Kinetic evaluation of [11C]dihydrotetrabenazine by dynamic PET: measurement of vesicular monoamine transporter

J Cereb Blood Flow Metab. 1996 Nov;16(6):1288-99. doi: 10.1097/00004647-199611000-00025.

Abstract

(+)-alpha-[11C]Dihydrotetrabenazine (DTBZ) binds to the vesicular monoamine transporter (VMAT2) located in presynaptic vesicles. The purpose of this work was to evaluate various model configurations for analysis of [11C]DTBZ with the aim of providing the optimal measure of monoamine vesicular transporter density obtainable from a single dynamic PET study. PET studies on seven young normal volunteer subjects, ages 20-35, were performed following i.v. injection of 666 +/- 37 MBq (18 +/- 1 mCi) of (+)-alpha-[11C]DTBZ. Dynamic acquisition consisted of a 15-frame sequence over 1 h. Analysis methods included both creation of pixel-by-pixel functional images of transport (K1) and binding (DVtot) and nonlinear least-squares analysis of volume-of-interest data. Pixel-by-pixel calculations were performed for both two-compartment weighted integral calculations and slope-intercept estimations from Logan plots. Nonlinear least-squares analysis was performed applying model configurations with both two-compartments, estimating K1 and DVtot and three compartments, estimating K1-k4. For the more complex configuration, we examined the stability of various binding-related parameters including k3 (konBmax'), k3/k4 (Bmax'/Kd), DVsp[(K1/k2)(k3/k4)], and DVtot [K1/k2(1 + k3/k4)]. The three-compartment model provided significantly improved goodness-of-fit compared to the two-compartment model, yet did not increase the uncertainty in the estimate of the DVtot. Without constraining parameters in the three-compartment model fits, DVtot was found to provide a more stable estimate of binding density than either k3, k3/k4, or DVsp. The two-compartment least-squares analysis yielded approximately 10% underestimations of the total distribution. However, this bias was found to be very consistent from region to region as well as across subjects as indicated by the correlation between two- and three-compartment DVtot estimates of 0.997. We conclude that (+)-alpha-[11C]DTBZ and PET can provide excellent measures of VMAT2 density in the human brain.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Binding Sites
  • Biological Transport
  • Humans
  • Kinetics
  • Membrane Glycoproteins / metabolism*
  • Membrane Transport Proteins*
  • Models, Theoretical
  • Neuropeptides*
  • Radioligand Assay
  • Tetrabenazine / analogs & derivatives*
  • Tetrabenazine / metabolism
  • Tetrabenazine / pharmacology
  • Tomography, Emission-Computed
  • Vesicular Biogenic Amine Transport Proteins
  • Vesicular Monoamine Transport Proteins

Substances

  • Membrane Glycoproteins
  • Membrane Transport Proteins
  • Neuropeptides
  • SLC18A2 protein, human
  • Vesicular Biogenic Amine Transport Proteins
  • Vesicular Monoamine Transport Proteins
  • dihydrotetrabenazine
  • Tetrabenazine