Biophysical studies of pulsed photothermal radiometry in tissues and tissue-like media

Abstract

<p>Pulsed Photothermal Radiometry (PPTR) is a remote sensing technique which monitors the temperature transient at the surface of a sample following the absorption of a brief optical pulse. In this work, it was used to investigate optical and thermal processes occurring in laser-irradiated, turbid, inhomogeneous media such as tissue. An optical diffusion approximation and heat conduction equation were used to derive the turbid PPTR model, for both homogeneous and layered semi-infinite media. These models were tested experimentally in a series of aqueous gel phantoms of known optical and thermal properties, and were found to be in good agreement. A study of discrete optical absorbers in a transparent medium necessitated the inclusion of the thermal radiative effects as an additional mode of heat transfer, and a corresponding PPTR model was derived and tested experimentally. Studies of intact biomolecules and of in-vivo tissue have also been performed to test and verify the derived formulations, and to determine the practical utility of PPTR for specific biomedical applications. The theoretical and experimental results presented in the thesis lay the groundwork for further inclusion of PPTR into the diagnostic arsenal of laser medicine.</p>