Satoshi YAMAMOTO^1*, Izumi FUJIWARA², Midori YAMAUCHI², Norimichi TSUMURA², and Keiko OGAWA-OCHIAI³

¹Center for Kampo Medicine, School of Medicine, Keio University, Shinjuku, Tokyo 160-8582, Japan
²Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan
³Clinic of Japanese–Oriental (Kampo) Medicine, Department of Otorhinolaryngology and Head and Neck Surgery, Kanazawa University Hospital, Kanazawa 920-8641, Japan

(Received April 26, 2012; Revised September 15, 2012; Accepted September 20, 2012)

In this article, we propose a new method — the optical path-length matrix method (OPLM) — as a faster alternative to the Monte Carlo for multi-layered media (MCML), which is often used to simulate the skin spectrum. Theoretically, peripheral oxygen saturation can be estimated by iterating MCML, but it is not a realistic strategy because it requires huge computation time. The optical path-length matrix is obtained as the probabilistic density histograms of the optical path length in skin using MCML, and once the matrix is obtained, skin spectral reflectance can be calculated by accumulating all combinations of elements in the matrix and by setting an absorption coefficient based on the Beer–Lambert law. The computational time of OPLM was approximately 26,000 times faster than that of MCML.

Key words: Monte Carlo for multi-layered media, probabilistic histograms, optical path-length matrix, spectral reflectance, human skin, high-speed simulation

^*E-mail address: may-s@umin.net