Dual-mode beam and dose regulation and control system, method and device for FLASH radiotherapy

Abstract

The invention discloses a dual-mode beam and dose regulation and control system, method and device for FLASH radiotherapy, and relates to the technical field of radiotherapy, the system comprises a mode switching module which drives an adjustable collimator arranged at an accelerator outlet or a transport line through a driving mechanism to realize dual-mode switching between a clinical mode and a FLASH mode, the switching position precision is guaranteed through a redundancy feedback mechanism; the beam shaping module adopts at least two materials with different physical properties based on proton and heavy ion Bragg peak characteristics, and realizes hierarchical modulation of beam range and dose distribution by adjusting the thickness and / or the number of the materials so as to optimize Bragg peak depth dose distribution; and the dose control module is used for realizing accurate dose control of FLASH radiotherapy by establishing a mapping relation between pulse parameters and monopulse dose and combining a target total dose to calculate a required pulse sequence. The accuracy of conventional radiotherapy is met, and ultrahigh dose rate beam regulation and control, accurate dose control and safe mode switching of FLASH radiotherapy can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radiotherapy, in particular to a dual-mode beam and dose regulation system, method and device for FLASH radiotherapy. BACKGROUND

[0002] Proton and heavy ion tumor treatment technology has become an internationally recognized advanced tumor radiotherapy method due to the unique depth dose distribution characteristics of the Bragg peak. It can accurately concentrate the radiation energy on the tumor target area, significantly improve the local control rate while reducing the damage to normal tissues, and is the mainstream development direction of current high-end radiotherapy equipment.

[0003] With the iteration of radiotherapy technology, FLASH radiotherapy, as a breakthrough technology, has attracted widespread attention. Its core feature is to deliver ultra-high dose (≥40 Gy) in a very short time (usually <1 s), significantly reducing normal tissue toxicity through "FLASH effect", and showing clinical potential better than traditional radiotherapy. However, this "short time-large dose" coupling characteristic poses new challenges to existing radiotherapy systems, and its clinical translation faces multiple technical bottlenecks:

[0004] 1. Beam regulation and mode compatibility problems

[0005] Existing proton therapy systems are mainly designed for conventional dose rates (fractionated radiotherapy) and cannot directly adapt to the ultra-high dose rate requirements (such as >40 Gy / s) of FLASH radiotherapy. Specifically:

[0006] Insufficient beam modulation accuracy: Traditional Bragg peak modulators mostly use single-stage regulation, resulting in SOBP flatness >5%, and significant scattering effects caused by high atomic number (high-Z) materials. Beam widening reduces the sharpness of the distal dose drop (R80-R20>3mm), making it difficult to meet the requirements of FLASH radiotherapy for dose distribution accuracy;

[0007] Mode switching safety risk: The switching between clinical mode and FLASH research mode lacks a reliable isolation mechanism, and the misuse of high-dose rate beams in clinical practice may cause safety accidents, and existing systems are difficult to support the flexible development of FLASH research while ensuring the normal operation of conventional treatment.

[0008] 2. Dose control technology bottlenecks

[0009] The extremely short time dose delivery requirement of FLASH radiotherapy puts traditional dose control systems in a dilemma:

[0010] Insufficient time accuracy: The response time of traditional dose servo systems is ≥100ms, which cannot meet the millisecond-level dose cutoff requirement, making it difficult to accurately deliver ultra-high dose in <1s;

[0011] Beam stability is poor: the flow intensity and pulse width of pulsed beam (such as proton beam generated by synchrocyclotron) will be amplified at ultra-high dose rate, resulting in significant increase of dose error;

[0012] Online monitoring failure: conventional ionization chamber is prone to saturation at ultra-high dose rate, and cannot realize real-time dose accurate measurement, and it is difficult to verify the accuracy of dose delivery.

[0013] 3. Insufficient adaptability of existing equipment

[0014] Current FLASH radiotherapy research relies on dedicated equipment, and the structural design of mainstream proton therapy systems (such as synchrocyclotron) does not consider the integration needs of FLASH mode, including ion source, radio frequency, vacuum, magnet and extraction subsystem. Although synchrocyclotron can produce proton beams through the synergistic effect of D-shaped electrodes, magnetic fields and radio frequency electric fields, its beam parameter adjustment and dose control logic are optimized for conventional radiotherapy and cannot directly support the "high stability and open-loop controllable" requirements of FLASH radiotherapy. If dedicated equipment is configured for FLASH research, it will significantly increase the research and development cost, and it is difficult to cooperate with existing clinical systems. SUMMARY

[0015] The purpose of the present application is to provide a dual-mode beam and dose regulation system, method and device for FLASH radiotherapy, which integrates beam shaping, dose control, mode switching and safety guarantee, to break through the technical bottleneck of FLASH radiotherapy, meet the accuracy of conventional radiotherapy, and realize ultra-high dose rate beam regulation, accurate dose control and safe mode switching of FLASH radiotherapy, and become the key to promote the clinical transformation of FLASH radiotherapy.

[0016] The purpose of the present application is achieved by adopting the following technical solutions:

[0017] In a first aspect, a dual-mode beam and dose regulation system for FLASH radiotherapy is provided, the system comprising:

[0018] A mode switching module is configured to drive an adjustable collimator at the outlet of an accelerator or a transport line through a driving mechanism to realize dual-mode switching between a clinical mode and a FLASH mode, and to guarantee the switching position accuracy through a redundant feedback mechanism.

[0019] A beam shaping module is configured to adjust the thickness and / or number of at least two materials with different physical properties based on the Bragg peak characteristics of protons and heavy ions to realize the hierarchical modulation of beam range and dose distribution, and to optimize the Bragg peak depth dose distribution.

[0020] The dose control module is used to establish a mapping relationship between pulse parameters and single-pulse dose, and calculate the required pulse sequence in combination with the target total dose, so as to achieve precise dose control of FLASH radiotherapy.

[0021] Preferably, the system further includes a security control module for providing security for the system, including:

[0022] The safety control module adopts an isolated connection method at the hardware level to achieve physical isolation between the FLASH dosage mode and the clinical mode;

[0023] The security control module software adopts a dual-mode independent switching mechanism, which provides independent access protection for FLASH mode and automatically disables FLASH-related configurations in clinical mode, and configures an independent mode parameter storage unit.

[0024] Preferably, mode switching is performed by driving an adjustable collimator with a motor; the adjustable collimator employs redundancy with dual potentiometers for real-time position feedback.

[0025] Preferably, the beam shaping module includes a beam modulation unit, which implements graded beam modulation through a graded modulator, which includes a coarse adjustment layer and a fine adjustment layer.

[0026] The coarse adjustment layer comprises multiple detachable first material components. The first material components are modularly designed through a detachable connection mechanism to achieve step-wise adjustment of the range. The material of the first material components is selected from high atomic number materials.

[0027] The fine adjustment layer includes multiple stacked layers of second material components with an adjustable number of layers. The second material components are used to achieve continuous fine adjustment of the range. The material of the second material components is selected from low atomic number materials.

[0028] Wherein, the total modulation range Ds of the coarse adjustment layer and the fine adjustment layer satisfies:

[0029] Ds=Σ(α i ×N i )+Σ(β j ×M j )+δ cal,

[0030] α i For the calibrated equivalent water thickness of the i-th first material component, N i The quantity of the i-th first material component used;

[0031] β j M is the calibrated equivalent water thickness of the j-th second material component. j Let j be the number of stacked layers of the j-th second material component;

[0032] delta cal is the scatter compensation, calibrated by Monte Carlo simulation.

[0033] Preferably, the equivalent water thickness of the first material assembly is an integer multiple of 5-20mm, the equivalent water thickness of the second material assembly is an integer multiple of 0.1-1mm, and the equivalent water thickness is calibrated by the following formula:

[0034] WET = [(R water -R air ) / (R material -R air )] x t material

[0035] Wherein, WET is the equivalent water thickness, R is the Bragg peak position, t material is the physical thickness of the material; R water is the Bragg peak range of the particle in water; R air is the Bragg peak range of the particle in air; R material is the Bragg peak range of the particle in the material.

[0036] Preferably, the dose control module comprises:

[0037] A dose rate pre-calibration unit, configured to dynamically set a dose rate range based on the tumor site radiosensitivity classification before establishing the mapping relationship between the pulse parameters and the single pulse dose; and a commissioning accelerator beam parameter, configured to stabilize the dose rate in the preset dose rate range.

[0038] A single pulse dose modeling unit, configured to determine the single pulse theoretical dose according to the dose rate and the pulse width; and correct the single pulse theoretical dose by experiment calibration to determine the calibrated single pulse dose, and establish the mapping relationship between the single pulse dose and the accelerator control parameter.

[0039] A pulse sequence generation unit, configured to calculate the required number of pulses according to the target total dose and the calibrated single pulse dose, and generate an executable pulse sequence.

[0040] A dose verification unit, configured to verify the difference between the actual output cumulative dose and the preset dose in real time; and send a feedback signal to the execution unit if the difference exceeds the preset threshold.

[0041] In a second aspect, the application provides a dual-mode beam and dose regulation method for FLASH radiotherapy, which comprises:

[0042] A drive mechanism is used to drive an adjustable collimator arranged at the outlet of the accelerator or the transport line to realize the dual-mode switching between the clinical mode and the FLASH mode, and a redundant feedback mechanism is used to ensure the switching position accuracy.

[0043] Based on the Bragg peak characteristics of proton heavy ions, at least two materials with different physical properties are used to realize the step modulation of the beam range and dose distribution by adjusting the thickness and / or number of materials, so as to optimize the Bragg peak depth dose distribution;

[0044] By establishing the mapping relationship between pulse parameters and single pulse dose, and combining the target total dose to calculate the required pulse sequence, the precise dose control of FLASH radiotherapy is realized.

[0045] Preferably, the beam step modulation is realized by a step modulator, which includes a coarse adjustment layer and a fine adjustment layer;

[0046] The coarse adjustment layer comprises a plurality of detachable first material assemblies, which are modularly designed by detachable connecting mechanisms for realizing the step adjustment of the range; the material of the first material assembly is selected from high atomic number materials;

[0047] The fine adjustment layer comprises a plurality of second material assemblies with adjustable number of superimposed layers, which are used to realize the continuous fine adjustment of the range; the material of the second material assembly is selected from low atomic number materials;

[0048] Wherein, the total modulation range Ds of the coarse adjustment layer and the fine adjustment layer satisfies:

[0049] Ds=Σ(α i ×N i )+Σ(β j ×M j )+δ cal

[0050] α i is the calibrated equivalent water thickness of the i-th first material assembly, N i is the number of use of the i-th first material assembly;

[0051] β j is the calibrated equivalent water thickness of the j-th second material assembly, M j is the number of superimposed layers of the j-th second material assembly;

[0052] δ cal is the scattering compensation amount, which is calibrated by Monte Carlo simulation.

[0053] Preferably, the equivalent water thickness of the first material assembly is an integer multiple of 5-20mm, the equivalent water thickness of the second material assembly is an integer multiple of 0.1-1mm, and the equivalent water thickness is calibrated by the following formula:

[0054] WET=[(R water -R air ) / (R material-R air )]×t material

[0055] wherein WET is the equivalent water thickness, R is the Bragg peak position, t material is the physical thickness of the material; R water is the Bragg peak range of the particle in water; R air is the Bragg peak range of the particle in air; R material is the Bragg peak range of the particle in the material.

[0056] Preferably, the precise dose control of FLASH radiotherapy is achieved by establishing a mapping relationship between pulse parameters and single pulse dose, combined with the calculation of the required pulse sequence based on the target total dose, which includes:

[0057] Before establishing the mapping relationship between pulse parameters and single pulse dose, the dose rate range is dynamically set based on the tumor site radiosensitivity grading; the beam parameters of the accelerator are adjusted so that the dose rate is stable within the preset dose rate range;

[0058] According to the dose rate and pulse width, the single pulse theoretical dose is determined; the single pulse theoretical dose is corrected through experimental calibration, the calibrated single pulse dose is determined, and the mapping relationship between the single pulse dose and the accelerator control parameters is established;

[0059] According to the target total dose and the calibrated single pulse dose, the number of required pulses is calculated, and an executable pulse sequence is generated;

[0060] The difference between the actual output cumulative dose and the preset dose is verified in real time; if the difference exceeds the preset threshold, a feedback signal is sent to the execution unit.

[0061] In a third aspect, the present application provides a hierarchical modulator for realizing hierarchical modulation of beam range and dose distribution, which includes a coarse adjustment layer and a fine adjustment layer.

[0062] The coarse adjustment layer comprises a plurality of detachable first material assemblies, the first material assemblies are modularly designed through detachable connecting mechanisms, and are used for realizing stepwise adjustment of the range; the material of the first material assemblies is selected from high-atomic-number materials;

[0063] The fine adjustment layer comprises a plurality of second material assemblies with adjustable number of superposed layers, the second material assemblies are used for realizing continuous fine adjustment of the range; the material of the second material assemblies is selected from low-atomic-number materials;

[0064] Wherein, the total modulation range Dsof the coarse adjustment layer and the fine adjustment layer satisfies:

[0065] Ds=Σ(α i ×N i )+Σ(βj ×M j )+δ cal

[0066] α i is the calibrated equivalent water thickness of the i-th first material assembly, N i is the number of use of the i-th first material assembly;

[0067] β j is the calibrated equivalent water thickness of the j-th second material assembly, M j is the number of superimposed layers of the j-th second material assembly;

[0068] δ cal is the scattering compensation amount, calibrated by Monte Carlo simulation.

[0069] In a fourth aspect, the application provides a beam current grading modulation method for realizing the grading modulation of beam range and dose distribution, which is realized by a grading modulator including a coarse adjustment layer and a fine adjustment layer;

[0070] The coarse adjustment layer comprises a plurality of detachable first material assemblies, which are modularly designed by detachable connecting mechanisms for realizing the stepwise adjustment of the range; the material of the first material assemblies is selected from high atomic number materials;

[0071] The fine adjustment layer comprises a plurality of second material assemblies with adjustable number of superimposed layers, which are used for realizing the continuous fine adjustment of the range; the material of the second material assemblies is selected from low atomic number materials;

[0072] Wherein, the total modulation range Dsof the coarse adjustment layer and the fine adjustment layer satisfies:

[0073] Ds=Σ(α i ×N i )+Σ(β j ×M j )+δ cal

[0074] α i is the calibrated equivalent water thickness of the i-th first material assembly, N i is the number of use of the i-th first material assembly;

[0075] β j is the calibrated equivalent water thickness of the j-th second material assembly, M j is the number of superimposed layers of the j-th second material assembly;

[0076] δ cal is the scattering compensation amount, calibrated by Monte Carlo simulation.

