1Clinical Neuroscience, University of Cambridge, Cambridge, United Kingdom, 2Department of neurosurgery, Chang Gung Memorial Hospital, Keelung, Taiwan, 3Department of neurosurgery, Chang Gung University College of Medicine, Taoyuan, Taiwan, 4Department of radiology (EB44), University of Groningen, Groningen, Netherlands, 5Brain tumour imaging laboratory, University of Cambridge, Cambridge, United Kingdom, 6Department of radiology, University of Cambridge, Cambridge, United Kingdom