Patent Publication Number: US-2022219018-A1

Title: Verification phantom

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 17/432,901, filed on Aug. 20, 2021, which is a US national phase of International Application No. PCT/CN2019/075761, filed on Feb. 21, 2019, the disclosure of each of which is herein incorporated by reference in its entirety. This application claims priority to Chinese Patent Application No. 202120665447.6 filed on Mar. 31, 2021, Chinese Patent Application No. 202120677566.3 filed on Mar. 31, 2021, Chinese Patent Application No. 202110354072.6 filed on Mar. 31, 2021, and Chinese Patent Application No. 202120664881.2 filed on Mar. 31, 2021, the disclosure of each of which is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the field of radiotherapy technologies, and in particular, relates to a verification phantom. 
     BACKGROUND 
     A radiotherapy system may generally include: a rotating gantry and a treatment head disposed on the rotating gantry. Rays emitted from the treatment head can be used to treat a patient at a target point on an affected part. Under normal circumstances, a beam focus (i.e., an isocenter of treatment) of the rays emitted from the treatment head should be in coincidence with an isocenter of mechanical rotation of the rotating gantry. When the target point is positioned at a position of the isocenter of mechanical rotation, the beam focus can accurately irradiate the target point, thereby realizing precise treatment. However, due to installation errors and other reasons, there may be a deviation between the isocenter of treatment and the isocenter of mechanical rotation. Here, if the target point is positioned to the isocenter of mechanical rotation, the beam focus may not accurately irradiate the position of the target point, such that the precise treatment cannot be realized. 
     SUMMARY 
     The present disclosure provides a verification phantom. The technical solutions are as follows. 
     The verification phantom is provided with a slot for holding a film, wherein the slot includes a first slot and a second slot; an opening of the first slot and an opening of the second slot are both disposed on a first outer surface of the verification phantom; and an extraction groove is disposed at a junction, on the first outer surface, of the opening of the first slot and the opening of the second slot. 
     It should be understood that both the foregoing general description and the following detailed description are merely exemplary and explanatory, and are not intended to limit the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To describe the technical solutions in the embodiments of the present disclosure more clearly, the following briefly introduces the accompanying drawings required for describing the embodiments. Apparently, the accompanying drawings in the following description show merely some embodiments of the present disclosure, and a person of ordinary skills in the art may still derive other drawings from these accompanying drawings without creative efforts. 
         FIG. 1  is a schematic structural diagram of a verification phantom according to an embodiment of the present disclosure; 
         FIG. 2  is a side view of a verification phantom according to an embodiment of the present disclosure; 
         FIG. 3  is a schematic structural diagram of another verification phantom according to an embodiment of the present disclosure; 
         FIG. 4  is a schematic structural diagram of another verification phantom according to an embodiment of the present disclosure; 
         FIG. 5  is a schematic structural diagram of another verification phantom according to an embodiment of the present disclosure; 
         FIG. 6  is a schematic structural diagram of another verification phantom according to an embodiment of the present disclosure: 
         FIG. 7  is a schematic structural diagram of another verification phantom according to an embodiment of the present disclosure; 
         FIG. 8  is a schematic structural diagram of another verification phantom according to an embodiment of the present disclosure; 
         FIG. 9  is a schematic structural diagram of another verification phantom according to an embodiment of the present disclosure; and 
         FIG. 10  is a schematic diagram of the connection of a verification phantom according to an embodiment of the present disclosure. 
     
    
    
     The embodiments of the present disclosure have been illustrated explicitly through the drawings above, and will be described in more detail below. These drawings and text descriptions are not intended to limit the scope of the inventive conception in any way, but to explain the concept of the present disclosure to persons skilled in the art by referring to particular embodiments. 
     DETAILED DESCRIPTION 
     To present the objects, technical solutions and advantages of the present disclosure more clearly, the embodiments of the present disclosure will be described in further detail with reference to the accompanying drawings. 
     In the related art, in order to ensure the precision of radiotherapy, a verification phantom for verifying the deviation between an isocenter of treatment and an isocenter of mechanical rotation is provided, such as a MIMI phantom. Before the radiotherapy is performed, this verification phantom may be configured to verify whether the isocenter of treatment is in coincidence with the isocenter of mechanical rotation (that is, whether a deviation exists). When a deviation is present between the isocenter of treatment and the isocenter of mechanical rotation, the position of a treatment couch can be adjusted in time based on the deviation, thereby improving the coincidence precision between the isocenter of mechanical rotation and an isocenter of a device. 
