Method and system for enhancing radiation imaging resolution

Abstract

The invention provides a method and a system for enhancing radiation imaging resolution. The device comprises a water tank, an optical photon high-sensitivity CCD (Charge Coupled Device) detector, a 360-degree detector rotating system and a computer processing unit, wherein the water tank is used for packaging a Cerenkov light emitting solution. According to the method, light intensity data of fluorescence emitted by Cerenkov light excitation quantum dots generated by MV-level rays in a water tank is acquired from multiple angles, light intensity distribution is obtained through three-dimensional reconstruction theory and technology reconstruction of limited optical detection information, and three-dimensional dose distribution of beams is finally obtained according to a quantitative relation between light intensity and dose deposition. The radiation therapy dose monitoring system provided by the invention can obtain three-dimensional dose distribution, is good in real-time linearity and simple in measurement, and can effectively ensure the curative effect of radiation therapy and guarantee the radiation safety of a patient.

Description

Technical Field

[0001] The present invention relates to the technical field of radiotherapy, and specifically, to a method and system for enhancing the resolution of radiation imaging. Background Art

[0002] As one of the three major means of treating tumors, the purpose of radiotherapy is to kill tumor cells to the greatest extent and effectively protect the surrounding normal tissues and vital organs. Large medical radiotherapy equipment, such as linear accelerators and treatment planning systems, must have strict quality control to ensure the correct radiotherapy for patients. The three-dimensional water tank ionization chamber, as an important tool for debugging and acceptance of various parameters of the accelerator and data acquisition of the treatment planning system, plays an important role in quality assurance and quality control work. Although the three-dimensional water tank ionization chamber system can automatically obtain various dosimetric parameters, it still has disadvantages such as low efficiency, long measurement time, and limited spatial resolution, and it is difficult to ensure the active implementation of relevant dose verification measurements in most domestic hospitals where the accelerator treatment time is tight. Therefore, there is an urgent need to develop a dose monitoring system with good real-time linearity, simple measurement, and high resolution. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a radiotherapy dose measurement device and measurement method that can obtain three-dimensional dose distribution, have good real-time linearity, simple measurement, and high resolution, aiming at the defects of the existing technology.

[0004] Specifically, the method includes:

[0005] A transparent acrylic water tank encapsulating a quantum dot solution;

[0006] Obtaining light intensity distribution frames and ambient light background frames in the water tank at 360 angles by a 360° detector rotation system carrying a high-sensitivity CCD detector for optical photon detection;

[0007] Using a computer processing unit to process the light intensity images obtained at each angle, and reconstructing the light intensity distribution based on the three-dimensional reconstruction theory and technology of limited optical detection information;

[0008] And finally obtaining the three-dimensional dose distribution of the beam according to the quantitative relationship between light intensity and dose deposition.

[0009] According to some embodiments of the present application, the transparent acrylic water tank encapsulating a quantum dot solution specifically includes:

[0010] The water tank is made of high-transparency acrylic plastic to ensure that the transmission of optical photons inside the water tank is not significantly affected by scattering or absorption, and the size is 50×50×50 cm 3, with a thickness of 5 mm to meet the spatial requirements for radiotherapy dose measurement; a water injection connector with upper and lower openings is provided at the side corner of the water tank, and a drain valve is provided at the lower edge of the front to facilitate rapid water injection and emptying, improving the operability of experimental measurements;

[0011] The concentration of the Cerenkov light-emitting solution encapsulated inside the water tank is 0.1 g / L, and the solute materials include quantum dots with stable luminescence such as carbon quantum dots, cadmium-based quantum dots, indium-based quantum dots, and perovskite quantum dots, ensuring stable fluorescence emission characteristics under high-energy radiation irradiation;

[0012] The absorption spectrum range of the quantum dots is 300 - 400 nm, and the emission peak is concentrated at 450 nm, which matches the optical sensitive intervals of the band-pass filter of the subsequent detection system and the CCD detector.

