At present, several radioactive ligands have been developed for imaging TSPO expression, biodistribution in normal physiological and pathological states, and measuring the correlation between expression and disease progression.14-17 [11C]PK11195 was the first generation of radioligand for TSPO, which was developed more than two decades ago and has been widely used for monitoring neuroinflammation in numerous neurodegenerative diseases. The gene discussed is TSPO; the disease is neurodegenerative disease.