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Please use this identifier to cite or link to this item: http://apo.ansto.gov.au/dspace/handle/10238/3025

Title: In-vivo imaging characteristics of two fluorinated flumazenil radiotracers in the rat.
Authors: Dedeurwaerdere, S
Gregoire, MC
Vivash, L
Roselt, P
Binns, D
Fookes, C
Greguric, I
Pham, T
Loc'h, C
Katsifis, A
Hicks, RJ
O'Brien, TJ
Myers, DE
Keywords: Rats
Radiopharmaceuticals
Tracer Techniques
In Vivo
Positron Computed Tomography
Fluorination
Issue Date: Jun-2009
Publisher: Springer
Citation: Dedeurwaerdere, S., Gregoire, M. C., Vivash, L., Roselt, P., Binns, D., Fookes, C., et al. (2009). In-vivo imaging characteristics of two fluorinated flumazenil radiotracers in the rat. European Journal of Nuclear Medicine and Molecular Imaging, 36(6), 958-965.
Abstract: Purpose: [11C]Flumazenil shows promise as a clinical and research PET radiotracer to image changes in GABAA central benzodiazepine receptor (cBZR), but its widespread use has been limited by practical limitations of [11C]. This study evaluated the imaging characteristics of two fluorinated PET radiotracers in rats in vivo: [18F]fluoroflumazenil ([18F]FFMZ) and [18F]flumazenil ([18F]FMZ). Methods: PET acquisitions were performed on a small-animal scanner following injection of [18F]FFMZ in nine rats and [18F]FMZ in eight rats. The following treatments were investigated: (1) injection of the tracer dose, (2) presaturation then injection of the tracer dose, and (3) injection of the tracer dose followed by a displacement injection. Unchanged tracer was measured in plasma and brain structures in four animals 10 and 30 min after injection, and ex-vivo autoradiography was also performed. Results: For both [18F]FFMZ and [18F]FMZ maximal brain activity peaked rapidly, and was highest in the hippocampus (1.12±0.06 SUV, 1.24±0.10 SUV, respectively), and lowest in the pons (1.00±0.07 SUV, 1.03±0.09 SUV, respectively). By 50 min after injection, maximal uptake for [18F]FFMZ and [18F]FMZ had decreased in the hippocampus to 18±3% and 80±1% (p<0.01), respectively. The presaturation and displacement studies showed a higher nonspecific component for [18F]FFMZ than for [18F]FMZ. Metabolite studies showed that at 30 min only 10% of the signal was from [18F]FFMZ in the brain. This nonspecific binding was apparent on autoradiography. In contrast, [18F]FMZ accounted for >70% of the signal in the brain, which resulted in well-defined regional binding on autoradiography. Conclusion These results demonstrate that [18F]FMZ is a superior radiotracer to [18F]FFMZ for in-vivo PET imaging of the GABAA/cBZR, having slower metabolism and leading to lower concentrations of metabolites in the brain that results in a substantially better signal-to-noise ratio. © 2009, Springer. The original publication is available at www.springerlink.com
URI: http://dx.doi.org/10.1007/s00259-009-1066-4
http://apo.ansto.gov.au/dspace/handle/10238/3025
ISSN: 619-7070
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