Oxygen-18 (18O)

Oxygen-18 (18O) is a naturally occurring, stable isotope of oxygen with eight protons and ten neutrons, comprising approximately 0.204% of natural oxygen [1, 5]. It is not a therapeutic target, such as a protein receptor or enzyme, but is rather a chemical entity used as a diagnostic tool and research tracer [1, 4]. Its primary application in medicine is as a precursor for Oxygen-18 enriched water (H2[18]O), which is irradiated to produce Fluorine-18 ([18]F) for use in Positron Emission Tomography (PET) imaging, most commonly in the form of [18]F-Fludeoxyglucose (FDG) [1, 2]. Beyond imaging, 18O is used in 'doubly labeled water' studies to measure metabolic rates and energy expenditure in humans [2]. It also serves as a tracer in breath analysis, where the 18O/16O ratio in carbon dioxide can monitor the activity of enzymes like carbonic anhydrase, providing a potential biomarker for metabolic diseases such as type 2 diabetes [3]. In pharmaceutical development, 18O-labeling allows researchers to elucidate drug metabolic pathways and clarify reaction mechanisms during biocatalytic processes [11].

Other names

18OO-18Heavy oxygenOxygen-18 isotope

Oxygen-18 functions as a stable isotope tracer for physiological pathways and as a precursor for generating Fluorine-18, used in positron emission tomography (PET) imaging [1, 2, 5].