Mathematical modelling of [11C]-(+)-PHNO human competition studies.

The D2/D3 agonist radioligand [11C]-(+)-PHNO is currently the most suitable D3 imaging agent available, despite its limited selectivity for the D3 over the D2. Given the collocation of D2 and D3 receptors, and generally higher densities of D2, the separation of D2 and D3 information from [11C]-(+)-PHNO PET data are somewhat complex. This complexity is compounded by recent data suggesting that [11C]-(+)-PHNO PET scans might be routinely performed in non-tracer conditions (with respect to D3 receptors), and that the cerebellum (used as a reference region) might manifest some displaceable binding signal.