1 Department of Diagnostic Imaging, Ng Teng Fong General Hospital, 1 Jurong East Street 21, Singapore 609606, Singapore. Electronic address: vincent_tiong@nuhs.edu.sg.
2 Department of Medical Oncology, National Cancer Centre Singapore, 11 Hospital Cres, Singapore 169610, Singapore.
3 Department of Neurosurgery, National Neuroscience Institute, 11 Jln Tan Tock Seng, Singapore 308433, Singapore; Department of Neuroradiology, National Neuroscience Institute, 11 Jln Tan Tock Seng, Singapore 308433, Singapore.