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CN-121978733-A - Quasi-adiabatic water system calorimetric measurement system and method for FLASH radiotherapy rays

CN121978733ACN 121978733 ACN121978733 ACN 121978733ACN-121978733-A

Abstract

A quasi-adiabatic water system calorimeter measurement system of FLASH radiotherapy rays and a method thereof are provided, wherein the system comprises a calorimeter and a constant temperature die body. The calorimeter comprises a calorimeter core, a jacket layer and a shielding layer, wherein the calorimeter core, the jacket layer and the shielding layer are arranged in a mutually non-contact nesting mode through a tensioning mechanism, and a gas or vacuum environment is arranged among the calorimeter core, the jacket layer and the shielding layer. The constant temperature die body forms a quasi-steady state constant temperature water die body approaching to constant temperature in the box body based on the constant temperature control unit so as to provide a quasi-heat insulation environment for the calorimeter. Under the condition that the calorimeter is arranged in the quasi-steady-state constant-temperature water mould body, when the FLASH radiotherapy rays irradiate the calorimeter through the box body, the probe temperature sensor collects temperature change signals of the calorimeter core and transmits the temperature change signals to the terminal. The system provides a quasi-adiabatic environment for the calorimeter, has quicker response and smaller disturbance compared with the traditional electric heating mode, and can accurately capture the tiny temperature rise signal generated by FLASH radiotherapy.

Inventors

  • HUANG JI
  • WANG KUN
  • ZHANG GUOLONG

Assignees

  • 中国计量科学研究院

Dates

Publication Date
20260505
Application Date
20260316

Claims (10)

  1. 1. A quasi-adiabatic water system calorimetric measurement system for FLASH radiation therapy rays, the system comprising: The calorimeter (400) comprises a calorimetric core (410), a jacket layer (420) and a shielding layer (430), wherein the calorimetric core (410), the jacket layer (420) and the shielding layer (430) are arranged in a mutually non-contact nested manner through a tensioning mechanism (450), and a gas or vacuum environment is arranged among the calorimetric core (410), the jacket layer (420) and the shielding layer (430); a constant temperature die body (100) which forms a quasi-steady-state constant temperature water die body approaching to constant temperature in the box body (150) based on a constant temperature control unit (300) so as to provide a quasi-heat insulation environment for the calorimeter (400); Under the condition that the calorimeter (400) is arranged in a quasi-steady-state constant-temperature water model body of the constant-temperature model body (100), when the FLASH radiotherapy rays irradiate the calorimeter (400) through the box body (150), a probe temperature sensor (460) collects temperature change signals of the calorimeter core (410) and transmits the temperature change signals to the terminal (500).
  2. 2. The system of claim 1, wherein the calorimetric core (410), the jacket layer (420), and the shielding layer (430) are disposed in an isocentric nested manner by a tensioning mechanism (450); Wherein a first annular gap (411) exists between the calorimetric core (410) and the jacket layer (420), and a second annular gap (421) exists between the jacket layer (420) and the shielding layer (430).
  3. 3. The system of claim 1 or 2, wherein the tensioning mechanism (450) within the calorimeter (400) tensions the calorimeter core (410) from at least two orientations by means of a pull wire in a manner that it passes through a through hole of the jacket layer (420) wall, causing the calorimeter core (410) to form a suspended structure with the jacket layer (420).
  4. 4. A system according to any one of claims 1-3, wherein the tensioning mechanism (450) in the calorimeter (400) tensions the calorimeter core (410) from three positions through the traction wire in a manner of passing through the through hole of the wall of the jacket layer (420), so that the calorimeter core (410) and the jacket layer (420) form a suspended structure, wherein the included angle between the three positions is equally divided, so as to realize the force balance of the calorimeter core (410).
  5. 5. The system according to any one of claims 1 to 4, wherein the constant temperature die body (100) comprises a lifting mechanism (200) arranged in the box body (150), a clamping mechanism and a constant temperature control unit (300) for circularly conveying the quasi-steady state constant temperature water die body to the box body (150); The lifting mechanism (200) moves the calorimeter (400) to an equivalent water depth position in the quasi-steady-state constant-temperature water model body in a manner of controlling the lifting of a clamping mechanism for clamping the calorimeter (400); The constant temperature control unit (300) circularly conveys the quasi-steady-state constant temperature water mold body with stable temperature to the box body (150) through the temperature control pipeline (350) so that the quasi-steady-state constant temperature water mold body in the box body (150) provides a quasi-heat insulation environment for the calorimeter (400).
  6. 6. The system according to any one of claims 1 to 5, characterized in that the box (150) is provided with at least one entrance interface (170) in a vertical and/or horizontal direction; the incidence interface (170) is used for intensively irradiating the calorimeter (400) by FLASH radiotherapy rays in a horizontal irradiation mode and/or a vertical irradiation mode.
  7. 7. The system according to any one of claims 1 to 6, characterized in that a stirring unit (360) is arranged in the box (150) of the constant temperature die body (100); the stirring unit (360) stirs the quasi-steady state constant temperature water phantom to provide a quasi-adiabatic environment for the calorimeter (400).
  8. 8. The system according to any one of claims 1 to 7, wherein the clamping mechanism in the constant temperature die body (100) clamps the calorimeter (400) in a three-dimensional rotation manner, so that the calorimeter (400) receives horizontal irradiation and/or vertical irradiation of FLASH radiotherapy rays.
  9. 9. The system according to any one of claims 1 to 8, wherein the calorimeter (400) is integrally encapsulated in a waterproof layer (440) such that the calorimeter (400) can be completely immersed in the constant temperature die body (100) for measurement; Wherein the shape of the waterproof layer (440) is adapted to the contour of the calorimeter (400), and the material of the waterproof layer (440) comprises a polystyrene solid water material.
  10. 10. The method for measuring the calorimetric quantity of the quasi-adiabatic water system of the FLASH radiotherapy rays is characterized by comprising the following steps of: The constant temperature control unit (300) injects a quasi-steady-state constant temperature water mold body which approaches to constant temperature into the box body (150) of the constant temperature mold body (100) so as to provide a quasi-heat insulation environment for the calorimeter (400); A lifting mechanism (200) moves the calorimeter (400) to an equivalent water depth position in a quasi-steady-state constant-temperature water model body in a manner of controlling the lifting of the clamping mechanism for clamping the calorimeter (400); Under the condition that the calorimeter (400) is arranged in a quasi-steady-state constant-temperature water model body of the constant-temperature model body (100), when FLASH radiotherapy rays irradiate the calorimeter (400) through the box body (150), a probe temperature sensor (460) collects a temperature change signal of a calorimeter core (410) and transmits the temperature change signal to a terminal (500); The calorimeter (400) comprises a calorimetric core (410), a jacket layer (420) and a shielding layer (430), wherein the calorimetric core (410), the jacket layer (420) and the shielding layer (430) are arranged in a mutually non-contact nesting mode through a tensioning mechanism (450), and a gas or vacuum environment is arranged among the calorimetric core (410), the jacket layer (420) and the shielding layer (430).

