Optical radiation propagation based on Green's functions in biological skin tissues for enhanced coherence contrast

Abstract

Medical applications of treatment, diagnosis and surgery can greatly benefit from the use of optical radiation. Every biomedical optical technique depends strongly on light propagation. The spatial configuration and the characteristics of optical radiation at each spatial point greatly influence the outcome of the previously mentioned applications. Light properties as it traverses biological tissues are particularly relevant in optical diagnosis. Diagnosis by optical radiation is usually based on pure intensity measurements. Consequently, there is a general lack of enough contrast, as it is based on pure absorption and scattering differences. Enhanced contrast can be achieved by taking into account other light parameters, such as coherence or polarization. These parameters present a much more complex evolution, and are strongly dependent on the incident optical beam properties, as long as on the biological medium characteristics. The statistical nature of the process makes it convenient to use random beams and even random media in the models. These additional parameters could represent the possibility to distinguish malignant from healthy biological tissues, when intensity contrast is not enough. What is more, beam characteristics could be chosen in order to produce desired spatial distributions of radiation inside biological tissues, or to provide an adequate interpretation of diagnostic parameters. In this work, optical random beams, mainly Gaussian-based, are employed to model light propagation in turbid biological tissues by Green's functions. Coherence and spectral characteristics of the beam are considered. The model is applied to skin pathologies, such as basocellular or squamous cell carcinoma.