     However, during usage of the above verification phantom, a film needs to be first inserted into a film cassette and then the film cassette with the film inserted needs to be placed into the verification phantom. Since the film cassette with the film inserted needs to be extracted from the verification phantom multiple times, abrasions may be present between the film cassette and the verification phantom after long-term use, which can affect the precision in detecting the deviation of the isocenter of treatment. 
       FIG. 1  is a schematic structural diagram of a verification phantom according to an embodiment of the present disclosure.  FIG. 2  is a side view of a verification phantom according to an embodiment of the present disclosure. As shown in  FIG. 1  and  FIG. 2 , the verification phantom  10  is provided with a slot  101  for holding a film. The slot  101  includes a first slot  1011  and a second slot  1012 . An opening K 1  of the first slot  1011  and an opening K 2  of the second slot  1012  may be both disposed on a first outer surface M 1  of the verification phantom  10 . An extraction groove A may be disposed at a junction, on the first outer surface M 1 , of the opening K 1  of the first slot  1011  and the opening K 2  of the second slot  1012 . The extraction groove A may be a groove near the intersection point of the two slots, and may be communicated with both the first slot  1011  and the second slot  1012 . 
     Since the verification phantom  10  is provided with the slot  101  for holding the film, when the verification phantom  10  is used for verifying the deviation between the isocenter of treatment and the isocenter of mechanical rotation, the film only needs to be inserted into the two slots disposed on the first outer surface M 1 . In addition, since the extraction groove A separately communicated with the two slots is disposed on the first outer surface M 1 , a therapist can insert and extract the film more conveniently. 
     In a case that the verification phantom  10  is configured to verify the deviation between the isocenter of treatment and the isocenter of mechanical rotation, a film may be first inserted into the first slot  1011  through the opening K 1  in the first outer surface M 1 ; a center of the verification phantom  10  is aligned with a mechanical isocenter; then, the radiation source (an initial rotation angle of a gantry may be 0 degrees) irradiates the verification phantom  10 , thereby forming a focal spot on the film inserted in the first slot  1011 ; a therapist takes out the film inserted in the first slot  1011 , and then inserts another film into the second slot  1012  through the opening K 2  in the first outer surface M 1 ; the radiation source (the rotation angle of the gantry may be 90 degrees) irradiates the verification phantom  10 , thereby forming a focal spot on the film inserted in the second slot  1012 ; and the therapist may take out the film inserted in the second slot  1012 . The two films are scanned by the scanner to obtain two images containing focal spots. Afterwards, the therapist may further upload the two images containing the focal spots to the image server. Since the beam focus of the radiation source is theoretically in coincidence with the mechanical isocenter, the image server may analyze the two images containing the focal spots to obtain actual coordinates of the beam focus, and then determine a deviation of the isocenter of treatment from the isocenter of mechanical rotation based on the actual coordinates of the beam focus and coordinates of the mechanical isocenter. Afterwards, the image server may send the deviation to the control host, such that the control host adjusts the position of the treatment couch based on the deviation. In addition, the control host may also store the deviation, and precisely position a patient based on the deviation during the radiotherapy. 
     In some embodiments, films inserted in the slots  101  may be self-developing films. The size of the film inserted into each slot  101  may be matched with the size of the slot  101  without shaking. That is, the size of a film inserted in the first slot  1011  may be matched with the size of the first slot  1011 , and the size of a film inserted in the second slot  1012  may be matched with the size of the second slot  1012 . Alternatively, the shape of the film may be also matched with an overall shape formed by the first slot  1011  and the second slot  1012 . For example, the film may be a film composed of two sub-films that are perpendicular to and intersected with each other, thereby improving the reliability in verifying the deviation between the isocenter of treatment and the isocenter of mechanical rotation. 
     In some embodiments, as shown in  FIG. 2 , the extraction groove A may be disposed, on the first outer surface M 1 , at an intersection point of the first slot  1011  and the second slot  1012 . For example, in a case that the intersection point of the first slot  1011  and the second slot  1012  is disposed at a center of the first outer surface M 1 , the extraction groove A may be disposed at the center of the first outer surface M 1 . 
