Quasi-thermal insulation water system calorimetric measurement system and method for FLASH radiotherapy rays

Abstract

The invention relates to a FLASH radiotherapy ray quasi-thermal insulation water system calorimetric measurement system and a method thereof. The system comprises a calorimeter and a constant temperature die body. The calorimeter comprises a calorimetric core, a jacket layer and a shielding layer, the calorimetric core, the jacket layer and the shielding layer are arranged in a non-contact nesting mode through a tensioning mechanism, and a gas or vacuum environment exists among the calorimetric core, the jacket layer and the shielding layer. And the constant-temperature mold body forms a quasi-steady-state constant-temperature water mold body approaching to constant temperature in the box body based on the constant-temperature control unit so as to provide a quasi-adiabatic environment for the calorimeter. And under the condition that the calorimeter is arranged in the quasi-steady-state constant-temperature water mold body, when FLASH radiotherapy rays penetrate through the box body to irradiate calorimetric timing, the probe temperature sensor acquires a temperature change signal of the calorimetric core and transmits the temperature change signal to the terminal. The system provided by the invention provides a quasi-adiabatic environment for the calorimeter, is faster in response and smaller in disturbance compared with a traditional electric heating mode, and can accurately capture a tiny temperature rise signal generated by FLASH radiotherapy.

Description

Technical Field

[0001] This invention relates to the field of radiotherapy dose measurement technology, and in particular to a quasi-adiabatic hot water system calorimetric measurement system and method for FLASH radiotherapy rays. Background Technology

[0002] Calorimetry is an absolute physical method for measuring the absorbed dose of ionizing radiation. Its principle lies in utilizing the physical process by which matter absorbs radiant energy and primarily converts it into heat. By detecting temperature changes in the irradiated medium using a highly sensitive instrument, the absolute absorbed dose deposited in the medium can be directly determined. Because its measurement process does not rely on the calibration of other dosimeters, calorimetry has become the benchmark method for radiation dose measurement, and the calorimeter is the dedicated instrument for performing this measurement. For example, CN216848160U relates to a graphite calorimeter suitable for multi-energy electron beam absorbed dose measurement, comprising a graphite absorber kit, an insulation layer, a graphite shell, a temperature control system, and an aluminum shell; the graphite absorber kit includes a graphite absorber layer and a expanded polystyrene filling layer; a thermistor is embedded in the graphite absorber layer; a slot is formed at the center of the insulation layer, the shape and size of which are the same as those of the graphite absorber kit, suitable for loading the graphite absorber kit; depending on the nominal energy of the accelerator being measured, graphite absorber kits with graphite absorber layers of different thicknesses are selected and assembled in the slot for measurement; the insulation layer respectively wraps the graphite absorber kit and the graphite shell; the heating element of the temperature control system is built into the graphite shell and connected to an aviation plug on the aluminum shell via a wire, and then connected to an external temperature controller; the temperature measuring element of the temperature control system is installed in the graphite shell and connected to the external temperature controller.

[0003] The measurement process of this type of calorimeter typically involves placing the calorimeter in a radiation field, monitoring temperature changes using a highly sensitive temperature sensor, acquiring the temperature drift baseline before and after irradiation, recording and fitting the temperature change over time, and finally calculating the radiation dose. However, traditional absolute calorimetry systems generally suffer from problems such as large size and long thermal equilibrium periods. Especially when facing the ultra-high pulsed dose rate of FLASH radiotherapy, traditional systems are limited by transient heat conduction effects and the limitations of conventional linear data fitting methods, resulting in a significant increase in measurement uncertainty. This makes it difficult to directly meet the clinical demand for efficient, flexible, and high-precision transient measurements.

[0004] Compared to conventional radiotherapy (a single pulse dose of approximately 0.3 mGy, lasting several minutes), FLASH radiotherapy can deliver ultra-high single-pulse doses of 1–10 Gy within sub-second or even microsecond time windows, drastically reducing the total irradiation time to the millisecond to hundreds of milliseconds range. This extremely short irradiation time not only significantly shortens the treatment cycle and reduces positioning errors caused by organ movement during treatment, but also shows the potential to reduce medical costs and improve patient tolerance. However, under the ultra-high pulse dose rate (UHDR) of FLASH radiotherapy, conventional active dosimeters (such as ionization chambers) suffer from severe ion recombination, leading to a loss of collection efficiency; while conventional passive dosimeters (such as alanine, film, and thermoluminescent dosimeters), although dose-rate stable, lack real-time performance and clinical applicability. Furthermore, although traditional absolute calorimetry systems are unaffected by high dose rates, they generally suffer from large size, long thermal equilibrium times, and cumbersome operation, making them unsuitable for flexible and efficient transient measurements under UHDR conditions. Therefore, there is an urgent need to develop a quasi-adiabatic water system calorimetry system. The system must be absolute, traceable, highly sensitive, and clinically applicable to effectively support the establishment of dose standards for FLASH radiotherapy, clinical quality control, and research validation.

[0005] Internationally, collaborative research to address the metrological challenges of FLASH radiotherapy has become a common goal for metrology institutions, academia, and industry. The EMPIR project, implemented under the EU's Horizon 2020 framework, unites multiple national metrology institutions, hospitals, and universities, including PTB, NPL, METAS, and NRC, conducting systematic research on reference devices, reference dosimetry standards, reference detectors, and real-time active detection methods. A series of experimental verifications have been carried out under ultra-high dose rate electron and proton beam conditions. The US AAPM has established the TG-359 working group (some members are related to the EMPIR project) to gradually develop a FLASH dose measurement and calibration protocol. Institutions such as the UK's NPL and Germany's PTB have conducted prototype modifications to existing graphite or water calorimetric reference devices to adapt to UHDR conditions, achieving preliminary results. For example, in 2022, NPL reported that its portable graphite calorimeter achieved water absorbed dose measurement under 250 MeV proton beam conditions and a dose rate of approximately 60 Gy / s, with a measurement uncertainty of approximately 1.5%, indicating that calorimetry is both feasible and challenging under UHDR conditions.

[0006] Current international research trends can be summarized into two main lines: first, continuing to optimize and validate the calorimetric-based reference traceability system (including comparative studies of hydrocalorimetry and graphite calorimetry, accurate evaluation of conversion factors, and uncertainty budgeting); second, improving active online detectors (such as ionization chambers, semiconductor detectors, and gemstone detectors) to reduce dose rate dependence and ion recombination loss under UHDR conditions. Geometric optimization techniques, such as reducing electrode spacing, can partially alleviate the collection efficiency problem of ionization chambers, but cannot yet replace absolute references. Overall, calorimetry, due to its absolute temperature-based measurement characteristics and its inherent advantage of being unaffected by ultra-high dose rates, is the most promising path to achieving FLASH dose references and metrological traceability. However, to achieve high-precision practical measurements under UHDR conditions, it is still necessary to overcome technical obstacles such as the extremely stringent construction of quasi-adiabatic environments, the clinical applicability of probes in water phantoms, and the accurate fitting of transient complex temperature rise signals.

[0007] Currently, CN111830080A discloses a precision adiabatic calorimeter and its calorimetric method. This method includes the following steps: based on the copper card's outer wall temperature measured by a copper card temperature sensor, the water bath temperature is controlled to be lower than the copper card's outer wall temperature, and this water bath temperature changes with the copper card's outer wall temperature, ultimately maintaining a first temperature difference. Simultaneously, a heat shield surrounding the copper card precisely tracks the copper card's outer wall temperature, ensuring the heat shield temperature is higher than the copper card's outer wall temperature, and this heat shield temperature changes with the copper card's outer wall temperature, ultimately maintaining a second temperature difference. This ensures that during the calorimeter's heating process, the heat absorbed by the copper card from the heating shield assembly is equal to the heat flowing from the copper card into the water bath, thus achieving active dynamic insulation of the copper card. However, this technical solution is still not suitable for dose measurement of FLASH radiotherapy rays.

[0008] The physical characteristics of FLASH radiation dictate the specific requirements for dose measurement. FLASH radiation therapy delivers single-pulse doses of 1-10 Gy within sub-second or even microsecond ranges, compressing the total irradiation time to the millisecond to hundred-millisecond range, with dose rates exceeding 40 Gy / s. This ultra-high dose rate and extremely short irradiation time impose stringent requirements on the measurement methods, demanding that the system possess rapid response capabilities, high sensitivity, and real-time performance.

[0009] The precision adiabatic calorimeter scheme disclosed in CN111830080A employs an active dynamic adiabatic mechanism, achieving adiabatic conditions for the copper card through temperature regulation of the water bath and thermal screen. However, this mechanism requires a duration of time to complete temperature regulation (typically on the order of seconds), which is completely incompatible with the millisecond-level irradiation time of FLASH radiotherapy. During the extremely short duration of FLASH irradiation, the calorimeter cannot dynamically regulate the water bath and thermal screen temperatures, resulting in the inability to establish adiabatic conditions and effectively implement the measurement process. Furthermore, the calorimeter itself suffers from thermal inertia; the large amount of heat generated in a short time at ultra-high dose rates cannot be responded to in a timely manner, further exacerbating measurement errors.

[0010] Furthermore, the CN111830080A technical solution is designed for low dose rate environments (typically <0.1 Gy / s) and lacks specific optimization for UHDR conditions. At the ultra-high dose rates of FLASH radiotherapy, the calorimeter's response speed and thermal stability cannot meet the requirements, leading to a significant decrease in measurement accuracy and failing to address key challenges such as temperature control response and thermal loss suppression. Its passive measurement method also results in a lack of real-time capability, failing to provide the immediate dose feedback required in clinical settings. Similar to conventional passive dosimeters (such as alanine and film dosimeters), it cannot meet the real-time monitoring needs of FLASH radiotherapy.

