Novel triggering imaging method

Abstract

The invention provides a novel trigger imaging method, which is characterized in that two silicon photomultiplier modules are respectively coupled with two different scintillator detectors, so that stray radiation operation in a treatment chamber is sensed, and a detected radiation signal is converted into an optical signal. The SiPM detects scintillation photons and outputs corresponding current signals, the current signals are converted into voltage pulses through the current-voltage amplifier and then serve as input signals of the logic AND gate, and the logic AND gate is used for executing coincidence judgment so as to eliminate false trigger signals caused by neutron activation products generated by high-energy pulses (larger than or equal to 10 MV). And after logic summation, a shutter of the time-gated CCD camera is triggered to carry out imaging, and an imaging signal is processed by the data processing device and then is fed back to the linear accelerator in real time. The system has the characteristics of remote triggering, high response precision and no limitation of a linear accelerator, and the imaging flexibility and the synchronization precision in the radiotherapy process are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of radiotherapy and radiation imaging, and in particular to a remote trigger imaging method based on Cerenkov luminescence imaging technology. Background Art

[0002] Cancer has now become one of the most common diseases in China. Tumor radiotherapy is a method of treating malignant tumors using radiation such as α, β, and γ rays produced by radioactive isotopes and X-rays, electron beams, proton beams, and other particle beams produced by various X-ray therapy machines or accelerators. Although X-rays are currently the most mature radiotherapy technology, they are limited by the mechanical properties of radiotherapy equipment, the execution process of treatment plans, and changes in beam parameters, which will inevitably cause dose deposition to the endangered organs around the target area, increasing the probability of radiation damage to normal tissues. Therefore, new real-time dose detection systems are in urgent need of further development.

[0003] Cherenkov radiation refers to a type of electromagnetic radiation with a short wavelength that is emitted when the speed of an object moving in a medium exceeds the speed of light in the medium. Cherenkov radiation also occurs when radioactive particles enter biological tissues. Robertson et al. first applied Cherenkov radiation to the field of biomedical imaging and proposed the concept of Cherenkov photoluminescence imaging. Cherenkov photoluminescence imaging is an emerging imaging technology with broad application prospects in the biomedical field, especially for monitoring the dose in tissues during radiotherapy.

[0004] However, the Cherenkov light signal generated by high-energy radiation passing through biological tissue is a very weak light signal with an intensity of about 10 -6 ~10 -9 W / cm 2 At the same time, the wavelength of Cherenkov light is mainly concentrated in the short wavelength region of blue-violet, and biological tissue has very strong absorption of it, so the Cherenkov light signal that can be collected for imaging is very weak. In addition, the beam of the medical linear accelerator is pulsed, that is, a 5μs radiation pulse is provided every 5ms, resulting in the ambient light captured by the CCD camera and the intensity of the Cherenkov light optical signal being almost the same even under light-shielding conditions. On the other hand, conventional gating technology is achieved by directly connecting the camera to the linear accelerator, but the output signal line of the linear accelerator is not always accessible, and the physical line connected to the output port may change the performance of the linear accelerator through electrical feedback. Therefore, the development of a new remotely triggered time-gated hardware system is a key technical problem that needs to be solved urgently. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a time-gated hardware system that can be remotely triggered, has the characteristics of high response accuracy and is not limited by a linear accelerator.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A novel trigger imaging method, comprising: two silicon photomultiplier tube modules, two silicon photomultiplier tubes (2) are respectively coupled with two different scintillation detectors (4, 5), the scintillator works by detecting the stray radiation in the treatment room, the scintillation detector is connected to a current-voltage amplifier (7) to convert the radiation signal into a voltage pulse, two different voltage pulses are used as the inputs of a logic AND gate (8), the logic AND gate (8) is used to eliminate the false trigger signals caused by the neutron activation products generated by high-energy pulses (≥10 MV), and after performing logic summation, the shutter of a trigger time-gated CCD camera (1) is output to perform imaging, and the imaging signal is processed by a data processing device and then fed back to the linear accelerator in real time.

[0008] The described scintillation detector works by detecting the stray radiation in the treatment room, and the stray radiation mainly comes from the high-energy photons and secondary electrons generated during the operation of the linear accelerator. When high-energy radiation hits the scintillation crystal, the excited state molecules in the crystal jump to the ground state and emit photons, and the wavelength of the photons is usually in the visible light or near-ultraviolet range, and the photon yield is proportional to the energy of the incident radiation, thereby providing a dose-related optical signal.

[0009] The described silicon photomultiplier tube (2) is used to detect the scintillation photons emitted by the scintillation detector and convert the scintillation photons into current pulses. The silicon photomultiplier tube is based on the semiconductor avalanche effect, and through an internal high-gain amplification mechanism, the electron-hole pairs induced by single photons are amplified into measurable current signals. It has a high quantum efficiency, can achieve high-sensitivity detection in a low photon flux environment, and at the same time has a short response time, which helps to accurately capture pulsed radiation signals.

