@article{vanwieringen90,
  author = {N. {van Wieringen} and S. A. Prahl and H. J. C. M. Sterenborg and M. J. C. van Gemert},
  title = {The Limitations of the Determination of the Optical Properties of Tissue Using a Double Integrating Sphere Set-Up with Collimated Incident Light},
  journal = {Lasers Med. Sci.},
  volume = {5},
  pages = {},
  year = {1990 abstract only},
  abstract = {\textbf{Introduction} The light distribution in a tissue can be characterized with the absorption coefficient \,$\mu_a$, the scattering coefficient \,$\mu_s$, and the anisotropy factor $g$. A method to calculate these from a measurement of total reflection $R_t$, collimated transmission $T_c$, and diffuse transmission $T_d$, of a slab of tissue, the inverse adding-doubling method, has been developed earlier. We developed an experimental set-up to measure $R_t$, $T_c$ and $T_d$ simultaneously. The accuracy of the system was tested using a known tissue phantom. \vskip2mm \textbf{Materials and Methods} A mathematical model of the set-up relating the radiance on the sphere wall to the reflection or transmission of the sample was developed. The model is calibrated using a set of standard reflection plates. Experiments are done using phantom solutions made of Evans Blue Intralipid-10\%. By mixing these solutions in different proportions albedos from 0.001 to 0.999 can be obtained. The optical thickness, $\tau$, of a phantom can be reduced by dilution. The range of $\tau$ thus obtained was from 50 to 0.1. The anisotropy factor is assumed to be constant. \vskip2mm \textbf{Results \& Conclusions} The experiments show that results with an accuracy better than 5\% are obtained if the optical depth $\tau$ of the sample in the direction of the laser beam is in the range $1\le\tau\le10$. Errors larger than 5\% may occur in the $\mu_s$ and $g$ if the albedo is smaller than 0.4 and in $\mu_a$ if the albedo is larger than 0.95. Within this range the combination of experimental set-up and method of data analysis are excellently suitable for measurements of $\mu_a$, $\mu_s$ and $g$.},
}