Automatic mechanical quality control method of medical ring-shaped linear accelerator and quality control phantom thereof

Abstract

The application discloses a kind of automatic mechanical quality control method and quality control phantom of medical ring linear accelerator.A kind of automatic mechanical quality control method of medical ring linear accelerator, steps are as follows: step one, quality control phantom is placed on accelerator treatment bed, and positioning structure is provided on quality control phantom and is positioned with accelerator cross-shaped positioning laser line, cross-shaped positioning laser line and the positioning structure on quality control phantom are mutually positioned, and quality control phantom is moved to accelerator theoretical isocenter position;Step two, then according to the measurement item, the corresponding prefabricated plan is introduced, the ring linear accelerator is controlled to work by executing prefabricated plan, the ring linear accelerator is emitted and EPID image is obtained, EPID image is analyzed, and the measurement result is obtained according to the corresponding calculation method, and the deviation from the preset value is calculated.Using the method, the source skin distance of medical ring linear accelerator, field size, bed moving precision, gantry angle and the like can be automatically measured.

Description

Technical Field

[0001] This invention relates to the field of quality control of medical accelerators, specifically to quality control phantoms and corresponding quality control methods. Background Technology

[0002] Quality control of accelerators is crucial for achieving clinical safety and precise radiotherapy. In clinical practice, accelerators rely on regular quality control to test relevant accelerator characteristics, thereby monitoring the stability and accuracy of various accelerator features and ensuring that the accelerator meets the requirements for clinical use.

[0003] For traditional C-arm linear accelerators, there are already mature and comprehensive quality control processes and methods. However, for toroidal linear accelerators, due to the differences in mechanical structure compared to traditional C-arm accelerators, some mechanical quality control items, such as source-to-skin distance, are difficult to complete using traditional quality control methods.

[0004] In accelerator quality control, confirming the source-skin distance (SPD) is fundamental. Generally, the SPD (distance from the isocenter to the virtual source) of an accelerator isocenter is 100 cm. After confirming the accelerator isocenter position using this 100 cm SPD, other mechanical and dose-related measurements are performed based on this isocenter position. The accuracy of the SPD affects most accelerator quality control items; therefore, SPD measurement is crucial for accelerator quality control.

[0005] Accelerator trainers suggest treating the image center of the EPID (Electronic Photodetector) built into the circular linear accelerator as the accelerator's isocenter. This isocenter position can be confirmed by moving the gantry to different angles and taking X-rays of the corresponding phantoms. However, this method only confirms the relative isocenter and cannot determine the specific source-skin distance of the image center, while many quality control projects require a source-skin distance of 100 centimeters as a prerequisite.

[0006] Because the ring accelerator is built into the machine head, parameters such as source-to-skin distance and frame angle cannot or are inconvenient to be achieved using the conventional methods applicable to C-arm linear accelerators. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention provides an automated mechanical quality control method and a quality control phantom for a medical circular linear accelerator, which solves at least one of the above-mentioned technical problems.

[0008] The technical solution of this invention is: an automated mechanical quality control method for a medical circular linear accelerator, characterized by the following steps:

[0009] Step 1: Place the quality control phantom on the treatment bed. The quality control phantom has a positioning structure that aligns with the cross-shaped laser line of the accelerator. Align the cross-shaped laser line with the positioning structure on the quality control phantom and move the quality control phantom to the theoretical isocenter position.

[0010] Step two: Then, import the corresponding pre-made plan according to the measurement project, control the ring linear accelerator to work through the pre-made plan, the ring linear accelerator outputs beam and obtains EPID image, analyzes the EPID image, and then obtains the measurement result according to the corresponding calculation method, and calculates the deviation from the preset value.

[0011] More preferably, the quality control phantom includes a cube-shaped calibration block and an isosceles trapezoidal calibration plate that is wider at the top and narrower at the bottom;

[0012] The calibration block is equipped with height-adjustable support feet at its bottom;

[0013] The calibration block is detachably connected to the calibration plate;

[0014] The calibration plate is provided with triangular prism-shaped measuring posts at its four corners;

[0015] The two triangular prism-shaped measuring posts at the top of the calibration plate are each provided with a prism surface flush with the top surface of the calibration plate.

[0016] The two triangular prism-shaped measuring posts at the lower end of the calibration plate are each provided with a prism surface flush with the bottom surface of the calibration plate.

[0017] More preferably, the calibration plate has a central hole for inserting the calibration block, and when the calibration block is inserted into the calibration plate, the front end of the calibration block partially protrudes from the calibration plate.

