A position correction system and method for a portal imaging device

Abstract

The present invention discloses a position correction system and method for a portal imaging device, wherein the position correction method comprises the following steps: establishing a position correction parameter database for a portal imaging device; obtaining the position parameters of the current portal imaging device; calling the position correction parameter database according to the current position parameters of the portal imaging device, obtaining the correction parameters by interpolation; and performing position correction on the grayscale image generated by the portal imaging device according to the correction parameters. The present invention can perform efficient and accurate position correction on the portal imaging device, and provide accurate images for subsequent radiation source intensity reconstruction, positioning and placement, etc.

Description

Technical Field

[0001] The present invention relates to the application fields of nuclear energy and nuclear technology such as radiotherapy and industrial non-destructive testing, and in particular to a position correction system and method for a portal imaging device. Background Art

[0002] The portal imaging device generates grayscale images when receiving radiation exposure. Based on the grayscale images, the radiation source and medium can be reconstructed and analyzed. It has been widely used in the fields of radiotherapy dose monitoring, radiotherapy positioning, industrial non-destructive testing, and medical image reconstruction. Due to the influence of gravity, the portal imaging device will have a certain position deviation at different spatial positions, resulting in a certain position deviation in the generated grayscale image. The grayscale image needs to be positionally corrected to provide accurate input information for the reconstruction of the radiation source and medium. Therefore, the study of the position correction method of the portal imaging device is of great significance to radiotherapy monitoring, industrial testing, radiotherapy positioning, and medical image reconstruction.

[0003] At present, the position correction of the portal imaging device generally adopts the marking point method. The marking points are used to obtain the position correction parameters of the portal imaging device at different positions. This method requires pasting marking points at fixed positions of the accelerator field. This makes the accuracy of the position correction parameters directly related to the accuracy of pasting the marking points. Therefore, it is necessary to develop a method for calculating the position correction parameters of the portal imaging device directly based on the grayscale image. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a position correction system and method for a portal imaging device that can accurately perform position correction on grayscale images.

[0005] Technical solution: The position correction system of the portal imaging device of the present invention includes a radiation source, a portal imaging device module, a position correction module and a storage medium, wherein the portal imaging device module is kept facing the radiation source; the position correction module includes a grayscale image transmission module, a grayscale image preprocessing module, a position correction parameter database calculation module and a position correction parameter calculation module, wherein the grayscale image transmission module transmits the grayscale image collected by the portal imaging device from the portal imaging device to the position correction module, the grayscale image preprocessing module smoothes the collected grayscale image, the position correction parameter database calculation module calculates the position correction parameter database according to the input grayscale image and the corresponding position, and the position correction parameter module calculates the position correction parameters of the current position according to the acquired position parameters of the portal imaging device when the radiation source is irradiating.

[0006] The vertical line of the center point of the portal imaging device module passes through the ray source point, and the distance between the portal imaging device and the ray source point is a fixed value.

[0007] The present invention also includes a method for correcting the position of a portal imaging device, comprising the following steps:

[0008] (1) Establishing a position correction parameter database for the portal imaging device;

[0009] (2) obtaining the position parameters of the current portal imaging device;

[0010] (3) Based on the current position parameters of the portal imaging device, the position correction parameter database is called to obtain the correction parameters by interpolation;

[0011] (4) Performing position correction on the grayscale image generated by the portal imaging device according to the correction parameters.

[0012] In step (1), the step of establishing a position correction parameter database of a portal imaging device comprises the following steps:

[0013] (1.1) Turn on the radiation source to form a radiation field, irradiate the radiation field imaging devices at different positions, and collect the resulting grayscale images;

[0014] (1.2) Calculate the gradient field of the collected grayscale image along the X and Y directions, and confirm the image boundary coordinates according to the gradient field;

[0015] (1.3) The length, width and center point coordinates of each grayscale image are calculated based on the image boundary coordinates, and compared with the corresponding values ​​of the grayscale image at the reference position to obtain the position correction parameters of the portal imaging device at different positions.

[0016] In step (1.2), the step of calculating the gradient field of the acquired grayscale image along the X and Y directions and confirming the image boundary coordinates according to the gradient field specifically includes the following steps:

[0017] (1.2.1) For the grayscale image collected at the i-th position, select the grayscale values ​​of the two line segments in the X and Y directions that pass through the geometric center point of the grayscale image, and calculate the gradient value of the grayscale of the X-direction line segment respectively And the gradient value of the grayscale of the line segment in the Y direction Where i = 0, 1, ..., N, Gray i is the grayscale image collected at the i-th position;

[0018] (1.2.2) From left to right Conduct point-by-point assessment and record Maximum value position X left,i , and the minimum position X right，i , from top to bottom Conduct point-by-point assessment and record Maximum position Y top,i and minimum position Y down,i .

