FLASH radiotherapy ray calorimeter and method

Abstract

The invention discloses a calorimeter and method for FLASH radiotherapy rays. The calorimeter comprises a calorimetric core, a jacket layer and a shielding layer. The calorimetric core is an absorber of FLASH radiotherapy rays, and the calorimetric core is nested in a first space in the jacket layer in a manner that a first interval exists between the calorimetric core and the jacket layer and the calorimetric core and the jacket layer are not in contact with each other; the jacket layer is nested in a second space in the shielding layer in a manner that the jacket layer and the shielding layer have a second interval and are not in contact with each other; no non-gas filler exists in the first interval and the second interval. Through the arrangement, the calorimeter aims to meet the strict requirements of ultrahigh dose rate and millisecond irradiation of FLASH radiotherapy rays, the defects that solid filler hinders heat transfer and increases heat capacity in the prior art are overcome, through the design that three layers do not make contact with each other and are free of solid filling, heat loss and heat conduction lag are reduced, heat is concentrated on the calorimetric core, and the heat loss is reduced. Meanwhile, the overall heat capacity is reduced, the millisecond-level thermal response speed is guaranteed, and high accuracy and traceability of dose measurement are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of radiotherapy dose measurement technology, and in particular to a calorimeter and method for FLASH radiotherapy rays. Background Technology

[0002] Malignant tumors are a major disease that seriously threatens human life and health. In the clinical treatment of tumors, radiotherapy is one of the core methods. It is estimated that about 70% of cancer patients need to receive radiotherapy at different stages of disease development.

[0003] In conventional radiotherapy (CONV), the average dose rate is typically in the range of 1–5 Gy / min, and a single irradiation often lasts for several minutes. Although conventional radiotherapy can kill tumor cells, it inevitably causes radiation damage to normal tissues surrounding the tumor during the irradiation process. Therefore, how to maintain or improve the probability of tumor control (TCP) while effectively reducing the probability of non-TCP complications in normal tissues has always been a core scientific problem that urgently needs to be solved in the field of radiotherapy.

[0004] In recent years, FLASH radiotherapy has attracted widespread attention as a novel radiotherapy technique. This technique is characterized by an ultra-high dose rate (UHDR), typically defined as no less than 40 Gy / s, which is more than three orders of magnitude higher than conventional radiotherapy. FLASH radiotherapy can deliver high-dose irradiation within a sub-millisecond to millisecond timescale.

[0005] Existing animal model studies and preliminary clinical research indicate that this technology can induce a unique FLASH effect: while maintaining tumor-killing efficiency comparable to conventional radiotherapy, it can significantly reduce radiation damage to irradiated normal tissues. This characteristic provides a new physical and biological basis for achieving a highly effective and low-toxicity radiotherapy modality, demonstrating significant clinical application potential and research value.

[0006] However, while FLASH radiotherapy has shown great potential for clinical applications, its extremely high dose rate also poses a severe challenge to the accurate measurement of absorbed dose. Because FLASH rays need to complete the deposition of large doses within an extremely short timescale of sub-millisecond to millisecond, existing conventional dose monitoring methods are insufficient to meet its requirements for high dynamic response and high precision.

[0007] Specifically, conventional active dosimeters commonly used in clinical practice (such as ionization chambers) are prone to significant collection efficiency losses and severe response nonlinearities when faced with ultra-high pulse dose rates due to aggravated compounding effects, making it impossible to obtain dose parameters in real time and accurately. While passive dosimeters such as alanine, film, and thermoluminescent dosimeters (TLDs) are less dependent on dose rate, their measurement procedures are complex and cannot achieve real-time measurement, making it difficult to support the immediate quality control requirements of FLASH radiotherapy in clinical practice and research.

[0008] Calorimetry, as the primary standard measurement method in radiation dosimetry, is based on the principle of utilizing the temperature rise effect generated after a medium absorbs ionizing radiation energy. The measured values ​​are directly reproduced through traceable temperature or electrical quantities. Because its detection mechanism is theoretically unaffected by radiation quality, energy spectrum, and dose rate, calorimetry is considered an ideal technical approach for solving dosimetric traceability problems under ultra-high dose rate conditions.

[0009] Therefore, for the special conditions of FLASH radiotherapy with ultra-high instantaneous dose and extremely short irradiation time, developing a calorimetric device with high sensitivity, high reliability and metrological traceability is of great technical significance for establishing a traceability system for ultra-high dose rate absorbed dose values, ensuring the safety of clinical application of FLASH radiotherapy and the accuracy of dosimetric research.

[0010] However, existing calorimeter technologies still face significant technical bottlenecks when dealing with extreme physical conditions such as ultra-high dose rates and millisecond-level transient irradiation in FLASH radiotherapy. For example, CN216848160U discloses 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 wraps around both 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.

[0011] For example, CN203479428U discloses a graphene sheet array calorimeter. The material is graphene sheets tens of micrometers in size, with a polytetrafluoroethylene (PTFE) ring used as insulation between two adjacent graphene sheets. A thermocouple wire is pressed between the graphene sheet and the PTFE ring to measure the temperature of the graphene sheet. The other end of the thermocouple wire is connected to a high-speed multi-channel data acquisition card via a sampling resistor. The signal is then transmitted to a computer system for data recording. This technical solution uses graphene as the material for the sheet array, retaining the advantages of graphite as a material for sheet array calorimeters while solving the problem of low mechanical strength in sheet arrays. It is suitable for measuring the depth distribution of high-current electron beam energy deposition.

[0012] The sandwich structure design of existing calorimeters in the two aforementioned technical solutions is insufficient to meet the requirements for high-accuracy thermal loss correction. These solutions introduce solid non-gaseous filling materials such as expanded polystyrene (EPS) or polytetrafluoroethylene (PTFE) insulation between the graphite absorber and the external structure, or between adjacent sensitive units. During the millisecond-level transient delivery of FLASH radiotherapy rays, the ultra-high dose rate induces transient, non-uniform, and nonlinear temperature rise in the aforementioned sandwich filling materials, leading to significant changes in the system's heat transfer behavior. Because the effective thermophysical parameters of the solid filling materials under extremely high dose rate transient irradiation conditions are difficult to accurately characterize, the thermal loss correction model of the calorimeter introduces a large uncertainty component, thus failing to meet the stringent requirements of high dose measurement accuracy and metrological traceability for FLASH radiotherapy.

[0013] Furthermore, the physical form of existing devices is mismatched with the requirements for clinical dose distribution measurement. The aforementioned existing calorimeter solutions generally suffer from drawbacks such as large overall structural size, complex material composition, and poor water equivalence. This not only limits the applicability of the detectors under complex clinical radiotherapy geometries but also makes it difficult to meet the application requirements for precise measurement of percentage depth dose (PDD) distribution in FLASH radiotherapy dosimetry studies.

[0014] Therefore, existing calorimeter technologies are difficult to adapt to the measurement requirements of FLASH radiotherapy rays in terms of structural design, temperature control dynamic response performance, water equivalence, and detector size, and cannot achieve high-accuracy, traceable absorbed dose measurement.

[0015] In summary, FLASH radiotherapy, with its ultra-high dose rate and millisecond-level irradiation time, places stringent requirements on calorimetric measurements. These requirements include high thermal conductivity to ensure rapid heat transfer, low heat capacity for rapid response to temperature changes, direct hot-surface contact for accurate sensing of surface temperature changes, and millisecond-level temporal resolution. However, existing calorimetric technologies have failed to meet these critical requirements. The inherent limitations of current technologies mean that existing calorimeters cannot provide the high accuracy and traceability required for FLASH radiotherapy dose measurements. Reliable biological and clinical validation relies on highly accurate, traceable, and absolute measurement and reproducibility of absorbed dose. Therefore, there is an urgent need to develop novel calorimeters adapted to the characteristics of FLASH radiotherapy to overcome the key technical bottlenecks in heat transfer and measurement response at ultra-high dose rates.

