Optical property determination of turbid media using frequency-domain infrared photothermal radiometry

Abstract

Among diffusion methods, photothermal radiometry (PTR) has the ability to penetrate and yield information about an opaque medium well beyond the range of conventional optical imaging. Owing to this ability, pulsed-laser PTR has been extensively used in turbid media such as biological tissues to study the sub-surface deposition of laser radiation, a task which may be difficult or impossible for conventional 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 radiometry. An approximate three-dimensional heat conduction formulation with the use of one-dimensional optical diffusion is developed to derive a turbid frequency-domain PTR model. The agreement in the absorption and transport scattering coefficients of model phantoms is investigated. The present opto-thermal model for frequency-domain PTR may prove useful for non-contact, non-invasive, in situ measurement of optical properties of tissues and other multiply-scattering media.