[0010] The described current-voltage amplifier (7) is used to convert the current signal into a voltage signal and amplify it. A low-noise operational amplifier structure is adopted to improve the signal-to-noise ratio and reduce the interference of background noise on weak signals. The bandwidth of the amplifier matches the output characteristics of the silicon photomultiplier tube to ensure that the amplified signal retains the original radiation information, which is convenient for subsequent signal processing and trigger decision-making.

[0011] The function of the described logic AND gate (8) is to eliminate the false trigger signals caused by the neutron activation products generated by high-energy pulses (≥10 MV). The logic AND gate (8) accepts the inputs from two different detectors, and through a dual-channel coincidence mechanism, it ensures that only when the two detectors simultaneously detect coincident radiation pulses, the CCD camera is triggered, thereby effectively suppressing the false positive signals caused by the mis-triggering of a single detector.

[0012] The described CCD camera is used to receive the output signal of the logic AND gate, and the shutter of the CCD camera is controlled by this signal. When the logic AND gate outputs a high-level signal, the shutter of the CCD camera opens to ensure that the camera only images when the synchrotron radiation pulse arrives, thereby significantly reducing ambient light interference and improving imaging contrast and signal quality.

[0013] There is a thin neutral filter (3) between the described scintillator and the silicon photomultiplier tube. This filter is used to regulate the light flux and optimize the incident light intensity of the silicon photomultiplier tube to avoid signal saturation and improve the photoelectric conversion efficiency. At the same time, this filter can effectively filter out low-energy background light and improve the selective detection ability of the system for high-energy radiation events.

[0014] The outer surface of the crystal of the described silicon photomultiplier tube is wrapped with white Teflon tape and shielded with an opaque housing to eliminate stray light detection. The high diffuse reflection characteristic of the Teflon tape helps to improve the light collection efficiency, make the photon direction distribution entering the silicon photomultiplier tube more uniform, and improve the detection sensitivity of the system. The opaque housing can shield ambient light interference and prevent the influence of background light on the detection signal, further optimizing the detection signal-to-noise ratio.

[0015] The described scintillator detector (5) is a BGO detector with a size of Ø3×20 mm 3 . This detector has a high density (7.13 g / cm³) and a high atomic number (Bi: 83, Ge: 32, O: 8), can provide excellent X-ray and γ-ray detection performance, has a high light yield, and has good radiation damage resistance to high-energy radiation.

[0016] The described scintillator detector (4) uses an array of 8 BGO crystals with a size of 5×5×5 cm 3 . This array structure improves the spatial detection coverage and enhances the sensitivity to incident radiation from different directions. In addition, multiple BGO crystal arrays can achieve multi-point sampling of the dose, improve the accuracy and reliability of the data, and help to optimize the synchronization of the remote gating system.

[0017] The described data processing device includes a signal transmission system, a processor, a non-transitory computer storage medium, and a data storage system (6), and is used to process the Cherenkov light signal obtained by the CCD camera and feedback it to the linear accelerator in real time. The data processing device uses a high-speed analog-to-digital conversion (ADC) unit to ensure the real-time conversion of the light signal. The processor analyzes the Cherenkov light distribution through a specific algorithm, corrects imaging artifacts, and calculates the dose distribution data. Finally, the processed information is transmitted to the linear accelerator through a feedback control mechanism to achieve dose closed-loop regulation and improve the safety and accuracy of radiotherapy.

[0018] The beneficial effects of the present invention include:

[0019] (1) The present invention uses a scintillator detector to convert stray radiation signals synchronized with the pulses of a linear accelerator into electrical signals to trigger a CCD camera. This method no longer requires a physical cable to connect to the linear accelerator, and can achieve remote synchronization even when the pulse signal is inaccessible.

[0020] (2) The wireless time gating technology proposed by the present invention significantly enhances the degree of freedom of spatial deployment, enabling the CCD camera to be flexibly placed at any position in the treatment room, without being restricted by the physical layout of the linear accelerator. This breakthrough improvement helps to optimize the imaging perspective, and enhances the adaptability and operational convenience of the system.

[0021] (3) The remote trigger time gating hardware architecture adopted by the present invention has high compatibility with the operating environment of the linear accelerator, does not introduce additional electronic feedback or impedance changes, avoids affecting the charge distribution and current in the tungsten target of the linear accelerator, and ensures the accuracy of radiation dose output.

[0022] (4) Considering the possible false positive triggers caused by neutron activation products, the present invention proposes to use two different detectors to form a coincidence detection mechanism, and control the CCD camera through the output AND gate of the two detectors, eliminating unnecessary false positive trigger events, and greatly improving the accuracy of remote trigger time gating. Brief Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the remote gating hardware system proposed by the present invention.

[0024] Figure 2 It is a physical diagram of the circuit board proposed by the present invention.

[0025] Figure 3 It is a working flow chart of the remote gating hardware system proposed by the present invention. Detailed Description of the Invention

[0026] The present invention will be further described in detail below in conjunction with the embodiments.

