Measurement method and phantom device of laser positioning system

Abstract

The present invention relates to a measurement method and a phantom device of a laser positioning system, and belongs to the field of radiotherapy. The measurement phantom device of the laser positioning system comprises a phantom and a fixing frame for fixing the phantom on one side of a bed board. The present invention uses a new phantom, which significantly improves the test efficiency. The complexity and time consumption of manual operation are reduced, so that the test can be completed in a shorter time and the risk of human error is reduced; the test results have high repeatability and reliability, which helps to verify the long-term stability and consistency of the laser positioning system and provide strong support for clinical treatment.

Description

Technical Field

[0001] The invention relates to the technical field of radiotherapy, in particular to a measurement method and a phantom device of a laser positioning system. Background Art

[0002] In the field of radiotherapy, the core of radiotherapy is to accurately locate the tumor and ensure that the radiation can act on the tumor tissue accurately and efficiently while minimizing damage to surrounding normal tissues. As one of the key technologies in modern radiotherapy, the accuracy and stability of laser positioning technology are directly related to the treatment effect and the patient's prognosis.

[0003] YY / T 1537-2017 "Performance and Test Methods of Laser Positioning Systems for Radiotherapy" specifies the performance and test methods of laser positioning systems for radiotherapy, including the straightness of the laser line, the verticality of the laser cross positioning line and the consistency with the reference point, etc. However, due to the update of detection technology and the complexity of on-site detection, there are difficulties in actual operation.

[0004] Therefore, this paper provides some new test methods and some new test phantoms to meet the test needs. Summary of the invention

[0005] The present invention is a new testing method for the straightness of laser lines, the verticality of laser cross positioning lines and the consistency with reference points. The method uses a laser tracker or an absolute arm measurement system for testing.

[0006] Principle of testing with a laser tracker: The laser tracker determines the spatial position of the target point by emitting a laser beam and receiving reflected light. When the laser beam moves along a predetermined path, the reflected light returns to the laser tracker according to the principle that the angle of incidence is equal to the angle of reflection. By measuring the angle and distance of the reflected light, the laser tracker can accurately calculate the three-dimensional coordinates of the target point. By measuring the coordinates of multiple points and fitting a straight line, the straightness of the target path can be calculated. Similarly, the straightness of other coordinate systems can be measured, and then the two straightness values ​​can be compared to calculate the verticality of the target surface.

[0007] Absolute arm measurement system measurement principle:

[0008] The absolute arm measurement system is a measuring device based on mechanical arm and sensor technology. Its measurement principle is different from that of the laser tracker, but it can also achieve high-precision measurement. It installs sensors such as laser rangefinders or contact probes at the end of the mechanical arm to contact the object to be measured and obtain measurement data. Then, using advanced algorithms and mathematical models, the measurement data is converted into the three-dimensional coordinates and shape information of the object, thereby achieving the measurement of straightness and verticality. Its advantages are: it can contact and measure some points that are blocked by the outside world and are inconvenient to measure with laser trackers; it is small in size, easy to carry and move, and suitable for on-site measurement.

[0009] The present invention provides a measurement method and a phantom device for a laser positioning system, and the technical scheme thereof is as follows:

[0010] In a first aspect, a measuring phantom device of a laser positioning system is installed on one side of a bed board, and is characterized in that: the measuring phantom device of the laser positioning system includes a phantom and a fixing frame for fixing the phantom on one side of the bed board.

[0011] As a further solution of the present invention, the model body is a rectangular parallelepiped structure, and is provided with a plurality of first test holes for placing a measuring target ball of a laser tracker. The model body is also provided with a plurality of second test holes for placing a ruby / sapphire detection head, and a crosshair groove is also provided in the center of the model body.

[0012] As a further solution of the present invention, the fixing frame includes two brackets, the brackets include two connecting plates, the connecting plates are provided with a plurality of long holes, the head and tail ends of the connecting plates are respectively provided with open grooves, a joint is provided between the tail end of the connecting plate and the mold body, and a fastener is provided between the head end of the connecting plate and the edge of the bed board.

[0013] As a further solution of the present invention, one end of the joint is connected to the mold body by bolts, and the other end of the joint is provided with a first protrusion adapted to the open groove, and the first protrusion is connected to the rear end of the connecting plate by bolts;

[0014] A slot matching the edge of the bed board is provided on one side of the fastener, and the fastener is connected to the bed board by bolts. A second protrusion matching the open slot is provided on the other side of the fastener, and the second protrusion is connected to the head end of the connecting plate by bolts.

