A constant-temperature high-precision radioactive micro-thermal device capable of rapid measurement

Abstract

The application belongs to the technical field of radionuclide measurement, and particularly relates to a constant-temperature high-precision radioactivity micro-heat device capable of rapid measurement, which comprises a high-precision constant-temperature unit and a rapid calorimetry unit. The high-precision constant-temperature unit comprises a shell, a constant-temperature water bath layer, an adiabatic layer and a temperature control layer, and is used for keeping a constant-temperature environment and reducing the influence of external environmental temperature fluctuation. The rapid calorimetry unit is located in the high-precision constant-temperature unit and comprises a calorimetry chamber and a calorimetry cup group and a thermocouple group arranged in the calorimetry chamber. The application adopts a double-cup type isothermal heat flow design to eliminate the fluctuation of parasitic potential, the refrigeration device can controllably adjust the cold end temperature, the adiabatic layer and the temperature control layer are arranged alternately to effectively improve the temperature control precision, the unique heat conduction insulation design between the calorimetry cup groups and the high-thermal-conductivity liquid strategy greatly reduce the heat balance time. The application has the characteristics of high-precision constant-temperature and rapid calorimetry, and is very suitable for precise measurement of medical isotope activity.

Description

Technical Field

[0001] The invention belongs to the technical field of radionuclide measurement, and in particular relates to a constant-temperature high-precision microcalorimeter capable of rapidly measuring medical radioactivity. Background Art

[0002] Currently, medical isotopes, as the material foundation of nuclear medicine diagnosis and treatment, are a key focus of research in the medical application of nuclear technology. During treatment, isotopes are typically introduced directly into the patient's body, where their radioactivity kills diseased tissue to achieve therapeutic efficacy. Therefore, accurate dosage is crucial for ensuring patient safety and therapeutic efficacy, and precise control of radioactivity is crucial during use. Calorimetry is a non-destructive measurement method with advantages such as no sampling or packaging required, no consideration of radionuclide self-absorption, energy-independent detection efficiency, and no secondary waste. It is suitable for measuring the radioactivity of low-energy α and β nuclides, particularly medical isotopes, within a volume. Due to their low activity, α and β nuclides, particularly medical isotopes, are often measured using microcalorimeters. Since the 1970s, specialized calorimeters have been developed for their respective applications, but calorimeters used for medical isotope measurement are rare.

[0003] A conventional calorimeter (application number: CN202211010536.2) is used to measure the content of radionuclides in a sample. Its structural assembly includes a vacuum chamber, a constant temperature body, a calorimetric container, a power measurement element, and a thermoelectric element. However, due to the short half-lives of commonly used medical isotopes, the vacuum chamber involved in this device is inconvenient to operate. Establishing a vacuum requires time, which prolongs the thermal equilibrium time and may affect the accurate measurement of the actual radioactivity of the medical isotope. Furthermore, the sample container and reference container of this device are mounted on the same thermally conductive base, resulting in heat conduction and radiation between the calorimetric cups, which in turn reduces the thermoelectric potential value converted by the thermopile.

[0004] A low-energy beta radioactivity measurement device (application number: CN201711379669.6) includes a calorimeter, a controller, measuring instruments, and a computer. The device utilizes a highly integrated computer, greatly simplifying operation and improving measurement accuracy. The thermal power measurement range is 160-1650 mW. However, the calorific value of commonly used medical isotopes is mostly in the microwatt range, so the lower limit of this calorimetric measurement device is relatively high, making it unsuitable for measuring the radioactivity of medical isotopes. Furthermore, the device uses copper-constantan thermocouples as thermoelectric elements. Compared to semiconductor thermocouples, these thermocouples have a slower response speed and are easily affected by the material's inherent properties. They are generally suitable for low-temperature environments.

[0005] A radioactivity measurement device (application number: CN202111589507.1) is provided with a sample chamber and a reference chamber in a closed metal box, wherein the bottom ends of the sample chamber and the reference chamber are sealed, and the top openings are sealed by metal covers. Both the sample chamber and the reference chamber are provided with heating devices and temperature sensors. Although passive measurement can be used when higher measurement accuracy is required, the lower limit of measurement of the device is relatively high when measuring the activity of medical radionuclides. The thermostatic unit of the entire device consists of only a metal box and a constant temperature water bath, with a temperature control accuracy of 10 -2 ℃, which will make the constant temperature unit of the calorimeter susceptible to the influence of external ambient temperature fluctuations, thereby reducing the measurement accuracy of the measurement system.

[0006] A radioactivity microcalorimetry device and method (application number: CN202211136074.9) provides a device and method for measuring radioactivity microcalorimetry. The device and method mainly determine the sample heat by identifying the sample cup and the reference cup, and using the double-cup compensation principle. Compared with directly measuring the sample heat, this method can reduce the impact of the environment. However, the calorimetric cup group is placed in the same constant temperature body, which increases the heat conduction and heat radiation between the two calorimetric cups, which will directly lead to an increase in the uncertainty of the measurement results.

[0007] In summary, current traditional calorimeters generally have low stability and long measurement time, and can generally only measure the radioactive activity of nuclides at the 0.1mW level. These factors significantly restrict the application of microcalorimeters. Summary of the Invention

[0008] The object of the present invention is to provide a constant temperature, high-precision radioactive microcalorimeter capable of rapid measurement, so as to solve the unresolved problems raised in the above-mentioned background technology.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] The application discloses a high-precision constant-temperature radioactive micro-thermal device capable of rapid measurement, which comprises a high-precision constant-temperature unit and a rapid calorimetric unit. The high-precision constant-temperature unit comprises an outer shell, an adiabatic layer, a constant-temperature water bath layer and a temperature control layer, wherein the adiabatic layer, the constant-temperature water bath layer and the temperature control layer are all sleeved in the stainless steel outer shell. The high-precision constant-temperature unit is used for reducing the influence of external environmental temperature fluctuation and maintaining a constant-temperature environment in the high-precision constant-temperature unit. The rapid calorimetric unit is located in the high-precision constant-temperature unit and comprises a calorimetric chamber and a calorimetric cup group arranged in the calorimetric chamber, a thermocouple group arranged on the outer wall and the bottom of the calorimetric cup and the like, which are used for detecting weak signals of radionuclide decay heat. The calorimetric chamber is made of aluminum, calorimetric cup supports for fixing the calorimetric cup group are arranged on the inner wall of the calorimetric chamber, the two supports are symmetrically distributed, a calorimetric cup baffle is arranged on the calorimetric cup support and is located on the outside of the calorimetric cup group and is used for fixing the calorimetric cup. The thermocouple group is a flat plate type thermocouple group and is fixed between the calorimetric cup group and the calorimetric cup baffle and the calorimetric cup support. The calorimetric cup group is composed of two calorimetric cups and a sample cup assembled in the calorimetric cup, one of the two calorimetric cups is used as a measuring cup and a sample cup is arranged in the measuring cup and a sample to be measured is arranged in the sample cup; the other calorimetric cup is used as a reference cup and a sample comparison bed body is arranged in the reference cup. A protrusion is arranged on the side wall of the calorimetric cup and is used for fixing and mounting the thermocouple. High-thermal-conductivity liquid is added in the calorimetric cup and is used for increasing the heat transfer area between the sample cup and the calorimetric cup and greatly reducing the measurement time. The constant-temperature water bath layer, the temperature control layer, the calorimetric cup group, the calorimetric chamber and the thermocouple group are connected with an external controller and finally connected with a computer.

[0011] The adiabatic layer comprises a first adiabatic layer, a second adiabatic layer, a third adiabatic layer and a fourth adiabatic layer. The first adiabatic layer is fixedly arranged on the inner wall of the stainless steel outer shell. The constant-temperature water bath layer is located between the first adiabatic layer and the second adiabatic layer, a water inlet and a water outlet are arranged on the top of the constant-temperature water bath layer and are connected with a refrigerating device, and the refrigerating device is used for cooling circulating water.

[0012] The temperature control layer comprises a first temperature control layer and a second temperature control layer, the first temperature control layer is located between the second adiabatic layer and the third adiabatic layer, and the second temperature control layer is located between the third adiabatic layer and the fourth adiabatic layer.

[0013] Heating wires are arranged at the upper end and the lower end of the calorimetric cup, the heating wires are wound on the calorimetric cup and are used for electrically heating the calorimetric cup, and the thermal performance parameters of the measuring cup and the reference cup are the same.

[0014] The sample cup is made of aluminum, the outer wall of the sample cup is subjected to sand blasting roughening treatment for improving the thermal emissivity, a cup cover made of polytetrafluoroethylene with low thermal conductivity is used for reducing heat loss of the sample, and the diameter of the sample cup is smaller than that of the calorimetric cup.