[0077] In a fifth aspect, the application provides a beam dose control method, comprising:

[0078] Before establishing the mapping relationship between the pulse parameters and the single-pulse dose, a dose rate range is dynamically set based on the radiation sensitivity classification of the tumor site; the beam parameters of the accelerator are adjusted so that the dose rate is stabilized within the preset dose rate range;

[0079] According to the dose rate and the pulse width, the single-pulse theoretical dose is determined; the single-pulse theoretical dose is corrected through experiments, the calibrated single-pulse dose is determined, and the mapping relationship between the single-pulse dose and the accelerator control parameters is established;

[0080] According to the target total dose and the calibrated single-pulse dose, the number of required pulses is calculated, and an executable pulse sequence is generated;

[0081] The difference between the actual output cumulative dose and the preset dose is verified in real time; if the difference exceeds the preset threshold, a feedback signal is sent to the execution unit.

[0082] In a sixth aspect, the application provides a radiotherapy system, comprising:

[0083] A cyclotron is used as a beam generation device to generate a proton beam for clinical radiotherapy or FLASH research;

[0084] The dual-mode beam and dose control system for FLASH radiotherapy is connected to the beam output end of the cyclotron and is used to adapt to the conventional dose requirement of clinical radiotherapy and the ultra-high dose rate requirement of FLASH radiotherapy, thereby achieving the functions of precise tumor radiotherapy and FLASH research.

[0085] In a seventh aspect, the application provides an electronic device, which comprises a memory and a processor, the memory stores a computer program, and the processor implements the steps of the method of any one of the aspects of the application or the functions of the system of the application when executing the computer program.

[0086] In an eighth aspect, the application provides a computer-readable storage medium, which stores computer instructions, and when a computer reads the computer instructions, the computer executes the steps of the method of any one of the aspects of the application.

[0087] Compared with the prior art, the application has at least the following beneficial effects: the adjustable collimator is driven by the driving mechanism to achieve convenient dual-mode switching between the clinical mode and the FLASH mode, which can quickly respond to different treatment requirements and greatly improve the use flexibility and adaptability of the radiotherapy equipment. The redundant feedback mechanism guarantees the switching position accuracy and ensures the accuracy and stability of the equipment operation during the mode switching process, thereby providing a solid foundation for the safety of treatment.

[0088] Based on the characteristics of proton heavy ion Bragg peak, the beam shaping module adopts at least two materials with different physical properties, and adjusts the thickness and / or quantity of the materials to realize the step-by-step modulation of the beam range and dose distribution, so as to effectively optimize the Bragg peak depth dose distribution. This modulation method can accurately control the beam parameters according to the specific position and shape of the tumor, improve the irradiation dose of the tumor tissue, reduce the radiation damage to the surrounding normal tissue, and significantly improve the accuracy and treatment effect of radiotherapy.

[0089] The dose control module establishes the mapping relationship between the pulse parameters and the single pulse dose, calculates the required pulse sequence combined with the target total dose, realizes the accurate dose control of FLASH radiotherapy. This can strictly output accurate dose according to the treatment plan during radiotherapy, avoid poor treatment effect or additional harm to patients caused by dose deviation, and provide safer and more effective treatment for patients.

[0090] The safety control module provides comprehensive safety protection for the system from two aspects of hardware and software. The hardware adopts isolated connection mode to realize the physical isolation of FLASH dose mode and clinical mode, effectively preventing mutual interference and potential risks between different modes. The software adopts a double-mode independent switching mechanism to independently protect the FLASH mode, automatically disable the FLASH related configuration in the clinical mode, and configure an independent mode parameter storage unit, further improving the safety and stability of the system, preventing safety accidents caused by misoperation, and fully protecting the safety of patients and medical staff. BRIEF DESCRIPTION OF DRAWINGS

[0091] Figure 1 is a dual-mode beam and dose regulation system for FLASH radiotherapy according to an embodiment of the present application;

[0092] Figure 2 is a dual-mode working diagram according to an embodiment of the present application;

[0093] Figure 3 is a dose distribution test result diagram according to an embodiment of the present application;

[0094] Figure 4 is an execution process diagram of a dual-mode beam and dose regulation system for FLASH radiotherapy according to an embodiment of the present application;

[0095] Figure 5 is a dual-mode beam and dose regulation method for FLASH radiotherapy according to an embodiment of the present application;

[0096] Figure 6 is a beam dose control method according to an embodiment of the present application;

[0097] Figure 7Figure 1 is a schematic diagram of a hardware connection of a cyclotron and a dual-mode beam and dose regulation system for FLASH radiotherapy according to an embodiment of the present application. DETAILED DESCRIPTION

[0098] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the implementations set forth herein; rather, these implementations are provided as non-limiting examples so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the figures, and thus description of the same will be simplified and omitted.

[0099] The words expressing position and direction described in the present application are described by taking the drawings as an example, but changes can also be made as needed, and the changes made are included in the protection scope of the present application.

[0100] A cyclotron generally includes five subsystems through which the five subsystems interact with each other in a complex manner to generate a proton beam for clinical treatment or research; the five subsystems include an ion source subsystem, a radio frequency (RF) subsystem, a vacuum subsystem, a magnet subsystem, and an extraction subsystem. From the appearance, the cyclotron usually looks like a cylinder with two semicircular cylindrical electric boxes separated by a small distance in the middle. The RF subsystem forms an alternating electric field through the separation distance to accelerate the protons when they pass through. With the dipole separating the cylinder into two independent parts, one electrode is in the shape of the letter "D", and the other electrode is in the shape of the reversed letter "D", which is the reason why the dipole electrode is commonly known as "D-shaped electrode". There is a magnetic field in the D-shaped electrode that guides the particles (i.e., protons) from one D-shaped electrode to the other D-shaped electrode, and the protons also gain energy when passing through the slit.

[0101] The protons turn around and return along a curved path to the slit and the reversed D-shaped electrode. The protons pass through the slit and are accelerated. Then they enter the reversed D-shaped electrode and return along a curved path to the slit and the reversed D-shaped electrode. This is repeated continuously until the protons reach the extraction point near the outer edge of one of the D-shaped electrodes. At this time, the extraction subsystem guides the proton beam into the downstream subsystem or conducts experiments or irradiates patients.

[0102] REFERENCE Figure 1 The present application proposes a dual-mode beam and dose regulation system for FLASH radiotherapy, which comprises:

[0103] A mode switching module is configured to drive an adjustable collimator arranged at the outlet of the accelerator or the transport line through a driving mechanism to realize dual-mode switching between the clinical mode and the FLASH mode, and to guarantee the switching position accuracy through a redundant feedback mechanism.

[0104] Beam shaping module, for realizing the stepwise modulation of the beam range and dose distribution by adjusting the thickness and / or quantity of the materials with at least two different physical properties based on the Bragg peak characteristics of protons and heavy ions, so as to optimize the Bragg peak depth dose distribution;

[0105] Dose control module, for realizing the precise dose control of FLASH radiotherapy by establishing the mapping relationship between the pulse parameters (current, pulse width) and the single pulse dose, and combining the target total dose to calculate the required pulse sequence.

[0106] Since the current required for conventional treatment or test is far lower than that required in FLASH, the greater the current, the higher the requirements for various parameters and indicators of the accelerator subsystem, and the higher the cost, the application designs a collimator at the outlet of the accelerator or the transport line to meet the switching requirements of the two modes, which is used for beam shaping in the conventional clinical mode, and can completely offline without collimating the beam in the FLASH mode, thereby reducing the beam loss and improving the dose rate. The collimator adopts a motor potentiometer driving control mode, the position and voltage signal of the collimator are calibrated, a double potentiometer real-time feedback position redundancy mode is adopted, the voltage value is displayed on the interface of the main control computer, and a limit two-end double-redundancy potentiometer is used to monitor the position in real time, so as to ensure the reliability of the position.

[0107] Refer to the attached Figure 2 , the double working modes include:

[0108] Clinical mode: the potentiometer is positioned to P2 (beam shaping position);

[0109] FLASH mode: the potentiometer is positioned to P1 (completely remove the beam restriction);

[0110] Redundancy monitoring: double potentiometers feed back the position deviation in real time to ensure safety and reliability.

[0111] In the region on the beam transport line at the outlet of the accelerator, a mechanical connection interface that can be quickly disassembled and assembled with the conventional treatment head is designed, the bracket is designed to be compatible with the mechanical interface of the conventional mode, and only needs to be quickly installed and disassembled through a simple screw structure, so as to switch the mechanical switching of the FLASH mode and the conventional mode.

[0112] From the safety level, the safety is ensured by combining software and hardware:

[0113] Hardware level: the FLASH dose module and the clinical system are connected only through a single optical fiber, without too many complex connections and each other;

[0114] Software level: FLASH mode and clinical mode adopt double mode independent switching mode, FLASH mode operation interface independent password protection, clinical mode automatically disable FLASH system configuration, the accelerator system parameters of the conventional mode are stored in the conventional mode of the Xml configuration file, the accelerator parameters of the FLASH mode are stored in the FLASH corresponding Xml file, which are independent of each other. The standardization Log display and export tool is provided at the FLASH software level, which can provide clues for process data recording and machine troubleshooting.

[0115] Through the double mode switching of the collimator (clinical mode P2, FLASH mode P1), the beam shaping is realized by the collimator in the conventional clinical mode to ensure the accuracy of the dose distribution of the conventional treatment; in the FLASH mode, the beam restriction is completely removed, the beam loss is reduced, and the dose rate is significantly improved to adapt to the core requirement of the "ultra-high dose rate" of FLASH radiotherapy. The rapid switching of the two modes makes the same device meet the dual scenes of conventional radiotherapy and cutting-edge FLASH research, improves the utilization rate of the device and the flexibility of clinical application.

[0116] Compared with the scheme of designing a high-index accelerator for FLASH mode alone, the system realizes beam regulation through collimator switching, avoids the requirement of maintaining ultra-high current in the conventional mode, reduces the manufacturing, maintenance cost and operating loss of the accelerator, and realizes high-precision mode switching at low cost through the motor potentiometer driving and redundant feedback design of the collimator, further controlling the investment of the device.

[0117] The collimator adopts a redundant design of double potentiometers for real-time feedback of position, combined with double-redundancy monitoring of limit position, through voltage signal calibration and visual interface of the main control, to ensure the accuracy and reliability of the switching position (P1 / P2); the real-time feedback mechanism of the deviation of the double potentiometers can timely find the position abnormality, avoid the beam parameter abnormality caused by mode switching error, and improve the safety of treatment.

[0118] The quick disassembly mechanical interface of the accelerator outlet beam line area is compatible with the mechanical connection of the conventional treatment head, and the mechanical switching between FLASH mode and conventional mode can be completed through simple screw structure, which greatly shortens the mode conversion time and reduces the operation complexity of medical staff, adapting to the requirement of fast switching scene in clinical treatment.

[0119] At the hardware level, the FLASH dose module and the clinical system are connected through a single optical fiber, reducing the interference risk caused by complex interaction; at the software level, double mode independent switching, independent password protection and parameter file isolation (Xml file is stored separately) are adopted to avoid parameter confusion and misoperation between modes, and the standardization Log tool of FLASH mode facilitates data tracing and troubleshooting, which fully guarantees the safety of treatment from operation process to data management.

[0120] The removal of the collimator restriction in FLASH mode reduces beam loss and directly improves dose rate; the beam shaping module based on the hierarchical modulation of Bragg peak characteristics, combined with the precise calculation of the pulse sequence of the dose control module, ensures the dose distribution uniformity and accuracy of short-time and large-dose delivery in FLASH mode, reduces the damage to normal tissues, and improves the treatment effect.

[0121] In summary, through the design of "precise switching, controllable cost, safe and reliable, and scene adaptation", the system effectively solves the compatibility problem of FLASH radiotherapy and conventional mode, and provides a practical and economical technical solution for the precision, high efficiency and frontier research of clinical radiotherapy.

[0122] In a possible implementation, the beam shaping module includes a beam modulation unit, which realizes hierarchical modulation of the beam through the hierarchical modulator, and the hierarchical modulator includes a coarse adjustment layer and a fine adjustment layer;

[0123] The coarse adjustment layer includes a plurality of first material assemblies with the same or different thicknesses and being detachable, the first material assemblies realize modular design through detachable connecting mechanisms, and are used to realize stepwise adjustment of the range; the material of the first material assembly is selected from high atomic number materials, including but not limited to at least one of lead, tungsten, tungsten carbide, and high-density alloy;

[0124] The fine adjustment layer includes a plurality of second material assemblies with the same or different thicknesses and adjustable number of superposed layers, and the second material assemblies are used to realize continuous fine adjustment of the range; the material of the second material assembly is selected from low atomic number materials; including but not limited to at least one of polyethylene, polypropylene, polystyrene, and water equivalent plastic.

[0125] The hierarchical modulation includes:

[0126] A large range of range adjustment is realized by combining different numbers of first material assemblies (N i The nominal WET of each first material assembly is α i (i=1,2,3,…);

[0127] The fine adjustment layer: a small range of range compensation is realized by combining different numbers of second material assemblies (M j The nominal WET of each second material assembly is β j (j=1,2,3,…);

[0128] Wherein, the total modulation range Ds of the coarse adjustment layer and the fine adjustment layer satisfies:

[0129] Ds=Σ(α i ×Ni )+Σ(β j ×M j )+δ cal

[0130] α i is the nominal equivalent water thickness of the i-th first material assembly, N i is the number of use of the i-th first material assembly;

[0131] β j is the nominal equivalent water thickness of the j-th second material assembly, M j is the number of superposition layers of the j-th second material assembly;

[0132] δ cal is the scattering compensation, calibrated by Monte Carlo simulation.

