China is now rapidly entering an aging society and is therefore facing the challenge of various diseases of the elderly. Osteoporosis, as a common sense topic of health care for the middle-aged and elderly, has been accepted by most of our elderly compatriots. Osteoporosis is a systemic skeletal disease characterized by the decrease of bone mass and the degeneration of bone microstructure, resulting in the increase of bone fragility and the ease of fracture, and has now risen to the seventh place of common diseases. In recent years, China’s medical technology has developed and reached international level, and advanced treatment equipment has been introduced. There are many ways to measure bone density in the medical field, here are a few convenient methods that are accepted by the majority of patients: 1, single photon absorptiometry (SPA) Single photon absorptiometry is the most common method of measuring bone density in China. The principle of this method is the use of bone tissue absorption of radioactive substances and bone mineral content is proportional to the principle of radioactive isotopes as a light source to determine the bone mineral content of human limb bone. The junction of the radius and the middle and distal 1/3 of the ulna (the middle and lower 1/3 of the forearm) is generally used as the measurement point. Generally right-handed people measure the left forearm, and “left-handed” people measure the right forearm. This method is more commonly used in China, and the equipment is simple, inexpensive and suitable for epidemiological screening. The disadvantage is that the method cannot measure cancellous bone and cortical bone separately, and cannot measure skeletal areas where soft tissue is not constant. Moreover, although brittle fractures are frequently detected in the distal radius, cancellous bone is not as abundant as vertebral bone, and unlike the hip, which is the most dangerous site for fracture, so it is not highly predictive of fractures in critical areas and has relatively large errors. DEXA is the gold standard for diagnosing osteoporosis and has been gradually carried out in major cities in China. . The instrument can measure bone mass in any part of the body, mainly measuring bone density in the lumbar spine, patella, tibia and other parts. It has the advantages of high precision, small error and high diagnostic rate. And it is less harmful to human body, the radiation dose of detecting one part is equal to 1/30 of a chest film and 1% of quantitative CT. The disadvantage is that because the machine is large, not easy to move, and relatively expensive, it is usually not feasible to measure bone density in large samples or in elderly people with limited mobility. In addition, the bone density of dense bone and cancellous bone with different bone conversion rate cannot be measured separately. Having back surgery or hip replacement surgery, severe arteriosclerosis, ligament calcification or osteophytes may lead to high bone density values and cause misdiagnosis, and if patients have the above conditions, they should tell their doctors to avoid measuring the bone density of the lesion. 3.Quantitative CT (QCT) In the past 20 years or so, computed tomography (CT) has been widely used in the field of clinical radiology. This method is mainly used to measure the cancellous bone of the lumbar spine. The advantage of this method is that it can selectively measure the bone mineral changes in specific areas, assess the bone mineral density of cortical bone and cancellous bone separately and the test results are accurate and reliable. In clinical application, this method can accurately determine osteoporosis caused by bone deficiency in various parts of the body. However, the presence of a variable amount of fat in the bone marrow causes measurement errors, and its use is limited by the large dose of irradiation, the large equipment, and the high cost of the test, so the method is currently used mainly in clinical research work. 4, ultrasound measurement method The principle of this method is to use the speed of sound transmission and amplitude attenuation can reflect the amount of bone mineral content and bone strength, elasticity and brittleness, and DEXA correlates well and can correctly evaluate the brittleness of the bone cortex. Bone ultrasound velocity can reflect bone strength, bone density, bone elasticity and brittleness, and is superior to simple bone density measurement from the perspective of bone biomechanics, especially for peripheral cortical bone measurement. It is especially suitable for peripheral cortical bone measurements. It is mainly used to measure bone density in the radius, heel, patella and tibia. Quantitative bone ultrasound is a good predictor of fracture risk and has the advantages of being simple, reproducible, easy to move and inexpensive. Because it does not irradiate radiation, children and pregnant women can also be measured, and small and medium-sized hospitals that do not have DEXA equipment can also screen people with osteoporosis with this test. However, the complexity and heterogeneity of the bone structure and the various conduction pathways and time differences can affect the accuracy of this measurement. Understanding the advantages and disadvantages of different measurement methods in terms of their applicability and the meaning of the parameters is a prerequisite for proper selection of the measurement method. The choice of method for screening and diagnosis of osteoporosis by clinicians will depend on whether the patient has risk factors for osteoporosis and the site of involvement, as well as the testing capabilities of the hospital, in order to obtain the correct measurement results and make better use of medical and social resources.