title: Test-retest reproducibility of dopamine D2/3 receptor binding in human brain measured by PET with [11C]MNPA and [11C]raclopride.
abstract: OBJECTIVE
  Dopamine D receptors (DRs) have two affinity states for endogenous dopamine, referred to as high-affinity state (D ), which has a high affinity for endogenous dopamine, and low-affinity state (D ). The density of D can be measured with (R)-2-CHO-N-n-propylnorapomorphine ([C]MNPA), while total density of D and D (DRs) can be measured with [C]raclopride using positron emission tomography (PET). Thus, the ratio of the binding potential (BP) of [C]MNPA to that of [C]raclopride ([C]MNPA/[C]raclopride) may reflect the proportion of the density of D to that of DRs. In the caudate and putamen, [C]MNPA/[C]raclopride reflects the proportion of the density of D to that of DRs. To evaluate the reliability of the PET paradigm with [C]MNPA and [C]raclopride, we investigated the test-retest reproducibility of non-displaceable BP (BP ) measured with [C]MNPA and of [C]MNPA/[C]raclopride in healthy humans.
  
  
  METHODS
  Eleven healthy male volunteers underwent two sets of PET studies on separate days that each included [C]MNPA and [C]raclopride scans. BP values in the caudate and putamen were calculated. Test-retest reproducibility of BP of [C]MNPA and [C]MNPA/[C]raclopride was assessed by intra-subject variability (absolute variability) and test-retest reliability (intraclass correlation coefficient: ICC).
  
  
  RESULTS
  The absolute variability of [C]MNPA BP was 5.30 ± 3.96 % and 12.3 ± 7.95 % and the ICC values of [C]MNPA BP were 0.72 and 0.82 in the caudate and putamen, respectively. The absolute variability of [C]MNPA/[C]raclopride was 6.11 ± 3.68 % and 11.60 ± 5.70 % and the ICC values of [C]MNPA/[C]raclopride were 0.79 and 0.80 in the caudate and putamen, respectively.
  
  
  CONCLUSIONS
  In the present preliminary study, the test-retest reproducibility of BP of [C]MNPA and of [C]MNPA/[C]raclopride was reliable in the caudate and putamen.
authors.affiliation: Molecular Neuroimaging Program, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan.
authors.forename: Fumitoshi
authors.initials: F
authors.lastname: Kodaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ito
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kimura
authors.forename: Saori
authors.initials: S
authors.lastname: Fujie
authors.forename: Harumasa
authors.initials: H
authors.lastname: Takano
authors.forename: Hironobu
authors.initials: H
authors.lastname: Fujiwara
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sasaki
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nakayama
authors.forename: Christer
authors.initials: C
authors.lastname: Halldin
authors.forename: Lars
authors.initials: L
authors.lastname: Farde
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Suhara
mesh_terms: D000328:Adult; D001058:Apomorphine / Q000031:analogs & derivatives*; D001921:Brain / Q000000981:diagnostic imaging*; D003627:Data Interpretation, Statistical; D006801:Humans; D008297:Male; D049268:Positron-Emission Tomography; D020891:Raclopride; D019275:Radiopharmaceuticals; D017448:Receptors, Dopamine D2 / Q000032:analysis*; D050637:Receptors, Dopamine D3 / Q000032:analysis*; D015203:Reproducibility of Results
chemical_list: D019275:Radiopharmaceuticals; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D020891:Raclopride; C009074:N-n-propylnorapomorphine; D001058:Apomorphine