title: Synthesis, biological evaluation, and baboon PET imaging of the potential adrenal imaging agent cholesteryl-p-[18F]fluorobenzoate.
abstract: Cholesteryl-p-[18F]fluorobenzoate ([18F]CFB) was investigated as a potential adrenal positron emission tomography (PET) imaging agent for the diagnostic imaging of adrenal disorders. We describe the synthesis, biodistribution, adrenal autoradiography, and baboon PET imaging of [18F]CFB. The synthesis of [18F]CFB was facilitated by the use of a specially designed microwave cavity that was instrumental in effecting 70-83% incorporation of fluorine-18 in 60 s via [18F]fluoro-for-nitro exchange. Tissue distribution studies in mature female Sprague-Dawley rats showed good accumulation of [18F]CFB in the steroid-secreting tissues, adrenals and ovaries, at 1 h postinjection. The effectiveness of [18F]CFB to accumulate in diseased adrenals was shown through biodistribution studies in hypolipidemic rats, which showed a greater than threefold increase in adrenal uptake at 1 h and increased adrenal/liver and adrenal/kidney ratios. Analysis of the metabolites at 1 h in the blood, adrenals, spleen, and ovaries of hypolipidemic and control rats showed the intact tracer representing greater than 86%, 93%, 92%, and 82% of the accumulated activity, respectively. [18F]CFB was confirmed to selectively accumulate in the adrenal cortex versus the adrenal medulla by autoradiography. Normal baboon PET imaging with [18F]CFB effectively showed adrenal localization as early as 15 min after injection of the tracer, with enhanced adrenal contrast seen at 60-70 min. These results suggest that [18F]CFB may be useful as an adrenal PET imaging agent for assessing adrenal disorders.
authors: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors: S D
authors: SD
authors: Jonson
authors: M J
authors: MJ
authors: Welch
mesh_terms: D000311:Adrenal Glands / Q000000981:diagnostic imaging* / Q000378:metabolism; D000818:Animals; D001565:Benzoates / Q000138:chemical synthesis / Q000493:pharmacokinetics; D002788:Cholesterol Esters / Q000138:chemical synthesis / Q000493:pharmacokinetics; D005260:Female; D005462:Fluorine Radioisotopes; D007668:Kidney / Q000000981:diagnostic imaging; D010053:Ovary / Q000000981:diagnostic imaging; D010215:Papio; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013154:Spleen / Q000000981:diagnostic imaging; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed
chemical_list: D001565:Benzoates; D002788:Cholesterol Esters; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; C120325:cholesteryl 4-fluorobenzoate