A method for measuring endogenous heat based on infrared skin temperature distribution field

Abstract

The present invention discloses an endogenous heat measurement method based on infrared skin temperature distribution field, comprising the following steps: S1. establishing a finite element model; S2. using the finite element analysis method to simulate the relationship between the position, temperature, and thermophysical parameters of the internal heat source and the body surface temperature distribution; S3. burying the developed constant temperature adjustable heat source in a uniform layered biological tissue, using a human body temperature measurement infrared thermal imager to capture the temperature of the tissue surface and each layer of tissue, and analyzing the distribution of the surface and internal temperature fields. The present invention simulates human skin through a biological simulation body, captures the skin temperature of the biological simulation body through a medical infrared thermal imager, and transmits data through the establishment of a data transmission system to form a temperature distribution infrared thermal map, which can provide a basis for diagnosing abnormal heat sources in the body. Finally, through simulation and analysis, it can provide a theoretical basis and guiding significance for the study of the formation mechanism of human body surface temperature distribution characteristics and the inverse problem of heat sources.

Description

Technical Field

[0001] The present invention belongs to the technical field of infrared temperature measurement, and in particular relates to an endogenous heat measurement method based on an infrared skin temperature distribution field. Background Art

[0002] Infrared thermal imaging tumor detection is harmless to the human body and is a promising method for breast cancer screening. However, current diagnosis relies solely on comparing the surface temperature of the tumor area with that of normal areas, and research on the relationship between infrared thermal imaging data and tumor metabolic heat production is lacking. In the past decade, the most common approach has been to develop simple heat transfer models based on the Pennes bioheat transfer equation to investigate the relationship between the surface temperature distribution of various tissues and abnormal internal heat sources.

[0003] When a lesion develops within a part of the human body, tissue metabolism changes first, predating changes in the body's morphological structure. When other clinical methods cannot detect such abnormalities, medical infrared thermal imaging cameras can detect these changes by capturing surface temperature information. Medical practice has proven that subcutaneous lesions manifest as abnormal skin temperature at the corresponding surface site. Medical infrared thermal imaging technology is simple, objective, accurate, non-invasive, and non-destructive. It is non-contact, radiation-free, and has no side effects, making it widely used in clinical practice. By using thermal images of the human body surface, which change regularly with abnormal heat sources within the body, the location of disease can be analyzed and diagnosed. Li Zili et al. used this method to study conditions such as spinal pain. Because infrared radiation has very low penetration through solids, simply capturing surface temperature distribution images cannot accurately capture the internal temperature field and internal heat sources, and the relationship between physiological processes and clinical manifestations remains unclear. Therefore, research on the relationship between parameters such as heat source depth, temperature, and thermophysical properties and surface temperature distribution is crucial to provide theoretical and experimental basis for thermal imaging technology for diagnosing abnormal heat sources within the body. The temperature field on the surface of an object depends entirely on the internal structure of the object, the thermophysical parameters of the material, and the heat exchange between the surface and the external environment. Summary of the Invention

[0004] The purpose of the present invention is to provide an endogenous heat measurement method based on infrared skin temperature distribution field to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for measuring endogenous heat based on infrared skin temperature distribution field, comprising the following steps:

[0006] S1. Establish finite element model;

[0007] S2. Use finite element analysis to simulate the relationship between the location, temperature, and thermophysical properties of internal heat sources and the body surface temperature distribution;

[0008] S3. The developed constant temperature adjustable heat source is buried in the uniform layered biological tissue. The temperature of the tissue surface and each layer is captured by a human body temperature measuring infrared thermal imager, and the distribution of the temperature field on the surface and inside the body is analyzed.

[0009] Preferably, the specific steps of S1 include:

[0010] S101. Use ANSYS software based on finite element analysis method;

[0011] S102. Establish a geometric model of the object, determine the material parameters and mesh the model, apply loads and boundary conditions, and solve the problem; establish a tissue heat transfer model for a cylinder with a radius of 8 cm and a length of 20 cm;

[0012] S103. Analyze the relationship between internal heat sources and surface temperature field distribution.

[0013] Preferably, the specific steps of the simulation in S2 are as follows:

[0014] S201 prepares the biosimulation body and places the heat source into the biosimulation body;

[0015] S202. Connect the heat source in the biosimulation body to the constant temperature heat source controller via a wire;

[0016] S203. Using a medical infrared thermal imager to capture the biological simulation body temperature;

[0017] S204 establishes a data transmission system to transmit the temperature data captured by the medical infrared thermal imager and transmits it to the computer to form an infrared thermal map of the temperature distribution;

[0018] S205. Simulate and analyze the temperature distribution infrared thermal image;

[0019] S206 changes the depth of the heat source in the biosimulation body and the temperature of the heat source and other environmental conditions, repeating S202-S205;

[0020] S207. Perform error analysis on the analysis results.