     In some embodiments, as shown in  FIG. 2 , a cross section of the extraction groove A may be circular. Alternatively, the cross section of the extraction groove A may be in other shapes, such as a rectangle or a triangle. The cross section is a plane parallel to the first outer surface M 1 . 
       FIG. 3  is a schematic structural diagram of another verification phantom according to an embodiment of the present disclosure. As shown in  FIG. 3 , from a position facing the first outer surface M 1  of the verification phantom  10 , an upper side surface of the verification phantom  10  is a second outer surface M 2 ; a left side surface of the verification phantom  10  is a third outer surface M 3 ; a lower bottom surface of the verification phantom  10  is a fourth outer surface M 4 ; and a right side surface of the verification phantom  10  is a fifth outer surface M 5 . The verification phantom  10  may be further provided with a first pinhole T 1  for communicating an outer surface (for example, the third outer surface M 3  or the fifth outer surface M 5 ) of the verification phantom  10  with the first slot  1011 , and a second pinhole T 2  for communicating an outer surface (for example, the second outer surface M 2  or the fourth outer surface M 4 ) of the verification phantom  10  with the second slot  1012 . 
     By the provision of the first pinhole T 1  and the second pinhole T 2 , a needle or a colored pen core may be used first during deviation verification to pass through the first pinhole T 1  and make a mark at a center of a film inserted in the first slot  1011 , and to pass through the second pinhole T 2  and make a mark at a center of a film inserted in the second slot  1012 . Then, the two films are irradiated by the radiation source in the image capture component to form focal spots which are then analyzed by the scanner to obtain images with the focal spots. Here, since the center point of the verification phantom  10  is theoretically in coincidence with the isocenter of mechanical rotation, the marks may be used as marks of the mechanical isocenter. Furthermore, it is convenient for the control host to subsequently determine a deviation between the mechanical isocenter and the isocenter of treatment, thereby improving the precision and efficiency in determining the deviation. 
     In some embodiments, an extending direction of the first pinhole T 1  is intersected with the insertion surface of the first slot  1011 , and an intersection point of the first pinhole T 1  and the insertion surface of the first slot  1011  is the center point of the insertion surface of the first slot  1011 . An extending direction of the second pinhole T 2  is intersected with the insertion surface of the second slot  1012 , and an intersection point of the second pinhole T 2  and the insertion surface of the second slot  1012  is the center point of the insertion surface of the second slot  1012 . In this way, a pin position, formed through the first pinhole T 1 , on a radiochromic film inserted in the first slot  1011  is the same as that a pin position, formed through the second pinhole T 2 , on a radiochromic film inserted in the second slot  1012 , thereby further improving accuracy of calculating spatial coordinates of a nuclear physical isocenter based on focal spots on the radiochromic films respectively inserted in the first slot  1011  and the second slot  1012 . 
     In some embodiments, as shown in  FIG. 4 , an intersection point by which the first pinhole T 1  is perpendicularly intersected with the second pinhole T 2  deviates from the geometric center of the verification phantom  10 . In other words, the intersection point by which the first pinhole T 1  is perpendicularly intersected with the second pinhole T 2  is not in coincidence with the geometric center of the verification phantom  10 . For example, the intersection point deviates from the geometric center by a preset distance in a preset direction. Since both the preset direction and the preset distance are known parameters, when the radiochromic films are pinned to determine a reference position, the preset direction and the preset distance may be added in advance for position pre-calculation and correction; and then verification is performed based on a reference position acquired after calculation and correction, such that the precision and efficiency of the verification can be guaranteed. In addition, disposing of the first pinhole T 1  and the second pinhole T 2  is more flexible, that is, positions of the first pinhole T 1  and the second pinhole T 2  can be conveniently adjusted and designed based on an actual shape and structure of the verification phantom and a position of another verification module. 
     In some embodiments, the first pinhole T 1  and/or the second pinhole T 2  may be through hole(s) that penetrate from one side surface of the verification phantom  10  to an opposite side surface the verification phantom  10 . In this way, when making a mark via pinning, an operator can flexibly select a position to make a mark on the radiochromic film. 
