Non-Invasive Molecular Imaging of β-Adrenoceptors In Vivo: Perspectives for PET-Radioligands

Recently, the spectrum of molecular imaging devices such as positron emission tomography (PET) was further expanded by the now clinically available combined imaging modalities such as PET-CT and the preclinically used small animal PET scanners. These are powerful tools that can bridge the gap between preclinical and clinical evaluation studies of new radiotracers for molecular imaging of healthy and diseased states in vivo.

The β-adrenoceptor (β-AR) radioligands discussed in this review represent a class of molecular probes for the non-invasive in vivo assessment of β-AR density eg. in the heart with PET. The β-AR radioligands (S)- [11C]CGP 12177 (1) or (S)-[11C]CGP 12388 (2) are currently investigated in clinical studies with PET. Additionally, subtype-selective b1-AR radioligands are used in preclinical research which show potential for the diagnostics of the "β1-AR organ" as such the heart can be defined. Non-invasive quantification of β-ARs could facilitate the accurate choice and control of therapeutic interventions. Here we summarize the state-ofthe- art of the radiochemistry of radioactive β-AR radioligands.