[0021] Preferably, the constant temperature heat source controller includes a constant temperature controller, the circuit composition of the constant temperature controller includes an electric heater circuit, a step-down circuit, a rectifier circuit, a voltage stabilizing circuit and a relay control circuit, the medical infrared thermal imager includes an infrared detector, the infrared detector includes a thermoelectric element, a current-voltage converter, a first amplifier and a second amplifier, a popcorn noise detector, an output circuit and a controller, the current-voltage converter is used to convert the current from the thermoelectric element into a voltage signal; the first amplifier is used to amplify the voltage signal received from the current-voltage converter with a first bandpass filter characteristic having a transmission band center at a first frequency; the second amplifier is used to amplify the voltage signal received from the current-voltage converter with a first bandpass filter characteristic having a transmission band center at a first frequency A second band-pass filter characteristic having a transmission band center at a second frequency higher than the first frequency is used to amplify the voltage signal received from the current-to-voltage converter; the popcorn noise detector is used to compare the output signal of the second amplifier with a threshold value to output a popcorn detection signal; the output circuit is used to compare the output signal of the first amplifier with a predetermined threshold value to output a detection signal; and the controller is used to control at least one of the current-to-voltage converter, the first amplifier, the output circuit, the second amplifier and the popcorn noise detector to prevent the output circuit from outputting the detection signal when receiving the popcorn detection signal from the popcorn noise detector.

[0022] Preferably, the data transmission system established in S204 includes an A / D conversion circuit, an uncooled focal plane detector, a signal amplifier, an FPGA infrared acquisition correction filter module and an ARM embedded module, and the ARM embedded module is electrically connected to the FPGA infrared acquisition correction filter module.

[0023] Preferably, the data transmission method for establishing a data transmission system comprises the following steps:

[0024] S301. After the captured temperature data is placed on the photosensitive surface of the uncooled focal plane detector, a sequence of analog image signals is output. The analog image signals are amplified by a signal amplifier and subjected to impedance conversion processing and then output through an A / D conversion circuit.

[0025] S302. The FPGA infrared acquisition correction and filtering module performs non-uniformity correction and filtering on the image signal output by the A / D conversion circuit to reduce noise, improve the signal-to-noise ratio, and compensate for dead spots. It then generates an interrupt signal to notify the ARM embedded module to read the image data.

[0026] S303. The ARM embedded module performs temperature calculation on the read image data, converts the grayscale data into temperature data, and displays it on a computer to form an infrared thermal map of temperature distribution.

[0027] Preferably, the heat source depth in S206 is 0.7-2.3 cm, the heat source temperature is 33-41° C., and the other environmental conditions include different blood perfusion rates and different metabolic heat production rates.

[0028] Preferably, the simulation and analysis in S205 are performed using a bioheat transfer equation based on tissue metabolism, blood circulation, and the external environment. The bioheat transfer equation is:

[0029]

[0030] Where ρ is the density of the biosimulation tissue, unit is kg / m 3 c is the specific heat capacity of the biomimetic tissue, in kJ / (kg·℃); k is the thermal conductivity of the biomimetic tissue, in W / (m·℃); w b is the blood perfusion rate, in kg / (s·m 3 );c b is the specific heat capacity of blood, unit is kJ / (kg·℃); T b is the arterial blood temperature, unit ℃); w b c b (T b -T) is the blood perfusion term; T is the temperature of the biosimulation tissue to be determined; Qm is the metabolic rate of the biosimulation tissue, unit is W / m 3 .

[0031] Preferably, in a steady state without considering blood circulation, the bioheat transfer equation can be simplified as follows:

[0032]

[0033] The heat exchange between the human body and the environment includes convection, radiation, and evaporation. The role of the first two heat exchange modes in the heat transfer process of homogeneous biosimulation tissue is considered. The boundary conditions are:

[0034]

[0035] Where h c is the convective heat transfer coefficient; T s and T a represent the surface temperature of the biosimulation tissue and the ambient temperature respectively; ε is the emissivity; σ is the Stefan-Boltzmann constant.

