A scatter correction method based on side illumination of a scintillator

Abstract

The application relates to a scattering correction method based on side irradiation of a scintillator. A cuboid scintillator is sliced into a stack along the long side with equal thickness; a collimated beam matched with the slice thickness is used to irradiate only the first slice from the side, a camera is directly opposite for imaging, and the brightness of each slice is extracted; a scattering correction factor is obtained based on the fitting of a scattering attenuation relationship of the irradiation experiment; and the actual measured brightness is deducted layer by layer to restore the real brightness and obtain a three-dimensional dose distribution according to the brightness-dose calibration. The method realizes the separation of the initial scintillation light and the interlayer scattering, is simple in structure, consistent in calibration-measurement, and significantly improves the three-dimensional dose measurement precision and reproducibility.

Description

Technical Field

[0001] This invention relates to the field of dose measurement and radiation detection technology, and in particular to a scattering correction method based on a side-illuminated scintillator. Background Technology

[0002] In three-dimensional dose measurement, imaging the three-dimensional light distribution generated by a scintillator using a camera and reconstructing the dose field is widely regarded as a measurement method with real-time performance and high spatial resolution. However, scintillators are approximately transparent to the scintillation light they emit, and the primary emission from the irradiated voxels undergoes scattering and multiple scattering superposition as it propagates within the voxel. Especially along the transmission path towards the camera, the emission from the rear voxels significantly "crosstalks" to the observed brightness of the front voxels, making the brightness distribution acquired by the camera a mixture of the true emission distribution and the scattered components. This results in systematic biases and blurred edges in the reconstructed dose distribution, making it difficult to accurately characterize high-gradient regions and fine structures.

[0003] To address biases caused by scattering, existing methods often employ mathematical inversion using scattering response functions (or point spread functions, system response matrices) to decompose the measured signal into "primary radiation contributions" and "scattering contributions." These methods typically rely on Monte Carlo or semi-analytical models to solve for high-dimensional response matrices and perform regularization for noise and ill-posedness during deconvolution. However, the response matrix is ​​enormous and sensitive to energy spectrum, geometry, material, and surface conditions; even slight parameter deviations can significantly impact solution stability and correction effectiveness. Furthermore, balancing time complexity and accuracy requires trade-offs between mesh density, statistical uncertainty, and prior constraints, making it difficult to meet the demands of efficient, repeatable, and portable scattering correction in clinical / field settings.

[0004] In summary, existing three-dimensional scintillator dose measurement still suffers from problems in scattering correction, such as high dependence on model and simulation accuracy, large computational load, and insufficient reproducibility across devices and conditions. There is still a lack of a scattering correction technology solution that has a well-defined device geometry, integrates calibration and measurement, and can improve reconstruction accuracy while ensuring efficiency.

[0005] In view of the above problems, this invention is proposed. Summary of the Invention

[0006] This invention discloses a scattering correction method based on a side-illuminated scintillator, which aims to solve the technical problems existing in the prior art.

[0007] To achieve the above objectives, according to the present invention, a scattering correction method based on a side-illuminated scintillator includes: The cuboid scintillator is cut into multiple scintillator slices of equal thickness along its long side and then tightly assembled into a pile. A ray generator is positioned above a first scintillator sheet on one side of the scintillator. The ray generator produces a collimated beam that matches the thickness of the multiple scintillator sheets. The collimated beam passes vertically from the side and only through the first scintillator sheet. The camera is adjusted so that its lens optical axis is perpendicular to the short side of the multiple scintillator sheets. Imaging is used to acquire luminescent images of multiple scintillator slices, and the first brightness is extracted from each slice; a scattering attenuation relationship is established based on the first brightness, and a scattering correction factor is obtained; The second brightness, i.e. the original brightness, of multiple scintillator slices was obtained by actual measurement, and the third brightness was obtained by layer-by-layer scattering subtraction based on the scattering correction factor. Based on the brightness-dose calibration relationship, the third brightness is mapped to the dose distribution layer by layer to obtain the three-dimensional dose reconstruction result corrected by the scattering correction factor.

