Kinetic analysis of the translocator protein positron emission tomography ligand [18F]GE-180 in the human brain
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Published version
Author(s)
Type
Journal Article
Abstract
PURPOSE: PET can image neuroinflammation by targeting the translocator protein (TSPO), which is upregulated in activated microglia. The high nonspecific binding of the first-generation TSPO radioligand [(11)C]PK-11195 limits accurate quantification. [(18)F]GE-180, a novel TSPO ligand, displays superior binding to [(11)C]PK-11195 in vitro. Our objectives were to: (1) evaluate tracer characteristics of [(18)F]GE-180 in the brains of healthy human subjects; and (2) investigate whether the TSPO Ala147Thr polymorphism influences outcome measures. METHODS: Ten volunteers (five high-affinity binders, HABs, and five mixed-affinity binders, MABs) underwent a dynamic PET scan with arterial sampling after injection of [(18)F]GE-180. Kinetic modelling of time-activity curves with one-tissue and two-tissue compartment models and Logan graphical analysis was applied to the data. The primary outcome measure was the total volume of distribution (V T) across various regions of interest (ROIs). Secondary outcome measures were the standardized uptake values (SUV), the distribution volume and SUV ratios estimated using a pseudoreference region. RESULTS: The two-tissue compartment model was the best model. The average regional delivery rate constant (K 1) was 0.01 mL cm(-3) min(-1) indicating low extraction across the blood-brain barrier (1 %). The estimated median V T across all ROIs was also low, ranging from 0.16 mL cm(-3) in the striatum to 0.38 mL cm(-3) in the thalamus. There were no significant differences in V T between HABs and MABs across all ROIs. CONCLUSION: A reversible two-tissue compartment model fitted the data well and determined that the tracer has a low first-pass extraction (approximately 1 %) and low V T estimates in healthy individuals. There was no observable dependency on the rs6971 polymorphism as compared to other second-generation TSPO PET tracers. Investigation of [(18)F]GE-180 in populations with neuroinflammatory disease is needed to determine its suitability for quantitative assessment of TSPO expression.
Date Issued
2016-06-28
Date Acceptance
2016-06-14
Citation
European Journal of Nuclear Medicine and Molecular Imaging, 2016, 43 (12), pp.2201-2210
ISSN
1619-7089
Publisher
Springer Verlag
Start Page
2201
End Page
2210
Journal / Book Title
European Journal of Nuclear Medicine and Molecular Imaging
Volume
43
Issue
12
Copyright Statement
© The Author(s) 2016. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Sponsor
National Institute for Health Research
Medical Research Council (MRC)
Multiple Sclerosis Trials Collaboration (MSTC)
Grant Number
NIRH-RP-011-048
MR/K023926/1
N/A
Subjects
GE180
Kinetic analysis
Neuroinflammation
Positron emission tomography (PET)
Quantification
Translocator protein (TSPO)
Nuclear Medicine & Medical Imaging
1103 Clinical Sciences
0299 Other Physical Sciences
Publication Status
Published