[0013] According to some embodiments of the present application, obtaining the light intensity distribution frames and ambient light background frames in the water tank at 360 angles by using a high-sensitivity CCD detector for optical photon detection carried by a 360° detector rotation system specifically includes:

[0014] According to the beam field, determine the geometric positions of the water tank encapsulating the quantum dot solution, the high-sensitivity CCD detector, and the 360° detector rotation system in the isocenter plane; to ensure the accuracy of measurement, this geometric position is fine-tuned by a high-precision laser calibration system to ensure that the center of the water tank is aligned with the beam isocenter plane, and at the same time, the axis of the detector rotation system is coaxial with the geometric center of the water tank. In addition, the installation angle of the CCD detector needs to match the beam projection direction to maximize the acquisition of Cerenkov light and quantum dot fluorescence signals and avoid signal distortion caused by detection angle deviation.

[0015] Before beam delivery, use a high-dynamic-range and high-transmittance imaging lens to obtain multi-angle ambient light background frames. During beam delivery, obtain multi-angle light intensity distribution frames under the same measurement parameter settings; during this process, the CCD detector pre-collects ambient light data at multiple angles and performs background noise analysis to construct an ambient light correction model. This model is used for background subtraction in subsequent data processing to improve the accuracy of the final dose measurement. During beam delivery, obtain multi-angle light intensity distribution frames under the same measurement parameter settings, and ensure that the exposure time of each frame of data is consistent with the beam pulse duration through a time synchronization control module to improve signal quality and reduce measurement errors.

[0016] The high-sensitivity CCD detector described above encapsulates a band-pass filter between the CCD element and the lens. The transmission band of the band-pass filter is 450±20nm, which matches the emission of the quantum dots and the sensitive band of the CCD detector. The band-pass filter uses a multi-layer interference coating technology, with high transmittance (≥95%) and high cut-off depth (OD > 5), which can effectively suppress background noise, improve signal selectivity, and ensure that the detected light intensity signal mainly comes from the fluorescence emission of quantum dots, rather than the direct contribution of ambient stray light or Cherenkov light.

[0017] The CCD detector lens described above is a high-dynamic-range and high-transmittance imaging lens, which has been optimized by coating to reduce aberration, improve optical transmission efficiency, ensure a large light input, and improve the detection performance of quantum dot fluorescence emission. The optical transmittance of the lens is greater than 98%, which can capture the weak fluorescence signal in the water tank to the greatest extent and improve the sensitivity of signal acquisition. In addition, the lens system has low distortion characteristics, which can ensure the geometric consistency of optical images obtained at different angles, thus enhancing the accuracy of three-dimensional reconstruction.

[0018] The CCD detector described above includes a scintillator + SiPM remote trigger time gating system to synchronize the CCD intensifier shutter with the beam pulse. The nanosecond-level time-resolved SiPM (silicon photomultiplier) is used as a pulse trigger. After detecting the initial signal of the beam pulse, it triggers the CCD shutter through a high-speed signal processing module, so that it only collects data during the action of the beam, thereby effectively reducing ambient light interference.

[0019] According to some embodiments of the present application, using a computer processing unit to process the light intensity images obtained at various angles, and reconstructing the light intensity distribution based on the three-dimensional reconstruction theory and technology of limited optical detection information specifically includes:

[0020] Using a computer processing unit to perform background subtraction, 5×5 median filtering, etc. on the light intensity images obtained at various angles. Background subtraction is mainly based on the previously collected ambient light background frame, and an adaptive background modeling method is used to remove ambient light interference, thereby improving the measurement accuracy. 5×5 median filtering is a non-linear denoising method, which can effectively suppress speckle noise and single-point abnormal signals, enhance the smoothness of the light intensity distribution, and at the same time keep the edge details intact. In addition, histogram equalization or contrast adaptive enhancement technology can also be used to optimize the dynamic range of optical signals and improve the signal visibility in weak fluorescence regions.