[0133] In a possible implementation, the equivalent water thickness of the first material assembly is an integer multiple of 5-20mm, the equivalent water thickness of the second material assembly is an integer multiple of 0.1-1mm, and the equivalent water thickness is calibrated by the following formula:

[0134] WET = [(R water -R air ) / (R material -R air )] × t material

[0135] where WET is the equivalent water thickness, R is the Bragg peak position, t material is the physical thickness of the material; R water is the Bragg peak range of the particle in water; R air is the Bragg peak range of the particle in air; R material is the Bragg peak range of the particle in the material.

[0136] For example, the coarse adjustment layer is composed of ≥4 carbon blocks with WET being an integer multiple of 10mm; the fine adjustment layer is composed of ≥4 polyethylene sheets with WET being an integer multiple of 1mm.

[0137] In a possible implementation, the beam shaping module further comprises a scattering suppression assembly, comprising:

[0138] a multi-leaf collimator closely attached to the rear end of the modulator, with a continuously adjustable aperture in the range of 5-40mm 2 ;

[0139] an ionization chamber support with coaxiality error ≤1mm with the collimator, for supporting a transmission type absolute dose ionization chamber.

[0140] In the beam shaping module, the result of optimizing the Bragg peak depth dose distribution satisfies:

[0141] Spread out Bragg peak (SOBP) flatness ≤ ± 3% measured by multi-layer ionization chamber array (step 0.1mm);

[0142] Distal dose fall-off gradient R80-R20≤2mm measured by Gafchromic film.

[0143] The scatter compensation amount δ cal The calibration method comprises the following steps:

[0144] Establishing a collimating aperture-lateral penumbra mapping table (example: 10x10mm 2 Aperture→penumbra 3.2±0.3mm);

[0145] Based on Monte Carlo simulation, the beam spreading effect under different material combinations is calculated;

[0146] The compensation amount is embedded in the range model, so that the distal dose fall-off gradient satisfies R80-R20≤2mm.

[0147] In a possible implementation, the dual-mode beam and dose regulation subsystem further comprises:

[0148] A special FLASH ionization chamber is installed downstream of the beam shaping module, which integrates a temperature / pressure / humidity calibration PCB circuit board, a humidity control area, a metal high-voltage plane, an optical fiber acquisition component, and a closed window, and is suitable for ultra-high dose rate beam acquisition; wherein the temperature / pressure / humidity compensation PCB is used to calibrate the influence of environmental parameters on the dose in real time; the metal high-voltage plate is sealed and isolated from the optical fiber signal acquisition end;

[0149] A dose cabinet is connected to the FLASH ionization chamber through an optical fiber, and a signal amplifier is built-in to realize fast dose measurement, data processing, and control;

[0150] A matching assembly includes a special computer (installed with measurement and analysis software), an optical fiber / connection cable (component interconnection), a Faraday cup / beam blocker (collects blocked beams).

[0151] Since conventional ionization chambers are prone to saturation and have slow response speed, a special FLASH ionization chamber is very important, which includes a set of temperature, pressure, and humidity calibration PCB circuit board functions, a humidity control function area, a metal plane for high-voltage area, an optical fiber signal acquisition component, and two closed windows, etc. A dose control cabinet is used to control and collect Dose-related information.

[0152] The working principle of the above technical solution is:

[0153] Traditional Bragg peak modulator has two major defects: single-stage regulation precision is insufficient: resulting in spread-out Bragg peak (SOBP) flatness > 5%; scattering effect is significant: high atomic number material causes beam spread, reducing the sharpness of the dose drop (R80-R20 > 3mm) at the far end.

[0154] When protons / heavy ions move in the medium, the energy loss increases with depth, and eventually forms an energy deposition peak (Bragg peak) at the end of the range. In order to better utilize the characteristics of the Bragg peak depth dose distribution unique to protons / heavy ions, the research area and experimental area are set in the region of the Bragg peak, and the core of beam shaping is to adjust the range of the beam in the medium to make the Bragg peak accurately cover the tumor target area while reducing the dose deposition of normal tissues. The graded modulator (coarse adjustment layer + fine adjustment layer) realizes the stepwise large-range adjustment and continuous small-range compensation of the range through the "stopping effect" of the material on the beam, and finally matches the depth requirement of the tumor.

[0155] The coarse adjustment layer uses high atomic number materials (such as lead, tungsten, tungsten carbide, etc.), which have strong stopping power (the energy loss of particles in the material is fast) and large equivalent water thickness (WET) (5-20mm integer multiples). When the beam passes through the coarse adjustment layer assembly, the high atomic number material will significantly shorten the Bragg peak range of the beam, and the increase or decrease of the number of assemblies can realize the "stepwise" large-range adjustment of the range (the range adjustment amount is equal to the equivalent water thickness ai for each increase of 1 assembly).

[0156] According to the approximate depth of the tumor target area (such as 10-100mm), the number of first material assemblies is increased or decreased through detachable connecting mechanism. For example, to increase the range by 30mm, 2 assemblies with ai = 15mm (15x2 = 30mm) can be combined to realize fast and large-span range coarse adjustment, laying the foundation for subsequent fine adjustment.

[0157] The fine adjustment layer uses low atomic number materials (such as polyethylene, water equivalent plastic, etc.), which have weak stopping power (slow energy loss of particles) and small equivalent water thickness (0.1-1mm integer multiples). When the beam passes through the fine adjustment layer assembly, the range changes little, and through the continuous adjustment of the number of layers (such as from 1 layer to 5 layers), the "continuous" small-range compensation of the range can be realized, making up for the insufficient precision of the coarse adjustment layer step interval.

[0158] After the coarse adjustment layer determines the approximate range, the fine depth of the tumor target area (such as ±2mm) is compensated accurately by increasing or decreasing the number of layers of the second material assembly. For example, if the coarse adjustment range deviates by 1.2mm, 12 layers of βj = 0.1mm assemblies (0.1x12 = 1.2mm) can be stacked to make the Bragg peak completely cover the target area.

[0159] The main reference factor for the thickness selection of the material is the equivalent water thickness of the particles in water, which is used to define the actual thickness of the material. The equivalent water thickness (WET) is a core parameter for measuring the stopping power of the material, and its calibration is based on the physical relationship of the Bragg peak range;

[0160] The physical thickness of the material is converted into the equivalent water thickness (WET) by the difference in Bragg peak range of particles in water, air, and material. Due to the high atomic number of the material, the R material <R water (Stopping power is stronger), and the R materia of low atomic number materials is close to R wate (Stopping power is weaker), which can accurately quantify the adjustment ability of different materials to the beam range, providing a reference for the selection of coarse / fine adjustment components.

[0161] Due to the difference in materials and processing, the range adjustment thickness and number of combinations can be changed during the test to measure the dose rate of each group. The dose rate is measured by an absolute dose ionization chamber, and the measurement position is calibrated using a position adjustment device and film to verify the accuracy of the measurement. After recording the material combination, equivalent water depth, and measured dose rate, the depth dose distribution of the particle at the spread Bragg peak can be seen, and a corresponding FLASH spread Bragg peak SOBP can be used to meet the test requirements; ensure that the area with FLASH dose rate is wide enough for the Bragg peak.

[0162] In summary, the beam shaping module realizes the accurate regulation of the beam depth dose distribution through the following steps:

[0163] WET calibration: equivalent water thickness of the stopping power of different materials is calculated using physical formulas to unify the quantitative standard;

[0164] SOBP verification: through ionization chamber and film measurement, ensure that the dose flatness of the platform area and the terminal drop gradient meet the clinical requirements; SOBP is a "platform area" formed by the superposition of multiple Bragg peaks, and its width needs to cover the tumor target area. The flatness (dose fluctuation in the platform area) and the far-end drop gradient (rapid decrease of dose at the end of the platform area) directly affect the dose of normal tissues:

[0165] Flatness ≤ ± 3%: ensure uniform dose in the tumor target area, avoid local over / under dose;

[0166] Far-end drop gradient (R80-R20 ≤ 2mm): make the dose drop rapidly outside the target area to protect normal tissues.

[0167] The measurement parameters of the spread Bragg peak are shown in Table 1:

[0168] Table 1

[0169]

[0170] Scatter compensation: record the correspondence between collimating aperture and penumbra, provide the basis for scatter compensation in clinical treatment; scatter compensation record table refers to Table 2;

[0171] Table 2

[0172] Collimating aperture (mm 2 )]]> Lateral half-shadow (mm) 10×10 3.2±0.3 20×20 4.1±0.2 40×40 5.8±0.4

[0173] Finally, the Bragg peak of the beam precisely covers the tumor target area, and through SOBP optimization and scatter compensation, normal tissues are protected, and the dose requirements of conventional radiotherapy and FLASH radiotherapy are adapted.

[0174] Among them, the adjustable collimator: through the motor-driven double potentiometer redundant control, switches between clinical mode and FLASH mode, shapes the beam cross section and optimizes the dose rate;

[0175] Square bracket: provide a mechanical interface to quickly disassemble and assemble different mode treatment heads, and ensure the stability of beam transmission;

[0176] Ionization chamber: real-time monitoring of beam dose parameters (intensity, distribution), feedback to the control system to form a closed loop, and ensure treatment accuracy.

[0177] The adjustment effect of the coarse adjustment layer and the fine adjustment layer is integrated through the total modulation range, ensuring that the final range accurately matches the depth of the tumor; the coarse adjustment layer quickly matches the approximate depth of the tumor target area through the large equivalent water thickness (5-20mm) of high atomic number materials, reducing the adjustment steps; the fine adjustment layer compensates for the step interval of the coarse adjustment through the small equivalent water thickness (0.1-1mm) of low atomic number materials, achieving fine adjustment of ±0.1mm level; whether it is a conventional clinical mode (which requires accurate dose distribution) or a FLASH mode (which requires range stability under high dose rate), the hierarchical modulation can be quickly adapted through component combination to ensure the dynamic matching of beam range and tumor depth.

[0178] In one possible implementation, the physical thickness t i The equivalent water thickness a i satisfies the following relationship:

[0179] a i =f1×t i where f1 is the equivalent water thickness coefficient of the material, f1≥2.0 (corresponding to high atomic number material), and the f1 value of each first material component deviates by ≤±0.5%;

[0180] The physical thickness t j of the second material component and the equivalent water thickness b j satisfy the following relationship:

[0181] β j = f2 x t j wherein f2 is the equivalent water thickness coefficient of the material, 0.8 ≤ f2 ≤ 1.2 (for low atomic number materials), and the f2 value of each second material component deviates by ≤ ± 0.3%.

[0182] The combination of the first material component and the second material component comprises:

[0183] Stacked arrangement: the first material component and the second material component are stacked in sequence along the beam direction;

[0184] Nested arrangement: the second material component is embedded in the preset groove of the first material component.

[0185] The working principle and effect of the above technical solution are:

[0186] By quantifying the material characteristics through the equivalent water thickness coefficient (f1 / f2) and optimizing the beam path through stacked / nested arrangement, the precise regulation of the beam range and the dose distribution is achieved, and the core logic is divided into two steps:

[0187] High atomic number material (first component): due to strong stopping power (fast particle energy loss), the coefficient f1 ≥ 2.0 is needed to amplify the contribution of physical thickness to equivalent water thickness. For example, 1mm thick tungsten (f1 = 2.5), the equivalent water thickness α i = 2.5 x 1 = 2.5mm, realizing "thin material large range adjustment", reducing the total thickness of the material on the beam path, and adapting to the "high dose rate requirement" of FLASH radiotherapy (the thinner the material, the smaller the beam loss, and the higher the dose rate).

[0188] Low atomic number material (second component): due to weak stopping power (slow particle energy loss), the coefficient 0.8 ≤ f2 ≤ 1.2 is used to fine-tune the relationship between physical thickness and equivalent water thickness. For example, 1mm thick polyethylene (f2 = 1.0), the equivalent water thickness β j = 1.0 x 1 = 1.0mm, realizing "thick material small range compensation", avoiding insufficient mechanical strength due to too thin material during fine tuning.

[0189] Stacked arrangement: the first component (high atomic number) and the second component (low atomic number) are stacked in sequence along the beam direction, first through high atomic number material to greatly shorten the range (coarse adjustment), and then use low atomic number material for fine tuning (fine adjustment). For example, when treating deep tumors (large range requirement), stacked arrangement can quickly compress the beam range, adapting to the "depth dose coverage" requirement of the conventional clinical mode.

[0190] Nested arrangement: the second component (low atomic number) is embedded in the pre-set groove of the first component, so that the thickness of the two materials in the beam direction is superimposed, and the lateral distribution is more uniform. For example, in the FLASH mode, the nested arrangement can reduce the lateral scattering of the beam (due to the low atomic number material filling the groove, the beam cross section uniformity is optimized), and the stability of the dose rate is improved.

[0191] The large coefficient f1 (≥2.0) of the high atomic number material makes "thin material achieve large range adjustment", reduces the total thickness of the material on the beam path (such as 1mm tungsten equivalent to 2.5mm water, reducing the thickness by 1.5mm compared with direct use of water), reduces the beam loss, and adapts to the high dose rate requirement of FLASH radiotherapy (dose rate is negatively correlated with beam loss);

[0192] The small coefficient f2 (0.8-1.2) of the low atomic number material makes "thick material achieve small range compensation", avoids mechanical deformation caused by too thin material during fine adjustment (such as polyethylene thickness ≥1mm, higher processability and stability), and ensures the fine adjustment accuracy.

[0193] The "coarse adjustment first and fine adjustment later" of the stacked arrangement adapts to the "depth dose coverage" of the conventional clinical mode (such as tumor depth 100mm, first compress the range to 90mm by stacking high atomic number material, and then fine adjust to 100mm by low atomic number material);

[0194] The deviation control of the material coefficient (f1 deviation ≤±0.5%, f2 deviation ≤±0.3%) ensures the consistency of the equivalent water thickness of different batches of components, reduces the "component replacement calibration" requirement of clinical treatment; the mechanical structure compatibility of the nested arrangement makes the component can adapt to the beam transport line of different accelerators (only need to adjust the groove size), improves the cross-platform universality of the equipment.