[0016] 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

[0017] In the field of radiotherapy for malignant tumors, FLASH radiotherapy, with its ultra-high dose rate and millisecond-level transient irradiation, has shown the potential to significantly reduce damage to normal tissues. However, it also poses a serious challenge to accurate dose measurement. Currently, clinically used active dosimeters such as ionization chambers are prone to significant collection efficiency losses and response nonlinearity problems at ultra-high pulse dose rates; while passive dosimeters such as film and thermoluminescent dosimeters are difficult to meet the requirements of immediate quality control due to their complex processes and inability to measure in real time.

[0018] Although calorimetry is considered an ideal approach to solving such traceability problems, existing graphite or graphene calorimeter solutions still have significant technical bottlenecks: First, the solid thermal insulation materials such as polystyrene and polytetrafluoroethylene introduced into their structure will produce non-uniform and non-linear temperature rises under extremely short transient irradiation, making it difficult to accurately characterize heat transfer behavior. This leads to huge uncertainties in the heat loss correction model, which cannot meet the high accuracy requirements of metrological traceability. Second, existing devices generally have defects such as large size, complex materials, and poor water equivalence, which not only limit their applicability under complex clinical geometry conditions, but also make it difficult to achieve precise measurement of percentage depth dose (PDD) distribution.

[0019] To address the shortcomings of existing technologies in terms of accuracy in ultra-high dose rate measurement, reliability of thermal loss correction, and suitability for clinical applications, this invention aims to solve the following problems: How to optimize the calorimeter structure to eliminate transient thermal interference from solid filler materials and improve the clinical adaptability of the device, thereby achieving high-accuracy traceability measurement of FLASH radiotherapy dose.

[0020] To address the shortcomings of existing technologies, this invention provides a calorimeter for FLASH radiotherapy, comprising a calorimeter core, a jacket layer, and a shielding layer. The calorimeter core serves as the absorber of the FLASH radiotherapy rays and is nested within a first space of the jacket layer with a first gap between it and the jacket layer, ensuring they do not contact each other. The jacket layer is nested within a second space of the shielding layer with a second gap between it and the shielding layer, ensuring they do not contact each other. Neither the first nor the second gap contains any non-gas-based filling material.

[0021] The calorimeter of this invention is designed to meet the stringent requirements of ultra-high dose rates and millisecond-level irradiation in FLASH radiotherapy. It avoids the defects of solid fillers in the prior art that hinder heat transfer and increase heat capacity. Through a three-layer non-contact design with no solid filler, heat loss and heat conduction hysteresis are reduced, allowing heat to be concentrated in the calorimeter core. At the same time, the overall heat capacity is reduced, ensuring millisecond-level thermal response speed and ensuring high accuracy and traceability of dose measurement.

[0022] According to a preferred embodiment, the first wall of the jacket layer is provided with at least two first holes for penetrating the suspension wire. The calorimeter core is pulled by the suspension wire from at least two directions through the first holes in the first wall of the jacket layer and is suspended in the first space. At the same time, the jacket layer is suspended in the second space of the shielding layer under the suspension of the suspension wire, so that the calorimeter core, the jacket layer and the shielding layer do not contact each other. One end of the suspension wire is connected to the calorimeter core and the other end is connected to the second wall of the shielding layer.

[0023] The calorimeter of this invention is designed to avoid heat conduction caused by direct contact between the three layers. A suspension wire passes through the first hole, and the calorimeter core and jacket layer are suspended from at least two directions, preventing them from contacting each other, eliminating the solid thermal bridge effect, and reducing heat loss and hysteresis. At the same time, the suspension wire connects the calorimeter core and the shielding layer, taking into account both structural stability and low thermal conduction interference, adapting to the requirements of ultra-high dose rate and millisecond-level response of FLASH radiotherapy, and ensuring accurate dose measurement.

[0024] According to a preferred embodiment, the distance between the first interval and the second interval is equal. The calorimeter of the present invention is configured in such a way, combined with a three-layer isocentric nested design, to make the heat conduction path completely symmetrical, avoid uneven heat distribution, minimize heat leakage, ensure that heat is concentrated in the calorimeter core, and guarantee millisecond-level thermal response; at the same time, it makes the calorimeter core subjected to uniform force, prevents tilting and overturning, improves structural stability, and avoids positional deviation from affecting the measurement.

[0025] According to a preferred embodiment, the calorimeter core, the jacket layer, and the shielding layer are nested together in an isocentric manner to achieve stable thermal isolation.

[0026] The calorimeter of this invention is configured such that the centers of the three components coincide to make the heat conduction path fully symmetrical, avoiding uneven heat distribution caused by eccentricity, minimizing heat leakage, concentrating heat in the calorimeter core, and ensuring millisecond-level thermal response; at the same time, it ensures structural stability, prevents the layers from shifting or contacting, enhances the thermal isolation effect, avoids external environmental interference, and thus ensures high accuracy and traceability of dose measurement.

[0027] According to a preferred embodiment, the calorimeter core is pulled from three directions through a first hole in the first wall of the jacket layer by suspension wires and is suspended in a first space; wherein the three directions are on the same plane and the angles between them are equal, so that the calorimeter core is stably fixed.

[0028] With the three directions on the same plane and the included angles equal, the calorimeter core is subjected to uniform force, avoiding displacement or flipping and achieving stable fixation. At the same time, the calorimeter core is kept suspended by the suspension wire, eliminating the heat conduction path of solid contact, reducing heat loss and hysteresis, and ensuring millisecond-level thermal response.

[0029] According to a preferred embodiment, gas is present in the first and / or second space; or, the first and / or second space is a vacuum environment.

[0030] Gases have extremely low heat capacity and low thermal conductivity, avoiding the drawbacks of solid fillers that hinder heat transfer and increase heat capacity, thus reducing heat loss and hysteresis. A vacuum environment almost completely blocks heat conduction and also avoids oxidation contamination. Both methods concentrate heat in the calorimeter core, enhancing thermal isolation and ensuring millisecond-level thermal response.

[0031] According to a preferred embodiment, a miniature temperature sensor is provided on the calorimeter core for collecting the temperature of the calorimeter core.

[0032] The calorimeter core is the core of X-ray energy absorption, and a miniature temperature sensor is directly placed on it to capture real-time temperature changes, avoiding the lag and environmental interference of embedded or shell-mounted temperature measurement in existing technologies; at the same time, it shortens the heat conduction path, improves the millisecond-level thermal response speed, and accurately captures mK-level temperature rise signals.

[0033] According to a preferred embodiment, the calorimeter further includes a thermostatic phantom for providing a quasi-adiabatic environment, wherein the liquid temperature within the thermostatic phantom approaches a quasi-thermal state; when the calorimeter is fixed at a specified depth range below the liquid surface, after FLASH radiation is applied to the calorimeter, a temperature sensor on the calorimeter core outputs the temperature data of the calorimeter core.

[0034] The constant temperature phantom provides a quasi-insulated environment, avoiding the temperature drift and noise of traditional electric heating. The liquid approaches a constant temperature, reducing heat exchange and ensuring that the temperature change of the calorimeter core originates only from radiation. The calorimeter is fixed at a specified depth below the liquid surface to avoid external interference and ensure temperature stability. Combined with a temperature sensor, it directly outputs data, achieving millisecond-level response and accurate temperature measurement.

[0035] According to a preferred embodiment, the thermostatic phantom is provided with an entrance window for the FLASH radiotherapy beam to enter, so that the ultra-high dose rate electron beam of the FLASH radiotherapy beam is concentrated and irradiated through the entrance window of the thermostatic phantom, thereby accurately irradiating the FLASH radiotherapy beam onto the calorimeter.

