A phantom for accelerator quality control and its application

Abstract

The present invention relates to a phantom for accelerator quality control and its application. The phantom includes a cube. Cross coordinate lines are provided at the central positions of the upper, front, rear, left, and right side surfaces of the cube. And 10*10 cm field frame lines are respectively provided on the upper, front, and rear side surfaces, and 9.4*9.4 cm field frame lines are respectively provided on the left and right side surfaces; on the upper side surface, cross marking lines are provided at the position 1.2 cm to the right and 1.5 cm forward from the center of the cross coordinate line, and a vertical hole for placing a laser ranging and leveling integrated machine is provided on the upper side surface; corresponding front and rear through holes are provided on the front and rear side surfaces, and an isocenter pointer with a pointed end is inserted into the front and rear through holes, and the isocenter pointer can move back and forth; on the left and right side surfaces, cross marking lines are provided at the position 1.4 cm upward and 1.5 cm forward from the cross coordinate line. The phantom has rich functions and can be used to conveniently and quickly perform quality control on the accelerator.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical devices, and particularly relates to a phantom for accelerator quality control and its application. Background Art

[0002] Radiation therapy is one of the three main means of tumor treatment. Radiation therapy plays a very important role in tumor treatment. For some tumors, such as nasopharyngeal carcinoma, cervical cancer, breast cancer, etc., high cure rates can also be obtained by using pure radiation therapy. Currently, nearly 70% of patients in tumor treatment need radical or adjuvant radiation therapy. The ultimate goal of radiation therapy is to strive to improve the therapeutic gain ratio of radiation therapy, that is, to give a sufficiently high irradiation dose to the tumor area, while minimizing the irradiation dose of surrounding critical organs as much as possible to avoid other complications caused by treatment.

[0003] Currently, in the clinical practice of radiation therapy, the main equipment used is a medical linear accelerator. At the same time, with the continuous development of radiation therapy technology, intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) using accelerators have been widely used in tumor radiation therapy units in China. And these technologies have higher and higher requirements for the accuracy of accelerators. While these new technologies improve the therapeutic gain ratio of radiation therapy, they also greatly increase the probability of uncertainty in radiation therapy. Because these technologies will make the high-dose area closely approach the tumor target area, and a huge dose drop steep area will be generated outside the high-dose area. And the corresponding mechanical precision control of the accelerator has a great impact on the treatment effects of high-precision IMRT and VMAT. Therefore, special attention needs to be paid to the quality control of the treatment accelerator. These quality control points include the isocenter of the accelerator, the laser isocenter, the field size of the accelerator, the moving accuracy of the treatment couch, the accuracy of the imaging equipment center of the accelerator, the consistency between the accelerator imaging and the actual ray output, etc. And the frequency of quality control of the accelerator, such as daily, is still difficult to achieve unified requirements and feasible implementation in China. And in many advanced foreign hospitals, daily quality control has already started, but only the most basic quality control points are guaranteed. Currently, the quality control of the accelerator mainly uses a variety of equipment to regularly detect the isocenter of the accelerator, the laser isocenter, the accuracy of the accelerator imaging, etc. It is very difficult to increase the frequency of accelerator quality control (such as daily) and ensure timely detection of the precision errors of the accelerator and related imaging equipment.

[0004] With the development of radiotherapy technology, the development and application of high-precision treatment technology must be premised on ensuring the normal operation of the accelerator equipment under very high-precision conditions. Being able to quickly perform high-precision quality control of the accelerator before daily treatment is the greatest guarantee for the treatment effect of patients. How to quickly perform quality control on the accelerator with minimal impact on the normal treatment of staff is one of the primary problems that treatment technicians, doctors, and physicists have to face. Summary of the Invention

[0005] The purpose of the present invention is to provide a phantom for accelerator quality control and its application. The phantom has rich functions and can be used to conveniently and quickly perform quality control on the accelerator.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a phantom for accelerator quality control, including a cube. According to the accelerator space coordinate system, the direction close to the accelerator gantry is the front side, and the direction far from the accelerator gantry is the rear side. Cross coordinate lines are provided at the central positions of the upper, front, rear, left, and right side faces of the cube. And 10*10 cm field lines are respectively provided on the upper, front, and rear side faces, and 9.4*9.4 cm field lines are respectively provided on the left and right side faces;

