Analytical and experimental aspects of optical property determination of turbid media using frequency-domain PTR

Among diffusion methods, photothermal radiometry (PTR) has the ability to p enetrate and yield information about an opaque medium well beyond the range of conventional optical imaging. Owing to this ability, pulsed-laser PTR h as been extensively used in turbid media such as biological tissues(1-3) to study the sub-surface deposition of laser radiation, a task that may be di fficult or impossible for many optical methods due to excessive scattering and absorption. In this work, the optical and thermal properties of tissue- like materials are observed using frequency-domain infrared photothermal ra diometry. A three-dimensional heat conduction formulation with the use of t hree-dimensional optical diffusion is developed to derive a turbid frequenc y-domain PTR model. The agreement in the absorption and transport scatterin g coefficients of model phantoms is investigated. The present opto-thermal model for frequency-domain PTR may prove useful for noncontact, non-invasiv e, in situ measurement of optical properties of tissues and other multiply- scattering media.