[0036] The entrance window allows for concentrated irradiation by an ultra-high dose rate electron beam, ensuring accurate irradiation of the calorimeter and preventing deviations from affecting measurements. It also solves the problem of irradiation aging of traditional materials, facilitating maintenance and replacement. The polystyrene material used is radiation-resistant and has equivalent tissue structure, without interfering with the radiation dose and distribution.

[0037] According to a preferred embodiment, the calorimeter core, jacket layer, and shielding layer are made of graphite; when the calorimeter is used in conjunction with the constant temperature phantom, a waterproof layer is provided outside the shielding layer, and the material of the removable entrance window and the waterproof layer on the constant temperature phantom is polystyrene with a density close to that of water.

[0038] Graphite has high thermal conductivity, making it suitable for calorimetry and capable of efficiently absorbing radiation energy; the waterproof layer outside the shielding layer can prevent liquid erosion and protect the internal structure; polystyrene has a density close to that of water, making the calorimeter stable in liquids, and it is also radiation resistant and has good radiation transmittance, which does not interfere with dose measurement. It also solves the problem of aging caused by radiation of traditional entrance windows. The detachable design facilitates maintenance and ensures accurate and reliable measurement.

[0039] This invention provides a calorimetric method for FLASH radiotherapy rays from a second aspect. The method includes: adjusting the liquid in a thermostatic phantom to a near-constant temperature state; fixing a calorimeter at a specified depth below the liquid surface of the thermostatic phantom; applying FLASH radiotherapy rays to the calorimeter; and a temperature sensor on the calorimeter core outputting the temperature data of the calorimeter core. The calorimeter includes a calorimeter core, a jacket layer, and a shielding layer. The calorimeter core is an absorber of the FLASH radiotherapy rays and is nested within a first space of the jacket layer with a first gap and without contact. The jacket layer is nested within a second space of the shielding layer with a second gap and without contact. There are no non-gas filling materials within the first and second gaps. A miniature temperature sensor is provided on the calorimeter core for collecting its temperature.

[0040] In the method of this invention, the isothermal phantom provides a quasi-adiabatic environment, reducing heat exchange interference; the calorimeter is fixed at a specified depth below the liquid surface to avoid the influence of external temperature fluctuations; the calorimeter's three-layer structure, without solid fillers and without contact with each other, reduces thermal hysteresis, allowing heat to concentrate in the calorimetric core; the temperature sensor directly collects the core temperature, providing a fast and accurate response. Overall, this method achieves highly accurate and traceable real-time dose measurement, overcoming the measurement bottleneck at ultra-high dose rates. Attached Figure Description

[0041] Figure 1 This is a schematic cross-sectional view of the calorimeter provided by the present invention. Figure 2 This is a schematic diagram of the calorimeter provided by the present invention; Figure 3 This is an enlarged schematic diagram of the cross-sectional structure of the calorimeter provided by the present invention; Figure 4 This is a schematic diagram of the internal suspension wire arrangement of the calorimeter provided by the present invention; Figure 5 This is a schematic diagram illustrating the application scenario of the calorimeter provided by the present invention; Figure 6 This is a schematic diagram of the temperature rise response curve of the FLASH beam calorimeter provided by the present invention; Figure 7 This is a schematic diagram of the percentage dose depth curve of the calorimeter probe provided by the present invention. List of reference numerals 100: Calorimeter; 101: Calorimeter core; 102: Jacket layer; 103: Shielding layer; 104: Waterproof layer; 105: Suspension wire; 106: Temperature sensor; 107: Wire; 108: First hole; 109: Second hole; 200: Constant temperature mold; 201: Box body; 202: Lifting mechanism; 203: Fixing clamp; 204: Entrance window; 205: Liquid inlet; 206: Liquid outlet; 207: Stirring assembly. Detailed Implementation

[0042] The following is a detailed explanation with reference to the accompanying drawings.

[0043] Example 1 In the field of radiotherapy dose measurement, existing technologies mainly employ conventional active dosimeters such as ionization chambers, or passive methods such as alanine, film, and thermoluminescent dosimeters (TLDs). Regarding the specific implementation of calorimeters, existing graphite or graphene calorimeter designs typically introduce solid non-gaseous materials such as aerogel, expanded polystyrene, or polytetrafluoroethylene as insulation layers and mechanical support structures between the graphite absorber and the external structure, or between adjacent sensitive units. Furthermore, to maintain a stable temperature during measurement, traditional devices generally rely on electric heaters or plate-type temperature control systems to create a constant temperature environment.

[0044] However, these technologies exhibit significant limitations when faced with the demanding conditions of ultra-high dose rates and millisecond-level irradiation in FLASH radiotherapy. Firstly, conventional active dosimeters suffer severe collection efficiency losses and response nonlinearities under ultra-high pulse dose rates due to aggravated recombination effects, while passive dosimeters lack real-time quality control due to their complex processes. For calorimeters, traditional graphite calorimeters typically employ aerogel as both a thermal insulation layer and a mechanical support structure. However, the changes in the thermal properties (thermal conductivity, specific heat capacity, density, etc.) of aerogel under ultra-high dose rate conditions in FLASH radiotherapy with dose are still unclear. Related studies indicate that this solid filler may introduce measurement uncertainty, and the aerogel structure is fragile and not resistant to long-term irradiation, easily undergoing structural and thermal performance degradation during long-term use, making it difficult to meet stringent dosimetric requirements.

[0045] In addition, solid filler materials induce transient, non-uniform, and nonlinear temperature rises under millisecond-level transient irradiation, making it difficult to accurately characterize the system's heat transfer behavior and introducing significant uncertainties into the heat loss correction model. Existing calorimeters also generally suffer from drawbacks such as large size, complex materials, and poor water equivalence, limiting their applicability in complex clinical geometries and making it difficult to achieve precise measurement of percentage depth dose (PDD) distribution. Finally, traditional electric heating temperature control systems are prone to temperature drift and control noise due to excessive thermal inertia. Furthermore, indirect temperature measurement methods, such as mounting the temperature sensing element in the outer casing, result in significant heat conduction delays, making their temperature measurement performance unsuitable for the millisecond-level rapid response requirements.

[0046] To address the shortcomings of existing technologies, this embodiment provides a calorimeter 100 for FLASH radiotherapy, proposing a nested assembly structure with a suspended wire 105. Specifically, a high-strength suspended wire 105 is installed between the three-layer sleeve structure of the calorimeter core 101, the jacket layer 102, and the shielding layer 103, ensuring that the three layers maintain a concentric, equiaxial, and non-contact nested structure. Preferably, the suspended wire 105 is made of a metal or ceramic filament with extremely small diameter and extremely low thermal conductivity, minimizing disturbance to the overall heat conduction path while possessing extremely high mechanical stability. In this way, the filling material of the entire calorimeter 100 contains only gas and graphite, eliminating the problem of uncontrollable thermophysical property changes caused by the complexity of composite material composition.

[0047] Furthermore, the present invention can also evacuate the calorimeter core 101, the jacket layer 102 and the shielding layer 103 to form a vacuum environment, so as to further reduce the disturbance of temperature by gas.

[0048] The calorimeter 100 of this invention features a significantly reduced overall size and lower internal heat capacity. Simultaneously, the radial and axial heat transfer paths of the calorimeter 100 are optimized, thereby achieving excellent lateral spatial resolution (better than 2 mm). Traditional graphite calorimeters 100, due to their large size and excessive thermal inertia, cannot be used for depth-based dose measurement, let alone for the depth-by-depth measurements required for FLASH radiotherapy. The compact design of this invention, through optimization of the size of the calorimeter core 101, the shielding structure layout, and the thermal isolation strategy, significantly improves the thermal response speed, enabling the direct acquisition of independent dose measurement signals at different depth locations.

