title: A simplified radiometabolite analysis procedure for PET radioligands using a solid phase extraction with micellar medium.
abstract: A solid phase extraction method has been developed for simple and high-speed direct determination of PET radioligands in plasma.
  
  
  METHODS
  This methodology makes use of a micellar medium and a solid-phase extraction cartridge for displacement of plasma protein bound radioligand and separation of PET radioligands from their radiometabolites without significant preparation. The plasma samples taken from monkey or human during PET measurements were mixed with a micellar eluent containing an anionic surfactant sodium dodecyl sulphate and loaded onto SPE cartridges. The amount of radioactivity corresponding to parent radioligand (retained on the cartridge) and its radioactive metabolites (eluted with micellar eluent) was measured.
  
  
  RESULTS
  Under the optimized conditions, excellent separation of target PET radioligands from their radiometabolites was achieved with a single elution and short run-time of 1 min. This method was successfully applied to study the metabolism for (11)C-labelled radioligands in human or monkey plasma. The amount of parent PET radioligands estimated by micellar solid phase extraction strongly corresponded with that determined by radio-LC. The improved throughput permitted the analysis of a large number of plasma samples (up to 13 samples per one PET study) for accurate estimation of metabolite-corrected input function during quantitative PET imaging studies.
  
  
  CONCLUSIONS
  Solid phase extraction together with micellar medium is fast, sensitive and easy to use, and therefore it is an attractive alternative method to determine relative composition of PET radioligands in plasma.
authors.affiliation: Department of Clinical Neuroscience, Center for Psychiatric Research, Karolinska Institutet, Stockholm, Sweden. ryuji.nakao@ki.se
authors.forename: Ryuji
authors.initials: R
authors.lastname: Nakao
authors.forename: Christer
authors.initials: C
authors.lastname: Halldin
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes; D005260:Female; D006801:Humans; D008024:Ligands; D008252:Macaca fascicularis; D008823:Micelles; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000097:blood / Q000302:isolation & purification* / Q000378:metabolism*; D015203:Reproducibility of Results; D052616:Solid Phase Extraction / Q000379:methods*; D013501:Surface-Active Agents / Q000737:chemistry; D013997:Time Factors
chemical_list: D002250:Carbon Radioisotopes; D008024:Ligands; D008823:Micelles; D019275:Radiopharmaceuticals; D013501:Surface-Active Agents