[0015] Four thermopiles are placed at a raised position in the middle of the outer wall of the calorimetric cup, and one thermopile is placed at the bottom. The thermopiles are made of customized semiconductor thermocouples of special size and number, including five thermopiles (5) for the measuring cup and five thermopiles (10) for the reference cup, with a total number of thermocouple pairs exceeding 500, and the electrical performance parameters thereof being the same.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0017] (1) Through reasonable material selection, optimized parameters and manufacturing process, under the premise of ensuring the sensitivity of characteristic signals, a partitioned flat-plate semiconductor thermocouple thermopile was developed, the spatial layout of the thermopile was optimized, and the measurement of weak signals was realized with high signal sensitivity; secondly, the calorimetric cup group was symmetrically fixed to the side wall (cold end) of the calorimetric chamber shell, with the bottom suspended in the air and separated by insulation material in the middle, blocking the heat flow path between the two calorimetric cups and avoiding thermal crosstalk between the calorimetric cup groups; thirdly, a dual temperature control structure with alternating insulation layers and temperature control layers was adopted, combined with a constant temperature water bath, which effectively improved the temperature stability and measurement accuracy of the calorimetric system. At present, the temperature control change of the calorimetric device has been reduced to 10 -5 ℃, the measured thermoelectric potential can change no more than 1.5μW within 4h, and the lower limit of measurement can reach below 1μW;

[0018] (2) A high thermal conductivity liquid is added between the calorimetric cup and the side wall of the sample cup, which increases the heat transfer area of ​​the sample to be measured and greatly reduces the measurement time. Secondly, a constant temperature water bath layer is used, and the cold end temperature can be adjusted at will, so that the temperature of the calorimetric unit is basically consistent with the ambient temperature, reducing heat exchange with the outside world and thus reducing the thermal equilibrium time, thereby reducing the measurement time. This meets the strict measurement time requirements of medical isotope activity measurements. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0020] Figure 2 This is a schematic structural diagram of a calorimetric cup according to an embodiment of the present invention;

[0021] Figure 3 is a graph showing changes in thermoelectric potential of a measuring cup over time in an embodiment of the present invention;

[0022] Figure 4 This is a graph showing the repeatability of the measuring cup at 100 μW in an embodiment of the present invention;

[0023] Figure 5 1 is a resistance value variation curve diagram during PID control in an embodiment of the present invention.

[0024] Serial numbers and names of the accompanying drawings: high-precision constant temperature unit 1, calorimetric chamber 2, calorimetric cup bracket 3, measuring cup 4, measuring cup thermopile 5, sample cup 6, heating wire 7, high thermal conductivity liquid 8, reference cup 9, reference cup thermopile 10, calorimetric cup baffle 11. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0027] like Figure 1-2 As shown, the present invention discloses a rapid, constant-temperature, high-precision radioactive microcalorimetry device capable of rapid measurement, comprising a rapid calorimetry unit and a high-precision constant-temperature unit. The high-precision constant-temperature unit 1 comprises an outer shell, an insulation layer, a constant-temperature water bath layer, and a temperature control layer. The high-precision constant-temperature unit 1 is used to reduce the impact of external temperature fluctuations and maintain a constant temperature environment within the high-precision constant-temperature unit 1. The rapid calorimetry unit, located within the high-precision constant-temperature unit 1, comprises a calorimetry chamber 2, a calorimetry cup assembly disposed within the calorimetry chamber, and a thermopile assembly on the outer wall and bottom of the calorimetry cup. It is used to detect weak signals from radionuclide decay heat. The constant-temperature water bath layer, temperature control layer, calorimetry cup assembly, calorimetry chamber, and thermopile assembly are all connected to an external controller. The controller is located on one side of the outer shell and is connected to the heating element, temperature measuring element, heating element, and power measurement element. It receives measurement signals and controls the heating wire to electrically heat the calorimetry cup. A computer, acting as a processing terminal, processes and stores data, issues instructions to the controller to control the measurement of the measuring element, and receives measurement data for subsequent data processing.