[0049] Specifically, the calorimeter 100 includes a calorimeter core 101, a jacket layer 102, and a shielding layer 103. Preferably, the calorimeter core 101, jacket layer 102, and shielding layer 103 are made of graphite. The calorimeter core 101 is the absorber of FLASH radiotherapy rays and is the smallest of the three structures. The jacket layer 102 is an intermediate layer used for heat insulation. Preferably, the jacket layer 102 forms a first gap with the calorimeter core 101 to prevent heat from being directly conducted from the calorimeter core 101 to the external structure, ensuring that heat is mainly concentrated inside the calorimeter core 101 during measurement, thereby improving the accuracy and response speed of temperature measurement.

[0050] The shielding layer 103 is the outermost layer, which not only isolates external electromagnetic interference, but also forms a second gap with the jacket layer 102, further enhancing the overall thermal isolation effect and preventing the influence of external ambient temperature changes on the measurement results.

[0051] Preferably, the calorimetric core 101 is nested within a first space of the jacket layer 102, with a first gap between it and the jacket layer 102, and without contact with it. The jacket layer 102 is nested within a second space of the shielding layer 103, with a second gap between it and the shielding layer 103, and without contact with it. Neither the first nor the second gap contains any non-gas-based filling material.

[0052] In this invention, the first space is defined as the volume enclosed by the inner wall of the jacket layer 102, and the second space is defined as the volume enclosed by the inner wall of the shielding layer 103. The absence of non-gaseous fillers means that within the aforementioned first and second intervals, solid insulating fillers such as aerogels and expanded polystyrene, widely used in the prior art, are excluded as large-area surface contacts or bulk fillers to provide thermal insulation and mechanical support, rather than excluding extremely fine connecting components used for point contacts and linear suspensions.

[0053] Specifically, the suspension wire 105 is in a rigid node position after passing through the first hole 108 and being cured and locked with a small amount of epoxy resin adhesive, so that the calorimeter core 101 and the jacket layer 102 have a stable and centrally coincident thermal isolation nesting relationship. Preferably, the extremely small cross-sectional area of ​​the suspension wire 105 fundamentally cuts off the transient, non-uniform, and non-linear temperature rise interference caused by the bulk filling material; while the suspension wire 105 is in a relaxed position when no multi-directional uniform tension force is applied or no adhesive is applied, so that the jacket layer 102 and the shielding layer 103 may have an eccentric or direct contact relationship due to gravity offset, thereby destroying the full symmetry of the heat conduction path.

[0054] like Figure 1 and Figure 3 As shown, the calorimeter core 101, the jacket layer 102, and the shielding layer 103 form a non-contact, suspended nested structure. Here, "non-contact, suspended nested structure" means that these three elements maintain a certain gap, do not directly contact each other physically, and are nested like nested dolls, yet independent of each other. The key to this design is to avoid heat conduction, electromagnetic interference, and thermal stress accumulation. If the calorimeter core 101 directly contacts the jacket layer 102, heat will be rapidly dissipated through solid conduction, affecting measurement accuracy; if the jacket layer 102 directly contacts the shielding layer 103, electromagnetic interference may be conducted through the conductor, reducing the shielding effect; while the suspended structure allows each layer to expand and contract freely with temperature changes, without restraining each other, thereby achieving better thermal management, electromagnetic shielding, and radiation protection, ensuring the stable and reliable operation of the entire system.

[0055] Preferably, unlike the prior art which fills the interlayer with insulating material, the present invention does not fill the interlayer with any non-gaseous material. This reduces the weight of the calorimeter 100, making it portable. Not filling it with any insulating material also avoids measurement errors caused by the heat capacity of the insulating material itself. Insulating materials absorb and release heat, affecting the thermal balance of the calorimeter 100, while gases such as air have extremely low heat capacity and hardly interfere with the measurement results. This design simplifies the structure of the calorimeter 100, eliminating the need to consider the stability, aging, or replacement cycle of the insulating material, thus improving the reliability and lifespan of the device. Simultaneously, it avoids potential chemical reactions or contamination from the insulating material, ensuring the purity of the measurement.

[0056] Preferably, a gas is present in the first and / or second interval. The gas is, for example, air or a gas with low thermal conductivity. Air is a mixture of gases in the Earth's atmosphere, and is a colorless, odorless, and transparent mixture. In this invention, "air" refers to the gas in the measurement environment where the calorimeter 100 is located. Air, as a natural insulating medium, has a low thermal conductivity, effectively blocking heat conduction and preventing heat transfer through solid media. Gases with low thermal conductivity include, for example, argon (Ar), krypton (Kr), xenon (Xe), and carbon dioxide (CO2).

[0057] With this design, the calorimeter 100 is composed only of gas and graphite, eliminating the problem of uncontrollable thermophysical property changes caused by the complexity of composite material composition. The calorimeter 100 adopts a segmented modular structure, with each part forming a highly stable layered structure through gas isolation and mechanical support. While maintaining extremely high thermal uniformity and isothermal characteristics, it still has a compact size. This allows the calorimeter 100 to not only be placed inside a small isothermal phantom 200, but also to perform rapid displacement measurements under low heat leakage conditions, thereby realizing direct PDD measurement capability based on graphite calorimetry.

[0058] Preferably, the first and / or second spacers can also be in a vacuum environment.

[0059] Setting the interval to a vacuum, while increasing production costs, offers numerous advantages. The vacuum environment almost completely blocks heat conduction. In the calorimeter 100, this characteristic ensures that heat from the calorimeter core 101 is not transferred to the external environment through the jacket layer 102, thus maintaining extremely high thermal uniformity and isothermal properties—crucial for accurate PDD measurements. In the calorimeter 100, the vacuum environment prevents potential oxidation, decarburization, and contamination between the calorimeter core 101 and the jacket layer 102, ensuring the purity and accuracy of the measurement results. The vacuum environment also eliminates thermal capacity interference that may arise from non-gaseous filling materials, making the temperature changes of the calorimeter core 101 more precise and controllable.

[0060] Preferably, there are several ways to form a non-contacting and suspended nested structure among the calorimeter core 101, the jacket layer 102, and the shielding layer 103. For example, a connecting component can be used to pass through the jacket layer 102, with one end connected to the calorimeter core 101 and the other end passing through the jacket layer 102 and connecting to the shielding layer 103, thus suspending both the calorimeter core 101 and the jacket layer 102. The connecting component can be, for example, a straight rod. However, this would increase the weight of the calorimeter 100. Therefore, to further reduce the weight of the calorimeter 100, the present invention selects a suspension wire 105 as the connecting body to achieve suspension. Compared to the traditional structure where the connecting component is a small rod, the suspension wire suspension technology has significant technical advantages in the calorimeter 100 for FLASH radiotherapy. The suspension wire 105 enables a truly non-contact connection between the calorimetric core 101, the jacket layer 102, and the shielding layer 103, fundamentally eliminating the heat conduction path generated by solid contact points and avoiding the unavoidable thermal bridging effect in traditional rod connection methods, thus significantly improving the thermal isolation effect. From the perspective of heat conduction mechanism, the cross-sectional area of ​​the suspension wire 105 is much smaller than that of the rod, greatly limiting heat conduction loss along the connecting components. This allows most of the heat to be retained inside the calorimetric core 101 for temperature measurement, rather than being dissipated into the external structure through the connecting components. This design also effectively avoids the problem of thermal stress concentration caused by the difference in the thermal expansion coefficients of the connecting component materials, maintaining structural stability and measurement reliability during the rapid temperature changes of FLASH radiotherapy rays.