[0007] On the upper side face, a cross marking line is provided at a position 1.2 cm to the right and 1.5 cm forward from the center of the cross coordinate line. A vertical hole for placing a laser distance measurement and leveling integrated machine is provided on the upper side face; Corresponding front and rear through holes are provided on the front and rear side faces, and an isocenter pointer with a pointed end is inserted into the front and rear through holes, and the isocenter pointer can move back and forth; On the left and right side faces, a cross marking line is provided at a position 1.4 cm upward and 1.5 cm forward from the cross coordinate line.

[0008] Further, the cube is a 12*12*12 cm hollow cube, which is mainly composed of a bottom plate and a hollow main body buckled on the bottom plate. A clamping groove is provided on the peripheral part of the upper side face of the bottom plate to clamp the hollow main body buckled on it; At least three horizontal adjusting feet are provided at the lower part of the bottom plate for horizontal adjustment when needed.

[0009] Further, a hollow cylinder is inserted into the front and rear through holes, and the isocenter pointer is inserted into the hollow cylinder; Corresponding upper and lower through holes are provided on the upper side face and the bottom plate of the hollow main body, and corresponding left and right through holes are provided on the left and right side faces. Hollow cylinders are respectively inserted into the upper and lower through holes and the left and right through holes.

[0010] Further, the isocenter pointer is mainly composed of a stepped pointed end, a cone, and a columnar body connected together in sequence from front to back. The stepped pointed end includes a front section with a diameter of 1 mm and a rear section with a diameter of 2 mm.

[0011] Further, the size range of the cross coordinate lines is 4*4 cm, and the line width changes in a stepped manner. The line width within the range of 2*2 cm is 1 mm, and the line width from outside the 2*2 cm range to the 4*4 cm range is 2 mm.

[0012] Further, the size range of the cross marking lines is 2*2 cm, and the line width is 1 mm.

[0013] Further, the radiation field frame lines are four folded lines provided inside the four corners of the corresponding side. The single-side length of the folded line is 2 cm, and the line width changes in a stepped manner. The line width from the intersection of the two sides of the folded line to 1 cm is 1 mm, and the line width from outside 1 cm to 2 cm is 2 mm.

[0014] Further, the phantom is fabricated by 3D printing.

[0015] The present invention also provides an application method of the above-mentioned phantom, which is used to detect the mechanical performance and imaging function of the accelerator to perform quality control on the accelerator;

[0016] The application of the phantom to detect the mechanical performance of the accelerator includes:

[0017] A1) Detecting the gantry and laser isocenter; pushing out the isocenter pointer from the phantom, using a laser distance measurement and leveling integrated machine to measure the horizontality of the upper surface of the phantom, moving the phantom until the gantry isocenter, laser isocenter and phantom isocenter are completely coincident; using the gantry at 0°, 90°, 270° to detect whether the center is completely consistent. If not, adjustment is required; then move 3.5 cm to the right, lower the treatment couch by 3.5 cm, and then adjust the position of the couch to make the tip of the pointer completely coincide with the vertical line of the 0° gantry cross line and the vertical line of the laser lamp, then the tip of the pointer is consistent with the center; secondly, rotate the accelerator gantry 360°, check any angle, especially when at 0°, 90°, 270°, 180°, whether the tip of the pointer is consistent with the cross center in the gantry. If not, record the error. If the error exceeds the threshold, adjustment is required, otherwise it meets the quality control requirements;

[0018] A2) Detecting the standard light field; setting the treatment couch according to the phantom isocenter and lowering it by 6 cm; setting the accelerator gantry to 0°, opening the light field area to 10*10 cm, and checking whether the edge of the light field is consistent with the 10*10 cm radiation field frame line on the phantom. If not, record the error. If the error exceeds the threshold, adjustment is required, otherwise it meets the quality control requirements;

[0019] A3) Measure the distance between the gantry and the treatment couch surface; Stand the laser distance measuring and leveling integrated machine upright on the treatment couch surface; Open the accelerator scale ruler, and measure and record the mechanical distance from the surface of the gantry to the treatment couch surface when the distance from the scale ruler to the treatment couch surface is 80, 90, 100, 105, 110, and 120 cm.

