Oxygen–18 (18. O) is a natural, stable isotope of oxygen and one of the environmental isotopes. 18.O is an important precursor for the production of fluorodeoxyglucose (FDG) used in positron emission tomography (PET). Generally, in the radiopharmaceutical industry, enriched water (H 218. O) is bombarded with hydrogen.

We can provide you O18 from Isoflex USA  and Medical Isotopes USA