Method and system for determining dual-dimensional dose modulation curve based on scout image

Abstract

The present application discloses a method and system for determining a two-dimensional dose modulation curve based on a positioning image. The method comprises: acquiring a positioning image and extracting a contour of a target; obtaining pixel-level attenuation projection data of the target scanning area, and reconstructing the attenuation curve of the target scanning area in the Z-axis direction and the X-Y plane; constructing a three-dimensional dose-noise-attenuation mapping table based on the calibration coefficient, noise standard deviation, and attenuation value obtained from a phantom test; and generating a dose modulation curve for 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 Z-axis direction attenuation curve, and the X-Y plane attenuation curve. The present application directly generates the Z-axis and X-Y plane dose modulation curves based on the positioning image, realizing combined dose modulation, thereby optimizing the radiation dose distribution in three-dimensional space. This not only reduces cost and radiation dose, but is also applicable to scanned subjects of different sizes.

Description

Technical Field

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

[0002] In CT imaging, dose modulation technology balances image quality and radiation safety by dynamically adjusting radiation dose. Its core is to establish a mapping relationship between anatomical structure attenuation and radiation dose. Existing technologies have the following bottlenecks:

[0003] 1. Limitations of single-dimensional modulation: Traditional methods only use forward positioning images to generate Z-axis dose modulation curves and cannot obtain tissue thickness differences in the cross-section, i.e., the XY plane. As a result, XY plane dose optimization relies on additional tomography or hardware upgrades, such as dual detectors, which increases costs and radiation exposure.

[0004] 2. Single algorithm path: Existing technologies mostly use regional segmentation or machine learning models, and no analytical algorithm based on geometric projection principles has been proposed, making it difficult to ensure universality for patients of different body shapes.

[0005] 3. Strong hardware dependence: Solutions involving XY plane modulation generally rely on additional equipment, such as stereo cameras and structured light, which limits compatibility with mainstream CT models. Summary of the Invention

[0006] The purpose of the present invention is to provide a method and system for determining a two-dimensional dose modulation curve based on a scouting image, so as to solve the problems of single-dimensional modulation limitation, single algorithm path and strong hardware dependence of existing dose modulation technology.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A method for determining a two-dimensional dose modulation curve based on a scout image comprises the following steps:

[0009] Perform positioning image acquisition and contour extraction on the target;

[0010] Obtain pixel-level attenuation projection data of the target scanning area and reconstruct the attenuation curve of the target scanning area in the Z-axis direction and XY plane;

[0011] A three-dimensional dose-noise-attenuation mapping table is constructed based on the calibration coefficients, noise standard deviations, and attenuation values ​​obtained from the phantom test.

[0012] Based on the dose-noise-attenuation three-dimensional mapping table, the Z-axis attenuation curve and the XY plane attenuation curve, the dose modulation curve of the target scanning area in the Z-axis direction and the XY plane is generated.

[0013] Furthermore, the positioning image is collected and the contour is extracted for the target, as follows:

[0014] Body position calibration to align the target's central axis with the long axis of the scanning bed;

[0015] Data acquisition: collecting the forward positioning image and lateral positioning image of the target;

[0016] Contour extraction: The Canny operator is used to extract the target contour in the forward positioning image and the lateral positioning image.

[0017] Furthermore, 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:

[0018] Step S1: determining the projection peak;

[0019] The cross section of the target is modeled as an ellipse. 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). The attenuation coefficient μ(z) is uniform within any ellipse and is zero outside the ellipse.

[0020] Perform forward projection along the Y-axis and calculate the forward projection attenuation data:

[0021] ;

[0022] Forward projection peak ;

[0023] Perform lateral projection along the X-axis and calculate the lateral projection attenuation data:

[0024] ;

[0025] Lateral projection peak ;

[0026] Where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value;

[0027] Step S2: reconstructing the attenuation curve in the Z-axis direction;

[0028] For each Z coordinate, the larger of the forward projection peak and the side projection peak is set as the maximum attenuation value, and the attenuation curve in the Z axis direction is obtained as follows:

[0029] ;

[0030] Step S3: reconstructing the XY plane attenuation curve;

[0031] Based on the principle of elliptical geometric projection, the attenuation curve of the XY plane at the projection angle θ is obtained as follows:

[0032] ;

[0033] The projection angle θ refers to the angle between the projection direction of the ray and the x-axis in the XY plane corresponding to any z coordinate.