[0020] A4) Detect the accuracy of the gantry rotation angle and the accuracy of the collimator angle in place; The detection method for the accuracy of the gantry rotation angle is as follows: When the gantry rotates to near 0°, 90°, 270°, and 180°, stick the surface of the laser distance measuring and leveling integrated machine along the left-right axis on the gantry. When the display of the laser distance measuring and leveling integrated machine is adjusted to absolute 0°, -90°, 90°, and 0°, read the display data of the gantry, which is the error of the gantry; The detection method for the accuracy of the collimator angle in place is as follows: Rotate the gantry to 90°, and when the collimator angle is adjusted to near 0°, 90°, 270°, and 180°, stick the surface of the laser distance measuring and leveling integrated machine along the left-right axis on the gantry. When the display of the laser distance measuring and leveling integrated machine is adjusted to absolute 0°, -90°, 90°, and 0°, read the display data of the collimator, which is the error of the collimator.

[0021] Using the said phantom to detect the imaging function of the accelerator includes:

[0022] B1) Detect the treatment beam center and the treatment field area; According to the isocenter setup of the phantom, use the EPID to take 10*10 cm field films at gantry 0° and 90° respectively; Then magnify the pictures obtained by the EPID to the maximum in the built-in software of the accelerator; Find the isocenter of the field according to the edge of the standard field, and compare it with the isocenter marking line of the phantom; Measure the moving distance of the center, which is the error of the isocenter; Then, according to the 10*10 cm field frame line at the proximal end of the phantom, check the difference between the field edge of the picture and the field frame line of the phantom, that is, measure the difference between the treatment field area and the light field area.

[0023] B2) Detect the EPID images of the treatment couch movement; According to the isocenter setup of the phantom, move the center 1.2 cm to the right, 1.4 cm up, and 1.5 cm forward; Move to the cross marking line; Use the EPID to take 10*10 cm field films at gantry 0° and 90° respectively, and then use these two pictures to register with the standard picture in the built-in software of the EPID respectively; Check whether the registration result is that the center moves 1.2 cm to the right, 1.4 cm up, and 1.5 cm forward, and record the error.

[0024] B3) Detect the scanning center of the CBCT image; according to the isocenter positioning of the phantom, use the single-shot function of the CBCT to take images at 0° and 90° of the gantry respectively; then magnify the images obtained by the CBCT to the maximum in the built-in software of the accelerator; find the isocenter of the radiation field according to the edge of the standard radiation field and compare it with the isocenter line of the phantom; measure the distance of the center movement, that is, the isocenter error.

[0025] B4) Detect the movement of the treatment couch and the CBCT registration accuracy; according to the isocenter positioning of the phantom, use the CBCT to take a set of CBCT images with 360° rotation, and then register them with the images of the standard phantom in the built-in software of the accelerator; according to the registration error, check whether the center error of the three-dimensional image is qualified and record the error; then move the center 1.2 cm to the right, 1.4 cm up, and 1.5 cm forward; take another set of CBCT images with 360° rotation, and then register them with the images before the center movement to obtain the registration error. Subtract the previous CBCT center error, which is the actual error after the CBCT movement. Check whether it matches the moved data and record the error.