[0018] More preferably, the area of ​​the calibration block exposed outside the calibration plate is provided with a first cross-shaped laser positioning groove on the upper side, left side and right side;

[0019] Metal markers are installed on all four sides of the calibration block;

[0020] The calibration plate has a second cross-shaped laser positioning groove on both its left and right sides.

[0021] More preferably, the measurement item includes source-to-skin distance. When the measurement item is source-to-skin distance, the corresponding pre-design plan includes a firing field with a frame angle of 0°, a collimator angle of 0°, and a firing field size of 28 cm × 28 cm.

[0022] The source-skin distance measurement result is obtained according to the source-skin distance measurement formula, and the deviation of the source-skin distance measurement result is compared with the preset value;

[0023] The formula for measuring source-skin distance is: ;

[0024] SSD refers to the source-to-skin distance, which is the distance from the center point to the virtual source.

[0025] d4 is the longitudinal length of the calibration plate;

[0026] d5 is the distance between the left and right ends of the two triangular prism-shaped measuring posts at the top of the calibration plate;

[0027] d6 is the distance between the left and right ends of the two triangular prism-shaped measuring posts at the bottom of the calibration plate;

[0028] d7 is the maximum distance between the projections of the two triangular prism-shaped measuring posts at the top of the calibration plate onto the EPID plate;

[0029] d8 is the maximum distance between the projections of the two triangular prism-shaped measuring posts at the bottom of the calibration plate onto the EPID plate;

[0030] dc is the distance between the upper edge of the calibration plate and the center of the central measuring column.

[0031] The center of the central measuring column is located at the laser center of the annular linear accelerator, which is also the isocenter of the accelerator.

[0032] More preferably, the top of the calibration block has two square calibration slots arranged vertically, with the cross-sectional area of ​​the upper square calibration slot being larger than that of the lower square calibration slot.

[0033] Furthermore, the cross-sectional area of ​​the square calibration slot is rectangular.

[0034] More preferably, the measurement item includes the size of the firing field. When the measurement item is the size of the firing field, the corresponding prefabrication plan includes 4 firing fields, all with a frame angle of 0° and a collimator angle of 0°. The size of the 4 firing fields are a cm × a cm, b cm × b cm, c cm × c cm, and d cm × d cm, respectively.

[0035] The four side lengths a, b, c, and d of the four firing fields are close to the length and width of the upper directional calibration slot and the length and width of the lower square calibration slot, respectively.

[0036] In the pre-fabrication plan, the vertical center of the square calibration slot needs to be moved to the center height of the annular linear accelerator before the beam is output for measurement and calibration.

[0037] Obtain the boundary coordinates of the square calibration slots and the field boundary coordinates in the images corresponding to the four firing fields. Use the boundary coordinates of the square calibration slots that are closest to the field size to perform image size measurement and calibration. Then calculate the calibrated field size from the image and the deviation from the preset field size.

[0038] The field sizes for the four shooting fields are: 5 cm × 5 cm, 10 cm × 10 cm, 15 cm × 15 cm, and 20 cm × 20 cm.

[0039] The measurement items include measuring the accuracy of the moving bed. When measuring the accuracy of the moving bed, the pre-made plan includes 3 shooting fields. The gantry angle of all 3 shooting fields is 0° and the collimator angle is 0°. According to the preset position in the plan, the treatment bed is moved to three different positions respectively.

[0040] Specifically, by obtaining the center coordinates of the edge metal markers, the coordinates of the center of the metal markers in the EPD images corresponding to the three radiation fields are obtained respectively. The distance of the coordinate offset is calculated, and the deviation from the preset value is calculated to determine whether it meets the requirements for clinical use.

[0041] More preferably, the front end of the calibration block is equipped with a cylindrical measuring column group extending forward, the cylindrical measuring column group including a central measuring column located at the center and peripheral measuring columns arranged at equal intervals around the central measuring column.

[0042] The outer diameter of the central measuring column is larger than the outer diameter of all the peripheral measuring columns;

[0043] The axial length of the central measuring column is less than the axial length of all the peripheral measuring columns.

[0044] The tilt angle of the radiotherapy head gantry is determined by projecting the image onto the EPID plate using a circular measuring column.

[0045] More preferably, the outer diameter of the peripheral measuring column decreases along the first circumferential direction, and the axial length of the peripheral measuring column decreases along the first circumferential direction.

[0046] More preferably, there is one central measuring column and eight peripheral measuring columns.

[0047] When using the phantom body to measure the frame angle, the prefabrication plan includes 8 firing fields, each with a field size of 28 cm × 28 cm, a collimator angle of 0°, and frame angles of 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315° respectively.

