A method of angle measurement for a cylindrical detector

Abstract

The application discloses a kind of cylindrical detector angle measurement method, comprising the following steps: setting the projection plane of cylindrical detector;Based on the single frame result obtained by actual measurement of cylindrical detector to radioactive source, all angles are traversed, and the assumed incident part and the assumed exit part are projected to the projection plane in a one-to-one manner to obtain the first projection point and the second projection point;The first projection point and the second projection point are made to correspond to each other by interpolation;The first projection point and the second projection point are multiplied and summed to obtain the inner product result;Based on Cauchy inequality, the angle with the maximum inner product is selected as the correct incident angle.The application utilizes the property of mathematical Cauchy inequality to accurately and efficiently calculate the incident angle, eliminating the trouble of estimating the attenuation factor in the traditional method and the error introduced thereby.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, and in particular to a method for measuring the angle of a cylindrical detector. Background Technology

[0002] Measuring the dose distribution generated by a medical linear accelerator executing a radiotherapy plan using a radiation detector is a widely adopted method for radiotherapy plan verification. One task in the plan verification process is to locate the position of the medical linear accelerator at a specific moment using measurement data, thereby determining the arm positioning error of the accelerator. Locating the radiation source position based on the measurement images is equivalent to determining the incident angle. Existing methods are mainly based on the assumption that a correct incident angle should be able to closely approximate the measurement results of the cylindrical incident portion after considering the cylinder's attenuation and the exit portion. The incident angle is determined by traversing all angles and finding the angle with the smallest difference between the attenuated incident and exit portions. However, the attenuation of the cylinder varies at different locations, making accurate estimation quite difficult. Inaccurate estimation affects the angle result, especially when the cylinder is hollow and other modules can be inserted.

[0003] This invention focuses on locating the radiation source position of a medical linear accelerator corresponding to a single frame measurement image based on a cylindrical double-layer high-energy ray detector. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for measuring the angle of a cylindrical detector.

[0005] The objective of this invention is achieved through the following technical solution: A method for measuring the angle of a cylindrical detector, comprising the following steps: S1, Set the projection plane of the cylindrical detector; S2, Based on the single-frame results obtained by the cylindrical detector for the actual measurement of the radiation source, traverse all angles and project the hypothetical incident part and hypothetical exit part onto the projection plane in a one-to-one correspondence manner to obtain the first projection point and the second projection point; S3, Make the first projection point and the second projection point correspond to each other by interpolation; S4, Multiply the first projection point and the second projection point and sum them to obtain the inner product result; S5, Based on Cauchy's inequality, select the angle with the largest inner product as the correct incident angle.

[0006] Preferably, the projection plane is determined as follows: any longitudinal section (A) passing through the center O of the cylindrical detector is selected as the projection plane (F).

[0007] Preferably, the first projection point and the second projection point are determined as follows: S201, the angle is defined by the angle between the second straight line between the radiation source S and the center O, and the third straight line perpendicular to the cross section of the cylindrical detector and passing through the center O, the angle range is 0°~359°, and it is traversed in increments of 1°; S202, the cylindrical detector is divided into an incident semicircle and an exit semicircle using the longitudinal section as the boundary; S203, the radiation source forms a fourth straight line in the cross section, which is divided into the hypothetical incident part and the hypothetical exit part using the projection plane as the boundary; S204, all points on the hypothetical incident part are selected and projected onto the projection plane to obtain several first projection points, or all points on the exit incident part are selected and projected onto the projection plane to obtain several second projection points.

[0008] Preferably, the first projection point and the second projection point are made to correspond to each other in the following manner: a number of points are inserted into the hypothetical incident portion and the hypothetical exit portion by linear interpolation, such that the number of the first projection point and the number of the second projection point are equal.

[0009] Preferably, the inner product result is derived from... Determine, where Iin is the projection of the incident surface and Iout is the projection of the exit surface.

