Tsukasa FUNANE^*, Hirokazu ATSUMORI, Hiroki SATO, Masashi KIGUCHI, and Atsushi MAKI

Advanced Research Laboratory, Hitachi, Ltd., Hatoyama, Saitama 350-0395, Japan

(Received February 3, 2009; Accepted April 16, 2009)

The signal-to-noise ratio (SNR), when using visible or near-infrared light to measure the change in hemoglobin concentration length (the product of hemoglobin concentration and optical path length in this study), depends on the wavelength combination and the analysis method. Although the SNRs increase when detected or incident optical power increases, the optical power should be limited because of safety standards. Considering these safety standards, we assumed that the total optical power was constant by using the relationship between optical power and measurement error. We investigated the theoretical estimation errors of the changes in hemoglobin concentration length using two, three, and four different wavelengths. The SNRs of the changes in hemoglobin concentration length were high when fewer wavelengths were used. These SNRs decreased when the redox state change in cytochrome oxidase was included in the analysis.

Key words: optical topography, wavelength combination, signal-to-noise ratio, hemoglobin concentration, near-infrared light, cytochrome oxidase, laser safety standards

^*E-mail address: tsukasa.funane.sb@hitachi.com