Beam spot testing method and apparatus

Abstract

The application provides a kind of beam spot test method and device, the beam spot test method includes: the corresponding relationship curve between the gray scale of radiation color film and the radiation dose of accelerating tube is established;Radiation color film is placed on test table, the distance between radiation color film and the beam end of accelerating tube is adjusted to measurement distance;Accelerating tube is controlled to be in working condition, to output the preset dose of electron beam irradiation on radiation color film;Remove the color change after radiation color film and scan to obtain gray scale image;According to corresponding relationship curve and gray scale image, dose contour map is obtained;According to dose contour map, the beam spot size of electron beam at measurement distance is obtained.In the process of testing beam spot size, the distance between radiation color film and the beam end of accelerating tube can be adjusted, and then the shape of beam spot can be corrected to the preset shape, to improve the accuracy of beam spot size measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of beam testing, and in particular relates to a beam spot testing method and device. Background Art

[0002] Radiochromic film changes color after absorbing a certain dose of ionizing radiation without the need for physical or chemical treatment. The photosensitive component of the sensitive layer in the film is a type of unsaturated hydrocarbon microcrystals. When exposed to ionizing radiation, the unsaturated hydrocarbon microcrystals, which are the radiochromic photosensitive component, polymerize to form a dye aggregate, causing the film to change color. The greater the absorbed dose, the darker the color, that is, measuring the color change can reveal the ionizing radiation dose received by the film. In the prior art, when using radiochromic film to test the beam spot size emitted by an accelerating tube, the radiochromic film is usually attached to the beam outlet end of the accelerating tube. During the test, the distance of the radiochromic film cannot be adjusted, and therefore the shape of the beam spot emitted from the accelerating tube cannot be adjusted, which in turn affects the final measurement of the beam spot size. Summary of the Invention

[0003] The main purpose of the present invention is to provide a beam spot testing method and device, aiming to solve the technical problem that the beam spot testing method in the prior art cannot correct the beam spot shape during the testing process.

[0004] In order to achieve the above object, the present invention provides a beam spot testing method, comprising the steps of:

[0005] Establish a corresponding relationship curve between the grayscale of radiochromic film and the radiation dose of the accelerating tube;

[0006] Place the radiochromic film on the test bench and adjust the distance between the radiochromic film and the beam outlet of the accelerating tube to the measuring distance;

[0007] Controlling the accelerating tube to be in a working state to output an electron beam of a preset dose to irradiate the radiochromic film;

[0008] The discolored radiochromic film was removed and scanned to obtain a grayscale image;

[0009] The dose contour map is obtained based on the corresponding relationship curve and the grayscale image;

[0010] The beam spot size of the electron beam at the measurement distance is obtained according to the dose contour map.

[0011] In an embodiment of the present invention, the step of obtaining a dose contour map according to the correspondence curve and the grayscale image includes:

[0012] Draw a rectangular area line through the center of the beam spot on the grayscale image;

[0013] Extract the grayscale curve within the rectangular area line;

[0014] Export the grayscale data corresponding to the grayscale curve within the rectangular area line;

[0015] The grayscale data within the rectangular area line is converted into a dose contour curve according to the corresponding relationship curve.

[0016] In an embodiment of the present invention, the step of obtaining the beam spot size of the electron beam at the measurement distance according to the dose contour map includes:

[0017] Analyze dose contour plots;

[0018] The length within the dose contour curve is the diameter of the beam spot.

[0019] In an embodiment of the present invention, the step of establishing a corresponding relationship curve between the grayscale of the radiochromic film and the radiation dose of the accelerating tube includes:

[0020] Applying electron beams of known radiation doses to a plurality of radiochromic films of the same specifications;

[0021] Scanning the irradiated radiochromic film into a digital image;

[0022] Select a color area of ​​a preset size in the digital image and collect the average grayscale value within the color area;

[0023] The corresponding relationship curve is drawn with the average gray value as the horizontal axis and the radiation dose as the vertical axis.

