Method and system for determining two-dimensional dose modulation curve based on positioning image

Abstract

The invention discloses a method and a system for determining a two-dimensional dose modulation curve based on a positioning image. The method for determining the two-dimensional dose modulation curve based on the positioning image comprises the following steps: performing positioning image acquisition and contour extraction on a target; acquiring pixel-level attenuation projection data of the target scanning area, and reconstructing an attenuation curve of the target scanning area in the Z-axis direction and the X-Y plane; constructing a dose-noise-attenuation three-dimensional mapping table according to the calibration coefficient, the noise standard deviation and the attenuation value obtained by the motif test; and based on the dose-noise-attenuation three-dimensional mapping table, the Z-axis direction attenuation curve and the X-Y plane attenuation curve, generating a dose modulation curve of the target scanning area in the Z-axis direction and the X-Y plane. According to the application, the z-axis and x-y plane dose modulation curves are directly generated based on the positioning image, and combined dose modulation is realized, so that radiation dose distribution in a three-dimensional space is optimized, the cost and the radiation quantity are reduced, and the method is also suitable for scanning objects of different body types.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and particularly to a method and system for determining a two-dimensional dose modulation curve based on a positioning image. Background Art

[0002] In CT imaging, dose modulation technology balances image quality and radiation safety by dynamically adjusting the radiation dose, and its core is to establish a mapping relationship between "anatomical structure attenuation - radiation dose". The following bottlenecks exist in the prior art: 1. Limitation of single-dimensional modulation: Traditional methods only use the forward positioning image to generate the dose modulation curve in the Z-axis direction, and cannot obtain the tissue thickness difference in the cross-section, that is, the X-Y plane, resulting in the dose optimization in the X-Y plane relying on additional tomographic scans or hardware upgrades, such as dual detectors, increasing costs and radiation dose.

[0003] 2. Single algorithm path: Most of the prior art uses region segmentation or machine learning models, and does not propose an analytical algorithm based on the principle of geometric projection, making it difficult to ensure the universality for patients with different body types.

[0004] 3. Strong hardware dependence: The solutions involving X-Y plane modulation generally rely on additional devices, such as stereo cameras and structured light, which limit the compatibility with mainstream CT models. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for determining a two-dimensional dose modulation curve based on a positioning image to solve the problems of single-dimensional modulation limitation, single algorithm path, and strong hardware dependence of the existing dose modulation technology.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is: A method for determining a two-dimensional dose modulation curve based on a positioning image includes the following steps: Performing positioning image acquisition and contour extraction on the target; Obtaining pixel-level attenuation projection data of the target scanning area, and reconstructing the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane; Constructing a three-dimensional dose-noise-attenuation mapping table according to the calibration coefficient, noise standard deviation, and attenuation value obtained from the phantom test; Generating the dose modulation curves of the target scanning area in the Z-axis direction and the X-Y plane based on the three-dimensional dose-noise-attenuation mapping table, the attenuation curve in the Z-axis direction, and the attenuation curve in the X-Y plane.

[0007] Further, performing positioning image acquisition and contour extraction on the target is specifically as follows: Performing body position calibration to align the central axis of the target with the long axis of the scanning bed; Performing data acquisition to acquire the forward positioning image and the lateral positioning image of the target; Contour extraction, the target contours in the forward positioning image and the lateral positioning image are extracted by the Canny operator.

[0008] Furthermore, the pixel-level attenuation projection data of the target scanning area is obtained, and the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane are reconstructed as follows: Step S1: Determine the projection peak value; The cross-section of the target is modeled as an ellipse. Define the semi-major axis of the elliptical cross-section corresponding to each Z coordinate as a(z), the semi-minor axis as b(z), which extends along the Z-axis direction. The attenuation coefficient μ(z) within any elliptical cross-section is uniform and is 0 outside the elliptical cross-section; Perform forward projection along the Y-axis direction and calculate the forward projection attenuation data: ; Forward projection peak value ; Perform lateral projection along the X-axis direction and calculate the lateral projection attenuation data: ; Lateral projection peak value ; where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Reconstruct the attenuation curve in the Z-axis direction; For each Z coordinate, set the larger value among the forward projection peak value and the lateral projection peak value as the maximum attenuation value, and the attenuation curve in the Z-axis direction is obtained as: ; Step S3: Reconstruct the attenuation curve in the X-Y plane; Based on the principle of elliptical geometric projection, the attenuation curve in the X-Y plane at the projection angle θ is obtained as: ; where the projection angle θ refers to the angle between the projection direction of the ray and the x-axis in the X-Y plane corresponding to any z coordinate.

