Every morning, a charter jet takes off from Helsinki, Finland, bound for Örebro, Sweden. Its cargo: radiotracers. These radioactive compounds are essential for molecular imaging scans, which reveal metabolic processes inside cells. Radiologist and nuclear medicine physician Håkan Geijer and his colleagues at Örebro University Hospital depend on positron emission tomography (PET) scans to diagnose disease — like cancer — and, perhaps most critically, identify the best course of treatment.