     In some embodiments, when the verification phantom  10  in this embodiment of the present disclosure is further provided with another verification structure, such as a geometric calibration structure or an isocenter verification structure, to make verification structures avoid each other on the verification phantom  10  to prevent impact on verification accuracy of each verification structure, the intersection line, in the verification phantom  10 , by which the first slot  1011  is perpendicularly intersected with the second slot  1012  may not pass the geometric center of the verification phantom  10 , that is, the intersection line, in the verification phantom  10 , by which the first slot  1011  is perpendicularly intersected with the second slot  1012  deviates from the geometric center of the verification phantom  10 , thereby making the verification structures avoid each other. 
     For example, as shown in  FIG. 5 , the insertion surface of the first slot  1011  is parallel to the third outer surface M 3  and the fifth outer surface M 5  of the verification phantom  10 ; a distance from the insertion surface of the first slot  1011  to the third outer surface M 3  is less than or equal to a distance from the insertion surface of the first slot  1011  to the fifth outer surface M 5 ; the insertion surface of the second slot  1012  is parallel to the second outer surface M 2  and the fourth outer surface M 4  of the verification phantom  10 ; a distance from the insertion surface of the second slot  1012  to the second outer surface M 2  is less than or equal to a distance from the insertion surface of the second slot  1012  to the fourth outer surface M 4 ; and the distance from the insertion surface of the second slot  1012  to the second outer surface M 2  is equal to the distance from the insertion surface of the first slot  1011  to the third outer surface M 3 . 
     Based on this, the first pinhole T 1  penetrates from the third outer surface M 3  of the verification phantom  10 ; and the second pinhole T 2  penetrates from the second outer surface M 2  of the verification phantom  10 . In one aspect, when pinning is performed on films respectively through the first pinhole T 1  and the second pinhole T 2  to make marks, pinning depths can be as small as possible. In another aspect, the pinning depths of the first pinhole T 1  and the second pinhole T 2  can be equal to each other. Therefore, the operation is convenient, and errors in the operation of making a mark can be reduced as far as possible. 
     In some embodiments, as shown in  FIG. 5 , cross-shaped dash lines  102  are formed on a surface of the verification phantom  10 . 
     The cross-shaped dash lines  102  are formed on at least three surfaces (for example, the second outer surface M 2 , the third outer surface M 3 , and the fifth outer surface M 5 ) of the verification phantom  10 . The cross center of the cross-shaped dash lines  102  on each surface is set to the position of a target point of the side surface. In this way, the position of the verification phantom  10  can be adjusted, thereby making cross-shaped dash lines  102  on each side surface be in coincidence with cross-shaped laser rays emitted by a laser light, thereby realizing positioning of the verification phantom. 
     In some embodiments, the cross-shaped dash lines  102  formed on the surface of the verification phantom  10  may be red cross-shaped dash lines, white cross-shaped dash lines, or black cross-shaped dash lines that are displayed on the surface of the verification phantom  10  relatively clearly, thereby facilitating the operation of aligning the cross-shaped rays emitted by the laser light with the red cross-shaped dash lines, white cross-shaped dash lines, or black cross-shaped dash lines. 
     Since the verification phantom in the related art has a single function and can only verify whether the isocenter of mechanical rotation is in coincidence with the isocenter of a device. 
     As shown in  FIG. 5 , in a case that the intersection line by which the first slot  1011  is perpendicularly intersected with the second slot  1012  deviates from a geometric center of the verification phantom, a first marker  103  is disposed at the geometric center of the verification phantom  10 . In this way, the mechanical isocenter of a radiotherapy equipment can be calibrated by using the first marker  103 ; and after the mechanical isocenter is calibrated, geometric calibration may be further performed on an IGRT system, for example, calibrating offsets of a flat panel and a bulb tube, a distance from the bulb tube to the flat panel, a distance from the bulb tube to a rotating shaft, or the like. 
     In some embodiments, the verification phantom  10  may be a regular hexahedron, namely, a cube structure, that is, each surface of the verification phantom  10  is square. In this way, the overall structure design of the verification phantom is facilitated; and distances from the first marker  103  to all surfaces of the regular hexahedron are all equal to each other. Therefore, geometric parameters of the radiotherapy equipment can be detected more accurately in a three-dimensional space; detected installation errors can be accurately corrected; and the precision in image-guided positioning can be improved. 
     In some embodiments, as shown in  FIG. 6 , the verification phantom  10  is further provided with a second marker  104 , and the second marker  104  deviates from the geometric center of the verification phantom  10 . 