[0036] Preferably, the calculation formula for the body surface temperature difference in the error analysis of the analysis result in S207 is:

[0037]

[0038] Among them, TS iis a point on the surface temperature distribution of the biosimulator, TE i is a point on the human body surface temperature distribution, i = 1, 2, ..., 21;

[0039] According to the Bessel formula, the standard deviation is defined as:

[0040]

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention simulates human skin through a biosimulator, captures the skin temperature of the biosimulator through a medical infrared thermal imager, and transmits data through the establishment of a data transmission system to form an infrared thermal map of the temperature distribution, which can provide a basis for diagnosing abnormal heat sources in the body. Finally, through simulation and analysis, it can provide a theoretical basis and guiding significance for the research on the formation mechanism of human body surface temperature distribution characteristics and the inverse problem of heat source. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a flow chart of the present invention;

[0044] Figure 2 This is a flow chart of the specific steps of S2 in the present invention. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] See also Figure 1 ,The present invention provides a technical solution: a method for measuring endogenous heat based on infrared skin temperature distribution field, comprising the following steps: S1. establishing a finite element model;

[0047] S2. Use finite element analysis to simulate the relationship between the location, temperature, and thermophysical properties of internal heat sources and the body surface temperature distribution;

[0048] S3. The developed constant temperature adjustable heat source is buried in the uniform layered biological tissue. The temperature of the tissue surface and each layer is captured by a human body temperature measuring infrared thermal imager, and the distribution of the temperature field on the surface and inside the body is analyzed.

[0049] In this embodiment, preferably, the specific steps of S1 include:

[0050] S101. Use ANSYS software based on finite element analysis method;

[0051] S102. Establish a geometric model of the object, determine the material parameters and mesh the model, apply loads and boundary conditions, and solve the problem; establish a tissue heat transfer model for a cylinder with a radius of 8 cm and a length of 20 cm;

[0052] S103. Analyze the relationship between internal heat sources and surface temperature field distribution.

[0053] In this embodiment, preferably, the specific steps of the simulation in S2 are as follows:

[0054] S201 prepares the biosimulation body and places the heat source into the biosimulation body;

[0055] S202. Connect the heat source in the biosimulation body to the constant temperature heat source controller via a wire;

[0056] S203. Using a medical infrared thermal imager to capture the biological simulation body temperature;

[0057] S204 establishes a data transmission system to transmit the temperature data captured by the medical infrared thermal imager and transmits it to the computer to form an infrared thermal map of the temperature distribution;

[0058] S205. Simulate and analyze the temperature distribution infrared thermal image;

[0059] S206 changes the depth of the heat source in the biosimulation body and the temperature of the heat source and other environmental conditions, repeating S202-S205;

[0060] S207. Perform error analysis on the analysis results.

[0061] In this embodiment, preferably, the constant temperature heat source controller includes a constant temperature controller, the circuit composition of the constant temperature controller includes an electric heater circuit, a step-down circuit, a rectifier circuit, a voltage stabilizing circuit and a relay control circuit, the medical infrared thermal imager includes an infrared detector, the infrared detector includes a thermoelectric element, a current-voltage converter, a first amplifier and a second amplifier, a popcorn noise detector, an output circuit and a controller, the current-voltage converter is used to convert the current from the thermoelectric element into a voltage signal; the first amplifier is used to amplify the voltage signal received from the current-voltage converter with a first bandpass filter characteristic having a transmission band center at a first frequency; the second amplifier is used to for amplifying the voltage signal received from the current-to-voltage converter with a second band-pass filter characteristic having a transmission band centered at a second frequency higher than the first frequency; the popcorn noise detector for comparing the output signal of the second amplifier with a threshold value to output a popcorn detection signal; the output circuit for comparing the output signal of the first amplifier with a predetermined threshold value to output a detection signal; and the controller for controlling at least one of the current-to-voltage converter, the first amplifier, the output circuit, the second amplifier and the popcorn noise detector to prevent the output circuit from outputting the detection signal when receiving the popcorn detection signal from the popcorn noise detector.

[0062] In this embodiment, preferably, the data transmission system established in S204 includes an A / D conversion circuit, an uncooled focal plane detector, a signal amplifier, an FPGA infrared acquisition correction filter module and an ARM embedded module, and the ARM embedded module is electrically connected to the FPGA infrared acquisition correction filter module.

[0063] In this embodiment, preferably, the data transmission method for establishing the data transmission system includes the following steps:

[0064] S301. After the captured temperature data is placed on the photosensitive surface of the uncooled focal plane detector, a sequence of analog image signals is output. The analog image signals are amplified by a signal amplifier and subjected to impedance conversion processing and then output through an A / D conversion circuit.

