Measuring phantom device of laser positioning system

Abstract

The utility model relates to a phantom measuring device of a laser positioning system, and belongs to the field of radiotherapy. The measuring phantom device of the laser positioning system comprises a phantom body and a fixing frame used for fixing the phantom body on one side of a bed board. According to the invention, a new die body is used, so that the test efficiency is remarkably improved. 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 errors is reduced; the repeatability and reliability of the test result are high, the long-term stability and consistency of the laser positioning system can be verified, and powerful support is provided for clinical treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radiotherapy technology, in particular to a measuring phantom device of a laser positioning system. BACKGROUND

[0002] In the field of radiotherapy, the core of radiotherapy is to accurately position the tumor position and ensure that the radiation can accurately and efficiently act on the tumor tissue while minimizing damage to the surrounding normal tissue. Laser positioning technology, as one of the key technologies in modern radiotherapy, its accuracy and stability are directly related to the treatment effect and the prognosis of patients.

[0003] YY / T 1537-2017 "Performance and Test Methods for Laser Positioning System for Radiotherapy" specifies the performance and test methods of the laser positioning system for radiotherapy, including the straightness of the laser line, the perpendicularity 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 provides some new test models to meet the needs of testing. SUMMARY

[0005] The present application is a new test method for the straightness of the laser line, the perpendicularity of the laser cross positioning line and the consistency with the reference point. This method uses a laser tracker or an absolute arm measurement system for testing.

[0006] The principle of using a laser tracker for testing: 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 the predetermined path, the reflected light will return to the laser tracker according to the principle of equal incidence angle and reflection angle. 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 by comparing the two straightness values, the perpendicularity of the target surface can be calculated.

[0007] Measurement principle of absolute arm measurement system:

[0008] An absolute arm measurement system is a measurement device based on robotic arm and sensor technology. While its measurement principle differs from that of a laser tracker, it can still achieve high-precision measurements. It uses sensors, such as laser rangefinders or contact probes, mounted at the end of a robotic arm to contact the object being measured and acquire measurement data. Then, using advanced algorithms and mathematical models, the measurement data is converted into the object's three-dimensional coordinates and shape information, thereby enabling the measurement of straightness and perpendicularity. Its advantages include: the ability to measure points obstructed by external forces that are inconvenient for laser trackers; and its small size, making it easy to carry and move, suitable for on-site measurements.

[0009] The technical solution of the present invention is as follows:

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

[0011] As a further embodiment of the present invention, the mold body is a cuboid structure, the mold body is provided with a plurality of first test holes for placing the measurement target ball of the laser tracker, the mold body is also provided with a plurality of second test holes for placing the ruby / sapphire probe, and a crosshair groove is provided in the center of the mold body.

[0012] As a further embodiment of the present invention, the fixing frame includes two supports, each support including two connecting plates, each connecting plate having multiple elongated holes, each connecting plate having an opening slot at both ends, a joint between the tail end of the connecting plate and the mold body, and a fastener between the head end of the connecting plate and the edge of the bed board.

[0013] As a further embodiment of the present invention, one end of the connector is bolted to the mold body, and the other end of the connector is provided with a first protrusion adapted to the opening groove, and the first protrusion is bolted to the tail end of the connecting plate.

[0014] One side of the fastener is provided with a slot that matches the edge of the bed board, and the fastener is bolted to the bed board. The other side of the fastener is provided with a second protrusion that matches the opening slot, and the second protrusion is bolted to the first end of the connecting plate.

[0015] Secondly, one method for measuring a laser positioning system, using the aforementioned laser positioning system's measuring phantom device, includes the following steps:

[0016] Step 1: Project the positioning line emitted by the laser positioning system onto the phantom, ensuring that the center point coincides with the center of the phantom; there are a total of 10 first and second test holes on the phantom. Place the target ball of the laser tracker or the ruby / sapphire probe at the first and second test holes respectively, and measure in the X, Y, and Z directions respectively.

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

[0018] Step 3: Through the above tests, we obtained the coordinate system in the three directions of X, Y and Z. We calculated the angles between X and Y, X and Z and Y and Z respectively, and calculated the perpendicularity. The calculated perpendicularity should not be greater than 0.2°.

