An optical tissue-like phantom is a useful tool to simulate the distribution of light in biological tissues. Many types of the phantoms such as solid plastic, resin, liquid solution, and gel state, have been developed in the biomedical optics field.
We have developed the agar gel phantoms to reproduce the diffuse reflectance spectra of human skin for visible to near-infrared wavelength range (l =400-900 nm). The basic phantom consists of epidermis layer and dermis layer and some types contain the local blood region with different shape. The agar solution was prepared by diluting agar powder with saline. To set the scattering condition, Intralipid 10% solution was added to the agar solution. The resultant solution was used as a base material for epidermis and dermis layers. Coffee solution was introduced as melanin substitute into the base material, and this mixture was used to make an epidermis layer. An oxygenated dermis layer was made by adding a small amount of fully oxygenated horse blood with Hct. = 44% to the base material. For the local blood region, an oxygenated blood material was prepared by mixing the agar solution with fully-oxygenated red blood cells of horse blood. All these layers were hardened in various molds having the required thickness, size, and shape by being cooled at about 5.5 ºC for 30 min. These layers were then piled to be a multilayered phantom and it was put between two slide glasses.