[0024] In an embodiment of the present invention, the beam spot testing method further includes:

[0025] Before using the radiochromic film to test the beam spot size, the shape of the beam spot is roughly adjusted by the fluorescent film so that the shape of the beam spot is a preset shape.

[0026] In an embodiment of the present invention, the step of coarsely adjusting the beam spot shape by using the fluorescent sheet includes:

[0027] Fix the fluorescent sheet tightly to the center of the beam outlet end of the accelerating tube;

[0028] Controlling the operation of the accelerating tube to emit electron beams to the fluorescent sheet;

[0029] Obtain the shape of the fluorescent sheet after emitting light, which is the shape of the beam spot;

[0030] When the shape of the beam spot is not a preset shape, the operating parameters of the accelerating tube are adjusted until the beam spot emitted from the accelerating tube conforms to the preset shape.

[0031] In an embodiment of the present invention, the beam spot testing method further includes:

[0032] Adjust the distance between the radiochromic film and the beam outlet of the accelerating tube multiple times, and obtain the beam spot shape at different distances;

[0033] When the beam spot shapes at different distances do not conform to the preset shapes, the operating parameters of the accelerating tube are continuously adjusted until the beam spot shapes conform to the preset shapes, and then the adjustment is stopped.

[0034] In an embodiment of the present invention, a beam spot testing device is further provided. The beam spot testing method described above is adopted. The beam spot testing device includes:

[0035] A test bench for supporting the radiochromic film, wherein the test bench is provided with two clamps for clamping the radiochromic film so that the radiochromic film adheres to the surface of the test bench;

[0036] An accelerator tube for generating a therapeutic electron beam, with the beam axis centerline of the accelerator tube perpendicular to the normal to the plane of the test platform; and

[0037] The connecting scale plate is connected between the accelerating tube and the test bench, and the test bench can move along the height direction of the connecting scale plate.

[0038] In an embodiment of the present invention, a locking member is provided on the connecting scale plate, and when the test bench is moved to a preset position, the locking member locks the connecting scale plate and the test bench.

[0039] In an embodiment of the present invention, the locking member is a locking screw, a slide rail is provided on the connecting scale plate, and a slider that slides with the slide rail is provided at one end of the test bench facing the slide rail. The slider is provided with a threaded hole for tightening the locking screw.

[0040] Through the above technical solution, the beam spot testing method provided by the embodiment of the present invention has the following beneficial effects:

[0041] When testing the size of the beam spot emitted by the accelerating tube, first establish a corresponding relationship curve between the grayscale of the radiochromic film and the radiation dose of the accelerating tube; then place the radiochromic film on the test bench, adjust the distance between the radiochromic film and the beam output end of the accelerating tube to the measurement distance; control the accelerating tube to be in a working state to output a preset dose of electron beam to irradiate the radiochromic film; remove the radiochromic film after discoloration and scan to obtain a grayscale image; obtain a dose contour map based on the corresponding relationship curve and the grayscale image, and finally obtain the beam spot size of the electron beam at the measurement distance based on the dose contour map. In the process of testing the beam spot size, the present application can adjust the distance between the radiochromic film and the beam output end of the accelerating tube, and then correct the shape of the beam spot to the preset shape, thereby improving the accuracy of the beam spot size measurement.

[0042] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings are used to provide an understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0044] Figure 1 is a schematic structural diagram of a beam spot testing device according to an embodiment of the present invention;

[0045] Figure 2 1 is a flow chart of a beam spot testing method according to an embodiment of the present invention;

[0046] Figure 3 FIG. 1 is a corresponding relationship curve diagram obtained according to the beam spot testing method of the present invention in one embodiment.

[0047] Description of Reference Numerals

[0048] Label name Label name 10 test bench 31 fixture 11 slider 40 Slide rails 20 Accelerator tube 50 Locking parts 30 Connecting the scale plate DETAILED DESCRIPTION

[0049] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0050] The beam spot testing method and device according to the present invention will be described below with reference to the accompanying drawings.