[0009] Furthermore, image acquisition and contour extraction of the target are performed as follows: Posture calibration to align the central axis of the target with the long axis of the scanning bed; Data acquisition, acquiring the forward positioning image or the lateral positioning image of the target; Contour extraction, extracting the target contour in the forward positioning image or the lateral positioning image by the Canny operator.

[0010] Furthermore, when acquiring the forward positioning image of the target, the pixel-level attenuation projection data of the target scanning area is obtained, and the attenuation curve of the target scanning area in the Z-axis direction and the XY plane is reconstructed, as follows: Step S1: determine the forward projection peak; The cross section of the target is modeled as an ellipse, and the semi-major axis of the ellipse corresponding to each Z coordinate is defined as a(z), and the semi-minor axis is defined as b(z). Extending along the Z axis, the attenuation coefficient μ(z) within any ellipse is uniform and is 0 outside the ellipse. Perform forward projection along the Y-axis direction and calculate the forward projection attenuation data: ; Forward projection width , find the semi-major axis ; Forward projection peak ; Where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Determine the lateral projection peak value by using the QUAD algorithm; Calculate the total forward projection attenuation and integrate along the X-axis: ; Simultaneous equations ; Find the peak value of the lateral projection ; Among them, π is the ratio of circumference to diameter; The relationship between the semi-major axis a(z) and the semi-minor axis b(z) is set to , based on the average proportion of human anatomy, the k value range is 0.6~0.8. After adding the k value constraint, the range of the attenuation coefficient μ(z) is: ; ; The average attenuation coefficient of the target scanning area is set to , and the lateral projection peak is obtained ; Step S3: reconstructing the attenuation curve in the Z-axis direction; For each Z coordinate, the larger of the forward projection peak and the lateral projection peak is set as the maximum attenuation value, and the attenuation curve in the Z axis direction is obtained as follows: ; Step S4: reconstructing the XY plane attenuation curve; Based on the principle of elliptical geometric projection, the attenuation curve of the XY plane at the projection angle θ is obtained as follows: .

[0011] Further, when acquiring the lateral localization image of the target, pixel-level attenuation projection data of the target scanning area is obtained, and the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane are reconstructed as follows: Step S1: Determine the lateral projection peak; Model the cross-section of the target as an ellipse, define the semi-major axis of the elliptical cross-section corresponding to each Z coordinate as a(z), the semi-minor axis as b(z), extend along the Z-axis direction, the attenuation coefficient μ(z) within any elliptical cross-section is uniform and 0 outside the elliptical cross-section; Perform lateral projection along the X-axis direction and calculate the lateral projection attenuation data: ; Lateral projection width , obtain the semi-minor axis ; Lateral projection peak ; where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Determine the forward projection peak through the QUAD algorithm; Calculate the total lateral projection attenuation and integrate along the Y-axis direction: ; Simultaneously solve the equations ; Obtain the forward projection peak ; where π is the ratio of the circumference of a circle to its diameter; Set the relationship between the semi-major axis a(z) and the semi-minor axis b(z) as , based on the average proportion of human anatomy, the range of the k value is 0.6 - 0.8, and the range of the attenuation coefficient μ(z) after adding the k value constraint is: ; ; Set the average attenuation coefficient of the target scanning area as , obtain the forward projection peak ; Step S3: Reconstruct the attenuation curve in the Z-axis direction; For each Z coordinate, set the larger value of the forward projection peak and the lateral projection peak as the maximum attenuation value, and obtain the attenuation curve in the Z-axis direction as: ; Step S4: Reconstruct the attenuation curve in the X-Y plane; Based on the principle of elliptical geometric projection, the attenuation curve in the X-Y plane at the projection angle θ is obtained as: 。

[0012] Furthermore, based on the calibration coefficient, noise standard deviation, and attenuation value obtained from the phantom test, a three-dimensional dose-noise-attenuation mapping table is constructed as follows: Use a water phantom for testing, collect water phantom images at different tube currents and different tube voltages, calculate the noise standard deviation σ, and establish a three-dimensional dose-noise-attenuation mapping table: , where K is the calibration coefficient determined through the phantom test, A is the attenuation value, and the noise standard deviation σ is defined as the noise threshold of the target scanning area.