[0015] In a second aspect, a measurement method of a laser positioning system, using the measurement phantom device of the laser positioning system, comprises the following steps:

[0016] Step 1, project the positioning line emitted by the laser positioning system onto the phantom to ensure that the isocenter and the center position of the phantom coincide with each other; there are a total of 10 first test holes and second test holes set on the phantom, and the target ball or red / sapphire detection head of the laser tracker is placed at the first test hole and the second test hole, respectively, and measurements are made in the three directions of X, Y, and Z;

[0017] Step 2: Fit the data points in each direction to obtain a straight line, and calculate the distance from each point to the fitted straight line. The maximum deviation should not exceed 0.5 mm.

[0018] Step 3: Through the above test, the coordinate systems of the three directions of X, Y and Z are obtained. The angles between X and Y, between X and Z, and between Y and Z are calculated respectively, and the verticality is calculated. The calculated verticality should not be greater than 0.2°.

[0019] As a further solution of the present invention, the method for calculating straightness comprises the following steps:

[0020] The goal of fitting a straight line is to find a straight line y=ax+b, and a and b are calculated according to the following formula:

[0021]

[0022] After calculating a and b, any point (x i ,y i ) to the fitting line i is straightness;

[0023]

[0024] The method for calculating verticality includes the following steps:

[0025] For the two straight lines L1 and L2, for the straight line L1 passing through the points (x1, y1) and (x2, y2), the slope k1 = (y2-y1) / (x2-x1), x2≠x1; for the straight line L2 passing through the points (x3, y3) and (x4, y4), the slope k2 = (y4-y3) / (x4-x3), x4≠x3;

[0026] The angle between the two lines is θ.

[0027] In the third aspect, in the measuring phantom device of the laser positioning system, the fixed frame includes a ladder frame, the ladder frame includes three connecting plates arranged in a "〔", a cross connector is arranged between two adjacent connecting plates, the connecting plate is provided with a plurality of long holes, the head and tail ends of the connecting plate are respectively provided with open slots, the left and right ends of the cross connector are both adapted to the open slots, and the bottom of the phantom is provided with a T-shaped connector adapted to the long holes; fasteners are provided between the two ends of the ladder frame and the edge of the bed board, one side of the fastener is provided with a slot adapted to the edge of the bed board, the fastener is bolted to the bed board, the other side of the fastener is provided with a second protrusion adapted to the open slot, the second protrusion is bolted to one of the connecting plates; the T-shaped connector is provided with a third protrusion adapted to the open slot, and the third protrusion is bolted to the connecting plate.

[0028] As a further solution of the present invention, the mold body is a cubic structure, and cross-line grooves are provided in the centers of the six faces of the mold body.

[0029] In a fourth aspect, another laser positioning system measurement method, using the measurement phantom device of the laser positioning system, comprises the following steps:

[0030] Step 1: Use a laser tracker to determine the reference point coordinate system of the radiotherapy system;

[0031] Step 2: Project the positioning lines emitted by the laser positioning system onto the phantom to ensure that three laser lines are within the crosshair grooves of the phantom;

[0032] Step 3: Use contact-type ruby ​​and sapphire probes to randomly select six test points on the six surfaces of the phantom to obtain the projection coordinates of the six points;

[0033] Step 4: Synthesize the spatial graph of the six faces according to the projection coordinates of the six points in step 3, fit the central planes of any two faces to the planes constructed in the front and back, left and right, and top and bottom of the phantom, and obtain the intersection points of the three central planes, i.e., the coordinates of X, Y, and Z (X2, Y2, Z2);

[0034] Step 5. The distance between the X, Y, Z coordinates (X2, Y2, Z2) and the reference point (X1, Y1, Z1) in the laser positioning system is d:

[0035]

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] 1. Improve test accuracy: The present invention uses high-precision measurement tools and algorithms to more accurately evaluate the performance of the laser positioning system in complex environments, reduce positioning errors, and ensure the accuracy of treatment.

[0038] 2. Improve test efficiency: The present invention uses a new phantom to significantly improve test efficiency, reduce the complexity and time consumption of manual operation, enable the test to be completed in a shorter time, and reduce the risk of human error.