[0051] like Figure 2 As shown, in an embodiment of the present invention, a beam spot testing method is provided, comprising the steps of:

[0052] S10: establishing a corresponding relationship curve between the grayscale of the radiochromic film and the radiation dose of the accelerating tube 20;

[0053] The establishment of a corresponding relationship curve is a preparatory step before the beam spot test. This correspondence curve can meet the needs of subsequent use, namely, establishing a corresponding relationship (linear relationship, response curve) between the grayscale of the radiation film and the radiation dose. Based on this correspondence, the corresponding radiation dose value can be calculated based on the grayscale value of subsequent radiochromic films of the same specifications, making the beam spot size measurement more accurate.

[0054] S20: placing the radiochromic film on the test bench 10, and adjusting the distance between the radiochromic film and the beam outlet end of the accelerating tube 20 to a measuring distance;

[0055] During radiation, the radiochromic film is first placed on the side of the test bench 10 facing the accelerating tube 20. The shape of the beam spot is adjusted by adjusting the distance between the radiochromic film and the accelerating tube 20, and the distance between the two is adjusted to the optimal measurement distance. This allows for more accurate measurement of the size of the beam spot under the preset shape.

[0056] S30: Controlling the accelerating tube 20 to be in a working state to output a preset dose of electron beam to irradiate the radiochromic film;

[0057] S40: removing the discolored radiochromic film and scanning it to obtain a grayscale image;

[0058] After the irradiation is completed, the discolored radiation-chromic film is removed and a scanning device is used to scan and obtain a grayscale image of the irradiated film.

[0059] S50: obtaining a dose contour map according to the corresponding relationship curve and the grayscale image;

[0060] S60: Obtaining the beam spot size of the electron beam at the measurement distance according to the dose contour map.

[0061] During the beam spot size test, the present application can adjust the distance between the radiochromic film and the beam output end of the accelerating tube 20, thereby correcting the shape of the beam spot to a preset shape, thereby improving the accuracy of the beam spot size measurement.

[0062] In an embodiment of the present invention, the step of obtaining a dose contour map according to the correspondence curve and the grayscale image includes:

[0063] Draw a rectangular area line through the center of the beam spot on the grayscale image;

[0064] Extract the grayscale curve within the rectangular area line;

[0065] Export the grayscale data corresponding to the grayscale curve within the rectangular area line;

[0066] The grayscale data within the rectangular area line is converted into a dose contour curve according to the corresponding relationship curve.

[0067] This application performs image analysis on the radiochromic film after color change. According to the ImageJ image analysis software, the grayscale data in the corresponding area can be exported, and the grayscale data in the rectangular area is converted into a dose curve according to the pre-calibrated correspondence curve. The dose curve is the dose contour curve. The dose contour curve obtained by combining the grayscale data and the correspondence curve is more accurate.

[0068] In an embodiment of the present invention, the step of obtaining the beam spot size of the electron beam at the measurement distance according to the dose contour map includes:

[0069] Analyze dose contour plots;

[0070] The length within the dose contour curve is the diameter of the beam spot.

[0071] The present invention can clearly obtain the length of the entire dose contour curve by analyzing the dose contour curve, and directly measure this length to obtain the beam spot diameter. Calculating the beam spot diameter in this way can reduce human error and improve measurement accuracy.

[0072] In an embodiment of the present invention, the step of establishing a corresponding relationship curve between the grayscale of the radiochromic film and the radiation dose of the accelerating tube 20 includes:

[0073] Applying electron beams of known radiation doses to a plurality of radiochromic films of the same specifications;

[0074] Scanning the irradiated radiochromic film into a digital image;

[0075] Select a color area of ​​a preset size in the digital image and collect the average grayscale value within the color area;

[0076] The corresponding relationship curve is drawn with the average gray value as the horizontal axis and the radiation dose as the vertical axis.

