Tadatoshi TANIFUJI, Takashi OHTOMO, Daisuke OHMORI and Takumi ISHIKAWA

Department of Electrical and Electronics Engineering, Kitami Institute of Technology, 165 Koen-cho Kitami-city, Hokkaido 090-8507, Japan

(Received August 20, 2004; Accepted November 2, 2004)

Time-resolved reflectance of an optical pulse in adult head models including non-scattering cerebrospinal fluid (CSF) has been analyzed by the finite difference time domain (FDTD) analysis formulated by the authors. Averaged light intensity and mean time of flight dependences on the source-detector separations calculated by the FDTD analysis are in good agreement with previous experiments, hybrid finite element method (FEM) and Monte Carlo calculations, which justify the FDTD analysis. Based on the analysis, time-resolved reflectance sensitivities to detect optical property changes in brain have been analyzed. As a result, it has been become clear that the sensitivities to detect absorption changes of brain are enhanced in time-resolved reflectance compared to the sensitivities in averaged light intensity, whereas the sensitivities to detect scattering property changes of brain are almost the same in time-resolved reflectance and in averaged light intensity.

Key words: brain activities, cerebrospinal fluid, diffusion equations, finite difference time domain (FDTD) analysis, near-infrared (NIR) spectroscopy, optical absorption, optical scattering, optical tomography, time-resolved reflectance