[0013] Furthermore, based on the three-dimensional dose-noise-attenuation mapping table, the attenuation curve in the Z-axis direction, and the attenuation curve in the X-Y plane, a dose modulation curve of the target scanning area in the Z-axis direction and the X-Y plane is generated as follows: Preset a reference dose according to the three-dimensional dose-noise-attenuation mapping table , where A avg is the average attenuation value of the target scanning area, , where N is the total number of z coordinates in the Z-axis direction within the target scanning area; Dose modulation curve in the Z-axis direction ; Dose modulation curve in the X-Y plane 。

[0014] This application also provides a two-dimensional dose modulation system based on a scout view, which uses the above method for determining a two-dimensional dose modulation curve based on a scout view, including: A scout view acquisition module, configured to acquire a scout view of the target; An attenuation reconstruction module, signal-connected to the scout view acquisition module, configured to reconstruct the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane; A dose calculation module, signal-connected to the attenuation reconstruction module, configured to generate dose modulation curves of the target scanning area in the Z-axis direction and the X-Y plane.

[0015] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are as follows: This application uses scout view analysis to obtain the attenuation curves in the Z-axis direction and the X-Y plane, combines the three-dimensional dose-noise-attenuation mapping table obtained from the phantom test, and reconstructs the two-dimensional attenuation distribution, breaking through the dependence of traditional technologies on additional tomographic scans or hardware upgrades. Based on the scout view, dose modulation curves in the z-axis and x-y planes are directly generated to achieve joint dose modulation in the z-axis and x-y planes, thereby optimizing the radiation dose distribution in three-dimensional space. This solution not only reduces costs and radiation dose but also is applicable to scanning objects of different body types. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a flowchart of the algorithm for the method of determining the two-dimensional dose modulation curve based on the positioning image in Embodiment 1 of the present invention; Figure 2 It is a process diagram of collecting the positioning image and extracting the contour of the target in Embodiment 1 of the present invention; Figure 3 It is a process diagram of collecting the positioning image and extracting the contour of the target in Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] In order to enable those skilled in the art of this technology to better understand the solution of this application, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0019] It should be noted that the terms "first", "second", etc. in the description and claims of this application and the above drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances for the embodiments of this application described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these process, method, product or device.

[0020] In this application, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0021] Moreover, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0022] In addition, the terms "install", "set", "provided with", "connect", "connected", "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there is internal communication between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will detail this application with reference to the drawings and in combination with the embodiments.

[0024] Embodiment 1 Please refer to Figure 1 and Figure 2 , this embodiment provides a method for determining a two-dimensional dose modulation curve based on a localization image, including the following steps: S100: Collect a localization image of the target and extract the contour.

[0025] In this embodiment, collecting a localization image of the target and extracting the contour are specifically as follows: S101: Body position calibration to align the central axis of the target with the long axis of the scanning bed; S102: Data collection, collecting the forward localization image and the lateral localization image of the target; S103: Contour extraction, extracting the target contour in the forward localization image and the lateral localization image through the Canny operator.

[0026] It should be noted that the Canny operator is a commonly used edge detection method in image processing. The human body contour is extracted from the localization image through the dual-threshold parameter. The high threshold is set to 200 HU based on the contrast between the human body and the background. At the same time, the low threshold is set to 100 HU to retain the connection of strong edges and weak edges. Then, the edge image is first eroded and then dilated to remove the small stray edges in the edge region. Finally, all connected edge regions are extracted, and the connected region with the largest area is selected as the human body contour. This will not be elaborated here.

[0027] S200: Obtain the pixel-level attenuation projection data of the target scanning area, and reconstruct the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane.

