What is infrared light? In 1800 AD, it was discovered that the Mitsubishi mirror had a light splitting effect and could distinguish between seven different wavelengths of visible light including white, red, orange, blue, yellow, green and black. At this time, it was also discovered that there is an abnormally high concentration of heat energy in the area above the red light, named infrared light. Physically any object with a temperature greater than absolute zero (-273.1 5°C) radiates energy outward, and in spectral analysis infrared light (lines) is divided into near-infrared (0.75-3 um), mid-infrared (3-6 um) and far-infrared (6-15 um) according to wavelength. The wavelength of electromagnetic waves radiated by living organisms is mainly in the far infrared region, so called far infrared (we are accustomed to collectively referred to as infrared), the wavelength range of the far infrared is 4 to 14µm, with a peak of 9.34µm. Therefore, we can easily detect the infrared radiation of living organisms using infrared detectors with a wavelength of 8 to 14µm. In 1800, the British astronomer Wilhelm von Wittig, who was a member of the British Academy of Astronomy, was a member of the British Academy of Science. In 1800, the British astronomer Will. Hershey discovered infrared thermography, the technology was soon used for monitoring important geographical areas such as consulates, borders, banks, factories or prisons. When there is an abnormal thermostat such as human or animal in the monitoring area, it can be detected by the instrument even in the darkness of the night. Humans and most animals are thermostats, and the automatic body temperature regulation mechanism keeps a physiological balance between heat production and heat dissipation. Heat production in the human body comes from the metabolism of various organs in the body and is mainly related to various biological reactions, muscle activity, hormones and sympathetic nerve activity. There are four forms of heat dissipation, of which radiation accounts for 44% of the total, conduction and convection accounts for 31%, and evaporation accounts for 21%. When heat dissipation and blood supply is different cloth will appear certain skin temperature differences, skin friction, underwear extrusion, environmental temperature, air flow, human mental state or sweat gland secretion activity will also affect the local temperature. As early as two thousand years ago, there are records of body skin temperature used to diagnose diseases, the ancient Greek doctor Hippocrates found that the heat emitted by the human body can be used to diagnose diseases, he applied a layer of mud on the patient, the earliest part of the mud dried and cracked is thought to be high temperature may have inflammation. With the development of science, medical thermal imaging technology has been widely used in various clinical specialties to assist in diagnosis, becoming one of the eight techniques of diagnostic imaging. 1956, the United States Lawson began to use infrared thermal imaging technology for the diagnosis of human breast cancer, and since the 21st century the instrument has been transformed from military infrared to medical infrared, becoming a new medical functional imaging technology. The medical infrared camera receives the infrared radiation emitted by the human body and uses imaging optics and computer technology to accurately determine the body surface temperature and display the temperature at various points on the human surface as a two-dimensional temperature field distribution in black and white or pseudo-color images. This modern physics detection technology has a resolution of up to 0.05°C and a spatial resolution of more than 1.5 milli-radians, and reflects many pathologies in the body by sensitively reflecting changes in the human surface temperature and its distribution characteristics (Figure: Infrared Thermography). The anatomical structure and physiological functions of the normal human body make the heat distribution on the body surface have certain rules. When the human body cells, tissues or organs are in different states, their metabolic activities and the heat radiation produced are not the same. The pattern of thermal image of healthy people is that the temperature of the head and face is higher, followed by the trunk, and the end of the extremities is the lowest, which is due to the rich blood supply to the brain, the trunk is at the proximal end, and the temperature is higher than that of the extremities. In principle, there is bilateral symmetry, with lower temperatures in places of fat, bone or muscle, and slightly higher temperatures in areas with superficial blood vessels and rich blood flow, such as the supraclavicular, axillary, inguinal and N-fossa areas. The average temperature value of the back was 32.58℃±0.91℃, which was lower than the average temperature value of the face, 34.04℃±1.68℃. The temperature symmetry of the left and right sides of the back and the left and right lateral regions of the trunk was better, and the difference in temperature values between the left and right sides was not statistically significant. The normal infrared thermograms of the waist and lower extremities were characterized by mostly uniform cold areas in the waist, especially in those with a fat body shape, and there could be light red hot areas in the lumbar and sacral spine locations but the temperature did not exceed 34℃, and the range of the hot areas was in accordance with the normal anatomy of the lumbosacral spine. The pattern of infrared thermogram of lower limbs was the average temperature of both thighs was 29.79℃±0.59℃, and the average temperature