Influence of patent ductus arteriosus (PDA) on middle cerebral artery blood flow velocity in preterm neonates less than 1 week old: F.J. Weira,c, A. Ohlssona,c, M.L. Ryana, T. Myhrc, K. Fongb,c, aDepartment of Newborn and Developmental Paediatrics, bDepartment of Diagnostic Imaging, cUniversity of Toronto Perinatal Clinical Epidemiology Unit, Women's College Hospital, Toronto, Ontario, Canada