     In some embodiments, as shown in  FIG. 6 , at least three second markers  104  are present. There are four second markers in  FIG. 6 . At least three second markers  104  are distributed, in the verification phantom  10 , at the periphery of a circle taking the first marker  103  as a circle center and having a preset radius. The first marker  103  is non-coplanar with a plane defined by any two second markers  104 . Distances between every two second markers  104  are equal to each other. 
     The verification phantom  10  is a regular hexahedron structure. The first marker  103  is disposed at the geometric center of the verification phantom  10 . Distances from all the second markers  104  to the first marker  103  are all equal to each other. The second markers  104  are disposed at different positions at the periphery of the circle taking the first marker  103  as the circle center and having the preset radius. The first marker  103  and any two second markers  104  can define a plane. Planes defined by different second markers  104  are non-coplanar. For example, the at least three second markers  104  may be respectively disposed in directions X, Y. and Z in a three-dimensional coordinate system taking the verification phantom  10  as the center. 
     It should be noted that, to avoid a bad influence of the first marker  103  and the second marker  104  on radiotherapy, the first marker  103  and the second markers  104  are usually made of a material whose density is approximate to the density of human bones. For example, the material may be at least one of aluminum, Teflon, glass, or ceramics. In addition, to facilitate the identification of setting and imaging, both the first marker  103  and the second marker  104  are globule structures. 
     In some embodiments, as shown in  FIG. 6 , the verification phantom  10  is further provided with a hollow marker  105 . The hollow marker  105  and the first marker  103  are respectively non-coplanar with planes defined by any two second markers  104 . 
     The interior of a hollow marker  105  is filled with air, and does not need to be filled with another special gas. A beam irradiates the verification phantom in this embodiment of the present disclosure. In an image received by the detector, a position corresponding to the hollow marker  105  is presented as a light spot. Particularly, when the verification phantom  10  is a cube, in a process in which the verification phantom is disposed on a treatment couch for verification, since all surfaces of the verification phantom are not clearly differentiated in appearance, orientations of the surfaces of the verification phantom are usually easy to be confused. For example, the position of the hollow marker  105  may be determined in advance. (The hollow marker  105  is not at the geometric center of the cube. For example, the hollow marker  105  may be disposed on a side near the first outer surface M 1  of the verification phantom  10 .) Therefore, by determining the position of a light spot in an image received by the detector, positioning directions of the head and bottom of the verification phantom on the treatment couch can be determined accurately and fast. 
     In addition, the hollow marker  105  and the first marker  103  are respectively non-coplanar with planes defined by any two second markers  104 , that is, disposing of the hollow marker  105  in the verification phantom  10  meets requirements of the disposing condition of the second marker  104 . Therefore, when the verification phantom is used for geometric calibration, the hollow marker  105  may also be used as the second marker  104  for presenting a deviation in a formed image. A greater quantity of second markers  104  leads to more dimensions for presenting the deviation in the formed image, and richer identification data and registration information for the deviation. 
     In some embodiments, a strip-shaped marker is fixedly disposed on an edge connected to two adjacent surfaces of the verification phantom  10 . For another example, a marking groove is further formed in the first outer surface M 1  of the verification phantom  10 . The cross section of the marking groove is an axially symmetric figure or a centrally symmetric figure. 
     A strip-shaped marker is fixedly disposed on a side edge of the verification phantom  10 . For example, the strip-shaped marker may be an aluminum strip fixedly bonded on the side edge. A marking groove may also be formed in the first outer surface M 1  of the verification phantom  10 . The cross section of the marking groove is an axially symmetric figure or a centrally symmetric figure. For example, the marking groove is a rectangular groove, a triangular groove, or the like. Various marking structures are disposed on the verification phantom  10 . When rays irradiate on the verification phantom, and multiple images in multiple angles that are received by the detector and transmitted to the image server are analyzed, the various marking structures can be all presented in the images, thereby enriching information of the verification phantom in this embodiment of the present disclosure for verifying the treatment center point of the radiotherapy equipment and the isocenter of mechanical rotation, and further improving the accuracy of verification. 