[0034] Furthermore, the positioning image is collected and the contour is extracted for the target, as follows:

[0035] Body position calibration to align the target's central axis with the long axis of the scanning bed;

[0036] Data acquisition: collecting the forward positioning image or lateral positioning image of the target;

[0037] Contour extraction: Use the Canny operator to extract the target contour in the forward positioning image or the lateral positioning image.

[0038] 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:

[0039] Step S1: determining the forward projection peak;

[0040] The cross section of the target is modeled as an ellipse. 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). The attenuation coefficient μ(z) is uniform within any ellipse and is zero outside the ellipse.

[0041] Perform forward projection along the Y-axis and calculate the forward projection attenuation data:

[0042] ;

[0043] Forward projection width , find the semi-major axis ;

[0044] Forward projection peak ;

[0045] Where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value;

[0046] Step S2: Determine the lateral projection peak using the QUAD algorithm;

[0047] Calculate the total forward projection attenuation and integrate along the X-axis:

[0048] ;

[0049] simultaneous equations ;

[0050] Obtain the peak value of the lateral projection ;

[0051] Among them, π is the ratio of circumference to diameter;

[0052] Assume the relationship between the semi-major axis a(z) and the semi-minor axis b(z) is , 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:

[0053] ;

[0054] ;

[0055] Set the average attenuation coefficient of the target scanning area to , get the lateral projection peak ;

[0056] Step S3: reconstructing the attenuation curve in the Z-axis direction;

[0057] For each Z coordinate, the larger of the forward projection peak and the side projection peak is set as the maximum attenuation value, and the attenuation curve in the Z axis direction is obtained as follows:

[0058] ;

[0059] Step S4: reconstructing the XY plane attenuation curve;

[0060] Based on the principle of elliptical geometric projection, the attenuation curve of the XY plane at the projection angle θ is obtained as follows:

[0061] .

[0062] Furthermore, when acquiring the lateral locator 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:

[0063] Step S1: determining the lateral projection peak;

[0064] The cross section of the target is modeled as an ellipse. 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). The attenuation coefficient μ(z) is uniform within any ellipse and is zero outside the ellipse.

[0065] Perform lateral projection along the X-axis and calculate the lateral projection attenuation data:

[0066] ;

[0067] Lateral projection width , find the semi-minor axis ;

[0068] Lateral projection peak ;

[0069] Where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value;

[0070] Step S2: Determine the forward projection peak using the QUAD algorithm;

[0071] Calculate the total attenuation of the lateral projection and integrate along the Y axis:

[0072] ;

[0073] simultaneous equations ;

[0074] Get the forward projection peak ;

[0075] Among them, π is the ratio of circumference to diameter;

[0076] Assume the relationship between the semi-major axis a(z) and the semi-minor axis b(z) is , 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:

[0077] ;

[0078] ;

[0079] Set the average attenuation coefficient of the target scanning area to , get the forward projection peak ;

[0080] Step S3: reconstructing the attenuation curve in the Z-axis direction;

[0081] For each Z coordinate, the larger of the forward projection peak and the side projection peak is set as the maximum attenuation value, and the attenuation curve in the Z axis direction is obtained as follows:

[0082] ;

[0083] Step S4: reconstructing the XY plane attenuation curve;

[0084] Based on the principle of elliptical geometric projection, the attenuation curve of the XY plane at the projection angle θ is obtained as follows:

[0085] .

[0086] 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:

[0087] Use a water phantom to test, collect water phantom images at different tube currents and 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 scanning area.

[0088] Furthermore, based on the dose-noise-attenuation three-dimensional mapping table, the Z-axis direction attenuation curve and the XY plane attenuation curve, the dose modulation curve of the target scanning area in the Z-axis direction and the XY plane is generated, as follows:

[0089] Preset the baseline 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 along the z-axis in the target scanning area;

[0090] Dose modulation curve in the Z-axis direction ;

[0091] Dose modulation curve in XY plane .