[0011] Therefore, the above-mentioned CN111830080A technical solution conflicts with the characteristics of FLASH radiotherapy rays in terms of physical principles and time scale. Its design flaws make it unsuitable for dose measurement under ultra-high dose rate conditions and cannot solve the core challenge of establishing a dose reference for FLASH radiotherapy.

[0012] To address the shortcomings of existing technologies, this invention aims to provide a quasi-adiabatic hot water system calorimetric measurement system and method for FLASH radiotherapy rays, filling the current technological gap.

[0013] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0014] Traditional calorimeters generally employ a passive structural design, lacking effective control over heat conduction and diffusion behavior under ultra-high dose rates. This results in significant response hysteresis and nonlinearity issues in FLASH radiotherapy applications. Even some improved active adiabatic calorimeter systems, such as those using water baths and thermal shields to regulate temperature, are limited by the time constant required for temperature adjustment, making it difficult to match the transient heat deposition process within ultrashort FLASH pulses, leading to signal distortion and decreased measurement accuracy. Furthermore, most of these systems do not consider the need to maintain structural stability and sealing under strong radiation environments, making them susceptible to irradiation aging, material deformation, and other factors, further affecting measurement accuracy and repeatability.

[0015] More critically, current calorimetric devices can only measure dose at a single depth point, making it difficult to obtain the complete percentage depth dose distribution (PDD), which poses a significant limitation to clinical dose validation. Although some studies have attempted to expand the measurement dimensions by mechanically moving the probe, problems such as inaccurate positioning and thermal disturbance interference still exist in practice. Therefore, how to construct a novel calorimetric system that can provide an efficient adiabatic environment and support multi-point measurements has become one of the key technical bottlenecks that urgently need to be addressed to promote the clinical translation of FLASH radiotherapy.

[0016] As mentioned above, the main shortcomings of existing technologies include: first, they cannot respond quickly and accurately capture transient temperature rise signals under ultra-high dose rate conditions; second, they lack effective thermal isolation measures to cope with thermal disturbances caused by high-intensity radiation; and third, the system structure is complex, maintenance is difficult, and they lack good depth dose measurement capabilities. These problems severely restrict the widespread application of calorimetry in FLASH radiotherapy dosimetry, and there is an urgent need to develop a novel calorimetric measurement system and method suitable for ultra-high dose rate environments to achieve precise quality control of ultra-high dose rate radiation.

[0017] To address the shortcomings of existing technologies, this invention provides, from a first aspect, a quasi-adiabatic water system calorimetric measurement system for FLASH radiotherapy rays. The system includes a calorimeter and a thermostatic phantom. The calorimeter comprises a calorimetric core, a jacket layer, and a shielding layer, which are nested together in a non-contact manner via a tensioning mechanism, with a gas or vacuum environment between them. The thermostatic phantom, based on a thermostatic control unit, forms a near-constant temperature quasi-steady-state thermostatic water phantom within a chamber, providing a quasi-adiabatic environment for the calorimeter. When the calorimeter is positioned within the quasi-steady-state thermostatic water phantom, and FLASH radiotherapy rays irradiate the calorimeter through the chamber, a probe temperature sensor collects the temperature change signal of the calorimetric core and transmits it to a terminal.

[0018] This system employs a nested design where the calorimeter core, jacket layer, and shielding layer do not contact each other. A tensioning mechanism achieves gas or vacuum isolation between the three layers, effectively blocking heat conduction paths and avoiding the performance degradation issues of traditional aerogel materials at high dose rates. The isothermal phantom utilizes a circulating quasi-steady-state isothermal water phantom to provide a quasi-adiabatic environment for the calorimeter, offering faster response and less disturbance compared to traditional electric heating methods, accurately capturing the minute temperature rise signals generated by FLASH radiotherapy. The three-layer nested structure of the calorimeter eliminates the influence of material composition complexity on measurement accuracy while ensuring the mechanical stability of the probe in strong radiation environments, achieving high accuracy and high reliability in dose measurement.

[0019] According to a preferred embodiment, the calorimeter core, the jacket layer, and the shielding layer are arranged in an isocentric nested manner by a tensioning mechanism; wherein, there is a first annular gap between the calorimeter core and the jacket layer; and there is a second annular gap between the jacket layer and the shielding layer.

[0020] This technology employs an isocentric nested design, precisely fixing the calorimetric core, jacket layer, and shielding layer onto a common central axis via a tensioning mechanism, ensuring concentric arrangement of each layer. This isocentric design avoids mechanical stress concentration and uneven heat conduction caused by eccentric loads, improving the system's structural stability and measurement consistency. The first and second annular gaps form a double thermal isolation barrier, significantly increasing radial and axial thermal resistance and effectively suppressing heat loss along the heat conduction path. The tensioning mechanism avoids large-area direct contact between layers, minimizing thermal bridging effects and ensuring the relative positional stability of components under high radiation environments. Specific technical advantages of this design include: significantly reduced thermal conduction interference, improved temperature measurement accuracy, enhanced system mechanical stability, and reduced measurement uncertainty, making it particularly suitable for the precise calorimetric measurement requirements under ultra-high dose rate conditions in FLASH radiotherapy.

[0021] According to a preferred embodiment, the tensioning mechanism within the calorimeter tensions the calorimeter core from at least two directions via traction lines through through-holes in the jacket wall, thereby creating a suspended structure between the calorimeter core and the jacket.

[0022] The tensioning mechanism applies a balanced tension to the calorimeter core through through-holes in the jacket wall using multi-directional traction lines, creating a stable suspension structure within the jacket. This design avoids heat conduction paths caused by direct contact between the calorimeter core and the jacket, minimizing thermal bridging effects. The multi-point tensioning method ensures precise positioning and stable suspension of the calorimeter core in three-dimensional space, preventing positional shifts due to gravity or vibration.

[0023] According to a preferred embodiment, the tensioning mechanism inside the calorimeter tensions the calorimeter core from three directions via traction lines through through holes in the jacket wall, thereby forming a suspension structure between the calorimeter core and the jacket layer; wherein the included angles between the three directions are equally divided to achieve force balance of the calorimeter core.

[0024] This invention employs three equally angled traction wires to tension the calorimetric core, forming a three-dimensional balanced structure divided into 120° sections. This equally angled design ensures uniform distribution of tension in all directions, allowing the calorimetric core to achieve optimal mechanical balance within the jacket layer, avoiding structural deformation or positional displacement caused by uneven stress. Compared to two-dimensional or unidirectional tensioning, the three-dimensional tensioning method offers higher structural stability and effectively resists external vibrations and gravity. The non-contact suspension structure achieved through through-holes completely eliminates direct contact between the calorimetric core and the jacket layer, minimizing heat conduction interference and significantly improving the accuracy and reliability of calorimetric measurements, making it particularly suitable for the precise detection of minute temperature rise signals in FLASH radiotherapy.

[0025] According to a preferred embodiment, the constant temperature phantom includes a lifting mechanism, a clamping mechanism, and a constant temperature control unit disposed within the chamber, which circulates and delivers a quasi-steady-state constant temperature water phantom to the chamber. The lifting mechanism moves the calorimeter to an equivalent water depth position within the quasi-steady-state constant temperature water phantom by controlling the lifting and lowering of the clamping mechanism used to clamp the calorimeter. The constant temperature control unit circulates and delivers a temperature-stable quasi-steady-state constant temperature water phantom to the chamber through pipelines, so that the quasi-steady-state constant temperature water phantom within the chamber provides a quasi-insulating environment for the calorimeter.

[0026] This invention achieves precise depth positioning and stable temperature control of the calorimeter within a quasi-steady-state isothermal water phantom through the coordinated design of a lifting mechanism and a constant temperature control unit. The lifting mechanism accurately moves the calorimeter to the equivalent water depth, ensuring the repeatability and accuracy of the measurement position. The constant temperature control unit provides a quasi-adiabatic environment for the calorimeter by circulating and supplying a temperature-stable quasi-steady-state isothermal water phantom, effectively suppressing external thermal interference. Specific technical advantages of this design include: achieving μK-level temperature drift control, significantly improving the signal-to-noise ratio of mK-level small temperature rise signals; supporting percentage depth dose (PDD) curve measurement through precise depth positioning, overcoming the limitation of traditional calorimeters that can only measure at a single point; and the circulation system avoids the response lag problem of traditional electric heating temperature control under ultra-high FLASH dose rate conditions, ensuring a stable environmental baseline during the measurement process.

[0027] According to a preferred embodiment, the housing is provided with at least one incident interface in the vertical and / or horizontal direction; the incident interface is used for the FLASH radiotherapy beam to be concentrated in a calorimeter in a manner of horizontal and / or vertical irradiation.

[0028] This invention features incident interfaces in both the vertical and horizontal directions of the enclosure, supporting FLASH radiotherapy beams to be concentrated at multiple angles for calorimeter irradiation. This multi-directional incident design meets the measurement needs under different irradiation geometries, particularly adapting to common clinical horizontal and vertical irradiation scenarios. The optimized incident interface design improves the beam transmission path, reduces scattering and energy loss, and ensures accurate and consistent dose delivery. These structures enable flexible measurement configurations for multiple irradiation angles, enhancing the system's versatility and practicality. By optimizing beam incident conditions, the accuracy and repeatability of dose measurement are significantly improved. Combined with the three-dimensional positioning function achieved through the lifting mechanism, a complete dose distribution measurement capability can be established, providing reliable technical support for quality assurance in FLASH radiotherapy.

[0029] According to a preferred embodiment, a stirring unit is provided inside the box of the constant temperature phantom; the stirring unit stirs the quasi-steady constant temperature water phantom to provide a quasi-insulating environment for the calorimeter.

