T R Bates1, C C Phatouros2, J Van Heerden3. 1. St John of God Midland Public and Private Hospital, 1 Clayton Street Midland 6056, Western Australia tim.bates@sjog.org.au. 2. Neurological Intervention and Imaging Service of Western Australia (NIISwa), Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands 6009, Western Australia. 3. Perth Radiological Clinic, 127 Hammersley Rd Subiaco 6008, Western Australia.