[0026] Compared with the prior art, the present invention has the following beneficial effects: A phantom for accelerator quality control is made by using 3D printing technology. This phantom integrates various structures and functions on one phantom, and it can be used to conveniently and quickly detect the mechanical performance and imaging function of the accelerator, including gantry and laser center verification, 10*10 cm radiation field verification, radiation field center electronic portal imaging device (EPID) radiography verification, cone beam CT (CBCT) image acquisition isocenter verification, verification of the movement accuracy of the treatment couch of the auxiliary imaging device, verification of the mechanical distance measurement from the gantry to the treatment couch, etc. It greatly saves the operation time of the staff for quality control, and at the same time can meet the accuracy requirements of detection, making it possible to quickly perform mechanical and imaging quality control of the accelerator every day. Therefore, the present invention has strong practicability and broad application prospects. Brief Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the structure of the phantom in the embodiment of the present invention.

[0028] Figure 2 It is a schematic diagram of the upper side of the phantom in the embodiment of the present invention.

[0029] Figure 3 It is a schematic diagram of the front side of the phantom in the embodiment of the present invention.

[0030] Figure 4 It is a schematic diagram of the rear side of the phantom in the embodiment of the present invention.

[0031] Figure 5 It is a schematic diagram of the left side of the phantom in the embodiment of the present invention.

[0032] Figure 6 It is a schematic diagram of the right side of the phantom in the embodiment of the present invention.

[0033] Figure 7 It is a schematic diagram of the structure of the bottom plate in the embodiment of the present invention.

[0034] Figure 8 It is a schematic diagram of the structure of the isocenter pointer in the embodiment of the present invention.

[0035] Figure 9 It is a flowchart of the method for accelerator quality control using the phantom in the embodiment of the present invention. Detailed implementation manners

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] As Figures 1-6 shown, the present invention provides a phantom for accelerator quality control, including a cube. According to the accelerator space coordinate system, the direction close to the accelerator gantry is the front side, and the direction away from the accelerator gantry is the rear side. Cross coordinate lines 1 are engraved at the central positions of the upper, front, rear, left, and right sides of the cube, and 10*10 cm field light frames 2 are respectively engraved on the upper, front, and rear sides, and 9.4*9.4 cm field light frames 3 are respectively engraved on the left and right sides.

[0038] In this embodiment, the size range of the cross coordinate lines is 4*4 cm, and the line width changes in a stepwise manner. The part within the range of 2*2 cm has a line width of 1 mm, and the part from outside the 2*2 cm range to the 4*4 cm range has a line width of 2 mm. The cross coordinate lines can be used to quickly compare the alignment degree of the accelerator light field and the model center by visual inspection. The field light frame is four folded lines provided inside the four corners of the corresponding side. The single side length of the folded line is 2 cm, and the line width changes in a stepwise manner. From the intersection of the two sides of the folded line to 1 cm, the line width is 1 mm, and from 1 cm outside to 2 cm, the line width is 2 mm. The field light frame can be used to quickly compare the accuracy of the 10*10 cm light field edge by visual inspection.

[0039] As Figure 2 shown, a cross marking line 4 is engraved on the upper side at a position 1.2 cm to the right and 1.5 cm forward from the center of the cross coordinate line. A vertical hole for placing a laser distance measuring and leveling integrated machine is opened on the upper side. The laser distance measuring and leveling integrated machine is placed in the vertical hole for measuring the distance from the accelerator gantry to the bed surface and the level of the phantom itself.

[0040] As Figures 3-4As shown, front and rear through holes 5 are correspondingly formed in the front and rear side faces. An isocenter pointer 6 with a pointed end is inserted into the front and rear through holes, and the isocenter pointer can move back and forth.

[0041] As Figures 5-6 shown, cross marking lines are engraved on the left and right side faces at positions 1.4 cm upward and 1.5 cm forward from the cross coordinate line. Thus, the combination of the coordinates of the left and right side faces plus the movement of the side faces is a shift of 1.2 cm to the right, 1.4 cm upward, and 1.5 cm forward.

[0042] In this embodiment, the size range of the cross marking lines is 2 * 2 cm, and the line width is 1 mm. The cross marking lines can be used to measure the image registration accuracy and treatment couch movement accuracy after the phantom moves.