[0030] A stirring unit is installed inside the isothermal phantom chamber to continuously agitate the quasi-steady-state isothermal water phantom, eliminating temperature gradients and flow dead zones within the liquid. The stirring unit's design ensures uniform temperature distribution throughout the chamber, preventing localized temperature fluctuations from affecting calorimeter measurements. This active stirring method offers faster temperature equalization and greater temperature stability compared to static isothermal systems. Adding a stirring unit significantly reduces the temperature gradient within the quasi-steady-state isothermal water phantom, providing a more ideal quasi-adiabatic environment for the calorimeter; it effectively suppresses natural convection and thermal stratification, improving the stability and reproducibility of the measurement environment.

[0031] According to a preferred embodiment, the clamping mechanism in the thermostatic phantom clamps the calorimeter in a three-dimensional rotational manner, so that the calorimeter receives horizontal and / or vertical irradiation from FLASH radiotherapy rays.

[0032] This invention employs a three-dimensional rotation clamping mechanism, achieving precise attitude control of the calorimeter in space through multi-degree-of-freedom adjustment. This design allows the calorimeter to be adjusted to the optimal irradiation angle according to actual measurement needs, fully adapting to the requirements of various X-ray incident directions, such as horizontal and vertical, in FLASH radiotherapy. The three-dimensional rotation function ensures that the calorimeter's sensitive element is always perpendicular to the X-ray beam direction, maximizing the measurement signal intensity and reducing directional errors. This design provides flexible spatial positioning capabilities, supporting precise measurements under complex irradiation geometry conditions; it improves measurement sensitivity and accuracy by optimizing the calorimeter's attitude; and, combined with the incident interface design, achieves perfect adaptation to all irradiation conditions, significantly expanding the system's application range and measurement accuracy.

[0033] According to a preferred embodiment, the calorimeter is entirely encapsulated in a waterproof layer so that the calorimeter can be completely immersed in a constant-temperature mold for measurement; wherein the shape of the waterproof layer is adapted to the contour of the calorimeter, and the material of the waterproof layer includes polystyrene solid water material.

[0034] This invention provides a quasi-adiabatic water system calorimetry measurement method for FLASH radiotherapy rays from a second aspect. The method includes: a constant temperature control unit injecting a quasi-steady-state constant temperature water phantom into a constant temperature phantom chamber to provide a quasi-adiabatic environment for the calorimeter; clamping the calorimeter using a clamping mechanism; and a lifting mechanism moving the calorimeter to an equivalent water depth position within the quasi-steady-state constant temperature water phantom by controlling the lifting and lowering of the clamping mechanism. When the calorimeter is placed within the quasi-steady-state constant temperature water phantom, when FLASH radiotherapy rays irradiate the calorimeter through the chamber, a probe temperature sensor collects the temperature change signal of the calorimeter core and transmits it to a terminal. The calorimeter includes a calorimeter core, a jacket layer, and a shielding layer, which are nested together in a non-contact manner via a tensioning mechanism, and the environment between the calorimeter core, jacket layer, and shielding layer is a gas or vacuum environment.

[0035] The method of this invention achieves high-precision calorimetric measurement of FLASH radiotherapy rays through the synergistic effect of a quasi-steady-state isothermal water phantom circulation, precise positioning by a lifting mechanism, and a multi-layered isolation structure of the calorimeter. The quasi-steady-state isothermal water phantom provides a stable quasi-adiabatic environment, the lifting mechanism ensures the calorimeter accurately reaches the designated depth, and the multi-layered isolation structure of the calorimeter effectively blocks heat conduction interference. Specific technical advantages include: achieving μK-level temperature drift control, significantly improving the signal-to-noise ratio of mK-level minute temperature rise signals; supporting three-dimensional dose distribution measurement through precise depth positioning; eliminating the influence of heat conduction through the multi-layered isolation structure, ensuring the accuracy of measurement results; and the quasi-steady-state isothermal water phantom circulation system adapting to the ultra-high dose rate conditions of FLASH, avoiding the response lag problem of traditional temperature control methods, and providing a reliable dosimetric measurement solution for sub-second ultra-short irradiation times. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the module of the quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays provided by the present invention. Figure 2 This is a flowchart illustrating the quasi-adiabatic hot water system calorimetric measurement method for FLASH radiotherapy rays provided by the present invention. Figure 3 This is a schematic cross-sectional view of the calorimeter provided by the present invention. Figure 4 This is an enlarged cross-sectional view of the calorimeter provided by the present invention. Figure 5 This is a top view of the internal structure of the calorimeter provided by the present invention. Figure 6 This is a frontal structural diagram of the quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays provided by the present invention. Figure 7 This is a schematic diagram of the back angle of the quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays provided by the present invention. Figure 8 This is a schematic diagram of the bottom structure of the quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays provided by the present invention; Figure 9 This is a schematic diagram of the internal structure of the quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays provided by the present invention from a first-side perspective. Figure 10 This is a schematic diagram of the internal structure of the quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays provided by the present invention from the first elevation angle. Figure 11 This is a schematic diagram of the internal structure of the quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays provided by the present invention from the second elevation angle. Figure 12 This is a schematic diagram of the internal structure of the quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays provided by the present invention, viewed from the second side.

[0037] List of reference numerals 100: Thermostatic mold body; 130: Lifting rod moving cavity; 140: Liquid outlet; 150: Box body; 151: First side panel; 152: Second side panel; 153: Third side panel; 154: Fourth side panel; 155: Top plate; 156: Bottom plate; 160: First temperature sensor; 170: Injection interface; 200: Lifting mechanism; 210: Vertical injection fixture; 220: Horizontal injection fixture; 300: Thermostatic control unit; 310: Heating component; 320: Second temperature sensor; 33 0: Temperature control module; 340: Circulation pump; 350: Temperature control pipeline; 360: Stirring unit; 361: Motor; 362: Motor bracket; 400: Calorimeter; 410: Calorimeter core; 411: First annular gap; 420: Jacket layer; 421: Second annular gap; 430: Shielding layer; 440: Waterproof layer; 450: Tensioning mechanism; 460: Probe temperature sensor; 470: Wire; 500: Terminal; 510: Signal receiving module; 520: Display unit; 530: Processing unit. Detailed Implementation

[0038] The following is a detailed explanation with reference to the accompanying drawings.

[0039] This invention provides explanations and clarifications for some terms and concepts.

[0040] Quasi-Adiabatic Environment: Through insulation design and dynamic temperature control, the heat exchange rate of the system approaches zero within a specific time scale, thereby achieving an engineering environment with near-insulation conditions.

[0041] The isothermal phantom 100 is a temperature-controlled device for radiation dose measurement. It maintains the phantom temperature at a preset value through a built-in isothermal system (such as a circulating water bath or thermoelectric cooling) to eliminate the interference of temperature fluctuations on the accuracy of dose measurement. Preferably, the temperature range of the isothermal phantom 100 is 20~35°C. Preferably, the preset value of the isothermal phantom 100 of the present invention is 23°C ± 0.1°C.

[0042] In the field of FLASH radiotherapy, the passive structural design of traditional calorimeters cannot effectively control the heat conduction and diffusion processes under ultra-high dose rate conditions, resulting in significant response delays and nonlinear deviations during measurement. Even improved systems employing active adiabatic technologies such as water baths and thermal shields for temperature control struggle to meet the real-time monitoring and high sensitivity requirements of FLASH radiotherapy. Furthermore, existing systems generally neglect the critical requirements of maintaining structural stability and sealing under intense radiation environments, making them susceptible to irradiation aging and material deformation, thus reducing measurement accuracy and repeatability. Current calorimetric devices can only achieve dose measurement at a single depth point, failing to acquire the complete percentage depth dose distribution (PDD), severely limiting the accuracy of clinical dose validation.

[0043] While some studies have attempted to expand the measurement dimensions by mechanically moving the probe, technical challenges such as positioning errors and thermal disturbances remain in practical applications. Therefore, developing an innovative calorimetric system that can provide both an efficient adiabatic environment and support multi-point measurements has become a key technological breakthrough for promoting the clinical translation of FLASH radiotherapy.

[0044] Existing technologies suffer from three main bottlenecks: they cannot respond quickly and accurately capture transient temperature rise signals under ultra-high dose rate conditions; they lack effective thermal isolation mechanisms to cope with thermal disturbances caused by high-intensity radiation; and their systems are complex, difficult to maintain, and lack depth dose measurement capabilities. These shortcomings severely hinder the practical application of calorimetry in FLASH radiotherapy dosimetry, necessitating the development of a novel calorimetric measurement system and method to achieve accurate dose monitoring and reliable quality control under ultra-high dose rate environments.

[0045] To address the shortcomings of existing technologies, this invention provides a quasi-adiabatic hot water system calorimetric measurement system and method for FLASH radiotherapy rays. This invention can also provide a calorimeter 400. Furthermore, this invention can provide a constant-temperature phantom 100 specifically for dose measurement of FLASH radiotherapy rays.

[0046] This invention proposes a quasi-adiabatic hot water system graphite calorimeter measuring device using a isothermal phantom 100 as the temperature control carrier. Its core innovation lies in utilizing a highly stable isothermal water bath to implement full-process temperature control of the isothermal phantom 100, constructing a quasi-adiabatic environment with extremely low heat leakage rate and minimal temperature disturbance. Traditional graphite calorimeters rely on electric heaters or plate-type temperature control devices to maintain a steady temperature, but in the case of FLASH radiotherapy with its unique ultra-high dose rate (10⁻⁶ ppm),... 6 Under conditions of Gy / s level and ultra-short irradiation time (≤1s), the electric heating temperature control system suffers from insufficient response speed and excessive thermal inertia, resulting in significant temperature drift and control noise, which cannot meet the requirements for instantaneous measurement.