[0021] The finite element method is used as the solution means to improve the reconstruction efficiency. The finite element method is based on the photon transport model, divides the entire imaging area into discrete units, and realizes the inverse reconstruction of the light intensity field by solving the radiative transfer equation (RTE) or the diffusion approximation (DA). An artificial intelligence algorithm is introduced for post-processing to improve the reconstruction quality. In terms of computational optimization, an efficient three-dimensional light intensity reconstruction method is developed based on GPU+CPU heterogeneous parallel acceleration. Using parallel computing technologies such as CUDA / OpenCL, matrix calculations and convolution operations are performed in parallel on the GPU to accelerate the calculation process of the optical photon distribution, while the CPU is responsible for data management and synchronization operations. This method can significantly reduce the calculation time and enable the acquisition of the three-dimensional dose distribution to reach the quasi-real-time level, thus meeting the rapid response requirements of radiotherapy dose monitoring.

[0022] According to some embodiments of the present application, based on the quantitative relationship between light intensity and dose deposition, finally obtaining the three-dimensional dose distribution of the beam specifically includes:

[0023] Combined with the beam conditions set by the TPS plan, such as parameters such as field size, energy, irradiation time, and beam direction, a physical model is constructed. The Monte Carlo toolkit Geant4 is used to establish a radiotherapy dose model based on a water tank, track the propagation path of rays in the medium, and calculate processes such as secondary electron excitation, scattering, and deposition to obtain dose deposition information at different depths and positions; through the above calculations, the conversion coefficient from optical photon light intensity to dose deposition is obtained, that is, a quantitative calibration relationship between the optical detection signal and the dose physical measurement is established.

[0024] On this basis, the three-dimensional light intensity distribution data in the water tank obtained by detection is input into the dose calculation model, and dose conversion is performed according to the conversion coefficient to obtain a high-precision radiotherapy dose distribution. Finally, the calculated dose distribution is compared with the theoretical dose distribution simulated by Geant4 to evaluate the measurement accuracy of the system and perform necessary error corrections.

[0025] The beneficial effects of the present invention are as follows: Using the weak Cherenkov light generated during the interaction between rays and matter to excite quantum luminescence, and reconstructing the light intensity distribution of the transparent acrylic water tank encapsulating the quantum dot solution using the multi-angle two-dimensional light intensity distribution; at the same time, based on the quantitative relationship between the optical photon intensity and dose deposition, combined with the computer processing unit for photon transport simulation and dose correction, and then the three-dimensional dose distribution in the quality assurance water tank before radiotherapy can be obtained quickly and in real time. Compared with the traditional ionization chamber dose measurement method, the present invention can achieve higher spatial resolution and has faster signal acquisition and reconstruction capabilities, meeting the clinical real-time dose monitoring requirements to ensure the efficacy of radiotherapy and the radiation safety of patients. Brief Description of the Drawings

[0026] Figure 1 It is a schematic diagram of a method and system for enhancing the resolution of radiation imaging;

[0027] Figure 2 It is a schematic flowchart of the method for enhancing the resolution of radiation imaging according to the present invention. Detailed Description of the Invention

[0028] The following further describes the specific embodiments of the present invention in detail in conjunction with the drawings and embodiments, so as to better understand the solution of the present invention and the advantages of its various aspects. However, the specific embodiments and examples described below are for illustrative purposes only and are not limitations to the present invention.

[0029] As Figure 1 shown: The system for enhancing the resolution of radiation imaging in radiotherapy dose measurement includes: a water tank encapsulating a quantum dot solution that can enhance the intensity of Cherenkov light, a high-sensitivity CCD detector for collecting optical photons, a matching-bandpass filter encapsulated at the front end of the CCD detector, a 360° detector rotation system that can carry the high-sensitivity CCD detector to obtain light intensity distribution frames and ambient light background frames at 360 angles, a computer processing unit processes the light intensity images obtained at each angle, and reconstructs the light intensity distribution based on the three-dimensional reconstruction theory and technology of limited optical detection information. According to the quantitative relationship between the light intensity and the dose deposition, the three-dimensional dose distribution of the beam is finally obtained.

