Slightly low-density shadow and low-density shadow are described above in imaging, and the difference between the two mainly includes the degree of coloration and the cause of formation. 1. Degree of color rendering: slightly low-density shadow is lighter than low-density shadow, low-density shadow is mainly black in color, slightly low-density shadow is mainly gray in color. 2. Causes: Slightly hypodense shadows are mostly caused by pathological reasons, such as tumors, cysts, lung abscesses, pneumonia, lung cysts and so on. Low-density shadow can be pathologic or normal, pathologic such as liver cysts, liver abscess, abdominal fluid, renal cysts; can be manifested as normal tissues, such as cerebrospinal fluid, normal soft tissues in the CT mostly manifested as low density. Low-density shadow and slightly low-density shadow need to be analyzed in conjunction with the actual condition, if the test results are abnormal, it should be timely to seek medical treatment.