     As shown in  FIG. 7 , the marking groove may be set to a circular groove  107 . The circular grooves formed in four different surfaces (the second outer surface M 2 , the third outer surface M 3 , the fourth outer surface M 4 , and the fifth outer surface M 5 ) of the verification phantom  10  may have different sizes. The upper surface (the second outer surface M 2 ) corresponds to the lower surface (the fourth outer surface M 4 ). The diameter of the circular groove in the upper surface of the verification phantom  10  is less than the diameter of the circular groove in the lower surface of the verification phantom  10 . When the circular groove takes the shape of the circular ring shown in  FIG. 7 , the width and the depth of the circular ring are preset; and the position of the circular groove avoids the positions of the first marker  103 , the second marker  104 , the hollow marker  105 , and the like of the verification phantom  10 . In this way, when the verification phantom in this embodiment of the present application is used for geometric calibration, registration information presenting a deviation in a formed image can be enriched; and by disposing circular grooves of different sizes, the direction and the disposing status of the verification phantom can be determined visually during forming of an image. Similarly, the diameter of the circular groove in the left surface (the third outer surface M 3 ) of the verification phantom  10  is less than the diameter of the circular groove in the right surface (the fifth outer surface M 5 ) of the verification phantom  10 . When the circular groove takes the shape of the circular ring shown in  FIG. 7 , the width and the depth of the circular ring are preset; and the position of the circular groove avoids the positions of the first marker  103 , the second marker  104 , the hollow marker  105 , and the like of the verification phantom  10 . Therefore, among the six outer side surfaces of the verification phantom  10 , two pairs of circular grooves having different sizes are formed in two pairs of opposite side surfaces, and no circular grooves are formed in the other pair of opposite surfaces (the first outer surface M 1  and a back surface opposite to the first outer surface M 1 ). Based on these disposing structures, it is convenient for an operator to visually and accurately determine the position and status of the verification phantom in the radiotherapy equipment through the image. 
     In some embodiments, the verification phantom in this embodiment of the present disclosure further includes: a first connecting post  20  and/or a second connecting post  30 . As shown in  FIG. 5 , a connecting opening  107  may be formed in the first outer surface M 1  of the verification phantom  10 . Referring to  FIG. 8 , the connecting opening  107  may be detachably connected to the first connecting post  20 ; and an ionization chamber probe  21  may be disposed at an end of the first connecting post  20 . Alternatively, referring to  FIG. 9 , the connecting opening  107  may also be detachably connected to the second connecting post  30 ; and a tungsten bead  31  may be disposed at an end of the second connecting post  30 . 
     For example, as shown in  FIG. 8 , the connecting opening  107  formed in the first outer surface M 1  of the verification phantom  10  may be detachably connected to the first connecting post  20 . The ionization chamber probe  21  disposed at the end of the first connecting post  20  may be configured to detect and verify an amount of rays at a preset position such as a treatment focus position (treatment isocenter), thereby determining whether the amount of rays at the preset position is within a range of required theoretical amounts. 
     In some embodiments, as shown in  FIG. 9 , the connecting opening  107  formed in the first outer surface M 1  of the verification phantom  10  may be further detachably connected to the second connecting post  30 ; and a tungsten bead  31  may be disposed at an end of the second connecting post  30 . During usage of the verification phantom in this embodiment of the present application, the tungsten bead  31  may be disposed at the mechanical isocenter. A radiation source is used to irradiate the tungsten bead  31  from different angles. Projection data is acquired from the detector disposed opposite to the radiation source, such as an EPID flat panel or an EPID detector; and an image is generated. The deviation between the mechanical isocenter and the treatment isocenter is verified by analyzing a light spot center and a shadow center in the image acquired by the EPID flat panel or the EPID detector. 
     In addition, to resolve the problem that the attenuation degrees of rays in different directions are inconsistent during imaging because the thicknesses of solid structures through which the rays in different directions irradiate the tungsten bead  31  are different, the interior of the second connecting post  30  may also be hollow, thereby resolving the problems that the brightness of the image is uneven and that subsequent image analysis is relatively difficult because the attenuation degrees of the rays irradiating the tungsten bead  31  in different directions are inconsistent during imaging. 
     In some embodiments, an internal thread is formed in an internal periphery wall of the connecting opening  107 . External threads are respectively formed on the first connecting post  20  and the second connecting post  30 . The first connecting post  20  and the second connecting post  30  are in threaded connection with the connecting opening  107 , respectively. The first connecting post  20  or the second connecting post  30  is disposed detachably and replaceably in this fashion, such that the detaching and the installation are relatively convenient; and the firmness and the accuracy of the connection can be guaranteed after the connection. 