[0030] The size of the water tank is 50×50×50 cm 3 , with a thickness of 5 mm, and the material is transparent acrylic plastic; a water injection and connection device with upper and lower openings is installed at the side corner of the box body, and a water discharge valve is installed at the middle lower edge of the front of the box body to achieve rapid water injection and discharge;

[0031] The concentration of the solution that can emit Cherenkov light is 0.1 g / L, and the solute materials include luminescently stable quantum dots such as carbon quantum dots, cadmium-based quantum dots, indium-based quantum dots, and perovskite quantum dots;

[0032] The absorption spectral band of the quantum dots is 300 - 400 nm, and the emission peak is 450 nm;

[0033] The transmission band of the matching-bandpass filter encapsulated at the front end of the CCD detector is 450±20 nm, which matches the emission of the quantum dots and the sensitive band of the CCD detector.

[0034] The lens of the CCD detector is a high-dynamic-range and high-transmittance imaging lens to ensure a large amount of incident light and improve the detection performance of the fluorescence emission of the quantum dots;

[0035] The CCD detector includes a scintillator + SiPM remote trigger time gating system to synchronize the CCD intensifier shutter with the beam pulse to reduce the impact of ambient light on optical imaging;

[0036] The high-sensitivity CCD detector is fixed on a 360° detector rotation system, and the detector can be rotated 360° in all directions through a rotating device. The 360° detector rotation system can realize uniform speed rotation and fixed-point stop. The system can transmit the spatial angle information of the high-sensitivity CCD detector to a computer processing unit.

[0037] The computer processing unit has the functions of realizing background frame subtraction, three-dimensional reconstruction based on limited optical detection information, and conversion of light intensity distribution into dose distribution.

[0038] Figure 2 The present invention is a flow chart of a method for enhancing radiation imaging resolution by measuring radiation therapy dose, and the specific process is as follows:

[0039] Step 1: A transparent acrylic water tank encapsulating the quantum dot solution; the water tank is made of highly transparent acrylic material, with a size of 50×50×50 cm³ and a wall thickness of 5 mm to ensure optical uniformity and mechanical stability. The inside of the water tank is filled with a quantum dot solution with a fluorescence enhancement effect, the concentration of the quantum dot solution is 0.1 g / L, and the quantum dot materials include carbon quantum dots, cadmium quantum dots, indium quantum dots, perovskite quantum dots, etc. The absorption spectrum band is 300-400 nm, and the emission peak is located at 450 nm to match the spectral sensitivity range of the CCD detector. A water injection device connected up and down is installed at the side corner of the water tank to quickly fill and drain the solution to ensure the repeatability of the experiment.

[0040] Step 2: According to the beam field, determine the geometric position of the encapsulated quantum dot solution water tank, high-sensitivity CCD detector, and 360° detector rotation system in the isocenter plane; use a high-precision mechanical positioning system to ensure that the center of the quantum dot water tank is consistent with the accelerator isocenter, and adjust the position of the CCD detector through a high-precision electric platform to align it with the center of the water tank to receive optical signals at the optimal angle. The 360° detector rotation system is driven by a precision stepper motor and can achieve rotation with an angle increment of ≤1° to ensure the accuracy of multi-angle data acquisition.

[0041] Step 3: Use a high-dynamic-range and high-transmittance imaging lens to obtain multi-angle light intensity distribution frames during beam delivery and the ambient light background frame before beam delivery; the optical aperture of the imaging lens is F / 1.2 to improve the fluorescence photon collection efficiency, and anti-reflection coating is used to reduce light loss. A band-pass filter with a central wavelength of 450 ± 20 nm is encapsulated at the front end of the CCD detector to effectively suppress background noise and improve the signal-to-noise ratio. The acquisition of the ambient light background frame adopts a high-dynamic-range imaging mode, combined with an automatic exposure correction algorithm, to compensate for the impact of ambient light changes on the imaging quality.

