Abstract

By measuring the adult human head during carotid endarterectomy, we investigate the depth sensitivity of two methods for deriving the absorption coefficient changes (Δμa) from time-resolved reflectance data to absorption changes in inhomogeneous media: (1) the curve-fitting method based on the diffusion equation (DE-fit method) and (2) the time-independent calculation based on the modified Lambert–Beer law (MLB method). Remarkable differences in the determined values of Δμa caused by clamping the external carotid artery and subsequently clamping the common carotid artery were observed between the methods. The DE-fit method was more sensitive to μa changes in cerebral tissues, whereas the MLB method was rather sensitive to μa changes in the extracerebral tissues. Our results indicated that the DE-fit was useful for monitoring the cerebral blood circulation and oxygenation during neurosurgical operations. In addition, the combined evaluation of μa changes with the DE-fit and MLB methods will provide us with more available information about the hemodynamic changes in the depth direction.

© 2007 Optical Society of America

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