title: Evaluation of a bolus/infusion protocol for 11C-ABP688, a PET tracer for mGluR5.
abstract: (11)C-ABP-688 is a selective tracer for the mGluR5 receptor. Its kinetics is fast and thus favourable for an equilibrium approach to determine receptor-related parameters. The purpose of this study was to test the hypothesis that the pattern of the (11)C-ABP688 uptake using a bolus-plus-infusion (B/I) protocol at early time points corresponds to the perfusion and at a later time point to the total distribution volume.
  
  
  METHODS
  A bolus and a B/I study (1 h each) was performed in five healthy male volunteers. With the B/I protocol, early and late scans were normalized to gray matter, cerebellum and white matter. The same normalization was done on the maps of the total distribution volume (Vt) and K(1) which were calculated in the study with bolus only injection and the Logan method (Vt) and a two-tissue compartment model (K(1)).
  
  
  RESULTS
  There was an excellent correlation close to the identity line between the pattern of the late uptake in the B/I study and Vt of the bolus-only study for all three normalizations. The pattern of the early uptake in the B/I study correlated well with the K(1) maps, but only when normalized to gray matter and cerebellum, not to white matter.
  
  
  CONCLUSIONS
  It is demonstrated that with a B/I protocol the (11)C-ABP688 distribution in late scans reflects the pattern of the total distribution volume and is therefore a measure for the density pattern of mGluR5. The early scans following injection are related to blood flow, although not in a fully quantitative manner. The advantage of the B/I protocol is that no arterial blood sampling is required, which is advantageous in clinical studies.
authors.affiliation: Department of Nuclear Medicine, University Hospital, PET Center, 8091 Zürich, Switzerland. cyrill.burger@usz.ch
authors.forename: Cyrill
authors.initials: C
authors.lastname: Burger
authors.forename: Alexandra
authors.initials: A
authors.lastname: Deschwanden
authors.forename: Simon
authors.initials: S
authors.lastname: Ametamey
authors.forename: Anass
authors.initials: A
authors.lastname: Johayem
authors.forename: Bruno
authors.initials: B
authors.lastname: Mancosu
authors.forename: Matthias
authors.initials: M
authors.lastname: Wyss
authors.forename: Gregor
authors.initials: G
authors.lastname: Hasler
authors.forename: Alfred
authors.initials: A
authors.lastname: Buck
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000378:metabolism*; D002250:Carbon Radioisotopes; D006801:Humans; D007261:Infusions, Intra-Arterial; D008297:Male; D008875:Middle Aged; D010091:Oximes; D049268:Positron-Emission Tomography; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: C510950:3-(6-methylpyridin-2-ylethynyl)cyclohex-2-enone-O-methyloxime; D002250:Carbon Radioisotopes; C578935:GRM5 protein, human; D010091:Oximes; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate