[OPTICAL REVIEW Vol. 12, No. 6 (2005) 480-485]
© 2005 The Optical Society of Japan

Finite Difference Time Domain Analysis of Diffusion Equations with Nonuniform Grids for Time-Resolved Reflectance of an Optical Pulse in Three-Dimensional Scattering Medium

Tadatoshi TANIFUJI and Khota ICHITSUBO

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

(Received July 1, 2005; Accepted September 30, 2005)

An integral form of diffusion equations and their finite difference time domain (FDTD) analysis have been formulated. The analysis is extended to FDTD analysis with nonuniform grids in three-dimensional (3-D) scattering medium. It has been confirmed that 600 time steps in calculation sequences of the time-resolved reflectance for 3-D medium 80 × 80 × 30 mm3 in volume is completed within 4 seconds by utilizing 23 and 43 mm3 nonuniform cubic grids, when a conventional personal computer with 3 GHz CPU clock is used. The conditions for keeping numerical accuracies comparable to those in 23 mm3 uniform grids are made clear. The proposed analysis greatly reduces time to run and memory space in 3-D scattering medium numerical analysis.

Key words: diffusion equations, diffused optical tomography, finite difference time domain (FDTD) analysis, nonuniform grids, near-infrared (NIR) spectroscopy, 3-D scattering media, time-resolved reflectance