[0092] The present application further provides a two-dimensional dose modulation system based on a scout image, which uses the above-mentioned two-dimensional dose modulation curve determination method based on a scout image to determine a two-dimensional dose modulation curve, including:

[0093] Positioning image acquisition module, used for acquiring positioning images of the target;

[0094] An attenuation reconstruction module, connected to the positioning image acquisition module, for reconstructing the attenuation curve of the target scanning area in the Z-axis direction and the XY plane;

[0095] The dose calculation module is connected to the attenuation reconstruction module signal and is used to generate a dose modulation curve of the target scanning area in the Z-axis direction and the XY plane.

[0096] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are:

[0097] This application uses scouting image analysis to obtain attenuation curves in the Z-axis and XY planes. Combined with the three-dimensional dose-noise-attenuation mapping table obtained from phantom testing, this approach reconstructs a two-dimensional attenuation distribution. This approach overcomes the traditional reliance on additional tomography scans or hardware upgrades. Directly generating dose modulation curves in the Z-axis and XY planes based on scouting images enables combined dose modulation in the Z-axis and XY planes, thereby optimizing the radiation dose distribution in three dimensions. This solution not only reduces cost and radiation exposure but is also applicable to scanned subjects of varying sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0099] Figure 1 This is an algorithm flow chart of the method for determining a two-dimensional dose modulation curve based on a scout image in Example 1 of the present invention;

[0100] Figure 2 This is a process diagram for capturing positioning images and extracting contours of a target in Example 1 of the present invention;

[0101] Figure 3 This is a process diagram for capturing positioning images and extracting contours of a target in Example 2 of the present invention. DETAILED DESCRIPTION

[0102] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0103] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0104] In this application, terms such as "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "center," "vertical," "horizontal," "transverse," and "longitudinal" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are primarily intended to better describe the present invention and its embodiments and are not intended to limit the devices, elements, or components indicated to having a specific orientation, or to being constructed or operated in a specific orientation.

[0105] Furthermore, some of the above terms may be used to express other meanings besides indicating a position or location. For example, the term "on" may also be used to indicate a dependency or connection in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0106] Furthermore, the terms "installed," "disposed," "provided with," "connected," "connected," and "socketed" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integral structures; mechanical connections or electrical connections; direct connections or indirect connections through an intermediary; or internal communication between two devices, elements, or components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0107] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0108] Example 1

[0109] See Figure 1 and Figure 2 This embodiment provides a method for determining a two-dimensional dose modulation curve based on a scout image, comprising the following steps:

[0110] S100: Capture positioning images and extract contours of the target.

[0111] In this embodiment, positioning image acquisition and contour extraction are performed on the target, specifically as follows:

[0112] S101: Body position calibration, aligning the target center axis with the long axis of the scanning bed;

[0113] S102: Data acquisition, collecting the forward positioning image and the lateral positioning image of the target;

[0114] S103: Contour extraction: extracting the target contour in the forward locator image and the lateral locator image using the Canny operator.

[0115] It should be noted that the Canny operator is a commonly used edge detection method in image processing. The human outline is extracted from the scouting image using dual threshold parameters. The upper threshold is set to 200 HU based on the contrast between the human body and the background, while the lower threshold is set to 100 HU to preserve the connection between strong and weak edges. The edge image is then eroded and then dilated to remove fine stray edges in the edge region. Finally, all connected edge regions are extracted, and the largest connected region is selected as the human outline. This process is not detailed here.

[0116] S200: Acquire pixel-level attenuation projection data of the target scanning area, and reconstruct the attenuation curve of the target scanning area in the Z-axis direction and the XY plane.

[0117] The details are as follows:

[0118] Step S1: determining the projection peak;

[0119] The cross section of the target is modeled as an ellipse. 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). The attenuation coefficient μ(z) is uniform within any ellipse and is zero outside the ellipse.

[0120] Perform forward projection along the Y-axis and calculate the forward projection attenuation data:

[0121] ;

[0122] Forward projection peak ;

[0123] Perform lateral projection along the X-axis and calculate the lateral projection attenuation data:

[0124] ;

[0125] Lateral projection peak ;

[0126] Where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value;

[0127] Step S2: reconstructing the attenuation curve in the Z-axis direction;

[0128] For each Z coordinate, the larger of the forward projection peak and the side projection peak is set as the maximum attenuation value, and the attenuation curve in the Z axis direction is obtained as follows:

[0129] ;

[0130] Step S3: reconstructing the XY plane attenuation curve;

[0131] Based on the principle of elliptical geometric projection, the attenuation curve of the XY plane at the projection angle θ is obtained as follows:

[0132] ;

[0133] The projection angle θ refers to the angle between the projection direction of the ray and the x-axis in the XY plane corresponding to any z coordinate.