[0061] like Figure 3 As shown, the first wall of the jacket layer 102 is provided with at least two first holes 108 for the suspension wire 105 to pass through. The calorimeter core 101 is provided with at least two second holes 109 for connecting the suspension wire 105. The calorimeter core 101 is pulled by the suspension wire 105 from at least two directions through the first holes 108 on the first wall of the jacket layer 102 and is suspended in the first space. At the same time, the jacket layer 102 is suspended in the second space of the shielding layer 103 under the suspension of the suspension wire 105, so that the calorimeter core 101, the jacket layer 102 and the shielding layer 103 do not contact each other. Preferably, one end of the suspension wire 105 is connected to the calorimeter core 101, for example, by attaching it to the second hole 109; the other end is connected to the second wall of the shielding layer 103.

[0062] During the assembly process of the above structure, this embodiment provides a specific positioning and fixing method: one end of the suspension wire 105 is fixedly connected to the second hole 109 of the calorimeter core 101, and the other end extends outward and connects to the second wall of the shielding layer 103. During the process of the suspension wire 105 passing through the jacket layer 102, a microscope is used to monitor and adjust the first interval between the calorimeter core 101 and the jacket layer 102, and the second interval between the jacket layer 102 and the shielding layer 103, until the dimensions of each interval meet the preset consistency requirements.

[0063] After precise positioning, epoxy resin adhesive is applied at the intersection where the suspension wire 105 passes through the first hole 108. The relative position of the suspension wire 105 and the jacket layer 102 is locked by the curing of the adhesive. This embodiment achieves stable support and limitation of the jacket layer 102 through the fixing point formed at the first hole 108, which can effectively prevent the position of the jacket layer 102 from shifting in the suspended state, thereby ensuring that the dimensions of the first interval and the second interval remain constant during the operation of the calorimeter.

[0064] Preferably, the suspension wires 105 can pull the heat sink 101 from two directions, with the two directions being in a straight line. For example, two suspension wires 105 symmetrically pull the heat sink 101. However, compared to a structure where each layer is suspended by an independent suspension wire 105, the design of simultaneously suspending the heat sink 101 and the jacket layer 102 with suspension wires 105 has significant technical advantages. This integrated suspension method, through the suspension wires 105 penetrating the first wall of the jacket layer 102 from at least two directions and connecting the heat sink 101 and the shielding layer 103, forms a unified mechanical support system, effectively simplifying the complexity of the overall structure.

[0065] From a mechanical stability perspective, the design of the suspension wire 105 eliminates the potential tension unevenness problem in multi-suspension wire systems, avoiding the risk of relative displacement and collision between layers due to slight differences in the length of different suspension wires 105. This design also significantly reduces the number of suspension wires 105 and connection points, lowering the probability of structural failure and improving the reliability and service life of the system.

[0066] In terms of thermal insulation performance, the single suspension wire 105 structure further reduces the heat conduction path because the heat capacity and heat conduction cross-section of the suspension wire 105 itself are already minimized, and reducing the number of suspension wires 105 means that the total heat conduction channels are further reduced. At the same time, this design ensures the spatially fixed relationship between the calorimeter core 101 and the jacket layer 102, avoiding frictional heat generation and mechanical interference that may be caused by the relative movement between the two.

[0067] Furthermore, the manufacturing and installation process of the suspension wire 105 is simpler and less expensive, and it is easier to operate during maintenance and calibration. The two ends of the suspension wire 105 are fixed to the second hole 109 of the calorimeter core 101 and the second wall of the shielding layer 103, respectively, forming stable mechanical boundary conditions, which is beneficial to improving measurement accuracy and system consistency.

[0068] The suspension wire 105 can also pull the heating element 101 from three directions, making the heating element 101 suspended. The suspension wire 105 can also pull the heating element 101 from four directions, making the heating element 101 suspended. The four directions are on two perpendicular straight lines, which makes the state of the heating element 101 stable and prevents it from flipping.

[0069] More preferably, such as Figure 4 As shown, the calorimeter core 101 is suspended in the first space by suspension wires 105 extending from three directions through holes in the first wall of the jacket layer 102. The three directions are on the same plane and at equal angles to each other, thus stably fixing the calorimeter core 101. That is, the three directions are on the same plane and at 120-degree angles to each other.

[0070] By pulling the calorimeter core 101 in three directions, the 120-degree angle ensures that the tension of the three suspension wires 105 is evenly distributed in space, forming a stable force balance system and preventing the calorimeter core 101 from shifting or flipping in any direction due to external forces. The symmetrical distribution of 120 degrees also ensures that the forces on the three suspension wires 105 are completely symmetrical. The 120-degree angle maximizes the use of space on the plane, allowing the three suspension wires 105 to maintain sufficient spacing to avoid mutual interference while ensuring the stable suspension of the calorimeter core 101. If the angle is less than 120 degrees (e.g., 90 degrees), the two suspension wires 105 will be too close, which may lead to mutual interference; if the angle is greater than 120 degrees (e.g., 150 degrees), the distance between the suspension wires 105 will be too large, which will reduce the stability of the calorimeter core 101.

[0071] Therefore, the present invention utilizes the suspension wire 105 to not only provide stable support but also avoid the thermomechanical uncertainties that may occur when using insulating materials such as aerogel. The assembly process of the calorimeter 100 requires precise machining of the groove and control of its width: too large a width will lead to an increase in the proportion of non-graphite materials and damage to material purity; too small a width will affect the tension of the suspension wire 105 and the assembly accuracy.

[0072] Regarding the internal nested mechanical structure of the calorimeter 100, the suspension wire 105 is connected to the jacket layer 102, which contains the calorimeter core 101, through a first hole 108 penetrating the first wall of the jacket layer 102. This jacket layer 105 is nested with the calorimeter core 101 in a completely isocentric nested manner and has a precise first interval relationship with the calorimeter core 101. This allows the jacket layer 102 within the second space to achieve a suspended isolation relationship with the outermost shielding layer 103, eliminating contact between them. This suspended isolation relationship eliminates the direct thermal bridging effect caused by solid contact points. The calorimeter 100 includes the calorimeter core 101, the suspension wire 105, and / or the jacket layer 102. The suspension wire 105 and the calorimeter core 101 can establish a completely symmetrical force balance relationship under symmetrical tension in three directions (i.e., 120 degrees) within the same plane. This ensures that the calorimeter core 101 is stably suspended and fixed to the absolute center of the first space within the jacket layer 102, preventing tilting or overturning in any direction.

[0073] According to a preferred embodiment, the distance between the first and second intervals is equal. This equal distance, combined with a 120° angle design, ensures uniform stress on the calorimeter core 101, preventing tilting or flipping in any direction. This symmetrical structure ensures a perfectly symmetrical heat conduction path, optimizing thermal uniformity and isothermal properties, and minimizing heat leakage. Simultaneously, it provides optimal structural stability and significantly improves measurement accuracy.

[0074] like Figure 3 As shown, according to a preferred embodiment, the calorimeter core 101, the jacket layer 102, and the shielding layer 103 are nested together in an isocentric manner to achieve stable thermal isolation. Isocentric means that the centers of the three layers coincide.

[0075] The central alignment of the calorimeter core 101, the jacket layer 102, and the shielding layer 103 ensures that the heat conduction path is completely symmetrical in all directions, avoiding uneven heat distribution caused by eccentricity. This results in a uniform and stable temperature field around the calorimeter core 101, which is the foundation for achieving high-precision PDD measurements. The symmetrical structure with central alignment eliminates measurement deviations caused by positional offsets, allowing the calorimeter 100 to maintain extremely high thermal uniformity and isothermal characteristics while still possessing a compact size.