[0019] As a further aspect of the present invention, the method for calculating straightness includes 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 using the following formulas:

[0021]

[0022] After calculating a and b, any point (x) i ,y i The distance d from the fitted line i For straightness;

[0023]

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

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

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

[0027] Thirdly, in the measurement phantom device of the laser positioning system, the fixing frame includes a trapezoidal frame, which includes three connecting plates arranged in a "〔" shape. A cross connector is provided between two adjacent connecting plates. The connecting plates are provided with multiple elongated holes. Opening slots are provided at both ends of the connecting plates. The left and right ends of the cross connector are adapted to the opening slots. A T-shaped connector adapted to the elongated holes is provided at the bottom of the phantom. Fasteners are provided between the two ends of the trapezoidal frame and the edge of the bed board. A slot adapted to the edge of the bed board is provided on one side of the fastener. The fastener is bolted to the bed board. A second protrusion adapted to the opening slot is provided on the other side of the fastener. The second protrusion is bolted to one of the connecting plates. The T-shaped connector is provided with a third protrusion adapted to the opening slot. The third protrusion is bolted to the connecting plate.

[0028] As a further embodiment of the present invention, the mold body is a cube structure, and a cross groove is provided in the center of each of the six faces of the mold body.

[0029] Fourthly, another measurement method using a laser positioning system, employing the aforementioned laser positioning system's measurement phantom device, includes 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 mold body, ensuring that there are three laser lines within the crosshair grooves of the mold body;

[0032] Step 3: Using contact-type ruby ​​and sapphire probes, select 6 test points on any of the six faces of the phantom to obtain the projected coordinates of the 6 points;

[0033] Step 4: Based on the projected coordinates of the 6 points in Step 3, synthesize the spatial diagram of the 6 surfaces. Fit the center plane of any two surfaces to the planes constructed by the front, back, left, right and up of the model to obtain the intersection point of the three center planes, that is, the coordinates of X, Y and Z (X2, Y2, Z2).

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

[0035]

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

[0037] 1. Improved testing accuracy: This invention utilizes high-precision measurement tools and algorithms to more accurately evaluate the performance of laser positioning systems in complex environments, reduce positioning errors, and ensure the accuracy of treatment.

[0038] 2. Improved Testing Efficiency: This invention utilizes a novel phantom, significantly improving testing efficiency. It reduces the complexity and time-consuming nature of manual operations, enabling tests to be completed in a shorter time and lowering the risk of human error.

[0039] 3. Enhanced repeatability and reliability: This invention can ensure the repeatability and reliability of test results, which helps to verify the long-term stability and consistency of the laser positioning system and provides strong support for clinical treatment. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the measuring phantom device of the laser positioning system in Example 1;

[0041] Figure 2 This is a schematic diagram of the measuring phantom device of the laser positioning system in Example 3;

[0042] Figure 3 This is a side view of the measurement phantom device of the laser positioning system in Example 3. Detailed Implementation

[0043] The present invention will be described in detail below with reference to specific embodiments. These embodiments are merely some, not all, implementations of the present invention. All other implementations obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] Introduction to test models and methods for straightness and perpendicularity

[0046] Introduction to using the phantom:

[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 to one side of the bed board 10.

[0048] The mold 30 has a cuboid structure and is provided with a plurality of first test holes for placing the measurement target ball of the laser tracker. The mold 30 is also provided with a plurality of second test holes for placing the ruby / sapphire probe. A crosshair groove 31 with a line width of ≤1mm is also provided in the center of the mold 30 to facilitate the positioning of the laser isocenter.

[0049] The fixing frame includes two supports, each support including two connecting plates 21. The connecting plates 21 are provided with multiple elongated holes 211. The first and last ends of the connecting plates 21 are respectively provided with opening slots 212. The last end of the connecting plate 21 is provided with a joint 23 between it and the mold body 30. The first end of the connecting plate 21 is provided with a fastener 22 between it and the edge of the bed board 10.

[0050] One end of the connector 23 is bolted to the mold body 30, and the other end of the connector 23 is provided with a first protrusion that matches the opening slot 212. The first protrusion is bolted to the tail end of the connecting plate 21.

[0051] One side of the fastener 22 is provided with a slot that matches the edge of the bed board 10. The fastener 22 is bolted to the bed board 10. The other side of the fastener 22 is provided with a second protrusion that matches the opening slot 212. The second protrusion is bolted to the first end of the connecting plate 21.