     In some embodiments, as shown in  FIG. 5 , the verification phantom  10  is further provided with a through channel  108  communicated with the connecting opening  107 . The internal diameter of the through channel  108  is less than or equal to the internal diameter of the connecting opening  107 . When the internal diameter of the through channel  108  is equal to the internal diameter of the connecting opening  107 , the first connecting post  20  or the second connecting post  30  is detachably mounted in the connecting opening  107 , that is, the position relationship between the first connecting post  20  or the second connecting post  30  and the verification phantom  10  can be adjusted by using the through channel  108 . When the internal diameter of the through channel  108  is less than the internal diameter of the connecting opening  107 , the convenience of installation and detaching can be guaranteed; and a connection structure can be mounted in the through channel  108  in time. 
     It should be noted that, the ionization chamber is a detector that uses the ionization effect of ionizing radiation to measure ionizing radiation, and is also referred to as an ion chamber. The ionization chamber probe  21  needs to be connected to a measurement result display device by using a wire. As the wire is easy to be damaged when being exposed in an environment having a large amount of rays, in order to make detection of an amount of rays be easier to be implemented and disposed on the verification phantom, the through channel  108  may be formed in the verification phantom  10  and the interior of the first connecting post  20  is also hollow. In this way, as shown in  FIG. 8 , when disposing the ionization chamber probe  21 , the ionization chamber probe  21  may be directly fed, through the through channel  108  from the rear of the phantom, into an end of the first connecting post  20  connected to the connecting opening  107 , thereby avoiding wire winding in the radiotherapy equipment, and avoiding damage of a wire exposed in an environment having a large amount of rays. 
     In some embodiments, the verification phantom  10  may be a solid structure. The verification phantom  10  may be a cube, namely, a regular hexahedron. All surfaces of the verification phantom  10  that is a regular hexahedron are square. In this way, the overall structure design of the verification phantom is facilitated. The first slot  1011  and the second slot  1012  are respectively disposed on any two adjacent surfaces of the regular hexahedron, which also facilitates disposing and machining of a structural size. 
     In some embodiments, the verification phantom  10  may also be a prismoid, such as a cuboid. Alternatively, the verification phantom  10  may be a cylinder. Since the verification phantom  10  having a cuboid structure or a cylinder structure has a definite length-to-width relationship, in addition to application of the verification function of the verification phantom, directions of the head and bottom of the treatment couch may also be identified conveniently based on the length direction of the cuboid or cylinder. 
     In some embodiments, the verification phantom  10  may also be a sphere; and the surface of the sphere is arc-shaped, such that the first slot  1011  and the second slot  1012  can be disposed more flexibly. The shape of the verification phantom  10  is not limited in this embodiment of the present disclosure. 
     In some embodiments, the verification phantom  10  is made of an organic glass material. For example, the verification phantom  10  is made of a black organic glass material; or the verification phantom  10  is made of a transparent organic glass material. 
     When the verification phantom  10  is made of an organic glass material that has relatively high permeability for both laser rays and a beam emitted by the radiation source, transmission and imaging of the laser rays and the beam emitted by the radiation source cannot be impacted. For example, the verification phantom  10  may be made of a black organic glass material or a transparent organic glass material. The verification phantom  10  made of the transparent organic glass material is transparent, such that structures such as the first marker  103 , the second marker  104 , the first slot  1011 , and the second slot  1012  in the verification phantom  10  can be seen visually, to facilitate disposing of the verification phantom during use. 
     In some embodiments, as shown in  FIG. 10 , a connecting rack  40  for connecting the treatment couch is connected to the verification phantom  10 . 
     Based on this, the connecting rack  40  may be set to a rotary installation structure, such that a relationship between the verification phantom  10  and the treatment couch or another installation position can be rotationally adjusted by adjusting the connecting rack  40 . The adjusting angle may be set within 45 degrees. 
     Different radiotherapy equipment have different device structures and disposing requirements for verification phantoms. To ensure that the verification phantom can be fixed on the radiotherapy equipment and that the verification phantom can be mounted in different radiotherapy equipment in a matching fashion as adaptive as possible, the connecting rack  40  is connected to a side surface, distal from the first outer surface M 1 , of the verification phantom  10 ; and the verification phantom  10  is connected to the treatment couch of the radiotherapy equipment through the connecting rack  40 . 
