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11Cmetomidate, a methyl ester analogue of etomidate, is used for positron emission tomography of adrenocortical cancer, and has been tested in recent clinical trials for lateralization in primary aldosteronism (PA). However, in PA, visualization as well as uptake quantification are hampered by the tracer's rather high non-specific liver uptake, and its overall clinical usefulness is also limited by the short 20-minute half-life of carbon-11. Therefore, we evaluated para-chloro-2-18Ffluoroethyl-etomidate, 18FCETO, a fluorine-18 (T1/2=109.8 min) analogue, as a potential new adrenocortical PET tracer. The aim of this study was to assess radiation dosimetry of 18FCETO. 18FCETO showed a high uptake in adrenal glands, still increasing at 5 h post injection. Adrenal glands (absorbed dose coefficients 0.100 ± 0.032 mGy/MBq in males and 0.124 ± 0.013 mGy/MBq in females) received the highest absorbed dose. The effective dose coefficient was 20 µSv/MBq. 18FCETO has a favourable biodistribution in humans for adrenal imaging. The effective dose for a typical clinical PET examination with 200 MBq 18FCETO is 4 mSv. ClinicalTrials.gov, NCT05361083 Retrospectively registered 29 April 2022. at, URL: https://clinicaltrials.gov/ct2/show/NCT05361083.
Silins et al. (Tue,) studied this question.