[0047] This invention continuously delivers a stable temperature field to the isothermal phantom 100 through a high-precision circulating isothermal water bath, supplemented by stirring to eliminate local temperature gradients, thus ensuring that the internal temperature fluctuations of the isothermal phantom 100 are stably controlled within the μK level. Under this extremely low temperature drift environment, the signal-to-noise ratio of the tiny radiation temperature rise signal (typically in the mK level) of the calorimeter 400 probe is significantly improved, thereby ensuring the traceability and repeatability of the measurement. Based on the quasi-adiabatic design of the isothermal phantom 100, the failure problem of traditional electric heating temperature control technology under the instantaneous irradiation conditions of FLASH radiotherapy is fundamentally solved, making calorimetry truly applicable to ultra-high-speed irradiation dose measurement scenarios. This technical approach not only significantly improves system stability and insulation effect, but also avoids the wiring interference of additional heating structures on the calorimetric structure, achieving a high degree of simplification of device configuration and systematic optimization of measurement interpretability.

[0048] like Figure 1 As shown, the quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays of the present invention includes a constant temperature phantom 100 and a calorimeter 400.

[0049] like Figure 3 and Figure 4 As shown, the calorimeter 400 includes a calorimeter core 410, a jacket layer 420, and a shielding layer 430. The materials of the calorimeter core 410, the jacket layer 420, and the shielding layer 430 are preferably graphite. Figure 5 As shown, the calorimeter core 410, the jacket layer 420 and the shielding layer 430 are arranged in a nested manner without contacting each other through the tensioning mechanism 450.

[0050] Preferably, with sufficient sealing, the space between the calorimeter core 410, the jacket layer 420, and the shielding layer 430 is a gaseous environment or a vacuum environment.

[0051] Preferably, the gas environment or vacuum environment refers to the space formed by filling the annular gap between the calorimeter core 410, the jacket layer 420, and the shielding layer 430 with a specific gas medium or by evacuating it. The gas environment can be an inert gas such as argon or helium, or a common gas medium such as air. This structural design effectively blocks heat conduction between the layers through the low thermal conductivity of the gas or vacuum, avoiding the influence of external thermal interference on the calorimeter core measurement signal. Simultaneously, the gas medium also acts as electrical insulation and damping, reducing the interference of mechanical vibration on precision measurements. Compared to direct contact solid heat transfer, the gas or vacuum environment significantly reduces the thermal conductivity coefficient, providing more ideal adiabatic measurement conditions for the calorimeter and ensuring the accuracy and stability of detecting ultra-weak temperature rise signals in FLASH radiotherapy.

[0052] To maintain the airtightness of the gas or vacuum environment, vacuum sealing plugs or glass sintering through-wall components are provided at the through holes on the wall of the jacket layer 420; when the traction wire of the tensioning mechanism 450 and the wire 470 of the probe temperature sensor 460 pass through the wall of each layer, they are all led out through the vacuum sealing plugs or through-wall components for heat insulation and sealing, so as to ensure that the vacuum isolation state between the layers is not damaged in the presence of through leads.

[0053] The isothermal phantom 100, based on the isothermal control unit 300, forms a near-constant-temperature quasi-steady-state isothermal water phantom within the housing 150, providing a quasi-adiabatic environment for the calorimeter 400. The time-temperature fluctuation rate of the quasi-steady-state isothermal water phantom is limited to the μK level. The calorimetric core 410 is in a quasi-adiabatic thermodynamically maintained position, protected by the first annular gap 411 and the second annular gap 421, at the micro-Kelvin level of the background temperature drift limit.

[0054] Preferably, the quasi-steady-state isothermal water phantom refers to the liquid medium used in the isothermal phantom 100 to provide a stable temperature environment. Its main function is to create quasi-adiabatic measurement conditions for the calorimeter 400. The quasi-steady-state isothermal water phantom is maintained at a near-constant temperature state through circulation and the isothermal control unit 300, ensuring the stability of the ambient temperature during calorimetric measurement. Preferably, the quasi-steady-state isothermal water phantom includes liquids with good thermal stability and chemical inertness, such as deionized water, silicone oil, and glycerol aqueous solution. These liquid media not only have excellent thermal conductivity, enabling the rapid establishment of a uniform temperature field, but also have low volatility and good biocompatibility, making them suitable for long-term use in medical radiometric measurement environments. More preferably, the quasi-steady-state isothermal water phantom does not use high-purity water or pure water containing many impurities or with high conductivity. By precisely controlling the temperature and flow state of the quasi-steady-state isothermal water phantom, the system can achieve μK-level temperature stability, providing a reliable environmental guarantee for the accurate detection of weak temperature rise signals in FLASH radiotherapy.

[0055] Preferably, such as Figures 6 to 8 As shown, the housing 150 defines a sealed receiving cavity, specifically including four side walls formed by sequentially splicing together a first side panel 151, a second side panel 152, a third side panel 153, and a fourth side panel 154, and a top plate 155 and a bottom plate 156 respectively closed and assembled to the top and bottom of the side walls. Preferably, the side panels are positioned by positioning surfaces to ensure the repeatability and accuracy of the overall assembly of the housing. Each panel of the housing 150 is made of thermal insulation material, or the housing 150 is provided with a thermal insulation layer to prevent heat exchange between the quasi-steady-state constant-temperature water mold inside the housing 150 and the outside environment. When the top plate 155 of the housing 150 is assembled and closed, a sealed and insulated environment is formed inside the housing 150. That is, as Figure 9 As shown, sealing components are provided at intervals along the sealing edges of the top plate 155 or each side panel of the enclosure 150 to form redundant seals, which are used to completely seal the internal environment of the enclosure 150 and reduce temperature conduction between the inside and outside of the enclosure 150. The sealing components are, for example, sealing rings.

[0056] Preferably, the housing 150 is placed on a stable, level platform to ensure that the structure does not deform or tilt. During the process of injecting the quasi-steady-state constant-temperature water phantom into the housing 150, the injection path of the quasi-steady-state constant-temperature water phantom must avoid cables, signal lines, and connectors to prevent electrical short circuits or connection failures caused by fluid contact.

[0057] A first temperature sensor 160 can also be installed inside the enclosure 150 to display the temperature inside the enclosure 150. Preferably, the first temperature sensor 160 can be made of physical hardware such as a high-precision platinum resistance thermometer or a thermocouple, which has extremely high temperature sensitivity and stability.

[0058] Preferably, the first temperature sensor 160 can be constructed using precision temperature sensing elements such as platinum resistance thermometers or thermocouples, possessing high precision and fast response physical hardware characteristics. The first temperature sensor 160 can consist of a temperature probe, a signal transmission line, and a protective housing, and is installed at an appropriate location inside the housing 150 of the constant temperature phantom 100, enabling real-time monitoring of the temperature state of the quasi-steady-state constant temperature water phantom within the housing 150. The first temperature sensor 160 is used to display and monitor the temperature distribution of the quasi-steady-state constant temperature water phantom within the housing 150 in real time, providing feedback signals to the constant temperature control unit 300 to ensure that the interior of the housing 150 is always maintained at the set quasi-constant temperature state. The quasi-constant temperature state refers to the situation where, under the target operating condition (i.e., the ultra-short measurement time window of FLASH radiotherapy rays), the spatial temperature gradient and temporal temperature fluctuation rate of the quasi-steady-state constant temperature water phantom are limited to within an allowable threshold range that does not affect the system's measurement accuracy. In other words, the temperature of the quasi-steady-state isothermal water phantom is in dynamic thermal equilibrium, and its temperature fluctuation rate is preferably controlled within a preset microKelvin (μK) or milliKelvin (mK) range, thereby providing a stable reference operating environment for the calorimeter. In the context of this invention, the quasi-steady-state isothermal water phantom refers to the liquid medium in this quasi-isothermal state, and should not be narrowly limited to an ideal fluid with an absolutely static temperature.

[0059] By continuously monitoring the temperature of the chamber 150, the first temperature sensor 160 provides an ambient temperature reference for the entire calorimetric measurement system, ensuring the stability and consistency of temperature conditions during the measurement process.

[0060] When the calorimeter 400 is placed inside the quasi-steady-state constant-temperature water phantom of the constant-temperature phantom 100, when the FLASH radiotherapy rays irradiate the calorimeter 400 through the chamber 150, the probe temperature sensor 460 collects the temperature change signal of the calorimeter core 410 and transmits it to the terminal 500 through the wire 470.

[0061] Preferably, such as Figure 1 As shown, the terminal 500 includes a signal receiving module 510, a display unit 520, and a processing unit 530. The signal receiving module 510 receives temperature change signals from the probe temperature sensor 460 of the calorimeter core 410 and converts them into electronic signals. The display unit 520 displays the electronic signal and the dose test results. The processing unit 530 calculates the absorbed dose of the FLASH radiotherapy rays based on the temperature change data of the calorimeter core 410.

[0062] Preferably, terminal 500 refers to a comprehensive data processing device that integrates signal reception, data processing, and result display functions. Terminal 500 can be, for example, an industrial control computer, a data acquisition and processing workstation, an embedded processing system, a server, a tablet computer, a smartphone, or other electronic device with real-time signal processing capabilities. This terminal 500 is used to realize the entire process of calorimetric measurement data processing. First, the analog signal of temperature change of the calorimetric core 410 collected by the probe temperature sensor 460 is converted into a digital signal by the signal receiving module; then, the processing unit 530 performs algorithmic processing and numerical calculation on the temperature change data based on thermodynamic principles and a calorimetric calculation model, ultimately obtaining the absorbed dose value of the FLASH radiotherapy rays; simultaneously, the display unit 520 visually presents the temperature change curve and dose test results, providing accurate dose measurement data.