[0043] In this embodiment, a G and an upward arrow mark are labeled in the upper right corner of the upper side face to illustrate the positioning direction of the phantom, and this direction is facing the accelerator gantry. SSD = 100 cm can be labeled in the lower right corner of the upper side face to illustrate that the front field is a field with a source-skin distance of 100 cm from the accelerator, that is, a standard 10 * 10 cm field frame. SSD = 94 cm can be labeled in the upper right corner of the left and right side faces to illustrate that the front field is a field with a source-skin distance of 94 cm from the accelerator. The fields are all standard 9.4 * 9.4 cm frames. The main reason is that the neutral section of the actual display area projection is a 10 * 10 cm field, which is used to detect the accuracy of the 10 * 10 cm field in the directions of gantry angles 90° and 270° during the isocenter positioning of the phantom.

[0044] In this embodiment, the cube is a hollow cube with dimensions of 12 * 12 * 12 cm. The hollow cube is mainly composed of a bottom plate 8 and a hollow main body buckled on the bottom plate, and they are respectively formed by 3D printing. As Figure 7 shown, a card slot 801 is provided on the peripheral part of the upper side face of the bottom plate to hold the hollow main body buckled on it; at least three horizontal adjusting feet 802 are provided at the lower part of the bottom plate for horizontal adjustment when needed.

[0045] To improve the resolution of the direction during image acquisition, a hollow cylinder penetrates three groups of parallel opposite faces. A hollow cylinder 7 is inserted into the front and rear through holes, and the isocenter pointer is inserted into the hollow cylinder. Upper and lower through holes are correspondingly formed in the upper side face and the bottom plate of the hollow main body, and left and right through holes are correspondingly formed in the left and right side faces. Hollow cylinders are respectively inserted into the upper and lower through holes and the left and right through holes. The outer diameter of the hollow cylinder is 2 cm, the diameter of the hollow part is 1.6 cm, and the wall thickness of the cylinder is 2 mm.

[0046] As Figure 8As shown, the isocenter pointer 6 mainly consists of a stepped tip 601, a cone 602, and a column 603 that are connected together in sequence from front to back. The stepped tip includes a front section with a diameter of 1 mm and a length of 5 mm, and a rear section with a diameter of 2 mm and a length of 5 mm. 2 mm is exactly the maximum error limit of the accelerator isocenter and the maximum error limit of the laser isocenter. The 1-mm error between the accelerator light field and the laser center can be well distinguished by the eyes. On the cylindrical section of the pointer, lines can be engraved at the positions of 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock on the clock face. When the isocenter pointer is combined on the upper surface of the phantom, lines are engraved at the corresponding positions on both the left and right sides. The left and right are 3.5 cm away from the center, and the horizontal is lowered by 3 cm.

[0047] As Figure 9 shown, the present invention also provides a method for accelerator quality control by applying the above-mentioned phantom, which realizes the quality control of the accelerator by detecting the mechanical performance and imaging function of the accelerator by applying the phantom.

[0048] Detecting the mechanical performance of the accelerator by applying the phantom includes:

[0049] A1) Detecting the gantry and the laser isocenter

[0050] Push out the isocenter pointer from the phantom, use the laser rangefinder and level integrated machine to measure the level of the upper surface of the phantom, and move the phantom until the gantry isocenter and the laser isocenter are completely coincident with the phantom isocenter; use the gantry at 0°, 90°, and 270° to detect whether the center is completely consistent. If not, adjustment is required; then move 3.5 cm to the right, lower the treatment couch by 3.5 cm, and then adjust the couch in and out to make the tip of the pointer completely coincide with the vertical line of the 0° gantry crosshair and the vertical line of the laser light. Then the tip of the pointer is consistent with the center; secondly, rotate the accelerator gantry 360°, check any angle, especially when at 0°, 90°, 270°, and 180°, whether the tip of the pointer is consistent with the cross center in the gantry. If not, record the error. If the error exceeds the threshold, adjustment is required; otherwise, the quality control requirements are met.

[0051] A2) Detecting the standard light field

[0052] According to the isocenter positioning of the phantom, lower the treatment couch by 6 cm; set the accelerator gantry to 0°, open the light field area to 10*10 cm, and check whether the edge of the light field is consistent with the 10*10 cm field frame line on the phantom. If not, record the error. If the error exceeds the threshold, adjustment is required; otherwise, the quality control requirements are met.