[0052] The phantom 30 is a cuboid, and it is recommended to use a metal material that is not easily deformed. The length is greater than 1.2m. Within a 1m range, 10 holes are equally spaced (for placing the measuring target ball of the laser tracker or for placing ruby ​​or sapphire probes. The diameter of the holes is different for different measuring devices. For example, the diameter of the holes for ruby ​​and sapphire probes should be less than 3mm and 6mm respectively, and the diameter of the holes for the target ball should be 10mm).

[0053] The mold 30 can be made into a detachable structure, which can be disassembled into three parts, making it convenient to carry to the test site.

[0054] 2. Testing Method:

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

[0056] 2. Fit a straight line to the data points in each direction. This can be done by using the built-in function of a laser tracker or absolute arm measurement system, or by using the least squares method in Excel to calculate the distance from each point to the fitted line. The maximum deviation should not exceed 0.5mm, which meets the straightness measurement requirements in the standard.

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

[0058] 3. Method for calculating straightness:

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

[0060] The goal of fitting a straight line is to find a straight line y = ax + b such that... The minimum is n, where n is 10 points. Where x i and y i These are the spatial coordinates of the measured point, x and y. i It is the coordinate point of the direction being measured, y i It is a coordinate system that can be chosen from any of the other two axes, where 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 respectively and setting them to 0, we obtain the formulas for calculating a and b:

[0062]

[0063] After calculating a and b, any point (x) i ,y i The distance d from the line y = ax + b (the fitted line) to the line y = ax + b i For straightness;

[0064]

[0065] 4. Method for calculating verticality:

[0066] One method that can be used is based on the slope product, namely:

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

[0068] Example 2

[0069] The method for calculating straightness and perpendicularity using Excel and the above formulas is as follows:

[0070] (1) Straightness calculation

[0071] ① Fitting a straight line

[0072] First, assume that the coordinates of 10 points along a certain straight line are: (X1, Y1) ~ (X... 10 ,Y 10 Enter A1 to A10 in column A and B1 to B10 in column B. Let the equation of the fitted line be Y = aX + b. Enter the X coordinates and Y coordinates of the 10 points into column A (from A1 to A10) and column B (from B1 to B10) of the Excel spreadsheet.

[0073] Enter "=SUM(A1:A10)" in a blank cell C1 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] Enter "=SUMSQ(A1:A10)" in the third blank cell C3 to calculate the sum of squares of the X coordinates;

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

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

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

[0079] ② Calculate the distance from each point to the fitted line.

[0080] Enter the distance formula in cell D1

[0081] The formula "=ABS(B1-C5A1-C6) / SQRT(1+C5C5)" is used to calculate the distance from the 10 points in cells D1 to D10 to the fitted line. The largest value among 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 the two straight lines.

[0084] If the coordinates of the first straight line are (X1, Y1) ~ (X 10 ,Y 10 Enter the values ​​into columns A and B respectively, i.e., A1 to A10 are X1 to X.10 B1 to B10 are Y1 to Y 10 The coordinates of the second line are entered into columns C and D, i.e., C1 to C10 correspond to X1 to X2. 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 to A10 are the coordinates of the changing direction of the measuring holes on the first straight line, and D1 to D10 are the coordinates of the changing direction of the measuring holes on the second straight line.

[0086] ② Calculate verticality

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

[0088] Advantages of using the phantom 30 of Example 1: It is convenient and quick, without moving the treatment bed, only the target ball or probe needs to be placed, and it can avoid the error of treatment bed displacement caused by the movement of the treatment bed; the phantom has openings for various measurement points, and can meet the needs of multiple measurement probes at the same time; each reference coordinate system does not need to be repeatedly set up in order to measure multiple points, and 10 coordinate points can be measured in one set up, which greatly improves the testing efficiency.

