the art that the detailed disclosure is merely illustrative and does not limit this specification. Although not explicitly stated herein, various modifications, improvements, and revisions to this specification may be made by those skilled in the art. Such modifications, improvements, and revisions are suggested in this specification and remain within the spirit and scope of the exemplary embodiments of this specification.

[0164] This specification also uses specific terms to describe the embodiments of this specification. For example, "one embodiment," "an embodiment," and / or "some embodiments" refer to a feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "one embodiment," "an embodiment," or "an alternative embodiment" two or more times in different locations in this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of this specification may be appropriately combined.

[0165] In addition, unless expressly stated in the claims, the order of the processing elements and sequences, the use of alphanumeric characters, or the use of other names described in this specification are not intended to limit the order of the processes and methods of this specification. Although the above disclosure discusses some of the invention embodiments currently considered useful through various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the spirit and scope of the embodiments of this specification. For example, although the system components described above can be implemented by hardware devices, they can also be implemented only by software solutions, such as installing the described system on an existing server or mobile device.

[0166] Similarly, it should be noted that, in order to simplify the presentation of this specification and thus facilitate understanding of one or more embodiments of the invention, the foregoing descriptions of the embodiments of this specification sometimes combine multiple features into a single embodiment, figure, or description thereof. However, this disclosure method does not imply that the subject matter of this specification requires more features than those recited in the claims. In fact, an embodiment may have fewer features than all of the features of a single disclosed embodiment.

[0167] In some embodiments, numbers are used to describe the quantity of components and attributes. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise stated, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the description and claims are approximate values, which may change according to the required characteristics of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of this specification are approximate values, in specific embodiments, the settings of such numerical values ​​are as accurate as possible within the feasible range.

[0168] Each patent, patent application, patent application publication, and other materials, such as articles, books, specifications, publications, and documents, cited in this specification is hereby incorporated by reference in its entirety. This includes application history documents that are inconsistent with or conflict with the content of this specification, as well as documents (currently or subsequently attached to this specification) that limit the broadest scope of the claims of this specification. It should be noted that if the descriptions, definitions, and / or terminology used in the accompanying materials are inconsistent or conflicting with the content of this specification, the descriptions, definitions, and / or terminology used in this specification will control.

[0169] Finally, it should be understood that the embodiments described in this specification are intended only to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, by way of example and not limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly described and illustrated in this specification.

Claims

1. A position tracking device (400) for a radioactive source, comprising: at least one entrance window (410), the entrance window (410) being arranged on the filtering device (330) of the radiation source (310); The detector (420) is used to receive the radiation passing through the incident window (410) so as to determine the position change of the radiation source (310) based on the received radiation.

2. The device according to claim 1, characterized in that The detector (420) is also used to receive radiation that passes through the target object (212) to obtain scanning data of the target object (212).

3. The device according to claim 1 or 2, characterized in that: The incident window (410) is a through hole, a concave structure or a convex structure on the filtering device (330).

4. The device according to any one of claims 1 to 3, characterized in that: The structure of the incident window (410) satisfies at least one of the following conditions: The edge thickness of the incident window (410) is different from the center thickness of the incident window (410); The thickness of the incident window (410) changes smoothly from the edge to the center; or The size of the incident window (410) is such that the difference between the attenuation degree of the rays passing through the incident window (410) and the attenuation degree of the rays passing through other positions outside the incident window (410) of the filtering device (330) is within a preset range.

5. The device according to any one of claims 1 to 4, characterized in that: The position tracking device (400) includes at least one first incident window (411 / 412 / 413 / 414 / 415 / 416 / 417 / 418 / 419 / 4110 / 4111 / 4112) arranged on the filtering device (330), and the size of the first incident window (411 / 412 / 413 / 414 / 415 / 416 / 417 / 418 / 419 / 4110 / 4111 / 4112) is determined based on a first distance between the radiation source (310) and the filtering device (330), and a second distance between the radiation source (310) and the detector (420).

6. The device according to claim 5, characterized in that The projection of the rays passing through the first incident window (411 / 412 / 413 / 414 / 415 / 416 / 417 / 418 / 419 / 4110 / 4111 / 4112) on the receiving area of ​​the detector (420) is located at the edge area of ​​the receiving area.