[0019] In step (1.3), the length, width and center point coordinate values ​​of each grayscale image are calculated and compared with the corresponding values ​​of the grayscale image at the reference position, specifically including the following steps:

[0020] (1.3.1) Calculate the coordinates of the center point of the grayscale image collected at the i-th position and the image length D in the X and Y directions x,i =X right,i -X left,i , D y,i =Y top,i -Y down,i ; Among them, X left,i is the left boundary value of the grayscale image field collected at the i-th position, X right,i is the right boundary value of the grayscale image field collected at the i-th position, Y top,i is the upper boundary value of the grayscale image field collected at the i-th position, Y down,i is the lower boundary value of the grayscale image field collected at the i-th position;

[0021] (1.3.2) Compare the calculated value of (1.3.1) with the corresponding value X of the grayscale image at the reference position mid,0 , Y mid,0 , D x,0 , D y,0 By comparison, the position correction parameters of the portal imaging device at the i-th position are calculated, which are the X-direction correction parameters dif x,i =X mid,i -X mid,0 , Y direction correction parameter dif y,i =Y mid,i -Y mid,0 , source to portal imaging device distance correction parameters

[0022] Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects: (1) the image boundary is obtained based on the grayscale gradient to obtain accurate position correction parameters, and there is no need to add marking points, thereby improving the applicability of the correction method; (2) it solves the problem that the traditional marking point method uses marking points to obtain the position correction parameters of the portal imaging device at different positions, and there is a need to stick marking points at fixed positions of the accelerator portal, and the accuracy of the position correction parameters is directly related to the accuracy of the marking point sticking. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described in detail below in conjunction with specific implementation methods and the accompanying drawings of the specification.

[0025] The position correction system of the present invention comprises a ray source module, a portal imaging device module, a position correction module and a corresponding storage medium. The portal imaging device module is kept facing the ray source, that is, the vertical line of the center point of the portal imaging device passes through the ray source point, and the distance between the portal imaging device and the ray source point is a fixed value;

[0026] The position correction module includes a grayscale image transmission module, a grayscale image preprocessing module, a position correction parameter database calculation module and a position correction parameter calculation module, wherein the grayscale image transmission module can transmit the grayscale image collected by the portal imaging device from the portal imaging device to the position correction module, the grayscale image preprocessing module smoothes the collected grayscale image, the position correction parameter database calculation module calculates the position correction parameter database based on the input grayscale image and the corresponding position, and the position correction parameter module calculates the position correction parameters of the current position based on the acquired position parameters of the portal imaging device when the radiation source is irradiated.

[0027] In this embodiment, position correction of a portal imaging device of a radiation dose detection system is taken as an example.

[0028] like Figure 1 As shown, the present invention also includes a method for correcting the position of a portal imaging device, comprising the following steps:

[0029] (1) Establishing a position correction parameter database of a portal imaging device, including the following steps:

[0030] (1.1) Turn on the radiation source to form a radiation field, irradiate the radiation field imaging devices at different positions, and collect the resulting grayscale images;

[0031] Specifically, 0 to 355 degrees are divided into 72 angles of 5 degrees. Each angle accelerator forms a 10 cm × 10 cm field at the position of the portal imaging device for irradiation. The irradiation intensity is 50 MU. No medium is placed between the source and the portal imaging device. The distance is 140 cm. 72 grayscale images generated on the portal imaging device are collected.

[0032] (1.2) Calculating the gradient field of the acquired grayscale image along the X and Y directions, and confirming the image boundary coordinates according to the gradient field, specifically including the following steps:

[0033] (1.2.1) For the grayscale image collected at the i-th position, select the grayscale values ​​of the two line segments in the X and Y directions that pass through the geometric center point of the grayscale image, and calculate the gradient value of the grayscale of the X-direction line segment respectively And the gradient value of the grayscale of the line segment in the Y direction Where i = 0, 1, ..., 72, Gray i is the grayscale image collected at the i-th position;

[0034] (1.2.2) From left to right Conduct point-by-point assessment and record Maximum value position X left,i , and the minimum position X right,i , from top to bottom Conduct point-by-point assessment and record Maximum position Y top,i and minimum position Y down,i .