[0053] A3) Measuring the distance between the gantry and the treatment couch surface

[0054] Stand the laser distance measurement and leveling integrated machine upright on the treatment couch surface; turn on the accelerator scale ruler, and measure and record the mechanical distance from the surface of the gantry to the treatment couch surface when the distance from the scale ruler to the treatment couch surface is 80, 90, 100, 105, 110, and 120 cm.

[0055] A4) Detect the accuracy of the gantry rotation angle and the accuracy of the collimator angle in place

[0056] The detection method for the accuracy of the gantry rotation angle is as follows: when the gantry rotates to near 0°, 90°, 270°, and 180°, attach the surface of the laser distance measurement and leveling integrated machine to the gantry along the left-right axis direction. When the display of the laser distance measurement and leveling integrated machine is adjusted to absolute 0°, -90°, 90°, and 0°, read the display data of the gantry, which is the error of the gantry.

[0057] The detection method for the accuracy of the collimator angle in place is as follows: rotate the gantry to 90°, and when the collimator angle is adjusted to near 0°, 90°, 270°, and 180°, attach the surface of the laser distance measurement and leveling integrated machine to the gantry along the left-right axis direction. When the display of the laser distance measurement and leveling integrated machine is adjusted to absolute 0°, -90°, 90°, and 0°, read the display data of the collimator, which is the error of the collimator.

[0058] The image functions of the accelerator detected by using the said phantom include:

[0059] B1) Detect the treatment beam center and the treatment field area

[0060] According to the isocenter positioning of the phantom, use the EPID to take 10*10 cm field films at gantry 0° and 90° respectively; then magnify the pictures obtained by the EPID to the maximum in the built-in software of the accelerator; find the isocenter of the field according to the edge of the standard field, and compare it with the isocenter scale line of the phantom; measure the moving distance of the center, which is the error of the isocenter; then according to the 10*10 cm field frame line at the proximal end of the phantom, check the difference between the field edge of the picture and the field frame line of the phantom, that is, measure the difference between the treatment field area and the light field area.

[0061] B2) Detect the EPID image of the treatment couch movement

[0062] According to the isocenter positioning of the phantom, move the center 1.2 cm to the right, 1.4 cm up, and 1.5 cm forward; move to the cross mark line; use the EPID to take 10*10 cm field films at gantry 0° and 90° respectively, and then use these two pictures to register with the standard picture in the built-in software of the EPID respectively; check whether the registration result is that the center moves 1.2 cm to the right, 1.4 cm up, and 1.5 cm forward, and record the error.

[0063] B3) Detect the CBCT image scanning center

[0064] According to the isocenter positioning of the phantom, take radiographic films using the single-shot function of CBCT at gantry angles of 0° and 90° respectively; then magnify the images obtained by CBCT to the maximum in the built-in software of the accelerator; find the isocenter of the radiation field according to the edge of the standard radiation field and compare it with the isocenter marking line of the phantom; measure the distance of the center movement, that is, the isocenter error.

[0065] B4) Detect the movement of the treatment couch and the registration accuracy of CBCT

[0066] According to the isocenter positioning of the phantom, take a set of CBCT images by CBCT 360° shooting, and then register them with the radiographic film of the standard phantom in the built-in software of the accelerator; according to the registration error, check whether the center error of the three-dimensional image is qualified and record the error.

[0067] Then move the center 1.2 cm to the right, 1.4 cm up, and 1.5 cm forward; take a set of CBCT images by 360° shooting again, and then register them with the radiographic film before the center movement. After obtaining the registration error and subtracting the previous CBCT center error, it is the actual error after CBCT movement. Check whether it matches the moved data and record the error.

[0068] Using this phantom can achieve rapid positioning and quality control of multi-functional mechanical and imaging functions, greatly reducing the operation time of the staff, and at the same time meeting the accuracy requirements of detection.