[0039] 3. Enhance repeatability and reliability: The present invention can ensure the repeatability and reliability of the test results, which helps to verify the long-term stability and consistency of the laser positioning system and provide strong support for clinical treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the structure of the measurement phantom device of the laser positioning system in Example 1;

[0041] Figure 2 Schematic diagram of the structure of the measurement phantom device of the laser positioning system in Example 3;

[0042] Figure 3 This is a schematic diagram of the measurement phantom device of the laser positioning system in Example 3 when viewed from the side. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with specific embodiments. The embodiments described below are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0044] Example 1

[0045] Introduction to the test phantom and method of straightness and verticality

[0046] Introduction to using the model:

[0047] like Figure 1 As shown, the measuring phantom device of the laser positioning system includes a bed board 10 , a phantom 30 , and a fixing frame for fixing the phantom 30 on one side of the bed board 10 .

[0048] The mold body 30 is a rectangular parallelepiped structure, and is provided with a plurality of first test holes for placing the measuring target ball of the laser tracker. The mold body 30 is also provided with a plurality of second test holes for placing the ruby / sapphire detection head. A cross-line groove 31 is also provided in the center of the mold body 30, and the line width should be ≤1mm to facilitate positioning of the laser isocenter.

[0049] The fixing frame includes two brackets, and the bracket includes two connecting plates 21. The connecting plates 21 are provided with multiple long holes 211. The head and tail ends of the connecting plates 21 are respectively provided with open grooves 212. A joint 23 is provided between the tail end of the connecting plate 21 and the mold body 30. A fastener 22 is provided between the head end of the connecting plate 21 and the edge of the bed board 10.

[0050] One end of the joint 23 is bolted to the mold body 30, and the other end of the joint 23 is provided with a first protrusion adapted to the opening groove 212, and the first protrusion is bolted to the rear end of the connecting plate 21;

[0051] A slot matching the edge of the bed board 10 is provided on one side of the fastener 22, and the fastener 22 is bolted to the bed board 10. A second protrusion matching the opening groove 212 is provided on the other side of the fastener 22, and the second protrusion is bolted to the head end of the connecting plate 21.

[0052] The mold body 30 is a rectangular parallelepiped, and it is recommended to use a metal material that is not easily deformed. The length is greater than 1.2m, and 10 holes are evenly spaced within a range of 1m (used to place the measuring target ball of the laser tracker or to place the ruby ​​or sapphire detection head. The hole diameters are different for different measuring devices. For example, the hole diameters for the ruby ​​and sapphire detection heads should be less than 3mm and 6mm respectively, and for the target ball, the hole diameter is 10mm).

[0053] The phantom 30 can be made into a detachable structure and can be disassembled into three parts for easy carrying to the test site.

[0054] 2. Test method:

[0055] 1. Project the positioning line emitted by the laser positioning system onto the phantom 30 to ensure that the isocenter coincides with the center of the phantom. Place the target ball or red / sapphire probe of the laser tracker at 10 points (the first test hole and the second test hole) and measure in the X, Y, and Z directions respectively.

[0056] 2. Fit the data points in each direction to obtain a straight line. The method can consider the functions of the laser tracker or absolute arm measurement system, or use EXCEL to calculate the least squares method, and calculate the distance from each point to the fitting straight line. The maximum deviation should not exceed 0.5mm, which meets the straightness measurement requirements of the standard.

[0057] 3. Through the above tests, the coordinate systems in the three directions of X, Y and Z are obtained. Through the functions of the laser tracker or the absolute arm measurement system, or the method of Excel calculating the perpendicularity of two lines in space, the angles between X and Y, between X and Z, and between Y and Z are calculated respectively, and the perpendicularity is calculated. The result should meet the requirements of the standard: it should not be greater than 0.2°.

[0058] 3. Calculation method of straightness:

[0059] The principle of least squares method can be used, that is:

[0060] The goal of fitting a straight line is to find a straight line y = ax + b such that Minimum, n is 10 points. Among them, x i and i are the spatial coordinates of the measured point, x i is the coordinate point of the measured direction, y i is one of the coordinate systems of the other two axes, a is the slope, and b is the intercept.