[0134] S300: Constructing a dose-noise-attenuation three-dimensional mapping table based on the calibration coefficient, noise standard deviation, and attenuation value obtained from the phantom test.

[0135] The details are as follows:

[0136] Use a water phantom to test, collect water phantom images at different tube currents and 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 scanning area.

[0137] 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:

[0138] (a) Determine the exposure voltage and current combination, keep other parameters fixed, and set different voltage and current combinations, for example, voltage is 80kV, 100kV, 120kV, 140kV, and current is 10mA, 50mA, 100mA, 150mA;

[0139] (b) Determine the specifications of the water phantom. Choose a 20 cm or 30 cm diameter water phantom. The 20 cm water phantom is used to simulate the head or child's body, and the 30 cm water phantom is used to simulate the adult body.

[0140] (c) Determine the dose measurement equipment. Common dose measurement equipment includes semiconductor detectors, photodetectors, thermoluminescent dosimeters, etc.;

[0141] (d) Exposure and data acquisition: Under the selected water phantom specifications, multiple exposures are performed using different voltage and current combinations to reduce random errors, acquire CT images, and measure the exposure dose D;

[0142] (e) Select a region of interest (ROI). A 100 × 100 pixel ROI was selected from the central region of the water phantom CT image. The noise standard deviation σ within the ROI was calculated. Specifically, all pixel values ​​within the ROI were extracted and their mean was calculated. The square of the difference between each pixel value and the mean was calculated. The square root of these squared differences was then averaged and taken to obtain the noise standard deviation σ.

[0143] (f) Calculate the linear attenuation coefficient. Determine the linear attenuation coefficient μ of the water phantom based on the voltage. The attenuation value A = μ × d, where d is the diameter of the water phantom.

[0144] (g) According to the relationship , and obtain K under fixed voltage, current, water model specifications and noise level.

[0145] The above method and calculation process are standard dose calibration procedures, 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 factor K can be ensured. The specific process includes combining exposure voltage and current, calculating the noise level, and estimating the linear attenuation coefficient. Because this is a standardized procedure, it will not be elaborated in detail in this article.

[0146] S400: Generate a dose modulation curve of the target scanning area in the Z-axis direction and the XY plane based on the dose-noise-attenuation three-dimensional mapping table, the Z-axis direction attenuation curve and the XY plane attenuation curve.

[0147] The details are as follows:

[0148] Preset the baseline 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 along the z-axis in the target scanning area;

[0149] Dose modulation curve in the Z-axis direction ;

[0150] Dose modulation curve in XY plane .

[0151] Example 2

[0152] See Figure 3This embodiment provides a method for determining a two-dimensional dose modulation curve based on a scout image. The difference from the method in Example 1 is that a forward scout image or a lateral scout image of the target is acquired.

[0153] In this embodiment, positioning image acquisition and contour extraction are performed on the target, specifically as follows:

[0154] S101: Body position calibration to align the target center axis with the long axis of the scanning bed.

[0155] S102: Data acquisition: acquiring a forward positioning image or a lateral positioning image of the target.

[0156] S103: Contour extraction: extracting the target contour in the forward locator image or the lateral locator image by using the Canny operator.

[0157] In some embodiments, a forward scout image of the target is acquired. When acquiring the forward scout image of the target, 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:

[0158] Step S1: determining the forward projection peak;

[0159] The cross section of the target is modeled as an ellipse. 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). The attenuation coefficient μ(z) is uniform within any ellipse and is zero outside the ellipse.

