Table 3.

PET outcome measures for calculation or estimation of target occupancy

Outcome measure	Estimation
	Definition	Rate constants	Distribution volumes	Occupancy calculation
BP ND (specific to nondisplaceable binding potential)	B max/K D ● f ND	k 3/k 4 a	V T/V ND − 1 b	BP ND baseline − BP ND drug / BP ND baseline
V T	V S+V ND	K 1/k 2 (1+k 3/k 4)	‐	V T drug − V T baseline = OCC ● (V T − V ND)
λk3 c	λ = K 1/k 2	K1/k2  ● k 3	‐	λk3  baseline − λk3  drug / λk3  baseline

B _max, max number of available receptors(targets); K _D, dissociation rate constant; PET, positron emission tomography; V _ND, nondisplaceable distribution volume (usually measured in a reference region); V _S, distribution volume of the radioligand bound to the target.

^a k ₃/k ₄ can be estimated with 2‐tissue compartment model (TCM) or with simplified reference tissue model (SRTM).

^b V _T and V _ND can be estimated with 1‐TCM or 2‐TCM or with linear or multilinear graphical analysis (Logan plot or multilinear analysis) or with reference Logan or MRTM in case a reference region in the brain is present.

^c λk₃ is the outcome measure conventionally used in case of an irreversible radioligand.