[0077] When calibrating the corresponding relationship curve, polynomial fitting is used. Specifically, a radiation dose film is exposed to multiple known radiation doses, and then one or more radiochromic films of the same specifications are subjected to these known radiation doses. After irradiation, the radiochromic films undergo color change without any additional treatment. An optical scanner is used to scan the irradiated radiochromic film into a digital image. The grayscale value of one color channel is collected and correlated with the applied radiation dose.

[0078] In order to obtain a more ideal fitting curve, it is preferred to sample at fixed dose values ​​and appropriately increase the number of samples in the commonly used dose range.

[0079] like Figure 3The figure shows the corresponding relationship curve of the calibration during an experiment. During this experiment, the grayscale values ​​of two films corresponding to cumulative absorbed doses of 1Gy, 2Gy, 3Gy, 4Gy, 6Gy, 8Gy, 10Gy, 12Gy, 14Gy, 16Gy, 18Gy, 20Gy, and 22Gy were measured. A dose-grayscale curve was plotted based on the average grayscale values ​​of the two films corresponding to absorbed doses of 1Gy, 2Gy, 3Gy, 4Gy, 6Gy, 8Gy, 10Gy, 12Gy, 14Gy, 16Gy, 18Gy, 20Gy, and 22Gy. The dose-grayscale curve was then converted to a polynomial using a curve fitting tool. The corresponding dose value was then calculated by inputting each grayscale value into the formula. The relative deviation between this dose value and the dose value measured by the corresponding dosimeter was then calculated. If the calculated relative deviations meet the requirements, the calibration result can be considered valid and reliable, and the calibration curve can be saved.

[0080] In addition, in order to ensure the measurement accuracy of the beam spot size, before measuring the beam spot size with the radiochromic film, the shape of the beam spot can be adjusted in the following two ways to adjust the shape of the beam spot to a circular or near-circular shape, so that the size of the beam spot can be obtained more accurately.

[0081] In the first embodiment, before the beam spot size is tested using the radiochromic film, the shape of the beam spot is roughly adjusted using the fluorescent film so that the shape of the beam spot is a preset shape.

[0082] Specifically, the steps of coarsely adjusting the beam spot shape through the fluorescent sheet include:

[0083] Fix the fluorescent sheet tightly to the center of the beam-emitting end of the accelerating tube 20;

[0084] Controlling the accelerating tube 20 to emit electron beams to the fluorescent sheet;

[0085] Obtain the shape of the fluorescent sheet after emitting light, which is the shape of the beam spot;

[0086] When the shape of the beam spot is not the preset shape, the operating parameters of the accelerating tube 20 are adjusted until the beam spot emitted from the accelerating tube 20 conforms to the preset shape.

[0087] When using a fluorescent sheet to coarsely adjust the beam spot shape, first use tape to firmly attach the fluorescent sheet to the center of the beam outlet of the accelerating tube 20. Then, adjust the treatment head's posture so that it is perpendicular to the ground. A reflector is then placed directly below the accelerating tube 20, through which the fluorescent sheet should be visible. A camera is then set up and aimed at the reflector. The circular knobs at the rear of the camera are used to adjust the field of view, focal length, and aperture so that the camera can clearly capture the fluorescent sheet. The image is then transmitted via a network cable to the computer monitor in the control room. The shape of the fluorescent sheet captured in the image represents the beam spot shape. After obtaining the beam spot shape, if the beam spot shape is not the preset shape, the operating parameters of the accelerating tube 20 are adjusted to ensure that the beam spot is circular or nearly circular and located at the center of the beam outlet of the accelerating tube 20.

[0088] Different from the first embodiment, in the second embodiment, only the radiochromic film itself is used to adjust the shape of the beam spot. Specifically, the beam spot testing method further includes the steps of:

[0089] Adjust the distance between the radiochromic film and the beam outlet end of the accelerating tube 20 multiple times, and obtain the beam spot shape at different distances;

[0090] When the beam spot shapes at different distances do not conform to the preset shape, the operating parameters of the accelerating tube 20 are continuously adjusted until the beam spot shape conforms to the preset shape, and then the adjustment is stopped.