[0008] As a preferred technical solution, the scattering correction factor is obtained by fitting the attenuation relationship of the first brightness with distance, using the interlayer center distance of multiple scintillator slices as the independent variable, and adopting the following formula: in, This is the scattering correction factor; The first brightness of multiple scintillator slices, =1 corresponds to the first scintillator slice; The center-to-center distance between multiple scintillator slices.

[0009] As a preferred technical solution, the interlayer center distance is obtained using the following formula: =( -1)· in, The thickness of the multiple scintillator slices.

[0010] As a preferred technical solution, the first brightness of multiple scintillator slices is obtained by averaging multiple data acquisitions and then fitting the results.

[0011] As a preferred technical solution, the third brightness is obtained by layer-by-layer scattering subtraction using the following formula: in, The second brightness; For the first The true luminous intensity of the layer, i.e., the third luminance; The thickness of multiple scintillator slices; For a specific scintillator thin film, =1 corresponds to the first scintillator slice.

[0012] As a preferred technical solution, after the three-dimensional dose reconstruction results, the system also includes outputting the corrected true brightness distribution and corresponding dose distribution image, and recalculating the scattering correction factor when the material surface condition, temperature, humidity or geometric conditions change.

[0013] As a preferred technical solution, the angle error between the beam width of the collimating beam and the normal of the short side of the first scintillator sheet is no greater than 0.5°.

[0014] As a preferred technical solution, the geometric penumbra of the collimating beam at the side of the first scintillator sheet is less than 10% of the thickness of the first scintillator sheet.

[0015] As a preferred technical solution, in establishing the scattering attenuation relationship based on the first brightness, the fitting of the scattering attenuation relationship adopts one of the following: exponential type, piecewise exponential type, or polynomial model with non-negativity and monotonicity constraints.

[0016] As a preferred technical solution, the camera is equipped with a bandpass filter and a light shield that match the emission spectrum of the scintillator during imaging.

[0017] The technical solution adopted in this invention can achieve at least one of the following beneficial effects: 1. This invention, through a geometric design of "side-side single-layer collimated incident light + stack of equal-thickness slices," experimentally separates the initial scintillation light from the interlayer scattering, and constructs a monotonically decaying scattering correction factor with the interlayer center distance as the independent variable. In actual measurements, based on Layer-by-layer subtraction (discrete deconvolution) can significantly suppress interlayer scattering superposition and beam hardening / depth mixing errors, improve the spatial fidelity and quantitative accuracy of three-dimensional dose, and obtain a clearer dose profile, especially in high gradient dose fields and edge regions.

[0018] 2. This invention exhibits good robustness and reproducibility to both the device and the environment: Maintaining consistency between materials, camera, and X-ray source allows for a closed-loop "calibration-measurement co-link"; for Repeated sampling is used to obtain the mean, and the data is fitted with monotonic / non-negativity constraints. and This reduces the risk of over- or under-calibration caused by random noise and system drift; when temperature, humidity, surface state, or geometric conditions change, calibration accuracy can be restored simply by quickly redoing the calibration steps; it also supports constraint recovery for incomplete fields of view or locally missing layers, and can propagate sampling variance and fitting residuals to... / Output level uncertainty to meet quality control and traceability requirements.

[0019] 3. This invention has low implementation cost and is easy to engineer: it can achieve high-precision scattering correction without relying on complex Monte Carlo simulation or heavy light-blocking structures. The device has a simple structure and low maintenance cost. The number and thickness of the thin film can be flexibly expanded. It can also establish a scattering nuclear library classified by energy spectrum or dose rate to adapt to multiple working conditions. It is suitable for rapid deployment and promotion in radiotherapy quality control, nuclear medicine / isotope dosimetry and related radiation detection scenarios. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of the placement method of the scintillator and the ray generator of the present invention; Figure 2 This is a schematic diagram of the scintillator light distribution in the multilayer thin film of the scintillator of the present invention; Figure 3 This is a schematic flowchart of a scattering correction method based on a side-illuminated scintillator according to the present invention.

