Measuring drug occupancy in the absence of a reference region: the Lassen plot re-visited

Vincent J. Cunningham, Eugenii A. Rabiner, Mark Slifstein, Marc Laruelle, Roger N. Gunn

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Quantitative estimation of neuroreceptor occupancy by exogenous drugs using positron emission tomography is based on the reduction in the total volume of distribution (VT) of site-specific radioligands after drug administration. An estimate of the distribution volume of free and nonspecifically bound radioligand (VND) is also required to distinguish specific from total binding. However, a true reference region, devoid of specific binding, is often not available. We present a transformation of a graphical method, originally introduced by Lassen, using regional estimates of VT alone to determine occupancy, together with an extension that does not require baseline data.

Original languageEnglish
Pages (from-to)46-50
Number of pages5
JournalJournal of Cerebral Blood Flow and Metabolism
Issue number1
Early online date9 Sep 2009
Publication statusPublished - Jan 2010


  • graphical analysis
  • occupancy
  • PET
  • positron-emission-tomography
  • brain transfer constants
  • time uptake data
  • in-vivo
  • binding
  • receptors
  • humans
  • model

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