[0048] The rack angle is calculated by acquiring the EPID image at the current rack angle and then obtaining the projection positions of the centers of the two outer measuring columns closest to the image center on the EPID board.

[0049] ;

[0050] For the frame angle;

[0051] d1 is the length projected onto EPID as twice the distance from the center of the outer measuring column to the center of the central measuring column;

[0052] d2 is the distance between the center projections of the two outer measuring columns closest to the center of the image in the EPID image of the phantom at any current frame angle.

[0053] More preferably, the longitudinal length of the calibration plate is 720 mm;

[0054] The distance between the left and right ends of the two triangular prism-shaped measuring posts at the top of the calibration plate is 136 mm.

[0055] The distance between the left and right ends of the two triangular prism-shaped measuring posts at the bottom of the calibration plate is 310 mm.

[0056] More preferably, the distance between the upper edge of the calibration plate and the center of the central measuring column is 460 mm.

[0057] The quality control phantom is characterized by comprising a cube-shaped calibration block and an isosceles trapezoidal calibration plate that is wider at the top and narrower at the bottom;

[0058] The calibration block is equipped with height-adjustable support feet at its bottom;

[0059] The calibration block is detachably connected to the calibration plate;

[0060] The calibration plate has triangular prism-shaped measuring posts at its four corners; the two triangular prism-shaped measuring posts at the top of the calibration plate each have a prism surface flush with the top surface of the calibration plate; the two triangular prism-shaped measuring posts at the bottom of the calibration plate each have a prism surface flush with the bottom surface of the calibration plate.

[0061] The calibration block is equipped with a positioning structure that aligns with the cross-shaped laser line, thereby aligning the cross-shaped laser line with the positioning structure on the quality control phantom.

[0062] The calibration block has a cylindrical measuring column assembly extending forward at its front end. The cylindrical measuring column assembly includes a central measuring column located at the center and peripheral measuring columns arranged at equal intervals around the central measuring column.

[0063] The outer diameter of the central measuring column is larger than the outer diameter of all the peripheral measuring columns;

[0064] The axial length of the central measuring column is less than the axial length of all the peripheral measuring columns;

[0065] The outer diameter of the peripheral measuring column decreases along the first circumferential direction, and the axial length of the peripheral measuring column decreases along the first circumferential direction.

[0066] More preferably, the area of ​​the calibration block exposed outside the calibration plate is provided with a first cross-shaped laser positioning groove on the upper side, left side and right side;

[0067] Metal markers are installed on all four sides of the calibration block;

[0068] The calibration plate has a second cross-shaped laser positioning groove on both its left and right sides.

[0069] This invention combines a calibration block and a calibration plate. The calibration block is placed on the treatment bed and aligned with the cross-shaped laser line using a first cross-shaped laser positioning groove. After assembling the calibration plate, alignment is achieved using a second cross-shaped laser positioning groove and the cross-shaped laser line.

[0070] The detachable calibration block and calibration plate facilitate storage and organization. The triangular prism-shaped measuring column allows for easy projection of the virtual source onto the EPID board, revealing the source-to-skin distance and enabling source-to-skin distance calibration.

[0071] More preferably, at least two of the upper, lower, left, and right sides of the calibration block are provided with sliding grooves;

[0072] The inner side of the socket is provided with a slider that is slidably connected to the slide groove.

[0073] Easy to slide and plug in.

[0074] More preferably, the triangular prism-shaped measuring posts at the four corners of the calibration plate have different lengths, making them easier to distinguish on the projected screen.

[0075] More preferably, the top of the calibration block has two square calibration slots arranged vertically, with the cross-sectional area of ​​the upper square calibration slot being larger than that of the lower square calibration slot.

[0076] Furthermore, the cross-sectional area of ​​the square calibration slot is rectangular.

[0077] The beneficial effects of this invention are:

[0078] 1) It makes the measurement of the source-skin distance of medical circular linear accelerators more convenient.

[0079] 2) It provides a convenient, low-cost and accurate method for measuring the gantry angle and field size of medical circular linear accelerators.