[0065] S302. The FPGA infrared acquisition correction and filtering module performs non-uniformity correction and filtering on the image signal output by the A / D conversion circuit to reduce noise, improve the signal-to-noise ratio, and compensate for dead spots. It then generates an interrupt signal to notify the ARM embedded module to read the image data.

[0066] S303. The ARM embedded module performs temperature calculation on the read image data, converts the grayscale data into temperature data, and displays it on a computer to form an infrared thermal map of temperature distribution.

[0067] In this embodiment, preferably, the heat source depth in S206 is 0.7-2.3 cm, the heat source temperature is 33-41° C., and the other environmental conditions include different blood perfusion rates and different metabolic heat production rates.

[0068] In this embodiment, preferably, the simulation and analysis in S205 are performed using a bioheat transfer equation based on tissue metabolism, blood circulation, and the external environment. The bioheat transfer equation is:

[0069]

[0070] Where ρ is the density of the biosimulation tissue, unit is kg / m 3 c is the specific heat capacity of the biomimetic tissue, in kJ / (kg·℃); k is the thermal conductivity of the biomimetic tissue, in W / (m·℃); w b is the blood perfusion rate, in kg / (s·m 3 );c b is the specific heat capacity of blood, unit is kJ / (kg·℃); T b is the arterial blood temperature, unit ℃); w b c b (T b -T) is the blood perfusion term; T is the temperature of the biosimulation tissue to be determined; Qm is the metabolic rate of the biosimulation tissue, unit is W / m 3 .

[0071] In this embodiment, preferably, in a steady state without considering blood circulation, the bioheat transfer equation can be simplified as follows:

[0072]

[0073] The heat exchange between the human body and the environment includes convection, radiation, and evaporation. The role of the first two heat exchange modes in the heat transfer process of homogeneous biosimulation tissue is considered. The boundary conditions are:

[0074]

[0075] Where h c is the convective heat transfer coefficient; T s and T a represent the surface temperature of the biosimulation tissue and the ambient temperature respectively; ε is the emissivity; σ is the Stefan-Boltzmann constant.

[0076] In this embodiment, preferably, the calculation formula for the body surface temperature difference in the error analysis of the analysis result in S207 is:

[0077]

[0078] Among them, TS i is a point on the surface temperature distribution of the biosimulator, TE i is a point on the human body surface temperature distribution, i = 1, 2, ..., 21;

[0079] According to the Bessel formula, the standard deviation is defined as:

[0080]

[0081] The principles and advantages of the present invention are as follows: The present invention simulates human skin through a biological simulation body, captures the skin temperature of the biological simulation body through a medical infrared thermal imager, and transmits data through the establishment of a data transmission system to form an infrared thermal map of the temperature distribution, which can provide a basis for diagnosing abnormal heat sources in the body. Finally, through simulation and analysis, it can provide a theoretical basis and guiding significance for the study of the formation mechanism of human body surface temperature distribution characteristics and the inverse problem of heat sources.