of lower legs was 29.37℃±0.34℃, and the temperature of thighs was higher than that of lower legs by about 0.4℃. The posterior lateral N fossa region has poor heat dissipation because of the distribution of N artery, rich blood supply and mutual radiation of skin folds, and the physiological high temperature area can be as high as 30.52℃±1.70℃. The anterior patellar region of the knee joint had the lowest temperature, 28.45℃±1.66℃, because this region belongs to the prominent part of the body and is easy to dissipate heat, forming a physiological low temperature zone. The infrared thermal images of both lower limbs showed basic symmetry between the left and right corresponding areas, with the anterior side of the knee joint showing a lower temperature and the posterior side showing a relatively high temperature area. Local hypermetabolism or accelerated blood flow can cause abnormally high temperature infrared thermogram color enhancement, such as inflammation, tumor, nerve entrapment, vasodilation, etc. During the test, the physician should try to keep the relevant conditions at the same level to ensure that a more objective result can be obtained. Pain is an abnormal signal from a nerve, and it is the pain physician’s responsibility to try to find and remove the site and cause of the nerve abnormality, that is, to clearly diagnose and treat the pain-causing cause. Infrared thermography accurately and objectively displays the body condition and nerve function response to pain in the human body in color images that could not be seen or felt in the past, providing a new scientific visual tool for clinical assessment of pain. All diseases that cause thermal changes in human tissues can be examined by infrared thermography. When the thermogram shows abnormal attenuation of local infrared light, it indicates that there are different degrees of local temperature reduction, such as insufficient blood supply to tissues, fluid accumulation, vasoconstriction or sympathetic hyperactivity. Changes in body surface temperature in pain patients can be influenced by a variety of factors, such as the amount of local skin microcirculatory blood flow, nerve entrapment, tissue inflammation, metabolic activity, and sympathetic excitability, among others. We found that the characteristic changes of infrared thermography have a high rate of agreement with the patient’s complaints, clinical symptoms and signs, as well as with the diagnosis of MRI, CT and other examinations, which can objectively indicate the specific location and the size of the range of pain. The degree of pain. After analyzing the pattern and trend of the abnormal heat source and temperature difference value on the infrared thermogram, the physician can determine the location, cause and health status of the patient’s pain and make a comprehensive treatment plan. It overcomes the difficulty that often some chronic pain patients or elderly people cannot express their pain well and correctly although they talk about a lot of sensations and processes. The physician’s targeted questioning and examination of the patient based on the infrared thermogram helps the physician to determine more quickly the location and nature of the inflammation occurring in the nerve, which nicely increases the patient’s medical compliance. We have found clinically that patients are surprised, convinced, and cooperative once the physician is able to more accurately determine the full range of pain-causing causes and develop a more complete treatment plan accordingly. We have found that the infrared thermograms of disc disease are characterized by abnormally high temperatures in the corresponding parts of the spine and abnormally low temperatures in the skin distribution areas of the upper arm or lower extremity where the corresponding nerves are innervated. Analyzing the anatomical and pathophysiological changes of the herniated disc, the reason for the abnormally high temperature in the spinal area on the infrared thermogram may be the rupture of the disc annulus fibrosus, the irritation of the herniated nucleus pulposus causing infiltration of myofascial and neuroinflammatory material around the spinal canal, the expansion of tissue microvasculature and the increase of blood flow rate. The more extensive and warmer the local thermal zone of the spine, the more severe the disc or nerve root vertebral lesion is reflected. The spinal nerve is accompanied by sympathetic nerves, and the compression of the affected spinal nerve root stimulates the sympathetic nerves accompanying the nerve, and the hyperactive sympathetic function causes vasoconstriction of the corresponding innervated tissues and a decrease in blood perfusion and metabolism. Therefore, the temperature of the tissue in the innervated area of the spinal nerve decreases, and prolonged lesions may even lead to neurodegenerative or trophic muscle atrophy, and the infrared thermogram shows a decrease in the volume of the affected limb. Therefore, when there is no local lesion at the site of clinical complaints of pain and the infrared thermogram shows abnormally low temperature, and localized high temperature and localized pressure pain are found at the proximal end of the nerve pathway, further imaging and targeted release therapy should be given for the possible nerve entrapment pain. (Figure 5: lumbar disc herniation) Myofascial pain syndrome has a wide range of etiologies and complex symptoms. In the past, there was no instrument that could directly and objectively depict the extent and degree of muscle pain, which made it more difficult for physicians to properly diagnose, treat, and conduct in-depth research. Infrared