[0080] 3) Using the integrated design of the multifunctional phantom and the corresponding automated mechanical quality control method in this invention, the mechanical quality control items of medical circular linear accelerators can be completed in a standardized and automated manner, thereby improving the accuracy, repeatability and efficiency of the clinical quality control process. Attached Figure Description

[0081] Figure 1 This is a schematic diagram of the structure of a specific embodiment 1 of the present invention;

[0082] Figure 2 This is a schematic diagram of the calibration block in specific embodiment 1 of the present invention;

[0083] Figure 3 This is a schematic diagram of the calibration plate in specific embodiment 1 of the present invention;

[0084] Figure 4 This is a partial enlarged view of the first cross-shaped positioning groove of the calibration block in specific embodiment 1 of the present invention;

[0085] Figure 5 This is a partial enlarged view of the second cross-shaped positioning groove on the calibration plate in specific embodiment 1 of the present invention;

[0086] Figure 6 This is a schematic diagram of the source-skin distance calculation formula in a specific embodiment 1 of the present invention;

[0087] Figure 7 This is a schematic diagram illustrating the projection distance from the center of the outer measuring column to the center of the central measuring column onto the EPID in a specific embodiment 1 of the present invention;

[0088] Figure 8 This is a schematic diagram of the frame angle calculation formula in specific embodiment 1 of the present invention;

[0089] In the diagram: 1 is the calibration block, 2 is the calibration plate, 10 is the beam direction when the gantry angle is 0 degrees, 11 is the first cross-shaped laser positioning groove, 21 is the second cross-shaped laser positioning groove, 23 is the virtual source, 24 is the triangular prism measuring column, 25 is the EPID plate, 26 is the upper edge, 27 is the accelerator isocenter point, 28 is the lower edge, and 29 is the gantry angle when the beam direction is 0 degrees. The beam direction is as follows: 41 is the central measuring post, 42 is the outer measuring post; 411 is the center of the central measuring post, 42a is the near-end outer measuring post, and 42b is the far-end outer measuring post. Detailed Implementation

[0090] See Figures 1 to 8 Specific embodiment 1, an automated mechanical quality control method for a medical circular linear accelerator, characterized by the following steps:

[0091] Step 1: Place the quality control phantom on the treatment bed. The quality control phantom has a positioning structure that aligns with the cross-shaped laser line. Align the cross-shaped laser line with the positioning structure on the quality control phantom and move the quality control phantom to the theoretical isocenter position.

[0092] Step two: Then, import the corresponding pre-made plan according to the measurement project, control the ring linear accelerator to work through the pre-made plan, the ring linear accelerator outputs beam and obtains EPID image, analyzes the EPID image, and then obtains the measurement result according to the corresponding calculation method, and calculates the deviation from the preset value.

[0093] The quality control phantom includes a cube-shaped calibration block 1 and an isosceles trapezoidal calibration plate 2 that is wider at the top and narrower at the bottom. The bottom of the calibration block 1 is equipped with height-adjustable support feet. The calibration block 1 and calibration plate 2 are detachably connected. Triangular prism-shaped measuring posts 24 are provided at the four corners of the calibration plate 2. The two upper triangular prism-shaped measuring posts 24 of the calibration plate 2 each have a prism surface flush with the top surface of the calibration plate; the two lower triangular prism-shaped measuring posts 24 of the calibration plate 2 each have a prism surface flush with the bottom surface of the calibration plate.

[0094] The calibration plate 2 has a hole in the center for inserting the calibration block 1. When the calibration block 1 is inserted into the calibration plate 2, the front end of the calibration block 1 is partially exposed outside the calibration plate 2.

[0095] The calibration block 1 has a first cross-shaped laser positioning groove 11 on the upper, left and right sides of the area exposed to the calibration plate 2; metal calibration bodies are installed on the four sides of the calibration block 1; and a second cross-shaped laser positioning groove 21 is opened on the left and right walls of the calibration plate 2.

[0096] The measurement items include source-to-skin distance. When the measurement item is source-to-skin distance, the corresponding pre-planning includes one firing field with a frame angle of 0°, a collimator angle of 0°, and a firing field size of 28 cm × 28 cm. The source-to-skin distance measurement result is obtained according to the source-to-skin distance measurement formula, and the deviation between the source-to-skin distance measurement result and the preset value is compared.

[0097] The formula for measuring source-skin distance is: ;

[0098] SSD is the source-to-skin distance (the distance from the accelerator isocenter 27 to the virtual source 23), d4 is the longitudinal length of calibration plate 2 (that is, the vertical distance between the upper edge 26 and the lower edge 28 of the calibration plate), d5 is the distance between the left and right ends of the two top triangular prism-shaped measuring pillars 24, d6 is the distance between the left and right ends of the two bottom triangular prism-shaped measuring pillars 24, d7 is the maximum distance between the projections of the two top triangular prism-shaped measuring pillars 24 onto EPID plate 25, d8 is the maximum distance between the projections of the two bottom triangular prism-shaped measuring pillars 24 onto EPID plate 25, and dc is the distance between the upper edge 26 of calibration plate 2 and the center of the central measuring pillar. The center of the central measuring pillar is located at the laser center of the C-arm linear accelerator, which is the accelerator isocenter.

