The reason there are two slices in a lung CT is because one slice is the lung window and the other is the mediastinal window. The lung window mainly looks at the lung tissue, and you can see that the lung texture is mostly bright white and clear, and the surrounding soft tissues are dark, which allows you to see small lesions in the lungs, such as pulmonary nodules, inflammatory exudates, bronchiectasis, lung tumors, and other lesions, and the tuberculosis can also be seen more clearly. The mediastinal window mainly shows the mediastinum as well as lymph nodes and large blood vessels, while the lungs are dark in color. The mediastinal window mainly looks at the presence or absence of enlarged lymph nodes, the relationship between the mass and the large blood vessels, and it can also visualize lesions within the mediastinum.