[0028] Specifically as follows: Step S1: Determine the projection peak; Model the cross-section of the target as an ellipse, define the semi-major axis of the elliptical cross-section corresponding to each Z coordinate as a(z), the semi-minor axis as b(z), extend along the Z-axis direction, the attenuation coefficient μ(z) within any elliptical cross-section is uniform and 0 outside the elliptical cross-section; Perform a forward projection along the Y-axis direction and calculate the forward projection attenuation data: ; Forward projection peak ; Perform a lateral projection along the X-axis direction and calculate the lateral projection attenuation data: ; Lateral projection peak ; where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Reconstruct the attenuation curve in the Z-axis direction; For each Z coordinate, set the larger value of the forward projection peak and the lateral projection peak as the maximum attenuation value, and obtain the attenuation curve in the Z-axis direction as: ; Step S3: Reconstruct the attenuation curve in the X-Y plane; Based on the elliptical geometric projection principle, obtain the attenuation curve in the X-Y plane at the projection angle θ as: ; where the projection angle θ refers to the angle between the projection direction of the ray and the x-axis in the X-Y plane corresponding to any z coordinate.

[0029] S300: Construct a three-dimensional dose-noise-attenuation mapping table according to the calibration coefficient, noise standard deviation, and attenuation value obtained from the phantom test.

[0030] The details are as follows: Use a water phantom for testing, collect water phantom images under different tube currents and different tube voltages, calculate the noise standard deviation σ, and establish a three-dimensional dose-noise-attenuation mapping table: , where K is the calibration coefficient determined through phantom testing, A is the attenuation value, and the noise standard deviation σ is defined as the noise threshold of the target scanning area.

[0031] It should be noted that the process of obtaining the calibration coefficient K, attenuation value A, and noise standard deviation σ through phantom testing is as follows: (a)Determine the exposure voltage and current combinations, keep other parameters fixed, and set different combinations of voltage and current respectively. For example, the voltages are 80 kV, 100 kV, 120 kV, 140 kV, and the currents are 10 mA, 50 mA, 100 mA, 150 mA; (b)Determine the water phantom specifications, select a water phantom with a diameter of 20 cm or 30 cm. The 20 cm water phantom is used to simulate the head or pediatric body, and the 30 cm water phantom is used to simulate the adult body; (c)Determine the dose measurement equipment. Common dose measurement equipment includes semiconductor detectors, photodetectors, thermoluminescent dosimeters, etc.; (d)Exposure and data acquisition. Under the selected water phantom specifications, use different combinations of voltage and current for multiple exposures to reduce random errors, obtain CT images, and measure the exposure dose D; (e)Select the region of interest ROI. Select a 100×100 pixel region of interest ROI in the central area of the water phantom CT image, and calculate the noise standard deviation σ within the region of interest ROI. Specifically: Extract all pixel values within the region of interest ROI and calculate the mean value, calculate the square of the difference between each pixel value and the mean value in this region, then find the average value of these squared differences and take the square root to obtain the noise standard deviation σ; (f)Calculate the linear attenuation coefficient. Determine the linear attenuation coefficient μ of the water phantom according to the voltage. The attenuation value A = μ×d, where d is the diameter of the water phantom; (g)According to the relationship , obtain K under fixed voltage, current, water phantom specifications, and noise level.

[0032] The above methods and calculation processes belong to conventional dose calibration steps and are widely used in the performance evaluation of medical imaging equipment. By controlling exposure parameters, selecting appropriate water phantom specifications, using dose measurement equipment, and performing multiple data acquisitions, the accuracy of the calibration coefficient K can be ensured. The specific process includes exposure voltage and current combinations, noise level calculation, and estimation of the linear attenuation coefficient. Since it is a standardized process, it will not be elaborated in detail in this article.

[0033] S400: Generate dose modulation curves for the target scanning area in the Z-axis direction and the X-Y plane based on the dose-noise-attenuation three-dimensional mapping table, the attenuation curve in the Z-axis direction, and the attenuation curve in the X-Y plane.

[0034] Specifically as follows: Preset a reference dose according to the dose-noise-attenuation three-dimensional mapping table , where A avg is the average attenuation value of the target scanning area, , where N is the total number of z coordinates in the Z-axis direction within the target scanning area; Dose modulation curve in the Z-axis direction ; Dose modulation curve in the X-Y plane .

[0035] Example 2 Please refer to Figure 3 , this example provides a method for determining a two-dimensional dose modulation curve based on a localization image. The difference from the method in Example 1 is: collect the forward localization image or the lateral localization image of the target.