[0021] Explanation of reference numerals in the attached figures: 1. Scintillator; 11. First scintillator sheet; 12. Second scintillator sheet; 13. Third scintillator sheet; 14. Fourth scintillator sheet; 15. Fifth scintillator sheet; 16. Sixth scintillator sheet; 17. Seventh scintillator sheet; 18. Eighth scintillator sheet; 19. Ninth scintillator sheet; 2. X-ray generator; 3. Camera. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a magnetic connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0024] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] To address the problems existing in the prior art, embodiments of the present invention provide a scattering correction method based on a side-illuminated scintillator, such as... Figure 1-2 As shown, it includes: S1: Preparation for material and geometric consistency; A scintillator 1 of the same model as that used in the actual dose measurement is selected. Preferably, the scintillator 1 is rectangular in shape to facilitate the creation of slices of uniform thickness along its long side. The scintillator 1 is cut into thin slices of uniform thickness along its long side and tightly assembled into a stack, which are sequentially labeled as the first to the ninth scintillator slices 11, 12, 13, 14, 15, 16, 17, 18, and 19 (thickness denoted as...). Camera 3 is the same model used in the actual measurement. S2: Side single-layer collimated irradiation; like Figure 1 As shown, the ray generator 2 is arranged parallel to the short side of the scintillator 1 and is positioned above the first scintillator sheet 11 of the scintillator 1. The ray generator 2 generates ray energy that is proportional to the thickness of the sheet. The matched collimating beam passes vertically from the side through only the first scintillator sheet 11 (without passing through other sheets). Preferably, the beam width of the collimating beam is equal to the sheet thickness. The beam axis and the angle error between the beam axis and the normal of the short side of the thin film are not greater than 0.5°, and the geometric penumbra of the collimated beam at the side of the first scintillator thin film 11 is less than 10% of the thickness of the first scintillator thin film, so as to ensure that the collimated beam passes through the first scintillator thin film 11 only perpendicularly; the optical axis of the lens of the camera 3 is perpendicular to the short side of the thin film, and the dark field / flat field and geometric calibration are completed to block the ambient light, that is, the optical axis of the camera 3 is coaxial with the normal of the short side of the thin film, facing the side imaging surface of the thin film stack, so that the sensor imaging plane is strictly parallel to the thin film layer; preferably, during imaging, the camera is equipped with a bandpass filter and a light shield that match the emission spectrum of the scintillator 1, and performs dark field and flat field calibration to compensate for gain unevenness and vignetting; S3: Calibration acquisition and interlayer brightness quantization; Under the condition of illuminating only the first scintillator sheet 11, the luminescent image of the entire stack of sheets is acquired, and the first brightness is extracted from each sheet. ,in For the floor number ( =1 corresponds to the first scintillator slice 11); as shown in Figure 2 As shown, the inter-layer center distance is defined. =( -1)· ; S4: Establish the scattering attenuation relationship and define the correction coefficient; Based on the center distance between floors Fit the attenuation relationship of scattered brightness with distance to the independent variable. The scattering correction factor is obtained. and restrict its following Increasing monotonically decreases and approaches zero; to reduce noise, [the following is applied]. The data is collected multiple times, averaged, and then fitted; preferably, The fitting adopts a physically constrained monotonically decaying model, which is one of the following: exponential, piecewise exponential, or polynomial model with non-negativity and monotonicity constraints. S5: Obtain the original distribution through actual irradiation; Actual dose measurements were performed under the same materials, camera, and geometry conditions as in steps S1-S2, and the original brightness (second brightness) of each layer was obtained through imaging. ; S6: Layer-by-layer scattering subtraction based on calibration kernel; Establish discrete convolution relationships: , in For the first Layer true luminous intensity (third luminance); The thickness of multiple scintillator slices; For a specific scintillator thin film, =1 corresponds to the first scintillator sheet; According to distance from near to far, use The scattering fractions of each other layer are subtracted from the target layer one by one until the residual stabilizes, yielding the true luminescence distribution (third brightness) T(n) of the entire stack; for example, when restoring the fourth scintillator sheet 14, the scattering fractions of the first scintillator sheet 11 are subtracted sequentially. · (3 ), the second scintillator thin film 12 · (2 ), the third scintillator thin film 13 · ( The scattering contribution of the fifth to ninth scintillator sheets 15-19 to the fourth layer; sequential iteration / damping or regularization may be used to improve numerical stability if necessary; S7: Luminance-dose mapping and 3D reconstruction; Based on the brightness-dose calibration relationship of camera 3 = ( ), will be scatter-corrected Layer-by-layer mapping to dose distribution The scattering-corrected three-dimensional dose reconstruction results were obtained. S8: Output and Review; Output corrected images of the true brightness distribution and corresponding dose distribution; when the material surface condition, temperature, humidity, or geometric conditions change, repeat steps S3-S4 to update. This is to ensure the effectiveness of the calibration and the reproducibility of the results.