     The following still uses a gamma knife as an example. When the verification phantom in this embodiment of the present application is applied to a head gamma knife, a U-shaped rack at a fixing position of the treatment couch of the head gamma knife is connected to the connecting rack  40 , thereby fixing the verification phantom in this embodiment of the present disclosure to the treatment couch of the head gamma knife. When the verification phantom in this embodiment of the present application is applied to a body gamma knife, a base plate is connected to the connecting rack  40 ; and the verification phantom in this embodiment of the present application is horizontally disposed on a treatment couch through the base plate. In this way, by disposing the connecting rack  40 , on the premise that the verification phantom in this embodiment of the present application cannot be damaged or impacted, the verification phantom in this embodiment of the present application can be applied to verification, registration, and positioning of various radiotherapy equipment; and universality of the verification phantom in this embodiment of the present application to radiotherapy equipment of different types, models, treatment positions can be improved. 
     An embodiment of the present disclosure further provides a radiotherapy system. The radiotherapy system may include: the verification phantom illustrated in any one of  FIGS. 1 to 10  and radiotherapy equipment. 
     In some embodiments, the radiotherapy equipment may include a radiation source and a treatment couch. Based on this, the radiotherapy equipment may further include an image capture component. The image capture component includes a detector disposed opposite to the radiation source, and/or an imaging apparatus (including a bulb tube and a flat panel detector disposed opposite to the bulb tube). The radiotherapy system may further include a control host, an image server, a scanner, and three laser lights. 
     The verification phantom may be disposed on the treatment couch; the image capture component may be connected to the image server; the image server may be connected to the control host; and the control host may be connected to the treatment couch. Alternatively, the image server may be directly integrated in the control host. The radiation source may be a radiation source of a treatment head in the radiotherapy equipment, that is, rays emitted by the radiation source may also be configured to irradiate a target point on a patient, so as to perform radiotherapy on the patient. 
     In an embodiment of the present disclosure, the scanner may be configured to scan a film, irradiated by the radiation source, in the verification phantom to develop a focal spot formed on the film, and a therapist may send an image containing the focal spot to the image server. The image capture component and the radiation source may be configured to capture images of the verification phantom and send the captured images to the image server. The image server may be configured to analyze the acquired images and determine a deviation (such as a deviation between the isocenter of treatment and the isocenter of mechanical rotation) based on an analysis result; and the image server may further send the determined deviation to the control host. The control host may be configured to adjust the position of the treatment couch based on the received deviation, and may store the deviation. Each laser light may be configured to emit rays to the verification phantom. In some embodiments, the rays emitted from the laser light may be cross-shaped rays. 
     In some embodiments, the control host may include an upper computer and a lower computer; the upper computer may be connected to the lower computer; and the lower computer may be connected to other parts (such as the treatment couch and the image capture component) in the radiotherapy system. The upper computer may be configured to send a control instruction to the lower computer; and the lower computer may control working statuses of other parts based on the received control instruction. 
     In summary, the embodiments of the present disclosure provide a radiotherapy system which includes a verification phantom. The radiation source in the radiotherapy equipment and the bulb tube in the image capture component may emit rays to the verification phantom; the detector disposed opposite to the radiation source and the detector disposed opposite to the bulb tube may receive the rays and capture images based on the rays; and the detector may send the captured images to the image server. The scanner may scan a film, irradiated by the radiation source, in the verification phantom to develop a focal spot formed on the film, and a therapist may send an image containing the focal spot to the image server. The image server may analyze the acquired images to determine the deviation between the isocenter of treatment and the isocenter of mechanical rotation or to determine the deviation of the isocenter of mechanical rotation, and may send the deviation to the control host, which will precisely position the patient based on the deviation. Therefore, the precision of radiotherapy is improved, and the quality of radiotherapy is guaranteed. 
     It may be clearly understood by a person skilled in the art that, for the purpose of convenient and brief description, for a detailed working process of the radiotherapy system and the verification phantom of the same as described above, reference may be made to a corresponding process in the forgoing method embodiments, and details are not described herein again. 
     Described above are merely optional embodiments of the present disclosure, but are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements and the like made within the spirit and principles of the present disclosure shall fall within the protection scope of the present disclosure.