[0036] In this example, the localization image of the target is collected and the contour is extracted. Specifically as follows: S101: Body position calibration to align the central axis of the target with the long axis of the scanning bed.

[0037] S102: Data collection, collect the forward localization image or the lateral localization image of the target.

[0038] S103: Contour extraction, extract the target contour in the forward localization image or the lateral localization image through the Canny operator.

[0039] In some embodiments, the forward localization image of the target is collected. When the forward localization image of the target is collected, obtain the pixel-level attenuation projection data of the target scanning area, and reconstruct the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane. Specifically as follows: Step S1: Determine the forward projection peak; Model the cross-section of the target as an ellipse, define the semi-major axis of the elliptical cross-section corresponding to each Z coordinate as a(z), the semi-minor axis as b(z), extend along the Z-axis direction, the attenuation coefficient μ(z) within any elliptical cross-section is uniform and 0 outside the elliptical cross-section; Perform a forward projection along the Y-axis direction and calculate the forward projection attenuation data: ; Forward projection width , obtain the semi-major axis ; Forward projection peak ; where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Determine the lateral projection peak value through the QUAD algorithm; Calculate the total forward projection attenuation, and integrate along the X-axis direction: ; Simultaneously solve the equations ; Obtain the lateral projection peak value ; where π is the pi; Set the relationship between the semi-major axis a(z) and the semi-minor axis b(z) as . Based on the average proportion of human anatomy, the range of the k value is 0.6 to 0.8, and the range of the attenuation coefficient μ(z) after adding the k value constraint is: ; ; Set the average attenuation coefficient of the target scanning area as , and obtain the lateral projection peak value ; Step S3: Reconstruct the attenuation curve in the Z-axis direction; For each Z coordinate, set the larger value of the forward projection peak value and the lateral projection peak value as the maximum attenuation value, and obtain the attenuation curve in the Z-axis direction as: ; Step S4: Reconstruct the attenuation curve in the X-Y plane; Based on the principle of elliptical geometric projection, obtain the attenuation curve in the X-Y plane at the projection angle θ as: .

[0040] In some other embodiments, acquire the lateral localization image of the target. When acquiring the lateral localization image of the target, obtain the pixel-level attenuation projection data of the target scanning area, and reconstruct the attenuation curves in the Z-axis direction and the X-Y plane of the target scanning area, specifically as follows: Step S1: Determine the lateral projection peak value; Model the cross-section of the target as an ellipse, define the semi-major axis of the elliptical cross-section corresponding to each Z coordinate as a(z), the semi-minor axis as b(z), extend along the Z-axis direction, the attenuation coefficient μ(z) within any elliptical cross-section is uniform and 0 outside the elliptical cross-section; Perform lateral projection along the X-axis direction, and calculate the lateral projection attenuation data: ; Lateral projection width , and obtain the semi-minor axis ; Lateral projection peak ; where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Determine the forward projection peak through the QUAD algorithm; Calculate the total attenuation of the lateral projection and integrate along the Y-axis direction: ; Simultaneous equations ; Obtain the forward projection peak ; where π is the ratio of the circumference of a circle to its diameter; Set the relationship between the semi-major axis a(z) and the semi-minor axis b(z) as , based on the average proportion of human anatomy, the range of the k value is 0.6 - 0.8, and the range of the attenuation coefficient μ(z) after adding the k value constraint is: ; ; Set the average attenuation coefficient of the target scanning area as , and obtain the forward projection peak ; Step S3: Reconstruct the attenuation curve in the Z-axis direction; For each Z coordinate, set the larger value of the forward projection peak and the lateral projection peak as the maximum attenuation value, and obtain the attenuation curve in the Z-axis direction as: ; Step S4: Reconstruct the attenuation curve in the X-Y plane; Based on the principle of elliptical geometric projection, obtain the attenuation curve in the X-Y plane at the projection angle θ as: .

[0041] Example 3 This example provides a two-dimensional dose modulation system based on a localization image, and uses the method for determining a two-dimensional dose modulation curve in Example 1 or Example 2 to determine the two-dimensional dose modulation curve.