[0195] The "thinning" of the high atomic number material (due to the large f1, the material usage can be reduced), reduces the procurement cost of the component (such as 40% reduction of tungsten usage); the simple structure of the stacked and nested arrangement facilitates the rapid replacement of the component in the clinic (such as completing the increase and decrease of the stacked component within 5 minutes), reduces the equipment downtime.

[0196] In one possible implementation, the component selection of the coarse adjustment layer and the fine adjustment layer satisfies:

[0197] Max (α i ×N i ) / Σ(β j ×M j )∈[Cmin,Cmax];

[0198] The critical value (Cmin, Cmax) of the component selection of the coarse adjustment layer and the fine adjustment layer is calibrated through the following simulation process:

[0199] (1) Constructing FLASH radiotherapy exclusive simulation environment

[0200] Based on the particle transport simulation program, integrate the dose rate dependent nonlinear scattering physical model, which is used to simulate the nonlinear behavior of the dynamic change of the scattering characteristics with the dose rate when the FLASH radiotherapy ultra-high dose rate beam interacts with the material;

[0201] Couple the thermal-dose synergistic conduction module to simulate the real-time change of material temperature caused by short-time high-dose deposition and its dynamic influence on the beam stopping power of the material.

[0202] (2) Perform scenario-based parameter scanning and indicator monitoring

[0203] The input parameters include typical beam characteristics and environmental parameters of FLASH radiotherapy, including beam intensity, pulse duration, material initial environmental state, etc., to match the actual beam conditions of clinical FLASH research;

[0204] The monitoring indicators include but are not limited to: the dose distribution uniformity of the spread Bragg peak (SOBP), the proportion of scattered dose to total dose, the beam dose rate stability, and the drift amplitude of the material equivalent water thickness with beam action time.

[0205] Cmin (coarse adjustment layer dominant threshold): When the ratio of the adjustment capacity of the coarse adjustment layer to the fine adjustment layer is lower than Cmin, the monitoring result shows that the SOBP dose distribution uniformity exceeds the preset acceptable range, and the beam dose rate stability decreases below the threshold, indicating that the coarse adjustment layer cannot effectively dominate the stepwise adjustment;

[0206] Cmax (fine adjustment layer safety threshold): When the above ratio is higher than Cmax, the monitoring result shows that the proportion of scattered dose exceeds the safety threshold, and the drift amplitude of the material equivalent water thickness exceeds the allowed range, indicating that the fine adjustment layer overcompensation leads to beam control out of control.

[0207] The working principle of the above technical solution is:

[0208] With the help of particle transport simulation program, consider the nonlinear behavior of the dynamic change of the scattering characteristics with the dose rate when the beam interacts with the material under FLASH radiotherapy ultra-high dose rate (≥40Gy / s). For example, ultra-high dose rate will cause changes in the material microstructure in a short time, and the scattering angle and probability no longer follow the conventional linear law, which can accurately simulate this complex change and provide a physical basis for subsequent regulation.

[0209] A short time and large dose (such as a single 10-40Gy) is deposited to the material, which can cause the temperature of the material to rise rapidly (possibly reaching tens or even hundreds of degrees Celsius), and the temperature change will affect the stopping power of the material to the beam (such as the temperature rise, which may reduce the stopping power of some materials). The module simulates the real-time temperature change and dynamically associates the stopping power, making the simulation more realistic in the real radiotherapy scene.

[0210] The actual beam characteristics (beam intensity may be several times higher than conventional radiotherapy, and pulse duration is as short as sub-millisecond) and environmental parameters (initial material temperature, air pressure, etc.) of FLASH radiotherapy are recorded to ensure that the simulation conditions are consistent with clinical FLASH research, so that the critical value of subsequent calibration can directly serve the clinic.

[0211] The spread-out Bragg peak (SOBP) is the key to accurately covering the tumor with FLASH radiotherapy. Poor uniformity can cause uneven "hot and cold" within the tumor, affecting treatment efficacy and increasing the risk of normal tissue damage, which needs to be strictly monitored (such as requiring a uniformity deviation of ≤±3%).

[0212] If the scattered dose is too high (such as more than 10% of the total dose), it will form unnecessary dose deposition in the normal tissue around the tumor, and its proportion needs to be controlled within a safe range (such as ≤5%).

[0213] FLASH radiotherapy relies on stable high dose rate to ensure treatment efficacy, and large dose rate fluctuations (such as more than ±2%) will cause the actual total dose to deviate from the target, so stability needs to be maintained (such as fluctuations ≤±1%).

[0214] The equivalent water thickness of the material will change due to temperature and dose effects, which will directly affect the accuracy of beam range control, and the drift amplitude needs to be limited (such as ≤0.1mm).

[0215] Dynamically determine the critical value, when Max(α i ×N i ) / Σ(β j ×M j )<Cmin, the coarse adjustment layer has weak adjustment ability and cannot dominate the stepwise large-range range control; simulation shows that the SOBP dose distribution uniformity is poor (such as deviation >±5%), and the beam dose rate stability drops below the threshold (such as fluctuation >±3%), at which point the coarse adjustment layer component needs to be increased or the material needs to be adjusted to strengthen the coarse adjustment.

[0216] When Max(α i ×N i ) / Σ(β j ×M jWhen Cmax, the fine-tuning layer overcompensates, the simulation exceeds the standard (e.g., >7%) of the scattered dose ratio, the material equivalent water thickness drifts out of control (e.g., >0.2mm), the beam flow control is chaotic, and the fine-tuning layer intervention needs to be reduced or the material combination needs to be optimized to return the fine-tuning to the "small range accurate compensation" positioning.

[0217] The effect of the above technical solution is:

[0218] Precise adaptation of FLASH radiotherapy physical characteristics specific simulation environment (nonlinear scattering model + thermal-dose coordination module), precise reproduction of the complex physical process of beam-material interaction under the "ultra-high dose rate, short time large dose deposition" scenario of FLASH radiotherapy, solving the problem of ignoring dose rate and temperature dynamic influence in conventional simulation, making the critical value calibration more in line with the actual needs of clinical practice. Improve the safety and effectiveness of beam flow control By monitoring indicators such as scattered dose ratio and equivalent water thickness drift, early warning of the risk of coarse adjustment deficiency and fine adjustment overcompensation, avoiding treatment safety problems caused by beam flow control out of control (such as high scattered dose damaging normal tissues, dose rate fluctuations causing total dose deviation), and ensuring patient safety. Clear division of labor between coarse adjustment layer "dominant stepwise adjustment" and fine adjustment layer "responsible for accurate compensation", so that beam range control can both efficiently cover the tumor (coarse adjustment quickly matches the approximate depth) and finely correct the deviation (fine adjustment compensates for small errors), improving the effectiveness of FLASH radiotherapy in killing tumors.

[0219] In one possible implementation, δ cal Calibrated through collimation aperture and material combination;

[0220]

[0221] A coll A is the collimation aperture area, A ref The reference area is determined by the collimator design parameters of the radiotherapy equipment;

[0222] μ is the material linear scattering coefficient (cm -1 Obtained by Monte Carlo simulation Geant4, positively correlated with material atomic number and beam energy);

[0223] T PE The total thickness of the fine-tuning layer (cm, the thickness of the low-atomic-number material stack);

[0224] N C The number of first material components (adapted to the step adjustment needs of the coarse adjustment layer);

[0225] δflash is the FLASH radiotherapy specific compensation term (nonlinear scattering caused by ultra-high dose rate, δflash = θ·D^0.5, θ is the nonlinear scattering coefficient, D is the dose rate, unit Gy / s);

[0226] b1, b2, theta are scattering coefficients fitted by Monte Carlo simulation + experiment (b1 e [0.1, 0.5], b2 e [0.01, 0.1], theta e [0.005, 0.02], adapt to beam energy, material combination).

[0227] The working principle of the above technical solution is:

[0228] The collimating hole area determines the initial cross-sectional size of the beam, and the ratio of the collimating hole area to the reference area reflects the change of the "initial scattering space" of the beam. The material scattering attenuation term The material scattering attenuation term describes the attenuation effect of the fine adjustment layer material on the beam scattering. The thicker the material, the greater the scattering coefficient, and the more obvious the suppression of beam scattering. The compensation amount needs to be adjusted accordingly. The more the number of coarse adjustment layer components, the more complex the scattering of the beam in the coarse adjustment stage, and the scattering deviation introduced by the coarse adjustment needs to be compensated through the linear term.

[0229] Due to the ultra-high dose rate (such as ≥40 Gy / s) of FLASH radiotherapy, the interaction between the beam and the material presents nonlinear scattering (the conventional linear scattering model fails), and the FLASH radiotherapy exclusive compensation term specially compensates for the nonlinear scattering deviation under the ultra-high dose rate, reflecting the particularity of the FLASH radiotherapy scene.

[0230] The effect of the above technical solution is: quantifying the nonlinear scattering caused by the ultra-high dose rate of FLASH radiotherapy, solving the problem of ignoring the nonlinear influence of dose rate in conventional modeling. Under the ultra-high dose rate of 60 Gy / s, the dose deviation caused by nonlinear scattering can be accurately compensated, ensuring the accuracy of FLASH radiotherapy dose. Coupling multiple physical parameters such as collimating hole area, material scattering coefficient, and number of coarse adjustment components, covering the whole process scattering influence of the beam from "collimation shaping → coarse adjustment scattering → fine adjustment attenuation", realizing "full-chain scattering compensation", and making the beam control more suitable for the complex physical environment of FLASH radiotherapy.

[0231] In one possible implementation, the dose control module comprises:

[0232] A dose rate pre-setting unit is configured to, before establishing a mapping relationship between pulse parameters and single-pulse dose, dynamically set a dose rate range based on the radiation sensitivity classification of the tumor site; and adjust the beam parameters of the accelerator so that the dose rate is stable within the preset dose rate range.

[0233] A single-pulse dose modeling unit is configured to calculate a single-pulse theoretical dose in combination with pulse width and dose rate, and correct the single-pulse theoretical dose through experimental calibration to establish a mapping relationship between the calibrated single-pulse dose and the control parameters of the accelerator.

[0234] D_pulse_theory = D x PW_opt

[0235] D_pulse_theory is a theoretical single-pulse dose; D is a dose rate; PW_opt is an optimal pulse width;

[0236] The optimal pulse width value with the minimum variation coefficient is selected as the optimal pulse width by testing different pulse widths and calculating the variation coefficient of the dose rate at each pulse width based on the monitoring data.

[0237] The single-pulse dose D_pulse_cal after calibration is determined by correcting the theoretical single-pulse dose through laboratory calibration (dual ionization chamber collaborative calibration (main ionization chamber measures total dose, micro-dose ionization chamber measures single-pulse dose)), and the mapping relationship between the single-pulse dose after calibration and the accelerator control parameters (such as magnetic field strength B and radio frequency voltage VRF) is established; D_pulse_cal=f(B, VRF); f() is a mapping relationship function; for example, a continuous function can be generated by polynomial fitting to specifically represent this mapping relationship;

[0238] The pulse sequence generation unit is used to receive the optimal pulse width and the single-pulse dose after calibration, calculate the required number of pulses according to the target total dose, and generate an executable pulse sequence; the executable pulse sequence includes pulse width and current; Map={Pulse1:(PW1, I1), Pulse2:(PW2, I2),..., PulseN:(PWN, IN)} Np Np Np );

[0239] Np=round(D_total / D_pulse_cal)

[0240] round() is automatic rounding; D_total is the target total dose;

[0241] The verification unit is configured with a fiber-coupled dose monitoring system (sampling frequency≥1kHz) and performs the following operations: the cumulative dose is monitored online by a transmission type absolute dose ionization chamber, the difference between the actual output cumulative dose and the preset dose, and the single-pulse dose difference are verified in real time, and if any difference exceeds the preset threshold, a feedback signal is sent to the execution unit.

[0242] For example: single-pulse dose difference |D_pulse_meas-D_pulse_cal| / D_pulse_cal≤3%

[0243] D_pulse_meas is the dose average of the pulse sequence;

[0244] (D_measured-D_total) / D_total×100%<5;

[0245] ​​D_measured is the real-time cumulative dose; D_total is the preset total dose;

[0246] An execution unit is configured to execute the pulse sequence, load the optimized pulse sequence Map to the accelerator control system, and strictly execute Np pulses according to the Map to achieve the ms-level dose truncation accuracy. The pulse emission interval is synchronized with the accelerator radio frequency cycle (error ≤ 10 ns).

[0247] The working principle of the above technical solution is as follows:

[0248] Based on the radiosensitivity of the tumor site (for example, intracranial tumors are more sensitive to dose), the dose rate range is dynamically set (for example, ≥ 40 Gy / s in FLASH mode and 2-10 Gy / s in conventional mode). By adjusting the accelerator beam core parameters (magnetic field strength B, radio frequency voltage VRF), the output dose rate is stabilized in the preset range, for example, for trunk tumors, the dose rate is locked at 50±2Gy / s, which provides a stable reference for subsequent single-pulse dose calculation and avoids initial errors caused by fluctuations in the dose rate.

[0249] Test different pulse widths (for example, 0.5-2 ms), collect dose rate data under each pulse width through the optical fiber coupling monitoring system, calculate the coefficient of variation (CV = standard deviation / mean), and select the pulse width with the smallest CV as the optimal pulse width (PW_opt). For example, when PW = 1 ms, the dose rate coefficient of variation is 1.2% (less than 0.8 ms of 2.5% and 1.5 ms of 1.8%), then PW_opt = 1 ms, which ensures the stability of the single-pulse dose.

[0250] Based on the optimal pulse width, the theoretical single-pulse dose (D_pulse_theory = D × PW_opt, D is the pre-calibrated dose rate) is calculated; then through double ionization chamber calibration, the main ionization chamber measures the total dose, and the micro-dose ionization chamber (high time resolution) measures the single-pulse dose, and the theoretical value is corrected to obtain the calibrated single-pulse dose (D_pulse_cal).

[0251] For example, a pulse with a theoretical value of 0.05 Gy is corrected to 0.048 Gy after calibration, which is more consistent with the actual output.

