A device and method for measuring the lateral distribution of a radiation dose

Abstract

The application discloses a kind of ray dose transverse distribution measuring device and method, comprising: scintillator luminescent material, optical mirror, optical imaging system and data analysis system;The scintillator luminescent material, optical mirror, optical imaging system are all arranged in shell, when the ray to be detected is incident along the direction perpendicular to scintillator luminescent material, the scintillator luminescent material emits photon under the irradiation of the ray to be detected;The optical mirror is used to reflect the photon emitted by the scintillator luminescent material to the optical imaging system;The optical imaging system is used to receive photon and image;The data analysis system is arranged outside the shell, for the image data of the optical imaging system real-time acquisition is analyzed, and the transverse dose profile distribution result of the ray to be detected is obtained.The application can be widely applied to the field of radiotherapy ray dose transverse distribution measurement.

Description

Technical Field

[0001] This invention belongs to the field of radiotherapy technology, specifically relating to a device and method for measuring the lateral distribution of radiation dose. Background Technology

[0002] In recent years, radiotherapy technology has developed rapidly. Accurately delivering a predetermined dose to the patient's tumor target area is a core issue in ensuring treatment effectiveness. Among these, beam quality assurance is crucial for ensuring consistency between beam parameters and the treatment planning system. Beam quality assurance includes measuring the beam's lateral position, lateral profile distribution, and longitudinal profile distribution.

[0003] Currently, the lateral position and cross-sectional distribution of a beam are generally measured using film, two-dimensional ionization chamber matrices, or scintillator detectors. The film method is the most widely used and traditional method, directly obtaining the lateral position and cross-sectional distribution of the beam. Its disadvantages include non-reusable film, high cost, and the need for offline data acquisition after a period of settling, resulting in significant time consumption. Two-dimensional ionization chamber matrices offer fast measurement speed, but suffer from low lateral resolution and require data fitting to obtain the lateral position, making it less intuitive and accurate. For two-dimensional ionization chamber matrices, improving lateral resolution comes at the cost of a dramatic increase in the number of electron channels. Scintillator detectors are a newer, optical-based measurement method that collects photons generated after the interaction of X-rays with luminescent materials, thus obtaining the lateral distribution of the X-rays. Scintillator detectors offer advantages such as simple measurement systems and short measurement times, but their disadvantage is the significant impact of scattering noise on the measurement results. Scattered X-rays introduce a large amount of discrete noise when incident on an image sensor, manifesting as numerous pixels with large amplitudes in the image. The image sensor cannot distinguish whether these noise signals originate from X-rays or stray scattered rays. Therefore, it is necessary to remove these noises to avoid affecting the measurement results.

[0004] When measuring the lateral distribution of scintillator rays using a scintillator detector, stray scattering is itself X-ray for X-ray therapy machines. The location of scattering noise generally differs across different images captured in succession. Therefore, by comparing the differences between a series of consecutively captured images, points with higher noise levels can be identified, and their values ​​can be corrected. For proton and heavy ion therapy machines, stray scattering includes both X-rays and the scattered protons and heavy ions themselves. In different consecutively captured images, some scattering noise is located differently, while some remains constant. The second denoising method uses median filtering and smoothing filtering. Median filtering can remove scattering noise to some extent, but it still retains some high-frequency components that affect the measurement results. Smoothing filtering is a low-pass filter that distributes pixels with larger amplitudes evenly among adjacent pixels, making the image "blurred." The uniformity of the "blurred" image "improves," but this improvement cannot be determined whether it is due to the inherent "uniformity" of the radiation field or the forced uniformity by the smoothing filter. Therefore, neither median filtering nor smoothing filtering is an ideal solution for measuring lateral profile uniformity. In conclusion, the noise reduction techniques currently used for scintillator detectors cannot achieve satisfactory results. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a device and method for measuring the lateral distribution of radiation dose, which can achieve high-resolution, short-time, and convenient measurement of the lateral distribution of radiation dose, providing a technical means for measuring beam parameters, conducting morning and monthly inspections, and verifying treatment plans for radiation therapy devices.

[0006] Another objective of this invention is to provide a method for measuring the lateral distribution of radiation dose, which provides an ideal method for eliminating scattering noise when measuring the lateral distribution of radiation dose using a scintillator detector.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a radiation dose transverse distribution measuring device, comprising:

[0009] Scintillator luminescent materials, optical mirrors, optical imaging systems, and data analysis systems;

[0010] The scintillator luminescent material, optical mirror, and optical imaging system are all housed inside the casing. When the ray to be detected is incident along a direction perpendicular to the scintillator luminescent material, the scintillator luminescent material emits photons under the irradiation of the ray to be detected.

