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Renal positron emission tomography (PET) functional imaging allows non-invasive and dynamic measurements of functional and metabolic parameters. [In 10 healthy subjects, dynamic PET acquisitions were performed after [Renal time activity curves of [In healthy subjects, over a wide range of renal perfusion, direct estimates of renal oxygen consumption as well as tissue perfusion can be obtained by PET with a single tracer [

Introduction 5-hydroxytryptamine (5-HT) 6 receptors represent one of the more recently discovered serotoninergic receptor family. However, no 5-HT 6 positron emission tomography (PET) radiotracer is currently used in clinical imaging studies. The purpose of this study was to propose the first fluorinated PET radiotracer for this brain receptor. Methods A new compound presenting in vitro high affinity towards the serotoninergic 5-HT 6 receptor, N -[2-(1-[(4-fluorophenyl)sulfonyl]-1 H -indol-4-yloxy)ethyl] -N , N -dimethylamine, was labelled with fluorine 18 via a nitro-/fluoronucleophilic substitution. Biological evaluations included (i) in vitro and ex vivo autoradiographies in rat brain and (ii) a PET scan on anaesthetized cat. Results and Conclusion Although the radioligand showed excellent brain penetration, it did not reveal any specific binding to the 5-HT 6 receptors indicating that this radiotracer is not suitable for mapping 5-HT 6 receptors using PET.

International audience; PURPOSE: The aim of this study was to investigate (a) in vitro the relationship between [(18)F]fluorocholine ([(18)F]FCH) uptake and cell growth in endocrine cell lines and (b) in vivo the uptake of [(18)F]FCH by tumoral sites in an animal model of metastasized endocrine tumor. METHODS: In vitro studies were conducted on three endocrine and two nonendocrine digestive tumoral cell lines. The proliferative ratio was estimated using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. The uptake of [(18)F]FCH and that of [(18)F]fluorodeoxyglucose ([(18)F]FDG) were measured before and after cytotoxic therapy. [(18)F]FCH biodistribution was studied in nude mice and in an endocrine xenografted mice model. RESULTS: The [(18)F]FCH uptake in tumoral cell lines was related to their proliferative capacities as measured by the MTT assay in basal conditions. After cytotoxic therapy, the IC(50) values calculated with the [(18)F]FCH incorporation test were very close to those determined with the MTT assay. Biodistribution studies showed that [(18)F]FCH was predominantly concentrated in the liver and kidney of nude mice. In the STC-1 xenografted animal model, the uptake of [(18)F]FCH in the primary tumor was only 1.1%. On autoradiography and micro-positron emission tomography, there was no uptake of [(18)F]FCH in liver metastases but there was a significant uptake of [(18)F]FDG. CONCLUSIONS: In vitro studies suggested that the incorporation of [(18)F]FCH in endocrine tumor cell lines was related to their growth capacities; however, in vivo studies conducted in an endocrine xenografted animal model showed an uptake of [(18)F]FCH in hepatic metastases lower than that in normal liver cells. An influence of the microenvironment or a competition phenomenon for [(18)F]FCH uptake between normal liver and endocrine tumor cells cannot be excluded.

A new compound, 8[[3-[4-(2-[(11)C]methoxyphenyl)piperazin-1-yl]-2-hydroxypropyl]oxy]thiochroman was labeled via O-methylation with [(11)C]methyl iodide in good yield and specific activity. Original biological evaluations included (i) the study in anesthetized rat with a beta-sensitive intracerebral probe (beta-Microprobe), allowing to measure locally the kinetic of the new PET ligand, and (ii) a PET-scan on a conditioned cat maintained awake during the acquisition. In both in vivo techniques, the new ligand did not reveal any specific binding in hippocampus indicating that this radiotracer is not suitable for mapping 5HT(1A) receptors using positron emission tomography.