[0099] The center of the central measuring column 41 is located at the laser center of the annular linear accelerator, which is also the center of the accelerator.

[0100] See Figure 6 Derivation process:

[0101] ----------------------- (Formula 1)

[0102] -------------------------- (Formula 2)

[0103] x3 is the vertical distance from the virtual source to the EPID board plane;

[0104] x5 is the vertical distance from the virtual source to the upper edge of calibration plate 2;

[0105] Based on formulas 1 and 2, the following calculations are obtained:

[0106] ;

[0107] And because ;

[0108] Therefore, .

[0109] The top of the calibration block 1 has two square calibration slots arranged vertically. The cross-sectional area of ​​the upper square calibration slot is larger than that of the lower square calibration slot. The cross-sectional area of ​​the square calibration slot is rectangular. The measurement items include the field size. When the field size is measured, the corresponding pre-fabrication plan includes four fields, all with a gantry angle of 0° and a collimator angle of 0°. The field sizes of the four fields are a cm × a cm, b cm × b cm, c cm × c cm, and d cm × d cm, respectively. The four side lengths a, b, c, and d of the four fields are close to the length and width of the upper directional calibration slot and the lower square calibration slot, respectively. In the pre-fabrication plan, the vertical center of the square calibration slot is moved to the center height of the annular linear accelerator before beam output for measurement and calibration. The boundary coordinates of the square calibration slot and the field boundary coordinates in the corresponding images of the four fields are obtained. The boundary coordinates of the square calibration slot that is closest to the field size are used to perform image size measurement and calibration. Then, the calibrated field size is calculated from the image, and the deviation from the preset field size is calculated. The field sizes for the four shooting fields are: 5 cm × 5 cm, 10 cm × 10 cm, 15 cm × 15 cm, and 20 cm × 20 cm.

[0110] The center of the cross-shaped laser positioning structure of calibration block 1 is set with a metal marker point; the measurement items include measuring the accuracy of the moving bed. When measuring the accuracy of the moving bed, the pre-made plan includes 3 shooting fields. The gantry angle of the 3 shooting fields is 0° and the collimator angle is 0°. According to the preset position in the plan, the treatment bed is moved to three different positions respectively.

[0111] Among them, by obtaining the center coordinates of the edge metal markers, the coordinates of the center of the metal markers in the corresponding images of the three radiation fields are obtained respectively. The distance of the coordinate offset is calculated, and the deviation from the preset value is calculated to determine whether it meets the requirements for clinical use.

[0112] The calibration block 1 has a forward-extending cylindrical measuring column assembly mounted on its front end. This assembly includes a central measuring column 41 and peripheral measuring columns 42 arranged at equal angular intervals around the central measuring column 41. The outer diameter of the central measuring column 41 is larger than the outer diameters of all the peripheral measuring columns 42; the axial length of the central measuring column 41 is smaller than the axial length of all the peripheral measuring columns 42. The tilt angle of the radiotherapy head gantry is determined by projecting the circular measuring column assembly onto the EPID board. The outer diameters and axial lengths of the peripheral measuring columns 42 decrease along the first circumferential direction. The first circumferential direction can be either clockwise or counterclockwise.

[0113] There is one central measuring column 41 and eight peripheral measuring columns 42.

[0114] When using the phantom body to measure the frame angle, the prefabrication plan includes 8 firing fields, each with a field size of 28 cm × 28 cm, a collimator angle of 0°, and frame angles of 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315° respectively.

[0115] The rack angle is calculated by acquiring the EPID image at the current rack angle and then obtaining the projection positions of the centers of the two outer measuring columns closest to the image center on the EPID board.

[0116] ;

[0117] For the frame angle;

[0118] d1 is the length projected onto the EPID board as twice the distance from the center of the outer perimeter measuring column 42b to the center of the central measuring column 411;

[0119] d2 is the distance between the projections of the two outer perimeter measurement column centers (far perimeter measurement column 42b and near perimeter measurement column 42a) in the EPID image of the phantom at any current frame angle.

[0120] d3 is the distance from the center of the outermost measuring column 42b to the center of the central measuring column 411;

[0121] The beam direction is 10 when the frame angle is 0 degrees, and the frame angle is... The beam direction at that time was 29.