[0011] The optical mirror is used to reflect photons emitted by the scintillator luminescent material into the optical imaging system;

[0012] The optical imaging system is used to receive photons and form images;

[0013] The data analysis system is located outside the housing and is used to analyze the image data acquired in real time by the optical imaging system to obtain the transverse dose profile distribution results of the ray to be detected.

[0014] Furthermore, the scintillator luminescent material is rectangular, and the width of the scintillator luminescent material is greater than the maximum lateral length of the ray to be detected.

[0015] Furthermore, the optical imaging system includes an optical lens, a filter, and a camera; the optical lens is used to collect the light generated by the scintillator luminescent material and reflected by the optical mirror, and to focus the collected light onto the imaging chip of the camera; the filter is used to select the wavelength of the light that can pass through; the camera is used to convert the collected and focused light into an image.

[0016] Furthermore, the size of the optical reflector is not less than the minimum size of the complete image of the scintillator luminescent material captured by the optical lens.

[0017] Furthermore, the angle between the scintillator luminescent material and the plane of the optical mirror, and the angle between the optical mirror and the axis of the optical lens, are both 45°.

[0018] Furthermore, the optical imaging system is installed inside the scattered ray shielding system; the scattered ray shielding system is installed outside the outer casing.

[0019] Furthermore, the interior of the outer shell is coated with a light-absorbing material.

[0020] Furthermore, the spectral range of the optical imaging system and the optical mirror includes the spectral peak of the scintillator luminescent material.

[0021] Secondly, the present invention provides a method for measuring the lateral distribution of radiation dose, comprising the following steps:

[0022] Before beam irradiation, images without radiation irradiation are acquired and sent to the data analysis system as background images.

[0023] After the beam begins to irradiate, several consecutively captured images during the irradiation process of the radiation to be detected are acquired as source images and sent to the data analysis system;

[0024] Based on the background image and the source images, the data analysis system obtains the profiles of the image to be detected in the horizontal and vertical directions.

[0025] Furthermore, the method for the data analysis system to obtain the profiles of the image to be detected in the horizontal and vertical directions based on the background image and each source image includes:

[0026] The obtained source images are each subtracted from the background image;

[0027] Select the region of interest from the image obtained by subtraction to obtain the image of interest;

[0028] The obtained image of interest is subjected to Fourier transform and spectral centering to obtain the matrix of interest;

[0029] The obtained matrix of interest is subjected to low-pass filtering to obtain the filtered matrix, wherein the cutoff frequency of the low-pass filter is obtained by simulation calculation;

[0030] The filtered image is obtained by performing an inverse Fourier transform on the filtered matrix.

[0031] The projections of the filtered image in the horizontal and vertical directions are obtained respectively, thus obtaining the cross-sections of the beam to be detected in the horizontal and vertical directions.

[0032] The present invention has the following advantages due to the adoption of the above technical solutions:

[0033] 1. Due to the rational arrangement of the scintillator luminescent material, optical mirror, and optical imaging system, this invention achieves a spatial resolution better than 0.5 mm, offering the advantage of higher spatial resolution compared to ionization chamber matrices. It also boasts the advantages of being fast, real-time, and online.

[0034] 2. This invention integrates scintillator light-emitting material, optical mirror, optical imaging system, etc. into the shell, making it compact, portable, and easy to carry. Data extraction can be completed with a computer, giving it the advantages of being convenient, portable, fast, and real-time.

[0035] 3. By installing the optical imaging system inside the scattered ray shielding system and installing the scattered ray shielding system outside the housing, the present invention can reduce the influence of scattered rays on the measurement results and improve the detection accuracy.

[0036] 4. When performing measurements, this invention obtains images before and after beam irradiation and performs subtraction, which can effectively remove X-ray scattering noise without removing the frequency components of the image, thus further improving the accuracy of the detection results.

[0037] In summary, this invention can be widely applied in the field of radiotherapy technology. Attached Figure Description

[0038] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0039] Figure 1 This is a schematic diagram of the structure of a radiation dose lateral distribution measuring device proposed in this invention;

[0040] Figure 2 This is a flowchart illustrating the implementation of a method for measuring the transverse distribution of radiation dose proposed in this invention.

[0041] Figure 3 These are images taken by the device in this embodiment of the invention under a carbon ion radiation field with an energy of 190 MeV / u and a lateral dimension of 100 mm × 100 mm.

[0042] Figure 4a and Figure 4b These are Fourier transform spectra of the regions of interest and the regions of sensory interest selected in the images of the embodiments of the present invention.