[0028] The outer shell is made of stainless steel, with the insulation layer, constant temperature water bath layer, and temperature control layer all located within it. The insulation layer is made of low thermal conductivity materials, such as polystyrene foam and polyurethane foot pads, to reduce the impact of ambient temperature fluctuations. It includes a first insulation layer, a second insulation layer, a third insulation layer, and a fourth insulation layer. The first insulation layer is fixed to the inner wall of the outer shell; the constant temperature water bath layer is located between the first and second insulation layers. The top of the constant temperature water bath layer is equipped with a water inlet and outlet, connected to the refrigeration device used to cool the circulating water. The temperature control layer includes a first temperature control layer and a second temperature control layer. The first temperature control layer is located between the second and third insulation layers, and the second temperature control layer is located between the third and fourth insulation layers. This improves the temperature and measurement stability of the calorimetric system.

[0029] Calorimetric chamber 2 is designed to maintain a constant temperature, providing a stable temperature environment. It is made of aluminum. Aluminum has a high thermal conductivity and weighs more than 15 kg, which facilitates stable temperature control within the chamber, achieving low thermal resistance and high specific heat capacity.

[0030] A calorimetric cup holder 3 for fixing the calorimetric cup group is fixedly provided on both sides of the calorimetric chamber 2. The calorimetric cup holder 3 can significantly reduce heat conduction between the calorimetric cup groups. A calorimetric cup baffle 11 is provided on the calorimetric cup holder 3 on the outside of the calorimetric cup group. The calorimetric cup baffle 11 is used to fix and separate the calorimetric cup group, effectively reducing heat convection and heat radiation between the calorimetric cup groups.

[0031] The calorimetric cup set consists of two calorimetric cups and a sample cup mounted inside each calorimetric cup. One calorimetric cup serves as the measuring cup 4, with the sample to be measured placed in the sample cup 6 inside. The other calorimetric cup serves as the reference cup 9, containing a sample comparison bed. The dual-cup isothermal heat flow design eliminates the effects of parasitic potentials and minor temperature fluctuations.

[0032] Heating wires 7 are provided at both ends of the calorimetric cup. The heating wires 7 are wound around the calorimetric cup to electrically heat the calorimetric cup. The thermal performance parameters of the measuring cup 4 and the reference cup 9 are the same. A protrusion for fixing the thermopile is provided on the side wall of the calorimetric cup. The protruding surface of the side wall is the same size as the thermopile 4, which is easier to conduct heat. Highly thermally conductive liquid 8 is added to both calorimetric cups to improve the heat conduction efficiency between the sample cup 6 and the calorimetric cup, greatly reducing the thermal equilibrium time.

[0033] The sample cup 6 is made of aluminum, and the outer wall of the sample cup 6 is sandblasted and roughened to increase the thermal emissivity of the sample cup 6; the cup wall diameter of the sample cup 6 is slightly smaller than the cup wall diameter of the calorimetric cup, which facilitates the assembly of the sample cup 6 in the calorimetric cup; the cup cover of the sample cup 6 is made of polytetrafluoroethylene material with low thermal conductivity to reduce heat loss of the sample.

[0034] The thermopile is a custom-made flat-plate thermopile composed of P-type Bi2Te3-Sb2Te3 and N-type Bi2Te3-Bi2Se3 thermocouples connected in series, with over 500 pairs. The thermopile includes five thermopiles each for the measuring cup (5) and the reference cup (10), each with identical electrical performance parameters. Four thermopiles are placed in a raised position in the center of the outer wall of the calorimetric cup, and one is placed at the bottom. The five thermopiles are connected in series with leads extending from the outer wall. The hot ends of the thermopiles are connected to the outer wall of the calorimetric cup, and the cold ends of the thermopiles are connected to the cup baffle (11). Thermally conductive silicone grease is used to bond the thermopiles to the cup wall and baffle (11) to achieve effective heat conduction. During specific use, a nanovoltmeter is used to measure the thermoelectric potential of the calorimetric cup through an intelligent controller, and a high-stability programmable DC regulated power supply is used to measure the current and voltage of the heating resistor through an intelligent controller. This can respond quickly to obtain its thermal power, effectively reduce the electric heating power noise, and improve the measurement power accuracy and operational stability.

[0035] Combined with attachment Figure 3-5 It can be seen that the present invention has the following characteristics:

[0036] 1) Effectively reduces the impact of external ambient temperature fluctuations;

[0037] 2) Effectively reduces the effects of heat conduction, heat convection and heat radiation between calorimetric cups;

[0038] 3) Improved heat conduction efficiency and greatly reduced thermal equilibrium time;

[0039] 4) Improved the measurement accuracy and operational stability of the calorimetric system;

[0040] 5) Has higher signal sensitivity.