[0091] Specifically, when the radiochromic film is placed under the accelerating tube 20, if the beam spot shape obtained at this time is not the preset shape, the distance between the radiochromic film and the beam output end of the accelerating tube 20 is adjusted multiple times. If the shape of the beam spot at different distances is not the preset shape, it means that the beam spot cannot reach the preset shape (such as a circle or a near circle) under the radiation dose. At this time, it is necessary to change the working parameters of the accelerating tube 20. In this way, the dose of the beam emitted from the accelerating tube 20 changes, and the shape of the beam spot will also change. The above adjustment method is used until the beam spot shape is the preset shape.

[0092] For the above beam spot test method, such as Figure 1 As shown, the present application also innovatively proposes a beam spot testing device, which adopts the beam spot testing method as described above. The beam spot testing device includes a test table 10, an accelerating tube 20 and a connecting scale plate 30; the test table 10 is located below the accelerating tube 20 and is used to support the radiochromic film. Two clamps 31 for clamping the radiochromic film are provided on the test table 10 so that the radiochromic film fits the surface of the test table 10; the accelerating tube 20 is used to generate an electron beam for treatment, and the center line of the beam axis of the accelerating tube 20 is perpendicular to the normal of the plane where the test table 10 is located to ensure that the rays emitted from the accelerating tube 20 can be vertically irradiated on the radiochromic film; the connecting scale plate 30 is connected between the accelerating tube 20 and the test table 10, and the test table 10 can move along the height direction of the connecting scale plate 30.

[0093] A scale line is provided on one side connected to the scale plate 30 . When the test platform 10 moves toward the accelerating tube 20 , the scale line allows the operator to observe the distance between the test platform 10 and the beam outlet end of the accelerating tube 20 .

[0094] Before the experiment begins, the radiochromic film is placed on the side of the test platform 10 facing the accelerating tube 20. Clamps 31 on either side secure the film from both sides to prevent it from shifting during the experiment. The distance between the test platform 10 and the beam output end of the accelerating tube 20 is then adjusted to the preset test distance. The accelerating tube 20 is then turned on to begin the experiment.

[0095] Compared with the prior art method of directly sticking a film on the accelerating tube 20 to test the beam spot, the present application uses the above-mentioned beam spot testing device to test the beam spot size, which can obtain ideal and accurate test results, and can perform shape correction before the beam spot size test, thereby accurately obtaining the beam spot size conditions of different radiation doses generated by the accelerating tube 20.

[0096] In an embodiment of the present invention, a locking member 50 is provided on the connecting scale plate 30 . When the test bench 10 moves to a preset position, the locking member 50 locks the connecting scale plate 30 and the test bench 10 .

[0097] Preferably, the locking member 50 is a locking screw, the connecting scale plate 30 is provided with a slide rail 40, and the end of the test bench 10 facing the slide rail 40 is provided with a slider 11 that slides with the slide rail 40, and the slider 11 is provided with a threaded hole for tightening the locking screw.

[0098] When the test bench 10 drives the slider 11 to reciprocate along the slide rail 40 toward or away from the accelerating tube 20 to a predetermined distance, the locking screw is tightened. The end of the locking screw passes through the slider 11 and abuts against the connecting scale plate 30, thereby locking the slider 11 and the connecting scale plate 30. When the distance between the accelerating tube 20 and the test bench 10 needs to be adjusted, the locking screw is reversed to disengage the end of the locking screw from the connecting scale plate 30, thereby unlocking the slider 11 and the connecting scale plate 30.