[0122] See Figure 7 and Figure 8 The derivation process is as follows:

[0123] ;

[0124] And because: 2 × d3 = d1;

[0125] Therefore .

[0126] The measurement items also include laser accuracy. When the measurement item is laser accuracy, the pre-fabrication plan includes 3 shooting fields. The size of each of the 3 shooting fields is 28 cm × 28 cm, the collimator angle is 0°, and the frame angles are 0°, 90°, and 270° respectively.

[0127] Specifically, by obtaining the coordinates of the center of the metal marker, the coordinates of the center of the metal marker in the corresponding images of the three radiation fields are obtained respectively. The deviation between the coordinates and the center of the EPD image is calculated, and then it is determined whether the clinical use requirements are met.

[0128] The measurement items also include the frame rotation center. When the measurement item is the frame rotation center, the prefabrication plan includes 8 firing fields. The firing field size of each of the 8 firing fields is 28 cm × 28 cm, the collimator angle is 0°, and the frame angles are 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315° respectively.

[0129] Specifically, by obtaining the coordinates of the center of the central measurement column in the EPID image, the coordinates of the center of the central measurement column in the EPID image corresponding to each of the eight radiation fields were obtained, and the deviation from the center of the EPID image was calculated to determine whether it meets the requirements for clinical use.

[0130] The measurement items also include the collimator rotation center. When the measurement item is the collimator rotation center, the prefabrication plan includes 7 firing fields. The frame angle of the 7 firing fields is 0°, the size of the firing field is 10 cm × 10 cm, and the collimator angles are 0°, 30°, 60°, 90°, 270°, 300° and 330° respectively.

[0131] Specifically, by obtaining the center coordinates of the metal markers, the coordinates of the centers of the metal markers in the EPID images corresponding to the seven radiation fields were obtained, and the deviations from the center of the EPID images were calculated to determine whether they meet the requirements for clinical use.

[0132] The measurement items also include collimator angle. When the measurement item is collimator angle, the prefabrication plan includes 7 firing fields. The frame angle of the 7 firing fields is 0°. The size of the firing field is 10 cm × 10 cm. The collimator angles are 0°, 30°, 60°, 90°, 270°, 300° and 330° respectively. In each firing field, a fixed numbered blade of the multi-leaf collimator (MLC) in the firing field is extended a certain distance to help determine the angle.

[0133] Specifically, by obtaining the angle between the phantom edge and the blades extending into the radiation field, the angles between the phantom edge and the blades extending into the radiation field in the EPID images corresponding to the seven radiation fields are obtained respectively, thereby obtaining the collimator angle, and calculating the deviation from the preset collimator angle, and then determining whether it meets the requirements for clinical use.

[0134] The quality control phantom includes a cube-shaped calibration block 1 and an isosceles trapezoidal calibration plate 2 that is wider at the top and narrower at the bottom. The bottom of the calibration block 1 is equipped with height-adjustable support feet. The calibration block 1 and calibration plate 2 are detachably connected. Triangular prism-shaped measuring columns 24 are provided at the four corners of the calibration plate 2. The calibration block 1 is equipped with a positioning structure that aligns with the cross-shaped laser line, ensuring mutual alignment between the cross-shaped laser line and the positioning structure on the quality control phantom. A forward-extending cylindrical measuring column assembly is installed at the front end of the calibration block 1. This assembly includes a central measuring column 41 located at the center and peripheral measuring columns 42 arranged at equal angular intervals around the central measuring column 41. The outer diameter of the central measuring column 41 is larger than the outer diameters of all the peripheral measuring columns 42. The axial length of the central measuring column 41 is smaller than the axial lengths of all the peripheral measuring columns 42. The outer diameters of the peripheral measuring columns 42 decrease along the first circumferential direction, and the axial lengths of the peripheral measuring columns 42 also decrease along the first circumferential direction.

[0135] The calibration block 1 has a first cross-shaped laser positioning groove 11 on its upper, left, and right sides, which are exposed on the calibration plate 2. Metal markers are installed on all four sides of the calibration block 1. A second cross-shaped laser positioning groove 21 is formed on the left and right walls of the calibration plate 2. This invention combines the calibration block 1 and the calibration plate 2. The calibration block 1 is placed on the treatment bed and aligned with the cross-shaped laser line using the first cross-shaped laser positioning groove 11. After assembling the calibration plate 2, it is aligned with the cross-shaped laser line using the second cross-shaped laser positioning groove. The detachable nature of the calibration block 1 and calibration plate 2 facilitates storage and organization. The triangular prism-shaped measuring column 24 allows for the projection of the virtual source irradiation onto the EPID plate, revealing the source-skin distance and enabling source-skin distance calibration.