[0252] D_pulse_cal is associated with the accelerator control parameters (B, VRF) to form a mapping function D_pulse_cal = f(B, VRF). For example, when B = 0.5T and VRF = 5MV, D_pulse_cal = 0.048Gy, and the subsequent single-pulse dose can be directly regulated by adjusting B or VRF to achieve parameterized precise control.

[0253] According to the target total dose (D_total, such as 4 Gy) and the calibrated single-pulse dose (D_pulse_cal = 0.048 Gy), the required number of pulses is calculated: Np = round(D_total / D_pulse_cal) = round(4 / 0.048) = 83. A sequence containing the width of each pulse (PW) and the flow intensity (I) is generated:

[0254] Map = {Pulse1: (PW_opt, I1), Pulse2: (PW_opt, I2),..., Pulse83: (PW_opt, I83)}

[0255] The verification unit configures the fiber-coupled dose monitoring system (sampling frequency ≥ 1 kHz) to perform two core verifications in real time:

[0256] Single-pulse dose difference verification: Calculate |D_pulse_meas - D_pulse_cal| / D_pulse_cal (D_pulse_meas is the measured average single-pulse dose), which should be ≤ 3%. For example, if D_pulse_cal = 0.048 Gy and the measured average is 0.049 Gy, the deviation is 2.1% (meets the requirements); if the deviation reaches 4%, a feedback signal is triggered.

[0257] Cumulative dose difference verification: Calculate |D_measured - D_total| / D_total x 100% (D_measured is the real-time cumulative dose), which should be < 5% for example. For example, the target total dose is 4 Gy, when the cumulative dose reaches 3.8 Gy, the deviation is 5%, triggering a warning; if it reaches 3.7 Gy (deviation 7.5%), an immediate cutoff signal is sent.

[0258] The execution unit loads the pulse sequence Map to the accelerator control system and strictly executes Np pulses according to the sequence:

[0259] Timing synchronization: The pulse emission interval is synchronized with the accelerator radio frequency period (error ≤ 10 ns), avoiding dose superposition errors caused by timing deviation;

[0260] Fast cutoff: After receiving the feedback signal from the verification unit, millisecond-level dose cutoff is achieved (response time ≤ 0.5 ms), for example, when the single-pulse deviation exceeds the limit, the current pulse is terminated within 0.3 ms to prevent excessive dose;

[0261] Redundancy guarantee: After cutoff, a redundant pulse sequence is enabled to ensure that the total dose still meets the accuracy requirements (such as the remaining 0.2 Gy dose is supplemented by the redundant sequence after the original sequence is interrupted).

[0262] The technical scheme has the following effects:

[0263] FLASH radiotherapy is a radiotherapy technology that delivers an ultra-high dose (≥40 Gy) in a very short time (usually <1 s), and its core advantage is that it can significantly reduce normal tissue toxicity (FLASH effect). However, the coupling of very short time and large dose poses a severe challenge to dose control. The present scheme meets the high-precision requirements of FLASH radiotherapy for "short-time large-dose deposition" through optimal pulse width screening (minimum coefficient of variation) and double ionization chamber calibration; the cumulative dose deviation is <5%, combined with real-time verification dynamic early warning, to avoid insufficient or excessive total dose due to equipment drift and ensure tumor killing effect. The sampling frequency of the fiber-coupled system is ≥1 kHz, which can capture the instantaneous dose fluctuation of the ultra-high dose rate (≥40 Gy / s) in FLASH mode, solving the "sampling deficiency" problem of conventional monitoring systems; millisecond-level dose truncation (≤0.5 ms) and radio frequency cycle synchronization (error ≤10 ns) adapt to the stringent timing requirements of FLASH radiotherapy with less than 1 s irradiation time, avoiding the risk of dose out-of-control at high dose rate.

[0264] Double-dimension verification bottom-up: dual monitoring of single-pulse dose difference and cumulative dose difference ensures dose safety from "instantaneous" and "overall" two levels, reducing damage to normal tissues caused by dose deviation;

[0265] Dynamic dose rate setting based on tumor radiosensitivity can adapt to the radiotherapy needs of different parts of the tumor (such as intracranial and trunk), achieving personalized dose control; redundant pulse sequences are enabled after truncation to ensure uninterrupted treatment, improving device fault tolerance and clinical treatment success rate.

[0266] The execution effects of specific parameters are shown in Table 3:

[0267] Table 3

[0268]

[0269] After 10 repeated verifications, the dose output error is <3%, and the stability is 97.2%.

[0270] In one possible implementation, the pre-calibration of the dose rate includes:

[0271] According to the radiosensitivity of the target tumor site, dynamically set the range of the dose rate D (such as 40-60 Gy / s for intracranial tumors and 60-100 Gy / s for trunk tumors); adjust the accelerator beam parameters to stabilize the dose rate D within the preset range;

[0272] Optimize the pulse current (I) and pulse width (PW) to ensure that the single-pulse dose stability meets the preset stability threshold.

[0273] The optimization of the pulse flow intensity (I) and the pulse width (PW) includes:

[0274] Fixing PW adjusts I, so that the inter-pulse dose fluctuation is less than a first fluctuation threshold (e.g., 3%);

[0275] Fixing I adjusts PW, so that the pulse width precision error is less than a first error threshold (e.g., 0.1 ms).

[0276] In a possible implementation, the mapping relationship D_pulse_cal = f(B, VRF) is established in the following manner:

[0277] Under constant PW, a two-dimensional lookup table is calibrated for the (B, VRF) combination and D_pulse_cal;

[0278] A continuous function is generated through polynomial fitting:

[0279] D_pulse_cal e = A0+A1*B+A2*VRF+A3*B 2 +A4*VRF 2

[0280] The coefficients Au are calibrated by the least square method; u = 0, 1, 2, 3, 4.

[0281] The above technical solution has the following effects:

[0282] According to the tumor site (intracranial / torso), the dose rate is dynamically set to balance "tumor killing" and "normal tissue protection". For example, for intracranial tumors, 40-60 Gy / s is used to reduce nerve damage, and for torso tumors, 60-100 Gy / s is used to strengthen tumor killing, thereby improving the level of personalized radiotherapy. Through the two-dimensional optimization of I and PW, the single pulse dose fluctuation is less than 3%, and the pulse width error is less than 0.1 ms, which meets the stringent requirements of FLASH radiotherapy "short time and large dose deposition" (conventional radiotherapy allows 5% fluctuation), and ensures the dose accuracy. The lookup table makes the association "visualized", and the clinical parameters can be quickly matched (e.g., the query is completed within 200 ms); the continuous polynomial function supports dose prediction for any parameter combination, breaks away from the limitations of lookup table, and adapts to complex radiotherapy schemes. The pre-calibration and optimization process reduces the time for repeatedly adjusting B and VRF to find the dose in the clinic (e.g., from 30 minutes to 5 minutes), improves the efficiency of radiotherapy equipment startup, and indirectly reduces medical costs.

[0283] In a possible implementation, the pulse sequence generation unit is configured to perform an intelligent prediction-based sequence optimization strategy:

[0284] Based on the number of pulses, it is divided into long sequences and short sequences (e.g., if Np>100, it is a long sequence, and if Np is less than or equal to 100, it is a short sequence), and an adaptive optimization strategy is used respectively: including:

[0285] Long sequence adopts uniform distribution strategy The average value of the pulse width of the long sequence is; The average value of the pulse flow intensity of the long sequence is;

[0286] Short sequence adopts flow intensity increasing compensation strategy:

[0287] I g = I1+ (g-1) · ΔI

[0288]

[0289] Wherein, I g is the flow intensity of the gth pulse in the pulse sequence, I1is the flow intensity of the 1st pulse in the pulse sequence; PWg is the pulse width of the gth pulse in the pulse sequence; I max is the upper limit of the flow intensity allowed by the accelerator hardware (determined by pre-calibration, such as <200nA, to avoid excessive single pulse dose); constraint condition: I g ≤ I max (Always limit the flow intensity within the hardware safety threshold);

[0290] The pulse sequence contains a preset emergency redundancy pulse, the parameters of which can be dynamically cancelled and only activated when the pre-sequence pulse dose is insufficient.

[0291] In a possible implementation, the pulse sequence generation unit is configured to perform an intelligent prediction-based sequence optimization strategy:

[0292] Based on the number of pulses, it is divided into long sequence and short sequence (for example, if Np>100, it is a long sequence, and if Np is less than or equal to 100, it is a short sequence), and an adaptive optimization strategy is adopted respectively:

[0293] The long sequence adopts a uniform distribution combined with a drift compensation strategy, and periodically corrects the parameters of subsequent pulses according to the drift trend of the beam parameters of the previous pulses; for example, one verification pulse is inserted every h pulses (for example, 10 pulses), and the pulse width of the subsequent pulses is corrected;

[0294] The corrected pulse width formula is:

[0295]

[0296] Wherein, PWg' is the pulse width of the gth pulse in the pulse sequence after correction; ΔPW = k_drift x ΔR (ΔR is the range drift measured by the verification pulse, k_drift is the pulse width correction coefficient, k_drift ∈ [0.1, 0.3] mm / Gy is calibrated through experiment); k = floor((g-1) / h) (k is the serial number of the verification pulse, k = 0, 1, 2,..., indicating the k+1 group of h pulses);

[0297] Constraint: PWg' ≤ PW_max (PW_max is the maximum pulse width allowed by hardware, to avoid excessive single pulse dose);

[0298] The short sequence adopts the strategy of increasing beam current combined with prediction compensation, predicts the beam parameter attenuation trend based on neural network, and compensates the dose rate attenuation through dynamic adjustment of beam current;

[0299] I g = I1+ (g-1) · ΔI · (1+ δ d ·D drift )

[0300]

[0301] Wherein, I g is the beam current of the gth pulse in the pulse sequence, I1 is the beam current of the 1st pulse in the pulse sequence; I max is the upper limit of the beam current allowed by the accelerator hardware (determined by pre-calibration, such as <200 nA, to avoid excessive single pulse dose); constraint: I g ≤ I max (Always limit the beam current within the hardware safety threshold); δ d is the dynamic compensation coefficient, determined by LSTM neural network and physical constraints; D drift is the dose rate drift, calculated in real time through temperature / vacuum monitoring.

[0302] The determination of the dynamic compensation coefficient by LSTM neural network and physical constraints includes:

[0303] Based on the historical pulse sequence data (beam parameters, dose rate, temperature, vacuum degree), the beam attenuation trend of the current pulse is predicted, and the initial compensation coefficient δ d _init is outputted;

[0304] The initial compensation coefficient is modified by the initial compensation coefficient and the physical constraint condition (such as the dose rate stability threshold), and the final compensation coefficient δ d is obtained.

[0305] δ d = δ d_init x (1 + λ · (Ca - C_threshold))

[0306] Wherein, Ca is the actual value of the constraint index (such as the current dose rate standard deviation σ_current), C_threshold is the constraint threshold (such as 2%), and λ is the constraint strength coefficient (λ ∈ [0.1, 0.3], calibrated by experiment, balancing the prediction bias and the constraint strength).

[0307] The effect of the above technical solution is:

[0308] In a long sequence (such as 500+ pulses for total bone marrow irradiation), small fluctuations in beam parameters (current, pulse width) will be amplified cumulatively, resulting in total dose deviation exceeding the clinical threshold. Through the uniform distribution strategy, all pulse parameters are forced to be consistent, the "fluctuation accumulation risk" is converted into "fixed deviation" (which can be compensated by pre-calibration), reducing the total dose error of long sequence, meeting the dose accuracy requirements of FLASH radiotherapy "large fraction, long sequence" (such as single 20Gy irradiation, error <0.4Gy).

[0309] Insert 1 verification pulse every h pulses, measure the range drift in real time, and correct the subsequent pulse width to improve the compensation rate of subsequent pulse range drift.

[0310] In a short sequence (such as 10-30 pulses for intracranial metastasis), the accelerator hardware (such as the radio frequency source, magnet) will have parameter drift (such as current attenuation 2-5% / pulse) due to instantaneous high load, resulting in insufficient dose at the end of the pulse. Adopting the current increment strategy, let the current linearly increase with the pulse number, compensate for the hardware attenuation, use LSTM neural network to learn historical pulse data (current, dose rate, temperature, vacuum degree), predict the beam attenuation trend of the current pulse, output dynamic compensation coefficient, and correct it through physical constraint, reduce the dose deviation of the end pulse in the short sequence, and adapt to the clinical demand of "precise ablation of small tumors".

[0311] Referring to the accompanying drawings Figure 4 In one possible implementation, the execution process of the dual-mode beam and dose regulation system for FLASH radiotherapy includes:

[0312] S1, in response to the FLASH radiotherapy research instruction, starting the mode switching process, triggering the driving mechanism to remove the conventional mode treatment head;

[0313] S2, install the FLASH dedicated kit to the accelerator outlet / transport line adaptive position, detect and correct the physical installation position of the FLASH kit through the laser lamp calibration function, ensure that the position accuracy meets the preset requirements (for example, ≤±0.1mm);

[0314] S3. Control TC (terminal controller) master computer switches from clinical mode to FLASH mode, executes dual-mode independent switching mechanism, automatically disables clinical mode configuration, and loads FLASH mode exclusive permissions and control logic;

[0315] S4. Security state verification:

[0316] Verify the state of the collimator, confirm that the regular mode collimator is completely pulled out of the accelerator beam channel;

[0317] Verify the compatibility of the FLASH kit and the accelerator in terms of physical connection, electrical signal, and dose control logic;

[0318] S5. FLASH parameter loading and beam output:

[0319] Load the pre-configured FLASH mode beam parameters (including dose rate, pulse width, and current intensity), drive the beam shaping module and dose control module to work together, and output the FLASH mode beam;

[0320] S6. Dose verification and test execution:

[0321] After verifying the output dose through the dedicated FLASH ionization chamber and dose cabinet and confirming that the dose accuracy meets the preset threshold (e.g., error ≤ 5%), start the FLASH radiotherapy research test;

[0322] S7. Mode switching back:

[0323] After the completion of the FLASH research test, trigger the driving mechanism to remove the FLASH kit, redeploy the regular mode treatment head, control the TC master computer to switch back to the clinical mode, and restore the clinical mode configuration and permissions.