[0063] According to a preferred embodiment, such as Figure 3 and Figure 4 As shown, the calorimeter core 410, the jacket layer 420, and the shielding layer 430 are arranged in an isocentric nested manner via a tensioning mechanism 450. Preferably, a first annular gap 411 exists between the calorimeter core 410 and the jacket layer 420. A second annular gap 421 exists between the jacket layer 420 and the shielding layer 430.

[0064] Preferably, the tensioning mechanism 450 refers to a mechanical adjustment device in the calorimetry system used to achieve precise positioning and stable support of each functional layer. It maintains the relative positional relationship between the calorimetric core 410, the jacket layer 420, and the shielding layer 430 through preload control and position adjustment, ensuring that the multi-layer structure remains concentric and stable in a non-contact state. In this invention, the tensioning mechanism 450 is implemented using a traction wire. The traction wire can be called a suspension wire. Preferably, the traction wire can be a metal or ceramic filament with extremely small diameter and extremely low thermal conductivity, which has minimal disturbance to the overall heat conduction path and possesses extremely high mechanical stability.

[0065] The calorimeter 400 adopts an isocentric nested design, such as Figure 5 As shown, the calorimeter core 410, jacket layer 420, and shielding layer 430 are precisely assembled in a concentric circle manner using a tensioning mechanism 450. The calorimeter core 410, as the core measuring element, is located in the innermost layer. The jacket layer 420 surrounds the calorimeter core, and the shielding layer 430 surrounds the jacket layer 420 to form the outermost protective structure. The tensioning mechanism 450 achieves non-contact levitation positioning between the layers, avoiding heat conduction paths caused by solid contact. The first annular gap 411 and the second annular gap 421 exist between adjacent layers, respectively. These gaps can be filled with gas or kept in a vacuum state to form an effective thermal insulation barrier.

[0066] Preferably, the interval between the first annular gap 411 and the second annular gap 421 is equal.

[0067] The design of the first annular gap 411 and the second annular gap 421 offers significant advantages. First, the isocentric nesting method ensures geometric symmetry during FLASH radiotherapy irradiation, improving the spatial resolution and directional consistency of the measurement. Second, the multi-layer gap structure creates multiple thermal barrier layers, significantly reducing the impact of external thermal interference on the calorimeter core and improving measurement accuracy. Third, the non-contact suspension positioning achieved by the tensioning mechanism 450 eliminates mechanical stress and thermal conduction coupling, ensuring the thermal isolation of the calorimeter core 410 during the measurement process. Finally, this design facilitates rapid replacement and maintenance of the calorimeter core 410 while maintaining the stability and repeatability of the overall structure, providing a reliable hardware foundation for high-precision dose measurement of FLASH radiotherapy rays.

[0068] This invention utilizes a tensioning mechanism 450 to provide controllable mechanical preload to the calorimeter core 410, enabling the calorimeter core 410, jacket layer 420, and shielding layer 430 to automatically adjust to their theoretically designed concentric positions during assembly, eliminating eccentricity problems caused by manufacturing and assembly errors. Simultaneously, the flexible support provided by the tensioning mechanism 450 maintains relative stability between layers under external vibration or temperature changes, preventing structural deformation due to differences in thermal expansion coefficients. Preferably, the tensioning mechanism 450 also possesses a certain degree of self-adjustment capability, compensating for minor displacements that may occur during long-term use, ensuring the reliability and repeatability of the measurement system during long-term operation.

[0069] According to a preferred embodiment, the tensioning mechanism 450 in the calorimeter 400 tensions the calorimeter core 410 from at least two directions via traction lines through through holes in the wall of the jacket layer 420, so that the calorimeter core 410 and the jacket layer 420 form a suspended structure.

[0070] like Figure 4 As shown, the jacket layer 420 has through holes or slots on its wall for the traction wires to pass through. By providing through holes in the jacket layer 420 wall and applying tension to the calorimeter core 410 using traction wires in at least two directions, the calorimeter core 410 achieves a non-contact suspension state within the jacket layer 420. This multi-point tensioning method ensures the positional accuracy of the calorimeter core 410 in three-dimensional space, preventing direct contact with the jacket layer 420 and thus avoiding thermal conduction interference.

[0071] According to a preferred embodiment, such as Figure 5 As shown, the tensioning mechanism 450 within the calorimeter 400 tensions the calorimeter core 410 from three directions via traction lines through through holes in the jacket layer 420 wall, thus forming a suspension structure between the calorimeter core 410 and the jacket layer 420. Preferably, the included angles between the three directions are equally divided, i.e., the included angle is 120°, to achieve force balance of the calorimeter core 410.

[0072] Specifically, the purpose of the three-directional tension is to achieve precise force balance and stable suspension of the calorimeter core 410 in space. By setting traction lines along three equally spaced angle directions, a 120° uniformly distributed three-directional tension system is formed, ensuring that the calorimeter core 410 is subjected to equal and symmetrical tensile forces in each direction. This three-directional equal-division tension design ensures that the calorimeter core 410 is completely balanced in the radial plane, avoiding the eccentric torque and instability that may occur with unidirectional or bidirectional tension.

[0073] To overcome the limitation of traditional graphite calorimeters 400, which can only measure single-point dose and cannot be used to measure percentage depth dose distribution (PDD), this invention uses a sealed assembly technology to encapsulate the calorimeter 400 entirely within a waterproof layer 440, allowing it to be completely immersed in a constant-temperature phantom 100 for measurement. A highly reliable waterproof servo motor and a precision lifting mechanism 200 are installed in the housing 150, enabling continuous and controllable fine movement of the calorimeter 400 along the X-ray axis. By changing the immersion depth of the calorimeter 400 relative to the surface of the housing 150, the equivalent water depth position of the calorimeter 400 in the water equivalent environment can be adjusted, thereby allowing for radiation calorimetry measurements at different X-ray depth positions.

[0074] Preferably, the shape of the waterproof layer 440 is adapted to the outline of the calorimeter 400. The material of the waterproof layer 440 is preferably polystyrene solid water material.

[0075] Traditional calorimeter probe waterproof sleeves are mostly made of PMMA, which has good tissue equivalence and ease of processing. However, PMMA undergoes rapid radiation aging under ultra-high dose rate irradiation by FLASH radiotherapy, resulting in molecular chain breakage, yellowing, and embrittlement, making it unusable. Current technology proposes using polycarbonate (PC), which has good radiation resistance, but its density is 1.20 g / cm³. 3 If it is not equivalent to human tissue, it will lead to radiation transmission deviation, thus affecting the accuracy of dose measurement.

[0076] This invention innovatively uses polystyrene solid water material as the waterproof layer 440 of the calorimeter 400. The material has a density of approximately 1.045 g / cm³. 3 This material is highly compatible with water and soft tissues, and possesses excellent radiation resistance. It maintains structural stability and shows no significant aging under FLASH radiation conditions, significantly improving the tissue equivalence, reliability, and long-term usability of measurements. The waterproof layer 440 prepared using this novel material not only solves the radiation aging problem of traditional PMMA materials under FLASH radiotherapy irradiation, but also overcomes the measurement deviation caused by the density mismatch of polycarbonate materials.

[0077] Because the system has a stable temperature field at the μK level and the ability to detect micro temperature rise at the mK level, the calorimeter 400 can obtain high-fidelity quantitative results of depth dose distribution under ultra-high dose rate beams, significantly filling the technical gap of traditional measurement methods in ultra-high dose rate dosimetry.

[0078] The isothermal phantom 100 is the core component of the quasi-adiabatic system, and its design goal is to ensure that the calorimeter 400 is always in an extremely low temperature disturbance environment during the measurement process. To achieve this goal, the present invention integrates a highly stable isothermal water bath circulation system into the isothermal phantom 100 and configures a stirring unit 360 to eliminate local temperature gradients.

[0079] Specifically, such as Figure 9 and Figure 12 As shown, the thermostatic phantom 100 includes a lifting mechanism 200, a clamping mechanism, and a thermostatic control unit 300 that circulates the quasi-steady-state thermostatic water phantom to the housing 150, all housed within a housing 150. A dedicated lifting rod moving cavity 130 is defined on one side of the housing 150 to isolate the internal quasi-steady-state thermostatic water phantom from direct fluid impact. The lifting mechanism 200 moves the calorimeter 400 to an equivalent water depth position within the quasi-steady-state thermostatic water phantom by controlling the lifting and lowering of the clamping mechanism used to hold the calorimeter 400. The equivalent water depth position refers to the detection position achieved in a water-equivalent environment by adjusting the immersion depth of the calorimeter 400 relative to the surface of the housing 150. The specified depth range of the equivalent water depth position can cover the measurement range of the percentage depth dose (PDD) curve of FLASH radiotherapy rays.

[0080] Preferably, the lifting mechanism 200 includes a waterproof servo motor and a lifting rod. For example... Figure 10 As shown, the lifting rod is housed within the lifting rod moving cavity 130, and constrained by the inner wall of the cavity 130, it is only allowed to perform axial lifting and lowering movements with a single degree of freedom relative to the housing 150, in order to avoid radial off-center loading. Figure 10 and Figure 11 As shown, a clamping mechanism is installed on the lifting rod. Specifically, the clamping mechanism includes a vertical incident clamp 210 and a horizontal incident clamp 220. To adapt to the requirements of complex dimensional X-ray incident radiation, the clamping mechanism specifically includes a vertical incident clamp 210 and a horizontal incident clamp 220. Preferably, an asymmetrical limiting structure is provided at the connection between the vertical incident clamp 210 or the horizontal incident clamp 220 and the lifting rod to achieve directional assembly with a unique orientation. Preferably, the vertical incident clamp 210 or the horizontal incident clamp 220 can clamp one calorimeter 400 individually, or they can be configured together to clamp two or more calorimeters 400 simultaneously.

