1 Department of Radiology, Royal Free London NHS Trust, London, Pond Street, London, NW3 2QJ, UK.
2 Department of Radiology, Royal United Hospitals Bath NHS Foundation Trust, Combe Park, Bath, BA1 3NG, UK.
3 Department of Respiratory Medicine, University College London, London, NW1 2BU, UK; Centre for Medical Image Computing, University College London, London, NW1 2BU, UK.
4 Department of Radiology, Southmead Hospital, North Bristol NHS Trust, Southmead Road, Bristol, BS10 5NB, UK.
5 Department of Radiology, The Royal Brompton & Harefield NHS Foundation Trust London, SW3 6NP, UK.
6 Department of Radiology, Leeds Teaching Hospitals NHS Trust, Leeds General Infirmary, Great George Street, Leeds, LS1 3EX, UK.
7 Department of Radiology, Freeman Hospital, Newcastle Upon Tyne Hospitals NHS Foundation Trust, Freeman Road, Newcastle Upon Tyne, NE7 7DN, UK.
8 Department of Radiology, University College London Hospital, 235 Euston Road, London NW1 2BU, UK.
9 Department of Radiology, Royal United Hospitals Bath NHS Foundation Trust, Combe Park, Bath, BA1 3NG, UK. Electronic address: grobinson1@nhs.net.