Abstract
This guideline on molar activity (A(m)) and specific activity (A(s)) focusses on small molecules, peptides and macromolecules radiolabelled for diagnostic and therapeutic applications. In this guideline we describe the definition of A(m) and A(s), and how these measurements must be standardised and harmonised. Selected examples highlighting the importance of A(m) and A(s) in imaging studies of saturable binding sites will be given, and the necessity of using appropriate materials and equipment will be discussed. Furthermore, common A(m) pitfalls and remedies are described. Finally, some aspects of A(m) in relation the emergence of a new generation of highly sensitive PET scanners will be discussed.