Lung nodules can manifest as single or multiple independent lung consolidation shadow in form of quasi-circular. These lung nodules are surrounded by normal lung tissues, and will not cause pulmonary atelectasis. In some early standards, all the quasi-circular shadows within 6cm found in lung are categorized as lung nodules. However, according to current standards, the lesion within 3cm can be identified as lung nodules. With widespread use of lung cancer CT screening, lung nodules were identified more and more frequently.