[0324] Referring to the accompanying Figure 5 , the embodiments of the present application also provide a dual-mode beam and dose regulation method for FLASH radiotherapy, characterized in that the method comprises:

[0325] Through the driving mechanism, the adjustable collimator arranged at the outlet of the accelerator or the transport line is driven to realize dual-mode switching between the clinical mode and the FLASH mode, and the switching position accuracy is guaranteed through a redundant feedback mechanism;

[0326] Based on the Bragg peak characteristics of protons and heavy ions, at least two materials with different physical properties are used to adjust the thickness and / or quantity of the materials to realize the step-by-step modulation of the beam range and dose distribution, thereby optimizing the Bragg peak depth dose distribution;

[0327] By establishing the mapping relationship between pulse parameters and single-pulse dose, and combining the target total dose to calculate the required pulse sequence, accurate dose control for FLASH radiotherapy is realized.

[0328] In a possible implementation, the beam current grading modulation is realized by a grading modulator, which comprises a coarse adjustment layer and a fine adjustment layer;

[0329] The coarse adjustment layer comprises a plurality of first material assemblies with same or different thicknesses and being detachable, which are modularly designed by detachable connecting mechanisms for realizing stepwise adjustment of the range; the material of the first material assemblies is selected from high-atomic-number materials;

[0330] The fine adjustment layer comprises a plurality of second material assemblies with same or different thicknesses and adjustable number of superposed layers, which are used for realizing continuous fine adjustment of the range; the material of the second material assemblies is selected from low-atomic-number materials;

[0331] Wherein, the total modulation range Dsof the coarse adjustment layer and the fine adjustment layer satisfies:

[0332] Ds=Σ(α i ×N i )+Σ(β j ×M j )+δ cal ,

[0333] α i is the calibrated equivalent water thickness of the i-th first material assembly, N i is the number of use of the i-th first material assembly;

[0334] β j is the calibrated equivalent water thickness of the j-th second material assembly, M j is the number of superposed layers of the j-th second material assembly;

[0335] δ cal is the scattering compensation amount, which is calibrated by Monte Carlo simulation.

[0336] In a possible implementation, the equivalent water thickness of the first material assembly is an integer multiple of 5-20 mm, the equivalent water thickness of the second material assembly is an integer multiple of 0.1-1 mm, and the equivalent water thickness is calibrated by the following formula:

[0337] WET=[(R water -R air ) / (R material -R air )]×t material

[0338] Wherein WET is the equivalent water thickness, R is the Bragg peak position, t material is the physical thickness of the material; R water is the Bragg peak range of the particle in water; R airthe Bragg peak range of the particle in air; R material the Bragg peak range of the particle in the material.

[0339] In a possible implementation, the physical thickness t i the equivalent water thickness α i satisfies the following relationship:

[0340] α i = f1 x t i where f1 is the equivalent water thickness coefficient of the material, f1≥2.0 (corresponding to high atomic number material), and the f1 value deviation of each first material assembly is ≤±0.5%;

[0341] the physical thickness t j the equivalent water thickness β j satisfies the following relationship:

[0342] β j = f2 x t j where f2 is the equivalent water thickness coefficient of the material, 0.8≤f2≤1.2 (corresponding to low atomic number material), and the f2 value deviation of each second material assembly is ≤±0.3%.

[0343] The combination mode of the first material assembly and the second material assembly includes:

[0344] Stacked arrangement: the first material assembly and the second material assembly are stacked in sequence along the beam direction;

[0345] Nested arrangement: the second material assembly is embedded in the preset groove of the first material assembly.

[0346] In a possible implementation, the assembly selection of the coarse adjustment layer and the fine adjustment layer satisfies:

[0347] Max (α i x N i ) / ∑ (β j x M j ) ∈ [Cmin, Cmax];

[0348] The critical values (Cmin, Cmax) of the coarse adjustment layer and the fine adjustment layer assembly selection are calibrated through the following simulation process:

[0349] (1) Construct a FLASH radiotherapy dedicated simulation environment

[0350] Based on the particle transport simulation program, the dose rate dependent nonlinear scattering physical model is integrated, which is used to simulate the nonlinear behavior of the dynamic change of the scattering characteristics with the dose rate when the FLASH radiotherapy ultrahigh dose rate beam interacts with the material;

[0351] Coupling thermal-dose synergy conduction module for simulating real-time changes in material temperature caused by short-time large-dose deposition and its dynamic impact on the material beam current stopping power.

[0352] (2) Perform scenario-based parameter scanning and index monitoring

[0353] The input parameters include typical beam characteristics and environmental parameters of FLASH radiotherapy, specifically including beam intensity, pulse duration, material initial environmental state, etc., to match the actual beam conditions of clinical FLASH research;

[0354] The monitoring indicators include but are not limited to: dose distribution uniformity of the spread-out Bragg peak (SOBP), proportion of scattered dose to total dose, beam dose rate stability, and drift amplitude of material equivalent water thickness with beam action time.

[0355] Cmin (coarse adjustment layer dominant threshold): When the ratio of the adjustment capacity of the coarse adjustment layer to the fine adjustment layer is lower than Cmin, the monitoring result shows that the SOBP dose distribution uniformity exceeds the preset acceptable range, and the beam dose rate stability decreases below the threshold, indicating that the coarse adjustment layer cannot effectively dominate the stepwise adjustment;

[0356] Cmax (fine adjustment layer safety threshold): When the above ratio is higher than Cmax, the monitoring result shows that the proportion of scattered dose exceeds the safety threshold, and the drift amplitude of material equivalent water thickness exceeds the allowed range, indicating that the fine adjustment layer overcompensation leads to beam control out of control.

[0357] In one possible implementation, δ cal Calibrated by collimating aperture and material combination;

[0358]

[0359] A coll is the collimating aperture area, A ref is determined by the collimator design parameters of the radiotherapy device;

[0360] μ is the material linear scattering coefficient (cm -1 , obtained by Monte Carlo simulation Geant4, positively correlated with material atomic number and beam energy);

[0361] T PE is the total thickness of the fine adjustment layer (cm, low atomic number material stacking thickness);

[0362] N C is the number of first material components (adapted to the stepwise adjustment requirements of the coarse adjustment layer);

[0363] δflash is a FLASH radiotherapy exclusive compensation term (nonlinear scattering caused by ultra-high dose rate, δflash=θ·D^0.5, θ is a nonlinear scattering coefficient, D is a dose rate, unit Gy / s);

[0364] b1, b2, θ are scattering coefficients fitted by Monte Carlo simulation + experiment (b1∈[0.1, 0.5], b2∈[0.01, 0.1], θ∈[0.005, 0.02], adapt to beam energy, material combination).

[0365] In one possible implementation, the precise dose control of FLASH radiotherapy is realized by establishing a mapping relationship between pulse parameters and single pulse dose, and calculating the required pulse sequence in combination with the target total dose, which includes:

[0366] Before establishing the mapping relationship between pulse parameters and single pulse dose, the dose rate range is dynamically set based on the tumor site radiosensitivity classification; the accelerator beam parameters are adjusted so that the dose rate is stable within the preset dose rate range;

[0367] According to the dose rate and pulse width, the single pulse theoretical dose is determined; the single pulse theoretical dose is corrected through experimental calibration to determine the calibrated single pulse dose, and a mapping relationship between the single pulse dose and the accelerator control parameters is established;

[0368] D_pulse_theory=D×PW_opt

[0369] D_pulse_theory is the theoretical single pulse dose; D is the dose rate; PW_opt is the optimal pulse width;

[0370] Among them, by testing different pulse widths, the coefficient of variation of the dose rate under each pulse width is calculated based on the monitoring data, and the pulse width value with the smallest coefficient of variation is selected as the optimal pulse width;

[0371] Through laboratory calibration (double ionization chamber collaborative calibration (main ionization chamber measures total dose, micro-dose ionization chamber measures single pulse dose)), the single pulse theoretical dose is corrected to determine the calibrated single pulse dose D_pulse_cal, and a mapping relationship between it and the accelerator control parameters (such as magnetic field strength B, radio frequency voltage VRF) is established; D_pulse_cal=f(B, VRF); f() is a mapping relationship function;

[0372] According to the target total dose and the calibrated single pulse dose, the number of required pulses is calculated to generate an executable pulse sequence; the executable pulse sequence includes pulse width and current;

[0373] Map={Pulse1:(PW1,I1),Pulse2:(PW2,I2),...,PulseNp : pulse width Np : pulse width Np : pulse width

[0374] Np = round(D_total / D_pulse_cal)

[0375] round() is automatic rounding; D_total is target total dose;

[0376] Real-time verification of the difference between the actual output cumulative dose and the preset dose; if the difference exceeds its preset threshold, a feedback signal is sent to the execution unit;

[0377] Load the optimized pulse sequence Map to the accelerator control system; strictly execute Np pulses according to the Map to achieve ms-level dose truncation accuracy. The pulse emission interval is synchronized with the accelerator radio frequency period (error ≤10 ns).

[0378] In a possible implementation, the pulse sequence generation unit is configured to execute an intelligent prediction-based sequence optimization strategy:

[0379] Based on the number of pulses, it is divided into long sequence and short sequence (for example, if Np>100, it is a long sequence, and if Np is less than or equal to 100, it is a short sequence), and an adaptive optimization strategy is used respectively: including:

[0380] Long sequence adopts uniform distribution strategy The average value of the pulse width of the long sequence; The average value of the pulse current of the long sequence;

[0381] Short sequence adopts current increasing compensation strategy:

[0382] I g = I1+ (g-1)·ΔI

[0383]

[0384] Where, I g is the current of the gth pulse in the pulse sequence, I1is the current of the 1st pulse in the pulse sequence; PWg is the pulse width of the gth pulse in the pulse sequence; I max is the upper limit of the current allowed by the accelerator hardware (determined by pre-calibration, such as <200nA, to avoid high single-pulse dose); constraint condition: I g ≤ I max (Always limit the current within the hardware safety threshold);

[0385] The pulse sequence contains a preset emergency redundancy pulse, the parameters of which can be dynamically cancelled and only activated when the dose of the previous pulse is insufficient.

[0386] In a possible implementation, the pulse sequence generation unit is configured to perform an intelligent prediction-based sequence optimization strategy:

[0387] Based on the number of pulses, it is divided into long sequences and short sequences (for example, if Np> 100, it is a long sequence, and if Np is less than or equal to 100, it is a short sequence), and an adaptive optimization strategy is used respectively:

[0388] The long sequence adopts uniform distribution combined with drift compensation strategy, and periodically corrects the subsequent pulse parameters according to the beam current parameter drift trend of the previous pulse; for example, 1 verification pulse is inserted every h (for example, 10) pulses, and the pulse width of the subsequent pulse is corrected;

[0389] The corrected pulse width formula is:

[0390]

[0391] Wherein, PWg' is the corrected pulse width of the gth pulse in the pulse sequence; ΔPW = k_drift x ΔR (ΔR is the range drift measured by the verification pulse, k_drift is the pulse width correction coefficient, and k_drift ∈ [0.1, 0.3] mm / Gy is calibrated through experiment); k = floor ((g-1) / h) (k is the sequence number of the verification pulse, k = 0, 1, 2,..., indicating the k+1 group of h pulses);

[0392] Constraint condition: PWg' ≤ PW_max (PW_max is the maximum pulse width allowed by the hardware, to avoid excessive single pulse dose);

[0393] The short sequence adopts the flow intensity increasing combined with the prediction compensation strategy, predicts the beam current parameter attenuation trend based on the neural network, and compensates the dose rate attenuation through the flow intensity dynamic adjustment;

[0394] I g =I1+(g-1)·ΔI·(1+δ d ·D drift )

[0395]

[0396] Wherein, I g is the flow intensity of the gth pulse in the pulse sequence, I1 is the flow intensity of the 1st pulse in the pulse sequence; I max is the upper limit of the flow intensity allowed by the accelerator hardware (determined by pre-calibration, such as <200nA, to avoid excessive single pulse dose); constraint condition: I g ≤I max (Always limit the flow intensity within the hardware safety threshold); δ d is a dynamic compensation coefficient, which is determined by the LSTM neural network and physical constraints; Ddrift The dose rate drift amount is calculated in real time by temperature / vacuum monitoring.

[0397] The dynamic compensation coefficient is determined by driving the LSTM neural network and physical constraints, including:

[0398] Based on historical pulse sequence data (beam current parameters, dose rate, temperature, vacuum), the beam current attenuation trend of the current pulse is predicted, and the initial compensation coefficient δ d _init is output.

[0399] The initial compensation coefficient is corrected by the initial compensation coefficient and the physical constraint condition (such as the dose rate stability threshold), and the final compensation coefficient δ d .

[0400] δ d = δ d _init×(1+λ·(Ca-C_threshold))

[0401] Wherein, Ca is the actual value of the constraint index (such as the current dose rate standard deviation σ_current), C_threshold is the constraint threshold (such as 2%), and λ is the constraint strength coefficient (λ∈[0.1, 0.3], calibrated by experiment, balance prediction bias and constraint strength).

[0402] The working principle and effect of the above technical solution are the same as those of the dual-mode beam and dose regulation system for FLASH radiotherapy of the embodiments of the present application, and will not be repeated here.

[0403] The embodiments of the present application also provide a hierarchical modulator for realizing hierarchical modulation of beam range and dose distribution, including a coarse adjustment layer and a fine adjustment layer;

[0404] The coarse adjustment layer includes a plurality of first material assemblies with the same or different thicknesses and being detachable, the first material assemblies are modularly designed through detachable connecting mechanisms, and are used for realizing stepwise adjustment of the range; the material of the first material assembly is selected from high-atomic-number materials;

[0405] The fine adjustment layer includes a plurality of second material assemblies with the same or different thicknesses and adjustable number of superposed layers, the second material assemblies are used for realizing continuous fine adjustment of the range; the material of the second material assembly is selected from low-atomic-number materials;

[0406] Wherein, the total modulation range Ds of the coarse adjustment layer and the fine adjustment layer satisfies:

[0407] Ds=Σ(α i ×N i )+Σ(β j ×M j)+δ cal ,

[0408] α i is the calibrated equivalent water thickness of the i-th first material assembly, N i is the number of use of the i-th first material assembly;

[0409] β j is the calibrated equivalent water thickness of the j-th second material assembly, M j is the number of superposition layers of the j-th second material assembly;

[0410] δ cal is the scattering compensation, calibrated by Monte Carlo simulation.

