Measurement Of Tissue Optical Properties By Using Double-integrating Sphere System

The applications of laser in biomedicine have attracted more and more attentions recently. Optical properties of biological tissue play an important role in the interactions between laser and tissues. The optical parameters, which are used to describe the optical properties of tissues and supply the index parameters for clinical therapy and diagnose, have great instructional significance for the application in medical.A variety of methods can be used to determine the optical properties of tissues, and the double-integrating-sphere system is the best precision one whose largest advantage is that all optical parameters can be determined in vitro simultaneously. This method has many advantages especially when the tissues undergo some external simulation, such as heat, pressure, or some other changes. To obtain the optical properties of tissues by the double-integrating-spheres system, the reflection, the total transmission, and the sample thickness should be measured and certain transfer theory model are used.A double-integrating-sphere system for measuring the optical properties of tissue based on the theory of two integrating spheres was developed. Firstly, the optical properties of tissue phantom 10%-intralipid were measured and the results are compared with the published paper. It showed that this system has the advantages of high precision, convenient operation. Secondly, we obtained the optical parameters of the phantom with different concentrations. The result showed that the absorption coefficient and scattering coefficient both have linear relation with the concentration. So the concentrations of phantom have great influence on optical properties. We compared this result with P₃ approximation, and both curves are similar. On the other hand, the sensitivity of P₃ approximation was described particularly and the influence of first-order parameter on P₃ approximation was explained.