[0027] Such as Figure 1,2, As shown, a new type of trigger imaging method includes: two silicon photomultiplier tube modules. Two silicon photomultiplier tubes (2) are respectively coupled with two different scintillation detectors (4, 5). The scintillator works by detecting the stray radiation in the treatment room. The scintillation detector is connected to a current-voltage amplifier (7) to convert it into a voltage pulse. The two different voltage pulses serve as the inputs of a logic AND gate (8). The logic AND gate (8) is used to eliminate the false trigger signals caused by the neutron activation products generated by high-energy pulses (≥10MV). After performing a logic sum, it outputs to trigger the shutter of the gated CCD camera (1) for imaging. The imaging signal is processed by a data processing device and then fed back to the linear accelerator in real time.

[0028] The described scintillation detector works by detecting the stray radiation in the treatment room. When the stray radiation hits the scintillation crystal, the crystal emits light radiation.

[0029] The silicon photomultiplier tube (2) is used to detect the scintillation photons emitted by the scintillation detector and convert the scintillation photons into current pulses.

[0030] The described current-voltage amplifier (7) is used to convert the current signal into a voltage signal and amplify it.

[0031] The function of the described logic AND gate (8) is to eliminate the false trigger signals caused by the neutron activation products generated by high-energy pulses (≥10MV). The logic AND gate (8) accepts the inputs from two different detectors and outputs after performing a logic sum.

[0032] The described CCD camera is used to receive the output signal of the logic AND gate, and the shutter of the CCD camera is controlled by this signal.

[0033] There is a thin neutral filter (3) between the described scintillator and the silicon photomultiplier tube.

[0034] The outer surface of the crystal of the described silicon photomultiplier tube is wrapped with white Teflon tape and shielded with an opaque outer shell to eliminate the detection of stray light.

[0035] The described scintillation detector (5) is a BGO detector with a size of Ø3×20 mm 3

[0036] The described scintillation detector (4) uses an array of 8 BGO crystals with a size of 5×5×5 cm 3

[0037] The described data processing device includes a signal transmission system, a processor, a non-transitory computer storage medium, and a data storage system (6), and is used to process the Cherenkov light signal obtained by the CCD camera and feed it back to the linear accelerator in real time.

[0038] Figure 3 A novel remotely triggered event-gated hardware system proposed by the present invention, and its working process includes steps S100 to S300.

[0039] In this embodiment, a 2100CD linear accelerator is used. The camera and the detector are placed 2 meters away from the water phantom. The CCD camera gain is set to 400, the exposure time is set to 15 milliseconds, and the intensifier is gated by an external or stray X-ray trigger signal. Therefore, the CMOS camera can only collect light when the linear accelerator transmits radiation pulses.

[0040] During the experiment, an X-ray beam with an energy of 6 MV, a dose of 100 MU, and a dose rate of 600 MU / min is used to irradiate a 5×5 cm² irradiation field, a water phantom containing 1 g / L quinine sulfate is injected, and the linear accelerator gantry is rotated to a 90° angle for irradiation.

[0041] In the case of an exposure time of 15 milliseconds, theoretically about 5 linear accelerator pulse signals can be captured per frame.

[0042] The collected Cherenkov light signals are analyzed in real time by the data processing system, and the processing results are immediately fed back to the linear accelerator. There is only a slight difference in Cherenkov intensity between the images obtained by using the remote trigger time-gating technology and the wired gating, and the wireless trigger technology is feasible and stable in high-precision synchronous acquisition.

Claims

1. A novel triggered imaging method, characterized in that: Through two silicon photomultiplier tube modules, two silicon photomultiplier tubes (2) are respectively coupled with two different scintillator detectors (4, 5) to detect stray radiation in the treatment room. The scintillator detector is connected to a current-voltage amplifier (7) to convert the radiation signal into a voltage pulse. The two different voltage pulses are used as inputs of a logic AND gate (8). The logic AND gate (8) is used to eliminate the false trigger signal caused by the neutron activation product generated by the high-energy pulse (≥10MV). After logical summation, the output triggers the shutter of the time-gated CCD camera (1) to perform imaging. The imaging signal is processed by a data processing device and then fed back to the linear accelerator in real time.

2. A novel triggered imaging method according to claim 1, characterized in that: A thin neutral filter (3) is provided between the scintillator and the silicon photomultiplier tube.

3. A novel triggered imaging method according to claim 1, characterized in that: The outer surface of the crystal of the silicon photomultiplier tube is wrapped with white Teflon tape and shielded with an opaque housing to eliminate stray light detection.

4. A novel triggered imaging method according to claim 1, characterized in that: The scintillator detector (5) has a size of Ø3×20 mm. 3 The BGO detector.

5. A novel triggered imaging method according to claim 1, characterized in that: The scintillator detector (4) uses 8 5×5×5 cm 3 BGO crystal array.

6. A novel triggered imaging method according to claim 1, characterized in that: The data processing device comprises a signal transmission system, a processor, a non-transient computer storage medium and a data storage system.

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