1. Division of Surgery and Interventional ScienceUniversity College London Charles Bell House, 43–45 Foley Street London W1W 7JN UK
2. Medical Radiation Science GroupNational Physical Laboratory Hampton Road Teddington Middlesex TW11 0LW UK
3. Department of Medical Physics and BioengineeringUniversity College London Malet Place Engineering Building, Gower Street London WC1E 6BT UK
4. Radiation and Medical Physics GroupFaculty of Engineering and Physical SciencesUniversity of Surrey 388 Stag Hill Guilford GU2 7XH UK
5. Healthcare Biomagnetics LaboratoryUniversity College London 21 Albemarle Street London W1S 4BS UK
6. Institut Lumière MatièreUniversité Claude Bernard Lyon 1 CNRS UMR 5306 Villeurbanne 69622 France
7. Nuclear Metrology GroupNational Physical Laboratory Hampton Road Teddington Middlesex TW11 0LW UK