RT Journal Article
SR Electronic
T1 Head-to-Head Comparison of 11C-PBR28 and 18F-GE180 for Quantification of the Translocator Protein in the Human Brain
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1260
OP 1266
DO 10.2967/jnumed.117.203109
VO 59
IS 8
A1 Paolo Zanotti-Fregonara
A1 Belen Pascual
A1 Gaia Rizzo
A1 Meixiang Yu
A1 Neha Pal
A1 David Beers
A1 Randall Carter
A1 Stanley H. Appel
A1 Nazem Atassi
A1 Joseph C. Masdeu
YR 2018
UL http://jnm.snmjournals.org/content/59/8/1260.abstract
AB 18F-GE180 is a third-generation PET tracer for quantifying the translocator protein (TSPO), a biomarker for inflammation. The aim of this study was to perform a head-to-head comparison of 18F-GE180 and the well-established TSPO tracer 11C-PBR28 by scanning with both tracers during the same day in the same subjects. Methods: Five subjects underwent a 90-min PET scan with 11C-PBR28 in the morning and 18F-GE180 in the afternoon. A metabolite-corrected arterial input function was obtained in each subject for both tracers, and the brain uptake was quantified with a 2-tissue-compartment model. Results: The rate of metabolism of 18F-GE180 in arterial blood was slower than that of 11C-PBR28 (the percentages of nonmetabolized parent in plasma at 90 min were 74.9% ± 4.15% [mean ± SD] and 11.2% ± 1.90%, respectively). The plasma free fractions were similar for both tracers: 3.5% ± 1.1% for 18F-GE180 and 4.1% ± 1.1% for 11C-PBR28. The average total volume of distribution (VT) of 18F-GE180 was about 20 times smaller than that of 11C-PBR28 (0.15 ± 0.03 mL/cm3 for 18F-GE180 and 3.27 ± 0.66 mL/cm3 for 11C-PBR28). 18F-GE180 was characterized by poor transfer from the vascular compartment to the brain (its plasma-to-tissue rate constant [K1] was about 10 times smaller than that of 11C-PBR28). Moreover, kinetic modeling was more difficult with 18F-GE180, as its VT values were identified with a lower precision than those of 11C-PBR28 and outlying values were more frequent. Conclusion: The VT of 18F-GE180 was about 20 times smaller than that of 11C-PBR28 because of low penetration into the brain from the vascular compartment. In addition, kinetic modeling of 18F-GE180 was more challenging than that of 11C-PBR28. Therefore, compared with 11C-PBR28, 18F-GE180 had unfavorable characteristics for TSPO imaging of the brain.