[0010] This invention has the following advantages: it accurately and efficiently calculates the incident angle using the properties of the mathematical Cauchy inequality, eliminating the hassle of estimating the attenuation factor and the errors introduced by traditional methods. Attached Figure Description

[0011] Figure 1 This is a schematic diagram illustrating the principle of the cylindrical detector angle measurement method of the present invention; In the diagram, S is the radiation source, A is the first straight line, B is the second straight line, C is the third straight line, D is the fourth straight line, D1 is the assumed incident part, D2 is the assumed exiting part, F is the projection plane, G1 is the incident semicircle, and G2 is the exiting semicircle. Detailed Implementation

[0012] The present invention will be further described below with reference to the accompanying drawings. The scope of protection of the present invention is not limited to the following description: like Figure 1 As shown, the present invention provides a method for measuring the angle of a cylindrical detector, comprising the following steps: S1, Set the projection plane of the cylindrical detector; S2, based on the single-frame result obtained by the cylindrical detector for the actual measurement of the radiation source S, traverses all angles and projects the assumed incident part and the assumed exit part onto the projection plane in a one-to-one correspondence manner to obtain the first projection point and the second projection point. S3, interpolation is used to make the first projection point and the second projection point correspond to each other; S4, Multiply the first projection point and the second projection point and sum them to obtain the inner product result; S5. Based on Cauchy's inequality, the angle with the largest inner product is selected as the correct angle of incidence.

[0013] Preferably, the projection plane is determined as follows: any longitudinal section (A) passing through the center O of the cylindrical detector is selected as the projection plane (F).

[0014] Preferably, the first projection point and the second projection point are determined in the following manner: S201, the angle is defined by the angle between the second straight line B between the radiation source S and the center O, and the third straight line C that is perpendicular to the cross section of the cylindrical detector and passes through the center O. The angle range is 0° to 359°, and it is traversed in 1° increments. S202, the cylindrical detector is divided into an incident semicircle G1 and an exit semicircle G2 by the longitudinal section A as the boundary; S203, the radiation source S forms a fourth straight line D in the cross section and is divided into a hypothetical incident part D1 and a hypothetical exit part D2 by the projection plane F. S204, select all points on the assumed incident portion D1 and project them onto the projection plane F to obtain several first projection points, or select all points on the exiting incident portion D2 and project them onto the projection plane F to obtain several second projection points. All selected points on either the incident portion D1 or the exiting portion D2 are projected onto the projection plane F, thereby forming several first projection points and several second projection points.

[0015] Preferably, the first projection point and the second projection point are made to correspond to each other in the following manner: several points are inserted into the assumed incident part D1 and the assumed exit part D2 by linear interpolation, so that the number of the first projection point and the second projection point are equal.

[0016] Preferably, the inner product result is derived from... Determine, where Iin is the projection of the incident surface and Iout is the projection of the exit surface.

[0017] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring the angle of a cylindrical detector, characterized in that, Includes the following steps: S1, Set the projection plane of the cylindrical detector; S2, based on the single-frame result obtained by the actual measurement of the radiation source (S) by the cylindrical detector, traverses all angles and projects the assumed incident part and the assumed exit part onto the projection plane in a one-to-one correspondence manner to obtain the first projection point and the second projection point. S3, interpolation is used to make the first projection point and the second projection point correspond to each other; S4, Multiply the first projection point and the second projection point and sum them to obtain the inner product result; S5. Based on Cauchy's inequality, the angle with the largest inner product is selected as the correct angle of incidence.

2. The method for measuring the angle of a cylindrical detector according to claim 1, characterized in that, The projection plane shall be set as follows: Select any longitudinal section (A) that passes through the center O of the cylindrical detector as the projection plane (F).

3. The method for measuring the angle of a cylindrical detector according to claim 2, characterized in that, The first projection point and the second projection point are determined as follows: S201, the angle is defined by the angle between the second straight line (B) between the radiation source S and the center O, and the third straight line (C) that is perpendicular to the cross section of the cylindrical detector and passes through the center O. The angle range is 0° to 359°, and it is traversed in increments of 1°. S202, the cylindrical detector is divided into an incident semicircle (G1) and an exit semicircle (G2) using the longitudinal section (A) as the boundary. S203, the radiation source (S) is formed into a fourth straight line (D) in the cross section, and the projection plane (F) is used as the boundary to divide it into the assumed incident part (D1) and the assumed exit part (D2). S204, select all points on the assumed incident portion (D1) and project them onto the projection plane (F) to obtain a plurality of first projection points, or select all points on the outgoing incident portion (D2) and project them onto the projection plane (F) to obtain a plurality of second projection points.

4. The method for measuring the angle of a cylindrical detector according to claim 3, characterized in that, The first projection point and the second projection point are made to correspond to each other in the following manner: a number of points are inserted into the hypothetical incident portion (D1) and the hypothetical exit portion (D2) by linear interpolation, such that the number of the first projection point and the number of the second projection point are equal.

5. The method for measuring the angle of a cylindrical detector according to claim 3, characterized in that, The inner product result is... Determine, where Iin is the projection of the incident surface and Iout is the projection of the exit surface.

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