[0026] Through the above-described correction method, and employing a geometry and process of "side-mounted single-layer collimated incidence + thin-film stacked layer calibration," the initial scintillation light and interlayer scattering can be experimentally separated. A scattering correction factor based on the distance-brightness relationship is proposed. This invention employs a layer-by-layer subtraction (deconvolution) restoration strategy based on discrete convolution, forming an integrated and reproducible calibration-measurement consistency framework encompassing materials, cameras, and X-rays. It significantly suppresses systematic biases caused by interlayer scattering superposition, improving the spatial fidelity and quantitative accuracy of three-dimensional dosimetry; it achieves high-precision calibration without relying on complex Monte Carlo modeling, with low hardware and computing costs, easy deployment, and repeatable calibration; it exhibits good scalability and robustness to varying sheet layers and thicknesses, and can quickly reproduce stable calibration results after changes in equipment or environmental conditions.

[0027] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A scattering correction method based on a side-illuminated scintillator, characterized in that, include: The cuboid scintillator is cut into multiple scintillator slices of equal thickness along its long side and then tightly assembled into a pile. A ray generator is positioned above a first scintillator sheet on one side of the scintillator. The ray generator produces a collimated beam that matches the thickness of the plurality of scintillator sheets. The collimated beam passes vertically from the side and only through the first scintillator sheet. The camera is adjusted so that its lens optical axis is perpendicular to the short side of the plurality of scintillator sheets. Imaging is used to acquire luminescent images of the plurality of scintillator thin films, and a first brightness is extracted from each film. A scattering attenuation relationship is established based on the first brightness, and a scattering correction factor is obtained. The scattering correction factor is obtained by fitting the attenuation relationship of the first brightness with distance, using the interlayer center distance of the plurality of scintillator thin films as the independent variable, and employing the following formula: in, The scattering correction factor; The first luminance of the plurality of scintillator sheets, =1 corresponds to the first scintillator sheet; The interlayer center-to-center distance of the plurality of scintillator sheets is obtained using the following formula: =( -1)· in, The thickness of the plurality of scintillator sheets; The second brightness, i.e., the original brightness, of the plurality of scintillator sheets is obtained by actual measurement, and the third brightness is obtained by layer-by-layer scattering subtraction based on the scattering correction factor; the third brightness is obtained by layer-by-layer scattering subtraction using the following formula: in, This is the second brightness; For the first The actual luminous intensity of the layer, i.e., the third luminance; The thickness of the plurality of scintillator sheets; For a specific scintillator thin film, =1 corresponds to the first scintillator sheet; Based on the brightness-dose calibration relationship, the third brightness is mapped layer by layer to the dose distribution, and the three-dimensional dose reconstruction result corrected by the scattering correction factor is obtained.

2. The scattering correction method according to claim 1, characterized in that, The first brightness of the multiple scintillator slices is obtained by averaging multiple data acquisitions and then fitting the results.

3. The scattering correction method according to claim 1, characterized in that, After the three-dimensional dose reconstruction results are obtained, the system also includes outputting the corrected true brightness distribution and corresponding dose distribution image. When the material surface condition, temperature, humidity or geometric conditions change, the scattering correction factor is recalculated.

4. The scattering correction method according to claim 1, characterized in that, The angle error between the beam width of the collimating beam and the normal of the short side of the first scintillator sheet is no greater than 0.5°.

5. The scattering correction method according to claim 1, characterized in that, The geometric penumbra of the collimating beam at the side of the first scintillator sheet is less than 10% of the thickness of the first scintillator sheet.

6. The scattering correction method according to claim 1, characterized in that, In establishing the scattering attenuation relationship based on the first brightness, the fitting of the scattering attenuation relationship adopts one of the following: an exponential model or a polynomial model with non-negativity and monotonicity constraints.

7. The scattering correction method according to claim 1, characterized in that, The camera is equipped with a bandpass filter and a light shield that match the emission spectrum of the scintillator during imaging.

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