Claims

1. A constant temperature high precision radioactive microcalorimeter capable of rapid measurement, characterized in that: include: High-precision constant temperature unit (1): the high-precision constant temperature unit (1) comprises an outer shell, a heat-insulating layer, a constant temperature water bath layer and a temperature control layer, wherein the heat-insulating layer, the constant temperature water bath layer and the temperature control layer are all sheathed in the stainless steel outer shell; the high-precision constant temperature unit (1) is used to reduce the influence of external environmental temperature fluctuations and maintain a constant temperature environment inside the high-precision constant temperature unit (1); and Rapid calorimetry unit: The rapid calorimetry unit is located inside the high-precision constant temperature unit (1), and includes a calorimetry chamber (2) and a calorimetry cup group arranged inside the calorimetry chamber, a thermopile group on the outer wall and bottom of the calorimetry cup, etc. It is used to detect weak signals of radionuclide decay heat; wherein The calorimetric chamber (2) is made of aluminum. Calorimetric cup brackets (3) for fixing the calorimetric cup group are respectively provided on both sides of the inner wall of the calorimetric chamber (2). The two brackets are symmetrically distributed. A calorimetric cup baffle (11) is provided on the calorimetric cup bracket (3). The baffle is located outside the calorimetric cup group and is used to fix the calorimetric cup. The thermopile group (5) is a flat-plate thermopile group, which is fixed between the calorimetric cup group, the calorimetric cup baffle (11) and the calorimetric cup bracket (3). The calorimetric cup set consists of two calorimetric cups and a sample cup assembled in the calorimetric cup, wherein one calorimetric cup serves as a measuring cup (4), and a sample to be measured is placed in a sample cup (6) inside the calorimetric cup; the other calorimetric cup serves as a reference cup (9), and a sample comparison bed is arranged inside the reference cup; a protrusion is arranged on the side wall of the calorimetric cup for fixing and installing the thermopile; a high thermal conductivity liquid (8) is added to the calorimetric cup to increase the heat transfer area between the sample cup and the calorimetric cup, thereby greatly reducing the measurement time; The constant temperature water bath layer, the temperature control layer, the calorimetric cup group, the calorimetric chamber and the thermopile group are all connected to an external controller and finally connected to a computer.

2. A constant temperature, high-precision radioactive microcalorimeter capable of rapid measurement according to claim 1, characterized in that: The insulation layer includes a first insulation layer, a second insulation layer, a third insulation layer and a fourth insulation layer. The first insulation layer is fixedly arranged on the inner wall of the stainless steel shell; the constant temperature water bath layer is located between the first insulation layer and the second insulation layer. A water inlet and a water outlet are arranged on the top of the constant temperature water bath layer, which are connected to a refrigeration device. The refrigeration device is used to cool the circulating water.

3. The constant temperature, high-precision radioactive microcalorimeter capable of rapid measurement according to claim 1, characterized in that: The temperature control layer includes a first temperature control layer and a second temperature control layer. The first temperature control layer is located between the second heat insulation layer and the third heat insulation layer, and the second temperature control layer is located between the third heat insulation layer and the fourth heat insulation layer.

4. The rapid measurement, constant temperature, high-precision radioactive microcalorimeter according to claim 1, characterized in that: The upper and lower ends of the calorimetric cup are both provided with heating wires (7), which are wound around the calorimetric cup to electrically heat the calorimetric cup, and the thermal performance parameters of the measuring cup (4) and the reference cup (9) are the same.

5. The constant temperature, high-precision radioactive microcalorimeter capable of rapid measurement according to claim 1, characterized in that: The sample cup (6) is made of aluminum, and the outer wall is sandblasted and roughened to increase its thermal emissivity. The cup cover is made of polytetrafluoroethylene with low thermal conductivity to reduce heat loss of the sample. The diameter of the sample cup (6) is smaller than the diameter of the calorimetric cup.

6. The constant temperature, high-precision radioactive microcalorimeter capable of rapid measurement according to claim 1, characterized in that: Four thermopiles are placed at a raised position in the middle of the outer wall of the calorimetric cup, and one thermopiles is placed at the bottom; the thermopiles are made of semiconductor thermocouples of a customized special size and number, including five thermopiles (5) for the measuring cup and five thermopiles (10) for the reference cup, with a total number of thermocouple pairs exceeding 500, and the electrical performance parameters thereof being the same.

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