[0081] The lifting mechanism 200 possesses high repeatability and low-noise mechanical movement characteristics, and its sealed structure isolates it from electrical risks in the aquatic environment. The lifting mechanism 200 can perform depth-by-depth scanning of the calorimeter 400 according to a preset program, enabling automated PDD measurement of FLASH radiotherapy rays. The combination of precise mechanical control and a low-temperature water-drift environment ensures that point-by-point calorimetry maintains high repeatability, high stability, and high measurement accuracy even under high dose rate and strong transient conditions.

[0082] According to a preferred embodiment, the clamping mechanism in the thermostatic phantom 100 clamps the calorimeter 400 in a three-dimensional rotational manner, so that the calorimeter 400 receives horizontal and / or vertical irradiation from FLASH radiotherapy rays. Specifically, the connecting rod of the clamping mechanism can be provided with a rotating component that can fix the angle, such as a universal joint connecting component, so that the clamping mechanism can rotate to various angles and be fixed in position after rotation.

[0083] Preferably, the clamping mechanism can be designed as a mechanical fastener with a specific geometry, such as a platform-type clamping mechanism, to accommodate calorimeters 400 of different sizes. The clamping mechanism can be made of elastic or rigid materials; the former includes materials with self-adaptive deformation capabilities, such as silicone or rubber, while the latter includes metal materials with high strength and precision machining characteristics, such as stainless steel or aluminum alloy.

[0084] In other words, the irradiation surface of the calorimeter 400 can be placed horizontally to receive vertical irradiation from the FLASH radiotherapy beams. Alternatively, the irradiation surface of the calorimeter 400 can be placed vertically to receive horizontal irradiation from the FLASH radiotherapy beams. Horizontal and vertical irradiation can be performed selectively or simultaneously. Preferably, the clamping mechanism can clamp one calorimeter 400 in the horizontal and one in the vertical directions respectively, so as to simultaneously receive both horizontal and vertical irradiation from the FLASH radiotherapy beams.

[0085] The constant temperature control unit 300 circulates a quasi-steady-state constant temperature water phantom at a stable temperature to the chamber 150 via the temperature control pipeline 350, so that the quasi-steady-state constant temperature water phantom within the chamber 150 provides a quasi-insulating environment for the calorimeter 400. Preferably, as shown... Figure 8 As shown, the bottom plate 156 of the housing 150 is provided with a liquid outlet 140 for discharging the quasi-steady-state constant-temperature water phantom. The temperature control pipeline 350 for transporting the quasi-steady-state constant-temperature water phantom is connected to the constant-temperature control unit 300 to realize the cyclic input and output of the quasi-steady-state constant-temperature water phantom. Preferably, the constant-temperature control unit 300 includes a heating component 310, a second temperature sensor 320, a temperature control module 330, and a circulation pump 340.

[0086] The heating element 310, acting as a heat source, typically employs an electric heating wire, a PTC heater, or other controllable heating elements to provide the necessary thermal energy compensation to the system. The second temperature sensor 320 monitors the temperature of the object being measured or the environment in real time and feeds the temperature signal back to the temperature control module 330. The temperature control module 330, as the core control component of the entire constant temperature control unit 300, receives the temperature feedback signal from the second temperature sensor 320, compares it with the preset target temperature value (constant temperature), and outputs corresponding control commands through a PID control algorithm or other control strategies. When a temperature deviation from the set value is detected, the temperature control module 330 adjusts the power output of the heating element 310 to achieve precise control of the heating amount. Simultaneously, under the coordinated control of the temperature control module 330, the circulating pump 340 promotes forced convection circulation of the fluid medium within the system, ensuring uniform temperature distribution and rapid response.

[0087] Throughout the operation, the heating element 310, the second temperature sensor 320, the temperature control module 330, and the circulation pump 340 form a closed-loop control system. The second temperature sensor 320 continuously collects temperature data and transmits it to the temperature control module 330. The temperature control module 330 simultaneously adjusts the heating power of the heating element 310 and the flow output of the circulation pump 340 according to the deviation, thereby achieving precise maintenance and dynamic balance of the system temperature, ensuring the temperature stability of the calorimetric measurement environment and the reliability of the measurement results.

[0088] According to a preferred embodiment, the housing 150 is provided with at least one incident interface 170 in the vertical and / or horizontal directions. That is, the housing 150 is provided with an incident interface 170 in either the vertical or horizontal direction. Alternatively, the housing 150 is provided with incident interfaces 170 in both the vertical and horizontal directions. The shape of the incident interface 170 is not limited. The number of incident interfaces 170 is not limited to one; it can be two, three, or even more. The incident interface 170 is detachable from the housing 150.

[0089] The incident interface 170 is used for a calorimeter 400 that concentrates FLASH radiotherapy rays in a horizontal and / or vertical manner. That is, the incident interface 170 is used for a calorimeter 400 that concentrates FLASH radiotherapy rays in a horizontal or vertical manner. Alternatively, the incident interface 170 is used for a calorimeter 400 that concentrates FLASH radiotherapy rays in a horizontal and vertical manner.

[0090] The ultra-high dose rate electron beam unique to FLASH radiotherapy rays causes concentrated irradiation to the incident interface 170 of the isothermal phantom 100. Traditional PMMA or PC incident interfaces 170 suffer from radiation aging, leading to decreased sealing or changes in material properties. The incident interface 170 proposed in this invention uses the same polystyrene solid water material as the waterproof layer 440 of the calorimeter 400, possessing both extremely high radiation resistance and tissue equivalence.

[0091] Preferably, the incident interface 170 adopts a modular and replaceable structure, facilitating periodic replacement after long-term use and significantly improving the robustness and maintainability of the overall measurement system. Furthermore, to adapt to different radiation directions, the present invention provides detachable incident interfaces 170 on both the top and side surfaces of the housing 150, enabling the housing 150 to simultaneously support horizontal and vertical irradiation. The incident interface 170, through its anti-deformation structural design and double waterproof sealing structure, ensures that the housing 150 maintains complete sealing performance under long-term circulating water pressure and external irradiation, thereby effectively guaranteeing the stability of the internal temperature field of the constant temperature phantom 100.

[0092] According to a preferred embodiment, a stirring unit 360 is provided inside the housing 150 of the constant temperature phantom 100. The stirring unit 360 stirs the quasi-steady-state constant temperature water phantom to provide a quasi-insulating environment for the calorimeter 400.

[0093] like Figure 8 As shown, the stirring unit 360 can adopt a rotary stirring structure, and its core components include a motor 361, a motor bracket 362, a drive shaft, stirring blades or impellers, and other mechanical parts. Figure 10 As shown, the motor 361 is securely mounted inside the housing 150 via a motor bracket 362. The motor bracket 362 extends along the direction of the motor's force to improve the moment of inertia and anti-warping stiffness, thereby stably transmitting the force of the motor operation to the base plate 156. Under the control of the temperature control module 330, it drives the drive shaft and stirring blades to rotate smoothly, achieving stable agitation of the steady-state constant-temperature water mold. The stirring blades can be designed in various forms such as propeller, turbine, anchor, or frame, with the specific structural selection depending on the required stirring intensity and fluid characteristics. The drive shaft connects the stirring motor and the stirring blades, transmitting the motor's rotational motion to the blades to achieve mechanical agitation of the medium. The stirring unit 360 is controlled by the temperature control module 330 in the constant-temperature control unit 300.

[0094] More preferably, the stirring unit 360 adopts a magnetic stirring structure, including a magnetic drive component disposed outside the housing 150 and a magnetic rotor (not shown in the figure) built into the bottom of the quasi-steady constant temperature water mold. The internal rotor is driven to rotate by an external alternating magnetic field, thereby avoiding the direct introduction of heat sources and mechanical vibration sources into the quasi-insulated environment.

[0095] The stirring unit 360 is used to eliminate temperature and concentration gradients in the measurement environment, ensuring the homogeneity and stability of the medium surrounding the calorimeter 400. Through continuous mechanical stirring, the stirring unit 360 effectively disrupts the boundary layer effect, promotes rapid heat and mass transfer, and avoids localized overheating or temperature inhomogeneity. This homogenization effect is crucial for improving the accuracy and repeatability of calorimetric measurements, especially under high-precision measurement requirements. The stirring unit 360 can significantly reduce measurement errors caused by insufficient natural convection or fluid stasis, providing ideal measurement environment conditions for the calorimeter 400.

[0096] The outer wall of the chamber 150 employs a multi-layered thermal insulation structure, combined with water bath circulation control, to stabilize the overall thermal environment temperature drift at the μK level. Since the instantaneous temperature rise of FLASH radiotherapy rays is typically only at the mK level, any environmental thermal noise or temperature disturbance will significantly reduce the calorimeter 400's accuracy in capturing transient signals. Through a quasi-insulated design, the internal thermal noise of the isothermal phantom 100 is effectively suppressed, the probe's initial temperature remains stable over a long period, and the repeatability of the measurement signal is significantly improved. This system constructs an experimental environment for the calorimeter 400 that approaches the ideal adiabatic boundary, while avoiding the drawbacks of traditional insulation structures being complex, difficult to manufacture, and difficult to maintain, making the water system the preferred engineering solution in the field of FLASH calorimetry.

