@inproceedings{keranen10a,
  author = {Ville T. Ker{\"a}nen and Amanda L. Dayton and Scott A. Prahl},
  title = {Polyurethane phantoms with homogeneous and nearly homogeneous optical properties},
  booktitle = {SPIE Proceedings on Design and Performance Validation of Phantoms used in Conjunction with Optical Measurement of Tissue},
  year = {2010},
  editor = {R. J. Nordstrom},
  pages = {1-4},
  volume = {7567D},
  abstract = {Phantoms with controlled optical properties are often used for calibration and standardization. The phantoms are typically prepared by adding absorbers and scatterers to a clear host material. It is usually assumed that the scatterers and absorbers are uniformly dispersed within the medium. To explore the effects of this assumption, we prepared paired sets of polyurethane phantoms (both with identical masses of absorber, india ink and scatterer, titanium dioxide). Polyurethane phantoms were made by mixing two polyurethane parts (a and b) together and letting them to cure in the polypropylene container. The mixture was degassed before curing to ensure sample without bubbles. The optical properties were controlled by mixing titanium dioxide or india ink into polyurethane part (a or b) before blending the parts together. By changing the mixing sequence, we could change the aggregation of the scattering and absorption particles. Each set had one sample with homogeneously dispersed scatterers and absorbers, and a second sample with slightly aggregated scatterers or absorbers. We found that the measured transmittance could easily vary by a factor of twenty. The estimated optical properties (using the inverse adding-doubling method) indicate that when aggregation is present, the optical properties are no longer proportional to the concentrations of absorbers or scatterers.},
}