The Effect of Optode Positioning on Optical Pathlength in Near Infrared Spectroscopy of Brain
The use of optical spectroscopy for the non-invasive monitoring of tissue oxygenation and metabolism is well established (Chance et al., 1975). Historically because of the high absorption by tissue of light in the visible range, optical monitoring was often restricted to measurements of reflected light (Jöbsis et al., 1977). Subsequently Jöbsis showed that by using near infrared light (NIR), tissue absorption became sufficiently low to make transillumination of the cat head possible (Jöbsis, 1977). In the near infrared region (700–1300 nm) there is sufficient spectral information available to permit changes in the concentration of haemoglobin and cytochrome aa3 to be calculated, and hence changes in the oxygenation state of the brain (Brazy et al., 1985, 1986; Ferrari et al., 1986; Fox et al., 1985). This technique is now used routinely to monitor cerebral oxygenation and haemodynamics in the human newborn infant (Wyatt et al., 1986; Edwards et al., 1988), using an instrument designed to transilluminate the heads of most newborn infants (Cope and Delpy, 1988). This instrument allows for measurements through heads up to 8–9 cm in diameter.
KeywordsPoint Spread Function Newborn Infant Cerebral Blood Volume Cerebral Oxygenation Near Infrared Spectroscopy
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- Wyatt, J.S., Cope, M., Delpy, D.T., Richardson, C.E., Edwards, A.D., Wray, S.C., Reynolds, E.O.R., 1989, Quantitation of cerebral blood volume in newborn infants by near infrared spectroscopy. J. Appl. Physiol. (submitted).Google Scholar