7. The device according to claim 5 or 6, characterized in that The first incident window (411 / 412 / 413 / 414 / 415 / 416 / 417 / 418 / 419 / 4110 / 4111 / 4112) is in the shape of a hemisphere, a cone or a spherical sector.

8. The device according to any one of claims 5 to 7, characterized in that: The at least one first incident window (411 / 412 / 413 / 414 / 415 / 416 / 417 / 418 / 419 / 4110 / 4111 / 4112) is arranged on the filtering device (330) along a first direction; the position tracking device (400) includes at least one second incident window (430) arranged on the filtering device (330) along a second direction, and the first direction is perpendicular to the second direction.

9. The device according to claim 8, characterized in that The position tracking device (400) comprises a plurality of second incident windows (431 / 432 / 433) arranged on the filtering device (330) at intervals along the second direction.

10. The device according to any one of claims 1 to 9, characterized in that: The incident window (410) is arranged at the top or bottom of the filtering device (330).

11. The device according to any one of claims 1 to 10, characterized in that: The detector (420) includes a plurality of detector modules (421 / 422 / 423 / 424 / 425 / 426 / 427), and a projection of the rays passing through the incident window (410) on a receiving area of ​​the detector (420) is located in a central area of ​​an edge detector module (421 / 427) among the plurality of detector modules (421 / 422 / 423 / 424 / 425 / 426 / 427).

12. The device according to any one of claims 1 to 11, characterized in that: The shape of the filtering device (330) includes a bow-tie structure, and / or the material of the filtering device (330) includes at least one of aluminum, tin and Teflon.

13. A position tracking device (900) for a radioactive source, comprising: A shielding structure (910), wherein at least one incident window (940) is provided on the shielding structure; Detector (930) for receiving radiation passing through the incident window (940) to determine a position change of the radiation source (310) based on the received radiation; as well as A ray passing through a target object (212) is received to obtain scanning data of the target object (212).

14. The device according to claim 13, characterized in that The shielding structure (910) includes at least one third incident window (941 / 942) arranged along a first direction, and / or at least one fourth incident window (943 / 944 / 945) arranged along a second direction, wherein the first direction is perpendicular to the second direction.

15. The device according to claim 13 or 14, characterized in that The structure of the incident window (940) satisfies at least one of the following conditions: The edge thickness of the incident window (940) is different from the center thickness of the incident window (940); The thickness of the incident window (940) changes smoothly from the edge to the center; or The size of the incident window (940) is such that the difference between the attenuation degree of the rays passing through the incident window (940) and the attenuation degree of the rays not passing through the incident window (940) is within a preset range.

16. The device according to any one of claims 13 to 15, characterized in that: The detector (930) includes a plurality of detector modules, and a projection of the rays passing through the incident window (940) on a receiving area of ​​the detector (930) is located in a central area of ​​an edge detector module among the plurality of detector modules.

17. A computer tomography device (300), comprising: A radiation source (310) for emitting radiation; a filtering device (330) for absorbing low-energy rays in the rays and making the energy distribution of the rays passing through the target object (212) and the filtering device (330) uniform and hardened; the filtering device (330) is provided with at least one incident window (410); a detector (320) for receiving radiation that has passed through the target object (212) and radiation that has passed through the incident window (410); The rays received by the detector (320) and passing through the incident window (410) are used to determine the position change of the radiation source (310).

18. The device according to claim 17, characterized in that It includes at least one first incident window (411 / 412 / 413 / 414 / 415 / 416 / 417 / 418 / 419 / 4110 / 4111 / 4112) arranged on the filtering device (330) along a first direction, and / or at least one second incident window (430) arranged on the filtering device (330) along a second direction, wherein the first direction is perpendicular to the second direction.

19. A method (1000) for tracking the position of a radiation source, the method being implemented using the position tracking device (400 / 900) according to any one of claims 1 to 16, the method comprising: Using a detector to receive the radiation emitted by the radiation source and passing through the incident window (1010); Determining an offset distance of a response intensity of the ray (1020); A change in position of the radiation source is determined based on the offset distance, a third distance between the radiation source and the entrance window, and a fourth distance between the entrance window and the detector (1030).

20. The method according to claim 19, characterized in that The determining of the offset distance of the response intensity of the ray comprises: Determine whether the incident window is blocked; In response to the presence of occlusion, determining a target incident window from two or more incident windows, wherein the target incident window is an incident window that is not occluded; The offset distance is determined based on the response intensity of the rays passing through the target incident window.

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