The T1 and T2 values of different tissues of the body are the basic factors of MRI, and the signals obtained during the actual scanning process of MRI contain both T1 and T2 signals. For example, a normal tissue structure such as cerebrospinal fluid appears as low signal on T1 and high signal on T2. In the case of some lesions, the presence of T1 low signal and T2 high signal often indicates that it is a cyst-like or liquefied structure.