[0097] In traditional vertical irradiation chamber 150 designs, a sealed structure is typically not used, making the water surface susceptible to environmental fluctuations, leading to unstable X-ray transmission and introducing measurement deviations. This invention employs a fully sealed constant-temperature phantom 100 structure; however, simply sealing the main body of chamber 150 can cause trapped air bubbles to form during water injection, disrupting the water density uniformity of the quasi-insulated system, affecting probe positioning accuracy, and inducing local refraction and scattering errors during beam injection.

[0098] To completely solve the problem of air bubble removal in the sealed housing 150, a liquid level expansion pipe (not shown in the figure) is provided on the top of the housing 150. The liquid level expansion pipe is fully connected to the interior of the housing 150, and the height of the liquid level expansion pipe is higher than the upper surface of the housing 150, so as to provide additional liquid level expansion height when injecting quasi-steady-state constant temperature water phantom.

[0099] When water is added, the liquid level overflows from the main body of tank 150 and rises along the liquid level expansion pipe. Residual air is continuously squeezed to the top of the pipe and discharged under liquid pressure. When the liquid level expansion pipe is stable and no continuous air bubbles escape, it indicates that tank 150 is completely filled and air-free. Subsequently, the liquid level expansion pipe is sealed by a sealing valve to achieve an air-free sealed water environment. This liquid level expansion pipe fundamentally solves the problem of incomplete venting in the sealed tank 150, ensuring high stability and high accuracy of the near-insulated hot water system.

[0100] This invention features a liquid level expansion pipe at the top of the housing 150, providing additional liquid level adjustment space during the injection process of the quasi-steady-state constant-temperature water phantom using the principle of communicating vessels. The design of the expansion pipe extending above the upper surface of the housing 150 effectively solves the volume compensation problem during thermal expansion of the quasi-steady-state constant-temperature water phantom, preventing liquid overflow or negative pressure. This design ensures stable filling and pressure balance of the quasi-steady-state constant-temperature water phantom within the housing 150, providing a reliable liquid environment for calorimetric measurement. Specifically, this design prevents overflow or bubble generation caused by volume expansion of the quasi-steady-state constant-temperature water phantom due to temperature changes; maintains stable liquid pressure within the housing 150, avoiding interference from liquid level fluctuations to the calorimeter 400 during measurement; simplifies the filling operation of the quasi-steady-state constant-temperature water phantom, and improves the system's ease of use and safety.

[0101] Existing technologies such as US4765749 only have conventional single-layer water baths and cannot isolate transient heat conduction in deep interiors. To overcome this structural defect, the multi-level combined thermal blocking calorimetry system of this application is configured with a fine three-dimensional spatial layout. The calorimeter 400 has a calorimeter core 410, a jacket layer 420 and a shielding layer 430. The calorimeter core 410 and the jacket layer 420 can establish an isocentric nested thermal insulation relationship with a first annular gap 411 when the shielding layer 430 is in the outermost radiation-resistant outer thermal isolation state. This allows the calorimeter 400 to be fixed to a specific equivalent water depth detection part inside the isothermal phantom 100, which is filled with a quasi-steady-state isothermal water phantom that is close to isothermal. The incident interface 170 is used to guide the ultra-high dose rate electromagnetic radiation emitted by FLASH radiotherapy rays to a specific simulated absorption site equivalent to the human body inside the isothermal phantom 100 without attenuation; the vertical incident clamp 210 is used to provide a stable mechanical clamping force along the direction of gravity; the horizontal incident clamp 220 is used to construct a support base that is vertically normal on the lateral beam-facing surface. When performing a vertical section percentage depth dose scan, the calorimeter 400, while maintaining a horizontally positioned probe surface, is attached to the vertical incident clamp 210. 10. An adaptive tight-fitting assembly relationship is established; when performing sidewall leveling lateral measurements, the vertical incident fixture 210 and the horizontal incident fixture 220 are spatially orthogonal and do not interfere with each other under idle clearance conditions where they retract along the lifting rod; and / or when verifying the dose distribution at the junction of multiple beams, the horizontal incident fixture 220 and the calorimeter 400 are in a multi-degree-of-freedom targeted cooperative positioning relationship according to a preset topological relationship of three-dimensional rotational positioning with an attached universal joint assembly.

[0102] The single-layer thermal shield system disclosed in EP1852714A1 exhibits significant thermal bridging effects under ultrashort pulses and cannot meet milliKelvin-level measurements. To address this technical deficiency, the tensioning mechanism 450 is connected to the calorimeter core 410, which has a first annular gap 411 and is in a gas-isolated thermal insulation relationship with the first annular gap 411, which is tightly filled with low-pressure inert gas. This allows the calorimeter core 410 to form a multi-level thermal blocking isocentric thermal insulation relationship with the shielding layer 430, which includes a second annular gap 421, to block multi-dimensional phonon heat transfer. When the calorimetric core 410 is subjected to high-frequency mechanical-fluid vibration caused by the circulating pump, it is in a spatial force equilibrium position where the tensioning mechanism 450 applies a uniform traction force at a 120-degree angle in three directions along the circumference. This allows the calorimetric core 410 and the jacket layer 420 to have a six-degree-of-freedom fully suspended spatial isolation relationship without any macroscopic solid rigid contact. When the calorimetric core 410 receives sub-second ultra-high dose rate transient pulse irradiation from FLASH radiotherapy, it is in a quasi-adiabatic thermodynamic maintenance position at the micro-Kelvin level background temperature drift limit, protected by the first annular gap 411 and the second annular gap 421. This allows the jacket layer 420 and the shielding layer 430 to have a secondary phonon scattering thermal blocking relationship within the second annular gap 421 that diffuses radially outward.

[0103] Preferably, the lifting rod moving cavity 130 has a rectangular guide rail inner wall, a waterproof sealing component, and a stroke limiter. The rectangular guide rail inner wall and the waterproof sealing component can establish a dynamic waterproof sealing constraint relationship with controlled friction coefficient in a dynamic adjustment state where the servo motor of the lifting mechanism 200 is energized and drives the lifting rod to move up and down. This fixes the lifting rod moving cavity 130 to one side inside the housing 150 and away from the side wall boundary anti-turbulence portion directly impacted by the main circulating fluid. The liquid level expansion tube (not shown in the figure) of this invention is used to guide the tiny residual bubbles generated by turbulent entrainment during the initial water injection process, as well as the redundant volume due to thermal expansion, to the external static pressure environment of the sealed housing 150. The waterproof layer 440 is used to seamlessly encapsulate the calorimeter 400 containing graphite elements to completely isolate the quasi-steady-state constant-temperature water phantom from physical penetration and chemical corrosion. The probe temperature sensor 460 is used to capture extremely weak voltage bias signals in transient response within the core area of ​​the graphite material. Specifically, during the initial preparation of the measurement system—specifically, the initial water injection and venting to establish a water system baseline—under the condition of absolute overflow from the communication vessel with the liquid level expansion pipe vertically connected at the top and its outlet elevation exceeding the upper surface of the tank 150, a hydrostatic relationship is established between the liquid level expansion pipe and the internal top-level space of the tank 150, where buoyancy drives the smooth unidirectional discharge of gas. Under stable operating conditions with high-energy beam irradiation on the quasi-adiabatic measurement platform, waterproofing... Layer 440, using polystyrene solid water material equivalent to water and without material damage under ultra-high dose rate electron beam irradiation without chain breakage or aging, forms a seamless conformal wrapping relationship with the cylindrical external geometric boundary of calorimeter 400; and / or, under the monitoring condition of closed-loop feedback control of temperature difference in deep water area, the probe temperature sensor 460, according to the leak-proof lead-out relationship of wire 470 passing through micropores and being cured by vacuum sealing resin, forms a closed-loop transmission relationship of real-time high-frequency sampling of heat change electrical signals with processing unit 530.

[0104] The constant temperature module 100 has a stirring unit 360, a constant temperature control unit 300, and a receiving cavity. The stirring unit 360, the constant temperature control unit 300, and the receiving cavity together with the box 150 form a bottom-mounted isolated dynamic water temperature equalization structure with a bottom heat insulation and turbulence-disrupting interlayer. This bottom-mounted isolated dynamic water temperature equalization structure has the characteristic of achieving global fluid temperature equalization under weak disturbances and remote forced convection. The motor 361 of the stirring unit 360 is positioned under the pre-set thickened heat insulation cover and heat sink guide position below the bottom plate 156, under the condition that the quasi-steady-state constant temperature water mold body is continuously injected by the circulation pump 340 of the constant temperature control unit 300 and a global macroscopic circulating flow field is established. This allows the parasitic mechanical waste heat generated by the electromagnetic conversion of the motor 361 to have a spatially attenuated physical thermal isolation and blocking relationship with the core quasi-steady-state calorimetric temperature measurement area above the inside of the box 150. The motor bracket 362 that fixes the motor is in a position that strongly maintains the anti-warping stiffness under the condition of bearing the high-speed rotation reverse torque of the blades and the fluid impact load. This allows the stirring blades mounted at the top of the drive shaft to have a three-dimensional full-space Gaussian flow field mixing relationship with the surrounding quasi-steady-state constant temperature water mold body that is close to constant temperature, without any local flow dead zones or eddy stagnation zones. Furthermore, the tensioning mechanism 450 for fixing the flexible traction line is connected to the calorimeter core 410, which is in a high-vacuum state maintained by the first annular gap 411, in a way that combines a rigid through-wall sleeve support made of alumina ceramic with extremely low thermal conductivity. This allows the calorimeter core 410 to maintain a flexible damping suspension U-shaped relationship with the jacket layer 420 without rigid heat transfer bridging when subjected to external mechanical impact.