[0043] Figure 5a and Figure 5b It is the spectrum of the region of interest image after low-pass filtering in the frequency domain and the image obtained by inverse Fourier transform;

[0044] Figure 6a and Figure 6b It is a two-dimensional distribution image and Fourier spectrum of a carbon ion field with a horizontal size of 100mm×100mm.

[0045] Figure 6c and Figure 6d It is a two-dimensional distribution image and Fourier spectrum of a carbon ion field with a horizontal size of 200mm×200mm.

[0046] Figure 7a and Figure 7b They are respectively for Figure 5a The horizontal and vertical profile distributions obtained after low-pass filtering the region of interest image;

[0047] Figure 8a and Figure 8b They are respectively for Figure 5a The image showing the region of interest is a comparison of horizontal and vertical cross-sections before and after low-pass filtering.

[0048] The markings in the attached diagram are as follows:

[0049] 1. Scintillator luminescent material; 2. Optical mirror; 3. Optical imaging system; 4. Scattered ray shielding system; 5. Outer shell; 6. Data analysis system. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 described embodiments of the present invention are within the scope of protection of the present invention.

[0051] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0052] In some embodiments of the present invention, a device for measuring the lateral dose distribution of radiation is provided. First, a scintillator luminescent material emits photons under irradiation by the radiation to be detected. Then, an optical mirror and an optical imaging system focus and image the photons emitted by the scintillator luminescent material to obtain the lateral dose profile distribution of the radiation to be detected. Through the rational design of the scintillator luminescent material, the optical mirror, and the optical imaging system, this device has the advantages of being fast, real-time, and online, and is also compact and portable.

[0053] Correspondingly, some other embodiments of the present invention provide a method for measuring the lateral distribution of radiation dose.

[0054] Example 1

[0055] like Figure 1 As shown, this embodiment provides a radiation dose lateral distribution measurement device, including: a scintillator luminescent material 1, an optical mirror 2, an optical imaging system 3, and a data analysis system 6. The scintillator luminescent material 1, the optical mirror 2, and the optical imaging system 3 are all housed within a housing 5. When the radiation to be detected is incident along a direction perpendicular to the scintillator luminescent material 1, the scintillator luminescent material 1 emits photons under the irradiation of the radiation, and the number of emitted photons is proportional to the power density of the radiation on a unit of the scintillator luminescent material 1. The optical mirror 2 reflects the photons emitted by the scintillator luminescent material 1 to the optical imaging system 3. The optical imaging system 3 receives the photons and forms an image. The data analysis system 6 is located outside the housing 5 and is used to analyze the image data acquired in real time by the optical imaging system 3 to obtain the lateral dose profile distribution result of the radiation to be detected.

[0056] Furthermore, the radiation to be detected includes, but is not limited to, X-rays, protons, carbon ions, and other heavy ions used for treatment.

[0057] Furthermore, the scintillator luminescent material 1 includes, but is not limited to, plastic scintillators, crystal scintillators, or powder screens.

[0058] Furthermore, the scintillator luminescent material 1 is a rectangular sheet, and the lateral dimension W of the rectangular sheet is greater than the maximum lateral dimension of the ray to be detected.

[0059] Furthermore, the scintillator luminescent material 1, the optical reflector 2, and the optical imaging system 3 are all installed in the housing 5 to avoid the influence of external natural light on the measurement results.

[0060] Furthermore, the optical imaging system 3 comprises an optical lens, a filter, and a camera. The optical lens is used to collect the light generated by the scintillator luminescent material 1 and reflected by the optical mirror 2, and to focus the collected light onto the imaging chip of the camera; the filter is used to select the wavelength of the light that can pass through; and the camera is used to convert the collected and focused light into an image.

[0061] Preferably, the filter is selected to allow light with a wavelength of 500–600 nm to pass through.

[0062] Preferably, the camera includes, but is not limited to, a CCD camera.

[0063] Furthermore, the size of the optical reflector 2 is not smaller than the minimum size required for the camera to capture a complete image of the scintillator luminescent material 1.

[0064] Furthermore, the angle α between the plane containing the scintillator luminescent material 1 and the optical mirror 2, and the angle β between the optical mirror 2 and the camera axis, are both 45°.

[0065] Furthermore, the optical imaging system 3 is installed inside the scattered ray shielding system 4 to reduce the influence of scattered rays on the measurement results; the scattered ray shielding system 4 is installed outside the housing 5.

[0066] Furthermore, the spectral range of the optical imaging system 3 and the optical mirror 2 must include the spectral peak of the scintillator luminescent material 1.

