Proceedings PaperProgress in theoretical, experimental, and computational investigations in turbid tissue phantoms and human teeth using laser infrared photothermal radiometry
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This paper reviews and describes the state-of-the-art in the development of frequency-domain infrared photothermal radiometry (FD-PTR) for biomedical and dental applications. The emphasis is placed on the measurement of the optical and thermal properties of tissue-like materials using FD-PTR. A rigorous three-dimensional thermal-wave formulation with three-dimensional diffuse and coherent photon-density-wave sources is presented, and is applied to data from model tissue phantoms and dental enamel samples. The combined theoretical, experimental and computational methodology shows good promise with regard to its analytical ability to measure optical properties of turbid media uniquely, as compared to PPTR, which exhibits uniqueness problems. From data sets obtained with calibrated test phantoms, the reduced optical scattering and absorption coefficients were found to be within 20% and 10%, respectively, from the independently derived values using Mie scattering theory and spectrophotometric measurements. Furthermore, the state-of-the-art and recent developments in applications of laser infrared FD-PTR to dental caries research is described, with examples and histological studies from carious dental tissue. The correlation of PTR signals with modulated dental luminescence is discussed as a very promising potential quantitative methodology for the clinical diagnosis of sub-surface incipient dental caries. The application of the turbid-medium thermal-wave model to the measurement of the optical absorption and scattering coefficients of enamel is also presented.