[0105] The operating principle of the system of this invention is as follows: Precise dose measurement of FLASH radiotherapy rays is achieved through the coordinated operation of the isothermal phantom 100 and the multi-layered isolation structure of the calorimeter 400. During system operation, the isothermal control unit 300 circulates a temperature-stable quasi-steady-state isothermal water phantom into the housing 150 of the isothermal phantom 100, while the stirring unit 360 eliminates the liquid temperature gradient, providing a quasi-adiabatic environment with μK-level stability for the calorimeter. The calorimeter 400 employs a nested structure with three layers of gas or vacuum isolation: a calorimeter core 410, a jacket layer 420, and a shielding layer 430. A tensioning mechanism 450 achieves non-contact suspension positioning, effectively blocking the heat conduction path. The lifting mechanism 200 drives the clamping mechanism to precisely position the calorimeter 400 at a specified depth within the quasi-steady-state isothermal water phantom, and a three-dimensional rotation function adjusts it for optimal irradiation posture. When the FLASH radiotherapy beam irradiates the calorimeter 400 through the incident interface 170, the calorimeter core 410 absorbs the radiation energy, generating a temperature rise in the mK range. The probe temperature sensor 460 collects the temperature change signal in real time and transmits it to the terminal 500 for dose calculation. The entire system solves the technical problems of traditional calorimetry, such as response lag, severe thermal interference, and inability to achieve depth distribution measurement under ultra-high dose rate conditions, through the organic combination of quasi-steady-state constant-temperature water phantom circulating temperature control, multi-layer thermal insulation structure, and precision positioning mechanism.

[0106] The physical principle behind this system's ability to achieve high-precision measurements using a quasi-isothermal fluid is as follows: First, the extremely high dose rate of FLASH radiotherapy rays results in an extremely short actual single irradiation time (typically on the order of milliseconds or even microseconds). Within this extremely small timescale, the background temperature drift generated by the quasi-steady-state isothermal water phantom in a quasi-isothermal state is minimal and can be considered a transient thermal constant, thus avoiding the thermal accumulation error caused by temperature fluctuations in conventional long-term measurements. Second, the calorimeter 400's internal calorimeter core 410, jacket layer 420, and shielding layer 430 form a high-resistance thermal isolation path through a multi-stage gas or vacuum environment. The quasi-isothermal state of the external fluid, combined with the internal nested insulation structure, constitutes a system-level quasi-insulated environment. Even if there are slight dynamic temperature fluctuations in the external quasi-steady-state isothermal water phantom, these thermal disturbances are greatly attenuated during inward conduction. This ensures that the tiny temperature rise signal (mK level) collected by the probe temperature sensor 460 is almost entirely derived from the radiation energy deposition of FLASH rays, fundamentally overcoming the strict dependence of traditional calorimetry on absolute constant temperature hardware conditions.

[0107] The calorimetric measurement method of the quasi-adiabatic hot water system for FLASH radiotherapy rays of the present invention is as follows: Figure 2 As shown.

[0108] S100: The constant temperature control unit 300 injects a quasi-steady-state constant temperature water phantom that is close to constant temperature into the box 150 of the constant temperature phantom 100 to provide a quasi-insulating environment for the calorimeter 400.

[0109] S200: The calorimeter 400 is held in place by a clamping mechanism.

[0110] S300: The lifting mechanism 200 moves the calorimeter 400 to the equivalent water depth position in the quasi-steady-state constant temperature water phantom by controlling the lifting of the clamping mechanism used to hold the calorimeter 400.

[0111] S400: When the calorimeter 400 is placed inside the quasi-steady constant temperature water phantom of the constant temperature phantom 100, when the FLASH radiotherapy rays irradiate the calorimeter 400 through the box 150, the probe temperature sensor 460 collects the temperature change signal of the calorimeter core 410 and transmits it to the terminal 500.

[0112] Furthermore, when the processing unit 530 performs calculations, the terminal 500 can pre-acquire and record the background temperature drift slope of the system under quasi-isothermal conditions. When calculating the actual temperature rise of the calorimetric core 410, the small background thermal drift parameter inherent in this quasi-isothermal state is subtracted by an algorithm to further improve the absolute measurement accuracy and fault tolerance of the system under extreme conditions of ultra-high dose rate.

[0113] It should be noted that the specific embodiments described above are exemplary. Those skilled in the art can devise various solutions inspired by the disclosure of this invention, and these solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents. This specification contains multiple inventive concepts; terms such as "preferredly," "according to a preferred embodiment," or "optionally" indicate that the corresponding paragraph discloses an independent concept. The applicant reserves the right to file divisional applications based on each inventive concept.

Claims

1. A quasi-adiabatic hot water system calorimetric measurement system for FLASH radiotherapy rays, characterized in that, The system includes: A calorimeter (400) includes a calorimeter core (410), a jacket layer (420), and a shielding layer (430). The calorimeter core (410), the jacket layer (420), and the shielding layer (430) are nested together without contacting each other by a tensioning mechanism (450), and the space between the calorimeter core (410), the jacket layer (420), and the shielding layer (430) is a gaseous or vacuum environment. The constant temperature phantom (100) forms a near-constant temperature quasi-steady-state constant temperature water phantom within the housing (150) based on the constant temperature control unit (300) to provide a quasi-insulating environment for the calorimeter (400); When the calorimeter (400) is placed in the quasi-steady-state constant-temperature water phantom of the constant-temperature phantom (100), when the FLASH radiotherapy rays irradiate the calorimeter (400) through the box (150), the probe temperature sensor (460) collects the temperature change signal of the calorimeter core (410) and transmits it to the terminal (500).

2. The system according to claim 1, characterized in that, The calorimeter core (410), the jacket layer (420), and the shielding layer (430) are arranged in an isocentric nesting manner by a tensioning mechanism (450); There is a first annular gap (411) between the calorimeter core (410) and the jacket layer (420); there is a second annular gap (421) between the jacket layer (420) and the shielding layer (430).

3. The system according to claim 1 or 2, characterized in that, The tensioning mechanism (450) within the calorimeter (400) tensions the calorimeter core (410) from at least two directions via traction lines through a through hole in the wall of the jacket layer (420), thereby forming a suspended structure between the calorimeter core (410) and the jacket layer (420).

4. The system according to any one of claims 1 to 3, characterized in that, The tensioning mechanism (450) inside the calorimeter (400) tensions the calorimeter core (410) from three directions via traction lines through the through holes in the wall of the jacket layer (420), so that the calorimeter core (410) and the jacket layer (420) form a suspension structure; wherein the included angles between the three directions are equally divided to achieve force balance of the calorimeter core (410).

5. The system according to any one of claims 1 to 4, characterized in that, The constant temperature mold (100) includes a lifting mechanism (200), a clamping mechanism and a constant temperature control unit (300) that circulates the quasi-steady constant temperature water mold to the box (150) within the box (150). The lifting mechanism (200) moves the calorimeter (400) to the equivalent water depth position in the quasi-steady-state constant temperature water phantom by controlling the lifting and lowering of the clamping mechanism used to hold the calorimeter (400). The constant temperature control unit (300) circulates a temperature-stable quasi-steady-state constant temperature water phantom to the box (150) through the temperature control pipeline (350) so that the quasi-steady-state constant temperature water phantom in the box (150) provides a quasi-insulating environment for the calorimeter (400).

6. The system according to any one of claims 1 to 5, characterized in that, The housing (150) has at least one incident interface (170) in the vertical and / or horizontal directions. The incident interface (170) is used to concentrate the calorimeter (400) with FLASH radiotherapy rays in a horizontal and / or vertical manner.

7. The system according to any one of claims 1 to 6, characterized in that, The constant temperature mold (100) is equipped with a stirring unit (360) inside the box (150). The stirring unit (360) stirs the quasi-steady-state constant temperature water phantom to provide a quasi-insulating environment for the calorimeter (400).

8. The system according to any one of claims 1 to 7, characterized in that, The clamping mechanism in the constant temperature phantom (100) clamps the calorimeter (400) in a three-dimensional rotation manner, so that the calorimeter (400) receives horizontal and / or vertical irradiation of FLASH radiotherapy rays.

9. The system according to any one of claims 1 to 8, characterized in that, The calorimeter (400) is entirely encapsulated in a waterproof layer (440) so that the calorimeter (400) can be completely immersed in the constant temperature mold (100) for measurement; The shape of the waterproof layer (440) is adapted to the outline of the calorimeter (400), and the material of the waterproof layer (440) includes polystyrene solid water material.

10. A method for calorimetric measurement of a quasi-adiabatic hot water system for FLASH radiotherapy rays, characterized in that, The method includes: The constant temperature control unit (300) injects a near-constant temperature quasi-steady constant temperature water phantom into the box (150) of the constant temperature phantom (100) to provide a quasi-insulating environment for the calorimeter (400); The calorimeter (400) is held by a clamping mechanism; the lifting mechanism (200) moves the calorimeter (400) to the equivalent water depth position in the quasi-steady-state constant temperature water phantom by controlling the lifting of the clamping mechanism used to hold the calorimeter (400); When the calorimeter (400) is placed in the quasi-steady-state constant-temperature water phantom of the constant-temperature phantom (100), when the FLASH radiotherapy rays irradiate the calorimeter (400) through the box (150), the probe temperature sensor (460) collects the temperature change signal of the calorimeter core (410) and transmits it to the terminal (500). The calorimeter (400) includes a calorimeter core (410), a jacket layer (420), and a shielding layer (430). The calorimeter core (410), the jacket layer (420), and the shielding layer (430) are nested together without contacting each other by a tensioning mechanism (450), and the space between the calorimeter core (410), the jacket layer (420), and the shielding layer (430) is a gas or vacuum environment.

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