[0067] Furthermore, the interior of the outer casing 5 is coated with a light-absorbing material.

[0068] Furthermore, the data analysis system 6 includes, but is not limited to, a computer.

[0069] Example 2

[0070] like Figure 2 As shown, based on the radiation dose lateral distribution measuring device disclosed in Embodiment 1, this embodiment discloses a radiation dose lateral distribution measuring method, including the following steps:

[0071] (1) Before beam irradiation, an image without radiation irradiation is acquired and sent as a background image to the data analysis system 6;

[0072] (2) After the beam begins to irradiate, a number of continuously captured images during the irradiation process of the ray to be detected are acquired as source images and sent to the data analysis system 6;

[0073] (3) Based on the background image and the source image, the data analysis system 6 obtains the lateral distribution of the rays to be detected.

[0074] Furthermore, step (3) above can be achieved through the following steps:

[0075] (3.1) Perform image subtraction operations between the obtained source images and the background image respectively;

[0076] (3.2) Select the region of interest from the image obtained by the subtraction operation to obtain the image of interest;

[0077] (3.3) Perform Fourier transform and spectral centering on the obtained image of interest to obtain the matrix of interest;

[0078] (3.4) Perform low-pass filtering on the obtained matrix of interest to obtain the filtered matrix, wherein the cutoff frequency of the low-pass filter is obtained by simulation calculation;

[0079] (3.5) Perform inverse Fourier transform and inverse spectrum centering on the filtered matrix to obtain the filtered image;

[0080] (3.6) The projections of the filtered image in the horizontal and vertical directions are obtained respectively, and the transverse distribution of the ray to be detected is obtained, that is, its cross-section in the horizontal and vertical directions.

[0081] Example 3

[0082] In the radiation dose lateral distribution testing device used in this embodiment, the outer shell 5 is made of aluminum alloy profile, and its inner surface is coated with black light-absorbing material. The scintillator luminescent material 1 is a plastic scintillator, and the size of the plastic scintillator 1 is preferably 200mm × 200mm. The size of the optical reflector 2 is 282mm × 200mm.

[0083] In this embodiment, the lens focal length is preferably 12mm. The center wavelength of the filter is preferably 550nm, and the bandwidth is preferably 100nm. In this embodiment, the camera's field of view is 798mm × 498mm, and the spatial resolution is 0.43mm / pixel. The field of view can cover the lateral dimension of the scintillator luminescent material 1.

[0084] In this embodiment, the spectral peak of the scintillator light-emitting material 1 is 550nm, and the reflectivity of the optical mirror 2 is greater than 90% in the range of 500-600nm.

[0085] Example 4

[0086] Based on the radiation dose lateral distribution measurement device in Example 3, this example further introduces the radiation dose lateral distribution measurement method disclosed in this invention.

[0087] (1) The camera takes an image when there is no radiation and stores it in the computer as the background image (denoted as P1).

[0088] (2) The camera takes an image when it is exposed to rays as the source image (denoted as P2).

[0089] (3) Perform data analysis to obtain the projections of the ray to be detected in the horizontal and vertical directions, and thus obtain the cross-sections in the two directions.

[0090] Specifically, it includes the following steps:

[0091] (3.1) The source image and the background image are subtracted to obtain an image with the background removed (denoted as P3). In this embodiment, the source image was captured in a carbon ion field with an energy of 190 MeV / u and a lateral size of 100 mm × 100 mm. Figure 3 As shown.

[0092] (3.2) Select the region of interest (ROI) on image P3 to obtain the image of the ROI (denoted as P4).

[0093] (3.3) Perform a two-dimensional Fourier transform and spectral centering on image P4 to obtain matrix M1. Image P4 and matrix M1 are as follows: Figure 4a and Figure 4b As shown.

[0094] (3.4) Perform low-pass filtering on matrix M1 to obtain matrix M2.

[0095] Low-pass filtering is applied to matrix M1 by multiplying the frequency components in M1 with frequency f by 0 and the frequency components with frequency f by 1, thus obtaining matrix M2. The cutoff frequency f of the low-pass filter is obtained as follows:

[0096] (3.4.1) Create simulated virtual images of shooting fields with sizes of 100mm×100mm and 200mm×200mm. The edges of the virtual images are simulated using a Gaussian distribution with a standard deviation of 5mm.

[0097] (3.4.2) Perform two-dimensional Fourier transform and spectral centering on the two sets of simulated virtual images respectively. View their spectral images, as shown... Figures 6a-6d As shown, the high-frequency components of the simulated virtual image are equal to zero. Additionally, for... Figure 3 Region of interest image ( Figure 4a Perform a two-dimensional Fourier transform and spectral centering to obtain the spectrum of the region of interest image. Figure 4b As can be seen, image P4 has abundant high-frequency components. Therefore, the high-frequency components in image P4 are mainly scattering noise from the rays.