[0069] The above are the preferred embodiments of the present invention. All changes made according to the technical solution of the present invention, when the functions and effects generated do not exceed the scope of the technical solution of the present invention, fall within the protection scope of the present invention.

Claims

1. A phantom for accelerator quality control, characterized in that, It includes a cube. According to the accelerator space coordinate system, the direction close to the accelerator gantry is the front side, and the direction far from the accelerator gantry is the rear side. Cross coordinate lines are provided at the central positions of the upper, front, rear, left, and right side faces of the cube. And 10*10 cm field size frame lines are respectively provided on the upper, front, and rear side faces, and 9.4*9.4 cm field size frame lines are respectively provided on the left and right side faces; On the upper side face, a cross marking line is provided at a position 1.2 cm to the right and 1.5 cm forward from the center of the cross coordinate line. A vertical hole for placing a laser distance measuring and leveling integrated machine is provided on the upper side face; Corresponding front and rear through holes are provided on the front and rear side faces. An isocenter pointer with a pointed end is inserted into the front and rear through holes, and the isocenter pointer can move back and forth; On the left and right side faces, a cross marking line is provided at a position 1.4 cm upward and 1.5 cm forward from the cross coordinate line; The cube is a 12*12*12 cm hollow cube, which is mainly composed of a bottom plate and a hollow main body buckled on the bottom plate. A clamping groove is provided at the peripheral part of the upper side face of the bottom plate to clamp the hollow main body buckled on it; At least three horizontal adjusting feet are provided at the lower part of the bottom plate for horizontal adjustment when needed; A hollow cylinder is inserted into the front and rear through holes, and the isocenter pointer is inserted into the hollow cylinder; Corresponding upper and lower through holes are provided on the upper side face and the bottom plate of the hollow main body, and corresponding left and right through holes are provided on the left and right side faces. Hollow cylinders are respectively inserted into the upper and lower through holes and the left and right through holes; The isocenter pointer is mainly composed of a stepped pointed end, a cone, and a columnar body connected together in sequence from front to back. The stepped pointed end includes a front section with a diameter of 1 mm and a rear section with a diameter of 2 mm.

2. The phantom for accelerator quality control according to claim 1, characterized in that, The size range of the cross coordinate line is 4*4 cm, and the line width changes in a stepped manner. The part within the 2*2 cm range has a line width of 1 mm, and the part from outside the 2*2 cm range to the 4*4 cm range has a line width of 2 mm.

3. The phantom for accelerator quality control according to claim 2, characterized in that, The size range of the cross marking line is 2*2 cm, and the line width is 1 mm.

4. The phantom for accelerator quality control according to claim 3, characterized in that, The field size frame line is four folded lines provided on the inner sides of the four corners of the corresponding side face. The single-side length of the folded line is 2 cm, and the line width changes in a stepped manner. From the intersection of the two sides of the folded line to 1 cm, the line width is 1 mm, and from 1 cm to 2 cm, the line width is 2 mm.

5. The phantom for accelerator quality control according to claim 1, characterized in that, The phantom is made by 3D printing.