[0082] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring endogenous heat based on infrared skin temperature distribution field, characterized in that: The following steps are involved: S1. Establish finite element model; S2. Use finite element analysis to simulate the relationship between the location, temperature, and thermophysical properties of internal heat sources and the body surface temperature distribution; S3. The developed constant-temperature adjustable heat source is embedded in a uniform biological simulated body. An infrared thermal imager is used to capture the temperatures of the tissue surface and various layers, and the distribution of the temperature field on the surface and inside the body is analyzed. The specific steps of S1 include: S101. Use ANSYS software based on finite element analysis method; S102. Establish a geometric model of the object, determine the material parameters and mesh the model, apply loads and boundary conditions, and solve the problem; establish a tissue heat transfer model for a cylinder with a radius of 8 cm and a length of 20 cm; S103. Analyze the relationship between internal heat sources and surface temperature distribution; The specific steps of the simulation in S2 are as follows: S201 prepares the biosimulation body and places the heat source into the biosimulation body; S202. Connect the heat source in the biosimulation body to the constant temperature heat source controller via a wire; S203. The biological simulation body temperature is captured by an infrared thermal imager; S204 establishes a data transmission system to transmit the temperature data captured by the infrared thermal imager and transmits it to the computer to form an infrared thermal map of the temperature distribution; S205. Simulate and analyze the temperature distribution infrared thermal image; The simulation and analysis in S205 are performed using a bioheat transfer equation based on tissue metabolism, blood circulation, and the external environment. The bioheat transfer equation is: ； Where ρ is the density of the biomimetic tissue, in kg / m3; c is the specific heat capacity of the biomimetic tissue, in kJ / (kg·℃); k is the thermal conductivity of the biomimetic tissue, in W / (m·℃); wb is the blood perfusion rate, in kg / (s·m3); cb is the specific heat capacity of blood, in kJ / (kg·℃); Tb is the arterial blood temperature, in °C); wbcb(Tb-T) is the blood perfusion term; T is the temperature of the biomimetic tissue to be determined; Qm is the metabolic rate of the biomimetic tissue, in W / m3; S206 changes the depth of the heat source in the biosimulation body and the temperature of the heat source and other environmental conditions, repeating S202-S205; The heat source depth in S206 is 0.7-2.3 cm, the heat source temperature is 33-41° C., and the other environmental conditions include different blood perfusion rates and different metabolic heat production rates; S207. Perform error analysis on the analysis results; The calculation formula for the body surface temperature difference in the error analysis of the analysis result in S207 is: ； Wherein, TSi is a point on the surface temperature distribution of the biosimulator, TEi is a point on the surface temperature distribution of the human body, i=1, 2,…, 21; According to the Bessel formula, the standard deviation is defined as: 。 2. The method for measuring endogenous heat based on infrared skin temperature distribution field according to claim 1, characterized in that: The constant temperature heat source controller includes a constant temperature controller, the circuit composition of the constant temperature controller includes an electric heater circuit, a step-down circuit, a rectifier circuit, a voltage stabilizing circuit and a relay control circuit. The infrared thermal imager includes an infrared detector, and the infrared detector includes a thermoelectric element, a current-voltage converter, a first amplifier and a second amplifier, a popcorn noise detector, an output circuit and a controller. The current-voltage converter is used to convert the current from the thermoelectric element into a voltage signal; the first amplifier is used to amplify the voltage signal received from the current-voltage converter with a first bandpass filter characteristic having a transmission frequency band center at a first frequency; the second amplifier is used to transmit the voltage signal received from the current-voltage converter with a first bandpass filter characteristic having a transmission frequency band center at a first frequency. a second band-pass filter characteristic having a frequency band centered at a second frequency higher than the first frequency to amplify the voltage signal received from the current-to-voltage converter; the popcorn noise detector is used to compare the output signal of the second amplifier with a threshold value to output a popcorn detection signal; the output circuit is used to compare the output signal of the first amplifier with a predetermined threshold value to output a detection signal; and the controller is used to control at least one of the current-to-voltage converter, the first amplifier, the output circuit, the second amplifier and the popcorn noise detector to prevent the output circuit from outputting the detection signal when receiving the popcorn detection signal from the popcorn noise detector.

3. The method for measuring endogenous heat based on infrared skin temperature distribution field according to claim 1, characterized in that: The data transmission system established in S204 includes an A / D conversion circuit, an uncooled focal plane detector, a signal amplifier, an FPGA infrared acquisition correction filter module and an ARM embedded module, and the ARM embedded module is electrically connected to the FPGA infrared acquisition correction filter module.

4. The method for measuring endogenous heat based on infrared skin temperature distribution field according to claim 1, characterized in that: The data transmission method for establishing a data transmission system comprises the following steps: S301. After the captured temperature data is placed on the photosensitive surface of the uncooled focal plane detector, a sequence of analog image signals is output. The analog image signals are amplified by a signal amplifier and subjected to impedance conversion processing and then output through an A / D conversion circuit. S302. The FPGA infrared acquisition correction and filtering module performs non-uniformity correction and filtering on the image signal output by the A / D conversion circuit to reduce noise, improve the signal-to-noise ratio, and compensate for dead spots. It then generates an interrupt signal to notify the ARM embedded module to read the image data. S303. The ARM embedded module performs temperature calculation on the read image data, converts the grayscale data into temperature data, and displays it on a computer to form an infrared thermal map of temperature distribution.

5. The method for measuring endogenous heat based on infrared skin temperature distribution field according to claim 1, characterized in that: In the steady state without considering blood circulation, the bioheat transfer equation can be simplified as: ； The heat exchange between the human body and the environment includes convection, radiation, and evaporation. The role of the first two heat exchange modes in the heat transfer process of homogeneous biosimulation tissue is considered. The boundary conditions are: ； Where hc is the convective heat transfer coefficient; Ts and Ta represent the surface temperature of the biosimulator tissue and the ambient temperature, respectively; ε is the emissivity; and σ is the Stefan-Boltzmann constant.

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