[0035] (1.3) Calculating the length, width and center point coordinates of each grayscale image according to the image boundary coordinates, and comparing them with the corresponding values ​​of the grayscale image at the reference position to obtain the position correction parameters of the portal imaging device at different positions; specifically comprising the following steps:

[0036] (1.3.1) Calculate the coordinates of the center point of the grayscale image collected at the i-th position and the image length D in the X and Y directions x,i =X right,i -X left,i , D y,i =Y top,i -Y down,i ; Among them, X left,i is the left boundary value of the grayscale image field collected at the i-th position, X right,i is the right boundary value of the grayscale image field collected at the i-th position, Y top,i is the upper boundary value of the grayscale image field collected at the i-th position, Y down,i is the lower boundary value of the grayscale image field collected at the i-th position;

[0037] (1.3.2) Compare the calculated value of (1.3.1) with the corresponding value X of the grayscale image at the reference position mid,0 , Y mid,0 , D x,0 , D y,0 By comparison, the position correction parameters of the portal imaging device at the i-th position are calculated, which are the X-direction correction parameters dif x,i =X mid,i -X mid,0 , Y direction correction parameter dif y,i =Y mid,i -Y mid,0 , source to portal imaging device distance correction parameters

[0038] (2) obtaining the position parameters of the current portal imaging device;

[0039] (3) Based on the current position parameters of the portal imaging device, the position correction parameter database is called to obtain the correction parameters by interpolation;

[0040] (4) Performing position correction on the grayscale image generated by the portal imaging device according to the correction parameters.

Claims

1. A method for position correction of a portal imaging device, characterized in that: The position correction method of the portal imaging device is applied to the position correction system of the portal imaging device, the position correction system of the portal imaging device includes a ray source, a portal imaging device, a position correction module and a storage medium, the portal imaging device and the ray source are kept facing each other; the position correction module includes a grayscale image transmission module, a grayscale image preprocessing module, a position correction parameter database calculation module and a position correction parameter calculation module, wherein the grayscale image transmission module transmits the grayscale image collected by the portal imaging device from the portal imaging device to the position correction module, the grayscale image preprocessing module performs smoothing on the collected grayscale image, the position correction parameter database calculation module calculates the position correction parameter database according to the input grayscale image and the corresponding position, and the position correction parameter calculation module calculates the position correction parameters of the current position according to the acquired position parameters of the portal imaging device when the ray source is irradiating; The correction method of the position correction system of the portal imaging device comprises the following steps: (1) Establishing a position correction parameter database for the portal imaging device; (2) obtaining the position parameters of the current portal imaging device; (3) Based on the current position parameters of the portal imaging device, the position correction parameter database is called to obtain the correction parameters by interpolation; (4) performing position correction on the grayscale image generated by the portal imaging device according to the correction parameters; In step (1), the step of establishing a position correction parameter database of a portal imaging device comprises the following steps: (1.1) Turn on the radiation source to form a radiation field, irradiate the radiation field imaging devices at different positions, and collect the resulting grayscale images; (1.2) Calculate the gradient field of the collected grayscale image along the X and Y directions, and confirm the image boundary coordinates according to the gradient field; (1.3) Calculating the length, width and center point coordinates of each grayscale image based on the image boundary coordinates, and comparing them with the corresponding values ​​of the grayscale image at the reference position to obtain the position correction parameters of the portal imaging device at different positions; In step (1.2), the step of calculating the gradient field of the acquired grayscale image along the X and Y directions and confirming the image boundary coordinates according to the gradient field specifically includes the following steps: (1.2.1) For the grayscale image collected at the i-th position, select the grayscale values ​​of the two line segments in the X and Y directions that pass through the geometric center point of the grayscale image, and calculate the gradient value of the grayscale of the X-direction line segment respectively And the gradient value of the grayscale of the line segment in the Y direction Where i = 0, 1, ..., N, Gray i is the grayscale image collected at the i-th position; (1.2.2) From left to right Conduct point-by-point assessment and record Maximum value position X left,i and minimum position X right，i , from top to bottom Conduct point-by-point assessment and record Maximum value position Y top，i and minimum position Y down，i .

2. The method for position correction of a portal imaging device according to claim 1, characterized in that: The vertical line of the center point of the portal imaging device passes through the ray source point, and the distance between the portal imaging device and the ray source point is a fixed value.

3. The position correction method of the portal imaging device according to claim 1, characterized in that: In step (1.3), the length, width and center point coordinate values ​​of each grayscale image are calculated and compared with the corresponding values ​​of the grayscale image at the reference position, specifically including the following steps: (1.3.1) Calculate the coordinates of the center point of the grayscale image collected at the i-th position and the image length D in the X and Y directions x,i =X right，i -X left,i , D y，i =Y top，i -Y down，i ; Among them, X left，i is the left boundary value of the grayscale image field collected at the i-th position, X right，i is the right boundary value of the grayscale image field collected at the i-th position, Y top，i is the upper boundary value of the grayscale image field collected at the i-th position, Y down，i is the lower boundary value of the grayscale image field collected at the i-th position; (1.3.2) Compare the calculated value of (1.3.1) with the corresponding value X of the grayscale image at the reference position mid，0 , Y mid，0 , D x,0 , D y,0 By comparison, the position correction parameters of the portal imaging device at the i-th position are calculated, which are the X-direction correction parameters dif x，i =X mid，i -X mid，0 , Y direction correction parameter dif y，i =Y mid，i -Y mid，0 , source to portal imaging device distance correction parameters

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