Layered optical property assessment by reflectance

Reflectance from a biological medium with multiple layers is influenced by the distribution of optical properties in the medium. A reflectance index is introduced to assess the layered optical properties. The index consists of the logarithm of reflectance ratios and is applied to in vitro layered media with different optical properties and to in vivo tissue. The measurement index varies with separation of source and detector. Blood volume changes in human skin in response to local heating are detected and related to index changes. The measurements at locations with a thick subcutaneous fat layer suggest minimal changes in the dermal blood fractional volume, indicating a different vascularization at these locations