Description

Quasi-adiabatic water system calorimetric measurement system and method for FLASH radiotherapy rays Technical Field The invention relates to the technical field of radiotherapy dose measurement, in particular to a quasi-adiabatic water system calorimetric measurement system and method for FLASH radiotherapy rays. Background Calorimetric is an absolute physical method for measuring the absorbed dose of ionizing radiation. The principle is that the physical process of absorbing radiant energy and mainly converting the radiant energy into heat energy by using a substance is utilized, and the temperature change of the irradiated medium is detected by a high-sensitivity instrument, so that the absolute absorption dose deposited in the medium is directly determined. Since its measurement process does not depend on the calibration of other dosimeters, calorimeter is the baseline method in radiation dose measurement, and calorimeter is a specialized instrument for performing such measurements. For example, CN216848160U relates to a graphite calorimeter suitable for measuring multi-energy electron beam absorption dose, comprising a graphite absorber set, a heat insulation layer, a graphite shell, a temperature control system and an aluminum shell, wherein the graphite absorber set comprises a graphite absorber layer and a foaming polystyrene filling layer, a thermistor is embedded in the graphite absorber layer, a hole groove is formed in the center of the heat insulation layer, the shape and the size of the hole groove are the same as those of the graphite absorber set, the graphite absorber set is suitable for being loaded, the combination of the graphite absorber sets comprising different thickness graphite absorber layers is selected according to the difference of the measured accelerator nominal energy to be loaded in the hole groove for measurement, the heat insulation layer is respectively wrapped in the graphite absorber set and the graphite shell, a heating element of the temperature control system is arranged in the graphite shell and connected with an aviation plug on the aluminum shell through a wire and then connected with an external temperature control meter, and a temperature measuring element of the temperature control system is arranged at the graphite shell and connected with the external temperature control meter. The measurement process of the calorimeter is that the calorimeter is placed in a radiation field, the temperature change is monitored by a high-sensitivity temperature sensor, a temperature drift baseline before and after irradiation is obtained, the change relation of the temperature with time is recorded and fitted, and finally the radiation dose is calculated. However, the conventional absolute calorimetric measurement system generally has the problems of large volume, long heat balance period and the like. Especially when facing the ultra-high pulse dose rate of FLASH radiotherapy rays, the traditional system is limited by transient heat conduction effect and the limitation of a conventional linear data fitting method, the measurement uncertainty is obviously increased, and the requirements of clinic on high-efficiency, flexible and high-precision transient measurement are difficult to be directly met. Compared with the traditional conventional radiotherapy (the single pulse dose is about 0.3 mGy, and the treatment process lasts for a few minutes), the FLASH radiotherapy rays can deliver the ultra-high dose of the single pulse of 1-10 Gy magnitude in a time window of subsecond or microsecond level, and the total irradiation time is greatly shortened to the millisecond-hundred millisecond magnitude. Such extremely short irradiation not only significantly shortens the treatment cycle, reduces positioning errors caused by organ movement during treatment, but also exhibits the potential to reduce medical costs and improve patient tolerance. However, at ultra-high pulse dose rates (UHDR) of FLASH radiotherapy radiation, conventional active dosimeters (e.g., ionization chambers) can produce severe ion recombination leading to loss of collection efficiency, whereas conventional passive dosimeters (e.g., alanine, film, pyroelectric) lack real-time and clinical applicability despite stable dose rate dependence. In addition, although the traditional absolute calorimetric measurement system is not affected by high dose rate, the traditional absolute calorimetric measurement system generally has the problems of huge volume, long heat balance time, complex operation and the like, and cannot be used for flexible and efficient transient measurement under UHDR conditions. Therefore, there is an urgent need to develop a quasi-adiabatic water system calorimetric system. The system needs to have absolute property, traceability, high sensitivity and good clinical applicability, so that the dose standard establishment, clinical quality control and research verification of FLASH radiotherapy rays are ef