“…This is mainly due to its versatility: It can function as nucleophile as well as electrophile, and [ 11 C]cyanide incorporation generates many different functionalities, such as nitriles, hydantoins, (thio)cyanates and, through subsequent reaction, carboxylic acids, aldehydes, amides and amines. Two extensive reviews on [ 11 C]hydrogen cyanide have been recently published, therefore this 11 C-building block will not be discussed in detail herein [ 70 , 71 ]. Since [ 11 C]hydrogen cyanide is one of the few 11 C-building blocks used for FIH PET tracers in recent years (vide infra), we will provide a brief summary of recent work that has not been covered by other reviews.…”