There is provided a process for the preparation of a pharmaceutical composition comprising an 18F-labelled gas selected from the group consisting of 18F-labelled sulphur hexafluoride ([18F]SF6) and 18F-labelled carbon tetrafluoride ([18F]CF4), comprising the steps: a) Filling a target with a gas mixture comprising a fluorinated gas selected from the group consisting of sulphur hexafluoride (SF6) and carbon tetrafluoride (CF4)； b) Irradiating the gas mixture of step a) with protons with energies from 0.1 to 50 MeV. The pharmaceutical composition obtainable by the process and its uses in diagnosis, prognosis and lung function studies based on positron emission tomography (PET) are also claimed.