[0076] To ensure the achievement of the core technology effect of millisecond-level mK-level ultra-fast thermal response and provide sufficient thermodynamic support, this invention does not simply involve attaching a sensor externally. The calorimeter core 101 has a miniature temperature sensor 106 directly disposed in tiny blind holes on its surface or inside, a first spacer without solid filler, and an isometric jacket layer 102. The temperature sensor 106, the solid-filler-free spacer, and the calorimeter core 101 together with the calorimeter 100 form a Z-structure with extremely low internal heat capacity and an extremely short direct heat conduction path, enabling the Z-structure to have millisecond-level zero-delay sensing characteristics for FLASH radiotherapy ray energy deposition. Preferably, this sensing characteristic relies on the direct and dense physical contact between the miniature temperature sensor 106 and the calorimeter core 101 body, which serves as the ray absorption core, thereby bypassing the interface thermal resistance and conduction delay that inevitably accompany indirect temperature measurement through a thick graphite shell in existing technologies (such as US3665762A). Meanwhile, based on the extremely low heat capacity of the gas or vacuum environment, the tiny mK-level heat absorbed by the calorimeter core 101 will not be dynamically absorbed and released by the surrounding insulating medium, thereby ensuring that the temperature change captured by the temperature sensor 106 can be accurately and in real time converted into the absorbed dose of FLASH rays through a formula.

[0077] According to a preferred embodiment, such as Figure 1 As shown, a miniature temperature sensor 106 is installed on the calorimeter core 101 to collect the temperature of the calorimeter core 101. The temperature sensor 106 transmits temperature data through the wire 107.

[0078] Because the calorimeter core 101 is heat-insulated, the heat absorbed by it from the FLASH radiotherapy rays causes its temperature to rise. Therefore, by detecting the temperature of the calorimeter core 101 and applying thermodynamic formulas, the dose of the FLASH radiotherapy rays can be accurately determined.

[0079] Preferably, the formula for calculating the dose of FLASH radiotherapy rays is: .

[0080] In the above formula, This is a cumulative term, representing the rate of change of internal energy (i.e., the accumulation or reduction of heat) per unit volume of fluid due to temperature changes over time. For conduction, it represents the heat conduction flux caused by the temperature gradient (following Fourier's law of heat conduction). For fluid convection, it represents the heat transfer caused by the macroscopic flow (velocity) of the fluid carrying heat from one region to another. Viscous heating refers to the portion of a fluid that converts mechanical energy into heat energy due to viscous friction. Pressure work represents the change in heat energy caused by the work done on a fluid due to pressure changes (compression or expansion).

[0081] In the above formula, Indicates fluid density; The fluid's specific heat capacity at constant pressure is represented by: T (absolute temperature); t (time); k (thermal conductivity); Q (heat source power density); and u (fluid velocity vector). represents the viscous stress tensor; S represents the strain rate tensor; Indicates absolute pressure; Represents the Hamiltonian operator. Denotes divergence, This represents the temperature gradient; the subscript p indicates that the partial derivative is obtained under constant pressure.

[0082] Compared to existing technologies that mount the temperature sensing element in a graphite shell, thus inevitably leading to conduction with the external environment, this invention directly places the temperature sensor 106 on the surface or inside the calorimeter core 101, offering significant advantages. In conventional methods, the temperature of the calorimeter 100's outer shell is affected not only by internal heat sources but also by ambient temperature fluctuations. This dual heat source effect introduces unwanted noise into the temperature measurement signal. The structural design of this invention allows the temperature sensor 106 to directly contact the calorimeter core 101, sensing the actual temperature changes of the core 101 in real time, avoiding the heat conduction delay and temperature gradient effects present when measuring temperature indirectly through a graphite shell. Since the calorimeter core 101 is the core component that directly absorbs radiant energy, using it as the direct temperature measurement object more accurately reflects the actual dose deposition. This invention, by directly placing the temperature sensor 106 on the calorimeter core 101, effectively avoids interference from heat exchange between the shielding layer 103 and the external environment, minimizing the contamination of the core temperature measurement signal by external temperature conduction.

[0083] Furthermore, the direct placement of the temperature sensor 106 on the calorimeter core 101 shortens the heat conduction path and improves the temperature measurement response speed, which matches the millisecond-level rapid dose measurement requirements of FLASH radiotherapy rays.

[0084] According to a preferred embodiment, the calorimeter 100 further includes a thermostatic phantom 200 for providing a quasi-adiabatic environment, such as... Figure 5 As shown.

[0085] The quasi-adiabatic environment refers to a stable thermal environment constructed by the isothermal phantom 200, characterized by extremely low heat leakage rate, extremely low temperature disturbance, and heat exchange approaching zero. Its core purpose is to isolate external temperature interference and ensure that the temperature change of the calorimetric core 101 originates only from the energy deposition of FLASH radiotherapy rays, providing a precise and stable thermal basis for the dose measurement of ultra-high dose rate rays.

[0086] The isothermal phantom 200 is a special carrier device that provides a quasi-insulated, low-disturbance, and highly stable thermal environment for FLASH radiotherapy dose measurement. Its core function is to isolate external temperature interference and ensure that the temperature change of the calorimeter core 101 of the calorimeter 100 originates only from the deposition of radiation energy, thus providing a stable thermal basis and structural support for the accurate dose measurement of ultra-high dose rate radiation.

[0087] The constant temperature mold 200 includes a heat-insulating box 201 and a lifting mechanism 202. The lifting mechanism 202 is equipped with a fixing clamp 203 for holding the calorimeter 100. Preferably, the box 201 is placed on a stable and level platform to ensure that the structure does not deform or tilt.

[0088] like Figure 5As shown, an entrance window 204 is provided on the housing 201. The entrance window 204 is used to guide the electromagnetic radiation emitted by the FLASH radiotherapy device to a specific part below the liquid surface inside the thermostatic phantom 200. When ultra-high dose rate millisecond-level precise measurement is required, the detachable entrance window 204 is in a tight fit with the opening of the housing of the thermostatic phantom 200 under the condition of precise alignment of the optical path. When internal calorimeter calibration or maintenance is required, the detachable entrance window 204 is physically separated from the housing of the thermostatic phantom 200 under the condition of releasing the edge friction engagement, and / or when the thermostatic liquid is continuously circulated, the shielding layer 103 is completely immersed and isolates the liquid thermal disturbance in a near-zero heat exchange relationship with the quasi-thermal liquid inside the thermostatic phantom 200.

[0089] The chamber 201 is also equipped with a liquid inlet 205 for inputting the constant-temperature liquid and a liquid outlet 206 for outputting the constant-temperature liquid. The liquid inlet 205 and liquid outlet 206 are connected to an external constant-temperature system, allowing the constant-temperature liquid inside the chamber 201 to circulate and reduce temperature gradient differences. A stirring assembly 207 is also provided at the bottom of the chamber 201 for stirring the constant-temperature liquid to reduce temperature differences at different locations within the liquid.

[0090] The temperature-controlled liquid inside the chamber 201 can be water or water containing substances that maintain a stable temperature. More preferably, the temperature-controlled liquid inside the chamber 201 is high-purity water or pure water, and water sources containing a lot of impurities or with high conductivity should not be used.

[0091] The liquid temperature within the isothermal phantom 200 approaches a quasi-isothermal state. The quasi-isothermal state described in this invention refers to a dynamic thermal equilibrium state achieved by the liquid environment within the isothermal phantom 200 through the synergistic effect of the isothermal phantom 200, the liquid circulation system, and the stirring assembly 207. In this quasi-isothermal state, the liquid temperature is not physically constant, but rather controlled within a very small fluctuation range approaching a set value. For example, by eliminating local temperature gradients, the liquid temperature fluctuation is stably suppressed within a micro-Kelvin (μK) drift range. The core characteristic of this quasi-isothermal state is that its instantaneous background temperature drift rate is significantly lower than the millisecond-level temperature rise signal caused by FLASH radiotherapy rays on the calorimetric core 101, which is typically in the milli-Kelvin (mK) range. By constructing this quasi-constant temperature state, the heat exchange between the calorimeter shielding layer 103 and the external liquid environment approaches zero, thereby providing the calorimeter with a low-disturbance, high-stability quasi-adiabatic physical background. This ensures that the temperature change data captured by the temperature sensor 106 can be accurately inverted into the absorbed dose of FLASH radiotherapy rays, effectively eliminating the interference of environmental fluctuations on minute thermal signals.

