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Rapid quantitative pharmacodynamic imaging by a novel method: theory, simulation testing and proof of principle

Authors
Journal
PeerJ
2167-8359
Publisher
PeerJ
Publication Date
Volume
1
Identifiers
DOI: 10.7717/peerj.117
Keywords
  • Neuroscience
  • Neurology
  • Pharmacology
  • Psychiatry And Psychology
  • Radiology And Medical Imaging
Disciplines
  • Biology
  • Pharmacology

Abstract

Pharmacological challenge imaging has mapped, but rarely quantified, the sensitivity of a biological system to a given drug. We describe a novel method called rapid quantitative pharmacodynamic imaging. This method combines pharmacokinetic-pharmacodynamic modeling, repeated small doses of a challenge drug over a short time scale, and functional imaging to rapidly provide quantitative estimates of drug sensitivity including EC50 (the concentration of drug that produces half the maximum possible effect). We first test the method with simulated data, assuming a typical sigmoidal dose-response curve and assuming imperfect imaging that includes artifactual baseline signal drift and random error. With these few assumptions, rapid quantitative pharmacodynamic imaging reliably estimates EC50 from the simulated data, except when noise overwhelms the drug effect or when the effect occurs only at high doses. In preliminary fMRI studies of primate brain using a dopamine agonist, the observed noise level is modest compared with observed drug effects, and a quantitative EC50 can be obtained from some regional time-signal curves. Taken together, these results suggest that research and clinical applications for rapid quantitative pharmacodynamic imaging are realistic.

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