What matters should I pay attention to when shooting long bones of limbs?

Bone contains a large number of calcium salts with high density, which is in sharp contrast with surrounding soft tissues. In the structure of the bone itself, the density of the surrounding cortex is higher, and the density of the internal cancellous bone and bone marrow is lower than that of the cortex, which is also in sharp contrast. Because there is a good natural contrast between bone and soft tissue, general photography can clearly show bone and joint diseases, which can be easily shown on X-ray films, and diagnosis can be made through observation and analysis. X-ray examination can not only show the scope and degree of the lesion, but also make a qualitative diagnosis. However, X-ray manifestations of many bone and joint diseases appear later than pathological changes and clinical manifestations. Therefore, the preliminary examination results are negative, and the existence of early lesions cannot be ruled out. For example, early inflammation and tumor infiltration into bone marrow may not be important, so we can regularly review and find lesions according to clinical diagnosis and the development law of different diseases. Sometimes the initial X-ray examination can find the lesions but can't make a definite diagnosis, and the qualitative diagnosis can only be made after re-examination. It must also be pointed out that many bone and joint diseases lack typical or special X-ray manifestations and need to be combined with clinical data, such as acute onset and severity of symptoms and signs. In order to make a clear diagnosis. X-ray inspection method. X-ray examination of common joints mainly uses photos instead of fluoroscopy. It is only used to find foreign bodies, locate gunshot wounds and repair traumatic fractures and dislocations. Attention should be paid to the following points when taking pictures: ① Any part, including the long bones of limbs, joints and spine, should be taken in a positive lateral position. Some parts should also use oblique position, tangent position and axial position. ② Surrounding soft tissues should be included. Photographs of long bones of limbs should include an adjacent joint. For example, when taking spinal photography, the lumbar vertebrae should include the lower thoracic vertebrae for counting; ③ Bilateral symmetrical bone and joint, if the lesion is on one side and the symptoms and signs are light, or the upper side of X-ray film has changed, but it is not obvious enough, the contralateral side should be photographed and compared under the same technical conditions. Second, the special examination (1) tomography can show the structure clearly in the parts where the structure of the bone joint itself is complex or overlaps with other structures. It can also clearly show the focus of the whole bone. (2) Zoom-in photography uses a micro-focus X-ray tube. Through direct magnification of X-ray images, we can observe the fine structure and subtle changes of bones. It is usually used to examine local trabecular structures and small joints. Three. Comparative examination (1) arthrography The joint space is composed of articular cartilage and a small amount of synovial fluid. There is an anatomical joint space between the opposite articular cartilage, which is obviously compared with the bones that make it up. Therefore, the joint space becomes narrower and wider, and the bone articular surface is destroyed and hardened, which can be clearly shown on plain film. The cartilage disc, joint capsule, synovium and ligament in the joint are all soft tissues with the same density, so there is no contrast on plain film. Some soft tissue injuries and lesions need to be observed by injecting contrast agent into the joint cavity to form artificial radiography, that is, arthrography. Arthrography usually uses gas as contrast agent or injects organic iodine solution into joint cavity. It is also possible to inject organic iodine solution and gas at the same time for double comparison. (2) Angiography Angiography is mostly used for limb arteries. It is mainly used for the diagnosis of vascular diseases and the differentiation of benign and malignant tumors. For the latter, the diagnosis was made according to the vascular morphological changes of the tumor, the blood flow of the tumor and the displacement of the adjacent blood vessels.