[0061] By taking the partial derivatives of the objective function with respect to a and b and setting them to 0, we get the calculation formulas for a and b:

[0062]

[0063] After calculating a and b, any point (x i ,y i ) to the straight line y = ax + b (fitting straight line) i is straightness;

[0064]

[0065] 4. Calculation method of verticality:

[0066] The method that can be determined based on the slope product is:

[0067] For two straight lines, assuming that their equations are y=k1x+b1 and y=k2x+b2, the condition for the two straight lines to be perpendicular is k1×k2=-1. If the points on the two straight lines are known to find the slope, for the straight line L1 passing through the points (x1, y1) and (x2, y2), the slope k1=(y2-y1) / (x2-x1), (x2≠x1); for the straight line L2 passing through the points (x3, y3) and (x4, y4), the slope k2=(y4-y3) / (x4-x3), (x4≠x3); if they are completely perpendicular, it can be defined as P=|k1×k2+1|, but there will be errors in the perpendicularity, so the formula for calculating the tangent value of the angle θ between the two straight lines is: The formula for calculating the angle based on inverse trigonometric functions is:

[0068] Example 2

[0069] The method of calculating straightness and verticality using Excel combined with the above calculation formula is as follows:

[0070] (1) Straightness calculation

[0071] ① Fitting straight line

[0072] First, suppose that the coordinates of the 10 points on a straight line are: (X1, Y1) ~ (X 10 ,Y 10 ), enter A1~A10 in column A, B1~B10 in column B, let the equation of the fitted line be Y=aX+b, and enter the X and Y coordinates of the 10 points into column A (from A1~A10) and column B (from B1~B10) in the Excel table respectively.

[0073] In a blank cell C1, enter “=SUM(A1:A10)” to calculate the sum of the X coordinates;

[0074] Similarly, enter "=SUM(B1:B10)" in the second blank cell C2 to calculate the sum of the Y coordinates;

[0075] In the third blank cell C3, enter "=SUMSQ(A1:A10)" to calculate the sum of the squares of the X coordinates;

[0076] In the fourth blank cell C4, enter "=SUMPRODUCT(A1:A10,B1:B10)" to calculate the sum of the products of the X and Y coordinates;

[0077] In the fifth blank cell C5, enter “=(10×C4-C1×C2) / (10×C3-C1×C1)” to calculate a (the slope of the fitted line);

[0078] In the sixth blank cell C6, enter “=(C2 / 10)-C5×(C1 / 10)” to calculate b (the intercept of the fitted line);

[0079] ②、Calculate the distance from each point to the fitting line

[0080] Enter the distance formula in cell D1

[0081] "=ABS(B1-C5A1-C6) / SQRT(1+C5C5)", calculate the distances from the 10 points in cells D1 to D10 to the fitted straight line in the same way. The largest value of the 10 points is the straightness value, and the result should not exceed 0.5mm.

[0082] (2) Verticality calculation

[0083] ①. Calculate the slope of two straight lines

[0084] If the coordinates of the first straight line are (X1, Y1)~(X 10 ,Y 10 ), enter them into columns A and B respectively, i.e. A1 to A10 are X1 to X10 , B1~B10 are Y1~Y 10 ; The coordinates of the second straight line are input into columns C and D, that is, C1 to C10 are X1 to X 10 , D1~D10 are Y1~Y 10 .

[0085] To calculate the slope of the first straight line, enter the formula "=SLOPE(A1:A10,B1:B10)" in cell E1. Similarly, to calculate the slope of the second straight line, enter the formula "=SLOPE(C1:C10,D1:D10)" in cell E2. Note that A1~A10 are the coordinates of the changing direction of the measuring hole of the first straight line, and D1~D10 are the coordinates of the changing direction of the measuring hole of the second straight line.

[0086] ② Calculate verticality

[0087] According to the calculation formula for the tangent of the angle between two straight lines, enter "=ATAN((E1-E2) / (1+E1*E2))" in cell F1 to get the radian value of the angle between the two straight lines. Enter "=F1*180 / 3.14" in cell F2 to get the angle value. The error between the absolute value of the calculated result and 90° is the perpendicularity, and the result should not be greater than 0.2°.

[0088] Advantages of using the phantom 30 of Example 1: convenient and fast, no need to move the treatment bed, only the target ball or the detection head needs to be placed, and the error of the treatment bed displacement introduced due to the movement of the treatment bed can be avoided; there are openings for various measurement points on the phantom, and a variety of measurement probes can be satisfied at the same time; each reference coordinate system does not need to be repeatedly positioned to measure multiple points, and 10 coordinate points can be measured in one positioning, which greatly improves the test efficiency.