[0092] The quasi-constant temperature refers to the target reference temperature set for the liquid within the constant temperature phantom 200. It is typically selected at a specific point within a certain range based on the laboratory environment, and allows for minimal static deviations conforming to industry standards. Preferably, the quasi-constant temperature is controlled between 20 and 35°C. More preferably, the quasi-constant temperature is 23 ± 0.15°C.

[0093] like Figure 5 As shown, when the calorimeter 100 is fixed at a specified depth below the liquid surface by the clamp 203, after applying FLASH radiation to the calorimeter 100, the temperature sensor 106 on the calorimeter core 101 outputs the temperature data of the calorimeter core 101. That is, the calorimeter 100 needs to be completely immersed in the constant-temperature liquid and submerged to a sufficient depth to avoid being affected by the ambient temperature of the constant-temperature liquid. If the calorimeter 100 is only slightly submerged below the surface of the constant-temperature liquid, due to insufficient immersion depth, the temperature of the constant-temperature liquid above it is easily affected by external disturbances and fluctuates, thus affecting the temperature stability of the calorimeter 100 itself. Therefore, it is essential to submerge the calorimeter 100 to a sufficient depth in the constant-temperature liquid.

[0094] Preferably, the calorimeter 100 is fixed by the fixing clamp 203 at a depth of not less than 0.5 cm below the liquid surface.

[0095] This invention is the first to propose a quasi-adiabatic hot water system calorimetric measurement device using a constant-temperature phantom 200 as the temperature control carrier. Its core idea is to utilize a highly stable constant-temperature water bath to control the temperature of the constant-temperature phantom 200 throughout its entire operation, thereby constructing a quasi-adiabatic environment with extremely low heat leakage rate and extremely low temperature disturbance. Traditional calorimeters 100 typically use electric heaters or plate-type temperature control devices to maintain a steady temperature. However, under the conditions of ultra-high dose rates and ultra-short irradiation times characteristic of FLASH radiotherapy, electric heating temperature control not only fails to provide a sufficiently fast thermal response but also introduces non-negligible temperature drift and control noise due to the excessive thermal inertia of the temperature control system itself. This invention can provide a quasi-adiabatic environment, making the heat exchange between the calorimeter 100 and the quasi-adiabatic environment approach zero, thereby accurately measuring the temperature change of the calorimetric core 101.

[0096] Preferably, such as Figure 2 As shown, when the calorimeter 100 is used in conjunction with the constant temperature phantom 200, a waterproof layer 104 is provided outside the shielding layer 103. The waterproof layer 104 is made of polystyrene with a density close to that of water.

[0097] Currently, the waterproof layer of existing calorimeters is made of polycarbonate (PC), but its density is 1.20 g / cm³. 3The lack of equivalence with human tissue can lead to radiation transmission deviations, thus affecting the accuracy of dose measurement. To address this deficiency, the waterproof layer 104 of the calorimeter 100 of this invention is preferably made of polystyrene solid water material, which has a density of approximately 1.045 g / cm³. 3 It is highly compatible with water and soft tissues, and has excellent radiation resistance, maintaining structural stability and showing no significant aging under FLASH conditions.

[0098] The waterproof layer 104 effectively protects the internal precision calorimeter 100 from moisture erosion, avoiding the potential impact of humidity changes on the electrical and thermal properties of the graphite material. Since the calorimeter 100 needs to be used in a thermostatic phantom 200, which typically contains water or other liquid media, the density-matched design ensures that the waterproof layer 104 has good suspension characteristics and mechanical stability in a quasi-insulating environment, avoiding additional mechanical stress or positional displacement caused by excessive density differences. Polystyrene itself has excellent waterproof performance and chemical inertness, effectively blocking moisture penetration, while its low thermal conductivity further enhances the thermal isolation effect between the calorimeter 100 and the quasi-insulating environment. Furthermore, polystyrene has good radiation transmittance, which will not significantly interfere with the dose distribution and intensity measurement of FLASH radiotherapy rays, ensuring the accuracy of the measurement results.

[0099] The ultra-high dose rate electron beam unique to FLASH radiotherapy delivers concentrated irradiation to the entrance window 204 on the thermostatic phantom 200. The entrance window 204 is detachable and its shape and size are not limited. Traditional PMMA or PC entrance windows 204 suffer from radiation aging, leading to decreased sealing or changes in material properties. The entrance window 204 of this invention uses the same polystyrene solid water material as the waterproof layer 104, exhibiting extremely high radiation resistance and tissue equivalence.

[0100] This invention continuously delivers a stable temperature field to the isothermal phantom 200 through a high-precision circulating isothermal water bath, and uses a stirring assembly 207 to eliminate local temperature gradients, thus ensuring that the internal temperature change of the isothermal phantom 200 is stably controlled within the μK-level temperature drift range. Under this low-temperature drift environment, the tiny radiative temperature rise signal of the calorimeter 100 (typically only at the mK level) can achieve a significantly improved signal-to-noise ratio, thereby ensuring the traceability and repeatability of the measurement.

[0101] Based on the quasi-adiabatic design of the isothermal phantom 200, this invention fundamentally solves the problem that traditional electric heating temperature control technology cannot function properly under the instantaneous irradiation conditions of FLASH radiotherapy, making calorimetry truly applicable to ultra-high-speed irradiation dose measurement scenarios. The technical solution of this invention not only has stronger stability and better insulation, but also avoids interference from additional heating structures on the wiring of the calorimetric structure, achieving a high degree of simplification of the device configuration and a significant improvement in measurement interpretability.

[0102] Example 2 This embodiment is a further improvement on embodiment 1, and repeated content will not be described again.

[0103] This invention provides a calorimetric method for FLASH radiotherapy rays, the method comprising: S100: Adjust the liquid in the thermostatic mold 200 to approach a quasi-thermostatic state.

[0104] A high-precision circulating constant-temperature water bath system controls the liquid temperature within the constant-temperature mold 200 to near a predetermined value, achieving temperature stability at the μK level. Simultaneously, the stirring assembly 207 is activated to ensure uniform temperature distribution within the liquid, eliminating localized temperature gradients and creating ideal thermal conditions for subsequent accurate temperature measurement.

[0105] S200: The calorimeter 100 is fixed at a specified depth below the liquid surface of the thermostatic phantom 200. The calorimeter 100 is clamped and fixed by the fixing clip 203 in the lifting mechanism 202. More preferably, the fixing clip 203 is a tabletop fixing clip. More preferably, the calorimeter 100 is placed horizontally on the fixing clip 203, and the incident surface of the calorimeter 100 is calibrated to a horizontal state using a level, and then the handle end of the calorimeter 100 is fixed to the connecting rod.

[0106] After the fixing clamp 203 moves, ensure that the calorimeter 100 is completely immersed in the constant temperature liquid and that the waterproof layer 104 is in full contact with the constant temperature liquid. Adjust the lifting mechanism 202 through the control unit of the constant temperature mold 200 to adjust the position of the fixing clamp 203, so that the calorimeter 100 is accurately positioned at the preset measurement depth, avoiding measurement errors caused by position deviation, and ensuring that the optical path between the entrance window 204 and the calorimeter core 101 is unobstructed.

[0107] Preferably, the measurement time for the calorimeter 100 to be continuously immersed in the constant-temperature liquid should be controlled within 8 hours. After the experiment, it should be removed immediately, the surface wiped dry, and stored in a sealed desiccant cabinet.