[0042] The two-dimensional dose modulation system based on a localization image includes a localization image acquisition module, an attenuation reconstruction module signal-connected to the localization image acquisition module, and a dose calculation module signal-connected to the attenuation reconstruction module. The localization image acquisition module is used to acquire a localization image of the target, the attenuation reconstruction module is used to reconstruct the attenuation curves in the Z-axis direction and the X-Y plane of the target scanning area, and the dose calculation module is used to generate dose modulation curves in the Z-axis direction and the X-Y plane of the target scanning area.

[0043] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for determining a two-dimensional dose modulation curve based on a localization image, characterized in that It includes the following steps: Locate the target for image acquisition and contour extraction; Obtain the pixel-level attenuation projection data of the target scanning area, and reconstruct the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane; Construct a three-dimensional dose-noise-attenuation mapping table based on the calibration coefficient, noise standard deviation, and attenuation value obtained from the phantom test; Generate the dose modulation curves of the target scanning area in the Z-axis direction and the X-Y plane based on the three-dimensional dose-noise-attenuation mapping table, the attenuation curve in the Z-axis direction, and the attenuation curve in the X-Y plane.

2. The method for determining a two-dimensional dose modulation curve based on a localization image according to claim 1, wherein Locate the target for image acquisition and contour extraction, specifically as follows: Body position calibration to align the central axis of the target with the long axis of the scanning bed; Data acquisition, acquiring the forward localization image and the lateral localization image of the target; Contour extraction, extracting the target contour in the forward localization image and the lateral localization image through the Canny operator.

3. The method for determining a two-dimensional dose modulation curve based on a positioning image according to claim 2, wherein Obtain the pixel-level attenuation projection data of the target scanning area, and reconstruct the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane, specifically as follows: Step S1: Determine the projection peak; Model the cross-section of the target as an ellipse, define the semi-major axis of the elliptical cross-section corresponding to each Z coordinate as a(z), the semi-minor axis as b(z), extend along the Z-axis direction, and the attenuation coefficient μ(z) within any elliptical cross-section is uniform and 0 outside the elliptical cross-section; Perform a forward projection along the Y-axis direction and calculate the forward projection attenuation data: ； Forward projection peak ; Perform a lateral projection along the X-axis direction and calculate the lateral projection attenuation data: ； Lateral projection peak ; where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Reconstruct the attenuation curve in the Z-axis direction; For each Z coordinate, set the larger of the forward projection peak and the lateral projection peak as the maximum attenuation value, and obtain the attenuation curve in the Z-axis direction as: ； Step S3: Reconstruct the attenuation curve in the X-Y plane; Based on the principle of elliptical geometric projection, obtain the attenuation curve in the X-Y plane at the projection angle θ as: ； where the projection angle θ refers to the angle between the projection direction of the ray and the x-axis in the X-Y plane corresponding to any z coordinate.

4. The method for determining a two-dimensional dose modulation curve based on a positioning image according to claim 1, wherein Locate the target for image acquisition and contour extraction, specifically as follows: Body position calibration to align the central axis of the target with the long axis of the scanning bed; Data acquisition, acquiring the forward localization image or the lateral localization image of the target; Contour extraction, extracting the target contour in the forward localization image or the lateral localization image through the Canny operator.

