Anwar R Padhani1, Olivier Rouvière2, Ivo G Schoots3. 1. Paul Strickland Scanner Centre, Mount Vernon Cancer Centre, Northwood, UK. Electronic address: anwar.padhani@stricklandscanner.org.uk. 2. Department of Urinary and Vascular Imaging, Hospices Civils de Lyon, Hôpital Edouard Herriot, Lyon, France; Faculté de Médecine Lyon Est, Université de Lyon 1, Lyon, France. 3. Department of Radiology & Nuclear Medicine, Erasmus MC University Medical Center, Rotterdam, The Netherlands; Department of Radiology, Netherlands Cancer Institute, Amsterdam, The Netherlands.