Reprints to :

Department of Physiology and Experimental Medicine [J.D.W., J.L.], The Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada; Thornhill Research Inc. [S.D.], Toronto, Ontario, M5G 2E8, Canada; Department of Anesthesiology [J.A.F], University Health Network, University of Toronto, Toronto, Ontario, M5G 2C4, Canada; Department of Medical Biophysics [K.S.L], University of Western Ontario, London, Ontario, N6A 5C1, Canada; Department of Medical Imaging [A.K.], University of Toronto, Toronto, Ontario, M5S 3E2, Canada. (* Corresponding author)