[0108] S300: FLASH radiotherapy rays are applied to the calorimeter 100 through the entrance window 204. During FLASH radiotherapy irradiation, the ray beam passes through the entrance window 204 and acts directly on the calorimeter core 101. Since the calorimeter core 101, the jacket layer 102, and the shielding layer 103 do not contact each other and are all suspended, the effective deposition and uniform distribution of heat inside the calorimeter core 101 are ensured, avoiding energy loss during heat conduction.

[0109] S400: The temperature sensor 106 on the calorimeter core 101 outputs the temperature data of the calorimeter core 101 to the connected terminal. The terminal displays the temperature data change curve in real time and directly calculates and displays the dose measurement data of the FLASH radiotherapy rays based on a preset calculation formula. The temperature sensor 106 is directly installed on the surface or inside the calorimeter core 101, and can accurately capture the mK-level temperature rise signal caused by FLASH radiotherapy irradiation. High-precision dose inversion calculation is achieved through the data processing algorithm of the terminal.

[0110] Specifically, in combination Figure 6 The data output and processing process of the aforementioned terminal is illustrated by example. Figure 6 The temperature rise response curve measured by calorimeter 100 under FLASH radiotherapy conditions is presented. The horizontal axis represents time (sampling interval 1s), and the vertical axis represents normalized temperature. The specific measurement procedure for this curve is as follows: (1) After the calorimeter 100 reaches a stable working state in the liquid of the constant temperature phantom 200, start the Wheatstone bridge measurement system connected to the temperature sensor 106. (2) During the 0s~60s time period, the FLASH radiotherapy beam is turned off (only the 30s~60s data is shown in the figure), and the baseline response before irradiation is recorded; (3) Turn on the FLASH radiotherapy beam: Set the pulse width to 3.7μs and the repetition frequency to 100Hz, irradiate 100 pulses (total duration 1s), and the temperature of the calorimeter core (101) will rise and generate a response in a short time; (4) Continue recording after the FLASH radiation therapy beam is turned off to obtain the response changes after irradiation; (5) The temperature difference before and after irradiation was obtained by extrapolation.

[0111] Furthermore, based on the above-described single-point fixed measurement method, this invention can also obtain spatial dose distribution. Combined with... Figure 7 The percentage depth dose (PDD) curve shows that the horizontal axis represents the position of the calorimeter at 100 (corresponding to different equivalent water depths for dose measurement, in mm); the vertical axis represents the percentage of dose at that position relative to the point of maximum dose. Specific explanations are as follows: like Figure 7As shown, based on the physical characteristics of the percentage depth dose (PDD) curve, the dose percentage reaches its peak (100%) at a corresponding equivalent water depth of approximately 15 mm. Subsequently, within the depth range of 15 mm to 50 mm, the dose percentage exhibits a continuous and smooth nonlinear decay trend with increasing depth, and finally decays to near 0 at a water depth of 50 mm.

[0112] With all other measurement conditions remaining unchanged (including FLASH radiation conditions, measurement system configuration, and the position of the thermostatic phantom 200 relative to the beam output device), the calorimeter 100 is moved at different depths (i.e., different equivalent water depths) below the liquid surface of the thermostatic phantom 200 by the lifting mechanism 202 (e.g., motor drive), and the dose values ​​are collected point by point and normalized to obtain the above-mentioned PDD curve.

[0113] The results show that the calorimeter 100 of the present invention can not only measure the dose at a reference point (fixed position), but also obtain the dose distribution at different water depths, realizing the expansion from single-point measurement to spatial distribution measurement (from one-dimensional to two-dimensional).

[0114] 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 calorimeter for FLASH radiotherapy, characterized in that, The calorimeter (100) includes a calorimeter core (101), a jacket layer (102), and a shielding layer (103). The calorimetric core (101) is an absorber of FLASH radiotherapy rays. The calorimetric core (101) is nested in the first space inside the jacket layer (102) in such a way that there is a first gap between it and the jacket layer (102) and they do not contact each other. The jacket layer (102) is nested within the second space of the shielding layer (103) in such a way that there is a second gap between it and the shielding layer (103) and they do not contact each other; There is no non-gas filling material in the first interval and the second interval.

2. The calorimeter according to claim 1, characterized in that, The first wall of the jacket layer (102) is provided with at least two first holes (108) for penetrating the suspension wire (105). The calorimetric core (101) is pulled from at least two directions by a suspension wire (105) through a first hole (108) on the first wall of the jacket layer (102) and is suspended in the first space. At the same time, the jacket layer (102) is suspended in the second space of the shielding layer (103) under the suspension of the suspension wire (105), so that the calorimetric core (101), the jacket layer (102) and the shielding layer (103) do not come into contact with each other. One end of the suspension wire (105) is connected to the calorimeter core (101), and the other end is connected to the second wall of the shielding layer (103).

3. The calorimeter according to claim 1 or 2, characterized in that, The distance between the first interval and the second interval is equal.

4. The calorimeter according to any one of claims 1 to 3, characterized in that, The calorimeter core (101), the jacket layer (102), and the shielding layer (103) are nested together in an isocentric manner to achieve stable thermal isolation.

5. The calorimeter according to any one of claims 1 to 4, characterized in that, The calorimetric core (101) is pulled from three directions by suspension wires (105) through the first hole (108) on the first wall of the jacket layer (102) and is suspended in the first space; The three directions are on the same plane and the angles between them are equal, so that the calorimeter core (101) is stably fixed.

6. The calorimeter according to any one of claims 1 to 5, characterized in that, Gas exists within the first and / or second interval; Alternatively, the first and / or second intervals may be in a vacuum environment.

7. The calorimeter according to any one of claims 1 to 6, characterized in that, A miniature temperature sensor (106) is provided on the calorimeter core (101) for collecting the temperature of the calorimeter core (101).

8. The calorimeter according to any one of claims 1 to 7, characterized in that, It also includes a thermostatic mold (200) for providing a quasi-insulated environment, wherein the liquid temperature within the thermostatic mold (200) approaches a quasi-thermal state; When the calorimeter (100) is fixed at a specified depth below the liquid surface, after FLASH radiation is applied to the calorimeter (100), the temperature sensor (106) on the calorimeter core (101) outputs the temperature data of the calorimeter core (101).

9. The calorimeter according to any one of claims 1 to 8, characterized in that, The thermostatic phantom (200) is provided with an entrance window (204) for FLASH radiotherapy rays to enter, so that the ultra-high dose rate electron beam of FLASH radiotherapy rays is concentrated and irradiated through the entrance window (204) of the thermostatic phantom (200), thereby accurately irradiating the FLASH radiotherapy rays onto the calorimeter (100).

10. A calorimetric method for FLASH radiotherapy rays, characterized in that, The method includes: Adjust the liquid in the thermostatic mold (200) to approach a quasi-thermostatic state; The calorimeter (100) is fixed at a specified depth below the liquid surface of the thermostatic phantom (200); FLASH radiation is applied to the calorimeter (100); The temperature sensor (106) on the calorimeter core (101) outputs the temperature data of the calorimeter core (101) of the calorimeter (100); The calorimeter (100) includes a calorimeter core (101), a jacket layer (102), and a shielding layer (103). The calorimetric core (101) is an absorber of FLASH radiotherapy rays. The calorimetric core (101) is nested in the first space inside the jacket layer (102) in such a way that there is a first gap between it and the jacket layer (102) and they do not contact each other. The jacket layer (102) is nested within the second space of the shielding layer (103) in such a way that there is a second gap between it and the shielding layer (103) and they do not contact each other; There is no non-gas filling material in the first interval and the second interval; A miniature temperature sensor (106) is provided on the calorimeter core (101) for collecting the temperature of the calorimeter core (101).

Images