thermography shows the pattern that the temperature of the myofascial pain lesion area is significantly higher than normal. Whether it is local inflammation and stimulation of the dermatomal nerve during acute myofascial injury, etc. resulting in increased blood flow, or chronic myofascial adhesive scars that jam the dermatomal nerve resulting in neuroinflammation, the patient will show abnormal lamellar hyperthermia consistent with the anatomical location of the muscle. After combining the clinical pain features and physical examination to exclude other inflammatory or neoplastic conditions, a definitive diagnosis and targeted treatment can be made. However, the infrared thermogram only reflects the local temperature of the body, such as local inflammation or changes in metabolism or blood flow. The temperature changes in the body are also influenced by many external factors, such as local scars, arthritis, varicose veins or even clothing strangulation, etc. The physician needs to examine the patient locally in that high temperature area in detail to exclude it. The technique cannot identify the benign or malignant nature of the inflammation, and the physician needs to make specific analysis based on the medical history and other ancillary examination data. In our long-term clinical practice of pain management, we have summarized and proposed the new concept of “pain is an abnormal signal from nerves” and used this concept to guide our pain management approach, focusing on finding and diagnosing the site and cause of neuropathy and providing de-cause treatment. Infrared thermography is a good tool to help physicians determine the site of pain, i.e., the site of neuropathy. It can objectively and sensitively reflect the location of neuropathy, especially nerve entrapment, and provide immediate results, allowing physicians time to quickly diagnose the cause of pain. Based on the infrared thermogram, we can perform targeted consultations, physical examinations, and select other tests and treatment options. The objective nature of infrared thermography often leads us to further confirm or detect diseases that are described or missed by the patient, such as neuralgia, myofascial pain, arthralgia, vascular disease, cancer pain, angina, breast swelling, cancer, liver disease, pelvic inflammatory disease, prostatitis, pneumonia or hepatitis, etc. Infrared receiver is a green examination technology by passively accepting the far infrared rays radiated by human body into images, which is non-contact, non-traumatic, non-painful and non-polluting to both doctors and patients. The microcomputer processing function of infrared thermal imaging technology can be repeatedly, long-term, continuous, dynamic tracking examination and objective records of patients, which is very beneficial for physicians to observe the progress of disease trends, especially tumors or inflammatory lesions in the body. We will strive to explore and apply the potential functions of infrared thermography, especially its role in providing scientific data for monitoring the response and effect of drugs or therapeutic measures, and hope that it will further contribute to clinical medicine, especially pain treatment and research. Infrared thermal imaging technology in pain clinical applications (II) The basic principle of infrared thermal imaging diagnostic technology is to display and record the different temperature distributions on the surface of the human body in black and white or pseudo-color images by receiving infrared radiation from the human body and using imaging optics and computer technology. Any object with a temperature greater than absolute zero (-273.1 5°C) is going to radiate energy outward, and the wavelength of electromagnetic waves radiated by the human body is mainly in the far infrared region, with a wavelength range of 4 to 14µm and a peak of 9.34µm. Therefore, the use of infrared detectors with a wavelength of 8 to 14µm can easily Detect the infrared radiation of the human body. The main imaging principle of medical far-infrared thermography is to receive the infrared radiation emitted by the human body, which can accurately determine the temperature of the body surface. The temperature of each point is expressed in the form of a two-dimensional temperature field, i.e. a thermal image. Its temperature resolution reaches 0.05℃, and the spatial resolution of the image is more than 1.5 milli-radians, which can reflect the change of the body surface temperature and its distribution characteristics sensitively. If the body surface temperature changes due to internal pathology, the far infrared thermography can be reflected by the thermal image. Human infrared imaging is a medical functional imaging technology developed by foreign military infrared technology to medical infrared technology since entering the 21st century. It is a modern physics detection technology that uses the principle of human infrared radiation imaging to study the state of temperature distribution on the body surface. From the discovery of British astronomer Will Hershey in 1800 to the discovery of American astronomer Will Hershey in 1956. Hershey’s discovery in 1800 and Lawson’s use in the diagnosis of breast cancer in 1956 ushered in a new era of infrared thermographic diagnosis. Today, we use it for pain diagnosis and treatment, so that the pain conditions and neurological reactions of the human body, which we could not see or feel in the past, can be accurately expressed in the form of a thermogram, providing a new means of detection for our clinical treatment. Heat production and heat dissipation in the human body are in physiological balance, because there