[0099] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0100] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0101] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0102] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A beam spot testing method, characterized in that: Including steps: Establishing a corresponding relationship curve between the grayscale of the radiochromic film and the radiation dose of the accelerating tube (20); Placing a radiochromic film on a test bench (10), and adjusting the distance between the radiochromic film and the beam-outlet end of the accelerating tube (20) to a measuring distance; Controlling the accelerating tube (20) to be in a working state to output an electron beam of a preset dose to irradiate the radiochromic film; The discolored radiochromic film was removed and scanned to obtain a grayscale image; Obtaining a dose contour map according to the corresponding relationship curve and the grayscale image; acquiring a beam spot size of the electron beam at the measuring distance according to the dose contour map; The step of obtaining a dose contour map according to the corresponding relationship curve and the grayscale image comprises: Draw a rectangular area line through the center of the beam spot on the grayscale image; Extracting the grayscale curve within the rectangular area line; Exporting grayscale data corresponding to the grayscale curve within the rectangular area line; Converting the grayscale data within the rectangular area line into a dose contour curve according to the corresponding relationship curve; The step of obtaining the beam spot size of the electron beam at the measuring distance according to the dose contour map comprises: analyzing the dose contour graph; Obtaining the length within the dose contour curve diagram, which is the diameter of the beam spot; Before the radiochromic film measures the beam spot size, the shape of the beam spot is adjusted to a preset shape.

2. The beam spot test method according to claim 1, characterized in that: The step of establishing a corresponding relationship curve between the grayscale of the radiochromic film and the radiation dose of the accelerating tube (20) comprises: Applying electron beams of known radiation doses to a plurality of radiochromic films of the same specifications; Scanning the irradiated radiochromic film into a digital image; Selecting a color area of ​​a preset size in the digital image and collecting the average grayscale value within the color area; A corresponding relationship curve is drawn with the average gray value as the horizontal axis and the radiation dose as the vertical axis.

3. The beam spot test method according to claim 1, characterized in that: The beam spot testing method further includes: Before the radiochromic film is used to test the beam spot size, the shape of the beam spot is roughly adjusted by a fluorescent film so that the shape of the beam spot is a preset shape.

4. The beam spot test method according to claim 3, characterized in that: The steps for coarsely adjusting the beam spot shape using the fluorescent sheet include: The fluorescent sheet is fixed closely to the center of the beam-outlet end of the accelerating tube (20); controlling the accelerating tube (20) to operate so as to emit an electron beam to the fluorescent sheet; Obtaining the shape of the fluorescent sheet after emitting light, which is the shape of the beam spot; When the shape of the beam spot is not a preset shape, the operating parameters of the accelerating tube (20) are adjusted until the beam spot emitted from the accelerating tube (20) conforms to the preset shape.

5. The beam spot testing method according to claim 1, characterized in that: The beam spot testing method further includes: Adjusting the distance between the radiochromic film and the beam output end of the accelerating tube (20) multiple times, and obtaining the beam spot shapes at different distances; When the beam spot shapes at different distances do not conform to the preset shape, the operating parameters of the accelerating tube (20) are continuously adjusted until the beam spot shape conforms to the preset shape, and the adjustment is stopped.

6. A beam spot test device, characterized in that: The beam spot testing method according to any one of claims 1 to 5 is adopted, wherein the beam spot testing device comprises: A test bench (10) for supporting a radiochromic film, wherein the test bench (10) is provided with two clamps (31) for clamping the radiochromic film so that the radiochromic film adheres to the surface of the test bench (10); An accelerating tube (20) for generating an electron beam for treatment, wherein the center line of the beam axis of the accelerating tube (20) is perpendicular to the normal line of the plane where the test platform (10) is located; and A connecting scale plate (30) is connected between the accelerating tube (20) and the test bench (10), and the test bench (10) is movable along the height direction of the connecting scale plate (30).

7. The beam spot test device according to claim 6, characterized in that: A locking member (50) is provided on the connecting scale plate (30), and when the test bench (10) moves to a preset position, the locking member (50) locks the connecting scale plate (30) and the test bench (10).

8. The beam spot test device according to claim 7, characterized in that: The locking member (50) is a locking screw, the connecting scale plate (30) is provided with a slide rail (40), and the test bench (10) is provided with a slider (11) at one end facing the slide rail (40) and slidably engaged with the slide rail (40), and the slider (11) is provided with a threaded hole for tightening the locking screw.

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