Imaging the cannabinoid CB1 receptor in humans with [11C]OMAR: assessment of kinetic analysis methods, test-retest reproducibility, and gender differences

J Cereb Blood Flow Metab. 2015 Aug;35(8):1313-22. doi: 10.1038/jcbfm.2015.46. Epub 2015 Apr 1.

Abstract

The Radiotracer [(11)C]OMAR was developed for positron emission tomography (PET) imaging of cannabinoid type-1 receptors (CB1R). The objectives of the present study were to evaluate kinetic analysis methods, determine test-retest reliability, and assess gender differences in receptor availability. Dynamic PET data were acquired in 10 human subjects, and analyzed with one-tissue (1T) and two-tissue (2T) compartment models and by the Logan and multilinear analysis (MA1) methods to estimate regional volume of distribution (VT). The 2T model inclusive of a vascular component (2TV) and MA1 were the preferred techniques. Test-retest reliability of VT was good (mean absolute deviation ~9%; intraclass correlation coefficient ~0.7). Tracer parent fraction in plasma was lower in women (P<0.0001). Cerebral uptake normalized by body weight and injected dose was higher in men by 17% (P<0.0001), but VT was significantly greater in women by 23% (P<0.0001). These findings show that [(11)C]OMAR binding can be reliably quantified by the 2T model or MA1 method and demonstrate the utility of this tracer for in vivo imaging of CB1R. In addition, results from the present study indicate that gender difference in receptor binding should be taken into consideration when [(11)C]OMAR is used to quantify CB1R availability in neuropsychiatric disorders.

Publication types

  • Clinical Trial
  • Multicenter Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Brain* / diagnostic imaging
  • Brain* / metabolism
  • Carbon Isotopes / administration & dosage
  • Cerebral Angiography / methods*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Positron-Emission Tomography / methods*
  • Radiopharmaceuticals / administration & dosage*
  • Receptor, Cannabinoid, CB1 / metabolism*
  • Sex Characteristics*

Substances

  • Carbon Isotopes
  • Radiopharmaceuticals
  • Receptor, Cannabinoid, CB1