is an automatic thermoregulatory mechanism in the body, and an imbalance in the balance of heat production or heat dissipation will lead to changes in body temperature. Heat production comes from the metabolism of various organs in the body, biological reactions, muscle activity, hormones and sympathetic nerve activity related. There are four forms of heat dissipation: radiation accounts for 44% of the total, conduction and convection for 31%, and evaporation for 21%. When human cells, tissues or organs are in different states, their metabolic activity and the heat radiation generated are different. If the tissue is in a chronic disease period, insufficient blood supply, or local tissue degeneration, necrosis, liquefaction and other states, its thermogram will have different degrees of attenuation and decrease. And the high level is generally manifested in painful, proliferative, inflammatory, tumor, and other metabolically vigorous stages. Infrared thermography is extremely sensitive (less than 0.05℃) to receive the thermal radiation generated by the metabolism of human cells, and through the unique imaging, from the surface to the inside of the layer analysis technology, to determine the distribution of abnormal heat sources in the human body, from the analysis of the morphology and trend of abnormal heat sources and thermal difference values, to understand the overall health status of people. 1. Temperature characteristics of the back and lower extremities of normal people The change of body surface temperature is affected by various factors, mainly related to the amount of blood flow in the microcirculation of the skin and the level of sympathetic excitability, as well as the metabolic activity of local tissues; in addition, it is also affected by the ambient temperature, air flow, human mental state and sweat gland secretion activity. During the test observation, the relevant conditions were controlled at the same level to ensure that more objective results could be obtained. Temperature characteristics of normal human back The test showed that the average temperature value of normal human back was 32.58℃±0.91℃, which was lower than the average temperature value of face 34.04℃±1.68℃, but it was consistent with the characteristics of normal human body surface temperature distribution, i.e., the temperature of head and face was higher, followed by the trunk and the end of the limbs was the lowest. This is due to the rich blood supply to the brain, the trunk is at the proximal end, and the temperature is higher than that of the extremities; and the temperature of the various body surface parts also differs to some extent due to different heat dissipation and blood supply. There is no significant difference between the temperature values of the left and right sides of the back and no statistically significant difference between the temperature values of the left and right sides of the trunk area in normal individuals, indicating that the temperature symmetry of the left and right sides of the back and the left and right sides of the trunk area is better in healthy individuals, which can provide a relevant basis for the diagnosis of disease on one or both sides of the spine [1]. Temperature characteristics of the lower extremities in normal subjects The results of the study showed that the average temperature of the thighs of both lower extremities was (29.79 ± 0.59) °C and the average temperature of the calves was (29.37 ± 0.34) °C. The temperature of the thighs was about 0.4 °C higher than that of the calves. The lowest temperature was (28.45±1.66)℃ in the anterior patellar region of the knee, mainly because this region belongs to the prominent part of the body, which is easy to dissipate heat and forms a physiological low temperature zone; while the temperature in the posterior carcass fossa region was higher than (30.52±1.70) ℃, because there is a local distribution of carcass artery, rich blood supply, and there are skin folds radiating from each other, which dissipates heat poorly, thus producing a physiological high temperature zone [2 ]. The characteristics of the far infrared thermogram of the waist and lower extremities in normal subjects: the waist is mostly a uniform cold area, especially in those with a fat body shape, and there can be light red hot areas in the lumbar and sacral spine locations, but the temperature does not exceed 34 ℃, and the range of the hot area conforms to the normal anatomical structure of the lumbosacral spine, without the phenomenon of expanding the range of the hot area; the infrared thermogram of both lower extremities shows basic symmetry between the left and right corresponding areas, with the anterior side of the knee joint showing a lower temperature and the posterior side showing a relatively high temperature area. The regularity of temperature distribution can provide theoretical basis for clinical diagnosis and treatment. The characteristics of infrared thermogram of lumbar disc herniation The characteristics of far-infrared thermogram of lumbar disc herniation are as follows: abnormal thermal zone appears in the lumbosacral region, rhombic or pike shaped, which can be uniformly red in color, mostly in the parts of L4-5 and L5-S1, and the range of thermal zone expands, and sometimes deep red thermal zone can appear within the red thermal zone, and it is mostly biased to the affected side. The temperature in the center of the abnormal hot zone is more than 34℃, and the temperature difference with the periphery is more than 3~4℃. Most of the lower extremities show hypothermia, the healthy extremities are mostly green, and the affected extremities can be