Flutriciclamide (18F-GE180) PET: First-in-Human PET Study of Novel Third-Generation In Vivo Marker of Human Translocator Protein.
Neuroinflammation is associated with neurodegenerative disease. PET radioligands targeting the 18-kDa translocator protein (TSPO) have been used as in vivo markers of neuroinflammation, but there is an urgent need for novel probes with improved signal-to-noise ratio. Flutriciclamide (18F-GE180) is a recently developed third-generation TSPO ligand. In this first study, we evaluated the optimum scan duration and kinetic modeling strategies for18F-GE180 PET in (older) healthy controls.


METHODS
Ten healthy controls, 6 TSPO high-affinity binders, and 4 mixed-affinity binders were recruited. All subjects underwent detailed neuropsychologic tests, MRI, and a 210-min18F-GE180 dynamic PET/CT scan using metabolite-corrected arterial plasma input function. We evaluated 5 different kinetic models: irreversible and reversible 2-tissue-compartment models, a reversible 1-tissue model, and 2 models with an extra irreversible vascular compartment. The minimal scan duration was established using 210-min scan data. The feasibility of generating parametric maps was also investigated using graphical analysis.


RESULTS
18F-GE180 concentration was higher in plasma than in whole blood during the entire scan duration. The volume of distribution (VT) was 0.17 in high-affinity binders and 0.12 in mixed-affinity binders using the kinetic model. The model that best represented brain18F-GE180 kinetics across regions was the reversible 2-tissue-compartment model (2TCM4k), and 90 min resulted as the optimum scan length required to obtain stable estimates. Logan graphical analysis with arterial input function gave a VThighly consistent with VTin the kinetic model, which could be used for voxelwise analysis.


CONCLUSIONS
We report for the first time, to our knowledge, the kinetic properties of the novel third-generation TSPO PET ligand18F-GE180 in humans: 2TCM4k is the optimal method to quantify the brain uptake, 90 min is the optimal scan length, and the Logan approach could be used to generate parametric maps. Although these control subjects have shown relatively low VT, the methodology presented here forms the basis for quantification for future PET studies using18F-GE180 in different pathologies.
Neurology Imaging Unit, Imperial College London, Hammersmith Hospital, London, United Kingdom.
Zhen
Z
Fan
Neurology Imaging Unit, Imperial College London, Hammersmith Hospital, London, United Kingdom.
Valeria
V
Calsolaro
Neurology Imaging Unit, Imperial College London, Hammersmith Hospital, London, United Kingdom.
Rebecca A
RA
Atkinson
Neurology Imaging Unit, Imperial College London, Hammersmith Hospital, London, United Kingdom.
Grazia D
GD
Femminella
Neurology Imaging Unit, Imperial College London, Hammersmith Hospital, London, United Kingdom.
Adam
A
Waldman
GE Healthcare, Grove Centre, Amersham, United Kingdom.
Christopher
C
Buckley
GE Healthcare, Grove Centre, Amersham, United Kingdom.
William
W
Trigg
Neurology Imaging Unit, Imperial College London, Hammersmith Hospital, London, United Kingdom.|Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark; and.
David J
DJ
Brooks
Wolfson Molecular Imaging Centre, University of Manchester, Manchester, United Kingdom.
Rainer
R
Hinz
Neurology Imaging Unit, Imperial College London, Hammersmith Hospital, London, United Kingdom paul.edison@imperial.ac.uk.
Paul
P
Edison
D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000378:metabolism; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D002227:Carbazoles / Q000097:blood / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D057054:Molecular Imaging / Q000379:methods*; D009928:Organ Specificity; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000097:blood / Q000493:pharmacokinetics; D018079:Receptors, GABA / Q000378:metabolism*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
D015415:Biomarkers; D002227:Carbazoles; C571664:GE-180; D019275:Radiopharmaceuticals; D018079:Receptors, GABA; C499229:TSPO protein, human
GE180; Logan analysis; PET; flutriciclamide; kinetic model