Oxygen-18 Water

Oxygen-18 water (H2-18O) is chemically pure water with a high isotopic enrichment of oxygen-18. It is used in particle accelerators to produce fluorine-18. A high enrichment level of the target material with the oxygen-18 isotope reduces the yield of the undesirable by-product nitrogen-13 during fluorine-18 production.

Oxygen-18 enriched water is used as a starting material for medical cyclotron production. Bombardment of oxygen-18 with hydrogen ions (protons) produces the nuclear reaction 18O(p,n)18F. The resulting fluorine-18 is the radionuclide precursor of diagnostic radiopharmaceuticals used for PET, including 18F-FDG, 18F-NaF, 18F-DOPA, 18F-Fluorocholine, 18F-FMISO, 18F-FET, 18F-FLT and 18F-PSMA-1007. 18F-FDG is the most widespread PET radiopharmaceutical - an analogue of D-glucose that is well absorbed by cells with increased metabolism, allowing evaluation of metabolic intensity and detection of pathological areas including many types of tumors.

Natural oxygen is a mixture of three stable isotopes: oxygen-16 (99.76 at.%), oxygen-17 (0.04 at.%) and oxygen-18 (0.20 at.%). To enrich water with oxygen-18, CMR uses the rectification method - separation of H2-16O and H2-18O occurs in distillation columns due to the difference in their boiling points.