6. An application of the phantom for accelerator quality control according to claim 4, characterized in that, The phantom is used to detect the mechanical performance and imaging function of the accelerator for quality control of the accelerator; Using the phantom to detect the mechanical performance of the accelerator includes: A1) Detection of the gantry and laser isocenter: Push out the isocenter pointer from the phantom, use the laser distance measurement and leveling integrated machine to measure the level of the upper surface of the phantom, move the phantom until the gantry isocenter, laser isocenter and phantom isocenter are completely aligned; Use the gantry at 0°, 90°, and 270° to detect whether the centers are completely in line, and if not, adjustment is required; Then move 3.5 cm to the right, lower the treatment couch by 3.5 cm, and then adjust the position of the couch in and out to make the tip of the pointer completely coincide with the vertical line of the 0° gantry crosshair and the vertical line of the laser lamp, then the tip of the pointer is consistent with the center; Secondly, rotate the accelerator gantry 360°, and check whether the tip of the pointer is consistent with the cross center in the gantry at 0°, 90°, 270°, and 180°. If not, record the error. If the error exceeds the threshold, adjustment is required, otherwise it meets the quality control requirements; A2) Detection of the standard light field: Set up the position according to the phantom isocenter, lower the treatment couch by 6 cm; Set the accelerator gantry to 0°, open the light field area to 10*10 cm, and check whether the edge of the light field is consistent with the 10*10 cm field frame line on the phantom. If not, record the error. If the error exceeds the threshold, adjustment is required, otherwise it meets the quality control requirements; A3) Measurement of the distance between the gantry and the treatment couch surface: Stand the laser distance measurement and leveling integrated machine upright on the treatment couch surface; Open the accelerator scale ruler, measure and record the mechanical distance from the scale ruler to the treatment couch surface at 80, 90, 100, 105, 110, and 120 cm, and the distance from the gantry surface to the treatment couch surface; A4) Detection of the accuracy of the gantry rotation angle and the accuracy of the collimator angle in place: The detection method for the accuracy of the gantry rotation angle is as follows: When the gantry is rotated to near 0°, 90°, 270°, and 180°, stick the surface of the laser distance measurement and leveling integrated machine along the left-right axis on the gantry. When the display of the laser distance measurement and leveling integrated machine is adjusted to absolute 0°, -90°, 90°, and 0°, read the display data of the gantry, which is the error of the gantry; The detection method for the accuracy of the collimator angle in place is as follows: Rotate the gantry to 90°, and when the collimator angle is adjusted to near 0°, 90°, 270°, and 180°, stick the surface of the laser distance measurement and leveling integrated machine along the left-right axis on the gantry. When the display of the laser distance measurement and leveling integrated machine is adjusted to absolute 0°, -90°, 90°, and 0°, read the display data of the collimator, which is the error of the collimator; The image function of the accelerator is detected by using the said phantom, including: B1) Detection of the treatment field center and treatment field area: Set up the position according to the phantom isocenter, and use the EPID to take 10*10 cm field films at the gantry at 0° and 90° respectively; Then magnify the pictures obtained by the EPID to the maximum in the built-in software of the accelerator; Find the isocenter of the field according to the edge of the standard field, and compare it with the isocenter scale line of the phantom; Measure the moving distance of the center, that is, the error of the isocenter; Then, according to the 10*10 cm field frame line at the proximal end of the phantom, check the difference between the field edge in the picture and the field frame line of the phantom, that is, measure the difference between the treatment field area and the light field area; B2) Detect the EPID images of the treatment couch movement; according to the isocenter positioning of the phantom, move the center 1.2 cm to the right, 1.4 cm upward, and 1.5 cm forward; move to the cross mark line; use the EPID to take 10*10 cm field films at gantry angles of 0° and 90° respectively, and then use these two pictures to register with the standard picture in the built-in software of the EPID; check whether the registration result is that the center moves 1.2 cm to the right, 1.4 cm upward, and 1.5 cm forward, and record the error. B3) Detect the CBCT image scanning center; according to the isocenter positioning of the phantom, use the single-shot function of the CBCT to take imaging films at gantry angles of 0° and 90° respectively; then magnify the pictures obtained by the CBCT to the maximum in the built-in software of the accelerator; find the isocenter of the field according to the edge of the standard field, and compare it with the isocenter scale line of the phantom; measure the distance of the center movement, that is, the error of the isocenter. B4) Detect the treatment couch movement and CBCT registration accuracy; according to the isocenter positioning of the phantom, use the CBCT to take a set of CBCT images with 360° rotation, and then register with the standard phantom imaging film in the built-in software of the accelerator; according to the registration error, check whether the center error of the three-dimensional image is qualified, and record the error; then move the center 1.2 cm to the right, 1.4 cm upward, and 1.5 cm forward; take another set of CBCT images with 360° rotation, and then register with the imaging film before the center movement, obtain the registration error, subtract the previous CBCT center error, which is the actual error after the CBCT movement, check whether it matches the moved data, and record the error.

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