Tissue optical property measurements: overestimation of absorption coefficient with spectrophotometric techniques.

This study examines the validity of optical property measurements by comparing surface temperatures rises predicted by a well-tested mathematical model with temperatures measured experimentally during laser irradiation. Analysis is based on the early temperature response that is proportional to the absorption coefficient. The results of the investigation suggest that values for tissue absorption coefficient can be greatly overestimated when current spectrophotometric techniques are used. This seems especially true when a broad light beam and a low port-to-beam-size ratio are used for transmission and reflection measurements with an integrating sphere.