[0160] Perform forward projection along the Y-axis and calculate the forward projection attenuation data:

[0161] ;

[0162] Forward projection width , find the semi-major axis ;

[0163] Forward projection peak ;

[0164] Where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value;

[0165] Step S2: Determine the lateral projection peak using the QUAD algorithm;

[0166] Calculate the total forward projection attenuation and integrate along the X-axis:

[0167] ;

[0168] simultaneous equations ;

[0169] Obtain the peak value of the lateral projection ;

[0170] Among them, π is the ratio of circumference to diameter;

[0171] Assume the relationship between the semi-major axis a(z) and the semi-minor axis b(z) is , 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:

[0172] ;

[0173] ;

[0174] Set the average attenuation coefficient of the target scanning area to , get the lateral projection peak ;

[0175] Step S3: reconstructing the attenuation curve in the Z-axis direction;

[0176] For each Z coordinate, the larger of the forward projection peak and the side projection peak is set as the maximum attenuation value, and the attenuation curve in the Z axis direction is obtained as follows:

[0177] ;

[0178] Step S4: reconstructing the XY plane attenuation curve;

[0179] Based on the principle of elliptical geometric projection, the attenuation curve of the XY plane at the projection angle θ is obtained as follows:

[0180] .

[0181] In other embodiments, a lateral scout image of the target is acquired. When acquiring the lateral scout image of the target, 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:

[0182] Step S1: determining the lateral projection peak;

[0183] The cross section of the target is modeled as an ellipse. 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). The attenuation coefficient μ(z) is uniform within any ellipse and is zero outside the ellipse.

[0184] Perform lateral projection along the X-axis and calculate the lateral projection attenuation data:

[0185] ;

[0186] Lateral projection width , find the semi-minor axis ;

[0187] Lateral projection peak ;

[0188] Where x is the X-axis coordinate value, y is the Y-axis coordinate value, and z is the Z-axis coordinate value;

[0189] Step S2: Determine the forward projection peak using the QUAD algorithm;

[0190] Calculate the total attenuation of the lateral projection and integrate along the Y axis:

[0191] ;

[0192] simultaneous equations ;

[0193] Get the forward projection peak ;

[0194] Among them, π is the ratio of circumference to diameter;

[0195] Assume the relationship between the semi-major axis a(z) and the semi-minor axis b(z) is , 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:

[0196] ;

[0197] ;

[0198] Set the average attenuation coefficient of the target scanning area to , get the forward projection peak ;

[0199] Step S3: reconstructing the attenuation curve in the Z-axis direction;

[0200] For each Z coordinate, the larger of the forward projection peak and the side projection peak is set as the maximum attenuation value, and the attenuation curve in the Z axis direction is obtained as follows:

[0201] ;

[0202] Step S4: reconstructing the XY plane attenuation curve;

[0203] Based on the principle of elliptical geometric projection, the attenuation curve of the XY plane at the projection angle θ is obtained as follows:

[0204] .

[0205] Example 3

[0206] This embodiment provides a two-dimensional dose modulation system based on a scouting image, and adopts the two-dimensional dose modulation curve determination method based on a scouting image as in Embodiment 1 or Embodiment 2 to determine a two-dimensional dose modulation curve.

[0207] The dual-dimensional dose modulation system based on scout images includes a scout image acquisition module, an attenuation reconstruction module connected to the scout image acquisition module, and a dose calculation module connected to the attenuation reconstruction module. The scout image acquisition module is used to acquire a scout image of the target, the attenuation reconstruction module is used to reconstruct the attenuation curve of the target scanning area in the Z-axis direction and the XY plane, and the dose calculation module is used to generate the dose modulation curve of the target scanning area in the Z-axis direction and the XY plane.

[0208] Finally, it should be noted that the above are only 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 aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining a two-dimensional dose modulation curve based on a scout image, characterized in that: The steps include: Perform positioning image acquisition and contour extraction on the target; Obtain pixel-level attenuation projection data of the target scanning area and reconstruct the attenuation curve of the target scanning area in the Z-axis direction and XY plane; A three-dimensional dose-noise-attenuation mapping table is constructed based on the calibration coefficients, noise standard deviations, and attenuation values ​​obtained from the phantom test. Based on the dose-noise-attenuation three-dimensional mapping table, the Z-axis attenuation curve and the XY-plane attenuation curve, the dose modulation curve of the target scanning area in the Z-axis direction and the XY-plane is generated; The positioning image acquisition and contour extraction of the target are as follows: Body position calibration to align the target's central axis with the long axis of the scanning bed; Data acquisition, collecting the forward positioning image and / or lateral positioning image of the target; Contour extraction: extract the target contour in the forward positioning image and / or lateral positioning image using the Canny operator.