[0098] (3.4.3) From the spectrum matrix of the simulated virtual image, when the coordinates of a frequency point are greater than 1 / 10 of the matrix length, the amplitude of that frequency point is less than 0.4% of the peak value. Therefore, high-frequency components with frequencies greater than 1 / 10 can be ignored. Therefore, f = 1 / 10 is chosen as the cutoff frequency of the low-pass filter.

[0099] (3.5) Perform inverse spectral centering and two-dimensional inverse Fourier transform on matrix M2 to obtain the processed image (denoted as P5). Matrix M2 and image P5 are as follows: Figure 5a and Figure 5b As shown.

[0100] (3.6) By obtaining the projections in the horizontal and vertical directions from image P5, the cross-sections in the two directions can be obtained, such as... Figure 7a and Figure 7b As shown. The details in the middle section of the cross-section demonstrate the effect before and after low-pass filtering, such as... Figure 8a and Figure 8b As shown, the profile before filtering contains a large amount of data with large fluctuations, which is noise introduced by scattered rays.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the lateral distribution of radiation dose, characterized in that, Includes the following steps: A radiation dose lateral distribution measurement device is provided, comprising a scintillator luminescent material, an optical mirror, an optical imaging system, and a data analysis system. The scintillator luminescent material, optical mirror, and optical imaging system are all housed within a housing. When the radiation to be detected is incident along a direction perpendicular to the scintillator luminescent material, the scintillator luminescent material emits photons under the illumination of the radiation. The optical mirror reflects the photons emitted by the scintillator luminescent material to the optical imaging system. The optical imaging system receives the photons and forms an image. The data analysis system is located outside the housing and is used to analyze the image data acquired in real time by the optical imaging system to obtain the lateral dose profile distribution result of the radiation to be detected. Before beam irradiation, images without radiation irradiation are acquired and sent to the data analysis system as background images. After the beam begins to irradiate, several consecutively captured images during the irradiation process of the radiation to be detected are acquired as source images and sent to the data analysis system; Based on the background image and each source image, the data analysis system obtains the profiles of the image to be detected in the horizontal and vertical directions; The method for obtaining the horizontal and vertical profiles of the image to be detected by the data analysis system based on the background image and each source image includes: The obtained source images are each subtracted from the background image; Select the region of interest from the image obtained by subtraction to obtain the image of interest; The obtained image of interest is subjected to Fourier transform and spectral centering to obtain the matrix of interest; The obtained matrix of interest is subjected to low-pass filtering to obtain the filtered matrix, wherein the cutoff frequency of the low-pass filter is obtained by simulation calculation; The filtered image is obtained by performing an inverse Fourier transform on the filtered matrix. The projections of the filtered image in the horizontal and vertical directions are obtained respectively, thus obtaining the cross-sections of the beam to be detected in the horizontal and vertical directions.

2. The method for measuring the transverse distribution of radiation dose as described in claim 1, characterized in that, The scintillator luminescent material is rectangular, and the width of the scintillator luminescent material is greater than the maximum lateral length of the ray to be detected.

3. The method for measuring the transverse distribution of radiation dose as described in claim 1, characterized in that, The optical imaging system includes an optical lens, a filter, and a camera; the optical lens is used to collect the light generated by the scintillator luminescent material and reflected by the optical mirror, and to focus the collected light onto the imaging chip of the camera; the filter is used to select the wavelength of light that can pass through. The camera is used to collect and focus light into an image.

4. The method for measuring the transverse distribution of radiation dose as described in claim 3, characterized in that, The size of the optical reflector is not less than the minimum size of the complete image of the scintillator luminescent material captured by the optical lens.

5. The method for measuring the transverse distribution of radiation dose as described in claim 3, characterized in that, The angle between the scintillator luminescent material and the plane of the optical mirror, and the angle between the optical mirror and the axis of the optical lens, are both 45°.

6. The method for measuring the transverse distribution of radiation dose as described in claim 1, characterized in that, The optical imaging system is installed inside the scattered ray shielding system; the scattered ray shielding system is installed outside the outer casing.

7. The method for measuring the transverse distribution of radiation dose as described in claim 1, characterized in that, The inside of the outer shell is coated with a light-absorbing material.

8. The method for measuring the transverse distribution of radiation dose as described in claim 1, characterized in that, The spectral range of the optical imaging system and optical mirror includes the spectral peak of the scintillator luminescent material.

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