[0089] Example 3

[0090] like Figure 2 , 3As shown, the fixing frame includes a ladder frame, the ladder frame includes three connecting plates 21 arranged in a "〔", a cross connector 24 is provided between two adjacent connecting plates 21, the connecting plate 21 is provided with a plurality of long holes 211, the first and last ends of the connecting plate 21 are respectively provided with open slots 212, the left and right ends of the cross connector 24 are both adapted to the open slots 212, and the bottom of the mold body 30 is provided with a T-shaped connector 32 adapted to the long holes 211; the ladder frame A fastener 22 is provided between both ends and the edge of the bed board 10, a slot matching the edge of the bed board 10 is provided on one side of the fastener 22, the fastener 22 and the bed board 10 are bolted together, and a second protrusion matching the opening slot 212 is provided on the other side of the fastener 22, and the second protrusion is bolted to one of the connecting plates 21; the T-shaped connecting piece 32 is provided with a third protrusion matching the opening slot 212, and the third protrusion is bolted to the connecting plate 21.

[0091] The mold body 30 is a cubic structure with a size of 15 cm×15 cm×15 cm. A cross-line groove 31 is provided in the center of each of the six faces of the mold body 30. The line width should be ≤1 mm and can be made of metal or epoxy resin.

[0092] Example 4

[0093] The test method corresponding to the measurement phantom device of the laser positioning system used in Example 3 is:

[0094] 1. Use a laser tracker to determine the reference point coordinate system of the radiotherapy system;

[0095] 2. Project the positioning lines emitted by the laser positioning system onto the mold body 30 to ensure that three laser lines are within the cross-line groove 31 of the mold body 30;

[0096] 3. Use contact-type ruby ​​and sapphire probes to randomly select 6 test points on the six surfaces, and the projection coordinates of the 6 points can be obtained;

[0097] 4. Through the above measurements, the synthesis function of a laser tracker (such as a laser tracker) can be used to synthesize the spatial graphs of the six surfaces, and the creation of the mid-plane function of the software function can be used to fit the center planes of any two surfaces of the planes constructed in the front and back, left and right, and top and bottom of the phantom 30, so as to obtain the intersection points of the three center planes, i.e., the coordinates of X, Y and Z;

[0098] 5. The distance between the X, Y, and Z coordinates of the laser positioning system obtained above and the reference point should not exceed 0.5 mm.

[0099] The formula for the distance between two points in space is:

[0100] In three-dimensional space, the distance formula between two points (X1, Y1, Z1) and (X2, Y2, Z2) is How to calculate reference point consistency using Excel:

[0101] Calculate the distance between two points in space

[0102] 1. Assume that the coordinates of the reference point of the radiotherapy system determined by the laser tracker are (X1, Y1, Z1), and the coordinates of the fitted center plane are (X2, Y2, Z2). Then: enter X1, Y1, Z1 in cells A1, B1, and C1 respectively, and enter X2, Y2, Z2 in cells A2, B2, and C2.

[0103] Enter the formula "=SQRT((A2-A1)^2+(B2-B1)^2+(C2-C1)^2)" in cell D1 to display the spatial distance between the two points. The result should not exceed 0.5mm.

[0104] In addition, it should be understood that those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A measuring phantom device of a laser positioning system, mounted on one side of a bed board (10), characterized in that: The measuring phantom device of the laser positioning system comprises a phantom (30) and a fixing frame used for fixing the phantom (30) on one side of a bed board (10).

2. The measuring phantom device of the laser positioning system according to claim 1, characterized in that: The mold body (30) is a rectangular parallelepiped structure, the mold body (30) is provided with a plurality of first test holes for placing a measuring target ball of a laser tracker, the mold body (30) is also provided with a plurality of second test holes for placing a ruby / sapphire detection head, and a crosshair groove (31) is also provided in the center of the mold body (30).

3. The measuring phantom device of the laser positioning system according to claim 2, characterized in that: The fixing frame comprises two brackets, and the brackets comprise two connecting plates (21), the connecting plates (21) are provided with a plurality of long holes (211), the connecting plates (21) are provided with opening grooves (212) at both ends, a joint (23) is provided between the rear end of the connecting plate (21) and the mold body (30), and a fastener (22) is provided between the front end of the connecting plate (21) and the edge of the bed board (10).

