Time-Domain Polarization-Sensitive Optical Coherence Tomography in Soft Biological Tissue
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A new, high-speed, fiber-based Mueller-matrix optical coherence tomography system with continuous source-polarization modulation is presented. For in vivo experimentation, the sample arm optics are integrated into a hand-held probe. The system?s parameters were verified through imaging standard optical elements. A unique feature of polarization-sensitive Mueller optical coherence tomography is that by measuring Jones or Mueller matrices, it can reveal the complete polarization properties of biological samples, even in the presence of diattenuation. Presented here for the first time are mapped local polarization properties of biological samples obtained by using polar decomposition in combination with least-squares fitting to differentiate measured integrated Jones matrices with respect to depth. In addition, a new concept of dual attenuation coefficients to characterize diattenuation per unit infinitesimal length in tissues is introduced. The algorithm was experimentally verified using measurements of a section of porcine tendon and the septum of a rat heart. The application of the system for burn imaging and healing monitoring was demonstrated on porcine skin because of its similarity to the human skin. The results showed a clear localization of the thermally damaged region. The local birefringence of the intravital porcine skin was mapped by using a differentiation algorithm. The burn areas in the OCT images agree well with the histology, thus demonstrating the system?s potential for burn-depth determination and post-injury healing monitoring. Another major application of the fiber-based Mueller-matrix optical coherence tomography system with continuous source-polarization modulation covered here is in vivo imaging of early stages of skin cancer. The OCT images of SENCAR mice skin affected by the tumorigenesis show the structural changes in skin resulting from precancerous papilloma formations that are consistent with histology, which proves the system?s potential for early skin cancer detection.