[18F]FETO for adrenocortical PET imaging: a pilot study in healthy volunteers.

Purpose: Functional imaging of the adrenal cortex by means of PET may play an important clinical role. Recently, we presented the synthesis and first evaluation of a novel 11β-hydroxylase inhibitor, [¹⁸F] FETO, in rats displaying high tracer accumulation in the adrenals. In this study, we aimed to investigate for the first time the potency of [¹⁸F]FETO as a PET tracer for the adrenal cortex in humans. Methods: An average preparation yielded 1-2 GBq of [¹⁸F]FETO ready to use. Ten healthy volunteers aged 24-57 years (five male and five female) were included in the study. After i.v. administration of 365 MBq [¹⁸F] FETO (246-391 MBq), dynamic images were acquired in 2D standard mode in 14 frames over 45 min. Afterwards, whole-body scanning was performed. In addition to visual interpretation, semi-quantitative analysis using standardised uptake values (SUVs) was conducted. Results: [¹⁸F]FETO distribution was similar in all scanned volunteers. Visually, pronounced accumulation of [¹⁸F] FETO was found in the adrenals, whereas moderate uptake was observed—at least in some of the subjects—for liver, renal calices, gallbladder, stomach walls and pancreas. Kidney and bowels showed only faint uptake. Median SUVs for the right and left adrenal glands were 15.6 (10.0-28.6) and 15.7 (10.3-35.9), respectively. The reference tissue (liver) displayed a median SUV of 2.5 (2.2-4.6). Conclusion: [¹⁸F]FETO is a valuable tracer for adrenocortical PET imaging, combining the longer half-life of ¹⁸F with a high 11β-hydroxylase selectivity. In accordance with our findings in rats, FETO PET revealed very high accumulation in the adrenal glands in healthy volunteers. [ABSTRACT FROM AUTHOR]