4. The measuring phantom device of the laser positioning system according to claim 3, characterized in that: One end of the joint (23) is connected to the mold body (30) by bolts, and the other end of the joint (23) is provided with a first protrusion adapted to the opening groove (212), and the first protrusion is connected to the rear end of the connecting plate (21) by bolts; A slot matching the edge of the bed board (10) is provided on one side of the fastener (22), and the fastener (22) and the bed board (10) are connected by bolts. A second protrusion matching the opening groove (212) is provided on the other side of the fastener (22), and the second protrusion is connected by bolts to the head end of the connecting plate (21).

5. The measurement phantom device of the laser positioning system according to claim 1, characterized in that: The fixing frame comprises a ladder frame, the ladder frame comprises three connecting plates (21) arranged in a "〔" shape, a cross connecting piece (24) is arranged between two adjacent connecting plates (21), the connecting plate (21) is provided with a plurality of long strip holes (211), the connecting plates (21) are respectively provided with opening grooves (212) at both ends, the left and right ends of the cross connecting piece (24) are both matched with the opening grooves (212), and the bottom of the mold body (30) is provided with a T-shaped connecting piece (32) matched with the long strip holes (211); the ladder frame A fastener (22) is provided between both ends and the edge of the bed board (10); a slot matching the edge of the bed board (10) is provided on one side of the fastener (22); the fastener (22) and the bed board (10) are bolted together; a second protrusion matching the opening slot (212) is provided on the other side of the fastener (22); the second protrusion is bolted together with one of the connecting plates (21); the T-shaped connecting piece (32) is provided with a third protrusion matching the opening slot (212); the third protrusion is bolted together with the connecting plate (21).

6. The measurement phantom device of the laser positioning system according to claim 5, characterized in that: The mold body (30) is a cubic structure, and the centers of the six faces of the mold body (30) are all provided with cross-line grooves (31).

7. A method for measuring a laser positioning system, characterized in that: The measuring phantom device using the laser positioning system as claimed in claims 1 to 4 comprises the following steps: Step 1, project the positioning line emitted by the laser positioning system onto the phantom to ensure that the isocenter and the center position of the phantom coincide with each other; there are a total of 10 first test holes and second test holes set on the phantom, and the target ball or red / sapphire detection head of the laser tracker is placed at the first test hole and the second test hole, respectively, and measurements are made in the three directions of X, Y, and Z; Step 2: Fit the data points in each direction to obtain a straight line, and calculate the distance from each point to the fitted straight line. The maximum deviation should not exceed 0.5 mm. Step 3: Through the above test, the coordinate systems of the three directions of X, Y and Z are obtained. The angles between X and Y, between X and Z, and between Y and Z are calculated respectively, and the verticality is calculated. The calculated verticality should not be greater than 0.2°.

8. The measuring method of the laser positioning system according to claim 7, characterized in that: The straightness calculation method includes the following steps: Calculate a and b according to the following formula: After calculating a and b, any point (x i ,y i ) to the fitting line i is straightness; The method for calculating verticality includes the following steps: For the two straight lines L1 and L2, for the straight line L1 passing through the points (x1, y1) and (x2, y2), the slope k1 = (y2-y1) / (x2-x1), x2≠x1; for the straight line L2 passing through the points (x3, y3) and (x4, y4), the slope k2 = (y4-y3) / (x4-x3), x4≠x3; The angle between the two lines is θ.

9. A method for measuring a laser positioning system, characterized in that: The measuring phantom device using the laser positioning system according to claim 5 or 6 comprises the following steps: Step 1: Use a laser tracker to determine the reference point coordinate system of the radiotherapy system; Step 2: Project the positioning lines emitted by the laser positioning system onto the phantom to ensure that three laser lines are within the crosshair grooves of the phantom; Step 3: Use contact-type ruby ​​and sapphire probes to randomly select six test points on the six surfaces of the phantom to obtain the projection coordinates of the six points; Step 4: Synthesize the spatial graph of the six faces according to the projection coordinates of the six points in step 3, fit the central planes of any two faces to the planes constructed in the front and back, left and right, and top and bottom of the phantom, and obtain the intersection points of the three central planes, i.e., the coordinates of X, Y, and Z (X2, Y2, Z2); Step 5. The distance between the X, Y, Z coordinates (X2, Y2, Z2) and the reference point (X1, Y1, Z1) in the laser positioning system is d:

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