1. Center for Environmental Medicine, Asthma and Lung Biology, University of North Carolina–Chapel Hill, Chapel Hill, North Carolina.
2. Department of Respiratory and Sleep Medicine, Royal Prince Alfred Hospital, Sydney, Australia.
3. Department of Medical Physics, Royal Free Hospital, London, United Kingdom.
4. Department of Clinical Physiology and Nuclear Medicine, Rigshospitalet, Copenhagen University Hospital, Denmark.
5. Department of Nuclear Medicine, Southampton University Hospitals, Southampton, United Kingdom.
6. Activaero GmbH, Gemuenden, Germany.