Optical properties of thermally-damaged porcine dermis and subcutaneous fat

Computational models are useful tools for simulating the thermal response of biological tissue to laser exposure. These models typically include a solution to a bio-heat equation and require a set of physical properties for each distinct tissue as inputs. In applications such as cauterization and surgery, the irradiated tissues may undergo severe heating, resulting in substantial denaturation and a probable change in one or more of their associated physical properties. While the wellestablished temperature-dependent behavior of water can approximate the changes in tissue thermal properties during heating, there is minimal available research on the dynamics of optical properties of tissue. This study characterized optical absorption and scattering of porcine skin tissues that had undergone temperature increases up to 90°C. We excised thin samples of porcine dermis and subcutaneous fat, placed them in a custom sealed tissue mount with a built-in temperature sensor, and raised them to various temperature intervals through submergence in a controlled hot water bath. Following heating, a series of goniometric spectrophotometry measurements of transmittance and reflectance, focusing on the near-infrared band, allowed for calculation of optical absorption and scattering coefficients as a function of tissue temperature and rate process model damage. The results allow for more accurate representation of tissue characteristics in computational models.