5. The method for determining a two-dimensional dose modulation curve based on a positioning image according to claim 4, wherein When acquiring the forward localization image of the target, obtain the pixel-level attenuation projection data of the target scanning area, and reconstruct the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane, specifically as follows: Step S1: Determine the forward projection peak; Model the cross-section of the target as an ellipse, define the semi-major axis of the elliptical cross-section corresponding to each Z coordinate as a(z), the semi-minor axis as b(z), extend along the Z-axis direction, and the attenuation coefficient μ(z) within any elliptical cross-section is uniform and 0 outside the elliptical cross-section; Perform a forward projection along the Y-axis direction and calculate the forward projection attenuation data: ； Positive projection width , the semi-major axis is obtained ; Forward projection peak ; where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Determine the lateral projection peak through the QUAD algorithm; Calculate the total forward projection attenuation and integrate along the X-axis direction: ； Simultaneous equations ; Obtain the peak value of the lateral projection ; where π is the ratio of the circumference of a circle to its diameter; Set the relationship between the semi-major axis a(z) and the semi-minor axis b(z) as , based on the average proportion of human anatomy, the range of the k value is 0.6 to 0.8, and the range of the attenuation coefficient μ(z) after adding the k value constraint is: ； ； Set the average attenuation coefficient of the target scanning area to be , and obtain the lateral projection peak value ; Step S3: Reconstruct the attenuation curve in the Z-axis direction; For each Z coordinate, set the larger value between the forward projection peak value and the lateral projection peak value as the maximum attenuation value, and the attenuation curve in the Z-axis direction is obtained as: ； Step S4: Reconstruct the attenuation curve in the X-Y plane; Based on the principle of elliptical geometric projection, the attenuation curve in the X-Y plane at the projection angle θ is obtained as: 。 6. The method for determining a two-dimensional dose modulation curve based on a positioning image according to claim 4, wherein When acquiring the lateral localization image of the target, obtain the pixel-level attenuation projection data of the target scanning area, and reconstruct the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane, specifically as follows: Step S1: Determine the lateral projection peak value; Model the cross-section of the target as an ellipse, define the semi-major axis of the elliptical cross-section corresponding to each Z coordinate as a(z), the semi-minor axis as b(z), extend along the Z-axis direction, the attenuation coefficient μ(z) within any elliptical cross-section is uniform and is 0 outside the elliptical cross-section; Perform lateral projection along the X-axis direction and calculate the lateral projection attenuation data: ； Lateral projection width , the semi-minor axis is obtained ; Lateral projection peak ; where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Determine the forward projection peak value through the QUAD algorithm; Calculate the total lateral projection attenuation and integrate along the Y-axis direction: ； Simultaneous equations ; Obtain the peak value of the forward projection ; where π is the pi; Set the relationship between the semi-major axis \(a(z)\) and the semi-minor axis \(b(z)\) as , based on the average proportion of human anatomy, the value range of \(k\) is \(0.6 - 0.8\), and the value range of the attenuation coefficient \(\mu(z)\) after adding the \(k\) value constraint is: ； ； Set the average attenuation coefficient of the target scanning area to be , and obtain the forward projection peak ; Step S3: Reconstruct the attenuation curve in the Z-axis direction; For each Z coordinate, set the larger value between the forward projection peak value and the lateral projection peak value as the maximum attenuation value, and the attenuation curve in the Z-axis direction is obtained as: ； Step S4: Reconstruct the attenuation curve in the X-Y plane; Based on the principle of elliptical geometric projection, the attenuation curve in the X-Y plane at the projection angle θ is obtained as: 。 7. A method for determining a two-dimensional dose modulation curve based on a positioning image according to claim 3 or 5 or 6, characterized in that, According to the calibration coefficient, noise standard deviation, and attenuation value obtained from the phantom test, construct a three-dimensional dose-noise-attenuation mapping table, specifically as follows: Use a water phantom for testing, acquire the water phantom images under different tube currents and different tube voltages, calculate the noise standard deviation σ, and establish a three-dimensional dose-noise-attenuation mapping table: , where K is the calibration coefficient determined by the phantom test, A is the attenuation value, and the noise standard deviation σ is defined as the noise threshold of the target scan area.

8. The method for determining a two-dimensional dose modulation curve based on a localization image according to claim 7, wherein Based on the three-dimensional dose-noise-attenuation mapping table, the attenuation curve in the Z-axis direction, and the attenuation curve in the X-Y plane, generate the dose modulation curves of the target scanning area in the Z-axis direction and the X-Y plane, specifically as follows: Preset a reference dose according to the three-dimensional dose-noise-attenuation mapping table , where A avg is the average attenuation value of the target scanning area, , where N is the total number of z coordinates along the Z-axis direction within the target scanning area; Z-axis direction dose modulation curve ; X-Y plane dose modulation curve 。 9. A two-dimensional dose modulation system based on a localization image, which determines a two-dimensional dose modulation curve by using the method for determining a two-dimensional dose modulation curve based on a localization image according to any one of claims 1-8, characterized in that Including: A localization image acquisition module for acquiring a localization image of the target; An attenuation reconstruction module, which is signal-connected to the localization image acquisition module, for reconstructing the attenuation curves of the target scanning area in the Z-axis direction and the X-Y plane; A dose calculation module, which is signal-connected to the attenuation reconstruction module, for generating the dose modulation curves of the target scanning area in the Z-axis direction and the X-Y plane.

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