title: The applicability of SRTM in [(18)F]fallypride PET investigations: impact of scan durations.
abstract: The high-affinity radioligand [(18)F]fallypride (FP) is frequently used for quantification of striatal/extrastriatal D(2/3) receptors and the receptor occupancies of antipsychotics (APs). Its 110 minutes half-life allows long scan durations. However, the optimum scan duration is a matter of debate. This investigation focuses on scan-duration-related effects on simplified reference tissue model (SRTM) results and the time point of transient equilibrium in a large sample of dynamic FP positron emission tomography (PET) scans. Fifty drug-free and 50 AP-treated subjects underwent FP-PET scans (180 minutes scan duration). The binding potential (BP(ND)) of the putamen, thalamus, and temporal cortex were calculated using the SRTM and the transient equilibrium model. Furthermore, receptor occupancies were calculated for AP-treated patients. Transient equilibrium in the unblocked putamen occurred after 121±29.6 minutes. The transient equilibrium occurred much earlier in the extrastriatal regions or under AP treatment. Stepwise scan shortening caused BP(ND) underestimations of 0.58% for the first 10-minute reduction (putamen, SRTM), finally reaching 5.76% after 1 hour scan-time reduction. We observed preferential extrastriatal AP binding irrespective of the analytical method. [(18)F]fallypride scan durations of 180 minutes reliably reach equilibrium even in D(2/3)-receptor-rich regions. Moderate reductions in FP scan durations only caused small changes to SRTM results even in receptor-rich regions. Apparently, the D(2/3) receptor occupancy results of APs, especially preferential extrastriatal binding observations, are not relevantly biased by inappropriate scan durations.
authors.affiliation: Department of Psychiatry and Psychotherapy, Medical Faculty, RWTH Aachen University, Aachen, Germany. ivernaleken@ukaachen.de
authors.forename: Ingo
authors.initials: I
authors.lastname: Vernaleken
authors.forename: Lisa
authors.initials: L
authors.lastname: Peters
authors.forename: Mardjan
authors.initials: M
authors.lastname: Raptis
authors.forename: Robert
authors.initials: R
authors.lastname: Lin
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Buchholz
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhou
authors.forename: Oliver
authors.initials: O
authors.lastname: Winz
authors.forename: Frank
authors.initials: F
authors.lastname: Rösch
authors.forename: Peter
authors.initials: P
authors.lastname: Bartenstein
authors.forename: Dean F
authors.initials: DF
authors.lastname: Wong
authors.forename: Wolfgang M
authors.initials: WM
authors.lastname: Schäfer
authors.forename: Gerhard
authors.initials: G
authors.lastname: Gründer
mesh_terms: D000293:Adolescent; D000328:Adult; D014150:Antipsychotic Agents / Q000627:therapeutic use*; D001549:Benzamides / Q000032:analysis*; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000188:drug therapy; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011759:Pyrrolidines / Q000032:analysis*; D011869:Radioligand Assay; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D050637:Receptors, Dopamine D3 / Q000378:metabolism*; D013997:Time Factors; D055815:Young Adult
chemical_list: D014150:Antipsychotic Agents; D001549:Benzamides; C094948:N-((1-allyl-2-pyrrolidinyl)methyl)-5-(3-fluoropropyl)-2,3-dimethoxybenzamide; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3