[0042] Step 4: Process the light intensity images obtained at each angle, and reconstruct the light intensity distribution based on the three-dimensional reconstruction theory and technology of limited optical detection information; the computer processing unit preprocesses the obtained light intensity images, including background subtraction, 5×5 median filtering for noise reduction, etc., to improve the image signal quality. The finite element method (FEM) is used for three-dimensional reconstruction to improve the reconstruction accuracy and calculation efficiency. At the same time, an artificial intelligence algorithm is combined for data optimization to reduce artifacts and improve the stability of the reconstruction results. In terms of the computing architecture, a GPU+CPU heterogeneous computing mode is adopted to achieve efficient parallel computing and reduce the computing time.

[0043] Step 5: According to the quantitative relationship between light intensity and dose deposition, finally obtain the three-dimensional dose distribution of the beam; combined with the beam conditions in the TPS planning system, use the Monte Carlo simulation tool Geant4 to calculate the mapping relationship between the optical photon distribution and the dose deposition distribution, and establish a conversion coefficient library between light intensity and dose. Perform dose mapping on the obtained three-dimensional light intensity distribution to obtain the radiotherapy dose distribution, and compare and analyze it with the TPS calculation results to verify the measurement accuracy of the system. Finally, this system can provide real-time and accurate three-dimensional dose measurement without affecting the clinical treatment efficiency, and improve the quality control level of radiotherapy.

[0044] The above has introduced the embodiments of the present application in detail. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A method and system for enhancing the resolution of radiation imaging, characterized in that: include: A water tank encapsulating a quantum dot solution that can enhance the intensity of Cherenkov light, a high-sensitivity CCD detector for collecting optical photons, a matching bandpass filter encapsulated in the front end of the CCD detector, and a 360° detector rotation system that can carry a high-sensitivity CCD detector to obtain 360-angle light intensity distribution frames and ambient light background frames. A computer processing unit processes the light intensity images obtained at each angle and reconstructs the light intensity distribution based on the three-dimensional reconstruction theory and technology of limited optical detection information. Based on the quantitative relationship between light intensity and dose deposition, the three-dimensional dose distribution of the beam is finally obtained.

2. A method and system for enhancing radiation imaging resolution according to claim 1, characterized in that: The dimensions of the water tank are 50×50×50cm 3 , thickness is 5mm, material is transparent acrylic plastic.

3. The water tank according to claim 2, characterized in that: The water injection communicating vessel with upper and lower openings is installed at the side corner of the box body, and the water discharge valve is installed at the lower middle edge of the front side of the box body, so as to realize rapid water injection and discharge.

4. A method and system for enhancing radiation imaging resolution according to claim 1, characterized in that: The concentration of the solution capable of emitting Cherenkov light is 0.1 g / L, and the solute material includes carbon quantum dots, cadmium quantum dots, indium quantum dots, perovskite quantum dots and other quantum dots with stable light emission.

5. The method and system for enhancing radiation imaging resolution according to claim 1, characterized in that: The quantum dot absorption spectrum band is 300-400nm, and the emission peak is 450nm.

6. The matching bandpass filter packaged between the CCD detector element and the lens according to claim 1, characterized in that: The transmission band of the bandpass filter is 450±20nm, which matches the emission of quantum dots and the sensitive band of the CCD detector.

7. The high-sensitivity CCD detector according to claim 1, characterized in that: The lens used is a high dynamic range and high transmittance imaging lens to ensure a large amount of light input and improve the detection performance of quantum dot fluorescence emission.

8. The method for enhancing the resolution of radiation imaging according to claim 1, characterized in that: The computer processing unit has the functions of realizing background frame subtraction, three-dimensional reconstruction based on limited optical detection information, and conversion of light intensity distribution into dose distribution.

9. The method for enhancing the resolution of radiation imaging according to claim 1, characterized in that: The high-sensitivity CCD detector includes a scintillator + SiPM remote trigger time gating system to synchronize the CCD intensifier shutter with the beam pulse to reduce the impact of ambient light on optical imaging.

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