light blue or blue. The skin temperature of the posterior femur of the affected limb may be lower than that of the healthy side [3]. The reason may be aseptic inflammation of nerve roots and their surrounding tissues due to disc herniation, local inflammatory material infiltration, microvascular dilation, increased blood flow rate, and increased local temperature, causing an increase in skin area temperature of the corresponding segment. In addition, local inflammatory material stimulation and pain caused by nerve root compression can cause local muscle tension and spasm, and enhanced metabolism, which can also increase the body surface temperature. The far-infrared thermographic manifestation of lumbar disc herniation corresponds to the anatomical features of lumbar disc herniation. The more extensive the thermal zone and the higher the local temperature, the more severe the inflammatory changes caused by the herniated disc and the more severe the impact on the nerve roots. The far-infrared thermogram of the affected limb mostly shows a hypothermic zone with a lower temperature than the healthy side, which may be caused by the compression of the nerve root on the affected side, affecting the contraction function of the blood vessels supplying the corresponding limb and resulting in reduced blood perfusion in the limb, which is hypometabolic and low blood flow. However, a small number of patients have increased skin temperature in the posterior femur of both lower extremities, which may be due to local skin vasodilation and enhanced metabolism caused by painful stimulation. Patients with lower extremity hypothermia mostly complain of lower extremity weakness and hypoesthesia. The analysis of the lower extremity far infrared thermogram should be specific to the patient and other factors affecting skin temperature changes, such as arthritis and degenerative joint degeneration, should be considered. The characteristic changes of the thermogram have a high rate of compliance with either the chief complaint, clinical symptoms, signs and with the diagnosis of MRI, CT and other examinations. The thermogram can indicate the specific location of pain, the size of the range, and the degree of pain. However, it should be pointed out that the same thermographic changes can be seen in any cause of lumbosacral damage affecting one nerve root, such as benign or malignant tumors of the lumbosacral region. Therefore, specific analysis based on medical history and other examinations is often required. Infrared thermography cannot make a clear localization diagnosis of lumbar disc herniation and cannot be localized to a specific segment. 3. Infrared thermographic features of ankylosing spondylitis Infrared thermography in patients with ankylosing spondylitis is characterized by warming changes in the sacroiliac joint area. Ankylosing spondylitis has a slow onset, long duration, and high disability rate. Early onset usually begins with inflammation of the sacroiliac joint, local pathological changes are vasodilatation, increased vascular permeability, hyperplasia and hypertrophy of the inflamed synovial tissue, formation of villi, infiltration of plasma cells and lymphocytes around small vessels, and active metabolism. The temperature difference between the warming area and the surrounding tissue is between 0.3 ℃ and 2.2 ℃, with an average temperature difference of 1.2 ℃. It has a temperature resolution of <0.05 °C, and weak inflammatory changes can be shown. The sacroiliac joint is located under the skin, and there are no surrounding tissues and organs that generate heat, so the interference of surrounding environmental heat sources is excluded, and the accuracy rate is high. Even in the early stage of inflammation, there are temperature changes, and the diagnostic compliance rate is 100%. The temperature difference between the warming area and the surrounding tissues is directly proportional to the degree of increase in the patient's blood sedimentation, and the faster the blood sedimentation, the greater the temperature difference [4]. 4. Infrared thermographic characteristics of myofascial pain syndrome Myofascial pain syndrome has many causes and complex symptoms, and there is no instrument that can directly and objectively describe the pain, which makes the correct diagnosis, treatment and in-depth research quite difficult. Some studies have shown that the temperature difference in the low back and the temperature difference between the affected side and the adjacent area are significantly higher than normal in patients with myofascial pain syndrome, and the infrared thermography is abnormal or significantly abnormal. Myofasciitis sites mostly show lamellar high temperature areas consistent with the anatomical location of the injured muscle. In pain diseases, the role of infrared thermography for all diseases that can cause thermal changes in human tissue can be used to examine it, which can guide clinical diagnosis and examination. It has a wide range of applications and high clinical value. Because the infrared sensor passively accepts the infrared light radiated by the human body, it is a green examination without contact, trauma, pain, pollution, and any harm to both doctors and patients. Its can both check both results, for emergency, serious patients to win time to rescue, can be repeated for many times to check, monitoring or on the efficacy, drug observation records. The digital image recording and rich image processing function of infrared thermography can provide long-term, continuous and dynamic tracking examination for the examinees, which adds a powerful tool for clinical diagnosis and treatment of pain.