2. The method for determining a two-dimensional dose modulation curve based on a scout image according to claim 1, wherein: Obtain pixel-level attenuation projection data of the target scanning area and reconstruct the attenuation curve of the target scanning area in the Z-axis direction and XY plane, as follows: Step S1: determining the projection peak; The cross section of the target is modeled as an ellipse. 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). The attenuation coefficient μ(z) is uniform within any ellipse and is zero outside the ellipse. Perform forward projection along the Y-axis and calculate the forward projection attenuation data: Forward projection peak Perform lateral projection along the X-axis 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: reconstructing the attenuation curve in the Z-axis direction; For each Z coordinate, the larger of the forward projection peak and the side projection peak is set as the maximum attenuation value, and the attenuation curve in the Z axis direction is obtained as follows: Step S3: 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: The projection angle θ refers to the angle between the projection direction of the ray and the x-axis in the XY plane corresponding to any z coordinate.

3. The method for determining a two-dimensional dose modulation curve based on a scout image according to claim 1, wherein: 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: determining the forward projection peak; The cross section of the target is modeled as an ellipse. 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). The attenuation coefficient μ(z) is uniform within any ellipse and is zero outside the ellipse. Perform forward projection along the Y-axis and calculate the forward projection attenuation data: Forward projection width W AP (z) = 2a(z), find the semi-major axis Forward projection peak Where x is the X-axis coordinate value, and z is the Z-axis coordinate value; Step S2: Determine the lateral projection peak using the QUAD algorithm; Calculate the total forward projection attenuation and integrate along the X-axis: simultaneous equations Obtain 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 b(z) = k·a(z). Based on the average proportion of human anatomy, the k value range is 0.6 to 0.

8. After adding the k value constraint, the range of the attenuation coefficient μ(z) is: Set the average attenuation coefficient of the target scanning area to μ tissue (z), get the lateral projection peak Step S3: reconstructing the attenuation curve in the Z-axis direction; For each Z coordinate, the larger of the forward projection peak and the side 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:

4. The method for determining a two-dimensional dose modulation curve based on a scout image according to claim 1, wherein: When acquiring the lateral 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: determining the lateral projection peak; The cross section of the target is modeled as an ellipse. 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). The attenuation coefficient μ(z) is uniform within any ellipse and is zero outside the ellipse. Perform lateral projection along the X-axis and calculate the lateral projection attenuation data: Lateral projection width W LAT (z) = 2b(z), find 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 using the QUAD algorithm; Calculate the total attenuation of the lateral projection and integrate along the Y axis: simultaneous equations Get the forward projection peak 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 b(z) = k·a(z). Based on the average proportion of human anatomy, the k value range is 0.6 to 0.

8. After adding the k value constraint, the range of the attenuation coefficient μ(z) is: Set the average attenuation coefficient of the target scanning area to μ tissue (z), get the forward projection peak Step S3: reconstructing the attenuation curve in the Z-axis direction; For each Z coordinate, the larger of the forward projection peak and the side 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:

5. The method for determining a two-dimensional dose modulation curve based on a scout image according to claim 2, 3 or 4, wherein: Based on the calibration coefficients, noise standard deviations, and attenuation values ​​obtained from the phantom test, a three-dimensional dose-noise-attenuation mapping table was constructed as follows: Use a water phantom to test, collect water phantom images at different tube currents and 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 scanning area.

6. The method for determining a two-dimensional dose modulation curve based on a scout image according to claim 5, wherein: Based on the dose-noise-attenuation three-dimensional mapping table, the Z-axis attenuation curve, and the XY-plane attenuation curve, the dose modulation curves of the target scanning area in the Z-axis direction and the XY-plane are generated as follows: Preset the baseline dose according to the dose-noise-attenuation three-dimensional mapping table Among them 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 in the target scanning area; Dose modulation curve in the Z-axis direction Dose modulation curve in XY plane 7. A two-dimensional dose modulation system based on a scout image, wherein the two-dimensional dose modulation curve is determined by using the two-dimensional dose modulation curve determination method based on a scout image according to any one of claims 1 to 6, characterized in that: include: Positioning image acquisition module, used for acquiring positioning images of the target; An attenuation reconstruction module, connected to the positioning image acquisition module, for reconstructing the attenuation curve of the target scanning area in the Z-axis direction and the XY plane; The dose calculation module is connected to the attenuation reconstruction module signal and is used to generate a dose modulation curve of the target scanning area in the Z-axis direction and the XY plane.

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