Dear Hao,
This is slightly off topic from your main concern, but it should be stated for the record that it
makes no sense to talk about binding potential (BP) maps at given points in time (10 min post
challenge compared to 20 min post challenge) because BP expresses a relationship between the
radioligand and the receptors at equilibrium. Estimation of BP can only be accomplished either by
measuring concentration ratios following attainment of a steady state (both of the ligand
concentration and the receptor pool) or, more commonly, by fitting an entire dynamic data set to
a model, again assuming the receptor system is in steady state for the duration of the scan. It
does make sense to look at the change in BP induced by a drug, either through receptor
occupancy or other change in receptor availability induced by the drug, but only under the
assumption that the system is approximately in equilibrium when the post-challenge scan is
performed, which would not be the case if there were quantifiable differences 10 and 20 min post
challenge, given that the kinetics of virtually all receptor ligands operate on a much slower
timescale than this.
If the appropriate conditions for BP estimation are met, one can, as Matthias says, easily compute
a brain map of BP, which then can be analyzed like any other statistical map.
Best Regards,
Mark
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