Direct measurement of the optical properties of human breast skin.

The optical properties of thin tissue samples are obtained using goniometric apparatus. Direct measurements of the scattering of 633 nm light by 20-120 microns thick samples of in vitro human breast epidermis and dermis are numerically integrated to obtain values for the scattering and absorption coefficients mu s and mu a, respectively, and the anisotropy parameter g. The total attenuation coefficient mu t is obtained from transmission measurements. The Beer-Lambert law is found to be sufficiently valid for congruent to 100 microns thick samples to be used as the basis of the numerical integration. However, normalisation errors involved with the integration mean that only approximate values of mu a could be obtained. Values of congruent to 40 mm-1 are obtained for mu t and mu s, with the value of mu a estimated as 1 mm-1. The optical properties of human breast epidermis and dermis are found to be similar at 633 nm, and the two could be considered as a single layer for modelling light propagation at this wavelength. Further, the intersubject variability seen in this study suggests that a model that uses a range of values for each optical property may be more useful in a clinical situation.