[0136] At least two of the top, bottom, left, and right sides of calibration block 1 are provided with sliding grooves; a slider that slides in conjunction with the sliding grooves is provided on the inner side of the insertion hole. This facilitates sliding insertion.

[0137] The triangular prism-shaped measuring posts 24 at the four corners of the calibration plate 2 have different lengths. This makes it easy to distinguish them on the projected screen.

[0138] The two triangular prism-shaped measuring posts at the upper end of the calibration plate 2 are each provided with a prism surface that is flush with the top surface of the calibration plate 2; the two triangular prism-shaped measuring posts at the lower end of the calibration plate 2 are each provided with a prism surface that is flush with the bottom surface of the calibration plate 2.

[0139] The top of the calibration block 1 has two square calibration slots arranged vertically. The cross-sectional area of ​​the upper square calibration slot is larger than that of the lower square calibration slot. The cross-sectional area of ​​the square calibration slot is rectangular.

[0140] A leveling base is installed at the bottom of calibration block 1. The bottom of the leveling base is detachably connected to four height-adjustable support feet.

[0141] The longitudinal length of calibration plate 2 is 720 mm; the distance between the left and right ends of the two prismatic measuring posts 24 at the top of calibration plate 2 is 136 mm; the distance between the left and right ends of the two prismatic measuring posts 24 at the bottom of calibration plate 2 is 310 mm. The distance between the centers of the measuring posts along the upper edge 26 of calibration plate 2 is 460 mm.

[0142] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An automated mechanical quality control method for a medical circular linear accelerator, characterized in that, The steps are as follows: Step 1: Place the quality control phantom on the accelerator treatment bed. The quality control phantom is equipped with a positioning structure that aligns with the cross-shaped positioning laser line of the accelerator. Align the cross-shaped laser line with the positioning structure on the quality control phantom and move the quality control phantom to the theoretical isocenter position of the accelerator. Step two: Then, import the corresponding pre-made plan according to the measurement project, control the ring linear accelerator to work through the pre-made plan, the ring linear accelerator outputs beam and obtains EPID image, analyzes the EPID image, and then obtains the measurement result according to the corresponding calculation method, and calculates the deviation from the preset value. The quality control phantom includes a cube-shaped calibration block and an isosceles trapezoidal calibration plate that is wider at the top and narrower at the bottom. The calibration block is equipped with height-adjustable support feet at its bottom; The calibration block is detachably connected to the calibration plate; The calibration plate is provided with triangular prism-shaped measuring posts at its four corners; The two triangular prism-shaped measuring posts at the top of the calibration plate are each provided with a prism surface flush with the top surface of the calibration plate. The two triangular prism-shaped measuring posts at the lower end of the calibration plate are each provided with a prism surface flush with the bottom surface of the calibration plate; The calibration block is provided with a first cross-shaped laser positioning groove on the upper, left and right sides of the area exposed outside the calibration plate; Metal markers are installed on all four sides of the calibration block; The calibration plate has a second cross-shaped laser positioning groove on both the left and right sides. The calibration block has a cylindrical measuring column assembly extending forward at its front end. The cylindrical measuring column assembly includes a central measuring column located at the center and peripheral measuring columns arranged at equal intervals around the central measuring column. The outer diameter of the central measuring column is larger than the outer diameter of all the peripheral measuring columns; The axial length of the central measuring column is less than the axial length of all the peripheral measuring columns; The outer diameter of the peripheral measuring column decreases along the first circumferential direction, and the axial length of the peripheral measuring column decreases along the first circumferential direction. There is one central measuring column and eight peripheral measuring columns.

2. The automated mechanical quality control method for a medical circular linear accelerator according to claim 1, characterized in that: The measurement items include source-to-skin distance. When the measurement item is source-to-skin distance, the corresponding pre-fabrication plan includes one firing field with a frame angle of 0°, a collimator angle of 0°, and a firing field size of 28 cm × 28 cm. The source-skin distance measurement result is obtained according to the source-skin distance measurement formula, and the deviation of the source-skin distance measurement result is compared with the preset value; The formula for measuring source-skin distance is: ; SSD refers to the source-to-skin distance, which is the distance from the center point to the virtual source. d4 is the longitudinal length of the calibration plate; d5 is the distance between the left and right ends of the two triangular prism-shaped measuring posts at the top of the calibration plate; d6 is the distance between the left and right ends of the two triangular prism-shaped measuring posts at the bottom of the calibration plate; d7 is the maximum distance between the projections of the two triangular prism-shaped measuring posts at the top of the calibration plate onto the EPID plate; d8 is the maximum distance between the projections of the two triangular prism-shaped measuring posts at the bottom of the calibration plate onto the EPID plate; dc is the distance between the upper edge of the calibration plate and the center of the central measuring column.

