A system for preparing and injecting H215O for use in Positron Emission Tomography, said system comprising； producing means for producing a saline solution of H215O, bolus means for establishing a first bolus for injection, said first bolus comprising said saline solution of H215O and having a predefined volume and radioactivity concentration, said bolus means comprising a valve 100, and regulating means for regulating an injection profile of the first bolus.