[0089] Example 3

[0090] like Figure 2 , 3As shown, the fixing frame includes a trapezoidal frame, which includes three connecting plates 21 arranged in a "〔" shape. A cross connector 24 is provided between adjacent connecting plates 21. The connecting plates 21 are provided with multiple elongated holes 211. Opening slots 212 are provided at both ends of the connecting plates 21. The left and right ends of the cross connector 24 are adapted to the opening slots 212. The bottom of the mold body 30 is provided with a T-shaped connector 32 adapted to the elongated holes 211. The trapezoidal frame Fasteners 22 are provided at both ends of the fastener and between the fastener and the edge of the bed board 10. One side of the fastener 22 is provided with a slot that matches the edge of the bed board 10. The fastener 22 is bolted to the bed board 10. The other side of the fastener 22 is provided with a second protrusion that matches the opening slot 212. The second protrusion is bolted to one of the connecting plates 21. The T-shaped connector 32 is provided with a third protrusion that matches the opening slot 212. The third protrusion is bolted to the connecting plate 21.

[0091] The mold 30 is a cube with dimensions of 15cm×15cm×15cm. Each of the six faces of the mold 30 has a cross groove 31 in the center with a line width of ≤1mm. It 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:

[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 30, ensuring that there are three laser lines within the crosshair groove 31 of the mold 30;

[0096] 3. By using a contact-type ruby ​​or sapphire probe to randomly select 6 test points on the six sides, the projected coordinates of the 6 points can be obtained;

[0097] 4. Based on the above measurements, the synthesis function of a laser tracker (such as a laser tracker) can be used to synthesize a spatial map of 6 faces. Then, using the software's midplane creation function, the center plane of any two faces can be fitted to the planes constructed by the front, back, left, right, and top and bottom of the model 30. This will give the intersection point of the three center planes, i.e., the coordinates of X, Y, and Z.

[0098] 5. The distance between the X, Y, 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:

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

[0101] Distance between two points in computation space

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

[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] Furthermore, it should be understood that those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can 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 for a laser positioning system, installed on one side of a bed board (10), characterized in that: The measuring phantom device of the laser positioning system includes a phantom (30) and a fixing frame for fixing the phantom (30) to one side of the bed board (10).

2. The measuring phantom device for the laser positioning system according to claim 1, characterized in that: The mold (30) has a cuboid structure. The mold (30) is provided with a plurality of first test holes for placing the measurement target ball of the laser tracker. The mold (30) is also provided with a plurality of second test holes for placing the ruby / sapphire probe. A cross groove (31) is also provided in the center of the mold (30).

3. The measuring phantom device for the laser positioning system according to claim 2, characterized in that: The fixing frame includes two supports, each support including two connecting plates (21). The connecting plates (21) are provided with multiple elongated holes (211). The two ends of the connecting plates (21) are respectively provided with opening slots (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).

4. The measuring phantom device for the laser positioning system according to claim 3, characterized in that: One end of the connector (23) is bolted to the mold body (30), and the other end of the connector (23) is provided with a first protrusion that matches the opening slot (212). The first protrusion is bolted to the tail end of the connecting plate (21). The fastener (22) has a slot on one side that matches the edge of the bed board (10), and the fastener (22) is bolted to the bed board (10). The fastener (22) has a second protrusion on the other side that matches the opening slot (212), and the second protrusion is bolted to the head end of the connecting plate (21).

5. The measuring phantom device for the laser positioning system according to claim 1, characterized in that: The fixing frame includes a trapezoidal frame, which includes three connecting plates (21) arranged in a "〔" shape. A cross connector (24) is provided between two adjacent connecting plates (21). The connecting plates (21) are provided with multiple elongated holes (211). Opening slots (212) are provided at both ends of the connecting plates (21). The left and right ends of the cross connector (24) are adapted to the opening slots (212). The bottom of the mold body (30) is provided with a T-shaped connector (32) adapted to the elongated holes (211). The trapezoidal frame Fasteners (22) are provided at both ends and between the edges of the bed board (10). One side of the fastener (22) is provided with a slot that matches the edge of the bed board (10). The fastener (22) is bolted to the bed board (10). The other side of the fastener (22) is provided with a second protrusion that matches the opening slot (212). The second protrusion is bolted to one of the connecting plates (21). The T-shaped connector (32) is provided with a third protrusion that matches the opening slot (212). The third protrusion is bolted to the connecting plate (21).

6. The measuring phantom device for the laser positioning system according to claim 5, characterized in that: The mold (30) has a cubic structure, and a cross groove (31) is provided in the center of each of the six faces of the mold (30).

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