Absolute absorber quantification in turbid media at small source–detector separations

Abstract

The aim of our studies was to develop a method to determine the absorption coefficient of a turbid medium in a reflection geometry with small source–detector separations. Therefore, the time-integrated microscopic Beer–Lambert law (MBL) was modified in order to obtain the absolute absorption coefficient from mean time of flight and dc-intensity measurements. The new technique was evaluated using turbid phantoms having varying scattering (μs′ between 0.2 and 2.2 mm-1) and absorbing properties (μa between 0.04 and 0.14 mm-1), comparable to many biological tissues at various source–detector separations between 3 and 11 mm. The measurements were performed at a wavelength of 1064 nm. We found that this new method was able to determine the absolute absorption coefficient of the selected phantoms with a standard error of less than 0.005 mm-1 over the range of optical properties investigated.