[0411] The embodiments of the present application also provide a beam current grading modulation method for realizing grading modulation of beam range and dose distribution, which is realized by a grading modulator including a coarse adjustment layer and a fine adjustment layer;

[0412] The coarse adjustment layer includes a plurality of first material assemblies with same or different thicknesses and being detachable, the first material assemblies are modularly designed by detachable connecting mechanisms for realizing stepwise adjustment of the range; the material of the first material assemblies is selected from high atomic number materials;

[0413] The fine adjustment layer includes a plurality of second material assemblies with same or different thicknesses and adjustable number of superposition layers, the second material assemblies are used for realizing continuous fine adjustment of the range; the material of the second material assemblies is selected from low atomic number materials;

[0414] Wherein, the total modulation range Dsof the coarse adjustment layer and the fine adjustment layer satisfies:

[0415] Ds=Σ(α i ×N i )+Σ(β j ×M j )+δ cal ,

[0416] α i is the calibrated equivalent water thickness of the i-th first material assembly, N i is the number of use of the i-th first material assembly;

[0417] β j is the calibrated equivalent water thickness of the j-th second material assembly, M j is the number of superposition layers of the j-th second material assembly;

[0418] δ cal is the scattering compensation, calibrated by Monte Carlo simulation.

[0419] In one possible implementation, the equivalent water thickness of the first material component is an integer multiple of 5-20 mm, the equivalent water thickness of the second material component is an integer multiple of 0.1-1 mm, and the equivalent water thickness is specified by the following formula:

[0420] WET = [(R water -R air ) / (R material -R air )]×t material

[0421] Where WET is the equivalent water thickness, R is the location of the Bragg peak, and t material R represents the physical thickness of the material. water R represents the Bragg peak range of the particle in water. air R represents the Bragg peak range of the particle in air. material The Bragg peak range of the particle in the material.

[0422] In one possible implementation, the physical thickness t of the first material component i With equivalent water thickness α i The following relationship must be satisfied:

[0423] α i =f1×t i Where f1 is the equivalent water thickness coefficient of the material, f1≥2.0 (corresponding to high atomic number materials), and the deviation of f1 value for each first material component is ≤±0.5%;

[0424] The physical thickness t of the second material component j With equivalent water thickness β j The following relationship must be satisfied:

[0425] β j =f2×t j Where f2 is the equivalent water thickness coefficient of the material, 0.8≤f2≤1.2 (corresponding to low atomic number materials), and the deviation of the f2 value of each second material component is ≤±0.3%.

[0426] The combination of the first material component and the second material component includes:

[0427] Layered arrangement: The first material component and the second material component are stacked sequentially along the beam direction;

[0428] Nested arrangement: The second material component is embedded in a preset groove of the first material component.

[0429] In one possible implementation, the component selection of the coarse adjustment layer and the fine adjustment layer satisfies the following:

[0430] Max(αi ×N i ) / Σ(β j ×M j )∈[Cmin,Cmax];

[0431] The critical values (Cmin, Cmax) of the coarse adjustment layer and the fine adjustment layer assembly are calibrated through the following simulation process:

[0432] (1) Construct a FLASH radiotherapy dedicated simulation environment

[0433] Based on the particle transport simulation program, integrate the dose rate dependent nonlinear scattering physical model, which is used to simulate the nonlinear behavior of the dynamic change of scattering characteristics with dose rate when the ultra-high dose rate beam interacts with the material in FLASH radiotherapy;

[0434] Couple the thermal-dose collaborative conduction module to simulate the real-time change of material temperature caused by short-time high-dose deposition and its dynamic influence on the beam stopping power of the material.

[0435] (2) Perform scenario-based parameter scanning and index monitoring

[0436] The input parameters include typical beam characteristics and environmental parameters of FLASH radiotherapy, specifically including beam intensity, pulse duration, material initial environmental state, etc., to match the actual beam conditions of clinical FLASH research;

[0437] The monitoring indicators include but are not limited to: the dose distribution uniformity of the spread Bragg peak (SOBP), the proportion of scattered dose to total dose, beam dose rate stability, and the drift amplitude of material equivalent water thickness with beam action time.

[0438] Cmin (coarse adjustment layer dominant threshold): When the adjustment capability ratio of the coarse adjustment layer and the fine adjustment layer is lower than Cmin, the monitoring results show that the SOBP dose distribution uniformity exceeds the preset acceptable range, and the beam dose rate stability decreases below the threshold, indicating that the coarse adjustment layer cannot effectively dominate the stepwise adjustment;

[0439] Cmax (fine adjustment layer safety threshold): When the above ratio is higher than Cmax, the monitoring results show that the proportion of scattered dose exceeds the safety threshold, and the drift amplitude of material equivalent water thickness exceeds the allowed range, indicating that the fine adjustment layer overcompensation leads to beam control out of control.

[0440] In one possible implementation, δ cal Calibrated through the collimation aperture and the combination of materials;

[0441]

[0442] A coll A is the collimation aperture area, Aref is a reference area; determined by the collimator design parameters of the radiotherapy device;

[0443] is the linear scattering coefficient of the material (cm -1 , obtained by Monte Carlo simulation Geant4, positively correlated with the atomic number of the material and the beam energy);

[0444] T PE is the total thickness of the fine adjustment layer (cm, the thickness of the low atomic number material stack);

[0445] N C is the number of first material assemblies (adapted to the step adjustment requirement of the coarse adjustment layer);

[0446] is a FLASH radiotherapy exclusive compensation term (nonlinear scattering caused by ultra-high dose rate, δflash = θ·D^0.5, θ is the nonlinear scattering coefficient, D is the dose rate, unit: Gy / s);

[0447] b1, b2, θ are scattering coefficients obtained by Monte Carlo simulation + experimental fitting (b1 ∈ [0.1, 0.5], b2 ∈ [0.01, 0.1], θ ∈ [0.005, 0.02], adapted to the beam energy and material combination).

[0448] The working principle and effects of the above technical solutions are the same as those of the beam shaping module of the dual-mode beam and dose control system for FLASH radiotherapy of the embodiments of the present application, and are not repeated here.

[0449] With reference to the accompanying Figure 6 , the embodiments of the present application also provide a beam dose control method, comprising:

[0450] Before establishing the mapping relationship between the pulse parameters and the single-pulse dose, based on the radiation sensitivity grading of the tumor site, dynamically set the dose rate range; adjust the beam parameters of the accelerator so that the dose rate is stable within the preset dose rate range;

[0451] According to the dose rate and the pulse width, determine the single-pulse theoretical dose; correct the single-pulse theoretical dose through experimental calibration to determine the calibrated single-pulse dose, and establish the mapping relationship between the single-pulse dose and the accelerator control parameters;

[0452] According to the target total dose and the calibrated single-pulse dose, calculate the required number of pulses to generate an executable pulse sequence;

[0453] Real-time verify the difference between the actual output cumulative dose and the preset dose; if the difference exceeds its preset threshold, send a feedback signal to the execution unit.

[0454] Before establishing the mapping relationship between the pulse parameters and the single pulse dose, the dose rate range is dynamically set based on the tumor site radiosensitivity classification; the accelerator beam parameters are adjusted to make the dose rate stable within the preset dose rate range;

[0455] According to the dose rate and the pulse width, the single pulse theoretical dose is determined; the single pulse theoretical dose is corrected through experiment calibration, the calibrated single pulse dose is determined, and the mapping relationship between the single pulse dose and the accelerator control parameters is established;

[0456] D_pulse_theory=D×PW_opt

[0457] D_pulse_theory is the theoretical single pulse dose; D is the dose rate; PW_opt is the optimal pulse width;

[0458] Among them, by testing different pulse widths, the variation coefficient of the dose rate under each pulse width is calculated based on the monitoring data, and the pulse width value with the smallest variation coefficient is selected as the optimal pulse width;

[0459] Through laboratory calibration (double ionization chamber cooperative calibration (main ionization chamber measures total dose, micro-dose ionization chamber measures single pulse dose)), the single pulse theoretical dose is corrected, the calibrated single pulse dose D_pulse_cal is determined, and the mapping relationship between it and the accelerator control parameters (such as magnetic field strength B, radio frequency voltage VRF) is established; D_pulse_cal=f(B,VRF); f() is the mapping relationship function;

[0460] According to the target total dose and the calibrated single pulse dose, the required pulse number is calculated, and the executable pulse sequence is generated; the executable pulse sequence includes pulse width, current;

[0461] Map={Pulse1:(PW1,I1),Pulse2:(PW2,I2),...,Pulse Np :(PW Np ,I Np )};

[0462] Np=round(D_total / D_pulse_cal)

[0463] round() is automatic rounding; D_total is the target total dose;

[0464] The difference between the actual output cumulative dose and the preset dose is verified in real time; if the difference exceeds its preset threshold, a feedback signal is sent to the execution unit;

[0465] The optimized pulse sequence Map is loaded to the accelerator control system; Np pulses are strictly executed according to the Map to achieve the ms-level dose truncation accuracy. The pulse emission interval is synchronized with the accelerator radio frequency period (error ≤10 ns).

[0466] In a possible implementation, the pulse sequence generation unit is configured to execute an intelligent prediction-based sequence optimization strategy.

[0467] Based on the number of pulses, the sequence is divided into long sequences and short sequences (for example, if Np>100, it is a long sequence, and if Np is less than or equal to 100, it is a short sequence), and an adaptive optimization strategy is used respectively, including:

[0468] The long sequence adopts a uniform distribution strategy The average value of the pulse width of the long sequence is; The average value of the pulse current of the long sequence is;

[0469] The short sequence adopts a current increment compensation strategy:

[0470] I g =I1+(g-1)·ΔI

[0471]

[0472] Wherein, I g is the current of the gth pulse in the pulse sequence, I1 is the current of the 1st pulse in the pulse sequence; PWg is the pulse width of the gth pulse in the pulse sequence; I max is the upper limit of the current allowed by the accelerator hardware (determined by pre-calibration, such as <200nA, to avoid high single-pulse dose); constraint condition: I g ≤I max (the current is always limited within the hardware safety threshold);

[0473] The pulse sequence contains a preset emergency redundancy pulse, the parameters of which can be dynamically cancelled and only activated when the dose of the previous pulse is insufficient.

[0474] In a possible implementation, the pulse sequence generation unit is configured to execute an intelligent prediction-based sequence optimization strategy.

[0475] Based on the number of pulses, the sequence is divided into long sequences and short sequences (for example, if Np>100, it is a long sequence, and if Np is less than or equal to 100, it is a short sequence), and an adaptive optimization strategy is used respectively, including:

[0476] The long sequence adopts a uniform distribution strategy combined with a drift compensation strategy, which periodically corrects the parameters of subsequent pulses according to the drift trend of the beam parameters of the previous pulses; for example, one verification pulse is inserted every h pulses (for example, 10 pulses), and the pulse width of the subsequent pulses is corrected;

[0477] Modified pulse width formula:

[0478]

[0479] Where, PWg' is the modified pulse width of the gth pulse in the pulse sequence; ΔPW = k_drift x ΔR (ΔR is the range drift measured by the verification pulse, k_drift is the pulse width correction coefficient, k_drift ∈ [0.1, 0.3] mm / Gy is calibrated through experiment); k = floor((g-1) / h) (k is the serial number of the verification pulse, k = 0, 1, 2,..., representing the k+1 group of h pulses);

[0480] Constraint: PWg' ≤ PW_max (PW_max is the maximum pulse width allowed by the hardware, to avoid excessive single pulse dose);

[0481] Short sequence adopts flow intensity increasing combined with prediction compensation strategy, based on neural network to predict the beam current parameter attenuation trend, through flow intensity dynamic adjustment to compensate the dose rate attenuation;

[0482] I g = I1+ (g-1) · ΔI · (1+ δ d ·D drift )

[0483]

[0484] Where, I g is the flow intensity of the gth pulse in the pulse sequence, I1 is the flow intensity of the 1st pulse in the pulse sequence; I max is the upper limit of the flow intensity allowed by the accelerator hardware (determined by pre-calibration, such as <200 nA, to avoid excessive single pulse dose); constraint: I g ≤ I max (Always limit the flow intensity within the hardware safety threshold); δ d is the dynamic compensation coefficient, determined by LSTM neural network and physical constraint; D drift is the dose rate drift, calculated in real time through temperature / vacuum monitoring.

[0485] The determination of the dynamic compensation coefficient by LSTM neural network and physical constraint includes:

[0486] Based on the historical pulse sequence data (beam current parameters, dose rate, temperature, vacuum degree), the beam current attenuation trend of the current pulse is predicted, and the initial compensation coefficient δ d _init is outputted;

[0487] The initial compensation coefficient is corrected by the initial compensation coefficient and a physical constraint condition (such as a dose rate stability threshold) to obtain a final compensation coefficient δ d .

[0488] δ d = δ d _init×(1+λ·(Ca-C_threshold))

[0489] Wherein, Ca is an actual value of a constraint index (such as a current dose rate standard deviation σ_current), C_threshold is a constraint threshold (such as 2%), and λ is a constraint strength coefficient (λ ∈ [0.1, 0.3], which is calibrated by experiments to balance the prediction deviation and the constraint strength).

[0490] The working principle and effect of the above technical solution are the same as those of the dose control module of the dual-mode beam and dose regulation system for FLASH radiotherapy of the embodiments of the present application, and are not repeated here.

[0491] With reference to the accompanying Figure 7 , the embodiments of the present application provide a radiotherapy system, comprising:

[0492] A cyclotron is used as a beam generation device to generate a proton beam for clinical radiotherapy or FLASH research through the synergistic action of an ion source subsystem, a radio frequency subsystem, a vacuum subsystem, a magnet subsystem and an extraction subsystem. The magnet subsystem accelerates and deflects the proton beam through a D-shaped electrode and a magnetic field, and the radio frequency subsystem continuously energizes the proton beam through an alternating electric field until the proton beam reaches the extraction subsystem output.

