Imaging wavelength and light penetration depth for water content distribution measurement of skin

BACKGROUND/PURPOSE: We investigate the measurement sensitivity for the water content distribution in Near-infrared (NIR) imaging ranging up to 2 μm. METHODS: To evaluate the sensitivity, our attention is focused to the light penetration depth in the skin tissue because the thickness of a layer where the water content can be varied is very thin and deep light penetration decreases the signal variation. The light penetration depths in the wavelengths of 1300, 1450, and 1920 nm are calculated theoretically based on the Monte Carlo light transport simulation. RESULTS: It is clarified that the wavelength of 1920 nm gives the smallest penetration depth. A NIR imaging experiment is demonstrated to verify the difference of imaging sensitivity. The experiment result shows that the NIR image taken at 1920 nm gives the most sensitive measurement of the water content distribution in skin.