Frequency-domain immersion technique for accurate optical property measurements of turbid media

We demonstrate that absorption coefficient mu(alpha) and reduced scattering coefficient mu(s)' of a small turbid object can be measured to high accura cy with a frequency-domain immersion technique. For this technique the samp le is immersed in a calibrated scattering medium and the optical properties are obtained from a differential measurement. Compared with conventional a pproaches, the immersion technique improves accuracy, minimizes variations owing to probe coupling and motion, reduces the effects of boundary conditi ons, and offers simple and rapid measurement once the immersion medium is c alibrated. Accuracy tests of immersion-based measurements of mu(alpha) and mu(s)' agree with reference values to within 3.6% and 2.6%, respectively. T hese tests are limited by the accuracy of the reference samples rather than by the accuracy of the immersion medium or the precision of the immersion approach. We demonstrate the in vivo capabilities of the technique through time-resolved measurements of mu(alpha) and mu(s)' for a human hand during cuff occlusion on the upper arm. (C) 1999 Optical Society of America.