[0493] Any of the embodiments of the dual-mode beam and dose regulation system for FLASH radiotherapy is connected to the beam output end of the cyclotron and comprises:

[0494] A mode switching module is used to drive an adjustable collimator (located at the outlet of the accelerator or the transport line) to realize double switching of the clinical mode and the FLASH mode, and to guarantee the switching position accuracy through a redundant feedback mechanism.

[0495] A beam shaping module is used to adjust the beam range and dose distribution by at least two different physical property materials based on the Bragg peak characteristics of protons and heavy ions, and to optimize the Bragg peak depth dose.

[0496] A dose control module is used to establish a mapping relationship between pulse parameters (flow rate, pulse width) and single pulse dose, to generate a pulse sequence in combination with the target total dose, and to realize precise dose control for FLASH radiotherapy.

[0497] The cyclotron provides an initial proton beam for a dual-mode beam and dose regulation system, and the dual-mode regulation system adapts to the conventional dose requirement and the ultra-high dose rate requirement of FLASH radiotherapy through mode switching, beam shaping, and dose control, and cooperatively realizes the functions of precise tumor radiotherapy and FLASH research.

[0498] The electronic device includes a memory and a processor, the memory stores a computer program, and the processor implements the steps of the method or the functions of the system when executing the computer program.

[0499] The computer readable storage medium is used to store a computer program, and the computer program is executed to implement the steps of the method, and the specific implementation manners and the achieved technical effects are the same as those of the above method embodiments, and some contents will not be described herein.

[0500] In the present application, the readable storage medium can be any tangible medium containing or storing a program, which can be used or combined with an instruction execution system, device or instrument. The program product can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium may, for example, be but is not limited to an electrical, magnetic, optical, electromagnetic, infrared or semiconductor system, device or instrument, or any combination of the above. More specific examples (non-exhaustive list) of the readable storage medium include an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0501] A computer readable storage medium can include a disk, tape, semiconductor memory, or other storage medium (e.g., memory). The computer readable program code can encode a computer program of instructions that, when executed in a computer, performs a method. The computer readable program code can be downloaded to a user's computer from an external data source via a communication channel. A user can enter commands and information into the computer through keyboard, mouse, touchpad, microphone, remote control, or other suitable means. The user can cause the entered commands and information to be displayed on a display device, such as a monitor or speaker. Other external devices coupled to the computer, such as a storage device (e.g., a disk drive, a compact disk drive, or a tape drive), a printer, a scanner, or a plurality of network devices, can provide storage of, and access to, information, data, and programs. The computer can be connected to a network of other computers through a communication connection. When connected to the network, the computer can communicate with other computers on the network. The network connection can be a local-area network (LAN) or a wide-area network (WAN). Such network connections can be through a modem, an Ethernet interface, an AppleTalk interface, a Bluetooth interface, or other means.

[0502] Although the embodiments of the present application have been shown and described above, it should be understood by those skilled in the art that the above embodiments are exemplary, and should not be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application without departing from the principles and spirit of the present application, and all these changes should be within the protection scope of the present application.

Claims

1. A dual mode beam and dose regulation system for FLASH radiotherapy, characterized in that, The system comprises: A mode switching module for driving a tunable collimator arranged at the outlet of the accelerator or the transport line by a driving mechanism to realize dual-mode switching between the clinical mode and the FLASH mode, and to guarantee the switching position accuracy by a redundant feedback mechanism; A beam shaping module for realizing the stepwise modulation of the beam range and the dose distribution by adjusting the thickness and / or the number of materials with at least two different physical properties based on the Bragg peak characteristics of protons and heavy ions, so as to optimize the Bragg peak depth dose distribution; A dose control module for realizing the precise dose control of FLASH radiotherapy by establishing the mapping relationship between the pulse parameters and the single-pulse dose, and calculating the required pulse sequence in combination with the target total dose.

2. The dual mode beam and dose regulation system of claim 1, wherein, The system further comprises a safety control module for providing safety guarantee for the system, including: The safety control module adopts an isolated connection mode at the hardware level to realize the physical isolation of the FLASH dose mode and the clinical mode; The safety control module adopts a dual-mode independent switching mechanism at the software level to independently protect the FLASH mode, automatically disable the FLASH-related configuration in the clinical mode, and configure an independent mode parameter storage unit.

3. The dual mode beam and dose regulation system of claim 1, wherein, The mode switching is performed by driving the tunable collimator by a motor, and the tunable collimator adopts a double potentiometer to realize the real-time feedback of the position in a redundant manner.

4. The dual mode beam steering and dose control system of claim 1, wherein, The beam shaping module comprises a beam modulation unit, and the beam modulation unit realizes the stepwise modulation of the beam by a stepwise modulator, and the stepwise modulator comprises a coarse adjustment layer and a fine adjustment layer; The coarse adjustment layer comprises a plurality of first material assemblies which are detachably connected by a detachable connection mechanism to realize the modular design and are used for realizing the stepwise adjustment of the beam range, and the material of the first material assembly is selected from high-atomic-number materials; The fine adjustment layer comprises a plurality of second material assemblies with adjustable number of stacked layers, and the second material assemblies are used for realizing the continuous fine adjustment of the beam range, and the material of the second material assemblies is selected from low-atomic-number materials; The total modulation range Ds of the coarse adjustment layer and the fine adjustment layer satisfies: Ds = ∑(α i ×N i )+∑(β j ×M j )+δ cal, α i N is the nominal equivalent water thickness of the i-th first material assembly i N is the usage number of the i-th first material assembly β j M is the nominal equivalent water thickness of the jth second material assembly j N is the number of superimposed layers of the jth second material assembly delta cal is the scatter compensation amount, calibrated by Monte Carlo simulation.

5. The dual mode beam and dose regulation system of claim 4, wherein, The equivalent water thickness of the first material assembly is an integer multiple of 5-20 mm, the equivalent water thickness of the second material assembly is an integer multiple of 0.1-1 mm, and the equivalent water thickness is calibrated by the following formula: WET = [(R water -R air ) / (R material -R air )] x t material where WET is the equivalent water thickness, R is the Bragg peak position, t material is the physical thickness of the material; R water is the Bragg peak range of the particle in water; R air is the Bragg peak range of the particle in air; R material is the Bragg peak range of the particle in the material.

6. The dual mode beam and dose regulation system of claim 1, wherein, The dose control module comprises: A dose rate pre-calibration unit for dynamically setting the dose rate range based on the tumor site radiosensitivity grading before establishing the mapping relationship between the pulse parameters and the single-pulse dose; and adjusting the accelerator beam parameters to stabilize the dose rate within the preset dose rate range; A single-pulse dose modeling unit for determining the single-pulse theoretical dose according to the dose rate and the pulse width; correcting the single-pulse theoretical dose by experiment calibration to determine the calibrated single-pulse dose, and establishing the mapping relationship between the single-pulse dose and the accelerator control parameters; A pulse sequence generation unit for calculating the required pulse number according to the target total dose and the calibrated single-pulse dose, and generating an executable pulse sequence; A dose verification unit for verifying the difference between the actual output cumulative dose and the preset dose in real time; and sending a feedback signal to the execution unit if the difference exceeds the preset threshold.

7. A dual mode beam and dose regulation method for FLASH radiotherapy, characterized in that, The method comprises: Driving the adjustable collimator at the outlet of the accelerator or the transport line through the driving mechanism to realize the dual-mode switching of the clinical mode and the FLASH mode, and to guarantee the switching position accuracy through the redundant feedback mechanism; Based on the characteristics of the proton heavy ion Bragg peak, at least two materials with different physical properties are used to realize the stepwise modulation of the beam range and the dose distribution by adjusting the thickness and / or quantity of the materials, so as to optimize the Bragg peak depth dose distribution; Through the mapping relationship between the pulse parameters and the single pulse dose, the required pulse sequence is calculated combined with the target total dose to realize the precise dose control of FLASH radiotherapy.

8. The dual mode beam and dose regulation method of claim 7, wherein, The beam is modulated by a stepwise modulator, which comprises a coarse adjustment layer and a fine adjustment layer; The coarse adjustment layer comprises a plurality of detachable first material assemblies, which are modularly designed through detachable connecting mechanisms to realize the stepwise adjustment of the range; the material of the first material assembly is selected from high atomic number materials; The fine adjustment layer comprises a plurality of second material assemblies with adjustable number of superposed layers, which are used to realize the continuous fine adjustment of the range; the material of the second material assembly is selected from low atomic number materials; The total modulation range Ds of the coarse adjustment layer and the fine adjustment layer satisfies: Ds = ∑(α i ×N i )+∑(β j ×M j )+δ cal α i N is the nominal equivalent water thickness of the i-th first material assembly i N is the usage number of the i-th first material assembly; β j M is the nominal equivalent water thickness of the jth second material assembly j Nj is the number of layers of the jth second material assembly delta cal The scatter compensation is calibrated by Monte Carlo simulation.

9. The dual mode beam and dose regulation method of claim 8, wherein, The equivalent water thickness of the first material assembly is an integer multiple of 5-20mm, and the equivalent water thickness of the second material assembly is an integer multiple of 0.1-1mm, and the equivalent water thickness is calibrated by the following formula: WET = [(R water -R air ) / (R material -R air )] x t material where WET is the equivalent water thickness, R is the Bragg peak position, t material is the physical thickness of the material; R water is the Bragg peak range of the particle in water; R air is the Bragg peak range of the particle in air; R material is the Bragg peak range of the particle in the material.

10. The dual mode beam and dose regulation method of claim 7, wherein, The precise dose control of FLASH radiotherapy is realized by establishing the mapping relationship between the pulse parameters and the single pulse dose, and calculating the required pulse sequence combined with the target total dose, which comprises: Before establishing the mapping relationship between the pulse parameters and the single pulse dose, the dose rate range is dynamically set based on the tumor site radiosensitivity grading; the accelerator beam parameters are adjusted to make the dose rate stable within the preset dose rate range; According to the dose rate and the pulse width, the single pulse theoretical dose is determined; the single pulse theoretical dose is corrected through experimental calibration to determine the calibrated single pulse dose, and the mapping relationship between the single pulse dose and the accelerator control parameters is established; According to the target total dose and the calibrated single pulse dose, the required pulse number is calculated to generate an executable pulse sequence; The difference between the actual output cumulative dose and the preset dose is verified in real time; if the difference exceeds the preset threshold, a feedback signal is sent to the execution unit.

11. A hierarchical modulator characterized by, The stepwise modulation of the beam range and the dose distribution comprises a coarse adjustment layer and a fine adjustment layer; The coarse adjustment layer comprises a plurality of detachable first material assemblies, which are modularly designed through detachable connecting mechanisms to realize the stepwise adjustment of the range; the material of the first material assembly is selected from high atomic number materials; The fine adjustment layer comprises a plurality of second material assemblies with adjustable number of superposed layers, which are used to realize the continuous fine adjustment of the range; the material of the second material assembly is selected from low atomic number materials; The total modulation range Ds of the coarse adjustment layer and the fine adjustment layer satisfies: Ds = ∑(α i ×N i )+∑(β j ×M j )+δ cal α i N is the nominal equivalent water thickness of the i-th first material assembly i N is the nominal equivalent water thickness of the i-th first material assembly β j M is the nominal equivalent water thickness of the jth second material assembly j Nj is the number of layers of the jth second material assembly delta cal is the scatter compensation amount, calibrated by Monte Carlo simulation.

12. A beam current fractionation modulation method for achieving fractionation modulation of beam range and dose distribution, characterized by, The method is realized by a stepwise modulator, which comprises a coarse adjustment layer and a fine adjustment layer; The coarse adjustment layer comprises a plurality of detachable first material components, which are modularly designed through detachable connecting mechanisms for realizing stepwise adjustment of the range; the material of the first material components is selected from high-atomic-number materials; The fine adjustment layer comprises a plurality of second material components with adjustable number of superposed layers, which are used for realizing continuous fine adjustment of the range; the material of the second material components is selected from low-atomic-number materials; Wherein, the total modulation range Dsof the coarse adjustment layer and the fine adjustment layer satisfies: Ds = ∑(α i ×N i )+∑(β j ×M j )+δ cal α i N is the nominal equivalent water thickness of the i-th first material assembly i N is the usage number of the i-th first material assembly β j M is the nominal equivalent water thickness of the jth second material assembly j Nj is the number of layers of the jth second material assembly delta cal The scatter compensation is calibrated by Monte Carlo simulation.

13. A beam dose control method, characterized by, Comprise: Before establishing the mapping relationship between the pulse parameters and the single-pulse dose, the dose rate range is dynamically set based on the radiation sensitivity classification of the tumor site; The accelerator beam parameters are debugged so that the dose rate is stabilized in the preset dose rate range; According to the dose rate and the pulse width, the single-pulse theoretical dose is determined; The single-pulse theoretical dose is corrected through experiments, the calibrated single-pulse dose is determined, and the mapping relationship between the single-pulse dose and the accelerator control parameters is established; According to the target total dose and the calibrated single-pulse dose, the required number of pulses is calculated, and an executable pulse sequence is generated; The difference between the actual output cumulative dose and the preset dose is verified in real time; If the difference exceeds the preset threshold, a feedback signal is sent to the execution unit.

14. A radiotherapy system, characterized by, Comprise: A cyclotron is used as a beam generation device to generate a proton beam for clinical radiotherapy or FLASH research; The dual-mode beam and dose regulation system for FLASH radiotherapy according to any one of claims 1-6 is connected to the beam output end of the cyclotron, which is used to adapt to the conventional dose requirement of clinical radiotherapy and the ultra-high dose rate requirement of FLASH radiotherapy, and cooperatively realize the functions of precise tumor radiotherapy and FLASH research.

15. An electronic device, comprising: The electronic device comprises a memory and a processor, the memory stores a computer program, and the processor realizes the functions of the device according to any one of claims 1-6 or executes the steps of the method according to any one of claims 7-10 and 12-13 when executing the computer program.

16. A computer-readable storage medium, characterized in that, The storage medium stores computer instructions, and when a computer reads the computer instructions, the computer executes the steps of the method according to any one of claims 7-10 and 12-13.

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