3. The automated mechanical quality control method for a medical circular linear accelerator according to claim 1, characterized in that: The top of the calibration block has two square calibration slots arranged vertically, with the cross-sectional area of ​​the upper square calibration slot being larger than that of the lower square calibration slot. Furthermore, the cross-sectional area of ​​the square calibration slot is rectangular.

4. The automated mechanical quality control method for a medical circular linear accelerator according to claim 3, characterized in that: The measurement items include the size of the firing field. When the measurement item is the size of the firing field, the corresponding prefabrication plan includes 4 firing fields. The frame angle is 0° and the collimator angle is 0°. The size of the 4 firing fields are a cm × a cm, b cm × b cm, c cm × c cm, and d cm × d cm. The four side lengths a, b, c, and d of the four firing fields are close to the length and width of the upper directional calibration slot and the length and width of the lower square calibration slot, respectively. In the pre-fabrication plan, the vertical center of the square calibration slot needs to be moved to the center height of the annular linear accelerator before the beam is output for measurement and calibration. Obtain the boundary coordinates of the square calibration slots in the EPID images corresponding to the four firing fields and the boundary coordinates of the firing fields. Use the boundary coordinates of the square calibration slots that are closest to the firing field size to perform image size measurement and calibration. Then calculate the calibrated firing field size from the image and calculate the deviation from the preset firing field size. The field sizes for the four shooting fields are: 5 cm × 5 cm, 10 cm × 10 cm, 15 cm × 15 cm, and 20 cm × 20 cm.

5. The automated mechanical quality control method for a medical circular linear accelerator according to claim 1, characterized in that: The calibration block has a metal marker point at the center of its cross-shaped laser positioning structure. The measurement items include measuring the accuracy of the moving bed. When measuring the accuracy of the moving bed, the pre-made plan includes 3 shooting fields. The gantry angle of all 3 shooting fields is 0° and the collimator angle is 0°. According to the preset position in the plan, the treatment bed is moved to three different positions respectively. Specifically, by obtaining the center coordinates of the metal markers, the coordinates of the center of the metal markers in the corresponding images of the three radiation fields are obtained respectively. The distance of the coordinate offset is calculated, and the deviation from the preset value is calculated to determine whether it meets the requirements for clinical use.

6. The automated mechanical quality control method for a medical circular linear accelerator according to claim 1, characterized in that: When using the phantom body to measure the frame angle, the prefabrication plan includes 8 firing fields, each with a field size of 28 cm × 28 cm, a collimator angle of 0°, and frame angles of 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315° respectively. The rack angle is calculated by acquiring the EPID image at the current rack angle and then obtaining the projection positions of the centers of the two outer measuring columns closest to the image center on the EPID board. ； For the frame angle; d1 is the length projected onto EPID as twice the distance from the center of the outer measuring column to the center of the central measuring column; d2 is the distance between the center projections of the two outer measuring columns closest to the center of the image in the EPID image of the phantom at any current frame angle.

7. A quality control phantom, characterized in that, It includes a cube-shaped calibration block and an isosceles trapezoidal calibration plate that is wider at the top and narrower at the bottom; The calibration block is equipped with height-adjustable support feet at its bottom; The calibration block is detachably connected to the calibration plate; The calibration plate is provided with triangular prism-shaped measuring posts at its four corners, and the two triangular prism-shaped measuring posts at the top of the calibration plate are provided with prism surfaces that are flush with the top surface of the calibration plate. The two triangular prism-shaped measuring posts at the lower end of the calibration plate are each provided with a prism surface flush with the bottom surface of the calibration plate. The calibration block is provided with a positioning structure that aligns with the cross-shaped laser line, so that the cross-shaped laser line and the positioning structure on the quality control phantom are aligned with each other. The calibration block has a cylindrical measuring column assembly extending forward at its front end. The cylindrical measuring column assembly includes a central measuring column located at the center and peripheral measuring columns arranged at equal intervals around the central measuring column. The outer diameter of the central measuring column is larger than the outer diameter of all the peripheral measuring columns; The axial length of the central measuring column is less than the axial length of all the peripheral measuring columns; The outer diameter of the peripheral measuring column decreases along the first circumferential direction, and the axial length of the peripheral measuring column decreases along the first circumferential direction.

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